bluuebunny/crossref_metadata_2025 huggingface dataset:
Usefulness of double gene construct for rapid identification of transgenic mice exhibiting tissue‐specific gene expression
Authors: Sato Masahiro , Watanabe Toshiteru , Oshida Akiko , Nagashima Ayako , Miyazaki Jun‐Ichi , Kimura Minoru
Published: November 2004

Identification of transgenics still requires PCR and genomic Southern blot hybridization of genomic DNA isolated from tail pieces. Furthermore, identification of transgene‐expressing transgenics (hereafter called “expressor”) requires mRNA analyses (RT‐PCR and Northern blot hybridization) or protein analysis (Western blotting and immunohistochemical staining using specific antibodies). These approaches are often labor‐intensive and time‐consuming. We developed a technique that simplifies the process of screening expressor transgenics using enhanced green fluorescent protein (EGFP), a noninvasive reporter recently utilized in a variety of organisms, including mice, as a tag. We constructed a MNCE transgene consisting of two expression units, MBP‐NCre (termed “MN”) and CAG‐EGFP (termed “CE”). MN consists of a myelin basic protein (MBP) promoter and NCre gene (Cre gene carrying a nuclear localization signal (NLS) sequence at its 5′ end). CE consists of a promoter element, CAG composed of cytomegalovirus (CMV) enhancer and chicken β‐actin promoter, and EGFP cDNA. Of a total of 72 F0 mice obtained after pronuclear injection of MNCE at 1‐cell egg stage, 15 were found to express EGFP when the tail, eye, and inner surface of the ear were inspected for EGFP fluorescence under UV illumination at weaning stage. These fluorescent mice were found to possess MNCE and to express NCre mRNA in a brain‐specific manner. Mice exhibiting no fluorescence were transgenic or nontransgenic. Mice carrying MNCE, but exhibiting no fluorescence, never expressed NCre mRNA in any organs tested. These findings indicate that (i) direct inspection of the surface of mice for fluorescence under UV illumination enables identification of expressor transgenics without performances of the molecular biological analyses mentioned above, and (ii) systemic promoters such as CAG do not affect the tissue‐specificity of a tissue‐specific promoter such as MBP promoter, which is located upstream of CAG by approximately 2 kb. Mol. Reprod. Dev. 60: 446–456, 2001. © 2001 Wiley‐Liss, Inc.
The temperament of pre‐term, low birth weight infants and its potential biological substrates
Authors: Weiss Sandra J. , Jonn‐Seed Mary St. , Wilson Peggy
Published: November 2004

Temperament profiles of pre‐term, low birth weight (LBW) infants were assessed at 6 months of age using standardized norms from the Revised Infant Temperament Questionnaire (RITQ). The contributions of perinatal risk, ethnicity, and gender to various temperament dimensions were examined. The sample included 152 infants with a mean birth weight of 1687 g and a mean gestational age of 31 weeks. Eighty percent of the infants were classified as having temperaments that were difficult to manage. Irregularity of the infants' biorhythms, slowness in their ability to adapt to changes, and distractibility were the most problematic. Birth weight, gestational age, and gender were not associated with temperament. Perinatal morbidity was related to the temperament dimension of infant persistence, with implications for the infant's attention span and task performance. Euro American infants were rated as more persistent and less intense in emotional expression than were infants of other ethnic groups. Results suggest the need for a more direct assessment of the effects of neurobiological processes on development of temperament phenotypes and for measurement of temperament that is socioculturally appropriate. © 2004 Wiley Periodicals, Inc. Res Nurs Health 27:392–402, 2004
Mortalin is over‐expressed by colorectal adenocarcinomas and correlates with poor survival
Authors: Dundas Sinclair R , Lawrie Laura C , Rooney Patrick H , Murray Graeme I
Published: November 2004

Using comparative proteomic analysis we have identified over‐expression of mortalin in colorectal adenocarcinomas. Mortalin, also known as mitochondrial heat‐shock protein 70 (mhsp 70), is involved in cell cycle regulation with important roles in cellular senescence and immortalization pathways. It is known to bind to and inactivate wild‐type tumour suppressor protein p53 and influences the Ras‐Raf‐MAPK pathway. By immunostaining a colorectal cancer tissue microarray linked to a patient database, we further found that mortalin over‐expression correlates with poor patient survival and, in multivariate analysis, is independent of standard prognostic variables (p = 0.04). Our findings demonstrate that mortalin over‐expression may predict outcome in colorectal cancer and suggest that this protein is involved in colorectal neoplasia. Our experimental approach emphasises the analytical power of combining proteomics with tissue microarray analysis in the context of a well‐defined tumour database. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Poly(ethyleneimine)/arginine–glycine–aspartic acid conjugates prepared with N‐succinimidyl 3‐(2‐pyridyldithio)propionate: An investigation of peptide coupling and conjugate stability
Authors: Bai Jiang , Açan Başak , Ghahary Aziz , Ritchie Bruce , Somayaji Vishwa , Uludağ Hasan
Published: November 2004

