662 research outputs found
On sectional and bisectional curvature of the H
Let M be an H-umbilical submanifold of an almost Hermitian
manifold MË. Some relations expressing the difference of
bisectional and of sectional curvatures of MË and of M
are obtained. The geometric notion of related bases for a pair of
oriented planes permits to write the second members in a
completely geometrical form. When the planes are not orthogonal,
more simple formulas are obtained. The paper ends with a remark,
concerning the vector field JH, and some special cases
Extreme nonlinear electrodynamics in metamaterials with very small linear dielectric permittivity
We consider a sub-wavelength periodic layered medium whose slabs are filled
by arbitrary linear metamaterials and standard nonlinear Kerr media and we show
that the homogenized medium behaves as a Kerr medium whose parameters can
assume values not available in standard materials. Exploiting such a parameter
availability, we focus on the situation where the linear relative dielectric
permittivity is very small thus allowing the observation of the extreme
nonlinear regime where the nonlinear polarization is comparable with or even
greater than the linear part of the overall dielectric response. The behavior
of the electromagnetic field in the extreme nonlinear regime is very peculiar
and characterized by novel features as, for example, the transverse power flow
reversing. In order to probe the novel regime, we consider a class of fields
(transverse magnetic nonlinear guided waves) admitting full analytical
description and we show that these waves are allowed to propagate even in media
with since the nonlinear polarization produces a
positive overall effective permittivity. The considered nonlinear waves
exhibit, in addition to the mentioned features, a number of interesting
properties like hyper-focusing induced by the phase difference between the
field components.Comment: 12 pages, 7 figure
Sex-related differences and chronobiology of ST-elevation myocardial infarction: findings from a single hub center in Italy
Objective: Type I acute myocardial infarction (AMI) is a life-threatening condition. Time of event and rescue procedures, and sex-specific differences may play a crucial role. We aimed to investigate chronobiological patterns and sex-specific differences in a cohort of AMI patients referred to a single hub center in Italy.
Patients and methods: We considered all patients consecutively admitted for AMI (STEMI) to the Hospital of the Heart, in Massa, Tuscany (a region of Italy), between 2006 to 2018, who underwent interventional procedures. Sex, age, time of hospital admission, outcome (discharged alive/deceased), main comorbidities, and time between symptom onset and emergency medical service (EMS) activation, were analyzed. Chronobiologic analysis was applied according to hour of day, month, and season of the year.
Results: Overall 2,522 patients (mean age 64.6±13.1 years, 73% males) were considered. In-hospital death (IHM) occurred in 96 subjects (3.8%). At univariate analysis, deceased subjects were more likely to be female, older, with longer wait for EMS activation and with interventional procedures during night-time. The multivariate analysis identified female sex, age, history of ischemic heart disease, and night-time interventional procedure as independently associated factors to IHM. Chronobiologic analysis showed a pattern with a main morning peak for total sample, males, and females (p=0.00027; p=0.0006); p=0.0121, respectively). Events showed a higher peak in summer, with no differences by sex, but IHM was higher in winter. Females showed a higher delay for EMS activation, compared to males (p<0.001), but with no effects on prognosis. On the contrary, males with a delay showed higher mortality.
Conclusions: Great effort should be spent to reduce patient-related delays in interventional procedures, being this issue crucial in both sexes
X-ray and Radio Interactions in the Cores of Cooling Flow Clusters
We present high resolution ROSAT x-ray and radio observations of three
cooling flow clusters containing steep spectrum radio sources at their cores.
All three systems exhibit strong signs of interaction between the radio plasma
and the hot intracluster medium. Two clusters, A133 and A2626, show enhanced
x-ray emission spatially coincident with the radio source whereas the third
cluster, A2052, exhibits a large region of x-ray excess surrounding much of the
radio source. Using 3-D numerical simulations, we show that a perturbed jet
propagating through a cooling flow atmosphere can give rise to amorphous radio
morphologies, particularly in the case where the jet was ``turned off'' and
allowed to age passively. In addition, the simulated x-ray surface brightness
produced both excesses and deficits as seen observationally.Comment: 25 pages, 10 figures, accepted for publication in A
TRAIL Dependent Fratricidal Killing of gp120 Primed Hepatocytes by HCV Core Expressing Hepatocytes
The mechanism by which HIV and HCV cooperatively accelerate hepatocyte damage is not clearly understood; however, each virus affects the TRAIL: TRAIL- receptor system. We, therefore, questioned whether the independent effects of HCV and HIV combine to synergistically result in TRAIL dependent hepatocyte killing. We describe that Huh7 hepatocytes treated with HIV gp120 results in both increase TRAIL-R2 expression and an acquired sensitivity to TRAIL mediated killing. Moreover HCV infection and HCV core expression alone in Huh7 cells upregulates TRAIL. Co-incubation of HIV gp120 primed hepatocytes with HCV core expressing hepatocytes results in the selective death of the HIV gp120 primed hepatocytes that is selectively blocked by TRAILâR2-Fc fusion protein. Liver biopsies from HIV mono-infected patients have increased TRAIL-R2; biopsies from HCV infected patients have increased TRAIL, while co-infected liver biopsies have increased PARP cleavage within hepatocytes indicating enhanced apoptosis. These findings suggest a pathogenic model to understand why HIV/HCV co-infection accelerates liver injury
