Combined Solutal and Thermal Buoyancy Thermocapillary Convection in a Square Open Cavity

Combined solutal and thermal buoyancy–thermocapillary convection in a square open cavity is studied numerically in the present article. The Forchheimer–Brinkman-extended Darcy model is used in the mathematical formulation for the porous layer and the COMSOL Multiphysics software is applied to solve the dimensionless governing equations. The governing parameters considered are the thermal Marangoni number, −1000 ≤ Ma_T ≤ 1000, the Darcy number, 10−5 ≤ Da ≤ 10−2, the porosity of porous medium, 0.4 ≤ ε ≤ 0.99 and the Lewis number, 10 ≤ Le ≤ 200. It is found that the global heat and solute transfer rate decreases by reducing the counteracting surface tension force and increases by augmenting the surface tension force. The minimum values of the global heat and solute transfer rate were obtained about Ma_T = −90 for the all porosities

Increase in bacteraemia cases in the East Midlands region of the UK due to MDREscherichia coliST73: high levels of genomic and plasmid diversity in causative isolates

Objectives: To determine the population structure of E. coli ST73 isolated from human bacteraemia and urinary tract infections. Methods: The genomes of 22 E.coli ST73 isolates were sequenced using the Illumina HiSeq platform. High resolution SNP typing was used to create a phylogenetic tree. Comparative genomics were also performed using a pangenome approach. In silico and S1-PFGE plasmid profiling was conducted, and isolates were checked for their ability to survive exposure to human serum. Results: E.coli ST73 isolates circulating in clinically unrelated episodes show a high degree of diversity at a whole genome level, though exhibit conservation in gene content, particularly in virulence associated gene carriage. The isolates also contain a highly diverse plasmid pool that confers multi-drug resistance via carriage of CTX-M genes. All strains are highly serum resistant and uniformly carry genes shown to be essential for serum resistance. Conclusions: Our data shows that a rise in incidence of multi-drug resistant E.coli ST73 clinical isolates is not due to a circulating outbreak strain as in E.coli ST131. Rather the ST73 circulating strains are distantly related and carry a diverse set of resistance plasmids. This suggests that the evolutionary events behind emergence of drug resistant E.coli differ between lineages

Phenotypic microarrays suggest Escherichia coli ST131 is not a metabolically distinct lineage of extra-intestinal pathogenic E. coli

Extraintestinal pathogenic E. coli (ExPEC) are the major aetiological agent of urinary tract infections (UTIs) in humans. The emergence of the CTX-M producing clone E. coli ST131 represents a major challenge to public health worldwide. A recent study on the metabolic potential of E. coli isolates demonstrated an association between the E. coli ST131 clone and enhanced utilisation of a panel of metabolic substrates. The studies presented here investigated the metabolic potential of ST131 and other major ExPEC ST isolates using 120 API test reagents and found that ST131 isolates demonstrated a lower metabolic activity for 5 of 120 biochemical tests in comparison to non-ST131 ExPEC isolates. Furthermore, comparative phenotypic microarray analysis showed a lack of specific metabolic profile for ST131 isolates countering the suggestion that these bacteria are metabolically fitter and therefore more successful human pathogens

Serum albumin and osmolality inhibit Bdellovibrio bacteriovorus predation in human serum

We evaluated the bactericidal activity of Bdellovibrio bacteriovorus, strain HD100, within blood sera against bacterial strains commonly associated with bacteremic infections, including E. coli, Klebsiella pneumoniae and Salmonella enterica. Tests show that B. bacteriovorus HD100 is not susceptible to serum complement or its bactericidal activity. After a two hour exposure to human sera, the prey populations decreased 15- to 7,300-fold due to the serum complement activity while, in contrast, the B. bacteriovorus HD100 population showed a loss of only 33%. Dot blot analyses showed that this is not due to the absence of antibodies against this predator. Predation in human serum was inhibited, though, by both the osmolality and serum albumin. The activity of B. bacteriovorus HD100 showed a sharp transition between 200 and 250 mOsm/kg, and was progressively reduced as the osmolality increased. Serum albumin also acted to inhibit predation by binding to and coating the predatory cells. This was confirmed via dot blot analyses and confocal microscopy. The results from both the osmolality and serum albumin tests were incorporated into a numerical model describing bacterial predation of pathogens. In conclusion, both of these factors inhibit predation and, as such, they limit its effectiveness against pathogenic prey located within sera

