| 1. |
- Phu, Vu Dinh, et al.
(författare)
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Ventilator-associated respiratory infection in a resource-restricted setting: impact and etiology
- 2017
-
Ingår i: Journal of Intensive Care. - : BioMed Central (BMC). - 2052-0492. ; 5
-
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. |
- 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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| 3. |
- 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
-
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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| 4. |
- 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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| 5. |
- 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
-
Ingår i: Asian Pacific Journal of Cancer Prevention. - 1513-7368. ; 17, s. 79-84
-
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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| 6. |
- Hoang-Anh, Ho, et al.
(författare)
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The Origins of Cultural Divergence: Evidence from a Developing Country
- 2017
-
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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| 7. |
- 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
-
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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| 8. |
- 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
-
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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| 9. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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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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| 10. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
-
Charge Transport in LDPE Nanocomposites Part I—Experimental Approach
- 2016
-
Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 8:3, s. 87:1-87:19
-
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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| 11. |
- 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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| 12. |
- Hoang, Tuan Anh, 1985
(författare)
-
Charge transport in polymer-based insulating materials for high voltage applications: effect of single- and multi-layered structures
- 2016
-
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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| 13. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
-
DC electrical conductivity of LDPE-based nanocomposites
- 2015
-
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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| 14. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Mechanisms of Surface Potential Decay on Enamel Wire Coatings
- 2015
-
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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| 15. |
- Hoang, Tuan Anh, 1985, et al.
(författare)
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Open-circuit Thermally Stimulated Currents in LDPE/Al2O3 Nanocomposite
- 2016
-
Ingår i: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. - 9781509046546 ; 2016-December, s. 611-614
-
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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| 16. |
- 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
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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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| 17. |
- 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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| 18. |
- 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
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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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| 19. |
- 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
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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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| 20. |
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| 21. |
- 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
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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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| 22. |
- 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
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:2
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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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