bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interfacing Mercury Porosimetry with Nitrogen Sorption
Authors: Rigby Sean P. , Fletcher Robin S. 
Published: September 2004

AbstractCombinations of gas sorption and mercury porosimetry experiments have been run in series on the same sample. This has been achieved by freezing entrapped mercury in place before a subsequent gas sorption experiment was carried out. Several different bidisperse materials with similarly shaped mercury intrusion curves and similar levels of mercury entrapment have been studied. The entrapment of mercury within certain pores in the porous medium can often lead to marked changes in the shape of the gas sorption hysteresis loop between the data obtained prior and subsequent to porosimetry. It was found that the degree of the change of shape of the sorption hysteresis loops differed markedly between different materials. The analysis of the gas sorption hysteresis loops using percolation theory has allowed information to be obtained on the pore length distribution, and/or the distribution of pore co‐ordination number and the spatial arrangement of pores within the sample, in addition to the pore connectivity and lattice size usually obtained. The interfaced experiments have also allowed the internal consistency of analysis methods based on percolation theory to be tested, semi‐empirical alternatives to the Washburn Equation for the analysis of raw mercury porosimetry data to be independently validated, and the mechanisms of mercury entrapment in various samples to be determined.
Site‐Bond Network Modeling of Disordered Porous Media
Authors: Cordero Salomón , Kornhauser Isaac , Domínguez Armando , Felipe Carlos , Esparza Juan Marcos , Rojas Fernando , López Raúl H. , Vidales Ana M. , Riccardo José L. , Zgrablich Giorgio 
Published: September 2004

AbstractThe description of disordered porous media through the Dual Site‐Bond Model (DSBM) is reviewed and updated with the inclusion of new results. After a brief discussion of the DSBM, the percolation properties of networks are studied. These present novel features with respect to classical percolation in non‐correlated networks. These properties are then used in discussing different processes in disordered porous media, namely, invasion percolation and adsorption‐desorption hysteresis. Finally, a method for the characterization of pore size distributions from experimental adsorption‐desorption isotherms is proposed.
Tracheal gas insufflation‐augmented continuous positive airway pressure in a spontaneously breathing model of neonatal respiratory distress
Authors: Miller Thomas L. , Blackson Thomas J. , Shaffer Thomas H. , Touch Suzanne M. 
Published: September 2004

AbstractRespiratory distress syndrome (RDS) in neonates is characterized by labored breathing and poor gas exchange, often requiring ventilatory support. Continuous positive airway pressure (CPAP) is a preferred intervention to support spontaneous ventilatory efforts by sustaining lung volume recruitment, while it prevents derecruitment during exhalation by maintaining end‐expiratory pressure. However, CO2 retention during CPAP often results in the need for mechanical ventilation. Since tracheal gas insufflation (TGI) promotes CO2 elimination by reducing prosthetic dead space, we hypothesized that TGI used with CPAP may reduce the need for more invasive therapies. The objective of this study was to evaluate the physiologic effect of TGI with CPAP in a spontaneously breathing model of acute lung injury with respect to gas exchange and pulmonary mechanics. Nineteen spontaneously breathing neonatal pigs (2.4 ± 0.4 kg) were anesthetized, sedated, instrumented, and placed on CPAP at 5 cmH2O. All piglets were injured with intravenous oleic acid (0.08 ml/kg), and then randomized to receive CPAP with TGI (TGI; n = 9) or CPAP alone (control; n = 10). FiO2 was titrated at 0.05 every 15 min during the protocol to maintain SaO2 > 93%. Vital signs, arterial blood gases, pulmonary mechanics, and thoracoabdominal motion (TAM) were evaluated 30 min after injury and at 1‐hr intervals for 4 hr. Following the 4‐hr measurement, the piglets were sacrificed and the lungs were grossly examined. After initiation of treatment, we found that the PaCO2 was lower (33.1 ± 5.0 vs. 47.0 ± 10.3 mmHg; P < 0.01), while the oxygenation indices were greater (PaO2, SaO2, a/A ratio; P < 0.01) in the TGI group than with control animals. Subsequently, the pH was greater (7.45 ± 0.08 vs. 7.36 ± 0.08; P < 0.01) and closer to baseline values with TGI. By 4 hr, the FiO2 was titrated lower (0.37 ± 0.06 vs. 0.49 ± 0.15; P < 0.05) and ventilation was accomplished with a lower minute ventilation (MV) in the TGI group than in the control group (445 ± 113 vs. 581 ± 223 ml/kg/min; P < 0.01). Respiratory compliance was greater with TGI than control (0.76 ± 0.13 vs. 0.63 ± 0.11 ml/cmH2O/kg; P < 0.01), whereas resistance and TAM were similar between groups. We conclude that the use of TGI with CPAP in the treatment of RDS results in improved gas exchange and pulmonary mechanics. As such, TGI‐augmented CPAP may prevent infants from requiring more invasive ventilation by reducing CO2 retention. © 2004 Wiley‐Liss, Inc.
Fetal development of striated and smooth muscle sphincters of the male urethra from a common primordium and modifications due to the development of the prostate: an anatomic and histologic study
Authors: Sebe Philippe , Schwentner Christian , Oswald Josef , Radmayr Christian , Bartsch Georg , Fritsch Helga 
Published: September 2004

