bluuebunny/crossref_metadata_2025 huggingface dataset:
Ein Vergleich unterschiedlicher Erfassungsmethoden der frühkindlichen Emotionalität * Die Studie wurde durch die Deutsche Forschungsgemeinschaft gefördert (Kennziffern: Pa 543/2-1,2-2,2-3,2-4).
Authors: Pauli-Pott Ursula , Mertesacker Bettina , Beckmann Dieter
Published: April 2005

Zusammenfassung: Das Konstrukt der «frühkindlichen Emotionalität» (synonym: affektive Temperamentsmerkmale) wird in der entwicklungspsychopathologischen, der entwicklungspsychologischen und der kinder- und jugendpsychiatrischen Theorienbildung und Forschung häufig verwendet. Die valide Erfassung des Konstrukts ist jedoch nicht unproblematisch. Elternurteile und naturalistische Verhaltensbeobachtungen in der Mutter-Kind-Interaktion können durch elterliche Merkmale verzerrt sein, standardisierte Beobachtungsroutinen sind oftmals nicht hinreichend validiert. Hier werden drei unterschiedliche Methoden im Hinblick auf drei affektive Temperamentsdimensionen zu drei Zeitpunkten im ersten Lebensjahr untersucht. Die Fragestellungen betreffen Aspekte der Validität der Verfahren und die Assoziation der Messwerte mit Merkmalen der Bezugsperson, ihrer Depressivität, Ängstlichkeit und Schulbildung. Untersucht wurde eine Stichprobe von 101 gesunden Erstgeborenen und deren primärer Bezugsperson im Alter der Säuglinge von 4, 8 und 12 Monaten. Erhoben wurden die positive Emotionalität, die negative Emotionalität und die Rückzugstendenz/Ängstlichkeit des Säuglings im Elternfragebogen, in Verhaltensbeobachtungen in der Mutter-Kind-Interaktion und in standardisierten Untersuchungen. Mit nur zwei Ausnahmen korrelierten die drei Verfahren zu allen drei Zeitpunkten in allen Dimensionen statistisch signifikant. Zufriedenstellende diskriminante Validität zeigten vor allem die standardisierten Beobachtungsroutinen. Die Messwerte aus dem Elternfragebogen korrelierten oftmals mit den mütterlichen Merkmalen, wobei diese Korrelationen unabhängig von den Korrelationen mit den Beobachtungsdaten waren. Die Elternurteile enthalten demnach objektive Komponenten und davon unabhängige subjektive Komponenten.
Ambulante Behandlung der Adipositas im Kindes- und Jugendalter
Authors: Munsch Simone , Biedert Esther , Roth Binia , Speck Vanessa , Roth Sandra
Published: April 2005

Zusammenfassung: Fragestellung: Adipositas im Kindesalter ist ein zunehmendes Problem in Industrie- und immer mehr auch in Entwicklungsländern. Die Prävalenzraten steigen bis zu 15% in den USA und bis zu 10% in Europa. Der vorliegende Artikel gibt einen Überblick über die aktuelle Forschungslage sowie über medizinische und psychosoziale Probleme, die mit kindlicher Adipositas verbunden sind. Es folgt eine umfassende Zusammenstellung und Beurteilung verschiedener Behandlungsmöglichkeiten, wobei detailliert auf die Behandlungsmerkmale und die Wirksamkeit von ambulanten Behandlungsansätzen bei kindlicher Adipositas eingegangen wird. Methode: Medline- und PsycINFO-Suche von 1966 bis 2003. Schlussfolgerungen: Die Aussagekraft und Generalisierbarkeit der Untersuchungsergebnisse wird insbesondere durch die begrenzte Vergleichbarkeit der Studien eingeschränkt. Implikationen zur Behandlung kindlicher und jugendlicher Adipositas und weiterer Forschung werden diskutiert.
Temperature independence of carbon dioxide supersaturation in global lakes
Authors: Sobek Sebastian , Tranvik Lars J. , Cole Jonathan J.
Published: April 2005

A growing body of evidence suggests that most of the world's lakes are supersaturated with CO2 and export significant amounts of CO2 to the atmosphere. Still, the temperature dependence of the partial pressure of CO2 (pCO2) in lakes, which is the main driver of carbon flux across the air‐water interface, has not yet been assessed. Analyzing a global‐scale database of 4902 lakes, we show that temperature is not an important regulator of pCO2 in lakes. Instead, the concentration of dissolved organic carbon (DOC), a substrate for microbial respiration, explains significant variation in lake pCO2. Contrary to what may be expected from the physiological constraints of temperature, effects of climate change on the carbon balance of lakes may not be due to rising temperature per se, but rather to climatically induced changes in the export of DOC from terrestrial soils to aquatic habitats.
Lava fingerprinting using paleomagnetism and innovative X‐ray fluorescence spectroscopy: A case study from the Coso volcanic field, California
Authors: Pluhar Christopher J. , Coe Robert S. , Sampson Daniel E. , Glen Jonathan M. G. , Monastero Francis C. , Tanner S. Bruce
Published: April 2005

We demonstrate an efficient method of rigorously separating difficult‐to‐distinguish lavas into eruptive units based on paleomagnetic remanence direction and rapid X‐ray fluorescence spectroscopy (XRF) for Rb, Sr, Y, Zr, and Nb of polished paleomagnetic core samples (called PC XRF). Combined use of paleomagnetic remanence and PC XRF for lava fingerprinting allows correlation of individual eruptive units from one locality to another, permitting compilation of composite stratigraphy and paleomagentic measurement of relative vertical axis rotation of fault‐bounded blocks. We test this lava fingerprinting method on rocks from the Coso volcanic field, California, against similar fingerprinting using XRF analysis by established methods. Resulting unit definitions and correlations are the same by both XRF techniques when coupled with paleomagnetic data, but at great time and cost savings with PC XRF. PC XRF analysis is possible because (1) matrix and grain size effects are minimal for the element set analyzed, (2) moderately phyric to aphyric polished paleomagnetic cores are already homogenous on spatial scales of 2 cm, and (3) use of element ratios cancels out some analytical uncertainties as well as minimizes effects of concentration variations due to fractional crystallization. Paleomagnetic remanence direction is an indispensable part of fingerprinting because it distinguishes flows of similar chemistry and can also place constraints on the duration of emplacement of each eruptive unit.
The significance of the grasshopper effect on the atmospheric distribution of persistent organic substances
Authors: Semeena V. S. , Lammel Gerhard
Published: April 2005

