Generation of High-Energy Photons with Large Orbital Angular Momentum by Compton Backscattering

Usually, photons are described by plane waves with a definite 4-momentum. In addition to plane-wave photons, "twisted photons" have recently entered the field of modern laser optics; these are coherent superpositions of plane waves with a defined projection hbar*m of the orbital angular momentum onto the propagation axis, where m is integer. In this paper, we show that it is possible to produce high-energy twisted photons by Compton backscattering of twisted laser photons off ultra-relativistic electrons. Such photons may be of interest for experiments related to the excitation and disintegration of atoms and nuclei, and for studying the photo-effect and pair production off nuclei in previously unexplored experimental regimes.Comment: 4 pages; RevTe

Learning and using mathematics software the natural way

AbstractWe motivate the need for more standard while natural ways of accessing the growing number of internet applications of mathematics software. We then identify a subset of natural language appropriate for this task, and describe an efficient logic programming transformation from this subset of language into the desired commands. We use substructural logic for dealing with different kinds of mathematical anaphora. We exemplify our ideas in the context of Maple, an advanced mathematics software for symbolic computing

Determination of electromagnetic medium from the Fresnel surface

We study Maxwell's equations on a 4-manifold where the electromagnetic medium is described by an antisymmetric $2\choose 2$-tensor $\kappa$. In this setting, the Tamm-Rubilar tensor density determines a polynomial surface of fourth order in each cotangent space. This surface is called the Fresnel surface and acts as a generalisation of the light-cone determined by a Lorentz metric; the Fresnel surface parameterises electromagnetic wave-speed as a function of direction. Favaro and Bergamin have recently proven that if $\kappa$ has only a principal part and if the Fresnel surface of $\kappa$ coincides with the light cone for a Lorentz metric $g$, then $\kappa$ is proportional to the Hodge star operator of $g$. That is, under additional assumptions, the Fresnel surface of $\kappa$ determines the conformal class of $\kappa$. The purpose of this paper is twofold. First, we provide a new proof of this result using Gr\"obner bases. Second, we describe a number of cases where the Fresnel surface does not determine the conformal class of the original $2\choose 2$-tensor $\kappa$. For example, if $\kappa$ is invertible we show that $\kappa$ and $\kappa^{-1}$ have the same Fresnel surfaces.Comment: 23 pages, 1 figur

Millimeter Wave Localization: Slow Light and Enhanced Absorption

We exploit millimeter wave technology to measure the reflection and transmission response of random dielectric media. Our samples are easily constructed from random stacks of identical, sub-wavelength quartz and Teflon wafers. The measurement allows us to observe the characteristic transmission resonances associated with localization. We show that these resonances give rise to enhanced attenuation even though the attenuation of homogeneous quartz and Teflon is quite low. We provide experimental evidence of disorder-induced slow light and superluminal group velocities, which, in contrast to photonic crystals, are not associated with any periodicity in the system. Furthermore, we observe localization even though the sample is only about four times the localization length, interpreting our data in terms of an effective cavity model. An algorithm for the retrieval of the internal parameters of random samples (localization length and average absorption rate) from the external measurements of the reflection and transmission coefficients is presented and applied to a particular random sample. The retrieved value of the absorption is in agreement with the directly measured value within the accuracy of the experiment.Comment: revised and expande

Differential gaze behavior towards sexually preferred and non-preferred human figures

The gaze pattern associated with image exploration is a sensitive index of our attention, motivation and preference. To examine whether an individual’s gaze behavior can reflect his/her sexual interest, we compared gaze patterns of young heterosexual men and women (M = 19.94 years, SD = 1.05) while viewing photos of plain-clothed male and female figures aged from birth to sixty years old. Our analysis revealed a clear gender difference in viewing sexually preferred figure images. Men displayed a distinctive gaze pattern only when viewing twenty-year-old female images, with more fixations and longer viewing time dedicated to the upper body and waist-hip region. Women also directed more attention at the upper body on female images in comparison to male images, but this difference was not age-specific. Analysis of local image salience revealed that observers’ eye-scanning strategies could not be accounted for by low-level processes, such as analyzing local image contrast and structure, but were associated with attractiveness judgments. The results suggest that the difference in cognitive processing of sexually preferred and non-preferred figures can be manifested in gaze patterns associated with figure viewing. Thus, eye-tracking holds promise as a potential sensitive measure for sexual preference, particularly in men

