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Sample records for extinction coefficient profile

  1. Ultraviolet Raman lidar for high-accuracy profiling of aerosol extinction coefficient

    Institute of Scientific and Technical Information of China (English)

    Fei Gao; Xiaoquan Song; Yufeng Wang; Yi Zhou; Dengxin Hua

    2009-01-01

    An ultraviolet (UV) Raman lidar system at 354.7 nm has been developed for accurately measuring the aerosol extinction profiles. A spectroscopic filter combining a high-spectral-resolution grating with two narrowband mirrors is used to separate the vibrational Raman scattering signal of N2 at a central wave-length of 386.7 nm and the elastic scattering signal at 354.7 nm. The aerosol extinction is derived from the Raman scattering of N2 and the elastic scattering by the use of Raman method and Klett method, respectively. The derived results of aerosol extinction are used to compare the difference of two retrieval methods, and the preliminary experiment shows that the Raman lidar system operated in analog detection mode has the capability of measuring aerosol profiles up to a height of 3 km with a laser energy of 250 mJ and an integration time of 8 min.

  2. Molar extinction coefficients of some fatty acids

    DEFF Research Database (Denmark)

    Sandhu, G.K.; Singh, K.; Lark, B.S.;

    2002-01-01

    ) and stearic acid (C18H36O2), has been measured at the photon energies 81, 356, 511, 662, 1173 and 1332 keV. Experimental values for the molar extinction coefficient, the effective atomic number and the electron density have been derived and compared with theoretical calculations. There is good agreement...

  3. Molar extinction coefficients of some fatty acids

    Science.gov (United States)

    Sandhu, G. K.; Singh, Kulwant; Lark, B. S.; Gerward, L.

    2002-10-01

    The attenuation of gamma rays in some fatty acids, viz. formic acid (CH 2O 2), acetic acid (C 2H 4O 2), propionic acid (C 3H 6O 2), butyric acid (C 4H 8O 2), n-hexanoic acid (C 6H 12O 2), n-caprylic acid (C 8H 16O 2), lauric acid (C 12H 24O 2), myristic acid (C 14H 28O 2), palmitic acid (C 16H 32O 2), oleic acid (C 18H 34O 2) and stearic acid (C 18H 36O 2), has been measured at the photon energies 81, 356, 511, 662, 1173 and 1332 keV. Experimental values for the molar extinction coefficient, the effective atomic number and the electron density have been derived and compared with theoretical calculations. There is good agreement between experiment and theory.

  4. Melanoidins extinction coefficient in the glucose/glycine Maillard reaction

    NARCIS (Netherlands)

    Martins, S.I.F.S.; Boekel, van M.A.J.S.

    2003-01-01

    Melanoidins (brown, nitrogenous polymers and co-polymers) are the final products of the Maillard reaction. The glucose/glycine melanoidins extinction coefficient was determined using C-14-labelled glucose at three different reaction conditions. The absorbance was measured at different wavelengths (4

  5. Determination of Backscatter-Extinction Coefficient Ratio for LIDAR-Retrieved Aerosol Optical Depth Based on Sunphotometer Data

    Directory of Open Access Journals (Sweden)

    Pak Wai Chan

    2010-09-01

    Full Text Available Backscattered power data from the Doppler LIght Detection And Ranging (LIDAR systems at the Hong Kong International Airport (HKIA could be used to obtain the extinction coefficient of the troposphere by combining with the meteorological optical range (MOR data from the nearby forward scatter sensor. The Range-height Indicator (RHI scan of the LIDAR is then utilized to derive the vertical profile of extinction coefficient, which is integrated with height to obtain the aerosol optical depth (AOD. In the retrieval of extinction coefficient profile, there is a power exponent of unknown value relating the backscattered power and the extinction coefficient. This exponent (called the backscatter-extinction coefficient ratio depends on the optical properties of the aerosol in the air, and is normally assumed to be 1. In the present study, the value of this ratio is established by comparing the AOD measurements by a hand-held sunphotometer and the LIDAR-based AOD estimate in one winter (October 2008 to January 2009, which is the season with the largest number of haze episodes, and one summer-winter-spring period of the following year (July 2009 to May 2010 at HKIA. It is found to be about 1.4. The sensitivity of extinction coefficient profile to the value of the ratio is also examined for two cases in the study period, one good visibility day and one hazy day.

  6. Titan Extinction Profiles Observed by Cassini Radio Occultations and Implications

    Science.gov (United States)

    Marouf, Essam; French, Richard; Flasar, F. Michael; Schinder, Paul J.; Rappaport, Nicole J.

    Three monochromatic and phase-coherent radio signals of wavelength = 0.9, 3.6, and 13 cm (Ka-, X-, and S-bands), were propagated by Cassini through the neutral atmosphere of Titan and the refracted signals were observed on the Earth. Abel inversion of observed changes in the signal frequency is used to recover the refractivity profile of the atmosphere, hence estimate the expected loss in signal strength due to defocusing of the radio signal by differential refraction. The refractive defocusing component (wavelength independent, in principle) is then removed from the actual measured signal strength profiles yielding the "true" signal extinction due to absorption and scattering integrated along the propagation path. Abel inversion of the integrated intensity profiles, tempered to combat noise contribution, yields localized estimates of the extinction coefficient (absorbtivity) as a function of altitude, or the extinction profiles. The initial radio measurements are diffraction-limited. We extend Fresnel transform based diffraction reconstruction procedures developed for radio occultation observations of planetary rings to remove diffraction effects from the initial radio measurements. The procedures are tested using idealized models of simple isothermal atmospheric profile extending above a hard-limb (knife-edge) model. Reconstruction of the simulated "observed" diffraction-limited data shows good agreement with the assumed atmospheric profile and the location of the hard-limb for a range of model parameters. We then apply a similar approach to the actual measured data. Strong wavelength-dependent extinction coefficient profile behavior is observed. Its large-scale structure appears well modeled by predictions based on N2-N2 collision-induced gaseous absorption for Titan's physical conditions. Interesting localized features of yet unexplained origin are also observed. Because the spatial scales of the extinction profile features are relatively large compared with

  7. Lidar method of measurement of atmospheric extinction and ozone profiles

    Science.gov (United States)

    Cooney, J. A.

    1986-01-01

    A description of a method of measurement of atmospheric extinction and of ozone profiles by use of the backscatter signal from a monostatic lidar is given. The central feature of the procedure involves a measurement of the ratio of the Raman backscatter returns of both the oxygen and nitrogen atmospheric content. Because the ratio of the number density of both species is known to high accuracy, the measurement itself becomes a measure of the ratio of two transmissions to altitude along with a ratio of the two system constants. The calibration measurement for determining the value of the ratio of the two system constants or electro-optical conversion constants is accomplished by a lidar measurement of identical atmospheric targets while at the same time interchanging the two optical filters in the two optical channels of the receiver. More details of the procedure are discussed. Factoring this calibrated value into the measured O2/N2 profile ratio provides a measured value of the ratio of the two transmissions. Or equivalently, it provides a measurement of the difference of the two extinction coefficients at the O2 and N2 Raman wavelengths as a function of the height.

  8. A new method for retrieval of the extinction coefficient of water clouds by using the tail of the CALIOP signal

    Directory of Open Access Journals (Sweden)

    J. Li

    2010-11-01

    Full Text Available A method is developed based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO level 1 attenuated backscatter profile data for deriving the mean extinction coefficient of water droplets close to cloud top. The method is applicable to low level (cloud top < 2 km, opaque water clouds in which the lidar signal is completely attenuated beyond about 100 m of penetration into the cloud. The photo multiplier tubes (PMTs of 532 nm detectors (parallel and perpendicular polarizations of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP both exhibit a non-ideal recovery of the lidar signal after striking a strongly backscattering target (such as water cloud or surface. Therefore, the effects of any transient responses of CALIOP on the attenuated backscatter profile of the water cloud must first be removed in order to obtain a reliable (validated attenuated backscatter profile. Then, the slope of the exponential decay of the validated water cloud attenuated backscatter profile, and the multiple scattering factor are used for deriving the mean extinction coefficient of low-level water cloud droplets close to cloud top. This novel method was evaluated and compared with the previous method by combining the cloud effective radius (3.7 μm reported by MODIS with the lidar depolarization ratios measured by CALIPSO to estimate the mean extinction coefficient. Statistical results show that the extinction coefficients derived by the new method based on CALIOP alone agree reasonably well with those obtained in the previous study using combined CALIOP and MODIS data. Their mean absolute relative difference in extinction coefficient is about 13.4%. An important advantage of the new method is that it can be used to derive the extinction coefficient also during night time, and it is also applicable when multi-layered clouds are present. Overall, the global mean cloud water extinction coefficients during different seasons range from 26

  9. HIRDLS/Aura Level 3 Extinction at 8.3 Microns Zonal Fourier Coefficients V007

    Data.gov (United States)

    National Aeronautics and Space Administration — The "HIRDLS/Aura Level 3 Extinction at 8.3 Microns Zonal Fourier Coefficients" version 7 data product (H3ZFC8MEXT) contains the entire mission (~3 years) of HIRDLS...

  10. An Improved Method of Predicting Extinction Coefficients for the Determination of Protein Concentration.

    Science.gov (United States)

    Hilario, Eric C; Stern, Alan; Wang, Charlie H; Vargas, Yenny W; Morgan, Charles J; Swartz, Trevor E; Patapoff, Thomas W

    2017-01-01

    Concentration determination is an important method of protein characterization required in the development of protein therapeutics. There are many known methods for determining the concentration of a protein solution, but the easiest to implement in a manufacturing setting is absorption spectroscopy in the ultraviolet region. For typical proteins composed of the standard amino acids, absorption at wavelengths near 280 nm is due to the three amino acid chromophores tryptophan, tyrosine, and phenylalanine in addition to a contribution from disulfide bonds. According to the Beer-Lambert law, absorbance is proportional to concentration and path length, with the proportionality constant being the extinction coefficient. Typically the extinction coefficient of proteins is experimentally determined by measuring a solution absorbance then experimentally determining the concentration, a measurement with some inherent variability depending on the method used. In this study, extinction coefficients were calculated based on the measured absorbance of model compounds of the four amino acid chromophores. These calculated values for an unfolded protein were then compared with an experimental concentration determination based on enzymatic digestion of proteins. The experimentally determined extinction coefficient for the native proteins was consistently found to be 1.05 times the calculated value for the unfolded proteins for a wide range of proteins with good accuracy and precision under well-controlled experimental conditions. The value of 1.05 times the calculated value was termed the predicted extinction coefficient. Statistical analysis shows that the differences between predicted and experimentally determined coefficients are scattered randomly, indicating no systematic bias between the values among the proteins measured. The predicted extinction coefficient was found to be accurate and not subject to the inherent variability of experimental methods. We propose the use of a

  11. [Reconstructed ambient light extinction coefficient and its contribution factors in Beijing in January, 2010].

    Science.gov (United States)

    Zhu, Li-Hua; Tao, Jun; Chen, Zhong-Ming; Zhao, Yue; Zhang, Ren-Jian; Cao, Jun-Ji

    2012-01-01

    Aerosol samples for PM2.5 were collected from 1st January to 31st January 2010, in Beijing. The concentrations of organic carbon, elemental carbon, water-solubile ions and soil elements of all particle samples were determined by thermal/optical carbon analyzer, ion chromatography and X-ray fluorescence spectrometer, respectively. The scattering coefficients (b(sp)), absorbing coefficients (b(ap)) and meteorological parameters for this period were also measured. Ambient light extinction coefficients were reconstructed by IMPROVE formula and were compared with measured light extinction coefficients. The results showed that the average mass concentration of PM2.5 was (144.3 +/- 89.1) microg x m(-3) during campaigning period. The average values of measured b(ap), b(sp) and extinction coefficient (b(ext)) were (67.4 +/- 54.3), (328.5 +/- 353.8) and (395.9 +/- 405.2) Mm(-1), respectively. IMPROVE formula is suitable for source apportionment of light extinction coefficient in campaign period. The average value of calculated b'(ext) was (611 +/- 503) Mm(-1) in January, 2010. The major contributors to ambient light extinction coefficients included (NH4) 2SO4 (24.6%), NH4NO3 (11.6%), OM (45.5%), EC (11.9%) and FS (6.4%), respectively.

  12. An Empirical Method for Estimating Background Stratospheric Aerosol Extinction Profiles over China

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The current paper introduces an empirical method for estimating the vertical distribution of background stratospheric aerosol extinction profiles covering the latitude bands of 50±5°N,40±5°N,30±5°N,and 20±5°N and the longitude range of 75 135°E based on Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction measurements at wavelengths of 1020 nm,525 nm,452 nm,and 386 nm for the volcanically calm years between 1998 2004.With this method,the vertical distribution of stratospheric aerosol extinction coefficients can be estimated according to latitude and wavelength.Comparisons of the empirically calculated aerosol extinction profiles and the SAGE II aerosol measurements show that the empirically calculated aerosol extinction coefficients are consistent with SAGE II values,with relative differences within 10% from 2 km above the tropopause to 33 km,and within 22% from 33 km to 35 km.The empirically calculated aerosol stratospheric optical depths (vertically integrated aerosol extinction coefficient) at the four wavelengths are also consistent with the corresponding SAGE II optical depth measurements,with differences within 2.2% in the altitude range from 2 km above the tropopause to 35 km.

  13. Measurement of tropospheric CO2 and aerosol extinction profiles with Raman lidar

    Institute of Scientific and Technical Information of China (English)

    Peitao Zhao; Yinchao Zhang; Lian Wang; Kaifa Cao; Jia Su; Shunxing Hu; Huanling Hu

    2008-01-01

    A prototype Raman lidar was designed for monitoring tropospheric CO2 profile and other scientific investigatious.The third harmonic of Nd:YAG laser (354.7-nm wavelength) was used as stimulated light source to provide nighttime measurements.Filter with high rejection ratio performance was used to extract CO2 Raman signals from Rayleigh-Mie scattering signals effectively.To improve the real time monitoring function,a two-channel signal collection system was designed to collect CO2 and N2 Raman scattering signals simultaneously. The N2 Raman scattering signals were used to retrieve aerosol extinction coefficient.Typical features of CO2 concentration profile and aerosol extinction coefficient in Herei were presented.The mixing ratio of atmospheric CO2 in Hefei can reach about 360-400 ppmv.

  14. Comparison of predicted extinction coefficients of monoclonal antibodies with experimental values as measured by the Edelhoch method.

    Science.gov (United States)

    Maity, Haripada; Wei, Alex; Chen, Ethan; Haidar, Jaafar N; Srivastava, Arvind; Goldstein, Joel

    2015-01-01

    Pace et al. (1995) [1] recommended an equation used to predict extinction coefficient of a protein. However, no antibody data was included in the development of this equation. The main objective of this study was to therefore investigate how the predicted value of the extinction coefficient is comparable to the experimentally determined extinction coefficient of antibodies measured by the Edelhoch method. We have measured the extinction coefficients (ɛ) of 13 IgG1 monoclonal antibodies (mAbs) in phosphate buffer at pH 7.2. The maximum variability in the experimentally measured extinction coefficient of a given mAb molecule was found to be about 2%. Experimentally determined extinction coefficients of all mAbs were found to be lower than the predicted value, with the maximum difference found to being 4.7%. The highest and lowest values of experimental extinction coefficient among the thirteen IgG1 monoclonal antibodies obtained were 230525.9M(-1)cm(-1) (i.e. 1.55(mg/ml)(-1)cm(-1)) and 191,411.6M(-1)cm(-1) (i.e. 1.29(mg/ml)(-1)cm(-1)). A difference of experimental and predicted values of the extinction coefficient. A comprehensive analysis and interpretation of the comparison of the predicted and experimentally determined extinction coefficient by the Edelhoch method is discussed in terms of structural characterization and accessible surface area (ASA).

  15. Determination of aerosol extinction coefficient and mass extinction efficiency by DOAS with a flashlight source

    Institute of Scientific and Technical Information of China (English)

    Si Fu-Qi; Liu Jian-Guo; Xie Pin-Hua; Zhang Yu-Jun; Liu Wen-Qing; Hiroaki Kuze; Liu Cheng; Nofel Lagrosas; Nobuo Takeuchi

    2005-01-01

    With the method of differential optical absorption spectroscopy (DOAS), average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter (SPM). Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency (MEE) to be possible in the lower troposphere. The average MEE value is about 7.6m2.g-1, and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.

  16. Does spatial arrangement of 3D plants affect light transmission and extinction coefficient within maize crops?

    Science.gov (United States)

    Row spacing effects on light interception and extinction coefficient have been inconsistent for maize (Zea mays L.) when calculated with field measurements. To avoid inconsistencies due to variable light conditions and variable leaf canopies, we used a model to describe three-dimensional (3D) shoot ...

  17. Refinement of Fourier Coefficients from the Stokes Deconvoluted Profile

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Computer-aided experimental technique was used to study the Stokes deconvolution of X-ray diffraction profile.Considerable difference can be found between the Fourier coefficients obtained from the deconvolutions of singlet and doublet experimental profiles. Nevertheless, the resultant physical profiles corresponding to singlet and doublet profiles are identical. An approach is proposed to refine the Fourier coefficients, and the refined Fourier coefficients coincide well with that obtained from the deconvolution of singlet experimental profile.

  18. Extinction coefficient of H2CC(3B2) at 137 nm

    Science.gov (United States)

    Fahr, A.; Laufer, A. H.

    1985-01-01

    In spite of the conduction of numerous studies regarding the vinylidene free radical, its role and importance as a reactive intermediate is not well characterized. Laufer (1980, 1983) has reported the absorption spectrum of metastable H2CC(3B2), the lowest excited state, in the vacuum ultraviolet and has measured several aspects of its quenching properties. The present study provides a measurement of the extinction coefficient of H2CC(3B2). Knowledge of the vinylidene concentration is required to convert readily available absorption data into an extinction coefficient or cross section. In the current work, the H2CC(3B2) concentration was determined in an investigation of the photodissociation of vinyl chloride.

  19. Revised bolometric corrections and interstellar extinction coefficients for the ACS and WFPC2 photometric systems

    CERN Document Server

    Girardi, L; Williams, B; de Jong, R; Gallart, C; Monelli, M; Groenewegen, M A T; Holtzman, J A; Olsen, K A G; Seth, A C; Weisz, D R

    2008-01-01

    We present extensive tables of bolometric corrections and interstellar extinction coefficients for the WFPC2 and ACS (both WFC and HRC) photometric systems. They are derived from synthetic photometry applied to a database of spectral energy distributions covering a large range of effective temperatures, surface gravity, and metal content. Carbon stars are also considered. The zero-points take into consideration the new high-accuracy Vega fluxes from Bohlin. These tables are employed to transform Padova isochrones into WFPC2 and ACS photometric systems using interstellar extinction coefficients on a star-to-star basis. All data are available either in tabular form or via an interactive web interface in the case of the isochrones. Preliminary tables for the WFC3 camera are also included in the database.

  20. Atmospheric extinction coefficients and night sky brightness at the Xuyi Observation Station

    Institute of Scientific and Technical Information of China (English)

    Hui-Hua Zhang; Xiao-Wei Liu; Hai-Bo Yuan; Hai-Bin Zhao; Jin-Sheng Yao; Hua-Wei Zhang; Mao-Sheng Xiang

    2013-01-01

    We present measurements of the optical broadband atmospheric extinction coefficients and the night sky brightness at the Xuyi Observation Station of Purple Mountain Observatory.The measurements are based on CCD imaging data taken in the Sloan Digital Sky Survey's g,r and i bands with the Xuyi 1.04/1.20m Schmidt Telescope for the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticenter (XSTPS-GAC),the photometric part of the Digital Sky Survey of the Galactic Anti-center (DSS-GAC).The data were collected during more than 140 winter nights from 2009 to 2011.We find that the atmospheric extinction coefficients for the g,r and i bands are 0.69,0.55 and 0.38 mag/airmass,respectively,based on observations taken on several photometric nights.The night sky brightness determined from images with good quality has median values of 21.7,20.8 and 20.0 mag arcsec-2 and reaches 22.1,21.2 and 20.4 mag arcsec-2 under the best observing conditions for the g,r and i bands,respectively.The relatively large extinction coefficients compared with other good astronomical observing sites are mainly due to the relatively low elevation (i.e.180 m) and high humidity at the station.

  1. Evaluating Nighttime CALIOP 0.532 micron Aerosol Optical Depth and Extinction Coefficient Retrievals

    Science.gov (United States)

    Campbell, J. R.; Tackett, J. L.; Reid, J. S.; Zhang, J.; Curtis, C. A.; Hyer, E. J.; Sessions, W. R.; Westphal, D. L.; Prospero, J. M.; Welton, E. J.; Omar, A. H.; Vaughan, M. A.; Winker, D. M.

    2012-01-01

    NASA Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) Version 3.01 5-km nighttime 0.532 micron aerosol optical depth (AOD) datasets from 2007 are screened, averaged and evaluated at 1 deg X 1 deg resolution versus corresponding/co-incident 0.550 micron AOD derived using the US Navy Aerosol Analysis and Prediction System (NAAPS), featuring two-dimensional variational assimilation of quality-assured NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR) AOD. In the absence of sunlight, since passive radiometric AOD retrievals rely overwhelmingly on scattered radiances, the model represents one of the few practical global estimates available from which to attempt such a validation. Daytime comparisons, though, provide useful context. Regional-mean CALIOP vertical profiles of night/day 0.532 micron extinction coefficient are compared with 0.523/0.532 micron ground-based lidar measurements to investigate representativeness and diurnal variability. In this analysis, mean nighttime CALIOP AOD are mostly lower than daytime (0.121 vs. 0.126 for all aggregated data points, and 0.099 vs. 0.102 when averaged globally per normalised 1 deg. X 1 deg. bin), though the relationship is reversed over land and coastal regions when the data are averaged per normalised bin (0.134/0.108 vs. 0140/0.112, respectively). Offsets assessed within single bins alone approach +/- 20 %. CALIOP AOD, both day and night, are higher than NAAPS over land (0.137 vs. 0.124) and equal over water (0.082 vs. 0.083) when averaged globally per normalised bin. However, for all data points inclusive, NAAPS exceeds CALIOP over land, coast and ocean, both day and night. Again, differences assessed within single bins approach 50% in extreme cases. Correlation between CALIOP and NAAPS AOD is comparable during both day and night. Higher correlation is found nearest the equator, both as a function of sample size and relative signal magnitudes inherent at

  2. Correlations between urban atmospheric light extinction coefficients and fine particle mass concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Trier, A.; Cabrini, N.; Ferrer, J. [Facultad de Ciencia, Universidad de Santiago de Chile, Santiago 2 (Chile); Olaeta, I. [SESMA, Santiago 1 (Chile)

    1997-07-01

    Total horizontal atmospheric light extinction coefficients as well as particle mass concentrations have been measured in downtown areas of Santiago de Chile, a heavily polluted city. Measurement campaigns were carried out in 1994 in 1995. Extinction measurements were made by a telephotometric technique in four wavelength bands; oscillating mass balance type instruments were used to measure PM2.5 and PM10 mass concentrations. The latter type instrument had not been available heretofore. The extensive continuous PM2.5 measurements are the first for this city. Strong and highly significant statistical correlations were found between extinction coefficients and mass concentrations, especially with the fine respirable or PM2.5 mass concentrations. Angstrom exponents and, in one case, mass extinction coefficients have been estimated. [Spanish] Se ha medido coeficientes atmosfericos totales horizontales de extincion de luz asi como concentraciones de masa de particulas atmosfericas en zonas centricas de Santiago de Chile, una ciudad altamente contaminada. Las campanas de medicion se han hecho en 1994 y en 1995. Las mediciones de extincion se han hecho por un metodo telefotometrico en cuatro bandas espectrales; las concentraciones de masa PM2.5 y PM10 se han medido con instrumentos del tipo de balanzas de masa oscilantes. Tales instrumentos no han estado disponibles durante trabajos anteriores. Las extensas mediciones continuas de concentraciones de masa PM2.5 son las primeras para Santiago de Chile. Se han encontrado fuertes correlaciones estadisticas, altamente significativas, entre coeficientes de extincion y concentraciones de masa, especialmente las concentraciones de particulas finas respirables PM2.5. Se han estimado tambien exponentes de Angstrom y, en un caso, coeficientes masicos de extincion.

  3. Validation of the CALIPSO-CALIOP extinction coefficients from in situ observations in midlatitude cirrus clouds during the CIRCLE-2 experiment

    Science.gov (United States)

    Mioche, Guillaume; Josset, Damien; Gayet, Jean-FrançOis; Pelon, Jacques; Garnier, Anne; Minikin, Andreas; Schwarzenboeck, Alfons

    2010-01-01

    This paper presents a comparison of combined Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) extinction retrievals with airborne lidar and in situ cirrus cloud measurements. Specially oriented research flights were carried out in western Europe in May 2007 during the Cirrus Cloud Experiment (CIRCLE-2) with the German Deutsches Zentrum für Luft- und Raumfahrt (DLR) and the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon aircraft equipped for remote and in situ measurements, respectively. Four cirrus cloud situations including thin cirrus layers and outflow cirrus linked to midlatitude fronts and convective systems were chosen to perform experimental collocated observations along the satellite overpasses. The measurements were carried out with temperatures ranging between -38°C and -60°C and with extinction coefficients no larger than 2 km-1. Comparisons between CALIOP and airborne lidar (LEANDRE New Generation (LNG)) attenuated backscatter coefficients reveal much larger CALIOP values for one frontal cirrus situation which could be explained by oriented pristine ice crystals. During the four selected cases the CALIOP cirrus extinction profiles were compared with in situ extinction coefficients derived from the Polar Nephelometer. The results show a very good agreement for two situations (frontal and outflow cases) despite very different cloud conditions. The slope parameters of linear fittings of CALIOP extinction coefficients with respect to in situ measurements are 0.90 and 0.94, with correlation coefficients of 0.69 and only 0.36 for the latter case because of a small number of measurements. On the contrary, significant differences are evidenced for two other situations. In thin frontal cirrus at temperatures ranging between -58°C and -60°C, systematic larger CALIOP extinctions can be explained by horizontally

  4. The functional correlation between rainfall rate and extinction coefficient for frequencies from 3 to 10 GHz

    Science.gov (United States)

    Jameson, A. R.

    1990-01-01

    The relationship between the rainfall rate (R) obtained from radiometric brightness temperatures and the extinction coefficient (k sub e) is investigated by computing the values of k sub e over a wide range of rainfall rates, for frequencies from 3 to 25 GHz. The results show that the strength of the relation between the R and the k sub e values exhibits considerable variation for frequencies at this range. Practical suggestions are made concerning the selection of particular frequencies for rain measurements to minimize the error in R determinations.

  5. Synthesis and photoelectrochemical characterization of a high molar extinction coefficient heteroleptic ruthenium(II) complex

    Indian Academy of Sciences (India)

    L Giribabu; Vrun Kumar Singh; M Srinivasu; Ch Vijay Kumar; V Gopal Reddy; Y Soujnya; P Yella Reddy

    2011-07-01

    A new high molar extinction coefficient heteroleptic ruthenium(II) complex (m-BL-1) that contains a 4,4'4"-tricaboxy-2,2':6’,2”-terpyridine, 4,4’-bis-[3,5-di-tert-butyl-phenyl)-vinyl]-[2,2']bipyridyl and a thiocyanate ligand in its molecular structure has been synthesized and completely characterized by CHN, Mass, 1H-NMR, UV-Vis, and fluorescence spectroscopies as well as cyclic voltammetry. The new sensitizer was tested in dye-sensitized solar cells using three different redox electrolytes and compared its performance to that of standard sensitizer black dye.

  6. Spectrophotometric method for the quantitative assay of N-hydroxysulfosuccinimide esters including extinction coefficients and reaction kinetics.

    Science.gov (United States)

    Presentini, Rivo

    2017-05-15

    A quantitative spectrophotometric method has been developed for the analysis of N-hydroxysulfosuccinimide (sulfo-NHS), a chromophore with a maximum absorbance at 268 nm. The extinction coefficients were determined between pH 6.0 and 8.0 and found to vary in a nonlinear manner. This spectrophotometric profile is not present in its esters which however release an equimolar amount of sulfo-NHS when they react with nucleophilic groups or hydrolyze in aqueous solution. This fact facilitates the determination in solution of the concentration and purity of bis(sulfosuccinimidyl) suberate (BS3) used as a model, as well as the examination of hydrolysis and aminolysis half-lives in different reaction conditions, these parameters being valuable in optimization of the use of the active esters. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Extinction coefficient for red-shifted chlorophylls: chlorophyll d and chlorophyll f.

    Science.gov (United States)

    Li, Yaqiong; Scales, Nicholas; Blankenship, Robert E; Willows, Robert D; Chen, Min

    2012-08-01

    Both chlorophyll f and chlorophyll d are red-shifted chlorophylls in oxygenic photosynthetic organisms, which extend photon absorbance into the near infrared region. This expands the range of light that can be used to drive photosynthesis. Quantitative determination of chlorophylls is a crucial step in the investigation of chlorophyll-photosynthetic reactions in the field of photobiology and photochemistry. No methods have yet been worked out for the quantitative determination of chlorophyll f. There is also no method available for the precise quantitative determination of chlorophyll d although it was discovered in 1943. In order to obtain the extinction coefficients (ε) of chlorophyll f and chlorophyll d, the concentrations of chlorophylls were determined by Inductive Coupled Plasma Mass Spectrometry according to the fact that each chlorophyll molecule contains one magnesium (Mg) atom. Molar extinction coefficient ε(chl f) is 71.11×10(3)Lmol(-1)A(707nm)cm(-1) and ε(chl d) is 63.68×10(3)Lmol(-1)A(697nm)cm(-1) in 100% methanol. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.

  8. Atmospheric Extinction Coefficients and Night Sky Brightness At the Xuyi Observational Station

    CERN Document Server

    Zhang, H -H; Yuan, H -B; Zhao, H -B; Yao, J -S; Zhang, H -W; Xiang, M -S

    2012-01-01

    We present measurements of the optical broadband atmospheric extinction coefficients and the night sky brightness at the Xuyi Observational Station of Purple Mountain Observatory (PMO). The measurements are based on CCD imaging data taken in the Sloan Digital Sky Survey g, r and i bands with the Xuyi 1.04/1.20m Schmidt Telescope for the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center (XSTPS-GAC), the photometric part of the Digital Sky Survey of the Galactic Anti-center (DSS-GAC). The data were collected in more than 130 winter nights from 2009 to 2011. We find that the atmospheric extinction coefficients for the g, r and i bands are 0.70, 0.55 and 0.38 mag/airmass, respectively, based on observations taken in several photometric nights. The night sky brightness determined from images of good quality has median val- ues of 21.7, 20.8 and 20.0 mag/arcsec2 and reaches 22.1, 21.2 and 20.4 mag/arcsec2 under the best observing conditions for the g, r and i bands, respectively. The relatively ...

  9. Effect of Nitrogen Fertilizer on Light Interception and Light Extinction Coefficient in Different Wheat Cultivars

    Directory of Open Access Journals (Sweden)

    F Samadiyan

    2016-07-01

    Full Text Available Introduction Wheat (Triticum aestivum is a cereal grain, originated from the levant region of the near east and Ethiopian highlands, currently cultivated worldwide. Light extinction coefficient K is a coefficient that represents the amount of light reduced by the plant. Light or radiation extinction coefficient is a concept that expresses the light penetration decrease into the canopy in the way the upper leaves of the canopy with less angles have lower amount of K in comparison with the horizontal leaves. Green et al., (2003 stated that nitrogen fertilizer increased light absorption by plant leaves; and affects the yield. The distribution patterns of nitrogen allocation in leaves are more exposed therefore photosynthesis rate per unit leaf area and canopy were optimized. Differences in canopy structure by the light extinction coefficient (k of the Act Lambert - Beer is described, along LAI differing due to different species and genotypes which are important factors in absorption and light use efficiency. This experiment was performed to evaluate the maximum light absorption and light extinction coefficient in different levels of nitrogen usage and wheat cultivars. Materials and Methods An experiment was conducted during 2011-2012 on a research farm of Islamic Azad University, Isfahan Branch, located in Khatoon Abad Village (northern latitude of 320 and 40´ and eastern longitude of 510 and 48´ with altitude of 1555 m above sea level. A split plot layout within randomized complete block design was used with three replications. Main plots were consisted in four levels of N fertilizer (0, 50, 100 and 150 kg ha-1 from an urea source in main plots and different cultivars of wheat included Pishtaz, Sepahan and SW-486 in sub plots. Planting was performed on 14 November 2011 and at a density of 400 plants per square meter. In order to strengthen the land and required elements for plant regarding soil test and treatments based on the test plan, the

  10. Nanofabrication of low extinction coefficient and high-aspect-ratio Si structures for metaphotonic applications

    Science.gov (United States)

    Lee, JeongYub; Song, Byonggwon; Kim, Jaekwan; Lee, Chang-Won; Han, Seunghoon; Baik, Chan-Wook; Jeong, Heejeong; Kim, Yongsung; Lee, Chang Seung

    2016-09-01

    We investigated forming of high refractive index (n), low extinction coefficient (k) of Si dielectrics in visible wavelength ranges. To decrease k, pulsed green laser annealing (GLA) with line beam of a 532-nm wavelength was applied in this study for homogeneous melting. By AFM, XRD and TEM analysis, we examined the defect reduction in various conditions during poly-crystallization. We achieved dielectric nanostructures having optical properties of n>4.2, k<0.06 at 550 nm wavelength and fine pitches down to 40 nm (aspect ratio 3:1) and 130 nm (aspect ratio 7:1) with +/-5% size accuracy. Finally, we realized optical metasurfaces for optical band filters, flat lens and beam deflectors.

  11. Expectation Maximization and the retrieval of the atmospheric extinction coefficients by inversion of Raman lidar data

    CERN Document Server

    Garbarino, Sara; Massone, Anna Maria; Sannino, Alessia; Boselli, Antonella; Wang, Xuan; Spinelli, Nicola; Piana, Michele

    2016-01-01

    We consider the problem of retrieving the aerosol extinction coefficient from Raman lidar measurements. This is an ill--posed inverse problem that needs regularization, and we propose to use the Expectation--Maximization (EM) algorithm to provide stable solutions. Indeed, EM is an iterative algorithm that imposes a positivity constraint on the solution, and provides regularization if iterations are stopped early enough. We describe the algorithm and propose a stopping criterion inspired by a statistical principle. We then discuss its properties concerning the spatial resolution. Finally, we validate the proposed approach by using both synthetic data and experimental measurements; we compare the reconstructions obtained by EM with those obtained by the Tikhonov method, by the Levenberg-Marquardt method, as well as those obtained by combining data smoothing and numerical derivation.

  12. Coumarin-bearing triarylamine sensitizers with high molar extinction coefficient for dye-sensitized solar cells

    Science.gov (United States)

    Zhong, Changjian; Gao, Jianrong; Cui, Yanhong; Li, Ting; Han, Liang

    2015-01-01

    Coumarin unit is introduced into triarylamine and three organic sensitizers are designed and synthesized with triarylamine bearing coumarin moiety as the electron donor, conjugated system containing thiophene unit as the π-bridge, and cyanoacetic acid moiety as the electron acceptor. The light-harvesting capabilities and photovoltaic performance of these dyes are investigated systematically with the comparison of different π-bridges. High molar extinction coefficients are observed in these triarylamine dyes and the photocurrent and photovoltage are increased with the introduction of another thiophene or benzene. Optimal photovoltaic performance (η = 6.24%, Voc = 690 mV, Jsc = 14.33 mA cm-2, and ff = 0.63) is observed in the DSSC based on dye with thiophene-phenyl unit as the π-conjugated bridge under 100 mW cm-2 simulated AM 1.5 G solar irradiation.

  13. Expectation maximization and the retrieval of the atmospheric extinction coefficients by inversion of Raman lidar data.

    Science.gov (United States)

    Garbarino, Sara; Sorrentino, Alberto; Massone, Anna Maria; Sannino, Alessia; Boselli, Antonella; Wang, Xuan; Spinelli, Nicola; Piana, Michele

    2016-09-19

    We consider the problem of retrieving the aerosol extinction coefficient from Raman lidar measurements. This is an ill-posed inverse problem that needs regularization, and we propose to use the Expectation-Maximization (EM) algorithm to provide stable solutions. Indeed, EM is an iterative algorithm that imposes a positivity constraint on the solution, and provides regularization if iterations are stopped early enough. We describe the algorithm and propose a stopping criterion inspired by a statistical principle. We then discuss its properties concerning the spatial resolution. Finally, we validate the proposed approach by using both synthetic data and experimental measurements; we compare the reconstructions obtained by EM with those obtained by the Tikhonov method, by the Levenberg-Marquardt method, as well as those obtained by combining data smoothing and numerical derivation.

  14. RELATIONSHIP BETWEEN HORIZONTAL EXTINCTION COEFFICIENT AND PM10 CONCENTRATION IN XI'AN, CHINA,DURING 1980-2002

    Institute of Scientific and Technical Information of China (English)

    Huizheng Che; Xiaoye Zhang; Yang Li; Zijiang Zhou; Zhenlin Chen

    2006-01-01

    Based on daily visibility data obtained from 1980-2002 and air pollution index data from 2001-2004 in Xi'an, long-term variations and relationships for daily horizontal extinction coefficient and mass concentration of PM10 have been evaluated. A decreasing trend was found in horizontal extinction coefficient during the past 23 years, with higher values observed in 1980s relative to 1990s, and the highest and lowest values in winter and summer, respectively.Significant correlation and similar seasonal variations existed between horizontal extinction coefficient and PM10 concentration, suggesting the high influence of PM10 to the visibility drop at a site in the Guanzhong Plain of central China during the past two decades.

  15. Using Airborne High Spectral Resolution Lidar Data to Evaluate Combined Active Plus Passive Retrievals of Aerosol Extinction Profiles

    Science.gov (United States)

    Burton, S. P.; Ferrare, R. A.; Hostetler, C. A.; Hair, J. W.; Kittaka, C.; Vaughn, M. A.; Remer, L. A.

    2010-01-01

    We derive aerosol extinction profiles from airborne and space-based lidar backscatter signals by constraining the retrieval with column aerosol optical thickness (AOT), with no need to rely on assumptions about aerosol type or lidar ratio. The backscatter data were acquired by the NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL) and by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite. The HSRL also simultaneously measures aerosol extinction coefficients independently using the high spectral resolution lidar technique, thereby providing an ideal data set for evaluating the retrieval. We retrieve aerosol extinction profiles from both HSRL and CALIOP attenuated backscatter data constrained with HSRL, Moderate-Resolution Imaging Spectroradiometer (MODIS), and Multiangle Imaging Spectroradiometer column AOT. The resulting profiles are compared with the aerosol extinction measured by HSRL. Retrievals are limited to cases where the column aerosol thickness is greater than 0.2 over land and 0.15 over water. In the case of large AOT, the results using the Aqua MODIS constraint over water are poorer than Aqua MODIS over land or Terra MODIS. The poorer results relate to an apparent bias in Aqua MODIS AOT over water observed in August 2007. This apparent bias is still under investigation. Finally, aerosol extinction coefficients are derived from CALIPSO backscatter data using AOT from Aqua MODIS for 28 profiles over land and 9 over water. They agree with coincident measurements by the airborne HSRL to within +/-0.016/km +/- 20% for at least two-thirds of land points and within +/-0.028/km +/- 20% for at least two-thirds of ocean points.

  16. Impact of extinction coefficient of phosphor on thermal load of color conversion elements of phosphor converted LEDs

    Institute of Scientific and Technical Information of China (English)

    F.P. Wenzl; G. Langer; J. Nicolics; P. Fulmek; C. Sommer; S. Schweitzer; W. Nemitz; P. Hartmann; P. Pachler; H. Hoschopf; F. Schrank

    2014-01-01

    Besides their direct impact on the respective correlated color temperature, the extinction coefficient and the quantum effi-ciency of the phosphor also have tremendous impact on the thermal load of the color conversion elements of phosphor converted LEDs under operation. Because of the low thermal conductivity of the silicone matrix in which the phosphor particles are typically embedded, the by far highest temperatures within the LED assembly are reached within the color conversion element. Based on a combined optical and thermal simulation procedure we show that in particular a larger value for the extinction coefficient might have a beneficial impact on the resulting thermal load.

  17. Empirical extinction coefficients for the GALEX, SDSS, 2MASS and WISE passbands

    CERN Document Server

    Yuan, Hai-Bo; Xiang, Mao-Sheng

    2013-01-01

    Using the "standard pair" technique of paring stars of almost nil and high extinction but otherwise of almost identical stellar parameters from the SDSS, and combing the SDSS, GALEX, 2MASS and WISE photometry ranging from the far UV to the mid-IR, we have measured dust reddening in the FUV-NUV, NUV-u, u-g, g-r, r-i, i-z, z-J, J-H, H-Ks, Ks-W1 and W1-W2 colors for thousands of Galactic stars. The measurements, together with the E(B-V) values given by Schlegel et al. (1998), allow us to derive the observed, model-free reddening coefficients for those colors. The results are compared with previous measurements and the predictions of a variety of Galactic reddening laws. We find that 1) The dust reddening map of Schlegel et al. (1998) over-estimates E(B-V) by about 14 per cent, consistent with the recent work of Schlafly et al. (2010) and Schlafly & Finkbeiner (2011); 2) All the new reddening coefficients, except those for NUV-u and u-g, prefer the R(V) = 3.1 Fitzpatrick reddening law rather than the R(V) = 3...

  18. Determination of a refractive index and an extinction coefficient of standard production of CVD-graphene

    Science.gov (United States)

    Ochoa-Martínez, Efraín; Gabás, Mercedes; Barrutia, Laura; Pesquera, Amaia; Centeno, Alba; Palanco, Santiago; Zurutuza, Amaia; Algora, Carlos

    2015-01-01

    The refractive index and extinction coefficient of chemical vapour deposition grown graphene are determined by ellipsometry analysis. Graphene films were grown on copper substrates and transferred as both monolayers and bilayers onto SiO2/Si substrates by using standard manufacturing procedures. The chemical nature and thickness of residual debris formed after the transfer process were elucidated using photoelectron spectroscopy. The real layered structure so deduced has been used instead of the nominal one as the input in the ellipsometry analysis of monolayer and bilayer graphene, transferred onto both native and thermal silicon oxide. The effect of these contamination layers on the optical properties of the stacked structure is noticeable both in the visible and the ultraviolet spectral regions, thus masking the graphene optical response. Finally, the use of heat treatment under a nitrogen atmosphere of the graphene-based stacked structures, as a method to reduce the water content of the sample, and its effect on the optical response of both graphene and the residual debris layer are presented. The Lorentz-Drude model proposed for the optical response of graphene fits fairly well the experimental ellipsometric data for all the analysed graphene-based stacked structures.The refractive index and extinction coefficient of chemical vapour deposition grown graphene are determined by ellipsometry analysis. Graphene films were grown on copper substrates and transferred as both monolayers and bilayers onto SiO2/Si substrates by using standard manufacturing procedures. The chemical nature and thickness of residual debris formed after the transfer process were elucidated using photoelectron spectroscopy. The real layered structure so deduced has been used instead of the nominal one as the input in the ellipsometry analysis of monolayer and bilayer graphene, transferred onto both native and thermal silicon oxide. The effect of these contamination layers on the optical

  19. An evaluation of the SAGE III Version 4 aerosol extinction coefficient and water vapor data products

    Directory of Open Access Journals (Sweden)

    L. W. Thomason

    2009-10-01

    Full Text Available Herein, we provide an assessment of the data quality of Stratospheric Aerosol and Gas Experiment (SAGE III Version 4 aerosol extinction coefficient and water vapor data products. The evaluation is based on comparisons with data from four instruments: SAGE II, the Polar Ozone and Aerosol Measurement (POAM III, the Halogen Occultation Experiment (HALOE, and the Microwave Limb Sounder (MLS. Since only about half of the SAGE III channels have a direct comparison with measurements by other instruments, we have employed some empirical techniques to evaluate measurements at some wavelengths. We find that the aerosol extinction coefficient measurements at 449, 520, 755, 869, and 1021 nm are reliable with accuracies and precisions on the order of 10% in the primary aerosol range of 15 to 25 km. We also believe this to be true of the aerosol measurements at 1545 nm though we cannot exclude some positive bias below 15 km. We recommend use of the 385 nm measurements above 16 km where the accuracy is on par with other aerosol channels. The 601 nm measurement is much noisier (~20% than other channels and we suggest caution in the use of these data. We believe that the 676 nm data are clearly defective particularly above 20 km (accuracy as poor as 50% and the precision is also low (~30%. We suggest excluding this channel under most circumstances. The SAGE III Version 4 water vapor data product appears to be high quality and is recommended for science applications in the stratosphere below 45 km. In this altitude range, the mean differences with all four corroborative data sets are no bigger than 15% and often less than 10% with exceptional agreement with POAM III and MLS. Above 45 km, it seems likely that SAGE III water vapor values are increasingly too large and should be used cautiously or avoided. We believe that SAGE III meets its preflight goal of 15% accuracy and 10% precision between 15 and 45 km. We do not currently recommend limiting the SAGE III

  20. Toward a Combined SAGE II-HALOE Aerosol Climatology: An Evaluation of HALOE Version 19 Stratospheric Aerosol Extinction Coefficient Observations

    Science.gov (United States)

    Thomason, L. W.

    2012-01-01

    Herein, the Halogen Occultation Experiment (HALOE) aerosol extinction coefficient data is evaluated in the low aerosol loading period after 1996 as the first necessary step in a process that will eventually allow the production of a combined HALOE/SAGE II (Stratospheric Aerosol and Gas Experiment) aerosol climatology of derived aerosol products including surface area density. Based on these analyses, it is demonstrated that HALOE's 3.46 microns is of good quality above 19 km and suitable for scientific applications above that altitude. However, it is increasingly suspect at lower altitudes and should not be used below 17 km under any circumstances after 1996. The 3.40 microns is biased by about 10% throughout the lower stratosphere due to the failure to clear NO2 but otherwise appears to be a high quality product down to 15 km. The 2.45 and 5.26 micron aerosol extinction coefficient measurements are clearly biased and should not be used for scientific applications after the most intense parts of the Pinatubo period. Many of the issues in the aerosol data appear to be related to either the failure to clear some interfering gas species or doing so poorly. For instance, it is clear that the 3.40micronaerosol extinction coefficient measurements can be improved through the inclusion of an NO2 correction and could, in fact, end up as the highest quality overall HALOE aerosol extinction coefficient measurement. It also appears that the 2.45 and 5.26 micron channels may be improved by updating the Upper Atmosphere Pilot Database which is used as a resource for the removal of gas species otherwise not available from direct HALOE measurements. Finally, a simple model to demonstrate the promise of mixed visible/infrared aerosol extinction coefficient ensembles for the retrieval of bulk aerosol properties demonstrates that a combined HALOE/SAGE II aerosol climatology is feasible and may represent a substantial improvement over independently derived data sets.

  1. A High Molar Extinction Coefficient Mono-Anthracenyl Bipyridyl Heteroleptic Ruthenium(II Complex: Synthesis, Photophysical and Electrochemical Properties

    Directory of Open Access Journals (Sweden)

    Peter A. Ajibade

    2011-06-01

    Full Text Available In our quest to develop good materials as photosensitizers for photovoltaic dye-sensitized solar cells (DSSCs, cis-dithiocyanato-4-(2,3-dimethylacrylic acid-2,2'-bipyridyl-4-(9-anthracenyl-(2,3-dimethylacrylic-2,2'-bipyridyl ruthenium(II complex, a high molar extinction coefficient charge transfer sensitizer, was designed, synthesized and characterized by spectroscopy and electrochemical techniques. Earlier studies on heteroleptic ruthenium(II complex analogues containing functionalized oligo-anthracenyl phenanthroline ligands have been reported and documented. Based on a general linear correlation between increase in the length of π-conjugation bond and the molar extinction coefficients, herein, we report the photophysical and electrochemical properties of a Ru(II bipyridyl complex analogue with a single functionalized anthracenyl unit. Interestingly, the complex shows better broad and intense metal-to ligand charge transfer (MLCT band absorption with higher molar extinction coefficient (λmax = 518 nm, e = 44900 M−1cm−1, and appreciable photoluminescence spanning the visible region than those containing higher anthracenyl units. It was shown that molar absorption coefficient of the complexes may not be solely depended on the extended π-conjugation but are reduced by molecular aggregation in the molecules.

  2. Analysis of influence of atmosphere extinction to Raman lidar monitoring CO2 concentration profile

    Institute of Scientific and Technical Information of China (English)

    Zhao Pei-Tao; Zhang Yin-Chao; Wang Lian; Zhao Yue-Feng; Su Jia; Fang Xin; Cao Kai-Fa; Xie Jun; Du Xiao-Yong

    2007-01-01

    Lidar (Light detection and ranging) system monitoring of the atmosphere is a novel and powerful technique tool. The Raman lidar is well established today as a leading research tool in the study of numerous important areas in the atmospheric sciences. In this paper, the principle of Raman lidar technique measurement CO2 concentration profile is presented and the errors caused by molecular and aerosol extinction for CO2 concentration profile measurement with Raman lidar are also presented. The standard atmosphere extinction profile and 'real-time' Hefei area extinction profile are used to conduct correction and the corresponding results are yielded. Simulation results with standard atmosphere mode correction indicate that the errors caused by molecule and aerosol extinction should be counted for the reason that they could reach about 8 ppm and 5 ppm respectively. The relative error caused by Hefei area extinction correction could reach about 6%. The errors caused by the two components extinction influence could produce significant changes for CO2 concentration profile and need to be counted in data processing which could improve the measurement accuracies.

  3. Recent Improvements to CALIOP Level 3 Aerosol Profile Product for Global 3-D Aerosol Extinction Characterization

    Science.gov (United States)

    Tackett, J. L.; Getzewich, B. J.; Winker, D. M.; Vaughan, M. A.

    2015-12-01

    With nine years of retrievals, the CALIOP level 3 aerosol profile product provides an unprecedented synopsis of aerosol extinction in three dimensions and the potential to quantify changes in aerosol distributions over time. The CALIOP level 3 aerosol profile product, initially released as a beta product in 2011, reports monthly averages of quality-screened aerosol extinction profiles on a uniform latitude/longitude grid for different cloud-cover scenarios, called "sky conditions". This presentation demonstrates improvements to the second version of the product which will be released in September 2015. The largest improvements are the new sky condition definitions which parse the atmosphere into "cloud-free" views accessible to passive remote sensors, "all-sky" views accessible to active remote sensors and "cloudy-sky" views for opaque and transparent clouds which were previously inaccessible to passive remote sensors. Taken together, the new sky conditions comprehensively summarize CALIOP aerosol extinction profiles for a broad range of scientific queries. In addition to dust-only extinction profiles, the new version will include polluted-dust and smoke-only extinction averages. A new method is adopted for averaging dust-only extinction profiles to reduce high biases which exist in the beta version of the level 3 aerosol profile product. This presentation justifies the new averaging methodology and demonstrates vertical profiles of dust and smoke extinction over Africa during the biomass burning season. Another crucial advancement demonstrated in this presentation is a new approach for computing monthly mean aerosol optical depth which removes low biases reported in the beta version - a scenario unique to lidar datasets.

  4. Measurement of atmospheric extinction coefficient in the visible spectral region at Bangi, Malaysia

    Science.gov (United States)

    Aljawi, Ohoud; Gopir, Geri; Kamil, W. M. A. Wan Mohd; Mohamad, Nor Sakinah

    2016-11-01

    The purpose of this study is to determine the total optical thickness for different atmospheric extinction and for different wavelengths through the visible region. A portable Avantes AvaSpec ULS 2048X64-USB2 spectrometer was used, over Bangi (2° 55' N, 101° 46' E, and 50 m above sea level) in Malaysia. Experimental techniques, sample observation, are presented for obtaining atmospheric extinction from spectrometer measurement. The study has revealed that the total atmospheric extinction for the wavelength 400 nm,500 nm, 600 nm, and 700 nm under cloudless sky was successful obtained by Langley methods.

  5. Profiling filaments: comparing near-infrared extinction and submillimetre data in TMC-1

    CERN Document Server

    Malinen, J; Rawlings, M G; Ward-Thompson, D; Palmeirim, P; Andre, Ph

    2012-01-01

    Interstellar filaments are an important part of star formation. To understand the structure of filaments, cross-section profiles are often fitted with Plummer profiles. This profiling is often done with submm studies, such as Herschel. It would be convenient if filament properties could also be studied using groundbased NIR data. We compare the filament profiles obtained by NIR extinction and submm observations to find out if reliable profiles can be derived using NIR data. We use J-, H-, and K-band data of a filament north of TMC-1 to derive an extinction map from colour excesses of background stars. We compare the Plummer profiles obtained from extinction maps with Herschel dust emission maps. We present 2 methods to estimate profiles from NIR: Plummer profile fits to median Av of stars or directly to the Av of individual stars. We compare the methods by simulations. In simulations extinction maps and the new methods give correct results to within ~10-20 for modest densities. Direct fit to data on individua...

  6. Toward a combined SAGE II-HALOE aerosol climatology: an evaluation of HALOE version 19 stratospheric aerosol extinction coefficient observations

    Directory of Open Access Journals (Sweden)

    L. W. Thomason

    2012-09-01

    Full Text Available Herein, the Halogen Occultation Experiment (HALOE aerosol extinction coefficient data is evaluated in the low aerosol loading period after 1996 as the first necessary step in a process that will eventually allow the production of a combined HALOE/SAGE II (Stratospheric Aerosol and Gas Experiment aerosol climatology of derived aerosol products including surface area density. Based on these analyses, it is demonstrated that HALOE's 3.46 μm is of good quality above 19 km and suitable for scientific applications above that altitude. However, it is increasingly suspect at lower altitudes and should not be used below 17 km under any circumstances after 1996. The 3.40 μm is biased by about 10% throughout the lower stratosphere due to the failure to clear NO2 but otherwise appears to be a high quality product down to 15 km. The 2.45 and 5.26 μm aerosol extinction coefficient measurements are clearly biased and should not be used for scientific applications after the most intense parts of the Pinatubo period. Many of the issues in the aerosol data appear to be related to either the failure to clear some interfering gas species or doing so poorly. For instance, it is clear that the 3.40 μm aerosol extinction coefficient measurements can be improved through the inclusion of an NO2 correction and could, in fact, end up as the highest quality overall HALOE aerosol extinction coefficient measurement. It also appears that the 2.45 and 5.26 μm channels may be improved by updating the Upper Atmosphere Pilot Database which is used as a resource for the removal of gas species otherwise not available from direct HALOE measurements. Finally, a simple model to demonstrate the promise of mixed visible/infrared aerosol extinction coefficient ensembles for the retrieval of bulk aerosol properties demonstrates that a combined HALOE/SAGE II aerosol climatology is feasible and may represent a substantial improvement over independently derived

  7. Extinction coefficients of CC and CC bands in ethyne and ethene molecules interacting with Cu+ and Ag+ in zeolites--IR studies and quantumchemical DFT calculations.

    Science.gov (United States)

    Kozyra, Paweł; Góra-Marek, Kinga; Datka, Jerzy

    2015-02-05

    The values of extinction coefficients of CC and CC IR bands of ethyne and ethene interacting with Cu+ and Ag+ in zeolites were determined in quantitative IR experiments and also by quantumchemical DFT calculations with QM/MM method. Both experimental and calculated values were in very good agreement validating the reliability of calculations. The values of extinction coefficients of ethyne and ethene interacting with bare cations and cations embedded in zeolite-like clusters were calculated. The interaction of organic molecules with Cu+ and Ag+ in zeolites ZSM-5 and especially charge transfers between molecule, cation and zeolite framework was also discussed in relation to the values of extinction coefficients.

  8. The CU Airborne MAX-DOAS instrument: vertical profiling of aerosol extinction and trace gases

    Science.gov (United States)

    Baidar, S.; Oetjen, H.; Coburn, S.; Dix, B.; Ortega, I.; Sinreich, R.; Volkamer, R.

    2013-03-01

    The University of Colorado Airborne Multi-Axis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument uses solar stray light to detect and quantify multiple trace gases, including nitrogen dioxide (NO2), glyoxal (CHOCHO), formaldehyde (HCHO), water vapor (H2O), nitrous acid (HONO), iodine monoxide (IO), bromine monoxide (BrO), and oxygen dimers (O4) at multiple wavelengths (absorption bands at 360, 477, 577, 632 nm) simultaneously in the open atmosphere. The instrument is unique as it (1) features a motion compensation system that decouples the telescope field of view from aircraft movements in real time (CHOCHO, HCHO, and H2O concentrations and aerosol extinction coefficients, ɛ, at 477 nm calculated from O4 measurements from a low approach at Brackett airfield inside the South Coast Air Basin (SCAB) are presented. These profiles contain ~12 degrees of freedom (DOF) over a 3.5 km altitude range, an independent information approximately every 250 m. The boundary layer NO2 concentration, and the integral aerosol extinction over height (aerosol optical depth, AOD) agrees well with nearby ground-based in situ NO2 measurement, and AERONET station. The detection limits of NO2, CHOCHO, HCHO, H2O442, ϵ360, ϵ477 for 30 s integration time spectra recorded forward of the plane are 5 ppt, 3 ppt, 100 ppt, 42 ppm, 0.004 km-1, 0.002 km-1 in the free troposphere (FT), and 30 ppt, 16 ppt, 540 ppt, 252 ppm, 0.012 km-1, 0.006 km-1 inside the boundary layer (BL), respectively. Mobile column observations of trace gases and aerosols are complimentary to in situ observations, and help bridge the spatial scales that are probed by satellites and ground-based observations, and predicted by atmospheric models.

  9. Radiative and thermodynamic responses to aerosol extinction profiles during the pre-monsoon month over South Asia

    Directory of Open Access Journals (Sweden)

    Y. Feng

    2015-06-01

    Full Text Available Aerosol radiative effects and thermodynamic responses over South Asia are examined with a version of the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem for March 2012. Model results of Aerosol Optical Depth (AOD and extinction profiles are analyzed and compared to satellite retrievals and two ground-based lidars located in the northern India. The WRF-Chem model is found to underestimate the AOD during the simulated pre-monsoon month and about 83 % of the model low-bias is due to aerosol extinctions below ~2 km. Doubling the calculated aerosol extinctions below 850 hPa generates much better agreement with the observed AOD and extinction profiles averaged over South Asia. To separate the effect of absorption and scattering properties, two runs were conducted: in one run (Case I, the calculated scattering and absorption coefficients were increased proportionally, while in the second run (Case II only the calculated aerosol scattering coefficient was increased. With the same AOD and extinction profiles, the two runs produce significantly different radiative effects over land and oceans. On the regional mean basis, Case I generates 48 % more heating in the atmosphere and 21 % more dimming at the surface than Case II. Case I also produces stronger cooling responses over the land from the longwave radiation adjustment and boundary layer mixing. These rapid adjustments offset the stronger radiative heating in Case I and lead to an overall lower-troposphere cooling up to −0.7 K day−1, which is smaller than that in Case II. Over the ocean, direct radiative effects dominate the heating rate changes in the lower atmosphere lacking such surface and lower atmosphere adjustments due to fixed sea surface temperature, and the strongest atmospheric warming is obtained in Case I. Consequently, atmospheric dynamics (boundary layer heights and meridional circulation and thermodynamic processes (water vapor and cloudiness are shown to

  10. Radiative and thermodynamic responses to aerosol extinction profiles during the pre-monsoon month over South Asia

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Y.; Kotamarthi, V. R.; Coulter, R.; Zhao, C.; Cadeddu, M.

    2016-01-01

    Aerosol radiative effects and thermodynamic responses over South Asia are examined with the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) for March 2012. Model results of aerosol optical depths (AODs) and extinction profiles are analyzed and compared to satellite retrievals and two ground-based lidars located in northern India. The WRF-Chem model is found to heavily underestimate the AOD during the simulated pre-monsoon month and about 83 % of the model's low bias is due to aerosol extinctions below ~2 km. Doubling the calculated aerosol extinctions below 850 hPa generates much better agreement with the observed AOD and extinction profiles averaged over South Asia. To separate the effect of absorption and scattering properties, two runs were conducted: in one run (Case I), the calculated scattering and absorption coefficients were increased proportionally, while in the second run (Case II) only the calculated aerosol scattering coefficient was increased. With the same AOD and extinction profiles, the two runs produce significantly different radiative effects over land and oceans. On the regional mean basis, Case I generates 48 % more heating in the atmosphere and 21 % more dimming at the surface than Case II. Case I also produces stronger cooling responses over the land from the longwave radiation adjustment and boundary layer mixing. These rapid adjustments offset the stronger radiative heating in Case I and lead to an overall lower-troposphere cooling up to -0.7 K day−1, which is smaller than that in Case II. Over the ocean, direct radiative effects dominate the heating rate changes in the lower atmosphere lacking such surface and lower atmosphere adjustments due to fixed sea surface temperature, and the strongest atmospheric warming is obtained in Case I. Consequently, atmospheric dynamics (boundary layer heights and meridional circulation) and thermodynamic processes (water vapor and cloudiness) are shown to

  11. A method based on iterative morphological filtering and multiple scattering for detecting layer boundaries and extinction coefficients with LIDAR

    Science.gov (United States)

    Li, Meng; Jiang, Li-Hui; Xiong, Xing-Long; Ma, Yu-Zhao; Liu, Jie-Sheng

    2016-08-01

    Layer boundaries detection with LIDAR is of great significance for the meteorological and environmental research. Apart from the background noise, multiple scattering can also seriously affect the detection results in LIDAR signal processing. To alleviate these issues, a novel approach was proposed based upon morphological filtering and multiple scattering correction with multiple iterations, which essentially acts as a weighted algorithm with multiple scattering factors in different filtering scales, and applies integral extinction coefficients as media to perform correction. Simulations on artificial signals and real LIDAR signals support this approach.

  12. The CU Airborne MAX-DOAS instrument: vertical profiling of aerosol extinction and trace gases

    Directory of Open Access Journals (Sweden)

    S. Baidar

    2013-03-01

    Full Text Available The University of Colorado Airborne Multi-Axis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS instrument uses solar stray light to detect and quantify multiple trace gases, including nitrogen dioxide (NO2, glyoxal (CHOCHO, formaldehyde (HCHO, water vapor (H2O, nitrous acid (HONO, iodine monoxide (IO, bromine monoxide (BrO, and oxygen dimers (O4 at multiple wavelengths (absorption bands at 360, 477, 577, 632 nm simultaneously in the open atmosphere. The instrument is unique as it (1 features a motion compensation system that decouples the telescope field of view from aircraft movements in real time ( The instrument is described, and data from flights over California during the CalNex (California Research at the Nexus of Air Quality and Climate Change and CARES (Carbonaceous Aerosols and Radiative Effects Study air quality field campaigns is presented. Horizontal distributions of NO2 VCD (below the aircraft maps are sampled with typically 1 km resolution, and show good agreement with two ground-based MAX-DOAS instruments (slope = 0.95 ± 0.09, R2 = 0.86. As a case study vertical profiles of NO2, CHOCHO, HCHO, and H2O concentrations and aerosol extinction coefficients, ε, at 477 nm calculated from O4 measurements from a low approach at Brackett airfield inside the South Coast Air Basin (SCAB are presented. These profiles contain ~12 degrees of freedom (DOF over a 3.5 km altitude range, an independent information approximately every 250 m. The boundary layer NO2 concentration, and the integral aerosol extinction over height (aerosol optical depth, AOD agrees well with nearby ground-based in situ NO2 measurement, and AERONET station. The detection limits of NO2, CHOCHO, HCHO, H2O442, ϵ360, ϵ477 for 30 s integration time spectra recorded forward of the plane are 5 ppt, 3 ppt, 100 ppt, 42 ppm, 0.004 km−1, 0.002 km−1 in the free troposphere (FT, and 30 ppt, 16 ppt, 540 ppt, 252 ppm, 0.012 km−1, 0.006 km−1

  13. Empirical extinction coefficients for the GALEX, SDSS, 2MASS and WISE passbands

    OpenAIRE

    2013-01-01

    Using the "standard pair" technique of paring stars of almost nil and high extinction but otherwise of almost identical stellar parameters from the SDSS, and combing the SDSS, GALEX, 2MASS and WISE photometry ranging from the far UV to the mid-IR, we have measured dust reddening in the FUV-NUV, NUV-u, u-g, g-r, r-i, i-z, z-J, J-H, H-Ks, Ks-W1 and W1-W2 colors for thousands of Galactic stars. The measurements, together with the E(B-V) values given by Schlegel et al. (1998), allow us to derive ...

