Sharif Digital Repository

Anatomical image segmentation is one of the foundations for medical planning. Recently, convolutional neural networks (CNN) have achieved much success in segmenting volumetric (3D) images when a large number of fully annotated 3D samples are available. However, rarely a volumetric medical image dataset containing a sufficient number of segmented 3D images is accessible since providing manual segmentation masks is monotonous and time-consuming. Thus, to alleviate the burden of manual annotation, we attempt to effectively train a 3D CNN using a sparse annotation where ground truth on just one 2D slice of the axial axis of each training 3D image is available. To tackle this problem, we propose... 

Coupling of side chain dynamics over long distances is an important component of allostery. Methionine side chains show the largest intrinsic flexibility among methyl-containing residues but the actual degree of conformational averaging depends on the proximity and mobility of neighboring residues. The 13C NMR chemical shifts of the methyl groups of methionine residues located at long distances in the same protein show a similar scaling with respect to the values predicted from the static X-ray structure by quantum methods. This results in a good linear correlation between calculated and observed chemical shifts. The slope is protein dependent and ranges from zero for the highly flexible... 

Carbon fiber (CF) as a multifunctional material with superb performance in aviation industry has serious drawback such as impedance mismatch which restricted the capability of using it as microwave absorber materials. In this research, a novel hierarchical carbon fiber@La0.7Sr0.3MnO@NiO (CF/LS/N) composite was facilely and successfully synthesized via sol-gel and subsequent hydrothermal reactions. The structural, morphological, magnetic and electromagnetic behavior of the composite were precisely evaluated via XRD, FESEM, XPS, VSM and VNA analysis. According to the systematic evaluation results, the synergistic positive effect of adding NiO nanoparticles is revealed in improving the... 

Polyamide 6 (PA6)/carbon nanotube (CNT)/conductive carbon black (CCB) nanocomposites with the incorporation of physical and chemical dispersants were prepared via melt blending method to examine the synergistic enhancement of electrical conductivity. Investigation of modified CNT with octadecyl triphenyl phosphonium chloride (OTPC-CNT) as physical dispersant was performed by Fourier transform infrared, nuclear magnetic resonance, Raman spectroscopy, and thermogravimetric analysis. Morphological, electrical, rheological, and mechanical properties of PA6/CNT/CCB nanocomposites were examined by field emission scanning electron microscopy, transmission electron microscopy, digital insulation... 

In recent studies, several methods have been suggested to decrease noise of magnetic resonance image (MRI) in order to raise the peak signal-to-noise ratio (PSNR) and the structural similarity index (SSIM). In this paper, we propose a novel method based on a minimization problem in Ripplet domain that uses singular value decomposition (SVD) in low rank learning to eliminate the noise of MRI images. We reschedule the weighted nuclear norm minimization (WNNM) problem in any edges of Ripplet domain transform and using an adaptive weighting structure to denoise the patches of Ripplet component matrix. The parameters of the proposed method are divided into two groups, some of them are calculated... 

In this study, water-soluble terpolymers containing highly hydrophilic monomers of acrylamide and maleic anhydride and highly hydrophobic monomers of styrene were synthesized (ASM) through the one-step inverse emulsion polymerization. Proton nuclear magnetic resonance (1H NMR), fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction pattern (XRD) were performed to investigate the chemical structures and structural transformations of ASM. Thermal stability and thermal decomposition steps of ASM were studied by thermogravimetric analysis (TGA). An Ubbelhode capillary viscometer and a rheological mechanical spectrometer (RMS) were employed to obtain the specific, relative, and... 

An example of zeolite selectivity (MFI → MOR) driven by synthesis aging time has been studied. Using N,N,N′,N′-tetramethyl-N,N′-dipropyl-ethylenediammonium diiodide (TMDP) as an organic structure-directing agent (OSDA), the zeolite phases obtained at 2 h (MFI 97%), 8 h (MFI 84%, MOR 16%) and 24 h (MFI 43%, MOR 57%) have been characterized by powder X-ray diffraction. The results suggest that at intermediate aging time, namely 8 h and 24 h, the dominant phase (MFI) is displaced by MOR. Different techniques (FT-IR, Raman, 13C MAS NMR, TGA/DTG and HC microanalysis) have been employed to verify the OSDA integrity and occlusion inside the zeolite micropores as well as to quantify the water and... 

