Absorption Angstrom Exponent in AERONET and related data as an indicator of aerosol composition
NASA Astrophysics Data System (ADS)
Russell, P. B.; Bergstrom, R. W.; Shinozuka, Y.; Clarke, A. D.; Decarlo, P. F.; Jimenez, J. L.; Livingston, J. M.; Redemann, J.; Dubovik, O.; Strawa, A.
2010-02-01
Recent results from diverse air, ground, and laboratory studies using both radiometric and in situ techniques show that the fractions of black carbon, organic matter, and mineral dust in atmospheric aerosols determine the wavelength dependence of absorption (often expressed as Absorption Angstrom Exponent, or AAE). Taken together, these results hold promise of improving information on aerosol composition from remote measurements. The main purpose of this paper is to show that AAE values for an Aerosol Robotic Network (AERONET) set of retrievals from Sun-sky measurements describing full aerosol vertical columns are also strongly correlated with aerosol composition or type. In particular, we find AAE values near 1 (the theoretical value for black carbon) for AERONET-measured aerosol columns dominated by urban-industrial aerosol, larger AAE values for biomass burning aerosols, and the largest AAE values for Sahara dust aerosols. These AERONET results are consistent with results from other, very different, techniques, including solar flux-aerosol optical depth (AOD) analyses and airborne in situ analyses examined in this paper, as well as many other previous results. Ambiguities in aerosol composition or mixtures thereof, resulting from intermediate AAE values, can be reduced via cluster analyses that supplement AAE with other variables, for example Extinction Angstrom Exponent (EAE), which is an indicator of particle size. Together with previous results, these results strengthen prospects for determining aerosol composition from space, for example using the Glory Aerosol Polarimetry Sensor (APS), which seeks to provide retrievals of multiwavelength single-scattering albedo (SSA) and aerosol optical depth (and therefore aerosol absorption optical depth (AAOD) and AAE), as well as shape and other aerosol properties. Multidimensional cluster analyses promise additional information content, for example by using the Ozone Monitoring Instrument (OMI) to add AAOD in the near
Absorption Angstrom Exponent in AERONET and related data as an indicator of aerosol composition
NASA Astrophysics Data System (ADS)
Russell, P. B.; Bergstrom, R. W.; Shinozuka, Y.; Clarke, A. D.; Decarlo, P. F.; Jimenez, J. L.; Livingston, J. M.; Redemann, J.; Holben, B.; Dubovik, O.; Strawa, A.
2009-10-01
Recent results from diverse air, ground, and laboratory studies using both radiometric and in situ techniques show that the fractions of black carbon, organic matter, and mineral dust in atmospheric aerosols determine the wavelength dependence of absorption (expressed as Absorption Angstrom Exponent, or AAE). Taken together, these results hold promise of improving information on aerosol composition from remote measurements. The purpose of this paper is to show that AAE values for Aerosol Robotic Network (AERONET) retrievals from Sun-sky measurements describing the full aerosol vertical column are also strongly correlated with aerosol composition or type. In particular, we find AAE values near 1 (the theoretical value for black carbon) for AERONET-measured aerosol columns dominated by urban-industrial aerosol, larger AAE values for biomass burning aerosols, and the largest AAE values for Sahara dust aerosols. Ambiguities in aerosol composition or mixtures thereof, resulting from intermediate AAE values, can be reduced via cluster analyses that supplement AAE with other variables, for example Extinction Angstrom Exponent (EAE), which is an indicator of particle size. Together with previous results, these results strengthen prospects for determining aerosol composition from space, for example using the Glory Aerosol Polarimetry Sensor (APS), which promises retrievals of multiwavelength single-scattering albedo (SSA) and aerosol optical depth (and therefore aerosol absorption optical depth (AAOD) and AAE), as well as shape and other aerosol properties. Cluster analyses promise additional information content, for example by using the Ozone Monitoring Instrument (OMI) to add AAOD in the near ultraviolet and CALIPSO aerosol layer heights to reduce height-absorption ambiguity.
NASA Astrophysics Data System (ADS)
Giles, D. M.; Holben, B. N.; Eck, T. F.; Schafer, J.; Crawford, J. H.; Kim, J.; Sano, I.; Liew, S.; Salinas Cortijo, S. V.; Chew, B. N.; Lim, H.; Smirnov, A.; Sorokin, M.; Kenny, P.; Slutsker, I.
2013-12-01
Aerosols can have major implications on human health by inducing respiratory diseases due to inhalation of fine particles from biomass burning smoke or industrial pollution and on radiative forcing whereby the presence of absorbing aerosol particles (e.g., black carbon) increases atmospheric heating. Aerosol classification techniques have utilized aerosol loading and aerosol properties derived from multi-spectral and multi-angle observations by ground-based (e.g., AERONET) and satellite instrumentation (e.g., MISR). Aerosol Robotic Network (AERONET) data have been utilized to determine aerosol types by implementing various combinations of measured aerosol optical depth or retrieved size and absorption aerosol properties (e.g., Gobbi et al., 2007; Russell et al., 2010). Giles et al. [2012] showed single scattering albedo (SSA) relationship with extinction Angstrom exponent (EAE) can provide an estimate of the general classification of dominant aerosol types (i.e., desert dust, urban/industrial pollution, biomass burning smoke, and mixtures) based on data from ~20 AERONET sites located in known aerosol source regions. In addition, the absorption Angstrom exponent relationship with EAE can provide an indication of the dominant absorbing aerosol type such as dust, black carbon, brown carbon, or mixtures of them. These classification techniques are applied to the AERONET Level 2.0 quality assured data sets collected during Distributed Regional Aerosol Gridded Observational Network (DRAGON) campaigns in Maryland (USA), Japan, South Korea, Singapore, Penang (Malaysia), and California (USA). An analysis of aerosol type classification for DRAGON sites is performed as well as an assessment of the spatial variability of the aerosol types for selected DRAGON campaigns. Giles, D. M., B. N. Holben, T. F. Eck, A. Sinyuk, A. Smirnov, I. Slutsker, R. R. Dickerson, A. M. Thompson, and J. S. Schafer (2012), An analysis of AERONET aerosol absorption properties and classifications
NASA Astrophysics Data System (ADS)
Russell, P. B.; Hamill, P.; Livingston, J. M.; Shinozuka, Y.; Strawa, A. W.; Redemann, J.; Omar, A. H.; Clarke, A. D.; Bergstrom, R. W.; Holben, B.; Ferrare, R. A.; Burton, S. P.
2010-12-01
Determining either aerosol composition or multiwavelength absorption from space is difficult at best, but recent research on many fronts has improved prospects for success. Results from diverse air, ground, and laboratory studies using both radiometric and in situ techniques show that the fractions of black carbon, organic matter, and mineral dust in atmospheric aerosols determine the wavelength dependence of absorption (often expressed as Absorption Angstrom Exponent, or AAE). Recent results include analyses of the Dubovik et al. (2002) set of Aerosol Robotic Network (AERONET) retrievals from Sun-sky measurements describing full aerosol vertical columns. AAE values in this set are strongly correlated with aerosol composition or type. Specifically, AAE values are near 1 (the theoretical value for black carbon) for AERONET-measured aerosol columns dominated by urban-industrial aerosol, larger (though partially overlapping) for biomass burning aerosols, and largest for Sahara dust aerosols. These AERONET results are consistent with results from other, very different, techniques, including solar flux-aerosol optical depth (AOD) analyses and airborne in situ analyses examined in this presentation, as well as many other previous results. Although AAE is therefore a useful tool for helping to distinguish aerosol types, it cannot unambiguously distinguish urban-industrial from biomass burning aerosols, even when supplemented by measurements of Extinction Angstrom Exponent (EAE). Hence there is a need to add information from other remotely sensible properties to improve remote identification of aerosol type. Supervised clustering, combined with Mahalanobis classification, provides an objective way of using multiple dimensions of data for this purpose. We demonstrate the application of this technique (previously used with High Spectral Resolution Lidar data) to (1) the Dubovik (2002) AERONET data set, (2) an in situ data set, and (3) a larger Version 2 AERONET data set
Garg, Saryu; Chandra, Boggarapu Praphulla; Sinha, Vinayak; Sarda-Esteve, Roland; Gros, Valerie; Sinha, Baerbel
2016-01-19
Angstrom exponent measurements of equivalent black carbon (BCeq) have recently been introduced as a novel tool to apportion the contribution of biomass burning sources to the BCeq mass. The BCeq is the mass of ideal BC with defined optical properties that, upon deposition on the aethalometer filter tape, would cause equal optical attenuation of light to the actual PM2.5 aerosol deposited. The BCeq mass hence is identical to the mass of the total light-absorbing carbon deposited on the filter tape. Here, we use simultaneously collected data from a seven-wavelength aethalometer and a high-sensitivity proton-transfer reaction mass spectrometer installed at a suburban site in Mohali (Punjab), India, to identify a number of biomass combustion plumes. The identified types of biomass combustion include paddy- and wheat-residue burning, leaf litter, and garbage burning. Traffic plumes were selected for comparison. We find that the combustion efficiency, rather than the fuel used, determines αabs, and consequently, the αabs can be ∼1 for flaming biomass combustion and >1 for older vehicles that operate with poorly optimized engines. Thus, the absorption angstrom exponent is not representative of the fuel used and, therefore, cannot be used as a generic tracer to constrain source contributions. PMID:26655249
The Angstrom Exponent and Bimodal Aerosol Size Distributions
NASA Technical Reports Server (NTRS)
Schuster, Gregory L.; Dubovik, Oleg; Holben, Brent H.
2005-01-01
Powerlaws have long been used to describe the spectral dependence of aerosol extinction, and the wavelength exponent of the aerosol extinction powerlaw is commonly referred to as the Angstrom exponent. The Angstrom exponent is often used as a qualitative indicator of aerosol particle size, with values greater than two indicating small particles associated with combustion byproducts, and values less than one indicating large particles like sea salt and dust. In this study, we investigate the relationship between the Angstrom exponent and the mode parameters of bimodal aerosol size distributions using Mie theory calculations and Aerosol Robotic Network (AERONET) retrievals. We find that Angstrom exponents based upon seven wavelengths (0.34, 0.38, 0.44, 0.5, 0.67, 0.87, and 1.02 micrometers) are sensitive to the volume fraction of aerosols with radii less then 0.6 micrometers, but not to the fine mode effective radius. The Angstrom exponent is also known to vary with wavelength, which is commonly referred to as curvature; we show how the spectral curvature can provide additional information about aerosol size distributions for intermediate values of the Angstrom exponent. Curvature also has a significant effect on the conclusions that can be drawn about two-wavelength Angstrom exponents; long wavelengths (0.67, 0.87 micrometers) are sensitive to fine mode volume fraction of aerosols but not fine mode effective radius, while short wavelengths (0.38, 0.44 micrometers) are sensitive to the fine mode effective radius but not the fine mode volume fraction.
Aerosol Angstrom Absorption Coefficient Comparisons during MILAGRO.
NASA Astrophysics Data System (ADS)
Marley, N. A.; Marchany-Rivera, A.; Kelley, K. L.; Mangu, A.; Gaffney, J. S.
2007-12-01
Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) by using a 7-channel aethalometer (Thermo- Anderson) during the month of March, 2006. The absorption measurements obtained in the field at 370, 470, 520, 590, 660, 880, and 950 nm were used to determine the aerosol Angstrom absorption exponents by linear regression. Since, unlike other absorbing aerosol species (e.g. humic like substances, nitrated PAHs), black carbon absorption is relatively constant from the ultraviolet to the infrared with an Angstrom absorption exponent of -1 (1), a comparison of the Angstrom exponents can indicate the presence of aerosol components with an enhanced UV absorption over that expected from BC content alone. The Angstrom exponents determined from the aerosol absorption measurements obtained in the field varied from - 0.7 to - 1.3 during the study and was generally lower in the afternoon than the morning hours, indicating an increase in secondary aerosol formation and photochemically generated UV absorbing species in the afternoon. Twelve-hour integrated samples of fine atmospheric aerosols (<0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. Samples were collected on quartz fiber filters with high volume impactor samplers. Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples. These continuous spectra have also been used to obtain the
First measurements of aerosol optical depth and Angstrom exponent number from AERONET's Kuching site
NASA Astrophysics Data System (ADS)
Salinas, Santo V.; Chew, Boon N.; Mohamad, M.; Mahmud, M.; Liew, Soo C.
2013-10-01
We report our first measurements, over the 2011 dry season period, of aerosol optical depth, Angstrom exponent number and its fine mode counterpart obtained from photometric measurements at AERONET's newest site located at the city of Kuching, Sarawak, East Malaysia. This site was set up as part of the collaborative efforts of the Seven South East Asian Studies (7SEAS) regional aerosol measurements initiative. Located at the converging zone between peninsular Malaysia and the land masses of Sumatra, Borneo, Java and Sulawesi, this site is expected to provide first hand evidence about the physical and optical characteristics of the regional aerosol environment, specially during the biomass burning months. Moreover, given its relative proximity to our Singapore radiation measurement super-site, Kuching is expected to provide further insight on aerosol transport pathways caused by seasonal winds transporting smoke to other parts of the maritime continent and the South Asia region.
Observed aerosol optical depth and angstrom exponent in urban area of Nanjing, China
NASA Astrophysics Data System (ADS)
Li, Shu; Wang, Tijian; Xie, Min; Han, Yong; Zhuang, Bingliang
2015-12-01
Aerosol optical properties at Gulou station in Nanjing, China were measured and analyzed from April 2011 to April 2012. The annual median of aerosol optical depth (hereafter called as AOD) at 440 nm was 0.73 and the corresponding annual median of angstrom exponent (hereafter called as AE) between 440 nm and 870 nm was 1.28. The monthly median of AOD440nm presented a seasonal variation, which revealed a maximum in August (1.22) and a minimum in February (0.51), while the monthly median of AE showed a minimum in May (0.79) and a maximum in December (1.42). AOD and AE accumulated mainly between 0.40-0.90 (68%) and 1.20-1.50 (68%) respectively in Nanjing. The observation data showed that high AODs (>1.00) were clustered in the fine mode growth wing and the coarse mode. Comparison was made between two typical cases under different weather conditions and the results showed that Nanjing is influenced by the dust aerosol from Northwest China and Mongolia under dust weather in spring and the anthropogenic aerosol from local emission and surrounding industrialization region under haze weather.
NASA Astrophysics Data System (ADS)
Sano, I.
This paper describes a procedure on how to estimate the aerosol characteristics over the land as well as over the ocean from satellite data. Several scientists have proposed their algorithm to retrieve aerosol properties over the ocean since early 90s. However, aerosols over the land are difficult to treat from space due to the over illumination of land surface. A POLDER sensor on board the satellites ADEOS-1 and ADEOS-2 provides us with the polarization information at three wavelengths (0.443, 0.670 and 0.865 um). The polarized light at the top of the atmosphere is mainly consisted of atmospheric light because of less contribution of polarized light from ground surface reflection. This fact suggests that the space based polarized light involves dominant signals of atmospheric constituents such as aerosols and molecules. Therefore this work uses the multi-angle polarimetric measurements by POLDER for extracting the aerosol optical thickness, and its wavelengths tendency (Angstrom exponent). The procedure of aerosol retrieval is based on the light scattering simu lation of the Earth's atmosphere model. The numerical results are stored into the look up tables (LUT). Then, the aerosols properties are extracted from comparison of simulated results in the LUT with space-based data by POLDER. The retrieved work is validated with the ground based measurements as AERONET during ADEOS-1 operational period.
NASA Technical Reports Server (NTRS)
Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.
2011-01-01
El Nino.Southern Oscillation (ENSO) is the dominant mode of interannual variability in the tropical atmosphere. ENSO could potentially impact local and global aerosol properties through atmospheric circulation anomalies and teleconnections. By analyzing aerosol properties, including aerosol optical depth (AOD) and Angstrom exponent (AE; often used as a qualitative indicator of aerosol particle size) from the Moderate Resolution Imaging Spectrometer, the Multiangle Imaging Spectroradiometer and the Sea ]viewing Wide Field ]of ]view Sensor for the period 2000.2011, we find a strong correlation between the AE data and the multivariate ENSO index (MEI) over the tropical Pacific. Over the western tropical Pacific (WTP), AE increases during El Nino events and decreases during La Nina events, while the opposite is true over the eastern tropical Pacific (ETP). The difference between AE anomalies in the WTP and ETP has a higher correlation coefficient (>0.7) with the MEI than the individual time series and could be considered another type of ENSO index. As no significant ENSO correlation is found in AOD over the same region, the change in AE (and hence aerosol size) is likely to be associated with aerosol composition changes due to anomalous meteorological conditions induced by the ENSO. Several physical parameters or mechanisms that might be responsible for the correlation are discussed. Preliminary analysis indicates surface wind anomaly might be the major contributor, as it reduces sea ]salt production and aerosol transport during El Nino events. Precipitation and cloud fraction are also found to be correlated with tropical Pacific AE. Possible mechanisms, including wet removal and cloud shielding effects, are considered. Variations in relative humidity, tropospheric ozone concentration, and ocean color during El Nino have been ruled out. Further investigation is needed to fully understand this AE ]ENSO covariability and the underlying physical processes responsible for
NASA Astrophysics Data System (ADS)
Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Slutsker, I.; Smirnov, A.; Schafer, J. S.; Dickerson, R. R.; Thompson, A. M.; Tripathi, S. N.; Singh, R. P.; Ghauri, B.
2012-12-01
various fuel types (e.g., from open agricultural waste, forest, or dung burning), combustion phases, or aging processes including aggregation or mixing with ambient aerosols. Other intensive aerosol properties (e.g., depolarization ratio or absorption Angstrom exponent) may provide improved definition of fine mode dominated aerosol types from U/I and BB sources [Burton et al., 2012, Giles et al., 2012]. Additional sites in India and Pakistan are also analyzed using available AERONET Version 2, Level 2.0 data.
NASA Astrophysics Data System (ADS)
Dimitriou, Konstantinos; Kassomenos, Pavlos
2016-05-01
In this paper, a cluster analysis of backward air mass trajectories, arriving in Avignon (Southern France), was combined with a Potential Source Contribution Function (PSCF) model on a 0.5° × 0.5° resolution grid, in order to indicate possible aerosol intrusions. A strict triple criterion was constructed from Aerosol Optical Thickness (AOT), Angstrom Exponent (AE), and PM (PM10 and PM2.5) concentration measurements, aiming to distinguish more effectively Episodes of Fine, Coarse and Overall Aerosols (FAE, CAE and OAE respectively). Large fractions of FAE (60.0%) and CAE (40.6%) were strongly attributed to the prevalence of Eastern and South-Southwest (S-SW) airflows respectively, whereas these distinct trajectory clusters also gathered large fractions of OAE (90.2% cumulatively). According to PSCF results, FAE events were strongly associated with the influence of air masses traveling over North Italy and Southern Germany, hence the impact of urban and industrial combustion was emerged. Main sources of coarse aerosols were principally isolated over the Mediterranean, thus the import of sea spray and dust from the Sahara desert is presumed. Satellite AOT observations were used for a more detailed identification of an intense 5-day intrusion of coarse aerosols. Short range slow moving air mass trajectories, were proven to be a clear marker of atmospheric stagnation, based on a wind speed analysis, triggering the accumulation of locally emitted anthropogenic aerosols (mainly PM2.5) and lack of city ventilation.
NASA Astrophysics Data System (ADS)
Korras-Carraca, Marios Bruno; Hatzianastassiou, Nikolaos; Matsoukas, Christos; Gkikas, Antonis; Papadimas, Christos; Sayers, Andy
2015-04-01
Atmospheric aerosols, both natural and anthropogenic, can cause climate change through their direct, indirect, and semi-direct effects on the radiative energy budget of the Earth-atmosphere system. In the present work, we study two of the most important optical properties of aerosols, the asymmetry parameter (gaer) and the Angstrom exponent (α). Both gaer and α are related with aerosol size, which is a very important parameter for climate and human health. The study region comprises North Africa, the Arabian peninsula, Europe, and the Mediterranean basin. These areas are of great interest, because of the variety of aerosol types they host, both anthropogenic and natural. Urban, industrial or biomass-burning aerosols are usually fine, while desert dust or sea-salt are basically coarse, making thus possible the establishment of a relationship between the type and the size of aerosols. Using satellite data from the collection 051 of MODIS (MODerate resolution Imaging Spectroradiometer, Aqua), we investigate the spatio-temporal characteristics of the asymmetry parameter and Angstrom exponent. We generally find significant spatial variability, with larger gaer values over regions dominated by larger size particles, e.g. outside the Atlantic coasts of north-western Africa, where desert-dust outflow is taking place. The gaer values tend to decrease with increasing wavelength, especially over areas dominated by small particulates. The intra-annual variability is found to be small in desert-dust areas, with maximum values during summer, while in all other areas larger values are reported during the cold season and smaller during the warm. Significant intra-annual and inter-annual variability is observed around the Black Sea. However, the inter-annual trends of gaer are found to be generally small. The geographical distributions for α (given for the pair of wavelengths 550-865 nm) affirm the conclusions drawn from the asymmetry parameter as regards the aerosol size over
Remote sensing of soot carbon - Part 2: Understanding the absorption Ångström exponent
NASA Astrophysics Data System (ADS)
Schuster, G. L.; Dubovik, O.; Arola, A.; Eck, T. F.; Holben, B. N.
2016-02-01
Recently, some authors have suggested that the absorption Ångström exponent (AAE) can be used to deduce the component aerosol absorption optical depths (AAODs) of carbonaceous aerosols in the AERONET database. This AAE approach presumes that AAE ≪ 1 for soot carbon, which contrasts the traditional small particle limit of AAE = 1 for soot carbon. Thus, we provide an overview of the AERONET retrieval, and we investigate how the microphysics of carbonaceous aerosols can be interpreted in the AERONET AAE product. We find that AAE ≪ 1 in the AERONET database requires large coarse mode fractions and/or imaginary refractive indices that increase with wavelength. Neither of these characteristics are consistent with the current definition of soot carbon, so we explore other possibilities for the cause of AAE ≪ 1. AAE is related to particle size, and coarse mode particles have a smaller AAE than fine mode particles for a given aerosol mixture of species. We also note that the mineral goethite has an imaginary refractive index that increases with wavelength, is very common in dust regions, and can easily contribute to AAE ≪ 1. We find that AAE ≪ 1 can not be caused by soot carbon, unless soot carbon has an imaginary refractive index that increases with wavelength throughout the visible and near-infrared spectrums. Finally, AAE is not a robust parameter for separating carbonaceous absorption from dust aerosol absorption in the AERONET database.
NASA Astrophysics Data System (ADS)
Utry, N.; Ajtai, T.; Filep, Á.; Pintér, M.; Török, Zs.; Bozóki, Z.; Szabó, G.
2014-07-01
Based on a two-week measurement campaign in an environment heavily polluted both by transit traffic and household heating in the inner city of Szeged (Hungary), correlations between the absorption Angström exponent (AAE) fitted to the optical absorption coefficients measured with a four wavelength (1064, 532, 355 and 266 nm) photoacoustic aerosol measuring system (4λ-PAS) and various aerosol parameters were identified. AAE was found to depend linearly on OCwb/EC and on NGM100/NGMD20, i.e. on the ratio of mass concentrations of elemental carbon (EC) to the fraction of organic carbon associated with wood burning (OCwb), and on the ratio of aerosol number concentrations in the 20 nm (NGMD20) to 100 nm (NGMD100) modes, with a regression coefficient of R = 0.95 and R = 0.86, respectively. In the daily fluctuation of AAE two minima were identified, which coincide with the morning and afternoon rush hours, during which NGMD20 exhibits maximum values. During the campaign the shape of the aerosol volume size distribution (dV/dlogD) was found to be largely invariant, supporting the assumption that the primary driver for the AAE variation was aerosol chemical composition rather than particle size. Furthermore, when wavelength segregated AAE values were calculated, AAE for the shorter wavelengths (AAE355-266) was also found to depend linearly on the above mentioned ratios with similar regression coefficients but with a much steeper correlation line, while the AAE for the longer wavelengths (AAE1064-532) exhibits only a considerably weaker correlation. These results prove the unique advantages of real time multi-wavelength photoacoustic measurement of optical absorption in case the wavelength range includes the ultra-violet too.
Zhang, Xiaolu; Lin, Ying-Hsuan; Surratt, Jason D; Weber, Rodney J
2013-04-16
We investigate the sources, chemical composition, and spectral properties of light-absorbing organic aerosol extracts (i.e., brown carbon, or BrC) in the Los Angeles (LA) Basin during the CalNex-2010 field campaign. Light absorption of PM2.5 water-soluble components at 365 nm (Abs365), used as a proxy for water-soluble BrC, was well correlated with water-soluble organic carbon (WSOC) (r(2) = 0.55-0.65), indicating secondary organic aerosol (SOA) formation from anthropogenic emissions was the major source of water-soluble BrC in this region. Normalizing Abs365 to WSOC mass yielded an average solution mass absorption efficiency (MAE365) of 0.71 m(2) g(-1) C. Detailed chemical speciation of filter extracts identified eight nitro-aromatic compounds that were correlated with Abs365. These compounds accounted for ∼4% of the overall water-soluble BrC absorption. Methanol-extracted BrC in LA was approximately 3 and 21 times higher than water-soluble BrC at 365 and 532 nm, respectively, and had a MAE365 of 1.58 m(2) g(-1) C (Abs365 normalized to organic carbon mass). The water-insoluble BrC was strongly correlated with ambient elemental carbon concentration, suggesting similar sources. Absorption Ångström exponent (Å(a)) (fitted between 300 and 600 nm wavelengths) was 3.2 (±1.2) for the PILS water-soluble BrC measurement, compared to 4.8 (±0.5) and 7.6 (±0.5) for methanol- and water-soluble BrC from filter extracts, respectively. These results show that fine particle BrC was prevalent in the LA basin during CalNex, yet many of its properties and potential impacts remain unknown. PMID:23506531
Whisper gallery mirrors reflectivities from 100 [angstrom] to 500 [angstrom
Hung, Tsen-Yu; Hagelstein, P.L.
1990-01-01
We have examined optical constants and predicted reflectivities of candidate surface coatings for whisper gallery mirrors in the extreme ultraviolet (100 [Angstrom] to 500 [Angstrom]). Previous work of Vinogradov and coworkers have identified the spectral regime near 100-150 [Angstrom] as particularly promising due to the high whisper gallery mirror reflectivities of the noble metals in the vicinity of their Cooper minima in this regime. We confirm this basic result using newer optical data, and we have sought surface materials which would extend the range over which the whisper gallery mirrors may be used: between 100 to 500 [Angstrom]. We find that substantial whisper gallery mirror reflectivities (near or greater than 50%) are predicted for a variety of elements, and that the TE peak reflection is larger than TM peak reflection by on the order of 10%. However, most of the elements which do reflect well have surfaces that are vulnerable to oxygen contamination, which seriously degrades mirror performance. A cryogenic mirror design using a dynamic solid rare gas surface which has the potential to defeat such surface contaminations is described: it has peak reflectivity of more than 50% centered near 280 [Angstrom]. 8 figs, 18 refs.
Whisper gallery mirrors reflectivities from 100 {angstrom} to 500 {angstrom}
Hung, Tsen-Yu; Hagelstein, P.L.
1990-12-31
We have examined optical constants and predicted reflectivities of candidate surface coatings for whisper gallery mirrors in the extreme ultraviolet (100 {Angstrom} to 500 {Angstrom}). Previous work of Vinogradov and coworkers have identified the spectral regime near 100-150 {Angstrom} as particularly promising due to the high whisper gallery mirror reflectivities of the noble metals in the vicinity of their Cooper minima in this regime. We confirm this basic result using newer optical data, and we have sought surface materials which would extend the range over which the whisper gallery mirrors may be used: between 100 to 500 {Angstrom}. We find that substantial whisper gallery mirror reflectivities (near or greater than 50%) are predicted for a variety of elements, and that the TE peak reflection is larger than TM peak reflection by on the order of 10%. However, most of the elements which do reflect well have surfaces that are vulnerable to oxygen contamination, which seriously degrades mirror performance. A cryogenic mirror design using a dynamic solid rare gas surface which has the potential to defeat such surface contaminations is described: it has peak reflectivity of more than 50% centered near 280 {Angstrom}. 8 figs, 18 refs.
NASA Astrophysics Data System (ADS)
Pokhrel, Rudra P.; Wagner, Nick L.; Langridge, Justin M.; Lack, Daniel A.; Jayarathne, Thilina; Stone, Elizabeth A.; Stockwell, Chelsea E.; Yokelson, Robert J.; Murphy, Shane M.
2016-08-01
Single-scattering albedo (SSA) and absorption Ångström exponent (AAE) are two critical parameters in determining the impact of absorbing aerosol on the Earth's radiative balance. Aerosol emitted by biomass burning represent a significant fraction of absorbing aerosol globally, but it remains difficult to accurately predict SSA and AAE for biomass burning aerosol. Black carbon (BC), brown carbon (BrC), and non-absorbing coatings all make substantial contributions to the absorption coefficient of biomass burning aerosol. SSA and AAE cannot be directly predicted based on fuel type because they depend strongly on burn conditions. It has been suggested that SSA can be effectively parameterized via the modified combustion efficiency (MCE) of a biomass burning event and that this would be useful because emission factors for CO and CO2, from which MCE can be calculated, are available for a large number of fuels. Here we demonstrate, with data from the FLAME-4 experiment, that for a wide variety of globally relevant biomass fuels, over a range of combustion conditions, parameterizations of SSA and AAE based on the elemental carbon (EC) to organic carbon (OC) mass ratio are quantitatively superior to parameterizations based on MCE. We show that the EC / OC ratio and the ratio of EC / (EC + OC) both have significantly better correlations with SSA than MCE. Furthermore, the relationship of EC / (EC + OC) with SSA is linear. These improved parameterizations are significant because, similar to MCE, emission factors for EC (or black carbon) and OC are available for a wide range of biomass fuels. Fitting SSA with MCE yields correlation coefficients (Pearson's r) of ˜ 0.65 at the visible wavelengths of 405, 532, and 660 nm while fitting SSA with EC / OC or EC / (EC + OC) yields a Pearson's r of 0.94-0.97 at these same wavelengths. The strong correlation coefficient at 405 nm (r = 0.97) suggests that parameterizations based on EC / OC or EC / (EC + OC) have good predictive
The Angstrom Project: a new microlensing candidate
NASA Astrophysics Data System (ADS)
Kerins, E.; Darnley, M. J.; Newsam, A. M.; Duke, J. P.; Gould, A.; Street, C. Han B.-G. Park R. A.
2008-12-01
We report the discovery of a new microlensing candidate in M31 by the Angstrom Project M31 bulge microlensing survey using the Liverpool Telescope (La Palma). The candidate was discovered using difference imaging techniques by the Angstrom Project Alert System (APAS) in a series of Sloan i'-band images of the bulge of M31.
Critical exponent for viscosity
NASA Technical Reports Server (NTRS)
Berg, Robert F.; Moldover, Michael R.
1990-01-01
The critical exponent y characterizing the divergence of the viscosity for carbon dioxide and xenon has been measured. The values of y for both fluids fall within the range y = 0.041 + or - 0.001 and are consistent with the range y = 0.042 + or - 0.002 spanned by earlier data for four binary liquid mixtures. This agreement is the strongest evidence that pure fluids and binary liquids are in the same dynamic universality class; however, the results for y are inconsistent with the recent theoretical value of 0.032.
Singularity detection using holder exponent.
Sohn, H.; Robertson, A. N.; Farrar, C. R.
2002-01-01
A signal processing technique called Holder exponent is presented to detect the presence of a discontinuity and when the discontinuity occurs in a dynamic signal. Wavelet transforms are incorporated with the Holder exponent to capture the time varying nature of discontinuities, and a classification procedure is developed to quantify when changes in the Holder exponent are significant, The proposed Holder exponent analysis is applied to acceleration response of a mechanical system with a rattling internal part. The experimental results demonstrate the effectiveness of the Holder exponent for identifying certain types of events that introduce discontinuities into the measured dynamic response data.
NASA Astrophysics Data System (ADS)
Murphy, S. M.; Pokhrel, R. P.; Beamesderfer, E.; Wagner, N. L.; Langridge, J.; Lack, D.
2015-12-01
We present results obtained during the Fire Lab at Missoula Experiment-4 (FLAME-4) with a combination of multi-wavelength photoacoustic and cavity ringdown spectrometers. It will be shown that the single scattering albedo and Angstrom exponent of biomass burning emissions can be better parameterized by the organic carbon to black carbon ratio than by the modified combustion efficiency. Two different methods to distinguish the contribution to aerosol absorption from brown carbon versus black carbon and enhanced black carbon absorption will be presented. One method is based on extending the absorption seen at 660 nm with an assumed Angstrom exponent while the other assumes a similar absorption enhancement (determined via thermal denuder) of black carbon at 660 and 405 nm. Potential errors and advantages of both methods will be discussed. Finally, chamber experiments that show degradation of brown carbon by photochemical oxidation will be presented along with a number of methods by which to assess the amount of brown carbon that is degraded.
212-Angstrom neonlike zinc laser of LULI
NASA Astrophysics Data System (ADS)
Jamelot, Gerard; Jaegle, Pierre; Rus, Bedrich; Carillon, Antoine; Klisnick, Annie; Nantel, Marc; Sebban, Stephane; Albert, F.; Zeitoun, Philippe; Plankl, E.; Sirgand, A.; Lewis, Ciaran L. S.; MacPhee, Andrew G.; Tallents, Gregory J.; Krishnan, J.; Holden, M.
