Effects of Solvents, Temperature, and Plasticizer on Film Coating of Tablets

The effects of solvent composition, temperature, solvent retention, plasticizers, and polishing on the disintegration and percent dissolution of various nonaqueous film coated tablets were studied. A mixture of isopropanol-dichloromethane used as solvent systems for the film coating of ranitidine hydrochloride tablets resulted in reduced film peel-off time, decreased disintegration time, and increased percent dissolution. The effect of prewarming the coating bed of cimetidine tablets revealed an increase in percent dissolution compared to no prewarming condition. In contrast, an increase in temperature of the tablet bed resulted in higher disintegration time and lower percent dissolution of ibuprofen tablets. Ranitidine hydrochloride film coated tablets polished with polyethylene glycol showed lower disintegration time and higher percent dissolution than those polished with beeswax. The presence of plasticizer in the coating solution resulted in decreased disintegration time and higher percent dissolution for norfloxacin tablets.     

Thermoreversible gelation of poly[hexyl isocyanate]: Effect of solvent type

The thermoreversible gelation of poly[hexyl isocyanate] (PHIC), a rather stiff polymer, has been studied in two closely-related solvents of the alcane series, namely heptane and octane. Temperature-concentrations phase diagrams have been established for both systems. The occurrence of polymer-solvent compound is suggested in heptane but not in octane. This conclusion receives further support from neutron diffraction investigations through the use of the isotopic labelling technique. Finally, it is observed that the morphology is also affected by the solvent type although still displaying a fibrillar network structure.     

Photomechanical degradation of thermoplastic elastomers

The photodegradation of thermoplastic elastomers designed for outdoor applications was studied with laboratory ultraviolet (UV) exposure in the unstrained state and under tensile strain (25 and 50%). Strained exposure caused a reduction of the strain to failure in subsequent tensile tests. For some combinations of material and exposure conditions, some recovery of extensibility occurred between 2 and 4 weeks. Microscopic examination revealed that this was probably due to embrittlement of the surface region that was sufficiently severe that surface cracks did not propagate into the interior and that the observed recovery did not correspond to repair or improvement of the material. Shielding the sample surface from UV irradiation reduced the formation of surface cracking very significantly, and it was deduced that the principal cause of degradation was photooxidation rather than ozone attack. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 150–161, 2006     

Boron-doped hydrogenated amorphous carbon films grown by surface-wave mode microwave plasma chemical vapor deposition

We report the effects of boron (B) doping on optical and structural properties of the hydrogenated amorphous carbon thin films grown by surface-wave mode microwave plasma (SW-MWP) chemical vapor deposition (CVD) on n-type silicon and quartz substrates at room temperature. Argon and acetylene were used as a carrier and carbon source gases respectively. Analytical methods such as X-ray photoelectron spectroscopy (XPS), Nanopics 2100/NPX200 surface profiler, JASCO V-570 UV/VIS/NIR spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy were employed to investigate the properties of the films. Low atomic concentration of B (0.08 at.%) was found in the doped film. The optical band gap of the undoped film was 2.6 eV and it decreased to 1.9 eV for the B-doped film. Structural property shows the crystalline structure of the film and it has changed after incorporating B as a dopant. The structural modifications of the films leading to being more graphite in nature were confirmed by the Raman and FT-IR characterization.     

Electron holography and AFM studies on styrenic block copolymers and a high impact polystyrene

Many of the artifacts of conventional electron microscopy can be avoided if the unstained polymers are studied by electron holography and atomic force microscopy (AFM). Holograms of thin sections (50–70 nm) of organic block copolymers were recorded, and the corresponding phase images were reconstructed. In this way, typical structures such as lamellae and cylinders could be imaged without any staining. In addition, we successfully recorded holograms and performed Lorentz microscopy of an impact‐modified polystyrene (high‐impact polystyrene). The results were compared with the tapping mode AFM phase images. Electron holography and AFM have been demonstrated as suitable tools to image unstained heterogeneous polymers, leading to the understanding of their structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1573–1583, 2005     

Distributed topology management for wireless multimedia sensor networks: exploiting connectivity and cooperation

