Coupled polynomial field approach for elimination of flexure and torsion locking phenomena in the Timoshenko and Euler-Bernoulli curved beam elements

The curvature related locking phenomena in the out-of-plane deformation of Timoshenko and Euler-Bernoulli curved beam elements are demonstrated and a novel approach is proposed to circumvent them. Both flexure and Torsion locking phenomena are noticed in Timoshenko beam and torsion locking phenomenon alone in Euler-Bernoulli beam. Two locking-free curved beam finite element models are developed using coupled polynomial displacement field interpolations to eliminate these locking effects. The coupled polynomial interpolation fields are derived independently for Timoshenko and Euler-Bernoulli beam elements using the governing equations. The presented of penalty terms in the couple displacement fields incorporates the flexure-torsion coupling and flexure-shear coupling effects in an approximate manner and produce no spurious constraints in the extreme geometric limits of flexure, torsion and shear stiffness. the proposed couple polynomial finite element models, as special cases, reduce to the conventional Timoshenko beam element and Euler-Bernoulli beam element, respectively. These models are shown to perform consistently over a wide range of flexure-to-shear (EI/GA) and flexure-to-torsion (EI/GJ) stiffness ratios and are inherently devoid of flexure, torsion and shear locking phenomena. The efficacy, accuracy and reliability of the proposed models to straight and curved beam applications are demonstrated through numerical examples. (C) 2012 Elsevier B.V. All rights reserved.

Air oxygenation chemistry of 4-TBC catalyzed by chloro bridged dinuclear copper(II) complexes of pyrazole based tridentate ligands: synthesis, structure, magnetic and computational studies

Four dinuclear bis(mu-Cl) bridged copper(II) complexes, Cu-2(mu-Cl)(2)(L-X)(2)](ClO4)(2) (L-X = N,N-bis(3,5-dimethylpyrazole-1-yl)-methyl]benzylamine with X = H(1), OMe(2), Me(3) and Cl(4)), have been synthesized and characterized by the single crystal X-ray diffraction method. In these complexes, each copper(II) center is penta-coordinated with square-pyramidal geometry. In addition to the tridentate L-X ligand, a chloride ion occupies the last position of the square plane. This chloride ion is also bonded to the neighboring Cu(II) site in its axial position forming an SP-I dinuclear Cu(II) unit that exhibits small intramolecular ferromagnetic interactions and supported by DFT calculations. The complexes 1-3 exhibit methylmonooxygenase (pMMO) behaviour and oxidise 4-tert-butylcatechol (4-TBCH2) with molecular oxygen in MeOH or MeCN to 4-tert-butyl-benzoquinone (4-TBQ), 5-methoxy-4-tert-butyl-benzoquinone (5-MeO-4-TBQ) as the major products along with 6,6'-Bu-t-biphenyl-3,4,3',4'-tetraol and others as minor products. These are further confirmed by ESI- and FAB-mass analyses. A tentative catalytic cycle has been framed based on the mass spectral analysis of the products and DFT calculations on individual intermediates that are energetically feasible.

Synthesis of a mixed-metal spinel, NiMn2O4, through site-selective substitution in MOF, (NiMn2){C6H3(COO)(3)}(2)]: synthesis, structure and magnetic studies

A mixed-metal metal-organic framework (MOF) compound NiMn2{C6H3(COO)(3)}(2)], I, is prepared hydrothermally by replacing one of the octahedral Mn2+ ions in Mn-3{C6H3(COO)(3)}(2)] by Ni2+ ions. Magnetic studies on I suggest antiferromagnetic interactions with weak canted antiferromagnetism below 8 K. On heating in flowing air I transforms to NiMn2O4 spinel at low temperature (T < 400 degrees C). The thermal decomposition of I at different temperatures results in NiMn2O4 with particle sizes in the nano regime. The nanoparticle nature of NiMn2O4 was confirmed using PXRD and TEM studies. Magnetic studies on the nanoparticles of NiMn2O4 indicate ferrimagnetism. The transition temperature of NiMn2O4 nanoparticles exhibits a direct correlation with the particle size. This study highlights the usefulness of MOF compound as a single-source precursor for the preparation of important ceramic oxides with better control on the stoichiometry and particle size.

