bluuebunny/crossref_metadata_2025 huggingface dataset:
The power of social structure: how we became an intelligent lineage
Authors: de Sousa António Marina Resendes , Schulze-Makuch Dirk
Published: July 2010

New findings pertinent to the human lineage origin (Ardipithecus ramidus) prompt a new analysis of the extrapolation of the social behavior of our closest relatives, the great apes, into human ‘natural social behavior’. With the new findings it becomes clear that human ancestors had very divergent social arrangements from the ones we observe today in our closest genetic relatives.

The social structure of chimpanzees and gorillas is characterized by male competition. Aggression and the instigation of fear are common place. The morphology ofA. ramiduspoints in the direction of a social system characterized by female-choice instead of male–male competition. This system tends to be characterized by reduced aggression levels, leading to more stable arrangements. It is postulated here that the social stability with accompanying group cohesion propitiated by this setting is favorable to the investment in more complex behaviors, the development of innovative approaches to solve familiar problems, an increase in exploratory behavior, and eventually higher intelligence and the use of sophisticated tools and technology.

The concentration of research efforts into the study of social animals with similar social systems (e.g., New World social monkeys(Callitrichidae), social canids (Canidae) and social rodents (Rodentia)) are likely to provide new insights into the understanding of what factors determined our evolution into an intelligent species capable of advanced technology.
Enhanced Detection Sensitivity with a New Windowless XEDS System for AEM Based on Silicon Drift Detector Technology
Authors: Schlossmacher P. , Klenov D.O. , Freitag B. , von Harrach H.S.
Published: July 2010

For many years now, the combination of the modern S/TEM system (scanning/transmission electron microscope) with the X-ray energy dispersive spectrometer (XEDS) has resulted in Analytical Electron Microscopes (AEMs) able to deliver both high-resolution imaging and elemental composition maps in the same instrument. This ability to correlate local elemental composition with microstructure has greatly broadened the applications realm of the S/TEM instrument. The boundaries of performance for many of these applications are now determined by limits in XEDS system detection sensitivity. In this article, we describe an AEM with greatly enhanced detection sensitivity due to a number of innovations in the system architecture, including: a high-brightness Schottky FEG source, four detectors integrated deeply into the objective lens, windowless silicon drift detector technology with shutters, and high-speed electronics readout. This new system architecture provides many performance benefits, such as improved light element detection, better sample tilt response, faster mapping, and especially enhanced system detection sensitivity.
Mapping the Heart
Authors: Carmichael Stephen W.
Published: July 2010

Some of the receptors on the surface of cardiac muscle cells (cardiomyocytes) mediate the response of these cells to catecholamines by causing the production of the common second messenger cyclic adenosine monophosphate (cAMP). An example of such receptors are the β1- and β2-adrenergic receptors (βARs) that are heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors. Selective stimulation of these two receptor subtypes leads to distinct physiological and pathophysiological responses, but their precise location on the surface of cardiomyocytes has not been correlated with these responses. In an ingenious combination of techniques, Viacheslav Nikolaev, Alexey Moshkov, Alexander Lyon, Michele Miragoli, Pavel Novak, Helen Paur, Martin Lohse, Yuri Korchev, Sian Harding, and Julia Gorelik have mapped the function of these receptors for the first time.
Phase Contrast Enhancement with Phase Plates in Biological Electron Microscopy
Authors: Nagayama Kuniaki , Danev Radostin , Shigematsu Hideki , Hosogi Naoki , Fukuda Yoshiyuki , Nitta Koji , Kaneko Yasuko
Published: July 2010

Theoretically, transmission electron microscopy (TEM) is compatible with three different types of phase plate: thin-film, electrostatic, and magnetic. However, designing functional phase plates has been an arduous process that has suffered from unavoidable technical obstacles such as phase-plate charging and difficulties associated with micro-fabrication of electrostatic and magnetic phase plates. This review discusses phase-contrast schemes that allow visualization of transparent objects with high contrast. Next it deals with recent studies on biological applications ranging from proteins and viruses to whole cells. Finally, future prospects for overcoming the problem of phase-plate charging and for designing the next generation of phase-plates to solve the problem of electron loss inherent in thin-film phase plates are discussed.
The TanDEM-X mission: overview and interferometric performance
Authors: Huber Sigurd , Younis Marwan , Krieger Gerhard
Published: July 2010

TanDEM-X (TDX; TerraSAR-X add-on for digital elevation measurement) is an innovative spaceborne X-band earth observation mission that will be launched in June 2010. This paper gives an overview of the TDX mission concept, summarizes the basic products and illustrates the achievable performance. In more detail the effect of quantization on the interferometric performance is discussed. Finally, new imaging techniques are outlined.
Integrated 79 GHz UWB automotive radar front-end based on Hi-Mission MCM-D silicon platform
Authors: Platt Duncan , Pettersson Lars , Jakonis Darius , Salter Michael , Haglund Joacim
Published: July 2010

A highly integrated silicon platform (Hi-Mission) for high frequency applications is introduced. This platform utilizes heterogeneous Multi-Chip Module-Deposited (MCM-D) technology with integrated passive devices together with silicon and GaAs Monolithic Microwave Integrated Circuit (MMIC) technology developed for the automotive Ultra Wide Band (UWB) radar (short-range radar) frequency band from 77 to 81 GHz. Developments are described in the area of MCM-D process development, MMIC, integrated phased array antenna, module design, and assembly process development. The demonstrator is composed of two test vehicles designed for conducted and radiated measurements, respectively. Test results are presented at the component and module level.
Fieber und Dysphagie einer jungen Frau
Authors: Heimgartner  , Knecht  , Oestmann
Published: July 2010

