bluuebunny/crossref_metadata_2025 huggingface dataset:
Response to James Lebovic's review of Why Intelligence Fails: Lessons from the Iranian Revolution and the Iraq War
Authors: Jervis Robert
Published: November 2010

Among the many issues raised by James Lebovic's perceptive review are two that strike me as crucial: the relationships between intelligence and social science and those between intelligence and policymaking. The first itself has two parts, one being how scholars can study intelligence. Both access and methods are difficult. For years, diplomatic historians referred to intelligence as the “hidden dimension” of their subject. Now it is much more open, and Great Britain, generally more secretive than the United States, has just issued the authorized history of MI5 (see Christopher Andrew, Defend the Realm: The Authorized History of MI5, 2009). Since the end of the Cold War, the CIA has released extensive, if incomplete, records, and the bright side (for us) of intelligence failures is that they lead to the release of treasure troves of documents, which can often be supplemented by memoirs and interviews. But even more than in other aspects of foreign policy analysis, we are stuck with evidence that is fragmentary. In this way, we resemble scholars of ancient societies, who forever lament the loss of most of the material they want to study.
Response to Eric Uslaner's review of A Culture of Corruption: Everyday Deception and Popular Discontent in Nigeria
Authors: Smith Daniel Jordan
Published: November 2010

I am grateful for Eric Uslaner's thoughtful review of my book. The exchange between us highlights for me, above all, the benefits of reading and conversing across disciplinary boundaries. Uslaner correctly notes that my book refers relatively little to a vast political science literature on corruption. My aim was to understand corruption in Nigeria as it is experienced by ordinary citizens, rather than to contribute to Western analytical debates about (possibly) more universal aspects of corruption and its consequences. But I certainly acknowledge and accept that my own analysis and understanding (as well as the larger contribution of my book) would have benefited from a deeper engagement with the political science literature on corruption. I would quibble with his contrast between anthropologists' “stories” and political scientists' “data.” To me, real people's lives and narratives are among the most powerful data in the social sciences—but that is why I am an anthropologist.
Response to Daniel Jordan Smith's review of Corruption, Inequality, and the Rule of Law: The Bulging Pocket Makes the Easy Life
Authors: Uslaner Eric M.
Published: November 2010

Daniel Jordan Smith has written a very perceptive review of my book. There is little to argue about, but some clarifying remarks may be useful. Smith raises two key issues on which we might disagree—but perhaps the disagreement is more in emphasis than it might appear. These issues are the relationship between petty and grand corruption and the need for a greater historical perspective.
Exit Rights and Entrance Paths: Accommodating Cultural Diversity in a Liberal Democracy
Authors: Ben-Porath Sigal
Published: November 2010

The debate over the accommodation of culture in liberal democracies tends to emphasize exit rights. Autonomy is typically taken as a pre-condition for exit, and public schools are often charged with promoting or facilitating it. I argue that diversity liberals have a more justifiable view than that of autonomy liberals on cultural accommodation, but diversity liberalism too should reframe its view of exit rights. Narrow exit rights that protect basic human rights should be maintained and augmented with entrance paths into general society. I further suggest that for exit rights along with entrance paths to provide the morally required conditions for accommodating culture while respecting freedom, policies in this realm should be designed to address adults rather than children. I consider the effect of this dual change of perspective on the accommodation of culture in democratic institutions, including schools.
Redefining Russia: Hybrid Regimes, Fieldwork, and Russian Politics
Authors: Goode J. Paul
Published: November 2010

All qualitative research faces fundamental hurdles in overcoming issues of access and ensuring the credibility of one's observations. These issues are particularly acute when conducting research in hybrid regimes when the area of investigation is explicitly political and local authorities are sensitive to scrutiny. In the study of Russian politics, growing authoritarianism has meant a shrinking of the field and a corresponding adjustment in fieldwork practices. The disciplinary silence concerning the impact of regime type on fieldwork further threatens the quality and usefulness of comparative research on non-democratic regimes beyond Eurasia. The danger is that interesting and necessary questions about hybrid regimes are sacrificed as scholars opt to conduct fieldwork in more congenial locales where high status methods may be utilized. One can already see this effect as Russianists leave Russia rather than risk isolation within the discipline.
Striking the Right Balance: Of High Walls and Divisions of Labor
Authors: Krebs Ronald R.
Published: November 2010

The academy and the military would seem to be radically different institutions. Militaries are fundamentally hierarchical: at the end of the day, orders must be obeyed. At least in principle—and the emphasis here is on principle, since anyone who has lived within the academy knows how far reality departs from this purported ideal—academic disciplines prize the questioning of presuppositions and foster an antiauthoritarian culture. In military units, individuals must sublimate themselves to the group. Scholarship, at least in the humanities and social sciences, is often a lonely enterprise, whose costs are borne by and whose rewards accrue to individuals. The contemporary US officer corps disproportionately identifies with the Republican Party, while academics tend to identify with Democrats, and sometimes farther to the left. Samuel Huntington (in)famously saw as inherent and necessary the cultural divergences between military and civilian life. This would all the more powerfully seem to apply to the armed forces and the academy, to uniform and gown.
Temporal variations in sea ice resistivity: Resolving anisotropic microstructure through cross‐borehole DC resistivity tomography
Authors: Jones K. A. , Ingham M. , Pringle D. J. , Eicken H.
Published: November 2010

