bluuebunny/crossref_metadata_2025 huggingface dataset:
Approximate analysis of tall buildings using sandwich beam models with variable cross‐section
Authors: Kaviani P. , Rahgozar R. , Saffari H.
Published: August 2007

In this paper an approximate method is carried out for determining the natural periods of multistory buildings subjected to earthquake. The building resists lateral forces through a combination of lateral resisting systems. These systems could be replaced by a cantilever Timoshenko or a sandwich beam with varying cross‐section that characterizes three kinds of stiffnesses: the global bending stiffness, the local bending stiffness and the shear stiffness. Using appropriate transformations, the differential equations for flexural and shear free vibration of a cantilever beam with variably distributed mass and stiffness are reduced to Bessel's equations and ordinary differential equations. The frequency equations can be solved by selecting suitable expressions such as exponential and power functions for stiffness and mass distribution along the height of the building. The calculated frequencies are combined appropriately by using approximate methods. Based on the fact that shear and bending deformations are all considered, the free vibration frequency of the structure could be calculated. The capability and accuracy of the proposed method are demonstrated by a numerical example in which finite element results are compared with the proposed methodology and other approximate methods. Copyright © 2007 John Wiley & Sons, Ltd.
Across‐wind dynamic response of high‐rise building under wind action with interference effects from one and two tall buildings
Authors: Xie Z. N. , Gu M.
Published: August 2007

Systematic studies on the across‐wind dynamic interference effects on two and three tall buildings are presented in this paper. It is found that surrounding and upstream interfering building(s) can significantly affect the across‐wind load on the interfered principal building. Generally speaking, two interfering buildings can cause more adverse dynamic effects on the principal building than a single one does. The results show that the maximum interference factor (IF) among three buildings increases 80% over that between two buildings in terrain category B which has been defined in Chinese load code for design of building structures; a noticeable difference of 29% of IF is also observed in terrain category D. Vortex shedding from the upstream buildings can lead to vortex‐induced resonance, resulting in excessive across‐wind loads on the downstream building. Although interference effects in terrain category D are much smaller than those in exposure category B, the maximum IF is found to be 1·83 in the case of three buildings with the same size in terrain category D and 2·27 in other configurations. Copyright © 2007 John Wiley & Sons, Ltd.
Properties, production, and applications of camelid single-domain antibody fragments
Authors: Harmsen M. M. , De Haard H. J.
Published: August 2007

Camelids produce functional antibodies devoid of light chains of which the single N-terminal domain is fully capable of antigen binding. These single-domain antibody fragments (VHHs or Nanobodies®) have several advantages for biotechnological applications. They are well expressed in microorganisms and have a high stability and solubility. Furthermore, they are well suited for construction of larger molecules and selection systems such as phage, yeast, or ribosome display. This minireview offers an overview of (1) their properties as compared to conventional antibodies, (2) their production in microorganisms, with a focus on yeasts, and (3) their therapeutic applications.
Phase Composition During Palm Olein Fractionation and its Effect on Soft PMF and Superolein Quality
Authors: Calliauw Gijs , Gibon Véronique , De Greyt Wim , Plees Laurence , Foubert Imogen , Dewettinck Koen
Published: August 2007

Refined palm olein was dry fractionated via three different cooling programs on laboratory‐scale fractionation equipment. The enrichment and depletion of the main triacylglycerols in the liquid and solid phase was plotted as a function of the crystallization degree of the oil. It was shown that for the given conditions and palm olein composition, the initial crystals mainly consisted of PPP, diacylglycerols, POP and PLP. At higher crystallization degrees, a sharp viscosity increase in the crystal suspension was primarily related to an obvious decrease of POP but also of POS in the recovered superolein, while the general crystallization rate of the system remained unchanged. Rather than a change in crystallization rate of POP, a change in the ratio between the crystallizing monounsaturated triacylglycerols is linked with the high viscosity of the crystal slurry. For a comparable degree of crystallization, the superolein of the more viscous crystal slurry, obtained through a membrane press filtration up to 15 bar, was more unsaturated than the superolein filtered from the less viscous slurry. Consequently, the high unsaturation in the corresponding soft palm mid fraction is only the result of an incomplete phase separation, and not due to an increased intersolubility of unsaturated triacylglycerols in the crystals.
Dietary, physiological, genetic and pathological influences on postprandial lipid metabolism
Authors: Lopez-Miranda José , Williams Christine , Lairon Denis
Published: August 2007

Most of diurnal time is spent in a postprandial state due to successive meal intakes during the day. As long as the meals contain enough fat, a transient increase in triacylglycerolaemia and a change in lipoprotein pattern occurs. The extent and kinetics of such postprandial changes are highly variable and are modulated by numerous factors. This review focuses on factors affecting postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and risk of CHD. Postprandial lipoprotein metabolism is modulated by background dietary pattern as well as meal composition (fat amount and type, carbohydrate, protein, fibre, alcohol) and several lifestyle conditions (physical activity, tobacco use), physiological factors (age, gender, menopausal status) and pathological conditions (obesity, insulin resistance, diabetes mellitus). The roles of many genes have been explored in order to establish the possible implications of their variability in lipid metabolism and CHD risk. The postprandial lipid response has been shown to be modified by polymorphisms within the genes for apo A-I, A-IV, A-V, E, B, C-I and C-III, lipoprotein lipase, hepatic lipase, fatty acid binding and transport proteins, microsomal triglyceride transfer protein and scavenger receptor class B type I. Overall, the variability in postprandial response is important and complex, and the interactions between nutrients or dietary or meal compositions and gene variants need further investigation. The extent of present knowledge and needs for future studies are discussed in light of ongoing developments in nutrigenetics.
The Dual Career of “Arirang”: The Korean Resistance Anthem That Became a Japanese Pop Hit
Authors: Atkins E. Taylor
Published: August 2007

