2,799 research outputs found
Pathwise optimal transport bounds between a one-dimensional diffusion and its Euler scheme
In the present paper, we prove that the Wasserstein distance on the space of
continuous sample-paths equipped with the supremum norm between the laws of a
uniformly elliptic one-dimensional diffusion process and its Euler
discretization with steps is smaller than where
is an arbitrary positive constant. This rate is intermediate
between the strong error estimation in obtained when coupling the
stochastic differential equation and the Euler scheme with the same Brownian
motion and the weak error estimation obtained when comparing the
expectations of the same function of the diffusion and of the Euler scheme at
the terminal time . We also check that the supremum over of the
Wasserstein distance on the space of probability measures on the real line
between the laws of the diffusion at time and the Euler scheme at time
behaves like .Comment: Published in at http://dx.doi.org/10.1214/13-AAP941 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Quantifying The Shortage of Mental Health Care in Venezuela Through Media Content Analysis
The aim of this thesis was to assess the gaps and deficits in the mental health care staffing and related prescription drug or therapeutic intervention availability in Venezuela using media content analysis. This thesis also assessed the measures suggested by Venezuelan medical professionals for addressing the population\u27s needs for mental health services amid the nation\u27s crisis. The shortage of mental health care in Venezuela was assessed because various stressors, including life events, chronic stressors, and daily hassles, are substantially less than optimal among Venezuelans. The mental health consequences of these factors, along with the detrimental psychosocial demands commonly faced by Venezuelans, was explored within this study. Such an investigation is critical in light of the poor prioritization of intangible mental health care within the already inadequate health care system existing in Venezuela. The used media content included newspapers and periodicals published in Venezuela and foreign newspapers covering the medical crisis in Venezuela, published or posted interviews with Venezuelan medical personnel describing the health care crisis, social media posts involving requests for or availability of medicine and services, and social media posts of videos or images as visual testimony of the crisis. Coder reliability was assessed, and descriptive and inferential statistical tests were implemented for deductive analysis of the study\u27s results and to find possible answers to the presented research questions
Drift dependence of optimal trade execution strategies under transient price impact
We give a complete solution to the problem of minimizing the expected
liquidity costs in presence of a general drift when the underlying market
impact model has linear transient price impact with exponential resilience. It
turns out that this problem is well-posed only if the drift is absolutely
continuous. Optimal strategies often do not exist, and when they do, they
depend strongly on the derivative of the drift. Our approach uses elements from
singular stochastic control, even though the problem is essentially
non-Markovian due to the transience of price impact and the lack in Markovian
structure of the underlying price process. As a corollary, we give a complete
solution to the minimization of a certain cost-risk criterion in our setting
Dynamic PRA: an Overview of New Algorithms to Generate, Analyze and Visualize Data
State of the art PRA methods, i.e. Dynamic PRA
(DPRA) methodologies, largely employ system
simulator codes to accurately model system dynamics.
Typically, these system simulator codes (e.g., RELAP5 )
are coupled with other codes (e.g., ADAPT,
RAVEN that monitor and control the simulation. The
latter codes, in particular, introduce both deterministic
(e.g., system control logic, operating procedures) and
stochastic (e.g., component failures, variable uncertainties)
elements into the simulation. A typical DPRA analysis is
performed by:
1. Sampling values of a set of parameters from the
uncertainty space of interest
2. Simulating the system behavior for that specific set of
parameter values
3. Analyzing the set of simulation runs
4. Visualizing the correlations between parameter values
and simulation outcome
Step 1 is typically performed by randomly sampling
from a given distribution (i.e., Monte-Carlo) or selecting
such parameter values as inputs from the user (i.e.,
Dynamic Event Tre
Proper orthogonal decomposition of solar photospheric motions
The spatio-temporal dynamics of the solar photosphere is studied by
performing a Proper Orthogonal Decomposition (POD) of line of sight velocity
fields computed from high resolution data coming from the MDI/SOHO instrument.
Using this technique, we are able to identify and characterize the different
dynamical regimes acting in the system. Low frequency oscillations, with
frequencies in the range 20-130 microHz, dominate the most energetic POD modes
(excluding solar rotation), and are characterized by spatial patterns with
typical scales of about 3 Mm. Patterns with larger typical scales of 10 Mm, are
associated to p-modes oscillations at frequencies of about 3000 microHz.Comment: 8 figures in jpg in press on PR
L'osservatorio ionosferico in Artide e Antartide: osservazioni sperimentali e risultati scientifici
The Italian Upper Atmosphere Observatory at polar latitude was firstly established during
the Antarctic campaign 1990-1991 to support the telecommunication logistic activity of
the National Program for Antarctic Research (PNRA). The Istituto Nazionale di
Geofisica e Vulcanologia (INGV), formerly Istituto Nazionale di Geofisica (ING), was
involved in this action as the long time experience in HF radar, ionospheric sounding and
ionospheric prediction services for radio communication purposes, managing two of the
most important and historical ionospheric observatories all over the world: Rome (41.8N,
12.5E) and Gibilmanna (37.9 N, 14.0 E). Since that time, starting from 1993 up to now,
several research projects have been carried on focusing on the multi instruments upper
atmosphere observations in Arctic and Antarctica with the aim to study the polar
ionosphere in different time and space domains, contributing both to the Global Change
and to the emerging Space Weather needs. Here we briefly report on the experimental
activities as well on the main scientific results obtained highlighting the latest findings in
the field of bipolar GNSS (Global Navigation Satellite Systems) ionospheric scintillation
measurements and investigation
Theoretical and Numerical Analysis of an Optimal Execution Problem with Uncertain Market Impact
This paper is a continuation of Ishitani and Kato (2015), in which we derived
a continuous-time value function corresponding to an optimal execution problem
with uncertain market impact as the limit of a discrete-time value function.
