bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of di‐ and tetra‐adducts by addition of polystyrene macroradicals onto fullerene C60
Authors: Audouin Fabrice , Nuffer Richard , Mathis Claude
Published: June 2004

Br‐terminated polystyrenes of controlled molar masses and low polydispersities prepared by atom transfer radical polymerization (ATRP) can be converted to macroradicals using an appropriate catalytic complex (CuBr/bipyridine/100 °C). The addition of this macroradicals PS° to 6–6 bonds of C60 follows a specific atom transfer radical addition mechanism that favors the grafting of even number of chains onto the fullerene core. This peculiar mechanism, resulting from the properties of C60, offers an easy synthetic route toward well‐defined di‐ and tetra‐adducts. In these adducts the disturbance of the electronic structure of the fullerene is kept at its minimum, as only one double bond needs to be opened on the C60 to add two PS chains and only two double bonds are converted to single bonds in the tetra‐adduct. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3456–3463, 2004
Ab‐initio study of the structural phase transition of SrSe and SrTe under pressure
Authors: Cortona Pietro
Published: June 2004

The cohesive properties and the behavior under pressure of SrSe and SrTe have been investigated by an ab initio method that allows the direct determination of the electron density and the total energy of a system in the framework of the density‐functional theory. A good agreement with the experiment has been found for all the properties considered: lattice parameters, bulk moduli, equations of state, transition pressure from the B1 to the B2 phase, and related quantities. The results are of special interest for the high‐pressure phase: as the experimental values of B and of dB/dp are affected by large uncertainties, the calculated values are probably a better evaluation of them. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Ab initio simulation of the short‐range order structure of Al ions and substitutional Fe, Cr impurities in S.S. Spinel (MgAl2O4)
Authors: Votyakov S. L. , Porotnikov A. V. , Shchapova Yu. V. , Yuryeva E. I. , Ivanovskii A. L.
Published: June 2004

The structure of the short‐range surrounding of aluminum, ferric iron and chromium octahedrally coordinated cations in s.s. spinel MgAl2O4:(Fe,Cr) has been established in the framework of the cluster model. The total energy minimum of [VIMecentIVMg6VIAl6O38]43‐ clusters (Mecent = Al, Fe, Cr) is realized when oxygens of the first coordination sphere of the central cation VIMe are displaced considerably relative to the initial ideal structure. The displacement depends on the central cation of the cluster. The estimated short‐range order parameters including the oxygen parameter u of the spinel are in satisfactory agreement with experimental data. Comparable analysis of the electronic structure of Al, Fe, Cr cations in octahedral positions of the spinel in ideal and relaxed clusters showed that octahedral distortions should be taken into account when interpreting spectroscopic parameters of the natural spinels and evaluating the charge balance in their structure. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Wigner intracule for the Kellner helium‐like ions
Authors: Gill Peter M. W. , Besley Nicholas A. , O'Neill Darragh P.
Published: June 2004

The Kellner wavefunction for a helium‐like ion is the Hartree–Fock solution wherein the orbital is a Slater‐type function with the variationally optimal exponent ζ = Z − 5/16. The Wigner intracule W(u, v) of a system gives the joint quasiprobability of finding two electrons whose position space and momentum space separations are |r1 − r2| = u and |p1 − p2| = v, respectively. In this article, we extend Wigner intracule theory beyond Gaussian‐type functions by deriving W(u, v) for the Kellner helium‐like ions. Although we have not been able to express W(u, v) in closed form, our formulation reduces it to a two‐dimensional integral that can be treated by quadrature. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Comments and references relating to early work in field electron emission
Authors: Kleint Christian
Published: June 2004

This paper adds to the contents of an earlier review entitled ‘On the early history of field emission including attempts of tunnelling spectroscopy’ (Prog. Surf. Sci. 1993; 42: 101) and covers the period up to 1958. In particular, it notes the work on (what one can now recognize as) field‐emission‐induced discharge phenomena in the period 1878–1905 and the work on the developing applications of field emission microscopy in the period 1952–1958, in what had become Drechsler's group in Berlin. Copyright © 2004 John Wiley & Sons, Ltd.
Fabrication of a sub‐wavelength size aperture from a nanosize Si tip using field emission techniques
Authors: Choi Seong S. , Jung M. Y. , Kim D. W. , Park M. J.
Published: June 2004

Explorations are reported that aim towards fabricating sub‐wavelength size metal apertures for near‐field optical probes by using Si microfabrication techniques. Nanosize Si tips on an Si(100) wafer were fabricated using conventional microfabrication techniques and then were coated with films of photoresist, gold or chromium. The objective is selective removal of the coating near the tip apex, using field‐assisted techniques, and the aim of this work has been to explore the behaviour of the coated tip when a voltage is applied. With negative bias on a photoresist‐coated tip, arcing leads to selective removal of the photoresist layer. A positively biased Au‐coated Si tip exhibited tip thickening due to field‐induced migration but no clear evidence of Au overlayer removal by field evaporation. With a Cr‐coated tip, an aperture of diameter ∼160 nm diameter has been fabricated using an Ne ion sputter‐etching technique. Copyright © 2004 John Wiley & Sons, Ltd.
Field emission current technique for investigating the energy gap in BCS‐like superconductors
Authors: Uimanov I. V.
Published: June 2004

