bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronology of Lava and Associated Soils Near San Miguel, New Mexico
Authors: Gile Leland H.
Published: December 2004

A lava flow in southern New Mexico extends into the Rio Grande Valley from the lower La Mesa geomorphic surface, a relict basin floor of middle Pleistocene age. Three buried soils occur beneath the lava at its east end. In places, the lava itself is buried by a sediment in which a soil has formed. Pedogenic carbonate was used to calculate the age of this soil, using a soil of lower La Mesa as a chronological guide. Both the latter soil and the Rio Grande Valley must be less than about 620,000 yr old according to dated volcanic ash, and are estimated to be about 500,000 yr old. Based upon this age and a total of 1200 kg/m2pedogenic carbonate in the lower La Mesa soil, the carbonate accumulated at an average rate of about 2.4 kg/m2/1000 yr. Using the same rate of carbonate accumulation, the postlava soil took about 180,000 yr to form. However, not quite all of the pedogenic carbonate in this soil has been accounted for, and a general figure of 200,000 yr is suggested for its approximate age. The geological setting indicates that the age of the lava should be very close to the age of the postlava soil, and a general figure of 200,000 yr is also suggested for approximate age of the lava. This contrasts with a new K/Ar age of 490,000 ± 30,000 yr, which is considered to be too old. However, two previously obtained K/Ar ages of 232,000 ± 80,000 and 154,000 ± 119,000 yr are much closer to the estimate based on pedogenic carbonate. The landscape of the soil that buries the lava differs from the landscape of the lower La Mesa soil that was used as a chronological guide. The rate of carbonate movement into the soils could also differ, and for this reason the age obtained by pedogenic carbonate is considered tentative.
Fission-Track Ages of Tuff Layers Related to the Pliocene-Pleistocene Boundary on the Boso Peninsula, Japan
Authors: Kasuya Masao
Published: December 2004

Fission-track ages of zircon crystals from four tuff layers in the late Cenozoic sediment sequence of the Boso Peninsula,.Japan, are 1.6 ± 0.2 myr (the Kurotaki Formation), 5.5 ± 0.6 and 5.2 ± 0.5 myr (the uppermost part of the Amatsu Formation), and 11.5 ± 0.8 myr (the middle part of the Amatsu Formation). These ages provide numerical age constraints on magneto-biostratigraphy. The normal polarity interval in the lower part of the Kiwada Formation corresponds to the Olduvai polarity subzone. The boundary between the Pliocene and Pleistocene lies slightly above the Olduvai polarity subzone.
Early Holocene Pecan, Carya Illinoensis, in the Mississippi River Valley Near Muscatine, Iowa
Authors: Bettis E. Arthur , Baker Richard G. , Nations Brenda K. , Benn David W.
Published: December 2004

A fossil pecan, Carya illinoensis (Wang.) K. Koch, from floodplain sediments of the Mississippi River near Muscatine, Iowa, was accelerator-dated at 7280 ± 120 yr B.P. This discovery indicates that pecan was at or near its present northern limit by that time. Carya pollen profiles from the Mississippi River Trench indicate that hickory pollen percentages were much higher in the valley than at upland locations during the early Holocene. Pecan, the hickory with the most restricted riparian habitat, is the likely candidate for producing these peaks in Carya pollen percentages. Therefore, pecan may have reached its northern limit as early as 10,300 yr B.P. Its abundance in Early Archaic archaeological sites and the co-occurrence of early Holocene Carya pollen peaks with the arrival of the Dalton artifact complex in the Upper Mississippi Valley suggest that humans may have played a role in the early dispersal of pecan.
Oxygen Isotope Ratios from Tree Rings Containing Compression Wood
Authors: Luckman Brian , Gray John
Published: December 2004

Oxygen isotope determinations on the α-cellulose of tree rings cut from two leaning Picea engelmannii revealed significant differences between results from normal and compression wood radii. Nine samples (10-year periods) from the normal wood radius (1721–1953) in one tree showed good agreement with proxy climate information and maximum differences of 1.8‰ between the “warmest” and “coolest” decades sampled. Differences of equivalent magnitude were found between samples from the same decade from normal and compression wood radii. These differences are strongly related to the amount and/or density of compression wood present and suggest that sampling for paleoclimatic work should be restricted to complacent, erect trees without compression wood rings.
Holocene raised beaches at Terra Nova Bay, Victoria Land, Antarctica
Authors: Baroni Carlo , Orombelli Giuseppe
Published: December 2004

More than 40 14C dates for raised beaches at Terra Nova Bay ranging from the present to 7505 ± 230 yr B.P. supply minimum or maximum limiting ages that bracket a relative sea-level curve for this part of Victoria Land. Most samples consist of guano and penguin remains collected from abandoned nesting sites on beach deposits. Up to four 14C dates in stratigraphic sequence have been obtained in two soil profiles. Other samples consist of marine shells collected both within and on the surface of raised beaches. All 14C ages for organisms that lived or fed in circumantarctic waters were corrected for a large reservoir effect. The calibrated ages delimit a first relative sea-level curve for Victoria Land. Rates of uplift ranged from about 10 mm/yr following deglaciation to about 2 mm/yr in the last 3 millennia. Widespread presence of Adélie penguin nesting sites suggests that Terra Nova Bay was deglaciated before 7065 ± 250 yr B.P. (7059/6439 cal yr B.P.), when environmental conditions in the coastal area were similar to the present ones.
Holocene deltaic sequence in the Saloum estuary, Senegal
Authors: Ausseil-Badie Josiane , Barusseau J.Paul , Descamps Cyr , Salif Diop E. H. , Giresse Pierre , Pazdur Mieczyslaw
Published: December 2004

