bluuebunny/crossref_metadata_2025 huggingface dataset:
Heart rate and blood pressure variability in subjects with vasovagal syncope
Authors: PICCIRILLO Gianfranco , NASO Camilla , MOISÈ Antonio , LIONETTI Marco , NOCCO Marialuce , DI CARLO Silvia , DE LAURENTIS Tiziana , MAGRÌ Damiano , CACCIAFESTA Mauro , MARIGLIANO Vincenzo
Published: June 2004

Autonomic nervous system control in subjects with vasovagal syncope is controversial. In the present study, we used short-term spectral analysis to evaluate autonomic control in subjects with recurrent vasovagal syncope. We assessed the ability of spectral indices of HR (heart rate) variability to predict tilt-test responses. A series of 47 outpatients with recurrent vasovagal syncope and with positive responses to head-up tilt testing underwent a further study of RR variability during controlled breathing at rest and during tilt testing. During controlled breathing, RR interval variability of total power (TPRR; P<0.001), low-frequency power (LFRR; P<0.05), high-frequency power (HFRR; P<0.001) and HF expressed in normalized units (HFnuRR; P<0.001) were all higher, and LF expressed in normalized units (LFnuRR) and LF/HF ratio were lower in subjects with vasovagal syncope than in controls (P<0.001). To assess the ability of spectral components of RR variability to predict tilt-test responses, we prospectively studied 109 subjects with recurrent vasovagal syncope. The two normalized measures, HFnuRR and LFnuRR, determined during controlled breathing alone predicted a positive tilt-test response (sensitivity, 76%; specificity, 99%; positive predictive value, 96%; and negative predictive value, 90%). During tilting, subjects with vasovagal syncope had lower SBP (systolic blood pressure; P<0.05), LF component of peak SBP variability (LFSBP) and LFnuRR than controls, and higher TPRR, HFRR, HFnuRR and α HF (P<0.001). These spectral data indicate that vagal sinus modulation is increased at rest in subjects with vasovagal syncope. Spectral analysis of RR variability during controlled breathing, a procedure that predicts tilt-test responses, could be a useful guide in choosing the method of tilt testing.
Mycophenolate mofetil treatment following renal transplantation decreases GTP concentrations in mononuclear leucocytes
Authors: JAGODZINSKI Piotr , LIZAKOWSKI Slawomir , SMOLENSKI Ryszard T. , SLOMINSKA Ewa M. , GOLDSMITH David , SIMMONDS H. Anne , RUTKOWSKI Boleslaw
Published: June 2004

MMF (mycophenolate mofetil) has been proven to provide an effective immunosuppression by non-competitive selective reversible inhibition of IMPDH (inosine monophosphate dehydrogenase), the enzyme playing a crucial role in GTP biosynthesis. However, the exact metabolic changes induced by inhibition of IMPDH in target cells of the immune system have been the subject of recent debate. The aim of the present study was to evaluate whether MMF treatment produced sustained changes in the guanosine nucleotide pool of MNLs (mononuclear leucocytes) in vivo. Sixty-two renal failure patients were divided into three groups: chronic renal failure patients undergoing haemodialysis (CRF-HD; n=20) and two groups of patients after renal transplantation, the first on AZA (azathioprine; TN-AZA; n=23) and the second treated with MMF (TN-MMF; n=19). In addition, MNLs from 25 healthy subjects were analysed as controls. Anion-exchange HPLC was used to quantify purine and pyrimidine nucleotides in MNLs. We report a significant decrease in GTP and the total MNL guanine nucleotide pool in the TN-MMF group (P<0.05) compared with control, CRF-HD and TN-AZA groups, although no significant differences were found between any of the other groups. Adenine nucleotide concentrations in MNLs were decreased in the TN-AZA group, but not in the TN-MMF group compared with the CRF-HD group and controls. There were no differences in CTP concentrations, but UTP concentrations were decreased in the CRF-HD, TN-AZA and TN-MMF groups compared with controls. MMF caused a significant and sustained decrease in the guanine nucleotide pool in MNLs from renal transplant recipients. This decrease contrasts with the elevation in GTP reported in erythrocytes of MMF-treated patients.
Role of cyclins in cAMP inhibition of glomerular mesangial cell proliferation
Authors: ITO Chiharu , YAMAMOTO Hisashi , FURUKAWA Yusuke , TAKEDA Shin-ichi , AKIMOTO Tetsu , IIMURA Osamu , ANDO Yasuhiro , ASANO Yasushi , KUSANO Eiji
Published: June 2004

MC (mesangial cell) proliferation is closely linked to the progression of glomerular disease. It has been reported that cAMP effectors suppress MC proliferation, inhibiting activation of MAPK (mitogen-activated protein kinase). In fibroblasts, activation of MAPK induces the expression of type D cyclin, whereas, in MCs, this induction has not been shown. In the present study, we explored the effects of cAMP on MAPK and expression of cell-cycle-regulated proteins. PDGF (platelet-derived growth factor) stimulated MAPK activity, up-regulated protein levels of cyclin D1, CDK2 (cyclin-dependent kinase 2) and PCNA (proliferating cell nuclear antigen), decreased the protein level of p27 and increased DNA synthesis. Fsk (forskolin) or PD98059 suppressed PDGF-induced DNA synthesis. Both agents inhibited PDGF-stimulated mRNA and protein expression of cyclin D1 and CDK2. Fsk or PD98059 also inhibited protein expression of PCNA and blocked a decrease in p27 protein. Fsk induced the phosphorylation of Raf-1 at Ser259, which was inhibited by KT5720. These data suggest that cAMP inhibits MC proliferation through inhibition of MAPK activity, and this mechanism partly involves alteration in the levels of cell-cycle-regulated proteins.
Programming of defective rat pancreatic β-cell function in offspring from mothers fed a low-protein diet during gestation and the suckling periods
Authors: HEYWOOD Wendy E. , MIAN Nasi , MILLA Peter J. , LINDLEY Keith J.
Published: June 2004