This paper considers the ‘current techniques’ for field emission investigations of the parameters of BCS‐like superconductors, which are based on observing the change in field emission current upon the superconducting‐to‐normal (or reverse) phase transition. Based on the results obtained, it has been shown that the field emission current density in the superconducting state is greater than that in the normal state everywhere over the temperature range. Comparison of the expressions obtained with available experimental results has shown that they are in good qualitative and quantitative agreement. Calculating the width of the superconducting gap with the use of the experimental data and the expressions derived in presented paper, we have obtained a value very closely approaching the tabulated one. Copyright © 2004 John Wiley & Sons, Ltd.
Characteristics of carbon‐fibre cold field emission tips with a dielectric coating
Authors: Mousa M. S. , Kelly T. F.
Published: June 2004

Field electron emitters have been prepared by coating a carbon fibre with an epoxylite resin, and their properties investigated. The emission stability is improved compared with an uncoated fibre. An optimum coating thickness of 0.2–0.3 µm has been found. Energy spectra have been measured and peak shifts of up to 1 eV as a function of emission current have been observed. Surprisingly, these peaks shifts are comparable with those found for uncoated carbon fibres and for resin‐coated tungsten emitters. Their origin is not clear, but it seems that resistive drop cannot be the whole explanation. We speculate that these peak shifts may be related to the dynamics of surface‐state occupation at the material/vacuum interface. Copyright © 2004 John Wiley & Sons, Ltd.
Large‐signal and small‐signal electronic equivalent circuits for a field electron emitter
Authors: Hagmann M. J. , Mousa M. S. , Brugat M. , Sheshin E. P. , Baturin A. S.
Published: June 2004

Large‐signal and small‐signal electronic equivalent circuits are developed to describe signal generation by a field electron emitter, with and without a ballast resistor. It is shown that different small‐signal equivalent circuits are needed for the cases where a small alternating voltage variation is applied and where the tunneling process is directly modulated, e.g. by directing a laser at the field emitter. The role of circuit resistances and of the parasitic capacitance between the emitter and its surroundings is crucially different in the two cases, with low‐pass filter behaviour exhibited in the first case and high‐pass filter behaviour in the second. Some consequences for the technical use of a field electron emitter as a non‐linear device are discussed, particularly in applications that involve laser‐assisted field electron emission and in the context of testing field emission tubes. Copyright © 2004 John Wiley & Sons, Ltd.
JCrasher: an automatic robustness tester for Java
Authors: Csallner Christoph , Smaragdakis Yannis
Published: June 2004

JCrasher is an automatic robustness testing tool for Java code. JCrasher examines the type information of a set of Java classes and constructs code fragments that will create instances of different types to test the behavior of public methods under random data. JCrasher attempts to detect bugs by causing the program under test to ‘crash’, that is, to throw an undeclared runtime exception. Although in general the random testing approach has many limitations, it also has the advantage of being completely automatic: o supervision is required except for off‐line inspection of the test ases that have caused a crash. Compared to other similar commercial and research tools, JCrasher offers several novelties: it transitively analyzes methods, determines the size of each tested method's parameter‐space and selects parameter combinations and therefore test cases at random, taking into account the time allocated for testing; it defines heuristics for determining whether a Java exception should be considered as a program bug or whether the JCrasher supplied inputs have violated the code's preconditions; it includes support for efficiently undoing all the state changes introduced by previous tests; it produces test files for JUnit, a popular Java testing tool; and it can be integrated in the Eclipse IDE. Copyright © 2004 John Wiley & Sons, Ltd.
A specification language and service‐oriented architecture to support distributed data management
Authors: Blake M. Brian
Published: June 2004

In some research analysis organizations, effort is duplicated when disseminating raw information to multiple research groups. Although the various groups work on different problems, many times, the initial raw information used is the same. A solution to this problem is creating a centralized process for storing and disseminating common information using database technologies. In this paper, the requirements that must be met to create this distributed database management architecture are described. To support these requirements, a specification language, Specialized Format Markup Language (SFML), and supporting service‐oriented architecture, Specialized Format Generation (SFG), are introduced. These implementations and technologies support the translation of data from relational database formats into user‐specified legacy formats. In addition, this implementation supports the presentation of the resulting data across a Web‐based, distributed medium. SFML and SFG incorporate current technologies such as the eXtensible Markup Language (XML), Java Servlets, the eXtensible Stylesheet Language (XSL), and other relational database approaches. Copyright © 2004 John Wiley & Sons, Ltd.
Blood platelets of the cheetah (Acinonyx jubatus)
Authors: du Plessis L. , Botha A.J. , Reyers F. , Stevens K.
Published: June 2004

The blood platelet count and platelet morphology of 22 adult cheetahs was investigated. The platelet counts of the animals displayed a normal distribution, with a mean count of 344×109/l and a mean platelet volume of 11 fl. Morphological and ultrastructural features of the cheetah platelets revealed the typical platelet morphology of anuclear cells, with granules scattered throughout the cytoplasm. The characteristic surface canalicular system and microtubules were present. True cross‐sections of the platelets had a mean area of 2.146 µm2, circumference of 6.805 µm, and mean minimum and maximum projections of 1.000 µm and 2.933 µm, respectively. Zoo Biol 23:263–271, 2004. © 2004 Wiley‐Liss, Inc.
Positive Status of α‐Fetoprotein and des‐γ‐Carboxy Prothrombin: Important Prognostic Factor for Recurrent Hepatocellular Carcinoma
Authors: Kaibori Masaki , Matsui Yoichi , Yanagida Hidesuke , Yokoigawa Norio , Kwon A‐Hon , Kamiyama Yasuo
Published: June 2004

