bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron effective attenuation lengths for applications in Auger electron spectroscopy and x‐ray photoelectron spectroscopy
Authors: Powell C. J. , Jablonski A. 
Published: August 2002

AbstractThe electron effective attenuation length (EAL) can be defined for the measurement of overlayer film thicknesses (the most common application) and for the measurement of the depth of a thin marker layer by Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS). For each of these applications, a local EAL can be defined for a narrow range of thicknesses or depths and a practical EAL can be defined for specified larger ranges of thicknesses or depths. We show the results of illustrative calculations of these different EALs for XPS of Si 2p3/2 photoelectrons with Mg Kα x‐rays, and point out situations where numerical differences occur. We compare practical EALs (with the overlayer film definition) for Si 2s, Si 2p3/2, Au 4s and Au 4f7/2 photoelectrons that were obtained from Monte Carlo simulations and from an analytical expression derived from solution of the Boltzmann equation within the transport approximation. The average of the percentage deviations between the EALs from the two approaches for various overlayer thicknesses and emission angles was 5.28%. This average percentage deviation was considered to be acceptably small and justifies the use of the more approximate analytical expression in calculations of practical EALs for the measurement of overlayer thicknesses by AES and XPS. This computational approach is much faster than Monte Carlo simulations. We report calculations of practical EALs for the principal photoelectron and Auger electron lines of Si, Cu, Ag and W. For overlayer thicknesses of practical relevance, the practical EALs do not change appreciably with film thickness for electron emission angles (with respect to the surface normal) of <60°. Under these conditions, average practical EALs can be used to determine overlayer film thicknesses. For emission angles of >60°, the practical EALs generally change rapidly with film thickness and emission angle and, for these conditions, an EAL should be determined for the particular conditions. We have compared our practical EALs for photoelectron and Auger electron lines of Si, Cu, Ag and W with similar EALs derived from Monte Carlo simulations by Cumpson and Seah. At an emission angle of 45°, we find a root‐mean‐square deviation of 1.6% between the EALs from the two approaches. Published in 2002 John Wiley & Sons, Ltd.
Monte Carlo simulation of x‐ray generation and energy dissipation in a W/Cu target for optimum design of a high‐power x‐ray source
Authors: Araki K. , Yoshioka A. , Shimizu R. , Nagatomi T. , Takahashi S. , Nihei Y. 
Published: August 2002

AbstractMonte Carlo simulation of x‐ray generation by electron impact was applied to a W/Cu target (tungsten W film on a copper substrate) to find the optimum conditions for a high‐power x‐ray source. To assess the performance of the high‐power x‐ray source, we propose using:

The total intensity of continuous x‐rays emitted from the target, $I_{E_{0}} = \int\limits_{\lambda_{\min}}^{\infty}{i_{E_{0}} (\lambda)}\,\hbox{d}\lambda$, where i(λ) is a spectrum of continuous x‐rays emitted from the target under bombardment of an electron beam of primary energy E0.
The cooling efficiency of the W/Cu target, which is

where $\left({\hbox{d} E\over \hbox{d} z}\right)_{j}$ and σj are the in‐depth energy dissipation in a target of element j and the thermal conductivity of element j, respectively, in the W/Cu target with tungsten film thickness ΔW.
Both I and γ were obtained from Monte Carlo calculations for different tungsten film thicknesses by varying the incidence angle of the electron beam and the take‐off angle of the x‐rays according to the primary energy levels of the electron beam. Copyright © 2002 John Wiley & Sons, Ltd.
Experimental estimation of surface excitation parameter for surface analysis
Authors: Gergely G. , Menyhard M. , Gurban S. , Sulyok A. , Toth J. , Varga D. , Tougaard S. 
Published: August 2002

