414 research outputs found
IGRJ17361-4441: a possible new accreting X-ray binary in NGC6388
IGRJ17361-4441 is a newly discovered INTEGRAL hard X-ray transient, located
in the globular cluster NGC6388. We report here the results of the X-ray and
radio observations performed with Swift, INTEGRAL, RXTE, and the Australia
Telescope Compact Array (ATCA) after the discovery of the source on 2011 August
11. In the X-ray domain, IGRJ17361-4441 showed virtually constant flux and
spectral parameters up to 18 days from the onset of the outburst. The
broad-band (0.5-100 keV) spectrum of the source could be reasonably well
described by using an absorbed power-law component with a high energy cut-off
(N_H\simeq0.8x10^(22) cm^(-2), {\Gamma}\simeq0.7-1.0, and E_cut\simeq25 keV)
and displayed some evidence of a soft component below \sim2 keV. No coherent
timing features were found in the RXTE data. The ATCA observation did not
detect significant radio emission from IGRJ17361-4441, and provided the most
stringent upper limit (rms 14.1 {\mu}Jy at 5.5 GHz) to date on the presence of
any radio source close to the NGC6388 center of gravity. The improved position
of IGRJ17361-4441 in outburst determined from a recent target of opportunity
observation with Chandra, together with the X-ray flux and radio upper limits
measured in the direction of the source, argue against its association with the
putative intermediate-mass black hole residing in the globular cluster and with
the general hypothesis that the INTEGRAL source is a black hole candidate.
IGRJ17361-4441 might be more likely a new X-ray binary hosting an accreting
neutron star. The ATCA radio non-detection also permits us to derive an upper
limit to the mass of the suspected intermediate massive black hole in NGC6388
of <600 M\odot. This is a factor of 2.5 lower than the limit reported
previously.Comment: Accepted for publication on A&A lette
De novo mitochondrial DNA alteration in child with complex neurilogical compromission.
neuromuscular human diseases have been associated with
mitochondrial DNA (mtDNA) variations, causing defects of
oxidative phosphorylation. These dysfunctions affect
preferentially tissues with high energy demands and give arise
to several degenerative disorders such as optic neuropathy,
cerebellar ataxia, movement disorders, dementia, muscle
weakness and deafness. The extremely heterogeneous clinical
phenotype is due to the involved tissue, to specific mtDNA
mutations and their heteroplasmic level, but also to nuclear
DNA alterations, environmental and epigenetic factors. In this
study we investigated a child affected by a complex
neurological disease whose clinical features were suggestive
of a mitochondrial involvement.
Methods: mtDNA from proband, her healthy relatives
(grandmother, mother and two sisters) and 80 controls were
collected and studied by sequencing. The enzymatic activity of
specific respiratory chain complex was tested on lymphocytes
by spectrophotometric assay. Bioinformatic analysis was
performed to predict the pathogenicity of the detected variants.
Results: In all subjects we detected 11 known polymorphisms,
whereas 1 novel heteroplasmic variant in complex I
[ND5:12514G>A (E60K)] was present only in the proband and
in her grandmother and absent in controls. The bioinformatics
predicted the novel variant to be deleterious. Further,
spectrophotometric assay of complex I activity was lower both
in the proband and in her relatives than in the controls.
Conclusions: We report a novel mtDNA variant detected in a
patient affected by a complex neurological disease. The
reduction of complex I respiratory chain activity associated to
this variant suggests it could exert a pathogenic role in the
disease
Accurate multi-robot targeting for keyhole neurosurgery based on external sensors monitoring
Robotics has recently been introduced in surgery to improve intervention accuracy, to reduce invasiveness and to allow new surgical procedures. In this framework, the ROBOCAST system is an optically surveyed multi-robot chain aimed at enhancing the accuracy of surgical probe insertion during keyhole neurosurgery procedures. The system encompasses three robots, connected as a multiple kinematic chain (serial and parallel), totalling 13 degrees of freedom, and it is used to automatically align the probe onto a desired planned trajectory. The probe is then inserted in the brain, towards the planned target, by means of a haptic interface. This paper presents a new iterative targeting approach to be used in surgical robotic navigation, where the multi-robot chain is used to align the surgical probe to the planned pose, and an external sensor is used to decrease the alignment errors. The iterative targeting was tested in an operating room environment using a skull phantom, and the targets were selected on magnetic resonance images. The proposed targeting procedure allows about 0.3 mm to be obtained as the residual median Euclidean distance between the planned and the desired targets, thus satisfying the surgical accuracy requirements (1 mm), due to the resolution of the diffused medical images. The performances proved to be independent of the robot optical sensor calibration accuracy
Altered alkaline phosphatase activity in obese Zucker rats liver respect to lean Zucker and Wistar rats discussed in terms of all putative roles ascribed to the enzyme
