Pore Stabilization in Cohesive Granular Systems

Cohesive powders tend to form porous aggregates which can be compacted by applying an external pressure. This process is modelled using the Contact Dynamics method supplemented with a cohesion law and rolling friction. Starting with ballistic deposits of varying density, we investigate how the porosity of the compacted sample depends on the cohesion strength and the friction coefficients. This allows to explain different pore stabilization mechanisms. The final porosity depends on the cohesion force scaled by the external pressure and on the lateral distance between branches of the ballistic deposit r_capt. Even if cohesion is switched off, pores can be stabilized by Coulomb friction alone. This effect is weak for round particles, as long as the friction coefficient is smaller than 1. However, for nonspherical particles the effect is much stronger.Comment: 10 pages, 15 figure

Inclusive production of a pair of hadrons separated by a large interval of rapidity in proton collisions

We consider within QCD collinear factorization the inclusive process $p+p\to h_1+h_2+X$, where the pair of identified hadrons, $h_1,h_2$, having large transverse momenta is produced in high-energy proton-proton collisions. In particular, we concentrate on the kinematics where the two identified hadrons in the final state are separated by a large interval of rapidity $\Delta y$. In this case the (calculable) hard part of the reaction receives large higher order corrections $\sim \alpha^n_s \Delta y^n$. We provide a theoretical input for the resummation of such contributions with next-to-leading logarithmic accuracy (NLA) in the BFKL approach. Specifically, we calculate in NLA the vertex (impact-factor) for the inclusive production of the identified hadron. This process has much in common with the widely discussed Mueller-Navelet jets production and can be also used to access the BFKL dynamics at proton colliders. Another application of the obtained identified-hadron vertex could be the NLA BFKL description of inclusive forward hadron production in DIS.Comment: 29 pages, 9 figures; corrected few typos and added an acknowledgment; version to be published on JHEP. arXiv admin note: substantial text overlap with arXiv:1202.108

Frictional coupling between sliding and spinning motion

We show that the friction force and torque, acting at a dry contact of two objects moving and rotating relative to each other, are inherently coupled. As a simple test system, a sliding and spinning disk on a horizontal flat surface is considered. We calculate, and also measure, how the disk is slowing down, and find that it always stops its sliding and spinning motion at the same moment. We discuss the impact of this coupling between friction force and torque on the physics of granular materials.Comment: 4 pages, 5 figures; submitte

Effect of growth conditions on optical properties of CdSe/ZnSe single quantum dots

In this work, we have investigated the optical properties of two samples of CdSe quantum dots by using submicro-photoluminescence spectroscopy. The effect of vicinal-surface GaAs substrates on their properties has been also assessed. The thinner sample, grown on a substrate with vicinal surface, includes only dots with a diameter of less than 10 nm (type A islands). Islands of an average diameter of about 16 nm (type B islands) that are related to a phase transition via a Stranski-Krastanow growth process are also distributed in the thicker sample grown on an oriented substrate. We have studied the evolution of lineshapes of PL spectra for these two samples by improving spatial resolution that was achieved using nanoapertures or mesa structures. It was found that the use of a substrate with the vicinal surface leads to the suppression of excitonic PL emitted from a wetting layer.Comment: 2pages, 2 figures, Proceedings of International Conference On Superlattices Nano-Structures And Nano-Devices, July, Toulouse, France, to appear in the special issue of Physica

A polarized version of the CCFM equation for gluons

A derivation for a polarized CCFM evolution equation which is suitable to describe the scaling behavior of the the unintegrated polarized gluon density is given. We discuss the properties of this polarized CCFM equation and compare it to the standard CCFM equation in the unpolarized case.Comment: 15 pages, 6 figures, RevTeX, some minor typos corrected, version to appear in Phys. Rev.

