Topological Censorship for Kaluza–Klein Space-Times

The standard topological censorship theorems require asymptotic hypotheses which are too restrictive for several situations of interest. In this paper we prove a version of topological censorship under significantly weaker conditions, compatible, e.g., with solutions with Kaluza–Klein asymptotic behavior. In particular we prove simple connectedness of the quotient of the domain of outer communications by the group of symmetries for models which are asymptotically flat, or asymptotically anti-de Sitter, in a Kaluza–Klein sense. This allows one, e.g., to define the twist potentials needed for the reduction of the field equations in uniqueness theorems. Finally, the methods used to prove the above are used to show that weakly trapped compact surfaces cannot be seen from Scri. Gregory J. Galloway was supported in part by NSF Grant DMS-0708048.     

On the stimulation of luminescence with green light emitting diodes

The present state of development of a green light emitting diode system, devised for convenient and economical optically stimulated luminescence dating, is described. The performance of the system is assessed in relation to use with feldspar and with quartz, both for material in which the latent signal was zeroed by heating and for material in which it was zeroed by bleaching. Aspects of assessment of the system include consideration of the measured signal-to-noise ratio and the consequently estimated minimum detectable dose, as well as the accuracy achieved in equivalent dose determination when simulating the dating process with laboratory dosed samples. A trial on quartz of equivalent dose determination by the single aliquot method is compared with use of the traditional multiple aliquot approach.     

Optical dating of the hydroponic farm at Korea

Red thermoluminescence (RTL) using a SAR (single-aliquot regenerative-dose) method has been applied to artificial ceramic samples to determine retrospective doses, and to estimate the naturally accumulated doses for natural quartz grains. In the RTL measurement of quartz grains, several preheating effects on equivalent doses around 200 °C were examined for extracted quartz grains from tephra (Medeshima, Miyagi). Preheating at 200 °C for 10 seconds gave better reproducibility and response than those for preheating at 80 °C for 5 minutes. The RTL/SAR method was used to quartz grain samples extracted from pottery pieces with preheating at 200 °C for 10 seconds.     

Identification of an anti-MRSA dihydrofolate reductase inhibitor from a diversity-oriented synthesis

The screening of a diversity-oriented synthesis library followed by structure-activity relationship investigations have led to the discovery of an anti-MRSA agent which operates as an inhibitor of Staphylococcus aureus dihydrofolate reductase.     

Studies on an ester-modified cationic amphiphile in aqueous systems: behavior of binary solutions and ternary mixtures with conventional surfactants

The aqueous behavior of an ester-modified cationic amphiphile with the molecular structure CH3CH2O(C=O)(CH2)6(C=O)O(CH2)8N+(CH3)3Br-, in the following referred to as A, has been investigated. Systems with A as the only solute, as well as different aqueous mixtures with conventional cationic surfactants, primarily dodecyltrimethylammonium bromide (DTAB), were included in the study. Isotropic solution samples were characterized using 1H NMR, 13C NMR, NMR diffusometry, and conductivity measurements, whereas liquid crystalline samples were investigated by optical polarization microscopy and small-angle X-ray diffraction. The results are compared to the behavior of the binary system of DTAB and water. A does not exhibit a typical surfactant behavior. When it is present as the only solute in a binary aqueous system, it forms neither conventional micelles nor liquid crystalline phases. However, there is clear evidence that it assembles with lower cooperativity into loose clusters at concentrations above 25-30 mM. When A is mixed with DTAB in solution, the two amphiphiles form mixed assemblies, the structure of which varies with the total amphiphile concentration. In concentrated mixtures with alkyltrimethylammonium surfactants, A can participate in hexagonal liquid crystalline phases even when it constitutes a significant fraction of the total amphiphile content.     

Some properties of luminescence lifetimes from quartz stimulated by blue light

Abstract

Measurements have been made of recombination lifetimes as a function of stimulation time in quartz, a natural dosimeter. Time-resolved luminescence techniques were used to study the influence on lifetimes of sustained 470nm optical stimulation of luminescence and modifications associated with beta irradiation of samples. Results are reported for samples differing in sensitivity to luminescence stimulation.     

Vinyldisiloxanes: their synthesis, cross coupling and applications

During the studies towards the development of pentafluorophenyldimethylsilanes as a novel organosilicon cross coupling reagent it was revealed that the active silanolate and the corresponding disiloxane formed rapidly under basic conditions. The discovery that disiloxanes are in equilibrium with the silanolate led to the use of disiloxanes as cross coupling partners under fluoride free conditions. Our previous report focused on the synthesis and base induced cross coupling of aryl substituted vinyldisiloxanes with aryl halides; good yields and selectivities were achieved. As a continuation of our research, studies into the factors which influence the successful outcome of the cross coupling reaction with both alkyl and aryl substituted vinyldisiloxanes were examined and a proposed mechanism discussed. Further investigation into expanding the breadth and diversity of substituted vinyldisiloxanes in cross coupling was explored and applied to the synthesis of unsymmetrical trans-stilbenes and cyclic structures containing the trans-alkene architecture.     

Nonexistence of Marginally Trapped Surfaces and Geons in 2 + 1 Gravity

We use existence results for Jang’s equation and marginally outer trapped surfaces (MOTSs) in 2 + 1 gravity to obtain nonexistence of geons in 2 + 1 gravity. In particular, our results show that any 2 + 1 initial data set, which obeys the dominant energy condition with cosmological constant Λ ≥ 0 and which satisfies a mild asymptotic condition, must have trivial topology. Moreover, any data set obeying these conditions cannot contain a MOTS. The asymptotic condition involves a cutoff at a finite boundary at which a null mean convexity condition is assumed to hold; this null mean convexity condition is satisfied by all the standard asymptotic boundary conditions. The results presented here strengthen various aspects of previous related results in the literature. These results not only have implications for classical 2 + 1 gravity but also apply to quantum 2 + 1 gravity when formulated using Witten’s solution space quantization.     

Estimation of trace elements in some medicinal plants used in anti‐cancer drugs by PIXE

A trace elemental analysis was carried out in various parts of 12 anticancer medicinal plants, using the PIXE (particle‐induced X‐ray emission) technique. A 3‐MeV proton beam was used to excite the samples, and spectra were recorded using a Si (Li) detector. Data analysis was done using the GUPIX software. The elements Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Br and Sr were identified, and their concentrations estimated. The results of the present study provide justification for the usage of these medicinal plants in the development of anticancer drugs. Copyright © 2012 John Wiley & Sons, Ltd.