Low-x evolution of parton densities

It is shown that a Bessel-like behaviour of the structure function F2 at small x, obtained for a flat initial condition in the DGLAP evolution equations, leads to good agreement with the deep inelastic scattering experimental data from HERA.Comment: 8 pages, 3 figures, in Proc. of the third International Workshop on Multiple Partonic Interactions at the LHC (21-25 November 2011, DESY, Hamburg

Ultrahigh-energy neutrino-nucleon deep-inelastic scattering and the Froissart bound

We present a simple formula for the total cross section sigma^{nu N} of neutral- and charged-current deep-inelastic scattering of ultrahigh-energy neutrinos on isoscalar nuclear targets, which is proportional to the structure function F_2^{nu N}(M_V^2/s, M_V^2), where M_V is the intermediate-boson mass and s is the square of the center-of-mass energy. The coefficient in the front of F_2^{nu N}(x, Q^2) depends on the asymptotic low-x behavior of F_2^{nu N}. It contains an additional ln(s) term if F_2^{nu N} scales with a power of ln(1/x). Hence, an asymptotic low-x behavior F_2^{nu N} propto ln^2(1/x), which is frequently assumed in the literature, already leads to a violation of the Froissart bound on sigma^{nu N}.Comment: 5 pages, 2 figures, to appear in Physical Review Letter

Metallic materials for medical use

This article provides a brief overview of the metallic materials used as implants in orthopedics, the alloying system and a complex of the physical-mechanical properties for metallic materials certified for medical use, as well as the advantages and drawbacks of using metallic materials as implants. Approaches to improve the quality of an implant made of metallic materials are noted

Small-x behavior of the structure function F_2 and its slope partial ln(F_2)/partial ln(1/x) for "frozen" and analytic strong-coupling constants

Using the leading-twist approximation of the Wilson operator product expansion with "frozen" and analytic versions of the strong-coupling constant, we show that the Bessel-inspired behavior of the structure function F_2 and its slope\break partial ln(F_2)/partial ln(1/x) at small values of x, obtained for a flat initial condition in the DGLAP evolution equations, leads to good agreement with experimental data of deep-inelastic scattering at DESY HERA.Comment: new curves added to Figs. 1 and 2, minor changes to the text, accepted for publication in Phys. Lett.

Heavy-quark contributions to the ratio F_L/F_2 at low x

We study the heavy-quark contribution to the proton structure functions F_2^i(x,Q^2) and F_L^i(x,Q^2), with i=c,b, for small values of Bjorken's x variable at next-to-lading order and provide compact formulas for their ratios R_i=F_L^i/F_2^i that are useful to extract F_2^i(x,Q^2) from measurements of the doubly differential cross section of inclusive deep-inelastic scattering at DESY HERA. Our approach naturally explains why R_i is approximately independent of x and the details of the parton distributions in the small-x regime.Comment: 11 pages, 1 figur

Review of solar energetic particle models

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.</p

FORMING OF STRUCTURE AND PROPERTIES OF TITANIUM-NIOBIUM ALLOYS WITH HYDROGEN, OF COMPLEXLY-ALLOYED ( alpha + beta )-COMPOUNDS AND PSEUDO- alpha -ALLOYS WITH YTTRIUM IN HEAT TREATMENT

There the study objects are the titanium alloys of titanium - niobium, titanium - niobium - hydrogen, VT18U, titanium - aluminium - iron - vanadium - molybdenum - chromium systems. The change of phase relation in the titanium -niobium alloys in hardening has been ascertained. The formation of massive extractions of omega -phase with size more 100 nm has been detected. The metastable diagram of titanium - niobium - hydrogen has been constructed, on this basis the compound low-alloyed by niobium for the superconductors has been offered. The formation of transitional hydride in the titanium - niobium - hydrogen system has been ascertained. It was showed that the yttrium favours the hindering of grain growth at the expense of adsorption in boundaries. The recommendations for use of complex yttrium - chromium, hafnium - chromium microadditives in VT18U alloy allow to decrease the metal losses by 10%Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

C’ ERA UNA VOLTA NELLA CULTURA CONTEMPORANEA: RIFLESSIONI PEDAGOGICHE E PROPOSTE FORMATIVE

Is Once upon a time still there? Beginning from this linguistic word-play, the present contribution approaches the current topicality of pedagogical value of fairy tale and attempts a possible comparison with another language of childhood that is represented by videogame

Structure, phase composition, physical properties of quenched VT16 alloy

Features of structural and phase composition, physical and mechanical properties formation of VT16 alloy during quenching from temperature range 700-875°C were determined. For the first time formation of athermal ω-phase during quenching of the VT16 alloy within initial (α+β)-structure was experimentally shown. According to the summarized XRD and TEM data diagram of volume fraction variation depending on quenching temperature was proposed. Minimum of yield strength in the certain quenching temperature range was confirmed to be connected with the behavior of martensitic β → α″-transformation during tensile testing. Fine correlation between the Young's Module and phase composition variation was shown