Fractura avulsión del troquin humeral : a propósito de un caso

La fractura-avulsión aislada del troquín humeral sin luxación escápulo-humeral, es una entidad rara, descrita muy pocas veces en la literatura internacional. Su mecanismo de producción es similar al de otras lesiones por avulsión: contracción violenta de un músculo sobre una relativamente pequeña apófisis de inserción; en este caso, el músculo subescapular a nivel del troquín. La combinación de abducción más rotación externa del húmero con una contractura súbita y violenta del músculo subescapular, podría provocar un arrancamiento del troquín con mayor o menor grado de desplazamiento. Aunque el tratamiento ortopédico mediante simple inmovilización puede indicarse en algunos casos, la reparación quirúrgica precoz, con osteosíntesis del fragmento óseo, o resección del fragmento óseo, permite obtener un excelente resultado. En este caso, el tratamiento se realizó mediante fijación con un único tornillo maleolar.Isolated avulsion fracture of the lesser tuberosity of the humerus, in absence of dislocation, is a extremely rare entity, with very few references in the international literature. This injury is produced by a similar mechanism to other avulsion injuries; violent muscular contraction upon small insertion apophysis; in this case, the subescapularis muscle on the lesser tuberosity of the humerus. This abdution and external rotation of the humerus combined with sudden and violent contracture of the subescapularis muscle can produce avulsion of the lesser tuberosity with more o less displacement. Although, some cases can be treated conservatively, surgical treatment by internal fixation or bone fragment excision provides excellent results. This case was treated by fixation with a single malleolar screw

Atmospheric methane, record from greenland ice core over the last 1000 years

The atmospheric methane concentration in ancient times can be reconstructed by analysing air entrapped in bubbles of polar ice sheets. We present results from an ice core from Central Greenland (Eurocore) covering the last 1000 years. We observe variations of about 70 ppbv around the mean pre-industrial level, which is confirmed at about 700 ppbv on a global average. According to our data, the beginning of the anthropogenic methane increase can be set between 1750 and 1800. Changes in the oxidizing capacity of the atmosphere may contribute significantly to the pre-industrial methane concentration variations, but changes in methane emissions probably play a dominant role. Since methane release depends on a host of influences it is difficult to specify clearly the reasons for these emission changes. Methane concentrations correlate only partially with proxy-data of climatic factors which influence the wetland release (the main source in pre-industrial times). A good correlation between our data and a population record from China suggests that man may already have influenced the CH4-cycle significantly before industrialisation

Mercury in the snow and firn at Summit Station, Central Greenland, and implications for the study of past atmospheric mercury levels

Gaseous Elemental Mercury (Hg° or GEM) was investigated at Summit Station, Greenland, in the interstitial air extracted from the perennial snowpack (firn) at depths ranging from the surface to 30 m, during summer 2005 and spring 2006. Photolytic production and destruction of Hg° were observed close to the snow surface during summer 2005 and spring 2006, and we observed dark oxidation of GEM up to 270 cm depth in June 2006. Photochemical transformation of gaseous elemental mercury resulted in diel variations in the concentrations of this gas in the near-surface interstitial air, but destruction of Hg° was predominant in June, and production was the main process in July. This seasonal evolution of the chemical mechanisms involving gaseous elemental mercury produces a signal that propagates downward through the firn air, but is unobservably small below 15 m in depth. As a consequence, multi-annual averaged records of GEM concentration should be well preserved in deep firn air at depths below 15 m, and available for the reconstruction of the past atmospheric history of GEM over the last decades

Atmospheric methane during the last four glacial-interglacial cycles: Rapid changes and their link with Antarctic temperature

Atmospheric methane (CH₄) recorded in Antarctic ice cores represents the closest ice proxy available for Greenland temperature changes beyond times when Greenland climate records are available. The record over four climatic cycles from the Vostok ice core offers the opportunity to study the phase relationship between Greenland and Antarctic climate changes through detailed CH₄ profiles. Combining American and French analytical efforts, we have improved the time resolution of the existing CH₄ record from Petit et al. [1999] . Spectral analyses reveal high- and low-frequency variability (including a strong precessional component). The phase relationship between CH₄ and the Antarctic temperature proxy (δD) shows a systematic lag of CH₄ versus temperature by 1100 ± 200 years, on long timescales (50–400 kyr) and a more complex behavior over shorter timescales (i.e., ≤25 kyr), suggesting that Dansgaard/Oeschger-type of climatic variability and associated interhemispheric linkage are robust features of late Quaternary climate

"EDML1": a chronology for the EPICA deep ice core from Dronning Maud Land, Antarctica, over the last 150 000 years.

