bluuebunny/crossref_metadata_2025 huggingface dataset:
Myocardial Ischemic‐reperfusion Injury in a Rat Model of Metabolic Syndrome
Authors: Mozaffari Mahmood S. , Schaffer Stephen W.
Published: August 2008

Hearts of NaCl‐induced hypertensive‐glucose intolerant (HGI) rats develop reduced infarcts after ischemia‐reperfusion injury (IRI) than their hypertensive (H) counterparts. Because high intake of saturated fat is a major risk factor for ischemic heart disease, we tested the hypothesis that chronic (18 weeks) consumption of a high saturated fat diet increases susceptibility to IRI, an effect more marked in the HGI rats than in the H rats. The fat‐fed H (HFAT) rat displayed significantly higher body weight and plasma leptin content compared to the H, HGI, or fat‐fed HGI (HGIFAT) rats which all showed similar values. In contrast, plasma triglyceride concentration was significantly higher in the HGIFAT rat than in the other three groups. Plasma insulin concentration was similar in the two H groups but higher than that of the two HGI groups. Compared to the H rat, the HGI rat was markedly glucose intolerant, with fat feeding causing comparable worsening of glucose intolerance in each group. The HGIFAT rats displayed a reduction in baseline myocardial contractility and relaxation and a higher end‐diastolic pressure compared to the other three groups. Infarct size was significantly lower in the HGI rats than in the H rats. Although fat feeding did not affect infarct size of the H rat, it worsened that of the HGIFAT rat thereby abrogating the differential that existed between the H and HGI rats. In conclusion, excess fat feeding impairs myocardial function of HGI rats and increases their susceptibility to IRI. These findings are of relevance to the metabolic syndrome that manifests as a cluster of insulin resistance, dyslipidemia, and systemic hypertension.
High‐fat Diet‐induced Obesity Leads to Resistance to Leptin‐induced Cardiomyocyte Contractile Response
Authors: Ren Jun , Zhu Bang‐Hao , Relling David P. , Esberg Lucy B. , Ceylan‐Isik Asli F.
Published: August 2008

Levels of the obese gene product leptin are often elevated in obesity and may contribute to obesity‐induced cardiovascular complications. However, the role of leptin in obesity‐associated cardiac abnormalities has not been clearly defined. This study was designed to determine the influence of high‐fat diet‐induced obesity on cardiac contractile response of leptin. Mechanical and intracellular Ca2+ properties were evaluated using an IonOptix system in cardiomyocytes from adult rats fed low‐ and high‐fat diets for 12 weeks. Cardiomyocyte contractile and intracellular Ca2+ properties were examined including peak shortening, duration and maximal velocity of shortening/relengthening (TPS/TR90, ±dl/dt), Fura‐2‐fluorescence intensity change (ΔFFI), and intracellular Ca2+ decay rate (τ). Expression of the leptin receptor (Ob‐R) was evaluated by western blot analysis. High‐fat diet increased systolic blood pressure and plasma leptin levels. PS and ±dl/dt were depressed whereas TPS and TR90 were prolonged after high‐fat diet feeding. Leptin elicited a concentration‐dependent (0–1,000 nmol/l) inhibition of PS, ±dl/dt, and ΔFFI in low‐fat but not high‐fat diet‐fed rat cardiomyocytes without affecting TPS and TR90. The Janus kinase 2 (JAK2) inhibitor AG490, the mitogen‐activated protein kinase (MAPK) inhibitor SB203580, and the nitric oxide synthase (NOS) inhibitor L‐NAME abrogated leptin‐induced cardiomyocyte contractile response in low‐fat diet group without affecting the high‐fat diet group. High‐fat diet significantly downregulated cardiac expression of Ob‐R. Elevation of extracellular Ca2+ concentration nullified obesity‐induced cardiomyocyte mechanical dysfunction and leptin‐induced depression in PS. These data indicate presence of cardiac leptin resistance in diet‐induced obesity possibly associated with impaired leptin receptor signaling.
Independent Influence of Insulin, Catecholamines, and Thyroid Hormones on Metabolic Syndrome
Authors: De Pergola Giovanni , Giorgino Francesco , Benigno Ritanna , Guida Pietro , Giorgino Riccardo
Published: August 2008

The objective of this study was to examine whether metabolic syndrome, defined according to adult treatment panel III criteria, is associated with insulin, catecholamines, and thyroid hormones, independently of age and gender. A cohort of 651 euthyroid overweight and obese patients, 440 women and 211 men, aged 18–68 years, were examined. Central fat accumulation (indirectly measured by waist circumference), fasting thyroid‐stimulating hormone (TSH), FT3, FT4, insulin, glucose, and lipid (cholesterol, HDL‐cholesterol, and triglyceride) serum concentrations, 24‐h urinary catecholamines, and the level of insulin resistance (estimated by homeostasis model assessment for insulin resistance (HOMAIR)) were measured. Patients with metabolic syndrome showed higher insulin (P < 0.001) and FT3 (P < 0.001) serum levels and higher 24‐h urinary noradrenaline (P < 0.001) than subjects without this syndrome. The number of metabolic syndrome parameters was directly associated with insulin (P < 0.001) and FT3 (P < 0.05) serum levels, and with 24‐h urinary noradrenaline (P < 0.001) in the whole population. When a multiple regression analysis was performed with the metabolic syndrome as the dependent variable, and age, gender, and insulin, and TSH, FT3, FT4 serum levels, and 24‐h urinary noradrenaline and adrenaline as independent variables, the metabolic syndrome maintained an independent positive association with age (P < 0.001), male sex (P < 0.001), insulin (P < 0.001), and 24‐h urinary noradrenaline (P < 0.001). In conclusion, this study suggests that insulin and noradrenaline cooperate independently to the development of the metabolic syndrome.
Family Meal Frequency and Weight Status Among Adolescents: Cross‐sectional and 5‐year Longitudinal Associations
Authors: Fulkerson Jayne A. , Neumark‐Sztainer Dianne , Hannan Peter J. , Story Mary
Published: August 2008

