bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linkage disequilibrium assessment via log‐linear modeling of SNP haplotype frequencies
Authors: Morris Andrew , Pedder Alan , Ayres Karen 
Published: August 2003

AbstractAnalyses of high‐density single‐nucleotide polymorphism (SNP) data, such as genetic mapping and linkage disequilibrium (LD) studies, require phase‐known haplotypes to allow for the correlation between tightly linked loci. However, current SNP genotyping technology cannot determine phase, which must be inferred statistically. In this paper, we present a new Bayesian Markov chain Monte Carlo (MCMC) algorithm for population haplotype frequency estimation, particulary in the context of LD assessment. The novel feature of the method is the incorporation of a log‐linear prior model for population haplotype frequencies. We present simulations to suggest that 1) the log‐linear prior model is more appropriate than the standard coalescent process in the presence of recombination (>0.02 cM between adjacent loci), and 2) there is substantial inflation in measures of LD obtained by a “two‐stage” approach to the analysis by treating the “best” haplotype configuration as correct, without regard to uncertainty in the recombination process.Genet Epidemiol25:106–114, 2003. © 2003 Wiley‐Liss, Inc.
Perceived organizational support and work status: a comparison of the employment relationships of part‐time and full‐time employees attending university classes
Authors: Gakovic Anika , Tetrick Lois E. 
Published: August 2003

AbstractEmployees who were attending classes at a local university responded to measures of perceived organizational support, the content of their psychological contracts (e.g., relational and transactional obligations), social and economic exchange, the level of fulfillment of both employee and organizational obligations, and organizational commitment. Part‐time employees (N=319) reported higher levels of perceived organizational support and stronger economic exchange relationships, while full‐time employees (N=282) reported higher levels of continuance commitment—sacrifice and greater relational and transactional obligations to their organizations. There were no significant differences between the two groups in terms of the strength of social exchange relationships, the levels of their organizations' relational and transactional obligations to them, the degree to which they had fulfilled their obligations to their organizations or their organizations had fulfilled their obligations to them, the level of continuance commitment—perceived alternatives, affective commitment, and normative commitment. There were no differences in the strength of the relations between perceived organizational support and the other exchange variables depending on work status. Overall, the findings suggested that social exchange processes operate similarly for part‐time and full‐time employees. Copyright © 2003 John Wiley & Sons, Ltd.
Employment relationships and firm performance: evidence from an emerging economy
Authors: Wang Duanxu , Tsui Anne S. , Zhang Yichi , Ma Li 
Published: August 2003

AbstractDefining employment relationships from the employer's perspective and based on the inducement‐contribution framework, this study examined the link between employment relationships and firm performance in a heterogeneous sample of firms in the largest emerging economy in the world, i.e., the People's Republic of China. It also analyzed the contingent role of both the firm's strategic orientation and its ownership structure. The results demonstrated that it is the combination of a high level of expected contributions coupled with a high level of provided inducements (i.e., organization‐focused employment relationship approach) rather than a high level of either expected contributions or provided inducements alone that is critical for firm performance. Further, we found that it is not the organization‐focused but the underinvestment employment relationship approach that offers a competitive advantage if the firm pursues the prospector strategy or if the firm is a domestic privately owned enterprise. In particular, the domestic privately owned enterprises reported the highest firm performance when they used the underinvestment approach with their middle managers, in contrast to the state‐owned or foreign‐invested enterprises. These results support both the universalistic and the contingency perspectives on the relationship between employment relationships and firm performance. They also contribute to our understanding of employment relationships in the global context. Copyright © 2003 John Wiley & Sons, Ltd.
Development of SNMP‐XML translator and gateway for XML‐based integrated network management
Authors: Yoon Jeong‐Hyuk , Ju Hong‐Taek , Hong James W. 
Published: August 2003