The present simulation aims to investigate adding NEPCM nanoparticles to water in the natural convection inside a cavity by using FVM method and SIMPLE algorithm. Nano-encapsulated phase change material (NEPCM) consists of a shell and core with phase change property. The NEPCM particles in base fluid have the ability to transfer heat by absorbing and dissipating heat in the liquid-solid phase change state. In this study, the energy wall phenomenon due to the phase change of NEPCM core has appeared that the whose energy transfer strength is proportional to the latent heat of NEPCM core and the thickness of the energy wall. Moreover, the relationship between the energy wall and the heat... 

A computationally efficient 3D human head finite element model was constructed. The model includes the mesoscale geometrical details of the brain including the distinction between white and grey matter, sulci and gyri, the ventricular system, foramen magnum, and cerebrospinal fluid. The heterogeneity and anisotropy from diffusion tensor imaging data were incorporated by applying a one-to-one voxel-based correspondence between diffusion voxels and finite elements. The voxel resolution of the model was optimized to obtain a trade-off between reduced computational cost and higher geometrical details. Three sets of constitutive material properties were extracted from the literature to validate... 

A diffusion tensor imaging (DTI) -based statistical micromechanical model was developed to study the effect of axonal fiber architecture on the inter- and intra-regional mechanical heterogeneity of the white matter. Three characteristic regions within the white matter, i.e., corpus callosum, brain stem, and corona radiata, were studied considering the previous observations of locations of diffuse axonal injury. The embedded element technique was used to create a fiber-reinforced model, where the fiber was characterized by a Holzapfel hyperelastic material model with variable dispersion of axonal orientations. A relationship between the fractional anisotropy and the dispersion parameter of... 

This paper analytically studies the effect of functionally graded materials (FGMs) on the primary resonances of large amplitude flexural vibration of in-extensional rotating shafts with nonlinear curvature as well as nonlinear inertia. The constituent material is assumed to vary along the radial direction according to a power-law gradation. The governing differential equations and the corresponding boundary conditions are derived employing the variational approach. Then, the Galerkin method and the multiple scales perturbation method are utilized to obtain the frequency–response equation. In a numerical case study, the effects of the power-law index on the steady-state responses and locus of... 

Monolayer band-reject frequency selective surfaces (FSS) based on curved coupled microstrip line (CCML) resonators are proposed. Each unit cell comprises a single- or multi-loop CCML resonator, featuring single-wideband or multi-band resonance, respectively. Design guidelines for achieving various responses are demonstrated and it is shown there is a great flexibility attaining desired frequency responses versus structural parameters. For instance, it is shown that the entire microwave X-band may be rejected, using a simple single-loop structure. The FSS is particularly useful for protecting buildings against parasitic microwave signals. A visual transparency factor for the FSS, when regular... 

Spin lattice relaxation rate is investigated for 3D tilted cone Weyl semimetals (TCWSMs). The nuclear spin relaxation rate is presented as a function of temperature and tilt parameter. We find that the relaxation rate behaves as (1-ζ2)-α with α ≈ 9 where 0 ζ < 1 is the tilt parameter. We demonstrate that such a strong enhancement for ζ ≲ 1 that gives rise to very fast relaxation rates, is contributed by a new hyperfine interactions arising from the tilt itself. This can be attributed to the combination of anisotropy of the Fermi surface and an additional part related to the structure of the spacetime: extracting an effective density of states (DOS) ρ from the Korringa relation, we show that... 

