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PubMed2005

The effects of ignored seabed variability in geoacoustic inversion.

Geoacoustic inversion using a matched-field inversion algorithm is a well-established technique for estimating the geoacoustic parameters of the seabed. This paper demonstrates how parameter estimation can be affected by unknown or wishfully ignored random range dependence of the true environment when the inversion model is--for practicality--assumed to be range independent. Simulations with controlled statistics were carried out using a simple shallow water model: an isospeed water column over a homogeneous elastic halfspace. The inversion parameters included water depth, compressional speed in the seabed, seabed density, and compressional wave attenuation. On average the environment is range independent: some parameters are constant while other parameters are random with range-independent means and variances. A Parabolic Equation underwater acoustic propagation model is used to calculate the simulated data fields for the range-dependent environment as well as to calculate the model fields for the range-independent inversion model. The Adaptive Simplex Simulated Annealing inversion algorithm is used to estimate the best-fit solution. It is found that ignoring the variability of even a single geoacoustic parameter leads to significant and correlated uncertainty (bias and variance) in the estimation of all inverted parameters. Results are presented for range variation of compressional sound speed and water depth.

Journal Article↗
PubMed2005

Long-term outcome for people with severe intellectual disabilities: impact of social impairment.

Results from a 25-year follow-up study of the Camberwell Cohort (L. Wing & Gould, 1978, 1979) were presented. Ninety-one people, ranging in age from 27 to 41 years, were traced, and an outcome measure was developed incorporating independent functioning, residential placement, employment, and quality of life. Outcome was rated as either poor (53%) or fair (43%), with only 3% having a good outcome. Using logistic regression methods, we found that the best predictor of outcome was social impairment, with those who were socially impaired, particularly those in the aloof category, having a poorer outcome. Higher IQ at Time 1 and lower challenging behavior were also predictive of better outcome. An in-depth look at social impairment revealed that social impairment remained stable over time.

Adaptation, Psychological↗
PubMed1995

Anxiety and its control.

First, a discussion is given of the several types of anxiety. Next, a review is given of the non-pharmaceutical methods of managing anxiety. Finally, an in-depth examination is made of the various types of drugs used to treat the different types of anxiety.

Adaptation, Psychological↗
PubMed2005

Effect of placement techniques on the marginal adaptation of Class V composite restorations.

STATEMENT OF THE PROBLEM: Several techniques are proposed for the restoration of Class V cavities but there is no agreement in the literature as to which technique is more effective. PURPOSE: To evaluate the effect of different techniques of composite increment placement on the marginal adaptation of Class V restorations. METHODS AND MATERIALS: Twenty-four human molars were selected and prepared with standardized saucer-shaped cavity dimensions of 3.0 mm (occlusal-gingival), 2.0 mm (mesial-distal), and 2.0 mm (depth). The margins are in reference to the cemento-enamel junction with 1.5 mm being located on enamel and 1.5 mm on dentin. The cavities were randomly assigned into three groups (n=8) and restored with composites as follows: Group 1, the occlusal increment was placed and cured first followed by the gingival increment; Group 2, the gingival increment was placed and cured first followed by the occlusal increment; and Group 3, the cavities were restored with one bulk increment. Restorations were immediately finished and stored for 24 h in tap water. Specimens were subjected to thermocycling (1000 cycles, 5 degrees C to 55 degrees C, 30 s dwell time) and immersed in 0.5% basic fuchsin solution for 24 h in room temperature. After rinsing with running water, the restorations were sectioned longitudinally and enamel and dentin margins were evaluated and scored according to the microleakage on a 0-3 scale. Data were subjected to Kruskal-Wallis test at p<0.05. RESULTS: Median of microleakage scores for all evaluated groups was zero. No statistical difference was observed among the three groups both in enamel (p = 0.5929) and dentin (p = 0.3679) margins CONCLUSION: The placement technique did not influence the marginal adaptation of moderate Class V restorations. CLINICAL SIGNIFICANCE: No differences on marginal adaptation were observed when restoring conservative Class V cavities using incremental or bulk placement techniques.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2005

Noncontact goniometry with optical coherence tomography.

