bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of oocyte collection technique on initial chromatin configuration, meiotic competence, and male pronucleus formation after intracytoplasmic sperm injection (ICSI) of equine oocytes*
Authors: Dell'Aquila Maria Elena , Masterson Mary , Maritato Filippo , Hinrichs Katrin
Published: August 2002

There is a great variability in the success of horse oocyte maturation and fertilization among laboratories. This study was conducted to determine if the meiotic and developmental competence of horse oocytes could be dependent on the method of oocyte collection, i.e., aspiration of follicular fluid with a vacuum apparatus, or opening follicles and scraping the granulosa layer. Horse oocytes were recovered from abattoir ovaries by aspiration or scraping and classified as having compact (Cp), expanded (Ex), or partial (P) cumuli. In Experiment 1 (Part A in May and Part B in October), oocytes were fixed immediately after collection to assess whether the collection method influenced the initial chromatin configuration of oocytes. In Experiment 2, in vitro maturation rates of oocytes recovered by aspiration or scraping were compared. In Experiment 3, oocytes were matured in vitro and submitted to intracytoplasmic sperm injection (ICSI). Initial chromatin configuration differed according to collection method in that there was a significantly higher prevalence of diffuse chromatin within the germinal vesicle in oocytes recovered by scraping than in oocytes recovered by aspiration (29/87, 33% and 28/166, 17%, respectively;P < 0.01). Maturation of oocytes to metaphase II did not significantly differ between scraped and aspirated oocytes (56/101, 55.4 % vs. 65/106, 61.4%, respectively). The overall pronucleus formation rate after ICSI of oocytes recovered by scraping was not significantly different than that of oocytes recovered by aspiration (50/99, 52.6% vs. 50/85, 68.5 %, respectively); however, the rate of abnormal fertilization was significantly higher for oocytes collected by aspiration (14/73, 19% vs. 6/94, 6%, respectively;P <0.05). These results demonstrate that the collection method affects the population of recovered oocytes and may contribute to differences in results observed among laboratories working with horse oocytes.Mol. Reprod. Dev.60: 79–88, 2001. © 2001 Wiley‐Liss, Inc.
Effect of two activation treatments and age of blastomere karyoplasts on in vitro development of bovine nuclear transfer embryos
Authors: Booth P.J. , Holm P. , Vajta G. , Greve T. , Callesen H.
Published: August 2002

The yield and quality of (a) parthenogenetic blastocysts produced by two activation treatments (cycloheximide [CHX] or 6‐dimethylaminopurine [DMAP]) and (b) nuclear transfer blastocysts generated using these two activation treatments and three different ages of karyoplast derived from day 3, 4, or 5 in vitro produced donor embryos, were examined in order to define an optimal nuclear transfer protocol. The two activation protocols comprised calcium ionophore followed by either CHX or DMAP. Parthenogenetic blastocyst yields were greater (P < 0.001) following activation with DMAP than CHX (59.7 ± 5.1 vs. 31.4 ± 4.5 [mean ± SEM]). In contrast, nuclear transfer blastocyst rates per fused embryo were lower (P < 0.0001) using cytoplasts activated with DMAP. The individual rates using day 3, 4, and 5 donors and using CHX and DMAP activation treatments were 31.9 ± 5.0, 31.7 ± 6.2, 20.4 ± 7.3 and 27.8 ± 4.7, 20.1 ± 7.5, 12.7 ± 8.3, respectively. Blastocyst rate per fused embryo was negatively correlated (P = 0.0091) with the total number of blastomeres per donor embryo. Despite this inverse relationship, the calculated potential blastocyst yield per donor embryo was positively correlated (P < 0.0048) to karyoplast age. The individual potential yields on days 3, 4, and 5 and for the two activation protocols (CHX and DMAP) were 4.7 ± 0.8, 7.2 ± 1.2, 10.1 ± 2.1 and 3.8 ± 0.8, 5.5 ± 2.1, 7.3 ± 4.1, respectively. One possible explanation for the observed inverse relationship is that differentiation events during early cleavage are able to reduce the ability of the cytoplast to reprogram the transferred karyoplast and hence reduce blastocyst yields. The mechanism that mediates the differential effect of the CHX and DMAP on blastocysts yields between parthenogenetic and nuclear transfer embryos remains to be elucidated. In conclusion, the results indicate that although activation of oocytes with DMAP can produce a higher percentage of blastocysts, CHX activation is superior for use in nuclear transfer. Mol. Reprod. Dev. 60:377‐383, © 2001 Wiley‐Liss, Inc.
Generation of cloned goats (Capra hircus) from transfected foetal fibroblast cells, the effect of donor cell cycle*
Authors: Zou Xiangang , Wang Yuge , Cheng Yong , Yang Yuefei , Ju Huiming , Tang Huilin , Shen Yu , Mu Zongyao , Xu Shaofu , Du Miao
Published: August 2002

