SEARCH · PubMed Health

Results for “depth adaptation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources

PubMed1988

Depth discrimination from optic flow.

A simple scheme for deriving relative depth (time-to-collision, or TTC) from optic flow is developed in which the total flow is first sensed by unconnected motion (imperfect filter) sensors and then the rotational component is subtracted to yield the translational component. Only the latter component yields depth information. This scheme is contrasted with one where the TTC sensors respond only to the translational component at the initial registration of the flow (perfect filter sensors or looming detectors). The simple scheme predicts the results of three experiments on discrimination of TTC: discrimination thresholds are elevated if the objects withdraw from rather than approach the observer, thresholds are elevated if a rotational component is added to the flow, and the amount of threshold elevation resulting from the addition of a rotational component is reduced by prior adaptation to a pure rotational flow. These results confirm the simple model and disconfirm predictions based on the looming detector scheme.

Attention↗

PubMed2004

Converting cultural capital among teen refugees and their families from Bosnia-Herzegovina.

OBJECTIVES: The objective of this study was to identify the processes by which teen refugees adapt and apply cultural capital in conditions of refuge in order to develop preventive interventions for refugee youths. METHODS: The study was a multisite ethnographic study in Chicago that involved observation of Bosnian participants in schools, community sites, service organizations, and households as well as in-depth interviews with a subsample of 30 Bosnian adolescents and their families. Field notes and interview data were subjected to thematic analysis. RESULTS: The concept of converting cultural capital emerged as a useful construct for representing the cultural resources that Bosnian teen refugees and their families bring to the refugee trauma experience. Conversion of cultural capital refers to processes of adapting and applying the meanings, knowledge, customs, achievements, and outlooks that teen refugees and their families bring to new environments in order to enhance teens' cultural vitality and social incorporation. Nine mechanisms of converting cultural capital were identified, labeled, and defined in emic terms: using our language, obliging family, sticking together, returning to religion, going ghetto, building a future, taking pride in tradition, critiquing America, and seeking freedom. These mechanisms represent cultural strategies by which teen refugees attempt to manage enormous historical, social, cultural, economic, familial, and psychological changes associated with refugee trauma. CONCLUSIONS: Ethnography is an important methodologic tool in mental health services research, and the concept of converting cultural capital is useful in designing preventive interventions for teen refugees and their families.

Adaptation, Psychological↗

PubMed2025

ZIPcnv: accurate and efficient inference of copy number variations from shallow whole-genome sequencing.

MOTIVATION: Shallow whole-genome sequencing (sWGS), a rapid and cost-effective sequencing technology, has gradually been widely adopted for CNV analyses. However, with genome‑wide coverage of only 0.1-5×, sWGS data display a pronounced zero‑inflation phenomenon-a large fraction of loci has zero sequencing reads. Zero inflation causes read counts to fluctuate by several‑fold between adjacent windows. As a result, random upward blips in coverage can be misinterpreted as copy‑number gains (false positives), and true deletions often become indistinguishable from pervasive zero‑coverage noise. In addition, existing CNV detection tools developed for sWGS data often struggle to adapt across different CNV sizes. These combined effects severely constrain the accuracy of CNV inference. RESULTS: To address above challenges, we propose ZIPcnv, a novel CNV detection tool specifically designed for sWGS data. First, we apply a segment sliding window to smooth the raw read depth signal, which transforms the original zero-inflated statistical characteristics into approximately normal distribution characteristics. We then design a statistical process model that robustly detects persistent shifts under high background noise using a cumulative sum strategy, classifying genomic regions into candidate and non-candidate CNV regions. Finally, dynamic sliding windows are used for one-pass detection of CNVs of varying lengths, with window size adapting to the CNV region size. We evaluated the performance of ZIPcnv on simulated data and 190 real whole-genome sequencing samples. Experimental results show that ZIPcnv consistently outperforms currently popular CNV detection tools. AVAILABILITY AND IMPLEMENTATION: The ZIPcnv source code is freely available at https://github.com/Nevermore233/ZIPcnv.

