bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of poly(ethylene terephthalate) containing epoxy‐functionalized polyhedral oligomeric silsesquioxane
Authors: Yoon Kwan Han , Polk Malcolm B , Park Jae Hong , Min Byung G , Schiraldi David A
Published: November 2004

Poly(ethylene terephthalate) (PET) containing epoxy‐functionalized polyhedral oligomeric silsesquioxane (POSS) was prepared by melt‐mixing and in situ polymerization methods. The melt‐mixed composite showed phase separation while the in situ polymerized composite did not, based on SEM characterization. During melt mixing, the reaction between the epoxy groups of POSS and hydroxyl groups of PET occurred, based on DSC results. DSC results on the in situ polymerization product showed formation of a lower‐melting component compared with PET. The tensile strength and modulus of the melt‐mixed composite fiber decreased compared with those properties of PET, whereas those of the in situ polymerized composite showed slightly higher values than PET despite the relatively small amounts (1 wt%) of POSS used. Dynamic mechanical analysis results showed an increase in storage modulus for the in situ polymerized composite of POSS and PET compared with PET over the temperature range of 40 °C to 140 °C. Copyright © 2004 Society of Chemical Industry
Polyethylenimine‐grafted and HSA‐immobilized poly(GMA–MMA) affinity adsorbents for bilirubin removal
Authors: Yakup Arıca M , Yalçın Emine , Bayramoǧlu Gülay
Published: November 2004

The epoxy‐group‐containing microspheres from cross‐linked glycidyl methacrylate and methyl methacrylate, poly(GMA–MMA), were prepared by suspension polymerisation. The epoxy groups of the poly(GMA–MMA) microspheres were used for grafting with an anionic polymer polyethylenimine (PEI) to prepare non‐specific affinity adsorbents (poly(GMA–MMA)–PEI) for bilirubin removal. The specificity of the poly(GMA–MMA)–PEI adsorbent to bilirubin was further increased by immobilization of human serum albumin (HSA) via adsorption onto PEI‐grafted poly(GMA–MMA) adsorbent. Various amounts of HSA were immobilized on the poly(GMA–MMA)–PEI adsorbent by changing the medium pH and initial HSA concentration. The maximum HSA content was obtained at 68.3 mg g−1 microspheres. The effects of pH, ionic strength, temperature and initial bilirubin concentration on the adsorption capacity of both adsorbents were investigated in a batch system. Separation of bilirubin from human serum was also investigated in a continuous‐flow system. The bilirubin adsorption on the poly(GMA–MMA)–PEI and poly(GMA–MMA)–PEI–HSA was not well described by the Langmuir model, but obeyed the Freundlich isotherm model. The poly(GMA–MMA)–PEI affinity microspheres are stable when subjected to sanitization with sodium hydroxide after repeated adsorption–desorption cycles. Copyright © 2004 Society of Chemical Industry
Particle size and morphology of poly[styrene‐co‐(butyl acrylate)]/nano‐silica composite latex
Authors: Li Hua , You Bo , Gu Guangxin , Wu Limin , Chen Guodong
Published: November 2004

Nanocomposite latex with nano‐silica of varying particle sizes was prepared via in situ polymerization and investigated by submicron particle size analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier‐transform infrared spectrometry (FTIR) and Raman spectrometry. It was found that nanocomposite latex exhibited a core–shell structure with nano‐silica particles enwrapped, resulting in an increase in the latex particle size. The smaller the nano‐silica particles, the more were embedded in each latex particle. The increase in the particle size of latex depended not only on the particle size of nano‐silica, but also on the number of nano‐silica particles in each latex particle. Copyright © 2004 Society of Chemical Industry
Quantifying adsorption of heparin on a PVC substrate using ATR‐FTIR
Authors: Harada Nikolas S , Oyama Helena T , Bártoli Julio R , Gouvêa Douglas , Cestari Idágene A , Hui Wang S
Published: November 2004

The surface modification of poly(vinyl chloride) (PVC) tubing by heparin was performed to increase its blood compatibility. A solution of benzalkonium heparinate was used in the treatment of two types of plasticized PVC. The modification of the PVC surface was monitored after various treatment conditions, and quantitative results were obtained by using ATR‐FTIR spectroscopy. The treatment times and the PVC type have a strong influence on the observed amount of heparin. A partial removal (20–30 %) of heparin was observed after rinsing the PVC surface with a 0.9 wt% NaCl aqueous solution. The more flexible PVC tubing, having a lower Tg, had a higher concentration of heparin. Final heparin concentrations on the PVC surfaces were found to be in the range 1–17 µg cm−2. Copyright © 2004 Society of Chemical Industry
Vertex and edge expansion properties for rapid mixing
Authors: Montenegro Ravi
Published: November 2004

We show a strict hierarchy among various edge and vertex expansion properties of Markov chains. This gives easy proofs of a range of bounds, both classical and new, on chi‐square distance, spectral gap and mixing time. The 2‐gradient is then used to give an isoperimetric proof that a random walk on the grid [k]n mixes in time O*(k2n). © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2005
The effect of venlafaxine on ongoing and experimentally induced pain in neuropathic pain patients: a double blind, placebo controlled study
Authors: Yucel A. , Ozyalcin S. , Talu G. Koknel , Kiziltan E. , Yucel B. , Andersen O.K. , Arendt‐Nielsen L. , Disci R.
Published: November 2004

Background and aim The aim of this randomized double blind placebo controlled study was to investigate the effectiveness and the safety of venlafaxine XR 75 and 150 mg on ongoing pain and on quantitative sensory tests in 60 patients with neuropathic pain for 8 weeks.

