bluuebunny/crossref_metadata_2025 huggingface dataset:
Political Survival Strategies: Political Career Decisions in the Brazilian Chamber of Deputies
Authors: LEONI EDUARDO , PEREIRA CARLOS , RENNÓ LÚCIO
Published: March 2004

As Brazilian federal deputies approach the end of their legislative terms, they have four major political career options: to retire from electoral politics; to run for state legislative office (regressive ambition); to run for re-election (static ambition); or to run for higher offices (progressive ambition). We developed a model that focuses on the determinants of political career choices by incumbent federal deputies in the 1998 Brazilian election. We argue that it is not the nature of political ambition that determines the career choices of federal deputies, but the evaluation of the risks and costs. A nested logit regression was used to estimate the impact of the distinct political strategies used by incumbents during their terms and their previous electoral campaigns in their choices of career. The main findings suggest that an incumbent's career choice is decisively influenced by the strategies they adopt to effectively use their resources.
Edmundo O'Gorman, Mexican National History and the ‘Great American Dichotomy’
Authors: HALE CHARLES A.
Published: March 2004

Over a period of half a century, from the 1940s to the 1990s, Edmundo O'Gorman came to occupy a unique place in Mexican historiography. Though he might be considered as quasi-aristocratic in his thought and in his bearing, he spent his entire career as teacher and scholar at the popular Universidad Nacional Autónoma de México (UNAM), not at the more elitist El Colegio de México. Unlike Daniel Cosío Villegas, with whom he is often paired as the leading Mexican historians of their generation, he was not politically engaged, nor was he a ‘cultural caudillo’; he appeared to shun the attractions of academic administration and power. He was, however, an avid intellectual organiser and provocateur, who relished debate and welcomed polemical interchanges with colleagues at home and abroad.
Perceptual similarity in loanword adaptation: English postvocalic word-final stops in Korean
Authors: Kang Yoonjung
Published: March 2004

When an English word with a postvocalic word-final stop is adapted to Korean, a vowel is variably inserted after the final stop. Vowel insertion in this position is puzzling not only because of its variability but also because of the fact that it is not motivated by the native phonology in any obvious way. After providing a thorough description of the vowel-insertion pattern on the basis of a survey of a large body of data, the paper proposes that vowel insertion is motivated to improve the perceptual similarity between the English input and the Korean output as well as to obey a morphophonemic restriction in Korean. The paper provides strong evidence that non-contrastive phonetic details of lending or borrowing languages are relevant in the process of loanword adaptation and at the same time suggests a richer view of loanword phonology, one which involves interaction of phonetic, phonemic and morphophonemic factors.
The kinetic shell model of coronal heating and acceleration by ion cyclotron waves: 3. The proton halo and dispersive waves
Authors: Isenberg Philip A.
Published: March 2004

The kinetic shell model seeks to test the collisionless kinetic response of coronal hole protons to the quasi‐linear resonant cyclotron dissipation of outwardly directed, parallel propagating ion cyclotron waves, which is often invoked as the mechanism responsible for generating the fast solar wind. In this model, we make the approximation that the resonant cyclotron interaction proceeds much faster than any other process affecting the protons, so that the resonant portions of the distribution are maintained in a state of marginal stability with respect to this interaction. Under this approximation, the resonant protons are organized on nested shells of constant density in velocity space, defined by the condition that the proton energy is conserved in the rest frame moving with the phase speed of the resonant wave. These shells then evolve on the slower nonresonant timescale, responding to the shell‐averaged forces of gravity, charge‐separation electric field, mirror force, and an inertial force due to the fact that the waves are propagating in the accelerating plasma frame. Since these kinetic shell distributions are held in a marginally stable state, they cannot exchange any more energy with the waves than that taken to maintain that state. Thus their evolution corresponds to the effect of the maximum possible dissipation of outward propagating waves. Our earlier work was simplified in two major respects: we considered only dispersionless waves and we assumed that all the antisunward protons were resonantly interacting with self‐generated inward propagating waves. In this paper, we first present an improved treatment of the antisunward protons which yields more plausible speeds and temperatures than obtained previously. We then incorporate the effects of ion cyclotron dispersion into the model. Dispersion creates resonant shells which are broader in υ∥ than our previous dispersionless distributions. We find that the nonresonant forces acting on these dispersive shell distributions invariably produce only weak acceleration and result in perpendicular cooling rather than the heating that is generally required for fast solar wind speeds. These effects are attributed to the weaker inertial force on the sunward dispersive shells and are essentially independent of the behavior of the antisunward particles. Since these results correspond to the maximum possible dissipation by this mechanism, we conclude that the heating of coronal hole protons and the generation of the fast solar wind are not caused by the collisionless dissipation of parallel propagating ion cyclotron waves.
Boundary mixing in a small stratified lake
Authors: Hondzo Miki , Haider Ziaul
Published: March 2004

