Toxic Chemical and their Neutralising Agents in Porous Media

The UK Government Decontamination Service advises central Govern- ment on the national capability for the decontamination of buildings, infrastructure, transport and open environment, and be a source of expertise in the event of a chemical, biological, radiological and nuclear (CBRN) incident or major release of HazMat materials. The study group constructed mathematical models to describe the depth to which a toxic chemical may seep into an initially dry porous substrate, and of the neutralisation process between a decontaminant and the imbibed chemical. The group recognised that capillary suction was the dominant process by which the contaminant spreads in the porous substrate. Therefore, in the first instance the absorption of the contaminant was modelled using Darcy’s law. At the next level of complication a diffuse interface model based on Richards’ equation was employed. The results of the two models were found to agree at early times, while at later times we found that the diffuse interface model predicted the more realistic scenario in which the contaminant has seeped deeper into the substrate even in the absence of further contaminant being supplied at the surface. The decontamination process was modelled in two cases; first, where the product of the decontamination reaction was water soluble, and the second where the reaction product formed soluble in the contaminant phase and of similar density. These simple models helped explain some of the key physics involved in the process, and how the decontamination process might be optimised. We found that decontamination was most effective in the first of these two cases. The group then sought to incorporate hydrodynamic effects into the reaction model. In the long wavelength limit, the governing equations reduced to a one-dimensional Stefan model similar to the one considered earlier. More detailed approximations and numerical simulations of this model were beyond the scope of this study group, but provide an entry point for future research in this area

On the Selection of Pairing-Friendly Groups

We propose a simple algorithm to select group generators suitable for pairing-based cryptosystems. The selected parameters are shown to favor implementations of the Tate pairing that are at once conceptually simple and efficient, with an observed performance about 2 to 10 times better than previously reported implementations, depending on the embedding degree. Our algorithm has beneficial side effects: various non-pairing operations become faster, and bandwidth may be saved

Use of a fluorescence-based approach to assess short-term responses of the alga Pseudokirchneriella subcapitata to metal stress

This work explores the use of fluorescent probes to evaluate the responses of the green alga Pseudokirchneriella subcapitata to the action of three nominal concentrations of Cd(II), Cr(VI), Cu(II) and Zn(II) for a short time (6 h). The toxic effect of the metals on algal cells was monitored using the fluorochromes SYTOX Green (SG, membrane integrity), fluorescein diacetate (FDA, esterase activity) and rhodamine 123 (Rh123, mitochondrial membrane potential). The impact of metals on chlorophyll a (Chl a) autofluorescence was also evaluated. Esterase activity was the most sensitive parameter. At the concentrations studied, all metals induced the loss of esterase activity. SG could be used to effectively detect the loss of membrane integrity in algal cells exposed to 0.32 or 1.3 mol L1 Cu(II). Rh123 revealed a decrease in the mitochondrial membrane potential of algal cells exposed to 0.32 and 1.3 mol L1 Cu(II), indicating that mitochondrial activity was compromised. Chl a autofluorescence was also affected by the presence of Cr(VI) and Cu(II), suggesting perturbation of photosynthesis. In conclusion, the fluorescence-based approach was useful for detecting the disturbance of specific cellular characteristics. Fluorescent probes are a useful diagnostic tool for the assessment of the impact of toxicants on specific targets of P. subcapitata algal cells.The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013. Manuela D. Machado gratefully acknowledges the post-doctoral grant from FCT (SFRH/BPD/72816/2010)

Batchversuche zur in situ-Denitrifikation von Grundwasser mit Methan als Kohlenstoffquelle

The purpose of the present study was to find out whether and under what conditions it is possible to denitrity groundwater using methane as hydrogen donor. In this connection it dealt, amongst other factors with oxygen demand, pH, nitrite formation, and the question of phosphate metering. Examinations were also made of the suitability of groundwater as the liquid medium and of denitrification performance at 10 C as a representative groundwater temperature. The most important bacteria groups were quantified. (orig.)In der vorliegenden Arbeit wurde untersucht, ob und unter welchen Bedingungen eine Denitrifikation von Grundwasser mit Methan als Wasserstoffdonator moeglich ist. Unter anderem wurde dabei auf den Sauerstoffbedarf, den pH-Wert, die Nitritbildung und die Frage der Phosphatdosierung eingegangen. Die Eignung von Grundwasser als Fluessigmedium und die Denitrifikation bei der im Grundwasser vorliegenden Temperatur von 10 C wurden untersucht. Die wichtigsten Bakteriengruppen wurden quantifiziert. (orig.)SIGLEAvailable from TIB Hannover: RO 6927(20) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The first examples of isonitrile insertion into a phosphido bridge and the crystal and molecular structures of [Pt2(mu-P(t)Bu2){mu,eta2-P(t)Bu-2)C(=NAr)}(CNAr)2] and [Pt{mu,eta2-P(t)Bu-2)C (NHAr)}(CNAr)]2(CF3SO3)2 (Ar = p-tolyl)