OBJECTIVE: To assess the value of noncontact goniometry with optical coherence tomography (OCT) compared with current clinical parameters in the evaluation of the anterior chamber angle (ACA). DESIGN: Prospective observational study of 138 eyes of 109 patients. METHODS: The ACA parameters and angle-opening distance (AOD) were measured with slitlamp-adapted OCT goniometry. The iris and scleral thickness and the iris convexity were assessed with OCT. Both ACA and AOD were compared with the clinical parameters of gonioscopy grade, limbal anterior chamber depth (ACD), ultrasonographic central ACD, and lens-axial length (LAL) ratio. RESULTS: Noncontact goniometry with OCT revealed mean +/- SD values of 28 degrees +/- 16 degrees for the ACA and 381 +/- 234 mum for the AOD. The mean +/- SD iris thickness was 369 +/- 84 mum, and the scleral thickness at the scleral spur was 943 +/- 148 mum. There was a significant correlation (P<.001) with the clinical parameters of gonioscopic grading, limbal ACD, ultrasonographic central ACD, and LAL ratio. The sensitivity and specificity of OCT goniometry to detect an occludable angle were 86% and 95% for ACA and 85% and 90% for AOD, respectively. CONCLUSIONS: Noncontact goniometry with OCT was helpful in evaluating the anterior chamber structures and as a screening modality. Goniometry with OCT could improve the noninvasive clinical assessment and treatment of patients with glaucoma.

Adult↗
PubMed1976

Purification and some properties of NADP+ -specific isocitrate dehydrogenase from an extreme thermophile, Thermus flavus AT-62.

Thermostable NADP+ -specific isocitrate dehydrogenase (EC 1.1.1.42) was purified from crude extract of an extremely thermophilic bacterium Thermus flavus AT-62 through DEAE-cellulose column, acetone fractionation, DEAE-Sephadex A-50 column and isoelectric focussing. The enzyme was purified about 500-folds in its specific activity and purity was found to be about 96%. The enzyme was not inactivated after 60 min at 70 degrees C, but 20 and 80% of the activity were lost after 60 min at 80 degrees and 90 degrees C, respectively. Oxalacetate plus glyoxylate (each 1 nM) demonstrated 75% inhibition of the activity in concerted manner. The degree of the inhibition and the affinity of the enzyme for isocitrate and NADP+ decreased with the rise of temperature, especially above 60 degrees C. The activation energy below and above 60 degrees C were 14,500 and 8,000 cal per mole respectively. In CD spectra negative bands at 210 and 220nm were observed and alpha-helix content was calculated to be about 26%. In the course of heating up to 60 degrees practically no change in CD bands are observed, but above 60 degrees the depth of CD bands decreased gradually and remarkably above 80 degrees C. The effect of temperature on kinetic parameters and secondary structures of the enzyme was discussed in relation to the temperature adaptation of the organism.

Circular Dichroism↗
PubMed1996

The multileaf collimator for fast neutron therapy at Louvain-la-Neuve.

The multileaf collimator of the fast neutron therapy facility at Louvain-la-Neuve is described, as well as some of the physics experiments performed in order to evaluate the attenuation of neutron beams in different materials and thus optimize the composition of the collimator leaves. The multileaf collimator consists of two sets of 22 leaves each, which can be moved independently. They are made of iron and their thickness is 95 cm. Seven borated polyethylene disks are located in the distal part of the leaves in order to absorb more efficiently the low-energy component of the neutron spectrum. The width of the leaves is 1 cm at their distal part. The leaves can move 11 cm outwards and 6 cm inwards from their reference position, and field sizes up to 25.7 x 24.8 cm, as well as irregular field shapes, can be obtained. The inner part of the leaves and their two sides are always focused on the target. The complete multileaf collimator can rotate around the beam axis, from -90 degrees to +90 degrees from the reference position. The width of the penumbra (80-20% isodoses) is 0.64 cm and 1.17 cm at the depth of the maximum buildup and at 10 cm in depth respectively, for a 10 x 10 cm field size. The collimator is adequate for the energy of the p(65)+Be neutron beam of Louvain-la-Neuve and has been adapted to the fixed vertical beam. It has been designed following the original plans of Scanditronix, adjusted and fully assembled at the workshop of the Centre de Recherches du Cyclotron (CRC). Systematic measurements were performed in order to optimize the design and the composition of the leaves. In particular the attenuations of the actual beam and of monoenergetic neutron beams were measured in different materials such as iron and polyethylene. Above (upstream) the multileaf collimator, a fixed pre-collimator (iron thickness 50 cm; section 1 x 1 m) defines a conical aperture aligned on the largest opening of the leaves. It contains the two transmission chambers and a 2 cm thick polyethylene layer used for hardening the beam.