Poor fetal and infant nutrition has been linked to impaired glucose tolerance in later life. We studied the effect of protein deficiency during gestation and the suckling period in a rat model and found that poor nutrition ‘programmes’ pancreatic β-cell GK (glucokinase; known as the glucose sensor) and glucose-stimulated insulin secretion response in newborn, suckling and adult rat offspring. Pregnant female rats were divided into three groups: a control group was kept on a normal protein (20%) diet, another group was fed a low-protein (LP) (6%) diet during gestation and suckling periods (LP-G + S group) and another was fed a LP diet during gestation then a normal protein diet during the suckling period (LP-G group). The pulsatile glucose-stimulated insulin secretion response was acutely disrupted and the peak insulin secretion was markedly decreased in newborn and 3-week-old offspring of the LP-G + S group compared with the control group. Also, there was an altered pulsatile secretory response in adults of the LP-G + S and 3-week-old and adult offspring of the LP-G groups compared with the control group. GK protein levels, detected by Western blotting, were decreased in newborn and 3-week-old offspring of both LP-G + S and LP-G groups compared with the control groups. The Km and Vmax of GK were altered. The prenatal and postnatal LP diet appeared to have a permanent effect in increasing the affinity of GK for glucose (indicated by decreased Km values) and decreasing the Vmax. This showed that the critical period of programming of the function of GK was after birth and during the postnatal weaning period, since the adult offspring of the LP-G + S group when fed a normal protein diet showed no reversal in the Km values of the enzyme. Similar experiments in adult offspring of the LP-G group showed normalization of the Km values of GK at 3 weeks of age. In conclusion, fetal and infantile nutrition ‘programmes’ pancreatic β-cell function; poor nutrition during this period caused irreversible effects on glucose homoeostatic mechanisms in the offspring, which may predispose the offspring to diabetes in later life.
Heart rate increment: an electrocardiological approach for the early detection of obstructive sleep apnoea/hypopnoea syndrome
Authors: ROCHE Frédéric , SFORZA Emilia , DUVERNEY David , BORDERIES Jean-René , PICHOT Vincent , BIGAIGNON Odile , ASCHER Gilles , BARTHÉLÉMY Jean-Claude
Published: June 2004

The prevalence of OSAHS (obstructive sleep apnoea/hypopnoea syndrome) is high in developed countries and it is estimated that the vast majority of patients remain undiagnosed. On the basis of physiological evidence, we evaluated the frequency component of HRI (heart rate increment) as a simple and inexpensive screening tool for OSAHS detection in a first group of patients (group 1) and validated their discriminant capacity in a second group (group 2). The predictive accuracy of hourly %VLFI (frequency-domain HRI variable obtained from nocturnal ECG Holter monitoring) was analysed by comparison with an hour-by-hour respiratory disturbances index assessed by complete polysomnography in 28 consecutive clinically suspected OSAHS patients for group 1 and in 35 patients for group 2. OSAHS was present in 20 patients according to a mean hourly apnoea plus hypopnoea index >10 in group 1, and prevalence reached 77.1% in group 2. Sensitivity, specificity and positive and negative predictive accuracy were calculated and an ROC (receiver operating characteristic) curve was constructed for several polysomnographic threshold values. In group 1, hourly %VLFI appeared as an evident predictor of the apnoea/hypopnoea index (W=0.848, P<0.0001; where W is the area under the curve obtained using ROC curve analysis). Using an appropriate threshold (value ≥3.2%), %VLFI demonstrated a sensitivity of 78.1% and a specificity of 70.4%. These thresholds applied to group 2 yielded a sensitivity of 73.9% and a specificity of 76.6%. Frequency-domain analysis of the HRI appears to be a powerful tool for OSAHS prediction. The simplicity of its analysis and use makes of it a particularly well-suited variable for routine mass screening in high-risk populations undergoing ECG Holter monitoring.
n–3 Fatty acids and cardiovascular disease: evidence explained and mechanisms explored
Authors: CALDER Philip C.
Published: June 2004

Long chain n–3 PUFAs (polyunsaturated fatty acids) are found in fatty fish and in fish oils. Substantial evidence from epidemiological and case-control studies indicates that consumption of fish, fatty fish and long-chain n–3 PUFAs reduces the risk of cardiovascular mortality. Secondary prevention studies using long-chain n–3 PUFAs in patients post-myocardial infarction have shown a reduction in total and cardiovascular mortality, with an especially potent effect on sudden death. Long-chain n–3 PUFAs have been shown to decrease blood triacylglycerol (triglyceride) concentrations, to decrease production of chemoattractants, growth factors, adhesion molecules, inflammatory eicosanoids and inflammatory cytokines, to lower blood pressure, to increase nitric oxide production, endothelial relaxation and vascular compliance, to decrease thrombosis and cardiac arrhythmias and to increase heart rate variability. These mechanisms most likely explain the primary and secondary cardiovascular protection afforded by long-chain n–3 PUFA consumption. A recent study suggests that long-chain n–3 PUFAs might also act to stabilize advanced atherosclerotic plaques, perhaps through their anti-inflammatory effects. As a result of the robust evidence in their favour, a number of recommendations to increase intake of long-chain n–3 PUFAs have been made.
Enhancement of infrared transmission in GaSb bulk crystals by carrier compensation
Authors: Pino R. , Ko Y. , Dutta P. S.
Published: June 2004

