Observations of dynamic strain aging in polycrystalline NiAl

Dynamic strain aging has been investigated at temperatures between 77 and 1100 K in eight polycrystalline NiAl alloys. The 0.2% offset yield stress and work hardening rates for these alloys generally decreased with increasing temperature. However, local plateaus or maxima were observed in conventional purity and carbon doped alloys at intermediate temperatures (600–900 K). This anomalous behavior was not observed in low interstitial high-purity, nitrogen doped, or in titanium doped materials. Low or negative strain rate sensitivities (SRS) were also observed in all eight alloys in this intermediate temperature range. Coincident with the occurrence of negative SRS was the occurrence of serrated flow in conventional purity alloys containing high concentrations of Si in addition to C. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main species causing strain aging in polycrystalline NiAl is C but indicate that residual Si impurities can enhance the strain aging effect.     

Accuracy of subsampling mill for granular materials

A subsampling mill was constructed with 19 subsample spouts similar to the 1 or 2 subsample spouts on the conventional subsampling mills. Samples of peanuts, each of which contained 1 kernel made radioactive by neutron activation, were comminuted in the mill. For treatment M the discharge from each spout was kept separate. For treatment R, the discharge from all 19 spouts was blended together in a twin-shelled blender and subdivided with a riffle divider into 16 subsamples which averaged the same weight as the M subsamples. Radioactivity counts/gram of each subsample were measured. Eleven samples were comminuted for each treatment which produced a total of 209 M samples and 176 R samples. An analysis of variance on the pooled data from each treatment showed a mean square error of 1318.3 for the M treatment and 1278.6 for the R treatment. The null hypothesis that the mean square errors for the two treatments are equal was not rejected by the F test (P=0.421).     

Thin-Disk Test for Adhesion-Bond Strength in Solvent Environments

A number of the popular tests for adhesive strength are difficult to apply to the study of adhesion under solvent environments. Complex applications, in which two different substrate materials need to be bonded and for which the substrates are thin sections, can be particularly difficult to study. The thin-disk test described here uses a thin annular disk of adhesive to bond two dissimilar materials while exposing the bond line to a circulating solvent. The new test was evaluated for a typical inkjet print-head application using surrogates for inkjet water-based inks. The joint is an epoxy adhesive joining a silicon wafer to a thermoplastic part (Rynite®), in which the silicon substrate, the thermoplastic, or the various adhesive interfaces might fail.

A conventional lap-shear test was compared with the thin-disk test for samples exposed to four different solvent systems plus water at two different temperatures. Lap-shear test failures occurred mostly in the thermoplastic part, with the exception of two samples exposed to the most aggressive solvents at high temperature. By contrast, thin-disk test failures occurred either in the silicon substrate or in the thermoplastic–adhesive interface. The thin-disk failure strengths at the thermoplastic–adhesive interface correlated with the equilibrium solvent swelling that could occur in the adhesive under the test conditions. This method could be adapted to other mixed-substrate bonding systems and would be particularly appropriate for thin section solids and thin adhesive layers.     

The North Carolina High School Athletic Injury Study: design and methodology

PURPOSE: Organized interscholastic athletics are an integral part of the educational program at almost every school level. With this growing popularity of sports and their inclusion in more public school programs, it becomes increasingly apparent that additional consideration must be given to the injury problem associated with sport. The North Carolina High School Athletic Injury Study (NCHSAIS) was undertaken to identify patterns of injury among male and female athletes in North Carolina high schools participating in any of 12 sports. Specific aims are to measure the incidence, severity and etiology of injuries; to determine the relationship of demographic factors and protective equipment, exposure to play, and school characteristics to injuries; to study the relationship of coaches' training and experience to injury occurrence; and to compare the incidence and severity of injury among female and male athletes in the same or comparable sports. METHODS: A two-stage cluster sample of 100 high schools in North Carolina was selected for this 4-yr prospective study. RESULTS: Participation by the initial sample or a random replacement was achieved for 91 of the 100 schools. Nonresponse occurred at multiple levels of the sample for this study, and the weekly participation form posed the greatest respondent burden. CONCLUSIONS: The NCHSIAS offers a successful methodology for addressing sports injuries. In this paper we describe the design, methodology, and implementation issues that emerge in conducting a large scale epidemiological study in a population of high school athletes.     

Genitourinary anomalies in the CHARGE association

PURPOSE: We identified the incidence and types of genital and urinary anomalies, and established a plan for evaluating the urinary system in the CHARGE association. MATERIALS AND METHODS: We retrospectively reviewed the charts of 32 patients in whom the CHARGE association was diagnosed. RESULTS: Of the 32 patients identified 22 (69%) had genitourinary abnormalities. Genital anomalies, including micropenis, penile agenesis, hypospadias, chordee, cryptorchidism, a bifid scrotum, atresia of the uterus, cervix and vagina, and hypoplastic labia majora, labia minora and clitoris, were present in 18 patients (56%). Of the 24 patients who underwent renal ultrasound 10 (42%) were diagnosed with urinary tract anomalies including a solitary kidney, hydronephrosis, renal hypoplasia and duplex kidneys. Further evaluation revealed vesicoureteral reflux, neurogenic bladder secondary to spinal dysraphism, nephrolithiasis, ureteropelvic junction obstruction and a nonfunctioning upper pole in both duplex kidneys. CONCLUSIONS: There is a high incidence of genitourinary anomalies in the CHARGE association. Because of this high incidence of anomalies, patients with this condition should undergo a careful genitourinary evaluation, including renal and bladder ultrasound, and voiding cystourethrography screening.