bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidenzbasierung als Argumentations- hilfe bei berufspolitischen Aktivitäten
Authors: Schoof-Tams Karin
Published: June 2007

Zusammenfassung: Klinisch neuropsychologische Behandlung ist heilkundliche Tätigkeit und bedarf deshalb der staatlichen Erlaubnis. Bei der berufsrechtlichen Etablierung der Klinischen Neuropsychologie als Psychotherapie war der Nachweis der wissenschaftlichen Anerkennung durch den Wissenschaftlichen Beirat Psychotherapie Voraussetzung für die Einbeziehung der Neuropsychologie durch Etablierung von Weiterbildungsordnungen und eine Musterweiterbildungsordnung bei den Kammern der Psychologischen Psychotherapeuten und Kinder- und Jugendlichenpsychotherapeuten. Für die sozialrechtlichen Regelungen gilt eine neue Verfahrensordnung des Gemeinsamen Bundesausschusses, die den Regeln der evidenzbasierten Medizin folgt. Neue Untersuchungs- und Behandlungsmethoden müssen danach u. a. bzgl. ihres Nutzens beurteilt werden, wenn sie in die ambulante Versorgung zu Lasten der gesetzlichen Krankenkassen übernommen werden sollen. Hier ist die Prüfung der ambulanten Neuropsychologie bereits weit fortgeschritten. Die Anerkennung und Übernahme in die ambulante Versorgung als Psychotherapieverfahren kann aber auch bei Nachweis von Evidenz derzeit aus Gründen der bisherigen Interpretation des Verfahrensbegriffs nicht erfolgen. Hier werden derzeit Lösungswege gesucht, um den betroffenen Patienten die dringend benötigte ambulante neuropsychologische Versorgung zu ermöglichen und die Klinische Neuropsychologie der berufsrechtlichen Situation entsprechend in Psychotherapierichtlinien zu regeln.
EbM und Wirksamkeit in der klinischen Neuropsychologie
Authors: Müller Sandra Verena
Published: June 2007

Zusammenfassung: Die Frage der Evidenzbasierung medizinischer und therapeutischer Leistungen ist im letzten Jahrzehnt in den Fokus des Interesses gerückt. Dargestellt wird die Entwicklung der Evidenzbasierten Medizin (EbM) und ihre Wurzeln in der Medikamentenforschung. Darauf aufbauend wird der Status Quo der EbM mit ihren Evidenzklassen zur Bewertung der vorliegenden Evaluationsstudien erläutert. Es werden die Besonderheiten und Herausforderungen der klinischen Neuropsychologie benannt und exemplarisch an der Evidenzbasierung der Therapie exekutiver Dysfunktionen erläutert. Ein Diskurs zeigt wie sich andere Fachdisziplinen, wie Physiotherapie, Ergotherapie und Pflegewissenschaften zu dem Thema Evidenzbasierung positionieren. Abschließend wird herausgearbeitet, dass die Kriterien der EbM für die Bewertung der Wirksamkeitsstudien in der neuropsychologischen Forschung nur selten umgesetzt werden können, und somit die Neuropsychologie grundsätzlich schlechtere Chancen hat hohe Evidenzklassen zu erreichen. Statt dessen wird vorgeschlagen, dass die klinische Neuropsychologie eigene Standards für die Definition der Evidenzklassen entwickelt, bei denen die Qualität nicht ausschließlich über das Studiendesign definiert ist, sondern diese durch weitere Kriterien ergänzt werden sollen, wie genaue Angaben über die Art und Frequenz der Intervention, Art und Qualität der Erhebungsinstrumente und die Stabilität des Therapieerfolgs mittels Follow-up Untersuchungen.
Enhanced CO2 outgassing in the Southern Ocean from a positive phase of the Southern Annular Mode
Authors: Lovenduski Nicole S. , Gruber Nicolas , Doney Scott C. , Lima Ivan D.
Published: June 2007

We investigate the interannual variability in the flux of CO2 between the atmosphere and the Southern Ocean on the basis of hindcast simulations with a coupled physical‐biogeochemical‐ecological model with particular emphasis on the role of the Southern Annular Mode (SAM). The simulations are run under either pre‐industrial or historical CO2 concentrations, permitting us to separately investigate natural, anthropogenic, and contemporary CO2 flux variability. We find large interannual variability (±0.19 PgC yr−1) in the contemporary air‐sea CO2 flux from the Southern Ocean (<35°S). Forty‐three percent of the contemporary air‐sea CO2 flux variance is coherent with SAM, mostly driven by variations in the flux of natural CO2, for which SAM explains 48%. Positive phases of the SAM are associated with anomalous outgassing of natural CO2 at a rate of 0.1 PgC yr−1 per standard deviation of the SAM. In contrast, we find an anomalous uptake of anthropogenic CO2 at a rate of 0.01 PgC yr−1 during positive phases of the SAM. This uptake of anthropogenic CO2 only slightly mitigates the outgassing of natural CO2, so that a positive SAM is associated with anomalous outgassing in contemporaneous times. The primary cause of the natural CO2 outgassing is anomalously high oceanic partial pressures of CO2 caused by elevated dissolved inorganic carbon (DIC) concentrations. These anomalies in DIC are primarily a result of the circulation changes associated with the southward shift and strengthening of the zonal winds during positive phases of the SAM. The secular, positive trend in the SAM has led to a reduction in the rate of increase of the uptake of CO2 by the Southern Ocean over the past 50 years.
A magnetospheric energy principle for hydromagnetic stability problems
Authors: Miura Akira
Published: June 2007