Observation of the nuclear magnetic octupole moment of Yb-173 from precise measurements of the hyperfine structure in the P-3(2) state

We measure hyperfine structure in the metastable P-3(2) state of Yb-173 and extract the nuclear magnetic octupole moment. We populate the state using dipole-allowed transitions through the P-3(1) and S-3(1) states. We measure frequencies of hyperfine transitions of the P-3(2) -> S-3(1) line at 770 nm using a Rb-stabilized ring cavity resonator with a precision of 200 kHz. Second-order corrections due to perturbations from the nearby P-3(1) and P-1(1) states are below 30 kHz. We obtain the hyperfine coefficients as A = -742.11(2) MHz and B = 1339.2(2) MHz, which represent a two orders-of-magnitude improvement in precision, and C = 0.54(2) MHz. From atomic structure calculations, we obtain the nuclear moments quadrupole Q = 2.46(12) b and octupole Omega = -34.4(21) b x mu(N). DOI: 10.1103/PhysRevA.87.012512

Computational interrogation of cis-regulatory elements of genes that are common targets of luteotropin and luteolysin in the primate corpus luteum

The rapid recent increase in microarray-based gene expression studies in the corpus luteum (CL) utilizing macaque models gathered increasing volume of data in publically accessible microarray expression databases. Examining gene pathways in different functional states of CL may help to understand the factors that control luteal function and hence human fertility. Co-regulation of genes in microarray experiments may imply common transcriptional regulation by sequence-specific DNA-binding transcriptional factors. We have computationally analyzed the transcription factor binding sites (TFBS) in a previously reported macaque luteal microarray gene set (n = 15) that are common targets of luteotropin (luteinizing hormone (LH) and human chorionic gonadotropin (hCG)) and luteolysin (prostaglandin (PG) F-2 alpha). This in silico approach can reveal transcriptional networks that control these important genes which are representative of the interplay between luteotropic and luteolytic factors in the control of luteal function. Our computational analyses revealed 6 matrix families whose binding sites are significantly over-represented in promoters of these genes. The roles of these factors are discussed, which might help to understand the transcriptional regulatory network in the control of luteal function. These factors might be promising experimental targets for investigation of human luteal insufficiency. (C) 2012 Elsevier B.V. All rights reserved.

Cu-II-azide polynuclear complexes of Cu-4 building clusters with Schiff-base co-ligands: synthesis, structures, magnetic behavior and DFT studies

Three new copper-azido complexes Cu-4(N-3)(8)(L-1)(2)](n) (1), Cu-4(N-3)(6)(L-2)(2)(H2O)(2)] (2), and Cu-4(N-3)(6)(L-3)(2)](n) (3) L-1 is the imine resulting from the condensation of pyridine-2-carboxaldehyde with N-methylethylenediamine, HL2 and HL3 are the condensation products of 2-hydroxy-3-methoxybenzaldehyde with N,N-diethylethylenediamine and N-ethylethylenediamine respectively] have been synthesized by using 0.5 molar equivalents of the Schiff base ligands with Cu(NO3)(2)center dot 3H(2)O and an excess of NaN3. Single crystal X-ray structures show that the basic unit of these complexes contains very similar Cu-4(II) building blocks. While 1 and 3 have overall 1D structures, 2 forms discrete tetranuclear clusters due to blocking of two coordination sites on the tetranuclear cluster by water molecules. Magnetic susceptibility measurements over a wide range of temperatures exhibit the presence of both antiferromagnetic and ferromagnetic exchanges within the tetranuclear unit structures. Density functional theory calculations (using B3LYP functional and two different basis sets) have been performed on the complexes 1-3 to provide a qualitative theoretical interpretation of their overall magnetic behavior.

An inquisitive analysis on the temporal variation of return stroke current essential for producing observed remote electro-magnetic fields

The gross characteristics of spatio-temporal current evolution in the return stroke phase of a cloud-to-ground lightning are rather well defined. However, they by themselves do not ensure the salient features for the resulting remote Electro- Magnetic Fields (EMFs). In spite of significant efforts in the engineering models wherein, the spatio-temporal current distribution all along the channel is specified by the design, all the salient features of remote EMFs could not be achieved. Only the current evolution that ensures the basic characteristics along with its ability to reproduce all the salient features of remote EMFs ranging from 50 m – 200 km from the lightning channel, can be considered as a realistic return stroke channel current. In view of this, the present work intends to investigate on the required fine features of the return stroke current evolution that yields all the desired features. To ensure that the current evolution is not arbitrary but obeys the involved basic physical processes, a recently developed physical model will be employed for the analysis.

