On-chip high-speed sorting of micron-sized particles for high-throughput analysis

A new design of particle sorting chip is presented. The device employs a dielectrophoretic gate that deflects particles into one of two microfluidic channels at high speed. The device operates by focussing particles into the central streamline of the main flow channel using dielectrophoretic focussing. At the sorting junction (T- or Y-junction) two sets of electrodes produce a small dielectrophoretic force that pushes the particle into one or other of the outlet channels, where they are carried under the pressure-driven fluid flow to the outlet. For a 40mm wide and high channel, it is shown that 6micron diameter particles can be deflected at a rate of 300particles/s. The principle of a fully automated sorting device is demonstrated by separating fluorescent from non-fluorescent latex beads

Dielectrophoresis of charged colloidal suspensions

We present a theoretical study of dielectrophoretic (DEP) crossover spectrum of two polarizable particles under the action of a nonuniform AC electric field. For two approaching particles, the mutual polarization interaction yields a change in their respective dipole moments, and hence, in the DEP crossover spectrum. The induced polarization effects are captured by the multiple image method. Using spectral representation theory, an analytic expression for the DEP force is derived. We find that the mutual polarization effects can change the crossover frequency at which the DEP force changes sign. The results are found to be in agreement with recent experimental observation and as they go beyond the standard theory, they help to clarify the important question of the underlying polarization mechanisms

Eta meson rescattering effects in the p + 6Li --> eta + 7Be reaction near threshold

The p + 6Li --> eta + 7Be reaction has been investigated with an emphasis on the eta meson and 7Be interaction in the final state. Considering the 6Li and 7Be nuclei to be alpha-d and alpha-3He clusters respectively, the reaction is modelled to proceed via the p + d [alpha] --> 3He [\alpha] + eta reaction with the alpha remaining a spectator. The eta meson interacts with 7Be via multiple scatterings on the 3He and alpha clusters inside 7Be. The individual eta-3He and eta-alpha scatterings are evaluated using few body equations for the eta-3N and eta-4N systems with a coupled channel eta-N interaction as an input. Calculations including four low-lying states of 7Be lead to a double hump structure in the total cross section corresponding to the $L = 1 (J = (1/2)^-, (3/2)^-)$ and $L = 3 (J = (5/2)^-, (7/2)^-)$ angular momentum states. The humps arise due to the off-shell rescattering of the eta meson on the 7Be nucleus in the final state.Comment: New results and references adde

Coset Space Dimensional Reduction and Wilson Flux Breaking of Ten-Dimensional N=1, E(8) Gauge Theory

We consider a N=1 supersymmetric E(8) gauge theory, defined in ten dimensions and we determine all four-dimensional gauge theories resulting from the generalized dimensional reduction a la Forgacs-Manton over coset spaces, followed by a subsequent application of the Wilson flux spontaneous symmetry breaking mechanism. Our investigation is constrained only by the requirements that (i) the dimensional reduction leads to the potentially phenomenologically interesting, anomaly free, four-dimensional E(6), SO(10) and SU(5) GUTs and (ii) the Wilson flux mechanism makes use only of the freely acting discrete symmetries of all possible six-dimensional coset spaces.Comment: 45 pages, 2 figures, 10 tables, uses xy.sty, longtable.sty, ltxtable.sty, (a shorter version will be published in Eur. Phys. J. C

Implications of Canonical Gauge Coupling Unification in High-Scale Supersymmetry Breaking

We systematically construct two kinds of models with canonical gauge coupling unification and universal high-scale supersymmetry breaking. In the first we introduce standard vector-like particles while in the second we also include non-standard vector-like particles. We require that the gauge coupling unification scale is from 5 x 10^{15} GeV to the Planck scale, that the universal supersymmetry breaking scale is from 10 TeV to the unification scale, and that the masses of the vector-like particles (M_V) are universal and in the range from 200 GeV to 1 TeV. Using two-loop renormalization group equation (RGE) running for the gauge couplings and one-loop RGE running for Yukawa couplings and the Higgs quartic coupling, we calculate the supersymmetry breaking scales, the gauge coupling unification scales, and the corresponding Higgs mass ranges. When the vector-like particle masses are less than 1 TeV, these models can be tested at the LHC.Comment: 25 pages, 4 figure

Confining QCD Strings, Casimir Scaling, and a Euclidean Approach to High-Energy Scattering

We compute the chromo-field distributions of static color-dipoles in the fundamental and adjoint representation of SU(Nc) in the loop-loop correlation model and find Casimir scaling in agreement with recent lattice results. Our model combines perturbative gluon exchange with the non-perturbative stochastic vacuum model which leads to confinement of the color-charges in the dipole via a string of color-fields. We compute the energy stored in the confining string and use low-energy theorems to show consistency with the static quark-antiquark potential. We generalize Meggiolaro's analytic continuation from parton-parton to gauge-invariant dipole-dipole scattering and obtain a Euclidean approach to high-energy scattering that allows us in principle to calculate S-matrix elements directly in lattice simulations of QCD. We apply this approach and compute the S-matrix element for high-energy dipole-dipole scattering with the presented Euclidean loop-loop correlation model. The result confirms the analytic continuation of the gluon field strength correlator used in all earlier applications of the stochastic vacuum model to high-energy scattering.Comment: 65 pages, 13 figures, extended and revised version to be published in Phys. Rev. D (results unchanged, 2 new figures, 1 new table, additional discussions in Sec.2.3 and Sec.5, new appendix on the non-Abelian Stokes theorem, old Appendix A -> Sec.3, several references added

Grain Surface Models and Data for Astrochemistry

AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions

Probing exotic phenomena at the interface of nuclear and particle physics with the electric dipole moments of diamagnetic atoms: A unique window to hadronic and semi-leptonic CP violation

The current status of electric dipole moments of diamagnetic atoms which involves the synergy between atomic experiments and three different theoretical areas -- particle, nuclear and atomic is reviewed. Various models of particle physics that predict CP violation, which is necessary for the existence of such electric dipole moments, are presented. These include the standard model of particle physics and various extensions of it. Effective hadron level combined charge conjugation (C) and parity (P) symmetry violating interactions are derived taking into consideration different ways in which a nucleon interacts with other nucleons as well as with electrons. Nuclear structure calculations of the CP-odd nuclear Schiff moment are discussed using the shell model and other theoretical approaches. Results of the calculations of atomic electric dipole moments due to the interaction of the nuclear Schiff moment with the electrons and the P and time-reversal (T) symmetry violating tensor-pseudotensor electron-nucleus are elucidated using different relativistic many-body theories. The principles of the measurement of the electric dipole moments of diamagnetic atoms are outlined. Upper limits for the nuclear Schiff moment and tensor-pseudotensor coupling constant are obtained combining the results of atomic experiments and relativistic many-body theories. The coefficients for the different sources of CP violation have been estimated at the elementary particle level for all the diamagnetic atoms of current experimental interest and their implications for physics beyond the standard model is discussed. Possible improvements of the current results of the measurements as well as quantum chromodynamics, nuclear and atomic calculations are suggested.Comment: 46 pages, 19 tables and 16 figures. A review article accepted for EPJ