174 research outputs found
Ancient mean curvature flows and their spacetime tracks
We study properly immersed ancient solutions of the codimension one mean
curvature flow in -dimensional Euclidean space, and classify the convex
hulls of the subsets of space reached by any such flow. In particular, it
follows that any compact convex ancient mean curvature flow can only have a
slab, a halfspace or all of space as the closure of its set of reach. The proof
proceeds via a bi-halfspace theorem (also known as a wedge theorem) for ancient
solutions derived from a parabolic Omori-Yau maximum principle for ancient mean
curvature flows.Comment: 14 pages; minor edits, added proof details and reference
Anti-asthmatics prescriptions in the paediatric population in the Lazio Region of Italy: association with socio-demographic childrenâs and physicianâs characteristics
Background Asthma is the most common chronic disease in childhood; inItaly its prevalence is estimated to be 9% in children (0-14 years old).
Objective Estimate the use of anti-asthmatics prescriptions in the paediatric population and to evaluate its association with childrenâs and physicianâs characteristics.
Methods The study was conducted in 728,830 children 1-14 years old residing in the Lazio region,Central Italy. Individual data on AA (ATC R03) prescriptions during 2009 were used. Prevalence was calculated according to childrenâs gender, age and area of residence.
The association, in terms of rate ratio (RR), between AA prescription with childrenâs and physiciansâ characteristics was estimated by multi level Poisson models.
Results Overall, 404,239 AA prescriptions were given to 178,850 (25%) children with the highest frequency in the 1-2 age group (39%). Boys were more likely to receive a prescription than girls. Beclomethasone was the most prescribed active ingredient (34%), followed by salbutamol (24%); 44% of children Âł6 years old had only 1 box prescription in the year, 48.9% of these subjects were treated with inhaled corticosteroids alone.
Childrenâs gender, age and area of residence were the major determinants in drug prescription while, as far as physiciansâ level, gender and number of patients in charge were associated to a greater probability of getting an AA prescription.
Conclusion Prescription data provide useful information to measure prevalence use and consumption of AA drugs. Variability between age groups as well as differences in doctorsâ characteristics suggests that specific strategies to optimise resource use of AA are needed
On the Modeling of the Donor/Acceptor Compensation Ratio in CarbonâDoped GaN to Univocally Reproduce Breakdown Voltage and Current Collapse in Lateral GaN Power HEMTs
The intentional doping of lateral GaN power high electron mobility transistors (HEMTs)
with carbon (C) impurities is a common technique to reduce buffer conductivity and increase
breakdown voltage. Due to the introduction of trap levels in the GaN bandgap, it is well known that
these impurities give rise to dispersion, leading to the soâcalled âcurrent collapseâ as a collateral
effect. Moreover, firstâprinciples calculations and experimental evidence point out that C introduces
trap levels of both acceptor and donor types. Here, we report on the modeling of the donor/acceptor
compensation ratio (CR), that is, the ratio between the density of donors and acceptors associated
with C doping, to consistently and univocally reproduce experimental breakdown voltage (VBD) and
currentâcollapse magnitude (ÎICC). By means of calibrated numerical device simulations, we
confirm that ÎICC is controlled by the effective trap concentration (i.e., the difference between the
acceptor and donor densities), but we show that it is the total trap concentration (i.e., the sum of
acceptor and donor densities) that determines VBD, such that a significant CR of at least 50%
(depending on the technology) must be assumed to explain both phenomena quantitatively. The
results presented in this work contribute to clarifying several previous reports, and are helpful to
device engineers interested in modeling Câdoped lateral GaN power HEMTs
The effects of carbon on the bidirectional threshold voltage instabilities induced by negative gate bias stress in GaN MIS-HEMTs
In this paper, numerical device simulations are used to point out the possible contributions of carbon doping to the threshold voltage instabilities induced by negative gate bias stress in AlGaN/GaN metalâinsulatorâsemiconductor high-electron
mobility transistors. It is suggested that carbon can have a role in both negative and positive threshold voltage shifts, as a
