1,132 research outputs found
Multi Sector Planning Tools for Trajectory-Based Operations
This paper discusses a suite of multi sector planning tools for trajectory-based operations that were developed and evaluated in the Airspace Operations Laboratory (AOL) at the NASA Ames Research Center. The toolset included tools for traffic load and complexity assessment as well as trajectory planning and coordination. The situation assessment tools included an integrated suite of interactive traffic displays, load tables, load graphs, and dynamic aircraft filters. The planning toolset allowed for single and multi aircraft trajectory planning and data communication-based coordination of trajectories between operators. Also newly introduced was a real-time computation of sector complexity into the toolset that operators could use in lieu of aircraft count to better estimate and manage sector workload, especially in situations with convective weather. The tools were used during a joint NASA/FAA multi sector planner simulation in the AOL in 2009 that had multiple objectives with the assessment of the effectiveness of the tools being one of them. Current air traffic control operators who were experienced as area supervisors and traffic management coordinators used the tools throughout the simulation and provided their usefulness and usability ratings in post simulation questionnaires. This paper presents these subjective assessments as well as the actual usage data that was collected during the simulation. The toolset was rated very useful and usable overall. Many elements received high scores by the operators and were used frequently and successfully. Other functions were not used at all, but various requests for new functions and capabilities were received that could be added to the toolset
A Comprehensive Emission Inventory of Bbiogenic Volatile Organic Compounds in Europe: Improved Seasonality and Land-cover
Biogenic volatile organic compounds (BVOC) emitted from vegetation are important for the formation of secondary pollutants such as ozone and secondary organic aerosols (SOA) in the atmosphere. Therefore, BVOC emission are an important input for air quality models. To model these emissions with high spatial resolution, the accuracy of the underlying vegetation inventory is crucial. We present a BVOC emission model that accommodates different vegetation inventories and uses satellite-based measurements of greenness instead of pre-defined vegetation periods. This approach to seasonality implicitly treats effects caused by water or nutrient availability, altitude and latitude on a plant stand. Additionally, we test the influence of proposed seasonal variability in enzyme activity on BVOC emissions. In its present setup, the emission model calculates hourly emissions of isoprene, monoterpenes, sesquiterpenes and the oxygenated volatile organic compounds (OVOC) methanol, formaldehyde, formic acid, ethanol, acetaldehyde, acetone and acetic acid. In this study, emissions based on three different vegetation inventories are compared with each other and diurnal and seasonal variations in Europe are investigated for the year 2006. Two of these vegetation inventories require information on tree-cover as an input. We compare three different land-cover inventories (USGS GLCC, GLC2000 and Globcover 2.2) with respect to tree-cover. The often-used USGS GLCC land-cover inventory leads to a severe reduction of BVOC emissions due to a potential miss-attribution of broad-leaved trees and reduced tree-cover compared to the two other land-cover inventories. To account for uncertainties in the land-cover classification, we introduce land-cover correction factors for each relevant land-use category to adjust the tree-cover. The results are very sensitive to these factors within the plausible range. For June 2006, total monthly BVOC emissions decreased up to â27% with minimal and increased up to +71% with maximal factors, while in January 2006, the changes in monthly BVOC emissions were â54 and +56% with minimal and maximal factors, respectively. The new seasonality approach leads to a reduction in the annual emissions compared with non-adjusted data. The strongest reduction occurs in OVOC (up to â32 %), the weakest in isoprene (as little as â19 %). If also enzyme seasonality is taken into account, however, isoprene reacts with the steepest decrease of annual emissions, which are reduced by â44% to â49 %, annual emissions of monoterpenes reduce between â30 and â35 %. The sensitivity of the model to changes in temperature depends on the climatic zone but not on the vegetation inventory. The sensitivity is higher for temperature increases of 3K (+31% to +64 %) than decreases by the same amount (â20 to â35 %). The climatic zones âCold except summerâ and âaridâ are most sensitive to temperature changes in January for isoprene and monoterpenes, respectively, while in June, âpolarâ is most sensitive to temperature for both isoprene and monoterpenes. Our model predicts the oxygenated volatile organic compounds to be the most abundant fraction of the annual European emissions (3571â5328 Gg yrâ1), followed by monoterpenes (2964â4124 