Wir berichten über eine 39-jährige Patientin mit septischem Zustandsbild nach antibiotisch behandelter Angina tonsillaris. Wegen Dysphagie konnte sie ihre Antibiotika vor der Hospitalisation nicht mehr schlucken. Radiologisch fanden sich pulmonale Infiltrate und eine Vena-iugularis-interna-Thrombose. Zusammen mit der Anamnese konnte trotz fehlendem Erregernachweis die Diagnose eines Lemierre-Syndroms gestellt werden. Nach Anpassung der antibiotischen Therapie und Beginn einer Antikoagulation war der weitere Verlauf günstig. Die lange Hospitalisationsdauer war Ausdruck der hohen Morbidität, die mit dem Lemierre-Syndrom einhergeht.
Contrasted styles of rifting in the eastern Gulf of Aden: A combined wide‐angle, multichannel seismic, and heat flow survey
Authors: Leroy Sylvie , Lucazeau Francis , d'Acremont Elia , Watremez Louise , Autin Julia , Rouzo Stéphane , Bellahsen Nicolas , Tiberi Christel , Ebinger Cynthia , Beslier Marie‐Odile , Perrot Julie , Razin Philippe , Rolandone Frédérique , Sloan Heather , Stuart Graham , Al Lazki Ali , Al‐Toubi Khalfan , Bache François , Bonneville Alain , Goutorbe Bruno , Huchon Philippe , Unternehr Patrick , Khanbari Khaled
Published: July 2010

Continental rifts and passive continental margins show fundamental along‐axis segmentation patterns that have been attributed to one or a number of different processes: extensional fault geometry, variable stretching along strike, preexisting lithospheric compositional and structural heterogeneities, oblique rifting, and the presence or absence of eruptive volcanic centers. The length and width scales of the rift stage fault‐bounded basin systems change during the late evolution of the new plate boundary, and the role of magmatism may increase as rifting progresses to continental rupture. Along obliquely spreading ridges, first‐order mid‐ocean ridge geometries originate during the synrift stage, indicating an intimate relationship between magma production and transform fault spacing and location. The Gulf of Aden rift is a young ocean basin in which the earliest synrift to breakup structures are well exposed onshore and covered by thin sediment layers offshore. This obliquely spreading rift is considered magma‐poor and has several large‐offset transforms that originated during late stage rifting and control the first‐order axial segmentation of the spreading ridge. Widely spaced geophysical transects of passive margins that produce only isolated 2‐D images of crust and uppermost mantle structure are inadequate for evaluation of competing rift evolution models. Using closely spaced new geophysical and geological observations from the Gulf of Aden we show that rift sectors between transforms have a large internal variability over short distances (∼10 km): the ocean‐continent transition (OCT) evolves from a narrow magmatic transition to wider zones where continental mantle is probably exhumed. We suggest that this small‐scale variability may be explained (1) by the distribution of volcanism and (2) by the along‐strike differences in time‐averaged extension rate of the oblique rift system. The volcanism may be associated with (1) the long‐offset Alula‐Fartak Fracture Zone, which may enhance magma production on its younger side, or (2) channeled flow from the Afar plume material along the newly formed OCT and the spreading ridge. Oblique extension and/or hot spot interactions may thereby have a significant control on the styles of rifting and continental breakup and on the evolution of many magma‐poor margins.
Comparative analysis and variability of the Jovian X‐ray spectra detected by the Chandra and XMM‐Newton observatories
Authors: Hui Yawei , Schultz David R. , Kharchenko Vasili A. , Bhardwaj Anil , Branduardi‐Raymont Graziella , Stancil Phillip C. , Cravens Thomas E. , Lisse Carey M. , Dalgarno Alexander
Published: July 2010

Expanding upon recent work, a more comprehensive spectral model based on charge exchange induced X‐ray emission by ions precipitating into the Jovian atmosphere is used to provide new understanding of the polar auroras. In conjunction with the Xspec spectral fitting software, the model is applied to analyze observations from both Chandra and XMM‐Newton by systematically varying the initial precipitating ion parameters to obtain the best fit model for the observed spectra. In addition to the oxygen and sulfur ions considered previously, carbon is included to discriminate between solar wind and Jovian magnetospheric ion origins, enabled by the use of extensive databases of both atomic collision cross sections and radiative transitions. On the basis of fits to all the Chandra observations, we find that carbon contributes negligibly to the observed polar X‐ray emission suggesting that the highly accelerated precipitating ions are of magnetospheric origin. Most of the XMM‐Newton fits also favor this conclusion with one exception that implies a possible carbon contribution. Comparison among all the spectra from these two observatories in light of the inferred initial energies and relative abundances of precipitating ions from the modeling show that they are significantly variable in time (observation date) and space (north and south polar X‐ray auroras).
Mechanical behavior of anhydrite caprock and implications for CO2 sealing capacity
Authors: Hangx Suzanne J. T. , Spiers Christopher J. , Peach Colin J.
Published: July 2010