Methods Evaluation parameters consisted of ongoing pain intensity (VAS), patient satisfaction, side effects, global efficacy and tolerance. Quantitative sensory measurements taken from the affected area before and after the drug treatment included pin‐prick hyperalgesia, allodynia, detection and pain thresholds to electrical and heat stimuli, temporal summation of repetitive electrical and heat stimuli.

Results A total of 55 patients completed the study. VAS scores decreased significantly compared to the baseline measurements in all groups. There was no significant difference between the groups regarding pain intensity and escape medication. The areas of allodynia and pin‐prick hyperalgesia decreased significantly in venlafaxine groups compared to the placebo. There was no significant difference between the groups regarding the detection thresholds (electrical and heat). The pain threshold and the summation threshold to electrical stimuli and the summation threshold to heat stimuli increased significantly following treatment in both venlafaxine groups. In addition, the degree of the temporal summation to electrical and heat stimuli decreased significantly following treatment in both venlafaxine groups compared to the placebo.

Conclusion The study showed significant effect of venlafaxine in the manifestations of hyperalgesia and temporal summation, but not on the ongoing pain intensity. Furthermore, the quantitative sensory tests provided complementing information to the clinical measures.
Update on Nonpharmacologic Approaches to Relieve Labor Pain and Prevent Suffering
Authors: Simkin Penny , Bolding April
Published: November 2004

The control of labor pain and prevention of suffering are major concerns of clinicians and their clients. Nonpharmacologic approaches toward these goals are consistent with midwifery management and the choices of many women. We undertook a literature search of scientific articles cataloged in CINAHL, PUBMED, the Cochrane Library, and AMED databases relating to the effectiveness of 13 non‐pharmacologic methods used to relieve pain and reduce suffering in labor. Suffering, which is different from pain, is not an outcome that is usually measured after childbirth. We assumed that suffering is unlikely if indicators of satisfaction were positive after childbirth. Adequate evidence of benefit in reducing pain exists for continuous labor support, baths, intradermal water blocks, and maternal movement and positioning. Acupuncture, massage, transcutaneous electrical nerve stimulation, and hypnosis are promising, but they require further study. The effectiveness of childbirth education, relaxation and breathing, heat and cold, acupressure, hypnosis, aromatherapy, music, and audioanalgesia are either inadequately studied or findings are too variable to draw conclusions on effectiveness. All the methods studied had evidence of widespread satisfaction among a majority of users.
The Neuromatrix Theory of Pain: Implications for Selected Nonpharmacologic Methods of Pain Relief for Labor
Authors: Trout Kimberly K.
Published: November 2004

Women experience the pain of labor differently, with many factors contributing to their overall perception of pain. The neuromatrix theory of pain provides a framework that may explain why selected nonpharmacologic methods of pain relief can be quite effective for the relief of pain for the laboring woman. The concept of a pain “neuromatrix” suggests that perception of pain is simultaneously modulated by multiple influences. The theory was developed by Ronald Melzack and represents an expansion beyond his original “gate theory” of pain, first proposed in 1965 with P. D. Wall. This article reviews several nonpharmacologic methods of pain relief with implications for the practicing clinician. Providing adequate pain relief during labor and birth is an important component of caring for women during labor and birth.
Framing as Path Dependence
Authors: GOLD NATALIE , LIST CHRISTIAN
Published: November 2004

A framing effect occurs when an agent's choices are not invariant under changes in the way a decision problem is presented, e.g. changes in the way options are described (violation of description invariance) or preferences are elicited (violation of procedure invariance). Here we identify those rationality violations that underlie framing effects. We attribute to the agent a sequential decision process in which a “target” proposition and several “background” propositions are considered. We suggest that the agent exhibits a framing effect if and only if two conditions are met. First, different presentations of the decision problem lead the agent to consider the propositions in a different order (the empirical condition). Second, different such “decision paths” lead to different decisions on the target proposition (the logical condition). The second condition holds when the agent's initial dispositions on the propositions are “implicitly inconsistent,” which may be caused by violations of “deductive closure.” Our account is consistent with some observations made by psychologists and provides a unified framework for explaining violations of description and procedure invariance.
Seroepidemiology of varicella-zoster virus antibodies among health-care workers and day-care-centre workers
Authors: LERMAN Y. , CHODICK G. , TEPPER S. , LIVNI G. , ASHKENAZI S.
Published: November 2004

Inclusion of live varicella vaccine in the routine occupational health vaccination schedule requires knowledge of the natural immunity to varicella zoster virus (VZV) among high-risk occupations. This study aims were to evaluate VZV antibody positivity among health-care workers (HCWs) and day-care-centre workers (DCWs) and to assess its association with potential risk factors. Three groups of workers were tested for VZV antibody positivity: hospitals and community clinic HCWs (n=335), DCWs (n=117) and blue-collar workers as controls (n=121). The total VZV antibody positivity was 94·4%. There was no significant difference in VZV antibody positivity among study groups. DCWs had the lowest VZV seroprevalence (90·9%, 95% CI 85·7–96·1) and controls the highest (96·6%, 95% CI 93·2–99·9). This high VZV antibody positivity suggests that no special occupational measures are indicated in health-care or day-care occupational settings in Israel. On-going monitoring of the natural immunity to VZV is necessary to detect trends over time.
The influence of competition and vaccination on the coexistence of two pneumococcal serotypes
Authors: ZHANG Y. , AURANEN K. , EICHNER M.
Published: November 2004

