Search

Analysis of mercury (Hg) in natural water samples has routinely been impractical in many environments, for example, artisanal and small-scale gold mines (ASGM), where difficult conditions make monitoring of harmful elements and chemicals used in the processes highly challenging. Current sampling methods require the use of hazardous or expensive materials, and so difficulties in sample collection and transport are elevated. To solve this problem, a solid-phase extraction-based method was developed for the sampling and preservation of dissolved Hg in natural water samples, particularly those found around ASGM sites. Recoveries of 85% ± 10% total Hg were obtained during 4 weeks of storage in refrigerated (4 °C, dark) and unrefrigerated (16 °C, dark) conditions, and from a representative river water spiked to 1 μg L−1Hg2+, 94% ± 1% Hg recovery was obtained. Solid-phase extraction loading flow rates were tested at 2, 5, and 10 mL min−1with no breakthrough of Hg, and sorbent stability showed no breakthrough of Hg up to 2 weeks after functionalisation. The method was deployed across five artisanal gold mines in Kakamega gold belt, Kenya, to assess Hg concentrations in mine shaft water, ore washing ponds, and river and stream water, including drinking water sources. In all waters, Hg concentrations were below the WHO guideline limit value of 6 μg L−1, but drinking water sources contained trace concentrations of up to 0.35 μg L−1total Hg, which may result in negative health effects from long-term exposure. The SPE method developed and deployed here is a robust sampling method that can therefore be applied in future Hg monitoring, toxicology, and environmental work to provide improved data that is representative of total dissolved Hg in water samples.

A case study of strategies of managing old-growth forests on Montana's school trust forestlands is presented.

Today we rely on power stations to generate electricity for our homes, so that we can watch television, listen to music, surf the internet or play computer games. What we [...]

The early stages of transform margin formation are associated with crustal fragmentation and block rotation. The restricted size of the resultant microcontinental blocks precludes palaeogeographical reconstructions and reliable estimations of the amount of rotation they can undergo. An example considered here is the Falkland Plateau. This is located adjacent to the Agulhas-Falkland Fracture Zone and its westernmost province is the Falkland Islands microcontinent. The position of the plateau and the islands prior to Gondwana break-up remains contentious. This study integrates seismic reflection and gravity data to propose a revised position of the Falkland Islands microcontinent constrained by (1) the presence of a megadécollement, controlling the Gondwanide Orogen, described north of the Falkland Islands and underneath South Africa and the Outeniqua Basin, and (2) the similar architecture of fault networks mapped north of the islands and in the northernmost Outeniqua Basin. This revised position requires a re-evaluation of the timing and rate of rotation of the Falkland Islands microcontinent and affects the expected crustal architecture adjacent to the islands. Our model yields rotation rates between 5.5° and 8° Ma-1 and two potential times for rotation, and predicts more unstretched crust beneath the basin east of the Falkland Islands than previous models. [ABSTRACT FROM AUTHOR]

Both nationally and in Montana, the manufacturing sector includes traditional heavy industries as well as a broad array of other activities ranging from the production of very complex and sophisticated [...]

Winds blow Sudden snow. White yard Frozen hard. Red tricycles Wear icicles! Can you find the objects hidden under the snow? Pig up more winter surprises at www.ladybumagkids.com/activities! by Nanci [...]

The role of dust as a source of bioavailable phosphorus (Bio‐P) is quantified using a new parameterization for apatite dissolution in combination with global soil data maps and a global aerosol transport model. Mineral dust provides 31.2 Gg‐P/year of Bio‐P to the oceans, with 14.3 Gg‐P/year from labile P present in the dust, and an additional 16.9 Gg‐P/year from acid dissolution of apatite in the atmosphere, representing an increase of 120%. The North Atlantic, northwest Pacific, and Mediterranean Sea are identified as important sites of Bio‐P deposition from mineral dust. The acid dissolution process increases the fraction of total‐P that is bioavailable from ~10% globally from the labile pool to 18% in the Atlantic Ocean, 42% in the Pacific Ocean, and 20% in the Indian Ocean, with an ocean global mean value of 22%. Strong seasonal variations, especially in the North Pacific, northwest Atlantic, and Indian Ocean, are driven by large‐scale meteorology and pollution sources from industrial and biomass‐burning regions. Globally constant values of total‐P content and bioavailable fraction used previously do not capture the simulated variability. We find particular sensitivity to the representation of particle‐to‐particle variability of apatite, which supplies Bio‐P through acid‐dissolution, and calcium carbonate, which helps to buffer the dissolution process. A modest 10% external mixing results in an increase of Bio‐P deposition by 18%. The total Bio‐P calculated here (31.2 Gg‐P/year) represents a minimum compared to previous estimates due to the relatively low total‐P in the global soil map used. Phosphorus (P) is an essential requirement for life. Natural sources of P on land are from rock weathering and fertilizers. By contrast over the open ocean, the major source of P is from falling dust. However, less than 10% of the P in dust is automatically available to phytoplankton for growth, a percentage we call bioavailable‐P. Therefore, changes to the supply of bioavailable‐P to oceans can have considerable impacts on marine ecosystems and the global carbon cycle. Previous work shows acid processes in the atmosphere can convert nonbioavailable minerals to bioavailable‐P. In our previous study we found a simple relationship between acid in the atmosphere and bioavailable‐P formed. Here we use this new relationship, together with global soil data maps on the amount and type of P in dust and a global aerosol transport model, which predicts where dust and acid interact. We calculate how much and where acid‐modified dust ends up in the ocean. We show atmospheric acid processing of dust is particularly important in the Mediterranean Sea, North Atlantic Ocean, northwest Pacific Ocean, and the Indian Ocean. As a result, atmospheric acid pollution increases the amount of oceanic plant growth and reduces the quantity of atmospheric anthropogenic carbon dioxide. New simple parameterization for production of bioavailable P from acid dissolution of mineral dust incorporated into a global aerosol modelInclusion of acid dissolution increases atmospheric flux of bioavailable P from dust to oceans by 120% and drives dust P bioavailabilityMajor increases in bioavailable P from atmospheric acid processes occur in Mediterranean Sea, North Atlantic, NW Pacific, and Indian Ocean