DNA Copy Number Variations↗

PubMed2000

In vivo determination of tumor optical parameters in esophageal carcinoma.

BACKGROUND AND OBJECTIVE: Dose dependence of light cannot be discussed on the basis of dose alone. On a more fundamental scientific level, the propagation of light in tissue depends on optical parameters of treated tumor tissue. In a prospective, nonrandomized study, in vivo optical parameters of esophageal carcinoma were studied. STUDY DESIGN/MATERIALS AND METHODS: Nineteen intraoperative measurements of tumor optical parameters in six patients with esophageal carcinoma were performed. After diagnostic work-up and clinical staging, right-sided, posterolateral thoracotomy, and dissection of the esophagus were carried out. The tumor site was exposed and continuous endoluminal irradiation was started during determination of light penetration at the level of the adventitia of the esophagus. The tumors were located exactly between the endoluminal irradiation source and measurement probe in the thoracic cavity. Measurements were performed on tumors having different diameters to show the relationship between tumor diameter, extinction coefficient, and light penetration depth. RESULTS: The endoluminal incident intensity was 18.5 mW/cm(2). At a tumor diameter of 4, 6, 8, and 9 mm measured intensity of 5.12, 2.28, 0.88 and 0.65 mW/cm(2), an extinction coefficient of 0.321, 0.349, 0.381, and 0.373, as well as penetration depth of 3.21, 2.87, 2.62, and 2. 68 mm, respectively, could be measured. The correlation of tumor optical parameters, tumor diameter, penetration depth, and treatment time were expressed by the relative correction factor for different tumor diameters. CONCLUSION: The knowledge of tumor optical properties seems to be necessary to adapt dosimetry to the individual situation and manage optimal results of PDT in esophageal cancer.

Aged↗

PubMed2001

In Situ Assessment on the Physiological State of Purple and Green Sulfur Bacteria through the Analyses of Pigment and 5S rRNA Content.

Time-depth distribution of the microbial anaerobic assemblage of Lake Cisó was analyzed by microscopy, pigment composition, and electrophoretic analysis of 5S rRNAs. Purple (Amoebobacter-like and Thiocystis minor-like cells) and green (Chlorobium-like) sulfur bacteria were very abundant. Both groups coexisted in depth and in time despite the fact that they compete for the same natural resources (e.g., light and sulfide). Cell abundance, group-specific pigment content, and group-specific 5S rRNA content did not change in parallel with depth. This was due to variations in the specific content of both RNA and pigments. Specific content of RNA was systematically higher in purple than in green sulfur bacteria. The latter, in turn, displayed a much higher pigment content. Specific content of both RNA and pigments changed with depth and time. Analysis of tRNA band patterns indicated no changes in the populations forming the assemblage. Changes in specific contents, therefore, were the result of physiological adaptations of the populations already present in the system. We concluded that each group of bacteria showed differential adaptations in both RNA and pigment content, and that the specific contents measured were good indicators of the physiological status of these bacteria in situ. The higher content of RNA in purple sulfur bacteria indicates that these organisms are the main contributors to anaerobic carbon fixation and sulfide oxidation processes in Lake Cisó.

Journal Article↗

PubMed2006

Optical aberrations in the mouse eye.

