bluuebunny/crossref_metadata_2025 huggingface dataset:
Bayesian Inference for Non-Stationary Spatial Covariance Structure via Spatial Deformations
Authors: Schmidt Alexandra M. , O'Hagan Anthony
Published: July 2003

In geostatistics it is common practice to assume that the underlying spatial process is stationary and isotropic, i.e. the spatial distribution is unchanged when the origin of the index set is translated and under rotation about the origin. However, in environmental problems, such assumptions are not realistic since local influences in the correlation structure of the spatial process may be found in the data. The paper proposes a Bayesian model to address the anisot- ropy problem. Following Sampson and Guttorp, we define the correlation function of the spatial process by reference to a latent space, denoted by D, where stationarity and isotropy hold. The space where the gauged monitoring sites lie is denoted by G. We adopt a Bayesian approach in which the mapping between G and D is represented by an unknown function d(·). A Gaussian process prior distribution is defined for d(·). Unlike the Sampson–Guttorp approach, the mapping of both gauged and ungauged sites is handled in a single framework, and predictive inferences take explicit account of uncertainty in the mapping. Markov chain Monte Carlo methods are used to obtain samples from the posterior distributions. Two examples are discussed: a simulated data set and the solar radiation data set that also was analysed by Sampson and Guttorp.
Semiparametric Models: A Generalized Self-Consistency Approach
Authors: Tsodikov A.
Published: July 2003

In semiparametric models, the dimension d of the maximum likelihood problem is potentially unlimited. Conventional estimation methods generally behave like O(d3). A new O(d) estimation procedure is proposed for a large class of semiparametric models. Potentially unlimited dimension is handled in a numerically efficient way through a Nelson–Aalen-like estimator. Discussion of the new method is put in the context of recently developed minorization–maximization algorithms based on surrogate objective functions. The procedure for semiparametric models is used to demonstrate three methods to construct a surrogate objective function: using the difference of two concave functions, the EM way and the new quasi-EM (QEM) approach. The QEM approach is based on a generalization of the EM-like construction of the surrogate objective function so it does not depend on the missing data representation of the model. Like the EM algorithm, the QEM method has a dual interpretation, a result of merging the idea of surrogate maximization with the idea of imputation and self-consistency. The new approach is compared with other possible approaches by using simulations and analysis of real data. The proportional odds model is used as an example throughout the paper.
A Sieve Bootstrap For The Test Of A Unit Root
Authors: CHANG YOOSOON , PARK JOON Y.
Published: July 2003

Abstract. In this paper, we consider a sieve bootstrap for the test of a unit root in models driven by general linear processes. The given model is first approximated by a finite autoregressive integrated process of order increasing with the sample size, and then the method of bootstrap is applied for the approximated autoregression to obtain the critical values for the usual unit root tests. The resulting tests, which may simply be viewed as the bootstrapped versions of Augmented Dickey–Fuller (ADF) unit root tests by Said and Dickey (1984), are shown to be consistent under very general conditions. The asymptotic validity of the bootstrap ADF unit root tests is thus established. Our conditions are significantly weaker than those used by Said and Dickey. Simulations show that bootstrap provides substantial improvements on finite sample sizes of the tests.
On Estimating Conditional Mean‐Squared Prediction Error in Autoregressive Models
Authors: ING CHING‐KANG , YU SHU‐HUI
Published: July 2003

Abstract. Zhang and Shaman considered the problem of estimating the conditional mean‐squared prediciton error (CMSPE) for a Gaussian autoregressive (AR) process. They used the final prediction error (FPE) of Akaike to estimate CMSPE and proposed that FPE's effectiveness be judged by its asymptotic correlation with CMSPE. However, as pointed out by Kabaila and He, the derivation of this correlation by Zhang and Shaman is incomplete, and the performance of FPE in estimating CMSPE is also poor in Kabaila and He's simulation study. Kabaila and He further proposed an alternative estimator of CMSPE, V, in the stationary AR(1) model. They reported that V has a larger normalized correlation with CMSPE through Monte Carlo simulation results. In this paper, we propose a generalization of V, V˜, in the higher‐order AR model, and obtain the asymptotic correlation of FPE and V˜ with CMSPE. We show that the limit of the normalized correlation of V˜ with CMSPE is larger than that of FPE with CMSPE, and hence Kabaila and He's finding is justified theoretically. In addition, the performances of the above estimators of CMSPE are re‐examined in terms of mean‐squared errors (MSE). Our main conclusion is that from the MSE point of view, V˜ is the best choice among a family of asymptotically unbiased estimators of CMSPE including FPE and V˜ as its special cases.
Reducing size distortions of parametric stationarity tests
Authors: LANNE MARKKU , SAIKKONEN PENTTI
Published: July 2003

The use of asymptotic critical values in stationarity tests against the alternative of a unit root process is known to lead to over‐rejections in finite samples when the considered process is stationary but highly persistent. We claim that, in recent parametric tests, this is caused by estimation errors which result when the autoregressive parameters used to describe the short‐run dynamics of the process are replaced by estimators. We suggest a modification that corrects for these errors. Simulation results show that the modified test works reasonably well when the persistence is moderate and there is no time trend in the model but it is less effective when the model contains a time trend. An empirical illustration with inflation rate data is provided.
Seasonal Unit Root Tests Based on Forward and Reverse Estimation
Authors: LEYBOURNE STEPHEN , TAYLOR A. M. ROBERT
Published: July 2003

