313 research outputs found
Elastic properties of small-world spring networks
We construct small-world spring networks based on a one dimensional chain and
study its static and quasistatic behavior with respect to external forces.
Regular bonds and shortcuts are assigned linear springs of constant and
, respectively. In our models, shortcuts can only stand extensions less
than beyond which they are removed from the network. First we
consider the simple cases of a hierarchical small-world network and a complete
network. In the main part of this paper we study random small-world networks
(RSWN) in which each pair of nodes is connected by a shortcut with probability
. We obtain a scaling relation for the effective stiffness of RSWN when
. In this case the extension distribution of shortcuts is scale free with
the exponent -2. There is a strong positive correlation between the extension
of shortcuts and their betweenness. We find that the chemical end-to-end
distance (CEED) could change either abruptly or continuously with respect to
the external force. In the former case, the critical force is determined by the
average number of shortcuts emanating from a node. In the latter case, the
distribution of changes in CEED obeys power laws of the exponent with
.Comment: 16 pages, 14 figures, 1 table, published versio
Design and Applications of In-Situ Differential Scanning Electron Microscopy
Contrast enhancement in the scanning electron microscope (SEM) is usually achieved by either of the two techniques of black level suppression, and differential imaging. This paper is mainly concerned with the latter method. Differential imaging of SEM images is commonly accomplished by either using a selective electronic filtering circuit (time sensitive) on the video signals, or the post processing of a collected digitized image (application of special kernel operatives). A technique is described that is capable of generating true in-situ SEM differential video signals of local sample features. Characteristics of this method are enhanced sample feature-boundary sensitivity, suppression of large background signals, and the ability to perform critical pattern alignments prior to feature measurements. Results are presented on the application of the technique to the general field of electron microscopy, as well as to integrated circuit micro-metrology
Towards a simplified description of thermoelectric materials: Accuracy of approximate density functional theory for phonon dispersions
We calculate the phonon-dispersion relations of several two-dimensional
materials and diamond using the density-functional based tight-binding approach
(DFTB). Our goal is to verify if this numerically efficient method provides
sufficiently accurate phonon frequencies and group velocities to compute
reliable thermoelectric properties. To this end, the results are compared to
available DFT results and experimental data. To quantify the accuracy for a
given band, a descriptor is introduced that summarizes contributions to the
lattice conductivity that are available already in the harmonic approximation.
We find that the DFTB predictions depend strongly on the employed repulsive
pair-potentials, which are an important prerequisite of this method. For
carbon-based materials, accurate pair-potentials are identified and lead to
errors of the descriptor that are of the same order as differences between
different local and semi-local DFT approaches
Molecular identification of Ornithobacterium rhinotracheale in turkeys in Isfahan province of Iran
Ornithobacterium rhinotracheale (ORT) is a gram negative, pleomorphic, rod shaped and non-motile bacterial pathogen mostly known to cause respiratory tract infections in turkeys. Ornithobacteriosis is an infectious disease of avian species that has been reported in almost all countries around the world. The objective of this study was to determine the prevalence of ORT in turkeys in Isfahan province of Iran. DNA was extracted from 375 collected tracheal swabs and lungs samples and amplified by ORT 16S rRNA gene specific primers using the PCR technique. ORT DNA was detected in 75 samples (19.93%) of broiler turkeys in Isfahan province of Iran. The results of this study demonstrated the widespread of ORT in broiler turkeys and confirmed that infection with ORT have a high prevalence in Iran.Key words: Ornithobacterium rhinotracheale (ORT), turkey, polymerase chain reaction, Iran
Modified Dolphin Monitoring Operator for Weight Optimization of Frame Structures
In this article, a modified dolphin monitoring (MDM) operatoris introduced and used to improve the performance of the collidingbodies optimization (CBO) algorithm for optimal designof steel structures (CBO-MDM). The performance of the CBO,enhanced colliding bodies optimization (ECBO) and CBOMDMare compared through three well-established structuralbenchmarks. The optimized designs obtained by thesealgorithms are compared, and the results show that the performanceof CBO-MDM is superior to those of the other twoalgorithms. The MDM is found to be a suitable tool to enhancethe performance of the CBO algorithm
An investigation on cardioprotective potential of Marrubium vulgare aqueous fraction against ischaemia-reperfusion injury in isolated rat heart
Background: The aim of this study was to evaluate the cardioprotective effects of aqueous fraction of Marrubium vulgare hydroalcoholic extract on cardiac parameters in ischaemic-reperfused isolated rat hearts.
