Positron Emission Tomography (PET) is a widely-used imaging modality for medical research and clinical diagnosis. Imaging of the radiotracer is obtained from the detected hit positions of the two ...positron annihilation photons in a detector array. The image is degraded by backgrounds from random coincidences and in-patient scatter events which require correction. In addition to the geometric information, the two annihilation photons are predicted to be produced in a quantum-entangled state, resulting in enhanced correlations between their subsequent interaction processes. To explore this, the predicted entanglement in linear polarisation for the two photons was incorporated into a simulation and tested by comparison with experimental data from a cadmium zinc telluride (CZT) PET demonstrator apparatus. Adapted apparati also enabled correlation measurements where one of the photons had undergone a prior scatter process. We show that the entangled simulation describes the measured correlations and, through simulation of a larger preclinical PET scanner, illustrate a simple method to quantify and remove the unwanted backgrounds in PET using the quantum entanglement information alone.
A Hadron Blind Detector (HBD) has been developed, constructed and successfully operated within the PHENIX detector at RHIC. The HBD is a Cherenkov detector operated with pure
CF
4
. It has a 50
cm ...long radiator directly coupled in a windowless configuration to a readout element consisting of a triple GEM stack, with a CsI photocathode evaporated on the top surface of the top GEM and pad readout at the bottom of the stack. This paper gives a comprehensive account of the construction, operation and in-beam performance of the detector.
X-ray mammography is a widely used technique for breast cancer screening. However, the technique is imprecise when it comes to radiographically dense breast tissue, and therefore a supplemental ...screening technique, such as molecular breast imaging (MBI), could increase the cancer detection rate. Emerging technologies within MBI require excellent detector performance, preferably with a submillimeter intrinsic spatial resolution. A collaboration between Kromek and DTU Space aims to advance the DTU Space developed 3-D CdZnTe (CZT) drift strip technology, for application in new emerging MBI systems. This collaboration has resulted in ten compact 3-D MBI test modules with the goal of producing high-performance and high yield detectors. In this article, we present overall excellent detector performance, submillimeter position resolution at both 122 and 661.6 keV, and good energy resolution for the applied electrode deposition and contact optimization. Although the current experimental setup and results suffer from high electronic noise (using discrete NIM standard charge sensitive preamplifiers), we conclude that the measured spatial and spectral performance fulfills the expected requirements for the modules, with room for improvement, especially within limiting electronic noise. The detector test modules indicate a promising future for the 3-D CZT drift strip technology within future emerging MBI systems.
The long-term effects of parental divorce on individuals' mental health after the transition to adulthood are examined using data from a British birth cohort that has been followed from birth to age ...33. Growth-curve models and fixed-effects models are estimated. The results suggest that part of the negative effect of parental divorce on adults is a result of factors that were present before the parents' marriages dissolved. The results also suggest, however, a negative effect of divorce and its aftermath on adult mental health. Moreover, a parental divorce during childhood or adolescence continues to have a negative effect when a person is in his or her twenties and early thirties.
Most of the heat that is released in the vertebrate body is produced in the muscles during contractile (during movement or trembling) and noncontractile (without muscle activity) thermogenesis. ...Contractile thermogenesis is characteristic of all vertebrates, but it is not able to maintain a constantly high body temperature in animals. The main idea discussed in this article and based on a large number of publications of recent years is as follows: the main biochemical basis of warm-bloodedness in vertebrates is part of the cycle of contraction–relaxation of striated skeletal muscles, in which the act of muscle contraction somehow falls out, and the energy that should have been used for it is dissipated in the form of heat. This noncontractile thermogenesis, which is able to support the regional and general endothermy in vertebrates, can be considered the real biochemical basis of warm-bloodedness. Thus, the presence of skeletal muscles in all vertebrates and the common biochemical foundations of the contraction–relaxation cycle represent a single preadaptive property of the manifestation of noncontractile thermogenesis in all vertebrates, starting with fish, which is a basis for the evolution of warm-bloodedness. Therefore, the modern data that the first terrestrial vertebrates were most likely animals with high levels of both metabolism and body temperature are quite understandable and not surprising.
We present the combined results on electron-pair production in 158 GeV/n Pb-Au (\(\sqrt{s}\) = 17.2 GeV) collisions taken at the CERN SPS in 1995 and 1996, and give a detailed account of the data ...analysis. The enhancement over the reference of neutral meson decays amounts to a factor of 2.31 \(\pm0.19 (stat.)\pm0.55 (syst.)\pm0.69 (decays)\) for semi-central collisions (28\(\%\)\(\sigma/\sigma_{geo}\)) when yields are integrated over m > 200 MeV/c2 in invariant mass. The measured yield, its stronger-than-linear scaling with \(N_{\rm ch}\), and the dominance of low pair pt strongly suggest an interpretation as thermal radiation from pion annihilation in the hadronic fireball. The shape of the excess centring at \(m\approx\) 500 MeV/c2, however, cannot be described without strong medium modifications of the \(\rho\) meson. The results are put into perspective by comparison to predictions from Brown-Rho scaling governed by chiral symmetry restoration, and from the spectral-function many-body treatment in which the approach to the phase boundary is less explicit.
The effects of parental divorce during childhood and adolescence on the mental health of young adults (age 23) were examined, using the National Child Development Study (NCDS), a longitudinal, ...multimethod, nationally representative survey of all children born in Great Britain during 1 week in 1958 (N = 17,414). Children were assessed at birth and subsequently followed up at ages 7, 11, 16, and 23 by means of maternal and child interviews, and by psychological, school, and medical assessments. Parental divorce had a moderate, long-term negative impact on adult mental health, as measured by the Malaise Inventory total score, and controlling for economic status, children's emotional problems, and school performance preceding marital dissolution. The likelihood of scoring above the clinical cutoff of the Malaise Inventory rose from 8% to 11% due to parental divorce. This indicated that the relative risk of serious emotional disorders increased in the aftermath of divorce, but that the large majority of individuals did not exhibit such risks. Path analyses revealed that the negative effects of divorce on adult mental health operated indirectly through higher emotional problems and lower levels of school achievement and family economic status at age 16. Results related to timing of divorce, remarriage, and interactions between age 7 emotional problems and divorce, and between age 7 emotional problems and child gender, are also discussed.
In this article I argue that public discussions of demographic issues are often conducted in a troubling pattern in which one extreme position is debated in relation to the opposite extreme. This ...pattern impedes our understanding of social problems and is a poor guide to sound public policies. To illustrate this thesis I use the case of social scientific research examining how children are affected by not living with two biological parents while they are growing up. Over the last decade, I maintain, most of the public, and even many social scientists, have been puzzled and poorly informed by this debate. In particular I consider Judith Wallerstein's clinically based claims of the pervasive, profound harm caused by divorce and, at the other extreme, Judith Rich Harris's reading of behavioral genetics and evolutionary psychology, which leads her to dismiss the direct effects of divorce. Neither extreme gives a clear picture of the consequences of growing up in a single-parent family or a stepfamily.
PDF
