bluuebunny/crossref_metadata_2025 huggingface dataset:
VUV spectroscopy of pure and Sm2+ doped SrFCl crystals
Authors: Kisand Vambola , Kink Rein , Kink Ilmar , Jaaniso Raivo , Martinson Indrek
Published: August 2003

The creation and relaxation of electronic excitations in pure crystalline SrFCl and Sm2+ doped SrFCl were investigated using vacuum ultraviolet (VUV) spectroscopic methods. In the emission spectra of pure SrFCl and SrFCl : Sm2+ a strong emission band in the vicinity of 4.7 eV was detected, connected to self‐trapped exciton (STE) having a Cl2− core. The threshold for creation of STE was detected at 8.5 eV in the excitation spectrum of pure SrFCl and at 7.6 eV for Sm2+ doped SrFCl. It was demonstrated that the excitation spectrum of Sm2+ emission is determined with direct excitation of a Sm2+ center below 7.6 eV and with excitation of the SrFCl host above 7.6 eV.
New sum rules relating the 1‐body momentum distribution of the homogeneous electron gas to the Kimball–Overhauser 2‐body wave functions (geminals) of its pair density
Authors: Ziesche P. , Pernal K. , Tasnádi F.
Published: August 2003

Recently, new sum rules for the scattering phase shifts of the pair‐density geminals (being 2‐body‐wave functions which parametrize the pair density together with an appropriately chosen occupancy) have been derived from the normalization of the pair density [P. Ziesche, Phys. Rev. B 67, 233102 (2003)]. Here, we present a generalization of these sum rules, which allows one in principle to calculate the momentum distribution from these geminals and their phase shifts. These contraction sum rules contain the afore mentioned (Friedel‐like) normalization sum rules as special cases.
Crystal field analysis of erbium doped yttrium oxide thin films in C2 and C3i sites
Authors: Dammak M. , Maalej R. , Kamoun M. , Deschanvres J.‐L.
Published: August 2003

Fluorescence measurements on Er ions in Y2O3 thin films have been analyzed with crystal‐field Hamiltonians of C2 and C3i symmetries including J‐mixing effects. Crystal‐field parameters have been determined based on the Racah theory, that minimize the rms deviation between calculated and experimentally found energy. This theoretical analysis confirms the dominance of the C2 symmetry site in the fluorescence spectrum; however in the infrared emission spectrum, the contribution of the two sites C2 and C3i is comparable.
Spin dephasing in n‐type GaAs quantum wells in the presence of high magnetic fields in Voigt configuration
Authors: Weng M. Q. , Wu M. W.
Published: August 2003

We perform a many‐body study of the spin dephasing due to the D'yakonov–Perel' (DP) effect in n‐type GaAs (100) quantum wells under high magnetic fields in the Voigt configuration by constructing and numerically solving the kinetic Bloch equations. We include all spin‐conserving scattering, such as electron–phonon, electron–non‐magnetic impurity as well as electron–electron Coulomb scattering, in our theory and investigate how the spin dephasing time (SDT) is affected by the initial spin polarization, impurity, and magnetic field. The dephasing obtained from our theory contains not only that due to the effective spin‐flipping scattering first proposed by DP [M. I. D'yakonov and V. I. Perel', Zh. Eksp. Teor. Fiz. 60, 1954 (1971); Sov. Phys. – JETP 38, 1053 (1971)], but also the recently proposed many‐body dephasing due to the inhomogeneous broadening provided by the DP term [M. W. Wu, J. Supercond.: incorp. Novel Mechanism 14, 245 (2001); M. W. Wu and C. Z. Ning, Eur. Phys. J. B 18, 373 (2000)]. We are able to investigate the spin dephasing with extra‐large spin polarization (up to 100%), which has not been discussed either theoretically or experimentally. A huge anomalous resonance of the SDT for large spin polarizations is predicted under the high magnetic field we used. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comment on “Some considerations concerning the detection of excitons by field ionization in a Schottky barrier” – [phys. stat. sol. (b) 234, No. 1, 23–35 (2002)]
Authors: Mysyrowicz A. , Leblanc P. J. , Fortin E.
Published: August 2003

We revisit the detection of excitons in Cu2O by the exciton‐mediated effect. It is shown that this type of detector is linear over a wide range of exciton densities, contrary to a recent claim that it should quickly saturate. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Response to “Comment on ‘Some considerations concerning the detection of excitons by field ionization in a Schottky barrier’” – [phys. stat. sol. (b)239, No. 1, 257–260 (2003)]
Authors: Klingshirn C. , Fleck T. , Jörger M.
Published: August 2003

A photocurrent signal and its temporal dependence on the excitation conditions observed in a Cu/Cu2O Schottky barrier after pulsed illumination of the Cu2O crystal has been used to claim excitonic superfluidity and Bose‐Einstein condensation. See, e.g., E. Benson, E. Fortin, and A. Mysyrowicz [phys. stat. sol. (b)191, 345 (1995)]. C. Klingshirn, T. Fleck, and M. Jörger [phys. stat. sol. (b)234, 23 (2002)] showed that a similar behaviour can be expected also from detector saturation which is very likely for the excitation conditions used in the above work. In the above comment [phys. stat. sol. (b)239, 257 (2003)], these arguments have been rejected, based on new experiments under resonant exciton creation. In this response we show that the excitation conditions used in these new experiments do not allow to question the statements in favour of detector saturation, but raise some additional questions. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strain effects in large‐scale atomistic quantum dot simulations
Authors: Oyafuso Fabiano , Klimeck Gerhard , von Allmen Paul , Boykin Tim , Bowen R. Chris
Published: August 2003

