Empirical models based on free-modulus magnitude estimation of perceived presence in virtual environments

A series of 3 studies was conducted to test free-modulus magnitude estimation as a measure of perceived presence in virtual environments (VEs) and to model the first- and second-order effects of 11 VE system parameters on perceived presence across 5 subtasks. Sequential experimentation techniques were used to build 4 empirical models using polynomial regression. An integrated empirical model of data combined across 2 experiments demonstrated that all significant factors had a positive effect on perceived presence. Three of these parameters--field of view, sound, and head tracking--had almost 3 times as much influence on presence than the other 4 significant parameters, which were visual display resolution, texture mapping, stereopsis, and scene update rate. Sequential experimentation was an efficient tool for building empirical models of perceived presence, but the subjective nature of this phenomenon and individual differences made data bridging across sequential studies problematic. It was concluded that magnitude estimation is a useful measure of perceived presence, and the resulting polynomial regression models can be used to facilitate VE system design decisions. This research has broad application in the selection and design of VE system components and overall design of VE systems.     

Effects of combined treatment with recombinant bovine somatotropin and immunization with live oocysts on performance of broiler chicks raised in coccidia-seeded floor pens

In our laboratory, preliminary studies have indicated that recombinant bovine somatotropin (rbST) can stimulate protective immunity against coccidia infection. A floor pen trial on coccidia-seeded litter was run to further test its activity as an adjuvant during immunization of chicks with a live oocyst vaccine. Five hundred day-old male broiler strain chicks were randomly assigned to five experimental Treatments: 1, medicated controls; 2, unimmunized, not treated with rbST; 3, unimmunized, rbST-treated; 4, immunized, not treated with rbST; 5, immunized, rbST-treated. Each treatment consisted of four pens of 25 chicks each. At the end of the growout period (7 wk), the chicks in Treatment 1 (medicated controls) had the highest mean BW, but mean BW of chickens in Treatment 3 (rbST treatment only) were not significantly less. On the other hand, the mean weights of chicks in Treatments 4 (immunized only) and 5 (immunized plus rbST) were significantly reduced, and not different from those of the untreated chickens (Treatment 2). However, when challenged at 3 wk, the chicks in Treatment 5 had a mean combined total lesion score that was significantly lower than that from Treatment 3, indicating that they had developed a higher degree of specific immunity, but of the expense of weight gain. The results suggest that rbST has a potential for use as an adjuvant with live oocyst vaccination, but that the ratio between rbST dose and numbers of oocysts in the live vaccine needs to be carefully controlled.     

Prognostic factors in the acute lymphoid and myeloid leukemias of infants

The age boundaries and prognostic factors that define the infant leukemias are still controversial. We therefore analyzed event-free survival according to age group in 96 children treated for acute lymphoblastic leukemia (ALL) and 51 treated for acute myeloid leukemia (AML) before the age of 2 years. The study population was registered in consecutive institutional trials of multiagent chemotherapy conducted between 1980 and 1994. Among infants with ALL, event-free survival was significantly poorer in the 0- to 6-month-old group than in patients treated between 6 and 12 months of age (P = 0.03), whose outcome was in turn inferior to that in the 12- to 18-month and 18- to 24-month age groups (P = 0.013). Leukemic cells from ALL patients younger than 12 months had a significantly higher frequency of 11q23/MLL abnormalities, as well as better growth in stromal cell culture, compared to lymphoblasts from the older groups (P < 0.01). The only independent predictor of adverse prognosis among infants diagnosed with ALL before age 12 months was the presence of an 11q23/MLL rearrangement (P = 0.03). These findings contrast sharply with results for the AML cohort, whose event-free survival did not vary significantly by age group (P = 0.58). Male sex (P = 0.01) and leukocyte count > or = 50 x 10(9/l) (P = 0.04), but not 11q23 abnormalities, were independently associated with a poorer outcome for children with AML younger than 12 months at diagnosis. Thus, in very young children with ALL (but not AML), the rearrangement status of the 11q23/MLL region supersedes age group as a determinant of treatment outcome.     

