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- Hoang-Minh, Thao, et al.
(författare)
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Mineralogical Characterization of Di Linh Bentonite, Vietnam: A Methodological Approach of X-ray Diffraction and Transmission Electron Microscopy
- 2014
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Ingår i: Proceedings of 13th International Symposium on Mineral Exploration (ISME-XIII). - Hanoi : Vietnam National University Press, Hanoi. - 9786046215400 ; , s. 143-148
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Konferensbidrag (refereegranskat)abstract
- Vietnam has decided to establish nuclear power as further energy option. In order to develop a Vietnamese reference bentonite as potential barrier in a final repository for high radioactive waste, a detailed mineralogical investigation of Di Linh bentonite (Lam Dong province), lacustrine clay, was carried out by different methods especially transmission electron microscopy (TEM) linked with energy-dispersive X-ray (EDX). From a sample homogenized from 5 tones of the bentonite, mineral formulae of clay particles was calculated The calculation also focuses on randomly interstratifications of two and three members. The fraction <2 μm of Di Linh bentonite is composed mainly by montmorillonite (Ca0.06Mg0.03Na0.09K0.03Al1.39Fe0.25Mg0.26(OH)2 Si3.96Al0.04O10) and regular ordering (R1) illite-smectite interstratifications with K- and charge-deficiency (Ca0.04Mg0.07Na0.18K0.16Al1.76Fe0.08Mg0.16(OH)2Si3.62Al0.38O10). Additionally, Fe-poor kaolinite-smectite-vermiculite interstratifications and trace of Fe-rich chloritesmectite- vermiculite interstatifications were identified. TEM-investigations showed analytical proofs of the sedimentary character of smectite formation in the Di Linh deposit. Parent muscovite was weathered in several steps in two different environments: (i) K-leaching and layer-wise alteration into kaolinite; (ii) further edge- controlled alteration of mica into lathlike montmorillonite particles under dissolution of kaolinite layers from former kaolinite-mica intergrowths. Mineralogical composition of the Di Linh bentonite with mainly montmorillonite and illite-rich illite-smectite interstratifications shows that the Di Linh bentonite can be a suitable barrier candidate in final repositories.
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| 2. |
- Cuc, Nguyen Thi Thu, et al.
(författare)
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Hot water treatment prevents Aphelenchoides besseyi damage to Polianthes tuberosa crops in the Mekong Delta of Vietnam
- 2010
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Ingår i: Crop Protection. - 0261-2194. ; 29:6, s. 599-602
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Tidskriftsartikel (refereegranskat)abstract
- Polianthes tuberosa is a commercially valuable flower crop in the Mekong Delta of Vietnam that is propagated by the harvesting and planting of bulbs. The cultivation of P. tuberosa is infected by an endemic Aphelenchoides besseyi nematode that damages a high proportion of plants and persists within the bulbs. Here we report on the comparison of hot water and pesticide treatments as control methods to protect P. tuberosa from A. besseyi damage, and conclude that a hot water treatment consisting of soaking bulbs in water for 30 minutes at 57 °C is the most efficacious method to produce healthy flowers in a cost-effective manner.
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| 3. |
- Tan, Ha Minh, 1989-, et al.
(författare)
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Self-heating Effect on Tin Oxide Nanowire Network Gas Sensor
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Self-heated gas sensors have attracted much of interests owing to the ultra-low power consumption as well as simple device fabrication. However, it still requires further improvement to overcome some technical difficulties such as high operation voltage, long-term stability, and mass production. In this work, we propose a nanowire nework structure to solve these problems. The self-heating effect on fabricated structures was tested and working temperature was evaluated by base resistance measurement and infrared emission microscopy methods. The fabricated sensor consumed an electric power of about 40 mW to reach the working temperature up to 250 oC. The NO2 sensing properties were initially studied on this sensor structure.
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| 4. |
- Thoa, Nguyen Thi Minh, et al.
(författare)
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The impact of economic growth on health care utilization : a longitudinal study in rural Vietnam
- 2013
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Ingår i: International Journal for Equity in Health. - : BioMed Central. - 1475-9276. ; 12, s. Article nr 19-
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: In many developing countries, including Vietnam, out-of-pocket payment is the principal source of health financing. The economic growth is widening the gap between rich and poor people in many aspects, including health care utilization. While inequities in health between high- and low-income groups have been well investigated, this study aims to investigate how the health care utilization changes when the economic condition is changing at a household level.METHOD: We analysed a panel data of 11,260 households in a rural district of Vietnam. Of the sample, 74.4% having an income increase between 2003 and 2007 were defined as households with economic growth. We used a double-differences propensity score matching technique to compare the changes in health care expenditure as percentage of total expenditure and health care utilization from 2003 to 2005, from 2003 to 2007, and from 2005 to 2007, between households with and without economic growth.RESULTS: Households with economic growth spent less percentage of their expenditure for health care, but used more provincial/central hospitals (higher quality health care services) than households without economic growth. The differences were statistically significant.CONCLUSIONS: The results suggest that households with economic growth are better off also in terms of health services utilization. Efforts for reducing inequalities in health should therefore consider the inequality in income growth over time.
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| 7. |
- Ahrens, Lutz, et al.
