Calibration of the Radiocarbon Time Scale for the Southern Hemisphere: AD 1850-950

We have conducted a series of radiocarbon measurements on decadal samples of dendrochronologically dated wood from both hemispheres, spanning 1000 years (McCormac et al. 1998; Hogg et al. this issue). Using the data presented in Hogg et al., we show that during the period AD 950-1850 the 14C offset between the hemispheres is not constant, but varies periodically (~130 yr periodicity) with amplitudes varying between 1 and 10‰ (i.e. 8-80 yr), with a consequent effect on the 14C calibration of material from the Southern Hemisphere. A large increase in the offset occurs between AD 1245 and 1355. In this paper, we present a Southern Hemisphere high-precision calibration data set (SHCal02) that comprises measurements from New Zealand, Chile, and South Africa. This data, and a new value of 41 ± 14 yr for correction of the IntCal98 data for the period outside the range given here, is proposed for use in calibrating Southern Hemisphere 14C dates.

ShCal04 Southern Hemisphere Calibration, 0–11.0 Cal Kyr BP

Recent measurements on dendrochronologically-dated wood from the Southern Hemisphere have shown that there are differences between the structural form of the radiocarbon calibration curves from each hemisphere. Thus, it is desirable, when possible, to use calibration data obtained from secure dendrochronologically-dated wood from the corresponding hemisphere. In this paper, we outline the recent work and point the reader to the internationally recommended data set that should be used for future calibration of Southern Hemisphere 14C dates.

WASP-4b: A 12th magnitude transiting hot Jupiter in the southern hemisphere

We report the discovery of WASP-4b, a large transiting gas-giant planet with an orbital period of 1.34 days. This is the first planet to be discovered by the SuperWASP-South observatory and CORALIE collaboration and the first planet orbiting a star brighter than 16th magnitude to be discovered in the southern hemisphere. A simultaneous fit to high-quality light curves and precision radial velocity measurements leads to a planetary mass of 1.22(-0.08)(+0.09) M-Jup and a planetary radius of 1.42(-0.04)(+0.07) R-Jup. The host star is USNO-B1.0 0479-0948995, a G7 V star of visual magnitude 12.5. As a result of the short orbital period, the predicted surface temperature of the planet is 1761 K, making it an ideal candidate for detections of the secondary eclipse at infrared wavelengths.

Wasp-7: A Bright Transiting-Exoplanet System in the Southern Hemisphere

We report that a Jupiter-mass planet, WASP-7b, transits the V = 9.5 star HD 197286 every 4.95 d. This is the brightest discovery from the WASP-South transit survey so far and is currently the brightest transiting-exoplanet system in the southern hemisphere. WASP-7b is among the densest of the known Jupiter-mass planets, suggesting that it has a massive core. The planet mass is 0.96+0.12 -0.18 M Jup, the radius is 0.915+0.046 -0.040 R Jup, and the density is 1.26+0.25 -0.21 ?Jup (1.67+0.33 -0.28 g cm-3).

WASP-25b: a 0.6 MJ planet in the Southern hemisphere

We report the detection of a 0.6 MJ extrasolar planet by WASP-South, WASP-25b, transiting its solar-type host star every 3.76 d. A simultaneous analysis of the WASP, FTS and Euler photometry and CORALIE spectroscopy yields a planet of Rp= 1.22 RJ and Mp= 0.58 MJ around a slightly metal-poor solar-type host star, [Fe/H]=- 0.05 ± 0.10, of R*= 0.92 Rsun and M*= 1.00 Msun. WASP-25b is found to have a density of ?p= 0.32 ?J, a low value for a sub-Jupiter mass planet. We investigate the relationship of planetary radius to planetary equilibrium temperature and host star metallicity for transiting exoplanets with a similar mass to WASP-25b, finding that these two parameters explain the radii of most low-mass planets well.