Atomistic computations of electronic properties for nanostructures with strain (such as self‐assembled quantum dots) typically consist of two components – a calculation of the individual atomic positions and the eigenstates of interest in the resulting Hamiltonian. Such simulations ultimately require artificial boundary conditions either through a truncation of the simulation domain or by the imposition of periodic boundary conditions, which necessarily introduce inaccuracies in both components of the computation. In simulations that include up to about 20 million atoms, it is demonstrated that the simulation domain truncation has little impact on the direct computation of the electronic energies but causes considerable inaccuracies in the calculation of the atomic positions unless the simulation domain is made much larger than the central quantum dot structure. The long‐range nature of the lattice distortions induced by lattice mismatch is consequently expected to significantly alter the electronic structure of nearby quantum dots. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phenomenological theory to model leakage currents in metal–insulator–metal capacitor systems
Authors: Ramprasad R.
Published: August 2003

A phenomenological model intended to provide a description of leakage behavior in metal–insulator–metal (MIM) capacitor devices is presented. The model is able to predict both transient and steady state leakage currents under constant voltage bias conditions (the J–t characteristics), as well as J–V characteristics for a given voltage sweep schedule. The electronic transport processes currently implemented in the model include trap assisted tunneling (TAT) of electrons from the electrode to defect or trap states in the dielectric, modified Poole–Frenkel (MPF) emission of part of the trapped electrons to the conduction band of the dielectric, and Schottky emission of Fermi level electrons directly from the electrode to the conduction band of the dielectric. The model is able to predict many of the observed features, including characteristic slopes in J–t and J–V plots, and dependences of the leakage current on dielectric thickness, temperature and the Schottky barrier height. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical excitations in small hydrogenated silicon clusters: comparison of theory and experiment
Authors: Vasiliev Igor
Published: August 2003

Excitation energies and absorption spectra of small hydrogenated silicon clusters are calculated within the framework of time‐dependent density‐functional response theory. The calculations employ several different approximations for the exchange‐correlation kernel, including the local density approximation as well as asymptotically correct Leeuwen–Baerends and Casida–Salahub potentials. The structures of the theoretical spectra are analyzed in detail and the positions of the absorption peaks obtained with different exchange‐correlation kernels are matched to the available experimental data based on the oscillator strength and symmetry of electronic transitions. The calculated absorption gaps are compared to the experimental values and discussed in terms of the applicability of common theoretical and experimental definitions for optical gaps to small clusters. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessing the Effect of Time in Factorial Designs: The Practical Application
Authors: Chatfield M. J. , Owen M. R.
Published: August 2003

The scientist asks a statistician the question: ‘should we incorporate time as a factor in our factorial designs or measure the response at various time‐points?’ Advantages and disadvantages of the approaches are discussed. The aspects to be considered include: the relative costs of performing the experiment, the response measurement and the statistical analysis; the quality of the data collected and the information to be gained from the experimentation; implications for possible designs; implications for setting up, analysis and interpretation of designs in standard software available to scientists; and pitfalls to avoid. The field of chemical process investigation is used to illustrate some of the issues involved. In some scientific areas the experimental or resource issues may be overriding and the answer obvious. For the chemist, in some cases the only choice will be the factorial design which includes time as a factor due to experimental reasons but in most cases the appropriate answer depends on careful consideration of the aspects listed above. The paper illustrates the importance of a partnership between scientist and statistician in addressing the practical application of statistical techniques. Copyright © 2003 John Wiley & Sons, Ltd.
Bayesian Analysis and Prediction of Failures in Underground Trains
Authors: Pievatolo Antonio , Ruggeri Fabrizio , Argiento Raffaele
Published: August 2003

Based upon failure data (date and odometer reading) in the early operating time, a public transportation company is interested in checking the actual reliability of the door opening system of its subway trains before their warranty expires. We consider non‐homogeneous Poisson processes with a double scale because both time and kilometres are recorded for each failure. Different choices to model the relation between operated time and kilometres run are possible: in this paper the kilometres run are incorporated within the intensity function as a random function of time, modelled as a gamma process. Furthermore a periodic component is introduced to deal with the seasonality in the data. Bayesian inference is then carried out via Monte Carlo simulation, obtaining prediction intervals for the expected number of failures during periods of desired length, using only part of the data. The predictions are then compared with the observed data. Copyright © 2003 John Wiley & Sons, Ltd.
A Comparison of Shewhart Individuals Control Charts Based on Normal, Non‐parametric, and Extreme‐value Theory
Authors: Vermaat M. B. (Thijs) , Ion Roxana A. , Does Ronald J. M. M. , Klaassen Chris A. J.
Published: August 2003