Field measurements in a small stratified lake were conducted to investigate the existence of a turbulent benthic boundary layer on a uniform sloping boundary. High levels of energy dissipation at the sloping boundaries indicate energy is drained from the internal waves so that turbulent fluxes are driven above these boundaries. Although the transitional value of the turbulent Reynolds number of Ret > 15 has been used to assess the capacity of stratified flow to sustain turbulent fluxes, the laboratory and field data presented in this study reveal turbulence activity in the range of Ret > 1. A scaling analysis indicates the turbulent boundary layer thickness depends on four parameters: the dissipation of turbulent kinetic energy, the strength of stratification, the length of the sloping boundary, and the angle of inclination of the sloping boundary. A proposed model of the boundary layer thickness is in good agreement with the laboratory and field measurements.
Physical supply of nitrogen to phytoplankton in the Atlantic Ocean
Authors: Mahaffey Claire , Williams Richard G. , Wolff George A. , Anderson William T.
Published: March 2004

Mechanisms supplying nitrogen (N) to phytoplankton, and thus constraining the levels of export production, over the oligotrophic subtropical Atlantic are assessed along a meridional transect. Stable nitrogen isotope signals reveal a localized region of N2 fixation over the northern subtropical gyre. Elsewhere, particulate organic nitrogen was isotopically enriched and there was no widespread evidence of a trophic bias. Thus phytoplankton are utilizing an enriched source of N along the transect through much of the oligotrophic Atlantic, which may reflect utilization of nitrate from the deep ocean or, possibly, a supply of dissolved organic nitrogen (DON) from a non‐N2 fixing source. While there is a significant supply of DON over the subtropical gyres, reaching 0.15 mol Nm−2 yr−1, less than 10% of the DON is semilabile and thus only implies a relatively small contribution to the nitrogen supply required for export production. Over the central part of the subtropical gyres, the supply of N to phytoplankton is probably from nitrate in the underlying thermocline, possibly from convection and diapycnic transfer, or more likely, from finescale upwelling by mesoscale eddies and frontal circulations. The lateral supply of dissolved organic phosphorus (DOP) appears to be a factor of 2–3 times more important than the lateral supply of semilabile DON, and thus might play a role in contributing to the phosphorus (P) supply for phytoplankton. The lateral supply of DON and DOP might also be important in closing the N and P budgets over the North Atlantic.
Long‐term trends in tropospheric ozone over the Indian tropical region
Authors: Saraf N. , Beig G.
Published: March 2004

We report a statistical regression model analysis of long‐term linear trends in the ozonesonde vertical profiles in the troposphere for the period 1972–2001 from the three tropical stations in tropical India. An analysis of tropospheric column ozone (TCO) data derived from ozonesonde and Nimbus7/Earth Probe ‐total ozone mapping spectrometer (TOMS) during the period 1979–2002 has also been done. There are no statistically significant trends over Trivandrum (8.3°N, 76.6°E, 61 m) but significant positive trend (within 2‐sigma error) are found to occur in the lower troposphere over Pune (18.3°N, 73.5°E, 559 m) and throughout the entire troposphere over a heavily air‐polluted urban center Delhi (28.4°N, 77.1°E, 216 m). However, over the last decade, variations in tropospheric ozone have become statistically insignificant even over Delhi in spite of increasing surface NOx concentrations. The TCO obtained by ozonesonde as well as TOMS satellite data over Trivandrum do not reveal any statistically significant trend.
Size and spatial distributions of fault populations: Empirically synthesized evolution laws for the fractal geometries
Authors: Goto Kazuhisa , Otsuki Kenshiro
Published: March 2004

We performed fractal analysis for 10 fault populations that are developed in continuous outcrops of Neogene sedimentary rocks. A transect line was set with reference to the principal stress axes, and the position and displacement of all faults that intersect the transect line were measured precisely. We found that both the fractal dimension of the size (net slip) frequency and that of the spatial distribution of fault displacements are determined by only two parameters: an input energy density and a dissipative energy density. These two kinds of fractal dimension evolve (decrease) as the ratio of the input energy to the dissipative energy increases, and are tied by a universal equation.
Multiple equilibrium states and the abrupt transitions in a dynamical system of soil water interacting with vegetation
Authors: Zeng Xiaodong , Shen Samuel S. P. , Zeng Xubin , Dickinson Robert E.
Published: March 2004

In semi‐arid areas, multiple equilibrium states of an ecosystem (e.g., grassland and desert) are found to coexist, and the transition from grassland to desert is often abrupt at the boundary. A simple ecosystem model is developed to provide the biophysical explanation of this phenomenon. The model has three variables: living biomass, wilted biomass, and soil wetness. The moisture index, which is the ratio of the annual precipitation to potential evaporation, is the only external climate driving force, and the key mechanism is the vegetation‐soil interaction. It is found that the maintenance of a grassland requires a minimum moisture index, and the abrupt transition occurs when the moisture index is around this critical value. These results are robust within a wide range for most model parameters, suggesting that the model may be applicable to other temperate grasslands. The characteristics of the wilted biomass also strongly influence the ecosystem's dynamics.
An alternative explanation for the “Buried Channels” on Mars: The gravity signal from a sharp boundary on partially compensated, long‐wavelength topography
Authors: Dombard Andrew J. , Searls Mindi L. , Phillips Roger J.
Published: March 2004

A trough observed in the free‐air gravity of Mars along the edge of Tempe Terra has been interpreted as a large channel that has been completely buried by sediments. Here, we show that this trough is likely real and not a product of ringing in a truncated harmonic expansion, but that it is poorly resolved. A detailed examination of the high‐resolution topographic data displays no evidence for a buried channel, instead showing that the trough straddles the highlands‐lowlands boundary. As an alternative, we propose this gravity trough in a large way arises from the surface topography, due to an effect that occurs when there exists a relatively sharp boundary on a long‐wavelength, partially compensated feature.
Simultaneous remote sensing and in situ observations of plasmaspheric drainage plumes
Authors: Goldstein J. , Sandel B. R. , Thomsen M. F. , Spasojević M. , Reiff P. H.
Published: March 2004