In this paper, we suggest a new set of regression‐based statistics for testing the seasonal unit root null hypothesis. These tests are based on combining conventional Hylleberg et al. (1990) ‐type seasonal unit root test statistics calculated from both forward and reverse estimation of the auxiliary regression equation. We derive the asymptotic distributions of the new test statistics under the seasonal unit root null hypothesis. We provide finite sample critical values appropriate for the case of quarterly data together with asymptotic critical values, the latter appropriate for any seasonal aspect. Monte Carlo simulation of the finite‐sample size and power properties of the new tests reveals that, overall, they perform rather better than extant tests of the seasonal unit root hypothesis.
Diagnostic Checking in a Flexible Nonlinear Time Series Model
Authors: MEDEIROS MARCELO C. , VEIGA ALVARO
Published: July 2003

This paper considers a sequence of misspecification tests for a flexible nonlinear time series model. The model is a generalization of both the smooth transition autoregressive (STAR) and the autoregressive artificial neural network (AR‐ANN) models. The tests are Lagrange multiplier (LM) type tests of parameter constancy against the alternative of smoothly changing ones, of serial independence, and of constant variance of the error term against the hypothesis that the variance changes smoothly between regimes. The small sample behaviour of the proposed tests is evaluated by a Monte‐Carlo study and the results show that the tests have size close to the nominal one and a good power.
Testing Composite Hypotheses for Locally Stationary Processes
Authors: SAKIYAMA KENJI , TANIGUCHI MASANOBU
Published: July 2003

For a class of locally stationary processes introduced by Dahlhaus, this paper discusses the problem of testing composite hypotheses. First, for the Gaussian likelihood ratio test (GLR), Wald test (W) and Lagrange multiplier test (LM), we derive the limiting distribution under a composite hypothesis in parametric form. It is shown that the distribution of GLR, W and LM tends to a χ2 distribution under the hypothesis. We also evaluate their local powers under a sequence of local alternatives, and discuss their asymptotic optimality. The results can be applied to testing for stationarity. Some examples are given. They illuminate the local power property via simulation. On the other hand, we provide a nonparametric LAN theorem. Based on this result, we obtain the limiting distribution of the GLR under both null and alternative hypotheses described in nonparametric form. Finally, the numerical studies are given.
Exploring complementarity in on‐ and off‐job training for apprenticeships
Authors: Harris Roger , Simons Michele , Willis Peter , Carden Pam
Published: July 2003

The differences between on‐ and off‐job learning environments continue to be the subject of much debate, and the notion of complementarity between them is a perennial issue for most forms of training and development. This paper grapples with this issue in relation to apprentices in the building industry in Australia. It analyses the different perceptions of complementarity held by apprentices, host employers and college teachers. It strives to understand the diverse meanings of complementarity within the context of communities of practice in which apprentices acquire not only vocational knowledge and skills, but also a sense of identity through internalising sometimes complementary but often contradictory messages from their different learning environments. Their development towards the status of ‘competent tradespersons’ heavily depends on their individual abilities to integrate and synthesise these messages.
Frame of reference rater training issues: recall, time and behavior observation training
Authors: Roch Sylvia G. , O'Sullivan Brian J.
Published: July 2003

This study investigated three controversial issues regarding frame of reference training (FOR), a type of rater training: (1) Does it improve behavioral recall, (2) Can it be improved by incorporating behavior observation training (BOT), and (3) Can its effects persist over time? Results suggested that even though FOR training increases the number of behaviors recalled, it does not necessarily improve the quality of the recalled behaviors, but a combined FOR + BOT program does improve recall quality. Lastly, results suggested that FOR training can improve rating accuracy, even after a two‐week delay between rater training and the rating task.
Corporate training and development policies and practices: a cross‐national study of India and Britain
Authors: Yadapadithaya P.S. , Stewart Jim
Published: July 2003

The aim of this paper is to report on the existing corporate training and development (T&D) policies and practices in India and Britain. The data were collected from written questionnaires mailed to 252 Indian and 174 British companies. The results and discussions are based on the most prominent comparative and international dimensions of T&D such as key responsibility for T&D function, corporate commitment to T&D, major drivers and key result areas of T&D; purposes, levels, instruments, timing, and designs of evaluation; major perceived deficiencies and challenges of T&D function. The two‐country comparisons revealed that while some of the findings related to corporate T&D policies and practices exhibited differences, others also reflected similarity. Compared with India, more training is done in Britain, more movement to delegating responsibilities or involving line managers in T&D in Britain, there seems also to be more focus on and involvement of individual employees in Britain. British organisations seem to be more concerned with business results from T&D. It may also be argued that the greater importance attached to business results brings about a growing involvement of employees and managers as opposed to HRD practitioners and that it is the greater movement in this direction in Britain compared with India that accounts for most if not all of the differences in the results of the two surveys.
Book reviews
Authors: Stewart Jim
Published: July 2003

Professor Paul Joyce   Nottingham Business School   Nottingham Trent University

The Leadership Lifecycle

Andrew Ward, 2003. Published by Palgrave Macmillan, Basingstoke, UK. ISBN 0‐3339‐9362‐4. £25.00 hardback, 178 pages.

