Strain rate effects on viscoelastic crack bifurcation

The effects of applied strain rate on the viscoelastic crack bifurcation phenomenon in Polymethyl Methacrylate (PMMA) were investigated. It was still verified that the product $\text{σ}{}_{\mathrm{f}}\text{C}{}_{\mathrm{b}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ was constant, as was already observed by Congleton and Petch, and Anthony, Chubb and Congleton, for brittle elastic materials, for any strain rate, where σ_f = the gross fracture stress and C_b= the main crack length until the bifurcation starts. However, it was found that the higher strain rate increases the main crack length C_b resulting in the decrease in the gross fracture stress σ_f and vice versa. This might be interpreted that the higher stress concentration at the initiation crack tip, which is realized by becoming more brittle due to the higher strain rate owing to the predominance of the elastic element in the viscoelastic material, decreases the gross fracture stress leading to the longer main crack length.     

Evaluation of myocardial protection in open heart surgery - with special reference to local cardiac hypothermia

Erythrocyte-granulocyte rosettes (EGR) were found in the capillary blood of two cases of autoimmune haemolytic anemia, the first caused by an IgM non-I antibody and the second by an IgG. Both antibodies activated complement, and C3b was demonstrated on the erythrocytes. The rosettes appeared as arrangements of 6-10 red cells adhering to a central granulocyte; phagocytosis was most generally absent. The finding of EGR in the capillary blood may be useful for the recognition of complement activation up to the C3b stage in some cases of autoimmune haemolytic anemia.     

Changes in thyroid hormones by treatment with aspirin and prednisolone in subacute thyroiditis with hyperthyroidism

Thyroid functions were studied in 11 patients with subacute thyroiditis accompanied by signs and symptoms of hyperthyroidism, and were compared with 13 patients with untreated thyrotoxicosis in which serum T4 was elevated to the identical level. Serum T3 was also elevated in subacute thyroiditis but to a significantly lower extent than in thyrotoxicosis. Therefore the ratio of T4/T3 was significantly higher in subacute thyroiditis than in thyrotoxicosis. Although duration of thyroid swelling was shorter in the group treated by prednisolone than by aspirin, the accelerated ESR, thyroid tenderness and fever subsided almost similarly in the two groups. Serum T4 and T3 levels declined more rapidly in treatment with prednisolone compared with aspirin. In patients treated by aspirin initial increase in T3 level occurred transiently with simultaneous decrease in the T4/T3 ratio. These changes suggest the increase in peripheral conversion of T4 to T3. Even in severe cases of subacute thyroiditis associated with hyperthyroidism, aspirin treatment is an effective therapy and there is no recurrence following withdrawal of the medication.     

Nonsteady shear flow of micropolar fluids

An application of Eringen's theory [1–3] of micropolar fluids has been made to the problem of nonsteady shear flow. An exact solution to the system of governing equations is given. Two nondimensional parameters, i.e. the coupling coefficient and the length ratio are introduced, and when the length ratio vanishes, the solution reduces to its classical form. Graphs representing fluid velocity for different values of those parameters are drawn at the end.     

Decarboxylation of the 6-nitrobenzisoxazole-3-carboxylate anion catalyzed by cross-linked poly(4-vinylpyridinium) salts

Summary Catalysis of cationic polyelectrolytes for the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate anion was studied in a buffer solution (pH=9.0). Cross-linked poly (4-vinylpyridinium) salts prepared from 4-vinylpyridine and , -dibromides were used as cationic catalysts. The cross-linked catalysts were found to accelerate markedly the decarboxylation in comparison with the linear water-soluble analogues. Effect of the polymer structure such as the length of (CH₂)_x linkages between positive charges on the catalytic activity was examined. It was suggested that the acceleration by the cross-linked polymer catalysts would be due to the hydrophobic microenvironment around the catalytic sites.     

Photoelectric properties of molecular layers of a fatty acid mixed with cyanine dyes

Photocurrents in Langmuir multimolecular layers of cadmium arachidate mixed with cyanine dyes between metal electrodes were studied. The photocurrent efficiency was found to depend on the applied voltage, the temperature and the distance between the dye molecules and the electrode. All samples exhibited non- ohmic behavior of the photocurrent. It was concluded that the photocurrent was initiated by the thermionic emission of electrons from the excited dyes. The activation energy necessary for the electron emission from the excited dye in the mixed layers was determined to be 0.52 eV. Absorption spectra were measured for layers deposited on an aluminum film and on a glass slide.     

Clinical significance of electrically evoked auditory brainstem response

Electrically evoked auditory brainstem responses (EABR) were recorded in 31 postlingually deafened adults, who had recently received cochlear implants (mini-system, Cochlear Ltd). The wave consisted of three distinct positive peaks labeled P1, P2, and P3 with latency of 1.35 (+/- 0.14), 2.17 (+/- 0.18) and 4.08 (+/- 0.31) ms, respectively. The P3 threshold (EABR-T) and slope (EABR-S) were 0.9 (+/- 0.47) mA and 0.6 (+/- 0.28) muv/mA, respectively. The relationships between the EABR parameters (EABR T and -S of the P3 wave) and age, duration of deafness, promontory test and subjective response (T and C-level) were investigated. The scattergram showed a strong negative linear relationship between EABR-S and subjective T-level. This finding suggests that EABR-S is good measure of postoperative perception.     

Synthetic lipid A produces antitumor effect in a hamster pancreatic carcinoma model through production of tumor necrosis factor from activated macrophages

The antitumor effect and biological activities of a newly synthesized lipid A analogue (ONO-4007) were investigated in a hamster pancreatic carcinoma model. Marked and dose-dependent inhibition of tumor growth was achieved by i.p. injection twice a week for 3 weeks of 10, 30 or 50 mg/kg of ONO-4007. Endogenous tumor necrosis factor (TNF) activities induced by ONO-4007 were significantly greater in tumor than in serum, spleen and liver. TNF production by macrophages stimulated with ONO-4007 after culture was much greater when culture was performed in the presence of hamster pancreatic carcinoma cells (no cell-to-cell contact). It was further found that the cytotoxic activity of TNF secreted by macrophages cultured with cancer cells was inhibited in the presence of anti-TNF neutralizing antibodies. These findings suggest that ONO-4007 displays antitumor effects by stimulating production of endogenous TNF in tumor macrophages, possibly through activation by soluble macrophage-stimulating factors in cancer cells.