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DUCHAMP, GÉRARD, et JEAN-GABRIEL LUQUE. « LAZARD'S ELIMINATION (IN TRACES) IS FINITE-STATE RECOGNIZABLE ». International Journal of Algebra and Computation 17, no 01 (février 2007) : 53–60. http://dx.doi.org/10.1142/s0218196707003433.
Texte intégralRésumé :
We prove that the codes issued from the elimination of any sub-alphabet in a trace monoid are finite-state recognizable. This implies in particular that the transitive factorizations of the trace monoids are recognizable by (boolean) finite-state automata.
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Köcher, Chris, Dietrich Kuske et Olena Prianychnykova. « The inclusion structure of partially lossy queue monoids and their trace submonoids ». RAIRO - Theoretical Informatics and Applications 52, no 1 (janvier 2018) : 55–86. http://dx.doi.org/10.1051/ita/2018003.
Texte intégralRésumé :
We model the behavior of a lossy fifo-queue as a monoid of transformations that are induced by sequences of writing and reading. To have a common model for reliable and lossy queues, we split the alphabet of the queue into two parts: the forgettable letters and the letters that are transmitted reliably. We describe this monoid by means of a confluent and terminating semi-Thue system and then study some of the monoid’s algebraic properties. In particular, we characterize completely when one such monoid can be embedded into another as well as which trace monoids occur as submonoids. Surprisingly, these are precisely those trace monoids that embed into the direct product of two free monoids – which gives a partial answer to a question raised by Diekert et al. at STACS 1995.
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Husainov, Ahmet A. « Cubical Sets and Trace Monoid Actions ». Scientific World Journal 2013 (2013) : 1–9. http://dx.doi.org/10.1155/2013/285071.
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This paper is devoted to connections between trace monoids and cubical sets. We prove that the category of trace monoids is isomorphic to the category of generalized tori and it is a reflective subcategory of the category of cubical sets. Adjoint functors between the categories of cubical sets and trace monoid actions are constructed. These functors carry independence preserving morphisms in the independence preserving morphisms. This allows us to build adjoint functors between the category of weak asynchronous systems and the category of higher dimensional automata.
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Janicki, Ryszard, et Łukasz Mikulski. « Algebraic Structure of Step Traces and Interval Traces ». Fundamenta Informaticae 175, no 1-4 (28 septembre 2020) : 253–80. http://dx.doi.org/10.3233/fi-2020-1956.
Texte intégralRésumé :
Traces and their extensions as comtraces, step traces and interval traces are quotient monoids over sequences or step sequences that play an important role in the formal analysis and verification of concurrent systems. Step traces are generalizations of comtraces and classical traces while interval traces are specialized traces that can deal with interval order semantics. The algebraic structures and their properties as projections, hidings, canonical forms and other invariants are very well established for traces and fairly well established for comtraces. For step traces and interval traces they are the main subject of this paper.
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Hygate, Alexander P. S., J. M. Diederik Kruijssen, Mélanie Chevance, Andreas Schruba, Daniel T. Haydon et Steven N. Longmore. « An uncertainty principle for star formation – IV. On the nature and filtering of diffuse emission ». Monthly Notices of the Royal Astronomical Society 488, no 2 (25 juillet 2019) : 2800–2824. http://dx.doi.org/10.1093/mnras/stz1779.
Texte intégralRésumé :
Abstract Diffuse emission is observed in galaxies in many tracers across the electromagnetic spectrum, including tracers of star formation, such as H α and ultraviolet (UV), and tracers of gas mass, such as carbon monoxide (CO) transition lines and the 21-cm line of atomic hydrogen (H i). Its treatment is key to extracting meaningful information from observations such as cloud-scale star formation rates. Finally, studying diffuse emission can reveal information about the physical processes taking place in the interstellar medium, such as chemical transitions and the nature of stellar feedback (through the photon escape fraction). We present a physically motivated method for decomposing astronomical images containing both diffuse emission and compact regions of interest, such as H ii regions or molecular clouds, into diffuse and compact component images through filtering in Fourier space. We have previously presented a statistical method for constraining the evolutionary timeline of star formation and mean separation length between compact star-forming regions with galaxy-scale observations. We demonstrate how these measurements are biased by the presence of diffuse emission in tracer maps and that by using the mean separation length as a critical length-scale to separate diffuse emission from compact emission, we are able to remove its biasing effect. Furthermore, this method provides, without the need for interferometry or ancillary spectral data, a measurement of the diffuse emission fraction in input tracer maps and decomposed diffuse and compact emission maps for further analysis.
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BERTONI, ALBERTO, et ROBERTO RADICIONI. « APPROXIMATING THE MEAN SPEEDUP IN TRACE MONOIDS ». International Journal of Foundations of Computer Science 19, no 03 (juin 2008) : 497–511. http://dx.doi.org/10.1142/s0129054108005796.
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Traces can be viewed as parallel processes and the "mean speedup" of a trace monoid has been introduced as a measure of "intrinsic parallelism" of the monoid. We study the problem of computing the mean speedup under two conditions: uniform distribution on the words of given length and uniform distribution on the traces of given height. In the first case, we give an approximability result showing a probabilistic fully polynomial time approximation scheme, while, in the second case, we prove that the problem is NP-hard to approximate within n1-c for every ∊ > 0, unless NP = coR. A further consequence is the hardness of the problem of generating traces of a given height uniformly at random.
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Dionatos, Odysseas, Lars E. Kristensen, Mario Tafalla, Manuel Güdel et Magnus Persson. « Feedback of molecular outflows from protostars in NGC 1333 revealed by Herschel and Spitzer spectro-imaging observations ». Astronomy & ; Astrophysics 641 (septembre 2020) : A36. http://dx.doi.org/10.1051/0004-6361/202037684.
Texte intégralRésumé :
Context. Far infrared cooling of excited gas around protostars has been predominantly studied in the context of pointed observations. Large-scale spectral maps of star forming regions enable the simultaneous, comparative study of the gas excitation around an ensemble of sources at a common frame of reference, therefore, providing direct insights in the multitude of physical processes involved. Aims. We employ extended spectral-line maps to decipher the excitation, the kinematical, and dynamical processes in NGC 1333 as revealed by a number of different molecular and atomic lines, aiming to set a reference for the applicability and limitations of different tracers in constraining particular physical processes. Methods. We reconstructed line maps for H2, CO, H2O, and [C I] using data obtained with the Spitzer infrared spectrograph and the Herschel HIFI and SPIRE instruments. We compared the morphological features revealed in the maps and derive the gas excitation conditions for regions of interest employing local thermodynamic equilibrium (LTE) and non-LTE methods. We also calculated the kinematical and dynamical properties for each outflow tracer in a consistent manner for all observed outflows driven by protostars in NGC 1333. We finally measured the water abundance in outflows with respect to carbon monoxide and molecular hydrogen. Results. CO and H2 are highly excited around B-stars and, at lower, levels trace protostellar outflows. H2O emission is dominated by a moderately fast component associated with outflows. H2O also displays a weak, narrow-line component in the vicinity of B-stars associated to their ultraviolet (UV) field. This narrow component is also present in a few of outflows, indicating UV radiation generated in shocks. Intermediate J CO lines appear brightest at the locations traced by the narrow H2O component, indicating that beyond the dominating collisional processes, a secondary, radiative excitation component can also be active. The morphology, kinematics, excitation, and abundance variations of water are consistent with its excitation and partial dissociation in shocks. Water abundance ranges between 5 × 10−7 and ~10−5, with the lower values being more representative. Water is brightest and most abundant around IRAS 4A, which is consistent with the latter hosting a hot corino source. [C I] traces dense and warm gas in the envelopes surrounding protostars. Outflow mass flux is highest for CO and decreases by one and two orders of magnitude for H2 and H2O, respectively. Conclusions. Large-scale spectral line maps can provide unique insights into the excitation of gas in star-forming regions. A comparative analysis of line excitation and morphologies at different locations allows us to decipher the dominant excitation conditions in each region in addition to isolating exceptional cases.
