263 research outputs found
Isotope Spectroscopy
The measurement of isotopic ratios provides a privileged insight both into
nucleosynthesis and into the mechanisms operating in stellar envelopes, such as
gravitational settling. In this article, we give a few examples of how isotopic
ratios can be determined from high-resolution, high-quality stellar spectra. We
consider examples of the lightest elements, H and He, for which the isotopic
shifts are very large and easily measurable, and examples of heavier elements
for which the determination of isotopic ratios is more difficult. The presence
of 6Li in the stellar atmospheres causes a subtle extra depression in the red
wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the
highest quality. But even with the best spectra, the derived Li abundance
can only be as good as the synthetic spectra used for their interpretation. It
is now known that 3D non-LTE modelling of the lithium spectral line profiles is
necessary to account properly for the intrinsic line asymmetry, which is
produced by convective flows in the atmospheres of cool stars, and can mimic
the presence of 6Li. We also discuss briefly the case of the carbon isotopic
ratio in metal-poor stars, and provide a new determination of the nickel
isotopic ratios in the solar atmosphere.Comment: AIP Thinkshop 10 "High resolution optical spectroscopy", invited
talk, AN in pres
Comparative genomic hybridization on microarray (a-CGH) in constitutional and acquired mosaicism may detect as low as 8% abnormal cells
Abstract. Background: The results of cytogenetic investigations on unbalanced chromosome anomalies, both constitutional and acquired, were largely improved by comparative genomic hybridization on microarray (a-CGH), but in mosaicism the ability of a-CGH to reliably detect imbalances is not yet well established. This problem of sensitivity is even more relevant in acquired mosaicism in neoplastic diseases, where cells carrying acquired imbalances coexist with normal cells, in particular when the proportion of abnormal cells may be low. We constructed a synthetic mosaicism by mixing the DNA of three patients carrying altogether seven chromosome imbalances with normal sex-matched DNA. Dilutions were prepared mimicking 5%, 6%, 7%, 8%, 10% and 15% levels of mosaicism. Oligomer-based a-CGH (244 K whole-genome system) was applied on the patients' DNA and customized slides designed around the regions of imbalance were used for the synthetic mosaics. Results and conclusions. The a-CGH on the synthetic mosaics proved to be able to detect as low as 8% abnormal cells in the tissue examined. Although in our experiment some regions of imbalances escaped to be revealed at this level, and were detected only at 10-15% level, it should be remarked that these ones were the smallest analyzed, and that the imbalances recurrent as clonal anomalies in cancer and leukaemia are similar in size to those revealed at 8% level
SURGERY IN MALIGNANT GERM CELL TUMORS OF CHILDHOOD. RESULTS OF THE SECOND ITALIAN COOPERATIVE STUDY TCG 98
Analysis of treatment and results of the patientsenrolled in the Italian TCG-98 Study, still open and comparison of data with those of the previous Studt TCG-9
Different loss of material in recurrent chromosome 20 interstitial deletions in Shwachman-Diamond syndrome and in myeloid neoplasms
Abstract
BACKGROUND:
An interstitial deletion of the long arms of chromosome 20, del(20)(q), is frequent in the bone marrow (BM) of patients with myelodysplastic syndromes (MDS), acute myeloid leukemia (AML), and myeloproliferative neoplasms (MPN), and it is recurrent in the BM of patients with Shwachman-Diamond syndrome (SDS), who have a 30-40% risk of developing MDS and AML.
RESULTS:
We report the results obtained by microarray-based comparative genomic hybridization (a-CGH) in six patients with SDS, and we compare the loss of chromosome 20 material with one patient with MDS, and with data on 92 informative patients with MDS/AML/MPN and del(20)(q) collected from the literature.