AbstractBackgroundThe aim of the study was to investigate the development of the human urethral sphincter complex during fetal development.Methods23 human male fetal specimens were investigated. The histological sections were processed according to the epoxy resin‐based plastination technology.ResultsAt 9th week of gestation, a combined sphincteric primordium of the rhabdosphincter and the lissosphincter is situated at the anterior and lateral aspects of the membranous and prostatic urethra. Both muscular components assume an omega‐shaped configuration due to the presence of a constant connective tissue raphe posterior to the urethra that anchors the rhabdosphincter in the perineal body. Development of the prostate laterally and posteriorly does not modify the growth of the urethral sphincter complex anteriorly but inhibits its development laterally and posteriorly.ConclusionsThe important morphological characteristics of the male adult rhabdosphincter and lissosphincter can be seen very early in fetal development. © 2004 Wiley‐Liss, Inc.
Analogues of arginine vasopressin modified in position 2 and 3 with conformationally constrained dipeptide fragments
Authors: Łempicka Elżbieta , Derdowska Izabela , Kowalczyk Wioleta , Dawidowska Olga , Prahl Adam , Janecki Marcin , Jasiński Tomasz , Trzeciak Henryk I. , Lammek Bernard 
Published: September 2004

AbstractThis study describes the synthesis and some pharmacological properties of ten new analogues of arginine vasopressin (AVP) containing a conformationally constrained dipeptide fragment in the N‐terminal part of their molecules. Amino acid residues in positions 2 and 3 of AVP and some of its agonistic analogues were replaced with $\newbox\sprulebox \newdimen\sprulewd \def\sprule#1#2{ \global\setbox\sprulebox=\hbox{#1} \sprulewd=\wd\sprulebox\advance \sprulewd by -2pt \matrix{\smash{\lower.67pc\hbox{#1}}\cr \vrule height #2pt\hbox to \sprulewd{\hrulefill}\vrule height #2pt\cr} } \sprule{-Phe-}{7}$Phe and D$\newbox\sprulebox \newdimen\sprulewd \def\sprule#1#2{ \global\setbox\sprulebox=\hbox{#1} \sprulewd=\wd\sprulebox\advance \sprulewd by -2pt \matrix{\smash{\lower.67pc\hbox{#1}}\cr \vrule height #2pt\hbox to \sprulewd{\hrulefill}\vrule height #2pt\cr} } \sprule{-Phe-}{7}$D‐Phe, dipeptides having a CH2CH2 link bridging two nitrogens. All the new peptides were tested for vasopressor and antidiuretic activities. Four peptides with pA2 values ranging from 5.96 to 7.21 turned out to be weak or moderately potent V1a antagonists. The results supplied new information about the structure—activity relationship of AVP analogues. As some of these were unexpected, they point to the need for caution when extrapolating previously known effects of modifications to analogues having conformationally constrained fragments in their molecules. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
Novel cladding structure for ZnSe‐based white LEDs with longer lifetime over 10,000 hours
Authors: Nakamura T. , Katayama K. , Mori H. , Fujiwara S. 
Published: September 2004