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García, A. R., R. Volkamer, L. T. Molina, M. J. Molina, J. Samuelson, J. Mellqvist, B. Galle, S. C. Herndon et C. E. Kolb. « Separation of emitted and photochemical formaldehyde in Mexico City using a statistical analysis and a new pair of gas-phase tracers ». Atmospheric Chemistry and Physics Discussions 5, no 6 (11 novembre 2005) : 11583–615. http://dx.doi.org/10.5194/acpd-5-11583-2005.
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Abstract. Photochemical pollution control strategies require an understanding of photochemical oxidation precursors, making it important to distinguish between primary and secondary sources of HCHO. Estimates for the relative strengths of primary and secondary sources of formaldehyde (HCHO) were obtained using a statistical regression analysis with time series data of carbon monoxide (CO) and glyoxal (CHOCHO) measured in the Mexico City Metropolitan Area (MCMA) during the spring of 2003. Differences between Easter week and more typical weeks are evaluated. The use of CO-CHOCHO as HCHO tracers is more suitable for differentiating primary and secondary sources than CO-O3. The application of the CO-O3 tracer pair to mobile laboratory data suggests a potential in-city source of background HCHO. A significant amount of HCHO observed in the MCMA is associated with primary emissions.
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Garcia, A. R., R. Volkamer, L. T. Molina, M. J. Molina, J. Samuelson, J. Mellqvist, B. Galle, S. C. Herndon et C. E. Kolb. « Separation of emitted and photochemical formaldehyde in Mexico City using a statistical analysis and a new pair of gas-phase tracers ». Atmospheric Chemistry and Physics 6, no 12 (9 octobre 2006) : 4545–57. http://dx.doi.org/10.5194/acp-6-4545-2006.
Texte intégralRésumé :
Abstract. Photochemical pollution control strategies require an understanding of photochemical oxidation precursors, making it important to distinguish between primary and secondary sources of HCHO. Estimates for the relative strengths of primary and secondary sources of formaldehyde (HCHO) were obtained using a statistical regression analysis with time series data of carbon monoxide (CO) and glyoxal (CHOCHO) measured in the Mexico City Metropolitan Area (MCMA) during the spring of 2003. Differences between Easter week and more typical weeks are evaluated. The use of CO-CHOCHO as HCHO tracers is more suitable for differentiating primary and secondary sources than CO-O3. The application of the CO-O3 tracer pair to mobile laboratory data suggests a potential in-city source of background HCHO. A significant amount of HCHO observed in the MCMA is associated with primary emissions.
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MÉTIVIER, YVES, et BRIGITTE ROZOY. « ON THE STAR OPERATION IN FREE PARTIALLY COMMUTATIVE MONOIDS ». International Journal of Foundations of Computer Science 02, no 03 (septembre 1991) : 257–65. http://dx.doi.org/10.1142/s0129054191000169.
Texte intégralRésumé :
Let X be a finite set of traces. In this paper we show that each connected iterative factor of X* has a power which may be expressed as the conjugate of a product of the elements of X. From this property we deduce that if the star of a finite set of traces is recognizable then maximal connected factors of iterative factors of X* have a power which is the conjugate of a product of the elements of X.
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Abalos, M., W. J. Randel, D. E. Kinnison et E. Serrano. « Quantifying tracer transport in the tropical lower stratosphere using WACCM ». Atmospheric Chemistry and Physics Discussions 13, no 5 (21 mai 2013) : 13245–83. http://dx.doi.org/10.5194/acpd-13-13245-2013.
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Abstract. The zonal mean transport of ozone and carbon monoxide (CO) near the tropical tropopause is investigated using the Whole-Atmosphere Community Climate Model version 4 (WACCM4). The variability in temperature, ozone and CO in the model shows good agreement with satellite and balloon observations. Modeled temperature and tracers exhibit large and closely coupled annual cycles in the tropical lower stratosphere, as in the observations. The thermodynamic and tracer budgets in the model are analyzed based on the Transformed Eulerian Mean (TEM) framework on log-pressure coordinates and also using the isentropic formulation. Results show that the coupled seasonal cycles are mainly forced by tropical upwelling over altitudes with large vertical tracer gradients, in agreement with previous observational studies. The model also allows explicit calculation of eddy transport terms, which make an important contribution to ozone tendencies in the tropical lower stratosphere. The character of the eddy fluxes changes with altitude. At higher levels (~2 km above the cold point tropopause), isentropic eddy transport occurs during winter and spring in each hemisphere in the sub-tropics, associated with transient Rossby waves acting on strong background latitudinal gradients. At lower altitudes, close to the tropical tropopause, there is a maximum in horizontal eddy transport during boreal summer associated with the Asian monsoon anticyclone. Sub-seasonal variability in ozone and CO, tied to fluctuations in temperature, is primarily driven by transient tropical upwelling. In isentropic coordinates, the overall tracer budgets are similar to the log-pressure results, highlighting cross-isentropic mean advection as the main term in the balance. However, in isentropic coordinates the tracer variability is largely reduced on both seasonal and sub-seasonal timescales, because the tracer and temperature fluctuations are highly correlated (as a response to upwelling).
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Abalos, M., W. J. Randel, D. E. Kinnison et E. Serrano. « Quantifying tracer transport in the tropical lower stratosphere using WACCM ». Atmospheric Chemistry and Physics 13, no 21 (1 novembre 2013) : 10591–607. http://dx.doi.org/10.5194/acp-13-10591-2013.
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Abstract. The zonal mean transport of ozone and carbon monoxide (CO) near the tropical tropopause is investigated using the Whole-Atmosphere Community Climate Model version 4 (WACCM4). The variability in temperature, ozone and CO in the model shows good agreement with satellite and balloon observations. Modeled temperature and tracers exhibit large and closely coupled annual cycles in the tropical lower stratosphere, as in the observations. The thermodynamic and tracer budgets in the model are analyzed based on the Transformed Eulerian Mean (TEM) framework on log-pressure coordinates and also using the isentropic formulation. Results show that the coupled seasonal cycles are mainly forced by tropical upwelling over altitudes with large vertical tracer gradients, in agreement with previous observational studies. The model also allows explicit calculation of eddy transport terms, which make an important contribution to ozone tendencies in the tropical lower stratosphere. The character of the eddy fluxes changes with altitude. At higher levels (~2 km above the cold point tropopause), isentropic eddy transport occurs during winter and spring in each hemisphere in the sub-tropics, associated with transient Rossby waves acting on strong background latitudinal gradients. At lower altitudes, close to the tropical tropopause, there is a maximum in horizontal eddy transport during boreal summer associated with the Asian monsoon anticyclone. Sub-seasonal variability in ozone and CO, tied to fluctuations in temperature, is primarily driven by transient tropical upwelling. In isentropic coordinates, the overall tracer budgets are similar to the log-pressure results, highlighting cross-isentropic advection as the main term in the time-mean balance, with large seasonality above the tropopause. However, in isentropic coordinates the tracer variability is largely reduced on both seasonal and sub-seasonal timescales, because tracer fluctuations are highly correlated with temperature (as a response to upwelling).
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Frey, W., R. Schofield, P. Hoor, D. Kunkel, F. Ravegnani, A. Ulanovsky, S. Viciani, F. D'Amato et T. P. Lane. « The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS) ». Atmospheric Chemistry and Physics Discussions 15, no 1 (14 janvier 2015) : 1041–91. http://dx.doi.org/10.5194/acpd-15-1041-2015.
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Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection to a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.
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Frey, W., R. Schofield, P. Hoor, D. Kunkel, F. Ravegnani, A. Ulanovsky, S. Viciani, F. D'Amato et T. P. Lane. « The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS) ». Atmospheric Chemistry and Physics 15, no 11 (12 juin 2015) : 6467–86. http://dx.doi.org/10.5194/acp-15-6467-2015.
Texte intégralRésumé :
Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection with a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere, but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.