Several control charts for individual observations are compared. Traditional ones are the well‐known Shewhart individuals control charts based on moving ranges. Alternative ones are non‐parametric control charts based on empirical quantiles, on kernel estimators, and on extreme‐value theory. Their in‐control and out‐of‐control performance are studied by simulation combined with computation. It turns out that the alternative control charts are not only quite robust against deviations from normality but also perform reasonably well under normality of the observations. The performance of the Empirical Quantile control chart is excellent for all distributions considered, if the Phase I sample is sufficiently large. Copyright © 2003 John Wiley & Sons, Ltd.
Simulation Models for Robust Design Using Location Depth Methods
Authors: Stadlober Ernst , Kocher Michael , Rappitsch Gerhard
Published: August 2003

For a cost‐effective production of integrated circuits, one important aspect is the accurate simulation of electronic circuits with regard to process variation. Process variation is described as the range of simulation (SPICE) parameters, but to reduce the costs of simulation they are replaced by easily available e‐test parameters. An approximate algorithm for the location depth (multivariate ranking) selects all data points with location depth less than or equal to one as boundary points for the multidimensional data set of e‐test parameters. The corresponding SPICE parameter values are simply obtained by linear mapping. To increase the robustness of the simulation the region covered by the set of boundary points is extended by determining the point with the deepest location (multivariate median) and adding to each boundary vector a fixed portion of the vector from the median to the boundary vector. This natural extension also covers moderate process shifts without changing the covariance structure of the data. These methods are integrated into an automated generation flow to be applicable in a production and circuit design environment. The statistical methods are validated by simulation experiments of typical analog/mixed‐signal circuit designs. Copyright © 2003 John Wiley & Sons, Ltd.
Visually Mining Off‐line Data for Quality Improvement
Authors: Porzio Giovanni C. , Ragozini Giancarlo
Published: August 2003

Highly automated modern manufacturing processes are yielding large databases with records on hundreds of process variables and product characteristics. This large amount of information calls for new approaches to production process analysis. In this paper, we discuss why a data mining framework can be appropriate for this goal, and we propose a visual data mining strategy to mine large and high‐dimensional off‐line data sets. The strategy allows users to achieve a deeper process understanding through a set of linked interactive graphical devices, and is illustrated within an industrial process case study. Copyright © 2003 John Wiley & Sons, Ltd.
Change Point Estimates for the Parameters of an AR(1) Process
Authors: Timmer Douglas H. , Pignatiello Joseph J.
Published: August 2003

Three change point estimates for the parameters of a first‐order autoregressive (AR(1)) model are developed. The estimators are applied once a control chart signals indicating the presence of a special or assignable cause of variability. The knowledge of the change point can greatly aid the quality practitioner in identifying and removing special causes of variability. Techniques for determining the change point for the location of the AR(1) process, the variance of the white noise process and the autoregressive parameter changed are presented. Simulation results are provided to evaluate the effectiveness of the three change point estimators. Copyright © 2003 John Wiley & Sons, Ltd.
Turán's theorem in sparse random graphs
Authors: Szabó Tibor , Vu Van H.
Published: August 2003

We prove the analogue of Turán's Theorem in random graphs with edge probability p(n) ≫ n−1/(k−1.5). With probability 1 − o(1), one needs to delete approximately ‐fraction of the edges in a random graph in order to destroy all cliques of size k. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 23: 225–234, 2003
On the distribution of the number of roots of polynomials and explicit weak designs
Authors: Hartman Tzvika , Raz Ran
Published: August 2003

Weak designs were defined in R. Raz, O. Reingold, and S. Vadhan [Extracting all the randomness and reducing the error in Trevisan's extractors, Proc 31st ACM Symp Theory of Computing, Atlanta, GA, May 1999, to appear in J Comput System Sci Special Issue on STOC 99] and are used there in constructions of extractors. Roughly speaking, a weak design is a collection of subsets satisfying some near‐disjointness properties. Constructions of weak designs with certain parameters are given in Raz et al. These constructions are explicit in the sense that they require time and space polynomial in the number of subsets. However, the constructions require time and space polynomial in the number of subsets even when needed to output only one specific subset out of the collection. Hence, the constructions are not explicit in a stronger sense. In this work we provide constructions of weak designs (with parameters similar to the ones of Raz et al.) that can be carried out in space logarithmic in the number of subsets. Moreover, our constructions are explicit even in a stronger sense: Given an index to a subset, we output the specified subset in time and space polynomial in the size of the index. Using our constructions, we obtain extractors similar to some of the ones given in Raz et al. in terms of parameters, and that can be evaluated in logarithmic space. Our main construction is algebraic. In order to prove the properties of weak designs, we prove some algebro‐combinatorial lemmas that may be interesting in their own right. These lemmas regard the number of roots of polynomials over finite fields. In particular, we prove that the number of polynomials (over any finite field) withkroots, vanishes exponentially ink.In other words, we prove that the number of roots of a random polynomial is not only bounded by its degree (a well‐known fact), but, furthermore, it is concentrated exponentially around its expectation (which is 1). Our lemmas are proved by algebro‐combinatorial arguments. The main lemma is also proved by a probabilistic argument. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 23: 235–263, 2003
Feed‐forward and recurrent neural networks for source code informal information analysis
Authors: Merlo Ettore , McAdam Ian , De Mori Renato
Published: August 2003