The distribution and connectivity of brine pockets in first year sea ice has a determining influence on the bulk properties of the ice and its interaction with the environment. The structure of the brine network depends upon both temperature and salinity, and a full understanding of the temporal evolution of sea ice physical properties requires measurements that are sensitive to the microstructure and can also be made without disturbing the natural state of the ice. Direct current resistivity techniques are suited to this as the brine fraction is orders of magnitude more conductive than solid ice. However, due to the preferential vertical alignment of brine inclusions, the bulk resistivity of first year sea ice is anisotropic. Although this makes the interpretation of surface resistivity soundings extremely difficult, consideration of the theory of resistivity measurements in an anisotropic medium shows that the anisotropic resistivity structure may be resolved through cross‐borehole measurements. Borehole pairs with one current and one potential electrode in each hole allow the determination of the horizontal component of the anisotropic bulk resistivity (ρH). Use of four boreholes allows an estimate of the geometric mean resistivity (ρm) to be derived. Combining these measurements allows calculation of the vertical resistivity (ρV). This is illustrated by measurements made in first year sea ice near Barrow, Alaska in April–June 2008. Over this period significant changes in resistivity are observed which may be shown to be related to both the brine volume fraction and the microstructure of the ice.
Particle‐based transport model with Markovian velocity processes for tracer dispersion in highly heterogeneous porous media
Authors: Meyer Daniel W. , Tchelepi Hamdi A.
Published: November 2010

Monte Carlo (MC) studies of flow in heterogeneous porous formations, in which the log‐conductivity field is multi‐Gaussian, have shown that as the log‐conductivity variance σY2 increases beyond about 0.5, the one‐point velocity probability density functions (PDFs) deviate significantly from Gaussian behavior. The velocity statistics become more complex due to the formation of preferential flow paths, or channels, as σY2 increases. Methods that employ low‐order approximations (e.g., truncated perturbation expansions) are limited to small σY2 and are unable to represent the complex velocity statistics associated with σY2 > 1. Here a stochastic transport model for highly heterogeneous domains (i.e., σY2 > 1) is proposed. In the model, the Lagrangian velocity components of tracer particles are represented using continuous Markovian stochastic processes in time. The Markovian velocity process (MVP) model is described using a set of first‐order ordinary and stochastic differential equations, which are easy to solve using a particle‐based method. Once the MVP model is calibrated based on velocity statistics from MC simulations of the flow (hydraulic head and velocity), the MVP‐based model can be used to describe the evolution of the tracer concentration field accurately and efficiently. Specifically, the MVP model is validated using MC simulations of longitudinal and transverse tracer spreading due to a point‐like injection in the domain. We demonstrate that for σY2 > 1, the ensemble‐averaged tracer cloud remains markedly non‐Gaussian for relatively large travel distances from the point source. The MVP transport model captures this behavior and reproduces the velocity statistics quite accurately.
Natural organobromine in marine sediments: New evidence of biogeochemical Br cycling
Authors: Leri Alessandra C. , Hakala J. Alexandra , Marcus Matthew A. , Lanzirotti Antonio , Reddy Christopher M. , Myneni Satish C. B.
Published: November 2010

Organobromine (Brorg) compounds, commonly recognized as persistent, toxic anthropogenic pollutants, are also produced naturally in terrestrial and marine systems. Several enzymatic and abiotic bromination mechanisms have been identified, as well as an array of natural Brorg molecules associated with various marine organisms. The fate of the carbon‐bromine functionality in the marine environment, however, remains largely unexplored. Oceanographic studies have noted an association between bromine (Br) and organic carbon (Corg) in marine sediments. Even so, there has been no direct chemical evidence that Br in the sediments exists in a stable form apart from inorganic bromide (Brinorg), which is widely presumed conservative in marine systems. To investigate the scope of natural Brorg production and its fate in the environment, we probed Br distribution and speciation in estuarine and marine sediments using in situ X‐ray spectroscopy and spectromicroscopy. We show that Brorg is ubiquitous throughout diverse sedimentary environments, occurring in correlation with Corg and metals such as Fe, Ca, and Zn. Analysis of sinking particulate carbon from the seawater column links the Brorg observed in sediments to biologically produced Brorg compounds that persist through humification of natural organic matter (NOM). Br speciation varies with sediment depth, revealing biogeochemical cycling of Br between organic and inorganic forms as part of the burial and degradation of NOM. These findings illuminate the chemistry behind the association of Br with Corg in marine sediments and cast doubt on the paradigmatic classification of Br as a conservative element in seawater systems.
Vertical thermal O+ flows at 850 km in dynamic auroral boundary coordinates
Authors: Redmon R. J. , Peterson W. K. , Andersson L. , Kihn E. A. , Denig W. F. , Hairston M. , Coley R.
Published: November 2010

