A Monte Carlo estimation of the marginal distributions in a problem of probabilistic dynamics

Modelling the effect of the dynamic behaviour of a system on its PSA study leads, in a Markovian framework, to a development at first order of the Chapman-Kolmogorov equation, whose solutions are the probability densities of the problem. Because of its size, there is no hope of solving directly these equations in realistic circumstances. We present in this paper a biased simulation giving the marginals and compare different ways of speeding up the integration of the equations of the dynamics.     

RBS/channelling study of ion-implanted and proton-exchanged LiNbO3:Nd:MgO planar waveguides

We present a structural study of two Nd³⁺/MgO codoped LiNbO₃ waveguides fabricated by two different methods: ion-implantation and proton-exchange. Rutherford backscattering spectrometry in combination with channelling was used to study the influence of the waveguide fabrication method on the possible modification of the LiNbO₃ crystal structure within the waveguiding layer. The results show that the ion-implanted waveguide mainly maintains the same properties as the virgin crystal, apart from a deterioration of a thin surface layer, whilst the proton-exchanged waveguide exhibits a quite different behaviour, although its surface is less damaged.     

Flow-dependent platelet behaviour in blood—material interactions

Platelet activation and adhesion are important parameters characterizing blood compatibility of biomaterials. A platelet transport theory based on convection diffusion, which describes the influence of wall shear rate, platelet concentration, axial position, hematocrit and red cell size, was originally proposed by Turitto and Baumgartner and later expanded by Aarts. This theory was applied in an in vitro perfusion system for three different materials with wall shear rates between 100s^-1 and 4300 s^-1 in order to cover the regions of diffusion controlled, reaction controlled and intermediate platelet adherence. Platelet diffusivity and platelet vessel wall surface reactivity were determined for these cases and the constants m and n were calculated using the relation between platelet diffusivity and shear rate as expressed by the following power law function: D _w=m*y ⁿ _w.     

A computational model for analysing interactive buckling and delamination growth in composite structures

In this paper, a unified method is presented: (i) to model delaminated stiffened laminated composite shells; (ii) for synthesising accurate multiple post-buckling solution paths under compressive loading; and (iii) for predicting delamination growth. A multi-domain modelling technique is used for modelling the delaminated stiffened shell structures. Error-free geometrically nonlinear element formulations — a 2-noded curved stiffener element (BEAM2) and a 3-noded shell element (SHELL3) — are used for the finite element analysis. An accurate and simple automated solution strategy based on Newton type iterations is used for predicting the general geometrically nonlinear and postbuckling behaviour of structures. A simple method derived from the 3-dimensionalJ-integral is used for computing the pointwise energy release rate at the delamination front in the plate/shell models. Finally, the influence of post-buckling structural behaviour and the delamination growth on each other has been demonstrated.     

Potassium uptake and water content in hepatocytes isolated from rat livers preserved in Euro-Collins and UW solutions and after transplantation

Isolated hepatocytes from the rat were used to assess the maintenance of liver cell function in relation to the composition of the preservation medium. After separation by collagenase, they were incubated in Krebs-Ringer-Bicarbonate medium (KRB), Euro-Collins (EC), or University of Wisconsin (UW) solutions. Potassium influx, cell volume, and transaminase release were measured in cells freshly separated from control livers or from livers preserved in vitro up to 12 h in these media or having undergone orthotopic liver transplantation (OLT). While ion exchange levels were retained in all media, cells shrank significantly in UW but were able to restore their volume after 3 h of liver preservation. With regard to in vivo conditions, UW appears to be the best medium to prevent edema and to maintain more stable potassium exchange and enzyme production. These results are of value for liver transplantation in humans.     

Examination of coping resources and family adaptation in mothers and daughters of incestuous versus nonclinical families.

