| 1. |
- Phu, Vu Dinh, et al.
(författare)
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Ventilator-associated respiratory infection in a resource-restricted setting: impact and etiology
- 2017
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Ingår i: Journal of Intensive Care. - : BioMed Central (BMC). - 2052-0492. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Ventilator-associated respiratory infection (VARI) is a significant problem in resource-restricted intensive care units (ICUs), but differences in casemix and etiology means VARI in resource-restricted ICUs may be different from that found in resource-rich units. Data from these settings are vital to plan preventative interventions and assess their cost-effectiveness, but few are available.
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| 2. |
- Pham, Thi Anh Mai, et al.
(författare)
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Evaluation of screening algorithms to detect rectal colonization with carbapenemase-producing Enterobacterales in a resource-limited setting
- 2024
-
Ingår i: JAC - Antimicrobial Resistance. - : OXFORD UNIV PRESS. - 2632-1823. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- Objectives To improve and rationalize the detection of carbapenemase-producing Enterobacterales (CPE) in rectal swabs in a high-prevalence and resource-constrained setting, addressing surveillance challenges typically encountered in laboratories with limited resources.Methods A point prevalence survey (PPS) was conducted on 15 August 2022, in a provincial children's hospital in northern Vietnam. Rectal swab samples of all admitted children were collected and plated on a selective medium for carbapenem-resistant Enterobacterales (CRE). Species identification and antimicrobial susceptibility testing (AST) were performed by MALDI-TOF, and VITEK2 XL and interpreted according to CLSI breakpoints (2022). Carbapenemases were detected by the carbapenem inactivation method (CIM) and quantitative real-time PCR (qRT-PCR).Results Rectal swab samples were obtained from 376 patients. Of 178 isolates growing on the CRE screening agar, 140 isolates were confirmed as Enterobacterales of which 118 (84.3%) isolates were resistant to meropenem and/or ertapenem. CIM and PCR showed that 90/118 (76.3%) were carbapenemase producers. Overall, 83/367 (22.6%) were colonized by CPE. Klebsiella pneumoniae, Escherichia coli and Enterobacter cloacae complex were the most common CPE detected, with NDM as the predominant carbapenemase (78/90; 86.7%). Phenotypic resistance to meropenem was the best predictor of CPE production (sensitivity 85.6%, specificity 100%) compared with ertapenem resistance (95.6% sensitivity, 36% specificity). CIM was 100% concordant with PCR in detecting carbapenemases.Conclusions These findings underscore the effectiveness of meropenem resistance as a robust indicator of the production of carbapenemases and the reliability of the CIM method to detect such carbapenemases in resource-limited settings where the performance of molecular methods is not possible.
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| 3. |
- Tran, Ngoc Hieu, et al.
(författare)
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Genetic profiling of Vietnamese population from large-scale genomic analysis of non-invasive prenatal testing data
- 2020
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The under-representation of several ethnic groups in existing genetic databases and studies have undermined our understanding of the genetic variations and associated traits or diseases in many populations. Cost and technology limitations remain the challenges in performing large-scale genome sequencing projects in many developing countries, including Vietnam. As one of the most rapidly adopted genetic tests, non-invasive prenatal testing (NIPT) data offers an alternative untapped resource for genetic studies. Here we performed a large-scale genomic analysis of 2683 pregnant Vietnamese women using their NIPT data and identified a comprehensive set of 8,054,515 single-nucleotide polymorphisms, among which 8.2% were new to the Vietnamese population. Our study also revealed 24,487 disease-associated genetic variants and their allele frequency distribution, especially 5 pathogenic variants for prevalent genetic disorders in Vietnam. We also observed major discrepancies in the allele frequency distribution of disease-associated genetic variants between the Vietnamese and other populations, thus highlighting a need for genome-wide association studies dedicated to the Vietnamese population. The resulted database of Vietnamese genetic variants, their allele frequency distribution, and their associated diseases presents a valuable resource for future genetic studies.
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| 4. |
- Afshin, Ashkan, et al.
(författare)
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Health effects of dietary risks in 195 countries, 1990-2017 : a systematic analysis for the Global Burden of Disease Study 2017
- 2019
-
Ingår i: The Lancet. - : Elsevier. - 0140-6736 .- 1474-547X. ; 393:10184, s. 1958-1972
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Tidskriftsartikel (refereegranskat)abstract
- Background: Suboptimal diet is an important preventable risk factor for non-communicable diseases (NCDs); however, its impact on the burden of NCDs has not been systematically evaluated. This study aimed to evaluate the consumption of major foods and nutrients across 195 countries and to quantify the impact of their suboptimal intake on NCD mortality and morbidity.Methods: By use of a comparative risk assessment approach, we estimated the proportion of disease-specific burden attributable to each dietary risk factor (also referred to as population attributable fraction) among adults aged 25 years or older. The main inputs to this analysis included the intake of each dietary factor, the effect size of the dietary factor on disease endpoint, and the level of intake associated with the lowest risk of mortality. Then, by use of diseasespecific population attributable fractions, mortality, and disability-adjusted life-years (DALYs), we calculated the number of deaths and DALYs attributable to diet for each disease outcome.Findings: In 2017, 11 million (95% uncertainty interval [UI] 10-12) deaths and 255 million (234-274) DALYs were attributable to dietary risk factors. High intake of sodium (3 million [1-5] deaths and 70 million [34-118] DALYs), low intake of whole grains (3 million [2-4] deaths and 82 million [59-109] DALYs), and low intake of fruits (2 million [1-4] deaths and 65 million [41-92] DALYs) were the leading dietary risk factors for deaths and DALYs globally and in many countries. Dietary data were from mixed sources and were not available for all countries, increasing the statistical uncertainty of our estimates.Interpretation: This study provides a comprehensive picture of the potential impact of suboptimal diet on NCD mortality and morbidity, highlighting the need for improving diet across nations. Our findings will inform implementation of evidence-based dietary interventions and provide a platform for evaluation of their impact on human health annually.
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| 5. |
- Bengtsson, Linus, et al.
(författare)
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Implementation of Web-Based Respondent-Driven Sampling among Men Who Have Sex with Men in Vietnam
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:11, s. e49417-
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Lack of representative data about hidden groups, like men who have sex with men (MSM), hinders an evidence-based response to the HIV epidemics. Respondent-driven sampling (RDS) was developed to overcome sampling challenges in studies of populations like MSM for which sampling frames are absent. Internet-based RDS (webRDS) can potentially circumvent limitations of the original RDS method. We aimed to implement and evaluate webRDS among a hidden population. Methods and Design: criteria were men, aged 18 and above, who had ever had sex with another man and were living in Vietnam. Participants were invited by an MSM friend, logged in, and answered a survey. Participants could recruit up to four MSM friends. We evaluated the system by its success in generating sustained recruitment and the degree to which the sample compositions stabilized with increasing sample size. Results: Twenty starting participants generated 676 participants over 24 recruitment waves. Analyses did not show evidence of bias due to ineligible participation. Estimated mean age was 22 years and 82% came from the two large metropolitan areas. 32 out of 63 provinces were represented. The median number of sexual partners during the last six months was two. The sample composition stabilized well for 16 out of 17 variables. Conclusion: Results indicate that webRDS could be implemented at a low cost among Internet-using MSM in Vietnam. WebRDS may be a promising method for sampling of Internet-using MSM and other hidden groups.
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| 6. |
- Chen, Xiangrong, et al.
