Phase-modulated binomial RF pulses for fast spectrally-selective musculoskeletal imaging

Two fat-suppressed three-dimensional gradient echo pulse sequences, FLASH and DESS (Double Echo in Steady-State), that have significantly reduced scan time compared with conventional chemical shift fat-suppression sequences are presented. This fat-suppression technique is based on selectively exciting water spins using a time-optimized binomial RF pulse pair at the water resonance frequency with a null in the excitation profile at the fat frequency. To minimize the total pulse length, the delay between the binomial components of the RF pulse is decreased from a standard jump-return implementation. To maintain the proper null frequency, the phase of the second RF pulse is shifted such that it returns the fat resonance back to its initial z position while further tipping the water spins. Nonselective phase-modulated RF pulse pairs can be implemented in 1.20 ms at 1.0 T, significantly reducing the minimum TR.     

Preference for sex of first child among women classified as androgynous and nonandrogynous

We propose a simple one-dimensional RF pulse sequence for the study of chemical shift and heteronuclear dipolar coupling tensors of oriented as well as unoriented solids. An off-resonance RF decoupling of protons during the signal acquisition of less sensitive nuclei is used to suppress homonuclear 1H-1H dipolar interactions. This method is experimentally demonstrated on peptide samples selectively labeled with 15N isotope.     

Different regional changes of fluorescence spectra of clear human lenses and nuclear cataracts

Fluorescence spectra are recorded from the cortex and nucleus of the same human lenses [clear and cataracta brunescens (nigra) with colorless cortex]. When comparing clear cortices with either the harder nucleus of a clear lens, or a cataracta brunescens for a given excitation wavelength, a shift of the fluorescence maxima of the nucleus to longer wavelengths is observed. The shift appears to be independent of the degree of coloring since it is very similar for different nuclei, and it is not increased in cataracta nigra. The fluorescence intensities are similar when comparing the clear cortex of clear lenses and cataracta brunescens. For the nuclei, however, the intensity increases by up to four to six times with increasing coloring. For constant excitation wavelength, the fluorescence band maximum of the nucleus (of clear lenses and of cataracta brunescens) exhibits roughly the same shift to longer wavelengths as that of the cortex. Upon 320 nm excitation the fluorescence intensity of a cataracta nigra is about twice that of a clear lens of juvenile age. Upon 380 nm excitation the factor increases to four. Therefore in older and colored lens nuclei a red shift of the fluorescence maximum with increasing excitation wavelength is observed. We discuss whether or not the changes in the molecular proteins, in addition to advanced glycolization end products, may be responsible for the different fluorescence properties (and the brown color) with increasing age.     

Neural substrate for brain stimulation reward in the rat: Cathodal and anodal strength-duration properties.

Studied the trade-off between current strength and duration of a stimulating pulse for the rewarding and priming effects of brain stimulation reward (BSR) in 2 experiments with male albino rats. With cathodal pulses, strength–duration functions for BSR had chronaxies of .8–3 msec. No differences were observed between the results for rewarding and priming efffects. With anodal pulses, strength–duration curves were parallel to the cathodal curves at pulse durations of .1–5 msec, but at pulse durations greater than 5 msec the anodal curves showed a greater drop in required current intensity than did the cathodal curves. The parallel portion of the anodal curves is interpreted as due to anode-make excitation and the drop at longer pulse durations to anode-break excitation. Cathodal strength–duration functions for the motor effect elicited through the BSR electrodes had chronaxies of .15–.48 msec. Measurements of the latency of the muscle twitch confirmed that anode-make and anode-break excitation occurred, the latter becoming evident at pulse durations as brief as .3–.4 msec. Results provide quantitative characterization of cathodal and anodal strength–duration properties of the neural substrate for BSR and are discussed in terms of their value in guiding electrophysiological investigation of that substrate. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

1H nuclear magnetic resonance studies of hen lysozyme-N-acetylglucosamine oligosaccharide complexes in solution. Application of chemical shifts for the comparison of conformational changes in solution and in the crystal

