bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐Term Sequelae after Surgery for Orbital Floor Fractures
Authors: Folkestad Lena , Westin Thomas
Published: November 2005

A surgical technique involving exact repositioning and rigid fixation is required for the reduction of fractures of the orbital floor. Even then, sequelae may be present long after the trauma. The aim of this study was to establish the frequency and type of sequelae after surgery for orbital floor fractures and to investigate the extent to which the method of surgery had any impact on the severity of the sequelae. A questionnaire was sent to all 107 patients (response rate 77%) 1 to 5 years after the injury. Further clinical data were obtained from the patients' charts. Eighty‐three percent of the patients were affected by some kind of permanent sequelae in terms of sensibility, vision, and/or physical appearance. A high frequency of diplopia (36%) was related to the reconstruction of the orbital floor with a temporary “supporting” antral packing in the maxillary sinus, a technique which has now been abandoned at our department in favor of orbital restoration with sheets of porous polyethylene. Our conclusion is that, because long‐term sequelae are common, the surgical technique must be subjected to continuous quality control to minimize future problems for this group of patients.
ANTHROPOLOGICAL INSIGHTS INTO THE USE OF RACE/ETHNICITY TO EXPLORE GENETIC CONTRIBUTIONS TO DISPARITIES IN HEALTH
Authors: OUTRAM SIMON M. , ELLISON GEORGE T. H.
Published: November 2005

Anthropological insights into the use of race/ethnicity to explore genetic contributions to disparities in health were developed using in-depth qualitative interviews with editorial staff from nineteen genetics journals, focusing on the methodological and conceptual mechanisms required to make race/ethnicity a genetic variable. As such, these analyses explore how and why race/ethnicity comes to be used in the context of genetic research, set against the background of continuing critiques from anthropology and related human sciences that focus on the social construction, structural correlates and limited genetic validity of racial/ethnic categories. The analyses demonstrate how these critiques have failed to engage geneticists, and how geneticists use a range of essentially cultural devices to protect and separate their use of race/ethnicity as a genetic construct from its use as a societal and social science resource. Given its multidisciplinary, biosocial nature and the cultural gaze of its ethnographic methodologies, anthropology is well placed to explore the cultural separation of science and society, and of natural and social science disciplines. Anthropological insights into the use of race/ethnicity to explore disparities in health suggest that moving beyond genetic explanations of innate difference might benefit from a more even-handed critique of how both the natural and social sciences tend to essentialize selective elements of race/ethnicity. Drawing on the example of HIV/AIDS, this paper demonstrates how public health has been undermined by the use of race/ethnicity as an analytical variable, both as a cipher for innate genetic differences in susceptibility and response to treatment, and in its use to identify ‘core groups’ at greater risk of becoming infected and infecting others. Clearly, a tendency for biological reductionism can place many biomedical issues beyond the scope of public health interventions, while socio-cultural essentialization has tended to stigmatize ‘unhealthy behaviours’ and the communities where these are more prevalent.
ANTHROPOLOGY, DOTS AND UNDERSTANDING TUBERCULOSIS CONTROL IN NEPAL
Authors: HARPER IAN
Published: November 2005

This paper argues for the inclusion of ethnography as a research methodology for understanding the effects of public health policy. To do this, the implementation of DOTS (Directly Observed Therapy, Short-course) – the World Health Organization (WHO) prescribed policy for the control of the infectious disease tuberculosis – is explored in the context of Nepal. A brief history of DOTS and its implementation in Nepal is outlined, and the way it has been represented by those within the Nepal Tuberculosis Programme (NTP) is described. This is followed by an outline of the research done in relation to this, and the ethnographic methods used. These ethnographic data are then interpreted and analysed in relation to two specific areas of concern. Firstly, the effects around the epidemiological uses of ‘cases’ is explored; it is argued that a tightening of the definitional categories so necessary for the programme to be stabilized for comparative purposes has profound material effects in marginalizing some from treatment. Secondly, the paper examines some of the implications and effects relating to the way that the ‘directly observed’ component was implemented. The discussion explores how current debate on DOTS has been played out in some medical journals. It argues for the importance of ethnography as a method for understanding certain questions that cannot be answered by particular, and increasingly dominant, research ideologies informed by randomized controlled trials. This raises important issues about the nature of ‘evidence’ in debates on the relationship of research to policy.
PERCEIVED NUISANCE OF MOSQUITOES ON THE ISLE OF SHEPPEY, KENT, UK
Authors: HUTCHINSON ROBERT A. , LINDSAY STEVE W.
Published: November 2005

Little is known about the biting nuisance of mosquitoes in the UK, despite the high numbers found in some locations. A telephone questionnaire survey was used to determine the perceived nuisance of biting insects on the Isle of Sheppey, Kent, a place notorious for mosquitoes. Two hundred randomly selected individuals were interviewed and asked if they suffered from mosquito bites. If they answered yes, they were asked to describe where and when they were bitten, and what measures they took against mosquitoes. Forty-six per cent of respondents completed the questionnaire. Of those, 50% reported being bitten by mosquitoes, mostly outside during the summer. Seventy per cent said that most biting occurred during the evening and night. Of those respondents who protected themselves against biting (27), most used repellents (70%), with the remainder changing their behaviour to avoid mosquitoes, including closing or screening windows (33%), wearing thicker clothes (7%) and spraying insecticide (4%). One person slept under a bednet in summer (4%). This study provides evidence that on the Isle of Sheppey mosquitoes are considered a major nuisance by a sizeable proportion of the population. Since there is growing interest in the threat posed by new and emerging diseases in the UK, health authorities will need to make substantial efforts to inform and reassure the public about the threats posed by mosquitoes in areas where they are common.
Second Generation Reform in Latin America: Reforming the public sector in Uruguay and Mexico
Authors: PANIZZA FRANCISCO , PHILIP GEORGE
Published: November 2005