Enhancement in room temperature infrared transmission (1.8–50 μm wavelength range) has been achieved in GaSb bulk crystals by tellurium (Te) compensation. Lattice vibrations have been observed at 488, 408, 355, 323, 327, 270, 255, 246, 237, 231, 221, 214, and 210 cm−1, respectively, which coincide with the theoretically predicted band positions from two-, three-, and four-phonon processes. The clear observation of lattice vibrations indicates the suppression of free carrier absorption in Te-compensated GaSb. Electrical characterization indicates that Te compensates native defects in GaSb that contribute to the enhancement in the transmission properties of GaSb bulk crystals.
Density functional theory study of H and H2 interacting with NiAl(110)
Authors: Rivière P. , Busnengo H. F. , Martı́n F.
Published: June 2004

We present results of extensive density functional theory (DFT) calculations for H and H2 interacting with NiAl(110). Continuous representations of the full dimensional potential energy surface (PES) for the H/NiAl(110) and H2/NiAl(110) systems are obtained by interpolation of the DFT results using the corrugation reducing procedure. We find a minimum activation energy barrier of ∼300 meV for dissociative adsorption of H2, which is consistent with the energy threshold obtained in molecular beam experiments for H2 (ν=0). We explain vibrational enhancement observed in experiments as the consequence of vibrational softening in the entrance channel over the most reactive surface site. The H2/NiAl(110) PES shows a high surface site selectivity: for energies up to 0.1 eV above threshold, H2 adsorption can only take place around top-Ni sites (within a circle of radius ∼0.3 Å). A strong energetic corrugation is observed: energy barriers for dissociation vary by more than 1 eV between the most and the least reactive sites. In contrast, geometric corrugation is much less pronounced and comparable to that of low index single metal surfaces like Cu or Pt.
Excitation density dependence of photocurrent efficiency in low mobility semiconductors
Authors: Tessler Nir , Rappaport Noam
Published: June 2004

We report numerical simulation of the charge transport in low mobility semiconductors under optical excitation. We choose the low mobility regime as it is typical of organic polymer semiconductor devices. We find that, contrary to common belief, the limiting factor for the photocurrent at high optical excitation density is the onset of space-charge limit and that bimolecular recombination is merely a result of the limited current. We also show that the power dependence of the photocurrent efficiency can be used to deduce which charge-carrier is the slow one and extract its mobility.
Noncatalytic kinetic study on site-selective H/D exchange reaction of phenol in sub- and supercritical water
Authors: Kubo Masahito , Takizawa Takeyuki , Wakai Chihiro , Matubayasi Nobuyuki , Nakahara Masaru
Published: June 2004

The site-selective H/D exchange reaction of phenol in sub- and supercritical water is studied without added catalysts. In subcritical water in equilibrium with steam at 210–240 °C, the H/D exchange proceeds both at the ortho and para sites in the phenyl ring, with no exchange observed at the meta site. The pseudo-first-order rate constants are of the order of 10−4 s−1; 50% larger for the ortho than for the para site. In supercritical water, the exchange is observed also at the meta site with the rate constant in the range of 10−6–10−4 s−1. As the bulk density decreases, the exchange slows down and the site selectivity toward the ortho is enhanced. The enhancement is due to the phenol–water interaction preference at the atomic resolution. The site selectivity toward the ortho is further enhanced when the reaction is carried out in benzene/water solution. Using such selectivity control and the reversible nature of the hydrothermal deuteration/protonation process, it is feasible to synthesize phenyl compounds that are deuterated at any topological combination of ortho, meta, and para sites.
Monte Carlo simulations of antibody adsorption and orientation on charged surfaces
Authors: Zhou Jian , Tsao Heng-Kwong , Sheng Yu-Jane , Jiang Shaoyi
Published: June 2004

Monte Carlo simulations were performed to study the adsorption and orientation of antibodies on charged surfaces based on both colloidal and all-atom models. The colloidal model antibody consists of 12 connected beads representing the 12 domains of an antibody molecule. The structure of the all-atom antibody model was taken from the protein databank. The effects of the surface charge sign and density, the solution pH and ionic strength on the adsorption and orientation of different colloidal model antibodies with different dipole moments were examined. Simulation results show that both the 12-bead and the all-atom models of the antibody, for which the dipole moment points from the Fc to (Fab)2 fragments, tend to have the desired “end-on” orientation on positively charged surfaces and undesired “head-on” orientation on negatively charged surfaces at high surface charge density and low solution ionic strength where electrostatic interactions dominate. At low surface charge density and high solution ionic strength where van der Waals interactions dominate, 12-bead model antibodies tend to have “lying-flat” orientation on surfaces. The orientation of adsorbed antibodies results from the compromise between electrostatic and van der Waals interactions. The dipole moment of an antibody is an important factor for antibody orientation on charged surfaces when electrostatic interactions dominate. This charge-driven protein orientation hypothesis was verified by our simulations results in this work. It was further confirmed by surface plasmon resonance biosensor and time-of-flight secondary ion mass spectrometry experiments reported elsewhere.
Some symmetry-induced isotope effects in the kinetics of recombination reactions
Authors: T Pack Russell , Walker Robert B.
Published: June 2004

