Numerical analysis of capillarity in packed spheres: planar hexagonal-packed spheres

General solutions of the capillary pressure for liquids as a function of contact angle and volume in planar close-packed spheres have been calculated numerically using Surface Evolver software. Applied pressure differences between liquid and vapor result in undulating (puckered) menisci exhibiting anticlastic curvature in the narrower spaces near particle contacts. The corresponding capillary pressures exhibit maxima with infiltration volume (minima with drainage), corresponding to critical pressures for engulfment of the spheres by the liquid (vapor). The analysis also reveals the formation of residual pendular rings of the wetting phase around particle contacts. Pendular ring formation is explored further by analyzing hexagonally packed spheres separated by 1/10 their radius. The results are discussed relative to the wide range of approximate solutions available in the literature.     

X-ray emission from clusters of galaxies and cosmological parameters

Clusters of galaxies are excellent probes of cosmic structure and evolution. X-ray studies of clusters provide some of their key parameters, viz., temperature of the hot intra-cluster gas, its metallicity, X-ray luminosity and surface brightness giving mass distribution and mass-flow rate in the case of cooling flows. X-ray measurements for a large sample of clusters have lead to estimates of the total gravitating mass in them, which can be compared to the virial masses derived from dynamical considerations and gravitational lensing in some of them. X-ray derived total masses are consistent with masses obtained from the other methods after the effects due to the presence of cooling flows are taken into account in the analyses. Estimated virial masses, lack of evolution in X-ray properties, and detection of several very hot clusters at high redshifts indicate a Universe with a low value (≤ 0.3) for the Ω parameter.     

Compounds based on meso-tri(4-pyridyl)-p-acrylamidophenylporphyrin able to interact with DNA

A new type of porphyrinyl-nucleoside was synthesized by the Heck reaction of meso-tri(4-pyndyl)-p-acrylamidophenylporphyrin with (+)5-iodo-2′-deoxyuridine. The porphyrin used in this reaction was also applied in obtaining a water soluble porphyrin polymer and a copolymer with acrylamide. The porphyrinyl-nucleoside and the polymer and copolymer were investigated for their interaction with ds DNA, oligonucleotides and oligonucleotide duplexes. The extend of the red-shift of the Soret band of porphyrins and the slowing of the mobolity of DNA during electrophoresis of the interacting systems suggested that intercalation of cationic porphyrin units into ds DNA cannot be solely responsible for the observed phenomena.     

Comparison of wire and fiber optics data transfer systems for large military aircraft

Methods for comparing the life-cycle cost of fiber optics and wire data transfer systems on large military aircraft are established. Using the B-1 as an example, the applicability of fiber optics to avionics/electrical systems on large aircraft is identified. Conceptual fiber optics data transfer systems are described. The present wire and the conceptual fiber optics designs form a basis for computerized lifecycle cost comparisons. Sensitivity analyses and cost trade-offs to determine cost drivers in the application of fiber optics are described. Results show that significant cost benefits can be gained by the implementation of fiber optics in newly designed data transfer subsystems having data rates in excess of 2-3 Mbits/sec.     

Exotic decay in cerium isotopes

Half life for the emission of exotic clusters like ⁸Be, ¹²C, ¹⁶O, ²⁰Ne, ²⁴Mg and ²⁸Si are computed taking Coulomb and proximity potentials as interacting barrier and many of these are found well within the present upper limit of measurement. These results lie very close to those values reported by Shanmugam et al using their cubic plus Yukawa plus exponential model (CYEM). It is found that ¹²C and ¹⁶O emissions from ¹¹⁶Ce and ¹⁶O from ¹¹⁸Ce are most favorable for measurement (T _1/2<10¹⁰ s). Lowest half life time for ¹⁶O emission from ¹¹⁶Ce stress the role of doubly magic ¹⁰⁰Sn daughter in exotic decay. Geiger-Nuttall plots were studied for different clusters and are found to be linear. Inclusion of proximity potential will not produce much deviation to linear nature of Geiger-Nuttall plots. It is observed that neutron excess in the parent nuclei slow down the exotic decay process. These findings support the earlier observations of Gupta and collaborators using their preformed cluster model (PCM).     

Scaphoid fractures and Kienbock's disease of the lunate: MR imaging with histopathologic correlation

Thirteen patients with scaphoid fractures and four patients with Kienbock's disease of the lunate underwent magnetic resonance imaging (MRI) prior to surgery. A total of 28 specimens had MR-histologic correlation. Biopsy specimens obtained by curettage provided pathologic correlation. MRI proved accurate in prospective evaluation of bone viability for both scaphoid fractures and Kienbock's disease. Normal marrow signal was shown to correlate with the presence of osteoid and osteocytes on light microscopy and a surface layer of fluorescence reflecting tetracycline uptake in viable bone. Decreased marrow signal corresponded to non-viable trabeculae with scant osteoid, without osteocytes and no tetracycline labeling. By virtue of its accurate identification of avascular necrosis, MRI may prove valuable in predicting prognosis for patients with scaphoid fractures and Kienbock's disease of the lunate.     

Interactions of porphyrinyl-nucleosides with DNA using the example of porphyrinyl-thymidine

meso-Tri(N-memyl-4-pyridinium)porphyrinyl-p-phenylene-5′-O-thymidine, interacting with plasmid ds DNA showed an 8 nm red-shift of the Soret band. The observed Soret band shift was 4 run less than the shift of the respective meso-tetra(N-methyl-4-pyridinium)porphyrin, which is usually assumed to indicate intercalation. Experimental spectra and the MMX- and AM-1 calculations of a series of model structures further suggest that the investigated porphyrinyl-thymidine also interacts with adenine due to its nucleobase. The possibility of intercalation was also viewed based on interaction of immobilized porphyrin with ds DNA. Theoretical considerations suggested that there are no steric limitations to the formation of a system in which the porphyrinyl-thymidine in question interacts with a molecule of porphyrinyl-adenosine, via A-T base pairing, to join two ds DNA molecules.     

Preparation and characterization of MgB2 superconductor

The MgB₂ superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been determined using magnetization data. The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition. The surface analysis using X-ray photoelectron spectroscopy shows that MgB₂ is sensitive to atmospheric degradation.