212 research outputs found
Venous thromboembolism in surgical practice.
A statistical retrospective analysis of the results of treatment of patients undergoing inpatient treatment in the surgical clinic, proctology and urology departments for 5 years was conducted, total number of patients – 27771, of them operated – 14849 (53.5%), postoperative mortality – 448 patients (3.0%), the overall mortality – 989 patients (3.6%). According to the analysis of the medical documentation, the total number of patients with pulmonary embolism (PE) was 98 (0.35%), the number of patients diagnosed during treatment – 56 (57.1%), at the time of pathoanatomical examination – 42 (42.9%); in 72 patients PE was directly responsible for death, 26 patients were cured by conservative methods. Of 98 patients with PE in 56 (56.1%), the main disease was oncological disease, in most cases in neglected form with distant metastases. A reduction in postoperative lethality by 40% was obtained, the reason for which, in our opinion, are: mandatory adherence to the recommended timing of the prevention of acute thromboembolic complications; prolongation of the prophylaxis term in patients who have undergone major surgical interventions or with postoperative complications that lead to a prolonged limitation of the patients' motor activity; a wider use of low molecular weight heparins
Venous thromboembolism in surgical practice.
A statistical retrospective analysis of the results of treatment of patients undergoing inpatient treatment in the surgical clinic, proctology and urology departments for 5 years was conducted, total number of patients – 27771, of them operated – 14849 (53.5%), postoperative mortality – 448 patients (3.0%), the overall mortality – 989 patients (3.6%). According to the analysis of the medical documentation, the total number of patients with pulmonary embolism (PE) was 98 (0.35%), the number of patients diagnosed during treatment – 56 (57.1%), at the time of pathoanatomical examination – 42 (42.9%); in 72 patients PE was directly responsible for death, 26 patients were cured by conservative methods. Of 98 patients with PE in 56 (56.1%), the main disease was oncological disease, in most cases in neglected form with distant metastases. A reduction in postoperative lethality by 40% was obtained, the reason for which, in our opinion, are: mandatory adherence to the recommended timing of the prevention of acute thromboembolic complications; prolongation of the prophylaxis term in patients who have undergone major surgical interventions or with postoperative complications that lead to a prolonged limitation of the patients' motor activity; a wider use of low molecular weight heparins
Constructive control of quantum systems using factorization of unitary operators
We demonstrate how structured decompositions of unitary operators can be
employed to derive control schemes for finite-level quantum systems that
require only sequences of simple control pulses such as square wave pulses with
finite rise and decay times or Gaussian wavepackets. To illustrate the
technique it is applied to find control schemes to achieve population transfers
for pure-state systems, complete inversions of the ensemble populations for
mixed-state systems, create arbitrary superposition states and optimize the
ensemble average of dynamic observables.Comment: 28 pages, IoP LaTeX, principal author has moved to Cambridge
University ([email protected]
Anharmonicity, vibrational instability and Boson peak in glasses
We show that a {\em vibrational instability} of the spectrum of weakly
interacting quasi-local harmonic modes creates the maximum in the inelastic
scattering intensity in glasses, the Boson peak. The instability, limited by
anharmonicity, causes a complete reconstruction of the vibrational density of
states (DOS) below some frequency , proportional to the strength of
interaction. The DOS of the new {\em harmonic modes} is independent of the
actual value of the anharmonicity. It is a universal function of frequency
depending on a single parameter -- the Boson peak frequency, which
is a function of interaction strength. The excess of the DOS over the Debye
value is at low frequencies and linear in in the
interval . Our results are in an excellent
agreement with recent experimental studies.Comment: LaTeX, 8 pages, 6 figure
Inelastic light, neutron, and X-ray scatterings related to the heterogeneous elasticity of glasses
The effects of plasticization of poly(methyl methacrylate) glass on the boson
peaks observed by Raman and neutron scattering are compared. In plasticized
glass the cohesion heterogeneities are responsible for the neutron boson peak
and partially for the Raman one, which is enhanced by the composition
