67 research outputs found
Near-infrared spectroscopy study of tourniquet-induced forearm ischaemia in patients with coronary artery disease
Near-Infrared Spectroscopy (NIR) can be employed to monitor local changes in haemodynamics and oxygenation of human tissues. A preliminary study has been performed in order to evaluate the NIRS transmittance response to induced forearm ischaemia in patients with coronary artery disease (CAD). The population consists in 40 patients with cardiovascular risk factors and angiographically documented CAD, compared to a group of 13 normal subjects. By inflating and subsequently deflating a cuff placed around the patient arm, an ischaemia has been induced and released, and the patients have been observed until recovery of the basal conditions. A custom LAIRS spectrometer (IRIS) has been used to collect the backscattered light intensities from the patient forearm throughout the ischaemic and the recovery phase. The time dependence of the near-infrared transmittance on the control group is consistent with the available literature. On the contrary, the magnitude and dynamics of the NIRS signal on the CAD patients show deviations from the documented normal behavior, which can be tentatively attributed to abnormal vessel stiffness. These preliminary results, while validating the performance of the IRIS spectrometer, are strongly conducive towards the applicability of the NIRS technique to ischaemia analysis and to endothelial dysfunction characterization in CAD patients with cardiovascular risk factors.Publisher PD
Chronic Cerebrospinal Venous Insufficiency (CCSVI) IN Meniere Disease. Case or Cause?
Abstract CCSVI is the acronym for Chronic Cerebrospinal Venous Insufficiency, initially described by P.Zamboni, as being strongly associated with multiple sclerosis (MS). It is a syndrome characterized by stenosis of the internal jugular veins (IJVs) and/or azygous vein (AZ) with opening of collaterals and insufficient drainage. Bavera PM carried out 823 Duplex exams on a control group of 60 patients without MS. As expected CCSVI was found only in few subjects of the control group, three, two females and one male, but all affected with Sudden Sensorineural Hearing Loss (SSHL). Successively, we reported a case of bilateral SSHL with vertigo, showing evidence of the CCSVI pattern at Duplex examination (not associated with MS). To the best of the authors' knowledge, this kind of association has never been reported. We studied 52 patients affected with cochleo-vestibular disturbances subdivided into two groups of out-patients:Definite unilateral Meniere (Men): 12 subjects (8 males and 4.females, mean age 41,6.yy) according to international AOO-HNS 1995 diagnostic criteria -No-Meniere (No-Men): 14 subjects (6.males and 8 females, mean age 44,7.yy) affected with unilateral cocleo-vestibular impairment A third group of subjects have been considered, as a "normal" group, 13 patients (8 females and 5 males, mean age 45,5 yy) affected with Benign Paroxismal Positioning Vertigo (BPPV) with cochlear involvement Asymmetrical artherious flow in VA or CA was revealed in 2 Men 9 no-Men and 1 BPPV, respectively 12,5 -60,7 -and 8,6 %. Differences between Men and NoMen and between each of this group with respect to BPPV were highly significant (p<0.001). Asymmetrical venous flow in IJV or VV was detected in 9 patients in MEN group and in 4 in no-MEN and 2 BPPV, respectively 79 -28,5 and 13 %. Differences between Men and No-Men and between each of this group with respect to BBV were highly significant (p<0.001
Chronic cerebro-spinal insufficiency in multiple sclerosis and meniere disease: same background, different patterns?