result of (1) the changes in the total negative charge stored in the carbon-related acceptor traps in the GaN buffer, and (2)
the attraction of carbon-related free holes to the device surface and their capture into interface traps or recombination with
gate-injected electrons. For a proper device optimization of carbon-doped MIS-HEMTs, it is therefore important to take
these mechanisms into account, in addition to those related to defects in the gate dielectric volume and interface which are
conventionally held responsible for threshold voltage instabilities
Dataset on gait patterns in degenerative neurological diseases
We collected the gait parameters and lower limb joint kinematics of patients with three different types of primary degenerative neurological diseases: (i) cerebellar ataxia (19 patients), (ii) hereditary spastic paraparesis (26 patients), and (iii) Parkinson's disease (32 patients). Sixty-five gender-age matched healthy subjects were enrolled as control group. An optoelectronic motion analysis system was used to measure time-distance parameters and lower limb joint kinematics during gait in both patients and healthy controls
Limits on Radio Continuum Emission from a Sample of Candidate Contracting Starless Cores
We used the NRAO Very Large Array to search for 3.6 cm continuum emission
from embedded protostars in a sample of 8 nearby ``starless'' cores that show
spectroscopic evidence for infalling motions in molecular emission lines. We
detect a total of 13 compact sources in the eight observed fields to 5 sigma
limiting flux levels of typically 0.09 mJy. None of these sources lie within 1'
of the central positions of the cores, and they are all likely background
objects. Based on an extrapolation of the empirical correlation between the
bolometric luminosity and 3.6 cm luminosity for the youngest protostars, these
null-detections place upper limits of ~0.1 L_sun (d/140pc)^2 on the
luminosities of protostellar sources embedded within these cores. These limits,
together with the extended nature of the inward motions inferred from molecular
line mapping (Lee et al. 2001), are inconsistent with the inside-out collapse
model of singular isothermal spheres and suggest a less centrally condensed
phase of core evolution during the earliest stages of star formation.Comment: Accepted to the Astronomical Journal; 12 pages, 1 figur
Molecular mechanism of tanshinone IIA and cryptotanshinone in platelet anti-aggregating effects: an integrated study of pharmacology and computational analysis.
Tanshinone IIA and cryptotanshinone are two pharmacologically active diterpenoids extracted from the roots of Salvia milthiorriza Bunge, a plant used in Chinese traditional medicine for the treatment of some cardiovascular and cerebrovascular disease. Until now, the molecular mechanisms of action of these two diterpenoids on platelets are partially known. To clarify this aspect, here we utilized an integrated study of pharmacology and computational analysis. Our results demonstrate that cryptotanshinone is able to inhibit in a concentration dependent manner the rat platelet aggregation and also is endowed of Gi-coupled P2Y12 receptor antagonist as demonstrated by docking studies. This computational method was also performed for tanshinone IIA demonstrating even for this diterpenoid an interaction with the same receptor. The findings from our study enable a better understanding of tanshinone IIA and cryptotanshinone biological properties, which could ultimately lead to the development of novel pharmaceutical strategies for the treatment and/or prevention of some cardiovascular disease
Can Computed Tomography Colonography Replace Optical Colonoscopy in Detecting Colorectal Lesions?: State of the Art
: Colorectal cancer is an important cause of morbidity and mortality worldwide. Optical colonoscopy (OC) is widely accepted as the reference standard for the screening of colorectal polyps and cancers, and computed tomography colonography (CTC) is a valid alternative to OC. The purpose of this review was to assess the diagnostic accuracy of OC and CTC for colorectal lesions. A literature search was performed in PubMed, Embase, and Cochrane Library, and 18 articles were included. CTC has emerged in recent years as a potential screening examination with high accuracy for the detection of colorectal lesions. However, the clinical application of CTC as a screening technique is limited because it is highly dependent on the size of the lesions and has poor performance in detecting individual lesions <5 mm or flat lesions, which, although rarely, can have a malignant potential
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