33 research outputs found
In situ study of magmatic processes: a new experimental approach
We present an internally heated autoclave, modified in order to allow in situ studies at pressure up to 0.5 GPa and temperature up to 1000°C. It is equipped with transparent sapphire windows, allowing the observation of the whole experiment along the horizontal axis. In the experimental cell the sample is held between two thick transparent plates of sapphire or diamond, placed in the furnace cylinder. The experimental volume is about 0.01 cm3. Video records are made during the whole experiment. This tool is developed mainly to study magmatic processes, as the working pressures and temperatures are appropriate for subvolcanic magma reservoirs. However other applications are possible such as the study of subsolidus phase equilibria as we have used well known phase transitions, such as the system of AgI, to calibrate the apparatus with respect to pressure and temperature. The principle of the apparatus is detailed. Applications are presented such as studies of melt inclusions at pressure and temperature and an in situ study of magma degassing through the investigation of nucleation and growth processes of gas bubbles in a silicate melt during decompression
Influence of glass polymerisation and oxidation on micro-Raman water analysis in alumino-silicate glasses
International audienceThe development of an accurate analytical procedure for determination of dissolved water in complex alumino-silicate glasses via micro-Raman analysis requires the assessment of the spectra topology dependence on glass composition. We report here a detailed study of the respective influence of bulk composition, iron oxidation state and total water content on the absolute and relative intensities of the main Raman bands related to glass network vibrations (LF: not, vert, similar490 cm−1; HF: not, vert, similar960 cm−1) and total water stretching (H2OT: not, vert, similar3550 cm−1) in natural glasses. The evolution of spectra topology was examined in (i) 33 anhydrous glasses produced by the re-melting of natural rock samples, which span a very large range of polymerisation degree (NBO/T from 0.00 to 1.16), (ii) 2 sets of synthetic anhydrous basaltic glasses with variable iron oxidation state (Fe3+/FeT from 0.05 to 0.87), and (iii) 6 sets of natural hydrous glasses (CH2OT from 0.4 to 7.0 wt%) with NBO/T varying from 0.01 to 0.76. In the explored domain of water concentration, external calibration procedure based on the H2OT band height is matrix-independent but its accuracy relies on precise control of the focusing depth and beam energy on the sample. Matrix-dependence strongly affects the internal calibrations based on H2OT height scaled to that of LF or HF bands but its effect decreases from acid (low NBO/T, SM) to basic (high NBO/T, SM) glasses. Structural parameters such as NBO/T (non-bridging oxygen per tetrahedron) and SM (sum of structural modifiers) describe the matrix-dependence better than simple compositional parameters (e.g. SiO2, Na2O + K2O). Iron oxidation state has only a minor influence on band topology in basalts and is thus not expected to significantly affect the Raman determinations of water in mafic (e.g. low SiO2, iron-rich) glasses. Modelling the evolution of the relative band height with polymerisation degree allows us to propose a general equation to predict the dissolved water content in natural glasses: View the MathML source where CH2OT is the total water content (in wt%) dissolved in glass; TOTN represents the computed ILF/IHF variation as a function of the calculated NBO/T and SM parameters; IH2ON is the H2O band height scaled to ratio of the reference bands; k is the linearity spectrometer response on the H2OT band in function of water content. The water concentrations of the reference glasses are reproduced using this equation with a standard deviation of 0.06 wt%. The adopted parameterisation provides a useful tool towards the characterisation of composition dependence of micro-Raman procedures for silicate glasses. We show, based on the widest range of glass compositions so far investigated, that accurate evaluation of dissolved water content is achieved by micro-Raman spectroscopy
The Luminous Type Ic SN 1992ar at z=0.145
We present spectroscopic and photometric observations of SN1992ar, the more
distant SN in the Calan/Tololo Survey. We compare its spectrum with those of
