bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison of three estimators of the Weibull parameters
Authors: Skinner Katina R. , Keats J. Bert , Zimmer William J. 
Published: August 2002

AbstractUsing mean square error as the criterion, we compare two least squares estimates of the Weibull parameters based on non‐parametric estimates of the unreliability with the maximum likelihood estimates (MLEs). The two non‐parametric estimators are that of Herd–Johnson and one recently proposed by Zimmer. Data was generated using computer simulation with three small sample sizes (5, 10 and 15) with three multiply‐censored patterns for each sample size. Our results indicate that the MLE is a better estimator of the Weibull characteristic value, θ, than the least squares estimators considered. No firm conclusions may be made regarding the best estimate of the Weibull shape parameter, although the use of maximum likelihood is not recommended for small sample sizes. Whenever least squares estimation of both Weibull parameters is appropriate, we recommend the use of the Zimmer estimator of reliability. Copyright © 2001 John Wiley & Sons, Ltd.
Reliability qualification of semiconductor devices based on physics‐of‐failure and risk and opportunity assessment
Authors: Gerling W. H. , Preussger A. , Wulfert F. W. 
Published: August 2002

AbstractQualification frequently is a time‐critical activity at the end of a development project. As time‐to‐market is a competitive issue, the most efficient qualification efforts are of interest. A concept is outlined, which proactively integrates qualification into the development process and provides a systematic procedure as a support tool to development and gives early focus on required activities. It converts requirements for a product into measures of development and qualification in combination with a risk and opportunity assessment step and accompanies the development process as a guiding and recording tool for advanced quality planning and confirmation. The collected data enlarge the knowledge database for DFR/BIR (designing for reliability/building‐in reliability) to be used for future projects. The procedure challenges and promotes teamwork of all the disciplines involved. Based on the physics‐of‐failure concept the reliability qualification methodology is re‐arranged with regard to the relationships between design, technology, manufacturing and the different product life phases at use conditions. It makes use of the physics‐of‐failure concept by considering the potential individual failure mechanisms and relates most of the reliability aspects to the technology rather than to the individual product design. Evaluation of complex products using common reliability models and the definition of sample sizes with respect to systematic inherent product properties and fractions of defects are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Ab initio quantum chemical studies of reactions in astrophysical ices. 4. Reactions in ices involving HCOOH, CH2NH, HCN, HNC, NH3, and H2O
Authors: Woon David E. 
Published: August 2002

AbstractIce‐bound condensed‐phase reactions involving formic acid (HCOOH), methylenimine (CH2NH), hydrogen cyanide (HCN), hydrogen isocyanide (HNC), and ammonia (NH3) were investigated in order to characterize possible pathways to larger organic species that are efficient at the cold temperatures prevalent in cometary nuclei and the interstellar medium. Previous laboratory and computational modeling has demonstrated that reactions between some closed‐shell species can be significantly enhanced when they occur within a matrix of water ice. Certain key reactions can occur at temperatures under 100 K, in spite of having gas phase barriers that may be 30 kcal/mol or higher. The present study considered one‐ and two‐step reactions of HCOOH and NH3 to yield formamide (NH2CHO), reactions between CH2NH and HCN, HNC, NH3, and H2O, and the reaction of HCOOH and CH2NH to yield glycine (NH2CH2COOH). The most favorable process identified in this work is production of NH2CH(OH)2, the intermediate in the two‐step pathway from HCOOH and NH3 to NH2CHO, which is enhanced considerably when it occurs within ice but not to the extent that it is likely to occur unassisted at temperatures below 100 K. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem 88: 226–235, 2002
Phthalocyanoiron complex with bridged ligands. Electronic structure of monomers and polymers
Authors: Mendizabal Fernando , Olea‐Azar Claudio , Briones Rodolfo 
Published: August 2002