Biliary complications often lead to acute and chronic liver injury after orthotopic liver transplantation (OLT). Bile composition and secretion depend on the integrated action of all the components of the biliary tree, starting from hepatocytes. Fatty livers are often discarded as grafts for OLT, since they are extremely vulnerable to conventional cold storage (CS). However, the insufficiency of donors has stimulated research to improve the usage of such marginal organs as well as grafts. Our group has recently developed a machine perfusion system at subnormothermic temperature (20°C; MP20) that allows a marked improvement in preservation of fatty and even of normal rat livers as compared with CS. We sought to evaluate the response of the biliary tree of fatty liver to MP20, and a suitable marker was essential to this purpose. Alkaline phosphatase (AlkP, EC 3.1.3.1), frequently used as marker of membrane transport in hepatocytes and bile ducts, was our first choice. Since no histochemical data were available on AlkP distribution and activity in fatty liver, we have first settled to investigate AlkP activity in the steatotic liver of fatty Zucker rats (fa/fa), using as controls lean Zucker (fa/+) and normal Wistar rats. The AlkP reaction in Wistar rats was in accordance with the existing data and, in particular, was present in bile canaliculi of hepatocytes in the periportal region and midzone, in the canals of Hering and in small bile ducts but not in large bile ducts. In lean ZR liver the AlkP reaction in Hering canals and small bile ducts was similar to Wistar rat liver but hepatocytes had lower canalicular activity and besides presented moderate basolateral reaction. The difference between lean Zucker and Wistar rats, both phenotypically normal animals, could be related to the fact that lean Zucker rats are genotypically heterozygous for a recessive mutated allele. In fatty liver, the activity in ductules and small bile ducts was unchanged, but most hepatocytes were devoid of AlkP activity with the exception of clusters of macrosteatotic hepatocytes in the mid-zone, where the reaction was intense in basolateral domains and in distorted canaliculi, a typical pattern of cholestasis. The interpretation of these data was hindered by the fact that the physiological role of AlkP is still under debate. In the present study, the various functions proposed for the role of the enzyme in bile canaliculi and in cholangiocytes are reviewed. Independently of the AlkP role, our data suggest that AlkP does not seem to be a reliable marker to study the initial step of bile production during OLT of fatty livers, but may still be used to investigate the behaviour of bile ductules and small bile ducts
Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity
Accretion-powered X-ray pulsars exhibit significant variability of the
Cyclotron Resonance Scattering Feature (CRSF) centroid energy on pulse-to-pulse
timescales, and also on much longer timescales. Two types of spectral
variability are observed. For sources in group 1, the CRSF energy is negatively
correlated with the variable source luminosity, and for sources in group 2, the
opposite behavior is observed. The physical basis for this bimodal behavior is
currently not understood. We explore the hypothesis that the accretion dynamics
in the group 1 sources is dominated by radiation pressure near the stellar
surface, and that Coulomb interactions decelerate the gas to rest in the group
2 sources. We derive a new expression for the critical luminosity such that
radiation pressure decelerates the matter to rest in the supercritical sources.
The formula for the critical luminosity is evaluated for 5 sources, using the
maximum value of the CRSF centroid energy to estimate the surface magnetic
field strength. The results confirm that the group 1 sources are supercritical
and the group 2 sources are subcritical, although the situation is less clear
for those highly variable sources that cross over the critical line. We also
explain the variation of the CRSF energy with luminosity as a consequence of
the variation of the characteristic emission height. The sign of the height
variation is opposite in the supercritical and subcritical cases, hence
creating the observed bimodal behavior.Comment: Accepted for publication in Astronomy & Astrophysic
A 0535+26 in the August/September 2005 outburst observed by RXTE and INTEGRAL
In this Letter we present results from INTEGRAL and RXTE observations of the
spectral and timing behavior of the High Mass X-ray Binary A 0535+26 during its
August/September 2005 normal (type I) outburst with an average flux
F(5-100keV)~400mCrab. The search for cyclotron resonance scattering features
(fundamental and harmonic) is one major focus of the paper. Our analysis is
based on data from INTEGRAL and RXTE Target of Opportunity Observations
performed during the outburst. The pulse period is determined. X-ray pulse
profiles in different energy ranges are analyzed. The broad band INTEGRAL and
RXTE pulse phase averaged X-ray spectra are studied. The evolution of the
fundamental cyclotron line at different luminosities is analyzed. The pulse
period P is measured to be 103.39315(5)s at MJD 53614.5137. Two absorption
features are detected in the phase averaged spectra at E_1~45keV and
E_2~100keV. These can be interpreted as the fundamental cyclotron resonance
scattering feature and its first harmonic and therefore the magnetic field can
be estimated to be B~4x10^12G.Comment: 4 pages, 5 figures, accepted for publication in A&A Letter
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