Seasonal exposure of carbon dioxide ice on the nucleus of comet 67P/Churyumov-Gerasimenko.

Carbon dioxide (CO2) is one of the most abundant species in cometary nuclei, but because of its high volatility, CO2 ice is generally only found beneath the surface. We report the infrared spectroscopic identification of a CO2 ice-rich surface area located in the Anhur region of comet 67P/Churyumov-Gerasimenko. Spectral modeling shows that about 0.1% of the 80- by 60-meter area is CO2 ice. This exposed ice was observed a short time after the comet exited local winter; following the increased illumination, the CO2 ice completely disappeared over about 3 weeks. We estimate the mass of the sublimated CO2 ice and the depth of the eroded surface layer. We interpret the presence of CO2 ice as the result of the extreme seasonal changes induced by the rotation and orbit of the comet.

Exposed water ice on the nucleus of comet 67P/Churyumov-Gerasimenko.

Although water vapour is the main species observed in the coma of comet 67P/Churyumov-Gerasimenko and water is the major constituent of cometary nuclei, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far. The absence of large regions of exposed water ice seems a common finding on the surfaces of many of the comets observed so far. The nucleus of 67P/Churyumov-Gerasimenko appears to be fairly uniformly coated with dark, dehydrated, refractory and organic-rich material. Here we report the identification at infrared wavelengths of water ice on two debris falls in the Imhotep region of the nucleus. The ice has been exposed on the walls of elevated structures and at the base of the walls. A quantitative derivation of the abundance of ice in these regions indicates the presence of millimetre-sized pure water-ice grains, considerably larger than in all previous observations. Although micrometre-sized water-ice grains are the usual result of vapour recondensation in ice-free layers, the occurrence of millimetre-sized grains of pure ice as observed in the Imhotep debris falls is best explained by grain growth by vapour diffusion in ice-rich layers, or by sintering. As a consequence of these processes, the nucleus can develop an extended and complex coating in which the outer dehydrated crust is superimposed on layers enriched in water ice. The stratigraphy observed on 67P/Churyumov-Gerasimenko is therefore the result of evolutionary processes affecting the uppermost metres of the nucleus and does not necessarily require a global layering to have occurred at the time of the comet's formation.

How to perform low-dose computed tomography for renal colic in clinical practice.

Computed tomography (CT) has become the reference technique in medical imaging for renal colic, to diagnose, plan treatment and explore differential diagnosis. Its main limitation is the radiation dose, especially as urinary stone disease tends to relapse and mainly affects young people. It is therefore essential to reduce the CT radiation dose when renal colic is suspected. The goal of this review was twofold. First, we wanted to show how to use low-dose CT in patients with suspected renal colic in current clinical practice. Second, we wished to discuss the different ways of reducing CT radiation dose by considering both behavioral and technological factors. Among the behavioral factors, limiting the scan coverage area is a straightforward and effective way to reduce the dose. Improvement of technological factors relies mainly on using automatic tube current modulation, lowering the tube voltage and current as well using iterative reconstruction.

Addressing requests for emergency ultrasonographic examinations when implementing teleradiology services.

PURPOSE: To prospectively assess how to address requests for ultrasonographic examinations when setting up an on-call teleradiology service. MATERIALS AND METHODS: An analytical prospective study was performed from January 2012 to December 2012 inclusively. All requests received for after-hours ultrasonographic examinations during this period were analyzed. Ultrasound requests were classified as being postponable until working hours, replaceable by an alternate cross-sectional imaging modality, or urgent and needing to be performed after hours. RESULTS: A total of 176 requests for ultrasonographic examinations were analyzed. They predominantly included requests for abdominal and pelvic ultrasonographic examinations (63%). Thirty-nine requests (22.2%) were considered as postponable, 49 (27.8%) as replaceable and 64 (36.4%) as both postponable and replaceable. Twenty-four requests (13.6%) were considered as urgent; they consisted of 10 requests for venous duplex Doppler ultrasonographic examinations of the lower limbs, eight requests for testicular ultrasonographic examinations, five for pelvic ultrasonographic examinations and one for soft-tissue ultrasonographic examination. In these urgent cases, realistic options were either to transfer the patient to another institution or to train emergency department physicians in ultrasonography for local handling. CONCLUSION: Although the need for addressing requests for ultrasonographic examinations should be taken into account when setting up an on-call teleradiology service, it should not impede such plans.