Symmetry-induced isotope effects in recombination and collision-induced dissociation reactions are discussed. Progress on understanding the anomalous isotope effects in ozone is reviewed. Then, calculations are performed for the simpler reaction Nxe+Nye+H⇔NxeNye+H, where x and y label either identical or different isotopes. The atomic masses in the model are chosen so that symmetry is the only difference between the systems. Starting from a single potential energy surface, the properties of the bound, quasibound, and continuum states of the neon dimer are calculated. Then, the vibration rotation infinite order sudden approximation is used to calculate cross sections for all possible inelastic and dissociative processes. A rate constant matrix that exactly satisfies detailed balance is constructed. It allows recombination to occur both via direct three-body collisions and via tunneling into the quasibound states of the energy transfer mechanism. The eigenvalue rate coefficients are determined. Significant isotope effects are clearly found, and their behavior depends on the pressure, temperature, and mechanism of the reaction. Both spin statistics and symmetry breaking produce isotope effects. Under most conditions the breaking of symmetry enhances the rates, but a wide spectrum of effects is observed; they range from isotope effects with a normal mass dependence to huge, mass-independent isotope effects to cancellation and even to reversal of the isotope effects. This is the first calculation of symmetry-induced isotope effects in recombination rates from first principles. The relevance of the present effects to ozone recombination is discussed.
A Ti-V-based bcc phase alloy for use as metal hydride electrode with high discharge capacity
Authors: Yu X. B. , Wu Z. , Xia B. J. , Xu N. X.
Published: June 2004

The electrochemical characteristics of single bcc phase Ti-30V-15Cr-15Mn alloy were investigated. It was demonstrated that the single bcc phase alloy has high electrochemical discharge performance at high temperature. Its discharge capacity is closely related with temperature and discharge current. The first discharge capacities of 580–814 mAh g−1 of the alloy powder were obtained at discharge current of 45–10 mA g−1 in 6 M KOH solution at 353 K. Although the electrochemical cycle life of the alloy is unsatisfactory at present, it opens up prospects for developing a new hydrogen storage alloy with high hydrogen capacity for use as high performance metal hydride electrodes in rechargeable Ni-MH battery.
Conformation studies on sol-gel transition in triblock copolymer solutions
Authors: Li Yunqi , Sun Zhaoyan , Shi Tongfei , An Lijia
Published: June 2004

The gelation of physically associating triblock copolymers in a good solvent was investigated by means of the Monte Carlo simulation and a gelation process based on the conformation transition of the copolymer that was described in detail. In our simulative system, it has been found that the gelation is closely related with chain conformations, and there exist four types of chains defined as free, dangling, loop, and bridge conformations. The copolymer chains with different conformations contribute to the formation of gel in different ways. We proposed a conformational transition model, by which we evaluated the role of these four types of chains in sol-gel transition. It was concluded that the free chains keeping the conformation transition equilibrium and the dangling conformation being the hinge of conformation transition, while the chain with loop conformation enlarges the size of the congeries and the chain with bridge conformations binds the congeries consisted of the copolymer chains. In addition, the effects of temperature and concentration on the physical gelation, the association of the copolymer congeries, and the copolymer chain conformations’ distribution were discussed. Furthermore, we employed the structure factor analysis to study the association of copolymer conformations and long-range order of the simulation system and found our results are in agreement with the previous experimental conclusions.
Dissipative quantum dynamics with the surrogate Hamiltonian approach. A comparison between spin and harmonic baths
Authors: Gelman David , Koch Christiane P. , Kosloff Ronnie
Published: June 2004

The dissipative quantum dynamics of an anharmonic oscillator coupled to a bath is studied with the purpose of elucidating the differences between the relaxation to a spin bath and to a harmonic bath. Converged results are obtained for the spin bath by the surrogate Hamiltonian approach. This method is based on constructing a system–bath Hamiltonian, with a finite but large number of spin bath modes, that mimics exactly a bath with an infinite number of modes for a finite time interval. Convergence with respect to the number of simultaneous excitations of bath modes can be checked. The results are compared to calculations that include a finite number of harmonic modes carried out by using the multiconfiguration time-dependent Hartree method of Nest and Meyer [J. Chem. Phys. 119, 24 (2003)]. In the weak coupling regime, at zero temperature and for small excitations of the primary system, both methods converge to the Markovian limit. When initially the primary system is significantly excited, the spin bath can saturate restricting the energy acceptance. An interaction term between bath modes that spreads the excitation eliminates the saturation. The loss of phase between two cat states has been analyzed and the results for the spin and harmonic baths are almost identical. For stronger couplings, the dynamics induced by the two types of baths deviate. The accumulation and degree of entanglement between the bath modes have been characterized. Only in the spin bath the dynamics generate entanglement between the bath modes.
Simple growth models of rigid multifilament biopolymers
Authors: Stukalin Evgeny B. , Kolomeisky Anatoly B.
Published: June 2004

