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At least 649 records · Page 36Linked to original sources
PubMed1990

A genetic study of the malaria vector Anopheles nuneztovari from western Venezuela.

A photomap of larval polytene chromosomes of Anopheles nuneztovari (population B) from western Venezuela is presented. Samples of An. nuneztovari B taken from 4 study sites in the states of Barinas and Táchira comprise a single panmictic population, which is chromosomally identical to the cytotype identified by Kitzmiller et al. (1973) from western Venezuela and Colombia. The frequency of polymorphism 2La has increased significantly in the 16 years that have elapsed since the 1973 study. In addition, inversion 2La does not conform to Hardy-Weinberg equilibrium. These 2 changes are most likely due to environmental alterations which have resulted in the heterozygous condition becoming more locally adaptive.

Animals↗
PubMed1988

Computer-aided detection of microcalcifications in mammograms. Methodology and preliminary clinical study.

The authors investigated the feasibility of using computer methods for automated detection of clustered microcalcifications on clinical mammograms. A new difference-image approach using a matched filter/box-rim filter combination effectively removed the structured background from the image. A locally adaptive gray-level thresholding technique was then used for extraction of the signals from the resulting difference image. Signal-extraction criteria based on the size, contrast, number, and clustering properties of microcalcifications were next imposed on the detected signals to distinguish true signals from noise or artifacts. The detection accuracy of the computer scheme was evaluated by means of a free response receiver operating characteristic (FROC) analysis. It was found that, for simulated subtle microcalcifications superimposed on normal mammograms, the difference-image approach with a matched filter/box-rim filter combination could yield a true-positive cluster detection rate of 80% at a false-positive detection rate of one cluster per image. In a study of 20 clinical images containing moderately subtle microcalcifications, the automated computer scheme obtained an 82% true-positive cluster detection rate at a false-positive detection rate of one cluster per image. These results indicate that the automated method has the potential to aid radiologists in screening mammograms for clustered microcalcifications.

Breast Diseases↗
PubMed1984

Specificity of arm training on aerobic power during swimming and running.

The specificity of aerobic training for upper-body exercise requiring differing amounts of muscle mass was evaluated in 25 college-aged male recreational swimmers who were randomly assigned to either a non-training control group (N = 9), a 10-wk swim(S)-training group (N = 9), or a group that trained with a standard swim-bench pulley system (SB; N = 7). For all subjects prior to training, tethered-swimming peak VO2 averaged 19% below treadmill values (P less than 0.01), while SB-ergometry peak VO2 was 50% and 39% below running and swimming values, respectively (P less than 0.01). Significant (P less than 0.01) increases of peak VO2 in tethered swimming (11%) and SB (21%) were observed for the SB-trained group, while the S-trained group improved (P less than 0.01) 18% and 19% on the tethered swimming and SB tests, respectively. No changes were observed during treadmill running, and the control subjects remained unchanged on all measures. Comparisons between training groups indicated that although both groups improved to a similar extent when measured on the swim bench, the 0.53 l X min-1 improvement in tethered-swimming peak VO2 for the S-trained group was greater (P less than 0.05) than the 0.32 l X min-1 increase noted for the SB-trained group. The comparisons between SB and S exercise vs treadmill exercise support the specificity of aerobic improvement with training and suggest that local adaptations contribute significantly to improvements in peak VO2. Furthermore, the present data indicate that SB exercise activates a considerable portion of the musculature involved in swimming, and that aerobic improvements with SB training are directly transferred to swimming.

Adult↗
PubMedDate not supplied

[The physician and primary health cares (author's transl)].

For many years in developing countries, rural or sub-urban populations are trying to set up some structures, through community effort, capable to provide to them elementary but indispensable health cares. Because of its fundamental commitment, medical and Public Health staff must participate to the improvement of such structures which are out of the local government health facilities, but have to be integrated in the National Health Plan. Therefore, simple but effective and locally adapted technology has to be set up. The physician must go beyond his conventional technical responsibility, and must supervise and stimulate the village health teams composed essentially of first-aid and sanitation workers and rural matrons, all of them selected by the concerned communities themselves.