“Arirang” is known worldwide as the quintessential Korean folk song. Its iconic status in contemporary Korea derives from its perceived role in strengthening Korean resolve to resist the cultural violence of the Japanese colonial occupation (1905–45). A musical “skeleton” capable of countless improvised variations and interpretations, some “Arirangs” explicitly assailed the Japanese and thus were censored by colonial authorities. However, in the 1930s and 1940s, precisely the time when assimilationist pressures in colonial Korea were intensifying, Japanese songsmiths, singers, and recording companies released “Arirang” renditions in prodigious quantities, sometimes in collaboration with Korean performers. “Arirang” became the most familiar song in the Japanese empire: Its persistent theme of loss spoke to Koreans of their lost sovereignty and to Japanese of the ravaging effects of modernity on traditional lifeways. For both peoples, it served as a mirror for self-contemplation and an “ethnographic lens” for gazing upon the other.
“Another Andalusia”: Images of Colonial Southeast Asia in Arabic Newspapers
Authors: Laffan Michael
Published: August 2007

This essay discusses changing images of island Southeast Asia and its Muslim populations in the modern Arabic press during the late colonial period. It commences by surveying the general informational letters sent to the largely pro-Ottoman papers of Beirut and Cairo during the 1890s by increasingly vocal local Arabs who were seeking to redress their situation as second-class colonial citizens. Thereafter, it considers the role played by Malays, Javanese, and other Southeast Asians in the globalizing Arabic media. In doing so, it demonstrates that although many Southeast Asians bought into and actively participated in the often Arabocentric program for Islamic reform in their homelands, they were by no means in agreement that their situations were any worse than those of other Muslims or that they could all be treated under one ethnic rubric.
Owen Lattimore, Asia, and Comparative History
Authors: Rowe William T.
Published: August 2007

Perhaps best known today as a pioneering scholar of Inner Asia and a victim of the McCarthy witch hunts of the 1950s, Owen Lattimore was more basically, like his friend Arnold Toynbee, a major player in the vogue of comparative history that captured wide public attention in the second quarter of the twentieth century. His lifelong intellectual project was to develop a “scientific” model of the way human societies form, evolve, grow, decline, mutate, and interact with one another along “frontiers.” In the process of working out this model, Lattimore appropriated for his own purposes, and often later discarded, some of the analytic devices most popular in his day, including ecological determinism, biological racism, economic geography and location theory, and Marxist modes of production. At every stage in his thinking, he sought to confound complacent teleologies, both those of Western “progress” and those of Chinese “civilization” of its pastoralist neighbors.
Expression of circadian clock genes in retinal dopaminergic cells
Authors: DORENBOS RONALD , CONTINI MASSIMO , HIRASAWA HAJIME , GUSTINCICH STEFANO , RAVIOLA ELIO
Published: August 2007

The mammalian neural retina contains single or multiple intrinsic circadian oscillators that can be directly entrained by light cycles. Dopaminergic amacrine (DA) cells represent an especially interesting candidate as a site of the retinal oscillator because of the crucial role of dopamine in light adaptation, and the widespread distribution of dopamine receptors in the retina. We hereby show by single-cell, end-point RT-PCR that retinal DA cells contain the transcripts for six core components of the circadian clock: Bmal1, Clock, Cry1, Cry2, Per1, and Per2. Rod photoreceptors represented a negative control, because they did not appear to contain clock transcripts. We finally confirmed that DA cells contain the protein encoded by theBmal1gene by comparing immunostaining of the nuclei of DA cells in the retinas of wildtype andBmal1−/−mice. It is therefore likely that DA cells contain a circadian clock that anticipates predictable variations in retinal illumination.
Reappraising elastic thickness variation at oceanic trenches
Authors: Bry Madeleine , White Nicky
Published: August 2007

