An investigation of optimization techniques for drawing computer graphics displays

Techniques for reducing vector data plotting time are studied. The choice of tolerances in optimization and the application of optimization to plots produced on real time interactive display devices are discussed. All results are developed relative to plotting packages and support hardware so that results are useful in real world situations

An investigation into linearity with cumulative emissions of the climate and carbon cycle response in HadCM3LC

We investigate the extent to which global mean temperature, precipitation, and the carbon cycle are constrained by cumulative carbon emissions throughout four experiments with a fully coupled climate-carbon cycle model. The two paired experiments adopt contrasting, idealised approaches to climate change mitigation at different action points this century, with total emissions exceeding two trillion tonnes of carbon in the later pair. Their initially diverging cumulative emissions trajectories cross after several decades, before diverging again. We find that their global mean temperatures are, to first order, linear with cumulative emissions, though regional differences in temperature of up to 1.5K exist when cumulative emissions of each pair coincide. Interestingly, although the oceanic precipitation response scales with cumulative emissions, the global precipitation response does not, due to a decrease in precipitation over land above cumulative emissions of around one trillion tonnes of carbon (TtC). Most carbon fluxes and stores are less well constrained by cumulative emissions as they reach two trillion tonnes. The opposing mitigation approaches have different consequences for the Amazon rainforest, which affects the linearity with which the carbon cycle responds to cumulative emissions. Averaged over the two fixed-emissions experiments, the transient response to cumulative carbon emissions (TCRE) is 1.95 K TtC-1, at the upper end of the IPCC’s range of 0.8-2.5 K TtC-1

Transient simulations of the carbon and nitrogen dynamics in northern peatlands: from the Last Glacial Maximum to the 21st century

The development of northern high-latitude peatlands played an important role in the carbon (C) balance of the land biosphere since the Last Glacial Maximum (LGM). At present, carbon storage in northern peatlands is substantial and estimated to be 500 ± 100 Pg C (1 Pg C = 1015 g C). Here, we develop and apply a peatland module embedded in a dynamic global vegetation and land surface process model (LPX-Bern 1.0). The peatland module features a dynamic nitrogen cycle, a dynamic C transfer between peatland acrotelm (upper oxic layer) and catotelm (deep anoxic layer), hydrology- and temperature-dependent respiration rates, and peatland specific plant functional types. Nitrogen limitation down-regulates average modern net primary productivity over peatlands by about half. Decadal acrotelm-to-catotelm C fluxes vary between −20 and +50 g C m−2 yr−1 over the Holocene. Key model parameters are calibrated with reconstructed peat accumulation rates from peat-core data. The model reproduces the major features of the peat core data and of the observation-based modern circumpolar soil carbon distribution. Results from a set of simulations for possible evolutions of northern peat development and areal extent show that soil C stocks in modern peatlands increased by 365–550 Pg C since the LGM, of which 175–272 Pg C accumulated between 11 and 5 kyr BP. Furthermore, our simulations suggest a persistent C sequestration rate of 35–50 Pg C per 1000 yr in present-day peatlands under current climate conditions, and that this C sink could either sustain or turn towards a source by 2100 AD depending on climate trajectories as projected for different representative greenhouse gas concentration pathways

Abrupt climate changes: from the past to the future - a review

A review of climatic variability is given with a focus on abrupt changes during the last glacial. Evidence from palaeoclimatic archives suggests that these were most likely due to reorganisations of the atmosphere–ocean system. The mechanisms responsible for these changes are presented. Their implication for future climate changes is discussed in light of recent climate model simulations

Aerodynamic performance of conventional and advanced design labyrinth seals with solid-smooth abradable, and honeycomb lands

Labyrinth air seal static and dynamic performance was evaluated using solid, abradable, and honeycomb lands with standard and advanced seal designs. The effects on leakage of land surface roughness, abradable land porosity, rub grooves in abradable lands, and honeycomb land cell size and depth were studied using a standard labyrinth seal. The effects of rotation on the optimum seal knife pitch were also investigated. Selected geometric and aerodynamic parameters for an advanced seal design were evaluated to derive an optimized performance configuration. The rotational energy requirements were also measured to determine the inherent friction and pumping energy absorbed by the various seal knife and land configurations tested in order to properly assess the net seal system performance level. Results indicate that: (1) seal leakage can be significantly affected with honeycomb or abradable lands; (2) rotational energy absorption does not vary significantly with the use of a solid-smooth, an abradable, or a honeycomb land; and (3) optimization of an advanced lab seal design produced a configuration that had leakage 25% below a conventional stepped seal