AbstractThe research objective of our work is to develop a SNMP MIB to XML translation algorithm and to implement an SNMP‐XML gateway using this algorithm. The gateway is used to transfer management information between an XML‐based manager and SNMP‐based agents. SNMP is widely used for Internet management, but SNMP is insufficient to manage continuously expanding networks because of constraints in scalability and efficiency. XML–based network management architectures are newly proposed as alternatives to SNMP‐based network management, but the XML‐based Network Management System (XML‐based NMS) cannot directly manage legacy SNMP agents. We also implemented an automatic specification translator (SNMP MIB to XML Translator) and an SNMP‐XML gateway. Copyright © 2003 John Wiley &Sons, Ltd.
Differential effects of dopamine on a potassium current in cultured rutabaga and wild‐type Drosophila cells
Authors: Alshuaib Waleed B. , Mathew Mini V. , Hasan Mohammed Y. , Fahim Mohamed A. 
Published: August 2003

AbstractThe rutabaga mutation which has a low intracellular cyclic adenosine monophosphate (cAMP) concentration is defective in short‐term memory. The aim of this study was to compare modulation effects of dopamine on the delayed‐rectifier potassium current (IKDR) in rutabaga and wild‐type Drosophila neurons. The conventional whole‐cell patch‐clamp technique was applied to cultured Drosophila neurons derived from embryonic neuroblasts. IKDR was measured from cultured (2 days) wild‐type and rutabaga neurons. IKDR was smaller in rutabaga neurons (373 ± 38 pA) than in wild‐type neurons (519 ± 40 pA) but there was no difference in IKDR activation in wild‐type inactivation between the two genotypes. We examined the effects of dopamine on IKDR in wild‐type and rutabaga neurons. IKDR was measured from neurons before and after addition of dopamine to the external solution. Dopamine application reduced IKDR in wild‐type neurons but did not significantly affect IKDR in rutabaga neurons (single‐cell studies). In the presence of dopamine there was no difference in IKDR between wild‐type (344 ± 29 pA) and rutabaga (338 ± 27pA) neurons (population studies). These results indicate that dopamine differentially affects the delayed‐rectifier channel in wild‐type and rutabaga neurons. This can alter neuronal excitability in rutabaga and may affect the processing of neural signals necessary for learning and memory.
Response properties of cat striate neurons to simulated optic flow stimuli
Authors: Li Bao‐Wang , Li Bing , Chen Yao , Diao Yun‐Cheng 
Published: August 2003

AbstractOptic flow analysis has been extensively investigated in several extrastriate visual areas of the primate, but it remains unclear whether and how the striate cortex is involved in the processing. In the present study 156 striate neurons in anaesthetized cats were tested with simulated optic flow patterns. More than 80% of the cells responded to the stimuli, about 30% significantly preferred translation to radiation and rotation, but few, if any, displayed clear preference for radial or circular motion. Most responsive neurons had fairly good direction sensitivity for their optimal stimuli. Generally, the differences between simple and complex cells were small and insignificant. Although translation obviously prevailed over radiation and rotation in driving more cells and eliciting stronger responses, the responsivity to complex flow fields was not predictable with the direction preference to planar motion. These results suggest that the striate contribution to optic flow analysis may go beyond the direction selectivity to local translation and there might be some kind of specific mechanism to complex motion features.
Reactions of halo‐ and dihaloadamantanes with nitromethane anions by the SRN1 mechanism
Authors: Santiago Ana N. , Toledo Carlos A. , Rossi Roberto A. 
Published: August 2003

AbstractThe reactions of 1‐bromo‐, 2‐bromo‐, 1,3‐dibromo‐ and 1,4‐dibromoadamantane with −CH2NO2 anions were studied in DMSO and in liquid ammonia. The photostimulated reaction of 1‐haloadamantane (1‐AdX, X = Br, I) or 2‐AdBr with −CH2NO2 anions gave good yields of the substitution product 1‐AdCH2NO2 and 2‐AdCH2NO2, respectively, in the presence of the enolate anions of acetone (entrainment conditions). On the other hand, 1‐adamantanol was the main product of the reaction performed in DMSO without irradiation, but not in liquid ammonia. 1,3‐Dibromo and 1,4‐dibromoadamantane reacted with −CH2NO2 anions under irradiation in the presence of the enolate anions of acetone. The first compound gave the disubstitution product 11, and the second the monobromo‐substitution products 15 and 16, together with the disubstitution product 17. Compounds 15 and 16 were shown to be intermediates in the formation of 17. Copyright © 2003 John Wiley & Sons, Ltd.
Reactions of lithiated aromatic heterocycles with carbon monoxide
Authors: Liñares Guadalupe E. García , Nudelman Norma S. 
Published: August 2003