Plasmaspheric drainage plumes are regions of dense plasma that extend outward from the plasmasphere into the outer magnetosphere. We present observations of plumes for two events, 2 June 2001 and 26–27 June 2000. Our observations come from two sources. A global perspective is provided by the IMAGE extreme ultraviolet (EUV) imager, which routinely obtains images of the helium portion of the plasmasphere above total densities of 30–50 e− cm−3. Simultaneous in situ observations of plasmaspheric plumes are obtained by the Magnetospheric Plasma Analyzer (MPA) instruments onboard the Los Alamos National Laboratory (LANL) geosynchronous satellites. The in situ measurements of LANL MPA and the remote sensing images of IMAGE EUV are complementary data sets that together provide a more complete picture than either alone. The MPA instruments measure density far below the EUV effective density threshold with greater spatial resolution and often see plasma outside the EUV field of view. Flow speeds are also measurable by MPA. EUV images place the single‐point measurements in a global dynamical context and allow separation of spatial and temporal effects. For the 2 June 2001 and 26–27 June 2000 events, both local and global measurements showed the same location, shape and temporal development of the plume(s), and a density distribution obtained from the EUV image at 0305 UT on 2 June agrees with the LANL MPA density recorded at that time. Analysis of MPA flow data verifies that plume plasma moves sunward, as expected. Sunward flow speeds weaken with decreasing disturbance level, and duskside flow speeds may be increased by the subauroral polarization stream. The fine‐scale density variations within plumes may be caused by a highly structured inner magnetospheric E‐field and/or may be existing plasma structure that is carried sunward. The good agreement between the local and global measurements also validates the EUV image mapping method and promises to help quantify EUV images in terms of number density.
Pathways of Pacific water across the Chukchi Sea: A numerical model study
Authors: Winsor Peter , Chapman David C.
Published: March 2004

Pathways of Pacific Water flowing from the North Pacific Ocean through Bering Strait and across the Chukchi Sea are investigated using a two‐dimensional barotropic model. In the no‐wind case, the flow is driven only by a prescribed steady northward flow of 0.8 Sv through Bering Strait. The resulting steady state circulation consists of a broad northeasterly flow, basically following the topography, with a few areas of intensified currents. About half of the inflow travels northwest through Hope Valley, while the other half turns somewhat toward the northeast along the Alaskan coast. The flow through Hope Valley is intensified as it passes through Herald Canyon, but much of this flow escapes the canyon to move eastward, joining the flow in the broad valley between Herald and Hanna Shoals, another area of slightly intensified currents. There is a confluence of nearly all of the flow along the Alaskan coast west of Pt. Barrow to create a very strong and narrow coastal jet that follows the shelf topography eastward onto the Beaufort shelf. Thus in this no‐wind case, nearly all of the Pacific Water entering the Chukchi Sea eventually ends up flowing eastward along the narrow Beaufort shelf, with no discernable flow across the shelf edge toward the interior Canada Basin. Travel times for water parcels to move from Bering Strait to Pt. Barrow vary tremendously according to the path taken; e.g., less than 6 months along the Alaskan coast, but about 30 months along the westernmost path through Herald Canyon. This flow field is relatively insensitive to idealized wind‐forcing when the winds are from the south, west or north, in which cases the shelf transports tend to be intensified. However, strong northeasterly to easterly winds are able to completely reverse the flows along the Beaufort shelf and the Alaskan coast, and force most of the throughflow in a more northerly direction across the Chukchi Sea shelf edge, potentially supplying the surface waters of the interior Canada Basin with Pacific Water. The entire shelf circulation reacts promptly to changing wind conditions, with a response time of ∼2–3 days. The intense coastal jet between Icy Cape and Pt. Barrow implies that dense water formed here from winter coastal polynyas may be quickly swept away along the coast. In contrast, there is a relatively quiet nearshore region to the west, between Cape Lisburne and Icy Cape, where dense water may accumulate much longer and continue to become denser before it is carried across the shelf.
How nonlinearities in the equation of state of seawater can confound estimates of steric sea level change
Authors: Gille Sarah T.
Published: March 2004

The process of mixing water masses that have differing temperatures, salinities, and pressures creates water that is typically denser than the average density of the source waters. Thus mixing the ocean, either along isopycnals or vertically, tends to decrease global sea level, even when no heat or salt is added to the ocean. This effect is small in the global ocean, but regional effects can be substantial. Two recommendations emerge from this study. First, numerical predictions of steric sea level rise should be designed to minimize sensitivity to erroneous isopycnal or vertical/diapycnal mixing rates that might over or under mix water masses. Second, retrospective analyses of steric sea level rise in historic data should avoid using gridded temperature and salinity fields to compute steric sea level change, since mapping smooths data in the same way that mixing does.
Methyl bromide in preindustrial air: Measurements from an Antarctic ice core
Authors: Saltzman Eric S. , Aydin Murat , De Bruyn Warren J. , King Daniel B. , Yvon‐Lewis Shari A.
Published: March 2004