Materials and methods: The aerial parts of the plant were extracted with methanol 70% by maceration. The water-soluble portion of the total hydroalcoholic extract was prepared with liquid-liquid extraction (LLE). Afterwards, the antioxidant activity, total phenolic and flavonoids content of the aqueous fraction were determined. In order to evaluate the effects of the aqueous fraction on cardiac parameters and ischaemia-reperfusion (I/R) injury, the Langendroff method was used on male Wistar rats. Harvested hearts were cannulated immediately to the Langendroff apparatus and subjected into 30 min regional ischaemia and 2 h reperfusion, either by a modified Krebs-Henseleit buffer (KHB) solution or enriched KHB solution with plant extract (10, 20, 40 μg/mL).
Results: The aqueous fraction was found to be a scavenger of DPPH radical with RC50 value of 47 μg/mL. The total phenolic and flavonoids content of the fraction was 6.05 g gallic acid equivalent and 36.13 mg quercetin equivalent per 100 g of dry plant material. In addition, 40 μg/mL of Marrubium vulgare aqueous fraction significantly decreased infarct size in comparison to control group. All doses considerably reduced the total ventricular ectopic beats during 30 min of ischaemia. The extract at dose of 40 μg/mL noticeably decreased the arrhythmias during the first 30 min of reperfusion.
Conclusions: The results of the study indicated aqueous fraction of Marrubium vulgare possesses a protective effect against I/R injuries in isolated rat heart
Stochastic Analysis and Regeneration of Rough Surfaces
We investigate Markov property of rough surfaces. Using stochastic analysis
we characterize the complexity of the surface roughness by means of a
Fokker-Planck or Langevin equation. The obtained Langevin equation enables us
to regenerate surfaces with similar statistical properties compared with the
observed morphology by atomic force microscopy.Comment: 4 pages, 7 figure
Bioinformatic Prioritization and Functional Annotation of GWAS-Based Candidate Genes for Primary Open-Angle Glaucoma
BACKGROUND: Primary open-angle glaucoma (POAG) is the most prevalent glaucoma subtype, but its exact etiology is still unknown. In this study, we aimed to prioritize the most likely 'causal' genes and identify functional characteristics and underlying biological pathways of POAG candidate genes. METHODS: We used the results of a large POAG genome-wide association analysis study from GERA and UK Biobank cohorts. First, we performed systematic gene-prioritization analyses based on: (i) nearest genes; (ii) nonsynonymous single-nucleotide polymorphisms; (iii) co-regulation analysis; (iv) transcriptome-wide association studies; and (v) epigenomic data. Next, we performed functional enrichment analyses to find overrepresented functional pathways and tissues. RESULTS: We identified 142 prioritized genes, of which 64 were novel for POAG. BICC1, AFAP1, and ABCA1 were the most highly prioritized genes based on four or more lines of evidence. The most significant pathways were related to extracellular matrix turnover, transforming growth factor-β, blood vessel development, and retinoic acid receptor signaling. Ocular tissues such as sclera and trabecular meshwork showed enrichment in prioritized gene expression (>1.5 fold). We found pleiotropy of POAG with intraocular pressure and optic-disc parameters, as well as genetic correlation with hypertension and diabetes-related eye disease. CONCLUSIONS: Our findings contribute to a better understanding of the molecular mechanisms underlying glaucoma pathogenesis and have prioritized many novel candidate genes for functional follow-up studies
Height Fluctuations and Intermittency of Films by Atomic Force Microscopy
The spatial scaling law and intermittency of the surface roughness
by atomic force microscopy has been investigated. The intermittency of the
height fluctuations has been checked by two different methods, first, by
measuring scaling exponent of q-th moment of height-difference fluctuations
i.e. and the second, by defining generating
function and generalized multi-fractal dimension . These methods
predict that there is no intermittency in the height fluctuations. The observed
roughness and dynamical exponents can be explained by the numerical simulation
on the basis of forced Kuramoto-Sivashinsky equation.Comment: 6 pages (two columns), 11 eps. figures, late
- …