Uruguay and Mexico have both passed laws aiming to professionalise the public sector bureaucracy according to what might be considered ‘second generation’ reform principles. They did so under what might initially have seemed to be politically unpropitious circumstances. The reforms might have been vetoed by interests that feared that they would lose out from the changes, but were not. They might have been blocked by conditions of minority presidentialism, but were not. This article seeks to explain the successful passing of this reform legislation. Framing issues played a significant role in reducing opposition. Notably important was the way in which the reforms were presented, and specifically the ability of their proponents to avoid presenting them as market-friendly reforms. The political context also provided the reformers with arguments that in the end proved persuasive.
Domestic Capital, Civil Servants and the State: Costa Rica and the Dominican Republic under Globalisation
Authors: ANCOCHEA DIEGO SÁNCHEZ
Published: November 2005

This article studies the impact of neoliberal globalisation on the relative strength of different social actors and on the relations between these actors and the state in Costa Rica and the Dominican Republic. In particular, the article analyses the responses of large domestic capitalists to the new global environment and to the new policies implemented, as well as the effect of these policies on public servants (who have traditionally been an influential political force, at least in Costa Rica). The paper makes two basic claims. First, globalisation has had some common effects on the politico-economic structures of Costa Rica and the Dominican Republic, despite the vastly different historical trajectory of state–society relations in the two countries. In both countries, there has been an increasing concentration and financialisation of capital and a weakening of the state bureaucracy. Second, these changes in the politico-economic structure have imposed new, country-specific constraints for the consolidation of the neoliberal economic model, signalling the need to introduce institutional reforms in the near future.
Monitoring Elections, Redefining Sovereignty: The 2000 Peruvian Electoral Process as an International Event
Authors: SANTA-CRUZ ARTURO
Published: November 2005

The issue of sovereignty has historically figured prominently in Latin American political discourse. From Simón Bolívar to Benito Juárez in the nineteenth century, to Juan Domingo Perón and Salvador Allende in the twentieth, to Fidel Castro and Hugo Chávez today, sovereignty and its corollary, the non-intervention principle, have been prominent among the region's watchwords. In the late 1950s a Mexican diplomat declared that ‘intransigent non-intervention’ was the ‘cornerstone of the Inter-American system’. Sometimes imbued with racialist elements, as in José E. Rodó's claim that Latin America had ‘an inheritance of race, a great ethnic tradition to maintain’, or in the recent claim by a Venezuelan general that the Latin American defence of sovereignty is ‘part of the legacy which our aboriginal ancestors have passed on to us through chromosomes’, the discourse on sovereignty and non-intervention has become a Latin American trademark.
Interdisciplinary Approaches to Human Rights Scholarship in Latin America
Authors: CESARINI PAOLA , HERTEL SHAREEN
Published: November 2005

Human rights are the focus of research and teaching in multiple fields including law, philosophy, political science, sociology, anthropology, economics, psychology, history, literature and public health. Human rights are also the focus of advocacy and on-the-ground investigation by activists affiliated with nongovernmental organisations (NGOs), labour unions and social movements. Scholars interested in rights-based issues thus often face a dual challenge: that of crossing disciplinary boundaries in order to explore human rights questions, and that of bridging the academic-practitioner divide.
Carbon and nitrogen geochemistry of sediments in the Central American convergent margin: Insights regarding subduction input fluxes, diagenesis, and paleoproductivity
Authors: Li Long , Bebout Gray E.
Published: November 2005

Carbon (C) and nitrogen (N) concentrations and isotopic compositions were determined for sediments from Ocean Drilling Program legs 170 and 205 offshore of Costa Rica, in an attempt to characterize C‐N flux into the Central America (CA) convergent margin and identify signatures of diagenesis and changing productivity in this sediment section. Samples from sites 1039 and 1253 (outboard of the trench) contain 62 to 2382 ppm total nitrogen (TN) with δ15NAir values of +2.4 to +8.5‰, 0.04–2.65 wt% total organic carbon (TOC) with δ13CVPDB values of −25.4 to −20.8‰, and 1.1–87.3 wt% carbonate with δ13C values of +0.1 to +3.2‰ and δ18OVSMOW values of +21.3 to +34.2‰. Total organic C and TN concentrations strongly depend on lithology, with carbonate‐rich samples containing smaller amounts of both. Total organic C and TN concentrations and isotopic compositions also vary systematically within single units, perhaps reflecting small degrees of diagenetic alteration but mostly significant increase in productivity since the early Pliocene. Sediment subduction feeds 1.3 × 1010 g yr−1 N (mean δ15N = +5.7‰), 1.4 × 1011 g yr−1 TOC (mean δ13C = −22.0‰) and 1.5 × 1012 g yr−1 oxidized C (mean δ13C = +1.9‰) into the 1100 km CA convergent margin. Incorporating possible inputs in altered oceanic crust (AOC) and by tectonic erosion, the C‐N inputs appear to be far larger than the arc outputs. A small part of this excess C and N is probably returning toward the surface by devolatilization, along structural heterogeneities in the forearc, and the remaining inventory is likely recycling into the deeper mantle.
Progressive shape evolution of a mineral inclusion under differential stress at high temperature: Example of garnet inclusions within a granulite‐facies quartzite from the Lützow‐Holm Complex, East Antarctica
Authors: Okamoto Atsushi , Michibayashi Katsuyoshi
Published: November 2005