(författare)
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Screening av perfluoralkylerade ämnen och flamskyddsmedel i svenska vattendrag
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med projektet var att studera förekomst av perfluoralkylerade ämnen (PFASs) samt relativt nya flamskyddsmedel (FRs) i svenska vattendrag. Vi provtog på 44 platser (totalt 41 vattendrag) och bestämde innehållet av PFASs (alla platser) och FRs (25 platser). Av de 12 utvalda FRs, kunde 3 kvantifieras. TCIPP var det klart dominerade ämnet med en halt på upp till 3900 ng L-1 (Fyrisån). 2,4,6-TBP uppvisade högre halter i åar i södra Sverige. Vattendragen med de högsta av σFRs var Fyrisån och Norrström. Den totala belastningen på östersjön av σFRs uppskattades till 38 kg dag-1, där ångermanlandsälven och Norrström stod för de största bidragen. Det ska noteras att i dessa belastningssiffror ingår inte äldre FRs med omfattande historisk användning, t.ex. PBDE. Totalt 13 av 25 de analyserade PFASs kunde kvantifieras. Medelvärdet av σPFASs i alla vattendrag var 9,5 ng L-1, och de högsta medelhalterna uppmättes för PFBS och PFHxS (~2 ng L-1). Det sammanlagda utflödet av σPFASs uppgick till 3,2 kg dag-1. PFOS överskred miljökvalitetsnormen på 0,65 ng L-1 (årligt medelvärde; AA-EQS; 2013/39/EU) på 12 av 44 platser.Den här fältstudien baseras på en provtagningskampanj med ögonblicksprovtagning, och därför ska alla rapporterade värden tolkas med försiktighet. Verifikation av höga resultat och mer detaljerade studier på platser med förhöjda värden rekommenderas. Studien pekar också på att uppströmsmätningar är nödvändiga för att finna viktiga föroreningskällor.
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| 8. |
- Ahrens, Lutz, et al.
(författare)
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Screening of perfluoroalkyl substances and organic flame retardants in Swedish Rivers : Screening av perfluoralkylerade ämnen och flamskyddsmedel i svenska vattendrag
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The occurrence and effects of ubiquitously present persistent organic pollutants (POPs) in the environment is one of the challenges the society is facing today. Two categories of chemicals that have gained increased public attention during the last decades are organic flame retardants (FRs) and perfluoroalkyl substances (PFASs). Many representatives from these compound groups have bioaccumulative, persistent and toxic properties. This has led to a ban of some of these compounds based on international agreements.FRs and PFASs end up in surface waters and sometimes also in ground water due to their widespread distribution, disinclination of getting removed at wastewater treatment plants (WWTPs), and persistence. However, the knowledge of the occurrence, fate, and effect in the environment of FRs and PFASs is still in great need of research, especially for recently introduced compounds (such as novel FRs). The objective of this project was to provide a snapshot of the current pollution situation of PFASs and selected novel FRs in Swedish surface waters. We sampled at 44 sites (representing 41 rivers and streams) along the whole coastline of Sweden and analysed their content of PFASs (all sites) and FRs (25 sites representing 23 rivers).Among the 12 target FRs, 3 could be quantified (2,4,6-TBP, TCIPP, and TPHP). TCIPP was the predominant compound with a level up to 3 900 ng L-1. The 2,4,6-TBP showed higher levels in southern rivers. The river with highest levels of ΣFRs was Fyrisån, and the total riverine input of the targeted FRs into the Baltic Sea was estimated to 38 kg day-1 with Ångermanlandsälven and Norrström as major contributors. It should be noted that these values only include the targeted, relatively novel FRs, while historically more important FRs such as the polybrominated diphenyl ethers (PBDEs), are not included.In total 13 PFASs were detected (PFBA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTeDA, FOSA, PFBS, PFHxS, PFOS) among the 25 target compounds. The mean ΣPFAS level of all sampled rivers was 9.5 ng L-1 and the median 4.2 ng L-1, and the highest mean values were found for PFBS and PFHxS (~2 ng L-1 for each compound). Streams in the north (e.g. Alterälven, Öre älv, Gide älv, Lögde älv and Ljungan) showed generally higher fractions of the longer chained perfluoroalkyl carboxylic acids (PFCAs; i.e. PFNA, PFDA, PFUnDA, PFDoDA, PFTeDA) whereas in the south the fractions of PFHpA and PFOA were higher. The total riverine input of all PFASs into recipient seas was estimated to 3.2 kg day-1 (1150 kg yr-1).PFOS exceeded the annual average Environmental Quality Standard (AA-EQS; 2013/39/EU) of 0.65 ng L-1 at 12 of 44 sampling sites, which are located in all parts of Sweden (Ume älv at Gubböle, Ångermanälven, Delångersån, Fyrisån, Norrström, Nyköpingsån, Emån, Lyckebyån, Rönneån, Nissan, Viskan and Göta älv at Alelyckan).As this study was a one-time grab sampling campaign for screening purposes, all values should be interpreted with care. A screening study like the current may, however, reveal hot spots. Verification and more detailed studies over a longer time period are recommended for sites with elevated levels. Our study also suggests that upstream monitoring is necessary to reveal important pollution sources.
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