bluuebunny/crossref_metadata_2025 huggingface dataset:
Orientation Distribution Functions Based upon Both 〈P1〉, 〈P3〉 Order Parameters and upon the Four 〈P1〉 up to 〈P4〉 Values: Application to an Electrically Poled Nonlinear Optical Azopolymer Film
Authors: Rodriguez V. , Lagugné-Labarthet F. , Sourisseau C.
Published: April 2005

The most probable orientational distribution functions of rod-like polar molecules contained in a noncentrosymmetric uniaxial system are established using the first-rank and third-rank Legendre polynomials, 〈 P1(cos θ)〉 and 〈 P3(cos θ)〉 order parameters, and the maximum entropy method. Emphasis is put on the different domains of existence in the (〈 P1〉, 〈 P3〉) plane for the various shapes of the distributions: it is thus shown that, for any positive 〈 P1(cos θ)〉 value and for decreasing 〈 P3(cos θ)〉 values, the distribution function may exhibit either a distorted oblate form with an intense maximum at 0°, or a three-leaved rose curve with maxima at 60°, 180°, and 300°, and finally another markedly oblate shape with a strong maximum at 180°. As an illustrative example, we have considered the azobenzene molecular orientations in an electrically poled p(DR1M) homopolymer thin film after a thermal process and several relaxation periods. We have made use not only of the 〈 P1〉 and 〈 P3〉 parameters determined from polarized second-harmonic generation (SHG) measurements, but also of the 〈 P2〉 values extracted from UV-visible spectra and of the 〈 P4〉 values adjusted according to the information entropy theory. In such a thin film with very large nonlinear properties (d33 coefficients were varying from 437.0 to 117.0 pm/V at 1064 nm) it is evidenced that a strong polar order is maintained even after a long relaxation period of 42 days. So, the distribution functions demonstrate that the poling treatment was quite efficient and they emphasize the importance in the determination of both couples of odd and even order parameters in such uniaxially oriented optical elements.
Profiling of Liquid Crystal Displays with Raman Spectroscopy: Preprocessing of Spectra
Authors: Stanimirovic Olja , Boelens Hans F. M. , Mank Arjan J. G. , Hoefsloot Huub C. J. , Smilde Age K.
Published: April 2005

Raman spectroscopy is applied for characterizing paintable displays. Few other options than Raman spectroscopy exist for doing so because of the liquid nature of functional materials. The challenge is to develop a method that can be used for estimating the composition of a single display cell on the basis of the collected three-dimensional Raman spectra. A classical least squares (CLS) model is used to model the measured spectra. It is shown that spectral preprocessing is a necessary and critical step for obtaining a good CLS model and reliable compositional profiles. Different kinds of preprocessing are explained. For each data set the type and amount of preprocessing may be different. This is shown using two data sets measured on essentially the same type of display cell, but under different experimental conditions. For model validation three criteria are introduced: mean sum of squares of residuals, percentage of unexplained information (PUN), and average residual curve. It is shown that the decision about the best combination of preprocessing techniques cannot be based only on overall error indicators (such as PUN). In addition, local residual analysis must be done and the feasibility of the extracted profiles should be taken into account.
Red-Excitation Dispersive Raman Spectroscopy is a Suitable Technique for Solid-State Analysis of Respirable Pharmaceutical Powders
Authors: Vehring Reinhard
Published: April 2005

Dispersive Raman spectroscopy with excitation by a red diode laser is suitable for quantitative crystallinity measurements in powders for pulmonary drug delivery. In spray-dried mixtures of salmon calcitonin and mannitol, all three crystalline polymorphs of mannitol and amorphous mannitol were unambiguously identified and their mass fractions were measured with a limit of quantification of about 5%. The instrument design offered high sensitivity and adequate background suppression, resulting in a low limit of detection in the range of 0.01% to 1%. This spectroscopy method has significant advantages over established techniques regarding specificity, sensitivity, and sample requirements.
Phase Transition in Poly(Vinylidene Fluoride) Investigated with Micro-Raman Spectroscopy
Authors: Constantino C. J. L. , Job A. E. , Simões R. D. , Giacometti J. A. , Zucolotto V. , Oliveira O. N. , Gozzi G. , Chinaglia D. L.
Published: April 2005

The phase transition from the non-polar α-phase to the polar β-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous because it is a nondestructive technique. Films of α-PVDF were subjected to stretching under controlled rates at 80 °C, while the transition to β-PVDF was monitored by the decrease in the Raman band at 794 cm−1 characteristic of the α-phase, along with the concomitant increase in the 839 cm−1 band characteristic of the β-phase. The α→β transition in our PVDF samples could be achieved even for the sample stretched to twice (2×-stretched) the initial length and it did not depend on the stretching rate in the range between 2.0 and 7.0 mm/min. These conclusions were corroborated by differential scanning calorimetry (DSC) and X-ray diffraction experiments for PVDF samples processed under the same conditions as in the Raman scattering measurements. Poling with negative corona discharge was found to affect the α-PVDF morphology, improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, i.e., X-ray diffraction and infrared spectroscopy.
Phase Correction of Interferograms Using Digital All-Pass Filters
Authors: Furstenberg Robert , White Jeffrey O.
Published: April 2005