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Rozoy, Brigitte, et P. S. Thiagarajan. « Event structures and trace monoids ». Theoretical Computer Science 91, no 2 (décembre 1991) : 285–313. http://dx.doi.org/10.1016/0304-3975(91)90087-i.
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Shahbazyan, K. V., et Yu H. Shoukourian. « Inclusion problems in trace monoids ». Cybernetics and Systems Analysis 46, no 4 (juillet 2010) : 546–53. http://dx.doi.org/10.1007/s10559-010-9231-0.
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Bacer, Sara, Theodoros Christoudias et Andrea Pozzer. « Projection of North Atlantic Oscillation and its effect on tracer transport ». Atmospheric Chemistry and Physics 16, no 24 (16 décembre 2016) : 15581–92. http://dx.doi.org/10.5194/acp-16-15581-2016.
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Abstract. The North Atlantic Oscillation (NAO) plays an important role in the climate variability of the Northern Hemisphere, with significant consequences on long-range pollutant transport. We investigate the evolution of pollutant transport in the 21st century influenced by the NAO under a global climate change scenario. We use a free-running simulation performed by the ECHAM/MESSy Atmospheric Chemistry (EMAC) model coupled with the ocean general circulation model MPIOM, covering the period from 1950 until 2100. Similarly to other works, the model shows a future northeastward shift of the NAO centres of action and a weak positive trend of the NAO index (over 150 years). Moreover, we find that NAO trends (computed over periods shorter than 30 years) will continue to oscillate between positive and negative values in the future. To investigate the NAO effects on transport we consider carbon monoxide tracers with exponential decay and constant interannual emissions. We find that at the end of the century, the south-western Mediterranean and northern Africa will, during positive NAO phases, see higher pollutant concentrations with respect to the past, while a wider part of northern Europe will, during positive NAO phases, see lower pollutant concentrations. Such results are confirmed by the changes observed in the future for tracer concentration and vertically integrated tracer transport, differentiating the cases of “high NAO” and “low NAO” events.
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Kunc, Michal, et Jan Meitner. « The Generalized Rank of Trace Languages ». International Journal of Foundations of Computer Science 30, no 01 (janvier 2019) : 135–69. http://dx.doi.org/10.1142/s0129054119400070.
Texte intégralRésumé :
Given a partially commutative alphabet and a set of words [Formula: see text], the rank of [Formula: see text] expresses the amount of shuffling required to produce a word belonging to [Formula: see text] from two words whose concatenation belongs to the closure of [Formula: see text] with respect to the partial commutation. In this paper, the notion of rank is generalized from concatenations of two words to an arbitrary fixed number of words. In this way, an infinite sequence of non-negative integers and infinity is assigned to every set of words. It is proved that in the case of alphabets defining free commutative monoids, as well as in the more general case of direct products of free monoids, sequences of ranks of regular sets are exactly non-decreasing sequences that are eventually constant. On the other hand, by uncovering a relationship between rank sequences of regular sets and rational series over the min-plus semiring, it is shown that already for alphabets defining free products of free commutative monoids, rank sequences need not be eventually periodic.
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Shah, Kasturi, et Peter H. Haynes. « How heating tracers drive self-lofting long-lived stratospheric anticyclones : simple dynamical models ». Weather and Climate Dynamics 5, no 2 (22 avril 2024) : 559–85. http://dx.doi.org/10.5194/wcd-5-559-2024.
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Abstract. Long-lived “bubbles” of wildfire smoke or volcanic aerosol have recently been observed in the stratosphere, co-located with ozone, carbon monoxide, and water vapour anomalies. These bubbles often survive for several weeks, during which time they ascend through vertical distances of 15 km or more. Meteorological analysis data suggest that this aerosol is contained within strong, persistent anticyclonic vortices. Absorption of solar radiation by the aerosol is hypothesised to drive the ascent of the bubbles, but the dynamics of how this heating gives rise to a single-sign anticyclonic vorticity anomaly have thus far been unclear. We present a description of heating-driven stratospheric vortices, based on an axisymmetric balanced model. The simplest version of this model includes a specified localised heating moving upwards at fixed velocity and produces a steadily translating solution with a single-signed anticyclonic vortex co-located with the heating, with corresponding temperature anomalies forming a vertical dipole, matching observations. A more complex version includes the two-way interaction between a heating tracer, representing the aerosol, and the dynamics. An evolving tracer provides heating which drives a secondary circulation, and this in turn transports the tracer. Through this two-way interaction an initial distribution of tracer drives a circulation and forms a self-lofting tracer-filled anticyclonic vortex. Scaling arguments show that upward velocity is proportional to heating magnitude, but the magnitude of peak quasigeostrophic vorticity is O(f) (f is the Coriolis parameter) and independent of the heating magnitude. Estimates of vorticity from observations match our theoretical predictions. We discuss 3-D effects such as vortex stripping and dispersion of tracer outside the vortex by the large-scale flow, which cannot be captured explicitly by the axisymmetric model and are likely to be important in the real atmosphere. The large O(f) vorticity of the fully developed anticyclones explains their observed persistence and their effective confinement of tracers. To further investigate the early stages of formation of tracer-filled vortices, we consider an idealised configuration of a homogeneous tracer layer. A linearised calculation reveals that the upper part of the layer is destabilised due to the decrease in tracer concentrations with height there, which sets up a self-reinforcing effect where upward lofting of tracer results in stronger heating and hence stronger lofting. Small amplitude disturbances form isolated tracer plumes that ascend out of the initial layer, indicative of a self-organisation of the flow. The relevance of these idealised models to formation and persistence of tracer-filled vortices in the real atmosphere is discussed, and it is suggested that a key factor in their formation is the time taken to reach the fully developed stage, which is shorter for strong heating rates.
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Silva, Pedro V. « The homomorphism problem for trace monoids ». Theoretical Computer Science 307, no 1 (septembre 2003) : 199–215. http://dx.doi.org/10.1016/s0304-3975(03)00101-4.
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Budisulistiorini, S. H., X. Li, S. T. Bairai, J. Renfro, Y. Liu, Y. J. Liu, K. A. McKinney et al. « Examining the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol formation during the 2013 Southern Oxidant and Aerosol Study (SOAS) at the Look Rock, Tennessee ground site ». Atmospheric Chemistry and Physics 15, no 15 (13 août 2015) : 8871–88. http://dx.doi.org/10.5194/acp-15-8871-2015.
