Formation of ions and radicals from icy grains in comets

Ion and radical formation in comets are thought to occur primarily by photodissociation of gas phase molecules. Experimental evidence and theoretical calculations are presented that show that some of the radical and ions can come directly from ice grains. The experimental evidence suggest that if the frozen molecules on the surface of grains undergo direct dissociation then they may be able to release radicals directly in the gas phase. If the molecules undergo predissociation it is unlikely that they will release radicals in the gas phase since they should be quenched. Calculations of this direct photodissociation mechanism further indicate that even if the parent molecule undergoes direct dissociation, the yield will not be high enough to explain the rays structure in comets unless the radicals are stored in the grains and then released when the grain evaporates. Calculations were also performed to determine the maximum number of ions that can be stored in an icy grain's radius. This number is compared with the ratio of the ion to neutral molecular density. The comparison suggests that some of the ions observed near the nucleus of the comet could have originally been present in the cometary nucleus. It is also pointed out that the presence of these ions in icy grains could lead to radical formation via electron recombination. Finally, an avalanche process was evaluated as another means of producing ions in comets

The impact of magnetic resonance imaging on juror perceptions of guilt

This study examined the impact of MRI-based evidence on juror perceptions of guilt in a criminal case. Jury eligible undergraduates read one of three mock trial summaries of a murder case wherein MRI evidence was manipulated: (1) MRI evidence with accompanying neuroimages, (2) MRI evidence without accompanying brain images, or (3) no MRI evidence. The proportion of guilty verdicts rendered was statistically similar across all conditions. In addition, participants did not list MRI evidence as the most influential piece of evidence for their verdict. Based on the results of this study it appears that MRI-based evidence and neuroimages do not significantly influence the juror decision making processes. Implications and future directions are discussed

Provision of Fluoride Varnish Treatment by Medical and Dental Care Providers: Variation by Race/Ethnicity and Levels of Urban Influence

Objective: In 2004, Wisconsin Medicaid policy changed to allow medical care providers to be reimbursed for fluoride varnish treatment (FVT) to children\u27s teeth to improve access and utilization. To date, no study has been published on whether geographic and racial/ethnic variation in the provision of FVT in response to this policy change exists. This study\u27s objective is to examine the association of rates of FVT for children enrolled in Wisconsin Medicaid with race/ethnicity, urban influence codes (UIC), and dental health professional shortage area (DHPSA) designation based on county of residence. Methods: A retrospective, pre–post design was used based on FVT claims for children in the Wisconsin Medicaid program from 2002 to 2006. Poisson regression models were used to evaluate the association of rates of FVT claims with race/ethnicity, UIC, and DHPSA designation. Results: The rate of FVT claims varied by resident county-type according to UIC and DHPSA designation, age, and race/ethnicity. Post-policy, the largest increases were observed for Native Americans residing in non-DHPSA counties, enrollees living in rural counties, and for Hispanics living in partial and entire DHPSA counties. African-Americans residing in partial DHPSA and metropolitan counties displayed the lowest rates of FVT claims. Conclusions: Overall access and utilization of FVT increased, but substantial racial/ethnic and geographic variation in the provision of FVT for children enrolled in Wisconsin Medicaid was observed. Future policies should incorporate measures that will specifically address the racial and geographic variations identified in this study

Simultaneous Measurements of Noncommuting Observables. Positive Transformations and Instrumental Lie Groups

We formulate a general program for [...] analyzing continuous, differential weak, simultaneous measurements of noncommuting observables, which focuses on describing the measuring instrument autonomously, without states. The Kraus operators of such measuring processes are time-ordered products of fundamental differential positive transformations, which generate nonunitary transformation groups that we call instrumental Lie groups. The temporal evolution of the instrument is equivalent to the diffusion of a Kraus-operator distribution function defined relative to the invariant measure of the instrumental Lie group [...]. This way of considering instrument evolution we call the Instrument Manifold Program. We relate the Instrument Manifold Program to state-based stochastic master equations. We then explain how the Instrument Manifold Program can be used to describe instrument evolution in terms of a universal cover[,] the universal instrumental Lie group, which is independent [...] of Hilbert space. The universal instrument is generically infinite dimensional, in which situation the instrument's evolution is chaotic. Special simultaneous measurements have a finite-dimensional universal instrument, in which case the instrument is considered to be principal and can be analyzed within the [...] universal instrumental Lie group. Principal instruments belong at the foundation of quantum mechanics. We consider the three most fundamental examples: measurement of a single observable, of position and momentum, and of the three components of angular momentum. These measurements limit to strong simultaneous measurements. For a single observable, this gives the standard decay of coherence between inequivalent irreps; for the latter two, it gives a collapse within each irrep onto the canonical or spherical phase space, locating phase space at the boundary of these instrumental Lie groups.Comment: 47 pages, 1 figur