AbstractThe reaction of lithium derivatives of aromatic heterocycles with carbon monoxide was studied under several reaction conditions: 2‐furyllithium afforded only one product, the tetrahydro‐2‐furaldehyde (25% yield). On the other hand, 2‐thienyllithium and 5‐methyl‐2‐furyllithium gave two and five products, respectively. Although in relatively low yields, formation of highly functionalized compounds takes place in a fast process under mild conditions. For 1,4‐dihydroxy‐1,4‐bis(5‐methyl‐2‐furanyl)butane‐2,3‐dione, reaction conditions were achieved to obtain this difficult to prepare derivative in 50% yield. To the best of our knowledge, this is the first report on the reaction of lithiated aromatic heterocycles with CO: evidence is given on the involvement of proton transfers in the reactions of 2‐furyllithium and 2‐thienyllithium, while the reaction of 5‐methyl‐2‐furyllithium seems to proceed through an electron transfer as the first step. Copyright © 2003 John Wiley & Sons, Ltd.
Antioxidant properties of extracts from Alchornea laxiflora (Benth) Pax and Hoffman
Authors: Olatunde Farombi E. , Ogundipe Oluyemisi O. , Samuel Uhunwangho E. , Adeyanju Mary A. , Olarenwaju Moody J. 
Published: August 2003

AbstractThe antioxidant activities of the leaf and root extracts of Alchornea laxiflora, a plant used locally for the preservation of food items in Nigeria, were evaluated using the ferric thiocyanate method, horseradish peroxidase catalysed oxidation of 2,2 azinobis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS), β‐carotene linoleate model system and Fe2+/ascorbate/H2O2‐induced rat liver microsomal lipid peroxidation. The crude hexane root (HR), methanol root (MR), methanol leaf (ML) and hexane leaf (HL) extracts from A. laxiflora were tested for antioxidant activities. Antioxidant activity decreased in the following order: HR (76.4%), MR (63%), ML (40%) and HL (38%) at a concentration of 0.05% v/v. The antioxidant activity of HR compared to that of butylated hydroxyanisole (BHA) (80%), a standard antioxidant. The total antioxidant activity (TAA) of the crude extracts suggests that activity is highest in the HR compared with the others. The TAA value was estimated to be 8.0 measured as mm of vitamin C equivalent. Six column chromatographic fractions (FI–FVI) from HR showed antioxidant activity to varying extents in the β‐carotene model system in the order of FII > FI > FVI > FIII > FIV > FV. FII exhibited the highest antioxidant activity in all model systems utilized, it recorded a higher antioxidant activity than BHA and quercetin in the β‐carotene linoleate and Fe2+/ascorbate/H2O2. TLC analysis of fraction II revealed the presence of terpenoid compounds (radiant green coloration with 2,4 dinitrophenylhydrazine). Our results suggest that A. laxiflora contains potent natural antioxidants and may therefore be relevant in the preservation of lipid food products, which are prone to oxidation and rancidity. Copyright © 2003 John Wiley & Sons, Ltd.
New methods for shape and depth determinations from SP data
Authors: Abdelrahman El‐Sayed M. , El‐Araby Hesham M. , Hassaneen Abdel‐Rady G. , Hafez Mahfooz A. 
Published: August 2003

We have extended our earlier derivative analysis method to higher derivatives to estimate the depth and shape (shape factor) of a buried structure from self‐potential (SP) data. We show that numerical second, third, and fourth horizontal‐derivative anomalies obtained from SP data using filters of successive window lengths can be used to simultaneously determine the depth and the shape of a buried structure. The depths and shapes obtained from the higher derivatives anomaly values can be used to determine simultaneously the actual depth and shape of the buried structure and the optimum order of the regional SP anomaly along the profile. The method is semi‐automatic and it can be applied to residuals as well as to observed SP data. We have also developed a method (based on a least‐squares minimization approach) to determine, successively, the depth and the shape of a buried structure from the residual SP anomaly profile. By defining the zero anomaly distance and the anomaly value at the origin, the problem of depth determination has been transformed into the problem of finding a solution of a nonlinear equation of form f(z) = 0. Knowing the depth and applying the least‐squares method, the shape factor is determined using a simple linear equation. Finally, we apply these methods to theoretical data with and without random noise and on a known field example from Germany. In all cases, the depth and shape solutions obtained are in good agreement with the actual ones.
Deconvolution and spatial resolution of airborne gamma‐ray surveys
Authors: Billings Stephen D. , Minty Brian R. , Newsam Garry N. 
Published: August 2003

