Eikonal zeros in the momentum transfer space from proton-proton scattering: An empirical analysis

By means of improved empirical fits to the differential cross section data on $pp$ elastic scattering at $19.4 \le\sqrt{s}\le 62.5$ GeV and making use of a semi-analytical method, we determine the eikonal in the momentum transfer space (the inverse scattering problem). This method allows the propagation of the uncertainties from the fit parameters up to the extracted eikonal, providing statistical evidence that the imaginary part of the eikonal (real part of the opacity function) presents a zero (change of signal) in the momentum space, at $q^2 \approx 7 \pm 1$ GeV$^2$. We discuss the implication of this change of signal in the phenomenological context, showing that eikonal models with one zero provide good descriptions of the differential cross sections in the full momentum transfer range, but that is not the case for models without zero. Empirical connections between the extracted eikonal and results from a recent global analysis on the proton electric form factor are also discussed, in special the Wu-Yang conjecture. In addition, we present a critical review on the $pp$ differential cross section data presently available at high energies.Comment: Two references and some misprints corrected, 22 pages; final version to be published in Eur.Phys. J. C (2008

Fast algorithm for the cutting angle method of global optimization

The cutting angle method for global optimization was proposed in 1999 by Andramonov et al. (Appl. Math. Lett. 12 (1999) 95). Computer implementation of the resulting algorithm indicates that running time could be improved with appropriate modifications to the underlying mathematical description. In this article, we describe the initial algorithm and introduce a new one which we prove is significantly faster at each stage. Results of numerical experiments performed on a Pentium III 750 Mhz processor are presented.<br /

Efficient serial and parallel implementations of the cutting angle global optimisation technique

We examine efficient computer implementation of one method of deterministic global optimisation, the cutting angle method. In this method the objective function is approximated from values below the function with a piecewise linear auxiliary function. The global minimum of the objective function is approximated from the sequence of minima of this auxiliary function. Computing the minima of the auxiliary function is a combinatorial problem, and we show that it can be effectively parallelised. We discuss the improvements made to the serial implementation of the cutting angle method, and ways of distributing computations across multiple processors on parallel and cluster computers.<br /

Predicting molecular structures: an application of the cutting angle method

The ability to predict molecular geometries has important applications in chemistry. Specific examples include the areas of protein space structure elucidation, the investigation of host&ndash;guest interactions, the understanding of properties of superconductors and of zeolites. This prediction of molecular geometries often depends on finding the global minimum or maximum of a function such as the potential energy. In this paper, we consider several well-known molecular conformation problems to which we apply a new method of deterministic global optimization called the cutting angle method. We demonstrate that this method is competitive with other global optimization techniques for these molecular conformation problems. <br /

Biocompatible microcapsules functionalized with inorganic nanoparticles for enhanced external triggering via light and ultrasound

Designing and fabricating functional composite capsules are of considerable interest to both academic and industrial fields. Inorganic nanoparticles (NPs) have great potential to modify properties of Layer-by-layer (LbL) polyelectrolyte (PE) capsules, but using prefabricated NPs to functionalize capsules still has considerable challenges such as poor distribution in the capsule walls. The present work proposed and validated a novel approach of fabricating functional capsules with in situ formation and incorporation of inorganic carbon dots (CDs), TiO2 and SiO2 NPs in PAH/PSS multilayers.[1,2] CDs were synthesized within capsule shells through autoclaving the PE capsules in dextran solution, while SiO2 and TiO2 NPs functionalized capsules were fabricated by hydrolysis of Titanium butoxide (TIBO), Tetraethyl orthosilicate (TEOS) respectively. The morphology, composition, shell thickness, permeability and stimuli sensitivity, etc. of the formed capsules with different composition were investigated, and characterized by SEM, TEM, EDX, FTIR, and CLSM. The three types of capsules demonstrated prominent properties compared with the traditional capsule without hybrid with inorganic NPs: i) the PE/CDs capsules displayed a rigid bowl-like morphology (Figure 1A), increased shell thickness (178.4nm, Figure 1B) and an excellent fluorescent property originated from the CDs (Figure 1D, E), and it can efficiently prevent the penetration of a small molecule Rhodamine B (Figure 1F); ii) the PE/SiO2 capsules showed a free-standing sphere morphology and a reduced permeability; iii) the capsules in situ composited with TiO2 NPs were found as a sphere shape and susceptible to UV irradiation (320-400nm, ~110 mW cm-2). Ultrasound irradiation tests demonstrated that all these three types of capsules possessed effective ultrasound sensitivity. It was validated by the fragmentation of PE/SiO2 and PE/TiO2 capsules in a few seconds of 50W ultrasound irradiation and the completely break of PE/CDs capsules in a few minutes of the treatment (Figure 1C). Besides, the cell viability data demonstrated that all the three types of composite capsules possessed good biocompatibility. In summary, those innovative composite capsules were demonstrated with great capability of small molecule encapsulation, high mechanical strength, good biocompatibility and high sensitivity to ultrasound and UV, which could be promising for various applications such as cosmetics, environment and biomedicine areas. Please click Additional Files below to see the full abstract

Optimal estimates of the diffusion coefficient of a single Brownian trajectory

Modern developments in microscopy and image processing are revolutionizing areas of physics, chemistry and biology as nanoscale objects can be tracked with unprecedented accuracy. The goal of single particle tracking is to determine the interaction between the particle and its environment. The price paid for having a direct visualization of a single particle is a consequent lack of statistics. Here we address the optimal way of extracting diffusion constants from single trajectories for pure Brownian motion. It is shown that the maximum likelihood estimator is much more efficient than the commonly used least squares estimate. Furthermore we investigate the effect of disorder on the distribution of estimated diffusion constants and show that it increases the probability of observing estimates much smaller than the true (average) value.Comment: 8 pages, 5 figure

Interfacial stresses in bimaterial composites with nanosized interface relief

The paper compares analytical and numerical solutions for two-dimensional solid mechanics problems of elastic bimaterial composites with a nanosized interface relief that arises on a boundary between two bulk layers and on an interface of a nearly circular inclusion. It is supposed that the uniform stress state takes place at infinity. Here, we use Gurtin–Murdoch model in which interphase domains are represented as negligibly thin layers ideally adhering to the bulk phases. Static boundary conditions at the interface are formulated according to the generalized Laplace–Young law. To solve corresponding boundary value we use first-order boundary perturbation method based on Goursat–Kolosov complex potentials. To examine the perturbation results, we use a finite element calculations