Contemporary magnetosphere models now include species‐dependent dynamics. Energetic O+ has significant consequences for the energy stored in the ring current, the rate of reconnection, and perhaps the timing of substorm injections. The mechanism by which thermal O+ escapes from the top of the ionosphere and into the magnetosphere is not fully understood. Previous studies have used dynamic auroral boundary coordinates to describe the outflowing energetic O+ ions above the ionosphere. In this study we focus on the vertical flow of O+ ions at lower altitudes before they are accelerated to escape velocity. An algorithm has been devised to identify auroral zone boundaries using precipitating electron observations from the Defense Meteorological Satellite Program (DMSP) spacecraft. Vertical ion flows measured by the DMSP special sensor for ions electrons and scintillation ion drift meter and the retarding potential analyzer instruments aboard the F12 (noon‐midnight) and F13 (dawn‐dusk) spacecraft from 1997 to 1998 were projected into dynamic auroral boundary coordinates and used to investigate the dependence of Southern Hemisphere bulk flows on interplanetary magnetic field (IMF) and geomagnetic conditions. Initial results show that (1) net upward flows occur primarily in the auroral zone and net downward flows occur primarily in the polar cap, (2) there exists a strong upward flow at 9 magnetic local time (MLT) near the polar cap boundary, 3) the downward ion flow orientation is strongly dependent on IMF By, and 4) the auroral boundary does not coincide exactly with the upward/downward boundary for bulk flows.
Preonset time sequence of auroral substorms: Coordinated observations by all‐sky imagers, satellites, and radars
Authors: Nishimura Y. , Lyons L. R. , Zou S. , Xing X. , Angelopoulos V. , Mende S. B. , Bonnell J. W. , Larson D. , Auster U. , Hori T. , Nishitani N. , Hosokawa K. , Sofko G. , Nicolls M. , Heinselman C.
Published: November 2010

Using two conjunction events of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) imagers and spacecraft as well as the Super Dual Auroral Radar Network (SuperDARN) and Poker Flat Incoherent Scatter Radars, we show that longitudinally narrow flow bursts in the nightside polar cap can precede poleward boundary intensifications (PBIs) that are followed by equatorward moving north‐south (N‐S) arcs, including those leading to substorm onset instability within the near‐Earth plasma sheet. The association between the ionospheric flows and PBIs indicates that enhanced flows on open field lines may contribute to parallel potential drop increase, triggering of magnetotail reconnection, and to the earthward flows leading to N‐S arcs and to substorm onset. We also investigated differences between N‐S arc sequences that do and do not lead to substorm expansion onset. We found that the two types of N‐S arcs have similar characteristics, indicating that their corresponding plasma sheet flow properties could also be similar. There is, however, one difference between the sequences of N‐S arc evolution. Each N‐S arc leads to small intensification of the growth phase arc, and when the onset‐related N‐S arc reaches the equatorward portion of the auroral oval, the preexisting growth phase arc is much brighter than at the times of non‐onset‐related N‐S arcs. Assuming that the growth phase arc is related to pressure gradients at the inner edge of the plasma sheet, this difference indicates that the near‐Earth plasma pressure distribution at the time of plasma sheet fast flows is crucial in substorm triggering. These observations suggest that substorm onset instability is possible only when the preexisting inner plasma sheet pressure is sufficiently large.
Assimilation of multiresolution radiation products into a downwelling surface radiation model: 1. Prior ensemble implementation
Authors: Forman B. A. , Margulis S. A.
Published: November 2010

An ensemble‐based method for deriving high‐resolution estimates of downwelling broadband shortwave and longwave radiation at the Earth's surface via merger of multiresolution (in space and time) satellite‐based inputs is presented. An ensemble of data‐derived, multiplicative, lognormal perturbations characterizes the uncertainty structure and is subsequently used to perturb nominal estimates of radiation model inputs. The resulting ensemble of model output implicitly contains radiative flux uncertainty associated with uncertain model inputs and explicitly accounts for clear sky versus cloudy sky uncertainties. The perturbations were generated using a two‐dimensional conditional turning bands algorithm that accounts for both cross correlations and spatial correlations. Verification studies using independent, ground‐based observations show the ensemble to perform well and to encapsulate the majority of observations with relatively little bias. The ensemble‐based scheme adequately reproduced hourly downwelling radiative fluxes (and their uncertainty) under diverse atmospheric conditions over a 14 month simulation period in the Southern Great Plains of the United States, and was shown to outperform a more traditional, scalar perturbation approach. The prior ensemble is intended for inclusion into an ensemble‐based data assimilation framework presented in part 2 of this study.
Effect of water table dynamics on land surface hydrologic memory
Authors: Lo Min‐Hui , Famiglietti James S.
Published: November 2010