1995-09-01
The main feature of x-ray laser research at LULI is the development of a saturated laser at 212 angstrom with a relatively small pump laser of 0.4 kJ in 600 ps. The laser works with the 3p- 3s J equals O yields 1 transition of neon-like zinc, by using the double-pass of amplified radiation in the active medium. Plasma parameters (temperature, density, homogeneity), and x-ray laser emission properties (intensity, pointing angle, divergence, and coherence) have been studied. Lasing action needs the main laser pulse to be preceded by a ten-prepulse train (contrast ratio less than 103) due to the remnant oscillator. The effect of a single prepulse was investigated as a function of contrast ratio and delay between the prepulse and the main pulse.
Spectral Absorption Properties of Atmospheric Aerosols
NASA Technical Reports Server (NTRS)
Bergstrom, R. W.; Pilewskie, P.; Russell, P. B.; Redemann, J.; Bond, T. C.; Quinn, P. K.; Sierau, B.
2007-01-01
We have determined the solar spectral absorption optical depth of atmospheric aerosols for specific case studies during several field programs (three cases have been reported previously; two are new results). We combined airborne measurements of the solar net radiant flux density and the aerosol optical depth with a detailed radiative transfer model for all but one of the cases. The field programs (SAFARI 2000, ACE Asia, PRIDE, TARFOX, INTEX-A) contained aerosols representing the major absorbing aerosol types: pollution, biomass burning, desert dust and mixtures. In all cases the spectral absorption optical depth decreases with wavelength and can be approximated with a power-law wavelength dependence (Absorption Angstrom Exponent or AAE). We compare our results with other recent spectral absorption measurements and attempt to briefly summarize the state of knowledge of aerosol absorption spectra in the atmosphere. We discuss the limitations in using the AAE for calculating the solar absorption. We also discuss the resulting spectral single scattering albedo for these cases.
Sub-Angstrom electron microscopy for sub-Angstrom nano-metrology
O'Keefe, Michael A.; Allard, Lawrence F.
2004-01-18
The revolution in nanoscale science and technology requires instrumentation for observation and metrology - we must be able to see and measure what we build. Because nano-devices operate on the level of a few molecules, or even a few atoms, accurate atomic-scale imaging is called for. High-resolution aberration-corrected electron microscopes (both TEM and STEM) can provide valuable measurements at the sub-Angstrom level. Over the next decade, extension of TEM and STEM resolutions to half-Angstrom levels by next-generation aberration-corrected electron microscopes will advance the capabilities of these essential tools for atomic-scale structural characterization. Because improvements in resolution allow for separation of atom columns in many more projection directions, these microscopes will provide much improved three-dimensional characterization of the shape and internal structure of nanodevices and catalyst nanoparticles (perhaps even true 3-D imaging), and hence provide essential feedback in the nano-theory/construction/measurement loop.
Contribution of particulate brown carbon to light absorption in the rural and urban Southeast US
NASA Astrophysics Data System (ADS)
Devi, J. Jai; Bergin, Michael H.; Mckenzie, Michael; Schauer, James J.; Weber, Rodney J.
2016-07-01
Measurements of wavelength dependent aerosol light absorption coefficients were carried out as part of the Southern Oxidant and Aerosol Study (SOAS) during the summer of 2013 to determine the contribution of light absorbing organic carbon (BrC) to total aerosol light absorption in a rural location (Centreville, AL) and an urban area (Atlanta, GA). The light absorption coefficients in the near UV and visible wavelengths were measured for both ambient air, as well as ambient air heated in a thermal denuder to 200 °C to remove the semi-volatile organic compounds. Atlanta measurements show dominance of semi-volatile brown carbon with an average absorption angstrom exponent (AAE) of 1.4 before heating and about 1.0 after heating. In urban Atlanta, a decrease of about ∼35% in the light absorption coefficient at 370 nm after heating indicates that light absorbing organic compounds are a substantial fraction of the light absorption budget. Furthermore, a considerable increase in the fraction of light absorption by the semi-volatile aerosol occurs during the daytime, likely linked with photochemistry. Measurements at rural Centerville, on the other hand, do not show any major change in AAE with values before and after heating of 0.99 and 0.98, respectively. Overall the results suggest that photochemical aged urban emissions result in the presence of light absorbing BrC, while at rural locations which are dominated by aged aerosol and local biogenic emissions (based on measurements of Angstrom exponents) BrC does not significantly contribute to light absorption.
The Angstrom Project: two new microlensing/nova transients
NASA Astrophysics Data System (ADS)
Kerins, Eamonn
2008-11-01
We report the discovery of two new optical transients in M31 by the Angstrom Project M31 bulge microlensing survey using the Liverpool Telescope (La Palma). These transients were discovered using difference imaging techniques by the Angstrom Project Alert System (APAS) in a series of Sloan i'-band images of the bulge of M31.
Grenfell, Thomas C.; Doherty, Sarah J.; Clarke, Antony D.; Warren, Stephen G.
2011-05-10
Light absorption by particulate impurities in snow and ice can affect the surface albedo and is important for the climate. The absorption properties of these particles can be determined by collecting and melting snow samples and extracting the particulate material by filtration of the meltwater. This paper describes the optical design and testing of a new instrument to measure the absorption spectrum from 400 to 750 nm wavelength of the particles collected on filters using an ''integrating-sandwich'' configuration. The measured absorption is shown to be unaffected by scattering of light from the deposited particulates. A set of calibration standards is used to derive an upper limit for the concentration of black carbon (BC) in the snow. The wavelength dependence of the absorption spectra from 450 to 600 nm is used to calculate an absorption Angstrom exponent for the aerosol. This exponent is used to estimate the actual BC concentration in the snow samples as well as the relative contributions of BC and non-BC constituents to the absorption of solar radiation integrated over the wavelength band 300 to 750 nm.
The Morphosyntax of Discontinuous Exponence
ERIC Educational Resources Information Center
Campbell, Amy Melissa
2012-01-01
This thesis offers a systematic treatment of discontinuous exponence, a pattern of inflection in which a single feature or a set of features bundled in syntax is expressed by multiple, distinct morphemes. This pattern is interesting and theoretically relevant because it represents a deviation from the expected one-to-one relationship between…
NASA Technical Reports Server (NTRS)
Lenoble, J.; Pruvost, P.
1983-01-01
SAGE four-channel transmission profiles are inverted to retrieve the extinction profiles from which the aerosol Angstrom coefficient alpha is obtained. The procedure allows one to check the influence of the NO2 absorption profile, which is small below 25 km. The results compare well with those obtained by a completely different procedure at NASA Langley Research Center, and the main features of the alpha profiles seem to be significant, even considering the rather large error bars. The relation between the retrieved Angstrom coefficient, the particle effective radius and the asymmetry factor is considered.
Observations on related ecological exponents.
Southwood, T Richard E; May, Robert M; Sugihara, George
2006-05-01
We observe a relationship among three independently derived power laws in ecology: (i) total number of species versus area, (ii) species frequency versus species length, and (iii) maximal body size versus area. Aside from showing how these historically disparate phenomena are connected, we show how recent empirical results relating the maximal body size of top terrestrial vertebrates to the square root of land area conform to a prior theoretical expectation given by two of the above power laws. Of particular interest is the observation that the exponent relating species length to species frequency suggests a dimension for niche space for terrestrial vertebrate assemblages of D approximately 3/2. This value, along with power law for maximal body size, versus area, gives rise to the canonical species area exponent z approximately 1/4. PMID:16641099
Critical exponents from cluster coefficients.
Rotman, Z; Eisenberg, E
2009-09-01
For a large class of repulsive interaction models, the Mayer cluster integrals can be transformed into a tridiagonal real symmetric matrix R_{mn} , whose elements converge to two constants. This allows for an effective extrapolation of the equation of state for these models. Due to a nearby (nonphysical) singularity on the negative real z axis, standard methods (e.g., Padé approximants based on the cluster integrals expansion) fail to capture the behavior of these models near the ordering transition, and, in particular, do not detect the critical point. A recent work [E. Eisenberg and A. Baram, Proc. Natl. Acad. Sci. U.S.A. 104, 5755 (2007)] has shown that the critical exponents sigma and sigma;{'} , characterizing the singularity of the density as a function of the activity, can be exactly calculated if the decay of the R matrix elements to their asymptotic constant follows a 1/n;{2} law. Here we employ renormalization group (RG) arguments to extend this result and analyze cases for which the asymptotic approach of the R matrix elements toward their limiting value is of a more general form. The relevant asymptotic correction terms (in RG sense) are identified, and we then present a corrected exact formula for the critical exponents. We identify the limits of usage of the formula and demonstrate one physical model, which is beyond its range of validity. The formula is validated numerically and then applied to analyze a number of concrete physical models. PMID:19905081
Scaling exponents for ordered maxima
Ben-Naim, E.; Krapivsky, P. L.; Lemons, N. W.
2015-12-22
We study extreme value statistics of multiple sequences of random variables. For each sequence with N variables, independently drawn from the same distribution, the running maximum is defined as the largest variable to date. We compare the running maxima of m independent sequences and investigate the probability S_{N} that the maxima are perfectly ordered, that is, the running maximum of the first sequence is always larger than that of the second sequence, which is always larger than the running maximum of the third sequence, and so on. The probability S_{N} is universal: it does not depend on the distribution from which the random variables are drawn. For two sequences, S_{N}~N^{–1/2}, and in general, the decay is algebraic, S_{N}~N^{–σm}, for large N. We analytically obtain the exponent σ_{3}≅1.302931 as root of a transcendental equation. Moreover, the exponents σ_{m} grow with m, and we show that σ_{m}~m for large m.
Scaling exponents for ordered maxima
Ben-Naim, E.; Krapivsky, P. L.; Lemons, N. W.
2015-12-22
We study extreme value statistics of multiple sequences of random variables. For each sequence with N variables, independently drawn from the same distribution, the running maximum is defined as the largest variable to date. We compare the running maxima of m independent sequences and investigate the probability SN that the maxima are perfectly ordered, that is, the running maximum of the first sequence is always larger than that of the second sequence, which is always larger than the running maximum of the third sequence, and so on. The probability SN is universal: it does not depend on the distribution frommore » which the random variables are drawn. For two sequences, SN~N–1/2, and in general, the decay is algebraic, SN~N–σm, for large N. We analytically obtain the exponent σ3≅1.302931 as root of a transcendental equation. Moreover, the exponents σm grow with m, and we show that σm~m for large m.« less
Particulate absorption and its variation with mixing status observed in-situ over Mexico
NASA Astrophysics Data System (ADS)
Shinozuka, Y.; Clarke, A. D.; Kapustin, V. N.; Howell, S. G.; Zhou, J.; McNaughton, C. S.; Pinkerton, M.
2006-12-01
Light absorbing particles of urban and rural origin were measured in-situ from C-130 and DC-8 aircraft in the troposphere over Mexico during MIRAGE and INTEX-B in March 2006. Thermal analysis of aerosol size distributions and direct measurements of mutiwavelength visible light scattering and absorption enabled evaluation of optical properties of the strongly absorbing soot with and without volatile coating material. As Angstrom exponent, the wavelength dependence of light scattering, increases from -0.2 to 1.5, single scattering albedo of the unheated total particles decreases from ~0.97 to 0.90, indicating transition from pure dust to its mixture with urban and biomass pollution. Greater Angstrom values of 1.5 - 2.1 are, however, associated with increasing total SSA to ~0.95, a trend presumably determined by the sources of the accumulation-mode aerosols. Preliminary attempts to quantify enhanced absorption due to volatile coatings on soot revealed a 0 - 20% reduction in absorption as particles were heated to 300 oC to evaporate those coatings. Variation in the mass scattering/absorption efficiency, submicron SSA and underlying microphysical and chemical properties are also discussed.
NASA Technical Reports Server (NTRS)
Giles, David M.; Holben, Brent N.; Eck, Thomas F.; Sinyuk, Aliaksandr; Smirnov, Alexander; Slutsker, Ilya; Dickerson, R. R.; Thompson, A. M.; Schafer, J. S.
2012-01-01
Partitioning of mineral dust, pollution, smoke, and mixtures using remote sensing techniques can help improve accuracy of satellite retrievals and assessments of the aerosol radiative impact on climate. Spectral aerosol optical depth (tau) and single scattering albedo (omega (sub 0) ) from Aerosol Robotic Network (AERONET) measurements are used to form absorption [i.e., omega (sub 0) and absorption Angstrom exponent (alpha(sub abs))] and size [i.e., extinction Angstrom exponent (alpha(sub ext)) and fine mode fraction of tau] relationships to infer dominant aerosol types. Using the long-term AERONET data set (1999-2010), 19 sites are grouped by aerosol type based on known source regions to: (1) determine the average omega (sub 0) and alpha(sub abs) at each site (expanding upon previous work); (2) perform a sensitivity study on alpha(sub abs) by varying the spectral omega (sub 0); and (3) test the ability of each absorption and size relationship to distinguish aerosol types. The spectral omega (sub 0) averages indicate slightly more aerosol absorption (i.e., a 0.0 < delta omega (sub 0) <= 0.02 decrease) than in previous work and optical mixtures of pollution and smoke with dust show stronger absorption than dust alone. Frequency distributions of alpha(sub abs) show significant overlap among aerosol type categories and at least 10% of the alpha(sub abs) retrievals in each category are below 1.0. Perturbing the spectral omega (sub 0) by +/- 0.03 induces significant alpha(sub abs) changes from the unperturbed value by at least approx. +/- 0.6 for Dust, approx. +/-0.2 for Mixed, and approx. +/-0.1 for Urban/Industrial and Biomass Burning. The omega (sub 0)440nm and alpha(sub ext) 440-870nm relationship shows the best separation among aerosol type clusters, providing a simple technique for determining aerosol type from surface- and future space-based instrumentation.
Han, S.; Wagner, R.S.; Gullikson, E.
1995-12-01
Due to the large bandgap of diamond, it is transparent to the visible spectrum, making it an attractive material for soft x-ray detection. Response of diamond photoconductors fabricated using Polycrystalline chemical-vapor-deposited (CVD) diamond to soft x-rays has been measured using x-rays emitted from a laser-produced plasma source in the spectral range 125 {Angstrom} to 240 {Angstrom}. These photoconductors have interdigitated electrode structure in order to increase the active area as well as detector sensitivity. Contributions to the detector sensitivity by the photoelectrons is discussed.
Dynamical selection of critical exponents
NASA Astrophysics Data System (ADS)
Wiese, Kay Jörg
2016-04-01
In renormalized field theories there are in general one or few fixed points that are accessible by the renormalization-group flow. They can be identified from the fixed-point equations. Exceptionally, an infinite family of fixed points exists, parameterized by a scaling exponent ζ , itself a function of a nonrenormalizing parameter. Here we report a different scenario with an infinite family of fixed points of which seemingly only one is chosen by the renormalization-group flow. This dynamical selection takes place in systems with an attractive interaction V (ϕ ) , as in standard ϕ4 theory, but where the potential V at large ϕ goes to zero, as, e.g., the attraction by a defect.
Finite-time braiding exponents
NASA Astrophysics Data System (ADS)
Budišić, Marko; Thiffeault, Jean-Luc
2015-08-01
Topological entropy of a dynamical system is an upper bound for the sum of positive Lyapunov exponents; in practice, it is strongly indicative of the presence of mixing in a subset of the domain. Topological entropy can be computed by partition methods, by estimating the maximal growth rate of material lines or other material elements, or by counting the unstable periodic orbits of the flow. All these methods require detailed knowledge of the velocity field that is not always available, for example, when ocean flows are measured using a small number of floating sensors. We propose an alternative calculation, applicable to two-dimensional flows, that uses only a sparse set of flow trajectories as its input. To represent the sparse set of trajectories, we use braids, algebraic objects that record how trajectories exchange positions with respect to a projection axis. Material curves advected by the flow are represented as simplified loop coordinates. The exponential rate at which a braid stretches loops over a finite time interval is the Finite-Time Braiding Exponent (FTBE). We study FTBEs through numerical simulations of the Aref Blinking Vortex flow, as a representative of a general class of flows having a single invariant component with positive topological entropy. The FTBEs approach the value of the topological entropy from below as the length and number of trajectories is increased; we conjecture that this result holds for a general class of ergodic, mixing systems. Furthermore, FTBEs are computed robustly with respect to the numerical time step, details of braid representation, and choice of initial conditions. We find that, in the class of systems we describe, trajectories can be re-used to form different braids, which greatly reduces the amount of data needed to assess the complexity of the flow.
Finite-time braiding exponents.
Budišić, Marko; Thiffeault, Jean-Luc
2015-08-01
Topological entropy of a dynamical system is an upper bound for the sum of positive Lyapunov exponents; in practice, it is strongly indicative of the presence of mixing in a subset of the domain. Topological entropy can be computed by partition methods, by estimating the maximal growth rate of material lines or other material elements, or by counting the unstable periodic orbits of the flow. All these methods require detailed knowledge of the velocity field that is not always available, for example, when ocean flows are measured using a small number of floating sensors. We propose an alternative calculation, applicable to two-dimensional flows, that uses only a sparse set of flow trajectories as its input. To represent the sparse set of trajectories, we use braids, algebraic objects that record how trajectories exchange positions with respect to a projection axis. Material curves advected by the flow are represented as simplified loop coordinates. The exponential rate at which a braid stretches loops over a finite time interval is the Finite-Time Braiding Exponent (FTBE). We study FTBEs through numerical simulations of the Aref Blinking Vortex flow, as a representative of a general class of flows having a single invariant component with positive topological entropy. The FTBEs approach the value of the topological entropy from below as the length and number of trajectories is increased; we conjecture that this result holds for a general class of ergodic, mixing systems. Furthermore, FTBEs are computed robustly with respect to the numerical time step, details of braid representation, and choice of initial conditions. We find that, in the class of systems we describe, trajectories can be re-used to form different braids, which greatly reduces the amount of data needed to assess the complexity of the flow. PMID:26328578
HRTEM Imaging of Atoms at Sub-Angstrom Resolution
O'Keefe, Michael A.; Allard, Lawrence F.; Blom, Douglas A.
2005-04-06
John Cowley and his group at Arizona State University pioneered the use of transmission electron microscopy (TEM) for high-resolution imaging. Images were achieved three decades ago showing the crystal unit cell content at better than 4 Angstrom resolution. This achievement enabled researchers to pinpoint the positions of heavy atom columns within the unit cell. Lighter atoms appear as resolution is improved to sub-Angstrom levels. Currently, advanced microscopes can image the columns of the light atoms (carbon, oxygen, nitrogen) that are present in many complex structures, and even the lithium atoms present in some battery materials. Sub-Angstrom imaging, initially achieved by focal-series reconstruction of the specimen exit surface wave, will become common place for next-generation electron microscopes with CS-corrected lenses and monochromated electron beams. Resolution can be quantified in terms of peak separation and inter-peak minimum, but the limits imposed on the attainable resolution by the properties of the micro-scope specimen need to be considered. At extreme resolution the ''size'' of atoms can mean that they will not be resolved even when spaced farther apart than the resolution of the microscope.
Imaging Lithium Atoms at Sub-Angstrom Resolution
O'Keefe, Michael A.; Shao-Horn, Yang
2005-01-03
John Cowley and his group at ASU were pioneers in the use of transmission electron microscopy (TEM) for high-resolution imaging. Three decades ago they achieved images showing the crystal unit cell content at better than 4A resolution. Over the years, this achievement has inspired improvements in resolution that have enabled researchers to pinpoint the positions of heavy atom columns within the cell. More recently, this ability has been extended to light atoms as resolution has improved. Sub-Angstrom resolution has enabled researchers to image the columns of light atoms (carbon, oxygen and nitrogen) that are present in many complex structures. By using sub-Angstrom focal-series reconstruction of the specimen exit surface wave to image columns of cobalt, oxygen, and lithium atoms in a transition metal oxide structure commonly used as positive electrodes in lithium rechargeable batteries, we show that the range of detectable light atoms extends to lithium. HRTEM at sub-Angstrom resolution will provide the essential role of experimental verification for the emergent nanotech revolution. Our results foreshadow those to be expected from next-generation TEMs with CS-corrected lenses and monochromated electron beams.
Soft x-ray amplification in lithium-like Al XI (154 /angstrom/) and Si XII (129 /angstrom/)
Kim, D.; Skinner, C.H.; Wouters, A.; Valeo, E.; Voorhees, D.; Suckewer, S.
1988-03-01
Recent experiments on soft x-ray amplification in lithium-like ions in a CO/sub 2/ laser-produced recombining plasma confined in a magnetic field are presented. The maximum gain-length products observed are GL approx. = 3 to 4 for the 154 /angstrom/, 4f-3d transition in Al XI and GL (approxreverse arrowequal/ 1 to 2 for the 129 /angstrom/, 4f-3d transition in Si XII, respectively. A one-dimensional hydrodynamic code with a collisional-radiative atomic model was used to model the plasma and the theoretical predictions of gain agree well with the observations. Descriptions of both hydrodynamic and atomic physics code are given. 36 refs., 10 figs.
Developing Students' Understanding of Exponents and Logarithms.
ERIC Educational Resources Information Center
Weber, Keith
In this paper, we describe instruction designed to teach students about exponents and logarithms and report a pilot study to test the effectiveness of this instruction. Based on the theoretical work of Dubinsky and Sfard, we postulate a set of mental constructions that a student could make to understand the concepts of exponents and logarithms. We…
EUVE Detection of the Local Interstellar Wind via Resonance Scattering of Solar He I 584 Angstroms
NASA Astrophysics Data System (ADS)
Flynn, B.; Vallerga, J.; Dalaudier, F.; Gladstone, G. R.
1996-05-01
We present initial results from EUVE measurements of interplanetary and geocoronal He I 584 Angstroms emission made during the all-sky survey. The data consist of count rates from the tin quadrants (520--750 Angstroms) of Scanner C obtained over a 1 year period from July 1992 to July 1993. During this period, EUVE was in survey mode so that the scanners made 360(deg) sweeps of the sky in a plane perpendicular to the Sun-Earth line. The interplanetary He I signal is morphologically consistent with previous observations, such as Prognoz 6 (Dalaudier et al. 1984, A&A, v134). However, unlike the Prognoz 6 data, the EUVE measurements were made from low Earth orbit (512 km) and so contain geocoronal emission as well. As a result, along sight lines where the relative speed between the interplanetary wind and the Earth is at a minimum, absorption of the interplanetary signal by the geocorona occurs. We anticipate model fits to our data to yield: (1) interplanetary He parameters; (2) solar He I Lyalpha line information; and (3) geocoronal He column abundance and temperature. This work is supported by NASA contract NAS5-29298.
Direct Measurements of Brown Carbon Absorption in A Wide Range of Biomass Burning Plumes
NASA Astrophysics Data System (ADS)
Murphy, S. M.; Pokhrel, R. P.; Beamesderfer, E.; Lack, D.; Langridge, J.; Wagner, N. L.
2014-12-01
Biomass burning represents one of the largest global sources of absorbing aerosol. Despite the importance of biomass burning emissions on the Earth's radiative balance, there remains significant uncertainty about the optical properties of emitted particles. Of particular interest is the impact of lensing on black carbon absorption and the impact of brown carbon. This presentation describes results from the Fire Lab at Missoula Experiment-4 (FLAME-4), which occurred in October 2012. Multi-channel photoacoustic (PAS) and Cavity Ringdown (CRDS) spectrometers were used to measure absorption, extinction, and absorption enhancement of aerosol particles produced from a wide range of globally relevant biomass fuels. Measurements were made at 405, 532, and 660 nm with duplicate channels at 405 and 660 measuring denuded particles, allowing for direct observation of the enhancement of absorption by black carbon particles caused by clear and brown organic coatings. Fuels were chosen based on their contribution to global wildfire emissions and a wide range of fuels will be discussed including some of the first optical measurements of Indonesian peat. The SSA and absorption angstrom exponent (AAE) of different biomass fuels will be explored and the relative importance of black and brown carbon emitted from different biomass fuels will be assessed, demonstrating that for certain fuels absorption from brown carbon is as important, or even more important than absorption from black carbon.
Identifying Aerosol Type/Mixture from Aerosol Absorption Properties Using AERONET
NASA Technical Reports Server (NTRS)
Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Dickerson, R. R.; Thompson, A. M.; Slutsker, I.; Li, Z.; Tripathi, S. N.; Singh, R. P.; Zibordi, G.
2010-01-01
Aerosols are generated in the atmosphere through anthropogenic and natural mechanisms. These sources have signatures in the aerosol optical and microphysical properties that can be used to identify the aerosol type/mixture. Spectral aerosol absorption information (absorption Angstrom exponent; AAE) used in conjunction with the particle size parameterization (extinction Angstrom exponent; EAE) can only identify the dominant absorbing aerosol type in the sample volume (e.g., black carbon vs. iron oxides in dust). This AAE/EAE relationship can be expanded to also identify non-absorbing aerosol types/mixtures by applying an absorption weighting. This new relationship provides improved aerosol type distinction when the magnitude of absorption is not equal (e.g, black carbon vs. sulfates). The Aerosol Robotic Network (AERONET) data provide spectral aerosol optical depth and single scattering albedo - key parameters used to determine EAE and AAE. The proposed aerosol type/mixture relationship is demonstrated using the long-term data archive acquired at AERONET sites within various source regions. The preliminary analysis has found that dust, sulfate, organic carbon, and black carbon aerosol types/mixtures can be determined from this AAE/EAE relationship when applying the absorption weighting for each available wavelength (Le., 440, 675, 870nm). Large, non-spherical dust particles absorb in the shorter wavelengths and the application of 440nm wavelength absorption weighting produced the best particle type definition. Sulfate particles scatter light efficiently and organic carbon particles are small near the source and aggregate over time to form larger less absorbing particles. Both sulfates and organic carbon showed generally better definition using the 870nm wavelength absorption weighting. Black carbon generation results from varying combustion rates from a number of sources including industrial processes and biomass burning. Cases with primarily black carbon showed
Tatchyn, R.; Bane, K.; Boyce, R.
1994-03-01
Electron bunch requirements for single-pass saturation of a Free-Electron Laser (FEL) operating at full transverse coherence in the Self-Amplified Spontaneous Emission (SASE) mode include: (1) a high peak current, (2) a sufficiently low relative energy spread, and (3) a transverse emittance {var_epsilon}[r-m] satisfying the condition {var_epsilon} {le} {lambda}A/4{pi}, where {lambda}[m] is the output wavelength of the FEL. In the insertion device that induces the coherent amplification, the prepared electron bunch must be kept on a trajectory sufficiently collinear with the amplified photons without significant dilution of its transverse density. In this paper we discuss a Linac Coherent Light Source (LCLS) based on a high energy accelerator such as, e.g., the 3km S-band structure at the Stanford Linear Accelerator Center (SLAC), followed by a long high-precision undulator with superimposed quadrupole (FODO) focusing, to fulfill the given requirements for SASE operation in the 1000{Angstrom}--1{Angstrom} range. The electron source for the linac, an RF gun with a laser-excited photocathode featuring a normalized emittance in the 1--3 mm-mrad range, a longitudinal bunch duration of the order of 3 ps, and approximately 10{sup {minus}9} C/bunch, is a primary determinant of the required low transverse and longitudinal emittances. Acceleration of the injected bunch to energies in the 5--25 GeV range is used to reduce the relative longitudinal energy spread in the bunch, as well as to reduce the transverse emittance to values consistent with the cited wavelength regime. Two longitudinal compression stages are employed to increase the peak bunch current to the 2--5 kA levels required for sufficiently rapid saturation. The output radiation is delivered, via a grazing-incidence mirror bank, to optical instrumentation and a multi-user beam line system. Technological requirements for LCLS operation at 40{Angstrom}, 4.5{Angstrom}, and 1.5{Angstrom} are examined.
Bayesian estimation of self-similarity exponent
NASA Astrophysics Data System (ADS)
Makarava, Natallia; Benmehdi, Sabah; Holschneider, Matthias
2011-08-01
In this study we propose a Bayesian approach to the estimation of the Hurst exponent in terms of linear mixed models. Even for unevenly sampled signals and signals with gaps, our method is applicable. We test our method by using artificial fractional Brownian motion of different length and compare it with the detrended fluctuation analysis technique. The estimation of the Hurst exponent of a Rosenblatt process is shown as an example of an H-self-similar process with non-Gaussian dimensional distribution. Additionally, we perform an analysis with real data, the Dow-Jones Industrial Average closing values, and analyze its temporal variation of the Hurst exponent.
Bayesian estimation of self-similarity exponent.
Makarava, Natallia; Benmehdi, Sabah; Holschneider, Matthias
2011-08-01
In this study we propose a bayesian approach to the estimation of the Hurst exponent in terms of linear mixed models. Even for unevenly sampled signals and signals with gaps, our method is applicable. We test our method by using artificial fractional brownian motion of different length and compare it with the detrended fluctuation analysis technique. The estimation of the Hurst exponent of a Rosenblatt process is shown as an example of an H-self-similar process with non-gaussian dimensional distribution. Additionally, we perform an analysis with real data, the Dow-Jones Industrial Average closing values, and analyze its temporal variation of the Hurst exponent. PMID:21928951
The 2.3-Angstrom Structure of Porcine Circovirus 2
Khayat, Reza; Brunn, Nicholas; Speir, Jeffrey A.; Hardham, John M.; Ankenbauer, Robert G.; Schneemann, Anette; Johnson, John E.
2012-10-25
Porcine circovirus 2 (PCV2) is a T = 1 nonenveloped icosahedral virus that has had severe impact on the swine industry. Here we report the crystal structure of an N-terminally truncated PCV2 virus-like particle at 2.3-{angstrom} resolution, and the cryo-electron microscopy (cryo-EM) image reconstruction of a full-length PCV2 virus-like particle at 9.6-{angstrom} resolution. This is the first atomic structure of a circovirus. The crystal structure revealed that the capsid protein fold is a canonical viral jelly roll. The loops connecting the strands of the jelly roll define the limited features of the surface. Sulfate ions interacting with the surface and electrostatic potential calculations strongly suggest a heparan sulfate binding site that allows PCV2 to gain entry into the cell. The crystal structure also allowed previously determined epitopes of the capsid to be visualized. The cryo-EM image reconstruction showed that the location of the N terminus, absent in the crystal structure, is inside the capsid. As the N terminus was previously shown to be antigenic, it may externalize through viral 'breathing'.
NASA Astrophysics Data System (ADS)
Olson, Michael R.; Victoria Garcia, Mercedes; Robinson, Michael A.; Van Rooy, Paul; Dietenberger, Mark A.; Bergin, Michael; Schauer, James Jay
2015-07-01
Quantification of the black carbon (BC) and brown carbon (BrC) components of source emissions is critical to understanding the impact combustion aerosols have on atmospheric light absorption. Multiple-wavelength absorption was measured from fuels including wood, agricultural biomass, coals, plant matter, and petroleum distillates in controlled combustion settings. Filter-based absorption measurements were corrected and compared to photoacoustic absorption results. BC absorption was segregated from the total light extinction to estimate the BrC absorption from individual sources. Results were compared to elemental carbon (EC)/organic carbon (OC) concentrations to determine composition's impact on light absorption. Multiple-wavelength absorption coefficients, Angstrom exponent (6.9 to <1.0), mass absorption cross section (MAC), and Delta C (97 µg m-3 to ~0 µg m-3) were highly variable. Sources such as incense and peat emissions showed ultraviolet wavelength (370 nm) BrC absorption over 175 and 80 times (respectively) the BC absorption but only 21 and 11 times (respectively) at 520 nm wavelength. The bulk EC MACEC, λ (average at 520 nm = 9.0 ± 3.7 m2 g-1; with OC fraction <0.85 = ~7.5 m2 g-1) and the BrC OC mass absorption cross sections (MACBrC,OC,λ) were calculated; at 370 nm ultraviolet wavelengths; the MACBrC,OC,λ ranged from 0.8 m2 g-1 to 2.29 m2 g-1 (lowest peat, highest kerosene), while at 520 nm wavelength MACBrC,OC,λ ranged from 0.07 m2 g-1 to 0.37 m2 g-1 (lowest peat, highest kerosene/incense mixture). These MAC results show that OC content can be an important contributor to light absorption when present in significant quantities (>0.9 OC/TC), source emissions have variable absorption spectra, and nonbiomass combustion sources can be significant contributors to BrC.
40-{angstrom} FEL designs for the PEP storage ring
Fisher, A.S.; Gallardo, J.C.; Nuhn, H.D.; Tatchyn, R.; Winick, H.; Pellegrini, C.
1991-12-31
We explore the use of the 2.2-km PEP storage ring at SLAC to drive a 40-{Angstrom} free-electron laser in the self-amplified spontaneous emission configuration. Various combinations for electron-beam and undulator parameters, as well as special undulator designs, are discussed. Saturation and high peak, in-band, coherent power (460 MW) are possible with a 67-m, hybrid permanent-magnet undulator in a ring bypass. A 100-m, cusp-field undulator can achieve high average, in-band, coherent power (0.25 W) in the main ring. The existing, 25.6-m, Paladin undulator at LLNL, with the addition of optical-klystron dispersive sections, is considered for both peak and average power. 35 refs., 4 figs., 1 tab.
40- angstrom FEL designs for the PEP storage ring
Fisher, A.S.; Gallardo, J.C. ); Nuhn, H.D.; Tatchyn, R.; Winick, H. . Stanford Synchrotron Radiation Lab.); Pellegrini, C. . Dept. of Physics)
1991-01-01
We explore the use of the 2.2-km PEP storage ring at SLAC to drive a 40-{Angstrom} free-electron laser in the self-amplified spontaneous emission configuration. Various combinations for electron-beam and undulator parameters, as well as special undulator designs, are discussed. Saturation and high peak, in-band, coherent power (460 MW) are possible with a 67-m, hybrid permanent-magnet undulator in a ring bypass. A 100-m, cusp-field undulator can achieve high average, in-band, coherent power (0.25 W) in the main ring. The existing, 25.6-m, Paladin undulator at LLNL, with the addition of optical-klystron dispersive sections, is considered for both peak and average power. 35 refs., 4 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Arain, Muzammil A.; Riza, Nabeel A.