Maintaining caprock integrity is prerequisite for geological storage of CO2. We investigated the mechanical strength and damage behavior of anhydrite‐rich caprock, which seals many potential CO2 storage sites around the world. Conventional triaxial tests were performed at temperatures of 20°C–80°C, confining pressures of 1.5–50 MPa and strain rates of ∼10−5 s−1. We determined the failure and dilatation envelopes for dry anhydrite and studied the effect upon strength and dilatation of high‐pressure pore fluids (Pf = 15 MPa), namely presaturated CaSO4 solution and CO2‐saturated CaSO4 solution. For dry samples, we observed an increase in strength with confining pressure and a slight weakening with temperature. Fluid penetration prior to failure resulted in a direct effective pressure effect on strength, but not on volumetric behavior. Fluid penetration during failure is too slow to influence mechanical and volumetric behavior. Overall, we found no short‐term chemical effects of CO2 and pore fluid on the strength of anhydrite. Penetration of the samples by CO2‐saturated pore fluid was more effective than by solution alone, most likely as a result of the lower interfacial tension of the CO2/water system. Simple analytical calculations based on the elastic flexure of a seal formation, combined with our failure and dilatation envelopes, show that, for realistic conditions, caprock integrity will not be compromised by mechanical damage. In addition, long‐term chemical reactions of anhydrite with CO2 will most likely not lead to significant CO2 penetration, though more research is needed.
Diffusion‐controlled tracer retention in crystalline rock on the field scale
Authors: Cvetkovic V.
Published: July 2010

Tracer retention is a key process for the barrier function of crystalline rock to any contaminant. Here we investigate the nature of retention mechanisms and their field‐scale parametrization using results of a comprehensive tracer transport experiment in crystalline rock on the field scale (Äspö Hard Rock Laboratory, Sweden). A method for identifying dominant retention mechanisms and inferring key parameters on the site scale is presented. Taking advantage of multiple tracer tests with a wide range of sorption affinities, retention is shown to be diffusion‐controlled. For the considered site, robust features of tracer migration can be reasonably well predicted within a rock volume on at least 200 m scale, by combining independent information with a simple model.
Locating nonvolcanic tremors beneath the San Andreas Fault using a station‐pair double‐difference location method
Authors: Zhang Haijiang , Nadeau Robert M. , Toksoz M. Nafi
Published: July 2010

It has been a challenging task to locate nonvolcanic tremors because of the lack of impulsive wave arrivals. A station‐pair double‐difference (DD) location method is developed to determine absolute tremor locations by directly using the station‐pair travel time differences measured from cross‐correlating tremor waveform envelopes. Multiple tremors are located together for inverting for station corrections to take into account velocity model inaccuracy. The new method is applied to tremors in the Parkfield region of central California between 27 July 2001 and 21 February 2009. Compared to the tremor catalog locations determined from a grid search location method, most of the newly located tremors are located at depths between 20 and 35 km, well below the seismogenic zone in the area. The tremors beneath Cholame, CA are more clearly separated into two zones laterally distributed across the San Andreas Fault, with most tremors occurring to the southwest and exhibiting a periodic pattern of occurrence. The new tremor locations help better delineate the spatial and temporal distribution of tremor activity and therefore are helpful for better understanding tremor origin and process.
Alternative approaches to antiviral treatments: focusing on glycosylation as a target for antiviral therapy
Authors: Merry Tony , Astrautsova Sviatlana
Published: July 2010

Development of effective and safe medication for the treatment of viral infections remains a major challenge for the pharmaceutical industry in the 21st Century. There are numerous problems with the existing antiviral treatments both in terms of their safety and, in some cases, their cost, and they cannot be used generally but only in special circumstances. However, the threat of viral diseases ranging from AIDS and hepatitis C to influenza is increasing each year and there is considerable interest in safer and more generally applicable alternative treatments. It has been recognized for some time that some viruses have glycosylation features that are essential to their infectivity, but a means of providing a therapeutic route that is based on this has not been easy to exploit. In recent years, a number of possible approaches have been investigated and some of these are now considered to be realistic forms of therapy. Generally, approaches based on inhibition of the host machinery to glycosylate viral proteins or the ability of compounds to mimic the surface glycosylation of the virus seem to offer the best potential approaches. In this mini‐review article, we look at recent advances in both of these areas and their potential to provide a new arsenal of antiviral therapeutics for AIDS, hepatitis C and influenza. Some of these are now entering clinical trials and others are at an advanced stage of preclinical development, but all of them represent good candidates for a therapy that could be more resilient to the problems of viral mutation and diversity.
Is There a Sex Ratio Difference in the Familial Aggregation of Specific Language Impairment? A Meta-Analysis
Authors: Whitehouse Andrew J. O.
Published: July 2010

Purpose

Specific language impairment (SLI) is known to aggregate in families. Debate exists on whether the male sex presents an additional risk for SLI. This meta-analysis examined whether there is a sex ratio difference in the risk for impairment among family members of an SLI proband and whether this is mediated by assessment method (direct assessment via psychometric tests vs. indirect assessment via questionnaire/interview) or relative type (sibling vs. parent).

Method

Twelve studies met inclusion criteria, including 11 parent and 9 sibling samples. Risk ratios, indicating relative risk for language difficulties for males versus females, were calculated as a function of assessment method and relative type.

Results

Direct assessments identified a male predominance of language impairment, with a pooled risk ratio of 1.73 for siblings (95% confidence interval [CI]: 1.20–2.52) and 1.54 for parents (95% CI: 1.14–2.07). No sex differences were observed for studies using indirect testing methods, with mean risk ratios of 1.12 (0.85–1.48) and 1.17 (0.92–1.49) for sibling and parent samples, respectively.

