128 research outputs found

    Surface-Induced Phase Transition During Coalescence of Au Nanoparticles: A Molecular Dynamics Simulation Study

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    In this study, the melting and coalescence of Au nanoparticles were investigated using molecular dynamics simulation. The melting points of nanoparticles were calculated by studying the potential energy and Lindemann indices as a function of temperature. The simulations show that coalescence of two Au nanoparticles of the same size occurs at far lower temperatures than their corresponding melting temperature. For smaller nanoparticles, the difference between melting and coalescence temperature increases. Detailed analyses of the Lindemann indices and potential energy distribution across the nanoparticles show that the surface melting in nanoparticles begins at several hundred degrees below the melting point. This suggests that the coalescence is governed by the liquid-phase surface diffusion. Furthermore, the surface reduction during the coalescence accelerates its kinetics. It is found that for small enough particles and/or at elevated temperatures, the heat released due to the surface reduction result in a melting transition of the two attached nanoparticles.Comment: 15 pages, 4 figures, 1 table, full length articl

    A phenomenological study on the production of Higgs bosons in the cSMCS model at the LHC

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    In the present work, we intend to predict the production rates of the Higgs bosons in the simplest extension of the Standard Model (SM) by a neutral complex singlet (cSMCS). This model has an additional source of CP violation and provides strong enough first-order electroweak phase transition to generate the baryon asymmetry of universe (BAU). The scalar spectrum of the cSMCS includes three neutral Higgs particles with the lightest one considered to be the 125 GeV Higgs boson found at LHC. The SM-like Higgs boson comes mostly from the SM-like SU(2) doublet, with a small correction from the singlet. To predict the production rates of the Higgs bosons, we use a conventional effective LO QCD framework and the unintegrated parton distribution functions (UPDF) of Kimber-Martin-Ryskin (KMR). We first compute the SM Higgs production cross-section and compare the results to the existing theoretical calculations from different frameworks as well as the experimental data from the CMS and ATLAS collaborations. It is shown that our framework is capable of producing sound predictions for these high-energy QCD events in the SM. Afterwards we present our predictions for the Higgs boson production in the cSMCS.Comment: Fitted by the published version, 1 figure and 2 benchmarks have been omitted, additional comparisons have been added and several misprints have been correcte

    Thickening of T1 Precipitates during Aging of a High Purity Al−4Cu−1Li−0.25Mn Alloy

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    The age hardening response of a high-purity Al–4Cu–1Li–0.25Mn alloy (wt. %) during isothermal aging without and with an applied external load was investigated. Plate shaped nanometer size T1 (Al2CuLi) and θ′ (Al2Cu) hardening phases were formed. The precipitates were analyzed with respect to the development of their structure, size, number density, volume fraction and associated transformation strains by conducting transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) studies in combination with geometrical phase analysis (GPA). Special attention was paid to the thickening of T1 phase. Two elementary types of single-layer T1 precipitate, one with a Li-rich (Type 1) and another with an Al-rich (Defect Type 1) central layer, were identified. The results show that the Defect Type 1 structure can act as a precursor for the Type 1 structure. The thickening of T1 precipitates occurs by alternative stacking of these two elementary structures. The thickening mechanism was analyzed based on the magnitude of strain associated with the precipitation transformation normal to its habit plane. Long-term aging and aging under load resulted in thicker and structurally defected T1 precipitates. Several types of defected precipitates were characterized and discussed. For θ′ precipitates, a ledge mechanism of thickening was observed. Compared to the normal aging, an external load applied to the peak aged state leads to small variations in the average sizes and volume fractions of the precipitates.DFG, 237105621, SPP 1713: Stark gekoppelte thermo-chemische und thermo-mechanische Zustände in Angewandten Materialie

    Epidemiological study on sand flies in an endemic focus of cutaneous leishmaniasis, Bushehr city, southwestern Iran

