bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation effects and Pekar bipolaron (arbitrary electron–phonon interaction)
Authors: Kashirina N. I. , Lakhno V. D. , Sychyov V. V.
Published: August 2003

The Buimistrov–Pekar method of canonical transformation was used to calculate the energies of the lowest singlet and triplet terms of bipolarons in crystals with ionic binding. An arbitrary electron–phonon interaction described by the Fröhlich Hamiltonian was considered. It was shown that, in the whole parametric range of electron–phonon interaction, the value of the free bipolaron ground state energy obtained by the Buimistrov–Pekar method is lower than all those found by Adamowski and Bednarek in the framework of direct variational approaches, and only slightly exceeds (relative error <0.3%) those obtained by Verbist, Peeters, and Devreese by integration over trajectories for α ≤ 7. The calculations have shown that any metastable triplet states corresponding to the lowest triplet term of a bipolaron are absent for all the parameters of the electron–phonon interaction, the results being in complete analogy with Hill's theorem about the absence of any bound excited states for an H− ion. Study of a wave function of more general form has demonstrated that a two‐center bipolaron is energetically less advantageous than a one‐center one for all the parameters of the electron–phonon interaction. Control calculations performed with the system of functions used in this paper have yielded 1.173 a.u. for the hydrogen molecule energy, which is in good agreement with the experimental value.
Optical band gap in relation to the average coordination number in Ge—S—Bi thin films
Authors: Saffarini G. , Schmitt H. , Shanak H. , Nowoczin J. , Müller J.
Published: August 2003

Chalcogenide glasses belonging to the GexS94 − xBi6 system (14 ≤ x ≤ 28.33 at%) have been prepared from high purity constituent elements. Thin films of the same materials have been deposited by vacuum thermal evaporation. Optical absorbance measurements have been performed on the as‐deposited films. The allowed optical transition is found to be indirect and the corresponding optical gaps, Eg, are determined. The variation of Eg with the average coordination number, 〈r〉, is also investigated. The observed Eg − 〈r〉 dependence is discussed on the basis of the chemical bonding between the constituents and the rigidity percolation threshold behavior of the network.
Vibrational dynamics at a surface atomic well
Authors: Tigrine R. , Khater A. , Rafil O. , Belhadi M. , Hardy J.
Published: August 2003

We investigate the dynamical phenomena at the inhomogeneous boundary of an extended atomic well in crystalline solid surfaces. The surfaces are considered as a semi‐infinite slab of two coupled atomic layers, and the well as a single atomic chain. This simplified geometric configuration models an atomic well in a surface. The breakdown of translation symmetry in the direction parallel to the surface and normal to the extended well gives rise to localized vibrational modes in its neighborhood. The matching method is used in this study, it may be applied to analyze both the vibrational and the scattering dynamical phenomena for surface inhomogeneities. Characteristic vibrational Green functions and spectral densities are calculated for this system, in particular for the atomic sites which constitute a representative ensemble for the well. The variations of these spectra are presented as a function of the variation of the elastic parameters of the well. This illustrates the variation of the spectra for the softening and the hardening situations of the surface atomic well. The calculated spectra could yield, in comparison with experimental results to come, useful information concerning the elastic parameters of such a surface atomic well.
Cyclotron resonance on anisotropic energy surfaces analyzed for a magnetic field tilted with respect to the crystallographic axes
Authors: Olszewski S. , Baszczak M.
Published: August 2003

Parameters characterizing the electron motion performed in the cyclotron resonance effect, especially the electron gyration frequency, are calculated as functions of the angle with which the direction of a constant magnetic field is tilted with respect to the direction of one of the crystallographic axes. Tightly bound s electrons forming bands of states in simple cubic and body‐centered cubic lattices have been chosen for the calculations as examples for the electron and crystal. In each lattice case an equation for the electron motion performed along a closed anisotropic surface of constant energy has been derived and solved on the basis of a semi‐classical theory.
Theory and simulation of dopant implantation and diffusion in SiGe
Authors: Liu Chun‐Li , Orlowski Marius , Thean Aaron , Beardmore Keith , Barr Alex , White Ted , Nguyen Bich‐Yen , Rueda Hernan , Liu Xiang‐Yang
Published: August 2003

Strained Si‐based technology has imposed a new challenge for understanding dopant implantation and diffusion in SiGe that is often used as the buffer layer for a strained Si cap layer. In this work, we describe our latest modeling effort investigating the difference in dopant implantation and diffusion between Si and SiGe. A lattice expansion theory was developed to account for the volume change due to Ge in Si and its effect on defect formation enthalpy. The theory predicts that As diffusion in SiGe is enhanced by a factor of ∼10, P diffusion by a factor of ∼2, and B diffusion is retarded by a factor of ∼6, when compared to bulk Si. These predictions are consistent with experiment. Dopant profiles for As, P, and B were simulatedusing process simulators FLOOPS and DIOS. The simulated profiles are in good agreement with experiment. Dopant implantation was simulated using REED‐MD. The results showed a noticeable difference in peak and tail positions SiGe compared to Si. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis dynamics of passivated silicon nanoclusters
Authors: Draeger Erik W. , Grossman Jeffrey C. , Williamson Andrew J. , Galli Giulia
Published: August 2003

