Adaptation in a revised inner-hair cell model

A revised computational model of the inner-hair cell (IHC) and auditory-nerve (AN) complex was recently presented [Sumner et al., J. Acoust. Soc. Am. 111, 2178-2188 (2002)]. One key improvement is that the model reproduces the rate-intensity functions of low- (LSR), medium- (MSR), and high-spontaneous rate (HSR) fibers in the guinea-pig. Here we describe the adaptation characteristics of the model, and how they vary with model fiber type. Adaptation of the revised model for a HSR fiber is in line with an earlier version of the model [Meddis and Hewitt, J. Acoust. Soc. Am. 90, 904-917 (1991)]. In guinea-pig, poststimulus time histograms (PSTH) have been found to show less adaptation in LSR fibers. Evidence from chinchilla suggests that this is due to chronic adaptation resulting from short interstimulus intervals, and that fully recovered LSR fibers actually show more adaptation. However, the model is able to account for both variations of PSTH shape when fully recovered from adaptation. Interstimulus interval can also affect recovery in the model. The model is further tested against data previously used to evaluate models of AN adaptation. The tests are (i) recovery from adaptation of spontaneous rate and (ii) the recovery of response to acoustic stimuli ("forward masking"), (iii) the response to stimulus increments and (iv) decrements, and (v) the conservation of transient components. A HSR model fiber performs similarly to the earlier version of the model. However, there is considerable variation in response to increments and decrements between different model fibers.     

The influence of pre-stressing on breakdown characteristics in liquid silicone rubber

Liquid silicone rubber (LSR) has increasingly been used as one kind of inner insulating material. Studies of space charge and its effect during pre-stressing and breakdown (BD) process in LSR were carried out. DC electrical breakdown field (BDF) of LSR specimens before and after DC electrical pre-stressing was measured. The space charge characteristics of LSR specimens under different DC electrical pre-stressing fields and that during the BD processes were measured by a pulsed electro-acoustic (PEA) method. It was found that the amount of homo space charges near electrodes increases obviously as a rising electric field is applied. Whether the polarity of BDF is the same as that of the pre-stressing field or not, the DC BDF of pre-stressed specimens is higher than that of specimens without pre-stressing. However, the pre-stressing does not show monotone and saturation effects, as generally occurs in the literature. In hetero BD experiments for example, with an increasing pre-stressing field, the DC BDF first increases up to 14.5% at the pre-stressing field of 25 kV/mm and then decreases. The influence of pre-stressing on the BD processes in LSR are discussed. The relationship between space charge and the DC BDF was related to the microstructure of nano-silica and LSR molecules.     

Microstructural modification by laser surface remelting and its effect on the corrosion resistance of an Al-9 wt%Si casting alloy

Aluminum alloys with silicon as a major alloying element constitute a class of materials, which provides the most significant part of all shaped castings manufactured. Such alloys have a wide range of applications in the automotive and aerospace industries. The literature presents contradictory results and no satisfactory explanations concerning to resulting microstructures provided by laser surface remelting (LSR) and its effect on the electrochemical behavior of Al-Si alloys. The aim of this study was to investigate the effect of microstructural refinement by LSR on corrosion resistance of an Al-9 wt%Si casting alloy. As-cast samples were subjected to a continuous 1 kW CO₂ laser. Corrosion resistance has been analyzed by an electrochemical impedance spectroscopy (EIS) technique and polarization curves carried out in both 0.5 M NaCl and 0.5 M H₂SO₄ solutions at 25 °C. An equivalent circuit has also been proposed and impedance parameters were simulated by the ZView^® software. It was found that the structural modification provided by the LSR process induces a decreasing effect on the corrosion resistance when compared to that of the untreated sample.     

