Rat insulinoma-derived pancreatic beta-cells express a functional leptin receptor that mediates a proliferative response

In addition to its interaction at hypothalamic sites to affect feeding and energy expenditure, leptin has been shown to exhibit a proliferative response in erythropoietic cells. The functional leptin receptor is also present in pancreatic islets and we now demonstrate that a commonly used clonal insulin secreting beta-cell line, RINm5F, expresses high levels of the Ob-Rb mRNA. Leptin causes an increase in tyrosine phosphorylation of a number of intracellular proteins and a dose related (10 nM-200 nM) increase in expression of the immediate-early gene, c-fos. This precedes a leptin induced proliferative response in serum-deprived RINm5F cells, which suggests that leptin might be involved in the complex regulation of proliferation of the pancreatic beta-cell.     

A dimensioning and tolerancing methodology for concurrent engineering applications II: comprehensive solution strategy

Dimensioning and tolerancing (D&T) is a multidisciplinary problem which requires the fulfillment of a large number of dimensional requirements. However, almost all of the currently available D&T tools are only intended for use by the designer. In addition, they typically provide solutions for the requirements one at time. This paper presents a methodology for determining the dimensional specifications of the component parts and sub-assemblies of a product by satisfying all of its requirements. The comprehensive solution strategy presented here includes: a strategy for separating D&T problems into groups, the determination of an optimum solution order for coupled functional equations, a generic tolerance allocation strategy, and strategies for solving different types of D&T problems. A number of commonly used cost minimization strategies, such as the use of standard parts, preferred sizes, preferred fits, and preferred tolerances, have also been incorporated into the proposed methodology. The methodology is interactive and intended for use in a concurrent engineering environment by members of a product development team.     

Deactivation of ICI low temperature methanol catalyst in an industrial reactor

The deactivation behavior of one of the ICI low temperature methanol catalysts (ICI-51-Z) in a typical ICI multibed quench reactor has been studied in relation to methanol production with respect to time of operation, using some representative sets of plant data collected over two years time span. A pseudo-homogeneous first order model of the methanol synthesis reactor was formulated for this purpose. The best set of catalyst deactivation parameters for different beds was found using a nonlinear parametric estimation technique. Catalyst in the entering bed was found to deactivate most with the time of operation, while subsequent beds deactivate progressively less quickly.     

Electronic Structure of InN/GaN Quantum Dots: Multimillion-Atom Tight-Binding Simulations

The theoretical calculation of the electronic structure of any constituent materials is the first step toward the interpretation and understanding of experimental data and reliable device design. This is essentially true for nanoscale devices where both the atomistic granularity of the underlying materials and the quantum-mechanical nature of charge carriers play critical roles in determining the overall device performance. In this paper, within a fully atomistic and quantum-mechanical framework, we investigate the electronic structure of wurtzite InN quantum dots (QDs) self-assembled on GaN substrates. The main objectives are threefold: 1) to explore the nature and the role of crystal atomicity, strain field, and piezoelectric and pyroelectric potentials in determining the energy spectrum and the wave functions; 2) to address the redshift in the ground state, the symmetry lowering and the nondegeneracy in the first excited state, and the strong band mixing in the overall conduction-band electronic states, which is a group of interrelated phenomena that has been revealed in recent spectroscopic analyses; and 3) to study the size dependence of the internal fields and its impact on the electronic structure as a whole. We also demonstrate the importance of 3-D atomistic material representation and the need for using realistically extended substrate and cap layers (multimillion-atom modeling) in studying the built-in structural and electric fields in these reduced dimensional QDs. The models used in this study are as follows: 1) valence-force-field Keating model for atomistic strain relaxation; 2) 20-band nearest neighbor sp ³ d ⁵ s* tight-binding model for the calculation of single-particle energy states; and 3) microscopically determined polarization constants in conjunction with an atomistic 3-D Poisson solver for the calculation of piezo- and pyroelectric contributions.     

Influence of Some Hofmeister Anions on the Krafft Temperature and Micelle Formation of Cetylpyridinium Bromide in Aqueous Solution

In this work, the effect of some Hofmeister anions on the Krafft temperature (T_K) and micelle formation of cetylpyridinium bromide (CPB) have been studied. The results show that more chaotropic anions increase, while the less chaotropic ones lower the T_K of the surfactant. More chaotropic I^? and SCN^? form contact ion pairs with the cetylpyridinium ion and reduce the electrostatic repulsion between the CPB molecules. As a result, these ions show salting‐out behavior, with a consequent increase in the T_K. In contrast, less chaotropic Cl^? and NO₃^? increase the activity of free water molecules and enhance hydration of CPB molecules, showing a decrease in the T_K. A rather unusual behavior was observed in the case of SO₄^2? and F^?. These strong kosmotropes shift from their usual position in the Hofmeister series and behave like moderate chaotropes, lowering the T_K of the surfactant. Because of the high charge density and the strong tendency for hydration these ions preferentially remain in the bulk. Rather than forming contact ion pairs, these ions stay away from the CPB molecules, decreasing the T_K of the surfactant. In term of decreasing the T_K, the ions follow the order NO₃^? > SO₄^2? > Cl^? > F^? > Br^? > SCN^? > I^?. The critical micelle concentration (CMC) of the surfactant decreases significantly in the presence of these ions due to the screening of the micelle surface charge by the excess counterions. The decreasing trend of the CMC in the presence of the salts follows the order SCN^? > I^? > SO₄^2? > NO₃^? > Br^? > Cl^? > F^?.     

An Environmentally Benign,Highly Efficient Catalytic Reduction of p‐Nitrophenol using a Nano‐Sized Nickel Catalyst Supported on Silica‐Alumina

A green and effective method is reported for the reduction of p‐nitrophenol to p‐aminophenol using a nano‐sized nickel catalyst supported on silica‐alumina in the presence of hydrazine hydrate as an alternative source of hydrogen. It was found that nickel loaded on a silica‐alumina support is a very effective catalyst in the hydrogenation of p‐nitrophenol to p‐aminophenol. Thus it attained 100% conversion in only 69 seconds instead of 260 seconds for commercial Raney nickel. In addition, the possibility to reuse it more than one time with great efficiency gives it another advantage over commercial Rainey nickel which cannot be used more than once. This economical and environmentally friendly method provides a potentially new approach for the synthesis of the intermediate product of paracetamol in industry, which overcomes the drawbacks of the known reduction methods. The prepared catalysts were fully characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), and electron spin resonance (ESR) tehniques.     

Coplanar Waveguide Fed Printed Antenna with Compact Size for Broadband Wireless Applications

A novel and simple coplanar waveguide fed compact antenna is introduced in this paper. The antenna structure combines the advantages of CPW with those of the broadband antenna and simplifies the structure of the antenna by reducing the number of metallization level to construct uni-planar antenna. Prototype of the proposed antenna have been constructed and studied experimentally. The measured results agrees well with the simulated prediction and shows a broad bandwidth of 6 GHz ranging from 3.5 GHz to 9.5 GHz with VSWR ≤2 (return loss ≤−10 dB), which is equivalent to 92.3% impedance bandwidth centered at 6.5 GHz. The proposed antenna shows stable radiation characteristics, gain and axial ratio of less than 1 dB over the whole operating bandwidth. Furthermore, an extensive parametric study was performed to realize the relationship between the resonance frequencies of the broadband antennas and different parameters which is helpful for advancement of the antenna design.