bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Environmentally Benign System for Synthesis of β‐Hydroxylketones: L‐Histidine Asymmetrically Catalyzed Direct Aldol Reactions in Aqueous Micelle and Water‐like Media
Authors: Peng Yi‐Yuan , Peng Shu‐Jun , Ding Qiu‐Ping , Wang Qi , Cheng Jin‐Pei 
Published: March 2007

AbstractThe first histidine catalyzed direct aldol reactions of ketones with nitrobenzaldehydes in water and in poly(ethylene glycol) (PEG) were reported. It reveals that histidine is a good aldol catalyst for synthesis of β‐hydroxylketones in water and in PEG, giving good to excellent yields of the respective products. Better enantio‐ and regioselectivity were achieved using low molecular weight PEG as the media. The results show that histidine and PEG‐200 or ‐300 may constitute a promising environmentally benign system for asymmetric synthesis of β‐hydroxylketones.
Synthesis, Structure Analysis, and Antitumor Activity of (R)‐2,4‐Dioxo‐5‐fluoro‐1‐[1‐(methoxycarbonyl) Ethylaminocarbonylmethyl]‐1,2,3,4‐tetrahydropyrimidine
Authors: Yuan Ji‐Xin , Cai Xiao‐Qing , Chen Di‐Mei , Hu Mao‐Lin 
Published: March 2007

AbstractA new dipeptide compound, (R)‐2,4‐dioxo‐5‐fluoro‐1‐[1‐(methoxycarbonyl) ethylaminocarbonylmethyl]‐1,2,3, 4‐tetrahydropyrimidine (5‐FUAPM), has been synthesized and identified by means of elemental analysis, IR, 1H NMR and 13C NMR spectra. The single crystal of compound 5‐FUAPM·DMF was also obtained and characterized by DSC‐TGA techniques. The crystal belongs to orthorhombic space group P2121 21 with the cell parameters: a=0.4740(7) nm, b=1.923(3) nm, c=1.9229 nm, α=β=γ=90°, V=1.753 nm3, Z=4, Dc=1.312 g/cm3, Mr=346.32, F(000) =728 and μ=0.111 mm−1. The final R and wR are 0.1378 and 0.2862, respectively. The result of the biological test showed that the compound 5‐FUAPM has certain antitumor activities.
Surface (Local) Coils as NMR Receivers
Authors: J. H. Ackerman Joseph 
Published: March 2007

AbstractThe advent of “wide bore,” high‐field, high‐homogeneity magnets in the 1970s provided the opportunity to use nuclear magnetic resonance spectroscopy for nondestructive chemical analysis of intact biological systems. Surface or local coils, when used as NMR receivers, provide the NMR experiment with both high signal‐to‐noise sensitivity and a good degree of spatial discrimination. Such attributes are critical to the examination of biological processes in laboratory animals and human patients when concentrations of the metabolites of interest are low and when the sample is characterized by large‐scale heterogeneity, i.e., there are different tissues and organs of interest. The high signal sensitivity also provides for very high spatial resolution when such receivers are used in magnetic resonance imaging of regions such as the spine. This article describes the basic principles of surface coil NMR with the aim of illuminating the concepts underlying its widespread application for in vivo systems.
Phase‐Sensitive Detection. Part I: Phase, Gates, Phase‐Sensitive Detectors, Mixers, and the Rotating Frame
Authors: D. Traficante Daniel 
Published: March 2007

AbstractThe fundamental principles of phase, semiconductor materials, and transformers are presented. The use of diodes and transformers in the construction and operation of product detectors is then described. It is shown that the output of a phase‐sensitive detector “PSD” is a direct‐current “d‐c” voltage when the two inputs have the same frequency, and that the polarity of this voltage depends on the phase difference between the inputs. It is also shown that when the two input frequencies are different, the same device can act as a non‐linear mixer, because its output consists of the difference and the sum of the input frequencies. In an NMR spectrometer, a PSD acts as the heart of the receiver. One of its inputs is the NMR signal from the probe, and the other is a reference frequency obtained from the transmitter. The filtered PSD output is the difference between the two input frequencies, and is referred to as the free induction decay, or FID. It is shown that the reference to the PSD is conceptually analogous to the “rotating frame”. Finally, it is explained that the basic limitation of a single PSD is its inability to determine whether an NMR signal is of a higher or lower frequency than the reference.
A fuzzy PIC multiuser detection/vector channel estimation scheme in Rayleigh fading channels
Authors: Tseng Shu‐Ming 
Published: March 2007

