bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative effects of weight adjustments in ℋ︁∞control
Authors: Anderson Brian D. O. , Lanzon Alexander , Dehghani Arvin , Bombois Xavier
Published: August 2008

In an ℋ︁∞design, when weights are adjusted, corresponding modifications occur in the synthesized ℋ︁∞controller and the resulting closed‐loop transfer function matrices of interest. In this paper, we seek to understand and provide quantitative results on how weight adjustments directly affect an ℋ︁∞controller and, more importantly, the corresponding closed‐loop transfer function matrices. Here, we explore issues such as whether one can find the new controller as a perturbation of the original controller. Copyright © 2008 John Wiley & Sons, Ltd.
Octreotide therapy in asparaginase‐associated pancreatitis in childhood acute lymphoblastic leukemia
Authors: Wu Shu‐Fen , Chen An‐Chyi , Peng Ching‐Tien , Wu Kang‐Hsi
Published: August 2008

Little is known about octreotide therapy in asparaginase‐associated pancreatitis (AAP) in children. Of the 59 children with acute lymphoblastic leukemia (ALL) receiving E. coli L‐asparaginase, 5 patients (8.5%) developed AAP. Octreotide was administered to four patients. Clinical and laboratory improvement were evident after octreotide therapy. There were no deaths and no severe adverse side effects were noted. No pseudocysts were detected; however, two of the four patients developed diabetes. One child without octreotide treatment developed chronic pancreatitis and pseudocyst. We conclude that octreotide therapy appears to be safe and potentially beneficial in the management of AAP in children. Pediatr Blood Cancer 2008;51:824–825. © 2008 Wiley‐Liss, Inc.
Dabigatran: oral prophylaxis for venous thromboembolism
Authors: Chaplin Steve , Frostick Simon
Published: August 2008

Dabigatran (Pradaxa) is a new orally active antithrombotic agent licensed for VTE prophylaxis following hip and knee replacement. In our New products review Steve Chaplin presents the clinical data relating to its efficacy and adverse effects and Professor Simon Frostick comments on its place in therapy. Copyright © 2008 Wiley Interface Ltd
Access to evidence (1): how to prioritise online resources
Authors: Hunter Jo , Glasziou Paul
Published: August 2008

GPs often turn to the Internet for help with clinical questions, but with an ever‐increasing volume of information available online it can be difficult to know where to begin. Here, using Haynes' 4S model, the authors discuss how to carry out Internet research to answer clinical queries. Copyright © 2008 Wiley Interface Ltd
Formation of nanovoids/microcracks in high dose hydrogen implanted AlN
Authors: Singh R. , Scholz R. , Christiansen S. H. , Gösele U.
Published: August 2008

Aluminium nitride (AlN) epitaxial layers grown on sapphire were implanted with 100 keV hydrogen, H2+ ions with doses in the range of 5 × 1016 cm–2 to 2.5 × 1017 cm−2 and subsequently annealed at temperatures up to 800 °C in order to observe the formation of surface blisters. The implantation‐induced damage in AlN was analyzed by cross‐sectional transmission electron microscopy, which revealed a band of defects extending from 330–550 nm from the surface of AlN. Higher magnification TEM images showed the formation of nanovoids that are distributed in the damage band. Upon annealing these nanovoids agglomerate leading to the formation of microcracks. Due to the overpressure of hydrogen trapped in the microcracks, surface blisters are eventually formed in the hydrogen implanted AlN. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved adhesion, growth and maturation of human bone‐derived cells on nanocrystalline diamond films
Authors: Kopecek Milan , Bacakova Lucie , Vacik Jiri , Fendrych Frantisek , Vorlicek Vladimir , Kratochvilova Irena , Lisa Vera , Van Hove Emilie , Mer Christine , Bergonzo Philippe , Nesladek Milos
Published: August 2008

Nanocrystalline diamond (NCD) films were deposited on microscopic glass slides using the MW PECVD method (20 Torr, 710 °C, 0.8–1% CH4). After the growth period, the films were oxidized and subsequently hydrogenated, and some of them were doped with boron (NCD‐B; 3,000–30,000 ppm B:C; leading to ρ ∼ 10–1 Ω cm for the highest doped films). The neutron depth profiling showed that in the near surface region (<800 nm) the boron (10B + 11B) content in the highest doped sample was about (1.9 ± 0.3) × 1021 B cm–3 (i.e., 1.1 ± 0.2 at% of B). The films were seeded with human osteoblast‐like MG 63 cells (∼17,000 cells/cm2). On day 3 after seeding, the cell number on NCD (56,280 ± 1,090 cells/cm2) was significantly higher than that on NCD‐B (by 27 ± 3%), glass slides (by 22 ± 3%) and polystyrene wells (by 36 ± 3%). On day 7, the cell numbers on both NCD and NCD‐B films (351,170 ± 16,530 cells/cm2 and 310,020 ± 10,410 cells/cm2, respectively) became significantly higher than the values on glass slides and polystyrene dishes (218,800 ± 12,340 cells/cm2 and 223,400 ± 9,290 cells/cm2, respectively). Immunofluorescence staining showed that the cells on both NCD films assembled fine streak‐ or dot‐like focal adhesion plaques containing alphav integrins or talin, and a mesh‐like beta‐actin cytoskeleton. The cells on NCD‐B were brightly stained for osteocalcin, an important marker of osteogenic differentiation. Thus, both tested nanocrystalline diamond films gave good support for the adhesion, growth and maturation of bone‐derived cells. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and structural studies of Diluted Magnetic Semiconductors by electrodeposition
Authors: Tortosa M. , Mollar M. , Marí B.
Published: August 2008

