Magnetic Field Effect in the Reaction of Recombination of Nitric Oxide and Superoxide Anion

Using a static magnetic field, we observed an important biological radical, nitric oxide, in solution by a spin-sensitive technique. Decomposition of 3-morpholinosydnonimine (SIN-1) in aqueous solution produces a radical pair consisting of nitric oxide and the superoxide anion which recombine to form peroxynitrite. The creation of this radical pair provides a favorable setting for the observation of magnetic field effects. Magnetic field effect of (1.8 ± 0.5)% on the yield of recombination was observed in a relatively high field of 4.7 T over the sampling of 96 samples. The effect is limited by extremely fast relaxation of nitric oxide in liquids due to unquenched orbital angular momentum, and develops in f-pairs via the Δg mechanism. Magnetic field effect due to a radical pair involving nitric oxide in a biological system would require either rather strong magnetic fields in the tesla range or an internal enhancer of magnetic field.     

A Simple Model for Understanding the Origin of the Amide Proton Transfer MRI Signal in Tissue

Amide proton transfer (APT) imaging is a new molecular magnetic resonance imaging (MRI) technique that gives contrast at the cellular protein level. To better understand the origin of the APT signal in tissue, fresh and cooked hen eggs (n = 4) were imaged at 4.7 T. The APT effect was quantified using the asymmetry in the magnetization transfer ratio (MTR_asym) at the composite amide proton resonance frequency (3.5 ppm from the water resonance). The measured APT signals were significantly higher in the fresh egg white (20.1 ± 0.9%) than in the fresh egg yolk (−1.4 ± 1.1%; P < 0.001), and in the cooked egg white (2.8 ± 0.7%; P < 0.001), all of which have similar absolute protein contents. The data support the notion that the APT effect observed in vivo is associated with mobile proteins in tissue, such as those in the cytoplasm.     

Magnetic properties of armchair graphene nanoribbons: A Monte Carlo study

The magnetic properties of armchair graphene nanoribbons have been studied using a Monte Carlo study. The ground state phase diagrams have been determined for mixed spins S={±2; ±1; 0} and σ={±5/2; ±3/2; ±1/2}. The topologies of the phase diagrams depend on the values of the parameters in the Hamiltonian such as exchange interactions, crystal field and external magnetic field. The some diagrams show some coexistence between regions. The Néel temperature t_N is obtained for different values of layer (n). The effect of reduced exchange interactions between the mixed spins σ and S and reduced crystal field on total magnetization has been given. Magnetic hysteresis cycles are given for different values of n, reduced exchange interactions and reduced temperatures. The double hysteresis loop and superparamagnetism were observed.     

The range of transferred hyperfine interactions in EuS

We report on a Mössbauer study of the transferred hyperfine fields at the ¹⁵¹Eu nuclei in the Eu_1?xSr_x series of mixed compounds. The totally transferred hyperfine field amount ?(5.3 ± 0.3) T corresponding to saturation values for the hyperfine field of ?(33.4 ± 0.2) T for x = 0 and ?(28.1 ± 0.2) T extrapolated for x = 1. Our results strongly support fairly long range magnetic interactions instead of the generally accepted model covering only nearest and next nearest neighbour interactions.     

Magnetic-field-induced changes in the photorefractive sensitivity of lithium niobate

The effect of a magnetic field on the average photorefractive sensitivity of an undoped LiNbO₃ crystal is studied by phase-mismatched second-harmonic generation. The experimental data obtained show the photorefractive sensitivity to reverse sign as the external magnetic field exceeds B ₁=?0.38±0.04 T. The magnetic field is oriented perpendicular to the crystal optical axis and to the plane of laser radiation polarization. The variation of the photorefractive sensitivity is associated with paramagnetic iron centers, whose photoionization probability depends on the direction of their magnetic moment relative to the optical axis.     

Neutron diffraction study of single crystal europium in an applied magnetic field

A single crystal of europium has been studied in applied magnetic fields up to 41.7 koe. At T_N = 90.5 ± 0.5°K a first order magnetic transition is observed. At 4.2°K the effect of an applied magnetic field in either a 〈100〉 or 〈110〉 direction is to stabilize a helix structure having τ along the field direction. This field stabilized structure remains even if the field is reduced to zero. The hysteresis associated with these transformations has been investigated and is discussed. No ferromagnetic components have been detected in fields up to 41.7 koe.     

High field Shubnikov-De-Haas effect and magnetoresistance in the organic metal (TMTSF)2 ClO4

The transverse magnetoresistance of (TMTSF)₂ ClO₄ has been investigated in magnetic fields up to 32 T at several temperatures down to 4.2 K and different angles between B and the crystalline axis. Shubnikov-de-Haas oscillations are observed directly on the magnetoresistance at fields higher than 10 T giving a fundamental field of 259± 10 T in a direction close to c¹ axis.     

