bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Cosine Phased BOC Modulation on the GNSS Receiver Search Process
Authors: Weiler Ruediger M. , Blunt Paul , Hodgart Stephen , Unwin Martin
Published: October 2008

The modernisation of GPS and the introduction of Galileo will introduce the use of Binary Offset Carrier (BOC) modulation. BOC will be implemented as either a sine or cosine sub-carrier modulation, which affects the spectral properties of the signal and the receiver search, acquisition and tracking processes. This paper addresses the effect of the various forms of BOC modulation on the receiver search process. Theory is developed to draw comparisons between search techniques and verified with computer simulation models.
MBOC and BOC(1,1) Performance Comparison
Authors: Hoult N. , Aguado L. E. , Xia P.
Published: October 2008

In recent months the US and the EU have agreed to change the modulation scheme for the new civil GPS and Galileo signals in the L1 band from Binary Offset Carrier (1,1) (BOC(1,1)) to a scheme having the so-called Multiplexed Binary Offset Carrier (MBOC) spectrum, although each system will implement this differently. This paper compares the performance of the new system in a number of areas against the original baseline. It is shown that the MBOC signal offers significant advantages in multipath and tracking performance, while retaining compatibility with BOC(1,1) receivers at the cost of a small correlation loss.
Minimal Time Route Computation for Ships with Pre-Specified Voyage Fuel Consumption
Authors: Bijlsma S. J.
Published: October 2008

The air pollution caused by the use of heavy fuel oil in shipping is a growing problem that is drawing increased attention. Methods have been developed to reduce air emissions from ships, more or less aimed at the choice of fuel and the related air emissions. However, the emissions of particulates, sulphur and carbon dioxide, which contribute to the greenhouse effect are not only related to the choice of fuel but also to the amount of fuel consumed in the combustion engines. This paper proposes an additional method that can contribute to the reduction of the air pollution from ships by decreasing the fuel consumption. This is done by specifying the amount of fuel that can be consumed on a specific ocean crossing and by computing a minimal-time route for that given amount of fuel, so decreasing the fuel consumption in a verifiable way.
Roll Motion of a Ship and the Roll Stabilising Effect of Bilge Keels
Authors: Iglesias Baniela Santiago
Published: October 2008

The roll motion of a ship on waves is one of the six degrees of freedom and is the most difficult to predict since it deals with a motion similar to a spring-mass damper system, poorly damped by ship generated waves, in addition to the action of waves from the high seas. This problem increased from the second half of the 19th century when sailing propulsion was replaced by steam machines and iron replaced wood, which led to design modifications in ships affecting transversal stability, with the result of an increment in the ship's roll motion. As a consequence, it has been necessary to develop different systems which, on the one hand, increase the natural period of this motion in order to decrease its amplitude and reduce the risks that the wave encounter frequency would resonate with the natural frequency of the ship's motion; and on the other hand, to generate a damping effect to this motion. Bilge keels, passive stabilisers with no moving parts, form the simplest and cheapest element that may be incorporated on a ship to reduce this motion. This paper studies roll motion in general and then analyses bilge keels from different points of view.
Trial by Fire: Surviving the Job Talk Q&A
Authors: Hassner Ron E.
Published: October 2008

There is a common misconception among graduate students regarding the purpose of the job interview. Many seem to treat the interview as if it were designed to identify and hire outstanding graduate students. Indeed, over the course of their brief interaction with a prospective hire, faculty strive to reassure themselves of the candidate's intelligence, training, and scholarly potential. But underlying all these, I would like to argue, is a persistent concern: Will this candidate make for a good colleague? This is the primary purpose of the interview: Identifying and hiring prospective peers.
Courting Success: The Supreme Court Fellows Program at 35
Authors: Gould Jon B. , Bell Lauren C. , Lau Terence J. , Domurad John M.
Published: October 2008

In 1973, then-Chief Justice Warren Burger, at the suggestion of his administrative assistant, Mark Cannon, created the Judicial Fellows Program to allow scholars to engage in “challenging work for a year” at the Supreme Court and other federal judicial agencies (Tobias 1996, 510). The program is designed to attract, in Justice Ruth Bader Ginsburg's words, “bright-minded, caring, uncommonly fine humans, people who remain … in permanent fellowship with the Federal Judiciary” after their year (Ginsburg 1998, 3).
Learning to Learn; Learning to Win: How to Succeed in the Simulated World of Model NATO
Authors: Meleshevich Andrey A. , Tamashiro Howard
Published: October 2008

Simulations and role-playing exercises have been used effectively as a teaching device in all areas of political science and international relations. One such simulation, with 20 years of success, is the Model NATO Conference, currently sponsored annually in Washington, D.C., by Howard University and Kent State University's Center for International and Comparative Studies. Model NATO is an intercollegiate, competitive, and experiential learning exercise that models the decision-making and crisis management processes of NATO. Student delegations, representing different NATO member-countries, negotiate consensus agreements while promoting their often conflicting national interests. According to the Model NATO web site, this competition is designed to
Social Science Expertise and Policymaking. Comparing U.S., French, and EU Think Tanks: Similar Model Different Paths
Authors: Monange Benoit F.
Published: October 2008