AbstractElectronic structure aspects related to the semiconducting properties of monomers and polymers of phthalocyanoiron with bidentate bridging ligands, PcFe–L2 and [PcFe(L)]n, have been investigated from density functional calculations [L = pyrazine, triazine, tetrazine, pyridine, 4,4′‐bipyridine, bipyridyacetylene, and bis(4‐pyridyl)bencene]. The following relevant results have been obtained: (a) an energy analysis in terms of electrostatic interaction, Pauli repulsion, and occupied/virtual orbital interactions show that the Pauli repulsion is the origin that the axial ligands (L) prefer be located toward the aza positions of the macrocycle, and (b) the intrinsic semiconducting properties depend of the frontier band. The valence band is composed largely by the transition metal dxy orbital. The conduction band is composed of a mixture between the metallomacrocycle and bridged ligand orbitals for systems formed by pyrazine, bipyridine, and bipyridyacetylene. However, this composition is different when the ligands are triazine and tetrazine, which show a band composed of π* orbitals. These systems are predicted to show the higher conductivity within the series, in agreement with experimental results. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 170–181, 2001
High‐speed liquid chromatography/tandem mass spectrometry using a monolithic column for high‐throughput bioanalysis
Authors: Wu Jing‐Tao , Zeng Hang , Deng Yuzhong , Unger Steve E. 
Published: August 2002

AbstractWith the ever‐increasing workload from a variety of in vitro and in vivo screening procedures, new analytical methodologies to perform bioanalysis in an accurate and high‐throughput manner are in great demand. In this work, monolithic columns were used instead of conventional particulate HPLC columns to perform chromatographic separations. Because the pressure drop on a monolithic column was considerably lower than that on a particulate column, a high flow rate (6 mL/min) was used for a 4.6 × 50 mm monolithic column with a total backpressure of about 61 bar measured using acetonitrile/water (50 : 50). The capability of using a regular column length at high flow rates, combined with the extremely small dependency of separation efficiency on linear flow velocity, allowed for the generation of sufficient chromatographic resolving power in a significantly reduced runtime. As demonstrated in this work, a plasma extract of a mixture of tempazepam, tamoxifen, fenfluramine, and alprozolam were baseline separated within a total analysis time of one minute. An average peak width at half maximum of approximately one second was noted using a generic broad gradient. It was also found that the separation efficiency and signal/noise (S/N) ratios for this separation remained almost constant at flow rates of 1, 3, and 6 mL/min, respectively. The ruggedness of the separation was evaluated by injecting 600 plasma extracts containing the replicates of a standard curve of the above mixture during an overnight run. The chromatographic retention time, separation quality, peak response and sensitivity were highly reproducible throughout the run. This high‐speed liquid chromatography/tandem mass spectrometry (LC/MS/MS) system has been used routinely in the authors' laboratory to support drug discovery programs. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of Synthetic chemical drugs in adulterated Chinese medicines by capillary electrophoresis/electrospray ionization mass spectrometry
Authors: Cheng Hsing Ling , Tseng Mei‐Chun , Tsai Pei‐Lun , Her Guor Rong 
Published: August 2002

AbstractSixteen synthetic chemical drugs, often found in adulterated Chinese medicines, were studied by capillary electrophoresis/UV absorbance (CE/UV) and capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI‐MS). Only nine peaks were detected with CZE/UV, but on‐line CZE/MS provided clear identification for most compounds. For a real sample of a Chinese medicinal preparation, a few adulterants were identified by their migration times and protonated molecular ions. For coeluting compounds, more reliable identification was achieved by MS/MS in selected reaction monitoring mode. Micellar electrokinetic chromatography (MEKC) using sodium dodecyl sulfate (SDS) provided better separation than capillary zone electrophoresis (CZE), and, under optimal conditions, fourteen peaks were detected using UV detection. In ESI, the interference of SDS was less severe in positive ion mode than in negative ion mode. Up to 20 mM SDS could be used in direct coupling of MEKC with ESI‐MS if the mass spectrometer was operated in positive ion mode. Because of better resolution in MEKC, adulterants can be identified without the use of MS/MS. Copyright © 2001 John Wiley & Sons, Ltd.
Evaluation of pyridoindoles, pyridylindoles and pyridylpyridoindoles as matrices for ultraviolet matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Nonami Hiroshi , Wu Feiyue , Thummel Randolph P. , Fukuyama Yuko , Yamaoka Hidenobu , Erra‐Balsells Rosa 
Published: August 2002