The 2250 km2 Saloum delta, south of Dakar, Senegal, consists of a Holocene sedimentary sequence deposited during five evolutionary stages: submerged postglacial ria, funnel-like estuary, barred estuary, cuspate delta, and reverse estuary. The passage from one stage to another was marked by the deposition of sedimentary units consisting of shelly sands, silty or sandy clays, and an extensive thick green mud. Muds in the lower strata, dating between 6130 and 3500 yr B.P., were deposited on a subtidal mudflat, while fine sands and silty clays characterize intertidal deposits. A drastic change in sedimentation patterns, resulting in the accumulation of a series of beach barriers, likely was associated with a major climatic change. The regional climate was then very dry, and silt and sand were trapped in the water behind the barriers in two stages, from 1990 to 1510 and 1020 to 600 yr B.P. Each event was accompanied by construction of shell middens that demonstrate the presence of humans who exploited newly available shallows and banks. Relative sea level did not change significantly between 6000 yr B.P. and the present. Morphological and sedimentological changes observed in the late Holocene sequences were apparently induced by a constraining climatic background.
Charophyte remains from Wadi Howar as evidence for deep mid-Holocene freshwater lakes in the eastern Sahara of Northwest Sudan
Authors: Kröpelin Stefan , Soulié-Märsche Ingeborg
Published: December 2004

Field research in the eastern Sahara (Northwest Sudan) revealed extensive early- to mid-Holocene lake marl deposits bearing gyrogonites of Charophytes (green algae, stoneworts) along the lower course of the Wadi Howar, an extinct tributary to the Nile. The Charophyte flora of a paleolake southwest of Jebel Rahib (17°31′N/26°52′E) dated prior to 4720 ± 110 yr B.P. is mainly composed of the ecologically sensitive speciesNitellopsis obtusawhich indicates permanent, relatively deep (4–12 m) and cool oligotrophic freshwater. The study ofNitellopsissites provides a new and promising approach to the reconstruction of Quaternary paleoenvironments of deserts.
Paleoecology of central Kentucky since the last glacial maximum
Authors: Wilkins Gary R. , Delcourt Paul A. , Delcourt Hazel R. , Harrison Frederick W. , Turner Manson R.
Published: December 2004

Pollen grains and spores, plant macrofossils, and sponge spicules from a 7.2-m sediment core from Jackson Pond dating back to 20,000 yr B.P. are the basis for new interpretations of vegetational, limnological, and climatic changes in central Kentucky. During the full-glacial interval (20,400 to 16,800 yr B.P.) upland vegetation was closed spruce forest with jack pine as a subdominant. Aquatic macrophyte and sponge assemblages indicate that the site was a relatively deep, open pond with low organic productivity. During late-glacial time (16,800 to 11,300 yr B.P.) spruce populations continued to dominate while jack pine declined and sedge increased as the vegetation became a more open, taiga-like boreal woodland. Between 11,300 and 10,000 yr B.P., abundances of spruce and oak pollen oscillated reciprocally, possibly reflecting the Younger Dryas oscillation as boreal taxa underwent a series of declines and increases at the southern limit of their ranges before becoming extirpated and replaced by deciduous forest. In the early Holocene (10,000 to 7300 yr B.P.) a mesic deciduous woodland developed; it was replaced by xeric oak-hickory forest during the middle Holocene between 7300 and 3900 yr B.P. Grass increased after 3900 yr B.P., indicating that the presettlement vegetation mosaic of mixed deciduous forest and prairie (the “Kentucky Barrens”) became established in central Kentucky after the Hypsithermal interval. Sponge spicules increased in number during the Holocene, reflecting reduced water depths in the pond. Sediment infilling, as well as climatic warming and the expansion of fringing shrub thickets, increased nutrient and habitat availability for freshwater sponges.
Paleoclimatic Significance of the Mineral Magnetic Record of the Chinese Loess and Paleosols
Authors: Maher Barbara A. , Thompson Roy
Published: December 2004

The origins of the magnetic susceptibility variations of the Chinese loess and paleosols are explored by scanning and transmission electron microscopy of magnetic extracts, and by magnetic modeling of magnetic hysteresis data, to provide quantified estimates of the major magnetic components. Microscopy identifies several distinct size and shape characteristics in the magnetic carriers. Lithogenic magnetites, intact and abraded, dominate the coarse-grained magnetic fraction. The smallest of the coarse grains is ∼ 2 μm. The remaining magnetic materal is ultrafine in size, with two types of magnetite particles present. Type A particles strongly resemble soil magnetites produced by inorganic precipitation. Type B particles, which occur rarely, are probably bacterial in origin. Quantitative modeling of these magnetic assemblages shows that over 90% of the susceptibility variations is accounted for by the superparamagnetic magnetite component. Compared to the loess units, the paleosols are richer in magnetite, particularly of superparamagnetic size, and have a threefold higher ratio of magnetite to hematite. We identify pedogenic formation of magnetite as the major contributor to the loess magnetic record. Matching this record against other paleoclimatic records, we find an extremely high correlation with the standard 18O record. The Chinese loess sequences record a very high resolution magnetic stratigraphy directly related to changing climate.
Evidence for the Dissolution of Magnetite in Recent Scottish Peats
Authors: Williams Martin
Published: December 2004