  14. Testing Method of Infrared Extinction Coefficient of Smoke Screen by Thermal Imager%烟幕红外消光系数的热像仪测试

    Institute of Scientific and Technical Information of China (English)

    阎俊宏; 高磊; 闵江

    2012-01-01

    The extinction principle of the smoke screen is explained,the infrared extinction coefficient is the basic foundation to assess the infrared extinction performance.The three test methods of the infrared extinction co efficient are introduced: the testing methods of Fourier spectrometer,infrared radiometer and thermal imager,and the testing method of infrared extinction coefficient for thermal imager is discussed further.The thermal imager can assess the extinction performance of the smoke screen materials by testing the extinction coefficient of the materi als.%阐述了烟幕的消光原理,提出了红外消光系数是评定烟幕对红外消光性能的基本依据,简单介绍了3种红外消光系数测试方法,即傅里叶光谱仪测试方法、红外辐射计测试方法、热像仪测试方法。并对其中热像仪测试材料红外消光系数的方法进一步探讨,并指出,通过材料消光系数测试,热像仪可以对烟幕材料消光性能进行定量评价。

  15. Verification and application of the extended Spectral Deconvolution Algorithm (SDA+ methodology to estimate aerosol fine and coarse mode extinction coefficients in the marine boundary layer

    Directory of Open Access Journals (Sweden)

    K. C. Kaku

    2014-03-01

    Full Text Available The Spectral Deconvolution Algorithm (SDA and SDA+ (extended SDA methodologies can be employed to separate the fine and coarse mode extinction coefficients from measured total aerosol extinction coefficients, but their common use is currently limited to AERONET Aerosol Optical Depth (AOD. Here we provide the verification of the SDA+ methodology on a non-AERONET aerosol product, by applying it to fine and coarse mode nephelometer and Particle Soot Absorption Photometer (PSAP data sets collected in the marine boundary layer. Using datasets collected on research vessels by NOAA PMEL, we demonstrate that with accurate input, SDA+ is able to predict the fine and coarse mode scattering and extinction coefficient partition in global data sets representing a range of aerosol regimes. However, in low-extinction regimes commonly found in the clean marine boundary layer, SDA+ output accuracy is sensitive to instrumental calibration errors. This work was extended to the calculation of coarse and fine mode scattering coefficients with similar success. This effort not only verifies the application of the SDA+ method to in situ data, but by inference verifies the method as a whole for a host of applications, including AERONET. Study results open the door to much more extensive use of nephelometers and PSAPs, with the ability to calculate fine and coarse mode scattering and extinction coefficients in field campaigns that do not have the resources to explicitly measure these values.

  16. Application of Finite Difference Technique to Raman Lidar Signals to Derive the Altitude Profiles of Atmospheric Aerosol Extinction

    Directory of Open Access Journals (Sweden)

    PURUSOTHAM S

    2015-06-01

    Full Text Available Lidars (Laser radars are the best suitable instruments to derive the range resolved parameters of atmosphere. Single wavelength and simple backscatter lidars have been widely used to study the height profiles of particle scattering and extinction in the atmosphere. However, atmospheric extinction derived using these lidars data undergo several assumptions and hence involve a significant amount of error in estimation of extinction. The Raman lidar methodology of deriving particle extinction in the atmosphere is a simplified straight-forward method that does not involve any assumptions. The Raman lidar method of atmospheric extinction computation employs derivative of logarithm of normalized range corrected Raman backscattered signal. Usually this causes gaps in the height profiles wherever there is a gradient in the signal under examination. In the present study, a new method is proposed to derive the particle extinction in the atmospheric boundary layer. In this new method, a scheme of alternative solution methodology has been proposed using “Finite Difference Technique”. The method has an advantage that, it does not involve the gradient as compared to conventional technique and hence reduces the error. Using this method, the height profiles of particle extinction has been derived. A code in MATLAB is developed to derive the altitude distribution of aerosol extinction. In this connection, the NOAA-REDY site data has been used as the reference data for calculating the molecular extinction in the lower atmosphere.

  17. Observations of particle extinction, PM2.5 mass concentration profile and flux in north China based on mobile lidar technique

    Science.gov (United States)

    Lv, Lihui; Liu, Wenqing; Zhang, Tianshu; Chen, Zhenyi; Dong, Yunsheng; Fan, Guangqiang; Xiang, Yan; Yao, Yawei; Yang, Nan; Chu, Baolin; Teng, Man; Shu, Xiaowen

    2017-09-01

    Fine particle with diameter limited by the lack of monitoring data obtained with multiple fixed site sampling strategies. Mobile monitoring has provided a means for broad measurement of fine particles. In this research, the potential use of mobile lidar to map the distribution and transport of fine particles was discussed. The spatial and temporal distributions of particle extinction, PM2.5 mass concentration and regional transport flux of fine particle in the planetary boundary layer were investigated with the use of vehicle-based mobile lidar and wind field data from north China. Case studies under different pollution levels in Beijing were presented to evaluate the contribution of regional transport. A vehicle-based mobile lidar system was used to obtain the spatial and temporal distributions of particle extinction in the measurement route. Fixed point lidar and a particulate matter sampler were operated next to each other at the University of Chinese Academy of Science (UCAS) in Beijing to determine the relationship between the particle extinction coefficient and PM2.5 mass concentration. The correlation coefficient (R2) between the particle extinction coefficient and PM2.5 mass concentration was found to be over 0.8 when relative humidity (RH) was less than 90%. A mesoscale meteorological model, the Weather Research and Forecasting (WRF) model, was used to obtain profiles of the horizontal wind speed, wind direction and relative humidity. A vehicle-based mobile lidar technique was applied to estimate transport flux based on the PM2.5 profile and vertical profile of wind data. This method was applicable when hygroscopic growth can be neglected (relatively humidity<90%). Southwest was found to be the main pathway of Beijing during the experiments.

  18. Spectro-ellipsometric studies of sputtered amorphous Titanium dioxide thin films: simultaneous determination of refractive index, extinction coefficient, and void distribution

    CERN Document Server

    Lee, S I; Oh, S G

    1999-01-01

    Amorphous titanium dioxide thin films were deposited onto silicon substrates by using RF magnetron sputtering, and the index of refraction, the extinction coefficient, and the void distribution of these films were simultaneously determined from the analyses of there ellipsometric spectra. In particular, our novel strategy, which combines the merits of multi-sample fitting, the dual dispersion function, and grid search, was proven successful in determining optical constants over a wide energy range, including the energy region where the extinction coefficient was large. Moreover, we found that the void distribution was dependent on the deposition conditions, such as the sputtering power, the substrate temperature, and the substrate surface.

  19. A subtle calculation method for nanoparticle’s molar extinction coefficient: The gift from discrete protein-nanoparticle system on agarose gel electrophoresis

    Science.gov (United States)

    Zhong, Ruibo; Yuan, Ming; Gao, Haiyang; Bai, Zhijun; Guo, Jun; Zhao, Xinmin; Zhang, Feng

    2016-03-01

    Discrete biomolecule-nanoparticle (NP) conjugates play paramount roles in nanofabrication, in which the key is to get the precise molar extinction coefficient of NPs. By making best use of the gift from a specific separation phenomenon of agarose gel electrophoresis (GE), amphiphilic polymer coated NP with exact number of bovine serum albumin (BSA) proteins can be extracted and further experimentally employed to precisely calculate the molar extinction coefficient of the NPs. This method could further benefit the evaluation and extraction of any other dual-component NP-containing bio-conjugates.

  20. Determination of refractive index, extinction coefficient and thickness of thin films by the method of waveguide mode excitation

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, V I; Marusin, N V; Panchenko, V Ya; Savelyev, A G; Seminogov, V N; Khaydukov, E V [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation)

    2013-12-31

    We propose a method for measuring simultaneously the refractive index n{sub f}, extinction coefficient m{sub f} and thickness H{sub f} of thin films. The method is based on the resonant excitation of waveguide modes in the film by a TE- or a TM-polarised laser beam in the geometry of frustrated total internal reflection. The values of n{sub f}, m{sub f} and H{sub f} are found by minimising the functional φ = [N{sup -1}Σ{sup N}{sub i=1}(R{sub exp}(θ{sub i}) – R{sub thr}(θ{sub i})){sup 2}]{sup 1/2}, where R{sub exp}(θ{sub i}) and R{sub thr}(θ{sub i}) are the experimental and theoretical coefficients of reflection of the light beam from the interface between the measuring prism and the film at an angle of incidence θ{sub i}. The errors in determining n{sub f}, m{sub f} and H{sub f} by this method are ±2 × 10{sup -4}, ±1 × 10{sup -3} and ±0.5%, respectively. (fiber and integrated optics)

  1. Relationships between aerosol extinction coefficients derived from airport visual range observations and alternative measures of airborne particle mass

    Energy Technology Data Exchange (ETDEWEB)

    Oezkaynak, H.; Schatz, A.D.; Thurston, G.D.; Isaacs, R.G.; Husar, R.B.

    1985-11-01

    This paper analyzes methods for predicting fine particle (M/sub f/ and inhalable particle (IP) mass concentrations using relative humidity corrected light extinction coefficient (b/sub ext/) estimated from airport visual range (V/sub r) observations. The analyses presented are based on theoretical determinations as well as statistical investigations utilizing EPA's NASN and Inhalable Particle Monitoring Network (IPMN) data bases and routine airport visual range observations in twelve large US cities. Our results indicate that, after controlling for certain limitations of airport visual range data, most of the regression models developed in this paper can be applied satisfactorily to predict M/sub f/ and IP. Furthermore, the findings indicate that a more representative formula than the commonly used meteorological range formula to predict atmospheric b/sub ext/ values in urban areas may be b/sub ext/ = (1.8 +/- 0.04)/V/sub r/. Because of known local or regional influences, however, the authors suggest calibration of any predictive model which utilizes airport visibility data against site-specific aerometric data on particle mass concentrations or scattering coefficient measurements.

  2. A novel method for determining the boundary value of the atmospheric extinction coefficient%一种新的大气消光系数边界值确定方法

    Institute of Scientific and Technical Information of China (English)

    熊兴隆; 冯帅; 蒋立辉; 庄子波

    2011-01-01

    In this paper,in order to measure the slam visibility at the airport runway using a lidar,a method based on the fixed-point principle is proposed to determine the boundary value of the atmospheric extinction coefficient. Using the method, the problem is reduced to the problem of searching for the fixed point of a function. A reference point in the bottom boundary layer was firstly selected and a boundary value of the extinction coefficient was assumed. The function between the mean extinction coefficient and its boundary value was constructed based on the Klett inversion algorithm. Secondly, the existence of the fixed point was judged according to the existence and uniqueness condition, and the extinction coefficient converged to the fixed point through iteration. Consequently, the mean extinction coefficient and its boundary value were obtained. After the availability of the method under non-uniform atmospheric conditions had been verified by numerical simulations, the method was applied to invert the extinction coefficient from the real lidar return signals. The vertical profiles of the atmospheric extinction coefficient were further obtained. The results show that under the lower atmospheric condition,the proposed method for determining the boundary value can be used to invert the atmospheric extinction coefficient more efficiently than the clean-layer method.%本文以激光雷达测量机场跑道斜程能见度为应用背景,提出了一种基于不动点原理的大气消光系数边界值确定方法,将确定消光系数边界值的问题转化为求解函数不动点。首先在边界层底部选取参考点,假设一个消光系数边界值,在Klett反演算法的基础上,构建消光系数均值与边界值之间的函数关系。然后依据函数不动点存在性和唯一性的条件判断不动点的存在,通过迭代使消光系数均值收敛到不动点,并同时获得消光系数均值和消光系数边界值。通过仿真实

  3. Digital cover photography for estimating leaf area index (LAI) in apple trees using a variable light extinction coefficient.

    Science.gov (United States)

    Poblete-Echeverría, Carlos; Fuentes, Sigfredo; Ortega-Farias, Samuel; Gonzalez-Talice, Jaime; Yuri, Jose Antonio

    2015-01-28

    Leaf area index (LAI) is one of the key biophysical variables required for crop modeling. Direct LAI measurements are time consuming and difficult to obtain for experimental and commercial fruit orchards. Devices used to estimate LAI have shown considerable errors when compared to ground-truth or destructive measurements, requiring tedious site-specific calibrations. The objective of this study was to test the performance of a modified digital cover photography method to estimate LAI in apple trees using conventional digital photography and instantaneous measurements of incident radiation (Io) and transmitted radiation (I) through the canopy. Leaf area of 40 single apple trees were measured destructively to obtain real leaf area index (LAI(D)), which was compared with LAI estimated by the proposed digital photography method (LAI(M)). Results showed that the LAI(M) was able to estimate LAI(D) with an error of 25% using a constant light extinction coefficient (k = 0.68). However, when k was estimated using an exponential function based on the fraction of foliage cover (f(f)) derived from images, the error was reduced to 18%. Furthermore, when measurements of light intercepted by the canopy (Ic) were used as a proxy value for k, the method presented an error of only 9%. These results have shown that by using a proxy k value, estimated by Ic, helped to increase accuracy of LAI estimates using digital cover images for apple trees with different canopy sizes and under field conditions.

  4. Digital Cover Photography for Estimating Leaf Area Index (LAI) in Apple Trees Using a Variable Light Extinction Coefficient

    Science.gov (United States)

    Poblete-Echeverría, Carlos; Fuentes, Sigfredo; Ortega-Farias, Samuel; Gonzalez-Talice, Jaime; Yuri, Jose Antonio

    2015-01-01

    Leaf area index (LAI) is one of the key biophysical variables required for crop modeling. Direct LAI measurements are time consuming and difficult to obtain for experimental and commercial fruit orchards. Devices used to estimate LAI have shown considerable errors when compared to ground-truth or destructive measurements, requiring tedious site-specific calibrations. The objective of this study was to test the performance of a modified digital cover photography method to estimate LAI in apple trees using conventional digital photography and instantaneous measurements of incident radiation (Io) and transmitted radiation (I) through the canopy. Leaf area of 40 single apple trees were measured destructively to obtain real leaf area index (LAID), which was compared with LAI estimated by the proposed digital photography method (LAIM). Results showed that the LAIM was able to estimate LAID with an error of 25% using a constant light extinction coefficient (k = 0.68). However, when k was estimated using an exponential function based on the fraction of foliage cover (ff) derived from images, the error was reduced to 18%. Furthermore, when measurements of light intercepted by the canopy (Ic) were used as a proxy value for k, the method presented an error of only 9%. These results have shown that by using a proxy k value, estimated by Ic, helped to increase accuracy of LAI estimates using digital cover images for apple trees with different canopy sizes and under field conditions. PMID:25635411

  5. Digital Cover Photography for Estimating Leaf Area Index (LAI in Apple Trees Using a Variable Light Extinction Coefficient

    Directory of Open Access Journals (Sweden)

    Carlos Poblete-Echeverría

    2015-01-01

    Full Text Available Leaf area index (LAI is one of the key biophysical variables required for crop modeling. Direct LAI measurements are time consuming and difficult to obtain for experimental and commercial fruit orchards. Devices used to estimate LAI have shown considerable errors when compared to ground-truth or destructive measurements, requiring tedious site-specific calibrations. The objective of this study was to test the performance of a modified digital cover photography method to estimate LAI in apple trees using conventional digital photography and instantaneous measurements of incident radiation (Io and transmitted radiation (I through the canopy. Leaf area of 40 single apple trees were measured destructively to obtain real leaf area index (LAID, which was compared with LAI estimated by the proposed digital photography method (LAIM. Results showed that the LAIM was able to estimate LAID with an error of 25% using a constant light extinction coefficient (k = 0.68. However, when k was estimated using an exponential function based on the fraction of foliage cover (ff derived from images, the error was reduced to 18%. Furthermore, when measurements of light intercepted by the canopy (Ic were used as a proxy value for k, the method presented an error of only 9%. These results have shown that by using a proxy k value, estimated by Ic, helped to increase accuracy of LAI estimates using digital cover images for apple trees with different canopy sizes and under field conditions.

  6. The CU Airborne MAX-DOAS instrument: ground based validation, and vertical profiling of aerosol extinction and trace gases

    Directory of Open Access Journals (Sweden)

    S. Baidar

    2012-09-01

    Full Text Available The University of Colorado Airborne Multi Axis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS instrument uses solar stray light remote sensing to detect and quantify multiple trace gases, including nitrogen dioxide (NO2, glyoxal (CHOCHO, formaldehyde (HCHO, water vapor (H2O, nitrous acid (HONO, iodine monoxide (IO, bromine monoxide (BrO, and oxygen dimers (O4 at multiple wavelengths (360 nm, 477 nm, 577 nm and 632 nm simultaneously, and sensitively in the open atmosphere. The instrument is unique, in that it presents the first systematic implementation of MAX-DOAS on research aircraft, i.e. (1 includes measurements of solar stray light photons from nadir, zenith, and multiple elevation angles forward and below the plane by the same spectrometer/detector system, and (2 features a motion compensation system that decouples the telescope field of view (FOV from aircraft movements in real-time (< 0.35° accuracy. Sets of solar stray light spectra collected from nadir to zenith scans provide some vertical profile information within 2 km above and below the aircraft altitude, and the vertical column density (VCD below the aircraft is measured in nadir view. Maximum information about vertical profiles is derived simultaneously for trace gas concentrations and aerosol extinction coefficients over similar spatial scales and with a vertical resolution of typically 250 m during aircraft ascent/descent.

    The instrument is described, and data from flights over California during the CalNex and CARES air quality field campaigns is presented. Horizontal distributions of NO2 VCDs (below the aircraft maps are sampled with typically 1 km resolution, and show good agreement with two ground based CU MAX-DOAS instruments (slope 0.95 ± 0.09, R2 = 0.86. As a case study vertical profiles of NO2, CHOCHO, HCHO, and H2O mixing ratios and aerosol extinction coefficients

  7. Molecular composition and extinction coefficient of native botulinum neurotoxin complex produced by Clostridium botulinum hall A strain.

    Science.gov (United States)

    Bryant, Anne-Marie; Davis, Jenny; Cai, Shuowei; Singh, Bal Ram

    2013-02-01

    Seven distinct strains of Clostridium botulinum (type A to G) each produce a stable complex of botulinum neurotoxin (BoNT) along with neurotoxin-associated proteins (NAPs). Type A botulinum neurotoxin (BoNT/A) is produced with a group of NAPs and is commercially available for the treatment of numerous neuromuscular disorders and cosmetic purposes. Previous studies have indicated that BoNT/A complex composition is specific to the strain, the method of growth and the method of purification; consequently, any variation in composition of NAPs could have significant implications to the effectiveness of BoNT based therapeutics. In this study, a standard analytical technique using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and densitometry analysis was developed to accurately analyze BoNT/A complex from C. botulinum type A Hall strain. Using 3 batches of BoNT/A complex the molar ratio was determined as neurotoxin binding protein (NBP, 124 kDa), heavy chain (HC, 90 kDa), light chain (LC, 53 kDa), NAP-53 (50 kDa), NAP-33 (36 kDa), NAP-22 (24 kDa), NAP-17 (17 kDa) 1:1:1:2:3:2:2. With Bradford, Lowry, bicinchoninic acid (BCA) and spectroscopic protein estimation methods, the extinction coefficient of BoNT/A complex was determined as 1.54 ± 0.26 (mg/mL)(-1)cm(-1). These findings of a reproducible BoNT/A complex composition will aid in understanding the molecular structure and function of BoNT/A and NAPs.

  8. High Molar Extinction Coefficient Ru(II-Mixed Ligand Polypyridyl Complexes for Dye Sensitized Solar Cell Application

    Directory of Open Access Journals (Sweden)

    Malapaka Chandrasekharam

    2011-01-01

    Full Text Available Two new ruthenium(II mixed ligand terpyridine complexes, “Ru(Htcterpy(NCS(L1 (N(C4H94, mLBD1” and Ru(Htcterpy(NCS(L2(N(C4H94, mLBD2 were synthesized and fully characterized by UV-Vis, emission, cyclic voltammogram, and other spectroscopic means, and the structures of the compounds are confirmed by 1H-NMR, ESI-MASS, and FT-IR spectroscopes. The influence of the substitution of L1 and L2 on solar-to-electrical energy conversion efficiency (η of dye-sensitized solar cells (DSSCs was evaluated relative to reference black dye. The dyes showed molar extinction coefficients of 17600 M−1 cm−1 for mLBD1 and 21300 M−1 cm−1 for mLBD2 both at λ maximum of 512 nm, while black dye has shown 8660 M−1 cm−1 at λ maximum of 615 nm. The monochromatic incident photon-to-collected electron conversion efficiencies of 60.71% and 75.89% were obtained for mLBD1 and mLBD2 dyes, respectively. The energy conversion efficiencies of mLBD1 and mLBD2 dyes are 3.15% (SC=11.86 mA/cm2, OC=613 mV, ff=0.4337 and 3.36% (SC=12.71 mA/cm2, OC=655 mV, ff=0.4042, respectively, measured at the AM1.5G conditions, the reference black dye-sensitized solar cell, fabricated and evaluated under identical conditions exhibited η-value of 2.69% (SC=10.95 mA/cm2, OC=655 mV, ff=0.3750.

  9. Monte Carlo simulation of diffuse attenuation coefficient in presence of non uniform profiles

    Digital Repository Service at National Institute of Oceanography (India)

    Desa, E.S.; Desai, R.G.P.; Desa, B.A.E.

    This paper presents a Monte Carlo simulation of the vertical depth structure of the downward attenuation coefficient (K sub(d)), and the irradiance reflectance (R) for a given profile of chlorophyll. The results are in quantitaive agreement...

  10. Aerosol extinction profiles at 525 nm and 1020 nm derived from ACE imager data: comparisons with GOMOS, SAGE II, SAGE III, POAM III, and OSIRIS

    Directory of Open Access Journals (Sweden)

    F. Vanhellemont

    2008-04-01

    Full Text Available The Canadian ACE (Atmospheric Chemistry Experiment mission is dedicated to the retrieval of a large number of atmospheric trace gas species using the solar occultation technique in the infrared and UV/visible spectral domain. However, two additional solar disk imagers (at 525 nm and 1020 nm were added for a number of reasons, including the retrieval of aerosol and cloud products. In this paper, we present first comparison results for these imager aerosol/cloud optical extinction coefficient profiles, with the ones derived from measurements performed by 3 solar occultation instruments (SAGE II, SAGE III, POAM III, one stellar occultation instrument (GOMOS and one limb sounder (OSIRIS. The results indicate that the ACE imager profiles are of good quality in the upper troposphere/lower stratosphere, although the aerosol extinction for the visible channel at 525 nm contains a significant negative bias at higher altitudes, while the relative differences indicate that ACE profiles are almost always too high at 1020 nm. Both problems are probably related to ACE imager instrumental issues.

  11. Determination of the boundary value of atmospheric aerosol extinction coefficient based on fixed point principle%基于不动点原理的大气气溶胶消光系数边界值确定方法

    Institute of Scientific and Technical Information of China (English)

    熊兴隆; 蒋立辉; 冯帅; 庄子波

    2012-01-01

    提出了一种基于不动点原理的大气气溶胶消光系数边界值确定方法,其核心思想是将确定大气气溶胶消光系数边界值的问题转化为求解函数不动点。首先建立大气消光系数边界值与大气光学厚度和激光雷达回波信号之间的函数关系;其次依据函数不动点存在性和唯一性的条件估计不动点的存在,通过不动点迭代求得大气消光系数边界值,并由此值来确定大气气溶胶消光系数边界值。将本方法应用于实际激光雷达回波信号的反演中,得到低层大气气溶胶消光系数垂直廓线,并与在对流层顶使用洁净层法确定边界值所得的结果进行了对比。结果表明,利用本方法确定边界值,可以较为准确地反演出低层大气气溶胶消光系数。本方法可以预先估计不动点的存在区间、合理选取迭代初始值,具有收敛速度快、迭代次数少的优点,实际应用价值较强。%In this paper a determination method for atmospheric aerosol extinction coefficient boundary value based on the fixed-point principle is proPosed. The core idea of the method is to convert the deterruination of the atmospheric aerosol extinction coefficient boundary value to searching for the fixed point of function. Firstly,the relationships between the atmospheric extinction coefficient boundary value and the optical depth of atmosphere as well as the return signals of lidar are established. Secondly,the existence of fixed point is judged according to the existence and uniqueness condition of function's fixed point, and then the atmospheric aerosol extinction coefficient boundary value is obtained by the fixed point iteration. The method is applied for real lidar return signals to invert the vertical profiles of lower atmospheric aerosol extinction coefficient, and it has been compared with the inversion results acquired by the clean layer method in the tropopause. The results show that

  12. Use of Lidar Derived Optical Extinction and Backscattering Coefficients Near Cloud Base to Explore Aerosol-Cloud Interactions

    Science.gov (United States)

    Han, Zaw; Wu, Yonhgua; Gross, Barry; Moshary, Fred

    2016-06-01

    Combination of microwave radiometer (MWR) and mutlifilter rotating shadowband radiometer (MFRSR) measurement data together with SBDART radiative transfer model to compute cloud optical depth (COD) and cloud droplet effective radius (Reff). Quantify the first aerosol indirect effect using calculated Reff and aerosol extinction from Raman lidar measurement in urban coastal region. Illustrate comparison between ground-based and satellite retrievals. Demonstrate relationship between surface aerosol (PM2.5) loading and Reff. We also explain the sensitivity of aerosol-cloud-index (ACI) depend on the aerosol layer from cloud base height. Potential used of less noisy elastic backscattering to calculate the ACI instead of using Raman extinction. We also present comparison of elastic backscattering and Raman extinction correlation to Reff.

  13. Characterizing the Vertical Profile of Aerosol Particle Extinction and Linear Depolarization over Southeast Asia and the Maritime Continent: The 2007-2009 View from CALIOP

    Science.gov (United States)

    Campbell, James R.; Reid, Jeffrey S.; Westphal, Douglas L.; Zhang, Jianglong; Tackett, Jason L.; Chew, Boon Ning; Welton, Ellsworth J.; Shimizu, Atsushi; Sugimoto, Nobuo; Aoki, Kazuma; Winker, David M.

    2012-01-01

    Vertical profiles of 0.532 µm aerosol particle extinction coefficient and linear volume depolarization ratio are described for Southeast Asia and the Maritime Continent. Quality-screened and cloud-cleared Version 3.01 Level 2 NASA Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) 5-km Aerosol Profile datasets are analyzed from 2007 to 2009. Numerical simulations from the U.S. Naval Aerosol Analysis and Predictive System (NAAPS), featuring two-dimensional variational assimilation of NASA Moderate Resolution Imaging Spectroradiometer and Multi-angle Imaging Spectro- Radiometer quality-assured datasets, combined with regional ground-based lidar measurements, are considered for assessing CALIOP retrieval performance, identifying bias, and evaluating regional representativeness. CALIOP retrievals of aerosol particle extinction coefficient and aerosol optical depth (AOD) are high over land and low over open waters relative to NAAPS (0.412/0.312 over land for all data points inclusive, 0.310/0.235 when the per bin average is used and each is treated as single data points; 0.102/0.151 and 0.086/0.124, respectively, over ocean). Regional means, however, are very similar (0.180/0.193 for all data points and 0.155/0.159 when averaged per normalized bin), as the two factors offset one another. The land/ocean offset is investigated, and discrepancies attributed to interpretation of particle composition and a-priori assignment of the extinction-to-backscatter ratio ("lidar ratio") necessary for retrieving the extinction coefficient from CALIOP signals. Over land, NAAPS indicates more dust present than CALIOP algorithms are identifying, indicating a likely assignment of a higher lidar ratio representative of more absorptive particles. NAAPS resolvesmore smoke overwater than identified with CALIOP, indicating likely usage of a lidar ratio characteristic of less absorptive particles to be applied that biases low AOD there. Over open waters except within the Bay of Bengal

  14. Vertically-resolved profiles of mass concentrations and particle backscatter coefficients of Asian dust plumes derived from lidar observations of silicon dioxide.

    Science.gov (United States)

    Noh, Youngmin; Müller, Detlef; Shin, Sung-Kyun; Shin, Dongho; Kim, Young J

    2016-01-01

    This study presents a method to retrieve vertically-resolved profiles of dust mass concentrations by analyzing Raman lidar signals of silicon dioxide (quartz) at 546nm. The observed particle plumes consisted of mixtures of East Asian dust with anthropogenic pollution. Our method for the first time allows for extracting the contribution of the aerosol component "pure dust" contained in the aerosol type "polluted dust". We also propose a method that uses OPAC (Optical Properties of Aerosols and Clouds) and the mass concentrations profiles of dust in order to derive profiles of backscatter coefficients of pure dust in mixed dust/pollution plumes. The mass concentration of silicon dioxide (quartz) in the atmosphere can be estimated from the backscatter coefficient of quartz. The mass concentration of dust is estimated by the weight percentage (38-77%) of mineral quartz in Asian dust. The retrieved dust mass concentrations are classified into water soluble, nucleation, accumulation, mineral-transported and coarse mode according to OPAC. The mass mixing ratio of 0.018, 0.033, 0.747, 0.130 and 0.072, respectively, is used. Dust extinction coefficients at 550nm were calculated by using OPAC and prescribed number concentrations for each of the 5 components. Dust backscatter coefficients were calculated from the dust extinction coefficients on the basis of a lidar ratio of 45±3sr at 532nm. We present results of quartz-Raman measurements carried out on the campus of the Gwangju Institute of Science and Technology (35.10°N, 126.53°E) on 15, 16, and 21 March 2010.

  15. CART and GSFC raman lidar measurements of atmospheric aerosol backscattering and extinction profiles for EOS validation and ARM radiation studies

    Science.gov (United States)

    Ferrare, R. A.; Turner, D. D.; Melfi, S. H.; Whiteman, D. N.; Schwenner, G.; Evans, K. D.; Goldsmith, J. E. M.; Tooman, T.

    1998-01-01

    The aerosol retrieval algorithms used by the Moderate-Resolution Imaging Spectroradiometer (MODIS) and Multi-Angle Imaging SpectroRadiometer (MISR) sensors on the Earth Observing Satellite (EOS) AM-1 platform operate by comparing measured radiances with tabulated radiances that have been computed for specific aerosol models. These aerosol models are based almost entirely on surface and/or column averaged measurements and so may not accurately represent the ambient aerosol properties. Therefore, to validate these EOS algorithms and to determine the effects of aerosols on the clear-sky radiative flux, we have begun to evaluate the vertical variability of ambient aerosol properties using the aerosol backscattering and extinction profiles measured by the Cloud and Radiation Testbed (CART) and NASA Goddard Space Flight Center (GSFC) Raman Lidars. Using the procedures developed for the GSFC Scanning Raman Lidar (SRL), we have developed and have begun to implement algorithms for the CART Raman Lidar to routinely provide profiles of aerosol extinction and backscattering during both nighttime and ,daytime operations. Aerosol backscattering and extinction profiles are computed for both lidar systems using data acquired during the 1996 and 1997 Water Vapor Intensive Operating Periods (IOPs). By integrating these aerosol extinction profiles, we derive measurements of aerosol optical thickness and compare these with coincident sun photometer measurements. We also use these measurements to measure the aerosol extinction/backscatter ratio S(sub a) (i.e. 'lidar ratio'). Furthermore, we use the simultaneous water vapor measurements acquired by these Raman lidars to investigate the effects of water vapor on aerosol optical properties.

  16. The CU Airborne MAX-DOAS instrument: ground based validation, and vertical profiling of aerosol extinction and trace gases

    Science.gov (United States)

    Baidar, S.; Oetjen, H.; Coburn, S.; Dix, B.; Ortega, I.; Sinreich, R.; Volkamer, R.

    2012-09-01

    The University of Colorado Airborne Multi Axis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument uses solar stray light remote sensing to detect and quantify multiple trace gases, including nitrogen dioxide (NO2), glyoxal (CHOCHO), formaldehyde (HCHO), water vapor (H2O), nitrous acid (HONO), iodine monoxide (IO), bromine monoxide (BrO), and oxygen dimers (O4) at multiple wavelengths (360 nm, 477 nm, 577 nm and 632 nm) simultaneously, and sensitively in the open atmosphere. The instrument is unique, in that it presents the first systematic implementation of MAX-DOAS on research aircraft, i.e. (1) includes measurements of solar stray light photons from nadir, zenith, and multiple elevation angles forward and below the plane by the same spectrometer/detector system, and (2) features a motion compensation system that decouples the telescope field of view (FOV) from aircraft movements in real-time (CHOCHO, HCHO, and H2O mixing ratios and aerosol extinction coefficients, ɛ, at 477nm calculated from O4 measurements from a low approach at Brackett airfield inside the South Coast Air Basin (SCAB) are presented. These profiles contain ~ 12 degrees of freedom (DOF) over a 3.5 km altitude range, independent of signal-to-noise at which the trace gas is detected. The boundary layer NO2 concentration, and the integral aerosol extinction over height (aerosol optical depth, AOD) agrees well with nearby ground-based in-situ NO2 measurement, and AERONET station. The detection limits of NO2, CHOCHO, HCHO, ɛ360, ɛ477 from 30 s integration time spectra recorded forward of the plane are 5 ppt, 3 ppt, 100 ppt, 0.004 km-1, 0.002 km-1 in the free troposphere (FT), and 30 ppt, 16 ppt, 540 ppt, 0.012 km-1, 0.006 km-1 inside the boundary layer (BL), respectively. Mobile column observations of trace gases and aerosols are complimentary to in-situ observations, and help bridge the spatial scales probed by ground-based observations, satellites, and predicted by atmospheric

  17. 玉米群体消光系数的动态变化及其模拟%Dynamic Variation and Simulation of Extinction Coefficient of Corn Population

    Institute of Scientific and Technical Information of China (English)

    祁红彦; 周广胜; 李荣平; 刘志

    2011-01-01

    [目的]研究玉米群体消光系数的动态变化,提高净第一性生产力或产量的准确评估。[方法]基于中国气象局锦州玉米农田生态系统野外观测站2006年玉米生长季(5~9月)的辐射观测数据和叶面积指数动态观测数据,分析玉米群体的消光系数动态变化。[结果]玉米群体生长季消光系数日变化较大,其最大值分别出现在7:00~9:00、15:00~17:00,最小值在12:00前后,但变化幅度在抽雄期变小;在较大的时间尺度上(〉5d),消光系数(K)与叶面积指数(LAI)呈抛物线关系,决定系数R2为0.9607。当仅考虑消光系数是太阳高度角或叶面积指数的函数时,方程在模拟玉米群体生长季不同时刻的消光系数K值时准确性较差,为此发展了新的消光系数动态模型K=λ(0.7848-0.0016θ)(0.1548LAI2-0.5586LAI+0.654)。[结论]新的消光系数动态模型综合考虑了太阳高度角和玉米生长季叶面积指数对消光系数的影响,模拟效果优于现有的单因子消光系数模型。%[Objective] The aim was to study the dynamic variation of extinction coefficient of corn population, so as to improve the accuracy of assessment on net primary productivity (NPP) or yield. [Method] Based on the data of photosynthetic active radiation and leaf area index during corn growing season (from May to September) in 2006, observed in Jinzhou observation station of corn farmland ecosystem, China Meteorological Administration, the dynamic variation of extinction coefficient of corn population was analyzed. [Result] There was a great daily variation in the extinction coefficient of corn population during growing season, and the maximum value appeared from 7:00 to 9:00 and from 15:00 to 17:00, while the minimum could be found around 12:00, but the amplitude of variation decreased in tasseling stage. On a large time scale (5 d), there was a parabolic relationship between

  18. Calculating the heat transfer coefficient of frame profiles with internal cavities

    DEFF Research Database (Denmark)

    Noyé, Peter Anders; Laustsen, Jacob Birck; Svendsen, Svend

    2004-01-01

    or by measurements in accordance to European or international standards. Comparing measured and calculated heat transfer coefficients for two typical frame profiles with cavities shows considerable differences. This investigation considers two typical frame profiles in aluminium and PVC with internal cavities...... and measurements have been performed at two German research institutes. The internal cavities have a large influence on the overall thermal performance of the frame profiles and the investigation shows that the applied method for modelling the heat transfer by radiation exchange in the internal cavities...... correspondence between measured and calculated values. Hence, when determining the heat transfer coefficient of frame profiles with internal cavities by calculations, it is necessary to apply a more detailed radiation exchange model than described in the prEN ISO 10077-2 standard. The ISO-standard offers...

  19. Evaluation of diffusion coefficients from composition profiles - the influence of trapping

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2006-01-01

    The applicability of the Boltzmann-Matano method for evaluation of a diffusion coefficient and its concentration dependency by line profile analysis is tested on three different (model) systems. All systems involve interstitial diffusion. It is shown that the occurrence of trapping corrupts...... the applicability of the Boltzmann-Matano method....

  20. Calculating the heat transfer coefficient of frame profiles with internal cavities

    DEFF Research Database (Denmark)

    Noyé, Peter Anders; Laustsen, Jacob Birck; Svendsen, Svend

    2004-01-01

    or by measurements in accordance to European or international standards. Comparing measured and calculated heat transfer coefficients for two typical frame profiles with cavities shows considerable differences. This investigation considers two typical frame profiles in aluminium and PVC with internal cavities....... The heat transfer coefficient is determined by two-dimensional numerical calculations and by measurements. Calculations are performed in Therm (LBNL (2001)), which is developed at Lawrence Berkeley National Laboratory, USA. The calculations are performed in accordance with the future European standards...... and measurements have been performed at two German research institutes. The internal cavities have a large influence on the overall thermal performance of the frame profiles and the investigation shows that the applied method for modelling the heat transfer by radiation exchange in the internal cavities...

  1. Latitudinal and altitudinal variation of size distribution of stratospheric aerosols inferred from SAGE aerosol extinction coefficient measurements at two wavelengths

    Science.gov (United States)

    Yue, G. K.; Deepak, A.

    1984-01-01

    A method of retrieving aerosol size distribution from the measured extinction of solar radiation at wavelengths of 0.45 microns and 1.0 microns has recently been proposed. This method is utilized to obtain latitudinal and altitudinal variations of size distributions of stratospheric aerosols from the Stratospheric Aerosol and Gas Experiment data for March 1979. Small particles are found in the lower stratosphere of the tropical region, and large particles are found at higher altitudes and latitudes in both hemispheres. Results of this study are consistent with the suggestion that the upper troposphere in tropical regions is a source of condensation nuclei in the stratosphere, and they become mature as they move to higher altitudes and latitude.

  2. Laser Transmission Measurements of Soot Extinction Coefficients in the Exhaust Plume of the X-34 60k-lb Thrust Fastrac Rocket Engine

    Science.gov (United States)

    Dobson, C. C.; Eskridge, R. H.; Lee, M. H.

    2000-01-01

    A four-channel laser transmissometer has been used to probe the soot content of the exhaust plume of the X-34 60k-lb thrust Fastrac rocket engine at NASA's Marshall Space Flight Center. The transmission measurements were made at an axial location about equal 1.65 nozzle diameters from the exit plane and are interpreted in terms of homogeneous radial zones to yield extinction coefficients from 0.5-8.4 per meter. The corresponding soot mass density, spatially averaged over the plume cross section, is, for Rayleigh particles, approximately equal to 0.7 micrograms/cubic cm and alternative particle distributions are briefly considered. Absolute plume radiance at the laser wavelength (515 nm) is estimated from the data at approximately equal to 2.200 K equivalent blackbody temperature, and temporal correlations in emission from several spatial locations are noted.

  3. Prediction of Molar Extinction Coefficients of Proteins and Peptides Using UV Absorption of the Constituent Amino Acids at 214 nm To Enable Quantitative Reverse Phase High-Performance Liquid Chromatography-Mass Spectrometry Analysis

    NARCIS (Netherlands)

    Kuipers, B.J.H.; Gruppen, H.

    2007-01-01

    The molar extinction coefficients of 20 amino acids and the peptide bond were measured at 214 nm in the presence of acetonitrile and formic acid to enable quantitative comparison of peptides eluting from reversed-phase high-performance liquid chromatography, once identified with mass spectrometry (R

  4. Prediction of Molar Extinction Coefficients of Proteins and Peptides Using UV Absorption of the Constituent Amino Acids at 214 nm To Enable Quantitative Reverse Phase High-Performance Liquid Chromatography-Mass Spectrometry Analysis

    NARCIS (Netherlands)

    Kuipers, B.J.H.; Gruppen, H.

    2007-01-01

    The molar extinction coefficients of 20 amino acids and the peptide bond were measured at 214 nm in the presence of acetonitrile and formic acid to enable quantitative comparison of peptides eluting from reversed-phase high-performance liquid chromatography, once identified with mass spectrometry

  5. Prediction of Molar Extinction Coefficients of Proteins and Peptides Using UV Absorption of the Constituent Amino Acids at 214 nm To Enable Quantitative Reverse Phase High-Performance Liquid Chromatography-Mass Spectrometry Analysis

    NARCIS (Netherlands)

    Kuipers, B.J.H.; Gruppen, H.

    2007-01-01

    The molar extinction coefficients of 20 amino acids and the peptide bond were measured at 214 nm in the presence of acetonitrile and formic acid to enable quantitative comparison of peptides eluting from reversed-phase high-performance liquid chromatography, once identified with mass spectrometry (R

  6. Vertical profiles of aerosol absorption coefficient from micro-Aethalometer data and Mie calculation over Milan.

    Science.gov (United States)

    Ferrero, L; Mocnik, G; Ferrini, B S; Perrone, M G; Sangiorgi, G; Bolzacchini, E

    2011-06-15

    Vertical profiles of aerosol number-size distribution and black carbon (BC) concentration were measured between ground-level and 500m AGL over Milan. A tethered balloon was fitted with an instrumentation package consisting of the newly-developed micro-Aethalometer (microAeth® Model AE51, Magee Scientific, USA), an optical particle counter, and a portable meteorological station. At the same time, PM(2.5) samples were collected both at ground-level and at a high altitude sampling site, enabling particle chemical composition to be determined. Vertical profiles and PM(2.5) data were collected both within and above the mixing layer. Absorption coefficient (b(abs)) profiles were calculated from the Aethalometer data: in order to do so, an optical enhancement factor (C), accounting for multiple light-scattering within the filter of the new microAeth® Model AE51, was determined for the first time. The value of this parameter C (2.05±0.03 at λ=880nm) was calculated by comparing the Aethalometer attenuation coefficient and aerosol optical properties determined from OPC data along vertical profiles. Mie calculations were applied to the OPC number-size distribution data, and the aerosol refractive index was calculated using the effective medium approximation applied to aerosol chemical composition. The results compare well with AERONET data. The BC and b(abs) profiles showed a sharp decrease at the mixing height (MH), and fairly constant values of b(abs) and BC were found above the MH, representing 17±2% of those values measured within the mixing layer. The BC fraction of aerosol volume was found to be lower above the MH: 48±8% of the corresponding ground-level values. A statistical mean profile was calculated, both for BC and b(abs), to better describe their behaviour; the model enabled us to compute their average behaviour as a function of height, thus laying the foundations for valid parametrizations of vertical profile data which can be useful in both remote sensing

  7. Scattering Effect of Iron Metallic Particles on the Extinction Coefficient of CaO-SiO2-B2O3-Na2O-Fe2O3-CaF2 Glasses

    Science.gov (United States)

    Yoon, Dae-Woo; Cho, Jung-Wook; Kim, Seon-Hyo

    2016-10-01

    The extinction coefficient of the CaO-SiO2-B2O3-Na2O-Fe2O3-CaF2 glasses has been studied using a FT-IR and a UV-visible spectrometer in the range of 0.5-5 μm to investigate thermal radiation through glassy flux film during continuous casting of steels. In present investigations, iron oxide has been reduced to metallic iron droplets by reaction with graphite crucible during melting, which brings considerable increase of the extinction coefficient due to the scattering. To analyze the scattering effect of these droplets on the extinction coefficient, the number density and size parameter of metallic particles have been measured using an automated scanning electron microscope. The number of metallic particles is intensively proportional to boron contents due to the transition of molar structure, BO4 to BO3, with increasing boron oxide. It is found that calculated scattering coefficients based on Mie scattering theory are in good agreement with measured ones. As the increased scattering coefficient of glassy film would not cause any serious side effects on casting operations, utilization of scattering effects is believed to be significantly essential for the future design of commercial mold fluxes.

  8. Dvnamic Variation of Extinction Coefficient of Corn Population and Its Simulation%玉米群体消光系数的动态变化及其模拟

    Institute of Scientific and Technical Information of China (English)

    祁红彦; 周广胜; 李荣平; 刘志

    2011-01-01

    [目的]研究玉米群体消光系数的动态变化,提高净第一性生产力或产量的准确评估.[方法]基于中国气象局锦州玉米农田生态系统野外观测站2006年玉米生长季(5~9月)的辐射观测数据和叶面积指数动态观测数据,分析玉米群体的消光系数动态变化.[结果]玉米群体生长季消光系数日变化较大,其最大值分别出现在07:00 ~09:00、15:00 ~ 17:00,最小值出现在12:00前后,但变化幅度在抽雄期变小;在较大的时间尺度上(>5 d),消光系数(K)与叶面积指数(LAI)呈抛物线关系,决定系数(R2)为0.960 7.当仅考虑消光系数是太阳高度角或叶面积指数的函数时,方程在模拟玉米群体生长季不同时刻的消光系数K值时准确性较差,为此发展了新的消光系数动态模型K=λ(0.784 8-0.001 6θ)(0.1548 LAI2 -0.558 6LAI+0.654).[结论]新的消光系数动态模型综合考虑了太阳高度角和玉米生长季叶面积指数对消光系数的影响,模拟效果优于现有的单因子消光系数模型.%[Objective] The aim was to study the dynamic variation of extinction coefficient of corn population and improve the accuracy of assessment on net primary productivity ( NPP) and yield. [ Method] Based on the data of radiation and leaf area index (LAI) during growing season of com (from May to September) in 2006, observed in Jinzhou observation station of com farmland ecosystem, China Meteorological Bureau, the dynamic variation of extinction coefficient of com population was analyzed. [Result] There was great daily variation in the extinction coefficient of com population during growing season, and the maximum vales appeared from 07:00 to 09:00 and from 15 :00 to 17:00, while the minimum value could be found around 12:00, but the amplitude of variation decreased in tasseling stage. On a large time scale ( >5 d) , there was a parabolic relationship between extinction coefficient (K) and LAI, with determination coefficient R2 of

  9. Approximating high angular resolution apparent diffusion coefficient profiles using spherical harmonics under BiGaussian assumption

    Science.gov (United States)

    Cao, Ning; Liang, Xuwei; Zhuang, Qi; Zhang, Jun

    2009-02-01

    Magnetic Resonance Imaging (MRI) techniques have achieved much importance in providing visual and quantitative information of human body. Diffusion MRI is the only non-invasive tool to obtain information of the neural fiber networks of the human brain. The traditional Diffusion Tensor Imaging (DTI) is only capable of characterizing Gaussian diffusion. High Angular Resolution Diffusion Imaging (HARDI) extends its ability to model more complex diffusion processes. Spherical harmonic series truncated to a certain degree is used in recent studies to describe the measured non-Gaussian Apparent Diffusion Coefficient (ADC) profile. In this study, we use the sampling theorem on band-limited spherical harmonics to choose a suitable degree to truncate the spherical harmonic series in the sense of Signal-to-Noise Ratio (SNR), and use Monte Carlo integration to compute the spherical harmonic transform of human brain data obtained from icosahedral schema.

  10. Combination of fluoxetine and extinction treatments forms a unique synaptic protein profile that correlates with long-term fear reduction in adult mice.

    Science.gov (United States)

    Popova, Dina; Ágústsdóttir, Arna; Lindholm, Jesse; Mazulis, Ulams; Akamine, Yumiko; Castrén, Eero; Karpova, Nina N

    2014-07-01

    The antidepressant fluoxetine induces synaptic plasticity in the visual and fear networks and promotes the structural remodeling of neuronal circuits, which is critical for experience-dependent plasticity in response to an environmental stimulus. We recently demonstrated that chronic fluoxetine administration together with extinction training in adult mice reduced fear in a context-independent manner. Fear conditioning and extinction alter excitatory and inhibitory transmissions within the fear circuitry. In this study, we investigated whether fluoxetine, extinction or their combination produced distinct long-lasting changes in the synaptic protein profile in the amygdala, hippocampus and prefrontal cortex of conditioned mice. We determined that extinction induced synaptophysin expression and down-regulated the GluA1:GluA2 ratio throughout the fear network in water- and fluoxetine-treated mice, suggesting a common fluoxetine-independent mechanism for increased synaptic transmission and re-arrangement of AMPA-receptors by extinction training. In contrast to common changes, the presynaptic vesicular neurotransmitter transporters VGAT and Vglut1 were upregulated after extinction in water- and fluoxetine-treated mice, respectively. The cortical levels of the GABA transporter Gat1 were reduced in high-freezing water-drinking mice, suggesting a maladaptive increase of GABA spillover at cortical inhibitory synapses. Fear conditioning decreased, and extinction induced the expression of GABA-receptor alpha1 and alpha2 subunits in water- and fluoxetine-treated mice, respectively. Only a combination of fluoxetine with extinction enhanced GluN2A expression in the amygdala and hippocampus, emphasizing the role of this NMDA-receptor subunit in the successful erasure of fear memories. Our finding provides novel data that may become helpful in developing beneficial pharmacological fear-reducing treatment strategies.

  11. Erreurs induites par l’utilisation d’un capteur de grande taille, un ceptomètre par exemple, pour calculer un coefficient d’extinction à partir de la mesure des rayonnements transmis sous une culture

    OpenAIRE

    Tournebize, Régis; Cornet, Denis; BONHOMME, Raymond

    2010-01-01

    L’estimation des rayonnements solaires interceptés par une culture est une donnée devenue courante en agronomie pour évaluer sa production. Cette estimation est le plus souvent faite à partir de la seule mesure de l’indice foliaire LAI et l’utilisation d’un coefficient d’extinction des rayonnements K. Ce coefficient K est souvent évalué à partir de mesures ponctuelles de l’indice foliaire et de la fraction des rayonnements solaires transmis sous une culture TR, en utilisant la for...

  12. 改进的牛顿法确定大气消光系数边界值%Using improved Newton method to determine the boundary value of atmospheric extinction coefficient

    Institute of Scientific and Technical Information of China (English)

    熊兴隆; 蒋立辉; 冯帅; 庄子波; 赵俊媛

    2012-01-01

    在用激光雷达方程反演大气消光系数时,大气消先系数边界值对反演精度影响较大,而在低层大气中该值较难确定.文中提出了一种基于改进牛顿法的大气消光系数边界值确定方法,其核心思想是,把确定大气消光系数边界值的问题转化为求非线性方程的数值解.首先,根据大气消光系数边界值与激光雷达回波信号功率以及大气光学厚度之间的关系,假设大气消光系数边界值为x,构建一个非线性方程.其次,采用改进的牛顿法求非线性方程的数值解,得到大气消光系数边界值.使用香港天文台装置在香港国际机场的多普勒激光雷达回波信号数据,对该方法的可行性和可靠性进行了验证.结果表明:利用该方法确定边界值,可以较为准确地反演出低层大气消光系数.该方法收敛速度快,迭代次数少,并且不需要计算导数值,极大地减少了运算量,具有较强的实际应用价值.%When using lidar equation to inverse the extinction coefficient of atmosphere, its boundary value has a great influence on the inversion precision, however, it is hard to be determined in the lower atmosphere. A method was proposed to determine the boundary value of the extinction coefficient of atmosphere based on improved Newton; the core idea was to transform the problem of determining boundary value of the extinction coefficient of atmosphere to get numerical solution of the nonlinear equation. First of all, according to the relationship between the boundary value of extinction coefficient of atmosphere and the power of laser radar echo as well as optical thickness of atmosphere, it was supposed the boundary value of the extinction coefficient of atmosphere was x, a nonlinear equation could be constructed. Secondly, by using the improved Newton method to get the numerical solution of the nonlinear equation, the boundary value of the extinction coefficient of atmosphere can be got. By means of

  13. A new technique for investigating the induced and profile drag coefficients of a smooth wing and a tubercled wing

    Directory of Open Access Journals (Sweden)

    Bolzon Michael

    2016-01-01

    Full Text Available The induced and profile drag coefficients of a wing are typically determined through a complex experimental technique, such as wake surveying. Such a technique requires measurement of all three orthogonal components of the downstream velocity to find the components of drag, which results in the necessary usage of a sophisticated and costly measurement device, such as multi-hole pressure probe. However, in this paper data is presented which demonstrate that the relative changes in the induced and profile drag coefficients can largely be determined through the sole measurement of the downstream, streamwise velocity. To demonstrate this, the induced and profile drags of two NACA 0021 wings, one with a smooth leading edge and the other wing a tubercled leading edge for comparison, are determined through the measurement of the three orthogonal velocities. The downstream, streamwise velocity distribution of each wing is then constructed and relationships can be determined. The wings were surveyed at 3°, 9°, and 12°. It has been found that the relative magnitude of the profile drag coefficient can be found for all considered angles of attack, while the relative magnitude of the induced drag coefficient can be found at 9° and 12°. These findings produce an innovative, simpler, and more cost effective experimental technique in determining the components of drag of a wing, and reduces the burdensome requirement of a sophisticated measurement device for such an experiment. Further investigation is required to determine the induced drag at 3°.

  14. An accuracy assessment of the CALIOP/CALIPSO version 2 aerosol extinction product based on a detailed multi-sensor, multi-platform case study

    OpenAIRE

    Kacenelenbogen, M.; VAUGHAN, M.A.; Redemann, J.; Hoff, R. M.; R. R. Rogers; Ferrare, R. A.; P. B. Russell; Hostetler, C. A.; J. W. Hair; Holben, B.N.

    2010-01-01

    The Cloud Aerosol LIdar with Orthogonal Polarization (CALIOP), on board the CALIPSO platform, has measured profiles of total attenuated backscatter coefficient (level 1 products) since June 2006. CALIOP's level 2 products, such as the aerosol backscatter and extinction coefficient profiles, are retrieved using a complex succession of automated algorithms. The goal of this study is to help identify potential shortcomings in the CALIOP version 2 level 2 aerosol extinction product and to il...

  15. Suspended sediment profiles derived from spectral attenuation coefficients measurements using neural network method

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, G.; Suresh, T.; Matondkar, S.G.P.; Desa, E.; Kamath, S.S.

    total suspended matter values from water samples obtained at discrete depths at the same location. An artificial neural network (ANN) model has been used to derive suspended matter from the spectral values of beam attenuation coefficients measured using...

  16. Direct evaluation of the position dependent diffusion coefficient and persistence time from the equilibrium density profile in anisotropic fluids.

    Science.gov (United States)

    Olivares-Rivas, Wilmer; Colmenares, Pedro J; López, Floralba

    2013-08-21

    We derive expressions for the transverse diffusion coefficient D(z) and the average persistence time τ(z; L) within a layer of width L, for particles of a non-homogeneous fluid enclosed in a planar nanopore. The method allows the direct evaluation of these position-dependent dynamical quantities from the equilibrium local particle density profile. We use results for the density and persistence time profiles from the virtual layer molecular dynamics method to numerically assess the significance of the Smoluchowski approximation.

  17. Use of In Situ Cloud Condensation Nuclei, Extinction, and Aerosol Size Distribution Measurements to Test a Method for Retrieving Cloud Condensation Nuclei Profiles From Surface Measurements

    Science.gov (United States)

    Ghan, Stephen J.; Rissman, Tracey A.; Ellman, Robert; Ferrare, Richard A.; Turner, David; Flynn, Connor; Wang, Jian; Ogren, John; Hudson, James; Jonsson, Haflidi H.; VanReken, Timothy; Flagan, Richard C.; Seinfeld, John H.

    2006-01-01

    If the aerosol composition and size distribution below cloud are uniform, the vertical profile of cloud condensation nuclei (CCN) concentration can be retrieved entirely from surface measurements of CCN concentration and particle humidification function and surface-based retrievals of relative humidity and aerosol extinction or backscatter. This provides the potential for long-term measurements of CCN concentrations near cloud base. We have used a combination of aircraft, surface in situ, and surface remote sensing measurements to test various aspects of the retrieval scheme. Our analysis leads us to the following conclusions. The retrieval works better for supersaturations of 0.1% than for 1% because CCN concentrations at 0.1% are controlled by the same particles that control extinction and backscatter. If in situ measurements of extinction are used, the retrieval explains a majority of the CCN variance at high supersaturation for at least two and perhaps five of the eight flights examined. The retrieval of the vertical profile of the humidification factor is not the major limitation of the CCN retrieval scheme. Vertical structure in the aerosol size distribution and composition is the dominant source of error in the CCN retrieval, but this vertical structure is difficult to measure from remote sensing at visible wavelengths.

  18. In situ vertical profiles of aerosol extinction, mass, and composition over the southeast United States during SENEX and SEAC4RS: observations of a modest aerosol enhancement aloft

    Directory of Open Access Journals (Sweden)

    N. L. Wagner

    2015-02-01

    Full Text Available Vertical profiles of submicron aerosol over the southeastern United States (SEUS during the summertime from in situ aircraft-based measurements were used to construct aggregate profiles of chemical, microphysical, and optical properties. Shallow cumulus convection was observed during many profiles. These conditions enhance vertical transport of trace gases and aerosol and create a cloudy transition layer on top of the sub-cloud mixed layer. The trace gas and aerosol concentrations in the transition layer were modeled as a mixture with contributions from the mixed layer below and the free troposphere above. The amount of vertical mixing, or entrainment of air from the free troposphere, was quantified using the observed mixing ratio of carbon monoxide (CO. Although the median aerosol mass, extinction, and volume decreased with altitude in the transition layer, they were ~10% larger than expected from vertical mixing alone. This enhancement was likely due to secondary aerosol formation in the transition layer. Although the transition layer enhancements of the particulate sulfate and organic aerosol (OA were both similar in magnitude, only the enhancement of sulfate was statistically significant. The column integrated extinction, or aerosol optical depth (AOD, was calculated for each individual profile, and the transition layer enhancement of extinction typically contributed less than 10% to the total AOD. Our measurements and analysis were motivated by two recent studies that have hypothesized an enhanced layer of secondary organic aerosol (SOA aloft to explain the summertime enhancement of AOD (2–3 times greater than winter over the southeastern United States. In contrast to this hypothesis, the modest enhancement we observed in the transition layer was not dominated by OA and was not a large fraction of the summertime AOD.

  19. EFFECT OF HYDROPLANE PROFILE ON HYDRODYNAMIC COEFFICIENTS OF AN AUTONOMOUS UNDERWATER VEHICLE

    Directory of Open Access Journals (Sweden)

    Ahmad Hajivand

    2016-03-01

    Full Text Available AUVs are the most suitable tool for conduction survey concerning with global environmental problems. AUVs maneuverability should be carefully checked so as to improve energy efficiency of the vehicle and avoid unexpected motion. Oblique towing test (OTT is simulated virtually in a computational fluid dynamic (CFD environment to obtain hydrodynamic damping coefficients of a full-scale autonomous underwater vehicle. Simulations are performed for bare hull and hull equipped with four different hydroplanes. The hydrodynamic forces and moment are obtained to calculate hydrodynamic coefficients. Nonlinear damping coefficients are also obtained by using suitable curve fitting. Experiments of resistance and OTT are carried out in specific condition, for validation purpose. Following the extracting numerical results a mathematical model is developed to calculate hydrodynamic force for different sail type in order to predict autonomous underwater vehicle (AUV maneuverability. The results shows good agreement between theory and experiment.

  20. UVI colour gradients of 0.4 < z < 1.4 star-forming main-sequence galaxies in CANDELS: dust extinction and star formation profiles

    Science.gov (United States)

    Wang, Weichen; Faber, S. M.; Liu, F. S.; Guo, Yicheng; Pacifici, Camilla; Koo, David C.; Kassin, Susan A.; Mao, Shude; Fang, Jerome J.; Chen, Zhu; Koekemoer, Anton M.; Kocevski, Dale D.; Ashby, M. L. N.

    2017-08-01

    This paper uses radial colour profiles to infer the distributions of dust, gas and star formation in z = 0.4-1.4 star-forming main-sequence galaxies. We start with the standard UVJ-based method to estimate dust extinction and specific star formation rate (sSFR). By replacing J with I band, a new calibration method suitable for use with ACS+WFC3 data is created (i.e. UVI diagram). Using a multi-wavelength multi-aperture photometry catalogue based on CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey), UVI colour profiles of 1328 galaxies are stacked in stellar mass and redshift bins. The resulting colour gradients, covering a radial range of 0.2-2.0 effective radii, increase strongly with galaxy mass and with global AV. Colour gradient directions are nearly parallel to the Calzetti extinction vector, indicating that dust plays a more important role than stellar population variations. With our calibration, the resulting AV profiles fall much more slowly than stellar mass profiles over the measured radial range. sSFR gradients are nearly flat without central quenching signatures, except for M⋆ > 1010.5 M⊙, where central declines of 20-25 per cent are observed. Both sets of profiles agree well with previous radial sSFR and (continuum) AV measurements. They are also consistent with the sSFR profiles and, if assuming a radially constant gas-to-dust ratio, gas profiles in recent hydrodynamic models. We finally discuss the striking findings that SFR scales with stellar mass density in the inner parts of galaxies, and that dust content is high in the outer parts despite low stellar mass surface densities there.

  1. The opacity of Spiral Disks IV : Radial Extinction Profiles from Counts of Distant Galaxies seen through Foreground Disks

    NARCIS (Netherlands)

    Holwerda, B. W.; González, R. A.; Allen, R. J.; Kruit, P.C. van der

    2004-01-01

    Dust extinction can be determined from the number of distant field galaxies seen through a spiral disk. To calibrate this number for the crowding and confusion introduced by the foreground image, Gonzalez et al. (1998) and Holwerda et al. (2005a) developed the ``Synthetic Field Method'' (SFM), which

  2. The opacity of spiral galaxy disks. IV. Radial extinction profiles from counts of distant galaxies seen through foreground disks

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; Allen, RJ; van der Kruit, PC

    2005-01-01

    Dust extinction can be determined from the number of distant field galaxies seen through a spiral disk. To calibrate this number for the crowding and confusion introduced by the foreground image, Gonzalez et al. and Holwerda et al. developed the Synthetic Field Method (SFM), which analyzes synthetic

  3. Calculation of transport coefficient profiles in modulation experiments as an inverse problem

    CERN Document Server

    Escande, D F

    2011-01-01

    The calculation of transport profiles from experimental measurements belongs in the category of inverse problems which are known to come with issues of ill-conditioning or singularity. A reformulation of the calculation, the matricial approach, is proposed for periodically modulated experiments, within the context of the standard advection-diffusion model where these issues are related to the vanishing of the determinant of a 2x2 matrix. This sheds light on the accuracy of calculations with transport codes, and provides a path for a more precise assessment of the profiles and of the related uncertainty.

  4. Evaluations on Profiles of the Eddy Diffusion Coefficients through Simulations of Super Typhoons in the Northwestern Pacific

    Directory of Open Access Journals (Sweden)

    Jimmy Chi Hung Fung

    2016-01-01

    Full Text Available The modeling of the eddy diffusion coefficients (also known as eddy diffusivity in the first-order turbulence closure schemes is important for the typhoon simulations, since the coefficients control the magnitude of the sensible heat flux and the latent heat flux, which are energy sources for the typhoon intensification. Profiles of the eddy diffusion coefficients in the YSU planetary boundary layer (PBL scheme are evaluated in the advanced research WRF (ARW system. Three versions of the YSU scheme (original, K025, and K200 are included in this study. The simulation results are compared with the observational data from track, center sea-level pressure (CSLP, and maximum surface wind speed (MWSP. Comparing with the original version, the K200 improves the averaged mean absolute errors (MAE of track, CSLP, and MWSP by 6.0%, 3.7%, and 23.1%, respectively, while the K025 deteriorates the averaged MAEs of track, CSLP, and MWSP by 25.1%, 19.0%, and 95.0%, respectively. Our results suggest that the enlarged eddy diffusion coefficients may be more suitable for super typhoon simulations.

  5. Force-clamp experiments reveal the free energy profile and diffusion coefficient of the collapse of proteins

    CERN Document Server

    Lannon, Herbert; Brujic, Jasna

    2012-01-01

    We present force-clamp data on the collapse of ubiquitin polyproteins in response to a quench in the force. These nonequilibrium trajectories are analyzed using a general method based on a diffusive assumption of the end-to-end length to reconstruct a downhill free energy profile at 5pN and an energy plateau at 10pN with a slow diffusion coefficient on the order of~100nm^2/s. The shape of the free energy and its linear scaling with the protein length give validity to a physical model for the collapse. However, the length independent diffusion coefficient suggests that internal rather than viscous friction dominates and thermal noise is needed to capture the variability in the measured times to collapse.

  6. Rethinking Extinction.

    Science.gov (United States)

    Dunsmoor, Joseph E; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A

    2015-10-07

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavioral technique, and consider whether traditional understandings warrant a re-examination. We discuss the neurobiology, cognitive factors, and major computational theories, and revisit the predominant view that extinction results in new learning that interferes with expression of the original memory. Additionally, we reconsider the limitations of extinction as a technique to prevent the relapse of maladaptive behavior and discuss novel approaches, informed by contemporary theoretical advances, that augment traditional extinction methods to target and potentially alter maladaptive memories. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Development of Extinction Imagers for the Determination of Atmospheric Optical Extinction

    Science.gov (United States)

    2014-08-01

    extinction coefficient > 0.4 km" ), the transmissometer tends to report higher values than the MSI. There are two possible reasons for this behavior ...REPORT TYPE Final Report 4. TITLE AND SUBTITLE Development of Extinction Imagers for the Determination of Atmospheric Optical Extinction 6. AUTHOR...further develop Extinction Imagers for use in the ocean environment, and to extend the capabilities into the Short Wave IR (SWIR). Extinction Imaging

  8. Rethinking Extinction

    OpenAIRE

    Dunsmoor, Joseph E.; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A.