The neomycin‐resistant gene (neor) is probably the most commonly used selectable marker gene in gene targeting and gene transfection research. In this study, the neor gene construct was introduced into in vitro cultured goat foetal fibroblast cells (IV‐5), and the cells were selected with 900 μg/ml G418. The G418‐resistant colonies were analysed by neo‐specific PCR, karyotyping and anti‐intermediate filament proteins antibody (anti‐vimentin) staining. Cell cycle analysis of the neor positive foetal fibroblast cell colony (IV‐5.1) cultured in a variety of cell cycle‐arresting medium indicated that 74.2% of cells cultured in serum‐deprived medium for 3 days and 71.7% of cells grown to confluence were at G0/G1 stage of cell cycle, respectively, in comparison to 61.6% of cells in normal culture (cycling) medium. Nocodazole treatment for 17 hr in vitro culture could increase the number of cells at G2/M stage of cell cycle from 20.3% (in cycling medium) to 39.7%. In total, one early pregnancy was observed by B ultra‐sound scanning in a surrogate transferred with cloned embryos from IV‐5.1 cells at M stage (cells were cultured in nocodazole medium). Seven cloned goats, including two that miscarried at a late stage, were derived from the IV‐5.1 cell clone cultured in starved medium (G0). Indeed, one surrogate receiving three blastocysts reconstituted from the starved donor cells, gave birth to three live cloned goats, all of which are healthy and doing well. PCR, Southern blot and G418 resistance in vitro of fibroblast cells from cloned goats confirmed that all cloned goats are positive for neor transgene. This study demonstrates that a foreign gene, such as the neo‐resistant gene, can be introduced into goat foetal fibroblast cells, and that the resulting transgenic cells are capable of being cloned to produce 100% transgenic animals. Mol. Reprod. Dev. 61: 164–172, 2002. © 2002 Wiley‐Liss, Inc.
Assignment of the T2 components of amphibian peripheral nerve to their microanatomical compartments
Authors: Wachowicz Keith , Snyder Richard E.
Published: August 2002

The proton transverse‐relaxation spectrum of peripheral nerve has been reported to consist of three components arising from microanatomical water compartments within the nerve. The component with the shortest decay time has been consistently seen to be a result of the myelin. In this study, experiments were performed to reveal the microanatomical sources of the two longest‐lived components. Transverse‐relaxation spectra were repeatedly obtained from samples of sciatic nerve of Xenopus laevis, the African clawed frog. These samples were maintained in vitro in a perfusion chamber, allowing for “on‐the‐fly” changes in perfusate composition. The changes in composition involved the addition of either 10‐mM Mn2+ or 30‐mM Gd‐DTPA to the perfusate, or the replacement of H2O in the perfusate by D2O. The D2O experiments revealed that >98% of the signal attributed to the nerve resulted from exchangeable water. Following the introduction of a paramagnetic agent into the perfusate, it was found that the intermediate‐lived component of the nerve T2 spectra disappeared within 10–50 min. However, the shortest‐ and longest‐lived components remained, experiencing much more gradual long‐term changes. It was thus concluded that the intermediate‐lived component corresponds to the interaxonal compartment of nerve tissue based upon its closer proximity to the outside environment of the nerve. Magn Reson Med 47:239–245, 2002. © 2002 Wiley‐Liss, Inc.
Coupled microstrip line transverse electromagnetic resonator model for high‐field magnetic resonance imaging
Authors: Bogdanov G. , Ludwig R.
Published: August 2002

The performance modeling of RF resonators at high magnetic fields of 4.7 T and more requires a physical approach that goes beyond conventional lumped circuit concepts. The treatment of voltages and currents as variables in time and space leads to a coupled transmission line model, whereby the electric and magnetic fields are assumed static in planes orthogonal to the length of the resonator, but wave‐like along its longitudinal axis. In this work a multiconductor transmission line (MTL) model is developed and successfully applied to analyze a 12‐element unloaded and loaded microstrip line transverse electromagnetic (TEM) resonator coil for animal studies. The loading involves a homogeneous cylindrical dielectric insert of variable radius and length. This model formulation is capable of estimating the resonance spectrum, field distributions, and certain types of losses in the coil, while requiring only modest computational resources. The boundary element method is adopted to compute all relevant transmission line parameters needed to set up the transmission line matrices. Both the theoretical basis and its engineering implementation are discussed and the resulting model predictions are placed in context with measurements. A comparison between a conventional lumped circuit model and this distributed formulation is conducted, showing significant departures in the resonance response at higher frequencies. This MTL model is applied to simulate two small‐bore animal systems: one of 7.5‐cm inner diameter, tuned to 200 MHz (4.7 T for proton imaging), and one of 13.36‐cm inner diameter, tuned to both 200 and 300 MHz (7 T). Magn Reson Med 47:579–593, 2002. © 2002 Wiley‐Liss, Inc.
Surface size, curvature analysis, and assessment of knee joint incongruity with MRI in vivo
Authors: Hohe Jan , Ateshian Gerard , Reiser Maximilian , Englmeier Karl‐Hans , Eckstein Felix
Published: August 2002

The purpose of this study was to develop an MR‐based technique for quantitative analysis of joint surface size, surface curvature, and joint incongruity and to assess its reproducibility under in vivo imaging conditions. The surface areas were determined after 3D reconstruction of the joint by triangulation and the incongruity by Gaussian curvature analysis. The precision was tested by analyzing four replicated MRI datasets of human knees in 14 individuals. The algorithms were shown to produce accurate data in geometric test objects. The interscan precision was <4% (CV%) for surface area, 2.9–5.7 m−1 (SD) for the mean principal curvature, and 4.1–7.4 m−1 for congruence indices. Incongruity was highest in the femoropatellar joint (79.7 m−1) and lowest in the medial femorotibial joint (28.6 m−1). This technique will permit identification of the specific role of surface size, curvature, and incongruity as potential risk factors for osteoarthritis. Magn Reson Med 47:554–561, 2002. © 2002 Wiley‐Liss, Inc.
Proton T2 relaxation study of water, N‐acetylaspartate, and creatine in human brain using Hahn and Carr‐Purcell spin echoes at 4T and 7T
Authors: Michaeli Shalom , Garwood Michael , Zhu Xiao‐Hong , DelaBarre Lance , Andersen Peter , Adriany Gregor , Merkle Hellmut , Ugurbil Kamil , Chen Wei
Published: August 2002

