Case study training for seeing school through adolescents' eyes

The first of two years of training in case study activities, adapted from the program originally developed by Fritz Redl, Daniel A. Prescott, and others at the Universities of Chicago and Maryland in the 1940s, is described. Excerpts from the case study of a 16-year-old female provide examples of activities, such as: (1) identifying recurring patterns of behavior, (2) selecting a pattern of behavior for analysis by the multiple hypotheses method, and (3) summarizing the case study record. The significance of this process is that high school personnel can learn to see what adolescents are up against in and out of school.     

Molecular events including p53 and k-ras alterations in the in vitro progression of a human colorectal adenoma cell line to an adenocarcinoma

The aim of the current study was to identify genetic abnormalities in human colorectal adenoma and carcinoma derived cell lines, and to determine whether the genetic changes which occur in vitro are relevant to the in vivo situation. Loss of 1p(33-35) region was shown to be the most common chromosome 1 abnormality and loss of heterozygosity (LOH) of the DCC gene and/or adjacent sequences was detected in all adenoma derived cells as well as the carcinoma cell lines. The level of p53 protein was also investigated as increased cellular p53 protein had previously been associated with mutation of the p53 gene. A further aim was to investigate genetic changes in our in vitro model of tumour progression, where the adenoma derived PC/AA cell line has previously been converted in vitro to two distinct tumorigenic phenotypes, producing either an adenocarcinoma or a mucinous carcinoma in athymic nude mice. Progression to the adenocarcinoma phenotype was shown to involve a specific chromosome 1 rearrangement, loss of both normal copies of chromosome 18 (although DCC gene sequences were retained), loss of the remaining wild type allele of k-ras resulting in homozygosity for the k-ras codon 12 mutation and increased cellular p53 protein as detected by SDS-PAGE Western blotting. The increase in p53 protein was shown not to be due to the acquisition of a mutation in the p53 gene. Interestingly, progression of the adenoma derived PC/AA cell line to the mucinous malignant phenotype did not involve any of these molecular rearrangements, suggesting that different genetically distinct pathways are involved in colorectal carcinogenesis. These studies show that the genetic changes in our in vitro model of human colorectal tumour progression are similar to those observed in in vivo studies.     

Models for binary and multicomponent solutions a new prospectus

We have examined in detail the principal series which have been used to represent the thermodynamcs of binary systems and have concluded that in every case the higher members suffer in some important way. The best choice for a third member is based upon a series expansion of the statistical mechanical treatment of Guggenheim. An entirely new form for the fourth term is suggested for accommodating the temperature dependent part of the asymmetry.We have also determined what constitutes proper treatment of the binary terms in representing higher order systems. Not all the previous treatments have been correct in this respect.     

Input VSWR of profiled E-plane tapers

An efficient method for determining the input VSWR characteristics of waveguide E-plane tapers is presented. The taper profile is approximated by radial waveguide sections and the junction wave transfer matrices are derived applying field matching. The input reflection coefficient is easily determined using these matrices. Results computed using the present method are compared with some measured and calculated results in the literature and very good agreement is obtained.     

Roughness-Induced Crack Closure: An Explanation for Microstructurally Sensitive Fatigue Crack Growth

The concept of roughness-induced crack closure is utilized to explain the role of prior austenite grain size and pearlite interlamellar spacing on near-threshold fatigue crack propagation in fully pearlitic eutectoid steel tested at low and high stress ratio in lab air and purified helium. It is shown that at low load ratios, near-threshold growth rates are significantly reduced for coarse-grained microstructures, compared to fine-grained at constant yield strength, due to roughness-induced crack closure. Using roughness-profile microscopy, it was found that fracture surface roughness near threshold scaled with grain size and inversely with yield strength, macroscopic roughnesses at threshold being considerably larger than the conventionally calculated cyclic crack tip opening displacement. Auger analysis of near-threshold corrosion products showed it to be iron oxide; the oxide thickness was seen to be decreased by increased stress ratio. The significance of this model to near-threshold fatigue crack growth behavior, in terms of load ratio, microstructure, and environment is discussed. Formerly with Carnegie-Mellon University.     

A STEM/X-ray microanalytical study of the equilibrium segregation of bismuth in copper

Combined scanning transmission electron microscopy (STEM) and X-ray microanalysis have been used to detect the equilibrium segregation of bismuth to grain boundaries in copper. Quantification of the X-ray data gives grain boundary bismuth concentrations close to those reported previously by Auger electron spectroscopy (AES). Samples tempered at low temperatures (773,873 K) had detectable bismuth concentrations at more boundaries than those samples tempered at high temperature (1073 K). There is evidence that the degree of segregation varies strongly from boundary to boundary.     

Excess-noise and receiver sensitivity measurements of In0.53Ga0.47As/InP avalanche photodiodes

We report the results of excess-noise and normalised receiver sensitivity measurements for In0.53Ga0.47As/InP avalanche photodiodes for use in the ?=0.95 ?m to 1.65 ?m spectral region. The excess-noise measurements are consistent with a hole-to-electron ionisation rate ratio in InP of ~ 0.4. The receiver sensitivity, measured at 45 Mbit/s and 10?9 bit-error-rate, was ?53.2 dBm at a gain of 20 assuming unity quantum efficiency for the detector. This sensitivity is the highest reported at ?=1.3 ?m and represents an improvement over a PIN detector using the same amplifier.