The effect of preparation conditions on the structural and optical properties of silicon nanoparticles is investigated using first‐principles molecular dynamics and quantum Monte Carlo techniques. We find that high‐temperature synthesis processes can produce kinetically‐limited nanostructures with different core structures than bulk‐derived crystalline clusters. These nanoparticles have optical gaps in better agreement with experimental measurements than crystalline clusters of the same size. The type of core structure that forms from a given synthesis process may depend on the passivation mechanism and time scale. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electric field effects on the octanedithiol wire
Authors: Li Jun , Tomfohr John K. , Sankey Otto F.
Published: August 2003

We theoretically study the electric field profile and the voltage profile across a model molecule in a metal‐molecule‐metal junction under bias. The model system is octanedithiol (S–(CH2)8–S) sandwiched between two gold electrodes (Au[111]). We use a simple, but approximate, method to investigate the voltage profile across the molecule and the change of electronic states under a given bias. The key simplification is to artificially shift the two metal (Au) Hamiltonians relative to each other within a closed system to simulate the external bias of an open system. The Hamiltonian of the closed system is calculated within density functional theory using local orbitals and the electronic structure of the entire system is determined self‐consistently. In the final step after charge transfer has taken place, we remove the artificial metal Hamiltonian shifts to reveal an oppositely biased system with a built‐in electric field across the molecule. The electric field effects on the electronic structure of the molecule are analyzed by tracking the on‐site orbital energies (diagonal Hamiltonian matrix elements) and the projected electronic density of states onto atoms along the molecular wire. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Short‐wavelength charge oscillations in semiconducting carbon nanotubes
Authors: Léonard François
Published: August 2003

Self‐consistent tight‐binding calculations for Carbon Nanotube devices have shown large oscillations of the charge from atom to atom. To explain this effect, we present a linear response theory for semiconducting carbon nanotubes subject to an external electrostatic potential perturbation. Within tight‐binding theory, it is demonstrated that the large charge oscillations originate from the polyatomic nature of the unit cell. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rattling guest atoms in Si, Ge, and Sn‐based type‐II clathrate materials
Authors: Myles Charles W. , Dong Jianjun , Sankey Otto F.
Published: August 2003

We have studied the vibrational properties of some of the compounds based on the Type II silicon, germanium, and tin‐based clathrate materials using LDA electronic structure methods. The lattices in these framework materials have open cages which can contain weakly bound guest impurities, and these guests produce local (“rattling”) vibrational modes. Such modes may scatter the extended, heat carrying acoustic vibrational modes of the framework, potentially reducing the thermal conductivity. We present results for the vibrational spectra of the Type II clathrate compounds Na16Cs8Si136, Na16Cs8Ge136, and Cs24Sn136. We discuss trends in the vibrational spectra of the framework host material and of the localized, rattling frequencies of the guest modes as the host changes from Si to Ge to Sn. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reaction enthalpies as selection criteria for tribological coatings
Authors: Ooi N. , Adams James B. , Singisetti Uttam
Published: August 2003

A wide range of coatings are used for a variety of applications. Selection criteria for these coatings include coating‐substrate adhesion, hardness, melting temperature, coefficient of thermal expansion mismatch, corrosion resistance, and cost. A factor often ignored is the possibility of reaction between the coating and the other surface which it contacts during use. This is especially important when frictional forces produce enough heat to locally melt asperities or even cause friction welding, as that heat will enhance the likelihood of chemical reactions at the interface. One aspect of this is to consider the reaction enthalpies between coatings and the surfaces they contact during operation. We explore the use of reaction enthalpies between coatings and opposing surfaces as a criteria for selecting coatings. Simple thermodynamic calculations are presented for several couples of coating – opposing surfaces. Conclusions are drawn about the relevance based on experimental evidence. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐equilibrium Green function implementation of boundary conditions for full band simulations of substrate‐nanowire structures
Authors: Rivas Cristian , Lake Roger
Published: August 2003

The density of states of a nanowire exhibits peaks at energies in which the individual transverse modes begin to propagate. Under ideal conditions these modes are eigenstates solely determined by the cross sectional size and shape of the nanowire. However, for realistic nanowires, which are grown on semiconductor substrates, the density of states of the subsrate‐nanowire structure is dependent on the distance from the nanowire endpoints. Near the substrate, the density of states is is nonzero far below the energy corresponding to the first eigenstate of the ideal nanowire. This initial increase in the density of states occurs at energies near the conduction and valence band edges of the semiconductor substrate on which the nanowire is grown. Away from the substrate, the density of states begins to acquire ideal nanowire characteristics. In the present work this effect is captured by imposing boundary conditions, with properties of bulk material, at the nanowire base. The calculations utilize a first neighbor sp3s*d5 orbital basis within the non‐equilibrium Green function formalism. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Difficulties of the microscopic theory of leakage current through ultra‐thin oxide barriers: point defects
Authors: Fonseca Leonardo R. C. , Demkov Alexander A. , Knizhnik Andrey
Published: August 2003