Carr‐Purcell and Hahn spin‐echo (SE) measurements were used to estimate the apparent transverse relaxation time constant (T) of water and metabolites in human brain at 4T and 7T. A significant reduction in the T values of proton resonances (water, N‐acetylaspartate, and creatine/phosphocreatine) was observed with increasing magnetic field strength and was attributed mainly to increased dynamic dephasing due to increased local susceptibility gradients. At high field, signal loss resulting from T decay can be substantially reduced using a Carr‐Purcell‐type SE sequence. Magn Reson Med 47:629–633, 2002. © 2002 Wiley‐Liss, Inc.
Respiration‐inducedB0fluctuations and their spatial distribution in the human brain at 7 Tesla
Authors: Van de Moortele Pierre‐François , Pfeuffer Josef , Glover Gary H. , Ugurbil Kamil , Hu Xiaoping
Published: August 2002

In functional magnetic resonance imaging (fMRI), it is known that physiological influences such as cardiac pulsation, respiration, and brain motion can induce fluctuations in signal intensity and phase. Some of the mechanisms potentially involved in those phenomena are expected to be amplified at higher magnetic fields. This study addresses the issue ofB0fluctuations induced by susceptibility changes during respiration attributed to movements of chest and diaphragm, and variations in the oxygen concentration. It is demonstrated that respiration‐induced resonance offsets (RIROs) are significant at 7T. Data were acquired with an RF pulse (no gradients), multislice echo‐planar imaging (EPI), and dynamic 3D fast low‐angle shot (3D‐ FLASH) imaging. Three main observations summarize the experimental findings. First, in FIDs measured after a single RF pulse, a RIRO with a large amplitude was consistently detected, although the average amplitude varied between subjects from 1.45 Hz to 4 Hz. Second, in transverse EPI images obtained in the occipital lobe, the RIRO amplitude showed a monotonic increase along thezaxis toward the lungs. Third, a more detailed spatial analysis with 3D‐FLASH phase maps revealed that a previously published analytical model can accurately describe the spatial distribution of RIRO. Consequential apparent motions in the EPI series, as well as the implications of slice orientation for correction strategies are discussed. Magn Reson Med 47:888–895, 2002. © 2002 Wiley‐Liss, Inc.
Volume correction for edema in single‐volume proton MR spectroscopy of contrast‐enhancing multiple sclerosis lesions
Authors: Helms Gunther
Published: August 2002

The effect of edema on metabolic changes in contrast‐enhancing multiple sclerosis lesions was studied by combining quantification of proton MR spectra with segmentation of the volume‐of‐interest, which was based on biexponential T2 relaxation. All lesions showed a second component (slong) with a longer T2 (185–450 ms), which was increased compared to healthy controls. Regression analysis indicated that slong replaces the short‐T2 component and total creatine. Since the water content was close to 100%, slong was used to correct for an increase in extracellular space. This compensated for the apparent loss of creatine and rendered cholines markedly increased, as observed in animals with experimental allergic encephalomyelitis. Total N‐acetyl aspartate (NAA) concentration was inversely correlated with slong and between 34–70% of its average reduction was assigned to edema. Thus, NAA loss exceeded cellular loss. Assessment of varying degrees of edema may be especially beneficial for quantitative longitudinal studies. Magn Reson Med 46:256–263, 2001. © 2001 Wiley‐Liss, Inc.
IMPACT: Image‐based physiological artifacts estimation and correction technique for functional MRI
Authors: Chuang Kai‐Hsiang , Chen Jyh‐Horng
Published: August 2002

Functional MRI (fMRI) signal variation induced by respiratory and cardiac motion affects the activation signal and limits the accuracy of analysis. Current physiological motion correction methods require either synchronization with external monitoring of respiration and heartbeat, specialized pulse sequence design, ork‐space data. The IMage‐based Physiological Artifacts estimation and Correction Technique (IMPACT), which is free from these constraints, is described. When images are acquired fast enough to sample physiological motion without aliasing, respiratory and cardiac signals can be directly estimated from magnitude images. Physiological artifacts are removed by reordering images according to the estimated respiratory and cardiac phases and then subtracting the Fourier‐fitted variation from magnitude images. Compared with thek‐space–based method, this method can efficiently and effectively reduce the overall signal fluctuation in the brain and increase the activated area. With this new technique, physiological artifacts can be reduced using traditional fMRI pulse sequences, and existing data can be corrected and reanalyzed without additional experiments. Magn Reson Med 46:344–353, 2001. © 2001 Wiley‐Liss, Inc.
In vivo hyperpolarized 129Xe NMR spectroscopy in tumors
Authors: Wolber Jan , McIntyre Dominick J.O. , Rodrigues Loreta M. , Carnochan Paul , Griffiths John R. , Leach Martin O. , Bifone Angelo
Published: August 2002

The first in vivo hyperpolarized 129Xe NMR study in experimental tumors is presented. Hyperpolarized 129Xe was dissolved in solutions, and was injected intratumorally in GH‐3 prolactinomas in rats and RIF‐1 fibrosarcomas in mice. The 129Xe NMR spectra and apparent spin‐lattice relaxation times in the two tumor types present characteristic differences. These differences are discussed in terms of xenon exchange between the carrier medium and the tissue compartments. Magn Reson Med 46:586–591, 2001. © 2001 Wiley‐Liss, Inc.
Analysis of MTR histograms in multiple sclerosis using principal components and multiple discriminant analysis
Authors: Dehmeshki J. , Ruto A.C. , Arridge S. , Silver N.C. , Miller D.H. , Tofts P.S.
Published: August 2002