Design recovery, which is a part of the reverse engineering process of source code, must supply programmers with all the information they need to fully understand a program or a system. In this paper, a connectionist method that can be used for design recovery in conjunction with more traditional approaches is proposed for analyzing the informal information (comments and mnemonics) in programs. An approach based on artificial neural networks (ANNs) was chosen because of its property of being robust (capable of tolerating noisy inputs), because of its associative memory ability (capable of retrieving a concept given only the context of the input word that originally fired the concept), and because of its generalization power (ability to learn conceptually relevant micro‐features of the domain). The proposed approach uses a combination of top down domain analysis (i.e., the creation of a concept hierarchy by a domain expert, to be used in the construction of the training set) and a bottom up approach (i.e., the analysis of the informal information using ANNs).

A preprocessing system that extracts the relevant comments and identifier names and transforms them into an input for the ANNs has been developed. Feed‐forward neural networks (FNNs) and recurrent neural networks (RNNs) were tried. RNN architectures are capable of learning sequences and are able to make use of the word ordering of the sentence. The networks were trained on part of the source code of an existing system and tested on a different portion of the system code. Test results, consisting of coverage and evaluation figures, are presented. They show a remarkably higher accuracy when ANNs, in general, are used as opposed to simple lexical methods. RNNs, in particular, also show higher coverage and accuracy than FNNs. Copyright © 2003 John Wiley & Sons, Ltd.
A case study on the adaptive maintenance of an Internet application
Authors: Bergin Susan , Keating John
Published: August 2003

We describe an Internet application for providing mobile phone tariff information for Northern Ireland and the Republic of Ireland. Using this application it is possible to accurately and easily determine and compare mobile phone packages offered by different service providers. One of the important features of such an Internet application is the potential for high maintenance associated with the data in the system and more importantly the structure of the system given the inevitable changes in the corresponding mobile phone market. We have identified the maintenance tasks associated with our system to reflect changes in the mobile phone market and outline an evaluation technique for describing the system's ability to cope with change. In particular, we evaluate the actual change required to our software system to implement various maintenance tasks. We have found that there is an upper bound (˜5%) on the maintenance effort associated with the system which is both acceptable and manageable for maintenance purposes. We show that at most the changes required to our system are no greater than 3.07%, when a complete new service provider is added or removed. We conclude that the development of a maintenance model in conjunction with system design is essential for estimating the maintenance effort associated with similar Internet applications. Copyright © 2003 John Wiley & Sons, Ltd.
Seasonal and interannual CO2 fluxes for the central and eastern equatorial Pacific Ocean as determined from fCO2‐SST relationships
Authors: Cosca Catherine E. , Feely Richard A. , Boutin Jacqueline , Etcheto Jacqueline , McPhaden Michael J. , Chavez Francisco P. , Strutton Peter G.
Published: August 2003

In order to determine high‐resolution variations of CO2 distributions in the equatorial Pacific, we have developed seasonal and interannual fCO2‐SST relationships from shipboard data. The data were gathered onboard NOAA ships from 1992 through 2001. The cruises during the 10‐year period included 89 transects of the equatorial Pacific between 95°W and 165°E, and spanned two El Niño events (1992–1994 and 1997–1998). Data were collected during the equatorial warm season (January–June) and cool season (July–December) as well as during all phases of the ENSO cycle, making it possible to examine the interannual and seasonal variability of the fCO2‐SST relationship. There is a significant difference between the regression lines for El Niño versus non‐El Niño data sets. During both non‐El Niño and El Niño periods we observed seasonal differences in the fCO2‐temperature relationship. With respect to the non‐El Niño period, the seasonal regression lines have lower root mean square (rms) deviations than the composite non‐El Niño regression line, and the slopes are significantly different at the 95% confidence level. The slope for the cool season is less negative than the slope for the warm season, suggesting higher biological productivity occurs during the latter half of the year. The derived fCO2‐SST relationships have been combined with satellite‐based temperature data to provide a composite time‐space map of fCO2 in the central and eastern equatorial Pacific and corresponding fluxes for the period between 1985 and 2001. The mean flux for the 16‐year record is 0.3 ± 0.1 PgC yr−1 for an area that covers approximately half of the Pacific equatorial belt.
Contrast of elastic properties between rock layers as a mechanism for the initiation and orientation of tensile failure under uniform remote compression
Authors: Bourne Stephen J.
Published: August 2003

Natural fracture systems are often influenced by the presence of different layers with contrasting rock mechanical properties. Understanding the distribution of stress between different mechanical layers is essential to the interpretation of fracture networks within these systems. A simple model of elastic stress states within mechanically layered media is presented as a description of fracture formation within layered rock. These stress states are based on analytic solutions in three dimensions for an idealized system of bonded, planar, isotropic, homogeneous, linear‐elastic layers in equilibrium with a uniform remote stress. Properties of these solutions indicate that tensile stress and failure will result in some layers in response to remote compression alone given sufficient contrast in elastic properties between the different layers. In this case, tensile stress arises without the requirement for an addition body force such as internal fluid pressure and will concentrate within either the stiffest or softest layers according to the relative amount or layer‐parallel versus layer‐perpendicular compression. Lithification and bonding of layers under remote stress leads to residual stresses within layers that enhance tensile failure of stiffer than average layers under remote compression. Any change in orientation of the remote stress may lead to significant differences in both stress magnitude and orientation between different layers. In turn, the mode and orientation of fractures within different layers may significantly differ despite forming under the same remote stress.
Study of the ionospheric total electron content response to the great flare on 15 April 2001 using the International GPS Service network for the whole sunlit hemisphere
Authors: Zhang D. H. , Xiao Z.
Published: August 2003