(författare)
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Surface Potential Decay on LDPE and its Nanocomposites
- 2017
-
Ingår i: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. ; 2017-October, s. 485-488
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Konferensbidrag (refereegranskat)abstract
- To elucidate capabilities of nanocomposites in a full extend, deep understanding of various physical processes induced by electric fields in the bulk and on surfaces of the materials is needed. This paper reports an investigation of surface potential decay on low-density polyethylene and its mixtures with Al2O3 and MgO nanofillers. Samples of two groups materials with various thicknesses prepeared using different manufacturing processes were used in the study. The samples were pre-charged by negative corona and surface potentials were measured by a non-contact technique at room temperature. The obtained results showed that the addition of nanofillers remarkably slowed down the potential decay process irrespectively of film thicknesses and fabrication processes. This is attributed to the significantly lower conductivities of LDPE nanocomposites as compared to pure material. Moreover, the conductivities of the filled materials exhibited strong electric field dependences. It is postulated that the effect can be related to the increased trap energy in the nanocomposites.
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| 7. |
- Duc, Duong M., 1984-, et al.
(författare)
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A Secular Trend in Birth Weight and Delivery Practices in Periurban Vietnam During 2005-2012
- 2017
-
Ingår i: Asia-Pacific journal of public health. - : SAGE PUBLICATIONS INC. - 1010-5395 .- 1941-2479. ; 29:5 Suppl., s. 18S-24S
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Tidskriftsartikel (refereegranskat)abstract
- The remarkable increase in Vietnamese economic conditions can increase the birth weight in neonates and better delivery practices among women. The Chi Linh Health and Demographic Surveillance System started in 2004. An open cohort of data consisting of about 57561 people from 17993 households has been followed primarily with respect to demography, economy, and education. The aim of this research is to study secular trends in delivery practice and birth weight in the past decade (2005-2012) in Chi Linh. We found a significant change in delivery rates at hospitals and cesarean section rates, but the birth weights over a decade of drastic economic development were stable. Furthermore, the findings show significant associations of birth weight and delivery practices with the child's sex, mother's age, and household income. Our results might be considered as representative for other similar periurban settings in Vietnam. We suggest that appropriate policies should be developed given the reduction in the use of delivery services in commune health centers in urban areas.
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| 8. |
- Giang, Kim Bao, et al.
(författare)
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Relative Importance of Different Attributes of Graphic Health Warnings on Tobacco Packages in Viet Nam
- 2016
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Ingår i: Asian Pacific Journal of Cancer Prevention. - 1513-7368. ; 17, s. 79-84
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Tidskriftsartikel (refereegranskat)abstract
- Graphic health warnings (GHW) on tobacco packages have proven to be effective in increasing quit attempts among smokers and reducing initial smoking among adolescents. This research aimed to examine the relative importance of different attributes of graphic health warnings on tobacco packages in Viet Nam. A discrete choice experimental (DCE) design was applied with a conditional logit model. In addition, a ranking method was used to list from the least to the most dreadful GHW labels. With the results from DCE model, graphic type was shown to be the most important attribute, followed by cost and coverage area of GHW. The least important attribute was position of the GHW. Among 5 graphic types (internal lung cancer image, external damaged teeth, abstract image, human suffering image and text), the image of lung cancer was found to have the strongest influence on both smokers and non-smokers. With ranking method, the image of throat cancer and heart diseases were considered the most dreadful images. GHWs should be designed with these attributes in mind, to maximise influence on purchase among both smokers and non-smokers.
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| 9. |
- Hoang-Anh, Ho
(författare)
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Essays on Culture, Institutions, and Economic Development
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Culture and institutions are important to understand individual behaviors and economic development. In this thesis, I study the origins of cultural divergence across societies, the emergence of private property rights, and the relationship between private property rights and economic development. First, I discover that the selective migration of individualistic people out of collectivistic societies in the past has left its trace in the cultural divergence along the individualism-collectivism dimension in the present. Second, I show that the state devises property rights to land to maximize tax revenue, producing the rise and fall of private property rights to land in response to changes in population density. Third, I find that private land tenure only has a modest impact on rural economic development. Thus, this thesis demonstrates the importance of history in understanding current economic issues, as well as provides valuable lessons on the privatization of agricultural land.
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| 10. |
- Hoang-Anh, Ho, et al.
(författare)
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The Origins of Cultural Divergence: Evidence from a Developing Country
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Cultural norms diverge substantially across societies, often even within the same country. In the present paper, we study the voluntary settlement hypoth- esis, proposing that individualistic people tend to self-select into migrating out of reach from collectivist states towards the periphery and that such patterns of historical migration are reflected even in the contemporary distribution of norms. During most of the first millennium CE, the modern north of Vietnam was under an exogenously imposed Chinese rule. From the eleventh to the eighteenth centuries, historical Vietnam gradually expanded its territory to the Mekong River Delta through various waves of conquest and migration. In contrast to some recent research, we find very little support from historical sources for any major discontinuities in this territorial expansion. Combining archives with household survey and lab-in-the-field experiment, we demon- strate that areas being annexed earlier into historical Vietnam are nowadays more (less) prone to collectivist (individualist) culture. We argue that the southward out-migration of individualistic people was the main mechanism behind this finding, which is also in line with many historical accounts.
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| 11. |
- Hoang Duc, Long, et al.
(författare)
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A new high-power low-loss air-dielectric stripline Gysel divider/combiner for particle accelerator applications at 352 MHz
- 2018
-
Ingår i: IET Control Theory & Applications. - : Institution of Engineering and Technology (IET). - 1751-8644 .- 1751-8652. ; :5, s. 264-267
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a new two-way Gysel combiner based on an air-dielectric stripline which allows to handle very high radio-frequency power levels with low-loss suitable for power combination in accelerator applications. The insertion loss of the combiner is 0.1 dB (2%). A thick stripline implementation allows improving the power capability in both continuous wave (CW) and pulsed operation. In addition, a mechanical tuner allows compensating for assembly and fabrication discrepancies. A methodology of designing the Gysel combiner as well as high-power measurements up to 22 kW in pulsed mode are presented. Simulations and measurements are in very good agreement.
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| 12. |
- Hoang-Minh, Thao, et al.
(författare)
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Use of TEM-EDX for structural formula identification of clay minerals : a case study of Di Linh bentonite, Vietnam
- 2019
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Ingår i: Journal of applied crystallography. - : International Union of Crystallography (IUCr). - 0021-8898 .- 1600-5767. ; 52:1, s. 133-147
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Tidskriftsartikel (refereegranskat)abstract
- Transmission electron microscopy linked with energy-dispersive X-ray spectroscopy (TEM-EDX) was applied to characterize mineralogical signals ofweathering processes in the Di Linh bentonite deposit (Vietnam) and to visualize the effects of Na activation on the smectitic phases. Modelling of X ray diffraction patterns (oriented mount) was applied in order to refine the computed structural formula. X-ray diffraction, X-ray fluorescence and Fouriertransform infrared spectroscopy (FT-IR) methods were also applied to verify the TEM-EDX results. An Excel-based routine has been developed in this research to allow fast computation of structural formulae and classification of the investigated clay particles. This routine supports the acquirement of 100 300 TEM-EDX analyses as a representative set of individual particles for each sample. The Excel-based routine involves end members of different clay mineral groups and interstratifications with two or three members (e.g. illite smectite interstratifications – IS-ml; dioctahedral vermiculite–smectite interstratifications – diVS-ml; and kaolinite–montmorillonite–dioctahedral vermiculite interstratifications – KSV-ml). The routine is now freely available. According to the identification procedure, the <2 mm fraction of the Di Linh bentonite (Vietnam) is composed mainly of K- and charge-deficient illite smectite interstratifications (or diVS-ml): montmorillonite-rich randomly ordered (R0) type and illite-rich regularly ordered (R1) type. Additionally, Fe-poor KSV-ml was identified.Industrial Na activation of the Di Linh bentonite resulted in an increase of theR1 diVS-ml portion and dissolution of a large part of the smectite-rich phases.The TEM-EDX approach also gave analytical proof of a sedimentary processfor Di Linh smectite. The parent muscovite was altered in two different environments: (i) K-leaching and layer-wise alteration into kaolinite (weathering), and (ii) further edge-controlled alteration of mica into lath-like montmorillonite particles associated with a dissolution of kaolinite layers from the former kaolinite–mica intergrowths by heat impact (basalt flow).