Magnetization transfer ratio (MTR) histograms have the potential to characterize subtle diffuse changes in multiple sclerosis (MS) and other white matter disease. A new method is described which gives improved correlation with the Expanded Disability Status Scale (EDSS). Classification of individual subjects into normal and MS subgroups is shown. Principal component analysis (PCA) and multiple discriminant analysis (MDA) are shown to give results superior to methods of MTR histogram analysis using traditional features such as peak height and peak location. Scatterplots confirm the improved separation between groups achieved using the MDA score. The histogram analysis provides a comparison of two classification approaches, based on PCA and MDA, to recognize differences between normal controls and the four different subgroups of MS disease (and all MS patients). Multiple linear regression of these PCs vs. EDSS established an MR‐based measure of disease. Using a central 60‐mm slab of brain tissue, the success rate of binary classification between control and MS subgroups using MDA was 75–95%, depending on which two groups were being compared. Multiple regression analysis of EDSS with the first three PCs as independent variables was significant (r = 0.83 for secondary progressive MS, and r = 0.80 for all MS patients). Magn Reson Med 46:600–609, 2001. © 2001 Wiley‐Liss, Inc.
Simultaneous antegrade/retrograde cardioplegia protects myocardium distal to a coronary occlusion: A study in isolated pig hearts
Authors: Tian Ganghong , Xiang Bo , Dai Guangping , Sun Jiankang , Lindsay William G. , Deslauriers Roxanne
Published: August 2002

This study was designed to assess the effects of simultaneous antegrade/retrograde cardioplegia (SARC) on myocardial perfusion and energy metabolism in the region supported by the occluded left anterior descending artery (LAD) in isolated pig hearts. It was found that injection of Gd‐DTPA into the aorta during antegrade cardioplegia (AC) did not result in signal increase in the LAD region on T1‐weighted images. During SARC, however, Gd‐DTPA was detected in the LAD region with the contrast agent injected into the aorta and the coronary sinus (CS), respectively. This suggests that SARC delivered blood cardioplegia to the jeopardized myocardium through both arterial and venous perfusion routes. Moreover, localized 31P spectra showed that occlusion of the LAD during AC resulted in severe ischemic changes in the LAD myocardium and the abnormal metabolic changes were completely abolished by use of SARC. Finally, recovery of myocardial contractile function during reperfusion in the hearts subjected to SARC was significantly better compared to those arrested with AC alone. It was concluded that the myocardium distal to a coronary occlusion can be fully protected by use of SARC. Magn Reson Med 46:773–780, 2001. Published 2001 Wiley‐Liss, Inc.
MR microscopy of multicomponent diffusion in single neurons
Authors: Grant S.C. , Buckley D.L. , Gibbs S. , Webb A.G. , Blackband S.J.
Published: August 2002

This study examines multicomponent diffusion in isolated single neurons and discusses the implications of the results for macroscopic water diffusion in tissues. L7 Aplysia neurons were isolated and analyzed using a 600 MHz Bruker wide‐bore instrument with a magnetic susceptibility‐matched radiofrequency microcoil. Using a biexponential fit, the apparent diffusion coefficients (ADCs) from the cytoplasm (with relative fraction) were 0.48 ± 0.14 × 10−3 mm2s−1 (61 ± 11%) for the fast component, and 0.034 ± 0.017 × 10−3 mm2s−1 (32 ± 11%) for the slow component (N = 10). Diffusion in the nucleus appears to be primarily monoexponential, but with biexponential analysis it yields 1.31 ± 0.32 × 10−3 mm2s−1 (89 ± 6%) for the fast component and 0.057 ± 0.073 × 10−3 mm2s−1 (11 ± 6%) for the slow (N = 5). The slow component in the nucleus may be explained by cytoplasmic volume averaging. These data demonstrate that water diffusion in the cytoplasm of isolated single Aplysia neurons supports a multiexponential model. The ADCs are consistent with previous measurements in the cytoplasm of single neurons and with the slow ADC measurement in perfused brain slices. These distributions may explain the multiple compartments observed in tissues, greatly aiding the development of quantitative models of MRI in whole tissues. Magn Reson Med 46:1107–1112, 2001. © 2001 Wiley‐Liss, Inc.
The utility of magnetic resonance imaging in evaluating peripheral nerve disorders
Authors: Grant Gerald A. , Britz Gavin W. , Goodkin Robert , Jarvik Jeffrey G. , Maravilla Kenneth , Kliot Michel
Published: August 2002

The evaluation of peripheral nerve injuries has traditionally relied primarily on information gained from the clinical history, physical examination, and electrodiagnostic testing. Taken together, all of this clinical and diagnostic information often allows one to determine the location and severity of the underlying peripheral nerve problem. However, it may not be sufficient in diagnosing a focal entrapment neuropathy superimposed upon a more generalized peripheral neuropathy; localizing a focal lesion along a long segment of nerve which may be difficult to assess accurately with electrodiagnostic sutdies; distinguishing early between an axonotmetic grade of injury, which can recover through axonal regeneration, and a neurotmetic grade which cannot and therefore may benefit from a surgical exploration and repair procedure; and noninvasively diagnosing and determining the surgical resectability of peripheral nerve mass lesions such as tumors. The goal of this review is to illustrate how standard and evolving magnetic resonance imaging techniques can provide additional information in dealing with some of these problems. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002 DOI 10.1002/mus.10013
Severe infantile axonal neuropathy with respiratory failure
Authors: Wilmshurst Jo M. , Bye Ann , Rittey Chris , Adams Coleen , Hahn Angelika F. , Ramsay David , Pamphlett Roger , Pollard John D. , Ouvrier Robert
Published: August 2002