A chronology called EDML1 has been developed for the EPICA ice core from Dronning Maud Land (EDML). EDML1 is closely interlinked with EDC3, the new chronology for the EPICA ice core from Dome-C (EDC) through a stratigraphic match between EDML and EDC that consists of 322 volcanic match points over the last 128 ka. The EDC3 chronology comprises a glaciological model at EDC, which is constrained and later selectively tuned using primary dating information from EDC as well as from EDML, the latter being transferred using the tight stratigraphic link between the two cores. Finally, EDML1 was built by exporting EDC3 to EDML. For ages younger than 41 ka BP the new synchronized time scale EDML1/EDC3 is based on dated volcanic events and on a match to the Greenlandic ice core chronology GICC05 via <sup>10</sup>Be and methane. The internal consistency between EDML1 and EDC3 is estimated to be typically ~6 years and always less than 450 years over the last 128 ka (always less than 130 years over the last 60 ka), which reflects an unprecedented synchrony of time scales. EDML1 ends at 150 ka BP (2417 m depth) because the match between EDML and EDC becomes ambiguous further down. This hints at a complex ice flow history for the deepest 350 m of the EDML ice core

Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core

International audienceAn important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (δD-δ18Oice , δ18Oatm , total air content, CO2 , CH4 , N2O, dust, high-resolution chemistry , ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the " basal clean ice facies ". Some of the data are consistent with a pristine paleocli-matic signal, others show clear anomalies. It is demonstrated that neither large-scale bottom refreezing of subglacial water , nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides

High variablity of Greenland surface temperature over the past 4000 years estimated from trapped air in ice core

第2回極域科学シンポジウム　氷床コアセッション 11月16日（水） 国立極地研究所 2階大会議

Climate and atmospheric history of the past 420,000 years from the Vostok ice core,

Antarctica has allowed the extension of the ice record of atmospheric composition and climate to the past four glacial-interglacial cycles. The succession of changes through each climate cycle and termination was similar, and atmospheric and climate properties oscillated between stable bounds. Interglacial periods differed in temporal evolution and duration. Atmospheric concentrations of carbon dioxide and methane correlate well with Antarctic air-temperature throughout the record. Present-day atmospheric burdens of these two important greenhouse gases seem to have been unprecedented during the past 420,000 years. The late Quaternary period (the past one million years) is punctuated by a series of large glacial-interglacial changes with cycles that last about 100,000 years (ref. 1). Glacial-interglacial climate changes are documented by complementary climate records 1,2 largely derived from deep sea sediments, continental deposits of flora, fauna and loess, and ice cores. These studies have documented the wide range of climate variability on Earth. They have shown that much of the variability occurs with periodicities corresponding to that of the precession, obliquity and eccentricity of the Earth's orbit 1,3 . But understanding how the climate system responds to this initial orbital forcing is still an important issue in palaeoclimatology, in particular for the generally strong ϳ100,000-year (100-kyr) cycle. Ice cores give access to palaeoclimate series that includes local temperature and precipitation rate, moisture source conditions, wind strength and aerosol fluxes of marine, volcanic, terrestrial, cosmogenic and anthropogenic origin. They are also unique with their entrapped air inclusions in providing direct records of past changes in atmospheric trace-gas composition. The ice-drilling project undertaken in the framework of a long-term collaboration between Russia, the United States and France at the Russian Vostok station in East Antarctica (78Њ S, 106Њ E, elevation 3,488 m, mean temperature −55 ЊC) has already provided a wealth of such information for the past two glacial-interglacial cycles [4][5][6][7][8][9] Here we present a series of detailed Vostok records covering this ϳ400-kyr period. We show that the main features of the more recent Vostok climate cycle resemble those observed in earlier cycles. In particular, we confirm the strong correlation between atmospheric greenhouse-gas concentrations and Antarctic temperature, as well as the strong imprint of obliquity and precession in most of the climate time series. Our records reveal both similarities and differences between the successive interglacial periods. They suggest the lead of Antarctic air temperature, and of atmospheric greenhousegas concentrations, with respect to global ice volume and Greenland air-temperature changes during glacial terminations. The ice record The data are shown in Figs 1, 2 and 3 (see Supplementary Information for the numerical data). They include the deuterium content of the ice (dD ice , a proxy of local temperature change), the dust content (desert aerosols), the concentration of sodium (marine aerosol), and from the entrapped air the greenhouse gases CO 2 and CH 4 , and the d 18 O are defined in the legends to Figs 1 and 2, respectively.) All these measurements have been performed using methods previously described except for slight modifications (see The detailed record of dD ic

Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core

An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (δD-δ18Oice, δ18Oatm, total air content, CO2, CH4, N2O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the "basal clean ice facies". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies. It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of debris from the ice sheet's substrate. We further discuss how the proposed mechanism is compatible with the other ice properties described. We conclude that the paleoclimatic signal is only marginally affected in terms of global ice properties at the bottom of EPICA Dome C, but that the timescale was considerably distorted by mechanical stretching of MIS20 due to the increasing influence of the subglacial topography, a process that might have started well above the bottom ice. A clear paleoclimatic signal can therefore not be inferred from the deeper part of the EPICA Dome C ice core. Our work suggests that the existence of a flat monotonic ice-bedrock interface, extending for several times the ice thickness, would be a crucial factor in choosing a future "oldest ice" drilling location in Antarctica