    2015-01-01

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavior...

  9. In situ vertical profiles of aerosol extinction, mass, and composition over the southeast United States during SENEX and SEAC4RS: observations of a modest aerosol enhancement aloft

    Science.gov (United States)

    Wagner, N. L.; Brock, C. A.; Angevine, W. M.; Beyersdorf, A.; Campuzano-Jost, P.; Day, D.; de Gouw, J. A.; Diskin, G. S.; Gordon, T. D.; Graus, M. G.; Holloway, J. S.; Huey, G.; Jimenez, J. L.; Lack, D. A.; Liao, J.; Liu, X.; Markovic, M. Z.; Middlebrook, A. M.; Mikoviny, T.; Peischl, J.; Perring, A. E.; Richardson, M. S.; Ryerson, T. B.; Schwarz, J. P.; Warneke, C.; Welti, A.; Wisthaler, A.; Ziemba, L. D.; Murphy, D. M.

    2015-06-01

    Vertical profiles of submicron aerosol from in situ aircraft-based measurements were used to construct aggregate profiles of chemical, microphysical, and optical properties. These vertical profiles were collected over the southeastern United States (SEUS) during the summer of 2013 as part of two separate field studies: the Southeast Nexus (SENEX) study and the Study of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS). Shallow cumulus convection was observed during many profiles. These conditions enhance vertical transport of trace gases and aerosol and create a cloudy transition layer on top of the sub-cloud mixed layer. The trace gas and aerosol concentrations in the transition layer were modeled as a mixture with contributions from the mixed layer below and the free troposphere above. The amount of vertical mixing, or entrainment of air from the free troposphere, was quantified using the observed mixing ratio of carbon monoxide (CO). Although the median aerosol mass, extinction, and volume decreased with altitude in the transition layer, they were ~10 % larger than expected from vertical mixing alone. This enhancement was likely due to secondary aerosol formation in the transition layer. Although the transition layer enhancements of the particulate sulfate and organic aerosol (OA) were both similar in magnitude, only the enhancement of sulfate was statistically significant. The column integrated extinction, or aerosol optical depth (AOD), was calculated for each individual profile, and the transition layer enhancement of extinction typically contributed less than 10 % to the total AOD. Our measurements and analysis were motivated by two recent studies that have hypothesized an enhanced layer of secondary aerosol aloft to explain the summertime enhancement of AOD (2-3 times greater than winter) over the southeastern United States. The first study attributes the layer aloft to secondary organic aerosol (SOA) while

  10. Characteristics of aerosol size distribution and vertical backscattering coefficient profile during 2014 APEC in Beijing

    Science.gov (United States)

    Zhang, Jiaoshi; Chen, Zhenyi; Lu, Yihuai; Gui, Huaqiao; Liu, Jianguo; Liu, Wenqing; Wang, Jie; Yu, Tongzhu; Cheng, Yin; Chen, Yong; Ge, Baozhu; Fan, Yu; Luo, Xisheng

    2017-01-01

    During the 2014 Asia-Pacific Economic Cooperation (APEC) conference period, Beijing's air quality was greatly improved as a result of a series of tough emission control measures being implemented in Beijing and its surrounding provinces. However, a moderate haze occurred during the period of 4-5 November. In order to evaluate the emission control measures and study the formation mechanism of the haze, a comprehensive field observation based on a supersite and a lidar network was carried out from 25 October 2014 to 20 January 2015. By investigating the variations in aerosol number concentration and mean backscattering coefficient before, during and after the APEC period, it was found that number concentration of accumulation mode and coarse mode particles experienced the most significant decrease by 47% and 68%, and mean backscattering coefficient below 1 km decreased by 34% during the APEC period. Being characterized as "rapidly accumulating and rapidly dispersing", the moderate haze occurred during the APEC period was probably initiated by a wind direction change to south and an increase of wind speed to 4 m/s. Sulfur dioxide involved plume nucleation without growth in size as well as a burst of particles ranging between 100 and 300 nm were observed simultaneously during the haze episode. The elevation of sulfur dioxide concentration and particle number concentration was highly correlated with the southerly wind, signifying the contribution of regional transport. It was observed by the lidar network that the aerosol backscattering coefficient increased in sequence among three sites along the southwest pathway, suggesting that aerosols might be transported from the southwest to the northeast of Beijing with a speed of approximately 17 km/h, which agreed with the movement of air masses modeled by Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT). The dual-wavelength lidar (355 and 532 nm) observation suggested that transportation of fine particles

  11. Determination of hydrogen diffusion coefficients in F82H by hydrogen depth profiling with a tritium imaging plate technique

    Energy Technology Data Exchange (ETDEWEB)

    Higaki, M.; Otsuka, T.; Hashizume, K. [Interdisciplinary Graduate School of Engineering and Sciences, Kyushu University, Kasuga, Fukuoka (Japan); Tokunaga, K. [Research Institute of Applied Mechanics, Kyushu University, Kasuga, Fukuoka (Japan); Ezato, K.; Suzuki, S.; Enoeda, M.; Akiba, M. [Japan Atomic Energy Agency - JAEA, Naka, Ibaraki (Japan)

    2015-03-15

    Hydrogen diffusion coefficients in a reduced activation ferritic/martensitic steel (F82H) and an oxide dispersion strengthened F82H (ODS-F82H) have been determined from depth profiles of plasma-loaded hydrogen with a tritium imaging plate technique (TIPT) in the temperature range from 298 K to 523 K. Data on hydrogen diffusion coefficients, D, in F82H, are summarized as D [m{sup 2}*s{sup -1}] =1.1*10{sup -7}exp(-16[kJ mol{sup -1}]/RT). The present data indicate almost no trapping effect on hydrogen diffusion due to an excess entry of energetic hydrogen by the plasma loading, which results in saturation of the trapping sites at the surface and even in the bulk. In the case of ODS-F82H, data of hydrogen diffusion coefficients are summarized as D [m{sup 2}*s{sup -1}] =2.2*10{sup -7}exp(-30[kJ mol{sup -1}]/RT) indicating a remarkable trapping effect on hydrogen diffusion caused by tiny oxide particles (Y{sub 2}O{sub 3}) in the bulk of F82H. Such oxide particles introduced in the bulk may play an effective role not only on enhancement of mechanical strength but also on suppression of hydrogen penetration by plasma loading.

  12. Profiling the Local Seebeck Coefficient with Nanometer Resolution Using Scanning Thermoelectric Microscopy (SThEM)

    Science.gov (United States)

    Lin, Yen-Hsiang; Walrath, Jenna; Goldman, Rachel

    2013-03-01

    Thermoelectric (TE) devices offer a method of recovering waste heat through solid state conversion of heat to electricity. Nanostructured thermoelectric materials may provide the key to increased efficiencies, which are sensitive to the Seebeck coefficients (S) However, traditional bulk measurement techniques can only provide a spatially averaged measurement of S over the whole sample, which can hardly investigate the effects of nanostructures on S on the nanoscale. A novel technique known as scanning thermoelectric microscopy (SThEM) has recently been developed to measure induced thermal voltages with nanometer resolution In SThEM, an unheated scanning tunneling microscopy tip acts as a high-resolution voltmeter probe to measure the thermally-induced voltage, V, in a heated sample. Here we present a local S measurement using SThEM across an InGaAs P-N junction. The thermovoltage shows an abrupt change of sign within 10 nanometers, which reveals nanometer spatial resolution. We will discuss local S measurements of AlAs/GaAs superlattices (SLs) with various SL periods and compare the local S with scanning tunneling spectroscopy measurements, which will reveal how local electronic states influence thermoelectric properties. This material is based upon work primarily supported by DOE under grant No. DE-FG02-06 and ER46339 the Department of Energy under Award Number DE-PI0000012.

  13. Traumatic stress causes distinctive effects on fear circuit catecholamines and the fear extinction profile in a rodent model of posttraumatic stress disorder.

    Science.gov (United States)

    Lin, Chen-Cheng; Tung, Che-Se; Lin, Pin-Hsuan; Huang, Chuen-Lin; Liu, Yia-Ping

    2016-09-01

    Central catecholamines regulate fear memory across the medial prefrontal cortex (mPFC), amygdala (AMYG), and hippocampus (HPC). However, inadequate evidence exists to address the relationships among these fear circuit areas in terms of the fear symptoms of posttraumatic stress disorder (PTSD). By examining the behavioral profile in a Pavlovian fear conditioning paradigm together with tissue/efflux levels of dopamine (DA) and norepinephrine (NE) and their reuptake abilities across the fear circuit areas in rats that experienced single prolonged stress (SPS, a rodent model of PTSD), we demonstrated that SPS-impaired extinction retrieval was concomitant with the changes of central DA/NE in a dissociable manner. For tissue levels, diminished DA and increased NE were both observed in the mPFC and AMYG. DA efflux and synaptosomal DA transporter were consistently reduced in the AMYG/vHPC, whereas SPS reduced NE efflux in the infralimbic cortex and synaptosomal NE transporter in the mPFC. Furthermore, a lower expression of synaptosomal VMAT2 was observed in the mPFC, AMYG, and vHPC after SPS. Finally, negative correlations were observed between retrieval freezing and DA in the mPFC/AMYG; nevertheless, the phenomena became invalid after SPS. Our results suggest that central catecholamines are crucially involved in the retrieval of fear extinction in which DA and NE play distinctive roles across the fear circuit areas. Copyright © 2016 Elsevier B.V. and ECNP. All rights reserved.

  14. A differential evolution algorithm for tooth profile optimization with respect to balancing specific sliding coefficients of involute cylindrical spur and helical gears

    Directory of Open Access Journals (Sweden)

    Hammoudi Abderazek

    2015-09-01

    Full Text Available Profile shift has an immense effect on the sliding, load capacity, and stability of involute cylindrical gears. Available standards such as ISO/DIS 6336 and BS 436 DIN/3990 currently give the recommendation for the selection of profile shift coefficients. It is, however, very approximate and usually given in the form of implicit graphs or charts. In this article, the optimal selection values of profile shift coefficients for cylindrical involute spur and helical gears are described, using a differential evolution algorithm. The optimization procedure is developed specifically for exact balancing specific sliding coefficients at extremes of contact path and account for gear design constraints. The obtained results are compared with those of standards and research of other authors. They demonstrate the effectiveness and robustness of the applied method. A substantial improvement in balancing specific sliding coefficients is found in this work.

  15. Validation of CALIPSO space-borne-derived attenuated backscatter coefficient profiles using a ground-based lidar in Athens, Greece

    Directory of Open Access Journals (Sweden)

    R. E. Mamouri

    2009-09-01

    Full Text Available We present initial aerosol validation results of the space-borne lidar CALIOP -onboard the CALIPSO satellite- Level 1 attenuated backscatter coefficient profiles, using coincident observations performed with a ground-based lidar in Athens, Greece (37.9° N, 23.6° E. A multi-wavelength ground-based backscatter/Raman lidar system is operating since 2000 at the National Technical University of Athens (NTUA in the framework of the European Aerosol Research LIdar NETwork (EARLINET, the first lidar network for tropospheric aerosol studies on a continental scale. Since July 2006, a total of 40 coincidental aerosol ground-based lidar measurements were performed over Athens during CALIPSO overpasses. The ground-based measurements were performed each time CALIPSO overpasses the station location within a maximum distance of 100 km. The duration of the ground–based lidar measurements was approximately two hours, centred on the satellite overpass time. From the analysis of the ground-based/satellite correlative lidar measurements, a mean bias of the order of 22% for daytime measurements and of 8% for nighttime measurements with respect to the CALIPSO profiles was found for altitudes between 3 and 10 km. The mean bias becomes much larger for altitudes lower that 3 km (of the order of 60% which is attributed to the increase of aerosol horizontal inhomogeneity within the Planetary Boundary Layer, resulting to the observation of possibly different air masses by the two instruments. In cases of aerosol layers underlying Cirrus clouds, comparison results for aerosol tropospheric profiles become worse. This is attributed to the significant multiple scattering effects in Cirrus clouds experienced by CALIPSO which result in an attenuation which is less than that measured by the ground-based lidar.

  16. A High Molar Extinction Coefficient Ru(II Complex Functionalized with cis-Dithiocyanato-bis-(9-anthracenyl-10-(2-methyl-2-butenoic acid-1,10-phenanthroline: Potential Sensitizer for Stable Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Adewale O. Adeloye

    2014-01-01

    Full Text Available New heteroleptic ruthenium(II complex was formulated as [Ru(L12(NCS2], where L1 = 9-anthracenyl-10-(2-methyl-2-butenoic acid-1,10-phenanthroline was synthesized and its photophysical properties were studied and compared to previously reported analogue complex containing no anthracene moiety [Ru(L22(NCS2], L2 = (2-methyl-2-butenoic acid-1,10-phenanthroline. The two complexes though exhibit very strong molar extinction coefficient values; however, [Ru(L12(NCS2] shows better characteristic broad and intense metal-to-ligand charge transfer (MLCT absorption band and higher molar absorptivity coefficient at (λmax=522 nm, ε=6.60×104 M−1 cm−1 than that of [Ru(L22(NCS2] complex, (λmax=446 nm, ε=4.82×104 M−1 cm−1. At room temperature, long wavelength emissions with strong intensity ratio centered at 660 nm were recorded for [Ru(L12(NCS2] complex with a bathochromic shift (λem=700 nm for [Ru(L22(NCS2] complex. It was shown that the luminescence wavelength characteristic of the complexes may be a function relating to the increasing length of π-conjugation and/or molecular weight. A preliminary cyclic voltammetry of [Ru(L12(NCS2] complex also exhibits good electroredox activity with oxidation potential of about 1.04 V, significantly better than other Ru(II polypyridine complexes containing bidentate ligands.

  17. Examination and assessment of available incoherent scattering S-matrix theory, also Compton profile information, and their impact on photon attenuation coefficient compilations

    Energy Technology Data Exchange (ETDEWEB)

    Hubbell, J.H.

    1999-07-01

    One task of this report is to examine the usefulness and advantages, if any, of S-matrix theory in providing significantly more accurate values of photon interaction cross sections and attenuation coefficients. The other tasks of this report is to examine the available Compton profile literature and to explore what, if any, effect the knowledge of this line-broadening has on theoretical computations of photon incoherent scattering cross sections and total mass attenuation coefficients.

  18. ASOS Surface Extinction Coefficient by STI

    Data.gov (United States)

    Washington University St Louis — ASOS_STI represents a 250-station subset of the national ASOS SURF_MET dataset. The unique feature of this data is that the visibility sensor values are available in...

  19. The atmospheric extinction of light

    CERN Document Server

    Hughes, Stephen W; Powell, Sean; Carroll, Joshua

    2015-01-01

    An experiment is described that enables students to understand the properties of atmospheric extinction due to Rayleigh scattering. The experiment requires the use of red, green and blue lasers attached to a travelling microscope or similar device. The laser beams are passed through an artificial atmosphere, made from milky water, at varying depths, before impinging on either a light meter or a photodiode integral to a Picotech Dr. DAQ ADC. A plot of measured spectral intensity verses depth reveals the contribution Rayleigh scattering has to the extinction coefficient. For the experiment with the light meter, the extinction coefficients for red, green and blue light in the milky sample of water were 0.27, 0.36 and 0.47 cm^-1 respectively and 0.032, 0.037 and 0.092 cm^-1 for the Picotech Dr. DAQ ADC.

  20. Study of MPLNET-Derived Aerosol Climatology over Kanpur, India, and Validation of CALIPSO Level 2 Version 3 Backscatter and Extinction Products

    Science.gov (United States)

    Misra, Amit; Tripathi, S. N.; Kaul, D. S.; Welton, Ellsworth J.

    2012-01-01

    The level 2 aerosol backscatter and extinction profiles from the NASA Micropulse Lidar Network (MPLNET) at Kanpur, India, have been studied from May 2009 to September 2010. Monthly averaged extinction profiles from MPLNET shows high extinction values near the surface during October March. Higher extinction values at altitudes of 24 km are observed from April to June, a period marked by frequent dust episodes. Version 3 level 2 Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol profile products have been compared with corresponding data from MPLNET over Kanpur for the above-mentioned period. Out of the available backscatter profiles, the16 profiles used in this study have time differences less than 3 h and distances less than 130 km. Among these profiles, four cases show good comparison above 400 m with R2 greater than 0.7. Comparison with AERONET data shows that the aerosol type is properly identified by the CALIOP algorithm. Cloud contamination is a possible source of error in the remaining cases of poor comparison. Another source of error is the improper backscatter-to-extinction ratio, which further affects the accuracy of extinction coefficient retrieval.

  1. Inter-comparison of MAX-DOAS Retrieved Vertical Profiles of Aerosol Extinction, SO2 and NO2 in the Alberta Oil Sands with LIDAR Data and GEM-MACH Air Quality Model.

    Science.gov (United States)

    Davis, Zoe; Friess, Udo; Strawbridge, Kevin; Whiteway, James; Aggarwal, Monika; Makar, Paul; Li, Shao-Meng; O'Brien, Jason; Baray, Sabour; Schnitzler, Elijah; Olfert, Jason S.; Osthoff, Hans D.; Lobo, Akshay; McLaren, Robert

    2016-04-01

    Understanding industrial emissions of trace gas pollutants in the Alberta oil sands is essential to maintaining air quality standards and informing public policy. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of trace gases can improve knowledge of pollutant levels, vertical distribution and chemical transformation. During an intensive air measurement campaign to study emissions, transport, transformation and deposition of oil sands air pollutants from August to September of 2013, a MAX-DOAS instrument was deployed at a site north of Fort McMurray, Alberta to determine the vertical profiles of aerosol extinction, NO2 and SO2 through retrieval from the MAX-DOAS spectral measurements using an optimal estimation method. The large complement of data collected from multiple instruments deployed during this field campaign provides a unique opportunity to validate and characterize the performance of the MAX-DOAS vertical profile retrievals. Aerosol extinction profiles determined from two Light Detection and Ranging (LIDAR) instruments, one collocated and the other on a Twin Otter aircraft that flew over the site during the study, will be compared to the MAX-DOAS aerosol extinction profile retrievals. Vertical profiles of NO2 and SO2 retrieved from the MAX-DOAS measurements will be further compared with the composite vertical profiles measured from the flights of a second aircraft, the NRC-Convair 580, over the field site during the same measurement period. Finally, the MAX-DOAS retrieved tropospheric vertical column densities (VCDs) of SO2 and NO2 will be compared to the predicted VCDs from Environment and Climate Change Canada's Global Environmental Multi-scale - Modelling Air quality and Chemistry (GEM-MACH) air quality model over the grid cell containing the field site. Emission estimates of SO2 from the major oil mining facility Syncrude Mildred Lake using the MAX-DOAS VCD results, validated through the detailed characterization above

  2. Interstellar Extinction

    Science.gov (United States)

    Gontcharov, G. A.

    2016-12-01

    This review describes our current understanding of interstellar extinction. This differ substantially from the ideas of the 20th century. With infrared surveys of hundreds of millions of stars over the entire sky, such as 2MASS, SPITZER-IRAC, and WISE, we have looked at the densest and most rarefied regions of the interstellar medium at distances of a few kpc from the Sun. Observations at infrared and microwave wavelengths, where the bulk of the interstellar dust absorbs and radiates, have brought us closer to an understanding of the distribution of the dust particles on scales of the Galaxy and the universe. We are in the midst of a scientific revolution in our understanding of the interstellar medium and dust. Progress in, and the key results of, this revolution are still difficult to predict. Nevertheless, (a) a physically justified model has been developed for the spatial distribution of absorbing material over the nearest few kiloparsecs, including the Gould belt as a dust container, which gives an accurate estimate of the extinction for any object just by its galactic coordinates. It is also clear that (b) the interstellar medium contains roughly half the mass of matter in the galactic vicinity of the solar system (the other half is made up of stars, their remnants, and dark matter) and (c) the interstellar medium and, especially, dust, differ substantially in different regions of space and deep space cannot be understood by only studying near space.

  3. Laboratory investigation on the role of tubular shaped micro resonators phononic crystal insertion on the absorption coefficient of profiled sound absorber

    Science.gov (United States)

    Yahya, I.; Kusuma, J. I.; Harjana; Kristiani, R.; Hanina, R.

    2016-02-01

    This paper emphasizes the influence of tubular shaped microresonators phononic crystal insertion on the sound absorption coefficient of profiled sound absorber. A simple cubic and two different bodies centered cubic phononic crystal lattice model were analyzed in a laboratory test procedure. The experiment was conducted by using transfer function based two microphone impedance tube method refer to ASTM E-1050-98. The results show that sound absorption coefficient increase significantly at the mid and high-frequency band (600 - 700 Hz) and (1 - 1.6 kHz) when tubular shaped microresonator phononic crystal inserted into the tested sound absorber element. The increment phenomena related to multi-resonance effect that occurs when sound waves propagate through the phononic crystal lattice model that produce multiple reflections and scattering in mid and high-frequency band which increases the sound absorption coefficient accordingly

  4. Interdiffusion in Ni-rich, Ni-Cr-Al alloys at 1100 and 1200 C. I - Diffusion paths and microstructures. II - Diffusion coefficients and predicted concentration profiles

    Science.gov (United States)

    Nesbitt, J. A.; Heckel, R. W.

    1987-01-01

    Interdiffusion in Ni-rich Ni-Cr-Al alloys is investigated experimentally after annealing at 1100 and 1200 C using gamma/gamma, gamma/gamma+beta, gamma/gamma+gamma prime, and gamma/gamma+alpha diffusion couples. The amount and location of Kirkendall porosity suggests that Al diffuses more rapidly than Cr which diffuses more rapidly than Ni in the gamma phase of Ni-Cr-Al alloys. The location and extent of maxima and minima in the concentration profiles of the diffusion couples indicate that both cross-term diffusion coefficients are positive. Measurements are also presented of the ternary interdiffusion coefficients of the gamma phase in the Ni-Cr-Al system. It is shown that the interdiffusion coefficients can be accurately predicted by using a ternary finite-difference interdiffusion model.

  5. Improved profile fitting and quantification of uncertainty in experimental measurements of impurity transport coefficients using Gaussian process regression

    Science.gov (United States)

    Chilenski, M. A.; Greenwald, M.; Marzouk, Y.; Howard, N. T.; White, A. E.; Rice, J. E.; Walk, J. R.

    2015-02-01

    The need to fit smooth temperature and density profiles to discrete observations is ubiquitous in plasma physics, but the prevailing techniques for this have many shortcomings that cast doubt on the statistical validity of the results. This issue is amplified in the context of validation of gyrokinetic transport models (Holland et al 2009 Phys. Plasmas 16 052301), where the strong sensitivity of the code outputs to input gradients means that inadequacies in the profile fitting technique can easily lead to an incorrect assessment of the degree of agreement with experimental measurements. In order to rectify the shortcomings of standard approaches to profile fitting, we have applied Gaussian process regression (GPR), a powerful non-parametric regression technique, to analyse an Alcator C-Mod L-mode discharge used for past gyrokinetic validation work (Howard et al 2012 Nucl. Fusion 52 063002). We show that the GPR techniques can reproduce the previous results while delivering more statistically rigorous fits and uncertainty estimates for both the value and the gradient of plasma profiles with an improved level of automation. We also discuss how the use of GPR can allow for dramatic increases in the rate of convergence of uncertainty propagation for any code that takes experimental profiles as inputs. The new GPR techniques for profile fitting and uncertainty propagation are quite useful and general, and we describe the steps to implementation in detail in this paper. These techniques have the potential to substantially improve the quality of uncertainty estimates on profile fits and the rate of convergence of uncertainty propagation, making them of great interest for wider use in fusion experiments and modelling efforts.

  6. An accuracy assessment of the CALIOP/CALIPSO version 2 aerosol extinction product based on a detailed multi-sensor, multi-platform case study

    Directory of Open Access Journals (Sweden)

    M. Kacenelenbogen

    2010-11-01

    Full Text Available The Cloud Aerosol LIdar with Orthogonal Polarization (CALIOP, on board the CALIPSO platform, has measured profiles of total attenuated backscatter coefficient (level 1 products since June 2006. CALIOP's level 2 products, such as the aerosol backscatter and extinction coefficient profiles, are retrieved using a complex succession of automated algorithms. The goal of this study is to help identify potential shortcomings in the CALIOP version 2 level 2 aerosol extinction product and to illustrate some of the motivation for the changes that will be introduced in the next version of CALIOP data (version 3, currently being processed. As a first step, we compared CALIOP version 2-derived AOD with the collocated MODerate Imaging Spectroradiometer (MODIS AOD retrievals over the Continental United States. The best statistical agreement between those two quantities was found over the Eastern part of the United States with, nonetheless, a weak correlation (R ~0.4 and an apparent CALIOP version 2 underestimation (by ~66% of MODIS AOD. To help quantify the potential factors contributing to the uncertainty of the CALIOP aerosol extinction retrieval, we then focused on a one-day, multi-instrument, multiplatform comparison study during the CALIPSO and Twilight Zone (CATZ validation campaign on August 04, 2007. This case study illustrates the following potential reasons for a bias in the CALIOP AOD: (i CALIOP's low signal-to-noise ratio (SNR leading to the misclassification and/or lack of aerosol layer identification, especially close to the Earth's surface; (ii the cloud contamination of CALIOP version 2 aerosol backscatter and extinction profiles; (iii potentially erroneous assumptions of the backscatter-to-extinction ratio (Sa used in CALIOP's extinction retrievals; and (iv calibration coefficient biases in the CALIOP daytime attenuated backscatter coefficient profiles.

  7. Single-ended measurement of infrared extinction using lidar.

    Science.gov (United States)

    Murray, E R; Williams, M F; van der Laan, J E

    1978-01-15

    The goal of this study was to investigate the feasibility of single-ended measurement of the total extinction coefficient using an ir lidar system. Extinction was measured using a CO(2) laser radar system at four wavelengths near 10.3 microm. The measured results agree with theoretical estimates of extinction over a wide range. Single-ended measurements of extinction appear feasible to a horizontal range of 10 km using commercially available components. The system could potentially generate extinction data in a 3-D grid, enabling one to determine ir transmission between any two points in the field.

  8. Profiling the Local Seebeck Coefficient of InAs-GaAs Quantum Dots Using Scanning Thermoelectric Microscopy

    Science.gov (United States)

    Lin, Yen-Hsiang; Walrath, Jenna; Huang, Simon; Goldman, Rachel

    2014-03-01

    Thermoelectric (TE) devices offer a method of recovering waste heat through solid state conversion of heat to electricity. However, the typical efficiencies of TE devices are 5-10% which constitutes a barrier to wide spread use. There have recently been a number of reports of an increase in the bulk thermopower due to nanostructuring. In addition to our recent report of enhanced thermopower for GaAs embedded with indium nanocrystals, a theoretical study by Mahan and Sofo suggested that the best thermoelectric materials have a delta function density of states. Quantum dots fit ideally into such a picture. To date, the influence of nanostructuring on the electronic LDOS and thermopower has been studied using spatially averaged measurements; a nanoscale investigation of the effects of nanostructures on thermopower has yet to be presented. To investigate the link between dimensionality and TE properties, we are examining structures ranging from QDs to bulk-like layers, comparing SThEM measurements of the local Seebeck coefficient, S, with STS measurements of the local density of states (LDOS). STM, STS, and SThEM performed on InAs quantum dots (QDs) grown on GaAs. SThEM reveals enhanced S-values near the QD edge; STS reveals band-bending at the QD/GaAs interface, suggesting that the S enhancement is due to interfacial charge accumulation.

  9. Lidar Ratios for Dust Aerosols Derived From Retrievals of CALIPSO Visible Extinction Profiles Constrained by Optical Depths from MODIS-Aqua and CALIPSO/CloudSat Ocean Surface Reflectance Measurements

    Science.gov (United States)

    Young, Stuart A.; Josset, Damien B.; Vaughan, Mark A.

    2010-01-01

    CALIPSO's (Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations) analysis algorithms generally require the use of tabulated values of the lidar ratio in order to retrieve aerosol extinction and optical depth from measured profiles of attenuated backscatter. However, for any given time or location, the lidar ratio for a given aerosol type can differ from the tabulated value. To gain some insight as to the extent of the variability, we here calculate the lidar ratio for dust aerosols using aerosol optical depth constraints from two sources. Daytime measurements are constrained using Level 2, Collection 5, 550-nm aerosol optical depth measurements made over the ocean by the MODIS (Moderate Resolution Imaging Spectroradiometer) on board the Aqua satellite, which flies in formation with CALIPSO. We also retrieve lidar ratios from night-time profiles constrained by aerosol column optical depths obtained by analysis of CALIPSO and CloudSat backscatter signals from the ocean surface.

  10. An accuracy assessment of the CALIOP/CALIPSO version 2/version 3 daytime aerosol extinction product based on a detailed multi-sensor, multi-platform case study

    Directory of Open Access Journals (Sweden)

    M. Kacenelenbogen

    2011-04-01

    Full Text Available The Cloud Aerosol LIdar with Orthogonal Polarization (CALIOP, on board the CALIPSO platform, has measured profiles of total attenuated backscatter coefficient (level 1 products since June 2006. CALIOP's level 2 products, such as the aerosol backscatter and extinction coefficient profiles, are retrieved using a complex succession of automated algorithms. The goal of this study is to help identify potential shortcomings in the CALIOP version 2 level 2 aerosol extinction product and to illustrate some of the motivation for the changes that have been introduced in the next version of CALIOP data (version 3, released in June 2010. To help illustrate the potential factors contributing to the uncertainty of the CALIOP aerosol extinction retrieval, we focus on a one-day, multi-instrument, multiplatform comparison study during the CALIPSO and Twilight Zone (CATZ validation campaign on 4 August 2007. On that day, we observe a consistency in the Aerosol Optical Depth (AOD values recorded by four different instruments (i.e. space-borne MODerate Imaging Spectroradiometer, MODIS: 0.67 and POLarization and Directionality of Earth's Reflectances, POLDER: 0.58, airborne High Spectral Resolution Lidar, HSRL: 0.52 and ground-based AErosol RObotic NETwork, AERONET: 0.48 to 0.73 while CALIOP AOD is a factor of two lower (0.32 at 532 nm. This case study illustrates the following potential sources of uncertainty in the CALIOP AOD: (i CALIOP's low signal-to-noise ratio (SNR leading to the misclassification and/or lack of aerosol layer identification, especially close to the Earth's surface; (ii the cloud contamination of CALIOP version 2 aerosol backscatter and extinction profiles; (iii potentially erroneous assumptions of the aerosol extinction-to-backscatter ratio (Sa used in CALIOP's extinction retrievals; and (iv calibration coefficient biases in the CALIOP daytime attenuated backscatter coefficient profiles. The use of version 3 CALIOP extinction

  11. An accuracy assessment of the CALIOP/CALIPSO version 2/version 3 daytime aerosol extinction product based on a detailed multi-sensor, multi-platform case study

    Science.gov (United States)

    Kacenelenbogen, M.; Vaughan, M. A.; Redemann, J.; Hoff, R. M.; Rogers, R. R.; Ferrare, R. A.; Russell, P. B.; Hostetler, C. A.; Hair, J. W.; Holben, B. N.

    2011-04-01

    The Cloud Aerosol LIdar with Orthogonal Polarization (CALIOP), on board the CALIPSO platform, has measured profiles of total attenuated backscatter coefficient (level 1 products) since June 2006. CALIOP's level 2 products, such as the aerosol backscatter and extinction coefficient profiles, are retrieved using a complex succession of automated algorithms. The goal of this study is to help identify potential shortcomings in the CALIOP version 2 level 2 aerosol extinction product and to illustrate some of the motivation for the changes that have been introduced in the next version of CALIOP data (version 3, released in June 2010). To help illustrate the potential factors contributing to the uncertainty of the CALIOP aerosol extinction retrieval, we focus on a one-day, multi-instrument, multiplatform comparison study during the CALIPSO and Twilight Zone (CATZ) validation campaign on 4 August 2007. On that day, we observe a consistency in the Aerosol Optical Depth (AOD) values recorded by four different instruments (i.e. space-borne MODerate Imaging Spectroradiometer, MODIS: 0.67 and POLarization and Directionality of Earth's Reflectances, POLDER: 0.58, airborne High Spectral Resolution Lidar, HSRL: 0.52 and ground-based AErosol RObotic NETwork, AERONET: 0.48 to 0.73) while CALIOP AOD is a factor of two lower (0.32 at 532 nm). This case study illustrates the following potential sources of uncertainty in the CALIOP AOD: (i) CALIOP's low signal-to-noise ratio (SNR) leading to the misclassification and/or lack of aerosol layer identification, especially close to the Earth's surface; (ii) the cloud contamination of CALIOP version 2 aerosol backscatter and extinction profiles; (iii) potentially erroneous assumptions of the aerosol extinction-to-backscatter ratio (Sa) used in CALIOP's extinction retrievals; and (iv) calibration coefficient biases in the CALIOP daytime attenuated backscatter coefficient profiles. The use of version 3 CALIOP extinction retrieval for our case

  12. An Accuracy Assessment of the CALIOP/CALIPSO Version 2/Version 3 Daytime Aerosol Extinction Product Based on a Detailed Multi-Sensor, Multi-Platform Case Study

    Science.gov (United States)

    Kacenelenbogen, M.; Vaughan, M. A.; Redemann, J.; Hoff, R. M.; Rogers, R. R.; Ferrare, R. A.; Russell, P. B.; Hostetler, C. A.; Hair, J. W.; Holben, B. N.

    2011-01-01

    The Cloud Aerosol LIdar with Orthogonal Polarization (CALIOP), on board the CALIPSO platform, has measured profiles of total attenuated backscatter coefficient (level 1 products) since June 2006. CALIOP s level 2 products, such as the aerosol backscatter and extinction coefficient profiles, are retrieved using a complex succession of automated algorithms. The goal of this study is to help identify potential shortcomings in the CALIOP version 2 level 2 aerosol extinction product and to illustrate some of the motivation for the changes that have been introduced in the next version of CALIOP data (version 3, released in June 2010). To help illustrate the potential factors contributing to the uncertainty of the CALIOP aerosol extinction retrieval, we focus on a one-day, multi-instrument, multiplatform comparison study during the CALIPSO and Twilight Zone (CATZ) validation campaign on 4 August 2007. On that day, we observe a consistency in the Aerosol Optical Depth (AOD) values recorded by four different instruments (i.e. spaceborne MODerate Imaging Spectroradiometer, MODIS: 0.67 and POLarization and Directionality of Earth s Reflectances, POLDER: 0.58, airborne High Spectral Resolution Lidar, HSRL: 0.52 and ground-based AErosol RObotic NETwork, AERONET: 0.48 to 0.73) while CALIOP AOD is a factor of two lower (0.32 at 532 nm). This case study illustrates the following potential sources of uncertainty in the CALIOP AOD: (i) CALIOP s low signal-to-noise ratio (SNR) leading to the misclassification and/or lack of aerosol layer identification, especially close to the Earth s surface; (ii) the cloud contamination of CALIOP version 2 aerosol backscatter and extinction profiles; (iii) potentially erroneous assumptions of the aerosol extinction-to-backscatter ratio (Sa) used in CALIOP s extinction retrievals; and (iv) calibration coefficient biases in the CALIOP daytime attenuated backscatter coefficient profiles. The use of version 3 CALIOP extinction retrieval for our case

  13. Gradual extinction reduces Reinstatement

    Directory of Open Access Journals (Sweden)

    Youssef eShiban

    2015-09-01

    Full Text Available The current study investigated whether gradually reducing the frequency of aversive stimuli during extinction can prevent the return of fear. Thirty-one participants of a three-stage procedure (acquisition, extinction and a reinstatement test on day two were randomly assigned to a standard extinction (SE and gradual extinction (GE procedure. The two groups differed only in the extinction procedure. While the SE group ran through a regular extinction process without any negative events, the frequency of the aversive stimuli during the extinction phase was gradually reduced for the GE group. The unconditioned stimulus was an air blast (5 bar, 10 ms. A spider and a scorpion were used as conditioned stimuli. The outcome variables were contingency ratings and physiological measures (skin conductance response and startle response. There were no differences found between the two groups for the acquisition and extinction phases concerning contingency ratings, SCR, or startle response. Gradual extinction compared to standard extinction significantly reduced the return of fear in the reinstatement test for the startle response but not for skin conductance response or contingency ratings. This study was successful in translating the findings in rodent to humans. The results suggest that the gradual extinction process is suitable for increasing the efficacy of fear extinction.

  14. Revealing the powdering methods of black makeup in Ancient Egypt by fitting microstructure based Fourier coefficients to the whole x-ray diffraction profiles of galena

    Science.gov (United States)

    Ungár, T.; Martinetto, P.; Ribárik, G.; Dooryhée, E.; Walter, Ph.; Anne, M.

    2002-02-01

    Galena (PbS) is a major ingredient in ancient Egyptian eye makeup. The microstructure of PbS in Egyptian cosmetic powders is used as a fingerprint and is matched with the microstructures produced artificially in geological galena minerals. The microstructure of PbS is determined by x-ray diffraction peak profile analysis in terms of dislocation density, crystallite size, and size distribution. High-resolution powder diffractograms were measured at the ESRF Grenoble synchrotron source with high resolution and high peak-to-background ratios. The Fourier coefficients of the first nine measured reflections of galena are fitted using physically based Fourier coefficients of strain and size functions. Strain anisotropy is accounted for by the dislocation model of the mean square strain. The x-ray data are supplemented by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs, and are compared with archæological documents. It enables us to describe the procedures of eye makeup manufacturing in the Middle and New Kingdoms of Egypt some 2000 years before Christ.

  15. Retrieval of aerosol backscatter and extinction from airborne coherent Doppler wind lidar measurements

    Directory of Open Access Journals (Sweden)

    F. Chouza

    2015-02-01

    Full Text Available A novel method for calibration and quantitative aerosol optical properties retrieval from Doppler wind lidars (DWL is presented in this work. Due to the strong wavelength dependence of the atmospheric molecular backscatter and the low sensitivity of the coherent detection to spectrally broad signals, calibration methods for aerosol lidars cannot be applied to a coherent DWLs usually operating at wavelengths between 1.5–2 μm. Instead, concurrent measurements of an airborne DWL at 2 μm and the POLIS ground-based aerosol lidar at 532 nm are used in this work, in combination with sun photometer measurements, for the calibration and retrieval of aerosol backscatter and extinction profiles. The proposed method was applied to measurements from the SALTRACE experiment in June–July 2013, which aimed at quantifying the aerosol transport and change in aerosol properties from the Sahara desert to the Caribbean. The retrieved backscatter and extinction coefficient profiles from the airborne DWL are within 20% of POLIS aerosol lidar and CALIPSO satellite measurements. Thus the proposed method extends the capabilities of coherent DWL to measure profiles of the horizontal and vertical wind towards aerosol backscatter and extinction profiles, which is of high benefit for aerosol transport studies.

  16. Is extinction forever?

    Science.gov (United States)

    Smith-Patten, Brenda D; Bridge, Eli S; Crawford, Priscilla H C; Hough, Daniel J; Kelly, Jeffrey F; Patten, Michael A

    2015-05-01

    Mistrust of science has seeped into public perception of the most fundamental aspect of conservation-extinction. The term ought to be straightforward, and yet, there is a disconnect between scientific discussion and public views. This is not a mere semantic issue, rather one of communication. Within a population dynamics context, we say that a species went locally extinct, later to document its return. Conveying our findings matters, for when we use local extinction, an essentially nonsensical phrase, rather than extirpation, which is what is meant, then we contribute to, if not create outright, a problem for public understanding of conservation, particularly as local extinction is often shortened to extinction in media sources. The public that receives the message of our research void of context and modifiers comes away with the idea that extinction is not forever or, worse for conservation as a whole, that an extinction crisis has been invented.

  17. Measuring Extinction with ALE

    Science.gov (United States)

    Zimmer, Peter C.; McGraw, J. T.; Gimmestad, G. G.; Roberts, D.; Stewart, J.; Smith, J.; Fitch, J.

    2007-12-01

    ALE (Astronomical LIDAR for Extinction) is deployed at the University of New Mexico's (UNM) Campus Observatory in Albuquerque, NM. It has begun a year-long testing phase prior deployment at McDonald Observatory in support of the CCD/Transit Instrument II (CTI-II). ALE is designed to produce a high-precision measurement of atmospheric absorption and scattering above the observatory site every ten minutes of every moderately clear night. LIDAR (LIght Detection And Ranging) is the VIS/UV/IR analog of radar, using a laser, telescope and time-gated photodetector instead of a radio transmitter, dish and receiver. In the case of ALE -- an elastic backscatter LIDAR -- 20ns-long, eye-safe laser pulses are launched 2500 times per second from a 0.32m transmitting telescope co-mounted with a 50mm short-range receiver on an alt-az mounted 0.67m long-range receiver. Photons from the laser pulse are scattered and absorbed as the pulse propagates through the atmosphere, a portion of which are scattered into the field of view of the short- and long-range receiver telescopes and detected by a photomultiplier. The properties of a given volume of atmosphere along the LIDAR path are inferred from both the altitude-resolved backscatter signal as well as the attenuation of backscatter signal from altitudes above it. We present ALE profiles from the commissioning phase and demonstrate some of the astronomically interesting atmospheric information that can be gleaned from these data, including, but not limited to, total line-of-sight extinction. This project is funded by NSF Grant 0421087.

  18. Inversion of tropospheric profiles of aerosol extinction and HCHO and NO2 mixing ratios from MAX-DOAS observations in Milano during the summer of 2003 and comparison with independent data sets

    Directory of Open Access Journals (Sweden)

    U. Platt

    2011-12-01

    Full Text Available We present aerosol and trace gas profiles derived from MAX-DOAS observations. Our inversion scheme is based on simple profile parameterisations used as input for an atmospheric radiative transfer model (forward model. From a least squares fit of the forward model to the MAX-DOAS measurements, two profile parameters are retrieved including integrated quantities (aerosol optical depth or trace gas vertical column density, and parameters describing the height and shape of the respective profiles. From these results, the aerosol extinction and trace gas mixing ratios can also be calculated. We apply the profile inversion to MAX-DOAS observations during a measurement campaign in Milano, Italy, September 2003, which allowed simultaneous observations from three telescopes (directed to north, west, south. Profile inversions for aerosols and trace gases were possible on 23 days. Especially in the middle of the campaign (17–20 September 2003, enhanced values of aerosol optical depth and NO2 and HCHO mixing ratios were found. The retrieved layer heights were typically similar for HCHO and aerosols. For NO2, lower layer heights were found, which increased during the day. The MAX-DOAS inversion results are compared to independent measurements: (1 aerosol optical depth measured at an AERONET station at Ispra; (2 near-surface NO2 and HCHO (formaldehyde mixing ratios measured by long path DOAS and Hantzsch instruments at Bresso; (3 vertical profiles of HCHO and aerosols measured by an ultra light aircraft. Depending on the viewing direction, the aerosol optical depths from MAX-DOAS are either smaller or larger than those from AERONET observations. Similar comparison results are found for the MAX-DOAS NO2 mixing ratios versus long path DOAS measurements. In contrast, the MAX-DOAS HCHO mixing ratios are generally higher than those from long path DOAS or Hantzsch instruments. The comparison of the HCHO and aerosol profiles from the aircraft showed reasonable

  19. Inversion of tropospheric profiles of aerosol extinction and HCHO and NO2 mixing ratios from MAX-DOAS observations in Milano during the summer of 2003 and comparison with independent data sets

    Directory of Open Access Journals (Sweden)

    X. Li

    2011-06-01

    Full Text Available We present aerosol and trace gas profiles derived from MAX-DOAS observations. Our inversion scheme is based on simple profile parameterisations used as input for an atmospheric radiative transfer model (forward model. From a least squares fit of the forward model to the MAX-DOAS measurements, two profile parameters are retrieved including integrated quantities (aerosol optical depth or trace gas vertical column density, and parameters describing the height and shape of the respective profiles. From these results, the aerosol extinction and trace gas mixing ratios can also be calculated. We apply the profile inversion to MAX-DOAS observations during a measurement campaign in Milano, Italy, September 2003, which allowed simultaneous observations from three telescopes (directed to north, west, south. Profile inversions for aerosols and trace gases were possible on 23 days. Especially in the middle of the campaign (17–20 September 2003, enhanced values of aerosol optical depth and NO2 and HCHO mixing ratios were found. The retrieved layer heights were typically similar for HCHO and aerosols. For NO2, lower layer heights were found, which increased during the day. The MAX-DOAS inversion results are compared to independent measurements: (1 aerosol optical depth measured at an AERONET station at Ispra; (2 near-surface NO2 and HCHO (formaldehyde mixing ratios measured by long path DOAS and Hantzsch instruments at Bresso; (3 vertical profiles of HCHO and aerosols measured by an ultra light aircraft. Depending on the viewing direction, the aerosol optical depths from MAX-DOAS are either smaller or larger than those from AERONET observations. Similar comparison results are found for the MAX-DOAS NO2 mixing ratios versus long path DOAS measurements. In contrast, the MAX-DOAS HCHO mixing ratios are generally higher than those from long path DOAS or Hantzsch instruments. The comparison of the HCHO and aerosol profiles from the aircraft showed reasonable

  20. Modern examples of extinctions

    DEFF Research Database (Denmark)

    Lövei, Gabor L

    2013-01-01

    No species lives forever, and extinction is the ultimate fate of all living species. The fossil record indicates that a recent extinction wave affecting terrestrial vertebrates was parallel with the arrival of modern humans to areas formerly uninhabited by them. These modern instances of extinction...... started at around 40,000 years ago. On continents, large mammals (especially those >50 kg body mass) were affected, while on islands, the impacts were mainly felt by birds. The causes of these extinctions are not well known but hunting, habitat alteration and the introduction of non-native species...... reasons (certain groups do not fossilize) and methodological problems (methods of excavation and identification). Consequently, we can only crudely estimate the current rate of extinction. Nonetheless, it is evident that humans generated a new mass extinction, affecting all species in all habitats, and...

  1. Modern examples of extinctions

    DEFF Research Database (Denmark)

    Lövei, Gabor L

    2013-01-01

    No species lives forever, and extinction is the ultimate fate of all living species. The fossil record indicates that a recent extinction wave affecting terrestrial vertebrates was parallel with the arrival of modern humans to areas formerly uninhabited by them. These modern instances of extinction...... started at around 40,000 years ago. On continents, large mammals (especially those >50 kg body mass) were affected, while on islands, the impacts were mainly felt by birds. The causes of these extinctions are not well known but hunting, habitat alteration and the introduction of non-native species...... are the main causes of extinction. Our knowledge about extinctions is very incomplete, due to bias in research by taxonomy (vertebrate groups are better studied), geography (northern areas have received more attention), habitat (terrestrial habitats are better known than marine ones), as well as biological...

  2. Mass extinction: a commentary

    Science.gov (United States)

    Raup, D. M.

    1987-01-01

    Four neocatastrophist claims about mass extinction are currently being debated; they are that: 1, the late Cretaceous mass extinction was caused by large body impact; 2, as many as five other major extinctions were caused by impact; 3, the timing of extinction events since the Permian is uniformly periodic; and 4, the ages of impact craters on Earth are also periodic and in phase with the extinctions. Although strongly interconnected the four claims are independent in the sense that none depends on the others. Evidence for a link between impact and extinction is strong but still needs more confirmation through bed-by-bed and laboratory studies. An important area for future research is the question of whether extinction is a continuous process, with the rate increasing at times of mass extinctions, or whether it is episodic at all scales. If the latter is shown to be generally true, then species are at risk of extinction only rarely during their existence and catastrophism, in the sense of isolated events of extreme stress, is indicated. This is line of reasoning can only be considered an hypothesis for testing. In a larger context, paleontologists may benefit from a research strategy that looks to known Solar System and Galactic phenomena for predictions about environmental effects on earth. The recent success in the recognition of Milankovitch Cycles in the late Pleistocene record is an example of the potential of this research area.

  3. A study on the aerosol extinction-to-backscatter ratio with combination of micro-pulse LIDAR and MODIS over Hong Kong

    Directory of Open Access Journals (Sweden)

    Q. S. He

    2006-01-01

    Full Text Available The aerosol extinction-to-backscatter ratio is an important parameter for inverting LIDAR signals in the LIDAR equation. It is a complicated function of the aerosol microphysical characteristics. In this paper, a method to retrieve the column-averaged aerosol extinction-to-backscatter ratio by constraining the aerosol optical depths (AOD from a Micro-pulse LIDAR (MPL by the AOD measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS is presented. Both measurements were taken on cloud free days between 1 May 2003 and 30 June 2004 over Hong Kong, a coastal city in south China. Simultaneous measurements of aerosol scattering coefficients with a forward scattering visibility sensor are compared with the LIDAR retrieval of aerosol extinction coefficients. The data are then analyzed to determine seasonal trends of the aetrosol extinction-to-backscatter ratio. In addition, the relationships between the extinction-to-backscatter ratio and wind conditions as well as other aerosol microphysical parameters are presented. The mean aerosol extinction-to-backscatter ratio for the whole period was found to be 29.1±5.8 sr, with a minimum of 18 sr in July 2003 and a maximum of 44 sr in March 2004. The ratio is lower in summer because of the dominance of oceanic aerosols in association with the prevailing southwesterly monsoon. In contrast, relatively larger ratios are noted in spring and winter because of the increased impact of local and regional industrial pollutants associated with the northerly monsoon. The extended LIDAR measurements over Hong Kong provide not only a more accurate retrieval of aerosol extinction coefficient profiles, but also significant substantial information for air pollution and climate studies in the region.

  4. Cavity Attenuated Phase Shift (CAPS) Method for Airborne Aerosol Light Extinction Measurement: Instrument Validation and First Results from Field Deployment

    Science.gov (United States)

    Petzold, A.; Perim de Faria, J.; Berg, M.; Bundke, U.; Freedman, A.

    2015-12-01

    Monitoring the direct impact of aerosol particles on climate requires the continuous measurement of aerosol optical parameters like the aerosol extinction coefficient on a regular basis. Remote sensing and ground-based networks are well in place (e.g., AERONET, ACTRIS), whereas the regular in situ measurement of vertical profiles of atmospheric aerosol optical properties remains still an important challenge in quantifying climate change. The European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; www.iagos.org) responds to the increasing requests for long-term, routine in situ observational data by using commercial passenger aircraft as measurement platform. However, scientific instrumentation for the measurement of atmospheric constituents requires major modifications before being deployable aboard in-service passenger aircraft. Recently, a compact and robust family of optical instruments based on the cavity attenuated phase shift (CAPS) technique has become available for measuring aerosol light extinction. While this technique was successfully deployed for ground-based atmospheric measurements under various conditions, its suitability for operation aboard aircraft in the free and upper free troposphere still has to be demonstrated. In this work, the modifications of a CAPS PMex instrument for measuring aerosol light extinction on aircraft, the results from subsequent laboratory tests for evaluating the modified instrument prototype, and first results from a field deployment aboard a research aircraft will be covered. In laboratory studies, the instrument showed excellent agreement (deviation < 5%) with theoretical values calculated from Rayleigh scattering cross-sections, when operated on pressurized air and CO2 at ambient and low pressure (~200 hPa). For monodisperse and polydisperse aerosols, reference aerosol extinction coefficients were calculated from measured size distributions and agreed with the CAPS PMex instrument

  5. Temporal Dynamics of Recovery from Extinction Shortly after Extinction Acquisition

    Science.gov (United States)

    Archbold, Georgina E.; Dobbek, Nick; Nader, Karim

    2013-01-01

    Evidence suggests that extinction is new learning. Memory acquisition involves both short-term memory (STM) and long-term memory (LTM) components; however, few studies have examined early phases of extinction retention. Retention of auditory fear extinction was examined at various time points. Shortly (1-4 h) after extinction acquisition…

  6. Mass extinction efficiency and extinction hygroscopicity of ambient PM2.5 in urban China.

    Science.gov (United States)

    Cheng, Zhen; Ma, Xin; He, Yujie; Jiang, Jingkun; Wang, Xiaoliang; Wang, Yungang; Sheng, Li; Hu, Jiangkai; Yan, Naiqiang

    2017-07-01

    The ambient PM2.5 pollution problem in China has drawn substantial international attentions. The mass extinction efficiency (MEE) and hygroscopicity factor (f(RH)) of PM2.5 can be readily applied to study the impacts on atmospheric visibility and climate. The few previous investigations in China only reported results from pilot studies and are lack of spatial representativeness. In this study, hourly average ambient PM2.5 mass concentration, relative humidity, and atmospheric visibility data from China national air quality and meteorological monitoring networks were retrieved and analyzed. It includes 24 major Chinese cities from nine city-clusters with the period of October 2013 to September 2014. Annual average extinction coefficient in urban China was 759.3±258.3Mm(-1), mainly caused by dry PM2.5 (305.8.2±131.0Mm(-1)) and its hygroscopicity (414.6±188.1Mm(-1)). High extinction coefficient values were resulted from both high ambient PM2.5 concentration (68.5±21.7µg/m(3)) and high relative humidity (69.7±8.6%). The PM2.5 mass extinction efficiency varied from 2.87 to 6.64m(2)/g with an average of 4.40±0.84m(2)/g. The average extinction hygroscopic factor f(RH=80%) was 2.63±0.45. The levels of PM2.5 mass extinction efficiency and hygroscopic factor in China were in comparable range with those found in developed countries in spite of the significant diversities among all 24 cities. Our findings help to establish quantitative relationship between ambient extinction coefficient (visual range) and PM2.5 & relative humidity. It will reduce the uncertainty of extinction coefficient estimation of ambient PM2.5 in urban China which is essential for the research of haze pollution and climate radiative forcing. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Hybridization and extinction.

    Science.gov (United States)

    Todesco, Marco; Pascual, Mariana A; Owens, Gregory L; Ostevik, Katherine L; Moyers, Brook T; Hübner, Sariel; Heredia, Sylvia M; Hahn, Min A; Caseys, Celine; Bock, Dan G; Rieseberg, Loren H

    2016-08-01

    Hybridization may drive rare taxa to extinction through genetic swamping, where the rare form is replaced by hybrids, or by demographic swamping, where population growth rates are reduced due to the wasteful production of maladaptive hybrids. Conversely, hybridization may rescue the viability of small, inbred populations. Understanding the factors that contribute to destructive versus constructive outcomes of hybridization is key to managing conservation concerns. Here, we survey the literature for studies of hybridization and extinction to identify the ecological, evolutionary, and genetic factors that critically affect extinction risk through hybridization. We find that while extinction risk is highly situation dependent, genetic swamping is much more frequent than demographic swamping. In addition, human involvement is associated with increased risk and high reproductive isolation with reduced risk. Although climate change is predicted to increase the risk of hybridization-induced extinction, we find little empirical support for this prediction. Similarly, theoretical and experimental studies imply that genetic rescue through hybridization may be equally or more probable than demographic swamping, but our literature survey failed to support this claim. We conclude that halting the introduction of hybridization-prone exotics and restoring mature and diverse habitats that are resistant to hybrid establishment should be management priorities.

  8. The Extinction Toward the Galactic Bulge from RR Lyrae Stars

    CERN Document Server

    Kunder, Andrea; Cook, Kem H; Chaboyer, Brian

    2007-01-01

    We present mean reddenings toward 3525 RR0 Lyrae stars from the Galactic bulge fields of the MACHO Survey. These reddenings are determined using the color at minimum $V$-band light of the RR0 Lyrae stars themselves and are found to be in general agreement with extinction estimates at the same location obtained from other methods. Using 3256 stars located in the Galactic Bulge, we derive the selective extinction coefficient $R_{V,VR}=A_V/E(V-R) = 4.3 \\pm 0.2$. This value is what is expected for a standard extinction law with $R_{V,BV} = 3.1 \\pm 0.3$.

  9. Switchgrass leaf area index and light extinction coefficients

    Science.gov (United States)

    Biomass production simulation modeling for plant species is often dependent upon accurate simulation or measurement of canopy light interception and radiation use efficiency. With the recent interest in converting large tracts of land to biofuel species cropping, modeling vegetative yield with grea...

  10. Profiling the PM2.5 mass concentration vertical distribution in the boundary layer

    OpenAIRE

    2015-01-01

    Fine particle (PM2.5) affects human life and activities directly; the detection of PM2.5 mass concentration profile is very essential due to its practical and scientific meanings (such as, quantifying of air quality and its variability, and improving air quality forecast and assessment). But so far, it is difficult to detect PM2.5 mass concentration profile. The proposed methodology to study the relationship between aerosol extinction coefficient and PM2.5 mass concentratio...

  11. Ecological model of extinctions

    CERN Document Server

    Abramson, G

    1997-01-01

    We present numerical results based on a simplified ecological system in evolution, showing features of extinction similar to that claimed for the biosystem on Earth. In the model each species consists of a population in interaction with the others, that reproduces and evolves in time. Each species is simultaneously a predator and a prey in a food chain. Mutations that change the interactions are supposed to occur randomly at a low rate. Extinctions of populations result naturally from the predator-prey dynamics. The model is not pinned in a fitness variable, and natural selection arises from the dynamics.

  12. Aircraft Measurements of BrO, IO, Glyoxal, NO2, H2O, O2-O2 and Aerosol Extinction Profiles in the Tropics: Comparison with Aircraft-/Ship-Based in Situ and Lidar Measurements

    Science.gov (United States)

    Volkamer, R.; Baidar, S.; Campos, T. L.; Coburn, S.; DiGangi, J. P.; Dix, B.; Eloranta, E. W.; Koenig, T. K.; Morley, B.; Ortega, I.; Pierce, B. R.; Reeves, M.; Sinreich, R.; Wang, S.; Zondlo, M. A.; Romashkin, P. A.

    2015-01-01

    Tropospheric chemistry of halogens and organic carbon over tropical oceans modifies ozone and atmospheric aerosols, yet atmospheric models remain largely untested for lack of vertically resolved measurements of bromine monoxide (BrO), iodine monoxide (IO) and small oxygenated hydrocarbons like glyoxal (CHOCHO) in the tropical troposphere. BrO, IO, glyoxal, nitrogen dioxide (NO2), water vapor (H2O) and O2-O2 collision complexes (O4/ were measured by the University of Colorado Airborne Multi-AXis Differential Optical Absorption Spectroscopy (CU AMAXDOAS) instrument, aerosol extinction by high spectral resolution lidar (HSRL), in situ aerosol size distributions by an ultra high sensitivity aerosol spectrometer (UHSAS) and in situ H2O by vertical-cavity surface-emitting laser (VCSEL) hygrometer. Data are presented from two research flights (RF12, RF17) aboard the National Science Foundation/ National Center for Atmospheric Research Gulfstream V aircraft over the tropical Eastern Pacific Ocean (tEPO) as part of the "Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated hydrocarbons" (TORERO) project (January/February 2012). We assess the accuracy of O4 slant column density (SCD) measurements in the presence and absence of aerosols. Our O4-inferred aerosol extinction profiles at 477 nm agree within 6% with HSRL in the boundary layer and closely resemble the renormalized profile shape of Mie calculations constrained by UHSAS at low (sub-Rayleigh) aerosol extinction in the free troposphere. CU AMAX-DOAS provides a flexible choice of geometry, which we exploit to minimize the SCD in the reference spectrum (SCDREF, maximize signal-to-noise ratio) and to test the robustness of BrO, IO and glyoxal differential SCDs. The RF12 case study was conducted in pristine marine and free tropospheric air. The RF17 case study was conducted above the NOAA RV Ka'imimoana (TORERO cruise, KA-12-01) and provides independent validation data from ship-based in situ cavity

  13. Aircraft Measurements of BrO, IO, Glyoxal, NO2, H2O, O2-O2 and Aerosol Extinction Profiles in the Tropics: Comparison with Aircraft-/Ship-Based in Situ and Lidar Measurements

    Science.gov (United States)

    Volkamer, R.; Baidar, S.; Campos, T. L.; Coburn, S.; DiGangi, J. P.; Dix, B.; Eloranta, E. W.; Koenig, T. K.; Morley, B.; Ortega, I.; hide

    2015-01-01

    Tropospheric chemistry of halogens and organic carbon over tropical oceans modifies ozone and atmospheric aerosols, yet atmospheric models remain largely untested for lack of vertically resolved measurements of bromine monoxide (BrO), iodine monoxide (IO) and small oxygenated hydrocarbons like glyoxal (CHOCHO) in the tropical troposphere. BrO, IO, glyoxal, nitrogen dioxide (NO2), water vapor (H2O) and O2-O2 collision complexes (O4/ were measured by the University of Colorado Airborne Multi-AXis Differential Optical Absorption Spectroscopy (CU AMAXDOAS) instrument, aerosol extinction by high spectral resolution lidar (HSRL), in situ aerosol size distributions by an ultra high sensitivity aerosol spectrometer (UHSAS) and in situ H2O by vertical-cavity surface-emitting laser (VCSEL) hygrometer. Data are presented from two research flights (RF12, RF17) aboard the National Science Foundation/ National Center for Atmospheric Research Gulfstream V aircraft over the tropical Eastern Pacific Ocean (tEPO) as part of the "Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated hydrocarbons" (TORERO) project (January/February 2012). We assess the accuracy of O4 slant column density (SCD) measurements in the presence and absence of aerosols. Our O4-inferred aerosol extinction profiles at 477 nm agree within 6% with HSRL in the boundary layer and closely resemble the renormalized profile shape of Mie calculations constrained by UHSAS at low (sub-Rayleigh) aerosol extinction in the free troposphere. CU AMAX-DOAS provides a flexible choice of geometry, which we exploit to minimize the SCD in the reference spectrum (SCDREF, maximize signal-to-noise ratio) and to test the robustness of BrO, IO and glyoxal differential SCDs. The RF12 case study was conducted in pristine marine and free tropospheric air. The RF17 case study was conducted above the NOAA RV Ka'imimoana (TORERO cruise, KA-12-01) and provides independent validation data from ship-based in situ cavity

  14. Aircraft measurements of BrO, IO, glyoxal, NO2, H2O, O2-O2 and aerosol extinction profiles in the tropics: comparison with aircraft-/ship-based in situ and lidar measurements

    Science.gov (United States)

    Volkamer, R.; Baidar, S.; Campos, T. L.; Coburn, S.; DiGangi, J. P.; Dix, B.; Eloranta, E. W.; Koenig, T. K.; Morley, B.; Ortega, I.; Pierce, B. R.; Reeves, M.; Sinreich, R.; Wang, S.; Zondlo, M. A.; Romashkin, P. A.

    2015-05-01

    Tropospheric chemistry of halogens and organic carbon over tropical oceans modifies ozone and atmospheric aerosols, yet atmospheric models remain largely untested for lack of vertically resolved measurements of bromine monoxide (BrO), iodine monoxide (IO) and small oxygenated hydrocarbons like glyoxal (CHOCHO) in the tropical troposphere. BrO, IO, glyoxal, nitrogen dioxide (NO2), water vapor (H2O) and O2-O2 collision complexes (O4) were measured by the University of Colorado Airborne Multi-AXis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument, aerosol extinction by high spectral resolution lidar (HSRL), in situ aerosol size distributions by an ultra high sensitivity aerosol spectrometer (UHSAS) and in situ H2O by vertical-cavity surface-emitting laser (VCSEL) hygrometer. Data are presented from two research flights (RF12, RF17) aboard the National Science Foundation/National Center for Atmospheric Research Gulfstream V aircraft over the tropical Eastern Pacific Ocean (tEPO) as part of the "Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated hydrocarbons" (TORERO) project (January/February 2012). We assess the accuracy of O4 slant column density (SCD) measurements in the presence and absence of aerosols. Our O4-inferred aerosol extinction profiles at 477 nm agree within 6% with HSRL in the boundary layer and closely resemble the renormalized profile shape of Mie calculations constrained by UHSAS at low (sub-Rayleigh) aerosol extinction in the free troposphere. CU AMAX-DOAS provides a flexible choice of geometry, which we exploit to minimize the SCD in the reference spectrum (SCDREF, maximize signal-to-noise ratio) and to test the robustness of BrO, IO and glyoxal differential SCDs. The RF12 case study was conducted in pristine marine and free tropospheric air. The RF17 case study was conducted above the NOAA RV Ka'imimoana (TORERO cruise, KA-12-01) and provides independent validation data from ship-based in situ cavity

  15. Optical Extinction Measurements of Laser Side-Scatter During Tropical Storm Colin

    Science.gov (United States)

    Lane, John E.; Kasparis, Takis; Metzger, Philip; Michaelides, Silas

    2017-01-01

    A side-scatter imaging (SSI) technique using a 447 nm, 500 mW laser and a Nikon D80 camera was tested at Kennedy Space Center, Florida during the passing of a rain band associated with Tropical Storm Colin. The June 6, 2016, 22:00 GMT rain event was intense but short-lived owing to the strong west-to-east advection of the rain band. An effort to validate the optical extinction measurement was conducted by setting up a line of three tipping rain gauges along an 80 m east-west path and below the laser beam. Differences between tipping bucket measurements were correlated to the extinction coefficient profile along the lasers path, as determined by the SSI measurement. In order to compare the tipping bucket to the optical extinction data, a Marshall-Palmer DSD model was assumed. Since this was a daytime event, the laser beam was difficult to detect in the camera images, pointing out an important limitation of SSI measurements: the practical limit of DSD density that can be effectively detected and analyzed under daylight conditions using this laser and camera, corresponds to a fairly moderate rainfall rate on the order of 20 mmh (night measurements achieve a much improved sensitivity). The SSI analysis model under test produced promising results, but in order to use the SSI method for routine meteorological studies, improvements to the math model will be required.