Impact of Surface Undulation on Flow and Heat Transfer Characteristics in an Enclosure Filled with Nanoencapsulated Phase Change Materials (NEPCMs)

The present study investigates the natural convection in a wavy enclosure caused by a thermal difference between a cold wall and a hot undulated wall. The enclosure is filled with hybrid nanofluids. The hybrid nanofluids are formed of a phase change material (PCM) suspended in the water. The PCM utilizes polyurethane as the shell and nonadecane as the core. The core absorbs or releases its energy in the shape of latent heat inside the water and contributes to thermal energy storage and heat transfer. The governing equations are expressed in PDEs and solved by the finite element method (FEM). Parametric studies were used to analyze the solid concentration, fusion temperature, amplitude of corrugation, number of corrugations, and Rayleigh number. It is found that the heat transfer rate enhances by the rise of the latent heat of the NEPCM cores. The global heat transfer can be improved by more than 12% by adding 1% of NEPCM particles volume fraction. However, the heat transfer tends to decrease by applying the wavy surface

Two-Temperature Semiconductor Model Photomechanical and Thermal Wave Responses with Moisture Diffusivity Process

In the context of the two-temperature thermoelasticity theory, a novel mathematical–physical model is introduced that describes the influence of moisture diffusivity in the semiconductor material. The two-dimensional (2D) Cartesian coordinate is used to study the coupling between the thermo-elastic plasma waves and moisture diffusivity. Dimensionless quantities are taken for the main physical fields with some initial conditions in the Laplace transform domain. The linear solutions are obtained analytically along with unknown variables when some conditions are loaded at the surface of the homogenous medium according to the two-temperature theory. The Laplace transform technique in inversion form is utilized with some numerical algebraic approximations in the time domain to observe the exact expressions. Due to the effects of the two-temperature parameter and moisture diffusivity, the numerical results of silicon material have been introduced. The impacts of thermoelectric, thermoelastic, and reference moisture parameters are discussed graphically with some physical explanations

Thermal-Diffusive Processes of an Electron-Hole Non-Local Semiconductor Model with Variable Thermal Conductivity and Hall Current Effect

In this work, a novel model is presented that describes thermal diffusion processes through non-local semiconductor materials. The material under study is subjected to the influence of a strong magnetic field, which creates a Hall current. Interference between the excited electrons and the excited holes of a non-local semiconductor that had been exposed to temperature was present, and thermal conductivity depending on changes in graduated temperature were accounted for. The governing equations are written in a dimensionless form in one dimension (1D) where the thermal conductivity is taken as a function of temperature through electronic and elastic deformation (ED and ED) processes. Laplace transforms in one dimension with initial conditions were used to convert partial differential equations to arrive at exact formulas of solutions. To obtain the exact linear solutions, some boundary conditions taken on the free surface of the non-local semiconductor were used. Using numerical methods of inverse Laplace transforms, the complete solutions of the physical quantities under study were obtained. To further understand how various variables (thermal memory, variable thermal conductivity, and Hall current) affect the non-local semiconductor, numerical physical fields were simulated, and are graphically depicted, and discussed herein

Genomic analysis of extra-intestinal pathogenic Escherichia coli urosepsis

AbstractUrosepsis is a bacteraemia infection caused by an organism previously causing an infection in the urinary tract of a patient, a diagnosis which has been classically confirmed by culture of the same species of bacteria from both blood and urine samples. Given the new insights afforded by sequencing technologies into the complicated population structures of infectious agents affecting humans, we sought to investigate urosepsis by comparing the genome sequences of blood and urine isolates of Escherichia coli from five patients with urosepsis. The results confirm the classical urosepsis hypothesis in four of the five cases, but also show the complex nature of extra-intestinal E. coli infection in the fifth case, where three distinct strains caused two distinct infections. Additionally, we show there is little to no variation in the bacterial genome as it progressed from urine to blood, and also present a minimal set of virulence genes required for bacteraemia in E. coli based on gene association. These suggest that most E. coli have the genetic propensity to cause bacteraemia