AbstractIn an effort to gain an understanding of the processes governing ultraviolet matrix‐assisted laser desorption/ionization (UV‐MALDI), direct comparison was made of the mass spectra of proteins, carbohydrates and synthetic polymers (polyethylene glycol, polyester and polyamide) by using pyridylindoles, pyridoindoles and pyridylpyridoindoles as UV (337 nm)‐MALDI‐TOFMS matrices in positive and negative ion mode. In order to study the combined effect of the indole N‐H and the pyridine nitrogen of the MALDI matrix on the desorption/ionization process in MALDI, compounds were selected that include either or both of these functions in their structure. Within the compounds studied only those that possess simultaneously both functions in a 1,4‐relation behave as very good matrices for proteins. These compounds also work as matrices for some carbohydrates and synthetic polymers used as analytes in the present study. Some of the compounds were also found to be useful for the post‐source decay (PSD) analysis of cyclodextrins in positive and negative ion mode. In several cases we also examined the matrix behavior of the corresponding N‐methylindole derivatives. Copyright © 2001 John Wiley & Sons, Ltd.
Micro‐high‐performance liquid chromatography/Fourier transform mass spectrometry with electron‐capture dissociation for the analysis of protein enzymatic digests
Authors: Davidson Walter , Frego Lee 
Published: August 2002

AbstractElectron‐capture dissociation (ECD) Fourier transform mass spectrometry (FTMS) employed to generate comprehensive sequence information for the chromatographic analysis of enzymatic protein digests is described. A pepsin digest of cytochrome c was separated by reversed‐phase micro‐high‐performance liquid chromatography (µHPLC) and ionized ‘on‐line’ by electrospray ionization (ESI). The ions thus formed were transferred to and trapped in the FTMS analyzer cell. Typically, no precursor ion isolation was performed. The trapped ions were subjected to a pulse of electrons to induce fragmentation. Mass spectra were acquired continuously to produce a three‐dimensional LC/MS data set. The spectra were dominated by c and, to a lesser degree, z ions, which provided near complete sequence coverage. External calibration provided good mass accuracy and resolution, typical of FTMS. Thus µHPLC/ECD − FTMS is shown to be a highly informative method for the analysis of enzymatic protein digests. Copyright © 2002 John Wiley & Sons, Ltd.
New IQC for quasi‐concave nonlinearities
Authors: Megretski Alexandre 
Published: August 2002

AbstractA new set of integral quadratic constraints (IQC) is derived for a class of ‘rate limiters’, modelled as a series connections of saturation‐like memoryless nonlinearities followed by integrators. The result, when used within the standard IQC framework (in particular, with finite gain/passivity‐based argiments, Lyapunov theory, structured singular values, etc.), is expected to be widely useful in nonlinear system analysis. For example, it enables ‘discrimination’ between ‘saturation‐like’ and ‘deadzone‐like’ nonlinearities and can be used to prove stability of systems with saturation in cases when replacing the saturation block by another memoryless nonlinearity with equivalent slope restrictions makes the whole system unstable. In particular, it is shown that the L2 gain of a unity feedback system with a rate limiter in the forward loop cannot exceed \sqrt{2}.In addition, a new, more flexible version of the general IQC analysis framework is presented, which relaxes the homotopy and boundedness conditions, and is more aligned with the language of the emerging IQC software. Copyright © 2001 John Wiley & Sons, Ltd.
Effects of river regulation on aquatic macrophyte growth and floods in the Hadejia‐Nguru Wetlands and flow in the Yobe River, northern Nigeria; implications for future water management
Authors: Goes B.J.M. 
Published: August 2002