  16. Context, Learning, and Extinction

    Science.gov (United States)

    Gershman, Samuel J.; Blei, David M.; Niv, Yael

    2010-01-01

    A. Redish et al. (2007) proposed a reinforcement learning model of context-dependent learning and extinction in conditioning experiments, using the idea of "state classification" to categorize new observations into states. In the current article, the authors propose an interpretation of this idea in terms of normative statistical inference. They…

  17. Unexpectedly many extinct hominins.

    Science.gov (United States)

    Bokma, Folmer; van den Brink, Valentijn; Stadler, Tanja

    2012-09-01

    Recent studies indicate that Neanderthal and Denisova hominins may have been separate species, while debate continues on the status of Homo floresiensis. The decade-long debate between "splitters," who recognize over 20 hominin species, and "lumpers," who maintain that all these fossils belong to just a few lineages, illustrates that we do not know how many extinct hominin species to expect. Here, we present probability distributions for the number of speciation events and the number of contemporary species along a branch of a phylogeny. With estimates of hominin speciation and extincton rates, we then show that the expected total number of extinct hominin species is 8, but may be as high as 27. We also show that it is highly unlikely that three very recent species disappeared due to natural, background extinction. This may indicate that human-like remains are too easily considered distinct species. Otherwise, the evidence suggesting that Neanderthal and the Denisova hominin represent distinct species implies a recent wave of extinctions, ostensibly driven by the only survivor, H. sapiens. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

  18. Ecology: Dynamics of Indirect Extinction.

    Science.gov (United States)

    Montoya, Jose M

    2015-12-01

    The experimental identification of the mechanism by which extinctions of predators trigger further predator extinctions emphasizes the role of indirect effects between species in disturbed ecosystems. It also has deep consequences for the hidden magnitude of the current biodiversity crisis.

  19. Dust properties along anomalous extinction sightlines. II. Studying extinction curves with dust models

    CERN Document Server

    Mazzei, Paola

    2010-01-01

    The large majority of extinction sight lines in our Galaxy obey a simple relation depending on one parameter, the total-to-selective extinction coefficient, Rv. Different values of Rv are able to match the whole extinction curve through different environments so characterizing normal extinction curves. In this paper more than sixty curves with large ultraviolet deviations from their best-fit one parameter curve are analyzed. These curves are fitted with dust models to shed light into the properties of the grains, the processes affecting them, and their relations with the environmental characteristics. The extinction curve models are reckoned by following recent prescriptions on grain size distributions able to describe one parameter curves for Rv values from 3.1 to 5.5. Such models, here extended down to Rv=2.0, allow us to compare the resulting properties of our deviating curves with the same as normal curves in a self-consistent framework, and thus to recover the relative trends overcoming the modeling unce...

  20. Mass Extinctions Past and Present.

    Science.gov (United States)

    Allmon, Warren Douglas

    1987-01-01

    Discusses some parallels that seem to exist between mass extinction recognizable in the geologic record and the impending extinction of a significant proportion of the earth's species due largely to tropical deforestation. Describes some recent theories of causal factors and periodicities in mass extinction. (Author/TW)

  1. Extinction-to-Backscatter Ratios of Saharan Dust Layers Derived from In-Situ Measurements and CALIPSO Overflights During NAMMA

    Science.gov (United States)

    Omar, Ali H.; Liu, Zhaoyan; Vaughan, Mark A.; Hu, Yongxiang; Ismail, Syed; Powell, Kathleen A.; Winker, David M.; Trepte, Charles R.; Anderson, Bruce E.

    2010-01-01

    We determine the aerosol extinction-to-backscatter (Sa) ratios of dust using airborne in-situ measurements of microphysical properties, and CALIPSO observations during the NASA African Monsoon Multidisciplinary Analyses (NAMMA). The NAMMA field experiment was conducted from Sal, Cape Verde during Aug-Sept 2006. Using CALIPSO measurements of the attenuated backscatter of lofted Saharan dust layers, we apply the transmittance technique to estimate dust Sa ratios at 532 nm and a 2-color method to determine the corresponding 1064 nm Sa. Using this method, we found dust Sa ratios of 39.8 plus or minus 1.4 sr and 51.8 plus or minus 3.6 sr at 532 nm and 1064 nm, respectively. Secondly, Sa ratios at both wavelengths is independently calculated using size distributions measured aboard the NASA DC-8 and estimates of Saharan dust complex refractive indices applied in a T-Matrix scheme. We found Sa ratios of 39.1 plus or minus 3.5 sr and 50.0 plus or minus 4 sr at 532 nm and 1064 nm, respectively, using the T-Matrix calculations applied to measured size spectra. Finally, in situ measurements of the total scattering (550 nm) and absorption coefficients (532 nm) are used to generate an extinction profile that is used to constrain the CALIPSO 532 nm extinction profile.

  2. Neuronal circuits of fear extinction.

    Science.gov (United States)

    Herry, Cyril; Ferraguti, Francesco; Singewald, Nicolas; Letzkus, Johannes J; Ehrlich, Ingrid; Lüthi, Andreas

    2010-02-01

    Fear extinction is a form of inhibitory learning that allows for the adaptive control of conditioned fear responses. Although fear extinction is an active learning process that eventually leads to the formation of a consolidated extinction memory, it is a fragile behavioural state. Fear responses can recover spontaneously or subsequent to environmental influences, such as context changes or stress. Understanding the neuronal substrates of fear extinction is of tremendous clinical relevance, as extinction is the cornerstone of psychological therapy of several anxiety disorders and because the relapse of maladaptative fear and anxiety is a major clinical problem. Recent research has begun to shed light on the molecular and cellular processes underlying fear extinction. In particular, the acquisition, consolidation and expression of extinction memories are thought to be mediated by highly specific neuronal circuits embedded in a large-scale brain network including the amygdala, prefrontal cortex, hippocampus and brain stem. Moreover, recent findings indicate that the neuronal circuitry of extinction is developmentally regulated. Here, we review emerging concepts of the neuronal circuitry of fear extinction, and highlight novel findings suggesting that the fragile phenomenon of extinction can be converted into a permanent erasure of fear memories. Finally, we discuss how research on genetic animal models of impaired extinction can further our understanding of the molecular and genetic bases of human anxiety disorders.

  3. The Gaia-ESO Survey: Tracing interstellar extinction

    CERN Document Server

    Schultheis, M; Recio-Blanco, A; de Laverny, P; Hill, V; Gilmore, G; Alfaro, E J; Costado, M T; Bensby, T; Damiani, F; Feltzing, S; Flaccomio, E; Lardo, C; Jofre, P; Prisinzano, L; Zaggia, S; Jimenez-Esteban, F; Morbidelli, L; Lanzafame, A C; Hourihane, A; Worley, C; Francois, P

    2015-01-01

    Large spectroscopic surveys have enabled in the recent years the computation of three-dimensional interstellar extinction maps thanks to accurate stellar atmospheric parameters and line-of-sight distances. Such maps are complementary to 3D maps extracted from photometry, allowing a more thorough study of the dust properties. Our goal is to use the high-resolution spectroscopic survey Gaia-ESO in order to obtain with a good distance resolution the interstellar extinction and its dependency as a function of the environment and the Galactocentric position. We use the stellar atmospheric parameters of more than 5000 stars, obtained from the Gaia-ESO survey second internal data release, and combine them with optical (SDSS) and near-infrared (VISTA) photometry as well as different sets of theoretical stellar isochrones, in order to calculate line-of-sight extinction and distances. The extinction coefficients are then compared with the literature to discuss their dependancy on the stellar parameters and position in ...

  4. The effect of experimental resolution on crystal reflectivity and secondary extinction in neutron diffraction

    DEFF Research Database (Denmark)

    Dietrich, O.W.; Als-Nielsen, Jens Aage

    1965-01-01

    The reflectivity for neutrons of a plane slab crystal is calculated in the transmission case when the crystal is placed between two Seller collimators. The calculations indicate that the crystal reflectivity, as well as the secondary extinction coefficient, depends signicantly on the angular...... resolution of the collimators. Curves are given for the extinction of the crystal with different crystal and collimator parameters....

  5. The role of inbreeding in the extinction of a European royal dynasty.

    Directory of Open Access Journals (Sweden)

    Gonzalo Alvarez

    Full Text Available The kings of the Spanish Habsburg dynasty (1516-1700 frequently married close relatives in such a way that uncle-niece, first cousins and other consanguineous unions were prevalent in that dynasty. In the historical literature, it has been suggested that inbreeding was a major cause responsible for the extinction of the dynasty when the king Charles II, physically and mentally disabled, died in 1700 and no children were born from his two marriages, but this hypothesis has not been examined from a genetic perspective. In this article, this hypothesis is checked by computing the inbreeding coefficient (F of the Spanish Habsburg kings from an extended pedigree up to 16 generations in depth and involving more than 3,000 individuals. The inbreeding coefficient of the Spanish Habsburg kings increased strongly along generations from 0.025 for king Philip I, the founder of the dynasty, to 0.254 for Charles II and several members of the dynasty had inbreeding coefficients higher than 0.20. In addition to inbreeding due to unions between close relatives, ancestral inbreeding from multiple remote ancestors makes a substantial contribution to the inbreeding coefficient of most kings. A statistically significant inbreeding depression for survival to 10 years is detected in the progenies of the Spanish Habsburg kings. The results indicate that inbreeding at the level of first cousin (F = 0.0625 exerted an adverse effect on survival of 17.8%+/-12.3. It is speculated that the simultaneous occurrence in Charles II (F = 0.254 of two different genetic disorders: combined pituitary hormone deficiency and distal renal tubular acidosis, determined by recessive alleles at two unlinked loci, could explain most of the complex clinical profile of this king, including his impotence/infertility which in last instance led to the extinction of the dynasty.

  6. The role of inbreeding in the extinction of a European royal dynasty.

    Science.gov (United States)

    Alvarez, Gonzalo; Ceballos, Francisco C; Quinteiro, Celsa

    2009-01-01

    The kings of the Spanish Habsburg dynasty (1516-1700) frequently married close relatives in such a way that uncle-niece, first cousins and other consanguineous unions were prevalent in that dynasty. In the historical literature, it has been suggested that inbreeding was a major cause responsible for the extinction of the dynasty when the king Charles II, physically and mentally disabled, died in 1700 and no children were born from his two marriages, but this hypothesis has not been examined from a genetic perspective. In this article, this hypothesis is checked by computing the inbreeding coefficient (F) of the Spanish Habsburg kings from an extended pedigree up to 16 generations in depth and involving more than 3,000 individuals. The inbreeding coefficient of the Spanish Habsburg kings increased strongly along generations from 0.025 for king Philip I, the founder of the dynasty, to 0.254 for Charles II and several members of the dynasty had inbreeding coefficients higher than 0.20. In addition to inbreeding due to unions between close relatives, ancestral inbreeding from multiple remote ancestors makes a substantial contribution to the inbreeding coefficient of most kings. A statistically significant inbreeding depression for survival to 10 years is detected in the progenies of the Spanish Habsburg kings. The results indicate that inbreeding at the level of first cousin (F = 0.0625) exerted an adverse effect on survival of 17.8%+/-12.3. It is speculated that the simultaneous occurrence in Charles II (F = 0.254) of two different genetic disorders: combined pituitary hormone deficiency and distal renal tubular acidosis, determined by recessive alleles at two unlinked loci, could explain most of the complex clinical profile of this king, including his impotence/infertility which in last instance led to the extinction of the dynasty.

  7. EXTINCTION OF A DISCRETE NONLINEAR PREDATOR-PREY SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this paper, we consider a discrete nonlinear predator-prey model with nonnegative coefficients bounded above and below by positive constants. We show that under some suitable assumptions the predator species is driven to extinction and the prey species x is globally attractive with any positive solution to a discrete Logistic equation.

  8. Easy to use program “Simkine3” for simulating kinetic profiles of multi-step chemical Systems and optimisation of predictable rate coefficients therein

    Directory of Open Access Journals (Sweden)

    S.B. Jonnalagadda

    2012-08-01

    Full Text Available ‘Simkine3’, a Delphi based software is developed to simulate the kinetic schemes of complex reaction mechanisms involving multiple sequential and competitive elementary steps for homogeneous and heterogeneous chemical reactions. Simkine3 is designed to translate the user specified mechanism into chemical first-order differential equations (ODEs and optimise the estimated rate constants in such a way that simulated curves match the experimental kinetic profiles. TLSoda which uses backward differentiation method is utilised to solve resulting ODEs and Downhill Simplex method is used to optimise the estimated rate constants in a robotic way. An online help file is developed using HelpScrible Demo to guide the users of Simkine3. The versatility of the software is demonstrated by simulating the complex reaction between methylene violet and acidic bromate, a reaction which exhibits complex nonlinear kinetics. The new software is validated after testing it on a 19-step intricate mechanism involving 15 different species. The kinetic profiles of multiple simulated curves, illustrating the effect of initial concentrations of bromate, and bromide were matched with the corresponding experimental curves.DOI: http://dx.doi.org/10.4314/bcse.v26i2.10

  9. Extinction Events Can Accelerate Evolution

    DEFF Research Database (Denmark)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific......Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate...... evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending...

  10. Extinction events can accelerate evolution.

    Directory of Open Access Journals (Sweden)

    Joel Lehman

    Full Text Available Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific in the long term.

  11. Extinction Events Can Accelerate Evolution

    Science.gov (United States)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific in the long term. PMID:26266804

  12. Altitude Differentiated Aerosol Extinction Over Tenerife (North Atlantic Coast) During ACE-2 by Means of Ground and Airborne Photometry and Lidar Measurements

    Science.gov (United States)

    Formenti, P.; Elias, T.; Welton, J.; Diaz, J. P.; Exposito, F.; Schmid, B.; Powell, D.; Holben, B. N.; Smirnov, A.; Andreae, M. O.; Devaux, C.; Voss, K.; Lelieveld, J.; Livingston, J. M.; Russell, P. B.; Durkee, P. A.

    2000-01-01

    Retrievals of spectral aerosol optical depths (tau(sub a)) by means of sun photometers have been undertaken in Tenerife (28 deg 16' N, 16 deg 36' W) during ACE-2 (June-July 1997). Five ground-based sites were located at four different altitudes in the marine boundary layer and in the free troposphere, from 0 to 3570 m asl. The goal of the investigation was to provide estimates of the vertical aerosol extinction over the island, both under clean and turbid conditions. Inversion of spectral tau(sub a) allowed to retrieve size distributions, from which the single scattering albedo omega(sub 0) and the asymmetry factor g could be estimated as a function of altitude. These parameters were combined to calculate aerosol forcing in the column. Emphasis is put on episodes of increased turbidity, which were observed at different locations simultaneously, and attributed to outbreaks of mineral dust from North Africa. Differentiation of tau(sub a) as a function of altitude provided the vertical profile of the extinction coefficient sigma(sub e). For dust outbreaks, aerosol extinction is concentrated in two distinct layers above and below the strong subsidence inversion around 1200 m asl. Vertical profiles of tau(sub a) and sigma(sub e) are shown for July 8. In some occasions, vertical profiles are compared to LIDAR observations, performed both at sea level and in the low free troposphere, and to airborne measurements of aerosol optical depths.

  13. Science with the Galactic O-Star Spectroscopic Survey (GOSSS) : The relationship between DIBs, ISM, and extinction

    CERN Document Server

    Ordaz, Miguel Penadés; Ballano, Alfredo Sota; Alfaro, Emilio J; Walborn, Nolan R; Barbá, Rodolfo H; Morrell, Nidia I; Arias, Julia I; Gamen, Roberto C

    2011-01-01

    In this poster we show our preliminary analysis of DIBs (Diffuse Interstellar Bands) and other interstellar absorption lines with the purpose of understanding their origin and their relationship with extinction. We use the biggest Galactic O-star blue-violet spectroscopic sample ever (GOSSS, see contribution by Ma\\'iz Apell\\'aniz at this meeting). This sample allows a new insight on this topic because of the adequacy of O-star spectra, the sample number (700 and increasing, 400 used here), and their distribution in the MW disk. We confirm the high correlation coefficients between different DIBs and E(B - V), though the detailed behavior of each case shows small differences. We also detect a moderately low correlation coefficient between Ca II {\\lambda}3934 (Ca K) and E(B - V) with a peculiar spatial distribution that we ascribe to the relationship between line saturation and velocity profiles for Ca II {\\lambda}3934.

  14. Polyandry prevents extinction.

    Science.gov (United States)

    Price, Tom A R; Hurst, Greg D D; Wedell, Nina

    2010-03-09

    Females of most animal species are polyandrous, with individual females usually mating with more than one male. However, the ubiquity of polyandry remains enigmatic because of the potentially high costs to females of multiple mating. Current theory to account for the high prevalence of polyandry largely focuses on its benefits to individual females. There are also higher-level explanations for the high incidence of polyandry-polyandrous clades may speciate more rapidly. Here we test the hypothesis that polyandry may also reduce population extinction risk. We demonstrate that mating with multiple males protects populations of the fruit fly Drosophila pseudoobscura against extinction caused by a "selfish" sex-ratio-distorting element. Thus, the frequency of female multiple mating in nature may be associated not only with individual benefits to females of this behavior but also with increased persistence over time of polyandrous species and populations. Furthermore, we show that female remating behavior can determine the frequency of sex-ratio distorters in populations. This may also be true for many other selfish genetic elements in natural populations.

  15. Extinction characterization of soot produced by laser ablating carbon fiber composite materials in air flow

    Science.gov (United States)

    Liu, Weiping; Ma, Zhiliang; Zhang, Zhenrong; Zhou, Menglian; Wei, Chenghua

    2015-05-01

    In order to research the dynamic process of energy coupling between an incident laser and a carbon fiber/epoxy resin composite material, an extinction characterization analysis of soot, which is produced by laser ablating and located in an air flow that is tangential to the surface of the composite material, is carried out. By the theory analyses, a relationship of mass extinction coefficient and extinction cross section of the soot is derived. It is obtained that the mass extinction coefficients of soot aggregates are the same as those of the primary particles when they contain only a few primary particles. This conclusion is significant when the soot is located in an air flow field, where the generations of the big soot aggregates are suppressed. A verification experiment is designed. The experiment employs Laser Induced Incandescence technology and laser extinction method for the soot synchronization diagnosis. It can derive a temporal curve of the mass extinction coefficient from the soot concentration and laser transmittance. The experiment results show that the mass extinction coefficient becomes smaller when the air flow velocity is higher. The reason is due to the decrease of the scatter effects of the soot particles. The experiment results agree with the theory analysis conclusion.

  16. Modelling dust extinction in the Magellanic Clouds

    CERN Document Server

    Zonca, Alberto; Mulas, Giacomo; Aresu, Giambattista; Cecchi-Pestellini, Cesare

    2015-01-01

    We model the extinction profiles observed in the Small and Large Magellanic clouds with a synthetic population of dust grains consisting by core-mantle particles and a collection of free-flying polycyclic aromatic hydrocarbons. All different flavors of the extinction curves observed in the Magellanic Clouds can be described by the present model, that has been previously (successfully) applied to a large sample of diffuse and translucent lines of sight in the Milky Way. We find that in the Magellanic Clouds the extinction produced by classic grains is generally larger than absorption by polycyclic aromatic hydrocarbons. Within this model, the non-linear far-UV rise is accounted for by polycyclic aromatic hydrocarbons, whose presence in turn is always associated to a gap in the size distribution of classical particles. This hints either a physical connection between (e.g., a common cause for) polycyclic aromatic hydrocarbons and the absence of middle-sized dust particles, or the need for an additional component...

  17. Pure rotational-Raman channels of the Esrange lidar for temperature and particle extinction measurements in the troposphere and lower stratosphere

    Directory of Open Access Journals (Sweden)

    P. Achtert

    2013-01-01

    Full Text Available The Department of Meteorology at Stockholm University operates the Esrange Rayleigh/Raman lidar at Esrange (68° N, 21° E near the Swedish city of Kiruna. This paper describes the design and first measurements of the new pure rotational-Raman channel of the Esrange lidar. The Esrange lidar uses a pulsed Nd:YAG solid-state laser operating at 532 nm as light source with a repetition rate of 20 Hz and a pulse energy of 350 mJ. The minimum vertical resolution is 150 m and the integration time for one profile is 5000 shots. The newly implemented channel allows for measurements of atmospheric temperature at altitudes below 35 km and is currently optimized for temperature measurements between 180 and 200 K. This corresponds to conditions in the lower Arctic stratosphere during winter. In addition to the temperature measurements, the aerosol extinction coefficient and the aerosol backscatter coefficient at 532 nm can be measured independently. Our filter-based design minimizes the systematic error in the obtained temperature profile to less than 0.51 K. By combining rotational-Raman measurements (5–35 km height and the integration technique (30–80 km height, the Esrange lidar is now capable of measuring atmospheric temperature profiles from the upper troposphere up to the mesosphere. With the improved setup, the system can be used to validate current lidar-based polar stratospheric cloud classification schemes. The new capability of the instrument measuring temperature and aerosol extinction furthermore enables studies of the thermal structure and variability of the upper troposphere/lower stratosphere. Although several lidars are operated at polar latitudes, there are few instruments that are capable of measuring temperature profiles in the troposphere, stratosphere, and mesosphere, as well as aerosols extinction in the troposphere and lower stratosphere with daylight capability.

  18. New Receiving Mode of Extinction for Determining Particle Size and Density without Convex Lens

    Institute of Scientific and Technical Information of China (English)

    WU Weiliang; CHEN Hanping; CAI Xiaoshu; WANG Naining

    2002-01-01

    In this article a new receiving mode for scattering light by particle is theoretically discussed. Using this receiving mode the convex lens can be omitted during determining the extinction of particle. Therefore the extinction coefficient of sphere particles is redefined by extrapolating the conventional one. In terms of the calculation results of light scattering the definition of near-field extinction coefficient of a swarm particle is depicted. Through the error analysis it is proved that the error coming from the new definition of extinction coefficient is acceptable for engineering application. In addition, a technique for determining the particle size and density is presented in this article and the advantage using this receiving mode is described.

  19. Development of ATLID-MSI synergy for retrieving the vertical profiles of aerosol components

    Science.gov (United States)

    Kudo, R.; Nishizawa, T.; Higurashi, A.; Sugimoto, N.; Oikawa, E.

    2014-12-01

    EarthCARE is an earth observation satellite and will be launched in 2016. Using its two sensors, ATLID (High spectral resolution lidar) and MSI (Multi-spectral imager), we are developing the synergy algorithm to retrieve the vertical profiles of extinction coefficients at 355 nm of four aerosol components (Water-soluble, black carbon, dust, and sea-salt particles), and the column mean of mode radii of water-soluble and dust particles. The ATLID data are extinction coefficient, backscatter coefficient, and depolarization ratio for total aerosols at 355 nm. The MSI data are radiances at 670 and 865 nm. The dry volume concentrations of four aerosol components at each altitude and the mode radii of water-soluble and dust particles in the column are simultaneously optimized to ATLID and MSI data by the gauss newton method. After the optimization, the vertical profiles of the extinction coefficient at 355 nm of four aerosol components are obtained. The size distributions of four aerosol components are assumed to be a lognormal distribution. The refractive indices of four aerosol components are given from previously observational studies. The humidity growth is considered for water-soluble and sea-salt particles. The volume concentration and the mode radius of the sea-salt particle are parameterized using the surface wind speed on the ocean. We assumed that the shape of the water-soluble, black carbon, and sea-salt particles are spherical, and the shape of the dust particle is spheroidal. We tested the algorithm using the ATLID and MSI data simulated using clean, dust-transported, and smoke-transported aerosols. The extinction coefficients of each component at 355 nm are retrieved well. The mode radius of water-soluble and dust particles were somehow overestimated.

  20. The end-Permian mass extinction: A complex, multicausal extinction

    Science.gov (United States)

    Erwin, D. H.

    1994-01-01

    The end-Permian mass extinction was the most extensive in the history of life and remains one of the most complex. Understanding its causes is particularly important because it anchors the putative 26-m.y. pattern of periodic extinction. However, there is no good evidence for an impact and this extinction appears to be more complex than others, involving at least three phases. The first began with the onset of a marine regression during the Late Permian and resulting elimination of most marine basins, reduction in habitat area, and increased climatic instability; the first pulse of tetrapod extinctions occurred in South Africa at this time. The second phase involved increased regression in many areas (although apparently not in South China) and heightened climatic instability and environmental degradation. Release of gas hydrates, oxidation of marine carbon, and the eruption of the Siberian flood basalts occurred during this phase. The final phase of the extinction episode began with the earliest Triassic marine regression and destruction of nearshore continental habitats. Some evidence suggests oceanic anoxia may have developed during the final phase of the extinction, although it appears to have been insufficient to the sole cause of the extinction.

  1. Functional Extinctions of Species in Ecological Networks

    OpenAIRE

    Säterberg, Torbjörn

    2016-01-01

    Current rates of extinctions are estimated to be around 1000 times higher than background rates that would occur without anthropogenic impacts. These extinction rates refer to the traditional view of extinctions, i.e. numerical extinctions. This thesis is about another type of extinctions: functional extinctions. Those occur when the abundance of a species is too small to uphold the species’ ecologically interactive role. I have taken a theoretical approach and used dynamical models to invest...

  2. Mass Extinctions in Earth's History

    Science.gov (United States)

    Ward, P. D.

    2002-12-01

    Mass extinctions are short intervals of elevated species death. Possible causes of Earth's mass extinctions are both external (astronomical) and internal (tectonic and biotic changes from planetary mechanisms). Paleontologists have identified five "major" mass extinctions (>50 die-off in less than a million years) and more than 20 other minor events over the past 550 million years. Earlier major extinction events undoubtedly also occurred, but we have no fossil record; these were probably associated with, for example, the early heavy bombardment that cleared out the solar system, the advent of oxygen in the atmosphere, and various "snowball Earth" events. Mass extinctions are viewed as both destructive (species death ) and constructive, in that they allow evolutionary innovation in the wake of species disappearances. From an astrobiological perspective, mass extinctions must be considered as able both to reduce biodiversity and even potentially end life on any planet. Of the five major mass extinctions identified on Earth, only one (the Cretaceous/Tertiary event 65 million years ago that famously killed off the dinosaurs ) is unambiguously related to the impact of an asteroid or comet ( 10-km diameter). The Permian/Triassic (250 Myr ago) and Triassic/Jurassic (202 Myr ago) events are now the center of debate between those favoring impact and those suggesting large volume flooding by basaltic lavas. The final two events, Ordovician (440 Myr ago) and Devonian (370 Myr ago) have no accepted causal mechanisms.

  3. The learning of fear extinction.

    Science.gov (United States)

    Furini, Cristiane; Myskiw, Jociane; Izquierdo, Ivan

    2014-11-01

    Recent work on the extinction of fear-motivated learning places emphasis on its putative circuitry and on its modulation. Extinction is the learned inhibition of retrieval of previously acquired responses. Fear extinction is used as a major component of exposure therapy in the treatment of fear memories such as those of the posttraumatic stress disorder (PTSD). It is initiated and maintained by interactions between the hippocampus, basolateral amygdala and ventromedial prefrontal cortex, which involve feedback regulation of the latter by the other two areas. Fear extinction depends on NMDA receptor activation. It is positively modulated by d-serine acting on the glycine site of NMDA receptors and blocked by AP5 (2-amino-5-phosphono propionate) in the three structures. In addition, histamine acting on H2 receptors and endocannabinoids acting on CB1 receptors in the three brain areas mentioned, and muscarinic cholinergic fibers from the medial septum to hippocampal CA1 positively modulate fear extinction. Importantly, fear extinction can be made state-dependent on circulating epinephrine, which may play a role in situations of stress. Exposure to a novel experience can strongly enhance the consolidation of fear extinction through a synaptic tagging and capture mechanism; this may be useful in the therapy of states caused by fear memory like PTSD.

  4. Modified cavity attenuated phase shift (CAPS) method for airborne aerosol light extinction measurement

    Science.gov (United States)

    Perim de Faria, Julia; Bundke, Ulrich; Freedman, Andrew; Petzold, Andreas

    2015-04-01

    Monitoring the direct impact of aerosol particles on climate requires the consideration of at least two major factors: the aerosol single-scattering albedo, defined as the relation between the amount of energy scattered and extinguished by an ensemble of aerosol particles; and the aerosol optical depth, calculated from the integral of the particle extinction coefficient over the thickness of the measured aerosol layer. Remote sensing networks for measuring these aerosol parameters on a regular basis are well in place (e.g., AERONET, ACTRIS), whereas the regular in situ measurement of vertical profiles of atmospheric aerosol optical properties remains still an important challenge in quantifying climate change. The European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System; www.iagos.org) responds to the increasing requests for long-term, routine in situ observational data by using commercial passenger aircraft as measurement platform. However, scientific instrumentation for the measurement of atmospheric constituents requires major modifications before being deployable aboard in-service passenger aircraft. Recently, a compact and robust family of optical instruments based on the cavity attenuated phase shift (CAPS) technique has become available for measuring aerosol light extinction. In particular, the CAPS PMex particle optical extinction monitor has demonstrated sensitivity of less than 2 Mm-1 in 1 second sampling period; with a 60 s averaging time, a detection limit of less than 0.3 Mm-1 can be achieved. While this technique was successfully deployed for ground-based atmospheric measurements under various conditions, its suitability for operation aboard aircraft in the free and upper free troposphere still has to be demonstrated. Here, we report on the modifications of a CAPS PMex instrument for measuring aerosol light extinction on aircraft, and subsequent laboratory tests for evaluating the modified instrument prototype: (1) In a

  5. EARLINET dust observations vs. BSC-DREAM8b modeled profiles: 12-year-long systematic comparison at Potenza, Italy

    Science.gov (United States)

    Mona, L.; Papagiannopoulos, N.; Basart, S.; Baldasano, J.; Binietoglou, I.; Cornacchia, C.; Pappalardo, G.

    2014-08-01

    In this paper, we report the first systematic comparison of 12-year modeled dust extinction profiles vs. Raman lidar measurements. We use the BSC-DREAM8b model, one of the most widely used dust regional models in the Mediterranean, and Potenza EARLINET lidar profiles for Saharan dust cases, the largest one-site database of dust extinction profiles. A total of 310 dust cases were compared for the May 2000-July 2012 period. The model reconstructs the measured layers well: profiles are correlated within 5% of significance for 60% of the cases and the dust layer center of mass as measured by lidar and modeled by BSC-DREAM8b differ on average 0.3 ± 1.0 km. Events with a dust optical depth lower than 0.1 account for 70% of uncorrelated profiles. Although there is good agreement in terms of profile shape and the order of magnitude of extinction values, the model overestimates the occurrence of dust layer top above 10 km. Comparison with extinction profiles measured by the Raman lidar shows that BSC-DREAM8b typically underestimates the dust extinction coefficient, in particular below 3 km. Lowest model-observation differences (below 17%) correspond to a lidar ratio at 532 nm and Ångström exponent at 355/532 nm of 60 ± 13 and 0.1 ± 0.6 sr, respectively. These are in agreement with values typically observed and modeled for pure desert dust. However, the highest differences (higher than 85%) are typically related to greater Ångström values (0.5 ± 0.6), denoting smaller particles. All these aspects indicate that the level of agreement decreases with an increase in mixing/modification processes.

  6. Aerosol extinction models based on measurements at two sites in Sweden.

    Science.gov (United States)

    Kaurila, Timo; Hågård, Arne; Persson, Rolf

    2006-09-10

    Two aerosol extinction models have been developed using statistical analysis of long-term optical transmission measurements in Sweden performed at two locations from July 1977 to June 1982. The aerosol volume extinction coefficient for infrared (IR) radiation is calculated by the models with visibility, temperature, and air pressure as input parameters. As in the MODTRAN model, the IR extinction coefficient is proportional to the coefficient at 550 nm, which depends on the visibility. In the new models, the wavelength dependence of the extinction also depends on the visibility. The models predict significantly higher attenuation in the IR than does the Rural aerosol model from MODTRAN, which is commonly used. Comparison with the Maritime model shows that the new models predict lower extinction values in the 3-5 microm region and higher values in the 8-12 microm region. The uncertainties in terms of variance levels are calculated by the models. The properties of aerosols, and thereby the extinction coefficient, are partly correlated to local meteorological parameters, which enables the calculation of a mean predicted value. A substantial part of the variation is, however, caused by conditions in the source area and along the trajectory path of the aerosols. They are not correlated to the local meteorological parameters and therefore cause the variance in the models.

  7. The Sixth Great Mass Extinction

    Science.gov (United States)

    Wagler, Ron

    2012-01-01

    Five past great mass extinctions have occurred during Earth's history. Humanity is currently in the midst of a sixth, human-induced great mass extinction of plant and animal life (e.g., Alroy 2008; Jackson 2008; Lewis 2006; McDaniel and Borton 2002; Rockstrom et al. 2009; Rohr et al. 2008; Steffen, Crutzen, and McNeill 2007; Thomas et al. 2004;…

  8. Extinction, relapse, and behavioral momentum.

    Science.gov (United States)

    Podlesnik, Christopher A; Shahan, Timothy A

    2010-05-01

    Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a discriminative stimulus depends upon the baseline rate or magnitude of reinforcement associated with that stimulus (i.e., the Pavlovian stimulus-reinforcer relation). Recently, we have shown that relapse of operant behavior in reinstatement, resurgence, and context renewal preparations also is a function of baseline stimulus-reinforcer relations. In this paper we present new data examining the role of baseline stimulus-reinforcer relations on resistance to extinction and relapse using a variety of baseline training conditions and relapse operations. Furthermore, we evaluate the adequacy of a behavioral momentum based model in accounting for the results. The model suggests that relapse occurs as a result of a decrease in the disruptive impact of extinction precipitated by a change in circumstances associated with extinction, and that the degree of relapse is a function of the pre-extinction baseline Pavlovian stimulus-reinforcer relation. Across experiments, relative resistance to extinction and relapse were greater in the presence of stimuli associated with more favorable conditions of reinforcement and were positively related to one another. In addition, the model did a good job in accounting for these effects. Thus, behavioral momentum theory may provide a useful quantitative approach for characterizing how differential reinforcement conditions contribute to relapse of operant behavior.

  9. Retrieving the aerosol lidar ratio profile by combining ground- and space-based elastic lidars.

    Science.gov (United States)

    Feiyue, Mao; Wei, Gong; Yingying, Ma

    2012-02-15

    The aerosol lidar ratio is a key parameter for the retrieval of aerosol optical properties from elastic lidar, which changes largely for aerosols with different chemical and physical properties. We proposed a method for retrieving the aerosol lidar ratio profile by combining simultaneous ground- and space-based elastic lidars. The method was tested by a simulated case and a real case at 532 nm wavelength. The results demonstrated that our method is robust and can obtain accurate lidar ratio and extinction coefficient profiles. Our method can be useful for determining the local and global lidar ratio and validating space-based lidar datasets.

  10. Thermal Transgressions and Phanerozoic Extinctions

    Science.gov (United States)

    Worsley, T. R.; Kidder, D. L.

    2007-12-01

    A number of significant Phanerozoic extinctions are associated with marine transgressions that were probably driven by rapid ocean warming. The conditions associated with what we call thermal transgressions are extremely stressful to life on Earth. The Earth system setting associated with end-Permian extinction exemplifies an end-member case of our model. The conditions favoring extreme warmth and sea-level increases driven by thermal expansion are also conducive to changes in ocean circulation that foster widespread anoxia and sulfidic subsurface ocean waters. Equable climates are characterized by reduced wind shear and weak surface ocean circulation. Late Permian and Early Triassic thermohaline circulation differs considerably from today's world, with minimal polar sinking and intensified mid-latitude sinking that delivers sulfate from shallow evaporative areas to deeper water where it is reduced to sulfide. Reduced nutrient input to oceans from land at many of the extinction intervals results from diminished silicate weathering and weakened delivery of iron via eolian dust. The falloff in iron-bearing dust leads to minimal nitrate production, weakening food webs and rendering faunas and floras more susceptible to extinction when stressed. Factors such as heat, anoxia, ocean acidification, hypercapnia, and hydrogen sulfide poisoning would significantly affect these biotas. Intervals of tectonic quiescence set up preconditions favoring extinctions. Reductions in chemical silicate weathering lead to carbon dioxide buildup, oxygen drawdown, nutrient depletion, wind and ocean current abatement, long-term global warming, and ocean acidification. The effects of extinction triggers such as large igneous provinces, bolide impacts, and episodes of sudden methane release are more potent against the backdrop of our proposed preconditions. Extinctions that have characteristics we call for in the thermal transgressions include the Early Cambrian Sinsk event, as well as

  11. Research and Development for the Mu2e Extinction Monitor

    Energy Technology Data Exchange (ETDEWEB)

    Mott, Casey Benjamin [Northern Illinois U.

    2016-01-01

    Mu2e is a planned experiment to search for flavor-violating conversion from a muon to an electron. The experiment will use a pulsed 8 GeV proton beam to produce muons which will then stop in an aluminum target. Mu2e will search for the $\\mu^- + Al \\rightarrow e^- + Al$ process. For Mu2e, an extinction rate of 10$^{-10}$ is required to reduce the backgrounds to an acceptable level. Extinction is the ratio of the amount of protons striking the production target between beam pulses to the number striking it during the beam pulse. One of the backgrounds, off-target interactions, was simulated using G4beamline and Fermilab's Grid setup to confirm that an extinction rate of 10$^{-10}$ is possible. The extinction level will be measured by the extinction monitor which will include scintillation counters read out by photomultiplier tubes. In order to build a beam time profile, low fake responses (after pulses) are needed in the photomultiplier tubes. This thesis determines the best combination of resistors, voltage, and other components that provide the lowest after pulse rate.

  12. Research and development for the Mu2E extinction monitor

    Science.gov (United States)

    Mott, Casey B.

    Mu2e is a planned experiment to search for flavor violating conversion from a muon to an electron. The experiment will use a pulsed 8 GeV proton beam to produce muons which will then stop in an aluminum target. Mu2e will search for the mu-- + Al → e-- + Al process. For Mu2e, an extinction rate of 10--10 is required to reduce the backgrounds to an acceptable level. Extinction is the ratio of the amount of protons striking the production target between beam pulses to the number striking it during the beam pulse. One of the backgrounds, off-target interactions, was simulated using G4beamline and Fermilab's Grid setup to confirm that an extinction rate of 10--10 is possible. The extinction level will be measured by the extinction monitor which will include scintillation counters read out by photomultiplier tubes. In order to build a beam time profile, low fake responses (after pulses) are needed in the photomultiplier tubes. This thesis determines the best combination of resistors, voltage, and other components that provide the lowest after pulse rate.

  13. The extinction of the dinosaurs.

    Science.gov (United States)

    Brusatte, Stephen L; Butler, Richard J; Barrett, Paul M; Carrano, Matthew T; Evans, David C; Lloyd, Graeme T; Mannion, Philip D; Norell, Mark A; Peppe, Daniel J; Upchurch, Paul; Williamson, Thomas E

    2015-05-01

    Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large-bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult.

  14. Measuring Galactic Extinction A Test

    CERN Document Server

    Arce, H G; Arce, Hector G.; Goodman, Alyssa A.

    1999-01-01

    We test the recently published all-sky reddening map of Schlegel, Finkbeiner & Davis (1998 [SFD]) using the extinction study of a region in the Taurus dark cloud complex by Arce & Goodman (1999 [AG]). In their study, AG use four different techniques to measure the amount and structure of the extinction toward Taurus, and all four techniques agree very well. Thus we believe that the AG results are a truthful representation of the extinction in the region and can be used to test the reliability of the SFD reddening map. The results of our test show that the SFD all-sky reddening map, which is based on data from COBE/DIRBE and IRAS/ISSA, overestimates the reddening by a factor of 1.3 to 1.5 in regions of smooth extinction with A_V > 0.5 mag. In some regions of steep extinction gradients the SFD map underestimates the reddening value, probably due to its low spatial resolution. We expect that the astronomical community will be using the SFD reddening map extensively. We offer this Letter as a cautionary n...

  15. Light extinction by secondary organic aerosol: an intercomparison of three broadband cavity spectrometers

    Science.gov (United States)

    Varma, R. M.; Ball, S. M.; Brauers, T.; Dorn, H.-P.; Heitmann, U.; Jones, R. L.; Platt, U.; Pöhler, D.; Ruth, A. A.; Shillings, A. J. L.; Thieser, J.; Wahner, A.; Venables, D. S.

    2013-11-01

    Broadband optical cavity spectrometers are maturing as a technology for trace-gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690 nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene + NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulfate particles, the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using the Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.

  16. Infectious Disease, Endangerment, and Extinction

    Directory of Open Access Journals (Sweden)

    Ross D. E. MacPhee

    2013-01-01

    Full Text Available Infectious disease, especially virulent infectious disease, is commonly regarded as a cause of fluctuation or decline in biological populations. However, it is not generally considered as a primary factor in causing the actual endangerment or extinction of species. We review here the known historical examples in which disease has, or has been assumed to have had, a major deleterious impact on animal species, including extinction, and highlight some recent cases in which disease is the chief suspect in causing the outright endangerment of particular species. We conclude that the role of disease in historical extinctions at the population or species level may have been underestimated. Recent methodological breakthroughs may lead to a better understanding of the past and present roles of infectious disease in influencing population fitness and other parameters.

  17. Mass extinctions and supernova explosions

    CERN Document Server

    Korschinek, Gunther

    2016-01-01

    A nearby supernova (SN) explosion could have negatively influenced life on Earth, maybe even been responsible for mass extinctions. Mass extinction poses a significant extinction of numerous species on Earth, as recorded in the paleontologic, paleoclimatic, and geological record of our planet. Depending on the distance between the Sun and the SN, different types of threats have to be considered, such as ozone depletion on Earth, causing increased exposure to the Sun's ultraviolet radiation, or the direct exposure of lethal x-rays. Another indirect effect is cloud formation, induced by cosmic rays in the atmosphere which result in a drop in the Earth's temperature, causing major glaciations of the Earth. The discovery of highly intensive gamma ray bursts (GRBs), which could be connected to SNe, initiated further discussions on possible life-threatening events in Earth's history. The probability that GRBs hit the Earth is very low. Nevertheless, a past interaction of Earth with GRBs and/or SNe cannot be exclude...

  18. Extinction debt on oceanic islands

    DEFF Research Database (Denmark)

    Triantis, Kostas A.; Borges, Paulo A. V.; Ladle, Richard J.

    2010-01-01

    Habitat destruction is the leading cause of species extinctions. However, there is typically a time-lag between the reduction in habitat area and the eventual disappearance of the remnant populations. These "surviving but ultimately doomed" species represent an extinction debt. Calculating...... the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species-area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands...... in the last 45 yr, despite the extensive sampling effort, offer support to the predictions made. We argue that immediate action to restore and expand native forest habitat is required to avert the loss of numerous endemic species in the near future...

  19. Extinction conditions of a premixed flame in a channel

    Energy Technology Data Exchange (ETDEWEB)

    Alliche, Mounir [LMP2M, Universite de Medea, Quartier Ain Dheb, 26000 Medea (Algeria); M2P2, UMR CNRS 6181, Universite de Provence, Marseille (France); Haldenwang, Pierre [M2P2, UMR CNRS 6181, Universite de Provence, Marseille (France); Chikh, Salah [LTPMP, Faculte de Genie Mecanique and de Genie des Procedes, USTHB, Bab Ezzouar (Algeria)

    2010-06-15

    A local refinement method is used to numerically predict the propagation and extinction conditions of a premixed flame in a channel considering a thermodiffusive model. A local refinement method is employed because of the numerous length scales that characterize this phenomenon. The time integration is self adaptive and the solution is based on a multigrid method using a zonal mesh refinement in the flame reaction zone. The objective is to determine the conditions of extinction which are characterized by the flame structure and its properties. We are interested in the following properties: the curvature of the flame, its maximum temperature, its speed of propagation and the distance separating the flame from the wall. We analyze the influence of heat losses at the wall through the thermal conductivity of the wall and the nature of the fuel characterized by the Lewis number of the mixture. This investigation allows us to identify three propagation regimes according to heat losses at the wall and to the channel radius. The results show that there is an intermediate value of the radius for which the flame can bend and propagate provided that its curvature does not exceed a certain limit value. Indeed, small values of the radius will choke the flame and extinguish it. The extinction occurs if the flame curvature becomes too small. Furthermore, this study allows us to predict the limiting values of the heat loss coefficient at extinction as well as the critical value of the channel radius above which the premixed flame may propagate without extinction. A dead zone of length 2-4 times the flame thickness appears between the flame and the wall for a Lewis number (Le) between 0.8 and 2. For small values of Le, local extinctions are observed. (author)

  20. Habituation, latent inhibition, and extinction.

    Science.gov (United States)

    Jordan, Wesley P; Todd, Travis P; Bucci, David J; Leaton, Robert N

    2015-06-01

    In two conditioned suppression experiments with a latent inhibition (LI) design, we measured the habituation of rats in preexposure, their LI during conditioning, and then extinction over days. In the first experiment, lick suppression, the preexposed group (PE) showed a significant initial unconditioned response (UR) to the target stimulus and significant long-term habituation (LTH) of that response over days. The significant difference between the PE and nonpreexposed (NPE) groups on the first conditioning trial was due solely to the difference in their URs to the conditioned stimulus (CS)-a habituated response (PE) and an unhabituated response (NPE). In the second experiment, bar-press suppression, little UR to the target stimulus was apparent during preexposure, and no detectable LTH. Thus, there was no difference between the PE and NPE groups on the first conditioning trial. Whether the UR to the CS confounds the interpretation of LI (Exp. 1) or not (Exp. 2) can only be known if the UR is measured. In both experiments, LI was observed in acquisition. Also in both experiments, rats that were preexposed and then conditioned to asymptote were significantly more resistant to extinction than were the rats not preexposed. This result contrasts with the consistently reported finding that preexposure either produces less resistance to extinction or has no effect on extinction. The effect of stimulus preexposure survived conditioning to asymptote and was reflected directly in extinction. These two experiments provide a cautionary procedural note for LI experiments and have shown an unexpected extinction effect that may provide new insights into the interpretation of LI.

  1. Extinction risk of soil biota.

    Science.gov (United States)

    Veresoglou, Stavros D; Halley, John M; Rillig, Matthias C

    2015-11-23

    No species lives on earth forever. Knowing when and why species go extinct is crucial for a complete understanding of the consequences of anthropogenic activity, and its impact on ecosystem functioning. Even though soil biota play a key role in maintaining the functioning of ecosystems, the vast majority of existing studies focus on aboveground organisms. Many questions about the fate of belowground organisms remain open, so the combined effort of theorists and applied ecologists is needed in the ongoing development of soil extinction ecology.

  2. Extinction Law at a Distance up to 25 kpc toward the Galactic Poles

    CERN Document Server

    Gontcharov, George

    2016-01-01

    Photometry from the Tycho-2, 2MASS, and WISE catalogues for clump and branch giants at a distance up to 25 kpc toward the Galactic poles has allowed the variations of various characteristics of the infrared interstellar extinction law with distance to be analyzed. The results obtained by the extinction law extrapolation method are consistent for different classes of stars and different characteristics as well as with previous studies. The conventional extinction law with a low infrared extinction is characteristic of only a thin layer no farther than 100 pc from the Galactic plane and of two thin layers near $Z=-600$ and $+500$ pc. Far from the Galactic plane, in the Galactic halo, the infrared extinction law is different: the extinction in the $Ks$, $W1$, $W2$, $W3$, and $W4$ bands is, respectively, $0.17$, $0.16$, $0.16$, $0.07$, and $0.03$ of the extinction in the $V$ band. The accuracy of these coefficients is $0.03$. If the extinction law reflects primarily the grain size distribution, then the fraction ...

  3. Interstellar Grains: Effect of Inclusions on Extinction

    CERN Document Server

    Katyal, Nisha; Vaidya, D B

    2011-01-01

    A composite dust grain model which simultaneously explains the observed interstellar extinction, polarization, IR emission and the abundance constraints, is required. We present a composite grain model, which is made up of a host silicate oblate spheroid and graphite inclusions. The interstellar extinction curve is evaluated in the spectral region 3.4-0.1$\\mu m$ using the extinction efficiencies of the composite spheroidal grains for three axial ratios. Extinction curves are computed using the discrete dipole approximation (DDA). The model curves are subsequently compared with the average observed interstellar extinction curve and with an extinction curve derived from the IUE catalogue data.

  4. Interstellar grains: Effect of inclusions on extinction

    Science.gov (United States)

    Katyal, N.; Gupta, R.; Vaidya, D. B.

    2011-10-01

    A composite dust grain model which simultaneously explains the observed interstellar extinction, polarization, IR emission and the abundance constraints, is required. We present a composite grain model, which is made up of a host silicate oblate spheroid and graphite inclusions. The interstellar extinction curve is evaluated in the spectral region 3.4-0.1 μm using the extinction efficiencies of composite spheroidal grains for three axial ratios. Extinction curves are computed using the discrete dipole approximation (DDA). The model curves are subsequently compared with the average observed interstellar extinction curve and with an extinction curve derived from the IUE catalogue data.

  5. The Interstellar Extinction Toward the Milky Way Bulge with Planetary Nebulae, Red Clump, and RR Lyrae stars

    CERN Document Server

    Nataf, David M

    2016-01-01

    I review the literature covering the issue of interstellar extinction toward the Milky Way bulge, with emphasis placed on findings from planetary nebulae, RR Lyrae, and red clump stars. I also report on observations from HI gas and globular clusters. I show that there has been substantial progress in this field in recent decades, most particularly from red clump stars. The spatial coverage of extinction maps has increased by a factor $\\sim 100 \\times$ in the past twenty years, and the total-to-selective extinction ratios reported have shifted by $\\sim$20-25\\%, indicative of the improved accuracy and separately, of a steeper-than-standard extinction curve. Problems remain in modelling differential extinction, explaining anomalies involving the planetary nebulae, and understanding the difference between bulge extinction coefficients and "standard" literature values.

  6. Endangered and Extinct Radioactivity

    Science.gov (United States)

    Leising, M. D.

    1993-07-01

    Gamma ray spectroscopy holds great promise for probing nucleosynthesis in individual nucleosynthesis events, via observations of short-lived radioactivity, and for measuring global galactic nucleosynthesis today with detections of longer-lived radioactivity. Many of the astrophysical issues addressed by these observations are precisely those that must be understood in order to interpret observations of extinct radioactivity in meteorites. It was somewhat surprising that the former case was realized first for a Type II supernova, when both 56Co [1] and 57Co [2] were detected in SN 1987A. These provide unprecedented constraints on models of Type II explosions. Live 26Al in the galaxy might come from Type II supernovae and their progenitors, and if this is eventually shown to be the case, can constrain massive star evolution, supernova nucleosynthesis, the galactic Type II supernova rate, and even models of the chemical evolution of the galaxy [3]. Titanium-44 is produced primarily in the alpha-rich freezeout from nuclear statistical equilibrium, possibly in Type Ia [4] and almost certainly in Type II supernovae [5]. The galactic recurrence time of these events is comparable to the 44Ti lifetime, so we expect to be able to see at most a few otherwise unseen 44Ti remnants at any given time. No such remnants have been detected yet [6]. Very simple arguments lead to the expectation that about 4 x 10^-4 M(sub)solar mass of 44Ca are produced per century. The product of the supernova frequency times the 44Ti yield per event must equal this number. Even assuming that only the latest event would be seen, rates in excess of 2 century^-1 are ruled out at >=99% confidence by the gamma ray limits. Only rates less than 0.3 century^-1 are acceptable at >5% confidence, and this means that the yield per event must be >10^-3 M(sub)solar mass to produce the requisite 44Ca. Rates this low are incompatible with current estimates for Type II supernovae and yields this high are also very

  7. A model of mass extinction

    CERN Document Server

    Newman, M E J

    1997-01-01

    A number of authors have in recent years proposed that the processes of macroevolution may give rise to self-organized critical phenomena which could have a significant effect on the dynamics of ecosystems. In particular it has been suggested that mass extinction may arise through a purely biotic mechanism as the result of so-called coevolutionary avalanches. In this paper we first explore the empirical evidence which has been put forward in favor of this conclusion. The data center principally around the existence of power-law functional forms in the distribution of the sizes of extinction events and other quantities. We then propose a new mathematical model of mass extinction which does not rely on coevolutionary effects and in which extinction is caused entirely by the action of environmental stresses on species. In combination with a simple model of species adaptation we show that this process can account for all the observed data without the need to invoke coevolution and critical processes. The model al...

  8. Extinction debt on oceanic islands

    DEFF Research Database (Denmark)

    Triantis, K.A.; Borges, Paulo A. V.; Ladle, R.J.;

    2010-01-01

    the magnitude of such future extinction events has been hampered by potentially inaccurate assumptions about the slope of species-area relationships, which are habitat- and taxon-specific. We overcome this challenge by applying a method that uses the historical sequence of deforestation in the Azorean Islands...

  9. Wave Reflection Coefficient Spectrum

    Institute of Scientific and Technical Information of China (English)

    俞聿修; 邵利民; 柳淑学

    2003-01-01

    The wave reflection coefficient frequency spectrum and directional spectrum for concrete face slope breakwaters and rubble mound breakwaters are investigated through physical model tests in the present study. The reflection coefficients of oblique irregular waves are analyzed by the Modified Two-Point Method (MTPM) proposed by the authors. The results show that the wave reflection coefficient decreases with increasing wave frequency and incident angle or decreasing structure slope. The reflection coefficient frequency spectrum and its variation with Iribarren number are given in this paper. The paper also suggests an empirical 3-dimensional reflection coefficient spectrum, i.e. reflection coefficient directional spectrum, which can be used to illustrate quantitatively the variation of reflection coefficient with the incident angle and the Iribarren number for oblique irregular waves.

  10. Interstellar Extinction by Spheroidal Dust Grains

    OpenAIRE

    Gupta, Ranjan; Mukai, Tadashi; Vaidya, D. B.; Sen, Asoke K.; Okada, Yasuhiko

    2005-01-01

    Observations of interstellar extinction and polarization indicate that the interstellar medium consists of aligned non-spherical dust grains which show variation in the interstellar extinction curve for wavelengths ranging from NIR to UV. To model the extinction and polarization, one cannot use the Mie theory which assumes the grains as solid spheres. We have used a T-matrix based method for computing the extinction efficiencies of spheroidal silicate and graphite grains of different shapes (...

  11. Further Evidence of Auditory Extinction in Aphasia

    Science.gov (United States)

    Marshall, Rebecca Shisler; Basilakos, Alexandra; Love-Myers, Kim

    2013-01-01

    Purpose: Preliminary research ( Shisler, 2005) suggests that auditory extinction in individuals with aphasia (IWA) may be connected to binding and attention. In this study, the authors expanded on previous findings on auditory extinction to determine the source of extinction deficits in IWA. Method: Seventeen IWA (M[subscript age] = 53.19 years)…

  12. Determining Extinction Ratio Of A Laser Diode

    Science.gov (United States)

    Unger, Glenn L.

    1992-01-01

    Improved technique to determine extinction ratio of pulsed laser diode based partly on definition of extinction ratio applicable to nonideal laser pulses. Heretofore, determinations involved assumption of ideal laser pulses, and neglected optical power from background light. Because power fluctuates during real pulse, more realistic to define extinction ratio in terms of energy obtained.

  13. Secondary Extinction in Cylindrical and Spherical Crystals for X-Ray and Neutron Diffraction

    Institute of Scientific and Technical Information of China (English)

    胡华琛; 李兆桓; 杨斌; 沈彩万; 乔英

    2001-01-01

    The distribution of the reflection power ratio for a neutron or x-ray diffracted from a cylindrical crystal immersed in an homogenous incident beam is obtained by the numerical solution of the transfer equations for the first time. The profile well reflects all the physical properties of the absorption and extinction behaviour in the crystals. A systematic investigation of the secondary extinction for cylindrical and spherical crystals was carried out based on these results.

  14. The Mid-Infrared Extinction Law in the Large Magellanic Cloud

    CERN Document Server

    Gao, Jian; Li, Aigen; Xue, M Y

    2013-01-01

    Based on the photometric data from the Spitzer/SAGE survey and with red giants as the extinction tracers, the mid-infrared (MIR) extinction laws in the Large Magellanic Cloud (LMC) are derived for the first time in the form of A_\\lambda/A_Ks, the extinction in the four IRAC bands (i.e., [3.6], [4.5], [5.8] and [8.0]um) relative to the 2MASS Ks band at 2.16um. We obtain the near-infrared (NIR) extinction coefficient to be E(J-H)/E(H-Ks)=1.29\\pm0.04 and E(J-Ks)/E(H-Ks)=1.94\\pm0.04. The wavelength dependence of the MIR extinction A_\\lambda/A_Ks in the LMC varies from one sightline to another. The overall mean MIR extinction is A_[3.6]/A_Ks=0.72\\pm0.03, A_[4.5]/A_Ks=0.94\\pm0.03, A_[5.8]/A_Ks=0.58\\pm0.04, and A_[8.0]/A_Ks=0.62\\pm0.05. Except for the extinction in the IRAC [4.5] band which may be contaminated by the 4.6um CO gas absorption of red giants (which are used to trace the LMC extinction), the extinction in the other three IRAC bands show a flat curve, close to the Milky Way Rv = 5.5 model extinction curve...

  15. Ångström coefficient as a tracer of the continental aerosols

    NARCIS (Netherlands)

    Kuśmierczyk-Michulec, J.T.; Eijk, A.M.J. van

    2007-01-01

    The variation of the extinction coefficient with wavelength can be presented as a power law function with a constant (related to the power factor) known as the Ångström coefficient. When the particle size distribution is dominated by small particles, usually associated with pollution, the Ångström c

  16. Ångström coefficient as a tracer of the continental aerosols

    NARCIS (Netherlands)

    Kuśmierczyk-Michulec, J.T.; Eijk, A.M.J. van

    2007-01-01

    The variation of the extinction coefficient with wavelength can be presented as a power law function with a constant (related to the power factor) known as the Ångström coefficient. When the particle size distribution is dominated by small particles, usually associated with pollution, the Ångström

  17. Estimating interstellar extinction toward to elliptical galaxies and star clusters

    Science.gov (United States)

    Amores, E. B.; Lépine, J. R. D.

    2006-08-01

    The ability to estimate interstellar extinction is essential for color corrections and distance calculations of all sorts of astronomical objects being fundamental for galactic structure studies. We performed comparisons of interstellar extinction models by Amores & Lépine ( 2005). These models are based on the hypothesis that gas and dust are homogeneously mixed, and make use of the dust-to gas ratio. The gas density distribution used in the models is obtained from the gas large scale surveys: Berkeley and Parkes HI surveys and from the Columbia University CO survey. In the present work, we compared these models with extinction predictions of elliptical galaxies (gE) and star clusters. We used the similar sample of gE galaxies proposed by Burstein for the comparison between the extinction calculation methods of Burstein & Heiles (1978, 1982) and of Schlegel et al. (1998) extending the comparison to our models. We found rms differences equal to 0.0179 and 0.0189 mag respectively, in the comparison of the predictions of our "model A" with the two methods mentioned. The comparison takes into account the "zero points" introduced by Burstein. The correlation coefficient obtained in the comparison is around 0.85. These results bring to light that our models can be safely used for the estimation of extinction in our Galaxy for extragalactic work, as an alternative method to the BH and SFD predictions. In the comparison with the globular clusters we found rms differences equal to 0.32 and 0.30 for our models A and S, respectively. For the open clusters we made comparisons using different samples and the rms differences were around 0.25.

  18. Estimating interstellar extinction towards elliptical galaxies and star clusters.

    Science.gov (United States)

    de Amôres, E. B.; Lépine, J. R. D.

    The ability to estimate interstellar extinction is essential for color corrections and distance calculations of all sorts of astronomical objects being fundamental for galactic structure studies. We performed comparisons of interstellar extinction models by Amores & Lépine (2005) that are available at: http://www.astro.iag.usp.br/\\symbol{126}amores. These models are based on the hypothesis that gas and dust are homogeneously mixed, and make use of the dust-to gas ratio. The gas density distribution used in the models is obtained from the gas large scale surveys: Berkeley and Parkes HI surveys and from the Columbia University CO survey. In the present work, we compared these models with extinction predictions of elliptical galaxies (gE) and star clusters. We used the similar sample of gE galaxies proposed by Burstein for the comparison between the extinction calculation methods of Burstein & Heiles (1978, 1982) and of Schlegel et al. (1998) extending the comparison to our models. We found rms differences equal to 0.0179 and 0.0189 mag respectively, in the comparison of the predictions of our "model A" with the two methods mentioned. The comparison takes into account the "zero points" introduced by Burstein. The correlation coefficient obtained in the comparison is around 0.85. These results bring to light that our models can be safely used for the estimation of extinction in our Galaxy for extragalactic work, as an alternative method to the BH and SFD predictions. In the comparison with the globular clusters we found rms differences equal to 0.32 and 0.30 for our models A and S, respectively. For the open clusters we made comparisons using different samples and the rms differences were around 0.25.

  19. Neanderthal extinction by competitive exclusion.

    Directory of Open Access Journals (Sweden)

    William E Banks

    Full Text Available BACKGROUND: Despite a long history of investigation, considerable debate revolves around whether Neanderthals became extinct because of climate change or competition with anatomically modern humans (AMH. METHODOLOGY/PRINCIPAL FINDINGS: We apply a new methodology integrating archaeological and chronological data with high-resolution paleoclimatic simulations to define eco-cultural niches associated with Neanderthal and AMH adaptive systems during alternating cold and mild phases of Marine Isotope Stage 3. Our results indicate that Neanderthals and AMH exploited similar niches, and may have continued to do so in the absence of contact. CONCLUSIONS/SIGNIFICANCE: The southerly contraction of Neanderthal range in southwestern Europe during Greenland Interstadial 8 was not due to climate change or a change in adaptation, but rather concurrent AMH geographic expansion appears to have produced competition that led to Neanderthal extinction.

  20. Exploring co-extinction correlates

    DEFF Research Database (Denmark)

    Carpaneto, Giuseppe Maria; Mazziotta, Adriano; Pittino, Riccardo

    2011-01-01

    Co-extinction is a recurring topic in conservation biology. Quantification of co-extinction has been generally restricted to parasite-host, predator-prey and herbivore-host plant interactions. The loss of detritivorous insects upon the depletion of herbivore mammals has been poorly explored. Here...... of scarab beetle communities. Rarefaction curves estimated that a 50% reduction in the number of sample units where squirrel faecal pellets are the only available food resource accounts for a reduction of 28% of all the scarab species, and of 24% of the squirrel-linked species. The current decline of ground...... that the conservation of ground squirrels and their affiliate scarab species may be ensured by a moderate livestock grazing, owing to the higher ecological success of these rodents in the presence of large herbivores keeping low the grass cover. © 2011 Springer Science+Business Media B.V....

  1. Extinction of radiant energy by large atmospheric crystals with different shapes

    Science.gov (United States)

    Shefer, Olga

    2016-07-01

    The calculated results of extinction characteristics of visible and infrared radiation for large semi-transparent crystals are obtained by hybrid technique, which is a combination of the geometric optics method and the physical optics method. Energy and polarization characteristics of the radiation extinction in terms of the elements of the extinction matrix for individual large crystals and ensemble of crystals are discussed. Influences of particle shapes, aspect ratios, parameters of size distribution, complex refractive index, orientation of crystals, wavelength, and the polarization state of an incident radiation on the extinction are illustrated. It is shown that the most expressive and stable features of energy and polarization characteristics of the extinction are observed in the midinfrared region, despite the fact that the ice particles significantly absorb the radiant energy of this spectrum. It is demonstrated that the polarized extinction characteristics can reach several tens of percent at IR wavelengths. For the large crystals, the conditions of occurrence of the spectral behavior of the extinction coefficient in the visible, near-IR, and mid-IR wavelength ranges are determined.

  2. The Mid-Infrared Extinction Law in the Large Magellanic Cloud

    OpenAIRE

    Gao, Jian; Jiang, B. W.; Li, Aigen; Xue, M. Y.

    2013-01-01

    Based on the photometric data from the Spitzer/SAGE survey and with red giants as the extinction tracers, the mid-infrared (MIR) extinction laws in the Large Magellanic Cloud (LMC) are derived for the first time in the form of A_\\lambda/A_Ks, the extinction in the four IRAC bands (i.e., [3.6], [4.5], [5.8] and [8.0]um) relative to the 2MASS Ks band at 2.16um. We obtain the near-infrared (NIR) extinction coefficient to be E(J-H)/E(H-Ks)=1.29\\pm0.04 and E(J-Ks)/E(H-Ks)=1.94\\pm0.04. The waveleng...