2005-05-01
Measurement of refractive index, surface quality and temperature of the process materials in defense, petrochemical, power systems, glass, and metal industries is a fundamental need for precision systems performance. However, making these measurements in a super noisy defense or industrial environment is a big challenge faced by sensor technologies. Reported in this paper is the first ever demonstration of a wavelength multiplexed heterodyne interferometer using a single acousto-optic device (AOD). Heterodyne interferometry is pivotal in realizing a highly stable low noise interferometer. Inspite of the physical separation of the two arms of the interferometer, the sensor demonstrates Angstrom level optical path length sensitivity. The proposed sensor can be used in optical path length measurement-based sensing of parameters such as surface profile, refractive index, temperature, and pressure. Proof-of-concept experiment features a high resolution, low-loss, ultra compact, free space scanning interferometer implementation. Results include measurement of surface quality of a test mirror.
Light Absorption of Brown Carbon Aerosol in the Pearl River Delta Region of China
NASA Astrophysics Data System (ADS)
Huang, X.
2015-12-01
X.F. Huang, J.F. Yuan, L.M. Cao, J. Cui, C.N. Huang, Z.J. Lan and L.Y. He Key Laboratory for Urban Habitat Environmental Science and Technology, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, ChinaCorresponding author. Tel.: +86 755 26032532; fax: +86 755 26035332. E-mail address: huangxf@pku.edu.cn (X. F. Huang). Abstract: The strong spectral dependence of light absorption of brown carbon (BrC) aerosol has been recognized in recent decades. The Absorption Angstrom Exponent (AAE) of ambient aerosol was widely used in previous studies to attribute light absorption of brown carbon at shorter wavelengths, with a theoretical assumption that the AAE of black carbon (BC) aerosol equals to unit. In this study, the AAE method was improved by statistical extrapolation based on ambient measurements in the polluted seasons in typical urban and rural areas in the Pearl River Delta (PRD) region of China. A three-wavelength photoacoustic soot spectrometer (PASS-3) and an aerosol mass spectrometer (AMS) were used to explore the relationship between the ambient measured AAE and the ratio of organic aerosol to BC aerosol, in order to extract the more realistic AAE by pure BC aerosol, which were found to be 0.86, 0.82 and 1.02 at 405nm and 0.70, 0.71, and 0.86 at 532nm in the campaigns of urban-winter, urban-fall, and rural-fall, respectively. Roadway tunnel experiment results further supported the effectiveness of the obtained AAE for pure BC aerosol. In addition, biomass burning experiments proved higher spectral dependence of more-BrC environment and further verified the reliability of the instruments' response. Then, the average light absorption contribution of BrC aerosol was calculated to be 11.7, 6.3 and 12.1% (with total relative uncertainty of 7.5, 6.9 and 10.0%) at 405nm and 10.0, 4.1 and 5.5% (with total relative uncertainty of 6.5, 8.6 and 15.4%) at 532nm of the three campaigns, respectively. These results indicate that the
Anomalous hopping exponents of ultrathin metal films
NASA Astrophysics Data System (ADS)
Phillips, J. C.
2001-07-01
Under the above title Markovic et al. [Phys. Rev. B 62, 2195 (2000)] summarized their and others' low-temperature data that show that a consistent underlying conduction mechanism is needed to explain thermally activated resistivities, with an exponent x=0.75(5), on films of Ag, Bi, Pb, and Pd, with thicknesses of 5-15 Å. While this x cannot be explained by any kind of conventional continuum hopping model, with or without Coulomb interactions, here it is shown that the exponent x=34 is the direct result of a filamentary vibron quantum percolation model appropriate to a granular network film. The concepts used in this model were recently used to derive finite-size scaling exponents and/or phase diagrams in many other contexts, including network glasses, the impurity band metal-insulator transition, high-temperature superconductors, and evolutionary biology.
Estimation of Renyi exponents in random cascades
Troutman, Brent M.; Vecchia, Aldo V.
1999-01-01
We consider statistical estimation of the Re??nyi exponent ??(h), which characterizes the scaling behaviour of a singular measure ?? defined on a subset of Rd. The Re??nyi exponent is defined to be lim?????0 [{log M??(h)}/(-log ??)], assuming that this limit exists, where M??(h) = ??i??h(??i) and, for ??>0, {??i} are the cubes of a ??-coordinate mesh that intersect the support of ??. In particular, we demonstrate asymptotic normality of the least-squares estimator of ??(h) when the measure ?? is generated by a particular class of multiplicative random cascades, a result which allows construction of interval estimates and application of hypothesis tests for this scaling exponent. Simulation results illustrating this asymptotic normality are presented. ?? 1999 ISI/BS.
Critical exponent of the fractional Langevin equation.
Burov, S; Barkai, E
2008-02-22
We investigate the dynamical phase diagram of the fractional Langevin equation and show that critical exponents mark dynamical transitions in the behavior of the system. For a free and harmonically bound particle the critical exponent alpha(c)=0.402+/-0.002 marks a transition to a nonmonotonic underdamped phase. The critical exponent alpha(R)=0.441... marks a transition to a resonance phase, when an external oscillating field drives the system. Physically, we explain these behaviors using a cage effect, where the medium induces an elastic type of friction. Phase diagrams describing the underdamped, the overdamped and critical frequencies of the fractional oscillator, recently used to model single protein experiments, show behaviors vastly different from normal. PMID:18352535
Computing Lyapunov exponents of switching systems
NASA Astrophysics Data System (ADS)
Guglielmi, Nicola; Protasov, Vladimir
2016-06-01
We discuss a new approach for constructing polytope Lyapunov functions for continuous-time linear switching systems. The method we propose allows to decide the uniform stability of a switching system and to compute the Lyapunov exponent with an arbitrary precision. The method relies on the discretization of the system and provides - for any given discretization stepsize - a lower and an upper bound for the Lyapunov exponent. The efficiency of the new method is illustrated by numerical examples. For a more extensive discussion we remand the reader to [8].
Lyapunov exponents for infinite dimensional dynamical systems
NASA Technical Reports Server (NTRS)
Mhuiris, Nessan Mac Giolla
1987-01-01
Classically it was held that solutions to deterministic partial differential equations (i.e., ones with smooth coefficients and boundary data) could become random only through one mechanism, namely by the activation of more and more of the infinite number of degrees of freedom that are available to such a system. It is only recently that researchers have come to suspect that many infinite dimensional nonlinear systems may in fact possess finite dimensional chaotic attractors. Lyapunov exponents provide a tool for probing the nature of these attractors. This paper examines how these exponents might be measured for infinite dimensional systems.
Superconductivity in 4-Angstrom carbon nanotubes--a short review
NASA Astrophysics Data System (ADS)
Wang, Zhe; Shi, Wu; Lortz, Rolf; Sheng, Ping
2011-12-01
We give an up-to-date review of the superconducting phenomena in 4-Angstrom carbon nanotubes embedded in aligned linear pores of the AlPO4-5 (AFI) zeolite, first discovered in 2001 as a fluctuation Meissner effect. With the introduction of a new approach to sample synthesis around 2007, new data confirming the superconductivity have been obtained. These comprise electrical, specific heat, and magnetic measurements which together yield a consistent yet complex physical picture of the superconducting state, largely owing to the one-dimensional (1D) nature of the 4-Angstrom carbon nanotubes. For the electrical transport characteristics, two types of superconducting resistive behaviors were reproducibly observed in different samples. The first type is the quasi 1D fluctuation superconductivity that exhibits a smooth resistance drop with decreasing temperature, initiating at 15 K. At low temperatures the differential resistance also shows a smooth increase with increasing bias current (voltage). Both are unaffected by an applied magnetic field up to 11 Tesla. These manifestations are shown to be consistent with those of a quasi 1D superconductor with thermally activated phase slips as predicted by the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory. The second type is the quasi 1D to 3D superconducting crossover transition, which was observed to initiate at 15 K with a slow resistance decrease switching to a sharp order of magnitude drop at ~7.5 K. The latter exhibits anisotropic magnetic field dependence and is attributed to a Berezinskii-Kosterlitz-Thouless (BKT)-like transition that establishes quasi-long-range order in the plane transverse to the c-axis of the aligned nanotubes, thereby mediating a 1D to 3D crossover. The electrical data are complemented by magnetic and thermal specific heat bulk measurements. By using both the SQUID VSM and the magnetic torque technique, the onset of diamagnetism was observed to occur at ~15 K, with a rapid increase of the
Kovalevskaya exponents of systems with exponential interaction
Emel'yanov, K V; Tsygvintsev, A V
2000-10-31
The Kovalevskaya exponents are calculated for a class of systems generalizing Toda chains: systems with exponential interaction. It is shown that the known cases of algebraic integrability have no direct analogues in the case of spaces with pseudo-Euclidean metrics because the full-parameter expansions of the general solution contain complex powers of the independent variable.
Kovalevskaya exponents of systems with exponential interaction
NASA Astrophysics Data System (ADS)
Emel'yanov, K. V.; Tsygvintsev, A. V.
2000-10-01
The Kovalevskaya exponents are calculated for a class of systems generalizing Toda chains: systems with exponential interaction. It is shown that the known cases of algebraic integrability have no direct analogues in the case of spaces with pseudo-Euclidean metrics because the full-parameter expansions of the general solution contain complex powers of the independent variable.
High harmonics from solids probe Angstrom scale structure
NASA Astrophysics Data System (ADS)
You, Yong Sing; Reis, David; Ghimire, Shambhu
2016-05-01
The basic microscopic mechanism for the high harmonics generation (HHG) in isolated atoms and molecules has been understood in the 90's. Since then the gas harmonics have been utilized widely in ultrafast x-ray science, from attosecond pulse generation to imaging molecular orbitals of the target molecule. In contrast, the solid-state harmonic generation mechanism is currently being investigated following the recent experimental discovery in zinc oxide crystal. In particular, because of the fundamental differences, attributed to the high density and periodicity of the crystal, it was not clear if the solid-state harmonics could be used to reveal bonding structures in crystals. Here we report our experimental results on generation of XUV harmonics in single crystal MgO subjected to the field strengths on the order of 1V/Å without damage. High harmonics in MgO show strong crystal orientation dependence as well as a strong laser ellipticity dependence. By exploiting these unique characteristics, we demonstrate that XUV harmonics from bulk crystals can probe Angstrom scale electronic structure of the crystal.
HRTEM at half-Angstrom resolution: From OAM to TEAM
O'Keefe, Michael A.
2003-02-17
Transmission electron microscopy (TEM) at sub-Angstrom resolution is important for nanotechnology. Identifying atom positions requires appropriate resolution, the ability to separate distinct objects in images. With Cs corrected, the information limit of the TEM controls resolution. The OAM has demonstrated that a resolution of 0.78A is possible. The TEAM (transmission electron achromatic microscope) will be a TEM using hardware correction of Cs with a monochromator to improve its information limit beyond that of the OAM by improvement of the electron-beam energy spread. It is shown that A 300keV HRTEM TEAM does not require a Cc corrector to reach 0.5A as long as beam energy spread and objective-lens current ripple are lowered sufficiently. A lower-voltage TEAM will require stricter limits on objective-lens current ripple to reach the targeted 0.5A resolution. No improvement in HT ripple or noise is required to improve the information limit per se since the monochromator determines the energy spread in the beam. However, improved HT ripple and noise will improve the beam current statistics (number of electrons passing through the monochromator) by placing more of the electrons closer to the center of the energy-spread distribution
Fe L-Shell Emission Lines at 7 - 9 Angstroms
NASA Astrophysics Data System (ADS)
Chen, Hui; Beiersdorfer, Peter; Brown, Greg; Behar, Edhud
Fe L-shell emission lines at wavelengths less than 10 angstroms come from n to 2 (n = 4 5 6..) transitions. These lines embed information such as electron density and/or temperature that is of fundamental importance to understanding the physics of astrophysical objects. Unresolved by previous x-ray observatories these low wavelength Fe lines are clearly observable by Chandra and XMM x-ray satellites. To meet the needs of using these lines as diagnostics we have studied the n to 2 transitions (n = 4 5 6..) Fe L-shell lines using the LLNL electron beam ion trap following our Fe L-shell emission line measurements for the 3-2 transitions (Brown et al APJ supp. 2002). Our measurement and its comparison with code simulations will be reported together with a discussion of the possible use of these lines as diagnostics for astrophysics. This work was performed under the auspices of the U.S. DOE by LLNL under contract No. W-7405-Eng-48 and supported by NASA SARA grants to LLNL GSFC and Columbia University.
NASA Astrophysics Data System (ADS)
Fawole, O. G.; Cai, X.; MacKenzie, A. R.
2015-12-01
Aerosol remote sensing techniques and back-trajectory modeling can be combined to identify aerosol types. We have clustered 7 years of AERONET aerosol signals using trajectory analysis to identify dominant aerosol sources at two AERONET sites in West Africa: Ilorin (4.34 oE, 8.32 oN) and Djougou (1.60 oE, 9.76 oN). Of particular interest are air masses that have passed through the gas flaring region in the Niger Delta area, of Nigeria, en-route the AERONET sites. 7-day back trajectories were calculated using the UK UGAMP trajectory model driven by ECMWF wind analyses data. Dominant sources identified, using literature classifications, are desert dust (DD), Biomass burning (BB) and Urban-Industrial (UI). Below, we use a combination of synoptic trajectories and aerosol optical properties to distinguish a fourth source: that due to gas flaring. Gas flaring, (GF) the disposal of gas through stack in an open-air flame, is believed to be a prominent source of black carbon (BC) and greenhouse gases. For these different aerosol source signatures, single scattering albedo (SSA), refractive index , extinction Angstrom exponent (EEA) and absorption Angstrom exponent (AAE) were used to classify the light absorption characteristics of the aerosols for λ = 440, 675, 870 and1020 nm. A total of 1625 daily averages of aerosol data were collected for the two sites. Of which 245 make up the GF cluster for both sites. For GF cluster, the range of fine-mode fraction is 0.4 - 0.7. Average values SSA(λ), for the total and GF clusters are 0.90(440), 0.93(675), 0.95(870) and 0.96(1020), and 0.93(440), 0.92(675), 0.9(870) and 0.9(1020), respectively. Values of for the GF clusters for both sites are 0.62 - 1.11, compared to 1.28 - 1.66 for the remainder of the clusters, which strongly indicates the dominance of carbonaceous particles (BC), typical of a highly industrial area. An average value of 1.58 for the real part of the refractive index at low SSA for aerosol in the GF cluster is also
5-D Choptuik critical exponent and holography
Bland, J.; Kunstatter, G.
2007-05-15
Recently, a holographic argument was used to relate the saturation exponent, {gamma}{sub BFKL}, of 4-dimensional Yang-Mills theory in the Regge limit to the Choptuik critical scaling exponent, {gamma}{sub 5d}, in 5-dimensional black hole formation via scalar field collapse [L. Alvarez-Gaume, C. Gomez, and M. A. Vazquez-Mozo, arXiv:hep-th/0611312.]. Remarkably, the numerical value of the former agreed quite well with previous calculations of the latter. We present new results of an improved calculation of {gamma}{sub 5d} with substantially decreased numerical error. Our current result is {gamma}{sub 5d}=0.4131{+-}0.0001, which is close to, but not in strict agreement with, the value of {gamma}{sub BFKL}=0.409 552 quoted in [L. Alvarez-Gaume, C. Gomez, and M. A. Vazquez-Mozo, arXiv:hep-th/0611312.].
Protein Folding Stages and Universal Exponents
NASA Astrophysics Data System (ADS)
Huang, Kerson
We propose three stages in protein folding, based on physical arguements involving the interplay between the hydrophobic effect and hydrogen bonding, and computer simulations using the CSAW (conditioned self-avoiding walk) model. These stages are characterized by universal exponents ν = 3/5, 3/7, 2/5 in the power law R ~ Nν, where R is the radius of gyration and N is the number of residues. They correspond to the experimentally observed stages: unfolded, preglobule, molten globule.
Protein Folding Stages and Universal Exponents
NASA Astrophysics Data System (ADS)
Huang, Kerson
2011-11-01
We propose three stages in protein folding, based on physical arguements involving the interplay between the hydrophobic effect and hydrogen bonding, and computer simulations using the CSAW (conditioned self-avoiding walk) model. These stages are characterized by universal exponents ν = 3/5, 3/7, 2/5 in the power law R ˜ Nν, where R is the radius of gyration and N is the number of residues. They correspond to the experimentally observed stages: unfolded, preglobule, molten globule.
Diophantine exponents for mildly restricted approximation
NASA Astrophysics Data System (ADS)
Bugeaud, Yann; Kristensen, Simon
2009-10-01
We are studying the Diophantine exponent μ n, l defined for integers 1≤ l< n and a vector α∈ℝ n by letting μ_{n,l}=sup\\{μ≥0: 0 < Vertx\\cdotαVert
Low Density Expansion for Lyapunov Exponents
NASA Astrophysics Data System (ADS)
Schulz-Baldes, Hermann
A perturbative formula for the Lyapunov exponent of a one-dimensional random medium for weakly coupled disorder was first given by Thouless [12] and then proven rigorously by Pastur and Figotin [9]. Anomalies in the perturbation theory at the band center were discovered by Kappus and Wegner [7] and further discussed by various other authors [2,3,11]. The Lyapunov exponent is then identified with the inverse localization length of the system. This short note concerns the behavior of the Lyapunov exponent for a low density of impurities, each of which may, however, be large. The presented method is as [6,10,11] a further application of diagonalizing the transfer matrices without perturbation (here the low density of impurities) and then rigorously controlling the error terms by means of oscillatory sums of rotating modi- fied Prüfer phases. Some of the oscillatory sums remain large if the rotation phases (here the quasi-momenta) are rational. This leads to supplementary contributions of the Kappus-Wegner type.
Neutrons measure phase behavior in pores at Angstrom size
Bardoel, Agatha A; Melnichenko, Yuri B
2012-01-01
Researchers have measured the phase behavior of green house gases in pores at the Angstrom-level, using small angle neutron scattering (SANS) at the Oak Ridge National Laboratory's High Flux Isotope Reactor. Yuri Melnichenko, an instrument scientist on the General Purpose Small Angle Neutron Scattering (GP SANS) Diffractometer at ORNL's High Flux Isotope Reactor, his postdoctoral associate Lilin He and collaborators Nidia Gallego and Cristian Contescu from the Material Sciences Division (ORNL) were engaged in the work. They were studying nanoporous carbons to assess their attractiveness as storage media for hydrogen, with a view to potential use for on-board hydrogen storage for transportation applications. Nanoporous carbons can also serve as electrode material for supercapacitors and batteries. The researchers successfully determined that the most efficiently condensing pore size in a carbon nanoporous material for hydrogen storage is less than one nanometer. In a paper recently published by the Journal of the American Chemical Society, the collaborators used small angle neutron scattering to study how hydrogen condenses in small pores at ambient temperature. They discovered that the surface-molecule interactions create internal pressures in pores that may exceed the external gas pressure by a factor of up to 50. 'This is an exciting result,' Melnichenko said, 'as you achieve extreme densification in pores 'for free', i.e. without spending any energy. These results can be used to guide the development of new carbon adsorbents tailored to maximize hydrogen storage capacities.' Another important factor that defines the adsorption capacity of sub-nanometer pores is their shape. In order to get accurate structural information and maximize sorption capacity, it is important that pores are small and of approximately uniform size. In collaboration with Drexel University's Yury Gogotsi who supplied the samples, Melnichenko and his collaborators used the GP SANS
Ultraviolet Observations of Uranus and Neptune Below 3000 Angstrom
NASA Technical Reports Server (NTRS)
Caldwell, J.; Wagener, R.; Owen, T.; Combes, M.; Encrenaz, T.
1984-01-01
From 2000 to 3000 A, both Uranus and Neptune have albedos that are about two times higher than Jupiter or Saturn's, implying that the outer giants have stratospheres that are relatively free of aerosol absorption. Uncertainties in the absolute calibration procedure allow discrepancies of order 15% between conservative models and the observations. A small amount of aerosol absorption is therefore possible. Below 2000 A the derived albedo is highly dependent on the solar spectrum source used in the data reduction. The most recent result for Uranus, first reported here, is consistent with a secular change in C2H2 mixing ratio from approximately three times ten to the minus eight in 1980 to less than or equal to ten to the minus ninth in 1983. These values are approximately 2 orders of magnitude less than the mixing ratios of this gas on Saturn, and comparable to the amount on Jupiter.
Gan, L.; Johnson, J.E.
2009-05-18
Studies of icosahedral virus capsids provide insights into the function of supramolecular machines. Virus capsid crystals have exceptionally large unit cells; as a result, they diffract weakly compared with protein crystals. HK97 is a dsDNA lambda-like bacteriophage whose 13 MDa capsid expands from 550 {angstrom} to 650 {angstrom} with large subunit conformational changes during virus maturation. The HK97 penultimate maturation intermediate was crystallized in a tetragonal unit cell that has lattice constants of 1010 {angstrom} x 1010 {angstrom} x 730 {angstrom}. The crystals could be cryoprotected, but diffracted to a modest resolution of 5 {angstrom} at a bending-magnet beamline. When these crystals were optimally exposed with two orders-of-magnitude more photons from a new insertion-device beamline, data extending to better than 3.8 {angstrom} resolution were obtained. Here, the strategies to collect and process such data are described. These strategies can be adapted for other crystals with large unit cells and for microcrystals.
Geometrical interpretation of the Knizhnik-Polyakov-Zamolodchikov exponents
NASA Astrophysics Data System (ADS)
Ambjørn, J.; Anagnostopoulos, K. N.; Magnea, U.; Thorleifsson, G.
1996-02-01
We provide evidence that the KPZ exponents in two-dimensional quantum gravity can be interpreted as scaling exponents of correlation functions which are functions of the invariant geodesic distance between the fields.
The Angstrom Project: M31 microlensing alert ANG-08B-M31-07
NASA Astrophysics Data System (ADS)
Darnley, M. J.; Kerins, E.; Newsam, A. M.; Duke, J. P.; Gould, A.; Street, C. Han B.-G. Park R. A.
2008-12-01
We report an ongoing microlensing candidate in M31 by the Angstrom Project M31 bulge microlensing survey using the Liverpool Telescope (La Palma). The candidate was detected from difference imaging photometry generated by the Angstrom Project Alert System (APAS) in a series of Sloan i'-band images of the bulge of M31.
Diverging Fluctuations of the Lyapunov Exponents
NASA Astrophysics Data System (ADS)
Pazó, Diego; López, Juan M.; Politi, Antonio
2016-07-01
We show that in generic one-dimensional Hamiltonian lattices the diffusion coefficient of the maximum Lyapunov exponent diverges in the thermodynamic limit. We trace this back to the long-range correlations associated with the evolution of the hydrodynamic modes. In the case of normal heat transport, the divergence is even stronger, leading to the breakdown of the usual single-function Family-Vicsek scaling ansatz. A similar scenario is expected to arise in the evolution of rough interfaces in the presence of suitably correlated background noise.
Critical viscosity exponent for classical fluids
NASA Astrophysics Data System (ADS)
Hao, Hong; Ferrell, Richard A.; Bhattacharjee, Jayanta K.
2005-02-01
A self-consistent mode-coupling calculation of the critical viscosity exponent zη for classical fluids is performed by including the memory effect and the vertex corrections. The incorporation of the memory effect is through a self-consistency procedure that evaluates the order parameter and shear momentum relaxation rates at nonzero frequencies, thereby taking their frequency dependence into account. This approach offers considerable simplification and efficiency in the calculation. The vertex corrections are also demonstrated to have significant effects on the numerical value for the critical viscosity exponent, in contrast to some previous theoretical work which indicated that the vertex corrections tend to cancel out from the final result. By carrying out all of the integrations analytically, we have succeeded in tracing the origin of this discrepancy to an error in earlier work. We provide a thorough treatment of the two-term epsilon expansion, as well as a complete three-dimensional analysis of the fluctuating order-parameter and transverse hydrodynamic modes. The study of the interactions of these modes is carried out to high order so as to arrive at zη=0.0679±0.0007 for comparison with the experimentally observed value, 0.0690±0.0006 .
Optimal transport exponent in spatially embedded networks
NASA Astrophysics Data System (ADS)
Li, G.; Reis, S. D. S.; Moreira, A. A.; Havlin, S.; Stanley, H. E.; Andrade, J. S., Jr.
2013-04-01
The imposition of a cost constraint for constructing the optimal navigation structure surely represents a crucial ingredient in the design and development of any realistic navigation network. Previous works have focused on optimal transport in small-world networks built from two-dimensional lattices by adding long-range connections with Manhattan length rij taken from the distribution Pij˜rij-α, where α is a variable exponent. It has been shown that, by introducing a cost constraint on the total length of the additional links, regardless of the strategy used by the traveler (independent of whether it is based on local or global knowledge of the network structure), the best transportation condition is obtained with an exponent α=d+1, where d is the dimension of the underlying lattice. Here we present further support, through a high-performance real-time algorithm, on the validity of this conjecture in three-dimensional regular as well as in two-dimensional critical percolation clusters. Our results clearly indicate that cost constraint in the navigation problem provides a proper theoretical framework to justify the evolving topologies of real complex network structures, as recently demonstrated for the networks of the US airports and the human brain activity.
Scale-free networks with exponent one
NASA Astrophysics Data System (ADS)
Timár, G.; Dorogovtsev, S. N.; Mendes, J. F. F.
2016-08-01
A majority of studied models for scale-free networks have degree distributions with exponents greater than two. Real networks, however, can demonstrate essentially more heavy-tailed degree distributions. We explore two models of scale-free equilibrium networks that have the degree distribution exponent γ =1 , P (q ) ˜q-γ . Such degree distributions can be identified in empirical data only if the mean degree of a network is sufficiently high. Our models exploit a rewiring mechanism. They are local in the sense that no knowledge of the network structure, apart from the immediate neighborhood of the vertices, is required. These models generate uncorrelated networks in the infinite size limit, where they are solved explicitly. We investigate finite size effects by the use of simulations. We find that both models exhibit disassortative degree-degree correlations for finite network sizes. In addition, we observe a markedly degree-dependent clustering in the finite networks. We indicate a real-world network with a similar degree distribution.
NASA Astrophysics Data System (ADS)
Aruna, K.; Lakshmi Kumar, T. V.; Rao, D. Narayana; Krishna Murthy, B. V.; Babu, S. Suresh; Krishnamoorthy, K.
2014-11-01
The scattering and absorption components of Aerosol Optical Depth (AOD) over a semi-urban coastal location (12.81°N, 80.03°E) near the mega city Chennai in peninsular India are separated using the collocated measurements of Black Carbon concentration and Atmospheric Boundary Layer Height (ABLH) from ERA Interim Reanalysis data assuming that most of the BC is contained and homogeneously mixed in the ABL. It is found that the absorption component to scattering component ratio has a strong seasonal variation with a pronounced maximum in the South West (SW) monsoon season. This is indicative of more effective wet removal of scattering aerosols than absorbing (BC) aerosols. There could also be an effect due to preferential removal of large particles which would have a lower content of BC. The Angstrom wavelength exponent shows a minimum in the SW monsoon season, the minimum being more pronounced for the scattering aerosols implying relative dominance of coarse mode particles. Investigation of the effect of Relative Humidity on scattering and absorption components of AOD revealed that the BC (absorbing) aerosols are non-hydrophilic/not coated with hydrophilic substance.
NASA Technical Reports Server (NTRS)
Mallet, M.; Dubovik, O.; Nabat, P.; Dulac, F.; Kahn, R.; Sciare, J.; Paronis, D.; Leon, J. F.
2013-01-01
Aerosol absorption properties are of high importance to assess aerosol impact on regional climate. This study presents an analysis of aerosol absorption products obtained over the Mediterranean Basin or land stations in the region from multi-year ground-based AERONET and satellite observations with a focus on the Absorbing Aerosol Optical Depth (AAOD), Single Scattering Albedo (SSA) and their spectral dependence. The AAOD and Absorption Angstrom Exponent (AAE) data set is composed of daily averaged AERONET level 2 data from a total of 22 Mediterranean stations having long time series, mainly under the influence of urban-industrial aerosols and/or soil dust. This data set covers the 17 yr period 1996-2012 with most data being from 2003-2011 (approximately 89 percent of level-2 AAOD data). Since AERONET level-2 absorption products require a high aerosol load (AOD at 440 nm greater than 0.4), which is most often related to the presence of desert dust, we also consider level-1.5 SSA data, despite their higher uncertainty, and filter out data with an Angstrom exponent less than 1.0 in order to study absorption by carbonaceous aerosols. The SSA data set includes both AERONET level-2 and satellite level-3 products. Satellite-derived SSA data considered are monthly level 3 products mapped at the regional scale for the spring and summer seasons that exhibit the largest aerosol loads. The satellite SSA dataset includes the following products: (i) Multi-angle Imaging SpectroRadiometer (MISR) over 2000-2011, (ii) Ozone Monitoring Instrument (OMI) near-UV algorithm over 2004-2010, and (iii) MODerate resolution Imaging Spectroradiometer (MODIS) Deep-Blue algorithm over 2005-2011, derived only over land in dusty conditions. Sun-photometer observations show that values of AAOD at 440 nm vary between 0.024 +/- 0.01 (resp. 0.040 +/- 0.01) and 0.050 +/- 0.01 (0.055 +/- 0.01) for urban (dusty) sites. Analysis shows that the Mediterranean urban-industrial aerosols appear "moderately
Fisher exponent from pseudo-ε expansion.
Sokolov, A I; Nikitina, M A
2014-07-01
The critical exponent η for three-dimensional systems with an n-vector order parameter is evaluated in the framework of the pseudo-ε expansion approach. The pseudo-ε expansion (τ series) for η found up to the τ(7) term for n = 0, 1, 2, 3 and within the τ(6) order for general n is shown to have a structure that is rather favorable for getting numerical estimates. The use of Padé approximants and direct summation of the τ series result in iteration procedures rapidly converging to the asymptotic values that are very close to the most reliable numerical estimates of η known today. The origin of such an efficiency is discussed and shown to lie in the general properties of the pseudo-ε expansion machinery interfering with some peculiarities of the renormalization group expansion of η. PMID:25122246
Nonperturbative moduli superpotential with positive exponents
NASA Astrophysics Data System (ADS)
Abe, Hiroyuki; Higaki, Tetsutaro; Kobayashi, Tatsuo; Seto, Osamu
2008-07-01
We study nonperturbative moduli superpotentials with positive exponents, i.e. the form like AeaT with a positive constant a and the modulus T. These effects can be generated, e.g., by D-branes which have negative Ramond-Ramond charge of the lower-dimensional D-brane. The scalar potentials including such terms have quite a rich structure. There are several local minima with different potential energies and a high barrier, whose height is of O(Mp4). We discuss their implications from the viewpoints of cosmology and particle phenomenology, e.g. the realization of inflation models, avoiding the overshooting problem. This type of potential would be useful to realize the inflation and low-energy supersymmetry breaking.
Characterization of Spectral Absorption Properties of Aerosols Using Satellite Observations
NASA Technical Reports Server (NTRS)
Torres, O.; Jethva, H.; Bhartia, P. K.; Ahn, C.
2012-01-01
The wavelength-dependence of aerosol absorption optical depth (AAOD) is generally represented in terms of the Angstrom Absorption Exponent (AAE), a parameter that describes the dependence of AAOD with wavelength. The AAE parameter is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses high spectral resolution measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measured reflectance (rho lambda) is approximately given by Beer's law rho lambda = rho (sub 0 lambda) e (exp -mtau (sub abs lambda)) where rho(sub 0 lambda) is the cloud reflectance, m is the geometric slant path and tau (sub abs lambda) is the spectral AAOD. The rho (sub 0 lambda) term is determined by means of radiative transfer calculations using as input the cloud optical depth derived as described in Torres et al. [JAS, 2012] that accounts for the effects of aerosol absorption. In the second step, corrections for molecular and aerosol scattering effects are applied to the cloud reflectance term, and the spectral AAOD is then derived by inverting the equation above. The proposed technique will be discussed in detail and application results will be presented. The technique can be easily applied to hyper-spectral satellite measurements that include UV such as OMI, GOME and SCIAMACHY, or to multi-spectral visible measurements by other sensors provided that the aerosol-above-cloud events are easily identified.
Retrieval of Aerosol Absorption Properties from Satellite Observations
NASA Technical Reports Server (NTRS)
Torres, Omar; Bhartia, Pawan K.; Jethva, H.; Ahn, Chang-Woo
2012-01-01
The Angstrom Absorption Exponent (AAE) is a parameter commonly used to characterize the wavelength-dependence of aerosol absorption optical depth (AAOD). It is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses multi-spectral measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measurement can be explained, using an approximations of Beer's Law (BL), as the upwelling reflectance at the cloud top attenuated by the absorption effects of the overlying aerosol layer. The upwelling reflectance at the cloud-top in an aerosol-free atmospheric column is mainly a function of cloud optical depth (COD). In the proposed method of AAE derivation, the first step is determining COD which is retrieved using a previously developed color-ratio based approach. In the second step, corrections for molecular scattering effects are applied to both the observed ad the calculated cloud reflectance terms, and the spectral AAOD is then derived by an inversion of the BL approximation. The proposed technique will be discussed in detail and application results making use of OMI multi-spectral measurements in the UV-Vis. will be presented.