Two-dimensional 1H nuclear magnetic resonance spectroscopy has been used to examine the complexes formed in solution between hen egg-white lysozyme and N-acetylglucosamine (GlcNAc) oligosaccharides. Changes in chemical shift have been measured for resonances of the majority of residues of lysozyme on binding the monomer, dimer and trimer of GlcNAc. The three inhibitors induce very similar changes in chemical shift, and these increase slightly with the length of the oligosaccharide. The largest changes are confined principally to the vicinity of site C in the active site cleft of the enzyme. These changes in chemical shift have been compared with differences in the ring current chemical shifts calculated from the crystal structures of unbound and GlcNAc3 bound lysozyme. This comparison suggests that the major conformational changes of residues in the vicinity of site C of the enzyme, that are caused by the binding of GlcNAc3, observed in the diffraction studies are at least consistent with the changes that occur in solution. Small changes in chemical shift are observed in the enzyme in regions remote from the active site, which indicate that the effects of inhibitor binding are felt throughout the enzyme. These changes in chemical shift correlate to a lesser extent than those near site C with the changes in chemical shift predicted from changes in conformation observed in the crystal structures. The results illustrate that chemical shifts are useful in assessing the significance of small conformational changes in proteins, although the usefulness of this approach will be limited by the resolution of the crystallographic structures, as well as the uncertainties in the origins of the chemical shift. Although conformational changes in site C account for many of the changes in the NMR spectrum of lysozyme, evidence is, however, presented for multiple binding sites for the GlcNAc oligosaccharides in solution, perhaps involving partial occupancy of site D.     

The specific interaction between LSD and serotonin-binding protein

In this report, we describe the chemical interaction between lysergic acid (LSD) and serotonin-binding protein (SBP) by a three-dimensional spectroscopic technique. This instrument records simultaneously the activation and fluorescence spectra, and plots fluorescence intensity level by a series of isointensity contours. Free LSD exhibits maximum fluorescence at 435 nm with excitation maximum at 330 nm. While SBP-bound LSD shifted its fluoresence and excitation maximum to 465 nm and 375 nm respectively. These results suggest that the drug-protein interaction caused an extensive delocalization of the molecular orbital electrons and thereby lengthen the electronic conjugation of the drug molecule. Such shift was not observed when LSD was incubated with bovine serum albumin under the same condition. This technique is sensitive and requires a small volume of samples. It permits us to determine both free and bound drug in the same sample and provides us specific information about the drug and protein interaction.     

Identification of group VS116 strains among Borrelia burgdorferi sensu lato grown from the hard tick, Ixodes ricinus (Linnaeus, 1758) by off-coupled restriction fragment length polymorphism analysis

The degree of chemical shift similarity for homologous proteins has been determined from a chemical shift database of over 50 proteins representing a variety of families and folds, and spanning a wide range of sequence homologies. After sequence alignment, the similarity of the secondary chemical shifts of C alpha protons was examined as a function of amino acid sequence identity for 37 pairs of structurally homologous proteins. A correlation between sequence identity and secondary chemical shift rmsd was observed. Important insights are provided by examining the sequence identity of homologous proteins versus percentage of secondary chemical shifts that fall within 0.1 and 0.3 ppm thresholds. These results begin to establish practical guidelines for the extent of chemical shift similarity to expect among structurally homologous proteins.     

Prediction of the peak shift in pigeons from gradients of excitation and inhibition.

