Accurate photoionisation cross section for He at non-resonant photon energies

The total single-photon ionisation cross section was calculated for helium atoms in their ground state. Using a full configuration-interaction approach the photoionisation cross section was extracted from the complex-scaled resolvent. In the energy range from ionisation threshold to 59\,eV our results agree with an earlier $B$-spline based calculation in which the continuum is box discretised within a relative error of $0.01\%$ in the non-resonant part of the spectrum. Above the \He^{++} threshold our results agree on the other hand very well to a recent Floquet calculation. Thus our calculation confirms the previously reported deviations from the experimental reference data outside the claimed error estimate. In order to extend the calculated spectrum to very high energies, an analytical hydrogenic-type model tail is introduced that should become asymptotically exact for infinite photon energies. Its universality is investigated considering also H$^-$, Li$^+$, and HeH$^+$. With the aid of the tail corrections to the dipole approximation are estimated.Comment: 20 pages, 7 figures, 2 table

The Business of Employing People with Disabilities: Four Case Studies

This exploratory study examines employer attitudes towards people with disabilities in the labor market. Through in-depth, semi-structured interviews with senior management, human resources staff, directors of diversity, and hiring managers at four corporations, it pinpoints reasons why businesses chose to hire people with disabilities, investigates the perceived benefits and barriers to hiring people with disabilities, and identifies strategies for successfully hiring and retaining workers with disabilities. It fills a gap in examining the attitudes and decision-making processes of U.S. companies that have been leaders in hiring people with disabilities, as well as delving into the special issues of small businesses that may lack exposure to disability employment. It closes with directions for future studies that could extend our understanding of employment of people with disabilities

Public Health Ethics: Cases Spanning the Globe

Public health ethics can be seen both as the application of principles and norms to guide the practice of public health and as a process for identifying, analyzing, and resolving ethical issues inherent in the practice of public health. Public health ethics helps us decide what we should do and why. Although the practice of public health has always considered ethical issues, the emergence of public health ethics as a discipline is relatively new. Although rooted in bioethics and clinical and research ethics, public health ethics has many characteristics that set it apart. The defining characteristics are its focus on achieving social goods for populations while respecting individual rights and recognizing the interdependence of people. Currently there are few practical training resources for public health practitioners that consider ethical issues and dilemmas likely to arise in the practice of public health. In public health ethics training, we have found it advantageous to use cases to illustrate how ethical principles can be applied in practical ways to decision making. The use of cases encourages reflection and discussion of ethics, reinforces basic ethical concepts through application to concrete examples, highlights practical decision making, allows learners to consider different perspectives, and sensitizes learners to the complex, multidimensional context of issues in public health practice. The case-based approach (known as casuistry) contrasts with the theoretical approach to considering moral principles, rules, and theories. By describing scenarios, cases allow the learner to use ethical principles in the context of a realistic situation that sheds light on ethical challenges and illustrates how ethical principles can help in making practical decisions. This casebook comprises a broad range of cases from around the globe to highlight the ethical challenges of public health. For those new to public health ethics, Section I introduces public health ethics. Chapter 1, “Public Health Ethics: Global Cases, Practice, and Context” by Ortmann and colleagues, summarizes basic concepts and describes how public health ethics differ from bioethics, clinical ethics, and research ethics. The chapter also includes an approach for conducting an ethical analysis in public health. In Chap. 2, “Essential Cases in the Development of Public Health Ethics,” Lee, Spector-Bagdady, and Sakhuja highlight important events that shaped the practice of public health and explain how practitioners address and prevent ethical challenges. Section II is organized into chapters that discuss the following public health topics: • Resource allocation and priority setting • Disease prevention and control • Chronic disease prevention and health promotion • Environmental and occupational public health • Vulnerability and marginalized populations • International collaboration for global public health • Public health research We have invited some of the leading writers and thinkers in public health ethics to provide an overview of the major ethical considerations associated with each topic. The topic overviews offer the authors’ perspectives about applicable ethical theories, frameworks, and tools and draw attention to the cases that follow. The cases are meant to highlight the ethical issues in practice. Each represents the work of authors from around the globe who responded to a solicitation from the U.S. Centers for Disease Control and Prevention. We worked with the authors to ensure that each case included a concise articulation of a public health situation that raises ethical tensions, challenges, or concerns that require decisions or recommendations from public health officials or practitioners. The cases are presented in a standard format that includes a background, case description, discussion questions, and references. However, we also allowed for variation in the amount of detail provided in each section and the approach used to set up the case. Our goal was to include just enough contextual information to orient the reader who is not an expert in the case topic. We include the case setting, population, or intervention in question, legal or regulatory landscape, and questions to stimulate discussion on core ethical issues. Each case—although fictionalized—is as realistic as possible to reflect the ethical challenges that public health practitioners face daily. Sometimes the cases were based on actual or composite events. In these instances, the case details were modified to exclude identifying information that could be considered private, sensitive, or disputable by others involved in the case. We deliberately did not attempt to provide a resolution or solution for the cases. Often in public health practice, there is no single correct answer. Instead, ethical analysis in public health is a process to identify the ethical dimensions of the options available and to arrive at a decision that is ethically justifiable, through deliberation and consideration of relevant facts, values, and contexts. The cases and other writings in this book represent the opinions, findings, and conclusions of the authors and do not necessarily reflect the official position, views, or policies of the editors, the editors’ host institutions, or the authors’ host institutions. We decided which topic category to place the case in to best distribute the cases across chapters. However, you may note that some cases cross topic areas and could just as easily have been included in another chapter. This casebook is written for public health practitioners, including frontline workers, field epidemiology trainers and trainees, and managers, planners, and decision makers with an interest in learning about how to integrate ethical analysis in their day-to-day public health practice. However, the casebook will also be useful to instructors in schools of public health and public health students as well as to academic ethicists who can use the book to teach public health ethics and distinguish it from clinical and research ethics. Our hope is that the casebook will increase awareness and understanding of public health ethics and the value of ethical analysis in public health practice in all of its forms. This includes applied public health research; public health policy development, implementation, and evaluation; and public health decision making in national and international field settings and training programs. By emphasizing prospective practical decision making, rather than just presenting a theoretical academic discussion of ethical principles, we hope this casebook will serve as a useful tool to support instruction, debate, and dialogue about the nature of ethical challenges encountered in public health practice and how to resolve these challenges. We recommend discussing the cases in small groups and using the discussion questions, the ethical framework described in Chap. 1, and the information provided in the topic area overview sections as a starting place for exploring the ethical issues reflected in the cases. The ultimate goal of case-based learning is to develop skills in ethical analysis and decision making in daily public health practice. The ethical framework provides a convenient tool for putting our ideas into practice