The characteristics of the ionospheric response to the solar flare on Apr. 15, 2001 were studied using the total electron content (TEC) obtained at GPS observational stations in the whole sunlit hemisphere under International GPS Service for Geodynamics. It was found that the largest enhancement of the sudden increase of total electron content during this flare is ∼2.6 TECU (1 TECU = 1016 m−2). The effects of solar flare radiation on the ionosphere can be recognized even in the region at 0600 or 1800 LT. Owing to ionospheric scintillation, the TEC enhancement could not be derived from temporal TEC variation curves in high latitudes. On the other hand, the synoptic picture of the sunlit ionospheric response to the flare was obtained, and the results showed the relationship of TEC enhancements with solar zenith angles. The larger the solar zenith angle, the smaller the TEC enhancement. Even minor fast changes in TEC during this flare are revealed in the changing rate of temporal TEC variations in midlatitudes and low latitudes. These small globally synchronous disturbances of TEC were compared with the solar X‐ray fluxes of this flare observed by satellites, and a close correlation between those small ionospheric disturbances and the hard X‐ray flux fluctuations was found.
Susceptibility of mid‐ocean ridge volcanic islands and seamounts to large‐scale landsliding
Authors: Mitchell Neil C.
Published: August 2003

With a view to assessing the incidence of large‐scale landsliding, a morphologic database was created for volcanic islands and seamounts on young oceanic lithosphere. The database included 44 mid‐ocean ridge seamounts, Jasper seamount and the islands of Ascension, Bouvet, Guadalupe, and several of the Galapagos and Azores Islands, supplemented with published reports from a further five volcanic edifices. The data reveal that major landslides are common on edifices taller than 2500 m but are rare in shorter edifices, implying a threshold of instability at around 2500 m. A number of causes of this threshold are discussed. For example, many structures taller than 2500 m are, or were originally, volcanic islands, and therefore their flanks probably include extensive weak hyaloclastite built up from lava‐sea interactions around coasts. Compaction of hyaloclastites in larger edifices lead to regions of low permeability, which may help to explain the more deeply seated slope failures. It is intriguing that the threshold also coincides with the edifice height at which volcanic ridges become observable, a stage at which dike intrusion is probably common because slope oversteepening or excess pore pressure associated with dike intrusions have been proposed elsewhere as landslide triggers. The current indications of landsliding reveal no observable relation to rainfall, as landslides occur equally in wet and dry climates, and no relation to tectonic setting, as there are relatively few major landslides in the seismically active Azores group.
Buoyancy‐driven current during cooling periods in Ise Bay, Japan
Authors: Fujiwara Tateki
Published: August 2003

The cooling effect on buoyancy‐driven current is studied in the coastal embayment of Ise Bay, Japan, by applying knowledge derived from studies of convection in a rotating fluid. This convection process is highly sensitive to the presence of inhomogeneities in the preexisting stratification and to differential buoyancy loss. On freshwater input the bay water is divided into two regions that differ in their response to the cooling from the surface. One region represents a river plume, which, in effect, shields the deeper regions from the cooler surface. In the other region, convective mixing is active. Although the mixed water forms and becomes extensive in this convection region, the mixed water hardly develops in the river plume region. The subsequent differential deepening of the mixed water causes gravitational circulation and yields a mixed water lens, which has a reversed dome shape and rotates anticyclonically in a thermal wind balance. In the mixed water lends, nonvanishing stratification remains because of the rotational effect. The location of the mixed water lens and associated anticyclonic circulation determines the basin‐wide circulation during cooling periods.
Validation and data characteristics of nitrous oxide and methane profiles observed by the Improved Limb Atmospheric Spectrometer (ILAS) and processed with the Version 5.20 algorithm
Authors: Kanzawa H. , Sugita T. , Nakajima H. , Bodeker G. E. , Oelhaf H. , Stowasser M. , Wetzel G. , Engel A. , Schmidt U. , Levin I. , Toon G. C. , Sen B. , Blavier J.‐F. , Aoki S. , Nakazawa T. , Jucks K. W. , Johnson D. G. , Traub W. A. , Camy‐Peyret C. , Payan S. , Jeseck P. , Murata I. , Fukunishi H. , von König M. , Bremer H. , Küllmann H. , Park J. H. , Pan L. L. , Yokota T. , Suzuki M. , Shiotani M. , Sasano Y.
Published: August 2003