This study examined cross‐sectional and 5‐year longitudinal associations between the frequency of family meals and overweight status (>85th percentile for age and gender) in a large, diverse population of adolescents (n= 2,516). The population included two cohorts (midadolescence to young adulthood,n= 1,710, and early adolescence to midadolescence,n= 806). Logistic regression models tested cross‐sectional and longitudinal (1999–2004) associations between family meal frequency and overweight status. Two sets of models are presented: (i) models adjusted only for baseline demographic characteristics and (ii) models also adjusted for physical activity, sedentary behaviors, and energy intake. Longitudinal models adjusted for baseline overweight status. Although significant inverse associations between family meal frequency and overweight status were observed for early adolescent females in all cross‐sectional models (P< 0.001), longitudinal associations were not significant. Neither cross‐sectional nor longitudinal associations were significant for males of either cohort and older females in any models. Young adolescent females who do not eat meals with their families may be at risk for overweight; however, the increased risk may not persist over a 5‐year period. Eating family meals during high school may not protect against overweight during young adulthood. Although previous longitudinal research has suggested significant dietary and psychosocial benefits related to family meal frequency, the weight‐related benefits of family meals may be more complex and deserving of further study, including an examination of the quality and quantity of food consumed at family meals.
Obesity and the Likelihood of Sexual Behavioral Risk Factors for HPV and Cervical Cancer
Authors: Wee Christina C. , Huang Annong , Huskey Karen W. , McCarthy Ellen P.
Published: August 2008

Obesity is associated with higher cervical cancer mortality, but its relationship with sexual behavioral risk factors that predispose women to human papilloma virus (HPV) and cervical cancer is unclear. We used data from 3,329 women participants, aged 20–59 years, of the 1999–2004 National Health and Nutrition Examination Survey, to analyze the relationship between BMI and age at first intercourse, number of sexual partners, condom use during sexual activity, history of sexually transmitted disease (STD), herpes simplex virus 2 (HSV‐2) seropositivity, and HPV prevalence. BMI was not associated with the prevalence of HPV. Mildly obese women (BMI 30.0–34.9 kg/m2) were least likely to report a STD history (9% vs. 13% in normal weight) and ≥2 sexual partners in the previous year (8% vs. 13%) while overweight women (BMI 25.0–29.9 kg/m2) were least likely to report ≥10 lifetime partners; among those with multiple partners, BMI was not associated with sexual activity without condoms in the past month. After adjustment for age, race/ethnicity, and education, women with higher BMI were less likely to report sexual behavioral risk factors than normal‐weight women; however, odds ratios were only significant for mildly obese women for reporting a STD history (0.74, 95% confidence interval 0.55–0.99) and having ≥2 sexual partners in the last year (0.57, 0.39–0.85). Higher BMI was not associated with HSV‐2 seropositivity after adjustment. HPV and sexual behavioral risk factors for HPV and cervical cancer are not more prevalent in obese than normal‐weight women and unlikely to account for higher‐observed cervical cancer mortality in obese women.
Analytic theory of the adsorption-desorption transition of Gaussian polymers interacting with a periodic lattice of adsorbing centers
Authors: Chervanyov A. I. , Heinrich G.
Published: August 2008

Based on the obtained exact analytic solution, we calculate the adsorption-desorption diagram that describes the adsorption of Gaussian polymers onto a rigid surface that bears a periodic array of the adsorbing centers. It is shown that the polymer adsorption onto this substrate is fully governed by a delicate balance between the entropic depletion repulsion of polymers from the rigid surface and their attraction to the adsorbing centers. Magnitudes of these competitive effects are calculated in terms of the reduced overall affinity of the substrate η−1 and the reduced separation between the adsorbing centers d¯. The calculated exact adsorption-desorption diagram η(d¯) that describes the equilibrium between the above depletion and adsorption interactions, is shown to obey the scaling law η∼d¯−1.17.
Crystallographic, magnetic, and ferroelectric structures of bulklike BiFeO3 thin films
Authors: Béa H. , Bibes M. , Zhu X.-H. , Fusil S. , Bouzehouane K. , Petit S. , Kreisel J. , Barthélémy A.
Published: August 2008

Bi Fe O 3 thin films deposited on (111)-SrTiO3 substrates present both structural (rhombohedral) and multiferroic properties similar to bulk. The structural relaxation occurring when thickness increases and the low critical thickness possibly indicate different defect types and distribution as compared to (001)-BiFeO3, which may influence multiferroic domain dynamics. The same G-type antiferromagnetic order as in bulk is observed by neutron diffraction, with a superimposed weak ferromagnetic moment (10emu∕cm3) showing a planar anisotropy of 5kJ∕m3. When doped with 5% Mn these films also exhibit a polarization of 95μC∕cm2 along the [111] direction at room temperature, similar to high-quality BiFeO3 single crystals.
An analytical approach to computing biomolecular electrostatic potential. II. Validation and applications
Authors: Gordon John C. , Fenley Andrew T. , Onufriev Alexey
Published: August 2008

