Observation of carbonyl oxygen-pi interaction in a metal complex

X-ray crystallography shows that [Ag2L2(H2O)(2)](BF4)(2) where L is a 1:1 condensate of 1,2-diphenylethane-1,2-dione and 2-(2-aminoethyl pyridine), contains an Ag(I)-Ag(I) bond of length 2.979(2) angstrom and an angular, intraligand interaction of the keto O with the pi cloud of the pyridine moiety (O-pyridine centroid = 3.12 angstrom). Model MP2/6-311++G(d,p) calculations indicate that the observed lone pair-pi type interaction is stabilising and not merely a tolerated short contact. (C) 2008 Elsevier B.V. All rights reserved.

Mixed ligand binuclear copper(I) complexes containing (Cu2N8)-N-I chromophores. Observation of emissions from MLCT excited states involving two different ligands

Using the 1:2 condensate (L) of diethylenetriamine and benzaldehyde as the main ligand, binuclear copper(l) complexes [Cu2L2(4,4'-bipyridine)](CIO4)(2).0.5H(2)O (1a) and [Cu2L2(1,2-bis(4-pyridyl)ethane)](CIO4)(2) (1b) are synthesised. The two metal ions in la are bridged by 4,4'-bipyridine and those in 1b by 1,2-bis(4-pyridyl)ethane, From the X-ray crystal structure of la, each metal ion is found to be bound to three N atoms of L and one of the two N atoms of the bridging ligand in a distorted tetrahedral fashion. The Cu(I)-N bond lengths in la lie in the range of 1.998(5)-2.229(6) Angstrom. Electrochemical studies in dichloromethane (DCM) show that the (Cu2N8)-N-I moieties in la and 1b are composed of two essentially non-interacting (CuN4)-N-I cores with Cu-II/I potential of 0.44 V vs. SCE. While la displays metal induced quenching of the inherent emission of 4,4'-bipyridine in DCM solution, 1b exhibits two weak emission bands in DCM solution at 425 and 477 nm (total quantum yield = 3.59 x 10(-5)) originating from MLCT excited states. With the help of Extended Huckel calculations it is established that the higher energy emission in 1b is from Cu(I) --> bridging-ligand charge transfer excited state and the lower energy one in 1b from Cu(I) --> L charge transfer excited state.

A cost-effective high-throughput digital system for observation and acquisition of animal behavioral data

We have designed and implemented a low-cost digital system using closed-circuit television cameras coupled to a digital acquisition system for the recording of in vivo behavioral data in rodents and for allowing observation and recording of more than 10 animals simultaneously at a reduced cost, as compared with commercially available solutions. This system has been validated using two experimental rodent models: one involving chemically induced seizures and one assessing appetite and feeding. We present observational results showing comparable or improved levels of accuracy and observer consistency between this new system and traditional methods in these experimental models, discuss advantages of the presented system over conventional analog systems and commercially available digital systems, and propose possible extensions to the system and applications to non-rodent studies.

Stereoscopic acuity and observation distance

The amount of depth perceived from a fixed pattern of horizontal disparities varies with viewing distance. We investigated whether thresholds for discriminating stereoscopic corrugations at a range of spatial frequencies were also affected by viewing distance or whether they were determined solely by the angular disparity in the stimulus prior to scaling. Although thresholds were found to be determined primarily by disparity over a broad range of viewing distances, they were on average a factor of two higher at the shortest viewing distance (28.5 cm) than at larger viewing distances (57 to 450 cm). We found the same pattern of results when subjects' accommodation was arranged to be the same at all viewing distances. The change in thresholds at close distances is in the direction expected if subjects' performance is limited by a minimum perceived depth.

Forecast impact of targeted observations: sensitivity to observation error and proximity to steep orography

For a targeted observations case, the dependence of the size of the forecast impact on the targeted dropsonde observation error in the data assimilation is assessed. The targeted observations were made in the lee of Greenland; the dependence of the impact on the proximity of the observations to the Greenland coast is also investigated. Experiments were conducted using the Met Office Unified Model (MetUM), over a limited-area domain at 24-km grid spacing, with a four-dimensional variational data assimilation (4D-Var) scheme. Reducing the operational dropsonde observation errors by one-half increases the maximum forecast improvement from 5% to 7%–10%, measured in terms of total energy. However, the largest impact is seen by replacing two dropsondes on the Greenland coast with two farther from the steep orography; this increases the maximum forecast improvement from 5% to 18% for an 18-h forecast (using operational observation errors). Forecast degradation caused by two dropsonde observations on the Greenland coast is shown to arise from spreading of data by the background errors up the steep slope of Greenland. Removing boundary layer data from these dropsondes reduces the forecast degradation, but it is only a partial solution to this problem. Although only from one case study, these results suggest that observations positioned within a correlation length scale of steep orography may degrade the forecast through the anomalous upslope spreading of analysis increments along terrain-following model levels.

Direct observation of time-resolved polymorphic states in the self-assembly of end-capped heptapeptides

Amyloid fibrils resulting from uncontrolled peptide aggregation are associated with several neurodegenerative diseases. Their polymorphism depends on a number of factors including pH, ionic strength, electrostatic interactions, hydrophobic interactions, hydrogen bonding, aromatic stacking interactions, and chirality. Understanding the mechanism of amyloid fibril formation can improve strategies towards the prevention of fibrillation processes and enable a wide range of potential applications in nanotemplating and nanotechnology.

Action observation and robotic agents: learning and anthropomorphism

The ‘action observation network’ (AON), which is thought to translate observed actions into motor codes required for their execution, is biologically tuned: it responds more to observation of human, than non-human, movement. This biological specificity has been taken to support the hypothesis that the AON underlies various social functions, such as theory of mind and action understanding, and that, when it is active during observation of non-human agents like humanoid robots, it is a sign of ascription of human mental states to these agents. This review will outline evidence for biological tuning in the AON, examining the features which generate it, and concluding that there is evidence for tuning to both the form and kinematic profile of observed movements, and little evidence for tuning to belief about stimulus identity. It will propose that a likely reason for biological tuning is that human actions, relative to non-biological movements, have been observed more frequently while executing corresponding actions. If the associative hypothesis of the AON is correct, and the network indeed supports social functioning, sensorimotor experience with non-human agents may help us to predict, and therefore interpret, their movements.

The general observation period 2007 within the priority program on quantitative precipitation forecasting: concept and first results

In the year 2007 a General Observation Period (GOP) has been performed within the German Priority Program on Quantitative Precipitation Forecasting (PQP). By optimizing the use of existing instrumentation a large data set of in-situ and remote sensing instruments with special focus on water cycle variables was gathered over the full year cycle. The area of interest covered central Europe with increasing focus towards the Black Forest where the Convective and Orographically-induced Precipitation Study (COPS) took place from June to August 2007. Thus the GOP includes a variety of precipitation systems in order to relate the COPS results to a larger spatial scale. For a timely use of the data, forecasts of the numerical weather prediction models COSMO-EU and COSMO-DE of the German Meteorological Service were tailored to match the observations and perform model evaluation in a near real-time environment. The ultimate goal is to identify and distinguish between different kinds of model deficits and to improve process understanding.