KERATOPLASTICS AND DONORS AND RECIPIENT'S SELECTION ACCORDING TO HUMAN TRANSPLANTATION ANTIGENIC SYSTEMS

No abstrac

Closing the stop gap

Light stops are a hallmark of the most natural realizations of weak-scale supersymmetry. While stops have been extensively searched for, there remain open gaps around and below the top mass, due to similarities of stop and top signals with current statistics. We propose a new fast-track avenue to improve light stop searches for R-parity conserving supersymmetry, by comparing top cross section measurements to the theoretical prediction. Stop masses below ~ 180 GeV can now be ruled out for a light neutralino. The possibility of a stop signal contaminating the top mass measurement is also briefly addressed.Comment: 6 pages, 6 figure

Time series analysis for financial market meltdowns

There appears to be a consensus that the recent instability in global financial markets may be attributable in part to the failure of financial modeling. More specifically, current risk models have failed to properly assess the risks associated with large adverse stock price behavior. In this paper, we first discuss the limitations of classical time series models for forecasting financial market meltdowns. Then we set forth a framework capable of forecasting both extreme events and highly volatile markets. Based on the empirical evidence presented in this paper, our framework offers an improvement over prevailing models for evaluating stock market risk exposure during distressed market periods. --ARMA-GARCH model,»-stable distribution,tempered stable distribution,value-at-risk (VaR),average value-at-risk (AVaR)

Optimized refractive surgery in keratoconus

Purpose: The aim of the study is to compare the refractive results after simultaneous TransPRK and Cross-linking procedure for treatment of keratoconus with optimized and non-optimized customized ablation profiles; to introduce the concept of optimization in keratoconus and discuss its clinical significance; to find predictive factors for better refractive outcomes in simultaneous combined procedures and to propose therapeutic algorithm.Methods: Syrius schimpflug aberrometer (Schwind) was used to create non-optimized custom and optimized custom ablation profiles in keratoconic corneas. TransPRK ablation was performed with Schwind Amaris Eximer Laser (500 Hz). Cross-linking was done with Avedro cross-linking suit. Analysis of preoperative and postoperative refraction, visual acuity, keratometric and aberometric data was done for both groups. Correlative analysis of the preoperative and postoperative variables was done with Pierson statistical analysis.Results: 44 patients (70 eyes), age 19-67, 29 eyes with optimization, 41 eyes without optimization were followed for 18 months. A positive correlation was found between CCT and the amount of postoperative flattening in patients over 40 years of age. No correlation was found with Kavg.Conclusions: Long term results after simultaneous TransPRK + Cross linking show stability and safety. Optimization of refraction brings better refractive results compared to non-optimized procedure. It can be safely performed in thinner corneas and compensates for the hypermetropic shift generated by the cross-linking procedure

Mössbauer study of nanodimensional nickel ferrite-mechanochemical synthesis and catalytic properties

Iron-nickel spinel oxide NiFe2O4 nanoparticles have been prepared by the combination of chemical precipitation and subsequent mechanical milling. For comparison, their analogue obtained by thermal synthesis is also studied. Phase composition and structural properties of iron-nickel oxides are investigated by X-ray diffraction and Mössbauer spectroscopy. Their catalytic behavior in methanol decomposition to CO and methane is tested. An influence of the preparation method on the reduction and catalytic properties of iron-nickel samples is established

B-hadron production in NNLO QCD: application to LHC t t¯ events with leptonic decays

We calculate, for the first time, the NNLO QCD corrections to identified heavy hadron production at hadron colliders. The calculation is based on a flexible numeric framework which allows the calculation of any distribution of a single identified heavy hadron plus jets and non-QCD particles. As a first application we provide NNLO QCD predictions for several differential distributions of $B$ hadrons in $t\bar t$ events at the LHC. Among others, these predictions are needed for the precise determination of the top quark mass. The extension of our results to other processes, like open or associated $B$ and charm production is straightforward. We also explore the prospects for extracting heavy flavor fragmentation functions from LHC data

B-hadron production in NNLO QCD: application to LHC t t¯ events with leptonic decays

We calculate, for the first time, the NNLO QCD corrections to identified heavy hadron production at hadron colliders. The calculation is based on a flexible numeric framework which allows the calculation of any distribution of a single identified heavy hadron plus jets and non-QCD particles. As a first application we provide NNLO QCD predictions for several differential distributions of $B$ hadrons in $t\bar t$ events at the LHC. Among others, these predictions are needed for the precise determination of the top quark mass. The extension of our results to other processes, like open or associated $B$ and charm production is straightforward. We also explore the prospects for extracting heavy flavor fragmentation functions from LHC data

On the Structure of Infrared Singularities of Gauge-Theory Amplitudes

A closed formula is obtained for the infrared singularities of dimensionally regularized, massless gauge-theory scattering amplitudes with an arbitrary number of legs and loops. It follows from an all-order conjecture for the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory. We show that the form of this anomalous dimension is severely constrained by soft-collinear factorization, non-abelian exponentiation, and the behavior of amplitudes in collinear limits. Using a diagrammatic analysis, we demonstrate that these constraints imply that to three-loop order the anomalous dimension involves only two-parton correlations, with the possible exception of a single color structure multiplying a function of conformal cross ratios depending on the momenta of four external partons, which would have to vanish in all two-particle collinear limits. We argue that such a function does not appear at three-loop order, and that the same is true in higher orders. Our formula predicts Casimir scaling of the cusp anomalous dimension to all orders in perturbation theory, and we explicitly check that the constraints exclude the appearance of higher Casimir invariants at four loops. Using known results for the quark and gluon form factors, we derive the three-loop coefficients of the 1/epsilon^n pole terms (with n=1,...,6) for an arbitrary n-parton scattering amplitude in massless QCD. This generalizes Catani's two-loop formula proposed in 1998.Comment: 46 pages, 9 figures; v2: improved treatment of collinear limits, references added; v3: improved discussion of non-abelian exponentiation, references updated; v4: typo in eq. (17) fixed, references updated; v5: additional term in (17

Causative factors for hyperopia regression in excimer keratorefractive surgery

Регресът и хипокорекцията са специфични усложнения в кераторефрактивната хирургия, които трудно се диференцират, пряко зависят от роговичната биомеханика и обуславят икономически значима тенденция към повторна корекция. Научен интерес буди въпросът кои са и от какво естество са факторите, предразполагащи към неочаквани или нетрайни рефрактивни резултати. Не по-малко важен въпрос е дали регресът е хирургична усложнение или само проблем на селекцията на пациенти, на избора на неподходяща процедура или на лазерна платформа. Настоящото изследване предлага напълно нов подход в измерването на регpеса, както и статистически обосновани резултати по отношение на възможните причини за него.Regression and hypocorrection are specific complications in refractive surgery that frequently lead to unexpected or perishable refractive results. They develop due to unforeseen alteration in corneal biomechanics and are hard to differentiate and presume. Their ethiology and pathogenesis are still vague and no statistical evidence on predisposing factors is present. Once more familiar, the regression might be controlled by patient selection, procedure planning or laser platform opting. This study offers a completely new approach to the measurement of regression and statistically sound results in terms of the possible reasons and biomarkers