Conclusion

A predominance of affected males among family members is observed when using direct assessments only. This finding is interpreted with reference to the strengths and weaknesses of different assessment methodologies and what sex differences may indicate about the biological mechanisms underlying the SLI phenotype.
The Etiology of Diverse Receptive Language Skills at 12 Years
Authors: Dale Philip S. , Harlaar Nicole , Hayiou-Thomas Marianna E. , Plomin Robert
Published: July 2010

Purpose

In the 2nd decade of life, language skills expand in both quantitative and qualitative ways. The etiology of these new skills and the relationships among them have been little explored.

Method

Taking advantage of widespread access to inexpensive and fast Internet connections in the United Kingdom, we administered four Web-based measures of receptive language development—Vocabulary, Listening Grammar, Figurative Language, and Making Inferences—to a sample of 12-year-old twin pairs (
N
= 4,892) participating in the Twins Early Development Study (TEDS; Oliver & Plomin, 2007).

Results

The 4 measures showed moderate phenotypic intercorrelation. All 4 showed moderate genetic influence (a
2
between .25 and .36) and low shared environmental influence (c
2
between .13 and .19). The median genetic correlation among the 4 measures was .87, indicating strong genetic overlap among them. A latent factor score for Language, based on the common variance among the measures, showed substantial genetic influence (a
2
= .59) and moderate shared environmental influence (c
2
= .28). A small but significant sex difference favored females on the Listening Grammar and Making Inferences tests, but there was no evidence for sex differences in the etiology of any of the measures.

Conclusion

Despite the emergence of new skills at this developmental period, from the etiological perspective, language skills remain relatively undifferentiated at an etiological level.
Characterization of inclined GaSb nanopillars by Mueller matrix ellipsometry
Authors: Nerbø I. S. , Le Roy S. , Foldyna M. , Kildemo M. , Søndergård E.
Published: July 2010

Inclined GaSb nanopillars prepared by low energy ion sputtering with oblique ion beam incidence have been characterized by two different Mueller matrix ellipsometric tools. The optical properties of the nanopillars were found to be well described by a uniaxial anisotropic graded effective medium model. The pillar height and inclination angle were determined by fitting the parameters of the effective medium model to spectroscopic (1.44–2.88 eV) Mueller matrix measurements at multiple azimuth sample orientations. A set of different samples with various average pillar height and inclination angle was studied; results from the optical characterization correspond well with those from scanning electron microscopy analysis. For samples with nanopillars inclined by 45° or less, the height could be determined from a single Mueller matrix measurement at only one azimuth orientation, allowing real-time in situ observation of the formation. The nanopillars were also studied using a single wavelength angle resolved Mueller polarimeter, which also can be used to determine height and inclination of the pillars, in addition to validating the optical model over a wide range of incident and azimuth angles.
Resonant characteristics of ultranarrow SiCN nanomechanical resonators
Authors: Guthy Csaba , Das Rahul M. , Drobot Brian , Evoy Stephane
Published: July 2010

We report the machining of doubly-clamped SiCN nanomechanical resonators as narrow as 16 nm and lengths of up to 10 μm with a yield approaching 100%. The resonators were actuated using a piezoelectric disk, and their resonant response was detected using optical interferometry. Resonators with widths ranging from 16 to 375 nm and lengths from 10 to 50 μm were analyzed at room temperature at pressures ranging from 10 to 50 mTorr. Resonant frequencies in the 4–15 MHz range and quality factors in the 1000–7000 range were measured. We observed a significant decrease in resonant frequency with decreasing resonator width. The results of finite element analysis (FEA) show that this width dependence is mainly due to the resonators vibrating in the horizontal rather than vertical direction. At widths below 50 nm the comparison of experimental and FEA data suggest a gradual tensile stress reduction in the resonators as their width is reduced. Material softening is the most likely cause of this stress reduction. Additionally, the resonant behavior of 16, 55, and 375 nm wide devices was studied as a function of ambient pressure in the 10−5–10 Torr range. Resonance quality becomes dominated by gas damping effects at pressures above a threshold determined by the intrinsic Q-factor of the resonator. The intrinsic Q-factor tended to decrease with decreasing resonator width but was independent of length or resonant frequency. This suggests that surface-related mechanisms dominate the dissipation of energy in these devices.
The trap state relaxation related polarization in CaCu3Ti4O12
Authors: Luo X. J. , Yang C. P. , Chen S. S. , Song X. P. , Wang H. , Bärner K.
Published: July 2010

Electrical conditioning properties and dielectric behavior of CaCu3Ti4O12 (CCTO) were investigated. A reversible current-voltage characteristic relaxation effect together with a corresponding dielectric relaxation was found in this material. A trap state model which combines a monopole and dipole relaxation was proposed to be the key element to explain the reported huge permittivity in CCTO. The work also supports the extrinsic origin of the giant dielectric constant.
Effect of bipolar electric fatigue on polarization switching in lead-zirconate-titanate ceramics
Authors: Zhukov Sergey , Fedosov Sergey , Glaum Julia , Granzow Torsten , Genenko Yuri A. , von Seggern Heinz
Published: July 2010