Poly(ethylene imine) (PEI), a highly cationic polymer, is being used for deoxyribonucleic acid (DNA) complexation and delivery into cells. To enhance the cellular uptake of polymer/DNA complexes, arginine–glycine–aspartic acid (RGD) peptides have been conjugated to PEI with N‐succinimidyl 3‐(2‐pyridyldithio)propionate (SPDP). This coupling scheme creates a disulfide‐linked conjugate, the stability of which in the presence of thiols is uncertain. We have investigated the conjugation of an RGD peptide, glycine–arginine–glycine–aspartic acid–serine–proline–cysteine (GRGDSPC), to PEI with SPDP and subsequently assessed the stability of the conjugates in the presence of two thiol compounds, mercaptoethanol and cysteine. SPDP effectively controls the extent of GRGDSPC substitution on PEI. The conjugates, however, are readily cleaved in the presence of the thiols; the cleavage is rapid (∼50% cleavage in 2–4 h) and inversely related to the degree of peptide substitution on the polymers. The peptide coupling is stable in the absence of thiols, and its cleavage is strongly dependent on the pH of the medium but not on the ionic strength of the medium. We conclude that RGD peptides coupled to PEI are labile in the presence of physiological concentrations of thiols, and this should be taken into account when such polymer–peptide conjugates are used for DNA delivery. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6143–6156, 2004
Heat capacity of poly(butylene terephthalate)
Authors: Pyda Marek , Nowak‐Pyda Elzbieta , Mays Jimmy , Wunderlich Bernhard
Published: November 2004

The low‐temperature heat capacity of poly(butylene terephthalate) (PBT) was measured from 5 to 330 K. The experimental heat capacity of solid PBT, below the glass transition, was linked to its approximate group and skeletal vibrational spectrum. The 21 skeletal vibrations were estimated with a general Tarasov equation with the parameters Θ1 = 530 K and Θ2 = Θ3 = 55 K. The calculated and experimental heat capacities of solid PBT agreed within better than ±3% between 5 and 200 K. The newly calculated vibrational heat capacity of the solid from this study and the liquid heat capacity from the ATHAS Data Bank were applied as reference values for a quantitative thermal analysis of the apparent heat capacity of semicrystalline PBT between the glass and melting transitions as obtained by differential scanning calorimetry. From these results, the integral thermodynamic functions (enthalpy, entropy, and Gibbs function) of crystalline and amorphous PBT were calculated. Finally, the changes in the crystallinity with the temperature were analyzed. With the crystallinity, a baseline was constructed that separated the thermodynamic heat capacity from cold crystallization, reorganization, annealing, and melting effects contained in the apparent heat capacity. For semicrystalline PBT samples, the mobile‐amorphous and rigid‐amorphous fractions were estimated to complete the thermal analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4401–4411, 2004
Classification of homogeneous copolymers of propylene and 1‐octene based on comonomer content
Authors: Poon B. , Rogunova M. , Chum S. P. , Hiltner A. , Baer E.
Published: November 2004

The solid‐state structure and properties of homogeneous copolymers of propylene and 1‐octene were examined. Based on the combined observations from melting behavior, dynamic mechanical response, morphology with primarily atomic force microscopy, X‐ray diffraction, and tensile deformation, a classification scheme with four distinct categories is proposed. The homopolymer constitutes Type IV. It is characterized by large α‐positive spherulites with thick lamellae, good lamellar organization, and considerable secondary crystallization. Copolymers with up to 5 mol % octene, with at least 28 wt % crystallinity, are classified as Type III. Like the homopolymer, these copolymers crystallize as α‐positive spherulites, however, they have smaller spherulites and thinner lamellae. Both Type IV and Type III materials exhibit thermoplastic behavior characterized by yielding with formation of a sharp neck, cold drawing, strong strain hardening, and small recovery. Copolymers classified as Type II have between 5 and 10 mol % octene with crystallinity in the range of 15–28%. Type II materials have smaller impinging spherulites and thinner lamellae than Type III copolymers. Moreover, the spherulites are α‐negative, meaning that they exhibit very little crystallographic branching. These copolymers also contain predominately α‐phase crystallinity. The materials in this category have plastomeric behavior. They form a diffuse neck upon yielding and exhibit some recovery. Type I copolymers have more than 10 mol % octene and less than 15% crystallinity. They exhibit a granular texture with the granules often assembled into beaded strings that resemble poorly developed lamellae. Type I copolymers crystallize predominantly in the mesophase. Materials belonging to this class deform with a very diffuse neck and also exhibit some recovery. They are identified as elastoplastomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4357–4370, 2004
A stochastic model of vaccine trials for endemic infections using group randomization
Authors: RIGGS T. W. , KOOPMAN J. S.
Published: November 2004

To clarify the determinants of vaccine trial power for non-typable Haemophilus influenzae, we constructed stochastic SIS models of infection transmission in small units (e.g. day-care centres) to calculate the equilibrium distribution of the number infected. We investigated how unit size, contact rate (modelled as a function of the unit size), external force of infection and infection duration affected the statistical power for detection of vaccine effects on susceptibility or infectiousness. Given a frequency-dependent contact rate, the prevalence, proportion of infections generated internally and the power to detect vaccine effects each increased slightly with unit size. Under a density-dependent model, unit size had much stronger effects. To maximize information allowing inference from vaccine trials, contact functions should be empirically evaluated by studying units of differing size and molecular methods should be used to help distinguish internal vs. external transmission.
Risk of fatal adverse events associated with 17DD yellow fever vaccine
Authors: STRUCHINER C. J. , LUZ P. M. , DOURADO I. , SATO H. K. , AGUIAR S. G. , RIBEIRO J. G. L. , SOARES R. C. R. , CODEÇO C. T.
Published: November 2004