The representation of groundwater dynamics in land surface models has received considerable attention in recent years. Most studies have found that soil moisture increases after adding a groundwater component because of the additional supply of water to the root zone. However, the effect of groundwater on land surface hydrologic memory (persistence) has not been explored thoroughly. In this study we investigate the effect of water table dynamics on National Center for Atmospheric Research Community Land Model hydrologic simulations in terms of land surface hydrologic memory. Unlike soil water or evapotranspiration, results show that land surface hydrologic memory does not always increase after adding a groundwater component. In regions where the water table level is intermediate, land surface hydrologic memory can even decrease, which occurs when soil moisture and capillary rise from groundwater are not in phase with each other. Further, we explore the hypothesis that in addition to atmospheric forcing, groundwater variations may also play an important role in affecting land surface hydrologic memory. Analyses show that feedbacks of groundwater on land surface hydrologic memory can be positive, negative, or neutral, depending on water table dynamics. In regions where the water table is shallow, the damping process of soil moisture variations by groundwater is not significant, and soil moisture variations are mostly controlled by random noise from atmospheric forcing. In contrast, in regions where the water table is very deep, capillary fluxes from groundwater are small, having limited potential to affect soil moisture variations. Therefore, a positive feedback of groundwater to land surface hydrologic memory is observed in a transition zone between deep and shallow water tables, where capillary fluxes act as a buffer by reducing high‐frequency soil moisture variations resulting in longer land surface hydrologic memory.
Influence of ozone recovery and greenhouse gas increases on Southern Hemisphere circulation
Authors: Karpechko Alexey Y. , Gillett Nathan P. , Gray Lesley J. , Dall'Amico Mauro
Published: November 2010

Stratospheric ozone depletion has significantly influenced the tropospheric circulation and climate of the Southern Hemisphere (SH) over recent decades, the largest trends being detected in summer. These circulation changes include acceleration of the extratropical tropospheric westerly jet on its poleward side and lowered Antarctic sea level pressure. It is therefore expected that ozone changes will continue to influence climate during the 21st century when ozone recovery is expected. Here we use two contrasting future ozone projections from two chemistry‐climate models (CCMs) to force 21st century simulations of the HadGEM1 coupled atmosphere‐ocean model, along with A1B greenhouse gas (GHG) concentrations, and study the simulated response in the SH circulation. According to several studies, HadGEM1 simulates present tropospheric climate better than the majority of other available models. When forced by the larger ozone recovery trends, HadGEM1 simulates significant deceleration of the tropospheric jet on its poleward side in the upper troposphere in summer, but the trends in the lower troposphere are not significant. In the simulations with the smaller ozone recovery trends the zonal mean zonal wind trends are not significant throughout the troposphere. The response of the SH circulation to GHG concentration increases in HadGEM1 includes an increase in poleward eddy heat flux in the stratosphere and positive sea level pressure trends in southeastern Pacific. The HadGEM1‐simulated zonal wind trends are considerably smaller than the trends simulated by the CCMs, both in the stratosphere and in the troposphere, despite the fact that the zonal mean ozone trends are the same between these simulations.
Hydrogen fluoride total and partial column time series above the Jungfraujoch from long‐term FTIR measurements: Impact of the line‐shape model, characterization of the error budget and seasonal cycle, and comparison with satellite and model data
Authors: Duchatelet P. , Demoulin P. , Hase F. , Ruhnke R. , Feng W. , Chipperfield M. P. , Bernath P. F. , Boone C. D. , Walker K. A. , Mahieu E.
Published: November 2010

Time series of hydrogen fluoride (HF) total columns have been derived from ground‐based Fourier transform infrared (FTIR) solar spectra recorded between March 1984 and December 2009 at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m asl) with two high‐resolution spectrometers (one homemade and one Bruker 120‐HR). Solar spectra have been inverted with the PROFFIT 9.5 algorithm, using the optimal estimation method. An intercomparison of HF total columns retrieved with PROFFIT and SFIT‐2–the other reference algorithm in the FTIR community–is performed for the first time. The effect of a Galatry line shape model on HF retrieved total columns and vertical profiles, on the residuals of the fits and on the error budget is also quantified. Information content analysis indicates that in addition to HF total vertical abundance, three independent stratospheric HF partial columns can be derived from our Bruker spectra. A complete error budget has been established and indicates that the main source of systematic error is linked to HF spectroscopy and that the random error affecting our HF total columns does not exceed 2.5%. Ground‐based middle and upper stratospheric HF amounts have been compared to satellite data collected by the HALOE or ACE‐FTS instruments. Comparisons of our FTIR HF total and partial columns with runs performed by two three‐dimensional numerical models (SLIMCAT and KASIMA) are also included. Finally, FTIR and model HF total and partial columns time series have been analyzed to derive the main characteristics of their seasonal cycles.
Bed topography and the development of forced bed surface patches
Authors: Nelson Peter A. , Dietrich William E. , Venditti Jeremy G.
Published: November 2010