AbstractThe surface excitation produced by impinging or escaping electrons is a competitive process to elastic backscattering. It affects the intensity of Auger and XPS peaks and is characterized by the surface excitation parameter Pse. This appears in the surface loss peak I(Epls), and possibly a surface plasmon. In our work Pse is defined as the ratio of the probability to create a surface plasmon/elastic scattering and is deduced from the integrated surface loss peak and elastic peak, respectively. Our procedure is based on reflection electron energy loss spectroscopy and elastic peak electron spectroscopy spectra and Kλi spectra (K is the inelastic scattering cross‐section and λi is the inelastic mean free path), determined using Tougaard's method. The normalized Kλi curves are fitted to the spectrum at E = 5 keV (primary energy) and EL = Epl1 (volume plasmon), approximated with the Lorentzian type three‐parameter formula of Tougaard. For E>Epl1, the normalized curves are overlapping and Pse is deduced from the integrated difference spectra fitted with the Tougaard cross‐sections. The procedure was applied on materials exhibiting surface and volume plasmons: III–V semiconductors (GaAs, InSb) and In and Sb metals. The REELS experiments were carried out with an ESA 31 HSA spectrometer covering the E = 0.2–5 keV energy range. Copyright © 2002 John Wiley & Sons, Ltd.
Estimating the number needed to treat (NNT) index when the data are subject to error
Authors: Walter S. D. , Irwig L. 
Published: August 2002

AbstractThe number needed to treat (NNT) index has been proposed as a clinically useful measure to assess the results of randomized trials and other clinical studies. In its usual form, NNT indicates the expected number of patients who must be treated with an experimental therapy in order to prevent one adverse event, compared to the expected event rates under the control therapy. It can be formulated as a function of the proportions of patients who respond to treatment by more than a certain amount, the clinically important difference. We may also wish to evaluate two group studies comparing treatment and control responses, and to consider net benefit from treatment (by also allowing for individuals who deteriorate as well as those who respond positively). In this paper, we investigate the effect on NNT caused by measurement errors in continuous outcome measures. Such errors can lead to bias in the estimated proportions of subjects with clinically important responses, and hence bias the associated values of NNT. General expressions for the bias are derived, and enumerated for typical scenarios. For many situations, reliability of 80 per cent or more in the observations is required to restrict the bias to tolerable levels. Copyright © 2001 John Wiley & Sons, Ltd.
Role of conventional radiology in the diagnosis and staging of gastrointestinal tract neoplasms
Authors: Gourtsoyiannis Nick , Grammatikakis John , Prassopoulos Panos 
Published: August 2002

AbstractPreoperative diagnosis and staging of primary gastrointestinal (GI) neoplasms are challenges for both clinicians and radiologists. Barium studies are very sensitive in disclosing primary malignancies, even at an early stage. Radiologic signs depend on the evolutional stage of the disease and its appearance on gross pathology. A neoplasm may be manifested on barium studies by a wide spectrum of findings, including mucosal abnormalities, mass presence, ulcerative lesions, submucosal infiltration, and lumen stenosis. Advanced disease can be accurately diagnosed, whereas early cancer should be differentiated from other neoplastic or inflammatory disorders by meticulous analysis of radiologic findings. The extent of GI involvement and multiplicity of the lesions can be assessed on barium studies. In the staging of GI neoplasms, barium studies are of little value. Skeletal survey by conventional radiographs and chest plain films can reveal distant metastases in a short time and with low cost, although they are not that sensitive to the detection of early or subtle lesions. The exact role of conventional radiology in the imaging workup of GI malignancies depends on local expertise and availability of other diagnostic techniques and modalities. Semin. Surg. Oncol. 20:91–108, 2001. © 2001 Wiley‐Liss, Inc.
Web dynamics
Authors: Levene Mark , Poulovassilis Alexandra 
Published: August 2002

AbstractThe global usage and continuing exponential growth of the World Wide Web poses a host of challenges to the research community. In particular, there is an urgent need to understand and manage the dynamics of the Web, in order to develop new techniques that will make the Web tractable. MARK LEVENE and ALEXANDRA POULOVASSILIS provide an overview of recent statistics relating to the size of the Web graph and its growth. They then briefly review some of the key areas relating to Web dynamics with reference to the recent literature. Finally, they summarise the talks given in a recent workshop devoted to Web dynamics, which was held in the beginning of January 2001 at the University of London. Copyright © 2001 John Wiley & Sons, Ltd.
Models for character animation
Authors: Collins Gordon , Hilton Adrian 
Published: August 2002

AbstractGORDON COLLINS and ADRIAN HILTON present a reviewof methods for the constructionand deformation of charactermodels. They consider both stateof the art research and common practice. In particular they review applications, data capture methods, manual model construction, polygonal, parametricand implicit surface representations, basic geometric deformations, free form deformations, subdivision surfaces, displacement map schemes and physical deformation. Copyright © 2001 John Wiley & Sons, Ltd.
L‐type calcium channels reduce ROS generation in cerebellar granule cells following kainate exposure
Authors: Leski Michael L. , Hassinger Linda C. , Valentine Stacey L. , Baer Jesse D. , Coyle Joseph T. 
Published: August 2002