The relationship between social science and policymaking, marked with “tension and ambiguity,” is one that scholars never ceased to be perplexed about (Anderson 2003). My research seeks to shed light on the interaction between the two by comparing how the “think tank model of expertise,” first developed in the U.S., is being emulated in the EU and in France where the political systems and the structures of social knowledge traditionally called for a different use of social science research. By looking at the comparative evolution of the think tank model I also wish to question the building of the expert as a modern figure that bridges a discursive regimen of “knowledge claim” used in the scientific world and a regimen of “truth-claim” consistent with political discourses (Veitl 2005; Leclerc 2001). Scrutinizing the activities of think tanks as a place where “experts” claim to inform and influence policymakers is, in that sense, a way to revisit and rethink the relations between power and knowledge (Ihl 2006).
The Interest Group—Staff Connection in Congress: Access and Influence in Personal, Committee, and Leadership Offices
Authors: Gerrity Jessica C. , Hardt Nancy S. , Lavelle Kathryn C.
Published: October 2008

One manual for lobbyists in Congress warns those new to the trade that “winning the confidence of staff—and maintaining it thereafter—is a prerequisite to an ongoing, successful political relationship with any political office (Wolpe 1990).” The author then details the organization and loyalties among personal and committee staffs. One thing staffers have in common is that each specializes in an issue area and thus develops expertise over the issue, the players and politics of the committee, the legislative process, the interest groups, and the constituencies involved with the legislation (Wolpe 1990). Despite the wide-ranging literature on interest group activity in Congress, few distinctions are made between the efforts of lobbyists to influence staff, or ways in which the staff-interest group relationship varies in different types of offices.
Treasurer's Report 2008: Another Year of Growth and Innovation in APSA's Financial Operations
Authors: Box-Steffensmeier Janet M. , Smith Robin
Published: October 2008

I am pleased to report that our Association's financial condition remains healthy, providing a resource base sufficient to continue current operations, while expanding the Association's activities in new directions as needed. Since our last annual report, we have seen our endowment and real estate holdings grow in value to about $32.1 million (June 2007), against which we are carrying just $1.6 million in mortgage debt. For the fiscal year that ended June 30, 2008, we estimate that total operating income ($4.8 million) was slightly above budget, with expenditures below. Our broad membership base continues to be the most important reason for our healthy financial condition, while the annual meeting and APSA publications also provide substantial income. In short, we are in the enviable position of enjoying stable membership, while holding substantial income- and growth-producing assets with minimal long-term liabilities. All of these factors combine to produce an operating budget that hews closely to anticipated income and expenses, year after year.
The biotic effects of large bolide impacts: size versus time and place
Authors: Walkden Gordon , Parker Julian
Published: October 2008

In estimating the biotic effects of large terrestrial impacts we are reliant upon apparent crater diameter as a proxy for impact magnitude. This underlies the ‘kill-curve’ approach which graphs crater diameter directly against likely percentage losses of taxa. However, crater diameter is a complex product of syn- and post-impact processes that can be site-dependent. Furthermore, location (global positioning) and timing (moment in geological history) also strongly influence biotic effects. We examine four of our largest and best-documented Phanerozoic impacts to explore this more holistic size–time–place relationship. Only the c. 180 km end-Cretaceous Chicxulub crater (Mexico) links to any substantial immediate extinction and some of the worst effects stem from where it struck the planet (a continental margin carbonate platform site) and when (a time of high regional and global biodiversity). Both the c. 100 km late Triassic Manicouagan crater in NE Canada (arid continental interior, low regional and world biodiversity) and the c. 35 Ma 100 km Popigai crater, Siberia (continental arctic desert) provide much less damaging scenarios. However the c. 90 km Chesapeake Bay crater, Eastern USA (also c. 35 Ma) marks a far more sensitive (Chicxulub-like) site but it also proved relatively benign. Here the rheologically varied shallow marine target site produced an anomalously broad crater, and the scale of the impact has evidently been overestimated. We offer a new approach to the graphical prediction of biotic risk in which both crater diameter and a generalised time/place factor we term ‘vulnerability’ are variables.
SNP in intron 5 of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) gene and its genetic effects on important economic traits in geese
Authors: Zhong Liang , Hong-Quan Chen , Hua-Yun Huang , Li-Sha Zha , Hua Chen
Published: October 2008

Intron 5 of the 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) gene was cloned and its single nucleotide polymorphism (SNP) was tested by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) in Wanxi White geese (WW) (Anser anser). The carcass, meat quality and feather-down traits of 116 geese from WW males×Sichuan White goose (A. anser) females were assessed and analysed in association with SNP. The results showed that the sequence length of intron 5 of the HMGR gene in geese was 704 bp, and the homology between goose and chicken was 44.0%. A SNP site was tested in intron 5 by PCR-SSCP, and frequencies of alleles A and B at the SNP site were 0.7716 and 0.2284, respectively. The effects of genotype AA were significant, not only on an increase of chest muscle weight, stomach gland weight (P<0.05), fibre diameter of chest muscle and 1000-down weight (P<0.01), but also on a decrease of down water-holding percentage and pH of chest muscle 45 min after slaughterP<0.05). The effect of genotype AB was in the opposite direction to that of genotype AA.
Plant gene targeting and gene replacement: application to crop genetic improvement
Authors: Xiao-hui Zhang , Zhi-biao Ye , Yu-yang Zhang , Zheng Hou , Han-xia Li
Published: October 2008