Channel topography in gravel‐bedded rivers interacts with the local flow and sediment transport fields to produce “forced patches,” which are temporally stable areas on the bed that display similar grain size and sorting. In an effort to enhance our empirical understanding of the mechanisms responsible for the formation of forced patches, we conducted a near‐field scale flume experiment in which a large (55 m long, 2.74 m wide), straight, sediment recirculating flume was provided a constant water discharge and a unimodal sediment mixture ranging in size from 2 to 45 mm. A sequence of alternate bars developed and became essentially fixed in space, producing quasi‐steady state bed topography over which we made measurements of local near‐bed velocity and sediment transport. The bed developed temporally and spatially persistent forced patches with a general pattern of coarse bar tops and fine pools, which we characterized by visual mapping and with the application of an automated image processing procedure to a high‐resolution (1 × 1 mm) digital elevation model of the bed surface. The boundary shear stress field, calculated from velocity measurements and with a quasi‐three‐dimensional hydraulic model (FaSTMECH), displayed substantial variability across the bar unit. Bed surface grain size did not correlate with local boundary shear stress; instead, topographically forced divergences in the boundary shear stress field were matched by divergences in the sediment transport field. The resultant cross‐stream sediment flux was size‐selective that in turn forced a bed surface textural response leading to coarse bar tops and fine pools. Our observations suggest that size‐selective cross‐stream bed load transport is a mechanism responsible for the development of forced bed surface patches in gravel bed channels that have topographically forced heterogeneous flow fields.
Multicriteria design of rain gauge networks for flash flood prediction in semiarid catchments with complex terrain
Authors: Volkmann Till H. M. , Lyon Steve W. , Gupta Hoshin V. , Troch Peter A.
Published: November 2010

Despite the availability of weather radar data at high spatial (1 km2) and temporal (5–15 min) resolution, ground‐based rain gauges continue to be necessary for accurate estimation of storm rainfall input to catchments during flash flood events, especially in mountainous catchments. Given economical considerations, a long‐standing problem in catchment hydrology is to establish optimal placement of a small number of rain gauges to acquire data on both rainfall depth and spatiotemporal variability of intensity during extreme storm events. Using weather radar observations and a dense network of 40 tipping bucket rain gauges, this study examines whether it is possible to determine a reliable “best” set of rain gauge locations for the Sabino Canyon catchment near Tucson, Arizona, USA, given its complex topography and dominant storm track pattern. High‐quality rainfall data are used to evaluate all possible configurations of a “practical” network having from one to four rain gauges. A multicriteria design strategy is used to guide rain gauge placement, by simultaneously minimizing the residual percent bias and maximizing the coefficient of correlation between the estimated and true mean areal rainfall and minimizing the normalized spatial mean squared error between the estimated and true spatiotemporal rainfall distribution. The performance of the optimized rain gauge network was then compared against randomly designed network ensembles by evaluating the quality of streamflows predicted using the Kinematic Runoff and Erosion (KINEROS2) event‐based rainfall‐runoff model. Our results indicate that the multicriteria strategy provided a robust design by which a sparse but accurate network of rain gauges could be implemented for semiarid basins such as the one studied.
Anthropogenic Venice uplift by seawater pumping into a heterogeneous aquifer system
Authors: Teatini P. , Ferronato M. , Gambolati G. , Baù D. , Putti M.
Published: November 2010

In recent years, a project of anthropogenic Venice uplift caused by seawater injection into a 600–850 m deep brackish aquifer underlying the lagoon has been advanced. While an extensive data set based on marker measurements from a number of gas‐producing wells of the northern Adriatic is available for a realistic evaluation of the geomechanical properties of the injected geologic formation, permeability data are very scarce and sparse throughout the area. Previous finite element (FE) predictions relying on a uniform hydraulic conductivity K as derived from pumping tests suggest that a flat uplift of the city is produced over 10 years from the inception of injection. However, it is well‐known and widely recognized that in natural porous media very seldom K exhibits an even spatial distribution. In this study, a random distribution is then assumed to address the influence of a variable K on the uniformity of the city uplift. To limit the otherwise prohibitive computational burden, the study is performed relative to the pilot project designed to raise a reduced area at the margin of the lagoon. Monte Carlo groundwater flow simulations are performed using a FE discretization of the injected aquifer system based upon a hydraulic conductivity distribution characterized by a lognormal, stationary random process. The resulting pore overpressure is then implemented into a deterministic FE geomechanical model. A sensitivity analysis is performed to account for the uncertainty on the stochastic process, reflected by both the log K variance σ2 and the correlation length λ over the ranges 0.2–1.0 and 20–1000 m, respectively, which are quite plausible for normally consolidated sedimentary formations such as the Northern Adriatic basin. The cumulative distribution function (CDF) of the ground surface uplift, uz, and its horizontal gradient, ρz, are computed and used to evaluate the probability for ρz to be larger than a few significant threshold values as discussed later. It is shown that, even within the most pessimistic scenario (i.e., σ2 = 1.0 and λ = 1000 m), the maximum ρz is comparable, namely of the same order, with the one obtained from the deterministic case and (1) 2–3 times smaller than the ρz caused in the city by groundwater withdrawal in the nearby industrial area over the 1960s (10 × 10−5), (2) 1 order of magnitude less than the maximum bound as indicated in the literature for the safety of multifloor masonry buildings (50 × 10−5), and (3) about 20 times smaller than the maximum ρz values that the city is currently experiencing (100 × 10−5). The results highlight the strong effect exerted by the overburden in smoothing the uneven expansion of the injected heterogeneous formation.
Flow and turbulence structure around an in‐stream rectangular cylinder with scour hole
Authors: Kirkil Gokhan , Constantinescu George
Published: November 2010