Jim Bray   Senior Lecturer in HRD   Department of Management and HR   University of Central England

Mediation for Managers: Resolving Conflict and Rebuilding Relationships at Work

John Crawley and Katherine Graham, 2002. Nicholas Brealey Publishing, London, UK and Maine, USA. ISBN: 1‐857‐8831‐5. £14.99 ($19.95 paperback), 227 pages.
Mexican Seasonal Migration to Canada and Development: A Community‐based Comparison
Authors: Basok Tanya
Published: July 2003

The article explores development and migration. Based on a comparison of investment‐related behaviour of participants of the Canadian Mexican Seasonal Workers Programme from eleven Mexican villages, the article explores the impact of the nature of the migrants' community of origin on development. Contrary to the findings reported by the “new economics of labour migration” theorists, it was found that migrants from the least endowed communities, not from the best endowed communities, are likely to invest in agricultural land. This pattern is related to variable prices of land and the composition of the participants of the Canadian guest worker programme, most of whom are poor. The article draws attention to the importance of considering composition of migrant workers in an analysis of the impact of migration on community development. Development is analysed in the article from both the “growth” and the “quality of living” perspectives and it is found that regardless of the perspective used, the nature of the community does not affect the impact of migration on development.
Migration and the Reproduction of Poverty: The Refugee Camps in Jordan
Authors: Khawaja Marwan
Published: July 2003

This study examines the link between poverty and migration into and out of camps, using 1999 household survey data on the refugee camp populations in Jordan and a binomial logistic regression. The findings show a clear clustering of poverty in the camps, where about one‐third of households are poor. Results from several nested regression models show that in‐migration is not the cause of persistent poverty in the camps. On the other hand, human capital variables, especially education, economic activity, and “social inheritance”, as well as demographic factors such as household headship and dependency rate have significant effects on poverty incidence. Some theoretical and policy implications of the findings are discussed.
Highly Skilled and Business Migrants: Information Processes and Settlement Outcomes
Authors: Benson‐Rea Maureen , Rawlinson Stephen
Published: July 2003

This paper reports on a research programme that has investigated the migration experiences of highly skilled professional and business migrants to New Zealand. Over a four‐year period, five separate studies have been conducted on the stages in the process of migration. The paper sets out a model of the stages of the migration process and the data and analysis which it has guided. Of particular interest are the information sources available to potential migrants and employers, the cultural sensitivity of settlement processes and the migrants' subsequent ease of access to the labour market. The paper analyses information flows available to migrants at crucial phases in the migration process based on a stages model of the migration process. The model indicates some of the critical steps, interactions, and decisions in the migration process from the individual's point of view. Crucial information gaps are identified and implications are drawn for actors involved at the different stages.
Finding an Adequate Job: Employment and Income of Recent Immigrants to Israel
Authors: Stier Haya , Levanon Varda
Published: July 2003

The study examines the early market experience of recent immigrants to Israel from the former Soviet Union (FSU) and their mobility patterns a few years after migration. The Labour Utilization Framework, proposed by Clogg and Sullivan (1983), was analysed to identify the employment difficulties immigrants experienced upon arrival, their short‐term mobility in the labour market, and the income consequences of their disadvantaged position in the market. Using a panel study of immigrants who arrived in Israel during 1990, we found that although most of them found employment, only a minority did not experience employment hardships. Four years after their arrival, most immigrants were still employed in occupations for which they were over‐qualified, and only a small portion of the group managed to find adequate employment. Women had more severe employment hardships and a lower rate of mobility into the better positions. For men and women alike, almost any deviation from a stable adequate employment entailed wage penalties.
Estimation of the Nakagami parameter from log-compressed ultrasonic backscattered envelopes (L)
Authors: Shankar P. M.
Published: July 2003

In commercial medical ultrasonic imaging systems, B mode images are displayed with the log-compressed backscattered envelope. While the Nakagami distribution can describe the statistics of the backscattered envelope, this nonlinear compression of the envelope modifies the statistics of the image pixels from the Nakagami distribution. An estimation of the Nakagami parameter from the log-compressed data has been undertaken, enabling its application in tissue classification. Results based on random number and A-line simulations indicate that the Nakagami parameter m can be easily obtained from the log-compressed data. The values of the parameter estimated from the log-compressed data are very close to those obtained directly from the envelope. This suggests the use of Nakagami statistics based techniques for tissue characterization even when rf data are not available.
Effectiveness of narrow-band versus tonal off-frequency maskers
Authors: Savel Sophie , Bacon Sid P.
Published: July 2003

The present study was a follow-up to a pilot study in which it was found that a 500-Hz-wide narrow-band noise (NBN) masker produced more masking than a tonal (T) masker for signal frequencies both above and below the masker frequency. The aim of the present study was to determine to what extent these results were influenced by an interaction of the relatively rapid temporal envelope fluctuations of the NBN and the short (10-ms) duration of the signal. In the first experiment, the masking produced by a regular NBN, a low-noise noise (LNN), and a T was compared. The LNN produced less masking than the NBN, and about as much as the T, suggesting that the inherent amplitude fluctuations in the NBN were largely responsible for the greater masking produced by that masker. In the second experiment, the masking produced by a regular NBN was compared with that by a T for a signal duration of 10 or 200 ms. The difference in masking between the two maskers was reduced or eliminated when the signal duration was 200 ms, because the threshold in the presence of the NBN masker decreased more with increasing signal duration. This could reflect a decreased “confusion” between the signal and the inherent fluctuations of the NBN masker.
Inferring Genetic Networks and Identifying Compound Mode of Action via Expression Profiling
Authors: Gardner Timothy S. , di Bernardo Diego , Lorenz David , Collins James J.
Published: July 2003

