Vibration characteristics of a cooling-tower shell

The work reported herein deals with problems of experimental method and the analysis of results in an investigation of the dynamic properties of a real cooling tower. Analysis of the most important experimental results has been completed. The experimental data are compared with theoretical results obtained using a finite-element method of solution.     

Skip technique as a variant of moving field irradiation

The skip-technique may be used either for screening or lessening the radiation load to sensitive sound organs or for an adjusted formation of the isodoses or for both. To show the possibilities of application of this elegant and quite practicable method, some examples are reported concerning spondylous processes, para-aortic lymph nodes and tumors in the small pelvis. The loss of radiation dose because of the additional opening and closing procedure of the diaphragm demands a correction of the duration of irradiation.     

Open systems interconnection — the teletex-based session protocol: Part 2

The development of an international standard for the teletex-based session protocol has involved combining the best points of two draft proposals, ECMA 75 and S.62. Recently, the ISO has completed a specification comprising three subsets: the ISO/ECMA subset, the ISO/CCITT subset and the null functionality subset. The paper discusses the development of the standard, lays out the specification and describes the operation of each of the protocol phases. Three appendices describe the conformance problem and the BAS subset, protocol machines and the interworking problem.     

Aliphatic polyesters. I. The degradation of poly(ϵ-caprolactone) in vivo

The degradation of poly(?-caprolactone) in rabbits, rats, and water was studied by measurement of changes in intrinsic viscosity, molecular weight, crystallinity, Young's modulus, and weight. Degradation proceeds by nonenzymatic random hydrolytic cleavage of ester linkages. The process is autocatalytic, and the kinetic relationship M_n/M_n^o = exp(–kt) is observed until the M_n has decreased to approximately 5000. Significant weight loss is not observed until this point but, once initiated, the rate of weight loss depends markedly on the particle size. Chain scission is associated with an increase in crystallinity, which partly determines the rate of degradation.     

Introducing a biosensor based technology for real-time biospecific interaction analysis

The peptido-leukotriene receptor(s) (PL) on the ferret isolated spleen strip have been characterised by functional studies using the naturally occurring leukotrienes (LTs), a range of structurally distinct PL antagonists, and by ligand binding studies. LTB4 (0.01-10 microM) was inactive on ferret spleen whereas LTC4, LTD4 and LTE4 produced concentration-related contractions with maximal responses, relative to noradrenaline, of 57% (EC50 0.28 microM), 60% (EC50 0.5 microM) and 7% respectively. The leukotriene responses were unaltered by L-serine borate, L-cysteine, indomethacin, phentolamine, propranolol, mepyramine, methysergide or atropine, suggesting that the peptido-leukotrienes were acting through distinct PL receptors. The PL1 antagonists, FPL 55712 (0.01-10 microM), ICI 198615 (10 microM), SK&F 104353 (10 microM) and MK541 (10 microM) were all inactive against LTC4- or LTD4-induced contractile responses. LTE4 was a partial agonist with respect to LTC4 and LTD4 with pKB values of 5.8 and 5.5 respectively. Nifedipine (0.1 microM) produced a rightward shift of the concentration-response curves to both LTC4 and LTD4 and depressed their maximal responses. An unacceptably high level of non-specific binding of [3H]LTD4 to membrane preparations of ferret spleen prevented characterisation of this receptor by ligand binding. These results suggest that the ferret spleen has a homogeneous population of a PL receptor type which is insensitive to existing PL1 receptor antagonists. The functional characteristics of this PL receptor type are similar to those of the PL2 receptor on other tissues. The absence of PL1 receptors on this tissue makes it particularly useful in identifying new and selective drug tools for the PL2 receptor.     

Defective acidification in human breast tumor cells and implications for chemotherapy

Multidrug resistance (MDR) is a significant problem in the treatment of cancer. Chemotherapeutic drugs distribute through the cyto- and nucleoplasm of drug-sensitive cells but are excluded from the nucleus in drug-resistant cells, concentrating in cytoplasmic organelles. Weak base chemotherapeutic drugs (e.g., anthracyclines and vinca alkaloids) should concentrate in acidic organelles. This report presents a quantification of the pH for identified compartments of the MCF-7 human breast tumor cell line and demonstrates that (a) the chemotherapeutic Adriamycin concentrates in acidified organelles of drug-resistant but not drug-sensitive cells; (b) the lysosomes and recycling endosomes are not acidified in drug-sensitive cells; (c) the cytosol of drug-sensitive cells is 0.4 pH units more acidic than the cytosol of resistant cells; and (d) disrupting the acidification of the organelles of resistant cells with monensin, bafilomycin A1, or concanamycin A is sufficient to change the Adriamycin distribution to that found in drug-sensitive cells, rendering the cell vulnerable once again to chemotherapy. These results suggest that acidification of organelles is causally related to drug resistance and is consistent with the hypothesis that sequestration of drugs in acidic organelles and subsequent extrusion from the cell through the secretory pathways contribute to chemotherapeutic resistance.