76 research outputs found

    QCD Corrections to QED Vacuum Polarization

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    We compute QCD corrections to QED calculations for vacuum polarization in background magnetic fields. Formally, the diagram for virtual eeˉe\bar{e} loops is identical to the one for virtual qqˉq\bar{q} loops. However due to confinement, or to the growth of αs\alpha_s as p2p^2 decreases, a direct calculation of the diagram is not allowed. At large p2p^2 we consider the virtual qqˉq\bar{q} diagram, in the intermediate region we discuss the role of the contribution of quark condensates \left and at the low-energy limit we consider the π0\pi^0, as well as charged pion π+π−\pi^+\pi^- loops. Although these effects seem to be out of the measurement accuracy of photon-photon laboratory experiments they may be relevant for Îł\gamma-ray burst propagation. In particular, for emissions from the center of the galaxy (8.5 kpc), we show that the mixing between the neutral pseudo-scalar pion π0\pi_0 and photons renders a deviation from the power-law spectrum in the TeVTeV range. As for scalar quark condensates \left and virtual qqˉq\bar{q} loops are relevant only for very high radiation density ∌300MeV/fm3\sim 300 MeV/fm^3 and very strong magnetic fields of order ∌1014T\sim 10^{14} T.Comment: 15 pages, 4 figures; Final versio

    International Consortium for Health Outcomes Measurement (ICHOM): Standardized Patient-Centered Outcomes Measurement Set for Heart Failure Patients

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    Whereas multiple national, international, and trial registries for heart failure have been created, international standards for clinical assessment and outcome measurement do not currently exist. The working group's objective was to facilitate international comparison in heart failure care, using standardized parameters and meaningful patient-centered outcomes for research and quality of care assessments. The International Consortium for Health Outcomes Measurement recruited an international working group of clinical heart failure experts, researchers, and patient representatives to define a standard set of outcomes and risk-adjustment variables. This was designed to document, compare, and ultimately improve patient care outcomes in the heart failure population, with a focus on global feasibility and relevance. The working group employed a Delphi process, patient focus groups, online patient surveys, and multiple systematic publications searches. The process occurred over 10 months, employing 7 international teleconferences. A 17-item set has been established, addressing selected functional, psychosocial, burden of care, and survival outcome domains. These measures were designed to include all patients with heart failure, whether entered at first presentation or subsequent decompensation, excluding cardiogenic shock. Sources include clinician report, administrative data, and validated patient-reported outcome measurement tools: the Kansas City Cardiomyopathy Questionnaire; the Patient Health Questionnaire-2; and the Patient-Reported Outcomes Measurement Information System. Recommended data included those to support risk adjustment and benchmarking across providers and regions. The International Consortium for Health Outcomes Measurement developed a dataset designed to capture, compare, and improve care for heart failure, with feasibility and relevance for patients and clinicians worldwide

    Democracy, Globalization and Private Investment in Ghana

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    The article examines the effects of democracy and globalization on private investment in Ghana for the period 1980–2012, using the autoregressive distributed lag (ARDL) bounds test for cointegration and the error correction model (ECM). Two models are used. In Model 1, democracy is proxy by an index for institutional quality (Polity 2), while Model 2 uses an index for civil liberties as proxy for democracy. The results for Model 1 show globalization and public investment increase private investment, while exchange rate volatility and trade openness decrease private investment in both the long and short run. In addition, national income and interest rate reduce private investment in the short run. In the case of Model 2, credit to the private sector and public investment increase private investment, while exchange rate volatility and trade openness decrease private investment in both the long and short run. Finally, national income and interest rate reduce private investment in the short run. The findings and policy recommendations of the article provide vital information for policy implementation in Ghana

    An above-barrier narrow resonance in <sup>15</sup>F

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    Intense and purified radioactive beam of post-accelerated 14^{14}O was used to study the low-lying states in the unbound 15^{15}F nucleus. Exploiting resonant elastic scattering in inverse kinematics with a thick target, the second excited state, a resonance at E_R\_R=4.757(6)(10)~MeV with a width of Γ\Gamma=36(5)(14)~keV was measured for the first time with high precision. The structure of this narrow above-barrier state in a nucleus located two neutrons beyond the proton drip line was investigated using the Gamow Shell Model in the coupled channel representation with a 12^{12}C core and three valence protons. It is found that it is an almost pure wave function of two quasi-bound protons in the 2s_1/22s\_{1/2} shell.Comment: 8 pages, 2 figures, 1 table, Submitted to Phys. Lett.

    TOI-132 b: A short-period planet in the Neptune desert transiting a v = 11.3 G-type star

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    The Neptune desert is a feature seen in the radius-period plane, whereby a notable dearth of short period, Neptune-like planets is found. Here, we report the Transiting Exoplanet Survey Satellite (TESS) discovery of a new short-period planet in the Neptune desert, orbiting the G-type dwarf TYC8003-1117-1 (TOI-132). TESS photometry shows transit-like dips at the level of ∌1400 ppm occurring every ∌2.11 d. High-precision radial velocity follow-up with High Accuracy Radial Velocity Planet Searcher confirmed the planetary nature of the transit signal and provided a semi-amplitude radial velocity variation of 11.38+0.84-0.85 ms-1, which, when combined with the stellar mass of 0.97 ± 0.06 M⊙, provides a planetary mass of 22.40+1.90-1.92 M⊕. Modelling the TESS light curve returns a planet radius of 3.42+0.13-0.14 R⊕, and therefore the planet bulk density is found to be 3.08+0.44-0.46 g cm-3. Planet structure models suggest that the bulk of the planet mass is in the form of a rocky core, with an atmospheric mass fraction of 4.3+1.2-2.3 per cent. TOI-132 b is a TESS Level 1 Science Requirement candidate, and therefore priority follow-up will allow the search for additional planets in the system, whilst helping to constrain low-mass planet formation and evolution models, particularly valuable for better understanding of the Neptune desert