Slowly degradable, semivolatile organic compounds (SOCs) may undergo more than one volatilization‐transport‐deposition cycle through the atmosphere (multi‐hopping). The significance of this process for the potential for long‐range transport (LRT) is addressed for the first time. We use a multicompartment model which in turn is based on a general circulation model. The results suggest that both transport by single‐hopping and multi‐hopping contribute significantly to LRT of DDT and γ‐HCH (lindane) and to accumulation in high latitudes. A larger fraction of the molecules transported by multi‐hopping than of the molecules transported by single‐hopping is deposited to the world's oceans. Multi‐hopping prevails in the boundary layer far from the source regions. However, single‐hopping contributes an almost equal amount to the deposition of DDT and γ‐HCH in the Arctic.
Evidence for melt lubrication during large earthquakes
Authors: Spray John G.
Published: April 2005

Rotary friction experiments have been performed on Westerly granite at start velocities of 2.0–4.0 m s−1, under loads of 250–500 N until the system stalls (up to ∼4 s). Interface temperature, velocity and force were measured at intervals of 0.2 milliseconds. The results show that kinetic friction increases in direct proportion to temperature up to a critical value Tcr, whereupon the system changes from boundary lubrication (slip strengthening) to hydrodynamic lubrication (slip weakening) with an associated decrease in friction and temperature. For Westerly granite Tcr is ∼1150°C. This corresponds to the melting point of feldspar, which constitutes ∼50% of the rock. If Tcr is exceeded in natural slip systems, which will depend on rock type, this can result in the generation of friction melt. Melt lubrication can explain the scaled energy of large earthquakes being 10 to 100 times more than that of small earthquakes.
Influence of the thermosphere on electromagnetic waves propagation: Application to GPS signal
Authors: Lilensten Jean , Delorme Philippe , Samouillan Sophie , Engel Elodie , Barthélémy Mathieu
Published: April 2005

We develop a model of wave propagation through the upper atmosphere taking into account the thermospheric collision frequencies and the Faraday rotation. We use this model to numerically test the effect of these collisions on the Global Positioning System (GPS) signal between 50 and 1000 km altitude. We study several characteristics of the GPS wave: ionospheric delay, dephasing, and variation of amplitude. We point out that the thermosphere influence is negligible, about 10−9 m on ionospheric delay, and may be considered as negligible on shorter‐frequency waves. This study is extended to satellite‐to‐satellite communications both for quiet and magnetic storm cases. In this case the influence on the wave is greater but remains very weak.
Field of an electric dipole impulse in a conducting medium: A full solution
Authors: Wu Chi‐Wei , Kan Yao‐Chiang , Lee Hung‐Mou
Published: April 2005

The impulse response from an infinitesimal electric dipole in a conducting medium is given in full. Behind the impulsive wave front, we split the electromagnetic field into a nonpropagating discharging static dipole field and call the remainder the wake. Large t asymptotic expansions of the field components of the wake to all orders at all distances are presented.
D‐Aspartate and NMDA, but not L‐aspartate, block AMPA receptors in rat hippocampal neurons
Authors: Gong Xiang‐Qun , Frandsen Anne , Lu Wei‐Yang , Wan Yudi , Zabek Rebecca L , Pickering Darryl S , Bai Donglin
Published: April 2005

The amino acid, D‐aspartate, exists in the mammalian brain and is an agonist at the N‐methyl‐D‐aspartate (NMDA) subtype of ionotropic glutamate receptors. Here, for the first time, we studied the actions of D‐aspartate on α‐amino‐3‐hydroxyl‐5‐methyl‐4‐isoxazolepropionate receptors (AMPARs) in acutely isolated rat hippocampal neurons.

In the presence of the NMDA receptor channel blocker, MK801, D‐aspartate inhibited kainate‐induced AMPAR current in hippocampal neurons. The inhibitory action of D‐aspartate on kainate‐induced AMPAR current was concentration‐dependent and was voltage‐independent in the tested voltage range (−80 to +60 mV).

The estimated EC50 of the L‐glutamate‐induced AMPAR current was increased in the presence of D‐aspartate, while the estimated maximum L‐glutamate‐induced AMPAR current was not changed. D‐aspartate concentration‐dependently shifted the dose–response curve of kainate to the right. Schild plot analysis indicated that D‐aspartate acts competitively to block AMPARs. The Kb for D‐aspartate was estimated to be 0.93 mM.

D‐Aspartate also blocked L‐glutamate‐induced current in Xenopus laevis oocytes that expressed recombinant homomeric AMPARs.

NMDA possessed similar inhibitory action on AMPARs. However, L‐aspartate had little inhibitory action on AMPARs.

D‐Aspartate, but not L‐aspartate, was found to reduce the amplitude of miniature excitatory postsynaptic current in cultured hippocampal neurons.

Our data are consistent with a model in which D‐aspartate directly competes with kainate and L‐glutamate in binding to the agonist binding site of AMPARs. The prevalence of D‐aspartate in the brain suggests a possible role of D‐aspartate in modulating AMPAR‐mediated fast excitatory synaptic transmission.