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Abstract. A suite of offline and real-time gas- and particle-phase measurements was deployed at Look Rock, Tennessee (TN), during the 2013 Southern Oxidant and Aerosol Study (SOAS) to examine the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol (SOA) formation. High- and low-time-resolution PM2.5 samples were collected for analysis of known tracer compounds in isoprene-derived SOA by gas chromatography/electron ionization-mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography/diode array detection-electrospray ionization-high-resolution quadrupole time-of-flight mass spectrometry (UPLC/DAD-ESI-HR-QTOFMS). Source apportionment of the organic aerosol (OA) was determined by positive matrix factorization (PMF) analysis of mass spectrometric data acquired on an Aerodyne Aerosol Chemical Speciation Monitor (ACSM). Campaign average mass concentrations of the sum of quantified isoprene-derived SOA tracers contributed to ~ 9 % (up to 28 %) of the total OA mass, with isoprene-epoxydiol (IEPOX) chemistry accounting for ~ 97 % of the quantified tracers. PMF analysis resolved a factor with a profile similar to the IEPOX-OA factor resolved in an Atlanta study and was therefore designated IEPOX-OA. This factor was strongly correlated (r2 > 0.7) with 2-methyltetrols, C5-alkene triols, IEPOX-derived organosulfates, and dimers of organosulfates, confirming the role of IEPOX chemistry as the source. On average, IEPOX-derived SOA tracer mass was ~ 26 % (up to 49 %) of the IEPOX-OA factor mass, which accounted for 32 % of the total OA. A low-volatility oxygenated organic aerosol (LV-OOA) and an oxidized factor with a profile similar to 91Fac observed in areas where emissions are biogenic-dominated were also resolved by PMF analysis, whereas no primary organic aerosol (POA) sources could be resolved. These findings were consistent with low levels of primary pollutants, such as nitric oxide (NO ~ 0.03 ppb), carbon monoxide (CO ~ 116 ppb), and black carbon (BC ~ 0.2 μg m−3). Particle-phase sulfate is fairly correlated (r2 ~ 0.3) with both methacrylic acid epoxide (MAE)/hydroxymethyl-methyl-α-lactone (HMML)- (henceforth called methacrolein (MACR)-derived SOA tracers) and IEPOX-derived SOA tracers, and more strongly correlated (r2 ~ 0.6) with the IEPOX-OA factor, in sum suggesting an important role of sulfate in isoprene SOA formation. Moderate correlation between the MACR-derived SOA tracer 2-methylglyceric acid with sum of reactive and reservoir nitrogen oxides (NOy; r2 = 0.38) and nitrate (r2 = 0.45) indicates the potential influence of anthropogenic emissions through long-range transport. Despite the lack of a clear association of IEPOX-OA with locally estimated aerosol acidity and liquid water content (LWC), box model calculations of IEPOX uptake using the simpleGAMMA model, accounting for the role of acidity and aerosol water, predicted the abundance of the IEPOX-derived SOA tracers 2-methyltetrols and the corresponding sulfates with good accuracy (r2 ~ 0.5 and ~ 0.7, respectively). The modeling and data combined suggest an anthropogenic influence on isoprene-derived SOA formation through acid-catalyzed heterogeneous chemistry of IEPOX in the southeastern US. However, it appears that this process was not limited by aerosol acidity or LWC at Look Rock during SOAS. Future studies should further explore the extent to which acidity and LWC as well as aerosol viscosity and morphology becomes a limiting factor of IEPOX-derived SOA, and their modulation by anthropogenic emissions.
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Budisulistiorini, S. H., X. Li, S. T. Bairai, J. Renfro, Y. Liu, Y. J. Liu, K. A. McKinney et al. « Examining the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol formation during the 2013 Southern Oxidant and Aerosol Study (SOAS) at the Look Rock, Tennessee, ground site ». Atmospheric Chemistry and Physics Discussions 15, no 5 (10 mars 2015) : 7365–417. http://dx.doi.org/10.5194/acpd-15-7365-2015.
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Abstract. A suite of offline and real-time gas- and particle-phase measurements was deployed at Look Rock, Tennessee (TN), during the 2013 Southern Oxidant and Aerosol Study (SOAS) to examine the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol (SOA) formation. High- and low-time resolution PM2.5 samples were collected for analysis of known tracer compounds in isoprene-derived SOA by gas chromatography/electron ionization-mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography/diode array detection-electrospray ionization-high-resolution quadrupole time-of-flight mass spectrometry (UPLC/DAD-ESI-HR-QTOFMS). Source apportionment of the organic aerosol (OA) was determined by positive matrix factorization (PMF) analysis of mass spectrometric data acquired on an Aerodyne Aerosol Chemical Speciation Monitor (ACSM). Campaign average mass concentrations of the sum of quantified isoprene-derived SOA tracers contributed to ~9% (up to 26%) of the total OA mass, with isoprene-epoxydiol (IEPOX) chemistry accounting for ~97% of the quantified tracers. PMF analysis resolved a factor with a profile similar to the IEPOX-OA factor resolved in an Atlanta study and was therefore designated IEPOX-OA. This factor was strongly correlated (r2>0.7) with 2-methyltetrols, C5-alkene triols, IEPOX-derived organosulfates, and dimers of organosulfates, confirming the role of IEPOX chemistry as the source. On average, IEPOX-derived SOA tracer mass was ~25% (up to 47%) of the IEPOX-OA factor mass, which accounted for 32% of the total OA. A low-volatility oxygenated organic aerosol (LV-OOA) and an oxidized factor with a profile similar to 91Fac observed in areas where emissions are biogenic-dominated were also resolved by PMF analysis, whereas no primary organic aerosol (POA) sources could be resolved. These findings were consistent with low levels of primary pollutants, such as nitric oxide (NO~0.03ppb), carbon monoxide (CO~116 ppb), and black carbon (BC~0.2 μg m−3). Particle-phase sulfate is fairly correlated (r2~0.3) with both MAE- and IEPOX-derived SOA tracers, and more strongly correlated (r2~0.6) with the IEPOX-OA factor, in sum suggesting an important role of sulfate in isoprene SOA formation. Moderate correlation between the methacrylic acid epoxide (MAE)-derived SOA tracer 2-methylglyceric acid with sum of reactive and reservoir nitrogen oxides (NOy; r2=0.38) and nitrate (r2=0.45) indicates the potential influence of anthropogenic emissions through long-range transport. Despite the lack of a~clear association of IEPOX-OA with locally estimated aerosol acidity and liquid water content (LWC), box model calculations of IEPOX uptake using the simpleGAMMA model, accounting for the role of acidity and aerosol water, predicted the abundance of the IEPOX-derived SOA tracers 2-methyltetrols and the corresponding sulfates with good accuracy (r2~0.5 and ~0.7, respectively). The modeling and data combined suggest an anthropogenic influence on isoprene-derived SOA formation through acid-catalyzed heterogeneous chemistry of IEPOX in the southeastern US. However, it appears that this process was not limited by aerosol acidity or LWC at Look Rock during SOAS. Future studies should further explore the extent to which acidity and LWC becomes a limiting factor of IEPOX-derived SOA, and their modulation by anthropogenic emissions.
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Dickman, R. L., Ronald L. Snell et F. Peter Schloerb. « Carbon monoxide as an extragalactic mass tracer ». Astrophysical Journal 309 (octobre 1986) : 326. http://dx.doi.org/10.1086/164604.
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Afsar, Zahra, Nadia S. Larsen et Sergey Neshveyev. « KMS States on Nica-Toeplitz $$\hbox {C}^*$$-algebras ». Communications in Mathematical Physics 378, no 3 (3 mars 2020) : 1875–929. http://dx.doi.org/10.1007/s00220-020-03711-6.
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Abstract Given a quasi-lattice ordered group (G, P) and a compactly aligned product system X of essential $$\hbox {C}^*$$ C ∗ -correspondences over the monoid P, we show that there is a bijection between the gauge-invariant $$\hbox {KMS}_\beta $$ KMS β -states on the Nica-Toeplitz algebra $$\mathcal {NT}(X)$$ NT ( X ) of X with respect to a gauge-type dynamics, on one side, and the tracial states on the coefficient algebra A satisfying a system (in general infinite) of inequalities, on the other. This strengthens and generalizes a number of results in the literature in several directions: we do not make any extra assumptions on P and X, and our result can, in principle, be used to study KMS-states at any finite inverse temperature $$\beta $$ β . Under fairly general additional assumptions we show that there is a critical inverse temperature $$\beta _c$$ β c such that for $$\beta >\beta _c$$ β > β c all $$\hbox {KMS}_\beta $$ KMS β -states are of Gibbs type, hence gauge-invariant, in which case we have a complete classification of $$\hbox {KMS}_\beta $$ KMS β -states in terms of tracial states on A, while at $$\beta =\beta _c$$ β = β c we have a phase transition manifesting itself in the appearance of $$\hbox {KMS}_\beta $$ KMS β -states that are not of Gibbs type. In the case of right-angled Artin monoids we show also that our system of inequalities for traces on A can be reduced to a much smaller system, a finite one when the monoid is finitely generated. Most of our results generalize to arbitrary quasi-free dynamics on $$\mathcal {NT}(X)$$ NT ( X ) .
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Win, Thida, Nicholas J. Screaton, Joanna Porter, Raymondo Endozo, Damian Wild, Irfan Kayani, John Dickson et al. « Novel Positron Emission Tomography/Computed Tomography of Diffuse Parenchymal Lung Disease Combining a Labeled Somatostatin Receptor Analogue and 2-Deoxy-2 [18F] Fluoro-D-Glucose ». Molecular Imaging 11, no 2 (1 mars 2012) : 7290.2011.00030. http://dx.doi.org/10.2310/7290.2011.00030.