Achieving high bit rate logical stochastic resonance in a bistable system by adjusting parameters

The phenomenon of logical stochastic resonance(LSR) in a nonlinear bistable system is demonstrated by numerical simulations and experiments. However, the bit rates of the logical signals are relatively low and not suitable for practical applications. First, we examine the responses of the bistable system with fixed parameters to different bit rate logic input signals, showing that an arbitrary high bit rate LSR in a bistable system cannot be achieved. Then, a normalized transform of the LSR bistable system is introduced through a kind of variable substitution. Based on the transform, it is found that LSR for arbitrary high bit rate logic signals in a bistable system can be achieved by adjusting the parameters of the system,setting bias value and amplifying the amplitudes of logic input signals and noise properly. Finally, the desired OR and AND logic outputs to high bit rate logic inputs in a bistable system are obtained by numerical simulations. The study might provide higher feasibility of LSR in practical engineering applications.     

NMR Studies of Drugs: Antipyrine and Analogs. I. Use of Achiral and Chiral Lanthanide Shift Reagents to Examine Hindered Rotation.

The 200 MHz ¹H NMR spectra of the analgesic, antipyrine, 1, have been studied in CDC1₃ solution at ambient temperatures with the achiral lanthanide shift reagent (LSR) tris (6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedionato) europium (III), Eu(FOD)₃, 2, and with the chiral LSR, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato]europium(III), Eu(HFC)₃, 3., Lanthanide-induced shift (LIS) magnitudes and broadening of selected signals are consistent with predominant LSR binding at the carbonyl oxygen with either 2 or 3. Of the different possible conformational regimes for the N-phenyl group of 1, our results appear to rule out a slow exchange limit (SEL) system with the N-phenyl coplanar with the heterocyclic ring. Perpendicular rings in an SEL regime can not be ruled out. A rapidly-rotating N-phenyl (fast exchange limit, FEL system) would also be consistent with observed results. Accurate chemical shifts for the aryl protons (overlapped in the 200 MHz spectrum of unshifted 1) are determined from spectra with added LSR by extrapolation to zero molar ratios of [LSR]:[1]. Relative slopes in the plots of chemical shift versus [LSR]:[1] molar ratios are calculated for each proton signal of 1.     

拟除虫菊酯类农药的NMR研究Ⅰ.α-对取代苯基异戊酸及其类似化合物的手性和前手性NMR研究

α-对取代苯基异戊酸是合成拟除虫菊酯的重要中间化合物,其结构中有手性和前手性两个甲基。为了解构效与活性的关系,本文对其结构特点进行了仔细的考察。用手性位移试剂Eu(hfbc)₃和位移试剂Eu(fod)₃^-分离了对映体的¹H和¹³C的信号,并作出了一定的解释,为鉴定化合物的光学纯度找出了一种简便的方法。对异丙基上的两个非对映异位甲基作了详细的观察,确定了优势构象,并对其作了标识,实验与由简单模型的计算结果一致。本文认为在对这两个非对映异位甲基信号位移差别大小的影响中,取代基的体积效应起了相当重要的作用。     

Spatial and spectral characteristics of laser-field synchrotron radiation

The spatial and spectral characteristics of laser-field synchrotron radiation (LSR) are investigated. The results show that LSR is emitted normal to the laser axis and emission in the X-ray wavelength can be obtained by increasing the intensity of the laser pulse and the initial energy of the electron. The unique feature offered by the laser-field synchrotron radiation (LSR) makes them a promising compact source of light at shorter wavelengths.     