We reassess the variation of elastic thickness as a function of lithospheric plate age using a global database of bathymetric and free‐air gravity profiles which are perpendicular to oceanic trenches. As in many previous studies, our starting point is the well‐known floating elastic plate model. In order to remove the influence of short‐wavelength features not associated with lithospheric bending, adjacent profiles from 10‐Myr bins have been stacked together to construct average profiles with standard deviations. Each average profile was then inverted in a two‐stage procedure. First, singular value decomposition was used to determine two unknown flexural parameters, together with a regional slope and offset, for any given elastic thickness. This procedure was repeated for a range of elastic thicknesses. Second, residual misfit was plotted as a function of elastic thickness, and the global minimum was identified. This two‐stage procedure makes no prior assumptions about magnitude of the load, size of the bending moment, or whether the elastic plate is broken/continuous. We obtained excellent fits between theory and observation for both bathymetric and gravity profiles from lithosphere with an age range of 0–150 Ma. The shape of the residual misfit function indicates the degree of confidence we have in our elastic thickness estimates. The lower limit of elastic thickness is usually well determined but upper limits are often poorly constrained. Inverse modeling was carried out using a range of profile lengths (250–300, 500, and 700 km). In general, our estimates show no consistent increase of elastic thickness as a function of plate age. This surprising result is consistent with recent reassessments of elastic thickness beneath seamounts and implies either that elastic thickness is independent of plate age or that elastic thickness cannot be measured with sufficient accuracy to reveal such a relationship. Modeling of short free‐air gravity profiles (250–300 km) does tentatively suggest that elastic thickness increases linearly from 5 to 10 km between 0 and 20 Ma and from 10 to 15 km between 20 and 150 Ma. This variation roughly matches the depth to the 200°C isotherm which corresponds to an homologous temperature of 0.4 for wet peridotite. Unfortunately, for longer profile lengths, there is no temporal dependence, and elastic thicknesses vary considerably for all plate ages. Bathymetric profile modeling yields similar results although uncertainties are larger.
Decay of aftershock activity for Japanese earthquakes
Authors: Nanjo K. Z. , Enescu B. , Shcherbakov R. , Turcotte D. L. , Iwata T. , Ogata Y.
Published: August 2007

Aftershock decay is often correlated with the modified Omori's law: dN/dt = τ−1(1 + t/c)−p, where dN/dt is the occurrence rate of aftershocks with magnitudes greater than a lower cutoff m, t is time since a mainshock, τ and c are characteristic times, and p is an exponent. Extending this approach, we derive two possibilities: (1) c is a constant independent of m and τ scales with m and (2) c scales with m and τ is a constant independent of m. These two are tested by using aftershock sequences of four relatively recent and large earthquakes in Japan. We first determine for each sequence the threshold magnitude above which all aftershocks are completely recorded and use only events above this magnitude. Then, visual inspection of the decay curves and statistical analysis shows that the second possibility is the better approximation for our sequences. This means that the power law decay of smaller aftershocks starts after larger times from the mainshock. We find a close association of our second result with a solution obtained for a damage mechanics model of aftershock decay. The time delays associated with aftershocks, according to the second possibility, can be understood as the times needed to nucleate microcracks (aftershocks). Our result supports the idea that the c value is a real consequence of aftershock dynamics associated with damage evolution.
A maximum hypothesis of transpiration
Authors: Wang Jingfeng , Bras Rafael L. , Lerdau Manuel , Salvucci Guido D.
Published: August 2007

We hypothesize that the system of liquid water in leaf tissues and the water vapor in the atmosphere tends to evolve towards a potential equilibrium as quickly as possible by maximization of the transpiration rate. We make two assumptions in formulating the transpiration rate: (1) stomatal aperture is directly controlled by guard cell turgor (or leaf water potential); (2) CO2 flux can be used as a nonparametric equivalent of stomatal conductance for a given stomatal function (not necessarily optimal in terms of the water use efficiency for photosynthesis). Transpiration is then expressed as a function of leaf temperature, CO2 flux (as a surrogate of stomatal conductance), and sensible heat flux characterizing the transport mechanism at a given level of radiative energy input. Maximization of transpiration constrained by the energy balance equation leads to vanishing derivatives of transpiration with respect to leaf temperature and CO2 flux. We have obtained observational evidence in support of the proposed hypothesis.
Influence of shifting flow paths on nitrogen concentrations during monsoon floods, San Pedro River, Arizona
Authors: Meixner T. , Huth A. K. , Brooks P. D. , Conklin M. H. , Grimm N. B. , Bales R. C. , Haas P. A. , Petti J. R.
Published: August 2007

Hydrologic flow paths control transport, and therefore are a major constraint on the cycling and availability of nutrients within stream ecosystems. This control is particularly evident in semiarid streams, where hydrologic connectivity between stream, riparian, and upland systems increases greatly during storms in the rainy season. We measured chloride concentrations in base flow, precipitation, soil water, and stream water to quantify the hydrologic connectivity and solute flux between soil water, groundwater, and the stream channel during six summer floods in 2001 (a wet year; 25 cm winter rain) and 2002 (a dry year; 5 cm winter rain) in the San Pedro River, southeastern Arizona. This hydrologic information was used to evaluate observed patterns in nitrate, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations in floods. The first floods of each year showed increased stream nitrate concentration that was approximately two orders of magnitude higher than base flow concentration. DOC consistently doubled to tripled during storm events, while DON in 2001 showed no response and showed a marked increase in 2002. A chloride mixing model indicated that soil and groundwater contributions to storm water discharge were related to antecedent conditions and to flood magnitude. Soil and groundwater contributions were the highest early in the 2001 monsoon season following the wet winter, much lower early in 2002 following a dry winter, and lowest during the largest floods of the 2002 monsoon season when flows were derived primarily from precipitation and overland flow. Stream water nitrate‐N concentrations during floods were consistently 0.2–0.5 mg/L higher in 2002 than during 2001, suggesting greater over‐winter accumulation of soil nitrate during the drier year. This result is consistent with higher mean nitrate‐N concentrations in soil water of the riparian zone in 2002 (3.1 mg/L) than in 2001 (0.56 mg/L). These data highlight the importance of seasonal and interannual variability of hydrology in semiarid regions, and the role of water availability in driving patterns of soil nutrient accumulation and their transport to the stream.
A core top assessment of proxies for the ocean carbonate system in surface‐dwelling foraminifers
Authors: Ni Yunyan , Foster Gavin L. , Bailey Trevor , Elliott Tim , Schmidt Daniela N. , Pearson Paul , Haley Brian , Coath Chris
Published: August 2007