Magnetic, hydrological, and geochemical data for 11 Scottish peat cores confirm previous reports that anthropogenic pollutants constitute the principal source of ferrimagnets to such environments, but indicate that postdepositional Fe3O4persistence may be more limited than formerly envisaged. In all cores, the lower stratigraphic limit of magnetic enrichment coincides with the water table, below which negative mV values and enhanced ratios of Fe/Mn and Cu/Zn depict an abrupt transition to a strongly anoxic regime. Dissolution of Fe3O4in the reducing, inundated zone is also signified by the more rapid down-core loss of magnetic properties in cores from topographically depressed “Sphagnum lawns” than in those from more elevated “Calluna hummocks”. As a consequence, the peak and cumulative SIRM values for cores from the former settings appear disproportionately low, and the magnetostratigraphic records from adjacent, but topographically variant sites are frequently asynchronous. In contrast to most marine and lacustrine sediments, dissolution of Fe3O4in peat induces a refinement of magnetic mineral assemblages, highlighted by declining SIRM/ARM ratios with depth and a “hardening” of remanence near the base of the magnetically enhanced strata. SEM micrographs of magnetic extracts from one Scottish core indicate that this refinement results from preferential dissolution along crystallographic weaknesses within multidomain phases, ultimately causing their disintegration and the adoption of “single domain-type” magnetic behavior. Rates of dissolution are considerably greater than those reported for marine sediments, probably due to the unusually high dissolved sulfide concentrations in mire waters.
The Mount Edgecumbe Tephra Deposits, a Marker Horizon in Southeastern Alaska Near the Pleistocene-Holocene Boundary
Authors: Riehle James R. , Mann Daniel H. , Peteet Dorothy M. , Engstrom Daniel R. , Brew David A. , Meyer Charles E.
Published: December 2004

Late Pleistocene tephra deposits found from Sitka to Juneau and Lituya Bay are assigned to a source at the Mount Edgecumbe volcanic field, based on similarity of glass compositions to nearvent deposits and on thinning away from Kruzof Island. The sequence of near-vent layers is basaltic andesite and andesite at the base, rhyolite, and mixed dacite and rhyolite on top. The only breaks in the tephra sequence are two 1-mm-thick silt partings in a lake-sediment core, indicating a depositional interval from basaltic andesite to dacite of no more than about a millennium. Tephra deposits at sites >30 km from the vent are solely dacite and rhyolite and are 10,600 to 11,40014C yr old based on interpretation of 18 radiocarbon ages, including 5 by accelerator mass spectrometry (AMS). Basaltic andesite and andesite deposits nearer the vent are as much as 12,000 yr old.

Discrepancy among radiocarbon ages of upland tephra deposits provisionally correlated as the same grainfall is resolvable within ±2 σ of analytical uncertainty. Comparison of bulk and AMS ages in one sediment core indicates a systematic bias of +600 to +1100 yr for the bulk ages; correlation of tephra deposits among upland and lacustrine sites implies an additional discrepancy of 200–400 yr between upland (relatively too young) and lacustrine ages. In any case, the Mount Edgecumbe tephra deposits are a widespread, latest Pleistocene stratigraphic marker that serves to emphasize the uncertainty in dating biogenic material from southeastern Alaska.
Late Quaternary Paleotemperatures Derived from a Speleothem from Cango Caves, Cape Province, South Africa
Authors: Talma A.S. , Vogel John C.
Published: December 2004

An oxygen isotope temperature record over a large part of the past 30,000 yr has been obtained for the southern Cape Province of South Africa by combining data on the isotopic composition of a stalagmite from a deep cave with that of a confined groundwater aquifer in the same region. Results show that temperatures during the last glacial maximum were on average about 6°C lower than those today, with peaks up to 7°C lower. A detailed analysis of the past 5000 yr suggests multiple fluctuations, with generally lower temperatures (1–2°C) around 4500 and 3000 yr B.P. The carbon isotopic composition of the stalagmite indicates significant vegetation changes between the late Pleistocene and today, and also during the second half of the Holocene.
Effect of acute nerve root compression on endoneurial fluid pressure and blood flow in rat dorsal root ganglia
Authors: Igarashi Tamaki , Yabuki Shoji , Kikuchi Shinichi , Myers Robert R.
Published: December 2004

The objective of the current study was to test the hypothesis that crush injury to nerve root increases endoneurial fluid pressure (EFP) and decreases blood flow in the associated dorsal root ganglion (DRG). A total of 21 adult, female Sprague‐Dawley rats had their left L5 nerve root and DRG exposed. The L5 nerve root was clamped for 2 s with a vascular suture clip just proximal to the DRG (compression group). Sham‐operated animals without compression were used for control (control group). EFP was recorded with a servo‐null micropipette system using a glass micropipette with tip diameter of 4 μm before and after 3 h of treatment. After the final measurement of EFP, DRG was excised and processed for histology. Blood flow in the DRG was continuously monitored by laser Doppler flow meter for 3 h. Three hours after treatment, EFP was 4.7 ± 2.7 cm H2O in the compression group and 2.2 ± 1.2 cm H2O in the control group (P < 0.05). Edema was the principal pathologic findings seen consistently in the DRG from animals in the compression group. Blood flow in the compression group was reduced 10 min after compression. This reduction was statistically significant compared with that of the control (P < 0.01). An acute compression to the nerve root increased endoneurial edema, increased EFP in the associated DRG, and reduced DRG blood flow. This combination of increased EFP and decreased blood flow in the DRG may result in neuronal ischemia and sensory dysfunction. These acute pathophysiologic changes may thus have a role in the pathogenesis of low back pain and sciatica due to disc herniation and spinal canal stenosis. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Varieties of Capitalist Democracy: What Difference Does East-Central Europe Make?
Authors: McMENAMIN IAIN
Published: December 2004

