bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperatures in two boreholes at Flüela Pass, Eastern Swiss Alps: the effect of snow redistribution on permafrost distribution patterns in high mountain areas
Authors: Luetschg Martina , Stoeckli Veronika , Lehning Michael , Haeberli Wilfried , Ammann Walter 
Published: September 2004

AbstractSnow cover distribution strongly affects soil temperatures and, thus, plays a decisive role in determining permafrost distribution patterns. Redistribution of snow by avalanches and snow drift significantly affects the snow‐melt pattern and soil temperatures in steep avalanche slopes of high mountain areas. At Flüela Pass, 2380 m a.s.l., eastern Swiss Alps, the presence and origin of permafrost that occurs at the base of an avalanche‐affected slope below the regional lower limit of discontinuous permafrost was studied by field investigations and numerical simulations. Local permafrost distribution has been determined in former studies by applying geophysical methods and this was confirmed with two boreholes drilled at the slope base and in the avalanche starting zone. Temperature measurements confirm the presence of a 10 m thick permafrost body with temperatures close to the freezing point at the slope base. Numerical simulations of different snow‐cover scenarios for 2002/03 demonstrate the particular effect on soil temperatures of high snow drift accompanying intense snow falls in early winter, controlling the duration of constant zero temperatures at the base of the snow pack at the beginning of the snow period. Copyright © 2004 John Wiley & Sons, Ltd.
Non‐Additivity of Attractive Potentials in Modeling of N2 and Ar Adsorption Isotherms on Graphitized Carbon Black and Porous Carbon by Means of Density Functional Theory
Authors: Ustinov Eugene A. , Do Duong D. 
Published: September 2004

AbstractWe present a new approach accounting for the non‐additivity of attractive parts of solid–fluid and fluid–fluid potentials to improve the quality of the description of nitrogen and argon adsorption isotherms on graphitized carbon black in the framework of non‐local density functional theory. We show that the strong solid–fluid interaction in the first monolayer decreases the fluid–fluid interaction, which prevents the two‐dimensional phase transition to occur. This results in smoother isotherm, which agrees much better with experimental data. In the region of multi‐layer coverage the conventional non‐local density functional theory and grand canonical Monte Carlo simulations are known to over‐predict the amount adsorbed against experimental isotherms. Accounting for the non‐additivity factor decreases the solid–fluid interaction with the increase of intermolecular interactions in the dense adsorbed fluid, preventing the over‐prediction of loading in the region of multi‐layer adsorption. Such an improvement of the non‐local density functional theory allows us to describe experimental nitrogen and argon isotherms on carbon black quite accurately with mean error of 2.5 to 5.8% instead of 17 to 26% in the conventional technique. With this approach, the local isotherms of model pores can be derived, and consequently a more reliable pore size distribution can be obtained. We illustrate this by applying our theory against nitrogen and argon isotherms on a number of activated carbons. The fitting between our model and the data is much better than the conventional NLDFT, suggesting the more reliable PSD obtained with our approach.
New Insights and Characterization Methods Through
Authors: Reichenauer Gudrun 
Published: September 2004

AbstractVia a sol‐gel process highly porous solids can be synthesized that consist of two homogeneous, isotropically distributed phases, i.e. a pore and a gel backbone phase. This route allows for an independent tuning of the specific surface area and the porosity over a wide range and thus provides model materials for a systematic investigation of complex effects.
Transition of an androgen‐dependent human prostate cancer cell line into an androgen‐independent subline is associated with increased angiogenesis
Authors: Gustavsson Heléne , Welén Karin , Damber Jan‐Erik 
Published: September 2004