Because of the emerging interest in spintronics, the possibility to obtain diluted magnetic semiconductors (DMS) by means of electrodeposition has been tested. In this work, we report on the preparation and characterization of ternary Zn1–xCoxO and Zn1–xMnxO alloy crystalline films grown by electrodeposition onto conductive substrates and using DMSO as solvent. The final composition of the films is controlled through the Co/Zn and Mn/Zn ratio present in the starting solution. Electrodeposited ternary Zn1–xCoxO and Zn1–xMnxO films were characterized of by X‐ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and optical spectroscopy. EDS results confirm the existence of Co and Mn ions into the films. All films exhibit a hexagonal wurtzite structure mainly oriented in the (002) direction. The incorporation of Co and Mn atoms into the ZnO lattice is confirmed by the presence of Co‐ and Mn‐related absorption bands. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemical solution deposited PbS thin films on Si(100)
Authors: Osherov Anna , Golan Yuval
Published: August 2008

The effect of reagent concentrations and deposition temperature on the morphology of chemical solution deposited PbS thin films on Si(100) substrates was studied using X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of laser profile, fluence, and spot size on sensitivity in orthogonal‐injection matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Qiao Hui , Spicer Victor , Ens Werner
Published: August 2008

The influence of incident laser parameters on sensitivity in matrix‐assisted laser desorption/ionization (MALDI) has been investigated using orthogonal‐injection time‐of‐flight (TOF) instruments. A qualitative comparison was first made between the beam profiles obtained with a N2 laser and a Nd:YAG laser using 2‐m long optical fibers. The N2 laser gives better sensitivity, consistent with a more uniform fluence distribution and therefore better coverage of the N2 laser profile. Most of the difference disappears when a 30‐m long fiber is used or when the fibers are twisted during irradiation to smooth out the fluence distribution. In more systematic measurements, the total integrated ion yield from a single spot (a measure of sensitivity) was found to increase rapidly with fluence to a maximum, and then saturate or decrease slightly. Thus, the optimum sensitivity is achieved at high fluence. For a fluence near threshold, the integrated yield has a steep (cubic) dependence on the spot size, but the yield saturates at higher fluence for smaller spots. The area dependence is much weaker (close to linear) for fluence values above saturation, with the result that the highest integrated yields per unit area are obtained with the smallest spot sizes. The results have particular relevance for imaging MALDI, where sensitivity and spatial resolution are important figures of merit. Copyright © 2008 John Wiley & Sons, Ltd.
Design of finite‐time stabilizing controllers for nonlinear dynamical systems
Authors: Nersesov Sergey G. , Nataraj C. , Avis Jevon M.
Published: August 2008

Finite‐time stability involves dynamical systems whose trajectories converge to an equilibrium state in finite time. Since finite‐time convergence implies nonuniqueness of system solutions in reverse time, such systems possess non‐Lipschitzian dynamics. Sufficient conditions for finite‐time stability have been developed in the literature using Hölder continuous Lyapunov functions. In this paper, we extend the finite‐time stability theory to revisit time‐invariant dynamical systems and to address time‐varying dynamical systems. Specifically, we develop a Lyapunov‐based stability and control design framework for finite‐time stability as well as finite‐time tracking for time‐varying nonlinear dynamical systems. Furthermore, we use the vector Lyapunov function approach to study finite‐time stabilization of compact sets for large‐scale dynamical systems. Copyright © 2008 John Wiley & Sons, Ltd.
Evaluation of volume vascularization index and flow index: a phantom study
Authors: Schulten‐Wijman M. J. N. C. , Struijk P. C. , Brezinka C. , De Jong N. , Steegers E. A. P.
Published: August 2008

Objectives

Three‐dimensional (3D) power Doppler ultrasonography provides indices to quantify moving blood within a volume of interest (e.g. ovary, endometrium, tumor or placenta). The purpose of this study was to determine the influence of ultrasound instrument settings on vascularization index (VI) and flow index (FI) at different flow velocities, using a specially built flow phantom with a small tube diameter.

Methods

Blood‐mimicking fluid was pumped at 10–100 mL/h through a plastic tube with a diameter of 0.65 mm within a virtual spherical volume (content 137.12 cm3) of a Voluson 730 Expert 3D power Doppler ultrasound instrument. VI and FI were determined at different pulse repetition frequency (PRF) settings, with minimal and maximal wall motion filter (WMF) settings. The measured VI was compared with the actual VI.