We use a combination of first‐principles density functional theory and non‐perturbative scattering theory to investigate the effect of point defects on the hole leakage current through ultra thin oxide films. In particular, we consider O vacancies and B interstitial in monoclinic HfO2; five different defects are considered: (1) O vacancy at a three‐ and (2) a four‐coordinated O site located in the HfO2 region, (3) O vacancy along a Hf–O–Si bond and (4) along a Si–O–Si bond at the Si/HfO2 interface, and (5) an interstitial Batom in the HfO2 region. We find that the neutral bulk vacancies and an interface vacancy along theSi–O–Si bond have little impact on the leakage current. On the contrary, an interface vacancy along the Hf–O–Si bridge and an interstitial B atom in the HfO2 region introduce states in the Si band gap and in the region just below the Si valence band edge thus strongly enhancing the leakage current at a low bias. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quality Improvement from the Viewpoint of Statistical Method
Authors: De Mast Jeroen
Published: August 2003

With the purpose of guiding professionals in conducting improvement projects in industry, several quality improvement strategies have been proposed which strongly rely on statistical methods. Examples are the Six Sigma programme, the Shainin System and Taguchi's methods. This paper seeks to make a rational reconstruction of these types of improvement strategies, which results in a methodological framework.

The paper gives a demarcation of the subject of study and proposes a reconstruction research approach. Thereupon, the elements of the methodological framework are listed and briefly discussed. Finally, the effectiveness of the framework is illustrated by showing to what extent it reconstructs Six Sigma's Breakthrough Cookbook. Copyright © 2003 John Wiley & Sons, Ltd.
The Use of Observational Data to Implement an Optimal Experimental Design
Authors: Berni Rossella
Published: August 2003

This paper is focused on observational data and on the use of large data sets to implement an experimental design without additional runs, for an efficient use of these data. More specifically, the proposed procedure is based on several steps, aimed at avoiding some problems, such as lack of randomization and efficiency, obtaining a final experimental design that can be assumed as optimal from the point of view of a sequential optimality. Copyright © 2003 John Wiley & Sons, Ltd.
Robust Design Methodology: Status in the Swedish Manufacturing Industry
Authors: Gremyr Ida , Arvidsson Martin , Johansson Per
Published: August 2003

While robust design methodology is a fairly common subject in the literature on quality and statistics, this paper shows that only 17% of Swedish manufacturing companies apply robust design methodology. The low level of use of robust design methodology is surprising since a majority of the companies think it is important to minimize performance variation. However, although knowledge and use of robust design methodology is poor, methods suitable in robust design methodology are often used. For example, 53% of the companies use design of experiments to some extent. The data presented in this paper were collected in a telephone survey of 105 companies in the Swedish manufacturing industry; the response rate was 83%. The sample was stratified with respect to company size, and it is shown that robust design methodology and related methods are used to a greater extent in large companies than in small and medium‐sized ones. Copyright © 2003 John Wiley & Sons, Ltd.
Statistical Efficiency: The Practical Perspective
Authors: Kenett Ron S. , Coleman Shirley , Stewardson Dave
Published: August 2003

The idea of adding a practical perspective to the mathematical definition of statistical efficiency is based on a suggestion by Churchill Eisenhart who, years ago gave, in an informal ‘Beer and Statistics’ seminar, a new definition of statistical efficiency. Later Bruce Hoadley from Bell Laboratories picked up where Eisenhart left off and added his version nicknamed ‘Vador’. Blan Godfrey, former CEO of the Juran Institute, more or less used Hoadley's idea during his Youden Address at the Fall Technical Conference of the American Society for Quality Control. We expand on this idea adding an additional component, the value of the data actually collected, which we believe is critical to the overall idea. The concept of Practical Statistical Efficiency (PSE) derived from these developments is introduced and demonstrated using five case studies. We suggest that PSE be considered before, during and after undertaking any quality improvement projects. Copyright © 2003 John Wiley & Sons, Ltd.
Integration of Sequential Process Adjustment and Process Monitoring Techniques
Authors: Pan Rong , del Castillo Enrique
Published: August 2003

Detecting abnormal disturbances and correcting them through adjustment are essential functions of quality control. This paper discusses a general sequential adjustment procedure based on stochastic approximation techniques and combines it with a control chart for detection. It is assumed that step‐like shifts of unknown size occur in the process mean at unknown points of time. The performance of the proposed methods depends on the sensitivity of the control chart to detect shifts in the process mean, on the accuracy of the initial estimate of the shift size, and on the number of sequential adjustments that are made. It is shown that sequential adjustments are superior to single adjustment strategies for almost all types of process shifts and magnitudes considered. A CUSUM (cumulative sum) chart used in conjunction with our sequential adjustment approach can improve the average squared deviations, the performance index considered herein, more than any other combined scheme unless the shift size is very large. The proposed integrated approach is compared with always applying a standard integral or exponentially weighted moving average controller with no monitoring component. Combining control charts and sequential adjustments is recommended for monitoring and adjusting a process when random shocks occur infrequently in time. Copyright © 2003 John Wiley & Sons, Ltd.
Control Charts for Monitoring Fault Signatures: Cuscore versus GLR
Authors: Runger George C. , Testik Murat C.
Published: August 2003