The complexity of cellular gene, protein, and metabolite networks can hinder attempts to elucidate their structure and function. To address this problem, we used systematic transcriptional perturbations to construct a first-order model of regulatory interactions in a nine-gene subnetwork of the SOS pathway in
Escherichia coli
. The model correctly identified the major regulatory genes and the transcriptional targets of mitomycin C activity in the subnetwork. This approach, which is experimentally and computationally scalable, provides a framework for elucidating the functional properties of genetic networks and identifying molecular targets of pharmacological compounds.
Role of Raf in Vascular Protection from Distinct Apoptotic Stimuli
Authors: Alavi Alireza , Hood John D. , Frausto Ricardo , Stupack Dwayne G. , Cheresh David A.
Published: July 2003

Raf kinases have been linked to endothelial cell survival. Here, we show that basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) differentially activate Raf, resulting in protection from distinct pathways of apoptosis in human endothelial cells and chick embryo vasculature. bFGF activated Raf-1 via p21-activated protein kinase–1 (PAK-1) phosphorylation of serines 338 and 339, resulting in Raf-1 mitochondrial translocation and endothelial cell protection from the intrinsic pathway of apoptosis, independent of the mitogen-activated protein kinase kinase–1 (MEK1). In contrast, VEGF activated Raf-1 via Src kinase, leading to phosphorylation of tyrosines 340 and 341 and MEK1-dependent protection from extrinsic-mediated apoptosis. These findings implicate Raf-1 as a pivotal regulator of endothelial cell survival during angiogenesis.
Control of Axon Branch Dynamics by Correlated Activity in Vivo
Authors: Ruthazer Edward S. , Akerman Colin J. , Cline Hollis T.
Published: July 2003

To determine how patterned visual activity regulates the development of axonal projections, we collected in vivo time-lapse images of retinal axons from albino
Xenopus
tadpoles in which binocular innervation of the optic tectum was induced. Axons added branch tips with nearly equal probability in all territories, but eliminated them preferentially from territory dominated by the opposite eye. This selective branch elimination was abolished by blockade of
N
-methyl-
d
-aspartate receptors. These results describe a correlation-based mechanism by which visual experience directly governs axon branch dynamics that contribute to the development of topographic maps.
Altered Patterns of Sleep and Behavioral Adaptability in NPAS2-Deficient Mice
Authors: Dudley Carol A. , Erbel-Sieler Claudia , Estill Sandi Jo , Reick Martin , Franken Paul , Pitts SiNae , McKnight Steven L.
Published: July 2003

Animal behavior is synchronized to the 24-hour light:dark (LD) cycle by regulatory programs that produce circadian fluctuations in gene expression throughout the body. In mammals, the transcription factor CLOCK controls circadian oscillation in the suprachiasmatic nucleus of the brain; its paralog, neuronal PAS domain protein 2 (NPAS2), performs a similar function in other forebrain sites. To investigate the role of NPAS2 in behavioral manifestations of circadian rhythm, we studied locomotor activity, sleep patterns, and adaptability to both light- and restricted food–driven entrainment in NPAS2-deficient mice. Our results indicate that NPAS2 plays a substantive role in maintaining circadian behaviors in normal LD and feeding conditions and that NPAS2 is critical for adaptability to food restriction.
Effects of Basal Debris on Glacier Flow
Authors: Iverson Neal R. , Cohen Denis , Hooyer Thomas S. , Fischer Urs H. , Jackson Miriam , Moore Peter L. , Lappegard Gaute , Kohler Jack
Published: July 2003

Glacier movement is resisted partially by debris, either within glaciers or under glaciers in water-saturated layers. In experiments beneath a thick, sliding glacier, ice containing 2 to 11% debris exerted shear traction of 60 to 200 kilopascals on a smooth rock bed, comparable to the total shear traction beneath glaciers and contrary to the usual assumption that debris-bed friction is negligible. Imposed pore-water pressure that was 60 to 100% of the normal stress in a subglacial debris layer reduced shear traction on the debris sufficiently to halt its deformation and cause slip of ice over the debris. Slip resistance was thus less than debris shearing resistance.
Increase in the Export of Alkalinity from North America's Largest River
Authors: Raymond Peter A. , Cole Jonathan J.
Published: July 2003

Chemical weathering and the subsequent export of carbonate alkalinity (HCO
3
–
+ CO
3
–
2
) from soils to rivers account for significant amounts of terrestrially sequestered atmospheric CO
2
. We show here that during the past half-century, the export of this alkalinity has increased dramatically from North America's largest river, the Mississippi. This increased export is in part the result of increased flow resulting from higher rainfall in the Mississippi basin. Subcatchment data from the Mississippi suggest that the increase in the export of alkalinity is also linked to amount and type of land cover. These observations have important implications for the potential management of carbon sequestration in the United States.
Low Potential for Climatic Stress Adaptation in a Rainforest
Drosophila
Species
Authors: Hoffmann A. A. , Hallas R. J. , Dean J. A. , Schiffer M.
Published: July 2003