Most of the erosion around obstacles present in alluvial streams takes place after the formation of a scour hole of sufficiently large dimensions to stabilize the large‐scale oscillations of the horseshoe vortex (HV) system. The present paper uses eddy resolving techniques to reveal the unsteady dynamics of the coherent structures present in the flow field around an in‐stream vertical cylinder (e.g., bridge pier) with a large scour hole at a channel Reynolds number defined with the channel depth and the bulk channel velocity of 2.4 × 105. The cylinder has a rectangular section and is placed perpendicular to the incoming flow. The geometry of the scour hole is obtained from an experiment conducted as part of the present work. The mechanisms driving the bed erosion during the advanced stages of the scour process around the vertical plate are discussed. Simulation results demonstrate the critical role played by these large‐scale turbulent eddies and their interactions in driving the local scour. The paper analyzes the changes in the flow and turbulence structure with respect to the initial stages of the scour process (flat bed conditions) for a cylinder of identical shape and orientation. Results show the wake loses its undular shape due to suppression of the antisymmetrical shedding of the roller vortices. Also, the nature of the interactions between the necklace vortices of the HV system and the eddies present inside the detached shear layers (DSLs) changes as the scour process evolves. This means that information on the vortical structure of the flow at the initiation of the scour process, or during its initial stages, are insufficient to understand the local scour mechanisms. The paper also examines the effect of the shape of the obstruction on the dynamics of the vortical eddies and how it affects the bed erosion processes during the advanced stages of the local scour. In particular, the paper provides an explanation for the observed increase in the maximum scour depth for bed‐mounted cylinders of rectangular section compared to cylinders of same width but of circular section. This increase is explained by the larger coherence of the HV system, the increased regularity of the interactions between the legs of the necklace vortices and the eddies shed in the DSLs, and the stronger coherence of the wake eddies, during both the initial and the later stages of the local scour process, for cases in which the obstruction has sharp edges that fix the separation point on the in‐stream obstacle at all flow depths (e.g., rectangular cylinder).
Stimulation of TLRs by LMW‐HA induces self‐defense mechanisms in vaginal epithelium
Authors: Dusio Giuseppina F , Cardani Diego , Zanobbio Laura , Mantovani Martina , Luchini Patrizia , Battini Lorenzo , Galli Valentina , Diana Angela , Balsari Andrea , Rumio Cristiano
Published: November 2010

The innate immune system is present throughout the female reproductive tract and functions in synchrony with the adaptive immune system to provide protection in a way that enhances the chances for fetal survival, while protecting against potential pathogens. Recent data show that activation of Toll‐like receptor (TLR)2 and 4 by low‐molecular weight hyaluronic acid (LMW‐HA) in the epidermis induces secretion of the antimicrobial peptide β‐defensin 2. In the present work, we show that LMW‐HA induces vaginal epithelial cells to release different antimicrobial peptides, via activation of TLR2 and TLR4. Further, we found that LMW‐HA favors repair of vaginal epithelial injury, involving TLR2 and TLR4, and independently from its classical receptor CD44. This wound‐healing activity of LMW‐HA is dependent from an Akt/phosphatidylinositol 3 kinase pathway. Therefore, these findings suggest that the vaginal epithelium is more than a simple physical barrier to protect against invading pathogens: on the contrary, this surface acts as efficient player of innate host defense, which may modulate its antimicrobial properties and injury restitution activity, following LMW‐HA stimulation; this activity may furnish an additional protective activity to this body compartment, highly and constantly exposed to microbiota, ameliorating the self‐defense of the vaginal epithelium in both basal and pathological conditions.
The Human Virome in Children and its Relationship to Febrile Illness
Authors: Jaffe David , Muenzer Jared , Storch Gregory , Weinstock George , Sodergren Erica , Wylie Kristine , Arens Max , Buller Richard
Published: November 2010

This study investigates the relationship of viruses to febrile illness in children. Subjects are normal children 2-36 months of age with fever along with normal children of the same age without fever, plus immunocompromised children with fever along with immunocompromised children without fever. Specimens obtained include blood, nasopharyngeal secretions, and feces. Specimens are analyzed using a panel of virus-specific PCR assays and also by high throughput sequencing using 454 and Illumina platforms.
Theory of quantum phase transitions in dimerized antiferromagnets
Authors: Kalita V. M. , Loktev V. M.
Published: November 2010

