912 research outputs found

    The lexicographic preference for a son: evidence from household data in Vietnam

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    This paper examines son preferences by specifying sex composition by birth order of existing children as key independent variables. The results indicate a lexicographic preference for a son by mothers aged 50 years and older. Mothers without a son are also under substantial pressure to bear more children and shorten their birth spacing. However, once a family includes a son, parents do not consider sex composition over other decisions on family size and fertility timing. It would appear that the preference for a son is relatively stronger for some birth orders in the northern regions of Vietnam but slightly weaker in the Central Highlands and South Central Coast. In addition, while women are important in the Vietnamese labor force, the level of preference for sons does not differ across income at lower birth orders. We also obtain mixed results for son preferences if we include mothers less than 50 years of age in our analysis.Son preference, Sex composition, Birth order, Birth spacing

    Optimizing the performance of a glass-ceramic storage phosphor as an imaging plate for medical use

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    Europium-doped-fluorochlorozirconate glass ceramics, known as ZBLAN, were produced in a glove box which has a controlled environment of argon gas. For imaging applications BaCl2 is used instead of BaF2. Their properties after different thermal processing and different amounts of europium-doping were investigated. After annealing the ZBLAN glass, BaCl2 nanoparticles are precipitated in the glass matrix. These glass ceramic storage phosphors are strong candidates for replacing traditional x-ray screen film system and commercial storage phosphors such as Agfa MD-30. Differential scanning calorimetry (DSC) was used to determine the crystallization temperature of the hexagonal phase of BaCl2, and orthorhombic BaCl2 this in turn determines the subsequent annealing temperature. X-ray diffraction (XRD) and photoluminescence (PL) show that the hexagonal phase of BaCl2 was formed upon annealing at temperatures between 250 °C and 280 °C for 5 minutes. The orthorhombic phase of BaCl2, which has storage properties, was formed at higher annealing temperatures, at approximately 290 °C and above. Secondary ion mass spectroscopy (SIMS) was used to determine adsorbed/diffused oxygen content of the glass. The weight loss of fluorine and chlorine is 3-5 % and was determined using ion chromatography (IC). The concentration of other cations was determined using inductively coupled plasma spectroscopy (ICP). Transmission electron microscopy (TEM) was used to take high resolution pictures and verify the composition of BaCl2 nanoparticles. The relative concentration of Eu2+ to Eu3+ of heated EuCl3 and ZBLAN was studied using Mössbauer spectroscopy. The oxidation of Eu2+ to Eu3+ was also observed during the experiment. This study has reinforced the strong potential for application of glass-ceramic storage phosphors for medical imaging

    The lexicographic preference for a son : evidence from household data in Vietnam

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    Home appliances and gender gap of time spent on unpaid housework : evidence using household data from Vietnam

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    We examined the gender gap between wives and husbands with regard to time spent on unpaid housework using interaction terms between the appearance of home appliances and gender among 36,480 Vietnamese households. We found the gender gap is persistent regardless of the number of co-residing children, age cohorts, household size and income, and working status of the couples. In household fixed-effect estimations, the gender gap of time increased with the appearance of home appliances such as gas cookers. One of the main reasons is the reduction in the probability of men participating in housework tasks related to home appliances

    Mixed matrix membranes for gas separation

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    Novel strategies to design and construct efficient semiconductor-based photocatalyst for enhancing photocatalytic hydrogen evolution and nitrogen fixation under sunlight irradiation