The growth dynamics of rigid biopolymers, consisting of N parallel protofilaments, is investigated theoretically using simple approximate models. In our approach, the structure of a polymer’s growing end and lateral interactions between protofilaments are explicitly taken into account, and it is argued that only few configurations are important for a biopolymer’s growth. As a result, exact analytic expressions for growth velocity and dispersion are obtained for any number of protofilaments and arbitrary geometry of the growing end of the biopolymer. Our theoretical predictions are compared with a full description of biopolymer growth dynamics for the simplest N=2 model. It is found that the results from the approximate theory are approaching the exact ones for large lateral interactions between the protofilaments. Our theory is also applied to analyze the experimental data on the growth of microtubules.
Potential energy surface discontinuities in local correlation methods
Authors: Russ Nicholas J. , Crawford T. Daniel
Published: June 2004

We have examined the occurence of discontinuities in bond-breaking potential energy surfaces given by local correlation methods based on the Pulay–Saebø orbital domain approach. Our analysis focuses on three prototypical dissociating systems: the C-F bond in fluoromethane, the C-C bond in singlet, ketene, and the central C-C bond in propadienone. We find that such discontinuities do not occur in cases of homolytic bond cleavage due to the inability of the Pipek–Mezey orbital localization method to separate singlet-coupled charges on distant fragments. However, for heterolytic bond cleavage, such as that observed in singlet ketene and propadienone, discontinuities occur both at stretched geometries and near equilibrium. These discontinuities are usually small, but may be of the same order of magnitude as the localization error in some cases.
Taming the rugged landscape: Production, reordering, and stabilization of selected cluster inherent structures in the X13−nYn system
Authors: Sabo Dubravko , Doll J. D. , Freeman David L.
Published: June 2004

We present studies of the potential energy landscape of selected binary Lennard-Jones 13 atom clusters. The effect of adding selected impurity atoms to a homogeneous cluster is explored. We analyze the energy landscapes of the studied systems using disconnectivity graphs. The required inherent structures and transition states for the construction of disconnectivity graphs are found by combination of conjugate gradient and eigenvector-following methods. We show that it is possible to controllably induce new structures as well as reorder and stabilize existing structures that are characteristic of higher-lying minima. Moreover, it is shown that the selected structures can have experimentally relevant lifetimes.
The katoite hydrogarnet Si-free Ca3Al2([OH]4)3: A periodic Hartree–Fock and B3-LYP study
Authors: Pascale F. , Ugliengo P. , Civalleri B. , Orlando R. , D’Arco P. , Dovesi R.
Published: June 2004

The structure of the Si-free katoite hydrogarnet (116 atoms in the unit cell) has been investigated at the periodic ab initio quantum mechanical level with the CRYSTAL program, by using a Gaussian type basis set and both the HF and the hybrid B3-LYP Hamiltonians. The structure has been fully optimized at various pressures in the 0–46 GPa range; the modifications of the structure, and in particular of the (OH)4 group, as a function of pressure are analyzed. At the B3-LYP level and P greater than 15 GPa, a O–H⋯O interaction of increasing strength appears, with important modifications in the local geometry of the tetrahedral site. The calculated ω01(O–H) fundamental vibrational frequency at zero pressure is in excellent agreement with experiment (3674 and 3663 cm−1, respectively); the ω01(O–H) stretching frequency remains essentially constant in the 0–15 GPa interval, whereas it dramatically decreases at higher pressures with a corresponding anharmonicity increase, as a consequence of the formation of a strong hydrogen bond. The hydration energy of grossular and the formation energy of Si-free katoite have also been computed, and the B3-LYP results are in quite good agreement with experiment.
Optical anisotropy of nanotube suspensions
Authors: Hobbie Erik K.
Published: June 2004

A semimacroscopic model of an optically anisotropic nanotube suspension is derived perturbatively from Maxwell’s equations in a dielectric medium. We calculate leading-order expressions, valid in the dilute and semidilute limits, for the intrinsic and form contributions to the complex dielectric tensor in terms of the volume fraction, mean orientation, aspect ratio, optical anisotropy, and optical contrast of the nanotubes. The birefringence and dichroism are derived explicitly to leading order in fluctuations, and the connection with depolarized light scattering is established. The results are generalized to include tube deformation.
Electromechanical actuation of composite material from carbon nanotubes and ionomeric polymer
Authors: Levitsky I. A. , Kanelos P. , Euler William B.
Published: June 2004

An actuating system composed of nafion ionomeric polymer coated with single-walled carbon nanotubes electrodes was studied as an electromechanical actuator. The actuator gives a sizable mechanical response to low voltages (turn-on voltage of ∼2.5 V) under open-air conditions, i.e., in the absence of a surrounding supporting electrolyte. The actuator is active under both dc and ac bias and has a strong resonance at low frequencies which is dependent upon the size of the actuator. The actuator was studied using Fourier transform infrared and vis-NIR spectroscopies, cyclic voltammetry, and by the current-time response under an applied step voltage. An analytical model is proposed to understand the electrical behavior, which is consistent with the spectroscopic results.
Tail molecule dependence of thiolate adsorption on Au(111) surface: Theoretical study
Authors: Higai Shin’ichi , Nara Jun , Ohno Takahisa
Published: June 2004

The adsorption of thiolates with various tail molecules on the Au(111) surface has been investigated by first-principles calculations. We have considered six typical thiolate molecules, that is, methylthiolate, ethylthiolate, ethylenethiolate, acetylenethiolate, benzenethiolate, and thiophenethiolate. It is found that these thiolates exhibit little difference in their stable adsorption geometries. They are adsorbed at the bridge site with being significantly tilted from the surface normal. The adsorption energy of thiolate on Au, on the other hand, largely varies depending on the type of tail molecule, and is linearly proportional to the binding energy of thiolate with H. We discuss the tail molecule dependence in terms of the bonding environment around the C atom connected to the head S atom.
Analytical energy gradients for local second-order Møller–Plesset perturbation theory using density fitting approximations
Authors: Schütz Martin , Werner Hans-Joachim , Lindh Roland , Manby Frederick R.
Published: June 2004