Cometary science. The organic-rich surface of comet 67P/Churyumov-Gerasimenko as seen by VIRTIS/Rosetta.

The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument on board the Rosetta spacecraft has provided evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 ± 0.003 at 0.55 micrometers), the spectral slopes in visible and infrared ranges (5 to 25 and 1.5 to 5% kÅ(-1)), and the broad absorption feature in the 2.9-to-3.6-micrometer range present across the entire illuminated surface are compatible with opaque minerals associated with nonvolatile organic macromolecular materials: a complex mixture of various types of carbon-hydrogen and/or oxygen-hydrogen chemical groups, with little contribution of nitrogen-hydrogen groups. In active areas, the changes in spectral slope and absorption feature width may suggest small amounts of water-ice. However, no ice-rich patches are observed, indicating a generally dehydrated nature for the surface currently illuminated by the Sun.

Acute severe neck pain and dysphagia following cervical maneuver: diagnostic approach.

INTRODUCTION: Overlooking an etiologic hypothesis in acute neck pain with dysphagia may lead to misdiagnosis. CASE REPORT: A 51-year-old man who had received cervical manipulation came to the emergency unit with evolutive acute neck pain, cervical spine stiffness and odynophagia, without fever or other signs of identified pathology. Cervical X-ray and CT angiography of the supra-aortic vessels ruled out traumatic etiology (fracture or arterial dissection) and revealed an accessory bone, orienting diagnosis toward retropharyngeal abscess, which was, however, belied by endoscopy performed under general anesthesia. A second CT scan with contrast injection and tissue phase ruled out infection, revealing a retropharyngeal calcification inducing retropharyngeal edema. Evolution under analgesics was favorable within 13 days. DISCUSSION: Given a clinical triad associating acute neck pain, cervical spine stiffness and odynophagia, traumatic or infectious etiology was initially suspected. Cervical CT diagnosed calcific tendinitis of the longus colli, revealing a pathognomic retropharyngeal calcification. Secondary to hydroxyapatite deposits anterior to the odontoid process of the axis, this is a rare form of tendinopathy, usually showing favorable evolution in 10-15 days under analgesic and anti-inflammatory treatment.

The surface composition and temperature of asteroid 21 Lutetia as observed by Rosetta/VIRTIS.

The Visible, InfraRed, and Thermal Imaging Spectrometer (VIRTIS) on Rosetta obtained hyperspectral images, spectral reflectance maps, and temperature maps of the asteroid 21 Lutetia. No absorption features, of either silicates or hydrated minerals, have been detected across the observed area in the spectral range from 0.4 to 3.5 micrometers. The surface temperature reaches a maximum value of 245 kelvin and correlates well with topographic features. The thermal inertia is in the range from 20 to 30 joules meter(-2) kelvin(-1) second(-0.5), comparable to a lunarlike powdery regolith. Spectral signatures of surface alteration, resulting from space weathering, seem to be missing. Lutetia is likely a remnant of the primordial planetesimal population, unaltered by differentiation processes and composed of chondritic materials of enstatitic or carbonaceous origin, dominated by iron-poor minerals that have not suffered aqueous alteration.

Cardiovascular toxicity of cancer treatment.

Drugs with potential cardiac toxicity are prominent in cancer treatment, not only the old chemotherapeutic agents, but also the newer targeted drugs and biologic agents. As the long-term survival of patients with malignancies has improved and cancer turned into a chronic disease, physicians must take into account the short-term as well as long-term consequences of cancer treatment, such as chemotherapy-induced cardiotoxicity. We summarize some general characteristics and subsequently review specific antineoplastic agents that are associated with cardiac toxicity.

[Evaluation of the knowledge of physicians prescribing CT examinations on the radiation protection of patients]. / Évaluation des connaissances des prescripteurs de scanner en matière de radioprotection des patients.