The paddlewheel complex Ru2(chp)4Cl (1-Cl, chp = 6-chloro-2-oxypyridinate), upon reduction with Zn, has been previously shown to dimerize to [Ru2(chp)4]2(2), blocking further chemistry at the Ru2(II,II) axial site [Inorg. Chem.2015, 54, 8571−8589]. Functionalization of the chp ligand at the 3 and 5 positions with either bromine (dbchpH = 3,5-dibromo-6-chloro-2-pyridone) or trimethylsilyl (TMS) groups (dsichpH = 6-chloro-3,5-bis(trimethylsilyl)-2-pyridone) allows for the preparation of the Ru2(II,II) paddlewheel complexes Ru2(dbchp)4(3) and Ru2(dsichp)4(6), respectively, neither of which shows evidence of dimerization. Though the utilization of 3is limited due to insolubility, complex 6is soluble even in typically non-coordinating solvents, forming a stable κ1-axial adduct in CH2Cl2(6-CH2Cl2) and showing evidence of an axial interaction with n-decane. The first example of an axially free Ru2(II,II) complex with a 3A ground state is observed upon crystallization of 6from benzene (6-C6D6). Complex 6is accessed via Zn reduction of Ru2(dsichp)4Cl (4-Cl), which along with Ru2(dsichp)4N3(4-N3), show similar structural and electronic properties to their non-TMS-substituted analogues, 1-Cland 1-N3. Photolysis of 4-N3in frozen solution generates Ru2(dsichp)4N (5); no N atom transfer to PPh3is observed upon room temperature photolysis in fluid solution.

Investigation of new materials capable of undergoing reversible electrochemical oxidation at very high potentials (> 4 V vs. Li/Li+) is important for overcharge protection in conventional lithium ion batteries as well as for the development of new catholytes in nonaqueous redox flow batteries. We have employed several strategies to prepare novel organic heterocycles that exhibit such behavior. First, parent molecules were designed such that the molecular reorganization associated with oxidation to the radical cation is impeded, leading to a shift to more positive potentials without sacrificing stability. Second, numerous phenothiazine-5,5-dioxide derivatives were prepared and characterized. These latter materials display highly reversible electrochemical oxidation and very good solubility in carbonate solvents, making them particularly attractive for flow battery applications.

Crustal heterogeneity is considered to play a critical role in the position of continental break-up, yet this can only be demonstrated when a fully constrained pre-break-up configuration of both conjugate margins is achievable. Limitations in our understanding of the pre-break-up crustal structure in the offshore region of many margins preclude this. In the southern South Atlantic, which is an archetypal conjugate margin, this can be achieved because of the high confidence in plate reconstruction. Prior to addressing the role of crustal heterogeneity, two questions have to be addressed: first, what is the location of the regionally extensive Gondwanan Orogeny that remains enigmatic in the Orange Basin, offshore South Africa; and, second, although it has been established that the Argentinian Colorado rift basin has an east–west trend perpendicular to the Orange Basin and Atlantic spreading, where is the western continuation of this east–west trend? We present here a revised structural model for the southern South Atlantic by identifying the South African fold belt offshore. The fold belt trend changes from north–south to east–west offshore and correlates directly with the restored Colorado Basin. The Colorado–Orange rifts form a tripartite system with the Namibian Gariep Belt, which we call the Garies Triple Junction. All three rift branches were active during the break-up of Gondwana, but during the Atlantic rift phase the Colorado Basin failed while the other two branches continued to rift, defining the present day location of the South Atlantic. In addressing these two outstanding questions, this study challenges the premise that crustal heterogeneity controls the position of continental break-up because seafloor spreading demonstrably cross-cuts the pre-existing crustal heterogeneity. Furthermore, we highlight the importance of differentiating between early rift evolution and subsequent rifting that occurs immediately prior to seafloor spreading.