Wang, Yue-si; Xin, Jin-yuan; Li, Zhan-qing; Wang, Pu-cai; Wang, Shi-gong; Wen, Tian-xue; Sun, Yang
2006-09-01
Atmospheric aerosol optical depth (AOD(lamda=500 nm)), Angstrom turbidity coefficient (beta) and Angstrom wavelength exponent (alpha) are obtained using the CERN sun hazemeter network from Aug to Dec, 2004. The results are as follows: At the Tibetan Plateau, Haibei and Lhasa, the mean of AOD is 0.09, 0.12; the mean of beta is 0.05, 0.13; the mean of a is 1.09, 0.06, respectively. At the Northeast of China, Hailun and Sanjiang, the mean of AOD is 0.14, 0.15; the mean of beta is 0.04, 0.06; the mean of a is 2.32, 1.58, respectively. At the desert region of North China, e.g., Fukang, Shapotou and Eerduosi, the range of averaged AOD is from 0.17 to 0.32; the range of averaged beta is from 0.09 to 0.19; the range of averaged a is from 0.68.to 1.28. At the forest areas, e.g. Changbai Mountain, Beijing forest and Xishuangbanna, the range of averaged AOD is from 0.19 to 0.42; the range of averaged beta is from 0.12 to 0.19; the range of averaged a is from 1.11 to 1.25. At agriculture areas, e.g. Shenyang, Fengqiu, Taoyuan and Yanting, the range of averaged AOD is from 0.34 to 0.68; the range of averaged beta is from 0.18 to 0.38; the range of averaged a is from 0.97 to 1.39. At the littoral areas and the lake of East China, e.g. Jiaozhou Bay, Shanghai City and Tai Lake, the range of averaged AOD is from 0.49 to 0.68; the range of averaged beta is from 0.21 to 0.29; the range of averaged a is from 1.24 to 1.37. At the inland cities, Beijing City and Lanzhou City, the mean of AOD is 0.47, 0.81; the mean of beta is 0.20, 0.45; the mean of a is 1.66, 0.89, respectively. The variations of aerosol properties at nineteen stations are explained in the paper. PMID:17117619
Anomalous Hopping Exponents of Ultrathin Metal Films
NASA Astrophysics Data System (ADS)
Phillips, J. C.
2001-03-01
Under this title [1] has summarized data that show that a consistent underlying conduction mechanism is needed to explain thermally activated resistivities, logR(T) = logR + x(T*/T), with x = 0.75(5) on films of Ag, Bi, Pb, and Pd, with thicknesses 5-15A. Conventional continuum semiconductor models, with or without Coulomb interactions, give 1/4 < x < 1/2, and so do not explain x = 3/4, but a filamentary quantum percolation granular network relaxation model does. The concepts used in this unified, broad, non-crystalline platform have successfully derived scaling exponents and/or phase diagrams for network glasses (including window glass), polymers, electrolytes and alcohols, fused salts, molecular organic glasses, a-Si:H, quasicrystals, the impurity band metal-insulator transition (d = 2,3), high-temperature superconductors, and metabolic evolutionary biology [2,3]. [1] N. Markovic et al., Phys. Rev. B, 62, 2195 (2000). [2] J. C. Phillips, Phil. Mag. B, 80, 1773 (2000). [3] J. C. Phillips, Rep. Prog. Phys., 59, 1133 (1996).
Lyapunov Exponents for Surface Group Representations
NASA Astrophysics Data System (ADS)
Deroin, Bertrand; Dujardin, Romain
2015-12-01
Let be a holomorphic family of representations of a surface group into , where S is a topological (possibly punctured) surface with negative Euler characteristic. Given a structure of Riemann surface of finite type on S we construct a bifurcation current on the parameter space Λ, that is a (1,1) positive closed current attached to the bifurcations of the family. It is defined as the dd c of the Lyapunov exponent of the representation with respect to the Brownian motion on the Riemann surface S, endowed with its Poincaré metric. We show that this bifurcation current describes the asymptotic distribution of various codimension 1 phenomena in Λ. For instance, the random hypersurfaces of Λ defined by the condition that a random closed geodesic on S is mapped under ρ λ to a parabolic element or the identity are asymptotically equidistributed with respect to the bifurcation current. The proofs are based on our previous work (Deroin and Dujardin, Invent Math 190:57-118, 2012), and on a careful control of a discretization procedure of the Brownian motion.
The Hurst exponent in energy futures prices
NASA Astrophysics Data System (ADS)
Serletis, Apostolos; Rosenberg, Aryeh Adam
2007-07-01
This paper extends the work in Elder and Serletis [Long memory in energy futures prices, Rev. Financial Econ., forthcoming, 2007] and Serletis et al. [Detrended fluctuation analysis of the US stock market, Int. J. Bifurcation Chaos, forthcoming, 2007] by re-examining the empirical evidence for random walk type behavior in energy futures prices. In doing so, it uses daily data on energy futures traded on the New York Mercantile Exchange, over the period from July 2, 1990 to November 1, 2006, and a statistical physics approach-the ‘detrending moving average’ technique-providing a reliable framework for testing the information efficiency in financial markets as shown by Alessio et al. [Second-order moving average and scaling of stochastic time series, Eur. Phys. J. B 27 (2002) 197-200] and Carbone et al. [Time-dependent hurst exponent in financial time series. Physica A 344 (2004) 267-271; Analysis of clusters formed by the moving average of a long-range correlated time series. Phys. Rev. E 69 (2004) 026105]. The results show that energy futures returns display long memory and that the particular form of long memory is anti-persistence.
Structural basis of transcription: RNA polymerase II at 2.8 angstrom resolution.
Cramer, P; Bushnell, D A; Kornberg, R D
2001-06-01
Structures of a 10-subunit yeast RNA polymerase II have been derived from two crystal forms at 2.8 and 3.1 angstrom resolution. Comparison of the structures reveals a division of the polymerase into four mobile modules, including a clamp, shown previously to swing over the active center. In the 2.8 angstrom structure, the clamp is in an open state, allowing entry of straight promoter DNA for the initiation of transcription. Three loops extending from the clamp may play roles in RNA unwinding and DNA rewinding during transcription. A 2.8 angstrom difference Fourier map reveals two metal ions at the active site, one persistently bound and the other possibly exchangeable during RNA synthesis. The results also provide evidence for RNA exit in the vicinity of the carboxyl-terminal repeat domain, coupling synthesis to RNA processing by enzymes bound to this domain. PMID:11313498
LCLS, a 1.5 Angstrom Free Electron Laser: Opportunities and Challenges
NASA Astrophysics Data System (ADS)
Hastings, Jerome
2005-05-01
The dream of a laser operating at hard x-ray wavelengths is about to be realized. The Linac Coherent Light Source will be the world's first hard x-ray free electron laser reaching 1.5 Angstroms in the fundamental. The scientific opportunities span the breadth of science studied today with photons and extends the photon matter interactions into unchartered regimes with unprecedented fields at Angstrom wavelengths. Along with these opportunities come technical challenges. The background, performance and opportunities for the LCLS will be described. The technical challenges will be highlighted and the status of their solutions will be discussed. Finally, as with other accelerator based light sources even before the first saturated 1.5 Angstrom beam has been produced ideas for shorter pulses, higher energies and variable polarization are being discussed. These `future' options will be highlighted.
Reaching sub-Angstrom resolution with a mid-voltage TEM
O'Keefe, Michael A.; Hetherington, Crispin J.D.; Nelson, E. Chris
2004-04-12
Phase-contrast imaging in the high-resolution electron microscope produces images with peaks at atom positions by extracting the spatial distribution of the relative phase from the electron wave. Usually, the electron wave is imaged by direct interference of diffracted beams at optimum focus. Instead, the One-Angstrom Microscope uses focal-series reconstruction software to derive the relative electron phase from a series of images taken over a range of focus, with peaks that correspond to the atom positions at a resolution that extends to the microscope information limit. Tests using a silicon specimen tilted into [112] orientation show that the O Angstrom M has achieved a world-record resolution of 0.78 Angstrom.
NASA Astrophysics Data System (ADS)
Kim, J. H.; Kim, S. W.; Yoon, S. C.; Park, R.; Ogren, J. A.
2014-12-01
Filter-based instrument, such as aethalometer, is being widely used to measure equivalent black carbon(EBC) mass concentration and aerosol absorption coefficient(AAC). However, many other previous studies have poited that AAC and its aerosol absorption angstrom exponent(AAE) are strongly affected by the multi-scattering correction factor(C) when we retrieve AAC from aethalometer EBC mass concentration measurement(Weingartner et al., 2003; Arnott et al., 2005; Schmid et al., 2006; Coen et al., 2010). We determined the C value using the method given in Weingartner et al. (2003) by comparing 7-wavelngth aethalometer (AE-31, Magee sci.) to 3-wavelength Photo-Acoustic Soot Spectrometer (PASS-3, DMT) at Gosan climate observatory, Korea(GCO) during Cheju ABC plume-asian monsoon experiment(CAPMEX) campaign(August and September, 2008). In this study, C was estimated to be 4.04 ± 1.68 at 532 nm and AAC retrieved with this value was decreased as approximately 100% as than that retrieved with soot case value from Weingartner et al (2003). We compared the AAC determined from aethalomter measurements to that from collocated Continuous Light Absorption Photometer (CLAP) measurements from January 2012 to December 2013 at GCO and found good agreement in both AAC and AAE. This result suggests the determination of site-specific C is crucially needed when we calculate AAC from aethalometer measurements.
Photoelectron holographic studies of As/Si(100) with sub-angstrom resolution
Reese, Paul J. E.; Miller, T.; Chiang, T.-C.
2001-09-15
The atomic structure of As-terminated Si(100) has been studied using the technique of derivative photoelectron holography. The resulting holographic images clearly resolve a 0.5-{angstrom} shift from the (1 x 1) geometry for each As atom as a result of dimerization. Detecting this shift requires a sub-angstrom resolution that has been difficult to achieve using photoelectron holography. The improvement in resolution can be attributed to a highly anisotropic electron-scattering factor resulting in an emission beacon that helps define the atomic images.
Chaotic Systems with Absorption
NASA Astrophysics Data System (ADS)
Altmann, Eduardo G.; Portela, Jefferson S. E.; Tél, Tamás
2013-10-01
Motivated by applications in optics and acoustics we develop a dynamical-system approach to describe absorption in chaotic systems. We introduce an operator formalism from which we obtain (i) a general formula for the escape rate κ in terms of the natural conditionally invariant measure of the system, (ii) an increased multifractality when compared to the spectrum of dimensions Dq obtained without taking absorption and return times into account, and (iii) a generalization of the Kantz-Grassberger formula that expresses D1 in terms of κ, the positive Lyapunov exponent, the average return time, and a new quantity, the reflection rate. Simulations in the cardioid billiard confirm these results.
Characteristic exponents of impulsive differential equations in a Banach space
Zabreiko, P.P.; Bainov, D.D.; Kostadinov, S.I.
1988-06-01
The notion of general exponent of impulsive homogeneous differential equations is defined. A formula for the solution of impulsive nonhomogeneous differential equations is obtained and is used to establish a dependence between the existence of bounded solutions of such equations and the general exponent of the respective homogeneous equation.
Calculating Lyapunov Exponents: Applying Products and Evaluating Integrals
ERIC Educational Resources Information Center
McCartney, Mark
2010-01-01
Two common examples of one-dimensional maps (the tent map and the logistic map) are generalized to cases where they have more than one control parameter. In the case of the tent map, this still allows the global Lyapunov exponent to be found analytically, and permits various properties of the resulting global Lyapunov exponents to be investigated…
The transport exponent in percolation models with additional loops
NASA Astrophysics Data System (ADS)
Babalievski, F.
1994-10-01
Several percolation models with additional loops were studied. The transport exponents for these models were estimated numerically by means of a transfer-matrix approach. It was found that the transport exponent has a drastically changed value for some of the models. This result supports some previous numerical studies on the vibrational properties of similar models (with additional loops).
A finite-time exponent for random Ehrenfest gas
Moudgalya, Sanjay; Chandra, Sarthak; Jain, Sudhir R.
2015-10-15
We consider the motion of a system of free particles moving on a plane with regular hard polygonal scatterers arranged in a random manner. Calling this the Ehrenfest gas, which is known to have a zero Lyapunov exponent, we propose a finite-time exponent to characterize its dynamics. As the number of sides of the polygon goes to infinity, when polygon tends to a circle, we recover the usual Lyapunov exponent for the Lorentz gas from the exponent proposed here. To obtain this result, we generalize the reflection law of a beam of rays incident on a polygonal scatterer in a way that the formula for the circular scatterer is recovered in the limit of infinite number of vertices. Thus, chaos emerges from pseudochaos in an appropriate limit. - Highlights: • We present a finite-time exponent for particles moving in a plane containing polygonal scatterers. • The exponent found recovers the Lyapunov exponent in the limit of the polygon becoming a circle. • Our findings unify pseudointegrable and chaotic scattering via a generalized collision rule. • Stretch and fold:shuffle and cut :: Lyapunov:finite-time exponent :: fluid:granular mixing.
Pseudo- ɛ expansion and critical exponents of superfluid helium
NASA Astrophysics Data System (ADS)
Sokolov, A. I.; Nikitina, M. A.
2016-02-01
The pseudo- ɛ expansions (τ-series) for critical exponents of the three-dimensional XY model describing λ-transition in liquid helium are derived up to the τ6 terms. Numerical estimates extracted from the τ-series obtained using the Padé-Borel resummation technique, scaling relations and the seven-loop (τ7) estimate for the Fisher exponent η are presented including those for the exponents α and ν measured in experiments with a record accuracy. For the exponent α the procedure argued to be most reliable gives α = - 0.0117, the number that is very close to the most accurate experimental values. It signals that the pseudo- ɛ expansion approach is a powerful tool robust enough to evaluate critical exponents with small absolute errors. The arguments in favor of such a robustness are presented.
On estimating the exponent of power-law frequency distributions.
White, Ethan P; Enquist, Brian J; Green, Jessica L
2008-04-01
Power-law frequency distributions characterize a wide array of natural phenomena. In ecology, biology, and many physical and social sciences, the exponents of these power laws are estimated to draw inference about the processes underlying the phenomenon, to test theoretical models, and to scale up from local observations to global patterns. Therefore, it is essential that these exponents be estimated accurately. Unfortunately, the binning-based methods traditionally used in ecology and other disciplines perform quite poorly. Here we discuss more sophisticated methods for fitting these exponents based on cumulative distribution functions and maximum likelihood estimation. We illustrate their superior performance at estimating known exponents and provide details on how and when ecologists should use them. Our results confirm that maximum likelihood estimation outperforms other methods in both accuracy and precision. Because of the use of biased statistical methods for estimating the exponent, the conclusions of several recently published papers should be revisited. PMID:18481513
Atomic emission line wavelength calculations below 2000 angstroms for Lithium II through Cobalt XXVI
NASA Technical Reports Server (NTRS)
Williams, M. D.
1971-01-01
Atomic-emission-line wavelengths are presented which were calculated from wavelengths of previously identified transition sequences using second-degree polynomials fitted to known wave numbers by the least squares method. Wavelengths less than 2000 angstroms are included for ions from Li II to Co XXVI. The computer program written in FORTRAN 4 is also included.
Sub-Angstrom Atomic-Resolution Imaging of Heavy Atoms to Light Atoms
O'Keefe, Michael A.; Shao-Horn, Yang
2003-05-23
Three decades ago John Cowley and his group at ASU achieved high-resolution electron microscope images showing the crystal unit cell contents at better than 4Angstrom resolution. Over the years, this achievement has inspired improvements in resolution that have enabled researchers to pinpoint the positions of heavy atom columns within the cell. More recently, this ability has been extended to light atoms as resolution has improved. Sub-Angstrom resolution has enabled researchers to image the columns of light atoms (carbon, oxygen and nitrogen) that are present in many complex structures. By using sub-Angstrom focal-series reconstruction of the specimen exit surface wave to image columns of cobalt, oxygen, and lithium atoms in a transition metal oxide structure commonly used as positive electrodes in lithium rechargeable batteries, we show that the range of detectable light atoms extends to lithium. HRTEM at sub-Angstrom resolution will provide the essential role of experimental verification for the emergent nanotech revolution. Our results foreshadow those to be expected from next-generation TEMs with Cs-corrected lenses and monochromated electron beams.
ERIC Educational Resources Information Center
Coridan, Robert Henry
2009-01-01
This thesis outlines how meV-resolution inelastic x-ray scattering and causality-enforcing mathematics can be used to measure the dynamical density-density linear response function for liquid water with Angstrom spatial resolution and 50fs temporal resolution. The results are compared to high-resolution spectroscopic and scattering experiments and…
Lyapunov exponent in two-leg ladder model
NASA Astrophysics Data System (ADS)
Datta, P. K.
2010-09-01
Lyapunov exponent is one of the properties to study localization-delocalization transition in disordered systems. Perfect as well as disordered two-leg ladder is studied in tight-binding description. In perfectly two-leg ladder two bands are obtained due to symmetric and antisymmetric wave functions. But, the analytical expression of Lyapunov exponent indicates the presence of extended states at the overlapping region of two bands. Beyond this region of energy states are localized. Two models of disordered ladder network are studied here numerically. These studies show that the Lyapunov exponent indicates the presence of extended states provided both the even and odd modes are extended in transmission analysis. If the transmission coefficient shows the localization behavior for one of the modes the Lyapunov exponent also indicates the localization of those states. The behavior of first Lyapunov exponent is consistent with that of the Lyapunov exponent. on the other hand, the study of second Lyapunov exponent is consistent with the transmission analysis.
The Hurst Exponent of Gamma-Ray Bursts
NASA Astrophysics Data System (ADS)
Sonbas, Eda; MacLachlan, Glen A.; Dhuga, Kalvir S.; Landay, Justin
2016-07-01
Using a wavelet decomposition technique, we have extracted the Hurst exponent for a sample of long and short Gamma-Ray Bursts (GRBs) detected by the Burst Alert Telescope (BAT) aboard the Swift satellite. The Hurst exponent is a scaling parameter that can be used to gauge the long-range behavior in a time series. The mean Hurst exponent for the short GRB sample is significantly smaller than that for the long GRB sample, suggesting that this index may serve as an unbiased criterion for distinguishing short and long GRBs. In addition, a K-S test for the two samples suggest that the null hypothesis can be rejected.
Nonlinear dynamics of the blood flow studied by Lyapunov exponents.
Bracic, M; Stefanovska, A
1998-05-01
In order to gain an insight into the dynamics of the cardiovascular system throughout which the blood circulates, the signals measured from peripheral blood flow in humans were analyzed by calculating the Lyapunov exponents. Over a wide range of algorithm parameters, paired values of both the global and the local Lyapunov exponents were obtained, and at least one exponent equaled zero within the calculation error. This may be an indication of the deterministic nature and finite number of degrees of freedom of the cardiovascular system governing the blood-flow dynamics on a time scale of minutes. A difference was observed in the Lyapunov dimension of controls and athletes. PMID:9608852
Superconductivity exponents in two- and three-dimensional percolation
NASA Astrophysics Data System (ADS)
Herrmann, H. J.; Derrida, B.; Vannimenus, J.
1984-10-01
The first transfer-matrix calculation of the superconductivity exponent s of a random mixture of normal and superconducting elements is presented: The exponent s is defined through the divergence of the conductivity Σ as the critical fraction pc of superconducting elements is approached: Σ~(p-pc)-s. We obtain very accurate values for the exponents which disagree with the Alexander-Orbach conjecture as well as other conjectures. Our results are sν=0.977+/-0.010 in two dimensions and sν=0.85+/-0.04 in three dimensions.
The impact of biogenic carbon emissions on aerosol absorption inMexico City
Marley, N; Gaffney, J; Tackett, M J; Sturchio, N; Hearty, L; Martinez, N; Hardy, K D; Machany-Rivera, A; Guilderson, T P; MacMillan, A; Steelman, K
2009-02-24
In order to determine the wavelength dependence of atmospheric aerosol absorption in the Mexico City area, the absorption angstrom exponents (AAEs) were calculated from aerosol absorption measurements at seven wavelengths obtained with a seven-channel aethalometer during two field campaigns, the Mexico City Metropolitan Area study in April 2003 (MCMA 2003) and the Megacity Initiative: Local and Global Research Observations in March 2006 (MILAGRO). The AAEs varied from 0.76 to 1.56 in 2003 and from 0.54 to 1.52 in 2006. The AAE values determined in the afternoon were consistently higher than the corresponding morning values, suggesting the photochemical formation of absorbing secondary organic aerosols (SOA) in the afternoon. The AAE values were compared to stable and radiocarbon isotopic measurements of aerosol samples collected at the same time to determine the sources of the aerosol carbon. The fraction of modern carbon (fM) in the aerosol samples, as determined from {sup 14}C analysis, showed that 70% of the carbonaceous aerosols in Mexico City were from modern sources, indicating a significant impact from biomass burning during both field campaigns. The {sup 13}C/{sup 12}C ratios of the aerosol samples illustrate the significant impact of Yucatan forest fires (C-3 plants) in 2003 and local grass fires (C-4 plants) at site T1 in 2006. A direct comparison of the fM values, stable carbon isotope ratios, and calculated aerosol AAEs suggested that the wavelength dependence of the aerosol absorption was controlled by the biogenically derived aerosol components.
NASA Astrophysics Data System (ADS)
Kalaidzidis, Yannis L.; Gopta, Oxana; Kalaidzidis, Inna V.
2009-12-01
Originally the maximum entropy method for exponent deconvolution was restricted to the positive exponent's amplitudes by the entropy S(f, m) definition. It limits application of the method, since many experimental kinetics show both the rise and the decay, which manifest themselves as positive and negative amplitudes in the exponent spectrum. The generalization of entropy formulation for non-negative distribution (S. F. Gull and J. Skilling) overcomes this limitation. The drawback of the approach was, that m lost the meaning of the prior distribution, since that maximum of generalized S(f, m) is independent on m and achieved at f ≡ 0. It is significant problem when there are apriori information about possible spectrum behaviour. In the present work some assumptions of the entropy generalization was relaxed and alternative entropy formulation, with non-uniform prior was used for analysis of simulated and experimental data. The new approach was applied to spectra analysis of the absorption kinetics of the bacteriorhodopsin (bR—light driven proton pump from archea Halobacterium salinarium) photocycle. It was shown that the process of the intermediate M formation is non-exponential in the wild type bR. The non-exponential process could be interpreted as result of the protein conformational changes during proton transfer from the Shiff-base of bR.
Luecke, Hartmut; Schobert, Brigitte; Lanyi, Janos K.; Spudich, Elena N.; Spudich, John L.
2016-01-01
We report an atomic-resolution structure for a sensory member of the microbial rhodopsin family, the phototaxis receptor sensory rhodopsin II (NpSRII), which mediates blue-light avoidance by the haloarchaeon Natronobacterium pharaonis. The 2.4 angstrom structure reveals features responsible for the 70- to 80-nanometer blue shift of its absorption maximum relative to those of haloarchaeal transport rhodopsins, as well as structural differences due to its sensory, as opposed to transport, function. Multiple factors appear to account for the spectral tuning difference with respect to bacteriorhodopsin: (i) repositioning of the guanidinium group of arginine 72, a residue that interacts with the counterion to the retinylidene protonated Schiff base; (ii) rearrangement of the protein near the retinal ring; and (iii) changes in tilt and slant of the retinal polyene chain. Inspection of the surface topography reveals an exposed polar residue, tyrosine 199, not present in bacteriorhodopsin, in the middle of the membrane bilayer. We propose that this residue interacts with the adjacent helices of the cognate NpSRII transducer NpHtrII. PMID:11452084
Local Lyapunov Exponent for the Bak Sneppen Model
NASA Astrophysics Data System (ADS)
Ma, Ke; Yang, Chun-Bin; Cai, Xu
2003-12-01
The chaotic property of the Bak-Sneppen model is studied from the local Lyapunov exponent in the same way as for dynamical nonlinear systems. Similar behaviour is found for the one- and two-dimensional Bak-Sneppen models. The Lyapunov exponents for the two cases have the same order of magnitude and both decrease at early evolution but show a slow increasing saturation at late evolution.
Lyapunov exponents, noise-induced synchronization, and Parrondo's paradox.
Kocarev, Ljupco; Tasev, Zarko
2002-04-01
We show that Lyapunov exponents of a stochastic system, when computed for a specific realization of the noise process, are related to conditional Lyapunov exponents in deterministic systems. We propose to use the term stochastically induced regularity instead of noise-induced synchronization and explain the reason why. The nature of stochastically induced regularity is discussed: in some instances, it is a dynamical analog of Parrondo's paradox. PMID:12005984
Potts ferromagnet: Transformations and critical exponents in planar hierarchical lattices
NASA Astrophysics Data System (ADS)
Hauser, Paulo R.; Curado, Evaldo M. F.
1988-07-01
We prove that the duality transformation for a Potts ferromagnet on two-rooted planar hierarchical lattices (HL) preserves the thermal eigenvalue. This leads to a relation between the correlation length critical exponents υ of a HL and its corresponding dual lattice. Using hyperscaling, we show that their specific heat critical exponents α coincide. For a smaller class of HL—namely of diamond and tress types—we prove that another transformation also preserves υ and α.
Arithmetic exponents in piecewise-affine planar maps
NASA Astrophysics Data System (ADS)
Roberts, John A. G.; Vivaldi, Franco
2015-04-01
We consider the growth of some indicators of arithmetical complexity of rational orbits of (piecewise) affine maps of the plane, with rational parameters. The exponential growth rates are expressed by a set of exponents; one exponent describes the growth rate of the so-called logarithmic height of the points of an orbit, while the others describe the growth rate of the size of such points, measured with respect to the p-adic metric. Here p is any prime number which divides the parameters of the map. We show that almost all the points in a domain of linearity (such as an elliptic island in an area-preserving map) have the same set of exponents. We also show that the convergence of the p-adic exponents may be non-uniform, with arbitrarily large fluctuations occurring arbitrarily close to any point. We explore numerically the behaviour of these quantities in the chaotic regions, in both area-preserving and dissipative systems. In the former case, we conjecture that wherever the Lyapunov exponent is zero, the arithmetical exponents achieve a local maximum.
NASA Technical Reports Server (NTRS)
Lauer, James L.; Abel, Phillip B.
1988-01-01
The recent development of the scanning electron tunneling microscope and the atomic force microscope requires absolute standards for measurements in the angstrom and subangstrom range. Optical interferometry with lasers and multiple mode laser resonances can provide absolute measurements as the laser wavelengths are very accurately known. A key feature of such measurements is the use of piezoelectric crystals as translators of the highest accuracy for very small disturbances. However, the dimensional changes of these crystals resulting from electrical potential changes depend on many variables, among them the method of mounting, so that accurate calibrations are necessary. Starting from advances in optical metrology made by physicists trying to find gravity waves, advances which led to measurements down to 10 to the -5 A, the author designed and built a much simpler system for the angstrom range. The major limiting factors were mechanical vibrations, air currents, thermal changes and laser instabilities.
Indication of Cesium Adsorption Into Angstrom-Scale Open Spaces in Saponite Clay Mineral
NASA Astrophysics Data System (ADS)
Numata, Kazuomi; Sato, Kiminori; Fujimoto, Koichiro
2012-12-01
Adsorption behavior of cesium (Cs) into angstrom-scale open spaces for the saponite clay mineral is investigated by making use of positronium (Ps) annihilation spectroscopy together with thermogravimetry and differential thermal analysis (TG-DTA). Ps annihilation spectroscopy reveals two kinds of open spaces with their sizes of 3 Å and 10 Å, respectively, after baking at 423 K for 8 h under the vacuum condition at 10-5 Torr. The large open space is found to survive for the Cs-type saponite due to less hydration of the Cs cations even after the exposure to the air for 200 h. It is thus inferred that Cs is locally adsorbed in the angstrom-scale open spaces in the saponite clay minerals.
Crystal structure of rat alpha-parvalbumin at 1.05 Angstrom resolution.
Bottoms, Christopher A; Schuermann, Jonathan P; Agah, Sayeh; Henzl, Michael T; Tanner, John J
2004-07-01
The crystal structure of rat alpha-parvalbumin has been determined at 1.05 Angstrom resolution, using synchrotron data collected at Advanced Photon Source beamline 19-ID. After refinement with SHELX, employing anisotropic displacement parameters and riding hydrogen atoms, R = 0.132 and R(free) = 0.162. The average coordinate estimated standard deviations are 0.021 Angstrom and 0.038 Angstrom for backbone atoms and side-chain atoms, respectively. Besides providing a more precise view of the alpha-isoform than previously available, these data permit comparison with the 0.91 Angstrom structure determined for pike beta-parvalbumin. Visualization of the anisotropic displacement parameters as thermal ellipsoids yields insight into the atomic motion within the Ca(2+)-binding sites. The asymmetric unit includes three parvalbumin (PV) molecules. Interestingly, the EF site in one displays uncharacteristic flexibility. The ellipsoids for Asp-92 are particularly large and non-spherical, and the shape of the Ca(2+) ellipsoid implies significant vibrational motion perpendicular to the plane defined by the four y and z ligands. The relative dearth of crystal-packing interactions in this site suggests that the heightened flexibility may be the result of diminished intermolecular contacts. The implication is that, by impeding conformational mobility, crystal-packing forces may cause serious overestimation of EF-hand rigidity. The high quality of the data permitted 11 residues to be modeled in alternative side-chain conformations, including the two core residues, Ile-97 and Leu-105. The discrete disorder observed for Ile-97 may have functional ramifications, providing a mechanism for communicating binding status between the CD and EF binding loops and between the PV metal ion-binding domain and the N-terminal AB region. PMID:15169955
Emission Line Spectra in the Soft X-ray Region 20 - 75 Angstroms
NASA Technical Reports Server (NTRS)
Lepson, J. K.; Beiersdorfer, P.; Chen, H.; Behar, E.; Kahn, S. M.
2002-01-01
As part of a project to complete a comprehensive catalogue of astrophysically relevant emission lines in support of new-generation X-ray observatories using the Lawrence Livermore electron beam ion traps EBIT-I and EDIT-II, emission lines of argon and sulfur in the soft X-ray and extreme ultraviolet region were studied. Observations of Ar IX through Ar XVI and S VII through S XIV between 20 and 75 Angstrom are presented to illustrate our work.
Emission Line Spectra in the Soft X-Ray Region 20-75 (Angstrom)
Lepson, J K; Beiersdorfer, P; Chen, H; Behar, E; Kahn, S M
2002-06-18
As part of a project to complete a comprehensive catalogue of astrophysically relevant emission lines in support of new-generation X-ray observatories using the Lawrence Livermore electron beam ion traps EBIT-I and EBIT-II, we studied emission lines of argon and sulfur in the soft X-ray and extreme ultraviolet region. Here we present observations of Ar IX through Ar XVI and S VII through S XIV between 20 and 75 {angstrom} to illustrate our work.
Lentzen, Markus
2008-02-01
The optimum imaging of an object structure at the sub-angstrom length scale requires precise adjustment of the lens aberrations of a high-resolution instrument up to the fifth order. A least-squares optimization of defocus aberration C1, third-order spherical aberration C3, and fifth-order spherical aberration C5 yields two sets of aberration coefficients for strong phase contrast up to the information limit: one for variable C1 and C3, at fixed C5, another for variable C1, C3, and C5. An additional correction to the defocus aberration, dependent on object thickness, is described, which becomes important for the use of image simulation programs in predicting optimum high-resolution contrast from thin objects at the sub-angstrom scale. For instruments with a sub-angstrom information limit the ultimate structure resolution, the power to resolve adjacent atom columns in a crystalline object, depends on both the instrumental pointspread and an object pointspread due to finite width of the atomic column potentials. A simulation study on a simple double-column model yields a range for structure resolutions, dependent on the atomic scattering power, from 0.070 nm down to 0.059 nm, for a hypothetical 300-kV instrument with an information limit of 0.050 nm. PMID:18096097
THE Na 8200 Angstrom-Sign DOUBLET AS AN AGE INDICATOR IN LOW-MASS STARS
Schlieder, Joshua E.; Simon, Michal; Lepine, Sebastien; Rice, Emily; Fielding, Drummond; Tomasino, Rachael E-mail: schlieder@mpia-hd.mpg.de E-mail: erice@amnh.org E-mail: tomas1r@cmich.edu
2012-05-15
We investigate the use of the gravity sensitive neutral sodium (Na I) doublet at 8183 Angstrom-Sign and 8195 Angstrom-Sign (Na 8200 Angstrom-Sign doublet) as an age indicator for M dwarfs. We measured the Na doublet equivalent width (EW) in giants, old dwarfs, young dwarfs, and candidate members of the {beta} Pic moving group using medium-resolution spectra. Our Na 8200 A doublet EW analysis shows that the feature is useful as an approximate age indicator in M-type dwarfs with (V - K{sub s}) {>=} 5.0, reliably distinguishing stars older and younger than 100 Myr. A simple derivation of the dependence of the Na EW on temperature and gravity supports the observational results. An analysis of the effects of metallicity shows that this youth indicator is best used on samples with similar metallicity. The age estimation technique presented here becomes useful in a mass regime where traditional youth indicators are increasingly less reliable, is applicable to other alkali lines, and will help identify new low-mass members in other young clusters and associations.
Reduction of Aerosol Absorption in Beijing Since 2007 from MODIS and AERONET
NASA Technical Reports Server (NTRS)
Lyapustin, A.; Smirnov, A.; Holben, B.; Chin, M.; Streets, D. G.; Lu, Z.; Kahn, R.; Slutsker, I.; Laszlo, I.; Kondragunta, S.; Tanre, D.; Dubovik, O.; Goloub, P.; Chen, H.-B.; Sinyuk, A.; Wang, Y.; Korkin, S.
