Vibration from a shaft-bearing-plate system due to an axial excitation of helical gears

In this paper, a simplified model is studied to predict analytically the vibration from the helical gear system due to an axial excitation of helical gears. The simplified model describes gear, shaft, bearing, and housing. In order to obtain the axial force of helical gears, the mesh stiffness is calculated in the load deflection relation. The axial force is obtained from the solution of the equation of motion, using the mesh stiffness. It is used as a longitudinal excitation of the shaft, which in turn drives the gear housing through the bearing. In this study, the shaft is modeled as a rod, while the bearing is modeled as a parallel spring and damper only supporting longitudinal forces. The gear housing is modeled as a clamped circular plate with viscous damping. For the modeling of this system, transfer matrices for the rod and bearing are used, using a spectral method with four pole parameters. The model is validated by finite element analysis. Using the model, parameter studies are carried out. As a result, the linearized dynamic shaft force due to the gear excitation in the frequency domain was proposed. Out-of-plan displacement from the forced vibrating circular plate and the renewed mode normalization constant of the circular plate were also proposed. In order to control the axial vibration of the helical gear system, the plate was more important than the shaft and the bearing. Finally, the effect of the dominant design parameters for the gear system can be investigated by this model.     

The solution structure of the complex of Lactobacillus casei dihydrofolate reductase with methotrexate

We have determined the three-dimensional solution structure of the complex of Lactobacillus casei dihydrofolate reductase (18.3 kDa, 162 amino acid residues) formed with the anticancer drug methotrexate using 2531 distance, 361 dihedral angle and 48 hydrogen bond restraints obtained from analysis of multidimensional NMR spectra. Simulated annealing calculations produced a family of 21 structures fully consistent with the constraints. The structure has four alpha-helices and eight beta-strands with two other regions, comprising residues 11 to 14 and 126 to 127, also interacting with each other in a beta-sheet manner. The methotrexate binding site is very well defined and the structure around its glutamate moiety was improved by including restraints reflecting the previously determined specific interactions between the glutamate alpha-carboxylate group with Arg57 and the gamma-carboxylate group with His28. The overall fold of the binary complex in solution is very similar to that observed in the X-ray studies of the ternary complex of L. casei dihydrofolate reductase formed with methotrexate and NADPH (the structures of the binary and ternary complexes have a root-mean-square difference over the backbone atoms of 0.97 A). Thus no major conformational change takes place when NADPH binds to the binary complex. In the binary complex, the loop comprising residues 9 to 23 which forms part of the active site has been shown to be in the "closed" conformation as defined by M. R. Sawaya & J. Kraut, who considered the corresponding loops in crystal structures of complexes of dihydrofolate reductases from several organisms. Thus the absence of the NADPH does not result in the "occluded" form of the loop as seen in crystal studies of some other dihydrofolate reductases in the absence of coenzyme. Some regions of the structure in the binary complex which form interaction sites for NADPH are less well defined than other regions. However, in general terms, the NADPH binding site appears to be essentially pre-formed in the binary complex. This may contribute to the tighter binding of coenzyme in the presence of methotrexate.     

Stretch-induced alkalinization of feline papillary muscle: an autocrine-paracrine system

Myocardial stretch is a well-known stimulus that leads to hypertrophy. Little is known, however, about the intracellular pathways involved in the transmission of myocardial stretch to the cytoplasm and nucleus. Studies in neonatal cardiomyocytes demonstrated stretch-induced release of angiotensin II (Ang II). Because intracellular alkalinization is a signal to cell growth and Ang II stimulates the Na+/H+ exchanger (NHE), we studied the relationship between myocardial stretch and intracellular pH (pHi). Experiments were performed in cat papillary muscles fixed by the ventricular end to a force transducer. Muscles were paced at 0.2 Hz and superfused with HEPES-buffered solution. pHi was measured by epifluorescence with the acetoxymethyl ester form of the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF-AM). Each muscle was progressively stretched to reach maximal developed force (Lmax) and maintained in a length that was approximately 92% Lmax (Li). During the "stretch protocol," muscles were quickly stretched to Lmax for 10 minutes and then released to Li; pHi significantly increased during stretch and came back to the previous value when the muscle was released to Li. The increase in pHi was eliminated by (1) specific inhibition of the NHE (EIPA, 5 micromol/L), (2) AT1-receptor blockade (losartan, 10 micromol/L), (3) inhibition of protein kinase C (PKC) (chelerythrine, 5 micromol/L), (4) blockade of endothelin (ET) receptors with a nonselective (PD 142,893, 50 nmol/L) or a selective ETA antagonist (BQ-123, 300 nmol/L). The increase in pHi by exogenous Ang II (500 nmol/L) was also reduced by both ET-receptor antagonists. Our results indicate that after myocardial stretch, pHi increases because of stimulation of NHE activity. This involves an autocrine-paracrine mechanism in which protein kinase C, Ang II, and ET play crucial roles.     