Selective effect of a weak DC magnetic field on triglycine sulfate crystals

The effect of the selective influence of a dc magnetic field on the characteristics of nominally pure triglycine sulfate crystals was detected for the first time. A short (minutes) exposure to a weak magnetic field B₀=0.08±0.01 T caused long-term (hundreds of hours) changes in the spontaneous polarization, coercive field, Curie temperature, and permittivity of the crystal at the Curie point. The effect is selective in nature presumably because of the participation of hydrogen bond protons in the spin-dependent processes of the transformation of defect complexes in real crystals.     

The effect of a weak magnetic field on the mobility of dislocations in silicon

The magnetoplastic effect in dislocation silicon is discovered. It is shown that in the presence of tensile stresses (up to 20 MPa), the mechanically activated path of surface dislocation half-loops is limited mainly by the dynamics of defects in various slip systems relative to the applied load. The activation barriers for the motion of dislocations controlled by various conditions in the temperature range T=850–950 K are E _aF=2.1±0.1 eV and E _aS=1.8±0.1 eV. An increase in the path of surface dislocation half-loops and a change in the activation barriers are detected (E _aF=1.4±0.1 eV and E _aS=1.6±0.1 eV) after subjecting silicon to a magnetic field (B=0.7 T) for 30 min. Possible reasons behind the observed effects are discussed.     

The Meissner effect of polysulfur nitride, (SN)x

The magnetic susceptibility of (SN)_x was measured by the a.c. method. The Meissner effect occurs at 250 ± 3 mK. The real part of the susceptibility nearly saturates at 100 mK and reaches 93 ± 7% of ?$\text{1}\text{4}\text{π}$ at 30 mK for weak field perpendicular to the polymer axis, while for the parallel direction it remains at 65 ± 10% of ?$\text{1}\text{4}\text{π}$. The susceptibility depends strongly on the a.c. magnetic field. There is a peak in the imaginary part of the susceptibility at the transition region to the superconducting state.     

Bestimmung desg R -Faktors des 2+-Rotationsniveaus von W182 durch differentielle γγ-Winkelkorrelationsmessungen in einem äußeren Magnetfeld

The time spectrum of the coincidences between theγ-group at 1150 keV and the 100 keV radiation in the decay of Ta¹⁸² was observed in an external magnetic field of 29300±300 Gauss at eight different angles. The analysis of these data which took into account the experimentally determined shape of the prompt resolution curve yields for theg-factor of the 2+ rotational state:

$$g_R = + 0 \cdot 336 \pm 0 \cdot 044.$$     

Mössbauer study of the magnetic high-Tc superconductor GdBa2Cu3O7−δ

The magnetic ordering of the Gd sublattice in superconducting GdBa₂Cu₃O_7-δ is studied by Mössbauer spectroscopy using the 86.5-keV gamma resonance of ¹⁵⁵Gd. Below the Néel temperature of T_N ≌ 2.4 K, the magnetic hyperfine field at the Gd nucleus reflects the increasing local sublattice magnetization extrapolating to a saturation value of B_eff(T=0 K) ≌ 31.5 T. The effective magnetic hyperfine field is found to be parallel to the main axis of the electric-field-gradient tensor, which is characterized by an asymmetry parameter of n = 0.40 ± 0.05. The observed isomer shift and the value of B_eff are typical for trivalent Gd compounds with negligible conduction-electron contributions.     

基于热图像的种蛋气室变化监测算法

种蛋气室的大小是监测种蛋孵化过程的重要指标之一。根据种蛋的热力学结构,种蛋在孵化过程中,包裹气室部分蛋壳会与其他部分蛋壳产生温差,从而可通过热红外图像进行观察。针对在种蛋孵化过程中,人工照蛋检测气室效率低的问题,探索设计了一种基于热图像的种蛋气室变化俯视监测算法。监测种蛋气室热图像的算法主要包括种蛋目标检测,种蛋图像分割和种蛋气室面积计算3个部分,其中种蛋的目标检测采用Faster-RCNN算法实现;种蛋图像分割采用BP神经网络算法实现;种蛋气室面积是在种蛋图像分割的基础上进行计算。使用孵化5天及以上的种蛋作为研究对象,并拍取种蛋的热图像进行试验。试验结果表明：种蛋热图像的目标检测的平均精度（mAP）为99.85%,拥有较好的检测效果。使用BP网络对种蛋进行图像分割。BP神经网络经过调参后,其网络最佳的结构为三层隐藏层,每个隐藏层拥有1 000个神经元,最优初始学习率为0.000 1,最优最大迭代次数为500。以F1-measure作为分割效果的评价指标,BP神经网络的图像分割总体结果为87.02%,Otsu算法的总体结果为65.25%。其中只有一个蛋的情况下,BP神经网络的分割结果为87.17%,Otsu算法的结果为68.86%。存在其他种蛋的干扰条件下,BP神经网络的分割结果为86.94%,Otsu算法的结果为61.64%,BP神经网络的分割效果优于Otsu分割算法,BP神经网络拥有更强的抗干扰能力。最后提取了孵化5～19 d种蛋的气室变化,通过观察种蛋气室大小曲线来监测种蛋的孵化情况,可看出随着天数的增加,气室有着明显变大的趋势。人工测量法与热红外测量法比较结果说明两者相关性为0.934 3,拥有较好的相关性。基于热图像的种蛋气室变化监测算法可在实际生产中实现种蛋的识别与气室大小的快速监测,为实现监测种蛋孵化的自动化提供了技术参考。     

Magnetic moment of the 1,307 keV state in69As

The Larmor precession of the 1,307 keV 2 ns state in⁶⁹As in an external magnetic field of 2 T has been observed in a time integral perturbed angular distribution experiment. The deducedg-factor ofg=1.05±0.13 confirms the rather pureg _9/2 proton structure of this state on which a triaxial rotational aligned band is built.     

