Surface properties of graft copolymers surfactants: Behavior at the water/toluene interface

Poly(propylene oxide-b-ethylene oxide) (PPOPEO) surfactant has been used as a surface tension modifier. In this study, the graft copolymer made of poly(methyl methacrylate) (PMMA) main chain and PPOPEO graft chain behavior at water/toluene interface was observed. Interfacial tension measurements were conducted by dissolving the graft copolymer in toluene at a concentration range 1 wt % ?0.0003. The results confirmed the surfactant behavior of graft copolymers, which presented a PMMA/PPOPEO ratio dependence. The critical micellar concentration (CMC) was observed. Above the CMC, the graft copolymers tend to form a monomolecular association that depends upon copolymer molecular weight. © 1992 John Wiley & Sons, Inc.     

On the high affinity of 8-cyclohexylcaffeine for the presynaptic inhibitory adenosine receptor present in rat motor nerve terminals

Rat neuromuscular junction was used to study the characteristics of presynaptic A1 adenosine receptors. We investigated the ability of the 8-substituted caffeine, 8-cyclohexylcaffeine (CHC), as well as of 1,3,8-substituted xanthines, 1,3-dipropyl-8-p-sulfophenylxanthine (DPSPX) and 8-p-sulfophenyl-1-isoamyl-3-isobutylxanthine (SPIIBX) to antagonize the inhibitory effect of 2-chloroadenosine on the amplitude of nerve-evoked twitches of the rat phrenic-hemidiaphragm, and we compared the affinity of these xanthines with that of 1,3-dipropyl-8-cyclopenthylxanthine (DPCPX). CHC, DPSPX and SPIIBX in a near parallel manner shifted to the right the log concentration-response curve for the inhibitory effect of 2-chloroadenosine on nerve-evoked twitch amplitude. Linear Schild plots with slopes near to unity were obtained for all these xanthines. The order of potency of the xanthines was DPCPX (Ki = 0.53 nM) > DPSPX (38 nM) = CHC (41 nM) > SPIIBX (404 nM). The affinities of DPSPX and SPIIBX for the A1 receptor at the rat neuromuscular junction are in agreement with the affinities described for A1 receptors at brain membranes. The now reported affinity of CHC for the presynaptic A1 receptor is 683 times higher than that obtained in binding studies in rat brain membranes, and is only 49 times higher than that obtained in functional assays (adenylate cyclase activity) in non-neuronal preparations (rat fat cells).     

On generalized two-dimensional cross constellations and the opportunistic secondary channel

An optimum bits-to-symbol mapping for square constellations is introduced which allows a simple detection in narrow-sense quadrature amplitude modulation (qam) systems. Then, a family of two-dimensional generalized cross constellations is presented as well as upper and lower bounds on the symbol error probability over an ideal band-limited channel which generalize those previously known for conventional qam. The application of this scheme to the opportunistic secondary channel is analysed and it is shown how fractional rates (in bits per 2-dimensional signal) can be supported on 2D generalized qam systems. These signaling schemes are compared with multidimensional generalized constellations recently proposed by Forney and Wei.     

Indefinite islet allograft survival in mice after a short course of treatment with anti-CD45 monoclonal antibodies

BACKGROUND: Although islet cell transplantation is considered an ideal form of endocrine replacement for type I diabetes, clinical application in humans is still not feasible. New immunosuppressive strategies are clearly needed to control inexorable rejection. CD45 is a family of transmembrane protein tyrosine phosphatases critically involved in the regulation of lymphocyte activation signals. Anti-CD45RB monoclonal antibody can prevent rejection of murine renal allografts. METHODS: Here, we examine the consequences of targeting CD45 in murine islet cell transplantation. Diabetic mice recipients received islet allografts under the kidney capsule and were divided into seven groups. Recipients received no treatment (controls) or anti-CD45RB monoclonal antibody (mAb; MB23G2 or C363.16A) at different dosages and treatment intervals. RESULTS: All untreated control animals lost islet function, becoming hyperglycemic within 10-17 days after transplantation. Animals treated with either anti-CD45RB mAb showed a significant prolongation of islet allograft survival when compared with controls. Anti-CD45RB MB23G2 at 100 microg/day, given on days -1, 0, and 5 was particularly effective, inducing indefinite islet allograft survival in 60% of recipients. CONCLUSIONS: These results indicate that anti-CD45 mAbs are potent immunomodulatory agents, able to sustain indefinite islet allograft function after a short treatment course in the highly immunogenic model of islet transplantation.     

