Shock Induced Chemical Reactions of Intermetallic Mixture of Nickel and Aluminum and Associated Transition States

In this paper, numerical simulation of shock-induced chemical reactions of intermetallic mixtures is discussed. Specifically, the paper focuses on intermetallic mixture of nickel and aluminum. To initiate the chemical reactions, the thermal input or the shockwave should supply the energy to take the reactants, mixture of nickel and aluminum, to the transition state. Thus, for any numerical simulation or analysis of the shock or thermally induced chemical reaction in a continuum scale or a meso scale, it is necessary to identify the transition state. The transition state for the intermetallic mixture of nickel and the aluminum is identified in this paper and a result of the numerical simulation of the shock-induced chemical reaction, in a continuum scale is presented. The numerical solutions clearly show the chemical reactions, release of heat energy, increase of the temperature and the formation of products, following the transition state and the resulting shock-induced chemical reaction of a binary intermetallic energetic mixture of nickel and aluminum. The studies also show that the collapse of porosity is a mechanism that takes the reactants to the transition state, in shock-induced chemical reactions of binary intermetallic mixtures.

A New Approach to Suppress Tip Leakage Flow Utilizing Induced Shock Wave in Tip Region of a TransonicCompressor Rotor

Tip leakage flow affects the flow stability of high-loading compressors significantly.Therefore,a novel approach via induced shock wave near suction-side edge of blade tip was proposed to suppress the strength and influence range of leakage flow in a transonic rotor.Three new schemes with different circumferentially diverging degrees of clearance were designed to reveal the mechanism of the new approach.Through the action of the circumferentially diverging clearance(from the pressure side to the suction side over blade tip),a much more dramatic acceleration of the supersonic leakage jet flow appeared over blade tip of the new schemes.An induced shock wave was produced near the suction side edge of blade tip due to the pressure difference between the discharging leakage flow and the surrounding high-pressure mainflow in tip channel.As a result,both the mass flow rate and the outlet velocity of leakage flow were reduced significantly via the induced shock wave.Meanwhile,the suppressing effect of the new approach on the tip leakage jet flow was closely related to the strength and circumferential location of the induced shock wave.With the aids of the induced shock wave,the largest improvement of tip flow characteristics with an over 5%increase in stall margin was realized in new transonic rotor when the circumferential divergence angle equals 8°,accompanied with no more than a 0.4%decrease in isentropic efficiency.

Is thioredoxin reductase involved in the defense againsi DNA fragmentation in varicocele？

We aimed to investigate the role of thioredoxin reductase （TR） and inducible heat shock protein 70 （iHsp70） and their relationship with sperm quality in varicocele （VAR） patients. Semen samples were obtained from 16 subfertile men diagnosed as VAR and 10 fertile men who applied to the Andrology Laboratory of Istanbul Medical Faculty of Istanbul University. The sperm TR and iHsp 70 expression levels were determined using Western blot analysis. The TR activity of the sperm was assayed spectrophometrically. The sperm quality was evaluated both by conventional sperm analysis and by a terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling （TUNEL） technique that assayed DNA-fragmented spermatozoa in semen samples. The percentage of TUNELopositive spermatozoa in the VAR group （16.3%±5.6%） was higher than that in the fertile group （5.5%±1.9%）. Significant inverse correlations were detected between the percentage of TUNEL-positive cells and both the concentration （r=--0.609; P=0.001） and motility （r=--0.550; P=-0.004） of spermatozoa. Both the TR expression and activity were increased significantly in the VAR group （U=22.0; P=0.001 and U=33.5 P=0.012, respectively） as analyzed using the Mann-Whitney UWilcoxon rank sum Wtest. Furthermore, significant positive correlations were found between TR expression and activity （r=-0.406; P=O.040） and between TR expression and the percentage of TUNEL-positive cells （r=0.665; P=-0.001）. Sperm iHsp70 expression did not differ between the VAR and fertile groups. In conclusion, increased sperm TR expression might be a defense mechanism against apoptosis in the spermatozoa of men with VAR.

