Radiation-induced wood plastic composites under combinations of monomers

Radiation-induced wood plastic composites (WPC) were prepared from five varieties of Bangladeshi timbers, using seven different types of monomers. The mixtures of double and triple monomers were investigated along with the single-monomer system for the preparation of composites. Among the three systems, single-monomer process showed the highest polymer loading with butylmethacrylate (BMA). Tensile strength (TS) property, represented as T_f = TS_wpc/TS_wood was determined. Highest T_f values were achieved with the soft wood. The effects of dose and dose rate, monomer concentration, and swelling agent were also studied. Suitable total dose was found to be 3 Mrad at 0.8 Mrad/h, and methanol exhibited the best swelling ability for the woods at a ratio of 1 : 9 v/v in all the monomer investigated.     

Solid-state NMR study of N labelled polyaniline upon reaction with DPPH

The quantitative investigation of the radical scavenging properties of polyaniline (PANI) upon reaction with excess of the stable DPPH radical (a 4:1 ratio of DPPH to aniline units in the polymer) was carried out using ¹⁵N and ¹³C solid state NMR spectroscopy. During the process the polyaniline was oxidised so that the imine content increased from 45 to 65%. The extent of oxidation measured by NMR was confirmed by N1s XPS analysis. However, within a 30 min reaction time, about 85% of the DPPH radicals were scavenged as monitored by the decay in its EPR signal. This is about 20 times greater than the fraction of DPPH required to oxidize PANI from an imine content of 45-65%. An identification of further redox processes is required to explain the high degree of radical scavenging. At the same time, there was no evidence of significant chemical binding or trapping of DPPH in the PANI structure.     

Evaluation and testing of a fracture critical bridge

The I-40 bridges over the Rio Grande in Albuquerque, New Mexico were due to be razed in the fall of 1993 due to geometry and traffic safety considerations, thus providing a unique opportunity for testing them. These medium span steel bridges represent a common design in the US and are classified by AASHTO as non-redundant ‘fracture critical’ two girder steel bridges (fracture critical classification means that failure of a primary member would probably cause collapse of the bridge). The subject bridge, built in 1963, is a 1275 foot (600m) bridge, and consists of three medium span continuous units with spans of 131′-163'−131′ each. The bridge was field tested to determine the impact of a near full depth girder fracture on the redistribution of loads, the load capacity, and the potential for collapse. Four levels of damage were introduced in the middle span of the north plate girder by making various cuts in the web and the flange of the girder. The final cut resulted in a six foot deep crack in the 10ft deep girder, extending from the bottom flange to the floor beam to girder connection. Data was taken under dead load and under a static live load consisting of an 82 000 lb truck. The after fracture response and the load redistribution in the fractured bridge were evaluated. The contribution of the different members to the redundancy of the structure was assessed.     

Laser and GTAW torch processing of Fe–Cr–B coatings on steel

A comparison has been made of the relationship between microstructure and microhardness developed by surface melting Nanosteel SHS 7170 Fe–Cr–B alloy powder onto a plain carbon steel surface. This powder was initially developed as a high velocity oxyfuel sprayed coating, giving a strength 10 times that of mild steel, and is particularly suitable for surface protection against wear and corrosion. In the present study, the alloy powder was injected into the laser melted surface, while a preplaced powder was melted using the gas tungsten arc welding (GTAW) technique. The laser track consisted of fine dendrites and needle-like microstructures, which produced a maximum hardness value of over 800 HV, while the GTAW track produced a mixture of equiaxed and columnar grain microstructures with a maximum hardness value of 670 HV. The lower hardness values are considered to be associated with dilution and grain size.     

