Prevalence of stress among Iranian medical students: A questionnaire survey

A cross-sectional study measured the frequency of self-reported stress symptoms among a weighted random sample of medical students in Isfahan, Islamic Republic of Iran. The data were gathered using the Kessler 10-item psychological distress scale. The overall prevalence of stress among 222 students was 61.3% and there were no statistically significant differences in stress levels between students in the pre-clinical and clinical phases or different years of study. Married students had significantly lower scores than single students but there were no differences between the sexes. Students who chose to study medicine had lower stress scores than those who were influenced by family or had no choice about the subject. Students with mild to moderate stress were significantly more likely to suffer physical problems (OR = 4.42). Interventions are needed to tackle stress and improve Iranian medical students' physical and psychological well-being

High-order harmonic generation by static coherent states method in single-electron atomic and molecular systems

We solve the time-dependent Schrodinger equation using the coherent states as basis sets for computing high harmonic generation (HHG) in a full-dimensional single-electron "realistic" system. We apply the static coherent states (SCS) method to investigate HHG in the hydrogen molecular ion induced by a linearly polarized laser field. We show that SCS gives reasonable agreement compared to the three dimensional unitary split-operator approach. Next, we study isolated attosecond pulse generation in H2+. To do so, we employ the well-known polarization gating technique, which combines two delayed counter-rotating circular laser pulses, and opens up a gate at the central portion of the superposed pulse. Our results suggest that the SCS method can be used for full-dimensional quantum simulation of higher dimensional systems such as the hydrogen molecule in the presence of an external laser field

Characterization of lung fibroblasts more than two decades after mustard gas exposure

Purpose: In patients with short-term exposure to the sulfur mustard gas, the delayed cellular effects on lungs have not been well understood yet. The lung pathology shows a dominant feature consistent with obliterative bronchiolitis, in which fibroblasts play a central role. This study aims to characterize alterations to lung fibroblasts, at the cellular level, in patients with delayed respiratory complications after short-term exposure to the sulfur mustard gas. Methods: Fibroblasts were isolated from the transbronchial biopsies of patients with documented history of exposure to single high-dose sulfur mustard during 1985-7 and compared with the fibroblasts of control subjects. Results: Compared with controls, patients' fibroblasts were thinner and shorter, and showed a higher population doubling level, migration capacity and number of filopodia. Sulfur mustard decreased the in vitro viability of fibroblasts and increased their sensitivity to induction of apoptosis, but did not change the rate of spontaneous apoptosis. In addition, higher expression of alpha smooth muscle actin showed that the lung's microenvironment in these patients is permissive for myofibroblastic differentiation. Conclusions: These findings suggest that in patients under the study, the delayed pulmonary complications of sulfur mustard should be considered as a unique pathology, which might need a specific management by manipulation of cellular components. © 2015 Pirzad Jahromi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Cohesin mutations alter DNA damage repair and chromatin structure and create therapeutic vulnerabilities in MDS/AML

The cohesin complex plays an essential role in chromosome maintenance and transcriptional regulation. Recurrent somatic mutations in the cohesin complex are frequent genetic drivers in cancer including myelodysplatic syndromes (MDS) and acute myeloid leukemia (AML). Here, using genetic dependency screens of STAG2-mutant AML, we identified DNA damage repair and replication as genetic dependencies in cohesin-mutant cells. We demonstrated increased levels of DNA damage and sensitivity of cohesin-mutant cells to PARP inhibition. We developed a mouse model of MDS in which Stag2 mutations arise as clonal secondary lesions in the background of clonal hematopoiesis driven by Tet2 mutations, and demonstrated selective depletion of cohesin-mutant cells with PARP inhibition in vivo. Finally, we demonstrated a shift from STAG2- to STAG1-containing cohesin complexes in cohesin-mutant cells, which is associated with longer DNA loop extrusion, more intermixing of chromatin compartments, and increased interaction with PARP and RPA proteins. Our findings inform the biology and therapeutic opportunities for cohesin-mutant malignancies

Optimal spare parts management for vessel maintenance scheduling

Condition-based monitoring is used as part of predictive maintenance to collect real-time information on the healthy status of a vessel engine, which allows for a more accurate estimation of the remaining life of an engine or its parts, as well as providing a warning for a potential failure of an engine part. An engine failure results in delays and down-times in the voyage of a vessel, which translates into additional cost and penalties. This paper studies a spare part management problem for maintenance scheduling of a vessel operating on a given route that is defined by a sequence of port visits. When a warning on part failure is received, the problem decides when and to which port each part should be ordered, where the latter is also the location at which the maintenance operation would be performed. The paper describes a mathematical programming model of the problem, as well as a shortest path dynamic programming formulation for a single part which solves the problem in polynomial time complexity. Simulation results are presented in which the models are tested under different scenarios

The Effect of Split Nitrogen Application on Patterns of Dry Matter partitioning in Sugar beet

