Formation and properties of single texture polyethylene produced by rolling

The formation of single textured low density polyethylene by unidirectional rolling has been investigated. It was found to be associated with the shear of the sample during annealing, which is a reversal of the shear imparted by the rolling process. Single texture could be produced from double texture by compressing it obliquely in such a way as to simulate this shear. It is concluded that the material probably contains another component besides the single orientation of lamellae which would need to be taken into account when using it as a model for the study of lamellar properties.     

Superconductors with crystalline-field split impurities: Upper critical field and specific heat

We continue the investigation of crystalline-field effects on the properties of superconductors containing rare-earth impurities. Attention is focused on impurities with a nonmagnetic ground state. We calculate the upper critical fieldH _{c 2} and the jump of the specific heat at the phase transition.     

Tracer diffusivity of Ca45and electrical conductivity in CaO-SiO2 melts

The tracer diffusivity of Ca⁴⁵ has been measured in CaO-SiO₂ melts in the temperature range 1500 to 1700°C. In addition the electrical conductivity has been determined. Both properties decrease with increasing silica content. The activation energies (~30 kcal g-atom−1) are of the same order of magnitude. The electrical conductivity as computed from the diffusivity on the assumption that the total current is transported exclusively by divalent calcium ions and that the usual Nernst-Einstein relationship is valid, is somewhat lower than the measured electrical conductivity with the difference increasing with increasing silica content.     

Sliding mode closed-loop control of FES: controlling the shank movement

Functional electrical stimulation (FES) enables restoration of movement in individuals with spinal cord injury. FES-based devices use electric current pulses to stimulate and excite the intact peripheral nerves. They produce muscle contractions, generate joint torques, and thus, joint movements. Since the underlying neuromuscular-skeletal system is highly nonlinear and time-varying, feedback control is necessary for accurate control of the generated movement. However, classical feedback/closed-loop control algorithms have so far failed to provide satisfactory performance and were not able to guarantee stability of the closed-loop system. Because of this, only open-loop controlled FES devices are in clinical use in spite of their limitations. The purpose of the reported research was to design a novel closed-loop FES controller that achieves good tracking performance and guarantees closed-loop stability. Such a controller was designed based on a mathematical neuromuscular-skeletal model and is founded on a sliding mode control theory. The controller was used to control shank movement and was tested in computer simulations as well as in actual experiments on healthy and spinal cord injured subjects. It demonstrated good robustness, stability, and tracking performance properties.     

Open tubular immobilized metal ion affinity chromatography combined with MALDI MS and MS/MS for identification of protein phosphorylation sites

Protein phosphorylation is one of the most important known posttranslational modifications. Tandem mass spectrometry has become an important tool for mapping out the phosphorylation sites. However, when a peptide generated from the enzymatic or chemical digestion of a phosphoprotein is highly phosphorylated or contains many potential phosphorylation residues, phosphorylation site assignment becomes difficult. Separation and enrichment of phosphopeptides from a digest mixture is desirable and often a critical step for MS/MS-based site determination. In this work, we present a novel open tubular immobilized metal ion affinity chromatography (OT-IMAC) method, which is found to be more effective and reproducible for phosphopeptide enrichment, compared to a commonly used commercial product, Ziptip from Millipore. A strategy based on a combination of OT-IMAC, sequential dual-enzyme digestion, and matrix-assisted laser desorption/ionization (MALDI) quadrupole time-of-flight tandem mass spectrometry for phosphoprotein characterization is presented. It is shown that MALDI MS/MS with collision-induced dissociation can be very effective in generating fragment ion spectra containing rich structural information, which enables the identification of phosphorylation sites even from highly phosphorylated peptides. The applicability of this method for real world applications is demonstrated in the characterization and identification of phosphorylation sites of a Na(+)/H(+) exchanger fusion protein, His182, which was phosphorylated in vitro using the kinase Erk2.     