Streptococcus pneumoniae (pneumococcus) is one of the most important bacterial pathogens and a leading cause of mucosal infections (e.g. otitis media) and various forms of serious diseases (e.g. pneumonia, meningitis, bacteraemia) in developing and developed countries. Based on the polysaccharide capsule, there are at least 90 different pneumococcal serotypes, which may compete with each other to colonize the nasopharynx. Newly developed protein–polysaccharide conjugated vaccines have been shown to provide protection against disease caused by the serotypes included in the vaccine, and also against colonization (carriage). It is feared that yet uncommon, but nonetheless pathogenic serotypes which have been suppressed by competition, may become more prevalent in carriage and disease after large-scale use of conjugate vaccines. In this paper, we use transmission models of pneumococcal carriage to study how competition and vaccination influence the coexistence of two serotypes. According to our results, direct (physical) competition between two pneumococcal serotypes only influences colonization if the duration of naturally acquired immunity is short. By contrast, indirect (antibody-mediated) competition is of influence only if naturally acquired immunity is long lasting. Vaccination reduces the prevalence of the target serotype – an effect that is enforced by the presence of directly competing bacteria. The emergence of a non-target serotype after vaccination is only observed if bacteria compete directly. These results emphasize the importance of studying whether bacteria compete directly or indirectly and for how long people are protected in order to assess the long-term effects of sero-competition.
A one-year survey of candidemia in Belgium in 2002
Authors: SWINNE D. , WATELLE M. , SUETENS C. , MERTENS K. , FONTEYNE P.-A. , NOLARD N.
Published: November 2004

A total of 211 episodes of bloodstream yeast infections in 207 patients, hospitalized in 28 Belgian hospitals participating in a National Surveillance Program, were evaluated. A total of 81% of the patients were more than 50 years of age. Candida albicans was the cause of infections in 55% of patients, 22% were due to C. glabrata and 13% to C. parapsilosis. The most common predisposing factors were antibacterial therapy (42%), residence in an intensive care unit (32·9%) and presence of an intravascular catheter (29·7%). Most patients had more than one predisposing factor. Fluconazole alone or in association with another antifungal agent was the treatment of choice for 89·7% of the cases. In vitro susceptibility testing of the isolates revealed that 99% were susceptible to amphotericin B, 95% to 5-fluorocytosine, 82% to fluconazole and 69% to itraconazole. Resistance to azoles was more common among C. glabrata isolates in the elderly. We conclude that the frequency of C. albicans infection is decreasing in Belgium and this is associated with the emergence of other species, most notably, C. glabrata.
Kognitive und körperliche Aktivität
Authors: Oswald Wolf D.
Published: November 2004

Zusammenfassung: Eine Analyse des aktuellen Forschungsstandes zeigt, dass lebenslang erhöhte kognitive Anforderungen einher gehen mit einem selteneren und auch späteren Auftreten von Demenzerkrankungen. In Bezug auf die Auswirkungen regelmäßiger körperlicher Aktivitäten auf das Auftreten demenzieller Erkrankungen zeigen sich die in der Literatur berichteten Befunde zwar teilweise widersprüchlich, scheinen jedoch auf einen positiven Einfluss hinsichtlich spezifischer kognitiver Funktionen sowie exekutiver Gedächtnisleistungen hinzuweisen. Die Ergebnisse der Literaturrecherche werden anschließend mit denjenigen der SimA-Studie verglichen, in der gezeigt werden konnte, dass die Kombination aus Psychomotorik- und Gedächtnistraining auch langfristig einerseits einen positiven Einfluss auf den kognitiven Status ausübt und andererseits das Risiko einer Demenzerkrankung deutlich vermindert. Schließlich wird die protektive Wirkung kombinierter Interventionsmaßnahmen vor dem Hintergrund neuerer neurophysiologischer Beobachtungen diskutiert.
Bedingungen der Erhaltung und Förderung von Selbstständigkeit im höheren Lebensalter (SimA)
Authors: Rupprecht Roland , Oswald Wolf D. , Fricke Christine
Published: November 2004

Zusammenfassung: Das Erzbistum Bamberg, das Bistum Eichstätt und das katholische Bildungswerk der Diözese Linz in Oberösterreich bilden seit 1996, auf der Grundlage der SimA-Trainingsmaterialien, Kursleiter aus, die zahlreiche Trainingsgruppen mit inzwischen mehreren Tausend Senioren durchgeführt haben. In Zusammenarbeit mit den kirchlichen Trägern führte das Institut für Psychogerontologie zwei Evaluierungsstudien durch. In Bayern konnten dabei 392 Personen (Alter: 44-88 Jahre) aus 29 Gruppen im Bereich der Erzdiözese Linz 668 Personen (Alter: 47-93 Jahre) aus 46 Gruppen in die Untersuchung einbezogen werden, Die Auswertung zeigt, dass sich sowohl das allgemeine Befinden als auch die subjektive körperliche Fitness der Teilnehmer durch das Training signifikant verbessert haben. Daneben berichteten die Teilnehmer, dass sich ihre vor dem Training beklagten Gedächtnisstörungen deutlich verringert hätten. Dieses Ergebnis lässt sich durch die objektiven Befunde zum Kurzzeit- und Langzeitgedächtnis bestätigen. Auch hier fanden sich signifikante Verbesserungen. Ähnlich positive Befunde lassen sich in der Zufriedenheit mit dem Training und in der subjektiven Einschätzung der Nützlichkeit erkennen.
Welche Rolle spielen proaktive Interferenzen zur Erklärung von Altersdifferenzen in der Gedächtnisspanne?
Authors: Titz Cora , Behrendt Jörg , Hasselhorn Marcus
Published: November 2004