It is commonly assumed that an assignable cause may shift a process mean persistently to an unknown but constant value. However, there are situations such that a mean change is not persistently constant but time varying, which is known as the signature of a fault. Different forms of fault signatures may arise, especially when a residuals control chart is used to monitor an autocorrelated or closed‐loop controlled process. Incorporating a priori knowledge of a fault signature, fault‐sensitized control charts may be developed. In this paper, we investigate two control charts of this kind: generalized likelihood ratio (GLR) and cumulative score (Cuscore) charts. A sine wave representing a bounded signal and a linear trend representing an unbounded signal are used as fault signatures for investigation purposes. Two different cases are analyzed, a known fault signature and parameter and a known fault signature but unknown parameter. Both the initial performances and steady‐state performances of these charts are analyzed. The former case is somewhat artificial since it is synchronizing the control statistic and the fault signature; the latter one is more realistic since time of the occurrence of a fault is unknown. Simulation results show that GLR charts are robust to unknown signal start times and perform better than the alternatives for the cases compared. Copyright © 2003 John Wiley & Sons, Ltd.
Late Cenozoic geological evolution of the foreland basin bordering the West Kunlun range in Pulu area: Constraints on timing of uplift of northern margin of the Tibetan Plateau
Authors: Wang Erchie , Wan Jinglin , Liu Jiaqi
Published: August 2003

With an average elevation of 5000 m the West Kunlun range marks northwestern margin of the Tibetan Plateau and formed as an orogen in response to the collision of India and Asia 50 Ma ago. Its history of uplift and erosion in the late Cenozoic is recorded in a unique sedimentary sequence exposed through the highest terrace along the southern margin of the Tarim basin in Pulu area. The terrace is composed of coarse‐grain conglomerate at the bottom, alkaline‐enriched volcanic rocks in the middle and eolian sediments on the top. The underlying basement rocks are formed by Neogene rocks and Paleozoic granite. Named the Xiyu conglomerate, the coarse‐grained conglomerate is assigned a depositional age in the late Pliocene and the early Pleistocene (3.4–1.6 ma) and generally considered to be the products of rapid uplift of the Tibetan Plateau. To reveal the relations between uplift, erosion, and sedimentation, we have collected samples of granite overlain by the Xiyu conglomerate for dating the fission track age of apatite. The fission track ages date the absolute time of cooling through the track retention temperature of the granite within the West Kunlun range to be Miocene to early Pliocene (20–4.8 Ma). The cooling event was coeval with the north‐verging thrusting along the northern boundary fault and the associated foreland basin deposition, suggesting that the West Kunlun range once underwent significant tectonic uplift in the Neogene. In contrast to the underlying Tertiary foreland basin strata, the Xiyu conglomerate thins toward the West Kunlun range and contains granite pebbles of cooling ages of 93, 18, and 12 Ma. Our study suggests that the primary cause for accumulation of the Xiyu conglomerate and the correspondent sediments is the increase of erosion and sedimentation rates after the main pulse of tectonic uplift due to Quaternary climate change.
Deformation and fluid pressure variation during initiation and evolution of the plate boundary décollement zone in the Nankai accretionary prism
Authors: Ujiie Kohtaro , Hisamitsu Toshio , Taira Asahiko
Published: August 2003

The plate boundary décollement zone in the Muroto region of the Nankai accretionary prism records deformation and consolidation histories that have been affected by temporal changes in fluid pressure. Microstructural observations and chemical analysis demonstrate that the décollement zone initiated in an interval of porous clayey sediments characterized by cementation due to intergranular bonding of authigenic clays. Crosscutting relations of microstructures indicate that the décollement zone records two compactive deformations. The early compactive deformation involved destruction of porous cemented structure, probably caused by fluid pressure fluctuation. The late compactive deformation was characterized by clay‐particle rotation and porosity collapse along the sets of slip surfaces, resulting in zones of preferred orientation of clay particles. These compactive deformations led to significantly higher bulk densities within the décollement zone compared to the compaction trend of the overlying prism sediments. Elevated fluid pressure following compactive deformations induced an overconsolidated state within the décollement zone, with fluid‐filled dilatant fractures. Bulk density abruptly decreases at the top of the underthrust sediments, but there is no microstructural evidence for cementation. Fluids in the dilated fractures and underconsolidated underthrust sediments are potential sources for the elevated fluid pressure in and below the décollement zone, resulting in mechanical decoupling of the accretionary prism from underthrust sediments. The fault‐fluid interactions in the Muroto region may be applicable to other convergent plate margins where high temperature associated with the subduction of a spreading ridge or hot, young oceanic crust enhances diagenesis and cementation.
Fluid flow and conduction in two‐dimensional fractures with rough, self‐affine surfaces: A comparative study
Authors: Madadi Mahyar , VanSiclen Clinton D. , Sahimi Muhammad
Published: August 2003