Obtained stimulus generalization gradients of excitation and inhibition from 2 groups of 5 Silver King pigeons each along the hue dimension. A predicted postdiscrimination gradient (PDG) was computed from the algebraic summation of these gradients. This predicted gradient was compared with the actual PDG obtained from a 3rd group of 5 Ss. The PDG computed from the gradients of excitation and inhibition predicted the peak shift found in the actual PDG, but there was a greater distribution shift in the actual than the predicted PDG. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

一种新型的全数字同步电动机励磁装置

介绍了一种全数字同步电动机励磁装置,该装置以PLC及微机控制器为控制核心,以触摸屏为操作界面,具有完善的励磁控制、系统保护、故障报警及显示功能。对该装置的投励、脉冲形成、灭磁、故障保护、通讯等关键技术作了较为详细的阐述。     

Dimensional Analysis of the Earthquake Response of a Pounding Oscillator

In this paper, the dynamic response of a pounding oscillator subjected to pulse type excitations is revisited with dimensional analysis. The study adopts the concept of the energetic length scale which is a measure of the persistence of the distinguishable pulse of strong ground motions and subsequently presents the dimensionless Π products that govern the response of the pounding oscillator. The introduction of Buckingham’s Π theorem reduces the number of variables that govern the response of the system from 7 to 5. The proposed dimensionless Π products are liberated from the response of an oscillator without impact and most importantly reveal remarkable order in the response. It is shown that, regardless the acceleration level and duration of the pulse, all response spectra become self-similar and, when expressed in the dimensionless Π products, follow a single master curve. This is true despite the realization of contacts with increasing durations as the excitation level increases. All physically realizable contacts (impacts, continuous contacts, and detachment) are captured via a linear complementarity approach. The proposed analysis stresses the appreciable differences in the response due to the directivity of the excitation (toward or away the stationary wall) and confirms the existence of three spectral regions where the response of the pounding oscillator amplifies, deamplifies, and equals the response of the oscillator without pounding.     

Early photolysis intermediates of gecko and bovine artificial visual pigments

Nanosecond laser photolysis measurements were conducted on digitonin extracts of artificial pigments prepared from the cone-type visual pigment, P521, of the Tokay gecko (Gekko gekko) retina. Artificial pigments were prepared by regeneration of bleached gecko photoreceptor membranes with 9-cis-retinal, 9-cis-14-methylretinal, or 9-cis-alpha-retinal. Absorbance difference spectra were recorded at a sequence of time delays from 30 ns to 60 microseconds following excitation with a pulse of 477-nm actinic light. Global analysis showed the kinetic data for all three artificial gecko pigments to be best fit by two-exponential processes. These two-exponential decays correspond to similar decays observed after photolysis of P521 itself, with the first process being the decay of the equilibrated P521 Batho<-->P521 BSI mixture to P521 Lumi and the second process being the decay of P521 Lumi to P521 Meta I. In spite of its large blue shift relative to P521, iso-P521 displays a normal chloride depletion induced blue shift. Iso-P521's early intermediates up to Lumi were also blue-shifted, with the P521 Batho<-->P521 BSI equilibrated mixture being 15 nm blue-shifted and P521 Lumi being 8 nm blue-shifted relative to the intermediates formed after P521 photolysis. The blue shift associated with the iso-pigment is reduced or disappears entirely by P521 Meta I. Similar blue shifts were observed for the early intermediates observed after photolysis of bovine isorhodopsin, with the Lumi intermediate blue-shifted 5 nm compared to the Lumi intermediate formed after photolysis of bovine rhodopsin. These shifts indicate that a difference exists between the binding sites of 9- and 11-cis pigments which persists for microseconds at 20 degrees C.     

Demonstration of protein-protein interaction specificity by NMR chemical shift mapping

Chemical shift mapping is becoming a popular method for studying protein-protein interactions in solution. The technique is used to identify putative sites of interaction on a protein surface by detecting chemical shift perturbations in simple (1H, 15N)-HSQC NMR spectra of a uniformly labeled protein as a function of added (unlabeled) target protein. The high concentrations required for these experiments raise questions concerning the possibility for non-specific interactions being detected, thereby compromising the information obtained. We demonstrate here that the simple chemical shift mapping approach faithfully reproduces the known functional specificities among pairs of closely related proteins from the phosphoenolpyruvate:sugar phosphotransferase systems of Escherichia coli and Bacillus subtilis.     

