Diffraction Enhancement of the Stern—Gerlach Effect for a Neutron in a Crystal

JETP Letters - The spatial splitting of an unpolarized neutron beam into two spin components in an inhomogeneous magnetic field (an analog of the Stern-Gerlach experiment) with small gradients has...     

Precise study of the Z/γ* boson transverse momentum distribution in pp collisions using a novel technique

Using 7.3 fb?1 of pp collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable φ(η)*, which probes the same physical effects as the Z/γ* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the φ(η)* distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.     

In situ synthesis of cobalt ferrite nanoparticle/polymer hybrid from a mixed Fe–Co methacrylate for magnetic hyperthermia

Hyperthermic CoFe₂O₄ nanoparticle (CFO NP)/polymer hybrids were synthesized by hydrolysis–condensation from a complex of Co and Fe possessing methacrylate ligands. Single-crystal analysis revealed that the complex consisted of two Co and four Fe metal atoms coordinated by methacrylate and 2-methoxyethoxy groups. The complex was copolymerized with 2-hydroxyethyl methacrylate (HEMA) and the resulting copolymer was then hydrolyzed to form a CFO NP/copolymer of poly(methacrylate) and poly(2-hydroxyethyl methacrylate) hybrid. Copolymerization with HEMA enhanced the stability of the hybrid in water. The size and magnetic properties of CFO in the hybrid were controlled by adjusting the hydrolysis conditions. Moreover, the hybrid generated heat under an alternating current magnetic field; its exothermal properties depended on the magnetic properties of the hybrid, the strength of the applied field, and the CFO NP content in the agar phantom matrix.     

Stability study of a model for the Klein–Gordon equation in Kerr space-time

The current early stage in the investigation of the stability of the Kerr metric is characterized by the study of appropriate model problems. Particularly interesting is the problem of the stability of the solutions of the Klein–Gordon equation, describing the propagation of a scalar field of mass $\mu $ in the background of a rotating black hole. Rigorous results prove the stability of the reduced, by separation in the azimuth angle in Boyer–Lindquist coordinates, field for sufficiently large masses. Some, but not all, numerical investigations find instability of the reduced field for rotational parameters $a$ extremely close to $1$ . Among others, the paper derives a model problem for the equation which supports the instability of the field down to $a/M \approx 0.97$ .     

Effect of calcination temperature on the structure and performance of CeOx–MnOx/TiO2 nanoparticles for the catalytic combustion of chlorobenzene

Journal of Nanoparticle Research - Janus droplets with two opposite faces of different physical or chemical properties have great potentials in many fields. This paper reports a new method for...     

Ionic conduction and phase separation studies in P(VdF-HFP))-LiClO4-dedoped polyaniline nanofiber composite polymer electrolytes — II: Effect of incorporation of PC and DEC

In the present work, ionic transport and interfacial stability of dedoped (insulating) polyaniline (PAni) nanofibers dispersed P(VdF-HFP) based nanocomposite gel polymer electrolytes have been investigated. Samples of P(VdF-HFP)-(PC+DEC)-LiClO₄-x wt. % dedoped PAni nanofibers (x = 0, 2, 4, 6, 8, 10) are prepared by conventional solution casting technique. By analysis of SEM, XRD and impedance spectroscopy results it has been demonstrated that the incorporation of up to 6 wt. % of dedoped PAni nanofibers to P(VdF-HFP)-(PC+DEC)-LiClO₄ polymer electrolyte system significantly enhances the ionic conductivity and interfacial stability of the electrolyte system. Above that concentration phase separation of PAni nanofibers is observed leading to decrease in ionic conductivity. The aggregated phase decreases the porosity, which results in lower ionic conductivity as confirmed by SEM. Experiments on the interfacial stability reveals that the stability of polymer electrolytes containing nanofibers is better than that of nanofiber free polymer electrolytes.     

The study of the valence bond property in a two—different—quantum—dot molecule

The electronic energy spectrum and wavefunction of a quantum-dot molecule are studied by means of the finite-element solution of the single electron Schr?dinger equation. We find that the nature of the coupling can be covalent, ionic, or "intermediate" new mixed states, depending on various parameters such as the separation distance between two dots, the height of potential barrier, matching of the energies and parities of the orbital localized on each dot. The bond property can be used to explain the experimental result obtained by Oosterkamp et al. (1998 Nature 395 873).     