AbstractThe Hadejia River is a tributary of the Yobe River in semi‐arid northern Nigeria and is regulated by two major dams. The other main tributary is uncontrolled. Comparison of the discharge data for the controlled and uncontrolled rivers shows an average decrease of 33% in annual flow in the upstream part of the Hadejia River. The total annual flow and the peak flow in the Hadejia River further downstream, just above the Hadejia‐Nguru Wetlands (HNW), however, did not show a significant reduction in discharge. This is related to a relatively small river flow reduction at lower flows in the upstream part of the Hadejia River and the fact that the formal large upstream water users are not (yet) working at full capacity. The major impact of the dams on the downstream part of the river is the change in regime from ephemeral to perennial. The introduced dry season flows created favourable circumstances for the development of aquatic macrophyte blockages in the HNW. Owing to these blockages, the Hadejia River stopped contributing to the flow in the Yobe River for much of the year. Furthermore, after the completion of the dams, the timing of the floods in the HNW became less predictable.Suggestions for improvement of water management are made. These comprise engineering structures, including a flow diversion structure to regulate flows in the HNW, implementation of environmentally acceptable river flow strategies and water allocation management. Copyright © 2002 John Wiley & Sons, Ltd.
Propagules in dry wetland sediments as indicators of ecological health: effects of salinity
Authors: Skinner Rachael , Sheldon Fran , Walker Keith F. 
Published: August 2002

AbstractIndicators of ecological health are problematic for wetlands in dry regions because distinctive communities are associated with dry and wet phases of indefinite duration. The propagule bank, including the resting stages of aquatic animals and plants, maintains the community's capacity to recover from drought or disturbance. This paper records observations of invertebrates, protists and algae emerging in laboratory microcosms following the inundation of dry sediments from two temporary lakes on the River Murray floodplain in South Australia. A simple experiment carried out on the sediment from one lake showed that increased salinity was associated with lower diversity (richness) but higher abundance of emergent organisms. The effect on diversity was evident at salinities above 11–17 mS cm−1, and the effect on abundances was evident above 6–11 mS cm−1 (salinity here is indicated by electrical conductivity at 25°C). These data suggest that propagule banks may be useful as complementary indicators of wetland health. Copyright © 2001 John Wiley & Sons, Ltd.
Summary of ISO/TC 201 Standard: VI ISO 14706:2000—Surface chemical analysis—Determination of surface elemental contamination on silicon wafers by total reflection x‐ray fluorescence (TXRF) spectroscopy
Authors: Gohshi Yohichi 
Published: August 2002

AbstractThis International Standard specifies a total reflection x‐ray fluorescence (TXRF) method for the measurement of the atomic surface density of elemental contamination on chemomechanically polished or epitaxial silicon wafer surfaces. This method is applicable to elements with atomic number from 16 (S) to 92 (U), and contamination elements with atomic surface densities from 1 × 1010 to 1 × 1014 atoms cm−2. It is applicable also to contamination elements with atomic surface densities of 5 × 108–5 × 1012 atoms cm−2 using a vapour‐phase decomposition specimen preparation method. Copyright © 2002 John Wiley & Sons, Ltd.
Statistical considerations of FDA and CPMP rules for the investigation of new anti‐bacterial products
Authors: Röhmel Joachim 
Published: August 2002

AbstractIn this paper I investigate statistical properties of some guidance given by the FDA and by the CPMP on the planning, conduct and analysis of clinical trials with new anti‐bacterial substances using an active control design. It is demonstrated that the non‐inferiority margin proposed by the FDA has some undesirable features, and that the CPMP guidance may need further interpretation with respect to a statement that the non‐inferiority margin may be smaller than 10 per cent for response rates >90 per cent. A new margin is proposed that combines the desirable properties from both the FDA and the CPMP guidance. It is also shown that the approximate unconditional tests that are in use in such trials are quite unreliable with respect to preserving the nominal type I error. Unconditional exact tests are presented as a remedy for this issue. Copyright © 2001 John Wiley & Sons, Ltd.
Minor stressors and depressed mood: reactivity is more strongly correlated than total stress
Authors: Felsten Gary 
Published: August 2002

AbstractThis study evaluated how strongly total stress and stress reactivity to minor stressors were correlated with depressed mood in traditional and non‐traditional college women (n = 146). Stress reactivity, which was conceptualized as mean stress per stressor, accounted more strongly than number of potentially stressful encounters for total stress, and was more strongly correlated than total stress with symptoms of depressed mood, after controlling for initial depressed mood and neuroticism. Reactivity was associated with greater use of avoidance coping and higher levels of neuroticism, which suggest that it may represent a stable individual difference and possibly serve as a predictor of depressed mood, especially in response to minor stressors. Copyright © 2002 John Wiley & Sons, Ltd.
Influence of interferon‐γ on radiation‐induced apoptosis in normal and ataxia‐telangiectasia fibroblast cell lines
Authors: Savoldi‐Barbosa Marcela , Sakamoto‐Hojo Elza T. 
Published: August 2002

