13 research outputs found
Superluminal Localized Solutions to the wave equation, in (vacuum or) dispersive media, for arbitrary frequencies and with adjustable bandwidth
In this paper we set forth new exact analytical Superluminal localized
solutions to the wave equation for arbitrary frequencies and adjustable
bandwidth. The formulation presented here is rather simple, and its results can
be expressed in terms of the ordinary, so-called "X-shaped waves". Moeover, by
the present formalism we obtain the first analytical localized Superluminal
approximate solutions which represent beams propagating in dispersive media.
Our solutions may find application in different fields, like optics,
microwaves, radio waves, and so on. [PACS nos.: 03.50.De ; 41.20.Jb ; 83.50.Vr
; 62.30.+d ; 43.60.+d ; 91.30.Fn ; 04.30.Nk ; 42.25.Bs ; 46.40.Cd ; 52.35.Lv.
Keywords: Wave equation; Wave propagation; Optics; Localized beams;
Superluminal waves; Bessel beams; X-shaped waves; Acoustics; Mechanical waves;
Dispersion compensation; Seismology; Geophysics; Gravitational Waves;
Elementary particle physics].Comment: plain LaTeX file (16 pages), plus 9 figure
Photon localization barrier can be overcome
In contradistinction to a widespread belief that the spatial localization of
photons is restricted by a power-law falloff of the photon energy density,
I.Bialynicki-Birula [Phys. Rev. Lett. 80, 5247 (1998)] has proved that any
stronger -- up to an almost exponential -- falloff is allowed. We are showing
that for certain specifically designed cylindrical one-photon states the
localization is even better in lateral directions. If the photon state is built
from the so-called focus wave mode, the falloff in the waist cross-section
plane turns out to be quadratically exponential (Gaussian) and such strong
localization persists in the course of propagation.Comment: Short communication -- 4 pages, 2 figure
Population Pharmacokinetics and Pharmacodynamics of Dobutamine in Neonates on the First Days of Life
Aims:
To describe the pharmacokinetics (PK) and concentrationârelated effects of dobutamine in critically ill neonates in the first days of life, using nonlinear mixed effects modelling.
Methods:
Dosing, plasma concentration and haemodynamic monitoring data from a doseâescalation study were analysed with a simultaneous population PK and pharmacodynamic model. Neonates receiving continuous infusion of dobutamine 5â20 ÎŒg kgâ1 minâ1 were included. Left ventricular ejection fraction (LVEF) and cardiac output of right and left ventricle (RVO, LVO) were measured on echocardiography; heart rate (HR), mean arterial pressure (MAP), peripheral arterial oxygen saturation and cerebral regional oxygen saturation were recorded from patient monitors.
Results:
Twentyâeight neonates with median (range) gestational age of 30.4 (22.7â41.0) weeks and birth weight (BW) of 1618 (465â4380) g were included. PK data were adequately described by 1âcompartmental linear structural model. Dobutamine clearance (CL) was described by allometric scaling on BW with sigmoidal maturation function of postmenstrual age (PMA). The final population PK model parameter mean typical value (standard error) estimates, standardised to median BW of 1618 g, were 41.2 (44.5) L hâ1 for CL and 5.29 (0.821) L for volume of distribution, which shared a common between subject variability of 29% (17.2%). The relationship between dobutamine concentration and RVO/LVEF was described by linear model, between concentration and LVO/HR/MAP/cerebral fractional tissue oxygen extraction by sigmoidal Emax model.
Conclusion:
In the postnatal transitional period, PK of dobutamine was described by a 1âcompartmental linear model, CL related to BW and PMA. A concentrationâresponse relationship with haemodynamic variables has been established
Debugging Data Transfers in CMS
The CMS experiment at CERN is preparing for LHC data taking in severalcomputing preparation activities. In early 2007 a traffic load generator infrastructure for distributed data transfer tests was designed and deployed to equip the WLCG tiers which support the CMS virtual organization with a means for debugging, load-testing and commissioning data transfer routes among CMS computing centres. The LoadTest is based upon PhEDEx as a reliable, scalable data set replication system. The Debugging Data Transfers (DDT) task force was created to coordinate the debugging of the data transfer links. The task force aimed to commission most crucial transfer routes among CMS tiers by designing and enforcing a clear procedure to debug problematic links. Such procedure aimed to move a link from a debugging phase in a separate and independent environment to a production environment when a set of agreed conditions are achieved for that link. The goal was to deliver one by one working transfer routes to the CMS data operations team. The preparation, activities and experience of the DDT task force within the CMS experiment are discussed. Common technical problems and challenges encountered during the lifetime of the taskforce in debugging data transfer links in CMS are explained and summarized
Focused X-shaped (Superluminal) pulses
The space-time focusing of a (continuous) succession of localized X-shaped
pulses is obtained by suitably integrating over their speed, i.e., over their
axicon angle, thus generalizing a previous (discrete) approach. First, new
Superluminal wave pulses are constructed, and then tailored in such a wave to
get them temporally focused at a chosen spatial point, where the wavefield can
reach for a short time very high intensities. Results of this kind may find
applications in many fields, besides electromagnetism and optics, including
acoustics, gravitation, and elementary particle physics.
PACS nos.: 41.20.Jb; 03.50.De; 03.30.+p; 84.40.Az; 42.82.Et; 83.50.Vr;
62.30.+d; 43.60.+d; 91.30.Fn; 04.30.Nk; 42.25.Bs; 46.40.Cd; 52.35.Lv.
Keywords: Localized solutions to Maxwell equations; Superluminal waves;
Bessel beams; Limited-diffraction pulses; Finite-energy waves; Electromagnetic
wavelets; X-shaped waves; Electromagnetism; Microwaves; Optics; Special
relativity; Localized acoustic waves; Seismic waves; Mechanical waves;
Elementary particle physics; Gravitational wavesComment: Latex file, with 6 Figure
Population pharmacokinetics and pharmacodynamics of dobutamine in neonates on the first days of life
Aims:
To describe the pharmacokinetics (PK) and concentrationârelated effects of dobutamine in critically ill neonates in the first days of life, using nonlinear mixed effects modelling.
Methods:
Dosing, plasma concentration and haemodynamic monitoring data from a doseâescalation study were analysed with a simultaneous population PK and pharmacodynamic model. Neonates receiving continuous infusion of dobutamine 5â20 ÎŒg kgâ1 minâ1 were included. Left ventricular ejection fraction (LVEF) and cardiac output of right and left ventricle (RVO, LVO) were measured on echocardiography; heart rate (HR), mean arterial pressure (MAP), peripheral arterial oxygen saturation and cerebral regional oxygen saturation were recorded from patient monitors.
Results:
Twentyâeight neonates with median (range) gestational age of 30.4 (22.7â41.0) weeks and birth weight (BW) of 1618 (465â4380) g were included. PK data were adequately described by 1âcompartmental linear structural model. Dobutamine clearance (CL) was described by allometric scaling on BW with sigmoidal maturation function of postmenstrual age (PMA). The final population PK model parameter mean typical value (standard error) estimates, standardised to median BW of 1618 g, were 41.2 (44.5) L hâ1 for CL and 5.29 (0.821) L for volume of distribution, which shared a common between subject variability of 29% (17.2%). The relationship between dobutamine concentration and RVO/LVEF was described by linear model, between concentration and LVO/HR/MAP/cerebral fractional tissue oxygen extraction by sigmoidal Emax model.
Conclusion:
In the postnatal transitional period, PK of dobutamine was described by a 1âcompartmental linear model, CL related to BW and PMA. A concentrationâresponse relationship with haemodynamic variables has been established