The aim of this study was to evaluate prognostic factors after the recurrence of hepatocellular carcinoma (HCC) in patients who had undergone hepatic resection. We used univariate and multivariate retrospective analyses of 29 clinicopathologic factors in 143 patients with recurrent HCC. Patients were classified into four groups according to the positivity of tumor markers at the time of recurrence. Survival rates and prognostic factors were then compared among the four groups. Multivariate analysis revealed four independent prognostic factors at recurrence: albumin level < 3.5 g/dl (p = 0.0003), period until recurrence ≤ 1 year (p = 0.0004), positive status of α‐fetoprotein and des‐γ‐carboxy prothrombin (AFP+/DCP+) (p < 0.0001), and portal vein invasion (p < 0.0001). Among groups with varying status of AFP/DCP, the survival rate in patients with AFP+/DCP+ at recurrence was significantly lower than those in the other three groups (+/+ 15.9% vs. +/‐ 47.2%, ‐/+ 44.8%, or ‐/‐ 61.1% at 3 years: p < 0.05). The AFP+/DCP+ group also had significantly higher rates of the recurrence appearing ≤ 1 year after operation (+/+ 68.3% vs. +/‐ 45.2%, ‐/+ 41.9%, or ‐/‐ 32.5%: p = 0.0108), extrahepatic recurrence (29.3% vs. 6.5%, 9.7%, or 5.0%: p = 0.0026), and no treatment at recurrence (29.3% vs. 9.7%, 9.7%, or 5.0%: p = 0.0115). These results indicate that the tumor markers AFP and DCP are significant prognostic factors for recurrent HCC, and their monitoring is essential for improving the prognosis after recurrence.
Functional Maps of Metastases from Breast Cancers: Proof of the Principle that Multidimensional Scaling Can Summarize Disease Progression
Authors: Gray Lincoln C. , Vaidya Jayant S. , Baum Michael , Badwe Rajendra A. , Mittra Indraneel , Siddiqui Tariq , Wiarda Dorothea
Published: June 2004

The mathematic technique of multidimensional scaling can create “functional maps” of metastases from breast cancer such that positions of organs in these maps are proportional to the probability of metastases. Areas that are likely to share disease are close together in a functional map, even though they may be physically distant, and vice versa. Two functional maps of breast cancers—one of local metastases to axillary levels I to III and another of distant metastases—are statistically significant and clinically meaningful. The maps accurately reflect the clinical data (r > 0.97, p < 0.01), and so the progression of disease is revealed in simple visual summaries. As an analogy, the metastatic sites are like buoys on a fluid surface, and cancer spreads from a primary tumor like waves emanating from a point of impact on that surface. Metastases are predicted when the waves swamp the buoys. Because breast cancers do not always spread to the next nearest site, these functional maps do not resemble anatomic maps. The maps are a view of the body as “seen” by the tumor. Several well known clinical features are seen in these maps: most local metastases are to axillary level I; upper‐inner primaries spread equally to levels II and III; in‐transit metastases in the lymph and blood vessels do not follow the pattern of other distant metastases. Future functional maps can expand these summary diagrams to include biologic parameters (gene‐expression profiles or endocrine response) and give valuable insights into patterns of recurrence in different populations.
Surgical Workload and Cost of Postoperative Adhesion‐related Intestinal Obstruction: Importance of Previous Surgery
Authors: Kössi Jyrki A.O. , Salminen Paulina T.P. , Laato Matti K.
Published: June 2004

Postoperative intraabdominal adhesions cause morbidity of varying degree. Intestinal obstruction is the most severe complication of adhesions. This study examined the importance of previous surgery on clinical and economic workloads caused by intestinal obstruction due to postoperative intraabdominal adhesions. All emergency hospitalizations due to adhesion‐related intestinal obstruction from January 1, 1999 to December 31, 1999 in a hospital district serving roughly 450,000 inhabitants was reviewed retrospectively. The patient population was divided into six groups according to the site of previous surgery, and the total as well as group‐related surgical workload and direct costs of inpatient care were analyzed. There were 123 hospitalizations due to postoperative adhesion‐related intestinal obstruction during the study period. A total of 101 patients had experienced 176 operations. The most prevalent operations were colorectal (with or without other operations), upper abdominal, and female reproductive system procedures. Colorectal surgery preceded 40% and 38% of inpatient episodes and inpatient days, respectively. Altogether, 40 operations were performed because of adhesion‐related intestinal obstruction. No differences between groups were seen in terms of the mean operating or theater time. Total annual inpatient costs due to emergency hospitalizations for intestinal adhesion‐related obstruction related to colorectal surgery in a hospital district serving roughly 450,000 inhabitants was $72,520.60 (U.S. dollars) which accounted for 35.3% of all annual costs caused by postoperative adhesion‐related intestinal obstructions. There were no significant differences between groups regarding the total mean inpatient episode costs. Intestinal obstruction due to postoperative adhesions poses substantial costs for the society. Colorectal operations are the most important procedures preceding adhesion‐related intestinal obstruction, accounting for 35.3% to 46.8% of the total clinical workload or costs attributable to postoperative adhesion‐related obstruction.
Vegetation burning in the year 2000: Global burned area estimates from SPOT VEGETATION data
Authors: Tansey Kevin , Grégoire Jean‐Marie , Stroppiana Daniela , Sousa Adélia , Silva João , Pereira José M. C. , Boschetti Luigi , Maggi Marta , Brivio Pietro Alessandro , Fraser Robert , Flasse Stéphane , Ershov Dmitry , Binaghi Elisabetta , Graetz Dean , Peduzzi Pascal
Published: June 2004