British Journal of Pharmacology (2005) 145, 449–459. doi:10.1038/sj.bjp.0706199
Artocarpol A stimulation of superoxide anion generation in neutrophils involved the activation of PLC, PKC and p38 mitogen‐activated PK signaling pathways
Authors: Kuan Yu‐Hsiang , Lin Ruey‐Hseng , Tsao Lo‐Ti , Lin Chun‐Nan , Wang Jih‐Pyang
Published: April 2005

Artocarpol A (ART), a natural phenolic compound isolated from Artocarpus rigida, stimulated a slow onset and long‐lasting superoxide anion generation in rat neutrophils, whereas only slightly activated the NADPH oxidase in a cell‐free system.

Pretreatment of neutrophils with pertussis toxin (1 μg ml−1), 50 μM 2′‐amino‐3′‐methoxyflavone (PD 98059), or 1 μM 1,4‐diamino‐2,3‐dicyano‐1,4‐bis(2‐aminophenylthio)butadiene (U0126) had no effect on ART‐stimulated superoxide anion generation. ART (30 μM) did not induce extracellular signal‐regulated kinase (ERK) phosphorylation.

4‐(4‐Fluorophenyl)‐2‐(4‐methylsulfinylphenyl)‐5‐(4‐pyridyl)‐1H‐imidazole (SB 203580) markedly attenuated the ART‐stimulated superoxide anion generation (IC50 value of 4.3±0.3 μM). Moreover, ART induced p38 mitogen‐activated PK (MAPK) phosphorylation and activation.

The superoxide anion generation in response to ART was also substantially inhibited in a Ca2+‐free medium, and by pretreatment with 1 μM 1‐[6‐((17β‐3‐methoxyestra‐1,3,5(10)‐trien‐17‐yl)amino)hexyl]‐1H‐pyrrole‐2,5‐dione (U‐73122) and 100 μM 2‐aminoethyldiphenyl borate (2‐APB). ART (30 μM) stimulated the [Ca2+]i elevation in the presence or absence of external Ca2+, and also increased the D‐myo‐inositol 1,4,5‐trisphosphate formation.

2‐[1‐(3‐Dimethylaminopropyl)‐1H‐indol‐3‐yl]‐3‐(1H‐indol‐3‐yl)‐maleimide (GF 109203X) greatly inhibited the ART‐stimulated superoxide anion generation (IC50 value of 7.8±1.0 nM). ART increased the recruitment of PKC‐α, ‐βI, and ‐βII to the plasma membrane of neutrophils, and stimulated Ca2+‐dependent PKC activation in the cytosol preparation.

ART induced the phosphorylation of p47phox, which was attenuated by GF 109203X. Moreover, ART evoked the membrane association of p47phox, which was inhibited by GF 109203X and SB 203580.

These results indicate that the ART stimulation of superoxide anion generation involved the activation of p38 MAPK, PLC/Ca2+, and PKC signaling pathways in rat neutrophils.

British Journal of Pharmacology (2005) 145, 460–468. doi:10.1038/sj.bjp.0706205
Protein kinase C‐αmediates TNF release process in RBL‐2H3 mast cells
Authors: Abdel‐Raheem Ihab T , Hide Izumi , Yanase Yuhki , Shigemoto‐Mogami Yukari , Sakai Norio , Shirai Yasuhito , Saito Naoaki , Hamada Farid M , El‐Mahdy Nagh A , Elsisy Alaa El‐Din E , Sokar Samya S , Nakata Yoshihiro
Published: April 2005

To clarify the mechanism of mast cell TNF secretion, especially its release process after being produced, we utilized an antiallergic drug, azelastine (4‐(p‐chlorobenzyl)‐2‐(hexahydro‐1‐methyl‐1H‐azepin‐4‐yl)‐1‐(2H)‐ phthalazinone), which has been reported to inhibit TNF release without affecting its production in ionomycin‐stimulated RBL‐2H3 cells.

Such inhibition was associated with the suppression of an ionomycin‐induced increase in membrane‐associated PKC activity rather than the suppression of Ca2+influx, suggesting that PKC might be involved in TNF release process.

To see whether conventional PKC family (cPKCs) are involved, we investigated the effects of a selective cPKC inhibitor (Gö6976) and an activator (thymeleatoxin) on TNF release by adding them 1 h after cell stimulation. By this time, TNF mRNA expression had reached its maximum. Gö6976 markedly inhibited TNF release, whereas thymeleatoxin enhanced it, showing a key role of cPKC in TNF post‐transcriptional process, possibly its releasing step.

To determine which subtype of cPKCs could be affected by azelastine, Western blotting and live imaging by confocal microscopy were conducted to detect the translocation of endogenous cPKC (α,βI andβII) and transfected GFP‐tagged cPKC, respectively. Both methods clearly demonstrated that 1 μMazelastine selectively inhibits ionomycin‐triggered translocation ofαPKC without acting onβI orβIIPKC.

In antigen‐stimulated cells, such a low concentration of azelastine did not affect eitherαPKC translocation or TNF release, suggesting a functional link betweenαPKC and the TNF‐releasing step.

These results suggest thatαPKC mediates the TNF release process and azelastine inhibits TNF release by selectively interfering with the recruitment ofαPKC in the pathway activated by ionomycin in RBL‐2H3 cells.

British Journal of Pharmacology(2005)145, 415–423. doi:10.1038/sj.bjp.0706207
Mechanisms of the protective effects of urocortin on coronary endothelial function during ischemia–reperfusion in rat isolated hearts
Authors: García‐Villalón Angel Luis , Amezquita Yesika María , Monge Luis , Fernández Nuria , Climent Belén , Sánchez Ana , Diéguez Godofredo
Published: April 2005

Urocortin is a vasodilator peptide related to corticotrophin‐releasing factor, which may protect endothelial function during coronary ischemia–reperfusion (I–R). The aim of this study was to study the mechanisms of this protective effect.

