Air jet Erosion Wear behavior of Al6061-SiC-Carbon fibre Hybrid Composite

Currently, the focus in materials development is on processing of hybrid metal matrix composites (MMC’s) in particular aluminum (Al) based owing to their flexibility in achieving tailor made properties. Till date, only processing, characterization of mechanical and adhesive wear behavior of various hybrid MMCs have received much attention. However, solid erosion wear of hybrid MMCs has not yet been reported. This assessment will further enlarge the range of applications of hybrid MMCs in particular for components in operation for military applications especially in desert areas. In the light of the above, the present paper discusses the air jet erosion behavior of developed Al6061-SiC-carbon fibre hybrid composite prepared by combination of powder metallurgy and casting process followed by hot extrusion at temperature of 550oC using extrusion ratio of 1:4. The solid sand erodent particle size used was 312 μm while the operating pressure and velocity was maintained at 1.4 bar and 30 m/sec respectively. The adopted feed rate of the sand particles was 2.0 g/min with standoff distance being 10 mm. The sample size was 25 mm x 25 mm x 10 mm. The effect of silicon carbide (SiC), Carbon fibre (Cf), test duration and angle of impingement of the erodent on the erosion wear loss of the developed hybrid composite will be discussed at length

Fog Robotics: An Introduction

Cloud Robotics (CR) is an emerging and successful approach to robotics. The number of robots or other IoT devices may increase drastically in the future which might need enormous bandwidth and there might be security concerns. If robots in CR are not secured then robots can even become surveillance bot by hackers. Moreover, if an internet connection is lost due to network hitches then in that crucial moment robot may not be available to complete its given task. For example, a robot assisting a person can stop working unexpectedly or work with the instructions from hacker. In order to address such problems, we propose a new approach to robotics - Fog Robotics (FR) in this paper, so a network of robots can be used more securely and efficiently as compared to CR

Influence of shear flow on vesicles near a wall: a numerical study

We describe the dynamics of three-dimensional fluid vesicles in steady shear flow in the vicinity of a wall. This is analyzed numerically at low Reynolds numbers using a boundary element method. The area-incompressible vesicle exhibits bending elasticity. Forces due to adhesion or gravity oppose the hydrodynamic lift force driving the vesicle away from a wall. We investigate three cases. First, a neutrally buoyant vesicle is placed in the vicinity of a wall which acts only as a geometrical constraint. We find that the lift velocity is linearly proportional to shear rate and decreases with increasing distance between the vesicle and the wall. Second, with a vesicle filled with a denser fluid, we find a stationary hovering state. We present an estimate of the viscous lift force which seems to agree with recent experiments of Lorz et al. [Europhys. Lett., vol. 51, 468 (2000)]. Third, if the wall exerts an additional adhesive force, we investigate the dynamical unbinding transition which occurs at an adhesion strength linearly proportional to the shear rate.Comment: 17 pages (incl. 10 figures), RevTeX (figures in PostScript

The possibility of a favourable outcome and reversibility of severe ankle joint damage on the example of a clinical observation

The problem of aseptic talus necrosis consists of the following features: a) manifestation of the disease in the form of acute articular syndrome without typical symptoms; b) inevitable serious consequences in the form of disfiguring deforming arthrosis of the ankle joint, development of gross deformities of the rearfoot, etc., resulting in disability. The lack of methods for monitoring the dynamics of the disease also plays an important role. This is particularly so with such an important issue as the substantiation of stopping immobilization and allowing the load on the foot in order to avoid collapsed talus and subsequent complications. It is believed that treatment started before radiographic changes helps to avoid severe complications, but for a number of reasons patients arrive already at the stage of late severe destructive changes. All of the above explains the high relevance of the problem of treatment of patients with aseptic talus necrosis. The importance of the presented clinical case and the value of this information can be considered several points: its  example demonstrates the possibility of early diagnosis of severe talus damage cause by aseptic necrosis; based on objective data, a substantiation was made for allowing the load on the leg with body weight in the complex of rehabilitation measures; the possibility of regression of pathological changes associated with aseptic talus necrosis and the dynamics of the course of aseptic talus necrosis with a favorable outcome were demonstrated, which is confirmed by modern research methods. Thus, the need for magnetic resonance imaging has been confirmed for all referred patients with a clinical picture of local articular syndrome in the ankle joint, the possibility of complete regression of avascular necrosis symptoms in case of conservative treatment at the early stages and the possibility of resolving the load on the leg in the complex of rehabilitation treatment have been demonstrated