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| 13. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Charge decay on enamel wire surface
- 2014
-
Ingår i: Proceedings of International Conference on High Voltage Engineering and Application 2014 (ICHVE 2014), ISBN 978-1-4799-6613-4. - 9781479966134 ; , s. 1-4, paper A-4-3-
-
Konferensbidrag (refereegranskat)abstract
- Partial discharge resistant enamel insulation filled with chromium oxide (Cr2O3) has been developed recently. In the paper, dynamics of surface charges on samples of the material is analyzed and is compared with that on conventional enamel. The experiments were conducted on test objects prepared as windings of enameled wires. Surface charging was implemented using dc corona from a needle electrode which was placed against the grounded winding. After charging, the potential induced by deposited charges was measured by non-contact technique. The surface charge density pattern was reconstructed utilizing Φ-matrix method. The decay of charges accumulated on insulation surfaces was recorded. It was found that the decay process was considerably faster for the filled enamel than for the conventional one, which may be one of the factors contributing to the improved partial discharge resistance of the former.
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| 14. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
-
Charge transport in a double-layered enamel insulation during surface potential decay
- 2018
-
Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 25:2, s. 702-712
-
Tidskriftsartikel (refereegranskat)abstract
- This work presents a numerical model for studying charge dynamics during decay of pre-deposited surface charges on an enamel insulation comprising two layers of different materials. It is shown that the considered surface charge decay is dominated by charge injection from insulation surface into the bulk and the drift of injected carriers along the direction of induced electric field. These features allow for estimating charge carriers' mobilities in the studied insulation. The developed model incorporates experimental outcomes as well as the proposed effect of an internal interface between insulating layers on hindering charge transport through the bulk. The transient process of charge accumulation at the internal interface is exhibited and correlated with the well-known Maxwell-Wagner-Sillars polarization model. Contribution of charge injection at each insulation surface into the bulk to the measured potential decay is evaluated and compared.
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| 15. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Charge Transport in LDPE Nanocomposites Part I—Experimental Approach
- 2016
-
Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 8:3, s. 87:1-87:19
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Tidskriftsartikel (refereegranskat)abstract
- This work presents results of bulk conductivity and surface potential decay measurements on low-density polyethylene and its nanocomposites filled with uncoated MgO and Al2O3, with the aim to highlight the effect of the nanofillers on charge transport processes. Material samples at various filler contents, up to 9 wt %, were prepared in the form of thin films. The performed measurements show a significant impact of the nanofillers on reduction of material’s direct current (dc) conductivity. The investigations thus focused on the nanocomposites having the lowest dc conductivity. Various mechanisms of charge generation and transport in solids, including space charge limited current, Poole-Frenkel effect and Schottky injection, were utilized for examining the experimental results. The mobilities of charge carriers were deduced from the measured surface potential decay characteristics and were found to be at least two times lower for the nanocomposites. The temperature dependencies of the mobilities were compared for different materials.
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| 16. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Charge Transport in LDPE Nanocomposites Part II—Computational Approach
- 2016
-
Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 8:4, s. 103:1-103:16
-
Tidskriftsartikel (refereegranskat)abstract
- A bipolar charge transport model is employed to investigate the remarkable reduction in dc conductivity of low-density polyethylene (LDPE) based material filled with uncoated nanofillers (reported in the first part of this work). The effect of temperature on charge transport is considered and the model outcomes are compared with measured conduction currents. The simulations reveal that the contribution of charge carrier recombination to the total transport process becomes more significant at elevated temperatures. Among the effects caused by the presence of nanoparticles, a reduced charge injection at electrodes has been found as the most essential one. Possible mechanisms for charge injection at different temperatures are therefore discussed.
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| 17. |
- Hoang, Tuan Anh, 1985
(författare)
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Charge transport in polymer-based insulating materials for high voltage applications: effect of single- and multi-layered structures
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Polymer composites have been widely employed as electrical insulating materials for high voltage components and devices such as power cables, gas-insulated systems, rotating machines, line and post insulators, etc. Such materials are usually made by introducing inorganic oxides (SiO2, TiO2, Al2O3, MgO) into polymeric matrices e.g. polyethylene (PE), epoxy, silicone rubber. Reported experimental evidences indicate improvements which can be achieved in dielectric strength, partial discharge resistance, and life time of the polymer composites as compared to their base materials. However, the reasons behind the advancements in materials’ electrical performance have not been clearly elucidated in many cases. In this context, the present thesis concentrates on analyzing the influence of filler particles on transport of charge carriers in two polymer-based insulations namely nanofilled PE and microfilled enamel, which are novel insulating materials for high voltage direct current (HVDC) cables and electric motors, respectively. The contribution of internal interfaces between insulating layers existing in multi-layered structures to their electrical conduction is also considered. As for PE nanocomposites and its unfilled counterpart, specimens of thin films were prepared, whereas multi-layered structures were made by pressing them together at high temperature. Charging currents measured at various temperatures indicated a remarkable reduction in DC conductivity of the nanofilled dielectrics as compared to PE, making the former preferable insulating materials for HVDC cables, especially for those working under enhanced electric stresses. The observed effect was associated with the decreased charge mobility and increased trap energy in the nanocomposites as compared to the corresponding properties of unfilled PE. By comparing the measured currents obtained on single-layered and multi-layered structures, the impact of insulation–insulation interface on electrical conduction was revealed and analyzed. Further, the field dependencies were established for the transient currents and the quasi-steady state currents that were utilized for examining the dominant conduction mechanisms in the studied materials. A computer model was employed for studying the generation and transport of charge carriers in the insulations at various temperatures. The simulations demonstrated that apart from the reasons mentioned above, the weakening charge transport process in the nanocomposites is in great extent caused by the suppression of charge injection at the electrode–insulation interfaces. On the other hand, the insulation coatings of enameled wires are inherently multi-layered structures consisting of at least two layers of different materials. This study focuses on partial discharge resistant enamel insulation that was created by introducing chromium oxide (Cr2O3) particles of micrometer size into the base polymer. Experiments were conducted mainly on multi-layered enamel coatings, while some tests were also performed on single-layered flat samples and filler powder. Thus, contributions of each phase (filler and polymer matrix) to the electrical conduction and dielectric response of the filled enamel were highlighted. Charge transport in the multi-layered enamel coatings was studied in details by analyzing the surface potential decay characteristics. Accordingly, potential decay mechanisms due to the combination of charge injection, polarization, and intrinsic conduction were revealed, each of them dominating within a certain time interval. Based on that, a computer model of charge transport in multi-layered insulating structures was developed to reproduce the measured surface potentials. In this model, the consideration of the barrier effect of the internal interface is of utmost importance.
