Channeling 5-min photospheric oscillations into the solar outer atmosphere through small-scale vertical magnetic flux tubes

We report two-dimensional MHD simulations which demonstrate that photospheric 5-min oscillations can leak into the chromosphere inside small-scale vertical magnetic flux tubes. The results of our numerical experiments are compatible with those inferred from simultaneous spectropolarimetric observations of the photosphere and chromosphere obtained with the Tenerife Infrared Polarimeter (TIP) at 10830 A. We conclude that the efficiency of energy exchange by radiation in the solar photosphere can lead to a significant reduction of the cut-off frequency and may allow for the propagation of the 5 minutes waves vertically into the chromosphere.Comment: accepted by ApJ

Perforation of aluminium alloy-CFRP bilayer plates under quasi-static and impact loading

The ability of a metallic surface layer to protect CFRP cross-ply plates against perforation is explored. Aluminium alloy plates (either AA1050A or AA6082-T6) were placed in front of a CFRP layer, and the bilayer was subjected to either quasi-static indentation or to ballistic impact by a spherical projectile, with rigid back support or an edge-clamped boundary condition. The observed perforation mechanism of the CFRP layer is neither influenced by the presence of the metallic layer nor by the choice of loading rate (i.e. quasi-static versus ballistic). In the back-supported condition, the CFRP layers fail by an indirect tension mode that consists of tensile failure of plies in the material directly beneath the indenter or projectile. Alternatively, in the edge-clamped condition, the CFRP layers fail by a shear plugging mechanism. Although the presence of metallic layers does not suppress the shear plugging of the underlying CFRP layer, the loaded area in the CFRP layer increases by the addition of the protective metallic layer, thereby increasing the perforation resistance of the CFRP layer.he research work was sponsored by the Office of Naval Research (ONR), U.S. (Prime Award No. N62909-14-1-N232). The raw composite materials and the autoclave manufacturing process were generously provided by Hexcel Ltd. Finally, the doctoral study of one of the authors (B. Yu) was sponsored by the Croucher Foundation and the Cambridge Commonwealth, European & International Trust

Nuclei of Double-Charm Hyperons

The ground states of double-charm hyperons form a spin 1/2 isospin 1/2 multiplet analogous to that of nucleons. Their main strong interaction may be inferred directly from the corresponding nucleon-nucleon interaction by multiplication of the interaction components by the appropriate fractional difference between interaction strengths for pairs of light flavor quarks and pairs of triplets, e.g. nucleons, of light flavor quarks. By construction of the interaction between the recently discovered double-charm hyperons by this method from several realistic nucleon-nucleon interaction models it is shown that double-charm hyperons are likely to form bound (or possibly meta-stable) states akin to the deuteron in the spin triplet state. Double beauty baryons would form corresponding deeply bound states. Nucleons and double charm (beauty) hyperons will also form bound states. The existence of hypernuclei with double-charm and double-beauty hyperons, which are stable against the strong decay, is very likely.Comment: Revised version. Conclusions unchange

Is the partial pressure of carbon dioxide in the blood related to the development of retinopathy of prematurity?

AIMS—To determine the role of carbon dioxide in the development of retinopathy of prematurity (ROP).
METHODS—This was a retrospective cohort study of 25 consecutive infants admitted to the neonatal unit with continuously recorded physiological data. The daily mean and standard deviation (SD) of transcutaneous carbon dioxide partial pressure (tcPCO(2)) was compared between infants who had stage 1 or 2 ROP and stage 3 ROP. The time spent hypocarbic (<3 kPa) and/or hypercarbic (>10 kPa and >12 kPa) was also compared between these groups. Intermittent arterial carbon dioxide tension was also measured and compared with the simultaneous tcPCO(2) data.
RESULTS—There were no significant differences in carbon dioxide variability or time spent hypocarbic and/or hypercarbic between the ROP groups on any day. 86% of transcutaneous values were within 1.5 kPa of the simultaneous arterial value.
CONCLUSION—TcPCO(2) measurement can be a very useful management technique. However, in this cohort neither variable blood carbon dioxide tension nor duration of hypercarbia or hypocarbia in the first 2 weeks of life was associated with the development or severity of ROP.


Powder metallurgy bearings for advanced rocket engines

Traditional ingot metallurgy was pushed to the limit for many demanding applications including antifriction bearings. New systems require corrosion resistance, better fatigue resistance, and higher toughness. With conventional processing, increasing the alloying level to achieve corrosion resistance results in a decrease in other properties such as toughness. Advanced powder metallurgy affords a viable solution to this problem. During powder manufacture, the individual particle solidifies very rapidly; as a consequence, the primary carbides are very small and uniformly distributed. When properly consolidated, this uniform structure is preserved while generating a fully dense product. Element tests including rolling contact fatigue, hot hardness, wear, fracture toughness, and corrosion resistance are underway on eleven candidate P/M bearing alloys and results are compared with those for wrought 440C steel, the current SSME bearing material. Several materials which offer the promise of a significant improvement in performance were identified

Lo-fi prototyping to design interactive-tabletop applications for children

Interactive tabletops are an exiting new platform for supporting children's collaboration. With design guidelines and standardized interaction principles still immature, there is a considerable need for iterative prototyping to define the task and interface. Lo-fi prototypes-using cardboard, paper, etc.- are easy to develop, flexible to adjust during design sessions, and intuitive for users to manipulate. Using them can be a valuable step in designing tabletop applications. In this paper, we detail the design process of two tabletop applications, concentrating on the role of lo-fi prototyping. TransTime is a pattern game for 5-6 year olds to engage how time progresses. OurSpace is a design tool for 7-9 year olds to arrange desks and assign seats for students in their classroom. By comparing the experiences, we arrive at a better understanding of the benefits, challenges, and limits of using lo-fi prototypes to design interactive-tabletop applications for children

Improved Semiclassical Approximation for Bose-Einstein Condensates: Application to a BEC in an Optical Potential

We present semiclassical descriptions of Bose-Einstein condensates for configurations with spatial symmetry, e.g., cylindrical symmetry, and without any symmetry. The description of the cylindrical case is quasi-one-dimensional (Q1D), in the sense that one only needs to solve an effective 1D nonlinear Schrodinger equation, but the solution incorporates correct 3D aspects of the problem. The solution in classically allowed regions is matched onto that in classically forbidden regions by a connection formula that properly accounts for the nonlinear mean-field interaction. Special cases for vortex solutions are treated too. Comparisons of the Q1D solution with full 3D and Thomas-Fermi ones are presented.Comment: 14 pages, 5 figure