Structural, EPR, optical and magnetic properties of alpha-Fe2O3 nanoparticles

alpha-Fe2O3 nanoparticles were synthesized by a low temperature solution combustion method. The structural, magnetic and luminescence properties were studied. Powder X-ray diffraction (PXRD) pattern of alpha-Fe2O3 exhibits pure rhombohedral structure. SEM micrographs reveal the dumbbell shaped particles. The EPR spectrum shows an intense resonance signal at g approximate to 5.61 corresponding to isolated Fe3+ ions situated in axially distorted sites, whereas the g approximate to 2.30 is due to Fe3+ ions coupled by exchange interaction. Raman studies show A(1g) (225 cm(-1)) and E-g (293 and 409 cm(-1)) phonon modes. The absorption at 300 nm results from the ligand to metal charge transfer transitions whereas the 540 nm peak is mainly due to the (6)A(1) + (6)A(1) —> T-4(1)(4G) + T-4(1)(4G) excitation of an Fe3+-Fe3+ pair. A prominent TL glow peak was observed at 140 C at heating rate of 5 degrees C s(-1). The trapping parameters namely activation energy (E), frequency factor (s) and order of kinetics (b) were evaluated and discussed. (C) 2012 Elsevier B.V. All rights reserved.

Hypernuclear matter in strong magnetic field

Compact stars with strong magnetic fields (magnetars) have been observationally determined to have surface magnetic fields of order of 10(14)-10(15) G, the implied internal field strength being several orders larger. We study the equation of state and composition of dense hypernuclear matter in strong magnetic fields in a range expected in the interiors of magnetars. Within the non-linear Boguta-Bodmer-Walecka model we find that the magnetic field has sizable influence on the properties of matter for central magnetic field B >= 10(17) G, in particular the matter properties become anisotropic. Moreover, for the central fields B >= 10(18) G, the magnetized hypernuclear matter shows instability, which is signalled by the negative sign of the derivative of the pressure parallel to the field with respect to the density, and leads to vanishing parallel pressure at the critical value B-cr congruent to 10(19) G. This limits the range of admissible homogeneously distributed fields in magnetars to fields below the critical value B-cr. (c) 2012 Elsevier B.V. All rights reserved.

Classification of Vehicles using Magnetic Dipole Model

This paper presents an efficient approach to the modeling and classification of vehicles using the magnetic signature of the vehicle. A database was created using the magnetic signature collected over a wide range of vehicles(cars). A vehicle is modeled as an array of magnetic dipoles. The strength of the magnetic dipole and the separation between the magnetic dipoles varies for different vehicles and is dependent on the metallic composition and configuration of the vehicle. Based on the magnetic dipole data model, we present a novel method to extract a feature vector from the magnetic signature. In the classification of vehicles, a linear support vector machine configuration is used to classify the vehicles based on the obtained feature vectors.

A Finite Element Method Based Approach for Evaluating the Sensitivity of Faraday-Type Electromagnetic Flow Meter for Liquid Sodium Flow

Faraday-type electromagnetic flow meters are employed for measuring the flow rate of liquid sodium in fast breeder reactors. The calibration of such flow meters, owing to the required elaborative arrangements is rather difficult. On the other hand, theoretical approach requires solution of two coupled electromagnetic partial differential equation with profile of the flow and applied magnetic field as the inputs. This is also quite involved due to the 3D nature of the problem. Alternatively, Galerkin finite element method based numerical solution is suggested in the literature as an attractive option for the required calibration. Based on the same, a computer code in Matlab platform has been developed in this work with both 20 and 27 node brick elements. The boundary conditions are correctly defined and several intermediate validation exercises are carried out. Finally it is shown that the sensitivities predicted by the code for flow meters of four different dimensions agrees well with the results given by analytical expression, thereby providing strong validation. Sensitivity for higher flow rates, for which analytical approach does not exist, is shown to decrease with increase in flow velocity.

Bearing capacity of two interfering strip footings from lower bound finite elements limit analysis

A rigorous lower bound solution, with the usage of the finite elements limit analysis, has been obtained for finding the ultimate bearing capacity of two interfering strip footings placed on a sandy medium. Smooth as well as rough footingsoil interfaces are considered in the analysis. The failure load for an interfering footing becomes always greater than that for a single isolated footing. The effect of the interference on the failure load (i) for rough footings becomes greater than that for smooth footings, (ii) increases with an increase in phi, and (iii) becomes almost negligible beyond S/B>3. Compared with various theoretical and experimental results reported in literature, the present analysis generally provides the lowest magnitude of the collapse load. Copyright (c) 2011 John Wiley & Sons, Ltd.