Results

The ability to measure VI and FI at different flow velocities was highly dependent on the PRF and WMF settings. In our experimental set‐up, using a PRF of 0.3 kHz, flow velocities of about 2 cm/s and higher could be registered. Measured VI was overestimated up to 44 times relative to actual VI.

Conclusions

Our main finding in a laboratory set‐up was a considerable overestimation of moving blood volume using 3D power Doppler ultrasound in a single small tube. The degree of overestimation depends on the spatial resolution and on the settings of the ultrasound instrument. When small vessels are involved in a clinical setting, interpretation of VI should take this overestimation of moving blood volume into account. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
A Multivariate Multilevel Approach to the Modeling of Accuracy and Speed of Test Takers
Authors: Klein Entink R. H. , Fox J.-P. , van der Linden W. J.
Published: August 2008

Response times on test items are easily collected in modern computerized testing. When collecting both (binary) responses and (continuous) response times on test items, it is possible to measure the accuracy and speed of test takers. To study the relationships between these two constructs, the model is extended with a multivariate multilevel regression structure which allows the incorporation of covariates to explain the variance in speed and accuracy between individuals and groups of test takers. A Bayesian approach with Markov chain Monte Carlo (MCMC) computation enables straightforward estimation of all model parameters. Model-specific implementations of a Bayes factor (BF) and deviance information criterium (DIC) for model selection are proposed which are easily calculated as byproducts of the MCMC computation. Both results from simulation studies and real-data examples are given to illustrate several novel analyses possible with this modeling framework.
Pattern recognition using transabdominal ultrasound to diagnose ovarian mature cystic teratoma
Authors: Tongsong Theera , Luewan Suchaya , Phadungkiatwattana Podjanee , Neeyalavira Vithida , Wanapirak Chanane , Khunamornpong Surapan , Sukpan Kornkanok
Published: August 2008

Objective

To determine the validity of sonographic pattern recognition in the diagnosis of mature cystic teratoma.

Methods

Consecutive patients scheduled for elective surgery for adnexal masses were included in the study. All patients underwent transabdominal ultrasound with color extended‐flow mapping within 24 hours prior to surgery. Examinations were performed by the same sonographer to identify benign cystic teratoma. The final diagnoses were based on histopathologic findings.

Results

A total of 329 consecutive patients were recruited; 23 were excluded because the masses were not adnexal masses. Of the remaining 306 patients, 36 masses were found to be mature cystic teratomas and 270 were nonteratomas. Sonographic pattern recognition showed a sensitivity of 94.4% and a specificity of 98.2%.

Conclusion

Sonographic pattern recognition using transabdominal ultrasound with color extended‐flow mapping can accurately diagnose mature cystic teratoma.
Histopathology‐based combined surgical approach to rectovaginal endometriosis
Authors: Mangler Mandy , Loddenkemper Christoph , Lanowska Malgorzata , Bartley Julia , Schneider Achim , Köhler Christhardt
Published: August 2008

Objective

To describe a new surgical approach to rectovaginal endometriosis. Rectovaginal endometriosis can be infiltrative or superficial involving the bowel. Only infiltrative disease should be treated by intestinal resection. However, infiltration of endometriosis cannot be confirmed by preoperative imaging techniques.

Methods

A total of 48 women with infiltrative rectovaginal endometriosis were included in this prospective study. Surgery was performed using a newly developed technique. All bowel resections were indicated according to operative findings and not on the basis of preoperative imaging technique results.

Results

The decision for rectosigmoidal resection was based on the results of the intraoperative dissection of the rectovaginal septum. Histologically, infiltration of the ventral bowel wall was confirmed in all cases.

Conclusion

This new surgical technique for the treatment of rectovaginal endometriosis allows precise diagnosis and treatment with low morbidity. A resection of the mesorectum is not necessary because the endometriotic nodules are always located on the antimesenteric surface of the bowel.
Tephrostratigraphy of the late glacial and Holocene sediments of Puyehue Lake (Southern Volcanic Zone, Chile, 40°S)
Authors: Bertrand Sébastien , Castiaux Julie , Juvigné Etienne
Published: August 2008

We document the mineralogical and geochemical composition of tephra layers identified in the late Quaternary sediments of Puyehue Lake (Southern Volcanic Zone of the Andes, Chile, 40°S) to identify the source volcanoes and to present the first tephrostratigraphic model for the region. For the last millennium, we propose a multi-criteria correlation model based on five tephra layers identified at seven coring sites. The two upper tephras are thin fine-grained green layers composed of more than 80% rhyodacitic glass shards, and associated to the AD 1960 and AD 1921–22 eruptions of the Puyehue-Cordon de Caulle volcanic complex. The third tephra is a sandy layer dominated by orthopyroxene, and related to the AD 1907 eruption of Rininahue maar. An olivine-rich tephra was deposited at the end of the 16th century, and a tephra characterized by a two-pyroxene association marks the second half of the first millennium AD. In addition, we detail the tephra succession of an 11.22-m-long sediment core covering the last 18,000 yr. The results demonstrate that the central province of the Southern Volcanic Zone has been active throughout the last deglaciation and the Holocene, with no increase in volcanic activity during glacial unloading.
Covariation, Causality, and Language
Authors: Rudolph Udo
Published: August 2008