Vertical profiles of nitrous oxide and methane at high latitudes (57–72°N; 64–89°S) were observed by the Improved Limb Atmospheric Spectrometer (ILAS) solar occultation sensor aboard Advanced Earth Observing Satellite. These measurements were made continuously from November 1996 through June 1997 with some additional periods in September–October 1996. A validation study of the nitrous oxide and methane data processed with the Version 5.20 ILAS retrieval algorithm is presented in this paper. Comparisons are made with (1) nitrous oxide and methane obtained by the ILAS validation balloon campaigns at Kiruna, Sweden, and at Fairbanks, Alaska, in the Arctic; (2) nitrous oxide and methane by the Photochemistry of Ozone Loss in the Arctic Region in Summer aircraft campaign in the Arctic; (3) nitrous oxide by the ground‐based spectroscopic measurements and by the aircraft‐based remote sensing measurements in the Arctic; and (4) methane by satellite measurements of the Version 19 Halogen Occultation Experiment in the Arctic and Antarctic. Comparisons of ILAS nitrous oxide and methane with Upper Atmosphere Research Satellite Reference Atmosphere data are also made. The results of the comparisons and additional ILAS internal consistency analyses are as follows: (1) the uncertainty of ILAS nitrous oxide is better than 10% over 10–30 km in altitude, and is larger than 50% over 30–40 km, which is comparable to the expected total errors of the ILAS measurements; (2) the uncertainty of ILAS methane is better than 10% over 10–50 km, except for 15–30 km in winter with positive biases exceeding 20%, which is smaller than or comparable to the expected total errors of the ILAS measurements (the quality of ILAS methane in the polar lower stratosphere is better in summer than in winter). In summary, the characteristics of ILAS measurements, i.e., high sampling frequency in polar latitudes with high vertical resolution, along with the good quality of ILAS Version 5.20 nitrous oxide for 10–40 km and the good quality of ILAS Version 5.20 methane for 10–50 km except for 15–30 km in winter, make the ILAS nitrous oxide and methane data set valuable for scientific study of various polar stratospheric phenomena.
Impact of lakes and wetlands on boreal climate
Authors: Krinner Gerhard
Published: August 2003

The role of lakes and wetlands in present‐day high latitude climate is quantified using a general circulation model of the atmosphere. The atmospheric model includes a lake module which is presented and validated. Seasonal and spatial wetland distribution can either be prescribed or calculated as a function of the hydrological budget of the wetlands themselves and of continental soil whose runoff feeds them. Simulated wetland extent is discussed both in simulations forced by observed climate and in general circulation model simulations. In off‐line simulations, forced by ECMWF reanalyses, the lake model simulates correctly observed lake ice durations, while the wetland extent is somewhat underestimated in the boreal regions. Coupled to the general circulation model, the lake model yields satisfying ice durations, although the climate model biases have impacts on the modeled lake ice conditions. Boreal wetland extents are overestimated in the general circulation model as simulated precipitation is too high. The impact of inundated surfaces on the simulated climate is strongest in summer when these surfaces are ice‐free. Wetlands seem to play a more important role than lakes in cooling the boreal regions in summer and in humidifying the atmosphere.
Surface aerosol radiative forcing at Gosan during the ACE‐Asia campaign
Authors: Bush Brett C. , Valero Francisco P. J.
Published: August 2003

Surface radiation measurements were made at Gosan, Jeju, Republic of Korea, during the ACE‐Asia field campaign aimed at assessing the impact of aerosols, specifically the “Asian yellow dust,” throughout the region. Downwelling total, direct, and diffuse radiative fluxes were measured in the total solar spectrum as well as near‐infrared and visible portions of the spectrum. Aerosol optical depth measurements at 500 nm were also made using a scanning shadow band radiometer. Surface radiative forcing values were determined during clear‐sky conditions made from 25 March to 4 May 2001. The diurnal forcing efficiency, determined by taking the slope of the best fit line through the flux versus optical depth plot, was found to be −73.0 ± 9.6, −35.8 ± 5.5, and − 42.2 ± 4.8 W m−2/τ500 for the total solar, near‐infrared, and visible spectral regions. We also introduce a new radiative forcing parameter, the fractional forcing efficiency, defined to express the radiative forcing relative to the total energy incident at the top of the atmosphere. The fractional diurnal forcing efficiency at Gosan during ACE‐Asia was −18.0 ± 2.3, −16.2 ± 2.4, and −26.7 ± 3.3%/τ500 for the same band passes, indicating that a larger percentage of the flux at visible wavelengths is radiatively forced compared to the total and near‐infrared portions of the solar spectrum.
Use of proton‐transfer‐reaction mass spectrometry to characterize volatile organic compound sources at the La Porte super site during the Texas Air Quality Study 2000
Authors: Karl Thomas , Jobson Tom , Kuster William C. , Williams Eric , Stutz Jochen , Shetter Rick , Hall Samuel R. , Goldan Paul , Fehsenfeld Fred , Lindinger Werner
Published: August 2003