Yellow fever (YF), an acute infectious disease, is endemic in the north and central-west of Brazil. This disease can be prevented by the use of a vaccine. In Brazil, four fatal adverse events have been associated with the YF vaccine used in the country (17DD vaccine). We briefly describe the last two fatalities, and estimate the risk of 17DD-associated fatal adverse events under different epidemiological scenarios. Controversies regarding the appropriate denominator that enters the estimation of risk serve as a motivation for each proposed scenario. The statistical procedures used show optimum behaviour when assessing the risk of rare events. Risk estimates vary from 0·043 (95% CI 0·017–0·110) to 2·131 (95% CI 0·109–12·071) fatalities per million doses administered. The robust estimates of the risk of fatal adverse events we present constitute an important element in future risk–benefit analysis and point to the need for good quality vaccine coverage and adverse-events surveillance data to assess the risk of vaccination. Although vaccination of YF endemic regions is necessary to maintain low disease prevalence, preventive administration of YF vaccine to the entire population should be cautiously analysed.
Preliminary report on the northern Australian melioidosis environmental surveillance project
Authors: INGLIS T. J. J. , FOSTER N. F. , GAL D. , POWELL K. , MAYO M. , NORTON R. , CURRIE B. J.
Published: November 2004

An environmental surveillance programme was developed to determine whether water supplies could be a source of Burkholderia pseudomallei as noted during previous melioidosis outbreak investigations. Water supplies to communities in the three northern Australian jurisdictions (Western Australia, Northern Territory and Queensland) were sampled periodically during 2001 and 2002. Water and soil samples were collected from communities known to have had recent culture-positive melioidosis cases and nearby communities where no cases had been diagnosed. Clinical isolates of B. pseudomallei obtained from northern Australian patients during 2001 and 2002 were compared with the environmental B. pseudomallei isolates by ribotyping and pulsed-field gel electrophoresis. B. pseudomallei was isolated from 11 distinct locations, all in the Northern Territory, seven of which were associated with culture-positive melioidosis cases (>1 case at three locations). Water was implicated as a possible environmental source of melioidosis in six locations. A variety of free-living amoebae including Acanthamoeba and Hartmannella spp. that are potential hosts to B. pseudomallei were recovered from environmental specimens. Culturable B. pseudomallei was not found to be widely dispersed in the environments sampled.
Outbreak of Salmonella Goldcoast infections linked to consumption of fermented sausage, Germany 2001
Authors: BREMER V. , LEITMEYER K. , JENSEN E. , METZEL U. , MECZULAT H. , WEISE E. , WERBER D. , TSCHAEPE H. , KREIENBROCK L. , GLASER S. , AMMON A.
Published: November 2004

Salmonella Goldcoast (SGC), an uncommon serotype in Germany, was identified in 25 isolates between 1 April and 7 May 2001. To determine the cause of the outbreak, we conducted a matched case-control study including 24 cases and 51 controls. In a multivariable regression model, only consumption of a raw fermented sausage manufactured by a local company remained significant (adjusted odds ratio 20·0, 95% confidence interval 2·7–302·5). SGC isolated from case-patients shared an indistinguishable pulsed-field gel electrophoresis pattern. A part of the produced raw fermented sausage was sold after only 4 days of fermentation. Samples from the premises and products of the company were negative for SGC. However, short-time raw fermented sausage is more likely to contain pathogens. Irradiation of raw ingredients is not accepted by German consumers, thus strict adherence to good manufacturing practices, the use of HACCP programmes as well as on-farm programmes remain crucial to reduce Salmonella.
Factors associated with transmission of severe acute respiratory syndrome among health-care workers in Singapore
Authors: TELEMAN M. D. , BOUDVILLE I. C. , HENG B. H. , ZHU D. , LEO Y. S.
Published: November 2004

Between 1 and 22 March 2003, a nosocomial outbreak of Severe Acute Respiratory Syndrome (SARS) occurred at the Communicable Disease Centre in Tan Tock Seng Hospital, Singapore, the national treatment and isolation facility for patients with SARS. A case-control study with 36 cases and 50 controls was conducted of factors associated with the transmission of SARS within the hospital. In univariate analysis, contact with respiratory secretions elevated the odds ratio to 6·9 (95% CI 1·4–34·6, P=0·02). Protection was conferred by hand washing (OR 0·06, 95% CI 0·007–0·5, P=0·03) and wearing of N95 masks (OR 0·1, 95% CI 0·03–0·4, P=0·001). Use of gloves and gowns had no effect. Multivariate analysis confirmed the strong role of contact with respiratory secretions (adjusted OR 21·8, 95% CI 1·7–274·8, P=0·017). Both hand washing (adjusted OR 0·07, 95% CI 0·008–0·66, P=0·02) and wearing of N95 masks (adjusted OR 0·1, 95% CI 0·02–0·86, P=0·04) remained strongly protective but gowns and gloves had no effect.
How the sperm lost its tail: the evolution of aflagellate sperm
Authors: Morrow Edward H.
Published: November 2004