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    Cutaneous leishmaniasis is the most important health problem in the city of Bushehr, southwestern Iran. The objective of the study was to determine some ecological aspects of sand flies in the city during 2010-2011. Sand flies were collected monthly from outdoors and indoors by sticky traps at four selected districts of the city. They were also dissected and examined by nested-PCR for identification of the parasite during August-September of 2011. A total of 1234 adult sand flies were collected and 6 species including 3 of Genus Phlebotomus and 3 of Genus Sergentomyia were identified. Four species including P. papatasi (3.98%), P. sergenti (1.14%), S. tiberiadis (87.18%), and S. baghdadis (7.7%) were found indoors. Six species including P. papatasi (3.47%), P. sergenti (3.17%), P. alexandri (0.1%), S. tiberiadis (77.74%), S. baghdadis (15.41%), and one female of S. clydei (0.11%) were collected from outdoors. Sand flies started to appear from March and disappear at the end of January. There was only one peak in the density curve in July. The study revealed that S. tiberiadis and S. baghdadis could enter indoors which 89 and 81.8% of them were found blood-fed, respectively. Moreover, P. papatasi, S. tiberiadis, and S. baghdadis were active indoors and outdoors in most months of the year. Nested-PCR of P. papatasi females was positive against kinetoplast DNA of L. major and L. turanica and also mixed natural infections were found by L. gerbilli and L. turanica. Moreover, mixed infections by L. major and L. turanica were observed in this species. Sergentomyia clydei and S. tiberiadis were found to be negative to any DNA of Leishmania species. Phlebotomus sergenti females were found infected with DNA of L. turanica and this is the first report of natural infection and detection of the parasite from this sand fly species in worldwide

    The prevalence of iron deficiency anemia during pregnancy in Iran (1991-2015): A systematic review and meta-analysis

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    Introduction: The prevalence of Iran Deficiency Anemia (IDA) in pregnant women is in Variable between 40-80 in developing countries. There are some differences among different studies on this disorder. So, this present study is been performed for evaluating the prevalence of IDA among pregnant Iranians with systematic review and Meta analysis method. Method: This study is based on received information achieved from Magiran, , Iran medex, SID, Med lib, IranDoc, Scopus, Pubmed, SceinceDirect, Cochrane, Embase, Medline, Springer, Online Library Wiley and Google Scholar in chronological order of 1 January 1991 to 31 march 2015 with using standard key words. Search and extraction of data were done by two independed reviewers. To pooled of results of studies random effects model in meta-analysis was used. Results: In the 32 eligible studies, the 63372 individuals were been evaluated. The prevalence of Anemia among pregnant Iranians was estimated 14.2 (95 CI: 12- 16.3). most prevalence of Anemia was seen in the study, which it is used the samples collected in several parts of country, (21.5) and the lowest prevalence was seen in the West of country(7). The prevalence of Anemia in urban and rural pregnant women was estimated 13.7 and 20 approximately, respectively. Conclusion: The prevalence of anemia among pregnant Iranians in current 24 years were less according to WHO system report for developing countries, that it is related to appropriate plan and care in pregnancy period in countries

    Clinical Reasoning in Nursing Students

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    Abstract Introduction: Diagnosis and understanding of patient conditions require nurses 'clinical reasoning skills, as in the absence of this skill; the nurses will not be able to diagnose the patients' condition and will impose harmful consequences on the patient. The purpose of this study is to evaluate and compare the clinical reasoning skills of the nursing students at Shahid Beheshti University of Medical Sciences at the end of theoretical courses in medical-surgical nursing in 2018. Methods: In this descriptive-comparative study, 150 nursing students from freshmen, sophomores, and juniors studying at the Faculty of Nursing and Midwifery of Shahid Beheshti University of Medical Sciences were selected by stratified sampling method. Students in each year comprised one category and the total number of was 3, also the number of students per category was 50, and the total number of categories will be equal to 9. Data were collected using a researcher-made questionnaire employing Key Feature Problem (KFP) method and analyzed using descriptive statistics by SPSS V.20 software. Results: The results showed that there is a significant difference between the grades of third-year students and those in their first and second years of study (P <0.001). Based on the results, the clinical reasoning skill in the first year was poor (51.59 ± 0.06%), in the second year was very weak (48.41 ± 0.09%) and in third-year students was very weak (37.62 ± 0.88). Also, the average skill of clinical reasoning of all students was very weak with a mean percentage of 46.01%. Conclusions: The findings indicate that the level of students' clinical reasoning skills has been declined comparatively from freshmen to juniors. In general, the level of clinical skills in nursing students of Shahid Beheshti University of Medical Sciences is disappointingly low
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