nearby Type Ia and Ic SNe and conclude that the latter type is a better match
to SN 1992ar. Using K-corrections based on the spectra of well observed Type Ic
and Ia SNe we compute different possible rest frame light curves of SN 1992ar
and compare them with those of representative SNe of each type observed in the
nearby universe. From the photometry and the spectra, we are able to conclude
that SN 1992ar cannot be matched by any known example of a Type Ia SN. Even
though the data set collected is fairly complete (one spectrum and 10
photometric points), it is not possible to decide whether SN 1992ar was a fast
Type Ic SN, like SN 1994I, or a slow one, like SN 1983V. The absolute V
magnitudes at maximum implied by each of these possibilities are -19.2 and
-20.2, respectively. The latter would make SN 1992ar one of the brightest SNe
on record. SN 1992ar, hence, illustrates the problem of contamination faced by
the high z Type Ia SNe samples whose luminosity distances are used to determine
the cosmological parameters of the Universe. We present observational criteria
to distinguish the two SN types when the SiII 6355 line is redshifted out of
the sensitivity range of typical CCD detectors, and discuss the effect that
these luminous Type Ic SNe would have on the measured cosmological parameters,
if not removed from the High-z Type Ia SN samples.Comment: 40 pages, 9 figures. Accepted for publication in Astrophysical
Journa
The type IC SN 1990B in NGC 4568
We present a study of the Type Ic supernova (SN) 1990B that includes most of the observations obtained from around the world. The combined data set comprises 84 BV(RI)c photometric points spanning approximately 360 days after maximum light and 14 spectra from 5 up to ~150 days after maximum light. In contrast to other Type Ic SNe, SN 1990B did not display a weak but distinct He I λ5876 line indicating that its He content was smaller or that the He layers were rather effectively shielded from the radioactive matter in the ejecta. The behavior of the Na I D line, however, suggests that He I λ5876 was blended with it. SN 1990B appeared on a sharply varying background that complicates the usual techniques of digital photometry. In order to do unbiased photometry, we modeled and subtracted the background of each image with the SN using images of NGC 4568 taken ~2500 days after the explosion, when SN 1990B had faded beyond detection. We compare the performance of standard point-spread function fitting photometry of the SN in the images with and without the background of the parent galaxy and find the results to differ systematically at late times. The photometry done on the images with the background light of NGC 4568 subtracted shows the light curves of SN 1990B to be of the slow Type Ic variety, with a slope steeper than that of the Type Ib SN 1983N or the Type II transition (Type IIb) SN 1993J but slower than that of the Type Ic SN 1994I. We estimate the reddening by foreground matter in the Galaxy and NGC 4568 and compute BV(RI)c light curves spanning ~110 days after maximum light
Optical and Infrared Photometry of the Nearby Type Ia Supernovae 1999ee, 2000bh, 2000ca, and 2001ba
We present near infrared photometry of the Type Ia supernova 1999ee; also,
optical and infrared photometry of the Type Ia SNe 2000bh, 2000ca, and 2001ba.
For SNe 1999ee and 2000bh we present the first-ever SN photometry at 1.035
microns (the Y-band). We present K-corrections which transform the infrared
photometry in the observer's frame to the supernova rest frame. Using our
infrared K-corrections and stretch factors derived from optical photometry, we
construct JHK templates which can be used to determine the apparent magnitudes
at maximum if one has some data in the window -12 to +10 d with respect to
T(B_max). Following up previous work on the uniformity of V minus IR loci of
Type Ia supernovae of mid-range decline rates, we present unreddened loci for
slow decliners. We also discuss evidence for a continuous change of color at a
given epoch as a function of decline rate.Comment: 53 pages, 14 figures, to be published in the March 2004 issue of the
Astronomical Journa
Colorectal Cancer Stage at Diagnosis Before vs During the COVID-19 Pandemic in Italy
IMPORTANCE Delays in screening programs and the reluctance of patients to seek medical
attention because of the outbreak of SARS-CoV-2 could be associated with the risk of more advanced
colorectal cancers at diagnosis.