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We prospectively investigated the potential of positron emission tomography (PET) using the somatostatin receptor (SSTR) analogue 68Ga-DOTATATE and 2-deoxy-2[18F]fluoro-D-glucose (18F-FDG) in diffuse parenchymal lung disease (DPLD). Twenty-six patients (mean age 68.9 ± 11.0 years) with DPLD were recruited for 68Ga-DOTATATE and 18F-FDG combined PET/high-resolution computed tomography (HRCT) studies. Ten patients had idiopathic pulmonary fibrosis (IPF), 12 patients had nonspecific interstitial pneumonia (NSIP), and 4 patients had other forms of DPLD. Using PET, the pulmonary tracer uptake (maximum standardized uptake value [SUVmax]) was calculated. The distribution of PET tracer was compared to the distribution of lung parenchymal changes on HRCT. All patients demonstrated increased pulmonary PET signal with 68Ga-DOTATATE and 18F-FDG. The distribution of parenchymal uptake was similar, with both tracers corresponding to the distribution of HRCT changes. The mean SUVmax was 2.2 ± 0.7 for 68Ga-DOTATATE and 2.8 ± 1.0 ( t-test, p = .018) for 18F-FDG. The mean 68Ga-DOTATATE SUVmax in IPF patients was 2.5 ± 0.9, whereas it was 2.0 ± 0.7 ( p = .235) in NSIP patients. The correlation between 68Ga-DOTATATE SUVmax and gas transfer (transfer factor of the lung for carbon monoxide [TLCO]) was r = .34 ( p = .127) and r = .49 ( p = .028) between 18F-FDG SUVmax and TLCO. We provide noninvasive in vivo evidence in humans showing that SSTRs may be detected in the lungs of patients with DPLD in a similar distribution to sites of increased uptake of 18F-FDG on PET.
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Krob, Daniel, Jean Mairesse et Ioannis Michos. « Computing the average parallelism in trace monoids ». Discrete Mathematics 273, no 1-3 (décembre 2003) : 131–62. http://dx.doi.org/10.1016/s0012-365x(03)00233-4.
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Rodaro, Emanuele, et Pedro V. Silva. « Fixed points of endomorphisms of trace monoids ». Semigroup Forum 89, no 1 (27 novembre 2013) : 266–79. http://dx.doi.org/10.1007/s00233-013-9553-0.
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Choffrut, Christian, et Massimiliano Goldwurm. « Determinants and Möbius functions in trace monoids ». Discrete Mathematics 194, no 1-3 (janvier 1999) : 239–47. http://dx.doi.org/10.1016/s0012-365x(98)00211-8.
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Eckhardt, S., A. Stohl, S. Beirle, N. Spichtinger, P. James, C. Forster, C. Junker, T. Wagner, U. Platt et S. G. Jennings. « The North Atlantic Oscillation controls air pollution transport to the Arctic ». Atmospheric Chemistry and Physics Discussions 3, no 3 (24 juin 2003) : 3222–40. http://dx.doi.org/10.5194/acpd-3-3222-2003.
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Abstract. This paper studies the interannual variability of pollution pathways from northern hemisphere (NH) continents into the Arctic. Using a 1-year model simulation of the dispersion of passive tracers representative of anthropogenic emissions from NH continents, we show that the North Atlantic Oscillation (NAO) exerts a strong control on the pollution transport into the Arctic, particularly in winter and spring. For tracer lifetimes of 5 (30) days, surface concentrations in the Arctic winter are enhanced by about 70% (30%) during high phases of the NAO (in the following referred to as NAO+) compared to its low phases (NAO−). This is mainly due to great differences in the pathways of European pollution during NAO+ and NAO− phases, respectively, but reinforced by North American pollution, which is also enhanced in the Arctic during NAO+ phases. In contrast, Asian pollution in the Arctic does not significantly depend on the NAO phase. The model results are confirmed using remotely-sensed NO2 vertical atmospheric columns obtained from seven years of satellite measurements, which show enhanced northward NO2 transport and reduced NO2 outflow into the North Atlantic from Central Europe during NAO+ phases. Surface measurements of carbon monoxide (CO) and black carbon at high-latitude stations further corroborate the overall picture of enhanced Arctic pollution levels during NAO+ phases.
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Eckhardt, S., A. Stohl, S. Beirle, N. Spichtinger, P. James, C. Forster, C. Junker, T. Wagner, U. Platt et S. G. Jennings. « The North Atlantic Oscillation controls air pollution transport to the Arctic ». Atmospheric Chemistry and Physics 3, no 5 (24 octobre 2003) : 1769–78. http://dx.doi.org/10.5194/acp-3-1769-2003.
Texte intégralRésumé :
Abstract. This paper studies the interannual variability of pollution pathways from northern hemisphere (NH) continents into the Arctic. Using a 15-year model simulation of the dispersion of passive tracers representative of anthropogenic emissions from NH continents, we show that the North Atlantic Oscillation (NAO) exerts a strong control on the pollution transport into the Arctic, particularly in winter and spring. For tracer lifetimes of 5 (30) days, surface concentrations in the Arctic winter are enhanced by about 70% (30%) during high phases of the NAO (in the following referred to as NAO+) compared to its low phases (NAO-). This is mainly due to great differences in the pathways of European pollution during NAO+ and NAO- phases, respectively, but reinforced by North American pollution, which is also enhanced in the Arctic during NAO+ phases. In contrast, Asian pollution in the Arctic does not significantly depend on the NAO phase. The model results are confirmed using remotely-sensed NO2 vertical atmospheric columns obtained from seven years of satellite measurements, which show enhanced northward NO2 transport and reduced NO2 outflow into the North Atlantic from Central Europe during NAO+ phases. Surface measurements of carbon monoxide (CO) and black carbon at high-latitude stations further corroborate the overall picture of enhanced Arctic pollution levels during NAO+ phases
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Doremus, Robert H. « Diffusion of oxygen and silicon in silicon : Silicon monoxide model ». Journal of Materials Research 16, no 1 (janvier 2001) : 185–91. http://dx.doi.org/10.1557/jmr.2001.0030.
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The diffusion of oxygen in silicon was modeled to result from the diffusion of dissolved silicon monoxide. The SiO molecule dissolved in the largest space in the diamond lattice of silicon, oriented in a 〈111〉 direction, with the oxygen lightly bonded to a network silicon atom. This configuration is consistent with infrared spectra, dichroism of infrared spectral lines, and internal friction of oxygen in silicon. The anomalous rapid diffusion of oxygen below 700 °C could result from the diffusion of molecular water or oxygen in silicon, but more evidence is needed to test these possibilities. Diffusion and exchange of silicon tracer in SiO with lattice silicon can possibly explain tracer diffusion of silicon in silicon.
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Starling, Charles. « $\mathrm C^*$-algebras of Boolean inverse monoids -- traces and invariant means ». Documenta Mathematica 21 (2016) : 809–40. http://dx.doi.org/10.4171/dm/546.
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Miyakawa, Takuma, Akinori Ito, Chunmao Zhu, Atsushi Shimizu, Erika Matsumoto, Yusuke Mizuno et Yugo Kanaya. « Trace elements in PM2.5 aerosols in East Asian outflow in the spring of 2018 : emission, transport, and source apportionment ». Atmospheric Chemistry and Physics 23, no 22 (27 novembre 2023) : 14609–26. http://dx.doi.org/10.5194/acp-23-14609-2023.
