An investigation of the magnetic anisotropy change in BaFe12−2xTixCoxO19 single crystals

This paper presents a study of BaFe_12−2xTi_xCo_xO₁₉, where the substitution-induced magnetic anisotropy change has been investigated through magnetic measurements and single-crystal neutron diffraction. The study shows that the magnetic structures of BaFe_12−2xTi_xCo_xO₁₉ change drastically when the temperature and the substitution rate are altered. It is proposed that an antiferromagnetic mode in doped Ba-hexaferrites is one of the key elements to understand the origin of their promising microwave properties.     

Sulfur isotope effect on95Mo nuclear magnetic shielding in MoS 4 2−

By Fourier transform high resolution NMR spectroscopy the⁹⁵Mo resonance lines of the tetrathiomolybdate species Mo³²S ₄ ^2? and Mo³²S₃ ³⁴S^2? have been resolved in aqueous solutions of potassium- and ammonium tetrathiomolybdate. An isotope effect on the Larmor frequency of (0.09±0.01) ppm to lower frequency was found for the substitution of a³²S atom by a³⁴S atom in the MoS ₄ ^2? ion.     

An investigation on the acoustic characteristics of microperforated muffler

I.lntroductionTheac0usticperformanccofmicropcrforatedmumerhasbeengreatlynoticedinre-ccntyears.Especially,itshighsi1encingva1ueandbroadsi1encingfrequencyrangeenableittobeusedwidelyinmanyyiclds,suchasvehicleexhaustsystem,ventilator.Butitisdifficulttodesignagoodsilcnccrbecauseoritscomp1exacousticperformanccwithinPerforatedtubes.Thegoverningwaveequationofmicroperforatedmufflerisnotlinearduetothenonuniformmassflowofgasaswc11asthetcmpcraturegradientalongthePerforatedducts.Inordertoutilizethegoodsi…     

Density-functional calculations of the nuclear magnetic shielding and indirect nuclear spin–spin coupling constants of three isomers of C20

The parameters of the nuclear magnetic resonance (NMR) spectrum – shielding constants and indirect spin–spin coupling constants – of three isomers of C₂₀ are studied using density-functional theory. The performance of different exchange–correlation functionals is analysed by optimising the geometry for the ring, bowl and cage isomers, followed by a computation of the NMR constants at the optimised structure. The results are analysed and rationalised by performing comparisons of the three isomers with one another and with related systems such as polyynes (for the ring), o-benzyne (for the bowl) and C₆₀ (for the cage). The shielding and spin–spin parameters calculated using the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional are sufficiently reliable to assist in future experimental NMR studies of C₂₀ and, in particular, the identification of its isomers.     

23Na nuclear magnetic resonance investigation of the lattice distortion in α-NaxV2O5

The full temperature dependence of the electric field gradient tensor at the Na sites has been determined by nuclear magnetic resonance (NMR) in the temperature range 8–330 K in α-Na_{x 2}O₅ (x = 0.996). Above the spin-Peierls transition (T _c = 34.7 K), only a single Na site is observed in agreement with the Pmmn space group proposed to describe this compound as the first example of a 1/4-filled ladder system. Below T_c, eight distinct quadrupolar²³Na sites are observed according to the distortion wave vector k_c = (1/2, 1/2, 1/4) previously reported. In addition, the opening of a spin gap is evidenced by a rapid drop of the magnetic hyperfine shift²³K at T_c. The results are discussed in the context of a charge-order-driven spin-Peierls transition.     

A nuclear magnetic resonance investigation of γ-aminobutyric acid (GABA)

The temperature dependence of the ¹⁴N nuclear quadrupole resonance frequency in hexamethylphosphorus traimide, P[N(CH₃)₂]₃, and hexamethylphosphoric triamide, O=P[N(CH₃)₂]₃, has been studied between 77 K and the melting points. Values for the torsional oscillation frequencies v _t and the empirical parameter b, a function of v _t and the associated moment of inertia I, and of the volume-dependence parameter α, are reported. The values are consistent with previously reported values for thiourea, S=C(NH₂)₂.     

Calculation of interaction of the stretching and bending vibrations of HF in the hydrogen-bonded complex [F(HF)2]?

Vibrations of the [F(HF)₂]^? complex are calculated with allowance for the anharmonic interactions of the stretching vibrations of HF monomers and their rotations about the centers of gravity of HF in the plane of the complex. A four-dimensional vibrational Schr?dinger equation is solved using a potential energy surface calculated in the MP2/6-311++G(3df,3pd) approximation with the superposition of atomic functions of the monomers taken into account. The equilibrium and vibrationally averaged structures of the complex are determined. The frequencies and intensities for spectral transitions from the ground state to a number of excited vibrational states are calculated. It is shown that, due to resonances between the excited states of the stretching modes and doubly excited states of the bending modes, the overtone transitions associated with the bending modes borrow a significant part of the intensity of fundamental stretching transitions.     