    Strategic targeting: the effect of institutions and interests on distributive transfers

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    Virtually every government provides distributive transfers for electoral purposes. However, the level and form of such transfers vary dramatically across countries. Although transfers take many forms, they can generally be characterized as being either broad (providing benefits to large segments of the electorate) or narrow (targeting benefits only to select groups of voters). Variation in the form of distributive transfers across countries can be explained by voters' economic interests and domestic institutions. Voters' preferences over transfer form, shaped in part by the mobility of their assets, together with a country's electoral rules determine the benefits politicians gain from providing either broad or narrow transfers. Using new measures of transfer form, the author finds that although majoritarian systems are more prone to narrow transfers, proportional systems are more responsive to increases in voter demand for narrow transfers, all else equal

    Proterozoic crustal evolution in southcentral Fennoscandia

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    The Transscandinavian Igneous Belt (TIB) and the Eastern Segment of the Southwest Scandinavian Domain reflect advanced stages of continental growth within the Fennoscandian Shield. The relationship between the two units is not clear, mainly because N-S trending shear zones of the Protogine Zone transect the border zone. The main goal of this thesis has been to investigate rocks in the border zone and to conclude how these rocks differ from each other. In this work two volcanic sequences and 24 granitoids in the border area, near Jönköping, were examined. The thesis reports geochemical and Sm-Nd isotope data as well as U-Pb ion microprobe zircon dates for extrusive and intrusive rocks in the southwestern part of the TIB and intrusive rocks in the eastern part of the southern Eastern Segment. The TIB rocks are subdivided into TIB-0, TIB-1 and TIB-2 groups based on their ages. In this work, the Habo Volcanic Suite and the MalmbÀck Formation are dated at 1795±13 Ma and 1796±7 Ma respectively, which establishes that they are part of the TIB-1 volcanic rocks. The MalmbÀck Formation is situated in the southwestern part of TIB, east of the Protogine Zone, whereas the Habo Volcanic Suite is located c. 50 km northwest of the MalmbÀck Formation, between shear zones of the Protogine Zone. Both suites comprise mafic to felsic components and the MalmbÀck Formation includes one of the largest mafic volcanic rock units of the TIB-1. The MalmbÀck Formation comprises fairly well preserved volcanic rocks, with primary textures, although mineral parageneses in some rocks suggest metamorphism at up to epidote-amphibolite facies conditions. Amphibolites facies metamorphism and deformation has largely obscured primary textures of the Habo Volcanic Suite. Dating of a Barnarp granite which intrudes the Habo Volcanic Suite gave an age of 1660±9 Ma, corresponding to TIB-2. The occurrences of MalmbÀck Formation megaxenoliths within TIB-1 granitoids are explained by stoping. Geochemical signatures of the two metavolcanic rock suites suggest emplacement in an active continental margin setting. It is further suggested that the TIB regime was complex, similar to what is seen in the Andes today, with different regions characterised by subduction-related magmatism, Andinotype extension as well as local compression. Twenty-one granitoids (including the granite intruding the Habo Volcanic Suite), across and in the border zone between the TIB and the Eastern Segment, were dated by U-Pb zircon ion probe analysis. Eighteen of the granitoids yielded TIB-2 magmatic ages, ranging between 1710 and 1660 Ma. Eighteen granitoids were analyzed for geochemistry and Sm-Nd isotopes. The geochemical and isotopic signatures of the granitoids proved to be similar, supporting the theory that the TIB and the Eastern Segment originated from the same type of source and experienced the same type of emplacement mechanisms. Further, it is concluded that the TIB-2 granitoids, from both the TIB and the Eastern Segment, were derived by reworking of juvenile, pre-existing crust, in an essentially east- to northeast-directed subduction environment. The U-Pb zircon ion microprobe analyses also dated zircon rims which formed by metamorphism during the 1460-1400 Ma Hallandian-Danopolonian orogeny, in granitoids of both the southern Eastern Segment and the western TIB. Leucosome formation, for two samples was dated at 1443±9 Ma and 1437±6 Ma. An aplitic dyke, cross-cutting NW-SE to E-W folding and leucosome formation in the Eastern Segment was dated at 1383±4 Ma, which sets a minimum age for the NW-SE to E-W folding in the area. Hence, it is concluded that the leucosome formation and the NW-SE to E-W folding in the investigated part of the Eastern Segment as well as NW-SE to E-W penetrative foliation and lineation in the western TIB took place during the 1470-1400 Ma Hallandian-Danopolonian orogeny. No c. 970 Ma Sveconorwegian ages were recorded in any of the areas investigated. Nevertheless, Sveconorwegian (in addition to earlier) block movements caused uplift of the Eastern Segment relative to the TIB, revealing from west to east: (1) the highly exhumed metamorphosed southern Eastern Segment, in which the effects of both the Hallandian-Danopolonian and the Sveconorwegian orogenies can be seen, (2) the partly exhumed westernmost TIB-2 showing the effects of the Hallandian-Danopolonian orogeny only, and (3) the easternmost TIB-2 granitoids, as well as the supracrustal and shallow emplaced TIB-1 granitoid rocks in the east. The main part of TIB was apparently unaffected by the Hallandian-Danopolonian orogeny, apart from the intrusion of subordinate felsic bodies and mafic dykes. Tilting and other block movements within the Eastern Segment also occurred during the uplift, revealing lower crustal sections in the south compared to the northern part
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