Recent advances and limitations of using zinc finger nuclease to stimulate a high efficiency of homologous recombination, and chimeric oligonucleotides to promote single base replacement in functional genomic research and plant genetic breeding, are systematically reviewed. Approaches to improve gene targeting efficiency through molecular modification of key pathways in plant homologous recombination are also discussed.
Mechanisms of abrupt climate change of the last glacial period
Authors: Clement Amy C. , Peterson Larry C.
Published: October 2008

More than a decade ago, ice core records from Greenland revealed that the last glacial period was characterized by abrupt climate changes that recurred on millennial time scales. Since their discovery, there has been a large effort to determine whether these climate events were a global phenomenon or were just confined to the North Atlantic region and also to reveal the mechanisms that were responsible for them. In this paper, we review the available paleoclimate observations of abrupt change during the last glacial period in order to place constraints on possible mechanisms. Three different mechanisms are then reviewed: ocean thermohaline circulation, sea ice feedbacks, and tropical processes. Each mechanism is tested for its ability to explain the key features of the observations, particularly with regard to the abruptness, millennial recurrence, and geographical extent of the observed changes. It is found that each of these mechanisms has explanatory strengths and weaknesses, and key areas in which progress could be made in improving the understanding of their long‐term behavior, both from observational and modeling approaches, are suggested. Finally, it is proposed that a complete understanding of the mechanisms of abrupt change requires inclusion of processes at both low and high latitudes, as well as the potential for feedbacks between them. Some suggestions for experimental approaches to test for such feedbacks with coupled climate models are given.
High‐velocity frictional properties of a clay‐bearing fault gouge and implications for earthquake mechanics
Authors: Brantut N. , Schubnel A. , Rouzaud J.‐N. , Brunet F. , Shimamoto T.
Published: October 2008

Frictional properties of natural kaolinite‐bearing gouge samples from the Median Tectonic Line (SW Japan) have been studied using a high‐velocity rotary shear apparatus, and deformed samples have been observed with optical and electron (scanning and transmission) microscopy. For a slip velocity of 1 m s−1 and normal stresses from 0.3 to 1.3 MPa, a dramatic slip‐weakening behavior was observed. X‐ray diffraction analysis of deformed samples and additional high‐velocity friction experiments on pure kaolinite indicate kaolinite dehydration during slip. The critical slip‐weakening distance Dc is of the order of 1 to 10 m. These values are extrapolated to higher normal stresses, assuming that Dc is rather a thermal parameter than a parameter related to a true characteristic length. The calculation shows that dimensionally, Dc ∝ 1/σn2, where σn is the normal stress applied on the fault. The inferred Dc values range from a few centimeters at 10 MPa normal stress to a few hundreds of microns at 100 MPa normal stress. Microscopic observations show partial amorphization and dramatic grain size reduction (down to the nanometer scale) localized in a narrow zone of about 1 to 10 μm thickness. Fracture energy Gc is calculated from the mechanical curves and compared to surface energy due to grain size reduction, and energies of mineralogic transformations. We show that most of the fracture energy is either converted into heat or radiated energy. The geophysical consequences of thermal dehydration of bonded water during seismic slip are then commented in the light of mineralogical and poromechanical data of several fault zones, which tend to show that this phenomenon has to be taken into account in most of subsurface faults and in hydrous rocks of subducted oceanic crust.
Polychlorinated biphenyls in air and water of the North Atlantic and Arctic Ocean
Authors: Gioia Rosalinda , Lohmann Rainer , Dachs Jordi , Temme Christian , Lakaschus Soenke , Schulz‐Bull Detlef , Hand Ines , Jones Kevin C.
Published: October 2008

Air and seawater samples were collected on board the R/V Polarstern during a scientific expedition from Germany to the Arctic Ocean during June–August 2004. The air data show a strong decline with latitude with the highest polychlorinated biphenyl (PCB) concentrations in Europe and the lowest in the Arctic. ΣICES PCBs in air range from 100 pg m−3 near Norway to 0.8 pg m−3 in the Arctic. A comparison with other data from previous and ongoing land‐based air measurements in the Arctic region suggests no clear temporal decline of PCBs in the European Arctic since the mid‐1990s. Dissolved concentrations of Σ6PCBs (28/31, 52, 101, 118, 138, 153) in surface seawater were <1 pg L−1. Dominant PCBs in seawater were 28/31 and 52 (0.1–0.44 pg L−1), with PCBs 101, 118, and 138 < 0.1 pg L−1. In seawater, PCB 52 displayed the highest concentrations in the northernmost samples, while PCBs 101, 118, and 138 showed slightly decreasing trends with increasing latitude. Fractionation was observed for PCBs in seawater with the relative abundance of PCBs 28 and 52 increasing and that of the heavier congeners decreasing with latitude. However, in air only 15–20% of the variability of atmospheric PCBs can be explained by temperature. Owing to large uncertainties in the Henry's Law constant (HLC) values, fugacity quotients for PCBs were estimated using different HLCs reported in the literature. These indicate that on average, deposition dominates over volatilization for PCBs in the Arctic region with a strong increase in the middle of the transect near the marginal ice zone (78–79°N). The increase in fugacity ratio is mainly caused by an increase in air concentration in this region (possibly indirectly caused by ice melting being a source of PCBs to the atmosphere).
Influence of El Niño–Southern Oscillation on the interannual variability of tropospheric ozone in the northern midlatitudes
Authors: Koumoutsaris S. , Bey I. , Generoso S. , Thouret V.
Published: October 2008