This paper presents the first ice core measurements of methyl bromide (CH3Br). Samples from a shallow Antarctic ice core (Siple Dome, West Antarctica), ranging in mean gas dates from 1671 to 1942, had a mean CH3Br mixing ratio of 5.8 ppt. These results extend the existing historical record derived from air and Antarctic firn air to about 350 years before present. Model simulations illustrate that the ice core results are consistent with estimates of the impact of anthropogenic activity (fumigation, combustion, and biomass burning) on the atmospheric CH3Br burden, given the large current uncertainties in the modern atmospheric CH3Br budget. A preindustrial scenario assuming no fumigation, no combustion, and a 75% reduction in biomass‐burning sources yields a Southern Hemisphere mean mixing ratio of 5.8 ppt, in good agreement with the ice core results. There is a significant imbalance between the known CH3Br sources and sinks in the modern atmospheric CH3Br budget. The ice core data do not sufficiently constrain the model to determine how much of the “unknown source” was present in the preindustrial budget. The results do indicate that most of the southern hemispheric component of this “unknown source” is not anthropogenic.
Automatic cloud amount detection by surface longwave downward radiation measurements
Authors: Dürr Bruno , Philipona R.
Published: March 2004

Naked‐eye observation of sky cloud cover has widely resisted automation. Automatic cloud cover detection systems suitable also for nighttime operation often demand large equipment investments and expensive data processing. An automatic partial cloud amount detection algorithm (APCADA) is presented, based only on accurate measurements of longwave downward radiation, temperature, and relative humidity at screen level height. APCADA provides cloud cover estimates every 10 min during daytime and nighttime and is applicable to radiation stations without knowledge of synoptic cloud observations. Naked‐eye observations from seven radiation sites spanning from arctic to tropical climates have been compared to APCADA estimates. Results show that about 86% of all cases agree within ±1‐octa cloud amount difference for sites with moderate climate, 82% for sites with arctic climate, and 78% for the site with tropical climate. For a maximum ±2‐octa cloud amount difference, average site percentages range from 90% up to 95%.
Admittance survey of type 1 coronae on Venus
Authors: Hoogenboom Trudi , Smrekar Suzanne E. , Anderson F. Scott , Houseman Greg
Published: March 2004

In this study, we analyze Magellan gravity and topography data for Type 1 coronae on Venus to estimate crustal thickness (Zc), elastic thickness (Te), and apparent depth of compensation (ZL). We examine the free‐air admittance for all 103 Type 1 coronae (defined as having greater than 50% complete fracture annuli) that are resolved in the gravity data. A spatio‐spectral method is used to calculate a localized admittance signature of each corona from a global admittance map. This method extracts spectral information from a region in space whose area is varied as a function of degree to make it large enough to yield robust results at every individual wavelength. Elastic flexure models with either bottom‐ or top‐loading compensation are used to fit the data. The estimated lithospheric flexural parameters span the range obtained for other topographic features on Venus, suggesting that the lithosphere on which coronae form is variable. We find no significant difference in lithospheric properties between Type 1 and 2 coronae. Fifty‐four percent of all coronae are consistent with local isostasy, which may indicate that they are no longer active. Very few coronae with dome or plateau morphologies have a bottom‐loading signature or the small Te and large ZL expected if a mantle plume were present. Approximately 71% have ZL estimates less than 70 km, indicating that compensation probably occurs within the crustal layer. We find no systematic relationship between Te or Zc and corona diameter, as would be expected for the spreading‐drop model of formation.
Volumetric MLFMA formulation for dielectric targets in the presence of a half‐space
Authors: Dong Xiaolong , Liu Zhijun , Carin Lawrence
Published: March 2004

The fast multipole method (FMM) and the multilevel fast multipole algorithm (MLFMA) are extended to the analysis of volumetric electric field integral equations (VEFIE) for targets in the presence of a half‐space, to calculate the electromagnetic fields scattered from dielectric scatterers situated above or within a half‐space environment. The “near” interactions are handled via rigorous evaluation of the dyadic Green's functions, by using the discrete complex image technique (DCIT); the “far” interactions are calculated by considering image source elements and groups. Numerical results are presented for comparisons between the VEFIE and surface combined‐field integral equation (SCFIE) MLFMA formulations.
Economic values for conjunctive use and water banking in southern California
Authors: Pulido‐Velazquez Manuel , Jenkins Marion W. , Lund Jay R.
Published: March 2004

The potential and limitations of conjunctive use of surface and groundwater are explored for southern California's water supply system. An economic‐engineering network flow optimization model, CALVIN, is used to analyze the economic and reliability benefits from different conjunctive use alternatives. Flexible management of additional conjunctive use facilities and groundwater storage capacity under flexible water allocation can generate substantial economic benefits to the region. Conjunctive use adds operational flexibility to take better advantage of water market transfers, and transfers provide the allocation flexibility to take better advantage of conjunctive use. The value of conjunctive use programs along the Colorado River Aqueduct, in Coachella Valley, and north of the Tehachapi Mountains under economically optimized operation of the system is examined. Results reveal reductions of economic demand for increased imports into southern California, suggest changes in the system operations, and indicate significant economic benefits from expanding some conveyance and storage facilities.
Spontaneous switching of permeability changes in a limestone fracture with net dissolution
Authors: Polak Amir , Elsworth Derek , Liu Jishan , Grader Abraham S.
Published: March 2004