The control of interfacial microstructural stability is of utmost importance to the reliability of liquid solder interconnects in high temperature electronic assemblies. This is primarily due to excessive intermetallic compounds (IMCs) that can form and continuously grow during high temperature operation, which renders conventional barrier metallisations inadequate. With the intention of reducing such excessive IMC growth, electrically conducting, NbOx containing Ni coatings were developed using electrodeposition and were assessed as solder diffusion barrier layers in terms of their electrical conductivity and barrier property. The present work adopts a novel electrochemical route to produce Ni-NbOx composite coatings of good uniformity, compactness and purity, from non-aqueous glycol-based electrolytes consisting of NiCl2 and NbCl5 as metal precursors. The effects of cathodic current density and NaBH4 concentrations on the surface morphology, composition and thickness of the coatings were examined. Increased NaBH4 concentrations were found to elevate the maximum deposit thickness (above 10 um), although these led to a reduction in the co-deposited Nb content. The composite coatings generally exhibited good electrical conductivity. The reaction between a liquid 52In-48Sn solder and Ni-NbOx, with Nb contents up to 6 at.%, was studied at 200oC. The results indicate that, Ni-NbOx with sufficient layer thickness and higher Nb content, offered longer service lifetime. Nb enrichment was generally observed at or close to the reaction front after high temperature storage which suggests evident effectiveness of the enhanced diffusion barrier characteristics. A mechanism for the role of Nb as a barrier performance enhancer was postulated.

Tactile displays promise to improve the information-processing capacity of operators, especially when used in conjunction with visual and auditory displays. In this article, we describe current applications and future directions in tactile cuing.

The control of interfacial microstructural stability is of utmost importance to the reliability of liquid solder interconnects in high temperature electronic assemblies. This is primarily due to excessive intermetallic compounds (IMCs) that can form and continuously grow during high temperature operation, which renders conventional barrier metallizations inadequate. With the intention of reducing such excessive IMC growth, electrically conducting, NbOx containing Ni coatings were developed using electrodeposition and were assessed as solder diffusion barrier layers in terms of their electrical conductivity and barrier property. The present work adopts a novel electrochemical route to produce Ni-NbOx composite coatings of good uniformity, compactness and purity, from non-aqueous glycol-based electrolytes consisting of NiCl2 and NbCl5 as metal precursors. The effects of cathodic current density and NaBH4 concentrations on the surface morphology, composition and thickness of the coatings were examined. Increased NaBH4 concentrations were found to elevate the maximum deposit thickness (above 10 um), although these led to a reduction in the co-deposited Nb content. The composite coatings generally exhibited good electrical conductivity. The reaction between a liquid 52In-48Sn solder and Ni-NbOx, with Nb contents up to 6 at.%, was studied at 200degC. The results indicate that, Ni-NbOx with sufficient layer thickness and higher Nb content, offered longer service lifetime. Nb enrichment was generally observed at or close to the reaction front after high temperature storage which suggests evident effectiveness of the enhanced diffusion barrier characteristics. A mechanism for the role of Nb as a barrier performance enhancer was postulated.

The present investigation demonstrates a novel electrochemical route for the production of bright, compact, dense and high purity Ni-NbOx nano-composite coatings on Cu, from glycol-based electrolytes consisting of NbCl5, NiCl2*6H2O and propylene glycol. The effects of both cathodic current density and metal electrodeposition bath concentrations on the surface morphology and composition of the coating were examined. The highest relative metal percentage of co-deposited Nb was 14.3 at% obtained at a current density of 400 mA/cm2. Scanning transmission electron microscopy (STEM) revealed a nanocrystalline FCC Ni structure without any significant lattice distortion, as well as an as-yet-unidentified compound. STEM X-ray mapping suggests Nb and O were uniformly distributed in the Ni matrix, without any significant phase segregation, which is consistent with XPS compositional depth profiling. Also, according to the XPS spectra, a 0.7 eV shift to lower binding energy for the Nb (V) species may suggest the partial chemical reduction of Nb2O5 due to possible Ni-Nb bonding. It is thus proposed that a Ni-NbOx deposit was formed by two parallel electrochemical reduction routes: 1) deposition of Ni metal; 2) deposition of a Ni-Nb-O compound as nano-clusters.

Aerosol-assisted chemical vapor deposition (AACVD) was used for the first time in the preparation of thin-film electrochromic nickel(II) oxide (NiO). The as-deposited films were cubic NiO, with an octahedral-like grain structure, and an optical band gap that decreased from 3.61 to 3.48 eV on increase in film thickness (in the range 500–1000 nm). On oxidative voltammetric cycling in aqueous KOH (0.1 mol dm–3) electrolyte, the morphology gradually changed to an open porous NiO structure. The electrochromic properties of the films were investigated as a function of film thickness, following 50, 100, and 500 conditioning oxidative voltammetric cycles in aqueous KOH (0.1 mol dm–3). Light modulation of the films increased with the number of conditioning cycles. The maximum coloration efficiency (CE) for the NiO (transmissive light green, the “bleached” state) to NiOOH (deep brown, the colored state) electrochromic process was found to be 56.3 cm2C–1(at 450 nm) for films prepared by AACVD for 15 min followed by 100 “bleached”-to-colored conditioning oxidative voltammetric cycles. Electrochromic response times were <10 s and generally longer for the coloration than the bleaching process. The films showed good stability when tested for up to 10 000 color/bleach cycles. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry the color stimuli of the electrochromic NiO films and the changes that take place on reversibly oxidatively switching to the NiOOH form were calculated from in situ visible spectra recorded under electrochemical control. Reversible changes in the hue and saturation occur on oxidation of the NiO (transmissive light green) form to the NiOOH (deep brown) form, as shown by the track of the CIE 1931 xychromaticity coordinates. As the NiO film is oxidized, a sharp decrease in luminance was observed. CIELAB L*a*b*coordinates were also used to quantify the electrochromic color states. A combination of a low L*and positive a*and b*values quantified the perceived deep brown colored state.

