1,899 research outputs found
Hierarchies from D-brane instantons in globally defined Calabi-Yau Orientifolds
We construct the first globally consistent semi-realistic Type I string vacua
on an elliptically fibered manifold where the zero modes of the Euclidean
D1-instanton sector allow for the generation of non-perturbative Majorana
masses of an intermediate scale. In another class of global models, a D1-brane
instanton can generate a Polonyi-type superpotential breaking supersymmetry at
an exponentially suppressed scale.Comment: 4 pages, 4 tables, uses revtex; v2: Discussion of instanton curves
improved, typos fixed, references added; v3: version published in PR
Texturing polymer surfaces by transfer casting
A technique for fabricating textured surfaces on polymers without altering their surface chemistries is described. A surface of a fluorocarbon polymer is exposed to a beam of ions to texture it. The polymer which is to be surface-roughened is then cast over the textured surface of the fluorocarbon polymer. After curing, the cast polymer is peeled off the textured fluorocarbon polymer, and the peeled off surface has negative replica of the textured surface. The microscopic surface texture provides large surface areas for adhesive bonding. In cardiovascular prosthesis applications the surfaces are relied on for the development of a thin adherent well nourished thrombus
Scanning-electron-microscopy observations and mechanical characteristics of ion-beam-sputtered surgical implant alloys
An electron bombardment ion thruster was used as an ion source to sputter the surfaces of orthopedic prosthetic metals. Scanning electron microscopy photomicrographs were made of each ion beam textured surface. The effect of ion texturing an implant surface on its bond to bone cement was investigated. A Co-Cr-W alloy and surgical stainless steel were used as representative hard tissue implant materials to determine effects of ion texturing on bulk mechanical properties. Work was done to determine the effect of substrate temperature on the development of an ion textured surface microstructure. Results indicate that the ultimate strength of the bulk materials is unchanged by ion texturing and that the microstructure will develop more rapidly if the substrate is heated prior to ion texturing
Status of a five-centimeter-diameter ion thruster technology program
Prototype auxiliary propulsion subsystem with isolated single tank propellant feed system and 5-cm-diameter ion thruste
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