Implicit verb causality refers to the phenomenon that even minimal descriptions of interpersonal events (e.g., A dominates B, A amuses B) elicit causal attributions. Two experiments investigated whether children of different age groups are able to (a) perceive the causality implicit in interpersonal verbs and (b) to detect patterns of cause-effect covariation (consensus and distinctiveness) presumably mediating the verb causality effect. Experiment 1 found that 5-year-old children detect the causal structure inherent in verbs describing interpersonal events and are able to indicate corresponding covariation patterns. Experiment 2 replicated these findings for 3-year-old children using a more sensitive method for assessing causal and covariation beliefs. Statistical mediation analyses supported the hypothesis that the verb causality effect is mediated by implicit beliefs about cause-effect covariation. Taken together, the results provide support for a covariation-based explanation of the verb causality effect.
Dynamic implications of discontinuous recrystallization in cold basal ice: Taylor Glacier, Antarctica
Authors: Samyn D. , Svensson A. , Fitzsimons S. J.
Published: August 2008

Crystallographic investigations have been conducted of cold (−17°C) debris‐bearing ice from the base of an Antarctic outlet glacier (Taylor Glacier). The 4‐m‐thick sequence studied has been retrieved from a 20‐m‐long tunnel dug from the glacier snout and has been analyzed with an automatic ice fabric analyzer (AIFA). The top and bottom of the sequence consists of clean meteoric ice (englacial facies), whereas alternating debris‐rich and clean bubbly ice layers are found in the middle part (stratified facies). Ice from the englacial facies displays a polygonal texture and a strong c‐axis clustering toward the vertical, denoting recrystallization through “subgrain rotation” (SGR). In contrast, clean ice from the stratified facies shows SGR fabrics which are delimited at the contact with debris‐rich layers by large, interlocking grains organized in ribbons. These two distinct textures within the stratified facies are associated with looser c‐axis patterns at the scale of single thin sections, which is interpreted as resulting from “migration recrystallization” (MR). The change from SGR to MR trends marks a clear increase in grain boundary and nucleation kinetics (hence the term “discontinuous recrystallization”) and may be associated with strain localization at rheological interfaces during basal ice genesis. Analogies with bottom ice from deep polar ice sheets, where temperature is commonly higher than at the studied site, are highlighted. Two recrystallization scenarios are proposed, accounting for the development of both types of fabrics. It is shown that by controlling the repartition of stress and strain energy within basal ice, the rheology of debris‐bearing ice layers plays a decisive role in recrystallization dynamics at structural interfaces. We also demonstrate how the same recrystallization regimes may occur in cold glaciers and temperate ice sheets, provided that strain accumulation has been high enough in the former. This challenges the common belief that migration fabrics observed in bottom ice from deep ice sheets are exclusive to warm, stagnant, annealed ice.
Low‐latitude ionospheric electric and magnetic field disturbances in response to solar wind pressure enhancements
Authors: Huang Chao‐Song , Yumoto Kiyohumi , Abe Shuji , Sofko George
Published: August 2008

We study the characteristics of the low‐latitude ionospheric electric field and geomagnetic field in response to a sudden enhancement of the solar wind pressure. When the magnetosphere is compressed by an interplanetary shock, a significant enhancement in the dayside equatorial ionospheric ion vertical velocity occurs over 30–40 min and is measured by the Jicamarca incoherent scatter radar. A similar enhancement occurs in the high‐latitude ionospheric convection and is detected by the SuperDRAN HF radars. The simultaneous enhancements of the ionospheric ion velocity at high and low latitudes provide strong evidence of the occurrence of penetration electric fields produced by solar wind pressure enhancements. The geomagnetic field first increases rapidly over 2–3 min and then falls over 30–40 min to an asymptotic value. The enhanced magnetic field occurs from the subauroral region to the equator at all local times. The time scale of 30–40 min is much longer than the conventional preliminary and main impulses of geomagnetic response to interplanetary shocks. There are two possible mechanisms that may be responsible for the generation of the enhanced ionospheric electric and magnetic fields. One mechanism is that the solar wind shock causes an over‐compression of the magnetosphere, and the other is that the field‐aligned and ionospheric currents driven by the solar wind shock cause the enhancements of the ionospheric electric and magnetic fields. However, neither of the mechanisms appears to be able to provide a complete explanation of all observed features.
Source processes of the 1978 and 2005 Miyagi‐oki, Japan, earthquakes: Repeated rupture of asperities over successive large earthquakes
Authors: Wu Changjiang , Koketsu Kazuki , Miyake Hiroe
Published: August 2008