An ability to efficiently compute the electrostatic potential produced by molecular charge distributions under realistic solvation conditions is essential for a variety of applications. Here, the simple closed-form analytical approximation to the Poisson equation rigorously derived in Part I for idealized spherical geometry is tested on realistic shapes. The effects of mobile ions are included at the Debye–Hückel level. The accuracy of the resulting closed-form expressions for electrostatic potential is assessed through comparisons with numerical Poisson–Boltzmann (NPB) reference solutions on a test set of 580 representative biomolecular structures under typical conditions of aqueous solvation. For each structure, the deviation from the reference is computed for a large number of test points placed near the dielectric boundary (molecular surface). The accuracy of the approximation, averaged over all test points in each structure, is within 0.6 kcal/mol/|e|∼kT per unit charge for all structures in the test set. For 91.5% of the individual test points, the deviation from the NPB potential is within 0.6 kcal/mol/|e|. The deviations from the reference decrease with increasing distance from the dielectric boundary: The approximation is asymptotically exact far away from the source charges. Deviation of the overall shape of a structure from ideal spherical does not, by itself, appear to necessitate decreased accuracy of the approximation. The largest deviations from the NPB reference are found inside very deep and narrow indentations that occur on the dielectric boundaries of some structures. The dimensions of these pockets of locally highly negative curvature are comparable to the size of a water molecule; the applicability of a continuum dielectric models in these regions is discussed. The maximum deviations from the NPB are reduced substantially when the boundary is smoothed by using a larger probe radius (3 Å) to generate the molecular surface. A detailed accuracy analysis is presented for several proteins of various shapes, including lysozyme whose surface features a functionally relevant region of negative curvature. The proposed analytical model is computationally inexpensive; this strength of the approach is demonstrated by computing and analyzing the electrostatic potential generated by a full capsid of the tobacco ring spot virus at atomic resolution (500 000 atoms). An analysis of the electrostatic potential of the inner surface of the capsid reveals what might be a RNA binding pocket. These results are generated with the modest computational power of a desktop personal computer.
Molecular dump processes induced by chirped laser pulses
Authors: Marquetand Philipp , Nuernberger Patrick , Brixner Tobias , Engel Volker
Published: August 2008

We focus on the applications of shaped-dump laser pulses in the femtosecond regime. Calculations on a model system show that a wealth of information on molecular properties can be obtained from spectroscopy with such pulses. Systematic parameter scans are presented for linearly chirped pulses and for colored double pulses, revealing the dynamical properties of the system. For characterization of the system, quantum control fitness landscapes prove to be a powerful tool.
On the interatomic electronic processes following Auger decay in neon dimer
Authors: Stoychev Spas D. , Kuleff Alexander I. , Tarantelli Francesco , Cederbaum Lorenz S.
Published: August 2008

The accessible relaxation channels of the electronic states of Ne++–Ne and Ne3+–Ne populated by KLL Auger decay are studied. In particular, we address the “direct” and “exchange” interatomic Coulombic decays (ICDs) and the electron-transfer-mediated decay following the population of one-site states Ne++(2s−2)–Ne and Ne++(2s−12p−1 P1)–Ne. Radiative charge transfer of the low lying Ne++(2p−2)–Ne states, three-electron ICD process from the Ne++(2s−2)–Ne states, as well as charge transfer at the points of curve crossing of the lowest in energy Ne3+(2p−3)–Ne states are also discussed. To carry out the present study, we have calculated the potential energy curves (from 1.75 to 5.00 Å) of the ground state Ne2, the core ionized state Ne+(1s−1)–Ne, and the dicationic and tricationic states with energies in the range of 45–140 eV using accurate ab initio methods and basis sets. Apart from being of interest by themselves, the results obtained may be helpful in interpreting the recent measurements of interatomic electronic processes following Auger decay in neon dimer [K. Kreidi et al., J. Phys. B 41, 101002 (2008)].
Electronic and atomic structure of the AlnHn+2 clusters
Authors: Martínez J. I. , Alonso J. A.
Published: August 2008

The electronic and atomic structure of the family of hydrogenated Al clusters AlnHn+2 with n=4–11 has been studied using the density functional theory with the generalized gradient approximation (GGA) for exchange and correlation. All these clusters have substantial gaps between the highest occupied and the lowest unoccupied molecular orbitals (HOMO-LUMO) and, consequently, they are chemically very stable. The largest gap of 2.81eV occurs for Al6H8. Five clusters of the family, Al4H6, Al5H7, Al6H8, Al7H9, and Al10H12, fulfill the Wade–Mingos rule. That is, in AlnHn+2, the Al matrix forms a polyhedron of n vertices and n H atoms form strong H–Al terminal bonds; one pair of electrons is involved in each of those bonds. The remaining n+1 electron pairs form a delocalized cloud over the surface of the Al cage. The clusters fulfilling the Wade–Mingos rule have wider HOMO-LUMO gaps and are chemically more stable. The trends in the gap have some reflections in the form of the photoabsorption spectra, calculated in the framework of time-dependent density functional theory using the GGA single-particle energies and orbitals and a local density approximation exchange-correlation kernel.
On the epistemic view of quantum states
Authors: Skotiniotis Michael , Roy Aidan , Sanders Barry C.
Published: August 2008