We have assessed the reliability of several foraminifer‐hosted proxies of the ocean carbonate system (δ11B, B/Ca, and U/Ca) using Holocene samples from the Atlantic and Pacific oceans. We examined chemical variability over a range of test sizes for two surface‐dwelling foraminifers (Globigerinoides sacculifer and Globigerinoides ruber). Measurements of δ11B in G. ruber show no significant relationship with test size in either Atlantic or Pacific sites and appear to provide a robust proxy of surface seawater pH. Likewise there is no significant variability in the δ11B of our Atlantic core top G. sacculifer, but we find that δ11B increases with increasing test size for G. sacculifer in the Pacific. These systematic differences in δ11B are inferred to be a consequence of isotopically light gametogenic calcite in G. sacculifer and its preferential preservation during postdepositional dissolution. The trace element ratio proxies of ocean carbonate equilibria, U/Ca and B/Ca, show systematic increases in both G. ruber and G. sacculifer with increasing test size, possibly as a result of changing growth rates. This behavior complicates their use in paleoceanographic reconstructions. In keeping with several previous studies we find that Mg/Ca ratios increase with increasing size fraction in our well‐preserved Atlantic G. sacculifer but not in G. ruber. In contrast to previous interpretations we suggest that these observations reflect a proportionally larger influence of compositionally distinct gametogenic calcite in small individuals compared to larger ones. As with δ11B this influences G. sacculifer but not G. ruber, which has negligible gametogenic calcite.
Plant response to the soil environment: An analytical model integrating yield, water, soil type, and salinity
Authors: Shani Uri , Ben‐Gal Alon , Tripler Effi , Dudley Lynn M.
Published: August 2007

An accessible solution capable of reliably predicting plant‐environmental interrelationships for variable species, climates, soils, and management options is a necessary tool for creating sustainable agriculture and environmental preservation. A mechanism‐based analytical solution, the first of its kind that considers multiple environmental variables and their combined effects on plant response, was developed and tested. Water uptake by plants, water and salt leakage below the roots, and yield are calculated by solving for transpiration in a single mathematical expression according to limitations imposed by root zone salinity and water status. Input variables include the quantity and salinity of applied water, terms for plant sensitivity to salinity and to water stress, potential evapotranspiration, and soil hydraulic parameters. Where water was not limiting, regression of predicted versus measured data resulted in r2 = 0.96 with slope of 0.937 and intercept of 0.033 (not different from 1 and 0 at 99% confidence), where irrigation varied and salinity was not limiting the r2 = 0.94 with slope of 0.906 and intercept of 0.044 (not different from 1 and 0 at 99% confidence), where both salinity and water levels varied r2 = 0.94 with slope of 0.966 and intercept of 0.033 (not different from 1 and 0 at 99% confidence). Application of the model for agricultural and environmental management and economic analysis is discussed. For example, a farmer in the Arava in Israel where irrigation water salinity is high (electrical conductivity of 3 dS m−1) cannot expect to reach greater than 70% of the potential yield for a pepper crop with any amount of irrigation. By choosing melon, the farmer can achieve 90% of potential yield with the same quality and quantity of water.
A semidiscrete finite volume formulation for multiprocess watershed simulation
Authors: Qu Yizhong , Duffy Christopher J.
Published: August 2007

Hydrological processes within the terrestrial water cycle operate over a wide range of time and space scales, and with governing equations that may be a mixture of ordinary differential equations (ODEs) and partial differential equations (PDEs). In this paper we propose a unified strategy for the formulation and solution of fully coupled process equations at the watershed and river basin scale. The strategy shows how a system of mixed equations can be locally reduced to ordinary differential equations using the semidiscrete finite volume method (FVM). Domain decomposition partitions the watershed surface onto an unstructured grid, and vertical projection of each element forms a finite volume on which all physical process equations are formed. The projected volume or prism is partitioned into surface and subsurface layers, leading to a fully coupled, local ODE system, referred to as the model “kernel.” The global ODE system is assembled by combining the local ODE system over the domain, and is then solved by a state‐of‐the‐art ODE solver. The unstructured grid, based on Delaunay triangulation, is generated with constraints related to the river network, watershed boundary, elevation contours, vegetation, geology, etc. The underlying geometry and parameter fields are then projected onto the irregular network. The kernel‐based formulation simplifies the process of adding or eliminating states, constitutive laws, or closure relations. The strategy is demonstrated for the Shale Hills experimental watershed in central Pennsylvania, and several phenomena are observed: (1) The enslaving principle is shown to be a useful approximation for soil moisture–water table dynamics for shallow soils in upland watersheds; (2) the coupling shows how antecedent moisture (i.e., initial conditions) can amplify peak flows; (3) the coupled equations predict the onset or threshold for upland ephemeral channel flow; and (4) the model shows how microtopographic information controls surface saturation and connectivity of overland flow paths for the Shale Hills site. The open‐source code developed in this research is referred to as the Penn State Integrated Hydrologic Model (PIHM).
Climate warming revealed by englacial temperatures at Col du Dôme (4250 m, Mont Blanc area)
Authors: Vincent Christian , Le Meur Emmanuel , Six Delphine , Possenti Philippe , Lefebvre Eric , Funk Martin
Published: August 2007