Hearts from Sprague–Dawley rats were isolated and perfused at constant flow and then exposed to 15 min global zero‐flow ischemia, followed by 15 min reperfusion. The relaxation to acetylcholine (10 nM–10 μM) was recorded after pre‐constriction of the coronary vasculature with U46619 (100–300 nM) in ischemic–reperfused or time‐control hearts.

After I–R, the coronary relaxation to acetylcholine was reduced and this reduction was attenuated by treatment with urocortin (10 pM), administered before ischemia and during reperfusion.

This urocortin‐induced improvement of the relaxation to acetylcholine was not modified by tetraethylammonium (10 mM), blocker of Ca2+ dependent‐potassium channels; glibenclamide (10 μM), blocker of KATP channels; Nw‐nitro‐L‐arginine methyl ester (L‐NAME, 100 μM), blocker of nitric oxide synthesis; or meclofenamate (10 μM), blocker of cyclooxygenase, but it was abolished by chelerythrine (3 μM), blocker of protein kinase C (PKC).

These results suggest that urocortin may protect coronary endothelial function during I–R by activation of PKC.

British Journal of Pharmacology (2005) 145, 490–494. doi:10.1038/sj.bjp.0706208
Effect of mast cell chymase inhibitor on the development of scleroderma in tight‐skin mice
Authors: Shiota Naotaka , Kakizoe Eiichi , Shimoura Keiko , Tanaka Tetsuya , Okunishi Hideki
Published: April 2005

Although the pathogenesis of scleroderma is not fully understood, activation of connective‐tissue‐type mast cells (CTMCs) has been implicated in various fibrotic diseases.

Our previous study showed that the number of CTMCs was markedly increased during fibrous proliferation in the skin of a scleroderma model, namely tight‐skin (Tsk) mice. Because mast cells express numerous bioactive factors, such as cytokines, growth factors, proteases, and others, it is crucial to identify the primary factors that may be involved in the pathogenesis of scleroderma. Our previous study also showed that a CTMC‐specific protease, chymase‐4, was selectively upregulated in accordance with the development of skin fibrosis in Tsk mice.

To further elucidate the role of chymase secreted from CTMCs, we evaluated the therapeutic effects of a synthetic chymase‐specific inhibitor, SUN‐C8257, on the development of skin fibrosis in Tsk mice. SUN‐C8257 (50 mg kg−1 day−1) was administered via intraperitoneal injection in 13‐week‐old Tsk mice for a period of 2 weeks.

Treatment with SUN‐C8257 significantly reduced chymase activity by 43% and the chymase‐4 mRNA level by 47%, and also decreased the thickness of the subcutaneous fibrous layer of Tsk mice by 42% compared with that of Tsk mice injected with vehicle.

Furthermore, immunohistochemical analysis revealed that transforming growth factor (TGF)‐beta1 staining in the fibrous layer of Tsk skin was markedly reduced by the treatment with SUN‐C8257. This chymase inhibitor may prevent the chymase‐dependent pathway that activates the latent TGF‐beta1 in fibrous tissue, and may exhibit beneficial effects that inhibit the development of fibrosis.

In conclusion, our results strongly support the assumption that CTMC‐derived chymase may play a key role in the pathogenesis of scleroderma.

British Journal of Pharmacology (2005) 145, 424–431. doi:10.1038/sj.bjp.0706209
Soft x-ray resonant magneto-optical Kerr effect as a depth-sensitive probe of magnetic heterogeneity: A simulation approach
Authors: Lee Ki-Suk , Jeong Dae-Eun , Kim Sang-Koog , Kortright J. B.
Published: April 2005

We report a noticeable depth sensitivity of soft x-ray resonant magneto-optical Kerr effect able to resolve depth-varying magnetic heterostructures in ultrathin multilayer films. For various models of depth-varying magnetization orientations in an ultrathin Co layer of realistic complex layered structures, we have calculated the Kerr rotation, ellipticity, intensity spectra versus grazing incidence angle ϕ, and their hysteresis loops at different values of ϕ for various photon energies hν’s near the Co resonance regions. It is found from the simulation results that the Kerr effect has a much improved depth sensitivity and that its sensitivity varies remarkably with ϕ and hν in the vicinity of the resonance regions. These properties originate from a rich variety of wave interference effects superimposed with noticeable features of the refractive and absorptive optical effects near the resonance regions. Consequently, these allow us to resolve depth-varying magnetizations and their reversals varying with depth in a single magnetic layer and allow us to distinguish interface magnetism from the bulk properties in multilayer films. In this paper, the depth sensitivity of the Kerr effect with an atomic-scale resolution is demonstrated and discussed in details in several manners with the help of model simulations for various depth-varying spin configurations.
Local existence of quasispherical space–time initial data
Authors: Sharples Jason
Published: April 2005

We consider the system of Einstein constraint equations in the special case when the spacelike 3-manifold is assumed to satisfy the quasispherical ansatz of Bartnik. We introduce two different time slicing conditions, under each of which we may view the resulting constraint equations as a parabolic∕elliptic∕ODE system of partial differential equations. We combine recent existence results for parabolic equations in Sobolev space with an iterative method to prove local existence results for the quasispherical Einstein constraint equations under the two different time slicing conditions.
Exact solutions of two complementary one-dimensional quantum many-body systems on the half-line
Authors: Hallnäs Martin , Langmann Edwin
Published: April 2005

