Aggregate stability of ZrO2 aqueous sols in electrolyte solutions

The aggregate stability of submicron and nanosized ZrO₂ aqueous sols of different origins and different dispersities at pH 3–10 in the KCl concentration range 10^?3–10^?1 M is investigated by flow ultramicroscopy and photometry. The results obtained are analyzed in the framework of the extended Derjaguin-Landau-Verwey-Overbeek theory and the Muller-Martynov theory of reversible aggregation. The extension of boundary layers of water near the surface of the ZrO₂ particles is estimated.     

Endothelial selectins and vascular cell adhesion molecule-1 promote hematopoietic progenitor homing to bone marrow

The adhesive mechanisms allowing hematopoietic progenitor cells (HPC) homing to the bone marrow (BM) after BM transplantation are poorly understood. We investigated the role of endothelial selectins and vascular cell adhesion molecule-1 (VCAM-1) in this process. Lethally irradiated recipient mice deficient in both P-and E-selectins (P/E-/-), reconstituted with minimal numbers (相似文献   

Expression of beta 2-integrins and L-selectin on polymorphonuclear leukocytes in septic patients

Adhesion molecules on polymorphonuclear leukocytes (PMNL) play an important role in nonspecific defense mechanisms directed at invading microorganisms. When local infection, however, cannot be controlled, a systemic inflammatory response syndrome (SIRS) ensues which may progress to septic shock and multiple organ failure, these being major determinants of the patient's outcome. In the present study, the expression of beta 2-integrins and L-selectin on blood PMNL was measured on subsequent days in patients with sepsis (n = 17) and in healthy volunteers (n = 15). beta 2-Integrins and L-selectin molecules were detected by flow cytometry, using the monoclonal antibodies IB4 (anti-CD18) and Dreg200 (anti-CD62L), respectively. Adhesion molecules were determined at baseline immediately after blood collection and also 45 min after incubation of cells in vitro at body temperature to allow for spontaneous regulation. In addition, PMNL were activated by receptor-dependent and receptor-independent stimuli to characterize stimulus-specific adhesion molecule expression. In parallel with the measurement of adhesion molecules, severity of sepsis was assessed by the Elebute score. The results demonstrate significant differences in the basal, spontaneous and stimulus-induced expression of adhesion molecules between healthy volunteers, survivors (n = 11) and nonsurvivors (n = 6). Moreover, when survivors and nonsurvivors with severe sepsis (Elebute score > 12) were compared, basal expressions of both beta 2-integrins and L-selectin were significantly lower in patients who did not survive. Thus, measurement of adhesion molecules on circulating PMNL may be useful to identify septic patients at high risk for lethal outcome.     

Suicide in the prime of life: current data

Suicide of people aged 25-59 years old is fastly increasing in France, especially for males, to 38.4 per 100,000 population in 1992 from 37.0 per 100,000 a decade earlier. In fact the suicide rate is decreasing among male adults having an occupation or a job (to 32.3 in 1992 from 33.8 in 1982). On the contrary, the economically inactive and the jobless are experiencing a tremendous growth in their suicide rate (to 74.9 per 100,000 population in 1992 from 60.9 a decade earlier). The trend is observed also among females aged 25-59 years old but the "employed/unemployed" gap is less pronounced. Marital status and occupational groups have also an influence upon the frequency of adult suicide. Since the work of Emile Durkheim a century ago, the profile of suicide has changed in France, due to societal upheavals.     

Weak evidence for determinants of citation frequency in ecological articles

Citation frequency has been considered a biased surrogate of publication merit. However, previous studies on this subject were based on small sample sizes and were entirely based on null-hypothesis significance testing. Here we evaluated the relative effects of different predictors on citation frequency of ecological articles using an information theory framework designed to evaluate multiple competing hypotheses. Supposed predictors of citation frequency (e.g., number of authors, length of articles) accounted for a low fraction of the total variation. We argue that biases concerning citation are minor in ecology and further studies that attempt to quantify the scientific relevance of an article, aiming to make further relationships with citation, are needed to advance our understanding of why an article is cited.     

Effect of p-n junction overheating on degradation of silicon high-power pulsed IMPATT diodes

The thermal limits of the two-drift impact avalanche and transit-time (IMPATT) diode operating in the pulsed mode in the 8-mm wavelength region with a microwave power as high as 30–35 W have been estimated. It is shown that p-n junction overheat at an operating pulse length of 300 ns and a supply current amplitude of 11.3–15 A amounts to 270–430°C relative to an ambient medium. The temperature limit of junction overheating, above which IMPATT diodes rapidly degrade, was determined as 350°C. The presented results of X-ray phase analysis and depth profiles of Au-Pt-Ti-Pd-Si ohmic contact components confirm thermal limits of the IMPATT diode operating in the pulsed mode.

     

Occupational and occupationally determined diseases

Medical definitions of occupational and professionally conditioned pathology are given in the article together with relevant examples. With the view to account appropriately occupational pathology in accordance with its severity classification based on the degree of working capacity loss is presented. Notions of acute occupational disease (intoxication) and professional accident are determined. International list of occupational diseases is considered. Suggestions intended at promotion of safe working conditions are made on perfection of the Ukrainian list.     

Cross flow around a cylinder at periodic disturbances in the boundary layer by electrolysis bubbles

Particularities of dynamic flow control in an open-loop system around a cylinder with a boundary layer by means of periodic generation of microbubbles are presented. Experiments were carried out in the range of Reynolds numbers of Re = (0.3?1.2) × 10⁵. It is shown that this method provides very similar results as in the case of continuous generation of microbubbles; however, the energy expenditure is two times less. The effect can be explained by the delayed response of the boundary layer separation on the disturbance cutoff. Lock-in modes of the natural vortex shedding frequency f _N and the frequency of forced oscillations f _E, as well as superposition of these frequencies, are registered. Maximal values of the amplitude of the drag and lift oscillations are registered in the range of low frequencies (f _E/f _N < 0.07).