Community Health Services↗
PubMed1980

[Noradrenaline concentration in peripheral organs and their adrenosensitivity following chemical desympathization].

The rats desympathised with guanetidine developed a 58% decrease of the noradrenaline content in the myocardium, 37% - in the deferent duct, and 82% - in the small intestine. No significant changes of the catecholamines content occurred either in adrenal glands or in the hypothalamus. Sensitivity of the deferent duct's adrenoreceptors increased by 9 times. Sensitivity of the small intestine to noradrenaline increased by 3.4 times whereas the sensitivity to the antagonistic transmitter acetylcholine decreased by 2.4 times. Local adaptation mechanisms maintaining functioning of the organism in chronic desympathisation, are regarded.

Acetylcholine↗
PubMed1995

Asymmetry in the human skeleton. A study on prehistoric Polynesians and Thais.

Atlantal, long bone, and craniofacial measurements of prehistoric Polynesian and Thai skeletons were analysed to ascertain the extent and direction of bilateral asymmetry. The atlantal articular mass was constantly and significantly higher on the right side than on the left. In Thais, the midlongitudinal axis of the atlanto-occipital facet on the right side had a steeper inclination than that on the left. In both groups the dental occlusion was less mesial on the right side and the mandible was shorter, significantly so in the Thais. The long bones were more asymmetric in the Polynesians than in the Thais. Height asymmetry of atlas lateral tuberculum correlated inversely with mandibular ramal width asymmetry. Atlanto-occipital facet length asymmetry correlated with asymmetry of the gonial angle and facet angulation asymmetry correlated inversely with radial length asymmetry. Our results suggest a pervading asymmetry of skeletal structures which we ascribe as local adaptations to functional demands rather than as due to a uniform asymmetric growth pattern.

Animals↗
PubMed1995

[Monitoring of coagulation status in the physician's laboratory].

The usual coagulation tests performed in the medical practitioner's office are the prothrombin time (PT) and, less frequently, the activated partial thromboplastin time (aPTT, PTT), PT and aPTT are used as screening tests for coagulation disorders and for the monitoring of oral anticoagulation or home treatment with unfractionated heparin, respectively. Considered a 'simple test', the PT requires important conditions to be fulfilled by the laboratory. The results expressed in seconds, as a ratio, as PT-index and in activity percentages depend on the PT method and its local adaptation. The only way to communicate the intensity of oral anticoagulation to other doctors, hospitals and countries is to convert the PT seconds into international normalized ratios (INR). This requires the determination of the mean normal prothrombin time by each laboratory and the knowledge of the appropriate international sensitivity index (ISI). Reference curves are needed for PT expression as activity percentages. The PT of capillary blood deserves special consideration. Test performance is guided by regular internal and external quality control procedures.

Anticoagulants↗
PubMed1994

Tackling infant malnutrition in The Gambia.

Malnutrition is common among young children in developing countries. Often it is caused by poor infant weaning practices. Karen Hoare describes a community-based infant weaning programme in The Gambia which adapted local foods to improve nutritional content. The project also resulted in the development of a simple but effective demonstration kit.

Community Health Nursing↗
PubMed1993

Transcutaneous oxygen pressure. An effective measure for prosthesis fitting on below-knee amputations.

After amputation for arterial occlusive disease of the lower limbs, healing and local adaptation to a prosthesis depend on the oxygen ratio in the tissue. Transcutaneous oxygen tension (TcPO2) is a noninvasive microcirculatory exploration. Forty six below-knee stumps were selected without any prosthetic problem excepting vascular, with a follow-up mean duration of 23 months. They were classified into different prosthetic categories. The first was the worst because it required further amputation on the thigh and the fourth the best, which displayed complete adaptation to a socket contact. These groups were related to their TcPO2 values on the anterior and exterior face of the stumps in both reclined and seated positions. It seems that it is impossible to achieve healing when the TcPO2 value is lower than 15 mm Hg in lying position. However, healing is possible above 20 mm Hg but socket contact is not possible when TcPO2 values are under 40 mm Hg. When TcPO2 values are above 40 mm Hg, a good prosthesis fitting is possible when no problems are encountered other than vascular ones.

