Mean 3D Research Articles

Magnetic field dependence of the critical current density in thin epitaxial HTS YBa 2Cu 3O 7− δ films with dislocation low-angle domain boundaries

Highly biaxially oriented YBa 2Cu 3O 7− δ (YBCO) films exhibit critical current densities, J c, two orders of magnitude higher than any sort of bulk samples. Out-of-plane edge dislocations (mean 2D density is 10 11 lines/cm 2 in the film area) in low-angle tilt domain boundaries are shown to play a crucial role in J c( H∥ c, T)-behavior. Measurements of the magnetic field dependence of J c for the pulse-laser deposited YBCO films are carried out by AC magnetic susceptibility technique. Dislocation cores are shown to provide an extremely strong pinning force leading to J c (77 K)≅2×10 6 A/cm 2. Peculiarities of J c( H∥ c) are found in the low-field range. A simple model of pinning by dislocation domain boundaries is developed. The model consistently describes the J c( H∥ c, T)/ J c(0, T)-dependencies, accounting for the fraction of vortices pinned by dislocations.

Design and implementation of a system for treating paediatric patients with stereotactically-guided conformal radiotherapy

Background and purpose: Stereotactically-guided conformal radiotherapy (SCRT) allows the delivery of highly conformal dose distributions to localised brain tumours. This is of particular importance for children, whose often excellent long-term prognosis should be accompanied by low toxicity. The commercial immobilisation system in use at our hospital for adults was felt to be too heavy for children, and precluded the use of anaesthesia, which is sometimes required for paediatric patients. This paper therefore describes the design and implementation of a system for treating children with SCRT. This system needed to be well tolerated by patients, with good access for treating typical childhood malignancies. Materials and methods: A lightweight frame was developed for immobilisation, with a shell-based alternative for patients requiring general anaesthetic. Procedures were set up to introduce the patients to the frame system in order to maximise patient co-operation and comfort. Film measurements were made to assess the impact of the frame on transmission and surface dose. The reproducibility of the systems was assessed using electronic portal images. Results: Both frame and shell systems are in clinical use. The frame weighs 0.6 kg and is well tolerated. It has a transmission of 92–96%, and fields which pass through it deliver surface doses of 58–82% of the dose at d max, compared to 18% when no frame is present. However, the frame is constructed to maximise the availability of unobstructed beam directions. Reproducibility measurements for the frame showed a mean random error of 1.0±0.2 mm in two dimensions (2D) and 1.4±0.7 mm in 3D. The mean systematic error in 3D was 2.2 mm, and 90% of all overall 3D errors were less than 3.4 mm. For the shell system, the mean 2D random error was 1.5±0.2 mm. Conclusions: Two well-tolerated immobilisation devices have been developed for fractionated SCRT treatment of paediatric patients. A lightweight frame system gives a wide range of possible unobstructed beam directions, although beams that intersect the frame are not precluded, provided that output corrections are applied. A shell system allows the use of general anaesthesia. Both systems give reproducible immobilisation to complement the high-precision treatment delivery.

LP‐1: Late‐News Poster: Strong Accommodation Bias to a Collimated Retinal Scanned Light Display

AbstractAccommodation was measured while subjects viewed a retinal scanned light display that has a focus plane near optical infinity. Compared with dark accommodation, subjects over‐accommodated to the display (mean 2D; 0–8D range). Subjects were unaware of blurring, suggesting open‐loop accommodation. Accommodation fluctuates greatly between subjects viewing a fixed‐focus retinal scanning display.

The ratio of 2nd to 4th digit length and male homosexuality

Sexual orientation may be influenced by prenatal levels of testosterone and oestrogen. There is evidence that the ratio of the length of 2nd and 4th digits (2D:4D) is negatively related to prenatal testosterone and positively to oestrogen. We report that (a) 2D:4D was lower in a sample of 88 homosexual men than in 88 sex- and age-matched controls recruited without regard to sexual orientation, (b) within the homosexual sample, there was a significant positive relationship between mean 2D:4D ratio and exclusive homosexuality, (c) overall, there was a decrease in 2D:4D from controls to homosexual men to bisexual men and (d) fraternal birth order, a positive predictor of male homosexuality, was not associated with 2D:4D in a sample of 240 Caucasian men recruited without regard to sexual orientation and 45 homosexual men. Further work is needed to confirm the relationships between 2D:4D and sexual orientation. However, these and other recent data tend to support an association between male homosexuality and high fetal testosterone. Very high testosterone levels may be associated with a sexual preference for both men and women.

The 2nd:4th digit ratio, sexual dimorphism, population differences, and reproductive success: evidence for sexually antagonistic genes?