In this paper, we propose a distributed topology management algorithm, named T‐Must, which orchestrates coalition formation game between camera and scalar sensor (SS) nodes, for use in wireless multimedia sensor networks. In the proposed solution, connectivity among the peer camera sensor (CS) nodes is maintained, and coverage is ensured between them. Only the scalar data are not sufficient to describe an event in a particular monitored area. In many cases, multimedia data (specifically, video data) are required to provide more precise information about the event. As the CS nodes, which sense and transmit multimedia data, are costlier than the SS nodes, the former are deployed in the monitored area in lesser numbers compared to the latter ones. In case of CS nodes, power consumption due to sensing is also significant, similar to power consumption for the transmission and reception of packets. Therefore, in this work, in order to increase the network lifetime, topology is controlled by forming coalition between the CS and SS nodes. Upon occurrence of an event, the SS nodes send scalar data to their associated CS nodes. If the scalar data received from SS nodes cross a preconfigured threshold, the associated CS node in the coalition starts sensing the event, captures the video data, and forwards the video data toward other coalitions or sink. Copyright © 2014 John Wiley & Sons, Ltd.     

Effective mechanical properties of hexagonal boron nitride nanosheets

We propose an analytical formulation to extract from energy equivalence principles the equivalent thickness and in-plane mechanical properties (tensile and shear rigidity, and Poisson's ratio) of hexagonal boron nitride (h-BN) nanosheets. The model developed provides not only very good agreement with existing data available in the open literature from experimental, density functional theory (DFT) and molecular dynamics (MD) simulations, but also highlights the specific deformation mechanisms existing in boron nitride sheets, and their difference with carbon-based graphitic systems.     

Vertically aligned ZnO nanowire arrays in Rose Bengal-based dye-sensitized solar cells

We fabricate dye-sensitized solar cells (DSSC) using vertically oriented, high density, and crystalline array of ZnO nanowires, which can be a suitable alternative to titanium dioxide nanoparticle films. The vertical nanowires provide fast routes or channels for electron transport to the substrate electrode. As an alternative to conventional ruthenium complex, we introduce Rose Bengal dye, which acts as a photosensitizer in the dye-sensitized solar cells. The dye energetically matches the ZnO with usual KII₂ redox couple for dye-sensitized solar cell applications.     

An Adaptive Learning Scheme for Medium Access with Channel Reservation in Wireless Networks

Providing effective medium access for wireless networks is a challenging task. Most of the existing protocols of IEEE 802.11 Medium Access Control (MAC) work towards the goal of achieving effective channel access by developing various backoff procedures. In this paper, we make an attempt to develop a new medium access protocol named Learning Automata (LA) based Wireless Channel Reservation (LAWCR). We use an LA approach to implement reservation for channel access for single hop wireless networks. Also, sequence procedure is used to improve the reservation mechanism. The performance of the proposed LAWCR scheme show significant improvements over the legacy DCF protocol with respect to important criteria such as the average time spent in the buffer and the throughput.     

Understanding the morphological effects of WO3 photocatalysts for the degradation of organic pollutants

Dimension and morphology of photocatalysts has extensive interest in order to use the effective concurrence of photon. Despite TiO₂ and ZnO, WO₃ has also been considered as a promising candidate in terms of remediation and purification that owes to its visible light absorption and non-toxic environmental friendliness. In this study, we report the preparation of nanostructured WO₃ with different morphologies for the photocatalytic degradation of organic pollutants without the presence of any sacrificial agents. The study envisages the effect of the aspect ratio of WO₃ particles on the photochemical process and their inherent reactive species mechanism. Mechanistic reasoning revealed that, apart from the hole and hydroxyl radicals as the participating species in both structures, a significant contribution from superoxide radicals takes place in the presence of nanorods and promotes the photochemical reaction. High aspect ratio facilitates the absorption coefficient and resultant efficiency. Both the catalysts retain its reactivity after regeneration and confirms the consistent catalytic reusability. Reactivity enhancement of any photocatalyst is possible through tuning the inherent structure of the material.