bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical Measures of Instability in Crop Output
Authors: Rai S. C. , Sarup Shanti 
Published: May 2007

AbstractSome aspects of methodological issues relating to statistical measures of instability in crop output has been discussed. Several existing techniques for detection and measurement of instability have been reviewed and some additions and modifications suggested. The application of distribution‐free tests has been indicated to test the significance of variability in the crop output over space and time. Various procedures have been explained by numerical data on crop output.
Generalized Maximum Range Tests for Pairwise Comparisons of Several Populations
Authors: Royen Th. 
Published: May 2007

AbstractA multiple comparison procedure (MCP) is proposed for the comparison of all pairs of several independent samples. This MCP is essentially the closed procedure with union‐intersection tests based on given single tests Qij for the minimal hypotheses Hij. In such cases where the α‐levels of the nominal tests associated with the MCP can be exhausted, this MCP has a uniformly higher all pair power than any refined Bonferroni test using the same Qij. Two different general algorithms are described in section 3. A probability inequality for ranges of i.i.d. random variables which is useful for some algorithms is proved in section 4. Section 5 contains the application to independent normally distributed estimates and section 6 the comparisons of polynomial distributions by multivariate ranges. Further applications are possible. Tables of the 0.05‐bounds for the tests of section 5 and 6 are enclosed.
A Closed‐form Jackknife Solution for the Behrens‐Fisher Problem
Authors: Schemper Michael 
Published: May 2007

AbstractA simple, closed‐form jackknife estimate of the actual variance of the Mann‐Whitney‐Wilcoxon statistic, as opposed to the standard permutational variance under the test's null hypothesis has been derived which permits avoiding anticonservative performance in the presence of heterosce‐dasticity. The formulation given allows modifications of the exponential scores test, of censored data tests by Gehan (1965), Peto & Peto (1977) and Prentice (1978), of tests for monotonic τ association by Kendall (1962) and for tests of ordered k‐sample hypotheses. A Monte Carlo study supports recommendations for the jackknife procedures, but also shows their limited advantages in exponential scores and censored data versions. Thus, the paper extends results by Fligner & Policello (1981).
A Note on Plots of P‐Values to Evaluate Many Tests Simultaneously
Authors: Koziol James A. 
Published: May 2007

AbstractSchweder and Spjøtvoll (1982) proposed an informal graphical procedure for simultaneous evaluation of possibly related tests, based on a plot of cumulative p‐values using the observed significance probabilities. We formalize this notion by application of Holm's (1979) sequentially rejective Bonferroni procedure: this maintains an overall experimentwise significance level, and yields an immediate estimate of the number of true hypotheses.
A Comparative Statistical Analysis of Genetic Distances. II–Confidence Intervals and Tests of Comparison
Authors: Katz Mariano 
Published: May 2007

AbstractWe present methods for constructing the confidence intervals of the estimations of absolute genetic distance and Nei's minimum and standard genetic distances. Two different estimators of the standard distance are considered: jack‐knife and corrected. A Monte‐Carlo simulation analysis permitted to choose the best adapted confidence interval type for each distance estimator and for each size of the samples of loci and of gametes, taking into account the magnitude of the estimation value. Simulated true confidence levels showed that the best results are obtained using abolute genetic distance. We also give rules for testing the significance of the difference of two distance estimations. Monte‐Carlo simulations were performed in order to obtain the distributions of the difference of two distance estimations under the null hypothesis and consequently the true type I errors of tests. Test powers, obtained by simulation under the alternative hypothesis, also showed the superiority of absolute genetic distance.
Potent Inhibitors of the Human UDP‐Glucuronosyltransferase 2B7 Derived from the Sesquiterpenoid Alcohol Longifolol
Authors: Bichlmaier Ingo , Kurkela Mika , Joshi Tanmaya , Siiskonen Antti , Rüffer Tobias , Lang Heinrich , Finel Moshe , Yli‐Kauhaluoma Jari 
Published: May 2007