The ratio between the length of the 2nd and 4th digit (2D:4D) is sexually dimorphic, with mean male 2D:4D lower than mean female 2D:4D. It recently was suggested that 2D:4D is negatively correlated with prenatal testosterone and positively correlated with prenatal estrogen. It is argued that high prenatal testosterone and low estrogen (indicated by low 2D:4D) favors the male fetus and low prenatal testosterone and high estrogen (indicated by high 2D:4D) favors the female fetus. The patterns of expression of 2D:4D are interpreted in terms of sexually antagonistic genes. We report data on the following. (a) reproductive success and 2D:4D from England, Germany, Spain, Hungary (ethnic Hungarians and Gypsy subjects), Poland, and Jamaica (women only). Significant negative associations were found between 2D:4D in men and reproductive success in the English and Spanish samples and significant positive relationships between 2D:4D in women and reproductive success in the English, German, and Hungarian samples. The English sample also showed that married women had higher 2D:4D ratios than unmarried women, suggesting male choice for a correlate of high ratio in women, and that a female 2D:4D ratio greater than male 2D:4D predicted high reproductive success within couples. Comparison of 2D:4D ratios of 62 father:child pairs gave a significant positive relationship. This suggested that genes inherited from the father had some influence on the formation of the 2D:4D ratio. Waist:hip ratio in a sample of English and Jamaican women was negatively related to 2D:4D. (b) Sex and population differences in mean 2D:4D in samples from England, Germany, Spain, Hungary (including ethnic Hungarians and Gypsy subjects), Poland, Jamaica, Finland, and South Africa (a Zulu sample). Significant sex and population differences in mean 2D:4D were apparent.

Second to fourth digit ratio in elite musicians: Evidence for musical ability as an honest signal of male fitness

Prenatal testosterone may facilitate musical ability. The ratio of the length of the second and fourth digit (2D:4D) is probably determined in utero and is negatively related to adult testosterone concentrations and sperm numbers per ejaculate. Therefore, 2D:4D may be a marker for prenatal testosterone levels. We tested the association between 2D:4D and musical ability by measuring the ratio in 70 musicians (54 men and 16 women) recruited from a British symphony orchestra. The men had significantly lower 2D:4D ratios (indicating high testosterone) than controls ( n = 86). The mean 2D:4D of women did not differ significantly from controls ( n = 78). Rankings of musical ability within the orchestra were associated with male 2D:4D (high rank = low 2D:4D). Differences in 2D:4D ratio were not found among instrument groups, suggesting that 2D:4D was not related to mechanical advantages in playing particular intruments. Concert audiences showed evidence of a female-biased sex ratio in seats close to the orchestra. This preliminary study supports the thesis that music is a sexually selected trait in men that indicates fertilizing capacity and perhaps good genes. However, the association between low 2D:4D ratio and orchestra membership and high status within the orchestra may result from testosterone-mediated competitive ability. Further tests of the association between 2D:4D and musical ability per se are necessary.

Image motion estimation algorithms using cumulants

A class of algorithms is presented that estimates the displacement vector from two successive image frames consisting of signal plus noise. In the model, the signals are assumed to be either non-Gaussian or (quasistationary) deterministic; and, via a consistency result for cumulant estimators, the authors unify the stochastic and deterministic signal viewpoints. The noise sources are assumed to be Gaussian (perhaps spatially and temporally correlated) and of unknown covariance. Viewing image motion estimation as a 2D time delay estimation problem, the displacement vector of a moving object is estimated by solving linear equations involving third-order auto-cumulants and cross-cumulants. Additionally, a block-matching algorithm is developed that follows from a cumulant-error optimality criterion. Finally, the displacement vector for each pel is estimated using a recursive algorithm that minimizes a mean 2D fourth-order cumulant criterion. Simulation results are presented and discussed.

The effects of turbulence on bluff-body mean flow

This paper describes the results of our recent investigation on the effects of turbulence on the mean flow past 3D and 2D bluff bodies. Emphasis is placed on finding possible effects of turbulence scale. It is shown that turbulence can significantly influence bluff-body mean flow at two main scales. Small-scale turbulence causes the separated shear layer to reattach earlier on the side face of a bluff body through enhanced mixing. Large-scale turbulence interacts with vortex shedding from a bluff body, thus changing the mean flow considerably.

DNA content and size of sex chromatin positive female nuclei during the cell cycle.

Relative nuclear DNA content and nuclear area were determined in fast growing, karyotypically normal, fibroblastic cell cultures derived from five human females. In two cultures H<sup>3</sup> thymidine autoradiographic and photometric determinations were combined on the same nuclei. This allowed the separation of nuclei into three groups: those with the lowest mean DNA values which did not take up H<sup>3</sup> thymidine are in the G<sub>1</sub> period (2d group); those with intermediate DNA values which did take up thymidine are presumably synthesizing DNA and are in the S period; those which have double the mean 2d group DNA value and did not take up thymidine are a mixture of nuclei in the G<sub>2</sub> period with some true tetraploids 4d group). The overall frequency of sex chromatin positive nuclei in the cultures studied ranges from 64 to 78%. Sex chromatin positive nuclei occur with about the same frequency in 2d and S nuclei but are somewhat more frequent in 4d nuclei. In three cultures the relative DNA content of sex chromatin was determined. Sex chromatin of 4d nuclei contain about twice as much DNA as those of 2d nuclei; the DNA content of sex chromatin of S nuclei is between that of 2d and 4a nuclei but closer to the mean 2d value. Sex chromatin can be identified in labelled S nuclei. These observations clearly indicate that the condensed, sex chromatin forming X chromosome does not despiralize completely during DNA replication as some authors have suggested. The DNA content of sex chromatin positive and negative nuclei is identical within each nuclear group. The areas of sex chromatin positive 2d group nuclei are larger than for negative nuclei, but this difference is only significant in one of the cultures where a large number of nuclei were measured. It is concluded that failure of the X chromosome to condense in some nuclei of females is not related to DNA