We investigate the strengths and limitations of the Spekkens toy model, which is a local hidden variable model that replicates many important properties of quantum dynamics. First, we present a set of five axioms that fully encapsulate Spekkens’ toy model. We then test whether these axioms can be extended to capture more quantum phenomena by allowing operations on epistemic as well as ontic states. We discover that the resulting group of operations is isomorphic to the projective extended Clifford group for two qubits. This larger group of operations results in a physically unreasonable model; consequently, we claim that a relaxed definition of valid operations in Spekkens’ toy model cannot produce an equivalence with the Clifford group for two qubits. However, the new operations do serve as tests for correlation in a two toy bit model, analogous to the well known Horodecki criterion for the separability of quantum states.
Electronic relaxation effects in condensed polyacenes: A high-resolution photoemission study
Authors: Rocco M. L. M. , Haeming M. , Batchelor D. R. , Fink R. , Schöll A. , Umbach E.
Published: August 2008

We present a high-resolution photoelectron spectroscopy investigation of condensed films of benzene, naphthalene, anthracene, tetracene, and pentacene. High spectroscopic resolution and a systematic variation of the molecular size allow a detailed analysis of the fine structures. The line shapes of the C 1s main lines are analyzed with respect to the different contributions of inhomogeneous broadening, vibronic coupling, and chemical shifts. The shake-up satellite spectra reveal trends, which give insight into the charge redistribution within the molecule upon photoexcitation. In particular, the shake-up between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) increases in intensity and moves closer toward the C 1s main line if the size of the aromatic system is increased. An explanation is given on the basis of the delocalization of the aromatic system and its capability in screening the photogenerated core hole. A comparison of the HOMO-LUMO shake-up position to the optical band gap gives additional insight into the reorganization of the electronic system upon photoexcitation.
Magnetic anisotropy of ferromagnetic Ga1−xMnxAs formed by Mn ion implantation and pulsed-laser melting
Authors: Cho Y. J. , Scarpulla M. A. , Zhou Y. Y. , Ge Z. , Liu X. , Dobrowolska M. , Yu K. M. , Dubon O. D. , Furdyna J. K.
Published: August 2008

We measured the magnetic anisotropy of nearly fully relaxed ferromagnetic Ga1−xMnxAs formed by Mn ion implantation followed by pulsed-laser melting (II-PLM) using magnetometry and ferromagnetic resonance. In qualitative terms the material formed by II-PLM exhibits all magnetic anisotropy features commonly found in Ga1−xMnxAs films fabricated by low-temperature molecular beam epitaxy (LT-MBE). Quantitatively, however, the magnetic anisotropy of II-PLM Ga1−xMnxAs is dominated by cubic anisotropy terms, which we attribute to the smaller strain in the II-PLM material due to the absence of Mn interstitials. One should note, however, that II-PLM Ga1−xMnxAs also exhibits a weak but finite uniaxial in-plane magnetic anisotropy similar to that observed in LT-MBE Ga1−xMnxAs, which can be ascribed to the small built-in compressive strain. The similarity between II-PLM and LT-MBE Ga1−xMnxAs clearly points to an intrinsic origin of this property, independent of the method of fabrication. At low temperatures the remnant in-plane magnetization of the II-PLM film exhibits single-domain characteristics, while perpendicular magnetization shows a multiple-domain behavior.
S
1
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S
transition of 2,3-benzofluorene at low temperatures in the gas phase
Authors: Staicu A. , Rouillé G. , Henning Th. , Huisken F. , Pouladsaz D. , Scholz R.
Published: August 2008

The S1(A1′)←S0(A1′) absorption spectrum of jet-cooled 2,3-benzofluorene (Bzf) has been measured by cavity ring-down spectroscopy. The potential energy surfaces of the Sn=0,1,2 states of Bzf have been investigated with calculations based on the time-dependent density functional theory (TD-DFT). At the B3LYP/TZ level of theory, TD-DFT does not deliver a realistic difference between the excited S1 and S2 potential energy surfaces, a problem which can be avoided by introducing a reference geometry where this difference coincides with the observation. In this geometry, an expression for the Herzberg–Teller corrected intensities of the vibronic bands is proposed, allowing a straightforward assignment of the observed a′ modes below 900 cm−1, including realistic calculated intensities. For vibronic bands at higher energies, the agreement between calculated and observed modes is deteriorated by substantial Dushinsky rotations and nonparabolicities of the potential energy surface S1.
Point contact readout for a quantum dot terahertz sensor
Authors: Pelling S. , Davis R. , Kulik L. , Tzalenchuk A. , Kubatkin S. , Ueda T. , Komiyama S. , Antonov V. N.
Published: August 2008

We introduce a terahertz radiation sensor in which the photon-induced ionization state of a quantum dot is monitored by a point contact formed in the same semiconductor heterostructure. For comparison we used a readout based on a single electron transistor coupled to the same quantum dot. The experiments prove functionality of the point contact-based device with additional practical advantage of a higher operation temperature up to 1.5K and ease of nanofabrication.
Structure and dielectric properties of high-pressure perovskite-type oxyfluorides xKTiO2F–(1−x)BaTiO3
Authors: Katsumata Tetsuhiro , Umemoto Hiroshi , Inaguma Yoshiyuki , Fu Desheng , Itoh Mitsuru
Published: August 2008