AbstractCerebellar granule cells (CGC) deprived of serum or trophic factors develop sensitivity to kainate neurotoxicity that is mediated by the α‐amino‐3‐hydroxy‐5‐methyl‐isoxazole proprionic acid (AMPA) subtypes of glutamate receptors (GluR). The L‐type voltage‐gated calcium channel (L‐type VGCC) blocker nifedipine increases the potency of kainate 50‐fold. Thus, one goal of this laboratory is to determine the underlying protective mechanism triggered by calcium influx through this channel. The cell‐permeable heavy metal chelator N,N,N′,N′‐tetrakis(2‐pyridylmethyl)ethylenediamine effected complete protection against kainate treatment in the presence of nifedipine, as did the iron chelator deferoxamine. The chelatable heavy metal pool decreased ∼70% immediately following treatment with kainate, but did not change following kainate/nifedipine treatment. Tetramethylrhhodamine ethyl ester (TMRE) fluorescence, an indicator of mitochondrial membrane potential, decreased ∼70% following kainate treatment but displayed a more modest decrease (∼15%) when CGC were treated with kainate/nifedipine. Reactive oxygen species (ROS) formation decreased in CGC immediately following kainate treatment but was slightly elevated following kainate/nifedipine treatment. Electron microscopic examinations of the CGC indicated severe swelling and distortion of mitochondria immediately following kainate/nifedipine treatment and the appearance of mitochondrial herniations, whorls, and bridges 2 h later, features that were rarely observed following kainate treatment. These results support the hypothesis that calcium entry through L‐type VGCCs protects CGC during kainate treatment by lowering the chelatable heavy metal pool and the mitochondrial membrane potential, thereby mitigating the formation of ROS. Synapse 43:30–41, 2002. © 2001 Wiley‐Liss, Inc.
Entopeduncular lesions facilitate and thalamic lesions depress spontaneous and drug‐evoked motor behavior in the hemiparkinsonian rat
Authors: Olds M.E. , Jacques D.B. , Kopyov O. 
Published: August 2002

AbstractPallidotomy is a neurosurgical procedure designed to ameliorate the akinesia and bradykinesia associated with Parkinson's disease. In the present study, the effects of pallidal‐like lesions on motor behavior in the hemiparkinsonian rat were compared to the effects of lesions in the ventrolateral thalamus, a target of entopeduncular projections feeding motor‐related information to motor cortex. Six aspects of spontaneous and evoked behavior induced by amphetamine and apomorphine in the hemiparkinsonian rat with either bilateral electrolytic entopeduncular lesions or bilateral electrolytic ventrolateral thalamic lesions were measured for 60 min. Saline or amphetamine, 5 mg/kg, or apomorphine, 0.3 mg/kg, were administered IP 5 min before the tests. The results show that on all measures except time spent resting the hemiparkinsonian rats with the entopeduncular lesions were more active than the hemiparkinsonian rats with the thalamic lesions. The asymmetrical rotation responses to dopamine receptor stimulation evoked by amphetamine and apomorphine were influenced by the general effect on gross motor behavior, as shown by the response being very large in the entopeduncular group and very small in the thalamic group. These results are consistent with current thinking about the functional organization of the basal ganglia according to which damage of the entopeduncular nucleus reduces its inhibitory control of the thalamic motor regions, thereby promoting thalamic facilitation of motor cortex, and damage to the thalamic motor regions has the opposite effect. These effects of the lesions translate, respectively, into hyperactivity and hypoactivity without blocking the asymmetrical rotation response of the hemiparkinsonian rat. Synapse 40:215–224, 2001. © 2001 Wiley‐Liss, Inc.
Homocysteine modifies development of neurulation and dorsal root ganglia in chick embryos
Authors: Epeldegui Marta , Peña‐Melian Angel , Varela‐Moreiras Gregorio , Pérez‐Miguelsanz Julia 
Published: August 2002