OBJECTIVE To evaluate whether the SARS-CoV-2 pandemic was associated with more advanced
oncologic stage and change in clinical presentation for patients with colorectal cancer.
DESIGN, SETTING, AND PARTICIPANTS This retrospective, multicenter cohort study included all
17 938 adult patients who underwent surgery for colorectal cancer from March 1, 2020, to December
31, 2021 (pandemic period), and from January 1, 2018, to February 29, 2020 (prepandemic period),
in 81 participating centers in Italy, including tertiary centers and community hospitals. Follow-up was
30 days from surgery.
EXPOSURES Any type of surgical procedure for colorectal cancer, including explorative surgery,
palliative procedures, and atypical or segmental resections.
MAIN OUTCOMES AND MEASURES The primary outcome was advanced stage of colorectal cancer
at diagnosis. Secondary outcomes were distant metastasis, T4 stage, aggressive biology (defined as
cancer with at least 1 of the following characteristics: signet ring cells, mucinous tumor, budding,
lymphovascular invasion, perineural invasion, and lymphangitis), stenotic lesion, emergency surgery,
and palliative surgery. The independent association between the pandemic period and the outcomes
was assessed using multivariate random-effects logistic regression, with hospital as the cluster
variable.
RESULTS A total of 17 938 patients (10 007 men [55.8%]; mean [SD] age, 70.6 [12.2] years)
underwent surgery for colorectal cancer: 7796 (43.5%) during the pandemic period and 10 142
(56.5%) during the prepandemic period. Logistic regression indicated that the pandemic period was
significantly associated with an increased rate of advanced-stage colorectal cancer (odds ratio [OR],
1.07; 95%CI, 1.01-1.13; P = .03), aggressive biology (OR, 1.32; 95%CI, 1.15-1.53; P < .001), and stenotic
lesions (OR, 1.15; 95%CI, 1.01-1.31; P = .03).
CONCLUSIONS AND RELEVANCE This cohort study suggests a significant association between the
SARS-CoV-2 pandemic and the risk of a more advanced oncologic stage at diagnosis among patients
undergoing surgery for colorectal cancer and might indicate a potential reduction of survival for
these patients
Liquides magmatiques piégés dans les cristaux applications pétrogénétiques
Clocchiatti Roberto. Liquides magmatiques piégés dans les cristaux applications pétrogénétiques. In: Bulletin de Minéralogie, volume 104, 4, 1981. 12e assemblée générale de l'I.M.A. - Orléans – Juillet 1980. Deuxième partie : inclusions magmatiques / silicates / gemmes / « open session »
L'Exoscopie, méthodes et applications. — Loïc Le Ribault. Notes et Mémoires n° 12, Total 1975
Clocchiatti Roberto. L'Exoscopie, méthodes et applications. — Loïc Le Ribault. Notes et Mémoires n° 12, Total 1975. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 99, 2-3, 1976. Les cavités intracristallines microscopiques des matériaux de la lithosphère
Liquides magmatiques piégés dans les cristaux applications pétrogénétiques
Clocchiatti Roberto. Liquides magmatiques piégés dans les cristaux applications pétrogénétiques. In: Bulletin de Minéralogie, volume 104, 4, 1981. 12e assemblée générale de l'I.M.A. - Orléans – Juillet 1980. Deuxième partie : inclusions magmatiques / silicates / gemmes / « open session »
Tavola rotonda : le inclusioni fluide. — Memorie Originali : Rendiconti della Societa Italiana di Mineralogia e Petrologia. 1974
Clocchiatti Roberto. Tavola rotonda : le inclusioni fluide. — Memorie Originali : Rendiconti della Societa Italiana di Mineralogia e Petrologia. 1974. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 99, 2-3, 1976. Les cavités intracristallines microscopiques des matériaux de la lithosphère