NMR Studies of Drugs. Application of Achiral and Chiral Lanthanide Shift Reagents to α-Ethyl-α-Phenylsuccinimide

The 60 MHz ¹H NMR spectra of 3-ethyl-3-phenylpyrrolidine-2,5-dione, 1, were studied in CDCl₃ at 28° using the achiral lanthanide shift reagent (LSR) tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), Eu(FOD)₃ 2, for spectral simplification, and the chiral LSR, tris[3-heptafluoropropylhydroxymethylene)-(+)-camphorato]-europium(III), Eu(HFC)₃ 3, to induce enantiomeric shift differences (δδδ) for several nuclei. A non-racemic sample of 1 was treated with 3 to determine the sense of magnetic nonequivalence of selected nuclei. Significant δδδ is seen for the signals of the methyl and aryl ortho protons. Modest δδδ can also be seen for the NH signal and for one of the H-4 protons, although LSR-induced broadening for the two latter signals is severe. The (-) enantiomer appeared to exhibit an upfield sense of magnetic nonequivalence (3:1 molar ratio ca. 0.15—0.35) for the methyl signal but a downfield sense for H_ortho (3:1 ratio ca. 0.6).     

NMR Studies of Drugs. Enantiomeric Excess Determination of N-acetylcathinone with Eu(HFC)3

A technique for determination of enantiomeric excess of cathinone, 2-amino-1-phenyl-1-propanone, by use of the chiral lanthanide shift reagent (LSR), tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]europium (III), Eu (HFC)₃, is described. The hydrochloride salt of the cathinone sample is first converted directly to the N-acetyl derivative without need for isolation of the potentially unstable cathinone free base. Addition of Eu (HFC)₃ to the crude acetylated cathinone resulted in near-baseline resolution of the CH ₃CO resonances of the enantiomers. Analytical utility and the sense of magnetic nonequivalence of this signal were demonstrated using “spiked” non-racemic samples.     

NMR Studies of Drugs. Applications of Achiral and Chiral Wthanide Shift Reagents to Bupropion

Abstract

The ¹H NMR spectra of racemic samples of the antidepressant drug, bupropion, 1, have been studied in CDCl₃ solution at 60 and 200 MHz with the achiral lanthanide shift reagent (LSR), tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium (III), 2, and the chiral reagent, tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]europium(III), 3. Both LSR produced substantial lanthanide induced shifts consistent with ¹H assignments, but the bound complexes of 1 with 2 versus 3 may not be isostructural. With 3, substantial enantiomeric shift differences were observed for the t-butyl, CH ₃CH, NCH, and the aryl H-2 and H-6 signals, which should permit potential direct determination of enantiomeric excess.     

Study on the spectral behavior of four fluorescent dyes and their interactions with nucleic acid by the luminescence method

The spectral characteristics of four fluorescent dyes: tetrabromofluorescein (TBF), tetrachlorotetrabromofluorescein (TTF), lissamine rhodamine RB 200 (LSR) and methylene violet (MV) were studied by fluorescence and paper substrate room temperature phosphorescence (PS-RTP) methods. The factors affected the luminescence were investigated including pH value, paper substrate and drying conditions, etc. The fluorescence polarizations and PS-RTP lifetimes of these compounds were obtained. The intensity of fluorescence and phosphorescence of TBF and TTF increased in the presence of DNA. Contrarily, that of LSR and MV decreased. The fluorescence quenching and polarization studies indicate that TTF, LSR and MV intercalate into DNA base pairs. In addition, the interaction of TBF with DNA is the comprehensive interaction of two modes: intercalation and groove binding. It was also found that ionic strength could affect the binding of fluorescent dyes and DNA.     

Use of a Lanthanide Shift Reagent for Simplified NMR Analysis of Borneol—Isoborneol Mixtures. Apparent Catalysis of OH Proton Exchange by LSR

The use of ¹H NMR at low field (60 MHz spectrometer frequency) for direct analysis of mixtures of borneol, 1, and isoborneol, 2, is considerably simplified by addition of the lanthanide shift reagent (LSR), tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), 3. The effect of added 3 is twofold. Firstly, the analytical marker signals of the methine proton CHOH in 1 and 2, which are partly overlapped at 60 MHz in CDCl₃ (28°), are separated and rendered baseline-resolved due to preferential LSR binding to the less hindered endo OH of 1. Secondly, the absorption signals of the CHOH methines actually sharpen in the presence of 3, and display clearly defined multiplet structure, attributed to full exchange decoupling of the vicinal OH as a result of enhanced OH exchange rates when LSR is present.     