A magnetospheric energy principle is formulated to study hydromagnetic stability of a magnetospheric plasma. The magnetospheric plasma is either in a two‐dimensional or three‐dimensional static equilibrium. It is surrounded by lateral perfectly conducting walls and ideal ionospheres in both cases and also by dawn‐dusk periodic boundaries in the two‐dimensional case. The two‐dimensional case has a translational symmetry and has no unperturbed magnetic field component in the dawn‐dusk direction. Unlike the conventional energy principle for a plasma surrounded by a perfectly conducting wall, field lines are assumed to vertically thread the ionospheric boundary, which is not a perfectly conducting rigid wall. Ideal ionospheric boundary conditions are obtained, so that the force operator becomes self‐adjoint and the magnetospheric energy principle is valid. There are four ideal ionospheric boundary conditions to satisfy these requirements: horizontally free, conducting, free, and rigid. A change in the potential energy becomes equal to the sum of the change in the fluid energy and an ionospheric surface contribution, which is negative and thus destabilizing for horizontally free and free ionospheric boundary conditions. A minimization condition for the change in the potential energy is obtained. When an unperturbed field‐aligned current vanishes, the horizontally free, conducting, free, and rigid boundary conditions allow interchange, incompressible ballooning, incompressible ballooning, and compressible ballooning modes, respectively. Different characteristics of those three pressure‐driven modes are clarified. Existing interchange stability criteria are compared and results of several different numerical stability analyses of ballooning instabilities for different magnetospheric equilibria are discussed systematically in light of the present magnetospheric energy principle.
Molecular ion composition measurements in the F1 region at Arecibo
Authors: Aponte Néstor , Sulzer Michael P. , Nicolls Michael J. , Nikoukar Romina , González Sixto A.
Published: June 2007

The molecular ion composition in the F1 region is extremely difficult to measure with incoherent scatter (IS) radars because of the temperature/ion composition ambiguity in the shape of the incoherent scatter ion line spectrum. In practice, this means that a nonlinear least squares fitting (LSF) analysis of IS ion line data in this region can find different combinations of ionospheric parameters to be equally good fits. The only way to mitigate this problem is to add additional information to reduce the number of unknown parameters that need to be determined by the nonlinear least squares fitting. Following the concept originally reported by Waldteufel (1971), we have implemented a technique to combine the very precise electron density information in the plasma line with very accurate ion line spectra to measure the F1 region molecular ion composition. In this study, we describe the technique and show the first results from this method.
A superposed epoch study of SuperDARN convection observations during substorms
Authors: Bristow W. A. , Jensen Poul
Published: June 2007

Case studies of flow patterns during substorms have revealed characteristic patterns in the period leading to expansion onset. Velocities in the premidnight region have been observed to become strongly sheared, and the premidnight convection reversal has been observed to extend across the midnight meridian. At expansion onset, the shear decreases and flow at midnight becomes meridional, out of the polar cap. The study presented here superposes flow patterns from 10 substorm intervals to determine the average flow patterns. The study confirms the findings of the case studies and extends them to additional local time sectors. In addition, changes to the flow pattern after expansion onset are examined.
Relativistic turning acceleration of resonant electrons by coherent whistler mode waves in a dipole magnetic field
Authors: Omura Yoshiharu , Furuya Naoki , Summers Danny
Published: June 2007

We report a very efficient process for accelerating high‐energy electrons by coherent whistler mode waves in the Earth's dipole magnetic field, which we have found in our recent test particle simulations. The efficient acceleration process takes place for weakly relativistic seed electrons of a few hundred kiloelectronvolts. Under an assumption that the whistler mode wave packets are excited near the equatorial plane of the inner magnetosphere and propagate away from the equator, the acceleration process becomes irreversible. With a sufficiently long whistler mode wave packet of the order of 1 s, the energetic electrons are accelerated to a relativistic energy range of a few megaelectronvolts through a single resonant trapping process. We call this particular acceleration process relativistic turning acceleration (RTA), which could be a viable mechanism for increasing relativistic electron fluxes in the outer radiation belt. Necessary conditions for RTA are a relatively large amplitude of whistler mode waves, in the range of 50 to a few hundred picoteslas, and an initial kinetic energy of trapped electrons in the energy range of a few hundred kiloelectronvolts. The minimum energy of electrons accelerated by the RTA process and the maximum energy attained by it are derived analytically and verified by the test particle simulations.
Physical mixing effects on iron biogeochemical cycling: FeCycle experiment
Authors: Croot P. L. , Frew R. D. , Sander S. , Hunter K. A. , Ellwood M. J. , Pickmere S. E. , Abraham E. R. , Law C. S. , Smith M. J. , Boyd P. W.
Published: June 2007