A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years

Southern Hemisphere westerly airflow has a significant influence on the ocean–atmosphere system of the mid- to high latitudes with potentially global climate implications. Unfortunately, historic observations only extend back to the late 19th century, limiting our understanding of multi-decadal to centennial change. Here we present a highly resolved (30-year) record of past westerly wind strength from a Falkland Islands peat sequence spanning the last 2600 years. Situated within the core latitude of Southern Hemisphere westerly airflow (the so-called furious fifties), we identify highly variable changes in exotic pollen and charcoal derived from South America which can be used to inform on past westerly air strength. We find a period of high charcoal content between 2000 and 1000 cal. years BP, associated with increased burning in Patagonia, most probably as a result of higher temperatures and stronger westerly airflow. Spectral analysis of the charcoal record identifies a pervasive ca. 250-year periodicity that is coherent with radiocarbon production rates, suggesting that solar variability has a modulating influence on Southern Hemisphere westerly airflow. Our results have important implications for understanding global climate change through the late Holocene.

Acute inactivation of the contralesional hemisphere for longer durations improves recovery after cortical injury

Au cours des dernières années, des méthodes non-invasives de stimulations permettant de moduler l’excitabilité des neurones suivant des lésions du système nerveux central ont été développées. Ces méthodes sont maintenant couramment utilisées pour étudier l’effet de l’inhibition du cortex contralésionnel sur la récupération motrice à la suite d’un accident vasculocérébral (AVC). Bien que plusieurs de ces études rapportent des résultats prometteurs, les paramètres permettant une récupération optimale demeurent encore inconnus. Chez les patients victimes d'un AVC, il est difficile de débuter les traitements rapidement et d'initier l’inhibition dans les heures suivant la lésion. L'impact de ce délai est toujours inconnu. De plus, aucune étude n’a jusqu’à maintenant évalué l’effet de la durée de l’inhibition sur la récupération du membre parétique. Dans le laboratoire du Dr Numa Dancause, nous avons utilisé un modèle bien établi de lésion ischémique chez le rat pour explorer ces questions. Nos objectifs étaient d’évaluer 1) si une inactivation de l’hémisphère contralésionnel initiée dans les heures qui suivent la lésion peut favoriser la récupération et 2) l’effet de la durée de l’inactivation sur la récupération du membre parétique. Suite à une lésion dans le cortex moteur induite par injections d’un vasoconstricteur, nous avons inactivé l’hémisphère contralésionnel à l’aide d’une pompe osmotique assurant l’infusion continue d’un agoniste du GABA (Muscimol). Dans différents groupes expérimentaux, nous avons inactivé l’hémisphère contralésionnel pour une durée de 3, 7 et 14 jours suivant la lésion. Dans un autre groupe, le Muscimol a été infusé pour 14 jours mais à un débit moindre de façon à pouvoir étudier le lien entre la fonction du membre non-parétique et la récupération du membre parétique. Les données comportementales de ces groupes ont été comparées à celles d’animaux ayant récupéré de façon spontanée d'une lésion similaire. Nos résultats indiquent que l’augmentation de la durée de l’inactivation (de 3 à 14 jours) accélère la récupération du membre parétique. De plus, les deux groupes ayant reçu une inactivation d'une durée de 14 jours ont montré une plus grande récupération fonctionnelle que le groupe n’ayant pas reçu d’inactivation de l’hémisphère contralésionnel, le groupe contrôle. Nos résultats suggèrent donc que l’inactivation de l’hémisphère contralésionnel initiée dans les heures suivant la lésion favorise la récupération du membre parétique. La durée d’inhibition la plus efficace (14 jours) dans notre modèle animal est beaucoup plus longues que celles utilisées jusqu’à maintenant chez l’homme. Bien qu’il soit difficile d’extrapoler la durée idéale à utiliser chez les patients à partir de nos données, nos résultats suggèrent que des traitements de plus longue durée pourraient être bénéfiques. Finalement, un message clair ressort de nos études sur la récupération fonctionnelle après un AVC: dans le développement de traitements basés sur l’inhibition de l’hémisphère contralésionnel, la durée de l’inactivation est un facteur clef à considérer.