We synthesized xKTiO2F–(1−x)BaTiO3 solid solution by the high pressure and temperature method. With regard to the temperature dependence of the dielectric permittivity, the three anomalies corresponding to the three phase transitions of BaTiO3 merged with the increase in x, and only one peak was observed for 0.12≤x≤0.20. The variation in TC with the composition, dTC/dx, of xKTiO2F–(1−x)BaTiO3 was approximately −14 K/mol % for x≥0.12, which is almost the same as and larger than that of the 1/3xBaLiF3−(1−1/3x)BaTiO3 and Ba(Ti1−xMx)O3 (B=Zr, Sn, Hf, and Ce) solid solutions, respectively. This result indicates that the phase transition temperature is significantly affected by the substitution with F ion. Furthermore, it was found that the 0.15KTiO2F−0.85BaTiO3 is an ideal relaxor and that the remnant polarization is 5.6 μC/cm2 at 70 K, which is comparable to that of Ba(Ti0.7Zr0.3)O3. However, the εm of 0.15KTiO2F−0.85BaTiO3 (≈5000 at 100 kHz) was smaller than that of the B-site ion-substituted relaxors: Ba(Ti0.7Zr0.3)O3 and Ba(Ti0.82Sn0.18)O3. Since the remnant polarization of 0.15KTiO2F−0.85BaTiO3 at 70 K was comparable to that of Ba(Ti0.7Zr0.3)O3 at 175 K, the small εm of 0.15KTiO2F−0.85BaTiO3 is found to be due to the decrease in the dielectric permittivity in the paraelectric region.
Modeling the soft backing layer thickness effect on adhesion of elastic microfiber arrays
Authors: Long Rong , Hui Chung-Yuen , Kim Seok , Sitti Metin
Published: August 2008

A recent experiment has shown that the force required to pull off a flat circular rigid punch in adhesive contact with an array of elastic fibrils is sensitive to the thickness of the elastic backing layer to which these fibrils are attached. This result motivates us to study the effect of sample compliance on the adhesion of fibril arrays. A closed form expression for the compliance of such arrays attached to a backing layer of finite thickness is derived. Our model is based on the assumption that the adhesive strength of a fibril is deterministic. In addition, we show that the normalized pull-off force is inversely proportional to the square root of a single dimensionless parameter β. For large β, the pull-off force is low as it is governed by the stress concentration at the punch edge. For small β, this pull-off force reaches a theoretical limit that is governed by the ability of fibrils to share load equally [equal load sharing (ELS) limit]. The pull-off force predicted by our model is compared with new experimental data. Our model shows the correct trend but underestimates the pull-off force in the ELS limit. The difference between our theoretical predictions and experimental results is attributed to alignment difficulties in the experiments and the fact that the adhesive strength of fibrils is governed by local statistics.
Fisher information of special functions and second-order differential equations
Authors: Yáñez R. J. , Sánchez-Moreno P. , Zarzo A. , Dehesa J. S.
Published: August 2008

We investigate a basic question of analytic information theory, namely, the evaluation of the Fisher information and the relative Fisher information with respect to a non-negative function, for the probability distributions obtained by squaring the special functions of mathematical physics which are solutions of second-order differential equations. We obtain explicit expressions for these information-theoretic properties via the expectation values of the coefficients of the differential equation. We illustrate our approach for various nonrelativistic D-dimensional wavefunctions and some special functions of physicomathematical interest. Emphasis is made in the Nikiforov–Uvarov hypergeometric-type functions, which include and generalize the Hermite functions and the Gauss and Kummer hypergeometric functions, among others.
Geometric phase for non-Hermitian Hamiltonians and its holonomy interpretation
Authors: Mehri-Dehnavi Hossein , Mostafazadeh Ali
Published: August 2008

For an arbitrary possibly non-Hermitian matrix Hamiltonian H that might involve exceptional points, we construct an appropriate parameter space M and line bundle Ln over M such that the adiabatic geometric phases associated with the eigenstates of the initial Hamiltonian coincide with the holonomies of Ln. We examine the case of 2×2 matrix Hamiltonians in detail and show that, contrary to claims made in some recent publications, geometric phases arising from encircling exceptional points are generally geometrical and not topological in nature.
Exothermic reactions in Co/Al nanolaminates
Authors: Adams D. P. , Hodges V. C. , Bai M. M. , Jones E. , Rodriguez M. A. , Buchheit T. , Moore J. J.
Published: August 2008

Vapor-deposited Co/Al nanolaminates having a net equiatomic stoichiometry exhibited rapid, high-temperature synthesis. When ignited locally, 7.5-μm-thick Co/Al foils were characterized by self-sustained propagating reactions with flame front speeds between ∼0.5 and 9 m/s. Speed was largely affected by bilayer thickness and premixed volume fraction, consistent with previous studies of other exothermic multilayers. Cobalt aluminide foils reacted by self-propagating synthesis developed a variety of rough surface morphologies characterized by a large amplitude (peak-to-valley ∼1.0 μm), multiperiod, wavelike structure. High-temperature reaction was also stimulated by rapid global heating. Tests revealed low ignition temperatures (Tig)∼240–460 °C compared with previous Co–Al powder reactant experiments. Ignition temperature was influenced by bilayer thickness. All foils ignited by global heating and those reacted in a self-propagating mode developed a single-phase B2 (CsCl-type) crystal structure. Thick Co/Al nanolaminates were used successfully to join a few different materials including metalized Al2O3 (by soldering) and polyetheretherketone (by direct attachment).
Electron transfer reactions for image and image-derived states in dielectric thin films
Authors: Jensen E. T. , Sanche L.
Published: August 2008

