1,410 research outputs found
On Higgs-exchange DIS, physical evolution kernels and fourth-order splitting functions at large x
We present the coefficient functions for deep-inelastic scattering (DIS) via
the exchange of a scalar phi directly coupling only to gluons, such as the
Higgs boson in the limit of a very heavy top quark and n_f effectively massless
light flavours, to the third order in perturbative QCD. The two-loop results
are employed to construct the next-to-next-to-leading order physical evolution
kernels for the system (F_2 F_phi) of flavour-singlet structure functions. The
practical relevance of these kernels as an alternative to MSbar factorization
is bedevilled by artificial double logarithms at small values of the scaling
variable x, where the large top-mass limit ceases to be appropriate. However,
they show an only single-logarithmic enhancement at large x. Conjecturing that
this feature persists to the next order also in the present singlet case, the
three-loop coefficient functions facilitate exact predictions (backed up by
their particular colour structure) of the double-logarithmic contributions to
the fourth-order singlet splitting functions, i.e., of the terms (1-x)^a
ln^k(1-x) with k = 4, 5, 6 and k = 3, 4, 5, respectively, for the off-diagonal
and diagonal quantities to all powers a in 1-x.Comment: 75 pages, LaTeX, 13 figures (.eps). FORM and Fortran files of main
results appended to sourc
Vestigial structures in the appendicular skeletons of eight African skink species (Squamata, Scincidae)
Limb reduction and loss, with reduction of limb and girdle skeletons to a vestigial state, has occurred several times independently within the skink family (Scincidae). The vestigial appendicular skeletons of most limbless skinks have not been described before now. Here we describe those of eight African skink species, all with a burrowing lifestyle: Acontias percivali, Acontias meleagris, Typhlosaurus cregoi, Typhlosaurus lineatus, Typhlacontias gracilis, Sepsina bayonii, Scelotes anguina and Scelotes arenicola. For all but two (A. meleagris and Sc. arenicola) the appendicular skeletons were previously undescribed. Limbs are absent in all specimens except for vestigial hindlimbs in Se. bayonii and vestigial femurs in one specimen of Sc. arenicola. In our sample, the pectoral girdle is reduced to a pair of tiny slivers in A. percivali, Ty. gracilis, Se. bayonii and Sc. anguina. It is absent in the other specimens. The pelvic girdle is absent in Ty. cregoi. In all the rest but Se. bayonii it is vestigial, retaining only the ilium in A. meleagris, Ty. lineatus and one specimen of Sc. arenicola. This study adds to the number of skink species with vestigial appendicular skeletons that have been described. It also adds to the rangeof documented intraspecific variation in the vestigial appendicular skeletons of A. meleagris, Sc. arenicola and the Australian skinks Lerista stylis and Lerista carpentariae. We observed asymmetry between the left and right sides in the vestigial appendicular skeletons of four of the African skink species: A. meleagris, Sc. anguina, Sc. arenicola and Se. bayoni
On QCD analysis of stucture function in alternative approach
The alternative approach to QCD analysis of the photon structure function
is presented. It differs from the conventional one by the
presence of the terms which in conventional approach appear in higher orders.
