The Composition Of Normative Groups And Diagnostic Decision Making: Shooting Ourselves In The Foot

Purpose: The normative group of a norm-referenced test is intended to provide a basis for interpreting test scores. However, the composition of the normative group may facilitate or impede different types of diagnostic interpretations. This article considers who should be included in a normative sample and how-this decision must be made relative to the purpose for which a test is intended. Method: The way in which the composition of the normative sample affects classification accuracy is demonstrated through a test review followed by a simulation study. The test review examined the descriptions of the normative group in a sample of 32 child language tests. The mean performance reported in the test manual for the sample of language impaired children was compared with the sample's norms, which either included or excluded children with language impairment. For the simulation, 2 contrasting normative procedures were modeled. The first procedure included a mixed group of representative cases (language impaired and normal cases). The second procedure excluded the language impaired cases from the norm. Results: Both the data obtained from test manuals and the data simulation based on population characteristics supported our claim that use of mixed normative groups decreases the ability to accurately identify language impairment. Tests that used mixed norms had smaller differences between the normative and language impaired groups in comparison with tests that excluded children with impairment within the normative sample. The simulation demonstrated mixed norms that lowered the group mean and increased the standard deviation, resulting in decreased classification accuracy. Conclusions: When the purpose of testing is to identify children with impaired language skills, including children with language impairment in the normative sample can reduce identification accuracy.Communication Sciences and Disorder

Landscape and smaller-scale effects of lugworm (Arenicola marina) deposit feeding on benthic bacterial assemblages

Objectives of this study were to (1) determine whether feeding by the lugworm, Arenicola marina, reduces abundance or alters composition of sedimentary bacterial assemblages, (2) examine recovery of “disturbed” patches of egesta, and (3) test for effects on bacterial abundance, diversity and composition at spatial scales larger than individual fecal mounds. Field comparative studies in Lubec, Maine, were conducted to test for the effects of ingestion, and manipulative experiments were done to assess rates and mechanisms of recolonization of egesta. Bacterial assemblage attributes were followed using epifluorescence microscopy and DGGE analysis of 16S rDNA. Next we examined landscape-scale effects using field addition experiments to manipulate lugworm density (0, 5, and 15 worms m-2). Findings indicate that (1) lugworm feeding qualitatively and quantitatively alters bacterial assemblages, (2) recovery in these biotically disturbed sediments is minimal during a single tidal emersion (∼4.5 h), (3) the small-scale patchiness caused by animal feeding is homogenized by sediment movement following tidal immersion, and (4) landscape-scale effects appear to be small, e.g. with respect to bacterial abundance and “species” richness. One notable landscape-scale effect, however, was a consistent and stable increase in relative abundance of a few specific bacterial phylotypes in high lugworm density plots

Elementary zeros of lie algebras of vector fields

WE CONSIDER a finite dimensional Lie algebra ℒ of ϐk (k ≥ 1) differentiable vector fields on a finite dimensional manifold M. A point p ∈ M is a zero for ℒ if X(p) = 0 for very X∈ ℒ. For the classical special case of (the Lie algebra spanned by) a single vector field X, the zero p is said to be elementary (or simple) if the derivative at p of the principal part of X is invertible. The equivalent coordinate-free formulation of this definition is that the vector field, regarded as a map X:M→TM, be transverse to the zero section at p [1]. From this point of view it can be seen that elementary zeros are stable, i.e. they persist under perturbation of X. In addition, such zeros can bc assipncd an index of + I or - I and, when all zeros arc elementary and M is compact, the vector field satisfies the Poincare-Hopf index formula. It is reasonable to ask how these notions should be formulated for zeros of an arbitrary Lie algebra. The correct definition turns out to involve the first Lit algebra cohomology of the linear part of ℒ at p. That the first cohomology is relevant is suggested by results of Hirsch [5, 6] and Stowe [14], which relate stability of stationary points of group actions with the group cohomology of the linear action, and the relationship between the cohomologies of Lit groups and Lie algebras [15]. Section I reviews basic results concerning cohomology of Lie algebras. Section 2 applies these results to the definition and description of elementary zeros for a Lie algebra of vector fields on a manifold. Section 3 contains examples and a result, concerning commuting vector fields on a compact surface, which illustrate limitations to defining an index for a zero of a Lie algebra of vector fields

Alien Registration- Plante, Marie J. (Caribou, Aroostook County)

https://digitalmaine.com/alien_docs/25994/thumbnail.jp

Transition to J-STD-001DS: A Guide for Implementation. NASA Workmanship Standards Program

No abstract availabl

Seasonal Variability in the Bacteriolytic Capacity of the Deposit Feeder Arenicola Marina: Environmental Correlates

Although deposit-feeding macrofauna consume and digest sedimentary bacteria, it is unclear whether feeding rates and digestion efficiencies are high enough to significantly impact the composition and abundance of bacteria in marine sediments. It is likely that both feeding rates and efficiency of digestion vary markedly through space and time. We used a turbidimetric assay to compare the rate of bacteriolysis by digestive fluids collected seasonally from the deposit-feeding polychaete Arenicola marina. Under standardized, experimental conditions, bacteriolytic rates represent concentrations of lytic agents. This concentration was found to vary significantly throughout the year (p = 0.001), showing greater than a 2x range. Lytic agent concentration was positively correlated with bioavailable amino acid concentrations in the surface sediment (r = 0.85, p = 0.03) but showed no apparent relationship to other proxies for food resources (e.g, chl a), sediment temperature, or gut throughput time. In vitro, temperature has been shown to have a strong positive influence on bacteriolytic rate. Temperature has no influence, however, on the in situ concentration of lytic agent in gut fluids, thus it appears that compensation for this temperature dependence is unimportant. These findings, combined with previous kinetics studies with A. marina gut fluids, predict that the quantitative influence of deposit feeding on the microbial ecology of sediments will exhibit clear seasonal variation