We have studied the cross section for electron trapping that occurs at the surfaces and interfaces of a variety of thin dielectric films (n-octane, methanol, n-butanol, and difluoromethane) that are grown on Kr buffer films. When such films are bombarded with electrons of very low incident energies (E≲300 meV), charging cross sections up to the order of 10−14 cm2 are measured for submonolayer quantities of a variety of coadsorbed molecules: CH3I, CH3Br, CH3Cl, and CO2. These huge cross sections are ascribed to the formation of image states at the dielectric film interfaces, which trap incoming electrons and, via coupling to the adsorbate electron affinity levels, dramatically enhance the capture probability. We have also shown that thin film dielectric layer structures can be created which display image-derived states, such as a “quantum well” in a sandwich structure with two “electron barrier” layers surrounding a Kr and adsorbate spacer film. These phenomena are shown to be of a general nature, occurring for a wide variety of molecular thin films, and depend on the dielectric constant and electron affinity of the selected species. We also report the absolute cross section for dissociative electron attachment of submonolayer CH3I adsorbed on Kr thin films.
Antiferromagnetic iridium manganese based intermediate layers for perpendicular magnetic recording media
Authors: Srinivasan Kumar , Piramanayagam S. N. , Sbiaa Rachid
Published: August 2008

Current generation CoCrPt oxide based perpendicular magnetic recording media use two Ru-based intermediate layers in order to grow crystallographically textured, and magnetically isolated granular media. In this work, the advantage of replacing the Ru grain isolation layer with antiferromagnetic IrMn is demonstrated. Media samples using 7.5nm thick IrMn intermediate layers show perpendicular texture with dispersion below 4°, coercivity of over 4000Oe alongside magnetic exchange decoupling, average grain sizes of 6nm with distributions under 14%, and thermal stability factor of 88. The IrMn layer may also help to stabilize the recording layer grains against thermal instability effects.
Ultrathin SiO2 layer on atomically flat Si(111) surfaces with excellent electrical characteristics formed by nitric acid oxidation method
Authors: Kim Woo-Byoung , Asuha  , Matsumoto Taketoshi , Kobayashi Hikaru
Published: August 2008

We have developed a method of formation of atomically smooth Si∕SiO2 interfaces by oxidation of atomically flat Si(111) surfaces by use of azeotropic nitric acid (HNO3) aqueous solutions (i.e., 68wt% HNO3 at 121°C). For the SiO2 layer on the atomically smooth Si substrates, the concentration of suboxide species, Si2+, is ∼50% of that on the rough Si substrates, and the valence band discontinuity is higher by ∼0.1eV. In this case, the leakage current flowing through the ∼1.2nm SiO2 is low, and further decreased by postmetallization annealing at 250°C in hydrogen (e.g., 0.5A∕cm2 at VG=1V).
Dynamics and rheology of wormlike micelles emerging from particulate computer simulations
Authors: Padding J. T. , Boek E. S. , Briels W. J.
Published: August 2008

We perform coarse-grained computer simulations of solutions of semidilute wormlike micelles and study their dynamic and rheological properties, both in equilibrium and under shear flow. The simulation model is tailored to the study of relatively large time and length scales (micrometers and several milliseconds), while it still retains the specific mechanical properties of the individual wormlike micelles. The majority of the mechanical properties (persistence length, diameter, and elastic modulus of a single worm) is determined from more detailed atomistic molecular dynamics simulations, providing the link with the chemistry of the surfactants. The method is applied to the case of a solution containing 8% (by weight) erucyl bis(hydroxymethyl)methylammonium chloride (EHAC). Different scission energies ranging from 15.5kbT to 19.1kBT are studied, leading to both unentangled and entangled wormlike micelles. We find a decrease in the average contour length and an increase in the average breaking rate with increasing shear rate. In equilibrium, the decay of the shear relaxation modulus of the unentangled samples agrees with predictions based on a theory of breakable Rouse chains. Under shear flow, transient over- and undershoots are measured in the stress tensor components. At high shear rates we observe a steady-state shear stress proportional to γ̇1/3, where γ̇ is the shear rate. This is confirmed by our high shear rate experiments of real EHAC in a parallel-plate geometry.
Nonlinear theory of resonant slow waves in anisotropic and dispersive plasmas
Authors: Clack Christopher T. M. , Ballai Istvan
Published: August 2008

The solar corona is a typical example of a plasma with strongly anisotropic transport processes. The main dissipative mechanisms in the solar corona acting on slow magnetoacoustic waves are the anisotropic thermal conductivity and viscosity [Ballai et al., Phys. Plasmas 5, 252 (1998)] developed the nonlinear theory of driven slow resonant waves in such a regime. In the present paper the nonlinear behavior of driven magnetohydrodynamic waves in the slow dissipative layer in plasmas with strongly anisotropic viscosity and thermal conductivity is expanded by considering dispersive effects due to Hall currents. The nonlinear governing equation describing the dynamics of nonlinear resonant slow waves is supplemented by a term which describes nonlinear dispersion and is of the same order of magnitude as nonlinearity and dissipation. The connection formulas are found to be similar to their nondispersive counterparts.
Temporal-spatial-resolved spectroscopic study on the formation of an atmospheric pressure microplasma jet
Authors: Ye Rubin , Zheng Wei
Published: August 2008