2011-01-01
An analysis of the time series of MODIS-based and AERONET aerosol records over Beijing reveals two distinct periods, before and after 2007. The MODIS data from both the Terra and Aqua satellites were processed with the new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. A comparison of MAIAC and AERONET AOT shows that whereas MAIAC consistently underestimated peak AOT values by 10-20% in the prior period, the bias mostly disappears after mid-2007. Independent analysis of the AERONET dataset reveals little or no change in the effective radii of the fine and coarse fractions and of the Angstrom exponent. At the same time, it shows an increasing trend in the single scattering albedo, by approx.0.02 in 9 years. As MAIAC was using the same aerosol model for the entire 2000-2010 period, the decrease in AOT bias after 2007 can be explained only by a corresponding decrease of aerosol absorption caused by a reduction in local black carbon emissions. The observed changes correlate in time with the Chinese government's broad measures to improve air quality in Beijing during preparations for the Summer Olympics of 2008.
Reduction of Aerosol Absorption in Beijing Since 2007 from MODIS and AERONET
NASA Technical Reports Server (NTRS)
Lyapustin, A.; Smirnov, A.; Holben, B.; Chin, M.; Streets, D. G.; Lu, Z.; Kahn, R.; Slutsker, I.; Laszlo, I.; Kondragunta, S.; Tanre, D.; Dubovik, O.; Goloub, P.; Chen, H.-B.; Sinyuk, A.; Wang, Y.; Korkin, S.
2011-01-01
An analysis of the time series of MODIS-based and AERONET aerosol records over Beijing reveals two distinct periods, before and after 2007. The MODIS data from both the Terra and Aqua satellites were processed with the new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. A comparison of MAIAC and AERONET AOT shows that whereas MAIAC consistently underestimated peak AOT values by 10-20% in the prior period, the bias mostly disappears after mid- 2007. Independent analysis of the AERONET dataset reveals little or no change in the effective radii of the fine and coarse fractions and of the Angstrom exponent. At the same time, it shows an increasing trend in the single scattering albedo, by 0.02 in 9 years. As MAIAC was using the same aerosol model for the entire 2000-2010 period, the decrease in AOT bias after 2007 can be explained only by a corresponding decrease of aerosol absorption caused by a reduction in local black carbon emissions. The observed changes correlate in time with the Chinese government's broad measures to improve air quality in Beijing during preparations for the Summer Olympics of 2008.
Critical decay exponent of the pair contact process with diffusion.
Park, Su-Chan
2014-11-01
We investigate the one-dimensional pair contact process with diffusion (PCPD) by extensive Monte Carlo simulations, mainly focusing on the critical density decay exponent δ. To obtain an accurate estimate of δ, we first find the strength of corrections to scaling using the recently introduced method [S.-C. Park. J. Korean Phys. Soc. 62, 469 (2013)KPSJAS0374-488410.3938/jkps.62.469]. For small diffusion rate (d≤0.5), the leading corrections-to-scaling term is found to be ∼t^{-0.15}, whereas for large diffusion rate (d=0.95) it is found to be ∼t^{-0.5}. After finding the strength of corrections to scaling, effective exponents are systematically analyzed to conclude that the value of critical decay exponent δ is 0.173(3) irrespective of d. This value should be compared with the critical decay exponent of the directed percolation, 0.1595. In addition, we study two types of crossover. At d=0, the phase boundary is discontinuous and the crossover from the pair contact process to the PCPD is found to be described by the crossover exponent ϕ=2.6(1). We claim that the discontinuity of the phase boundary cannot be consistent with the theoretical argument supporting the hypothesis that the PCPD should belong to the DP. At d=1, the crossover from the mean field PCPD to the PCPD is described by ϕ=2 which is argued to be exact. PMID:25493748
NASA Astrophysics Data System (ADS)
Costabile, F.; Barnaba, F.; Angelini, F.; Gobbi, G. P.
2013-03-01
Characterizing chemical and physical aerosol properties is important to understand their sources, effects, and feedback mechanisms in the atmosphere. This study proposes a scheme to classify aerosol populations based on their spectral optical properties (absorption and scattering). The scheme is obtained thanks to the outstanding set of information on particle size and composition these properties contain. The spectral variability of the aerosol single scattering albedo (dSSA), and the extinction, scattering and absorption Angstrom exponents (EAE, SAE and AAE, respectively) were observed on the basis of two-year measurements of aerosol optical properties (scattering and absorption coefficients at blue, green and red wavelengths) performed in the suburbs of Rome (Italy). Optical measurements of various aerosol types were coupled to measurements of particle number size distributions and relevant optical properties simulations (Mie theory). These latter allowed the investigation of the role of the particle size and composition in the bulk aerosol properties observed. The combination of simulations and measurements suggested a general "paradigm" built on dSSA, SAE and AAE to optically classify aerosols. The paradigm proved suitable to identify the presence of key aerosol populations, including soot, biomass burning, organics, dust and marine particles. The work highlights that (i) aerosol populations show distinctive combinations of SAE and dSSA times AAE, these variables being linked by a linear inverse relation varying with varying SSA; (ii) fine particles show EAE > 1.5, whilst EAE < 2 is found for both coarse particles and ultrafine soot-rich aerosols; (iii) fine and coarse particles both show SSA > 0.8, whilst ultrafine urban Aitken mode and soot particles show SSA < 0.8. The proposed paradigm agrees with aerosol observations performed during past major field campaigns, this indicating that relations concerning the paradigm have a general validity.
Universal persistence exponents in an extremally driven system
NASA Astrophysics Data System (ADS)
Head, D. A.
2002-02-01
The local persistence R(t), defined as the proportion of the system still in its initial state at time t, is measured for the Bak-Sneppen model. For one and two dimensions, it is found that the decay of R(t) depends on one of two classes of initial configuration. For a subcritical initial state, R(t)~t-θ, where the persistence exponent θ can be expressed in terms of a known universal exponent. Hence θ is universal. Conversely, starting from a supercritical state, R(t) decays by the anomalous form 1-R(t)~tτall until a finite time t0, where τall is also a known exponent. Finally, for the high dimensional model R(t) decays exponentially with a nonuniversal decay constant.
Testing universality in critical exponents: The case of rainfall
NASA Astrophysics Data System (ADS)
Deluca, Anna; Puig, Pedro; Corral, Álvaro
2016-04-01
One of the key clues to consider rainfall as a self-organized critical phenomenon is the existence of power-law distributions for rain-event sizes. We have studied the problem of universality in the exponents of these distributions by means of a suitable statistic whose distribution is inferred by several variations of a permutational test. In contrast to more common approaches, our procedure does not suffer from the difficulties of multiple testing and does not require the precise knowledge of the uncertainties associated to the power-law exponents. When applied to seven sites monitored by the Atmospheric Radiation Measurement Program the tests lead to the rejection of the universality hypothesis, despite the fact that the exponents are rather close to each other. We discuss the reasons of the rejection.
Anisotropies in magnetic field evolution and local Lyapunov exponents
Tang, X.Z.; Boozer, A.H.
2000-01-13
The natural occurrence of small scale structures and the extreme anisotropy in the evolution of a magnetic field embedded in a conducting flow is interpreted in terms of the properties of the local Lyapunov exponents along the various local characteristic (un)stable directions for the Lagrangian flow trajectories. The local Lyapunov exponents and the characteristic directions are functions of Lagrangian coordinates and time, which are completely determined once the flow field is specified. The characteristic directions that are associated with the spatial anisotropy of the problem, are prescribed in both Lagrangian and Eulerian frames. Coordinate transformation techniques are employed to relate the spatial distributions of the magnetic field, the induced current density, and the Lorentz force, which are usually followed in Eulerian frame, to those of the local Lyapunov exponents, which are naturally defined in Lagrangian coordinates.
Vertex Exponents of Two-Colored Extremal Ministrong Digraphs
NASA Astrophysics Data System (ADS)
Suwilo, Saib
2011-06-01
The exponent of a vertex v in a two-colored digraph D(2) is the smallest positive integer h+k such that for each vertex x in D(2) there is a walk of length h+k consisting of h red arcs and k blue arcs. Let D(2) be a primitive two-colored extremalministrong digraphon n vertices. If D(2) has one blue arc, the exponent of the vertices of D(2) lieson the interval [n2-5n+8,n2-3n+1]. If D(2) has two blue arcs, the exponent of the vertices in D(2) lies on the interval [n2-4n+4,n2-n].
Does the Viscosity Exponent Derive from Ultrasonic Attenuation Spectra?
NASA Astrophysics Data System (ADS)
Bhattacharjee, J. K.; Mirzaev, S. Z.; Kaatze, U.
2012-03-01
Based on a representation of the sound velocity of critical liquids in terms of a frequency-dependent complex specific heat at constant pressure, a simple relation between the low-frequency normalized sonic attenuation coefficient and the correlation length of fluctuations is derived. This relation provides a promising alternative for the determination of the dynamics exponent and thus the critical exponent of the shear viscosity. Sonic attenuation data from the literature, measured at frequencies down to 50 kHz, are re-evaluated with a view of the viscosity exponent determination. It is found that only in a small temperature range, the major requirement of the approach is fulfilled with the available data. Close to the critical temperature, the frequencies of measurement are still insufficiently small as compared to the inverse relaxation time of order parameter fluctuations. Criteria for future experiments are discussed briefly.
Lyapunov exponents of stochastic systems—from micro to macro
NASA Astrophysics Data System (ADS)
Laffargue, Tanguy; Tailleur, Julien; van Wijland, Frédéric
2016-03-01
Lyapunov exponents of dynamical systems are defined from the rates of divergence of nearby trajectories. For stochastic systems, one typically assumes that these trajectories are generated under the ‘same noise realization’. The purpose of this work is to critically examine what this expression means. For Brownian particles, we consider two natural interpretations of the noise: intrinsic to the particles or stemming from the fluctuations of the environment. We show how they lead to different distributions of the largest Lyapunov exponent as well as different fluctuating hydrodynamics for the collective density field. We discuss, both at microscopic and macroscopic levels, the limits in which these noise prescriptions become equivalent. We close this paper by providing an estimate of the largest Lyapunov exponent and of its fluctuations for interacting particles evolving with Dean-Kawasaki dynamics.
Quantum computation of multifractal exponents through the quantum wavelet transform
Garcia-Mata, Ignacio; Giraud, Olivier; Georgeot, Bertrand
2009-05-15
We study the use of the quantum wavelet transform to extract efficiently information about the multifractal exponents for multifractal quantum states. We show that, combined with quantum simulation algorithms, it enables to build quantum algorithms for multifractal exponents with a polynomial gain compared to classical simulations. Numerical results indicate that a rough estimate of fractality could be obtained exponentially fast. Our findings are relevant, e.g., for quantum simulations of multifractal quantum maps and of the Anderson model at the metal-insulator transition.
NASA Technical Reports Server (NTRS)
Wesemael, F.; Holberg, J. B.; Veilleux, S.; Lamontagne, R.; Fontaine, G.
1985-01-01
Voyager ultraviolet spectrometer observations of the subdwarf B or OB stars HD 205805, UV 1758+36 and Feige 66 are presented. All three objects display the H I Layman series in absorption. These observations are combined with low dispersion IUE spectrophotometry and with Stroemgren photometry to construct virtually complete energy distributions, which extend over the range 950-5500 angstroms. Effective temperatures based on model atmosphere calculations for high gravity, hydrogen rich stars are determined. Our analyses yield T Sub e 28,200 + or - 1300 K for HD 205805, T sub e 31, 800 + or - 1100 K for UV 1758+36, and T sub e 35,700 + or - 1500 K for Feige 66. The importance of far ultraviolet observations below L sub alpha in reducing the uncertainties associated with the interstellar extinction and the degradation of the IUE sensitivity is emphasized.
Structure of Coenzyme A-Disulfide Reductase from Staphylococcus aureus at 1.54 Angstrom Resolution
Mallett,T.; Wallen, J.; Karplus, P.; Sakai, H.; Tsukihara, T.; Claiborne, A.
2006-01-01
Coenzyme A (CoASH) replaces glutathione as the major low molecular weight thiol in Staphylococcus aureus; it is maintained in the reduced state by coenzyme A-disulfide reductase (CoADR), a homodimeric enzyme similar to NADH peroxidase but containing a novel Cys43-SSCoA redox center. The crystal structure of S. aureus CoADR has been solved using multiwavelength anomalous dispersion data and refined at a resolution of 1.54 {angstrom}. The resulting electron density maps define the Cys43-SSCoA disulfide conformation, with Cys43-S{gamma} located at the flavin si face, 3.2 {angstrom} from FAD-C4aF, and the CoAS- moiety lying in an extended conformation within a cleft at the dimer interface. A well-ordered chloride ion is positioned adjacent to the Cys43-SSCoA disulfide and receives a hydrogen bond from Tyr361'-OH of the complementary subunit, suggesting a role for Tyr361' as an acid-base catalyst during the reduction of CoAS-disulfide. Tyr419'-OH is located 3.2 {angstrom} from Tyr361'-OH as well and, based on its conservation in known functional CoADRs, also appears to be important for activity. Identification of residues involved in recognition of the CoAS-disulfide substrate and in formation and stabilization of the Cys43-SSCoA redox center has allowed development of a CoAS-binding motif. Bioinformatics analyses indicate that CoADR enzymes are broadly distributed in both bacterial and archaeal kingdoms, suggesting an even broader significance for the CoASH/CoAS-disulfide redox system in prokaryotic thiol/disulfide homeostasis.
YOHKOH Bragg Crystal Spectrometer Light Curves for S XV (5.0163 - 5.1143 Angstroms)
NASA Astrophysics Data System (ADS)
Mariska, John T.; Bentley, R. D.; Pike, C. D.
1997-12-01
This memorandum report summarizes the data produced during the sixth year of operation by the Bragg Crystal Spectrometer (BCS) on the Yohkoh spacecraft. Each page shows the total count rate in the S XV channel of the BCS for a single day. This channel nominally observes the Sun in the wavelength range from 5.0163 - 5.1143 Angstroms. These plots are useful for identifying flare data for further analysis and for determining the data file name and tape number that contains the data.
Lyapunov exponent for aging process in induction motor
NASA Astrophysics Data System (ADS)
Bayram, Duygu; Ünnü, Sezen Yıdırım; Şeker, Serhat
2012-09-01
Nonlinear systems like electrical circuits and systems, mechanics, optics and even incidents in nature may pass through various bifurcations and steady states like equilibrium point, periodic, quasi-periodic, chaotic states. Although chaotic phenomena are widely observed in physical systems, it can not be predicted because of the nature of the system. On the other hand, it is known that, chaos is strictly dependent on initial conditions of the system [1-3]. There are several methods in order to define the chaos. Phase portraits, Poincaré maps, Lyapunov Exponents are the most common techniques. Lyapunov Exponents are the theoretical indicator of the chaos, named after the Russian mathematician Aleksandr Lyapunov (1857-1918). Lyapunov Exponents stand for the average exponential divergence or convergence of nearby system states, meaning estimating the quantitive measure of the chaotic attractor. Negative numbers of the exponents stand for a stable system whereas zero stands for quasi-periodic systems. On the other hand, at least if one of the exponents is positive, this situation is an indicator of the chaos. For estimating the exponents, the system should be modeled by differential equation but even in that case mathematical calculation of Lyapunov Exponents are not very practical and evaluation of these values requires a long signal duration [4-7]. For experimental data sets, it is not always possible to acquire the differential equations. There are several different methods in literature for determining the Lyapunov Exponents of the system [4, 5]. Induction motors are the most important tools for many industrial processes because they are cheap, robust, efficient and reliable. In order to have healthy processes in industrial applications, the conditions of the machines should be monitored and the different working conditions should be addressed correctly. To the best of our knowledge, researches related to Lyapunov exponents and electrical motors are mostly
Stochastic Approximation of Dynamical Exponent at Quantum Critical Point
NASA Astrophysics Data System (ADS)
Suwa, Hidemaro; Yasuda, Shinya; Todo, Synge
We have developed a unified finite-size scaling method for quantum phase transitions that requires no prior knowledge of the dynamical exponent z. During a quantum Monte Carlo simulation, the temperature is automatically tuned by the Robbins-Monro stochastic approximation method, being proportional to the lowest gap of the finite-size system. The dynamical exponent is estimated in a straightforward way from the system-size dependence of the temperature. As a demonstration of our novel method, the two-dimensional S = 1 / 2 quantum XY model, or equivalently the hard-core boson system, in uniform and staggered magnetic fields is investigated in the combination of the world-line quantum Monte Carlo worm algorithm. In the absence of a uniform magnetic field, we obtain the fully consistent result with the Lorentz invariance at the quantum critical point, z = 1 . Under a finite uniform magnetic field, on the other hand, the dynamical exponent becomes two, and the mean-field universality with effective dimension (2+2) governs the quantum phase transition. We will discuss also the system with random magnetic fields, or the dirty boson system, bearing a non-trivial dynamical exponent.Reference: S. Yasuda, H. Suwa, and S. Todo Phys. Rev. B 92, 104411 (2015); arXiv:1506.04837
Bayesian Estimation of the Logistic Positive Exponent IRT Model
ERIC Educational Resources Information Center
Bolfarine, Heleno; Bazan, Jorge Luis
2010-01-01
A Bayesian inference approach using Markov Chain Monte Carlo (MCMC) is developed for the logistic positive exponent (LPE) model proposed by Samejima and for a new skewed Logistic Item Response Theory (IRT) model, named Reflection LPE model. Both models lead to asymmetric item characteristic curves (ICC) and can be appropriate because a symmetric…
Comment on the conductivity exponent in continuum percolation
NASA Astrophysics Data System (ADS)
Machta, J.
1988-05-01
The field theory introduced by Lubensky and Tremblay [Phys. Rev. B 34, 3408 (1986)] for continuum percolation is reanalyzed. Dynamical exponents are found which agree with those found by Straley [J. Phys. C 15, 2343 (1982)] and Machta et al. [Phys. Rev. B 33, 4818 (1986)] using a nodes-links-blobs approach.
Applications of accurate isentropic exponent determination for fuel gas measurement
Pack, D.J.; Edwards, T.J.; Fawcett, D.
1996-07-01
This paper discusses the determination and application of the isentropic exponent to the various thermodynamic processes found in a high-pressure natural gas transmission system. Increasing demands for more precise measurement of natural gas, coupled with the need for greater efficiency and accountability of transportation and processing operations, had led to the research and development of gas thermodynamic properties including isentropic exponent. The isentropic exponent has many applications, some of which include: the determination of the expansion factor {epsilon}, for calculation of flow using an orifice or venturi-type meter; the volumetric efficiency in a reciprocating compressor; the determination of the compression head for a centrifugal compressor; the engine power required for the given conditions for a gas compressor; the calculation of discharge temperatures for compressors; and the direct measurement of gas density. As can be appreciated, the application of an incorrect value for the isentropic exponent represents an error in the parameter determined. For large volume gas flows, this can translate into a significant cost penalty.
River flow mass exponents with fractal channel networks and rainfall
Troutman, B.M.; Over, T.M.
2001-01-01
An important problem in hydrologic science is understanding how river flow is influenced by rainfall properties and drainage basin characteristics. In this paper we consider one approach, the use of mass exponents, in examining the relation of river flow to rainfall and the channel network, which provides the primary conduit for transport of water to the outlet in a large basin. Mass exponents, which characterize the power-law behavior of moments as a function of scale, are ideally suited for defining scaling behavior of processes that exhibit a high degree of variability or intermittency. The main result in this paper is an expression relating the mass exponent of flow resulting from an instantaneous burst of rainfall to the mass exponents of spatial rainfall and that of the network width function. Spatial rainfall is modeled as a random multiplicative cascade and the channel network as a recursive replacement tree; these fractal models reproduce certain types of self-similar behavior seen in actual rainfall and networks. It is shown that under these modeling assumptions the scaling behavior of flow mirrors that of rainfall if rainfall is highly variable in space, and on the other hand flow mirrors the structure of the network if rainfall is not so highly variable. ?? 2001 Elsevier Science Ltd. All rights reserved.
Analytical solutions of the Rayleigh equation for arbitrary polytropic exponent
NASA Astrophysics Data System (ADS)
Kudryashov, Nikolay A.; Sinelshchikov, Dmitry I.
2016-06-01
The Rayleigh equation for the description of spherical gas-filled bubbles dynamics is considered. It is shown that this equation can be transformed into an equation for the elliptic function for arbitrary values of the polytropic exponent. General analytical solutions of the Rayleigh equation are studied for some particular cases, such as the isothermal case.
Singularity detection for structural health monitoring using holder exponents.
Robertson, A. N.; Farrar, C. R.; Sohn, H.
2003-01-01
The majority of structural health monitoring studies reported in the technical literature focus on identifying damage sensitive features that can be extracted from dynamic response data . However, many of these studies assume the structure can be modeled as a linear system before and after damage and use parameters of these models as the damage sensitive features. The study summarized in this paper proposes a damage sensitive feature that takes advantage of the nonlinearities associated with discontinuities introduced into the dynamic response data as a result of certain types of damage. Specifically, the Holder exponent, a measure of the degree to which a signal is differentiable, is the feature that is used to detect the presence of damage and when that damage occurred . A procedure for capturing the time varying nature of the Holder exponent based on wavelet transforms is demonstrated through applications to non-stationary random signals with underlying discontinuities and then to a harmonically excited mechanical system that contains a loose part . Also, a classification procedure is developed to quantify when changes in the Holder exponent are significant . The results presented herein show the Holder exponent to be an effective feature for identifying damage that introduces discontinuities into the measured dynamic response data .
Inverted rank distributions: Macroscopic statistics, universality classes, and critical exponents
NASA Astrophysics Data System (ADS)
Eliazar, Iddo; Cohen, Morrel H.
2014-01-01
An inverted rank distribution is an infinite sequence of positive sizes ordered in a monotone increasing fashion. Interlacing together Lorenzian and oligarchic asymptotic analyses, we establish a macroscopic classification of inverted rank distributions into five “socioeconomic” universality classes: communism, socialism, criticality, feudalism, and absolute monarchy. We further establish that: (i) communism and socialism are analogous to a “disordered phase”, feudalism and absolute monarchy are analogous to an “ordered phase”, and criticality is the “phase transition” between order and disorder; (ii) the universality classes are characterized by two critical exponents, one governing the ordered phase, and the other governing the disordered phase; (iii) communism, criticality, and absolute monarchy are characterized by sharp exponent values, and are inherently deterministic; (iv) socialism is characterized by a continuous exponent range, is inherently stochastic, and is universally governed by continuous power-law statistics; (v) feudalism is characterized by a continuous exponent range, is inherently stochastic, and is universally governed by discrete exponential statistics. The results presented in this paper yield a universal macroscopic socioeconophysical perspective of inverted rank distributions.
Fermat's Last Theorem for Factional and Irrational Exponents
ERIC Educational Resources Information Center
Morgan, Frank
2010-01-01
Fermat's Last Theorem says that for integers n greater than 2, there are no solutions to x[superscript n] + y[superscript n] = z[superscript n] among positive integers. What about rational exponents? Irrational n? Negative n? See what an undergraduate senior seminar discovered.
Anomalous charge storage exponents of organic bulk heterojunction solar cells.
NASA Astrophysics Data System (ADS)
Nair, Pradeep; Dwivedi, Raaz; Kumar, Goutam; Dept of Electrical Engineering, IIT Bombay Team
2013-03-01
Organic bulk heterojunction (BHJ) devices are increasingly being researched for low cost solar energy conversion. The efficiency of such solar cells is dictated by various recombination processes involved. While it is well known that the ideality factor and hence the charge storage exponents of conventional PN junction diodes are influenced by the recombination processes, the same aspects are not so well understood for organic solar cells. While dark currents of such devices typically show an ideality factor of 1 (after correcting for shunt resistance effects, if any), surprisingly, a wide range of charge storage exponents for such devices are reported in literature alluding to apparent concentration dependence for bi-molecular recombination rates. In this manuscript we critically analyze the role of bi-molecular recombination processes on charge storage exponents of organic solar cells. Our results indicate that the charge storage exponents are fundamentally influenced by the electrostatics and recombination processes and can be correlated to the dark current ideality factors. We believe that our findings are novel, and advance the state-of the art understanding on various recombination processes that dictate the performance limits of organic solar cells. The authors would like to thank the Centre of Excellence in Nanoelectronics (CEN) and the National Centre for Photovoltaic Research and Education (NCPRE), IIT Bombay for computational and financial support
Chaotic systems with absorption.
Altmann, Eduardo G; Portela, Jefferson S E; Tél, Tamás
2013-10-01
Motivated by applications in optics and acoustics we develop a dynamical-system approach to describe absorption in chaotic systems. We introduce an operator formalism from which we obtain (i) a general formula for the escape rate κ in terms of the natural conditionally invariant measure of the system, (ii) an increased multifractality when compared to the spectrum of dimensions D(q) obtained without taking absorption and return times into account, and (iii) a generalization of the Kantz-Grassberger formula that expresses D(1) in terms of κ, the positive Lyapunov exponent, the average return time, and a new quantity, the reflection rate. Simulations in the cardioid billiard confirm these results. PMID:24138240
Breaking the Attosecond, Angstrom and TV/M Field Barriers with Ultra-Fast Electron Beams
Rosenzweig, James; Andonian, Gerard; Fukasawa, Atsushi; Hemsing, Erik; Marcus, Gabriel; Marinelli, Agostino; Musumeci, Pietro; O'Shea, Brendan; O'Shea, Finn; Pellegrini, Claudio; Schiller, David; Travish, Gil; Bucksbaum, Philip; Hogan, Mark; Krejcik, Patrick; Ferrario, Massimo; Full, Steven; Muggli, Patric; /Southern California U.
2012-06-22
Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This use of very low Q beams may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the LCLS have produced {approx}2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments in cryogenic undulator technology, to create compact accelerator-undulator systems that can lase below 0.15 {angstrom}, or be used to permit 1.5 {angstrom} operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications.
Interfacial atomic structure analysis at sub-angstrom resolution using aberration-corrected STEM
2014-01-01
The atomic structure of a SiGe/Si epitaxial interface grown via molecular beam epitaxy on a single crystal silicon substrate was investigated using an aberration-corrected scanning transmittance electron microscope equipped with a high-angle annular dark-field detector and an energy-dispersive spectrometer. The accuracy required for compensation of the various residual aberration coefficients to achieve sub-angstrom resolution with the electron optics system was also evaluated. It was found that the interfacial layer was composed of a silicon single crystal, connected coherently to epitaxial SiGe nanolaminates. In addition, the distance between the dumbbell structures of the Si and Ge atoms was approximately 0.136 nm at the SiGe/Si interface in the [110] orientation. The corresponding fast Fourier transform exhibited a sub-angstrom scale point resolution of 0.78 Å. Furthermore, the relative positions of the atoms in the chemical composition line scan signals could be directly interpreted from the corresponding incoherent high-angle annular dark-field image. PMID:25426003
Streptococcus pneumonia YlxR at 1.35 {angstrom} shows a putative new fold.
Osipiuk, J.; Gornicki, P.; Maj, L.; Dementieva, I.; Joachimiak, A.; Biosciences Division; Univ. of Chicago
2001-11-01
The structure of the YlxR protein of unknown function from Streptococcus pneumonia was determined to 1.35 Angstroms. YlxR is expressed from the nusA/infB operon in bacteria and belongs to a small protein family (COG2740) that shares a conserved sequence motif GRGA(Y/W). The family shows no significant amino-acid sequence similarity with other proteins. Three-wavelength diffraction MAD data were collected to 1.7 Angstroms from orthorhombic crystals using synchrotron radiation and the structure was determined using a semi-automated approach. The YlxR structure resembles a two-layer {alpha}/{beta} sandwich with the overall shape of a cylinder and shows no structural homology to proteins of known structure. Structural analysis revealed that the YlxR structure represents a new protein fold that belongs to the {alpha}-{beta} plait superfamily. The distribution of the electrostatic surface potential shows a large positively charged patch on one side of the protein, a feature often found in nucleic acid-binding proteins. Three sulfate ions bind to this positively charged surface. Analysis of potential binding sites uncovered several substantial clefts, with the largest spanning 3/4 of the protein. A similar distribution of binding sites and a large sharply bent cleft are observed in RNA-binding proteins that are unrelated in sequence and structure. It is proposed that YlxR is an RNA-binding protein.
Avalanche shape and exponents beyond mean-field theory
NASA Astrophysics Data System (ADS)
Dobrinevski, Alexander; Le Doussal, Pierre; Jörg Wiese, Kay
2014-12-01
Elastic systems, such as magnetic domain walls, density waves, contact lines, and cracks, are pinned by substrate disorder. When driven, they move via avalanches, with power law distributions of size, duration and velocity. Their exponents, and the shape of an avalanche, defined as its mean velocity as a function of time, were studied. They are known approximatively from experiments and simulations, and were predicted from mean-field models, such as the Brownian force model (BFM), where each point of the elastic interface sees a force field which itself is a random walk. As we showed in EPL, 97 (2012) 46004, the BFM is the starting point for an \\varepsilon = d\\text{c}-d expansion around the upper critical dimension, with d\\text{c}=4 for short-ranged elasticity, and d\\text{c}=2 for long-ranged elasticity. Here we calculate analytically the O}(\\varepsilon) , i.e. 1-loop, correction to the avalanche shape at fixed duration T, for both types of elasticity. The exact expression, though different from the phenomenological form presented by Laurson et al. in Nat. Commun., 4 (2013) 2927, is well approximated by ≤ft< \\dot u(t=x T)\\right>_T≃ [ Tx(1-x)]γ-1 \\exp≤ft( A}≤ft[\\frac12-x\\right]\\right) , 0 < x < 1. The asymmetry A}≈ - 0.336 (1-d/d\\text{c}) is negative for d close to d\\text{c} , skewing the avalanche towards its end, as observed in numerical simulations in d = 2 and 3. The exponent γ=(d+\\zeta)/z is given by the two independent exponents at depinning, the roughness ζ and the dynamical exponent z. We propose a general procedure to predict other avalanche exponents in terms of ζ and z. We finally introduce and calculate the shape at fixed avalanche size, not yet measured in experiments or simulations.
Numerical investigation on the Ångström exponent of black carbon aerosol
NASA Astrophysics Data System (ADS)
Li, Ji; Liu, Chao; Yin, Yan; Kumar, K. Raghavendra
2016-04-01
Black carbon (BC) plays an important role on the global and regional climate, whereas there are significant uncertainties on its optical properties. Among various optical properties, the Ångström exponent (AE) indicates the spectral variation of the particle-optic interaction and is widely used to understand the aerosol properties. We consider the influence of BC geometry on its optical properties and assess the sensitivity of the AE to particle geometry and size distribution. The fractal aggregates with different fractal dimensions are used to represent realistic BC particles, and popular equivalent volume spherical and spheroidal models are also considered for comparison. Even if the fractal aggregates become highly compact and spherical, their optical properties are still significantly different from those of equivalent volume spheres or spheroids. Meanwhile, the Rayleigh-Debye-Gans approximation can hardly provide accurate results for all optical quantities of aggregates with different dimensions. The extinction Ångström exponent (EAE) and absorption Ångström exponent (AAE) are sensitive to both particle geometry and size distribution. With BC becoming more compact (from fractal aggregate to spheroid and to sphere), the AE becomes more sensitive to particle size distribution. The EAE and AAE of aggregates with different size distributions vary between 1.10-1.63 and 0.87-1.50, respectively, whereas those of the spheres or spheroids have wider ranges. Furthermore, the AE at smaller wavelengths (between 0.35 µm and 0.55 µm) is more sensitive to geometry and size distribution than that given by optical properties at larger wavelengths (between 0.55 µm and 0.88 µm).
NASA Astrophysics Data System (ADS)
Lyamani, H.; Olmo, F. J.; Alados-Arboledas, L.
Surface measurements of optical and physical aerosol properties were made at an urban site, Granada (Spain) (37.18°N, 3.58°W, 680 m a.s.l), during winter 2005-2006. Measurements included the aerosol scattering, σsca, and backscattering coefficients, σbsca, at three wavelengths (450, 550 and 700 nm) measured at low relative humidity (RH<50%) by an integrating nephelometer, the absorption coefficient at 670 nm, σabs, measured with a multi-angle absorption photometer, and aerosol size distribution in the 0.5-20 μm aerodynamic diameter range registered by an aerodynamic aerosol sizer (APS-3321, TSI). The hourly average of σsca (550 nm) ranged from 2 to 424 M m -1 with an average value of 84±62 M m -1 (±S.D.). The Angstrom exponent presented an average value of 1.8±0.3, suggesting a large fraction of fine particles at the site, an observation confirmed by aerosol size distribution measurements. The hourly average of σabs (670 nm) ranged from 1.7 to 120.5 M m -1 with an average value of 28±20 M m -1. The results indicate that the aerosol absorption coefficient in Granada was relatively large. The largest σsca value was associated with air masses that passed over heavily polluted European areas and local stagnation conditions. High absorbing aerosol level was obtained during dust transport from North Africa probably due to the presence of hematite. Based on the measured scattering and absorption coefficients, a very low average value of the single scattering albedo of 0.66±0.11 at 670 nm was calculated, suggesting that urban aerosols in this region contain a large fraction of absorbing material. A clear diurnal pattern was observed in scattering and absorption coefficients and particle concentrations with two local maxima occurring in early morning and late evening. This behavior can be explained in terms of local conditions that control the particle sources associated with traffic and upward mixing of the aerosol during the daytime development of a
Light absorption of brown carbon aerosol in the PRD region of China
NASA Astrophysics Data System (ADS)
Yuan, J.-F.; Huang, X.-F.; Cao, L.-M.; Cui, J.; Zhu, Q.; Huang, C.-N.; Lan, Z.-J.; He, L.-Y.
