Formation of nickel-thiolate aggregates via reaction with CH2Cl2

Reaction of the mononuclear nickel-thiolate complex [Ni(L-1)(dppe)] with CH2Cl2 affords the novel pentanuclear complex Ni5Cl2(L-1)(4)(dppe)(2)], while [Ni(L-1)(dcpe)] reacts with CH2Cl2 to give the binuclear species [Ni2Cl2(L-2)(dcpe)(2)] in which two L-1 units are linked by a methylene group derived from CH2Cl2.

“The Role of Judges in the Formation of Public Law: Activism or Autolimitation?

(with G. Anthony).

The Role of Subjectivity and Knowledge Power Struggles in the Formation of Public Policy

There is a growing incentive for sociologists to demonstrate the use value of their research. Research ‘impact’ is a driver of research funding and a measure of academic standing. Academic debate on this issue has intensified since Burawoy’s (2004) call for a ‘public’ sociology. However the academy is no longer the sole or primary producer of knowledge and empirical sociologists need to contend with the ‘huge swathes’ of social data that now exist (Savage and Burrows, 2007). This article furthers these debates by considering power struggles between competing forms of knowledge. Using a case study, it specifically considers the power struggle between normative and empirical knowledge, and how providers of knowledge assert legitimacy for their truth claims. The article concludes that the idea of ‘impact’ and ‘use-value’ are extremely complex and depends in the policy context on knowledge power struggles, and on how policy makers want to view the world. © The Author(s) 2012

Uptake, translocation and transformation of arsenate and arsenite in sunflower (Helianthus annuus):formation of arsenic-phytochelatin complexes during exposure to high arsenic concentrations

The aim of the study was to determine the time-dependent formation of arsenic-phytochelatin (As-PC) complexes in the roots, stems and leaves of an arsenic-nontolerant plant (Helianthus annuus) during exposure to 66 mol l(-1) arsenite (As(III)) or arsenate (As(V)). We used our previously developed method of simultaneous element-specific (inductively coupled plasma mass spectrometry, ICP-MS) and molecular-specific (electrospray-ionization mass spectrometry, ES-MS) detection systems interfaced with a suitable chromatographic column and eluent conditions, which enabled us to identify and quantify As-PC complexes directly. Roots of As-exposed H. annuus contained up to 14 different arsenic species, including the complex of arsenite with two (gamma-Glu-Cys)(2)-Gly molecules [As((III))-(PC(2))(2)], the newly identified monomethylarsonic phytochelatin-2 or (gamma-Glu-Cys)(2)-Gly CH(3)As (MA((III))-PC(2)) and at least eight not yet identified species. The complex of arsenite with (gamma-Glu-Cys)(3)-Gly (As((III))-PC(3)) and the complex of arsenite with glutathione (GSH) and (gamma-Glu-Cys)(2)-Gly (GS-As((III))-PC(2)) were present in all samples (roots, stems and leaves) taken from plants exposed to As. The GS-As((III))-PC(2) complex was the dominant complex after 1 h of exposure. As((III))-PC(3) became the predominant As-PC complex after 3 h, binding up to 40% of the As present in the exposed plants. No As-PC complexes were found in sap (mainly xylem sap from the root system), in contrast to roots, stems and leaves, which is unequivocal evidence that As-PC complexes are not involved in the translocation of As from root to leaves of H. annuus.

Demographic noise can lead to the spontaneous formation of species

When a collection of phenotypically diverse organisms compete with each other for limited resources, the population can evolve into tightly localised clusters. Past studies have neglected the effects of demographic noise and studied the population on a macroscopic scale, where cluster formation is found to depend on the shape of the curve describing the decline of competition strength with phenotypic distance. Here we show how including the effects of demographic noise leads to a radically different conclusion. Two situations are identified: a weak-noise regime in which the population exhibits patterns of fluctuation around the macroscopic description, and a strong-noise regime where clusters appear spontaneously even in the case that all organisms have equal fitness. editor's choice Copyright (C) EPLA, 2012

The partially reversible formation of Li-metal particles on a solid Li electrolyte:applications toward nanobatteries

The feasibility of large-scale implementation of Li-air batteries (LABs) hinges on understanding the thermodynamic and kinetic factors that control charge-discharge rates, efficiency and life times. Here, the kinetics of bias-induced reactions is explored locally on the surface of Li-ion conductive glass ceramics, a preferred electrolyte for LABs, using direct current-voltage and strain spectroscopies. Above a critical bias, particle growth kinetics were found to be linear in both the bias and time domains. Partial reversibility was observed for Li particles as evidenced by the presence of anodic peaks following the Li(+) reduction, as well an associated reduction in particle height. The degree of reversibility was highest for the smallest particles formed. These observations thus suggest the possibility of producing nanobatteries with an active anode volume of the order of 0.1 al.

