The effect of cocaine on gastric mucosal PGE2, LTC4 and ulcerations

The association between cocaine use and acute gastroduodenal perforation is known. The effect of cocaine and stress on gastric mucosal ulceration and the levels of prostaglandin E2 (PGE2) and leukotriene C4 (LTC4) was studied in 40 Sprague–Dawley rats. Controls received intraperitoneal (i.p.) saline, ten received i.p. cocaine (35 mg/kg), ten were stressed by the cold restraint method, and ten had i.p. cocaine and stress. Cocaine alone did not induce ulceration, but decreased PGE2 levels. Stress alone caused ulceration, but was not associated with a change in either PGE2 or LTC4 levels. When combined with stress, however, cocaine caused a three-fold increase in ulceration and a significant increase in PGE2 and LTC4 levels. Stress may predispose the cocaine addict to loss of gastroduodenal mucosal integrity, which is related to an imbalance of PGE2 and LTC4 synthesis

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

Reconciling MOND and dark matter?

Observations of galaxies suggest a one-to-one analytic relation between the inferred gravity of dark matter at any radius and the enclosed baryonic mass, a relation summarized by Milgrom's law of modified Newtonian dynamics (MOND). However, present-day covariant versions of MOND usually require some additional fields contributing to the geometry, as well as an additional hot dark matter component to explain cluster dynamics and cosmology. Here, we envisage a slightly more mundane explanation, suggesting that dark matter does exist but is the source of MOND-like phenomenology in galaxies. We assume a canonical action for dark matter, but also add an interaction term between baryonic matter, gravity, and dark matter, such that standard matter effectively obeys the MOND field equation in galaxies. We show that even the simplest realization of the framework leads to a model which reproduces some phenomenological predictions of cold dark matter (CDM) and MOND at those scales where these are most successful. We also devise a more general form of the interaction term, introducing the medium density as a new order parameter. This allows for new physical effects which should be amenable to observational tests in the near future. Hence, this very general framework, which can be furthermore related to a generalized scalar-tensor theory, opens the way to a possible unification of the successes of CDM and MOND at different scales.Comment: 9 page

Tunneling-percolation origin of nonuniversality: theory and experiments

A vast class of disordered conducting-insulating compounds close to the percolation threshold is characterized by nonuniversal values of transport critical exponent t, in disagreement with the standard theory of percolation which predicts t = 2.0 for all three dimensional systems. Various models have been proposed in order to explain the origin of such universality breakdown. Among them, the tunneling-percolation model calls into play tunneling processes between conducting particles which, under some general circumstances, could lead to transport exponents dependent of the mean tunneling distance a. The validity of such theory could be tested by changing the parameter a by means of an applied mechanical strain. We have applied this idea to universal and nonuniversal RuO2-glass composites. We show that when t > 2 the measured piezoresistive response \Gamma, i. e., the relative change of resistivity under applied strain, diverges logarithmically at the percolation threshold, while for t = 2, \Gamma does not show an appreciable dependence upon the RuO2 volume fraction. These results are consistent with a mean tunneling dependence of the nonuniversal transport exponent as predicted by the tunneling-percolation model. The experimental results are compared with analytical and numerical calculations on a random-resistor network model of tunneling-percolation.Comment: 13 pages, 12 figure

Spiral Galaxies Rotation Curves with a Logarithmic Corrected Newtonian Gravitational Potential

We analyze the rotation curves of 10 spiral galaxies with a newtonian potential corrected with an extra logarithmic term, using a disc modelization for the spiral galaxies. There is a new constant associated with the extra term in the potential. The rotation curve of the chosen sample of spiral galaxies is well reproduced for a given range of the new constant. It is argued that this correction can have its origin from string configurations. The compatibility of this correction with local physics is discussed.Comment: Latex file, 6 pages, 20 figure

Dark Energy, scalar-curvature couplings and a critical acceleration scale

We study the effects of coupling a cosmologically rolling scalar field to higher order curvature terms. We show that when the strong coupling scale of the theory is on the 10^{-3}-10^{-1}eV range, the model passes all experimental bounds on the existence of fifth forces even if the field has a mass of the order of the Hubble scale in vacuum and non-suppressed couplings to SM fields. The reason is that the coupling to certain curvature invariant acts as an effective mass that grows in regions of large curvature. This prevents the field from rolling down its potential near sources and makes its effects on fifth-force search experiments performed in the laboratory to be observable only at the sub-mm scale. We obtain the static spherically symmetric solutions of the theory and show that a long-range force appears but it is turned on only below a fixed Newtonian acceleration scale of the order of the Hubble constant. We comment on the possibility of using this feature of the model to alleviate the CDM small scale crisis and on its possible relation to MOND.Comment: 12 pages, 2 figure

Limits to Poisson's ratio in isotropic materials

A long-standing question is why Poisson's ratio v nearly always exceeds 0.2 for isotropic materials, whereas classical elasticity predicts v to be between -1 to 1/2. We show that the roots of quadratic relations from classical elasticity divide v into three possible ranges: -1 < v <= 0, 0 <= v <= 1/5, and 1/5 <= v < 1/2. Since elastic properties are unique there can be only one valid set of roots, which must be 1/5 <= v < 1/2 for consistency with the behavior of real materials. Materials with Poisson's ratio outside of this range are rare, and tend to be either very hard (e.g., diamond, beryllium) or porous (e.g., auxetic foams); such substances have more complex behavior than can be described by classical elasticity. Thus, classical elasticity is inapplicable whenever v < 1/5, and the use of the equations from classical elasticity for such materials is inappropriate.Comment: Physical Review B, in pres

Dispersively detected Pauli Spin-Blockade in a Silicon Nanowire Field-Effect Transistor

We report the dispersive readout of the spin state of a double quantum dot formed at the corner states of a silicon nanowire field-effect transistor. Two face-to-face top-gate electrodes allow us to independently tune the charge occupation of the quantum dot system down to the few-electron limit. We measure the charge stability of the double quantum dot in DC transport as well as dispersively via in-situ gate-based radio frequency reflectometry, where one top-gate electrode is connected to a resonator. The latter removes the need for external charge sensors in quantum computing architectures and provides a compact way to readout the dispersive shift caused by changes in the quantum capacitance during interdot charge transitions. Here, we observe Pauli spin-blockade in the high-frequency response of the circuit at finite magnetic fields between singlet and triplet states. The blockade is lifted at higher magnetic fields when intra-dot triplet states become the ground state configuration. A lineshape analysis of the dispersive phase shift reveals furthermore an intradot valley-orbit splitting $\Delta_{vo}$ of 145 $\mu$eV. Our results open up the possibility to operate compact CMOS technology as a singlet-triplet qubit and make split-gate silicon nanowire architectures an ideal candidate for the study of spin dynamics