AbstractThe tricyclic sesquiterpenol (+)‐longifolol served as a lead structure for the design of inhibitors of the human UDP‐glucuronosyltransferase (UGT) 2B7. Twenty‐four homochiral and epimeric longifolol derivatives were synthesized and screened for their ability to inhibit the enzyme. The absolute configuration at the stereogenic center C1′ was determined by X‐ray crystallography and 2D NMR spectroscopy (gHSQC, gNOESY). The phenyl‐substituted secondary alcohol 16 b (β‐phenyllongifolol) displayed the highest affinity toward UGT2B7, and its inhibitory dissociation constant was 0.91 nM. The mode of inhibition was rapidly reversible and competitive. The inhibitor was not glucuronidated by UGT2B7 or other hepatic UGTs, presumably as a result of the high steric demand exerted by the phenyl group. Inhibition assays employing 14 other UGT isoforms suggested that inhibitor 16 b was highly selective for UGT2B7.
Phase‐rotation in in‐vivo localized spectroscopy
Authors: Ramadan Saadallah 
Published: May 2007

AbstractPhase‐rotation is an alternative method to phase‐cycling in acquisition of magnetic resonance spectroscopic data. However, there has only been two papers describing its implementation in point resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) to date. This article aims to introduce and explain the principles of phase‐rotation, describe the implementations that were carried out so far in the current literature, compare phase‐rotation and phase‐cycling experimentally, and introduce the application of phase‐rotation in double‐quantum filtered (DQF) spectroscopy. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 147–153, 2007
NMR application for a study of reversible photochemical kinetics: A multisite case
Authors: Babailov S.P. , Mainichev D.A. , Purtov P.A. 
Published: May 2007

AbstractExpressions describing the NMR signal shape for photoinduced chemical exchange in a multi‐site system without spin‐spin splitting are obtained by dynamic NMR techniques. The methods provide a framework for planning experimental strategies aimed at studies of photoinduced chemical exchange in dissolved substances. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 140–146, 2007
Introducing dimensionless parameters into the correlation of NMR relaxation time to transport properties of porous media
Authors: Tomadakis Manolis M. 
Published: May 2007

AbstractDimensionless parameters representing the viscous permeability (k) and NMR relaxation time (T1) of particle beds, while accounting also for the particle size, are shown to improve drastically the accuracy of k‐T1 correlations in the slow diffusion regime, in the absence of bulk relaxation effects. The finding is based on a regression analysis of numerical results for k and T1 in both random and ordered isotropic and anisotropic beds of fibers. Use of the formation factor (F) improves further the accuracy of the correlations only for the strongly anisotropic unidirectional arrays of fibers. A survey of related literature reveals an extensive effort in recent years in upgrading k‐T1 correlations, driven primarily by applications in petroleum and gas field exploration and recovery. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 154–164, 2007.
Ammonium channel expression is essential for brain development and function in the larva of Ciona intestinalis
Authors: Marino Rita , Melillo Daniela , Di Filippo Miriam , Yamada Atsuko , Pinto Maria Rosaria , De Santis Rosaria , Brown Euan R. , Matassi Giorgio 
Published: May 2007

AbstractAmmonium uptake into the cell is known to be mediated by ammonium transport (Amt) proteins, which are present in all domains of life. The physiological role of Amt proteins remains elusive; indeed, loss‐of‐function experiments suggested that Amt proteins do not play an essential role in bacteria, yeast, and plants. Here we show that the reverse holds true in the tunicate Ciona intestinalis. The genome of C. intestinalis contains two AMT genes, Ci‐AMT1a and Ci‐AMT1b, which we show derive from an ascidian‐specific gene duplication. We analyzed Ci‐AMT expression during embryo development. Notably, Ci‐AMT1a is expressed in the larval brain in a small number of cells defining a previously unseen V‐shaped territory; these cells connect the brain cavity to the external environment. We show that the knockdown of Ci‐AMT1a impairs the formation of the brain cavity and consequently the function of the otolith, the gravity‐sensing organ contained in it. We speculate that the normal mechanical functioning (flotation and free movement) of the otolith may require a close regulation of ammonium salt(s) concentration in the brain cavity, because ammonium is known to affect both fluid density and viscosity; the cells forming the V territory may act as a conduit in achieving such a regulation. J. Comp. Neurol. 503:135–147, 2007. © 2007 Wiley‐Liss, Inc.
Morphometric analysis of the fiber populations of the rat sciatic nerve, its spinal roots, and its major branches
Authors: Prodanov Dimiter , Feirabend Hans K.P. 
Published: May 2007