Aged↗
PubMed1994

Evaluation of variable parameters in neutrophil function test using chemiluminescence assay.

Variable parameters in chemiluminescence assay, one of the methods used to assess the functional capacity of neutrophils, were evaluated for suitable adaptation locally. The use of pooled normal human serum as compared to single normal human serum in opsonizing particles for phagocytosis was found to exhibit lower chemiluminescence activity (reduction range of 30%-50%). A similar degree of depression was observed when the particles were opsonized using normal human serum in comparison to that using autologous serum. Different intensity of chemiluminescence was also noted when the opsonized particle used was the Oxford strain of Staphylococcus aureus (NCTC 6571) in contrast to a strain of Staphylococcus aureus isolated from a patient. The results obtained warrant clinicians to deliver appropriate samples as best they can when the chemiluminescence assay is requested.

Biological Assay↗
PubMed1998

Advances in high-speed, three-dimensional imaging and automated segmentation algorithms for thick and overlapped clusters in cytologic preparations. Application to cervical smears.

OBJECTIVE: To use three-dimensional (3-D) imaging and localized adaptive image analysis to enable automated cervical smear screening systems to efficiently and effectively process thick and overlapped cell clusters currently left unprocessed. STUDY DESIGN: Instrumentation was developed to perform high-speed (50-200 optical sections per second at 256 x 256 resolution), 3-D imaging of thick regions of cervical smears. Normal and abnormal ThinPrep smears were imaged at two levels of resolution to approximate higher-resolution, wide-area imaging. Improved dual-resolution, 3-D image analysis algorithms were developed for segmenting nuclei in these clusters. RESULTS: Despite low contrast, high variability and dense overlaps, the algorithms detected 89% and correctly segmented 76% of nuclei in clusters from normal smears and detected 75% and correctly segmented 45% of nuclei in clusters from abnormal smears in low-resolution images. In high-resolution images they detected 88% and segmented 76% of nuclei from normal specimens and detected 55% and segmented 45% of nuclei from abnormal specimens. At least one nucleus from each cell cluster was correctly segmented. CONCLUSION: Selective application of 3-D imaging and 3-D image analysis to thick and overlapped regions can enable a significant fraction (45-89%) of clustered and embedded cells to be accessed by an automated analysis system. These regions are, for the most part, unprocessable by current two-dimensional methods.

Algorithms↗
PubMed1998

Detection of MRI brain contour using isotropic and anisotropic diffusion filter. A comparative study.

Reconstructed brain surface from MRI are still based on either interactive or manual edge detection methods which are time consuming and subjective. In order to overcome such inadequate result, the scale-space technique was applied using isotropic and anisotropic diffusion filter. Isotropic diffusion was not adequate because it did not allow locally adaptive blurring. On the contrary, stopping the anisotropic diffusion process at the best time of diffusion, edge detector provided the true location and morphology of the sulci and gyri. Although some sulci appeared open curves this one didn't have to be considered as failure of anisotropic diffusion because it was related to the resolution of the original MR image. Nevertheless the human vision subjectively made explicit their closure.

Anisotropy↗
PubMed2005

Composite adaptive control with locally weighted statistical learning.

This paper introduces a probably stable learning adaptive control framework with statistical learning. The proposed algorithm employs nonlinear function approximation with automatic growth of the learning network according to the nonlinearities and the working domain of the control system. The unknown function in the dynamical system is approximated by piecewise linear models using a nonparametric regression technique. Local models are allocated as necessary and their parameters are optimized on-line. Inspired by composite adaptive control methods, the proposed learning adaptive control algorithm uses both the tracking error and the estimation error to update the parameters. We first discuss statistical learning of nonlinear functions, and motivate our choice of the locally weighted learning framework. Second, we begin with a class of first order SISO systems for theoretical development of our learning adaptive control framework, and present a stability proof including a parameter projection method that is needed to avoid potential singularities during adaptation. Then, we generalize our adaptive controller to higher order SISO systems, and discuss further extension to MIMO problems. Finally, we evaluate our theoretical control framework in numerical simulations to illustrate the effectiveness of the proposed learning adaptive controller for rapid convergence and high accuracy of control.

