bluuebunny/crossref_metadata_2025 huggingface dataset:
New insights into mountain permafrost occurrence and characteristics in glacier forefields at high altitude through the application of 2D resistivity imaging
Authors: Kneisel Chr.
Published: September 2004

Investigation of permafrost in glacier forefields at high altitude in the Upper Engadine has been undertaken during recent years (1996–1998) using one‐dimensional geoelectrical soundings as the standard geophysical technique to detect mountain permafrost. In summer 2002, two of the glacier forefields were revisited and two‐dimensional electrical resistivity tomography applied at the same survey locations. The findings based on the interpretation of one‐dimensional vertical geoelectrical soundings were confirmed by two‐dimensional resistivity imaging. Furthermore, the application of electrical resistivity tomography provides more detailed insights into the occurrence and characteristics of permafrost in recently deglaciated glacier forefields as compared to the results obtained by traditional one‐dimensional vertical soundings. Additionally, the more effective data acquisition enables new fields of application, which in turn will allow a more complete interpretation of the factors influencing the distribution of discontinuous and sporadic mountain permafrost. Copyright © 2004 John Wiley & Sons, Ltd.
The thermal regime of the active layer at the Murtèl rock glacier based on data from 2002
Authors: Hanson Susanne , Hoelzle Martin
Published: September 2004

Active layer temperatures are presented from a rock glacier in the Swiss Alps. The data represent a full year (2002) covering parts of two very different winters. Winter/spring 2002 was very cold and dry; fall 2002 was characterized by an unusual amount of snow. Active layer temperatures are examined together with climate data and are used to discuss the processes which control the thermal regime of an active layer on a slope of a bouldery rock glacier surface. The development of the snow cover as well as the snow depth are shown to be essential, but the non‐linear heating of the bouldery material with increasing air temperatures and the micro‐topography of the rock glacier surface are also shown to have an influence on the thermal regime of the active layer. Furthermore, it is shown that the advective air movement within the blocky deposit has much less influence on the thermal regime than the vertical displacement of air masses. This is contradicts earlier literature on the subject. Copyright © 2004 John Wiley & Sons, Ltd.
Interfacing Mercury Porosimetry with Nitrogen Sorption
Authors: Rigby Sean P. , Fletcher Robin S.
Published: September 2004

Combinations 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

The 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

Respiratory 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

Background

The aim of the study was to investigate the development of the human urethral sphincter complex during fetal development.

Methods

23 human male fetal specimens were investigated. The histological sections were processed according to the epoxy resin‐based plastination technology.

Results

At 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.

Conclusions

The 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

This 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

We 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

The 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

We 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

High‐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

Polarization 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

We 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

The 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

Polycrystalline 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

Cubic 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

The 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

In 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

Here 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

To 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.
Functionalized nanoparticles for liquid atmospheric pressure matrix‐assisted laser desorption/ionization peptide analysis
Authors: Turney Kevin , Drake Timothy J. , Smith Joshua E. , Tan Weihong , Harrison W. W.
Published: September 2004

Nanoparticles for the extraction of peptides and subsequent analysis using atmospheric pressure matrix‐assisted laser desorption/ionization (APMALDI) have been evaluated. The atmospheric pressure source allows for particles to be directly introduced in the liquid matrix, minimizing sample loss and analysis time. Described in this work are two sample preparation procedures for liquid APMALDI analysis: a C18 functionalized silica nanoparticle for hydrophobic extractions, and an aptamer functionalized magnetite core nanoparticle for rapid, affinity extractions. The C18 particles provide a non‐selective support for rapid profiling applications, while the aptamer particles are directed towards reducing the complexity in biological samples. The aptamer functionalized particles provide a more selective analyte–nanoparticle interaction whereby the tertiary structure of the analyte becomes more critical to the extraction. In both cases, the liquid APMALDI matrix provides a support for ionization, and acts as the releasing agent for the analyte–particle interaction. Additionally, analyte enrichment was possible due to the large surface‐to‐volume ratio of the particles. The experiments conducted with functionalized nanoparticles, in an atmospheric pressure liquid matrix, present a basis for further methodologies and utilities of silica nanoparticles to be developed. Copyright © 2004 John Wiley & Sons, Ltd.
Efficient in‐gel digestion procedure using 5‐cyclohexyl‐1‐pentyl‐β‐D‐maltoside as an additive for gel‐based membrane proteomics
Authors: Katayama Hiroyuki , Tabata Tsuyoshi , Ishihama Yasushi , Sato Toshitaka , Oda Yoshiya , Nagasu Takeshi
Published: September 2004