Heat transfer in the flow of blood‐gold Carreau nanofluid induced by partial slip and buoyancy

Dynamics of blood containing gold nanoparticles on a syringe and other objects with a nonuniform thickness is of importance to experts in the industry. This study presents the significance of partial slip (i.e. combination of linear stretching and velocity gradient) and buoyancy on the boundary layer flow of blood‐gold Carreau nanofluid over an upper horizontal surface of a paraboloid of revolution (uhspr). In this report, the viscosity of the Carreau fluid corresponding to an infinite shear‐rate is assumed as zero, meanwhile, the viscosity corresponding to zero shear‐rate, density, thermal conductivity, and heat capacity were assumed to vary with the volume fraction of nanoparticles. The governing equation that models the transport phenomenon were non‐dimensionalized and parameterized using suitable similarity variables and solved numerically using classical Runge–Kutta method with shooting techniques and MATLAB bvp4c package for validation. The results show that temperature distribution across the flow decreases more significantly with buoyancy‐related parameter when the influence of partial slip was maximized. Maximum velocity of the flow is ascertained at larger values of partial slip and buoyancy parameters. At smaller values of Deborah number and large values of volume fraction, maximum local skin friction coefficient, and local heat transfer rate are ascertained.     

INFLUENCE OF THE AMMONIUM SALT ANION ON THE SYNERGISTIC SOLVENT EXTRACTION OF LANTHANIDES WITH MIXTURES OF THENOYLTRDJLUOROACETONE AND TRIDECYLAMINE

ABSTRACT

The synergistic solvent extraction of Pr, Gd and Yb with mixtures of thenoyltnfluoroacetone ( HTTA) and primary ammonium salt ( tridecylammonium chloride or perchlorate, TDAH( C1, CI0) in dHhas been studied. The composition of the extracted species have been determined as Ln( TTA)₃ TDAHA( A= CI or CIO⁴ ) The values of the equilibrium constant K_{T. s} have been calculated. The influence of the ammonium salt anion on the extraction process has been discussed. The separation factors of the pairs Gd/ Pr and Yb/ Gd have been determined.     

Zircon SHRIMP U-Pb geochronology,geochemistry and petrogenesis of the upper Eocene Shuangmaidi peraluminous granite in Baoshan Block,Western Yunnan Terrain,southwestern China

The Baoshan Block is tectonically located in the middle segment of the Sibumasu plate.Granitic magmatism within the Baoshan Block has been considered weakly active due mainly to very limited exposures during the Himalaya orogenic episode.The geochronological study on the buried Shuangmaidi granite has confirmed the existence of the Cenozoic granitoids in the Baoshan Block.The present study indicates that:(1) It is medium-to coarse-grained two mica phyric granite,characterized by high SiO 2 (73.55%-77.16%) a...     

Complete point symmetry group of the barotropic vorticity equation on a rotating sphere

The complete point symmetry group of the barotropic vorticity equation on a rotating sphere is determined. The method we use relies on the invariance of megaideals of the maximal Lie invariance algebra of a system of differential equations under automorphisms generated by the associated point symmetry group. A convenient set of megaideals is found for the maximal Lie invariance algebra of the spherical vorticity equation. We prove that there are only two independent (up to composition with continuous point symmetry transformations) discrete symmetries for this equation.