Temperatures were measured in two deep boreholes drilled at the same location in the ice at Col du Dôme (4250 m) in 1994 and 2005, providing clear evidence of atmospheric warming. The 1994 temperature profile was already far from steady state conditions. Results from a heat transfer model reveal that the englacial temperature increase cannot be explained solely by atmospheric temperature rise. The latent heat produced by the refreezing of surface meltwater below the surface also contributes to the englacial temperature increase. Although surface melting is normally very low at this altitude, this contribution became significant after 1980 for temperatures at the top of the borehole. Simulations for different climatic scenarios show that glaciated areas located between 3500 and 4250 m could become temperate in the future. This warming could have a major impact on the stability of hanging glaciers frozen to their beds if the melting point is reached.
Global water cycle agreement in the climate models assessed in the IPCC AR4
Authors: Waliser D. , Seo K.‐W. , Schubert S. , Njoku E.
Published: August 2007

This study examines the fidelity of the global water cycle in the climate model simulations assessed in the IPCC Fourth Assessment Report. The results demonstrate good model agreement in quantities that have had a robust global observational basis and that are physically unambiguous. The worst agreement occurs for quantities that have both poor observational constraints and whose model representations can be physically ambiguous. In addition, components involving water vapor (frozen water) typically exhibit the best (worst) agreement, and fluxes typically exhibit better agreement than reservoirs. These results are discussed in relation to the importance of obtaining accurate model representation of the water cycle and its role in climate change. Recommendations are also given for facilitating the needed model improvements.
Fully nonlinear inversion of fundamental mode surface waves for a global crustal model
Authors: Meier U. , Curtis A. , Trampert J.
Published: August 2007

We use neural networks to find 1‐dimensional marginal probability density functions (pdfs) of global crustal parameters. The information content of the full posterior and prior pdfs can quantify the extent to which a parameter is constrained by the data. We inverted fundamental mode Love and Rayleigh wave phase and group velocity maps for pdfs of crustal thickness and independently of vertically averaged crustal shear wave velocity. Using surface wave data with periods T > 35 s for phase velocities and T > 18 s for group velocities, Moho depth and vertically averaged shear wave velocity of continental crust are well constrained, but vertically averaged shear wave velocity of oceanic crust is not resolvable. The latter is a priori constrained by CRUST2.0. We show that the resulting model allows to compute global crustal corrections for surface wave tomography for periods T > 50 s for phase velocities and T > 60 s for group velocities.
Phaseollidin stored in vacuoles and the phytoalexin response in bean
Authors: Soriano‐Richards E. , Uribe‐Salas D. , Ibarra‐Barrera G.
Published: August 2007

In time‐course experiments, the amounts of phytoalexin in hypocotyls of the resistant bean cultivar Flor de Mayo were determined after infection with Colletotrichum lindemuthianum. Phaseollin and phaseollidin accumulated as a defence response. However, phaseollidin accumulated earlier than phaseollin and at greater concentrations (155 + 14 compared with 120 + 9 μg g−1 fresh weight). Phaseollidin was found conjugated as a glucoside in the tissue. Fungal treatment apparently led to a decline of approximately 50% in phaseollidin conjugate after only 7 h after infection. Isolation of vacuoles confirmed the presence of phaseollidin glucosides in this organelle. Treatment of the tissue or isolated protoplasts with a fungal elicitor also produced a decrease, by half, of phaseollidin conjugate concentrations from vacuoles isolated from both sources. The contribution of pre‐existing pools of phaseollidin glycoside to the accumulation of this phytoalexin is discussed.
Paramagnetic point defects in (100)Si∕LaAlO3 structures: Nature and stability of the interface
Authors: Clémer K. , Stesmans A. , Afanas’ev V. V. , Edge L. F. , Schlom D. G.
Published: August 2007