We study fluid flow and conduction in a two‐dimensional model of a fracture with rough, self‐affine internal surfaces. The model consists of two parallel flat plates on which two rough, self‐affine surfaces, characterized by a roughness exponent H, are superimposed. The methods that we use for computing the effective flow and transport properties of the fracture include the lattice Boltzmann method for computing the flow properties, a random walk method for determining the effective conductivity of the (fluid‐saturated) fracture, and the Reynolds approximation. We also develop an asymptotic expression for the effective conductivity. The aperture of the fracture, as well as the roughness of its rough surface, are systematically varied in order to assess their effect on the effective permeability and conductivity of the fracture, and also test the accuracy and consistency of the methods. For large mean apertures, and all values of the roughness exponent H, all the methods yield essentially the same results. However, as the mean aperture decreases, the differences between the predictions of the methods increase significantly. We find that the Reynolds approximation provides relatively accurate estimates of the (hydraulic or electrical) apertures only if the fracture is at least moderately wide and that, similar to real three‐dimensional fractures, the electrical aperture is always smaller than the hydraulic fracture.
Climate change scenarios from a regional climate model: Estimating change in runoff in southern Africa
Authors: Arnell N. W. , Hudson D. A. , Jones R. G.
Published: August 2003

This paper describes an analysis of different ways of constructing climate change scenarios using output from three climate models. It focuses on using the HadRM3H regional climate model applied across southern Africa and a macroscale runoff model operating at a scale of 0.5 × 0.5° to simulate river runoff. HadRM3H has a spatial resolution of 0.44 × 0.44° and is driven by boundary conditions from HadAM3H, a global atmosphere general circulation model with a spatial resolution of 1.875 × 1.25°. This, in turn, used sea‐surface boundary conditions from HadCM3, a coupled global ocean‐atmosphere general circulation model that operates at a spatial resolution of 3.75 × 2.5°. Sixteen climate scenarios were constructed from the three models, representing different combinations of model scale, whether the climate model simulations were used directly or changes were applied to an observed baseline, and whether observed or simulated variations from year‐to‐year were used. The different ways of deriving climate scenarios from a single initial climate model experiment result in a range in change in average annual runoff at a location of at least 10%, and often more than 20%. There is a clear difference in the large‐scale spatial pattern of change in runoff from HadCM3 to HadRM3H. Many of the climate features in HadRM3H are already present in HadAM3H simulations, as would be expected from the experimental design. This suggests that for studies over a large geographic domain, an intermediate‐resolution global climate model can produce useful scenarios for impact assessments. HadRM3H overestimates rainfall across much of southern Africa and so results in too much runoff: This leads to smaller estimates of future change in runoff than arise when changes in climate are applied to an observed climate baseline. It is concluded that under these circumstances it is preferable to apply modeled changes in climate to observed data to construct climate scenarios rather than derive these directly from the regional climate model simulations. Incorporating increases in interannual variability as simulated by HadRM3H leads to little change in simulated annual mean runoff. However, it has a larger impact on the frequency distributions of runoff, with extreme flows predicted to increase more than mean flows and even to increase in areas where the mean flow decreases. This demonstrates the importance of considering not only changes in mean climate but also climate variability.
Conjugate strike‐slip faulting along the Bangong‐Nujiang suture zone accommodates coeval east‐west extension and north‐south shortening in the interior of the Tibetan Plateau
Authors: Taylor Michael , Yin An , Ryerson Frederick J. , Kapp Paul , Ding Lin
Published: August 2003

Geologic investigations of how the Tibetan plateau is currently deforming have focused primarily on its boundary faults. Consequently, how the interior of the plateau deforms remains poorly understood. To fill this gap in knowledge, we conducted field mapping, analysis of remote sensing and digital topographic data, and reinterpretation of existing geologic maps in central Tibet. This study reveals a 200–300 km wide and 1500–1800 km long east trending zone conjugate strike‐slip faults across central Tibet. The central Tibet conjugate fault zone is comprised of northeast striking left‐slip faults north of the Bangong‐Nujiang suture and northwest striking right‐slip faults south of the suture zone. These strike‐slip faults are kinematically linked with north trending Tibetan rifts located north and south of the conjugate fault systems. Without exception, all conjugate faults intersect or merge toward one another along the Bangong‐Nujiang suture zone. Motion on these faults accommodates coeval east‐west extension and north‐south contraction. To determine the fault kinematics and the magnitude of fault slip, we investigated three conjugate fault sets in the central Tibet fault zone. These include from east to west, the Dong Co, Bue Co, and Aishi Co conjugate fault systems, which are adjacent to the Bangong‐Nujiang suture zone and separated by a distance of 400 and 70 km, respectively. The average magnitude of fault motion on individual strike‐slip faults is ∼12 km as determined by offsets of Tertiary thrusts and Paleozoic‐Mesozoic lithologic units. The conjugate fault configuration requires ∼12 km of north‐south contraction across the 200–300 km fault zone since its initiation. Because the conjugate strike‐slip faults are kinematically linked with the north trending Tibetan rifts which initiated between 14 and 8 Ma, our estimated magnitude of north‐south contraction implies a contraction rate of ∼1–2 mm/yr across central Tibet. The relatively closely spaced (<150 km) basins may result from a series of conjugate strike‐slip fault systems in the interior of Tibet. These structures likely formed by eastward spreading of the Tibetan crust via distributed eastward extrusion of small (<150 km wide) wedge‐shaped crustal blocks that leave a space at their trailing end.
Runoff production on forest roads in a steep, mountain catchment
Authors: Wemple Beverley C. , Jones Julia A.
Published: August 2003