PURPOSE: The mouse eye is a widely used model for retinal disease and has potential to become a model for myopia. Studies of retinal disease will benefit from imaging the fundus in vivo. Experimental models of myopia often rely on manipulation of the visual experience. In both cases, knowledge of the optical quality of the eye, and in particular, the retinal image quality degradation imposed by the ocular aberrations is essential. In this study, we measured the ocular aberrations in the wild type mouse. METHODS: Twelve eyes from six four-week old black C57BL/6 wild type mice were studied. Measurements were done on awake animals, one being also measured under anesthesia for comparative purposes. Ocular aberrations were measured using a custom-built Hartmann-Shack system (using 680-nm illumination). Wave aberrations are reported up to fourth order Zernike polynomials. Spherical equivalent and astigmatism were obtained from the 2nd order Zernike terms. Modulation Transfer Functions (MTF) were estimated for the best focus, and through-focus, to estimate depth-of-focus. All reported data were for 1.5-mm pupils. RESULTS: Hartmann-Shack refractions were consistently hyperopic (10.12+/-1.41 D, mean and standard deviation) and astigmatism was present in many of the eyes (3.64+/-3.70 D, on average). Spherical aberration was positive in all eyes (0.15+/-0.07 microm) and coma terms RMS were significantly high compared to other Zernike terms (0.10+/-0.03 microm). MTFs estimated from wave aberrations show a modulation of 0.4 at 2c/deg, for best focus (and 0.15 without cancelling the measured defocus). For that spatial frequency, depth-of-focus estimated from through-focus modulation data using the Rayleigh criterion was 6D. Aberrations in the eye of one anesthetized mouse were higher than in the same eye of the awake animal. CONCLUSIONS: Hyperopic refractions in the mouse eye are consistent with previous retinoscopic data. The optics of the mouse eye is far from being diffraction-limited at 1.5-mm pupil, with significant amounts of spherical aberration and coma. However, estimates of MTFs from wave aberrations are higher than previously reported using a double-pass technique, resulting in smaller depth-of-field predictions. Despite the large degradation imposed by the aberrations these are lower than the amount of aberrations typically corrected by available correction techniques (i.e., adaptive optics). On the other hand, aberrations do not seem to be the limiting factor in the mouse spatial resolution. While the mouse optics are much more degraded than in other experimental models of myopia, its tolerance to large amounts of defocus does not seem to be determined entirely by the ocular aberrations.

Animals↗

PubMed1996

Figural aftereffects and spatial attention.

Distracting attention away from the location of an adaptation figure reduces the positional shift of a displaced test figure in the figural aftereffect (FAE). Participants performed an alignment task after adaptation involving various manipulations of spatial attention. In 1 condition, participants counted how often numbers occurred in an alphanumeric sequence presented during adaptation. (The sequence also appeared in a comparison condition, but no attention was required.) The FAE was reduced when the alphanumeric sequence attended to was in the center of the display while the adaptation figure was 3 degrees eccentric but not when the pattern was superimposed on the adaptation figure. Forced attention to 1 feature of the adaptation figure, its orientation, did not reduce the FAE (Experiment 3). To obtain a maximum FAE, the span of attention must cover the adaptation figure.

Adult↗

PubMed2002

Spherical and irregular aberrations are important for the optimal performance of the human eye.

Contrast sensitivity measured psychophysically at different levels of defocus can be used to evaluate the eye optics. Possible parameters of spherical and irregular aberrations, e.g. relative modulation transfer (RMT), myopic shift, and depth of focus, can be determined from these measurements. The present paper compares measured results of RMT, myopic shift, and depth of focus with the theoretical results found in the two eye models described by Jansonius and Kooijman (1998). The RMT data in the present study agree with those found in other studies, e.g. Campbell and Green (1965) and Jansonius and Kooijman (1997). A new theoretical eye model using a spherical aberration intermediate between those of the eye models described by Jansonius and Kooijman (1998) and an irregular aberration with a typical S.D. of 0.3-0.5 D could adequately explain the measured RMT, myopic shift, and depth of focus data. Both spherical and irregular aberrations increased the depth of focus, but decreased the modulation transfer (MT) at high spatial frequencies at optimum focus. These aberrations, therefore, play an important role in the balance between acuity and depth of focus.

Adaptation, Ocular↗

PubMed2006

An experimental study on pedestrian classification.