Zusammenfassung: Der Befund geringerer Gedächtnisspannen älterer im Vergleich zu jüngeren Erwachsenen gilt als gut belegt. Als Erklärung werden Kapazitätseinbußen des Arbeitsgedächtnisses (AG) diskutiert. Ein Aufgabenbeginn mit langen (absteigend), statt wie üblich mit kurzen Sequenzen (aufsteigend), scheint jedoch eine Aufhebung von Altersunterschieden zu bewirken, was auf verringerte proaktive Interferenzen bzw. eine Entlastung kognitiver Hemmungsfähigkeiten zurückgeführt wird ( Lustig, May & Hasher, 2001 ). Altersunterschiede in der Gedächtnisspanne würden somit eher eine geringere Hemmungseffizienz als Kapazitätseinbußen reflektieren. Eine Studie an 60 jüngeren (18-35 Jahre) und älteren Erwachsenen (58-84 Jahre) mit vier Versionen einer Ziffernspannenaufgabe (vorwärts und rückwärts, auf- und absteigend) bestätigt zwar eine Abhängigkeit der Spannenmaße vom Ausmaß proaktiver Interferenzen. Altersunterschiede bleiben aber entgegen der Erwartung Lustig et al.'s (2001) auch bei modifizierter Darbietung bestehen.
Visual Information Processing in Augmented Reality: Some Aspects of Background Motion
Authors: Menozzi Marino , Koga Kazuo
Published: November 2004

We assessed discomfort, time and number of saccades for reading a text superimposed to a moving background. When background moved in the main directions of reading (left to right or top to bottom), discomfort was rated significantly lower than when background moved in the opposite directions. Neither time for reading nor number of saccades are affected by background motion. We therefore conclude that increased arousal might be responsible to cope with effects of background motion, resulting in an increased stress and rising discomfort when background moves opposite to main directions of reading. The findings suggest that reading in Augmented Reality for mobile use must be considered as a robust process. However, load may be increased and cause complaints in a prolonged reading task.
Detailed Analyses of Ganzfeld Phenomena as Perceptual Events in Stimulus-Reductive Situations
Authors: Tsuji Keiichiro , Hayashibe Keikichi , Hara Masatoshi , Kato Yoshinobu
Published: November 2004

Experiment 1 reexamined in detail conscious experiences in Ganzfeld situations with homogeneous light (red, green, or blue). Subjects were instructed to report everything, including phenomena attributed to the external world (colour, brightness, space) and those of the self (somatosensory experience, body movement, and emotion). The reports were richer in the red-light condition. Naïve subjects reported a larger variety of events than sophisticated subjects. In Experiment 2 pupillary responses were recorded while the subjects were exposed to a Ganzfeld at two different levels of illumination. Pupillary size for high illumination decreased with time and then recovered to the initial level, while for low illumination it remained constant. Subjective brightness correlated with pupillary size. Experiment 3 revealed a temporal pattern of spatial events. The findings obtained are discussed in relation to the ontogenetic process of visual space perception and emotion.
Validierung und Normierung von kindgerechten, standardisierten Bildmotiven aus dem International Affective Picture System
Authors: Müller Bodo , Winter Britta , Schürkens Anette , Herpertz-Dahlmann Beate , Herpertz Sabine
Published: November 2004

Zusammenfassung: Fragestellung: Ziel der vorliegenden Untersuchung war die Validierung und Normierung einer Auswahl von Bildmotiven aus dem International Affective Picture System von Lang ( CSEA-NIMH, 1999 ; Lang et al., 1999 ) bezüglich der Dimensionen Arousal und Valenz an 57 Jungen und 63 Mädchen im Alter zwischen sechs und zwölf Jahren. Methodik: 18 Bildmotive mit jeweils sechs positiven, sechs negativen und sechs neutralen Reizen wurden Kindern im Alter zwischen sechs und zwölf Jahren präsentiert. Die Kinder bewerteten mit Hilfe des Self-Assessment-Manikin (SAM; Lang et al., 1980 ; Bradley et al., 1994 ), einer visuellen Analogskala, die Bildmotive in Bezug auf die Dimensionen Valenz und Arousal. Ergebnisse: Kinder im Alter zwischen sechs und zwölf Jahren sind in der Lage, die dargebotenen Bildmotive ihrem Inhalt nach zu erkennen und diese den Dimensionen Valenz und Arousal adäquat zuzuordnen. Schlussfolgerungen: Mit unserer Auswahl aus dem International Affective Picture System von Lang steht eine Anzahl von standardisierten Bildmotiven zur Verfügung, die zur Affektinduktion z.B. bei psychophysiologischen und bildgebenden Untersuchungen in der Altersgruppe von sechs bis zwölf Jahren geeignet sind.
Die Wirksamkeit von Stimulanzien-Retardpräparaten bei Kindern und Jugendlichen mit ADHD - eine systematische Übersicht
Authors: Sevecke Kathrin , Döpfner Manfred , Lehmkuhl Gerd
Published: November 2004