PURPOSE: To evaluate the knowledge of physicians prescribing CT examinations on the radiation protection of patients. MATERIALS AND METHODS: A questionnaire was distributed to all clinicians on medical staff who prescribe CT examinations. Several questions related to their prescription pattern and their knowledge of radiation protection. RESULTS: Forty-four questionnaires were analyzed. While 70% of physicians claimed that they considered the risks from exposure to ionizing radiation when prescribing a CT examination, only 25% informed their patients about those risks. Knowledge of the radiation dose delivered during CT evaluation of the abdomen and pelvis was poorly understood and the risks related to small doses of radiation were grossly underestimated. Finally, only a third of clinicians had received training with regards to radiation protection. CONCLUSION: While most clinicians claim that they consider the risks from exposure to ionizing radiation when prescribing a CT examination, the risks are either not well known or not known at all. Increased formation of clinicians with regards to the radiation protection of patients, maybe through a dedicated clinical rotation while in medical school, could be a solution to improve the knowledge of hospital clinicians with regards to radiation protection.

Macrophage gene expression is related to obesity and the metabolic syndrome in human subcutaneous fat as well as in visceral fat.

AIMS/HYPOTHESIS: Our goal was to identify a set of human adipose tissue macrophage (ATM)-specific markers and investigate whether their gene expression in subcutaneous adipose tissue (SAT) as well as in visceral adipose tissue (VAT) is related to obesity and to the occurrence of the metabolic syndrome. METHODS: ATM-specific markers were identified by DNA microarray analysis of adipose tissue cell types isolated from SAT of lean and obese individuals. We then analysed gene expression of these markers by reverse transcription quantitative PCR in paired samples of SAT and VAT from 53 women stratified into four groups (lean, overweight, obese and obese with the metabolic syndrome). Anthropometric measurements, euglycaemic-hyperinsulinaemic clamp, blood analysis and computed tomography scans were performed. RESULTS: A panel of 24 genes was selected as ATM-specific markers based on overexpression in ATM compared with other adipose tissue cell types. In SAT and VAT, gene expression of ATM markers was lowest in lean and highest in the metabolic syndrome group. mRNA levels in the two fat depots were negatively correlated with glucose disposal rate and positively associated with indices of adiposity and the metabolic syndrome. CONCLUSIONS/INTERPRETATION: In humans, expression of ATM-specific genes increases with the degree of adiposity and correlates with markers of insulin resistance and the metabolic syndrome to a similar degree in SAT and in VAT.

[Retrospective study conducted in northern Finistère about the role of breast MRI in normal breast screening, experience in 51 patients]. / Etude rétrospective dans le Nord-Finistère sur la place de l'IRM mammaire devant un bilan sénologique normal, à propos de 51 cas.

OBJECTIVES: To study the role and indications of breast MRI in normal breast screening. PATIENTS AND METHODS: Retrospective study of 51 patients (mean age of 51 years) conducted in northern Finistère. Each patient had a normal (BI-RADS 1 or 2) breast screening (mammography and echography). Four indications for MRI were chosen: screening of high-risk patients, high-density breasts, radio-clinical discordance, and breasts prostheses. Breast MRI were reviewed according to BI-RADS classification. Abnormalities categorized in BI-RADS 4 or 5 were confirmed histologically. RESULTS: Thirteen patients underwent histological analysis. Nine invasive carcinomas were identified (six invasive lobular carcinomas (ILC), two mixed carcinomas, one invasive ductal carcinoma). For these patients, the reason for performing MRI was a radio-clinical discordance. DISCUSSION AND CONCLUSION: The study demonstrates the breast MRI value for radio-clinical discordance and the key role of MRI in diagnostic challenge of ILC. In literature review, MRI has a role even if breast screening is normal: radio-clinical discordance, screening of patients with high-risk, breasts prostheses in certain cases. Breast density comes as an additional criteria to perform this exam.

Surface composition of Hyperion.