Highly similar seismograms commonly observed along transform or convergent plate boundaries indicate that repeated small to moderate earthquakes occur within a single area. The results of source‐process inversions for seismic events within the northeastern Japan subduction zone suggest that large earthquakes and their component asperities also exhibit this repeating nature under certain conditions. However, sets of similar seismograms that might provide direct evidence of the repeated rupture of large‐earthquake asperities have not been observed. This paper analyzes two offshore earthquakes near Miyagi Prefecture, Japan, the most recent occurring in 2005 with a JMA magnitude (M) of 7.2 in the source region of the 1978 earthquake (M7.4). We demonstrate the similarity in waveforms from the seismograms recorded during the 1978 and 2005 earthquakes. The early portions of the 2005 seismograms resemble the 1978 seismograms, suggesting that the asperities located close to the 1978 hypocenter ruptured again during the 2005 event. The seismogram similarities provide the first direct evidence for the repeated rupture of asperities during successive large earthquakes. The results of our waveform inversions further indicate that the two asperities of the 2005 event largely coincide with the southern two asperities of the 1978 event. These repeating asperities are recorded in the early portions of the 2005 seismograms with 60% of the amplitude recorded in the 1978 seismograms. The characteristic behavior of the asperities supports the slip‐predictable recurrence model of earthquake rupture rather than the time‐predictable recurrence model.
Application of spatial correlation functions in permeability estimation of deformation bands in porous rocks
Authors: Torabi Anita , Fossen Haakon , Alaei Behzad
Published: August 2008

Millimeter‐thick strain localization structures in porous sandstones, known as deformation bands, are reported to perturb the permeability structure of petroleum reservoirs and aquifers. However, the internal permeability structure of deformation bands is difficult to assess by means of classical methods. We have used spatial correlation functions to estimate the porosity and specific surface area in deformed sandstones from high‐resolution backscatter images. This work demonstrates the use of a modified version of the Kozeny‐Carman relation to calculate permeability based on the information obtained from image processing. We have identified anisotropy with regard to petrophysical properties in deformed sandstones, and demonstrated variations in microstructure and properties across and along the deformation bands. Our results show that properties outside the deformation bands (in the host rock) differ significantly from those inside the band (up to three orders of magnitude). Moreover permeability varies by up to two orders of magnitude along a single band. Furthermore, our porosity and permeability estimates are lower than those obtained from plug measurements. While plug measurements measure the effective permeability across a 2.54 cm (inch) long sample, the method demonstrated here provides a means to estimate porosity and permeability on the microscale, and to map out the variations in these properties both along and across deformation bands and similar structures.
A double branching model for earthquake occurrence
Authors: Marzocchi Warner , Lombardi Anna Maria
Published: August 2008

The purpose of this work is to put forward a double branching model to describe the spatiotemporal earthquake occurrence. The model, applied to two worldwide catalogs in different time‐magnitude windows, shows a good fit to the data, and its earthquake forecasting performances are superior to what was obtained by the ETAS (first‐step branching model) and by the Poisson model. The results obtained also provide interesting insights about the physics of the earthquake generation process and the time evolution of seismicity. In particular, the so‐called background seismicity, i.e., the catalog after removing short‐time clustered events, is described by a further (second‐step model) branching characterized by a longer time‐space clustering that may be due to long‐term seismic interaction. Notably, this branching highlights a long‐term temporal evolution of the seismicity that is never taken into account in seismic hazard assessment or in the definition of reference seismicity models for a large earthquake occurrence. Another interesting issue is related to the parameters of the short‐term clustering that appear constant in a different magnitude window, supporting some sort of universality for the generating process.
Decadal variability of East Australian Current transport inferred from repeated high‐density XBT transects, a CTD survey and satellite altimetry
Authors: Ridgway K. R. , Coleman R. C. , Bailey R. J. , Sutton P.
Published: August 2008

A time series of the net geostrophic transport through the Tasman Sea (representing the flow of the East Australian Current (EAC) Extension) is determined from a full‐depth CTD section, 15 years of high‐density XBT transects, and satellite altimetry data. A section between Sydney and Wellington (PX34) has been occupied four times per year since 1991 with high resolution XBT sampling. Two methods to infer baroclinic transport from proxy data along the section are presented. The first uses shallow XBT transects to derive geostrophic transport relative to a deep (2000 m) reference level. In the second approach (SynTS) the subsurface temperature and salinity structure are inferred from satellite surface height and temperature fields using a model developed from historical in situ observations. The baroclinic transport is then computed in the usual manner. The methods are validated using both a full‐depth CTD occupation of the PX34 section and further transects crossing the EAC in the northern Tasman Sea. There is close agreement between the 49 XBT and SynTS PX34 transport estimates obtained between 1992 and 2006. The time series of transport through the Sydney–Wellington section shows a range of temporal signals from eddyscale, seasonal, interannnual to decadal. In particular, we note that the net EAC flow ranges from 5 Sv in 1995 to a maximum of 16 Sv in 2000/2001. This decadal variation confirms the EAC response to a spin‐up of the South Pacific circulation forced by changes in the basin‐wide winds and matches the changes in oceanic properties observed in the Tasman Sea.
Shape and excitation optimization for conformal array antennas
Authors: Halleröd T. , Rylander T.
Published: August 2008