AbstractBackgroundAndrogen‐independent prostate cancer is today an incurable disease, but increased understanding of the mechanisms for the transition into an androgen‐independent state may increase the possibilities for more efficient strategies in the future.MethodsAn androgen‐independent subline, LNCaP‐19, to the androgen‐dependent prostate cancer cell line LNCaP was developed in vitro under standard culture conditions. The characteristics of LNCaP‐19 regarding androgen responsiveness, PSA, and VEGF secretion was studied in vitro. The growth in vivo and the microvessel density (MVD) of the tumors were studied after inoculation in nude mice.ResultsLNCaP‐19 grows equally well in dextran‐charcoal stripped FBS (DCC‐FBS) as in normal FBS, and rapidly gives rise to tumors in both intact and castrated mice, indicating a true androgen‐independent growth. The PSA secretion from LNCaP‐19 cells was lower than from LNCaP cells, while the VEGF level was comparable to the secretion from LNCaP cells without androgen stimulation. The MVD was increased in the LNCaP‐19 tumors, and the vessels also displayed a changed morphology with exclusively small microvessels without lumen.ConclusionsLNCaP‐19 shows characteristics resembling those of androgen‐independent prostate cancer. An increased MVD and changed vessel morphology in the tumor, makes it an interesting model system for studies regarding angiogenesis in the context of the acquisition of androgen independence. © 2004 Wiley‐Liss, Inc.
Modelling of anti‐HSV activity of lactoferricin analogues using amino acid descriptors
Authors: Jenssen Håvard , Gutteberg Tore J. , Lejon Tore 
Published: September 2004

AbstractHerpes simplex virus (HSV) causes a number of diseases and new therapies are being pursued vigorously. Earlier studies have shown that modified peptides based on lactoferricins reduce HSV‐1 and HSV‐2 infection, and structure–activity studies indicate that the anti‐viral activity correlates with the binding affinity for heparan sulphate and chondroitin sulphate. In this study it is shown that theoretically derived amino acid descriptors can be used to model the anti‐viral activity of peptides, as well as other peptide properties, even more accurately. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
Growth of bulk GaN on GaN/sapphire templates by a high N2 pressure method
Authors: Boćkowski M. , Grzegory I. , Łucznik B. , Krukowski S. , Wróblewski M. , Kwiatkowski P. , Jasik K. , Wawer W. , Borysiuk J. , Kamler G. , Porowski S. 
Published: September 2004

AbstractThe results of high‐pressure directional growth of GaN on GaN/sapphire templates are presented. The GaN growth rate as a function of the temperature gradient and time is determined. Changes of the growth rate with time are explained. The results of the crystallization process are briefly compared with those obtained for directional growth on pressure‐grown GaN crystals. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence from InGaN/GaN MQWs on sapphire and membranes fabricated by laser lift‐off
Authors: Yu Tongjun , Li Zilan , Qin Z. X. , Chen Z. Z. , Yang Z. J. , Hu X. D. , Zhang G. Y. 
Published: September 2004

AbstractPhotoluminescence and Raman scattering spectra of InGaN/GaN MQWs on sapphire and membranes free of substrate fabricated by laser lift‐off have been studied. It is observed that photoluminescence peak of 850 °C annealed sample red‐shifts from that of as grown sample, while in the case of membrane samples, the luminescence peak blue‐shifts when annealed at 700 °C. In Raman scattering spectra, InGaN/GaN MQWs film without sapphire substrate has a lower E2 mode frequency (569.3 cm–1) than that of the films with substrate (570.8 cm–1), which indicates that compressive stress in the films releases partially when the sapphire substrate is taken off. It is believed that the piezoelectric field decrease leads to the blue‐shift in luminescence spectra. Compared with the samples with sapphire substrate, the free‐standing membranes showed blue‐shift of luminescence peak after relatively low temperature annealing, because the piezoelectric field reduced more easily in the films without substrate. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of InGaN nanorods with indium mole fractions by hydride vapor phase epitaxy
Authors: Kim Hwa‐Mok , Lee Hosang , Kim Suk Il , Ryu Sung Ryong , Kang Tae Won , Chung Kwan Soo 
Published: September 2004

AbstractThis work demonstrates the formation of InGaN nanorod arrays with indium mole fractions by hydride vapor phase epitaxy. The nanorods grown on (0001) sapphire substrates are preferentially oriented in the c‐axis direction. We found that the In mole fractions in the nanorods were linearly increased at x < 0.1. However, In mole fractions were slightly increased at x ≥ 0.1 and then were gradually saturated at x = 0.2. CL spectra show strong emissions from 380 nm (x = 0.04, 3.26 eV) to 470 nm (x = 0.2, 2.64 eV) at room temperature. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MBE growth of Zn‐polar ZnO on MOCVD‐ZnO templates
Authors: Kato Hiroyuki , Sano Michihiro , Miyamoto Kazuhiro , Yao Takafumi , Zhang Bao‐Ping , Wakatsuki Katsuki , Segawa Yusaburo 
Published: September 2004