NMR Studies of Drugs. Applications of Achiral and Chiral Lanthanide Shift Reagents to the Analgesic,Famprofazone: “Anomalous Shifts”

The 200 MHz ¹H NMR spectra of the analgesic, famprofazone, 1, have been studied in CDCl₃ solution at ambient temperatures with the achiral lanthanide shift reagent (LSR) tris (6, 6, 7, 7, 8, 8, 8-heptaf luoro-2, 2-dimethyl-3, 5-octanedionato) europium (III), Eu(FOD)₃, 2, for spectral simplification, and with the chiral LSR, tris [3-(heptafluoropropylhydroxymethylene) - (+) camphorato] europium (III), Eu (HFC)₃, 3. Lanthanide induced shift (LIS) magnitudes suggested predominant LSR binding at the carbonyl oxygen. Substantial enantiomeric shift differences were observed for several nuclei of 1 with added 3 which could permit direct determinations of enantiomeric excess.     

Resonance effects in the nonadiabatic nonlinear quantum dimer

In the presence of 1/f ^β noise, we investigate the logical stochastic resonance (LSR) in an asymmetric bistable model driven by various cycling combinations of two logic inputs. The probability of correct logic outputs is calculated according to true table of logic relationships. Two major results are presented. Firstly, it is shown that the LSR effect can be obtained by changing noise strength. Over entire range of noise variance, white noise can be considered to be better than 1/f noise or 1/f ² noise to obtain clean logic operation. At a smaller noise level, 1/f noise can realize higher output probability than white noise or 1/f ² noise. In the sense, 1/f noise can be considered to be better than white noise or 1/f ². On the other hand, the correct probability can evolves nonmonotonically as noise exponent β increases, and a kind of SR-like effect can be obtained as a result of β. At certain intermediate noise variance, the output probability is able to attain its minimum at β = 1. It is also shown that actually some finite β sometime can be better than β = 0 at small range of noise variance. The study might provide some potential complement to LSR effect in the presence of 1/f ^β noise.     

CRYRING at the LSR at FLAIR

FLAIR will be the next-generation facility for physics with low-energy antiprotons, providing antiprotons at energies from tens of MeV down to rest. It will also offer unique possibilities for physics with highly charged ions at very low energies. The FLAIR facility will have two deceleration rings, the LSR which will decelerate antiprotons to 300 keV and the USR which will bring them down further to 20 keV. The LSR will consist of the present CRYRING at the Manne Siegbahn Laboratory. During the next few years, CRYRING will be modified with respect to injection and extraction, to allow injection of 30 MeV antiprotons and to provide it with both fast (single-turn) and slow (resonant) extraction at a variable energy. We here describe plans and preparations for the transfer of CRYRING to FLAIR, giving, in particular, an overview of new components for injection and extraction.     

双稳动力学系统中耦合效应对逻辑随机共振现象的增强作用

研究了电路耦合作用对逻辑随机共振现象以及逻辑门器件稳定性的影响．相对于单个的逻辑门电路,耦合的逻辑门器件可以在更宽的噪声范围内都保持逻辑运算的准确性,即耦合作用可以增强逻辑随机共振现象．此外,这种增强效应随着耦合体系尺度的增大而增大,但是当体系尺度达到一定程度时,这种增强作用达到一个稳定值．最后还考察了耦合强度的影响,发现随着耦合强度的增加,逻辑门器件可以保持逻辑运算准确性所对应的噪声区间非单调地改变,表现出一种共振的行为.     

