Effect of Fluid Inertia on Journal Bearing Parameters

In the modeling and analysis of rotordynamic systems with journal bearings, the stiffness and damping parameters are usually obtained from the Reynolds equation of hydrodynamic lubrication. The Reynolds equation is derived from the continuity and momentum equations with several assumptions; the principal one among them being that the inertia terms are negligible since the lubricant flow is viscosity-dominated. Some previous work has shown, however, that the effect of fluid inertia on the static and dynamic properties of a bearing is not negligible in many circumstances.

This paper uses a perturbation approach to present a rigorous derivation of the correction terms to be added to account for the effect of inertia in the case of a journal on a short bearing. The governing equation for pressure correction is derived and the corrected stiffness, damping, and inertia coefficients to the first order are displayed as a function of the equilibrium position.     

The intragraft CD8+ T cell response in renal allograft rejection in the mouse

To identify the role of donor class I alloantigens in regulating the CD8+ T cell response to a kidney allograft, we analyzed and compared the CD8+ infiltrate in kidney transplants from MHC class I-deficient (class I-) mouse donors and class I+ controls. One week after transplantation, there was a prominent CD8+ infiltrate in control allografts, whereas CD8+ T cells were virtually absent in grafts from class I- donors. In class I+ allografts, infiltrating CD8+ cells utilized a wide range of T cell receptor (TCR) Vbeta families and their Vbeta usage was similar to that of the systemic CD8+ population. However, there was a modest but significant overrepresentation of cells bearing Vbeta8 in the graft compared with the spleen due to an expansion of CD8+ Vbeta8.3+ cells. This could be detected as early as 1 week and became more pronounced by 3 weeks after transplantation. In 3-week allografts, only 52% of CD8+ cells expressed alphabetaTCR. Among T cells isolated from class I+ grafts, the CD8+ Vbeta8+ cells demonstrated allospecific responses that were numerically larger than responses of the CD8+ Vbeta8- population. In contrast to the early (1 week) time point, significant numbers of CD8+ cells could be isolated from class I- grafts by 3 weeks after transplantation and their Vbeta repertoire resembled that seen in controls. While increasing numbers of CD8+ Vbeta8+ were present in the class I- grafts at 3 weeks, this increase was not statistically significant. Thus, expression of class I alloantigens on a kidney graft plays an important role in regulating the rate of accumulation of CD8+ T cells in rejecting kidney grafts. However, the TCR Vbeta repertoire of the CD8+ T cell infiltrate is largely determined by factors that are independent of normal class I expression on the graft.     

Polyacrylonitrile-based nanofibers—A state-of-the-art review

Polyacrylonitrile (PAN), a well-known polymer with good stability and mechanical properties, has been widely used in producing carbon nanofibers (CNFs) as these have attracted much recent attention due to their excellent characteristics, such as spinnability, environmentally benign nature and commercial viability. Among the various precursors to produce CNFs, PAN has been extensively studied due to its high carbon yield and flexibility for tailoring the structure of the final CNFs as well as the ease of obtaining stabilized products due to the formation of a ladder structure via nitrile polymerization. In view of this, they have applications in areas such as electronics, tissue engineering, membrane filtration and high performance composites. This review presents various combinations of PAN and PAN-based precursors in producing CNFs from the PAN homopolymer or its modified precursors, copolymers, blends and various composites. Various modifications of PAN and their future prospects in different scientific and technological disciplines are addressed.     

Signal-to-noise measurements utilizing a novel dual-energymultimedia detector

Dual-energy measurements are presented utilizing a novel slot-scan digital radiographic imaging detector, operating on gaseous solid state ionization principles. The novel multimedia detector has two basic functional components: a noble gas-filled detector volume operating on gas microstrip principles, and a solid state detector volume. The purpose of this study is to investigate the potential use of this multimedia detector for enhanced dual-energy imaging. The experimental results indicate that the multimedia detector exhibits a large subtracted signal-to-noise ratio. Although the intrinsic merit of this device is being explored for medical imaging, potential applications of the multimedia detector technology In other industrial areas, such as aerospace imaging, aviation security, and surveillance, are also very promising     

Lattice Boltzmann simulations of a radiatively participating fluid in Rayleigh–Benard convection

Thermal radiation is an integral part of the heat transfer process but it is often neglected due to the complexity involved in the analysis of radiative transfer. We use the lattice Boltzmann method as a common computational tool to solve all three modes of heat transfer: conduction, convection, and radiation. This tool is then used to analyze the effect of radiatively participating medium on Rayleigh–Benard convection. We find that increasing the effects of radiation (i) increases the critical Rayleigh number required for the onset of Rayleigh–Benard convection and (ii) affects the temperature and flow patterns of convection rolls significantly changing the net heat transfer between the hot and cold plates. Both these effects are due to the presence of radiation available as an additional mode of heat transfer. Thus, we establish that the unified lattice Boltzmann framework is an effective computational tool for heat transfer and propose to use this method for a large range of problems in science and engineering involving radiative heat transfer.     

Antioxidant activity of two traditional Indian vegetables: Solanum nigrum L. and Solanum torvum L.