We describe 5 infants (4 male, 1 female) with a severe intractable form of motor‐sensory axonal neuropathy. All became ventilator‐dependent, 4 have since died and 1 remains static. Diaphragmatic paralysis was an early feature with generalized neuropathy evolving rapidly. Nerve conduction studies and biopsies were consistent with axonal disease. This disorder could be a new condition or part of the spectrum of inherited neuropathies of the axonal degenerative type. It may be that there is a “switching‐off” in the infant's Schwann cell–axonal interactions in utero or in the early postnatal period, resulting in severe progressive deterioration and then a static period without recovery. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 760–768, 2001
Phrenic nerve conduction study in patients with traumatic brachial plexus palsy
Authors: Chen Zheng Yong , Xu Jian Guang , Shen Li Ying , Gu Yu Dong
Published: August 2002

Phrenic nerve conduction studies were performed to assess the ipsilateral nerve in 100 patients with traumatic brachial plexus palsy. Open exploration and intraoperative recordings of somatosensory evoked potentials and nerve action potentials were used to confirm the level of root lesions. The relationship between C‐5 preganglionic root lesion and the functional integrity of the ipsilateral phrenic nerve was examined. The phrenic nerves were normal in 80 cases, partially injured in 7, and severely injured in 13. We found C‐5 preganglionic root lesions in 13 (100%) patients with severely injured, 5 (71.4%) with partially injured, and 24 (30%) with normal phrenic nerves. This correlation suggests phrenic nerve conduction study is a useful tool in the diagnosis of C‐5 preganglionic root lesions in patients with traumatic brachial plexopathy. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1388–1390, 2001
Tactile directional sensibility and diabetic neuropathy
Authors: Norrsell Ulf , Eliasson Björn , Frizell Martin , Wallin B. Gunnar , Wesslau Christian , Olausson Håkan
Published: August 2002

Five different procedures used to diagnose neuropathy were compared in a “blind” study with diabetic patients. The aim was to evaluate tests of tactile directional sensibility. Three matched groups were examined, two groups with type I diabetes, either with or without suspected neuropathy, and one of healthy controls. Testing consisted of: (1) examination by a specialist in neurology, (2) electrophysiologic measurement of nerve conduction velocity and determination of cool sensitivity, and (3) determination of directional sensibility in two stages, with categorical and quantitative techniques. Abnormal test results were obtained for both groups of diabetic patients. Quantitatively measured directional sensibility had the highest sensitivity (89%) and specificity (85%) when calculated for patients who had received a diagnosis of neuropathy from the neurologist, despite one case of abnormal directional sensibility among the healthy controls. Conduction velocity testing was almost comparably sensitive (80%) and cool sensitivity, comparably specific (85%) when calculated in the same manner. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1496–1502, 2001
Drained cavity expansion in sands exhibiting particle crushing
Authors: Russell A. R. , Khalili N.
Published: August 2002

The expansion of cylindrical and spherical cavities in sands is modelled using similarity solutions. The conventional Mohr–Coulomb failure criterion and the state parameter sand behaviour model, which enables hardening–softening, are used in the analysis. The sand state is defined in terms of a new critical state line, designed to account for the three different modes of compressive deformation observed in sands across a wide range of stresses including particle rearrangement, particle crushing and pseudoelastic deformation. Solutions are generated for cavities expanded from zero and finite radii and are compared to those solutions where a conventional critical state line has been used. It is shown that for initial states typical of real quartz sand deposits, pseudoelastic deformation does not occur around an expanding cavity. Particle crushing does occur at these states and causes a reduction in the stress surrounding the cavity. This has major implications when using cavity expansion theory to interpret the cone penetration test and pressuremeter test. Copyright © 2002 John Wiley & Sons, Ltd.
Estimating the probability that a simulated system will be the best
Authors: Miller J.O. , Nelson Barry L. , Reilly Charles H.
Published: August 2002

Consider a stochastic simulation experiment consisting ofvindependent vector replications consisting of an observation from each ofkindependent systems. Typical system comparisons are based on mean (long‐run) performance. However, theprobabilitythat a system will actually be the best is sometimes more relevant, and can provide a very different perspective than the systems' means. Empirically, we select one system as the best performer (i.e., it wins) on each replication. Each system has an unknown constant probability of winning on any replication and the numbers of wins for the individual systems follow a multinomial distribution. Procedures exist for selecting the system with the largest probability of being the best. This paper addresses the companion problem of estimating the probability that each system will be the best. The maximum likelihood estimators (MLEs) of the multinomial cell probabilities for a set ofvvector replications acrossksystems are well known. We use these samevvector replications to formvkunique vectors (termed pseudo‐replications) that contain one observation from each system and develop estimators based on AVC (AllVectorComparisons). In other words, we compare every observation from each system with every combination of observations from the remaining systems and note the best performer in each pseudo‐replication. AVC provides lower variance estimators of the probability that each system will be the best than the MLEs. We also derive confidence intervals for the AVC point estimators, present a portion of an extensive empirical evaluation and provide a realistic example. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 341–358, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10019
A secure multicast protocol for the internet's multicast backbone
Authors: Yang Wen‐Her , Fan Kai‐Wei , Shieh Shiuh‐Pyng
Published: August 2002