An efficient method to compute analytical energy derivatives for local second-order Møller–Plesset perturbation energy is presented. Density fitting approximations are employed for all 4-index integrals and their derivatives. Using local fitting approximations, quadratic scaling with molecular size and cubic scaling with basis set size for a given molecule is achieved. The density fitting approximations have a negligible effect on the accuracy of optimized equilibrium structures or computed energy differences. The method can be applied to much larger molecules and basis sets than any previous second-order Møller–Plesset gradient program. The efficiency and accuracy of the method is demonstrated for a number of organic molecules as well as for molecular clusters. Examples of geometry optimizations for molecules with 100 atoms and over 2000 basis functions without symmetry are presented.
Classical spin and quantum-mechanical descriptions of geometric spin frustration
Authors: Dai Dadi , Whangbo Myung-Hwan
Published: June 2004

Geometric spin frustration (GSF) in isolated plaquettes with local spin s, i.e., an equilateral-triangle spin trimer and a regular-tetrahedron spin tetramer, was examined on the basis of classical spin and quantum-mechanical descriptions to clarify their differences and similarities. An analytical proof was given for how the state degeneracy and the total spin S of their ground states depend on the local spin s. The quantum-mechanical conditions for the occurrence of GSF in isolated plaquettes were clarified, and their implications were explored. Corner sharing between plaquettes and how it affects GSF in the resulting spin systems was examined.
Bulk nanocomposite magnets produced by dynamic shock compaction
Authors: Chen K. H. , Jin Z. Q. , Li J. , Kennedy G. , Wang Z. L. , Thadhani N. N. , Zeng H. , Cheng S.-F. , Liu J. P.
Published: June 2004

Exchange-coupled R2Fe14B/α-Fe (R=Nd or Pr) nanocomposite bulk magnets with nearly full density have been successfully produced by shock compaction of melt-spun powders. X-ray diffraction and transmission electronic microscopy analyses of the shock-consolidated compacts showed no grain growth upon compaction, in fact, a decrease in the crystallite size of both the hard and soft phases was observed. As a consequence, magnetic properties were retained and even improved after compaction. Hysteresis loops of the shock-consolidated powder compacts showed a smooth single-phaselike behavior, indicating effective exchange coupling between hard and soft magnetic phases.
Nucleation in binary polymer blends: Effects of foreign mesoscopic spherical particles
Authors: Wang Jiafang , Wang Zhen-Gang , Yang Yuliang
Published: June 2004

We study nucleation in binary polymer blends in the presence of mesoscopic spherical particles using self-consistent field theory, considering both heterogeneous and homogeneous nucleation mechanisms. Heterogeneous nucleation is found to be highly sensitive to surface selectivity and particle size, with rather subtle dependence on the particle size. Particles that preferentially adsorb the nucleating species generally favor heterogeneous nucleation. For sufficiently strong adsorption, barrierless nucleation is possible. By comparing the free energy barrier for homogeneous and heterogeneous nucleation, we construct a kinetic phase diagram.
Coherent low-frequency motions of hydrogen bonded acetic acid dimers in the liquid phase
Authors: Heyne Karsten , Huse Nils , Dreyer Jens , Nibbering Erik T. J. , Elsaesser Thomas , Mukamel Shaul
Published: June 2004

Ultrafast vibrational dynamics of cyclic hydrogen bonded dimers and the underlying microscopic interactions are studied in temporally and spectrally resolved pump–probe experiments with 100 fs time resolution. Femtosecond excitation of the O–H and/or O–D stretching mode gives rise to pronounced changes of the O–H/O–D stretching absorption displaying both rate-like kinetic and oscillatory components. A lifetime of 200 fs is measured for the v=1 state of the O–H stretching oscillator. The strong oscillatory absorption changes are due to impulsively driven coherent wave packet motions along several low-frequency modes of the dimer between 50 and 170 cm−1. Such wave packets generated via coherent excitation of the high-frequency O–H/O–D stretching oscillators represent a clear manifestation of the anharmonic coupling of low- and high-frequency modes. The underdamped low-frequency motions dephase on a time scale of 1–2 ps. Calculations of the vibrational potential energy surface based on density functional theory give the frequencies, anharmonic couplings, and microscopic elongations of the low-frequency modes, among them intermolecular hydrogen bond vibrations. Oscillations due to the excitonic coupling between the two O–H or O–D stretching oscillators are absent as is independently confirmed by experiments on mixed dimers with uncoupled O–H and O–D stretching oscillators.
Experimental determination of the hole capture kinetics of H4F deep trap in electron-irradiated highly doped p-type InP
Authors: Darwich R. , Massarani B.
Published: June 2004

The hole capture kinetics of the main trap H4F in electron-irradiated p-type InP has been investigated by experimentally determining the exponential and nonexponential parts. The contribution of the slow part of the total kinetics is about 30% in our samples. An indication to a possible capture rate enhancement due to the electric field in the space-charge region is pointed out.
Determination of bonding structure of Si, Ge, and N incorporated amorphous carbon films by near-edge x-ray absorption fine structure and ultraviolet Raman spectroscopy
Authors: Jung Hae-Suk , Park Hyung-Ho , Mendieta I. R. , Smith D. A.
Published: June 2004