The article considers electrochromic materials, materials which alter their color in response to electrical voltage. The use of a thin film of electrochromic material in an electric circuit to create an electrochemical cell which can change colors is discussed. Commercial products and proposed which use electrochromic materials are noted including automobile mirrors, protective eyewear and use as building materials for energy conservation.

AbstractAssessment feedback plays a crucial role in the learning experience. However, recent National Student Survey (NSS) results have shown there to be a large degree of student dissatisfaction regarding assessment feedback right across the Higher Education sector in the UK. Evaluating feedback mechanisms in the School of Earth and Environment was a project at the University of Leeds, designed to evaluate the provision of assessment feedback through in-depth consultation with staff and students about current practices, with a view to building upon good practice and creating a strategy for further improvement. Data gathered via focus groups and questionnaires was distilled into a key set of recommendations for ways forward. The recommendations focused on two main strategies: a) the creation of a new comprehensive feedback code of practice for staff, and b) raising student awareness of their rights regarding feedback provision as well as their responsibility to engage with feedback and how to get the most from it. These initiatives have been supported by a distinct, highly visual and sustained advertising campaign designed to act as a corollary to raising staff and student awareness of assessment feedback.

The Equal Access to Justice Act (EAJA) provides for attorneys fees and court costs to be awarded to parties prevailing in litigation against US federal agencies. We examined EAJA awards paid by the US Forest Service from 1999 to 2005, finding more than $6 million awarded to various plaintiffs. Awards were most commonly paid to environmental litigants, although all categories of litigant stakeholders made use of the law. Although it remains uncertain whether EAJA provides an incentive to sue the US Forest Service in any specific instance, because litigation against the US Forest Service generally has a low probability of success, EAJA one-way fee shifting does alter litigation risks among potential plaintiffs. Frequent EAJA claimants often possess considerable financial resources calling into question how the purposes of the law have evolved in the last 20 years.

Electrochromic materials have the property of a change, evocation, or bleaching of color as effected either by an electron-transfer (redox) process or by a sufficient electrochemical potential. The main classes of electrochromic materials are surveyed here, with descriptions of representative examples from the metal oxides, viologens (in solution and as adsorbed or polymeric films), conjugated conducting polymers, metal coordination complexes (as polymeric, evaporated, or sublimed films), and metal hexacyanometallates. Examples of the applications of such electrochromic materials are included. Other materials aspects important for the construction of electrochromic devices include optically transparent electrodes, electrolyte layers, and device encapsulation. Commercial successes, current trends, and future challenges in electrochromic materials research and development are summarized.

Interdisciplinary (ID) teams were created by the US Forest Service in response to environmental legislation. In 2008, we surveyed ID team leaders for National Environmental Policy Act (NEPA) analysis of 106 recreation-related projects conducted between 2005 and 2008. Results were compared with current workforce data and previous studies of ID team leadership and composition for NEPA assessments. ID teams were large in size and diverse in composition, with representatives of a broad range of disciplines and functional areas. The composition of ID teams may be changing from traditional natural resource management to more discipline-specific expertise. The role of social scientists and other human dimension specialists remains modest, despite the importance of social science questions inherent in recreation projects. Results reflect changes in agency hiring practices in the last 20 years and raise questions about the interdisciplinary nature of US Forest Service ID teams.

The National Environmental Policy Act (NEPA) and its accompanying regulations provide a spectrum of alternative analytical pathways for federal agencies proposing major actions that might significantly impact the human environment. Although guidance from the President's Council on Environmental Quality suggests the decision to develop an environmental impact statement (EIS), which requires the most rigorous level of analysis, should be based on the likelihood of significant environmental impacts, findings from an Internet survey with US Forest Service project leaders suggest that the decision may more commonly be based on process-related risks, including the threat of litigation, perceived defensibility in court, and the level of public and political interest in the agency's proposed action. An analysis of judicial decisions in NEPA-related litigation reveals that EISs do not appear to be more defensible than environmental assessments in the courts, suggesting that current decisionmaking about NEPA documentation may be misguided, leading to unnecessary project expenditures and delays.