A method for the phase correction of interferograms in Fourier transform infrared spectroscopy is presented. It is shown that phase error can be canceled to within an arbitrary angular precision by a low-order digital all-pass filter. Such a filter only modifies the phase of the Fourier transform of the interferogram and keeps the magnitude unchanged, like the Mertz method, for example. However, our method minimizes the asymmetric apodization that results in photometric errors when using the Mertz method alone. A practical example is provided in which phase correction over a frequency range of 800 cm−1 to 4000 cm−1 using a 9-pole all-pass filter resulted in a photometric error of <0.01%, much less than the 0.3% error of the Mertz method. An alternative and faster (∼100 ms) approach is to use an all-pass filter with lower angular precision followed by the Mertz method. Removing most of the phase error with the filter brings the interferogram to an optimal state so that the residual phase error can be completely removed with the Mertz procedure without introducing photometric error. The method can be used in most experiments, including emission spectroscopy, where conventional techniques are inadequate. A simple all-pass filter design algorithm is given.
Comparison of Near-Infrared and Laser-Induced Breakdown Spectroscopy for Determination of Magnesium Stearate in Pharmaceutical Powders and Solid Dosage Forms
Authors: Green Robert L. , Mowery Mark D. , Good Julie A. , Higgins John P. , Arrivo Steven M. , McColough Kristen , Mateos Arthur , Reed Robert A.
Published: April 2005

Near-infrared (NIR) spectroscopy has become well established in both the pharmaceutical arena and other areas as a useful technique for rapid quantitative analysis of solid materials. Though laser-induced breakdown spectroscopy (LIBS) has not been widely applied in the pharmaceutical industry, the technique has been used for rapid quantitative analysis of solids in many other applications. One analysis amenable to each technique is the determination of magnesium stearate in solids during the lubrication blending unit operation of pharmaceutical processing. A comparative study of the utility of these two techniques for this application will be presented. Necessary sample preparations and the extent and type of matrix effects will be discussed. Additionally, it will be shown that NIR provides better accuracy and precision than LIBS with the experimental parameters used; however, LIBS showed superior selectivity as it was demonstrated to be more robust to sample matrix perturbations. Examples of blending applications will also be presented.
Method for Quantitative Determination of Spatial Polymer Distribution in Alginate Beads Using Raman Spectroscopy
Authors: Heinemann Matthias , Meinberg Holger , Büchs Jochen , Koß Hans-Jürgen , Ansorge-Schumacher Marion B.
Published: April 2005

A new method based on Raman spectroscopy is presented for noninvasive, quantitative determination of the spatial polymer distribution in alginate beads of approximately 4 mm diameter. With the experimental setup, a two-dimensional image is created along a thin measuring line through the bead comprising one spatial and one spectral dimension. For quantitative analysis of the Raman spectra, the method of indirect hard modeling was applied to make use of the information contained in the entire recorded spectra. For quantification of the alginate signals from within the beads, a calibration curve acquired from sodium alginate solutions was used after it was shown that only negligible differences occur between signals from alginate solutions and alginate gels. The distribution of alginate over the bead gel matrix was acquired with high spatial (51 μm) and time (12 s) resolution. The inhomogeneous distribution obtained using the new measuring technique is qualitatively in excellent agreement with data from the literature. In contrast to known measuring techniques, correct quantitative information about the spatial polymer distribution within the matrix was derived. It gave an alginate mass fraction of approximately 0.045 g/g at the edges and 0.02 g/g in the center of the beads. Next to the determination of mere polymer concentrations, the excellent time resolution of the presented method will enable investigation of the dynamic process of gel formation and it will also serve as a basis for investigation of mass transfer of small diffusing molecules in alginate matrices.
Noninvasive Method for the Assessment of Dermal Uptake of Pesticides Using Attenuated Total Reflectance Infrared Spectroscopy
Authors: Carden Angela , Yost Michael G. , Fenske Richard A.
Published: April 2005

Dermal absorption of pesticides is a primary exposure route for agricultural workers, but is not well characterized. Current measurement techniques are either invasive, such as tape-stripping, or require extensive sample preparation or analysis time, such as urinary metabolite monitoring or wipe sampling followed by gas chromatography analysis. We present the application of a noninvasive, spectroscopic approach for the measurement of pesticide absorption into skin. Attenuated total reflectance infrared spectroscopy (ATR-IR) was used to monitor directly the absorption of two pesticides—captan and azinphos-methyl—in ten volunteers over 20 min under occlusive conditions. We found substantial variability in absorption across subjects. Our results were comparable to those measured by the more traditional method of wipe-sampling followed by extraction and gas chromatography analysis. Multivariate data analysis, in the form of multivariate curve resolution (MCR), is a novel addition to this type of experiment, yielding time-resolved information unachievable by standard methods. These data are potentially more informative than the monitoring of blood or urinary metabolites because they can be acquired in essentially real-time, allowing observations of pesticide absorption on a rapid timescale rather than over hours or days.
Multiplex Single Strand Conformation Polymorphism Analysis by Capillary Electrophoresis with On-the-Fly Fluorescence Lifetime Detection
Authors: Snyder Tara Morcone , McGown Linda B.
Published: April 2005