AbstractCorrespondence between the nerve composition and the functional characteristics of its fiber populations is not always evident. To investigate such correspondence and to give a systematic picture of the morphology of the rat hind limb nerves, extensive morphometric study was performed on the sciatic nerve, its founding dorsal and ventral spinal roots, and its major branches. Nerve histology was examined in semithin sections via microscopic image analysis. Variation in the density of myelinated fibers, fiber interspace, and nerve cross‐sectional area was studied in individual roots and nerves. In the dorsal roots, fiber numbers and cross‐sectional areas were directly linearly proportional to the spinal root level number. Constituent fiber populations were identified using multicomponent lognormal models, and an optimal model for every nerve or root was selected by using an information theoretic approach. For the dorsal and ventral roots and the sciatic and peroneal nerves, optimal fiber population models consisted of three components, whereas, for the tibial and sural nerves, two components were optimal. Functional identities of the revealed fiber populations were established by using calculations of corresponding conduction velocities according to Arbuthnott et al. (J. Physiol. [1980] 308:125–157) and anatomical considerations. It is anticipated that morphological parameters established in this study would advance the development of neural prostheses in humans. The proximodistal correspondences among the fiber populations of different nerves were established by parametric statistical comparisons. The proposed approach provides a conceptual framework for understanding the comparative anatomy of the peripheral nerves and spinal roots and can be further applied in other species. J. Comp. Neurol. 503:85–100, 2007. © 2007 Wiley‐Liss, Inc.
Reduced axon sprouting after treatment that diminishes microglia accumulation at lesions in the leech CNS
Authors: Ngu Emmanuel Mbaku , Sahley Christie L. , Muller Kenneth J. 
Published: May 2007

AbstractThe role of mammalian microglia in central nervous system (CNS) repair is controversial. Microglia accumulate at lesions where they act as immune cells and phagocytize debris, and they may secrete neurotrophins, but they also produce molecules that can be cytotoxic, like nitric oxide (NO). To determine the importance of microglial accumulation at lesions on growth of severed CNS axons in the leech (Hirudo medicinalis), in which axon and synapse regeneration are notably successful even when isolated in tissue culture medium, microglial migration to lesions was reduced. Pressure (P) sensory neurons were injected with biocytin to reveal the extent of their sprouting 24 hours after lesioning. To reduce microglia accumulation at lesions, cords were treated for 3.5 hours with 3 mM ATP or 2 mM Nω‐nitro‐L‐arginine methyl ester (L‐NAME) or 50 μM Reactive blue‐2 (RB2) beginning 30 minutes before injury. Lesioned controls were either not treated with drug or treated 3 hours later with one of the drugs, after the migration and subsequent accumulation of most microglia had occurred, but before the onset of axon sprouting, for a total of seven separate conditions. There was a significant reduction in total sprout lengths compared with controls when microglial accumulation was reduced. The results suggest that microglial cells are necessary for the usual sprouting of injured axons. J. Comp. Neurol. 503:101–109, 2007. © 2007 Wiley‐Liss, Inc.
Developmental and adult expression of semaphorin 2a in the cricket Gryllus bimaculatus
Authors: Maynard Kristen R. , McCarthy Sarah S. , Sheldon Elizabeth , Horch Hadley Wilson 
Published: May 2007

