Jovan Moacanin

A surface energy analysis of bioadhesion

Abstract This report applies recently developed surface energy and fracture mechanics relations to the analysis of bioadhesion and biocompatibility. The dispersion α and polar β components of 190 biological and implant surfaces are analysed. The surface energetics relations between bioadhesion and biocompatibility point out that a strongly adsorbed plasma protein film on the implant surface provides the best blood compatibility and low thrombogenic effects. The surface energy relations provide means of selecting optimum implant surface properties and mapping on surface energy diagrams the three phase interactions which define bioadhesion.

Thermal diffusivity measurements using a pulsed dual‐beam thermal lens technique

A novel pulsed dual‐beam thermal lens technique for the determination of thermal diffusivity of liquids and solids was developed. In this technique a transient thermal lens is formed in the test specimen by using a dye laser pulse as a heating source and the thermal lens decay is monitored by means of a cw He‐Ne laser. The technique is fast and contactless and avoids some of the major difficulties of conventional methods. Thermal diffusivities for water and a polycarbonate plastic were measured and found to be in agreement with literature values. Considerable simplification and minimization of certain errors was achieved by use of a reference material.

Internal conversion in poly(1-vinylnaphthalene)—IV. Photochemical processes in polymeric systems☆☆☆

Abstract Quantum yields of all major photoprocesses have been measured on poly(1-vinylnaphthalene) in fluid solution. These measurements indicate that approx. 84% of the excitation energy is deactivated through internal conversion processes ( S 0 ↞ S 1 ). Time resolved emission and absorbance measurements have been used to characterize the excited states in this system. It appears that several different types of singlet and triplet traps may be distinguished, one of which is the monomeric excited singlet. Existence of two different singlet excimers are postulated in order to interpret the time resolved emission data.

Time-resolved spectroscopy of solid poly(1-vinyl naphthalene)following electron beam pulse radiolysis: pulse radiolytic studies on polymers☆

Transient emission studies following pulse radiolysis of solid poly(1-vinyl naphthalene) show existence of excited monomers and two excimers. Quenching experiments indicate that excimers are not formed directly by recombination of ions but probably by trapping of migrating monomeric excitation in performed traps whose density is approximately one in 103.

Chemicals from biomass—the U.S. prospects for the turn of the century

Abstract Historically, chemicals from biomass have been and are expected to be economical in three major areas: byproducts, specialty items and polymers. Assessments of producing major chemicals from biomass in a processing plant based on the available conversion techniques indicate that they are not economically attractive, with the possible exception of conversion to ammonia and ethanol. The deterrents are the heavy capital investments, dependability of raw material supply and transportation costs for large plants, lack of operation experience, inadaptability to market variations, and competition from petroleum and coal. More importantly, it is also shown that even if chemicals from biomass were economical today, the resultant savings in petroleum would be far less than those achieved through other options available for the utilization of biomass as fuel and structural material. Thus, it is concluded that near-term research and development must be toward improved conversion processes, recovery of valuable products from waste streams at existing plants, more efficient use of biomass for energy and more efficient production of superior material products.

Determination of the Si-conducting polymer interfacial properties using A C impedanc techniques

A study was made of the interfacial properties of Poly(pyrrole) (PP) deposited electrochemically onto single crystal p-Si surfaces. The interfacial properties are dependent upon the counterions. The formation of “Quasi-Ohmic” and “non-Ohmic” contacts, respectively, of PP(C1O4) and PP films doped with other counterions (BF4 and para-toluene sulfonate) with p-Si, are explained in-terms of the conductivity of these films and the flat band potential,Vfb, of PP relative to that ofp-Si. The PP film seems to passivate or block intrinsic surface states present on thep-Si surface. The differences in the impedance behavior of para-toluene sulfonate doped and C1O4 doped PP are compared.

A failure model for sealed nickel-cadmium batteries

A model has been developed to describe failure in electrochemical batteries. The model is based on the concept of the existence and subsequent growth of flaws which ultimately lead to battery failure. This model provides, in a natural way, for the statistical variability of lifetime data. The model as applied to the Crane data indicates that when the effects of temperature and depth of discharge are taken into account, the observed variability in lifetime data is due almost entirely to statistical variability inherent in the battery itself.

Characterization of Thermal and Optical Properties of Polymers by Thermal Lensing Technique

When a light beam passes through a material, some of the absorbed light energy may be converted into heat, generating a time dependent temperature gradient. Increase in temperature causes a change in the index of refraction. Hence, a transient thermal lens is formed in the volume element absorbing the radiation. The temperature rise is typically of the order of 10-2°C within a volume element of less than 10-3 cm3. Several physical and chemical properties of materials such as thermal diffusivity, optical absorption coefficient, multiphoton crossections quantum yield of photoprocesses etc... may be determined by monitoring the time dependence of the amplitude of the thermal lens. This technique is fast, precise and contactless.