Electrosprayed poly(vinyl alcohol) particles: preparation and evaluation of their drug release profile

Encapsulation of bioactive molecules within polymeric particles is a challenge because of several limitations, including low drug‐loading efficiency, unwanted release profile, polydispersity and batch‐to‐batch variation in reproducibility, along with the limitations of scaling up the process. It is essential to control the morphology of pure polymer particles in the first instance, in order to obtain the desired release profile of drugs from the particles during a later stage. Here we report the preparation of electrosprayed particles from a water‐soluble US Food and Drug Administration‐recognized polymer, namely poly(vinyl alcohol) (PVA), as an approach towards a short‐term drug delivery vehicle. Through electrospraying and varying the solvent ratios, three different sizes of particles were prepared, with sizes ranging from 500 to 2000 nm. Insulin was chosen as a model bioactive molecule, and the release profile of the drug was studied after its incorporation in the PVA particles. Fractional release plots obtained showed short‐term release of insulin within the first 60 min. Release curves were analyzed according to the Ritger–Peppas model, suggesting Fickian diffusion as the predominant insulin release mechanism from the PVA particles. This work suggests electrosprayed PVA particles as an innovative drug delivery system for short‐term administration of drugs. © 2015 Society of Chemical Industry     

Freeform Gelcasting of Porous Tubular Alumina Substrate

The present work demonstrates a new method for fabrication of thin-walled tubular alumina substrate by combining the principles of gelcasting and freeform fabrication. A tube made up of filter paper or organic preform was filled with 4 N nitric acid and dipped in a 55 vol% alumina (average particle size 0.34 μm) slurry containing methylolurea and urea. A thin layer of alumina slurry was gelled on the filter paper tube by in situ polymerization of methylolurea and urea monomers present in the slurry by delivering the acid through the walls of the filter paper tube. The thickness of the alumina tube obtained depended on the dipping time. Alumina tubes with thicknesses in the range 0.7–2 mm were obtained for dipping times in the range 1–8 min. The tubes obtained had good surface finishes and profiles. These tubes were sintered at 1150°C and microstructural observation indicated uniform grain size and pore morphology. A porosity of 40% and an average pore size of 300 nm were obtained.     

Sniffing and smelling: separate subsystems in the human olfactory cortex

The sensation and perception of smell (olfaction) are largely dependent on sniffing, which is an active stage of stimulus transport and therefore an integral component of mammalian olfaction. Electrophysiological data obtained from study of the hedgehog, rat, rabbit, dog and monkey indicate that sniffing (whether or not an odorant is present) induces an oscillation of activity in the olfactory bulb, driving the piriform cortex in the temporal lobe, in other words, the piriform is driven by the olfactory bulb at the frequency of sniffing. Here we use functional magnetic resonance imaging (fMRI) that is dependent on the level of oxygen in the blood to determine whether sniffing can induce activation in the piriform of humans, and whether this activation can be differentiated from activation induced by an odorant. We find that sniffing, whether odorant is present or absent, induces activation primarily in the piriform cortex of the temporal lobe and in the medial and posterior orbito-frontal gyri of the frontal lobe. The source of the sniff-induced activation is the somatosensory stimulation that is induced by air flow through the nostrils. In contrast, a smell, regardless of sniffing, induces activation mainly in the lateral and anterior orbito-frontal gyri of the frontal lobe. The dissociation between regions activated by olfactory exploration (sniffing) and regions activated by olfactory content (smell) shows a distinction in brain organization in terms of human olfaction.     

Synchronization representation and traffic source modeling inorchestrated presentation

Multimedia applications comprise several media streams, which are semantically synchronized at different time instants. The application behavior is stored along with the multimedia database using representation mechanisms such as OCPN (object composition Petri nets) or dynamic timed Petri nets (DTPN). It is imperative that one translates the application behavior to the corresponding schedulable entities, such as packets, so that the performance engineering of any system can be done, using the traffic model arising out of the (media related) application behavior as opposed to individual media level behavior. This requires that a function be defined, which takes the stored temporal representation as input and produces packets as output, preserving the semantic relationships among the streams. The authors propose a methodology based on probabilistic, attributed context free grammar (PACFG) to address this issue. They demonstrate the appropriateness of this methodology by applying it to the OCPN/DTPN representation of a typical multimedia application vis-a-vis orchestrated presentation     

Retrieval scheduling for collaborative multimedia presentations

The single-system approach is no longer sufficient to handle the load on popular Internet servers, especially for those offering extensive multimedia content. Such services have to be replicated to enhance their availability, performance, and reliability. In a highly replicated and available environment, server selection is an important issue. In this paper, we propose an application-layer broker (ALB) for this purpose. ALB employs a content-based, client-centric approach to negotiate with the servers and to identify the best server for the requested objects. ALB aims to maximize client buffer utilization in order to efficiently handle dynamic user interactions such as skip, reverse presentation, go back in time. We also present details of a collaborative multimedia presentation platform that we have developed based on ALB.     

Gel Casting of Alumina using Boehmite as a Binder

The process for alumina gel casting was developed using an inorganic binder The monohydroxy aluminium oxide (boehmite, AlOOH) was incorporated with ultrafine alumina of particles (0·5 μm) and the slurry rheology was studied and presented. The effect of boehmite in slurry viscosity was observed with respect to different amounts of boehmite and time. The alumina 54 vol% slurry with 10 wt% boehmite showed the viscosity of 880 mPa s at 93 s⁻¹. An external coagulating agent, HMTA, was incorporated with alumina–boehmite slurry and the effective change in slurry viscosity with respect to concentration and time was studied. The addition of HMTA results in faster gelation and the optimum concentration was determined as 0·21 mol L⁻¹. The alumina gelcast body was dried under humidity conditions at 40°C, RH 70%. The defect free dried green body was obtained and the total linear drying shrinkage was calculated as 3·2% and the green density observed was 59·3% of theoretical value. The sintered density of 98% (TD) was achieved at 1450°C in 2 h. The mechanical hardness of sintered alumina measured as 2286 kg mm⁻². The sintered ceramic showed an extremely fine grained microstructure with an average grain size <2 μm. The boehmite acts as an excellent binder and sintering aid for alumina ceramics.     

Recent advances in the heterogeneously catalysed aerobic selective oxidation of alcohols

The heterogeneously catalysed selective aerobic oxidation of alcohols is an important tool for the synthesis of valuable chemical intermediates and a hot topic within both academic and industrial arenas. In this mini‐review, selected aspects of catalyst formulation, process operating conditions, and progress in identifying the active sites and surface reaction mechanisms notably through the application of synchrotron radiation, are highlighted. Copyright © 2010 Society of Chemical Industry