This paper describes the use of on-the-fly fluorescence lifetime detection (OFLD) for multiplex single strand conformation polymorphism (SSCP) analysis by capillary electrophoresis (CE). The dye labels studied for multiplex SSCP-OFLD-CE analyses included RG, NBD, and BODIPY-FL. The dyes were first investigated for a model system of “Wild Type” and “Mutant” 43-base fragments designed to vary by a single A/T substitution. Two dye pairs, BODIPY-FL/RG and BODIPY-FL/NBD, were then used to detect the G20210A mutation in the human prothrombin gene. Mobility correction was required for the BODIPY-FL/RG system. Three “blind” analyses were performed of three mixtures that combined a control fragment (wild type-BODIPY-FL) with two “unknown” fragments selected among four possibilities (wild type or mutant labeled with NBD or RG). In each multiplex analysis, the “origin” of the unknown fragments was correctly identified on the basis of fluorescence lifetime of the dye label and the presence or absence of the mutation was correctly determined on the basis of conformation-induced differences in migration time.
1H and 13C Nuclear Magnetic Resonance Studies of the Hindered Phencyclone Adducts of Some Smaller Branched N-Alkyl Maleimides: Rigorous Aryl Proton Assignments with High-Resolution Two-Dimensional (COSY45) Spectroscopy, and Anisotropic Shielding Effects and Ab Initio Geometry Optimizations
Authors: Callahan Ronald , Prip Ron , Shariff Navroz , Sklyut Olga , Rothchild Robert , Bynum Kevin
Published: April 2005

Phencyclone, 1, a potent Diels-Alder diene, reacts with a series of N-alkylmaleimides, 2, to form hindered adducts, 3. The 300 MHz 1H and 75 MHz 13C NMR studies of these adducts at ambient temperatures have demonstrated slow rotations on the nuclear magnetic resonance (NMR) timescales for the unsubstituted bridgehead phenyl groups, and have revealed substantial magnetic anisotropic shielding effects in the 1H spectra of the N-alkyl groups of the adducts. The selected N-alkyl groups for the target compounds emphasized smaller branched alkyls, including C3 (isopropyl, a); C4 (isobutyl, b; and t-butyl, c); C5 (n-pentyl, d; isopentyl [isoamyl], e; 1-ethylpropyl, f; t-amyl, g;) and a related C8 isomer (1,1,3,3-tetramethylbutyl [“t-octyl”], h). The straight-chain n-pentyl analog was included as a reference. This present work on the branched N-alkylmaleimide adducts appreciably extends our earlier compilation on the N-n-alkylmaleimide adducts. Key methods for proton assignments included “high-resolution” 1H–1H chemical shift correlation spectroscopy, COSY45. 13C NMR of the adducts, 3, verified the expected number of aryl carbons for slow exchange limit (SEL) spectra of the bridgehead phenyl groups. The synthetic routes involved reaction of the corresponding amines, 4, with maleic anhydride to give the N-alkylmaleamic acids, 5, which underwent cyclodehydration to form the maleimides, 2. Magnetic anisotropic shielding magnitudes for alkyl group protons in the adducts were calculated relative to corresponding proton chemical shifts in the maleimides. Geometry optimizations for the above adducts (and for the N-n-butylmaleimide adduct) were performed at the Hartree-Fock level with the 6–31G* basis set. The existence of different contributing conformers for the adducts is discussed with respect to their calculated energies and implications regarding experimentally observed anisotropic shielding magnitudes.
Equilibrium Modeling of Mixtures of Methanol and Water
Authors: Puxty Graeme , Maeder Marcel , Radack Kyle P. , Gemperline Paul J.
Published: April 2005

An understanding of the species that form in mixtures of alcohol and water is important for their use in liquid chromatography applications. In reverse-phase liquid chromatography the retention of solutes on a chromatography column is influenced by the composition of the mobile phase, and in the case of alcohol and water mobile phases, the amount of free alcohol and water present. Previous and similar modeling studies of methanol (MeOH) and water mixtures by near-infrared (NIR) spectroscopy have found up to four species present including free MeOH and water and MeOH and water complexes formed by hydrogen bonding associations. In this work an equilibrium model has been applied to NIR measurements of MeOH and water mixtures. A high-performance liquid chromatography (HPLC) pump was coupled to an NIR flow cell to produce a gradual change in mixture composition. This resulted in a greater mixture resolution than has been achieved previously by manual mixture preparation. It was determined that five species contributed to the data. An equilibria model consisting of MeOH, H2O, MeOH(H2O) (log KMeOHH2O = 0.10 ± 0.03), MeOH(H2O)4 (log KMeOH4H2O = −2.14 ± 0.08), and MeOH(H2O)9 (log KMeOH9H2O = −8.6 ± 0.1) was successfully fitted to the data. The model supports the results of previous work and highlights the progressive formation of MeOH and water complexes that occur with changing mixture composition. The model also supports that mixtures of MeOH and water are not simple binary mixtures and that this is responsible for observed deviations from expected elution behavior.
Diels-Alder Adducts of 3,6-Dibromophencyclone with Short-Chain N-n-Alkylmaleimides: 1H and 13C Nuclear Magnetic Resonance Studies of Hindered Rotations and Magnetic Anisotropy, and Ab Initio Calculations for Optimized Structures
Authors: Rosmarion Kerstin , Rothchild Robert
Published: April 2005