2016-02-01
The strong spectral dependence of light absorption of brown carbon (BrC) aerosol is regarded to influence aerosol's radiative forcing significantly. The Absorption Angstrom Exponent (AAE) method has been widely used in previous studies to attribute light absorption of BrC at shorter wavelengths for ambient aerosols, with a theoretical assumption that the AAE of "pure" black carbon (BC) aerosol equals to 1.0. In this study, the AAE method was applied to both urban and rural environments in the Pearl River Delta (PRD) region of China, with an improvement of constraining the realistic AAE of "pure" BC through statistical analysis of on-line measurement data. A three-wavelength photo-acoustic soot spectrometer (PASS-3) and aerosol mass spectrometers (AMS) were used to explore the relationship between the measured AAE and the relative abundance of organic aerosol to BC. The regression and extrapolation analysis revealed that more realistic AAE values for "pure" BC aerosol (AAEBC) were 0.86, 0.82, and 1.02 between 405 and 781 nm, and 0.70, 0.71, and 0.86 between 532 and 781 nm, in the campaigns of urbanwinter, urbanfall, and ruralfall, respectively. Roadway tunnel experiments were conducted and the results further confirmed the representativeness of the obtained AAEBC values for the urban environment. Finally, the average light absorption contributions of BrC (± relative uncertainties) at 405 nm were quantified to be 11.7 % (±5 %), 6.3 % (±4 %), and 12.1 % (±7 %) in the campaigns of urbanwinter, urbanfall, and ruralfall, respectively, and those at 532 nm were 10.0 % (±2 %), 4.1 % (±3 %), and 5.5 % (±5 %), respectively. The relatively higher BrC absorption contribution at 405 nm in the ruralfall campaign could be reasonably attributed to the biomass burning events nearby, which was then directly supported by the biomass burning simulation experiments performed in this study. This paper indicates that the BrC contribution to total aerosol light absorption at shorter
Light absorption of brown carbon aerosol in the PRD region of China
NASA Astrophysics Data System (ADS)
Yuan, J.-F.; Huang, X.-F.; Cao, L.-M.; Cui, J.; Zhu, Q.; Huang, C.-N.; Lan, Z.-J.; He, L.-Y.
2015-10-01
The strong spectral dependence of light absorption of brown carbon (BrC) aerosol is regarded to influence aerosol's radiative forcing significantly. The Absorption Angstrom Exponent (AAE) method was widely used in previous studies to attribute light absorption of BrC at shorter wavelengths for ambient aerosol, with a theoretical assumption that the AAE of "pure" black carbon (BC) aerosol equals to 1.0. In this study, the previous AAE method was improved by statistical analysis and applied in both urban and rural environments in the Pearl River Delta (PRD) region of China. A three-wavelength photo-acoustic soot spectrometer (PASS-3) and aerosol mass spectrometers (AMS) were used to explore the relationship between the measured AAE and the relative abundance of organic aerosol to BC. The regression and extrapolation analysis revealed that the more realistic AAE values for "pure" BC aerosol were 0.86, 0.82, and 1.02 at 405 nm, and 0.70, 0.71, and 0.86 at 532 nm, in the campaigns of urban_winter, urban_fall, and rural_fall, respectively. Roadway tunnel experiments were also conducted, and the results further supported the representativeness of the obtained AAE values for "pure" BC aerosol in the urban environments. Finally, the average aerosol light absorption contribution of BrC was quantified to be 11.7, 6.3, and 12.1 % (with relative uncertainties of 4, 4, and 7 %) at 405 nm, and 10.0, 4.1, and 5.5 % (with relative uncertainties of 2, 2, and 5 %) at 532 nm, in the campaigns of urban_winter, urban_fall, and rural_fall, respectively. The relatively higher BrC absorption contribution at 405 nm in the rural_fall campaign was likely a result of the biomass burning events nearby, which was supported by the biomass burning simulation experiments performed in this study. The results of this paper indicate that the brown carbon contribution to aerosol light absorption at shorter wavelengths is not negligible in the highly urbanized and industrialized PRD region.
Lee, Hanlim; Kim, Young J; Jung, Jinsang; Lee, Chulkyu; Heue, Klaus-Peter; Platt, Ulrich; Hu, Min; Zhu, Tong
2009-04-01
During the CAREBEIJING campaign in 2006, imaging differential optical absorption spectroscopy (I-DOAS) measurements were made from 08:00 to 16:00 on September 9 and 10 over Beijing, China. Detailed images of the near-surface NO(2) differential slant column density (DSCD) distribution over Beijing were obtained. Images with less than a 30-min temporal resolution showed both horizontal and vertical variations in NO(2) distributions. For DSCD to mixing ratio conversion, path length along the lines of I-DOAS lines of sight was estimated using the light-extinction coefficient and Angstrom exponent data obtained by a transmissometer and a sunphotometer, respectively. Mixing ratios measured by an in-situ NO(2) analyzer were compared with those estimated by the I-DOAS instrument. The obtained temporal and spatial variations in NO(2) distributions measured by I-DOAS for the two days are interpreted with consideration of the locations of the major NO(x) sources and local wind conditions. I-DOAS measurements have been applied in this study for estimating NO(2) distribution over an urban area with multiple and distributed emission sources. Results are obtained for estimated temporal and spatial NO(2) distributions over the urban atmosphere; demonstrating the capability of the I-DOAS technique. We discuss in this paper the use of I-DOAS measurements to estimate the NO(2) distribution over an urban area with multiple distributed emission sources. PMID:19111964
Critical exponents of a self-propelled particles system
NASA Astrophysics Data System (ADS)
Cambui, Dorilson S.; de Arruda, Alberto S.; Godoy, Maurício
2016-02-01
The Vicsek model of self-propelled particles is an important tool in the study of the collective motion of live organisms. The model consists of particles that move with a constant velocity and adopt, in a region called the zone of repulsion, the average motion direction of their neighbors disturbed by an external noise. A second-order phase transition from a disordered state, with motion in random directions, to an ordered motion state was observed. In this work, we have estimated, using finite-size scaling arguments, the critical exponents β, γ and ν of the original Vicsek model as a function of parameters important to the model, such as the orientation radius size, density, and velocity modulus. Our results show that the critical exponents depend greatly on these parameters.
Largest Lyapunov exponents for lattices of interacting classical spins.
de Wijn, A S; Hess, B; Fine, B V
2012-07-20
We investigate how generic the onset of chaos in interacting many-body classical systems is in the context of lattices of classical spins with nearest-neighbor anisotropic couplings. Seven large lattices in different spatial dimensions were considered. For each lattice, more than 2000 largest Lyapunov exponents for randomly sampled Hamiltonians were numerically computed. Our results strongly suggest the absence of integrable nearest-neighbor Hamiltonians for the infinite lattices except for the trivial Ising case. In the vicinity of the Ising case, the largest Lyapunov exponents exhibit a power-law growth, while further away they become rather weakly sensitive to the Hamiltonian anisotropy. We also provide an analytical derivation of these results. PMID:22861854
Estimation of Hurst Exponent for the Financial Time Series
NASA Astrophysics Data System (ADS)
Kumar, J.; Manchanda, P.
2009-07-01
Till recently statistical methods and Fourier analysis were employed to study fluctuations in stock markets in general and Indian stock market in particular. However current trend is to apply the concepts of wavelet methodology and Hurst exponent, see for example the work of Manchanda, J. Kumar and Siddiqi, Journal of the Frankline Institute 144 (2007), 613-636 and paper of Cajueiro and B. M. Tabak. Cajueiro and Tabak, Physica A, 2003, have checked the efficiency of emerging markets by computing Hurst component over a time window of 4 years of data. Our goal in the present paper is to understand the dynamics of the Indian stock market. We look for the persistency in the stock market through Hurst exponent and fractal dimension of time series data of BSE 100 and NIFTY 50.
NASA Astrophysics Data System (ADS)
Penton, Steven
2011-10-01
We fully calibrate a new COS/G130M wavelength setting in this program. This setting, G130M/1222, places Geocoronal Lya on the detector gap {to mitigate FUV detector gain sag} and covers the astrophysically important UV bandpass of 1065-1327 Angstrom. At the focus mechanism position requested {-850}, this mode provides 4-10 times the resolution of the G130M/1055 and G130M/1096 central wavelength settings at the same sensitivity. The sensitivity, waveband, and increased resolution of the G130M/1222 central wavelength {R=17,000 at 1065 Angstrom, 15,000 at 1222 Angstrom, and 12,000 at 1369 Angstrom} is beneficial to many UV scientific studies, including, but not limited to, molecular hydrogen in planetary nebulae and translucent clouds, the HeII lyman-alpha forest in the epoch of HeII re-ionization, AGN intrinsic absorbers and high-ionization outflows, low-redshift IGM, galaxy halos, galaxy feedback, and the WHIM using O VI, MgX, NeVIII, Lyman beta, and other important atomic and molecular transitions. At 1100 Angstrom, this mode has 10 times the effective area of FUSE {per channel} with almost non-existent detector background. This program is designed to completely calibrate this wavelength setting with minimal use of STScI personnel and resources.
Quartz Microbalance Study of 400-angstrom Thick Films near the lambda Point
NASA Technical Reports Server (NTRS)
Chan, Moses H. W.
2003-01-01
In a recent measurement we observed the thinning of an adsorbed helium film induced by the confinement of critical fluctuations a few millikelvin below the lambda point. A capacitor set-up was used to measure this Casimir effect. In this poster we will present our measurement of an adsorbed helium film of 400 angstroms near the lambda point with a quartz microbalance. For films this thick, we must take into account the non-linear dynamics of the shear waves in the fluid. In spite of the added complications, we were able to confirm the thinning of the film due to the Casimir effect and the onset of the superfluid transition. In addition, we observe a sharp anomaly at the bulk lambda point, most likely related to critical dissipation of the first sound. This work is carried out in collaboration with Rafael Garcia, Stephen Jordon and John Lazzaretti. This work is funded by NASA's Office of Biological and Physical Research under grant.
Membrane of Functionalized Reduced Graphene Oxide Nanoplates with Angstrom-Level Channels
Lee, Byeongho; Li, Kunzhou; Yoon, Hong Sik; Yoon, Jeyong; Mok, Yeongbong; Lee, Yan; Lee, Hong H.; Kim, Yong Hyup
2016-01-01
Membranes with atomic level pores or constrictions are valuable for separation and catalysis. We report a graphene-based membrane with an interlayer spacing of 3.7 angstrom (Å). When graphene oxide nanoplates are functionalized and then reduced, the laminated reduced graphene oxide (rGO) nanoplates or functionalized rGO membrane is little affected by an intercalated fluid, and the interlayer spacing of 3.7 Å increases only to 4.4 Å in wetted state, in contrast to the graphene oxide (GO) membrane whose interlayer spacing increases from 9 Å to 13 Å in wetted state. When applied to ion separation, this membrane reduced the permeation rate of small ions such as K+ and Na+ by three orders of magnitude compared to the GO membrane. PMID:27306853
The structure of rat liver vault at 3.5 angstrom resolution.
Tanaka, Hideaki; Kato, Koji; Yamashita, Eiki; Sumizawa, Tomoyuki; Zhou, Yong; Yao, Min; Iwasaki, Kenji; Yoshimura, Masato; Tsukihara, Tomitake
2009-01-16
Vaults are among the largest cytoplasmic ribonucleoprotein particles and are found in numerous eukaryotic species. Roles in multidrug resistance and innate immunity have been suggested, but the cellular function remains unclear. We have determined the x-ray structure of rat liver vault at 3.5 angstrom resolution and show that the cage structure consists of a dimer of half-vaults, with each half-vault comprising 39 identical major vault protein (MVP) chains. Each MVP monomer folds into 12 domains: nine structural repeat domains, a shoulder domain, a cap-helix domain, and a cap-ring domain. Interactions between the 42-turn-long cap-helix domains are key to stabilizing the particle. The shoulder domain is structurally similar to a core domain of stomatin, a lipid-raft component in erythrocytes and epithelial cells. PMID:19150846
NASA Astrophysics Data System (ADS)
Atabak, Mehrdad; Ünverdi, Özhan; Özer, H. Özgür; Oral, Ahmet
2009-12-01
We report the first results from novel sub-Angstrom oscillation amplitude non-contact atomic force microscopy developed for lateral force gradient measurements. Quantitative lateral force gradients between a tungsten tip and Si(1 1 1)-(7 × 7) surface can be measured using this microscope. Simultaneous lateral force gradient and scanning tunnelling microscope images of single and multi atomic steps are obtained. In our measurement, tunnel current is used as feedback. The lateral stiffness contrast has been observed to be 2.5 N/m at single atomic step, in contrast to 13 N/m at multi atomic step on Si(1 1 1) surface. We also carried out a series of lateral stiffness-distance spectroscopy. We observed lateral stiffness-distance curves exhibit sharp increase in the stiffness as the sample is approached towards the surface. We usually observed positive stiffness and sometimes going into slightly negative region.
1D Superconducting behavior in 4-Angstrom carbon nanotube-zeolite composite
NASA Astrophysics Data System (ADS)
Shi, Wu; Wang, Zhe; Xie, Hang; Zhang, Ting; Wang, Ning; Tang, Zikang; Zhang, Xixiang; Lortz, Rolf; Sheng, Ping
2010-03-01
We report 4-probe electrical measurements on a sample of 4-Angstrom carbon nanotubes-zeolite composite that exhibit 1D superconducting behavior. The resistance displays a smooth decrease as a function of temperature that is characteristic of the phase slip fluctuation effects, and the differential resistance measured as a function of current shows a quasigap that is characteristic of the fluctuating condensate. Both data sets show very little variation upon the application of a magnetic field, up to 9 Tesla. These behaviors are explainable in terms of the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory of phase slips. We also show and discuss an interesting phenomenon in which a sharp zero current (bias) peak appears in the differential resistance above 3 K.
Inner-Shell Photon-Ionized X-Ray Laser at 45(Angstrom)
Weber, F; Celliers, P; Moon, S; Snavely, R; Da Silva, L
2002-02-01
This report summarizes the major accomplishments of this three-year Laboratory Directed Research and Development (LDRD) Lab Wide (LW) project entitled, ''An Inner-Shell Photo-Ionized X-Ray Laser at 45 {angstrom}'', tracking code 99-LW-042. The most significant accomplishments of this project include the design of a suitable x-ray laser target, the invention of a measurement technique for the determination of rise times of x-ray pulses on the order of 50 femtoseconds, and a novel setup for generating a traveling wave with an ultrashort optical laser pulse. The pump probe technique for rise time measurement will allow us to detect ultrashort x-ray pulses, whose generation by means of a variety of 4th generation light sources is currently under planning elsewhere.
Membrane of Functionalized Reduced Graphene Oxide Nanoplates with Angstrom-Level Channels.
Lee, Byeongho; Li, Kunzhou; Yoon, Hong Sik; Yoon, Jeyong; Mok, Yeongbong; Lee, Yan; Lee, Hong H; Kim, Yong Hyup
2016-01-01
Membranes with atomic level pores or constrictions are valuable for separation and catalysis. We report a graphene-based membrane with an interlayer spacing of 3.7 angstrom (Å). When graphene oxide nanoplates are functionalized and then reduced, the laminated reduced graphene oxide (rGO) nanoplates or functionalized rGO membrane is little affected by an intercalated fluid, and the interlayer spacing of 3.7 Å increases only to 4.4 Å in wetted state, in contrast to the graphene oxide (GO) membrane whose interlayer spacing increases from 9 Å to 13 Å in wetted state. When applied to ion separation, this membrane reduced the permeation rate of small ions such as K(+) and Na(+) by three orders of magnitude compared to the GO membrane. PMID:27306853
Membrane of Functionalized Reduced Graphene Oxide Nanoplates with Angstrom-Level Channels
NASA Astrophysics Data System (ADS)
Lee, Byeongho; Li, Kunzhou; Yoon, Hong Sik; Yoon, Jeyong; Mok, Yeongbong; Lee, Yan; Lee, Hong H.; Kim, Yong Hyup
2016-06-01
Membranes with atomic level pores or constrictions are valuable for separation and catalysis. We report a graphene-based membrane with an interlayer spacing of 3.7 angstrom (Å). When graphene oxide nanoplates are functionalized and then reduced, the laminated reduced graphene oxide (rGO) nanoplates or functionalized rGO membrane is little affected by an intercalated fluid, and the interlayer spacing of 3.7 Å increases only to 4.4 Å in wetted state, in contrast to the graphene oxide (GO) membrane whose interlayer spacing increases from 9 Å to 13 Å in wetted state. When applied to ion separation, this membrane reduced the permeation rate of small ions such as K+ and Na+ by three orders of magnitude compared to the GO membrane.
Development of XUV-interferometry (155 {angstrom}) using a soft x-ray laser
Da Silva, L.B.; Barbee, T.W.; Cauble, R.
1995-08-01
Over the past several years the authors have developed a variety of techniques for probing plasmas with x-ray lasers. These have included direct high resolution plasma imaging to quantify laser produced plasma uniformities and moire deflectometry to measure electron density profiles in one-dimension. Although these techniques have been valuable, a need existed for direct two dimensional measurements of electron densities in large high density plasmas. For this reason the authors have worked on developing a xuv interferometer compatible with the harsh environment of laser produced plasmas. This paper describes the design and presents some results showing excellent fringe visibility using the neon-like yttrium x-ray laser operating at 155 {angstrom}. The coherence properties of this x-ray laser source were measured using interferometry and are also discussed.
Persistence exponent of the diffusion equation in ε dimensions
NASA Astrophysics Data System (ADS)
Hilhorst, H. J.
2000-03-01
We consider the d-dimensional diffusion equation ∂ tφ( x,t)= Δφ( x,t) with random initial condition, and observe that, when appropriately scaled, φ(0, t) is Gaussian and Markovian in the limit d→0. This leads via the Majumdar-Sire perturbation theory to a small d expansion for the persistence exponent θ( d). We find θ(d)= {1}/{4}d-0.12065…d 3/2+⋯
Removing zero Lyapunov exponents in volume-preserving flows
NASA Astrophysics Data System (ADS)
Bessa, Mário; Rocha, Jorge
2007-04-01
Baraviera and Bonatti (2003 Ergod. Theory Dyn. Syst. 23 1655-70) proved that it is possible to perturb, in the C1-topology, a stably ergodic, volume-preserving and partially hyperbolic diffeomorphism in order to obtain a non-zero sum of all the Lyapunov exponents in the central direction. In this paper we obtain the analogous result for volume-preserving flows.
Clustering of Casablanca stock market based on hurst exponent estimates
NASA Astrophysics Data System (ADS)
Lahmiri, Salim
2016-08-01
This paper deals with the problem of Casablanca Stock Exchange (CSE) topology modeling as a complex network during three different market regimes: general trend characterized by ups and downs, increasing trend, and decreasing trend. In particular, a set of seven different Hurst exponent estimates are used to characterize long-range dependence in each industrial sector generating process. They are employed in conjunction with hierarchical clustering approach to examine the co-movements of the Casablanca Stock Exchange industrial sectors. The purpose is to investigate whether cluster structures are similar across variable, increasing and decreasing regimes. It is observed that the general structure of the CSE topology has been considerably changed over 2009 (variable regime), 2010 (increasing regime), and 2011 (decreasing regime) time periods. The most important findings follow. First, in general a high value of Hurst exponent is associated to a variable regime and a small one to a decreasing regime. In addition, Hurst estimates during increasing regime are higher than those of a decreasing regime. Second, correlations between estimated Hurst exponent vectors of industrial sectors increase when Casablanca stock exchange follows an upward regime, whilst they decrease when the overall market follows a downward regime.
Lyapunov Exponent Criterion in the CR3BP
NASA Astrophysics Data System (ADS)
Quarles, Billy; Eberle, Jason; Cuntz, Manfred; Musielak, Zdzislaw
2010-10-01
Our specific focus is to describe the motion of an extra solar planet in a binary star system. We aim to accomplish this by using the methods of chaos theory as an alternate method to our previously established Hodograph method in the circular restricted 3-body problem (CR3BP). Previously Eberle et al. (2010) has shown that a parameter space exists depending only on the mass ratio μ and distance ratio ρo which allowed them to identify regions of stability. Our method will validate the previous results while also providing more information relating to the presence of resonances and their effects on orbital stability. We extend the previous studies by increasing the simulation time, applying the method of Lyapunov exponents, calculating the time series spectrum of the orbit, and determining the Lyapunov dimension. The obtained results demonstrate when a system becomes unstable by orbital energy criterion and the method of Lyapunov exponents provides a quantitative classification scale to characterize the instability. By applying the maximum Lyapunov exponent (MLE) to the parameter space, we determine a region of stability with MLE values larger than the surrounding region. The time series spectra and the Lyapunov Dimension methods are used to illustrate the reasons behind the stability plateau which eludes to the resonance phenomena.
Stochastic approximation of dynamical exponent at quantum critical point
NASA Astrophysics Data System (ADS)
Yasuda, Shinya; Suwa, Hidemaro; Todo, Synge
2015-09-01
We have developed a unified finite-size scaling method for quantum phase transitions that requires no prior knowledge of the dynamical exponent z . During a quantum Monte Carlo simulation, the temperature is automatically tuned by the Robbins-Monro stochastic approximation method, being proportional to the lowest gap of the finite-size system. The dynamical exponent is estimated in a straightforward way from the system-size dependence of the temperature. As a demonstration of our novel method, the two-dimensional S =1 /2 quantum X Y model in uniform and staggered magnetic fields is investigated in the combination of the world-line quantum Monte Carlo worm algorithm. In the absence of a uniform magnetic field, we obtain the fully consistent result with the Lorentz invariance at the quantum critical point, z =1 , i.e., the three-dimensional classical X Y universality class. Under a finite uniform magnetic field, on the other hand, the dynamical exponent becomes two, and the mean-field universality with effective dimension (2 +2 ) governs the quantum phase transition.
Scaling exponents for lattice quantum gravity in four dimensions
NASA Astrophysics Data System (ADS)
Hamber, Herbert W.
2015-09-01
In this work nonperturbative aspects of quantum gravity are investigated using the lattice formulation, and some new results are presented for critical exponents, amplitudes, and invariant correlation functions. Values for the universal scaling dimensions are compared with other nonperturbative approaches to gravity in four dimensions, and specifically to the conjectured value for the universal critical exponent ν =1 /3 . The lattice results are generally consistent with gravitational antiscreening, which would imply a slow increase in the strength of the gravitational coupling with distance, and presented herein are detailed estimates for exponents and amplitudes characterizing this slow rise. Furthermore, it is shown that in the lattice approach (as for gauge theories) the quantum theory is highly constrained, and eventually, by virtue of scaling, depends on a rather small set of physical parameters. Arguments are given in support of the statement that the fundamental reference scale for the growth of the gravitational coupling G with distance is represented by the observed scaled cosmological constant λ , which in gravity acts as an effective nonperturbative infrared cutoff. In this nonperturbative vacuum condensate picture a fundamental relationship emerges among the scale characterizing the running of G at large distances, the macroscopic scale for the curvature as described by the observed cosmological constant, and the behavior of invariant gravitational correlation functions at large distances. Overall, the lattice results suggest that the slow infrared growth of G with distance should become observable only on very large distance scales, comparable to λ . One may hope that future high precision satellite experiments could possibly come within reach of this small quantum correction, as suggested by the vacuum condensate picture of quantum gravity.
Zipf exponent of trajectory distribution in the hidden Markov model
NASA Astrophysics Data System (ADS)
Bochkarev, V. V.; Lerner, E. Yu
2014-03-01
This paper is the first step of generalization of the previously obtained full classification of the asymptotic behavior of the probability for Markov chain trajectories for the case of hidden Markov models. The main goal is to study the power (Zipf) and nonpower asymptotics of the frequency list of trajectories of hidden Markov frequencys and to obtain explicit formulae for the exponent of the power asymptotics. We consider several simple classes of hidden Markov models. We prove that the asymptotics for a hidden Markov model and for the corresponding Markov chain can be essentially different.
The experimental observation on Lyapunov exponent in type V intermittency
NASA Astrophysics Data System (ADS)
Wang, Yingmei; He, Da-Ren; Hou, Yuqing
1998-03-01
We have obtained the first experimental proof for the scaling law of Lyapunov exponent in type V intermittency[1] in an electronic relaxation oscillator[2]. The results are in good agreement with the theoretical prediction obtained by a simplified model[1], and with numerical computations conducted with the theoretical model of the oscillator. [1]: S.Wu,E.J.Ding,D.-R.He, Phys.Lett.A, 197(1995)287. [2]: F.Ji and D.-R.He, Phys.Lett.A, 177(1993)125.
A critical exponent of an aniseed-based liquor
NASA Astrophysics Data System (ADS)
Mayorga, A.; Thompson, D.
1996-05-01
We present the results of a simple experiment suitable for the undergraduate laboratory in which the onset of turbidity when an aniseed-based liquor is diluted with water is observed. The optical transmission shows the behavior typical of the order parameter in a second-order phase transition. The changes in the transmission are due to the precipitation of terpenes and the amount of precipitated terpenes also shows critical behavior of the form n=k'(c-cc)y, where c is the fraction of water in the solution. The critical exponent is determined to be y=1.01±0.06.
Critical exponents and scaling relations for self-organized critical phenomena
NASA Technical Reports Server (NTRS)
Tang, Chao; Bak, Per
1988-01-01
Critical indices beta, gamma delta, nv, etc. are defined and calculated for self-organized critical phenomena. Scaling relations are derived and checked numerically. The order-parameter exponent beta describes the spontaneous current and the relaxation to the criticl point. The power spectrum has 'l/f' behavior with the exponent phi = nv x z, where z is the dynamical critical exponent.
Federal Register 2010, 2011, 2012, 2013, 2014
2012-04-02
... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Angstrom Microsystems Corp., Bedminster National Corp., Brake Headquarters U.S.A., Inc., and Brand... information concerning the securities of BrandPartners Group, Inc. because it has not filed any...
J Bachega; l Bleicher; E Horjales; p Santiago; R Garratt; M Tabak
2011-12-31
Glossoscolex paulistus is a free-living earthworm encountered in south-east Brazil. Its oxygen transport requirements are undertaken by a giant extracellular haemoglobin, or erythrocruorin (HbGp), which has an approximate molecular mass of 3.6 MDa and, by analogy with its homologue from Lumbricus terrestris (HbLt), is believed to be composed of a total of 180 polypeptide chains. In the present work the full 3.6 MDa particle in its cyanomet state was purified and crystallized using sodium citrate or PEG8000 as precipitant. The crystals contain one-quarter of the full particle in the asymmetric unit of the I222 cell and have parameters of a = 270.8 {angstrom}, b = 320.3 {angstrom} and c = 332.4 {angstrom}. Diffraction data were collected to 3.15 {angstrom} using synchrotron radiation on beamline X29A at the Brookhaven National Laboratory and represent the highest resolution data described to date for similar erythrocruorins. The structure was solved by molecular replacement using a search model corresponding to one-twelfth of its homologue from HbLt. This revealed that HbGp belongs to the type I class of erythrocruorins and provided an interpretable initial electron density map in which many features including the haem groups and disulfide bonds could be identified.
Seely, J. F.; Kowalski, M. P.; Cruddace, R. G.; Rife, J. C.; Osterried, K.; Kleineberg, U.; Menke, D. Hunter, W. R.
1997-11-01
We characterized a laminar grating with a Mo/Si multilayer coating by using synchrotron radiation and atomic force microscopy. The grating substitute had 2400 grooves/mm, 40-{Angstrom} groove depth, and 2080-{Angstrom} groove width. The microroughness of the grating substrate was 5 {Angstrom} rms. The multilayer coating was optimized to have peak normal-incidence reflectance at a wavelength near 150 {Angstrom}. For an angle of incidence of 10{degree} the peak grating efficiency was 16.3{percent} in the +1 order and 15.0{percent} in the {minus}1 order. The efficiency in the zero order was lower by a factor of 40 owing to the excellent matching of the groove depth and groove width to the wavelength of the incident radiation. By dividing the grating efficiencies by the measured reflectance of the multilayer coating, we obtained inferred groove efficiencies of 34{percent} and 32{percent} in the +1 and {minus}1 orders, respectively. {copyright} 1997 Optical Society of America
Sub Angstrom imaging of dislocation core structures: How well areexperiments comparable with theory?
Kisielowski, C.; Freitag, B.; Xu, X.; Beckman, S.P.; Chrzan, D.C.
2005-12-16
During the past 50 years Transmission Electron Microscopy (TEM) has evolved from an imaging tool to a quantitative method that approaches the ultimate goal of understanding the atomic structure of materials atom by atom in three dimensions both experimentally and theoretically. Today's TEM abilities are tested in the special case of a Ga terminated 30 degree partial dislocation in GaAs:Be where it is shown that a combination of high-resolution phase contrast imaging, Scanning TEM, and local Electron Energy Loss Spectroscopy allows for a complete analysis of dislocation cores and associated stacking faults. We find that it is already possible to locate atom column positions with picometer precision in directly interpretable images of the projected crystal structure and that chemically different elements can already be identified together with their local electronic structure. In terms of theory, the experimental results can be quantitatively compared with ab initio electronic structure total energy calculations. By combining elasticity theory methods with atomic theory an equivalent crystal volume can be addressed. Therefore, it is already feasible to merge experiments and theory on a picometer length scale. While current experiments require the utilization of different, specialized instruments it is foreseeable that the rapid improvement of electron optical elements will soon generate a next generation of microscopes with the ability to image and analyze single atoms in one instrument with deep sub Angstrom spatial resolution and an energy resolution better than 100 meV.
Molecular structure of an apolipoprotein determined at 2. 5- angstrom resolution
Breiter, D.R.; Benning, M.M.; Wesenberg, G.; Holden, H.M.; Rayment, I. ); Kanost, M.R.; Law, J.H.; Wells, M.A. )
1991-01-22
The three-dimensional structure of an apolipoprotein isolated from the African migratory locust Locusta migratoria has been determined by X-ray analysis to a resolution of 2.5 {angstrom}. The overall molecular architecture of this protein consists of five long {alpha}-helices connected by short loops. As predicted from amino acid sequence analyses, these helices are distinctly amphiphilic with the hydrophobic residues pointing in toward the interior of the protein and the hydrophilic side chains facing outward. The molecule falls into the general category of up-and-down {alpha}-helical bundles as previously observed, for example, in cytochrome c{prime}. Although the structure shows the presence of five long amphiphilic {alpha}-helices, the {alpha}-helical moment and hydrophobicity of the entire molecule fall into the range found for normal globular proteins. Thus, in order for the amphiphilic helices to play a role in the binding of the protein to a lipid surface, there must be a structural reorganization of the protein which exposes the hydrophobic interior to the lipid surface. The three dimensional motif of this apolipoprotein is compatible with a model in which the molecule binds to the lipid surface via a relatively nonpolar end and then spreads on the surface in such a way as to cause the hydrophobic side chains of the helices to come in contact with the lipid surface, the charged and polar residues to remain in contact with water, and the overall helical motif of the protein to be maintained.
Structure of a yeast spliceosome at 3.6-angstrom resolution.
Yan, Chuangye; Hang, Jing; Wan, Ruixue; Huang, Min; Wong, Catherine C L; Shi, Yigong
2015-09-11
Splicing of precursor messenger RNA (pre-mRNA) in yeast is executed by the spliceosome, which consists of five small nuclear ribonucleoproteins (snRNPs), NTC (nineteen complex), NTC-related proteins (NTR), and a number of associated enzymes and cofactors. Here, we report the three-dimensional structure of a Schizosaccharomyces pombe spliceosome at 3.6-angstrom resolution, revealed by means of single-particle cryogenic electron microscopy. This spliceosome contains U2 and U5 snRNPs, NTC, NTR, U6 small nuclear RNA, and an RNA intron lariat. The atomic model includes 10,574 amino acids from 37 proteins and four RNA molecules, with a combined molecular mass of approximately 1.3 megadaltons. Spp42 (Prp8 in Saccharomyces cerevisiae), the key protein component of the U5 snRNP, forms a central scaffold and anchors the catalytic center. Both the morphology and the placement of protein components appear to have evolved to facilitate the dynamic process of pre-mRNA splicing. Our near-atomic-resolution structure of a central spliceosome provides a molecular framework for mechanistic understanding of pre-mRNA splicing. PMID:26292707
The 2.3 {angstrom} crystal structure of cholera toxin B subunit pentamer: Choleragenoid
Zhang, Rong-Guang; Westbrook, M.L.; Maulik, P.R.; Reed, R.A.; Shipley, G.; Westbrook, E.M. |; Scott, D.L.; Otwinowski, Z.
1996-02-01
Cholera toxin, a heterohexameric AB{sub 5} enterotoxin released by Vibrio cholera, induces a profuse secretory diarrhea in susceptible hosts. Choleragenoid, the B subunit pentamer of cholera toxin, directs the enzymatic A subunit to its target by binding to GM{sub 1} gangliosides exposed on the luminal surface of intestinal epithelial cells. We have solved the crystal structure of choleragenoid at 2.3 {Angstrom} resolution by combining single isomorphous replacement with non-crystallographic symmetry averaging. The structure of the B subunits, and their pentameric arrangement, closely resembles that reported for the intact holotoxin (choleragen), the heat-labile enterotoxin from E. coli, and for a choleragenoid-GM{sub 1} pentasaccharide complex. In the absence of the A subunit the central cavity of the B pentamer is a highly solvated channel. The binding of the A subunit or the receptor pentasaccharide to choleragenoid has only a modest effect on the local stereochemistry and does not perceptibly alter the subunit interface.