A cycloalkyl aliphatic saccharide, 5‐cyclohexyl‐1‐pentyl‐β‐D‐maltoside (CYMAL‐5), was evaluated as a novel additive in a high‐throughput in‐gel protein digestion system using 96‐well plates. Addition of 0.1% CYMAL‐5 (final concentration) during trypsin treatment was compatible with both matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis, and gave a better digestion efficiency than n‐octylglucoside, which we previously reported. In‐gel reduction and alkylation of Cys residues under denaturing conditions also improved the sequence coverage of peptides. In‐gel tryptic digestion with the optimum combination of 0.5 mm thick gels, negative staining, alkylation under denaturing conditions (6 M guanidine hydrochloride), and digestion in the presence of CYMAL‐5, gave excellent performance especially for membrane protein analysis, where recovery of hydrophobic peptides was markedly enhanced. The new protocol is simple and convenient, and should be widely applicable to gel‐based proteomics. Copyright © 2004 John Wiley & Sons, Ltd.
Multiphoton dissociation/ionization of CHCl3 and CFCl3 at 355 nm: an experimental and theoretical study
Authors: Sharma P. , Vatsa R. K. , Maity D. K. , Kulshreshtha S. K.
Published: September 2004

Nonresonant laser‐induced multiphoton dissociation/ionization studies have been conducted for trichloromethane (CHCl3) and trichlorofluoromethane (CFCl3) at 355 nm, using time‐of‐flight mass spectrometry (TOFMS). The molecular ion signal was found to be missing for both these compounds, and very similar fragmentation patterns were observed. Ab initio molecular electronic structure calculations were performed to help understand the fragmentation pattern of these molecules in the laser field. The energetics of different dissociation channels in the ground states of [CHCl3]+., [CHCl2]+, [CFCl3]+. and [CFCl2]+, as well as neutral CHCl3, CHCl, CFCl3 and CFCl systems, were calculated. On comparing theoretical results with experimentally observed ion signals and their relative abundances in TOFMS, it is inferred that these molecules undergo sequential Cl atom elimination followed by photoionization of the fragments. The absence of [CFCl]+ has been interpreted on the basis of resonant Ã state‐mediated two‐photon absorption by CFCl, and the subsequent prompt photodissociation processes occurring for this state. Copyright © 2004 John Wiley & Sons, Ltd.
Applications of a travelling wave‐based radio‐frequency‐only stacked ring ion guide
Authors: Giles Kevin , Pringle Steven D. , Worthington Kenneth R. , Little David , Wildgoose Jason L. , Bateman Robert H.
Published: September 2004