3,6-Dibromophencyclone, 2, reacted with N-ethylmaleimide, 3a; N- n-propylmaleimide, 3b; and N- n-butylmaleimide, 3c; to form the corresponding Diels-Alder adducts, 4a, 4b, and 4c. The nuclear magnetic resonance (NMR) spectra of the adducts were studied at ambient temperatures at 300 MHz for proton and 75 MHz for carbon-13. Full proton assignments were achieved by high-resolution COSY45 spectra for the aryl proton regions. Rigorous assignments for protonated carbons were obtained with the heteronuclear chemical shift correlation spectra (HETCOR). Slow exchange limit (SEL) spectra were observed for both proton and carbon-13 NMR for each adduct, with slow rotation on the NMR timescales for the unsubstituted bridgehead phenyl groups. Endo Diels-Alder adduct stereochemistry was supported by substantial magnetic anisotropic shielding effects in the 1H NMR spectra of the alkyl groups. Proton NMR shifts are compared with those previously reported for the corresponding adducts, 5b and 5c, obtained from 3b and 3c, respectively, with the parent compound, phencyclone, 1. Results of ab initio molecular modeling calculations at the Hartree-Fock level using the LACVP* basis set for conformers of the dibrominated adducts, 4a–4c, are presented, together with HF/6–31G* results for the non-brominated adducts, 5a, 5b, and 5c. Novel aspects of this present work include: (a) attempts to quantitatively evaluate alkyl proton NMR shielding magnitudes in the adducts, relative to maleimide precursors, and (b) use of ab initio Hartree-Fock level calculations to try to reconcile adduct geometries with the observed shielding magnitudes. Our results here complement and extend studies of: (a) adducts of the parent phencyclone with straight-chain N- n-alkylmaleimides, and (b) adducts of 3,6-dibromophencyclone with other symmetrical dienophiles.
Repeated Cocaine Administration Increases Voltage-Sensitive Calcium Currents in Response to Membrane Depolarization in Medial Prefrontal Cortex Pyramidal Neurons
Authors: Nasif Fernando J. , Hu Xiu-Ti , White Francis J.
Published: April 2005

The medial prefrontal cortex (mPFC) plays a critical role in cocaine addiction. However, evidence to elucidate how the mPFC is functionally involved in cocaine addiction remains incomplete. Recent studies have revealed that repeated cocaine administration induces various neuroadaptations in pyramidal mPFC neurons, including a reduction in voltage-gated K+currents (VGKCs) and a possible increase in voltage-sensitive Ca2+currents (ICa). Here, we performed both current-clamp recordings in brain slices and voltage-clamp recordings in freshly dissociated cells to determine whetherICais altered in mPFC pyramidal neurons after chronic cocaine treatment with a short-term or long-term withdrawal. In addition, a critical role of VGKCs in regulating the generation of Ca2+plateau potential was also studied in mPFC neurons. Repeated cocaine administration significantly prolonged the duration of evoked Ca2+plateau potentials and increased the whole-cellICain mPFC neurons after a 3 d withdrawal. Selective blockade of L-type Ca2+channels by nifedipine not only significantly increased the threshold but also reduced the duration and amplitude of Ca2+plateau potentials in both saline- and cocaine-withdrawn mPFC neurons. However, there was no significant difference in the increased threshold, reduced duration, and decreased amplitude of Ca2+potentials between saline- and cocaine-withdrawn neurons after blockade of L-type Ca2+channels. Moreover, an increase in amplitude was also observed, whereas the prolonged duration persisted, in Ca2+potentials after 2-3 weeks of withdrawal. These findings indicate that chronic exposure to cocaine facilitates the responsiveness ofICa, particularly via the activated L-type Ca2+channels, to excitatory stimuli in rat mPFC pyramidal neurons.
Continuous and Overlapping Expression Domains of Odorant Receptor Genes in the Olfactory Epithelium Determine the Dorsal/Ventral Positioning of Glomeruli in the Olfactory Bulb
Authors: Miyamichi Kazunari , Serizawa Shou , Kimura Hiroko M. , Sakano Hitoshi
Published: April 2005

In mammals, olfactory signals received by odorant receptors (ORs) in the olfactory epithelium (OE) are converted to a topographical map of activated glomeruli in the olfactory bulb (OB). It has been reported that the OE can be divided into four topographically distinct zones and that olfactory sensory neurons (OSNs) expressing a particular OR gene are randomly distributed within one zone. Here, we analyzed 80 different class II OR genes for their expression patterns in the OE byin situhybridization. It was found that the expression area in the OE does not always fit into one of the four conventional zones. Expression areas are specific to each OR gene and are arranged in an overlapping and continuous manner in the OE. We also analyzed a spatial relationship between the OE and the OB for OSN projection. Our transgenic as well as DiI retrograde staining experiments demonstrated that the dorsal/ventral arrangement of glomeruli in the OB is correlated with the expression areas of corresponding ORs along the dorsomedial/ventrolateral axis in the OE. The present study indicates that the OR gene choice may be more restricted by the OSN location in the OE than what has been thought.
Plexin-A4 Mediates Axon-Repulsive Activities of Both Secreted and Transmembrane Semaphorins and Plays Roles in Nerve Fiber Guidance
Authors: Suto Fumikazu , Ito Keisuke , Uemura Masato , Shimizu Masayuki , Shinkawa Yutaka , Sanbo Makoto , Shinoda Tomoyasu , Tsuboi Miu , Takashima Seiji , Yagi Takeshi , Fujisawa Hajime
Published: April 2005

It has been proposed that four members of the plexin A subfamily (plexin-As; plexin-A1, -A2, -A3, and -A4) and two neuropilins (neuropilin-1 and neuropilin-2) form complexes and serve as receptors for class 3 secreted semaphorins (Semas), potent neural chemorepellents. The roles of given plexin-As in semaphorin signaling and axon guidance, however, are mostly unknown. Here, to elucidate functions of plexin-A4 in semaphorin signaling and axon guidance eventsin vivo, we generatedplexin-A4null mutant mice by targeted disruption of theplexin-A4gene.Plexin-A4mutant mice were defective in the trajectory and projection of peripheral sensory axons and sympathetic ganglion (SG) axons and the formation of the anterior commissure and the barrels. The defects in peripheral sensory and SG axons were fundamentally related to those ofneuropilin-1orSema3Amutant embryos reported but were more moderate than the phenotype in these mutants. The growth cone collapse assay showed that dorsal root ganglion axons and SG axons ofplexin-A4mutant embryos partially lost their responsiveness to Sema3A. These results suggest that plexin-A4 plays roles in the propagation of Sema3A activities and regulation of axon guidance and that other members of the plexin-A subfamily are also involved in the propagation of Sema3A activities. Plexin-A4-deficient SG axons did not lose their responsiveness to Sema3F, suggesting that plexin-A4 serves as a Sema3A-specific receptor, at least in SG axons. In addition, the present study showed that plexin-A4 bound class 6 transmembrane semaphorins, Sema6A and Sema6B, and mediated their axon-repulsive activities, independently of neuropilin-1. Our results imply that plexin-A4 mediates multiple semaphorin signals and regulates axon guidancein vivo.
Dendrodendritic Synaptic Signals in Olfactory Bulb Granule Cells: Local Spine Boost and Global Low-Threshold Spike
Authors: Egger Veronica , Svoboda Karel , Mainen Zachary F.
Published: April 2005