In the present study, chloroform, acetone, and methanol extracts of Solanum torvum and Solanum nigrum leaves and fruit were evaluated for their in vitro antioxidant activity using ferric reducing antioxidant power, 2,2-diphenyl-1-picryl-hydrazyl (DPPH), ABTS^·+, iron chelation, and antihemolytic activity. Among the various solvents used, the maximum yield was obtained in chloroform followed by acetone and methanol. The total phenolics were also significantly higher in the chloroform extracts and the in vitro antioxidant activity was shown to be highly dependant on the total phenolic content (p<0.01). The DPPH^· and 2,2′azinobis(3-ethylbenzothiozoline-6-sulfonic acid) diammonium salt (ABTS) cation radical scavenging activities were well proved with the ferric reducing antioxidant capacity of the extracts. The potential of multiple antioxidant activity of samples can be further evidenced by inhibition of reactive oxygen mediated erythrocyte cell lysis and metal ion chelating activity. In conclusion, the results presented here implied leaves and fruits of S. torvum and S. nigrum could be considered as health supplements and nutraceuticals/functional foods.     

Optical investigations on indium oxide nano-particles prepared through precipitation method

Visible light emitting indium oxide nanoparticles were synthesized by precipitation method. Sodium hydroxide dissolved in ethanol was used as a precipitating agent to obtain indium hydroxide precipitates. Precipitates, thus formed were calcined at 600 °C for 1 h to obtain indium oxide nanoparticles. The structure of the particles as determined from the X-Ray diffraction pattern was found to be body centered cubic. The phase transformation of the prepared nanoparticles was analyzed using thermogravimetry. Surface morphology of the prepared nanoparticles was analyzed using high resolution-scanning electron microscopy and transmission electron microscopy. The results of the analysis show cube-like aggregates of size around 50 nm. It was found that the nanoparticles have a strong emission at 427 nm and a weak emission at 530 nm. These emissions were due to the presence of singly ionized oxygen vacancies and the nature of the defect was confirmed through Electron paramagnetic resonance analysis.     

A QFT Procedure for Generating Design Frequencies and Bounds of Guaranteed Accuracy

In this paper, a QFT procedure is presented to systematically determine the following (i) the set of design frequency intervals from a given design frequency range, (ii) the controller bounds of prescribed accuracy at each design frequency interval, and (iii) the controller phase intervals for efficient bound generation at each design frequency interval. The procedure is given for the robust gain-phase margin specifications, based on several new results derived in the paper in the interval analysis framework. The procedure is demonstrated on a significant practical problem concerning the longitudinal motion of an aircraft.     

Multiple-model based predictive control of nonlinear hybrid systems based on global optimization using the Bernstein polynomial approach

In this paper, we propose a Bernstein polynomial based global optimization algorithm for the optimal feedback control of nonlinear hybrid systems using a multiple-model approach. Specifically, we solve at every sampling instant a polynomial mixed-integer nonlinear programming problem arising in the model predictive control strategy. The proposed algorithm uses the Bernstein polynomial form in a branch-and-bound framework, with new ingredients such as branching for integer decision variables and fathoming for each subproblem in the branch-and-bound tree. The performance of the proposed algorithm is tested and compared with existing algorithms on a benchmark three-spherical tank system. The test results show the superior performance of the proposed algorithm.     

Enhanced screening of glutathione-trapped reactive metabolites by in-source collision-induced dissociation and extraction of product ion using UHPLC-high resolution mass spectrometry

A selective and sensitive approach, called extraction of product ion (XoPI) method, was developed for the detection of l-glutathione (GSH)-trapped reactive metabolites employing an Orbitrap high resolution mass spectrometer. Fragmentation of GSH conjugates in the negative ion mode leads to a product ion, deprotonated γ-glutamyl-dehydroalanyl-glycine (m/z 272.0888). As a means of utilizing this property, negative ion high resolution MS data were collected from in vitro incubations by monitoring ions from m/z 269.5 to 274.5 under in-source collision-induced dissociation. Extraction of product ions at m/z 272.0888 ± 5 ppm from this data resulted in a chromatogram exhibiting deprotonated γ-glutamyl-dehydroalanyl-glycine as the major peaks with no or very few interferences. Therefore, peaks in this extracted product ion chromatogram potentially came from GSH-trapped reactive metabolites. The GSH conjugate parent ions were then confirmed in the corresponding full scan MS data, and their structures were identified from their MS(2) fragmentation patterns. The effectiveness of the approach was assessed with four model compounds, amodiaquine, clozapine, diclofenac, and fipexide, all well-known to form GSH-trapped reactive metabolites, following incubation in human liver microsomes supplemented with β-nicotinamide adenine dinucleotide 2'-phosphate reduced tetrasodium salt (NADPH) and GSH. The results from XoPI method were compared to two other commonly employed liquid chromatography-mass spectrometry (LC-MS) methods: precursor ion scan method and mass defect filter method. Overall, the XoPI method was more selective and sensitive in detecting the GSH conjugates. Many GSH conjugates previously not reported were detected and characterized in this study.