Detecting people in images is key for several important application domains in computer vision. This paper presents an in-depth experimental study on pedestrian classification; multiple feature-classifier combinations are examined with respect to their ROC performance and efficiency. We investigate global versus local and adaptive versus nonadaptive features, as exemplified by PCA coefficients, Haar wavelets, and local receptive fields (LRFs). In terms of classifiers, we consider the popular Support Vector Machines (SVMs), feed-forward neural networks, and k-nearest neighbor classifier. Experiments are performed on a large data set consisting of 4,000 pedestrian and more than 25,000 nonpedestrian (labeled) images captured in outdoor urban environments. Statistically meaningful results are obtained by analyzing performance variances caused by varying training and test sets. Furthermore, we investigate how classification performance and training sample size are correlated. Sample size is adjusted by increasing the number of manually labeled training data or by employing automatic bootstrapping or cascade techniques. Our experiments show that the novel combination of SVMs with LRF features performs best. A boosted cascade of Haar wavelets can, however, reach quite competitive results, at a fraction of computational cost. The data set used in this paper is made public, establishing a benchmark for this important problem.

Algorithms↗

PubMed1998

Real-time automated detection and quantitative analysis of seizures and short-term prediction of clinical onset.

PURPOSE: We describe an algorithm for rapid real-time detection, quantitation, localization of seizures, and prediction of their clinical onset. METHODS: Advanced digital signal processing techniques used in time-frequency localization, image processing, and identification of time-varying stochastic systems were used to develop the algorithm, which operates in generic or adaptable "modes." The "generic mode" was tested on (a) 125 partial seizures (each contained in a 10-min segment) involving the mesial temporal regions and recorded using depth electrodes from 16 subjects, and (b) 205 ten-minute segments of randomly selected interictal (nonseizure) data. The performance of the algorithm was compared with expert visual analysis, the current "gold standard." RESULTS: The generic algorithm achieved perfect sensitivity and specificity (no false-positive and no false-negative detections) over the entire data set. Seizure intensity, a novel measure that seems clinically relevant, ranged between 35.7 and 6129. Detection was sufficiently rapid to allow prediction of clinical onset in 92% of seizures by a mean of 15.5 s. CONCLUSIONS: This algorithm, which was implemented with a personal computer, represents a definitive step toward rapid and accurate detection and prediction of seizures. It may also enable development of intelligent devices for automated seizure warning and treatment and stimulate new study of the dynamics of seizures and of the epileptic brain.

Algorithms↗

PubMed1998

The effect of working parameters on root substance removal using a piezoelectric ultrasonic scaler in vitro.

This study assessed defect depth and volume resulting from root instrumentation using a piezoelectric ultrasonic scaler with a slim scaling tip in vitro. Combinations of the following working parameters were analyzed: lateral forces of 0.5 N, 1 N, and 2 N; tip angulations of 0 degrees, 45 degrees, and 90 degrees; power settings of low, medium and high; and instrumentation time of 10 s, 20 s, 40 s, and 80 s. Defects were quantified using a 3D optical laser scanner. Overall, lateral force had the greatest influence on defect volume compared to instrument power setting and tip angulation (beta-weights 0.49 +/- 0.04, 0.25 +/- 0.04, and 0.14 +/- 0.04, respectively). The effects on defect depth were highest for tip angulation followed by lateral force and instrument power setting (beta-weights 0.48 +/- 0.04, 0.34 +/- 0.04, and 0.25 +/- 0.04, respectively). Interestingly, at all power settings, the highest defect volume and depth by far were found after combining 45 degrees tip angulation with 2 N of lateral force. The efficacy of the assessed piezoelectric ultrasonic scaler may be adapted to the various clinical needs by adjusting the lateral force, tip angulation, and power setting. To prevent severe root damage it is crucial to use the assessed scaler at a tip angulation of close to 0 degrees.

Dental Instruments↗

PubMed1992

Local and systemic responses to dental composites and glass ionomers.