Results are reported for water flow‐through experiments conducted on an artificial fracture in limestone at room temperature and under ambient confining stress of 3.5 MPa. Tests are concurrently monitored for mineral mass loss or gain and for changes in differential pressure between the inlet and outlet, throughout the 1500‐hour duration of the experiment. Periodic imaging by X‐ray computed tomography augments the fluid and mineral mass balance data and provides a third independent constraint on dissolution processes. The sample is sequentially circulated by water of two different compositions through the 1500‐hour duration of the experiment, the first 935 hours by sampled groundwater (pH ≈ 8), followed by 555 hours of distilled water (pH ≈ 6). Large changes in the differential pressure are recorded throughout the experiment, for the constant flow rate of 2 cm2/m; these are used as a proxy for recorded changes in fracture permeability, under invariant effective stress conditions. Mass of Ca and Mg were net‐removed throughout the experiment. During the initial circulation of groundwater, the differential pressure increased almost threefold and is interpreted as a net reduction in permeability as the contacting asperities across the fracture are removed and the fracture closes. With the circulation of distilled water, permeability initially reduced threefold and ultimately increased by 2 orders of magnitude as a “wormhole” developed in the sample. This spontaneous switch from net decrease in permeability to net increase occurred with no change in experimental conditions of flow rate or applied effective stress, and Ca was net dissolved throughout. This behavior is attributed to the evolving localization of mass removal, triggered as free‐face dissolution outcompetes stress‐mediated dissolution at the asperity contacts.
The Psychology of Worldviews
Authors: Koltko-Rivera Mark E.
Published: March 2004

A worldview (or “world view”) is a set of assumptions about physical and social reality that may have powerful effects on cognition and behavior. Lacking a comprehensive model or formal theory up to now, the construct has been underused. This article advances theory by addressing these gaps. Worldview is defined. Major approaches to worldview are critically reviewed. Lines of evidence are described regarding worldview as a justifiable construct in psychology. Worldviews are distinguished from schemas. A collated model of a worldview's component dimensions is described. An integrated theory of worldview function is outlined, relating worldview to personality traits, motivation, affect, cognition, behavior, and culture. A worldview research agenda is outlined for personality and social psychology (including positive and peace psychology).
Alu insertion polymorphisms in the Balkans and the origins of the Aromuns
Authors: Comas D. , Schmid H. , Braeuer S. , Flaiz C. , Busquets A. , Calafell F. , Bertranpetit J. , Scheil H.‐G. , Huckenbeck W. , Efremovska L. , Schmidt H.
Published: March 2004

We have analysed 11 human‐specific Alu insertion polymorphisms in the Balkans to elucidate the origins of the Aromuns, a linguistic isolate inhabiting scattered areas in the Balkan Peninsula. Four Aromun samples (two from the Republic of Macedonia, one from Albania, and one from Romania) and five neighbouring populations (Macedonians, Albanians, Romanians, Greeks, and Turks) were analysed by means of genetic distances, principal components and analyses of the molecular variance (AMOVA). Three hypotheses were tested: Aromuns are Romanophonic Greeks; the result of a Romanian southward migration; or local descendants of the Thracians. The analyses show that the Aromuns do not constitute a homogeneous group separated from the rest of the Balkan populations. Grouping by language or geography does not explain the genetic differences observed in the region, suggesting a lack of genetic structure in the area. Aromuns do not seem to be particularly related to Greeks, Romanians, or to other Romance speakers. The Aromuns might have their origin to the south of the Danube river, with extensive gene flow with the neighbouring populations. The present results suggest a common ancestry of all Balkan populations, including Aromuns, with a lack of correlation between genetic differentiation and language or ethnicity, stressing that no major migration barriers have existed in the making of the complex Balkan human puzzle.
Admixture in the Hispanics of the San Luis Valley, Colorado, and its implications for complex trait gene mapping
Authors: Bonilla C. , Parra E. J. , Pfaff C. L. , Dios S. , Marshall J. A. , Hamman R. F. , Ferrell R. E. , Hoggart C. L. , McKeigue P. M. , Shriver M. D.
Published: March 2004

Hispanic populations are a valuable resource that can and should facilitate the identification of complex trait genes by means of admixture mapping (AM). In this paper we focus on a particular Hispanic population living in the San Luis Valley (SLV) in Southern Colorado.We used a set of 22 Ancestry Informative Markers (AIMs) to describe the admixture process and dynamics in this population. AIMs are defined as genetic markers that exhibit allele frequency differences between parental populations ≥30%, and are more informative for studying admixed populations than random markers. The ancestral proportions of the SLV Hispanic population are estimated as 62.7 ± 2.1% European, 34.1 ± 1.9% Native American and 3.2 ± 1.5% West African. We also estimated the ancestral proportions of individuals using these AIMs. Population structure was demonstrated by the excess association of unlinked markers, the correlation between estimates of admixture based on unlinked marker sets, and by a highly significant correlation between individual Native American ancestry and skin pigmentation (R2= 0.082, p < 0.001). We discuss the implications of these findings in disease gene mapping efforts.
A Multiwavelength Study of CC Eridani
Authors: Slee O. B. , Budding E. , Carter B. D. , Mengel M. W. , Waite I. , Donati J.-F.
Published: March 2004

Radio and optical observations from December 2001 and January 2002 of the active RS CVn-like binary CC Eri are presented. The star was monitored at 4.80 and 8.64 GHz over 3 × 12 h allocations with the Australia Telescope Compact Array on 28 to 30 December 2001. The Anglo-Australian Telescope was used for simultaneous optical spectropolarimetry during a 0.5 h period on 30 December. Data from four nights of broadband photometry gathered around the same period are also included in this present multiwavelength study.