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| 18. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Charging and Discharge Currents in Low-Density Polyethylene and its Nanocomposite
- 2020
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 13:6, s. 1518-1535
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Tidskriftsartikel (refereegranskat)abstract
- Charging and discharge currents measured in low-density polyethylene (LDPE) and LDPE/Al2O3 nanocomposite are analyzed. The experiments were conducted at temperatures of 40–80 °C utilizing a consecutive charging–discharging procedure, with the charging step at electric fields varying between 20 and 60 kV/mm. A quasi-steady state of the charging currents was earlier observed for the nanofilled specimens and it was attributed to the enhanced trapping process at polymer–nanofiller interfaces. An anomalous behavior of the discharge currents was found at elevated temperatures for both the studied materials and its occurrence at lower temperatures in the nanofilled LDPE was due to the presence of deeply trapped charges at polymer–nanofiller interfaces. The field dependence of the quasi-steady charging currents is examined by testing for different conduction mechanisms. It is shown that the space-charge-limited process is dominant and the average trap site separation is estimated at less than 2 nm for the pristine LDPE and it is at about 5–7 nm for the LDPE/Al2O3 nanocomposite. Also, location of the trapping sites in the band gap structure of the nanofilled material is altered, which substantially weakens electrical transport as compared to the unfilled counterpart.
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| 19. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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DC electrical conductivity of LDPE-based nanocomposites
- 2015
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Ingår i: 9th International Conference on Insulated Power Cables, Jicable’15, 21 – 25 June 2015, Versailles – France (2015). ; , s. paper B6.5-
-
Konferensbidrag (refereegranskat)abstract
- This work presents studies of the effect of nanofillers on dc electrical conductivity of polymeric materials, potentially applicable in high voltage direct current (HVDC) cable insulation. Samples of low-density polyethylene (LDPE) filled with nanoparticles of aluminium oxide (Al2O3) and magnesium oxide (MgO) up to 3 wt% were prepared, on which charging currents were measured at 40 and 60 °C and electric stress of 32 kV/mm. Experimental results for nanocomposites were compared with those of reference LDPE. It was found that the addition of nanofillers led to a significant decrease in electrical volume conductivity and the decline depended strongly on filler type, its content and surface treatment. Further, the influence of specimen thickness on the conductivity was examined for verifying the operating conduction mechanisms. An indication was found that the space charge limited current (SCLC) mechanism dominated the conduction process in the reference material, while this effect ceased for the nanocomposites.
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| 20. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Electrical Characterization of a New Enamel Insulation
- 2014
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Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 21:3, s. 1291-1301
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Tidskriftsartikel (refereegranskat)abstract
- Investigations of dielectric properties of a newly developed enamel wire insulation created by adding chromium (III) oxide (Cr2O3) filler to polyamide-imide enamel base are presented. Results of measurements of electrical conductivity and complex permittivity at various temperatures as well as surface potential decay are discussed and compared with corresponding properties of standard enamel insulation. Contributions of different polarization relaxation processes in both enamels are examined based on the obtained master curves of dielectric response. In addition, the properties of chromium oxide filler are characterized separately and utilized further for analyzing its impact on the performance of enamel wire insulation by means of computer simulations. The experimental and simulated results demonstrate that the introduction of chromium oxide yields changes in the electrical properties that allow for mitigating the voltage stress in a wound insulation system. Furthermore, a correlation between the obtained results and the earlier described improved resistance to partial discharge activity of the chromium oxide filled enamel is discussed.
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| 21. |
- Hoang, Tuan Anh, 1985
(författare)
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Electrical Characterization of Partial Discharge Resistant Enamel Insulation
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Adjustable speed drives for rotating machines have become increasingly popular as they provide possibilities of smooth and accurate process control as well as for energy savings. In such systems, due to the fact that the voltage applied at terminals of motor windings is no longer purely sinusoidal but characterized by a high content of harmonics, the appearing electrical and thermal stresses yield premature failures of the winding insulation, mainly because of an increased partial discharge (PD) activity. To tackle the problem effectively, PD-resistant enamels have been developed, by introducing various inorganic fillers into the base polymer of the wire insulation, that exhibit an increased resistance to PD activity. The effect seems, in most of the cases, to be strongly dependent on the dielectric properties of the filler used and the degree of interactions with the host materials.In this respect, a recently developed enamel insulation, in which the top layer of the multilayer coating is filled with micro-particles of chromium (III) oxide (Cr2O3), has demonstrated exceptional properties. To elucidate the effect of material properties on the PD behavior, the presented in this thesis study concentrates on electrical characterizations of the new enamel insulation by measuring and analyzing its electric conductivity and complex dielectric permittivity and comparing these parameters with of the properties of enamel without the filler. In addition, the decay of surface potential induced by deposition on the enamel wire surfaces electric charges from a corona source is examined. The performed analyses show that the addition of Cr2O3 filler results in a highly conductive and dispersive material, as compared to the base enamel. As a consequence, the top coating layer of the enamel wire insulation activates suppression of PD activity, while the insulating properties of the bulk material are kept unchanged. The presence of chromium oxide results in enhanced interfacial polarization and low frequency dispersion (hopping conduction) of the enamel. The material conductivity is increased because of enhancement of charge carrier mobility as well as a shift of the maximum of trap density distributions towards lower energy levels.. The mechanism of the surface potential decay is analyzed by means of a model in which the combination of charge injection, dipolar polarization and intrinsic conduction appear to be the most important contributors to the observed surface charge dynamics.
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| 22. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Mechanisms of Surface Potential Decay on Enamel Wire Coatings
- 2015
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Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-4135 .- 1070-9878. ; 22:6, s. 3470-3480
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Tidskriftsartikel (refereegranskat)abstract
- Results of measurements of surface potential decay on coating layer of enameled wires are presented. In experiments, surfaces of winding samples were charged by dc corona of both polarities and decay of surface potential induced by charges deposited on the materials was recorded utilizing non-contact technique. The power-law type of time dependences of surface potential decay rates was obtained that indicated a dominant role of charge injection and/or dipolar polarization in the decay process. Furthermore, several decay mechanisms were employed for examining the experimental data, which revealed that potential decay was initially governed by the injection of charges due to electron transfer between the deposited charges and the material. Later on, the contribution of polarization to decay process was significant, while intrinsic conduction became the prevailing decay mechanism only at the latest stage as polarization was stabilized.
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| 23. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Open-circuit Thermally Stimulated Currents in LDPE/Al2O3 Nanocomposite
- 2016
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Ingår i: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781509046546 ; 2016-December, s. 611-614
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Konferensbidrag (refereegranskat)abstract
- Polyethylene doped with nanoparticles of inorganic oxides has been studied extensively during the last decade, aiming at its possible use as suitable material in insulation of high voltage direct current cables. To elucidate electrical properties of such material, thermally stimulated discharge (TSD) currents are analyzed in samples of low-density polyethylene (LDPE) filled with Al2O3 nanoparticles and compared with the response of pure LDPE. The latter exhibits a presence of two peaks in the TSD spectrum, which yield levels of activation energies close to earlier published data. For LDPE nanocomposite, a single broad peak is found instead, which when decomposed into a number of single peaks yields higher and broadly spreading activation energies. This indicates a presence of deep traps in the nanocomposite and explains significant reduction of its DC conductivity and strong suppression of space charge accumulation, as compared with unfilled LDPE.