Variation of the colorimetric properties as a function of the film thickness and morphology has been investigated for two spray-coated electrochromic disubstituted 3,4-propylenedioxythiophene polymers. Changes in the luminance, hue, and saturation have been tracked using CIE 1931 Lxychromaticity coordinates, with CIELAB 1976 color space coordinates, L*, a*, and b*, being used to quantify the colors. For (precycled) neutral PProDOT-(Hx)2films, with an increase in the thickness, L* is seen to decrease, with a* and b* coordinates moving in positive and negative directions, respectively, with quantification of the pink/purple (magenta) color as the summation of red and blue. For all thicknesses, L* is comparable, pre- and postcycling, with a* decreasing (less red) and b* becoming more negative (more blue) and the film now appearing as purple in the neutral state. Color coordinates for the reverse (reduction) direction exhibited hysteresis in comparison with the initial oxidation, with the specific choice of perceived color values depending not only on the film thickness but also on both the potential applied and from which direction the potential is changed. Neutral PProDOT-(2-MeBu)2films appear blue/purple to the eye both as-deposited and after potential cycling to the transparent oxidized state. For the neutral, colored state, with an increase in the thickness, L* is seen to decrease, with a* and b* coordinates moving in positive and negative directions, respectively. For PProDOT-(2-MeBu)2films, the a* coordinates are lower positive values and the b* coordinates are higher negative values, thus quantifying the high dominance of the blue color in the blue/purple films compared to the pink/purple PProDOT-(Hx)2films. As for the PProDOT-(Hx)2films, the tracks of the color coordinates show that the specific choice of perceived color values depends on the film thickness. Unlike the PProDOT-(Hx)2films, hysteresis is absent in the oxidation/reduction track of the x−ycoordinates for the PProDOT-(2-MeBu)2films, although slight hysteresis is present in the luminance. Characterization of the film morphologies through atomic force microscopy reveals a much rougher, higher surface area morphology for the PProDOT-(2-MeBu)2films versus the PProDOT-(Hx)2films. The branched repeat unit in the PProDOT-(2-MeBu)2films provides a structure that allows ions to ingress/egress more effectively, thus removing hysteresis from the optical response.

Eleven executives of the US Forest Service were interviewed to explore the current status and meaning of ecosystem management (EM). The main method of inquiry was open-ended questions, but these questions were complemented by a questionnaire, designed to elicit further conversation about ideas often associated with EM. Participants indicated that EM is still practiced by managers but is seldom used in the agency's environmental speech. The idea that EM is of declining importance to the agency's discourse was also supported by the lack of agreement in participant definitions of EM, where the importance of “scale” and “systems thinking” were the only commonly included ideas in participant definitions of EM. Participants commonly noted the ambiguity and controversy surrounding objectives-oriented components of EM, while process-oriented components were widely accepted by our participants. Our analysis suggests that despite the reduced importance of the term ecosystem management, many of EM's component ideas, particularly those addressing management processes, continue to compete in the agency's broader environmental discourse.

Titanium carbide (TiC) nanoparticles are readily deposited onto tin-doped indium oxide (ITO) electrodes in the form of thin porous films. The nanoparticle deposits are electrically highly conducting and electrochemically active. In aqueous media (at pH 7) and at applied potentials positive of 0.3 V vs. SCE partial anodic surface oxidation and formation (at least in part) of novel core-shell TiC–TiO2 nanoparticles is observed. Significant thermal oxidation of TiC nanoparticles by heating in air occurs at a temperature of 250 °C and leads first to core-shell TiC–TiO2 nanoparticles, next at ca. 350 °C to TiO2 (anatase), and finally at temperatures higher than 750 °C to TiO2 (rutile). Electrochemically and thermally partially oxidized TiC nanoparticles still remain very active and for some redox systems electrocatalytically active. Scanning and transmission electron microscopy (SEM and TEM), temperature dependent XRD, quartz crystal microbalance, and voltammetric measurements are reported. The electrocatalytic properties of the core-shell TiC–TiO2 nanoparticulate films are surveyed for the oxidation of hydroquinone, ascorbic acid, and dopamine in aqueous buffer media. In TiC–TiO2 core-shell nanoparticle films TiO2 surface reactivity can be combined with TiC conductivity.

Eine rotationsgehinderte und dadurch stereogene Biarylachse ist das strukturell und stereochemisch entscheidende Element einer ständig wachsenden Zahl von Naturstoffen, chiralen Auxiliaren und Katalysatoren. Daher ist es nicht überraschend, dass im letzten Jahrzehnt bedeutende Fortschritte in der asymmetrischen Synthese axial‐chiraler Biaryle erzielt worden sind. Neben dem klassischen Zugangsweg, der direkten Aryl‐Aryl‐Kupplung, sind innovative Konzepte entwickelt worden, in denen die asymmetrische Information in ein schon vorhandenes, aber nicht optisch aktives – symmetrisches oder konfigurativ labiles – Biaryl eingeführt oder eine Aryl‐C‐Einfachbindung stereoselektiv in eine Achse umgewandelt wird. In diesem Aufsatz werden die Strategien nach den zugrunde liegenden Konzepten klassifiziert, und ihre Anwendungsbreite und ihre Beschränkungen werden anhand ausgewählter Beispiele kritisch beurteilt. Ferner werden die Voraussetzungen für das Auftreten von Axialchiralität diskutiert. Nicht nur die klassischen, atropselektiven Biarylkupplungenführen zu stereochemisch reinen axial‐chiralen Biarylen, sondern auch neuartige, hochgradig originelle Strategien (siehe Schema). Nach einer Diskussion der strukturellen Voraussetzungen für Axialchiralität werden die erfolgreichsten und innovativsten Ansätze vorgestellt.

A rotationally hindered and thus stereogenic biaryl axis is the structurally and stereochemically decisive element of a steadily growing number of natural products, chiral auxiliaries, and catalysts. Thus, it is not surprising that significant advances have been made in the asymmetric synthesis of axially chiral biaryl compounds over the past decade. In addition to the classic approach (direct stereoselective aryl–aryl coupling), innovative concepts have been developed in which the asymmetric information is introduced into a preformed, but achiral—that is, symmetric or configurationally labile—biaryl compound, or in which an aryl&bond;C single bond is stereoselectively transformed into an axis. This Review classifies these strategies according to their underlying concepts and critically evaluates their scope and limitations with reference to selected model reactions and applications. Furthermore, the preconditions required for the existence of axial chirality in biaryl compounds are discussed.