Time-varying coupling-induced logical stochastic resonance in a periodically driven coupled bistable system

Coupling-induced logical stochastic resonance(LSR) can be observed in a noise-driven coupled bistable system where the behaviors of system can be interpreted consistently as a specific logic gate in an appropriate noise level. Here constant coupling is extended to time-varying coupling, and then we investigate the effect of time-varying coupling on LSR in a periodically driven coupled bistable system. When coupling intensity oscillates periodically with the same frequency with periodic force or relatively high frequency, the system successfully yields the desired logic output. When coupling intensity oscillates irregularly with phase disturbance, large phase disturbance reduces the area of optimal parameter region of coupling intensity and response speed of logic devices. Although the system behaves as a desired logic gate when the frequency of time-periodic coupling intensity is precisely equal to that of periodic force, the desired logic gate is not robust against tiny frequency difference and phase disturbance. Therefore, periodic coupling intensity with high frequency ratio is an optimal option to obtain a reliable and robust logic operation.     

NMR Studies of Drugs. Applications of Achiral and Chiral Lanthanide Shift Reagents to a 5-Substituted-4-thiazolidinone

The 60 MHz ¹H NMR spectra of racemic 5-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-4-thiazolidinone, 1, have been studied in CDCl₃ solution at 28° with the achiral lanthanide shift reagent (LSR), tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium (III), 2, and the chiral LSRs, tris[3-(heptafluoropropylhydroxymethylene)- (+)-camphoratojeuropium(III), 3, and tris[3-(trifluoromethylhydroxymethylene-(+) -camphorato]europium (III), 4, Significant enantiomeric shift differences were observed in the presence of added 3, for the aryl protons of 1 that should permit direct determination of enantiomeric excess. Relative magnitudes of lanthanide-induced shift for the different nuclei of 1 with the three LSRs are compared and discussed in terms of preferred LSR binding sites. A favored conformation of 1 with respect to rotation about the C(5)-CH₂ bond is suggested.     

NMR Studies of Agricultural Compounds. Applications of Achiral and Chiral Lanthanide Shift Reagents to the Herbicide,Fenoxaprop-Ethyl

The 200 MHz H NMR spectra of the herbicide, fenoxaprop-ethyl, 1, have been studied in CDCl₃ solution at ambient temperatures as the racemic ester free base with the added chiral lanthanide shift reagent (LSR), tris [3 - (heptafluoropropylhydroxymethylene) - (+) - camphorato]europium(III), Eu(HFC)₃, 2, with some additional runs using the achiral LSR, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), Eu(FOD)₃, 3, for supplemental spectral simplification. With 2, definite enantiomeric shift differences (ΔΔδ) were observed only for the CH₃CH₂O resonance. Although increased spectral complexity for the CH₂O signal was seen with added 2, this could have resulted from anisochrony of the diastereotopic protons, H_a and H_b, of this methylene group rather than true ΔΔδ, since the achiral 3 led to near-baseline separation between the CH_aH_bO signals. Lanthanide-induced shift (LIS) magnitudes were interpreted as consistent with predominant LSR binding at the ester carbonyl.     

NMR Studies of Hindered Rotations in Drugs. Use of Achiral and Chiral Lanthanide Shift Reagents with Mecloqualone,an Axially Chiral Drug of Abuse. Rigorous Definition of Spin Systems.

The axially chiral sedative/hypnotic drug of abuse, mecloqualone, 1, has been studied in CDC1₃ by ¹H NMR at 60 and 300 MHz with the added achiral lanthanide shift reagent (LSR), tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5- octanedionato)europium(III), 2, and the chiral LSR, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato] europium-(III), 3. Rigorous distinctions between the two (CH)₄ spin systems of 1 with added 2 or 3 were achieved by two-dimensional homonuclear chemical shift correlation spectroscopy, COSY. Substantial up field (“anomalous”) shifts were observed for several nuclei of 1 with each LSR. Use of the chiral 3 elicited enantiomeric shift differences with baseline separations for several nuclei that should permit direct determinations of enantiomeric excess. COSY spectra allow determination of the relative sense of magnetic nonequivalence of selected nuclei of 1 with 3.