Microbiota-host interplay at the gut epithelial level,health and nutrition

Growing evidence suggests the implication of the gut microbiota in various facets of health and disease. In this review, the focus is put on microbiota-host molecular cross-talk at the gut epithelial level with special emphasis on two defense systems： intestinal alkaline phosphatase（IAP） and inducible heat shock proteins（iHSPs）. Both IAP and iHSPs are induced by various microbial structural components（e.g. lipopolysaccharide, flagellin, CpG DNA motifs）,metabolites（e.g. n-butyrate） or secreted signal molecules（e.g., toxins, various peptides, polyphosphate）. IAP is produced in the small intestine and secreted into the lumen and in the interior milieu. It detoxifies microbial components by dephosphorylation and, therefore, down-regulates microbe-induced inflammation mainly by inhibiting NF-κB pro-inflammatory pathway in enterocytes. IAP gene expression and enzyme activity are influenced by the gut microbiota. Conversely, IAP controls gut microbiota composition both directly, and indirectly though the detoxification of pro-inflammatory free luminal adenosine triphosphate and inflammation inhibition. Inducible HSPs are expressed by gut epithelial cells in proportion to the microbial load along the gastro-intestinal tract. They are also induced by various microbial components, metabolites and secreted molecules. Whether iHSPs contribute to shape the gut microbiota is presently unknown. Both systems display strong anti-inflammatory and anti-oxidant properties that are protective to the gut and the host. Importantly, epithelial gene expressions and protein concentrations of IAP and iHSPs can be stimulated by probiotics, prebiotics and a large variety of dietary components, including macronutrients（protein and amino acids, especially L-glutamine, fat, fiber）, and specific minerals（e.g. calcium）and vitamins（e.g. vitamins K1 and K2）. Some food components（e.g. lectins, soybean proteins, various polyphenols） may inhibit or disturb these systems. The general cel ular and molecular mechanisms involved in the microbiota-host epithelial crosstalk and subsequent gut protection through IAP and iHSPs are reviewed along with their nutritional modulation.Special emphasis is also given to the pig, an economically important species and valuable biomedical model.

Comparison of aerodynamic characteristics between a novel highly loaded injected blade with curvature induced pressure-recovery concept and one with conventional design

This paper introduces a novel design method of highly loaded compressor blades with air injection.CFD methods were firstly validated with existing data and then used to develop and investigate the new method based on a compressor cascade.A compressor blade is designed with a curvature induced pressure-recovery concept.A rapid drop of the local curvature on the blade suction surface results in a sudden increase in the local pressure,which is referred to as a curvature induced ‘Shock＇.An injection slot downstream from the ‘Shock＇ is used to prevent ‘Shock＇ induced separation,thus reducing the loss.As a result,the compressor blade achieves high loading with acceptable loss.First,the design concept based on a 2D compressor blade profile is introduced.Then,a 3D cascade model is investigated with uniform air injection along the span.The effects of the incidence are also investigated on emphasis in the current study.The mid-span flow field of the 3D injected cascade shows excellent agreement with the 2D designed flow field.For the highly loaded cascade without injection,the flow separates immediately downstream from the ‘Shock＇;the initial location of separation shows little change in a large incidence range.Thus air injection with the same injection configuration effectively removes the flow separation downstream from the curvature induced ‘Shock＇ and reduces the size of the separation zone at different incidences.Near the endwall,the flow within the incoming passage vortex mixes with the injected flow.As a result,the size of the passage vortex reduces significantly downstream from the injection slot.After air injection,the loss coefficient along spanwise reduces significantly and the flow turning angle increases.

Compressible flow characteristics around a biconvex arc airfoil in a channel

Shock wave-boundary layer interactions(SWBLI)are observed in several practical high-speed internal flows,such as compressor blades,turbine cascades,nozzles and so on.Shock induced oscillations(SIO),aerodynamic instabilities so-called buffet flows,flutter,aeroacoustic noise and vibration are the detrimental consequences of this unsteady shockboundary layer interactions.In the present study,a numerical computation has been performed to investigate the compressible flow characteristics around a 12%thick biconvex circular arc airfoil in a two dimensional channel.Reynolds averaged Navier-Stokes equations with two equation k-ωshear stress transport(SST)turbulence model have been applied for the computational analysis.The flow field characteristics has been studied from pressure ratio(ratio of back pressure,pb to inlet total pressure,p01)of 0.75 to 0.65.The present computational results have been compared and validated with the available experimental data.The results showed that the internal flow field characteristics such as shock wave structure,its behavior(steady or unsteady)and the corresponding boundary layer interaction are varied with pressure ratio.Self-excited shock oscillation was observed at certain flow conditions.Moreover,the mode of unsteady shock oscillation and its frequency are varied significantly with change of pressure ratio.