The quantum phase transition induced by an external magnetic field in a dimerized spin crystal from its singlet ground state to an antiferromagnetic ordered state is examined under the assumption that the exchange interaction is antiferromagnetic, both within dimers and between them. It is shown that during this transition the magnetic polarization of the ions within a dimer and, therefore, of the dimers as a whole, is critical. The orientations and projections of the spin vectors in the magnetically ordered phase depend on the applied magnetic field, while the magnetic susceptibility of this essentially quantum phase remains (similarly to the case of a classical Neel antiferromagnet) constant as the spins of the magnetic sublattices undergo reorientation.
Problems of spin and orbital dynamics associated with femtosecond optical magnetic reversal
Authors: Kurkin M. I. , Orlova N. B.
Published: November 2010

Features of the orbital and spin dynamics of ferromagnets irradiated by femtosecond laser pulses are discussed. A model in which only the orbital momenta of the electrons can change during femtosecond optical pumping is used. The spins undergo reorientation over the subnanosecond times characteristic of spin dynamics after the pump pulse ends. The spin reorientation is caused by the spin-orbital field of the orbital momenta created by the optical pump. Producing the coherent state of the nonequilibrium orbital momenta needed for spin reorientation requires suppression of the quantum fluctuations of the orbital momenta. These fluctuations are caused by tunnel transitions between degenerate (in terms of the sign of the magnetic quantum number) states of the orbital momenta in the crystal field. The possibility of suppressing them by an interatomic interaction of the orbital momenta, similar to the intra-atomic interorbital interaction responsible for Hund’s second rule, is discussed.
A high energy “kink” in the quasiparticle spectrum as evidence of the importance of charge density fluctuations in the mechanism for high temperature superconductivity in cuprates
Authors: Pashitskii É. A. , Pentegov V. I.
Published: November 2010

It is suggested that kink-like features in the band spectra of quasiparticles of metal oxide cuprates obtained by photoemission spectroscopy at high energies ε⩾0.3eV may be related to the appearance of collective charge density fluctuations with quasi-acoustic dispersion (acoustic plasmons) which are caused both by the layered crystalline structure of the metal oxide cuprates and by the strong anisotropy of the electron spectra in the plane of two-dimensional CuO2 layers. These charge density fluctuations should play a significant role in the mechanism for high temperature superconductivity by significantly enhancing the critical temperature for the superconducting transition in metal oxide cuprates.
Bloch oscillations of spin waves in a nonuniform magnetic field
Authors: Gann V. V. , Kosevich Yu. A.
Published: November 2010

Single-particle excitations in quasi-one dimensional ferromagnetic spin chains located in nonuniform magnetic fields with large gradients are examined. Spin waves are dynamically localized in a magnetic field with a constant gradient and a system of local levels with equidistant energies develops with a form similar to the Wannier-Zeeman “ladder.” This effect is similar to Bloch oscillations of an electron in a weak electric field. In a semi-infinite chain the spectrum of spin excitations is bounded below; with increasing energy a gradual transition from spin waves in a uniform magnetic field to states with Bloch-like oscillations occurs. An infinite spin chain in a magnetic field that is constant for x<0 and increases linearly for x>0 is considered. Under these conditions a system of local Wannier-Zeeman states develops above the spin wave zone; their spectrum becomes equidistant at high energies. Possibilities for the experimental observation of Bloch oscillations of spin waves are discussed.
Terahertz radiation from Josephson sandwiches
Authors: Malishevskii A. S. , Silin V. P. , Uryupin S. A. , Uspenskii S. G.
Published: November 2010

Basic results are presented from a study of the Cerenkov emission of electromagnetic waves by solitary vortices and Swihart waves moving in a long Josephson sandwich embedded in a dielectric. The energy fluxes of the electromagnetic field along a long sandwich are examined. The magnitudes of the fluxes are compared over a wide range of frequencies and wave numbers of surface waves in the sandwich.
Double nonlinear resonance in ferromagnets and other dynamic systems
Authors: Bakai A. S.
Published: November 2010

The phenomenon of double nonlinear resonances in nonlinear oscillators of general type is described. The results are used to describe a double nonlinear ferromagnetic resonance in a uniaxial ferromagnet. The possibility of a similar resonance in the system of brain biocurrents is considered.
High-fidelity operation of quantum photonic circuits
Authors: Laing Anthony , Peruzzo Alberto , Politi Alberto , Verde Maria Rodas , Halder Matthaeus , Ralph Timothy C. , Thompson Mark G. , O’Brien Jeremy L.
Published: November 2010

We demonstrate photonic quantum circuits that operate at the stringent levels that will be required for future quantum information science and technology. These circuits are fabricated from silica-on-silicon waveguides forming directional couplers and interferometers. While our focus is on the operation of quantum circuits, to test this operation required construction of a photon source that produced near-identical pairs of photons. We show nonclassical interference with two photons and a two-photon entangling logic gate that operate with near-unit fidelity. These results are a significant step toward large-scale operation of photonic quantum circuits.
Magnetic domains in spinor Bose-Einstein condensates
Authors: Matuszewski Michal , Alexander Tristram J. , Kivshar Yuri S.
Published: November 2010