The platinum(I) dinuclear carbonyl [Pt-2(mu -PBu2t)(2)((PBu2H)-H-t)(CO)] (1) reacts with organic isonitriles RNC (R = p-tolyl, Bu-t, PhCH2), yielding the mono- and disubstituted derivatives [Pt-2(mu -PBu2t)(2)((PBu2H)-H-t)(CNR)] (2, R = p-tolyl; 3, R = Bu-t; 4, R = PhCH2) and [Pt(mu -PBu2t)(CNR)](2) (5, R = p-tolyl; 6, R = Bu-t; 7, R = PhCH2). Only with the aromatic isonitrile does the reaction proceed through two further well-separated steps, giving [Pt-2(mu -PBu2t){mu,eta (2)-P(Bu-2(t))C(=NAr)}(CNAr)(2)] (8) and [Pt{mu,eta (2)-P(Bu-2(t))C(=NAr)}(CNAr)](2) (9). These arise from the unprecedented reversible isonitrile insertion into the M-P bonds of the phosphido-bridges. When 8 or 9 are reacted with CF3SO3H, the cyclic carbenes [Pt-2(mu -PBu2t){mu,eta (2)-P(Bu-2(t))C(NHAr)}(CNAr)(2)]CF3SO3 (10) and [Pt{mu,eta (2)-P(Bu-2(t))C(NHAr)}(CNAr)](2) (CF3SO3)(2) (11) are respectively formed. The crystal and molecular structures of complexes 8 and 11 were solved by X-ray diffraction

The first examples of isonitrile insertion into a phosphido bridge and the crystal and molecular structures of [Pt-2(mu-PBu2t){mu,eta(2)-P(Bu-2(t))C(=NAr)}(CNAr)(2)] and [Pt{mu,eta(2)-P(Bu-2(t))C (NHAr)}(CNAr)](2)(CF3SO3)(2) (Ar = p-tolyl)

The platinum(I) dinuclear carbonyl [Pt-2(mu -PBu2t)(2)((PBu2H)-H-t)(CO)] (1) reacts with organic isonitriles RNC (R = p-tolyl, Bu-t, PhCH2), yielding the mono- and disubstituted derivatives [Pt-2(mu -PBu2t)(2)((PBu2H)-H-t)(CNR)] (2, R = p-tolyl; 3, R = Bu-t; 4, R = PhCH2) and [Pt(mu -PBu2t)(CNR)](2) (5, R = p-tolyl; 6, R = Bu-t; 7, R = PhCH2). Only with the aromatic isonitrile does the reaction proceed through two further well-separated steps, giving [Pt-2(mu -PBu2t){mu,eta (2)-P(Bu-2(t))C(=NAr)}(CNAr)(2)] (8) and [Pt{mu,eta (2)-P(Bu-2(t))C(=NAr)}(CNAr)](2) (9). These arise from the unprecedented reversible isonitrile insertion into the M-P bonds of the phosphido-bridges. When 8 or 9 are reacted with CF3SO3H, the cyclic carbenes [Pt-2(mu -PBu2t){mu,eta (2)-P(Bu-2(t))C(NHAr)}(CNAr)(2)]CF3SO3 (10) and [Pt{mu,eta (2)-P(Bu-2(t))C(NHAr)}(CNAr)](2) (CF3SO3)(2) (11) are respectively formed. The crystal and molecular structures of complexes 8 and 11 were solved by X-ray diffraction

An Experimental and Theoretical Study of the Electronic and Molecular Structure of [Zn4(\u3bc4-S){\u3bc-S2P(OC2H5)(2)}(6)]: the First Molecular Model of ZnS

The electronic and molecular structure of hexakis[\u3bc-(O,O\u2032-diethyl dithiophosphate-S:S\u2032)]-\u3bc4-thiotetrazinc, [Zn4(\u3bc4-S){\u3bc-S2P(OC2H5)2}6] (1), has been investigated by combining X-ray diffraction measurements, UV\u2013vis absorption spectroscopy and density functional calculations. The title compound is characterized by a Zn4(\u3bc4-S)(\u3bc-S12) core consisting of a S atom at the center of a distorted tetrahedron of Zn ions, each of them placed at the center of an irregular tetrahedron of S atoms. Theoretical results point out that 1, at variance to the isostructural [Zn4(\u3bc4-S){\u3bc-S2As(CH3)2}6] recently investigated by Albinati et al. [Inorg. Chem. 38 (1999) 1145], can be considered a well tailored molecular model of ZnS. Theoretical outcomes also indicate that the low energy region of the UV absorption spectrum of 1 includes transitions having a ligand-to-metal-charge transfer nature involving the excitation of an electron from the occupied \u3bc4-S 3p based atomic orbitals to the empty Zn 4s based levels