AbstractBackgroundThe formation of the neural tube (neurulation) involves two mechanisms: primary and secondary neurulation. In chicks, there is also an overlap zone, where both mechanisms work together. Homocysteine (Hcy) may have an important teratogenic role in neural tube defects (NTD) when folic acid levels are considered normal. Recently, Hcy capability to generate NTD and modify neural crest cell migration has been demonstrated in chick embryos. This study was aimed to evaluate the effects of Hcy on neurulation and the development of the dorsal root ganglia (DRG).MethodsChick embryos were treated with L‐Hcy thiolactone 20 μmol to produce the highest rate of survival with embryos carrying neural tube defect (NTD) in the spine. Embryos at stages (st) 3–10 were treated and harvested at st 18–23. Only externally normal embryos or those carrying spinal NTD embryos were considered.ResultsHistological sections of Hcy‐treated embryos showed: open spina bifida (39% of embryos), more than one tube forming the spinal cord (26%), disorganized spinal cord (26%), always affecting lumbosacral regions, probably in the overlap zone. Additionally, 32% of embryos had small and continuous DRG, associated with a slimmed roof plate. Three‐dimensional reconstruction showed unsegmented DRG until the C8 ganglion level. There was a 75% reduction of C3 DRG cells in treated embryos in comparison to untreated ganglia.ConclusionHcy teratogenicity in avian embryos affected the neural tube in the overlap zone, secondary neurulation and the cervical DRG. Teratology 65:171–179, 2002. © 2002 Wiley‐Liss, Inc.
Placental transfer of vigabatrin (γ‐vinyl GABA) and its effect on concentration of amino acids in the embryo of TO mice
Authors: Abdulrazzaq Yousef M. , Padmanabhan R. , Bastaki Salim M.A. , Ibrahim Ahmed , Bener Abdulbari 
Published: August 2002

AbstractBackgroundThe mechanism of the teratogenicity of vigabatrin (VGB) is unknown. The objectives of this study were to determine the placental transfer of VGB and to evaluate the effect of VGB on maternal, placental, and fetal concentrations of amino acids.MethodsA single dose of 400 mg/kg VGB in physiological saline was administered intraperitoneally to a group of Theiler outbred (TO) mice on gestational day (GD) 10. The controls received a proportionate volume of saline. Maternal blood samples, embryos, and placentas were collected at 3.5, 6.0, and 9.0 hr after treatment and their total amino acid concentrations determined in an ion‐exchange amino acid analyzer.ResultsAt 3.5 hr, there was a decrease in concentrations of some amino acids in the blood, placenta, and embryos of VGB‐treated mice, but the decrease in methionine was most marked. γ‐aminobutyric acid (GABA) was significantly higher in the VGB group in both the embryos and the placentas at 3.5 hr but at 6.0 and 9.0 hr the differences were not significant. Vigabatrin levels were higher in the placenta than in the embryo at 3.5 hr, but at 6.0 hr there was an overlap of the VGB peak with that of tryptophan with very much lower levels than at 3.5 hr. At 9.0 hr, there was no vigabatrin peak in either the placenta or the embryo.ConclusionsMaternal exposure to VGB results in peak levels of the drug after 3.5 hr in the placenta and embryo. Methionine concentration is most severely affected in VGB‐treated mothers, placentas, and fetuses. We speculate that this deficiency could be a possible mechanism for the teratogenic effects of vigabatrin. Teratology 63:127–133, 2001. © 2001 Wiley‐Liss, Inc.
A population‐based study of coarctation of the aorta: Comparisons of infants with and without associated ventricular septal defect
Authors: Wollins Dana Swartzberg , Ferencz Charlotte , Boughman Joann A. , Loffredo Christopher A. 
Published: August 2002

AbstractBackgroundCoarctation of the aorta (CoA) is a congenital cardiovascular malformation (CCVM) sometimes associated with ventricular septal defect (VSD). Although the phenotypic association is well documented, little research exists on the epidemiological features distinguishing CoA with and without VSD.MethodsThe Baltimore–Washington Infant Study (1981–1989), a population‐based study of CCVM, evaluated 126 infants with “pure” CoA (free of associated cardiac defects) and 67 infants with CoA and VSD (COA/VSD) in comparison to 3,572 controls.ResultsThe proportion of infants with associated extracardiac anomalies was greater among CoA/VSD than among pure CoA (31% versus 11%). Infants with CoA/VSD were twice as likely as those with pure CoA to be born small for gestational age (23% versus 12%, respectively, compared with 6% of controls). All‐cause mortality during the first year of life was higher in CoA/VSD than in pure CoA (21% vs. 7%). Multiple logistic regression models revealed that family history of CCVM was associated with pure CoA (adjusted case‐control odds ratio [OR] = 4.6; 99% confidence interval [CI] = 1.5–13.9) and with CoA/VSD (OR = 5.9, CI = 1.2–23.5); maternal history of organic solvent exposures early in pregnancy was also associated with pure CoA (OR = 3.2, CI = 1.0–10.2) and with CoA/VSD (OR = 3.7, CI 0.9–14.9). Additional risk factors, including maternal epilepsy (OR = 5.3, CI = 0.9–30.6), and use of macrodantin (OR = 6.7, CI = 1.4–31.8) were associated only with pure CoA.ConclusionsThese findings highlight possible genetic and environmental differences between pure CoA and CoA/VSD and may stimulate further investigations of the etiology of CoA. Teratology 64:229–236, 2001. © 2001 Wiley‐Liss, Inc.
Derivative Ruination in the 1990s: Les Apparences sont Trompeuses
Authors: Sanders Thomas B. 
Published: August 2002