The typical sperm is comprised of a head, midpiece and flagellum. Around this theme there is an enormous diversity of form ‐ giant sperm, multi‐flagellate sperm and also sperm that lack flagella entirely. Explaining this diversity in sperm morphology is a challenging question that evolutionary biologists have only recently engaged in. Nonetheless, one of the selective forces identified as being an important factor in the evolution of sperm form is sperm competition, which occurs when the sperm of two or more males compete to fertilize a female's ova. In species with a truly monandrous mating system, the absence of sperm competition means that the selection pressure on males to produce motile sperm may be relaxed. Potentially aflagellate sperm are less costly to produce, both in terms of energy and time. Thus, selection may therefore favour the loss of the sperm flagellum and any other motile mechanisms in monandrous taxa. A review of the literature revealed that 36 taxonomic groups, from red algae to fish, were found independently to have evolved aflagellate sperm. I review what is known about the mating systems of each of these taxa and their nearest sister taxa. A sister‐group analysis using this information provided weak evidence suggesting that the evolution of aflagellate sperm could be linked to the removal of selective pressures generated by sperm competition.
Cophylogeny of the Ficus microcosm
Authors: Jackson Andrew P.
Published: November 2004

The various mutualistic and antagonistic symbioses between fig trees (Ficus: Moraceae) and chalcid wasps comprise a community in microcosm. Phylogenetic estimates of figs and fig wasps show general topological correspondence, making the microcosm a model system for cophylogeny. Incongruence between phylogenies from associated organisms can be reconciled through a combination of evolutionary events. Cophylogeny mapping reconciles phylogenies by embedding an associate tree into a host tree, finding the optimal combinations of events capable of explaining incongruence and evaluating the level of codivergence. This review addresses the results of cophylogeny analysis concerning Ficus and discusses the plausibility of different evolutionary events. Five different associations encompassing fig‐pollinator, fig‐parasite and pollinator‐parasitoid interactions are reconciled. The method improves on previous comparisons by employing‘jungles’to provide an exhaustive and quantitative analysis of cophylogeny. A jungle is a mechanism for inferring host switches and obtaining all potentially optimal solutions to the reconciliation problem. The results support the consensus that figs codiverge significantly with pollinators but not non‐pollinators. However, pollinators still appear to have switched between hosts in contradiction to the traditional model of faithful codivergence. This emphasises the growing realisation that evolutionary transitions in the microcosm are more flexible than previously thought and host specificity is necessary but not sufficient for codivergence. The importance of sampling strategy is emphasised by the influence of taxon set on the fig‐pollinator and fig‐parasite jungles. Spurious significant results for fig‐parasite and fig‐parasitoid jungles indicate that the choice of congruence measure influences significance; the total number of events required to reconcile two trees ('total cost') is not a good measure of congruence when switches cannot be realistically weighted.
Earthquake nucleation on dip‐slip faults
Authors: Zhang Chuanli , Oglesby David D. , Xu Guanshui
Published: November 2004

The nucleation of unstable slip on a fault is of key importance in our understanding of the seismic cycle. We investigate how the asymmetric geometry of dip‐slip faults affects the nucleation of unstable slip on such faults. Previous researchers have devoted much effort to understanding this nucleation process on geometrically simple faults, using a variety of frictional parameterizations. However, there are many reasons to believe that earthquake nucleation may be affected by fault complexity. The breakdown of symmetry on a nonvertical dip‐slip fault means that normal stress is not constant during the slip process and that the hanging wall and footwall may not necessarily move equally. Using a slip‐strengthening and ‐weakening friction law in a two‐dimensional quasi‐static model based on a variational boundary integral method, we show that nucleation on dip‐slip faults is affected by both the dip angle and the direction of slip (normal versus thrust/reverse). Under otherwise identical conditions in a homogeneous half‐space (i.e., neglecting depth‐dependent frictional or material properties), thrust faults nucleate closer to the Earth's surface than normal faults and take less time to do so. These differences decrease as the dip angle of the fault increases to 90°. The amount of preseismic surface slip is a much more complicated function of dip angle. The results show that fault geometry may have an important role in the nucleation process as well as the process of dynamic rupture. Further research is needed to combine rigorous nucleation models with full rupture dynamics.
Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica
Authors: Norabuena Edmundo , Dixon Timothy H. , Schwartz Susan , DeShon Heather , Newman Andrew , Protti Marino , Gonzalez Victor , Dorman LeRoy , Flueh Ernst R. , Lundgren Paul , Pollitz Fred , Sampson Dan
Published: November 2004

New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short (∼1 year) observation period. We also estimate northwest motion of a coastal “sliver block” at 8 ± 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos‐Caribbean relative motion is partitioned here, with ∼8 cm/yr on the Cocos‐Panama block boundary (including a component of permanent shortening across the Fila Costeña fold and thrust belt) and ∼1 cm/yr on the Panama block–Caribbean boundary. The GPS data suggest that the Cocos plate–Panama block boundary is completely locked from ∼10–50 km depth. This large locked zone, as well as associated forearc and back‐arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence.
Gravity waves in the arctic mesosphere during the MaCWAVE/MIDAS summer rocket program
Authors: Williams B. P. , Fritts D. C. , Wang L. , She C. Y. , Vance J. D. , Schmidlin F. J. , Goldberg R. A. , Müllemann A. , Lübken F.‐J.
Published: November 2004