To discuss the effects of inhaled corticosteroids on bone and their potential public health implications.

TiO2(anatase) nanoparticles are readily deposited layer-by-layer in the form of thin films with a carboxymethyl-γ-cyclodextrate binder. Electron microscopy, voltammetric, and quartz crystal microbalance data demonstrate that the film grows homogeneously and is electrically connected to the ITO electrode surface. 1,1′-Ferrocenedimethanol is employed as an adsorbing redox system to study the voltammetric characteristics of the mesoporous host film. The binding constants for the homogeneous complexation of 1,1′-ferrocenedimethanol with carboxymethyl-γ-cyclodextrin at pH 7, Kred= 1300 ± 200 M−1, and at pH 2, Kred= 1000 ± 200 M−1, are determined assuming 1 1 complex formation. In the presence of the TiO2carboxymethyl-γ-cyclodextrate films, solution phase voltammetric responses are affected due to a lower rate of diffusion of 1,1′-ferrocenedimethanol across the film (possibly due to binding to receptor sites) and due to slow electron transfer at pH 7 but not at pH 2. The TiO2carboxymethyl-γ-cyclodextrate modified electrode, when dipped into 1,1′-ferrocenedimethanol containing solution, rinsed, and transferred into clean buffer solution, shows characteristic signals for adsorbed 1,1′-ferrocenedimethanol, consistent with weak binding and fast release upon oxidation. There is evidence for two distinct binding sites for 1,1′-ferrocenedimethanol both at pH 7 and at pH 2.

The USDA Forest Service appeals process has affected the management of national forests for nearly a century. Concerns over wildfire and forest health have recently focused attention on the role of the appeals process in agency decisionmaking and management. A policy analysis framework is useful to illustrate the relationships in complex national forest management questions. Although reformation of the appeals process has previously been identified and recommended, stakeholders' interest in maintaining the current appeals process creates an obstacle. The current use of the appeals process represents a policy choice designed to address a particular national forest management concern, but changes in management priorities and methods suggest reconsidering the utility of the appeals process.

A number of inorganic and organic materials exhibit redox states (reduced and/or oxidised forms) with distinct UV-Visible (electronic) absorption bands. When electrochemical switching of these redox states gives rise to different colours (i.e. new or different visible region bands), the material is described as being electrochromic. By virtue of their numerous applications, both of academic and commercial interest, electrochromic materials are currently attracting a great deal of interest. This review provides an introduction to the major classes of electrochromic materials, namely transition metal oxides, Prussian blue systems, viologens, conducting polymers, transition metal and lanthanide coordination complexes and metallopolymers, and metal phthalocyanines. Examples of some new materials and of prototype and commercial electrochromic devices are cited.

Substantial levels of hydrogen, up to 6.5 wt %, have been stored in carbon nanofibers (CNFs) under conditions of 12 MPa pressure and ambient temperature. The magnitude of this result cannot be interpreted in terms of physisorption on the external surface alone. Kinetic studies indicate that a slow chemisorption process is involved. The rate of uptake corresponds to that of hydrogen dissociation on graphite edge sites. Such a finding proposes a novel mechanism, offering a plausible explanation for these unusually high experimental observations. This involves the initial dissociation of hydrogen, believed to be catalyzed by carbon edge sites, which constitute the majority of the nanofiber surface, a property which is probably an important contributory factor toward their high hydrogen storage capacities.

Photophysical properties in dilute MeCN solution are reported for seven Ru^II complexes containing two 2,2'-bipyridine (bpy) ligands and different third ligands, six of which contain a variety of 4,4'-carboxamide-disubstituted 2,2'-bipyridines, for one complex containing no 2,2'-bipyridine, but 2 of these different ligands, for three multinuclear Ru^II complexes containing 2 or 4 [Ru(bpy)2] moieties and also coordinated via 4,4'-carboxamide-disubstituted 2,2'-bipyridine ligands, and for the complex [(Ru(bpy)2(L)]²⁺ where L is N,N'-([2,2'-bipyridine]-4,4'-diyl)bis[3-methoxypropanamide]. Absorption maxima are red-shifted with respect to [Ru(bpy)3]²⁺, as are phosphorescence maxima which vary from 622 to 656 nm. The lifetimes of the lowest excited triplet metal-to-ligand charge transfer states ³MLCT in de-aerated MeCN are equal to or longer than for [Ru(bpy)3]²⁺ and vary considerably, i.e., from 0.86 to 1.71 μs. Rate constants kq for quenching by O2 of the ³MLCT states were measured and found to be well below diffusion-controlled, ranging from 1.2 to 2.0·10⁹ dm³ mol⁻¹ s⁻¹. The efficiencies f of singlet-oxygen formation during oxygen quenching of these ³MLCT states are relatively high, namely 0.53 – 0.89. The product of kq and f gives the net rate constant k for quenching due to energy transfer to produce singlet oxygen, and kq−k equals k, the net rate constant for quenching due to energy dissipation of the excited ³MLCT states without energy transfer. The quenching rate constants were both found to correlate with ΔG^CT, the free-energy change for charge transfer from the excited Ru complex to oxygen, and the relative and absolute values of these rate constants are discussed.