Manganese-enhanced magnetic resonance imaging investigation of the interferon-α model of depression in rats

Therapeutic effects of interferon-α (IFN-α) are known to be associated with CNS toxicity in humans, and in particular with depression symptoms. Animal models of IFN-α-induced depression (sickness behaviour) have been developed in rodents using various preparations, dosing schedules or routes of administrations. In this work, Manganese Enhanced MRI (MEMRI) has been applied to investigate an experimental model of sickness behaviour induced by administration of IFN-α in rats. IFN-α (3.10⁵ U/kg), or vehicle, was daily administered i.p., for 7 days in rats (n = 20 IFN-α treated and n = 20 controls). After treatment, animals were assigned to behavioural (n = 10 treated, n = 10 control) or MRI (n = 10 treated and n = 10 control) studies. Animals assigned to the MRI study received two repeated i.p. injections of MnCl₂, before image acquisition. Images were acquired at 4.7 T using T₁ mapping for determination of Mn concentration in brain. After co-registration of T₁ maps to a digital brain atlas, differences between brains of treated and untreated animals were assessed pixel-to-pixel by statistical analysis.     

An investigation on dysphotopsia of a sigma-edged intraocular lens

A sigma-edged design of intraocular lens (IOL) is proposed to minimize the reflected glare images associated with the edge. The optimal sigma inverse edge is investigated when pupil diameter is 5.0 mm by the established Escudero-Sanz's wide angle model. The non-sequential ray tracing program of Zemax-EE (Zemax Development Corp., San Diego, USA) is used to investigate the sigma edge of reducing the potential for edge glare phenomena. The results show that sigma-edged design can significantly reduce the reflected glare intensity on retina if the angle of its inverse edge is taken from 20 to 70 degrees.     

An ab initio study of the Ne-CO complex

A new ab initio potential energy surface of the Ne-CO complex is developed using single and double excitation coupled-cluster theory with noniterative treatment of triple excitations [CCSD(T)].The potential has a minimum value of 49.396 cm 1 at R e = 6.40a 0 with approximately T-shaped geometry(θ e = 82.5).Bound state energies are calculated up to J = 12.The theoretically predicted transition frequencies and spectroscopic constants are in good agreement with the available experimental results.     

Density-functional theory calculation of the nuclear magnetic resonance indirect nuclear spin—spin coupling constants in C60

Density-functional theory is used to study the nuclear magnetic resonance (NMR) indirect nuclear spin-spin coupling constants in C₆₀. Knowledge of these coupling constants may help in the analysis of future experimental NMR studies of ¹³C-enriched C₆₀. At the Becke 3-parameter Lee-Yang-Parr (B3LYP) Kohn-Sham level, the one-bond couplings within pentagons and between pentagons are 62 Hz and 77 Hz, respectively; the corresponding geminal couplings are 7 Hz and 1 Hz, respectively. Except for the vicinal couplings (about 4 Hz), the long-range couplings are all 1 Hz or smaller. This is the largest theoretical calculation to date of the complete set of indirect nuclear spin-spin coupling constants of a molecular system; it has been made possible by solving the response equations only for the perturbing operators related to one nuclear magnetic moment, making the calculation feasible.     

Experimental and theoretical study of the ν(HF) absorption band structure in the H2O…HF complex

The νHF absorption band shape of the H₂O…HF complex is studied in the gas phase at a temperature of 293 K. The spectra of H₂O/HF gaseous mixtures in the range 4000–3400 cm^?1 are recorded at a resolution of 0.2–0.02 cm^?1 with Bruker IFS-113v and Bruker IFS-120 HR vacuum Fourier spectrometers in a 20-cm cell. The spectra of the H₂O…HF complex in the region of the ν₁(HF) absorption band are obtained by subtracting the calculated spectra of free H₂O and HF molecules from the experimental spectrum. The ν₁ band of the H₂O…HF complex has an asymmetric shape with a low-frequency head, an extended high-frequency wing, and a characteristic vibrational structure. Two approaches are used to calculate the ν1 band shape as a superposition of rovibrational bands of the fundamental and hot transitions involving the low-frequency modes of the complex. The first approach is based on a simplified semiempirical procedure. The second approach relies on a nonempirical anharmonic calculation of the vibrational energy levels, the frequencies and intensities of the corresponding transitions, and the rotational constants. These parameters are obtained by calculating ab initio the potential energy and dipole moment surfaces in the second-order Möller-Plesset approximation and using the variational method to solve one-, two-, and three-dimensional anharmonic vibrational problems. The absorption spectrum of the complex in the range 3600–3720 cm^?1, reconstructed using the nonempirical electro-optical parameters, reproduces rather well the main features of the experimental spectrum, including the relative intensities of peaks of the vibrational structure. However, the interpretation of most of the structural features of the spectrum differs from that adopted in the semiempirical scheme. First of all, it follows from the results of nonempirical calculation that the central, most intense, maximum of the experimental spectrum should correspond to the v ₁=1←0 transition from the ground vibrational state. This fact gives rise to a new value of the vibrational transition frequency ν ₁ ⁰ in the H₂O…HF complex equal to 3635 cm^?1, which is higher than the commonly accepted value of 3608 cm^?1.     