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Abstract. Trace metals in aerosol particles impact Earth's radiative budget, human health, and ocean biogeochemistry. Semi-continuous measurements of the elemental composition of fine-mode (PM2.5) aerosols were conducted using an automated X-ray fluorescence analyzer on a remote island of Japan during the spring of 2018. Temporal variations in mass concentrations of geochemically important elements for this period, such as Pb, Cu, Si, Fe, and Mn, and their relationships with the emission tracers, carbon monoxide (CO) and black carbon (BC), were reported. The Integrated Massively Parallel Atmospheric Chemical Transport (IMPACT) model was used to evaluate the source apportionment of these components and was evaluated in terms of emissions and wet removal processes. Pb and Cu originated mainly from anthropogenic sources (98 % and 93 % on average, respectively) over the East Asian continent. Positive correlations of Pb and Cu with BC and CO and the similarity of their concentration-weighted trajectories indicated that the emission sources of these metals share the region where the large CO (and BC) emission sources are located and that CO can be regarded as a tracer of continental anthropogenic emissions. The air masses with minimized impacts of the wet removal during transport were extracted to elucidate the “top-down” emission ratio of Pb and Cu to CO, which were, for the first time, evaluated as 152.7 and 63.1 µg g−1, respectively, during the spring of 2018 in the East Asian outflow. The analysis of the tagged tracer simulations by the IMPACT model confirmed that BC and Si could be used as tracers for anthropogenic and dust emissions, respectively, during the observation period. The source apportionment of Fe and Mn in PM2.5 aerosols was conducted using Si and BC tracers, which revealed that the anthropogenic contribution was 17 % and 44 % on average, respectively. Based on the air mass origins of Fe and Mn, their anthropogenic fraction varied from 2 % to 29 % and 9 % to 68 %, respectively, during the high-PM2.5-concentration periods. However, despite the non-dominant anthropogenic contributions of Fe, they could adversely affect human health and ocean biogeochemistry, owing to their higher water solubility. The modeled BC, Pb, Cu, and Fe were evaluated by separately diagnosing their emission and transport. Ratios of modeled to observed concentrations for these components were analyzed in terms of the accumulated precipitation along the transport from the East Asian continent. The current model simulations were found to overestimate the emissions (based on the Community Emissions Data System, CEDS v2021-02-05) of BC by 44 % and underestimate Cu by 45 %, anthropogenic Fe by 28 % in East Asia, and the wet deposition rates for BC and Pb. Overall, Cu in East Asia exhibited a different nature from BC and Pb in terms of emission sources and wet removal.
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Choffrut, C. « A remark on the representation of trace monoids ». Semigroup Forum 40, no 1 (décembre 1990) : 143–52. http://dx.doi.org/10.1007/bf02573262.
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Kęskiewicz, Anna. « INTRODUCTION TO FORENSICS - APPLICATION OF NATURAL SCIENCES ». International Journal of Legal Studies ( IJOLS ) 4, no 2 (30 décembre 2018) : 185–202. http://dx.doi.org/10.5604/01.3001.0013.0014.
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A well-known forensic material used in forensic technique is carbon monoxide on environment. In literature an important element that makes it difficult to assess the circumstances of fatal poisoning is the individual way of reacting the body to the action of carbon monoxide. Often staying in the same conditions cause that some people are poisoned while others alive. ''Introduction to forensics - application of natural sciences '' is a scientific presentation in order to disseminate preventive methods. The policy on environment is undoubtedly a theme to these important research methods. In order to analyze in the written work that toxic gas in strictly defined cases are the base of evidence. Empirical studies on the example of environmental protection included: quantitative analysis based on the Legalis Legal Information System, directions, noticeable tendencies in described scope, results of empirical research. Toxic gases on environment are used in the evaluation of the material for palynological analyze. The study took into account the analysis of the most suitable places on the body or clothing for taking palynological samples. The analysis covered whether the forensic traces of carbon dioxide recorded on the surface of the body or clothing, reflect the composition of vegetation occurring in the area of research and whether they can be used to mark the time of the event. The obtained results indicate that traces of carbon dioxide may be useful in determining the time of the event in practice in forensic science.
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Itodo, Isaac N., Dorcas K. Yakubu et Theresa K. Kaankuka. « The Effects of Biogas Fuel in an Electric Generator on Greenhouse Gas Emissions, Power Output, and Fuel Consumption ». Transactions of the ASABE 62, no 4 (2019) : 951–58. http://dx.doi.org/10.13031/trans.13394.
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Abstract. The rising cost of fossil fuels, global warming from greenhouse gas (GHG) emissions, unreliable grid supply electricity, and overdependence on hydropower electricity have resulted in low electricity per capita in Nigeria. This study was undertaken to produce, purify, and use biogas as a fuel to generate electricity with a 3.5 kW spark-ignition engine generator and determine its effect on GHG emissions, power output, and fuel consumption. Unpurified and purified biogas were used as fuels. The biogas was purified in water and in a calcium chloride solution. The fuels used to power the generator were gasoline, unpurified biogas, water-purified biogas, and calcium chloride-purified biogas. The GHGs measured were carbon monoxide, carbon dioxide, nitrogen oxide, and sulfur dioxide. The biogas was produced with a 3 m3 capacity floating-drum biogas plant. The total solids concentration and carbon/nitrogen ratio of the influent and effluent slurries were determined. The effects of fuel type on GHG emissions were determined in a 4 × 4 factorial experiment with three replicates in a completely randomized design. The effects of fuel type on power output and fuel consumption of the generator were determined in a 4 × 2 factorial experiment with three replicates in a completely randomized design. The results were analyzed using analysis of variance at p = 0.05. Duncan’s new multiple range test was used to separate means when there was significant difference. The results obtained showed that carbon dioxide emission was not affected by purification of the biogas because the carbon dioxide emissions from the fuel types were not significantly different. The carbon monoxide emission was much higher from the unpurified biogas than from the purified biogas fuels, although gasoline had the highest carbon monoxide emission. The water-purified biogas had the least carbon monoxide and sulfur dioxide emissions. The unpurified biogas had the least nitrogen oxide emission compared to the purified biogas fuels and gasoline. The power output from the unpurified biogas was not significantly different from that of gasoline and was higher than the purified biogas fuels. The fuel consumptions of the purified biogas fuels were not significantly different. The water-purified biogas is recommended for use as fuel for the production of electricity from a spark-ignition engine generator. Keywords: Biogas, Effects, Electricity, Fuel consumption, Greenhouse gas emissions, Power output.
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Graham, Brian L., Vito Brusasco, Felip Burgos, Brendan G. Cooper, Robert Jensen, Adrian Kendrick, Neil R. MacIntyre, Bruce R. Thompson et Jack Wanger. « Executive Summary : 2017 ERS/ATS standards for single-breath carbon monoxide uptake in the lung ». European Respiratory Journal 49, no 1 (janvier 2017) : 16E0016. http://dx.doi.org/10.1183/13993003.e0016-2016.
Texte intégralRésumé :
This document summarises an update to the European Respiratory Society (ERS)/American Thoracic Society (ATS) technical standards for single-breath carbon monoxide uptake in the lung that was last updated in 2005. The full standards are also available online as https://doi.org/10.1183/13993003.00016-2016. The major changes in these technical standards relate to DLCO measurement with systems using rapidly responding gas analysers for carbon monoxide and the tracer gas, which are now the most common type of DLCO instrumentation being manufactured. Technical improvements and the increased capability afforded by these new systems permit enhanced measurement of DLCO and the opportunity to include other optional measures of lung function.
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Shrestha, Sujan, Shan Zhou, Manisha Mehra, Meghan Guagenti, Subin Yoon, Sergio L. Alvarez, Fangzhou Guo et al. « Evaluation of aerosol- and gas-phase tracers for identification of transported biomass burning emissions in an industrially influenced location in Texas, USA ». Atmospheric Chemistry and Physics 23, no 19 (4 octobre 2023) : 10845–67. http://dx.doi.org/10.5194/acp-23-10845-2023.