The first part of the paper presents a method for frequency domain deconvolution of airborne gamma‐ray surveys using a Wiener filter. A geometrical detector model is used to model gamma‐ray detection, with aircraft movement simply incorporated by a multiplicative term. The method requires estimation of the autocorrelation functions governing both signal and noise. The former is estimated through the radially averaged power spectrum of the survey data, whereas an error propagation analysis is used to estimate the latter, which is assumed white. Slight manual adjustments to the noise level are used to tune the reconstruction.The technique is applied to a low‐altitude radiometric survey collected along closely spaced transects. Results are good for thorium, but are poor for both potassium and uranium. This can be attributed to the high noise levels in the potassium and uranium estimates, principally due to scattered gamma‐rays from high thorium concentration. Much better results are obtained when the method is applied to a survey with more typical radioelement concentrations. The reconstructions are improved significantly if an adaptive 2D Lee filter is applied prior to deconvolution.The second part of the paper addresses how noise in the data and attenuation of signal due to the flying height limit the spatial resolution. The autocorrelation functions of signal and noise, along with the gamma‐ray model, can be used to determine how signal‐to‐noise ratio degrades with increasing height. The frequency where signal and noise are present in equal quantity can be used as an estimate of the spatial resolution. Predicted critical sampling rates range from 30 m at 20 m elevation to 60 m at 60 m elevation and 90 m at 120 m elevation.
3D ray+Born migration/inversion—Part 2: Application to the SEG/EAGE overthrust experiment
Authors: Operto Stéphane , Lambaré Gilles , Podvin Pascal , Thierry Philippe 
Published: August 2003

The SEG/EAGE overthrust model is a synthetic onshore velocity model that was used to generate several large synthetic seismic data sets using acoustic finite‐difference modeling. From this database, several realistic subdata sets were extracted and made available for testing 3D processing methods. For example, classic onshore‐type data‐acquisition geometries are available such as a swath acquisition, which is characterized by a nonuniform distribution of long offsets with azimuth and midpoints.In this paper, we present an application of 2.5D and 3D ray‐Born migration/inversion to several classical data sets from the SEG/EAGE overthrust experiment. The method is formulated as a linearized inversion of the scattered wavefield. The method allows quantitative estimates of short wavelength components of the velocity model.First, we apply a 3D migration/inversion formula formerly developed for marine acquisitions to the swath data set. The migrated sections exhibit significant amplitude artifacts and acquisition footprints, also revealed by the shape of the local spatial resolution filters. From the analysis of these spatial resolution filters, we propose a new formula significantly improving the migrated dip section. We also present 3D migrated results for the strike section and a small 3D target containing a channel.Finally, the applications demonstrate, that the ray+Born migration formula must be adapted to the acquisition geometry to obtain reliable estimates of the true amplitude of the model perturbations. This adaptation is relatively straightforward in the frame of the ray+Born formalism and can be guided by the analysis of the resolution operator.
Traveltime calculations from frequency‐domain downward‐continuation algorithms
Authors: Shin Changsoo , Ko Seungwon , Kim Wonsik , Min Dong‐Joo , Yang Dongwoo , Marfurt Kurt J. , Shin Sungryul , Yoon Kwangjin , Yoon Cheol Ho 
Published: August 2003