Research drill hole at the summit of Kilauea Volcano, Hawaii

An exploration hole has been drilled to a depth of 1262 m beneath the summit of Kilauea Volcano on the Island of Hawaii in order to obtain information about the potential for the occurrence of geothermal energy in a basalt environment. The hole was started at an elevation of 1102 m, and bottomed at an elevation of −160 m. Short intervals were cored, but the principal information obtained from the hole was in the form of physical measurements. The temperature profile through the hole was complicated, showing several reversals, and reached a maximum value of 137°C at the bottom. Geophysical logs indicate that rocks are fully water saturated to an elevation of about 500 m above sea level, and that the water in the rock has a salinity about equal to or slightly greater than that of sea water. This result supports the pre-drilling hypothesis that there should be a convection cell formed of warm saline water above a shallow magma chamber at Kilauea Volcano.     

Remedial and second language English teaching using computer assisted learning

The problem addressed is that of teaching collegial and entering level university students the requisite skills to write intelligible papers and reports in English.This is a real problem in Montreal because a high proportion of the students have English as a second or third language in which their proficiency is limited or. though English may be their native language, their training in it is not adequate for the pursuit of further education.Several hundred students have worked through 20 or more CAL lessons each year for 3 years, and appreciable gains in skills have been measured. However, where it was possible to duplicate the CAL lessons as programmed texts, equal gains were achieved by those using the programmed texts.Current work is in two divergent directions: (i) providing simple template software for ESL and other teachers to write lessons; (ii) providing a measure of artificial intelligence and auto-adaptation, via a student-constructed sentence diagnosis and remediation package.A service and record system in CDC BASIC was produced to support the grammar lessons. However, a more powerful language is needed for the sentence diagnostician remediator. This was initially written in APL but used too much CPU time in that language and is now being re-written in NATAL (the Canadian standard CAL language).Three quasi-technical questions which also have paedogogical implications occurred and are answered: (i) To what extent can access procedures and frame formats (typography, etc.) be standardized for all studyware on the system? (ii) How: much data needs to be collected automatically to ensure that studyware is working properly and to identify needed improvements? (iii) To what extent should self-documentation of source-code be used, and to what extent should it be in a standardized format?Although a CAL language. CITCAN. was used initially on the CDC system, the level of expertise required to maintain it was too high, and subsequently the present system, written in BASIC, was developed. Personal computers, although available in this environment, are not as yet cost-effective when compared to time-shared access.We expect to move to a hybrid system, with studyware and records stored on the maxi-system. but actual “delivery” being provided by personal computers to which the studyware will be downloaded in blocks and from which the usage data will be collected back at sign-off.     

Origin of contrast effects in the electron microscopy of polymers

When polyethylene single crystals are mounted on a substrate less rigid than the usual evaporated carbon, they undergo considerable dimensional changes in the electron beam. In particular, crystals mounted on collodion expand by 22±2% in every direction in the plane of the lamellae. No induction period is observed and the expansion continues after all crystalline order has been destroyed. Since irradiation increases the density of bulk polyethylene, it is presumed that the lamellae become thinner as they expand. A similar but lesser expansion occurs on irradiation in the electron microscope at liquid helium temperatures, and when crystals are mounted on formvar films. In a solution grown lamellar crystal of polyethylene, most of each molecule is straight and aligned along thec axis, which is nearly perpendicular to the plane of the lamella. Radiation damage in the electron microscope introduces disorder, and these results imply that the effect of this disorder is to reduce the mean molecular dimension alongc, and increase it in the plane perpendicular toc. Polymer chains are generally highly oriented in crystalline regions, so this qualitative explanation would imply similar effects in other systems. These effects have important implications for the contrast observed in the electron microscopy of polymers.     

A statistical model for identifying proteins by tandem mass spectrometry

A statistical model is presented for computing probabilities that proteins are present in a sample on the basis of peptides assigned to tandem mass (MS/MS) spectra acquired from a proteolytic digest of the sample. Peptides that correspond to more than a single protein in the sequence database are apportioned among all corresponding proteins, and a minimal protein list sufficient to account for the observed peptide assignments is derived using the expectation-maximization algorithm. Using peptide assignments to spectra generated from a sample of 18 purified proteins, as well as complex H. influenzae and Halobacterium samples, the model is shown to produce probabilities that are accurate and have high power to discriminate correct from incorrect protein identifications. This method allows filtering of large-scale proteomics data sets with predictable sensitivity and false positive identification error rates. Fast, consistent, and transparent, it provides a standard for publishing large-scale protein identification data sets in the literature and for comparing the results obtained from different experiments.