898 resultados para least absolute deviation (LAD) fitting
Resumo:
An increased leftward asymmetry of the planum temporale (PT) in absolute-pitch (AP) musicians has been previously reported, with speculation that early exposure to music influences the degree of PT asymmetry. To test this hypothesis and to determine whether a larger left PT or a smaller right PT actually accounts for the increased overall PT asymmetry in AP musicians, anatomical magnetic resonance images were taken from a right-handed group of 27 AP musicians, 27 nonmusicians, and 22 non-AP musicians. A significantly greater leftward PT asymmetry and a significantly smaller right absolute PT size for the AP musicians compared to the two control groups was found, while the left PT was only marginally larger in the AP group. The absolute size of the right PT and not the left PT was a better predictor of music group membership, possibly indicating “pruning” of the right PT rather than expansion of the left underlying the increased PT asymmetry in AP musicians. Although early exposure to music may be a prerequisite for acquiring AP, the increased PT asymmetry in AP musicians may be determined in utero, implicating possible genetic influences on PT asymmetry. This may explain why the increased PT asymmetry of AP musicians was not seen in the group of early beginning non-AP musicians.
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Four experiments were conducted to examine the ability of people without "perfect pitch" to retain the absolute pitch offamiliar tunes. In Experiment 1, participants imagined given tunes, and then hummed their first notes four times either between or within sessions. The variability of these productions was very low. Experiment 2 used a recognition paradigm, with results similar to those in Experiment 1 for musicians, but with some additional variability shown for unselected subjects. In Experiment 3, subjects rated the suitability ofvarious pitches to start familiar tunes. Previously given preferred notes were rated high, as were notes three or four semitones distant from the preferred notes, but not notes one or two semitones distant. In Experiment 4, subjects mentally transformed the pitches of familiar tunes to the highest and lowest levels possible. These experiments suggest some retention of the absolute pitch of tunes despite a paucity of verbal or visual cues for the pitch.
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Objectives To examine the extent of multiplicity of data in trial reports and to assess the impact of multiplicity on meta-analysis results. Design Empirical study on a cohort of Cochrane systematic reviews. Data sources All Cochrane systematic reviews published from issue 3 in 2006 to issue 2 in 2007 that presented a result as a standardised mean difference (SMD). We retrieved trial reports contributing to the first SMD result in each review, and downloaded review protocols. We used these SMDs to identify a specific outcome for each meta-analysis from its protocol. Review methods Reviews were eligible if SMD results were based on two to ten randomised trials and if protocols described the outcome. We excluded reviews if they only presented results of subgroup analyses. Based on review protocols and index outcomes, two observers independently extracted the data necessary to calculate SMDs from the original trial reports for any intervention group, time point, or outcome measure compatible with the protocol. From the extracted data, we used Monte Carlo simulations to calculate all possible SMDs for every meta-analysis. Results We identified 19 eligible meta-analyses (including 83 trials). Published review protocols often lacked information about which data to choose. Twenty-four (29%) trials reported data for multiple intervention groups, 30 (36%) reported data for multiple time points, and 29 (35%) reported the index outcome measured on multiple scales. In 18 meta-analyses, we found multiplicity of data in at least one trial report; the median difference between the smallest and largest SMD results within a meta-analysis was 0.40 standard deviation units (range 0.04 to 0.91). Conclusions Multiplicity of data can affect the findings of systematic reviews and meta-analyses. To reduce the risk of bias, reviews and meta-analyses should comply with prespecified protocols that clearly identify time points, intervention groups, and scales of interest.
Resumo:
Murray's law describes the optimal branching anatomy of vascular bifurcations. If Murray's law is obeyed, shear stress is constant over the bifurcation. Associations between Murray's law and intravascular ultrasound (IVUS) assessed plaque composition near coronary bifurcations have not been investigated previously.
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The experimental verification of matrix diffusion in crystalline rocks largely relies on indirect methods performed in the laboratory. Such methods are prone to perturbations of the rock samples by collection and preparation and therefore the laboratory-derived transport properties and fluid composition might not represent in situ conditions. We investigated the effects induced by the drilling process and natural rock stress release by mass balance considerations and sensitivity analysis of analytical out-diffusion data obtained from originally saturated, large-sized drillcore material from two locations drilled using traced drilling fluid. For in situ stress-released drillcores of quartz-monzodiorite composition from the Aspo HRL, Sweden, tracer mass balance considerations and 1D and 2D diffusion modelling consistently indicated a contamination of <1% of the original pore water. This chemically disturbed zone extends to a maximum of 0.1 mm into the drillcore (61.8 mm x 180.1 mm) corresponding to about 0.66% of the total pore volume (0.77 vol.%). In contrast, the combined effects of stress release and the drilling process, which have influenced granodioritic drillcore material from 560 m below surface at Forsmark. Sweden, resulted in a maximum contamination of the derived porewater Cl(-) concentration of about 8%. The mechanically disturbed zone with modified diffusion properties covers the outermost similar to 6 mm of the drillcore (50 mm x 189 mm), whereas the chemically disturbed zone extends to a maximum of 0.3 mm based on mass balance considerations, and to 0.15 mm to 0.2 mm into the drillcore based on fitting the observed tracer data. This corresponds to a maximum of 2.4% of the total pore volume (0.62 vol.%) being affected by the drilling-fluid contamination. The proportion of rock volume affected initially by drilling fluid or subsequently with experiment water during the laboratory diffusion and re-saturation experiments depends on the size of the drillcore material and will become larger the smaller the sample used for the experiment. The results are further in support of matrix diffusion taking place in the undisturbed matrix of crystalline rocks at least in the cm range.
