360 research outputs found

    A quark model framework for the study of nuclear medium effects

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    A quark-model framework for studying nuclear medium effects on nucleon resonances is described and applied here to pion photoproduction on the deuteron, which is the simplest composite nucleon system and serves as a first test case. Pion photoproduction on nuclei is discussed within a chiral constituent quark model in which the quark degrees of freedom are explicitly introduced through an effective chiral Lagrangian for the quark-pseudoscalar-meson coupling. The advantage of this model is that a complete set of nucleon resonances can be systematically included with a limited number of parameters. Also, the systematic description of the nucleon and its resonances at quark level allows us to self-consistently relate the nuclear medium's influence on the baryon properties to the intrinsic dynamic aspects of the baryons. As the simplest composite nucleus, the deuteron represents the first application of this effective theory for meson photoproduction on light nuclei. The influence of the medium on the transition operators for a free nucleon is investigated in the Delta resonance region. No evidence is found for a change of the Delta properties in the pion photoproduction reaction on the deuteron since the nuclear medium here involves just one other nucleon and the low binding energy implies low nuclear density. However, we show that the reaction mechanism is in principle sensitive to changes of Delta properties that would be produced by the denser nuclear medium of heavier nuclei through the modification of the quark model parameters.Comment: Revtex, 8 pages, 4 figure

    Capturing Economic Rents From Resources Through Royalties and Taxes

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    Oil price fluctuations, concerns over the division of resource revenues, and unconventional oil and gas developments are forcing governments to confront the same issue: how to design optimal royalty and corporate tax systems that bring in a publicly acceptable share of revenues without discouraging private investment. This paper surveys tax and royalty systems across six countries, as well as four US states and five Canadian provinces, offering concise analyses of their strengths and shortcomings to describe the best and simplest approaches to both. As in a public-private partnership, government owns the resources and allows private agents to maximize the rents resources generate. An optimal royalty system will thus be rent-based, ensuring that both owner and agent obtain maximally competitive returns so that each has incentives to continue the partnership. Such a system will also be simple, making compliance easy, manipulation difficult, and risks affordable. And it will be stable, instilling in the private sector the confidence needed to invest for the long term. As for corporate income taxes, they should be neutral across business activities, and applied at equal effective rates on economic income, to avoid distorting market forces through subsidies or needless complexity. A clean rent-based tax that allows all costs incurred by producers to be expensed or carried over, along with a corporate income tax system shorn of many of the preferences that negatively affect business activity, should be the way forward for any government looking to update their fiscal regimes for the 21st century

    Correlation of microarray-based breast cancer molecular subtypes and clinical outcomes: implications for treatment optimization

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    <p>Abstract</p> <p>Background</p> <p>Optimizing treatment through microarray-based molecular subtyping is a promising method to address the problem of heterogeneity in breast cancer; however, current application is restricted to prediction of distant recurrence risk. This study investigated whether breast cancer molecular subtyping according to its global intrinsic biology could be used for treatment customization.</p> <p>Methods</p> <p>Gene expression profiling was conducted on fresh frozen breast cancer tissue collected from 327 patients in conjunction with thoroughly documented clinical data. A method of molecular subtyping based on 783 probe-sets was established and validated. Statistical analysis was performed to correlate molecular subtypes with survival outcome and adjuvant chemotherapy regimens. Heterogeneity of molecular subtypes within groups sharing the same distant recurrence risk predicted by genes of the Oncotype and MammaPrint predictors was studied.</p> <p>Results</p> <p>We identified six molecular subtypes of breast cancer demonstrating distinctive molecular and clinical characteristics. These six subtypes showed similarities and significant differences from the Perou-Sørlie intrinsic types. Subtype I breast cancer was in concordance with chemosensitive basal-like intrinsic type. Adjuvant chemotherapy of lower intensity with CMF yielded survival outcome similar to those of CAF in this subtype. Subtype IV breast cancer was positive for ER with a full-range expression of HER2, responding poorly to CMF; however, this subtype showed excellent survival when treated with CAF. Reduced expression of a gene associated with methotrexate sensitivity in subtype IV was the likely reason for poor response to methotrexate. All subtype V breast cancer was positive for ER and had excellent long-term survival with hormonal therapy alone following surgery and/or radiation therapy. Adjuvant chemotherapy did not provide any survival benefit in early stages of subtype V patients. Subtype V was consistent with a unique subset of luminal A intrinsic type. When molecular subtypes were correlated with recurrence risk predicted by genes of Oncotype and MammaPrint predictors, a significant degree of heterogeneity within the same risk group was noted. This heterogeneity was distributed over several subtypes, suggesting that patients in the same risk groups require different treatment approaches.</p> <p>Conclusions</p> <p>Our results indicate that the molecular subtypes established in this study can be utilized for customization of breast cancer treatment.</p

    The sedimentation of an institution: changing governance in UK financial services

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    Post-print version. Final version published by Sage; available online at http://jmi.sagepub.com/The Financial Services Act (FSA) 1986 was the first comprehensive attempt to create a unified statutorily based system of regulation within the UK financial sector. It generated a framework of regulation that is in a continuous state of development and modification. In this paper we study the development of UK financial regulation between 1986 and 2011. We trace how competing theorizations and logics of regulation have led to the institutionalization of a meta-form of financial regulation. In doing so, we address the conundrum of conscious, strategic theorizations leading to cognitive taken-for-granted institutions by identifying four catalysts that contribute to institutionalization when concurring with theorization. These are: the evocation of political ideologies, the appropriation of scandals, the growing number of actors and the increasing organization of actors. Finally, we argue that sedimentation is the appropriate metaphor for the version of institutionalization occurring in this setting

    Heavy Ions at LHC: A Quest for Quark-Gluon Plasma

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    Quantum Chromo Dynamics (QCD), the theory of strong interactions, predicts a transition of the usual matter to a new phase of matter, called Quark-Gluon Plasma (QGP), at sufficiently high temperatures. The non-perturbative technique of defining a theory on a space-time lattice has been used to obtain this and other predictions about the nature of QGP. Heavy ion collisions at the Large Hadron Collider in CERN can potentially test these predictions and thereby test our theoretical understanding of confinement. This brief review aims at providing a glimpse of both these aspects of QGP.Comment: 26 pages, 31 Figures, Invited article for the volume on LHC physics to celebrate the Platinum Jubilee of the Indian National Science Academy, edited by Amitava Datta, Biswarup Mukhopadhyaya and Amitava Raychaudhuri. Needs style file insa.sty (included
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