65 research outputs found

    N=2 Quantum Field Theories and their BPS quivers

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    We explore the relationship between four-dimensional N = 2 quantum field theories and their associated BPS quivers. For a wide class of theories including super-Yang-Mills theories, Argyres- Douglas models, and theories defined by M5-branes on punctured Riemann surfaces, there exists a quiver which implicitly characterizes the field theory. We study various aspects of this correspondence including the quiver interpretation of flavor symmetries, gauging, decoupling limits, and field theory dualities. In general a given quiver describes only a patch of the moduli space of the field theory, and a key role is played by quantum mechanical dualities, encoded by quiver mutations, which relate distinct quivers valid in different patches. Analyzing the consistency conditions imposed on the spectrum by these dualities results in a powerful and novel mutation method for determining the BPS states. We apply our method to determine the BPS spectrum in a wide class of examples, including the strong coupling spectrum of super-Yang-Mills with an ADE gauge group and fundamental matter, and trinion theories defined by M5-branes on spheres with three punctures. \ua9 2014 International Press

    Pulsatile blood flow, shear force, energy dissipation and Murray's Law

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    BACKGROUND: Murray's Law states that, when a parent blood vessel branches into daughter vessels, the cube of the radius of the parent vessel is equal to the sum of the cubes of the radii of daughter blood vessels. Murray derived this law by defining a cost function that is the sum of the energy cost of the blood in a vessel and the energy cost of pumping blood through the vessel. The cost is minimized when vessel radii are consistent with Murray's Law. This law has also been derived from the hypothesis that the shear force of moving blood on the inner walls of vessels is constant throughout the vascular system. However, this derivation, like Murray's earlier derivation, is based on the assumption of constant blood flow. METHODS: To determine the implications of the constant shear force hypothesis and to extend Murray's energy cost minimization to the pulsatile arterial system, a model of pulsatile flow in an elastic tube is analyzed. A new and exact solution for flow velocity, blood flow rate and shear force is derived. RESULTS: For medium and small arteries with pulsatile flow, Murray's energy minimization leads to Murray's Law. Furthermore, the hypothesis that the maximum shear force during the cycle of pulsatile flow is constant throughout the arterial system implies that Murray's Law is approximately true. The approximation is good for all but the largest vessels (aorta and its major branches) of the arterial system. CONCLUSION: A cellular mechanism that senses shear force at the inner wall of a blood vessel and triggers remodeling that increases the circumference of the wall when a shear force threshold is exceeded would result in the observed scaling of vessel radii described by Murray's Law

    Heading Frequency and Risk of Cognitive Impairment in Retired Male Professional Soccer Players

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    Importance Although professional soccer players appear to be at higher risk of neurodegenerative disease, the reason remains unknown.Objective To examine whether heading frequency is associated with risk of cognitive impairment in retired professional soccer players.Design, Setting, and Participants A UK nationwide cross-sectional study was conducted between August 15, 2020, and December 31, 2021, in 459 retired male professional soccer players older than 45 years and registered with the Professional Footballers’ Association or a League Club Players’ Association.Exposure Data on heading frequency in 3 bands—0 to 5, 6 to 15, and more than 15 times per match or training session and other soccer-specific risk factors, such as player position and concussion—were collected through a self-reported questionnaire.Main Outcomes and Measures Cognitive impairment was defined using the Telephone Interview for Cognitive Status-modified as scores of less than or equal to 21. Hopkins Verbal Learning Test, verbal fluency, and independent activities of daily living were also assessed. Test Your Memory and physician-diagnosed dementia/Alzheimer disease were self-reported via the questionnaire. Adjusted odds ratios (AORs) with 95% CIs were calculated.Results Of 468 retired male professional soccer players who completed questionnaires (mean [SD] age, 63.68 [10.48]; body mass index, 27.22 [2.89]), 459 reported heading frequency: 114 headed 0 to 5 times, 185 headed 6 to 15 times, 160 headed more than 15 times per match, and 125 headed 0 to 5 times, 174 headed 6 to 15 times, and 160 headed more than 15 times per training session during their careers. The prevalence of cognitive impairment was 9.78% (0-5 times), 14.78% (6-15 times), and 15.20% (>15 times) per match (P = .51). Compared with players reporting 0 to 5 headers per match, the AORs were 2.71 (95% CI, 0.89-8.25) for players reporting 6 to 15 headers per match and 3.53 (95% CI, 1.13-11.04) for players reporting more than 15 headers per match (P = .03 for trend). Corresponding AORs for heading frequency per training session were 2.38 (95% CI, 0.82-6.95) for those reporting 6 to 15, and 3.40 (95% CI, 1.13-10.23) for those reporting more than 15 in comparison with those who reported 0 to 5 (P = .03 for trend). Concussion involving memory loss was also associated with a greater risk of cognitive impairment (AOR, 3.16; 95% CI, 1.08-9.22). Similar results were observed with other cognitive tests and self-reported physician-diagnosed dementia/Alzheimer disease.Conclusions and Relevance The findings of this study suggest that repetitive heading during a professional soccer career is associated with an increased risk of cognitive impairment in later life. Further study is needed to establish the upper threshold for heading frequency to mitigate this risk

    The Role of Information and Financial Reporting in Corporate Governance and Debt Contracting

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    We review recent literature on the role of financial reporting transparency in reducing governance-related agency conflicts among managers, directors, and shareholders, as well as in reducing agency conflicts between shareholders and creditors, and offer researchers some suggested avenues for future research. Key themes include the endogenous nature of debt contracts and governance mechanisms with respect to information asymmetry between contracting parties, the heterogeneous nature of the informational demands of contracting parties, and the heterogeneous nature of the resulting governance and debt contracts. We also emphasize the role of a commitment to financial reporting transparency in facilitating informal multiperiod contracts among managers, directors, shareholders, and creditors