The scientific community interested in atmospheric chemistry, gas emissions from vegetation fires, and carbon cycling is currently demanding information on the extent and timing of biomass burning at the global scale. In fact, the area and type of vegetation that is burned on a monthly or annual basis are two of the parameters that provide the greatest uncertainty in the calculation of gas and aerosol emissions and burned biomass. To address this need, an inventory of burned areas at monthly time periods for the year 2000 at a resolution of 1 km2has been produced using satellite data and has been made freely available to the scientific community. In this paper, estimates of burned area and number of burn scars for four broad vegetation classes and reported at the country level for the year 2000 are presented using data taken from the inventory. Over 3.5 million km2of burned areas were detected in the year 2000, of which approximately 80% occurred in areas described as woodlands and shrublands. Approximately 17% of the burned area occurred in grasslands and croplands, the remaining 3% occurred in forests. Almost 600,000 separate burn scars were detected. Descriptions of vegetation burning activity are given for ten regions. Finally, monthly burned area estimates are presented for the Central African Republic to illustrate the usefulness of these data for understanding, monitoring and managing vegetation burning activities.
Global Wildland Fire Emission Model (GWEM): Evaluating the use of global area burnt satellite data
Authors: Hoelzemann Judith J. , Schultz Martin G. , Brasseur Guy P. , Granier Claire , Simon Muriel
Published: June 2004

The new Global Wildland Fire Emission Model (GWEM) has been developed on the basis of data from the European Space Agency's monthly Global Burnt Scar satellite product (GLOBSCAR) and results from the Lund‐Potsdam‐Jena Dynamic Global Vegetation Model (LPJ‐DGVM). GWEM computes monthly emissions of more than 40 chemical compounds and aerosols from forest and savanna fires. This study focuses on an evaluation of the GLOBSCAR data set. The GWEM version presented here makes use of the Moderate‐Resolution Imaging Spectroradiometer (MODIS) land cover map. Emission totals for the year 2000 are 1741 Tg C, 5716 Tg CO2, 271 Tg CO, 12.52 Tg CH4, 9.09 Tg C (as nonmethane hydrocarbons), 8.08 Tg NOx (as NO), 24.30 Tg PM2.5, 15.80 Tg OC, and 1.84 Tg black carbon. These emissions are lower than other estimates found in literature. An evaluation assesses the uncertainties of the individual input data. The GLOBSCAR product yields reasonable estimates of burnt area for large wildland fires in most parts of the globe but experiences problems in some regions where small fires dominate. The seasonality derived from GLOBSCAR differs from other satellite products detecting active fires owing to the different algorithms applied. Application of the presented GWEM results in global chemistry transport modeling will require additional treatment of small deforestation fires in the tropical rain forest regions and small savanna fires, mainly in subequatorial Africa. Further improvements are expected from a more detailed description of the carbon pools and the inclusion of anthropogenic disturbances in the LPJ model.
Comparison between archived and off‐line diagnosed convective mass fluxes in the chemistry transport model TM3
Authors: Olivié D. J. L. , van Velthoven P. F. J. , Beljaars A. C. M. , Kelder H. M.
Published: June 2004

The 40‐year reanalysis data set ERA‐40 from the European Centre for Medium‐Range Weather Forecasts includes, unlike ERA‐15, archived convective mass fluxes. These convective fluxes are useful for off‐line chemistry transport modeling. The impact of using these archived convective mass fluxes (based on a convective parameterization described in Gregory et al. [2000]) instead of off‐line diagnosed mass fluxes (based on a convective parameterization described in Tiedtke [1989]) was investigated with the chemistry transport model TM3. At first sight the two types of mass fluxes look similar. However, some differences can be noted: the archived updrafts extend higher than the off‐line diagnosed ones; they are also less intense below 500 hPa over sea. The archived downdrafts are much weaker than the off‐line diagnosed downdrafts. With archived convective mass fluxes, we found slightly higher 222Rn concentrations in the boundary layer, lower 222Rn values in the free troposphere and significantly higher 222Rn values in the upper troposphere and lower stratosphere. The effect on tropospheric chemistry of using archived mass fluxes instead of diagnosed ones is an increase of NOx and O3 in the free troposphere, but a decrease in the upper troposphere. The differences amount to up to 20% for O3 in the zonal and seasonal mean. Our results thus underline the sensitivity of tropospheric ozone chemistry to the description of convective transport. Comparison with 222Rn observations shows that the archived convective mass fluxes give better agreement in the tropical upper troposphere. More comparisons to free tropospheric observations of 222Rn or another tracer of convective transport will be needed to unambiguously identify either of the convective data sets as optimal for use in chemistry transport models.
Borehole climate reconstructions: Spatial structure and hemispheric averages
Authors: Pollack Henry N. , Smerdon Jason E.
Published: June 2004