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    L'Ă©nergie solaire est la source d'Ă©nergie la plus abondante au monde et elle peut ĂȘtre convertie en Ă©nergie chimique via des processus photocatalytiques. Au cours des derniĂšres dĂ©cennies, la photocatalyse sous la lumiĂšre du soleil est apparue comme une alternative innovante aux combustibles fossiles afin de rĂ©soudre et prĂ©venir des problĂšmes graves liĂ©s Ă  la crise environnementale et Ă©nergĂ©tique. Actuellement, les matĂ©riaux Ă  base de semi-conducteurs (tels que TiO₂, C₃N₄, In₂O₃, WO₃) sont intensivement Ă©tudiĂ©s pour diverses applications photocatalytiques, y compris la rĂ©action d’évolution d'hydrogĂšne (HER) et la rĂ©duction de l'azote en ammoniac (NRR). Par consĂ©quent, diverses approches telles que l'ingĂ©nierie structurelle, les hĂ©tĂ©rojonctions nanocomposites ont Ă©tĂ© Ă©tudiĂ©es afin de surmonter les problĂšmes de ces matĂ©riaux et ainsi augmenter l'activitĂ© catalytique. Dans le cadre de cette thĂšse, nous avons dĂ©veloppĂ© des nouvelles stratĂ©gies pour la synthĂšse des quatre types de photocatalyseurs efficaces pour la production d'hydrogĂšne et la fixation de l'azote sous la lumiĂšre du soleil. Nos matĂ©riaux prĂ©sentent une structure unique, qui favorise l'absorption de la lumiĂšre visible, la sĂ©paration des charges Ă©lectrons-trous et l’augmentation du nombre de sites actifs.Pour l'application de la gĂ©nĂ©ration d'hydrogĂšne photocatalytique, nous avons d'abord synthĂ©tisĂ© les sphĂšres de type Ă©ponge CdI₂nS₄ monophasĂ©es via une mĂ©thode solvothermique suivie d'un traitement au gaz contenant H₂S. La formation du complexe Cd/In avec une distribution uniforme de CdÂČâș et InÂłâș a jouĂ© un rĂŽle crucial dans la formation du spinelle monophasĂ© CdIn₂S₄. L'Ă©nergie de la bande interdite s'est avĂ©rĂ©e ĂȘtre significativement rĂ©duite, ce qui permet une absorption Ă©tendue de la lumiĂšre visible jusqu'Ă  700 nm, ceci est principalement attribuĂ© Ă  la dispersion d'espĂšce sulfure sur la bande de valence du CdIn₂S₄ monophasĂ©. Avec le dĂ©pĂŽt de Ni mĂ©tallique comme cocatalyseur de rĂ©duction, le photocatalyseur hybride Ni-CdIn₂S₄ a montrĂ© une efficacitĂ© amĂ©liorĂ©e pour la production d'hydrogĂšne sous la lumiĂšre solaire, ce qui reprĂ©sente une augmentation de l’activitĂ© d’environ, respectivement, 5,5 et 3,6 fois que celle des Ă©chantillons Pt-CdIn₂S₄ et Pd-CdIn₂S₄. Le deuxiĂšme systĂšme photocatalytique dĂ©veloppĂ© implique la prĂ©paration de nitrure de carbone graphitique dopĂ© au S (Ni-SCN). Ce dernier est chimiquement ancrĂ© au nickel par une technique connue sous le nom de processus de photo-dĂ©pĂŽt assistĂ© par sulfuration. L'origine de la structure distinctive du Ni-SCN est dĂ» Ă  l'existence de liaisons chimiques NiS-C-N dans le systĂšme, ce qui favorisait la sĂ©paration des charges photogĂ©nĂ©rĂ©es et amĂ©liorait la capacitĂ© d’absorption lumineuse du photocatalyseur. Par consĂ©quent, l’échantillon NiSCN synthĂ©tisĂ© prĂ©sente une excellente activitĂ© photocatalytique pour la production d'hydrogĂšne sous la lumiĂšre du soleil. En effet, ce systĂšme prĂ©sente une activitĂ© beaucoup plus Ă©levĂ©e que celle des systĂšmes g-C₃N₄ dopĂ©s au S, Ni supportĂ© g-C₃N₄ et Pt supportĂ© g-C₃N₄ dopĂ©s au S. Pour une application photo (Ă©lectro) catalytique de fixation de l'azote, nos travaux sont les premiers Ă  rapporter la synthĂšse de nanoparticules d'Au chargĂ©es de nanoparticules W₁₈O₄₉ dopĂ©es au Fe (notĂ©es WOF-Au) par une synthĂšse solvothermique suivie d'un dĂ©pĂŽt in situ des nanoparticules d'Au. L'incorporation de dopants Fe peut non seulement guĂ©rir les Ă©tats de dĂ©faut de masse dans les rĂ©seaux non stƓchiomĂ©triques W₁₈O₄₉, mais Ă©galement favoriser la sĂ©paration et la migration interfaciale des Ă©lectrons du photocatalyseur vers les molĂ©cules N₂ chimisorbĂ©es; tandis que les nanoparticules Au dĂ©corĂ©es sur la surface dopĂ©e au Fe W₁₈O₄₉ ont fourni les Ă©lectrons Ă  haute Ă©nergie pour la rĂ©duction de N₂ via l'effet de rĂ©sonance plasmonique de