The ability of sensitive rainforest species to evolve in response to climate change is largely unknown. We show that the Australian tropical rainforest fly
Drosophila birchii
exhibits clinal variation in desiccation resistance, but the most resistant population lacks the ability to evolve further resistance even after intense selection for over 30 generations. Parent-offspring comparisons indicate low heritable variation for this trait but high levels of genetic variation for morphology.
D. birchii
also exhibits abundant genetic variation at microsatellite loci. The low potential for resistance evolution highlights the importance of assessing evolutionary potential in targeted ecological traits and species from threatened habitats.
Intracellular Bacterial Biofilm-Like Pods in Urinary Tract Infections
Authors: Anderson Gregory G. , Palermo Joseph J. , Schilling Joel D. , Roth Robyn , Heuser John , Hultgren Scott J.
Published: July 2003

Escherichia coli
entry into the bladder is met with potent innate defenses, including neutrophil influx and epithelial exfoliation. Bacterial subversion of innate responses involves invasion into bladder superficial cells. We discovered that the intracellular bacteria matured into biofilms, creating pod-like bulges on the bladder surface. Pods contained bacteria encased in a polysaccharide-rich matrix surrounded by a protective shell of uroplakin. Within the biofilm, bacterial structures interacted extensively with the surrounding matrix, and biofilm associated factors had regional variation in expression. The discovery of intracellular biofilm-like pods explains how bladder infections can persist in the face of robust host defenses.
Evolution of Planetary Cores and the Earth-Moon System from Nb/Ta Systematics
Authors: Münker Carsten , Pfänder Jörg A. , Weyer Stefan , Büchl Anette , Kleine Thorsten , Mezger Klaus
Published: July 2003

It has been assumed that Nb and Ta are not fractionated during differentiation processes on terrestrial planets and that both elements are lithophile. High-precision measurements of Nb/Ta and Zr/Hf reveal that Nb is moderately siderophile at high pressures. Nb/Ta values in the bulk silicate Earth (14.0 ± 0.3) and the Moon (17.0 ± 0.8) are below the chondritic ratio of 19.9 ± 0.6, in contrast to Mars and asteroids. The lunar Nb/Ta constrains the mass fraction of impactor material in the Moon to less than 65%. Moreover, the Moon-forming impact can be linked in time with the final core-mantle equilibration on Earth 4.533 billion years ago.
White-Light Filaments for Atmospheric Analysis
Authors: Kasparian J. , Rodriguez M. , Méjean G. , Yu J. , Salmon E. , Wille H. , Bourayou R. , Frey S. , André Y.-B. , Mysyrowicz A. , Sauerbrey R. , Wolf J.-P. , Wöste L.
Published: July 2003

Most long-path remote spectroscopic studies of the atmosphere rely on ambient light or narrow-band lasers. High-power femtosecond laser pulses have been found to propagate in the atmosphere as dynamically self-guided filaments that emit in a continuum from the ultraviolet to the infrared. This white light exhibits a directional behavior with enhanced backward scattering and was detected from an altitude of more than 20 kilometers. This light source opens the way to white-light and nonlinear light detection and ranging applications for atmospheric trace-gas remote sensing or remote identification of aerosols. Air ionization inside the filaments also opens promising perspectives for laser-induced condensation and lightning control. The mobile femtosecond-terawatt laser system, Teramobile, has been constructed to study these applications.
Desulfurization of Transportation Fuels with Zeolites Under Ambient Conditions
Authors: Yang Ralph T. , Hernández-Maldonado Arturo J. , Yang Frances H.
Published: July 2003

Deep desulfurization of transportation fuels (gasoline, diesel, and jet fuels) is being mandated by U.S. and foreign governments and is also needed for future fuel cell applications. However, it is extremely difficult and costly to achieve with current technology, which requires catalytic reactors operated at high pressure and temperature. We show that Cu
+
and Ag
+
zeolite Y can adsorb sulfur compounds from commercial fuels selectively and with high sulfur capacities (by π complexation) at ambient temperature and pressure. Thus, the sulfur content was reduced from 430 to <0.2 parts per million by weight in a commercial diesel at a sorbent capacity of 34 cubic centimeters of clean diesel produced per gram of sorbent. This sulfur selectivity and capacity are orders of magnitude higher than those obtained by previously known sorbents.
Catalytic Reduction of Dinitrogen to Ammonia at a Single Molybdenum Center
Authors: Yandulov Dmitry V. , Schrock Richard R.
Published: July 2003

Dinitrogen (N
2
) was reduced to ammonia at room temperature and 1 atmosphere with molybdenum catalysts that contain tetradentate [HIPTN
3
N]
3–
triamidoamine ligands {such as [HIPTN
3
N]Mo(N
2
), where [HIPTN
3
N]
3–
is [{3,5-(2,4,6-i-Pr
3
C
6
H
2
)
2
C
6
H
3
NCH
2
CH
2
}
3
N]
3–
} in heptane. Slow addition of the proton source [{2,6-lutidinium}{BAr′
4
}, where Ar′ is 3,5-(CF
3
)
2
C
6
H
3
]and reductant (decamethyl chromocene) was critical for achieving high efficiency (∼66% in four turnovers). Numerous x-ray studies, along with isolation and characterization of six proposed intermediates in the catalytic reaction under noncatalytic conditions, suggest that N
2
was reduced at a sterically protected, single molybdenum center that cycled from Mo(III) through Mo(VI) states.
Reactions at Interfaces As a Source of Sulfate Formation in Sea-Salt Particles
Authors: Laskin Alexander , Gaspar Daniel J. , Wang Weihong , Hunt Sherri W. , Cowin James P. , Colson Steven D. , Finlayson-Pitts Barbara J.
Published: July 2003