We use the Goddard Earth Observing System Chem (GEOS‐Chem) model to interpret long‐term measurements of tropospheric ozone (O3) and carbon monoxide (CO) and to investigate the factors that contribute to their interannual variation (IAV) during the period from 1987 to 2005. The model reproduces relatively well the observed IAV of CO. The simulation of O3 IAV is not as successful. In particular, the negative anomalies in 1991–1993 and the following upward trend in 1993–1996 observed at several sites in the northern midlatitudes are not reproduced by the model, which may result from a poor representation of stratospheric chemistry and dynamics. We examine in detail the period of 1998–1999 when a large anomaly in tropospheric ozone column is observed and simulated over Europe (maximum of +4.9 Dobson units). Three consecutive periods can be distinguished from January 1998 to April 1999, during which different processes affected the O3 burden over Europe. Spring 1998 is largely influenced by the preceding 1997 El Niño that affects (1) stratosphere‐troposphere exchange and (2) Asian pollution export and transport toward Europe by a change in convective activity in East Asia and a strengthening of the subtropical jet stream. An enhanced pollution export from North America is also noticed for this period. The second period (summer‐fall 1998) shows a mixed influence from both boreal wildfires and Asian pollution. The third period is influenced by enhanced wildfires in Southeast Asia. Throughout the period from 1987 to 2005, positive anomalies in tropospheric O3 column and in surface O3 are found over Europe in the spring following an El Niño year.
Responses of streamflow to changes in climate and land use/cover in the Loess Plateau, China
Authors: Zhang Xiaoping , Zhang Lu , Zhao Jing , Rustomji Paul , Hairsine Peter
Published: October 2008

To control the severe soil erosion in the Loess Plateau, China, a great number of soil conservation measures including terracing, afforestation, and construction of sediment‐trapping dams have been implemented since the 1950s. These measures have resulted in large‐scale land use and land cover change. It is important to evaluate the impacts of these soil conservation measures on streamflow as streamflow is an important determinant on catchment sediment yield and obviously is related to water security in the region. In this study, data from 11 catchments in the Loess Plateau were analyzed to investigate the responses of streamflow to the land use/cover changes. The nonparametric Mann‐Kendall test and the Pettitt test were used to identify trends and change points in the streamflow records. All 11 catchments had significant negative trend in annual streamflow of −0.13 to −1.58 mm a−1. Change points in streamflow occurred between 1971 and 1985. A method was employed to evaluate the impacts of climate variability and land use/cover changes on mean annual streamflow on the basis of precipitation and potential evaporation. It was estimated that the land use/cover changes accounted for over 50% of the reduction in mean annual streamflow in 8 out of the 11 catchments. However, climate (i.e., precipitation and potential evaporation) played a more important role in reducing the streamflow in the three remaining catchments. Among the soil conservation measures, construction of sediment‐trapping dams and reservoirs, with associated irrigation water extractions from the latter, appeared to be the main cause of the reduced streamflow.
Capturing the Acoustic Fingerprint of Stratospheric Ash Injection
Authors: Garcés Milton , Fee David , Steffke Andrea , McCormack David , Servranckx Rene , Bass Henry , Hetzer Claus , Hedlin Michael , Matoza Robin , Yepes Hugo , Ramon Patricio
Published: October 2008

More than 100 separate incidents of interactions between aircraft and volcanic ash were documented between 1973 and 2003. Incidents on international flight paths over remote areas have resulted in engine failures and significant damage and expense to commercial airlines. To protect aircraft from volcanic ash, pilots need rapid and reliable notification of ash‐ generating events. A global infrasound array network, consisting of the International Monitoring System (IMS) and other national networks, has demonstrated a capability for remote detection of Vulcanian to Plinian eruptions that can inject ash into commercial aircraft cruise altitudes (approximately 12 kilometers) near the tropopause. The identification of recurring sound signatures associated with high‐ altitude ash injection implies that acoustic remote sensing can improve the reliability and reduce the latency of these notifications.
Temporary Seismic Broadband Network Acquired Data on Hellenic Subduction Zone
Authors: Friederich Wolfgang , Meier Thomas
Published: October 2008

Data acquired from a network of seismic broadband stations that recently operated in the eastern Mediterranean region will be made available to the seismological community after the project concludes, in June 2011. The network, which consisted of both land and ocean bottom seismographs, functioned from October 2005 until its deinstallation in March 2007 as part of the Exploring the Geodynamics of Subducted Lithosphere Using an Amphibian Deployment of Seismo graphs (EGELADOS) project (Figure 1). The network, which covered the entire southern Aegean Sea from the Peloponnesus region in the west to western Turkey in the east, was designed to study seismicity as well as the distribution of the elastic and anelastic material properties in the Hellenic subduction zone to better understand its complex geotectonic setting and evolution.

