Synthesis and characterization of polycaprolactone/acrylic acid (PCL/AA) hydrogel for controlled drug delivery

In the present work biodegradable pH-sensitive polycaprolactone/acrylic acid (PCL/AA) hydrogels have been developed using ethylene glycol dimethacrylate (EGDMA) as a cross-linker and benzoyl peroxide as initiator. For these prepared hydrogels swelling studies, sol-gel fraction analysis and porosity measurements were performed. Results show that swelling of the hydrogels decreases on increasing the concentration of PCL and EGDMA, however swelling of hydrogels increases on increasing the concentration of AA. Results of sol-gel fraction analysis show that gel fraction increases on increasing concentration of monomer AA, polymer PCL as well as cross-linker EGDMA. As far as porosity is concerned, it increases on increasing the concentration of AA and PCL while porosity decreases on increasing the concentration of EGDMA. Hydrogels were characterized by measuring diffusion coefficient (D) and equilibrium water content (EWC). Network formation, morphology and crystallinity of PCL/AA hydrogels were investigated using FTIR, SEM and XRD, respectively. Tramadol hydrochloride was loaded as model drug and its release pattern was analysed using various kinetic models like zero order, first order, Higuchi and Peppas. Results indicated that most of the samples followed non-Fickian release mechanism.     

Anxiolytic activity of glycine-B antagonists and partial agonists--no relation to intrinsic activity in the patch clamp

On the basis of animal models, anxiety was one of the first suggested clinical applications of partial agonists of the glycineB site coupled to the NMDA receptor. It is not certain, however, whether these findings can be extended to full glycineB antagonists and what is the relation between intrinsic activity (degree of NMDA receptor antagonism) and anxiolytic effect. In the present study several NMDA receptor antagonists, including several glycineB antagonists/partial agonists, were tested for anxiolytic activity in the Vogel conflict test and the elevated plus-maze. Additionally, the intrinsic activities of the glycineB partial agonists used [ACPC, (R,+)-HA-966 and D-cycloserine] were compared in patch-clamp experiments in cultured neurones. In the plus-maze the most striking increase in the time spent in open arms (index of anxiolytic effect) was seen after diazepam and D-cycloserine (at doses that did not change locomotion). Also reliable (dose-dependent), although weaker, anxiolytic activity was produced by the uncompetitive NMDA receptor antagonist (+)MK-801 and the competitive antagonist CGP 39551. Modest anxiolytic-like effect in the plus-maze was also observed after the glycineB antagonist L-701,324 and the partial agonist (+,R)-HA-966. Uncompetitive antagonists memantine and amantadine, the glycineB partial agonist ACPC (up to 600 mg/kg) or the full antagonists MRZ 2/570, MRZ 2/571 and MRZ 2/576 had no effect. In the Vogel conflict test neither memantine, nor any of the full glycineB antagonists tested (L-701,324 and MRZ 2/576), showed anxiolytic activity. Patch-clamp studies revealed that the intrinsic activity of (+,R)-HA-966, D-cycloserine and ACPC was 13, 57 and 92%, respectively, as compared to that of glycine itself (100%). In conclusion, for the agents tested there is no clear relation between the levels of intrinsic activity, i.e. degree of NMDA receptor inhibition, and anxiolytic activity. Moreover, L-701,324 and MRZ-type glycineB full antagonists do not exchibit anxiolytic activity in the elevated plus-maze and Vogel conflict test.     

