Synthesis and characterization of block copolymers from D,L-lactide and poly(tetramethylene ether glycol)

The copolymer from D ,L -lactide and poly(tetramethyene ether glycol) (PTMG) was prepared in bulk with an isotributyl aluminum–water–phosphoric acid complex catalyst as the initiator and characterized by H-NMR, GPC, and DSC. The effects of the temperature and the amount of PTMG on the polymerization rate and the molecular weight of copolymers were studied. The behavior of the degradation and delivery rate of Levonorgestrel microspheres in vitro was observed. The results show that the degradation and the delivery rate can be controlled by adjusting the molar rate of hydrophilic and hydrophobic segments of the copolymer © 1995 John Wiley & Sons, Inc.     

Synthesis ofE,E-diene hydroperoxides via photoisomerization of protected hydroperoxides

A general approach toE,E-diene hydroperoxides is described based upon photoisomerization of readily availableZ,E-diene monoperoxyketals. Protection of aZ,E-diene hydroperoxide as the 2-methoxypropyl peroxyketal is followed by iodine-mediated photoisomerization to produce a mixture enriched in theE,E isomer. After chromatographic purification, deprotection of the peroxyketal with mild acid furnishes theE,E-diene hydroperoxide.     

Image compression by self-organized Kohonen map

Presents a compression scheme for digital still images, by using Kohonen's neural network algorithm, not only for its vector quantization feature, but also for its topological property. This property allows an increase of about 80% for the compression rate. Compared to the JPEG standard, this compression scheme shows better performances (in terms of PSNR) for compression rates higher than 30.     

Prevalence and role of anticardiolipin antibodies in Crohn disease

OBJECTIVES: Anticardiolipin antibodies belong to the group of antiphospholid antibodies, and may be seen in association with endothelial damage and recurrent vascular thrombosis. The aim of our study was to determine in patients with Crohn's disease the frequency of anticardiolipin antibodies, and to correlate their presence with clinical activity and treatment of the disease. METHODS: One hundred and thirty-eight sera from patients with Crohn's disease and 118 from age-matched controls were tested for IgG anticardiolipin antibodies. In the Crohn's disease group, we determined whether the patients had a past history of vascular thrombosis, a clinically active intestinal disease, or a current immunosuppressive therapy (steroids or azathioprine). RESULTS: Anticardiolipin antibodies were found significantly more often in patients with Crohn's disease than in controls: 11.0% versus 2.5%, P < 0.02. Three patients with Crohn's disease had a past history of vascular thrombosis, but none of them had anticardiolipin antibodies. The presence of anticardiolipin antibodies was not correlated with the fact that patients had a clinically active disease (P = 0.77), or a current immunosuppressive therapy at the time of the serological test (P = 0.95). CONCLUSIONS: There is a significantly high prevalence of patients with anticardiolipin antibodies during Crohn's disease. The positivity of the test does not seem to be correlated to the existence of a past history of vascular thrombosis, nor to the clinical activity of the disease.     

The dependency of calcium set point on basal plasma calcium in dialysis patients: a better explanation for the discrepancies regarding its link with PTH secretion than methodological differences

BACKGROUND: The increase of calcium (Ca) set point in uremic hyperparathyroid patients and its decrease with calcitriol therapy are controversial. Besides methodological differences regarding the experimental protocol for obtaining the sigmoidal curve, mainly differences in definitions of maximal PTH (peak or steady value) and of calcium set point itself have been proposed for the discrepant conclusions. However, two other explanations are possible: the various aluminum load of the patients and the dependency of Ca set point upon the basal plasma ionized calcium (PCa). PATIENTS AND METHODS: Therefore the Ca set point was measured in 2 groups of patients on maintenance dialysis never exposed to aluminum, one of 7 patients with normosecretion of PTH (NPT) and the other of 8 patients with hyperparathyroidism (HPT) before and after 3 intravenous administration of 4 microg of alfacalcidol in a week. The sigmoidal curve was established during a zero Ca dialysis, without Ca replacement for the first 90 minutes and with intravenous infusion of 41 mmoles of Ca during the 150 last minutes. The curvilinear decrease of PCa induced a peak of PTH followed by a decrease while PCa was still decreasing up to the 90th minute. Therefore PTHmax was taken both at the peak and at its lower value observed at the 90th minute (steady PTHmax). Experimental determinations of the Ca set point were made using both definitions of Brown and Felsenfeld and both PTHmax values. In basal conditions, while using any of the values given by the same calculation methodology, Ca set point was not different in NPT and HPT patients. After alfacalcidol, no change in plasma PTH nor in Ca set point was observed in HPT patients. In contrast, in NPT patients alfacalcidol induced a significant decrease of plasma PTH concentrations in association with an increase in basal PCa and in Ca set point, whatever the definitions of the latter and of PTHmax. Calcitriol induced changes in Ca set point and basal PCa were correlated. CONCLUSIONS: 1) In normocalcemic dialysis patients never exposed to aluminium hyperparathyroidism is not explained by an increased Ca set point 2) Calcitriol suppressive effect on PTH secretion is neither explained by a decrease in Ca set point. 3) Ca set point as measured in vivo does not reflect an intrinsic characteristic of the parathyroid glands since it varies with basal PCa. Better than methodological differences, this dependency may explain the discrepant conclusions between the various clinical investigations.     

Common problems in wound care: caring for the skin around wounds

A case of pyogenic granuloma of the prepuce is presented. This to our knowledge, is the first reported case of this condition affecting this site.     

Statistical analysis of decision threshold for parallel acquisitionwith reference filtering in Rician fading channel

Statistical analysis of the decision threshold for parallel PN code acquisition in a Rician fading channel is presented. It is shown that in the performance analysis of the acquisition system with reference filtering, the statistical evaluation of the decision threshold seems more appropriate than the approximation of the decision threshold     

Multiband properties of a fractal tree antenna generated byelectrochemical deposition

Experimental results on a fractal tree-like antenna are reported. The fractal structure is generated by electrochemical deposition. The antenna presents a multiband behaviour with a denser band distribution than the previously reported Sierpinski fractal antenna. The matched frequencies are related to the length distribution over the fractal shape