The network encompassed 45 Güralp 60‐second seismometers, four Streckeisen STS‐2 seismo meters, and seven 1‐hertz Mark seismometers at land sites. The seismometers were supplemented by 22 ocean bottom seismographs equipped with Güralp 60‐second seismometers and broadband hydrophones. In addition, the network was designed to incorporate the seven permanent broadband seismographs of the GeoForschungsNetz (GEOFON) network and one Mediterranean Very Broadband Seismographic Network (MedNet) station.
Seasonal and spatial variability in dissolved organic matter quantity and composition from the Yukon River basin, Alaska
Authors: Spencer Robert G. M. , Aiken George R. , Wickland Kimberly P. , Striegl Robert G. , Hernes Peter J.
Published: October 2008

The seasonal and spatial variability of dissolved organic matter (DOM) quantity and chemical composition were investigated in the Yukon River basin of Alaska, United States, and northwestern Canada. Dissolved organic carbon (DOC), chromophoric DOM (CDOM), and dissolved lignin phenols were measured across a range of source waters and the seasonal hydrograph. Strong relationships were determined between CDOM and both DOC and lignin phenols, highlighting the potential for deriving detailed spatial and temporal distributions of DOM composition from CDOM monitoring. Maximum concentrations of measured parameters were observed during the spring flush, when DOM had a remarkably high content of aromatic vascular plant material derived from surface soil and litter layers. A larger portion of riverine DOM was attributed to vascular plant sources than previously believed by utilizing representative vegetation leachates and a soil pore water as end‐members. In combination with recent studies highlighting export of young, labile DOM during the spring flush in northern high‐latitude river systems, our results suggest riverine DOM is less degraded and more labile than previously thought with clear ramifications for its biomineralization or photo‐oxidation in marine environments.
Frequency of severe storms and global warming
Authors: Aumann Hartmut H. , Ruzmaikin Alexander , Teixeira Joao
Published: October 2008

We use five years of data from the Atmospheric Infrared Sounder (AIRS) to develop a correlation between the frequency of Deep Convective Clouds (DCC) and the zonal mean tropical surface temperature. AIRS data show that the frequency of DCC in the tropical oceans is very temperature sensitive, increasing 45% per 1 K increase of the zonal mean surface temperature. The combination of the sensitivity of the DCC frequency to temperature indicates that the frequency of DCC, and as a consequence the frequency of severe storms, increases at the rate of 6%/decade with the current +0.13 K/decade rate of global warming. This result is only qualitatively consistent with state‐of‐the‐art climate models, where the frequency of the most intense rain events increases with global warming.
Sub‐surface signatures of the Atlantic Multidecadal Oscillation
Authors: Frankcombe L. M. , Dijkstra H. A. , von der Heydt A.
Published: October 2008

Sub‐surface signatures of the Atlantic Multidecadal Oscillation (AMO) are identified using expendable bathythermograph (XBT) measurements of temperature from the surface down to a depth of 400 m. Basin averaged temperature anomalies in the North Atlantic at different depths display multidecadal variability with a phase shift between temperature anomalies at the surface and at depth. Westward propagation of temperature anomalies is observable at depth and there is a lag correlation between east‐west and north‐south temperature gradients, with the east‐west temperature gradient leading. These sub‐surface characteristics of the AMO agree with those expected from the noise‐driven internal ocean mode view of the AMO, as derived from a hierarchy of ocean‐atmosphere models.
Phase velocities from seismic noise using beamforming and cross correlation in Costa Rica and Nicaragua
Authors: Harmon Nicholas , Gerstoft Peter , Rychert Catherine A. , Abers Geoffrey A. , Salas de la Cruz Mariela , Fischer Karen M.
Published: October 2008

An expression for the cross correlation of noise between seismic stations and the 2D Green's function is derived assuming that noise travels as 2D surface waves. The phase velocity is obtained directly from the noise correlation function with a phase shift of +π/4. Mean phase velocity dispersion curves are calculated for the TUCAN seismic array in Costa Rica and Nicaragua from ambient seismic noise using two independent methods, noise cross correlation and beamforming. The noise cross correlation and beamforming methods are compared and contrasted by evaluating results from the TUCAN array. The results of the two methods as applied to the TUCAN array agree within 1%, giving good confidence in the phase velocities extracted from noise.
A SST based large multi‐model ensemble forecasting system for Indian summer monsoon rainfall
Authors: Sahai A. K. , Chattopadhyay R. , Goswami B. N.
Published: October 2008

An ensemble mean and probabilistic approach is essential for reliable forecast of the All India Summer Monsoon Rainfall (AIR) due to the seminal role played by internal fast processes in interannual variability (IAV) of the monsoon. In this paper, we transform a previously used empirical model to construct a large ensemble of models to deliver useful probabilistic forecast of AIR. The empirical model picks up predictors only from global sea surface temperature (SST). Methodology of construction implicitly incorporates uncertainty arising from internal variability as well as from the decadal variability of the predictor‐predictand relationship. The forecast system demonstrates the capability of predicting monsoon droughts with high degree of confidence. Results during independent verification period (1999–2008) suggest a roadmap for generating empirical probabilistic forecast of monsoon IAV for practical delivery to the user community.
Quasilinear‐based simulations of bidirectional type III bursts
Authors: Li Bo , Robinson Peter A. , Cairns Iver H.
Published: October 2008