  3. Modified Biserial Correlation Coefficients.

    Science.gov (United States)

    Kraemer, Helena Chmura

    1981-01-01

    Asymptotic distribution theory of Brogden's form of biserial correlation coefficient is derived and large sample estimates of its standard error obtained. Its relative efficiency to the biserial correlation coefficient is examined. Recommendations for choice of estimator of biserial correlation are presented. (Author/JKS)

  4. Characterization and source apportionment of aerosol light extinction with a coupled model of CMB-IMPROVE in Hangzhou, Yangtze River Delta of China

    Science.gov (United States)

    Wang, Jiao; Zhang, Yu-fen; Feng, Yin-chang; Zheng, Xian-jue; Jiao, Li; Hong, Sheng-mao; Shen, Jian-dong; Zhu, Tan; Ding, Jing; Zhang, Qi

    2016-09-01

    To investigate the characteristics and sources of aerosol light extinction in the Yangtze River Delta of China, a campaign was carried out in Hangzhou from December 2013 to November 2014. Hourly data for air pollutants including PM2.5, SO2, NO2, O3 and CO, and aerosol optical properties including aerosol scattering coefficient and aerosol absorbing coefficient was obtained in the environmental air quality automatic monitoring station. Meteorological parameters were measured synchronously in the automated meteorology monitoring station. Additionally, around seven sets of ambient PM2.5 samples per month were collected and analyzed during the campaign. The annual mean aerosol scattering coefficient, aerosol absorbing coefficient and aerosol single scattering albedo measured in this study was 514 ± 284 Mm- 1, 35 ± 20 Mm- 1 and 94% respectively. The aerosol extinction coefficient reconstructed using the modified IMPROVE (Interagency Monitoring of Protected Visual Environment) formula was compared to the measured extinction coefficient. Better correlations could be found between the measured and reconstructed extinction coefficient when RH was under 90%. A coupled model of CMB (chemical mass balance) and modified IMPROVE was used to apportion the sources of aerosol light extinction in Hangzhou. Vehicle exhaust, secondary nitrate and secondary sulfate were identified as the most significant sources for aerosol light extinction, accounted for 30.2%, 24.1% and 15.8% respectively.

  5. The ethics of reviving long extinct species.

    Science.gov (United States)

    Sandler, Ronald

    2014-04-01

    There now appears to be a plausible pathway for reviving species that have been extinct for several decades, centuries, or even millennia. I conducted an ethical analysis of de-extinction of long extinct species. I assessed several possible ethical considerations in favor of pursuing de-extinction: that it is a matter of justice; that it would reestablish lost value; that it would create new value; and that society needs it as a conservation last resort. I also assessed several possible ethical arguments against pursuing de-extinction: that it is unnatural; that it could cause animal suffering; that it could be ecologically problematic or detrimental to human health; and that it is hubristic. There are reasons in favor of reviving long extinct species, and it can be ethically acceptable to do so. However, the reasons in favor of pursuing de-extinction do not have to do with its usefulness in species conservation; rather, they concern the status of revived species as scientific and technological achievements, and it would be ethically problematic to promote de-extinction as a significant conservation strategy, because it does not prevent species extinctions, does not address the causes of extinction, and could be detrimental to some species conservation efforts. Moreover, humanity does not have a responsibility or obligation to pursue de-extinction of long extinct species, and reviving them does not address any urgent problem. Therefore, legitimate ecological, political, animal welfare, legal, or human health concerns associated with a de-extinction (and reintroduction) must be thoroughly addressed for it to be ethically acceptable. © 2013 Society for Conservation Biology.

  6. Transport Coefficients of Fluids

    CERN Document Server

    Eu, Byung Chan

    2006-01-01

    Until recently the formal statistical mechanical approach offered no practicable method for computing the transport coefficients of liquids, and so most practitioners had to resort to empirical fitting formulas. This has now changed, as demonstrated in this innovative monograph. The author presents and applies new methods based on statistical mechanics for calculating the transport coefficients of simple and complex liquids over wide ranges of density and temperature. These molecular theories enable the transport coefficients to be calculated in terms of equilibrium thermodynamic properties, and the results are shown to account satisfactorily for experimental observations, including even the non-Newtonian behavior of fluids far from equilibrium.

  7. From Dusty Filaments to Cores to Stars: An Infrared Extinction Study of Lupus 3

    CERN Document Server

    Teixeira, P S; Alves, J F; Teixeira, Paula S.; Lada, Charles J.; Alves, Joao F.

    2005-01-01

    We present deep NIR observations of a dense region of Lupus 3 obtained with ESO's NTT and VLT. Using the NICE method we construct a dust extinction map of the cloud, which reveals embedded globules, a dense filament, and a dense ring structure. We derive dust column densities and masses for the entire cloud and for the individual structures therein. We construct radial extinction profiles for the embedded globules and find a range of profile shapes from relatively shallow profiles for cores with low peak extinctions, to relatively steep profiles for cores with high extinction. Overall the profiles are similar to those of pressure truncated isothermal spheres of varying center-to-edge density contrast. We apply Bonnor-Ebert analysis to compare the density profiles of the embedded cores in a quantitative manner and derive physical parameters such as temperatures, central densities, and external pressures. We examine the stability of the cores and find that two cores are likely stable and two are likely unstable...

  8. A lesson in defining "extinct"

    OpenAIRE

    Asimow, Paul D.

    2014-01-01

    Toni Feder’s Issues and Events news item about the High-Altitude Water Cherenkov Gamma-Ray Observatory under construction in Mexico ( Physics Today, October 2013, page 22) begins by describing the site as “nestled at 4100 m on the slopes of Sierra Negra, an extinct volcano.” However, as the picture accompanying her piece or a cursory examination in Google Earth makes clear, the site is not on the slopes of Sierra Negra. It sits in the saddle between Sierra Negra and its much larger companion ...

  9. Extinction by the long dielectric needles

    CERN Document Server

    Cherkas, Nadejda L

    2016-01-01

    Electromagnetic wave extinction by the very long but finite dielectric needle is compared with that by the infinite dielectric cylinder for an oblique incidence of the electromagnetic wave. It is shown that the renormalized Hankel functions without the logarithmic terms should be used for the calculation of the extinction per unit length of the infinite dielectric cylinder to apply it for extinction calculations by the finite dielectric cylinder.

  10. Resistance to extinction and behavioral momentum

    OpenAIRE

    Nevin, John A.

    2012-01-01

    In the metaphor of behavioral momentum, reinforcement is assumed to strengthen discriminated operant behavior in the sense of increasing its resistance to disruption, and extinction is viewed as disruption by contingency termination and reinforcer omission. In multiple schedules of intermittent reinforcement, resistance to extinction is an increasing function of reinforcer rate, consistent with a model based on the momentum metaphor. The partial-reinforcement extinction effect, which opposes ...

  11. Mass Extinctions vs. Uniformitarianism in Biological Evolution

    OpenAIRE

    Bak, Per; Paczuski, Maya

    1996-01-01

    It is usually believed that Darwin's theory leads to a smooth gradual evolution, so that mass extinctions must be caused by external shocks. However, it has recently been argued that mass extinctions arise from the intrinsic dynamics of Darwinian evolution. Species become extinct when swept by intermittent avalanches propagating through the global ecology. These ideas are made concrete through studies of simple mathematical models of coevolving species. The models exhibit self-organized criti...

  12. Extinction Maps in the WFAU Archives

    CERN Document Server

    Cross, Nicholas

    2015-01-01

    A brief set of notes about the database design for 3D maps of dust extinction in the WFAU Archives, which support data from UKIRT-WFCAM, VISTA and VST. The notes also detail typical use cases, such as getting colour-excesses, extinction-corrections, spectral energy distributions and colour-magnitude diagrams and demonstrate the SQL queries to return data, along with examples from VVV DR2 with bulge extinction maps from Chen et al. (2013).

  13. The Astronomical Pulse of Global Extinction Events

    Directory of Open Access Journals (Sweden)

    David F.V. Lewis

    2006-01-01

    Full Text Available The linkage between astronomical cycles and the periodicity of mass extinctions is reviewed and discussed. In particular, the apparent 26 million year cycle of global extinctions may be related to the motion of the solar system around the galaxy, especially perpendicular to the galactic plane. The potential relevance of Milankovitch cycles is also explored in the light of current evidence for the possible causes of extinction events over a geological timescale.

  14. The astronomical pulse of global extinction events.

    Science.gov (United States)

    Lewis, David F V; Dorne, Jean-Lou C M

    2006-06-23

    The linkage between astronomical cycles and the periodicity of mass extinctions is reviewed and discussed. In particular, the apparent 26 million year cycle of global extinctions may be related to the motion of the solar system around the galaxy, especially perpendicular to the galactic plane. The potential relevance of Milankovitch cycles is also explored in the light of current evidence for the possible causes of extinction events over a geological timescale.

  15. Mass extinctions vs. uniformitarianism in biological evolution

    Energy Technology Data Exchange (ETDEWEB)

    Bak, P.; Paczuski, M.

    1995-12-31

    It is usually believed that Darwin`s theory leads to a smooth gradual evolution, so that mass extinctions must be caused by external shocks. However, it has recently been argued that mass extinctions arise from the intrinsic dynamics of Darwinian evolution. Species become extinct when swept by intermittent avalanches propagating through the global ecology. These ideas are made concrete through studies of simple mathematical models of co-evolving species. The models exhibit self-organized criticality and describe some general features of the extinction pattern in the fossil record.

  16. Enhancing Divergent Search through Extinction Events

    DEFF Research Database (Denmark)

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    A challenge in evolutionary computation is to create representations as evolvable as those in natural evolution. This paper hypothesizes that extinction events, i.e. mass extinctions, can significantly increase evolvability, but only when combined with a divergent search algorithm, i.e. a search...... for the capacity to evolve. This hypothesis is tested through experiments in two evolutionary robotics domains. The results show that combining extinction events with divergent search increases evolvability, while combining them with convergent search offers no similar benefit. The conclusion is that extinction...

  17. Secondary extinction in Pavlovian fear conditioning.

    Science.gov (United States)

    Vurbic, Drina; Bouton, Mark E

    2011-09-01

    Pavlov (1927/1960) reported that following the conditioning of several stimuli, extinction of one conditioned stimulus (CS) attenuated responding to others that had not undergone direct extinction. However, this secondary extinction effect has not been widely replicated in the contemporary literature. In three conditioned suppression experiments with rats, we further explored the phenomenon. In Experiment 1, we asked whether secondary extinction is more likely to occur with target CSs that have themselves undergone some prior extinction. A robust secondary extinction effect was obtained with a nonextinguished target CS. Experiment 2 showed that extinction of one CS was sufficient to reduce renewal of a second CS when it was tested in a neutral (nonextinction) context. In Experiment 3, secondary extinction was observed in groups that initially received intermixed conditioning trials with the target and nontarget CSs, but not in groups that received conditioning of the two CSs in separate sessions. The results are consistent with the hypothesis that CSs must be associated with a common temporal context during conditioning for secondary extinction to occur.

  18. Dust Extinction in Compact Planetary Nebulae

    OpenAIRE

    Lee, TH; Kwok, S.

    2005-01-01

    The effects of dust extinction on the departure from axisymmetry in the morphology of planetary nebulae (PNs) are investigated through a comparison of the radio free-free emission and hydrogen recombination line images. The dust extinction maps from five compact PNs are derived using high-resolution (̃0"1) Hα and radio maps of the HST and VLA. These extinction maps are then analyzed by an ellipsoidal shell ionization model including the effects of dust extinction to infer the nebulae's intrin...

  19. Climate predictors of late quaternary extinctions

    DEFF Research Database (Denmark)

    Nogués-Bravo, David; Ohlemüller, Ralf; Batra, Persaram

    2010-01-01

    Between 50,000 and 3,000 years before present (BP) 65% of mammal genera weighing over 44 kg went extinct, together with a lower proportion of small mammals. Why species went extinct in such large numbers is hotly debated. One of the arguments proposes that climate changes underlie Late Quaternary...... extinctions, but global quantitative evidence for this hypothesis is still lacking. We test the potential role of global climate change on the extinction of mammals during the Late Quaternary. Our results suggest that continents with the highest climate footprint values, in other words, with climate changes...

  20. Long-term maintenance of immediate or delayed extinction is determined by the extinction-test interval

    OpenAIRE

    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively long extinction-test interval was used; a relatively short extinction-test interval yielded the opposite result (Experiment 2). Previous data appear co...

  1. Extinction-Optimized Volume Illumination.

    Science.gov (United States)

    Ament, Marco; Zirr, Tobias; Dachsbacher, Carsten

    2016-05-16

    We present a novel method to optimize the attenuation of light for the single scattering model in direct volume rendering. A common problem of single scattering is the high dynamic range between lit and shadowed regions due to the exponential attenuation of light along a ray. Moreover, light is often attenuated too strong between a sample point and the camera, hampering the visibility of important features. Our algorithm employs an importance function to selectively illuminate important structures and make them visible from the camera. With the importance function, more light can be transmitted to the features of interest, while contextual structures cast shadows which provide visual cues for perception of depth. At the same time, more scattered light is transmitted from the sample point to the camera to improve the primary visibility of important features. We formulate a minimization problem that automatically determines the extinction along a view or shadow ray to obtain a good balance between sufficient transmittance and attenuation. In contrast to previous approaches, we do not require a computationally expensive solution of a global optimization, but instead provide a closed-form solution for each sampled extinction value along a view or shadow ray and thus achieve interactive performance.

  2. Phylogenetic Clustering of Origination and Extinction across the Late Ordovician Mass Extinction.

    Directory of Open Access Journals (Sweden)

    Andrew Z Krug

    Full Text Available Mass extinctions can have dramatic effects on the trajectory of life, but in some cases the effects can be relatively small even when extinction rates are high. For example, the Late Ordovician mass extinction is the second most severe in terms of the proportion of genera eliminated, yet is noted for the lack of ecological consequences and shifts in clade dominance. By comparison, the end-Cretaceous mass extinction was less severe but eliminated several major clades while some rare surviving clades diversified in the Paleogene. This disconnect may be better understood by incorporating the phylogenetic relatedness of taxa into studies of mass extinctions, as the factors driving extinction and recovery are thought to be phylogenetically conserved and should therefore promote both origination and extinction of closely related taxa. Here, we test whether there was phylogenetic selectivity in extinction and origination using brachiopod genera from the Middle Ordovician through the Devonian. Using an index of taxonomic clustering (RCL as a proxy for phylogenetic clustering, we find that A both extinctions and originations shift from taxonomically random or weakly clustered within families in the Ordovician to strongly clustered in the Silurian and Devonian, beginning with the recovery following the Late Ordovician mass extinction, and B the Late Ordovician mass extinction was itself only weakly clustered. Both results stand in stark contrast to Cretaceous-Cenozoic bivalves, which showed significant levels of taxonomic clustering of extinctions in the Cretaceous, including strong clustering in the mass extinction, but taxonomically random extinctions in the Cenozoic. The contrasting patterns between the Late Ordovician and end-Cretaceous events suggest a complex relationship between the phylogenetic selectivity of mass extinctions and the long-term phylogenetic signal in origination and extinction patterns.

  3. Selectivity of terrestrial gastropod extinctions on an oceanic archipelago and insights into the anthropogenic extinction process

    OpenAIRE

    Chiba, Satoshi; Roy, Kaustuv

    2011-01-01

    Anthropogenic impacts have led to widespread extinctions of species on oceanic islands but the nature of many of these extinctions remains poorly known. Here we investigate extinction selectivities of terrestrial gastropods from the Ogasawara archipelago in the northwest Pacific, where anthropogenic threats have changed over time, shifting primarily from the effects of habitat loss to predation by a variety of different predators. Across all of the islands, extinct species had significantly s...

  4. Timing of extinction relative to acquisition: A parametric analysis of fear extinction in humans

    NARCIS (Netherlands)

    Norrholm, S.D.; Vervliet, B.; Jovanovic, T.; Boshoven, W.; Myers, K.M.; Davis, M.; Rothbaum, B.O.; Duncan, E.J.

    2008-01-01

    Fear extinction is a reduction in conditioned fear following repeated exposure to the feared cue in the absence of any aversive event. Extinguished fear often reappears after extinction through spontaneous recovery. Animal studies suggest that spontaneous recovery can be abolished if extinction occu

  5. Constraints on Enhanced Extinction Resulting from Extinction Treatment in the Presence of an Added Excitor

    Science.gov (United States)

    Urcelay, Gonzalo P.; Lipatova, Olga; Miller, Ralph R.

    2009-01-01

    Three Pavlovian fear conditioning experiments with rats as subjects explored the effect of extinction in the presence of a concurrent excitor. Our aim was to explore this particular treatment, documented in previous studies to deepen extinction, with novel control groups to shed light on the processes involved in extinction. Relative to subjects…

  6. Evidence and mapping of extinction debts for global forest-dwelling reptiles, amphibians and mammals

    Science.gov (United States)

    Chen, Youhua; Peng, Shushi

    2017-03-01

    Evidence of extinction debts for the global distributions of forest-dwelling reptiles, mammals and amphibians was tested and the debt magnitude was estimated and mapped. By using different correlation tests and variable importance analysis, the results showed that spatial richness patterns for the three forest-dwelling terrestrial vertebrate groups had significant and stronger correlations with past forest cover area and other variables in the 1500 s, implying the evidence for extinction debts. Moreover, it was likely that the extinction debts have been partially paid, given that their global richness patterns were also significantly correlated with contemporary forest variables in the 2000 s (but the absolute magnitudes of the correlation coefficients were usually smaller than those calculated for historical forest variables). By utilizing species-area relationships, spatial extinction-debt magnitudes for the three vertebrate groups at the global scale were estimated and the hotspots of extinction debts were identified. These high-debt hotspots were generally situated in areas that did not spatially overlap with hotspots of species richness or high extinction-risk areas based on IUCN threatened status to a large extent. This spatial mismatch pattern suggested that necessary conservation efforts should be directed toward high-debt areas that are still overlooked.

  7. Evidence and mapping of extinction debts for global forest-dwelling reptiles, amphibians and mammals

    Science.gov (United States)

    Chen, Youhua; Peng, Shushi

    2017-01-01

    Evidence of extinction debts for the global distributions of forest-dwelling reptiles, mammals and amphibians was tested and the debt magnitude was estimated and mapped. By using different correlation tests and variable importance analysis, the results showed that spatial richness patterns for the three forest-dwelling terrestrial vertebrate groups had significant and stronger correlations with past forest cover area and other variables in the 1500 s, implying the evidence for extinction debts. Moreover, it was likely that the extinction debts have been partially paid, given that their global richness patterns were also significantly correlated with contemporary forest variables in the 2000 s (but the absolute magnitudes of the correlation coefficients were usually smaller than those calculated for historical forest variables). By utilizing species-area relationships, spatial extinction-debt magnitudes for the three vertebrate groups at the global scale were estimated and the hotspots of extinction debts were identified. These high-debt hotspots were generally situated in areas that did not spatially overlap with hotspots of species richness or high extinction-risk areas based on IUCN threatened status to a large extent. This spatial mismatch pattern suggested that necessary conservation efforts should be directed toward high-debt areas that are still overlooked. PMID:28300200

  8. SAGE III aerosol extinction validation in the Arctic winter: comparisons with SAGE II and POAM III

    Directory of Open Access Journals (Sweden)

    L. W. Thomason

    2006-11-01

    Full Text Available The use of SAGE III multiwavelength aerosol extinction coefficient measurements to infer PSC type is contingent on the robustness of both the extinction magnitude and its spectral variation. Past validation with SAGE II and other similar measurements has shown that the SAGE III extinction coefficient measurements are reliable though the comparisons have been greatly weighted toward measurements made at mid-latitudes. Some aerosol comparisons made in the Arctic winter as a part of SOLVE II suggested that SAGE III values, particularly at longer wavelengths, are too small with the implication that both the magnitude and the wavelength dependence are not reliable. Comparisons with POAM III have also suggested a similar discrepancy. Herein, we use SAGE II data as a common standard for comparison of SAGE III and POAM III measurements in the Arctic winters of 2002/2003 through 2004/2005. During the winter, SAGE II measurements are made infrequently at the same latitudes as these instruments. We have mitigated this problem through the use potential vorticity as a spatial coordinate and thus greatly increased the number of coincident events. We find that SAGE II and III extinction coefficient measurements show a high degree of compatibility at both 1020 nm and 450 nm except a 10–20% bias at both wavelengths. In addition, the 452 to 1020 nm extinction ratio shows a consistent bias of ~30% throughout the lower stratosphere. We also find that SAGE II and POAM III are on average consistent though the comparisons show a much higher variability and larger bias than SAGE II/III comparisons. In addition, we find that the two data sets are not well correlated below 18 km. Overall, we find both the extinction values and the spectral dependence from SAGE III are robust and we find no evidence of a significant defect within the Arctic vortex.

  9. SAGE III Aerosol Extinction Validation in the Arctic Winter: Comparisons with SAGE II and POAM III

    Science.gov (United States)

    Thomason, L. W.; Poole, L. R.; Randall, C. E.

    2007-01-01

    The use of SAGE III multiwavelength aerosol extinction coefficient measurements to infer PSC type is contingent on the robustness of both the extinction magnitude and its spectral variation. Past validation with SAGE II and other similar measurements has shown that the SAGE III extinction coefficient measurements are reliable though the comparisons have been greatly weighted toward measurements made at mid-latitudes. Some aerosol comparisons made in the Arctic winter as a part of SOLVE II suggested that SAGE III values, particularly at longer wavelengths, are too small with the implication that both the magnitude and the wavelength dependence are not reliable. Comparisons with POAM III have also suggested a similar discrepancy. Herein, we use SAGE II data as a common standard for comparison of SAGE III and POAM III measurements in the Arctic winters of 2002/2003 through 2004/2005. During the winter, SAGE II measurements are made infrequently at the same latitudes as these instruments. We have mitigated this problem through the use potential vorticity as a spatial coordinate and thus greatly increased the number of coincident events. We find that SAGE II and III extinction coefficient measurements show a high degree of compatibility at both 1020 nm and 450 nm except a 10-20% bias at both wavelengths. In addition, the 452 to 1020-nm extinction ratio shows a consistent bias of approx. 30% throughout the lower stratosphere. We also find that SAGE II and POAM III are on average consistent though the comparisons show a much higher variability and larger bias than SAGE II/III comparisons. In addition, we find that the two data sets are not well correlated below 18 km. Overall, we find both the extinction values and the spectral dependence from SAGE III are robust and we find no evidence of a significant defect within the Arctic vortex.

  10. Extinction characteristic of graphite smoke for terahertz wave

    Science.gov (United States)

    Wang, Qi-chao; Wang, Jia-chun; Zhao, Da-peng; Zhang, Ji-kui; Liu, Hao; Shi, Jia-ming

    2016-10-01

    Graphite with good extinction performance can be used as electro-optical passive jamming material for infrared and laser detection. In order to acquire the extinction characteristic of graphite smoke for terahertz wave (THz wave), graphite powder was dispersed in a KBr matrix with concentrations of 0.6 wt% and 1.0 wt% respectively, and those composites were processed in the stoving system and were then pressed into pellets. Meanwhile, the pure KBr powder pellet was prepared with same method under same condition. By utilizing THz-TDS, the THz transmission spectrums of those samples were measured in the frequency range 0.2-1.1 THz. Then, the absorption coefficients of those samples were deduced based on the material parameter estimation method. The experimental results indicate that the absorption coefficients of those samples are enhanced with the increasing THz frequency and that of them are improved with the concentrations of graphite at the same frequency. The results obtained demonstrate that THz wave has strong penetration capacity through graphite smoke and THz radar will be promising for use to make up for the deficiency of the infrared and laser detection system and to detect the targets coated with graphite smoke.

  11. Long-Term Maintenance of Immediate or Delayed Extinction Is Determined by the Extinction-Test Interval

    Science.gov (United States)

    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively…

  12. On the Source of the Dust Extinction in Type Ia Supernovae and the Discovery of Anomalously Strong Na I Absorption

    CERN Document Server

    Phillips, M M; Morrell, Nidia; Burns, Christopher R; Cox, Nick L J; Foley, Ryan J; Karakas, Amanda I; Patat, F; Sternberg, A; Williams, R E; Gal-Yam, A; Hsiao, E Y; Leonard, D C; Persson, Sven E; Stritzinger, Maximilian; Thompson, I B; Campillay, Abdo; Contreras, Carlos; Folatelli, Gastón; Freedman, Wendy L; Hamuy, Mario; Roth, Miguel; Shields, Gregory A; Suntzeff, Nicholas B; Chomiuk, Laura; Ivans, Inese I; Madore, Barry F; Penprase, B E; Perley, Daniel; Preston, G Pignata G; Soderberg, Alicia M

    2013-01-01

    High-dispersion observations of the Na I D 5890, 5896 and K I 7665, 7699 interstellar lines, and the diffuse interstellar band at 5780 Angstroms in the spectra of 32 Type Ia supernovae are used as an independent means of probing dust extinction. We show that the dust extinction of the objects where the diffuse interstellar band at 5780 Angstroms is detected is consistent with the visual extinction derived from the supernova colors. This strongly suggests that the dust producing the extinction is predominantly located in the interstellar medium of the host galaxies and not in circumstellar material associated with the progenitor system. One quarter of the supernovae display anomalously large Na I column densities in comparison to the amount of dust extinction derived from their colors. Remarkably, all of the cases of unusually strong Na I D absorption correspond to "Blueshifted" profiles in the classification scheme of Sternberg et al. (2011). This coincidence suggests that outflowing circumstellar gas is resp...

  13. Extinction-Induced Variability in Human Behavior

    Science.gov (United States)

    Kinloch, Jennifer M.; Foster, T. Mary; McEwan, James S. A.

    2009-01-01

    Participants earned points by pressing a computer space bar (Experiment 1) or forming rectangles on the screen with the mouse (Experiment 2) under differential-reinforcement-of-low-rate schedules, followed by extinction. Variability in interresponse time (the contingent dimension) increased during extinction, as for Morgan and Lee (1996);…

  14. Periodicity of extinction: A 1988 update

    Science.gov (United States)

    Sepkowski, J. John, Jr.

    1988-01-01

    The hypothesis that events of mass extinction recur periodically at approximately 26 my intervals is an empirical claim based on analysis of data from the fossil record. The hypothesis has become closely linked with catastrophism because several events in the periodic series are associated with evidence of extraterrestrial impacts, and terrestrial forcing mechanisms with long, periodic recurrences are not easily conceived. Astronomical mechanisms that have been hypothesized include undetected solar companions and solar oscillation about the galactic plane, which induce comet showers and result in impacts on Earth at regular intervals. Because these mechanisms are speculative, they have been the subject of considerable controversy, as has the hypothesis of periodicity of extinction. In response to criticisms and uncertainties, a data base was developed on times of extinction of marine animal genera. A time series is given and analyzed with 49 sample points for the per-genus extinction rate from the Late Permian to the Recent. An unexpected pattern in the data is the uniformity of magnitude of many of the periodic extinction events. Observations suggest that the sequence of extinction events might be the result of two sets of mechanisms: a periodic forcing that normally induces only moderate amounts of extinction, and independent incidents or catastrophes that, when coincident with the periodic forcing, amplify its signal and produce major-mass extinctions.

  15. Can Parallelingualism Save Norwegian from Extinction?

    Science.gov (United States)

    Linn, Andrew R.

    2010-01-01

    Language extinction is one of the most pressing issues in linguistics today, and the literature is full of discussion about how to combat it. Statements that Norwegian is amongst the languages that are already extinct are merely examples of a widespread tendency in the literature towards erroneous information about Norwegian. Nonetheless, there is…

  16. Current extinction rates of reptiles and amphibians.

    Science.gov (United States)

    Alroy, John

    2015-10-20

    There is broad concern that a mass extinction of amphibians and reptiles is now underway. Here I apply an extremely conservative Bayesian method to estimate the number of recent amphibian and squamate extinctions in nine important tropical and subtropical regions. The data stem from a combination of museum collection databases and published site surveys. The method computes an extinction probability for each species by considering its sighting frequency and last sighting date. It infers hardly any extinction when collection dates are randomized and it provides underestimates when artificial extinction events are imposed. The method also appears to be insensitive to trends in sampling; therefore, the counts it provides are absolute minimums. Extinctions or severe population crashes have accumulated steadily since the 1970s and 1980s, and at least 3.1% of frog species have already disappeared. Based on these data and this conservative method, the best estimate of the global grand total is roughly 200 extinctions. Consistent with previous results, frog losses are heavy in Latin America, which has been greatly affected by the pathogenic chytrid fungus Batrachochytrium dendrobatidis. Extinction rates are now four orders-of-magnitude higher than background, and at least another 6.9% of all frog species may be lost within the next century, even if there is no acceleration in the growth of environmental threats.

  17. Extinct mountain goat ( Oreamnos harringtoni) in Southeastern Utah

    Science.gov (United States)

    Mead, Jim I.; Agenbroad, Larry D.; Phillips, Arthur M.; Middleton, Larry T.

    1987-05-01

    The extinct Harrington's mountain goat ( Oreamnos harringtoni Stock) is predominantly known from dry cave localities in the Grand Canyon, Arizona, in addition to two sites in the Great Basin, Nevada, and from San Josecito Cave, Nuevo Leon, Mexico. A dry shelter in Natural Bridges National Monument, on the central Colorado Plateau, southeastern Utah, preserves numerous remains of the extinct mountain goat in addition to pack rat middens. Remains from a 100-cm stratigraphic profile indicate that O. harringtoni lived on the plateau >39,800 yr B.P., the oldest directly dated find of extinct mountain goat. Plant macrofossils indicate that Engelmann's spruce ( Picea engelmannii), limber pine ( Pinus flexilis), rose ( Rosa cf. woodsii), and Douglas fir ( Pseudotsuga menziesii) grew during the late Pleistocene where a riparian and a pinyon-juniper ( Pinus edulis-Juniperus osteosperma) community now predominates; Douglas fir are found only in mesic, protected, north-facing areas. Limber pine, Douglas fir, bark, and grasses were the major dietary components in the dung. A springtime diet of birch ( Betula) is determined from pollen clumps in dung pellets.

  18. Multidimensional extremal dependence coefficients

    OpenAIRE

    2017-01-01

    Extreme values modeling has attracting the attention of researchers in diverse areas such as the environment, engineering, or finance. Multivariate extreme value distributions are particularly suitable to model the tails of multidimensional phenomena. The analysis of the dependence among multivariate maxima is useful to evaluate risk. Here we present new multivariate extreme value models, as well as, coefficients to assess multivariate extremal dependence.

  19. Synchronous extinction of North America's Pleistocene mammals

    Science.gov (United States)

    Faith, J. Tyler; Surovell, Todd A.

    2009-12-01

    The late Pleistocene witnessed the extinction of 35 genera of North American mammals. The last appearance dates of 16 of these genera securely fall between 12,000 and 10,000 radiocarbon years ago (≈13,800-11,400 calendar years B.P.), although whether the absence of fossil occurrences for the remaining 19 genera from this time interval is the result of sampling error or temporally staggered extinctions is unclear. Analysis of the chronology of extinctions suggests that sampling error can explain the absence of terminal Pleistocene last appearance dates for the remaining 19 genera. The extinction chronology of North American Pleistocene mammals therefore can be characterized as a synchronous event that took place 12,000-10,000 radiocarbon years B.P. Results favor an extinction mechanism that is capable of wiping out up to 35 genera across a continent in a geologic instant.

  20. Mass extinction in poorly known taxa.

    Science.gov (United States)

    Régnier, Claire; Achaz, Guillaume; Lambert, Amaury; Cowie, Robert H; Bouchet, Philippe; Fontaine, Benoît

    2015-06-23

    Since the 1980s, many have suggested we are in the midst of a massive extinction crisis, yet only 799 (0.04%) of the 1.9 million known recent species are recorded as extinct, questioning the reality of the crisis. This low figure is due to the fact that the status of very few invertebrates, which represent the bulk of biodiversity, have been evaluated. Here we show, based on extrapolation from a random sample of land snail species via two independent approaches, that we may already have lost 7% (130,000 extinctions) of the species on Earth. However, this loss is masked by the emphasis on terrestrial vertebrates, the target of most conservation actions. Projections of species extinction rates are controversial because invertebrates are essentially excluded from these scenarios. Invertebrates can and must be assessed if we are to obtain a more realistic picture of the sixth extinction crisis.

  1. The Mid-infrared Extinction Law in the Large Magellanic Cloud

    Science.gov (United States)

    Gao, Jian; Jiang, B. W.; Li, Aigen; Xue, M. Y.

    2013-10-01

    Based on photometric data from the Spitzer/SAGE survey, using red giants as extinction tracers, the mid-infrared (MIR) extinction laws in the Large Magellanic Cloud (LMC) are derived for the first time in the form of A_\\lambda /A_{K_S}. This quantity refers to the extinction in the four Infrared Array Camera (IRAC) bands (i.e., [3.6], [4.5], [5.8], and [8.0] μm) relative to the Two Micron All Sky Survey KS band at 2.16 μm. We obtain the near-infrared extinction coefficient to be E(J - H)/E(H - KS ) ≈ 1.29 ± 0.04 and E(J - KS )/E(H - KS ) ≈ 1.94 ± 0.04. The wavelength dependence of the MIR extinction A_{\\lambda }/A_{K_S} in the LMC varies from one sightline to another. The overall mean MIR extinction is A_{[3.6]}/A_{K_S}\\approx 0.72+/- 0.03, A_{[4.5]}/A_{K_S}\\approx 0.94+/- 0.03, A_{[5.8]}/A_{K_S}\\approx 0.58+/- 0.04, and A_{[8.0]}/A_{K_S}\\approx 0.62+/- 0.05. Except for the extinction in the IRAC [4.5] μm band, which may be contaminated by the 4.6 μm CO gas absorption of red giants used to trace LMC extinction, the extinction in the other three IRAC bands show a flat curve, close to the Milky Way RV = 5.5 model extinction curve, where RV is the optical total-to-selective extinction ratio. The possible systematic bias caused by the correlated uncertainties of KS - λ and J - KS is explored in terms of Monte Carlo simulations. We find that this bias could lead to an overestimation of A_{\\lambda }/A_{K_S} in the MIR.

  2. Prestarlike functions with negative coefficients

    Directory of Open Access Journals (Sweden)

    H. Silverman

    1979-01-01

    Full Text Available The extreme points for prestarlike functions having negative coefficients are determined. Coefficient, distortion and radii of univalence, starlikeness, and convexity theorems are also obtained.

  3. Compact LIDAR for Aerosol Extinction Profiling from Small UAV's Project

    Data.gov (United States)

    National Aeronautics and Space Administration — It is increasingly recognized that the Arctic is a bellwether for climate change. As the Arctic region responds to climate forcings, monitoring how aerosol...

  4. Gorenstein Hilbert Coefficients

    CERN Document Server

    Khoury, Sabine El

    2012-01-01

    We prove upper and lower bounds for all the coefficients in the Hilbert Polynomial of a graded Gorenstein algebra $S=R/I$ with a quasi-pure resolution over $R$. The bounds are in terms of the minimal and the maximal shifts in the resolution of $R$ . These bounds are analogous to the bounds for the multiplicity found in \\cite{S} and are stronger than the bounds for the Cohen Macaulay algebras found in \\cite{HZ}.

  5. Solid-solution partitioning of Cd and factors controlling the partitioning coefficient in paddy soil profiles: A case study of the Chengdu Plain in Sichuan Province%重金属元素Cd在水稻土剖面中的分配系数及其影响因素研究:以四川省成都平原区为例

    Institute of Scientific and Technical Information of China (English)

    杨晓燕; 侯青叶; 杨忠芳

    2013-01-01

    以四川省成都平原区农田生态系统水稻土剖面为例,探讨了Cd分配系数及其影响因素.结果表明:Cd分配系数(Kd)在污染土壤环境和本底土壤环境中是不同的,在剖面PM3、PM-6和PM8剖面中污染环境中分配系数(Kd)大于本底环境中的分配系数.而在剖面PM-7中,本底环境中的分配系数(Kd)大于污染环境中的值.在污染环境Cd分配系数受土壤pH值、交换性Mg和铁硅氧化物的影响比较大,而在非污染环境中分配系数受到土壤可溶性Al、Cd全量和铁锰铝氧化物的影响较大.这些土壤的物化性质对分配系数造成影响,使得土壤滤渣和土壤原土中Cd形态含量存在差异.%For understanding geochemical behaviors of cadmium (Cd). it is essential to study the partitioning coefficient (Kd) of Cd and the factors controlling the Kd in soil environment. This study focuses on the distribution of Cd between the soil solution and soil solid phase in paddy soil profiles in Chengdu agro-ecosystems in Sichuan Province, in order to discuss the factors controlling the partition coefficient. It is known that the KA value of Cd in contaminated soils is different from that in the original soils. In profile PM-3, PM-6 and PM-8. the Kd in the contaminated soil layer is larger than that in the original layers, however, in profile PM-7 it is on the contrary. The results show that the partition coefficient of Cd is closely related with soil physical-chemical properties. The partition coefficient (Kd) is influenced by soil pH. exchangeable Al, and iron and silicon oxides in the contaminated soils, while in the original soils it is extremely sensitive to soil soluble Al, total cadmium and oxides of iron, manganese and aluminum. Because of the impact of these soil physical and chemical properties on the partiliun coefficient, the different distribution of geochemical species of cadmium between the soil residues and the original soils exists.

  6. Immediate extinction causes a less durable loss of performance than delayed extinction following either fear or appetitive conditioning

    OpenAIRE

    Woods, Amanda M.; Bouton, Mark E.

    2008-01-01

    Five experiments with rat subjects compared the effects of immediate and delayed extinction on the durability of extinction learning. Three experiments examined extinction of fear conditioning (using the conditioned emotional response method), and two experiments examined extinction of appetitive conditioning (using the food-cup entry method). In all experiments, conditioning and extinction were accomplished in single sessions, and retention testing took place 24 h after extinction. In both f...

  7. Retention of perceptual generalization of fear extinction.

    Science.gov (United States)

    Pappens, Meike; Schroijen, Mathias; Van den Bergh, Omer; Van Diest, Ilse

    2015-12-01

    Fear reduction obtained during a fear extinction procedure can generalize from the extinction stimulus to other perceptually similar stimuli. Perceptual generalization of fear extinction typically follows a perceptual gradient, with increasing levels of fear reduction the more a stimulus resembles the extinction stimulus. The current study aimed to investigate whether perceptual generalization of fear extinction can be observed also after a retention interval of 24h. Fear was acquired to three geometrical figures of different sizes (CS(+), CS1(+) and CS2(+)) by consistently pairing them with a short-lasting suffocation experience (US). Three other geometrical figures that were never followed by the US served as control stimuli (CS(-), CS1(-), CS2(-)). Next, only the CS(+) was extinguished by presenting it in the absence of the US. One day later, fear responses to all stimuli were assessed without any US-presentation. Outcome measures included startle blink EMG, skin conductance, US expectancy, respiratory rate and tidal volume. On day 2 spontaneous recovery of fear was observed in US expectancy and tidal volume, but not in the other outcomes. Evidence for the retention of fear extinction generalization was present in US expectancy and skin conductance, but a perceptual gradient in the retention of generalized fear extinction could not be observed.

  8. Resistance to extinction and behavioral momentum.

    Science.gov (United States)

    Nevin, John A

    2012-05-01

    In the metaphor of behavioral momentum, reinforcement is assumed to strengthen discriminated operant behavior in the sense of increasing its resistance to disruption, and extinction is viewed as disruption by contingency termination and reinforcer omission. In multiple schedules of intermittent reinforcement, resistance to extinction is an increasing function of reinforcer rate, consistent with a model based on the momentum metaphor. The partial-reinforcement extinction effect, which opposes the effects of reinforcer rate, can be explained by the large disruptive effect of terminating continuous reinforcement despite its strengthening effect during training. Inclusion of a term for the context of reinforcement during training allows the model to account for a wide range of multiple-schedule extinction data and makes contact with other formulations. The relation between resistance to extinction and reinforcer rate on single schedules of intermittent reinforcement is exactly opposite to that for multiple schedules over the same range of reinforcer rates; however, the momentum model can give an account of resistance to extinction in single as well as multiple schedules. An alternative analysis based on the number of reinforcers omitted to an extinction criterion supports the conclusion that response strength is an increasing function of reinforcer rate during training.

  9. Extinction as discrimination: the molar view.

    Science.gov (United States)

    Baum, William M

    2012-05-01

    The traditional molecular view of behavior explains extinction as the dissipation or inhibition of strength, formerly built up by contiguous reinforcement. In obstinate opposition to this explanation was the partial-reinforcement extinction effect: a partially reinforced response extinguishes more slowly than a continuously reinforced response. It suggests instead that extinction is discrimination. Four pigeons were exposed to daily sessions in which a variable period of food delivery, produced by pecking on a variable-interval schedule, was followed by extinction. The rate of food delivery was varied over a wide range across conditions. Varying the amount of food per delivery inversely with rate of delivery kept response rate from varying excessively. The results confirmed and extended the partial-reinforcement effect; persistence of pecking and time to extinction were inversely related to rate of obtaining food. The results support the molar view of extinction, not as loss of strength of a particular discrete response, but as a transition from one allocation of time among activities to another. Although molecular theories dismiss discrimination due to repeated training and extinction as an impurity or complication, repeated cycles of availability and privation are probably typical of the environment in which most vertebrate species evolved.

  10. Estimating extinction using unsupervised machine learning

    Science.gov (United States)

    Meingast, Stefan; Lombardi, Marco; Alves, João

    2017-05-01

    Dust extinction is the most robust tracer of the gas distribution in the interstellar medium, but measuring extinction is limited by the systematic uncertainties involved in estimating the intrinsic colors to background stars. In this paper we present a new technique, Pnicer, that estimates intrinsic colors and extinction for individual stars using unsupervised machine learning algorithms. This new method aims to be free from any priors with respect to the column density and intrinsic color distribution. It is applicable to any combination of parameters and works in arbitrary numbers of dimensions. Furthermore, it is not restricted to color space. Extinction toward single sources is determined by fitting Gaussian mixture models along the extinction vector to (extinction-free) control field observations. In this way it becomes possible to describe the extinction for observed sources with probability densities, rather than a single value. Pnicer effectively eliminates known biases found in similar methods and outperforms them in cases of deep observational data where the number of background galaxies is significant, or when a large number of parameters is used to break degeneracies in the intrinsic color distributions. This new method remains computationally competitive, making it possible to correctly de-redden millions of sources within a matter of seconds. With the ever-increasing number of large-scale high-sensitivity imaging surveys, Pnicer offers a fast and reliable way to efficiently calculate extinction for arbitrary parameter combinations without prior information on source characteristics. The Pnicer software package also offers access to the well-established Nicer technique in a simple unified interface and is capable of building extinction maps including the Nicest correction for cloud substructure. Pnicer is offered to the community as an open-source software solution and is entirely written in Python.

  11. Vertical profiles of aerosol optical properties and the solar heating rate estimated by combining sky radiometer and lidar measurements

    Science.gov (United States)

    Kudo, Rei; Nishizawa, Tomoaki; Aoyagi, Toshinori

    2016-07-01

    The SKYLIDAR algorithm was developed to estimate vertical profiles of aerosol optical properties from sky radiometer (SKYNET) and lidar (AD-Net) measurements. The solar heating rate was also estimated from the SKYLIDAR retrievals. The algorithm consists of two retrieval steps: (1) columnar properties are retrieved from the sky radiometer measurements and the vertically mean depolarization ratio obtained from the lidar measurements and (2) vertical profiles are retrieved from the lidar measurements and the results of the first step. The derived parameters are the vertical profiles of the size distribution, refractive index (real and imaginary parts), extinction coefficient, single-scattering albedo, and asymmetry factor. Sensitivity tests were conducted by applying the SKYLIDAR algorithm to the simulated sky radiometer and lidar data for vertical profiles of three different aerosols, continental average, transported dust, and pollution aerosols. The vertical profiles of the size distribution, extinction coefficient, and asymmetry factor were well estimated in all cases. The vertical profiles of the refractive index and single-scattering albedo of transported dust, but not those of transported pollution aerosol, were well estimated. To demonstrate the performance and validity of the SKYLIDAR algorithm, we applied the SKYLIDAR algorithm to the actual measurements at Tsukuba, Japan. The detailed vertical structures of the aerosol optical properties and solar heating rate of transported dust and smoke were investigated. Examination of the relationship between the solar heating rate and the aerosol optical properties showed that the vertical profile of the asymmetry factor played an important role in creating vertical variation in the solar heating rate. We then compared the columnar optical properties retrieved with the SKYLIDAR algorithm to those produced with the more established scheme SKYRAD.PACK, and the surface solar irradiance calculated from the SKYLIDAR

  12. Interstellar extinction by fractal polycrystalline graphite clusters?

    CERN Document Server

    Andersen, A C; Pustovit, V N; Niklasson, G A

    2001-01-01

    Certain dust particles in space are expected to appear as clusters of individual grains. The morphology of these clusters could be fractal or compact. To determine how these structural features would affect the interpretation of the observed interstellar extinction peak at $\\sim 4.6~\\mu$m, we have calculated the extinction by compact and fractal polycrystalline graphite clusters consisting of touching identical spheres. We compare three general methods for computing the extinction of the clusters, namely, a rigorous solution and two different discrete-dipole approximation methods.

  13. A model for evolution and extinction

    CERN Document Server

    Roberts, B W; Roberts, Bruce W

    1995-01-01

    We present a model for evolution and extinction in large ecosystems. The model incorporates the effects of interactions between species and the influences of abiotic environmental factors. We study the properties of the model by approximate analytic solution and also by numerical simulation, and use it to make predictions about the distribution of extinctions and species lifetimes that we would expect to see in real ecosystems. It should be possible to test these predictions against the fossil record. The model indicates that a possible mechanism for mass extinction is the coincidence of a large coevolutionary avalanche in the ecosystem with a severe environmental disturbance.

  14. Volcanogenic Dark Matter and Mass Extinctions

    CERN Document Server

    Abbas, S; Abbas, Samar; Abbas, Afsar

    1996-01-01

    The passage of the Earth through dense clumps of dark matter, the presence of which are predicted by certain cosmologies, would produce large quantities of heat in the interior of this planet through the capture and subsequent annihilation of dark matter particles. This heat can cause large-scale volcanism which could in turn have caused the extinction of the dinosaurs and other mass extinctions. The periodicity of such volcanic outbursts agrees with the frequency of palaeontological mass extinctions as well as the observed periodicity in the occurrence of the largest flood basalt provinces on the globe.

  15. A mathematical model for Neanderthal extinction

    CERN Document Server

    Flores, J C

    1997-01-01

    A simple mathematical homogeneous model of competition is used to describe Neanderthal extinction in Europe. It considers two interacting species, Neanderthals and Early Modern Men, in the same ecological niche. Using paleontological data we claim that the parameter of similarity, between both species, fluctuates between 0.992 and 0.997. An extension of the model including migration (diffusion) is also discussed nevertheless, extinction of Neanderthal seems unavoidable. Numerical analysis of travelling wave solution (fronts) comfirms the extinction. The wave-front-velocity is estimated from linear analysis and numerical simulations confirm this estimation. We conjecture a mathematical formulation for the principle of exclusion between competitive interacting species (Gause).

  16. The Truth About Ballistic Coefficients

    CERN Document Server

    Courtney, Michael

    2007-01-01

    The ballistic coefficient of a bullet describes how it slows in flight due to air resistance. This article presents experimental determinations of ballistic coefficients showing that the majority of bullets tested have their previously published ballistic coefficients exaggerated from 5-25% by the bullet manufacturers. These exaggerated ballistic coefficients lead to inaccurate predictions of long range bullet drop, retained energy and wind drift.

  17. Extinction from a rationalist perspective.

    Science.gov (United States)

    Gallistel, C R

    2012-05-01

    The merging of the computational theory of mind and evolutionary thinking leads to a kind of rationalism, in which enduring truths about the world have become implicit in the computations that enable the brain to cope with the experienced world. The dead reckoning computation, for example, is implemented within the brains of animals as one of the mechanisms that enables them to learn where they are (Gallistel, 1990, 1995). It integrates a velocity signal with respect to a time signal. Thus, the manner in which position and velocity relate to one another in the world is reflected in the manner in which signals representing those variables are processed in the brain. I use principles of information theory and Bayesian inference to derive from other simple principles explanations for: (1) the failure of partial reinforcement to increase reinforcements to acquisition; (2) the partial reinforcement extinction effect; (3) spontaneous recovery; (4) renewal; (5) reinstatement; (6) resurgence (aka facilitated reacquisition). Like the principle underlying dead-reckoning, these principles are grounded in analytic considerations. They are the kind of enduring truths about the world that are likely to have shaped the brain's computations. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Biogeographic and bathymetric determinants of brachiopod extinction and survival during the Late Ordovician mass extinction

    DEFF Research Database (Denmark)

    Finnegan, Seth; Mac Ørum Rasmussen, Christian; Harper, David A. T.

    2016-01-01

    The Late Ordovician mass extinction (LOME) coincided with dramatic climate changes, but there are numerous ways in which these changes could have driven marine extinctions. We use a palaeobiogeographic database of rhynchonelliform brachiopods to examine the selectivity of Late Ordovician......–Early Silurian genus extinctions and evaluate which extinction drivers are best supported by the data. The first (latest Katian) pulse of the LOME preferentially affected genera restricted to deeper waters or to relatively narrow (less than 35°) palaeolatitudinal ranges. This pattern is only observed...... in the latest Katian, suggesting that it reflects drivers unique to this interval. Extinction of exclusively deeper-water genera implies that changes in water mass properties such as dissolved oxygen content played an important role. Extinction of genera with narrow latitudinal ranges suggests that interactions...

  19. Mutation induced extinction in finite populations: lethal mutagenesis and lethal isolation.

    Directory of Open Access Journals (Sweden)

    C Scott Wylie

    Full Text Available Reproduction is inherently risky, in part because genomic replication can introduce new mutations that are usually deleterious toward fitness. This risk is especially severe for organisms whose genomes replicate "semi-conservatively," e.g. viruses and bacteria, where no master copy of the genome is preserved. Lethal mutagenesis refers to extinction of populations due to an unbearably high mutation rate (U, and is important both theoretically and clinically, where drugs can extinguish pathogens by increasing their mutation rate. Previous theoretical models of lethal mutagenesis assume infinite population size (N. However, in addition to high U, small N can accelerate extinction by strengthening genetic drift and relaxing selection. Here, we examine how the time until extinction depends jointly on N and U. We first analytically compute the mean time until extinction (τ in a simplistic model where all mutations are either lethal or neutral. The solution motivates the definition of two distinct regimes: a survival phase and an extinction phase, which differ dramatically in both how τ scales with N and in the coefficient of variation in time until extinction. Next, we perform stochastic population-genetics simulations on a realistic fitness landscape that both (i features an epistatic distribution of fitness effects that agrees with experimental data on viruses and (ii is based on the biophysics of protein folding. More specifically, we assume that mutations inflict fitness penalties proportional to the extent that they unfold proteins. We find that decreasing N can cause phase transition-like behavior from survival to extinction, which motivates the concept of "lethal isolation." Furthermore, we find that lethal mutagenesis and lethal isolation interact synergistically, which may have clinical implications for treating infections. Broadly, we conclude that stably folded proteins are only possible in ecological settings that support sufficiently

  20. Epidemic extinction and control in heterogeneous networks

    CERN Document Server

    Hindes, Jason

    2016-01-01

    We consider epidemic extinction in finite networks with broad variation in local connectivity. Generalizing the theory of large fluctuations to random networks with a given degree distribution, we are able to predict the most probable, or optimal, paths to extinction in various configurations, including truncated power-laws. We find that paths for heterogeneous networks follow a limiting form in which infection first decreases in low-degree nodes, which triggers a rapid extinction in high- degree nodes, and finishes with a residual low-degree extinction. The usefulness of the approach is further demonstrated through optimal control strategies that leverage finite-size fluctuations. Interestingly, we find that the optimal control is a mix of treating both high and low-degree nodes based on large-fluctuation theoretical predictions.

  1. Protostars at Low Extinction in Orion A

    CERN Document Server

    Lewis, John Arban

    2016-01-01

    In the list of young stellar objects compiled by Megeath et al. (2012) for the Orion A molecular cloud, only 44 out of 1208 sources found projected onto low extinction (Ak<0.8 mag) gas are identified as protostars. These objects are puzzling because protostars are not typically expected to be associated with extended low extinction material. Here, we use high resolution extinction maps generated from Herschel data, optical/infrared and Spitzer Space Telescope photometry and spectroscopy of the low extinction protostellar candidate sources to determine if they are likely true protostellar sources or contaminants. Out of 44 candidate objects, we determine that 10 sources are likely protostars, with the rest being more evolved young stellar objects (18), galaxies (4), false detections of nebulosity and cloud edges (9), or real sources for which more data are required to ascertain their nature (3). We find none of the confirmed protostars to be associated with recognizable dense cores and we briefly discuss po...

  2. UV extinction properties of carina nebular dust

    Science.gov (United States)

    Massa, Derck

    1993-01-01

    I have performed an analysis of the UV extinction by dust along the line of sight to the young open cluster Tr 16. The observed curves are parameterized in order to extract quantitative information about the structure of the curves. Furthermore, by constructing differential extinction curves, obtained by differencing curves for stars which lie within a few arc seconds of each other on the sky, I was able to obtain a curve which is free of the effects of foreground extinction, and represents the extinction by the dust in the Tr 16 molecular cloud. I then show that this curve is nearly identical to one due to dust in the Orion molecular cloud. This result shows that dust in the Carina arm exhibits the same behavior as that in the local arm.

  3. Possible involvement of serotonin in extinction.

    Science.gov (United States)

    Beninger, R J; Phillips, A G

    1979-01-01

    In Experiment 1, rats were trained to leverpress for continuous reinforcement with food; half were then intubated with the serotonin synthesis inhibitor parachlorophenylalanine (PCPA: 400 mg/kg) and half with water. In extinction the PCPA-treated rats responded at a higher rate. In Experiment 2, rats were trained on a random interval schedule and then assigned to two groups, treated as in Experiment 1, and tested in extinction. There was no significant difference in the resistance to extinction of the two groups. In Experiment 3, the responding of rats trained in a punished stepdown response paradigm and then given an intragastric injection of PCPA took longer to recover than the responding of water-injected controls. These observations suggest that serotonergic neurons might play a role in extinction processes.

  4. Calibrating the end-Permian mass extinction.

    Science.gov (United States)

    Shen, Shu-zhong; Crowley, James L; Wang, Yue; Bowring, Samuel A; Erwin, Douglas H; Sadler, Peter M; Cao, Chang-qun; Rothman, Daniel H; Henderson, Charles M; Ramezani, Jahandar; Zhang, Hua; Shen, Yanan; Wang, Xiang-dong; Wang, Wei; Mu, Lin; Li, Wen-zhong; Tang, Yue-gang; Liu, Xiao-lei; Liu, Lu-jun; Zeng, Yong; Jiang, Yao-fa; Jin, Yu-gan

    2011-12-09

    The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 million years ago, after a decline of 2 per mil (‰) in δ(13)C over 90,000 years, and coincided with a δ(13)C excursion of -5‰ that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.

  5. Periodicity of extinctions in the geologic past.

    Science.gov (United States)

    Raup, D M; Sepkoski, J J

    1984-02-01

    The temporal distribution of the major extinctions over the past 250 million years has been investigated statistically using various forms of time series analysis. The analyzed record is based on variation in extinction intensity for fossil families of marine vertebrates, invertebrates, and protozoans and contains 12 extinction events. The 12 events show a statistically significant periodicity (P less than 0.01) with a mean interval between events of 26 million years. Two of the events coincide with extinctions that have been previously linked to meteorite impacts (terminal Cretaceous and Late Eocene). Although the causes of the periodicity are unknown, it is possible that they are related to extraterrestrial forces (solar, solar system, or galactic).

  6. Three Color Particle Optical Extinction Monitor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to design, build and test a multi-color (red, green, blue) particle optical extinction monitor suitable for use in either land or airborne applications....

  7. Optical atmospheric extinction over Cerro Paranal

    National Research Council Canada - National Science Library

    Patat, F; Moehler, S; O'Brien, K; Pompei, E; Bensby, T; Carraro, G; Ugarte Postigo, de, A; Fox, A; Gavignaud, I; James, G; Korhonen, H; Ledoux, C; Randall, S; Sana, H.A.A; Smoker, J; Stefl, S; Szeifert, T

    2011-01-01

    Aims. The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with the purpose of providing the community with a function...

  8. Extinction in the Lotka-Volterra model.

    Science.gov (United States)

    Parker, Matthew; Kamenev, Alex

    2009-08-01

    Birth-death processes often exhibit an oscillatory behavior. We investigate a particular case where the oscillation cycles are marginally stable on the mean-field level. An iconic example of such a system is the Lotka-Volterra model of predator-prey interaction. Fluctuation effects due to discreteness of the populations destroy the mean-field stability and eventually drive the system toward extinction of one or both species. We show that the corresponding extinction time scales as a certain power-law of the population sizes. This behavior should be contrasted with the extinction of models stable in the mean-field approximation. In the latter case the extinction time scales exponentially with size.

  9. Biomarker Records Associated with Mass Extinction Events

    Science.gov (United States)

    Whiteside, Jessica H.; Grice, Kliti

    2016-06-01

    The history of life on Earth is punctuated by a series of mass extinction episodes that vary widely in their magnitude, duration, and cause. Biomarkers are a powerful tool for the reconstruction of historical environmental conditions and can therefore provide insights into the cause and responses to ancient extinction events. In examining the five largest mass extinctions in the geological record, investigators have used biomarkers to elucidate key processes such as eutrophy, euxinia, ocean acidification, changes in hydrological balance, and changes in atmospheric CO2. By using these molecular fossils to understand how Earth and its ecosystems have responded to unusual environmental activity during these extinctions, models can be made to predict how Earth will respond to future changes in its climate.

  10. Anthropogenic stressors and riverine fish extinctions

    NARCIS (Netherlands)

    Dias, M.S.; Tedesco, P.A.; Hugueny, B.; Jézéquel, C.; Beauchard, O.; Brosse, S.; Oberdorff, T.

    2017-01-01

    Human activities are often implicated in the contemporary extinction of contemporary species. Concerningriverine fishes, the major biotic and abiotic threats widely cited include introduction of non-nativespecies, habitat fragmentation and homogenization in stream flow dynamics due to the damming

  11. Caracterizacion de nueve genotipos de maiz (Zea mays L. en relacion a area foliar y coeficiente de extincion de luz Caracterização de nove genótipos de milho (Zea mays L. en relação à área foliar e coeficiente de extinção de luz Evaluation of nine corn (Zea mays L. genotypes in relation to leaf area and light extinction coefficient

    Directory of Open Access Journals (Sweden)

    R.G. Camacho

    1995-08-01

    .A field experiment was carried out to evaluate nine corn genotypes (Arichuna, Baraure, B raquitico, Expe-rimental-2, Foremaiz PB, FM-6, Obregón, Proseca-71 and Tocorón in relation to: mean leaf area per plant, total leaf area per plant (TLA, leaf area index (LAI, grain yield (Y and light extinction coefficient (K at 0.50m, 1.00m, 1.50m, 2.00m and 2.50m of plant height (from soil to flag leaf. Also, correlation and single regression between LAI and yield was performed. Significant genotypical differences for all variables were found, except for mean leaf area per plant Ranging was: mean leaf area per plant (471 cm² for Foremaiz PB and 606 cm² for Baraure; TLA (5,327 cm² for Foremaiz PB and 8,411 for Braquítico; LAI (4.26, Foremaiz PB and 6.67, Braquítico; K (0.23 for Braquítico and 0.42, Arichuna; Y (2, 877, Braquítico and 4,784 kg.ha-1 for Tocoron.The relationship between Y and LAI was not significant (r = 0.07. The relationship of LAI and K was described very well by Beer's law.

  12. Extinction in the Galaxy from surface brightnesses of ESO-LV galaxies: testing 'standard' extinction maps

    OpenAIRE

    Choloniewski, Jacek; Valentijn, Edwin A.

    2003-01-01

    The relative extinction in the Galaxy computed with our new method (Choloniewski and Valentijn 2003, CV) is compared with three patterns: Schlegel, Finkbeiner and Davis (1998, SFD), Burstein and Heiles (1978, BH) and the cosecans law. It is shown that extinction of SFD is more reliable then that of BH since it stronger correlates with our new extinction. The smallest correlation coeffcient have been obtained for the cosecans law. Linear regression analysis show that SFD overestimate the extin...

  13. An Analysis of the Shapes of Ultraviolet Extinction Curves. IV. Extinction without Standards

    OpenAIRE

    Fitzpatrick, Edward L.; Massa, Derck

    2005-01-01

    We present a new method for deriving UV-through-IR extinction curves, based on the use of stellar atmosphere models to provide estimates of the intrinsic (i.e., unreddened) stellar spectral energy distributions (SEDs), rather than unreddened (or lightly reddened) standard stars. We show that this ``extinction-without-standards'' technique greatly increases the accuracy of the derived extinction curves and allows realistic estimations of the uncertainties. An additional benefit of the techniqu...

  14. Demography and the extinction of European Neanderthals

    DEFF Research Database (Denmark)

    Sørensen, Bent

    2011-01-01

    Causes previously suggested for the sudden extinction of Neanderthals (Homo neanderthalensis) in Europe, starting around 35,000 years ago, comprise food shortage, climatic effects and violence from Modern Humans. The aim here is to formulate a demographic model with reconstructed fertility and de...... Human newcomers during the last part of the period. The conclusion is that other reasons for extinction than climate or starvation must be sought....

  15. Software fires detection and extinction for forest

    Directory of Open Access Journals (Sweden)

    Juan Carlos García Seco

    2008-12-01

    Full Text Available This article shows the most usual fire detection and forest extinction application technologies at present. We will see all different methods used by these applications that can be found in the Market and some examples. Also, some basic questions about the most influent parameters when a fire must be extinct are shown. Finally, after having shown all the technologies, we will build a model about an intelligent system which not only detects, but also extinguish wildfires.

  16. Extinction rates of established spatial populations

    Science.gov (United States)

    Meerson, Baruch; Sasorov, Pavel V.

    2011-01-01

    This paper deals with extinction of an isolated population caused by intrinsic noise. We model the population dynamics in a “refuge” as a Markov process which involves births and deaths on discrete lattice sites and random migrations between neighboring sites. In extinction scenario I, the zero population size is a repelling fixed point of the on-site deterministic dynamics. In extinction scenario II, the zero population size is an attracting fixed point, corresponding to what is known in ecology as the Allee effect. Assuming a large population size, we develop a WKB (Wentzel-Kramers-Brillouin) approximation to the master equation. The resulting Hamilton’s equations encode the most probable path of the population toward extinction and the mean time to extinction. In the fast-migration limit these equations coincide, up to a canonical transformation, with those obtained, in a different way, by Elgart and Kamenev [Phys. Rev. EPHYADX1539-375510.1103/PhysRevE.70.041106 70, 041106 (2004)]. We classify possible regimes of population extinction with and without an Allee effect and for different types of refuge, and solve several examples analytically and numerically. For a very strong Allee effect, the extinction problem can be mapped into the overdamped limit of the theory of homogeneous nucleation due to Langer [Ann. Phys. (NY)APNYA60003-491610.1016/0003-4916(69)90153-5 54, 258 (1969)]. In this regime, and for very long systems, we predict an optimal refuge size that maximizes the mean time to extinction.

  17. Extinction as the loss of evolutionary history

    OpenAIRE

    Erwin, Douglas H.

    2008-01-01

    Current plant and animal diversity preserves at most 1–2% of the species that have existed over the past 600 million years. But understanding the evolutionary impact of these extinctions requires a variety of metrics. The traditional measurement is loss of taxa (species or a higher category) but in the absence of phylogenetic information it is difficult to distinguish the evolutionary depth of different patterns of extinction: the same species loss can encompass very different losses of evolu...

  18. Demography and the extinction of European Neanderthals

    DEFF Research Database (Denmark)

    Sørensen, Bent

    2011-01-01

    Causes previously suggested for the sudden extinction of Neanderthals (Homo neanderthalensis) in Europe, starting around 35,000 years ago, comprise food shortage, climatic effects and violence from Modern Humans. The aim here is to formulate a demographic model with reconstructed fertility and de...... Human newcomers during the last part of the period. The conclusion is that other reasons for extinction than climate or starvation must be sought....

  19. How does climate change cause extinction?

    Science.gov (United States)

    Cahill, Abigail E; Aiello-Lammens, Matthew E; Fisher-Reid, M Caitlin; Hua, Xia; Karanewsky, Caitlin J; Ryu, Hae Yeong; Sbeglia, Gena C; Spagnolo, Fabrizio; Waldron, John B; Warsi, Omar; Wiens, John J

    2013-01-07

    Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical support. We find 136 case studies of climatic impacts that are potentially relevant to this topic. However, only seven identified proximate causes of demonstrated local extinctions due to anthropogenic climate change. Among these seven studies, the proximate causes vary widely. Surprisingly, none show a straightforward relationship between local extinction and limited tolerances to high temperature. Instead, many studies implicate species interactions as an important proximate cause, especially decreases in food availability. We find very similar patterns in studies showing decreases in abundance associated with climate change, and in those studies showing impacts of climatic oscillations. Collectively, these results highlight our disturbingly limited knowledge of this crucial issue but also support the idea that changing species interactions are an important cause of documented population declines and extinctions related to climate change. Finally, we briefly outline general research strategies for identifying these proximate causes in future studies.