Effect of the shape of an organic water–coal fuel particle on the condition and characteristics of its ignition in a hot air flow

The results of experimental studies of the effect of the shape of an organic water–coal fuel (OCWF) particle on its ignition delay time and the time of its complete burnout in a hot air flow are reported. Three most common shapes of real particles, such as spherical, ellipsoidal, and irregular-polyhedron-like, are considered. It is shown that the shortest ignition delay time and the time of complete burnout correspond to polyhedron- shaped OCWF particles. Conditions are identified under which this factor significantly influences the ignition characteristics. The experiments were carried out at initial particle sizes (averaged maximum values) of 0.5–5 mm and temperatures and velocities of the oxidant flow of 600–900 K and 0.5–5 m/s, respectively. The main components of the studied fuels were coal processing wastes and waste motor, turbine, and transformer oils.     

Application of liquid scintillation inclusion techniques for the simultaneous determination of alpha and beta activities in composite samples – A preliminary study

Present work highlights liquid scintillation inclusion techniques as a tool for simultaneous determination of gross α and β activities in composite samples. This preliminary study comprises a preamble exercise to check whether Automatic Efficiency Control (AEC) and knee point inclusion techniques which are conventionally used for analysis of two β-emitting radio-nuclides in a mixture, can be implemented for quantification of gross α and β activities in composite samples. In inclusion techniques, two counting regions are set such that there are spill-up and spill-down of pulse events in each region from both types of radio-nuclides. AEC which is built-in feature in Packard Tri-Carb 2900 TR Liquid Scintillation Counter (LSC) provides automatic counting region adjustments for single and dual label samples according to the degree of quench present in sample. While knee point inclusion technique requires manual Lower Level (LL) and Upper Level (UL) discriminator setting to define two counting regions. In the present study, α/β spiked composite samples were treated as dual label samples with α and β radio-nuclides as two distinct entities contributing to the gross activities and analyzed employing AEC and knee point inclusion techniques. Instrument discriminator settings and regions of interest (ROI) were evaluated to determine optimum counting conditions for both the techniques. Three sets of pure alpha and pure beta standards simulating the activity concentrations of real samples in terms of α/β activity ratios were used to calibrate LSC. Calibration methodology for Packard Tri-Carb 2900 TR LSC with respect to the above measurements using ²⁴¹Am, ³⁶Cl and ⁹⁰Sr/⁹⁰Y calibration standards is explained in detail. The practicability and working performance of these techniques was checked by the validation trials with spiked synthetic samples covering range of α/β activity ratios from 1:1 to 1:50 and 50:1. Procedures have been tested by comparison with, established PSA technique and repeatability has been evaluated.     

Effect of water–methanol content on the structure of Nafion in the sandwich model and solvent dynamics in nano-channels; a molecular dynamics study

Continuing an ongoing study, molecular dynamics (MD) simulations were performed to investigate the effects of methanol concentration on Nafion morphology, such as the size of solvent cluster, solvent location, and polymer structure via the sandwich model. Our survey shows that high methanol concentrations resulted in increment of solvent cluster size in Nafion membrane. The sulfonic acid clusters also befall much in order as subsequent layers of such ionic clusters are formed. The number of neighbouring hydronium ions around a sulfur atom is independent of methanol concentration, but the first shell of hydronium and water around sulfonic acid clusters is broader. Although methanol would prefer to interact with water molecules rather than sulfonic acid groups, gathering of methanol molecules via hydrophobic self-aggregation is preferred. Methanol is located closer to the hydrophobic part of the polymer than water, while water is located closer to the hydrophilic part of the polymer. It was found that methanol distributes specifically more than water in nano-channels. Investigation of solvent dynamics in nano-channels shows that diffusion coefficients (D) of water, methanol, and hydronium decrease with increasing methanol concentration and they may be ordered as follows: D _Water?>?D _Methanol?>?D _Hydronium (D _Water?≈?1.6–2.0D _Methanol and D _Methanol?≈?2.1–3.0D _Hydronium).     

Improvement in the discharge characteristics of zinc–carbon primary cells: a comparative study with various carbon additives

The discharge capacity of zinc–carbon cells (Leclanche cell) is limited by the performance of the cathode material (MnO₂) and physical properties of carbon powder added to MnO₂. Acetylene black, Vulcan XC 72, Black Pearls 2000, and a carbon composite (consisting of 50% acetylene black and 50% Black Pearls 2000®) were evaluated as cathode additives in test cells and were compared. The study indicated that cathode mixture with Black Pearls 2000®showed improvement in performance than acetylene black, the most commonly used carbon in commercial zinc–carbon cells. The performance of the test cells was found to have a correlation with the physical properties of the carbons used.     