In this paper we propose a secure and efficient multicast protocol where the key management is distributed to local groups. The proposed protocol takes advantage of MBone topology to maintain scalability and efficiency at the same time. Copyright © 2001 John Wiley & Sons, Ltd.
A LAN emulation model for wireless ATM
Authors: Hać Anna , Hossain Asif
Published: August 2002

An architecture based on emulated LAN is proposed which can efficiently provide the required bandwidth of mobiles as they migrate between cells. The proposed solution (1) ensures the required bandwidth of a mobile when its path changes because of handoff, (2) efficiently reserves bandwidth resulting in higher bandwidth/network utilization, (3) has the flexibility of reserving bandwidth depending upon the mobility (rate of handoff). Copyright © 2001 John Wiley & Sons, Ltd.
A new approach of polling efficiency based on network topology
Authors: Han Jeong‐Soo , Ahn Seong‐Jin , Chung Jin‐Wook
Published: August 2002

In this article we present significantly effective algorithms which allow the manager who already knows failure in one system or more in the managed network to choose which to manage. Using this information, we compare and analyze management efficiency affected by whether we are fully aware of the network topology or not, and carry out an experiment to generalize efficiency according to the location(s) of failed system(s). Copyright © 2001 John Wiley & Sons, Ltd.
Resource allocation scheme for QoS provisioning in microcellular networks carrying multimedia traffic
Authors: Hać Anna , Armstrong Abhinay
Published: August 2002

We propose a new resource allocation scheme based on the concept of resource reservation and resource renegotiation. The new scheme is aimed at improving performance with regard to new call blocking rate, handoff dropping rate, forced call termination rate, and average bandwidth use. We compare our scheme with other schemes. The performance is evaluated by using simulation. Copyright © 2001 John Wiley & Sons, Ltd.
ARCMA—adaptive request channel multiple access protocol for wireless ATM networks
Authors: Hać Anna , Chew Boon Ling
Published: August 2002

We propose a new multiple access protocol based on demand assignment. This protocol is designed to reduce contention in the request phase while minimizing transmission delay under various network (ATM) environments. Our protocol uses an adaptive scheme that changes under heavy traffic conditions, and also provides priority to certain delay‐sensitive traffic. Copyright © 2001 John Wiley & Sons, Ltd.
On multiroute maximum flows in networks
Authors: Aggarwal Charu C. , Orlin James B.
Published: August 2002

Let G = (N, A) be a network with a designated source node s, a designated sink node t, and a finite integral capacity uij on each arc (i, j) ∈ A. An elementary K‐flow is a flow of K units from s to t such that the flow on each arcis 0 or 1. A K‐route flow is a flow from s to t that may be expressed as a nonnegative linear sum of elementary K‐flows. In this paper, we show how to determine a maximum K‐route flow as a sequence of O(min {log (nU), K}( maximum‐flow problems. This improves upon the algorithm by Kishimoto, which solves this problem as a sequence of K maximum‐flow problems. In addition, we have simplified and extended some of the basic theory. We also discuss the application of our technique to Birkhoff's theorem and a scheduling problem. © 2001 John Wiley & Sons, Inc.
Degree‐ and time‐constrained broadcast networks
Authors: Dinneen Michael J. , Pritchard Geoffrey , Wilson Mark C.
Published: August 2002

We consider the problem of constructing networks with as many nodes as possible, subject to upper bounds on the degree and broadcast time. This paper includes the results of an extensive empirical study of broadcasting in small regular graphs using a stochastic search algorithm to approximate the broadcast time. Significant improvements on known results are obtained for cubic broadcast networks. © 2002 Wiley Periodicals, Inc.
Efficient algorithms for centers and medians in interval and circular‐arc graphs
Authors: Bespamyatnikh Sergei , Bhattacharya Binay , Keil Mark , Kirkpatrick David , Segal Michael
Published: August 2002

Thep‐center problem is to locatepfacilities on a network so as to minimize the largest distance from a demand point to its nearest facility. Thep‐median problem is to locatepfacilities on a network so as to minimize the average distance from a demand point to its closest facility. We consider these problems when the network can be modeled by an interval or circular‐arc graph whose edges have unit lengths. We provide, given the interval model of annvertex interval graph, anO(n) time algorithm for the 1‐median problem on the interval graph. We also show how to solve thep‐median problem, for arbitraryp, on an interval graph inO(pnlogn) time and on a circular‐arc graph inO(pn2logn) time. We introduce a spring representation of the objective function and show how to solve thep‐center problem on a circular‐arc graph inO(pn) time, assuming that the arc endpoints are sorted. © 2002 Wiley Periodicals, Inc.
Multigraph augmentation under biconnectivity and general edge‐connectivity requirements
Authors: Ishii Toshimasa , Nagamochi Hiroshi , Ibaraki Toshihide
Published: August 2002

Given an undirected multigraphG= (V,E) and a requirement functionrλ: () →Z+(where () is the set of all pairs of vertices andZ+is the set of nonnegative integers), we consider the problem of augmentingGby the smallest number of new edges so that the local edge‐connectivity and vertex‐connectivity between every pairx,y∈Vbecome at leastrλ(x,y) and two, respectively. In this paper, we show that the problem can be solved inO(n3(m+n) log(n2/(m+n))) time, wherenandmare the numbers of vertices and pairs of adjacent vertices inG, respectively. This time complexity can be improved toO((nm+n2logn) logn), in the case of the uniform requirementrλ(x,y)= 𝓁 for allx,y∈V. Furthermore, for the generalrλ, we show that the augmentation problem that preserves the simplicity of the resulting graph can be solved in polynomial time for any fixed 𝓁*= max{rλ(x,y) |x,y∈V}. © 2001 John Wiley & Sons, Inc.
Minimum spanners of butterfly graphs
Authors: Hwang Shien‐Ching , Chen Gen‐Huey
Published: August 2002