Interfacial tension (γ) and differential stress (σ) affect the shape of a mineral grain included within a crystalline host. We present a simple model that predicts the progressive change in aspect ratio of an ellipsoidal inclusion. Three processes are considered in the model: dislocation creep, interface diffusion creep, and rounding by interface diffusion. The model reveals that (1) the inclusion aspect ratio (L) evolves toward a steady state value, (2) the time taken to achieve a steady state aspect ratio increases with increasing grain size (R), and (3) the dominant deformation mechanism varies from diffusion creep to dislocation creep with increasing grain size and/or differential stress. The L‐R distribution pattern of garnets in a granulite‐facies quartzite from the Lützow‐Holm Complex, East Antarctica is compared with the model result. The garnet aspect ratio systematically varies with respect to grain size, and the most elongate ones are of intermediate grain size (∼250 μm). A two‐stage deformation with high and low differential stresses (stage A and B) best explains for the observed L‐R pattern of garnets. The duration (tA) at stage A is determined only when the differential stress (σA) is assumed due to the size independency of dislocation creep. Assuming γgrtqtz = 1.0 N m−1, Dgb,A = 1.0 × 10−12 m2 s−1, Dgb,B = 1.0 × 10−11 m2 s−1, and σA = 1.0 MPa, the garnet data are fitted to a theoretical curve under condition of σB = 1.4 × 10−2 MPa, tA = 0.5 Myr, and tB = 14.4 Myr.
Drought early warning system in reservoir operation: Theory and practice
Authors: Huang Wen‐Cheng , Chou Chia‐Ching
Published: November 2005

This paper revises the drought early warning system (DEWS) for reservoir operation, originally developed by Huang and Yuan (2004). The changes are made in response to requirements raised by the Water Resources Agency in Taiwan. We extend the DEWS to include a number of new factors: in particular, to take into account meteorological drought and the determination of alert levels in policy making based on information entropy. The goals of this paper are critical: (1) revising the DEWS based on experience, (2) examining a specific case study of how the system works, (3) involving users in decision making, and (4) comparing theory with practice. The Shihmen reservoir in northern Taiwan was picked by the agency as a real‐case study. In hindsight, the revised drought early warning system performed well over a simulation of five consecutive years (1999–2003). These results verify the applicability of this renewed DEWS in reservoir operation for lowering potential drought threats.
Variations in upper crustal structure due to variable mantle temperature along the Southeast Indian Ridge
Authors: Baran Janet M. , Cochran James R. , Carbotte Suzanne M. , Nedimović Mladen R.
Published: November 2005

There is a systematic variation in axial morphology and axial depth along the Southeast Indian Ridge (SEIR) with distance away from the Australian Antarctic Discordance, an area of cold uppermost mantle. Since spreading rate (72–76 mm/yr) and mantle geochemistry appear constant along this portion of the SEIR, the observed variations in axial morphology and axial depth are attributed to a gradient in mantle temperature. In this study, we report results from a multichannel seismic investigation of on‐axis crustal structure along this portion of the SEIR. Three distinct forms of ridge crest morphology are found within our study area: axial highs, rifted axial highs, and shallow axial valleys. Axial highs have a shallow (∼1500 m below seafloor (bsf)) magma lens and a thin (∼300 m) layer 2A along the ridge crest. Rifted axial highs have a deeper (∼2100 m bsf) magma lens and thicker (∼450 m) layer 2A on‐axis. Beneath shallow axial valleys, no magma lens is imaged, and layer 2A is thick (∼450 + m). There are step‐like transitions in magma lens depth and layer 2A thickness with changes in morphology along the SEIR. The transitions between the different modes of axial morphology and shallow structure are abrupt, suggesting a threshold‐type mechanism. Variations in crustal structure along the SEIR appear to be steady state, persisting for at least 1 m.y. Portions of segments in which a magma lens is found are characterized by lower relief abyssal hills on the ridge flank, shallower ridge flank depths, and at the location of along‐axis Mantle Bouguer Anomaly (MBA) lows. The long‐wavelength variation in ridge morphology along the SEIR from axial high segments to the west to axial valley segments to the east is linked to the regional gradient in mantle temperature. Superimposed on the long‐wavelength trend are segment to segment variations that are related to the absolute motion of the SEIR to the northeast which influence mantle melt production and delivery to the ridge.
Light absorption and scattering by particles and CDOM at the New England shelfbreak front
Authors: Vaillancourt Robert D. , Marra John , Prieto Laura , Houghton Robert W. , Hales Burke , Hebert Dave
Published: November 2005