HIV-1 Nef limits communication between linker of activated T cells and SLP-76 to reduce formation of SLP-76-signaling microclusters following TCR stimulation

Signal initiation by engagement of the TCR triggers actin rearrangements, receptor clustering, and dynamic organization of signaling complexes to elicit and sustain downstream signaling. Nef, a pathogenicity factor of HIV, disrupts early TCR signaling in target T cells. To define the mechanism underlying this Nef-mediated signal disruption, we employed quantitative single-cell microscopy following surface-mediated TCR stimulation that allows for dynamic visualization of distinct signaling complexes as microclusters (MCs). Despite marked inhibition of actin remodeling and cell spreading, the induction of MCs containing TCR-CD3 or ZAP70 was not affected significantly by Nef. However, Nef potently inhibited the subsequent formation of MCs positive for the signaling adaptor Src homology-2 domain-containing leukocyte protein of 76 kDa (SLP-76) to reduce MC density in Nef-expressing and HIV-1-infected T cells. Further analyses suggested that Nef prevents formation of SLP-76 MCs at the level of the upstream adaptor protein, linker of activated T cells (LAT), that couples ZAP70 to SLP-76. Nef did not disrupt pre-existing MCs positive for LAT. However, the presence of the viral protein prevented de novo recruitment of active LAT into MCs due to retargeting of LAT to an intracellular compartment. These modulations in MC formation and composition depended on Nef's ability to simultaneously disrupt both actin remodeling and subcellular localization of TCR-proximal machinery. Nef thus employs a dual mechanism to disturb early TCR signaling by limiting the communication between LAT and SLP-76 and preventing the dynamic formation of SLP-76-signaling MCs.

Time-Resolved Characterization of the Formation of a Collisionless Shock

We report on the temporally and spatially resolved detection of the precursory stages that lead to the formation of an unmagnetized, supercritical collisionless shock in a laser-driven laboratory experiment. The measured evolution of the electrostatic potential associated with the shock unveils the transition from a current free double layer into a symmetric shock structure, stabilized by ion reflection at the shock front. Supported by a matching particle-in-cell simulation and theoretical considerations, we suggest that this process is analogous to ion reflection at supercritical collisionless shocks in supernova remnants.

Time-Resolved DRIFTS, MS, and Resistance Study of SnO2 Materials: The Role of Surface Hydroxyl Groups in Formation of Donor States

Time-resolved DRIFTS, MS, and resistance measurements were used to study the interaction of undoped and Pd-doped SnO2 with H-2 in air and argon at 300 degrees C. Using first-order kinetics, we compare the time constants for the resistance drop and its partial recovery with those of the surface hydroxyl evolution and water formation in the gas phase upon exposure to hydrogen. In the case of the undoped oxide, resistance and bridging hydroxyls (BOHs) evolve similarly, manifesting a fast main drop followed by recovery at a similar rate. The rate of water formation for this material was found to be much slower than that of the main drop in both the resistance and BOHs. In contrast, the resistance change for SnO2-Pd appeared to be similar to that of water formation, and no correlation was found between the evolution of resistance and surface OHs. Isotopic exchange on both materials revealed that water formation occurs via fast and slow hydrogen transfer to surface oxygen species. While the former originates from just-adsorbed hydrogen, the latter appears to proceed from the preadsorbed OHs. Both surfaces exhibit close interaction between chemisorbed oxygen and existing bridging OH groups, indicating that the latter is an intermediate in the hydrogen oxidation and generation of donor states on the surface.

Coprolites from the Cretaceous Bearpaw Formation of Saskatchewan

Coprolites from the Beechy Member of the Cretaceous Bearpaw Formation, southern Saskatchewan, presumably deposited by one or more species of mosasaur or large fish/shark, were recovered and analyzed using SEM/EDS. The data reveal the presence of pseudomorphous coccoid bacteria, potential filamentous bacteria, bacterial endospores and filamentous fungi. No recorded fossil plant or bone material could be identified, either within the highly compressed coprolitic mat-flattened full coprolite bolus - of recovered marine sediment encased in a mixed mat of hematite-apatite primary minerals heavily coated with Ca-smectite and nontronite, or the full coprolite bolus. The presence of fossil bacteria with morphological characteristics similar to those of endospores in other environments suggests that only robust microbial forms such as these survive diagenesis, partly with some carbon still intact, the remainder replaced with silica and iron. The data support the view that coprolites can serve as a useful source of information on the ancient microbial world. © 2012 Elsevier Ltd.