AbstractWe propose a fuzzy parallel interference cancellation (PIC) multiuser detection/vector channel estimation (VCE) scheme in Rayleigh fading channels. The VCE is based on a first‐order auto‐regressive model and an expectation‐maximization algorithm. The signal‐to‐interference ratio and signal‐to‐noise ratio are estimated from the vector channel model's parameters, and we adapt the weight of each interference cancellation pathviafuzzy inference mechanism. The proposed fuzzy PIC and VCE cooperate in a way such that some of the fuzzy PIC input parameters come from the channel predictor and the fuzzy PIC makes the channel predictor be more accurate at the next PIC stage. Computing weightsviafuzzy adaptive method adds insignificant complexity because it involves only table lookup. The simulation results show that the proposed fuzzy PIC/VCE scheme performs better than theimprovedPIC/vector channel estimation scheme with optimal parameter in fast‐varying Rayleigh fading channels. Copyright © 2007 John Wiley & Sons, Ltd.
Range‐Doppler imaging
Authors: Feig Ephraim 
Published: March 2007

AbstractWe review various narrow‐band range‐Doppler imaging methods that have been proposed for radar and highlight the difficulties in their implementation and their limitations. We also present two new imaging schemes. The first involves the transmission of multiplexed chirps, and the second involves simple frequency division multiplexing. The second approach seems to yield the most promising range‐Doppler imaging methods.
SQUID tomographic neuromagnetic imaging
Authors: Singh Manbir , Brechner R. Ricardo 
Published: March 2007

AbstractThe human brain emits a measurable magnetic field in response to stimulation. The aim of neuromagnetic imaging is to produce maps of the underlying neuronal activity from measurements of the emitted magnetic field. Modeling neuronal activity by dipolar current sources, we have previously reported simulation studies to reconstruct planar source distributions using the algebraic reconstruction technique, with the constraint that the sources could only have two orientations. We now present a general solution for two‐dimensionally distributed sources, which is based on measuring both the normal and tangential components of the magnetic field. Also, using a single‐channel SQUID neuromagnetometer, we present results of a tomographic imaging experiment conducted with wires carrying currents to demonstrate the potential of neuromagnetic imaging in reconstructing extended cortical sources.
Low‐level bayesian segmentation of piecewise‐homogeneous noisy and textured images
Authors: Gimel'farb G. L. , Zalesny A. V. 
Published: March 2007

AbstractWe present a novel approach to image segmentation, differing from the known “simulated annealing” method in the following ways: the compound Bayesian decision rule and consequent maximal marginala posterioriprobability (MMAP) estimates of desired region labels in pixels; the two‐ or three‐level piecewise‐homogeneous Gibbs random field with constant control parameters as the probabilistic model of the images and region maps (in the general case such a model integrates the submodels of the region map, of the ideal intensities within each region, and of the noise distorting the ideal intensities); the stochastic relaxation with the constant control parameters of the Gibbs probability distribution only as a tool to obtain the samples of this field and estimate the unknown marginala posterioriprobabilities of the region labels by collecting in each pixel the histogram of labels for these samples; the like stochastic relaxation with directed variation of the control parameters of the Gibbs probability distribution as a tool to find maximal likelihood estimates of the unknown these parameters. Some experimental results are presented.
Experimental comparison of fourier transformation and model‐fitting methods of spectral analysis
Authors: Gardner William A. 
Published: March 2007

AbstractA summary of the results of an extensive comparative experimental study of Fourier transformation and model‐fitting methods of spectral analysis of random time‐series data is presented. It is illustrated that Fourier transformation methods can be an essential companion to model‐fitting methods even for short data segments with underlying sharp spectral peaks. The best spectrum estimates can be obtained by taking advantage of the strengths of both types of methods. For example, it is shown that detection and estimation of the frequencies of spectral lines for short data segments can be best accomplished using certain parametric methods in conjunction with Fourier transformation methods to aid in model‐order selection and identification of spurious peaks in the parametric spectrum estimate, and that estimation of amplitude and phase for sine‐wave removal, given frequency estimates, and spectrum estimation after sine‐wave removal can often be best accomplished with Fourier transformation methods alone.
Radar imaging
Authors: Mensa Dean L. 
Published: March 2007