Quasilinear‐based simulations are presented of bidirectional type III bursts that originate in the corona and are observed at Earth, assuming plasma emission. By extending a recent simulation model to more realistic three‐dimensional source structures and including Langmuir collisional damping, dynamic spectra of both the normal‐drifting (normal) and the reverse‐slope‐drifting (RS) bursts are simulated and studied in detail for realistic electron‐release and coronal parameters. The radio flux, brightness temperature, frequency drift rate, and time duration of the bursts agree semiquantitatively with typical observations. The flux of 2fp emission is significantly higher than that of fp emission, which is below the noise thresholds of typical radio instruments. This is mainly because the fp emission is strongly free‐free absorbed and further damped by scattering off density fluctuations. The 2fp emission is asymmetric between the normal and RS bursts, with the normal burst stronger and lasting longer than the RS burst, consistent with observations. This occurs primarily because of the downgoing beam being weaker, not faster, and narrower in velocity space than the upgoing beam, and because of stronger free‐free absorption for the RS burst than for the normal burst, consistent with a semiquantitative theory. Furthermore, the RS burst terminates at frequencies lower than the maximum simulated, and the normal burst extends to lower frequencies not simulated because of computational limitations. Collisional damping reduces the Langmuir wave levels and consequently suppresses the flux levels and washes out the dynamic spectral structures associated with successive wave‐wave interactions when the damping is switched off.
Regional sensitivities of mean and peak river discharge to climate variability in Europe
Authors: Bouwer Laurens M. , Vermaat Jan E. , Aerts Jeroen C. J. H.
Published: October 2008

Variability of atmospheric circulation is thought to be the most important factor causing annual and decadal variability of fresh water fluxes from the continents. Previous studies, however, have rarely established the sensitivity of the basins to atmospheric circulation variability. Here we present an analysis of long‐term (>30 years) links between atmospheric forcing and winter (December–February) precipitation, and sensitivities of annual mean and maximum winter discharges observed at up to 608 stations across Europe. Links to four atmospheric indices are examined: the North Atlantic Oscillation (NAO) index, the Arctic Oscillation (AO) index, the frequency of west circulation (FWC) as described by the subjective Großwetterlagen classification, and the north to south sea level pressure difference across the European continent (SLPD). The results show that annual maximum discharges are more sensitive to variability of atmospheric circulation than mean discharges. Mean discharges vary on average between 8 and 44%, while peak discharges vary between 10 and 54% per unit index change. Discharges in Iberia and Scandinavia are more sensitive than those in central and northwest Europe. Discharge closely follows variability of atmospheric circulation. Compared with FWC and SLPD, the NAO and AO indices have only limited use for analyzing climate impacts in river basins in northwest Europe.
A shallow convective model for Jupiter's alternating wind bands
Authors: Chan K. L. , Mayr H. G.
Published: October 2008

The dynamics of a thin atmospheric layer (1–340 bar) below the cloud tops of Jupiter is simulated with a three‐dimensional, nonlinear transformed spectral model. The gas is compressible and stratified. Commensurate with the observed emitted radiation from Jupiter's atmosphere, the transport of the planet's internal energy in the lower region is taken to be convective, but solar heating is not accounted for. In qualitative agreement with observations, the model produces alternating wind bands and a dominant prograde equatorial jet. The zonal wind speed at the equator is within a factor of 2 of the observed values.
A statistical comparison of commonly used external magnetic field models
Authors: McCollough J. P. , Gannon J. L. , Baker D. N. , Gehmeyr M.
Published: October 2008

Accurate geomagnetic field models are crucial to the study of radiation belt phenomena. We quantitatively examine the accuracy of several external models widely in use via the Office National d'Etudes et de Recherche Aérospatiales‐Département Environnement Spatial (ONERA‐DESP) libraries. We study 2 years characterized by very different space weather conditions, 1996 and 2003. The year 1996, at solar minimum, exhibited many high‐speed streams and a few corotating interaction regions but was generally quiet. In contrast, 2003 included the Halloween storm, one of the most intense geomagnetic storms on record caused by a coronal mass ejection. The performance of each model, as measured by prediction efficiency and skill score, is evaluated as a function of magnetospheric conditions (reflected by the geomagnetic index Kp) and magnetic local time (MLT). Not surprisingly, the newer models tend to perform better and interesting comparisons arise between the performances of the models during different periods of the solar cycle and across different Kp and MLT values. For Kp < 4, most models show similar performance, but for higher values, there are large differences between newer and older model performance. As a function of MLT, noticeable dips in the performance of older models are observed near dawn. These dips are suspected to be effects of field‐aligned and partial ring currents that are not fully incorporated into the models, but their exact nature is unknown.
Increased Myocardial Susceptibility to Repetitive Ischemia With High‐fat diet‐induced Obesit
Authors: Thakker Geeta D. , Frangogiannis Nikolaos G. , Zymek Pawel T. , Sharma Saumya , Raya Joe L. , Barger Philip M. , Taegtmeyer Heinrich , Entman Mark L. , Ballantyne Christie M.
Published: October 2008