A fine‐scale survey of physical, chemical, and optical properties was done across the shelfbreak front in the Middle Atlantic Bight region south of Martha's Vineyard, Cape Cod (70.5°W) during late summer 2002. The front displayed physical and biological structure typical for this region and season: a density‐compensating front with strong horizontal T and S and optical gradients, and a chlorophyll maximum layer that deepened in the seaward direction across the front, became detached beneath the shelfbreak jet, reappeared on a deeper and greater density surface on the seaward side of the shelfbreak front, and then shoaled again in the seaward direction. At times the shoreward leading edge of the chlorophyll maximum layer seaward of the front was situated beneath the chlorophyll maximum layer shoreward of the front. Hydrography on the shoreward side of the front was dominated by a bolus of cold pool water of shelf origin with minimum salinity and temperature of 33 and 10°C, respectively. The cold pool was also a pool of high CDOM absorption whose distribution coincided with the temperature and salinity across the front. The persistence of sharp horizontal T, S, and CDOM gradients indicated that advective processes exceed diffusive mixing processes at the front. CDOM in the euphotic zone showed a strong inverse relationship to temperature and, below the euphotic zone, a strong inverse relationship to salinity, indicating a terrestrial CDOM source within the cold pool and a photodegradation sink at the surface. Cross‐frontal exchange of shelf CDOM and upper slope waters is inferred from the T‐S properties of the CDOM pool and previously reported measurements of the mixing and circulation at this site. The chlorophyll specific absorption coefficients of discrete samples collected within the chlorophyll maximum layers, along with LPS surveys of dissolved and particulate absorption and scattering, indicate that the variability of optics at the shelfbreak front is influenced mostly by particle optics. Due to the presence of the cold pool with its high CDOM signature, the waters masses across the shelfbreak front can be considered as case 1 for particles but case 2 for dissolved materials.
The glacial North Atlantic Oscillation
Authors: Justino Flávio , Peltier W. Richard
Published: November 2005

Based upon coupled climate simulations driven by present day and glacial boundary conditions, we demonstrate that the glacial North Atlantic Oscillation was characterized by four distinct centres of action and thus by an atmospheric circulation that differed radically in terms of its internal variability from modern conditions. Moreover, we show that although simulated modern climate supports a coupled atmosphere‐ocean mode characterized by a timescale near 30 years (so‐called Atlantic Multidecadal Oscillation, AMO), this mode is predicted to be absent under LGM conditions.
High heat flux on ancient Mars: Evidence from rift flank uplift at Coracis Fossae
Authors: Grott M. , Hauber E. , Werner S. C. , Kronberg P. , Neukum G.
Published: November 2005

We have identified flexural uplift at the flanks of the Coracis Fossae Rift valley. Modeling the topography the elastic thickness is constrained to 10.3–12.5 km, the corresponding mechanical thickness and thermal gradient are 15–19 km and 27–33 K km−1, respectively. The time of rifting is dated by evaluating the crater size‐frequency distribution of key surface units related to the rifting. Thus, the heat flux between 3.5 and 3.9 Ga is calculated to be 54–66 mW m−2. Furthermore, the stresses supported by the rift bounding faults are estimated to be below 5 MPa. We speculate that this weakness may be connected to the presence of water below the surface.
Postseismic relaxation and transient creep
Authors: Savage J. C. , Svarc J. L. , Yu Shui‐Beih
Published: November 2005

Postseismic deformation has been observed in the epicentral area following the 1992 Landers (M = 7.3), 1999 Chi‐Chi (M = 7.6), 1999 Hector Mine (M = 7.1), 2002 Denali (M = 7.9), 2003 San Simeon (M = 6.5), and 2004 Parkfield (M = 6.0) earthquakes. The observations consist of repeated GPS measurements of the position of one monument relative to another (separation ∼100 km). The early observations (t < 0.1 year) are well fit by the function a′ + c′log(t), where t is the time after the earthquake and a′ and c′ are constants chosen to fit the data. Because a log(t) time dependence is characteristic of transient (primary) creep, the early postseismic response may be governed by transient creep as Benioff proposed in 1951. That inference is provisional as the stress conditions prevailing in postseismic relaxation are not identical to the constant stress condition in creep experiments. The observed logarithmic time dependence includes no characteristic time that might aid in identifying the micromechanical cause.
Distinguishing barriers and asperities in near‐source ground motion
Authors: Page Morgan T. , Dunham Eric M. , Carlson J. M.
Published: November 2005

We investigate the ground motion produced by rupture propagation through circular barriers and asperities in an otherwise homogeneous earthquake rupture. Using a three‐dimensional finite difference method, we analyze the effect of asperity radius, strength, and depth in a dynamic model with fixed rupture velocity. We gradually add complexity to the model, eventually approaching the behavior of a spontaneous dynamic rupture, to determine the origin of each feature in the ground motion. A barrier initially resists rupture, which induces rupture front curvature. These effects focus energy on and off the fault, leading to a concentrated pulse from the barrier region and higher velocities at the surface. Finally, we investigate the scaling laws in a spontaneous dynamic model. We find that dynamic stress drop determines fault‐parallel static offset, while the time it takes the barrier to break is a measure of fracture energy. Thus, given sufficiently strong heterogeneity, the prestress and yield stress (relative to sliding friction) of the barrier can both be determined from ground motion measurements. In addition, we find that models with constraints on rupture velocity have less ground motion than constraint‐free spontaneous dynamic models with equivalent stress drops. This suggests that kinematic models with such constraints overestimate the actual stress heterogeneity of earthquakes.
Upper mantle anisotropy beneath the Seychelles microcontinent
Authors: Hammond J. O. S. , Kendall J.‐M. , Rümpker G. , Wookey J. , Teanby N. , Joseph P. , Ryberg T. , Stuart G.
Published: November 2005