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Abstract. As criteria pollutants from anthropogenic emissions have declined in the US in the last 2 decades, biomass burning (BB) emissions are becoming more important for urban air quality. Tracking the transported BB emissions and their impacts is challenging, especially in areas that are also burdened by anthropogenic sources like the Texas Gulf Coast. During the Corpus Christi and San Antonio (CCSA) field campaign in spring 2021, two long-range-transport BB events (BB1 and BB2) were identified. The observed patterns of an absorption Ångström exponent (AAE), a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) BB tracer (f60), equivalent black carbon (eBC), acetonitrile and carbon monoxide (CO) during BB1 and BB2 indicated differences in the mixing of transported BB plumes with local anthropogenic sources. The combined information from HYSPLIT backward-trajectory (BT) and satellite observations revealed that BB1 had mixed influence of transported smoke plumes from fires in central Mexico, the Yucatán Peninsula and the central US, whereas BB2 was influenced by fires in the central US. The estimated transport times of smoke from the Mexican fires and the central US fires to our study site were not too different (48–54 and 24–36 h, respectively), and both events appeared to have undergone similar levels of atmospheric processing, as evident in the elemental ratios of bulk organic aerosol (OA). We observed an aging trend for f44 vs. f60 and f44 vs. f43 as a function of time during BB2 but not during BB1. Positive matrix factorization (PMF) analysis of OA showed that BB1 had a mixture of organics from aged BB emissions with an anthropogenic marine signal, while the oxidized organic compounds from aged BB emissions dominated the aerosols during BB2. The size distribution of aerosol composition revealed distinct characteristics between BB1 and BB2, where BB1 was found to be externally mixed, exhibiting a combination of BB and anthropogenic marine aerosols. On the other hand, BB2 exhibited internal mixing dominated by aged BB aerosol. Our analysis from mobile and stationary measurements highlights that both CO and acetonitrile are likely impacted by local sources even during the BB events and specifically that acetonitrile cannot be used as a unique BB tracer for dilute BB plumes in an industrially influenced location. A suitable volatile organic compound (VOC) tracer would need to be emitted in high concentrations during BB, resistant to degradation during transport, unique to BB and able to be measured in the field. This study effectively demonstrates that AAE and aerosol BB tracers served as precise and effective tracers in these complex emission scenarios. Network deployment of multiwavelength photometers holds promise for enhancing our understanding of BB impacts on air quality and supporting informed decision-making for effective mitigation strategies in locations with mixed sources and influence of dilute BB plumes. To demonstrate the relevance of such an aerosol optical network, we provide evidence of the potential regional impacts of these transported BB events on urban O3 levels using measurements from the surface air quality monitoring network in Texas.
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Husainov, Ahmet A. « The global dimension of a trace monoid ring ». Semigroup Forum 82, no 2 (21 septembre 2010) : 261–70. http://dx.doi.org/10.1007/s00233-010-9264-8.
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Wrathall, C. « Trace monoids with some invertible generators : two decision problems ». Discrete Applied Mathematics 32, no 2 (juillet 1991) : 211–22. http://dx.doi.org/10.1016/0166-218x(91)90101-2.
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Metivier, Y., et G. Richomme. « New Results on the Star Problem in Trace Monoids ». Information and Computation 119, no 2 (juin 1995) : 240–51. http://dx.doi.org/10.1006/inco.1995.1088.
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VERSHININ, VLADIMIR V. « ON VASSILIEV INVARIANTS FOR LINKS IN HANDLEBODIES ». Journal of Knot Theory and Its Ramifications 07, no 05 (août 1998) : 701–12. http://dx.doi.org/10.1142/s021821659800036x.
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The notion of Vassiliev algebra in case of handlebodies is developed. Analogues of the results of J. Baez for links in handlebodies are proved. This implies that there is a one-to-one correspondence between the special class of finite type invariants of links in hanlebodies and the homogeneous Markov traces on Vassiliev algebras. This approach uses the singular braid monoid and braid group in a handlebody and the generalizations of the theorem of J. Alexander and the theorem of A. A. Markov for singular links and braids and the relative version of Markov's theorem.
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Tilmes, S., L. K. Emmons, K. S. Law, G. Ancellet, H. Schlager, J. D. Paris, H. E. Fuelberg et al. « Source contributions to Northern Hemisphere CO and black carbon during spring and summer 2008 from POLARCAT and START08/preHIPPO observations and MOZART-4 ». Atmospheric Chemistry and Physics Discussions 11, no 2 (21 février 2011) : 5935–83. http://dx.doi.org/10.5194/acpd-11-5935-2011.
Texte intégralRésumé :
Abstract. Anthropogenic pollution and wildfires are main producers of carbon monoxide (CO) and black carbon (BC) in the Northern Hemisphere. High concentrations of these compounds are transported into the Arctic troposphere, influencing the ecosystem in high northern latitudes and the global climate. The global chemical transport model MOZART-4 is used to quantify the seasonal evolution of the contribution of CO and BC from different source regions in spring and summer 2008 by tagging their emissions. Aircraft observations from the POLARCAT experiments, in particular NASA ARCTAS, NOAA ARCPAC, POLARCAT-France, DLR GRACE and YAK-AEROSIB, as well as the NSF START08/preHIPPO experiments during Spring-Summer 2008 are combined to quantify the representation of simulated tracer characteristics in anthropogenic and fire plumes. In general, the model reproduces CO and BC well. Based on aircraft measurements and FLEXPART back-trajectories, the altitude contribution of emissions coming from different source regions is well captured in the model. Uncertainties of the MOZART-4 model are identified by comparing the data with model results on the flight tracks and using MOPITT satellite observations. Anthropogenic emissions are underestimated by about 10% in high northern latitudes in spring, and shortcomings exist in simulating fire plumes. The remote impact of East-Siberian fire emissions is underestimated for spring, whereas the impact of Southeast Asian fire emissions to mid-latitude CO values is overestimated by the model. In summer, mid-latitude CO values agree well between model and observations, whereas summer high latitude East-Siberian fire emissions in the model are overestimated by 20% in comparison to observations in the region. On the other hand, CO concentrations are underestimated by about 30% over Alaska and Canada at altitudes above 4 km. BC values are overestimated by the model at altitudes above 4 km in summer. Based on MOZART-4, with tagged CO and BC tracers, anthropogenic emissions of Asia, Europe and the US have the largest contribution to the CO and BC in mid- and high latitudes in spring and summer. Southeast Asian, Chinese and Indian fires have a large impact on CO pollution in spring in low latitudes with a maximum between 20° and 30°, whereas Siberian fires contribute largely to the pollution in high latitudes, up to 10% in spring and up to 30% in summer. The largest contributions to BC values in high latitudes are from anthropogenic emissions (about 70%). CO and BC have larger mass loadings in April than in July, as a result of photochemistry and dynamics.
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Roscioli, J. R., T. I. Yacovitch, C. Floerchinger, A. L. Mitchell, D. S. Tkacik, R. Subramanian, D. M. Martinez et al. « Measurements of methane emissions from natural gas gathering facilities and processing plants : measurement methods ». Atmospheric Measurement Techniques Discussions 7, no 12 (11 décembre 2014) : 12357–406. http://dx.doi.org/10.5194/amtd-7-12357-2014.
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Abstract. Increased natural gas production in recent years has spurred intense interest in methane (CH4) emissions associated with its production, gathering, processing, transmission and distribution. Gathering and processing facilities (G&P facilities) are unique in that the wide range of gas sources (shale, coal-bed, tight gas, conventional, etc.) results in a wide range of gas compositions, which in turn requires an array of technologies to prepare the gas for pipeline transmission and distribution. We present an overview and detailed description of the measurement method and analysis approach used during a 20-week field campaign studying CH4 emissions from the natural gas G&P facilities between October 2013 and April 2014. Dual tracer flux measurements and onsite observations were used to address the magnitude and origins of CH4 emissions from these facilities. The use of a second tracer as an internal standard revealed plume-specific uncertainties in the measured emission rates of 20–47%, depending upon plume classification. Combining downwind methane, ethane (C2H6), carbon monoxide (CO), carbon dioxide (CO2), and tracer gas measurements with onsite tracer gas release allows for quantification of facility emissions, and in some cases a more detailed picture of source locations.