The low levels of radio emission were circularly polarised at ∼20% with slightly positive spectral indices of ∼0.26. Two flare-like increases were observed on successive nights with steep positive spectral indices and no detectable polarisation. Cross-correlation analysis of the 4.80 and 8.64 GHz intensities over the stronger flare showed that the higher frequency emission preceded that at the lower frequency by ∼5 min, a result consistent with the propagation of a hydromagnetic disturbance outwards through the corona. On the same night, a significant cross-correlation in the ‘quiescent’ emission indicates the presence of micro-flaring, although its low intensity does not permit the evaluation of a time delay. The emission parameters on the three nights are compatible with a gyrosyncrotron mechanism, in which the radio source becomes optically thick during strong flaring. We develop a simple model, which is based on assuming that the number of radiating electrons is a given function of the magnetic field in the source region, and derive feasible values for the field, source radius, and number of emitting electrons, which are not strongly dependent on the field modelling function or the aspect ratio of the source. Spectropolarimetry demonstrates the presence of a strong surface magnetic field. Optical photometry, covering a sufficient amount of the orbit, indicates a maculation region of significant size (∼14° radius).

The results help develop a three-dimensional picture of a large stellar magnetically active region and encourage more detailed follow-up multiwavelength studies of this and similar stars.
Spontaneous nucleotide exchange in low molecular weight GTPases by fluorescently labeled γ-phosphate-linked GTP analogs
Authors: Korlach Jonas , Baird Daniel W. , Heikal Ahmed A. , Gee Kyle R. , Hoffman Gregory R. , Webb Watt W.
Published: March 2004

Regulated guanosine nucleotide exchange and hydrolysis constitute the fundamental activities of low molecular weight GTPases. We show that three guanosine 5′-triphosphate analogs with BODIPY fluorophores coupled via the gamma phosphate bind to the GTPases Cdc42, Rac1, RhoA, and Ras and displace guanosine 5′-diphosphate with high intrinsic exchange rates in the presence of Mg
2+
ions, thereby acting as synthetic, low molecular weight guanine nucleotide exchange factors. The accompanying large fluorescence enhancements (as high as 12-fold), caused by a reduction in guanine quenching of the environmentally sensitive BODIPY dye fluorescence on protein binding, allow for real-time monitoring of this spontaneous nucleotide exchange in the visible spectrum with high signal-to-noise ratios. Binding affinities increased with longer aliphatic linkers connecting the nucleotide and BODIPY fluorophore and were in the 10–100 nM range. Steady-state and time-resolved fluorescence spectroscopy showed an inverse relationship between linker length and fluorescence enhancement factors and differences in protein-bound fluorophore mobilities, providing optimization criteria for future applications of such compounds as efficient elicitors and reporters of nucleotide exchange. EDTA markedly enhanced nucleotide exchange, enabling rapid loading of GTPases with these probes. Differences in active site geometries, in the absence of Mg
2+
, caused qualitatively different reporting of the bound state by the different analogs. The BODIPY analogs also prevented the interaction of Cdc42 with p21 activated kinase. Together, these results validate the use of these analogs as valuable tools for studying GTPase functions and for developing potent synthetic nucleotide exchange factors for this important class of signaling molecules.
Phosphoinositide binding and phosphorylation act sequentially in the activation mechanism of ezrin
Authors: Fievet Bruno T. , Gautreau Alexis , Roy Christian , Del Maestro Laurence , Mangeat Paul , Louvard Daniel , Arpin Monique
Published: March 2004

Ezrin, a membrane–actin cytoskeleton linker, which participates in epithelial cell morphogenesis, is held inactive in the cytoplasm through an intramolecular interaction. Phosphatidylinositol 4,5-bisphosphate (PIP2) binding and the phosphorylation of threonine 567 (T567) are involved in the activation process that unmasks both membrane and actin binding sites. Here, we demonstrate that ezrin binding to PIP2, through its NH2-terminal domain, is required for T567 phosphorylation and thus for the conformational activation of ezrin in vivo. Furthermore, we found that the T567D mutation mimicking T567 phosphorylation bypasses the need for PIP2 binding for unmasking both membrane and actin binding sites. However, PIP2 binding and T567 phosphorylation are both necessary for the correct apical localization of ezrin and for its role in epithelial cell morphogenesis. These results establish that PIP2 binding and T567 phosphorylation act sequentially to allow ezrin to exert its cellular functions.
Distinct roles for ADAM10 and ADAM17 in ectodomain shedding of six EGFR ligands
Authors: Sahin Umut , Weskamp Gisela , Kelly Kristine , Zhou Hong-Ming , Higashiyama Shigeki , Peschon Jacques , Hartmann Dieter , Saftig Paul , Blobel Carl P.
Published: March 2004

