Heat and Mass Transport in Heat Pipe Wick Structures

Anovel experimental approach is developed for characterizing the performance of heat pipe wick structures. This approach simulates the actual operation of wick structures in a heat pipe. Open, partially submerged, sintered copper wicks of varying pore size are studied under the partially saturated conditions found in normal heat pipe operation. A vertical wick orientation, where the capillary lift is in opposition to gravity, is selected to test the wicks under the most demanding conditions. Mass transport measurements of the working fluid, in addition to the temperature field, are obtained for the porous wicks under the action of a discrete heat source (evaporator) mounted on one end. The working fluid, supplied from a condenser pool, evaporates from the wick surface primarily in the evaporator region and is condensed and collected into a container separate from the pool, to yield mass flow rates. Thus the liquid-pumping capability of the wick, coupled with flow impedance, is measured as a function of applied heat flux. Repeatable results with low uncertainty are obtained.Acareful analysis of the transport paths for heat and mass transfer in the wick structure confirms that mass transfer due to vaporization of the working fluid is the largest contributor to heat dissipation from the wick. The expected and measured values of evaporation rate are in good agreement. Results are also presented in terms of overall effective conductance based on measured temperatures

Avalanche Dynamics in Wet Granular Materials

We have studied the dynamics of avalanching wet granular media in a rotating drum apparatus. Quantitative measurements of the flow velocity and the granular flux during avalanches allow us to characterize novel avalanche types unique to wet media. We also explore the details of viscoplastic flow (observed at the highest liquid contents) in which there are lasting contacts during flow, leading to coherence across the entire sample. This coherence leads to a velocity independent flow depth at high rotation rates and novel robust pattern formation in the granular surface.Comment: 5 pages, 3 figures in color, REVTeX4, for smaller pdfs see http://angel.elte.hu/~tegzes/condmat.htm

Covariant Quantization of d=4 Brink-Schwarz Superparticle with Lorentz Harmonics

Covariant first and second quantization of the free d=4 massless superparticle are implemented with the introduction of purely gauge auxiliary spinor Lorentz harmonics. It is shown that the general solution of the condition of maslessness is a sum of two independent chiral superfields with each of them corresponding to finite superspin. A translationally covariant, in general bijective correspondence between harmonic and massless superfields is constructed. By calculation of the commutation function it is shown that in the considered approach only harmonic fields with correct connection between spin and statistics and with integer negative homogeneity index satisfy the microcausality condition. It is emphasized that harmonic fields that arise are reducible at integer points. The index spinor technique is used to describe infinite-component fields of finite spin; the equations of motion of such fields are obtained, and for them Weinberg's theorem on the connection between massless helicity particles and the type of nongauge field that describes them is generalized.Comment: V2: 1 + 26 pages, published versio

Verifying head impacts recorded by a wearable sensor using video footage in rugby league: A preliminary study

Background: Rugby league is a full-contact collision sport with an inherent risk of concussion. Wearable instrumented technology was used to observe and characterize the level of exposure to head impacts during game play. Purpose: To verify the impacts recorded by the x-patch™ with video analysis. Study design: Observational case series. Methods: The x-patch™ was used on eight men’s semi-professional rugby league players during the 2016 Newcastle Rugby League competition (five forwards and three backs). Game day footage was recorded by a trained videographer using a single camera located at the highest midfield location to verify the impact recorded by the x-patch™. Videographic and accelerometer data were time synchronized. Results: The x-patch™ sensors recorded a total of 779 impacts ≥ 20 g during the games, of which 732 (94.0%) were verified on video. In addition, 817 impacts were identified on video that did not record an impact on the sensors. The number of video-verified impacts ≥ 20 g, per playing hour, was 7.8 for forwards and 4.8 for backs (range = 3.9–19.0). Impacts resulting in a diagnosed concussion had much greater peak linear acceleration (M = 76.1 g, SD = 17.0) than impacts that did not result in a concussion (M = 34.2g, SD = 18.0; Cohen’s d = 2.4). Conclusions: The vast majority (94%) of impacts ≥ 20 g captured by the x-patch™ sensor were video verified in semi-professional rugby league games. The use of a secondary source of information to verify impact events recorded by wearable sensors is beneficial in clarifying game events and exposure levels

Retelling racialized violence, remaking white innocence: the politics of interlocking oppressions in transgender day of remembrance

Transgender Day of Remembrance has become a significant political event among those resisting violence against gender-variant persons. Commemorated in more than 250 locations worldwide, this day honors individuals who were killed due to anti-transgender hatred or prejudice. However, by focusing on transphobia as the definitive cause of violence, this ritual potentially obscures the ways in which hierarchies of race, class, and sexuality constitute such acts. Taking the Transgender Day of Remembrance/Remembering Our Dead project as a case study for considering the politics of memorialization, as well as tracing the narrative history of the Fred F. C. Martinez murder case in Colorado, the author argues that deracialized accounts of violence produce seemingly innocent White witnesses who can consume these spectacles of domination without confronting their own complicity in such acts. The author suggests that remembrance practices require critical rethinking if we are to confront violence in more effective ways. Description from publisher's site: http://caliber.ucpress.net/doi/abs/10.1525/srsp.2008.5.1.2

Covariant quantization of infinite spin particle models, and higher order gauge theories

Further properties of a recently proposed higher order infinite spin particle model are derived. Infinitely many classically equivalent but different Hamiltonian formulations are shown to exist. This leads to a condition of uniqueness in the quantization process. A consistent covariant quantization is shown to exist. Also a recently proposed supersymmetric version for half-odd integer spins is quantized. A general algorithm to derive gauge invariances of higher order Lagrangians is given and applied to the infinite spin particle model, and to a new higher order model for a spinning particle which is proposed here, as well as to a previously given higher order rigid particle model. The latter two models are also covariantly quantized.Comment: 38 pages, Late

Observation of Plasma Focusing of a 28.5 GeV Positron Beam

The observation of plasma focusing of a 28.5 GeV positron beam is reported. The plasma was formed by ionizing a nitrogen jet only 3 mm thick. Simultaneous focusing in both transverse dimensions was observed with effective focusing strengths of order Tesla per micron. The minimum area of the beam spot was reduced by a factor of 2.0 +/- 0.3 by the plasma. The longitudinal beam envelope was measured and compared with numerical calculations

Results on Plasma Focusing of High Energy Density Electron and Positron Beams

We present results from the SLAC E-150 experiment on plasma focusing of high energy density electron and, for the first time, positron beams. We also discuss measurements on plasma lens-induced synchrotron radiation, longitudinal dynamics of plasma focusing, and laser- and beam-plasma interactions.Comment: LINAC 2000 paper No. THC13, Monterey, CA. Aug.21-25,2000, 3 pages, 2 figure