Multiple sclerosis (MS) is a chronic disease of the central nervous system characterized by demyelinating lesions with acute phases and progressive loss of sensori-motor functions. M\ue8ni\ue9re disease (MD) is a disorder of the inner ear characterized by acute spells of vertigo and hearing loss and progressive loss of cochleo-vestibular function. Both the diseases have a multifactorial pathogenesis and quite the same chronic cerebro-spinal insufficiency (CCSVI) frequency. However, as far as Author\u2019s knowledge concerns, no patients affected with both diseases are described so far. The aim of this paper is to investigate whether MS and MD present different CCSVI patterns. Three groups of patients were enrolled: 60 definite MS - 27 definite unilateral MD (MEN) - 41 with other no-M\ue8ni\ue9re, audio-vestibular disorders (OVD). All subjects underwent magnetic resonance venography (MRV) and venous Duplex (ECD) and only patients that satisfied both MRV and ECD CCSVI diagnostic criteria were considered. J1 was normal in 57% of MS, 88% of MEN and 95% of OVD. Stenosis (ST) were detected, respectively, in 30% of MS and 2% in MEN and OVD. J2 was normal in 78% of MS, 64% of MEN and 95% of OVD. At this level alterations of the trunk (AT) were detected in 17% in MS and 26% in MEN; J3 was normal in 74% of MS, 64% of MEN and 86% of OVD. AT were found in 15% of MS, 26% of MEN and 8% of OVD. Hyperplasia of the Vertebral Veins was observed in 35% of MS, 40% of MEN and in 15% of OVD. Other compensatory collaterals were detected in 25% in MS and only in 5% in MEN and OVD. Our results indicate that the MS pattern is characterized by J1 stenosis, J2 trunk alterations, a prevalence of J1-J2 medial-distal alterations, compensatory collaterals besides vertebral venous system. MD pattern is characterized by trunk alteration in J3, a prevalence of J3-J2 medial-proximal alterations and vertebral veins hyperplasia without other detectable collaterals. Although the group of patients with venous alterations is very small, OVD patients show a CCSVI pattern that is more similar to MD than MS pattern. The difference between MS and MD patterns indicates that CCSVI is not a unique entity and it could be an explanation of the fact that subjects affected with both the diseases are not reported
One Channel to Rule Them All? Constraining the Origins of Binary Black Holes using Multiple Formation Pathways
The second LIGO-Virgo catalog of gravitational wave transients has more than
quadrupled the observational sample of binary black holes. We analyze this
catalog using a suite of five state-of-the-art binary black hole population
models covering a range of isolated and dynamical formation channels and infer
branching fractions between channels as well as constraints on uncertain
physical processes that impact the observational properties of mergers. Given
our set of formation models, we find significant differences between the
branching fractions of the underlying and detectable populations, and that the
diversity of detections suggests that multiple formation channels are at play.
A mixture of channels is strongly preferred over any single channel dominating
the detected population: an individual channel does not contribute to more than
of the observational sample of binary black holes. We calculate
the preference between the natal spin assumptions and common envelope
efficiencies in our models, favoring natal spins of isolated black holes of
, and marginally preferring common envelope efficiencies of
while strongly disfavoring highly inefficient common envelopes.
We show that it is essential to consider multiple channels when interpreting
gravitational wave catalogs, as inference on branching fractions and physical
prescriptions becomes biased when contributing formation scenarios are not
considered or incorrect physical prescriptions are assumed. Although our
quantitative results can be affected by uncertain assumptions in model
predictions, our methodology is capable of including models with updated
theoretical considerations and additional formation channels.Comment: 27 pages (14 pages main text + 13 pages appendices/references), 8
figures, 1 table, published in Ap
Prevention of venous thrombosis and thrombophlebitis in long-haul flights with pycnogenol.