surface localisĂ© (LSPR). Le systĂšme WOF-Au plasmonique rĂ©sultant montre un rendement amĂ©liorĂ© pour la production de NH₃, beaucoup plus Ă©levĂ© que celui du W₁₈O₄₉ pur ainsi qu'une trĂšs grande stabilitĂ©. L'amĂ©lioration des performances photoĂ©lectrocatalytiques est principalement due Ă  l'effet synergique des dopants Fe et des nanoparticules Au dans l'hĂŽte W₁₈O₄₉. Enfin, les cacahuĂštes creuses de In₂O₃ dopĂ©es au Ru (dĂ©notĂ©es Ru-In₂O₃ HPN) ont Ă©tĂ© fabriquĂ©es par la nouvelle stratĂ©gie d'auto-matrice suivie de la calcination des prĂ©curseurs synthĂ©tisĂ©s. Les nanoparticules uniformes In₂O₃ sont Ă©troitement agglomĂ©rĂ©es ensemble pour former une structure de cacahuĂšte creuse, ce qui facilite la sĂ©paration et le transport des l'Ă©lectrons-trous photoexcitĂ©s, amĂ©liorant l’absorption de la lumiĂšre par multi-rĂ©flexion. De plus, l'introduction des dopants Ru induit de nombreuses lacunes en oxygĂšne Ă  la surface et rĂ©duit l'Ă©nergie de la bande interdite du systĂšme photocatalytique. Ces lacunes d'oxygĂšne agissent comme des centres de piĂ©geage, facilitant la sĂ©paration des Ă©lectrons trous photoexcitĂ©s. Par consĂ©quent, le taux de production d'ammoniac des Ru-In₂O₃ HPNs est 5,6 fois plus Ă©levĂ© que celui des In₂O₃ HPNs purs et largement supĂ©rieur au matĂ©riau en vrac d'In₂O₃, lorsqu’il est soumis Ă  l’irradiation solaire.Solar energy is the most abundant energy source in the world, and it can be converted into chemical energy via photocatalytic processes. Over the last decades, sunlight-driven photocatalysis has emerged as an innovative alternative to fossil fuels for solving the severe problems related to environmental diseases and the energy crisis. Currently, semiconductorbased materials (such as TiO₂, C₃N₄, In₂O₃, WO₃, BiVO₄) have been intensively studied for diverse photocatalytic applications, including the hydrogen evolution reaction (HER) and the nitrogen reduction reaction (NRR) to produce ammonia. However, the drawbacks of weak visible light absorption, low electron-hole separation with high recombination rate, and lack of surface active-sites have limited the photocatalytic performance of these semiconductorbased photocatalysts. Therefore, various approaches such as structural engineering, nanocomposite heterojunctions have been applied to overcome the limitations of these materials and boosting the catalytic activity. In this thesis, we employed novel strategies to develop four efficient photocatalytic systems for hydrogen production and nitrogen fixation. Our materials possessed a unique structure, which is advantageous to promote the visiblelight absorption, facilitate the separation of charge carrier, and increase the number of surface-active sites. For the photocatalytic hydrogen evolution application, we firstly synthesized the singlephase CdIn₂S₄ sponge-like spheres via solvothermal method followed by H₂S gas treatment. The formation of CdIn-complex with uniform distribution of CdÂČâș and InÂłâș played a crucial role in achieving the spinel structured-single phase CdIn₂S₄. The bandgap energy was found to be significantly reduced, resulting in the extended visible light absorption up to 700 nm, which was primarily attributed to the sulfide species-mediated modification of the valence band in CdIn₂S₄ single-phase. With the deposition of Ni metal as a reduction cocatalyst, the hybrid Ni-CdIn₂S₄ photocatalyst showed enhanced solar light-driven photocatalytic hydrogen evolution efficiency, which is around 5.5 and 3.6 folds higher than that of Pt-CdIn₂S₄ and Pd-CdIn₂S₄ samples, respectively. The second developed photocatalytic system involved the preparation of chemically bonded nickel anchored S-doped graphitic-carbon nitride (Ni-SCN) through a technique known as sulfidation assisted photo-deposition process. The origin of the distinctive structure of Ni-SCN was due to the existence of Ni-S-C-N chemical bonds in the system, which fundamentally favored the separation of photogenerated electron-hole and improved