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Biomedical subjects

F Guyot

Publications and source records attributed to F Guyot.

At least 19 recordsLinked to original sources
PubMed2005

Time trends in the treatment and survival of recurrences from colorectal cancer.

BACKGROUND: Little is known about the management of recurrences from colorectal cancer at a population level. MATERIALS AND METHODS: Data was obtained from the population-based cancer registry of Cote d'Or (Burgundy, France) over a 28-year period. Univariate and multivariate analyses were performed to analyse trends in treatment and survival for local recurrence and distant metastases. RESULTS: The proportion of patients resected for cure increased from 6.7% (1976-1984) to 23.7% (1994-2003; P <0.001) for distant metastases and from 15.9% to 58.1% (P <0.001) for local recurrence. Age and period of diagnosis were independent factors associated with a resection for cure. Rectal cancer local recurrence was less often resected for cure than colon cancer local recurrence (P=0.05). Long-term survival was observed only after resection for cure: 5-year relative survival rates were 36.1% for local recurrence and 24.0% for distant metastases. In the multivariate analysis, survival decreased with age and increased over time but significantly only over the last study period. Surgical resection and palliative chemotherapy were other determinants of prognosis for distant metastases whereas surgical resection and palliative radiotherapy did influence the prognosis for local recurrence. CONCLUSION: Substantial advances in the management of recurrences have been achieved over time. More effective treatments and mass screening represent promising approaches to decrease this problem.

Age Distribution↗
PubMed2004

Generation of a double shock driven by laser.

The feasibility and reliability of a multiple laser shock generation to study the equation of state surface off the principal Hugoniot curve and to approach an isentropic compression has been demonstrated. The technique is based on the use of a double laser pulse. A strong shock was generated in iron targets precompressed by a first weak shock. The effect of precompression was studied. The experiment was performed at the Laboratoire pour l'Utilisation des Lasers Intenses laboratory.

Journal Article↗
PubMed2001

Sound velocities in iron to 110 gigapascals.

The dispersion of longitudinal acoustic phonons was measured by inelastic x-ray scattering in the hexagonal closed-packed (hcp) structure of iron from 19 to 110 gigapascals. Phonon dispersion curves were recorded on polycrystalline iron compressed in a diamond anvil cell, revealing an increase of the longitudinal wave velocity (VP) from 7000 to 8800 meters per second. We show that hcp iron follows a Birch law for VP, which is used to extrapolate velocities to inner core conditions. Extrapolated longitudinal acoustic wave velocities compared with seismic data suggest an inner core that is 4 to 5% lighter than hcp iron.

Journal Article↗
PubMed2001

[A French tool for evaluation of home palliative care: adaptation of the Support Team Assessment Schedule].

The authors describe the utilisation of a quality assessment tool for palliative care administered at home. The questionnaire entitled Support Team Assessment Schedule (STAS) was translated from English for this study. It was then utilised comparatively with different quality of life evaluation instruments. Only the results of the STAS are described here. The approach allows for the unresolved problems in the care to come to the surface week after week. The STAS comprises nine items pertaining to the patient and his/her family, and seven items concerning the services provided. The study exhibits the results of 107 evaluations completed from 50 patients stricken with cancer or AIDS in an advanced phase. The availability of this auto clinical audit tool, employable at home or in a hospital, constitutes an essential initial step in the field of French-speaking clinical evaluation of palliative care.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Bacteria in the Tatahouine meteorite: nanometric-scale life in rocks.

We present a study of the textural signature of terrestrial weathering and related biological activity in the Tatahouine meteorite. Scanning and transmission electron microscopy images obtained on the weathered samples of the Tatahouine meteorite and surrounding soil show two types of bacteria-like forms lying on mineral surfaces: (1) rod-shaped forms (RSF) about 70-80 nm wide and ranging from 100 nm to 600 nm in length; (2) ovoid forms (OVF) with diameters between 70 and 300 nm. They look like single cells surrounded by a cell wall. Only Na, K, C, O and N with traces of P and S are observed in the bulk of these objects. The chemical analyses and electron diffraction patterns confirm that the RSF and OVF cannot be magnetite or other iron oxides, iron hydroxides, silicates or carbonates. The sizes of the RSF and OVF are below those commonly observed for bacteria but are very similar to some bacteria-like forms described in the Martian meteorite ALH84001. All the previous observations strongly suggest that they are bacteria or their remnants. This conclusion is further supported by microbiological experiments in which pleomorphic bacteria with morphology similar to the OVF and RSF objects are obtained from biological culture of the soil surrounding the meteorite pieces. The present results show that bacteriomorphs of diameter less than 100 nm may in fact represent real bacteria or their remnants.