From comparison of experimental results on polarization switching in fresh and electrically fatigued lead-zirconate-titanate (PZT) over a wide range of applied fields and switching times it is concluded that fatigue alters the local field distribution inside the sample due to the generation of discrete defects, such as voids and cracks. Such defects have a strong influence on the overall electric field distribution by their shape and dielectric permittivity. On this hypothesis, a new phenomenological model of polarization switching in fatigued PZT is proposed. The model assumes that the fatigued sample can be composed of different local regions which exhibit different field strengths but otherwise can be considered as unfatigued. Consequently the temporal response of a fatigued sample is assumed to be the superposition of the field-dependent temporal responses of unfatigued samples weighted by their respective volume fraction. A certain part of the volume is excluded from the overall switching process due to the domain pinning even at earlier stages of fatigue, which can be recovered by annealing. Suitability of the proposed model is demonstrated by a good correlation between experimental and calculated data for differently fatigued samples. Plausible cause of the formation of such regions is the generation of defects such as microcracks and the change in electrical properties at imperfections such as pores or voids.
Internal motion of an electronically excited molecule in viscoelastic media
Authors: Jee Ah-Young , Bae Eunhye , Lee Minyung
Published: July 2010

The twisting motion of trans-4-[4-(dimethylamino)-styryl]-1-methylpyridinium iodide (4-DASPI) in the excited state was investigated in solutions and various polymers in order to understand dependence of molecular rotor dynamics on viscoelasticity. It was observed that the internal motion of electronically excited 4-DASPI correlates strongly with dynamic viscosity and elastic modulus. Our results also showed that condensed phase dynamics of 4-DASPI are governed by the explicit mode coupling between the rotamerizing coordinate and mechanical properties of viscoelastic media.
Applying the extended molecule approach to correlated electron transport: Important insight from model calculations
Authors: Bâldea Ioan , Köppel Horst , Maul Robert , Wenzel Wolfgang
Published: July 2010

Theoretical approaches of electric transport in correlated molecules usually consider an extended molecule, which includes, in addition to the molecule itself, parts of electrodes. In the case where electron correlations remain confined within the molecule, and the extended molecule is sufficiently large, the current can be expressed by means of Landauer-type formulas. Electron correlations are embodied into the retarded Green’s function of a sufficiently large but isolated extended molecule, which represents the key quantity that can be accurately determined by means of ab initio quantum-chemical calculations. To exemplify these ideas, we present and analyze numerical results obtained within full configuration interaction calculations for an extended molecule described by the interacting resonant level model. Based on them, we argue that for narrower-band (organic) electrodes, the transport properties can be reliably computed because the extended molecule can be chosen sufficiently small to be tackled within accurate ab initio methods. For wider-band (metallic) electrodes, larger extended molecules have to be considered, in general, but a (semi)quantitative description of the transport should still be possible in the typical cases where electron transport proceeds by off-resonant tunneling. Our numerical results also demonstrate that, contrary to the usual claim, the ratio between the characteristic Coulomb strength and the level width due to molecule-electrode coupling is not the only quantity needed to assess whether electron correlation effects are strong or weak.
Catalystlike behavior of Si adatoms in the growth of monolayer Al film on Si(111)
Authors: Teng Jing , Zhang Lixin , Jiang Ying , Guo Jiandong , Guo Qinlin , Wang Enge , Ebert Philipp , Sakurai T. , Wu Kehui
Published: July 2010

The formation mechanism of monolayer Al(111)1×1 film on the Si(111)√3×√3-Al substrate was studied by scanning tunneling microscopy and first-principles calculations. We found that the Si adatoms on the √3×√3-Al substrate play important roles in the growth process. The growth of Al-1×1 islands is mediated by the formation and decomposition of SiAl2 clusters. Based on experiments and theoretical simulations we propose a model where free Si atoms exhibit a catalystlike behavior by capturing and releasing Al atoms during the Al film growth.
Phase space structure and dynamics for the Hamiltonian isokinetic thermostat
Authors: Collins Peter , Ezra Gregory S. , Wiggins Stephen
Published: July 2010

We investigate the phase space structure and dynamics of a Hamiltonian isokinetic thermostat, for which ergodic thermostat trajectories at fixed (zero) energy generate a canonical distribution in configuration space. Model potentials studied consist of a single bistable mode plus transverse harmonic modes. Interpreting the bistable mode as a reaction (isomerization) coordinate, we establish connections with the theory of unimolecular reaction rates, in particular the formulation of isomerization rates in terms of gap times. In the context of molecular reaction rates, the distribution of gap times (or associated lifetimes) for a microcanonical ensemble initiated on the dividing surface is of great dynamical significance; an exponential lifetime distribution is usually taken to be an indicator of “statistical” behavior. Moreover, comparison of the magnitude of the phase space volume swept out by reactive trajectories as they pass through the reactant region with the total phase space volume (classical density of states) for the reactant region provides a necessary condition for ergodic dynamics. We compute gap times, associated lifetime distributions, mean gap times, reactive fluxes, reactive volumes, and total reactant phase space volumes for model thermostat systems with three and four degrees of freedom at three different temperatures. At all three temperatures, the necessary condition for ergodicity is approximately satisfied. At high temperatures a nonexponential lifetime distribution is found, while at low temperatures the lifetime is more nearly exponential. The degree of exponentiality of the lifetime distribution is quantified by computing the information entropy deficit with respect to pure exponential decay. The efficacy of the Hamiltonian isokinetic thermostat is examined by computing coordinate distributions averaged over single long trajectories initiated on the dividing surface.
Ethene adsorption and dehydrogenation on clean and oxygen precovered Ni(111) studied by high resolution x-ray photoelectron spectroscopy
Authors: Lorenz M. P. A. , Fuhrmann T. , Streber R. , Bayer A. , Bebensee F. , Gotterbarm K. , Kinne M. , Tränkenschuh B. , Zhu J. F. , Papp C. , Denecke R. , Steinrück H.-P.
Published: July 2010