In the mammalian olfactory bulb, axonless granule cells process synaptic input and output reciprocally within large spines. The nature of the calcium signals that underlie the presynaptic and postsynaptic function of these spines is mostly unknown. Using two-photon imaging in acute rat brain slices and glomerular stimulation of mitral/tufted cells, we observed two forms of action potential-independent synaptic Ca2+signals in granule cell dendrites. Weak activation of mitral/tufted cells produced stochastic Ca2+transients in individual granule cell spines. These transients were strictly localized to the spine head, indicating a local passive boosting or spine spike. Ca2+sources for these local synaptic events included NMDA receptors, voltage-dependent calcium channels, and Ca2+-induced Ca2+release from internal stores. Stronger activation of mitral/tufted cells produced a low-threshold Ca2+spike (LTS) throughout the granule cell apical dendrite. This global spike was mediated by T-type Ca2+channels and represents a candidate mechanism for subthreshold lateral inhibition in the olfactory bulb. The coincidence of local input and LTS in the spine resulted in summation of local and global Ca2+signals, a dendritic computation that could endow granule cells with subthreshold associative plasticity.
Stimulus Dependence of Neuronal Correlation in Primary Visual Cortex of the Macaque
Authors: Kohn Adam , Smith Matthew A.
Published: April 2005

Nearby cortical neurons often have correlated trial-to-trial response variability, and a significant fraction of their spikes occur synchronously. These two forms of correlation are both believed to arise from common synaptic input, but the origin of this input is unclear. We investigated the source of correlated responsivity by recording from pairs of single neurons in primary visual cortex of anesthetized macaque monkeys and comparing correlated variability and synchrony for spontaneous activity and activity evoked by stimuli of different orientations and contrasts. These two stimulus manipulations would be expected to have different effects on the cortical pool providing input to the recorded pair: changing stimulus orientation should recruit different populations of cells, whereas changing stimulus contrast affects primarily the relative strength of sensory drive and ongoing cortical activity. Consistent with this predicted difference, we found that correlation was affected by these stimulus manipulations in different ways. Synchrony was significantly stronger for orientations that drove both neurons well than for those that did not, but correlation on longer time scales was orientation independent. Reducing stimulus contrast resulted in a decrease in the temporal precision of synchronous firing and an enhancement of correlated response variability on longer time scales. Our results thus suggest that correlated responsivity arises from mechanisms operating at two distinct timescales: one that is orientation tuned and that determines the strength of temporally precise synchrony, and a second that is contrast sensitive, of low temporal frequency, and present in ongoing cortical activity.
Secreted Semaphorins Modulate Synaptic Transmission in the Adult Hippocampus
Authors: Sahay Amar , Kim Chong-Hyun , Sepkuty Jehuda P. , Cho Edward , Huganir Richard L. , Ginty David D. , Kolodkin Alex L.
Published: April 2005

Modulation of synaptic activity is critical for neural circuit function and behavior. The semaphorins are a large, phylogenetically conserved protein family with important roles in neural development. However, semaphorin function in the adult brain has yet to be determined. Here, we show that the coreceptors for secreted semaphorins, the neuropilins, are found at synapses and localize to molecular layers of the adult mouse hippocampus and accessory olfactory cortex. Moreover, application of the secreted semaphorin Sema3F to acute hippocampal slices modulates both the frequency and amplitude of miniature EPSCs in granule cells of the dentate gyrus and pyramidal neurons of CA1. Finally, we show that mice lacking Sema3F are prone to seizures. These results suggest a novel role for semaphorins as synaptic modulators and illustrate the diverse repertoire of these guidance cues in both the formation and function of neural circuits.
Rapid Upregulation of α7 Nicotinic Acetylcholine Receptors by Tyrosine Dephosphorylation
Authors: Cho Chang-Hoon , Song Weifeng , Leitzell Katherine , Teo Esther , Meleth Annal D. , Quick Michael W. , Lester Robin A. J.
Published: April 2005