Staphylococcal Toxic Epidermal Necrolysis: Pathogenesis And Studies On The Subcellular Site Of Action Of Exfoliatin

An exfoliating substance elaborated by certain phage Group 2 staphylococci causes toxic epidermal necrolysis. Both in man and in the newborn mouse, intraepidermal cleavage is the predominant histologic feature following exposure to this toxin. Electron microscopic study of sequential biopsy specimens obtained from neonatal mice and from organ cultures of human skin revealed intercellular cleavage and cell separation. The extracellular nature of the exfoliative process was confirmed in several ways: (1) perfused tracers did not penetrate cells during cell separation; (2) cultured cells exposed to high doses of exfoliating fractions demonstrated no signs of injury; and (3) cleaved surfaces examined by scanning electron microscopy and surface replication demonstrated intact plasma membranes. When fractions capable of inducing exfoliation were applied to cultured keratinocytes or fibroblasts, sperm, or lymphocyte suspensions, and to human or mouse skin in vivo, they did not alter the distribution or intensity of concanavalin A binding, ruthenium red staining, pemphigus antibody binding, or HL-A surface antigens. Therefore, while the pathogenesis of staphylococcal toxic epidermal necrolysis involves intercellular cleavage, the molecular cell surface target remains unknown

Domestic Violence and the Mental Health and Well-being of Victims and Their Children

Almost one third of women worldwide report some form of physical or sexual violence by a partner in their lifetime, yet little is known about the mental health and well-being effects for either victims or their children. We study the costs associated with domestic violence (DV) in the context of Norway, where we can link offenders to victims and their children over time. Our difference-in-differences framework uses those who will be victimized in the future as controls. We find that a DV report involving the police is associated with large changes in the home environment, including marital dissolution and a corresponding decline in financial resources. A DV report increases mental health visits by 35% for victims and by 19% for their children in the year of the event, effects which taper off over time for the victim, but not for children. Victims also experience more doctor visits, lower employment, reduced earnings and a higher use of disability insurance while their children are more likely to receive child protective services and commit a crime. Using a complementary RD design, we find that a DV report results in declines both in children’s test scores and completion of the first year of high school

Attitudes of cannabis growers to regulation of cannabis cultivation under a non-prohibition cannabis model

Background: How cannabis cultivation is dealt with under various examples of cannabis legalization or regulation is an important consideration in design of such schemes. This study aimed to (i) investigate support among current or recent cannabis growers, for various potential policy options for cannabis cultivation if prohibition were repealed, and (ii) explore the support for these options across countries, scale of growing operations, demographics, drug use and cannabis supply involvement variables. Methods: This study utilized data from the online web survey of largely 'small-scale' cannabis cultivators, aged 18. yrs and over, in eleven countries conducted by the Global Cannabis Cultivation Research Consortium (GCCRC). Data from 1722 current and recent cannabis growers in Australia, Denmark and the UK, who were all asked about policy, were included in the analysis. It investigated support for various frameworks for cultivation: (no regulation (. free market); adult only; growing licenses; restrictions on plant numbers; licensed business-only sale; approved commercial growing; etc.). Among current growers, support for these options were compared across countries, across scale of growing operations, and by demographics, drug use and crime variables. Results: Although there were some between country differences in support for the various policy options, what was striking was the similarity of the proportions for each of the eight most popular policy options. Among current growers, many of these positions were predicted by demographic, drug use and cannabis growing variables which were conceptually congruent with these positions. Conclusion: The results have relevance for the provisions regarding cannabis cultivation in the design of new non-prohibitionist models of cannabis which are increasingly under consideration. It should be of interest to policy makers, drug policy researchers, law enforcement and cannabis cultivators