AbstractWe have demonstrated ZnSe‐based white LEDs with longer lifetime over 10,000 h at 14.5 A/cm2 by introducing an i‐ZnMgBeSe/p‐ZnMgSe double cladding structure, which combined a very thin i‐ZnMgBeSe layer for suppressing electron overflow and p‐ZnMgSSe for efficient p‐type carrier concentration. By adopting the double cladding layer instead of the conventional p‐ZnMgSSe cladding layer, rapid degradation is suppressed. The device simulation and the temperature dependence of optical power showed that the i‐ZnMgBeSe layer played the main role in increasing electron confinement. Our reliability test results indicate that the suppression of the electron overflow is essential to obtain long lifetime acceptable for truly practical use. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study on the stability of the high‐brightness white LED
Authors: Chen Z. Z. , Zhao J. , Qin Z. X. , Hu X. D. , Yu T. J. , Tong Y. Z. , Yang Z. J. , Zhou X. Y. , Yao G. Q. , Zhang B. , Zhang G. Y. 
Published: September 2004

AbstractThe high‐power white light emitting diode (LED) is packaged by GaN‐based blue LED chip with the size of 1 × 1 mm2, YAG:Ce yellow fluorescer, epoxy and an effective heat sinking. The wavelength of the LED chip emission blue‐shifts from 482 to 475 nm, while that of the fluorescer emission does not change in electroluminescence (EL) spectrum when the injection current increases from 5 to 200 mA. And the correlated color temperature decreases from 5300 to 4800 K. When the injection current increases to 200 mA, the luminous power (Pe) increases to 13.8 mW, which is about 10 times of those of the normal size (0.3 × 0.3 mm2) diodes fabricated with the same wafer and same injection density. Pe and forward bias (Vf) at 200 mA are measured for the aging high‐power white LED. At the beginning, Pe decreases dramatically 20% and Vf decreases about 0.2 V in 2 days. And then Pe and Vf decrease slowly in the remaining 79 days aging. The contact metals electro migration along the channels induced by the threading dislocations may be the dominant aging mechanism. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Metal/GaN reaction chemistry and their electrical properties
Authors: Kim C. C. , Seol S. K. , Kim J. K. , Lee J.‐L. , Hwu Y. , Ruterana P. , Magaritondo G. , Je J. H. 
Published: September 2004

AbstractWe investigated the reaction chemistry of metal contacts to GaN during annealing using X‐ray photoelectron spectroscopy (XPS). GaN decomposition was estimated, using XPS, to occur in N2 annealed Ni‐alloy contacts at 550 °C. The reaction was greatly accelerated by the catalytic effect of Au and Pt. The decomposition was correlated with the rapid degradation of electrical properties during annealing. The results suggest that high‐temperature applications may be critically limited by the degradation of metal contacts especially due to activated Ni reactivity in Ni‐alloyed contacts. Meanwhile, the thermal stability of Ni/Au contact greatly improves by suppressing the activated Ni reactivity, which is able to be obtained by forming preferential Ni–O bonding through annealing in air. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐quality GaN films grown on Si(111) by a reversed Stranski–Krastanov growth mode
Authors: Chen N. C. , Shih C. F. , Chang C. A. , Chiu A. P. , Teng S. D. , Liu K. S. 
Published: September 2004

AbstractHigh‐quality GaN film has been successfully grown on Si(111) substrates by metal‐organic vapor phase epitaxy (MOVPE). Low‐temperature GaN layers were inserted into high‐temperature grown GaN as the intermediate layers. High‐resolution transmission electron microscope (HRTEM) images revealed that the GaN tends to form large islands (∼25–50 nm) during temperature cycles. The formation of islands plays an important role in improving the crystal quality. Then, layer‐by‐layer growth was enhanced by ramping temperature to 1050 °C and increasing the growth rate. Finally, a mirror‐like smooth surface was obtained. We describe the observed change in growth mode from three‐dimensional (3D) to two‐dimensional (2D) as a reversed Stranski–Krastanov growth mode. The ω‐rocking curve measurement gave a full width at half‐maximum of 500 arcsec for GaN grown on Si. This is comparable to GaN grown on sapphire and is among the best results reported. The detailed epitaxial growth mechanism of GaN on Si (111) is also discussed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier injection and light emission in visible and UV nitride LEDs by modeling
Authors: Karpov S. Yu. , Bulashevich K. A. , Zhmakin I. A. , Nestoklon V. O. , Mymrin V. F. , Makarov Yu. N. 
Published: September 2004