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| 24. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Partial Discharge Behavior of a Newly Developed Enamel Insulation at Various Voltage Rise Times
- 2014
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Ingår i: Proceedings of 2014 International Symposium on Electrical Insulating Materials (ISEIM 2014), June 1-5, 2014, Niigata City, Japan. - 9784886860866 ; , s. 241-244
-
Konferensbidrag (refereegranskat)abstract
- Investigations of partial discharge (PD) characteristics in twisted pairs are presented. The test objects were made of conventional and chromium oxide filled enameled wires and were exposed to pulse width modulated (PWM) voltages of different rise times. To compare the performance of each insulation system, measurements of both PD inception and extinction voltages were conducted. Additionally, the number of PDs per cycle and their amplitude at different voltage levels were determined. Experimental results showed that the total PD exposure was considerably reduced for the chromium oxide filled enamel insulation as compared to that of the conventional material at the shortest voltage rise time. However, for filtered PWM waveforms with relatively longer rise times this difference became less prominent. The analysis of the results indicated that the observed effects are determined by the presence of chromium oxide filler and its electrical properties.
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| 25. |
- Le, Ha Vu, et al.
(författare)
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Bacterial Cellulose Aerogels Derived from Pineapple Peel Waste for the Adsorption of Dyes
- 2023
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Ingår i: ACS Omega. - 2470-1343. ; 8:37, s. 33098-34195
-
Tidskriftsartikel (refereegranskat)abstract
- Valorization of pineapple peel waste is an attractive research topic because of the huge quantities of this byproduct generated from pineapple processing industries. In this study, the extract from pineapple waste was collected to produce a hydrogel-like form containing bacterial cellulose fibers with a three-dimensional structure and nanoscale diameter by the Acetobacter xylinum fermentation process. The bacterial cellulose suspension was subsequently activated by freeze-drying, affording lightweight aerogels as potential adsorbents in wastewater treatment, in particular the adsorptive removal of organic dyes. Intensive tests were carried out with the adsorption of methylene blue, a typical cationic dye, to investigate the influence of adsorption conditions (temperature, pH, initial dye concentration, time, and experiment scale) and aerogel-preparation parameters (grinding time and bacterial cellulose concentration). The bacterial cellulose-based aerogels exhibited high adsorption capacity not only for methylene blue but also for other cationic dyes, including malachite green, rhodamine B, and crystal violet (28-49 mg/g). However, its activity was limited for most of the anionic dyes, such as methyl orange, sunset yellow, and quinoline yellow, due to the repulsion of these anionic dyes with the aerogel surface, except for the case of congo red. It is also an anionic dye but has two amine groups providing a strong interaction with the hydroxyl group of the aerogel via hydrogen bonding. Indeed, the aerogel has a substantially large congo red-trapping capacity of 101 mg/g. Notably, the adsorption process exhibited similar performances, upscaling the solution volume to 50 times. The utilization of abundant agricultural waste in the simple aerogel preparation to produce a highly efficient and biodegradable adsorbent is the highlight of this work.
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| 26. |
- Liu, Dongming, 1987-, et al.
(författare)
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Influence of Nanoparticle Surface Coating on Electrical Conductivity of LDPE/Al2O3 Nanocomposites for HVDC Cable Insulations
- 2017
-
Ingår i: IEEE transactions on dielectrics and electrical insulation. - : IEEE. - 1070-9878 .- 1558-4135. ; 24:3, s. 1396-1404
-
Tidskriftsartikel (refereegranskat)abstract
- LDPE/metal oxide nanocomposites are promising materials for future high-voltage DC cable insulation. This paper presents data on the influence of the structure of the nanoparticle coating on the electrical conductivity of LDPE/Al2O3 nanocomposites. Al2O3 nanoparticles, 50 nm in size, were coated with a series of silanes with terminal alkyl groups of different lengths (methyl, n-octyl and n-octadecyl groups). The density of the coatings in vacuum was between 200 and 515 kg m(-3,) indicating substantial porosity in the coating. The dispersion of the nanoparticles in the LDPE matrix was assessed based on statistics for the nearest-neighbor particle distance. The electrical conductivity of the nanocomposites was determined at both 40 and 60 degrees C. The results show that an appropriate surface coating on the nanoparticles allowed uniform particle dispersion up to a filler loading of 10 wt.%, with a maximum reduction in the electrical conductivity by a factor of 35. The composites based on the most porous octyl-coated nanoparticles showed the greatest reduction in electrical conductivity and the lowest temperature coefficient of electrical conductivity of the composites studied.
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| 27. |
- Minh, Hoang Van, et al.
(författare)
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Tobacco Control Policies in Vietnam : Review on MPOWER Implementation Progress and Challenges
- 2016
-
Ingår i: Asian Pacific Journal of Cancer Prevention. - 1513-7368. ; 17, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- In Vietnam, the WHO Framework Convention on Tobacco Control (WHO FCTC) took effect in March 2005 while MPOWER has been implemented since 2008. This paper describes the progress and challenges of implementation of the MPOWER package in Vietnam. We can report that, in term of monitoring, Vietnam is very active in the Global Tobacco Surveillance System, completing two rounds of the Global Adult Tobacco Survey (GATS) and three rounds of the Global Youth Tobacco Survey (GYTS). To protect people from tobacco smoke, Vietnam has issued and enforced a law requiring comprehensive smoking bans at workplaces and public places since 2013. Tobacco advertising and promotion are also prohibited with the exception of points of sale displays of tobacco products. Violations come in the form of promotion girls, corporate social responsibility activities from tobacco manufacturers and packages displayed by retail vendors. Vietnam is one of the 77 countries that require pictorial health warnings to be printed on cigarette packages to warn about the danger of tobacco and the warnings have been implemented effectively. Cigarette tax is 70% of factory price which is equal to less than 45% of retail price and much lower than the recommendation of WHO. However, Vietnam is one of the very few countries that require manufacturers and importers to make "compulsory contributions" at 1-2% of the factory price of cigarettes sold in Vietnam for the establishment of a Tobacco Control Fund (TCF). The TCF is being operated well. In 2015, 67 units of 63 provinces/cities, 22 ministries and political-social organizations and 6 hospitals received funding from TCF to implement a wide range of tobacco control activities. Cessation services have been starting with a a toll-free quit-line but need to be further strengthened. In conclusion, Vietnam has constantly put efforts into the tobacco control field with high commitment from the government, scientists and activists. Though several remarkable achievements have been gained, many challenges remain. To overcome those challenges, implementation strategies that take into account the contextual factors and social determinants of tobacco use in Vietnam are needed.
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| 28. |
- Nguyen Hoang, Anh Thu
(författare)
-
Tissue regulation of dendritic cells : with focus on chemokines, function and migration
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tissue-specific cells, such as fibroblasts and epithelial cells in local microenvironments have been recognized to influence the function and phenotype of hematopoietic cells, such as dendritic cells (DC). The interaction and cooperation between DC and the cells of the tissue is important for the maintenance of immune homeostasis as well as orchestrating immune responses against pathogens. However, a majority of studies on human DC are performed under conditions absent of a relevant physiological milieu allowing interactions between different cell types. Thus, there is a need to develop in vitro human tissue models with immune cells that can capture cellular responses under conditions similar to those found in real tissue. In my thesis work, I have developed a human three-dimensional (3D) lung tissue model that has morphological and functional features mimicking those of human lung epithelial tissue. The model has a stratified epithelial layer with human DC that are situated closely to the epithelium and an underlying collagen matrix rich in fibroblasts. We have found that the lung tissue model supports DC survival for at least eleven days in the absence of exogenous growth factors. The tissue model also regulates chemokine production by DC leading to enhanced production of CCL18 and downregulation of CCL17 and CCL22, which resemble chemokine production under physiological conditions in lung tissue. In addition, using live cell imaging, we could observe that stimulation with toll-like receptor-ligands and CCL2 attracted DC to the epithelial layer as well as increased their speed and their ability to survey a larger area in the tissue model. We also found, using our newly established 3D tumour spheroid tissue model of non-small cell lung cancer, that DC are recruited to the tumour area and engulf tumour cells more readily than normal epithelial cells. Another major focus of this thesis work is the study of stromal cell-derived chemokines supporting regulatory DC development during L. donovani infection. Stromal cells are known to regulate hematopoiesis in the bone marrow and spleen by secretion of chemokines, cytokines and growth factors. Studies have shown that murine splenic stromal cells have the ability to support differentiation of hematopoietic stem and progenitor cells (HSPC) into regulatory DC and this ability is enhanced during L. donovani infection. We further showed that stromal cell-derived chemokines CXCL12 and CCL8 cooperate to recruit HSPC with the ability to differentiate into regulatory DC. In addition, we observed that direct infection of MBA-1 cells by L. donovani enhanced their ability to support regulatory DC as well as their ability to produce CCL8. Interestingly, CCL8 expression was strongly induced in splenic stromal cells of mice infected with L. donovani, which enhanced their ability to attract HSPC. Our findings suggest that L. donovani infection modulates the ability of stromal cells to recruit and support HSPC differentiation into regulatory DC, and this may be a mechanism used by the parasite to establish persistent infection. Together, the studies in this thesis show the impact of tissue specific cells on DC differentiation and function, and highlights the importance of taking into account tissue-specific components when studying DC biology.