Bacteria↗
PubMed1999

Multi-parameter observation of environmental asbestos pollution at the Institut de Physique du Globe de Paris (Jussieu Campus, France).

An original multi-parameter system has been used to study the nature of dust in the ambient air, particularly the total fibers and asbestos fibers, in eight areas of the Institut de Physique de Globe de Paris (France). These analyses provide a detailed case study of environmental pollution by asbestos fibers at low levels. The levels of total fibers with a length greater than 3 microns, measured with a real time fiber analyser monitor (FAM), give a baseline of 2.5 fibers per l., throughout the duration of sampling. The same levels, calculated during periods of effective presence of staff, are smaller than 10 fb per l. During these periods, the instantaneous value can show high peaks, reaching a maximum of 60 fb per l., but more often of about 5 to 10 fb per l. A direct cause and effect relationship exists between fiber concentrations and the presence of people, and indirectly with the variation of the other environmental parameters (temperature, humidity, air velocity). The baseline concentration of asbestos fibers, determined by analytical transmission electron microscopy (ATEM), is about 10(-1) fb per l., with a mean value during the presence of people always less than 1.5 fb per l. The low levels of asbestos fibers do not allow us to establish a precise correlation between the concentration of total fibers and the asbestos concentration, but a rough estimate suggests that asbestos could represent 10-20% of the airborne fibers monitored with the FAM. The statistical study of fiber sizes shows that 70 and 55% of analyzed chrysotile and amosite fibers respectively are smaller than 5 microns. These numbers are 40 and 35% for fibers smaller than 3 microns, which are undetected by the FAM. Amosite, which characterizes most of the asbestos-containing materials (ACM) in the analyzed areas, is detected in the ambient air in quantities ten times less important than chrysotile. The low asbestos levels and the difference between the nature of building asbestos and airborne fibers, show that the mean measured asbestos contents in the ambient air represent the geochemical background of chrysotile asbestos fibers in the Parisian air.

Air Pollution↗
PubMed1998

Pressure-induced landau-type transition in stishovite

A Rietveld structural analysis of stishovite, with angle-dispersive x-ray diffraction synchrotron source at the European Synchrotron Radiation Facility, confirmed a CaCl2 form of stishovite distortion at 54 +/- 1 gigapascals but confirmed no further phase transformation up to 120 gigapascals. The deviatoric stress that is usually encountered at such pressures was relaxed after yttrium-aluminum-garnet-laser heating. A single Birch-Murnaghan equation of state fits volumes of stishovite and a CaCl2 form, showing that the tetragonal distortion occurs without a substantial change in volume. At the 54-gigapascal transition, the pressure-induced lattice modifications were similar to those found in a Landau-type temperature-induced transition. It is proposed that, above the transition pressure, the critical temperature increases above 300 kelvin, so that the lower entropy form becomes stable.

Journal Article↗
PubMed1997

The Breakdown of Olivine to Perovskite and Magnesiowustite

San Carlos olivine crystals under laboratory conditions of 26 gigapascals and 973 to 1473 kelvin (conditions typical of subducted slabs at a depth of 720 kilometers) for periods of a few minutes to 19 hours transformed to the phase assemblage of perovskite and magnesiowustite in two stages: (i) the oxygen sublattice transformed into a cubic close-packed lattice, forming a metastable spinelloid, and (ii) at higher temperatures or longer run durations, this spinelloid broke down to perovskite and magnesiowustite by redistributing silicon and magnesium while maintaining the general oxygen framework. The breakdown was characterized by a blocking temperature of 1000 kelvin, below which olivine remained metastable, and by rapid kinetics once the reaction was activated.

Journal Article↗
PubMed1992

[Surgery of the aortic bifurcation and heart diseases: peroperative hemodynamics].

During aorto-biiliac by-pass, patients with heart disease are exposed at many haemodynamic problems. Mixed venous oxygen saturation monitoring help anesthetist along clamping and unclamping periods. This study concerning 13 patients with pre-operative NYHA class II and III congestive heart disease, discusses therapeutic algorithm especially for choosing inotropic or vasodilatator drugs.

Aged↗
PubMed1989

[The cortical column, a new processing unit for cortex-like networks].

We propose in this paper a new connectionnist model which is the result of a collaboration between computer science and neurobiology researchers. This model is based upon a cortical-like network close to cortical function simulation. We present its functional and architectural characteristics together with the very encouraging results obtained for the first simulations on the visual and auditory cortical functions in speech and character recognition.

Auditory Cortex↗