Mother–daughter dyads from incestuous vs nonclinical families were compared in terms of (1) family life stress, (2) problem-solving appraisal, (3) direct coping behaviors, (4) mother–daughter communication, and (5) family adaptation and cohesion. 15 mother–daughter pairs from an incestuous family involving an adult male caretaker were matched on several variables to 16 mother–daughter pairs from a nonclinical family. The results revealed that mothers from the incest group (compared with the nonclinical group) reported greater amounts of family life stress, had more negative perceptions of their problem-solving appraisal, and reported more communication difficulties. The daughters from the incest group appeared to be quite similar to the nonclinical group daughters, although they did acknowledge more family stress. Implications of the results for therapeutic interventions as well as future research were discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right atrial thrombosis with concomitant thrombus attached to a central venous catheter. Clinical case

A clinical case of a patient in whom a right atrial thrombosis was casually discovered by transthoracic echocardiography is described. The hypothesis that also the central venous catheter (CVC) could be seat of thrombosis was done, and was confirmed by chest X-ray with dye injection in the CVC. A thrombolytic therapy with plasminogen tissular activator and with heparin infusion was started. After 24 hours from the beginning of therapy instrumental control were performed (transesophageal echocardiography ECOTEE, chest X-ray with dye injection in CVC), showing the completely dissolution of the thrombus. It is observed that, when in a patient with CVC high degree of thrombogenic factors (age over 60 years, presence of cardiac arrhythmias with ventricular hypokinesis, polyglobulia due to chronic obstructive pulmonary disease, CVC, low levels of antithrombin III) are present, the usual prophylactic measures (subcutaneous heparin, hydrophylic catheter) couldn't be sufficient to avoid superior caval vein thrombosis. The conclusion is drawn that these patient should be studied with ECOTEE and eco Doppler. Chest tomography and superior caval venography are also useful its early diagnosis of superior caval thrombosis.     

Apoptosis in the failing human heart

BACKGROUND: Loss of myocytes is an important mechanism in the development of cardiac failure of either ischemic or nonischemic origin. However, whether programmed cell death (apoptosis) is implicated in the terminal stages of heart failure is not known. We therefore studied the magnitude of myocyte apoptosis in patients with intractable congestive heart failure. METHODS: Myocardial samples were obtained from the hearts of 36 patients who underwent cardiac transplantation and from the hearts of 3 patients who died soon after myocardial infarction. Samples from 11 normal hearts were used as controls. Apoptosis was evaluated histochemically, biochemically, and by a combination of histochemical analysis and confocal microscopy. The expression of two proto-oncogenes that influence apoptosis, BCL2 and BAX, was also determined. RESULTS: Heart failure was characterized morphologically by a 232-fold increase in myocyte apoptosis and biochemically by DNA laddering (an indicator of apoptosis). The histochemical demonstration of DNA-strand breaks in myocyte nuclei was coupled with the documentation of chromatin condensation and fragmentation by confocal microscopy. All these findings reflect apoptosis of myocytes. The percentage of myocytes labeled with BCL2 (which protects cells against apoptosis) was 1.8 times as high in the hearts of patients with cardiac failure as in the normal hearts, whereas labeling with BAX (which promotes apoptosis) remained constant. The near doubling of the expression of BCL2 in the cardiac tissue of patients with heart failure was confirmed by Western blotting. CONCLUSIONS: Programmed death of myocytes occurs in the decompensated human heart in spite of the enhanced expression of BCL2; this phenomenon may contribute to the progression of cardiac dysfunction.     

In the beginning [junction transistor]

The junction transistor, technologically the most important solid-state device, invented theoretically by W.B. Shockley on January 23, 1948, brought about the semiconductor revolution. That invention was triggered by the experimental discovery of the point-contact transistor by W. Brattain and J. Bardeen 38 days earlier. Bardeen's notebook entries at Bell Telephone Laboratories for the crucial 100-day period November 21, 1947-February 29, 1948 have been examined to ascertain why this winner of two Nobel Prizes in physics could not invent the junction transistor. It was found that the boundary between the thin p-type inversion layer and the n-type bulk germanium semiconductor in their original point-contact transistor discovery was characterized as a “high resistance boundary” in macroscopic electrical engineering terms by Bardeen, the electrical engineer turned mathematical physicist. Pages from Shockley's notebook are reproduced in full to show what exactly he was thinking on December 16, 1947, the day the point-contact transistor was experimentally discovered by Brattain and Bardeen. The origin of U.S. Patent 2524035 has been traced to the Bell Telephone Laboratories notebook pages of its inventors and examined. It is shown that this patent could not be considered as the first patent describing Shockley's revolutionary theoretical invention of the minority carrier injection concept underlying bipolar transistor action