Southern hemispheric halon trends and global halon emissions, 1978–2011

The atmospheric records of four halons, H-1211 (CBrClF2), H-1301 (CBrF3), H-2402 (CBrF2CBrF2) and H-1202 (CBr2F2), measured from air collected at Cape Grim, Tasmania, between 1978 and 2011, are reported. Mixing ratios of H-1211, H-2402 and H-1202 began to decline in the early to mid-2000s, but those of H-1301 continue to increase up to mid-2011. These trends are compared to those reported by NOAA (National Oceanic and Atmospheric Administration) and AGAGE (Advanced Global Atmospheric Experiment). The observations suggest that the contribution of the halons to total tropospheric bromine at Cape Grim has begun to decline from a peak in 2008 of about 8.1 ppt. An extrapolation of halon mixing ratios to 2060, based on reported banks and predicted release factors, shows this decline becoming more rapid in the coming decades, with a contribution to total tropospheric bromine of about 3 ppt in 2060. Top-down global annual emissions of the halons were derived using a two-dimensional atmospheric model. The emissions of all four have decreased since peaking in the late 1980s–mid-1990s, but this decline has slowed recently, particularly for H-1301 and H-2402 which have shown no decrease in emissions over the past five years. The UEA (University of East Anglia) top-down model-derived emissions are compared to those reported using a top-down approach by NOAA and AGAGE and the bottom-up estimates of HTOC (Halons Technical Options Committee). The implications of an alternative set of steady-state atmospheric lifetimes are discussed. Using a lifetime of 14 yr or less for H-1211 to calculate top-down emissions estimates would lead to small, or even negative, estimated banks given reported production data. Finally emissions of H-1202, a product of over-bromination during the production process of H-1211, have continued despite reported production of H-1211 ceasing in 2010. This raises questions as to the source of these H-1202 emissions

The effect of neural adaptation of population coding accuracy

Most neurons in the primary visual cortex initially respond vigorously when a preferred stimulus is presented, but adapt as stimulation continues. The functional consequences of adaptation are unclear. Typically a reduction of firing rate would reduce single neuron accuracy as less spikes are available for decoding, but it has been suggested that on the population level, adaptation increases coding accuracy. This question requires careful analysis as adaptation not only changes the firing rates of neurons, but also the neural variability and correlations between neurons, which affect coding accuracy as well. We calculate the coding accuracy using a computational model that implements two forms of adaptation: spike frequency adaptation and synaptic adaptation in the form of short-term synaptic plasticity. We find that the net effect of adaptation is subtle and heterogeneous. Depending on adaptation mechanism and test stimulus, adaptation can either increase or decrease coding accuracy. We discuss the neurophysiological and psychophysical implications of the findings and relate it to published experimental data.Comment: 35 pages, 8 figure

Liquid Argon Hadronic EndCap Production Database

This document describes the contents of the Liquid Argon Hadronic EndCap (HEC) Production Database. At the time of the PRR (Production Readiness Review), the groups responsible for the production of the LAr HEC components and modules were required to provide a detailed plan as to what data should be stored in the production database and how the data should be accessed, displayed and queried in all reasonable foreseeable circumstances. This document describes the final database

Liquid Argon HEC Wheel Assembly Database

This document describes the details of the contents of the LAr Hadronic EndCap Wheel Assembly Database. This database contains the important data from the wheel assembly: mechanical alignment, electrical properties, cabling, and a summary of the readout gap failures. This document describes the final database that is intended mainly for archival purposes. This database should be viewed in conjunction with the HEC module production database that describes the modules that form the wheel and the Feedthrough database that describes the signal feedthroughs. This wheel database lists for instance the location of the modules, the amplifiers to which they are connected, and the details of the alignment measurements. It also details all non-conformances. It is important that for all non-conformances, whether they occurred during wheel assembly or in the B180 cold tests, that a single table be produced of all the non-conformances listing the non-conformance in a format suitable for making offline corrections to the data. This non-conformance table will be derived from a set of queries of this database

The as-built parameters of the Hadronic End Cap

The intent of this document is to present the as-built parameters of the Hadronic EndCap, and to discuss aspects that have changed since the Liquid Argon TDR was written in 1996. In addition we discuss the effect of ion build-up at high luminosity as this was not addressed in the TDR. This as built description will concentrate on aspects that will affect the calorimeter operation

Root interactions in a diverse grassland : the role of root traits in belowground productivity and decomposition