Algorithms↗
PubMed2004

Local co-adaptation leading to a geographical mosaic of coevolution in a social parasite system.

The geographical mosaic theory of coevolution predicts differences in the advance or trajectory of the coevolutionary process between local communities due to their composition and the strength of ecological selection pressures through competition and resource availability. In this study, we investigate local co-adaptation in different populations of a social parasite. We conducted cross-fostering experiments to test for interpopulational differences in raiding efficiency between various populations of a slave-making ant and the defence abilities of local hosts. Here, we demonstrate that the success of raids strongly depends on the combination of populations of the parasite Harpagoxenus sublaevis and its host Leptothorax acervorum, indicating very localized coevolution. We found no absolute differences between slave-maker populations; the outcome of an encounter depended more on whether the two opponents occur in sympatry or allopatry. Furthermore, this study supports the results of our earlier work, that the unparasitized English L. acervorum population is most aggressive against the parasite.

Adaptation, Biological↗
PubMed2006

Local image registration by adaptive filtering.

We propose a new adaptive filtering framework for local image registration, which compensates for the effect of local distortions/displacements without explicitly estimating a distortion/displacement field. To this effect, we formulate local image registration as a two-dimensional (2-D) system identification problem with spatially varying system parameters. We utilize a 2-D adaptive filtering framework to identify the locally varying system parameters, where a new block adaptive filtering scheme is introduced. We discuss the conditions under which the adaptive filter coefficients conform to a local displacement vector at each pixel. Experimental results demonstrate that the proposed 2-D adaptive filtering framework is very successful in modeling and compensation of both local distortions, such as Stirmark attacks, and local motion, such as in the presence of a parallax field. In particular, we show that the proposed method can provide image registration to: a) enable reliable detection of watermarks following a Stirmark attack in nonblind detection scenarios, b) compensate for lens distortions, and c) align multiview images with nonparametric local motion.

Algorithms↗
PubMed1980

Distortion and adaptation in underwater sound localization.

Sounds should be localized at more medial positions under water than in air, because the values of the interaural temporal and intensity differences are reduced in water. Thirteen blindfolded divers were required to move a pointer towards the apparent location of a sound source under water, and they showed significant errors towards the median plane. In a second experiment, five divers were tested in air before and after underwater training at swimming towards a sound source. The search patterns of these divers showed systematic errors towards the median plane. A comparison of the first and second air tests showed some evidence of an aftereffect away from the median plane, discounting the most lateral angles (80 degrees left and right) where little effect would be expected. It is concluded that both a distortion of localization and some adaptation to the distortion occur under water.

Auditory Perception↗
PubMed2006

Vibrotactile adaptation enhances spatial localization.

A two-interval forced choice tracking procedure was used to evaluate the effects of a pre-exposure to vibrotactile stimulation ("adaptation") on the capacity of human subjects to spatially localize a subsequent tactile stimulus. A 25 Hz flutter adapting stimulus was presented at a randomly selected position within a 20 mm linear array oriented transversely on the hand dorsum. Two flutter stimuli delivered subsequently were applied to different sites along the linear array; one to the same locus that received the adapting stimulation (the "standard" stimulus), the other to a distant site (the "test" stimulus). Following each trial, subjects were queried as to which of the two stimuli was delivered to the same skin site that received adapting stimulation. A correct response resulted in a reduced distance between the sites contacted by the standard and test stimuli in the following trial. Four subjects participated in 10 sessions each. A session consisted of two sets of 20 trials (one set at 0.5 s and another at 5 s adapting stimulus duration). For every subject, 5 s adaptation resulted in an approximately 2-fold improvement in spatial discrimination performance over that achieved following 0.5 s adaptation. It is proposed that the improved human vibrotactile spatial localization performance following 5 s of 25 Hz stimulation is due to enhanced spatial funneling of the global neuronal population response of primary somatosensory cortex (SI) that has been demonstrated to accompany increases in duration of 25 Hz flutter stimuli delivered to the skin.

Acclimatization↗