Geometry of good sets in n-fold Cartesian product

We propose here a multidimensional generalisation of the notion of link introduced in our previous papers and we discuss some consequences for simplicial measures and sums of function algebras.Comment: 17 pages, no figures, no table

Modification of crystallinity and structure in powder processing of polytetra fluoroethylene

The modification of structure, crystallinity and orientation have been studied in powder processed polytetrafluoroethylene by various techniques. It was found that crystallinity (as determined from regression curve analysis) in unsintered samples decreased with increase of compaction pressure while in sintered specimen it increased with increase of pressure. The crystallinity was also found to vary inversely with logarithm of cooling rate. Microfocus X-ray diffraction revealed the orientation of c-axis lying preferentially in the plane perpendicular to applied pressure. There was slight variation in the lattice dimension especially the c-axis in completely sintered specimen. The infrared studies showed the presence of some of the bands depended upon the molding/sintering conditions. These various findings have been explained on the basis of compaction and recrystallization behaviour under constrained conditions

Hamel bases and measurability

This is a note - set in the background of some historic comments - discussing the relationship between measurability and Hamel bases for R over Q. We explicitly note that such a basis must necessarily fail to be Borel measurable (or even 'analytic' in the sense of descriptive set theory). We also discuss some constructions in the literature which yield Hamel bases which even fail to be Lebesgue measurable, and discussan elementary construction of a Hamel basis which is Lebesgue measurable

Phenol-crotonaldehyde resins. II. Effect of crotonaldehyde purity on resin properties

Acid-catalyzed polycondensation of phenol and crotonaldehyde results in soluble thermoplastic resins over a broad range of compositions. The thermal and curing behavior of the resins are found to vary markedly with the phenol to crotonaldehyde mole ratio and the purity of crotonaldehyde. Infrared analysis of the resins and their fractions separated by column chromatography indicates that all the resins are structurally similar. The number-average molecular weights of the resins fall in the range of 400 to 600. The resins from distilled crotonaldehyde exhibit higher molecular weights than those from crude crotonaldehyde. The thermal properties of the resins are comparable to the Novolak-type phenol-formaldehyde resins. The thermoplastic nature is retained even at higher fraction of crotonaldehyde, unlike for the conventional Novolak resins

Phenol-crotonaldehyde resins. III. Curing behavior with hexamethylenetetramine

Solid thermoplastic resins were prepared by acid-catalyzed condensation of phenol and crotonaldehyde (both crude and distilled). The thermal and curing properties were compared with the conventional phenol-formaldehyde (PF) novolak resins. Phenol-crotonaldehyde (PC) resins were found to be thermoplastic even after curing with the crosslinking agent hexamethylenetetramine up to 160°C. This curing behavior was observed irrespective of the purity of the crotonaldehyde or the phenol-to-crotonaldehyde mole ratio in the resin. Postcuring of these resins at elevated temperatures yielded insoluble and infusible thermoset products. This unique thermal characteristic could lead to interesting processing possibilities for the resins. The technical feasibility of thermoplastic processing of the PC resins followed by postcure heat treatment for transforming the molded part into a thermoset has been demonstrated

From melt flow index to rheogram

A knowledge of the complete flow curve or rheogram of a polymeric melt depicting the variation of the melt viscosity over industrially relevant range of shear rate and temperature is essential in the design of polymer processing equipment, process optimization and trouble-shooting. These data are generated on sophisticated rheometers that are beyond the financial and technical means of most plastics processors. The only flow parameter available to the processor is the melt flow index of the material. In the present work, a method has been proposed to estimate the rheograms of a melt at temperatures relevant to its processing conditions with the use of a master curve, knowing the melt flow index and glass transition temperature of the material. Master curves that coalesce rheograms of different grades at various temperatures have been generated and presented for low density polyethylene, high density polyethylene, polypropylene, polystyrene and styrene-acrylonitrile copolymer

Structure, growth and morphology polyphenylene sulphide

The crystaIIinity, particle size and morphology of polyphenylene sulphide synthesized under various conditions have been investigated by X-ray diffraction and scanning electron microscopy. It was found that crystaIIinity decreased from 71 to 66% with increase of reaction time. The growth of particle size as well as total polymer mass followed a time dependence of the form X = X 0 (1 -e -αt). The particle size distribution curve was noted to be sharp centring at 3 μn for short reaction time, high speed of stirring and also for low concentration of reactants. The particle morphology showed very strong dependence on various reaction parameters. Intricate sheaf-like morphology was noted for the particles at long reaction times or low stirring speeds while oblong platelet type two-dimensional morphology was noted when a low concentration of reactants was used

Management of intra-articular fractures of distal end radius in adults

Background: Incidence of intra articular fracture L/3rd radius is significantly on rise due to high velocity accidents in young and adults. Painless wrist function is of vital importance for functioning of upper extremity in almost all activities of daily living and precise function of hand. Intra articular fracture of L/3rd radius has generally gross comminution and so also small articular fragments. Orthopaedic community differ about specific implants to fix this complex injury. The present study was undertaken to know efficacy of different modalities of treatment for different fracture pattern. Comminuted intra articular fracture geometry varies widely, to fix these small fragments to achieve stable anatomical reduction is a challenging task.   Methods: It is a combined i.e. retrospective and prospective study conducted at Hardikar Hospital, Pune, India from 1999 to December 2000. Patients of intra-articular fracture of distal end radius by different modes of treatment are included in the study. 1 patient with unilateral fracture was lost for follow-up. Thus 50 fractures, in 49 patients. were included in study. Clinico-radiological assessment was carried out by Lidstrom's (1959) criteria.Results: Satisfactory early functional end results with plaster treatment is 72.2% whereas with other modality of treatment it rises to 87.5%, indicating superiority of other modalities of treatment as far as early functional end results are concerned.Conclusions: Manipulation and plaster cast method continues to be the treatment of choice in the stable intra articular distal radial fractures. Hence there is a need for a "differentiated therapy for distal radial fractures". The treatment plan for patients must be based not only on fracture pattern identified on plain radiographs but also on factors such as bone quality, bone comminution, energy of injury and associated soft tissue damage. Additional factors to be considered in individual patient are-life style associated medical conditions and compliance

Wilson Loop and the Treatment of Axial Gauge Poles

We consider the question of gauge invariance of the Wilson loop in the light of a new treatment of axial gauge propagator proposed recently based on a finite field-dependent BRS (FFBRS) transformation. We remark that as under the FFBRS transformation the vacuum expectation value of a gauge invariant observable remains unchanged, our prescription automatically satisfies the Wilson loop criterion. Further, we give an argument for {\it direct} verification of the invariance of Wilson loop to O(g^4) using the earlier work by Cheng and Tsai. We also note that our prescription preserves the thermal Wilson loop to O(g^2).Comment: 8 pages, LaTex; some typos related to equation (18) correcte