Interference in strong-field ionization of a two-centre atomic system

Strong-field photoionization of argon dimers by a few-cycle laser pulse is investigated using electron-ion coincidence momentum spectroscopy. The momentum distribution of the photoelectrons exhibits interference due to the emission from the two atomic argon centres, in analogy with a Young's doubleslit experiment. However, a simulation of the dimer photoelectron momentum spectrum based on the atomic spectrum supplemented with a theoretically derived interference term leads to distinct deviations from the experimental result. The deviations may have their origin in a complex electron dynamics during strong-field ionization of the Ar2 dimer. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

Testing Scalar-Tensor Gravity with Gravitational-Wave Observations of Inspiralling Compact Binaries

Observations of gravitational waves from inspiralling compact binaries using laser-interferometric detectors can provide accurate measures of parameters of the source. They can also constrain alternative gravitation theories. We analyse inspiralling compact %binaries in the context of the scalar-tensor theory of Jordan, Fierz, Brans and Dicke, focussing on the effect on the inspiral of energy lost to dipole gravitational radiation, whose source is the gravitational self-binding energy of the inspiralling bodies. Using a matched-filter analysis we obtain a bound on the coupling constant $\omega_{\rm BD}$ of Brans-Dicke theory. For a neutron-star/black-hole binary, we find that the bound could exceed the current bound of $\omega_{\rm BD}>500$ from solar-system experiments, for sufficiently low-mass systems. For a $0.7 M_\odot$ neutron star and a $3 M_\odot$ black hole we find that a bound $\omega_{\rm BD} \approx 2000$ is achievable. The bound decreases with increasing black-hole mass. For binaries consisting of two neutron stars, the bound is less than 500 unless the stars' masses differ by more than about $0.5 M_\odot$. For two black holes, the behavior of the inspiralling binary is observationally indistinguishable from its behavior in general relativity. These bounds assume reasonable neutron-star equations of state and a detector signal-to-noise ratio of 10.Comment: 10 pages, (3 figures upon request), WUGRAV-94-