Gg yrâ1), isoprene (1450â2650 Gg yrâ1) and sesquiterpenes (150â257 Gg yrâ1). We find regions with high isoprene emissions (most notably the Iberian Peninsula), but overall, oxygenated VOC dominate with 43â45% (depending on the vegetation inventory) contribution to the total annual BVOC emissions in Europe. Isoprene contributes between 18â21 %, monoterpenes 33â36% and sesquiterpenes contribute 1â2 %.We compare the concentrations of biogenic species simulated by an air quality model with measurements of isoprene and monoterpenes in Hohenpeissenberg (Germany) for both summer and winter. The agreement between observed and modelled concentrations is better in summer than in winter. This can partly be explained with the difficulty to model weather conditions in winter accurately, but also with the increased anthropogenic influence on the concentrations of BVOC compounds in winter. Our results suggest that land-cover inventories used to derive tree-cover must be chosen with care. Also, uncertainties in the classification of land-cover pixels must be taken into account and remain high. This problem must be addressed together with the remote sensing community. Our new approach using a greenness index for addressing seasonality of vegetation can be implemented easily in existing models. The importance of OVOC for air quality should be more deeply addressed by future studies, especially in smog chambers. Also, the fate of BVOC from the dominant region of the Iberian Peninsula should be studied more in detail
Geometric shape of invariant manifolds for a class of stochastic partial differential equations
Invariant manifolds play an important role in the study of the qualitative
dynamical behaviors for nonlinear stochastic partial differential equations.
However, the geometric shape of these manifolds is largely unclear. The purpose
of the present paper is to try to describe the geometric shape of invariant
manifolds for a class of stochastic partial differential equations with
multiplicative white noises. The local geometric shape of invariant manifolds
is approximated, which holds with significant likelihood. Furthermore, the
result is compared with that for the corresponding deterministic partial
differential equations
Probing the ISM Near Star Forming Regions with GRB Afterglow Spectroscopy: Gas, Metals, and Dust
We study the chemical abundances of the interstellar medium surrounding high
z gamma-ray bursts (GRBs) through analysis of the damped Lya systems (DLAs)
identified in afterglow spectra. These GRB-DLAs are characterized by large HI
column densities N(HI) and metallicities [M/H] spanning 1/100 to nearly solar,
with median [M/H]>-1. The majority of GRB-DLAs have [M/H] values exceeding the
cosmic mean metallicity of atomic gas at z>2, i.e. if anything, the GRB-DLAs
are biased to larger metallicity. We also observe (i) large [Zn/Fe] values
(>+0.6) and sub-solar Ti/Fe ratios which imply substantial differential
depletion, (ii) large a/Fe ratios suggesting nucleosynthetic enrichment by
massive stars, and (iii) low C^0/C^+ ratios (<10^{-4}). Quantitatively, the
observed depletion levels and C^0/C^+ ratios of the gas are not characteristic
of cold, dense HI clouds in the Galactic ISM. We argue that the GRB-DLAs
represent the ISM near the GRB but not gas directly local to the GRB (e.g. its
molecular cloud or circumstellar material). We compare these observations with
DLAs intervening background quasars (QSO-DLAs). The GRB-DLAs exhibit larger
N(HI) values, higher a/Fe and Zn/Fe ratios, and have higher metallicity than
the QSO-DLAs. We argue that the differences primarily result from
galactocentric radius-dependent differences in the ISM: GRB-DLAs preferentially
probe denser, more depleted, higher metallicity gaslocated in the inner few kpc
whereas QSO-DLAs are more likely to intersect the less dense, less enriched,
outer regions of the galaxy. Finally, we investigate whether dust obscuration
may exclude GRB-DLA sightlines from QSO-DLA samples; we find that the majority
of GRB-DLAs would be recovered which implies little observational bias against
large N(HI) systems.Comment: 16 pages, 9 figures. Submitted to Ap
The Reddest DR3 SDSS/XMM Quasars
We have cross-correlated the SDSS DR3 Schneider et al. (2005) quasar catalog
with the XMM-Newton archive. Color and redshift selections (g - r > 0.5 and 0.9
z < 2.1) result in a sample of 17 red, moderate redshift quasars. The redshift
selection minimizes possible contamination due to host galaxy emission and
Lyalpha forest absorption. Both optical and X-ray information are required to
distinguish between the two likely remaining causes of the red colors: 1)
dust-reddening and 2) an intrinsically red continuum. We find that 7 of 17
quasars can be classified as probable `intrinsically red' objects. These 7
quasars have unusually broad MgII emission lines (=10,500 km s^{-1}),
moderately flat, but unabsorbed X-ray spectra =1.66+/-0.08), and low
accretion rates (mdot/mdot_{Edd}} ~ 0.01). We suggest low accretion rates as a
possible physical explanation for quasars with intrinsically red optical
continua. We find that 8 of 17 quasars can be classified as dust-reddened.