The Seychelles plateau is a prime example of a microcontinent, yet mechanisms for its creation and evolution are poorly understood. Recently acquired teleseismic data from a deployment of 26 stations on 18 islands in the Seychelles are analyzed to study upper mantle seismic anisotropy using SKS splitting results. Strong microseismic noise is attenuated using a polarization filter. Results show significant variation in time delays (δt = 0.4–2.4 s) and smooth variations in orientation (ϕ = 15°–69°, where ϕ is the polarization of the fast shear wave). The splitting results cannot be explained by simple asthenospheric flow associated with absolute plate motions. Recent work has suggested that anisotropy measurements for oceanic islands surrounding Africa can be explained by mantle flow due to plate motion in combination with density‐driven flow associated with the African superswell. Such a mechanism explains our results only if there are lateral variations in the viscosity of the mantle. It has been suggested that the Seychelles are underlain by a mantle plume. Predictions of flow‐induced anisotropy from plume‐lithosphere interaction can explain our results with a plume possibly impinging beneath the plateau. Finally, we consider lithospheric anisotropy associated with rifting processes that formed the Seychelles. The large variation in the magnitude of shear wave splitting over short distances suggests a shallow source of anisotropy. Fast directions align parallel to an area of transform faulting in the Amirantes. Farther from this area the orientation of anisotropy aligns in similar directions as plate motions. This supports suggestions of transpressive deformation during the opening of the Mascarene basin.
Estimation of stratospheric age spectrum from chemical tracers
Authors: Schoeberl Mark R. , Douglass Anne R. , Polansky Brian , Boone Chris , Walker Kaley A. , Bernath Peter
Published: November 2005

We have developed a technique to diagnose the stratospheric age spectrum and estimate the mean age of air using the distributions of at least four constituents with different photochemical lifetimes. We demonstrate the technique using a 3‐D CTM and then apply the technique to OMS tropical balloon observations, UARS CLAES January 1993, and ACE February–March 2005 observations of CFC11, CFC12, CH4, and N2O. Our results using the ACE and OMS data are generally in agreement with mean age of air estimates from the chemical model and from observations of SF6 and CO2; however, the UARS‐derived mean age estimates show an intrusion of very young tropical air into the midlatitude stratosphere. The UARS CLAES values of F11 and F12 appear to be significantly higher than ACE and model values and bias our lower‐stratospheric estimates of the age derived from UARS data toward younger values.
Impact‐induced hydrothermal activity on early Mars
Authors: Abramov Oleg , Kring David A.
Published: November 2005

We report on numerical modeling results of postimpact cooling of craters with diameters of 30, 100, and 180 km in an early Martian environment, with and without the presence of water. The effects of several variables, such as ground permeability and the presence of a crater lake, were tested. Host rock permeability is the main factor affecting fluid circulation and lifetimes of hydrothermal systems, and several permeability cases were examined for each crater. The absence of a crater lake decreases the amount of circulating water and increases the system lifetime; however, it does not dramatically change the character of the system as long as the ground remains saturated. It was noted that vertical heat transport by water increases the temperature of localized near‐surface regions and can prolong system lifetime, which is defined by maximum near‐surface temperature. However, for very high permeabilities this effect is negated by the overall rapid cooling of the system. System lifetimes, which are defined by near‐surface temperatures and averaged for all permeability cases examined, were 67,000 years for the 30‐km crater, 290,000 years for the 100‐km crater, and 380,000 for the 180‐km crater. Also, an approximation of the thermal evolution of a Hellas‐sized basin suggests potential for hydrothermal activity for ∼10 Myr after the impact. These lifetimes provide ample time for colonization of impact‐induced hydrothermal systems by thermophilic organisms, provided they existed on early Mars. The habitable volume reaches a maximum of 6,000 km38,500 years after the impact in the 180‐km crater model.
An intense terminal epoch of widespread fluvial activity on early Mars: 1. Valley network incision and associated deposits
Authors: Howard Alan D. , Moore Jeffrey M. , Irwin Rossman P.
Published: November 2005

We present evidence that a final epoch of widespread fluvial erosion and deposition in the cratered highlands during the latest Noachian or early to mid‐Hesperian was characterized by integration of flow within drainage networks as long as 4000 km and trunk valley incision of 50 to 350 m into earlier Noachian depositional basins. Locally deltaic sediments were deposited where incised valley systems debouched into basins. Large alluvial fans of sediment deposited from erosion of alcoves in steep crater walls probably formed contemporaneously. The depth of incision below Noachian surfaces correlates strongly with the gradient and the total valley length, suggesting consistent regional hydrology. Estimated discharges from channel dimensions indicate flow rates equivalent to mean annual floods in terrestrial drainage basins of equivalent size. Such high flow rates imply either runoff directly from precipitation or rapid melting of accumulated snow. Development of duricrusts on the Noachian landscape may have contributed to focusing of late‐stage erosion within major trunk drainages. This late‐stage epoch of intense fluvial activity appears to be fundamentally different than the fluvial environment prevailing during most of the Noachian Period, which was characterized by widespread fluvial erosion of highlands and crater rims, deeply infilling crater floors, and intercrater basins through ephemeral fluvial activity, and development of local rather than regionally integrated drainage networks.
Multipole-based integral estimates for the rigorous description of distance dependence in two-electron integrals
Authors: Lambrecht Daniel S. , Ochsenfeld Christian
Published: November 2005