We show that this difference concerns also the photonic parton distribution
functions. In the alternative approach, the complete LO analysis of
can be performed as all required quantities are known. At the
NLO, however, one of the coefficient function is so far not available and thus
only the photonic parton distribution function can be computed and compared to
those of standard approach. We discuss the numerical difference of these
approaches at the LO and the NLO approximation and show that in case of
this difference is non-negligible and may play an important role
in the analysis on photon data of the future experiments.Comment: 25 page
Small x resummation in collinear factorisation
The summation of the small x-corrections to hard-scattering QCD amplitudes by
collinear factorisation method is reconsidered and the K-factor is derived in
leading ln x approximation with a result differing from the corresponding
expression by Catani and Hautmann (Nucl. Phys. B 427, 475, 1994). The
significance of the difference is demonstrated in the examples of structure
function F_L and of exclusive vector meson electroproduction. The formulation
covers the channels of non-vanishing conformal spin n paving the way for new
applications.Comment: 34 pages, 6 figure
General massive one-loop off-shell three-point functions
In this work we compute the most general massive one-loop off-shell
three-point vertex in D-dimensions, where the masses, external momenta, and
exponents of propagators are arbitrary. This follows our previous paper in
which we have calculated several new hypergeometric series representations for
massless and massive (with equal masses) scalar one-loop three-point functions,
in the negative dimensional approach.Comment: 16 pages, 2 figures, 4 table
Parton distribution functions from the precise NNLO QCD fit
We report the parton distribution functions (PDFs) determined from the NNLO
QCD analysis of the world inclusive DIS data with account of the precise NNLO
QCD corrections to the evolution equations kernel. The value of strong coupling
constant \alpha_s^{NNLO}(M_Z)=0.1141(14), in fair agreement with one obtained
using the earlier approximate NNLO kernel by van Neerven-Vogt. The intermediate
bosons rates calculated in the NNLO using obtained PDFs are in agreement to the
latest Run II results.Comment: 8 pages, LATEX, 2 figures (EPS
Personalized cancer medicine and the future of pathology
In February 2011, a group of pathologists from different departments in Europe met in Zurich, Switzerland, to discuss opportunities and challenges for pathology in the era of personalized medicine. The major topics of the meeting were assessment of the role of pathology in personalized medicine, its future profile among other biomedical disciplines with an interest in personalized medicine as well as the evolution of companion diagnostics. The relevance of novel technologies for genome analysis in clinical practice was discussed. The participants recognize that there should be more initiatives taken by the pathology community in companion diagnostics and in the emerging field of next-generation sequencing and whole genome analysis. The common view of the participants was that the pathology community has to be mobilized for stronger engagement in the future of personalized medicine. Pathologists should be aware of the challenges and the analytical opportunities of the new technologies. Challenges of clinical trial design as well as insurance and reimbursement questions were addressed. The pathology community has the responsibility to lead medical colleagues into embracing this new area of genomic medicine. Without this effort, the discipline of pathology risks losing its key position in molecular tissue diagnostic
Two-loop amplitudes with nested sums: Fermionic contributions to e+ e- --> q qbar g
We present the calculation of the nf-contributions to the two-loop amplitude
for e+ e- --> q qbar g and give results for the full one-loop amplitude to
order eps^2 in the dimensional regularization parameter. Our results agree with
those recently obtained by Garland et al.. The calculation makes extensive use
of an efficient method based on nested sums to calculate two-loop integrals
with arbitrary powers of the propagators. The use of nested sums leads in a
natural way to multiple polylogarithms with simple arguments, which allow a
straightforward analytic continuation.Comment: 31 pages, a file "coefficients.h" with the results in FORM format is
include
Hopf algebras, coproducts and symbols: an application to Higgs boson amplitudes
We show how the Hopf algebra structure of multiple polylogarithms can be used
to simplify complicated expressions for multi-loop amplitudes in perturbative
quantum field theory and we argue that, unlike the recently popularized
symbol-based approach, the coproduct incorporates information about the zeta
values. We illustrate our approach by rewriting the two-loop helicity
amplitudes for a Higgs boson plus three gluons in a simplified and compact form
involving only classical polylogarithms.Comment: 46 page
p53 protein expression but not mdm-2 protein expression is associated with rapid tumor cell proliferation and prognosis in renal cell carcinoma
The clinical course of renal cell carcinoma (RCC) is highly variable. Overexpression of the p53 protein has been suggested as a possible prognostic parameter in RCC. Overexpression of the mdm-2 oncogene product has been shown to interact with the p53 function. To investigate the immunohistochemical overexpression of mdm-2 protein in comparison with that of p53 protein in RCC, 50 nonpapillary pT3 RCCs were immunostained for p53 protein (DO-7) and mdm-2 (1172). Tumor growth fraction (Ki-67 labeling index; MIB-1) was determined by immunohistochemistry. p53 positivity was detected in 16% of tumors. mdm-2 overexpression was seen in 30% of RCCs. There was a significant association between p53 and mdm-2 immunostaining (P=0.0006), suggesting that mdm-2 protein may contribute to p53 protein stabilization in RCC. p53 overexpression was associated with a high Ki-67 LI (P=0.0002), suggesting that p53 overexpression is involved in growth control in RCC. Survival analysis showed that Ki-67 LI (P=0.04) and p53 overexpression were associated with poor prognosis (P=0.0021), whereas mdm-2 overexpression was not related to patient outcome (P=0.73). A Cox regression analysis revealed tumor stage (P<0.001) and p53 overexpression (P<0.05) to be independent prognostic parameters. It is concluded that p53 but not mdm-2 may be of practical relevance in predicting patient prognosis in RC
- …