Zusammenfassung: Stimulanzien sind das Mittel der Wahl zur pharmakologischen Behandlung einer Aufmerksamkeits-/Hyperaktivitätsstörung. Jedoch ist die Wirkdauer von schnell freisetzenden Präparaten oft nicht ausreichend. Mittlerweile wurden verschiedene retardierte Methylphenidat-, aber auch Amphetaminformen entwickelt, um die Probleme einer mehrfach täglichen Einnahme zu minimieren. Der Artikel stellt die klinischen Studien zu Wirksamkeit, Wirkdauer und Nebenwirkungsprofil verschiedener Stimulanzienformen dar. In der klinischen Anwendung sind die neuen Retard-Produkte wirkungsvolle Alternativen. Eine kontinuierliche mehrstufige Freisetzung des Wirkstoffs über den Tag verteilt nach einmaliger Medikamentengabe bietet Vorteile. Allerdings müssen Nebenwirkungen durch die verlängerte Wirkungsdauer genau beobachtet werden. Eine genauere Anpassung an die jeweiligen Erfordernisse der verschiedenen Tagesabschnitte und -bedürfnisse der Kinder und Jugendlichen ist schwierig. Die Erprobung von Titrierungsschemata unter Einbeziehung von schnell und verzögert freisetzenden Präparaten bleibt eine Aufgabe zukünftiger Forschung.
A model study of the influence of aerosol size and chemical properties on precipitation formation in warm clouds
Authors: Roelofs Geert‐Jan , Jongen Suzanne
Published: November 2004

We present simulations of size‐resolved cloud drop activation, condensational growth, and collision/coalescence performed with a cloud microphysics parcel model. The study investigates the efficiency of precipitation formation in a warm cumulus cloud with emphasis on the timescale of precipitation formation and on the amount of precipitation produced and examines the response of these parameters to modifications of aerosol size and chemical properties at different updraft velocities. Both parameters affect the lifetime of a cloud, but it depends on environmental conditions whether their responses have similar or opposite influences. In relatively clean clouds (with a cloud drop number concentration below ∼200 cm−3) the growth rate of precipitation drops and the precipitation water content decrease with increasing aerosol abundance, whereas in more polluted clouds (∼400 cm−3 and more) precipitation formation is delayed, but the amount of precipitation increases. Precipitation formation depends in a complex way on the updraft speed, especially in polluted clouds that are characterized by a relatively dispersed drop size distribution. In clouds with updraft speeds between 20 and 50 cm/s, an increase of the aerosol abundance causes a slight suppression of the growth of precipitation drops, but this effect is more pronounced in clouds with smaller or larger updraft speeds. The results suggest that global aerosol‐climate models may simulate the second indirect effect more consistently when the dispersion of the drop size distribution is accounted for.
Using chemistry transport modeling in statistical analysis of stratospheric ozone trends from observations
Authors: Guillas S. , Stein M. L. , Wuebbles D. J. , Xia J.
Published: November 2004

Since the implementation of the international controls on ozone‐depleting chemicals, an important focus in studies of stratospheric ozone has been on the detection of a turnaround in the downward trend. The usual statistical assumption of a piecewise linear representation of the trend does not account for the chemistry involved. Because the actual change is not expected to be piecewise linear, we model the trend using results from a University of Illinois at Urbana‐Champaign two‐dimensional (UIUC 2‐D) chemical transport model of the global atmosphere. As part of the analysis, ozone observations are considered in the spectral domain using a cohesive data set from the SBUV‐SBUV/2 satellite system at northern midlatitudes. In this study we find that the new model is better at capturing the long‐range correlation of the data than assuming a linear trend. We also compare several statistical trend models, based either on a regression on a linear trend or on the Effective Equivalent Stratospheric Chlorine (EESC). Including a constant halocarbon emissions run of the UIUC 2‐D model in the regression, the controlled EESC approach shows the best fit. The smallest future data length necessary to detect a recovery with a certain probability is obtained in this latter case.
Why Kp is such a good measure of magnetospheric convection
Authors: Thomsen M. F.
Published: November 2004

The 3‐hour magnetic activity index, Kp, is widely used for measuring the level of magnetospheric activity, and many magnetospheric properties are known to correlate with it. The common denominator for these different properties is the strength of the magnetospheric convection electric field, the large‐scale electric field imposed across the magnetosphere by the flow of the magnetized solar wind past the Earth. While the relationship between Kp and the global convection field has long been known, the question of why the relationship exists has apparently not been addressed. In this report, it is proposed that because Kp is derived from magnetic variations obtained at subauroral stations, it is extremely sensitive to the latitudinal distance to the equatorial edge of the auroral region, where the principal causative currents flow. Since the auroral region maps to the plasma sheet in the magnetosphere, motion of the inner edge of the plasma sheet, which is determined by the strength of the convection field, causes significant changes in Kp. Thus, through its dependence on the latitude of the auroral current region, Kp can be viewed as a direct monitor of the strength of magnetospheric convection, explaining the success of previous Kp‐dependent models of the global electric field.
Designing generalized statistical ensembles for numerical simulations of biopolymers
Authors: La Penna Giovanni , Morante Silvia , Perico Angelo , Rossi Gian Carlo
Published: November 2004