Understanding the formation of sulfate particles in the troposphere is critical because of their health effects and their direct and indirect effects on radiative forcing, and hence on climate. Laboratory studies of the chemical and physical changes in sodium chloride, the major component of sea-salt particles, show that sodium hydroxide is generated upon reaction of deliquesced sodium chloride particles with gas-phase hydroxide. The increase in alkalinity will lead to an increase in the uptake and oxidation of sulfur dioxide to sulfate in sea-salt particles. This chemistry is missing from current models but is consistent with a number of previously unexplained field study observations.
Pharmacological Modulation of Perceptual Learning and Associated Cortical Reorganization
Authors: Dinse Hubert R. , Ragert Patrick , Pleger Burkhard , Schwenkreis Peter , Tegenthoff Martin
Published: July 2003

The pharmacological basis of perceptual learning and associated cortical reorganizations remains elusive. We induced perceptual learning by Hebbian coactivation of the skin of the tip of the right index finger in humans. Under placebo, tactile two-point discrimination was improved on the coactivated but not on the left index finger. This augmentation was blocked by an
N
-methyl-D-aspartate–receptor blocker, but doubled by amphetamine. No drug effects were found on the left index finger. The individual amount of cortical reorganization as assessed by mapping of somatosensory evoked potentials was linearly correlated with the pharmacological modulation of discrimination thresholds, implying that perceptual learning and associated cortical changes are controlled by basic mechanisms known to mediate and modulate synaptic plasticity.
Active Nonmetallic Au and Pt Species on Ceria-Based Water-Gas Shift Catalysts
Authors: Fu Qi , Saltsburg Howard , Flytzani-Stephanopoulos Maria
Published: July 2003

Traditional analysis of reactions catalyzed by supported metals involves the structure of the metallic particles. However, we report here that for the class of nanostructured gold– or platinum–cerium oxide catalysts, which are active for the water-gas shift reaction, metal nanoparticles do not participate in the reaction. Nonmetallic gold or platinum species strongly associated with surface cerium-oxygen groups are responsible for the activity.
Stratigraphy's Founding Saint
Authors: Thomson Keith S.
Published: July 2003

The Seashell on the Mountaintop
A Story of Science, Sainthood, and the Humble Genius who Discovered a New History of the Earth. Alan Cutler. Dutton (Penguin), New York, 2003. 240 pp. $23.95, C$36. ISBN 0-525-94708-6.

Cutler offers an account of Nicholas Steno and his pioneering contributions to our understanding of fossils, stratigraphy, and Earth History.
Clouded Picture of a Big Bang
Authors: Simkin Tom , Fiske Richard S.
Published: July 2003

Krakatoa
The Day the World Exploded: August 27, 1883. Simon Winchester. HarperCollins, New York, 2003. 432 pp. $25.95, C$39.95. ISBN 0-06-621285-5. Viking, London, £16.99. ISBN 0-670-91126-7.

Writing for a popular audience, Winchester offers an engaging, anecdotal account of the 1883 eruption of Krakatau and its effects.
Rapid Diagnosis of Bacteremic Pneumococcal Infections in Adults by Using the Binax NOW
Streptococcus pneumoniae
Urinary Antigen Test: a Prospective, Controlled Clinical Evaluation
Authors: Smith Michael D. , Derrington Petra , Evans Rachel , Creek Marjorie , Morris Rhonwen , Dance David A. B. , Cartwright Keith
Published: July 2003

The diagnosis of severe pneumococcal infections is inadequate, relying heavily on culture of
Streptococcus pneumoniae
from blood or other normally sterile fluids, and is severely limited by prior administration of antibiotics. We evaluated prospectively the Binax NOW
S. pneumoniae
urinary antigen test, a rapid immunochromatographic assay, for the diagnosis of bacteremic pneumococcal infections in hospitalized adult patients. Antigen was detected in 88 of 107 cases overall, resulting in a test sensitivity of 82% (95% confidence interval [95% CI], 74 to 89%). Antigen detection was greater in those with pneumonia (67 of 77 [87%]) than in those without pneumonia (21 of 30 [70%]) (
P
= 0.04). Urinary antigen was also detected in 3 of 106 adult patients with community-acquired septicemic infections caused by other organisms, giving a test specificity of 97% (95% CI, 92 to 99%). For 45 pneumococcal bacteremia patients with a positive test on treatment day 1, urinary antigen excretion was monitored for the first week of antibiotic treatment. Antigen was still detectable in 83% (29 of 35 tested; 95% CI, 66 to 93%) on treatment day 3. Detection of urinary antigen is a valuable, sensitive, and rapid test for the early diagnosis of bacteremic pneumococcal infections in adult patients, even after antibiotic treatment has commenced.
Whole-Blood Agglutination Assay for On-Site Detection of Human Immunodeficiency Virus Infection
Authors: Gupta Amita , Chaudhary Vijay K.
Published: July 2003

