Elementary simulation of tethered Brownian motion

We describe a simple numerical simulation, suitable for an undergraduate project (or graduate problem set), of the Brownian motion of a particle in a Hooke-law potential well. Understanding this physical situation is a practical necessity in many experimental contexts, for instance in single molecule biophysics; and its simulation helps the student to appreciate the dynamical character of thermal equilibrium. We show that the simulation succeeds in capturing behavior seen in experimental data on tethered particle motion.Comment: Submitted to American Journal of Physic

Stability of Premixed H₂/O₂/N₂ Combusting Turbulent Jets

Experimental measurements and theoretical predictions of the stability of hydrogen-air-nitrogen premixed turbulent flames have been carried out. The turbulent flame is theoretically modeled using finite rate chemical kinetics and a well-stirred reactor. The model contains a free parameter, which is evaluated by comparing the theoretical predictions to experimental results. A hydrogen flame stability experiment was carried out and the results were compared to the theory. The theory and experiment were found to agree, if the free parameter in the theory varied as the reciprocal of the turbulent jet radius squared

A New Concept for Controlled Lifting Entry Flight Experiments

Feasibility of trajectory guidance and control concept for lifting configuration with roll modulatio

Genetically Modified Crops, an Input Distance Function Approach

Our initial findings indicate that GM crops do not contribute to the decline of traditional family farms. We make a significant methodological impact by using the within transformation to remove unobserved individual effects and demonstrate that the within transformation results in ML estimates that are identical to OLS estimates.Production Economics, Genetically Modified Crops, Distance Function, Stochastic Frontier Analysis, Production Economics, Research Methods/ Statistical Methods,

Effect of a finite ionization rate on the radiative heating of outer planet atmospheric entry probes

The influence of finite rate ionization in the inviscid gas just behind the stagnation shock wave on the radiation heating of probes entering the hydrogen helium atmospere of the major planets was investigated. At the present time, there is disagreement as to whether the radiative flux increases or decreases relative to its equilibrium value when finite rate ionization is considered. Leibowitz and Kuo content that the finite rate ionization in the hydrogen gas just behind the shock wave reduces the radiative flux to the probe, whereas Tiwari and Szema predict that it increases the radiative flux. The radiation modeling used in the calculations of both pairs of these investigators was reviewed. It is concluded that finite rate ionization in the inviscid region of the shock layer should reduce the cold wall radiative heating below the values predicted by equilibrium chemistry assumptions

Effect of a finite ionization rate on the radiative heating of outer planet atmospheric entry probes

The influence of finite rate ionization in the inviscid gas just behind the stagnation shock wave on the radiative heating of probes entering the hydrogen-helium atmosphere of the major plants was investigated. Two opposing conclusions were reached as to how the ionization rate assumption affects the radiative transfer. Hydrogen-helium shock waves with a cold nonblowing wall boundary condition at the probe heat shield are emphasized. The study is limited to the stagnation shock layer

Interacting Crumpled Manifolds: Exact Results to all Orders of Perturbation Theory

In this letter, we report progress on the field theory of polymerized tethered membranes. For the toy-model of a manifold repelled by a single point, we are able to sum the perturbation expansion in the strength g of the interaction exactly in the limit of internal dimension D -> 2. This exact solution is the starting point for an expansion in 2-D, which aims at connecting to the well studied case of polymers (D=1). We here give results to order (2-D)^4, where again all orders in g are resummed. This is a first step towards a more complete solution of the self-avoiding manifold problem, which might also prove valuable for polymers.Comment: 8 page

Axial Anomaly from the BPHZ regularized BV master equation

A BPHZ renormalized form for the master equation of the field antifiled (or BV) quantization has recently been proposed by De Jonghe, Paris and Troost. This framework was shown to be very powerful in calculating gauge anomalies. We show here that this equation can also be applied in order to calculate a global anomaly (anomalous divergence of a classically conserved Noether current), considering the case of QED. This way, the fundamental result about the anomalous contribution to the Axial Ward identity in standard QED (where there is no gauge anomaly) is reproduced in this BPHZ regularized BV framework.Comment: 10 pages, Latex, minor changes in the reference

Free Energies of Isolated 5- and 7-fold Disclinations in Hexatic Membranes

We examine the shapes and energies of 5- and 7-fold disclinations in low-temperature hexatic membranes. These defects buckle at different values of the ratio of the bending rigidity, $\kappa$, to the hexatic stiffness constant, $K_A$, suggesting {\em two} distinct Kosterlitz-Thouless defect proliferation temperatures. Seven-fold disclinations are studied in detail numerically for arbitrary $\kappa/K_A$. We argue that thermal fluctuations always drive $\kappa/K_A$ into an ``unbuckled'' regime at long wavelengths, so that disclinations should, in fact, proliferate at the {\em same} critical temperature. We show analytically that both types of defects have power law shapes with continuously variable exponents in the ``unbuckled'' regime. Thermal fluctuations then lock in specific power laws at long wavelengths, which we calculate for 5- and 7-fold defects at low temperatures.Comment: LaTeX format. 17 pages. To appear in Phys. Rev.