The effects of physical processes on the distribution, speciation, and sources/sinks for Fe in a high‐nutrient low‐chlorophyll (HNLC) region were assessed during FeCycle, a mesoscale SF6 tracer release during February 2003 (austral summer) to the SE of New Zealand. Physical mixing processes were prevalent during FeCycle with rapid patch growth (strain rate γ = 0.17–0.20 d−1) from a circular shape (50 km2) into a long filament of ∼400 km2 by day 10. Slippage between layers saw the patch‐head overlying noninfused waters while the tail was capped by adjacent surface waters resulting in a SF6 maximum at depth. As the patch developed it entrained adjacent waters containing higher chlorophyll concentrations, but similar dissolved iron (DFe) levels, than the initial infused patch. DFe was low ∼60 pmol L−1 in surface waters during FeCycle and was dominated by organic complexation. Nighttime measurements of Fe(II) ∼20 pmol L−1 suggest the presence of Fe(II) organic complexes in the absence of an identifiable fast Fe(III) reduction process. Combining residence times and phytoplankton uptake fluxes for DFe it is cycled through the biota 140–280 times before leaving the winter mixed layer (WML). This strong Fe demand throughout the euphotic zone coupled with the low Fe:NO3− (11.9 μmol:mol) below the ferricline suggests that vertical diffusion of Fe is insufficient to relieve chronic iron limitation, indicating the importance of atmospheric inputs of Fe to this region.
Sea surface temperature signatures of oceanic internal waves in low winds
Authors: Farrar J. Thomas , Zappa Christopher J. , Weller Robert A. , Jessup Andrew T.
Published: June 2007

In aerial surveys conducted during the Tropical Ocean–Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment and the low‐wind component of the Coupled Boundary Layer Air‐Sea Transfer (CBLAST‐Low) oceanographic field programs, sea surface temperature (SST) variability at relatively short spatial scales (O(50 m) to O(1 km)) was observed to increase with decreasing wind speed. A unique set of coincident surface and subsurface oceanic temperature measurements from CBLAST‐Low is used to investigate the subsurface expression of this spatially organized SST variability, and the SST variability is linked to internal waves. The data are used to test two previously hypothesized mechanisms for SST signatures of oceanic internal waves: a modulation of the cool‐skin effect and a modulation of vertical mixing within the diurnal warm layer. Under conditions of weak winds and strong insolation (which favor formation of a diurnal warm layer), the data reveal a link between the spatially periodic SST fluctuations and subsurface temperature and velocity fluctuations associated with oceanic internal waves, suggesting that some mechanism involving the diurnal warm layer is responsible for the observed signal. Internal‐wave signals in skin temperature very closely resemble temperature signals measured at a depth of about 20 cm, indicating that the observed internal‐wave SST signal is not a result of modulation of the cool‐skin effect. Numerical experiments using a one‐dimensional upper ocean model support the notion that internal‐wave heaving of the warm‐layer base can produce alternating bands of relatively warm and cool SST through the combined effects of surface heating and modulation of wind‐driven vertical shear.
Effect of the space charge layer created by corona at ground level on the inception of upward lightning leaders from tall towers
Authors: Becerra M. , Cooray V. , Soula S. , Chauzy S.
Published: June 2007

Electric field measurements above ground have shown that the space charge layer created by corona at ground level shields the background electric field produced by the thundercloud. Therefore it is expected that this space charge layer can also influence the conditions required to initiate upward lightning from tall objects. For this reason, a numerical model that describes the evolution of the main electrical parameters below a thunderstorm is used to compute the space charge layer development. The time variation of the electric field measured at 600 m above ground during the 1989 rocket triggered lightning experiment at the Kennedy Space Center (Florida) is used to drive the model. The obtained space charge density profiles are used to compute the conditions required to initiate stable upward lightning positive leaders from tall towers. Corona at the tip of the tower is neglected. It is found that the space charge layer significantly affects the critical thundercloud electric fields required to initiate upward lightning leaders from tall objects. The neutral aerosol particle concentration is observed to have a significant influence on the space charge density profiles and the critical thundercloud electric fields, whereas the corona current density does not considerably affect the results for the cases considered in the analysis. It is found that a lower thundercloud electric field is required to trigger a lightning flash from a tall tower or other tall slender grounded structure in the case of sites with a high neutral aerosol particle concentration, like polluted areas or coastal regions.
Radon and Abel Transform equivalence in atmospheric radio occultation
Authors: Thomson Fraser S. , Tyler G. Leonard
Published: June 2007

The Radon Transform plays a central role in the image reconstruction technique known as computed tomography, used commonly in radio astronomy and medical imaging. Although usually formulated as a projection of a spatial density function along straight ray paths, the Radon Transform kernel also permits curved path projections, providing the path can be defined. Reformulation of the Radon Transform as a path integral for the case of a radio ray refracting in a spherically symmetric atmosphere leads directly to the Abel Transform formulation commonly used in atmospheric radio occultation.
Strain and rotation rate from GPS in Tibet, Anatolia, and the Altiplano
Authors: Allmendinger Richard W. , Reilinger Robert , Loveless Jack
Published: June 2007

