339 research outputs found
The (human) respiratory rate at rest
All schoolchildren know how often they breathe, but even experts don't know
exactly why. The aim of this publication is to develop a model of the resting
spontaneous breathing rate using physiological, physical and mathematical
methods with the aid of the principle that evolution pushes physiology in a
direction that is as economical as possible. The respiratory rate then follows
from an equation with the parameters CO2-production rate of the organism,
resistance, static compliance and dead space of the lungs, the inspiration
duration: expiration duration - ratio and the end-expiratory CO2 fraction. The
derivation requires exclusively secondary school mathematics. Using the example
of an adult human or a newborn child, data from the literature then result in
normal values for their breathing rate at rest. The reason for the higher
respiratory rate of a newborn human compared to an adult is the relatively high
CO2-production rate together with the comparatively low compliance of the
lungs. A side result is the fact that the common alveolar pressure throughout
the lungs and the common time constant is a consequence of the economical
principle as well. Since the above parameters are not human-specific, there is
no reason to assume that the above equation could not also be applicable to
many animals breathing through lungs within a thorax, especially mammals. Not
only physiology and biology, but also medicine, could benefit: Applicability is
being discussed in pulmonary function diagnostics, including pathophysiology.
However, the present publication only claims to be a theoretical concept for
the spontaneous quiet breathing rate. In the absence of comparable animal data,
this publication is intended to encourage further scientific tests.Comment: 41 pages, 6 figures, 4 table
Influence of high-dose aprotinin treatment on blood loss and coagulation patterns in open-heart surgery
Intraoperative administration of the proteinase Inhibitor aprotinin causes reduction in blood loss and homologous blood requirement in patients undergoing cardiac surgery. To ascertain the blood-saving effect of aprotinin and to obtain further information about the mode of action, 40 patients undergoing primary myocardial revascularization were randomly assigned to receive either aprotinin or placebo treatment. Aprotinin was given as a bolus of 2 X 105 kallikrein inactivator units (KIU) before surgery followed by a continuous infusion of 5 X 105 KIU/h during surgery. Additionally, 2 X 105 KIU were added to the pump prime. Strict criteria were used to obtain a homogeneous patient selection. Total blood loss was reduced from 1,431 +/- 760 ml in the control group to 738 +/- 411 ml in the aprotinin group (P < 0.05) and the homologous blood requirement from 838 +/- 963 ml to 163 +/- 308 ml (P < 0.05). In the control group, 2.3 +/- 2.2 U of homologous blood or blood products were given, and in the aprotinin group, 0.63 +/- 0.96 U were given (P < 0.05). Twenty-five percent of patients in the control group and 63% in the aprotinin group did not receive banked blood or homologous blood products. The activated clotting time as an indicator of inhibition of the contact phase of coagulation was significantly Increased before heparinization in the aprotinin group (141 +/- 13 s vs. 122 +/- 25 s) and remained significantly Increased until heparin was neutralized after cardiopulmonary bypass (CPB). The concentration of the thrombin-antithrombin III complex was significantly decreased at the end of CPB in the aprotinin group, indicating less thrombin generation in the aprotinin-treated group. The total concentration of the fibrinogen-fibrin split products (FSP) and the split products of the cross-linked fibrin (D-dimers) were also significantly reduced due to attenuated proteolytic activities of thrombin and plasmin. The results of the fibrin plate assay revealed higher fibrinolytic activity during CPB in the control group. The results demonstrate the beneficial effect of high-dose aprotinin treatment on blood loss and homologous blood requirement. This effect can be attributed to the inhibition of the contact phase of coagulation and the consequently reduced thrombotic and fibrionolytic activity during and after CPB
Consequences of voluntary job changes in Germany: A multilevel analysis for 1985-2013
Analyzing the development of the consequences of voluntary job changes in Germany between 1985 and 2013, the study focuses on income gains and job satisfaction increases. Drawing on arguments of the job-search literature on the one hand and the proliferation of choices on the other we investigate whether the returns of job changes have increased or decreased. Results show that income gains have decreased over time while the job satisfaction surplus has remained stable. We further conclude that in determining the outcomes of job changes over time, structural factors seem to be more important than individual ones
Imaging correlated wave functions of few-electron quantum dots: Theory and scanning tunneling spectroscopy experiments
We show both theoretically and experimentally that scanning tunneling
spectroscopy (STS) images of semiconductor quantum dots may display clear
signatures of electron-electron correlation. We apply many-body tunneling
theory to a realistic model which fully takes into account correlation effects
and dot anisotropy. Comparing measured STS images of freestanding InAs quantum
dots with those calculated by the full configuration interaction method, we
explain the wave function sequence in terms of images of one- and two-electron
states. The STS map corresponding to double charging is significantly distorted
by electron correlation with respect to the non-interacting case.Comment: RevTeX 4.0, 5 pages, 3 B/W figures, 1 table. This paper is based on
an invited talk presented by the authors at the 28th International Conference
on the Physics of Semiconductors, which was held 24-28 July 2006, in Vienna,
Austri
Myelodysplastic syndromes: Aspects of current medical care and economic considerations in Germany
Myelodysplastic syndromes (MDS) are a heterogeneous group of diseases mainly affecting older people. The use of an increasing number of therapeutic options depends on a systematic risk stratification of the patients. A high percentage of MDS patients need blood transfusions as supportive care, which influence quality of life and cause a great part of the costs generated by MDS therapy. In this article which is based on a workshop about the burden of MDS held in October 2006 in Munich, MDS is discussed with regard to different aspects: current therapies, transfusion medicine, geriatrics, quality of life, and health economic aspects
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