The Richardson's Law in Large-Eddy Simulations of Boundary Layer flows
Relative dispersion in a neutrally stratified planetary boundary layer (PBL)
is investigated by means of Large-Eddy Simulations (LES). Despite the small
extension of the inertial range of scales in the simulated PBL, our Lagrangian
statistics turns out to be compatible with the Richardson law for the
average of square particle separation. This emerges from the application of
nonstandard methods of analysis through which a precise measure of the
Richardson constant was also possible. Its values is estimated as
in close agreement with recent experiments and three-dimensional direct
numerical simulations.Comment: 15 LaTex pages, 4 PS figure
Management and efficacy of intensified insulin therapy starting in outpatients
Diabetic patients under multiple injection insulin therapy (i.e., intensified insulin therapy, IIT) usually start this treatment during hospitalization. We report here on the logistics, efficacy, and safety of IIT, started in outpatients. Over 8 months, 52 type I and type II diabetics were followed up whose insulin regimens consecutively had been changed from conventional therapy to IIT. Two different IIT strategies were compared: free mixtures of regular and intermediate (12 hrs)-acting insulin versus the basal and prandial insulin treatment with preprandial injections of regular insulin, and ultralente (24 hrs-acting) or intermediate insulin for the basal demand. After 8 months HbA1 levels had decreased from 10.6%±2.4% to 8.0%±1.3% (means±SD). There was no difference between the two regimens with respect to metabolic control; but type II patients maintained the lowered HbA1 levels better than type I patients. Only two patients were hospitalized during the follow-up time because of severe hypoglycemia. An increase of body weight due to the diet liberalization during IIT became a problem in one-third of the patients. Our results suggest that outpatient initiation of IIT is safe and efficacious with respect to near-normoglycemic control. Weight control may become a problem in IIT patients
An ISOCAM survey through gravitationally lensing galaxy clusters. III. New results from mid-infrared observations of th e cluster Abell 2219
The massive cluster of galaxies Abell 2219 (z = 0.228) was observed at 14.3
m with the Infrared Space Observatory and results were published by
Barvainis et al. (1999). These observations have been reanalyzed using a method
specifically designed for the detection of faint sources that had been applied
to other clusters. Five new sources were detected and the resulting cumulative
total of ten sources all have optical counterparts. The mid-infrared sources
are identified with three cluster members, three foreground galaxies, an
Extremely Red Object, a star and two galaxies of unknown redshift. The spectral
energy distributions (SEDs) of the galaxies are fit with models from a
selection, using the program GRASIL. Best-fits are obtained, in general, with
models of galaxies with ongoing star formation. For three cluster members the
infrared luminosities derived from the model SEDs are between ~5.7x10^10 Lsun
and 1.4x10^11 Lsun, corresponding to infrared star formation rates between 10
and 24 Msun yr^-1. The two cluster galaxies that have optical classifications
are in the Butcher-Oemler region of the color-magnitude diagramme. The three
foreground galaxies have infrared luminosities between 1.5x10^10 Lsun and
9.4x10^10 Lsun yielding infrared star formation rates between 3 and 16 Msun
yr^-1. Two of the foreground galaxies are located in two foreground galaxy
enhancements (Boschin et al. 2004). Including Abell 2219, six distant clusters
of galaxies have been mapped with ISOCAM and luminous infrared galaxies (LIRGs)
have been found in three of them. The presence of LIRGs in Abell 2219
strengthens the association between luminous infrared galaxies in clusters and
recent or ongoing cluster merger activity.Comment: 8 pages, 4 figures, A&A accepted, full paper with high-resolution
figures available at http://bermuda.ucd.ie/~dcoia/papers/. Reference adde
Diffuse light and building history of the galaxy cluster Abell 2667
We have searched for diffuse intracluster light in the galaxy cluster Abell
2667 (z=0.233) from HST images in three filters. We have applied to these
images an iterative multi-scale wavelet analysis and reconstruction technique,
which allows to subtract stars and galaxies from the original images. We detect
a zone of diffuse emission south west of the cluster center (DS1), and a second
faint object (ComDif), within DS1. Another diffuse source (DS2) may be
detected, at lower confidence level, north east of the center. These sources of
diffuse light contribute to 10-15% of the total visible light in the cluster.
Whether they are independent entities or are part of the very elliptical
external envelope of the central galaxy remains unclear. VLT VIMOS integral
field spectroscopy reveals a faint continuum at the positions of DS1 and ComDif
but do not allow to compute a redshift. A hierarchical substructure detection
method reveals the presence of several galaxy pairs and groups defining a
similar direction as the one drawn by the DS1-central galaxy-DS2 axis. The
analysis of archive XMM-Newton and Chandra observations shows X-ray emission
elongated in the same direction. The X-ray temperature map shows the presence
of a cool core, a broad cool zone stretching from north to south and hotter
regions towards the north east, south west and north west. This possibly
suggests shock fronts along these directions produced by infalling material.
These various data are consistent with a picture in which diffuse sources are
concentrations of tidal debris and harassed matter expelled from infalling
galaxies by tidal stripping and undergoing an accretion process onto the
central cluster galaxy; as such, they are expected to be found along the main
infall directions.Comment: Accepted for publication in Astronomy and Astrophysic
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