The use of radio‐frequency (RF)‐only ion guides for efficient transport of ions through regions of a mass spectrometer where the background gas pressure is relatively high is widespread in present instrumentation. Whilst multiple collisions between ions and the background gas can be beneficial, for example in inducing fragmentation and/or decreasing the spread in ion energies, the resultant reduction of ion axial velocity can be detrimental in modes of operation where a rapidly changing influx of ions to the gas‐filled ion guide needs to be reproduced at the exit. In general, the RF‐only ion guides presently in use are based on multipole rod sets. Here we report investigations into a new mode of ion propulsion within an RF ion guide based on a stack of ring electrodes. Ion propulsion is produced by superimposing a voltage pulse on the confining RF of an electrode and then moving the pulse to an adjacent electrode and so on along the guide to provide a travelling voltage wave on which the ions can surf. Through appropriate choice of the travelling wave pulse height, velocity and gas pressure it will be shown that the stacked ring ion guide with the travelling wave is effective as a collision cell in a tandem mass spectrometer where fast mass scanning or switching is required, as an ion mobility separator at pressures around 0.2 mbar, as an ion delivery device for enhancement of duty cycle on an orthogonal acceleration time‐of‐flight (oa‐TOF) mass analyser, and as an ion fragmentation device at higher wave velocities. Copyright © 2004 John Wiley & Sons, Ltd.
Trace determination of anthracyclines in urine: a new high‐performance liquid chromatography/tandem mass spectrometry method for assessing exposure of hospital personnel
Authors: Sottani Cristina , Tranfo Giovanna , Bettinelli Maurizio , Faranda Paolo , Spagnoli Mariangela , Minoia Claudio
Published: September 2004

Health‐care workers handling antineoplastic agents may be exposed to extremely low doses of these drugs. Very sensitive and specific analytical methods are therefore needed for biological monitoring. The aim of this study was to develop and validate a method for trace level determination of doxorubicin, epirubicin, daunorubicin and idarubicin in human urine, using epi‐daunorubicin as an internal standard. Solid‐phase extraction (SPE) was used for sample preparation. Urine samples were loaded onto Bond Elut C18 cartridges. The analytes were eluted in methylene chloride/2‐propanol (1:1, v/v) and then evaporated to dryness. The residue was reconstituted with the mobile phase prior to high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) analysis. Quantitation of each analyte was performed using the multiple reaction monitoring (MRM) method. The urine assay was linear over the range 0.1–2.0 μg/L, with a lower limit of quantification (LLOQ) of 0.10 μg/L for doxorubicin and epirubicin, and 0.03 μg/L for daunorubicin and idarubicin. The respective limits of detection (LODs) were 0.04 and 0.01 μg/L. The precision and accuracy of the assay were determined on three different days. The within‐series precision was found to be always less than 13.9% for all the analytes. The overall precision expressed as relative standard deviation (RSD) was always less than 10.6%. The recovery of anthracyclines was assessed at two concentrations of the range tested (0.1 and 2.0 μg/L) and it ranged from 87.7% (daunorubicin) to 102.0% (doxorubicin) and from 79.1% (daunorubicin) to 90.7% (idarubicin) for the lower and the higher level, respectively, with a RSD always less than 9.1%. The uncertainty of the present assay was also evaluated and the combined uncertainty was always less than 20% over all the days of the validation study. This is the first method that makes use of LC/MS/MS for the biological monitoring of occupational exposure to anthracyclines. Copyright © 2004 John Wiley & Sons, Ltd.
A distributed fuzzy logic controller for an autonomous vehicle
Authors: Hodge Neil Eugene , Shi Linda Zhixia , Trabia Mohamed B.
Published: September 2004

Autonomous vehicles can be used in a variety of applications such as hazardous environments or intelligent highway systems. Fuzzy logic is an appropriate choice for this application as it can describe human behavior well. This paper proposes two fuzzy logic controllers for the steering and the velocity control of an autonomous vehicle. The two controllers are divided into separate modules to mimic the way humans think while driving. The steering controller is divided into four modules; one module drives the vehicle toward the target while another module avoids collision with obstacles. A third module drives the vehicle through mazes. The fourth module adjusts the final orientation of the target. The velocity controller is divided into three modules; the first module speeds up the vehicle to reach the target and slows it down as it moves toward the target. The second module controls the velocity in the neighborhood of obstacles. A third module controls the velocity of the vehicle as it turns sharp corners. A method for automatic tuning of the first module of the velocity controller is proposed to stabilize the velocity of the vehicle as it approaches the target. Two examples to demonstrate the interaction among the seven control modules are included. Results of the simulation are compared with those in the literature. © 2004 Wiley Periodicals, Inc.
On using flexure‐hinge five‐bar linkages to develop novel walking mechanisms and small‐scale grippers for microrobots
Authors: Wang Guo‐bao , Wang Shi‐gang , Xu Wei
Published: September 2004