Simple and rapid diagnostic tests are needed to curtail human immunodeficiency virus (HIV) infection, especially in the developing and underdeveloped nations of the world. The visible-agglutination assay for the detection of HIV with the naked eye (NEVA HIV, which represents naked eye visible-agglutination assay for HIV) is a hemagglutination-based test for the detection of antibodies to HIV in whole blood. The NEVA HIV reagent is a cocktail of highly stable recombinant bifunctional antibody fusion proteins with HIV antigens which can be produced in large quantities with a high degree of purity. The test procedure involves mixing of one drop of the NEVA HIV reagent with one drop of blood sample on a glass slide. The presence of anti-HIV antibodies in the blood sample leads to clumping of erythrocytes (agglutination) that can be seen with the naked eye. Evaluation with commercially available panels of sera and clinical samples has shown that the performance of NEVA HIV is comparable to those of U.S. and European Food and Drug Administration-approved rapid as well as enzyme-linked immunosorbent assay kits. The test detects antibodies to both HIV type 1 (HIV-1) and HIV-2 in a single spot and gives results in less than 5 min. The test was developed by keeping in mind the practical constraints of testing in less developed countries and thus is completely instrument-free, requiring no infrastructure or even electricity. Because the test is extremely rapid, requires no sample preparation, and is simple enough to be performed by a semiskilled technician in any remote area, NEVA HIV is a test for the hard-to-reach populations of the world.
Use of Molecular Methods To Identify the
Mycobacterium tuberculosis
Complex (MTBC) and Other Mycobacterial Species and To Detect Rifampin Resistance in MTBC Isolates following Growth Detection with the BACTEC MGIT 960 System
Authors: Somoskovi Akos , Song Qunfeng , Mester Judit , Tanner Charise , Hale Yvonne M. , Parsons Linda M. , Salfinger Max
Published: July 2003

A prospective study was organized by using a total of 1,585 consecutive clinical specimens to determine whether biomass obtained from positive growth in the MGIT 960 system could be used directly in AccuProbe DNA hybridization tests, the PCR-based Inno-LiPA Rif.TB (LiPA) assay, and a PCR-based DNA sequencing of the
rpoB
gene for the rapid identification of the
Mycobacterium tuberculosis
complex (MTBC) and other mycobacterial species and for the determination of rifampin (RIF) resistance in MTBC strains. The results were compared to routine culture, identification, and susceptibility testing techniques performed on the same samples. The study results revealed that the DNA AccuProbe assay (on the day of growth positivity) readily identified 95.7%, the LiPA assay readily identified 98.6%, and
rpoB
sequencing readily identified 97.1% of the 70 MTBC isolates from mycobacterial growth indicator tubes (MGIT). In addition, application of the LiPA for the identification and RIF susceptibility testing of the MTBC in growth-positive MGIT resulted in a turnaround time of less than 2 weeks after specimen receipt. Although DNA sequencing of
rpoB
required a slightly longer (16 days) turnaround time, this method was capable of identifying several species of nontuberculous mycobacteria in addition to identifying MTBC and determining RIF susceptibility or resistance. The molecular methods were also found to rapidly identify RIF-susceptible and -resistant MTBC in two of the three mixed mycobacterial cultures weeks earlier than conventional methods. In conclusion, the biomass obtained in MGIT at the time of growth positivity in the 960 system is sufficient for use in all three molecular tests, and this approach can reduce the turnaround time for reporting results.
Polymer-Based Enzyme-Linked Immunosorbent Assay Using Human Papillomavirus Type 16 (HPV16) Virus-Like Particles Detects HPV16 Clade-Specific Serologic Responses
Authors: Studentsov Yevgeniy Y. , Ho Gloria Y. F. , Marks Morgan A. , Bierman Robert , Burk Robert D.
Published: July 2003

Human papillomavirus type 16 (HPV16) virus-like particles (VLP) were used as antigen in a polymer enzyme-linked immunosorbent assay (ELISA) to measure antibodies to HPV capsid proteins. Serum samples from 575 college women, previously tested for the presence of cervicovaginal HPV DNA, were analyzed. The prevalences of anti-HPV16 VLP antibodies at baseline were 14.1% for immunoglobulin G (IgG) and 6.4% for IgA. The seroprevalences of IgG in women with cervicovaginal HPV16, HPV16-related types, and other HPV types were 55, 33, and 19%, respectively (
P
< 0.001), compared to the prevalence in women without an HPV infection (10%). HPV VLP IgA seropositivity was associated with high HPV16 VLP IgG optical density values. The seropositivity of IgG antibodies was independently associated with infection with HPV16 or HPV16-related types, increased number of lifetime male partners for vaginal sex, having sex with men ≥5 years older, history of abnormal PAP smear, older age, and living separately from parents. Use of HPV16 VLP polymer ELISA detects clade-specific responses and suggests an HPV16 VLP vaccine may have broader protection that initially anticipated.
Identification of Hepatitis C Virus (HCV) Subtype 1b Strains That Are Highly, or Only Weakly, Associated with Hepatocellular Carcinoma on the Basis of the Secondary Structure of an Amino-Terminal Portion of the HCV NS3 Protein
Authors: Ogata Satoshi , Huab Florese Ruth , Nagano-Fujii Motoko , Hidajat Rachmat , Deng Lin , Ku Yonson , Yoon Seitetsu , Saito Takafumi , Kawata Sumio , Hotta Hak
Published: July 2003

