Expansion-Free Cavity Evolution: Some exact Analytical Models

We consider spherically symmetric distributions of anisotropic fluids with a central vacuum cavity, evolving under the condition of vanishing expansion scalar. Some analytical solutions are found satisfying Darmois junction conditions on both delimiting boundary surfaces, while some others require the presence of thin shells on either (or both) boundary surfaces. The solutions here obtained model the evolution of the vacuum cavity and the surrounding fluid distribution, emerging after a central explosion. This study complements a previously published work where modeling of the evolution of such kind of systems was achieved through a different kinematical condition.Comment: 9 pages, Revtex. Typos corrected. Published in Int. J. Mod. Phys.

Ductility Characterization of U-6Nb and Ta-W Alloys

We have previously evaluated the ductility behaviors of U-6Nb and pure Ta. One important observation was that both alloys have very stable necking ductility independent of test conditions. In contrast, uniform ductility varied significantly depending upon strain rates and temperatures. In general, higher strain rate and lower temperature reduce the uniform ductility. Using literature data, we have developed two dynamic ductility models to predict the ductility behaviors of pure-Ta and water-quenched U-6Nb respectively under extreme conditions. In this study we further evaluate the aging effect on U-6Nb and the W-addition effect on Ta. For U-6Nb, the objective is to determine whether or not the ductility degradation by low-temperature aging mostly measured in quasi-static condition can still be observed under dynamic loading (high strain rate) condition. For Ta-W alloys, the focus is to identify the key control parameter so that the optimal condition of high-strength/high-ductility of Ta-10W can be achieved for certain defense-related applications

Relativistic static thin dust disks with an inner edge: An infinite family of new exact solutions

An infinite family of new exact solutions of the Einstein vacuum equations for static and axially symmetric spacetimes is presented. All the metric functions of the solutions are explicitly computed and the obtained expressions are simply written in terms of oblate spheroidal coordinates. Furthermore, the solutions are asymptotically flat and regular everywhere, as it is shown by computing all the curvature scalars. These solutions describe an infinite family of thin dust disks with a central inner edge, whose energy densities are everywhere positive and well behaved, in such a way that their energy-momentum tensor are in fully agreement with all the energy conditions. Now, although the disks are of infinite extension, all of them have finite mass. The superposition of the first member of this family with a Schwarzschild black hole was presented previously [G. A. Gonz\'alez and A. C. Guti\'errez-Pi\~neres, arXiv: 0811.3002v1 (2008)], whereas that in a subsequent paper a detailed analysis of the corresponding superposition for the full family will be presented.Comment: 9 pages, 3 figure

Stab Sensitivity of Energetic Nanolaminates

This work details the stab ignition, small-scale safety, and energy release characteristics of bimetallic Al/Ni(V) and Al/Monel energetic nanolaminate freestanding thin films. The influence of the engineered nanostructural features of the energetic multilayers is correlated with both stab initiation and small-scale energetic materials testing results. Structural parameters of the energetic thin films found to be important include the bi-layer period, total thickness of the film, and presence or absence of aluminum coating layers. In general the most sensitive nanolaminates were those that were relatively thick, possessed fine bi-layer periods, and were not coated. Energetic nanolaminates were tested for their stab sensitivity as freestanding continuous parts and as coarse powders. The stab sensitivity of mock M55 detonators loaded with energetic nanolaminate was found to depend strongly upon both the particle size of the material and the configuration of nanolaminate material, in the detonator cup. In these instances stab ignition was observed with input energies as low as 5 mJ for a coarse powder with an average particle dimension of 400 {micro}m. Selected experiments indicate that the reacting nanolaminate can be used to ignite other energetic materials such as sol-gel nanostructured thermite, and conventional thermite that was either coated onto the multilayer substrate or pressed on it. These results demonstrate that energetic nanolaminates can be tuned to have precise and controlled ignition thresholds and can initiate other energetic materials and therefore are viable candidates as lead-free impact initiated igniters or detonators

Fractura de Maisonneuve abierta: una entidad infrecuente: a propósito de un caso y revisión de la literatura

Introducción. La fractura de Maisonneuve representa aproximadamente el 5% de todas las fracturas de tobillo tratadas quirúrgicamente. Debido a que suelen ser fracturas cerradas, presentamos el caso de una fractura de Maisonneuve abierta por su infrecuencia. Caso Clínico. Varón de 63 años que acudió a urgencias tras traumatismo de miembro inferior derecho. En la exploración se evidenció una solución de continuidad de la piel en cara medial de tobillo con exposición de maléolo tibial. La radiografía mostró una apertura de la mortaja tibio-peronea y una fractura espiroidea en el tercio proximal del peroné. Se realizó osteosíntesis con dos tornillos canulados. Tras 12 meses de seguimiento, el paciente presenta una puntuación media de 86,8 puntos en la escala AOFAS. Conclusión. Ante una luxación abierta de tobillo, debe sospecharse una fractura de Maisonneuve aunque sea poco frecuente, siendo la osteosíntesis una opción terapéutica eficaz en este tipo de fracturas.Introduction. Maisonneuve fracture represents approximately 5% of all surgically treated ankle fractures. Because these fractures are usually closed, we present the case of a Maisonneuve open fracture owing to its rarity. Case report. A 63-year-old man presented to his emergency department after a right leg trauma. Physical examination revealed a skin solution of continuity above the ankle joint, with a medial tibial malleolus exposure. The radiography showed an opening of the tibiofibular mortise and a spiral fracture of the proximal third of the fibula. Fixation with two cannulated screws was performed. After 12 months of follow up, the patient has an average score of 86.8 points on the AOFAS scale. Conclusion. In the face of an open ankle dislocation, a Maisonneuve open fracture should be suspected in spite of its infrequency, being the osteosynthesis an effective therapeutic option in this type of fracture

Ribose 2′-O-methylation provides a molecular signature for the distinction of self and non-self mRNA dependent on the RNA sensor Mda5

The 5'-cap-structures of higher eukaryote mRNAs are ribose 2'-O-methylated. Likewise, a number of viruses replicating in the cytoplasm of eukayotes have evolved 2'-O-methyltransferases to modify autonomously their mRNAs. However, a defined biological role of mRNA 2'-O-methylation remains elusive. Here we show that viral mRNA 2'-O-methylation is critically involved in subversion of type-I-interferon (IFN-I) induction. We demonstrate that human and murine coronavirus 2'-O-methyltransferase mutants induce increased IFN-I expression, and are highly IFN-I sensitive. Importantly, IFN-I induction by 2'-O-methyltransferase-deficient viruses is dependent on the cytoplasmic RNA sensor melanoma differentiation-associated gene 5 (MDA5). This link between MDA5-mediated sensing of viral RNA and mRNA 2'-O-methylation suggests that RNA modifications, such as 2'-O-methylation, provide a molecular signature for the discrimination of self and non-self mRNA

Synthesis and Characterization of Bimodal Nanoporous Cu Foams: Working Towards Inertial Fusion Energy

For the National Ignition Facility, at the Lawrence Livermore National Laboratory, nanoporous structures play a crucial role in the development of targets for high energy density experiments. Here we present a new bottom-up synthesis technique termed filter-casting for the creation of bimodal macro/nanoporous Cu structures. Homogeneous nanoporous monoliths can be synthesized using Cu nanoparticles and bimodal porosities can be achieved using sacrificial polystyrene spheres as a template. Control over the structure and composition is critical for target manufacturing. The measured densities of the Cu foam range between 1070-3390 mg/cm{sup 3}. Filter-casting is a powerful new method for directly synthesizing large nanoporous monoliths with predetermined composition, pore size, and pore structure