heterogeneities. Because the composition heterogeneities have a size similar to
that of the cohesion ones and form quasiperiodic clusters, as observed by small
angle X-ray scattering, it is inferred that the cohesion heterogeneities in a
normal glass form nearly periodic arrangements too. Such structure at the
nanometric scale explains the linear dispersion of the vibrational frequency
versus the transfer momentum observed by inelastic X-ray scattering.Comment: 9 pages, 2 figures, to be published in J. Non-Cryst. Solids
(Proceedings of the 4th IDMRCS
Selective Excitation of Vibrational States by Shaping of Light-Induced Potentials
In this Letter we describe a method for population transfer using intense, ultrafast laser pulses. The selectivity is accomplished by careful shaping of light-induced potentials (LIPs). Creation and control of the LIPs is accomplished by choosing pairs of pulses with proper frequency detunings and time delays. As an example, selective population transfer is demonstrated for a three-state model of the sodium dimer
Physical Origin of the Boson Peak Deduced from a Two-Order-Parameter Model of Liquid
We propose that the boson peak originates from the (quasi-) localized
vibrational modes associated with long-lived locally favored structures, which
are intrinsic to a liquid state and are randomly distributed in a sea of
normal-liquid structures. This tells us that the number density of locally
favored structures is an important physical factor determining the intensity of
the boson peak. In our two-order-parameter model of the liquid-glass
transition, the locally favored structures act as impurities disturbing
crystallization and thus lead to vitrification. This naturally explains the
dependence of the intensity of the boson peak on temperature, pressure, and
fragility, and also the close correlation between the boson peak and the first
sharp diffraction peak (or prepeak).Comment: 5 pages, 1 figure, An error in the reference (Ref. 7) was correcte
Coherent control using adaptive learning algorithms
We have constructed an automated learning apparatus to control quantum
systems. By directing intense shaped ultrafast laser pulses into a variety of
samples and using a measurement of the system as a feedback signal, we are able
to reshape the laser pulses to direct the system into a desired state. The
feedback signal is the input to an adaptive learning algorithm. This algorithm
programs a computer-controlled, acousto-optic modulator pulse shaper. The
learning algorithm generates new shaped laser pulses based on the success of
previous pulses in achieving a predetermined goal.Comment: 19 pages (including 14 figures), REVTeX 3.1, updated conten
Electronic structure of nuclear-spin-polarization-induced quantum dots
We study a system in which electrons in a two-dimensional electron gas are
confined by a nonhomogeneous nuclear spin polarization. The system consists of
a heterostructure that has non-zero nuclei spins. We show that in this system
electrons can be confined into a dot region through a local nuclear spin
polarization. The nuclear-spin-polarization-induced quantum dot has interesting
properties indicating that electron energy levels are time-dependent because of
the nuclear spin relaxation and diffusion processes. Electron confining
potential is a solution of diffusion equation with relaxation. Experimental
investigations of the time-dependence of electron energy levels will result in
more information about nuclear spin interactions in solids
Adiabatic population transfer via multiple intermediate states
This paper discusses a generalization of stimulated Raman adiabatic passage
(STIRAP) in which the single intermediate state is replaced by intermediate
states. Each of these states is connected to the initial state \state{i} with
a coupling proportional to the pump pulse and to the final state \state{f}
with a coupling proportional to the Stokes pulse, thus forming a parallel
multi- system. It is shown that the dark (trapped) state exists only
when the ratio between each pump coupling and the respective Stokes coupling is
the same for all intermediate states. We derive the conditions for existence of
a more general adiabatic-transfer state which includes transient contributions
from the intermediate states but still transfers the population from state
\state{i} to state \state{f} in the adiabatic limit. We present various
numerical examples for success and failure of multi- STIRAP which
illustrate the analytic predictions. Our results suggest that in the general
case of arbitrary couplings, it is most appropriate to tune the pump and Stokes
lasers either just below or just above all intermediate states.Comment: 14 pages, two-column revtex style, 10 figure
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