An integrated simulation and statistical technique for?investigating the effect of interpenetration polymer brushes in a good solvent

This study presents a novel approach for analyzing the interaction between two parallel surfaces grafted with polymer brushes in a good solvent. In the proposed approach, MD simulations are performed to establish the mean brush height and the standard deviation of the brush height distribution for a given value of the surface separation. The corresponding probability density function (PDF) of the brush height is then determined both with and without the assumption of a brush interpenetration effect, respectively, and a statistical technique is applied to compute the corresponding interaction free energy per unit area of the grafted substrates. Finally, the Derjaguin approximation is employed to determine the corresponding value of the interaction force between the two surfaces. The results obtained for the interaction free energy and interaction force are compared with those derived using the Alexander and de Gennes (AdG) model and the Milner, Witten and Cates (MWC) model, respectively. The value of the normalized interaction free energy computed using the present method is higher than that obtained from the AdG and MWC models at larger surface separations when the brush interpenetration effect is ignored. However, the results obtained by the current method for the interaction force are found to be in better agreement with the experimental data than those obtained using the AdG or MWC models. The enhanced performance of the proposed method is attributed primarily to the use of an adaptive non-Gaussian PDF of the brush height to model the effects of brush interpenetration and fluctuations in the brush conformation at different distances from the grafting plane.     

Numerical study of friction-induced instability and acoustic radiation – Effect of ramp loading on the squeal propensity for a simplified brake model

This paper presents a numerical study of the influence of loading conditions on the vibrational and acoustic responses of a disc brake system subjected to squeal. A simplified model composed of a circular disc and a pad is proposed. Nonlinear effects of contact and friction over the frictional interface are modelled with a cubic law and a classical Coulomb?s law with a constant friction coefficient. The stability analysis of this system shows the presence of two instabilities with one and two unstable modes that lead to friction-induced nonlinear vibrations and squeal noise. Nonlinear time analysis by temporal integration is conducted for two cases of loadings and initial conditions: a static load near the associated sliding equilibrium and a slow and a fast ramp loading. The analysis of the time responses shows that a sufficiently fast ramp loading can destabilize a stable configuration and generate nonlinear vibrations. Moreover, the fast ramp loading applied for the two unstable cases generates higher amplitudes of velocity than for the static load cases. The frequency analysis shows that the fast ramp loading generates a more complex spectrum than for the static load with the appearance of new resonance peaks. The acoustic responses for these cases are estimated by applying the multi-frequency acoustic calculation method based on the Fourier series decomposition of the velocity and the Boundary Element Method. Squeal noise emissions for the fast ramp loading present lower or higher levels than for the static load due to the different amplitudes of velocities. Moreover, the directivity is more complex for the fast ramp loading due to the appearance of new harmonic components in the velocity spectrum. Finally, the sound pressure convergence study shows that only the first harmonic components are sufficient to well describe the acoustic response.     

In-beam study of the level crossing resonance on the 4 μs 2 9+ isomer of69Ge in a Zn single crystal

The time-integral angular distribution was measured as a function of an external magnetic field for γ-rays from the 398 keV ₂ ⁹⁺ state of⁶⁹Ge populated by bombarding a Zn single crystal with a natural α-beam from a cyclotron. Clear resonances of dispersion as well as Lorentz type having a narrow width consistent with the natural width (τ=4 μs) were observed at B_res=9.15 kG corresponding to the first level-crossing resonance of the ₂ ⁹⁺ state due to the combined collinear magnetic and quadrupole interactions. The effects of noncollinearity were also demonstrated and compared with theory. As an application of this resonance method, the temperature dependence of the quadrupole interaction frequency was measured.     

Effect of low level laser irradiation on the proliferation of myoblasts—the skeletal muscle precursor cells: an experimental in vitro study

The aim of this paper is to study the effect of low-level laser irradiation (LLLI) on proliferation of myoblasts in culture. Myoblasts derived from rat skeletal muscle were irradiated by He-Ne laser with different doses. Compared with nonirradiated control group, the number of myoblasts increased when the cells in normal culture conditions were exposed to the laser of specific energy density. The amount of cells with proliferating cell nuclear antigen (PCNA) positive expression and the 5-bromo-2′-deoxyuridine (BrdU) incorporation rate after laser irradiation were also higher than that of the control group, suggesting that LLLL at certain doses can effectively enhance myoblasts growth activity in vitro. This study firstly demonstrated that stimulating myoblasts to enter into proliferative stage from initial resting state was an important mechanism of regeneration and repair of injured skeletal muscle promoted by LLLI in clinical treatment.     