Deformation measured by regional GPS networks in continental plateaus reflects the geologic and tectonic variability of the plateaus. For two collisional plateaus (Tibet and Anatolia) and one noncollisional (the Altiplano), we analyze the regional strain and rotation rate by inverting GPS velocities to calculate the full two‐dimensional velocity gradient tensor. To test the method, we use gridded velocities determined from an elastic block model for the eastern Mediterranean/Middle East region and show that to a first order, the deformation calculated directly from the GPS vectors provides an accurate description of regional deformation patterns. Principal shortening and extension rate axes, vertical axis rotation, and two‐dimensional (2‐D) volume strain (dilatation) are very consistent with long‐term geological features over large areas, indicating that the GPS velocity fields reflect processes responsible for the recent geologic evolution of the plateaus. Differences between geological and GPS descriptions of deformation can be attributed either to GPS networks that are too sparse to capture local interseismic deformation, or to permanent deformation that accrues during strong earthquakes. The Altiplano has higher internal shortening magnitudes than the other two plateaus and negative 2‐D dilatation everywhere. Vertical axis rotation changes sign across the topographic symmetry axis and is due to distributed deformation throughout the plateau. In contrast, the collisional plateaus have large regions of quasi‐rigid body rotation bounded by strike‐slip faults with the opposite rotation sense from the rotating blocks. Tibet and Anatolia are the mirror images of each other; both have regions of positive dilatation on the outboard sides of the rotating blocks. Positive dilatation in the Aegean correlates with a region of crustal thinning, whereas that in eastern Tibet and Yunnan province in China is associated with an area of vertical uplift. Rollback of the Hellenic trench clearly facilitates the rotation of Anatolia; rollback of the Sumatra–Burma trench probably also enables rotation about the eastern syntaxis of Tibet.
Generalized extreme value distribution fitted by LH moments for low‐flow frequency analysis
Authors: Hewa G. A. , Wang Q. J. , McMahon T. A. , Nathan R. J. , Peel M. C.
Published: June 2007

This study introduces a method based on LH moments to use the generalized extreme value (GEV) distribution for low‐flow frequency analysis and investigates the capability of the GEV distribution fitted by LH moments to effectively model the lower tail of the low‐flow frequency curve, without explicitly censoring the data sample. The performance of the GEV/L moment (the GEV distribution fitted by L moments) and GEV/LH moment (the GEV distribution fitted by LH moments) methods are assessed by evaluating the bias, mean square error, and relative accuracy of quantile estimates through Monte Carlo simulations. It is shown that when both frequent low flows and extreme low flows can be adequately described by an assumed parent distribution, both GEV/L2 moment and GEV/L moment methods make equally accurate quantile estimates. However, when frequent low flows and extreme low flows do not follow a single trend, the bias of the GEV/L2 moment estimator is negligible, while the bias of the GEV/L moment estimator is significant at large annual recurrence intervals. On average, the GEV/L2 moment quantile estimator displays less bias than the GEV/L moment quantile estimator. Furthermore, as the annual recurrence interval increases, the relative accuracy of the GEV/L2 moment method consistently improves over the GEV/L moment method. The GEV/LH moment method is thus considered to be the more suitable method to model low flows.
Robust detection of discordant sites in regional frequency analysis
Authors: Neykov N. M. , Neytchev P. N. , Van Gelder P. H. A. J. M. , Todorov V. K.
Published: June 2007

The discordancy measure in terms of the sample L‐moment ratios (L‐CV, L‐skewness, L‐kurtosis) of the at‐site data is widely recommended in the screening process of atypical sites in the regional frequency analysis (RFA). The sample mean and the covariance matrix of the L‐moments ratios, on which the discordancy measure is based, are not robust against outliers in the data, and consequently, this measure can be strongly affected by the discordant sites present in the region. We propose to replace the classical mean and covariance matrix estimates by their robust alternatives on the basis of the minimum covariance determinant estimator. The performance of the classical and robust measures for discordant sites identification is assessed in a series of Monte Carlo simulation experiments within the framework of the RFA. The simulation study shows that the robust discordant measure outperforms the classical one and is consistent with the heterogeneity measureH. Thus we recommend its use as a tool for discordant sites detection and formation of homogeneous regions in RFA.
Advancing the identification and evaluation of distributed rainfall‐runoff models using global sensitivity analysis
Authors: Tang Y. , Reed P. , van Werkhoven K. , Wagener T.
Published: June 2007

This study provides a step‐wise analysis of a conceptual grid‐based distributed rainfall‐runoff model, the United States National Weather Service (US NWS) Hydrology Laboratory Research Distributed Hydrologic Model (HL‐RDHM). It evaluates model parameter sensitivities for annual, monthly, and event time periods with the intent of elucidating the key parameters impacting the distributed model's forecasts. This study demonstrates a methodology that balances the computational constraints posed by global sensitivity analysis with the need to fully characterize the HL‐RDHM's sensitivities. The HL‐RDHM's sensitivities were assessed for annual and monthly periods using distributed forcing and identical model parameters for all grid cells at 24‐hour and 1‐hour model time steps respectively for two case study watersheds within the Juniata River Basin in central Pennsylvania. This study also provides detailed spatial analysis of the HL‐RDHM's sensitivities for two flood events based on 1‐hour model time steps selected to demonstrate how strongly the spatial heterogeneity of forcing influences the model's spatial sensitivities. Our verification analysis of the sensitivity analysis method demonstrates that the method provides robust sensitivity rankings and that these rankings could be used to significantly reduce the number of parameters that should be considered when calibrating the HL‐RDHM. Overall, the sensitivity analysis results reveal that storage variation, spatial trends in forcing, and cell proximity to the gauged watershed outlet are the three primary factors that control the HL‐RDHM's behavior.
Last Glacial Maximum ocean thermohaline circulation: PMIP2 model intercomparisons and data constraints
Authors: Otto‐Bliesner B. L. , Hewitt C. D. , Marchitto T. M. , Brady E. , Abe‐Ouchi A. , Crucifix M. , Murakami S. , Weber S. L.
Published: June 2007