Ground surface temperature (GST) reconstructions determined from temperature profiles measured in terrestrial boreholes, when averaged over the Northern Hemisphere, estimate a surface warming of ∼1 K during the interval AD 1500–2000. Other traditional proxy‐based estimates suggest less warming during the same interval. Mann et al. [2003a] have raised two issues with regard to borehole‐based reconstructions. The first focuses on the need for spatial gridding and area‐weighting of the ensemble of borehole‐based GST reconstructions to yield an average hemispheric reconstruction. The second asserts that application of optimal detection techniques show that the GST only weakly displays the spatial structure of the surface air temperature (SAT). We demonstrate the consistency of GST warming estimates by showing that over a wide range of grid element area and occupancy weighting schemes, the five‐century GST change falls in the range of 0.89–1.05 K. We examine the subhemispheric spatial correlation of GST and SAT trends at various spatial scales. In the 5‐degree grid employed for optimal detection, we find that the majority of grid element means are determined from three or fewer boreholes, a number that is insufficient to suppress site‐specific noise via ensemble averaging. Significant spatial correlation between SAT and GST emerges in a 5‐degree grid if low‐occupancy grid elements are excluded, and also in a 30‐degree grid in which grid element means are better determined through higher occupancy. Reconstructions assembled after excluding low‐occupancy grid elements show a five‐century GST change in the range of 1.02–1.06 K.
Daily changes in global cloud cover and Earth transits of the heliospheric current sheet
Authors: Kniveton D. R. , Tinsley B. A.
Published: June 2004

Changes in cloud cover are found to occur for periods of a few days following Earth transits of the heliospheric current sheet (HCS), provided also that the transits occur in years of high stratospheric aerosol loading. Using global cloud products from the International Satellite Cloud Climatology Project (ISCCP) D1 data series, epoch superposition analyses were made for various samples of HCS events. For the period August 1991 to June 1994 for the stratospheric aerosol loading due to the Pinatubo eruption, the analysis of the data in 30° geomagnetic latitude intervals revealed that cloud anomalies that were significant and negative were located in the Southern Hemisphere high and middle latitudes, and anomalies that were significant and positive were found in both hemispheres at low latitudes. When the key days in the superposed epoch analysis were determined by minima in the relativistic electron flux, rather than by the HCS crossings, the location of the significant negative anomalies was in the northern high latitudes, and the location of the significant positive anomalies was in middle latitudes in the Northern Hemisphere. The spatial and temporal patterns of these cloud cover variations are in broad agreement with the expected opposite variations at high and low latitudes of the current density Jz in the global electric circuit caused by the relativistic electron flux variations, during periods when the aerosol loading has made a large increase in stratospheric resistivity.
Global estimates of biomass burning emissions based on satellite imagery for the year 2000
Authors: Ito Akinori , Penner Joyce E.
Published: June 2004

A synthesis of ground‐based measurements and satellite information is described for estimating the amount of monthly averaged biomass burned in year 2000 with a spatial resolution of 1 × 1 km on a global scale. Emissions of trace gases and aerosols from open biomass burning are estimated from burned areas, fuel load maps, combustion factors, and emission factors. Burned area was quantified by using satellite data in conjunction with a fractional vegetation cover map. To account for spatial heterogeneity in the main types of vegetation within each 1‐km grid cell, global fuel load maps have been developed from biomass density data sets for herbaceous and tree‐covered land together with global fractional tree and vegetation cover maps. In regions with 40–60% tree cover a relationship between combustion completeness (or combustion factor) in fine fuels and tree cover based on recent field studies is implemented. In regions with <40% tree cover the combustion factor and emissions are related to global satellite‐derived data for leaf area index. In regions with >60% tree cover and for coarse fuels in regions with 40–60% tree cover, average values for combustion factors and emission factors from field measurements are used. In addition to biomass burning from open vegetation fires, the emissions from biofuel burning in 2000 are estimated. Our best estimate for the global amount of burned biomass in 2000 is 5613 Tg DM yr−1, of which 2814 Tg DM yr−1is associated with open burning and the remainder with biofuels. The total emissions are 2290 Tg C yr−1(as CO2), 496 Tg CO yr−1, 32.2 Tg CH4yr−1, 38.0 Tg NHMC yr−1, 11.5 Tg HCHO yr−1, 9.2 Tg CH3OH yr−1, 21.7 Tg CH3COOH yr−1, and 38.3 Tg PM2.5yr−1. Our estimates for CO2, CO, and CH4emissions from open biomass burning combined with estimates of those from biofuel burning are in the range of the estimates constrained by chemical transport models and measurements. Our use of spatially and temporally explicit data and these comparisons to global models support the conclusion that our source map offers improvements in the emission data sets for estimating the global effects of biomass burning.
Surviving the heavy bombardment: Ancient material at the surface of South Pole‐Aitken Basin
Authors: Petro Noah E. , Pieters Carlé M.
Published: June 2004