On spontaneous scalarization

We study in the physical frame the phenomenon of spontaneous scalarization that occurs in scalar-tensor theories of gravity for compact objects. We discuss the fact that the phenomenon occurs exactly in the regime where the Newtonian analysis indicates it should not. Finally we discuss the way the phenomenon depends on the equation of state used to describe the nuclear matter.Comment: 41 pages, RevTex, 10 ps figures, submitted to Phys. Rev.

Coherent bremsstrahlung, boherent pair production, birefringence and polarimetry in the 20-170 GeV energy range using aligned crystals

The processes of coherent bremsstrahlung (CB) and coherent pair production (CPP) based on aligned crystal targets have been studied in the energy range 20-170 GeV. The experimental arrangement allowed for measurements of single photon properties of these phenomena including their polarization dependences. This is significant as the theoretical description of CB and CPP is an area of active theoretical debate and development. With the theoretical approach used in this paper both the measured cross sections and polarization observables are predicted very well. This indicates a proper understanding of CB and CPP up to energies of 170 GeV. Birefringence in CPP on aligned crystals is applied to determine the polarization parameters in our measurements. New technologies for high energy photon beam optics including phase plates and polarimeters for linear and circular polarization are demonstrated in this experiment. Coherent bremsstrahlung for the strings-on-strings (SOS) orientation yields a larger enhancement for hard photons than CB for the channeling orientations of the crystal. Our measurements and our calculations indicate low photon polarizations for the high energy SOS photons.Comment: 23 pages, 27 figures, 2 tables, REVTeX4 two column

The LAGUNA design study- towards giant liquid based underground detectors for neutrino physics and astrophysics and proton decay searches

The feasibility of a next generation neutrino observatory in Europe is being considered within the LAGUNA design study. To accommodate giant neutrino detectors and shield them from cosmic rays, a new very large underground infrastructure is required. Seven potential candidate sites in different parts of Europe and at several distances from CERN are being studied: Boulby (UK), Canfranc (Spain), Fr\'ejus (France/Italy), Pyh\"asalmi (Finland), Polkowice-Sieroszowice (Poland), Slanic (Romania) and Umbria (Italy). The design study aims at the comprehensive and coordinated technical assessment of each site, at a coherent cost estimation, and at a prioritization of the sites within the summer 2010.Comment: 5 pages, contribution to the Workshop "European Strategy for Future Neutrino Physics", CERN, Oct. 200

Employing phylogenetic tree shape statistics to resolve the underlying host population structure

BACKGROUND: Host population structure is a key determinant of pathogen and infectious disease transmission patterns. Pathogen phylogenetic trees are useful tools to reveal the population structure underlying an epidemic. Determining whether a population is structured or not is useful in informing the type of phylogenetic methods to be used in a given study. We employ tree statistics derived from phylogenetic trees and machine learning classification techniques to reveal an underlying population structure. RESULTS: In this paper, we simulate phylogenetic trees from both structured and non-structured host populations. We compute eight statistics for the simulated trees, which are: the number of cherries; Sackin, Colless and total cophenetic indices; ladder length; maximum depth; maximum width, and width-to-depth ratio. Based on the estimated tree statistics, we classify the simulated trees as from either a non-structured or a structured population using the decision tree (DT), K-nearest neighbor (KNN) and support vector machine (SVM). We incorporate the basic reproductive number ([Formula: see text]) in our tree simulation procedure. Sensitivity analysis is done to investigate whether the classifiers are robust to different choice of model parameters and to size of trees. Cross-validated results for area under the curve (AUC) for receiver operating characteristic (ROC) curves yield mean values of over 0.9 for most of the classification models. CONCLUSIONS: Our classification procedure distinguishes well between trees from structured and non-structured populations using the classifiers, the two-sample Kolmogorov-Smirnov, Cucconi and Podgor-Gastwirth tests and the box plots. SVM models were more robust to changes in model parameters and tree size compared to KNN and DT classifiers. Our classification procedure was applied to real -world data and the structured population was revealed with high accuracy of [Formula: see text] using SVM-polynomial classifier