Brief neuropsychological assessment of adults post-stroke in the left hemisphere

The neuropsychological assessment investigates cognitive deficits to improve the diagnosis, the prognosis and the rehabilitation of patients. In Brazil, stroke is a major cause of hospitalization and the leading cause of mortality and disability. The stroke in the left hemisphere (LH) is associated with different degrees of loss of language and other cognitive impairments, for example, in the memory. We compared the performance in brief neuropsychological tasks of the left hemisphere poststroke patients, without moderate or severe aphasia, with healthy controls. A list of 135 patients was selected based on inclusion criteria. The study included 15 patients with left stroke, paired by sex, age and education to 30 neurologically healthy adults. The data resulting from application of the Neupsilin Brief Neuropsychological Assessment Instrument were analyzed with the nonparametric Mann-Whitney U. Adults with LH stroke showed a significant reduction in performance when compared to healthy controls on language, working memory and ideomotor praxis, results also found in other studies of patients with left hemisphere stroke

Market access in the western hemisphere: implications for the Andean Community

Este estudio busca contribuir a la evaluación del impacto económico que una mayor liberalización comercial en el Hemisferio Occidental, puede tener sobre los países miembros de la Comunidad Andina. Los escenarios de liberalización comercial más significativos se identifican y simulan, mediante el uso del modelo GTAP en su versión estándar de rendimientos constantes a escala. Los resultados básicos indican una muy baja coincidencia en la dirección de los cambios de bienestar esperables para los países andinos, bajo los cuatro escenarios analizados. De una forma muy simplificada, puede decirse que una mayor liberalización comercial implica pérdidas de bienestar para Colombia, Perú y Ecuador-Bolivia, en tanto que para Venezuela se encuentran ganancias bajo los escenarios que implementan el Área de Libre Comercio de las Américas y pérdidas bajo el que implementa el Acuerdo de Libre Comercio entre sus socios andinos y Estados Unidos. Los términos de intercambio juegan un papel determinante en estos resultados. En general se mueven en contra de estas economías, con la notoria excepción de Venezuela. Al parecer, los países andinos se han beneficiado en el pasado de la desviación de comercio que otras regiones han sufrido, como consecuencia de los acuerdos preferenciales de comercio en los cuales los primeros han participado. Con la erosión del acceso preferencial a otros mercados, implícita en los escenarios simulados, el aumento en la competencia tanto por el lado de las exportaciones como por el de las importaciones, tiende a ajustar la posición internacional de estos países, trayendo con ello nuevos retos para el manejo de sus economías.

A new perspective on Southern hemisphere storm-tracks.

A detailed view of Southern Hemisphere storm tracks is obtained based on the application of filtered variance and modern feature-tracking techniques to a wide range of 45-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data. It has been checked that the conclusions drawn in this study are valid even if data from only the satellite era are used. The emphasis of the paper is on the winter season, but results for the four seasons are also discussed. Both upper- and lower-tropospheric fields are used. The tracking analysis focuses on systems that last longer than 2 days and are mobile (move more than 1000 km). Many of the results support previous ideas about the storm tracks, but some new insights are also obtained. In the summer there is a rather circular, strong, deep high-latitude storm track. In winter the high-latitude storm track is more asymmetric with a spiral from the Atlantic and Indian Oceans in toward Antarctica and a subtropical jet–related lower-latitude storm track over the Pacific, again tending to spiral poleward. At all times of the year, maximum storm activity in the higher-latitude storm track is in the Atlantic and Indian Ocean regions. In the winter upper troposphere, the relative importance of, and interplay between, the subtropical and subpolar storm tracks is discussed. The genesis, lysis, and growth rate of lower-tropospheric winter cyclones together lead to a vivid picture of their behavior that is summarized as a set of overlapping plates, each composed of cyclone life cycles. Systems in each plate appear to feed the genesis in the next plate through downstream development in the upper-troposphere spiral storm track. In the lee of the Andes in South America, there is cyclogenesis associated with the subtropical jet and also, poleward of this, cyclogenesis largely associated with system decay on the upslope and regeneration on the downslope. The genesis and lysis of cyclones and anticyclones have a definite spatial relationship with each other and with the Andes. At 500 hPa, their relative longitudinal positions are consistent with vortex-stretching ideas for simple flow over a large-scale mountain. Cyclonic systems near Antarctica have generally spiraled in from lower latitudes. However, cyclogenesis associated with mobile cyclones occurs around the Antarctic coast with an interesting genesis maximum over the sea ice near 150°E. The South Pacific storm track emerges clearly from the tracking as a coherent deep feature spiraling from Australia to southern South America. A feature of the summer season is the genesis of eastward-moving cyclonic systems near the tropic of Capricorn off Brazil, in the central Pacific and, to a lesser extent, off Madagascar, followed by movement along the southwest flanks of the subtropical anticyclones and contribution to the “convergence zone” cloud bands seen in these regions.