We derive multipole-based integral estimates (MBIE) as rigorous and tight upper bounds to four-center two-electron integrals in order to account for the 1∕R distance decay between the charge distributions, which is missing in the Schwarz screening commonly used in ab initio methods. Our screening criteria are valid for all angular momenta and can be formulated for any order of multipoles. We have found the expansion limited to dipoles to be sufficiently tight for estimating the integrals in Hartree-Fock and density-functional theories, while the screening effort is negligible. For, e.g., a DNA fragment with 1052 atoms and 10 674 basis functions (6–31G*) the exchange part is faster by a factor of 2.1 as compared to the Schwarz screening both within our linear exchange scheme, whereas a smaller factor of 1.3 is gained for the Coulomb part within the continuous fast multipole method. Most importantly, our new MBIE screening is perfectly suited to exploit the strong distance decay of electron-correlation effects of at least 1∕R4 in atomic-orbital-based formulations of correlation methods.
Rigorous integral screening for electron correlation methods
Authors: Lambrecht Daniel S. , Doser Bernd , Ochsenfeld Christian
Published: November 2005

We derive rigorous multipole-based integral estimates (MBIE) in order to account for the distance dependence occurring in atomic-orbital (AO) formulations of electron correlation theory, where our focus is on AO-MP2 theory within a Laplace scheme. We find for the exact transformed integral products an extremely early onset of a linear-scaling behavior and a very small number of significant products. To preselect the significant integral products we adapt our MBIE method as rigorous upper bound. In this way it is possible to exploit the favorable scaling behavior observed and to reduce the scaling of estimated products asymptotically to linear, without sacrificing accuracy or reliability. By separating Coulomb- and exchange-type contractions only half-transformed integrals need to be computed. Furthermore, our scheme of rigorously preselecting transformed integral products via MBIE seems to offer particularly interesting perspectives for a direct formation of half- or fully transformed integrals by using multipole expansions and auxiliary basis sets.
Transition state theory: Variational formulation, dynamical corrections, and error estimates
Authors: Vanden-Eijnden Eric , Tal Fabio A.
Published: November 2005

Transition state theory (TST) is revisited, as well as evolutions upon TST such as variational TST in which the TST dividing surface is optimized so as to minimize the rate of recrossing through this surface and methods which aim at computing dynamical corrections to the TST transition rate constant. The theory is discussed from an original viewpoint. It is shown how to compute exactly the mean frequency of transition between two predefined sets which either partition phase space (as in TST) or are taken to be well-separated metastable sets corresponding to long-lived conformation states (as necessary to obtain the actual transition rate constants between these states). Exact and approximate criterions for the optimal TST dividing surface with minimum recrossing rate are derived. Some issues about the definition and meaning of the free energy in the context of TST are also discussed. Finally precise error estimates for the numerical procedure to evaluate the transmission coefficient κS of the TST dividing surface are given, and it is shown that the relative error on κS scales as 1∕κS when κS is small. This implies that dynamical corrections to the TST rate constant can be computed efficiently if and only if the TST dividing surface has a transmission coefficient κS which is not too small. In particular, the TST dividing surface must be optimized upon (for otherwise κS is generally very small), but this may not be sufficient to make the procedure numerically efficient (because the optimal dividing surface has maximum κS, but this coefficient may still be very small).
Surface-plasmon resonance with infrared excitation: Studies of phospholipid membrane growth
Authors: Lirtsman Vladislav , Ziblat Roy , Golosovsky Michael , Davidov Dan , Pogreb Roman , Sacks-Granek Vered , Rishpon Judith
Published: November 2005

We report on a surface-plasmon resonance (SPR) technique based on a Fourier transform infrared spectrometer for biological and surface-sensitive applications. In contrast with conventional surface-plasmon techniques, which operate at a fixed wavelength and a variable angle of incidence, our setup allows independent variation of the wavelength and the angle of incidence. By the proper choice of these parameters, we achieve optimal coupling to the surface plasmon and high sensitivity. Moreover, by using infrared rather than visible light, we achieve an extremely narrow angular-dependent surface-plasmon resonance. This results in a very sensitive SPR technique that can easily sense one molecular layer. We take advantage of the extremely narrow SPR in the infrared range and use it to study the growth dynamics of the phospholipid layer, which is the main constituent of the biological cell membrane. In particular, we distinguish the difference in the growth dynamics of this artificial membrane from a solution under different conditions of liquid flow (continuous flow or injection).
Effect of Y doping and composition-dependent elastic strain on the electrical properties of (Ba,Sr)TiO3 thin films deposited at 520 °C
Authors: Wang Ruey-Ven , McIntyre Paul C. , Baniecki John D. , Nomura Kenji , Shioga Takeshi , Kurihara Kazuaki , Ishii Masatoshi
Published: November 2005