同步电动机过电流故障原因分析

针对济钢烧结主抽风机同步电机运行过程中,在工艺参数及相关设备均正常的情况下出现的过电流故障,进行了电能质量分析及励磁系统检测。结果表明,只有母线基波平均电压偏差（9.6%）超出国标限值（7.0%）,其他基本正常;故障时,励磁电流突升46%,由于励磁方式设置为恒励磁电流,因此故障原因是励磁系统晶闸管脉冲控制的问题。改造采用可靠性高的励磁控制系统的升级换代产品,避免了电流突升现象。     

Tyrosine and tryptophan structure markers in hemoglobin ultraviolet resonance Raman spectra: mode assignments via subunit-specific isotope labeling of recombinant protein

Phenyl-deuterated tyrosine (Tyr-d4) and indole-deuterated tryptophan (Trp-d5) have been selectively incorporated into hemoglobin (Hb) by expressing the gene in auxotrophic strains of Escherichia coli. Ultraviolet resonance Raman (UVRR) spectra, using 229-nm excitation, show that difference features characteristic of the Hb quaternary R --> T transition are not perturbed by the incorporation of the isotopes. All the UVRR bands between 800 and 1700 cm-1 are assigned to either Tyr or Trp except for the 1511 cm-1 band, which had been thought to arise from the Trp 2 x W18 overtone. This band does not shift upon Trp or Tyr labeling but does shift 5 cm-1 in D2O, suggesting assignment to a histidine (His) residue. Its intensification in the T-state is consistent with His protonation. The alpha- and beta-subunits were selectively labeled, by reconstitution of labeled subunits with unlabeled subunits, to make isotope hybrids. Selective Tyr labeling identified the alpha subunits as the locus of the Y8a upshift observed in Hb, supporting the previous inference that this shift is associated with the T-state H-bond involving the interfacial Tyr alpha42 [Rodgers, Su, Subramaniam, & Spiro (1992) J. Am. Chem. Soc. 114, 3697]. Selective Trp labeling showed the Trp alpha14 contributions to the T - R difference spectrum to be negligible and confirmed Trp beta37 as the locus of the W3 difference signal, and probably of the remaining Trp signals as well. The observed downshift of W17 and upshift of Wd5 in the T-state are consistent with a stronger T-state H-bond between Trp beta37 and Asp alpha94; the resulting excitation profile red shift accounts for the dominance of the Trp beta37 contribution to the T - R difference UVRR spectrum.     

Structure and polymorphism of the upstream region of the pfg27/25 gene, transcriptionally regulated in gametocytogenesis of Plasmodium falciparum

Multi-photon transitions with two simultaneously interacting IR laser fields lead to final excited states with frequencies nnu = n1nu1 + n2nu2, with n the total number of photons absorbed and (n, n1, n2) = (2, 1, 1), (3, 2, 1), (4, 1, 3), etc. The nature of the actual transition is determined by shift measurements, where the lasers are frequency-tuned by deltanui in opposite directions keeping the sum frequency, nnu, resonant with the molecular transition. This technique opens a new spectral range for multi-photon transitions and a unique identification of the observed features. For n1 and n2 both positive the excitation will lead to a "normal" up-up multi-photon transition. Many three- and four-photon transitions in the nu3 vibrational ladder of SF6 could be resolved with a resolution of 1 MHz, as well as four new two-photon transitions. As long as n1 + n2 >/= 0, one of the two ni may be negative resulting in an, e.g., up-down excitation pathway with its particular selection rules. The up-down excitations are demonstrated both for one- and two-photon transitions using the frequency shift technique. The different possible excitation schemes which meet the resonance condition for these transitions lead to interference effects and local couplings to highly excited states. Changes in resonance frequency for a one-photon transition (n = 1), due to these effects, are demonstrated. Evidently, the radiative coupling of participating levels to high-lying or quasi-continuum states may drastically change for different deltanui leading both to ac Stark shift and transition probability variations.     