AbstractA spectacular financial revolution spanning 20 years created new securities deriving from other securities, which trade in volumes of trillions of dollars in markets, now thought to be the largest and more important in the world. Known as swaps, swaptions, index futures, puttable bonds, collateralized mortgage obligations, stripped bonds, options, and futures, among other exotic names, these financial contracts were designed as a means of laying off risk involving conventional business transactions. This article details massive abuses in the proper use of these insurance products, which resulted in billions of dollars of speculation losses suffered by Procter & Gamble, Gibson Greeting Cards, Orange County California, Metallgesellschaft AG, various‐public employees' retirement funds—and which brought down one of Europe's oldest merchant banks, Barings PLC. © 2001 John Wiley & Sons, Inc.
Analysis of hierarchical cellular networks with mobile base stations
Authors: Cui Wei , Bassiouni Mostafa A. 
Published: August 2002

AbstractIn this paper, we develop and evaluate a hierarchical cellular architecture for totally mobile wireless networks (TMWNs). Extensive performance tests were conducted to evaluate the performance of a two‐tier system and compare its throughput, handoff blocking rate and new call success rate with those obtained by a one‐tier model. Our tests have shown that when the total number of channels is kept the same, the two‐tier system outperformed the one‐tier counterpart under all load conditions. Under the constraint of equal power consumption, the two‐tier system still achieved improvement over the one‐tier system, especially at light and medium load levels. The improvement of the two‐tier system over the one‐tier system was observed to diminish as the degree of randomness in the mobility model is reduced; scenarios where the one‐tier system outperforms the two‐tier system are given. Load balancing schemes based on the concept of reversible handoffs are introduced and their performance improvements are analyzed. Comparison results on the percentage of terminal coverage are presented. An analytical model to compute the new call and handoff blocking probabilities in TMWN is given and evaluated. The model extends the Markov chain approach previously used in hierarchical architectures with stationary base stations and uses a corrected derivation for the handoff blocking probability. Copyright © 2002 John Wiley & Sons, Ltd.
Use of data permutation to reduce the peak‐to‐average power ratio of an OFDM signal
Authors: Jayalath A. D. S. , Tellambura C. 
Published: August 2002

AbstractA set of fixed permutations is used in this paper to reduce the peak‐to‐average power ratio (PAR) of an orthogonal frequency division multiplexing (OFDM) signal. For this technique, K − 1 interleavers are used to produce K − 1 permuted sequences from the same information sequence. The peak powers of the permuted sequences and the original information sequence are computed using K inverse discrete Fourier transforms; the sequence with the lowest PAR is chosen for transmission. Before the optimization process begins the identity of each interleaver is embedded into the data frame as side information (SI). SI which is critical to the receiver operation, is coded using a simple forward error correction code in order to increase its reliability. An adaptive approach is proposed for the reduction of this technique's complexity. Furthermore, theoretical expressions are derived for the complementary cumulative distribution function of the PAR and for the average number of permutations required by the adaptive approach. Computer simulations are performed for finding the PAR reduction capability of several types of interleavers. It is subsequently found that random interleavers and odd–even symmetric interleavers are performing equally well in reducing the PAR. Results are also presented for the out of band radiation and the bit error rate performance of interleaved OFDM (IOFDM) and conventional OFDM in an additive white Gaussian noise channel. IOFDM also has less adjacent channel interference than that of conventional OFDM. Copyright © 2002 John Wiley & Sons, Ltd.