Given a connected graphG, a spanning subgraphG′ofGis called at‐spanner if every pair of two adjacent vertices inGhas a distance of at mosttinG′. At‐spanner of a graphGis minimum if it contains minimum number of edges among allt‐spanners ofG. Finding minimum spanners for general graphs is rather difficult. Most of previous results were obtained for some particular graphs, for example, butterfly graphs, cube‐connected cycles, de Bruijn graphs, Kautz graphs, complete bipartite graphs, and permutation graphs. The butterfly graphs were originally introduced as the underlying graphs of FFT networks which can perform the fast Fourier transform (FFT) very efficiently. In this paper, we successfully construct most of the minimumt‐spanners for thek‐aryr‐dimensional butterfly graphs for 2 ≤t≤ 6 andt= 8. © 2001 John Wiley & Sons, Inc.
The structured total least‐squares approach for non‐linearly structured matrices
Authors: Lemmerling P. , Van Huffel S. , De Moor B.
Published: August 2002

In this paper, an extension of the structured total least‐squares (STLS) approach fornon‐linearly structuredmatrices is presented in the so‐called ‘Riemannian singular value decomposition’ (RiSVD) framework. It is shown that this type of STLS problem can be solved by solving a set of Riemannian SVD equations. For small perturbations the problem can be reformulated into finding the smallest singular value and the corresponding right singular vector of this Riemannian SVD. A heuristic algorithm is proposed. Some examples of Vandermonde‐type matrices are used to demonstrate the improved accuracy of the obtained parameter estimator when compared to other methods such as least squares (LS) or total least squares (TLS). Copyright © 2002 John Wiley & Sons, Ltd.
A numerical method for the determination of dextrous workspaces of Gough–Stewart platforms
Authors: du Plessis L. J. , Snyman J. A.
Published: August 2002

An optimization approach to the computation of the boundaries of different dextrous workspaces of parallel manipulators is presented. A specific dextrous workspace is the region in space in which, at each position of the working point, a manipulator can control the orientation of its upper working platform through a specified range of orientation angles. Here the dextrous workspace is determined from the intersection of suitably chosen fixed orientation workspaces, which are found by application of a constrained optimization algorithm. The procedure is simple and has the considerable advantage that it may easily be automated. The method is illustrated by its application to both a planar and spatial Gough–Stewart platform. Copyright © 2001 John Wiley & Sons, Ltd.
Real qualitative researchers do not count: The use of numbers in qualitative research
Authors: Sandelowski Margarete
Published: August 2002

Two myths about qualitative research are that real qualitative researchers do not count and cannot count. These antinumber myths have led to the underutilization of numbers in qualitative research and to the simplistic view of qualitative research as non‐ or antinumber. Yet numbers are integral to qualitative research, as meaning depends, in part, on number. As in quantitative research, numbers are used in qualitative research to establish the significance of a research project, to document what is known about a problem, and to describe a sample. But they are also useful for showcasing the labor and complexity of qualitative work and to generate meaning from qualitative data; to document, verify, and test researcher interpretations or conclusions; and to re‐present target events and experiences. Although numbers are important in the treatment of qualitative data, qualitative researchers should avoid the counting pitfalls of verbal counting, overcounting, misleading counting, and acontextual counting. © 2001 John Wiley & Sons, Inc. Res Nurs Health 24: 230–240, 2001
State reform and the ‘privatized state’ in Paraguay
Authors: Nickson Andrew , Lambert Peter
Published: August 2002

This article uses Paraguay, in Latin America, as a case study in order to examine the difficulties of introducing state reform where the state itself has a long history of control by private interests. It shows how the ‘privatized’ nature of the Paraguayan state is central to an understanding of how it has functioned and responded to recent reform efforts. The article provides an overview of the Paraguayan public sector and identifies several of its peculiar features that are relevant to understanding the state reform process: its small size, high levels of inefficiency and ineffectiveness, rampant politicization and endemic corruption. The article examines the three major components of an externally driven state reform process that began with democratization in 1989: privatization of loss‐making state corporations, civil service reform and decentralization. It shows how the ‘privatized’ nature of the state has proved a major obstacle to these efforts and is a major factor in explaining their limited success. The article concludes by offering a pessimistic assessment of the likely prospects for state reform and highlights the danger that Paraguay could descend into a ‘failed state’. Copyright © 2002 John Wiley & Sons, Ltd.
Benchmarking: a tool for facilitating organizational learning?
Authors: Auluck Randhir
Published: August 2002

This article looks at benchmarking as a tool for promoting performance improvement and the ‘learning organization’ ideal. Specifically, it considers some of the ways the European Foundation for Quality Management Excellence Model and self‐assessment approach are being applied within the UK public service. Further, the article introduces ‘Dolphin’, a new self‐assessment tool based on the Excellence Model, and describes how the tool can be applied in practice. Finally, whether benchmarking can aid organizational improvement, organizational learning and establish the basis for a ‘learning culture’ is discussed. Copyright © Crown Copyright 2002. Recorded with the permission of the controller of Her Majestry's Stationery Office. Published by John Wiley & Sons, Ltd.
Critical aspects for the reliable headspace analysis of plants cultivated in vitro
Authors: Maes Katrien , Vercammen Joeri , Pham‐Tuan Hai , Sandra Pat , Debergh Pierre C.
Published: August 2002