The NS3 protein of hepatitis C virus subtype 1b (HCV-1b) isolates obtained from 89 patients with hepatocellular carcinoma (HCC) and 78 patients without HCC were analyzed. On the basis of the secondary structure of the amino-terminal 120 residues of NS3, HCV-1b isolates were classified into group A, group B, and an indeterminate group, each of which was further divided into a number of subgroups, such as A1-1, A1-2, A2-1, A2-2, B1-1, B1-2, B2-1, B2-2, C-1, C-2, and C-3. HCV-1b isolates of subgroup B1-1 were found in 53 (59.6%) of 89 patients with HCC and 19 (24.4%) of 78 patients without HCC, with the difference between the two patient groups being statistically significant (
P
< 0.00001). Although the number of isolates was small, subgroup B2-1 was also highly associated with HCC, with all five isolates in that subgroup being found in patients with HCC (
P
< 0.05). On the other hand, HCV-1b isolates of subgroup A1-1 were associated only weakly with HCC; they were found in 6 (6.7%) of 89 patients with HCC and in 25 (32.1%) of 78 patients without HCC, with the difference between the two patient groups being statistically significant (
P
< 0.0001). The other subgroups, such as A1-2, A2-1, B1-2, C-1, C-2, and C-3, were moderately associated with HCC; their distribution patterns among patients with HCC did not differ significantly from those among patients without HCC. Taken together, our results suggest that HCV-1b isolates of subgroups B1-1 and B2-1 are highly associated with HCC and that this secondary structure analysis may be useful for predicting the relative risk of developing HCC.
Comparison of Diagnostic Techniques forHelicobacter cetorumInfection in Wild Atlantic Bottlenose Dolphins (Tursiops truncatus)
Authors: Harper Claudia G. , Whary Mark T. , Feng Yan , Rhinehart Howard L. , Wells Randall S. , Xu Shilu , Taylor Nancy S. , Fox James G.
Published: July 2003

Helicobacter cetorumsp. nov. has been cultured from the stomach of Atlantic white-sided dolphins (Lagenorhynchus acutus) and the feces of Pacific white-sided (L. obliquidens) and Atlantic bottlenose (Tursiops truncatus) dolphins and a beluga whale (Delphinapterus leucas).H. cetorumhas high homology toHelicobacter pylorias shown by 16S rRNA sequencing, andH. cetoruminfection has been associated with gastritis and clinical signs in cetaceans. Because the prevalence ofH. cetorumin wild populations is unknown, minimally invasive techniques for detectingH. cetorumwere compared for 20 wild bottlenose dolphins sampled as part of a long-term health study. Fecal samples were tested for helicobacter by culture, Southern blotting, and PCR using genus-specific andH. cetorum-specific primers. An enzyme-linked immunosorbent assay (ELISA) was developed to measureH. cetorumimmunoglobulin G (IgG).H. cetorumwas cultured from 4 of 20 fecal samples, 7 samples were positive usingHelicobactersp. PCR, and 8 samples were positive forH. cetorumusing species-specific primers. Two additional fecal samples were positive byHelicobactersp. Southern blotting, suggesting infection with another helicobacter. All 20 sera contained high levels of IgG antibodies toH. cetorumthat were significantly lowered by preabsorption of the sera with whole-cell suspensions ofH. cetorum(P< 0.02). Until the specificity of the serum ELISA can be determined by testing sera from dolphins confirmed to be uninfected, PCR and Southern blot screenings of feces are the most sensitive techniques for detection ofH. cetorum, and results indicate there is at least a 50% prevalence ofH. cetoruminfection in these dolphins.
Randomly Amplified Polymorphic DNA as a Valuable Tool for Epidemiological Studies ofParacoccidioides brasiliensis
Authors: Hahn Rosane Christine , Macedo Andréa Mara , Fontes Cor Jesus Fernandes , Batista Renata Dias , Santos Niriana Lara , Hamdan Júnia Soares
Published: July 2003

Randomly amplified polymorphic DNA (RAPD) has been successfully used to detect genetic variations among isolates ofParacoccidioides brasiliensis.However, the usefulness of this technique for assessing important parasitic properties is still unconfirmed. In the present work we further investigated the applicability of RAPD in revealing important intrinsic and extrinsic features of this fungus associated with geographical origin, time of isolation, source of clinical specimen, clinical forms of human disease and also in vitro and in vivo susceptibility to antimicrobial and antifungal drugs. The RAPD patterns allowed us to distinguish all of the analyzed strains, which included 26 clinical isolates, 2 animal isolates, and 1 environmental isolate ofP. brasiliensisobtained from different geographic regions, confirming the strong discriminating power of this technique. A phenetic tree, build from the RAPD data, showed that although the two nonclinical Brazilian strains were set together the majority of the clinical Brazilian strains were randomly distributed through different sub-branches of a major cluster without any correlation to any of the parameters analyzed. A second major cluster, however, has grouped isolates from Mato Grosso and Roraima (Brazil) that not only were susceptible in vitro to trimethoprim-sulfamethoxazole but also produced a good in vivo response. These results open new vistas for epidemiological and clinical studies ofP. brasiliensis.