Belgium↗
PubMed2006

The "Kluge-Lüttge Kammer": a preliminary evaluation of an enclosed, Crassulacean acid metabolism (CAM) Mesocosm that allows separation of synchronized and desynchronized contributions of plants to whole system gas exchange.

Crassulacean acid metabolism (CAM) is recognized as a photosynthetic adaptation of plants to arid habitats. This paper presents a proof-of-concept evaluation of partitioning net CO2 exchanges for soil and plants in an arid, exclusively CAM mesocosm, with soil depth and succulent plant biomass approximating that of natural Sonoran Desert ecosystems. We present the first evidence that an enclosed CAM-dominated soil and plant community exposed to a substantial day/night temperature difference (30/20 degrees C), exhibits a diel gas exchange pattern consisting of four consecutive phases with a distinct nocturnal CO2 uptake. These phases were modulated by plant assimilation and soil respiration processes. Day-time stomatal closure of the CAM cycle during phase III was used to eliminate aboveground photosynthetic assimilation and respiration and thereby to estimate belowground plant plus soil respiration. Rapid changes in temperature appeared to synchronize single plant gas exchange but individual plant gas exchange patterns were desynchronized at constant day/night temperatures (25 degrees C), masking the distinct mesocosm pattern. Overall, the mean carbon budget of this CAM model Sonoran Desert system was negative, releasing an average of 22.5 mmol CO2 m-2 d-1. The capacity for nocturnal CO2 assimilation in this exclusively CAM mesocosm was inadequate to recycle CO2 released by plant and soil respiration.

Agave↗
PubMed1999

Thermal gradient gel electrophoresis analysis of bioprotection from pollutant shocks in the activated sludge microbial community.

We used a culture-independent approach, namely, thermal gradient gel electrophoresis (TGGE) analysis of ribosomal sequences amplified directly from community DNA, to determine changes in the structure of the microbial community following phenol shocks in the highly complex activated sludge ecosystem. Parallel experimental model sewage plants were given shock loads of chlorinated and methylated phenols and simultaneously were inoculated (i) with a genetically engineered microorganism (GEM) able to degrade the added substituted phenols or (ii) with the nonengineered parental strain. The sludge community DNA was extracted, and 16S rDNA was amplified and analyzed by TGGE. To allow quantitative analysis of TGGE banding patterns, they were normalized to an external standard. The samples were then compared with each other for similarity by using the coefficient of Dice. The Shannon index of diversity, H, was calculated for each sludge sample, which made it possible to determine changes in community diversity. We observed a breakdown in community structure following shock loads of phenols by a decrease in the Shannon index of diversity from 1.13 to 0.22 in the noninoculated system. Inoculation with the GEM (Pseudomonas sp. strain B13 SN45RE) effectively protected the microbial community, as indicated by the maintenance of a high diversity throughout the shock load experiment (H decreased from 1.03 to only 0.82). Inoculation with the nonengineered parental strain, Pseudomonas sp. strain B13, did not protect the microbial community from being severely disturbed; H decreased from 1.22 to 0.46 for a 3-chlorophenol-4-methylphenol shock and from 1.03 to 0.70 for a 4-chlorophenol-4-methylphenol shock. The catabolic trait present in the GEM allowed for bioprotection of the activated sludge community from breakdown caused by toxic shock loading. In-depth TGGE analysis with similarity and diversity algorithms proved to be a very sensitive tool to monitor changes in the structure of the activated sludge microbial community, ranging from subtle shifts during adaptation to laboratory conditions to complete collapse following pollutant shocks.

Bacteria↗
PubMed1976

Assessment of vertical excursions and open-sea psychological performance at depths to 250 fsw.