    The audit reporting model: current research synthesis and implications

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    This research synthesis evaluates relevant research concerning the audit report. For too long, there has been a significant “expectations gap” between what financial statement users expect an audit is delivering and what the audit profession believes it is providing. This gap becomes particularly problematic for auditors when there is a “business crisis” and attention is directed to the role of the auditor. Two related gaps are considered in this synthesis, a communications gap, and an information gap. All of these gaps relate to the demand for, understanding of, and use of auditor communications, which is the focus of this synthesis. Our synthesis is driven by two primary research questions: What do financial statement users perceive as information that should be communicated, and what does research show to be the effects on users of existing and other auditor communications currently being considered? As we discuss in detail, prior research does address many aspects of these two questions, but many of the findings are mixed and some important aspects have not been studied. Further research, particularly in areas regarding changes to the audit reporting model currently being considered, could lead to the improvement of the value relevance of auditor services, disclosures, and assurances. The clear interest by regulators and standard setters in such applied research should serve as a strong incentive for academics to conduct such research and for the practicing profession to support it.Theodore J. Mock, Jean BĂ©dard, Paul J. Coram, Shawn M. Davis, Reza Espahbodi, and Rick C. Warn

    The audit reporting model: current research synthesis and implications

    No full text
    This research synthesis evaluates relevant research concerning the audit report. For too long, there has been a significant “expectations gap” between what financial statement users expect an audit is delivering and what the audit profession believes it is providing. This gap becomes particularly problematic for auditors when there is a “business crisis” and attention is directed to the role of the auditor. Two related gaps are considered in this synthesis, a communications gap, and an information gap. All of these gaps relate to the demand for, understanding of, and use of auditor communications, which is the focus of this synthesis. Our synthesis is driven by two primary research questions: What do financial statement users perceive as information that should be communicated, and what does research show to be the effects on users of existing and other auditor communications currently being considered? As we discuss in detail, prior research does address many aspects of these two questions, but many of the findings are mixed and some important aspects have not been studied. Further research, particularly in areas regarding changes to the audit reporting model currently being considered, could lead to the improvement of the value relevance of auditor services, disclosures, and assurances. The clear interest by regulators and standard setters in such applied research should serve as a strong incentive for academics to conduct such research and for the practicing profession to support it.Theodore J. Mock, Jean BĂ©dard, Paul J. Coram, Shawn M. Davis, Reza Espahbodi and Rick C. Warn

    Colour Doppler ultrasound of the lumbar arteries: A novel application and reproducibility study in healthy subjects

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    Lumbar arteries are important because they are the main source of blood supply to the lumbar spine structures. However, these vessels and their flow characteristics have received little attention and their role in conditions such as low back pain remains unclear. The present study 1. describes the application of duplex ultrasonography in the assessment of lumbar artery blood flow and 2. evaluates the interobserver and intraobserver reproducibility of lumbar artery Doppler velocimetry. A total of 13 healthy volunteers were evaluated by two different examiners successively on the same day and measurements repeated by the same examiners I week later. Peak systolic velocities of lumbar arteries were recorded at an optimal angle below 60 degrees. Overall mean peak systolic velocity (+/- SD) for lumbar arteries was 0.158 +/- 0.051 m/s, and mean Doppler angle (+/- SD) was 24.6 +/- 14.5 degrees. For interobserver variability, the coefficient of variation was 23.4% and SD of differences 0.037 m/s. Reliable results of lumbar artery Doppler velocimetry demonstrate its applicability in future clinical investigations in patients with low back disorders. (E-mail: [email protected]) (C) 2006 World Federation for Ultrasound in Medicine & Biology

    Potential Inhibitory Effect of Miltefosine against Terbinafine-Resistant <i>Trichophyton indotineae</i>

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    Several prolonged and significant outbreaks of dermatophytosis caused by Trichophyton indotineae, a new emerging terbinafine-resistant species, have been ongoing in India in recent years, and have since spread to various countries outside Asia. Miltefosine, an alkylphosphocholine, is the most recently approved drug for the treatment of both visceral and cutaneous leishmaniasis. Miltefosine in vitro activity against terbinafine-resistant and susceptible T. mentagrophytes/T. interdigitale species complex, including T. indotineae, is limited. The current study aimed to assess miltefosine’s in vitro activity against dermatophyte isolates, which are the most common causes of dermatophytosis. Miltefosine, terbinafine, butenafine, tolnaftate, and itraconazole susceptibility testing was performed using Clinical and Laboratory Standards Institute broth microdilution methods (CLSI M38-A3) against 40 terbinafine-resistant T. indotineae isolates and 40 terbinafine-susceptible T. mentagrophytes/T. interdigitale species complex isolates. Miltefosine had MIC ranges of 0.063–0.5 ”g/mL and 0.125–0.25 ”g/mL against both terbinafine-resistant and susceptible isolates. In terbinafine-resistant isolates, the MIC50 and MIC90 were 0.125 ”g/mL and 0.25 ”g/mL, respectively, and 0.25 ”g/mL in susceptible isolates. Miltefosine had statistically significant differences in MIC results when compared to other antifungal agents (p-value 0.05) in terbinafine-resistant strains. Accordingly, the findings suggest that miltefosine has a potential activity for treating infections caused by terbinafine-resistant T. indotineae. However, further studies are needed to determine how well this in vitro activity translates into in vivo efficacy
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