We discuss the structure of spin-1 Bose-Einstein condensates in the presence of a homogenous magnetic field. We demonstrate that phase separation can occur in the ground state of antiferromagnetic (polar) condensates, while the spin components of ferromagnetic condensates are always miscible, so that no phase separation occurs in them. Our analysis predicts that this phenomenon takes place when the energy of the lowest homogenous state is a concave function of the magnetization. We propose a method for creating spin domains by adiabatic switching-on of a magnetic field. We also discuss the phenomena of dynamical instability and spin domain formation.
Interactions in low-dimensional spinor bosonic gases
Authors: Kolezhuk Alexei K.
Published: November 2010

The renormalization group approach for low-dimensional dilute Bose gases is generalized to the case of multicomponent bosons. As an example, systems of two- and three-component spinor bosons are considered. It is shown that interatomic interactions are strongly renormalized with a tendency to enhance the interaction symmetry.
The dominant nonlinear wave interaction in the energy balance of a wind-driven sea
Authors: Zakharov V. E.
Published: November 2010

Here some aspects of the physics of a wind-driven sea are investigated theoretically. It is demonstrated that an effective four-wave nonlinear interaction plays a leading role in the formation of the spectra of turbulent waves. In particular, this interaction leads to non-linear damping which exceeds standard observations at least by an order of magnitude. The theory developed here is compared with available experimental data.
Triangular hysteresis loops in the spin-rotation region of orthoferrites
Authors: Bazaliy Ya. B. , Tsymbal L. T.
Published: November 2010

A theory is proposed that qualitatively explains the shapes of the hysteresis loops in orthoferrites within the temperature interval of the magnetic reorientation transition. Triangular loops result from the strong temperature dependence of both the magnetic moment and the magnetic domain wall structure.
Electrothermal theory of photomodulated optical reflectance on active doping profiles in silicon
Authors: Bogdanowicz Janusz , Dortu Fabian , Clarysse Trudo , Vandervorst Wilfried , Salnik Alex
Published: November 2010

The electrical characterization of the source and drain extension regions of complementary metal oxide semiconductor (CMOS) transistors is highlighted in the international technology roadmap for semiconductors (ITRS) as a major challenge for future technology nodes. In practice, there is a clear need for techniques which are simultaneously accurate, nondestructive, fast, local, and highly reproducible. The photomodulated optical reflectance (PMOR) technique has shown to be a very promising candidate to solve this need. However, even though this technique has been widely studied on homogeneous bulk material and on as-implanted (i.e., unannealed) doping profiles, the extension toward active doping profiles requires a detailed investigation (due to the presence of a built-in electric field). In this paper, after performing an in-depth investigation of the optical and transport models involved in a PMOR experiment, we derive an analytical theory to explain the PMOR signal behavior observed on active doping profiles. In the optical model, we show that only the electrorefractive Drude and thermorefractive effects are to be considered for red and near-infrared wavelengths on Si. In the transport model, we begin the discussion with the study of homogeneous Si substrates. We show that, due to the high carrier injection induced by the lasers, the only important effects are, for the free carriers, the Auger recombinations, the (ambipolar) diffusion and the bandgap narrowing-induced quasidrift; the thermoelectric effects being negligible. Based on the results on homogeneous substrates and on the assumption that the quasi-Fermi levels are flat through the space-charge region, we derive an analytical formula for PMOR signals on active doping profiles. We discuss this formula based on experimental PMOR data measured on active doping profiles with a simple boxlike shape. This formula proves to be in good qualitative agreement with the experimental data both when the power of the pump laser is varied (power curves) and when the distance between the lasers is changed (offset curves). We also show that, for the formula to be quantitative, a very good knowledge of the bandgap profile throughout the sample would be required.
Ultrafast thermoelectric properties of gold under conditions of strong electron-phonon nonequilibrium
Authors: Hopkins Patrick E. , Bauer Matthew L. , Duda John C. , Smoyer Justin L. , English Timothy S. , Norris Pamela M. , Beechem Thomas E. , Stewart Derek A.
Published: November 2010

The electronic scattering rates in metals after ultrashort pulsed laser heating can be drastically different than those predicted from free electron theory. The large electron temperature achieved after ultrashort pulsed absorption and subsequent thermalization can lead to excitation of subconduction band thermal excitations of electron orbitals far below the Fermi energy. In the case of noble metals, which all have a characteristic flat d-band several electron volts well below the Fermi energy, the onset of d-band excitations has been shown to increase electron-phonon scattering rates by an order of magnitude. In this paper, we investigate the effects of these large electronic thermal excitations on the ultrafast thermoelectric transport properties of gold, a characteristic noble metal. Under conditions of strong electron-phonon nonequilibrium (relatively high electron temperatures and relatively low lattice temperatures, Te⪢TL), we find that the Wiedemann–Franz law breaks down and the Seebeck coefficient is massively enhanced. Although we perform representative calculations for Au, these results are expected to be similar for the other noble metals (Ag and Cu) due to the characteristic large d-band separation from the Fermi energy.