Microscopic mechanisms of thermal and driven diffusion of non rigid molecules on surfaces

The motion of molecules on solid surfaces is of interest for technological applications such as catalysis and lubrication, but it is also a theoretical challenge at a more fundamental level. The concept of activation barriers is very convenient for the interpretation of experiments and as input for Monte Carlo simulations but may become inadequate when mismatch with the substrate and molecular vibrations are considered. We study the simplest objects diffusing on a substrate at finite temperature $T$, namely an adatom and a diatomic molecule (dimer), using the Langevin approach. In the driven case, we analyse the characteristic curves, comparing the motion for different values of the intramolecular spacing, both for T=0 and $T\ne 0$. The mobility of the dimer is higher than that of the monomer when the drift velocity is less than the natural stretching frequency. The role of intramolecular excitations is crucial in this respect. In the undriven case, the diffusive dynamics is considered as a function of temperature. Contrary to atomic diffusion, for the dimer it is not possible to define a single, temperature independent, activation barrier. Our results suggest that vibrations can account for drastic variations of the activation barrier. This reveals a complex behaviour determined by the interplay between vibrations and a temperature dependent intramolecular equilibrium length.Comment: 6 pages, 5 figures, Proceeding of the EMRS 2002 Conference, to be published in Thin Solid Film

Normalization factors for magnetic relaxation of small particle systems in non-zero magnetic field

We critically discuss relaxation experiments in magnetic systems that can be characterized in terms of an energy barrier distribution, showing that proper normalization of the relaxation data is needed whenever curves corresponding to different temperatures are to be compared. We show how these normalization factors can be obtained from experimental data by using the $T \ln(t/\tau_0)$ scaling method without making any assumptions about the nature of the energy barrier distribution. The validity of the procedure is tested using a ferrofluid of Fe_3O_4 particles.Comment: 5 pages, 6 eps figures added in April 22, to be published in Phys. Rev. B 55 (1 April 1997

A learning-based algorithm to quickly compute good primal solutions for Stochastic Integer Programs

We propose a novel approach using supervised learning to obtain near-optimal primal solutions for two-stage stochastic integer programming (2SIP) problems with constraints in the first and second stages. The goal of the algorithm is to predict a "representative scenario" (RS) for the problem such that, deterministically solving the 2SIP with the random realization equal to the RS, gives a near-optimal solution to the original 2SIP. Predicting an RS, instead of directly predicting a solution ensures first-stage feasibility of the solution. If the problem is known to have complete recourse, second-stage feasibility is also guaranteed. For computational testing, we learn to find an RS for a two-stage stochastic facility location problem with integer variables and linear constraints in both stages and consistently provide near-optimal solutions. Our computing times are very competitive with those of general-purpose integer programming solvers to achieve a similar solution quality

Advances in Hormone-Free Contraceptive Devices

Up to (99%) of women worldwide may use birth control for at least 30 years. However, most modern female contraceptives containing hormones can have undesirable side effects. Among the limited hormone-free options, the fertility awareness method is the safest and most effective when used correctly. This study explores a time-tested, safe, and effective barrier contraceptive called FemCap. FemCap not only aids in pinpointing the day of ovulation but also integrates electronic period-tracking technology to enhance the efficacy of the fertility awareness method. Stress Urinary Incontinence is a prevalent issue affecting women of all ages, often suffering in silence. Our research aims to address the unmet needs in women’s reproductive health. We have discovered that FemCap can function as a pessary to manage Stress Urinary Incontinence by providing support to the bladder neck and straightening the urethra, thereby restoring the competence of the urethral sphincters. FemCap has emerged as a powerhouse for fertility awareness and stress urinary incontinence. However, due to the limitations of this study, the authors welcome any investigators who can validate our findings as well as provide suggestions to enhance the overall value of this research for the benefit of all women

Branching on multi-aggregated variables

open5siopenGamrath, Gerald; Melchiori, Anna; Berthold, Timo; Gleixner, Ambros M.; Salvagnin, DomenicoGamrath, Gerald; Melchiori, Anna; Berthold, Timo; Gleixner, Ambros M.; Salvagnin, Domenic