Particle image velocimetry in molten plastic

Injection molding is a standard manufacturing process for plastic parts. The most important process step, mold filling, involves unsteady nonisothermal flow of a non‐Newtonian molten plastic. Mold‐filling flow largely determines molecular orientation within the final part and thereby influences final part properties. This article describes techniques for successfully applying particle image velocimetry (PIV) to molten plastic flow during injection molding. The primary experimental challenges include the following: engineering optical access to the molten plastic flow at elevated temperatures (230–245°C) and pressures (～20 MPa), finding particles that survive the thermal‐mechanical environment that melts the plastic, and developing experimental and data‐reduction techniques that allow multiple imperfect planar PIV measurements to be combined. Here, a custom optical‐access mold allowed mold center‐plane PIV to be performed in molten polystyrene. Simple statistical assessments of the velocimetry data and scaled residuals of the continuity equation suggest that the PIV can be conducted in molten plastics with an uncertainty of ±2%. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

The effect of defects on structural failure: A two-criteria approach

The two-criteria approach to the study of defects in structures assumes that failure occurs when the applied load reaches the lower of either a load to cause brittle failure in accordance with the theories of linear elastic fracture mechanics or a collapse load dependent on the ultimate stress of the material and the structural geometry. This simple approach is described and compared with previously published experimental results for various geometries and materials. The simplicity of this method of defect analysis lies in the fact that each criterion is sufficiently well understood to permit scaling and geometry changes to be accommodated readily.It becomes apparent that a sizeable transition region exists between the two criteria but this can be described in an expression relating the criteria. This expression adequately predicts the behaviour of cracked structures of both simple and complex geometry. A design curve for defect assessment is proposed for which it is unnecessary to consider the transition region.     

Strategic planning for video-assisted thoracic surgery

As with any operative procedure, careful preoperative and intraoperative planning are vital to achieving a safe and effective video-assisted thoracic surgical intervention. We outline some of our basic strategies for enhancing the success of this approach in the management of thoracic surgical problems.     

Radiation effects on a lithium tantalate optical waveguide structure

The effects of X- and gamma radiation on an optical waveguide, fabricated in lithium tantalate, are described and discussed. The measurements indicate that quite severe radiation environments would be necessary to produce significant problems with LiTaO/sub 3/ devices. However, the level of the radiation effects may depend, like those in semiconductor devices and fibre optics, on the details of the composition of the material and the constructional methods employed. Because there appear to be effects due to a radiation-induced, internal, electric field, there will be a dependence on the cut of the crystal used.<>     

Characterization of a thermally induced irreversible conformational transition of amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase in enantioseparation of dihydropyrimidinone acid by quasi-equilibrated liquid chromatography and solid-state NMR

A thermally induced irreversible conformational transition of amylose tris(3,5-dimethylphenylcarbamate) (i.e., Chiralpak AD) chiral stationary phase (CSP) in the enantioseparation of dihydropyrimidinone (DHP) acid racemate was studied for the first time by quasi-equilibrated liquid chromatography with cyclic van't Hoff and step temperature programs and solid-state ((13)C CPMAS and (19)F MAS) NMR using ethanol and trifluoroacetic acid (TFA)-modified n-hexane as the mobile phase. The conformational transition was controlled by a single kinetically driven process, as evidenced by the chromatographic studies. Solid-state NMR was used to study the effect of the temperature on the conformational change of the solvated phase (with or without the DHP acid enantiomers and TFA) and provided some viable structural information about the CSP and the enantiomers.     

Correlation of patient and staff doses in interventional cardiology

The purpose of this study was to measure staff radiation doses in representative institutions of five European countries performing coronary angiographies (CA) and percutaneous transluminal coronary angioplasties (PTCA), as well as to investigate any correlation with patient doses. Patient doses were recorded in terms of dose-area product (DAP). Staff doses were measured by thermoluminescence dosemeters placed on the operator's left shoulder and left foot. Radiation protection measures were also recorded. Third quartile shoulder and foot doses were 90 and 66 microSv in CA, and 157 and 173 microSv in PTCA, respectively. Shoulder dose was poorly correlated with DAP in CA (R2 = 0.29) and only moderately correlated in PTCA (R2 = 0.69). DAP and foot dose correlation was poor both in CA (R2 = 0.16) and in PTCA (R2 = 0.02). Protective measures taken by staff varied between countries, which may explain the poor correlation of patient and staff radiation doses.     

Zebrafish retinal mutants

BACKGROUND: Development of coronary artery disease in cardiac allograft recipients is the major cause of graft failure after the first year of transplantation. Unfortunately, there is no noninvasive method of identifying patients at greatest risk of developing this disease. We have asked whether serum concentrations of cardiac troponin-T predict development of coronary artery disease. METHODS: Annual coronary angiograms, serial endomyocardial biopsies, and serum cardiac troponin-T concentrations were obtained from 68 cardiac transplant patients who were followed for 68.8+/-11.9 months after surgery. Troponin-T concentrations were measured by using an enzyme-linked immunosorbent assay, and biopsies were assessed histologically for rejection grades and immunohistochemically for cellular infiltrates, arteriolar endothelial activation, fibrin deposits, and vascular fibrinolytic and anticoagulant components. RESULTS: Troponin-T values did not associate with demographic, clinical, or laboratory findings, but they significantly associated with arteriolar endothelial activation (P<0.001), fibrin deposition (P<0.001), depletion of vascular fibrinolytic (P=0.007) and anticoagulant components (P=0.02), and infiltration of macrophages (P <0.001) but not T lymphocytes (P=0.36). Troponin-T concentrations also significantly associated with future development of coronary artery disease (P<0.001). Patients with persistent troponin-T values of 0.10 ng/ml or greater were found to develop the disease within 8.7+/-2.1 months, whereas patients who had initial troponin-T values of 0.10 ng/ml or greater and subsequently fell and remained below 0.10 ng/ml did not develop coronary artery disease in 40 months. CONCLUSIONS: Troponin-T concentrations significantly associated with macrophage infiltrates, microvascular fibrin deposits, arteriolar endothelial activation, depletion of vascular fibrinolytic and anticoagulant components, and the future development of coronary artery disease. The troponin-T assay is an outpatient procedure performed on small amounts of blood at little cost, risk, or inconvenience, and it appears to be the first biochemical predictor of transplant-induced coronary artery disease.     

Collapse of stiffened box-girder diaphragms

The results of two large-scale tests on stiffened load bearing box-girder diaphragms which were designed to collapse in different modes are described in detail. A comparison is made between the experimental behaviour up to collapse and that predicted by a recently developed large-deflection elasto-plastic finite element analysis. It is shown that it is now possible to predict accurately the complex interaction between stiffeners and plate panels in such a diaphragm. Attention is drawn to the important effect the stiffness of the flanges and webs of the box has on the overall response and ultimate load of the diaphragm. It is concluded that the powerful computer programs which are now available have been validated by test results and provide suitable bases on which sound design rules may be formulated. Comments on the new British design rules for diaphragms are made in the light of the results of this study.