Water-soluble peptide-coated nanoparticles: control of the helix structure and enhanced differential binding to immune cells

The stabilizing action of C(α)-tetrasubstituted α-amino acids inserted into a sequence of short peptides allowed for the first time the preparation of water-soluble nanoparticles of different materials coated with a helix-structured undecapeptide. This peptide coating strongly favors nanoparticle uptake by human immune system cells.     

The LHCf experiment at LHC

The LHCf experiment will be installed in 2007 on the LHC collider in the forward direction at ±140m from the ATLAS interaction point. The purpose of LHCf is to precisely measure the pion production cross section near zero degrees through the measurement of the photons produced in neutral pion decay. This measurement is crucial for the simulation of the showers induced in the atmosphere by very high energy cosmic rays; the 14 TeV energy available in the center of mass frame corresponds in fact to an equivalent energy of 10¹⁷ eV in the laboratory system. The paper focus on the proposed experiment and on the physics results that we expect from it.     

Effect of quantum entanglement on Aharonov-Bohm oscillations, spin-polarized transport and current magnification effect

We present a simple model of transmission across a metallic mesoscopic ring. In one of its arm an electron interacts with a single magnetic impurity via an exchange coupling. We show that entanglement between electron and spin impurity states leads to reduction of Aharonov-Bohm oscillations in the transmission coefficient. The spin-conductance is asymmetric in the flux reversal as opposed to the two-probe electrical conductance which is symmetric. In the same model, in contradiction to the naive expectation of a current magnification effect, we observe enhancement as well as suppression of this effect depending on the system parameters. The limitations of this model to the general notion of dephasing or decoherence in quantum systems are pointed out.     

Exact conformally flat solutions of Einstein equations for neutral superfluids

A family of exact conformally flat solutions of Einstein equations (with Λ term) is presented. They correspond to a class of relativistic neutral superfluids. The particular velocity field chosen and the field equations determine the thermodynamical variables of the superfluid and restrict the form of the equation of state. One of the solution provides a geometrical interpretation for merons. In principle, a measurement of the time change of the circulation quantum, would distinguish among the various cosmologies of the Dirac-Canuto type.     

An estimate of the secondary-proton spectrum at small atmospheric depths

Summary We have calculated the energy spectrum of secondary protons produced in the atmosphere as a function of the atmospheric depth and zenith angles at a location with zero geomagnetic cut-off. In this calculation, we have included all relevant energy losses and production processes. It is shown that the protons produced from the target nuclei through recoil and evaporation processes dominate the spectrum below 350 MeV. These calculations have been carried out over an energy region from 20 MeV to 40 GeV and up to a depth of 40 g/cm² of the atmosphere over a latitude with zero geomagnetic cut-off for both the periods of minimum and maximum solar modulation.     

Gravitons in Minkowski space-time interactions and results of astrophysical interest

A review is presented of the quantization procedures applicable to linear gravitational fields in Minkowski space-time and of various interactions processes involving gravitons. The discussion is mainly concerned with those processes that in the Feynman diagrammatic approach involve gravitons on external lines and are of particular astrophysical interest because of their contribution to background gravitational radiation in the universe. More specifically they are graviton production from particle-antiparticle annihilation, gravitational bremsstrahlung, scattering of gravitons and photoproduction. Among the topics discussed are also, the graviton-particle vertex and some of its applications, and the problem of coherent emission of gravitational radiation in the laboratory.     

Location Problems with Different Norms for Different Points

Given a finite set in a linear space X, we consider two problems. The first problem consists of finding the points minimizing the maximum distance to the points in A; the second problem looks for the points that minimize the average distance to the points in A. In both cases, we assume that the distances at different points are defined as

A combined measurement of thermal and mechanical relaxation

In order to describe relaxation the thermodynamic coefficient can be generalized into a complex frequency-dependent cross response function. We explore theoretically the possibility of measuring for a supercooled liquid near the glass transition. This is done by placing a thermistor in the middle of the liquid which itself is contained in a spherical piezoelectric shell. The piezoelectric voltage response to a thermal power generated in the thermistor is found to be proportional to but factors pertaining to heat diffusion and adiabatic compressibility κ_S(ω) do also intervene. We estimate a measurable piezoelectric voltage of 1 mV to be generated at 1 Hz for a heating power of 0.3 mW. Together with κ_S(ω) and the longitudinal specific heat c_l(ω) which may also be found in the same setup a complete triple of thermoviscoelastic response functions may be determined when supplemented with shear modulus data.     

On Some Types of Rigid Sets in Banach Spaces

One of the properties characterizing Euclidean spaces says - roughly speaking- that their unit sphere has nice invariant properties. More precisely, a finite dimensional normed space has an Euclidean norm if and only if the group of isometries acts transitively on its unit sphere (the norm is “transitive”); such property of the sphere is also called “rigidity”. More recently, another notion of “rigidity” for compact sets, connected with “isometric sequences”, received some attention. Infinite rigid sets are diametral; moreover, under suitable assumptions on the space, they are also contained in the boundary of a sphere. These notions are connected with many problems, in different areas. Here we discuss and compare these two notions of rigid set, trying to indicate new relations among them and with some other properties of sets. Several examples complete the paper.