We present a procedure for the optimization of array antennas that conform to circular cylinders in two space dimensions. For a phase‐mode excitation of the antenna, a large number of antenna element designs are compared in terms of two objectives: (1) the active reflection coefficient and (2) the far‐field distortion with respect to the excited phase‐mode. This analysis yields Pareto fronts with respect to the two objectives and appropriate designs are selected based on the information collected for the useful phase modes given a specific frequency band. This antenna element design is used for the pattern synthesis, where we optimize a linear combination of (1) requirements on the directive gain and (2) similar requirements on the power reflected from the array antenna aperture.
A combined sea clutter and noise model appropriate to the operation of high‐frequency pulsed Doppler radar in regions constrained by external noise
Authors: Gill Eric W. , Walsh John
Published: August 2008

In recent years, bistatic pulsed high‐frequency ground wave radar models of the ocean clutter have been developed. Several new features, distinct from earlier monostatic developments, appear as products of those analyses. One question that needs to be addressed is, “What characteristics of the theoretical clutter models are likely to be visible in experimental data collected from the ocean surface?” A major consideration in answering this question is the development of an appropriate noise model. Such a model along with an analogous clutter model is derived. This allows a simulation of time series data for both clutter and noise which may be treated using standard Fourier transform techniques to provide a periodogram for the typical combined noise/clutter spectrum of scattering from the ocean surface. The analysis proceeds on the assumption of an externally noise‐limited system, with the noise being characterized as a white Gaussian zero‐mean process. The aliasing due to noise undersampling is seen to be an integral part of the model. Statistical stationarity is assumed throughout. Both infinite and finite pulse trains are considered.
Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 1. Revised conceptualization of groundwater flow
Authors: Renken Robert A. , Cunningham Kevin J. , Shapiro Allen M. , Harvey Ronald W. , Zygnerski Michael R. , Metge David W. , Wacker Michael A.
Published: August 2008

The Biscayne aquifer is a highly transmissive karst limestone that serves as the sole source of drinking water to over two million residents in south Florida. The aquifer is characterized by eogenetic karst, where the most transmissive void space can be an interconnected, touching‐vug, biogenically influenced porosity of biogenic origin. Public supply wells in the aquifer are in close proximity to lakes established by surface mining. The mining of the limestone has occurred to the same depths as the production wells, which has raised concerns about pathogen and chemical transport from these surface water bodies. Hydraulic and forced gradient tracer tests were conducted to augment geologic and geophysical studies and to develop a hydrogeologic conceptual model of groundwater flow and chemical transport in the Biscayne aquifer. Geologic and geophysical data indicate multiple, areally extensive subhorizontal preferential flow zones of vuggy limestone separated by rock with a matrix pore system. The hydraulic response from an aquifer test suggests that the Biscayne aquifer behaves as a dual‐porosity medium; however, the results of the tracer test showed rapid transport similar to other types of karst. The tracer test and concurrent temperature logging revealed that only one of the touching‐vug flow zones dominates transport near the production wells. On the basis of the rising limb of the breakthrough curve, the dispersivity is estimated to be less than 3% of the tracer travel distance, which suggests that the fastest flow paths in the formation are likely to yield limited dilution of chemical constituents.
Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 2. Chemical retention from diffusion and slow advection
Authors: Shapiro Allen M. , Renken Robert A. , Harvey Ronald W. , Zygnerski Michael R. , Metge David W.
Published: August 2008

A tracer experiment, using a nonreactive tracer, was conducted as part of an investigation of the potential for chemical and pathogen migration to public supply wells that draw groundwater from the highly transmissive karst limestone of the Biscayne aquifer in southeastern Florida. The tracer was injected into the formation over approximately 1 h, and its recovery was monitored at a pumping well approximately 100 m from the injection well. The first detection of the tracer occurred after approximately 5 h, and the peak concentration occurred at about 8 h after the injection. The tracer was still detected in the production well more than 6 days after injection, and only 42% of the tracer mass was recovered. It is hypothesized that a combination of chemical diffusion and slow advection resulted in significant retention of the tracer in the formation, despite the high transmissivity of the karst limestone. The tail of the breakthrough curve exhibited a straight‐line behavior with a slope of −2 on a log‐log plot of concentration versus time. The −2 slope is hypothesized to be a function of slow advection, where the velocities of flow paths are hypothesized to range over several orders of magnitude. The flow paths having the slowest velocities result in a response similar to chemical diffusion. Chemical diffusion, due to chemical gradients, is still ongoing during the declining limb of the breakthrough curve, but this process is dwarfed by the magnitude of the mass flux by slow advection.
Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 3. Use of microspheres to estimate the transport potential of Cryptosporidium parvum oocysts
Authors: Harvey Ronald W. , Metge David W. , Shapiro Allen M. , Renken Robert A. , Osborn Christina L. , Ryan Joseph N. , Cunningham Kevin J. , Landkamer Lee
Published: August 2008