The establishment of capitalist democracies in East-Central Europe raises the question of whether existing accounts of varieties of capitalist democracy need to be revised. This article provides a systematic quantitative comparison of varieties of capitalist democracy in the Czech Republic, Hungary and Poland with 19 other OECD countries. It finds that the East-Central European cases constitute a distinctive cluster; that they have much in common with Greece, Iberia and Ireland and that they are closer to the continental European than the liberal variety of capitalist democracy. These results have important implications for the internal politics of the European Union, prospects of an East-Central European repeat of the relative success of Ireland and the Mediterranean in the European Union, and debates about the influence of neo-liberalism on public policy.
What Role for Learning? The Diffusion of Privatisation in OECD and Latin American Countries
Authors: MESEGUER COVADONGA
Published: December 2004

In this paper, I enquire whether 37 governments in industrial and in Latin American countries privatised as a result of learning from experience. Using a rational updating model, I examine whether the decision in the 1980s and 1990s to streamline the public sector was the outcome of a revision of beliefs about the effectiveness of privatisation or whether, alternatively, it was triggered by international pressures or mimicry. The results suggest that rational learning and especially emulation were two important factors in the decision to privatise. International pressures, here proxied by the presence or absence of an agreement with the International Monetary Fund and by European Union membership, are irrelevant to explanations of the decision to privatise. Finally, domestic political conditions appear relevant to the decision to launch privatisation but only when the analysis is carried out for each of the regional sub-samples. In the OECD countries, centre-left governments were more likely to privatise whereas in Latin American more repressive regimes were more willing to divest.
‘Armed Attack’ after the Oil Platforms Case
Authors: RAAB DOMINIC
Published: December 2004

The International Court of Justice rendered its judgement on the merits in the case concerning Oil Platforms (Islamic Republic of Iran v. United States of America) on 6 November 2003. This article reviews the judgement, focusing on the Court's substantive legal determinations on the scope of ‘armed attack’ under the right of self-defence. The review further considers the implications of the judgement as regards the role of the Court in the judicial settlement of disputes. It concludes by considering the impact of the judgement on the legal framework for international peace and security as applied in the maritime context.
Residual currents in a semi‐enclosed bay of the Seto Inland Sea, Japan
Authors: Guo Xinyu , Futamura Akira , Takeoka Hidetaka
Published: December 2004

On the basis of the Princeton Ocean Model, a robust diagnostic model is developed to calculate the residual currents in the Hiuchi‐Nada, a semi‐enclosed bay of the Seto Inland Sea. The input water temperature and salinity data are from six hydrographic surveys in 2002, and the model results in the summer show a clockwise eddy in the western part of the bay and an anticlockwise eddy in the eastern part. The magnitude of two eddies is ∼10 cm/s. The modeled flow pattern is consistent with early observations derived from moored arrays. The two eddies are persistent throughout the summer because winds are usually weak and cannot influence their existence. The tide‐induced residual currents are appreciable only in the close vicinity of the Kurushima Strait and Bisan Strait, the two straits connecting the bay to the other bays, and have little affect on the two eddies that are inside the bay. Thus the two density‐driven eddies in the Hiuchi‐Nada are the basic pattern of circulation in the summer. Using the calculated residual currents, we examined the intrusion route of waters from the Kurushima Strait and Bisan Strait with passive tracer experiments. The results show that the water in the Kurushima Strait intrudes into the bay mainly through the middle and bottom layers while the water in the Bisan Strait intrudes mainly through the surface layer. Furthermore, the tracer cannot reach the center of the anticlockwise eddy in the eastern part of the bay. This indicates that the eddy prevents water exchange between its center and outer edges and provides favorable conditions for the formation of oxygen‐deficient waters in the central part of the eddy.
Verification of mesoscale modeling for the severe rainfall event over southern Ontario in May 2000
Authors: Cao Zuohao , Pellerin Pierre , Ritchie Harold
Published: December 2004

A coupled atmospheric‐hydrological model (CAHM) with a high‐resolution, self‐nesting and one‐way coupling capability is employed to simulate the severe rainfall event that lead to a flood in May 2000 over southern Ontario. Three verification approaches are carried out to evaluate the atmospheric mesoscale model performance. The results show that the 48‐h accumulated peak precipitation simulated by a mesoscale model successfully captures the observed peak rainfall recorded over a spatially dense rain gauge network in southern Ontario. Furthermore, the quantitative evaluation of the model predicted precipitation demonstrates that there is a systematic improvement in terms of the accuracies and skills when the model resolution is increased. In addition, an independent verification by comparing the CAHM simulated streamflow with the observed hourly streamflow shows the excellent agreement between the simulations and the observations in terms of magnitudes and timing of peak streamflows, indicating that precipitation is well simulated by the atmospheric mesoscale model.
Determining reflectivity measurement error from serial measurements using paired disdrometers and profilers
Authors: Gage Kenneth S. , Clark Wallace L. , Williams Christopher R. , Tokay Ali
Published: December 2004