AbstractHigh‐quality Zn‐polar ZnO films were grown on metal‐organic chemical‐vapor deposition (MOCVD) grown ZnO/a‐sapphire templates by plasma‐assisted molecular beam epitaxy (MBE). Annealing of the MOCVD‐ZnO layer in an O2 atmosphere improved the surface roughness and crystallinity of the template. Reflection high‐energy electron diffraction and atomic force microscopy observations revealed that MBE‐ZnO maintained its Zn‐polarity, which is the polarity of the underlying MOCVD‐ZnO, and that the optimized growth condition is the O‐rich flux regime. Structural and optical properties of the MBE‐ZnO films were significantly improved by growth under O‐rich flux condition and introducing a low‐temperature ZnO buffer. The line widths of (0002) and (10 $ \bar 1 $ 0) X‐ray ω‐rocking curves for MBE‐ZnO films were 533 and 582 arcsec, respectively. The ground and excited (n = 2) states of A‐exciton were clearly evident at 3.377 and 3.423 eV in low‐temperature (4.2 K) photoluminescence of the Zn‐polar ZnO film. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The influence of aluminum composition of AlxGa1–xAs in distributed Bragg reflector on surface morphology
Authors: Kim B. , Yoon M. , Kim S. , Son J. , Kim B. , Jhin J. , Byun D. 
Published: September 2004

AbstractSurface morphology of the AlGaAs/GaAs Vertical Cavity Surface Emitting Laser (VCSEL) grown by metalorganic vapor phase epitaxy (MOVPE) was investigated using atomic force microscopy. It is shown that the morphology of the structure strongly depends on the aluminum composition of the low Al content layer of distributed Bragg reflector (DBR) pairs and epi thickness. Whereas a high Al content layer in DBRs had little effect on the surface morphology, it was attributed that the influence of Al composition on the morphology of AlxGa1–xAs on GaAs was stronger in the range of 0 < x < 0.5 than 0.5 < x < 1. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatially resolved cathodoluminescence study on AlGaN layer fabricated by air‐bridged lateral epitaxial growth
Authors: Ishibashi Akihiko , Kawaguchi Yasutoshi , Sugahara Gaku , Shimamoto Toshitaka , Yokogawa Toshiya , Yamada Yoichi , Ueki Yusuke , Nakamura Kohzo , Taguchi Tsunemasa 
Published: September 2004

AbstractStructural properties of AlGaN layer on the GaN seed layer fabricated by air‐bridged lateral epitaxial growth (ABLEG) have been studied by spatially resolved cathodoluminescence (CL) microscopy. The cross‐sectional spatially resolved CL images of the ABLEG‐AlGaN layer reveal that there are roughly three regions which have different main CL peaks. This result suggests that there are roughly three regions with the different Al contents. Before coalescence of the overgrown AlGaN wings, there are two regions of Al content, such as about 6.5, 10.6%. On the other hand, after coalescence of the wings, the Al content of the AlGaN layer becomes uniform (Al content = 8.9%). These results suggest that the facet growth of the overgrown AlGaN wings causes the modulation of Al content in the ABLEG‐AlGaN layer. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emission properties and thermal annealing of InGaN/GaN multiple quantum wells with different protection layers
Authors: Cho H. K. , Park T. E. , Kim D. C. , Shin J. E. , Lee J. S. 
Published: September 2004

AbstractWe investigated the effect of two‐monolayer thick protection layers of GaN and AlGaN at the well growth temperature after the growth of InGaN well in InGaN/GaN MQW structures by MOCVD. The protection layers were very effective in inhibiting the re‐evaporation of indium atoms regardless of the growth of GaN barriers at high temperature from TEM and PL. In addition, the use of GaN barrier grown at high temperature using GaN protection layers improved the emission efficiency due to the growth of high quality GaN without indium desorption. From the thermal treatment of as‐grown samples, the redshift of emission was observed, which was ascribed to the increased quantum confined Stark effect by thermal stress, showing negligible indium gathering and atomic intermixing. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Built‐in electric field at cubic GaN/GaAs(001) heterointerfaces investigated by phase‐selected photoreflectance excitation
Authors: Katayama Ryuji , Onabe Kentaro , Shiraki Yasuhiro 
Published: September 2004