Influence of transient pressure changes on speech intelligibility: Implications for nextgeneration train travel

High-speed trains are operated in increasingly complex railway networks and continual improvement of driver assistance systems is necessary to maintain safety. Speech offers the opportunity to provide information to the driver without disrupting visual attention. However, it is not known whether the transient pressure changes inside trains passing through tunnels interfere with speech intelligibility. Our primary goal was to test whether the most severe pressure variations occurring in high-speed trains (25 hPa in 2 s) affect speech intelligibility in individuals with normal hearing ability and secondly whether a potential effect would depend on the direction of the pressure change. A cross-over design was used to compare speech intelligibility, measured with the monosyllable word test by Wallenberg and Kollmeier, in steady ambient pressure versus subsequent to pressure events, both realised in a pressure chamber. Since data for a power calculation did not exist, we conducted a pilot study with 20 participants to estimate variance of intra-individual differences. The upper 80% confidence limit guided sample size of the main campaign, which was performed with 72 participants to identify a 10% difference while limiting alpha (5%) and beta error (10%). On average, a participant understood 0.7 fewer words following a pressure change event compared to listening in steady ambient pressure. However, this intra-individual differences varied strongly between participants, standard deviation (SD) +/- 4.5 words, resulting in a negligible effect size of 0.1 and the Wilcoxon signed rank test (Z = -1.26; p = 0.21) did not distinguish it from chance. When comparing decreasing and increasing pressure events an average of 0.2 fewer words were understood (+/- 3.9 SD). The most severe pressure changes expected to occur in high-speed trains passing through tunnels do not interfere with speech intelligibility and are in itself not a risk factor for loss of verbal information transmission

QCD evolution and skewedness effects in color dipole description of DVCS

We show the role played by QCD evolution and skewedness effects in the DVCS cross section at large $Q^2$ within the color dipole description of the process at photon level. The dipole cross section is given by the saturation model, which can be improved by DGLAP evolution at high photon virtualities. We investigate both possibilities as well as the off-forward effect through a simple phenomenological parametrisation. The results are compared to the recent ZEUS DVCS data.Comment: LaTeX, 6 pages, 5 Figs. Vers 2: Minor modifications. Accepted by EPJ

The impact factor for the virtual photon to light vector meson transition

We evaluate in the next-to-leading approximation the forward impact factor for the virtual photon to light vector meson transition in the case of longitudinal polarization. We find that in the hard kinematic domain, both in the leading and in the next-to-leading approximation, the expression for the impact factor factorizes, up to power suppressed corrections, into the convolution of a perturbatively calculable hard-scattering amplitude and a meson twist-2 distribution amplitude.Comment: 31 pages latex; few comments and one reference added; version to appear in Eur. Phys. Journal

The perioperative use of oral anticoagulants during surgical procedures for carpal tunnel syndrome. A preliminary study

Contains fulltext : 87781.pdf (publisher's version ) (Closed access)BACKGROUND: To evaluate the feasibility of designing a randomized controlled study whether open carpal tunnel release (OCTR) surgery can be performed safely under systemic anticoagulant therapy using acetylsalicylacid (ASA) or acenocoumarol (ACM), this preliminary, observational study was performed. METHODS: Prospectively, during 1 year, data were collected from all patients who underwent conventional OCTR at the neurosurgical department of the Canisius Wilhelmina Hospital, Nijmegen, The Netherlands. Patients continued anticoagulant treatment perioperatively. RESULTS: A total of 364 patients were operated on, of whom 45 continued ASA and seven ACM treatment. Only one patient using ASA complained of a postoperative subcutaneous hemorrhage. In the control group without anticoagulants, none of the patients had a bleeding postoperatively. CONCLUSION: Continuation of anticoagulant treatment is safe for OCTR. The adverse effects of stopping treatment for surgery can be severe. As a result of this study, we have changed our surgery protocol for OCTR and continue anticoagulant treatment perioperatively.1 juli 201

Ultralow phase noise microwave generation with an Er:fiber-based optical frequency divider

We present an optical frequency divider based on a 200 MHz repetition rate Er:fiber mode-locked laser that, when locked to a stable optical frequency reference, generates microwave signals with absolute phase noise that is equal to or better than cryogenic microwave oscillators. At 1 Hz offset from a 10 GHz carrier, the phase noise is below -100 dBc/Hz, limited by the optical reference. For offset frequencies > 10 kHz, the phase noise is shot noise limited at -145 dBc/Hz. An analysis of the contribution of the residual noise from the Er:fiber optical frequency divider is also presented.Comment: 4 pages, 3 figure