Sharif Digital Repository

Aim: Hepatitis E is a form of acute viral hepatitis, which is caused by hepatitis E virus (HEV). The study objective was to evaluate the prevalence of HEV to provide an overall relative frequency in Iran. Methods: In this study, databases such as PubMed and Scopus were searched using the following keywords according to MeSH, "Hepatitis E virus", "Epidemiology", "Enzyme-linked immunosorbent assay (ELISA)" and "Iran". Then studies which had reported prevalence of HEV were selected. Results: We selected 36 researches out of 9246 for our study. From all the samples, the pooled estimated prevalence of HEV positive was 9.7%. It should be noted that HEV infection's relative frequency varied from... 

The dielectric constant e of interfacial water has been predicted to be smaller than that of bulk water (e ≈ 80) because the rotational freedom of water dipoles is expected to decrease near surfaces, yet experimental evidence is lacking. We report local capacitance measurements for water confined between two atomically flat walls separated by various distances down to 1 nanometer. Our experiments reveal the presence of an interfacial layer with vanishingly small polarization such that its out-of-plane e is only ~2. The electrically dead layer is found to be two to three molecules thick. These results provide much-needed feedback for theories describing water-mediated surface interactions and... 

The ability to predict the cellular dynamics of intracellular transport has enormous potential to impact human health. A key transporter is kinesin-1, an ATP-driven molecular motor that shuttles cellular cargos along microtubules (MTs). The dynamics of kinesins depends critically on their unbinding rate from MT, which varies depending on the force direction applied on the motor, i.e. the force-unbinding rate relation is asymmetric. However, it remains unclear how changing the force direction from resisting (applied against the motion direction) to assisting (applied in the motion direction) alters the kinesin's unbinding and stepping. Here, we propose a theoretical model for the influence of... 

The first asymmetric synthesis of α,β-disubstituted γ-phosphono sulfonates is reported. The key step is the Michael addition of a lithiated enantiopure sulfonate bearing an inexpensive chiral sugar auxiliary to α,β-unsaturated phosphonates in good diastereoselectivities. After chromatographic purification, the cleavage of the chiral sugar auxiliary proceeds without any epimerization or racemization to form the corresponding isopropyl sulfonate in very good overall yield (75%) and excellent diastereomeric and enantiomeric excess (de, ee ≥ 95%). © 2009 Elsevier Ltd. All rights reserved  

A simple and green route to synthesis of (4 or 5)-aryl-2-aryloyl-(1H)-imidazoles is described. Two isomers can tautomerize to each other by the heat absorption. The tauto-isomerization process was studied by NMR technique. Acidity and stability of products were studied using B3LYP method. © 2009 Elsevier Ltd. All rights reserved  

Introduction: Endothelial cells (ECs) morphology strongly depends on the imposed mechanical stimuli. These mechanical stimuli include wall shear stress (WSS) and biaxial cyclic stretches (CS). Under combined loading, the effect of CS is not as simple as pure CS. The present study investigates the morphological response of ECs to the realistic mechanical stimuli. Methods: The cell population is theoretically studied using our previous validated model. The mechanical stimuli on ECs are described using four parameters; WSS magnitude (0 to 2.0 Pa), WSS angle (− 50° to 50°), and biaxial CS in two perpendicular directions (0 to 10%). The morphology of ECs is reported using four parameters; average... 

One of the major problems in underdetermined Sparse Component Analysis (SCA) in the field of (semi) Blind Source Separation (BSS) is the appropriate estimation of the mixing matrix, A, in the linear model X = AS, especially where more than one source is active at each instant of time. Most existing algorithms require the restriction that at each instant (i.e. in each column of the source matrix S), there is at most one single dominant component. Moreover, these algorithms require that the number of sources must be determined in advance. In this paper, we proposed a new algorithm for estimating the matrix A, which does not require the restriction of single dominant source at each instant.... 

Electrocardiogram (ECG) and magnetocardiogram (MCG) signals are among the most considerable sources of noise for other biomedical signals. In some recent works, a Bayesian filtering framework has been proposed for denoising the ECG signals. In this paper, it is shown that this framework may be effectively used for removing cardiac contaminants such as the ECG, MCG and ballistocardiographic artifacts from different biomedical recordings such as the electroencephalogram, electromyogram and also for canceling maternal cardiac signals from fetal ECG/MCG. The proposed method is evaluated on simulated and real signals. © 2008 Institute of Physics and Engineering in Medicine  

Purpose: Quantification of teeth is of clinical importance for various computer assisted procedures such as dental implant, orthodontic planning, face, jaw and cosmetic surgeries. In this regard, segmentation is a major step. Methods: In this paper, we propose a method for segmentation of teeth in volumetric computed tomography (CT) data using panoramic re-sampling of the dataset in the coronal view and variational level set. The proposed method consists of five steps as follows: first, we extract a mask in a CT images using Otsu thresholding. Second, the teeth are segmented from other bony tissues by utilizing anatomical knowledge of teeth in the jaws. Third, the proposed method is followed... 