Abstract\ud The effect of split application of nitrogen fertilizer on dry matter (DM) partitioning patterns, yield and quality of sugar beet was studied in a field experiment at Brat Abad, Fariman during 2001 growing season. Three levels of nitrogen fertilizer (N ,70 ; N2 ,140 ; N3 ,210 kg N/ha) were split as S1, %100 at sowing ; S2, %75 at sowing and %25 at thinning; S3, %50 at sowing and %50 at thinning ;S4, %25 at sowing and %75 at thinning. Factorial experiment based on a randomized complete block design with 4 replications was used. Dry matter partitioning towards storage roots in N1 and in N2 treatments switched at 66 and 76 day after emergence, respectively. In S1 spliting pattern more DM was allocated to root in all growth stages. So that in 1400 GDD (5 Aug) amount of dry matter partitioning to storage roots and tops was equal to %50 while at this stage, partitioning of dry matters to storage roots in S2, S3 and S4 were % 47, % 44 and % 38 , respectively. Nitrogen levels had significant effect on polarity, Na, K, recoverable sugar yield, white sugar content and molass sugar. However, these effects on root and sugar yield and N-amino was not significant. Higher rates of nitrogen fertilizer, led to decrease in polarity, white sugar content and recoverable sugar yield. However, root yield, Na, K, N-amino and molas sugar increased in response to N levels. Maximum net sugar yield (4.4 ton/ha) was obtained in the lowest N application. In this study, effect of different patterns of nitrogen spliting and interaction between spliting patterns and nitrogen rates on quality and quantity of sugar beet was not significant. However, maximum net sugar yield (4.8 ton/ha) was obtained in N1S1 where the lowest level of N fertilizer was applied at sowing. \ud \ud Keywords: Sugar beet, Dry matters partitioning, Root yield, Sugar yield, Nitroge

Detailed Simulation of Transformer Internal Fault in Power System by Diakoptical Concept

This paper presents a novel method for modeling internal faults in a power transformer. This method uses a distributed computing approach for analysis of internal fault in transient stability (T/S) studies of electrical networks using Diakoptics and large change sensitivity (LCS) concepts. The combination of these concepts by phase frame model of transformer will be used here to develop an internal fault simulation of transformers. This approach leads to a model which is compatible with commercial phasor-based software packages. Consequently, it enables calculation of fault currents in any branch of the network due to a winding fault of a power transformer. The proposed method is implemented successfully and validated by time domain software and GEC group measurement results

Effect of Plant Diversity on Diversity and Abundance of Arthropods in Winter Wheat Fields

Abstract Plant biomass and diversity play an important role in enhancing of biodiversity of other trophic levels, specially arthropods in terrestrial ecosystems. In order to determine the effects of plants on diversity and abundance of arthropods, a study was carried out in three regions of Razavi and northern Khorasan provinces, Shirvan, Mashhad and Gonabad. In each region, high and low input fields of winter wheat and a natural system for comparison were selected. In ripening stage of wheat growth (90 stage of Zadoks), sampling was done by use of quadrate in each system with five replications. Plants in each quadrate were counted and species richness of plants was determined. Insect sampling was done by sweep net from surface of plants, then species richness and abundance of collected insects were determined. As a result, agricultural practices decreased plant species richness but diversity and abundance of insects and spiders increased in agricultural systems. Our finding revealed that abundance of insects and spiders were not affected by plant species richness and plant biomass was the main factor affecting on species richness and abundance of insects, spiders and beneficial insects. Therefore, decreasing plant species richness that arose from agricultural practices doesn’t effect on arthropods diversity and abundance and doesn’t decrease sustainability of agricultural systems. Irregular use of chemical inputs, specially pesticides, is the main factor to decreasing of plants and arthropods species richness in agricultural systems. Keywords: Plant diversity, Arthropod diversity, Arthropod abundance, Plant-insect interactions, Agricultural system

The influence of condition-based maintenance on workforce planning and maintenance scheduling

<p>Condition-based maintenance (CBM) is generally considered an attractive maintenance policy for a single component: it uses the operating condition of the component to predict a failure event and therefore tries to avoid any unplanned downtime and unnecessary maintenance activities. However, operations managers tend to be much more interested in optimising the performance of the entire asset-system, where the grouping of maintenance activities and the availability of maintenance workers may play a role. Therefore, this paper focuses on the impact of using either CBM or age-based replacement (ABR) in serial and parallel multi-component systems (1) without worker constraints, (2) with a single internal maintenance worker, and (3) with external maintenance workers with a significant response time. With an internal maintenance worker, the sequential execution of maintenance activities prevents efficiency gains in the serial configuration and here CBM performs better. Also in the parallel configurations, the efficiency under CBM is generally better than under ABR. However, with external maintenance workers, CBM is not able to group maintenance activities as well as ABR, which results in a lower efficiency in the serial configuration. CBM performs better than ABR with respect to total maintenance costs, while ABR results in a smoother maintenance plan.</p>