Synthesis of crosslinked poly(styrene-<Emphasis Type="Italic">co</Emphasis>-divinylbenzene-<Emphasis Type="Italic">co</Emphasis>-sulfopropyl methacrylate) nanoparticles by emulsion polymerization: Tuning the particle size and surface charge density

We have synthesized highly charged, crosslinked poly (styrene-co-divinylbenzene-co-sulfopropyl methacrylate) copolymer colloidal particles using emulsion polymerization. The effects of concentration of the emulsifier and the initiator on the particle size and the charge density of the colloidal particles are studied. Colloidal particle size is highly dependent upon the concentration of the emulsifier and the initiator. The colloidal particle diameter decreases with increasing concentration of the emulsifier and increases with increasing concentration of the initiator in the polymerization mixture. Number of particles, surface charge density and charges per particle are also functions of both the emulsifier and the initiator concentration. The surface charge density and the number of charges per sphere increase with increasing particle diameter. These copolymer colloid particles self assemble readily and diffract visible light. Polymer hydrogel imbibed with these colloids shows the light diffraction.     

Facile Plasma‐Enhanced Deposition of Ultrathin Crosslinked Amino Acid Films for Conformal Biometallization

A novel method for the facile fabrication of conformal, ultrathin, and uniform synthetic amino acid coatings on a variety of practical surfaces by plasma‐enhanced chemical vapor deposition is introduced. Tyrosine, which is utilized as an agent to reduce gold nanoparticles from solution, is sublimed into the plasma field and directly deposited on a variety of substrates to form a homogeneous, conformal, and robust polyamino acid coating in a one‐step, solvent‐free process. This approach is applicable to many practical surfaces and allows surface‐induced biometallization while avoiding multiple wet‐chemistry treatments that can damage many soft materials. Moreover, by placing a mask over the substrate during deposition, the tyrosine coating can be micropatterned. Upon its exposure to a solution of gold chloride, a network of gold nanoparticles forms on the surface, replicating the initial micropattern. This method of templated biometallization is adaptable to a variety of practical inorganic and organic substrates, such as silicon, glass, nitrocellulose, polystyrene, polydimethylsiloxane, polytetrafluoroethylene, polyethylene, and woven silk fibers. No special pretreatment is necessary, and the technique results in a rapid, conformal amino acid coating that can be utilized for further biometallization.     

Infective endocarditis of the tricuspid valve in an orthotopic heart transplant recipient

A 43-year-old orthotopic heart transplant recipient had coagulase-negative staphylococcus endocarditis 26 weeks after the operation. A diagnosis of endocarditis was confirmed and followed up by serial transoesophageal echocardiography. Treatment with intravenous gentamycin and vancomycin cured her endocarditis, and a 2.5 cm vegetation regressed significantly. She has been well since and, at 14 months after transplantation, was back to her normal activities. Although repeated blood culture yielded only intermittent light growths of coagulase-negative staphylococci, there were several positive samples. In a setting of infective features, light growths of coagulase-negative staphylococcus should be taken seriously if repeatedly positive in heart transplant recipients or other immunocompromised patients. Transesophageal echocardiography offers significant advantages over the transthoracic modality in suspected endocarditis.     

Two neighbouring quasi-trapezoidal holes in discs with minimum s.c.f.

Using a two dimensional photoelastic technique, hole shapes have been optimised in diametrically loaded circular discs with two neighbouring holes leading to minimum stress concentration factor (s.c.f.). Two neighbouring holes symmetrically located side by side with the load axis perpendicular to the line joining the centres of the holes are considered. Results are given for a range of disc diameter/hole diameter ratios (11.44≥D/d≥4.16). Optimised quasi-trapezoidal hole geometries, stress distributions around these holes and the effect of tilting the load direction are presented. In comparison with circular holes, the s.c.fs. have been reduced up to about 14% with quasi-trapezoidal holes at regions of peak stresses and up to 23% at peak tensile stress regions.     

Speaker verification: a tutorial

The task of speaker verification, a subset of the general problem of speaker recognition is defined. The feature selection and pattern matching steps of the recognition procedure are examined. Speaker verification system design and performance are discussed, and databases for evaluating them are briefly considered. An example of a speaker verification system is described. An overview of industry research in this area is given     

The in Vitro and in Vivo Performance of a Novel Slow Release Capsule-Compared with a Conventional Capsule

A comparative in vitro and in vivo performance study of a novel slow release capsule (prepared using the new laser drilled controlled drug delivery system) and a conventional capsule dosage from has been made using tetracycline hydrochloride as a model drug. The influence of variation in drug delivery system design on the in vivo performance was studied by urinary excretion rate studies in human volunteers. Slow release capsules released its contents relatively slowly, over a period of time, both in vitro and in vivo, as compared to conventional capsules, with significantly similar K_e and t_1/2 values. Plasma C_max and t_max and AUC values were predicted based on the reported correlation between serum and urinary excretion data in single dose trials.     

Ceramic nanoparticle assemblies with tailored shapes and tailored chemistries via biosculpting and shape-preserving inorganic conversion

A novel biosynthetic paradigm is introduced for fabricating three-dimensional (3-D) ceramic nanoparticle assemblies with tailored shapes and tailored chemistries: biosculpting and shape-preserving inorganic conversion (BaSIC). Biosculpting refers to the use of biomolecules that direct the precipitation of ceramic nanoparticles to form a continuous 3-D structure with a tailored shape. We used a peptide derived from a diatom (a type of unicellular algae) to biosculpt silica nanoparticle based assemblies that, in turn, were converted into a new (nonsilica) composition via a shape-preserving gas/silica displacement reaction. Interwoven, microfilamentary silica structures were prepared by exposing a peptide, derived from the silaffin-1A protein of the diatom Cylindrotheca fusiformis, to a tetramethylorthosilicate solution under a linear shear flow condition. Subsequent exposure of the silica microfilaments to magnesium gas at 900 degrees C resulted in conversion into nanocrystalline magnesium oxide microfilaments with a retention of fine (submicrometer) features. Fluid(gas or liquid)/silica displacement reactions leading to a variety of other oxides have also been identified. This hybrid (biogenic/synthetic) approach opens the door to biosculpted ceramic microcomponents with multifarious tailored shapes and compositions for a wide range of environmental, aerospace, biomedical, chemical, telecommunications, automotive, manufacturing, and defense applications.     

OptiRNAi, an RNAi design tool

RNA interference (RNAi), a recently developed reverse genetics tool, has many advantages compared to traditional gene knockout methods. Appropriate selection of double stranded RNAs identical to a specific region(s) of the target gene is critical for the successful implementation of this technology. Recently, Elbashir et al. [Methods 26 (2002) 199] has established empirical criteria for siRNA sequence selection that significantly improved the success rate for RNAi attempts. We have developed OptiRNAi, a computational tool, which uses the Elbashir et al. criteria to predict appropriate target sequences for siRNA production. Specificity of these siRNAs for the target of interest can then be assessed by the investigator using the embedded Blast search engine optimized for RNAi design. Thus, OptiRNAi is an efficient and user friendly tool for RNAi design based on criteria that are more stringent than other available tools.