TNF alpha and the TNF receptor superfamily: structure-function relationship(s)

Tumour Necrosis Factor alpha (TNF alpha), is an inflammatory cytokine produced by macrophages/monocytes during acute inflammation and is responsible for a diverse range of signalling events within cells, leading to necrosis or apoptosis. The protein is also important for resistance to infection and cancers. TNF alpha exerts many of its effects by binding, as a trimer, to either a 55 kDa cell membrane receptor termed TNFR-1 or a 75 kDa cell membrane receptor termed TNFR-2. Both these receptors belong to the so-called TNF receptor superfamily. The superfamily includes FAS, CD40, CD27, and RANK. The defining trait of these receptors is an extra cellular domain comprised of two to six repeats of cysteine rich motifs. Additionally, a number of structurally related "decoy receptors" exist that act to sequester TNF molecules, thereby rescuing cells from apoptosis. The crystal structures of TNF alpha, TNF beta, the extracellular domain of TNFR-1 (denoted sTNFR-1), and the TNF beta sTNFR-1 complex have been defined by crystallography. This article will review the structure/function relationships of the TNF alpha and the TNF receptor superfamily. It will also discuss insights as to how structural features play a role in the pleiotropic effects of TNF alpha.     

Effect of an ultraviolet/ozone treatment on the surface texture and functional groups on polyacrylonitrile carbon fibres

The effect of an ultraviolet generated ozone treatment (UV/O₃), on the surface and near surface functionality and structure of polyacrylonitrile based carbon fibres has been studied using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and Raman spectroscopy. Results were compared to electrochemically treated fibres. The UV/O₃ treated fibres showed increased levels of oxygen functionalities. Levels of oxygen comparable to a high level electrochemical shear treatment were achieved within 5 min of treatment (O/C 0.11 ± 0.03 for both treatments). XPS O1s/C1s ratios as high as 0.3 were produced, with saturation occurring at approximately 40 min exposure. The main functional groups introduced were, in addition to hydroxyl species, alkoxides (ca. 286.5 eV), carbonyl (288.0 eV), and carboxyl (289.5 eV). Examination of the full width half maximum of the graphite peak from XPS C1s showed some disorder was introduced to the first few layers of the fibre with treatment but the effect was not evident in the Raman, i.e. in the bulk of the fibre.     

Evolution of the AgCdO Contact Material Surface Microstructure with the Number of Arcs

This paper describes a study of the evolution of the AgCdO contact material surface microstructure as a function of the number of electrical arcs imposed on the switching surface. Five power switching devices were tested under different conditions. They were subjected to, respectively, 1, 2, 3, 10, and 100 electrical arcs under the same operating conditions: supply current of 400 A, circuit voltage of 28 V direct current (DC), and resistive load. For the analysis, a binocular microscope and a scanning electron microscope with an energy-dispersive x-ray spectrometer were used.     

The development of the globally harmonized system (GHS) of classification and labelling of hazardous chemicals

The hazards of chemicals can be classified using classification criteria that are based on physical, chemical and ecotoxicological endpoints. These criteria may be developed be iteratively, based on scientific or regulatory processes. A number of national and international schemes have been developed over the past 50 years, and some, such as the UN Dangerous Goods system or the EC system for hazardous substances, are in widespread use. However, the unnecessarily complicated multiplicity of existing hazard classifications created much unnecessary confusion at the user level, and a recommendation was made at the 1992 Rio Earth summit to develop a globally harmonized chemical hazard classification and compatible labelling system, including material safety data sheets and easily understandable symbols, that could be used for manufacture, transport, use and disposal of chemical substances. This became the globally harmonized system for the Classification and Labelling of Chemicals (GHS). The developmental phase of the GHS is largely complete. Consistent criteria for categorising chemicals according to their toxic, physical, chemical and ecological hazards are now available. Consistent hazard communication tools such as labelling and material safety data sheets are also close to finalisation. The next phase is implementation of the GHS. The Intergovernmental Forum for Chemical Safety recommends that all countries implement the GHS as soon as possible with a view to have the system fully operational by 2008. When the GHS is in place, the world will finally have one system for classification of chemical hazards.     

A rapid method for evaluation of the oxidation stability of castor oil FAME: influence of antioxidant type and concentration

The oxidation stability of castor oil fatty methyl ester (FAME), doped with four different phenolic antioxidants, was evaluated using a rapid method of thermal and air-contact degradation. The methodology is based on the induction times observed when the samples are contacted with pure oxygen at elevated pressures and temperatures. The results indicate different performances of the antioxidants as well as synergisms between antioxidants and biodiesel. In general, the addition of antioxidants increased from 6-15 times the stability of castor oil FAME., with BHA (butylated hydroxyanisol) showing the best results for improving antioxidation in castor oil biodiesel.