This work represents a comparative analysis of bonding structure in Si, Ge, and N incorporated amorphous carbon (a-C) films using near-edge x-ray absorption fine structure (NEXAFS) and ultraviolet (UV) Raman spectroscopy. From NEXAFS analyses, changes in the π and σ bonding states of the films with Si, Ge, and N incorporation could be determined. It is also revealed that incorporation of Si, Ge, and N play a role of increasing sp3 fractions of sputtered a-C in different ways of formation of sp3 bonds. Incorporated Si and Ge atoms substitute C atoms and open up the ring structure, promoting the sp3 hybridized bonds with its neighboring atoms. Compared to Si, incorporated Ge easily facilitated the formation of sp3 hybridized bond with neighboring C atoms due to small hybridization energy. By comparing with UV Raman spectra, incorporation of N induces N substituted five-membered ring structure without destroying the ring structure. For N incorporated a-C, the increased sp3 fraction is shown to be due to five-membered ring structure, giving rise to a cross linking between ring structures by sp3 hybridized bonds.
Magnetic and transport properties of evaporated Fe/SiO multilayers
Authors: Anas M. , Bellouard C. , Vergnat M.
Published: June 2004

Fe/SiO discontinuous multilayers consisting of layers of Fe particles embedded in an insulating SiO matrix have been prepared by evaporation. Their structural, magnetic, and transport properties have been studied as a function of Fe and SiO thickness. For small iron thicknesses, magnetic measurements show a superparamagnetic behavior above a blocking temperature determined by field-cooled and zero-field-cooled magnetization curves. Negative magnetoresistance due to spin-dependent tunneling has been observed in both current-in-plane and current-perpendicular-to-the-plane geometries. For the smaller iron thickness (5 Å), a Coulomb blockade effect is observed at low temperature together with an increase of the magnetoresistance.
Ultrasonic enrichment of microspheres for ultrasensitive biomedical analysis in confocal laser-scanning fluorescence detection
Authors: Wiklund M. , Toivonen J. , Tirri M. , Hänninen P. , Hertz H. M.
Published: June 2004

An ultrasonic particle concentrator based on a standing-wave hemispherical resonator is combined with confocal laser-scanning fluorescence detection. The goal is to perform ultrasensitive biomedical analysis by concentration of biologically active microspheres. The standing-wave resonator consists of a 4 MHz focusing ultrasonic transducer combined with the optically transparent plastic bottom of a disposable 96-well microplate platform. The ultrasonic particle concentrator collects suspended microspheres into dense, single-layer aggregates at well-defined positions in the sample vessel of the microplate, and the fluorescence from the aggregates is detected by the confocal laser-scanning system. The biochemical properties of the system are investigated using a microsphere-based human thyroid stimulating hormone assay.
Aluminum oxide layers as possible components for layered tunnel barriers
Authors: Cimpoiasu E. , Tolpygo S. K. , Liu X. , Simonian N. , Lukens J. E. , Likharev K. K. , Klie R. F. , Zhu Y.
Published: June 2004

We have studied transport properties of Nb/Al/AlOx/Nb tunnel junctions with ultrathin aluminum oxide layers formed by (i) thermal oxidation and (ii) plasma oxidation, before and after rapid thermal postannealing of the completed structures at temperatures up to 550 °C. Postannealing at temperatures above 300 °C results in a significant decrease of the tunneling conductance of thermally grown barriers, while plasma-grown barriers start to change only at annealing temperatures above 450 °C. Fitting the experimental I-V curves of the junctions using the results of the microscopic theory of direct tunneling shows that the annealing of thermally grown oxides at temperatures above 300 °C results in a substantial increase of their average tunnel barriers height, from ∼1.8 eV to ∼2.45 eV, versus the practically unchanged height of ∼2.0 eV for plasma-grown layers. This difference, together with high endurance of annealed barriers under electric stress (breakdown field above 10 MV/cm) may enable all-AlOx and SiO2/AlOx layered “crested” barriers for advanced floating-gate memory applications.
The depth-profiled carrier concentration and scattering mechanism in undoped GaN film grown on sapphire
Authors: Huang Y. , Chen X. D. , Fung S. , Beling C. D. , Ling C. C. , Wei Z. F. , Xu S. J. , Zhi C. Y.
Published: June 2004

Temperature-dependent Hall (TDH) measurements and confocal micro-Raman spectroscopy have been used to study the free carrier spatial distribution and scattering mechanism in unintentionally doped GaN film grown on the sapphire substrate with the method of metalorganic chemical vapor deposition. Both the TDH data and the depth-profiled Raman spectra agreed with the existence of a nonuniform spatial distribution of free carriers in the GaN film with a highly conductive layer of ∼1 μm thickness near the GaN sapphire boundary. With the consideration of this parallel conduction channel adjacent to GaN sapphire boundary, detailed analysis of the TDH mobility data suggests that a relatively high concentration of nitrogen vacancies exists and nitrogen vacancy scattering has an important influence on limiting the electron mobility in the bulk film of the present GaN sample.
Transborder Ethnic Minorities and Their Impact on the Security of Southeastern Europe*
Authors: Atanasova Ivanka Nedeva
Published: June 2004