  20. Compound Stimulus Extinction Reduces Spontaneous Recovery in Humans

    Science.gov (United States)

    Coelho, Cesar A. O.; Dunsmoor, Joseph E.; Phelps, Elizabeth A.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design ("deepened extinction") shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately…

  1. The extinction of the West African lion: whose responsibility?

    NARCIS (Netherlands)

    Nollkaemper, A.

    2014-01-01

    A recently published study showed that the lion in West Africa is now critically endangered and faces extinction. From one angle, this would be just one of the large (though unknown) number of species that has previously faced extinction or has even become extinct. But the risk of extinction of some

  2. The extinction of the West African lion: whose responsibility?

    NARCIS (Netherlands)

    A. Nollkaemper

    2014-01-01

    A recently published study showed that the lion in West Africa is now critically endangered and faces extinction. From one angle, this would be just one of the large (though unknown) number of species that has previously faced extinction or has even become extinct. But the risk of extinction of some

  3. Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles

    Science.gov (United States)

    Mamouri, Rodanthi-Elisavet; Ansmann, Albert

    2017-09-01

    We applied the recently introduced polarization lidar-photometer networking (POLIPHON) technique for the first time to triple-wavelength polarization lidar measurements at 355, 532, and 1064 nm. The lidar observations were performed at Barbados during the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in the summer of 2014. The POLIPHON method comprises the traditional lidar technique to separate mineral dust and non-dust backscatter contributions and the new, extended approach to separate even the fine and coarse dust backscatter fractions. We show that the traditional and the advanced method are compatible and lead to a consistent set of dust and non-dust profiles at simplified, less complex aerosol layering and mixing conditions as is the case over the remote tropical Atlantic. To derive dust mass concentration profiles from the lidar observations, trustworthy extinction-to-volume conversion factors for fine, coarse, and total dust are needed and obtained from an updated, extended Aerosol Robotic Network sun photometer data analysis of the correlation between the fine, coarse and total dust volume concentration and the respective fine, coarse, and total dust extinction coefficient for all three laser wavelengths. Conversion factors (total volume to extinction) for pure marine aerosol conditions and continental anthropogenic aerosol situations are presented in addition. As a new feature of the POLIPHON data analysis, the Raman lidar method for particle extinction profiling is used to identify the aerosol type (marine or anthropogenic) of the non-dust aerosol fraction. The full POLIPHON methodology was successfully applied to a SALTRACE case and the results are discussed. We conclude that the 532 nm polarization lidar technique has many advantages in comparison to 355 and 1064 nm polarization lidar approaches and leads to the most robust and accurate POLIPHON products.

  4. Night-sky brightness and extinction at Mt. Shatdzhatmaz

    CERN Document Server

    Kornilov, V; Voziakova, O; Shatsky, N; Safonov, B; Gorbunov, I; Potanin, S; Cheryasov, D; Senik, V

    2016-01-01

    The photometric sky quality of Mt. Shatdzhatmaz, the site of Sternberg Astronomical Institute Caucasian Observatory 2.5 m telescope, is characterized here by the statistics of the night-time sky brightness and extinction. The data were obtained as a by-product of atmospheric optical turbulence measurements with the MASS (Multi-Aperture Scintillation Sensor) device conducted in 2007--2013. The factors biasing night-sky brightness measurements are considered and a technique to reduce their impact on the statistics is proposed. The single-band photometric estimations provided by MASS are easy to transform to the standard photometric bands. The median moonless night-sky brightness is 22.1, 21.1, 20.3, and 19.0 mag per square arcsec for the $B$, $V$, $R$, and $I$ spectral bands, respectively. The median extinction coefficients for the same photometric bands are 0.28, 0.17, 0.13, and 0.09 mag. The best atmospheric transparency is observed in winter.

  5. Night-sky brightness and extinction at Mt Shatdzhatmaz

    Science.gov (United States)

    Kornilov, V.; Kornilov, M.; Voziakova, O.; Shatsky, N.; Safonov, B.; Gorbunov, I.; Potanin, S.; Cheryasov, D.; Senik, V.

    2016-11-01

    The photometric sky quality of Mt Shatdzhatmaz, the site of the Sternberg Astronomical Institute Caucasian Observatory 2.5-m telescope, is characterized here by the statistics of the night-time sky brightness and extinction. The data were obtained as a by-product of atmospheric optical turbulence measurements with the MASS (Multi-Aperture Scintillation Sensor) device conducted in 2007-2013. The factors biasing night-sky brightness measurements are considered and a technique to reduce their impact on the statistics is proposed. The single-band photometric estimations provided by MASS are easy to transform to the standard photometric bands. The median moonless night-sky brightness is 22.1, 21.1, 20.3 and 19.0 mag arcsec-2 for the B, V, R and I spectral bands, respectively. The median extinction coefficients for the same photometric bands are 0.28, 0.17, 0.13 and 0.09 mag. The best atmospheric transparency is observed in winter.

  6. Variations in the light extinction coefficient of elemental carbon in the Indian outflow

    Science.gov (United States)

    Andersson, August; Sheesley, Rebecca J.; Krusâ, Martin; Kirillova, Elena; Budhavant, Krishnakant; Rao, P. S. P.; Praveen, P. S.; Gustafsson, Örjan

    2010-05-01

    High wintertime concentrations of black carbon aerosols (BCA) over South Asia and the northern Indian Ocean are thought to have a large impact on the regional climate. Direct absorption of sunlight by BCAs causes heating of the atmosphere and cooling at the surface. To quantify such effects it is important to characterize a number of different properties of the aerosols. Here we report the concentrations of the organic carbon (OC) and elemental carbon (EC) as well as absorptive properties of these aerosols. Samples were collected during a continuous 14-month campaign Dec 2008 - Mar 2009 at Sinaghad in Western India and on Hanimaadhoo, the Northernmost Island in the Maldives. This data set suggests that the absorptive properties of the BCAs are variable, sometimes by a factor of 4 compared to the mean. This observation adds to the complexity of calculating the radiative forcing for BCAs, reinforcing previous observations that parameters such as internal mixing and knowledge about the sources need to be taken into account.

  7. Extinction rates in North American freshwater fishes, 1900-2010

    Science.gov (United States)

    Burkhead, Noel M.

    2012-01-01

    Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). In the twentieth century, freshwater fishes had the highest extinction rate worldwide among vertebrates. The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

  8. Raman Lidar Measurements of Aerosol Extinction and Backscattering. Report 1; Methods and Comparisons

    Science.gov (United States)

    Ferrare, R. A.; Melfi, S. H.; Whiteman, D. N.; Evans, K. D.; Leifer, R.

    1998-01-01

    This paper examines the aerosol backscattering and extinction profiles measured at night by the NASA Goddard Space Flight Center Scanning Raman Lidar (SRL) during the remote cloud sensing (RCS) intensive operations period (IOP) at the Department of Energy Atmospheric Radiation Measurement (ARM) southern Great Plains (SGP) site in April 1994. These lidar data are used to derive aerosol profiles for altitudes between 0.0 1 5 and 5 km. Since this lidar detects Raman scattering from nitrogen and oxygen molecules as well as the elastic scattering from molecules and aerosols, it measures both aerosol backscattering and extinction simultaneously. The aerosol extinction/backscattering ratio varied between approximately 30 sr and 75 sr at 351 nm. Aerosol optical thicknesses derived by integrating the lidar profiles of aerosol extinction measured at night between 0. I and 5 km are found to be about 10-40% lower than those measured by a Sun photometer during the day. This difference is attributed to the contribution by stratospheric aerosols not included in the lidar estimates as well as to diurnal differences in aerosol properties and concentrations. Aerosol profiles close to the surface were acquired by pointing the lidar nearly horizontally. Measurements of aerosol scattering from a tower-mounted nephelometer are found to be 40% lower than lidar measurements of aerosol extinction over a wide range of relative humidities even after accounting for the difference in wavelengths. The reasons for this difference are not clear but may be due to the inability of the nephelometer to accurately measure scattering by large particles.

  9. Coeficiente de ensanchamiento “Ce” en la laminación de perfiles con una cara inclinada. // Coefficient of widening “Ce” in the rolling of profiles with an inclined side

    Directory of Open Access Journals (Sweden)

    H. F. Cabrera Araujo

    2001-04-01

    Full Text Available Se presenta la deducción teórica del coeficiente de ensanchamiento “Ce” para el caso de la laminación de perfiles con una cara inclinada, norecogido en la literatura especializada, aplicando el método propuesto por A. V. Minkin. Además se deduce una ecuación que expresa larelación entre las dimensiones del calibre con los parámetros de la deformación.Palabras claves: laminación, deformación plástica, calibres, ensanchamiento________________________________________________________________________AbstractThe theorical deduction of the coefficient of widening “Ce” is presented for the case of the rolled steel shapes with an inclinedside, not presented in the specialized literature, applying the metod proposed by A. V. Minkin. Its also deduced an ecuation thatexpresses the relatonship between the dimensions of the caliber and the parameters of the deformation.Key words: plastic deformation, caliber, widening, rolling mill

  10. Immediate Extinction Causes a Less Durable Loss of Performance than Delayed Extinction following Either Fear or Appetitive Conditioning

    Science.gov (United States)

    Woods, Amanda M.; Bouton, Mark E.

    2008-01-01

    Five experiments with rat subjects compared the effects of immediate and delayed extinction on the durability of extinction learning. Three experiments examined extinction of fear conditioning (using the conditioned emotional response method), and two experiments examined extinction of appetitive conditioning (using the food-cup entry method). In…

  11. A photometricity and extinction monitor at the Apache Point Observatory

    CERN Document Server

    Hogg, D W; Schlegel, D J; Gunn, J E; Hogg, David W.; Finkbeiner, Douglas P.; Schlegel, David J.; Gunn, James E.

    2001-01-01

    An unsupervised software ``robot'' that automatically and robustly reduces and analyzes CCD observations of photometric standard stars is described. The robot measures extinction coefficients and other photometric parameters in real time and, more carefully, on the next day. It also reduces and analyzes data from an all-sky $10 \\mu m$ camera to detect clouds; photometric data taken during cloudy periods are automatically rejected. The robot reports its findings back to observers and data analysts via the World-Wide Web. It can be used to assess photometricity, and to build data on site conditions. The robot's automated and uniform site monitoring represents a minimum standard for any observing site with queue scheduling, a public data archive, or likely participation in any future National Virtual Observatory.

  12. Trophically Unique Species Are Vulnerable to Cascading Extinction

    OpenAIRE

    Petchey, Owen L.; Eklöf, Anna; Borrvall, Charlotte; Ebenman, Bo

    2008-01-01

    Understanding which species might become extinct and the consequences of such loss is critical. One consequence is a cascade of further, secondary extinctions. While a significant amount is known about the types of communities and species that suffer secondary extinctions, little is known about the consequences of secondary extinctions for biodiversity. Here we examine the effect of these secondary extinctions on trophic diversity, the range of trophic roles played by the species in a communi...

  13. Finite time extinction for nonlinear fractional evolution equations and related properties

    Directory of Open Access Journals (Sweden)

    Jesus Ildefonso Diaz

    2016-08-01

    Full Text Available The finite time extinction phenomenon (the solution reaches an equilibrium after a finite time is peculiar to certain nonlinear problems whose solutions exhibit an asymptotic behavior entirely different from the typical behavior of solutions associated to linear problems. The main goal of this work is twofold. Firstly, we extend some of the results known in the literature to the case in which the ordinary time derivative is considered jointly with a fractional time differentiation. Secondly, we consider the limit case when only the fractional derivative remains. The latter is the most extraordinary case, since we prove that the finite time extinction phenomenon still appears, even with a non-smooth profile near the extinction time.

  14. Conservation Risks: When Will Rhinos be Extinct?

    Science.gov (United States)

    Haas, Timothy C; Ferreira, Sam M

    2016-08-01

    We develop a risk intelligence system for biodiversity enterprises. Such enterprises depend on a supply of endangered species for their revenue. Many of these enterprises, however, cannot purchase a supply of this resource and are largely unable to secure the resource against theft in the form of poaching. Because replacements are not available once a species becomes extinct, insurance products are not available to reduce the risk exposure of these enterprises to an extinction event. For many species, the dynamics of anthropogenic impacts driven by economic as well as noneconomic values of associated wildlife products along with their ecological stressors can help meaningfully predict extinction risks. We develop an agent/individual-based economic-ecological model that captures these effects and apply it to the case of South African rhinos. Our model uses observed rhino dynamics and poaching statistics. It seeks to predict rhino extinction under the present scenario. This scenario has no legal horn trade, but allows live African rhino trade and legal hunting. Present rhino populations are small and threatened by a rising onslaught of poaching. This present scenario and associated dynamics predicts continued decline in rhino population size with accelerated extinction risks of rhinos by 2036. Our model supports the computation of extinction risks at any future time point. This capability can be used to evaluate the effectiveness of proposed conservation strategies at reducing a species' extinction risk. Models used to compute risk predictions, however, need to be statistically estimated. We point out that statistically fitting such models to observations will involve massive numbers of observations on consumer behavior and time-stamped location observations on thousands of animals. Finally, we propose Big Data algorithms to perform such estimates and to interpret the fitted model's output.

  15. Elevational distribution and extinction risk in birds.

    Directory of Open Access Journals (Sweden)

    Rachel L White

    Full Text Available Mountainous regions are hotspots of terrestrial biodiversity. Unlike islands, which have been the focus of extensive research on extinction dynamics, fewer studies have examined mountain ranges even though they face increasing threats from human pressures - notably habitat conversion and climate change. Limits to the taxonomic and geographical extent and resolution of previously available information have precluded an explicit assessment of the relative role of elevational distribution in determining extinction risk. We use a new global species-level avian database to quantify the influence of elevational distribution (range, maximum and midpoint on extinction risk in birds at the global scale. We also tested this relationship within biogeographic realms, higher taxonomic levels, and across phylogenetic contrasts. Potential confounding variables (i.e. phylogenetic, distributional, morphological, life history and niche breadth were also tested and controlled for. We show that the three measures of elevational distribution are strong negative predictors of avian extinction risk, with elevational range comparable and complementary to that of geographical range size. Extinction risk was also found to be positively associated with body weight, development and adult survival, but negatively associated with reproduction and niche breadth. The robust and consistent findings from this study demonstrate the importance of elevational distribution as a key driver of variation in extinction dynamics in birds. Our results also highlight elevational distribution as a missing criterion in current schemes for quantifying extinction risk and setting species conservation priorities in birds. Further research is recommended to test for generality across non-avian taxa, which will require an advance in our knowledge of species' current elevational ranges and increased efforts to digitise and centralise such data.

  16. Converting Sabine absorption coefficients to random incidence absorption coefficients

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2013-01-01

    Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a sample and non-uniform intensity in the reverberation chambers under test. In this study, conversion methods from Sabine absorption...... coefficients to random incidence absorption coefficients are proposed. The overestimations of the Sabine absorption coefficient are investigated theoretically based on Miki's model for porous absorbers backed by a rigid wall or an air cavity, resulting in conversion factors. Additionally, three optimizations...

  17. Impact of Life History on Fear Memory and Extinction

    Directory of Open Access Journals (Sweden)

    Jasmin Remmes

    2016-10-01

    Full Text Available Behavioral profiles are strongly shaped by an individual’s whole life experience. The accumulation of negative experiences over lifetime is thought to promote anxiety-like behavior in adulthood (‘allostatic load hypothesis’. In contrast, the ‘mismatch hypothesis’ of psychiatric disease suggests that high levels of anxiety-like behavior are the result of a discrepancy between early and late environment. The aim of the present study was to investigate how different life histories shape the expression of anxiety-like behavior and modulate fear memory. In addition, we aimed to clarify which of the two hypotheses can better explain the modulation of anxiety and fear. For this purpose, male mice grew up under either adverse or beneficial conditions during early phase of life. In adulthood they were further subdivided in groups that either matched or mismatched the condition experienced before, resulting in four different life histories. The main results were: (i Early life benefit followed by late life adversity caused decreased levels of anxiety-like behavior. (ii Accumulation of adversity throughout life history led to impaired fear extinction learning. Late life adversity as compared to late life benefit mainly affected extinction training, while early life adversity as compared to early life benefit interfered with extinction recall. Concerning anxiety-like behavior, the results do neither support the allostatic load nor the mismatch hypothesis, but rather indicate an anxiolytic effect of a mismatched early beneficial and later adverse life history. In contrast, fear memory was strongly affected by the accumulation of adverse experiences over the lifetime, therefore supporting allostatic load hypothesis. In summary, this study highlights that anxiety-like behavior and fear memory are differently affected by specific combinations of adverse or beneficial events experienced throughout life.

  18. Measurements of DSD Second Moment Based on Laser Extinction

    Science.gov (United States)

    Lane, John E.; Jones, Linwood; Kasparis, Takis C.; Metzger, Philip

    2013-01-01

    Using a technique recently developed for estimating the density of surface dust dispersed during a rocket landing, measuring the extinction of a laser passing through rain (or dust in the rocket case) yields an estimate of the 2nd moment of the particle cloud, and rainfall drop size distribution (DSD) in the terrestrial meteorological case. With the exception of disdrometers, instruments that measure rainfall make in direct measurements of the DSD. Most common of these instruments are the rainfall rate gauge measuring the 1 1/3 th moment, (when using a D(exp 2/3) dependency on terminal velocity). Instruments that scatter microwaves off of hydrometeors, such as the WSR-880, vertical wind profilers, and microwave disdrometers, measure the 6th moment of the DSD. By projecting a laser onto a target, changes in brightness of the laser spot against the target background during rain, yield a measurement of the DSD 2nd moment, using the Beer-Lambert law. In order to detect the laser attenuation within the 8-bit resolution of most camera image arrays, a minimum path length is required, depending on the intensity of the rainfall rate. For moderate to heavy rainfall, a laser path length of 100 m is sufficient to measure variations in optical extinction using a digital camera. A photo-detector could replace the camera, for automated installations. In order to spatially correlate the 2nd moment measurements to a collocated disdrometer or tipping bucket, the laser's beam path can be reflected multiple times using mirrors to restrict the spatial extent of the measurement. In cases where a disdrometer is not available, complete DSD estimates can be produced by parametric fitting of DSD model to the 2nd moment data in conjunction with tipping bucket data. In cases where a disdrometer is collocated, the laser extinction technique may yield a significant improvement to insitu disdrometer validation and calibration strategies

  19. Serotonin transporter polyadenylation polymorphism modulates the retention of fear extinction memory.

    Science.gov (United States)

    Hartley, Catherine A; McKenna, Morgan C; Salman, Rabia; Holmes, Andrew; Casey, B J; Phelps, Elizabeth A; Glatt, Charles E

    2012-04-01

    Growing evidence suggests serotonin's role in anxiety and depression is mediated by its effects on learned fear associations. Pharmacological and genetic manipulations of serotonin signaling in mice alter the retention of fear extinction learning, which is inversely associated with anxious temperament in mice and humans. Here, we test whether genetic variation in serotonin signaling in the form of a common human serotonin transporter polyadenylation polymorphism (STPP/rs3813034) is associated with spontaneous fear recovery after extinction. We show that the risk allele of this polymorphism is associated with impaired retention of fear extinction memory and heightened anxiety and depressive symptoms. These STPP associations in humans mirror the phenotypic effects of serotonin transporter knockout in mice, highlighting the STPP as a potential genetic locus underlying interindividual differences in serotonin transporter function in humans. Furthermore, we show that the serotonin transporter polyadenylation profile associated with the STPP risk allele is altered through the chronic administration of fluoxetine, a treatment that also facilitates retention of extinction learning. The propensity to form persistent fear associations due to poor extinction recall may be an intermediate phenotype mediating the effects of genetic variation in serotonergic function on anxiety and depression. The consistency and specificity of these data across species provide robust support for this hypothesis and suggest that the little-studied STPP may be an important risk factor for mood and anxiety disorders in humans.

  20. Facilitation of extinction and re-extinction of operant behavior in mice by chlordiazepoxide and D-cycloserine.

    Science.gov (United States)

    Leslie, Julian C; Norwood, Kelly

    2013-05-01

    The aim was to compare operant extinction with re-extinction following re-acquisition and to investigate neuropharmacological mechanisms through administration of drugs potentiating GABAergic or glutamatergic systems. Groups of C57Bl/6 mice were trained to lever press for food on a fixed ratio schedule, then extinguished with or without pre-session chlordiazepoxide or post-session d-cycloserine administration (15mg/kg in each case), then retrained to lever press for food, then re-extinguished with or without pre-session chlordiazepoxide or post-session d-cycloserine. Under vehicle injections, extinction and re-extinction curves were indistinguishable, but drug treatments showed that there was less resistance to extinction in the re-extinction phase. Chlordiazepoxide facilitated extinction and re-extinction, with an earlier effect during re-extinction. d-Cycloserine also facilitated extinction and re-extinction, with some evidence of an earlier effect during re-extinction. These results replicate and extend earlier findings with operant extinction, but differ from some previous reports of d-cycloserine on re-extinction of Pavlovian conditioned fear. Implications for accounts of the similarities and differences between neural mechanisms of extinction following either Pavlovian or operant conditioning, and applications of these findings, are discussed.

  1. Quantitative analysis of forest fire extinction efficiency

    Directory of Open Access Journals (Sweden)

    Miguel E. Castillo-Soto

    2015-08-01

    Full Text Available Aim of study: Evaluate the economic extinction efficiency of forest fires, based on the study of fire combat undertaken by aerial and terrestrial means. Area of study, materials and methods: Approximately 112,000 hectares in Chile. Records of 5,876 forest fires that occurred between 1998 and 2009 were analyzed. The area further provides a validation sector for results, by incorporating databases for the years 2010 and 2012. The criteria used for measuring extinction efficiency were economic value of forestry resources, Contraction Factor analysis and definition of the extinction costs function. Main results: It is possible to establish a relationship between burnt area, extinction costs and economic losses. The method proposed may be used and adapted to other fire situations, requiring unit costs for aerial and terrestrial operations, economic value of the property to be protected and speed attributes of fire spread in free advance. Research highlights: The determination of extinction efficiency in containment works of forest fires and potential projection of losses, different types of plant fuel and local conditions favoring the spread of fire broaden the admissible ranges of a, φ and Ce considerably.

  2. Fluoxetine Facilitates Fear Extinction Through Amygdala Endocannabinoids.

    Science.gov (United States)

    Gunduz-Cinar, Ozge; Flynn, Shaun; Brockway, Emma; Kaugars, Katherine; Baldi, Rita; Ramikie, Teniel S; Cinar, Resat; Kunos, George; Patel, Sachin; Holmes, Andrew

    2016-05-01

    Pharmacologically elevating brain endocannabinoids (eCBs) share anxiolytic and fear extinction-facilitating properties with classical therapeutics, including the selective serotonin reuptake inhibitor, fluoxetine. There are also known functional interactions between the eCB and serotonin systems and preliminary evidence that antidepressants cause alterations in brain eCBs. However, the potential role of eCBs in mediating the facilitatory effects of fluoxetine on fear extinction has not been established. Here, to test for a possible mechanistic contribution of eCBs to fluoxetine's proextinction effects, we integrated biochemical, electrophysiological, pharmacological, and behavioral techniques, using the extinction-impaired 129S1/Sv1mJ mouse strain. Chronic fluoxetine treatment produced a significant and selective increase in levels of anandamide in the BLA, and an associated decrease in activity of the anandamide-catabolizing enzyme, fatty acid amide hydrolase. Slice electrophysiological recordings showed that fluoxetine-induced increases in anandamide were associated with the amplification of eCB-mediated tonic constraint of inhibitory, but not excitatory, transmission in the BLA. Behaviorally, chronic fluoxetine facilitated extinction retrieval in a manner that was prevented by systemic or BLA-specific blockade of CB1 receptors. In contrast to fluoxetine, citalopram treatment did not increase BLA eCBs or facilitate extinction. Taken together, these findings reveal a novel, obligatory role for amygdala eCBs in the proextinction effects of a major pharmacotherapy for trauma- and stressor-related disorders and anxiety disorders.

  3. Determining the extragalactic extinction law with SALT

    CERN Document Server

    Finkelman, Ido; Kniazev, Alexei Y; Buckley, David; O'Donoghue, Darragh; Hashimoto, Yas; Loaring, Nicola; Romero, Encarni; Still, Martin; Vaisanen, Petri

    2008-01-01

    We present CCD imaging observations of early-type galaxies with dark lanes obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. We derive the extinction law by the extragalactic dust in the dark lanes in the spectral range 1.11mu m^{-1} < lambda^{-1} < 2.94 mu m^{-1} by fitting model galaxies to the unextinguished parts of the image, and subtracting from these the actual images. We find that the extinction curves run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic enviroment are similar to those of the Milky Way. The ratio of the total V band extinction to the selective extinction between the V and B bands is derived for each galaxy with an average of 2.82+-0.38, compared to a canonical value of 3.1 for the Milky Way. The similar values imply that galaxies with well-defined dark lanes have characteristic dust grain sizes similar to those of Galactic dust.

  4. Disease and the dynamics of extinction.

    Science.gov (United States)

    McCallum, Hamish

    2012-10-19

    Invading infectious diseases can, in theory, lead to the extinction of host populations, particularly if reservoir species are present or if disease transmission is frequency-dependent. The number of historic or prehistoric extinctions that can unequivocally be attributed to infectious disease is relatively small, but gathering firm evidence in retrospect is extremely difficult. Amphibian chytridiomycosis and Tasmanian devil facial tumour disease (DFTD) are two very different infectious diseases that are currently threatening to cause extinctions in Australia. These provide an unusual opportunity to investigate the processes of disease-induced extinction and possible management strategies. Both diseases are apparently recent in origin. Tasmanian DFTD is entirely host-specific but potentially able to cause extinction because transmission depends weakly, if at all, on host density. Amphibian chytridiomycosis has a broad host range but is highly pathogenic only to some populations of some species. At present, both diseases can only be managed by attempting to isolate individuals or populations from disease. Management options to accelerate the process of evolution of host resistance or tolerance are being investigated in both cases. Anthropogenic changes including movement of diseases and hosts, habitat destruction and fragmentation and climate change are likely to increase emerging disease threats to biodiversity and it is critical to further develop strategies to manage these threats.

  5. Mass Extinctions and Biosphere-Geosphere Stability

    Science.gov (United States)

    Rothman, Daniel; Bowring, Samuel

    2015-04-01

    Five times in the past 500 million years, mass extinctions have resulted in the loss of greater than three-fourths of living species. Each of these events is associated with significant environmental change recorded in the carbon-isotopic composition of sedimentary rocks. There are also many such environmental events in the geologic record that are not associated with mass extinctions. What makes them different? Two factors appear important: the size of the environmental perturbation, and the time scale over which it occurs. We show that the natural perturbations of Earth's carbon cycle during the past 500 million years exhibit a characteristic rate of change over two orders of magnitude in time scale. This characteristic rate is consistent with the maximum rate that limits quasistatic (i.e., near steady-state) evolution of the carbon cycle. We identify this rate with marginal stability, and show that mass extinctions occur on the fast, unstable side of the stability boundary. These results suggest that the great extinction events of the geologic past, and potentially a "sixth extinction" associated with modern environmental change, are characterized by common mechanisms of instability.

  6. The transition from memory retrieval to extinction

    Directory of Open Access Journals (Sweden)

    Cammarota Martín

    2004-01-01

    Full Text Available Memory is measured by measuring retrieval. Retrieval is often triggered by the conditioned stimulus (CS; however, as known since Pavlov, presentation of the CS alone generates extinction. One-trial avoidance (IA is a much used conditioned fear paradigm in which the CS is the safe part of a training apparatus, the unconditioned stimulus (US is a footshock and the conditioned response is to stay in the safe area. In IA, retrieval is measured without the US, as latency to step-down from the safe area (i.e., a platform. Extinction is installed at the moment of the first unreinforced test session, as clearly shown by the fact that many drugs, including PKA, ERK and protein synthesis inhibitors as well as NMDA receptor antagonists, hinder extinction when infused into the hippocampus or the basolateral amygdala at the moment of the first test session but not later. Some, but not all the molecular systems required for extinction are also activated by retrieval, further endorsing the hypothesis that although retrieval is behaviorally and biochemically necessary for the generation of extinction, this last process constitutes a new learning secondary to the unreinforced expression of the original trace.

  7. Aerosol extinction in a remote continental region of the Iberian Peninsula during summer

    Science.gov (United States)

    Elias, Thierry; Silva, Ana Maria; Belo, Nuno; Pereira, Sergio; Formenti, Paola; Helas, Günter; Wagner, Frank

    2006-07-01

    Summer in Évora (38°34'N, 7°54'W), Portugal, is described in terms of aerosol properties of extinction of the solar radiation. We create a data set composed of (1) cloud-screened half-day averaged values of aerosol optical thickness (AOT) measured at 7 wavelengths by both a CIMEL Sun/sky-photometer and a YES shadowband radiometer and (2) half day averaged values of aerosol scattering coefficient (ASC) measured at the surface level at two wavelengths by a TSI nephelometer. Spectral dependence of both AOT and ASC gives the column and the surface Ångström exponents, αC and αS, respectively. Measurements are acquired in both 2002 and 2003 summers. Back trajectories are computed. A statistical study of the data set provides thresholds in AOT and αC for a classification of the days. The classification is applied with success to the case study of the 2003 summer heat wave episode and is generalized to the whole data set. In 23% of the cases, the turbidity in Évora is very low, with AOT441 1.2, and to desert dust plumes transported from North Africa within 72 to 120 hours at 700 hPa, with 0.10 < AOT873 < 1.10 and 0.1 < αC < 1.0. The vertical profile is highly variable, and several cases of aerosol mixing in the column are identified. The duration of the aerosol episode during the 2003 summer heat wave is 16 days, which is exceptionally long.

  8. Dust extinction and absorption: the challenge of porous grains

    CERN Document Server

    Voshchinnikov, N V; Henning, T; Dubkova, D N; Henning, Th.

    2005-01-01

    In many models of dusty objects in space the grains are assumed to be composite or fluffy. However, the computation of the optical properties of such particles is still a very difficult problem. We analyze how the increase of grain porosity influences basic features of cosmic dust -- interstellar extinction, dust temperature, infrared bands and millimeter opacity. Porous grains can reproduce the flat extinction across the $3 - 8 \\mkm$ wavelength range measured for several lines of sight by {\\it ISO} and {\\it Spitzer}. Porous grains are generally cooler than compact grains. At the same time, the temperature of very porous grains becomes slightly larger in the case of the EMT-Mie calculations in comparison with the results found from the layered-sphere model. The layered-sphere model predicts a broadening of infrared bands and a shift of the peak position to larger wavelengths as porosity grows. In the case of the EMT-Mie model variations of the feature profile are less significant. It is also shown that the mi...

  9. Astrophysical life extinctions what killed the dinosaurs?

    CERN Document Server

    Dar, Arnon

    1999-01-01

    Geological records indicate that the exponential diversification of marine and continental life on Earth in the past 500 My was interrupted by many life extinctions. They also indicate that the major mass extinctions were correlated in time with large meteoritic impacts, gigantic volcanic eruptions, sea regressions and drastic changes in global climate. Some of these catastrophes coincided in time. The astrophysical life extinction mechanisms which were proposed so far, in particular, meteoritic impacts, nearby supernova explosions, passage through molecular or dark matter clouds, and Galactic gamma/cosmic ray bursts cannot explain the time coincidences between these catastrophes. However, recent observations suggest that many planetary-mass objects may be present in the outer solar system between the Kuiper belt and the Oort cloud. Gravitational perturbations may occasionally bring them into the inner solar system. Their passage near Earth could have generated gigantic tidal waves, large volcanic eruptions, ...

  10. Life extinctions by neutron star mergers

    CERN Document Server

    Dar, Arnon; Shaviv, N J; Dar, Arnon; Laor, Ari; Shaviv, Nir J.

    1997-01-01

    High energy cosmic ray jets from nearby mergers or accretion induced collapse (AIC) of neutron stars (NS) that hit the atmosphere can produce lethal fluxes of atmospheric muons at ground level, underground and underwater, destroy the ozone layer and radioactivate the environment. They could have caused most of the massive life extinctions on planet Earth in the past 600 My. Biological mutations due to ionizing radiations could have caused the fast appearance of new species after the massive extinctions. An early warning of future extinctions due to NS mergers may be obtained by identifying, mapping and timing all the nearby binary neutron stars systems. A warning of an approaching cosmic ray burst from a nearby NS merger/AIC may be provided by a very intense gamma ray burst which preceeds it.

  11. Mammal extinctions, body size, and paleotemperature

    Science.gov (United States)

    Bown, T.M.; Holroyd, P.A.; Rose, K.D.

    1994-01-01

    There is a general inverse relationship between the natural logarithm of tooth area (a body size indicator) of some fossil mammals and paleotemperature during approximately 2.9 million years of the early Eocene in the Bighorn Basin of northwest Wyoming. When mean temperatures became warmer, tooth areas tended to become smaller. During colder times, larger species predominated; these generally became larger or remained the same size. Paleotemperature trends also markedly affected patterns of local (and, perhaps, regional) extinction and immigration. New species appeared as immigrants during or near the hottest (smaller forms) and coldest (larger forms) intervals. Paleotemperature trend reversals commonly resulted in the ultimate extinction of both small forms (during cooling intervals) and larger forms (during warming intervals). These immigrations and extinctions mark faunal turnovers that were also modulated by sharp increases in sediment accumulation rate.

  12. Does supplementary reinforcement of stereotypy facilitate extinction?

    Science.gov (United States)

    Dozier, Claudia L; Iwata, Brian A; Wilson, David M; Thomason-Sassi, Jessica L; Roscoe, Eileen M

    2013-01-01

    Results of several studies suggest that delivery of supplemental (social) reinforcement for stereotypy might facilitate its subsequent extinction. We examined this possibility with 9 subjects who engaged in stereotypy by including methodological refinements to ensure that (a) subjects' stereotypy was maintained in the absence of social consequences, (b) supplementary reinforcers were highly preferred and were shown to be reinforcers for some behavior, and (c) subjects were exposed to lengthy reinforcement and extinction conditions. In spite of these modifications, only 4 subjects' stereotypy increased when supplementary reinforcement was delivered contingent on stereotypy, and no subject's stereotypy decreased below initial baseline levels when social reinforcement was subsequently withheld. Decreases in stereotypy occurred with the implementation of noncontingent reinforcement. Thus, delivery of supplementary reinforcers either did not increase stereotypy or did not facilitate extinction of stereotypy maintained by automatic reinforcement. We discuss the practical and conceptual bases of these results with respect to our current understanding of function-based interventions.

  13. Opportunities and costs for preventing vertebrate extinctions

    DEFF Research Database (Denmark)

    Conde, Dalia Amor; Colchero, Fernando; Güneralp, Burak

    2015-01-01

    -oriented organisations that aims to protect Critically Endangered and Endangered species restricted to single sites, has identified 920 species of mammals, birds, amphibians, reptiles, conifers and reef-building corals in 588 ‘trigger’ sites [3] . These are arguably the most irreplaceable category of important...... causes of biodiversity loss in part by establishing protected areas (Target 11) and preventing species extinctions (Target 12). To achieve this, increased interventions will be required for a large number of sites and species. The Alliance for Zero Extinction (AZE) [2] , a consortium of conservation...... biodiversity conservation sites. Protected area coverage of AZE sites is a key indicator of progress towards Target 11 [1] . Moreover, effective conservation of AZE sites is essential to achieve Target 12, as the loss of any of these sites would certainly result in the global extinction of at least one species...

  14. Extinction in four species cyclic competition

    Science.gov (United States)

    Intoy, Ben; Pleimling, Michel

    2013-08-01

    When four species compete stochastically in a cyclic way, the formation of two teams of mutually neutral partners is observed. In this paper we study through numerical simulations the extinction processes that can take place in this system both in the well mixed case as well as on different types of lattices. The different routes to extinction are revealed by the probability distribution of the domination time, i.e. the time needed for one team to fully occupy the system. If swapping is allowed between neutral partners, then the probability distribution is dominated by very long-lived states where a few very large domains persist, each domain being occupied by a mix of individuals from species that form one of the teams. Many aspects of the possible extinction scenarios are lost when only considering averaged quantities, such as for example the mean domination time.

  15. Opportunities and costs for preventing vertebrate extinctions

    DEFF Research Database (Denmark)

    Conde, Dalia Amor; Colchero, Fernando; Güneralp, Burak

    2015-01-01

    -oriented organisations that aims to protect Critically Endangered and Endangered species restricted to single sites, has identified 920 species of mammals, birds, amphibians, reptiles, conifers and reef-building corals in 588 ‘trigger’ sites [3] . These are arguably the most irreplaceable category of important...... causes of biodiversity loss in part by establishing protected areas (Target 11) and preventing species extinctions (Target 12). To achieve this, increased interventions will be required for a large number of sites and species. The Alliance for Zero Extinction (AZE) [2] , a consortium of conservation...... biodiversity conservation sites. Protected area coverage of AZE sites is a key indicator of progress towards Target 11 [1] . Moreover, effective conservation of AZE sites is essential to achieve Target 12, as the loss of any of these sites would certainly result in the global extinction of at least one species...

  16. Abrupt climate change and extinction events

    Science.gov (United States)

    Crowley, Thomas J.

    1988-01-01

    There is a growing body of theoretical and empirical support for the concept of instabilities in the climate system, and indications that abrupt climate change may in some cases contribute to abrupt extinctions. Theoretical indications of instabilities can be found in a broad spectrum of climate models (energy balance models, a thermohaline model of deep-water circulation, atmospheric general circulation models, and coupled ocean-atmosphere models). Abrupt transitions can be of several types and affect the environment in different ways. There is increasing evidence for abrupt climate change in the geologic record and involves both interglacial-glacial scale transitions and the longer-term evolution of climate over the last 100 million years. Records from the Cenozoic clearly show that the long-term trend is characterized by numerous abrupt steps where the system appears to be rapidly moving to a new equilibrium state. The long-term trend probably is due to changes associated with plate tectonic processes, but the abrupt steps most likely reflect instabilities in the climate system as the slowly changing boundary conditions caused the climate to reach some threshold critical point. A more detailed analysis of abrupt steps comes from high-resolution studies of glacial-interglacial fluctuations in the Pleistocene. Comparison of climate transitions with the extinction record indicates that many climate and biotic transitions coincide. The Cretaceous-Tertiary extinction is not a candidate for an extinction event due to instabilities in the climate system. It is quite possible that more detailed comparisons and analysis will indicate some flaws in the climate instability-extinction hypothesis, but at present it appears to be a viable candidate as an alternate mechanism for causing abrupt environmental changes and extinctions.

  17. Extinction Mapping of Nearby Galaxies Using LEGUS

    Science.gov (United States)

    Kahre, Lauren; Walterbos, Rene A. M.; Calzetti, Daniela; Sabbi, Elena; Ubeda, Leonardo; LEGUS Collaboration

    2017-01-01

    Extinction by dust affects studies of star formation and stellar evolution in galaxies. There are different ways to measure the distribution of dust column densities across galaxies. Here we present work based on extinctions measured towards individual massive stars.Isochrones of massive stars lie in the same location on a color-color diagram with little dependence on metallicity and luminosity class, so the extinction can be directly derived from the observed photometry. We develop a method for generating extinction maps using photometry of massive stars from the Hubble Space Telescope for the nearly 50 galaxies observed by the Legacy Extragalactic Ultraviolet Survey (LEGUS). The derived extinction maps will allow us to correct ground-based and HST Halpha maps for extinction, and will be used to constrain changes in the dust-to-gas ratio across the galaxy sample and in different star formation, metallicity and morphological environments. Previous studies have found links between galaxy metallicity and the dust-to-gas mass ratio. Dust abundance and gas metallicity are critical constraints for chemical and galaxy evolution models. We present a study of LEGUS galaxies spanning a range of distances, metallicities, and galaxy morphologies, including metal-poor dwarfs Holmberg I and II and giant spirals NGC 6503 and NGC 628. We see clear evidence for changes in the dust-to-gas mass ratio with changing metallicity. We also examine changes in the dust-to-gas mass ratio with galactocentric radius. Ultimately, we will provide constraints on the dust-to-gas mass ratio across a wide range of galaxy environments.

  18. Extinction rate fragility in population dynamics.

    Science.gov (United States)

    Khasin, M; Dykman, M I

    2009-08-01

    Population extinction is of central interest for population dynamics. It may occur from a large rare fluctuation. We find that, in contrast to related large-fluctuation effects like noise-induced interstate switching, quite generally extinction rates in multipopulation systems display fragility, where the height of the effective barrier to be overcome in the fluctuation depends on the system parameters nonanalytically. We show that one of the best-known models of epidemiology, the susceptible-infectious-susceptible model, is fragile to total population fluctuations.

  19. Extinction space--a method for the quantification and classification of changes in morphospace across extinction boundaries.

    Science.gov (United States)

    Korn, Dieter; Hopkins, Melanie J; Walton, Sonny A

    2013-10-01

    Three main modes of extinction are responsible for reductions in morphological disparity: (1) random (caused by a nonselective extinction event); (2) marginal (a symmetric, selective extinction event trimming the margin of morphospace); and (3) lateral (an asymmetric, selective extinction event eliminating one side of the morphospace). These three types of extinction event can be distinguished from one another by comparing changes in three measures of morphospace occupation: (1) the sum of range along the main axes; (2) the sum of variance; and (3) the position of the centroid. Computer simulations of various extinction events demonstrate that the pre-extinction distribution of taxa (random or normal) in the morphospace has little influence on the quantification of disparity changes, whereas the modes of the extinction events play the major role. Together, the three disparity metrics define an "extinction-space" in which different extinction events can be directly compared with one another. Application of this method to selected extinction events (Frasnian-Famennian, Devonian-Carboniferous, and Permian-Triassic) of the Ammonoidea demonstrate the similarity of the Devonian events (selective extinctions) but the striking difference from the end-Permian event (nonselective extinction). These events differ in their mode of extinction despite decreases in taxonomic diversity of similar magnitude.

  20. Sabine absorption coefficients to random incidence absorption coefficients

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho

    2014-01-01

    Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a specimen and non-uniform intensity in the test chamber. In this study, several methods that convert Sabine absorption coefficients...... into random incidence absorption coefficients for porous absorbers are investigated. Two optimization-based conversion methods are suggested: the surface impedance estimation for locally reacting absorbers and the flow resistivity estimation for extendedly reacting absorbers. The suggested conversion methods...

  1. A History of Infrared Extinction at CTIO, Chile, and A Possible Connection with the el Niño Phenomenon

    CERN Document Server

    Frogel, J A

    1997-01-01

    Extinction coefficients and sensitivity values in the JHKL band-passes measured on nearly 200 nights of observing between 1978 and 1992 on the 1.5-meter and the Blanco 4- meter telescopes at Cerro Tololo Inter-American Observatory are presented and discussed. Analysis of these data shows the following: There are seasonal variations in both the extinction coefficients and sensitivity values that are qualitatively consistent with expected variations in the amount of H2O in the atmosphere - relatively high in the summer months lower in the winter months. The linear correlation coefficients between most of these quantities are statistically significant. The yearly mean values of these quantities also show significant variability of a few hundredths of a magnitude. The correlations between these yearly means are again consistent with variations in the H2O content of the atmosphere. At least some of these longer term variations are closely correlated with quantitative measures of the strength of the atmospheric and...

  2. Beam Extinction Monitoring in the Mu2e Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Prebys, Eric [Fermilab; Bartoszek, Larry [Technicare; Gaponenko, Andrei [Fermilab; Kasper, Peter [Fermilab

    2015-06-01

    The Mu2e Experiment at Fermilab will search for the conversion of a muon to an electron in the field of an atomic nucleus with unprecedented sensitivity. The experiment requires a beam consisting of proton bunches approximately 200ns FW long, separated by 1.7 microseconds, with no out-of-time protons at the 10⁻¹⁰ fractional level. The verification of this level of extinction is very challenging. The proposed technique uses a special purpose spectrometer which will observe particles scattered from the production target of the experiment. The acceptance will be limited such that there will be no saturation effects from the in-time beam. The precise level and profile of the out-of-time beam can then be built up statistically, by integrating over many bunches.

  3. Quadrature formulas for Fourier coefficients

    KAUST Repository

    Bojanov, Borislav

    2009-09-01

    We consider quadrature formulas of high degree of precision for the computation of the Fourier coefficients in expansions of functions with respect to a system of orthogonal polynomials. In particular, we show the uniqueness of a multiple node formula for the Fourier-Tchebycheff coefficients given by Micchelli and Sharma and construct new Gaussian formulas for the Fourier coefficients of a function, based on the values of the function and its derivatives. © 2009 Elsevier B.V. All rights reserved.

  4. Coefficient Alpha: A Reliability Coefficient for the 21st Century?

    Science.gov (United States)

    Yang, Yanyun; Green, Samuel B.

    2011-01-01

    Coefficient alpha is almost universally applied to assess reliability of scales in psychology. We argue that researchers should consider alternatives to coefficient alpha. Our preference is for structural equation modeling (SEM) estimates of reliability because they are informative and allow for an empirical evaluation of the assumptions…

  5. Measuring of heat transfer coefficient

    DEFF Research Database (Denmark)

    Henningsen, Poul; Lindegren, Maria

    Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure...... the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot...

  6. Measuring of heat transfer coefficient

    DEFF Research Database (Denmark)

    Henningsen, Poul; Lindegren, Maria

    Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure...... the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot...

  7. Optical atmospheric extinction over Cerro Paranal

    NARCIS (Netherlands)

    Patat, F.; Moehler, S.; O'Brien, K.; Pompei, E.; Bensby, T.; Carraro, G.; de Ugarte Postigo, A.; Fox, A.; Gavignaud, I.; James, G.; Korhonen, H.; Ledoux, C.; Randall, S.; Sana, H.A.A.; Smoker, J.; Stefl, S.; Szeifert, T.

    2011-01-01

    Aims. The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with the purpose of providing the community with a function to be used to correct the observed spectra, with an accuracy of 0.01 mag airmass-1.

  8. Extinction and renewal of conditioned sexual responses

    NARCIS (Netherlands)

    Brom, M.; Laan, E.; Everaerd, W.; Spinhoven, P.; Both, S.

    2014-01-01

    INTRODUCTION: Extinction involves an inhibitory form of new learning that is highly dependent on the context for expression. This is supported by phenomena such as renewal and spontaneous recovery, which may help explain the persistence of appetitive behavior, and related problems such as

  9. Time to extinction of bird populations

    NARCIS (Netherlands)

    Sæther, B-E.; Engen, S.; Møller, A.P.; Visser, M.E.; Matthysen, E.; Fiedler, W.; Lambrechts, M.M.; Becker, P.H.; Brommer, J.E.; Dickinson, J.; du Feu, C.; Gehlbach, F.R.; Merilä, J.; Rendell, W.; Robertson, R.J.; Thomson, D.L.; Török, J.

    2005-01-01

    The risk of extinction of populations has not previously been empirically related to parameters characterizing their population dynamics. To analyze this relationship, we simulated how the distribution of population dynamical characters changed as a function of time, in both the remaining and the ex

  10. Extinction and renewal of conditioned sexual responses

    NARCIS (Netherlands)

    Brom, M.; Laan, E.; Everaerd, W.; Spinhoven, P.; Both, S.

    2014-01-01

    INTRODUCTION: Extinction involves an inhibitory form of new learning that is highly dependent on the context for expression. This is supported by phenomena such as renewal and spontaneous recovery, which may help explain the persistence of appetitive behavior, and related problems such as addictions

  11. Attentional, Associative, and Configural Mechanisms in Extinction

    Science.gov (United States)

    Larrauri, Jose A.; Schmajuk, Nestor A.

    2008-01-01

    The participation of attentional and associative mechanisms in extinction, spontaneous recovery, external disinhibition, renewal, reinstatement, and reacquisition was evaluated through computer simulations with an extant computational model of classical conditioning (N. A. Schmajuk, Y. Lam, & J. A. Gray, 1996; N. A. Schmajuk & J. A. Larrauri,…

  12. Methylphenidate Enhances Extinction of Contextual Fear

    Science.gov (United States)

    Abraham, Antony D.; Cunningham, Christopher L.; Lattal, K. Matthew

    2012-01-01

    Methylphenidate (MPH, Ritalin) is a norepinephrine and dopamine transporter blocker that is widely used in humans for treatment of attention deficit disorder and narcolepsy. Although there is some evidence that targeted microinjections of MPH may enhance fear acquisition, little is known about the effect of MPH on fear extinction. Here, we show…

  13. Extinction and renewal of conditioned sexual responses.

    Directory of Open Access Journals (Sweden)

    Mirte Brom

    Full Text Available INTRODUCTION: Extinction involves an inhibitory form of new learning that is highly dependent on the context for expression. This is supported by phenomena such as renewal and spontaneous recovery, which may help explain the persistence of appetitive behavior, and related problems such as addictions. Research on these phenomena in the sexual domain is lacking, where it may help to explain the persistence of learned sexual responses. METHOD: Men (n = 40 and women (n = 62 participated in a differential conditioning paradigm, with genital vibrotactile stimulation as US and neutral pictures as conditional stimuli (CSs. Dependent variables were genital and subjective sexual arousal, affect, US expectancy, and approach and avoid tendencies towards the CSs. Extinction and renewal of conditioned sexual responses were studied by context manipulation (AAA vs. ABA condition. RESULTS: No renewal effect of genital conditioned responding could be detected, but an obvious recovery of US expectancy following a context change after extinction (ABA was demonstrated. Additionally, women demonstrated recovery of subjective affect and subjective sexual arousal. Participants in the ABA demonstrated more approach biases towards stimuli. CONCLUSIONS: The findings support the context dependency of extinction and renewal of conditioned sexual responses in humans. This knowledge may have implications for the treatment of disturbances in sexual appetitive responses such as hypo- and hypersexuality.

  14. Time to extinction of bird populations

    NARCIS (Netherlands)

    Sæther, B-E.; Engen, S.; Møller, A.P.; Visser, M.E.; Matthysen, E.; Fiedler, W.; Lambrechts, M.M.; Becker, P.H.; Brommer, J.E.; Dickinson, J.; du Feu, C.; Gehlbach, F.R.; Merilä, J.; Rendell, W.; Robertson, R.J.; Thomson, D.L.; Török, J.

    2005-01-01

    The risk of extinction of populations has not previously been empirically related to parameters characterizing their population dynamics. To analyze this relationship, we simulated how the distribution of population dynamical characters changed as a function of time, in both the remaining and the

  15. Mass extinctions caused by large bolide impacts

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, L.W.

    1987-07-01

    Evidence indicates that the collision of Earth and a large piece of Solar System derbris such as a meteoroid, asteroid or comet caused the great extinctions of 65 million years ago, leading to the transition from the age of the dinosaurs to the age of the mammals.

  16. Stressor controllability modulates fear extinction in humans.

    Science.gov (United States)

    Hartley, Catherine A; Gorun, Alyson; Reddan, Marianne C; Ramirez, Franchesca; Phelps, Elizabeth A

    2014-09-01

    Traumatic events are proposed to play a role in the development of anxiety disorders, however not all individuals exposed to extreme stress experience a pathological increase in fear. Recent studies in animal models suggest that the degree to which one is able to control an aversive experience is a critical factor determining its behavioral consequences. In this study, we examined whether stressor controllability modulates subsequent conditioned fear expression in humans. Participants were randomly assigned to an escapable stressor condition, a yoked inescapable stressor condition, or a control condition involving no stress exposure. One week later, all participants underwent fear conditioning, fear extinction, and a test of extinction retrieval the following day. Participants exposed to inescapable stress showed impaired fear extinction learning and increased fear expression the following day. In contrast, escapable stress improved fear extinction and prevented the spontaneous recovery of fear. Consistent with the bidirectional controllability effects previously reported in animal models, these results suggest that one's degree of control over aversive experiences may be an important factor influencing the development of psychological resilience or vulnerability in humans.

  17. Self-extinction through optimizing selection

    Science.gov (United States)

    Parvinen, Kalle; Dieckmann, Ulf

    2013-01-01

    Evolutionary suicide is a process in which selection drives a viable population to extinction. So far, such selection-driven self-extinction has been demonstrated in models with frequency-dependent selection. This is not surprising, since frequency-dependent selection can disconnect individual-level and population-level interests through environmental feedback. Hence it can lead to situations akin to the tragedy of the commons, with adaptations that serve the selfish interests of individuals ultimately ruining a population. For frequency-dependent selection to play such a role, it must not be optimizing. Together, all published studies of evolutionary suicide have created the impression that evolutionary suicide is not possible with optimizing selection. Here we disprove this misconception by presenting and analyzing an example in which optimizing selection causes self-extinction. We then take this line of argument one step further by showing, in a further example, that selection-driven self-extinction can occur even under frequency-independent selection. PMID:23583808

  18. Subwoofer and nanotube butterfly acoustic flame extinction

    Science.gov (United States)

    Aliev, Ali E.; Mayo, Nathanael K.; Baughman, Ray H.; Mills, Brent T.; Habtour, Ed

    2017-07-01

    Nonchemical flame control using acoustic waves from a subwoofer and a lightweight carbon nanotube thermoacoustic projector was demonstrated. The intent was to manipulate flame intensity, direction and propagation. The mechanisms of flame suppression using low frequency acoustic waves were discussed. Laminar flame control and extinction were achieved using a thermoacoustic ‘butterfly’ projector based on freestanding carbon nanotube sheets.

  19. Modeling the Infrared Extinction toward the Galactic Center

    CERN Document Server

    Gao, Jian; Jiang, B W

    2013-01-01

    We model the ~1--19$\\mum$ infrared (IR) extinction curve toward the Galactic Center (GC) in terms of the standard silicate-graphite interstellar dust model. The grains are taken to have a power law size distribution with an exponential decay above some size. The best-fit model for the GC IR extinction constrains the visual extinction to be Av~38--42 mag. The limitation of the model, i.e., its difficulty in simultaneously reproducing both the steep ~1--3$\\mum$ near-IR extinction and the flat ~3--8$\\mum$ mid-IR extinction is discussed. We argue that this difficulty could be alleviated by attributing the extinction toward the GC to a combination of dust in different environments: dust in diffuse regions (characterized by small Rv and steep near-IR extinction), and dust in dense regions (characterized by large Rv and flat UV extinction).

  20. Preservation of Natural Diversity: The Problem of Extinction Prone Species

    Science.gov (United States)

    Terborgh, John

    1974-01-01

    Examines threatened extinction of birds and recommends agencies adopt policies which minimize the pace of extinctions through the setting aside of large preserves which protect natural vegetation formation and the animal life. (BR)

  1. A REMARK ON EXTINCTION OF A CLASS OF SUPERPROCESSES

    Institute of Scientific and Technical Information of China (English)

    ZHAOXUELEI

    1996-01-01

    The extinction of a class of superprocesses associated with general branching characteristics and underlying Markov processes is investigted, The extinction is closely associated with the branching characteristics and the recurrence and transience of underlying processes.

  2. Inferring modern extinction risk from fossil occupancy trajectories

    Science.gov (United States)

    Kiessling, Wolfgang; Kocsis, Adam

    2016-04-01

    Besides providing information on ancient mass extinctions and intrinsic extinction risk, the fossil record may also provide useful data for assessing the extinction risk of extant species. Here we analyse the palaeontological trajectories of geographical occupancy in extant marine species to identify species that have been declining over geological time scales and may thus be more prone to extinction than expanding species. The slopes of these occupancy trajectories are used to categorize evolutionary extinction risk. Mapping the risk at global scale we find that low to mid latitude regions are at significantly higher risk than high latitude regions. We also find a moderate correspondence between high extinction risk on geological time scales and modern extinction risk for reef corals and propose to add fossil data to the assessment of current extinction risk, especially for the notoriously data deficient marine taxa.

  3. Fractai Estimation of Joint Roughness Coefficients

    Institute of Scientific and Technical Information of China (English)

    谢和平; Willian G.Pariseau

    1994-01-01

    Based on the triadic Koch curve,a generalized fractal model of joint profiles is establishedto simulate joint roughness.The fractal dimension of a joint profile can be directly obtained from the two pa-rameters,L~* and h~*, the average base length and average height of asperities of the joint,respectively,i,e D=log4/log[2(1+cos tan~1(2h’/L’))]This fractal dimension is strongly correlated with the value of the joint roughness coefficient (JRC). An empirical relationship is found in the form,JRC=85.2671·(D-1)~0.5679 Thus, the fractal analysis proposed provides a new method of estimating JRC values

  4. Uranium plasma emission coefficient in the visible and near UV.

    Science.gov (United States)

    Mack, J. M., Jr.; Usher, J. L.; Schneider, R. T.; Campbell, H. D.

    1971-01-01

    Measurements of the specific emission coefficient in the near ultra-violet and visible region of a uranium arc plasma are reported. Spatial unfolding of the intensity profile is used to determine the emission coefficient in the spectral range of 2000 A to 6000 A. The uranium partial pressure is estimated to range between .001 and .01 atmosphere, and the corresponding temperature range is 5000 - 10,000 K.

  5. Uranium plasma emission coefficient in the visible and near UV.

    Science.gov (United States)

    Mack, J. M., Jr.; Usher, J. L.; Schneider, R. T.; Campbell, H. D.

    1971-01-01

    Measurements of the specific emission coefficient in the near ultra-violet and visible region of a uranium arc plasma are reported. Spatial unfolding of the intensity profile is used to determine the emission coefficient in the spectral range of 2000 A to 6000 A. The uranium partial pressure is estimated to range between .001 and .01 atmosphere, and the corresponding temperature range is 5000 - 10,000 K.

  6. Endangered Species and Natural Resource Exploitation: Extinction vs. Coexistence

    OpenAIRE

    Tsur, Yacov; Zemel, Amos

    1994-01-01

    The threat on the survival of animal species due to intensive use of natural resources is incorporated within resource management models, paying special attention to uncertainty regarding the conditions that lead to extinction. The manner in which the potential benefits forgone due to the species extinction (denoted extinction penalty) induce more conservative exploitation policies is studied in detail. When the extinction penalty is ignored, the optimal policy is to drive the resource stock ...

  7. Grey Milky Way Extinction from SDSS Stellar Photometry

    OpenAIRE

    Gorbikov, Evgeny; Brosch, Noah

    2009-01-01

    We report results concerning the distribution and properties of galactic extinction at high galactic latitudes derived from stellar statistics using the Sloan Digital Sky Survey (SDSS). We use the classical Wolf diagram method to identify regions with extinction, and derive the extinction and the extinction law of the dust using all five SDSS spectral bands. We estimate the distance to the extinguishing medium using simple assumptions about the stellar populations in the line of sight. We rep...

  8. Extinction of chained instrumental behaviors: Effects of consumption extinction on procurement responding.

    Science.gov (United States)

    Thrailkill, Eric A; Bouton, Mark E

    2016-03-01

    Operant behavior is typically organized into sequences of responses that eventually lead to a reinforcer. Response elements can be categorized as those that directly lead to reward consumption (i.e., a consumption response) and those that lead to the opportunity to make the consumption response (i.e., a procurement response). These responses often differ topographically and in terms of the discriminative stimuli that set the occasion for them. We have recently shown that extinction of the procurement response acts to weaken the specific associated consumption response, and that active inhibition of the procurement response is required for this effect. To expand the analysis of the associative structure of chains, in the present experiments we asked the reverse question: whether extinction of consumption behavior results in a decrease in the associated procurement response in a discriminated heterogeneous chain. In Experiment 1, extinction of consumption alone led to an attenuation of the associated procurement response only when rats were allowed to make the consumption response in extinction. Exposure to the consumption stimulus alone was not sufficient to produce weakened procurement responding. In Experiment 2, rats learned two distinct heterogeneous chains, and extinction of one consumption response specifically weakened the procurement response associated with it. The results add to the evidence suggesting that rats learn a highly specific associative structure in behavior chains, emphasizing the role of learning response inhibition in extinction.

  9. Psychological and neural mechanisms of experimental extinction: a selective review.

    Science.gov (United States)

    Delamater, Andrew R; Westbrook, R Frederick

    2014-02-01

    The present review examines key psychological concepts in the study of experimental extinction and implications these have for an understanding of the underlying neurobiology of extinction learning. We suggest that many of the signature characteristics of extinction learning (spontaneous recovery, renewal, reinstatement, rapid reacquisition) can be accommodated by the standard associative learning theory assumption that extinction results in partial erasure of the original learning together with new inhibitory learning. Moreover, we consider recent behavioral and neural evidence that supports the partial erasure view of extinction, but also note shortcomings in our understanding of extinction circuits as these relate to the negative prediction error concept. Recent work suggests that common prediction error and stimulus-specific prediction error terms both may be required to explain neural plasticity both in acquisition and extinction learning. In addition, we suggest that many issues in the content of extinction learning have not been fully addressed in current research, but that neurobiological approaches should be especially helpful in addressing such issues. These include questions about the nature of extinction learning (excitatory CS-No US, inhibitory CS-US learning, occasion setting processes), especially as this relates to studies of the micro-circuitry of extinction, as well as its representational content (sensory, motivational, response). An additional understudied problem in extinction research is the role played by attention processes and their underlying neural networks, although some research and theory converge on the idea that extinction is accompanied by attention decrements (i.e., habituation-like processes).

  10. Inhibition of Estradiol Synthesis Impairs Fear Extinction in Male Rats

    Science.gov (United States)

    Graham, Bronwyn M.; Milad, Mohammed R.

    2014-01-01

    Emerging research has demonstrated that the sex hormone estradiol regulates fear extinction in female rodents and women. Estradiol may also regulate fear extinction in males, given its role in synaptic plasticity in both sexes. Here we report that inhibition of estradiol synthesis during extinction training, via the aromatase inhibitor fadrozole,…

  11. Slower Reacquisition after Partial Extinction in Human Contingency Learning

    Science.gov (United States)

    Morís, Joaquín; Barberia, Itxaso; Vadillo, Miguel A.; Andrades, Ainhoa; López, Francisco J.

    2017-01-01

    Extinction is a very relevant learning phenomenon from a theoretical and applied point of view. One of its most relevant features is that relapse phenomena often take place once the extinction training has been completed. Accordingly, as extinction-based therapies constitute the most widespread empirically validated treatment of anxiety disorders,…

  12. Fibroblast Growth Factor-2 Alters the Nature of Extinction

    Science.gov (United States)

    Graham, Bronwyn M.; Richardson, Rick

    2011-01-01

    These experiments examined the effects of the NMDA-receptor (NMDAr) antagonist MK801 on reacquisition and re-extinction of a conditioned fear that had been previously extinguished before injection of fibroblast growth factor-2 (FGF2) or vehicle. Recent findings have shown that relearning and re-extinction, unlike initial learning and extinction,…

  13. Global distribution and drivers of language extinction risk

    DEFF Research Database (Denmark)

    Amano, Tatsuya; Sandel, Brody; Eager, Heidi;

    2014-01-01

    Many of the world's languages face serious risk of extinction. Efforts to prevent this cultural loss are severely constrained by a poor understanding of the geographical patterns and drivers of extinction risk. We quantify the global distribution of language extinction risk-represented by small...

  14. Estimating how many undescribed species have gone extinct.

    Science.gov (United States)

    Tedesco, P A; Bigorne, R; Bogan, A E; Giam, X; Jézéquel, C; Hugueny, B

    2014-10-01

    Because both descriptions of species and modern human-driven extinctions started around the same time (i.e., eighteenth century), a logical expectation is that a large proportion of species may have gone extinct without ever having been recorded. Despite this evident and widely recognized assumption, the loss of undescribed species has never been estimated. We quantified this loss for several taxonomic groups and regions for which undescribed species extinctions are likely to have occurred. Across a wide range of taxonomic groups, we applied known extinction rates computed from recorded species losses to assumed exponential decay in the proportion of species remaining undiscovered. Because all previous modeling attempts to project total species richness implicitly assumed that undescribed species extinctions could be neglected, we also evaluated the effect of neglecting them. Finally, because we assumed constant description and extinction probabilities, we applied our model to simulated data that did not conform to this assumption. Actual species losses were severely underestimated by considering only known species extinctions. According to our estimates, the proportion of undiscovered extinct species over all extinctions ranged from 0.15 to 0.59, depending on the taxonomic group and the region considered. This means that recent extinctions may be up to twice as large as the number recorded. When species differed in their extinction or description probabilities, our model underestimated extinctions of undescribed species by up to 20%. © 2014 Society for Conservation Biology.