For many years, the dental profession worked mainly with rather inert restorative materials that had a limited contact with vital tissue, and the opportunity for local and systemic complications was minimal. However, conditions have changed in recent years where the two leading non-mercury-containing materials, resin composites and glass-ionomer cements, are chemically active compounds and can have detrimental effects on pulp tissue. With the advent of light-curing techniques with incremental layering, resin component formulae that were formerly found to be quite irritating to the pulp have become less so with the elimination of the need for matrices and pressure for good adaptation to be gained. As experience revealed the deficiencies and dangers of ultraviolet-light-curing techniques, visible-light-curing systems were developed that provided greater depth of cure, a higher degree of polymerization with less shrinkage with incremental layers, and less porosity. When glass-ionomer cements (GICs) were first introduced, with just one acid (polyacrylic), pulpal responses were classified as bland. With the addition of many more acids to enhance certain characteristics and reduce the setting time, GICs have become more irritating, especially when used as luting agents in areas where the remaining dentin thickness is 0.5 mm or less. Gold foil and amalgam are inert and innocuous restorative materials but require pressure for condensation which creates an exaggerated inflammatory response. This presentation emphasizes the pulpal responses and side-effects of these non-mercury-containing restorative materials and how to keep them within an acceptable range of biocompatibility. Despite the lack of any substantial appearance of soft tissue and systemic responses to resin composites and GICs, the results of a survey of recent literature are included.

Composite Resins↗

PubMed1996

Psychological impact of injuries in athletes.

Although research on the psychological impact of injury is in its infancy, this article reviews relevant literature focusing on post-injury emotional response, self-esteem, and the effect of mood disturbance on rehabilitation from sport injury. Injury is often accompanied by depression, tension, anger and low self-esteem, particularly in competitive, seriously injured athletes. Mood disturbance seems to relate to the athlete's perceived progress in rehabilitation and has been shown to negatively relate to attendance at rehabilitation sessions. This article also describes how the Emotional Responses of Athletes to Injury Questionnaire (ERAIQ) serves as a guide for the initial interview of an injured athlete. Interventions such as positive self-talk, relaxation, goal setting and healing imagery, all used by a faster healing group of athletes, and although not well researched, seem appropriate to assist athletes in coping with injury. Modelling interventions during injury rehabilitation have also been shown to have a positive effect on rehabilitation and should be used. These relationships are described in more depth and in the context of a theoretical model. Directions for future research are suggested.

Adaptation, Psychological↗

PubMed2000

Is the Prunella (Lamiaceae) hybrid zone structured by an environmental gradient? Evidence from a reciprocaltransplant experiment.

Hybrid zones may be structured by environmentally independent selection against intrinsically unfit hybrids (tension zone models), or by environmentally dependent fitness differences among parental species and hybrids (ecological selection-gradient models). A 30-m slope in a mountain grassland harbors a hybrid zone of the clonal perennials, Prunella grandiflora and P. vulgaris (Lamiaceae), with P. grandiflora in the upper, P. vulgaris in the lower, and both parental species and P. grandiflora × P. vulgaris Hybrids in a narrow middle part. We found gradients for soil depth and water content, and vegetation height and biomass along the slope. A reciprocal transplant experiment yielded crossing reaction norms for vegetative reproduction. Parental species were locally adapted to their home sites, while the three taxa did not differ in vegetative reproduction in the Hybrid transplant site. Local adaptation for vegetative reproduction of P. grandiflora was mediated through higher survival and that of P. vulgaris through higher ramet number, indicating adaptation of their clonal growth strategies (phalanx vs. guerrilla) to the different habitats. Hybrid performance was intermediate between that of the parental species in all three sites, although Hybrids flowered more often than the parental species in the Hybrid site. Our results support ecological selection-gradient rather than tension zone models.

Journal Article↗

PubMed1988

Relationship of in vitro cell motility and colonization potential in a mouse colon adenocarcinoma (MCA-38) cell line.