X-ray structure of trypanothione reductase from Crithidia fasciculata at 2. 4- angstrom resolution
Kuriyan, J.; Xiangpeng Kong; Krishna, T.S.R.; Murgolo, N.J.; Field, H.; Cerami, A.; Henderson, G.B. ); Sweet, R.M. )
1991-10-01
Trypanosomes and related protozoan parasites lack glutathione reductase and possess instead a closely related enzyme that serves as the reductant of a bis(glutathione)-spermidien conjugate, trypanothione. The human and parasite enzymes have mutually exclusive substrate specificities, providing a route for the design of therapeutic agents by specific inhibition of the parasite enzyme. The authors report here the three-dimensional structure of trypanothione reductase from Crithidia fasciculata and show that it closely resembles the structure of human glutathione reductase. In particular, the core structure surrounding the catalytic machinery is almost identical in the two enzymes. However, significant differences are found at the substrate binding sites. A cluster of basic residues in glutathione reductase is replaced by neutral, hydrophobic, or acidic residues in trypanothione reductase, consistent with the nature of the spermidine linkage and the change in overall charge of the substrate from {minus}2 to +1, respectively. The binding site is more open in trypanothione reductase due to rotations of about 4{degree} in the domains that form in site, with relative shifts of as much as 2-3 {angstrom} in residues that can interact with potential inhibitors and complement previous modeling and mutagenesis studies on the two enzymes.
Bell, David C.; Russo, Christopher J.; Benner, Gerd
2011-01-01
Lowering the electron energy in the transmission electron microscope allows for a significant improvement in contrast of light elements, and reduces knock-on damage for most materials. If low-voltage electron microscopes are defined as those with accelerating voltages below 100 kV, the introduction of aberration correctors and monochromators to the electron microscope column enables Ångstrom-level resolution, which was previously reserved for higher voltage instruments. Decreasing electron energy has three important advantages: 1) knock-on damage is lower, which is critically important for sensitive materials such as graphene and carbon nanotubes; 2) cross sections for electron-energy-loss spectroscopy increase, improving signal-to-noise for chemical analysis; 3) elastic scattering cross sections increase, improving contrast in high-resolution, zero-loss images. The results presented indicate that decreasing the acceleration voltage from 200 kV to 80 kV in a monochromated, aberration-corrected microscope enhances the contrast while retaining sub-angstrom resolution. These improvements in low-voltage performance are expected to produce many new results and enable a wealth of new experiments in materials science. PMID:20598206
Near-ideal theoretical strength in gold nanowires containing angstrom scale twins
Wang, Jiangwei; Sansoz, Frederic; Huang, Jianyu; Liu, Yi; Sun, Shouheng; Zhang, Ze; Mao, Scott X.
2013-01-01
Although nanoscale twinning is an effective means to enhance yield strength and tensile ductility in metals, nanotwinned metals generally fail well below their theoretical strength limit due to heterogeneous dislocation nucleation from boundaries or surface imperfections. Here we show that Au nanowires containing angstrom-scaled twins (0.7 nm in thickness) exhibit tensile strengths up to 3.12 GPa, near the ideal limit, with a remarkable ductile-to-brittle transition with decreasing twin size. This is opposite to the behaviour of metallic nanowires with lower-density twins reported thus far. Ultrahigh-density twins (twin thickness<2.8 nm) are shown to give rise to homogeneous dislocation nucleation and plastic shear localization, contrasting with the heterogeneous slip mechanism observed in single-crystalline or low-density-twinned nanowires. The twin size dependent dislocation nucleation and deformation represent a new type of size effect distinct from the sample size effects described previously. PMID:23612283
Cryoelectron Microscopy Structure of Purified gamma-Secretase at 12 angstrom Resolution
Osenkowski, P.; Li, H.; Li, H.; Ye, W.; Li, D.; Aeschbach, L.; Fraering, P. C.; Wolfe, M. S.; Selkoe, D. J.
2009-01-06
{gamma}-Secretase, an integral membrane protein complex, catalyzes the intramembrane cleavage of the {beta}-amyloid precursor protein (APP) during the neuronal production of the amyloid {beta}-peptide. As such, the protease has emerged as a key target for developing agents to treat and prevent Alzheimer's disease. Existing biochemical studies conflict on the oligomeric assembly state of the protease complex, and its detailed structure is not known. Here, we report that purified active human {gamma}-secretase in digitonin has a total molecular mass of {approx} 230 kDa when measured by scanning transmission electron microscopy. This result supports a complex that is monomeric for each of the four component proteins. We further report the three-dimensional structure of the {gamma}-secretase complex at 12 {angstrom} resolution as obtained by cryoelectron microscopy and single-particle image reconstruction. The structure reveals several domains on the extracellular side, three solvent-accessible low-density cavities, and a potential substrate-binding surface groove in the transmembrane region of the complex.
Critical exponents in two dimensions and pseudo-ε expansion.
Nikitina, M A; Sokolov, A I
2014-04-01
The critical behavior of two-dimensional n-vector λϕ4 field model is studied within the framework of pseudo-ε expansion approach. Pseudo-ε expansions for Wilson fixed-point location g* and critical exponents originating from five-loop two-dimensional renormalization-group series are derived. Numerical estimates obtained within Padé and Padé-Borel resummation procedures as well as by direct summation are presented for n=1, n=0, and n=-1, i.e., for the models which are exactly solvable. The pseudo-ε expansions for g*, critical exponents γ, and ν have small lower-order coefficients and slow increasing higher-order ones. As a result, direct summation of these series with optimal cutoff provides numerical estimates that are no worse than those given by the resummation approaches mentioned. This enables one to consider the pseudo-ε expansion technique itself as some specific resummation method. PMID:24827231
Pixel classification based color image segmentation using quaternion exponent moments.
Wang, Xiang-Yang; Wu, Zhi-Fang; Chen, Liang; Zheng, Hong-Liang; Yang, Hong-Ying
2016-02-01
Image segmentation remains an important, but hard-to-solve, problem since it appears to be application dependent with usually no a priori information available regarding the image structure. In recent years, many image segmentation algorithms have been developed, but they are often very complex and some undesired results occur frequently. In this paper, we propose a pixel classification based color image segmentation using quaternion exponent moments. Firstly, the pixel-level image feature is extracted based on quaternion exponent moments (QEMs), which can capture effectively the image pixel content by considering the correlation between different color channels. Then, the pixel-level image feature is used as input of twin support vector machines (TSVM) classifier, and the TSVM model is trained by selecting the training samples with Arimoto entropy thresholding. Finally, the color image is segmented with the trained TSVM model. The proposed scheme has the following advantages: (1) the effective QEMs is introduced to describe color image pixel content, which considers the correlation between different color channels, (2) the excellent TSVM classifier is utilized, which has lower computation time and higher classification accuracy. Experimental results show that our proposed method has very promising segmentation performance compared with the state-of-the-art segmentation approaches recently proposed in the literature. PMID:26618250
Temperature Dependence of the Flare Fluence Scaling Exponent
NASA Astrophysics Data System (ADS)
Kretzschmar, M.
2015-12-01
Solar flares result in an increase of the solar irradiance at all wavelengths. While the distribution of the flare fluence observed in coronal emission has been widely studied and found to scale as f(E)˜ E^{-α}, with α slightly below 2, the distribution of the flare fluence in chromospheric lines is poorly known. We used the solar irradiance measurements observed by the SDO/EVE instrument at a 10 s cadence to investigate the dependency of the scaling exponent on the formation region of the lines (or temperature). We analyzed all flares above the C1 level since the start of the EVE observations (May 2010) to determine the flare fluence distribution in 16 lines covering a wide range of temperatures, several of which were not studied before. Our results show a weak downward trend with temperature of the scaling exponent of the PDF that reaches from above 2 at lower temperature (a few 104 K) to {˜ }1.8 for hot coronal emission (several 106 K). However, because colder lines also have fainter contrast, we cannot exclude that this behavior is caused by including more noise for smaller flares for these lines. We discuss the method and its limitations and tentatively associate this possible trend with the different mechanisms responsible for the heating of the chromosphere and corona during flares.
Semiclassical treatment of Wannier's theory when the exponent diverges
NASA Astrophysics Data System (ADS)
Condren, D. S.; McCann, J. F.; Crothers, D. S. F.
2006-09-01
We consider a non-standard application of the Wannier model. A physical example is the single ionization of a hydrogenic beryllium ion with a fully stripped beryllium ion, where the ratio of the charge of the third particle to the charges of the escaping particles is 1/4; we investigate the single ionization by an electron of an atom comprising an electron and a nucleus of charge 1/4. An infinite exponent is obtained suggesting that this process is not tractable within the Wannier model. A modified version of Crothers' uniform semiclassical wavefunction for the outgoing particles has been adopted, since the Wannier exponents m_{12}=1/4[i\\sqrt{(100Z-9)/(4Z-1)}-1] and m_{21}=-1/4[i\\sqrt{(9-4Z)/(4Z-1)}+1] are infinite for an effective charge of Z = 1/4. We use Bessel functions to describe the Peterkop functions u1 and u2 and derive a new turning point ρ+. Since u1 is well behaved at infinity, there exists only the singularity in u2 at infinity, thus we employ a one- (rather than two-) dimensional change of dependent variable, ensuring that a uniform solution is obtained that avoids semiclassical breakdown on the Wannier ridge. The regularized final-state asymptotic wavefunction is employed, along with a continuum-distorted-wave approximation for the initial-state wavefunction to obtain total cross sections on an absolute scale.
Spectra Aerosol Light Scattering and Absorption for Laboratory and Urban Aerosol
NASA Astrophysics Data System (ADS)
Gyawali, Madhu S.
Atmospheric aerosols considerably influence the climate, reduce visibility, and cause problems in human health. Aerosol light absorption and scattering are the important factors in the radiation transfer models. However, these properties are associated with large uncertainties in climate modeling. In addition, atmospheric aerosols widely vary in composition and size; their optical properties are highly wavelength dependent. This work presents the spectral dependence of aerosol light absorption and scattering throughout the ultraviolet to near-infrared regions. Data were collected in Reno, NV from 2008 to 2010. Also presented in this study are the aerosol optical and physical properties during carbonaceous aerosols and radiative effects study (CARES) conducted in Sacramento area during 2010. Measurements were made using photoacoustic instruments (PA), including a novel UV 355 nm PA of our design and manufacture. Comparative analyses are presented for three main categories: (1) aerosols produced by wildfires and traffic emissions, (2) laboratory-generated and wintertime ambient urban aerosols, and (3) urban plume and biogenic emissions. In these categories, key questions regarding the light absorption by secondary organic aerosols (SOA), so-called brown carbon (BrC), and black carbon (BC) will be discussed. An effort is made to model the emission and aging of urban and biomass burning aerosol by applying shell-core calculations. Multispectral PA measurements of aerosols light absorption and scattering coefficients were used to calculate the Angstrom exponent of absorption (AEA) and single scattering albedo (SSA). The AEA and SSA values were analyzed to differentiate the aerosol sources. The California wildfire aerosols exhibited strong wavelength dependence of aerosol light absorption with AEA as lambda -1 for 405 and 870 nm, in contrast to the relatively weak wavelength dependence of traffic emissions aerosols for which AEA varied approximately as lambda-1. By using
Advances Toward Inner-Shell Photo-Ionization X-Ray Lasing at 45 (Angstrom)
Moon, S J; Weber, F A; Celliers, P M; Eder, D C
2002-07-18
The inner-shell photo-ionization (ISPI) scheme requires photon energies at least high enough to photo-ionize the K-shell. {approx}286 eV, in the case of carbon. As a consequence of the higher cross-section, the inner-shell are selectively knocked out, leaving a hole state 1s2s{sup 2}2p{sup 2} in the singly charged carbon ion. This generates a population inversion to the radiatively connected state 1s{sup 2}2s{sup 2}2p in C+, leading to gain on the 1s-2p transition at 45 {angstrom}. The resonant character of the lasing transition in the single ionization state intrinsically allows much higher quantum efficiency compared to other schemes. Competing processes that deplete the population inversion include auto-ionization, Auger decay, and in particular collisional ionization of the outer-shell electrons by electrons generated during photo-ionization. These competing processes rapidly quench the gain. Consequently, the pump method must be capable of populating the inversion at a rate faster than the competing processes. This can be achieved by an ultra-fast, high intensity laser that is able to generate an ultra-fast, bright x-ray source. With current advances in the development of high-power, ultra-short pulse lasers it is possible to realize fast x-ray sources based that can deliver powerful pulses of light in the multiple hundred terawatt regime and beyond. They will discuss in greater detail concept, target design and a series of x-ray spectroscopy investigations they have conducted in order to optimize the absorber/x-ray converter--filter package.
Exploring EUV Spicules Using 304 Angstrom He II Data from SDO AIA
NASA Technical Reports Server (NTRS)
Snyder, Ian R.; Sterling, Alphonse C.; Falconer, David A.; Moore, Ron L.
2014-01-01
We present results from a statistical study of He II 304 Angstrom Extreme Ultraviolet (EUV) spicules at the limb of the Sun. We also measured properties of one macrospicule; macrospicules are longer than most spicules, and much broader in width than spicules. We use high-cadence (12 second) and high-resolution (0.6 arcseconds pixels) resolution data from the Atmospheric Imaging Array (AIA) instrument on the Solar Dynamic Observatory (SDO). All of the observed events occurred near the solar north pole, where quiet Sun or coronal hole environments ensued. We examined the maximum lengths, maximum rise velocities, and lifetimes of 33 Extreme Ultraviolet (EUV) spicules and the macrospicule. For the bulk of the Extreme Ultraviolet (EUV) spicules these quantities are, respectively, approximately 10,000-40,000 kilometers, 20-100 kilometers per second, and approximately 100- approximately 1000 seconds. For the macrospicule the corresponding quantities were respectively approximately 60,000 kilometers, approximately 130 kilometers per second, approximately 1800 seconds, which is typical of macrospicules measured by other workers. Therefore macrospicules are taller, longer-lived, and faster than most Extreme Ultraviolet (EUV) spicules. The rise profiles of both the spicules and the macrospicules match well a second-order ("parabolic" ) trajectory, although the acceleration was often weaker than that of solar gravity in the profiles fitted to the trajectories. Our macrospicule also had an obvious brightening at its base at birth, while such brightening was not apparent for the Extreme Ultraviolet (EUV) spicules. Most of the Extreme Ultraviolet (EUV) spicules remained visible during their descent back to the solar surface, although a small percentage of the spicules and the macrospicule faded out before falling back to the surface. Our sample of macrospicules is not yet large enough to determine whether their initiation mechanism is identical to that of Extreme Ultraviolet (EUV
Lorenz, B.; Orgzall, I.; Dorhout, P.K.; Raymond, C.C.; Brister, K.; Weishaupt, K.; DAdamo, R.; Hochheimer, H.D.
1997-02-01
Cesium thiomolybdate, Cs{sub 2}MoS{sub 4}, has been investigated at pressures up to 12 GPa. Two phase transitions have been detected by absorption measurements, Raman spectroscopy, and energy dispersive x-ray diffraction. The first phase transition to a monoclinic phase II [a=14.061(9) {Angstrom}, b=11.552(7) {Angstrom}, c=9.852(6) {Angstrom}, {beta}=97.14(6){degree}] has been observed at 8.0 GPa. The second transition at 9.7 GPa has been observed from the monoclinic phase II to an orthorhombic phase III [a=12.085(4) {Angstrom}, b=15.707(6) {Angstrom}, c=11.828(5) {Angstrom}]. Absorption and luminescence measurements have indicated an increase in the absorption edge energy with pressure up to {approximately}3 GPa. At pressures greater than 3.5 GPa, the absorption energy decreases. Raman spectroscopy has revealed a low-frequency phonon mode with a negative pressure shift in the low-pressure phase I. The pressure-temperature phase diagram has been determined up to 250{degree}C. The transition pressures decrease linearly with slopes of {approximately}{minus}0.013 GPa/{degree}C. Models for the pressure-induced structural and electronic transitions are proposed. {copyright} {ital 1997} {ital The American Physical Society}
Analysis of cancellation exponents in two-dimensional Vlasov turbulence
De Vita, G.; Valentini, F.; Servidio, S.; Primavera, L.; Carbone, V.; Veltri, P.; Sorriso-Valvo, L.
2014-07-15
Statistical properties of plasma turbulence are investigated by means of two-dimensional Vlasov simulations. In particular, a classical technique called signed measure is used to characterize the scaling behavior and the topology of sign-oscillating structures in simulations of the hybrid Vlasov-Maxwell model. Exploring different turbulence regimes, varying both the plasma β and the level of fluctuations, it is observed that Vlasov turbulence manifests two ranges with different exponents, the transition being observed near the ion skin depth. These results, which may have applications to both laboratory and astrophysical systems, further confirm the singular nature of small scale fluctuations in a plasma, mainly classified as intermittent, narrow, and intense current sheets.
The Effect of the Underlying Distribution in Hurst Exponent Estimation
Sánchez, Miguel Ángel; Trinidad, Juan E.; García, José; Fernández, Manuel
2015-01-01
In this paper, a heavy-tailed distribution approach is considered in order to explore the behavior of actual financial time series. We show that this kind of distribution allows to properly fit the empirical distribution of the stocks from S&P500 index. In addition to that, we explain in detail why the underlying distribution of the random process under study should be taken into account before using its self-similarity exponent as a reliable tool to state whether that financial series displays long-range dependence or not. Finally, we show that, under this model, no stocks from S&P500 index show persistent memory, whereas some of them do present anti-persistent memory and most of them present no memory at all. PMID:26020942
Computation of entropy and Lyapunov exponent by a shift transform
Matsuoka, Chihiro; Hiraide, Koichi
2015-10-15
We present a novel computational method to estimate the topological entropy and Lyapunov exponent of nonlinear maps using a shift transform. Unlike the computation of periodic orbits or the symbolic dynamical approach by the Markov partition, the method presented here does not require any special techniques in computational and mathematical fields to calculate these quantities. In spite of its simplicity, our method can accurately capture not only the chaotic region but also the non-chaotic region (window region) such that it is important physically but the (Lebesgue) measure zero and usually hard to calculate or observe. Furthermore, it is shown that the Kolmogorov-Sinai entropy of the Sinai-Ruelle-Bowen measure (the physical measure) coincides with the topological entropy.
A Hyperchaotic Attractor with Multiple Positive Lyapunov Exponents
NASA Astrophysics Data System (ADS)
Hu, Guo-Si
2009-12-01
There are many hyperchaotic systems, but few systems can generate hyperchaotic attractors with more than three PLEs (positive Lyapunov exponents). A new hyperchaotic system, constructed by adding an approximate time-delay state feedback to a five-dimensional hyperchaotic system, is presented. With the increasing number of phase-shift units used in this system, the number of PLEs also steadily increases. Hyperchaotic attractors with 25 PLEs can be generated by this system with 32 phase-shift units. The sum of the PLEs will reach the maximum value when 23 phase-shift units are used. A simple electronic circuit, consisting of 16 operational amplifiers and two analogy multipliers, is presented for confirming hyperchaos of order 5, i.e., with 5 PLEs.
Spectrum-based estimators of the bivariate Hurst exponent.
Kristoufek, Ladislav
2014-12-01
We discuss two alternate spectrum-based estimators of the bivariate Hurst exponent in the power-law cross-correlations setting, the cross-periodogram and local X-Whittle estimators, as generalizations of their univariate counterparts. As the spectrum-based estimators are dependent on a part of the spectrum taken into consideration during estimation, a simulation study showing performance of the estimators under varying bandwidth parameter as well as correlation between processes and their specification is provided as well. These estimators are less biased than the already existent averaged periodogram estimator, which, however, has slightly lower variance. The spectrum-based estimators can serve as a good complement to the popular time domain estimators. PMID:25615143
Spectrum-based estimators of the bivariate Hurst exponent
NASA Astrophysics Data System (ADS)
Kristoufek, Ladislav
2014-12-01
We discuss two alternate spectrum-based estimators of the bivariate Hurst exponent in the power-law cross-correlations setting, the cross-periodogram and local X -Whittle estimators, as generalizations of their univariate counterparts. As the spectrum-based estimators are dependent on a part of the spectrum taken into consideration during estimation, a simulation study showing performance of the estimators under varying bandwidth parameter as well as correlation between processes and their specification is provided as well. These estimators are less biased than the already existent averaged periodogram estimator, which, however, has slightly lower variance. The spectrum-based estimators can serve as a good complement to the popular time domain estimators.
Computation of entropy and Lyapunov exponent by a shift transform
NASA Astrophysics Data System (ADS)
Matsuoka, Chihiro; Hiraide, Koichi
2015-10-01
We present a novel computational method to estimate the topological entropy and Lyapunov exponent of nonlinear maps using a shift transform. Unlike the computation of periodic orbits or the symbolic dynamical approach by the Markov partition, the method presented here does not require any special techniques in computational and mathematical fields to calculate these quantities. In spite of its simplicity, our method can accurately capture not only the chaotic region but also the non-chaotic region (window region) such that it is important physically but the (Lebesgue) measure zero and usually hard to calculate or observe. Furthermore, it is shown that the Kolmogorov-Sinai entropy of the Sinai-Ruelle-Bowen measure (the physical measure) coincides with the topological entropy.
Computation of entropy and Lyapunov exponent by a shift transform.
Matsuoka, Chihiro; Hiraide, Koichi
2015-10-01
We present a novel computational method to estimate the topological entropy and Lyapunov exponent of nonlinear maps using a shift transform. Unlike the computation of periodic orbits or the symbolic dynamical approach by the Markov partition, the method presented here does not require any special techniques in computational and mathematical fields to calculate these quantities. In spite of its simplicity, our method can accurately capture not only the chaotic region but also the non-chaotic region (window region) such that it is important physically but the (Lebesgue) measure zero and usually hard to calculate or observe. Furthermore, it is shown that the Kolmogorov-Sinai entropy of the Sinai-Ruelle-Bowen measure (the physical measure) coincides with the topological entropy. PMID:26520076
Characterizing heart rate variability by scale-dependent Lyapunov exponent
NASA Astrophysics Data System (ADS)
Hu, Jing; Gao, Jianbo; Tung, Wen-wen
2009-06-01
Previous studies on heart rate variability (HRV) using chaos theory, fractal scaling analysis, and many other methods, while fruitful in many aspects, have produced much confusion in the literature. Especially the issue of whether normal HRV is chaotic or stochastic remains highly controversial. Here, we employ a new multiscale complexity measure, the scale-dependent Lyapunov exponent (SDLE), to characterize HRV. SDLE has been shown to readily characterize major models of complex time series including deterministic chaos, noisy chaos, stochastic oscillations, random 1/f processes, random Levy processes, and complex time series with multiple scaling behaviors. Here we use SDLE to characterize the relative importance of nonlinear, chaotic, and stochastic dynamics in HRV of healthy, congestive heart failure, and atrial fibrillation subjects. We show that while HRV data of all these three types are mostly stochastic, the stochasticity is different among the three groups.
GPU and APU computations of Finite Time Lyapunov Exponent fields
NASA Astrophysics Data System (ADS)
Conti, Christian; Rossinelli, Diego; Koumoutsakos, Petros
2012-03-01
We present GPU and APU accelerated computations of Finite-Time Lyapunov Exponent (FTLE) fields. The calculation of FTLEs is a computationally intensive process, as in order to obtain the sharp ridges associated with the Lagrangian Coherent Structures an extensive resampling of the flow field is required. The computational performance of this resampling is limited by the memory bandwidth of the underlying computer architecture. The present technique harnesses data-parallel execution of many-core architectures and relies on fast and accurate evaluations of moment conserving functions for the mesh to particle interpolations. We demonstrate how the computation of FTLEs can be efficiently performed on a GPU and on an APU through OpenCL and we report over one order of magnitude improvements over multi-threaded executions in FTLE computations of bluff body flows.
Skeleton graph expansion of critical exponents in "cultural revolution" years
NASA Astrophysics Data System (ADS)
Hao, Bailin
Kenneth Wilson's Nobel Prize winning breakthrough in the renormalization group theory of phase transition and critical phenomena almost overlapped with the violent "cultural revolution" years (1966-1976) in China. An unexpected chance in 1972 brought the author of these lines close to the Wilson-Fisher є-expansion of critical exponents and eventually led to a joint paper with Lu Yu published entirely in Chinese without any English title and abstract. Even the original acknowledgment was deleted because of mentioning foreign names like Kenneth Wilson and Kerson Huang. In this article I will tell the 40-year old story as a much belated tribute to Kenneth Wilson and to reproduce the essence of our work in English. At the end, I give an elementary derivation of the Callan-Symanzik equation without referring to field theory.
Hybrid Percolation Transition in Cluster Merging Processes: Continuously Varying Exponents.
Cho, Y S; Lee, J S; Herrmann, H J; Kahng, B
2016-01-15
Consider growing a network, in which every new connection is made between two disconnected nodes. At least one node is chosen randomly from a subset consisting of g fraction of the entire population in the smallest clusters. Here we show that this simple strategy for improving connection exhibits a more unusual phase transition, namely a hybrid percolation transition exhibiting the properties of both first-order and second-order phase transitions. The cluster size distribution of finite clusters at a transition point exhibits power-law behavior with a continuously varying exponent τ in the range 2<τ(g)≤2.5. This pattern reveals a necessary condition for a hybrid transition in cluster aggregation processes, which is comparable to the power-law behavior of the avalanche size distribution arising in models with link-deleting processes in interdependent networks. PMID:26824550
Spectral dependence of aerosol light absorption over the Amazon Basin
NASA Astrophysics Data System (ADS)
Rizzo, L. V.; Correia, A. L.; Artaxo, P.; Procópio, A. S.; Andreae, M. O.
2011-09-01
In this study, we examine the spectral dependence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pasture site (Fazenda Nossa Senhora, Rondônia) and at a primary forest site (Cuieiras Reserve, Amazonas), from 1999 to 2004. Aerosol absorption spectra were measured using two Aethalometers: a 7-wavelength Aethalometer (AE30) that covers the visible (VIS) to near-infrared (NIR) spectral range, and a 2-wavelength Aethalometer (AE20) that measures absorption in the UV and in the NIR. As a consequence of biomass burning emissions, about 10 times greater absorption values were observed in the dry season in comparison to the wet season. Power law expressions were fitted to the measurements in order to derive the absorption Ångström exponent, defined as the negative slope of absorption versus wavelength in a log-log plot. At the pasture site, about 70 % of the absorption Ångström exponents fell between 1.5 and 2.5 during the dry season, indicating that biomass burning aerosols have a stronger spectral dependence than soot carbon particles. Ångström exponents decreased from the dry to the wet season, in agreement with the shift from biomass burning aerosols, predominant in the fine mode, to biogenic and dust aerosols, predominant in the coarse mode. The lowest absorption Ångström exponents (90 % of data below 1.5) were observed at the forest site during the dry season. Also, results indicate that low absorption coefficients were associated with low Ångström exponents. This finding suggests that biogenic aerosols from Amazonia have a weaker spectral dependence for absorption than biomass burning aerosols, contradicting our expectations of biogenic particles behaving as brown carbon. In a first order assessment, results indicate a small (<1 %) effect of variations in absorption Ångström exponents on 24-h aerosol forcings, at least in the spectral
NASA Astrophysics Data System (ADS)
Srinivas, B.; Rastogi, N.; Sarin, M. M.; Singh, A.; Singh, D.
2016-01-01
The mass absorption efficiency (MAE) of light absorbing water-soluble organics, representing a significant fraction of brown carbon (BrC), has been studied in fine mode aerosols (PM2.5) from a source region (Patiala: 30.2 °N, 76.3 °E) of biomass burning emissions (BBEs) in the Indo-Gangetic Plain (IGP). The mass absorption coefficient of BrC at 365 nm (babs-365), assessed from absorption spectra of aqueous extracts, exhibits significant linear relationship with water-soluble organic carbon (WSOC) for day (R2 = 0.37) and night time (R2 = 0.77) samples; and slope of regression lines provides a measure of MAE of BrC (daytime: ˜0.75 m2 g-1 and night time: 1.13 m2 g-1). A close similarity in the temporal variability of babs-365 (for BrC) and K+ in all samples suggests their common source from BBEs. The babs-365 of BrC follows a power law (babs-λ ≈ λ-α; where α = angstrom exponent) and averages around 5.2 ± 2.0 M m-1 (where M = 10-6). A significant decrease in the MAE of BrC from the source region (this study) to the downwind oceanic region (over Bay of Bengal, Srinivas and Sarin, 2013) could be attributed to relative increase in the contribution of non-absorbing WSOC and/or photo-bleaching of BrC during long-range atmospheric transport. The atmospheric radiative forcing due to BrC over the study site accounts for ˜40% of that from elemental carbon (EC).
NASA Technical Reports Server (NTRS)
Rigby, Jane Rebecca; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.
2014-01-01
We examine the Mg II 2796, 2803 Angstrom, Lyman alpha, and nebular line emission in five bright star-forming galaxies at 1.66 less than z less than 1.91 that have been gravitationally lensed by foreground galaxy clusters. All five galaxies show prominent Mg II emission and absorption in a P Cygni profile. We find no correlation between the equivalent widths of Mg II and Lyman alpha emission. The Mg II emission has a broader range of velocities than do the nebular emission line profiles; the Mg II emission is redshifted with respect to systemic by 100 to 200 km s(exp-1). When present, Lyman alpha is even more redshifted. The reddest components of Mg II and Lyman alpha emission have tails to 500-600 km s(exp-1), implying a strong outflow. The lack of correlation in the Mg II and Lyman alpha equivalent widths, the differing velocity profiles, and the high ratios of Mg II to nebular line fluxes together suggest that the bulk of Mg II emission does not ultimately arise as nebular line emission, but may instead be reprocessed stellar continuum emission.
Fedin, D.A.; Fedorchuk, R.V.; Koshevoi, M.O.; Lukjantsev, I.V.; Rupasov, A.A.; Shikanov, A.S.; Gullikson, E.
1995-12-31
Investigations of spectral sensitivity, contrast coefficient, and spatial resolution of widely used x-ray films have been undertaken at the P.N. Lebedev Institute. A description of experimental methodologies and results are presented. These studies were carried out using synchrotron radiation in the range of 20--150 {angstrom}. Spectral sensitivity and contrast coefficient dependencies on wavelength for Kodak 10106, DEF, RAR2490, and TPF films and spatial resolution for Kodak 10106 and RAR2490 films are presented and discussed.
Xue, G.; Wang, D.; Hont, R.De; Fiedler, A.T.; Shan, X.; Munck, E.; Que, L.; Jr.
2009-06-04
Intermediate Q, the methane-oxidizing species of soluble methane monooxygenase, is proposed to have an [Fe{sup IV}{sub 2}({mu}-O){sub 2}] diamond core. In an effort to obtain a synthetic precedent for such a core, bulk electrolysis at 900 mV (versus Fc{sup +/0}) has been performed in MeCN at -40{sup o}C on a valence-delocalized [Fe{sup III}Fe{sup IV}({mu}-O){sub 2}(L{sup b}){sub 2}]{sup 8+} complex (1b) (E{sub 1/2} = 760 mV versus Fc{sup +/0}). Oxidation of 1b results in the near-quantitative formation of a deep red complex, designated 2b, that exhibits a visible spectrum with {lambda}{sub max} at 485 nm (9,800 M{sup -1}{center_dot}cm{sup -1}) and 875 nm (2,200 M{sup -1}{center_dot}cm{sup -1}). The 4.2 K Moessbauer spectrum of 2b exhibits a quadrupole doublet with {delta} = -0.04(1) mm{center_dot}s{sup -1} and {Delta}E{sub Q} = 2.09(2) mm{center_dot}s{sup -1}, parameters typical of an iron(IV) center. The Moessbauer patterns observed in strong applied fields show that 2b is an antiferromagnetically coupled diiron(IV) center. Resonance Raman studies reveal the diagnostic vibration mode of the [Fe{sub 2}({mu}-O){sub 2}] core at 674 cm{sup -1}, downshifting 30 cm{sup 01} upon {sup 18}O labeling. Extended x-ray absorption fine structure (EXAFS) analysis shows two O/N scatterers at 1.78 {angstrom} and an Fe scatterer at 2.73 {angstrom}. Based on the accumulated spectroscopic evidence, 2b thus can be formulated as [Fe{sup IV}{sub 2}({mu}-O){sub 2}(L{sup b}){sub 2}]{sup 4+}, the first synthetic complex with an [Fe{sup IV}{sub 2}({mu}-O){sub 2}] core. A comparison of 2b and its mononuclear analog [Fe{sup IV}(O)(L{sup b})(NCMe)]{sup 2+} (4b) reveals that 4b is 100-fold more reactive than 2b in oxidizing weak C-H bonds. This surprising observation may shed further light on how intermediate Q carries out the hydroxylation of methane.
Fractal Aircraft Trajectories, Scaling Stratification, Nonclassical Turbulent Exponents
NASA Astrophysics Data System (ADS)
Lovejoy, S.; Schertzer, D.; Tuck, A.