the light-harvesting capabilities of the photocatalyst. Consequently, the synthesized Ni-SCN exhibited an excellent sunlight-driven photocatalytic activity toward hydrogen evolution, which was several times higher than Sdoped g-C₃N₄, Ni supported g-C₃N₄ and Pt loaded S-doped C₃N₄ systems. For photo(electro)catalytic nitrogen fixation application, our work is the first to report the synthesis of Au nanoparticles loaded Fe doped W₁₈O₄₉ (denoted as WOF-Au) nanorods through a solvothermal synthesis following by in situ deposition of Au nanoparticles. The incorporation of Fe dopants can not only heal the bulk-defect-states in nonstoichiometric W₁₈O₄₉ lattices but also promote the separation and interfacial migration of electrons from photocatalyst to chemisorbed N₂ molecules; while Au nanoparticles decorated on the Fe doped W₁₈O₄₉ surface provided the high energetic electrons for N₂ reduction via the localized surface plasmon resonance effect (LSPR). The obtained plasmonic WOF-Au system shows an enhanced NH₃ yield, which is much higher than that of the bare W₁₈O₄₉, as well as very high stability. The enhancement in photoelectrocatalytic performance is mainly contributed by the synergetic effect of Fe dopants and plasmonic Au nanoparticles on the W₁₈O₄₉ host. Lastly, Ru doped In₂O₃ hollow peanuts (demoted as Ru-In₂O₃ HPNs) were fabricated by the novel self-template strategy followed by the calcination of the as-synthesis precursors. The uniform In₂O₃ nanoparticles were closely packed together to form a hollow peanut structure, which facilitated the separation and transportation of photoinduced electron-hole and favored the light-harvesting ability by the internal multi-reflection process. Furthermore, the introduction of Ru dopants induced numerous surface oxygen vacancies and narrow down the bandgap energy of the photocatalytic system. These oxygen vacancies act as trapping centers, facilitating the separation of photoexcited electrons and holes. Consequently, the ammonia production rate of Ru-In₂O₃ HPNs was 5.6 times and much higher as compared to pure In₂O₃ HPNs and bulk material of In₂O₃ under solar light irradiation

    Modelling the effect of individual differences in punishment sensitivity on behaviour in a public goods game

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    Previous research on social dilemmas demonstrated that various forms of punishment for free-riding can increase contribution levels in public goods games. The way individual group members react to the possibility of punishment can be also affected by individual differences in punishment sensitivity. Therefore, depending individual differences in punishment sensitivity of group members, different levels of punishment can be more or less effective to prevent free riding behaviour. This paper uses agent-based modelling to model the effect of punishment sensitivity on contribution levels in a public goods game. The paper then examines the correlation between punishment sensitivity and variability of free riding behaviour under different punishment conditions

    Persistent legacy of the 1075–1919 Vietnamese imperial examinations in contemporary quantity and quality of education

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    We investigated the impact of individuals who passed the Vietnamese imperial examinations (1075–1919) on the present-day quantity and quality of education in their home districts. We layered the 2009 Population and Housing Census and the 2009 National Entrance Exams to University (NEEU) test scores on the geographical distribution of imperial test takers’ home districts. We constructed a novel instrumental variable representing the average distance between the examinees’ home districts and the corresponding imperial examination venues. We found a persistent legacy in the average years of schooling, literacy rate, school attendance rate, NEEU test scores, and primary school dropout rate
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