Ethnic issues have a paramount impact on the security of Southeastern Europe. The most recent proof of that has been NATO's involvement in the conflict between the Serbian government and the ethnic Albanians in Kosovo. Only NATO's involvement could reverse the highly destabilizing effect of the expulsion of over a million of the Kosovar Albanians by the Serb army and paramilitary forces beyond Kosovo's borders.
National Identity, Political Interest and Human Rights in Europe: The Charter of Fundamental Rights of the European Union
Authors: Bojkov Victor D.
Published: June 2004

This article is about national identity, political interest and the creation of international human rights regimes. Geographically, it is focused on Western Europe and the very recent process of establishing the Charter of Fundamental Rights of the European Union. Both national identity and political interest are seen as important determinants of this process, defining its discourse and outcome. The relationship between the two is complex and recursive. They influence each other to an extent that warrants seeing them as mutually constitutive. On one hand, the social, political and economic projects elites engage in have to resonate positively with dearly held elements of national identity but have also the power to modify them. Being a psychological phenomenon, on the other hand, national identity is a dynamic concept that employs common historically defined memories, traditions and customs but is also subject to the influence of the political context within which it operates.
Regional Induction of CYP1A1 in Rat Liver Following Treatment with Mixtures of PCB 126 and PCB 153
Authors: Chubb Laura S. , Andersen Melvin E. , Broccardo Carolyn J. , Legare Marie E. , Billings Ruth E. , Dean Charles E. , Hanneman William H.
Published: June 2004

Liver enzyme induction has been shown previously to be regional with clear borders between induced and uninduced regions in vivo, and cells either fully induced or not induced in vitro. The current study examined this phenomenon in vivo by evaluating enzyme induction after exposure to PCB 126 and PCB 153 in female Fisher 344 (F344) and male Sprague—Dawley (SD) rats. IHC revealed a regional induction of CYP1A1 after exposure to PCB 126, apparent in the centrilobular region at lower doses and progressing to panlobular with higher doses. PCB 153 exposure induced CYP2B1/2 in the centrilobular region, which spread to the midzonal region as the dose increased, but never became panlobular even at the highest dosage tested. In rats treated with PCB 126 in combination with high doses of PCB 153, induction of CYP1A1 occurred preferentially in the periportal region, a reversal from the pattern seen with PCB 126 alone. This CYP1A1 induction pattern reversal is a unique example of complex biological interactions between coplanar (PCB 126) and noncoplanar (PCB 153) halogenated aromatic hydrocarbons.
Fetal alcohol syndrome at the cellular level
Authors: Olney John
Published: June 2004

A single exposure of infant rats or mice to ethanol during synaptogenesis (mid to late pregnancy for humans) can cause developing neurons to commit suicide (die by apoptosis) on a massive scale. The neuronal loss demonstrated in recent studies is more severe and much more widely distributed (many brain regions, plus spinal cord and retina) than has been documented in prior animal ethanol studies. By suppressing neuronal activity via NMDA glutamate and GABAA receptors, ethanol disrupts synaptogenesis, thereby activating in developing neurons a programmed signal to commit suicide. These recent findings help clarify important aspects of the fetal alcohol syndrome, and demonstrate the usefulness of an in vivo infant rodent model for studying the neurotoxic effects of ethanol on the developing central nervous system.
Fetal alcohol syndrome in the United States corrections system
Authors: Burd Larry , Selfridge Rachael , Klug Marilyn , Bakko Stacy
Published: June 2004

Prenatal alcohol exposure can result in fetal alcohol syndrome (FAS), which may increase the risk of confinement in the corrections system. In the United States each state and four major cities' corrections systems were asked to complete a questionnaire on the prevalence of FAS and alcohol‐related neurodevelopmental disorder (ARND) in the offender population, the availability of screening and diagnostic services to identify offenders with FAS and staff training needs related to FAS. The total population in the 54 entities was 3 080 904 inmates. Completed questionnaires were obtained from 42 entities (78%). The mean rate of reported substance abuse in offenders was 60.1%. Specialized programs for persons with mental retardation were reported for 44.4% of corrections facilities and 25.9% of community corrections facilities. Programs for pregnant women were reported for 46.3% of corrections facilities and 29.6% of community facilities. One program (1.9%) reported having a screening program for FAS in the corrections system. Only four programs (7.4%) reported having access to diagnostic services for FAS in the corrections facilities. Of the 3 080 904 offenders, only one offender was reported to have a diagnosis of FAS. Reported staff training needs were very large. In conclusion, corrections systems have high unmet needs to screen, identify, and treat offenders with FAS and ARND. Staff training needs are substantial.
Increased sibling mortality in children with fetal alcohol syndrome
Authors: Burd Larry , Klug Marilyn , Martsolf John
Published: June 2004

We compared the rate of all‐cause mortality in siblings of children diagnosed with fetal alcohol syndrome (FAS) with the siblings of matched controls. The siblings of children with FAS had increased mortality (11.4%) compared with matched controls (2.0%), a 530% increase in mortality. The age of death in case siblings deaths occurred later (between 1 day and 7 years) compared with the controls (1 day to 4 years) [odds ratio (OR) = 2.4 (0.4 ‐ 15.6)]. Siblings of children with FAS had increased risk of death due to infectious illness [OR = 13.7 (1.2 ‐ 361)] and sudden infant death syndrome compared with controls [OR = 10.2 (1.2 ‐ 75.1)]. A diagnosis of FAS is an important risk marker for mortality in the siblings of the proband even if they do not have FAS. Maternal alcoholism appears to be a useful risk marker for increased mortality risk in diagnosed cases and their siblings. This has important implications in the management of family members of children with FAS.