Iron compounds catalyze the oxidation of 10-formyl-5,6,7,8 tetrahydrofolic acid to 10-formyl-7,8 dihydrofolic acid

It is shown how to calculate random errors in chemical shift tensor components and in the Euler angles which fix the orientation of the sigma tensor in the molecular frame, as obtained from spinning sideband analysis of MAS NMR spectra of powdered solids, when heteronuclear dipolar coupling interactions occur in a two spin system. The procedure was applied to experimental data corresponding to the chemical shift tensor of a carbon-13 bonded to a phosphorus-31 nucleus. Clues are given concerning the experimental variables to be set in order to obtain the desired accuracy in the orientation angles.     

SrAl2O4 :Eu2+, Dy3+ Long Afterglow Phosphors Prepared by Chemical Coprecipitation Method

SrAl2 O4: Eu2 , Dy3 long afterglow phosphors were prepared by chemical coprecipitation method. Ammonium carbonate and ammonium hydrogen carbonate were used as the precipitants. The preparation of the SrAl2 O4: Eu2 ,Dy3 precursor was completed at room temperature by controlling the concentration of the metal-salt solution, pH value of the system, etc. The phosphors were prepared by sintering the precursor at 1000 ～ 1200 ℃ in a weak reducing atmosphere for 2 h. The XRD, SEM, excitation spectra, emission spectra and afterglow decay of the samples were tested and the optimal synthesis conditions of the SrAl2O4: Eu2 , Dy3 long afterglow phosphors prepared by precipitation method were determined. The phosphor which had good luminescent properties is prepared and its persistent time can reach more than 1600 min. In the coprecipitation process, a small amount of glucose operates to refe the luminescent powders. The particle size of the phosphor can be less than 1 μm. The sintering temperature of the sample prepared by the coprecipitation method is much lower than that of the one prepared by the high temperature solid state method.Compared with the high temperature solid state method, a clear blue shift occurs in the excitation and emission spectra of the samples.     

Study on(Y,Gd)3(Al,Ga)5O12∶Ce3+ Phosphor

(Y1-a, Gda)3-x(Al1-b, Gab)5O12∶Ce3 x was synthesized by high-temperature solid state reaction in reducing atmosphere based on high purity raw materials. The influences of Y3 , Gd3 , Al3 , Ga3 and activator-Ce3 on the performance of the phosphor were investigated. Ce3 is the luminescent center and activates the phosphor after it replaces Y partially. When x is less than 0.12, the volume of the crystal and the emission intensity of the phosphor increase with the quantity of Ce3 . When CeO2 is added too much, the phase CeAlO3 will appear. The excitation and emission peaks of the phosphor will shift to longer wavelength when the amount of Gd3 increases. The wavelength of the emission peak can shift about 20 nm when a equals 0.45. In opposite, the excitation and emission peaks will shift to shorter wavelength, when part of Al3 is replaced by Ga3 . The wavelength of the emission peak can shift about 20 nm when b equals 0.55. Through the replacemeat of Y3 or Al3 by Gd3 or Ga3 , the emission peak of the phosphor can be adjusted from 520 to 560 nm. In this way, the phosphor is more suitable for different chips.     

Proton-decoupled 31P chemical shift imaging of the human brain in normal volunteers

Proton-decoupled, 31P three-dimensional (3-D) chemical shift imaging (CSI) spectra have been acquired from the entire human brain using a new dual tuned resonator. The resonator operates in quadrature mode to provide improved sensitivity, excellent B1 homogeneity and reduced power deposition at both frequencies. Proton-decoupled and fully NOE enhanced, 31P spectra were acquired from normal volunteers using Waltz-4 proton decoupling with continuous wave bi-level excitation applied through a second radio frequency channel. Well resolved peaks in the phosphomonoester (PME) and phosphodiester regions were obtained from nonlocalized FIDs and spectra localized with 3-D CSI without processing for resolution enhancement. pH measurements made over large regions of the brain using the P(i) resonance show no significant variations (6.9 +/- 0.02) for a single individual. The improved spectral resolution and sensitivity of the PME resonances results in more well defined metabolite images of the PME peak region.