This paper presents the micromotion analysis of five‐bar linkages and demonstrates the approximate linearity of motion transmission of five‐bar mechanisms within a micromotion range. A novel walking mechanism used for a microrobot and a small‐scale gripper with a high transmission ratio are introduced, based on the flexure‐hinge five‐bar mechanism analysis. Results of numerical simulation show the validity of design and analysis on the introduced mechanisms and the feasibility of corresponding thoughts. The presented micromotion‐based robot mechanisms are devoid of friction and fitting errors, and particularly suitable for microrobot applications. © 2004 Wiley Periodicals, Inc.
Characterization of siloxane films on titanium substrate derived from three aminosilanes
Authors: Matinlinna J. P. , Areva S. , Lassila L. V. J. , Vallittu P. K.
Published: September 2004

The aim of this investigation was to study the siloxane, SiOSi, film formation on Ti substrate by using mono‐, bis‐ and tris‐aminosilanes. The ultimate goal was to obtain a smooth, well‐organized and stable siloxane film with suitable surface energy. Such films are expected to perform well in adhering resins to dental metal alloys when the films contain reactive functional groups. Aminosilanes were prepared as 0.5 vol.% solutions in dilute ethanol (50 vol.% ethanol in deionized water), with their natural pH of ∼ 9. The substrates were silanized in two ways: silane was allowed to react at room temperature or was cured for 1 h at 110°C. The surface characterization was carried out by reflectance–absorbance Fourier transform infrared spectroscopy (RA‐FTIR), x‐ray photoelectron spectroscopy (XPS), contact angle measurement and atomic force microscopy (AFM). Siloxane film thickness measurements were not made. According to spectral analysis, all silanes indicated covalent bond formation with titanium. SiOTi and SiOSi bonds were clearly seen in the spectra, suggesting that chemical retention had taken place. After curing at elevated temperature, the spectral bands seemed to be stronger than those on samples cured at room temperature. Curing of hydrolyzed silanes at elevated temperature seemed to enhance the siloxane layer formation, derived from aminosilanes, on the Ti substrate. This might have an influence on the hydrolytic stability of organosilane‐promoted adhesion between Ti and dental resins. Copyright © 2004 John Wiley & Sons, Ltd.
Friction coefficient mapping using the atomic force microscope
Authors: Breakspear S. , Smith J. R. , Nevell T. G. , Tsibouklis J.
Published: September 2004

A friction coefficient map of the surface of an immiscible polymer blend has been constructed using data obtained with the atomic force microscope. Spatially resolved friction coefficients, obtained from gradients of linear plots of frictional force versus applied load, were used to construct the map, with corresponding frictional forces being derived from lateral force data and the lateral spring constant. Values of the friction coefficient were confirmed using an Si3N4/Si3N4 couple, for which literature values were available. Excellent agreement with the literature was observed through the use of this method. Copyright © 2004 John Wiley & Sons, Ltd.
Electrochromic nickel oxide films made by reactive r.f. sputtering from different targets
Authors: Ottaviano L. , Pennisi A. , Simone F.
Published: September 2004

We describe the preparation and optical–electrical characterization of thin electrochromic layers based on nickel oxide (NiOx). These layers were deposited by reactive radiofrequency (r.f.) sputtering from nickel or nickel oxide targets, maintaining the r.f. power and varying the oxygen flow in a gas mixture of Ar and O2 from 5% up to 30%. The Ni/O ratio in the deposited thin films was determined by Rutherford backscattering spectroscopy (RBS) and the microstructure was investigated by x‐ray diffraction. The deposition rate was found to be strongly dependent on the type of target used. The electrochromic behaviour in aqueous alkaline electrolyte (0.1 N KOH solution) was investigated by electrochemical cyclization. Samples deposited by the NiO target exhibited the lowest N/O ratio (0.5) and the highest value of intercalated charge (∼4.9 × 10−2 mC cm−2 nm−1). Among the same samples the highest value of the intercalated charge was found for those deposited at low oxygen flow, but these samples exhibit the smallest reversible changes in optical absorption in the wavelength range 330–1200 nm.