Serial reflectivity measurements from paired instruments are examined during two field campaigns in order to examine the precision of the measurements. The instruments studied are two collocated Joss‐Waldvogel disdrometers (JWD) at Wallops Island, VA and two collocated profilers deployed at Ji‐Parana, Brazil during Tropical Rainfall Measuring Mission (TRMM) Large‐Scale Biosphere‐Atmosphere Experiment. Differencing the measured reflectivity from the instrument pairs eliminated most of the temporal and large‐scale precipitation variability, reducing the error fluctuations to those of the instrument precision plus fluctuations due to precipitation variability over the small differences in sample volume and distances between the instruments. For both pairs of calibrated instruments we found that the observed time‐series of one‐minute dBZ differences were not autocorrelated and exhibited a Gaussian‐like distribution. Consequently, the difference time‐series could be meaningfully characterized by their standard statistics, including the rms difference or standard deviation, and the standard error about the mean. While the disdrometer pair exhibited an rms difference of 2.1 dBZ, a standard error about the mean of less than 0.1 dBZ for the 12‐hour rain event was achieved. The profiler pair exhibited an rms difference of 0.4 dBZ, with a standard error of only 0.05 dBZ for the 90‐minute stratiform rain event. Since it is currently difficult to routinely calibrate radars in an absolute sense to better than 1–3 dBZ, the precisions of a few tenths of a dBZ obtained here suggest the potential for substantially improving these calibrations, and open the door to examination of subtle sampling and stability effects.
Galileo stereo topography of the lunar north polar region
Authors: Schenk Paul M. , Bussey D. Ben J.
Published: December 2004

Estimates of the elevation of the lunar polar regions are uncertain to a few km. Galileo stereo images of the north polar region were used to derive a new topographic map, partially filling the gap in Clementine LIDAR topography northward of 80°, and providing an independent constraint on lunar polar topography and solar illumination. Our Galileo elevation model has an estimated vertical precision of ∼200 m, and a measurement footprint of ∼9 km. These new data show that the north polar region (frontside) is, to within the margin of error, consistent with radar derived estimates.
Solutocapillary convection in spherical shells
Authors: Subramanian Pravin , Zebib Abdelfattah , McQuillan Barry
Published: December 2004

A linear stability study of solutocapillary driven Marangoni instabilities in small spherical shells is presented. The shells contain a binary fluid with an evaporating solvent. The viscosity is a strong function of the solvent concentration, the inner surface of the shell is assumed impermeable and stress free, while nonlinear boundary conditions are modeled and prescribed at the receding outer boundary. A time-dependent diffusive state is possible and may lose stability through the Marangoni mechanism due to surface tension dependence on solvent concentration (buoyant forces are negligible in this microscale problem). A frozen-time or quasisteady state linear stability analysis is performed to compute the critical Reynolds number and degree of surface harmonics, as well as the maximum growth rate of perturbations at specified parameters. The development of maximum growth rates in time was also computed by solving the initial value problem with random initial conditions. Results from both approaches are in good agreement except at short times where there is dependence on initial conditions. The physical problem models the manufacturing of spherical shells used as targets in inertial confinement fusion experiments where perfect sphericity is demanded for efficient fusion ignition. It is proposed that the Marangoni instability might be the source of observed surface roughness. Comparisons with the available experiments are made with reasonable qualitative and quantitative agreement.
Modified Zakharov equations for plasmas with a quantum correction
Authors: Garcia L. G. , Haas F. , de Oliveira L. P. L. , Goedert J.
Published: December 2004

Quantum Zakharov equations are obtained to describe the nonlinear interaction between quantum Langmuir waves and quantum ion-acoustic waves. These quantum Zakharov equations are applied to two model cases, namely, the four-wave interaction and the decay instability. In the case of the four-wave instability, sufficiently large quantum effects tend to suppress the instability. For the decay instability, the quantum Zakharov equations lead to results similar to those of the classical decay instability except for quantum correction terms in the dispersion relations. Some considerations regarding the nonlinear aspects of the quantum Zakharov equations are also offered.
Structure of reconnection layer with a shear flow perpendicular to the antiparallel magnetic field component
Authors: Sun Xiaoxia , Lin Yu , Wang Xiaogang
Published: December 2004

A one-dimensional resistive magnetohydrodynamic (MHD) simulation of the Riemann problem is carried out for the structure of reconnection layer, i.e., outflow region of quasisteady magnetic reconnection, in the presence of a sheared flow tangential to the initial current (Jy) sheet. Unlike previous studies, the shear flow is in the y direction, perpendicular to the antiparallel component of the magnetic field Bz, with a total change of flow ΔVy≠0 across the current sheet. Cases with symmetric or asymmetric current sheet and various guide magnetic fields By are investigated. The simulation shows that in the reconnection layer, the structure of MHD discontinuities changes significantly with the strength of the shear flow. The main findings are the following: (1) In the case initially with a zero guide field (By=0, for the so-called “antiparallel reconnection”), the shear flow in Vy produces a finite By in the reconnection layer and two time-dependent intermediate shocks with rotation angle of tangential magnetic field less than 180°. (2) For initial By≠0 (the “component reconnection”) the sheared Vy leads to very different magnetic field structures in the two outflow regions on the two sides of the X line. (3) In the cases with the initial By≠0, the existence of the sheared Vy can lead to the reversal of the rotation sense of tangential magnetic field through the reconnection layer. The critical value of ΔVy for the occurrence of this field reversal is discussed. The general simulation results can be applied to space and laboratory plasmas.
Nonlocal energetic particle mode in a JT-60U plasma
Authors: Todo Y. , Shinohara K. , Takechi M. , Ishikawa M.
Published: December 2004