Obesity and diabetes are frequently associated with cardiovascular disease. When a normal heart is subjected to brief/sublethal repetitive ischemia and reperfusion (I/R), adaptive responses are activated to preserve cardiac structure and function. These responses include but are not limited to alterations in cardiac metabolism, reduced calcium responsiveness, and induction of antioxidant enzymes. In a model of ischemic cardiomyopathy inducible by brief repetitive I/R, we hypothesized that dysregulation of these adaptive responses in diet‐induced obese (DIO) mice would contribute to enhanced myocardial injury. DIO C57BL/6J mice were subjected to 15 min of daily repetitive I/R while under short‐acting anesthesia, a protocol that results in the development of fibrotic cardiomyopathy. Cardiac lipids and candidate gene expression were analyzed at 3 days, and histology at 5 days of repetitive I/R. Total free fatty acids (FFAs) in the cardiac extracts of DIO mice were significantly elevated, reflecting primarily the dietary fatty acid (FA) composition. Compared with lean controls, cardiac FA oxidation (FAO) capacity of DIO mice was significantly higher, concurrent with increased expression of FA metabolism gene transcripts. Following 15 min of daily repetitive I/R for 3 or 5 days, DIO mice exhibited increased susceptibility to I/R and, in contrast to lean mice, developed microinfarction, which was associated with an exaggerated inflammatory response. Repetitive I/R in DIO mice was associated with more profound significant downregulation of FA metabolism gene transcripts and elevated FFAs and triglycerides. Maladaptive metabolic changes of FA metabolism contribute to enhanced myocardial injury in diet‐induced obesity.
Postnatal Catch‐up Growth After Fetal Protein Restriction Programs Proliferation of Rat Preadipocytes
Authors: Bol Vanesa V. , Reusens Brigitte M. , Remacle Claude A.
Published: October 2008

We studied the in vitro proliferation and differentiation of rat preadipocytes to investigate whether catch‐up growth after prenatal protein restriction may program adipose precursor cells leading to development of increased adipose tissue mass. Pregnant rat dams were fed either an isocaloric low‐protein diet (LP‐8%) or control diet (C‐20%). During lactation, in order to induce catch‐up growth, dams from LP group were fed with the C diet and litter size was reduced to four pups instead of eight. Preadipocytes were isolated from weanling male pups (28 days of age). Differentiation and proliferation were assessed across time. At late stages of preadipocyte differentiation, no difference was observed in lipid accumulation of C or LP cultures but the mRNA expression of leptin was enhanced in LP cells. At early stages of culture, a higher DNA and protein content accompanied by a higher rate of proliferation was measured in adipocytes from LP cultures. Moreover, the mRNA expression of cyclin D1 was increased in these cells whereas the expression of peroxisome proliferators‐activated receptor γ (PPARγ) and steroyl regulatory element binding protein (SREBP‐1c) was significantly reduced during early stages. The results suggest that prenatal exposure to a LP followed by rapid catch‐up growth is associated with a higher rate for proliferation in preadipocytes.
TOF‐SIMS Analysis of Lipid Accumulation in the Skeletal Muscle of ob/ob Mice
Authors: Magnusson Ylva K. , Friberg Peter , Sjövall Peter , Malm Jakob , Chen Yun
Published: October 2008

Skeletal muscle lipid accumulation is associated with several chronic metabolic disorders, including obesity, insulin resistance (IR) and type 2 diabetes. The aim of this study is to evaluate whether static imaging time‐of‐flight‐secondary‐ion mass spectrometry (TOF‐SIMS) equipped with a Bismuth‐cluster ion source can be used for studying skeletal muscle lipid accumulation associated with obesity. Mouse gastrocnemius muscle tissues in 10‐week‐old obese ob/ob (n = 8) and lean wild‐type C57/BL6 (n = 6) mice were analyzed by TOF‐SIMS. Our results showed that signal intensities of fatty acids (FAs) and diacylglycerols (DAGs) were significantly increased in skeletal muscle of the obese ob/ob mice as compared to the lean wild‐type mice. These differences were revealed through a global analytical approach, principal component analysis (PCA) of TOF‐SIMS spectra, and ion‐specific TOF‐SIMS images. Region‐of‐interest (ROI) analysis showed that FA signal intensities within the muscle cell were significantly increased in ob/ob mice. Moreover, analysis of the ratio between different FA peaks revealed changes in monounsaturated FAs (MUFAs) and polyunsaturated FAs (PUFAs), which is in agreement with previous reports on obesity. These changes in FA composition were also reflected in the ratio of different DAGs or phosphatidylcholines (PCs) that contain different FA residues. Imaging TOF‐SIMS together with PCA of TOF‐SIMS spectra is a promising tool for studying skeletal muscle lipid accumulation associated with obesity.
Improvement of rectification effects in diffuser/nozzle structures with viscoelastic fluids
Authors: Nguyen Nam-Trung , Lam Yee-Cheong , Ho Soon-Seng , Low Cassandra Lee-Ngo
Published: October 2008