Studies of the action of venom and venom constituents on Escherichia coli

Studies of the action of venom and venom constituents on Escherichia coli. The antibacterial activity of honeybee venom (Apis mellifera) , three snake venoms (Naja naja sputatrix, Vipera russellii and Crotalus adamanteus) and the polypeptide melittin (a component of honeybee venom) was investigated against the gram-negative organism Escherichia coli. Minimum inhibitory concentration (MIC) values were determined and action against proliferating and non-proliferating cells was in the order: Apis mellifera venom > melittin > Naja naja sputatrix > Vipera russellii venom > Crotalus adamanteus venom. Cell lysis was determined by absorbancy changes and was caused by the more active venoms (Apis mellifera and Naja naja sputatrix) and melittin. Alteration of the permeability of the cell envelope of Escherichia coli cells harvested in mid-log phase was followed principally by measuring β-galactosidase release from cells. Venom activity decreased in the same order as MIC above. Phospholipases A₂ from Apis mellifera and Naja naja sputatrix venoms, melittin and polymixin B (polypeptide antibiotic) increased β-galactosidase release. No synergism between the phospholipases A₂ and melittin was seen under the conditions employed. Separation of Apis mellifera and Naja naja sputatrix venoms was carried out by gel filtration and electrophoresis. The action of venom components implies that the antibacterial activity of whole venom is not totally accounted for by that of the venom polypeptide toxins melittin or direct lytic factor (DLF). That the antibacterial activity of Apis mellifera and Naja naja sputatrix venoms and melittin is due at least in part to membrane disruption is supported by electron microscopy studies

The Drosophila Larva as a Model for Studying Chemosensation and Chemosensory Learning: A Review

Understanding the relationship between brain and behavior is the fundamental challenge in neuroscience. We focus on chemosensation and chemosensory learning in larval Drosophila and review what is known about its molecular and cellular bases. Detailed analyses suggest that the larval olfactory system, albeit much reduced in cell number, shares the basic architecture, both in terms of receptor gene expression and neuronal circuitry, of its adult counterpart as well as of mammals. With respect to the gustatory system, less is known in particular with respect to processing of gustatory information in the central nervous system, leaving generalizations premature. On the behavioral level, a learning paradigm for the association of odors with food reinforcement has been introduced. Capitalizing on the knowledge of the chemosensory pathways, we review the first steps to reveal the genetic and cellular bases of olfactory learning in larval Drosophila. We argue that the simplicity of the larval chemosensory system, combined with the experimental accessibility of Drosophila on the genetic, electrophysiological, cellular, and behavioral level, makes this system suitable for an integrated understanding of chemosensation and chemosensory learnin

Improving Access to Precipitation Data for GIS Users: Designing for Ease of Use

The Global Precipitation Measurement Mission (GPM) is a NASA/JAXA led international mission to configure a constellation of space-based radiometers to monitor precipitation over the globe. The GPM goal of making global 3-hour precipitation products available in near real-time will make such global products more useful to a broader community of modelers and Geographic Information Systems (GIS) users than is currently the case with remote sensed precipitation products. Based on the existing interest to make Tropical Rainfall Measuring Mission (TRMM) data available to a growing community of GIS users as well as what will certainly be an expanded community during the GPM era, it is clear that data systems must make a greater effort to provide data in formats easily used by GIS. We describe precipitation GIS products being developed for TRMM data. These products will serve as prototypes for production efforts during the GPM era. We describe efforts to convert TRMM precipitation data to GeoTIFF, Shapefile, and ASCII grid. Clearly, our goal is to format GPM data so that it can be easily used within GIS applications. We desire feedback on these efforts and any additions or direction changes that should be undertaken by the data system

TRMM Version 7 Level 3 Gridded Monthly Accumulations of GPROF Precipitation Retrievals

In July 2011, improved versions of the retrieval algorithms were approved for TRMM. All data starting with June 2011 are produced only with the version 7 code. At the same time, version 7 reprocessing of all TRMM mission data was started. By the end of August 2011, the 14+ years of the reprocessed mission data became available online to users. This reprocessing provided the opportunity to redo and enhance upon an analysis of V7 impacts on L3 data accumulations that was presented at the 2010 EGU General Assembly. This paper will discuss the impact of algorithm changes made in th GPROF retrieval on the Level 2 swath products. Perhaps the most important change in that retrieval was to replacement of a model based a priori database with one created from Precipitation Radar (PR) and TMI brightness temperature (Tb) data. The radar pays a major role in the V7 GPROF (GPROF2010) in determining existence of rain. The level 2 retrieval algorithm also introduced a field providing the probability of rain. This combined use of the PR has some impact on the retrievals and created areas, particularly over ocean, where many areas of low-probability precipitation are retrieved whereas in version 6, these areas contained zero rain rates. This paper will discuss how these impacts get translated to the space/time averaged monthly products that use the GPROF retrievals. The level 3 products discussed are the gridded text product 3G68 and the standard 3A12 and 3B31 products. The paper provides an overview of the changes and explanation of how the level 3 products dealt with the change in the retrieval approach. Using the .25 deg x .25 degree grid, the paper will show that agreement between the swath product and the level 3 remains very high. It will also present comparisons of V6 and V7 GPROF retrievals as seen both at the swath level and the level 3 time/space gridded accumulations. It will show that the various L3 products based on GPROF level 2 retrievals are in close agreement. The paper concludes by outlining some of the challenges of the TRMM version 7 level 3 products