Aerodynamic characteristics of forebody and nose strakes based on F-16 wind tunnel test experience. Volume 1: Summary and analysis

The YF-16 and F-16 developmental wind tunnel test program was reviewed. Geometrical descriptions, general comments, representative data, and the initial efforts toward the development of design guides for the application of strakes to future aircraft are presented

Small-X Quarks at HERA Predict the Ultra High Energy Neutrino-Nucleon Cross Section

New structure function data at small Bjorken $x$ from HERA are used along with next-to-leading order QCD evolution to predict a cross section for charged-current interactions of ultrahigh energy neutrinos with nucleons. This new result is over twice the size of previous estimates and has important implications for cosmic ray experiments now underway as well as for KM3 arrays (cubic kilometer-scale neutrino telescopes) now in the planning stages.Comment: KITCS94-9-1, 9 pages (REVTeX) plus 3 postscript figures all uuencode

Trogocytosis by Entamoeba histolytica Mediates Acquisition and Display of Human Cell Membrane Proteins and Evasion of Lysis by Human Serum.

We previously showed that Entamoeba histolytica kills human cells through a mechanism that we termed trogocytosis ("trogo-" means "nibble"), due to its resemblance to trogocytosis in other organisms. In microbial eukaryotes like E. histolytica, trogocytosis is used to kill host cells. In multicellular eukaryotes, trogocytosis is used for cell killing and cell-cell communication in a variety of contexts. Thus, nibbling is an emerging theme in cell-cell interactions both within and between species. When trogocytosis occurs between mammalian immune cells, cell membrane proteins from the nibbled cell are acquired and displayed by the recipient cell. In this study, we tested the hypothesis that through trogocytosis, amoebae acquire and display human cell membrane proteins. We demonstrate that E. histolytica acquires and displays human cell membrane proteins through trogocytosis and that this leads to protection from lysis by human serum. Protection from human serum occurs only after amoebae have undergone trogocytosis of live cells but not phagocytosis of dead cells. Likewise, mutant amoebae defective in phagocytosis, but unaltered in their capacity to perform trogocytosis, are protected from human serum. Our studies are the first to reveal that amoebae can display human cell membrane proteins and suggest that the acquisition and display of membrane proteins is a general feature of trogocytosis. These studies have major implications for interactions between E. histolytica and the immune system and also reveal a novel strategy for immune evasion by a pathogen. Since other microbial eukaryotes use trogocytosis for cell killing, our findings may apply to the pathogenesis of other infections.IMPORTANCE Entamoeba histolytica causes amoebiasis, a potentially fatal diarrheal disease. Abscesses in organs such as the liver can occur when amoebae are able to breach the intestinal wall and travel through the bloodstream to other areas of the body. Therefore, understanding how E. histolytica evades immune detection is of great interest. Here, we demonstrate for the first time that E. histolytica acquires and displays human cell membrane proteins by taking "bites" of human cell material in a process named trogocytosis ("trogo-" means "nibble"), and that this allows amoebae to survive in human serum. Display of acquired proteins through trogocytosis has been previously characterized only in mammalian immune cells. Our study suggests that this is a more general feature of trogocytosis not restricted to immune cells and broadens our knowledge of eukaryotic biology. These findings also reveal a novel strategy for immune evasion by a pathogen and may apply to the pathogenesis of other infections

The GZK Bound and Strong Neutrino-Nucleon Interactions above 10^19eV: a Progress Report

Cosmic ray events above 10^19 eV have posed a fundamental problem for more than thirty years. Recent measurements indicate that these events do not show the features predicted by the GZK bound. The events may, in addition, display angular correlations with point sources. If these observations are confirmed for point sources further than 50 - 100 Mpc, then strong interactions for the neutrino are indicated. Recent work on extra spatial dimensions provides a context for massive spin-2 exchanges capable of generating cross sections in the 1 - 100 mb range, as indicated by data. Applications of extra-dimension physics are controversial, and we comment on several contentious issues.Comment: 4 pages, 1 figure; talk by JPR at 7th Conference on the Intersections of Particle and Nuclear Physics, Quebec City, May, 200

A critical study of the chromium to n-type gallium-arsenide surface barrier

The purpose of this work is to clarify the causes of non-ideal behavior observed in the current-voltage characteristics of chromium to n-type gallium-arsenide surface barrier diodes

Knudsen gas provides nanobubble stability

We provide a model for the remarkable stability of surface nanobubbles to bulk dissolution. The key to the solution is that the gas in a nanobubble is of Knudsen type. This leads to the generation of a bulk liquid flow which effectively forces the diffusive gas to remain local. Our model predicts the presence of a vertical water jet immediately above a nanobubble, with an estimated speed of $\sim3.3\,\mathrm{m/s}$, in good agreement with our experimental atomic force microscopy measurement of $\sim2.7\,\mathrm{m/s}$. In addition, our model also predicts an upper bound for the size of nanobubbles, which is consistent with the available experimental data

The Greisen Equation Explained and Improved

Analytic description of the evolution of cosmic ray showers is dominated by the Greisen equation nearly five decades old. We present an alternative approach with several advantages. Among the new features are a prediction of the differential distribution, replacing Greisen's form which fails to be positive definite. Explicit comparison with Monte Carlo simulations shows excellent agreement after a few radiation lengths of development. We find a clear connection between Monte Carlo adjustment of Greisen's form and underlying physics, and present a concise derivation with all steps explicit. We also reconstruct the steps needed to reproduce Greisen's approximate formula, which appears not to have been published previously.Comment: 8 pages, 7 figures, revised version, accepted for publication in Phys. Rev.

Evidence for Adsorption of Chlorine Species on Iron(III) (hydr)oxides in the Sheepbed Mudstone, Gale Crater, Mars

Chlorine is a widespread element on Mars present in dust, soils and rocks, including the Sheepbed mudstone at Yellowknife Bay, Gale crater. Combined elemental and volatile analyses of two drilled samples, Cumberland and John Klein, indicated that chloride (Cl-) and perchlorate (ClO4 -) are likely present in the mudstone. The nature of chlorine species in Sheepbed mudstone is still not well constrained. It has been proposed that both are present as amorphous or crystalline salts physically mixed with mudstone minerals. We alternatively hypothesize that adsorbed perchlorate and chloride exist in the mudstone and adsorption could occur, in particular, on Fe(III) (hydr)oxide phases as supported by laboratory observations on terrestrial materials. Mineralogical and compositional analyses of the drilled Cumberland mudstone sample revealed the presence of ~30 wt% of a Fe-rich X-ray amorphous phase. Ferrihydrite has been proposed as a component of the Fe-rich X-ray amorphous material. The objectives of this work were to determine adsorption of perchlorate and chloride on ferrihydrite and to enable data comparison by characterizing adsorbed chloride and perchlorate with thermal and evolved gas analysis run under operating conditions similar to the SAM instrument onboard the Curiosity rover