α7 nicotinic acetylcholine receptors (nAChRs) modulate network activity in the CNS. Thus, functional regulation of α7 nAChRs could influence the flow of information through various brain nuclei. It is hypothesized here that these receptors are amenable to modulation by tyrosine phosphorylation. In bothXenopusoocytes and rat hippocampal interneurons, brief exposure to a broad-spectrum protein tyrosine kinase inhibitor, genistein, specifically and reversibly potentiated α7 nAChR-mediated responses, whereas a protein tyrosine phosphatase inhibitor, pervanadate, caused depression. Potentiation was associated with an increased expression of surface α7 subunits and was not accompanied by detectable changes in receptor open probability, implying that the increased function results from an increased number of α7 nAChRs. SolubleN-ethylmaleimide-sensitive factor attachment protein receptor-mediated exocytosis was shown to be a plausible mechanism for the rapid delivery of additional α7 nAChRs to the plasma membrane. Direct phosphorylation/dephosphorylation of α7 subunits was unlikely because mutation of all three cytoplasmic tyrosine residues did not prevent the genistein-mediated facilitation. Overall, these data are consistent with the hypothesis that the number of functional cell surface α7 nAChRs is controlled indirectly via processes involving tyrosine phosphorylation.
Constrained price, address, or logit brand demand models: An econometric comparison in the Boston fluid milk market
Authors: Tian Li , Cotterill Ronald W.
Published: April 2005

This article estimates a general linear demand model for three fluid milk brands. It finds perverse signs and complementarity among these substitutes. We develop three constrained models to eliminate perverse signs: a price conduct constraint in the linear model that links private label and Garelick pricing, a generalized Mills address model, and the logit model. Statistical tests indicate that each of the three constrained models produces acceptable substitution patterns and that none is preferred to the other two. On nonstatistical grounds, however, the Mills and price‐constrained models perform best. This is the first empirical study of the Mills address model of private‐label pricing. Finally, we demonstrate that estimated price‐reaction functions and the corresponding total elasticities, which capture only strategic non‐collusive interaction in these Nash Bertrand models, provide interesting insight into competition among brands. EconLit citation: L670, L130.] © 2005 Wiley Periodicals, Inc. Agribusiness 21: 149–166, 2005.
Inversion of Stereoselectivity by Applying Mutants of the Hydroxynitrile Lyase from Manihot esculenta
Authors: Bühler Holger , Miehlich Burkhard , Effenberger Franz
Published: April 2005

The influence of Trp128‐substituted mutants of the hydroxynitrile lyase from Manihot esculenta (MeHNL) on the stereoselectivity of MeHNL‐catalyzed HCN additions to aldehydes with stereogenic centers, which yield the corresponding cyanohydrins, is described. In rac‐2‐phenylpropionaldehyde (rac‐1) reactions, wild‐type (wtMeHNL) and all MeHNL Trp128 mutants are highly (S)‐selective toward the (R) enantiomer of rac‐1; this results exclusively in (2S,3R)‐cyanohydrin ((2S,3R)‐2) with ≥96 % de. The (S) enantiomer of rac‐1, however, only reacts (S)‐selectively with wtMeHNL to give (2S,3S)‐2 with 80 % de, whereas with Trp128 mutants, (R) selectivity increases with decreasing size of the amino acids exchanged. The MeHNL W128A mutant is exclusively (R)‐selective, resulting in (2R,3S)‐2 with 86 % de. The reaction behavior of rac‐phenylbutyraldehyde (rac‐5) is comparable with rac‐1, which also inverts the stereoselectivity from (S) to (R) when the enzyme is exchanged from wtMeHNL to the W128A mutant. Stereogenic centers not adjacent to the aldehyde group, as in 7 and 9, do not influence the stereoselectivity of MeHNL catalysis, and (S) selectivity is observed in all cases. Stereoselectivity and inversion of stereoselectivity of MeHNL Trp128 mutant‐catalyzed cyanohydrin formation can be explained and rationalized with crystal‐structure‐based molecular modeling.
Highly Ordered Arrays of Metal/Semiconductor Core—Shell Nanoparticles with Tunable Nanostructures and Photoluminescence.
Authors: Lei Yong , Chim Wai‐Kin
Published: April 2005

For Abstract see ChemInform Abstract in Full Text.
Pr4N2S3 and Pr4N2Se3: Two Non‐Isostructural Praseodymium(III) Nitride Chalcogenides.
Authors: Lissner Falk , Schleid Thomas
Published: April 2005

For Abstract see ChemInform Abstract in Full Text.
Broensted Acid TfOH‐Mediated Reactions of Methylenecyclopropanes with Nitriles.
Authors: Huang Jin‐Wen , Shi Min
Published: April 2005

For Abstract see ChemInform Abstract in Full Text.
Second Generation Fluorous DEAD Reagents Have Expanded Scope in the Mitsunobu Reaction and Retain Convenient Separation Features.
Authors: Dandapani Sivaraman , Curran Dennis P.
Published: April 2005

For Abstract see ChemInform Abstract in Full Text.
Facile and Chemoselective Microwave‐Assisted Cleavage of Oximes to Their Corresponding Carbonyl Compounds Using N,N′‐Dibromo‐N,N′‐1,3‐propylene‐bis[(4‐methylphenyl)sulfonamide] as a Deoximating Reagent.
Authors: Khazaei Ardeshir , Manesh Abbas Amini , Ghasemi Amir Hoshang
Published: April 2005

For Abstract see ChemInform Abstract in Full Text.
Zeolite‐Mediated Conversion of Alcohols to p‐Methoxybenzyl Ethers.
Authors: Sharma G. V. M. , Punna Sreenivas , Ratnamala A. , Kumari V. Durga , Subrahmanyam M.
Published: April 2005

For Abstract see ChemInform Abstract in Full Text.
Regioselectivity in the Addition of Vinylmagnesium Bromide to Heteroarylic Ketones: C‐versus O‐Alkylation.
Authors: Boga Carla , Stengel Rayk , Abdayem Rodolphe , Del Vecchio Erminia , Forlani Luciano , Todesco Paolo E.
Published: April 2005

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Reaction of Carbon Tetrachloride with Hydrogen Peroxide
Authors: Tatarova L. A. , Trofimova K. S. , Gorban' A. V. , Khaliullin A. K.
Published: April 2005