Three of these have upper-limits on the absorption column from X-ray spectral
fits of N_H = 3-13 x 10^{22} cm^2, while the other five quasars must be
absorbed by at least N_H = 10^{23} cm^2 in order to be consistent with a
comparably selected alpha_{ox}-l_{uv} distribution. Two objects in the sample
are unclassified.Comment: 20 pages, 12 figures, Accepted for publication in Ap
Effects of various meteorological conditions and spatial emissionresolutions on the ozone concentration and ROG/NO<sub>x</sub> limitationin the Milan area (I)
The three-dimensional photochemical model UAM-V is used to investigate the effects of various meteorological conditions and of the coarseness of emission inventories on the ozone concentration and ROG/NO<sub>x</sub> limitation of the ozone production in the Po Basin in the northern part of Italy. As a base case, the high ozone episode with up to 200ppb on 13 May 1998 was modelled and previously thoroughly evaluated with measurements gained during a large field experiment. Systematic variations in meteorology are applied to mixing height, air temperature, specific humidity and wind speed. Three coarser emission inventories are obtained by resampling from 3x3km<sup>2</sup> up to 54x54km<sup>2</sup> emission grids. The model results show that changes in meteorological input files strongly influence ozone in this area. For instance, temperature changes peak ozone by 10.1ppb/°C and the ozone concentrations in Milan by 2.8ppb/°C. The net ozone formation in northern Italy is more strongly temperature than humidity dependent, while the humidity is very important for the ROG/NO<sub>x</sub> limitation of the ozone production. For all meteorological changes (e.g. doubling the mixing height), the modelled peak ozone remains ROG limited. A strong change towards NO<sub>x</sub> sensitivity in the ROG limited areas is only found if much coarser emission inventories were applied. Increasing ROG limited areas with increasing wind speed are found, because the ROG limited ozone chemistry induced by point sources is spread over a larger area. Simulations without point sources tend to increase the NO<sub>x</sub> limited areas
New Improved Photometric Redshifts of Galaxies in the HDF
We report new improved photometric redshifts of 1048 galaxies in the Hubble
Deep Field (HDF). A standard chi^2 minimizing method is applied to seven-color
UBVIJHK photometry by Fernandez-Soto, Lanzetta, & Yahil (1999). We use 187
template SEDs representing a wide variety of morphology and age of observed
galaxies based on a population synthesis model by Kodama & Arimoto (1997). We
introduce two new recipes. First, the amount of the internal absorption is
changed as a free parameter in the range of E(B-V)=0.0 to 0.5 with an interval
of 0.1. Second, the absorption due to intergalactic HI clouds is also changed
by a factor of 0.5, 1.0, and 1.5 around the opacity given by Madau (1995). The
total number of template SEDs is thus 187x6x3=3,366, except for the redshift
grid. The dispersion sigma_z of our photometric redshifts with respect to
spectroscopic redshifts is sigma_z=0.08 and 0.24 for z2, respectively,
which are smaller than the corresponding values (sigma_z=0.09 and 0.45) by
Fernandez-Soto et al. Improvement is significant, especially in z>2. This is
due to smaller systematic errors which are largely reduced mainly by including
three opacities due to intergalactic HI clouds. We discuss redshift
distribution N(z) and cosmic star formation rate based on our new photometric
redshifts.Comment: 24 pages including 16 eps figures; accepted for publication in Ap
Gemini-South + FLAMINGOS Demonstration Science: Near-Infrared Spectroscopy of the z=5.77 Quasar SDSS J083643.85+005453.3
We report an infrared 1-1.8 micron (J+H-bands), low-resolution (R=450)
spectrogram of the highest-redshift radio-loud quasar currently known, SDSS
J083643.85+005453.3, obtained during the spectroscopic commissioning run of the
FLAMINGOS multi-object, near-infrared spectrograph at the 8m Gemini-South
Observatory. These data show broad emission from both CIV 1549 and CIII] 1909,
with strengths comparable to lower-redshift quasar composite spectra. The