The vulnerability of a municipal well in the Northwest well field in southeastern Florida to potential contamination by Cryptosporidium parvum oocysts was assessed in a large‐scale, forced‐gradient (convergent) injection and recovery test. The field study involved a simultaneous pulse introduction of a nonreactive tracer (SF6, an inert gas) and oocyst‐sized (1.6, 2.9, and 4.9 μm diameter) carboxylated polystyrene microspheres into karst limestone of the Biscayne aquifer characterized by a complex triple (matrix, touching‐vug, and conduit) porosity. Fractional recoveries 97 m down gradient were inversely related to diameter and ranged from 2.9% for the 4.9 μm microspheres to 5.8% for 1.6 μm microspheres. Their centers of mass arrived at the pumping well approximately threefold earlier than that of the nonreactive tracer SF6 (gas), underscoring the need for use of colloid tracers and field‐scale tracer tests for these kinds of evaluations. In a modified triaxial cell using near in situ chemical conditions, 2.9 and 4.9 μm microspheres underestimated by fourfold to sixfold the attachment potential of the less electronegative 2.9–4.1 μm oocysts in the matrix porosity of limestone core samples. The field and laboratory results collectively suggested that it may take 200–300 m of transport to ensure even a 1‐log unit removal of oocysts, even though the limestone surfaces exhibited a substantive capability for their sorptive removal. The study further demonstrated the utility of microspheres as oocyst surrogates in field‐scale assessments of well vulnerability in limestone, provided that differences in attachment behaviors between oocysts and microspheres are taken into account.
Extracting phreatic evaporation from remotely sensed maps of evapotranspiration
Authors: Brunner P. , Li H. T. , Kinzelbach W. , Li W. P. , Dong X. G.
Published: August 2008

One of the most important parameters related to soil salinization is the direct evaporation from the groundwater (phreatic evaporation). If the groundwater table is sufficiently close to the surface, groundwater will evaporate through capillary rise. In recent years, several methods have been suggested to map evapotranspiration (ET) on the basis of remote sensing images. These maps represent the sum of both transpiration of vegetation and evaporation from the bare soil. However, identifying the amount of phreatic evaporation is important as it is the dominant flux in the salt balance of the soil. The interpretation of stable isotope profiles at nonirrigated areas in the unsaturated zone allows one to quantify phreatic evaporation independently of the transpiration of the vegetation. Such measurements were carried out at different locations with a different depth to groundwater. The benefit is twofold. (1) A relation between phreatic evaporation rates and the depth to groundwater can be established. (2) By subtracting the measured values of phreatic evaporation from remotely sensed values of ET, vadose ET consisting of transpiration and excess irrigation water in the unsaturated zone can be estimated at the sampling locations. A correlation between the normalized differential vegetation index and the calculated vadose ET rates could be established (R2 = 0.89). With this correlation the contribution of phreatic evaporation can be estimated. This approach has been tested for the Yanqi basin located in western China. Finally, the distribution of phreatic evaporation was compared to a soil salinity map of the project area on a qualitative basis.
Temporal evolution of low‐flow regimes in Canadian rivers
Authors: Khaliq M. N. , Ouarda T. B. M. J. , Gachon P. , Sushama L.
Published: August 2008

This study investigates temporal evolution of 1‐, 7‐, 15‐, and 30‐day annual and seasonal low‐flow regimes of pristine river basins, included in the Canadian reference hydrometric basin network (RHBN), for three time frames: 1974–2003, 1964–2003, and 1954–2003. For the analysis, the RHBN stations are classified into three categories, which correspond to stations where annual low flows occur in winter only, summer only, and both summer and winter seasons, respectively. Unlike in previous studies for the RHBN, such classification is essential to better understand and interpret the identified trends in low‐flow regimes in the RHBN. Nonparametric trend detection and bootstrap resampling approaches are used for the assessment of at‐site temporal trends under the assumption of no persistence or short‐term persistence (STP). The results of the study demonstrate that previously suggested prewhitening and trend‐free prewhitening approaches, for incorporating the effect of STP on trend significance, are not adequate for reliably identifying trends in low‐flow regimes compared to a simple bootstrap‐based approach. The analyses of 10 relatively longer records reveal that trends in low‐flow regimes exhibit fluctuating behavior, and hence, their temporal and spatial interpretations appear to be sensitive to the time frame chosen for the analysis. Furthermore, under the assumption of long‐term persistence (LTP), which is a possible explanation for the fluctuating behavior of trends, many of the significant trends in low‐flow regimes, noted under the assumption of STP, become nonsignificant and their field significance also disappears. Therefore correct identification of STP or LTP in time series of low‐flow regimes is very important as it has serious implications for the detection and interpretation of trends.
Multiobjective training of artificial neural networks for rainfall‐runoff modeling
Authors: de Vos N. J. , Rientjes T. H. M.
Published: August 2008