A Quantitative Structure-Property Relationship (QSPR) relating atom-based calculated descriptors to 13C NMR chemical shifts was developed to accurately simulate 13C NMR spectra of polyhydroxy and methoxy substituted dibenzo pyrons (xanthones). A dataset consisting of 35 xanthones was employed for the present analysis. A set of 132 topological, geometrical, and electronic descriptors representing various structural characteristics was calculated for each of 497 unique carbon atoms in the dataset. Principal Component Analysis (PCA)-ranking and Artificial Neural Networks (ANNs) were used as descriptor selection and model building methods, respectively. Analyses of the results revealed a... 

Accurate estimation of muscle forces in various occupational tasks is critical for a reliable evaluation of spinal loads and subsequent assessment of risk of injury and management of back disorders. The majority of biomechanical models of multi-segmental spine estimate muscle forces and spinal loads based on the balance of net moments at a single level with no consideration for the equilibrium at remaining levels. This work aimed to quantify the extent of equilibrium violation and alterations in estimations when such models are performed at different levels. Results are compared with those of kinematics-driven model that satisfies equilibrium at all levels and EMG data. Regardless of the... 

The effects of external resistance on the recruitment of trunk muscles and the role of intrinsic and reflexive mechanisms to ensure the spinal stability are significant issues in spinal biomechanics. A computational model of spine under the control of 48 anatomically oriented muscle actions was used to simulate iso-resistive trunk movements. Neural excitation of muscles was attained based on inverse dynamics approach along with the stability-based optimization. The effect of muscle spindle reflex response on the trunk movement stability was evaluated upon the application of a perturbation moment. In this study, the trunk extension movement at various resistance levels while extending from... 

At room temperature, ZrOCl2·8H2O on montmorillonite K10 efficiently catalyzes conjugate addition of amines to a variety of conjugated alkenes such as α,β-unsaturated carbonyl compounds, carboxylic esters, nitriles and amides under solvent-free conditions. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency. © 2005 Elsevier Ltd. All rights reserved  

Benzopyrans, or chromenes, are widespread in nature and are considered to be a privileged scaffold in medicinal chemistry. Herein, we report the first organocatalyzed asymmetric synthesis of chiral benzopyrans. The benzopyran unit is constructed through a domino reaction involving an oxa-Michael attack of salicylic aldehyde derivatives onto α,β-unsaturated aldehydes, activated through iminium-ion formation with the organocatalyst, followed by an intramolecular aldol reaction and subsequent elimination of water. This overall reaction sequence provides benzopyrans with aromatic C-2 substituents in up to 60% yield and 60% enantioselectivity, while C-2 aliphatic analogues can be obtained in 90%... 

Membrane nanotubes, ubiquitous in cellular systems, adopt a spectrum of curvatures and shapes that are dictated by their intrinsic physical characteristics as well as their interactions with the local cellular environment. A high bending flexibility is needed in the crowded cytoplasm where tubes often need to bend significantly in the axial direction at sub-micron length scales. We find the stiffness of spontaneously formed membrane nanotubes by measuring the persistence length of reconstituted membrane nanotubes freely suspended in solution and imaged by fluorescence microscopy. By quantifying the tube diameter we demonstrate for the first time that the persistence length scales linearly... 

It is estimated that 20% of couples are infertile, and half of these infertility cases are linked to men. One of conditions that can affect male fertility is asthenozoospermia. We applied Raman spectroscopy to the analysis of the metabolome of the human seminal plasma, and used chemometrics on the patterns of Raman spectra obtained. Significant changes were observed in the metabolome of the human seminal plasma of asthenozoospermic patients  

In this study we will show that the variation rate of the memristance of the memristive device depends completely on its current memristance which means that it can change significantly with time during the learning phase. This phenomenon can degrade the performance of learning methods like Spike Timing-Dependent Plasticity (STDP) and cause the corresponding neuromorphic systems to become unstable  

Amyloid beta fibrillation can lead to major disorder of neurons processes and is associated with several neuronal diseases (e.g., Alzheimer's disease). We report here an importance of slight temperature changes, in the physiological range (35-42 °C), on the amyloid fibrillation process in the presence and absence of hydrophilic (silica) and hydrophobic (polystyrene) nanoparticles (NPs). The results highlight the fact that slight increases in temperature can induce inhibitory and acceleratory effects of hydrophobic and hydrophilic NPs on the fibrillation process, respectively. Using further in vivo considerations, the outcomes of this study can be used for considerable modifications on the... 

A supramolecular linear-dendritic copolymer consisting of a polystyrene backbone and hanging hyperbranched polyglycerols was prepared and characterized. Host-guest interactions between β-cyclodextrin incorporated in the core of polyglycerol as a host and aromatic rings of polystyrene as guests lead to the formation of a supramolecular linear-dendritic copolymer. Supramolecules formed micelles in aqueous solutions which were able to encapsulate and transfer paclitaxel with a high loading capacity