Temporal-spatial-resolved optical emission spectroscopy was employed to shed light on the dynamic behavior and the propagation mechanism of a plasma, originating from a dielectric barrier discharge in helium inside a quartz tube for microplasma jet formation. The plasma propagated, regardless of the gas flow direction, in an accelerating manner at a high velocity up to 17 km/s, suggesting that the propagation was sustained by photoionization. A theoretical analysis demonstrated that the enhancement of the local electric field ahead of the ionization front was mainly responsible for the acceleration of the plasma near the electrode.
Wedgelike ultrathin epitaxial BaTiO3 films for studies of scaling effects in ferroelectrics
Authors: Petraru A. , Kohlstedt H. , Poppe U. , Waser R. , Solbach A. , Klemradt U. , Schubert J. , Zander W. , Pertsev N. A.
Published: August 2008

To study ferroelectric size effects in heteroepitaxial SrRuO3∕BaTiO3∕SrRuO3 capacitors, ultrathin BaTiO3 layers were deposited in wedge form across SrTiO3 substrates. The wedgelike films were fabricated by using either an off-center substrate-target geometry or via a moveable shutter during high-pressure sputter deposition. The crystallinity, composition, and surface roughness along wedgelike BaTiO3 films were verified by x-ray diffraction, Rutherford backscattering spectrometry, and atomic force microscopy, respectively. The electrical measurements performed at 77K showed that, despite progressive reduction in remanent polarization as the film thickness decreases even the 3.5-nm-thick BaTiO3 film retains a large remanent polarization of 28μC∕cm2.
Thermophysical properties of Si, Ge, and Si–Ge alloy melts measured under microgravity
Authors: Chathoth S. M. , Damaschke B. , Samwer K. , Schneider S.
Published: August 2008

We have investigated density, thermal expansion, and surface tension of Si, Ge, and Si–Ge alloys in the melt and undercooled state under microgravity conditions. The experiments were conducted in the TEMPUS facility on board a Zero-G aircraft. The density of the liquid alloys as a function of composition show a nonideal behavior. Thermal expansion coefficients were found to be in the order of 10−4K−1 and was highest for Si75Ge25 melt. The surface tension is lowered with the addition of 25at.% Si in Ge. The further addition of Si increases the surface tension almost linearly with composition.
Conducting polymer formed by low energy gold ion implantation
Authors: Salvadori M. C. , Cattani M. , Teixeira F. S. , Brown I. G.
Published: August 2008

A buried conducting layer of metal/polymer nanocomposite was formed by very low energy gold ion implantation into polymethylmethacrylate. The conducting layer is ∼3 nm deep and of width ∼1 nm. In situ resistivity measurements were performed as the implantation proceeded, and the conductivity thus obtained as a function of buried gold concentration. The measured conductivity obeys the behavior well established for composites in the percolation regime. The critical concentration, below which the polymer remains an insulator, is attained at a dose ∼1.0×1016 atoms/cm2 of implanted gold ions.
Monitoring the small-scale distribution of sympatric European pine martens (Martes martes) and stone martens (Martes foina): a multievidence approach using faecal DNA analysis and camera-traps
Authors: Rosellini Stefano , Osorio Enrique , Ruiz-González Aritz , Piñeiro Ana , Barja Isabel
Published: August 2008

The European pine marten (Martes martes) and stone marten (Martes foina) are two closely related mustelids that live sympatrically over a large area of Europe. In the northern Iberian Peninsula, the distribution ranges of both species overlap extensively. The objectives of this study were (1) to verify whether, on a small scale, both species also live sympatrically and (2) to compare camera traps and scat DNA as methods for detecting marten species. The study was conducted in a protected area (province of Ourense, north-west Spain), which covers 6700 ha. To test the sympatry hypothesis, 90 fresh faecal samples, identified as faeces of genus Martes on the basis of their morphology, were collected from June 2004 to August 2006. The specific identification of faecal samples was conducted using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) techniques. In addition, 20 camera-traps (916 camera-trap-nights) were in operation during the study period. Of the faecal samples collected, 88.8% were attributed to the European pine marten, while the remaining 11.2% were not amplified by PCR and thus could not be assigned. The European pine marten was identified in 57.9% of the photos of carnivores and the stone marten was not detected in any. The faecal DNA analysis and camera-trap results supported previous conclusions about habitat preferences and the distribution of the two species obtained using other methods. The two non-invasive methods that were used in this study were shown to be reliable techniques that can be employed simultaneously, because each method has advantages and disadvantages that are influenced by the size of the area inventoried, sampling effort, and cost and efficiency of the method. The data gathered using these methods provided important information on the understanding of trophic and competitive interactions between the species.
Philopatry and site fidelity of New Zealand sea lions (Phocarctos hookeri)
Authors: Chilvers B. Louise , Wilkinson Ian S.
Published: August 2008