implication is that there is substantial enrichment of the quasar environment,
even at times less than a billion years after the Big Bang. The redshift
derived from these features is z = 5.774 +/- 0.003, more accurate and slightly
lower than the z = 5.82 reported in the discovery paper based on the
partially-absorbed Lyman-alpha emission line. The infrared continuum is
significantly redder than lower-redshift quasar composites. Fitting the
spectrum from 1.0 to 1.7 microns with a power law f(nu) ~ nu^(-alpha), the
derived power law index is alpha = 1.55 compared to the average continuum
spectral index = 0.44 derived from the first SDSS composite quasar.
Assuming an SMC-like extinction curve, we infer a color excess of E(B-V) = 0.09
+/- 0.01 at the quasar redshift. Only approximately 6% of quasars in the
optically-selected Sloan Digital Sky Survey show comparable levels of dust
reddening.Comment: 10 pages, 1 figure; to appear in the Astrophysical Journal Letter
Role of ammonia in European air quality with changing land and ship emissions between 1990 and 2030
The focus of this modeling study is on the role of ammonia in European air quality in the past as well as in the future. Ammonia emissions have not decreased as much as the other secondary inorganic aerosol (SIA) precursors â nitrogen oxides (NOx) and sulfur dioxide (SO2) â since the 1990s and are still posing problems for air quality and the environment. In this study, air quality simulations were performed with a regional chemical transport model at decadal intervals between 1990 and 2030 to understand the changes in the chemical species associated with SIA under varying land and ship emissions. We analyzed the changes in air concentrations of ammonia, nitric acid, ammonium, particulate nitrate and sulfate as well as changes in the dry and wet deposition of ammonia and ammonium. The results show that the approximately 40â% decrease in SIA concentrations between 1990 and 2010 was mainly due to reductions in NOx and SO2 emissions. The ammonia concentrations on the other hand decreased only near the high-emission areas such as the Netherlands and northern Italy by about 30â%, while there was a slight increase in other parts of Europe. Larger changes in concentrations occurred mostly during the first period (1990â2000). The model results indicate a transition period after 2000 for the composition of secondary inorganic aerosols due to a larger decrease in sulfate concentrations than nitrate. Changes between 2010 and 2030 â assuming the current legislation (CLE) scenario â are predicted to be smaller than those achieved earlier for all species analyzed in this study. The scenario simulations suggest that if ship emissions will be regulated more strictly in the future, SIA formation will decrease especially around the Benelux area, North Sea, Baltic Sea, English Channel and the Mediterranean region, leaving more ammonia in the gas phase, which would lead to an increase in dry deposition. In the north of the domain, the decrease in SIA would be mainly due to reduced formation of particulate nitrate, while the change around the Mediterranean would be caused mainly by decreased sulfate aerosol concentrations. One should also keep in mind that potentially higher temperatures in the future might increase the evaporation of ammonium nitrate to form its gaseous components NH3 and HNO3. Sensitivity tests with reduced NOx and NH3 emissions indicate a shift in the sensitivity of aerosol formation from NH3 towards NOx emissions between 1990 and 2030 in most of Europe except the eastern part of the model domain.The focus of this modeling study is on the role of ammonia in European air quality in the past as well as in the future Ammonia emissions have not decreased as much as the other secondary inorganic aerosol (SIA) precursors - nitrogen oxides (NOx) and sulfur dioxide (SO2) - since the 1990s and are still posing problems for air quality and the environment. In this study, air quality simulations were performed with a regional chemical transport model at decadal intervals between 1990 and 2030 to understand the changes in the chemical species associated with SIA under varying land and ship emissions. We analyzed the changes