Photophysical properties in dilute acetonitrile solution are reported for a number of vinyl-linked benzoaza-15-crown-5-bipyridine ruthenium(ii) complexes and for three multinuclear Ru(ii) bipyridine complexes. Absorption and emission spectra are found to depend on the number of conjugated benzoaza-15-crown-5-bipyridine ligands present in the complex. The bi-, tri- and tetranuclear Ru(ii) complexes show absorption and emission maxima very close to those of the parent mono-complex, Ru(ii) tris-bipyridine. For those complexes with similar phosphorescence maxima, in the range 607–615 nm, the lifetimes of the lowest excited triplet metal to ligand charge-transfer (³MLCT) states in de-aerated acetonitrile are also very similar, i.e., in the range 0.71 to 0.88 μs. However, for two of the studied compounds, where the phosphorescence maxima shift to 692 and 699 nm, the phosphorescence lifetimes increase to 2.2 and 3.0 μs, respectively. Rate constants, k_q, for quenching by molecular oxygen of the lowest excited ³MLCT states are in the range (2.4–4.6)×10⁹ d mol^-1 s^-1. Efficiencies of singlet oxygen production, f_Δ^T, sensitized by these ruthenium complexes are in the range of 0.26–0.69, lower values being associated with those compounds showing low potentials for oxidation of conjugated ligands. The product of k_q and f_Δ^T gives the net rate constant for quenching due to energy transfer to produce singlet oxygen k_q¹, and k_q-k_q¹ equals k_q³, the net rate constant for quenching due to energy dissipation of the excited ³MLCT states without energy transfer. Quenching rate constants, k_q and k_q³, were found to give an inverse correlation with the energy of the excited state being quenched. However, the dependence of k_q¹ values on the energy of the excited states being quenched by oxygen was more complicated, with complexes falling into two groups showing either high or low efficiencies for quenching with energy transfer.

A novel mode of containment for metal ions which participate in longer-range interactions with aryl rings (≥ 2.5 Å) is demonstrated in the preorganized cylindrical host 1. Three equatorial sulfur atoms in 1 hold metals in a trigonal planar ligand field between two apical benzene centroids at an M–Ar distance of about 3 Å. Evidence of an interaction between the π electrons and the metals is gained by ¹H NMR spectroscopy of the complexes, and support for the general description of metal–arene contacts in the 2.5–3.5 Å range as ‘‘bonds’’ is derived from a statistical study of η⁶-coordination in the solid state. Crystal structures of [Ag(1)]BF4 and [Cu(1)]BF4 confirm the first examples of arene Ag^I and Cu^I sandwich complexation and indeed the only structurally characterized Cu^I-aryl centroid interaction. The two isomeric tris-sulfoxides derived from 1 show less tendency to interact with metals ions.

Photophysical properties of 10 substituted methoxybenzene or vinyl linked benzo-crown-ether−2,2‘-bipyridyl ruthenium(II) complexes are reported. The lifetimes of the excited triplet metal to ligand charge transfer states, ³MLCT, of the complex ions are in the range 0.85 ± 0.12 μs with two exceptions where the lifetime drops to about half this value. The rate constants, kq, for quenching in acetonitrile of the ³MLCT states of these ruthenium complex ions by molecular oxygen, O2(³Σg^-), and the variations in the efficiency, %@mt;sys@%%@ital@%f%@rsf@%%@sx@%Δ%@be@%T%@sxx@%%@mx@% , with which excited singlet oxygen, O2*(¹Δg), is thereby produced are reported. The quenching rate constants are in the range 2.2−4.2 × 10⁹ dm³ mol^-1 s^-1, and efficiencies of singlet oxygen production are in the range 0.21−0.74. Those complexes with the highest values of kq tend to be those with lowest %@mt;sys@%%@ital@%f%@rsf@%%@sx@%Δ%@be@%T%@sxx@%%@mx@% values; that is, kq and %@mt;sys@%%@ital@%f%@rsf@%%@sx@%Δ%@be@%T%@sxx@%%@mx@% show a reasonable inverse correlation. The product kq%@mt;sys@%%@ital@%f%@rsf@%%@sx@%Δ%@be@%T%@sxx@%%@mx@% gives the rate constant for oxygen quenching with energy transfer to oxygen, %@mt;sys@%%@ital@%k%@rsf@%%@sx@%q%@be@%1%@sxx@%%@mx@% , and kq − %@mt;sys@%%@ital@%k%@rsf@%%@sx@%q%@be@%1%@sxx@%%@mx@% gives the rate constant, %@mt;sys@%%@ital@%k%@rsf@%%@sx@%q%@be@%3%@sxx@%%@mx@% , for oxygen quenching by any path which does not lead to energy transfer. The values of %@mt;sys@%%@ital@%k%@rsf@%%@sx@%q%@be@%1%@sxx@%%@mx@% , %@mt;sys@%%@ital@%k%@rsf@%%@sx@%q%@be@%3%@sxx@%%@mx@% , and kq are compared with those in the literature which are mainly available for organic sensitizers of singlet oxygen. The similarities and differences between these two classes of compounds are discussed taking into account the fact that ruthenium complex ions are likely to show enhanced intersystem crossing, due to the heavy atom effect and the likely dependence of %@mt;sys@%%@ital@%k%@rsf@%%@sx@%q%@be@%1%@sxx@%%@mx@%[S_EL2;space] and %@mt;sys@%%@ital@%k%@rsf@%%@sx@%q%@be@%3%@sxx@%%@mx@% , and thereby the efficiencies of singlet oxygen production, on the energies of the excited ³MLCT states and on steric factors.