This study investigated how roads interact with hillslope flow in a steep, forested landscape dominated by subsurface flow and how road interactions with hillslope flow paths influence hydrologic response during storms in a second‐order catchment. Runoff was measured continuously from 12 subcatchments draining to road segments and covering 14% of a 101‐ha, second‐order catchment (WS3) in the Andrews Forest, Oregon. Observed runoff over the 1996 water year was compared to predictions for runoff timing and interception of a hillslope water table based on a simple model of kinematic subsurface storm flow. Observed runoff behavior was consistent with model estimates, a finding that underscores the utility of this simple approach for predicting and explaining runoff dynamics on forest roads constructed on steep hillslopes. Road segments in the study area interacted in at least four distinct ways with complex landforms, potentially producing very different effects depending on landform characteristics. Hillslope length, soil depth, and cutbank depth explained much of the variation in road runoff production among subcatchments and among storm events. Especially during large storm events, a majority of instrumented road segments intercepted subsurface flow and routed it to ditches and thence directly to streams with a timing that contributed to the rising limb of the catchment‐wide hydrograph. The approach used in this study may be useful for model development and for targeting road segments for removal or restoration.
Remote sensing of surface energy fluxes at 101‐m pixel resolutions
Authors: Norman J. M. , Anderson M. C. , Kustas W. P. , French A. N. , Mecikalski J. , Torn R. , Diak G. R. , Schmugge T. J. , Tanner B. C. W.
Published: August 2003

Many applications exist within the fields of agriculture, forestry, land management, and hydrologic assessment for routine estimation of surface energy fluxes, particularly evapotranspiration (ET), at spatial resolutions of the order of 101 m. A new two‐step approach (called the disaggregated atmosphere land exchange inverse model, or DisALEXI) has been developed to combine low‐ and high‐resolution remote sensing data to estimate ET on the 101–102 m scale without requiring any local observations. The first step uses surface brightness‐temperature‐change measurements made over a 4‐hour morning interval from the GOES satellite to estimate average surface fluxes on the scale of about 5 km with an algorithm known as ALEXI. The second step disaggregates the GOES 5‐km surface flux estimates by using high‐spatial‐resolution images of vegetation index and surface temperature, such as from ASTER, Landsat, MODIS, or aircraft, to produce high‐spatial‐resolution maps of surface fluxes. Using data from the Southern Great Plains field experiment of 1997, the root‐mean‐square difference between remote estimates of surface fluxes and ground‐based measurements is about 40 W m−2, comparable to uncertainties associated with micrometeorological surface flux measurement techniques. The DisALEXI approach was useful for estimating field‐scale, surface energy fluxes in a heterogeneous area of central Oklahoma without using any local observations, thus providing a means for scaling kilometer‐scale flux estimates down to a surface flux‐tower footprint. Although the DisALEXI approach is promising for general applicability, further tests with varying surface conditions are necessary to establish greater confidence.
Modeling the impacts of climatic change and variability on the reliability, resilience, and vulnerability of a water resource system
Authors: Fowler H. J. , Kilsby C. G. , O'Connell P. E.
Published: August 2003

During the last decade, there have been increasing concerns over water resource drought in northern England, brought about by the 1995 Yorkshire drought with an estimated 5‐month rainfall return period of 200 years. The impacts of climatic change and variability on water resource reliability, resilience, and vulnerability in this region are examined by modeling changes to weather type frequency, mean rainfall statistics, and potential evapotranspiration. Results indicate future improvements in water resource reliability due to increased winter rainfall but reductions in resource resilience and an increased vulnerability to drought. Severe droughts comparable to that of 1995 show only a slight increase in frequency by 2080. However, there are significant increases in both the magnitude and duration of severe water resource drought, as a consequence of summer rainfall reductions and increased climatic variability. This research provides a basis for the future planning and management of the Yorkshire water resource system.
Estimated accuracies of regional water storage variations inferred from the Gravity Recovery and Climate Experiment (GRACE)
Authors: Swenson Sean , Wahr John , Milly P. C. D.
Published: August 2003