New perspectives on the Northern Hemisphere winter storm tracks

The aim of this paper is to explore the use of both an Eulerian and system-centered method of storm track diagnosis applied to a wide range of meteorological fields at multiple levels to provide a range of perspectives on the Northern Hemisphere winter transient motions and to give new insight into the storm track organization and behavior. The data used are primarily from the European Centre for Medium-Range Weather Forecasts reanalyses project extended with operational analyses to the period 1979-2000. This is supplemented by data from the National Centers for Environmental Prediction and Goddard Earth Observing System 1 reanalyses. The range of fields explored include the usual mean sea level pressure and the lower- and upper-tropospheric height, meridional wind, vorticity, and temperature, as well as the potential vorticity (PV) on a 330-K isentropic surface (PV330) and potential temperature on a PV = 2 PVU surface (theta(PV2)). As well as reporting the primary analysis based on feature tracking, the standard Eulerian 2-6-day bandpass filtered variance analysis is also reported and contrasted with the tracking diagnostics. To enable the feature points to be identified as extrema for all the chosen fields, a planetary wave background structure is removed at each data time. The bandpass filtered variance derived from the different fields yield a rich picture of the nature and comparative magnitudes of the North Pacific and Atlantic storm tracks, and of the Siberian and Mediterranean candidates for storm tracks. The feature tracking allows the cyclonic and anticyclonic activities to be considered seperately. The analysis indicates that anticyclonic features are generally much weaker with less coherence than the cyclonic systems. Cyclones and features associated with them are shown to have much greater coherence and give tracking diagnostics that create a vivid storm track picture that includes the aspects highlighted by the variances as well as highlighting aspects that are not readily available from Eulerian studies. In particular, the upper-tropospheric features as shown by negative theta(PV2), for example, occur in a band spiraling around the hemisphere from the subtropical North Atlantic eastward to the high latitudes of the same ocean basin. Lower-troposphere storm tracks occupy more limited longitudinal sectors, with many of the individual storms possibly triggered from the upper-tropospheric disturbances in the spiral band of activity.

Unimodality of wave amplitude in the northern Hemisphere

A novel statistic for local wave amplitude of the 500-hPa geopotential height field is introduced. The statistic uses a Hilbert transform to define a longitudinal wave envelope and dynamical latitude weighting to define the latitudes of interest. Here it is used to detect the existence, or otherwise, of multimodality in its distribution function. The empirical distribution function for the 1960-2000 period is close to a Weibull distribution with shape parameters between 2 and 3. There is substantial interdecadal variability but no apparent local multimodality or bimodality. The zonally averaged wave amplitude, akin to the more usual wave amplitude index, is close to being normally distributed. This is consistent with the central limit theorem, which applies to the construction of the wave amplitude index. For the period 1960-70 it is found that there is apparent bimodality in this index. However, the different amplitudes are realized at different longitudes, so there is no bimodality at any single longitude. As a corollary, it is found that many commonly used statistics to detect multimodality in atmospheric fields potentially satisfy the assumptions underlying the central limit theorem and therefore can only show approximately normal distributions. The author concludes that these techniques may therefore be suboptimal to detect any multimodality.