Energetic-ion driven instability in a Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [S. Ishida et al., Phys. Plasmas 11, 2532 (2004)] plasma was investigated using a simulation code for magnetohydrodynamics and energetic particles. The spatial profile of the unstable mode peaks near the plasma center where the safety factor profile is flat. The unstable mode is not a toroidal Alfvén eigenmode (TAE) because the spatial profile deviates from the expected location of TAE and the spatial profile consists of a single primary harmonic m∕n=2∕1 where m and n are poloidal and toroidal mode numbers. The real frequency of the unstable mode is close to the experimental starting frequency of the fast frequency sweeping mode. Simulation results demonstrate that energetic-ion orbit width and energetic-ion pressure significantly broaden radial profile of the unstable mode. For the smallest value among the investigated energetic-ion orbit width, the unstable mode is localized within 20% of the minor radius. This gives an upper limit of the spatial profile width of the unstable mode which the magnetohydrodynamic effects alone can induce. For the experimental condition of the JT-60U plasma, energetic ions broaden the radial width of the unstable mode spatial profile by a factor of 3. The unstable mode is primarily induced by the energetic particles.
A friction factor bound for transitional pipe flow
Authors: Plasting S. C. , Kerswell R. R.
Published: December 2004

An upper bound λmax on the friction factor λ is found for transitional pipe flow up to Reynolds numbers of Re=4000. This bound corresponds to the laminar Hagen–Poiseuille value until the energy stability point of Re=81.52 (where λmax=0.7851) after which it decreases monotonically to approach a viscosity-independent asymptote of 0.27±0.01 as Re→∞. Comparison is made with the friction factors associated with recently discovered, finite-amplitude traveling waves in rotating and nonrotating pipe flow as well as experimental data.
Amplification of boundary layer instability by hot wall thermal oscillation in a side heated cavity
Authors: Kim Sung Ki , Kim Seo Young , Choi Young Don
Published: December 2004

A numerical study has been conducted to investigate the amplification of boundary layer instability in a side-heated enclosure with a thermal oscillation of vertical hot wall. The impetus of the present study is to elucidate the influence of wall thermal oscillation, in which the imposing frequency is one order of magnitude higher than that of the internal gravity wave on the fluctuation characteristics of boundary layer flow and internal flow in an enclosure. The numerical results show that the intensity of fluctuation of boundary layer flow is augmented and the internal flow in the cavity core is substantially influenced when the wall thermal oscillation is in tune with the characteristic frequency of boundary layer instability. For the wall thermal oscillation with a specific frequency, the modulated frequency fluctuation appears in the corner region due to the flow interaction between the vertical boundary layer flow and the wall jet along the horizontal walls. The amplified fluctuation of boundary layer flow affects the time-averaged heat transfer. The maximum enhancement of Nusselt number is obtained for the wall thermal oscillation in tune with the boundary layer instability frequency. The effect of wall thermal oscillation on heat transfer is more pronounced when the forcing amplitude is the average value of nondimensional temperature difference between the hot and cold walls.
The Baryonic Tully–Fisher Relation
Authors: Gurovich Sebastián , McGaugh Stacy S. , Freeman Ken C. , Jerjen Helmut , Staveley-Smith Lister , De Blok W. J. G.
Published: December 2004

We validate the baryonic Tully–Fisher (TF) relation by exploring the Tully–Fisher (TF) and BTF properties of optically and Hi-selected disk galaxies. The data includes galaxies from Sakai et al. (2000) calibrator sample, McGaugh et al. (2000: M2000) I-band sample, and 18 newly acquired Hi-selected field dwarf galaxies observed with the ANU 2.3-m telescope and the ATNF Parkes telescope (Gurovich 2005a).

As in M2000, we re-cast the TF and BTF relations as relationships between baryon mass and W20. First we report some numerical errors in M2000. Then, we calculate weighted bi-variate linear fits to the data, and finally we compare the fits of the intrinsically fainter dwarfs with the brighter galaxies of Sakai et al. (2000). With regards to the local calibrator disk galaxies of Sakai et al. (2000), our results suggest that the BTF relation is indeed tighter than the TF relation and that the slopes of the BTF relations are statistically flatter than the equivalent TF relations. Further, for the fainter galaxies which include the I-band M2000 and Hi-selected galaxies of Gurovich's sample, we calculate a break from a simple power law model because of what appears to be real cosmic scatter. Not withstanding this point, the BTF models are marginally better models than the equivalent TF ones with slightly smaller Χred2 values.
Securing the Faint End of the Galaxy Luminosity Function
Authors: Jerjen Helmut , Tully Brent , Trentham Neil
Published: December 2004

The history of the formation of galaxies must leave an imprint in the properties of the mass function of collapsed objects and in its observational manifestation, the galaxy luminosity function. At present the faint end of the luminosity function is poorly known. Accurate knowledge of the luminosity function over the full range of galaxy clustering scales would provide serious constraints on both initial cosmological conditions and modulating astrophysical processes.