  15. Limb-Darkening Coefficients for Eclipsing White Dwarfs

    CERN Document Server

    Gianninas, A; Kilic, Mukremin; Bergeron, P

    2013-01-01

    We present extensive calculations of linear and non-linear limb-darkening coefficients as well as complete intensity profiles appropriate for modeling the light-curves of eclipsing white dwarfs. We compute limb-darkening coefficients in the Johnson-Kron-Cousins UBVRI photometric system as well as the Large Synoptic Survey Telescope (LSST) ugrizy system using the most up-to-date model atmospheres available. In all, we provide the coefficients for seven different limb-darkening laws. We describe the variations of these coefficients as a function of the atmospheric parameters, including the effects of convection at low effective temperatures. Finally, we discuss the importance of having readily available limb-darkening coefficients in the context of present and future photometric surveys like the LSST, Palomar Transient Factory (PTF), and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). The LSST, for example, may find ~10^5 eclipsing white dwarfs. The limb-darkening calculations presented h...

  16. Vertical profiles of urban aerosol complex refractive index in the frame of ESQUIF airborne measurements

    Directory of Open Access Journals (Sweden)

    J.-C. Raut

    2007-07-01

    Full Text Available A synergy between lidar, sunphotometer and in situ measurements has been applied to airborne observations performed during the Etude et Simulation de la QUalité de l'air en Ile-de-France (ESQUIF, enabling the retrieval of vertical profiles for the aerosol complex refractive index (ACRI and single-scattering albedo with a vertical resolution of 200 m over Paris area. The averaged value over the entire planetary boundary layer (PBL for the ACRI is close to 1.51(±0.02–i0.017(±0.003 at 532 nm. The single-scattering albedo of the corresponding aerosols is found to be ~0.9 at the same wavelength. A good agreement is found with previous studies for urban aerosols. A comparison of vertical profiles of ACRI with simulations combining in situ measurements and relative humidity (RH profiles has highlighted a modification in aerosol optical properties linked to their history and the origin of the air mass. The determination of ACRI in the atmospheric column enabled to retrieve vertical profiles of extinction coefficient in accordance with lidar profiles measurements.

  17. Compound stimulus extinction reduces spontaneous recovery in humans

    Science.gov (United States)

    Coelho, Cesar A.O.; Dunsmoor, Joseph E.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design (“deepened extinction”) shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately paired with an electric shock. The target CS (CSA) was extinguished alone followed by compound presentations of the extinguished CSA and nonextinguished CSB. Recovery of conditioned skin conductance responses to CSA was reduced 24 h after compound extinction, as compared with a group who received an equal number of extinction trials to the CSA alone. PMID:26572649

  18. Mass Extinction in a Simple Mathematical Biological Model

    CERN Document Server

    Tokita, K; Tokita, Kei; Yasutomi, Ayumu

    1997-01-01

    Introducing the effect of extinction into the so-called replicator equations in mathematical biology, we construct a general model of ecosystems. The present model shows mass extinction by its own extinction dynamics when the system initially has a large number of species ( diversity). The extinction dynamics shows several significant features such as a power law in basin size distribution, induction time, etc. The present theory can be a mathematical foundation of the species-area effect in the paleontologic theory for mass extinction.

  19. Taste-immunosuppression engram: reinforcement and extinction.

    Science.gov (United States)

    Niemi, Maj-Britt; Härting, Margarete; Kou, Wei; Del Rey, Adriana; Besedovsky, Hugo O; Schedlowski, Manfred; Pacheco-López, Gustavo

    2007-08-01

    Several Pavlovian conditioning paradigms have documented the brain's abilities to sense immune-derived signals or immune status, associate them with concurrently relevant extereoceptive stimuli, and reinstate such immune responses on demand. Specifically, the naturalistic relation of food ingestion with its possible immune consequences facilitates taste-immune associations. Here we demonstrate that the saccharin taste can be associated with the immunosuppressive agent cyclosporine A, and that such taste-immune associative learning is subject to reinforcement. Furthermore, once consolidated, this saccharin-immunosuppression engram is resistant to extinction when avoidance behavior is assessed. More importantly, the more this engram is activated, either at association or extinction phases, the more pronounced is the conditioned immunosuppression.

  20. The role of extraterrestrial phenomena in extinction.

    Science.gov (United States)

    Raup, D M

    1988-01-01

    In the several years since the Alvarez report of anomalously high iridium concentrations at the Cretaceous-Tertiary boundary, evidence for the involvement of meteorite impacts in biological extinction has increased dramatically. Much more research will be needed, however, before meteorite impact is established as a general causal factor in extinction. Of ever greater long-term interest is the possibility that other extraterrestrial forces have had important influences on the evolution of life. To recognize the effects of such forces, it will be necessary to coordinate the research of astronomy and paleontology so that testable predictions can be formulated. It is possible that known, systematic changes in the Solar System or Galaxy have had effects on global biology and that these effects have been preserved in the paleontological record.

  1. Visuomotor links in awareness: evidence from extinction.

    Science.gov (United States)

    Ricci, Raffaella; Genero, Rosanna; Colombatti, Simona; Zampieri, Daniela; Chatterjee, Anjan

    2005-05-31

    In patients with extinction, ipsilesional stimuli may abolish awareness of contralesional stimuli. Explanations of extinction often assume a serial model of processing in which sensory competition and identification precedes the selection of responses. We tested the adequacy of this assumption by examining the effects of response variables on visual awareness in six patients using signal detection analysis. Ipsilesional stimuli modulated patients' response criteria in deciding whether a contralesional stimulus was a target, and response modality (verbal or motor) modulated patients' abilities to discriminate between contralesional targets and distractors. This pattern of input variables modulating response criteria and output variables modulating discriminability indicates the extent to which attentional and intentional systems are tightly intertwined, with bi-directional effects in producing visual awareness.

  2. Cannabinoid facilitation of fear extinction memory recall in humans

    Science.gov (United States)

    Rabinak, Christine A.; Angstadt, Mike; Sripada, Chandra S.; Abelson, James L.; Liberzon, Israel; Milad, Mohammed R.; Phan, K. Luan

    2012-01-01

    A first-line approach to treat anxiety disorders is exposure-based therapy, which relies on extinction processes such as repeatedly exposing the patient to stimuli (conditioned stimuli; CS) associated with the traumatic, fear-related memory. However, a significant number of patients fail to maintain their gains, partly attributed to the fact that this inhibitory learning and its maintenance is temporary and conditioned fear responses can return. Animal studies have shown that activation of the cannabinoid system during extinction learning enhances fear extinction and its retention. Specifically, CB1 receptor agonists, such as Δ9-tetrahydrocannibinol (THC), can facilitate extinction recall by preventing recovery of extinguished fear in rats. However, this phenomenon has not been investigated in humans. We conducted a study using a randomized, double-blind, placebo-controlled, between-subjects design, coupling a standard Pavlovian fear extinction paradigm and simultaneous skin conductance response (SCR) recording with an acute pharmacological challenge with oral dronabinol (synthetic THC) or placebo (PBO) 2 hours prior to extinction learning in 29 healthy adult volunteers (THC = 14; PBO = 15) and tested extinction retention 24 hours after extinction learning. Compared to subjects that received PBO, subjects that received THC showed low SCR to a previously extinguished CS when extinction memory recall was tested 24 hours after extinction learning, suggesting that THC prevented the recovery of fear. These results provide the first evidence that pharmacological enhancement of extinction learning is feasible in humans using cannabinoid system modulators, which may thus warrant further development and clinical testing. PMID:22796109

  3. Predicting extinction risk of Brazilian Atlantic forest angiosperms.

    Science.gov (United States)

    Leão, Tarciso C C; Fonseca, Carlos R; Peres, Carlos A; Tabarelli, Marcelo

    2014-10-01

    Understanding how plant life history affects species vulnerability to anthropogenic disturbances and environmental change is a major ecological challenge. We examined how vegetation type, growth form, and geographic range size relate to extinction risk throughout the Brazilian Atlantic Forest domain. We used a database containing species-level information of 6,929 angiosperms within 112 families and a molecular-based working phylogeny. We used decision trees, standard regression, and phylogenetic regression to explore the relationships between species attributes and extinction risk. We found a significant phylogenetic signal in extinction risk. Vegetation type, growth form, and geographic range size were related to species extinction risk, but the effect of growth form was not evident after phylogeny was controlled for. Species restricted to either rocky outcrops or scrub vegetation on sandy coastal plains exhibited the highest extinction risk among vegetation types, a finding that supports the hypothesis that species adapted to resource-limited environments are more vulnerable to extinction. Among growth forms, epiphytes were associated with the highest extinction risk in non-phylogenetic regression models, followed by trees, whereas shrubs and climbers were associated with lower extinction risk. However, the higher extinction risk of epiphytes was not significant after correcting for phylogenetic relatedness. Our findings provide new indicators of extinction risk and insights into the mechanisms governing plant vulnerability to extinction in a highly diverse flora where human disturbances are both frequent and widespread. © 2014 Society for Conservation Biology.

  4. Simple models of evolution and extinction

    CERN Document Server

    Newman, M E J

    1999-01-01

    This article gives a brief introduction to the mathematical modeling of large-scale biological evolution and extinction. We give three examples of simple models in this field: the coevolutionary avalanche model of Bak and Sneppen, the environmental stress model of Newman, and the increasing fitness model of Sibani, Schmidt, and Alstrom. We describe the features of real evolution which these models are intended to explain and compare the results of simulations against data drawn from the fossil record.

  5. Clumpy cold dark matter and biological extinctions

    CERN Document Server

    Collar, J I

    1995-01-01

    Cosmological models with cosmic string and texture seeded universes predict a present abundance of very dense clumps of Cold Dark Matter particles. Their crossing through the solar system would induce a non-negligible amount of radiation damage to all living tissue; the severity of such an episode is assessed. The estimated frequency of these crossings agrees with the apparent periodicity of the paleontological record of biological extinctions. (Phys. Lett. B, in press)

  6. Effects of broken affordance on visual extinction.

    Science.gov (United States)

    Wulff, Melanie; Humphreys, Glyn W

    2015-01-01

    Previous studies have shown that visual extinction can be reduced if two objects are positioned to "afford" an action. Here we tested if this affordance effect was disrupted by "breaking" the affordance, i.e., if one of the objects actively used in the action had a broken handle. We assessed the effects of broken affordance on recovery from extinction in eight patients with right hemisphere lesions and left-sided extinction. Patients viewed object pairs that were or were not commonly used together and that were positioned for left- or right-hand actions. In the unrelated pair conditions, either two tools or two objects were presented. In line with previous research (e.g., Riddoch et al., 2006), extinction was reduced when action-related object pairs and when unrelated tool pairs were presented compared to unrelated object pairs. There was no significant difference in recovery rate between action-related (object-tool) and unrelated tool pairs. In addition, performance with action-related objects decreased when the tool appeared on the ipsilesional side compared to when it was on the contralesional side, but only when the tool handle was intact. There were minimal effects of breaking the handle of an object rather than a tool, and there was no effect of breaking the handle on either tools or objects on single item trials. The data suggest that breaking the handle of a tool lessens the degree to which it captures attention, with this attentional capture being strongest when the tool appears on the ipsilesional side. The capture of attention by the ipsilesional item then reduces the chance of detecting the contralesional stimulus. This attentional capture effect is mediated by the affordance to the intact tool.

  7. Effects of broken affordance on visual extinction

    Directory of Open Access Journals (Sweden)

    Melanie eWulff

    2015-09-01

    Full Text Available Previous studies have shown that visual extinction can be reduced if two objects are positioned to afford an action. Here we tested if this affordance effect was disrupted by breaking the affordance – if one of the objects actively used in the action had a broken handle. We assessed the effects of broken affordance on recovery from extinction in eight patients with right hemisphere lesions and left-sided extinction. Patients viewed object pairs that were or were not commonly used together and that were positioned for left- or right-hand actions. In the unrelated pair conditions, either two tools or two objects were presented. In line with previous research (e.g., Riddoch et al., 2006, extinction was reduced when action-related object pairs and when unrelated tool pairs were presented compared to unrelated object pairs. There was no significant difference in recovery rate between action-related (object-tool and unrelated tool-tool pairs. In addition, performance with action-related objects decreased when the tool appeared on the ipsilesional side compared to when it was on the contralesional side, but only when the tool handle was intact. There were minimal effects of breaking the handle of an object rather than a tool, and there was no effect of breaking the handle on either tools or objects on single item trials. The data suggest that breaking the handle of a tool lessens the degree to which it captures attention, with this attentional capture being strongest when the tool appears on the ipsilesional side. The capture of attention by the ipsilesional item then reduces the chance of detecting the contralesional stimulus. This attentional capture effect is mediated by the affordance to the intact tool.

  8. Opportunities and costs for preventing vertebrate extinctions.

    Science.gov (United States)

    Conde, Dalia A; Colchero, Fernando; Güneralp, Burak; Gusset, Markus; Skolnik, Ben; Parr, Michael; Byers, Onnie; Johnson, Kevin; Young, Glyn; Flesness, Nate; Possingham, Hugh; Fa, John E

    2015-03-16

    Despite an increase in policy and management responses to the global biodiversity crisis, implementation of the 20 Aichi Biodiversity Targets still shows insufficient progress [1]. These targets, strategic goals defined by the United Nations Convention on Biological Diversity (CBD), address major causes of biodiversity loss in part by establishing protected areas (Target 11) and preventing species extinctions (Target 12). To achieve this, increased interventions will be required for a large number of sites and species. The Alliance for Zero Extinction (AZE) [2], a consortium of conservation-oriented organisations that aims to protect Critically Endangered and Endangered species restricted to single sites, has identified 920 species of mammals, birds, amphibians, reptiles, conifers and reef-building corals in 588 'trigger' sites [3]. These are arguably the most irreplaceable category of important biodiversity conservation sites. Protected area coverage of AZE sites is a key indicator of progress towards Target 11 [1]. Moreover, effective conservation of AZE sites is essential to achieve Target 12, as the loss of any of these sites would certainly result in the global extinction of at least one species [2]. However, averting human-induced species extinctions within AZE sites requires enhanced planning tools to increase the chances of success [3]. Here, we assess the potential for ensuring the long-term conservation of AZE vertebrate species (157 mammals, 165 birds, 17 reptiles and 502 amphibians) by calculating a conservation opportunity index (COI) for each species. The COI encompasses a set of measurable indicators that quantify the possibility of achieving successful conservation of a species in its natural habitat (COIh) and by establishing insurance populations in zoos (COIc).

  9. Rewinding the process of mammalian extinction

    OpenAIRE

    Saragusty, J.; Diecke, S.; Drukker, M.; Durrant, B.; Friedrich Ben-Nun, I.; Galli, C; Goeritz, F.; Hayashi, K; Hermes, R.; Holtze, S.; Johnson, S.; Lazzari, G.; Loi, P; Loring, J. F.; Okita, K

    2016-01-01

    With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name "Conservation by Cellular Technologies." The outcome of this meeting and the proposed road m...

  10. Dynamics of extinction debt across five taxonomic groups.

    Science.gov (United States)

    Halley, John M; Monokrousos, Nikolaos; Mazaris, Antonios D; Newmark, William D; Vokou, Despoina

    2016-07-25

    Species extinction following habitat loss is well documented. However, these extinctions do not happen immediately. The biodiversity surplus (extinction debt) declines with some delay through the process of relaxation. Estimating the time constants of relaxation, mainly the expected time to first extinction and the commonly used time for half the extinction debt to be paid off (half-life), is crucial for conservation purposes. Currently, there is no agreement on the rate of relaxation and the factors that it depends on. Here we find that half-life increases with area for all groups examined in a large meta-analysis of extinction data. A common pattern emerges if we use average number of individuals per species before habitat loss as an area index: for mammals, birds, reptiles and plants, the relationship has an exponent close to a half. We also find that the time to first determined extinction is short and increases slowly with area.

  11. Role of the hippocampus in contextual modulation of fear extinction

    Institute of Scientific and Technical Information of China (English)

    Lingzhi Kong; Xihong Wu; Liang Li

    2008-01-01

    Fear extinction is an important form of emotional learning, and affects neural plasticity. Cue fear extinction is a classical form of inhibitory learning that can be used as an exposure-based treatment for phobia, because the long-term extinction memory produced during cue fear extinction can limit the over-expression of fear. The expression of this inhibitory memory partly depends on the context in which the extinction learning occurs. Studies such as transient inhibition, electrophysiology and brain imaging have proved that the hippocampus - an important structure in the limbic system - facilitates memory retrieval by contextual cues.Mediation of the hippocampus-medial prefrontal lobe circuit may be the neurobiological basis of this process.This article has reviewed the role of the hippocampus in the learning and retrieval of fear extinction.Contextual modulation of fear extinction may rely on a neural network consisting of the hippocampus, the medial prefrontal cortex and the amygdala.

  12. Extinction and dust properties in a clumpy medium

    CERN Document Server

    Scicluna, P

    2015-01-01

    (abridged) The dust content of the universe is primarily explored via its interaction with stellar photons, producing interstellar extinction. However, owing to the physical extension of the observing beam, observations may detect scattered photons, resulting in a change in the observed (or effective) extinction, depending on the spatial distribution of the dust and the resolution of the instrument. We investigate the influence of clumpy dust distributions on effective extinction toward embedded sources and those in the diffuse ISM. We use Monte Carlo radiative transfer to examine effective extinction for various geometries. By varying the number, optical depth and volume-filling factor of clumps in models of spherical shells and the diffuse ISM, we explore the evolution of extinction. Depending on the number of scattering events in the beam, the extinction curve steepens in homogeneous media and flattens in clumpy media. As a result, clumpy dust distributions can to reproduce extinction curves with arbitrary...

  13. Minimizing extinction risk through genetic rescue

    Directory of Open Access Journals (Sweden)

    Waite, T. A.

    2005-12-01

    Full Text Available According to the genetic rescue hypothesis, immigrants can improve population persistence through their genetic contribution alone. We investigate the potential for such rescue using small, inbred laboratory populations of the bean beetle (Callosobruchus maculatus. We ask how many migrants per generation (MPG are needed to minimize the genetic component of extinction risk. During Phase 1, population size was made to fluctuate between 6 and 60 (for 10 generations. During this phase, we manipulated the number of MPG, replacing 0, 1, 3, or 5 females every generation with immigrant females. During Phase 2, we simply set an upper limit on population size (.10. Compared with the 0-MPG treatment, the other treatments were equivalently effective at improving reproductive success and reducing extinction risk. A single MPG was sufficient for genetic rescue, apparently because effective migration rate was inflated dramatically during generations when population size was small. An analysis of quasi-extinction suggests that replicate populations in the 1-MPG treatment benefited from initial purging of inbreeding depression. Populations in this treatment performed so well apparently because they received the dual benefit of purging followed by genetic infusion. Our results suggest the need for further evaluation of alternative schemes for genetic rescue.

  14. Glucocorticoids enhance extinction-based psychotherapy.

    Science.gov (United States)

    de Quervain, Dominique J-F; Bentz, Dorothée; Michael, Tanja; Bolt, Olivia C; Wiederhold, Brenda K; Margraf, Jürgen; Wilhelm, Frank H

    2011-04-19

    Behavioral exposure therapy of anxiety disorders is believed to rely on fear extinction. Because preclinical studies have shown that glucocorticoids can promote extinction processes, we aimed at investigating whether the administration of these hormones might be useful in enhancing exposure therapy. In a randomized, double-blind, placebo-controlled study, 40 patients with specific phobia for heights were treated with three sessions of exposure therapy using virtual reality exposure to heights. Cortisol (20 mg) or placebo was administered orally 1 h before each of the treatment sessions. Subjects returned for a posttreatment assessment 3-5 d after the last treatment session and for a follow-up assessment after 1 mo. Adding cortisol to exposure therapy resulted in a significantly greater reduction in fear of heights as measured with the acrophobia questionnaire (AQ) both at posttreatment and at follow-up, compared with placebo. Furthermore, subjects receiving cortisol showed a significantly greater reduction in acute anxiety during virtual exposure to a phobic situation at posttreatment and a significantly smaller exposure-induced increase in skin conductance level at follow-up. The present findings indicate that the administration of cortisol can enhance extinction-based psychotherapy.

  15. Rewinding the process of mammalian extinction.

    Science.gov (United States)

    Saragusty, Joseph; Diecke, Sebastian; Drukker, Micha; Durrant, Barbara; Friedrich Ben-Nun, Inbar; Galli, Cesare; Göritz, Frank; Hayashi, Katsuhiko; Hermes, Robert; Holtze, Susanne; Johnson, Stacey; Lazzari, Giovanna; Loi, Pasqualino; Loring, Jeanne F; Okita, Keisuke; Renfree, Marilyn B; Seet, Steven; Voracek, Thomas; Stejskal, Jan; Ryder, Oliver A; Hildebrandt, Thomas B

    2016-07-01

    With only three living individuals left on this planet, the northern white rhinoceros (Ceratotherium simum cottoni) could be considered doomed for extinction. It might still be possible, however, to rescue the (sub)species by combining novel stem cell and assisted reproductive technologies. To discuss the various practical options available to us, we convened a multidisciplinary meeting under the name "Conservation by Cellular Technologies." The outcome of this meeting and the proposed road map that, if successfully implemented, would ultimately lead to a self-sustaining population of an extremely endangered species are outlined here. The ideas discussed here, while centered on the northern white rhinoceros, are equally applicable, after proper adjustments, to other mammals on the brink of extinction. Through implementation of these ideas we hope to establish the foundation for reversal of some of the effects of what has been termed the sixth mass extinction event in the history of Earth, and the first anthropogenic one. Zoo Biol. 35:280-292, 2016. © 2016 The Authors. Zoo Biology published by Wiley Periodicals, Inc.

  16. Permo-Triassic vertebrate extinctions: A program

    Science.gov (United States)

    Olson, E. C.

    1988-01-01

    Since the time of the Authors' study on this subject, a great deal of new information has become available. Concepts of the nature of extinctions have changed materially. The Authors' conclusion that a catastrophic event was not responsible for the extinction of vertebrates has modified to the extent that hypotheses involving either the impact of a massive extra-terrestrial body or volcanism provide plausible but not currently fully testable hypotheses. Stated changes resulted in a rapid decrease in organic diversity, as the ratio of origins of taxa to extinctions shifted from strongly positive to negative, with momentary equilibrium being reached at about the Permo-Triassic boundary. The proximate causes of the changes in the terrestrial biota appear to lie in two primary factors: (1) strong climatic changes (global mean temperatures, temperature ranges, humidity) and (2) susceptibility of the dominant vertebrates (large dicynodonts) and the glossopteris flora to disruption of the equlibrium of the world ecosystem. The following proximate causes have been proposed: (1) rhythmic fluctuations in solar radiation, (2) tectonic events as Pangea assembled, altering land-ocean relationships, patterns of wind and water circulation and continental physiography, (3) volcanism, and (4) changes subsequent to impacts of one or more massive extra terrestrial objects, bodies or comets. These hypotheses are discussed.

  17. Resurrecting extinct interactions with extant substitutes.

    Science.gov (United States)

    Griffiths, Christine J; Hansen, Dennis M; Jones, Carl G; Zuël, Nicolas; Harris, Stephen

    2011-05-10

    There is increasing evidence that restoration ecologists should be most concerned with restoring species interactions rather than species diversity per se [1]. Rewilding with taxon substitutes, the intentional introduction of exotic species to replace the ecosystem functions of recently extinct species, is one way to reverse ecosystem dysfunction following the loss of species interactions [2]. This is highly controversial [3], in part because of a lack of rigorous scientific studies [4]. Here we present the first empirical evidence of an in situ rewilding project undertaken as a hypothesis-driven ecosystem management option. On Ile aux Aigrettes, a 25-hectare island off Mauritius, the critically endangered large-fruited endemic ebony, Diospyros egrettarum (Ebenaceae), was seed-dispersal limited after the extinction of all native large-bodied frugivores, including giant tortoises. We introduced exotic Aldabra giant tortoises, Aldabrachelys gigantea, to disperse the ebony seeds. Not only did the tortoises ingest the large fruits and disperse substantial numbers of ebony seeds, but tortoise gut passage also improved seed germination, leading to the widespread, successful establishment of new ebony seedlings. Our results demonstrate that the introduction of these exotic frugivores is aiding the recovery of ebonies. We argue for more reversible rewilding experiments to investigate whether extinct species interactions can be restored.

  18. Theoretical and Numerical Investigation of Radiative Extinction of Diffusion Flames

    Science.gov (United States)

    Ray, Anjan

    1996-01-01

    The influence of soot radiation on diffusion flames was investigated using both analytical and numerical techniques. Soot generated in diffusion flames dominate the flame radiation over gaseous combustion products and can significantly lower the temperature of the flame. In low gravity situations there can be significant accumulation of soot and combustion products in the vicinity of the primary reaction zone owing to the absence of any convective buoyant flow. Such situations may result in substantial suppression of chemical activities in a flame, and the possibility of a radiative extinction may also be anticipated. The purpose of this work was to not only investigate the possibility of radiative extinction of a diffusion flame but also to qualitatively and quantitatively analyze the influence of soot radiation on a diffusion flame. In this study, first a hypothetical radiative loss profile of the form of a sech(sup 2) was assumed to influence a pure diffusion flame. It was observed that the reaction zone can, under certain circumstances, move through the radiative loss zone and locate itself on the fuel side of the loss zone contrary to our initial postulate. On increasing the intensity and/or width of the loss zone it was possible to extinguish the flame, and extinction plots were generated. In the presence of a convective flow, however, the movement of the temperature and reaction rate peaks indicated that the flame behavior is more complicated compared to a pure diffusional flame. A comprehensive model of soot formation, oxidation and radiation was used in a more involved analysis. The soot model of Syed, Stewart and Moss was used for soot nucleation and growth and the model of Nagle and Strickland-Constable was used for soot oxidation. The soot radiation was considered in the optically thin limit. An analysis of the flame structure revealed that the radiative loss term is countered both by the reaction term and the diffusion term. The essential balance for

  19. The Kauffman Constraint Coefficients Kw

    CERN Document Server

    Griggs, Kenneth A

    2011-01-01

    The Kauffman Constraint Coefficients Kw and their corresponding Elementals Ew are presented as solutions to the construction of the (beta)-derivative of Kauffman's Theta-function. Additionally, a new recursion relation is provided to construct the (beta)-derivative of Theta that requires only operational substitutions and summations; this algorithmically simplifies Kauffman's original technique. To demonstrate Kw, we generate the 30 Kw Coefficients from the corresponding Elementals Ew for the (9)-derivative of Theta and find that our results are in complete agreement with Kauffman's Mathematica\\texttrademark solutions. We further present a calculation of two coefficients for the (12)-derivative of Theta and invite readers to use Mathematica\\texttrademark or any other means to calculate and verify our results. Finally, we present a challenging calculation for a coefficient of the (40)-derivative of Theta; owing to the vast numbers of permutations involved, a Mathematica\\texttrademark approach may require subst...

  20. Kappa Coefficients for Circular Classifications

    NARCIS (Netherlands)

    Warrens, Matthijs J.; Pratiwi, Bunga C.

    2016-01-01

    Circular classifications are classification scales with categories that exhibit a certain periodicity. Since linear scales have endpoints, the standard weighted kappas used for linear scales are not appropriate for analyzing agreement between two circular classifications. A family of kappa coefficie

  1. Properties of Traffic Risk Coefficient

    Institute of Scientific and Technical Information of China (English)

    TANG Tie-Qiao; HUANG Hai-Jun; SHANG Hua-Yan; XUE Yu

    2009-01-01

    We use the model with the consideration of the traffic interruption probability (Physica A 387(2008)6845) to study the relationship between the traffic risk coefficient and the traffic interruption probability.The analytical and numerical results show that the traffic interruption probability will reduce the traffic risk coefficient and that the reduction is related to the density, which shows that this model can improve traffic security.

  2. Wrong Signs in Regression Coefficients

    Science.gov (United States)

    McGee, Holly

    1999-01-01

    When using parametric cost estimation, it is important to note the possibility of the regression coefficients having the wrong sign. A wrong sign is defined as a sign on the regression coefficient opposite to the researcher's intuition and experience. Some possible causes for the wrong sign discussed in this paper are a small range of x's, leverage points, missing variables, multicollinearity, and computational error. Additionally, techniques for determining the cause of the wrong sign are given.

  3. Comparison of the MK-801-induced appetitive extinction deficit with pressing for reward and associated pERK1/2 staining in prefrontal cortex and nucleus accumbens.

    Science.gov (United States)

    Holahan, Matthew R; Westby, Erin P; Albert, Katrina

    2012-03-01

    Administration of the noncompetitive N-methyl-d-aspartate (NMDA)-receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) has been shown to produce extinction deficits on appetitive operant tasks. The present study sought to further explore this by comparing extinction pressing to pressing for the primary reward and examining associated neural correlates to determine if the MK-801 extinction profile resembled the behavioral and neural profile associated with pressing for primary reward. Immunohistochemical labeling of phosphorylated extracellular signal-regulated kinase-1 and -2(pERK1/2) in the prelimbic (PrL) and infralimbic (IL) cortices and nucleus accumbens shell (AcbSh) and core (AcbC) was examined after rewarded or extinction lever pressing conditions. A dose-response curve revealed a within-day extinction deficit following administration of 0.05 mg/kg MK-801. All doses of MK-801 were associated with reduced IL pERK1/2 staining but only the 0.05 mg/kg dose was associated with elevated AcbSh pERK1/2 labeling. Extinction pressing under the influence of MK-801 was elevated compared to that seen during rewarded pressing-whether on MK-801 or saline. Rewarded pressing following saline or MK-801 was associated with elevated pERK1/2 in the PrL with no similar patterns in the MK-801/extinction group. There was more pERK1/2 labeling in the AcbSh of the MK-801 extinction group than any other condition. These data suggest that the MK-801-induced extinction deficit may be due to the combination of an underactive cortical behavioral inhibition system and an overactive AcbSh reward system.

  4. Extinction of chained instrumental behaviors: Effects of procurement extinction on consumption responding.

    Science.gov (United States)

    Thrailkill, Eric A; Bouton, Mark E

    2015-07-01

    Instrumental behavior often consists of sequences or chains of responses that minimally include procurement behaviors that enable subsequent consumption behaviors. In such chains, behavioral units are linked by access to one another and eventually to a primary reinforcer, such as food or a drug. The present experiments examined the effects of extinguishing procurement responding on consumption responding after training of a discriminated heterogeneous instrumental chain. Rats learned to make a procurement response (e.g., pressing a lever) in the presence of a distinctive discriminative stimulus; making that response led to the presentation of a second discriminative stimulus that set the occasion for a consumption response (e.g., pulling a chain), which then produced a food-pellet reinforcer. Experiment 1 showed that extinction of either the full procurement-consumption chain or procurement alone weakened the consumption response tested in isolation. Experiment 2 replicated the procurement extinction effect and further demonstrated that the opportunity to make the procurement response, as opposed to simple exposure to the procurement stimulus alone, was required. In Experiment 3, rats learned 2 distinct discriminated heterogeneous chains; extinction of 1 procurement response specifically weakened the consumption response that had been associated with it. The results suggest that learning to inhibit the procurement response may produce extinction of consumption responding through mediated extinction. The experiments suggest the importance of an associative analysis of instrumental behavior chains. (PsycINFO Database Record

  5. Aerosol profiling with the Jenoptik ceilometer CHM15kx

    Directory of Open Access Journals (Sweden)

    M. Wiegner

    2012-08-01

    Full Text Available Since a few years, the number of active remote sensing systems has been rapidly increasing as national weather services started to build up networks of ceilometers. As ceilometers can be considered as "simple" backscatter lidars, it is obvious to investigate to which extent they can provide quantitative aerosol information. In this context, the calibration of the ceilometer is the most crucial point: whereas previous studies primarily have relied on the comparisons with co-incident sun photometer measurements and the Rayleigh calibration, we provide an absolute calibration of the ceilometer. The advantage of this approach is that backscatter profiles can be derived during daytime and nighttime, and even in cases when the signal-to-noise ratio of signals from the free troposphere is very low. Moreover, the retrieval can easily be automated. In this paper, we consider the Jenoptik CHM15kx-ceilometer. We discuss the methodology and the achievable accuracy and present a set of examples to highlight the wide range of applications, and the limitations. The achievable temporal resolution is of the order of a few minutes; the relative error of the particle backscatter coefficient is less than 10%. It is emphasized that the accuracy of extinction coefficients and – as a consequence – of the aerosol optical depth is limited due to the unknown lidar ratio. This is, however, an inherent problem of any backscatter lidar and not a special feature of the ceilometer.

  6. Measurement of heat transfer coefficient using termoanemometry methods

    Directory of Open Access Journals (Sweden)

    Dančová P.

    2014-03-01

    Full Text Available This work deals with a measurement of heat transfer from a heated flat plate on which a synthetic jet impacts perpendicularly. Measurement of a heat transfer coefficient (HTC is carried out using the hot wire anemometry method with glue film probe Dantec 55M47. The paper brings also results of velocity profiles measurements and turbulence intensity calculations.

  7. Effect of partition coefficient on microsegregation during solidification of aluminium alloys

    Institute of Scientific and Technical Information of China (English)

    MH Avazkonandeh-Gharavol; M Haddad-Sabzevar; H Fredriksson

    2014-01-01

    In the modeling of microsegregation, the partition coefficient is usually calculated using data from the equilibrium phase diagrams. The aim of this study was to experimentally and theoretically analyze the partition coefficient in binary aluminum-copper alloys. The sam-ples were analyzed by differential thermal analysis (DTA), which were melted and quenched from different temperatures during solidifica-tion. The mass fraction and composition of phases were measured by image processing and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) unit. These data were used to calculate as the experimental partition coefficients with four different methods. The experimental and equilibrium partition coefficients were used to model the concentration profile in the primary phase. The modeling results show that the profiles calculated by the experimental partition coefficients are more consistent with the experi-mental profiles, compared to those calculated using the equilibrium partition coefficients.

  8. Cortisol modifies extinction learning of recently acquired fear in men.

    Science.gov (United States)

    Merz, Christian Josef; Hermann, Andrea; Stark, Rudolf; Wolf, Oliver Tobias

    2014-09-01

    Exposure therapy builds on the mechanism of fear extinction leading to decreased fear responses. How the stress hormone cortisol affects brain regions involved in fear extinction in humans is unknown. For this reason, we tested 32 men randomly assigned to receive either 30 mg hydrocortisone or placebo 45 min before fear extinction. In fear acquisition, a picture of a geometrical figure was either partially paired (conditioned stimulus; CS+) or not paired (CS-) with an electrical stimulation (unconditioned stimulus; UCS). In fear extinction, each CS was presented again, but no UCS occurred. Cortisol increased conditioned skin conductance responses in early and late extinction. In early extinction, higher activation towards the CS- than to the CS+ was found in the amygdala, hippocampus and posterior parahippocampal gyrus. This pattern might be associated with the establishment of a new memory trace. In late extinction, the placebo compared with the cortisol group displayed enhanced CS+/CS- differentiation in the amygdala, medial frontal cortex and nucleus accumbens. A change from early deactivation to late activation of the extinction circuit as seen in the placebo group seems to be needed to enhance extinction and to reduce fear. Cortisol appears to interfere with this process thereby impairing extinction of recently acquired conditioned fear.

  9. A window of vulnerability: impaired fear extinction in adolescence.

    Science.gov (United States)

    Baker, Kathryn D; Den, Miriam L; Graham, Bronwyn M; Richardson, Rick

    2014-09-01

    There have been significant advances made towards understanding the processes mediating extinction of learned fear. However, despite being of clear theoretical and clinical significance, very few studies have examined fear extinction in adolescence, which is often described as a developmental window of vulnerability to psychological disorders. This paper reviews the relatively small body of research examining fear extinction in adolescence. A prominent finding of this work is that adolescents, both humans and rodents, exhibit a marked impairment in extinction relative to both younger (e.g., juvenile) and older (e.g., adult) groups. We then review some potential mechanisms that could produce the striking extinction deficit observed in adolescence. For example, one neurobiological candidate mechanism for impaired extinction in adolescence involves changes in the functional connectivity within the fear extinction circuit, particularly between prefrontal cortical regions and the amygdala. In addition, we review research on emotion regulation and attention processes that suggests that developmental changes in attention bias to threatening cues may be a cognitive mechanism that mediates age-related differences in extinction learning. We also examine how a differential reaction to chronic stress in adolescence impacts upon extinction retention during adolescence as well as in later life. Finally, we consider the findings of several studies illustrating promising approaches that overcome the typically-observed extinction impairments in adolescent rodents and that could be translated to human adolescents. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Cortisol modifies extinction learning of recently acquired fear in men

    Science.gov (United States)

    Hermann, Andrea; Stark, Rudolf; Wolf, Oliver Tobias

    2014-01-01

    Exposure therapy builds on the mechanism of fear extinction leading to decreased fear responses. How the stress hormone cortisol affects brain regions involved in fear extinction in humans is unknown. For this reason, we tested 32 men randomly assigned to receive either 30 mg hydrocortisone or placebo 45 min before fear extinction. In fear acquisition, a picture of a geometrical figure was either partially paired (conditioned stimulus; CS+) or not paired (CS−) with an electrical stimulation (unconditioned stimulus; UCS). In fear extinction, each CS was presented again, but no UCS occurred. Cortisol increased conditioned skin conductance responses in early and late extinction. In early extinction, higher activation towards the CS− than to the CS+ was found in the amygdala, hippocampus and posterior parahippocampal gyrus. This pattern might be associated with the establishment of a new memory trace. In late extinction, the placebo compared with the cortisol group displayed enhanced CS+/CS− differentiation in the amygdala, medial frontal cortex and nucleus accumbens. A change from early deactivation to late activation of the extinction circuit as seen in the placebo group seems to be needed to enhance extinction and to reduce fear. Cortisol appears to interfere with this process thereby impairing extinction of recently acquired conditioned fear. PMID:23945999

  11. Community stability and selective extinction during the Permian-Triassic mass extinction

    Science.gov (United States)

    Roopnarine, Peter D.; Angielczyk, Kenneth D.

    2015-10-01

    The fossil record contains exemplars of extreme biodiversity crises. Here, we examined the stability of terrestrial paleocommunities from South Africa during Earth's most severe mass extinction, the Permian-Triassic. We show that stability depended critically on functional diversity and patterns of guild interaction, regardless of species richness. Paleocommunities exhibited less transient instability—relative to model communities with alternative community organization—and significantly greater probabilities of being locally stable during the mass extinction. Functional patterns that have evolved during an ecosystem's history support significantly more stable communities than hypothetical alternatives.

  12. Transport coefficients of heavy baryons

    Science.gov (United States)

    Tolos, Laura; Torres-Rincon, Juan M.; Das, Santosh K.

    2016-08-01

    We compute the transport coefficients (drag and momentum diffusion) of the low-lying heavy baryons Λc and Λb in a medium of light mesons formed at the later stages of high-energy heavy-ion collisions. We employ the Fokker-Planck approach to obtain the transport coefficients from unitarized baryon-meson interactions based on effective field theories that respect chiral and heavy-quark symmetries. We provide the transport coefficients as a function of temperature and heavy-baryon momentum, and analyze the applicability of certain nonrelativistic estimates. Moreover we compare our outcome for the spatial diffusion coefficient to the one coming from the solution of the Boltzmann-Uehling-Uhlenbeck transport equation, and we find a very good agreement between both calculations. The transport coefficients for Λc and Λb in a thermal bath will be used in a subsequent publication as input in a Langevin evolution code for the generation and propagation of heavy particles in heavy-ion collisions at LHC and RHIC energies.

  13. Wind Dynamics and Circumstellar Extinction Variations in the T Tauri Star RY Tau

    CERN Document Server

    Babina, Elena V; Petrov, Peter P

    2016-01-01

    The wind interaction with the dusty environment of the classical T Tauri star RY Tau has been investigated. During two seasons of 2013-2015 we carried out a spectroscopic and photometric (BVR) monitoring of the star. A correlation between the stellar brightness and the radial velocity of the wind determined from the H-alpha and Na D line profiles has been found for the first time. The irregular stellar brightness variations are shown to be caused by extinction in a dusty disk wind at a distance of about 0.2 AU from the star. We suppose, that variations of the circumstellar extinction results from cyclic rearrangements of the stellar magnetosphere and coronal mass ejections, which affect the dusty disk wind near the inner boundary of the circumstellar disk.

  14. Aerosols and lightning activity: The effect of vertical profile and aerosol type

    Science.gov (United States)

    Proestakis, E.; Kazadzis, S.; Lagouvardos, K.; Kotroni, V.; Amiridis, V.; Marinou, E.; Price, C.; Kazantzidis, A.

    2016-12-01

    The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite has been utilized for the first time in a study regarding lightning activity modulation due to aerosols. Lightning activity observations, obtained by the ZEUS long range Lightning Detection Network, European Centre for Medium range Weather Forecasts (ECMWF) Convective Available Potential Energy (CAPE) data and Cloud Fraction (CF) retrieved by MODIS on board Aqua satellite have been combined with CALIPSO CALIOP data over the Mediterranean basin and for the period March to November, from 2007 to 2014. The results indicate that lightning activity is enhanced during days characterized by higher Aerosol Optical Depth (AOD) values, compared to days with no lightning. This study contributes to existing studies on the link between lightning activity and aerosols, which have been based just on columnar AOD satellite retrievals, by performing a deeper analysis into the effect of aerosol profiles and aerosol types. Correlation coefficients of R = 0.73 between the CALIPSO AOD and the number of lightning strikes detected by ZEUS and of R = 0.93 between ECMWF CAPE and lightning activity are obtained. The analysis of extinction coefficient values at 532 nm indicates that at an altitudinal range exists, between 1.1 km and 2.9 km, where the values for extinction coefficient of lightning-active and non-lightning-active cases are statistically significantly different. Finally, based on the CALIPSO aerosol subtype classification, we have investigated the aerosol conditions of lightning-active and non-lightning-active cases. According to the results polluted dust aerosols are more frequently observed during non-lightning-active days, while dust and smoke aerosols are more abundant in the atmosphere during the lightning-active days.

  15. High time resolution observation and statistical analysis of atmospheric light extinction properties and the chemical speciation of fine particulates

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In recent years,the visibility deterioration caused by regional fine particulate pollution becomes one of the crucial air pollution problems in the urban areas of our country.The rapid variation of visibility and fine particulates make it difficult to estimate the relationship between them precisely and accurately unless high time resolution observation data can be accessed.This study aims to fill this gap in the field of atmospheric science by establishing a formula using multiple linear regressions.Excellent fitting goodness (R2=0.913,n=3167) was obtained using 10 min average of high-resolution real-time light scattering coefficients,light absorption coefficients,main chemical speciation concentration in PM1 and some meteorological parameters from 17 Jan to 16 Feb,2009.It shows that the average light extinction coefficient during the observation in the winter of Shenzhen was measured to be 290 ± 183 Mm?1,consisting of 72% of light scattering and 21% of absorption.In terms of the percentage contribution of PM1 chemical species to the total light extinction,the organic matter was estimated to be most with an average of 45%,followed by ammonium sulfate with an average of 24%.The contributions of black carbon and ammonium nitrate were 17% and 12%,respectively.Besides,the diurnal variation of light extinction was investigated as well in this study.

  16. On the source of the dust extinction in type Ia supernovae and the discovery of anomalously strong Na I absorption

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, M. M.; Morrell, Nidia; Hsiao, E. Y.; Campillay, Abdo; Contreras, Carlos [Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena (Chile); Simon, Joshua D.; Burns, Christopher R.; Persson, Sven E.; Thompson, I. B.; Freedman, Wendy L. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Cox, Nick L. J. [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D bus 2401, 3001 Leuven (Belgium); Foley, Ryan J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Karakas, Amanda I. [Research School of Astronomy and Astrophysics, The Australian National University, Weston, ACT 2611 (Australia); Patat, F. [European Southern Observatory (ESO), Karl Schwarschild Strasse 2, D-85748, Garching bei München (Germany); Sternberg, A. [Max Planck Institute for Astrophysics, Karl Schwarzschild Strasse 1, D-85741 Garching bei München (Germany); Williams, R. E. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gal-Yam, A. [Benoziyo Center for Astrophysics, Faculty of Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Leonard, D. C. [Department of Astronomy, San Diego State University, San Diego, CA 92182 (United States); Stritzinger, Maximilian [Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Folatelli, Gastón, E-mail: mmp@lco.cl [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa 277-8583 (Japan); and others

    2013-12-10

    High-dispersion observations of the Na I D λλ5890, 5896 and K I λλ7665, 7699 interstellar lines, and the diffuse interstellar band at 5780 Å in the spectra of 32 Type Ia supernovae are used as an independent means of probing dust extinction. We show that the dust extinction of the objects where the diffuse interstellar band at 5780 Å is detected is consistent with the visual extinction derived from the supernova colors. This strongly suggests that the dust producing the extinction is predominantly located in the interstellar medium of the host galaxies and not in circumstellar material associated with the progenitor system. One quarter of the supernovae display anomalously large Na I column densities in comparison to the amount of dust extinction derived from their colors. Remarkably, all of the cases of unusually strong Na I D absorption correspond to 'Blueshifted' profiles in the classification scheme of Sternberg et al. This coincidence suggests that outflowing circumstellar gas is responsible for at least some of the cases of anomalously large Na I column densities. Two supernovae with unusually strong Na I D absorption showed essentially normal K I column densities for the dust extinction implied by their colors, but this does not appear to be a universal characteristic. Overall, we find the most accurate predictor of individual supernova extinction to be the equivalent width of the diffuse interstellar band at 5780 Å, and provide an empirical relation for its use. Finally, we identify ways of producing significant enhancements of the Na abundance of circumstellar material in both the single-degenerate and double-degenerate scenarios for the progenitor system.

  17. An analysis of the characteristics of aerosol light scattering coefficients at Seoul and Baengnyeongdo

    Science.gov (United States)

    Kim, B.; Eun, S.; Seo, W.; Park, J.; Ahn, J.; Moon, K.

    2013-12-01

    Aerosols in the atmosphere can scatter and absorb solar radiation and their spatial/temporal distributions are highly inhomogeneous due to short lifetimes (about a few weeks or less). Through scattering and absorption of solar radiation, aerosols directly affect visibility and climate through the modification of the Earth's energy budget (Charlson et al., 1992; Yan, 2007; Wang, 2012). This study investigates long-term trends and characteristics of aerosol light scattering coefficient at Seoul and Baengnyeongdo, 100 km upstream of Seoul, in Korea. Aerosol scattering coefficients were measured continuously with nephelometers. The analysis period is limited to one year of 2011. For the relationship analysis of extinction coefficients (σext) to visibility and aerosol optical depth, σsp observed at 3 p.m. have been used with help of aerosol absorption coefficients (σap) in order to remove its dependence upon relative humidity (RH), and also those of rainy period have been excluded. As expected, σext estimated are inversely proportional to visibility observation by eye. Aerosol extinction coefficients have been vertically integrated with an assumption of nearly well-mixed within an e-folding height to determine aerosol optical depth (τa), and compared with those retrieved from sunphotometer. The results show a reasonable agreement in spite of an inherent difference of each definition. We expect these findings would help to eventually understand aerosol radiative forcing and its effect on the regional climate change around Korea.

  18. Long-term expression of human contextual fear and extinction memories involves amygdala, hippocampus and ventromedial prefrontal cortex: a reinstatement study in two independent samples.

    Science.gov (United States)

    Lonsdorf, Tina B; Haaker, Jan; Kalisch, Raffael

    2014-12-01

    Human context conditioning studies have focused on acquisition and extinction. Subsequent long-term changes in fear behaviors not only depend on associative learning processes during those phases but also on memory consolidation processes and the later ability to retrieve and express fear and extinction memories. Clinical theories explain relapse after successful exposure-based treatment with return of fear memories and remission with stable extinction memory expression. We probed contextual fear and extinction memories 1 week (Day8) after conditioning (Day1) and subsequent extinction (Day2) by presenting conditioned contexts before (Test1) and after (Test2) a reinstatement manipulation. We find consistent activation patterns in two independent samples: activation of a subgenual part of the ventromedial prefrontal cortex before reinstatement (Test1) and (albeit with different temporal profiles between samples) of the amygdala after reinstatement (Test2) as well as up-regulation of anterior hippocampus activity after reinstatement (Test2 > Test1). These areas have earlier been implicated in the expression of cued extinction and fear memories. The present results suggest a general role for these structures in defining the balance between fear and extinction memories, independent of the conditioning mode. The results are discussed in the light of hypotheses implicating the anterior hippocampus in the processing of situational ambiguity.

  19. Late Pennsylvanian climate changes and palynomorph extinctions

    Energy Technology Data Exchange (ETDEWEB)

    Kosanke, R.M.; Cecil, C.B. [US Geological Survey, Denver, CO (United States)

    1996-01-01

    A major floral change occurs in the Upper Pennsylvanian strata in the Midcontinent, Illinois basin, and in the northern Appalachian basin of eastern United States. Lycospora spp. (derived from arborescent lycopsids) became extinct along with some other palynomorph taxa. This investigation is concerned with the importance of this major floral change. Samples were studied from western Pennsylvania, eastern Ohio, and West Virgina (from a previous study) cover the stratigraphic interval from the Upper Freeport coal bed, uppermost part of the Allegheny Formation, to the Mahoning, Mason, Brush Creek, Wilgus, and Anderson coal beds in the lower part of the Conemaugh Formation. The floral change occurs either at or below the accepted Desmoinesian-Missourian boundary in the Midcontinent and Illinois basin, whereas in the northern Appalachians this change occurs in the lower part of the Conemaugh Formation, between the Mahoning and Brush Creek coal beds, or when the Mason is present, between the Mahoning and Mason coal beds. The first coal bed above the extinction of Lycospora spp. is dominated by the palynomorph taxon Endosporites globiformis which is derived from a heterosporous, herbaceous lycopsid. However, Sigillaria, another arborescent lycopsid, did not become extinct at this time as evidenced by the presence of the palynomorph genus Crassispora which is derived from Sigillaria. The reason for the survival of Sigillaria is now known, but it may have been able to adapt, in a limited fashion, to some sort of specialized microenvironment. The ferns, based on palynomorph occurrence, become numerically more important throughout the balance of the Conemaugh Formation, and dominate the Pittsburgh No. 8 and Pomeroy coal beds in the overlying Monogahela Formation.

  20. Harmonic functions with varying coefficients

    Directory of Open Access Journals (Sweden)

    Jacek Dziok

    2016-05-01

    Full Text Available Abstract Complex-valued harmonic functions that are univalent and sense preserving in the open unit disk can be written in the form f = h + g ‾ $f=h+\\overline{g}$ , where h and g are analytic. In this paper we investigate some classes of univalent harmonic functions with varying coefficients related to Janowski functions. By using the extreme points theory we obtain necessary and sufficient convolution conditions, coefficients estimates, distortion theorems, and integral mean inequalities for these classes of functions. The radii of starlikeness and convexity for these classes are also determined.

  1. Self-Organized Criticality and Mass Extinction in Evolutionary Algorithms

    DEFF Research Database (Denmark)

    Krink, Thiemo; Thomsen, Rene

    2001-01-01

    niches after mass extinction events. Furthermore, paleontological studies have shown that there is a power law relationship between the frequency of species extinction events and the sue of the extinction impact. Power law relationships of this kind are typical for complex systems, which operate...... at a critical state between chaos and order, known as self-organized criticality (SOC). Based on this background, we used SOC to control the size of spatial extinction zones in a diffusion model. The SOC selection process was easy to implement and implied only negligible computational costs. Our results show...... that the SOC spatial extinction model clearly outperforms simple evolutionary algorithms (EAs) and the difffision model (CGA). Further, our results support the biological hypothesis that mass extinctions might play an important role in evolution. However, the success of simple EAs indicates that evolution...

  2. [GABA-Receptors in Modulation of Fear Memory Extinction].

    Science.gov (United States)

    Dubrovina, N I

    2016-01-01

    GABA is the major inhibitory neurotransmitter in the central nervous system determining the efficacy of neuronal interaction. GABA-receptors play a key role in different aspects of fear memory--acquisition and consolidation, retention, reconsolidation and extinction. Extinction is an important behavioural phenomenon which allows organism to adapt its behavior to a changing environment. Extinction of fear memory is a form of new inhibitory learning which interferes with expression of the initial acquired fear conditioning. Resistance to extinction is symptom of depression and posttraumatic stress disorder. The aim of the present review was to summarize own and literary data about GABAergic modulation of fear extinction and pharmacological correction of extinction impairment at influences on GABA(A)- and GABA(B)- receptors.

  3. Chemical antipredator defence is linked to higher extinction risk

    Science.gov (United States)

    2016-01-01

    Many attributes of species may be linked to contemporary extinction risk, though some such traits remain untested despite suggestions that they may be important. Here, I test whether a trait associated with higher background extinction rates, chemical antipredator defence, is also associated with current extinction risk, using amphibians as a model system—a group facing global population declines. I find that chemically defended species are approximately 60% more likely to be threatened than species without chemical defence, although the severity of the contemporary extinction risk may not relate to chemical defence. The results confirm that background and contemporary extinction rates can be predicted from the same traits, at least in certain cases. This suggests that associations between extinction risk and phenotypic traits can be temporally stable over long periods. The results also provide novel insights into the relevance of antipredator defences for species subject to conservation concerns. PMID:28018657

  4. Modeling Extinction Risk of Endemic Birds of Mainland China

    Directory of Open Access Journals (Sweden)

    Youhua Chen

    2013-01-01

    Full Text Available The extinction risk of endemic birds of mainland China was modeled over evolutionary time. Results showed that extinction risk of endemic birds in mainland China always tended to be similar within subclades over the evolutionary time of species divergence, and the overall evolution of extinction risk of species presented a conservatism pattern, as evidenced by the disparity-through-time plot. A constant-rate evolutionary model was the best one to quantify the evolution of extinction risk of endemic birds of mainland China. Thus, there was no rate shifting pattern for the evolution of extinction risk of Chinese endemic birds over time. In a summary, extinction risk of endemic birds of mainland China is systematically quantified under the evolutionary framework in the present work.

  5. Late Devonian red tide and mass extinction

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Molecular stratigraphical, carbonate carbon isotopic, stratigraphical and paleontological data show that algal booming, eutrophication, anoxia, hypersalinity, positive ( 13C excursion and biomass decreasing occurred in the offshore carbonate environments of the Frasnian-Famennian (F-F) transition, which hints that red tide might frequently take place in the F-F transition of Guangxi, South China. We suggest that the mass extinction of the reef ecosystems and the shallow-water marine organisms in the F-F transition of the lower-middle latitudes may be related to the frequent occurrence of red tide in that time.

  6. Mass Extinctions and a Dark Disk

    CERN Document Server

    Kramer, Eric David

    2016-01-01

    We consider whether the observed periodicity of mass extinctions and of comet impacts on Earth is consistent with Solar oscillation about the Galactic midplane and spiral arm crossings. It is of further interest to determine whether a hypothetical thin dark disk is necessary to give the right periodicity, and whether such a dark disk is allowed given kinematic and other observational constaints on the Galaxy's gravitational potential. We show that a dark disk consistent with recent bounds, combined with data for spiral arm crossing, can lead to the required periodicity. Moreover, we find that the best fit values correctly predict the date of the Chicxulub crater dated to 66 My ago.

  7. Extinct 244Pu in Ancient Zircons

    Science.gov (United States)

    Turner, Grenville; Harrison, T. Mark; Holland, Greg; Mojzsis, Stephen J.; Gilmour, Jamie

    2004-10-01

    We have found evidence, in the form of fissiogenic xenon isotopes, for in situ decay of 244Pu in individual 4.1- to 4.2-billion-year-old zircons from the Jack Hills region of Western Australia. Because of its short half-life, 82 million years, 244Pu was extinct within 600 million years of Earth's formation. Detrital zircons are the only known relics to have survived from this period, and a study of their Pu geochemistry will allow us to date ancient metamorphic events and determine the terrestrial Pu/U ratio for comparison with the solar ratio.

  8. Gray Extinction in the Orion Trapezium

    Science.gov (United States)

    Krełowski, J.; Galazutdinov, G. A.; Strobel, A.; Mulas, G.

    2016-12-01

    We estimated distances to several Orion Trapezium stars using our CaII-method and confirm the distance recommended by Menten et al. However, we found that in the case of HD 37020 both individual distances (based on the trigonometric VLBI parallax and/or CaII-method) differ from the spectrophotometric distance by a factor of 2.5. We interpret this fact as a result of presence of gray (neutral) extinction of about 1.8 mag in front of this star. The correctness of the applied spectral type/ luminosity class, Sp/L, (based on new original spectra from HARPS-N) and measurements of color indices is discussed.

  9. [The evoked activity of the lateral hypothalamus during extinction and differential inhibition].

    Science.gov (United States)

    Vanetsian, G L

    1995-01-01

    Character of interaction between symmetric points of the cat's auditory cortex (A1) and the lateral hypothalamus (HL) was determined by calculating Spearman correlation coefficients between averaged summed sound-evoked activity (AEP) of the structures before, during elaboration, extinction and restoration, as well as differentiation of food-procuring conditioned reflex and in the eating full. Close mutual co-tuning between the cortex and hypothalamus characteristic for stable conditioned reflex was found to disrupted during its extinction, elaboration of differentiation and fullness eat inhibition due to entire reduction of hypothalamic AEP and disappearance of correlated with negativity of HL AEP "doubling" of the first positive wave of A1 AEP. Hyperactivity stage, expressed at the beginning of extinction and at the end of differentiation, preceded inactivation of hypothalamic afferents during elaboration of conditioned inhibition. The stage of hyperactivity, initiated by the elevated emotional state of the animal, testifies to an important role of emotional brain structures in the process of internal inhibition. The stage of HL and A1 hyperactivity initiated by emotional stress of the animal and following HL inactivation during inhibition of the conditioned response point to an important role of emotional subcortical brain structures in the mechanisms of inhibitory conditioning.

  10. The risk of extinction - the mutational meltdown or the overpopulation

    OpenAIRE

    Malarz, K.

    2006-01-01

    The phase diagrams survival-extinction for the Penna model with parameters: (mutations rate)-(birth rate), (mutation rate)-(harmful mutations threshold), (harmful mutation threshold)-(minimal reproduction age) are presented. The extinction phase may be caused by either mutational meltdown or overpopulation. When the Verhulst factor is responsible for removing only newly born babies and does not act on adults the overpopulation is avoided and only genetic factors may lead to species extinction.

  11. Compound stimulus extinction reduces spontaneous recovery in humans

    OpenAIRE

    Coelho, Cesar A.O.; Dunsmoor, Joseph E.; Phelps, Elizabeth A.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design (“deepened extinction”) shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately paired with an electric shock. The target CS (CSA) was extinguished alone followed by compound presentations of the extinguished CSA and nonextinguished CSB. Reco...

  12. Extinction and dust properties in a clumpy medium

    OpenAIRE

    Scicluna, P.; Siebenmorgen, R.

    2015-01-01

    (abridged) The dust content of the universe is primarily explored via its interaction with stellar photons, producing interstellar extinction. However, owing to the physical extension of the observing beam, observations may detect scattered photons, resulting in a change in the observed (or effective) extinction, depending on the spatial distribution of the dust and the resolution of the instrument. We investigate the influence of clumpy dust distributions on effective extinction toward embed...

  13. A Comprehensive Quantitative Assessment of Bird Extinction Risk in Brazil

    OpenAIRE

    Nathália Machado; Rafael Dias Loyola

    2013-01-01

    In an effort to avoid species loss, scientists have focused their efforts on the mechanisms making some species more prone to extinction than others. However, species show different responses to threats given their evolutionary history, behavior, and intrinsic biological features. We used bird biological features and external threats to (1) understand the multiple pathways driving Brazilian bird species to extinction, (2) to investigate if and how extinction risk is geographically structured,...

  14. Experience with Dynamic Reinforcement Rates Decreases Resistance to Extinction

    OpenAIRE

    Craig, Andrew R.; Shahan, Timothy A

    2016-01-01

    The ability of organisms to detect reinforcer-rate changes in choice preparations is positively related to two factors: the magnitude of the change in rate and the frequency with which rates change. Gallistel (2012) suggested similar rate-detection processes are responsible for decreases in responding during operant extinction. Although effects of magnitude of change in reinforcer rate on resistance to extinction are well known (e.g., the partial-reinforcement-extinction effect), effects of f...

  15. The Effect of Size and Ecology on Extinction Susceptibility

    Science.gov (United States)

    Huynh, C.; Yuan, A.; Heim, N.; Payne, J.

    2015-12-01

    Although life on Earth first emerged as prokaryotic organisms, it eventually evolved into billions of different species. However, extinctions on Earth, especially the five mass extinctions, have decimated species. So what leads to a species survival or demise during a mass extinction? Are certain species more susceptible to extinctions based on their size and ecology? For this project, we focused on the data of marine animals. To examine the impact of size and ecology on a species's likelihood of survival, we compared the sizes and ecologies of the survivors and victims of the five mass extinctions. The ecology, or life mode, of a genus consists of the combination of tiering, motility, and feeding mechanism. Tiering refers to the animal's typical location in the water column and sediments, motility refers to its ability to move, and feeding mechanism describes the way the organism eats; together, they describe the animal's behavior. We analyzed the effect of ecology on survival using logistic regression, which compares life mode to the success or failure of a genus during each mass extinction interval. For organism size, we found the extinct organisms' mean size (both volume and length) and compared it with the average size of survivors on a graph. Our results show that while surviving genera of mass extinctions tended to be slightly larger than those that went extinct, there was no significant difference. Even though the Permian (Changhsingian) and Triassic (Rhaetian) extinctions had larger surviving species, likewise the difference was small. Ecology had a more obvious impact on the likelihood of survival; fast-moving, predatory pelagic organisms were the most likely to go extinct, while sedentary, infaunal suspension feeders had the greatest chances of survival. Overall, ecology played a greater role than size in determining the survival of a species. With this information, we can use ecology to predict which species would survive future extinctions.

  16. Evaluating the presence versus absence of the reinforcer during extinction.

    Science.gov (United States)

    Castillo, Mariana I; Borrero, John C; Mendres-Smith, Amber E

    2014-01-01

    The purpose of this study was to assess the effects of extinction when the reinforcer was present versus absent. These effects were examined with 2 human operant procedures (i.e., a computer program and a mechanical apparatus) with college students as participants. Discriminable properties of the apparatus appeared to influence responding during extinction. In general, responding during extinction was less likely with the mechanical apparatus when the reinforcer was absent and more likely with the computer program.

  17. How humans drive speciation as well as extinction

    DEFF Research Database (Denmark)

    Bull, Joseph William; Maron, M.

    2016-01-01

    A central topic for conservation science is evaluating how human activities influence global species diversity. Humanity exacerbates extinction rates. But by what mechanisms does humanity drive the emergence of new species? We review human-mediated speciation, compare speciation and known extinct...... and other metrics, risk aversion, taboo trade-offs and spatial heterogeneity. We conclude that evaluating speciation alongside extinction could result in more nuanced understanding of biosphere trends, clarifying what it is we actually value about biodiversity....

  18. Extinction in the Galaxy from surface brightnesses of ESO-LV galaxies : Testing "standard" extinction maps

    NARCIS (Netherlands)

    Choloniewski, J.; Valentijn, E. A.

    2003-01-01

    A new method for the determination of the extinction in the Galaxy is proposed. The method uses surface brightnesses of external galaxies in the B and R-bands. The observational data have been taken from the ESO-LV galaxy catalog. As a first application of our model we derive the ratio of R-band to

  19. Primate extinction risk and historical patterns of speciation and extinction in relation to body mass.

    Science.gov (United States)

    Matthews, Luke J; Arnold, Christian; Machanda, Zarin; Nunn, Charles L

    2011-04-22

    Body mass is thought to influence diversification rates, but previous studies have produced ambiguous results. We investigated patterns of diversification across 100 trees obtained from a new Bayesian inference of primate phylogeny that sampled trees in proportion to their posterior probabilities. First, we used simulations to assess the validity of previous studies that used linear models to investigate the links between IUCN Red List status and body mass. These analyses support the use of linear models for ordinal ranked data on threat status, and phylogenetic generalized linear models revealed a significant positive correlation between current extinction risk and body mass across our tree block. We then investigated historical patterns of speciation and extinction rates using a recently developed maximum-likelihood method. Specifically, we predicted that body mass correlates positively with extinction rate because larger bodied organisms reproduce more slowly, and body mass correlates negatively with speciation rate because smaller bodied organisms are better able to partition niche space. We failed to find evidence that extinction rates covary with body mass across primate phylogeny. Similarly, the speciation rate was generally unrelated to body mass, except in some tests that indicated an increase in the speciation rate with increasing body mass. Importantly, we discovered that our data violated a key assumption of sample randomness with respect to body mass. After correcting for this bias, we found no association between diversification rates and mass.