Distribution and Efficiency of Bacteriolysis in the Gut of Arenicola Marina and Three Additional Deposit Feeders

A simple technique was developed to measure the bacteriolytic activities of the digestive fluids of the deposit-feeding polychaete Arenicola marina. Lysis of a cultured environmental isolate, incubated with extracts of gut luminal contents, was monitored spectrophotometrically. Concurrent direct counts were used to verify cell lysis. The ability of extracts from 8 longitudinal sections of the gut to lyse the bacterium was monitored. The digestive ceca, anterior stomach, and posterior stomach regions exhibited high lytic activities, whereas bacteriolytic activities in all other regions of the gut were negligible. Similarly, extracts of surface sediments and fecal castings showed negligible lytic capabilities. The sharply limited distribution of lytic activity implicates the ceca as the source of bacteriolytic agent and suggests a true plug-flow system, with little axial mixing. Questions regarding the fate of lytic agents, which disappear abruptly posterior to the stomach, remain unanswered. Localization of lysis in the gut coupled with estimates of gut residence time permit the calculation that ingested bacteria are exposed to strong lytic activity for approximately 20 min. Incubation of in situ sediment samples with gut fluids corroborates the distributional findings of the in vitro work although the efficiency of lysis is much reduced, possibly due to exopolymer capsules and slimes of natural sedimentary bacteria. Cross-phyletic comparisons of bacteriolytic activities reveal both qualitative and quantitative differences. Much less demarcation of lytic activity is observed in the guts of a holothuroid (Caudina arenata) and a hemichordate (Stereobalanus canadensis), with a pattern more similar to that of A. marina observed in another polychaete, Amphitrite johnstoni. Quantitatively, the polychaetes showed higher levels of activity with rates in A. marina exceeding those of the hemichordate and holothuroid by more than 10-fold

Risk of asthmatic episodes in children exposed to sulfur dioxide stack emissions from a refinery point source in Montreal, Canada.

BACKGROUND: Little is known about the respiratory effects of short-term exposures to petroleum refinery emissions in young children. This study is an extension of an ecologic study that found an increased rate of hospitalizations for respiratory conditions among children living near petroleum refineries in Montreal (Canada). METHODS: We used a time-stratified case-crossover design to assess the risk of asthma episodes in relation to short-term variations in sulfur dioxide levels among children 2-4 years of age living within 0.5-7.5 km of the refinery stacks. Health data used to measure asthma episodes included emergency department (ED) visits and hospital admissions from 1996 to 2004. We estimated daily levels of SO2 at the residence of children using a) two fixed-site SO2 monitors located near the refineries and b) the AERMOD (American Meteorological Society/Environmental Protection Agency Regulatory Model) atmospheric dispersion model. We used conditional logistic regression to estimate odds ratios associated with an increase in the interquartile range of daily SO2 mean and peak exposures (31.2 ppb for AERMOD peaks). We adjusted for temperature, relative humidity, and regional/urban background air pollutant levels. RESULTS: The risks of asthma ED visits and hospitalizations were more pronounced for same-day (lag 0) SO2 peak levels than for mean levels on the same day, or for other lags: the adjusted odds ratios estimated for same-day SO2 peak levels from AERMOD were 1.10 [95% confidence interval (CI), 1.00-1.22] and 1.42 (95% CI, 1.10-1.82), over the interquartile range, for ED visits and hospital admissions, respectively. CONCLUSIONS: Short-term episodes of increased SO2 exposures from refinery stack emissions were associated with a higher number of asthma episodes in nearby children

Unilateral deafness in children affects development of multi-modal modulation and default mode networks

Monaural auditory input due to congenital or acquired unilateral hearing loss (UHL) may have neurobiological effects on the developing brain. Using functional magnetic resonance imaging (fMRI), we investigated the effect of UHL on the development of functional brain networks used for cross-modal processing. Children ages 7–12 with moderate or greater unilateral hearing loss of sensorineural origin (UHL-SN; N = 21) and normal-hearing controls (N = 23) performed an fMRI-compatible adaptation of the Token Test involving listening to a sentence such as “touched the small green circle and the large blue square” and simultaneously viewing an arrow touching colored shapes on a video. Children with right or severe-to-profound UHL-SN displayed smaller activation in a region encompassing the right inferior temporal, middle temporal, and middle occipital gyrus (BA 19/37/39), evidencing differences due to monaural hearing in cross-modal modulation of the visual processing pathway. Children with UHL-SN displayed increased activation in the left posterior superior temporal gyrus, likely the result either of more effortful low-level processing of auditory stimuli or differences in cross-modal modulation of the auditory processing pathway. Additionally, children with UHL-SN displayed reduced deactivation of anterior and posterior regions of the default mode network. Results suggest that monaural hearing affects the development of brain networks related to cross-modal sensory processing and the regulation of the default network during processing of spoken language