2004-05-01
The dimension (D) of aircraft trajectories is fundamental in interpretating airborne data. To estimate D, we studied data from 18 trajectories of stratospheric aircraft flights 1600km long taken during a "Mach cruise" (near constant Mach number) autopilot flight mode. Mach cruise implies correlated temperature and wind fluctuations so that ?Z??xHz where Z is the (fluctuating) vertical and x the horizontal coordinate of the aircraft. Over the range ? 3 to 300km, we found Hz? 0.58±0.02 close to the theoretical 5/9=0.56 and implying D=1+Hz = 14/9 i.e. the trajectories are fractal. For distances <3km aircraft inertia smooths the trajectories, for distances > 300km, D=1 again because of a rise of 1m/km due to fuel consumption. In the fractal regime, the horizontal velocity and temperature exponents are close to the nonclassical fractal value HF=1/2 (rather than the Kolmogorov value HK=1/3). Taking into account (multifractal) intermittency corrections, this implies the corresponding spectral slopes =1.9. We also discuss ESS and cross-ESS estaimtes of multfractal exponents. We show that there exists a critical average trajectory slope s=(?x/ls)Hz-1; when the aircraft exceeds this, the velocity, temperature fluctuations are dominated by the vertical rather than horizontal statistics; ls is the scale where average horizontal and vertical temperature and velocity fluctuations are equal, we find it to be ?4cm (although it fluctuates depending on energy and buoyancy force variance fluxes). At this scale, even even small deviations from perfectly flat horizontal trajectories (of the order of 1m/km) will lead to Bolgiano-Obhukov (HBO=3/5)) rather than HF= or HK. We show that this can explain recently published data from MOZAIC; we also review over a dozen other aircraft and radiosonde experiments showing that they are all compatible with the 23/9 dimensional unified scaling model. Finally we compare this with some direct estimates of Hz from passive scalar surrogates (lidar
Ultraviolet observations of Uranus and Neptune below 3,000 Angstrom
Caldwell, J.; Wagener, R.
1984-10-01
From 2000 to 3000 A, both Uranus and Neptune have albedos that are about two times higher than Jupiter or Saturn's, implying that the outer giants have stratospheres that are relatively free of aerosol absorption. Uncertainties in the absolute calibration procedure allow discrepancies of order 15% between conservative models and the observations. A small amount of aerosol absorption is therefore possible. Below 2000 A the derived albedo is highly dependent on the solar spectrum source used in the data reduction. The most recent result for Uranus, first reported here, is consistent with a secular change in C2H2 mixing ratio from approximately three times ten to the minus eight in 1980 to less than or equal to ten to the minus ninth in 1983. These values are approximately 2 orders of magnitude less than the mixing ratios of this gas on Saturn, and comparable to the amount on Jupiter.
Search for Lyman Limit Absorption Edge in Quasar Continuum
NASA Astrophysics Data System (ADS)
Sun, W.-H.; Malkan, M. A.; Chang, Thomas H. W.
1993-12-01
We examine the low resolution UV spectra of the 37 quasars in HST Key Project to search for intrinsic Lyman absorption edge which may be a signature of thermal accretion disks. Only 28 QSOs have proper redshifts to place the region of interest in the G160L window. We fit the L_β with two gaussians to remove the line. We then avoid 20 and 50 Angstroms on the blue and red sides of 912 Angstroms in the rest frame, and take 80 Angstroms bins (rest frame) on both sides but further out for analysis. We compare the single power-law fitting (to the entire range across the edge), with the two power-law fitting to blue and red bands. We also measure the percentage drop of flux over the Lyman limit. There are 7 objects with intrinsically noisy spectra, which were presumably caused by intervening Lyman absorption systems. Applying the two methods on the rest 21 objects, we found {24%} candidates to have possible rest frame Lyman limit absorption edges. Same analyses have also been performed on optical spectra of medium- to high-redshift QSOs from Lick Observatory and Hale Observatory. Similar results were also found.
Ostlund, Richard E
2002-03-01
Cholesterol absorption is a key regulatory point in human lipid metabolism because it determines the amount of endogenous biliary as well as dietary cholesterol that is retained, thereby influencing whole body cholesterol balance. Plant sterols (phytosterols) and the drug ezetimibe reduce cholesterol absorption and low-density lipoprotein cholesterol in clinical trials, complementing the statin drugs, which inhibit cholesterol biosynthesis. The mechanism of cholesterol absorption is not completely known but involves the genes ABC1, ABCG5, and ABCG8, which are members of the ATP-binding cassette protein family and appear to remove unwanted cholesterol and phytosterols from the enterocyte. ABC1 is upregulated by the liver X (LXR) and retinoid X (RXR) nuclear receptors. Acylcholesterol acytransferase-2 is an intestinal enzyme that esterifies absorbed cholesterol and increases cholesterol absorption when dietary intake is high. New clinical treatments based on better understanding of absorption physiology are likely to substantially improve clinical cholesterol management in the future. PMID:17033296
Ubeyli, Elif Derya
2008-01-01
The implementation of probabilistic neural networks (PNNs) with the Lyapunov exponents for Doppler ultrasound signals classification is presented. This study is directly based on the consideration that Doppler ultrasound signals are chaotic signals. This consideration was tested successfully using the nonlinear dynamics tools, like the computation of Lyapunov exponents. Decision making was performed in two stages: computation of Lyapunov exponents as representative features of the Doppler ultrasound signals and classification using the PNNs trained on the extracted features. The present research demonstrated that the Lyapunov exponents are the features which well represent the Doppler ultrasound signals and the PNNs trained on these features achieved high classification accuracies. PMID:17709103
Equifinality and the Scaling Exponent of the Structure Function
NASA Astrophysics Data System (ADS)
Fitton, G. F.; Mezematy, Y.; Schertzer, D. J. M.; Tchiguirinskaia, I.
2014-12-01
In turbulence the structure function is by far the most widely used tool for the empirical analysis of the velocity field. This is due mainly to the work of Kolmogorov (1941) who hypothesised a homogeneous flux of energy and derived the famous 2/3 power law for the second-order structure function; — which corresponds to a 5/3 law for the energy spectrum (Obukhov, 1942). In 1962 Kolmogorov refined his hypothesis to take into account the intermittency of the flux, with the consequence that the exponent ξ(q) of the structure function is not longer proportional to its statistical order q. In this communication, we first show that the refined hypothesis can lead to different models that can have opposite intermittency corrections. Secondly, we demonstrate that the inverse problem, i.e., starting from a given expression of ξ(q) to recover the involved flux leads to an interesting problem of equifinality for the definition of this flux. This is done in particular in the framework of the Fractionally Integrated Flux model that gives a precise meaning to the refined hypothesis. The theoretical and practical consequences are illustrated with the help data analysis and simulations of turbulence in wind farms and urban lakes.
An Eulerian approach for computing the finite time Lyapunov exponent
NASA Astrophysics Data System (ADS)
Leung, Shingyu
2011-05-01
We propose efficient Eulerian methods for approximating the finite-time Lyapunov exponent (FTLE). The idea is to compute the related flow map using the Level Set Method and the Liouville equation. There are several advantages of the proposed approach. Unlike the usual Lagrangian-type computations, the resulting method requires the velocity field defined only at discrete locations. No interpolation of the velocity field is needed. Also, the method automatically stops a particle trajectory in the case when the ray hits the boundary of the computational domain. The computational complexity of the algorithm is O(Δ x-( d+1) ) with d the dimension of the physical space. Since there are the same number of mesh points in the x- t space, the computational complexity of the proposed Eulerian approach is optimal in the sense that each grid point is visited for only O(1) time. We also extend the algorithm to compute the FTLE on a co-dimension one manifold. The resulting algorithm does not require computation on any local coordinate system and is simple to implement even for an evolving manifold.
Lyapunov exponents for the Miles’ spherical pendulum equations
NASA Astrophysics Data System (ADS)
Tritton, D. J.; Groves, M.
1999-02-01
Lyapunov exponents and hence the Lyapunov dimension have been evaluated for the equations developed by Miles [Quart. Appl. Math. 20 (1962) 21; Physica D 11 (1984) 309] as an approximation to the equations of motion of a spherical pendulum forced at a frequency close to its natural frequency. Computations have been performed throughout the frequency range in which there are no stable fixed points and a little on either side of this range, for various values of the damping parameter. The results include: strong dependence on the damping of both the probability of finding chaotic motion and the typical Lyapunov dimension of such motion; the co-existence of alternative types of attractor in regions both inside and outside the range with no stable fixed points; and the occurrence of metastable chaos. The transitions to chaos at either end of a limit cycle window, chosen as one that has also been observed in the laboratory, have been explored in some detail. The results are compared with other computations and with observations with laboratory pendulums, and the implications of the results for future laboratory studies are discussed. Some results are presented for the mathematically related problem of liquid surface waves in a vibrating cylinder.
[A Standing Balance Evaluation Method Based on Largest Lyapunov Exponent].
Liu, Kun; Wang, Hongrui; Xiao, Jinzhuang; Zhao, Qing
2015-12-01
In order to evaluate the ability of human standing balance scientifically, we in this study proposed a new evaluation method based on the chaos nonlinear analysis theory. In this method, a sinusoidal acceleration stimulus in forward/backward direction was forced under the subjects' feet, which was supplied by a motion platform. In addition, three acceleration sensors, which were fixed to the shoulder, hip and knee of each subject, were applied to capture the balance adjustment dynamic data. Through reconstructing the system phase space, we calculated the largest Lyapunov exponent (LLE) of the dynamic data of subjects' different segments, then used the sum of the squares of the difference between each LLE (SSDLLE) as the balance capabilities evaluation index. Finally, 20 subjects' indexes were calculated, and compared with evaluation results of existing methods. The results showed that the SSDLLE were more in line with the subjects' performance during the experiment, and it could measure the body's balance ability to some extent. Moreover, the results also illustrated that balance level was determined by the coordinate ability of various joints, and there might be more balance control strategy in the process of maintaining balance. PMID:27079089
Decadal ENSO variability as reflected by Local Lyapunov Exponents
NASA Astrophysics Data System (ADS)
Karamperidou, C.; Cane, M. A.; Wittenberg, A. T.; Lall, U.; Di Nezio, P. N.
2011-12-01
Decadal variability of ENSO is present in historical and paleo records, and has been simulated by a hierarchy of dynamical and statistical models. The ENSO variability in the IPCC AR4 Coupled GCMs ranges from constant periodicity or amplitude to significant inter-decadal variability in both period and amplitude. While long runs of intermediate dynamical models that exhibit inter-decadal and inter-centennial variability, such as the ZC model, have been a subject of numerous studies, only recently have long runs of coupled GCMs, such as the GFDL CM2.1 2000-yr control run, become available. The presence of such rich variability in the absence of external forcing that could induce persistent regimes, along with the length of the simulation, provides new ground for investigation of the causes of long-term modulation of ENSO behavior and the implications for predictability at multiple time-scales from the short-range to the decadal. In this work, we investigate ENSO predictability in long unforced runs of a fully coupled GCM (GFDL's CM2.1) and the intermediate ZC model in a dynamical systems theory context. We compute the Local Lyapunov Exponents (LLEs) of the NINO3 time series, and use them as a means of classifying epochs of distinct ENSO behavior. The 'loss' or 'gain' of predictability across these epochs and their relation to the physical evolution of the ENSO events is examined. The correspondence of the LLE statistics with prediction error in 'perfect-model' reforecasts is also discussed.
NASA Astrophysics Data System (ADS)
Kanda, Yoshihiko; Kariya, Yoshiharu; Oto, Yuji
2012-03-01
The fatigue ductility exponent in the Coffin-Manson law for a Sn-Ag-Cu micro-solder joint was investigated in terms of the cyclic strain-hardening property and the inelastic strain energy in fracture for isothermal fatigue. The fatigue ductility exponent was found to increase with temperature and holding time under strain at high temperature. This exponent is closely related to the cyclic strain-hardening exponent, which displays the opposite behavior in that it decreases with increasing temperature and with coarsening of intermetallic compound particles while holding under strain at high temperature. This result differs from the creep damage mechanism (grain boundary fracture), which is a primary reason for the significant reduction in fatigue life for all strain ranges for large-size specimens.
NASA Astrophysics Data System (ADS)
Kim, H.; Zhang, Q.; Young, D. E.; Parworth, C.
2015-12-01
Light absorption properties of water soluble organic aerosol were investigated at Fresno, CA from 13 January to 11 February, 2013 as part of the NASA DISCOVER-AQ campaign. The light absorption spectra of water soluble organic aerosol in PM2.5 was measured using a UV/vis diode array detector (DAD) coupled with a particle into liquid sampler (PILS) that sampled downstream of a PM2.5 cyclone (URG). The PILS was also coupled with two ion chromatographs (IC) to measure inorganic and organic ionic species in PM2.5. In addition, an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed at the same site to measure size-resolved chemical composition of submicrometer aerosol (PM1) in real time during this study. Light absorption at 365 nm (Abs365), which is typically used as a proxy of water-soluble brown carbon (BrC), showed strong enhancement during night time and appeared to correlate well (r = 0.71) with biomass burning organic aerosol (BBOA) from residential wood burning for heating in the Fresno area. The tight correlations between Abs365 and biomass burning relevant tracers such as acetonitrile (r = 0.69), AMS-signature ions for phenolic compounds (r = 0.52-0.71), PAH (r = 0.74), and potassium (r = 0.67) further confirm that biomass burning contributed significantly to water soluble brown carbon during this study. The absorption angstrom exponent (Åa) values fitted between 300 and 700 nm wavelength were 3.3 ± 1.1, 2.0 ± 0.9 and 4.0 ± 0.8, respectively, in the morning, afternoon and nighttime, indicating that BrC is prevalent at night in Fresno during wintertime. However, there are also indications that small amount of BrC existed during the daytime as well, likely due to daytime wood burning and other sources such as the formation of light-absorbing secondary organic aerosol (SOA). Finally, light absorption at 300 nm, 330 nm, and 390 nm were found to correlate tightly with BBOA, which indicate that biomass burning also emits
Research and development toward a 4.5-1.5{angstrom} linac coherent light source (LCLS) at SLAC
Tatchyn, R.; Arthur, J.; Baltay, M.
1995-12-31
In recent years significant studies have been initiated on the theoretical and technical feasibility of utilizing a portion of the 3km S-band accelerator at the Stanford Linear Accelerator Center (SLAC) to drive a short wavelength (4.5-1.5 {Angstrom}) Linac Coherent Light Source (LCLS), a Free-Electron Laser (FEL) operating in the Self-Amplified Spontaneous Emission (SASE) regime. Electron beam requirements for single-pass saturation include: (1) a peak current in the 3-7 kA range, (2) a relative energy spread of <0.05%, ad (3) a transverse emittance, {epsilon}{le}{lambda}/4{pi}, where {lambda}[m] is the output wavelength. Requirements on the insertion device include field error levels of 0.1-0.2% for keeping the electron bunch centered on and in phase with the amplified photons, and a focusing beta of 4-8 m for inhibiting the dilution of its transverse density. Although much progress techniques necessary for LCLS operation down to {approximately}20 {angstrom}, a substantial amount of research and development is still required in a number of theoretical and experimental areas leading to the construction and operation of a 4.5-1.5 {angstrom} LCLS. In this paper we report on a research and development program underway and in planning at SLAC for addressing critical questions in these areas. These include the construction and operation of a linac test stand for developing laser-driven photocathode rf guns with normalized emittances approaching 1 mm-mr; development of advanced beam compression, stability, an emittance control techniques at multi-GeV energies; the construction and operation of a FEL Amplifier Test Experiment (FATE) for theoretical and experimental studies of SASE at IR wavelengths; an undulator development program to investigate superconducting, hybrid/permanent magnet (hybrid/PM), and pulsed-Cu technologies; theoretical and computational studies of high-gain FEL physics and LCLS component designs.
NASA Astrophysics Data System (ADS)
Lan, Zi-Juan; Huang, Xiao-Feng; Yu, Kuang-You; Sun, Tian-Le; Zeng, Li-Wu; Hu, Min
2013-04-01
The effects of black carbon (BC) aerosol on climate warming have been the study focus in the recent decade, and the reduction of BC is now expected to have significant near-term climate change mitigation. Large uncertainties of BC optical properties, however, still exist and seriously restrict the ability to quantify BC's climate effects. In this study, advanced instrumentation (a three-wavelength photoacoustic soot spectrometer (PASS-3) and a single particle soot photometer (SP2)) were used to measure black carbon aerosol and analyze its optical properties in a mega-city in South China, Shenzhen, during the summer of 2011. The results indicated that the average BC mass concentration was 4.0 ± 3.1 μg m-3 during the campaign, accounting for ˜11% of the total PM2.5 mass concentration. The PM2.5 light absorption at 405, 532 and 781 nm was 37.1 ± 28.1, 25.4 ± 19.0 and 17.6 ± 12.9 Mm-1, respectively. The average absorption Angstrom exponent of PM2.5 in visual spectrum (AAE405-781 nm) was 1.1 ± 0.1 during the campaign, indicating that the light absorbing carbon mainly came from vehicular emissions, with little contributions from biomass burning emissions. The mass absorption efficiency (MAE) of BC at 532 nm ranged from 5.0 to 8.5 m2 g-1 during the campaign, with an average of 6.5 ± 0.5 m2 g-1, and showed an obvious diurnal pattern with high values in the daytime. The average percentage of internally mixed BC was 24.3 ± 7.9% during the campaign, showing significant positive correlation relationship with the MAE of BC. More quantitative data analysis indicated that the internally mixed BC would amplify MAE by about 7% during the campaign, which stands in accordance with the new finding of a very recent Science magazine paper (Cappa et al., 2012) that the BC absorption enhancement due to internal mixing in the real atmosphere is relatively low, in apparent contrast to theoretical model predictions.
Hurst exponent and prediction based on weak-form efficient market hypothesis of stock markets
NASA Astrophysics Data System (ADS)
Eom, Cheoljun; Choi, Sunghoon; Oh, Gabjin; Jung, Woo-Sung
2008-07-01
We empirically investigated the relationships between the degree of efficiency and the predictability in financial time-series data. The Hurst exponent was used as the measurement of the degree of efficiency, and the hit rate calculated from the nearest-neighbor prediction method was used for the prediction of the directions of future price changes. We used 60 market indexes of various countries. We empirically discovered that the relationship between the degree of efficiency (the Hurst exponent) and the predictability (the hit rate) is strongly positive. That is, a market index with a higher Hurst exponent tends to have a higher hit rate. These results suggested that the Hurst exponent is useful for predicting future price changes. Furthermore, we also discovered that the Hurst exponent and the hit rate are useful as standards that can distinguish emerging capital markets from mature capital markets.
NASA Technical Reports Server (NTRS)
Horai, K.-I.
1981-01-01
A theory of the measurement of the thermal diffusivity of a sample by the modified Angstrom method is developed for the case in which radiative heat loss from the end surface of the sample is not negligible, and applied to measurements performed on lunar samples. Formulas allowing sample thermal diffusivity to be determined from the amplitude decay and phase lag of a temperature wave traveling through the sample are derived for a flat disk sample for which only heat loss from the end surface is important, and a sample of finite diameter and length for which heat loss through the end and side surfaces must be considered. It is noted that in the case of a flat disk, measurements at a single angular frequency of the temperature wave are sufficient, while the sample of finite diameter and length requires measurements at two discrete angular frequencies. Comparison of the values of the thermal diffusivities of two lunar samples of dimensions approximately 1 x 1 x 2 cm derived by the present methods and by the Angstrom theory for a finite bar reveals them to differ by not more than 5%, and indicates that more refined data are required as the measurement theory becomes more complicated.
Structure of Acid-Sensing Ion Channel 1 at 1.9 angstrom Resolution and Low pH
Jasti,J.; Furukawa, H.; Gonzales, E.; Gouaux, E.
2007-01-01
Acid-sensing ion channels (ASICs) are voltage-independent, proton-activated receptors that belong to the epithelial sodium channel/degenerin family of ion channels and are implicated in perception of pain, ischaemic stroke, mechanosensation, learning and memory. Here we report the low-pH crystal structure of a chicken ASIC1 deletion mutant at 1.9 Angstroms resolution. Each subunit of the chalice-shaped homotrimer is composed of short amino and carboxy termini, two transmembrane helices, a bound chloride ion and a disulphide-rich, multidomain extracellular region enriched in acidic residues and carboxyl-carboxylate pairs within 3 Angstroms, suggesting that at least one carboxyl group bears a proton. Electrophysiological studies on aspartate-to-asparagine mutants confirm that these carboxyl-carboxylate pairs participate in proton sensing. Between the acidic residues and the transmembrane pore lies a disulphide-rich 'thumb' domain poised to couple the binding of protons to the opening of the ion channel, thus demonstrating that proton activation involves long-range conformational changes.
Merits of a sub-harmonic approach to a single-pass, 1.5-{Angstrom} FEL
Fawley, W.M.; Nuhn, H.D.; Bonifacio, R.; Scharlemann, E.T.
1995-03-01
SLAC/SSRL and collaborators elsewhere are studying th physics of a single-pass, FEL amplifier operating in th 1 -- 2 {Angstrom}, wavelength region based on electron beams from the SLAC linac at {approximately} 15 GeV energy. Hoping to reduce the total wiggler length needed to reach saturation when starting from shot noise, we have examined the benefits of making the first part of the wiggler resonant at a subharmonic wavelength (e.g. 4.5 {Angstrom}) at which the gain length can be significantly shorter. This leads to bunching of the electron beam at both the subharmonic and fundaments wavelengths, thus providing a strong coherent ``seed`` for exponential growth of radiation at the fundamental in the second part of the wiggler. Using both multi-harmonic and multi-frequency 2D FEL simulation codes, we have examined the predicted performance of such devices and the sensitivity to electron beam parameters such as current, emittance, and instantaneous energy spread.
NASA Technical Reports Server (NTRS)
Beegle, L. W.; Wdowiak, T. J.; Robinson, M. S.; Cronin, J. R.; McGehee, M. D.; Clemett, S. J.; Gillette, S.
1997-01-01
Experiments where the simple polycyclic aromatic hydrocarbon (PAH) naphthalene (C10H8) is subjected to the energetic environment of a plasma have resulted in the synthesis of a molecular aggregate that has ultraviolet spectral characteristics that suggest it provides insight into the nature of the carrier of the 2175 angstroms interstellar extinction feature and may be a laboratory analog. Ultraviolet, visible, infrared, and mass spectroscopy, along with gas chromatography, indicate that it is a molecular aggregate in which an aromatic double ring ("naphthalene") structural base serves as the electron "box" chromophore that gives rise to the envelope of the 2175 angstroms feature. This chromophore can also provide the peak of the feature or function as a mantle in concert with another peak provider such as graphite. The molecular base/chromophore manifests itself both as a structural component of an alkyl-aromatic polymer and as a substructure of hydrogenated PAH species. Its spectral and molecular characteristics are consistent with what is generally expected for a complex molecular aggregate that has a role as an interstellar constituent.
Koppel, L.; Barbee, T.W. Jr.
1980-08-06
Layered synthetic microstructures have been built and tested for use as medium-resolution x-ray diffraction monochromators, in the 1 to 10 angstrom wavelength region. They can be employed to good advantage in spectrometry and imaging instruments that are used to determine the nature of the x-ray emission of high-temperature plasmas. When the micro-structures are used in spectrometers, we find that they gather much more light than natural crystals and are not troubled by high order diffraction response, yet have better spectral resolution than that provided by spectrometer channels formed by Ross filter or filter/fluorescer techniques. For use in imaging instruments such as the grazing-incidence reflection Kirkpatrick-Baez microscope, the microstructures provide high reflectivity at wavelengths shorter than the practical limit of total external reflection. We will present calibration data that describes the diffraction properties and piece-to-piece uniformity of microstructures built especially for use in the 1 to 10 angstrom region. We will also describe in detail two instruments that will be used at the Shiva laser system to determine the spectral and spatial distributions of x-rays radiated by inertial confinement fusion targets.
Gupta,K.; Selinsky, B.; Loll, P.
2006-01-01
Prostaglandin H{sub 2} synthase (EC 1.14.99.1) is a clinically important drug target that catalyzes two key steps in the biosynthesis of the eicosanoid hormones. The enzyme contains spatially distinct cyclooxygenase and peroxidase active sites, both of which require a heme cofactor. Substitution of ferric heme by Mn{sup III} protoporphyrin IX greatly diminishes the peroxidase activity, but has little effect on the cyclooxygenase activity. Here, the 2.0 Angstrom resolution crystal structure of the Mn{sup III} form of ovine prostaglandin H{sub 2} synthase-1 is described (R = 21.8%, R{sub free} = 23.7%). Substitution of Mn{sup III} for Fe{sup III} causes no structural perturbations in the protein. However, the out-of-plane displacement of the manganese ion with respect to the porphyrin is greater than that of the iron by approximately 0.2 Angstroms. This perturbation may help to explain the altered catalytic properties of the manganese enzyme.
Spectral dependence of aerosol light absorption over the Amazon Basin
NASA Astrophysics Data System (ADS)
Rizzo, L. V.; Correia, A. L.; Artaxo, P.; Procópio, A. S.; Andreae, M. O.
2011-04-01
In this study, we examine the spectral dependence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pasture site (Fazenda Nossa Senhora, Rondônia) and at a primary forest site (Cuieiras Reserve, Amazonas), from 1999 to 2004. Aerosol absorption spectra were measured using two Aethalometers: a 7-wavelength Aethalometer (AE30) that covers the visible (VIS) to near-infrared (NIR) spectral range, and a 2-wavelength Aethalometer (AE20) that measures absorption in the UV and in the visible. As a consequence of biomass burning emissions, about 10 times greater absorption values were observed in the dry season in comparison to the wet season. Power law expressions were fitted to the measurements in order to derive the Ångström exponent for absorption, defined as the negative slope of absorption vs. wavelength in a log-log plot. At the pasture site, about 70% of the Ångström exponents fell between 1.5 and 2.5 during the dry season, indicating that biomass burning aerosols have a stronger spectral dependence than soot carbon particles. Ångström exponents decreased from the dry to the wet season, in agreement with the shift from biomass burning aerosols, predominant in the fine mode, to biogenic and dust aerosols, predominant in the coarse mode. The lowest Ångström exponents (90% of data below 1.5) were observed at the forest site during the dry season. Also, results indicate that low absorption coefficients were associated with Ångström exponents below 1.0. This finding suggests that biogenic aerosols from Amazonia may have a weak spectral dependence for absorption, contradicting our expectations of biogenic particles behaving as brown carbon. Nevertheless, additional measurements should be taken in the future, to provide a complete picture of biogenic aerosol absorption spectral characteristics from different seasons and geographic locations. The
Huang, Jr-Chuan; Lee, Tsung-Yu; Teng, Tse-Yang; Chen, Yi-Chin; Huang, Cho-Ying; Lee, Cheing-Tung
2014-01-01
The exponent decay in landslide frequency-area distribution is widely used for assessing the consequences of landslides and with some studies arguing that the slope of the exponent decay is universal and independent of mechanisms and environmental settings. However, the documented exponent slopes are diverse and hence data processing is hypothesized for this inconsistency. An elaborated statistical experiment and two actual landslide inventories were used here to demonstrate the influences of the data processing on the determination of the exponent. Seven categories with different landslide numbers were generated from the predefined inverse-gamma distribution and then analyzed by three data processing procedures (logarithmic binning, LB, normalized logarithmic binning, NLB and cumulative distribution function, CDF). Five different bin widths were also considered while applying LB and NLB. Following that, the maximum likelihood estimation was used to estimate the exponent slopes. The results showed that the exponents estimated by CDF were unbiased while LB and NLB performed poorly. Two binning-based methods led to considerable biases that increased with the increase of landslide number and bin width. The standard deviations of the estimated exponents were dependent not just on the landslide number but also on binning method and bin width. Both extremely few and plentiful landslide numbers reduced the confidence of the estimated exponents, which could be attributed to limited landslide numbers and considerable operational bias, respectively. The diverse documented exponents in literature should therefore be adjusted accordingly. Our study strongly suggests that the considerable bias due to data processing and the data quality should be constrained in order to advance the understanding of landslide processes. PMID:24852019
The Evolution of the Exponent of Zipf's Law in Language Ontogeny
Baixeries, Jaume; Elvevåg, Brita; Ferrer-i-Cancho, Ramon
2013-01-01
It is well-known that word frequencies arrange themselves according to Zipf's law. However, little is known about the dependency of the parameters of the law and the complexity of a communication system. Many models of the evolution of language assume that the exponent of the law remains constant as the complexity of a communication systems increases. Using longitudinal studies of child language, we analysed the word rank distribution for the speech of children and adults participating in conversations. The adults typically included family members (e.g., parents) or the investigators conducting the research. Our analysis of the evolution of Zipf's law yields two main unexpected results. First, in children the exponent of the law tends to decrease over time while this tendency is weaker in adults, thus suggesting this is not a mere mirror effect of adult speech. Second, although the exponent of the law is more stable in adults, their exponents fall below 1 which is the typical value of the exponent assumed in both children and adults. Our analysis also shows a tendency of the mean length of utterances (MLU), a simple estimate of syntactic complexity, to increase as the exponent decreases. The parallel evolution of the exponent and a simple indicator of syntactic complexity (MLU) supports the hypothesis that the exponent of Zipf's law and linguistic complexity are inter-related. The assumption that Zipf's law for word ranks is a power-law with a constant exponent of one in both adults and children needs to be revised. PMID:23516390
Huang, Jr-Chuan; Lee, Tsung-Yu; Teng, Tse-Yang; Chen, Yi-Chin; Huang, Cho-Ying; Lee, Cheing-Tung
2014-01-01
The exponent decay in landslide frequency-area distribution is widely used for assessing the consequences of landslides and with some studies arguing that the slope of the exponent decay is universal and independent of mechanisms and environmental settings. However, the documented exponent slopes are diverse and hence data processing is hypothesized for this inconsistency. An elaborated statistical experiment and two actual landslide inventories were used here to demonstrate the influences of the data processing on the determination of the exponent. Seven categories with different landslide numbers were generated from the predefined inverse-gamma distribution and then analyzed by three data processing procedures (logarithmic binning, LB, normalized logarithmic binning, NLB and cumulative distribution function, CDF). Five different bin widths were also considered while applying LB and NLB. Following that, the maximum likelihood estimation was used to estimate the exponent slopes. The results showed that the exponents estimated by CDF were unbiased while LB and NLB performed poorly. Two binning-based methods led to considerable biases that increased with the increase of landslide number and bin width. The standard deviations of the estimated exponents were dependent not just on the landslide number but also on binning method and bin width. Both extremely few and plentiful landslide numbers reduced the confidence of the estimated exponents, which could be attributed to limited landslide numbers and considerable operational bias, respectively. The diverse documented exponents in literature should therefore be adjusted accordingly. Our study strongly suggests that the considerable bias due to data processing and the data quality should be constrained in order to advance the understanding of landslide processes. PMID:24852019
Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta of China
NASA Astrophysics Data System (ADS)
Zhuang, B. L.; Wang, T. J.; Liu, J.; Ma, Y.; Yin, C. Q.; Li, S.; Xie, M.; Han, Y.; Zhu, J. L.; Yang, X. Q.; Fu, C. B.
2015-06-01
Absorbing aerosols can significantly modulate shortwave solar radiation in the atmosphere, affecting regional and global climate. Aerosol absorption coefficient (AAC) is an indicator to assess the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption angstrom exponent (AAE) in urban Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the 7-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which show consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m-1 in urban Nanjing, which is much lower than that in Pearl River Delta and as the same as that in rural areas (Lin'an) in Yangtze River Delta. The AAC in urban Nanjing shows strong seasonality (diurnal variations), high in cold seasons (at rush hours) and low in summer (in afternoon). It also show synoptic and quasi-two-week cycles in response to weather systems. Its frequency distribution follows a typical lognormal pattern. The 532 nm-AAC ranging from 15 to 65 M m-1 dominates, accounting for more than 72% of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollutions. Air masses from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable compared to that from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly appear in summer in response to the relative humidity (RH). AAC increases with increasing AAE at a fixed aerosol loading. The RH-AAC relationship is more complex. Overall, AAC peaks around RH values
Power-law exponent of the Bouchaud-Mézard model on regular random networks
NASA Astrophysics Data System (ADS)
Ichinomiya, Takashi
2013-07-01
We study the Bouchaud-Mézard model on a regular random network. By assuming adiabaticity and independency, and utilizing the generalized central limit theorem and the Tauberian theorem, we derive an equation that determines the exponent of the probability distribution function of the wealth as x→∞. The analysis shows that the exponent can be smaller than 2, while a mean-field analysis always gives the exponent as being larger than 2. The results of our analysis are shown to be in good agreement with those of the numerical simulations.
Temperature Dependence of the Gorter-Mellink Exponent m Measured in a Channel Containing He II
Sato, A.; Maeda, M.; Dantsuka, T.; Yuyama, M.; Kamioka, Y.
2006-04-27
Steady state heat transport through He II was investigated. The exponent m in the Gorter-Mellink equation which gives heat flux dependence of the temperature gradient was measured in a wide range of heat flux. Our results indicate that there is no heat flux dependency of the exponent m in the heat flux region of our measurement. The exponent m is 3.4 at temperatures much lower than the lambda point and decreases down to 3.3 as the temperature approaches the lambda point.
Chaos and stiffness exponents for short-range Gaussian Ising spin glasses
NASA Astrophysics Data System (ADS)
Almeida, Sebastião T. O.; Curado, Evaldo M. F.; Nobre, Fernando D.
2013-06-01
Two important exponents in spin-glass theory, namely, the chaos (ζ) and stiffness (y) exponents, are studied for Ising spin glasses with nearest-neighbor Gaussian interactions on different approaches to Bravais lattices. We consider hierarchical lattices of the Migdal-Kadanoff type (both diamond and tress families), with varying fractal dimensions, as well as two lattices of the Wheatstone-bridge family, more specifically, those with fractal dimensions D ≈ 2.32 and D ≈ 3.58. Whenever it is possible to compare, our estimates agree with those obtained from extensive numerical simulations on Bravais lattices, suggesting the present results represent good approximations for these exponents.