The MaCWAVE/MIDAS rocket campaign occurred at the Andøya Rocket Range (69°N,16°E) on July 1–2 and 4–5, 2002. This paper investigates gravity waves in the mesosphere using falling spheres dropped from rockets and the Weber sodium lidar at the ALOMAR observatory. The vertical displacement of a sodium sporadic layer on July 5 showed great variability at periods from minutes to hours with an observed frequency spectral slope of −1.89. The 2 salvos had similar wave amplitudes at the mesopause, whereas Salvo 2 had stronger amplitudes in the lower atmosphere. The dominant wave period varied strongly with height, possibly due to wave breaking on the strong mean gradients or oblique propagation of wave packets. One long‐period wave appeared to propagate vertically from 75–95 km with a reduction of its vertical wavelength consistent with the mean wind gradient, but it is unclear whether it was a single wave or a superposition of waves.
On the size of the Antarctic ozone hole
Authors: Newman Paul A. , Kawa S. Randolph , Nash Eric R.
Published: November 2004

A primary estimate of the severity of the Antarctic ozone hole is its size. The size is calculated from the area contained by total column ozone values less than 220 Dobson Units (DU) during September–October. The 220‐DU value is used because it is lower than pre‐1980 observed ozone values, and because it is in the strong ozone gradient region. We quantitatively show that the ozone hole size is primarily sensitive to effective stratospheric chlorine trends, and secondarily to the year‐to‐year variations in temperatures near the edge of the polar vortex. Temperatures are in turn sensitive to variations in tropospheric planetary wave forcing of the Southern Hemisphere stratosphere. Currently the average hole size reaches approximately 25 million km2 each spring. Slow decreases of ozone depleting substances will only result in a decrease of about 1 million km2 by 2015. This slow size decrease will be obscured by large dynamically forced year‐to‐year variations of 4 million km2 (1σ), and possibly delayed by greenhouse gas cooling of the Antarctic stratosphere.
Quantifying probabilities of volcanic events: The example of volcanic hazard at Mount Vesuvius
Authors: Marzocchi Warner , Sandri Laura , Gasparini Paolo , Newhall Christopher , Boschi Enzo
Published: November 2004

We describe an event tree scheme to quantitatively estimate both long‐ and short‐term volcanic hazard. The procedure is based on a Bayesian approach that produces a probability estimation of any possible event in which we are interested and can make use of all available information including theoretical models, historical and geological data, and monitoring observations. The main steps in the procedure are (1) to estimate an a priori probability distribution based upon theoretical knowledge, (2) to modify that using past data, and (3) to modify it further using current monitoring data. The scheme allows epistemic and aleatoric uncertainties to be dealt with in a formal way, through estimation of probability distributions at each node of the event tree. We then describe an application of the method to the case of Mount Vesuvius. Although the primary intent of the example is to illustrate the methodology, one result of this application merits special mention. The present emergency response plan for Mount Vesuvius is referenced to a maximum expected event (MEE), the largest out of all the possible eruptions within the next few decades. Our calculation suggest that there is a nonnegligible (1–20%) chance that the next eruption could be larger than that stipulated in the present MEE. The methodology allows all assumptions and thresholds to be clearly identified and provides a rational means for their revision if new data or information are obtained.
Stress orientations at intermediate angles to the San Andreas Fault, California
Authors: Hardebeck Jeanne L. , Michael Andrew J.
Published: November 2004

There are currently two competing models for the frictional strength of the San Andreas Fault in California: the strong‐fault model and the weak‐fault model. The strong‐fault model predicts the maximum horizontal compressive stress axis to be at low angles to the fault, while the relatively weak fault model predicts it to be at high angles. Previous studies have disagreed as to which model is supported by observed stress orientations. We review and compare these studies and present results from several new focal mechanism stress inversions. We find that the observed stress orientations of different studies are generally consistent, implying that the disagreement is one of interpretation. The majority of studies find compressive stress orientations at intermediate angles to the fault, not strictly consistent with either current model. The strong‐fault model is acceptable if the San Andreas is assumed to be a nonoptimally orientated fault that fails because optimally oriented, preexisting planes are not present. The relatively weak fault model is not consistent with the stress orientations. We propose two alternative models to better explain the observed intermediate stress orientations: an intermediate‐strength San Andreas model and a model in which all major active faults are weak.
Digital elevation model construction from structured topographic data: The DEST algorithm
Authors: Favalli Massimiliano , Pareschi M. Teresa
Published: November 2004

