Rapid Removal of Organics and Oil Spills from Waters Using Silicone Rubber “Sponges”

We have developed a simple, robust, and efficient technology utilizing cheap and recoverable materials based on commercially available silicone elastomer networks for removing organic solvents and crude oil from waters. Hydrophobic and oleophilic properties of silicone elastomers endow poly(dimethyl siloxane) (PDMS) with the capacity to absorb a large variety of organics, including benzene (B), toluene (T), ethylbenzene (E), and xylene (X), commonly referred to as BTEX, and also crude oils, while at the same time enabling the organic “sponges” to float on waters, which facilitates straightforward handling. We developed a method for generating PDMS particles with variable sizes (ranging from hundreds nanometers to few millimeters) by drop-wise depositing siloxane/cross-linker mixtures into warm water, a process which leads to the cross-linking of the PDMS components. We have tested the capability of the PDMS particles to remove toluene and benzene from water. We also performed similar experiments by utilizing PDMS sheets. In both instances we observed a rapid sorption of the organic phase into PDMS; the amount of absorbed organic solvent depended on the concentration in water and the total mass (volume) of PDMS and did not depend on the geometry of the PDMS “sponge.” In addition, we have examined the uptake of toluene and benzene from toluene/benzene (T/B) mixtures dissolved in water. Our results indicate that the amount of benzene absorbed from the T/B mixtures into PDMS increases relative to the uptake from pure benzene/water solutions. This behavior is associated with toluene acting as a “surfactant” that effectively replaces the more unfavorable PDMS/B contacts with less costly T/B ones. Finally, a simple experiment demonstrates qualitatively that PDMS is also capable of removing crude oils from oil-contaminated waters.     

Experimental Investigation of Electric Signal Transmission Through Vestibular Organ Tissues

Russian Physics Journal - Experimental data on electric signal transmission through tissues of the vestibular organ of a guinea pig are presented. Stimulating electrodes are implanted in three...     

Two Novel Lyso-Ornithine Lipids Isolated from an Arctic Marine Lacinutrix sp. Bacterium

The Lacinutrix genus was discovered in 2005 and includes 12 Gram-negative bacterial species. To the best of our knowledge, the secondary metabolite production potential of this genus has not been explored before, and examination of Lacinutrix species may reveal novel chemistry. As part of a screening project of Arctic marine bacteria, the Lacinutrix sp. strain M09B143 was cultivated, extracted, fractionated and tested for antibacterial and cytotoxic activities. One fraction had antibacterial activity and was subjected to mass spectrometry analysis, which revealed two compounds with elemental composition that did not match any known compounds in databases. This resulted in the identification and isolation of two novel isobranched lyso-ornithine lipids, whose structures were elucidated by mass spectrometry and NMR spectroscopy. Lyso-ornithine lipids consist of a 3-hydroxy fatty acid linked to the alpha amino group of an ornithine amino acid through an amide bond. The fatty acid chains were determined to be iso-C15:0 (1) and iso-C16:0 (2). Compound 1 was active against the Gram-positive S. agalactiae, while 2 showed cytotoxic activity against A2058 human melanoma cells.     

A History of Blast Exposure May Affect the Transmission Properties of Cranial Bone

An individual who has sustained mild traumatic brain injury (mTBI) due to impact is more susceptible to a second concussion for a time, presumably due to the vulnerability of the injured brain tissue. This knowledge informed military guidelines regarding return to duty following blast-related TBI (bTBI). However, bone mechanics studies have shown that bone experiences hysteresis above certain strains as a result of microdamage, which suggests that blast exposure may also reduce the ability of the cranium itself to protect the brain from another blast. In the present study, the response of deer skull bone to blast wave exposure was measured. Oxy-acetylene driven laboratory scale shock tubes were used to produce realistic blast loading profiles. When a skull was exposed to peak blast pressures of about 600 kPa (measured with the sensor facing the direction of propagation of the blast wave) from a 41 mm diameter shock tube, the peak transmitted pressure gradually increased from 13.1 % to 40.2 % over five trials. This hysteresis was persistent and repeatable but was not observed with more localized loading. Future work could more specifically quantify blast thresholds at which persistent changes could be expected. Results from such work would further inform clinical decisions regarding return to activity following bTBI. The present results show that blast loading history of cranial bone should be understood and controlled in the design of related experiments. The results also underscore the need for accurate material properties and experimental validation of numerical models of the interaction of blast waves with the cranium.     

Explicit solutions for a general class of Markov processes

We derive explicit solutions for the matrix-geometric stationary distribution (and related measures) of a general class of infinite multidimensional Markov processes based on the probabilistic interpretations of the fundamental solution matrices and Bernoulli excursions, leading to explicit expressions for these matrix elements in terms of hypergeometric functions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrospray ionization ion-trap multiple-stage mass spectrometry of Quillaja saponins

Fifteen identified C-18 fatty acyl-containing saponin structures from Quillaja saponaria Molina have been investigated by electrospray ionization ion-trap multiple-stage mass spectrometry (ESI-IT-MS(n)) in positive ion mode. Their MS(1)-MS(3) spectra were analyzed and ions corresponding to useful fragments, important for the structural identification of Quillaja saponins, were recognized. A few key fragments could describe the structural variations in the C-3 and the C-28 oligosaccharides of the Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from the MS(1)-MS(3) spectra of these saponins, together with key fragments from these saponins and 13 previously investigated saponins, was constructed for the identification of structural elements in Quillaja saponins. Peak intensity ratios in MS(3) spectra were found to be correlated to structural features of the investigated saponins and is therefore of value for the identification of regioisomers.     

Heat Content Asymptotics for Planar Regions with Cusps

Asymptotic results are given for the heat content of planarregions with cusps.     

Laser-induced fluorescence of seeded nitric oxide as a flame thermometer

Received: 10 June 1997/Revised version: 25 November 1997     

Weight diagrams for lie group representations: A computer implementation of Freudenthal's algorithm in ALGOL and FORTRAN

Implementations in FORTRAN and ALGOL of the Dynkin and Freudenthal algorithms for computing weight systems and for determining the multiplicities of the weights for irreducible representations of simple Lie algebras are described. Reasonable computing times are found for algebras of rank less than or equal to 8 and for representations of dimension less than 1000.