The ocean thermohaline circulation is important for transports of heat and the carbon cycle. We present results from PMIP2 coupled atmosphere‐ocean simulations with four climate models that are also being used for future assessments. These models give very different glacial thermohaline circulations even with comparable circulations for present. An integrated approach using results from these simulations for Last Glacial Maximum (LGM) with proxies of the state of the glacial surface and deep Atlantic supports the interpretation from nutrient tracers that the boundary between North Atlantic Deep Water and Antarctic Bottom Water was much shallower during this period. There is less constraint from this integrated reconstruction regarding the strength of the LGM North Atlantic overturning circulation, although together they suggest that it was neither appreciably stronger nor weaker than modern. Two model simulations identify a role for sea ice in both hemispheres in driving the ocean response to glacial forcing.
Mesoscale eddies and high chlorophyll concentrations off central Chile (29°–39°S)
Authors: Correa‐Ramirez Marco A. , Hormazábal Samuel , Yuras Gabriel
Published: June 2007

The offshore propagation of mesoscale eddies contributes significantly to expanding the area of high chlorophyll concentration beyond the coastal upwelling center as shown by satellite data of chlorophyll, wind stress, sea level anomalies between (1997–2003) off central Chile. Mesoscale eddies (∼6.45 × 103 km2) formed near the coastal zone in spring‐summer have mean seaward speeds of ∼1.68 km d−1 and reach ∼500 km offshore in winter. Chlorophyll concentrations along eddy paths are elevated by nutrient pumping and by nutrients and/or chlorophyll transported from the coastal zone. Eddies make up >50% of the winter (weak upwelling) chlorophyll peak in the coastal transition zone. Coupling between eddies and upwelling extends central Chile's high productivity area offshore and prolongs it towards winter.
Plasma sheet response to the ionosphere's demand for field‐aligned current
Authors: Pritchett P. L. , Coroniti F. V.
Published: June 2007

The response of the near‐Earth plasma sheet to the extraction of a longitudinally‐limited field‐aligned current is investigated using three‐dimensional particle‐in‐cell simulations. Polarization electric fields produce localized (in y), thin (in z), enhanced electron Hall currents, thus augmenting the cross‐tail current. The current diversion forces reconnection to occur locally and leads to the formation of a complex magnetic field pattern of adjacent regions of negative and positive Bz.
Phytomass and phenology of three alpine snowpatch species across a natural snowmelt gradient
Authors: Venn Susanna E. , Morgan John W.
Published: June 2007

Alpine snowpatch vegetation in Australia is restricted to high mountain areas and occurs in locations where winter snow persists longest into the summer. The timing of annual snowmelt is considered an important determinant of vegetation patterns in alpine areas because it affects the length of the growing season for plant species at landscape scales. There are few studies in Australia that have examined the effects of the date of snowmelt on the performance of plant species at small spatial scales. The phytomass and phenology of three common snowpatch species (Celmisia pugioniformis, Luzula acutifolia, Poa fawcettiae) was examined during one growing season across a natural snowmelt gradient to examine their response to time of snow release. Peak phytomass was significantly higher in early than late-melting zones for L. acutifolia and marginally higher there for C. pugioniformis. P. fawcettiae, however, produced higher mean peak phytomass in late-melting zones where soil was initially wetter in the growing season. Flower buds of L. acutifolia were evident as the snow melted, and flowering occurred at the same time in all areas of the snowpatch. The number of days from the date of snowmelt to the date of the first observed flower bud in C. pugioniformis and P. fawcettiae was 22–25 days shorter in late-melting areas than in early melting areas. For both of these species, flowering and subsequent seed set occurred simultaneously across the snowpatch regardless of the date of the initial snowmelt, suggesting that photoperiod controls flowering in these species. Our study suggests that the predicted declines in snow cover in Australia in coming decades may affect the phytomass of species that are currently constrained by late-lying snow. This, in turn, may affect their long-term patterns of distribution. If plants respond to photoperiod for flowering, as seems to be important here for C. pugioniformis and P. fawcettiae, it is unlikely that the periods following earlier than usual snowmelt will be fully utilised by these species. Any attempts at predicting or modelling future alpine plant distribution on the basis of warming scenarios may therefore need to account for photoperiod constraints on flowering as well changes in phytomass production.
Can age be predicted from diameter for the obligate seeder Allocasuarina littoralis (Casuarinaceae) by using dendrochronological techniques?
Authors: Burley Alana L. , Phillips Stephen , Ooi Mark K. J.
Published: June 2007

In fire-prone regions, assessing stand age of obligate-seeding species provides an estimate of time since last fire. If a relationship exists between tree age and diameter, measuring the stem diameter of trees is a simple field method for determining age-class distribution within a stand. In this study, we examined whether age of the obligate seeder Allocasuarina littoralis could be estimated from diameter by using dendrochronological applications. Analysis of radial samples established that A. littoralis puts down annual growth rings. The relationship between the number of growth rings and stem diameter was tested for both male and female stems by using regression analysis. For female plants, this relationship varied significantly between sites. In contrast, male stems provided a strong relationship between age (as a function of the number of growth rings) and diameter, regardless of site. A regression model estimating age from stem diameter, based on male trees only, was subsequently developed and tested with data collected from trees of known age. Predicted estimates from stem diameter were within 3.76 years of the true age. Field measures of stem diameters can therefore provide a tool for estimating the fire history, especially time since last fire, in areas where stands of this species occur.
Lenalidomide inhibits the malignant clone and up-regulates theSPARCgene mapping to the commonly deleted region in 5q− syndrome patients
Authors: Pellagatti Andrea , Jädersten Martin , Forsblom Ann-Mari , Cattan Helen , Christensson Birger , Emanuelsson Emma K. , Merup Mats , Nilsson Lars , Samuelsson Jan , Sander Birgitta , Wainscoat James S. , Boultwood Jacqueline , Hellström-Lindberg Eva
Published: June 2007