An algorithm, Determination of Earth Surface Structures (DEST), is presented to reconstruct digital terrain models of complex landforms from topographic data, such as contour lines and spot heights. The algorithm provides a triangular irregular network (TIN) of the source data, based on a modified Delaunay approach. Delaunay triangulation can introduce artificial terraces from a nonrandom distribution of input points such as a sampled contour line. The algorithm proposed here constructs the three‐dimensional principal skeletons of these artificial flat areas, eliminating the unwanted effects of contour lines. The algorithm can also be applied to topographic data from a variety of mixed sources such as photogrammetric information, radar altimetry measurements, and traditional contour lines. The sparse fine‐surface structures present in the source data are preserved, allowing accurate morphological evaluations, tectonic lineament extraction, and volume estimation. A methodology (D‐DEST) to easily derive, from a TIN computed by DEST, the drainage path and the catchment areas is also presented. A comparison of DEST with other methodologies is performed. It results that our approach does not introduce sensible biased effects in slopes, aspects, drainage network, and catchment areas. The evolution of the upper cone of Vesuvius volcano (Italy) during the last century, as derived from historical cartography, is presented as an application of DEST. The algorithm implemented in C can be requested at DEST_pareschi@pi.ingv.it.
Hydrodynamics simulations of 2ω laser propagation in underdense gasbag plasmas
Authors: Meezan N. B. , Divol L. , Marinak M. M. , Kerbel G. D. , Suter L. J. , Stevenson R. M. , Slark G. E. , Oades K.
Published: November 2004

Recent 2ω laser propagation and stimulated Raman backscatter (SRS) experiments performed on the Helen laser have been analyzed using the radiation-hydrodynamics code HYDRA [M. M. Marinak, G. D. Kerbel, N. A. Gentile, O. Jones, D. Munro, S. Pollaine, T. R. Dittrich, and S. W. Haan, Phys. Plasmas 8, 2275 (2001)]. These experiments utilized two diagnostics sensitive to the hydrodynamics of gasbag targets: a fast x-ray framing camera (FXI) and a SRS streak spectrometer. With a newly implemented nonlocal thermal transport model, HYDRA is able to reproduce many features seen in the FXI images and the SRS streak spectra. Experimental and simulated side-on FXI images suggest that propagation can be explained by classical laser absorption and the resulting hydrodynamics. Synthetic SRS spectra generated from the HYDRA results reproduce the details of the experimental SRS streak spectra. Most features in the synthetic spectra can be explained solely by axial density and temperature gradients. The total SRS backscatter increases with initial gasbag fill density up to ≈0.08 times the critical density, then decreases. Data from a near-backscatter imaging camera show that severe beam spray is not responsible for the trend in total backscatter. Filamentation does not appear to be a significant factor in gasbag hydrodynamics. The simulation and analysis techniques established here can be used in ongoing experimental campaigns on the Omega laser facility and the National Ignition Facility.
Lagrangian simulation of evaporating droplet sprays
Authors: Salman Hayder , Soteriou Marios
Published: November 2004

In this paper we present the purely Lagrangian approach for the high fidelity simulation of evaporating sprays as a potentially advantageous alternative to the widely used Lagrangian–Eulerian approach. We motivate our arguments using analytical solutions which we derive from a set of simplified spray (droplet and vapor) equations, albeit ones that retain key physical complexities of the two-phase flow. These solutions are obtained for two model flows: the stagnation point flow and the point vortex flow. By comparing numerical results with these analytical solutions we demonstrate limitations of the Lagrangian–Eulerian approach in providing solutions that are consistent with the governing equations. The problem alluded to here is specific to evaporating sprays and is over and above the well known issue of the point source approximation. Moreover, while it is related to the presence of interpolations between the disperse and continuous phases, it is not inherent in them—an interpolation scheme that effectively eliminates this problem is identified. Rather it has to do with the fact that in the Lagrangian–Eulerian approach the evaporated volume information is lost and is substituted with an arbitrary, with respect to the evaporation process, grid related volume. The result is grid dependency of the solution and the inability to satisfy physical constraints on both the intensive and extensive properties as dictated by the governing equations. To alleviate these problems, we present the first of a potential family of purely Lagrangian numerical schemes. The scheme is three dimensional and unsteady and naturally captures the key physics inherent in the spray equations. Moreover, it is able to properly resolve the vapor scales that are smaller than the flow dynamical scales. Comparisons of results from this model with the analytical solutions demonstrate the correctness of the approach. The model is also implemented in the simulation of a shear layer flow seeded with evaporating droplets. In these simulations the velocity field is obtained using the Lagrangian vortex element method thus yielding a completely grid free and naturally adaptive computation of an evaporating spray.
Infrared absorption properties of carbon nanotubes synthesized by chemical vapor deposition
Authors: Kouklin N. , Tzolov M. , Straus D. , Yin A. , Xu J. M.
Published: November 2004

We present an infrared (IR) optical absorbance study of highly uniform nanotubes grown by chemical vapor deposition in the self-assembled porous matrix in alumina. For unambiguous IR spectral measurement, nanotubes were extracted from their growth template, purified, and evenly dispersed on a reflecting substrate. The findings, which are consistent with previous results from conduction studies, reveal that the nanotubes are semiconducting with a band gap of ∼100meV. This suggests the potential of nanotube arrays for IR electro-optical device applications.
Planar magnetoinductive wave transducers: Theory and applications
Authors: Freire M. J. , Marqués R. , Medina F. , Laso M. A. G. , Martín F.
Published: November 2004