AbstractThe built‐in electric field applied at the cubic GaN/GaAs(001) heterointerfaces and its evolution during the growth process were evaluated using a phase‐selected photoreflectance technique in combination with a variable‐wavelength excitation light, to clarify the origin of the higher‐electric‐field signal observed in the previous photoreflectance study. The spectrum from LT‐GaN/GaAs after 900 °C annealing contains a extremely‐slow signal with a high electric‐field strength and this signal became dominant with decreasing the penetration depth of the modulating light. This confirms the presence of a triangular well just beneath the GaN/GaAs interface regarding the direction of the band‐bending investigated by the previous work, which can be attributed to the parallel‐conduction path ideal for the holes to drift through. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of the phonon‐induced electron transfer between semiconductor bulk and surface states
Authors: Zeiser Andreas , Bücking Norbert , Götte Jörg , Förstner Jens , Hahn Patrick , Schmidt Wolf Gero , Knorr Andreas 
Published: September 2004

AbstractThe coupling of surface and bulk states at semiconductor surfaces through electron–phonon interaction is discussed. The governing equations are derived from a microscopic theory in the framework of the density matrix theory. To gain a first insight, model wave functions are used to simulate the dynamics of nonequilibrium electron distributions in three‐ and two‐dimensional states, coupled by Fröhlich interaction. Typical time scales for the coupling are found to be in the order of few hundreds of femtoseconds. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐frequency vibrational modes of viruses used for nanoelectronic self‐assemblies
Authors: Fonoberov Vladimir A. , Balandin Alexander A. 
Published: September 2004

AbstractViruses of cylindrical shape have recently attracted attention as templates for assembly of nanostructured materials and as elements of nanoelectronic circuits. We have calculated the dispersion relations for the lowest vibrational frequencies of the tobacco mosaic virus (TMV) and M13 bacteriophage immersed in air or water. The radial breathing modes of TMV and M13 viruses in air (water) are 1.85 cm–1 and 6.42 cm–1 (2.10 cm–1 and 6.12 cm–1), respectively. Elastic vibrations of the two viruses in water are damped with the quality factor of 3.6 for the radial breathing modes. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Choice of alpha spending function and time points in clinical trials with one or two interim analyses
Authors: Selwyn Murray R. , Fish Susan M. 
Published: September 2004

AbstractOne characterization of group sequential methods uses alpha spending functions to allocate the false positive rate throughout a study. We consider and evaluate several such spending functions as well as the time points of the interim analyses at which they apply. In addition, we evaluate the double triangular test as an alternative procedure that allows for early termination of the trial not only due to efficacy differences between treatments, but also due to lack of such differences. We motivate and illustrate our work by reference to the analysis of survival data from a proposed oncology study.Such group sequential procedures with one or two interim analyses are only slightly less powerful than fixed sample trials, but provide for the strong possibility of early stopping. Therefore, in all situations where they can practically be applied, we recommend their routine use in clinical trials. The double triangular test provides a suitable alternative to the group sequential procedures in that they do not provide for early stopping with acceptance of the null hypothesis. Again, there is only a modest loss in power relative to fixed sample tests. Copyright © 2004 John Wiley & Sons, Ltd.
The relationship between osteoporotic fracture risk and a surrogate: Apparent discrepancies between analyses based on individual patient data and summary statistics
Authors: Barton Ian 
Published: September 2004

AbstractThere is debate within the osteoporosis research community about the relationship between the risk of osteoporotic fracture and the surrogate measures of fracture risk. Meta‐regression analyses based on summary data have shown a linear relationship between fracture risk and surrogate measures, whereas analyses based on individual patient data (IPD) have shown a nonlinear relationship. We investigated the association between changes in a surrogate measure of fracture incidence, in this case a bone turnover marker for resorption assessed in the three risedronate phase III clinical programmes, and incident osteoporosis‐related fracture risk using regression models based on patient‐level and trial‐level information. The relationship between osteoporosis‐related fracture risk and changes in bone resorption was different when analysed on the basis of IPD than when analysed on the basis of a meta‐analytic approach (i.e., meta‐regression) using summary data (e.g., treatment effect based on treatment group estimates). This inconsistency in our findings was consistent with those in the published literature. Meta‐regression based on summary statistics at the trial level is not expected to reflect causal relationships between a clinical outcome and surrogate measures. Analyses based on IPD make possible a more comprehensive analysis since all relevant data on a patient level are available. Copyright © 2004 John Wiley & Sons Ltd.
Sample sizes for estimation in clinical research
Authors: Julious Steven A. , Patterson Scott D. 
Published: September 2004