AbstractPolarization effects on carrier injection and light emission are considered by modeling with reference to single‐quantum‐well blue light emitting diode heterostructures of either Ga‐ or N‐polarity. The model accounts for specific features of nitride semiconductors, spontaneous and piezo‐polarization, strong non‐radiative recombination on threading dislocation cores, complex valence band structure, etc., and allows detailed analysis of the device operation. The modeling results are compared with available observations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarization properties of nonpolar GaN films and (In,Ga)N/GaN multiple quantum wells
Authors: Grahn H. T. 
Published: September 2004

AbstractWe have realized nonpolar GaN films and (In,Ga)N/GaN multiple quantum wells (MQWs) by plasma‐assisted molecular‐beam epitaxy on γ‐LiAlO2(100) substrates. The GaN films and (In,Ga)N/GaN MQWs are grown in an M‐plane configuration, i.e., the c‐axis of the wurtzite unit cell lies in the growth plane. For compressively and anisotropically strained M‐plane GaN films, the band structure of the valence band changes in such a way that the optical transmittance becomes 100% linearly polarized for two orthogonal in‐plane directions, where one of these directions is parallel to the c‐axis of the GaN film. Within a certain energy range, the M‐plane GaN film thereby acts as a polarization filter. The photoluminescence spectra of M‐plane In0.1Ga0.9N/GaN MQWs exhibit a strong in‐plane optical anisotropy for linear polarization with an energy‐dependent polarization degree of up to 96%, which is presumably also due to a large valence‐band splitting induced by the large compressive strain in the QWs. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of oxygen plasma treatment on the formation of ohmic contacts to GaN and AlGaN
Authors: Yan J. , Kappers M. J. , Crossley A. , McAleese C. , Phillips W. A. , Humphreys C. J. 
Published: September 2004

AbstractThe effects of oxygen plasma treatment prior to metal contact deposition have been studied for both n‐ and p‐GaN, as well as n‐AlGaN. In n‐GaN, the as‐deposited Ti/Al contacts change from rectifying to ohmic, and further improvements are observed after rapid thermal annealing (RTA). A specific contact resistivity better than 10–7 Ω cm2 was obtained using a plasma treatment of 20 s at 30 W and 0.2 mbar, followed by RTA at 500 °C in argon. The I–V characteristics of the Ti/Al contacts degraded when plasma treatments were performed for a longer time and/or at increased plasma pressure. However, in contrast to n‐GaN, the electrical properties of the Ni/Au contacts to p‐GaN and Ti/Al contacts to n‐Al0.15Ga0.85N deteriorated following oxygen plasma treatment. X‐ray photoelectron spectroscopy (XPS) was used in order to help elucidate the mechanisms behind these effects. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cathodoluminescence of polycrystalline GaN grown by a hot wall epitaxy technique
Authors: Inoue Y. , Hoshino T. , Takeda S. , Ishida A. , Fujiyasu H. , Kominami H. , Mimura H. , Nakanishi Y. , Sakakibara S. 
Published: September 2004

AbstractPolycrystalline GaN nanostructures were grown on Si(111) substrates by a hot wall epitaxy technique using metallic gallium and ammonia sources. Self‐organized pillar‐like GaN nanostructures (GaN nanopillar) were grown without intentional pre‐processing to the Si substrate. It is found that the columnar growth was initiated by the GaN dots of 50 nm in diameter, which act as the low temperature buffer, and it resulted in the high photoluminescence and cathodoluminescence emissions due to the high crystal quality of the GaN nanopillars. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly luminescent cubic GaN microcrystals grown on GaAs(001) substrates by RF‐MBE
Authors: Katayama Ryuji , Onabe Kentaro , Shiraki Yasuhiro 
Published: September 2004

AbstractCubic GaN microcrystals have been grown on a cubic GaN template by radio‐frequency plasma molecular beam epitaxy (RF‐MBE) using a relatively thin low‐temperature‐grown GaN buffer layer, which promotes the generation of Ga droplets acting as the nuclei for three‐dimensional (3D) growth. These crystals are found to be highly luminescent compared to those grown by metalorganic vapour‐phase epitaxy (MOVPE). Their optical quality is much better than that of the two‐dimensionally (2D) growth c‐GaN region as investigated by microcathodoluminescence (micro‐CL) and photoluminescence (PL). These results suggest that defects or local strain, originating from the large lattice mismatch and thermal mismatch between GaN and GaAs, could be avoided by the transition from 2D to 3D growth mode with the use of this nucleation process. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient conversion of blue light into white light by means of rare‐earth‐ion‐doped transparent material
Authors: Mita Y. , Kobayashi Takeshi , Miyamoto Yoshinobu , Ishii Osamu , Sawanobori Naruhito 
Published: September 2004