Effect of Ni/Mn ratio on the performance of LiNi x Mn2 − x O4 cathode material for lithium-ion battery

Lithium nickel manganate is recognized as a type of promising cathode material for lithium-ion battery, due to its advantages such as high voltage, high power density, and relative lower cost. In this paper, a series of LiNi _x Mn_2???x O₄ cathode materials with various molar ratio of Ni/Mn have been prepared with a co-precipitation method, followed by a solid state reaction, and the effect of the molar ratio of Ni/Mn on the structure and properties of materials are intensively investigated by means of X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), and performance measurements, etc. It is revealed that all the samples with x from 0 to 0.5 have well-defined spinel structure and fit well to Fd-3 m space group. With the increase of the molar ratio of Ni/Mn, the diffraction peaks shift to higher angle slightly and the lattice parameter decreases gradually by the XRD results. Furthermore, it is found that the capacity at the 4.0 V plateau decreases while the capacity at 4.7 V plateau increases with the increase of the ratio of Ni/Mn, and the total discharge capacity shows growth trend with the increase of Ni content. It is important that all the samples with various molar ratio of Ni/Mn exhibit good cyclic stability. Based on the experimental results, we suggest that the Ni may incorporate into the lattice of LiMn₂O₄ substituting of Mn. The plateau at 4.7 V is related to the Ni ions and the plateau at 4.0 V is related to the Mn ions in the materials.     

Conductivity or rheology? Tradeoff for competing properties in the fabrication of a gel polymer electrolyte based on chitosan-barbiturate derivative

Chitosan-barbiturate (Ch-Ba) derivative was synthesized to afford organosolubility. Attachment of Ba onto the Ch backbone was confirmed by ¹H NMR with peaks at 8.2 and 11.1 ppm, and FTIR with bands at 1679 and 1739 cm^?1 belonging to the Ba ring. This derivative was used as a host polymer in the preparation of gel polymer electrolytes. The components of the gel consist of tetrapropylammonium iodide (TPAI) as the salt, SiO₂ nanofiller (NF) as the mechanical stabilizer, and dimethyl sulfoxide (DMSO) as the solvent. The necessary formulation required to produce the gel was studied using response surface models by means of artificial neural networks. Electrochemical and rheological behaviors were studied and the simulated model predicted conductivities were as high as 8.51 mS cm^?1 while still maintaining a solid-like gel structure in the region where storage modulus dominated loss modulus, G″/G′?<?1.     

Assessment of metabolic changes in the striatum of a MPTP-intoxicated canine model: in vivo ¹H-MRS study of an animal model for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta, which projects to the striatum. We induced a selective loss of nigrostriatal dopamine neurons, by infusing the mitochondrial complex 1 inhibitor 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) into adult beagle dogs (N=5). Single voxel ¹H water suppressed magnetic resonance spectroscopy (¹H-MRS) at 3 T was used to assess the metabolic changes in the striatum of canine before and after MPTP intoxication. The metabolite spectra obtained from the striatum (voxel size: 2 cm³) showed a lower N-acetyl aspartate to total creatine (creatine+phosphocreatine) ratio after MPTP intoxication. There were no significant differences in other metabolite ratios such as glutamate+glutamine, choline-containing compounds (glycerophosphocholine+phophorylcholine and myo-inositol). Our findings indicated that ¹H-MRS is a sensitive, noninvasive measure of neural toxicity and biochemical alterations of the striatum in a canine model of PD, and further studies are needed to confirm brain metabolic changes in association with progression of MPTP-intoxication.     

The calculation of singular points in the supercritical region for a system with a Lennard—Jones interaction potential

In this work the positions of the critical point, the supercritical point, and the maximum fluctuation point in a supercritical isotherm were found for a system with the Lennard—Jones interaction potential. Virial coefficients and methods based on accelerated convergence of the perturbation-theory series, which are well known for such systems, were used. The results were compared with computer-simulation data. As has been established, if one uses the positively defined Weeks—Chandler—Andersen potential as a reference system, the calculated parameters tend monotonically to exact values as a function of the number of virial coefficients. This decomposition is favorably different from the virial one, where the aspiration is not monotonic. These results indicate that this method makes it possible to determine the positions of the three vertices of the supercritical triangle with an accuracy that is comparable to that of a simulated experiment.     

A simple method of extracting the polarization charge density in the AlGaN/GaN heterostructure from current—voltage and capacitance—voltage characteristics

An Ni Schottky contact on the AlGaN/GaN heterostructure is fabricated. The flat-band voltage for the Schottky contact on the AlGaN/GaN heterostructure is obtained from the forward current-voltage characteristics. With the measured capacitance-voltage curve and the flat-band voltage, the polarization charge density in the AlGaN/GaN heterostructure is investigated, and a simple formula for calculating the polarization charge density is obtained and analyzed. With the approach described in this paper, the obtained polarization charge density agrees well with the one calculated by self-consistently solving Schrodinger's and Poisson's equations.