367 research outputs found
Subtraction at NNLO
We propose a framework for the implementation of a subtraction formalism at
NNLO in QCD, based on an observable- and process-independent cancellation of
infrared singularities. As a first simple application, we present the
calculation of the contribution to the e+e- dijet cross section proportional to
C_F T_RComment: 42 pages Latex; 7 figures included. Modifications to the text, and
references added; the results are unchange
Fully differential QCD corrections to single top quark final states
A new next-to-leading order Monte Carlo program for calculation of fully
differential single top quark final states is described and first results
presented. Both the s- and t-channel contributions are included.Comment: 3 pages, 3 figures, talk presented at DPF2000, August 9-12, 2000. To
appear in International Journal of Modern Physics
Machines on Genes: Enzymes that Make, Break and Move DNA and RNA
As the vital information repositories of the cell, the nucleic acids DNA and RNA pose many challenges as enzyme substrates. To produce, maintain and repair DNA and RNA, and to extract the genetic information that they encode, a battery of remarkable enzymes has evolved, which includes translocases, polymerases/replicases, helicases, nucleases, topoisomerases, transposases, recombinases, repair enzymes and ribosomes. An understanding of how these enzymes function is essential if we are to have a clear view of the molecular biology of the cell and aspire to manipulate genomes and gene expression to our advantage. To bring together scientists working in this fast-developing field, the Biochemical Society held a Focused Meeting, âMachines on Genes: Enzymes that Make, Break and Move DNA and RNAâ, at Robinson College, University of Cambridge, U.K., in August 2009. The present article summarizes the research presented at this meeting and the reviews associated with the talks which are published in this issue of Biochemical Society Transactions
On-the-fly memory compression for multibody algorithms.
Memory and bandwidth demands challenge developers of particle-based codes that have to scale on new architectures, as the growth of concurrency outperforms improvements in memory access facilities, as the memory per core tends to stagnate, and as communication networks cannot increase bandwidth arbitrary. We propose to analyse each particle of such a code to find out whether a hierarchical data representation storing data with reduced precision caps the memory demands without exceeding given error bounds. For admissible candidates, we perform this compression and thus reduce the pressure on the memory subsystem, lower the total memory footprint and reduce the data to be exchanged via MPI. Notably, our analysis and transformation changes the data compression dynamically, i.e. the choice of data format follows the solution characteristics, and it does not require us to alter the core simulation code
Tissue-Protective Mechanisms of Bioactive Phytochemicals in Flap Surgery
Despite careful preoperative planning, surgical flaps are prone to ischemic tissue damage
and ischemiaâreperfusion injury. The resulting wound breakdown and flap necrosis
increase both treatment costs and patient morbidity. Hence, there is a need for
strategies to promote flap survival and prevent ischemia-induced tissue damage.
Phytochemicals, defined as non-essential, bioactive, and plant-derived molecules, are
attractive candidates for perioperative treatment as they have little to no side effects and
are well tolerated by most patients. Furthermore, they have been shown to exert beneficial
combinations of pro-angiogenic, anti-inflammatory, anti-oxidant, and anti-apoptotic
effects. This review provides an overview of bioactive phytochemicals that have been
used to increase flap survival in preclinical animal models and discusses the underlying
molecular and cellular mechanisms
One-loop N-point equivalence among negative-dimensional, Mellin-Barnes and Feynman parametrization approaches to Feynman integrals
We show that at one-loop order, negative-dimensional, Mellin-Barnes' (MB) and
Feynman parametrization (FP) approaches to Feynman loop integrals calculations
are equivalent. Starting with a generating functional, for two and then for
-point scalar integrals we show how to reobtain MB results, using
negative-dimensional and FP techniques. The point result is valid for
different masses, arbitrary exponents of propagators and dimension.Comment: 11 pages, LaTeX. To be published in J.Phys.
Bromelain Protects Critically Perfused Musculocutaneous Flap Tissue from Necrosis
Bromelain has previously been shown to prevent ischemia-induced necrosis in different
types of tissues. In the present study, we, therefore, evaluated for the first time, the tissue-protective
effects of bromelain in musculocutaneous flaps in mice. Adult C57BL/6N mice were randomly
assigned to a bromelain treatment group and a control group. The animals were treated daily with
intraperitoneal injections of 20 mg/kg bromelain or saline (control), starting 1 h before the flap
elevation throughout a 10-day observation period. The random-pattern musculocutaneous flaps
were raised on the backs of the animals and mounted into a dorsal skinfold chamber. Angiogenesis,
nutritive blood perfusion and flap necrosis were quantitatively analyzed by means of repeated
intravital fluorescence microscopy over 10 days after surgery. After the last microscopy, the flaps
were harvested for additional histological and immunohistochemical analyses. Bromelain reduced
necrosis of the critically perfused flap tissue by ~25%. The bromelain-treated flaps also exhibited
a significantly higher functional microvessel density and an elevated formation of newly devel oped microvessels in the transition zone between the vital and necrotic tissues when compared
to the controls. Immunohistochemical analyses demonstrated a markedly lower invasion of the
myeloperoxidase-positive neutrophilic granulocytes and a significantly reduced number of cleaved
caspase 3-positive apoptotic cells in the transition zone of bromelain-treated musculocutaneous
flaps. These findings indicate that bromelain prevents flap necrosis by maintaining nutritive tissue
perfusion and by suppressing ischemia-induced inflammation and apoptosis. Hence, bromelain may
represent a promising compound to prevent ischemia-induced flap necrosis in clinical practice
Feynman graph polynomials
The integrand of any multi-loop integral is characterised after Feynman
parametrisation by two polynomials. In this review we summarise the properties
of these polynomials. Topics covered in this article include among others:
Spanning trees and spanning forests, the all-minors matrix-tree theorem,
recursion relations due to contraction and deletion of edges, Dodgson's
identity and matroids.Comment: 35 pages, references adde
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