Cell motility is an important factor in the metastatic process that can be affected by environmental conditions. A quantitative study was made of the relationship between cell motility and the colonization potential of a mouse colon adenocarcinoma cell line (MCA-38). MCA-38 cells grown in culture did not produce hepatic or pulmonary colonies following ileocolic or tail vein injection, respectively. In contrast, MCA-38 cells adapted to grow in the mouse produced colonies in both organs. The motility of the MCA-38 cells that did not produce colonies, as determined by the depth of penetration into cellulose nitrate filters (8 micron pore size), was significantly less than that of MCA-38 cells with colony-forming potential. Return to in vitro growth resulted in both a loss of colonization potential and a reduction in motility. In this system, secondary organ colonization and in vitro cell motility are positively correlated, suggesting an association between cell motility and metastatic potential.

Adenocarcinoma↗

PubMed1985

[Optimization of the dosage of volatile anesthetics based on pharmacokinetic and dynamic models].

The quantitative aspects of dosing of volatile anaesthetics to establish and maintain constant alveolar concentrations are in general only discussed in the framework of closed circuit anaesthesia. A systematic approach to determine the appropriate dosage for arbitrary flows on the basis of pharmacokinetic models and to adjust the parameters of the model to the individual patient is described. A pharmacodynamic model of the volatile agents isoflurane, enflurane and halothane based on the electroencephalogram is worked out and added to the kinetic model. The median of the EEG power spectrum serves as a monoparametric correlate of depth of anaesthesia. A system theoretic consideration of the coupled subsystems, anaesthesia machine and patient, enables the establishment of interactive dosing strategies, thus offering the possibility of adapting dosage to the different painful phases of surgery. The implications of these dosing strategies for feed back control of anaesthesia by electroencephalographic means are discussed.

Anesthesia, Inhalation↗

PubMed2006

Adaptation of parent-child interaction therapy for Puerto Rican families: a preliminary study.

This study examines how parent-child interaction therapy (PCIT) was adapted for Puerto Rican parents of children aged 4-6 with hyperactivity and other significant behavior problems. Four steps were followed: (1) translation and preliminary adaptation of the treatment manual, (2) application of the treatment to 9 families as part of an exploratory study using repeated measures, (3) treatment revision and refinement, and (4) in-depth interviews with parents (n=15) and clinical psychologists (n=5) from Puerto Rico who provided feedback on treatment process and components. Throughout this process, cultural elements and modifications were recommended to be incorporated into the treatment protocol. Both quantitative and qualitative results suggest that PCIT seems to be an acceptable intervention for this population, with some minor changes. Parents reported a high level of satisfaction, a significant reduction in children's externalizing behavior problems, and reduction of parenting stress and improvement in their parenting practices. Psychologists also evaluated positively the treatment protocol and recommended its use. Results from this study may inform clinicians and researchers who work with Latino families about relevant issues to be considered to promote their participation in behavioral family interventions and to enhance their acceptability and effectiveness.

Adaptation, Physiological↗

PubMed2003

Fetal lung development in the elephant reflects the adaptations required for snorkeling in adult life.

The adult elephant is unique among mammals in that the pleural membranes are thickened and the pleural cavity is obliterated by connective tissue. It has been suggested that this peculiar anatomy developed because the animal can snorkel at depth, and this behavior subjects the microvessels in the parietal pleura to a very large transmural pressure. To investigate the development of the parietal pleura, the thickness of the endothoracic fascia (ET) was measured in four fetal African elephants of approximate gestational age 111-130 days, and the appearances were compared with those in human, rabbit, rat and mouse fetuses of approximately the same stage of lung organogenesis. The mean thicknesses of ET in the elephant, human, rabbit, rat and mouse were 403, 53, 29, 27 and 37 microm, respectively. This very early development of a thick parietal pleura in the elephant fetus is consistent with the hypothesis of a long history of snorkeling in the elephant's putative aquatic ancestors.

Adaptation, Biological↗