Precision electromagnet for a mass spectrometer

A precision electromagnet generating a magnetic field with an induction ranging from 0.05 to 0.50 T is designed, manufactured, and studied. It is intended for a magnetic resonance mass spectrometer with a rated resolution of about 10⁶. The magnetic field inhomogeneity on a circular orbit with a diameter of 400 mm along which the ion beam moves is no more than ±1 × 10^?5 of induction B ₀ at the center of the magnetic gap. At any point of the orbit, the magnetic field is kept constant with an accuracy of higher than 10^?6 for several minutes, which is sufficient to record mass spectra.     

Magneto-acoustic attenuation in AuSb2

Quantum oscillations in the ultrasonic attenuation in AuSb₂ were studied as a function of temperature, magnetic field and crystal orientation. The effective masses of the carriers associated with the F₅ and F₆ oscillations were measured in a (110) plane. For the F₅ oscillations, the Dingle temperature and apparent magnetic breakdown field appear to depend strongly upon orientation. For the F₆ oscillations, however, there were no signs of magnetic breakdown up to the highest magnetic fields available (70 kOe) and the Dingle temperature was roughly independent of orientation. From the acoustic velocities, the elastic constants were determined at 77 K: C₁₁ = (14·7 ± 0·9) × 10¹¹ dyne/cm², C₁₂ = (6·0 ± 0·9) × 10¹¹ dyne/cm², and C₄₄ = (2·59 ± 0·06) × 10¹¹ dyne/cm². These elastic constants give an adiabatic compressibility K_s = (1·13 ± 0·12) × 10^?12 cm²/dyne and a Debye temperature ?_D = (203 ± 15) K.     

Spurenanalyse von Cu in ZnS-Phosphoren mittels Neutronenaktivierung

The half life of the 206 kev state of Re¹⁸⁷ was determined with delayed coincidence technic to be:T _1/2=(5·70±0·05)·10^?7 s. The rotation of the spin of the 206 kev state in a magnetic field has been observed in a differential angular correlation measurement with the 480 kev?72 kevγ?γ cascade. From the observed Larmor frequency a magnetic moment ofμ=(5·02±0·06)μ _K for the 206 kev level has been derived. The 480 kev?72 kevγ?γ angular correlation was found to be undisturbed in an aqueous solution of ammoniumtungstate.     

Magnetic anisotropy in multilayers

Magnetic anisotropy between in-plane and out of plane magnetic alignments is studied in a variety of multilayer systems using Mössbauer spectrosopy to observe the (Fe) magnetic orientation. The surface anisotropy in Fe/Au (1 1 1) multilayers is measured as K _s = 0.9 × 10^?3 Jm^?2. In Fe/Ni multilayers the dependence of magnetic orientation on external field applied normal to the layers enables volume and interface anisotropies K _v = (?5 ± 1) × 10⁴ Jm^?3 and K _s = (?0.6 ± 0.4)× 10^?3 Jm^?2 to be evaluated. In similar applied field experiments coherent rotation of the magnetic Fe and NiFe layers in Fe/Cu/NiFe/Cu multilayers was observed for intervening Cu layer thickness x = 5 Å but independent rotation for x = 50 Å. Out of plane magnetic components are observed for DyFe₂, YFe₂ thin films and DyFe₂/YFe₂ multilayers. In fields of up to 0.25 T applied inplane only the moments of the YFe₂ film showed significant rotation.     

Optical decoherence and persistent spectral hole burning in Tm:LiNbO3

We report studies of decoherence and spectral hole burning for the 794 nm optical transition of thulium-doped lithium niobate. In addition to transient spectral holes due to the ³H₄ and ³F₄ excited states of Tm³⁺, persistent spectral holes with lifetimes of up to minutes were observed when a magnetic field of a few hundred Gauss was applied. The observed anti-hole structure identified the hole burning mechanism as population storage in the ¹⁶⁹Tm nuclear hyperfine levels. In addition, the magnetic field was effective in suppressing spectral diffusion, increasing the phase memory lifetime from 11 μs at zero field to 23 μs in a field of 320 Gauss applied along the crystal’s c-axis. Coupling between Tm³⁺ and the ⁷Li and ⁹³Nb spins in the host lattice was also observed and a quadrupole shift of 22 kHz was measured for ⁷Li at 1.7 K. A Stark shift of 18 kHz cm/V was measured for the optical transition with the electric field applied parallel to the c-axis.