Simultaneous Momentum and Position Measurement and the Instrumental Weyl-Heisenberg Group

The canonical commutation relation, $[Q,P] = i\hbar$, stands at the foundation of quantum theory and the original Hilbert space. The interpretation of $P$ & $Q$ as observables has always relied on the analogies that exist between the unitary transformations of Hilbert space and the canonical (a.k.a. contact) transformations of classical phase space. Now that the theory of quantum measurement is essentially complete (this took a while), it is possible to revisit the canonical commutation relation in a way that sets the foundation of quantum theory not on unitary transformations, but on positive transformations. This paper shows how the concept of simultaneous measurement leads to a fundamental differential geometric problem whose solution shows us the following: The simultaneous $P$ & $Q$ measurement (SPQM) defines a universal measuring instrument, which takes the shape of a 7-dimensional manifold, a universal covering group we call the Instrumental Weyl-Heisenberg Group, IWH. The group IWH connects the identity to classical phase space in unexpected ways that are significant enough that the positive-operator-valued measure (POVM) offers a complete alternative to energy quantization. Five of the dimensions define processes that can be easily recognized and understood. The other two dimensions, the normalization and phase in the center of IWH, are less familiar. The normalization, in particular, requires special handling in order to describe and understand the SPQM instrument.Comment: 53 pages, 0 figures (so sorry

Deconstructing Superconductivity

We present a dimensionally deconstructed model of an s-wave holographic superconductor. The 2+1 dimensional model includes multiple charged Cooper pair fields and neutral exciton fields that have interactions governed by hidden local symmetries. We derive AdS/CFT-like relations for the current and charge density in the model, and we analyze properties of the Cooper pair condensates and the complex conductivity.Comment: 24 pages, 10 eps figures. v2: Sign conventions clarified, references adde

The food safety culture in a large South African food service complex: Perspectives on a case study

Published ArticleThe purpose of this paper is to assess elements of food safety management and food safety culture within a prominent South African entertainment, hotel and food service complex. Design/methodology/approach In this paper a qualitative case study approach was used. Following a comprehensive literature review, based on factors known to be important in developing a food safety culture, in combination with national and international food safety standards, an interview guide was constructed and utilised in a series of semi-structured interviews. The interviewees represented different management levels involved in food delivery but did not include board level managers. Findings Many of the factors considered important in good food safety management, including the presence of a formal food safety policy and the creation and maintenance of a positive food safety culture, were absent. Although a formal system of internal hygiene auditing existed and food safety training was provided to food handlers they were not integrated into a comprehensive approach to food safety management. Food safety leadership, communication and support were considered deficient with little motivation for staff to practise good hygiene. Originality/value Food safety culture is increasingly recognised as a contributory factor in foodborne disease outbreaks and is the focus of increasing research. However, although every food business has a unique food safety culture there are relatively few published papers concerning its analysis, application and use within specific businesses. This case study has identified food safety culture shortcomings within a large food service facility suggesting there was a potentially significant food safety risk and indicates ways in which food safety could be improved and the risk reduced. The results also suggest further work is needed in the subject of food safety culture and its potential for reducing foodborne disease

Burnout Prevalence in PA Students

2016 AAPA Poster Session Abstrac

Assessing a Hydrodynamic Description for Instabilities in Highly Dissipative, Freely Cooling Granular Gases

An intriguing phenomenon displayed by granular flows and predicted by kinetic-theory-based models is the instability known as particle "clustering," which refers to the tendency of dissipative grains to form transient, loose regions of relatively high concentration. In this work, we assess a modified-Sonine approximation recently proposed [Garz\'o et al., Physica A 376, 94 (2007)] for a granular gas via an examination of system stability. In particular, we determine the critical length scale associated with the onset of two types of instabilities -vortices and clusters- via stability analyses of the Navier-Stokes-order hydrodynamic equations by using the expressions of the transport coefficients obtained from both the standard and the modified-Sonine approximations. We examine the impact of both Sonine approximations over a range of solids fraction \phi <0.2 for small restitution coefficients e=0.25--0.4, where the standard and modified theories exhibit discrepancies. The theoretical predictions for the critical length scales are compared to molecular dynamics (MD) simulations, of which a small percentage were not considered due to inelastic collapse. Results show excellent quantitative agreement between MD and the modified-Sonine theory, while the standard theory loses accuracy for this highly dissipative parameter space. The modified theory also remedies a (highdissipation) qualitative mismatch between the standard theory and MD for the instability that forms more readily. Furthermore, the evolution of cluster size is briefly examined via MD, indicating that domain-size clusters may remain stable or halve in size, depending on system parameters.Comment: 4 figures; to be published in Phys. Rev.

A U.S. Carbon Cycle Science Plan: First Meeting of the Carbon Cycle Science Working Group; Washington, D. C., 17–18 November 2008

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95400/1/eost16754.pd