AbstractRadar systems combining coherent signals with frequency and angular diversity offer the possibility of synthesizing images of complex objects with spatial resolution of a few wavelengths. The availability of high‐quality microwave sources and components, high‐speed digital computers, and efficient signal‐processing algorithms allows radar imaging to be implemented in laboratory environments using commercially‐available equipment. The paper summarizes fundamental issues by addressing conceptual and practical limits of radar imaging and presents examples obtained from results of measurements in a laboratory environment. Implementation details of sophisticated operational imaging radars are not covered.©1993 John Wiley & Sons Inc
Digital electro‐optical imaging sensors
Authors: Schueler Carl , Woody Loren 
Published: March 2007

AbstractA key source of digital images is the electro‐optical imaging sensor. The basic characteristic that identifies a digital electro‐optical sensor is conversion of reflected or emitted light from a scene or object into a digital image signal. Examples include television cameras with digital output, and scanning or staring cameras with digital output. We describe general system design techniques to derive optimum imaging sensor specifications, and we offer examples for two applications. One example application is for terrestrial thermal imaging of nearby objects, such as vehicles. The other example is a sensor to create a color image of small targets in low‐light, such as an automobile license plate from a distance of several meters.©1993 John Wiley & Sons Inc
The residual error of the reflectivity displacement method of SAR motion extraction
Authors: Moreira João R. 
Published: March 2007

AbstractReported herein is the estimation of the residual error of the reflectivity displacement method (RDM) and the dependence of RDM on terrain characteristics. The RDM is a method to be implemented on airborne synthetic aperture radars (SAR). It extracts the motion of the aircraft from the radar backscatter signal, allowing for motion compensation without using an inertial navigation system. An extended error analysis of this method and its dependence on the terrain type and contrast is performed. Results proving the estimated performance are shown.
On waveform design for optimal target discrimination
Authors: Riggs Lloyd S. , Richards Michael A. , Shumpert Thomas H. , Smith C. Ray 
Published: March 2007

AbstractProbability theory is applied to the problem of radar target discrimination. The theory is used to construct an excitation waveform (an enhanced discrimination pulse) which maximizes the posterior odds in favor of one target over the other. It is shown that the enhanced discrimination pulse has its spectrum concentrated near the frequency where the difference in the impulse spectrum of the two targets reaches a maximum. Enhanced discrimination pulses are calculated using analytical models of thin cylindrical targets and experimental data collected from simplified aircraft models.©1993 John Wiley & Sons Inc
Multifrequency backscattering tomography for constant and vertically varying backgrounds
Authors: Wu Ru‐Shan , Araújo Fernanda Vieira , Huang Lian‐Jie 
Published: March 2007

AbstractTo improve the resolution and image quality of the SFDT (Sigle‐Frequency Diffraction Tomography), a special fast multi‐frequency imaging method: Multi‐Frequency Backscattering Tomography (MFBT) is introduced in this paper. The method uses only the backscattered waves (after plane wave decomposition) while maintaining the merit of multi‐frequency method. The method is formulated for both the constant and vertically varying backgrounds. For the latter case the WKBJ approximation is used for the background Green's function. Formulas are derived both for volume scattering using the Born approximation and for boundary scattering using the physical optics approximation. Two reconstruction methods are presented. The backpropagation method can be used and has the same computation speed for both the constant and vertically varying backgrounds. Meanwhile the direct FT method is only formulated for the constant background, in which the backpropagation in z‐direction is implemented by FFT and therefore the computation speed is significantly increased. Compared with the SFDT using backpropagation reconstruction, the MFBT is nearlyNz/log2Nzfaster, whereNzis the number of grid points in z‐direction, and at the same time has a much better resolution and image quality. WhenNzis big, the time saving is remarkable. Compared with other multi‐frequency methods such as the multi‐frequency holography (prestack migration), the speeding factor becomesNfNz/log2Nz, whereNf, is the number of frequencies used. Numerical simulations for both constant and vertically varying backgrounds are performed to demonstrate the feasibility of the method and the quality of reconstructed images for different situations. Examples are also given to show that when the reconstruction procedure of constant background is applied to the case of vertically varying background, the image quality will be greatly deteriorated.©1994 John Wiley & Sons Inc
Orthogonal decomposition framework for ionospheric tomography algorithms
Authors: Sutton Eric , Na Helen 
Published: March 2007