in air concentrations of ammonia, nitric acid, ammonium, particulate nitrate and sulfate as well as changes in the dry and wet deposition of ammonia and ammonium. The results show that the approximately 40 % decrease in SIA concentrations between 1990 and 2010 was mainly due to reductions in NOx and SO2 emissions. The ammonia concentrations on the other hand decreased only near the high-emission areas such as the Netherlands and northern Italy by about 30 %, while there was a slight increase in other parts of Europe. Larger changes in concentrations occurred mostly during the first period (1990-2000). The model results indicate a transition period after 2000 for the composition of secondary inorganic aerosols due to a larger decrease in sulfate concentrations than nitrate. Changes between 2010 and 2030 - assuming the current legislation (CLE) scenario - are predicted to be smaller than those achieved earlier for all species analyzed in this study. The scenario simulations suggest that if ship emissions will be regulated more strictly in the future, SIA formation will decrease especially around the Benelux area, North Sea, Baltic Sea, English Channel and the Mediterranean region, leaving more ammonia in the gas phase, which would lead to an increase in dry deposition. In the north of the domain, the decrease in SIA would be mainly due to reduced formation of particulate nitrate, while the change around the Mediterranean would be caused mainly by decreased sulfate aerosol concentrations. One should also keep in mind that potentially higher temperatures in the future might increase the evaporation of ammonium nitrate to form its gaseous components NH3 and HNO3. Sensitivity tests with reduced NOx and NH3 emissions indicate a shift in the sensitivity of aerosol formation from NH3 towards NOx emissions between 1990 and 2030 in most of Europe except the eastern part of the model domain.Peer reviewe
Monteggia fracture associated with ipsilateral intercondylar distal humeral fracture with posterior interosseous nerve palsy: case report, medico-legal implications, and methodological assessment analysis
BACKGROUND: The Monteggia fracture, defined as a fracture of the proximal third of the ulnar shaft associated with an anterior or posterior dislocation of the proximal radial epiphysis, is a serious injury accounting for 0.7% of all elbow fractures and dislocations in adults. For adult patients, good results can only be obtained through early diagnosis and adequate surgical treatment. Monteggia fracture-dislocations associated with distal humeral fracture are extremely rare injuries in adults and there are few cases described in the literature. Medico-legal implications arising from such conditions have a host of complexities that cannot be discounted.CASE REPORT: This case report revolves around a patient affected by a type I Monteggia fracture-dislocation, according to the Bado classification, associated with an ipsilateral intercondylar distal humeral fracture. To our knowledge, this combination of lesions has never been reported before in adult patients. A positive result was obtained due to early diagnosis, achievement of anatomical reduction, and optimal stabilization with internal fixation which made it possible to achieve early functional recovery.CONCLUSIONS: Monteggia fracture -dislocations associated with ipsilateral intercondylar distal humeral fracture are extremely rare in adults. In the case herein reported, a favorable outcome was obtained due to early diagnosis, achievement of anatomical reduction and management with internal fixation with plate and screws, as well as early functional training. Misdiagnosis makes such lesions risky in terms of potentially delayed treatment, increasing the need for surgical interventions and the possibility of high-risk complications and disabling sequelae, with possible medico -legal implications. In the case of unrecognized injuries under urgent circumstances, the injuries may become chronic, making the treatment more complex. The ultimate outcomes of a misdiagnosed Monteggia lesion can lead to very serious functional and aesthetic damage
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