Various factors controlling the recoveries of volatile organic compounds in in vitro headspace analysis of tomato plants (Lycopersicon esculentum Mill. ‘Moneymaker’), sampled using solid phase micro‐extraction, were evaluated and optimised. The variations in composition of the headspaces were determined as a function of time, and following in vitro wounding of the plant. Copyright © 2001 John Wiley & Sons, Ltd.
Population screening for isoniazid acetylator phenotype
Authors: Seifart Heiner I. , Parkin Donald P. , Botha Frederik J. H. , Donald Peter R. , Van Der Walt Ben J.
Published: August 2002

Purpose

To establish a useful method for acetylator phenotypification and therapeutic drug monitoring of patients receiving isoniazid.

Methods

Sixty patients with uncomplicated pulmonary tuberculosis were given a 5‐mg/kg oral dose of isoniazid each. Plasma concentrations of isoniazid and its metabolite, acetyl‐isoniazid, were determined by HPLC analyses at various post‐dose times. From the isoniazid concentration and the concentration ratio of acetyl‐isoniazid and isoniazid (metabolic ratio), phenotypification methods were assessed.

Results

The metabolic ratios at 3 h post‐dose revealed a trimodal distribution; a fast, intermediate and slow acetylator phenotype group. The 2‐h and 6‐h data showed different bimodal combinations of these phenotype groups. The metabolic ratio phenotypification method could be simplified by using the HPLC data directly without converting it to absolute concentrations.

Conclusions

A single‐sample test based upon the plasma isoniazid concentration, combined with the metabolic ratio of acetyl‐isoniazid and isoniazid, appears to be a reliable parameter for phenotype discrimination and for bioavailability testing. Copyright © 2001 John Wiley & Sons, Ltd.
Living free‐radical polymerization of styrene under a constant source of γ radiation
Authors: Quinn John F. , Barner Leonie , Rizzardo Ezio , Davis Thomas P.
Published: August 2002

Living polymerization of styrene was observed using γ radiation as a source of initiation and 1‐phenylethyl phenyldithioacetate as a reversible addition–fragmentation chain transfer (RAFT) agent. The γ radiation had little or no detrimental effect on the RAFT agent, with the molecular weight of the polymer increasing linearly with conversion (up to the maximum measured conversions of 30%). The polymerization had kinetics (polym.) consistent with those of a living polymerization (first order in monomer) and proportional to the square root of the radiation‐dose rate. This initiation technique may facilitate the grafting of narrow polydispersity, well‐defined polymers onto existing polymer surfaces as well as allow a wealth of kinetic experiments using the constant radical flux generated by γ radiation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 19–25, 2002
Preparation of partially hydrolyzed oligo(vinylacetate) as polyol for polyurethane formation
Authors: Zimmermann Jörg , Sunder Alexander , Mülhaupt Rolf
Published: August 2002

Polyols based on oligo(vinylacetate) were synthesized using a convenient one‐pot, two‐step process. Polymerization of vinylacetate was performed in 2‐propanol as a chain‐transfer agent using di‐tert‐butylperoxide as a free‐radical initiator. Saponification of the oligomers was performed in both tetrahydrofuran and 2‐propanol using stoichiometric amounts of methanol in the presence of a basic catalyst. Well‐defined oligo(vinylacetate‐co‐vinylalcohol) polyols with a degree of polymerization below 12 and a hydroxyfunctionality smaller than 4 were obtained. Oligo(vinylacetate‐co‐vinylalcohol) was used as a polyol component in the formation of polyurethanes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2085–2092, 2002
Polyurethanes containing sulfur. III. New thermoplastic HDI‐based segmented polyurethanes with diphenylmethane unit in their structure
Authors: Kultys Anna , Pikus Stanisław
Published: August 2002

Three series of new thermoplastic, high molecular weight, segmented thiopolyurethanes were synthesized by a one‐step melt polymerization from newly obtained thiodiols, including bis[4‐(2‐hydroxyethyl)thiomethylphenyl]methane, bis[4‐(3‐hydroxypropyl)thiomethylphenyl]methane, and bis[4‐(6‐hydroxyhexyl)thiomethylphenyl]methane (BHHM), as chain extenders; hexamethylene diisocyanate; and 20–80 mol % poly(oxytetramethylene) glycol (PTMG; number‐average molecular weight = 1000) as the soft segment. Solution polymerization with the chain extender BHHM gave considerably lower molecular weight polymers. The structures of all the polyurethanes were determined with Fourier transform infrared and X‐ray diffraction analysis. The thermal properties of the polyurethanes were examined with differential scanning calorimetry and thermogravimetric analysis. Shore A/D hardness and tensile properties were also determined. All the polyurethanes showed partially crystalline structures; those obtained with 40–80 mol % PTMG were elastomers. An increase in the PTMG content decreased hardness, modulus of elasticity, and tensile strength, whereas elongation at break increased. BHHM‐based polyurethanes obtained in the melt showed the best tensile properties. The polyurethanes exhibited definite glass transitions (−70 to −59 °C) that were nearly independent of the hard‐segment content up to about 50 wt % (40–80 mol % PTMG), indicating the existence of mainly microphase‐separated soft and hard segments. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1733–1742, 2001