A novel instrument using reflected near-infra-red light spectroscopy to measure cerebral oxygen saturation non-invasively was evaluated during carotid endarterectomy; cerebral perfusion was compared with jugular bulb venous oxygen saturation and transcranial Doppler ultrasonographic measurements. Initially, oximetry sensors with light source-detector separation distances of 10 and 27 mm were positioned over the frontal area, while a cannula positioned in the jugular bulb permitted sampling for jugular bulb venous oxygen saturation. To increase cerebral oxygen saturation sensitivity, modified sensors with light source-detector separation distances of 30 and 40 mm were relocated over the middle cerebral artery territory. The changes in cerebral and jugular bulb venous oxygen saturation, and in peak blood flow velocity before and 30 s after carotid clamping and declamping were recorded. The modified cerebral perfusion system achieved improved correlations between cerebral and jugular bulb venous oxygen saturation changes during carotid clamping and declamping (r= 0·92, P<0·001). The correlation between change in cerebral oxygen saturation and the percentage change in peak flow velocity on both cross-clamping and declamping was equally strong (r=0·90, P< 0·001). Near-infra-red cerebral spectroscopy reliably detects changes in cerebral oxygen saturation during carotid endarterectomy and may have wide applications in monitoring brain perfusion during neurosurgery and cardiopulmonary bypass surgery, and in closed head injury.

Transcranial Doppler ultrasonography (TCD) of the middle cerebral artery (MCA), light-reflective cerebral oximetry and measurement of internal carotid artery stump pressure were compared as methods of monitoring cerebral perfusion during carotid surgery in 33 patients. Median cerebral oxygen saturation was 70 (range 62–85) per cent and TCD-measured mean blood velocity 42 (range 19–91) cm/s before carotid cross-clamping, falling to 68 (53–83) per cent and 16 (0–50) cm/s respectively on application of the clamps (P< 0·001). Stump pressure correlated closely with MCA blood velocity 30 s after the start of cross-clamping (rs= 0·58, P< 0·001), but not with cerebral oxygen saturation. A fall of 5 per cent or more in cerebral oxygen saturation following cross-clamp application was predicted by a decrease in mean MCA blood velocity of at least 60 per cent. Changes in cerebral oxygen saturation correlated significantly with systolic blood pressure throughout the perioperative period (rs= 0·41, P< 0·001). Significant falls in cerebral oxygenation were not predicted by low stump pressure but were associated with large reductions in the mean MCA blood velocity measured by TCD.

This review covers the effects of self-irradiation damage on the physical properties of the α-emitting actinide metals Th, Pa, U, Np, and Pu and some of their alloys: compounds are not considered. The damage to the lattice caused by the α-particles and recoiling nuclei anneals out below room temperature so that the experiments have to be carried out at cryogenic temperatures, mainly in liquid helium. The properties that have been studied include resistivity, length, lattice parameters, thermal conductivity, and specific heat. Most work has been done on the resistivities. These increase with time, showing an exponential approach to saturation after some thousands of hours. In addition to the main exponential law, smaller exponential terms can be separated in some cases, indicating that more than one damage mechanism occurs. The lengths and lattice parameters also saturate exponentially. For most materials these increase but the metastable phases β- and δ-plutonium contract with time. Because the α-particle and, particularly, the recoiling nucleus have only short ranges in these metals, large numbers of atoms are displaced from the lattice in a small volume. The defects are thus not independent of each other, and this, combined with the complex electronic and crystal structures of the actinides, makes calculations on the detailed structure of the defects very difficult. The subject has therefore been approached from a phenomenological standpoint.

The case study outlines how Barclays Bank has used a viewdata system in a pilot scheme for basic procedural training. The viewdata system is explained in the context of the bank's traditional training methods. An interactive system is described using a carefully structured referencing index. Reports giving test results are fed to the branch where the student works. The results use weighted point scores for the most important questions. The system has had an enthusiastic reception from branch managers and students. Problems that were identified included siting of terminals, organization of time and branch involvement.

A critical analysis of the data for the specific heat from 15 K to 300 K of two samples of 241Am and one sample of 243Am leads to a set of “best” values. From these the thermodynamic functions are calculated, giving (Cp)298 = 25.5 ± 1 J mol-1 K-1 and S298 = 55.4 ± 2 J mol-1 K-1. The derived Debye characteristic temperature ?D is estimated as 120 ± 20 K and the electronic specific heat coefficient ? as 1 ± 1 mJ mol-1 K-2.

The specific heats of the UAsY (Y = S, Se, Te) ternary compounds have been studied in the temperature range 1–300K. ?-type anomalies are reported at 125.8, 108.8, and 62.8 K, respectively, corresponding to ferromagnetic ordering. The experimental results are analyzed in terms of the Debye model and electronic contributions. Debye temperatures, electronic specific heat coefficients, and magnetic entropies are derived. A comparison is made with the isostructural binary compounds UX2 (X = P, As, Sb, Bi).