Conformational properties of polymers, such as average dihedral angles or molecular α-helicity, display a rather weak dependence on the detailed arrangement of the elementary constituents (atoms). We propose a computer simulation method to explore the polymer phase space using a variant of the standard multicanonical method, in which the density of states associated to suitably chosen configurational variables is considered in place of the standard energy density of states. This configurational density of states is used in the Metropolis acceptance/rejection test when configurations are generated with the help of a hybrid Monte Carlo algorithm. The resulting configurational probability distribution is then modulated by exponential factors derived from the general principle of the maximal constrained entropy by requiring that certain average configurational quantities take preassigned (possibly temperature dependent) values. Thermal averages of other configurational quantities can be computed by using the probability distributions obtained in this way. Moments of the energy distribution require an extra canonical sampling of the system phase space at the desired temperature, in order to locally thermalize the configurational degrees of freedom. As an application of these ideas we present the study of the structural properties of two simple models: a bead-and-spring model of polyethylene with independent hindered torsions and an all-atom model of alanine and glycine oligomers with 12 amino acids in vacuum.
Growth dynamics and intracluster reactions in Ni+(CO2)n complexes via infrared spectroscopy
Authors: Walker N. R. , Walters R. S. , Grieves G. A. , Duncan M. A.
Published: November 2004

Ni + ( CO 2 ) n ,  Ni+(CO2)nAr, Ni+(CO2)nNe, and Ni+(O2)(CO2)n complexes are generated by laser vaporization in a pulsed supersonic expansion. The complexes are mass-selected in a reflectron time-of-flight mass spectrometer and studied by infrared resonance-enhanced photodissociation (IR-REPD) spectroscopy. Photofragmentation proceeds exclusively through the loss of intact CO2 molecules from Ni+(CO2)n and Ni+(O2)(CO2)n complexes, and by elimination of the noble gas atom from Ni+(CO2)nAr and Ni+(CO2)nNe. Vibrational resonances are identified and assigned in the region of the asymmetric stretch of CO2. Small complexes have resonances that are blueshifted from the asymmetric stretch of free CO2, consistent with structures having linear Ni+–O=C=O configurations. Fragmentation of larger Ni+(CO2)n clusters terminates at the size of n=4, and new vibrational bands assigned to external ligands are observed for n⩾5. These combined observations indicate that the coordination number for CO2 molecules around Ni+ is exactly four. Trends in the loss channels and spectra of Ni+(O2)(CO2)n clusters suggest that each oxygen atom occupies a different coordination site around a four-coordinate metal ion in these complexes. The spectra of larger Ni+(CO2)n clusters provide evidence for an intracluster insertion reaction assisted by solvation, producing a metal oxide-carbonyl species as the reaction product.
The accuracy of diffusion quantum Monte Carlo simulations in the determination of molecular equilibrium structures
Authors: Lu Shih-I
Published: November 2004

For a test set of 17 first-row small molecules, the equilibrium structures are calculated with Ornstein–Uhlenbeck diffusion quantum Monte Carlo simulations guiding by trial wave functions constructed from floating spherical Gaussian orbitals and spherical Gaussian geminals. To measure performance of the Monte Carlo calculations, the mean deviation, the mean absolute deviation, the maximum absolute deviation, and the standard deviation of Monte Carlo calculated equilibrium structures with respect to empirical equilibrium structures are given. This approach is found to yield results having a uniformly high quality, being consistent with empirical equilibrium structures and surpassing calculated values from the coupled cluster model with single, double, and noniterative triple excitations [CCSD(T)] with the basis sets of cc-pCVQZ and cc-pVQZ. The nonrelativistic equilibrium atomization energies are also presented to assess performance of the calculated methods. The mean absolute deviations regarding experimental atomization energy are 0.16 and 0.21 kcal/mol for the Monte Carlo and CCSD(T)/cc-pCV(56)Z calculations, respectively.
Effect of electric fields on electron thermal transport in laser-produced plasmas
Authors: Goncharov V. N. , Li G.
Published: November 2004

Gradients in the laser-induced electric field introduce ponderomotive terms in the current flow, heat flux, and electric stress tensor. The transport coefficients, previously derived in the limit Z≫1, are obtained for an arbitrary ion charge Z using the Chapman–Enskog method [S. Chapman and T. G. Cowling, The Mathematical Theory of Non-Uniform Gases (Cambridge University Press, Cambridge, 1970)]. It is shown that the ponderomotive terms significantly modify the thermal transport near the laser turning points and the critical surface.
Nonlinear interaction of a Gaussian intense laser beam with plasma: Relativistic modulational instability
Authors: Pajouh H. Hakimi , Abbasi H. , Shukla P. K.
Published: November 2004