The satellite Gravity Recovery and Climate Experiment (GRACE) provides data describing monthly changes in the geoid, which are closely related to changes in vertically integrated terrestrial water storage. Unlike conventional point or gridded hydrologic measurements, such as those from rain gauges, stream gauges, rain radars, and radiometric satellite images, GRACE data are sets of Stokes coefficients in a truncated spherical harmonic expansion of the geoid. Swenson and Wahr [2002] describe techniques for constructing spatial averaging kernels, with which the average change in vertically integrated water storage within a given region can be extracted from a set of Stokes coefficients. This study extends that work by applying averaging kernels to a realistic synthetic GRACE gravity signal derived in part from a large‐scale hydrologic model. By comparing the water storage estimates inferred from the synthetic GRACE data with the water storage estimates predicted by the same hydrologic model, we are able to assess the accuracy of the GRACE estimates and to compare the performance of different averaging kernels. We focus specifically on recovering monthly water storage variations within North American river basins. We conclude that GRACE will be capable of estimating monthly changes in water storage to accuracies of better than 1 cm of water thickness for regions having areas of 4.0 · 105 km2 or larger. Accuracies are better for larger regions. The water storage signal of the Mississippi river basin (area = 3.9 · 106 km2), for example, can be obtained to better than 5 mm. For regional‐ to global‐scale water balance analyses, this result indicates that GRACE will provide a useful, direct measure of seasonal water storage for river‐basin water balance analyses; such data are without precedent in hydrologic analysis.
Sensitivity of a statistical solar proton fluence model to the size of the event data set
Authors: Rosenqvist Lisa , Hilgers Alain
Published: August 2003

Statistical models of high‐energy (typically above 10 MeV) solar proton fluences are needed to assess a broad range of cumulative effects observed in the solar system. Most models rely on a description of event fluences and occurrence based on a compound Poisson process for which the parameters are derived from observations. In this paper the effect of the size of the observation data set on the prediction of cumulated fluence by such models is assessed. The study shows that with the current size of the event data set of Solar Proton Events (about a couple of hundred events) the estimated parameters used as input to the model may lead to significant errors on the prediction of the quantiles of the fluence probability distribution function. Furthermore, it is shown that no significant accuracy improvement is expected unless the data set contains a much larger number of events (typically one thousand), which requires a long‐term data acquisition infrastructure.
Atmospheric response to South Atlantic SST dipole
Authors: Haarsma Reindert J. , Campos Edmo J. D. , Molteni Franco
Published: August 2003

Recent analyses of historical data and output of numerical models have suggested a dipolar mode of decadal variability in the South Atlantic. In this work, the the atmospheric response to such anomalous SST dipole in the South Atlantic is investigated with a numerical model. The results show a deep baroclinic response over the equatorward pole and a shallow equivalent barotropic response over the poleward pole. The baroclinic response is strongest during the austral summer. It affects the meridional circulation over the tropical Atlantic with anomalous downward motion north of the ITCZ and anomalous ascending motion southward of it, resulting in a southward shift of the ITCZ. The ITCZ response is enhanced due to a positive feedback induced by anomalous low level convergence of moisture. Changes in cloud cover counteract the variations in latent heat flux north of the ITCZ, thereby prohibiting the generation of an SSTA of opposite sign as suggested by the wind‐evaporation‐SST (WES) feedback.
An investigation of the effect of thalidomide on anti‐gal antibody production in baboons
Authors: Yamamoto S. , Cooper D. K. C.
Published: August 2003

Abstract:  Previous data suggest that natural anti‐Galα1,3Gal (Gal) antibody (Ab) is produced by mature plasma cells. As thalidomide is effectively used in the treatment of patients with multiple myeloma, its effect on natural anti‐Gal Ab production has been assessed in two baboons. During a 10‐week course of thalidomide administration (until it reached toxic levels in one baboon), there was no major reduction in Ab levels or in their rate of return after a course of extracorporeal immunoadsorption. A significant reduction of CD3+ cells (75%), and particularly of CD4+ cells (65 to 95%), was measured in the blood by flow cytometry. This was associated with general hyporesponsiveness on mixed lymphocyte reactivity in one baboon, but not in the other. Thalidomide would appear to have little effect on the production of natural Ab, but these observations lend some support to previous work by others indicating that thalidomide may suppress the cellular response to an allograft or xenograft.
The effect of mitoxantrone on anti‐pig immunization in baboons
Authors: Petzold Thomas , Barreau Nathalie , Ashton‐Chess Joanna , Edan Gilles , Boulday Gwénola , Roussel Jean‐Christian , Le Berre Ludmilla , Minault David , Soulillou Jean‐Paul , Blancho Gilles
Published: August 2003

Abstract:  Besides virological and physiological concerns, the success of xenotransplantation (Xt) is still dependent on the prevention of delayed xenograft rejection (DXR). Although multifactorial, DXR is mainly due to xenonatural antibody (Ab) recognizing their xenogenic antigen (Ag) followed by complement activation. Despite the use of intensive treatments capable of inhibiting the humoral response, DXR can still not be avoided and always occurs within weeks following transplantation. Moreover, these latter treatments currently used in Xt could not be used clinically in humans because of their high risk of over‐immunosuppressing the patients. Mitoxantrone (Mx) is a drug well known for its antiproliferative properties and is used clinically in oncology and in the treatment of relapsing multiple sclerosis. In models of arthritis in rats, it has been shown to be 10 to 20 times more powerful than cyclophosphamide (CyP) at blocking both inflammatory and B‐cell responses. Because of its B‐cell inhibitory capacity and considering the implication of the humoral response in xenograft rejection, we have compared Mx with CyP for its ability to block in vivo anti‐pig immunization induced via subcutaneous injections of pig red blood cells into baboons. Neither drug was able to inhibit the anti‐pig responses following the first and second immunizations, emphasizing the particularity of preformed Ab responses. However, the rise in Ab in the Mx treated animals was significantly delayed as compared with the non‐treated as well as the CyP treated animals and was mainly because of a profound depletion of circulating B‐cells. Mx displays an interesting antihumoral effect that we now intend to test in a pig kidney to baboon Xt model, with anticipated administration of the drug allowing an early B‐cell depletion.
The long‐term survival of baboon‐to‐monkey kidney and liver xenografts*
Authors: Zhong Robert , Tucker Jane , Zhang Zheng , Wall William , Grant David , Quan Douglas , Garcia Bertha , Gao Zu‐hua , Asfar Sami , Sharpe Michael , Gelb Adrian , Bailey Michele , Stiller Calvin
Published: August 2003

