1,166 research outputs found
Leptonic Observables in Ultra-Relativistic Heavy Ion Collisions
We report on leptonic observables by the PHENIX experiment from data taken
during Run II at the Relativistic Heavy Ion Collider (RHIC). We show first
results on phi -> K+K-, e+e-, low and intermediate mass dielectron continuum,
single electrons from charm, and J/psi yields in proton-proton and Au-Au
collisions at sqrt{s_{NN}}=200 GeV.Comment: 10 pages, 11 figures, Talk presented at Quark Matter 2002, Nantes,
France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A
Size dependent symmetry breaking in models for morphogenesis
A general property of dynamical systems is the appearance of spatial and temporal patterns due to a change of stability of a homogeneous steady state. Such spontaneous symmetry breaking is observed very frequently in all kinds of real systems, including the development of shape in living organisms. Many nonlinear dynamical systems present a wide variety of patterns with different shapes and symmetries. This fact restricts the applicability of these models to morphogenesis, since one often finds a surprisingly small variation in the shapes of living organisms. For instance, all individuals in the Phylum Echinodermata share a persistent radial fivefold symmetry. In this paper, we investigate in detail the symmetry-breaking properties of a Turing reaction–diffusion system confined in a small disk in two dimensions. It is shown that the symmetry of the resulting pattern depends only on the size of the disk, regardless of the boundary conditions and of the differences in the parameters that differentiate the interior of the domain from the outer space. This study suggests that additional regulatory mechanisms to control the size of the system are of crucial importance in morphogenesis
Optically induced coherent intra-band dynamics in disordered semiconductors
On the basis of a tight-binding model for a strongly disordered semiconductor
with correlated conduction- and valence band disorder a new coherent dynamical
intra-band effect is analyzed. For systems that are excited by two, specially
designed ultrashort light-pulse sequences delayed by tau relatively to each
other echo-like phenomena are predicted to occur. In addition to the inter-band
photon echo which shows up at exactly t=2*tau relative to the first pulse, the
system responds with two spontaneous intra-band current pulses preceding and
following the appearance of the photon echo. The temporal splitting depends on
the electron-hole mass ratio. Calculating the population relaxation rate due to
Coulomb scattering, it is concluded that the predicted new dynamical effect
should be experimentally observable in an interacting and strongly disordered
system, such as the Quantum-Coulomb-Glass.Comment: to be published in Physical Review B15 February 200
Pursuing the Real Vancomycin Clearance during Continuous Renal Replacement Therapy in Intensive Care Unit Patients:Is There Adequate Target Attainment?
Introduction: Vancomycin is used in intensive care unit (ICU) patients for the treatment of infections caused by gram-positive bacteria. The vancomycin pharmacokinetic/pharmacodynamic index is a ratio of the area under the concentration to the minimum inhibitory concentration ≥400-600 h∗mg/L. This target can generally be achieved by a plasma concentration of 20-25 mg/L. Together with the pathophysiological alterations and pharmacokinetic variability associated with critical illness, the use of continuous renal replacement therapy (CRRT) may complicate the attainment of adequate vancomycin concentrations. The primary objective was the prevalence of attainment of vancomycin concentrations 20-25 mg/L after 24 h in adult ICU patients receiving CRRT. Secondary outcomes were to evaluate target attainment at days 2 and 3 and to calculate vancomycin clearance (CL) by CRRT and residual diuresis. Methods: We performed a prospective observational study in adult ICU patients on CRRT, which received at least 24 h continuous infusion of vancomycin. Between May 2020 and February 2021, daily vancomycin residual blood gas and dialysate samples were collected from 20 patients, every 6 h and if possible vancomycin urine samples. Vancomycin was analysed with an immunoassay method. The CL by CRRT was calculated by a different approach correcting for the downtime and providing insight into the degree of filter patency. Results: The proportion of patients with vancomycin concentrations <20 mg/L was 50% 24 h after starting vancomycin (n = 10). No differences were observed in patient characteristics. The target vancomycin concentration 20-25 mg/L was only achieved in 30% of the patients. On days 2 and 3, despite the use of TDM and albeit in lower percentages, sub- and supratherapeutic levels were still observed. Taking downtime and filter patency into account resulted in lower vancomycin CL. Conclusions: 50% of the studied ICU patients on CRRT showed subtherapeutic vancomycin concentrations 24 h after starting therapy. The results reveal that optimization of vancomycin dosage during CRRT therapy is needed.</p