The nonlinear interaction of a circularly polarized Gaussian intense laser pulse in a collisionless cold plasma with immobile ions is analyzed. The laser beam is assumed to have a nonuniform intensity distribution (along its wave front) in a plane transverse to the direction of propagation. To properly include the nonuniformity of the laser field, the wave equation is integrated over the transversal distribution. In this way, the mean transversal effects are taken into account. In this frame of work the relativistic modulational instability (RMI) of a long pulse is analyzed. A general dispersion relation is derived and solved. Plots of the temporal growth rate as a function of the laser beam power and the modulation wave number are presented and compared with the case when a uniform intensity distribution along the laser wave front is assumed. It is found that the nonuniformity of the laser beam has a significant effect on the characteristics of RMI. It is shown as a conclusion that the effect of transverse distribution in the growth rate reduction, in comparison with the case when it was neglected, becomes more significant for shorter wavelength of the RMI and stronger pump waves.
First-order mean spherical approximation for inhomogeneous fluids
Authors: Tang Yiping
Published: November 2004

The first-order mean-spherical approximation (FMSA) [Y. Tang, J. Chem. Phys., 118, 4140 (2003)] is extended to the studies of inhomogeneous fluids by combining with Rosenfeld’s perturbative method [Y. Rosenfeld, J. Chem. Phys. 98, 8126 (1993)]. In the extension, the key input—direct correlation function of FMSA—is applied to constructing the free energy density functional. Preserving its high fidelity at the bulk limit, the FMSA shows satisfactory performance for Yukawa fluids near hard and attractive walls. The results are better than or comparable to several other theories reported before for the geometry. The FMSA is found, in particular, more satisfactory than the traditional mean-field theory for predicting density profiles around hard walls. The FMSA is also compared with the full MSA for inhomogeneous fluids, showing no appreciable differences. The inhomogeneous FMSA goes successfully through the self-consistency test for reproducing the radial distribution function of the bulk Yukawa fluid. As far as the computation is concerned, the FMSA can be executed much faster than any nonmean-field theories, and the speed is virtually identical to that of the mean-field theory.
Experimental evidence of distance-dependent diffusion coefficients of a globular protein observed in polymer aqueous solution forming a network structure on nanometer scale
Authors: Masuda Akiko , Ushida Kiminori , Nishimura Goro , Kinjo Masataka , Tamura Mamoru , Koshino Hiroyuki , Yamashita Koichi , Kluge Thomas
Published: November 2004

The distance dependence of the diffusion coefficient (DDDC) of a globular protein (cytchrome c) in aqueous hyaluronan (HA) solution, which is a model system for extracellular matrices (ECMs), was measured by a combination of three kinds of spectroscopic measurements of diffusion coefficients, the time and space samplings of which are different. The results of the three methods are plotted against the diffusion distance derived from the consideration of each experimental condition. Due to the characteristic morphology of HA with an effective mesh structure, the proteins showed two extreme diffusion modes: (1) short (<10 nm) diffusion with rare contact with polymer chains; (2) long (>100 nm) diffusion significantly disrupted by polymer chains showing an ≈30% reduction in diffusion coefficient. The transition from the short diffusion to the long one occurs in a very narrow range (10–100 nm) of diffusion distance and this unique character of HA realizing anomalous diffusion should provide suitable environments for various bioactivities when involved in ECM.
Surface hopping simulation of the vibrational relaxation of I2 in liquid xenon using the collective probabilities algorithm
Authors: Bastida Adolfo , Cruz Carlos , Zúñiga José , Requena Alberto , Miguel Beatriz
Published: November 2004

A surface hopping simulation of the vibrational relaxation of highly excited I2 in liquid xenon is presented. The simulation is performed by using the collective probabilities algorithm which assures the coincidence of the classical and quantum populations. The agreement between the surface hopping simulation results and the experimental measurements for the vibrational energy decay curves at different solvent densities and temperatures is shown to be good. The overlap of the decay curves when the time axis is linearly scaled is explained in terms of the perturbative theory for the rate constants. The contribution of each solvent atom to the change of the quantum populations of the solute molecule is used to analyze the mechanism of the relaxation process.
Efficient white light emission in conjugated polymer homojunctions
Authors: Ho Guey-Kai , Meng Hsin-Fei , Lin Shi-Chang , Horng Sheng-Fu , Hsu Chain-Shu , Chen Lai-Cheng , Chang Shu-Mei
Published: November 2004

We study polymer light-emitting diodes with a homojunction, i.e., junction between two layers with the same host material. One layer is poly (9,9-dioctylfluorene-2,7-diyl) (PFO) host blended with a small amount of poly (2-methoxy-5 (2'-ethyl-hexyloxy)-1,4-phenylene vinylene), another layer is either pure PFO or PFO host blended with green-emitting polyfluorene copolymers. Such homojunction devices are solution processed and show efficient white light emission. The peak luminance 3000cd∕m2 is reached at 10V with Internationale de L’Eclairage (CIE) coordinate (0.34, 0.34).
Nonlinear dust acoustic waves in magnetized two-ion-temperature dusty plasmas
Authors: Lin Mai-mai , Duan Wen-shan
Published: November 2004

A Zakharov–Kuznetsov (ZK) equation, a modified ZK equation and a coupled ZK equation for small but finite amplitude dust acoustic waves in a magnetized two-ion-temperature dusty plasma with dust size distribution have been obtained in this paper. It seems that the soliton velocity for a dusty plasma with power law dust size distribution is larger than that of monosized dusty plasmas. The solitary waves with opposite polarity particles are investigated as well. It is found that rarefactive and compressive solitary waves exist in this system which depend on different conditions. On the other hand, the solitary wave is unstable at certain regions when the wave numbers of the transverse perturbations satisfies the conditions of 0<K<Kc and 0<L<Lc.
Effect of layer thickness on the electrostatic potential in InGaN quantum wells
Authors: Stevens M. , Bell A. , McCartney M. R. , Ponce F. A. , Marui H. , Tanaka S.
Published: November 2004