This paper reports the improvement of rectification effects in diffuser/nozzle structures with viscoelastic fluids. Since rectification in a diffuser/nozzle structure with Newtonian fluids is caused by inertial effects, micropumps based on this concept require a relatively high Reynolds numbers and high pumping frequencies. In applications with relatively low Reynolds numbers, anisotropic behavior can be achieved with viscoelastic effects. In our investigations, a solution of dilute polyethylene oxide was used as the viscoelastic fluid. A microfluidic device was fabricated in silicon using deep reactive ion etching. The microfluidic device consists of access ports for pressure measurement, and a series of ten diffuser/nozzle structures. Measurements were carried out for diffuser/nozzle structures with opening angles ranging from 15° to 60°. Flow visualization, pressure drop and diodicity of de-ionized water and the viscoelastic fluid were compared and discussed. The improvement of diodicity promises a simple pumping concept at low Reynolds numbers for lab-on-a-chip applications.
Transient ordering in a quasi-two-dimensional binary liquid near freezing
Authors: Sheu Alice Shu-Yao , Rice Stuart A.
Published: October 2008

We report the results of a theoretical study of locally ordered fluctuations in a quasi-two-dimensional (quasi-2D) binary hard sphere mixture as monitored by the aperture cross-correlation function. Systems with thickness less than two large hard sphere diameters were studied, over a range of large hard sphere density and relative concentration of large and small hard spheres in the liquid state, for two ratios of sphere diameters, 0.2 and 0.3. In several major respects the occurrence and character of the structured fluctuations in a quasi-2D binary hard sphere mixture have similarities with those in a quasi-2D one-component hard sphere fluid, as reported by Sheu and Rice [J. Chem. Phys. 128, 244517 (2008)]. Specifically, our studies establish that structured fluctuations with both hexagonal and square symmetries can be found in the liquid phase well below the freezing density and that the occurrence of particular structured fluctuations is correlated with the symmetry of the solid to which the liquid freezes. However, there is also a major difference, specifically, the presence of the smaller spheres in the binary mixture can suppress the occurrence of all structured fluctuations. We attribute the affect of a small volume fraction of small spheres in a dense binary mixture of small and large spheres on the occurrence of structured fluctuations to the unfavorable entropy change associated with demixing of the small and large spheres.
Excitation of lower hybrid waves by a spiraling ion beam in a magnetized dusty plasma cylinder
Authors: Sharma Suresh C. , Walia Ritu
Published: October 2008

A spiraling ion beam propagating through a magnetized dusty plasma cylinder drives electrostatic lower hybrid waves to instability via cyclotron interaction. Numerical calculations of the growth rate and unstable mode frequencies have been carried out for the Princeton Q-1 device using the experimental dusty plasma parameters [e.g., Barkan et al., Planet. Space Sci. 43, 905 (1995)]. It is found that as the density ratio δ(=nio∕neo, where ni0 is the ion plasma density and ne0 is the electron density) of negatively charged dust grains to electrons increases, the unstable mode frequency of the lower hybrid waves increases. In addition, the growth rate of the instability also increases with the density ratio δ. In other words, the presence of negatively charged dust grains can further destabilize the lower hybrid wave instability. The growth rate has the largest value for the modes where Jl(pnro) is maximum [here pn=xn∕r0, where pn is the perpendicular wave number in cm−1, r0 is the plasma radius, and xn are the zeros of the Bessel function J1(x)] i.e., whose eigenfunctions peak at the location of the beam. The growth rate scales as one third power of the beam current.
An improved variational approach to off-diagonal exciton-phonon coupling
Authors: Zhao Yang , Li Guangqi , Sun Jin , Wang Weihua
Published: October 2008

A state-of-the-art variational wave function incorporating Jastrow-type exciton-phonon correlations, the global-local Ansatz, is utilized to elucidate exciton-phonon correlations in a generalized form of the Holstein Hamiltonian with the simultaneous presence of diagonal and off-diagonal exciton-phonon coupling. Much lowered ground-state energies are found for the global-local Ansatz when compared with the previously studied Toyozawa Ansatz. A three-dimensional phase diagram spanned by the transfer integral and two forms of exciton-phonon coupling is given to illustrate polaronic self-trapping near the zone center.
Development and calibration of a Thomson parabola with microchannel plate for the detection of laser-accelerated MeV ions
Authors: Harres K. , Schollmeier M. , Brambrink E. , Audebert P. , Blažević A. , Flippo K. , Gautier D. C. , Geißel M. , Hegelich B. M. , Nürnberg F. , Schreiber J. , Wahl H. , Roth M.
Published: October 2008

This article reports on the development and application of a Thomson parabola (TP) equipped with a (90×70) mm2 microchannel-plate (MCP) for the analysis of laser-accelerated ions, produced by a high-energy, high-intensity laser system. The MCP allows an online measurement of the produced ions in every single laser shot. An electromagnet instead of permanent magnets is used that allows the tuning of the magnetic field to adapt the field strength to the analyzed ion species and energy. We describe recent experiments at the 100 TW laser facility at the Laboratoire d’Utilization des Lasers Intenses (LULI) in Palaiseau, France, where we have observed multiple ion species and charge states with ions accelerated up to 5 MeV/u (O+6), emitted from the rear surface of a laser-irradiated 50 μm Au foil. Within the experiment the TP was calibrated for protons and for the first time conversion efficiencies of MeV protons (2–13 MeV) to primary electrons (electrons immediately generated by an ion impact onto a surface) in the MCP are presented.
A fifth force farce
Authors: Krauss Lawrence M.
Published: October 2008

A decade before Alan Sokal’s famous hoax was published in Social Text, a thinly veiled spoof was submitted to Physical Review Letters. But in that case the editors gave as good as they got.