Heavy quark radiation in NLO+PS POWHEG generators

In this paper we deal with radiation from heavy quarks in the context of next-to-leading order calculations matched to parton shower generators. A new algorithm for radiation from massive quarks is presented that has considerable advantages over the one previously employed. We implement the algorithm in the framework of the ${\tt POWHEG-BOX}$, and compare it with the previous one in the case of the ${\tt hvq}$ generator for bottom production in hadronic collisions, and in the case of the ${\tt bb4l}$ generator for top production and decay.Comment: 14 pages, 13 figures, LaTe

A chemically driven fluctuating ratchet model for actomyosin interaction

With reference to the experimental observations by T. Yanagida and his co-workers on actomyosin interaction, a Brownian motor of fluctuating ratchet kind is designed with the aim to describe the interaction between a Myosin II head and a neighboring actin filament. Our motor combines the dynamics of the myosin head with a chemical external system related to the ATP cycle, whose role is to provide the energy supply necessary to bias the motion. Analytical expressions for the duration of the ATP cycle, for the Gibbs free energy and for the net displacement of the myosin head are obtained. Finally, by exploiting a method due to Sekimoto (1997, J. Phys. Soc. Jpn., 66, 1234), a formula is worked out for the amount of energy consumed during the ATP cycle.Comment: 15 pages. 1 figur

A stochastic model for the stepwise motion in actomyosin dynamics

A jump-diffusion process is proposed to describe the displacements performed by single myosin heads along actin filaments during the rising phases. The process consists of the superposition of a Wiener and a jump process, with jumps originated by sequences of Poisson-distributed energy-supplying pulses. In a previous paper, the amplitude of the jumps was described by a mixture of two Gaussian distributions. To embody the effects of ATP hydrolysis, we now refine such a model by assuming that the jumps' amplitude is described by a mixture of three Gaussian distributions. This model has been inspired by the experimental data of T. Yanagida and his co-workers concerning observations at single molecule processes level.Comment: 9 pages, 4 figure

On Myosin II dynamics in the presence of external loads

We address the controversial hot question concerning the validity of the loose coupling versus the lever-arm theories in the actomyosin dynamics by re-interpreting and extending the phenomenological washboard potential model proposed by some of us in a previous paper. In this new model a Brownian motion harnessing thermal energy is assumed to co-exist with the deterministic swing of the lever-arm, to yield an excellent fit of the set of data obtained by some of us on the sliding of Myosin II heads on immobilized actin filaments under various load conditions. Our theoretical arguments are complemented by accurate numerical simulations, and the robustness of the model is tested via different choices of parameters and potential profiles.Comment: 6 figures, 8 tables, to appear on Biosystem

The qT subtraction method: electroweak corrections and power suppressed contributions

Building upon the formulation of transverse-momentum resummation for heavy-quark hadroproduction, we present the first application of the qT subtraction formalism to the computation of electroweak corrections to massive lepton pairs through the Drell–Yan mechanism. We then study the power suppressed contributions to the qT subtraction formula in the parameter rcut, defined as the minimum transverse momentum of the lepton pair normalised to its invariant mass. We analytically compute the leading power correction from initial and final-state radiation to the inclusive cross section. In the case of initial-state radiation the power correction is quadratic in rcut and our analytic result is consistent with results previously obtained in the literature. Final-state radiation produces linear contributions in rcut that may challenge the efficiency of the qT subtraction procedure. We explicitly compute the linear power correction in the case of the inclusive cross section and we discuss the extension of our calculation to differential distributions

An Appreciative Approach to Diversity Training

One way to combat "diversity fatigue" is to take an appreciative approach to diversity training. This article highlights the six phases of Appreciative Education and how diversity trainers can use specific activities for each phase to deliver effective diversity training

Leptons in the proton

As is the case for all light coloured Standard Model particles, also photons and charged leptons appear as constituents in ultrarelativistic hadron beams, and admit a parton density function (PDF). It has been shown recently that the photon PDF can be given in terms of the structure functions and form factors for electron-proton scattering. The same holds for lepton PDFs. In the present work we set up a calculation of the lepton PDFs at next-to-leading order, using the same data input needed in the photon case. A precise knowledge of the lepton densities allows us to study lepton-initiated processes even at a hadron collider, with all possible combinations of same-charge, opposite-charge, same-flavour, different-flavour leptons and leptons-quarks, most of which cannot be realized in any other forseable experiment. The lepton densities in the proton are extremely small, so that their contribution to Standard Model processes is generally shadowed by processes initiated by coloured partons. We will show, however, that there are cases where these processes can be relevant, giving rise to rare Standard Model signatures and to new production channels, that can enlarge the discovery potential of New Physics at the LHC and future high energy colliders with hadrons in the initial state

CysMap and CysJoin: Database and tools for protein disulphide localization

We have developed a computer program able to make user-customised databases derived from the public PIR non-redundant reference protein database. When the database of interest has been created, the user will generate the map of all the possible linear peptides containing one and two cysteines for each protein and combine them to calculate the mass of all the possible clusters of linear peptides linked by a disulphide bridge with a cysteine pair. It is also possible to create selected maps corresponding to peptides formed by the action of specific proteases. In this way, mass spectrometric data obtained from the hydrolysis of proteins of unknown sequence can be related to that contained in the database for quick disulphide assignment and protein identification. To confirm signal attribution, the program will also furnish the expected mass of cluster peptides after performing a cycle of Edman degradation. The utility of the program is discussed and examples of application are given. © 2005 Federation of European Biochemical Societies