A series of 10 two-man descending vertical excursion dives was carried out in the open sea from an ocean-floor habitat off the coast of Puerto Rico by four aquanauts saturated on a normoxic-nitrogen breathing mixture at a depth of 106 fsw. The purpose of these dives was two-fold: to validate laboratory findings with respect to decompression schedules and to determine whether such excursions would produce evidence of adaptation to nitrogen narcosis. For the latter, tests designed to measure time estimation, short-term memory, and auditory vigilance were used. The validation of experimental excursion tables was carried out without incidence of decompression sickness. Although no signs of nitrogen narcosis were noted during testing, all subjects made significantly longer time estimates in the habitat and during the excursions than on the surface. Variability and incomplete data prevented a statistical analysis of the short-term memory results, and the auditory vigilance proved unusable in the water.

Analysis of Variance↗
PubMed1999

Adaptation model of nearwork-induced transient myopia.

A nearwork model was developed to determine whether variation in accommodative adaptation gain, KA, can account for the differences in the dynamic decay timecourse following near work in hyperopes (HYP), emmetropes (EMM), early-onset myopes (EOM), and late-onset myopes (LOM). The model incorporated a proximal component into a previously-developed adaptation model of accommodation and vergence. It was used to simulate the nearwork-induced transient myopia (NITM) response following 10 min of congruent binocular near viewing (5 D, 5 MA). The accommodative adaptation gain, KA, value was varied from 1.0 to 6.0 in increments of 0.5. For the hyperopes, an additional constraint was imposed wherein the accommodative response was biased on the under-accommodated side of the deadspace operator (i.e., depth-of-focus). In addition, the effect of prolonged nearwork was simulated by alternating between 1 hr of congruent near viewing (3 D, 3 MA) and 5 min of congruent far viewing (0.25 D, 0.25 MA) over a 160 hr period representing one work-month with 40 hours of nearwork per week. The steady-state rms value of the accommodative error was measured as a function of KA. It was found that the NITM timecourses for HYP, EMM, EOM, and LOM could be simulated accurately using KA values of 2.0, 2.5, 4.0 and 5.5, respectively. The long-term final steady-state rms of the accommodative error was found to increase from 0.182 D to 0.188 D as KA increased from 1 to 6. This indicated a small and progressive increase in residual accommodative error for higher KA values, which was associated with EOM and LOM. Thus, NITM for the different refractive groups could be quantified by the accommodative adaptation gain element, with KA for the HYP, EMM, and EOM and LOM groups having lower, intermediate, and higher values, respectively. The larger rms for higher KA values suggests that a myopic individual may have a predisposition to exhibit a slightly larger long-term accommodative error, which may stimulate axial elongation and in turn promote the progression of axial myopia.

Accommodation, Ocular↗
PubMed1999

Synchronous ileal autotransplantation impairs adaptation of remaining gut in pigs with proximal small bowel resection.

This study investigates the effects of ileal autotransplantation on morphology, crypt cell proliferation, and brush border disaccharidases of the remaining jejunoileum and colon in growing pigs with 75% proximal small bowel resection. Resection was performed on 30 pigs, of which 15 underwent an autotransplantation of the remaining ileum. The autotransplanted pigs showed reduced weight gain and remnant ileal length when compared to the resected controls. In the autotransplanted pigs, small bowel diameter and weight, mucosal weight and protein content, villus height and surface area, crypt depth, and the number of proliferating crypt cells were reduced similarly both in the intact jejunum and in the autotransplanted ileal remnant. Autotransplantation also decreased the number of proliferative crypt cells of the colon. Specific activities of maltase and sucrase tended to increase in the autotransplanted ileal remnant, whereas the total enzyme activities decreased. These results suggest that ileal autotransplantation disturbs postresectional adaptation of the remaining gut.

Adaptation, Physiological↗
PubMed1996

Does the colon adopt small bowel features in a small bowel environment?

BACKGROUND: Isoperistaltic colon interposition is one of several surgical options available in the treatment of short bowel syndrome. It functions primarily by slowing the rapid intestinal transit that follows small bowel resection (SBR). Previous studies have interposed distal colonic segments and although there is evidence of adaptation by the interposed colon it is not known whether these segments develop histologic or functional small bowel characteristics. METHODS: In this study evidence was sought of metaplasia in the interposed segments after 80% SBR and, because proximal colon is a midgut derivative, the differences between proximal and distal colonic segments were examined. RESULTS: There was no qualitative histological evidence of metaplasia by the interposed segments. There was a significant increase in crypt depth, mucosal thickness and maltase concentration of the interposed segments compared with the nontransposed colon of the controls. The maltase concentations were increased to the extent that they were not significantly different from the concentration present in normal ileum. CONCLUSIONS: Although there was no gross evidence of small bowel intestinalization by the interposed segments, there was evidence of adaptation which was not merely an extension of the adaptive process seen after SBR alone. These changes resulted in the colon taking on some small bowel features. There was no significant difference between proximal vs distal interposed segments.