AbstractThe possibility and applicability limit of rare‐earth‐ion‐doped transparent materials as wavelength conversion materials for white‐light‐emitting light sources have been investigated. In a previous paper an efficient conversion from blue to white light was reported using a YAG:Ce single crystal. It is now shown that a high conversion efficiency from blue or UV light to green light can be expected in Er3+‐doped glass having a low Er3+ ion content. However, the practical usefulness is limited because of a low absorption constant and narrow spectral absorption band of Er3+ ions. Luminescence processes in Er3+‐containing materials have been examined and compared with the results of simulation. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of the molecular structure and catalytic activity of the new fullerene‐based catalyst (η2‐c60)pd(PPh3)2: An application in the reaction of selective hydrogenation of acetylenic alcohols
Authors: Yanov Ilya , Leszczynski Jerzy , Sulman E. , Matveeva V. , Semagina N. 
Published: September 2004

AbstractIn this article we finalize our experimental and theoretical studies on the (η2‐C60)Pd(PPh3)2 palladium–phosphine fullerene complex. Full scale ab initio quantum‐chemical calculations up to the B3LYP/SDDALL level of theory have been performed to determine the structure and electronic spectrum of (η2‐C60)Pd(PPh3)2. Based on the results of calculations and experimental data we conclude that the preliminary interaction of the catalyst with the substrate facilitates the interaction of the substrate–catalyst complex with H2 by decreasing the energy barrier. In conclusions we summarize the results of our studies of the structure and electronic spectrum of the investigated complex, the kinetics of catalytic reactions, the influence of the solvents on the catalyst's activity in the heterogeneous phase, and provide the possible mechanism of catalytic reaction. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Relativistic electron theory: Is spin a property of the electron in vacuo or of the electromagnetic field interaction
Authors: Ritchie Burke , Weatherford Charles A. 
Published: September 2004

AbstractHere we investigate electron spin as a property of the electron–magnetic field interaction, rather than as a property of the free electron in the absence of electromagnetic fields. We show that, within the phase of the interaction linear in the vector potential, the Pauli or Dirac magnetic moment interaction Hamiltonian can be derived by using a form of the vector potential that depends on the Pauli spin vector and by consistently using electron and field four‐vectors to ensure Lorentz invariance of quantities related to physical observables. The Dirac equation itself is shown to follow from this procedure. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Evaluation of methods to measure differential 15N labeling of soil and root N pools for studies of root exudation
Authors: Hertenberger Gerhard , Wanek Wolfgang 
Published: September 2004

AbstractTo study patterns of root exudation, the effectiveness of different techniques for in situ 15N labeling of Brassica napus, Centaurea jacea and Lolium perenne with ammonium nitrate was tested. Stem infiltration was found to effectively label plants with thicker stems, whereas, for grass species, cutting and immersing the leaf tips into 15N solution proved to be most effective. A microdiffusion technique to isolate ammonium, combined with conventional cation‐exchange chromatography to separate nitrate from amino‐N compounds thereafter, was found suitable for separation of the N fractions of plant and soil extracts for 15N determination. All three species were then cultivated in nutrient solution and labeled with 15NHNO3 by stem feeding for 42 hours. Kinetics of 15N labeling of bulk roots and shoots as well as hot water extractable material were assessed, and up to 1.1 at% 15N excess (APE) was found in nutrient solutions. The main amino acids exuded by L. perenne were glycine, serine, alanine and aspartic acid. To assess the suitability of this set of methods to study root exudation in field settings, L. perenne was grown without fertiliser addition in pots containing low‐nutrient soil. Plants were 15N labeled via tip immersion and 15N and N concentrations were analysed in shoots, roots and soils during a 48‐h interval. Shoots reached 1.25 APE, roots and soil 0.10 and 0.005 APE, respectively. Between 4% (48 h) and 6% (24 h) of total plant 15N was exuded by roots into the soil. In roots amino acids comprised the largest proportion of the soluble 15N pool, whereas soil 15N levels were similar for amino acids and ammonium, exceeding those of nitrate. Mechanisms for the shift within N fractions from roots to soils are briefly discussed. Copyright © 2004 John Wiley & Sons, Ltd.