The atomic nature of the interface in (100)Si∕LaAlO3 structures with nanometer-thin amorphous LaAlO3 layers of high dielectric constant (κ), deposited directly on clean (100)Si by molecular beam deposition at ∼100°C, was assessed through probing of paramagnetic point defects. On the as-grown samples K-band electron spin resonance indicated the absence of a Si∕SiO2-type interface in terms of the archetypal Si-dangling bond-type Si∕SiO2 interface defects (Pb0, Pb1). With no Pb-type defects observed, this state is found to persist during subsequent annealing (1atm N2 or 5% O2 in N2 ambient) up to the temperature Tan∼800°C, referring to a thermally stable abrupt Si∕LaAlO3 interface, quite in contrast with other high-κ metal oxide∕Si structures. However, in the range Tan∼800–860°C a Si∕SiO2-type interface starts forming as evidenced by the appearance of Pb0 defects and, with some delay in Tan, the EX center—a SiO2 associated defect, attesting to significant structural∕compositional modification. The peaking of the defect density versus Tan curves indicates the SiOx nature of the interlayer to break up again upon annealing at Tan⩾930°C, possibly related to crystallization and∕or degrading silicate formation. No specific LaAlO3-specific point defects could be traced.
Three-dimensional capillary-gravity waves generated by a moving disturbance
Authors: Părău E. I. , Vanden-Broeck J.-M. , Cooker M. J.
Published: August 2007

Steady three-dimensional capillary-gravity waves generated by a moving pressure distribution are considered. Solutions of the full Euler equations are computed by using a boundary integral equation method. The radiation condition is imposed by introducing a small Rayleigh viscosity in the dynamic boundary condition. The results generalize previous linear findings.
Linear and nonlinear ion-acoustic waves in an unmagnetized electron-positron-ion quantum plasma
Authors: Ali S. , Moslem W. M. , Shukla P. K. , Schlickeiser R.
Published: August 2007

The linear and nonlinear properties of the ion-acoustic waves (IAWs) are investigated by using the quantum hydrodynamic equations together with the Poisson equation in a three-component quantum electron-positron-ion plasma. For this purpose, a linear dispersion relation, a Korteweg-de Vries equation and an energy equation containing quantum corrections are derived. Computational investigations have been performed to examine the quantum mechanical effects on the linear and nonlinear waves. It is found that both the linear and nonlinear properties of the IAWs are significantly affected by the inclusion of the quantum corrections. The relevance of the present investigation to dense white dwarfs (where the electron-positron annihilation can be unimportant) is discussed.
Automatically generated Coulomb fitting basis sets: Design and accuracy for systems containing H to Kr
Authors: Yang Rui , Rendell Alistair P. , Frisch Michael J.
Published: August 2007

For intermediate sized chemical systems the use of an auxiliary basis set (ABS) to fit the charge density provides a useful means of accelerating the performance of various quantum chemical methods. As a consequence much effort has been devoted to the design of various ABSs. This paper explores a fundamentally new approach where the ABS is created dynamically based on the specific orbital basis set (OBS) being used. The new approach includes a parameter that is used to coalesce candidate fitting functions together but which can also be used to provide some coarse grain control over the number of functions in the ABS. The accuracy of the new automatically generated ABS (auto-ABS) is systemically studied for a variety of small systems containing the elements H–Kr. Errors in the Coulomb energy computed using auto-ABS and with a variety of OBSs are shown to be small compared to errors in the Hartree-Fock energy due to incompleteness in the OBS. In contrast to fixed size ABSs, the use of auto-ABS is shown to lead to smaller errors as the size (quality) of the OBS is expanded. The performance of auto-ABS is also compared with the use of the recently proposed universal fitting sets [Weigend, Phys. Chem. Chem. Phys. 8, 1057 (2006)] for 180 compounds containing atoms from H to Kr.
Ultrafast exciton-exciton coherent transfer in molecular aggregates and its application to light-harvesting systems
Authors: Hyeon-Deuk Kim , Tanimura Yoshitaka , Cho Minheang
Published: August 2007

Effects of the exciton-exciton coherence transfer (EECT) in strongly coupled molecular aggregates are investigated from the reduced time-evolution equation which we have developed to describe EECT. Starting with the nonlinear response function, we obtained explicit contributions from EECT to four-wave-mixing spectrum such as photon echo, taking into account double exciton states, static disorder, and heat-bath coupling represented by arbitrary spectral densities. By using the doorway-window picture and the projection operator technique, the transfer rates between two different electronic coherent states are obtained within a framework of cumulant expansion at high temperature. Applications of the present theory to strongly coupled B850 chlorophylls in the photosynthetic light harvesting system II (LH2) are discussed. It is shown that EECT is indispensable in properly describing ultrafast phenomena of strongly coupled molecular aggregates such as LH2 and that the EECT contribution to the two-dimensional optical spectroscopy is not negligible.
Kinetic coefficient of steps at the Si(111) crystal-melt interface from molecular dynamics simulations
Authors: Buta Dorel , Asta Mark , Hoyt Jeffrey J.
Published: August 2007