The adsorption and thermal evolution of ethene (ethylene) on clean and oxygen precovered Ni(111) was investigated with high resolution x-ray photoelectron spectroscopy using synchrotron radiation at BESSY II. The high resolution spectra allow to unequivocally identify the local environment of individual carbon atoms. Upon adsorption at 110 K, ethene adsorbs in a geometry, where the two carbon atoms within the intact ethene molecule occupy nonequivalent sites, most likely hollow and on top; this new result unambiguously solves an old puzzle concerning the adsorption geometry of ethene on Ni(111). On the oxygen precovered surface a different adsorption geometry is found with both carbon atoms occupying equivalent hollow sites. Upon heating ethene on the clean surface, we can confirm the dehydrogenation to ethine (acetylene), which adsorbs in a geometry, where both carbon atoms occupy equivalent sites. On the oxygen precovered surface dehydrogenation of ethene is completely suppressed. For the identification of the adsorbed species and the quantitative analysis the vibrational fine structure of the x-ray photoelectron spectra was analyzed in detail.
High temperature conductance characteristics of LaAlO3/SrTiO3-heterostructures under equilibrium oxygen atmospheres
Authors: Gunkel F. , Hoffmann-Eifert S. , Dittmann R. , Mi S. B. , Jia C. L. , Meuffels P. , Waser R.
Published: July 2010

The interface conductance of LaAlO3/SrTiO3 heterostructures was investigated under high temperature oxygen equilibrium. The dependence of the heterostructure’s conductance on oxygen partial pressure (from 10−22 to 1 bar) and temperature (800 to 1100 K) was compared to the characteristic of SrTiO3 single crystals, which is described in terms of a defect chemistry model. Up to 950 K the equilibrated heterostructures reveal an additional influence of a metallic-like conduction path with a very slight dependence on the oxygen partial pressure. Donor-type interface states which may result from either lattice distortions or A-site cation intermixing during processing are discussed as a possible origin for the exceptional interface conduction of LaAlO3/SrTiO3 heterostructures.
Long-wavelength optical transmission of extremely narrow slits via hybrid surface-plasmon and Fabry–Pérot modes
Authors: Li X. F. , Yu S. F.
Published: July 2010

We have verified that extraordinary transmission of long-wavelength light through extremely narrow slits in a thick metal film can be achieved by hybrid surface-plasmon and Fabry–Pérot modes. Transmittance of these ultranarrow slits, which have width and thickness of 0.56 μm and 100 μm, respectively, for a terahertz light with wavelength of 225 μm can be 2.1×108 times higher than that predicted by using classic theory. Furthermore, the corresponding ratio between transmission wavelength and slit width can be up to 400, which is over 60 times larger than that the conventional grating-based surface-plasmon modes can provide.
Strong correlation in hydrogen chains and lattices using the variational two-electron reduced density matrix method
Authors: Sinitskiy Anton V. , Greenman Loren , Mazziotti David A.
Published: July 2010

The variational two-electron reduced-density-matrix (2-RDM) method, scaling polynomially with the size of the system, was applied to linear chains and three-dimensional clusters of atomic hydrogen as large as H64. In the case of the 4×4×4 hydrogen lattice of 64 hydrogen atoms, a correct description of the dissociation requires about 1018 equally weighted determinants in the wave function, which is too large for traditional multireference methods. The correct energy in the dissociation limit was obtained from the variational 2-RDM method in contrast to Hartree–Fock and single-reference methods. Analysis of the occupation numbers demonstrates that even for 1.0 Å bond distances the presence of strong electron correlation requires a multireference method. Three-dimensional systems exhibit a marked increase in electron correlation from one-dimensional systems regardless of size. The metal-to-insulator transition upon expansion of the clusters was studied using the decay of the 1-RDM off-diagonal elements. The variational 2-RDM method was shown to capture the metal-to-insulator transition and dissociation behavior accurately for all systems.
Electrostatic topology of ferroelectric domains in YMnO3
Authors: Jungk Tobias , Hoffmann Ákos , Fiebig Manfred , Soergel Elisabeth
Published: July 2010

Trimerization-polarization domains in ferroelectric hexagonal YMnO3 were resolved in all three spatial dimensions by piezoresponse force microscopy. Their topology is dominated by electrostatic effects with a range of 100 unit cells and reflects the unusual electrostatic origin of the spontaneous polarization. The response of the domains to locally applied electric fields explains difficulties in transferring YMnO3 into a single-domain state. Our results demonstrate that the wealth of nondisplacive mechanisms driving ferroelectricity that emerged from the research on multiferroics are a rich source of alternative types of domains and domain-switching phenomena.
Two-photon spectral hole burning spectroscopy of InAs/GaAs quantum dots
Authors: Moldaschl T. , Parz W. , Müller T. , Golka S. , Strasser G. , Unterrainer K.
Published: July 2010

