Mold susceptibility of rigid PVC/wood‐flour composites

Rigid PVC/wood‐flour composite lumber containing either hardwood (maple) or a softwood (southern pine) wood flour at different levels of wood‐flour content was evaluated for susceptibility to fungal colonization and discoloration by using standard tests that mimicked exterior (ASTM G21) and interior (ASTM D3273) environments, respectively. In the exterior test protocol, although both types of PVC/wood‐flour composite lumber exhibited fungal colonization and discoloration, the composites containing maple exhibited greater discoloration than those containing pine. Irrespective of wood species, fungal colonization and discoloration in the composite lumber were greater at the bottom faces where they were in constant contact with moisture. The wood content range (50–100 phr) used in this study showed no effect on extent of fungal colonization and discoloration. All composites showed no discoloration in the interior test protocol. Both optical microscopy and environmental scanning electron microscopy clearly demonstrated that wood flour particulates are not completely encapsulated by the PVC matrix, so that exposed wood flour in the surface crevices of the composite lumber may serve as points of moisture sorption and staging points for fungal colonization and discoloration. J. Vinyl Addit. Technol. 10:179–186, 2004. © 2004 Society of Plastics Engineers.     

Model complexes of tumor necrosis factor-{alpha} with receptors Rl and R2

The biological activities of tumor necrosis factor- (TNF-) aremediated by two different receptors, TNFR1 and TNFR2. To analyzethe receptor binding site(s) of TNF-, molecular models havebeen built of the complexes of TNF- with the extracellular regionsof receptors Rl and R2, based on the known crystal structuresof TNF- and lymphotoxin bound to Rl. The model structure ofR2 from residues 18-160 was built by analogy to the crystalstructure of Rl in complex with lymphotoxin. The amino acidsequences of Rl and R2 show 27.5% identity over this regionand were aligned with five insertions and three deletions. Thereare 18 conserved cysteines that form disulfides. R2 has lostone pair of cysteines compared with Rl, but two new cysteineswere modeled as forming a new disulfide bond. Both symmetricand asymmetric trimers of TNF- were used to model the complexeswith TNFR1 and R2. An analysis of differences in the model complexesshowed good agreement with data on the differential bindingof TNF mutants to its two receptors.     

Liquid crystal polymer/polyethylene blends for thin film applications

A series of liquid crystal polymer/polyethylene (LCP/PE) blends have been studied to determine the potential of such a system to produce a high modulus film material which retains fabrication and low temperature characteristics of some current PE films. The subject of liquid crystalline polymer blends has been the focus of significant attention for the last decade due to the novel rheological and mechanical properties of this class of polymers. It has been demonstrated that if an LCP blend is processed under elongational flow conditions, the partially ordered LCP meso-phase intermediate allows the development of an oriented fibrillar morphology which is retained upon solidification. In this study, blown films of blends of 5 and 15% LCP in PE have been produced which show an enhancement in modulus over the neat PE matrix. These results are discussed in terms of processing conditions, LCP reinforcement aspect ratio, fibril diameter, and LCP/PE modulus ratio.     

Experimental studies on the development of a cast film

The cast film process is of significant industrial interest. This work presents quantitative experimental results for the characterization of a film casting operation in the region between the die exit and the chill roll. The polymer melt employed is a commercial PET sample that has been characterized in both shear and extension‐dominated flows. Pointwise measurements of both the film temperature and the local velocity are made over the entire region between the die and the chill roll. The velocity increases in the gap, although the strain rate decreases as the polymer moves from the die to the chill roll. For a particular axial position, the velocity decreases significantly near the edges of the film. There are modest (～20 °C) decreases in the temperature between the die and the chill roll, with the greatest variations again occurring near the edges of the film. The experimental results are explained by the coupling between the temperature, velocity fields, and geometry of the experimental apparatus. POLYM. ENG. SCI. 45:443–450, 2005. © 2005 Society of Plastics Engineers.     

Predicted ligand interactions for 3',5'-cyclic nucleotide-gated channel binding sites: comparison of retina and olfactory binding site models

Cyclic nucleotide-gated channels (CNGC) open in response tothe binding of 3',5'-cyclic nucleotides. Members of the CNGCfamily vary as much as 100-fold in their ability to respondto cAMP and cGMP. Molecular models of the nucleotide bindingdomains of the bovine retina and catfish and rat olfactory CNGCswere built from the crystal structure of cAMP bound to catabolitegene activator protein (CAP) with AMMP, a program for molecularmechanics and dynamics. The nucleotide conformation can be predictedfrom the number of strong and weak interactions between thepurine ring and the binding site. The amino acids predictedto be important for determining the nucleotide affinity andspecificity are residues 61, 83 (mediated through a water molecule),119 and 127 (CAP sequence numbers) which interact with the purinering. These residues also dictate the conformation of the ligandin the binding pocket cGMP is preferentially bound in the synconformation in bovine retina, bovine olfactory and rat olfactoryCNGCs due to Thr83, while either conformation can bind in catfisholfactory CNGC. cAMP is predicted to bind either in syn or anticonformation, depending on the interaction with residue 119:the anti conformation is preferentially bound in olfactory CNGCs.     