Background Plant diversity influences ecosystem functioning. A positive relation between plant diversity and productivity above- and belowground has been established. Aboveground, this effect has been shown to be due to complementarity effects, interactions between species in a mixture that lead species to, on average, produce more biomass than expected based on their productivity in monoculture. The mechanisms underlying complementarity effects and the positive diversity-productivity relation are predicted to lie belowground, e.g. resource partitioning and/or facilitation. The relation between plant diversity and decomposition is less clear, and research on the diversity-decomposition relation belowground is limited. This is an important gap in biodiversity knowledge, as the decomposition of plant litter is the major source of nutrients and carbon in terrestrial ecosystems, and most plant litter in grasslands is belowground. Methods This thesis explored the effect of plant diversity on belowground productivity and decomposition. Belowground complementarity effects were quantified in the Jena Trait Based Experiment, and the diversity of or plasticity in species-specific vertical root distribution as underlying mechanism was tested. The plant diversity- root decomposition relation was quantified in the Jena Experiment and the Jena Trait Based Experiment. The role of root traits and the soil environment as mediating factors were tested. Major findings Plant diversity had a positive effect on root biomass production, and this relation was attributed to complementarity effects. The diversity in species-specific vertical root distribution did not explain complementarity effects, and thus, is not likely a major mechanism underlying the diversity-productivity relation. Species altered their vertical root distribution in response to inter-specific neighbours. The direction of this change differed between functional groups: grasses became shallower in mixture, forbs became deeper. This change did not explain species-specific belowground relative productivity (relative to monoculture productivity). Therefore, plasticity in vertical root distribution was not a major factor underlying belowground complementarity effects or the diversity-productivity relation. Functional group composition, not plant diversity, had a consistent effect on root decomposition. The presence or abundance of grasses consistently reduced root litter quality and decomposition. In the Jena Experiment, plant diversity had a negative effect on root decomposition, mainly due to shifts in functional group composition over a diversity gradient. In the Jena Trait Based Experiment, root decomposition was unaffected by plant diversity, but decreased as the abundance of grass roots increased. Root traits were found to be important in explaining variation in root decomposition. Conclusions Plant diversity had a positive effect on belowground productivity, which could be attributed to complementarity effects. Functional group composition, not plant diversity, had consistent effects on root decomposition. Root traits were important in explaining root decomposition throughout this thesis. Root traits may also be important in explaining complementarity effects, however, the diversity of or plasticity in vertical root distribution did not. This thesis highlights the role of belowground interactions in facilitating the positive diversity-productivity relation, and the role of plant functional groups and root traits in explaining how plant diversity alters root decomposition. </p

Response Features Determining Spike Times

Interpreting messages encoded in single neuronal responses requires knowing which features of the responses carry information. That the number of spikes is an important part of the code has long been obvious. In recent years, it has been shown that modulation of the firing rate with about 25 ms precision carries information that is not available from the total number of spikes across the whole response. It has been proposed that patterns of exactly timed (1 ms precision) spikes, such as repeating triplets or quadruplets, might carry information that is not available from knowing about spike count and rate modulation. A model using the spike count distribution, the low pass filtered PSTH (bandwidth below 30 Hz), and, to a small degree, the interspike interval distribution predicts the numbers and types of exactly-timed triplets and quadruplets that are indistinguishable from those found in the data. From this it can be concluded that the coarse (<30 Hz) sequential correlation structure over time gives rise to the exactly timed patterns present in the recorded spike trains. Because the coarse temporal structure predicts the fine temporal structure, the information carried by the fine temporal structure must be completely redundant with that carried by the coarse structure. Thus, the existence of precisely timed spike patterns carrying stimulus-related information does not imply control of spike timing at precise time scales

Identification of D-arabinan-degrading enzymes in mycobacteria

Bacterial cell growth and division require the coordinated action of enzymes that synthesize and degrade cell wall polymers. Here, we identify enzymes that cleave the D-arabinan core of arabinogalactan, an unusual component of the cell wall of Mycobacterium tuberculosis and other mycobacteria. We screened 14 human gut-derived Bacteroidetes for arabinogalactan-degrading activities and identified four families of glycoside hydrolases with activity against the D-arabinan or D-galactan components of arabinogalactan. Using one of these isolates with exo-D-galactofuranosidase activity, we generated enriched D-arabinan and used it to identify a strain of Dysgonomonas gadei as a D-arabinan degrader. This enabled the discovery of endo- and exo-acting enzymes that cleave D-arabinan, including members of the DUF2961 family (GH172) and a family of glycoside hydrolases (DUF4185/GH183) that display endo-D-arabinofuranase activity and are conserved in mycobacteria and other microbes. Mycobacterial genomes encode two conserved endo-D-arabinanases with different preferences for the D-arabinan-containing cell wall components arabinogalactan and lipoarabinomannan, suggesting they are important for cell wall modification and/or degradation. The discovery of these enzymes will support future studies into the structure and function of the mycobacterial cell wall