The aim of this study was to evaluate the occurrence of deep venous thrombosis (DVT) and superficial vein thrombosis (SVT) and its prophylaxis with an oral anti-edema and antithrombotic agent (Pycnogenol®, Horphag, Research Management SA, Geneva, Switzerland) in long-haul flights, in subjects at moderate to high-risk of DVT and SVT. The study pre-included 244 pre-selected subjects; 211 were included (33 were excluded for several reasons due to logistic problems) and 198 completed the study; 13 subjects were lost for follow-up at the end of the flight, all for non-medical problems (i.e., for difficult connections). All subjects were scanned within 90 minutes before the flight and within 2 hours after disembarking. Subjects were supplemented with 100 mg Pycnogenol® per capsule. Treatment subjects received two capsules between 2 and 3 hours before flights with 250 mL of water; two capsules were taken 6 hours later with 250 mL of water and one capsule the next day. The control group received comparable placebo at the same intervals. The flight duration was on average 8 hours and 15 minutes (SD 55 min) (range, 7.45-12.33). In the control group there were five thrombotic events (one DVT and four superficial thromboses) while only nonthrombotic, localized phlebitis was observed in the Pycnogenol®group (5.15% vs. no events; p<0.025). The ITT (intention to treat) analysis detects 13 failures in the control group (eight lost to follow up + five thrombotic events) of 105 subjects (12.4%) vs. five failures (4.7%; all lost, no thrombotic events) in the treatment group (p<0.025). No unwanted effects were observed. In conclusion, this study indicates that Pycnogenol® treatment was effective in decreasing the number of thrombotic events (DVT and SVT) in moderate-to-high risk subjects, during long-haul flights
Active Learning for Computationally Efficient Distribution of Binary Evolution Simulations
Binary stars undergo a variety of interactions and evolutionary phases,
critical for predicting and explaining observed properties. Binary population
synthesis with full stellar-structure and evolution simulations are
computationally expensive requiring a large number of mass-transfer sequences.
The recently developed binary population synthesis code POSYDON incorporates
grids of MESA binary star simulations which are then interpolated to model
large-scale populations of massive binaries. The traditional method of
computing a high-density rectilinear grid of simulations is not scalable for
higher-dimension grids, accounting for a range of metallicities, rotation, and
eccentricity. We present a new active learning algorithm, psy-cris, which uses
machine learning in the data-gathering process to adaptively and iteratively
select targeted simulations to run, resulting in a custom, high-performance
training set. We test psy-cris on a toy problem and find the resulting training
sets require fewer simulations for accurate classification and regression than
either regular or randomly sampled grids. We further apply psy-cris to the
target problem of building a dynamic grid of MESA simulations, and we
demonstrate that, even without fine tuning, a simulation set of only
the size of a rectilinear grid is sufficient to achieve the same classification
accuracy. We anticipate further gains when algorithmic parameters are optimized
for the targeted application. We find that optimizing for classification only
may lead to performance losses in regression, and vice versa. Lowering the
computational cost of producing grids will enable future versions of POSYDON to
cover more input parameters while preserving interpolation accuracies.Comment: 20 pages (16 main text), 10 figures, submitted to Ap
Bridging the gap between chronic cerebrospinal venous insufficiency and Ménière disease
M\ue9ni\ue8re disease (MD) is a chronic illness of the inner ear that affects a substantial number of patients every year worldwide. Because of a dearth of well-controlled studies, the medical and surgical management of MD remains quite empirical. The main reason is that it is very difficult to investigate patients affected with \u201cCertain MD\u201d due to the post-mortem criterion necessary for this diagnostic grade. The aim of this paper is an attempt to approach MD into the context of the more recent findings about the global brain waste clearance system, to which inner ear is anatomically and functionally connected, in order to build a reasonable model of MD pathogenesis. it seems nowadays reasonable to state that CCSVI may be the anatomical background to develop endolymphatic hydrops in MD, the worldwide accepted pathogenetic mechanism of the disease. The mechanism leading from CCSVI to MD is still debated. Since MD has been correlated mostly to a wide and different diseases and treatments, CCSVI may be considered more than a cause of MD per se, rather the anatomical predisposition to develop the disease. CCSVI may lead to endolymphatic hydrops through a pure \u201chydraulic\u201d mechanism but in the model proposed in this paper CCSVI interplays with the Glymphatic (GS) and Brain Lymphatic System (LS) and MD development is due to a failure of the congenital venous abnormalities: MD develops when vascular and/or glymphatic and/or lymphatic compensation fails
Revisiting the explodability of single massive star progenitors of stripped-envelope supernovae
Stripped-envelope supernovae (Types IIb, Ib, and Ic) that show little or no
hydrogen comprise roughly one-third of the observed explosions of massive
stars. Their origin and the evolution of their progenitors are not yet fully
understood. Very massive single stars stripped by their own winds ( at solar metallicity) are considered viable progenitors of
these events. However, recent 1D core-collapse simulations show that some
massive stars may collapse directly into black holes after a failed explosion,
with a weak or no visible transient. In this letter, we estimate the effect of
direct collapse into a black hole on the rates of stripped-envelope supernovae
that arise from single stars. For this, we compute single-star MESA models at
solar metallicity and map their final state to their core-collapse outcome
following prescriptions commonly used in population synthesis. According to our
models, no single stars that have lost their entire hydrogen-rich envelope are
able to explode, and only a fraction of progenitors left with a thin hydrogen
envelope do (IIb progenitor candidates), unless we use a prescription that
takes the effect of turbulence into account or invoke increased wind mass-loss
rates. This result increases the existing tension between the single-star
paradigm to explain most stripped-envelope supernovae and their observed rates
and properties. At face value, our results point toward an even higher
contribution of binary progenitors to stripped-envelope supernovae.
