30 research outputs found
QCD factorization for forward hadron scattering at high energies
We consider the QCD factorization of DIS structure functions at small x and
amplitudes of 2->2 -hadronic forward scattering at high energy. We show that
both collinear and k_T-factorization for these processes can be obtained
approximately as reductions of a more general (totally unintegrated) form of
the factorization. The requirement of ultraviolet and infrared stability of the
factorization convolutions allows us to obtain restrictions on the fits for the
parton distributions in k_T- and collinear factorization.Comment: 18 pages, 10 figures In the present version misprints found in the
prevcious version are corrected and some more details are explaine
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Vascular Remodeling in Health and Disease
The term vascular remodeling is commonly used to define the structural changes in blood vessel geometry that occur in response to long-term physiologic alterations in blood flow or in response to vessel wall injury brought about by trauma or underlying cardiovascular diseases.1, 2, 3, 4 The process of remodeling, which begins as an adaptive response to long-term hemodynamic alterations such as elevated shear stress or increased intravascular pressure, may eventually become maladaptive, leading to impaired vascular function. The vascular endothelium, owing to its location lining the lumen of blood vessels, plays a pivotal role in regulation of all aspects of vascular function and homeostasis.5 Thus, not surprisingly, endothelial dysfunction has been recognized as the harbinger of all major cardiovascular diseases such as hypertension, atherosclerosis, and diabetes.6, 7, 8 The endothelium elaborates a variety of substances that influence vascular tone and protect the vessel wall against inflammatory cell adhesion, thrombus formation, and vascular cell proliferation.8, 9, 10 Among the primary biologic mediators emanating from the endothelium is nitric oxide (NO) and the arachidonic acid metabolite prostacyclin [prostaglandin I2 (PGI2)], which exert powerful vasodilatory, antiadhesive, and antiproliferative effects in the vessel wall
Computed tomography angiography-guided percutaneous coronary intervention in chronic total occlusion*
Objective: The aim of this study is to investigate if dual-source computed tomography (DSCT) could guide the percutaneous coronary intervention (PCI) of chronic total occlusion (CTO). Methods: We enrolled patients who were confirmed to have at least one native coronary artery CTO by DSCT before they underwent selective PCI in the period from December 2007 to October 2008. A CTO was defined as an obstruction of a native coronary artery with no luminal continuity. The CT-guided PCI procedure involved placing CT and fluoroscopic images side-by-side on the screen. DSCT images were analyzed for location, segment, plaque characteristics, calcification, and proximal lumen diameter of the CTO before PCI. The guidewire was advanced and manipulated under CT guidance. The PCI was carried out and the results were compared. Results: Seventy-four CTOs were assessed. PCI was successful in 57 cases of CTOs (77.0%). According to the results, CTOs were divided into two groups: successful-PCI and failed-PCI. All coronary artery paths of CTOs were clearly recognized by DSCT. In the successful-PCI group, soft plaques were detected much more often than those in the failed-PCI group, but fibrous and calcified plaques were seen more often in the failed-PCI group. Calcification severity in CTO segments showed a significant difference between the groups (P=0.014). Calcified plaques were detected in 20 (35.1%) lesions in the successful-PCI group. More than 70% of the failures were calcified plaques, of which there were two arc-calcified and one circular-calcified lesions. Occlusions were longer in the failed-PCI group than those in the successful-PCI group [(38.8±25.0) vs. (18.0±15.3) mm, respectively, P<0.01]. Fewer guidewires were used in the successful-PCI group compared with the failed-PCI group (1.7±1.0 vs. 2.5±0.9, respectively, P<0.01). The logistic regression analysis indicated that predictors of recanalization of CTOs included occlusion length (P=0.0035, risk ratio (RR)=0.93) and calcification severity (P=0.05, RR=0.27). Multi-linear trends analysis showed that the factors affecting procedural time were CTO location (P=0.0141) and occlusion length (P=0.0035). Conclusions: DSCT could delineate the path of CTOs and characterize plaques. The outcomes of PCI were related to thrombolysis in myocardial infarction (TIMI) flow grade, CTO characteristics, severity of calcified plaques, and the length of occlusive segments. Occlusion length and calcification severity were independent predictors of CTOs. Occlusion length and CTO segments could also help to estimate the duration of interventional procedures