AbstractDevelopmental guidance cues act to direct growth cones to their correct targets in the nervous system. Recent experiments also demonstrate that developmental cues are expressed in the adult mammalian nervous system, although their function in the brain is not yet clear. The semaphorin gene family has been implicated in the growth of dendrites and axons in a number of different species. While the expression of semaphorin and its influence on tibial pioneer neurons in the developing limb bud have been well characterized in the grasshopper, the expression of semaphorin 2a (sema2a) has not been explored in the adult insect. In this study we used polymerase chain reaction (PCR) with degenerate and gene‐specific primers to clone part of the secreted form of sema2a from Gryllus bimaculatus. Using in situ hybridization and immunohistochemistry, we confirmed that sema2a mRNA and protein expression patterns in the embryonic cricket were similar to that seen in the grasshopper. We also showed that tibial neuron development in crickets was comparable to that described in grasshopper. An examination of both developing and adult cricket brains showed that sema2a mRNA and protein were expressed in the Kenyon cells in mushroom bodies, an area involved in learning and memory. Sema2a expression was most obvious near the apex of the mushroom body in a region surrounding the neurogenic tip, which produces neurons throughout the life of the cricket. We discuss the role of neurogenesis in learning and memory and the potential involvement of semaphorin in this process. J. Comp. Neurol. 503:169–181, 2007. © 2007 Wiley‐Liss, Inc.
Chemotopic odorant coding in a mammalian olfactory system
Authors: Johnson Brett A. , Leon Michael 
Published: May 2007

AbstractSystematic mapping studies involving 365 odorant chemicals have shown that glomerular responses in the rat olfactory bulb are organized spatially in patterns that are related to the chemistry of the odorant stimuli. This organization involves the spatial clustering of principal responses to numerous odorants that share key aspects of chemistry such as functional groups, hydrocarbon structural elements, and/or overall molecular properties related to water solubility. In several of the clusters, responses shift progressively in position according to odorant carbon chain length. These response domains appear to be constructed from orderly projections of sensory neurons in the olfactory epithelium and may also involve chromatography across the nasal mucosa. The spatial clustering of glomerular responses may serve to “tune” the principal responses of bulbar projection neurons by way of inhibitory interneuronal networks, allowing the projection neurons to respond to a narrower range of stimuli than their associated sensory neurons. When glomerular activity patterns are viewed relative to the overall level of glomerular activation, the patterns accurately predict the perception of odor quality, thereby supporting the notion that spatial patterns of activity are the key factors underlying that aspect of the olfactory code. A critical analysis suggests that alternative coding mechanisms for odor quality, such as those based on temporal patterns of responses, enjoy little experimental support. J. Comp. Neurol. 503:1–34, 2007. © 2007 Wiley‐Liss, Inc.
Analysis of a clock‐recovery technique for circuit emulation services over packet networks
Authors: Aweya James , Montuno Delfin Y. , Ouellette Michel , Felske Kent 
Published: May 2007

AbstractOne important requirement of circuit emulation services (CES) over packet networks is clock synchronization and timing distribution among the nodes. CES depends on reliable and high‐quality timing for operations. In the time division multiplexing (TDM) world, whether plesiochronous digital hierarchy (PDH), synchronous digital hierarchy (SDH) or synchronous optical network (SONET) based, timing and synchronization is inherent in the design of the network. However, when timing critical services such PDH and SDH/SONET are carried over packet network (e.g. IP, Ethernet, etc.), the timing element is lost and has to be carried across the packet network by other means. A well‐known and widely implemented technique for clock recovery in CES is one that is based on packet inter‐arrival time (sometimes called time difference of arrival) averaging. The technique is very simple to implement but provides good performance only when packet losses and packet delay variation (PDV) are very low and well controlled. This technique has been extensively analysed through simulations but has not been fully characterized analytically with correlated traffic in the literature. In this paper, we provide a full analytical examination of this well‐known clock recovery technique. We analyse the effects of correlation of the delay variation in the traffic stream on the quality of the clock recovered by a receiver. We prove analytically that, for a general input process, high correlation of the delay variation produces a large variance of the recovered clock. Copyright © 2007 John Wiley & Sons, Ltd.
Structural, Electrochemical, and Spectroscopic Properties of a Class of Dodecasubstituted Iron Porphyrins Bearing Four Positive Charges Close to the Metal
Authors: Renner Mark W. , Bochot Constance , Héroux Annie , Mansuy Daniel , Battioni Pierrette 
Published: May 2007