Alternatively, they may suggest inconsistencies in the common practice of
mapping different stellar models to core-collapse outcomes and/or higher
overall mass loss in massive stars.Comment: Published in Astronomy & Astrophysics Letters; One main enhancement:
added Couch et al. (2020) in the list of supernova engine
The impact of mass-transfer physics on the observable properties of field binary black hole populations
We study the impact of mass-transfer physics on the observable properties of
binary black hole populations formed through isolated binary evolution. We
investigate the impact of mass-accretion efficiency onto compact objects and
common-envelope efficiency on the observed distributions of ,
and . We find that low common envelope efficiency translates to
tighter orbits post common envelope and therefore more tidally spun up
second-born black holes. However, these systems have short merger timescales
and are only marginally detectable by current gravitational-waves detectors as
they form and merge at high redshifts (), outside current detector
horizons. Assuming Eddington-limited accretion efficiency and that the
first-born black hole is formed with a negligible spin, we find that all
non-zero systems in the detectable population can come only from
the common envelope channel as the stable mass-transfer channel cannot shrink
the orbits enough for efficient tidal spin-up to take place. We find the local
rate density () for the common envelope channel is in the range
considering a range of while for the stable mass transfer channel the rate density is . The latter drops by two orders of magnitude if the mass
accretion onto the black hole is not Eddington limited because conservative
mass transfer does not shrink the orbit as efficiently as non-conservative mass
transfer does. Finally, using GWTC-2 events, we constrain the lower bound of
branching fraction from other formation channels in the detected population to
be . Assuming all remaining events to be formed through either stable
mass transfer or common envelope channels, we find moderate to strong evidence
in favour of models with inefficient common envelopes.Comment: 26 pages, 13 figures, accepted for publication in A&
Investigating the Lower Mass Gap with Low Mass X-ray Binary Population Synthesis
Mass measurements from low-mass black hole X-ray binaries (LMXBs) and radio
pulsars have been used to identify a gap between the most massive neutron stars
(NSs) and the least massive black holes (BHs). BH mass measurements in LMXBs
are typically only possible for transient systems: outburst periods enable
detection via all-sky X-ray monitors, while quiescent periods enable
radial-velocity measurements of the low-mass donor. We quantitatively study
selection biases due to the requirement of transient behavior for BH mass
measurements. Using rapid population synthesis simulations (COSMIC), detailed
binary stellar-evolution models (MESA), and the disk instability model of
transient behavior, we demonstrate that transient-LMXB selection effects
introduce observational biases, and can suppress mass-gap BHs in the observed
sample. However, we find a population of transient LMXBs with mass-gap BHs form
through accretion-induced collapse of a NS during the LMXB phase, which is
inconsistent with observations. These results are robust against variations of
binary evolution prescriptions. The significance of this accretion-induced
collapse population depends upon the maximum NS birth mass . To reflect the observed dearth of low-mass BHs, COSMIC and MESA
models favor . In the absence of
further observational biases against LMXBs with mass-gap BHs, our results
indicate the need for additional physics connected to the modeling of LMXB
formation and evolution.Comment: 21 pages, accepted to Ap
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