Myelodysplastic syndromes (MDSs) are a group of hematopoietic stem cell disorders characterized by ineffective hematopoiesis and peripheral blood cytopenias. Lenalidomide has dramatic therapeutic effects in patients with low-risk MDS and a chromosome 5q31 deletion, resulting in complete cytogenetic remission in >60% of patients. The molecular basis of this remarkable drug response is unknown. To gain insight into the molecular targets of lenalidomide we investigated itsin vitroeffects on growth, maturation, and global gene expression in isolated erythroblast cultures from MDS patients with del(5)(q31). Lenalidomide inhibited growth of differentiating del(5q) erythroblasts but did not affect cytogenetically normal cells. Moreover, lenalidomide significantly influenced the pattern of gene expression in del(5q) intermediate erythroblasts, with theVSIG4,PPIC,TPBG, activin A, andSPARCgenes up-regulated by >2-fold in all samples and many genes involved in erythropoiesis, includingHBA2,GYPA, andKLF1, down-regulated in most samples. Activin A, one of the most significant differentially expressed genes between lenalidomide-treated cells from MDS patients and healthy controls, has pleiotropic functions, including apoptosis of hematopoietic cells. Up-regulation and increased protein expression of the tumor suppressor geneSPARCis of particular interest because it is antiproliferative, antiadhesive, and antiangiogenic and is located at 5q31-q32, within the commonly deleted region in MDS 5q− syndrome. We conclude that lenalidomide inhibits growth of del(5q) erythroid progenitors and that the up-regulation ofSPARCand activin A may underlie the potent effects of lenalidomide in MDS with del(5)(q31).SPARCmay play a role in the pathogenesis of the 5q− syndrome.
p120 catenin regulates lamellipodial dynamics and cell adhesion in cooperation with cortactin
Authors: Boguslavsky Shlomit , Grosheva Inna , Landau Elad , Shtutman Michael , Cohen Miriam , Arnold Katya , Feinstein Elena , Geiger Benjamin , Bershadsky Alexander
Published: June 2007

The armadillo-family protein, p120 catenin (p120), binds to the juxtamembrane domain of classical cadherins and increases cell–cell junction stability. Overexpression of p120 modulates the activity of Rho family GTPases and augments cell migratory ability. Here we show that down-regulation of p120 in epithelial MCF-7 cells by siRNA leads to a striking decrease in lamellipodial persistence and focal adhesion formation. Similar alterations in lamellipodial activity were observed in MCF-7 cells treated with siRNA to cortactin, an activator of Arp2/3-dependent actin polymerization. We found that, in many cell types, p120 is colocalized with cortactin-containing actin structures not only at cell–cell junctions, but also at extrajunctional sites including membrane ruffles and actin-rich halos around endocytotic vesicles. p120 depletion led to dramatic loss of cortactin and its partner, Arp3, from the cell leading edges. Cortactin and p120 are shown to directly interact with each other via the cortactin N-terminal region. We propose that the mechanism underlying p120 functions at the leading edge involves its cooperation with cortactin.
Canonical Wnt signaling is a positive regulator of mammalian cardiac progenitors
Authors: Kwon Chulan , Arnold Joshua , Hsiao Edward C. , Taketo Makoto M. , Conklin Bruce R. , Srivastava Deepak
Published: June 2007

Guiding multipotent cells into distinct lineages and controlling their expansion remain fundamental challenges in developmental and stem cell biology. Members of the Wnt pathway control many pivotal embryonic events, often promoting self-renewal or expansion of progenitor cells. In contrast, canonical Wnt ligands are thought to negatively regulate cardiomyogenesis in several species. However, the cell-autonomous role of canonical Wnt signaling within precardiac mesoderm, through its obligatory transcriptional mediator, β-catenin, is unknown. Using tissue-specific
in vivo
genetic manipulation, we found that β-catenin is required for development of cardiac progenitors and is a positive regulator of proliferative expansion of such progenitor cells. At discrete windows of development in embryonic stem cells, activation of canonical Wnt signaling promoted expansion of cardiac progenitors after initial commitment and was required for cardiac differentiation. Together, these data provide
in vivo
and
in vitro
evidence that canonical Wnt signaling promotes the expansion of cardiac progenitors and differentiation of cardiomyocytes.
The primate semicircular canal system and locomotion
Authors: Spoor Fred , Garland Theodore , Krovitz Gail , Ryan Timothy M. , Silcox Mary T. , Walker Alan
Published: June 2007

The semicircular canal system of vertebrates helps coordinate body movements, including stabilization of gaze during locomotion. Quantitative phylogenetically informed analysis of the radius of curvature of the three semicircular canals in 91 extant and recently extinct primate species and 119 other mammalian taxa provide support for the hypothesis that canal size varies in relation to the jerkiness of head motion during locomotion. Primate and other mammalian species studied here that are agile and have fast, jerky locomotion have significantly larger canals relative to body mass than those that move more cautiously.
Requirements for survivin in terminal differentiation of erythroid cells and maintenance of hematopoietic stem and progenitor cells
Authors: Leung Cindy G. , Xu Yanfei , Mularski Bretton , Liu Hui , Gurbuxani Sandeep , Crispino John D.
Published: June 2007