CONCLUSIONS:
The chromosome material lost in MDS/AML/MPN is highly variable with no identifiable common deleted regions, whereas in SDS the loss is more uniform: in 3/6 patients it was almost identical, and the breakpoints that we defined are probably common to most patients from the literature. In some SDS patients less material may be lost, due to different distal breakpoints, but the proximal breakpoint is in the same region, always leading to the loss of the EIF6 gene, an event which was related to a lower risk of MDS/AML in comparison with other patients
Deletion of chromosome 20 in bone marrow of patients with Shwachman-Diamond syndrome, loss of the EIF6 gene and benign prognosis
Shwachman-Diamond Syndrome (SDS; On-line Mendelian Inheritance in Man database number 260400) is an autosomal recessive disorder caused by mutations in the SBDS gene in at least 90% of cases (Boocock et al, 2003). It is characterized by exocrine pancreatic insufficiency, skeletal anomalies, and bone marrow failure with variable severity of neutropenia, thrombocytopenia and anaemia (Rothbaum et al, 2002). Acquired clonal chromosome anomalies are commonly found in the bone marrow (BM), being an isochromosome for the long arms of a 7, i(7)(q10), and a deletion of the long arms of a 20, del(20)(q11), the most frequent. The relationship between these chromosome changes and the risk of patients with SDS to develop myelodysplastic syndromes and acute myeloid leukaemia (MDS/AML) has been discussed (Dror, 2005). This risk increases with the age (Shimamura, 2006), and we have also shown that the acquisition of BM clonal anomalies is age-related (Maserati et al, 2009)
Ph-positive CML in blastic phase with monosomy 7 in a Down syndrome patient. Monitoring by interphase cytogenetics and demonstration of maternal allelic loss
We report a case of Ph-positive chronic myelocytic leukemia in blastic phase in an 11-year-old boy with Down syndrome. Monosomy 7 was the only additional chromosomal anomaly in the blastic clone. Fluorescence in situ hybridization analysis on interphase nuclei with a centromeric probe specific to chromosome 7 proved to be efficient in disease monitoring; and showed, together with the results of chromosome analysis on metaphases, that B- lymphocytes at the origin of an EBV-established line were not part of the leukemic clone. The study of DNA polymorphisms showed that the origin of the constitutional trisomy 21 was a maternal anaphase I nondisjunction, that the chromosome 7 lost in the blastic marrow clone was the maternal one, and led us to postulate that the mother's chromosomes are prone to impairment of normal disjunction. The study of allelic losses of chromosome 7 loci proved to be a further possibility for disease monitoring
HD 178892 - a cool Ap star with extremely strong magnetic field
We report a discovery of the Zeeman resolved spectral lines, corresponding to
the extremely large magnetic field modulus =17.5 kG, in the cool Ap star HD
178892. The mean longitudinal field of this star reaches 7.5 kG, and its
rotational modulation implies the strength of the dipolar magnetic component
Bp>=23 kG. We have revised rotation period of the star using the All Sky
Automated Survey photometry and determined P=8.2478 d. Rotation phases of the
magnetic and photometric maxima of the star coincide with each other. We
obtained Geneva photometric observation of HD 178892 and estimated
Teff=7700+/-250 K using photometry and the hydrogen Balmer lines. Preliminary
abundance analysis reveals abundance pattern typical of rapidly oscillating Ap
stars.Comment: Accepted by Astronomy & Astrophysics; 4 pages, 4 figure
Multi-wavelength observations of 1RXH J173523.7-354013: revealing an unusual bursting neutron star
On 2008 May 14, the Burst Alert Telescope aboard the Swift mission triggered
on a type-I X-ray burst from the previously unclassified ROSAT object 1RXH
J173523.7-354013, establishing the source as a neutron star X-ray binary. We
report on X-ray, optical and near-infrared observations of this system. The
X-ray burst had a duration of ~2 h and belongs to the class of rare,
intermediately long type-I X-ray bursts. From the bolometric peak flux of
~3.5E-8 erg/cm^2/s, we infer a source distance of D<9.5 kpc. Photometry of the
field reveals an optical counterpart that declined from R=15.9 during the X-ray
burst to R=18.9 thereafter. Analysis of post-burst Swift/XRT observations, as
well as archival XMM-Newton and ROSAT data suggests that the system is
persistent at a 0.5-10 keV luminosity of ~2E35 (D/9.5 kpc)^2 erg/s. Optical and
infrared photometry together with the detection of a narrow Halpha emission
line (FWHM=292+/-9 km/s, EW=-9.0+/-0.4 Angstrom) in the optical spectrum
confirms that 1RXH J173523.7-354013 is a neutron star low-mass X-ray binary.
The Halpha emission demonstrates that the donor star is hydrogen-rich, which
effectively rules out that this system is an ultra-compact X-ray binary.Comment: Accepted for publication in MNRAS, 13 pages, 6 figures, 5 table
Clonal chromosome anomalies and propensity to myeloid malignancies in congenital amegakaryocytic thrombocytopenia (OMIM 604498)
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