Nonequilibrium molecular dynamics simulations are applied to the investigation of step-flow kinetics at crystal-melt interfaces of silicon, modeled with the Stillinger-Weber potential [Phys. Rev. B 31, 5262 (1985)]. Step kinetic coefficients are calculated from crystallization rates of interfaces that are vicinals of the faceted (111) orientation. These vicinal interfaces contain periodic arrays of bilayer steps, and they are observed to crystallize in a step-flow growth mode at undercoolings lower than 40K. Kinetic coefficients for both [110] and [121] oriented steps are determined for several values of the average step separation, in the range of 7.7–62.4Å. The values of the step kinetic coefficients are shown to be highly isotropic, and are found to increase with increasing step separation until they saturate at step separations larger than ∼50Å. The largest step kinetic coefficients are found to be in the range of 0.7–0.8m∕(sK), values that are more than five times larger than the kinetic coefficient for the rough (100) crystal-melt interface in the same system. The dependence of step mobility on step separation and the relatively large value of the step kinetic coefficient are discussed in terms of available theoretical models for crystal growth kinetics from the melt.
Gauge-origin independent calculation of magnetizabilities and rotational g tensors at the coupled-cluster level
Authors: Gauss Jürgen , Ruud Kenneth , Kállay Mihály
Published: August 2007

An implementation of the gauge-origin independent calculation of magnetizabilities and rotational g tensors at the coupled-cluster (CC) level is presented. The properties of interest are obtained as second derivatives of the energy with respect to the external magnetic field (in the case of the magnetizability) or with respect to magnetic field and rotational angular momentum (in the case of the rotational g tensor), while gauge-origin independence and fast basis-set convergence are ensured by using gauge-including atomic orbitals (London atomic orbitals) as well as their extension to treat rotational perturbations (rotational London atomic orbitals). The implementation within our existing CC analytic second-derivative code is described, focusing on the required modifications concerning integral evaluation and treatment of the unperturbed and perturbed two-particle density matrices. An extensive set of test calculations for LiH and BH (up to the full configuration-interaction limit), for a series of simple hydrides (HF, H2O, NH3, and CH4) as well as the more challenging molecules CO, N2, and O3 [employing the CC singles and doubles (CCSD) and the CCSD approximation augmented by a perturbative treatment of triple excitations] demonstrates the importance of electron correlation for high-accuracy predictions of magnetizabilities and rotational g tensors.
Ultrafast studies of gold, nickel, and palladium nanorods
Authors: Sando Gerald M. , Berry Alan D. , Owrutsky Jeffrey C.
Published: August 2007

Steady state and ultrafast transient absorption studies have been carried out for gold, nickel, and palladium high aspect ratio nanorods. For each metal, nanorods were fabricated by electrochemical deposition into ∼6μm thick polycarbonate templates. Two nominal pore diameters(10 and 30nm, resulting in nanorod diameters of about 40 and 60nm, respectively) were used, yielding nanorods with high aspect ratios (>25). Static spectra of nanorods of all three metals reveal both a longitudinal surface plasmon resonance (SPRL) band in the mid-infrared as well as a transverse band in the visible for the gold and larger diameter nickel and palladium nanorods. The appearance of SPRL bands in the infrared for high aspect ratio metal nanorods and the trends in their maxima for the different aspect ratios and metals are consistent with calculations based on the Gans theory. For the gold and nickel samples, time resolved studies were performed with a subpicosecond resolution using 400nm excitation and a wide range of probe wavelengths from the visible to the mid-IR as well as for infrared excitation (near 2000cm−1) probed at 800nm. The dynamics observed for nanorods of both metals and both diameters include transients due to electron-phonon coupling and impulsively excited coherent acoustic breathing mode oscillations, which are similar to those previously reported for spherical and smaller rod-shaped gold nanoparticles. The dynamics we observe are the same within the experimental uncertainty for 400nm and infrared (5μm) excitation probed at 800nm. The transient absorption using 400nm excitation and 800nm probe pulses of the palladium nanorods also reveal coherent acoustic oscillations. The results demonstrate that the dynamics for high aspect ratio metal nanorods are similar to those for smaller nanoparticles.
Air gaps in metal stripe waveguides supporting long-range surface plasmon polaritons
Authors: Berini Pierre
Published: August 2007

The effects of air gaps in metal stripe waveguides supporting long-range surface plasmon polaritons have been determined theoretically. The study is motivated by a recently adopted fabrication approach based on direct bonding, where various kinds of air gaps may form near the metal stripe due to fabrication imperfections. Specifically, “Air wings,” a top air gap, and side air gaps have been considered as possible perturbations. The main effects of the air gaps on the propagation of the long-range surface plasmon-polariton wave are that its attenuation and confinement decrease as the gaps become more invasive, and that its mode fields become strongly perturbed. Taken together, these effects are deleterious, so air gaps do not appear suitable for range extension. In general, very small air gaps can only be tolerated before confinement is completely lost. A lower-index planarizing layer could be used to help eliminate air gaps but the waveguide design space becomes constrained. The air gaps perturb the long-range mode such that its main transverse electric-field component (Ey) develops a maximum within the gaps and some localization therein. This feature could be interesting in applications where high-intensity fields in nanometric air gaps are sought, but only if coupling and radiation losses are not much of a concern.
Thermodynamic pressure of simple fluids confined in cylindrical nanopores by isothermal-isobaric Monte Carlo: Influence of fluid/substrate interactions
Authors: Puibasset Joël
Published: August 2007