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Platinum(II)/Europium(III)‐Catalyzed Intramolecular Hydroalkylation of 4‐Pentenyl β‐Dicarbonyl Compounds.
Authors: Liu Cong , Widenhoefer Ross A.
Published: April 2005

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Synthesis, Antimicrobial and Analgesic Activity of 4‐Aryl‐2‐tert‐butylamino‐4‐oxo‐2‐butenoic Acids.
Authors: Koz'minykh V. O. , Belyaev A. O. , Koz'minykh E. N. , Odegova T. F. , Makhmudov R. R.
Published: April 2005

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Direct Microwave Synthesis of N,N′‐Diacylhydrazines and Boc‐Protected Hydrazides by in situ Carbonylations under Air.
Authors: Herrero Maria Antonia , Wannberg Johan , Larhed Mats
Published: April 2005

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One‐Pot Approach for the Regioselective Synthesis of β‐Keto Sulfones Based on Acid‐Catalyzed Reaction of Sulfonyl Chlorides with Arylacetylenes and Water.
Authors: Lai Chunbo , Xi Chanjuan , Jiang Yanfeng , Hua Ruimao
Published: April 2005

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An Efficient Synthesis of Some Bis‐(2‐alkylthio‐5‐furfurylidene‐4H‐imidazol‐4‐one) Derivatives Bearing Potential Fungicidal Activities.
Authors: Sun Yong , Ding Ming‐Wu
Published: April 2005

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Linear Polynuclear Tetrazole‐Containing Compounds
Authors: Morozova S. E. , Komissarov A. V. , Esikov K. A. , Zubarev V. Yu. , Malin A. A. , Ostrovskii V. A.
Published: April 2005

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Discovery of Novel Tetrahydroisoquinoline Derivatives as Potent and Selective Factor Xa Inhibitors.
Authors: Ueno Hiroshi , Yokota Katsuyuki , Hoshi Jun‐ichi , Yasue Katsutaka , Hayashi Mikio , Uchida Itsuo , Aisaka Kazuo , Hase Yasunori , Katoh Susumu , Cho Hidetsura
Published: April 2005

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A Novel One‐Pot Procedure for the Synthesis of Stable Dioxadiazastannepines and Dioxadiazasilepines.
Authors: Singh M. S. , Singh A. K.
Published: April 2005

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A New ent‐Kaurane Diterpenoid from Isodon excisoides (Sun ex C. H. Hu) C. Y. Wu et H. W. Li
Authors: Ding Lan , Wang Han , Liu Guoan , Yang Dongjuan
Published: April 2005

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Limonoids from Cedrela sinensis.
Authors: Mitsui Kumiko , Maejima Masato , Fukaya Haruhiko , Hitotsuyanagi Yukio , Takeya Koichi
Published: April 2005

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New Method for the Synthesis of 5‐Hydroxycamptothecin Derivatives.
Authors: He Xungui , Gao Heyong , Lu Wei , Cai Junchao
Published: April 2005

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Synthesis of (‐)‐DAPD.
Authors: Sznaidman Marcos L. , Du Jinfa , Pesyan Amir , Cleary Darryl G. , Hurley Kevin P. , Waligora Frank , Almond Merrick R.
Published: April 2005

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Structures of New Aromatics Glycosides from a Japanese Folk Medicine, the Roots of Angelica furcijuga.
Authors: Morikawa Toshio , Matsuda Hisashi , Nishida Norihisa , Ohgushi Teruki , Yoshikawa Masayuki
Published: April 2005

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Dissociative Recombination of N2+, O2+, and NO+: Rate Coefficients for Ground State and Vibrationally Excited Ions
Authors: Sheehan Clint H. , St.‐Maurice J.‐P.
Published: April 2005

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Chemistry of Tetravalent Actinide Phosphates. Part 2
Authors: Brandel V. , Dacheux N.
Published: April 2005

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Chemistry of Tetravalent Actinide Phosphates. Part 1
Authors: Brandel V. , Dacheux N.
Published: April 2005

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Nickel‐Catalyzed Electrochemical Conjugate Addition of Organic Halides on Electron‐Deficient Olefins
Authors: Condon Sylvie , Nedelec Jean‐Yves
Published: April 2005

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Radical Reactions. Part 1.
Authors: Clark A. J. , Sherringham J.
Published: April 2005

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Transient 2H‐Phospholes as Powerful Synthetic Intermediates in Organophosphorus Chemistry
Authors: Mathey Francois
Published: April 2005

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Luminescent Chemosensors: From Molecules to Nanoparticles
Authors: Prodi Luca
Published: April 2005

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The Metathesis Reactions: From a Historical Perspective to Recent Developments.
Authors: Astruc Didier
Published: April 2005

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Pyrazol‐3‐ones. Part 2. Reactions of the Ring Atoms
Authors: Varvounis George , Fiamegos Yiannis , Pilidis George
Published: April 2005

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Confusion Approach to Porphyrinoid Chemistry
Authors: Srinivasan Alagar , Furuta Hiroyuki
Published: April 2005

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β‐Lactones: Intermediates from Natural Product Total Synthesis and New Transformations
Authors: Wang Yingcai , Tennyson Reginald L. , Romo Daniel
Published: April 2005

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Organometallic Complexes of the Bidentate Porphyrin
Authors: Setsune Jun‐ichiro
Published: April 2005

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C—H and C—Cl Activation by Mononuclear and Dinuclear Platinum Complexes with 7‐Azaindolyl‐Containing Chelates
Authors: Song Datong , Wang Suning
Published: April 2005