We present a new, fast 3D traveltime calculation algorithm that employs existing frequency‐domain wave‐equation downward‐continuation software. By modifying such software to solve for a few complex (rather than real) frequencies, we are able to calculate not only the first arrival and the approximately most energetic traveltimes at each depth point but also their corresponding amplitudes. We compute traveltimes by either taking the logarithm of displacements obtained by the one‐way wave equation at a frequency or calculating derivatives of displacements numerically. Amplitudes are estimated from absolute value of the displacement at a frequency.By using the one‐way downgoing wave equation, we also circumvent generating traveltimes corresponding to near‐surface upcoming head waves not often needed in migration. We compare the traveltimes computed by our algorithm with those obtained by picking the most energetic arrivals from finite‐difference solutions of the one‐way wave equation, and show that our traveltime calculation method yields traveltimes comparable to solutions of the one‐way wave equation. We illustrate the accuracy of our traveltime algorithm by migrating the 2D IFP Marmousi and the 3D SEG/EAGE salt models.
Feasibility of seismic characterization of multiple fracture sets
Authors: Grechka Vladimir , Tsvankin Ilya 
Published: August 2003

Estimation of parameters of multiple fracture sets is often required for successful exploration and development of naturally fractured reservoirs. The goal of this paper is to determine the maximum number of fracture sets of a certain rheological type which, in principle, can be resolved from seismic data. The main underlying assumption is that an estimate of the complete effective stiffness tensor has been obtained, for example, from multiazimuth, multicomponent surface seismic and vertical seismic profiling (VSP) data. Although typically only a subset of the stiffness elements (or some of their combinations) may be available, this study helps to establish the limits of seismic fracture‐detection algorithms.The number of uniquely resolvable fracture systems depends on the anisotropy of the host rock and the rheology and orientation of the fractures. Somewhat surprisingly, it is possible to characterize fewer vertical fracture sets than dipping ones, even though in the latter case the fracture dip has to be found from the data. For the simplest, rotationally invariant fractures embedded in either isotropic or transversely isotropic with a vertical symmetry axis (VTI) host rock, the stiffness tensor can be inverted for up to two vertical or four dipping fracture sets. In contrast, only one fracture set of the most general (microcorrugated) type, regardless of its orientation, is constrained by the effective stiffnesses. These results can be used to guide the development of seismic fracture‐characterization algorithms that should address important practical issues of data acquisition, processing, and inversion for particular fracture models.
Evolution of the cellular stress proteome: from monophyletic origin to ubiquitous function
Authors: Kültz Dietmar 
Published: August 2003

SUMMARYCells respond to acute environmental change by activating a stress response that is widely studied. However, knowledge of this stress response is fragmentary, and a unifying concept explaining its universality for many different species and types of stress is lacking. The need for a holistic view emphasizing the key aspects of the stress response is addressed by the following hypothesis. The cellular stress response is a reaction to any form of macromolecular damage that exceeds a set threshold, independent of the underlying cause. It is aimed at temporarily increasing tolerance limits towards macromolecular damage by utilizing a phylogenetically conserved set of genes and pathways that mediate global macromolecular stabilization and repair to promote cellular and organismal integrity under suboptimal conditions. This mechanism affords time for a separate set of stressor-specific adaptations,designed to re-establish cellular homeostasis, to take action. Supporting evidence, emerging conclusions, and ways to test this hypothesis are presented.
Regulation of a renal urea transporter with reduced salinity in a marine elasmobranch,Raja erinacea
Authors: Morgan Robyn L. , Ballantyne James S. , Wright Patricia A. 
Published: August 2003

SUMMARYMarine elasmobranchs retain urea and other osmolytes, e.g. trimethylamine oxide (TMAO), to counterbalance the osmotic pressure of seawater. We investigated whether a renal urea transporter(s) would be regulated in response to dilution of the external environment. A 779 bp cDNA for a putative skate kidney urea transporter (SkUT) was cloned, sequenced and found to display relatively high identity with facilitated urea transporters from other vertebrates. Northern analysis using SkUT as a probe revealed three signals in the kidney at 3.1, 2.8 and 1.6 kb. Upon exposure to 50% seawater, the levels of all three SkUT transcripts were significantly diminished in the kidney (by 1.8- to 3.5-fold). In response to environmental dilution, renal tissue osmolality and urea concentration decreased, whereas water content increased. There were no significant differences in osmolyte and mRNA levels between the dorsal–lateral bundle and ventral sections of the kidney. Taken together, these findings provide evidence that the downregulation of SkUT may play a key role in lowering tissue urea levels in response to external osmolality.