Transduction of magnetoinductive waves (MIWs) in planar technology is demonstrated. A transducer consisting of a one-dimensional periodic array of metallic split squared ring resonators (SSRR), placed between a pair of microstrip lines on a planar substrate has been fabricated and measured. The microstrip lines are inductively coupled to the SSRRs located at the ends of the periodic array and excite MIWs that propagate along the array. The theoretical model for the dispersion of MIWs is used to predict the dispersion relation and the delay time in the device. The delay time was measured and a good agreement was found with the theoretical predictions. The transmission coefficient of the device was also measured. The theoretical and experimental results suggest that the proposed configuration can find application in the design of delay lines and other microwave devices. In fact, the behavior of the proposed transducer is similar to that of the conventional ferrite magnetostatic-wave transducer. However, ferrite devices are fragile, difficult to integrate, and require a heavy external magnet or electromagnet to magnetize the ferrite to saturation. Since all these drawbacks are not present in the proposed configuration, it may be a useful alternative to those devices for many practical applications.
Looking 100 Å deep into spatially inhomogeneous dilute systems with hard x-ray photoemission
Authors: Dallera C , Duò L. , Braicovich L. , Panaccione G. , Paolicelli G. , Cowie B. , Zegenhagen J.
Published: November 2004

We present hard x-ray photoemission measurements from GaAs samples with a 10-Å-thick layer of AlAs buried at different depths. The intensity trend versus kinetic energy of the Al 1s signal allows extraction of the x-ray attenuation length, which we find to reach ∼100Å at a kinetic energy of 6 keV. On one sample exposed to air for several days we obtain qualitative information on the oxidation at different depth scales by exploiting the energy dependence of the attenuation length. This suggests the strong potential of hard x-ray photoemission in the nondestructive characterization of diluted materials on a depth scale interesting to modern nanotechnologies.
Fabrication of InAs quantum dots on InP(100) by metalorganic vapor-phase epitaxy for 1.55 μm optical device applications
Authors: Kawaguchi Kenichi , Ekawa Mitsuru , Kuramata Akito , Akiyama Tomoyuki , Ebe Hiroji , Sugawara Mitsuru , Arakawa Yasuhiko
Published: November 2004

A change in the density and wavelength of InAs quantum dots (QDs) on InGaAsP/InP(100) substrate grown by metalorganic vapor-phase epitaxy (MOVPE) in accordance with variation in the growth conditions was studied, aiming at optical device applications in the 1.55 μm region. In the moderate V/III ratio region, the size of QDs was found to decrease while the density increased as the group-V source was reduced, but on the other hand, both of them increased monotonously with increasing InAs supply. The combination of changing the V/III ratio and InAs supply allowed us to control the density and wavelength of QDs independently so that QDs with a density as high as 5.6×1010 and a 1.6 μm emission were obtained. The letter reports the MOVPE growth technique of QDs on InGaAsP/InP(100), which connects QDs with mature 1.55 μm device technology.
Two-dimensional colloid-based photonic crystals for distributed feedback polymer lasers
Authors: Mafouana Rodrigue , Rehspringer Jean-Luc , Hirlimann Charles , Estournes Claude , Dorkenoo Kokou D.
Published: November 2004

We report on a process to design highly ordered monolayers of two-dimensional photonic crystals, made of silica nanoparticules, that can be used for the development of organic optical devices. We have used a photopolymerization process to incorporate a dye gain medium into the nanoparticle layers in order to achieve a laser cavity. The high spatial coherence of the deposits allows for single-mode laser emission in the plane of the layer when the light excitation is perpendicular to the plane. Such periodic films should help in reducing the number of layers needed for future electrically pumped distributed feedback lasers.
Macroscopic characterization of cell electroporation in biological tissue based on electrical measurements
Authors: Cima Lionel F. , Mir Lluis M.
Published: November 2004

A method is described to experimentally determine the temporal evolution of state variables involved in the electroporation of biological tissue, i.e., the transmembrane voltage and the macroscopic current flowing in the electropores. Indeed, the electrical parameters of the extracellular, intracellular, and unaltered membrane contributions as well as the electropores electrical characteristics can be deduced from the measurement of the tissue bioimpedance and from the variations of both the macroscopic voltage applied to the tissue and the delivered current.
Theoretical study of the group-IV antisite acceptor defects in CdGeAs2
Authors: Blanco Miguel A. , Costales Aurora , Luaña Victor , Pandey Ravindra
Published: November 2004

Native and impurity antisite point defects in CdGeAs2 are studied here using an embedded quantum cluster model based on density functional theory. The calculated geometric relaxations and spin densities of the antisite defects considered here show a clear and distinct difference in the nature of native (i.e. [GeAs]) and impurity (i.e. [CAs] and [SiAs]) antisite defects in CdGeAs2. For the native antisite acceptor, the hole appears to be delocalized in contrast to impurity antisites where the hole is mainly localized at the acceptor site.
n
-type organic field-effect transistor based on interface-doped pentacene
Authors: Ahles Marcus , Schmechel Roland , von Seggern Heinz
Published: November 2004