We present an LC circuit model that supports a tilted “Dirac cone” in its spectrum. The tilt of the Dirac cone is specified by the parameters of the model consisting of mutual inductance between the neighboring sites and a capacitance C0 at every lattice site. These parameters can be completely measured by impedance spectroscopy. Given that a tilted Dirac cone can be described by a background spacetime metric, the impedance spectroscopy can perfectly provide (local) information about the metric of the spacetime. Nonuniform spatial dependence of the mutual inductance or capacitance induces a nontrivial geometrical structure on the emergent spacetime. Our work extends the range of usefulness... 

Semiconductor-based photocatalysis is an efficient approach for degradation of organic pollutants. In this context, ZnO/g-C3N4 composite nanofibers containing carbonaceous species with different concentrations of g-C3N4 nanosheets (x = 0.25, 0.5, 1, 2, 10 wt%) noted as ZnO/carbon/(x wt%) g-C3N4 are prepared by electrospinning technique. For preparation of the composite nanofibers, bulk g-C3N4 is exfoliated to nanosheets, and then it is mixed with polyvinyl alcohol and appropriate zinc acetate content followed by electrospinning process. Thermal annealing of the as spun zinc acetate/poly(vinyl alcohol)/g-C3N4 nanosheets sample under N2 atmosphere leads to the formation of carbonaceous species... 

In this article, a dual-band sixth order double symmetric T-slot filter is proposed for the 5G communication systems. This filter contains two duplicate square resonators and a T-shape feedline on the Rogers RT duroid 5880 substrate. Operating at the 28 and 38.5 GHz frequencies from licensed 5G frequency bands and small size make this filter appropriate for different 5G applications. Furthermore, an LC equivalent circuit for the filter has been considered that helps us to have a better sight of this filter. Measurement results show good agreement with simulations. The attenuation on the passband is less than 1 dB. In order to evaluate the filter performance besides other millimeter waves... 

Biogenic amines (BAs) are known as substantial indicators of the quality and safety of food. Developing rapid and visual detection methods capable of simultaneously monitoring BAs is highly desired due to their harmful effects on human health. In the present study, we have designed a multicolor sensor array consisting of two types of gold nanostructures (i.e., gold nanorods (AuNRs) and gold nanospheres (AuNSs)) for the discrimination and determination of critical BAs (i.e., spermine (SM), tryptamine (TT), ethylenediamine (EA), tyramine (TR), spermidine (SD), and histamine (HT)). The design principle of the probe was based on the metallization of silver ions on the surface of AuNRs and AuNSs... 

A new magnetic quaternary photocatalyst, K4Nb6O17/α-Fe2O3/Fe3N/g-C3N4, was synthesized via a simple one-step thermal pyrolysis process. The prepared photocatalyst was well characterized, and its photocatalytic activity was evaluated towards acetamiprid pesticide degradation, CO2 reduction reaction, and U87-MG cell eradication. The coexistence of four different crystalline structures in the prepared photocatalyst could simultaneously facilitate photoelectron transport and suppress charge recombination through their coupled heterogeneous interfaces. Because of the coexistence of various photosensitive compounds, the prepared photocatalyst showed the excellent capability to harvest the visible... 

Background: Over the last two decades, breast cancer remains the main cause of cancer deaths in women. To treat this type of cancer, radiation therapy (RT) has proved to be efficient. RT for breast cancer is, however, challenged by intrafractional motion caused by respiration. The problem is more severe for the left-sided breast cancer due to the proximity to the heart as an organ-at-risk. While particle therapy results in superior dose characteristics than conventional RT, due to the physics of particle interactions in the body, particle therapy is more sensitive to target motion. Conclusions: This review highlights current and emerging strategies for the management of intrafractional... 

With significant advancements in research technologies, and an increasing global population, microfluidic and nanofluidic systems (such as point-of-care, lab-on-a-chip, organ-on-a-chip, etc) have started to revolutionize medicine. Devices that combine micron and nanotechnologies have increased sensitivity, precision and versatility for numerous medical applications. However, while there has been extensive research on microfluidic and nanofluidic systems, very few have experienced wide-spread commercialization which is puzzling and deserves our collective attention. For the above reasons, in this article, we review research advances that combine micro and nanotechnologies to create the next...