Stability and bifurcations analysis of a competition model with piecewise constant arguments

In this paper, we investigate local and global asymptotic stability of a positive equilibrium point of system of differential equations where t ≥ 0, the parameters r₁, k₁, α₁, α₂, r₂, k₂, and d₁ are positive, and [t] denotes the integer part of t ∈ [0, ∞ ). x(t) and y(t) represent population density for related species. Sufficient conditions are obtained for the local and global stability of the positive equilibrium point of the corresponding difference system. We show through numerical simulations that periodic solutions arise through Neimark–Sacker bifurcation. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of Li2CO3 on formation temperature of hBN by modified O'Connor model

This study is interested in the effect of lithium carbonate on the formation of hexagonal boron nitride (hBN) by means of the available experimental methods including TGA, XRD, FTIR, SEM and HR‐TEM. hBN samples were synthesized at the 1450 °C with different molar ratios of lithium carbonate by modified O'Connor routine. The crystalline hBN formation tended to improve with the increment of the Li₂CO₃ concentration level (especially after more 20 %). The dopant quantity decreased the residual stresses due to the presence of possible relaxation mechanisms along with the nanocrystal structure, even favored by XRD experimental findings regarding the enhancement of crystal plane alignments, crystallite sizes and lattice parameters. As for the FTIR surveys, the Li₂CO₃ foreign impurities strengthened more and more the covalent bonds between boron and nitrogen atoms. At the same time, the samples with 40 % lithium carbonate were annealed at the varied temperatures of 1000, 1150, 1300 and 1450 °C to determine the optimum annealing temperature. The XRD+FTIR investigations indicated that the degree of hexagonality improved with the increased annealing temperature. Similarly, the surface morphology confirmed not only the formation of regularity and flaky hexagonal BN structures, but also the strengthening of covalent bonds between the atoms.     

The Rhodium(II) Carbenoid Cyclization-Cycloaddition Cascade of alpha-Diazo Dihydroindolinones for the Synthesis of Novel Azapolycyclic Ring Systems

Tandem carbonyl ylide formation-1,3-dipolar cycloaddition of α-diazo N-acetyl-tetrahydro-β-carbolin-1-one derivatives occur efficiently in the presence of a dirhodium catalyst to afford bimolecular cycloadducts in high yield. The Rh(II)-catalyzed reaction also takes place intramolecularly to give products derived from trapping of the carbonyl ylide dipole with a tethered alkene. The power of the intramolecular cascade sequence is that it rapidly assembles a pentacyclic ring system containing three new stereocenters and two adjacent quaternary centers stereospecifically in a single step and in high yield.     

Substitution and cyclization reactions involving the quasi-antiaromatic 2H-indol-2-one ring system

The quasi-antiaromatic 2H-indol-2-one ring system is readily generated by treating a 3-hydroxy-substituted 1,3-dihydroindol-2-one with a Lewis acid. Stepwise addition of various pi-nucleophiles to the highly reactive 2H-indol-2-one system occurs smoothly to afford substituted oxindoles. The cyclization was also carried out in an intramolecular fashion to give spiro-substituted oxindoles in good yield.     

Investigating pedestrian evacuation using ant algorithms

We have presented non-linear analytical formula for fusion–fission cross-sections. This is achieved by analysing many fusion–fission experiments of the compound nuclei of atomic number range \(23 \le Z \le 146\) available in literature. Our parametrised formula can reproduce the fusion–fission cross-sections which agree well with the experiments. Our parametrisations depend on the charges and masses of the compound nuclei and fission fragments only. These results can be used as a guideline for estimating the fusion–fission cross-sections in those cases where measurements do not exist and also for studying new nuclei which are not yet explored.     

Study on bi-directional pedestrian movement using ant algorithms

A cellular automata model is proposed to simulate bi-directional pedestrian flow. Pedestrian movement is investigated by using ant algorithms. Ants communicate with each other by dropping a chemical, called a pheromone, on the substrate while crawling forward. Similarly, it is considered that oppositely moving pedestrians drop ‘visual pheromones' on their way and the visual pheromones might cause attractive or repulsive interactions. This pheromenon is introduced into modelling the pedestrians' walking preference. In this way, the decision-making process of pedestrians will be based on ‘the instinct of following'. At some densities, the relationships of velocity–density and flux–density are analyzed for different evaporation rates of visual pheromones. Lane formation and phase transition are observed for certain evaporation rates of visual pheromones.     

An Efficient Computational Framework for the Analysis of Whole Slide Images: Application to Follicular Lymphoma Immunohistochemistry

Follicular Lymphoma (FL) is one of the most common non-Hodgkin Lymphoma in the United States. Diagnosis and grading of FL is based on the review of histopathological tissue sections under a microscope and is influenced by human factors such as fatigue and reader bias. Computer-aided image analysis tools can help improve the accuracy of diagnosis and grading and act as another tool at the pathologist's disposal. Our group has been developing algorithms for identifying follicles in immunohistochemical images. These algorithms have been tested and validated on small images extracted from whole slide images. However, the use of these algorithms for analyzing the entire whole slide image requires significant changes to the processing methodology since the images are relatively large (on the order of 100k × 100k pixels). In this paper we discuss the challenges involved in analyzing whole slide images and propose potential computational methodologies for addressing these challenges. We discuss the use of parallel computing tools on commodity clusters and compare performance of the serial and parallel implementations of our approach.     

Effect of extraction conditions on measured total polyphenol contents and antioxidant and antibacterial activities of black tea

Black tea was extracted for 2, 8 and 18 h with absolute acetone, N,N-dimethyl-formamide (DMF), ethanol and methanol and their 50% aqueous solutions. The extracts were screened for total polyphenol contents, antioxidant and antibacterial activities. The polyphenol content of the extracts was found to be in the range of 0.44-114.01 mg gallic acid equivalents (GAE)/g dry weight tea, depending on the solvent used and the length of the extraction process. In general, aqueous acetone or DMF extracts displayed the highest polyphenol contents and antioxidant activity, while absolute acetone was the least efficient solvent. Antioxidant activities of tea extracts tested using the reducing power and 2,2-diphenyl-1-picryhydrazyl (DPPH) radical methods ranged from 0.09 to 1.18 and from 2.60 to 95.42 %, respectively, depending on the extraction conditions and the antioxidant activities correlated well with the polyphenol concentrations. Aqueous solvent black tea extracts also possessed antibacterial activity, depending on the solvent used and bacterial species tested. Staphylococcus aureus was found to be the most sensitive to all tea extracts, except for the methanol extract. Tea extracts were not effective against Y. enterocolitica, L. monocytogenes and E. coli O157:H7.     

Single peptide bonds exhibit poly(pro)II ("random coil") circular dichroism spectra

The far-UV circular dichroism spectra of a series of amino acid derivatives containing single peptide bonds have been measured. The N-acetyl-alanine displays a polyproline (PP) II-like spectrum, but alaninamide shows a very weak positive signal. Similarly Gly-Ala shows a PPII spectrum, but Ala-Gly does not. On heating, the spectrum shows a two-state transition also shown by long PPII polypeptides. Thus the characteristic PPII negative maximum at <200 nm results from the coupling of a peptide bond N-terminal to the chiral alpha-carbon, and therefore the simplest peptide bonds have a preferred conformation that defines the spectrum of disordered proteins of any size.