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| 29. |
- Nguyen-Tien, Thang, et al.
(författare)
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Knowledge and practice on prevention of mosquito-borne diseases in livestock-keeping and non-livestock-keeping communities in Hanoi city, Vietnam : A mixed-method study
- 2021
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 16:2
-
Tidskriftsartikel (refereegranskat)abstract
- Mosquito-borne diseases (MBDs) are causing high morbidity and mortality for humans. Urban livestock keeping is still common in cities around the world. The animals may serve as reservoirs for zoonotic MBDs, which increase the risks for humans. Here we assess the knowledge and practices related to MBDs in households with livestock and without livestock and explore the perceptions of the health care sector about MBDs and livestock keeping in Hanoi city of Vietnam in a cross-sectional study. A quantitative survey was conducted including 513 households with and without livestock-keeping in six districts and complemented with qualitative surveys with four health staff from Hanoi Center of Disease Control and three district health centers. The quantitative survey indicated that the participants possessed basic knowledge on MBDs with an average score of 18.3 out of 35, of which non-livestock-keeping households had a better knowledge than households keeping livestock (p<0.05). Both household categories had low score, 3.5 out of 11, regarding preventive practices against MBDs. The negative binomial model showed that occupation and location of living were factors associated to the knowledge on MBDs. Farmers were likely to have better preventive practices as compared to office workers (p<0.05). Those who had better knowledge also had more adequate preventive practices against MBDs (p<0.001). The qualitative survey revealed that livestock keeping was determined as increasing risks of MBDs due to the increase of mosquito population. It is recommended that community campaigns to raise the awareness and change behavior on MBDs should be organized based on collaboration between the health sector and the veterinary sector for households with and without livestock living in central urban and peri-urban areas. Further studies are needed to confirm the association between urban livestock keeping and potential increasing risks of MBDs such as dengue and Japanese encephalitis.
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| 30. |
- Nguyen-Tien, Thang, et al.
(författare)
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The Distribution and Composition of Vector Abundance in Hanoi City, Vietnam : Association with Livestock Keeping and Flavivirus Detection
- 2021
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Ingår i: Viruses. - : MDPI. - 1999-4915. ; 13:11
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Dengue virus and Japanese encephalitis virus are two common flaviviruses that are spread widely by Aedes and Culex mosquitoes. Livestock keeping is vital for cities; however, it can pose the risk of increasing the mosquito population. Our study explored how livestock keeping in and around a large city is associated with the presence of mosquitoes and the risk of them spreading flaviviruses.Methods: An entomological study was conducted in 6 districts with 233 households with livestock, and 280 households without livestock, in Hanoi city. BG-Sentinel traps and CDC light traps were used to collect mosquitoes close to animal farms and human habitats. Adult mosquitoes were counted, identified to species level, and grouped into 385 pools, which were screened for flaviviruses using a pan-flavivirus qPCR protocol and sequencing.Results: A total of 12,861 adult mosquitoes were collected at the 513 households, with 5 different genera collected, of which the Culex genus was the most abundant. Our study found that there was a positive association between livestock keeping and the size of the mosquito population-most predominantly between pig rearing and Culex species (p < 0.001). One pool of Cx. tritaeniorhynchus, collected in a peri-urban district, was found to be positive for Japanese encephalitis virus.Conclusions: The risk of flavivirus transmission in urban areas of Hanoi city due to the spread of Culex and Aedes mosquitoes could be facilitated by livestock keeping.
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| 31. |
- Pallon, Love K. H., et al.
(författare)
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Formation and the structure of freeze-dried MgO nanoparticle foams and their electrical behaviour in polyethylene
- 2015
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:14, s. 7523-7534
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically insulating low-density polyethylene (LDPE) nanocomposites based on dispersed MgO nanoparticle foams are reported. The foams were obtained via freeze-drying aqueous suspensions of precipitated ca. 40 nm wide and 10 nm thick Mg(OH)(2) nanoparticles and dewatering (calcining) at 400 degrees C, resulting in a 25 times more voluminous powder compared to conventionally dried nanoparticles. This powder handling prior to extrusion melt-processing greatly facilitated the nanocomposite preparation since no particle grinding was necessary. Large quantities of particles were prepared (>5 g), and the nanoparticle foams showed improved dispersion in the LDPE matrix with 70% smaller aggregate sizes compared to the conventionally dried and ground nanopowders. The nature of the nanoparticle foams was evaluated in terms of their dispersion on Si-wafers using ultrasonication as a dispersing aid, which showed to be detrimental for the nanoparticle separation into solitary particles and induced severe aggregation of the calcined nanoparticles. The grind-free MgO nanoparticles/LDPE-composite was evaluated by electrical measurement. The prepared composite showed an initial ca. 1.5 orders of magnitude lower charging current at 10(2) s, and a 4.2 times lower charging current after 16 hours compared to unfilled LDPE. The results open a way for improved insulation to be implemented in the future high-voltage cable system and present a new promising nanoparticle powder handling technique that can be used on a large scale.
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| 32. |
- Pallon, L. K. H., et al.
(författare)
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The impact of MgO nanoparticle interface in ultra-insulating polyethylene nanocomposites for high voltage DC cables
- 2016
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:22, s. 8590-8601
-
Tidskriftsartikel (refereegranskat)abstract
- Low density polyethylene (LDPE) nanocomposites with a reduced conductivity of two orders of magnitude are reported as a novel insulation material for high voltage distribution of renewable energy. The key to the high insulation capacity was to provide 70 nm hexagonal MgO nanoparticles with relatively tong, preferably 18 units long, hydrocarbon functional silsesquioxane coatings. This rendered the surface of the particles completely hydrophobic and also served as a protective layer against adsorption of polar low molecular weight atmospheric substances (H2O and CO2). The elimination of trace amounts of water, in combination with the provided carbon functionality, dramatically improved the dispersion of MgO nanoparticles. The lowest volume conductivity was ca. 7 x 10(-16) s m(-1) for 3 wt% surface coated nanoparticles. Extensive electron microscopy characterization was further used to relate the measured volume conductivity, acquired under conditions that resemble 800 kV high voltage direct current (HVDC) cables, to the distribution of the nanoparticles in the polymer matrix. The results show that an appropriate surface-modification approach yielded uniformly dispersed MgO nanoparticles up to contents as high as 9 wt%, with maintained 10-100 times reduced volume conductivity. Simulations of the MgO nanoparticles distribution revealed that the required interaction radius of the MgO-phase was 775 nm, setting a lower limit of particle amount to effectively work as electrical insulation promoters. The reduced volume conductivity values and scalable processing chemistry reported allow for the production of the next generation insulation material for HVDC cables.