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The objective of this systematic review was to assess the 5- and 10-year survival of implant-supported fixed dental prostheses (FDPs) and to describe the incidence of biological and technical complications.
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To assess whether diffusion-weighted magnetic resonance imaging (DW-MRI) including bi-exponential fitting helps to detect residual/recurrent tumours after (chemo)radiotherapy of laryngeal and hypopharyngeal carcinoma.
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With improvements in acquisition speed and quality, the amount of medical image data to be screened by clinicians is starting to become challenging in the daily clinical practice. To quickly visualize and find abnormalities in medical images, we propose a new method combining segmentation algorithms with statistical shape models. A statistical shape model built from a healthy population will have a close fit in healthy regions. The model will however not fit to morphological abnormalities often present in the areas of pathologies. Using the residual fitting error of the statistical shape model, pathologies can be visualized very quickly. This idea is applied to finding drusen in the retinal pigment epithelium (RPE) of optical coherence tomography (OCT) volumes. A segmentation technique able to accurately segment drusen in patients with age-related macular degeneration (AMD) is applied. The segmentation is then analyzed with a statistical shape model to visualize potentially pathological areas. An extensive evaluation is performed to validate the segmentation algorithm, as well as the quality and sensitivity of the hinting system. Most of the drusen with a height of 85.5 microm were detected, and all drusen at least 93.6 microm high were detected.
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While rifaximin was able to improve symptoms in patients with irritable bowel syndrome (IBS) in phase III trials, these results are yet to be repeated in phase IV studies.
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Numerous studies have shown that animals have a sense of quantity and can distinguish between relative amounts. The concepts of relative numerousness, estimation, and subitizing are well established in species as diverse as chimpanzees and salamanders. Mobile animals have practical use for an understanding of number in common situations such as predation, mating, and competition. However, the ability to identify discrete quantities has only been firmly established in humans. The purpose of this study was to test for such “absolute numerousness” judgments in three lion-tailed macaques (Macaca silenus), a non-human primate. The three macaques tested had previously been trained on a computerized matchto- sample (MTS) task using geometric shapes. In this study, they were introduced to a MTS task containing a numerical cue, which required the monkeys to match stimuli containing either one or two items for rewards. If monkeys were successful at the initial matching task, they were tested with stimuli in which the position of the items and then the surface area of the items was controlled. If the monkeys could match successfully without using these non-numerical cues, they would demonstrate the capability to make absolute numerousness judgments. None of the monkeys matched successfully using the numerical cue, so no evidence of absolute numerosity was found. Each macaque progressed through the experiment in an individualized manner, attempting a variety of strategies to obtain rewards. These included side preferences and an alternating-side strategy that were unrelated to the numerical cues in the stimuli. When it became clear that the monkeys were not matching based on a stimulus-based cue, they were tested again on matching geometric shapes. All three macaques stopped using their alternate strategies and were able to match shapes successfully, demonstrating that they were still capable of completing the matching task. The data suggest that the monkeys could not transfer this ability to the numerical stimuli. This indicates that the macaques lack a sense of exact quantity, or that they could not recognize the numerical cues in the stimuli as being relevant to the task.
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Carbon dioxide (CO2) has been of recent interest due to the issue of greenhouse cooling in the upper atmosphere by species such as CO2 and NO. In the Earth’s upper atmosphere, between altitudes of 75 and 110 km, a collisional energy exchange occurs between CO2 and atomic oxygen, which promotes a population of ground state CO2 to the bend excited state. The relaxation of CO2 following this excitation is characterized by spontaneous emission of 15-μm. Most of this energy is emitted away from Earth. Due to the low density in the upper atmosphere, most of this energy is not reabsorbed and thus escapes into space, leading to a local cooling effect in the upper atmosphere. To determine the efficiency of the CO2- O atom collisional energy exchange, transient diode laser absorption spectroscopy was used to monitor the population of the first vibrationally excited state, 13CO2(0110) or ν2, as a function of time. The rate coefficient, kO(ν2), for the vibrational relaxation 13CO2 (ν2)-O was determined by fitting laboratory measurements using a home-written linear least squares algorithm. The rate coefficient, kO(ν2), of the vibrational relaxation of 13CO2(ν2), by atomic oxygen at room temperature was determined to be (1.6 ± 0.3 x 10-12 cm3 s-1), which is within the uncertainty of the rate coefficient previously found in this group for 12CO2(ν2) relaxation. The cold temperature kO(ν2) values were determined to be: (2.1 ± 0.8) x 10-12 cm3 s-1 at Tfinal = 274 K, (1.8 ± 0.3) x 10-12 cm3 s-1 at Tfinal = 239 K, (2 ± 1) x 10-12 cm3 s-1 at Tfinal = 208 K, and (1.7 ± 0.3) x 10-12 cm3 s-1 at Tfinal = 186 K. These data did not show a definitive negative temperature dependence comparable to that found for 12CO2 previously.