We consider two particular one-dimensional quantum many-body systems with local interactions related to the root system CN. Both models describe identical particles moving on the half-line with nontrivial boundary conditions at the origin, but in the first model the particles interact with the delta interaction while in the second via a particular momentum dependent interaction commonly known as delta-prime interaction. We show that the Bethe ansatz solution of the delta-interaction model is consistent even for the general case where the particles are distinguishable, whereas for the delta-prime interaction it only is consistent and nontrivial in the fermion case. We also establish a duality between the bosonic delta- and the fermionic delta-prime model, and we elaborate on the physical interpretations of these models.
Electronic and magnetic structure of multilayered Cox=1,3,5 on Pd5(111) systems
Authors: Louzazna K. , Haroun A.
Published: April 2005

In the present work, the electronic structure and the magnetic behavior of multilayered Cox∕Pd5(111), where x=1, 3, and 5 monolayers, are investigated using the self-consistent tight-binding linear muttin-tin method with local-density approximation. Such artificially layered magnetic structures attract a great attention, because of their interesting physical properties, which are quite different from that of the bulks, and their potential device applications. At the interface, the Co–Pd spacing distance dCo–Pd is found to be close to the average ⟨d⟩Co–Pd of the bulk fcc Co and fcc Pd spacing. This is the reason for which all the investigated systems show a large Co magnetic moment at their interfaces (I). From a magnetic point of view, the multilayered magnetic films of Co exhibit a ferromagnetic interlayer and intralayer order, i.e., between the Co atoms in successive planes and in the same plane. The magnetic moments of the Co atoms at the interface (I) are found to be larger than that obtained for the magnetic atoms located at the central planes. Particularly, the monolayer of Co in the multilayered Co1∕Pd5(111) shows a magnetic moment (2.03μB) bigger than that of the isolated Co1 monolayer (1.97μB). The Palladium layers were slightly polarized (∼0.3μB) by the epitaxied magnetic films.
A combined zero electronic kinetic energy spectroscopy and ion-pair dissociation imaging study of the F2+(XΠg2) structure
Authors: Yang Jie , Hao Yusong , Li Juan , Zhou Chang , Mo Yuxiang
Published: April 2005

Rotationally resolved pulsed field ionization and zero electronic kinetic energy photoelectron spectra for the transition F2+(XΠg2)←F2(XΣg+1) have been recorded using the extreme ultraviolet coherence radiation. The vibrational energy spacings, rotational constants, and spin orbit coupling constants for the first three vibrational states of F2+(XΠg2) have been determined accurately. The first adiabatic ionization potential (IP) of F2 is determined as IP(F2)=126 585.7±0.5cm−1. To determine the threshold Etipp for ion-pair production of F2, the images of F−(S01) in the velocity mapping conditions have also been recorded at the photon energy of 126 751cm−1. Taking the Stark effect into account, the Etipp is determined as Etipp(F2)=126 045±8cm−1 (15.628±0.001eV). By combing the IP(F2) and the Etipp(F2) determined in this work and together with the reported ionization potential and electronic affinity of the F atom, the bond dissociation energies of F2 and F2+ are determined as D0(F2)=1.606±0.001eV and D0(F2+)=3.334±0.001eV, respectively.
Rotational spectrum, inversion, and geometry of 2,5-dihydrofuran⋯ethyne and a generalization about Z⋯H–C hydrogen bonds
Authors: Cole G. C. , Hughes R. A. , Legon A C.
Published: April 2005

The ground-state rotational spectra of nine isotopomers of a complex formed between 2,5-dihydrofuran and ethyne were recorded with a pulsed-jet, Fourier-transform microwave spectrometer. Rotational and centrifugal distortion constants were obtained for C4H6O⋯HCCH, C4H6O⋯DCCH, C4H6O⋯HCCD, C4H6O⋯DCCD, [3,4-D2]–C4H6O⋯HCCH, C4H6O⋯HC13CH, C4H6O⋯HCC13H, [2-C13]–C4H6O⋯HCCH, and [3-C13]–C4H6O⋯HCCH. The C13 substituted species were studied in their natural abundances. For the more abundant isotopomers, weak c-type transitions as well as strong a-type transitions were observed. The primary intermolecular binding was shown to consist of a hydrogen bond formed by the ethyne subunit acting as the proton donor and the O atom of 2,5-dihydrofuran as the proton acceptor. The complex has a plane of symmetry that includes the O atom and the ethyne subunit, with a pyramidal configuration at oxygen. A fit of the principal moments of inertia of all nine isotopomers under the assumption of unperturbed 2,5-dihydrofuran and ethyne geometries yielded the values r(O⋯H)=2.127(8)Å, ϕ=57.8(18)°, and θ=16.2(32)°, where ϕ is the angle made by the HCCH subunit at O and θ is the angular deviation of the O⋯H–C nuclei from collinearity. This geometry is compared with those obtained by ab initio calculations conducted with a range of basis sets and with electron correlation taken into account at the MP2 (Møller-Plesset second order) level of theory. A small inversion doubling (≈20–30kHz) of c-type transitions, well resolved only for the parent isotopomer and [3,4-D2]–C4H6O⋯HCCH, was attributed to a vibrational motion that inverts the configuration at oxygen. A one-dimensional model for this motion was used with a double minimum potential energy function of the type V(ϕ)=αϕ4+βϕ2 to estimate the observed separation ΔE01 of the lowest pair (v=0 and v=1) of associated energy levels. The predicted ΔE01 had the same magnitude as that deduced from the inversion doubling of the c-type transitions. The geometry of C4H6O⋯HCCH is compared with those other B⋯HCCH, where B is vinyl fluoride, oxirane, and thiirane. A rationalization of the angular geometries of various B⋯HX, where X=F, Cl, Br, or CCH, is presented.
Analytic controllability of time-dependent quantum control systems
Authors: Lan Chunhua , Tarn Tzyh-Jong , Chi Quo-Shin , Clark John W.
Published: April 2005