Survivin, which is the smallest member of the inhibitor of apoptosis protein (IAP) family, is a chromosomal passenger protein that mediates the spindle assembly checkpoint and cytokinesis, and also functions as an inhibitor of apoptosis. Frequently overexpressed in human cancers and not expressed in most adult tissues, survivin has been proposed as an attractive target for anticancer therapies and, in some cases, has even been touted as a cancer-specific gene. Survivin is, however, expressed in proliferating adult cells, including human hematopoietic stem cells, T-lymphocytes, and erythroid cells throughout their maturation. Therefore, it is unclear how survivin-targeted anticancer therapies would impact steady-state blood development. To address this question, we used a conditional gene-targeting strategy and abolished survivin expression from the hematopoietic compartment of mice. We show that inducible deletion of survivin leads to ablation of the bone marrow, with widespread loss of hematopoietic progenitors and rapid mortality. Surprisingly, heterozygous deletion of survivin causes defects in erythropoiesis in a subset of the animals, with a dramatic reduction in enucleated erythrocytes and the presence of immature megaloblastic erythroblasts. Our studies demonstrate that survivin is essential for steady-state hematopoiesis and survival of the adult, and further, that a high level of survivin expression is critical for proper erythroid differentiation.
Reactive oxygen species induce chondrocyte hypertrophy in endochondral ossification
Authors: Morita Kozo , Miyamoto Takeshi , Fujita Nobuyuki , Kubota Yoshiaki , Ito Keisuke , Takubo Keiyo , Miyamoto Kana , Ninomiya Ken , Suzuki Toru , Iwasaki Ryotaro , Yagi Mitsuru , Takaishi Hironari , Toyama Yoshiaki , Suda Toshio
Published: June 2007

Chondrocyte hypertrophy during endochondral ossification is a well-controlled process in which proliferating chondrocytes stop proliferating and differentiate into hypertrophic chondrocytes, which then undergo apoptosis. Chondrocyte hypertrophy induces angiogenesis and mineralization. This step is crucial for the longitudinal growth and development of long bones, but what triggers the process is unknown. Reactive oxygen species (ROS) have been implicated in cellular damage; however, the physiological role of ROS in chondrogenesis is not well characterized. We demonstrate that increasing ROS levels induce chondrocyte hypertrophy. Elevated ROS levels are detected in hypertrophic chondrocytes. In vivo and in vitro treatment with N-acetyl cysteine, which enhances endogenous antioxidant levels and protects cells from oxidative stress, inhibits chondrocyte hypertrophy. In ataxia telangiectasia mutated (Atm)–deficient (Atm−/−) mice, ROS levels were elevated in chondrocytes of growth plates, accompanied by a proliferation defect and stimulation of chondrocyte hypertrophy. Decreased proliferation and excessive hypertrophy in Atm−/− mice were also rescued by antioxidant treatment. These findings indicate that ROS levels regulate inhibition of proliferation and modulate initiation of the hypertrophic changes in chondrocytes.
A LAD-III syndrome is associated with defective expression of the Rap-1 activator CalDAG-GEFI in lymphocytes, neutrophils, and platelets
Authors: Pasvolsky Ronit , Feigelson Sara W. , Kilic Sara Sebnem , Simon Amos J. , Tal-Lapidot Guy , Grabovsky Valentin , Crittenden Jill R. , Amariglio Ninette , Safran Michal , Graybiel Ann M. , Rechavi Gideon , Ben-Dor Shifra , Etzioni Amos , Alon Ronen
Published: June 2007

Leukocyte and platelet integrins rapidly alter their affinity and adhesiveness in response to various activation (inside-out) signals. A rare leukocyte adhesion deficiency (LAD), LAD-III, is associated with severe defects in leukocyte and platelet integrin activation. We report two new LAD cases in which lymphocytes, neutrophils, and platelets share severe defects in β1, β2, and β3 integrin activation. Patients were both homozygous for a splice junction mutation in their CalDAG-GEFI gene, which is a key Rap-1/2 guanine exchange factor (GEF). Both mRNA and protein levels of the GEF were diminished in LAD lymphocytes, neutrophils, and platelets. Consequently, LAD-III platelets failed to aggregate because of an impaired αIIbβ3 activation by key agonists. β2 integrins on LAD-III neutrophils were unable to mediate leukocyte arrest on TNFα-stimulated endothelium, despite normal selectin-mediated rolling. In situ subsecond activation of neutrophil β2 integrin adhesiveness by surface-bound chemoattractants and of primary T lymphocyte LFA-1 by the CXCL12 chemokine was abolished. Chemokine inside-out signals also failed to stimulate lymphocyte LFA-1 extension and high affinity epitopes. Chemokine-triggered VLA-4 adhesiveness in T lymphocytes was partially defective as well. These studies identify CalDAG-GEFI as a critical regulator of inside-out integrin activation in human T lymphocytes, neutrophils, and platelets.
False promises: females spurn cheating males in a field cricket
Authors: Wagner William E , Smith Andrew R , Basolo Alexandra L
Published: June 2007