Abstract:  The present study was undertaken to develop an optimum immunosuppressive regimen in baboon‐to‐monkey life‐supporting kidney xenografts. Baseline therapy for all groups include cyclosporine (CsA) and steroids. We compared adding (1) cyclophosphamide (CyP) at dose of 20 mg/kg/day given on post‐operative day (POD) 0, 2, 5 and 7; (2) mycophenolic mofetil (MMF) at a dose of 40 mg/kg/day by daily gavage; or (3) CyP + rapamycin (Rap). The latter group was divided into high and low dose subgroups. Untreated xenografts were rejected on POD 6, CsA alone treated xenografts survived for 35 days and CsA + CyP treated xenografts survived for 45 days. Adding MMF significantly prolonged mean survival to 111 ± 53 days, but the xenografts eventually developed rejection. Combination therapy including CsA, CyP and Rap reliably prevented xenogenic rejection and achieved a mean survival of 290 ± 30 days. However, high dose CyP + Rap led to high incidence of post‐transplant lymphoproliferation disorders (PTLD), while the incidence of PTLD was significantly less in the low dose subgroup (P < 0.01). Four animals in this subgroup survived for more than 300 days with normal renal function and histology. In addition, two liver recipients treated with CsA + CyP survived for 91 and 1076 days. We conclude that long‐term survival of kidney or liver xenografts can be achieved in a non‐human concordant xenograft model using currently available immunosuppressive agents.
Characteristics of CD59 up‐regulation induced in porcine endothelial cells by αGal ligation and its association with protection from complement
Authors: Grubbs Brian C. , Benson Barbara A. , Dalmasso Agustin P.
Published: August 2003

Abstract: Background: Activation of endothelial cells may result in proinflammatory and procoagulant changes, or in changes that protect the endothelial cells (EC) from injurious insults. Stimulation of porcine EC with human anti‐porcine antibodies, or lectins from Bandeiraea simplicifolia that bind terminal Galα(1–3)Gal (abbreviated αGal), can induce EC protection from cytotoxicity by human complement. These EC also exhibit up‐regulation of CD59 protein and mRNA expression. Porcine CD59 has been reported to protect porcine cells from human complement. Therefore we investigated the specificity requirements and other characteristics of the induced CD59 up‐regulation, as well as the role of up‐regulated CD59 in lectin‐induced protection of EC from human complement. Methods: Aortic EC were incubated in vitro with αGal‐binding lectins B. simplicifolia lectin I isolectin B4 (IB4) and B. simplicifolia lectin I (BS‐I) and CD59 expression was assessed by flow cytometry and enzyme linked immunosorbent assay (ELISA). Binding requirement was studied using disaccharides containing either αgalactosyl or βgalactosyl moieties to inhibit CD59 up‐regulation. Protection from complement killing was assessed after incubation of EC with human serum as a source of anti‐porcine antibodies and complement. The role of CD59 in lectin‐induced protection was studied in the presence of an anti‐pig CD59 antibody and after removal of CD59 using phosphatidylinositol (PI)‐specific phospholipase C (PI‐PLC). Results: We found that induction of CD59 up‐regulation required specific binding of the lectin to terminal αGal and was not induced either by soluble factors that may be released from EC by stimulation with the lectin or by TNF‐α, IFN‐γ, or IL‐1α. Unstimulated or BS‐I‐treated EC showed little or no expression of decay accelerator factor (DAF). Removal of membrane‐associated CD59 (and other proteins that are associated with the membrane through PI linkage) with PI‐PLC from EC that had been exposed to lectin restored their complement sensitivity to various degrees, depending on the extent of lectin‐induced protection. Cytotoxicity was completely restored in cells that exhibited partial protection induced with lectin at low doses or for a short period of time. However, EC that were fully resistant to complement did not regain sensitivity to complement after removal of CD59. Changes in CD59 expression did not modify the degree of C9 binding. Conclusion: Induction of CD59 expression required specific binding of the lectin to terminal αGal and was not induced by soluble factors that may be released from EC by lectin stimulation. Increased CD59 expression may contribute to this form of protection from complement; however, mechanisms other than CD59 up‐regulation appear to be essential for the development of full protection.