AbstractCombination of interferon‐γ (IFN‐γ) with radiation, or chemotherapeutic agents, produces different kind of modulatory effects, depending on the cell types and experimental conditions. The objective of the present study was verify the influence of IFN‐γ on the induction of apoptosis by gamma‐radiation. Experiments were carried out on human fibroblast cell lines: VH‐25 (primary), MRC‐5, and AT‐5BIVA (SV40‐transformed). Exponentially growing cells were irradiated and exposed to IFN‐γ (1,000, 2,000, and 3,000 UI/mL) until in situ cell staining performed at 6, 24, and 48 h. Induction of apoptosis by ionising radiation was not verified in primary VH‐25 cells. A significant increase in the frequencies of apoptotic cells was observed in SV‐40‐transformed cells lines, MRC‐5, and AT‐5BIVA fibroblasts, which were irradiated with 1.0 Gy, but the frequencies of necrotic cells were similar to the control levels. In MRC‐5 cells, combined treatments with radiation and IFN‐γ induced a statistically significant reduction in the frequencies of apoptotic cells detected at 24 and 48 h after cell irradiation, while for AT cells the interaction effect (reduction of apoptosis frequency) was significant even at earlier time collection (6 h) after γ‐irradiation, and higher when compared to MRC‐5 cells. The present study demonstrated that IFN‐γ showed an anti‐apoptotic activity in SV40‐transformed fibroblasts, normal and AT cells, which were irradiated with γ‐rays, thus indicating a mechanism dependent on the cellular type. Teratogenesis Carcinog. Mutagen. 21:417–429, 2001. © 2001 Wiley‐Liss, Inc.
The two sites of fusion of the neural folds and the two neuropores in the human embryo
Authors: O'Rahilly Ronan , Müller Fabiola 
Published: August 2002

AbstractBackgroundSince reports on a pattern of multiple sites of fusion of the neural folds in the mouse appeared, it has been widely assumed that a similar pattern must be valid for the human. In the absence of embryological evidence, claims have been made that such a pattern can be discerned by classifying neural tube defects.MethodsThe neural folds and tube, as well as the neuropores, were reassessed in 98 human embryos of Stages 8–13; 61 were controlled by precise graphic reconstructions.ResultsCareful study of an extensive series of staged human embryos shows that two de novo sites of fusion of the neural folds appear in succession: α in the rhombencephalic region and β in the prosencephalic region, adjacent to the chiasmatic plate. Fusion from Site α proceeds bidirectionally (rostrad and caudad), whereas that from β is unidirectional (caudad only). The fusions terminate in neuropores, of which there are two: rostral and caudal. Highly variable accessory loci of fusion, without positional stability and of unknown frequency, may be encountered in Stage 10 but seemingly not later, and their existence has been known for more than half a century.ConclusionsTwo sites of fusion (a term preferred to closure) of the neural folds and two neuropores are found in the human embryo. No convincing embryological evidence of a pattern of multiple sites of fusion, such as has been described in the mouse, is available for the human. The construction of embryological details from information derived from other species or from the examination of later anomalies is liable to error. Neural tube defects are reviewed and although they have been considered on the basis of five, four, or three sites of fusion, interpretations based on two sites can as readily be envisaged. Teratology 65:162–170, 2002. © 2002 Wiley‐Liss, Inc.
Doing business in Vietnam
Authors: Scheela William , Van Dinh Nguyen 
Published: August 2002

AbstractThis article examines the opportunities and challenges of doing business in Vietnam. We focus on the
seven‐year development process of the venture capital industry in Vietnam as an indicator of the
long‐term process of creating and managing business investments there. Although there are many lucrative
business opportunities in Vietnam, there are also significant challenges that must be carefully analyzed before
making an investment. Challenges include finding quality investments, long payback periods, a lengthy and expensive
process to develop a management team, and significant misunderstandings because of cultural differences between
Western and Vietnamese investors. © 2001 John Wiley & Sons, Inc.