Femtosecond spectral hole burning experiments were performed on InAs/GaAs quantum dots to investigate the influence of high excitation intensities. The observation of additional spectral holes, as well as distinct absorption line broadening are both attributed to two-photon absorption processes. These spectral holes can be unambiguously assigned to degenerate two-photon biexciton creation, whereas the absorption line broadening is a direct result of Coulomb renormalization, initiated by carriers created through two-photon absorption in the surrounding GaAs crystal matrix and the InAs wetting layer.
Possible electronic decay channels in the ionization spectra of small clusters composed of Ar and Xe: A four-component relativistic treatment
Authors: Faßhauer Elke , Kryzhevoi Nikolai V. , Pernpointner Markus
Published: July 2010

Electronic decay of the inner-valence Ar 3s−1 vacancy is energetically forbidden in an isolated argon atom and in all rare gas dimers where argon is present. However, if an argon atom has at least two suitable rare gas atoms in its neighborhood, the Ar 3s−1 vacancy may decay electronically via an electron transfer mediated decay (ETMD) mechanism. An ArXe2 cluster is considered in the present paper as an example of such systems. The single and double ionization spectra of different ArXe2 isomers as well as of homonuclear Ar2 and Xe2 and heteronuclear ArXe clusters have been calculated by means of propagator methods to reveal possible electronic decay channels. A four-component version of the one-particle propagator utilizing the Dirac–Coulomb Hamiltonian was employed to obtain the single ionization potentials of the clusters studied. Hereby electron correlation, scalar relativistic effects, and spin-orbit couplings are described in a consistent manner. A two-particle propagator in its one-component form, in conjunction with effective core potentials to account consistently for correlation and scalar relativistic effects, was used to calculate the double ionization potentials. ETMD is shown to be the only possible electronic decay process of the Ar 3s−1 vacancy in the ArXe2 cluster. In clusters with more Xe atoms, alternative electronic decay mechanisms may appear.
Structure and vibrational spectra of small water clusters from first principles simulations
Authors: Kang Dongdong , Dai Jiayu , Hou Yong , Yuan Jianmin
Published: July 2010

The structure and vibrational spectra of (H2O)n (n=2–5) clusters have been studied based on first-principles molecular dynamics simulations. Trends of the cluster structures with the cluster size show that water molecules in cluster are bound more tightly. The vibrational spectra as a function of cluster size and temperature are obtained using Fourier transformation of the velocity autocorrelation function. Results of the clusters in ground state show that when the cluster size increases, the librational peaks shift to blue and the bonded intramolecular OH stretching bands shift to red due to the clusterization and hydrogen-bond strengthening. Meanwhile, there are no significant shifts in the intramolecular bending and free OH stretching modes, indicating that the free hydrogen atoms are insensitive to the local bonding environment. The temperature-dependent vibrational spectra, which exhibit similar behaviors from the dimer to pentamer, show that there are significant broadenings of the spectra with temperature caused by thermal motions. Moreover, different bands shift to different directions, where librational bands shift to red while bonded OH stretching bands shift to blue, although the blueshifts are quite small for the dimer and trimer.
Inverted Al0.25Ga0.75N/GaN ultraviolet p-i-n photodiodes formed on p-GaN template layer grown by metalorganic vapor phase epitaxy
Authors: Chang Kuo-Hua , Sheu Jinn-Kong , Lee Ming-Lun , Tu Shang-Ju , Yang Chih-Ciao , Kuo Huan-Shao , Yang J. H. , Lai Wei-Chih
Published: July 2010

Inverted Al0.25Ga0.75N/GaN ultraviolet (UV) p-i-n photodiodes (PDs) were grown by selective-area regrowth on p-GaN template. The inverted devices with low-resistivity n-type AlGaN top-contact layers exhibited a typical zero-bias peak responsivity of 66.7 mA/W at 310 nm corresponding to the external quantum efficiency of 26.6%. The typical UV-to-visible (310/400 nm) spectral rejection ratio at zero-bias was over three orders of magnitude. The differential resistance and detectivity were obtained at approximately 6.2×1012 Ω and 3.4×1013 cm Hz1/2 W−1, respectively. Compared with conventional AlGaN/GaN-based UV p-i-n PDs, the proposed device structure can potentially achieve solar-blind AlGaN/GaN-based p-i-n PDs with low-aluminum content or aluminum-free p-contact layer and reduce excessive tensile strain due to the lattice mismatch between AlGaN and GaN layers.
Therapeutic potential of appropriately evaluated safe-induced pluripotent stem cells for spinal cord injury
Authors: Tsuji Osahiko , Miura Kyoko , Okada Yohei , Fujiyoshi Kanehiro , Mukaino Masahiko , Nagoshi Narihito , Kitamura Kazuya , Kumagai Gentaro , Nishino Makoto , Tomisato Shuta , Higashi Hisanobu , Nagai Toshihiro , Katoh Hiroyuki , Kohda Kazuhisa , Matsuzaki Yumi , Yuzaki Michisuke , Ikeda Eiji , Toyama Yoshiaki , Nakamura Masaya , Yamanaka Shinya , Okano Hideyuki
Published: July 2010