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Israel, F. P., et Th De Graauw. « Carbon Monoxide in the Magellanic Clouds ». Symposium - International Astronomical Union 148 (1991) : 45–49. http://dx.doi.org/10.1017/s007418090019998x.
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Molecular gas is a major constituent of the interstellar medium of all late-type galaxies. Virtually all of it is in the form of cold molecular hydrogen (H2) which today cannot be observed directly. However, the tracer molecule carbon monoxide (CO) (relative abundance 10−5) is easily detected. For the Magellanic Clouds (MCs), CO studies are of specific importance. The Clouds are rich in HI, and if we can establish the presence of significant amounts of H2 as well, this will influence our estimates of the global rate of star formation and its history. Complexes of presently quiescent molecular gas may betray regions primed for star formation, but not yet in action. Detailed studies of the HI, HII and H2 and young star content may provide estimates of star formation efficiences on scales of a kiloparsec.
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Monks, S. A., S. R. Arnold, L. K. Emmons, K. S. Law, S. Turquety, B. N. Duncan, J. Flemming et al. « Multi-model study of chemical and physical controls on transport of anthropogenic and biomass burning pollution to the Arctic ». Atmospheric Chemistry and Physics Discussions 14, no 18 (2 octobre 2014) : 25281–350. http://dx.doi.org/10.5194/acpd-14-25281-2014.
Texte intégralRésumé :
Abstract. Using observations from aircraft, surface stations and satellite, we comprehensively evaluate multi-model simulations of carbon monoxide (CO) and ozone (O3) in the Arctic and over lower latitude emission regions, as part of the POLARCAT Model Inter-comparison Project (POLMIP). Evaluation of eleven atmospheric models with chemistry shows that they generally underestimate CO throughout the Arctic troposphere, with the largest biases found during winter and spring. Negative CO biases are also found throughout the Northern Hemisphere, with multi-model mean gross errors (9–12%) suggesting models perform similarly over Asia, North America and Europe. A multi-model annual mean tropospheric OH (10.8 ± 0.6 × 105 molec cm−3) is found to be slightly higher than previous estimates of OH constrained by methyl chloroform, suggesting negative CO biases in models may be improved through better constraints on OH. Models that have lower Arctic OH do not always show a substantial improvement in their negative CO biases, suggesting that Arctic OH is not the dominant factor controlling the Arctic CO burden in these models. In addition to these general biases, models do not capture the magnitude of CO enhancements observed in the Arctic free troposphere in summer, suggesting model errors in the simulation of plumes that are transported from anthropogenic and biomass burning sources at lower latitudes. O3 in the Arctic is also generally underestimated, particularly at the surface and in the upper troposphere. Summer O3 comparisons over lower latitudes show several models overestimate upper tropospheric concentrations. Simulated CO, O3 and OH all demonstrate a substantial degree of inter-model variability. Idealised CO-like tracers are used to quantitatively compare the impact of inter-model differences in transport and OH on CO in the Arctic troposphere. The tracers show that model differences in transport from Europe in winter and from Asia throughout the year are important sources of model variability at the Barrow. Unlike transport, inter-model variability in OH similarly affects all regional tracers at Barrow. Comparisons of fixed lifetime and OH-loss idealised CO-like tracers throughout the Arctic troposphere show that OH differences are a much larger source of inter-model variability than transport differences. The concentration of OH in the models is found to be correlated with inter-model differences in H2O, suggesting it to be an important driver of differences in simulated concentrations of CO and OH at high latitudes in these simulations. Despite inter-model differences in transport and OH, the relative contributions from the different source regions (North America, Europe and Asia) and different source types (anthropogenic and biomass burning) are comparable across the models. Fire emissions from the boreal regions in 2008 contribute 33, 43 and 19% to the total Arctic CO-like tracer in spring, summer and autumn, respectively, highlighting the importance of boreal fire emissions in controlling pollutant burdens in the Arctic.
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Monks, S. A., S. R. Arnold, L. K. Emmons, K. S. Law, S. Turquety, B. N. Duncan, J. Flemming et al. « Multi-model study of chemical and physical controls on transport of anthropogenic and biomass burning pollution to the Arctic ». Atmospheric Chemistry and Physics 15, no 6 (31 mars 2015) : 3575–603. http://dx.doi.org/10.5194/acp-15-3575-2015.
Texte intégralRésumé :
Abstract. Using observations from aircraft, surface stations and a satellite instrument, we comprehensively evaluate multi-model simulations of carbon monoxide (CO) and ozone (O3) in the Arctic and over lower latitude emission regions, as part of the POLARCAT Model Inter-comparison Project (POLMIP). Evaluation of 11- atmospheric models with chemistry shows that they generally underestimate CO throughout the Arctic troposphere, with the largest biases found during winter and spring. Negative CO biases are also found throughout the Northern Hemisphere, with multi-model mean gross errors (9–12%) suggesting models perform similarly over Asia, North America and Europe. A multi-model annual mean tropospheric OH (10.8 ± 0.6 × 105 molec cm−3) is found to be slightly higher than previous estimates of OH constrained by methyl chloroform, suggesting negative CO biases in models may be improved through better constraints on OH. Models that have lower Arctic OH do not always show a substantial improvement in their negative CO biases, suggesting that Arctic OH is not the dominant factor controlling the Arctic CO burden in these models. In addition to these general biases, models do not capture the magnitude of CO enhancements observed in the Arctic free troposphere in summer, suggesting model errors in the simulation of plumes that are transported from anthropogenic and biomass burning sources at lower latitudes. O3 in the Arctic is also generally underestimated, particularly at the surface and in the upper troposphere. Summer O3 comparisons over lower latitudes show several models overestimate upper tropospheric concentrations. Simulated CO, O3 and OH all demonstrate a substantial degree of inter-model variability. Idealised CO-like tracers are used to quantitatively compare the impact of inter-model differences in transport and OH on CO in the Arctic troposphere. The tracers show that model differences in transport from Europe in winter and from Asia throughout the year are important sources of model variability at Barrow. Unlike transport, inter-model variability in OH similarly affects all regional tracers at Barrow. Comparisons of fixed-lifetime and OH-loss idealised CO-like tracers throughout the Arctic troposphere show that OH differences are a much larger source of inter-model variability than transport differences. Model OH concentrations are correlated with H2O concentrations, suggesting water vapour concentrations are linked to differences in simulated concentrations of CO and OH at high latitudes in these simulations. Despite inter-model differences in transport and OH, the relative contributions from the different source regions (North America, Europe and Asia) and different source types (anthropogenic and biomass burning) are comparable across the models. Fire emissions from the boreal regions in 2008 contribute 33, 43 and 19% to the total Arctic CO-like tracer in spring, summer and autumn, respectively, highlighting the importance of boreal fire emissions in controlling pollutant burdens in the Arctic.
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Williams, Jonathan. « Organic Trace Gases in the Atmosphere : An Overview ». Environmental Chemistry 1, no 3 (2004) : 125. http://dx.doi.org/10.1071/en04057.
Texte intégralRésumé :
Environmental Context. The major carbon-containing atmospheric gases (carbon dioxide, carbon monoxide, and methane) are found in the atmosphere at the parts-per-million levels, where they affect physical phenomena such as the greenhouse effect. There are however many more carbon-containing gases at much lower levels with many and varied roles; in the main these gases are more chemically active and affect principally chemical phenomena such as the ozone budget. Abstract. An overview of atmospheric organic trace gases is presented. This work is suited to those new to the field and to those seeking to place related activities in a broader context.
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Abbes, Samy, et Jean Mairesse. « Uniform and Bernoulli measures on the boundary of trace monoids ». Journal of Combinatorial Theory, Series A 135 (octobre 2015) : 201–36. http://dx.doi.org/10.1016/j.jcta.2015.05.003.
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Bertoni, Alberto, Carlo Mereghetti et Beatrice Palano. « Trace monoids with idempotent generators and measure-only quantum automata ». Natural Computing 9, no 2 (4 octobre 2009) : 383–95. http://dx.doi.org/10.1007/s11047-009-9154-8.
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