Proton‐transfer‐reaction mass spectrometry (PTR‐MS) was deployed for continuous real‐time monitoring of volatile organic compounds (VOCs) at a site near the Houston Ship Channel during the Texas Air Quality Study 2000. Overall, 28 ions dominated the PTR‐MS mass spectra and were assigned as anthropogenic aromatics (e.g., benzene, toluene, xylenes) and hydrocarbons (propene, isoprene), oxygenated compounds (e.g., formaldehyde, acetaldehyde, acetone, methanol, C7 carbonyls), and three nitrogen‐containing compounds (e.g., HCN, acetonitrile and acrylonitrile). Biogenic VOCs were minor components at this site. Propene was the most abundant lightweight hydrocarbon detected by this technique with concentrations up to 100+ nmol mol−1, and was highly correlated with its oxidation products, formaldehyde (up to ∼40 nmol mol−1) and acetaldehyde (up to ∼80 nmol/mol), with typical ratios close to 1 in propene‐dominated plumes. In the case of aromatic species the high time resolution of the obtained data set helped in identifying different anthropogenic sources (e.g., industrial from urban emissions) and testing current emission inventories. A comparison with results from complimentary techniques (gas chromatography, differential optical absorption spectroscopy) was used to assess the selectivity of this on‐line technique in a complex urban and industrial VOC matrix and give an interpretation of mass scans obtained by “soft” chemical ionization using proton‐transfer via H3O+. The method was especially valuable in monitoring rapidly changing VOC plumes which passed over the site, and when coupled with meteorological data it was possible to identify likely sources.
Modeled size‐segregated wet and dry deposition budgets of soil dust aerosol during ACE‐Asia 2001: Implications for trans‐Pacific transport
Authors: Zhao T. L. , Gong S. L. , Zhang X. Y. , McKendry I. G.
Published: August 2003

Size‐segregated budgets of soil dust aerosols in Asia for spring 2001 during ACE‐Asia were investigated using the NARCM model [Gong et al., 2003b]. Simulated mass size distributions of dust deposition showed a similar size distribution to the dust emission fluxes over the source regions and a decreased peak corresponding to a 1–3 μm diameter range over downwind regions. The simulations suggest that dry deposition was a dominant dust removal process near the source areas and the removal of dust particles by precipitation was the major process over the trans‐Pacific transport pathway, where wet deposition exceeded dry deposition by up to a factor of 10. The Asian dust deposition from the atmosphere to the North Pacific Ocean was correlated not only with precipitation over the North Pacific but also with the dust transport patterns. Variations of monthly Asian dust outflow were identified with the latitudinal center of transport at 38°N in March, 42°N in April, and 47°N in May. The monthly trans‐Pacific transport patterns of Asian dust in spring were characterized. The transport axis extended around 30°N and 40°N from the east Asian subcontinent to the North Pacific in March. A zonal transport pathway around 40°N was well developed in April over the North Pacific and reached North America. However, the transport in May was separated into two pathways: an eastward zonal path over the North Pacific and a meridional path from the source regions to the northeast Asian continent. On the basis of the averaged dust budgets during spring 2001, it was found that the major sources of Asian dust were located in the desert regions in China and Mongolia with an estimated dust emission of 21.5 tons km−2, and the regions from the Loess Plateau to the North Pacific were sinks of soil dust aerosols with the Loess Plateau as the main sink for Asian dust.
Tidal heating and convection in Io
Authors: Moore W. B.
Published: August 2003

The prodigious heat flux emitted from the surface of Jupiter's moon Io is produced in the interior of the satellite by viscoelastic dissipation of tidal energy and is generally thought to be brought to the surface by convective motions. New models of Io's equilibrium thermal state are constructed using self‐consistent calculations of tidal heating and convective heat transport. These models show that while a high‐temperature convective equilibrium exists, it falls an order of magnitude short of explaining the observed heat flux. Either Io is currently out of thermal equilibrium, or another heat transport mechanism such as melt segregation determines Io's thermal state.
Dissolution effects on foraminiferal Mg/Ca records of sea surface temperature in the western equatorial Pacific
Authors: de Villiers S.
Published: August 2003

Mg sea surface temperature (SST) records from different planktonic foraminifera (G. sacculifer and G. ruber), size fractions, and core depths (1600 and 2600 m) suggest similar amplitudes of cyclic change over the last 425 kyr. However, there are significant differences in the detail recorded by different size fractions and between cores in close geographic proximity. These differences may be induced by dissolution, but artifacts resulting from divergent cleaning protocols and a dependency of the magnitude of these on preservation status cannot be ruled out. These and issues such as reproducibility require greater scrutiny for the true significance and credibility of down core Mg SST variability to be established.
Tectonic evolution of the early Mesozoic blueschist‐bearing Qiangtang metamorphic belt, central Tibet
Authors: Kapp Paul , Yin An , Manning Craig E. , Harrison T. Mark , Taylor Michael H. , Ding Lin
Published: August 2003