AbstractA sample size justification should be given for all clinical investigations. However, sometimes the objective of a trial is to estimate an effect with a view to planning a later definitive study. This paper describes the calculations for designing studies where one wishes to adopt an estimation approach through using confidence intervals around the overall response. Calculations are given for data anticipated to take a Normal form. Copyright © 2004 John Wiley & Sons, Ltd.
Thermal and Thermo‐mechanical Analysis for Design Evaluation of an Automotive Radar Module
Authors: Lindgren Mats , Belov Ilja , Leisner Peter 
Published: September 2004

AbstractThe influence of the substrate technology, assembly method, and housing material on the thermal, thermo‐mechanical and cost performance of a radar module for automotive applications has been studied to address the product reliability aspects during the design phase. Flip chip and wire bonding have been evaluated for Multi‐Chip Module—Laminate/Deposition (MCM‐L/D) and Multi‐Chip Module—Deposition (MCM‐D) substrate technologies used for electronic packaging solutions in a harsh environment. Solder ball and direct attachment have been investigated as second‐level assembly. As a result of thermal and thermo‐mechanical simulations and cost analysis, radar module designs combining MCM‐D and MCM‐L/D with wire bonding have been revealed, which are preferable for use in different temperature environments with respect to two performance criteria, the maximum junction temperature and the manufacturing cost. Simulation‐based guidelines have been developed for designing radar modules used in automotive applications while satisfying temperature and stress constraints provided for the module. Copyright © 2004 John Wiley & Sons, Ltd.
A theoretical study of the structure and properties of uric acid: A potent antioxidant
Authors: Allen Reeshemah N. , Shukla M. K. , Leszczynski Jerzy 
Published: September 2004

AbstractA detailed study of tautomeric properties of uric acid, its different anions, and radical species was performed at the DFT level, employing B3LYP functional and the 6‐311++G(d,p) basis set. Single‐point energy calculations were also performed at the MP2 level using B3LYP/6‐311++G(d,p) optimized geometries and the cc‐pVTZ and 6‐311++G(d,p) basis sets. The effect of aqueous solvation on the relative stability of the neutral and anionic species was investigated using Tomasi's polarized continuum model. The keto form of the molecule was found to be the most stable in the gas phase and in aqueous medium. The proton transfer barrier height was also computed. The gas‐phase barrier height is high; however, the inclusion of a water molecule in the proton transfer reaction path reduces the barrier significantly. Among monoanions of uric acid, the species obtained by the deprotonation of the N3 site is the most stable, whereas among dianions, the anion obtained by deprotonation of both N3 and N9 sites is the most stable both in the gas phase and in aqueous medium. It appears that both forms of radicals UAN and UAN would exist. Among radical anions, the species obtained by the dehydrogenation of the N3 site of the N7 anion (the N7 anion was obtained by deprotonation of the N7 site of uric acid) is the most stable in the gas phase and in aqueous solution. The molecular electrostatic potential, ionization potential, and electron affinity are also reported. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Attosecond localization of electrons in molecules
Authors: Bandrauk André D. , Chelkowski Stephane , Nguyen Hong Shon 
Published: September 2004

AbstractNumerical solutions of the time‐dependent Schrödinger equation for a 1D model non‐Born–Oppenheimer H are used to illustrate the nonlinear nonperturbative response of molecules to intense (I ≥ 1013 W/cm2), ultrashort (t < 10 fs) laser pulses. Molecular high‐order harmonic generation (MHOHG) is shown to be an example of such response and the resulting nonlinear photon emission spectrum is shown to lead to the synthesis of single attosecond (10−18 s) pulses. Application of such ultrashort pulses to the H system results in localized electron wavepackets whose motion can be detected by asymmetry in the photoelectron spectrum generated by a subsequent probe attosecond pulse, thus leading to measurement of electron motion in molecules on the attosecond time scale. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004