Analytical solution of an advective zone model

An analytical solution of a model of contaminant transport in the advective zone of rivers was derived and tested. Although the standard one-dimensional model of transport cannot be applied near the contaminant source, the transport model proposed by Reichert and Wanner (1991), which requires only one more parameter to be specified, applies over much of the advective zone. The model was solved with Laplace transforms for the case of a Gaussian pulse injected into the center of the channel and verified through an analysis of the spatial and temporal moments. The moment analysis demonstrated the importance of carefully evaluating the integrals in the analytical solution. To help in applying the model to field measurements, the effects of the model parameters were investigated and a procedure for determining the parameters from measurements was devised. The model was applied to measurements in the advective zone of a mountain stream. Predictions from the Reichert and Wanner model fit the measurements--especially the peak concentration and arrival time--better than predictions from the one-dimensional model

Chemistry of chromium bis-acetylide complexes

Stable paramagnetic Cr(II) and Cr(III) bis(alkynyl) complexes of the type [trans(RC≡C)2Cr(dmpe)2] n+ (R=Ph, SiMe3, SiEt3, C≡C-SiMe3 n=0, 1) were prepared and characterised by NMR, cyclic voltammetry, EPR, magnetic measurements, and X-ray single-crystal diffraction studies. Graphical Abstrac

Geoarchaeological Investigation of the Coats-Hines Site (40WM31), Williamson County, Tennessee

The Coats-Hines site (40WM31) is a potential pre-Clovis site located in Franklin, Tennessee. The site rests, geographically, at the convergence of the Central Basin and Western Highland Rim. The site was discovered during the construction of a nearby golf course when a salvage team uncovered a mature female mastodon.. The site was later excavated in 1994-1995, during which time two additional mastodons were uncovered, in direct association with lithic artifacts. Preliminary radiocarbon dates reveal the site was deposited during the late Pleistocene epoch at roughly 12,000^(14)C yr BP. During the summer of 2012, the site was excavated with the goal of determining the depositional setting of the site and geographic region, as well as establishing the antiquity of the archaeological remains. The site geology was determined through field interpretation and texturing, micromorphological analysis, laboratory particle size analysis, and radiocarbon dating. Sedimentation at the site is a combination of cherty colluvium from upslope as well as alluvium. Four chronostratigraphic sequences of sedimentation were determined to have occurred during the last glacial, the Pleistocene-Holocene transition, the Holocene, and modern time periods. The volume, distribution, and composition of the nine defined stratigraphic units are dependent on the fluctuations occurring in the climate during these time periods. The climate changes and rates of deposition occurring at Coats-Hines were correlated to similar sites in the region. The Coats-Hines site was surveyed along the wet-weather drainage that bounds the site during in the spring of 2013. A channel unconformity was discovered, likely dating to the Pleistocene-Holocene transition and providing context to the 1994/1995 excavation

Bis[1,2-bis­(dimethyl­phosphino)­ethane]­dichloridonitro­syltungsten(0) chloride

In the crystal structure of the title compound, [WCl2(NO)(C6H16P2)2]Cl, the seven-coordinated tungsten(II) center displays a distorted penta­gonal–bipyramidal geometry with trans nitrosyl and chloride ligands. The NO and Cl ligands are disordered over two positions; the site occupancy factors are 0.6 and 0.4

3-(3-Fluoro­benz­yl)isochroman-1-one

In the mol­ecule of the title compound, C16H13FO2, the aromatic rings are oriented at a dihedral angle of 74.46 (4)°. The heterocyclic ring adopts a twisted conformation. In the crystal structure, there is a weak C—H⋯π inter­action

3-(4-Methoxy­phen­yl)isochroman-1-one

In the mol­ecule of the title compound, C16H14O3, the aromatic rings are oriented at a dihedral angle of 72.02 (6)°. The heterocyclic ring adopts a twisted conformation. In the crystal structure, there are C—H⋯π contacts between the heterocyclic and phenyl rings, and between the methyl group and methoxy­phenyl ring

μ-1,2-Bis(diethyl­phosphino)ethane-κ2 P:P′-bis­{[1,2-bis­(diethyl­phosphino)ethane-κ2 P,P′]trichloridonitrosyl­tungsten(II)}

The title binuclear compound, [W2Cl6(NO)2(C10H22P2)3], contains two W atoms which are bridged by a bis­(diethyl­phosphino)­ethane (depe) ligand. The seven-coord­inated tungsten(II) centres display distorted penta­gonal–bipyramidal geometries with trans nitrosyl and chloride ligands. The title mol­ecule lies on a crystallographic inversion centre. The ethane group of the non-bridging depe ligand is positionally disordered, with site-occupancy factors of 0.63 and 0.37. In the crystal structure, the binuclear mol­ecules are linked by weak inter­molecular C—H⋯O and C—H⋯Cl inter­actions. In addition, weak intra­molecular C—H⋯Cl inter­actions are also present

(E)-1-(3-Bromo­phen­yl)-3-(4-ethoxy­phen­yl)prop-2-en-1-one

The title compound, C17H15BrO2, adopts an E configuration. The dihedral angle between the two benzene rings is 10.09 (11)°. The enone plane makes dihedral angles of 12.05 (11) and 9.87 (11)°, respectively, with the bromo­phenyl and ethoxy­phenyl rings. The eth­oxy group is nearly coplanar with the attached benzene ring. In the crystal structure, the mol­ecules are linked by C—H⋯O hydrogen bonds, forming a zigzag ribbon-like structure along the b-axis direction

Efficient Palladium-Catalyzed Cyclotrimeriza- tion of Arynes: Synthesis of Triphenylenes**

Over the last 15 years much effort has been devoted to the preparation and characterization of transition metal complexes of arynes. [1] Parallel studies on the reactivity of these complexesÐparticularly those of Ti, Zr, As part of a project aimed at the development of new reactions of arynes promoted by metal complexes, here we report on the metal-mediated cyclotrimerization of arynes. These preliminary results show that the reaction proceeds in the presence of catalytic amounts of metal and that it has great potential for the preparation of triphenylenes, which are found at the core of many discotic liquid crystals [9] An example of the formation of triphenylene as side product of a palladium-catalyzed domino reaction has also been reported. [10] However, to the best of our knowledge, efficient preparation of triphenylenes by metalcatalyzed reaction of arynes is without precedent. Development of a catalytic procedure for the trimerization of arynes requires careful selection of the catalyst and the method for generation of the aryne. The catalyst was chosen from among the various metal systems used for trimerization of alkynes; suitable candidates contained metals such as Ni, Co, Pd, and Pt. We decided to carry out the first trials with palladium complexes because they are easy to handle and in general stable. Among the many procedures available for the generation of arynes [9] S