The question of controllability is investigated for a quantum control system in which the Hamiltonian operator components carry explicit time dependence which is not under the control of an external agent. We consider the general situation in which the state moves in an infinite-dimensional Hilbert space, a drift term is present, and the operators driving the state evolution may be unbounded. However, considerations are restricted by the assumption that there exists an analytic domain, dense in the state space, on which solutions of the controlled Schrödinger equation may be expressed globally in exponential form. The issue of controllability then naturally focuses on the ability to steer the quantum state on a finite-dimensional submanifold of the unit sphere in Hilbert space—and thus on analytic controllability. A relatively straightforward strategy allows the extension of Lie-algebraic conditions for strong analytic controllability derived earlier for the simpler, time-independent system in which the drift Hamiltonian and the interaction Hamiltonian have no intrinsic time dependence. Enlarging the state space by one dimension corresponding to the time variable, we construct an augmented control system that can be treated as time independent. Methods developed by Kunita can then be implemented to establish controllability conditions for the one-dimension-reduced system defined by the original time-dependent Schrödinger control problem. The applicability of the resulting theorem is illustrated with selected examples.
X-ray scattering study of the interactions between magnetic nanoparticles and living cell membranes
Authors: Koh Isaac , Cipriano Bani H. , Ehrman Sheryl H. , Williams Darryl N. , Pulliam Holoman Tracey R. , Martínez-Miranda L. J.
Published: April 2005

Magnetic nanoparticles (MNPs) have found increased applicability in drug delivery, cancer treatment, and immunoassays. There is a need for an improved understanding of how MNPs interact with living cell membranes in applied magnetic fields to use them effectively. The interactions between Escherichia coli (E. coli) and SiO2∕γ-Fe2O3 composite particles in magnetic fields were studied using x-ray scattering. Magnetic field strengths up to 423mT were applied to the samples to see the effects of the magnetic fields on the E. coli membranes in the presence of the magnetic particles in the cell cultures. X-ray scattering results from continuous cultures of E. coli showed two peaks, a sharp peak at q=0.528Å−1 (1.189nm) up to 362mT of magnetic field strength and a diffuse one at q=0.612Å−1 (1.027nm). The sharp peak was shifted to the smaller side of q when magnetic particles were added and the magnitude of the applied magnetic field strength was increased from 227to298mT, to 362mT, whereas the diffuse peak did not changed. A critical magnetic field strength where the sharp peak disappears was found at 362mT.
Tunneling dynamics of double proton transfer in formic acid and benzoic acid dimers
Authors: Smedarchina Zorka , Fernández-Ramos Antonio , Siebrand Willem
Published: April 2005

Direct dynamics calculations based on instanton techniques are reported of tunneling splittings due to double proton transfer in formic and benzoic acid dimers. The results are used to assign the observed splittings to levels for which the authors of the high-resolution spectra could not provide a definitive assignment. In both cases the splitting is shown to be due mainly to the zero-point level rather than to the vibrationally or electronically excited level whose spectrum was investigated. This leads to zero-point splittings of 375MHz for (DCOOH)2 and 1107MHz for the benzoic acid dimer. Thus, contrary to earlier calculations, it is found that the splitting is considerably larger in the benzoic than in the formic acid dimer. The calculations are extended to solid benzoic acid where the asymmetry of the proton-transfer potential induced by the crystal can be overcome by suitable doping. This has allowed direct measurement of the interactions responsible for double proton transfer, which were found to be much larger than those in the isolated dimer. To account for this observation both static and dynamic effects of the crystal forces on the intradimer hydrogen bonds are included in the calculations. The same methodology, extended to higher temperatures, is used to calculate rate constants for HH, HD, and DD transfers in neat benzoic acid crystals. The results are in good agreement with reported experimental rate constants measured by NMR relaxometry and, if allowance is made for small structural changes induced by doping, with the transfer matrix elements observed in doped crystals. Hence the method used allows a unified description of tunneling splittings in the gas phase and in doped crystals as well as of transfer rates in neat crystals.
A temperature-programed time-of-flight secondary ion mass spectroscopy study of intermixing of amorphous ethanol and heavy-water films at 15–200 K
Authors: Souda Ryutaro
Published: April 2005

On the basis of time-of-flight secondary ion mass spectrometry, the intermolecular interactions of amorphous ethanol and heavy-water films have been investigated in terms of the translational molecular diffusion, hydrogen-bond reorganization, and isotope scrambling. The morphology of the ethanol film (heavy-water film) changes at 120 K (165 K), and the isotope scrambling takes place between the ethanol and heavy-water molecules above 140 K. The intermixing of the layered binary films of ethanol and heavy water is induced at 120 K as a consequence of the increased mobility of the ethanol molecules but the mixing is incomplete at the molecular level. The complete mixing occurs above 140–150 K provided that the highly mobile water molecules emerge. It is concluded that the viscous liquid phase evolves above the conventional glass-transition temperatures (97 and 136 K for ethanol and heavy water, respectively), which is followed by the drastic morphological change (120 and 165 K) as a consequence of the increased fluidity of the films.
Internal dynamics features in the free jet rotational spectrum of the acetaldehyde-Kr molecular complex
Authors: Melandri S. , Favero P. G. , Caminati W. , Velino B.
Published: April 2005

The structure and the dynamics of internal motions in the complex formed between acetaldehyde and Kr are studied by free jet absorption microwave spectroscopy performed in the range 60–78GHz. The fourfold structure of each rotational line is evidence of the vibration-rotation coupling between the overall rotation of the complex, a tunneling motion of the Kr atom between two equivalent positions and the internal rotation of the methyl group in the acetaldehyde moiety. The four sets of transitions could be fitted with a coupled Hamiltonian which allows for the Coriolis interaction obtaining the energy separation between the vibrational energy levels related to the tunneling motion, while the observed splittings due to the methyl group internal rotation were analyzed independently with an appropriate model. The potential energy barriers for the tunneling motion and the internal rotation of the methyl group have been calculated and the interaction of the rare gas atom with the acetaldehyde moiety is reflected in the change of the V3 barrier to internal rotation in going from the molecule to the weakly bound complex.
Epitaxial and polycrystalline HfNx (0.8⩽x⩽1.5) layers on MgO(001): Film growth and physical properties
Authors: Seo H.-S. , Lee T.-Y. , Petrov I. , Greene J. E. , Gall D.
Published: April 2005