Hyperion, Saturn's eighth largest icy satellite, is a body of irregular shape in a state of chaotic rotation. The surface is segregated into two distinct units. A spatially dominant high-albedo unit having the strong signature of H2O ice contrasts with a unit that is about a factor of four lower in albedo and is found mostly in the bottoms of cup-like craters. Here we report observations of Hyperion's surface in the ultraviolet and near-infrared spectral regions with two optical remote sensing instruments on the Cassini spacecraft at closest approach during a fly-by on 25-26 September 2005. The close fly-by afforded us the opportunity to obtain separate reflectance spectra of the high- and low-albedo surface components. The low-albedo material has spectral similarities and compositional signatures that link it with the surface of Phoebe and a hemisphere-wide superficial coating on Iapetus.

Introgressive hybridization between the allotetraploid Coffea arabica and one of its diploid ancestors, Coffea canephora, in an exceptional sympatric zone in New Caledonia.

The importance of introgressive hybridization in plant evolution has long been recognized. Nevertheless, information on gene flow between allopolyploids and their diploid relatives is very limited, even though gene flow could play a major role in polyploid establishment and evolution. Here, we investigated the processes governing hybrid formation and introgression between the allotetraploid Coffea arabica and one of its ancestral diploid progenitors, C. canephora, in a sympatric zone of New Caledonia. The occurrence of a large assortment of hybridization events between the 2 coffee species is clearly established. First-generation hybrids (F1) and post-F1 hybrids were characterized. The involvement of unreduced gametes of C. canephora is suggested, because tetraploid F1 hybrid plants were detected. Moreover, although bidirectional mating was observed, only unidirectional gene flow from C. canephora to C. arabica was noted in post-F1 hybrids. Most of the collected post-F1 hybrid plants exhibited a high level of introgression, and the frequency of introgression observed among the different analyzed loci was homogeneous, suggesting no significant counterselection against introgressions from C. canephora. Overall, the New Caledonian central mountains appear to be a highly favourable environment for introgressive hybridization and a genetic diversity center for C. arabica.

Composition and physical properties of Enceladus' surface.

Observations of Saturn's satellite Enceladus using Cassini's Visual and Infrared Mapping Spectrometer instrument were obtained during three flybys of Enceladus in 2005. Enceladus' surface is composed mostly of nearly pure water ice except near its south pole, where there are light organics, CO2, and amorphous and crystalline water ice, particularly in the region dubbed the "tiger stripes." An upper limit of 5 precipitable nanometers is derived for CO in the atmospheric column above Enceladus, and 2% for NH3 in global surface deposits. Upper limits of 140 kelvin (for a filled pixel) are derived for the temperatures in the tiger stripes.

Rain, winds and haze during the Huygens probe's descent to Titan's surface.

The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent.

Phyllosilicates on Mars and implications for early martian climate.

The recent identification of large deposits of sulphates by remote sensing and in situ observations has been considered evidence of the past presence of liquid water on Mars. Here we report the unambiguous detection of diverse phyllosilicates, a family of aqueous alteration products, on the basis of observations by the OMEGA imaging spectrometer on board the Mars Express spacecraft. These minerals are mainly associated with Noachian outcrops, which is consistent with an early active hydrological system, sustaining the long-term contact of igneous minerals with liquid water. We infer that the two main families of hydrated alteration products detected-phyllosilicates and sulphates--result from different formation processes. These occurred during two distinct climatic episodes: an early Noachian Mars, resulting in the formation of hydrated silicates, followed by a more acidic environment, in which sulphates formed.

The evolution of Titan's mid-latitude clouds.

Spectra from Cassini's Visual and Infrared Mapping Spectrometer reveal that the horizontal structure, height, and optical depth of Titan's clouds are highly dynamic. Vigorous cloud centers are seen to rise from the middle to the upper troposphere within 30 minutes and dissipate within the next hour. Their development indicates that Titan's clouds evolve convectively; dissipate through rain; and, over the next several hours, waft downwind to achieve their great longitude extents. These and other characteristics suggest that temperate clouds originate from circulation-induced convergence, in addition to a forcing at the surface associated with Saturn's tides, geology, and/or surface composition.