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| 33. |
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| 34. |
- Pourrahimi, Amir Masoud, et al.
(författare)
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Polyethylene nanocomposites for the next generation of ultra-low transmission-loss HVDC cables: insulations containing moisture-resistant MgO nanoparticles
- 2016
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 8:23, s. 14824-14835
-
Tidskriftsartikel (refereegranskat)abstract
- The use of MgO nanoparticles in polyethylene for cable insulation has attracted considerable interest, although in humid media the surface regions of the nanoparticles undergo a conversion to a hydroxide phase. A facile method to obtain MgO nanoparticles with a large surface area and remarkable inertness to humidity is presented. The method involves (a) low temperature (400 °C) thermal decomposition of Mg(OH)2, (b) a silicone oxide coating to conceal the nanoparticles and prevent interparticle sintering upon exposure to high temperatures, and (c) heat treatment at 1000 °C. The formation of the hydroxide phase on these silicone oxide-coated MgO nanoparticles after extended exposure to humid air was assessed by thermogravimetry, infrared spectroscopy, and X-ray diffraction. The nanoparticles showed essentially no sign of any hydroxide phase compared to particles prepared by the conventional single-step thermal decomposition of Mg(OH)2. The moisture-resistant MgO nanoparticles showed improved dispersion and interfacial adhesion in the LDPE matrix with smaller nanosized particle clusters compared with conventionally prepared MgO. The addition of 1 wt % moisture-resistant MgO nanoparticles was sufficient to decrease the conductivity of polyethylene 30 times. The reduction in conductivity is discussed in terms of defect concentration on the surface of the moisture-resistant MgO nanoparticles at the polymer/nanoparticle interface.
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| 35. |
- Quang-Thuy, Ha, et al.
(författare)
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A Bisimulation-based Method of Concept Learning for Knowledge Bases in Description Logics
- 2012
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Ingår i: SoICT 2012 - 3rd International Symposium on Information and Communication Technology. - New York, New York, USA : ACM Press. ; , s. 241-249
-
Konferensbidrag (refereegranskat)abstract
- We develop the first bisimulation-based method of concept learning, called BBCL, for knowledge bases in description logics (DLs). Our method is formulated for a large class of useful DLs, with well-known DLs like ALC, SHIQ, SHOIQ, SROIQ. As bisimulation is the notion for characterizing indis-cernibility of objects in DLs, our method is natural and very promising.
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| 36. |
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| 37. |
- Ramanarao Parasa, Venkata, et al.
(författare)
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Modeling Mycobacterium tuberculosis early granuloma formation in experimental human lung tissue
- 2014
-
Ingår i: Disease Models and Mechanisms. - : Company of Biologists: OAJ / Company of Biologists. - 1754-8403 .- 1754-8411. ; 7:2, s. 281-288
-
Tidskriftsartikel (refereegranskat)abstract
- The widely used animal models for tuberculosis ( TB) display fundamental differences from human TB. Therefore, a validated model that recapitulates human lung TB is attractive for TB research. Here, we describe a unique method for establishment of TB infection in an experimental human lung tissue model. The model is based on cell lines derived from human lungs and primary macrophages from peripheral blood, and displays characteristics of human lung tissue, including evenly integrated macrophages throughout the epithelium, production of extracellular matrix, stratified epithelia and mucus secretion. Establishment of experimental infection in the model tissue with Mycobacterium tuberculosis, the bacterium that causes TB, resulted in clustering of macrophages at the site of infection, reminiscent of early TB granuloma formation. We quantitated the extent of granuloma formation induced by different strains of mycobacteria and validated our model against findings in other TB models. We found that early granuloma formation is dependent on ESAT-6, which is secreted via the type VII secretion machinery of virulent mycobacteria. Our model, which can facilitate the discovery of the interactions between mycobacteria and host cells in a physiological environment, is the first lung tissue model described for TB.
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| 38. |
- Sundstrom, Karin B., et al.
(författare)
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Andes Hantavirus-Infection of a 3D Human Lung Tissue Model Reveals a Late Peak in Progeny Virus Production Followed by Increased Levels of Proinflammatory Cytokines and VEGF-A
- 2016
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:2
-
Tidskriftsartikel (refereegranskat)abstract
- Andes virus (ANDV) causes hantavirus pulmonary syndrome (HPS), a severe acute disease with a 40% case fatality rate. Humans are infected via inhalation, and the lungs are severely affected during HPS, but little is known regarding the effects of ANDV-infection of the lung. Using a 3-dimensional air-exposed organotypic human lung tissue model, we analyzed progeny virus production and cytokine-responses after ANDV-infection. After a 7-10 day period of low progeny virus production, a sudden peak in progeny virus levels was observed during approximately one week. This peak in ANDV-production coincided in time with activation of innate immune responses, as shown by induction of type I and III interferons and ISG56. After the peak in ANDV production a low, but stable, level of ANDV progeny was observed until 39 days after infection. Compared to uninfected models, ANDV caused long-term elevated levels of eotaxin-1, IL-6, IL-8, IP-10, and VEGF-A that peaked 20-25 days after infection, i.e., after the observed peak in progeny virus production. Notably, eotaxin-1 was only detected in supernatants from infected models. In conclusion, these findings suggest that ANDV replication in lung tissue elicits a late proinflammatory immune response with possible long-term effects on the local lung cytokine milieu. The change from an innate to a proinflammatory response might be important for the transition from initial asymptomatic infection to severe clinical disease, HPS.
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| 39. |
- Tardivo, Alessio, et al.
(författare)
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Effectiveness of EU-funded R&I programmes from the perspective of the European railway sector stakeholders
- 2023
-
Ingår i: 2022 Conference Proceedings Transport Research Arena, TRA Lisbon 2022. - : Elsevier B.V.. ; , s. 1256-1263
-
Konferensbidrag (refereegranskat)abstract
- The paper provides a methodology for measuring the adherence of Research & Innovation (R&I) actions in railways to the stakeholders' requirements and expected benefits. After collecting the stakeholders' requirements, the R&I objectives are extracted from high-level documents such as Europe's Rail Joint Undertaking Master Plan and Multi Annual Work Programme. Lastly, after standardization of the requirements and the technology concepts, a top-down analysis is performed. The results show that network management and vehicle technologies have the highest benefit for the stakeholders, and ERRAC and Regulatory Bodies' requirements are well addrebed. However, the end-users requirements are only partially fulfilled. The necessity of increasing multimodal transport and cooperation with other transport modes is shown, while stronger focus can be placed on the employees and education/training.
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| 40. |
- Thai, Quan Ke, et al.