While many transition metal (TM) nitrides—including TiN, ZrN, and TaN—have been widely studied and are currently used as hard wear-resistant coatings, diffusion barriers, and optical coatings, little is known about a related TM nitride, HfN. Here, we report the results of a systematic investigation of the growth and physical properties of HfNx layers, with 0.80⩽x⩽1.50, deposited on MgO(001) by ultrahigh vacuum reactive magnetron sputtering at 650°C in mixed N2∕Ar discharges. HfNx layers with 0.80⩽x⩽1.20 crystallize in the B1–NaCl structure with a cube-on-cube epitaxial relationship to the MgO(001) substrate, while films with 1.24⩽x⩽1.50 contain a N-rich second phase. The relaxed bulk lattice parameter of HfNx(001) decreases only slightly with increasing N∕Hf ratio, ranging from 0.4543nm with x=0.80to0.4517nm with x=1.20. The room-temperature resistivity ρ of stoichiometric HfN(001) is 14.2μΩcm and ρ(x) increases with both increasing and decreasing x to 140μΩcm with x=0.80 and 26.4μΩcm with x=1.20. The hardness H and elastic modulus E of HfN(001) are 25.2 and 450GPa, respectively. H(x) initially increases for both over- and understoichiometric layers due to defect-induced hardening, while E(x) remains essentially constant. Single-phase HfNx(001) is metallic with a positive temperature coefficient of resistivity (TCR) between 50 and 300K and a temperature-independent carrier density. It is also superconducting with the highest critical temperature, 9.18K, obtained for layers with x=1.00. In the two phase regime, ρ ranges from 59.8μΩcm with x=1.24 to 2710μΩcm with x=1.50. TCR becomes positive with x⩾1.38, no superconducting transition is observed, and both H and E decrease.
Lattice Monte Carlo simulations of a charged polymer chain: Effect of valence and concentration of the added salt
Authors: Kłos J. , Pakula T.
Published: April 2005

The configurational properties of a single polyelectrolyte chain accompanied by counterions and added salt are simulated using the cooperative motion algorithm on the face-centered cubic lattice. In particular, a greater emphasis is put on the effect of valence zs and concentration of the added positive (negative) salt ions ns on the polymer behavior. This is achieved by inspecting two families of systems with widely varying numbers ns of monovalent (zs=1) or multivalent (zs=4) salt ions at two fixed reduced temperatures T*=0.5, 1. The calculations indicate that especially at the lower temperature the addition of some amount of multivalent salt has a tremendous impact on chain conformations compared to the situation with monovalent salt. Even for relatively low concentrations of the former, the mean radius of gyration ⟨s2⟩1∕2 and the mean end-to-end distance ⟨R2⟩1∕2 decrease sharply, i.e., the polymer exists in strongly collapsed forms. This reduction of polymer size is also accompanied by a drop in the system inner energy e* and the effective mean charge per monomer q*. The analysis of various pair-correlation functions gab(r) indicates that the latter effect—caused by condensation of ions onto the chain—is dominated by the multivalent ones. Furthermore, it is found that for zs=4, the uncondensed salt ions tend to group themselves into small clusters.
Molecular dynamics simulations of grafted polyelectrolytes on two apposing walls
Authors: Hehmeyer Owen J. , Stevens Mark J.
Published: April 2005

Molecular dynamics simulations of polyelectrolytes grafted to two apposing surfaces were performed. Bead-spring polymer models are used to treat flexible chains [e.g., sodium poly(styrene sulfonate)] and stiff chains (double-stranded DNA). The counterions are explicitly treated. The effect of the surface density of the grafted polymer, the chain length, and the gap width on the structure and the pressure were studied. Results are compared to experimental measurements and to simulations of polyelectrolyte brushes on a single surface. The density profiles exhibit a maximum not found in single surface data. The maximum is due to the brushes shrinking to avoid interpenetration.
Photostimulated luminescence from fluorochlorozirconate glass ceramics and the effect of crystallite size
Authors: Schweizer Stefan , Hobbs Linn W. , Secu Mihail , Spaeth Johann-Martin , Edgar Andrew , Williams Grant V. M. , Hamlin John
Published: April 2005

We report the results from a study of europium-doped fluorochlorozirconate glasses that have been thermally processed to induce nucleation and crystallization of BaCl2 crystallites. The resulting glass ceramics show a photostimulated luminescence (PSL) effect with a conversion efficiency which is up to 80% of that found in the commercial crystalline x-ray storage phosphor material BaFBr:Eu2+. Thermal processing for 20 min in the range 240–260 °C produces small (∼6–11nm) hexagonal BaCl2 crystallites, while temperatures in the range 270–290 °C lead to the formation and growth of larger (∼15–100nm) orthorhombic BaCl2 crystallites, as well as additional unidentified phases. We observe only weak PSL from glass ceramics containing hexagonal BaCl2 (∼0.1% conversion efficiency compared to BaFBr:Eu2+ at room temperature), but orthorhombic phase crystallites give rise to a much larger relative efficiency that increases with particle size, and reaches ∼80% for 100 nm diameter particles. The PSL is attributed to the excitation of electrons trapped as F centers in the BaCl2 crystallites, while the dependence on crystallite size is consistent with a PSL-inert surface shell of thickness ∼7nm surrounding the BaCl2 crystallites.
Ferroelectric properties of polycrystalline bismuth titanate films by Nd3+/W6+ cosubstitution
Authors: Li Wei , Yin Yuan , Su Dong , Zhu Jinsong
Published: April 2005