Here, we investigate some properties of the derived value function. In
particular, we show that the function is continuous and has the semigroup
property, which is strongly related to the Hamilton-Jacobi-Bellman
quasi-variational inequality. Moreover, we show that noise in market impact
causes risk-neutral assessment to underestimate the impact cost. We also study
typical examples under a log-linear/quadratic market impact function with
Gamma-distributed noise.Comment: 24 pages, 14 figures. Continuation of the paper arXiv:1301.648
Calibration of optimal execution of financial transactions in the presence of transient market impact
Trading large volumes of a financial asset in order driven markets requires
the use of algorithmic execution dividing the volume in many transactions in
order to minimize costs due to market impact. A proper design of an optimal
execution strategy strongly depends on a careful modeling of market impact,
i.e. how the price reacts to trades. In this paper we consider a recently
introduced market impact model (Bouchaud et al., 2004), which has the property
of describing both the volume and the temporal dependence of price change due
to trading. We show how this model can be used to describe price impact also in
aggregated trade time or in real time. We then solve analytically and calibrate
with real data the optimal execution problem both for risk neutral and for risk
averse investors and we derive an efficient frontier of optimal execution. When
we include spread costs the problem must be solved numerically and we show that
the introduction of such costs regularizes the solution.Comment: 31 pages, 8 figure
THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation
We report on the results of an extensive R&D program aimed at the evaluation
of Thick-Gas Electron Multipliers (THGEM) as potential active elements for
Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad
multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1
cm2 readout pads. The detector is comprised of single- or double-THGEM
multipliers coupled to the pad electrode either directly or via a resistive
anode. Investigations employing standard discrete electronics and the KPiX
readout system have been carried out both under laboratory conditions and with
muons and pions at the CERN RD51 test beam. For detectors having a
charge-induction gap, it has been shown that even a ~6 mm thick single-THGEM
detector reached detection efficiencies above 95%, with pad-hit multiplicity of
1.1-1.2 per event; discharge probabilities were of the order of 1e-6 - 1e-5
sparks/trigger, depending on the detector structure and gain. Preliminary beam
tests with a WELL hole-structure, closed by a resistive anode, yielded
discharge probabilities of <2e-6 for an efficiency of ~95%. Methods are
presented to reduce charge-spread and pad multiplicity with resistive anodes.
The new method showed good prospects for further evaluation of very thin
THGEM-based detectors as potential active elements for DHCAL, with competitive
performances, simplicity and robustness. Further developments are in course.Comment: 15 pages, 11 figures, MPGD2011 conference proceedin
Apixaban Concentrations with Lower than Recommended Dosing in Older Adults with Atrial Fibrillation
OBJECTIVES: Lower than recommended doses of direct-acting oral anticoagulants are often prescribed to older adults with nonvalvular atrial fibrillation (NVAF). Our goal was to determine the consequences of lower than recommended dosing on plasma apixaban concentrations during the clinical care of older adults with NVAF. DESIGN: Convenience sample of patients receiving anticoagulation during 2017. SETTING: Academic medical center. PARTICIPANTS: Stable adults older than 65 years with NVAF receiving apixaban on a chronic basis. MEASUREMENTS: Patient age, weight, creatinine, co-medications, and apixaban concentrations. RESULTS: A total of 110 older adults with NVAF (mean age = 80.4 y; range = 66-100 y with 45% women) were studied. Overall, 48 patients received recommended dosing of 5 mg twice/day, and 42 received lower than recommended dosing. One patient in each category had concentrations below the expected 5% to 95% range at time of peak concentrations. Differences in proportion of apixaban concentrations within or outside expected ranges were not significant between patients receiving lower than recommended doses and those dosed as recommended at 5 mg twice/day (P =.35). However, in patients dosed as recommended with 5 mg twice/day, four had concentrations above the 5% to 95% range for peak levels expected at 3 to 4 hours after dosing; in two, this occurred around the midpoint of the dosing interval. Twenty patients received 2.5 mg twice/day as recommended. One-third had apixaban concentrations higher than expected peak concentrations compared with the clinical trials, and more than two-thirds had levels above the reported median for peak concentrations. CONCLUSIONS: Apixaban concentrations in older adults with NVAF seen clinically were higher than expected based on clinical trial data. The findings raise questions about the optimal dosing of apixaban in older adults with NVAF encountered outside of clinical trials and suggest a role for the monitoring of apixaban concentrations during care of patients that differ from those in randomized trials or when considering dosing outside of published guidelines. J Am Geriatr Soc 67:1902â1906, 2019
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