Wide field imaging surveys with large ground-based telescopes now provide the capability to identify dwarf galaxy candidates to very faint levels (μR ≈ 26 mag arcsec–2), too low in surface brightness for spectroscopy (measuring redshifts) even with telescopes like Keck. Other means have to be explored to get distance information for these candidates in order to separate cluster members from back/foreground systems beyond doubt. On the quest to establish the properties (slope and possible turning point) of the the faint end of the galaxy luminosity function we are employing the surface brightness fluctuation (SBF) method to determine adequate distances, potentially resulting in the best definition ever of the luminosity function to MR ≈ –11 in the cluster and group environments.
Structure and Dynamics in the Local Universe: A Workshop in Honour of Brent Tully's 60th Birthday
Authors: Bland-Hawthorn Joss
Published: December 2004

We present a summary of a recent meeting held in honour of Brent Tully's 60th birthday. We also provide a retrospective on his career to date.
Neuronal membrane cholesterol loss enhances amyloid peptide generation
Authors: Abad-Rodriguez Jose , Ledesma Maria Dolores , Craessaerts Katleen , Perga Simona , Medina Miguel , Delacourte Andre , Dingwall Colin , De Strooper Bart , Dotti Carlos G.
Published: December 2004

Recent experimental and clinical retrospective studies support the view that reduction of brain cholesterol protects against Alzheimer's disease (AD). However, genetic and pharmacological evidence indicates that low brain cholesterol leads to neurodegeneration. This apparent contradiction prompted us to analyze the role of neuronal cholesterol in amyloid peptide generation in experimental systems that closely resemble physiological and pathological situations. We show that, in the hippocampus of control human and transgenic mice, only a small pool of endogenous APP and its β-secretase, BACE 1, are found in the same membrane environment. Much higher levels of BACE 1–APP colocalization is found in hippocampal membranes from AD patients or in rodent hippocampal neurons with a moderate reduction of membrane cholesterol. Their increased colocalization is associated with elevated production of amyloid peptide. These results suggest that loss of neuronal membrane cholesterol contributes to excessive amyloidogenesis in AD and pave the way for the identification of the cause of cholesterol loss and for the development of specific therapeutic strategies.
DNA replication checkpoint control of Wee1 stability by vertebrate Hsl7
Authors: Yamada Ayumi , Duffy Brad , Perry Jennifer A. , Kornbluth Sally
Published: December 2004

G2/M checkpoints prevent mitotic entry upon DNA damage or replication inhibition by targeting the Cdc2 regulators Cdc25 and Wee1. Although Wee1 protein stability is regulated by DNA-responsive checkpoints, the vertebrate pathways controlling Wee1 degradation have not been elucidated. In budding yeast, stability of the Wee1 homologue, Swe1, is controlled by a regulatory module consisting of the proteins Hsl1 and Hsl7 (histone synthetic lethal 1 and 7), which are targeted by the morphogenesis checkpoint to prevent Swe1 degradation when budding is inhibited. We report here the identification of Xenopus Hsl7 as a positive regulator of mitosis that is controlled, instead, by an entirely distinct checkpoint, the DNA replication checkpoint. Although inhibiting Hsl7 delayed mitosis, Hsl7 overexpression overrode the replication checkpoint, accelerating Wee1 destruction. Replication checkpoint activation disrupted Hsl7–Wee1 interactions, but binding was restored by active polo-like kinase. These data establish Hsl7 as a component of the replication checkpoint and reveal that similar cell cycle control modules can be co-opted for use by distinct checkpoints in different organsims.
Terminal osteoblast differentiation, mediated by runx2 and p27KIP1, is disrupted in osteosarcoma
Authors: Thomas David M. , Johnson Sandra A. , Sims Natalie A. , Trivett Melanie K. , Slavin John L. , Rubin Brian P. , Waring Paul , McArthur Grant A. , Walkley Carl R. , Holloway Andrew J. , Diyagama Dileepa , Grim Jonathon E. , Clurman Bruce E. , Bowtell David D.L. , Lee Jong-Seo , Gutierrez Gabriel M. , Piscopo Denise M. , Carty Shannon A. , Hinds Philip W.
Published: December 2004

The molecular basis for the inverse relationship between differentiation and tumorigenesis is unknown. The function of runx2, a master regulator of osteoblast differentiation belonging to the runt family of tumor suppressor genes, is consistently disrupted in osteosarcoma cell lines. Ectopic expression of runx2 induces p27KIP1, thereby inhibiting the activity of S-phase cyclin complexes and leading to the dephosphorylation of the retinoblastoma tumor suppressor protein (pRb) and a G1 cell cycle arrest. Runx2 physically interacts with the hypophosphorylated form of pRb, a known coactivator of runx2, thereby completing a feed-forward loop in which progressive cell cycle exit promotes increased expression of the osteoblast phenotype. Loss of p27KIP1 perturbs transient and terminal cell cycle exit in osteoblasts. Consistent with the incompatibility of malignant transformation and permanent cell cycle exit, loss of p27KIP1 expression correlates with dedifferentiation in high-grade human osteosarcomas. Physiologic coupling of osteoblast differentiation to cell cycle withdrawal is mediated through runx2 and p27KIP1, and these processes are disrupted in osteosarcoma.
A lipid boundary separates APP and secretases and limits amyloid β-peptide generation
Authors: Kaether Christoph , Haass Christian
Published: December 2004