Samples deposited by the nickel target do not exhibit significant variations in the value of the exchanged charge; the measured Ni/O ratio indicates a stoichiometry closer to NiO. We also observed the switching behaviour by analysing the films in cyclic time mode at a fixed wavelength. The commutation response time is estimated by measurement under the application of a step waveform potential. Copyright © 2004 John Wiley & Sons, Ltd.
Scanning force microscopy study of the morphology of spin‐cast molecular‐imprinted nylon thin films
Authors: Maier Petra , Werner‐Allen Jonathan , Gibson Ursula J. , Richter Asta , BelBruno Joseph J.
Published: September 2004

The morphology of thin, selectively imprinted films of Nylon‐6 was investigated by scanning force microscopy. Four amino acids were used as template molecules in the spin‐cast films. Film thickness ranged from 2 µm to 500 nm, depending on the nylon and template concentration in the casting solution. The thin‐film properties, including the presence of nanometer‐ to micrometer‐sized pores, are clearly associated with the imprinting process. The larger features observed by scanning force microscopy are attributed to amino acid clustering during the casting process. Copyright © 2004 John Wiley & Sons, Ltd.
Some Physical and Chemical Properties of Starch Isolates of Cassava Genotypes
Authors: Charles Albert L. , Chang Yung‐Ho , Ko Wen‐Ching , Sriroth Klanarong , Huang Tzou‐Chi
Published: September 2004

Cassava starches (Manihot esculenta Crantz) were prepared from tubers of Kaesetsart 50 (KU50), Rayong 5, Hanatee and KMUL 36‐YOO2 (YOO2) and their physicochemical properties studied using the Rapid Visco Analyser (RVA), differential scanning calorimetry (DSC) and rheometry. Amylose content was determined by iodine potentiometric titration (IPT) and gel permeation chromatography (GPC). Starch contents of the tubers varied from 34.2 to 35.1% and protein and fiber contents in the starches varied from 0.8 to 1.1% and 0.6 to 0.8%, respectively. The cassava starches contained 0.06–0.12% lipid and 0.7% to 0.9% ash. Amylose content determined by IPT (15.9 to 22.4%) had higher positive correlation with peak viscosity, breakdown and gel consistencies (R2 = 0.835, 0.772, 0.859), respectively, whereas GPC (18.1 to 25.3%) showed high correlation with setback (R2 = 0.923) and ΔH (R2 = 0.579). The onset gelatinization temperatures varied from 59.7–64.4°C, and KU50 exhibited highest ΔH of 13.7 J/g. Hanatee and YOO2 formed clear gels with higher peak viscosities, setback and gel consistency viscosities attributed to their higher amylose contents. Retrogradation of KU50 and Rayong 5 tended to be more severe on cooling and formed opaque gels, showing higher resistance to shearing, properties attributed to recrystallized amylopectin fractions.
Grafting of Poly(Methacrylic Acid) on Starch and Poly(Vinyl Alcohol)
Authors: Beliakova Margarita K. , Aly Amal A. , Abdel‐Mohdy Fikry A.
Published: September 2004

Grafting of methacrylic acid (MAA) on starch, poly(vinyl alcohol) (PVA), and a mixture of starch and PVA, using a potassium persulfate/ sodium thiosulfate redox initiation system was carried out. Polymerization was studied with respect to graft yield, homopolymer formation and total conversion. These polymerization criteria were found to depend largely on the concentration of both MAA and initiators, duration and method of polymerization.

The results reveal a number of interesting points which reflect the impact of the condition of the treatment. The main product of the polymerization reaction [poly(MAA)‐starch/PVA graft copolymer] was formed and precipitated during polymerization and can be easily separated by filtration as pure product.