  20. Requirement for BDNF in the reconsolidation of fear extinction.

    Science.gov (United States)

    Radiske, Andressa; Rossato, Janine I; Köhler, Cristiano A; Gonzalez, Maria Carolina; Medina, Jorge H; Cammarota, Martín

    2015-04-22

    Therapies based on the impairment of reconsolidation or the enhancement of extinction offer the possibility of decreasing the persistent recollection of distressing memories. However, the direct interplay between reconsolidation and extinction has rarely been considered. Previously, we reported that reactivation induces reconsolidation of fear extinction memory. Here, using a step-down inhibitory avoidance learning paradigm in rats, we show that intrahippocampus infusion of function-blocking anti-BDNF antibody immediately or 6 h after extinction memory reactivation impairs the reconsolidation of extinction. Extinction memory reactivation increases proBDNF, BDNF, and tropomyosin receptor kinase B (TrkB) phosphorylation levels in dorsal CA1, while blocking BDNF maturation in the hippocampus with plasminogen activator inhibitor 1 hinders the persistence of extinction and induces the recurrence of fear. Moreover, coinfusion of recombinant BDNF (0.25 μg/side) after extinction memory reactivation impedes the recovery of the avoidance response induced by inhibiting gene expression and protein synthesis in the dorsal hippocampus. Our findings unravel a new role for BDNF, suggesting that this neurotrophin is necessary and sufficient to maintain the reactivated fear extinction engram.

  1. Extinction of Learned Fear Induces Hippocampal Place Cell Remapping.

    Science.gov (United States)

    Wang, Melissa E; Yuan, Robin K; Keinath, Alexander T; Ramos Álvarez, Manuel M; Muzzio, Isabel A

    2015-06-17

    The extinction of learned fear is a hippocampus-dependent process thought to embody new learning rather than erasure of the original fear memory, although it is unknown how these competing contextual memories are represented in the hippocampus. We previously demonstrated that contextual fear conditioning results in hippocampal place cell remapping and long-term stabilization of novel representations. Here we report that extinction learning also induces place cell remapping in C57BL/6 mice. Specifically, we observed cells that preferentially remapped during different stages of learning. While some cells remapped in both fear conditioning and extinction, others responded predominantly during extinction, which may serve to modify previous representations as well as encode new safe associations. Additionally, we found cells that remapped primarily during fear conditioning, which could facilitate reacquisition of the original fear association. Moreover, we also observed cells that were stable throughout learning, which may serve to encode the static aspects of the environment. The short-term remapping observed during extinction was not found in animals that did not undergo fear conditioning, or when extinction was conducted outside of the conditioning context. Finally, conditioning and extinction produced an increase in spike phase locking to the theta and gamma frequencies. However, the degree of remapping seen during conditioning and extinction only correlated with gamma synchronization. Our results suggest that the extinction learning is a complex process that involves both modification of pre-existing memories and formation of new ones, and these traces coexist within the same hippocampal representation.

  2. Hypoxia, global warming, and terrestrial late Permian extinctions.

    Science.gov (United States)

    Huey, Raymond B; Ward, Peter D

    2005-04-15

    A catastrophic extinction occurred at the end of the Permian Period. However, baseline extinction rates appear to have been elevated even before the final catastrophe, suggesting sustained environmental degradation. For terrestrial vertebrates during the Late Permian, the combination of a drop in atmospheric oxygen plus climate warming would have induced hypoxic stress and consequently compressed altitudinal ranges to near sea level. Our simulations suggest that the magnitude of altitudinal compression would have forced extinctions by reducing habitat diversity, fragmenting and isolating populations, and inducing a species-area effect. It also might have delayed ecosystem recovery after the mass extinction.

  3. Experience with dynamic reinforcement rates decreases resistance to extinction.

    Science.gov (United States)

    Craig, Andrew R; Shahan, Timothy A

    2016-03-01

    The ability of organisms to detect reinforcer-rate changes in choice preparations is positively related to two factors: the magnitude of the change in rate and the frequency with which rates change. Gallistel (2012) suggested similar rate-detection processes are responsible for decreases in responding during operant extinction. Although effects of magnitude of change in reinforcer rate on resistance to extinction are well known (e.g., the partial-reinforcement-extinction effect), effects of frequency of changes in rate prior to extinction are unknown. Thus, the present experiments examined whether frequency of changes in baseline reinforcer rates impacts resistance to extinction. Pigeons pecked keys for variable-interval food under conditions where reinforcer rates were stable and where they changed within and between sessions. Overall reinforcer rates between conditions were controlled. In Experiment 1, resistance to extinction was lower following exposure to dynamic reinforcement schedules than to static schedules. Experiment 2 showed that resistance to presession feeding, a disruptor that should not involve change-detection processes, was unaffected by baseline-schedule dynamics. These findings are consistent with the suggestion that change detection contributes to extinction. We discuss implications of change-detection processes for extinction of simple and discriminated operant behavior and relate these processes to the behavioral-momentum based approach to understanding extinction.

  4. Has the Earth's sixth mass extinction already arrived?

    Science.gov (United States)

    Barnosky, Anthony D; Matzke, Nicholas; Tomiya, Susumu; Wogan, Guinevere O U; Swartz, Brian; Quental, Tiago B; Marshall, Charles; McGuire, Jenny L; Lindsey, Emily L; Maguire, Kaitlin C; Mersey, Ben; Ferrer, Elizabeth A

    2011-03-03

    Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis. Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.

  5. Extinction and ecosystem function in the marine benthos.

    Science.gov (United States)

    Solan, Martin; Cardinale, Bradley J; Downing, Amy L; Engelhardt, Katharina A M; Ruesink, Jennifer L; Srivastava, Diane S

    2004-11-12

    Rapid changes in biodiversity are occurring globally, yet the ecological impacts of diversity loss are poorly understood. Here we use data from marine invertebrate communities to parameterize models that predict how extinctions will affect sediment bioturbation, a process vital to the persistence of aquatic communities. We show that species extinction is generally expected to reduce bioturbation, but the magnitude of reduction depends on how the functional traits of individual species covary with their risk of extinction. As a result, the particular cause of extinction and the order in which species are lost ultimately govern the ecosystem-level consequences of biodiversity loss.

  6. Effective Viscosity Coefficient of Nanosuspensions

    Science.gov (United States)

    Rudyak, V. Ya.; Belkin, A. A.; Egorov, V. V.

    2008-12-01

    Systematic calculations of the effective viscosity coefficient of nanosuspensions have been performed using the molecular dynamics method. It is established that the viscosity of a nanosuspension depends not only on the volume concentration of the nanoparticles but also on their mass and diameter. Differences from Einstein's relation are found even for nanosuspensions with a low particle concentration.

  7. Irrational "Coefficients" in Renaissance Algebra.

    Science.gov (United States)

    Oaks, Jeffrey A

    2017-06-01

    Argument From the time of al-Khwārizmī in the ninth century to the beginning of the sixteenth century algebraists did not allow irrational numbers to serve as coefficients. To multiply by x, for instance, the result was expressed as the rhetorical equivalent of . The reason for this practice has to do with the premodern concept of a monomial. The coefficient, or "number," of a term was thought of as how many of that term are present, and not as the scalar multiple that we work with today. Then, in sixteenth-century Europe, a few algebraists began to allow for irrational coefficients in their notation. Christoff Rudolff (1525) was the first to admit them in special cases, and subsequently they appear more liberally in Cardano (1539), Scheubel (1550), Bombelli (1572), and others, though most algebraists continued to ban them. We survey this development by examining the texts that show irrational coefficients and those that argue against them. We show that the debate took place entirely in the conceptual context of premodern, "cossic" algebra, and persisted in the sixteenth century independent of the development of the new algebra of Viète, Decartes, and Fermat. This was a formal innovation violating prevailing concepts that we propose could only be introduced because of the growing autonomy of notation from rhetorical text.

  8. Enhanced extinction of visible radiation due to hydrated aerosols in mist and fog

    Directory of Open Access Journals (Sweden)

    T. Elias

    2015-01-01

    Full Text Available The study assesses the contribution of aerosols to the extinction of visible radiation in the mist-fog-mist cycle. Measurements of the microphysical and optical properties of hydrated aerosols with diameters larger than 400 nm, composing the accumulation mode, which are the most efficient to interact with visible radiation, were carried out near Paris, during November 2011, in ambient conditions. Eleven mist-fog-mist cycles were observed, with cumulated fog duration of 95 h, and cumulated mist-fog-mist duration of 240 h. In mist, aerosols grew up by taking up water at relative humidities larger than 93%, causing a visibility decrease below 5 km. While visibility decreased down to few km, the mean size of the hydrated aerosols increased, and their number concentration (Nha increased from approximately 160 to approximately 600 cm−3. When fog formed, droplets became the strongest contributors to visible radiation extinction, and liquid water content (LWC increased beyond 7 mg m−3. Hydrated aerosols of the accumulation mode co-existed with droplets, as interstitial non-activated aerosols. Their size continued to increase, and a significant proportion of aerosols achieved diameters larger than 2.5 μm. The mean transition diameter between the accumulation mode and the small droplet mode was 4.0 ± 1.1 μm. Moreover Nha increased on average by 60% after fog formation. Consequently the mean aerosol contribution to extinction in fog was 20 ± 15% for diameter smaller than 2.5 μm and 6 ± 7% beyond. The standard deviation is large because of the large variability of Nha in fog, which could be smaller than in mist or three times larger. The particle extinction coefficient in fog can be computed as the sum of a droplet component and an aerosol component, which can be approximated by 3.5 Nha (Nha in cm−3 and particle extinction coefficient in Mm−1. We observed an influence of the main formation process on Nha, but not on the contribution to fog

  9. Enhanced extinction of visible radiation due to hydrated aerosols in mist and fog

    Science.gov (United States)

    Elias, T.; Dupont, J.-C.; Hammer, E.; Hoyle, C. R.; Haeffelin, M.; Burnet, F.; Jolivet, D.

    2015-06-01

    The study assesses the contribution of aerosols to the extinction of visible radiation in the mist-fog-mist cycle. Relative humidity is large in the mist-fog-mist cycle, and aerosols most efficient in interacting with visible radiation are hydrated and compose the accumulation mode. Measurements of the microphysical and optical properties of these hydrated aerosols with diameters larger than 0.4 μm were carried out near Paris, during November 2011, under ambient conditions. Eleven mist-fog-mist cycles were observed, with a cumulated fog duration of 96 h, and a cumulated mist-fog-mist cycle duration of 240 h. In mist, aerosols grew by taking up water at relative humidities larger than 93%, causing a visibility decrease below 5 km. While visibility decreased down from 5 to a few kilometres, the mean size of the hydrated aerosols increased, and their number concentration (Nha) increased from approximately 160 to approximately 600 cm-3. When fog formed, droplets became the strongest contributors to visible radiation extinction, and liquid water content (LWC) increased beyond 7 mg m-3. Hydrated aerosols of the accumulation mode co-existed with droplets, as interstitial non-activated aerosols. Their size continued to increase, and some aerosols achieved diameters larger than 2.5 μm. The mean transition diameter between the aerosol accumulation mode and the small droplet mode was 4.0 ± 1.1 μm. Nha also increased on average by 60 % after fog formation. Consequently, the mean contribution to extinction in fog was 20 ± 15% from hydrated aerosols smaller than 2.5 μm and 6 ± 7% from larger aerosols. The standard deviation was large because of the large variability of Nha in fog, which could be smaller than in mist or 3 times larger. The particle extinction coefficient in fog can be computed as the sum of a droplet component and an aerosol component, which can be approximated by 3.5 Nha (Nha in cm-3 and particle extinction coefficient in Mm-1. We observed an influence of

  10. Science observed: The mass-extinction debates

    Science.gov (United States)

    Glen, W.

    1994-01-01

    The upheaval triggered in 1980 by the Alvarez-Berkeley group impact hypothesis transformed the literature of mass extinctions from an unfocused, sporadic collection of papers that virtually ignored extraterrestrial causes and treated endogenous ones only sparingly better to an integrated, diverse body of literature. Research programs organized seemingly overnight spawned collaborative teams whose members, often from distant, isolated disciplines, redirected their careers in order to address the captivating, high-stakes issues. The initial, generally skeptical, cool reception of the impact hypothesis might have been predicted for any of a number of reasons: such an instantaneous catastrophe contravened earth science's reigning philosophy of uniformitarianism; it was formulated from a form of evidence - siderophile element anomalies - alien to the community charged with its appraisal; it advanced a causal mechanism that was improbable in terms of canonical knowledge; and it was proffered mainly by specialists alien to earth and biological science, especially paleobiology. Early on it became clear that irrespective of which causal hypothesis was chosen, the chosen one would be the strongest predictor of how the chooser would select and apply standards in assessing evidence bearing on all such hypothesis. Less strong correlation also appeared between disciplinary speciality and the assessment of evidence. Such correlations varied with the level of specialization; the most robust correlations appeared in the broadest areas of science practice. The gestalt (mindset) seemingly engendered by the embrace of an extinction hypothesis overrode, or was stronger than, the intellectual predispositions attributable to disciplinary specialty.

  11. Critical Multitype Branching Systems: Extinction Results

    CERN Document Server

    Kevei, Peter

    2011-01-01

    We consider a critical branching particle system in $\\R^d$, composed of individuals of a finite number of types $i\\in\\{1,...,K\\}$. Each individual of type $i$ moves independently according to a symmetric $\\alpha_i$-stable motion. We assume that the particle lifetimes and offspring distributions are type-dependent. Under the usual independence assumptions in branching systems, we prove extinction theorems in the following cases: (1) all the particle lifetimes have finite mean, or (2) there is a type whose lifetime distribution has heavy tail, and the other lifetimes have finite mean. We get a more complex dynamics by assuming in case (2) that the most mobile particle type corresponds to a finite-mean lifetime: in this case, local extinction of the population is determined by an interaction of the parameters (offspring variability, mobility, longevity) of the long-living type and those of the most mobile type. The proofs are based on a precise analysis of the occupation times of a related Markov renewal process...

  12. Patterns of species ranges, speciation, and extinction.

    Science.gov (United States)

    Birand, Aysegul; Vose, Aaron; Gavrilets, Sergey

    2012-01-01

    The exact nature of the relationship among species range sizes, speciation, and extinction events is not well understood. The factors that promote larger ranges, such as broad niche widths and high dispersal abilities, could increase the likelihood of encountering new habitats but also prevent local adaptation due to high gene flow. Similarly, low dispersal abilities or narrower niche widths could cause populations to be isolated, but such populations may lack advantageous mutations due to low population sizes. Here we present a large-scale, spatially explicit, individual-based model addressing the relationships between species ranges, speciation, and extinction. We followed the evolutionary dynamics of hundreds of thousands of diploid individuals for 200,000 generations. Individuals adapted to multiple resources and formed ecological species in a multidimensional trait space. These species varied in niche widths, and we observed the coexistence of generalists and specialists on a few resources. Our model shows that species ranges correlate with dispersal abilities but do not change with the strength of fitness trade-offs; however, high dispersal abilities and low resource utilization costs, which favored broad niche widths, have a strong negative effect on speciation rates. An unexpected result of our model is the strong effect of underlying resource distributions on speciation: in highly fragmented landscapes, speciation rates are reduced.

  13. Evolutionary Catastrophes: The Science of Mass Extinction

    Science.gov (United States)

    Hames, Willis

    The stories behind the greatest scientific controversies are more than entertaining. They provide windows into the evolution of scientific thought, scientific method, technological achievements and their research applications, and the influence of individuals and personalities on a community's acceptance of a theory Epic controversies surround the theories for Earth's mass extinction events, and none is more spectacular than the continuing polemic over the Cretaceous-Tertiary (K/T) mass extinctions and ultimate demise of the dinosaurs.In contrast to other great scientific debates, we tend to view the K/T event in the context of a crime scene, where the spectacularly diverse flora and fauna of a primordial Eden were unwittingly slain by one or more ruthless and efficient killers. A “foreign” suspect has been fingered; an intruder that killed suddenly and randomly has become the principal suspect. The main clues uncovered in the case include a global K/T iridium anomaly; shock-deformed minerals in K/T boundary sediments; the ˜6 5 m.y-old Deccan flood-basalt province, which covered an area roughly the size of France; and the ˜6 5 m.y-old Chicxulub impact crater in the Yucatan peninsula, which seems to be among the largest to have formed in the inner solar system over the past billion years.

  14. Extinction and reinstatement to cocaine-associated cues in male and female juvenile rats and the role of D1 dopamine receptor.

    Science.gov (United States)

    Brenhouse, Heather C; Thompson, Britta S; Sonntag, Kai C; Andersen, Susan L

    2015-08-01

    Extinction of behaviors in response to drug-associated cues and prevention of reinstatement are integral for addiction treatment, and can reverse or ameliorate the harmful consequences of drug use. The mechanisms controlling extinction and reinstatement involve prefrontal cortical dopamine receptors, which change in expression and activity during the juvenile and adolescent transitions until they mature in adulthood. Little is known about the role that PFC D1 dopamine receptors play in extinction of drug-paired associations early in life. We used extinction of place preferences for cocaine in juvenile male and female rats following genetic, cell-specific overexpression of D1 on glutamatergic cells in the PFC. All subjects needed to demonstrate cocaine preferences for inclusion in the extinction studies. Here, male juveniles with a preference to 10 mg/kg cocaine took longer to extinguish preferences compared to both male adults and female juveniles. Female juveniles extinguished more rapidly than male juveniles at 20 mg/kg cocaine. Overexpression of D1 in juvenile males significantly facilitated extinction relative to juvenile male controls, whereas D1 prolonged expression of extinction in adults overexpressing D1 and adolescents who naturally have elevated D1 expression. These data suggest that an immature D1 profile in juveniles prevented the learning of new associations, and D1 overexpression may provide sufficient activity to facilitate extinction learning. D1 overexpression reduced reinstatement to a priming dose of cocaine in juvenile males. Together, these data show D1 expression may re-program motivational circuitry to facilitate extinction learning during juvenility that is normally unavailable to juveniles and that sex differences exist.

  15. Intercomparison of a Cavity Attenuated Phase Shift-based extinction monitor (CAPS PMex) with an integrating nephelometer and a filter-based absorption monitor

    Science.gov (United States)

    Petzold, A.; Onasch, T.; Kebabian, P.; Freedman, A.

    2013-05-01

    An evaluation of the Cavity Attenuated Phase Shift particle light extinction monitor (CAPS PMex) using a combination of a 3-wavelength Integrating Nephelometer (NEPH) and a 3-wavelength filter-based Particle Soot Absorption Photometer (PSAP) was carried out using both laboratory-generated test particles and ambient aerosols. An accurate determination of a fixed pathlength correction for the CAPS PMex was made by comparing extinction measurements using monodisperse PSL spheres in combination with Mie scattering calculations to account for the presence of PSL conglomerates. These studies yielded a linear instrument response over the investigated dynamical range from 20 to 450 Mm-1 (10-6 m-1) with a linear correlation coefficient of R2 > 0.98. The adjustment factor was determined to be 1.05 times that previously reported. Correlating CAPS extinction to extinction measured by the NEPH + PSAP combination using laboratory-generated polydisperse mixtures of purely scattering ammonium sulfate and highly absorbing black carbon provided a linear regression line with slope m = 1.00 (R2 = 0.994) for single-scattering albedo values (λ = 630 nm) ranging from 0.35 (black carbon) to 1.00 (ammonium sulfate). For ambient aerosol, light extinction measured by CAPS was highly correlated (R2 = 0.995) to extinction measured by the NEPH + PSAP combination with slope m = 0.95.

  16. Intercomparison Study of the CAPS PMex (Cavity Attenuated Phase Shift Particle Light Extinction Monitor) with the combination of an Integrating Nephelometer and a Particle Soot Absorption Photometer

    Science.gov (United States)

    Petzold, A.; Onasch, T.; Kebabian, P.; Freedman, A.

    2012-10-01

    An evaluation of the Cavity Attenuated Phase Shift particle light extinction monitor (CAPS PMex) by means of a combination of a 3-wavelength Integrating Nephelometer (NEPH; TSI Model 3563) and a 3-wavelength filter-based Particle Soot Absorption Photometer (PSAP) was carried out using both laboratory generated test particles and ambient aerosols. An accurate determination of a fixed pathlength correction for the CAPS PMex was made by comparing extinction measurements using polystyrene latex (PSL) spheres in combination with Mie scattering calculations to account for the presence of PSL conglomerates. These studies yielded a linear instrument response over the investigated dynamical range from 20 to 450 M m-1 (10-6 m-1) with a linear correlation coefficient of R2 > 0.98. The adjustment factor was determined to be 1.05 times that previously reported. Correlating CAPS extinction to extinction measured by the NEPH-PSAP combination using laboratory-generated polydisperse mixtures of purely scattering ammonium sulfate and highly absorbing black carbon provided a linear regression line with slope m = 0.99 (R2 = 0.996) for single-scattering albedo values (λ = 630 nm) ranging from 0.35 (black carbon) to 1.00 (ammonium sulfate). For ambient aerosol, light extinction measured by CAPS PMex was highly correlated (R2 = 0.995) to extinction measured by the NEPH-PSAP combination with slope m = 0.95.

  17. Measuring the Soret coefficient of nanoparticles in a dilute suspension.

    Science.gov (United States)

    Zhao, Chao; Fu, Jinxin; Oztekin, Alparslan; Cheng, Xuanhong

    2014-10-01

    Thermophoresis is an efficient process for the manipulation of molecules and nanoparticles due to the strong force it generates on the nanoscale. Thermophoresis is characterized by the Soret coefficient. Conventionally, the Soret coefficient of nanosized species is obtained by fitting the concentration profile under a temperature gradient at the steady state to a continuous phase model. However, when the number density of the target is ultralow and the dispersed species cannot be treated as a continuous phase, the bulk concentration fluctuates spatially, preventing extraction of temperature-gradient induced concentration profile. The present work demonstrates a strategy to tackle this problem by superimposing snapshots of nanoparticle distribution. The resulting image is suitable for the extraction of the Soret coefficient through the conventional data fitting method. The strategy is first tested through a discrete phase model that illustrates the spatial fluctuation of the nanoparticle concentration in a dilute suspension in response to the temperature gradient. By superimposing snapshots of the stochastic distribution, a thermophoretic depletion profile with low standard error is constructed, indicative of the Soret coefficient. Next, confocal analysis of nanoparticle distribution in response to a temperature gradient is performed using polystyrene nanobeads down to 1e-5% (v/v). The experimental results also reveal that superimposing enhances the accuracy of extracted Soret coefficient. The critical particle number density in the superimposed image for predicting the Soret coefficient is hypothesized to depend on the spatial resolution of the image. This study also demonstrates that the discrete phase model is an effective tool to study particle migration under thermophoresis in the liquid phase.

  18. Sedimentation coefficient distributions of large particles.

    Science.gov (United States)

    Schuck, Peter

    2016-07-21

    The spatial and temporal evolution of concentration boundaries in sedimentation velocity analytical ultracentrifugation reports on the size distribution of particles with high hydrodynamic resolution. For large particles such as large protein complexes, fibrils, viral particles, or nanoparticles, sedimentation conditions usually allow migration from diffusion to be neglected relative to sedimentation. In this case, the shape of the sedimentation boundaries of polydisperse mixtures relates directly to the underlying size-distributions. Integral and derivative methods for calculating sedimentation coefficient distributions g*(s) of large particles from experimental boundary profiles have been developed previously, and are recapitulated here in a common theoretical framework. This leads to a previously unrecognized relationship between g*(s) and the time-derivative of concentration profiles. Of closed analytical form, it is analogous to the well-known Bridgman relationship for the radial derivative. It provides a quantitative description of the effect of substituting the time-derivative by scan differences with finite time intervals, which appears as a skewed box average of the true distribution. This helps to theoretically clarify the differences between results from time-derivative method and the approach of directly fitting the integral definition of g*(s) to the entirety of experimental boundary data.

  19. Acute stress impairs the retrieval of extinction memory in humans.

    Science.gov (United States)

    Raio, Candace M; Brignoni-Perez, Edith; Goldman, Rachel; Phelps, Elizabeth A

    2014-07-01

    Extinction training is a form of inhibitory learning that allows an organism to associate a previously aversive cue with a new, safe outcome. Extinction does not erase a fear association, but instead creates a competing association that may or may not be retrieved when a cue is subsequently encountered. Characterizing the conditions under which extinction learning is expressed is important to enhancing the treatment of anxiety disorders that rely on extinction-based exposure therapy as a primary treatment technique. The ventromedial prefrontal cortex, which plays a critical role in the expression of extinction memory, has been shown to be functionally impaired after stress exposure. Further, recent work in rodents has demonstrated that exposure to stress leads to deficits in extinction retrieval, although this has yet to be tested in humans. To explore how stress might influence extinction retrieval in humans, participants underwent a differential aversive learning paradigm, in which one image was probabilistically paired with an aversive shock while the other image denoted safety. Extinction training directly followed, at which point reinforcement was omitted. A day later, participants returned to the lab and either completed an acute stress manipulation (i.e., cold pressor), or a control task, before undergoing an extinction retrieval test. Skin conductance responses and salivary cortisol concentrations were measured throughout each session as indices of fear arousal and neuroendocrine stress response, respectively. The efficacy of our stress induction was established by observing significant increases in cortisol for the stress condition only. We examined extinction retrieval by comparing conditioned responses during the last trial of extinction (day 1) with that of the first trial of re-extinction (day 2). Groups did not differ on initial fear acquisition or extinction, however, a day later participants in the stress group (n=27) demonstrated significantly

  20. A robust nonparametric method for quantifying undetected extinctions.

    Science.gov (United States)

    Chisholm, Ryan A; Giam, Xingli; Sadanandan, Keren R; Fung, Tak; Rheindt, Frank E

    2016-06-01

    How many species have gone extinct in modern times before being described by science? To answer this question, and thereby get a full assessment of humanity's impact on biodiversity, statistical methods that quantify undetected extinctions are required. Such methods have been developed recently, but they are limited by their reliance on parametric assumptions; specifically, they assume the pools of extant and undetected species decay exponentially, whereas real detection rates vary temporally with survey effort and real extinction rates vary with the waxing and waning of threatening processes. We devised a new, nonparametric method for estimating undetected extinctions. As inputs, the method requires only the first and last date at which each species in an ensemble was recorded. As outputs, the method provides estimates of the proportion of species that have gone extinct, detected, or undetected and, in the special case where the number of undetected extant species in the present day is assumed close to zero, of the absolute number of undetected extinct species. The main assumption of the method is that the per-species extinction rate is independent of whether a species has been detected or not. We applied the method to the resident native bird fauna of Singapore. Of 195 recorded species, 58 (29.7%) have gone extinct in the last 200 years. Our method projected that an additional 9.6 species (95% CI 3.4, 19.8) have gone extinct without first being recorded, implying a true extinction rate of 33.0% (95% CI 31.0%, 36.2%). We provide R code for implementing our method. Because our method does not depend on strong assumptions, we expect it to be broadly useful for quantifying undetected extinctions. © 2016 Society for Conservation Biology.

  1. Atmospheric extinction in simulation tools for solar tower plants

    Science.gov (United States)

    Hanrieder, Natalie; Wilbert, Stefan; Schroedter-Homscheidt, Marion; Schnell, Franziska; Guevara, Diana Mancera; Buck, Reiner; Giuliano, Stefano; Pitz-Paal, Robert

    2017-06-01

    Atmospheric extinction causes significant radiation losses between the heliostat field and the receiver in a solar tower plants. These losses vary with site and time. State of the art is that in ray-tracing and plant optimization tools, atmospheric extinction is included by choosing between few constant standard atmospheric conditions. Even though some tools allow the consideration of site and time dependent extinction data, such data sets are nearly never available. This paper summarizes and compares the most common model equations implemented in several ray-tracing tools. There are already several methods developed and published to measure extinction on-site. An overview of the existing methods is also given here. Ray-tracing simulations of one exemplary tower plant at the Plataforma Solar de Almería (PSA) are presented to estimate the plant yield deviations between simulations using standard model equations instead of extinction time series. For PSA, the effect of atmospheric extinction accounts for losses between 1.6 and 7 %. This range is caused by considering overload dumping or not. Applying standard clear or hazy model equations instead of extinction time series lead to an underestimation of the annual plant yield at PSA. The discussion of the effect of extinction in tower plants has to include overload dumping. Situations in which overload dumping occurs are mostly connected to high radiation levels and low atmospheric extinction. Therefore it can be recommended that project developers should consider site and time dependent extinction data especially on hazy sites. A reduced uncertainty of the plant yield prediction can significantly reduce costs due to smaller risk margins for financing and EPCs. The generation of extinction data for several locations in form of representative yearly time series or geographical maps should be further elaborated.

  2. 3,4-Methylenedioxymethamphetamine facilitates fear extinction learning.

    Science.gov (United States)

    Young, M B; Andero, R; Ressler, K J; Howell, L L

    2015-09-15

    Acutely administered 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') has been proposed to have long-term positive effects on post-traumatic stress disorder (PTSD) symptoms when combined with psychotherapy. No preclinical data support a mechanistic basis for these claims. Given the persistent nature of psychotherapeutic gains facilitated by MDMA, we hypothesized that MDMA improves fear extinction learning, a key process in exposure-based therapies for PTSD. In these experiments, mice were first exposed to cued fear conditioning and treated with drug vehicle or MDMA before extinction training 2 days later. MDMA was administered systemically and also directly targeted to brain structures known to contribute to extinction. In addition to behavioral measures of extinction, changes in mRNA levels of brain-derived neurotrophic factor (Bdnf) and Fos were measured after MDMA treatment and extinction. MDMA (7.8 mg kg(-1)) persistently and robustly enhanced long-term extinction when administered before extinction training. MDMA increased the expression of Fos in the amygdala and medial prefrontal cortex (mPFC), whereas increases in Bdnf expression were observed only in the amygdala after extinction training. Extinction enhancements were recapitulated when MDMA (1 μg) was infused directly into the basolateral complex of the amygdala (BLA), and enhancement was abolished when BDNF signaling was inhibited before extinction. These findings suggest that MDMA enhances fear memory extinction through a BDNF-dependent mechanism, and that MDMA may be a useful adjunct to exposure-based therapies for PTSD and other anxiety disorders characterized by altered fear learning.

  3. Partially linear varying coefficient models stratified by a functional covariate

    KAUST Repository

    Maity, Arnab

    2012-10-01

    We consider the problem of estimation in semiparametric varying coefficient models where the covariate modifying the varying coefficients is functional and is modeled nonparametrically. We develop a kernel-based estimator of the nonparametric component and a profiling estimator of the parametric component of the model and derive their asymptotic properties. Specifically, we show the consistency of the nonparametric functional estimates and derive the asymptotic expansion of the estimates of the parametric component. We illustrate the performance of our methodology using a simulation study and a real data application.

  4. Partially Linear Varying Coefficient Models Stratified by a Functional Covariate.

    Science.gov (United States)

    Maity, Arnab; Huang, Jianhua Z

    2012-10-01

    We consider the problem of estimation in semiparametric varying coefficient models where the covariate modifying the varying coefficients is functional and is modeled nonparametrically. We develop a kernel-based estimator of the nonparametric component and a profiling estimator of the parametric component of the model and derive their asymptotic properties. Specifically, we show the consistency of the nonparametric functional estimates and derive the asymptotic expansion of the estimates of the parametric component. We illustrate the performance of our methodology using a simulation study and a real data application.

  5. Influence of the vertical absorption profile of mixed Asian dust plumes on aerosol direct radiative forcing over East Asia

    Science.gov (United States)

    Noh, Young Min; Lee, Kwonho; Kim, Kwanchul; Shin, Sung-Kyun; Müller, Detlef; Shin, Dong Ho

    2016-08-01

    We estimate the aerosol direct radiative forcing (ADRF) and heating rate profiles of mixed East Asian dust plumes in the solar wavelength region ranging from 0.25 to 4.0 μm using the Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART) code. Vertical profiles of aerosol extinction coefficients and single-scattering albedos (SSA) were derived from measurements with a multi-wavelength Raman lidar system. The data are used as input parameters for our radiative transfer calculations. We considered four cases of radiative forcing in SBDART: 1. dust, 2. pollution, 3. mixed dust plume and the use of vertical profiles of SSA, and 4. mixed dust plumes and the use of column-averaged values of SSA. In our sensitivity study we examined the influence of SSA and aerosol layer height on our results. The ADRF at the surface and in the atmosphere shows a small dependence on the specific shape of the aerosol extinction vertical profile and its light-absorption property for all four cases. In contrast, at the top of the atmosphere (TOA), the ADRF is largely affected by the vertical distribution of the aerosols extinction. This effect increases if the light-absorption capacity (decrease of SSA) of the aerosols increases. We find different radiative effects in situations in which two layers of aerosols had different light-absorption properties. The largest difference was observed at the TOA for an absorbing aerosol layer at high altitude in which we considered in one case the vertical profile of SSA and in another case the column-averaged SSA only. The ADRF at the TOA increases when the light-absorbing aerosol layer is located above 3 km altitude. The differences between height-resolved SSA, which can be obtained from lidar data, and total layer-mean SSA indicates that the use of a layer-mean SSA can be rather misleading as it can induce a large error in the calculation of the ADRF at the TOA, which in turn may cause errors in the vertical profiles of heating rates.

  6. Study of Dispersion Coefficient Channel

    Science.gov (United States)

    Akiyama, K. R.; Bressan, C. K.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.

    2016-08-01

    The issue of water pollution has worsened in recent times due to releases, intentional or not, of pollutants in natural water bodies. This causes several studies about the distribution of pollutants are carried out. The water quality models have been developed and widely used today as a preventative tool, ie to try to predict what will be the concentration distribution of constituent along a body of water in spatial and temporal scale. To understand and use such models, it is necessary to know some concepts of hydraulic high on their application, including the longitudinal dispersion coefficient. This study aims to conduct a theoretical and experimental study of the channel dispersion coefficient, yielding more information about their direct determination in the literature.

  7. Clustering Coefficients in Multiplex Networks

    CERN Document Server

    Cozzo, Emanuele; De Domenico, Manlio; Solé, Albert; Arenas, Alex; Gómez, Sergio; Porter, Mason A; Moreno, Yamir

    2013-01-01

    Recent advances in the study of complex networked systems has highlighted that our interconnected world is made of networks that are coupled together through different layers that each stand for one type of interaction or system. Despite this situation, it is traditional to aggregate multiplex data into a single weighted network in order take advantage of existing tools. This is admittedly convenient, but it is also extremely problematic. In this paper, we generalize the concept of clustering coefficients for multiplex networks. We show how the layered structure of multiplex networks introduces a new degree of freedom that has a fundamental effect on transitivity. We compute our new multiplex clustering coefficients for several real multiplex networks and illustrate why generalizing monoplex concepts to multiplex networks must be done with great care.

  8. Late Pennsylvanian climate changes and palynomorph extinctions

    Science.gov (United States)

    Kosanke, R.M.; Cecil, C.B.

    1996-01-01

    A major floral change occurs in the Upper Pennsylvanian strata in the Midcontinent, Illinois basin, and in the northern Appalachian basin of eastern United States. Lycospora spp. (derived from arborescent lycopsids) became extinct along with some other palynomorph taxa. This investigation is concerned with the importance of this major floral change. Samples were studied from western Pennsylvania, eastern Ohio, and West Virginia (from a previous study) cover the stratigraphic interval from the Upper Freeport coal bed, uppermost part of the Allegheny Formation, to the Mahoning, Mason, Brush Creek, Wilgus, and Anderson coal beds in the lower part of the Conemaugh Formation. The floral change occurs either at or below the accepted Desmoinesian-Missourian boundary in the Midcontinent and Illinois basin, whereas in the northern Appalachians this change occurs in the lower part of the Conemaugh Formation, between the Mahoning and Brush Creek coal beds, or when the Mason is present, between the Mahoning and Mason coal beds. With the advent of late Middle Pennsylvanian time, the climate began to change from wet tropical to seasonal tropical. The Middle-Upper Pennsylvanian boundary is the culmination of this drying trend, which was marked by reduction of available water. The peat swamps are interpreted as having changed from the domed type of bog to the planar type under these circumstances. Thus, in general, the coals of the Conemaugh Formation are characteristically much thinner than those of the Allegheny Formation. This was caused by a number of factors including reduced or more seasonal rainfall, decline of arborescent lycopsids, and the increased dominance of herbaceous and fern plants. As a result, there are fewer minable coal beds in the Conemaugh Formation. The first coal bed above the extinction of Lycospora spp. is dominated by the palynomorph taxon Endosporites globiformis which is derived from a heterosporous, herbaceous lycopsid. However, Sigillaria, another

  9. Reproducibility of The Random Incidence Absorption Coefficient Converted From the Sabine Absorption Coefficient

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho; Chang, Ji-ho

    2015-01-01

    Absorption coefficients measured in reverberation chambers, Sabine absorption coefficients, suffer from two major problems. Firstly, they sometimes exceed unity. Secondly, the reproducibility of the Sabine absorption coefficients is quite poor, meaning that the Sabine absorption coefficients vary...

  10. A comprehensive quantitative assessment of bird extinction risk in Brazil.

    Directory of Open Access Journals (Sweden)

    Nathália Machado

    Full Text Available In an effort to avoid species loss, scientists have focused their efforts on the mechanisms making some species more prone to extinction than others. However, species show different responses to threats given their evolutionary history, behavior, and intrinsic biological features. We used bird biological features and external threats to (1 understand the multiple pathways driving Brazilian bird species to extinction, (2 to investigate if and how extinction risk is geographically structured, and (3 to quantify how much diversity is currently represented inside protected areas. We modeled the extinction risk of 1557 birds using classification trees and evaluated the relative contribution of each biological feature and external threat in predicting extinction risk. We also quantified the proportion of species and their geographic range currently protected by the network of Brazilian protected areas. The optimal classification tree showed different pathways to bird extinction. Habitat conversion was the most important predictor driving extinction risk though other variables, such as geographic range size, type of habitat, hunting or trapping and trophic guild, were also relevant in our models. Species under higher extinction risk were concentrated mainly in the Cerrado Biodiversity Hotspot and were not quite represented inside protected areas, neither in richness nor range. Predictive models could assist conservation actions, and this study could contribute by highlighting the importance of natural history and ecology in these actions.

  11. Extinction of drug seeking: Neural circuits and approaches to augmentation.

    Science.gov (United States)

    McNally, Gavan P

    2014-01-01

    Extinction training can reduce drug seeking behavior. This article reviews the neural circuits that contribute to extinction and approaches to enhancing the efficacy of extinction. Extinction of drug seeking depends on cortical-striatal-hypothalamic and cortical-hypothalamic-thalamic pathways. These pathways interface, in the hypothalamus and thalamus respectively, with the neural circuits controlling reinstatement of drug seeking. The actions of these pathways at lateral hypothalamic orexin neurons, and of perifornical/dorsomedial hypothalamic derived opioid peptides at kappa opioid receptors in the paraventricular thalamus, are important for inhibiting drug seeking. Despite effectively reducing or inhibiting drug seeking in the short term, extinguished drug seeking is prone to relapse. Three different strategies to augment extinction learning or retrieval are reviewed: pharmacological augmentation, retrieval - extinction training, and provision of extinction memory retrieval cues. These strategies have been used in animal models and with human drug users to enhance extinction or cue exposure treatments. They hold promise as novel strategies to promote abstinence from drug seeking. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.

  12. Deepened Extinction following Compound Stimulus Presentation: Noradrenergic Modulation

    Science.gov (United States)

    Janak, Patricia H.; Corbit, Laura H.

    2011-01-01

    Behavioral extinction is an active form of new learning involving the prediction of nonreward where reward has previously been present. The expression of extinction learning can be disrupted by the presentation of reward itself or reward-predictive stimuli (reinstatement) as well as the passage of time (spontaneous recovery) or contextual changes…

  13. Asymptotic behaviour near extinction of continuous-state branching processes

    OpenAIRE

    Pardo, Juan Carlos; Berzunza, Gabriel

    2016-01-01

    In this note, we study the asymptotic behaviour near extinction of (sub-) critical continuous state branching processes. In particular, we establish an analogue of Khintchin's law of the iterated logarithm near extinction time for a continuous state branching process whose branching mechanism satisfies a given condition and its reflected process at its infimum.

  14. Late Pleistocene and Holocene mammal extinctions on continental Africa

    Science.gov (United States)

    Faith, J. Tyler

    2014-01-01

    Understanding the cause of late Quaternary mammal extinctions is the subject of intense debate spanning the fields of archeology and paleontology. In the global context, the losses on continental Africa have received little attention and are poorly understood. This study aims to inspire new discussion of African extinctions through a review of the extinct species and the chronology and possible causes of those extinctions. There are at least 24 large mammal (> 5 kg) species known to have disappeared from continental Africa during the late Pleistocene or Holocene, indicating a much greater taxonomic breadth than previously recognized. Among the better sampled taxa, these losses are restricted to the terminal Pleistocene and early Holocene, between 13,000 and 6000 yrs ago. The African extinctions preferentially affected species that are grazers or prefer grasslands. Where good terrestrial paleoenvironmental records are present, extinctions are associated with changes in the availability, productivity, or structure of grassland habitats, suggesting that environmental changes played a decisive role in the losses. In the broader evolutionary context, these extinctions represent recent examples of selective taxonomic winnowing characterized by the loss of grassland specialists and the establishment of large mammal communities composed of more ecologically flexible taxa over the last million years. There is little reason to believe that humans played an important role in African extinctions.

  15. Chronic Cannabinoid Administration in Vivo Compromises Extinction of Fear Memory

    Science.gov (United States)

    Lin, Hui-Ching; Mao, Sheng-Chun; Chen, Po-See; Gean, Po-Wu

    2008-01-01

    Endocannabinoids are critically involved in the extinction of fear memory. Here we examined the effects of repeated cannabinoid administration on the extinction of fear memory in rats and on inhibitory synaptic transmission in medial prefrontal cortex (mPFC) slices. Rats were treated with the CB1 receptor agonist WIN55212-2 (WIN 10 mg/kg, i.p.)…

  16. High-precision timeline for Earth's most severe extinction.

    Science.gov (United States)

    Burgess, Seth D; Bowring, Samuel; Shen, Shu-zhong

    2014-03-04

    The end-Permian mass extinction was the most severe loss of marine and terrestrial biota in the last 542 My. Understanding its cause and the controls on extinction/recovery dynamics depends on an accurate and precise age model. U-Pb zircon dates for five volcanic ash beds from the Global Stratotype Section and Point for the Permian-Triassic boundary at Meishan, China, define an age model for the extinction and allow exploration of the links between global environmental perturbation, carbon cycle disruption, mass extinction, and recovery at millennial timescales. The extinction occurred between 251.941 ± 0.037 and 251.880 ± 0.031 Mya, an interval of 60 ± 48 ka. Onset of a major reorganization of the carbon cycle immediately precedes the initiation of extinction and is punctuated by a sharp (3‰), short-lived negative spike in the isotopic composition of carbonate carbon. Carbon cycle volatility persists for ∼500 ka before a return to near preextinction values. Decamillenial to millennial level resolution of the mass extinction and its aftermath will permit a refined evaluation of the relative roles of rate-dependent processes contributing to the extinction, allowing insight into postextinction ecosystem expansion, and establish an accurate time point for evaluating the plausibility of trigger and kill mechanisms.

  17. The Effects of Context Extinction on US Signal Value

    Science.gov (United States)

    Goddard Murray J.

    2007-01-01

    Two experiments with rats examined the effects of context extinction on responding to the signal value of an unconditioned stimulus (US). In Experiment 1, US signal value was first trained when a single food pellet signaled the delivery of three additional pellets. After training, rats received either context extinction (CE) or home cage (HC)…

  18. Extinction risks from climate change: macroecological and historical insights.

    Science.gov (United States)

    Jansson, Roland

    2009-06-09

    Human-induced climate change may threaten a large proportion of Earth's biota, but the uncertainties involved in projecting the future geographical distributions of species make quantitative predictions of extinction risk difficult to make. I discuss how insight from recent advances in macroecology and knowledge about species responses to past climate change can help predict extinction risks more accurately.

  19. Extinction can be estimated from moderately sized molecular phylogenies.

    Science.gov (United States)

    Beaulieu, Jeremy M; O'Meara, Brian C

    2015-04-01

    Hundreds of studies have been dedicated to estimating speciation and extinction from phylogenies of extant species. Although it has long been known that estimates of extinction rates using trees of extant organisms are often uncertain, an influential paper by Rabosky (2010) suggested that when birth rates vary continuously across the tree, estimates of the extinction fraction (i.e., extinction rate/speciation rate) will appear strongly bimodal, with a peak suggesting no extinction and a peak implying speciation and extinction rates are approaching equality. On the basis of these results, and the realistic nature of this form of rate variation, it is now generally assumed by many practitioners that extinction cannot be understood from molecular phylogenies alone. Here, we reevaluated and extended the analyses of Rabosky (2010) and come to the opposite conclusion-namely, that it is possible to estimate extinction from molecular phylogenies, even with model violations due to heritable variation in diversification rate. Note that while it may be tempting to interpret our study as advocating the application of simple birth-death models, our goal here is to show how a particular model violation does not necessitate the abandonment of an entire field: use prudent caution, but do not abandon all hope. © 2015 The Author(s).

  20. Experimental Measurement of Diffusive Extinction Depth and Soil Moisture Gradients in Southwestern Saudi Arabian Dune Sand

    KAUST Repository

    Mughal, Iqra

    2013-05-01

    In arid lands, a major contribution to water loss is by soil water evaporation. Desert sand dunes in arid regions are devoid of runoff and have high rates of infiltration. Rainwater is commonly stored within them because of the low permeability soils in the underlying desert pavement. In such cases, moisture is confined in the sand dune below a depth, termed as the “extinction depth”, where it is protected from evaporation during long dry periods. Moreover, desert sand dunes have sparse vegetation, which results in low transpiration losses from the stored water. The water accumulated below the extinction depth of the sand dunes can be utilized for various purposes such as in irrigation to support desert agriculture. In this study, field experiments were conducted in Western Saudi Arabia to monitor the soil moisture gradients and determine the diffusive extinction depth of dune sand. The dune sand was saturated with water and was exposed to natural conditions (evaporation and precipitation). The decline of the water level in the sand column was continuously recorded using transducers and sensors installed at different depths monitored the temporal variation of temperature and moisture content within the sand. The hydrological simulator HYDRUS-1D was used to construct the vertical profiles of soil water content and temperature and the results obtained from HYDRUS-1D were compared to the gradients monitored by the sensors.

  1. Dependence of the coefficient of ultrasonic velocity on the coefficient of free length in organic liquids

    Institute of Scientific and Technical Information of China (English)

    LU Yigang; PENG Jianxin; TONG Jie; DONG Yanwu

    2000-01-01

    On the basis of Jacobson's free length theory and the theory of pressure coefficient and temperature coefficient of free length in liquids, the relationship between the pressure coefficient of ultrasonic velocity and the pressure coefficient of free length, and the relationship between the temperature coefficient of ultrasonic velocity and the temperature coefficient of free length were studied. Relevant equations were given, and the pressure coefficient and temperature coefficient of ultrasonic velocity were calculated, which are in agreement with the measured values.

  2. Carriers of the astronomical 2175 ? extinction feature

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, J; Dai, Z; Ernie, R; Browning, N; Graham, G; Weber, P; Smith, J; Hutcheon, I; Ishii, H; Bajt, S; Floss, C; Stadermann, F

    2004-07-20

    The 2175 {angstrom} extinction feature is by far the strongest spectral signature of interstellar dust observed by astronomers. Forty years after its discovery the origin of the feature and the nature of the carrier remain controversial. The feature is enigmatic because although its central wavelength is almost invariant its bandwidth varies strongly from one sightline to another, suggesting multiple carriers or a single carrier with variable properties. Using a monochromated transmission electron microscope and valence electron energy-loss spectroscopy we have detected a 5.7 eV (2175 {angstrom}) feature in submicrometer-sized interstellar grains within interplanetary dust particles (IDPs) collected in the stratosphere. The carriers are organic carbon and amorphous silicates that are abundant and closely associated with one another both in IDPs and in the interstellar medium. Multiple carriers rather than a single carrier may explain the invariant central wavelength and variable bandwidth of the astronomical 2175 {angstrom} feature.

  3. Scientists Drill for Clues to Dinosaur Extinction

    Institute of Scientific and Technical Information of China (English)

    张一

    2001-01-01

    @@ [选注者言:20世纪70年代,墨西哥的Yucatan半岛的石油勘探发现了著名的Chicxulub大坑.直到20世纪90年代,科学家才认定,此大坑是由6千5百万年的一颗小行星撞击地球而形成,这次撞击导致地球上的恐龙灭绝.现在,科学家拟再次对此大坑作一番发掘研究,旨在:to determine once andfor all(一劳永逸的;彻底地)whatled to the global extinction(消灭)of the dinosaurs(恐龙)millions of years ago.

  4. [Silphium from Cyrenaica, an extinct medicinal plant].

    Science.gov (United States)

    Haas, Charles

    2008-01-01

    Silphium was both a spice and a medicinal plant. It was regarded as "one of the most precious gifts of Nature to man" (Pliny), and was one of the main sources of revenue contributing to Cyrenaica's wealth. It was so critical to the Cyrenian economy that most of their coins bore a picture of the plant. But, by the time of Nero, the plant had become extinct, probably as a result of overgrazing and overcropping. The botanical identification of silphium is dificult, but the plant was an Umbellifera and most closely resembled Ferula tingitana. Hippocrates, Celsus, Galen and Oribasius recommended it for quartan fever, but it was also said to be useful for many other diseases.

  5. Light extinction method for solubility measurement

    Institute of Scientific and Technical Information of China (English)

    Shui Wang; Jingkang Wang; Qiuxiang Yin; Yongli Wang

    2005-01-01

    A novel measurement method for chemical solubility determination is brought forward, in which the advantages of two kinds of traditional methods are united. The results show that the concentration of unsolved particles suspending in the solution can be determined by measuring I/I0 (ratio of the transmission intensity to the incident intensity) of the laser beam permeating through the solution according to Lamben-Beer law. The biggest relative deviation for the solubility data determined is less than 1.5% for the sparingly soluble substances and 0.3% for the opulently soluble substances. By comparison of the experimental solubility data with previous data, the light extinction method is demonstrated to be stable and reliable.

  6. Promotion of cooperation by selective group extinction

    Science.gov (United States)

    Böttcher, Marvin A.; Nagler, Jan

    2016-06-01

    Multilevel selection is an important organizing principle that crucially underlies evolutionary processes from the emergence of cells to eusociality and the economics of nations. Previous studies on multilevel selection assumed that the effective higher-level selection emerges from lower-level reproduction. This leads to selection among groups, although only individuals reproduce. We introduce selective group extinction, where groups die with a probability inversely proportional to their group fitness. When accounting for this the critical benefit-to-cost ratio is substantially lowered. Because in game theory and evolutionary dynamics the degree of cooperation crucially depends on this ratio above which cooperation emerges, previous studies may have substantially underestimated the establishment and maintenance of cooperation.

  7. Biometrical studies upon hominoid teeth: the coefficient of variation, sexual dimorphism and questions of phylogenetic relationship.

    Science.gov (United States)

    Blumenberg, B

    1985-01-01

    Sexual dimorphism as a function of variation in hominoid tooth metrics has been investigated for four groups of taxa: Recent great apes (two subfamilies), Dryopiths (one subfamily), Ramapiths (one subfamily) and hominids (one family). Gorilla, and to a lesser extent Pan, appear characterized by very high levels of sexual dimorphism and meet several criteria for statistical outliers. Recent great apes are the only group exhibiting consistently high levels of sexual dimorphism. Ramapiths are the only group characterized by low levels of sexual dimorphism and their relative canine length is most similar to Dryopiths. Both Dryopiths and hominids contain taxa with low and intermediate levels of sexual dimorphism. The Gingerich and Shoeninger hypothesis relating coefficients of variation to occlusal complexity is supported. Non-parametric statistics suggest that homogeneity of coefficient of variation profiles over most of the tooth row is characteristic of only the Dryopiths and a composite data set composed of the Dryopith plus Ramapith tooth measurements. Oxnard's model for the multifactorial basis of multiple sexual dimorphisms is also supported. The Dryopith and hominid patterns of sexual dimorphism are similar, an observation that suggests phylogenetic relationship. At the taxonomic level of subfamily or family, sexual dimorphism is a character of cladistic usefulness and possible phylogenetic valence. Assuming that breeding system and sexual dimorphism are functional correlates as many workers suggest, then Ramapithecus sp. China, Sivapithecus indicus and possibly Australopithecus boisei are good candidates for having possessed monogamous breeding/social structures. All Dryopith taxa, S. sivalensis, Sivapithecus sp. China, A. afarensis, Homo habilis and H. erectus emerge as the best candidates for having possessed a polygynous breeding/social structure. No biometrical affinities of Ramapiths with hominids can be demonstrated and some phylogenetic relationship with

  8. Scientists Drill for Clues to Dinosaur Extinction

    Institute of Scientific and Technical Information of China (English)

    张一

    2001-01-01

    20世纪70年代,墨西哥的Yucatan半岛的石油勘探发现了著名的Chicxulub大坑。直到20世纪90年代,科学家才认定,此大坑是由6千5百万年的一颗小行星撞击地球而形成,这次撞击导致地球上的恐龙灭绝。现在,科学家拟再次对此大坑作一番发掘研究,旨在:to determine once andfor all(一劳永逸的;彻底地)what led to the global extinction(消灭)of the dinosaurs(恐龙)millions of years ago。 本文为读者描绘了当年地球遭受此灭顶之灾时的可怕情景: Millions of years before humans even existed,a huge meteorite(陨星)measuring about 6 miles across and weighing perhaps billions of tons crashed intothe planet in a ball of fire,shrouding the Earth in a dense cloud of dust that blocked out sunlight and sent temperatures plummeting(垂直落下). 文中有一句话颇能引起读者的共鸣: It’s a 100 million-year event—they don’t occur that often,thank God. 文中的一个成语的使用却值得商榷: …hoping to determine once and for all(一劳永逸的;彻底地)what led to theglobal extinction(消灭)of the dinosaurs(恐龙)millions of years ago.在科学探索的道路上,once and for all也许只是一种良好

  9. Is chytridiomycosis driving Darwin's frogs to extinction?

    Directory of Open Access Journals (Sweden)

    Claudio Soto-Azat

    Full Text Available Darwin's frogs (Rhinoderma darwinii and R. rufum are two species of mouth brooding frogs from Chile and Argentina that have experienced marked population declines. Rhinoderma rufum has not been found in the wild since 1980. We investigated historical and current evidence of Batrachochytrium dendrobatidis (Bd infection in Rhinoderma spp. to determine whether chytridiomycosis is implicated in the population declines of these species. Archived and live specimens of Rhinoderma spp., sympatric amphibians and amphibians at sites where Rhinoderma sp. had recently gone extinct were examined for Bd infection using quantitative real-time PCR. Six (0.9% of 662 archived anurans tested positive for Bd (4/289 R. darwinii; 1/266 R. rufum and 1/107 other anurans, all of which had been collected between 1970 and 1978. An overall Bd-infection prevalence of 12.5% was obtained from 797 swabs taken from 369 extant individuals of R. darwinii and 428 individuals representing 18 other species of anurans found at sites with current and recent presence of the two Rhinoderma species. In extant R. darwinii, Bd-infection prevalence (1.9% was significantly lower than that found in other anurans (7.3%. The prevalence of infection (30% in other amphibian species was significantly higher in sites where either Rhinoderma spp. had become extinct or was experiencing severe population declines than in sites where there had been no apparent decline (3.0%; x(2 = 106.407, P<0.001. This is the first report of widespread Bd presence in Chile and our results are consistent with Rhinoderma spp. declines being due to Bd infection, although additional field and laboratory investigations are required to investigate this further.

  10. Mechanisms of renewal after the extinction of instrumental behavior.

    Science.gov (United States)

    Todd, Travis P

    2013-07-01

    Four experiments with rats examined renewal of extinguished instrumental behavior when the reinforcement histories of the contexts were equated by giving complementary training and extinction of a different response (lever press and chain pull) in each context. In Experiments 1 through 3, renewal occurred when the response was tested in the acquisition context (ABA) or outside the extinction context (AAB and ABC). Further, in Experiments 1 through 3, when both responses were simultaneously available, there was a clear preference for the response that was not in its extinction context. In Experiment 4, renewal was not reduced when testing occurred in a context that had been associated with extinction of the other instrumental response. The experimental designs rule out differential context-reinforcer associations being the only contributing mechanism of renewal, and also raise questions about configural and occasion-setting accounts. The results are consistent with the idea that during extinction an inhibitory association is formed between the context and the response.

  11. Double Mass Extinctions and the Volcanogenic Dark Matter Scenario

    CERN Document Server

    Abbas, S; Mohanty, S; Abbas, Samar; Abbas, Afsar; Mohanty, Shukadev

    1998-01-01

    A few of the major mass extinctions of paleontology have recently been found to consist of two distinct extinction peaks at higher resolution. A viable explanation for this remains elusive. In this paper it is shown that the recently proposed volcanogenic dark matter model can explain this puzzling characteristic of these extinctions. The accumulation and annihilation of dark matter in the center of the Earth due to the passage of a clump leads to excess heat generation with the consequent ejection of superplumes, followed by massive volcanism and attendant mass extinctions. This is preceded by an extinction pulse due to carcinogenesis arising from the direct interaction of the clumped dark matter with living organisms.

  12. Cretaceous stem chondrichthyans survived the end-Permian mass extinction.

    Science.gov (United States)

    Guinot, Guillaume; Adnet, Sylvain; Cavin, Lionel; Cappetta, Henri

    2013-01-01

    Cladodontomorph sharks are Palaeozoic stem chondrichthyans thought to go extinct at the end-Permian mass extinction. This extinction preceded the diversification of euselachians, including modern sharks. Here we describe an outer-platform cladodontomorph shark tooth assemblage from the Early Cretaceous of southern France, increasing the fossil record of this group by circa 120 million years. Identification of this material rests on new histological observations and morphological evidence. Our finding shows that this lineage survived mass extinctions most likely by habitat contraction, using deep-sea refuge environments during catastrophic events. The recorded gap in the cladodontomorph lineage represents the longest gap in the fossil record for an extinct marine vertebrate group. This discovery demonstrates that the deep-sea marine diversity, poorly known during most of the fish evolutionary history, contains essential data for a complete understanding of the long-term evolution of marine fish paleobiodiversity.

  13. Porous and Fluffy Grains in the Regions of Anomalous Extinction

    Indian Academy of Sciences (India)

    D. B. Vaidya; B. G. Anandarao; J. N. Desai; R. Gupta

    2000-06-01

    It has long been established that the ratio of total to selective extinction is anomalously large (≥ 5) in certain regions of the interstellar medium. In these regions of anomalous extinction the dust grains are likely to be irregular in shape and fluffy in structure. Using discrete dipole approximation (DDA) we calculate the extinction for porous and fluffy grains. We apply DDA first to solid spheroidal particles assumed to be made of a certain (large) number of dipoles. Then we systematically reduce the number of dipoles to model the porous grains. The aggregates of these particles are suggested to form the fluffy grains. We study the extinction for these particles as a function of grain size, porosity and wavelength. We apply these calculations to interpret the observed extinction data in the regions of star formation (e.g. the Orion complex).

  14. Mass Extinctions and The Sun's Encounters with Spiral Arms

    CERN Document Server

    Leitch, E M; Vasisht, Erik M. Leitch & Gautam

    1998-01-01

    The terrestrial fossil record shows that the exponential rise in biodiversity since the Precambrian period has been punctuated by large extinctions, at intervals of 40 to 140 Myr. These mass extinctions represent extremes over a background of smaller events and the natural process of species extinction. We point out that the non-terrestrial phenomena proposed to explain these events, such as boloidal impacts (a candidate for the end-Cretaceous extinction), and nearby supernovae, are collectively far more effective during the solar system's traversal of spiral arms. Using the best available data on the location and kinematics of the Galactic spiral structure (including distance scale and kinematic uncertainties), we present evidence that arm crossings provide a viable explanation for the timing of the large extinctions.

  15. Perseveration of the partial reinforcement effect in extinction with rats over two phases of extinction and two stages of continuous reinforcement.

    Science.gov (United States)

    Calef, Richard S; Choban, Michael C; Glenney, Katherine R; Calef, Ruth A; Schmitt, Erik; Hinte, Sarah; Clegg, Megan; Kraynok, Joseph E; Richards, Sallie D

    2007-02-01

    One group of 10 male albino rats was given partial reinforcement while the other 10 rats received continuous reinforcement in a straight alley. Subjects then experienced five consecutive stages of Extinction 1, Continuous Reinforcement 1, Extinction 2, Continuous Reinforcement 2, and finally, Extinction 3. Analysis showed the partial reinforcement effect in extinction was sustained over two stages of extinction and two stages of continuous reinforcement, since subjects receiving partial reinforcement ran faster than rats given continuous reinforcement throughout all three of the extinction periods. The results seem to support those of Amsel's (1967) and Cabpaldi's (1967) theoretical formulations of the partial reinforcement effect in extinction.

  16. Glutamate Receptors in Extinction and Extinction-Based Therapies for Psychiatric Illness

    OpenAIRE

    Myers, Karyn M.; William A Carlezon; Davis, Michael

    2010-01-01

    Some psychiatric illnesses involve a learned component. For example, in posttraumatic stress disorder, memories triggered by trauma-associated cues trigger fear and anxiety, and in addiction, drug-associated cues elicit drug craving and withdrawal. Clinical interventions to reduce the impact of conditioned cues in eliciting these maladaptive conditioned responses are likely to be beneficial. Extinction is a method of lessening conditioned responses and involves repeated exposures to a cue in ...

  17. How to detect and visualize extinction thresholds for structured PVA models

    NARCIS (Netherlands)

    Hildenbrandt, H.; Grimm, V.

    2006-01-01

    An extinction threshold is a population size below which extinction risk increases to beyond critical values. However, detecting extinction thresholds for structured population models is not straightforward because many different population structures may correspond to the same population size. More

  18. Unpaired shocks during extinction weaken the contextual renewal of a conditioned discrimination

    NARCIS (Netherlands)

    Vervliet, B.; Vansteenwegen, D.; Hermans, D.

    2010-01-01

    Extinction is generally more fragile than conditioning, as illustrated by the contextual renewal effect. The traditional extinction procedure entails isolated presentations of the conditioned stimulus. Extinction may be boosted by adding isolated presentations of the unconditioned stimulus, as this

  19. Behavioral and neural bases of extinction learning in Hermissenda

    Directory of Open Access Journals (Sweden)

    Joel S. Cavallo

    2014-08-01

    Full Text Available Extinction of classical conditioning is thought to produce new learning that masks or interferes with the original memory. However, research in the nudibranch Hermissenda crassicornis (H.c. has challenged this view, and instead suggested that extinction erased the original associative memory. We have re-examined extinction in H.c. to test whether extinguished associative memories can be detected on the behavioral and cellular levels, and to characterize the temporal variables involved. Associative conditioning using pairings of light (CS and rotation (US produced characteristic suppression of H.c. phototactic behavior. A single session of extinction training (repeated light-alone presentations reversed suppressed behavior back to pre-training levels when administered 15 min after associative conditioning. This effect was abolished if extinction was delayed by 23 hr, and yet was recovered using extended extinction training (three consecutive daily extinction sessions. Extinguished phototactic suppression did not spontaneously recover at any retention interval tested (2-, 24-, 48-, 72-hr, or after additional US presentations (no observed reinstatement. Extinction training (single session, 15 min interval also reversed the pairing-produced increases in light-evoked spike frequencies of Type B photoreceptors, an identified site of associative memory storage that is causally related to phototactic suppression. These results suggest that the behavioral effects of extinction training are not due to temporary suppression of associative memories, but instead represent a reversal of the underlying cellular changes necessary for the expression of learning. In the companion article, we further elucidate mechanisms responsible for extinction-produced reversal of memory-related neural plasticity in Type B photoreceptors.

  20. Adrenal-dependent diurnal modulation of conditioned fear extinction learning.

    Science.gov (United States)

    Woodruff, Elizabeth R; Greenwood, Benjamin N; Chun, Lauren E; Fardi, Sara; Hinds, Laura R; Spencer, Robert L

    2015-06-01

    Post traumatic stress disorder (PTSD) is associated with altered conditioned fear extinction expression and impaired circadian function including dysregulation of glucocorticoid hormone secretion. We examined in adult male rats the relationship between conditioned fear extinction learning, circadian phase, and endogenous glucocorticoids (CORT). Rats maintained on a 12h light:dark cycle were trained and tested across 3 separate daily sessions (conditioned fear acquisition and 2 extinction sessions) that were administered during either the rats' active or inactive circadian phase. In an initial experiment we found that rats at both circadian phases acquired and extinguished auditory cue conditioned fear to a similar degree in the first extinction session. However, rats trained and tested at zeitgeber time-16 (ZT16) (active phase) showed enhanced extinction memory expression during the second extinction session compared to rats trained and tested at ZT4 (inactive phase). In a follow-up experiment, adrenalectomized (ADX) or sham surgery rats were similarly trained and tested across 3 separate daily sessions at either ZT4 or ZT16. ADX had no effect on conditioned fear acquisition or conditioned fear memory. Sham ADX rats trained and tested at ZT16 exhibited better extinction learning across the two extinction sessions compared to all other groups of rats. These results indicate that conditioned fear extinction learning is modulated by time of day, and this diurnal modulation requires the presence of adrenal hormones. These results support an important role of CORT-dependent circadian processes in regulating conditioned fear extinction learning, which may be capitalized upon to optimize effective treatment of PTSD.