We demonstrate that large and simultaneous improvements in permittivity, tunability, and leakage current density of (Ba,Sr)TiO3 (BST)-based thin-film capacitors can be achieved by yttrium doping. We have found that, for a low deposition temperature (520 °C) sputtering process, Y-doped BST capacitors exhibit tenfold lower leakage current density (<10−9A∕cm2 at 100KV∕cm) and 70% higher permittivity than nominally undoped BST-based capacitors. Furthermore, this work suggests an intriguing correlation between dopant concentration-dependent elastic strain in the films and their enhanced dielectric properties.
Deep donor-acceptor pair recombination in InGaAs-based heterostructures grown on InP substrates
Authors: Gfroerer T. H. , Gillespie C. E. , Campbell J. P. , Wanlass M. W.
Published: November 2005

We are investigating a series of lattice-matched InxGa1−xAs∕InAsyP1−y double heterostructures with indium concentrations ranging between x=0.53 and x=0.78. The double heterostructures incorporating indium-rich alloys (x>0.53) experience lattice mismatch relative to the InP substrate. Previous work has produced convincing but indirect evidence that the distribution of defect levels in the InxGa1−xAs changes dramatically when the epistructure deviates from the lattice-matched condition. In particular, deep midgap states appear to give way to shallower near-band-edge states with increasing mismatch. Here, we report sub-band-gap photoluminescence measurements that explore these changes directly. We observe a broad low-energy peak in the spectra of the lattice-matched and nearly lattice-matched epistructures that is not present in the more mismatched case. The sub-band-gap emission blueshifts and grows superlinearly with photoexcitation up to and exceeding 1000W∕cm2. This unusual behavior is attributed to transitions between ordinary acceptor levels and deep, defect-related donorlike states. We find no evidence for the shallower defect states that we expected to arise with increasing lattice mismatch.
Stress deformations and structural quenching in charge-ordered Sm0.5Ca0.5MnO3 thin films
Authors: Rauwel E. , Prellier W. , Mercey B. , de Brion S. , Chouteau G.
Published: November 2005

Sm 0.5 Ca 0.5 MnO 3 manganite thin films with charge ordering (CO) and colossal magnetoresistance were synthesized by pulsed laser deposition on (100)-SrTiO3 and (100)-LaAlO3 substrates. We first compare the structural modifications as functions of the substrate and film thickness. Secondly, transport properties in magnetic fields up to 24 T were studied and the temperature-field phase diagram describing the stability of the CO state was established. This enables us to compare the thin film to the bulk material. We show that some substrate-induced structural modifications exist as a result of which the CO melting magnetic field is greatly reduced. Moreover, no modification of the lattice parameters is observed with temperature decrease. We then propose an explanation based on the quenching of the thin film’s unit cell which then adopts the in-plane lattice parameters of the substrate and thus prevents the complete setting in of the CO state at low temperatures.
Raman scattering of polar modes of ZnO crystallites
Authors: Bergman Leah , Chen Xiang-Bai , Huso Jesse , Morrison John L. , Hoeck Heather
Published: November 2005

One of the key issues of phonon dynamics of nano- and micrometer-scale crystals is the identification of the observed Raman modes. Due to the tilted orientation of small crystallites, the usual Raman selection rules pertaining to the symmetry axes no longer hold, and mixed-symmetry modes need to be considered in order to explain the polar phonon properties of the crystallites. The Raman modes of ZnO crystallites of the wurtzite structure were investigated via micro-Raman scattering. The nonpolar E2 mode was the predominant mode in the spectra for out-of-resonant conditions. In resonance the crystallites exhibited a predominant mode at ∼580cm−1, intermediate to the frequencies of the A1(LO) and the E1(LO) modes of a reference ZnO single crystal at 568 and 586cm−1, respectively. Our analysis indicates that the observed frequency of the crystallite ensemble can be explained in terms of Loudon’s model of a quasimode behavior that is due to a preferential orientation of a crystallite ensemble. Additionally, model calculation of the quasi-LO frequency of totally random ensemble is presented.
The role of Si as surfactant and donor in molecular-beam epitaxy of AlN
Authors: Lebedev V. , Morales F. M. , Romanus H. , Krischok S. , Ecke G. , Cimalla V. , Himmerlich M. , Stauden T. , Cengher D. , Ambacher O.
Published: November 2005

The growth of Si-doped AlN(0001) thin films on Al2O3(0001) substrates by plasma-induced molecular-beam epitaxy is reported. We have found that Si positively affects the epitaxy being an effective surfactant for AlN growth with a remarkable impact on the crystal quality. It was proven that the characteristic surface reconstruction sequences frequently related to the Al adatoms are obviously Si induced on AlN(0001) surfaces. It was also observed that heavy doping conditions result in volume segregation of Si on the threading dislocation network and in the formation of an amorphous (AlO)(SiO)N cap layer caused by surface oxidation of the accumulated Al and segregated Si. The electron affinity was measured to be smaller than 0.5eV on the clean AlN surface after removing of the cap layer using Ar+ sputtering.
Growth and properties of nanocrystalline germanium films
Authors: Niu Xuejun , Dalal Vikram L.
Published: November 2005