All ligands of the epidermal growth factor receptor (EGFR), which has important roles in development and disease, are released from the membrane by proteases. In several instances, ectodomain release is critical for activation of EGFR ligands, highlighting the importance of identifying EGFR ligand sheddases. Here, we uncovered the sheddases for six EGFR ligands using mouse embryonic cells lacking candidate-releasing enzymes (a disintegrin and metalloprotease [ADAM] 9, 10, 12, 15, 17, and 19). ADAM10 emerged as the main sheddase of EGF and betacellulin, and ADAM17 as the major convertase of epiregulin, transforming growth factor α, amphiregulin, and heparin-binding EGF-like growth factor in these cells. Analysis of adam9/12/15/17−/− knockout mice corroborated the essential role of adam17−/− in activating the EGFR in vivo. This comprehensive evaluation of EGFR ligand shedding in a defined experimental system demonstrates that ADAMs have critical roles in releasing all EGFR ligands tested here. Identification of EGFR ligand sheddases is a crucial step toward understanding the mechanism underlying ectodomain release, and has implications for designing novel inhibitors of EGFR-dependent tumors.
Recruitment of Eph receptors into signaling clusters does not require ephrin contact
Authors: Wimmer-Kleikamp Sabine H. , Janes Peter W. , Squire Anthony , Bastiaens Philippe I.H. , Lackmann Martin
Published: March 2004

Eph receptors and their cell membrane–bound ephrin ligands regulate cell positioning and thereby establish or stabilize patterns of cellular organization. Although it is recognized that ephrin clustering is essential for Eph function, mechanisms that relay information of ephrin density into cell biological responses are poorly understood. We demonstrate by confocal time-lapse and fluorescence resonance energy transfer microscopy that within minutes of binding ephrin-A5–coated beads, EphA3 receptors assemble into large clusters. While remaining positioned around the site of ephrin contact, Eph clusters exceed the size of the interacting ephrin surface severalfold. EphA3 mutants with compromised ephrin-binding capacity, which alone are incapable of cluster formation or phosphorylation, are recruited effectively and become phosphorylated when coexpressed with a functional receptor. Our findings reveal consecutive initiation of ephrin-facilitated Eph clustering and cluster propagation, the latter of which is independent of ephrin contacts and cytosolic Eph signaling functions but involves direct Eph–Eph interactions.
Sox5 and Sox6 are needed to develop and maintain source, columnar, and hypertrophic chondrocytes in the cartilage growth plate
Authors: Smits Patrick , Dy Peter , Mitra Srijeet , Lefebvre Véronique
Published: March 2004

Sox5 and Sox6 encode Sry-related transcription factors that redundantly promote early chondroblast differentiation. Using mouse embryos with three or four null alleles of Sox5 and Sox6, we show that they are also essential and redundant in major steps of growth plate chondrocyte differentiation. Sox5 and Sox6 promote the development of a highly proliferating pool of chondroblasts between the epiphyses and metaphyses of future long bones. This pool is the likely cellular source of growth plates. Sox5 and Sox6 permit formation of growth plate columnar zones by keeping chondroblasts proliferating and by delaying chondrocyte prehypertrophy. They allow induction of chondrocyte hypertrophy and permit formation of prehypertrophic and hypertrophic zones by delaying chondrocyte terminal differentiation induced by ossification fronts. They act, at least in part, by down-regulating Ihh signaling, Fgfr3, and Runx2 and by up-regulating Bmp6. In conclusion, Sox5 and Sox6 are needed for the establishment of multilayered growth plates, and thereby for proper and timely development of endochondral bones.
Can telomerase be put in its place?
Authors: Pederson Thoru
Published: March 2004

The Cajal body is an intriguing nuclear structure present in a great variety of plant, animal, and some fungal cells. Recent work on the ribonucleoprotein enzyme telomerase has indicated an unanticipated degree of intranuclear dynamics of both its RNA and protein subunits. In this issue, Jady et al. place the Cajal body on the intranuclear traffic route of telomerase RNA (Jady et al., 2004).
A Novel Virulence Gene in Klebsiella pneumoniae Strains Causing Primary Liver Abscess and Septic Metastatic Complications
Authors: Fang Chi-Tai , Chuang Yi-Ping , Shun Chia-Tung , Chang Shan-Chwen , Wang Jin-Town
Published: March 2004

Primary Klebsiella pneumoniae liver abscess complicated with metastatic meningitis or endophthalmitis is a globally emerging infectious disease. Its pathogenic mechanism remains unclear. The bacterial virulence factors were explored by comparing clinical isolates. Differences in mucoviscosity were observed between strains that caused primary liver abscess (invasive) and those that did not (noninvasive). Hypermucoviscosity correlated with a high serum resistance and was more prevalent in invasive strains (52/53 vs. 9/52; P < 0.0001). Transposon mutagenesis identified candidate virulence genes. A novel 1.2-kb locus, magA, which encoded a 43-kD outer membrane protein, was significantly more prevalent in invasive strains (52/53 vs. 14/52; P < 0.0001). The wild-type strain produced a mucoviscous exopolysaccharide web, actively proliferated in nonimmune human serum, resisted phagocytosis, and caused liver microabscess and meningitis in mice. However, magA− mutants lost the exopolysaccharide web and became extremely serum sensitive, phagocytosis susceptible, and avirulent to mice. Virulence was restored by complementation using a magA-containing plasmid. We conclude that magA fits molecular Koch's postulates as a virulence gene. Thus, this locus can be used as a marker for the rapid diagnosis and for tracing the source of this emerging infectious disease.
NF-κB and p53 Are the Dominant Apoptosis-inducing Transcription Factors Elicited by the HIV-1 Envelope
Authors: Perfettini Jean-Luc , Roumier Thomas , Castedo Maria , Larochette Nathanael , Boya Patricia , Raynal Brigitte , Lazar Vladimir , Ciccosanti Fabiola , Nardacci Roberta , Penninger Josef , Piacentini Mauro , Kroemer Guido
Published: March 2004