Protective Performance of Environmentally Stressed Fabrics Containing Melamine Fiber Blends

In this study, the mechanical properties critical to the protective performance of firefighter turnout gear were evaluated for environmentally stressed outer shell (OS) fabrics containing melamine fiber blends. Environmental stress factors that affect the durability of turnout gear include temperature, ultraviolet (UV) radiation, moisture, abrasion, and laundering. The effect of fiber blend, fabric construction, and finishing processes including water repellent coatings and pigmented melamine-containing OS fabrics were also studied. Melamine-containing OS fabrics show comparable thermal protective performance and have superior tear resistance when compared to the traditionally used polyaramid blends. This study reveals that the thermal protective protection (TPP) rating of fabric assemblies incorporating environmentally stressed OS fabrics containing melamine fiber blends is well above the NFPA minimum TPP requirement of 35 cal/cm². However, the tear strength (measured using ASTM D 5587 standard test method) of all melamine-containing OS fabrics exposed to environmental stresses was observed to have significantly deteriorated, and most OS fabrics, depending on fiber blend and fabric structure, would fail to meet requirements of NFPA 1971 standard. The study thus suggests that environmental stressing has a more detrimental impact on the tear strength than the thermal protective performance of OS fabrics. Deterioration in tear strength of all UV exposed OS fabrics is largely due to photodegradation of constituent fibers. Changes in tear strength of OS fabrics subjected to thermal exposures and laundering is cumulative effect of loss in tensile strength of single yarns and dimensional stability of the fabric itself. Furthermore, finishing treatments affect performance properties of fabric by increasing fiber packing factor in yarn, changing yarn crimp and yarn spacing thereby making dimensional changes to the fabric. Surface coatings alter tear resistance of fabric by influencing yarn slippage and fabric rigidity. Fabrics dyed with black and dark blue dyes cause less UV degradation of fibers than bright yellow and brown dyes.     

Composition-dependence of photoconduction band gap in cadmium zinc phosphate glasses

Photoconduction in cadmium zinc phosphate glasses of various compositions has been measured in the spectral energy range 1.5 to 6.2 eV. With the P₂O₅ percentage remaining fixed at 60 mol %, CdO and ZnO contents have been varied between 0 and 40 mol %. Photocurrents start at about 3.85 eV and rise sharply above 4.5 eV. The optical band gap obtained by the extrapolation of the linear region of the photoresponse curve shows a slow decrease with an increase in the applied field. The optical band gap at a particular applied field decreases with increasing ZnO content. The field-dependence of the optical band gap may be explained in terms of an energy band scheme for non-crystalline solids. The composition-dependence may be due some structural changes in the glasses.     

Analysis and Performance of a Fixed Filter-Thyristor Controlled Reactor (FF-TCR) Compensator

A fixed Filter-Thyristor Controlled Reactor (FF-TCR) type of compensator is proposed to improve the power factor of a single phase thyristor-controlled inductive load and it is shown that this compensator gives better power factor improvement than the more generally used FC-TCR type of compensator. Analysis is carried out for the exact equivalent circuit of an FF-TCR compensator containing two filter branches tuned to the third and the fifth harmonics respectively. It is shown that with an FF-TCR compensator the power factor improvement is much better when the source impedance is large. However, even with a small source impedance, a reasonable improvement in power factor is realised. It is further shown that even when the source impedance is large the distortion in the terminal voltage waveform is kept within reasonable limits. The analytical results are verified experimentally.     

The use of gas-generating mold coatings for the grain refinement of aluminum

Experiments are described in which an effervescent mold coating containing hexachloroethane has been used to promote the dynamic grain refinement of commercial purity aluminum ingots. The influence of the amount of hexa chloroethane in the mold coating, the degree of superheat of the cast metal and the nature of the mold material was assessed. Comparison has been made with unrefined ingots and with ingots grain refined using conventional inoculation procedures. It is concluded that low levels of hexa chloroethane (10 to 20 wt pct in the mold coating) can produce effective refinement provided conditions exist favorable for the survival of dendrite fragments or nucleating particles generated by the remelting associated with turbulence in the liquid or chemical and/or mechanical interactions between the effervescing gas and the mold coating. The effectiveness of refinement is enhanced by high rates of heat transfer and low pouring superheats. Visiting Professor in the Department of Mechanical Engineering, State University of Campinas.