We report on the growth characteristics and structure of nanocrystalline germanium films using low-pressure plasma-assisted chemical vapor deposition process in a remote electron-cyclotron-resonance reactor. The films were grown from mixtures of germane and hydrogen at deposition temperatures varying between 130°C and 310°C. The films were measured for structure using Raman and x-ray spectroscopy. It is shown that the orientation of the film depends strongly upon the deposition conditions. Low-temperature growth leads to both ⟨111⟩ and ⟨220⟩ orientations, whereas at higher temperatures, the ⟨220⟩ grain strongly dominates. The Raman spectrum reveals a sharp crystalline peak at 300cm−1 and a high ratio between crystalline and amorphous peak that is at 285cm−1. The grain size in the films is a strong function of hydrogen dilution, with higher dilutions leading to smaller grain sizes. Growth temperature also has a strong influence on grain size, with higher temperatures yielding larger grain sizes. From these results, which are seen to be compatible with the growth of nanocrystalline Si films, it is seen that the natural growth direction for the film is ⟨220⟩, and that bonded hydrogen interferes with the growth of ⟨220⟩ grains. High hydrogen dilutions lead to more random nucleation.
Influence of dislocations in strained Si∕relaxed SiGe layers on n+∕p-junctions in a metal-oxide-semiconductor field-effect transistor technology
Authors: Eneman Geert , Simoen Eddy , Delhougne Romain , Verheyen Peter , Loo Roger , De Meyer Kristin
Published: November 2005

We present an investigation of junction leakage in highly doped n+∕p-junctions, fabricated in strained silicon/relaxed SiGe substrates. The leakage is shown to scale linearly with the threading dislocation density of the virtual substrate, which allows to estimate minority carrier generation lifetimes in good agreement with literature values. Even the highest-defective substrates in this work give a junction leakage density below 100mA∕cm2, and are not expected to significantly increase the power consumption of metal-oxide-semiconductor field-effect transistor (MOSFET) technologies. Threading dislocations will increase the junction leakage by ∼1nA in a small number of transistors in MOSFET circuits, but are not expected to have a negative impact on yield.
Biexciton lasing of submicron-sized ZnO particle in a Fabry-Perot cavity
Authors: Harada Yoshiyuki , Kondo Hisao , Hashimoto Satoshi
Published: November 2005

We have observed the lasing of submicron-sized ZnO particle in a Fabry-Perot cavity at low temperatures. A thin alkali-halide crystal including a small amount of ZnO particles are sandwiched between two quartz plates arranged as a pair of opposite mirrors, that is, a Fabry-Perot cavity. Under low excitation due to a He–Cd laser, emissions of free and bound excitons and their phonon replicas are recognized markedly, while a biexciton emission band appears under high-dense excitation by a pulsed N2 laser. Biexciton lasing is demonstrated as a narrowed emission by focusing the excitation light beam on an appropriate position being a ZnO particle in the cavity. When a cavity length satisfies the resonant condition, the lasing occurs in the spectral region of the biexciton emission band and with the very small divergence angle. The obtained threshold of excitation-power density is about 0.50MW∕cm2. We discuss lasing in terms of stimulated emission caused by population inversion between biexciton and exciton states.
Photovoltaic operation up to 270 K of a strain-compensated AlAs∕In0.84Ga0.16As∕AlAs∕InAlAs quantum well infrared photodetector
Authors: Lai K. T. , Haywood S. K. , Mohamed A. H. , Missous M. , Gupta R.
Published: November 2005

We report operation up to 270 K of a strain-compensated AlAs∕In0.84Ga0.16As∕AlAs∕In0.52Al0.48As double barrier quantum well infrared photodetector, grown on an InP substrate. The n=1 to n=2 intersubband transition gives a peak detection wavelength of 2.09μm at 77 K which is in good agreement with the calculated value for a 3 nm quantum well. The conduction band discontinuity between In0.52Al0.48As and In0.84Ga0.16As is calculated to be 0.675 eV, which offers the possibility of room temperature operation for optimized detectors.
Si 3 N 4 single-crystal nanowires grown from silicon micro- and nanoparticles near the threshold of passive oxidation
Authors: Farjas J. , Rath Chandana , Pinyol A. , Roura P. , Bertran E.
Published: November 2005

A simple and most promising oxide-assisted catalyst-free method is used to prepare silicon nitride nanowires that give rise to high yield in a short time. After a brief analysis of the state of the art, we reveal the crucial role played by the oxygen partial pressure: when oxygen partial pressure is slightly below the threshold of passive oxidation, a high yield inhibiting the formation of any silica layer covering the nanowires occurs and thanks to the synthesis temperature one can control nanowire dimensions.
Atomistic study of the dissolution of small boron interstitial clusters in c-Si
Authors: Cogoni Marco , Mattoni Alessandro , Uberuaga Blas P. , Voter Arthur F. , Colombo Luciano
Published: November 2005

The dissolution of boron-interstitial clusters (BICs) in crystalline silicon, often formed after ion implantation, is investigated by temperature accelerated dynamics of their formation using the Si–B Stillinger-Weber potential. We find that the dominant breakup event for small BICs is the emission of either Si mono- or di-interstitials, though the dominant reaction for the reactivation of boron is via emission of a boron interstitial defect B1I1. Most reactions are well approximated by the assumption that they are diffusion limited. Finally, the rate limiting step for breakup of clusters with three B atoms involves the B3I2 cluster, which also dissolves via emission of B1I1.