The coculture of cells expressing the HIV-1 envelope glycoprotein complex (Env) with cells expressing CD4 results into cell fusion, deregulated mitosis, and subsequent cell death. Here, we show that NF-κB, p53, and AP1 are activated in Env-elicited apoptosis. The nuclear factor κB (NF-κB) super repressor had an antimitotic and antiapoptotic effect and prevented the Env-elicited phosphorylation of p53 on serine 15 and 46, as well as the activation of AP1. Transfection with dominant-negative p53 abolished apoptosis and AP1 activation. Signs of NF-κB and p53 activation were also detected in lymph node biopsies from HIV-1–infected individuals. Microarrays revealed that most (85%) of the transcriptional effects of HIV-1 Env were blocked by the p53 inhibitor pifithrin-α. Macroarrays led to the identification of several Env-elicited, p53-dependent proapoptotic transcripts, in particular Puma, a proapoptotic “BH3-only” protein from the Bcl-2 family known to activate Bax/Bak. Down modulation of Puma by antisense oligonucleotides, as well as RNA interference of Bax and Bak, prevented Env-induced apoptosis. HIV-1–infected primary lymphoblasts up-regulated Puma in vitro. Moreover, circulating CD4+ lymphocytes from untreated, HIV-1–infected donors contained enhanced amounts of Puma protein, and these elevated Puma levels dropped upon antiretroviral therapy. Altogether, these data indicate that NF-κB and p53 cooperate as the dominant proapoptotic transcription factors participating in HIV-1 infection.
Chemotaxis Inhibitory Protein of Staphylococcus aureus, a Bacterial Antiinflammatory Agent
Authors: de Haas Carla J.C. , Veldkamp Karin Ellen , Peschel Andreas , Weerkamp Floor , Van Wamel Willem J.B. , Heezius Erik C.J.M. , Poppelier Miriam J.J.G. , Van Kessel Kok P.M. , van Strijp Jos A.G.
Published: March 2004

Leukocyte migration is a key event both in host defense against invading pathogens as well as in inflammation. Bacteria generate chemoattractants primarily by excretion (formylated peptides), complement activation (C5a), and subsequently through activation of leukocytes (e.g., leukotriene B4, platelet-activating factor, and interleukin 8). Here we describe a new protein secreted by Staphylococcus aureus that specifically impairs the response of neutrophils and monocytes to formylated peptides and C5a. This chemotaxis inhibitory protein of S. aureus (CHIPS) is a 14.1-kD protein encoded on a bacteriophage and is found in >60% of clinical isolates. CHIPS reduces the neutrophil recruitment toward C5a in a mouse peritonitis model, even though its activity is much more potent on human than on mouse cells. These findings suggest a new immune escape mechanism of S. aureus and put forward CHIPS as a potential new antiinflammatory therapeutic compound.
The BCR-ABL1 Kinase Bypasses Selection for the Expression of a Pre–B Cell Receptor in Pre–B Acute Lymphoblastic Leukemia Cells
Authors: Klein Florian , Feldhahn Niklas , Harder Lana , Wang Hui , Wartenberg Maria , Hofmann Wolf-Karsten , Wernet Peter , Siebert Reiner , Müschen Markus
Published: March 2004

The BCR-ABL1 kinase expressed in acute lymphoblastic leukemia (ALL) drives malignant transformation of human pre–B cells. Comparing genome-wide gene expression profiles of BCR-ABL1+ pre–B ALL and normal bone marrow pre–B cells by serial analysis of gene expression, many genes involved in pre–B cell receptor signaling are silenced in the leukemia cells. Although normal pre–B cells are selected for the expression of a functional pre–B cell receptor, BCR-ABL1+ ALL cells mostly do not harbor a productively rearranged IGH allele. In these cases, we identified traces of secondary VH gene rearrangements, which may have rendered an initially productive VH region gene nonfunctional. Even BCR-ABL1+ ALL cells harboring a functional VH region gene are unresponsive to pre–B cell receptor engagement and exhibit autonomous oscillatory Ca2+ signaling activity. Conversely, leukemia subclones surviving inhibition of BCR-ABL1 by STI571 restore responsiveness to antigen receptor engagement and differentiate into immature B cells expressing immunoglobulin light chains. BCR-ABL1 kinase activity is linked to defective pre–B cell receptor signaling and the expression of a truncated isoform of the pre–B cell receptor–associated linker molecule SLP65. Also in primary leukemia cells, truncated SLP65 is expressed before but not after treatment of the patients with STI571. We conclude that inhibition of BCR-ABL1 reconstitutes selection for leukemia cells expressing a functional (pre–) B cell receptor.