The oldest, deepest, and largest basin recognized on the lunar surface is the South Pole‐Aitken (SPA) basin. In the time since its formation, several processes have modified the original interior of the basin, including the introduction of foreign material by impact basins during the period of heavy bombardment. These later basins redistributed material ballistically across the lunar surface forming a mixed and crushed zone on the scale of about one‐kilometer deep. Models of crater excavation, ejected material transport, and mixing during emplacement are used to estimate the amount of foreign material from each basin event introduced into SPA and the degree to which that material mixes with the surface of the interior of SPA. We varied the size of the transient craters for all basins, the degree of mixing between foreign and local material, and the number of basins considered in our evaluation. Our modeling results indicate that materials derived from the original SPA melt breccia comprise at least 15% of the present regolith. The most realistic combinations of model parameters predict a SPA melt breccia component that ranges from 50–80% of the current surface regolith. The compositional character of the SPA interior has apparently not been obliterated by aeons of subsequent basin‐forming events.
An insight into the breakup of Gondwana: Identifying events through low‐temperature thermochronology from the basement rocks of Madagascar
Authors: Seward Diane , Grujic D. , Schreurs G.
Published: June 2004

Fission track analysis was applied to the Precambrian suites of Madagascar in order to identify the lower‐temperature cooling histories and their relationships to the Phanerozoic events that affected the island. Apatite ages range from 431 to 68 Ma, and zircon ages range from 452 to 238 Ma. Thermochronologically, the island can be divided into a southern, central, and northern region each with a subdivision on an east‐west basis. The southern region is sharply separated from the central region by strongly contrasting apparent apatite ages over the northwest‐southeast striking Ranotsara Shear Zone (RSZ). The change in apparent ages over the RSZ is indicative of later reactivation along younger brittle faults. The central region has the oldest ages of the island and has a diffuse contact to the third region northward. Along the entire western margin of the Precambrian basement initial Paleozoic exhumation was followed by heating (burial by sediments) during Jurassic and Cretaceous times. A decrease in ages along the eastern margin from 119 to 68 Ma coincides with the predicted positions of the Marion hot spot after effects of erosion are considered. On the other hand, these ages may represent progressive opening of the margin in a southward direction together with associated denudation of the rift shoulder. The eastern part of the central region has remained very stable since at least Devonian times, undergoing only long‐term very slow exhumation at rates of 1–5 m/Myr.
Irrigated agriculture in Italy and water regulation under the European Union water framework directive
Authors: Bazzani G. M. , Di Pasquale S. , Gallerani V. , Viaggi D.
Published: June 2004

The legal framework in the EU is faced today with the new water framework directive (WFD) (60/2000) that sets up new criteria for water management, regulation, and pricing. The aim of this paper is to analyze the problem of water regulation in agriculture in connection to the WFD. This is done by setting up and testing a simulation model based on the integration of a mathematical programming model at farm level and an optimal regulation model at the level of irrigation boards. The model allows quantifying water demand and optimal regulation from the policy maker's point of view. When implementing both full cost recovery and the polluter pays principle, the results show likely major impacts of water pricing on farm income and employment. The optimal policy is a combination of pricing instruments related at the same time to crop mix, water consumption, and pollution. Transaction costs connected to policy implementation have to be weighted against the incentive benefits of volumetric pricing. Altogether, economic, social, and environmental issues have to be carefully considered in order to design suitable water policies.
The mixed layer depth in the North Pacific as detected by the Argo floats
Authors: Ohno Yuko , Kobayashi Taiyo , Iwasaka Naoto , Suga Toshio
Published: June 2004

The spatial and temporal distributions of the mixed layer depth (MLD) in the North Pacific were examined using the Argo float data for 2000–2003. The MLD distributions generally corresponded to those obtained from the WOA01 except in the northwestern Pacific (30°–45°N, 140°E–170°W), where the MLDs detected by the floats were systematically shallower (deeper) in the region to the north (south) of the Kuroshio Extension (KE) than the climatological MLDs. This region was also characterized by considerable mesoscale variability in the spatial distribution of the MLD. A detailed examination of the seasonal evolution of MLD in selected small areas revealed that both the timing and amplitude of the seasonal changes obtained from the Argo floats differed remarkably from the climatology in the south of the KE.
CO2 seasonality indicates origins of post‐Pinatubo sink
Authors: Angert A. , Biraud S. , Bonfils C. , Buermann W. , Fung I.
Published: June 2004

An enhanced carbon sink of ∼2PgC/yr was observed following the Mount Pinatubo eruption. In this study we used a biogeochemical model (CASA) linked to an atmospheric tracer model (MATCH) with interannually varying transport, to predict the atmospheric CO2 response to various hypotheses for the enhanced sink. By comparing the modeled CO2 growth rate, and seasonal minimum with observation we found that global Net Primary Production could not have increased following the eruption. The enhanced sink is explained by several land and ocean sink mechanisms acting in concert.
Dimensionality‐reduction approach to the thermal radiative transfer equation inverse problem
Authors: Masiello G. , Serio C.
Published: June 2004

