243 research outputs found
Cardiac index monitoring by pulse contour analysis and thermodilution after pediatric cardiac surgery
ObjectivesTo validate a new device (PiCCO system; Pulsion Medical Systems, Munich, Germany), we compared cardiac index derived from transpulmonary thermodilution and from pulse contour analysis in pediatric patients after surgery for congenital heart disease. We performed a prospective clinical study in a pediatric cardiac intensive care unit of a university hospital.MethodsTwenty-four patients who had had cardiac surgery for congenital heart disease (median age 4.2 years, range 1.4-15.2 years) were investigated in the first 24 hours after admission to the intensive care unit. A 3F thermodilution catheter was inserted in the femoral artery. Intracardiac shunts were excluded by echocardiography intraoperatively or postoperatively. Cardiac index derived from pulse contour analysis was documented in each patient 1, 4, 8, 12, 16, 20, and 24 hours after admission to the intensive care unit. Subsequently, a set of three measurements of thermodilution cardiac indices derived by injections into a central venous line was performed and calculated by the PiCCO system.ResultsThe mean bias between cardiac indices derived by thermodilution and those derived by pulse contour analysis over all data points was 0.05 (SD 0.4) L · min · m−2 (95% confidence interval 0.01-0.10). A strong correlation between thermodilution and contour analysis cardiac indices was calculated (Pearson correlation coefficient r = 0.93; coefficient of determination r2 = 0.86).ConclusionsPulse contour analysis is a suitable method to monitor cardiac index over a wide range of indices after surgery for congenital heart disease in pediatric patients. Pulse contour analysis allows online monitoring of cardiac index. The PiCCO device can be recalibrated with the integrated transpulmonary thermodilution within a short time frame
The cohesin ring concatenates sister DNA molecules
Sister chromatid cohesion, which is essential for mitosis, is mediated by a multi-subunit
protein complex called cohesin whose Scc1, Smc1, and Smc3 subunits form a tripartite
ring structure. It has been proposed that cohesin holds sister DNAs together by trapping
them inside its ring. To test this, we used site-specific cross-linking to create chemical
connections at the three interfaces between the ring’s three constituent polypeptides,
thereby creating covalently closed cohesin rings. As predicted by the ring entrapment
model, this procedure produces dimeric DNA/cohesin structures that are resistant to
protein denaturation. We conclude that cohesin rings concatenate individual sister
minichromosome DNAs
Transmission time of wave packets through tunneling barriers
The transmission of wave packets through tunneling barriers is studied in
detail by the method of quantum molecular dynamics. The distribution function
of the times describing the arrival of a tunneling packet in front of and
behind a barrier and the momentum distribution function of the packet are
calculated. The behavior of the average coordinate of a packet, the average
momentum, and their variances is investigated. It is found that under the
barrier a part of the packet is reflected and a Gaussian barrier increases the
average momentum of the transmitted packet and its variance in momentum space.Comment: 23 pages, 5 figure
Time of arrival in the presence of interactions
We introduce a formalism for the calculation of the time of arrival t at a
space point for particles traveling through interacting media. We develop a
general formulation that employs quantum canonical transformations from the
free to the interacting cases to construct t in the context of the Positive
Operator Valued Measures. We then compute the probability distribution in the
times of arrival at a point for particles that have undergone reflection,
transmission or tunneling off finite potential barriers. For narrow Gaussian
initial wave packets we obtain multimodal time distributions of the reflected
packets and a combination of the Hartman effect with unexpected retardation in
tunneling. We also employ explicitly our formalism to deal with arrivals in the
interaction region for the step and linear potentials.Comment: 20 pages including 5 eps figure
Density Matrix Kinetic Equation Describing a Passage of Fast Atomic Systems Through Matter
The quantum-mechanical consideration of a passage of fast dimesoatoms through
matter is given. A set of quantum-kinetic equations for the density matrix
elements describing their internal state evolution is derived. It is shown that
probabilistic description of internal dynamics of hydrogen-like atoms is
impossible even at sufficiently low energies because of the ``accidental''
degeneracy of their energy levels.Comment: 12 pages, LATEX, submitted to J. Phys.
Chromomagnetic Catalysis of Color Superconductivity in a (2+1)-dimensional NJL Model
The influence of a constant uniform external chromomagnetic field on the
formation of color superconductivity has been investigated. The consideration
was performed in the framework of a (2+1)-dimensional Nambu--Jona-Lasinio model
with two different four-fermionic structures responsible for condensates. In particular, it was shown that there exists a
critical value of the external chromomagnetic field such that at
a nonvanishing diquark condensate is dynamically created (the so-called
chromomagnetic catalysis effect of color superconductivity). Moreover, external
chromomagnetic fields may in some cases enhance the diquark condensate of color
superconductivity.Comment: 32 pages, 2 figures, revte
The Elg1 Clamp Loader Plays a Role in Sister Chromatid Cohesion
Mutations in the ELG1 gene of yeast lead to genomic instability, manifested in high levels of genetic recombination, chromosome loss, and gross chromosomal rearrangements. Elg1 shows similarity to the large subunit of the Replication Factor C clamp loader, and forms a RFC-like (RLC) complex in conjunction with the 4 small RFC subunits. Two additional RLCs exist in yeast: in one of them the large subunit is Ctf18, and in the other, Rad24. Ctf18 has been characterized as the RLC that functions in sister chromatid cohesion. Here we present evidence that the Elg1 RLC (but not Rad24) also plays an important role in this process. A genetic screen identified the cohesin subunit Mcd1/Scc1 and its loader Scc2 as suppressors of the synthetic lethality between elg1 and ctf4. We describe genetic interactions between ELG1 and genes encoding cohesin subunits and their accessory proteins. We also show that defects in Elg1 lead to higher precocious sister chromatid separation, and that Ctf18 and Elg1 affect cohesion via a joint pathway. Finally, we localize both Ctf18 and Elg1 to chromatin and show that Elg1 plays a role in the recruitment of Ctf18. Our results suggest that Elg1, Ctf4, and Ctf18 may coordinate the relative movement of the replication fork with respect to the cohesin ring
Phase-space formulation of quantum mechanics and quantum state reconstruction for physical systems with Lie-group symmetries
We present a detailed discussion of a general theory of phase-space
distributions, introduced recently by the authors [J. Phys. A {\bf 31}, L9
(1998)]. This theory provides a unified phase-space formulation of quantum
mechanics for physical systems possessing Lie-group symmetries. The concept of
generalized coherent states and the method of harmonic analysis are used to
construct explicitly a family of phase-space functions which are postulated to
satisfy the Stratonovich-Weyl correspondence with a generalized traciality
condition. The symbol calculus for the phase-space functions is given by means
of the generalized twisted product. The phase-space formalism is used to study
the problem of the reconstruction of quantum states. In particular, we consider
the reconstruction method based on measurements of displaced projectors, which
comprises a number of recently proposed quantum-optical schemes and is also
related to the standard methods of signal processing. A general group-theoretic
description of this method is developed using the technique of harmonic
expansions on the phase space.Comment: REVTeX, 18 pages, no figure
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