The New Zealand sea lion (NZ sea lion), Phocarctos hookeri, is New Zealand’s only endemic pinniped, and one of the worlds rarest otariids. It is classified as ‘Threatened’ based primarily on the low number of breeding sites and restricted distribution. In New Zealand, a species listed as ‘threatened’ is required to be managed to allow its recovery and removal from the list within 20 years. For NZ sea lions this is dependant on the establishment of new breeding areas. However, understanding the recolonisation processes for pinnipeds is still in its infancy with factors such as philopatry needing more research to understand individual dispersal and the recolonisation process. This paper presents the first quantitative investigation into the level of site fidelity and philopatry to breeding beaches in NZ sea lions. Data from resights of NZ sea lions marked as pups from the northern Auckland Island breeding area suggest that both site fidelity and philopatry are important characteristics of this species. Our results show that overall: (1) females have a higher resighting rate than males, particularly at natal sites; (2) female non-natal resightings are predominantly restricted to locations within the northern Auckland Island breeding area (an area of ~10 km2), whereas male resightings are more widely dispersed (up to 700 km to NZ mainland); and (3) philopatry occurs for both sexes, but is more predominant in females than males, with males displaying delay related to sexual and social maturity. The colonisation of new breeding habitats rarely occurs when philopatry is strong and population density is low, stable or declining such as seen for NZ sea lions. Therefore, this research indicates that management of NZ sea lions needs to minimise anthropogenic mortality and encourage population growth to maximise density at breeding sites and encourage females to disperse to establish new breeding areas.
Predicting habitat suitability for the endemic mountain nyala (Tragelaphus buxtoni) in Ethiopia
Authors: Evangelista Paul H. , Norman John , Berhanu Lakew , Kumar Sunil , Alley Nathaniel
Published: August 2008

The use of statistical models to predict species distributions and suitable habitat has become an essential tool for wildlife management and conservation planning. Models have been especially useful with rare and endangered wildlife species. One such species is the mountain nyala (Tragelaphus buxtoni), a spiral-horned antelope endemic to the Ethiopian highlands. The full range of the species has never been adequately defined and recent discoveries of new populations suggest that others may exist undetected. To identify potential mountain nyala occurrences, we used classification tree analysis to predict suitable habitat using 76 climatic, topographical and vegetative variables. Three model evaluation methods showed a strong performance of the final model with an overall accuracy of 90%, Cohen’s maximised κ of 0.80 and area under the receiver operating characteristic curve (AUC) value of 0.89. Minimum temperature and maximum precipitation generally had the greatest predictive contributions to suitable mountain nyala habitat. The predicted habitat covered an area of 39 378 km2, with the majority occurring in remote forests on the southern escarpment of the Bale Mountains. Other areas within the predicted range may be too impacted by human and livestock populations to support mountain nyala; however, the model will be useful in directing future surveys for new populations while offering clues to the species historical range.
Fluctuating asymmetry and preferences for sex-typical bodily characteristics
Authors: Brown William M. , Price Michael E. , Kang Jinsheng , Pound Nicholas , Zhao Yue , Yu Hui
Published: August 2008

Body size and shape seem to have been sexually selected in a variety of species, including humans, but little is known about what attractive bodies signal about underlying genotypic or phenotypic quality. A widely used indicator of phenotypic quality in evolutionary analyses is degree of symmetry (i.e., fluctuating asymmetry, FA) because it is a marker of developmental stability, which is defined as an organism's ability to develop toward an adaptive end-point despite perturbations during its ontogeny. Here we sought to establish whether attractive bodies signal low FA to observers, and, if so, which aspects of attractive bodies are most predictive of lower FA. We used a 3D optical body scanner to measure FA and to isolate size and shape characteristics in a sample of 77 individuals (40 males and 37 females). From the 3D body scan data, 360° videos were created that separated body shape from other aspects of visual appearance (e.g., skin color and facial features). These videos then were presented to 87 evaluators for attractiveness ratings. We found strong negative correlations between FA and bodily attractiveness in both sexes. Further, sex-typical body size and shape characteristics were rated as attractive and correlated negatively with FA. Finally, geometric morphometric analysis of joint configurations revealed that sex-typical joint configurations were associated with both perceived attractiveness and lower FA for male but not for female bodies. In sum, body size and shape seem to show evidence of sexual selection and indicate important information about the phenotypic quality of individuals.
Receptor density balances signal stimulation and attenuation in membrane-assembled complexes of bacterial chemotaxis signaling proteins
Authors: Besschetnova Tatiana Y. , Montefusco David J. , Asinas Abdalin E. , Shrout Anthony L. , Antommattei Frances M. , Weis Robert M.
Published: August 2008

All cells possess transmembrane signaling systems that function in the environment of the lipid bilayer. In the
Escherichia coli
chemotaxis pathway, the binding of attractants to a two-dimensional array of receptors and signaling proteins simultaneously inhibits an associated kinase and stimulates receptor methylation—a slower process that restores kinase activity. These two opposing effects lead to robust adaptation toward stimuli through a physical mechanism that is not understood. Here, we provide evidence of a counterbalancing influence exerted by receptor density on kinase stimulation and receptor methylation. Receptor signaling complexes were reconstituted over a range of defined surface concentrations by using a template-directed assembly method, and the kinase and receptor methylation activities were measured. Kinase activity and methylation rates were both found to vary significantly with surface concentration—yet in opposite ways: samples prepared at high surface densities stimulated kinase activity more effectively than low-density samples, whereas lower surface densities produced greater methylation rates than higher densities. FRET experiments demonstrated that the cooperative change in kinase activity coincided with a change in the arrangement of the membrane-associated receptor domains. The counterbalancing influence of density on receptor methylation and kinase stimulation leads naturally to a model for signal regulation that is compatible with the known logic of the
E. coli
pathway. Density-dependent mechanisms are likely to be general and may operate when two or more membrane-related processes are influenced differently by the two-dimensional concentration of pathway elements.