AbstractComputerized ionospheric tomography (CIT) is one of the most recent developments in the area of remote sensing of the ionosphere. This system is a special case of limited angle tomography in which not only are projection angles limited, but the number of samples per projection varies. This article presents an orthogonal decomposition framework for unifying CIT algorithms including both generalized classical algorithms such as the algebraic reconstruction technique, the direct Fourier method, and filtered backprojection, and algorithms using basis functions from a priori information. This article discusses the orthogonality of the basis functions associated with the classical techniques and presents simulations comparing the use of a priori information in filtered backprojection and orthogonal decomposition.©1994 John Wiley & Sons Inc
Differential and semidifferential invariant signature functions for space curve recognition
Authors: Holt Robert J. , Netravali Arun N. 
Published: March 2007

AbstractA space curve distorted by certain transformations may be recognized if an invariant description of it is available. Recent research in this area, primarily dealing with plane curves, has shown that it is possible to identify transformed curves through the use of various combinations of differential invariants and point correspondences. Purely differential invariants usually require very high order derivatives of the space curves. However, taking advantage of point correspondences sharply reduces the order of derivatives necessary, especially when the correspondences are between points on the curves. In this case, invariant signature functions requiring the computation of just first‐order derivatives can be constructed with one point correspondence for similarity transformations and two point correspondences for affine transformations. Determining the equivalence of objects reduces to partial function matching when a suitable invariant is known. A detailed example is provided to illustrate our results.©1994 John Wiley & Sons Inc
An intuitive guide to the T1 based perfusion model
Authors: Chesler David A. , Kwong Kenneth K. 
Published: March 2007

AbstractWe explored a number of theoretical and practical approaches used to understand and optimize contrast to noise of the versatile T1 based perfusion model. The interplay between tissue T1 and blood T1 was investigated. We also provided a succinct evaluation of the several popular T1 based methods currently applied to measure flow and flow change.
Pixon‐based multiresolution image reconstruction and the quantification of picture information content
Authors: Puetter R. C. 
Published: March 2007

AbstractThis article reviews pixon‐based image reconstruction, which in its current formulation uses a multiresolution language to quantify an image's algorithmic information content (AIC) using Bayesian techniques. Each pixon (or its generalization, theinformation) represents a fundamental quanta of an image's AIC, and an image's pixon basis represents the minimum degrees of freedom necessary to describe the image within the accuracy of the noise. We demonstrate with a number of examples that pixon‐based image reconstruction yields results consistently superior to popular competing methods, including maximum likelihood and maximum entropy methods. Typical improvements include higher spatial resolution, greater sensitivity to faint sources, and immunity to the production of spurious sources and signal correlated residuals. Finally, we show how the pixon provides a generalization of the Akaike information criterion, and how it relates to concepts of “coarse graining” and the role of the Heisenberg uncertainly principle in statistical mechanics, provides a mechanism for optimal data compression, and represents a more optimal basis for image compression or reconstruction than wavelets.
The catalytically inactive precursor of cathepsin D induces apoptosis in human fibroblasts and HeLa cells
Authors: Schestkowa Olga , Geisel Dominik , Jacob Ralf , Hasilik Andrej 
Published: March 2007

AbstractIn several reports cathepsin D has been implicated in apoptosis. In some systems the effects of agents considered to be mediated by cathepsin D were inhibited in the presence of pepstatin A, an inhibitor of the enzyme. In other studies the effect of a mutant cathepsin D deprived of activity was indistinguishable from that of the normal enzyme. Here we show that in human fibroblasts and in HeLa cells apoptosis can be induced by microinjecting into cytosol either mature cathepsin D or its inactive precursor procathepsin D. The microinjected precursor remains in the uncleaved form. These results confirm that the proapoptotic effect of cathepsin D in the cytosol is independent of its catalytic activity and suggest that the interaction of cathepsin D with the downstream effector does not involve the active site of the enzyme, since in the proenzyme the active site is masked by the prosequence. J. Cell. Biochem. J. Cell. Biochem. 101: 1558–1566, 2007. © 2007 Wiley‐Liss, Inc.
The DNA topoisomerase IIβ binding protein 1 (TopBP1) interacts with poly (ADP‐ribose) polymerase (PARP‐1)
Authors: Wollmann Yvonne , Schmidt Uta , Wieland Gerhard D. , Zipfel Peter F. , Saluz Hans‐Peter , Hänel Frank 
Published: March 2007