The realization of an n-type pentacene field-effect transistor based on interface-doped pentacene is demonstrated, laying a headstone for an organic complementary-metal–oxide–semiconductor technology. The doping is performed by depositing traces of calcium onto the gate insulator before applying the organic semiconductor. Electron field-effect mobilities of 0.19cm2V−1s−1 are achieved. The field effect, i.e., the electron accumulation behavior, is studied by impedance spectroscopy and charge measurements on a metal–insulator–semiconductor (MIS) diode. A good correlation between the physical properties of the transistor and the MIS diode can be reported. A temporal dynamics and a hysteresislike accumulation behavior are observed, both explainable by the influence of deep electron traps.
Percolation model for electrical breakdown in insulating polymers
Authors: Wu Kai , Dissado L. A. , Okamoto Tatsuki
Published: November 2004

It is suggested that an electric field above a given value eliminates the barriers to the transport of trapped charge carriers so as to produce an extended state in the form of a percolation cluster, and that the consequent current multiplication results in electrical breakdown. This model provides an estimated value of intrinsic breakdown strength close to the actual value. By considering the interactions between trap barrier potentials, the effect of electrical aging can be explained in terms of an increase in trap density. Many phenomena, such as the effect of weak points and the change of breakdown strength with the content of co-monomers or additives, can also be explained using this model.
Low-resistance and high-reflectance Ni∕Ag∕Ru∕Ni∕Au ohmic contact on p-type GaN
Authors: Jang Ho Won , Lee Jong-Lam
Published: November 2004

We report a metallization scheme of low-resistance, high-reflectance, and thermally-stable ohmic contact on p-type GaN. The specific contact resistivity as low as 5.2×10−5Ωcm2 and the high reflectance of 91% were simultaneously obtained from Ni(50Å)∕Ag(1200Å)∕Ru(500Å)∕Ni(200Å)∕Au(500Å) contact annealed at 500°C in O2 ambient. The oxidation annealing promoted the outdiffusion of Ga atoms to dissolve in the Ag layer, leaving Ga vacancies below the contact. The Ru layer could act as a diffusion barrier for intermixing of the reflective Ag with upper layers of Ni and Au. Thus, suppression of the intermixing results in the high reflectance and good thermal stability of the contact.
Energy-band alignments at ZrO2∕Si, SiGe, and Ge interfaces
Authors: Wang S. J. , Huan A. C. H. , Foo Y. L. , Chai J. W. , Pan J. S. , Li Q. , Dong Y. F. , Feng Y. P. , Ong C. K.
Published: November 2004

The energy-band alignments for the ZrO2∕Si, ZrO2∕Si0.75Ge0.25, and ZrO2∕Ge interfaces have been studied using x-ray photoemission. The valence-band offsets of ZrO2∕Si, ZrO2∕Si0.75Ge0.25, and ZrO2∕Ge interfaces are determined to be 2.95, 3.13, and 3.36eV, respectively, while the conduction-band offsets are found to be the same value of 1.76±0.03eV for three interfaces. The upward shift of valence-band top accounts for the difference in the energy-band alignment at three interfaces.
Estuaries, lagoons and enclosed embayments: habitats that enhance population subdivision of inshore fishes
Authors: Watts Robyn J. , Johnson Michael S.
Published: November 2004

Several studies have suggested that estuaries, lagoons and enclosed embayments may offer special opportunities for local subdivision in marine species. We used data from published papers and unpublished theses to examine the effect of such water bodies on allozyme differentiation of seven species of inshore fishes in Western Australia. We included species that differ in their dispersal, and hence their intrinsic potential for gene flow. Over large distances, subdivision was generally greater among estuarine populations than among conspecific marine populations collected over similar distances. Over small distances, paired marine and estuarine samples were generally more divergent than pairs of marine samples separated by similar distances. For species with a low capability for dispersal, estuaries appear to add to the high levels of genetic subdivision that commonly result from other factors. Under special circumstances estuaries may also provide opportunities for genetic divergence in species with a high capability of dispersal that are rarely subdivided at a large geographical scale. These observations indicate that estuaries can increase the genetic subdivision of populations of inshore fishes, and that species that use both marine and estuarine habitats are likely to have greater genetic subdivision than those that are restricted to marine habitats.
Relative abundances and size compositions of champagne crabs, Hypothalassia acerba, on two coasts and in different water depths and seasons
Authors: Smith Kim D. , Hall Norman G. , Potter Ian C.
Published: November 2004

Hypothalassia acerba was sampled seasonally using traps at depths of 35, 90, 145, 200, 255, 310 and 365 m on the west and south coasts of Western Australia. Catch rates peaked at depths of 200 m on the west coast and 145 m on the south coast but at similar temperatures of 16.1–17.1°C. The west and south coast catches contained 69% and 84% males respectively. The carapace length of H. acerba declined significantly by 4 mm for each 100 m increase in depth. The maximum carapace length of males was greater than females on the west coast (135 v. 113 mm) and south coast (138 v. 120 mm). Furthermore, after adjustment to a depth of 200 m, the mean carapace lengths of males were greater than females on both the west coast (96.6 v. 94.6 mm) and south coast (101.5 v. 91.4 mm), with the difference on the south coast being significant (P < 0.001). Thus, in summary, (1) distribution was related to depth and temperature; (2) body size was inversely related to water depth; and (3) males grew larger and were caught in greater numbers than females. There was also evidence that the distribution changed slightly with season and of spatial partitioning by H. acerba and other large deep-water invertebrate predators.