Adaptation, Physiological↗
PubMedDate not supplied

Disparity-tuned channels of the human visual system.

Traditionally, it has been thought that the processing of binocular disparity for the perception of stereoscopic depth is accomplished via three types of disparity-selective channels--"near," "far," and "tuned." More recent evidence challenges this notion. We have derived disparity-tuning functions psychophysically using a subthreshold summation (i.e. low-level masking) technique. We measured correlation-detection thresholds for dynamic random-element stereograms containing either one or two surfaces in depth. The resulting disparity-tuning functions show an opponent-type profile, indicating the presence of inhibition between disparity-tuned units in the visual system. Moreover, there is clear inhibition between disparities of the same sign, obviating a strict adherence to near-far opponency. These results compare favorably with tuning functions derived psychophysically using an adaptation technique, and with the tuning profiles from published single-unit recordings. Our results suggests a continuum of overlapping disparity-tuned channels, which is consistent with recent physiological evidence as well as models based on other psychophysical data.

Depth Perception↗
PubMed2004

[A comparative study on water use characteristics and eco-adaptability of Hippophae rhamnoides and Caragana korshinskii in semi-arid loess hilly-gully region].

This study compared the seasonal dynamics of soil water content, biomass productivity, and leaf photosynthetic physiology and water potential between about ten years old Hippophae rhamnoides and Caragana korshinskii planted on the hilly slope land of semi-arid loess hilly-gully region. The results showed that there existed dry soil layer in the stands. The seasonal compensation depth of soil water in Hippophae rhamnoides stand was deeper and its water use capability was better than those of C. korshinskii. The yearly productivity of Hippophae rhamnoides was about 2.56 times of C. korshinskii. Hippophae rhamnoides leaf had an increased water use efficiency under improved soil water condition. C. korshinskii had higher photosynthetic and transpiration rates, but its leaf WUE was smaller than Hippophae rhamnoides. These two forests all had drought resistance and tolerance characteristics, but Hippophae rhamnoides was more active than C. korshinskii adapting to drought.

Adaptation, Physiological↗
PubMed2005

Masters of adaptation: learning in late life adjustments.

The purpose of this research is to understand the relationship between human development in older adults and personal learning. Personal or self-directed learning (SDL) refers to a style of learning where the individual directs, controls, and evaluates what is learned. It may occur with formal classes, but most often takes place in non-formal situations. This study employed a descriptive qualitative design incorporating in-depth, semistructured interviews for data collection. The sample of 10 purposefully selected older adults from a rural area reflected diversity in gender, race, education, and employment. Data analysis was guided by the constant comparative method. The primary late life adjustments of these older adults were in response to having extra time, changes in family, and social and physical loss. This research also indicated that late life adjustments are a primary incentive for self-directed learning. The results of this study indicated that older adults become masters of adaptation through the use of self-directed learning activities.

Adaptation, Psychological↗
PubMed1989

Retinal inhomogeneity and motion in depth.

The relation between retinal inhomogeneity and motion in depth was explored by means of a circularly symmetric but nonuniform stimulus pattern, designed to fit the inhomogeneity of the subject's retina. Radial motion of the quasi-sinusoidal rings of this target evokes an illusion of motion in depth: forward if the frontal-plane motion is centrifugal, backward if it is centripetal. Like the Plateau spiral, this stimulus produces strong motion aftereffects (MAE's) over a wide range of spatial and temporal frequencies. Over a much more limited frequency range, the forward MAE is significantly more adaptable than the backward MAE. This forward effect was found to occur only at very low spatial frequencies (approximately 0.05-0.5 cycles/deg at the fovea) and velocities near 20 deg/sec. The effect was destroyed by decentering the target or by varying its homogeneity so that it no longer matched the retina. These results suggest a hard-wired collision-avoidance system.

Depth Perception↗