Mathematical models in biology

Aerotaxis is the particular form of chemotaxis in which oxygen plays the role of both the attractant and the repellent. Aerotaxis occurs without methylation adaptation, and it leads to fast and complete aggregation toward the most favorable oxygen concentration. Biochemical pathways of aerotaxis remain largely elusive, however, aerotactic pattern formation is well documented. This allows mathematical modeling to test plausible hypotheses about the biochemical mechanisms. Our model demonstrates that assuming fast, non-methylation adaptation produces theoretical results that are consistent with experimental observations. We obtain analytical estimates for parameter values that are difficult to obtain experimentally. Chemotaxis in growth cones differs from gradient sensing in other animal cells, because growth cones can change their attractive or repulsive response to the same chemical gradient based on their internal calcium or cAMP levels. We create two models describing different aspects of growth cone guidance. One model describes the internal switch that determines the direction of movement. However, this model allows chemotaxis under certain conditions only, so a second model is created to propose a mechanism that allows growth cone guidance in any environment. Endothelial cells go through extensive morphological changes when exposed to shear stress due to blood flow. These morphological changes are thought to be at least partially the result of mechanical signals, such as deformations, transmitted to the cell structures. Our model describes an endothelial cell as a network of viscoelastic Kelvin bodies with experimentally obtained parameters. Qualitative predictions of the model agree with experiments.Comment: Dissertation. 214 pages with 82 figures. Parts of the dissertation have been submitted for publication. The chapter on modeling deformation of endothelial cells is published; the reference is given belo

Bullous pemphigoid and comorbidities: a case-control study in Portuguese patients

BACKGROUND: Although rare, bullous pemphigoid (BP) is the most common autoimmune blistering disease. Recent studies have shown that patients with bullous pemphigoid are more likely to have neurological and psychiatric diseases, particularly prior to the diagnosis of bullous pemphigoid. OBJECTIVE: The aims were: (i) to evaluate the demographic and clinical features of bullous pemphigoid from a database of patients at a Portuguese university hospital and (ii) to compare the prevalence of comorbid conditions before the diagnosis of bullous pemphigoid with a control group. METHODS: Seventy-seven patients with bullous pemphigoid were enrolled in the study. They were compared with 176 age- and gender-matched controls, which also had the same inpatient to outpatient ratio, but no history of bullous or cutaneous malignant disease. Univariate and multivariate analyses were used to calculate odds ratios for specific comorbid diseases. RESULTS: At least one neurologic diagnosis was present in 55.8% of BP patients compared with 20.5% controls (p<0.001). Comparing cases to controls, stroke was seen in 35.1 vs. 6.8%, OR 8.10 (3.80-17.25); dementia in 37.7 vs. 11.9%, OR 5.25 (2.71-10.16); and Parkinson's disease in 5.2 vs. 1.1%, OR 4.91 (0.88-27.44). Using multivariate analysis, all diseases except Parkinson's retained their association with BP. Patients under systemic treatment were eight times more likely to have complications than those treated with topical steroids (p< 0.017). CONCLUSIONS: The results of this study substantiate the association between BP and neurological diseases. In addition, they highlight the potential complications associated with the treatment of BP

PKA Mediates Constitutive Activation of CFTR in Human Sweat Duct

The cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channels are constitutively activated in sweat ducts. Since phosphorylation-dependent and -independent mechanisms can activate CFTR, we sought to determine the actual mechanism responsible for constitutive activation of these channels in vivo. We show that the constitutively activated CFTR Cl− conductance (gCFTR) in the apical membrane is completely deactivated following α-toxin permeabilization of the basolateral membrane. We investigated whether such inhibition of gCFTR following permeabilization is due to the loss of cytoplasmic glutamate or due to dephosphorylation of CFTR by an endogenous phosphatase in the absence of kinase activity (due to the loss of kinase agonist cAMP, cGMP or GTP through α-toxin pores). In order to distinguish between these two possibilities, we examined the effect of inhibiting the endogenous phosphatase activity with okadaic acid (10−8 M) on the permeabilization-induced deactivation of gCFTR. We show that okadaic acid (1) inhibits an endogenous phosphatase responsible for dephosphorylating cAMP but not cGMP or G protein-activated CFTR and (2) prevents deactivation of CFTR following permeabilization of the basolateral membrane. These results indicate that distinctly different phosphatases may be responsible for dephosphorylating different kinase-specific sites on CFTR. We conclude that the phosphorylation by PKA alone appears to be primarily responsible for constitutive activation of gCFTR in vivo

Anemia prevalence in women of reproductive age in low- and middle-income countries between 2000 and 2018

Anemia is a globally widespread condition in women and is associated with reduced economic productivity and increased mortality worldwide. Here we map annual 2000–2018 geospatial estimates of anemia prevalence in women of reproductive age (15–49 years) across 82 low- and middle-income countries (LMICs), stratify anemia by severity and aggregate results to policy-relevant administrative and national levels. Additionally, we provide subnational disparity analyses to provide a comprehensive overview of anemia prevalence inequalities within these countries and predict progress toward the World Health Organization’s Global Nutrition Target (WHO GNT) to reduce anemia by half by 2030. Our results demonstrate widespread moderate improvements in overall anemia prevalence but identify only three LMICs with a high probability of achieving the WHO GNT by 2030 at a national scale, and no LMIC is expected to achieve the target in all their subnational administrative units. Our maps show where large within-country disparities occur, as well as areas likely to fall short of the WHO GNT, offering precision public health tools so that adequate resource allocation and subsequent interventions can be targeted to the most vulnerable populations