A >500‐km‐long east‐west trending metamorphic belt in the Qiangtang terrane of central Tibet consists of tectonic melange that occurs in the footwalls of Late Triassic–Early Jurassic domal low‐angle normal faults. The melange is comprised of a strongly deformed matrix of metasedimentary and mafic schists that encloses lesser‐deformed blocks of metabasites, Carboniferous–Triassic metasedimentary rocks, and early Paleozoic gneiss. Both the blocks and melange matrix exhibit greenschist, epidote‐blueschist, and locally, epidote‐amphibolite facies mineral assemblages. Thermobarometry reveals that the metamorphic belt experienced pressures of >10 kbar. Maximum equilibration temperatures for mafic schists in the melange matrix decrease from east to west, from ∼660°C near Shuang Hu (33°N, 89°E), ∼500°C near Rongma (33°N, 87°E), to ∼425°C near Gangma Co (34°N, 84°E). Equilibration at consistently high pressures over a large range of temperatures is compatible with metamorphism of Qiangtang melange within a low‐angle subduction zone beneath a continental margin. Coupled structural, thermobarometric, and 40Ar/39Ar studies suggest that Qiangtang melange was exhumed in an intracontinental setting from depths of >35 km to upper crustal levels in <12 Myr by Late Triassic–Early Jurassic crustal‐scale normal faulting. Detrital zircons from metasandstones within the melange matrix yield U‐Pb ion‐microprobe ages that range from early Paleozoic to Early Archean, and could have been sourced from terranes to the north of the Jinsha suture. Our results support a model in which Qiangtang melange was underthrust ∼200 km beneath the Qiangtang terrane during early Mesozoic flat‐slab southward subduction of Paleo‐Tethyan oceanic lithosphere along the Jinsha suture. This model predicts that significant portions of the central Tibetan continental mantle lithosphere were removed during early Mesozoic low‐angle oceanic subduction and that the present‐day central Tibetan deeper crust includes large volumes of underthrust early Mesozoic melange.
Late‐twentieth century changes in glacier extent in the Ak‐shirak Range, Central Asia, determined from historical data and ASTER imagery
Authors: Khromova T. E. , Dyurgerov M. B. , Barry R. G.
Published: August 2003

Global analysis of glacier regimes reveals widespread wastage since the late 1970s, with a marked acceleration in the late 1980s. We investigate changes in the heavily glacierized Ak‐shirak Range, central Tien Shan plateau (43°N, 75°E) using air photo mapping surveys (1943 and 1977), an ASTER imagery (2001), and long term glaciological and meteorological observations. The wasting of the Ak‐shirak glacier system features a decrease in average glacier size, and an increase in the area of outcrops. A small shrinkage during 1943–1977 was followed by a greater than 20% reduction during 1977–2001 in response to increases in summer and annual air temperature and decreases in annual precipitation.
Multi‐decadal elevation changes on Bagley Ice Valley and Malaspina Glacier, Alaska
Authors: Muskett Reginald R. , Lingle Craig S. , Tangborn Wendell V. , Rabus Bernhard T.
Published: August 2003

Digital elevation models (DEMs) of Bagley Ice Valley and Malaspina Glacier produced by (i) Intermap Technologies, Inc. (ITI) from airborne interferometric synthetic aperture radar (InSAR) data acquired 4–13 September 2000, (ii) the German Aerospace Center (DRL) from spaceborne InSAR data acquired by the Shuttle Radar Topography Mission (SRTM) 11–22 February 2000, and (iii) the US Geological Survey (USGS) from aerial photographs acquired in 1972/73, were differenced to estimate glacier surface elevation changes from 1972 to 2000. Spatially non‐uniform thickening, 10 ± 7 m on average, is observed on Bagley Ice Valley (accumulation area) while non‐uniform thinning, 47 ± 5 m on average, is observed on the glaciers of the Malaspina complex (mostly ablation area). Even larger thinning is observed on the retreating tidewater Tyndall Glacier. These changes have resulted from increased temperature and precipitation associated with climate warming, and rapid tidewater retreat.
Oxygenated volatile organic chemicals in the oceans: Inferences and implications based on atmospheric observations and air‐sea exchange models
Authors: Singh H. B. , Tabazadeh A. , Evans M. J. , Field B. D. , Jacob D. J. , Sachse G. , Crawford J. H. , Shetter R. , Brune W. H.
Published: August 2003

Airborne measurements of oxygenated volatile organic chemicals (OVOC), OH free radicals, and tracers of pollution were performed over the Pacific during Winter/Spring of 2001. We interpret atmospheric observations of acetaldehyde, propanal, methanol, and acetone with the help of a global 3‐D model and an air‐sea exchange model to assess their oceanic budgets. We infer that surface waters of the Pacific are greatly supersaturated with acetaldehyde and propanal. Bulk surface seawater concentration of 7 nM (10−9 mol L−1) and 2 nM and net fluxes of 1.1 × 10−12 g cm−2 s−1 and 0.4 × 10−12 g cm−2 s−1 are calculated for acetaldehyde and propanal, respectively. Large surface seawater concentrations are also estimated for methanol (100 nM) and acetone (10 nM) corresponding to an under‐saturation of 6% and 14%, and a deposition velocity of 0.08 cm s−1 and 0.10 cm s−1, respectively. These data imply a large oceanic source for acetaldehyde and propanal, and a modest sink for methanol and acetone. Assuming a 50–100 meter mixed layer, an extremely large oceanic reservoir of OVOC, exceeding the atmospheric reservoir by an order of magnitude, can be inferred to be present. Available seawater data are both preliminary and extremely limited but indicate rather low bulk OVOC concentrations and provide no support for the existence of a large oceanic reservoir. We speculate on the causes and implications of these findings.