Millions of patients suffer from Alzheimer's disease, and intensive efforts to find a cure for this devastating disorder center on the proteases, which release the deadly amyloid β-peptide from its precursor. The cutting procedure is thought to be cholesterol dependent and strategies to lower cholesterol as therapeutic treatment are under intensive investigation. Recent findings suggest that the complete proteolytic machinery required for amyloid β-peptide generation is located within lipid rafts. Data by Dotti and colleagues (Abad-Rodriguez et al., 2004), in this issue, suggest that rafts isolate the cutting machinery away from its deadly substrate. These findings describe a novel mechanism for controlling proteolytic activity by building a lipid boundary between proteases and their substrates.
SIGN-R1 Contributes to Protection against Lethal Pneumococcal Infection in Mice
Authors: Lanoue Astrid , Clatworthy Menna R. , Smith Philippa , Green Sheila , Townsend Michael J. , Jolin Helen E. , Smith Kenneth G.C. , Fallon Padraic G. , McKenzie Andrew N.J.
Published: December 2004

Rapid clearance of pathogens is essential for successful control of pyogenic bacterial infection. Previous experiments have shown that antibody to specific intracellular adhesion molecule-grabbing nonintegrin (SIGN)-R1 inhibits uptake of capsular polysaccharide by marginal zone macrophages, suggesting a role for SIGN-R1 in this process. We now demonstrate that mice lacking SIGN-R1 (a mouse homologue of human dendritic cell–SIGN receptor) are significantly more susceptible to Streptococcus pneumoniae infection and fail to clear S. pneumoniae from the circulation. Marginal zone and peritoneal macrophages show impaired bacterial recognition associated with an inability to bind T-independent type 2 antigens such as dextran. Our work represents the first evidence for a protective in vivo role for a SIGN family molecule.
Centromeric Repositioning of Coreceptor Loci Predicts Their Stable Silencing and the CD4/CD8 Lineage Choice
Authors: Merkenschlager Matthias , Amoils Shannon , Roldan Esther , Rahemtulla Amin , O'Connor Eric , Fisher Amanda G. , Brown Karen E.
Published: December 2004

The differentiation of CD4+ CD8+ double positive (DP) thymocytes requires the irreversible choice between two alternative lineages, distinguished by the mutually exclusive expression of either CD4 or CD8. Differentiating DP cells transiently down-regulate both CD4 and CD8, and this has complicated the debate whether the mechanism of CD4/CD8 lineage choice is instructive, stochastic/selective, or more complex in nature. Using fluorescence in situ hybridization, we show that the stable silencing of coreceptor loci, and ultimately lineage choice, is predicted by the spatial repositioning of coreceptor alleles to centromeric heterochromatin domains. These data provide evidence that lineage-specific developmental programs are established early during the transition from the DP to the single positive stage.
T Cell Cross-Reactivity and Conformational Changes during TCR Engagement
Authors: Lee Jean K. , Stewart-Jones Guillaume , Dong Tao , Harlos Karl , Di Gleria Kati , Dorrell Lucy , Douek Daniel C. , van der Merwe P. Anton , Jones E. Yvonne , McMichael Andrew J.
Published: December 2004

All thymically selected T cells are inherently cross-reactive, yet many data indicate a fine specificity in antigen recognition, which enables virus escape from immune control by mutation in infections such as the human immunodeficiency virus (HIV). To address this paradox, we analyzed the fine specificity of T cells recognizing a human histocompatibility leukocyte antigen (HLA)-A2–restricted, strongly immunodominant, HIV gag epitope (SLFNTVATL). The majority of 171 variant peptides tested bound HLA-A2, but only one third were recognized. Surprisingly, one recognized variant (SLYNTVATL) showed marked differences in structure when bound to HLA-A2. T cell receptor (TCR) recognition of variants of these two peptides implied that they adopted the same conformation in the TCR–peptide–major histocompatibility complex (MHC) complex. However, the on-rate kinetics of TCR binding were identical, implying that conformational changes at the TCR–peptide–MHC binding interface occur after an initial permissive antigen contact. These findings have implications for the rational design of vaccines targeting viruses with unstable genomes.
Evidence for Selective Transformation of Autoreactive Immature Plasma Cells in Mice Deficient in Fasl
Authors: Zhang Jian Qiao , Okumura Cheryl , McCarty Thomas , Shin Min Sun , Mukhopadhyay Partha , Hori Mitsuo , Torrey Ted A. , Naghashfar Zohreh , Zhou Jeff X. , Lee Chang Hoon , Roopenian Derry C. , Morse Herbert C. , Davidson Wendy F.
Published: December 2004

Germline mutations in Fas and Fasl induce nonmalignant T cell hyperplasia and systemic autoimmunity and also greatly increase the risk of B cell neoplasms. B lymphomas occurring in Fasl mutant (gld) mice usually are immunoglobulin (Ig) isotype switched, secrete Ig, and are plasmacytoid in appearance but lack Myc translocations characteristic of other plasma cell (PC) neoplasms. Here, we explore the relationship between B cell autoreactivity and transformation and use gene expression profiling to further classify gld plasmacytoid lymphomas (PLs) and to identify genes of potential importance in transformation. We found that the majority of PLs derive from antigen-experienced autoreactive B cells producing antinuclear antibody or rheumatoid factor and exhibit the skewed Ig V gene repertoire and Ig gene rearrangement patterns associated with these specificities. Gene expression profiling revealed that both primary and transplanted PLs share a transcriptional profile that places them at an early stage in PC differentiation and distinguishes them from other B cell neoplasms. In addition, genes were identified whose altered expression might be relevant in lymphomagenesis. Our findings provide a strong case for targeted transformation of autoreactive B cells in gld mice and establish a valuable model for understanding the relationship between systemic autoimmunity and B cell neoplasia.