Global Existence and Uniqueness of Solutions to the Maxwell-Schr{\"o}dinger Equations
The time local and global well-posedness for the Maxwell-Schr{\"o}dinger
equations is considered in Sobolev spaces in three spatial dimensions. The
Strichartz estimates of Koch and Tzvetkov type are used for obtaining the
solutions in the Sobolev spaces of low regularities. One of the main results is
that the solutions exist time globally for large data.Comment: 30 pages. In the revised version, the following modification was
made. (1) A line for dedication was added in the first page. (2) Some lines
were added at the bottom in page 4 and the top in page 5 in the first section
to make the description accurate. (3) Some typographical errors were
corrected throughout the pape
Fluctuating Fuzzy Funnels
It is well known that a D-string ending on a D3, D5 or D7 brane is described
in terms of a non-commutative fuzzy funnel geometry. In this article, we give a
numerical study of the fluctuations about this leading geometry. This allows us
to investigate issues related to the stability and moduli space of these
solutions. We comment on the comparison to the linearized fluctuations in
supergravity.Comment: 24 pages, 3 figures; v2 references added and correcte
Thermally assisted magnetization reversal in the presence of a spin-transfer torque
We propose a generalized stochastic Landau-Lifshitz equation and its
corresponding Fokker-Planck equation for the magnetization dynamics in the
presence of spin transfer torques. Since the spin transfer torque can pump a
magnetic energy into the magnetic system, the equilibrium temperature of the
magnetic system is ill-defined. We introduce an effective temperature based on
a stationary solution of the Fokker-Planck equation. In the limit of high
energy barriers, the law of thermal agitation is derived. We find that the
N\'{e}el-Brown relaxation formula remains valid as long as we replace the
temperature by an effective one that is linearly dependent of the spin torque.
We carry out the numerical integration of the stochastic Landau-Lifshitz
equation to support our theory. Our results agree with existing experimental
data.Comment: 5 figure
Isospin splitting in heavy baryons and mesons
A recent general analysis of light-baryon isospin splittings is updated and
extended to charmed baryons.
The measured and splittings stand out as being difficult
to understand in terms of two-body forces alone.
We also discuss heavy-light mesons; though the framework here is necessarily
less general, we nevertheless obtain some predictions that are not strongly
model-dependent.Comment: 12 pages REVTEX 3, plus 4 uuencoded ps figures, CMU-HEP93-
The Clearance of Midazolam and Metabolites during Continuous Renal Replacement Therapy in Critically Ill Patients with COVID-19
Introduction: Midazolam-based continuous intravenous sedation in patients admitted to the intensive care unit (ICU) was a necessity during the COVID-19 pandemic. However, benzodiazepine-based sedation is associated with a high incidence of benzodiazepine-related delirium and additional days on mechanical ventilation. Due to the requirement of high midazolam doses in combination with the impaired renal clearance (CL) of the pharmacological active metabolite 1-OH-midazolam-glucuronide (10% compared to midazolam), ICU patients with COVID-19 and continuous renal replacement therapy (CRRT) were at risk of unintended prolonged sedation. Several CRRT-related factors may have influenced the delivered CL of midazolam and its metabolites. Therefore, the aim of the study was to identify and describe these CRRT-related factors. Methods: Pre-filter blood samples and ultrafiltrate samples were collected simultaneously. Midazolam, 1-OH-midazolam, and 1-OH-midazolam-glucuronide plasma samples were analyzed using an UPLC-MS/MS method. The prescribed CRRT dose was corrected for downtime and filter integrity using the urea ratio (urea concentration in effluent/urea concentration plasma). CL of midazolam and its metabolites were calculated with the delivered CRRT dose (corrected for downtime and saturation coefficient [SD]). Results: Three patients on continuous venovenous hemodialysis (CVVHD) and 2 patients on continuous venovenous hemodiafiltration (CVVHDF) were included. Midazolam, 1-OH-midazolam, and 1-OH-midazolam-glucuronide concentrations were 2,849 (0-6,700) μg/L, 153 (0-295) μg/L, and 27,297 (1,727-39,000) μg/L, respectively. The SD was 0.03 (0.02-0.03) for midazolam, 0.05 (0.05-0.06) for 1-OH-midazolam, and 0.33 (0.23-0.43) for 1-OH-midazolam-glucuronide. The delivered CRRT CL was 1.4 (0-1.7) mL/min for midazolam, 2.7 (0-3.5) mL/min for 1-OH-midazolam, and 15.7 (4.0-27.7) mL/min for 1-OH-midazolam-glucuronide. Conclusions: Midazolam and 1-OH-midazolam were not removed during CVVHD and CVVHDF. However, 1-OH-midazolam-glucuronide was removed reasonably, approximately up to 43%. CRRT modality, filter integrity, and downtime affect this removal. These data imply a personalized titration of midazolam in critically ill patients with renal failure and awareness for the additional sedative effects of its active metabolites.</p
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