AbstractWe investigated the physical association of the DNA topoisomerase IIβ binding protein 1 (TopBP1), involved in DNA replication and repair but also in regulation of apoptosis, with poly(ADP‐ribose) polymerase‐1 (PARP‐1). This enzyme plays a crucial role in DNA repair and interacts with many DNA replication/repair factors. It was shown that the sixth BRCA1 C‐terminal (BRCT) domain of TopBP1 interacts with a protein fragment of PARP‐1 in vitro containing the DNA‐binding and the automodification domains. More significantly, the in vivo interaction of endogenous TopBP1 and PARP‐1 proteins could be shown in HeLa‐S3 cells by co‐immunoprecipitation. TopBP1 and PARP‐1 are localized within overlapping regions in the nucleus of HeLa‐S3 cells as shown by immunofluorescence. Exposure to UVB light slightly enhanced the interaction between both proteins. Furthermore, TopBP1 was detected in nuclear regions where poly(ADP‐ribose) (PAR) synthesis takes place and is ADP‐ribosylated by PARP‐1. Finally, cellular (ADP‐ribosyl)ating activity impairs binding of TopBP1 to Myc‐interacting zinc finger protein‐1 (Miz‐1). The results indicate an influence of post‐translational modifications of TopBP1 on its function during DNA repair. J. Cell. Biochem. 102: 171–182, 2007. © 2007 Wiley‐Liss, Inc.
Comparison of the numerical stability of methods for anharmonic calculations of vibrational molecular energies
Authors: Daněček Petr , Bouř Petr 
Published: March 2007

AbstractOn model examples, we compare the performance of the vibrational self‐consistent field, variational, and four perturbational schemes used for computations of vibrational energies of semi‐rigid molecules, with emphasis on the numerical stability. Although the accuracy of the energies is primarily dependent on the quality of the potential energy surface, approximate approaches to the anharmonic vibrational problem often do not converge to the same results due to the approximations involved. For furan, the sensitivity to variations of the anharmonic potential was systematically investigated by adding random noise to the cubic and quartic constants. The self‐consistent field methods proved to be the most resistant to the potential variations. The second order perturbational techniques are sensitive to random degeneracies and provided the least stable results. However, their stability could be significantly improved by a simple generalization of the perturbational formula. The variational configuration interaction is practically limited by the size of the matrix that can be diagonalized for larger molecules; however, relatively fewer states need to be involved than for smaller ones, in favor of the computing. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Enzyme immunoassay for c‐reactive protein analysis
Authors: Unten Sharon K. , Hokama Y. 
Published: March 2007

AbstractA solid‐phase enzyme immunoassay method using goat anti‐CRP sensitized to polyvinyl 96 well plates and a second rabbit anti‐CRP highly specific for gamma mobility CRP is described in this study. Examination of serum samples of normal healthy individuals from cord blood, children (2–12 yr) and adults (16–83 yr) by this EIA method showed a progressive increase in CRP levels with age. The mean and standard error of the mean in ng/ml CRP was as follows with respect to age distribution: cord blood, 310 ± 54; children (2–12 yr), 664 ± 87; adults (16–35 yr), 1,145 ± 116; adults (36–50 yr), 3,775 ± 605; and adults (51–83 yr), 7,718 ± 1,482. Individuals in the age range of 22–34 yr with one or more abnormality in the chemistry profile analysis showed CRP levels with a higher X ± S.E.M. (3,615 ± 925). This is in contrast to the normal individuals of the same age range (1,145 ± 116). This EIA method is sensitive, reproducible, and specific. It should be a useful quantitative method for monitoring low level CRP responders, such as newborn and cord blood serum.