This paper presents results on the application of various optimization algorithms for the training of artificial neural network rainfall‐runoff models. Multilayered feed‐forward networks for forecasting discharge from two mesoscale catchments in different climatic regions have been developed for this purpose. The performances of the multiobjective algorithms Multi Objective Shuffled Complex Evolution Metropolis–University of Arizona (MOSCEM‐UA) and Nondominated Sorting Genetic Algorithm II (NSGA‐II) have been compared to the single‐objective Levenberg‐Marquardt and Genetic Algorithm for training of these models. Performance has been evaluated by means of a number of commonly applied objective functions and also by investigating the internal weights of the networks. Additionally, the effectiveness of a new objective function called mean squared derivative error, which penalizes models for timing errors and noisy signals, has been explored. The results show that the multiobjective algorithms give competitive results compared to the single‐objective ones. Performance measures and posterior weight distributions of the various algorithms suggest that multiobjective algorithms are more consistent in finding good optima than are single‐objective algorithms. However, results also show that it is difficult to conclude if any of the algorithms is superior in terms of accuracy, consistency, and reliability. Besides the training algorithm, network performance is also shown to be sensitive to the choice of objective function(s), and including more than one objective function proves to be helpful in constraining the neural network training.
Contrail cirrus supporting areas in model and observations
Authors: Burkhardt Ulrike , Kärcher Bernd , Ponater Michael , Gierens Klaus , Gettelman Andrew
Published: August 2008

Contrails form and persist dependent on the surrounding moisture, temperature and pressure fields and on fuel and aircraft specific variables. After formation, contrail persistence requires only supersaturation relative to ice. The fractional area in which contrails can form is called potential contrail coverage. We introduce a potential contrail cirrus coverage equivalent to the cloud free supersaturated area. This field, simulated by the ECHAM4 climate model, agrees fairly well with estimates of supersaturation frequency as inferred from aircraft and satellite measurements. In areas where the two potential coverages are different, especially at lower flight levels, potential contrail coverage is not a valid estimate of maximum attainable contrail cirrus coverage. We parameterize both potential coverages consistently with the ECHAM4 cloud cover parameterization. A comparison of the potential contrail coverage with an earlier estimate reveals substantial differences especially at upper height levels in the tropics.
Global gravity wave activity in the tropopause region from CHAMP radio occultation data
Authors: Schmidt T. , de la Torre A. , Wickert J.
Published: August 2008

We discuss the global gravity wave (GW) activity expressed by the specific potential energy in the altitude range from 5 km below to 10 km above the tropopause, derived from GPS radio occultation data from CHAMP (2001–2008). The GW analysis is based on vertical detrending of the individual measured temperature profiles by applying a Gaussian filter in two different ways: (i) filtering of the complete temperature profiles and (ii) separate filtering of the profiles for the tropospheric and lower stratospheric parts. The separate filtering method significantly reduces the usually observed wave activity enhancement in the tropopause region which highly depends on the performance of the complete filtering method to reproduce the change in the temperature gradient at the tropopause. We only consider vertical wavelengths less than 10 km. The global mean potential energy in the tropopause region deduced with these different background temperatures will be analyzed, differences will be emphasized and possible error sources of the new method will be considered.
Assessing functional novelty of PSI structures via structure-function analysis of large and diverse superfamilies
Authors: Dessailly Benoit , Redfern Oliver , Orengo Christine
Published: August 2008

The structural genomics initiatives have had as one of their aims to improve our understanding of protein function by providing representative structures for many structurally uncharacterised protein families. As suggested by the recent assessment of the Protein Structure Initiative (Structural Genomics Initiative, funded by the NIH), doubts have arisen as to whether Structural Genomics as initially planned were really beneficial to our understanding of biological issues, and in particular of protein function.A few protein domain superfamilies have been shown to account for unexpectedly large numbers of proteins encoded in fully sequenced genomes. These large superfamilies are generally very diverse, spanning a wide range of functions, both in terms of molecular activities and biological processes. Some of these superfamilies, such as the Rossmann-fold P-loop nucleotide hydrolases or the TIM-barrel glycosidases, have been the subject of extensive structural studies which in turn have shed light on how evolution of the sequence and structure properties produce functional diversity amongst homologues. Recently, the Structure-Function Linkage Database (SFLD) has been setup with the aim of helping the study of structure-function correlations in such superfamilies. Since the evolutionary success of these large superfamilies suggests biological importance, several Structural Genomics Centers have focused on providing full structural coverage for representatives of all sequence families in these superfamilies.In this work we evaluate structure/function diversity in a set of these large superfamilies and attempt to assess the quality and quantity of biological information gained from Structural Genomics.
Towards realising Darwin’s dream: setting the trees free
Authors: Page Roderic
Published: August 2008

The fact that all living organisms are related by common descent is one of the central principles of modern biology. Since the early 1990's the amount of data available to evolutionary biologists has exploded, and Elsevier’s journal Molecular Phylogenetics and Evolution, has become the largest single publisher of evolutionary trees (phylogenies). These trees and their supporting data potentially form a tremendous resource for biologists, with applications in genomics, evolutionary biology, biodiversity, and public health. However, most published trees are not available in any public database, but instead languish as images, "locked up" in the pages of journals. A long term solution to this problem is to invert the relationship between journal and database, such that the database is the primary repository, and the journal article becomes effectively a "report" on that data, albeit a report that is citable, and thus has the same status as a scientific article. This vision is some way off being achieved. However, publishers could greatly enhance the scientific value of their digital content by expanding article metadata to include taxonomic names, shared digital identifiers, geographical coordinates, and data structures such as evolutionary trees. This metadata doesn’t require making the full text available, but could substantially improve the findability of that text.