Ethical implications of research on craving

Cravings, intense desires to experience the effects of a drug, are widely regarded as significant impediments to overcoming addiction, although their role in relapse may be overstated. Scientists and clinicians wish to better understand the neurobiological and cognitive basis of craving so that they may develop psychotherapeutic, pharmacological and other medical methods to reduce craving and thereby drug use. The conduct of such research raises significant ethical issues. When recruiting individuals and conducting this research, scientists need to ensure that substance dependent participants have the capacity to provide free and uncoerced consent. This is especially the case in studies in which dependent participants are given their drug of addiction or provided with other inducements to participate (e.g. financial incentives) that may undermine their ability to fully consider the risks of participation.Treatments for addiction that seek to reduce cravings may also carry risks. This includes psychotherapeutic approaches, as well as pharmacological and medical treatments. Clinicians need to consider the risks and benefits of treatment and carefully communicate these to patients. The desire to reduce urges to use drugs should not be employed to justify potentially harmful and ineffective treatments. The safety and effectiveness of emerging treatments should be assessed by well conducted randomized controlled clinical trials

Is deep brain stimulation a prospective "cure" for addiction?

Deep brain stimulation has been put forward as a potential “cure” for intractable drug addiction. This is largely based on preclinical studies in animal models of addiction and small case series of positive, but short-term, effects on addictive behaviour in highly selected individuals. The history of neurosurgical treatment for psychiatric disorders suggests that we should be cautious in prematurely advocating invasive neurosurgical procedures on the basis of such limited evidence. Further research is required in animal models of addiction and in people treated for other neurological or psychiatric disorders before trials in addicted populations can be justified

Element rotation tolerance in a low-frequency aperture array polarimeter

We present a rotation error tolerance analysis for dual-polarized dipole-like antennas commonly found in low-frequency radio astronomy. A concise Jones matrix expression for the phased array is derived which facilitates calculations of rotation error effects in polarimetry. As expected, for random rotation error and number of elements approaching infinity, the estimation error converges to that of the error-free case. However, as in practice large but finite number of antennas are involved, we present a simple analysis to estimate rotation error effects. An example calculation based on a “baseline” design for a low-frequency Square Kilometre Array (SKA) “station” is discussed

Intrinsic cross-polarization ratio of dual-linearly polarized antennas for low-frequency radio astronomy

This note discusses the intrinsic cross-polarization ratio (IXR) from an antenna engineering perspective in that we seek to identify an a priori (coordinate) system where IXR is well approximated by the raw cross-polarization numbers. We begin by establishing a special case where IXR is identical to the raw cross-polarization ratios for in-phase dual-linearly-polarized antennas when the Jones matrix is expressed using circular polarization bases. This insight allows physical interpretation of IXR which may be useful in antenna design and system calculations. In addition, we discuss comparisons between direct IXR calculations and circular polarization approximations for more realistic cases involving dual-polarized Murchison widefield array (MWA) bow-tie antennas

Antenna rotation error tolerance for a low-frequency aperture array polarimeter

We present antenna rotation error tolerance analysis for a polarimeter consisting of dual-linearly polarized dipole-like elements. Treating the elements as a phased array and expressing the measurement basis as circularly polarized (CP) results in a concise expression for the Jones matrix for the array. For the type of elements being considered, the matrix shows that the intrinsic cross-polarization ratio (IXR) of the array at the intended beam scanning direction is unaffected by small rotation errors. For random rotation error and very large number of elements, we further find that the relative Jones matrix estimation error converges to that of the error-free case at the intended beam scanning direction; however, the effect of element rotation error on array directivity and radiation pattern remains. Recasting the analysis with the array observing an unpolarized source, a relation between rotation error and cross-polarization “leakage” is obtained, wherein similar trends with very large number of elements hold true. Practical examples involving “large” number of elements such as the low frequency Square Kilometre Array are discussed

The Age of Onset of Substance Use Disorders

Illicit drug use frequently starts during adolescence and young adulthood. Early initiation of illicit drug use in this period is associated with continued drug use in adulthood, the development of dependence, polydrug use and a number of adverse social, educational and mental health outcomes. Understanding when and why illicit drug use starts has important implications for preventing a major source of personal and financial cost to individuals, families and communities. In this chapter, we review research on the prevalence of drug use in the early years, the impact of early illicit drug use on psychosocial outcomes in young adulthood and widely researched models that explain the early initiation of drug use. We explore the implications of evidence-based models for prevention of the early initiation of illicit drug use