The thermodynamic pressure or grand potential density is calculated by isobaric-isothermal Monte Carlo algorithm for simple Lennard-Jones fluid confined in cylindrical pores presenting chemical heterogeneities along their axis. Heuristic arguments and simulation results show that the thermodynamic pressure of the confined fluid contains two contributions. The first term is the usual pressure of the bulk fluid for a density equal to the confined fluid density defined as the total number of confined particles divided by the accessible volume due to thermal agitation. A second term has to be added, which is empirically shown to be proportional to the fluid/wall interface area and almost constant along the adsorption and desorption branches. This interfacial contribution, calculated for various pore models, has small variations reminiscent of the fluid adsorption/desorption properties calculated in the various pores. In particular, it is shown that this interfacial quantity is maximum for a fluid/substrate interaction intensity of the same order as the fluid/fluid one, while the thermodynamic pressure at which rapid desorption occurs presents a minimum. Stronger or weaker fluid/wall affinity favors gas state nucleation on the desorption of confined fluids.
Texture and phase analysis of a Ca3Co4O9∕Si (100) thermoelectric film
Authors: Wong-Ng W. , Vaudin M. D. , Otani M. , Lowhorn N. D. , Hu Y. F. , Li Q. , He B.
Published: August 2007

This paper reports the texture analysis as well as the identification of two crystalline phases between a thin film of monoclinic Ca3Co4O9 and a cubic (100) Si substrate, using a diffractometer equipped with a two-dimensional area detector. No reflections other than 00ℓ were observed in the symmetric configuration using an x-ray powder diffraction scan (Bragg-Brentano geometry). Pole figures collected for six reflections using asymmetric configurations did not show ab-plane epitaxial relationships between the film and the substrate. These results establish the Ca3Co4O9 fiber texture of the film with the (001) pole parallel to the surface normal. Single-crystal-like second phases, CaCoSi2O6 and CoO, presumably the interface reaction products of Ca3Co4O9 with the substrate Si, were identified. The near four-fold symmetry and the similar intensity displayed by the 220 reflection from the CaCoSi2O6 structure indicated an epitaxial relation between CaCoSi2O6 and Si, with four symmetry-induced variants being generated with approximately equal volume fractions.
Quantum dot resonant tunneling diode for telecommunication wavelength single photon detection
Authors: Li H. W. , Kardynał B. E. , See P. , Shields A. J. , Simmonds P. , Beere H. E. , Ritchie D. A.
Published: August 2007

The authors present a quantum dot (QD) based single photon detector operating at a fiber optic telecommunication wavelength. The detector is based on an AlAs∕In0.53Ga0.47As∕AlAs double-barrier resonant tunneling diode containing a layer of self-assembled InAs QDs grown on an InP substrate. The device shows an internal efficiency of about 6.3% with a dark count rate of 1.58×10−6ns−1 for 1310nm photons.
Using atomistic computer simulations to analyze x-ray diffraction data from metallic glasses
Authors: Mendelev M. I. , Sordelet D. J. , Kramer M. J.
Published: August 2007

We propose a method of using atomistic computer simulations to obtain partial pair correlation functions from wide angle diffraction experiments with metallic liquids and their glasses. In this method, a model is first created using a semiempirical interatomic potential and then an additional atomic force is added to improve the agreement with experimental diffraction data. To illustrate this approach, the structure of an amorphous Cu64.5Zr35.5 alloy is highlighted, where we present the results for the semiempirical many-body potential and fitting to x-ray diffraction data. While only x-ray diffraction data were used in the present work, the method can be easily adapted to the case when there are also data from neutron diffraction or even in combination. Moreover, this method can be employed in the case of multicomponent systems when the data of several diffraction experiments can be combined.
Direct measurement of density oscillation induced by a radio-frequency wave
Authors: Yamada T. , Ejiri A. , Shimada Y. , Oosako T. , Tsujimura J. , Takase Y. , Kasahara H.
Published: August 2007

An O-mode reflectometer at a frequency of 25.85GHz was applied to plasmas heated by the high harmonic fast wave (21MHz) in the TST-2 spherical tokamak. An oscillation in the phase of the reflected microwave in the rf range was observed directly for the first time. In TST-2, the rf (250kW) induced density oscillation depends mainly on the poloidal rf electric field, which is estimated to be about 0.2kV∕m rms by the reflectometer measurement. Sideband peaks separated in frequency by ion cyclotron harmonics from 21MHz, and peaks at ion cyclotron harmonics which are suggested to be quasimodes generated by parametric decay, were detected.
Lead zirconate titanate ferroelectric thin film capacitors: Effects of surface treatments on ferroelectric properties
Authors: Chen Ye , McIntyre Paul C.
Published: August 2007

X-ray photoelectron spectroscopy (XPS) revealed a lead-rich carbonatelike surface layer on polycrystalline lead zirconate titanate films grown by metal-organic chemical vapor deposition. In situ XPS studies indicated that lead originally present in the oxide film reacted with Pt during its deposition, forming a Ti∕Zr-rich defective interfacial layer. Lead zirconate titanate films that underwent a nitric acid treatment, which effectively removed the surface layer, exhibited a stretched out of the hysteresis loop in the vicinity of the coercive field, consistent with the presence of a nonferroelectric passive layer. Reasonable agreement between the XPS-measured interface layer thickness and the thickness determined by electrical characterization was obtained.