Effect of the Aharonov-Bohm flux on the magnetic gap soliton in antiferromagnetic chain

Employing the double-sublattice, the coherent state ansatz, and the time-dependent variational principle, we have studied the effects of the Aharonov-Bohm flux on the soliton in one-dimensional antiferromagnetic chain. The results show that the Aharonov-Bohm flux have an effect on the peak, the width, the energy and the spatial configuration of the spin of the soliton.     

Effects of Fe－Fe bond length change in NaZn13-type intermetallic compounds on magnetic properties and magnetic entropy change

In this paper the effects of Fe－Fe bond length change on magnetic properties and magnetic entropy change have been investigated on LaFe_{12.4-x}Si_xCo_{0.6} and LaFe_{12.3-x}Al_xCo_{0.7} intermetallic compounds. According to the analyses of Fe－Fe bond length change, the variation of Curie temperature and the unusual magnetic phase transition which results in the large magnetic entropy change were explained. The effects of the substitution of Co and Si for Fe on magnetic entropy change and field-induced itinerant-electron metamagnetic transition in LaFe_{12.4-x}Si_xCo_{0.6} compounds were also studied and the considerable magnetic entropy change has been achieved.     

An investigation of the gate dependence in an electronic Aharonov–Bohm interferometer

In this study we have obtained the dependence of the electronic distribution on the gate shape and the applied gate voltage in a quantum Hall effect based Aharonov–Bohm interferometer using a method presented in our previous studies. We have discussed the relation between the distribution of incompressible strips and observation of Aharonov–Bohm oscillations. We have obtained the distributions of the incompressible strips for various gate voltages and have shown that a gate potential sweep and a magnetic field sweep would be equivalent. Our calculations also predict that for wider gate separations it is possible observe a silent region while sweeping the magnetic field or the gate voltage.     

Shift of proton magnetic shielding in ClH ··· Y dimers (Y = N2, CO,BF)

The change in the proton magnetic shielding constant of ClH on the formation of the linear hydrogen-bonded ClH?·?·?·?Y (Y?=?N₂,?CO,?BF) complexes was determined by GIAO ab initio computations at the B3LYP/aug-cc-pVQZ level of theory. The characteristic downfield shift of the isotropic proton magnetic resonance in the vibrationally red-shifted complexes (ClH?·?·?·?N₂, ClH?·?·?·?CO and ClH?·?·?·?BF) is significantly larger than in the blue-shifted complexes (ClH?·?·?·?OC and ClH?·?·?·?FB). These results are rationalized by considering the changes in the magnetic and electric contributions to the proton shielding in ClH.     

Measurement of the magnetic field-dependent refractive index of magnetic fluids in bulk

An optical alignment-free and highly accurate method is employed to measure the magnetic field-dependent refractive index of magnetic fluid(MF)in bulk.The measured refractive index decreases significantly with the increasing magnetic strength and then tends to saturate in the high intensity range.By applying a tunable magnetic field ranging between 0 and 1661 Oe,the maximum shift of the refractive index of MF in bulk is found to be 0.0231.     

Influence of strong magnetic field on β decay in the crusts of neutron stars

βdecay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions ⁶⁷ Ni(β^-)⁶⁷ Cu and ⁶² Mn\beta ^-62 Fe are investigated as examples. The results show that a weak magnetic field has little effect on βdecay but a strong magnetic field (B>10¹²G) increases β decay rates obviously. The conclusion derived may be crucial to the research of late evolution of neutron stars and nucleosynthesis in r-process.     

An experimental investigation on sound transmission loss and vibration reduction of a vessel in water

Experimental results of sound transmission loss in a rangeof frequency through bubbly curtains were obtained,where the air contentwas in a wide range by means of varying pressure differences and thediameters of the pores of bubble-produce apparatus.Vibration reductionof a vessel in water due to the bubbly curtain was found.     

Influence of cooperativity on the frequency shift of the Ar–H stretch vibration in HArF complexes

CH₃Li–FArH–X (X?=?H₂, OC, N₂, P₂, CO₂, CO, BeH₂) trimers have been investigated using quantum chemical calculations at the QCISD/6-311++G(2d,2p) level. The results show that the lithium bonding has a prominent effect on the strength and properties of the hydrogen bonding. The hydrogen-bonding interaction energy is increased by 160–340% due to the presence of lithium bonding. The Ar–H stretch vibration shows a blue shift in the FArH–X (X?=?H₂, OC, N₂, CO₂, CO) dimer, but a red shift in the FArH–X (X?=?P₂, BeH₂) dimer. The red shift is increased in the corresponding trimer, while the blue shift shows a different change. The blue shift is also increased in CH₃Li–FArH–X (X?=?H₂, OC, N₂, CO₂) trimers, but it changes to a red shift in the CH₃Li–FArH–CO trimer. The shift change is consistent with the explanation given by Joseph and Jemmis.