5,145 research outputs found
Recommended from our members
Evaluation of the Linear Relationship Between Pulse Arrival Time and Blood Pressure in ICU Patients: Potential and Limitations
A variety of techniques based on the indirect measurement of blood pressure (BP) by Pulse Transit Time (PTT) have been explored over the past few years. Such an approach has the potential in providing continuous and non-invasive beat to beat blood pressure without the use of a cuff. Pulse Arrival Time (PAT) which includes the cardiac pre-ejection period has been proposed as a surrogate of PTT, however, the balance between its questioned accuracy and measurement simplicity has yet to be established. The present work assessed the degree of linear relationship between PAT and blood pressure on 96 h of continuous electrocardiography and invasive radial blood pressure waveforms in a group of 11 young ICU patients. Participants were selected according to strict exclusion criteria including no use of vasoactive medications and presence of clinical conditions associated with cardiovascular diseases. The average range of variation for diastolic BP was 60 to 79 mmHg while systolic BP varied between 123 and 158 mmHg in the study database. The overall Pearson correlation coefficient for systolic and diastolic blood pressure was −0.5 and −0.42, respectively, while the mean absolute error was 3.9 and 7.6 mmHg. It was concluded that the utilization of PAT for the continuous non-invasive blood pressure estimation is rather limited according to the experimental setup, nonetheless the correlation coefficient performed better when the range of variation of blood pressure was high over periods of 30 min suggesting that PAT has the potential to be used as indicator of changes relating to hypertensive or hypotensive episodes
The labor wedge as a matching friction
The labor wedge accounts for a large fraction of business cycle fluctuations. This paper uses a search and matching model to decompose the labor wedge into three classes of labor market frictions and evaluate their role. We find that frictions to job destruction and bargaining commonly considered in the search literature are not helpful in explaining the labor wedge. We also identify an asymmetric effect of separation, bargaining and matching frictions on unemployment, as well as a potential solution to Shimer's puzzle.Business cycles - Econometric models ; Labor supply ; Unemployment ; Labor turnover
Synchronization in large directed networks of coupled phase oscillators
We extend recent theoretical approximations describing the transition to
synchronization in large undirected networks of coupled phase oscillators to
the case of directed networks. We also consider extensions to networks with
mixed positive/negative coupling strengths. We compare our theory with
numerical simulations and find good agreement
Critical behavior of ferromagnetic pure and random diluted nanoparticles with competing interactions: variational and Monte Carlo approaches
The magnetic properties and critical behavior of both ferromagnetic pure and
metallic nanoparticles having concurrently atomic disorder, dilution and
competing interactions, are studied in the framework of an Ising model. We have
used both the free energy variational principle based on the Bogoliubov
inequality and Monte Carlo simulation. As a case of study for random diluted
nanoparticles we have considered the FeMnAl alloy
characterized for exhibiting, under bulk conditions, low temperature reentrant
spin glass (RSG) behavior and for which experimental and simulation results are
available. Our results allow concluding that the variational model is
successful in reproducing features of the particle size dependence of the Curie
temperature for both pure and random diluted particles. In this last case, low
temperature magnetization reduction was consistent with the same type of RSG
behavior observed in bulk in accordance with the Almeida-Thouless line at low
fields and a linear dependence of the freezing temperature with the reciprocal
of the particle diameter was also obtained. Computation of the correlation
length critical exponent yielded the values via Bogoliubov
and via Monte Carlo. This fact indicates that even though
thermodynamical models can be indeed used in the study of nanostructures and
they can reproduce experimental features, special attention must be paid
regarding critical behavior. From both approaches, differences in the
exponent with respect to the pure Ising model agree with Harris and Fisher
arguments.Comment: 11 pages, 11 figures. Submitted to Phys. Rev.
Negative-energy perturbations in cylindrical equilibria with a radial electric field
The impact of an equilibrium radial electric field on negative-energy
perturbations (NEPs) (which are potentially dangerous because they can lead to
either linear or nonlinear explosive instabilities) in cylindrical equilibria
of magnetically confined plasmas is investigated within the framework of
Maxwell-drift kinetic theory. It turns out that for wave vectors with a
non-vanishing component parallel to the magnetic field the conditions for the
existence of NEPs in equilibria with E=0 [G. N. Throumoulopoulos and D.
Pfirsch, Phys. Rev. E 53, 2767 (1996)] remain valid, while the condition for
the existence of perpendicular NEPs, which are found to be the most important
perturbations, is modified. For ( is the
electrostatic potential) and ( is
the total plasma pressure), a case which is of operational interest in magnetic
confinement systems, the existence of perpendicular NEPs depends on ,
where is the charge of the particle species . In this case the
electric field can reduce the NEPs activity in the edge region of tokamaklike
and stellaratorlike equilibria with identical parabolic pressure profiles, the
reduction of electron NEPs being more pronounced than that of ion NEPs.Comment: 30 pages, late
Neutralino Phenomenology at LEP2 in Supersymmetry with Bilinear Breaking of R-parity
We discuss the phenomenology of the lightest neutralino in models where an
effective bilinear term in the superpotential parametrizes the explicit
breaking of R-parity. We consider supergravity scenarios where the lightest
supersymmetric particle (LSP) is the lightest neutralino and which can be
explored at LEP2. We present a detailed study of the LSP decay properties and
general features of the corresponding signals expected at LEP2. We also
contrast our model with gauge mediated supersymmetry breaking.Comment: 21 pages, Latex, uses axodraw.sty (included), 13 figures included as
ps- and eps-files, figures slightly changed after bug-fixing, comparison with
GMSB and a few references added, version to appear in NP
From old wars to new wars and global terrorism
The 9/11 attacks created an urgent need to understand contemporary wars and their relationship to older conventional and terrorist wars, both of which exhibit remarkable regularities. The frequency-intensity distribution of fatalities in "old wars", 1816-1980, is a power-law with exponent 1.80. Global terrorist attacks, 1968-present, also follow a power-law with exponent 1.71 for G7 countries and 2.5 for non-G7 countries. Here we analyze two ongoing, high-profile wars on opposite sides of the globe - Colombia and Iraq. Our analysis uses our own unique dataset for killings and injuries in Colombia, plus publicly available data for civilians killed in Iraq. We show strong evidence for power-law behavior within each war. Despite substantial differences in contexts and data coverage, the power-law coefficients for both wars are tending toward 2.5, which is a value characteristic of non-G7 terrorism as opposed to old wars. We propose a plausible yet analytically-solvable model of modern insurgent warfare, which can explain these observations.
- …