An original algorithm is illustrated for the inversion of geophysical parameters from spectral observations in the thermal band. The algorithm exploits the Hotelling transform and projects the linearized version of the radiative transfer equation in a space of reduced dimensionality. The inversion is performed in this latter space, which speeds up the computations and makes the method attractive for real‐time retrieval from high spectral resolution infrared observations.
The role of trench retreat on the geometry and stress regime in the subduction complexes of the Mediterranean
Authors: Rizzetto Catia , Marotta Anna Maria , Sabadini Roberto
Published: June 2004

Numerical modelling of the Aegean and Calabrian subductions using geological reconstructions starting 75–80 Myr before the present reproduces the present‐day geometries of the slabs and mantle wedges imaged by seismic tomography. The change from a shallow subduction dip of about 15° from the surface to a depth of 200 km into a dip of 60° below this depth in the Aegean subduction is caused by the south‐west migration of the trench at the velocity of 3 cm/yr, obtained from GPS and geological data. The largest dip of 70° Calabrian subduction is caused by the termination of the active phase of opening of the Tyrrhenian back‐arc basin and by the essentially purely gravitational sinking of the slab, in agreement with the null trench‐migration velocity obtained from GPS data in Calabria. These two different tectonic settings are the ultimate causes of the different styles of seismicity within the two subduction complexes.
Anatomy of a flux transfer event seen by Cluster
Authors: Sonnerup B. U. Ö. , Hasegawa H. , Paschmann G.
Published: June 2004

Data from Cluster are used to study the structure of a flux transfer event (FTE), seen near the northern cusp. We employ Grad‐Shafranov reconstruction, using measured fields from all four spacecraft to produce a map of the FTE cross section. The FTE consists of a flux rope of approximate size 1RE and irregular shape, embedded in the magnetopause. Its axis is tangential to the magnetopause. Since no reconnection signatures are seen, the map provides a fossil record of the prior reconnection process that created the flux rope: the strong core field indicates that it was generated by component merging. An average reconnection electric field ≥0.18 mV/m must have occurred in the burst of reconnection that created the FTE. The total axial () current and magnetic flux in the FTE were −0.66 MAmp and +2.07 MWeber, respectively.
Energetic electrons in the inner part of the Jovian magnetosphere and their relation to auroral emissions
Authors: Tomás A. T. , Woch J. , Krupp N. , Lagg A. , Glassmeier K.‐H. , Kurth W. S.
Published: June 2004

The energetic particle distribution in the magnetosphere of Jupiter changes significantly between the inner and the middle magnetosphere. One of the most prominent changes is a transition of the electron pitch angle distribution (PAD) from a pancake to a bidirectional distribution. The transition is a persistent and localized feature defining a distinct spatial boundary between 10 and 17 RJ. We discuss the possible relation between the PAD boundary and some of the observed structures in the Jovian aurora. A comparison between the Hubble Space Telescope observations and the predicted ionospheric footprints of the PAD boundary indicates a good correlation, with a discrete belt of emissions equatorward of the main auroral oval. Furthermore, the precipitation energy flux associated with the energetic electron distribution at the PAD boundary is compatible with the brightness range of these auroral emissions.
Resonance Raman contribution to the D band of carbon materials: Modeling defects with quantum chemistry
Authors: Negri Fabrizia , di Donato Eugenio , Tommasini Matteo , Castiglioni Chiara , Zerbi Giuseppe , Müllen Klaus
Published: June 2004

Polycyclic aromatic hydrocarbons (PAHs) are employed to model the Raman features that are generally associated with sp2 nanostructures in carbon materials or with disorder and defects in graphitic materials. To this end molecular parameters (geometry changes upon electronic excitation, vibrational normal modes, and displacement parameters) are computed with semiempirical quantum-chemical methods for a series of PAHs ranging from 6 to 384 carbon atoms, and Raman intensities are evaluated according to Albrecht’s formalism restricted to the A term. The computed preresonance and resonance Raman intensities are compared with available experimental data for hexa-peri-hexabenzocoronene and for pyrene. For the latter compound, simulations carried out at semiempirical and ab initio levels of theory are shown to be of comparable quality. Finally, the collection of displacement parameters computed for the sample of conjugated molecules is used to model the effect of disorder and defects in the Raman response of a carbon material containing sp2 islands. It is shown that the computed D-band frequency dispersion, with respect to excitation wavelength, reproduces closely the experimental data measured for sp2 hybridized carbon materials.
Second order average Hamiltonian theory of symmetry-based pulse schemes in the nuclear magnetic resonance of rotating solids: Application to triple-quantum dipolar recoupling
Authors: Brinkmann Andreas , Edén Mattias
Published: June 2004