Females commonly prefer to mate with males that provide greater material benefits, which they often select using correlated male signals. When females select higher-benefit males based on correlated signals, however, males can potentially deceive females by producing exaggerated signals of benefit quality. The handicap mechanism can prevent lower-quality males from producing exaggerated signals, but cannot prevent cheating by higher-quality males that choose to withhold the benefit, and this poses a major problem for the evolution of female choice based on direct benefits. In a field cricket,
Gryllus lineaticeps
, females receive seminal fluid products from males with preferred songs that increase their fecundity and lifespan. We tested the hypothesis that female behaviour penalizes males that provide lower-quality benefits. When females were paired with males that varied in benefit quality but had experimentally imposed average songs, they were less likely to re-mate with males that provided lower-quality benefits in the initial mating. This type of conditional female re-mating may be a widespread mechanism that penalizes males that cheat on direct benefits.
Speed limits on swimming of fishes and cetaceans
Authors: Iosilevskii G , Weihs D
Published: June 2007

Physical limits on swimming speed of lunate tail propelled aquatic animals are proposed. A hydrodynamic analysis, applying experimental data wherever possible, is used to show that small swimmers (roughly less than a metre long) are limited by the available power, while larger swimmers at a few metres below the water surface are limited by cavitation. Depending on the caudal fin cross-section, 10–15 m s−1is shown to be the maximum cavitation-free velocity for all swimmers at a shallow depth.
Variation in host susceptibility and infectiousness generated by co-infection: the myxoma–Trichostrongylus retortaeformiscase in wild rabbits
Authors: Cattadori Isabella M , Albert Réka , Boag Brian
Published: June 2007

One of the conditions that can affect host susceptibility and parasite transmission is the occurrence of concomitant infections. Parasites interact directly or indirectly within an individual host and often these interactions are modulated by the host immune response. We used a free-living rabbit population co-infected with the nematodeTrichostrongylus retortaeformis, which appears to stimulate an acquired immune response, and the immunosuppressive poxvirus myxoma. Modelling was used to examine how myxoma infection alters the immune-mediated establishment and death/expulsion ofT. retortaeformis, and consequently affects parasite intensity and duration of the infection. Simulations were based on the general TH1–TH2 immunological paradigm that proposes the polarization of the host immune response towards one of the two subsets of T helper cells. Our findings suggest that myxoma infections contribute to alter host susceptibility to the nematode, as co-infected rabbits showed higher worm intensity compared with virus negative hosts. Results also suggest that myxoma disrupts the ability of the host to clearT. retortaeformisas worm intensities were consistently high and remained high in old rabbits. However, the co-infection model has to include some immune-mediated nematode regulation to be consistent with field data, indicating that the TH1–TH2 dichotomy is not complete. We conclude that seasonal myxoma outbreaks enhance host susceptibility to the nematode and generate highly infected hosts that remain infectious for a longer time. Finally, the virus–nematode co-infection increases heterogeneities among individuals and potentially has a large effect on parasite transmission.
Extensions of Lighthill's acoustic analogy with application to computational aeroacoustics
Authors: Morfey C.L , Wright M.C.M
Published: June 2007

Lighthill's aeroacoustic analogy is formulated for bounded domains in a general way that allows pressure-based alternatives to the fluid density as wave variable. The advantage relative to the standard version (Ffowcs Williams & Hawkings 1969
Phil. Trans. R. Soc. A
264
, 321–342) is that the equivalent surface source terms needed for boundary value problems do not involve the local density. Difficulties encountered in computational aeroacoustics with standard wave extrapolation procedures, due to advection of density inhomogeneities across the control surface, are thereby avoided. Likewise, in initial-value problems, the equivalent volume source terms that represent initial conditions do not involve the density either. The paper ends with an extension to parallel shear flows, in which a modified aeroacoustic analogy due to Goldstein (Goldstein 2001
J. Fluid Mech
.
443
, 231–236) is formulated for bounded domains using a similar windowed-variable approach. The results provide a basis for acoustic wave extrapolation from jets and boundary layers, where the control surface cuts through a sheared mean flow.
A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia
Authors: Butler Richard J , Smith Roger M.H , Norman David B
Published: June 2007

Although the group played an important role in the evolution of Late Mesozoic terrestrial ecosystems, the early evolutionary history of the ornithischian dinosaurs remains poorly understood. Here, we report on a new primitive ornithischian,Eocursor parvusgen. et sp. nov., from the Late Triassic (?Norian) Lower Elliot Formation of South Africa.Eocursoris known from a single specimen comprising substantial cranial and postcranial material and represents the most complete Triassic member of Ornithischia, providing the earliest evidence for the acquisition of many key ornithischian postcranial characters, including an opisthopubic pelvis. A new phylogenetic analysis positions this taxon near the base of Ornithischia, as the sister taxon to the important and diverse clade Genasauria. The problematic clade Heterodontosauridae is also positioned basal to Genasauria, suggesting that an enlarged grasping manus may represent a plesiomorphic ornithischian condition. This analysis provides additional phylogenetic support for limited ornithischian diversity during the Late Triassic, and suggests that several major ornithischian clades may have originated later than generally believed. There are few morphological differences between Late Triassic and Early Jurassic ornithischians, supporting previous suggestions that the Early Jurassic ornithischian radiation may simply represent the filling of vacant ecological space following Late Triassic terrestrial extinctions.