Rapid formation of robust auditory memories: Insights from noise

Before a natural sound can be recognized, an auditory signature of its source must be learned through experience. Here we used random waveforms to probe the formation of new memories for arbitrary complex sounds. A behavioral measure was designed, based on the detection of repetitions embedded in noises up to 4 s long. Unbeknownst to listeners, some noise samples reoccurred randomly throughout an experimental block. Results showed that repeated exposure induced learning for otherwise totally unpredictable and meaningless sounds. The learning was unsupervised and resilient to interference from other task-relevant noises. When memories were formed, they emerged rapidly, performance became abruptly near-perfect, and multiple noises were remembered for several weeks. The acoustic transformations to which recall was tolerant suggest that the learned features were local in time. We propose that rapid sensory plasticity could explain how the auditory brain creates useful memories from the ever-changing, but sometimes repeating, acoustical world. © 2010 Elsevier Inc.

Modification of the formation of high-Mach number electrostatic shock-like structures by the ion acoustic instability

The formation of unmagnetized electrostatic shock-like structures with a high Mach number is examined with one- and two-dimensional particle-in-cell (PIC) simulations. The structures are generated through the collision of two identical plasma clouds, which consist of equally hot electrons and ions with a mass ratio of 250. The Mach number of the collision speed with respect to the initial ion acoustic speed of the plasma is set to 4.6. This high Mach number delays the formation of such structures by tens of inverse ion plasma frequencies. A pair of stable shock-like structures is observed after this time in the 1D simulation, which gradually evolve into electrostatic shocks. The ion acoustic instability, which can develop in the 2D simulation but not in the 1D one, competes with the nonlinear process that gives rise to these structures. The oblique ion acoustic waves fragment their electric field. The transition layer, across which the bulk of the ions change their speed, widens and their speed change is reduced. Double layer-shock hybrid structures develop.

In Situ Formation of Micron-Scale Li-Metal Anodes with High Cyclability

Scanning probe microscopy methods have been used to electrodeposit and cycle micron-scale Li anodes deposited electrochemically under nanofabricated Au current collectors. An average Li volume of 5 x 10(8) nm(3) was deposited and cycled with 100% coulombic efficiency for similar to 160 cycles. Integrated charge/discharge values agree with before/after topography, as well as in situ dilatometry, suggesting this is a reliable method to study solid-state electrochemical processes. In this work we illustrate the possibility to deposit highly cyclable nanometer thick Li electrodes by mature SPM and nanofab techniques which can pave the way for inexpensive nanoscale battery arrays. 

Hybrid Polyoxovanadates: Anion-Influenced Formation of Nanoscopic Cages and Supramolecular Assemblies of Asymmetric Clusters

Organoarsonate-functionalized polyoxovanadates form upon the reduction of vanadates(V) in aqueous systems, whereby the underlying condensation reactions are influenced by the nature of the employed acid. In the presence of Cl− ions that derive from hydrochloric acid, a tetradecanuclear cage [VIV14O16(OH)8(O3AsC6H4-4-NH2)10]4– is obtained. When nitric acid is used, a condensed, decanuclear complex [V10O18(O3AsC6H4-4-NH2)7(DMF)2]5– forms. The latter organizes into a hexagonal packing arrangement in the solid state.

Human parietal and primary motor cortical interactions are selectively modulated during the transport and grip formation of goal-directed hand actions

Posterior parietal cortex (PPC) constitutes a critical cortical node in the sensorimotor system in which goal-directed actions are computed. This information then must be transferred into commands suitable for hand movements to the primary motor cortex (M1). Complexity arises because reach-to-grasp actions not only require directing the hand towards the object (transport component), but also preshaping the hand according to the features of the object (grip component). Yet, the functional influence that specific PPC regions exert over ipsilateral M1 during the planning of different hand movements remains unclear in humans. Here we manipulated transport and grip components of goal-directed hand movements and exploited paired-pulse transcranial magnetic stimulation (ppTMS) to probe the functional interactions between M1 and two different PPC regions, namely superior parieto-occipital cortex (SPOC) and the anterior region of the intraparietal sulcus (aIPS), in the left hemisphere. We show that when the extension of the arm is required to contact a target object, SPOC selectively facilitates motor evoked potentials, suggesting that SPOC-M1 interactions are functionally specific to arm transport. In contrast, a different pathway, linking the aIPS and ipsilateral M1, shows enhanced functional connections during the sensorimotor planning of grip. These results support recent human neuroimaging findings arguing for specialized human parietal regions for the planning of arm transport and hand grip during goal-directed actions. Importantly, they provide new insight into the causal influences these different parietal regions exert over ipsilateral motor cortex for specific types of planned hand movements