The average Hamiltonian theory (AHT) of several classes of symmetry-based radio-frequency pulse sequences is developed to second order, allowing quantitative analyses of a wide range of recoupling and decoupling applications in magic-angle-spinning solid state nuclear magnetic resonance. General closed analytical expressions are presented for a cross term between any two interactions recoupled to second order AHT. We classify them into different categories and show that some properties of the recoupling pulse sequence may be predicted directly from this classification. These results are applied to examine a novel homonuclear recoupling strategy, effecting a second order average dipolar Hamiltonian comprising trilinear triple quantum (3Q) spin operators. We discuss general features and design principles of such 3Q recoupling sequences and demonstrate by numerical simulations and experiments that they provide more efficient excitation of C13 3Q coherences compared to previous techniques. We passed up to 15% of the signal through a state of 3Q coherence in rotating powders of uniformly C13-labeled alanine and tyrosine. Second order recoupling-based C13 homonuclear 3Q correlation spectroscopy is introduced and demonstrated on tyrosine.
Ultrafast dynamics for electron photodetachment from aqueous hydroxide
Authors: Crowell Robert A. , Lian Rui , Shkrob Ilya A. , Bartels David M. , Chen Xiyi , Bradforth Stephen E.
Published: June 2004

Charge-transfer-to-solvent reactions of hydroxide induced by 200 nm monophotonic or 337 and 389 nm biphotonic excitation of this anion in aqueous solution have been studied by means of pump–probe ultrafast laser spectroscopy. Transient absorption kinetics of the hydrated electron, eaq−, have been observed, from a few hundred femtoseconds out to 600 ps, and studied as function of hydroxide concentration and temperature. The geminate decay kinetics are bimodal, with a fast exponential component (∼13 ps) and a slower power “tail” due to the diffusional escape of the electrons. For the biphotonic excitation, the extrapolated fraction of escaped electrons is 1.8 times higher than for the monophotonic 200 nm excitation (31% versus 17.5% at 25 °C, respectively), due to the broadening of the electron distribution. The biphotonic electron detachment is very inefficient; the corresponding absorption coefficient at 400 nm is <4 cm TW−1 M−1 (assuming unity quantum efficiency for the photodetachment). For [OH−] between 10 mM and 10 M, almost no concentration dependence of the time profiles of solvated electron kinetics was observed. At higher temperature, the escape fraction of the electrons increases with a slope of 3×10−3 K−1 and the recombination and diffusion-controlled dissociation of the close pairs become faster. Activation energies of 8.3 and 22.3 kJ/mol for these two processes were obtained. The semianalytical theory of Shushin for diffusion controlled reactions in the central force field was used to model the geminate dynamics. The implications of these results for photoionization of water are discussed.
Quantum chemical ab initio calculations of correlation effects in complex polymers: Poly(para-phenylene)
Authors: Willnauer Christa , Birkenheuer Uwe
Published: June 2004

Different quantum chemical approaches to the ground state correlation energy per unit cell of infinite poly(para-phenylene) (PPP) chains are presented. PPP is an organic polymer with interesting optical properties, due to its conjugated, aromatic π system. The inclusion of correlation effects is crucial for a sound quantum chemical description of such a system. The correlation calculations were performed on the coupled cluster with single and double excitations (CCSD) level of theory using Dunning’s spd correlation consistent polarized valence double-zeta basis sets. The correlation energy per unit cell is determined by means of the incremental method, which comprises series of CCSD calculations with partial excitation spaces. The resulting correlation energy per unit cell of PPP is −21.797 eV and compares well with that obtained by a simple but much more demanding cluster convergence approach (−21.775 eV). In addition, the accuracy and performance of the incremental scheme is discussed with respect to full CCSD benchmark calculations on PPP oligomers. Two variants are considered, the conventional one based on bond-type local units, and an extended one based on natural chemical subunits. Whereas it is difficult to reach “chemical” accuracy with the first variant, the second variant allows an accurate and efficient treatment with only a few individual CCSD calculations for a polymer with an aromatic π system such as PPP.
Spontaneous transformation of water’s high-density amorph and a two-stage crystallization to ice VI at 1 GPa: A dielectric study
Authors: Andersson Ove , Johari G. P.
Published: June 2004

Dielectric relaxation spectra of a metastable crystal phase formed on implosive and exothermic transformation of pressure-amorphized hexagonal ice have been measured in situ at 0.97 GPa pressure over a range of temperature. The metastable phase showed no relaxation peak at 130 K and 0.97 GPa. When heated at a fixed pressure of 0.97 GPa, it began to transform at ∼145 K exothermally to a phase whose relaxation rate and equilibrium dielectric permittivity increased. A second, but slower exothermic transformation also occurred at ∼175 K. After keeping at 213 K, the relaxation rate and equilibrium permittivity reached the known values of these two quantities for ice VI. Thus the metastable phase transformed to ice VI in two stages. It is conjectured that the intermediate phase in this transformation could be ice XII. The rate of transformation is not determined by the reorientational relaxation rate of water molecules in the ices.
Calculation of indirect nuclear spin–spin coupling constants within the regular approximation for relativistic effects
Authors: Filatov Michael , Cremer Dieter
Published: June 2004

A new method for calculating the indirect nuclear spin–spin coupling constant within the regular approximation to the exact relativistic Hamiltonian is presented. The method is completely analytic in the sense that it does not employ numeric integration for the evaluation of relativistic corrections to the molecular Hamiltonian. It can be applied at the level of conventional wave function theory or density functional theory. In the latter case, both pure and hybrid density functionals can be used for the calculation of the quasirelativistic spin–spin coupling constants. The new method is used in connection with the infinite-order regular approximation with modified metric (IORAmm) to calculate the spin–spin coupling constants for molecules containing heavy elements. The importance of including exact exchange into the density functional calculations is demonstrated.