Effect of sodium iodide on growth and chemical composition of lucerne and ryegrass

Growth of lucerne was inhibited by sodium iodide even more than that of ryegrass above a concentration equivalent to 1µg cm^–3 of iodine in an applied solution. In sand-culture the extent to which the iodide depressed yield of dry matter depended on the type of nutrient-solution used to stimulate and maintain vigorous growth. In contrast, where the plants were grown in soil the depression was independent of the nutrient-solution used. This difference between solutions is a reflection of the extent to which growing plants can modify pH in the root-zone of a sandy unbuffered substrate and leads to a conclusion that acidity greatly enhances the toxic effect of the iodine. There are reasons for believing that in sunlight iodine may be lost by volatilization even from living plant-tissue. The implication of these findings is discussed in relation to using either iodized fertilizers or iodized salt-blocks in order to maintain iodine in pastoral systems at levels satisfactory for animal-health.     

Making epistemological trouble: Third-paradigm HCI as successor science

Epistemological issues have long been debated by feminist philosophers aiming to answer the question, “what difference does it make to take gendered points of view seriously in the construction of knowledge?” Coming out of this history, a strand of work in feminist science studies has argued for the necessity of “successor science:” new forms of science based in standpoint epistemology, i.e. a recognition of the necessarily situated points of view of scientific knowledge-makers. In this paper, we argue that such a successor science has already come into being within the field of HCI, though it is perhaps not recognized as such by its practitioners.In particular, we identify a cluster of research we term the ‘third paradigm.’ This cluster of research cuts across HCI research areas as typically organized by topic area. Instead, this research shares an underlying epistemological orientation closely aligned with standpoint epistemology, focused around an acknowledgment of the social, cultural, and physical situatedness of both users and analysts. Feminist philosophers of science argue that a logical outcome of standpoint epistemology is the need for science to reflexively grapple with the limitations of its own ways of knowing; we conclude such an outcome may also be in store for the third paradigm.     

Correction for piezoelectric creep in scanning probe microscopy images using polynomial mapping

We describe a method for using polynomial mapping to correct scanning probe microscope images for distortion due to piezoelectric creep. Because such distortion varies from image to image, this method can be used when the actual locations of some features within an image are known absolutely, or in a series of images in which the actual locations of some features are known not to vary. While the general case of polynomial mapping of degree N requires the determination of 2(N+ 1)2 matrix elements by regression, we find that by understanding the mechanism by which piezoelectric creep distorts scanning probe microscope images, we can fix most of these coefficients at 0 or 1 a priori, leaving only 2(N+ 1) coefficients to be determined by regression. We describe our implementation of this strategy using the Interactive Data Language (IDL) programming language, and demonstrate our technique on a series of atomic force microscopy (AFM) images of diblock copolymer microdomains. Using our simplified scheme, we are able to reduce the effects of distortion in an AFM image from 5% of the scan width to a single pixel, using only five reference points.     

Precision and efficiency of laser assisted jet electrochemical machining

Laser assisted jet electrochemical machining (LAJECM) is a hybrid process, that combines a laser beam with an electrolyte jet thereby giving a non-contact tool electrode that removes metal by electrochemical dissolution. The laser beam effectively improves the precision of LAJECM as it is able to direct the dissolution to specifically targeted areas. This prevents the machining from unwanted areas due to stray current. This parallel application of a laser beam with the electrolyte jet enables an improvement of machining accuracy, also productivity. LAJECM has shown that machining with laser assistance can effectively facilitate material removal of 20, 25, 33, and 54% for Hasteloy, titanium alloy, stainless steel and aluminium alloy, respectively. There is also a noticeable improvement in the shape accuracy and slight decrease in surface roughness of the holes and cavities produced due to more focused machining (the order of 20%). The measured reduction in taper is of the order of 38, 40, 41, 65% for aluminium alloy, stainless steel, Hasteloy and titanium alloy, respectively.     

Physico-chemical speciation of selected metals in the treated effluent of a lead-acid battery manufacturer and in the receiving river

A scheme for the speciation of metals in freshwaters has been applied to the metals Pb, Cd, Cu, Fe and Mn in the treated effluent of a lead-acid battery manufacturer and the receiving river upstream and downstream of the effluent outfall. The speciation is inferred from measurements of the size-associations of the metals, the lability with respect to anodic stripping voltammetry and Chelex resin and by u.v. irradiation to destroy organic complexing agents. The results are related to chemical and physical interactions within the waters and are discussed in terms of the impact of the effluent discharge upon the receiving river.