Equine monocyte-derived macrophage cultures and their applications for infectivity and neutralization studies of equine infectious anemia virus

Equine infectious anemia virus (EIAV) has been shown to infect cells of monocyte/macrophage lineage. These primary cells are intrinsically difficult to obtain, to purify and to culture in vitro for extended periods of time. As a result, most in vitro studies concerning this lentivirus make use of primary equine fibroblasts or transformed canine or feline cell lines. We describe methods that yield reproducibly pure cultures of equine blood monocytes from peripheral blood mononuclear cells. The in vitro differentiation of these cells into mature equine macrophage was verified using various cytochemical staining methods. The equine monocyte-derived macrophage (MDM) cultures were found to replicate cell-adapted and field strains of EIAV more efficiently than cultures of fully differentiated equine splenic macrophage. Having established reproducible and fully differentiated cultures of equine macrophage, in vitro assays of virus infectivity and serum neutralization were developed using the in vivo target cell of EIAV. These procedures, while developed for the EIAV system, should be equally useful for in vitro cultures of other macrophage-tropic pathogens of horses.     

Recall by expert medical practitioners and novices as a record of processing attention.

Using recall of clinical protocols as a measure of expertise in medicine has yielded disappointingly small effects. Experiments using recall of clinical laboratory data are presented to provide an explanation. In one experiment, subjects either deliberately memorized or first diagnosed and then were incidentally asked for memory. With incidental instructions, experts recalled over twice as much data as did students, but with memorization instructions, student performance approximated that of experts. Experts also showed a large advantage over students in incidental recall of data that were not relevant to the problem solution. These results suggest that expert processing in this "discrete, independent inputs" domain requires effortful analysis with minimal reliance on default values, rather than relatively effortless pattern perception reported in highly visual areas of expertise. For this area, intentional memory is a misleading measure of expertise. However, incidental memory is a valuable measure of processing during diagnosis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Double mutagenesis of a positive charge cluster in the ligand-binding site of the ferric enterobactin receptor, FepA

Siderophores and colicins enter bacterial cells through TonB-dependent outer membrane proteins. Using site-directed substitution mutagenesis, we studied ligand recognition by a prototypic Escherichia coli siderophore receptor, FepA, that binds the iron chelate ferric enterobactin and colicins B and D. These genetic experiments identified a common binding site for two of the three ligands, containing multiple positive charges, within cell surface residues of FepA. Elimination of single residues in this region did not impair the adsorption or transport of ferric enterobactin, but double mutagenesis in the charge cluster identified amino acids (Arg-286 and Arg-316) that participate in siderophore binding and function in FepA-mediated killing by colicins B and D. Ferric enterobactin binding, furthermore, prevented covalent modification of FepA within this domain by either a fluorescent probe or an arginine-specific reagent, corroborating the involvement of this site in ligand recognition. These results identify, for the first time, residues in a TonB-dependent outer membrane protein that participate in ligand binding. They also explain the competition between ferric enterobactin and the colicins on the bacterial cell surface: all three ligands interact with the same arginine residues within FepA during their penetration through the outer membrane.     

A meta-analytic investigation of cognitive ability in employment interview evaluations: Moderating characteristics and implications for incremental validity.

The purpose of this investigation was to explore the extent to which employment interview evaluations reflect cognitive ability. A meta-analysis of 49 studies found a corrected mean correlation of .40 between interview ratings and ability test scores, suggesting that on average about 16% of the variance in interview constructs represents cognitive ability. Analysis of several design characteristics that could moderate the relationship between interview scores and ability suggested that (a) the correlation with ability tends to decrease as the level of structure increases; (b) the type of questions asked can have considerable influence on the magnitude of the correlation with ability; (c) the reflection of ability in the ratings tends to increase when ability test scores are made available to interviewers; and (d) the correlation with ability generally is higher for low-complexity jobs. Moreover, results suggest that interview ratings that correlate higher with cognitive ability tend to be better predictors of job performance. Implications for incremental validity are discussed, and recommendations for selection strategies are outlined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)