Application of these copolymers to cotton fabric was also carried out to evaluate the suitability of such modified products as sizing agents.
Xenobiotic substances such as PCB mixtures (Aroclor 1254) and TBT can influence swimming behavior and biotransformation activity (GST) of carp (Cyprinus carpio)
Authors: Schmidt Katja , Steinberg Christian E. W. , Pflugmacher Stephan , Staaks Georg B. O.
Published: September 2004

Different groups of carp were treated with polychlorinated biphenyl (PCB) or tributyltin (TBT), and possible effects of the chemicals on the swimming behavior of the carp were examined using the BehavioQuant system. By evaluating quantitative behavioral parameters of the animals, it became evident that exposure to high concentrations of chemicals (organotin, 7 μg L−1, or polychlorinated biphenyl, 22 μg L−1) severely affected the carp, causing a significant change in their swimming speed. TBT stress led to a rapid decrease in mean swimming activity. A decrease in the preferred swimming depth was observed in TBT‐ and PCB‐exposed fish. Animals exposed to PCB reduced their mean daily activity and increased their mean swimming speed in the nighttime during the second week of exposure. Therefore, our findings imply that the fish were adapted to cope with the chemicals after the second week of exposure. Furthermore, our results showed that low concentrations (TBT, 0.3 and 2 μg L−1, or PCB, 14 μg L−1) did not significantly alter any quantified parameters of swimming behavior. In addition, the direct effects of chemicals on enzyme activity (GST) were determined. Measurement of soluble glutathione‐S‐transferase activity of fish liver or gills showed a significant elevation after exposure to PCB (0.1 or 22 μg L−1) or TBT (0.8 or 7 μg L−1). We had to conclude that the two different end points tested generally are useful as biomarkers of exposure and for investigations of energy resources in organisms under the influence of toxic stress. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 460–470, 2004.
Assessing cytotoxicity of photosensitized transformation products of 2,4,6‐trinitrotoluene (TNT) and atrazine with freshwater microbial assemblages
Authors: Zeng Kui , Hwang Huey‐Min , Zhang Yi , Cook Sean
Published: September 2004

In this study of riboflavin‐sensitized photolysis of 2,4,6‐trinitrotoluene (TNT), the final photoproducts were found to include 2‐amino‐4,6‐dinitrotoluene, 4‐amino‐2,6‐dinitrotoluene, and 3,5‐dinitroaniline. After exposure to TNT (10 mg/L) for 90 min, in a river water sample there was inhibition of the viability count of heterotrophic bacterial assemblages by 28.3% and 24.3% and of bacterial heterotrophic mineralization of glucose by 99.5% and 93.6% relative to the light control and dark control groups, respectively. After exposure separately to 10 mg/L 2‐amino‐4,6‐dinitrotoluene, 4‐amino‐2,6‐dinitrotoluene, or 3,5‐dinitroaniline, the viability count of heterotrophic bacterial assemblages was enhanced by 30.0%, 98.2%, and 148.7%, respectively, relative to the TNT group in light and by 12.2%, 40.2%, and 36.5%, respectively, relative to TNT group in dark. After exposure to the same aforementioned test chemicals, heterotrophic activity of bacterial assemblages was inhibited by 75.7%, 72.4%, and 56.0%, respectively, relative to light control group, and there were no significant changes in the dark. A similar study was conducted with atrazine (10 mg/L). The main products of atrazine riboflavin–sensitized phototransformation include desethylatrazine (DEA) and desisopropylatrazine (DIA). It was found that DEA and DIA did not inhibit microbial heterotrophic activity. However, after 72 h the viable count was enhanced by 52.8% and 63.3% in the DEA and DIA exposure groups, respectively, in comparison to the control. These results suggested that photosensitized transformation decreased TNT and atrazine cytotoxicity to microbial assemblages in the natural water. Photoproducts of atrazine–DEA and –DIA, and of TNT could become growth substrates for bacterial assemblages in natural water. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 490–496, 2004.