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Heterocycles with Built‐in Pseudothiourea Pharmacophores. Part 2. Synthesis and Biological Activities of Thiazole‐ and [1,3]Thiazine‐fused Benzimidazoles, Quinazolines and Perimidines
Authors: Hsu Ling‐Yih , Hu Ming‐Kuan , Liu Kang‐Chien
Published: April 2005

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Photo‐ and Electroactive Amorphous Molecular Materials‐molecular Design, Syntheses, Reactions, Properties, and Applications
Authors: Shirota Yasuhiko
Published: April 2005

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The Application of Single‐Bead FTIR and Color Test for Reaction Monitoring and Building Block Validation in Combinatorial Library Synthesis
Authors: Cournoyer Jason J. , Krueger Clinton A. , Wade Janice V. , Yan Bing
Published: April 2005

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Neuregulin‐1 enhances survival of human astrocytic glioma cells
Authors: Ritch Patricia S. , Carroll Steven L. , Sontheimer Harald
Published: April 2005

Malignant astrocytic gliomas, referred to as astrocytomas, represent the most commonly diagnosed adult primary brain tumor. These tumors are characterized by unrelenting growth that is often resistant to chemotherapy and radiation therapy. Tumor expansion into the healthy surrounding brain tissue produces severe and often fatal consequences. In this study, we examine the potential for the neuregulin‐1/erbB receptor signaling cascade to contribute to this process by modulating glioma cell growth. Using antibodies specific for the erbB receptors, we demonstrate the expression patterns for the erbB2, erbB3, and erbB4 receptors in human glioma biopsy samples. We then verify receptor expression in a panel of human glioma cell lines. Next, we investigate the status of the erbB2 and erbB3 receptors in the human glioma cell lines and find that they are constitutively tyrosine‐phosphorylated and heterodimerized. Subsequently, we demonstrate that theses same cell lines express membrane bound and released forms of neuregulins, the erbB receptor ligands, suggesting a possible autocrine or paracrine signaling network. Furthermore, we show that exogenous activation of erbB2 and erbB3 receptors in U251 glioma cells by recombinant Nrg‐1β results in enhanced glioma cell growth under conditions of serum‐deprivation. This enhancement is due to an increase in cell survival rather than an increase in cell proliferation and is dependent on the activation of erbB2 and phosphatidylinositol‐3 kinase (PI3K). Moreover, Nrg‐1β activates an inhibitor of apoptosis, Akt, implying a possible role for this kinase in mediating Nrg‐1β effects in gliomas. This data suggests that glioma cells may use autocrine or paracrine neuregulin‐1/erbB receptor signaling to enhance cell survival under conditions where growth would otherwise be limited. © 2005 Wiley‐Liss, Inc.
Theoretical study on the reaction mechanism of the methyl radical with nitrogen oxides
Authors: Zhang Jia‐Xu , Liu Jing‐Yao , Li Ze‐Sheng , Sun Chia‐Chung
Published: April 2005

The radical‐molecule reaction mechanism of CH3 with NOx (x = 1, 2) has been explored theoretically at the B3LYP/6‐311G(d,p) and MC‐QCISD (single‐point) levels of theory. For the singlet potential energy surface (PES) of the CH3 + NO2 reaction, it is found that the carbon to middle nitrogen attack between CH3 and NO2 can form energy‐rich adduct a (H3CNO2) with no barrier followed by isomerization to b1 (CH3ONO‐trans), which can easily convert to b2 (CH3ONO‐cis). Subsequently, starting from b (b1, b2), the most feasible pathway is the direct NO bond cleavage of b (b1, b2) leading to P1 (CH3O + NO) or the 1,3‐H‐shift and NO bond rupture of b1 to form P2 (CH2O + HNO), both of which may have comparable contribution to the reaction CH3 + NO2. Much less competitively, b2 can take a concerted H‐shift and NO bond cleavage to form product P3 (CH2O + HON). Because the intermediates and transition states involved in the above three channels are all lower than the reactants in energy, the CH3 + NO2 reaction is expected to be rapid, as is consistent with the experimental measurement in quality. For the singlet PES of the CH3 + NO reaction, the major product is found to be P1 (HCN + H2O), whereas the minor products are P2 (HNCO + H2) and P3 (HNC +H2O). The CH3 + NO reaction is predicted to be only of significance at high temperatures because the transition states involved in the most feasible pathways lie almost above the reactants. Compared with the singlet pathways, the triplet pathways may have less contributions to both reactions. The present study may be helpful for further experimental investigation of the title reactions. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 807–817, 2005
FIB cross‐sectioning of a single rapidly solidified hypereutectic Al‐Si powder particle for HRTEM
Authors: Rea K.E. , Agarwal A. , McKechnie T. , Seal S.
Published: April 2005

A creative technique of in‐situ focused ion beam (FIB) extraction was introduced to prepare a gas atomized rapidly solidified hypereutectic Al‐Si single particle's cross‐section for High Resolution Transmission Electron Microscopy (HRTEM) analysis. This preparation technique may be employed to characterize very inimitable samples that are abnormally wrought or intricate to prepare through traditional techniques. TEM results revealed that a gas‐atomization/rapid solidification process leads to a homogeneous dispersion of 50–100‐nm Si phase in the Al matrix. Stacking faults and dislocations are observed in the microstructure and will ultimately lead to the increased strength in a resultant bulk material manufactured from this powder to be further examined. Microsc. Res. Tech. 66:10–16, 2005. © 2005 Wiley‐Liss, Inc.