(författare)
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HV1 mtDNA Reveals the High Genetic Diversity and the Ancient Origin of Vietnamese Dogs
- 2023
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Ingår i: Animals. - : MDPI AG. - 2076-2615. ; 13:6, s. 1036-
-
Tidskriftsartikel (refereegranskat)abstract
- Simple Summary This study evaluated the genetic diversity and investigated the origin of Vietnamese domestic dogs on the basis of genetic data. A total of 56 haplotypes (group of genes inherited together from a single parent), including 14 indigenous ones (two of them have not been previously reported) were observed, with some of them implying that Australian dingo and Polynesian dogs originated from Southeast Asian ones, reinforcing the theory of domestication of dogs to the south of the Yangtze River. In this study, samples from 429 dog individuals across three main regions of Vietnam (Southern Vietnam (SVN), Central Vietnam (CVN), and Northern Vietnam (NVN)) were collected to analyze the 582 bp region mtDNA HVI, so as to study the genetic diversity and to screen the rare haplotype E in the Vietnamese village dog population. Nine new haplotypes A, two new haplotypes B, and three haplotypes C were unique to Vietnam dogs, in which the new haplotypes An3, An7, Cn1, and Cn3 concerned mutations at new polymorphism sites (15,517, 15,505, 15,479, and 15,933, respectively) which have not been previously reported. The detection of haplotypes A9 and A29, and the appearance of haplotype A200 in the two individual dogs sampled support that the Southeast Asian dog is the ancestor of today's Australian dingo and Polynesian dog. The two rare haplotypes E (E1 and E4) were reconfirmed in Vietnamese dogs and discussed. This study also contributes to strengthening the theory of domestication of dogs to the south of the Yangtze River and the Southeast Asian origin of the dingo.
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| 41. |
- Van Minh, Hoang, et al.
(författare)
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Primary healthcare system capacities for responding to storm and flood-related health problems : a case study from a rural district in central Vietnam
- 2014
-
Ingår i: Global Health Action. - : Co-Action publishing. - 1654-9716 .- 1654-9880. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: As a tropical depression in the East Sea, Vietnam is greatly affected by climate change and natural disasters. Knowledge of the current capacity of the primary healthcare system in Vietnam to respond to health issues associated with storms and floods is very important for policy making in the country. However, there has been little scientific research in this area. OBJECTIVE: This research was to assess primary healthcare system capacities in a rural district in central Vietnam to respond to such health issues. DESIGN: This was a cross-sectional descriptive study using quantitative and qualitative approaches. Quantitative methods used self-administered questionnaires. Qualitative methods (in-depth interviews and focus groups discussions) were used to broaden understanding of the quantitative material and to get additional information on actions taken. RESULTS: 1) Service delivery: Medical emergency services, especially surgical operations and referral systems, were not always available during the storm and flood seasons. 2) Governance: District emergency plans focus largely on disaster response rather than prevention. The plans did not clearly define the role of primary healthcare and had no clear information on the coordination mechanism among different sectors and organizations. 3) Financing: The budget for prevention and control of flood and storm activities was limited and had no specific items for healthcare activities. Only a little additional funding was available, but the procedures to get this funding were usually time-consuming. 4) Human resources: Medical rescue teams were established, but there were no epidemiologists or environmental health specialists to take care of epidemiological issues. Training on prevention and control of climate change and disaster-related health issues did not meet actual needs. 5) Information and research: Data that can be used for planning and management (including population and epidemiological data) were largely lacking. The district lacked a disease early-warning system. 6) Medical products and technology: Emergency treatment protocols were not available in every studied health facility. CONCLUSIONS: The primary care system capacity in rural Vietnam is inadequate for responding to storm and flood-related health problems in terms of preventive and treatment healthcare. Developing clear facility preparedness plans, which detail standard operating procedures during floods and identify specific job descriptions, would strengthen responses to future floods. Health facilities should have contingency funds available for emergency response in the event of storms and floods. Health facilities should ensure that standard protocols exist in order to improve responses in the event of floods. Introduction of a computerized health information system would accelerate information and data processing. National and local policies need to be strengthened and developed in a way that transfers into action in local rural communities.
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| 42. |
- Van Minh, Hoang, et al.
(författare)
-
Progress toward universal health coverage in ASEAN
- 2014
-
Ingår i: Global Health Action. - : Informa UK Limited. - 1654-9716 .- 1654-9880. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The Association of Southeast Asian Nations (ASEAN) is characterized by much diversity in terms of geography, society, economic development, and health outcomes. The health systems as well as healthcare structure and provisions vary considerably. Consequently, the progress toward Universal Health Coverage (UHC) in these countries also varies. This paper aims to describe the progress toward UHC in the ASEAN countries and discuss how regional integration could influence UHC.DESIGN: Data reported in this paper were obtained from published literature, reports, and gray literature available in the ASEAN countries. We used both online and manual search methods to gather the information and 'snowball' further data.RESULTS: We found that, in general, ASEAN countries have made good progress toward UHC, partly due to relatively sustained political commitments to endorse UHC in these countries. However, all the countries in ASEAN are facing several common barriers to achieving UHC, namely 1) financial constraints, including low levels of overall and government spending on health; 2) supply side constraints, including inadequate numbers and densities of health workers; and 3) the ongoing epidemiological transition at different stages characterized by increasing burdens of non-communicable diseases, persisting infectious diseases, and reemergence of potentially pandemic infectious diseases. The ASEAN Economic Community's (AEC) goal of regional economic integration and a single market by 2015 presents both opportunities and challenges for UHC. Healthcare services have become more available but health and healthcare inequities will likely worsen as better-off citizens of member states might receive more benefits from the liberalization of trade policy in health, either via regional outmigration of health workers or intra-country health worker movement toward private hospitals, which tend to be located in urban areas. For ASEAN countries, UHC should be explicitly considered to mitigate deleterious effects of economic integration. Political commitments to safeguard health budgets and increase health spending will be necessary given liberalization's risks to health equity as well as migration and population aging which will increase demand on health systems. There is potential to organize select health services regionally to improve further efficiency.CONCLUSIONS: We believe that ASEAN has significant potential to become a force for better health in the region. We hope that all ASEAN citizens can enjoy higher health and safety standards, comprehensive social protection, and improved health status. We believe economic and other integration efforts can further these aspirations.
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| 43. |
- Vu Nu, Anh, et al.
(författare)
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A systematic review on the direct approach to elicit the demand-side cost-effectiveness threshold : implications for low- and middle-income countries
- 2024
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 19:2
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Forskningsöversikt (refereegranskat)abstract
- Several literature review studies have been conducted on cost-effectiveness threshold values. However, only a few are systematic literature reviews, and most did not investigate the different methods, especially in-depth reviews of directly eliciting WTP per QALY. Our study aimed to 1) describe the different direct approach methods to elicit WTP/QALY; 2) investigate factors that contribute the most to the level of WTP/QALY value; and 3) investigate the relation between the value of WTP/QALY and GDP per capita and give some recommendations on feasible methods for eliciting WTP/QALY in low- and middle-income countries (LMICs). A systematic review concerning select studies estimating WTP/QALY from a direct approach was carried out in seven databases, with a cut off date of 03/2022. The conversion of monetary values into 2021 international dollars (i$) was performed via CPI and PPP indexes. The influential factors were evaluated with Bayesian model averaging. Criteria for recommendation for feasible methods in LMICs are made based on empirical evidence from the systematic review and given the resource limitation in LMICs. A total of 12,196 records were identified; 64 articles were included for full-text review. The WTP/QALY method and values varied widely across countries with a median WTP/QALY value of i$16,647.6 and WTP/QALY per GDP per capita of 0.53. A total of 11 factors were most influential, in which the discrete-choice experiment method had a posterior probability of 100%. Methods for deriving WTP/QALY vary largely across studies. Eleven influential factors contribute most to the level of values of WTP/QALY, in which the discrete-choice experiment method was the greatest affected. We also found that in most countries, values for WTP/QALY were below 1 x GDP per capita. Some important principles are addressed related to what LMICs may be concerned with when conducting studies to estimate WTP/QALY.
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