A unified model for the dynamics of driven ribbon with strain and magnetic order parameters

We develop a unified model to explain the dynamics of driven one dimensional ribbon for materials with strain and magnetic order parameters. We show that the model equations in their most general form explain several results on driven magnetostrictive metallic glass ribbons such as the period doubling route to chaos as a function of a dc magnetic field in the presence of a sinusoidal field, the quasiperiodic route to chaos as a function of the sinusoidal field for a fixed dc field, and induced and suppressed chaos in the presence of an additional low amplitude near resonant sinusoidal field. We also investigate the influence of a low amplitude near resonant field on the period doubling route. The model equations also exhibit symmetry restoring crisis with an exponent close to unity. The model can be adopted to explain certain results on magnetoelastic beam and martensitic ribbon under sinusoidal driving conditions. In the latter case, we find interesting dynamics of a periodic one orbit switching between two equivalent wells as a function of an ac magnetic field that eventually makes a direct transition to chaos under resonant driving condition. The model is also applicable to magnetomartensites and materials with two order parameters. (C) 2013 American Institute of Physics. http://dx.doi.org/10.1063/1.4790845]

A possible connection between antidiabetic and antilipemic properties of psoralea corylifolia seeds and the trace elements present: a LIBS based study

Psoralea corylifolia (PC), a medicinal plant, is used in traditional medicine to treat diabetes. Purpose of the research was to examine the antidiabetic and antilipemic potential of PC and to determine the relationship between its antidiabetic potential and the trace elements present. Wistar rats (150-200 g) with fasting blood glucose (FBG) of 80-110 mg dl(-1)(sub-diabetic) and 150-200 mg dl(-1)(mild diabetic) were selected for the short term antidiabetic studies and severely diabetic rats (FBG > 300 mg dl(-1)) were chosen for the long term antidiabetic and hypolipemic studies of PC seed extract. Laser induced breakdown spectroscopy (LIBS) was used to detect trace elements in the PC extract and the intensity ratios of trace elements were estimated. The dose of 250 mg kg(-1) of PC extract was found to be the most effective in lowering blood glucose level (BGL) of normal, sub, mild and severely diabetic rats during FBG and glucose tolerance test (GTT) studies. Lipid profile studies on severely diabetic rats showed substantial reduction in total cholesterol, triglycerides, very low density lipoprotein, and low density lipoprotein and an increase in the total protein, body weight, high density lipoprotein, and hemoglobin after 28 days of treatment. Significant reduction in urine sugar and protein levels was also observed. LIBS analysis of the PC extract revealed the presence of Mg, Si, Na, K, Ca, Zn and Cl. The study validates the traditional use of PC in the treatment of diabetes and confirms its antilipemic potential. The antidiabetic activity of PC extract may partly be due to the presence of appreciable amounts of insulin potentiating elements like Mg, Ca, and K.

Charge transport and magnetic properties of coaxial composite fibrils of polypyrrole/multiwall carbon nanotubes at low temperature

We report the low temperature electrical and magnetic properties of polypyrrole (PPy)/multiwall carbon nanotube (MWNT) coaxial composite fibrils synthesized by the electro-polymerization method. The iron-filled MWNTs were first grown by chemical vapor deposition of a mixture of liquid phase organic compound and ferrocene by the one step method. Then the PPy/MWNT fibrils were prepared by the electrochemical polymerization process. Electron microscopy studies reveal that PPy coating on the surface of nanotube is quite uniform throughout the length. The temperature dependent electrical resistivity and magnetization measurements were done from room temperature down to 5 and 10 K, respectively. The room temperature resistivity (rho) of PPy/MWNT composite fibril sample is similar to 3.8 Omega m with resistivity ratio R-5 K/R-300 K] of similar to 300, and the analysis of rho(T) in terms of reduced activation energy shows that resistivity lies in the insulating regime below 40 K. The resistivity varies according to three dimensional variable range hopping mechanism at low temperature. The magnetization versus applied field (M-H loop) data up to a field of 20 kOe are presented, displaying ferromagnetic behavior at all temperatures with enhanced coercivities similar to 680 and 1870 Oe at room temperature and 10 K, respectively. The observation of enhanced coercivity is due to significant dipolar interaction among encapsulated iron nanoparticles, and their shape anisotropy contribution as well.