AbstractThe first iron complexes of the tetracationic 2,3,7,8,12,13,17,18‐octaethyl‐5,10,15,20‐tetra‐N‐pyridiniumylporphyrin, (OEPy4P)4+, in which four pyridine molecules are attached to the meso‐carbon atoms through their nitrogen atoms, were synthesized in three steps starting from Zn(OEP) (Zn‐β‐octaethylporphyrin) with an overall yield of ca. 30 %. The X‐ray structure of [FeII(OEPy4P)(pyridine)2](CF3SO3)3(Br) established that the molecule adopts a severely distorted nonplanar saddle conformation. 1H NMR spectroscopy showed that the [FeII(OEPy4P)(B)2]4+ ligated complexes, B = pyridine (Py) or imidazole (Im), are low‐spin, FeII, S = 0. These complexes exhibit redox potentials for the FeIII/FeII couple that range between 0.62 and 0.38 V (vs. Ag/AgCl) and are shifted by as much as +0.7 V relative to those of the corresponding planar iron complexes of OEP and of the nonplanar complexes of OETPP. Such highly positive redox potentials explain the stability of these iron(II) porphyrins in air. As previously found for dodecasubstituted iron porphyrins bearing electron‐withdrawing groups, the UV/Vis spectra of the[FeII(OEPy4P)(B)2]4+ complexes exhibit Soret and visible bands which are redshifted by ca. 40 nm relative to those of Fe(OEP)(Py)2. These metallo‐OEPy4P4+complexes offer promising synthetic avenues to novel classes of highly charged porphyrins and multiporphyrin arrays, which are soluble in aqueous and polar organic solvents.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Modular N,O‐Chelating Ligands: Group‐4 Amidate Complexes for Catalytic Hydroamination
Authors: Lee Alison V. , Schafer Laurel L. 
Published: May 2007

AbstractAmidate ligands have been used as a modular ligand set for early transition‐metal complexes, and have been found to exhibit high reactivity in the catalytic hydroamination of alkynes, allenes, and alkenes. This microreview focuses on coordination metal complexes containing amidate functionality including their bonding, structure and reactivity trends. The synthesis and characterization of a number of different group‐4 metal complexes is presented, and their applications in both hydroamination and organic synthesis are discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Transfer Hydrogenation Reactions Catalyzed by Free or Silica‐Immobilized [RuCl2(ampy){RN(CH2PPh2)2}] Complexes
Authors: Del Zotto Alessandro , Greco Carla , Baratta Walter , Siega Katia , Rigo Pierluigi 
Published: May 2007

AbstractThe complexes cis‐[RuCl2(ampy){R1N(CH2PPh2)2}] [ampy = (2‐aminomethyl)pyridine, R1 = C6H5 or (CH3CH2O)3Si(CH2)3] showed very high catalytic activity in the homogeneous transfer hydrogenation of acetophenone (TOF > 300000 h–1) with the use of 2‐propanol as the hydrogen donor and in the presence of sodium isopropoxide. The ligand (CH3CH2O)3Si(CH2)3N(CH2PPh2)2 (ATM) was prepared in high yield by reacting (3‐aminopropyl)triethoxysilane, paraformaldehyde, and diphenylphosphane in toluene heated at 80 °C. The –N(CH2PPh2)2 function was attached to the surface of three different kinds of silica by means of two alternative methods. Thus, MA‐Si‐150 and mesoporous MA‐Si‐MCM‐41 were prepared by the reaction of the inorganic matrix with ATM, whereas MA‐Si‐60 was synthesized by reaction of the commercially available 3‐aminopropyl‐functionalized silica gel with HCHO and PHPh2 in refluxing toluene. The –(CH2)3N(CH2PPh2)2 functionalized inorganic materials were used to anchor the RuCl2(ampy) moiety; thus, three different silica‐immobilized versions of the cis‐[RuCl2(ampy)(ATM)] complex were obtained. The silica‐anchored complexes were tested in the transfer hydrogenation of acetophenone, which was found to be fast and quantitative; the effect of the nature of the silica support on the activity of the catalyst was almost negligible. It was possible to reuse the catalytic system for a second cycle without a decrease in the activity, but the efficiency of the catalyst considerably diminished in successive reuses.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)