High-resolution electron holography in the transmission electron microscope has the capability to profile the spatial variation of the electrostatic potential in semiconductors, at subnanometer resolution. We have used electron holography to measure the internal electrostatic potential and fields across quantum wells with well thickness ranging from 2to10nm, at a nominal indium concentration of x=0.13. A comparison of field strength versus well width shows a precipitous drop in field strength beyond 6nm. A close look at the microstructure of the widest well shows additional contrast at the growth interface. An explanation consistent with both observations supports the possibility of compositional fluctuations in combination with strain relaxation at the early stages of growth of the quantum well.
Kelvin probe force microscopy on corona charged oxidized semiconductor surfaces
Authors: Lägel B. , Ayala M. D. , Schlaf R.
Published: November 2004

We present results demonstrating that Kelvin probe force microscopy (KPFM) can be used with high accuracy for corona charge aided oxide thickness mapping. In our experiments, corona charge layers of varying density were deposited onto the surface of thermally oxidized silicon wafers with different oxide thicknesses. After deposition, the surface potentials of the samples were characterized using both the standard Kelvin probe method and KPFM. Comparison of the surface potentials measured by both techniques showed that the values are in excellent agreement, and that only insignificant discharging of the corona charge layer occurred during the topography scan necessary in KPFM measurements.
Raman study of Bi site-occupancy effect on orientation and polarization in Bi4Ti3O12 thin films
Authors: Yau C. Y. , Palan R. , Tran K. , Buchanan R. C.
Published: November 2004

Our Raman study of 0–6mol% Bi excess Bi4Ti3O12 (BIT) films implies that symmetry breaking effect occurs in 0mol% Bi excess film, which is restored to BIT symmetry in 2–6mol% Bi excess films. The “rigid layer” mode at 59.22cm−1 implies a higher stability of Bi in the Bi2O2 layer than the perovskite layer and that Bi has high preference to incorporate into the Bi2O2 layer. Increasing Bi incorporation in the A site enhances the Jahn–Teller distortion of TiO6 octahedra and the c orientation. This implies that doping by an ion without an outer orbital like La can decrease the TiO6 distortion, change the orientation, and tilt the polarization vector.
Periodicity and alignment of large-scale carbon nanotubes arrays
Authors: Wang Y. , Rybczynski J. , Wang D. Z. , Kempa K. , Ren Z. F. , Li W. Z. , Kimball B.
Published: November 2004

Intensive studies have been carried out on controlling the periodicity and alignment of large-scale periodic arrays of carbon nanotubes (CNTs) using plasma-enhanced chemical vapor deposition. Catalytic dots are first prepared by self-assembly of polystyrene spheres on chromium-coated silicon substrates. Preparation parameters for CNTs growth including temperature, thickness of catalytic dots, plasma current intensity, and pregrowth plasma etching time are fine tuned and analyzed to achieve optimal combinations. High-quality aligned CNTs arrays with long-range periodicity and controlled diameters have been achieved. The good periodicity and alignment are critical for their applications such as photonic crystals, negative index of refraction, etc.
Bending of dislocations in GaN during epitaxial lateral overgrowth
Authors: Gradečak S. , Stadelmann P. , Wagner V. , Ilegems M.
Published: November 2004

Bending of dislocations in GaN during epitaxial lateral overgrowth (ELO) has been experimentally studied using transmission electron microscopy. The orientational dependence of the dislocation energy factor K has been calculated on the basis of anisotropic elasticity theory for different types of perfect dislocation in GaN. Image forces act on dislocations during the growth and dislocations bend to achieve the minimum energy. Bending behavior depends on a dislocation type and we show that the measured bending angles correspond to the calculated energy minima. The results allow us to quantitatively discuss the most advantageous ELO GaN mask direction for the largest dislocation density reduction.
Pot culture studies of the copper and molybdenum content of certain pasture plants
Authors: Moore CWE
Published: November 2004

Erodium cygnorum, Medicago denticulata, and Hordeum leporinum were grown in pots on soils from toxaemic jaundice enzootic areas and from reputedly non-affected areas. The copper and molybdenum content of each species at flowering was determined. The mean copper content of the plants grown on soils from the enzootic areas did not differ from that of the plants grown on soils from reputedly non-affected areas. The copper-molybdenum ratio of the plants varied widely. The values obtained for plants grown on soils from the enzootic areas were no higher than those obtained for plants grown on other soils. There was a significant difference between the copper contents of the three species. Although the copper content was not abnormally high in any of the species examined, the differences are great enough to indicate that variations in the botanical composition of the pasture may considerably influence the amount of copper ingested by the grazing animal.
Yellow dwarf of tobacco in Australia. IV. Some host plants of the virus
Authors: Hill AV
Published: November 2004

Yellow dwarf of tobacco was transmitted by grafting to six species of the Solanaceae. The results of preliminary transmission experiments with the insect vector indicated that three commonly occurring weeds were probably autumn-spring host plants of the virus.