Various types of induced pluripotent stem (iPS) cells have been established by different methods, and each type exhibits different biological properties. Before iPS cell-based clinical applications can be initiated, detailed evaluations of the cells, including their differentiation potentials and tumorigenic activities in different contexts, should be investigated to establish their safety and effectiveness for cell transplantation therapies. Here we show the directed neural differentiation of murine iPS cells and examine their therapeutic potential in a mouse spinal cord injury (SCI) model. “Safe” iPS-derived neurospheres, which had been pre-evaluated as nontumorigenic by their transplantation into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mouse brain, produced electrophysiologically functional neurons, astrocytes, and oligodendrocytes in vitro. Furthermore, when the safe iPS-derived neurospheres were transplanted into the spinal cord 9 d after contusive injury, they differentiated into all three neural lineages without forming teratomas or other tumors. They also participated in remyelination and induced the axonal regrowth of host 5HT
+
serotonergic fibers, promoting locomotor function recovery. However, the transplantation of iPS-derived neurospheres pre-evaluated as “unsafe” showed robust teratoma formation and sudden locomotor functional loss after functional recovery in the SCI model. These findings suggest that pre-evaluated safe iPS clone-derived neural stem/progenitor cells may be a promising cell source for transplantation therapy for SCI.
Heightened mitochondrial priming is the basis for apoptotic hypersensitivity of CD4+CD8+thymocytes
Authors: Ryan Jeremy A. , Brunelle Joslyn K. , Letai Anthony
Published: July 2010

It is well established that CD4+CD8+thymocytes are more sensitive to myriad death stimuli than CD4+or CD8+single positive (SP) thymocytes. The mechanism behind this hypersensitivity to apoptosis of CD4+CD8+thymocytes is not understood. To test whether the difference lay in the apoptotic preset of mitochondria, established by the BCL-2 family of proteins, we developed a method, FACS-based BH3 profiling. Using this tool, we could discriminate thymocyte subpopulations and demonstrate that mitochondria in double positive (DP) thymocytes are more primed for death than those in single positive counterparts. Loss of proapoptotic BIM, known to cause autoimmunity, also causes loss of “priming.” Priming is a phenotype with physiologic consequences, which can be measured at the single-cell level in complex samples using FACS-based BH3 profiling.
Generation of functional human T-cell subsets with HLA-restricted immune responses in HLA class I expressing NOD/SCID/IL2rγnullhumanized mice
Authors: Shultz Leonard D. , Saito Yoriko , Najima Yuho , Tanaka Satoshi , Ochi Toshiki , Tomizawa Mariko , Doi Takehiko , Sone Akiko , Suzuki Nahoko , Fujiwara Hiroshi , Yasukawa Masaki , Ishikawa Fumihiko
Published: July 2010

Whereas humanized mouse models have contributed significantly to human immunology research, human T cells developing in mouse thymic environment fail to demonstrate HLA-restricted function. To achieve HLA-restricted human immune response, we created an immune-compromised non-obese diabetic/SCID/IL2rgnullstrain (NSG) with homozygous expression of HLA class I heavy chain and light chain (NSG-HLA-A2/HHD). Transplantation of purified Lin−CD34+CD38− human hematopoietic stem cells into NSG-HLA-A2/HHD newborns resulted in the development of human CD4+ and CD8+ TCRαβ+ T cells and CD4−CD8− and CD8+ TCRγδ+ cells in recipient bone marrow and spleen. Human cytotoxic T lymphocytes (CTLs) become functionally mature, as evidenced by the production of granzyme corresponding to phenotypic transition from naïve to effector memory CTLs. In these recipients, human Th17 cells developed along with Th1 and Th2 cells. Epstein–Barr virus (EBV) infection in the humanized NSG-HLA-A2/HHD recipients resulted in the formation of lymphoproliferative lesions consisting mainly of human B cells with scattered human T cells. Human CTLs developing in the recipients recognized EBV-derived peptides in an HLA-restricted manner and exerted HLA-restricted cytotoxicity against EBV-infected human B cells. The HLA-expressing humanized mouse with functional HLA-restricted T cells and consistent representation of rare T-cell subsets overcomes a major constraint in human immunology, and serves as a useful model for investigation of human immune responses against pathogens and for the development of therapeutic strategies against human diseases.
Natural killer cells trigger osteoclastogenesis and bone destruction in arthritis
Authors: Söderström Kalle , Stein Emily , Colmenero Paula , Purath Ulrich , Müller-Ladner Ulf , Teixeira de Matos Cristina , Tarner Ingo H. , Robinson William H. , Engleman Edgar G.
Published: July 2010

Osteoclasts are bone-eroding cells that develop from monocytic precursor cells in the presence of receptor activator of NF-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). Osteoclasts are essential for physiological bone remodeling, but localized excessive osteoclast activity is responsible for the periarticular bone destruction that characteristically occurs in patients with rheumatoid arthritis (RA). The origin of osteoclasts at sites of bone erosion in RA is unknown. Natural killer (NK) cells, as well as monocytes, are abundant in the inflamed joints of patients with RA. We show here that such NK cells express both RANKL and M-CSF and are frequently associated with CD14+monocytes in the RA synovium. Moreover, when synovial NK cells are cocultured with monocytes in vitro, they trigger their differentiation into osteoclasts, a process dependent on RANKL and M-CSF. As in RA, NK cells in the joints of mice with collagen-induced arthritis (CIA) express RANKL. Depletion of NK cells from mice before the induction of CIA reduces the severity of subsequent arthritis and almost completely prevents bone erosion. These results suggest that NK cells may play an important role in the destruction of bone associated with inflammatory arthritis.