Bi 3.15 Nd 0.85 Ti 3 − x W x O 12 (x=0, 2%, 4%, 6%, and 8%) thin films were fabricated on ⟨111⟩Pt/Ti/SiO2/Si substrates by a chemical solution deposition technique. These films possessed random-oriented polycrystalline structure. Their grain size, Raman spectra, dielectric, hysteresis loops, switching, leakage current, fatigue, and retention, etc., were systemically investigated as a function of the W content. It is found that a low concentration of donor doping efficiently enhanced the ferroelectric nature and a high concentration of donor doping deteriorated the ferroelectric nature. The origin of the donor doping effect on the ferroelectric properties was discussed based on oxygen vacancies and Bi vacancies inside thin films.
Progress in AlInN–GaN Bragg reflectors: Application to a microcavity light emitting diode
Authors: Dorsaz J. , Carlin J.-F. , Gradecak S. , Ilegems M.
Published: April 2005

We report on the progress in the growth of highly reflective AlInN–GaN distributed Bragg reflectors deposited by metalorganic vapor phase epitaxy. Al1−xInxN layers with an In content around x∼0.17 are lattice-matched to GaN, thus avoiding strain-related issues in the mirror while keeping a high refractive index contrast of about 7%. Consequently, a reflectivity value as high as 99.4% at 450nm was achieved with a 40-pair crack-free distributed Bragg reflector. We measured an average absorption coefficient α[cm−1] in the AlInN–GaN Bragg reflectors of 43±14cm−1 at 450nm and 75±19cm−1 at 400nm. Application to blue optoelectronics is demonstrated through the growth of an InGaN–GaN microcavity light emitting diode including a 12-pair Al0.82In0.18N–GaN distributed Bragg reflector as bottom mirror. The device exhibits clear microcavity effects, improved directionality in the radiation pattern and an optical output power of 1.7mW together with a 2.6% external quantum efficiency at 20mA.
Formation and role of graphite and nickel silicide in nickel based ohmic contacts to n-type silicon carbide
Authors: Nikitina I. P. , Vassilevski K. V. , Wright N. G. , Horsfall A. B. , O’Neill A. G. , Johnson C. M.
Published: April 2005

Nickel-based contacts, deposited on 4H-SiC C-face substrates, were annealed at temperatures ranging from 800to1040°C and the phase composition of the contact layers analyzed by x-ray diffraction techniques. Ni2Si was identified as the dominant phase for annealing temperatures exceeding 925°C, with further increases in concentration with increasing temperature. At the highest annealing temperature of 1040°C, a 40nm thick nanocrystalline graphite film at the Ni2Si–SiC interface was discovered and its presence confirmed by Raman spectroscopy. The roles of the Ni2Si and graphite films in the formation of ohmic contacts were determined by their subsequent exclusion from the contact composition. Following deposition and annealing, the Ni2Si and graphite layers were etched away selectively and replaced with new metal films deposited at room temperature and without any annealing. Measurement of the current-voltage characteristics revealed that the ohmic nature of the contacts was preserved after removal of the Ni2Si and the graphite layers. It is concluded that the main reason for the conversion of Schottky to ohmic contacts during high-temperature annealing is a change of the electrical properties of the underlying SiC rather than being attributable to the presence of nickel silicides or graphite. It is proposed that a solid-state reaction between nickel and silicon carbide, similar to catalytic graphitization of carbon, may take place during Ni–SiC contact annealing at the temperature of 1040°C. This process may result in the creation of sufficient carbon vacancies in the near-interface region of the SiC to allow increased electron transport through the Schottky barrier.
Optimized detection of normal vibration modes of atomic force microscope cantilevers with the optical beam deflection method
Authors: Schäffer Tilman E. , Fuchs Harald
Published: April 2005

Recently, higher-order normal vibration modes of atomic force microscope cantilevers were utilized for functional imaging applications. Here, we present a detailed theoretical investigation of the sensitivities with which these modes are detected using the optical beam deflection method. The detection sensitivities depend strongly on the size and position of the focused optical spot. Optimization of the sensitivities is performed for the individual (transverse) normal modes. For the case that multiple normal modes need to be detected simultaneously, a universal sensitivity function is constructed. This function generates accurate values for the detection sensitivity as a function of spot diameter and mode number. Finally, different optimization strategies for the simultaneous detection of multiple normal modes are presented.
Electroabsorption spectroscopy of Ge∕Si self-assembled islands
Authors: El kurdi M. , Boucaud P. , Sauvage S. , Aniel F. , Fishman G. , Kermarrec O. , Campidelli Y. , Bensahel D. , Saint-Girons G. , Sagnes I. , Patriarche G.
Published: April 2005

We have performed an electroabsorption spectroscopy of Ge∕Si self-assembled islands simultaneously in the near-infrared and in the midinfrared spectral range. The investigated structure consists of self-assembled Ge∕Si islands embedded in a p-i-n junction. This active region is inserted into a 3-μm-thick Si0.98Ge0.02 waveguiding layer. Under a positive applied bias, the injected carriers give rise to a current-induced absorption resonant at 185 meV along with an enhanced transmission around 800 meV. The 185-meV resonance is polarized along the growth axis of the islands. The assignment of the optical transitions is made on the basis of a 14-band quantum well k∙p calculation. We show that the midinfrared electroabsorption of the islands is associated with a bound-to-continuum transition between the ground states and the wetting layer states. The enhancement of the transmission is correlated to the bleaching of the interband absorption which results from hole injection in the islands. The carrier density and the parameters governing the carrier dynamics in the islands are deduced from the midinfrared modulation amplitude. An Auger recombination coefficient in the islands, C=1.6×10−30cm6s−1, is deduced at room temperature.