360 research outputs found

    Oscillatory thermopower of carbon chains: First-principles calculations

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    We investigate the thermoelectric transport through carbon chains connected by two Al leads. Using a Landauer-Buttiker-like formula, we calculate the thermopower and thermoconductance of Al-Cn-Al from first principles. We find that the charge transfer plays an important role in the thermoelectric transport. Because of the charge transfer, the thermopower changes sign for even-odd number of carbon atoms. The thermopower and electric conductance as a function of the gate voltage also exhibit oscillatory behaviors with a phase difference of pi/2.published_or_final_versio

    Factors associated with sleep quality among Malaysian undergraduate students during the COVID-19 pandemic

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    Poor sleep quality has become a public health concern due to its association with several health risks. Recent studies had shown that university students had poor sleep quality during the COVID-19 pandemic. Thus, this study aimed to determine the factors associated with sleep quality among undergraduate students in Malaysia during the COVID-19 pandemic. This cross-sectional study involved 377 undergraduates from public and private universities in Malaysia. The study ws conducted between 16 June 2021 to 31 July 2021. Respondents completed an online survey reagarding to their sociodemographic background, sleep quality, chronotype pattern, night eating syndrome, food security, physical activity, internet addiction and self-reported body weight and height. There was poor sleep quality in 62.3% of the respondents. Respondents who were Malay (AOR = 3.84, 95% CI =2.07-7.11), in the arts stream (AOR = 2.55, 95% CI = 1.20-5.42) and internetaddicted (AOR = 2.14, 95% CI = 1.22-3.77) had higher risk of poor sleep quality. Respondents who lived in a rented house (AOR = 0.38, 95% CI = 0.16-0.88), were sophomores (AOR = 0.49, 95% CI = 0.25-0.99) and were the morning chronotype (AOR = 0.35, 95% CI = 0.17-0.72) had lower risk for developing poor sleep quality. This study underscored the high prevalence of poor sleep quality among undergraduate students during the COVID-19 pandemic. The findings suggested that by preventing internet addiction and the evening chronotype can improve sleep quality

    Effect of magnetic bias field on magnetoelectric coupling in magnetoelectric composites

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    Salt reduction policy for out of home sectors: a supplementary document for the salt reduction strategy to prevent and control non-communicable diseases (NCDS) in Malaysia 2021-2025.

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    Cardiovascular diseases (CVDs) are the major cause of death among Malaysians. Reduction of salt intake in populations is one of the most cost-effective strategies in the prevention of CVDs. It is very feasible as it requires low cost for implementation and yet could produce a positive impact on health. Thus, salt reduction initiatives have been initiated since 2010, and two series of strategies have been launched. However, there are issues on its delivery and outreach to the target audience. Further, strategies targeting out of home sectors are yet to be emphasized. Our recent findings on the perceptions, barriers and enablers towards salt reduction among various stakeholders including policy-makers, food industries, food operators, consumers and schools showed that eating outside of the home contributed to high salt intake. Foods sold outside the home generally contain a high amount of salt. Thus, this supplementary document is being proposed to strengthen the Salt Reduction Strategy to Prevent and Control Non-communicable Diseases (NCDs) for Malaysia 2021-2025 by focussing on the strategy for the out-of-home sectors. In this supplementary document, the Monitoring, Awareness and Product (M-A-P) strategies being used by the Ministry of Health (MOH) are adopted with a defined outline of the plan of action and indicators to ensure that targets could be achieved. The strategies will involve inter-sectoral and multi-disciplinary approaches, including monitoring of salt intake and educating consumers, strengthening the current enforcement of legislation on salt/sodium labelling and promoting research on reformulation. Other strategies included in this supplementary document included reformulation through proposing maximum salt targets for 14 food categories. It is hoped that this supplementary document could strengthen the current the Salt Reduction Strategy to Prevent and Control NCDs for Malaysia 2021-2025 particularly, for the out-of-home sector, to achieve a reduction in mean salt intake of the population to 6.0 g per day by 2025

    Challenges facing an understanding of the nature of low-energy excited states in photosynthesis

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    © 2016 Elsevier B.V. While the majority of the photochemical states and pathways related to the biological capture of solar energy are now well understood and provide paradigms for artificial device design, additional low-energy states have been discovered in many systems with obscure origins and significance. However, as low-energy states are naively expected to be critical to function, these observations pose important challenges. A review of known properties of low energy states covering eight photochemical systems, and options for their interpretation, are presented. A concerted experimental and theoretical research strategy is suggested and outlined, this being aimed at providing a fully comprehensive understanding

    Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay

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    The decay channel ψπ+πJ/ψ(J/ψγppˉ)\psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) is studied using a sample of 1.06×1081.06\times 10^8 ψ\psi^\prime events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the ppˉp\bar{p} invariant mass spectrum. The enhancement can be fit with an SS-wave Breit-Wigner resonance function with a resulting peak mass of M=186113+6(stat)26+7(syst)MeV/c2M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2 and a narrow width that is Γ<38MeV/c2\Gamma<38 {\rm MeV/}c^2 at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics

    Evaluation of image quality with four positron emitters and three preclinical PET/CT systems

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    Background We investigated the image quality of C-11, Ga-68, F-18 and Zr-89, which have different positron fractions, physical half-lifes and positron ranges. Three small animal positron emission tomography/computed tomography (PET/CT) systems were used in the evaluation, including the Siemens Inveon, RAYCAN X5 and Molecubes beta-cube. The evaluation was performed on a single scanner level using the national electrical manufacturers association (NEMA) image quality phantom and analysis protocol. Acquisitions were performed with the standard NEMA protocol for F-18 and using a radionuclide-specific acquisition time for C-11, Ga-68 and Zr-89. Images were assessed using percent recovery coefficient (%RC), percentage standard deviation (%STD), image uniformity (%SD), spill-over ratio (SOR) and evaluation of image quantification. Results Ga-68 had the lowest %RC ( 85%) and lowest %STD for the 5 mm rod across all systems. For C-11 and Zr-89, the maximum %RC was close (> 76%) to the %RC with F-18. A larger SOR were measured in water with C-11 and Ga-68 compared to F-18 on all systems. SOR in air reflected image reconstruction and data correction performance. Large variation in image quantification was observed, with maximal errors of 22.73% (Zr-89, Inveon), 17.54% (Zr-89, RAYCAN) and - 14.87% (Ga-68, Molecubes). Conclusions The systems performed most optimal in terms of NEMA image quality parameters when using F-18, where C-11 and Zr-89 performed slightly worse than F-18. The performance was least optimal when using Ga-68, due to large positron range. The large quantification differences prompt optimization not only by terms of image quality but also quantification. Further investigation should be performed to find an appropriate calibration and harmonization protocol and the evaluation should be conducted on a multi-scanner and multi-center level

    Analysis of temporal transcription expression profiles reveal links between protein function and developmental stages of Drosophila melanogaster

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    Accurate gene or protein function prediction is a key challenge in the post-genome era. Most current methods perform well on molecular function prediction, but struggle to provide useful annotations relating to biological process functions due to the limited power of sequence-based features in that functional domain. In this work, we systematically evaluate the predictive power of temporal transcription expression profiles for protein function prediction in Drosophila melanogaster. Our results show significantly better performance on predicting protein function when transcription expression profile-based features are integrated with sequence-derived features, compared with the sequence-derived features alone. We also observe that the combination of expression-based and sequence-based features leads to further improvement of accuracy on predicting all three domains of gene function. Based on the optimal feature combinations, we then propose a novel multi-classifier-based function prediction method for Drosophila melanogaster proteins, FFPred-fly+. Interpreting our machine learning models also allows us to identify some of the underlying links between biological processes and developmental stages of Drosophila melanogaster

    Gating of aquaporins by heavy metals in Allium cepa L. epidermal cells

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    Changes in the water permeability, aquaporin (AQP) activity, of leaf cells were investigated in response to different heavy metals (Zn2+, Pb2+, Cd2+, Hg2+). The cell pressure probe experiments were performed on onion epidermal cells as a model system. Heavy metal solutions at different concentrations (0.05 μM–2 mM) were used in our experiments. We showed that the investigated metal ions can be arranged in order of decreasing toxicity (expressed as a decrease in water permeability) as follows: Hg>Cd>Pb>Zn. Our results showed that β-mercaptoethanol treatment (10 mM solution) partially reverses the effect of AQP gating. The magnitude of this reverse differed depending on the metal and its concentration. The time course studies of the process showed that the gating of AQPs occurred within the first 10 min after the application of a metal. We also showed that after 20–40 min from the onset of metal treatment, the water flow through AQPs stabilized and remained constant. We observed that irrespective of the metal applied, the effect of AQP gating can be recorded within the first 10 min after the administration of metal ions. More generally, our results indicate that the toxic effects of investigated metal ions on the cellular level may involve AQP gating
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