Women''s opinion on abortion legalization in a middle size county in southern Brazil

To study pancreas enzyme content regulation when the diet was modified in suckling goats, a comparison was made between kids fed a milk replacer and ones fed maternal milk. A total of 25 preruminant Granadina breed goats were bottle-fed a milk replacer ad libitum from postnatal days 3 to 28 (until the age of 3 days kids had been fed colostrum). Body weight, pancreas weight, total protein concentration, and enzyme activities in pancreatic tissue were determined at 3, 7, 14, 21 and 28 days of age, and the results were compared to those previously obtained in kids fed maternal milk for the same period. Lipase activity was significantly lower in the group fed milk replacer, which was poorer in fat. Amylase activity was higher in this group, perhaps due to the starch products present in the milk substitute. However, the postnatal evolution of chymotrypsin activity followed a similar pattern regardless of diet. Our results seem to confirm that in preruminant kids there is a nutritional regulation of pancreatic amylase and lipase activities, depending on the amounts of their respective substrates in the diet, similar to that described in nonruminants.     

Pathogenic action of Penicillium species on mosquito vectors of human tropical diseases

In vitro bioassays were performed in order to assess the pathogenicity of 13 Penicillium strains in 2nd stage larvae of Aedes aegypti, Aedes fluviatilis, Anopheles aquasalis and Culex quinquefasciatus. Mortality rates began in the first 24 hours, ranging from 0 to 100%. P. corylophilum, P. fellutanum, P. implicatum, P. janthinellum, P. viridicatum and P. waksmanii species tested on Aedes aegypti larvae and at different concentrations presented mortality rates from 0 to 6.6%. These species, when tested on Aedes fluviatilis, Anopheles aquasalis and Culex quinquefasciatus larvae, presented a mortality rate of 3.33% to 100%. Susceptibility of Aedes fluviatilis, Aedes aegypti, Anopheles aquasalis and Culex quinquefasciatus mosquitoes to the tested agents, turn P. corylophilum and P. janthinellum into candidates for potential use in biological control of vectors.     

Design of a stable adaptive controller for driving aerobic fermentation processes near maximum oxygen transfer capacity

In many industrial fermentation processes oxygen availability is the main limiting factor for product production. Typically the dissolved oxygen (DO) concentration decreases continuously at the beginning of the batch until it reaches a critical level where the oxygen transfer rate is very close to the vessel's maximum transfer capacity. The process may be further driven close to this sensitive operating point with a controller that manipulates the carbon source feed rate. This operating strategy is linked with important productivity issues and is still frequently realised in open-loop at production scale. The main purpose of the present study is to derive an effective closed-loop control solution and to demonstrate its economical advantage in relation to the open-loop form of operation. A stable model reference adaptive controller (MRAC) was designed based on a phenomenological model of the process. The implementation requires two on-line measurements: the DO tension and oxygen transfer rate (OTR) between gas–liquid phases, which are nowadays standard and easily available in production facilities. The controller performance is accessed with a simulation case study. The main results show that the adaptive controller is precise, stable and robust to disturbances and to inaccuracies like variability in raw materials typical in fermentations run in complex media. The controller is simple, easy to implement, and could possibly improve productivity in processes for which oxygen transfer capacity is limiting growth and product production.