bluuebunny/crossref_metadata_2025 huggingface dataset:
Nontrivial carrier recombination dynamics and optical properties of over‐excited GaN/AlN quantum dots
Authors: Kalliakos S. , Bretagnon T. , Lefebvre P. , Juillaguet S. , Taliercio T. , Guillet T. , Gil B. , Grandjean N. , Damilano B. , Dussaigne A. , Massies J.
Published: September 2004

We analyze the low temperature photoluminescence properties of two multi‐layer stacking of GaN/AlN quantum dots. We report drastic differences of linewidths between continuous wave and time‐resolved photoluminescence experiments. After the pulsed excitation, time‐resolved photoluminescence reveals a substantial red shift of the line, which keeps a fairly constant width. In continuous wave experiments, the screening of internal electric fields by accumulation of e–h pairs in quantum dot planes induces a blue‐shift. For samples with large number of quantum dot planes an unexpected narrowing of the emission line is observed when the laser intensity is increased. We assign the observed behaviors of energies and linewidths to the contributions of the in‐depth decrease of the degree of excitation of the different planes. Our interpretation is supported by the use of a model based on a self‐consistent solution of the Schrödinger and Poisson equations within the envelope function approximation. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical properties of rare‐earth doped quantum dots grown by plasma‐assisted MBE
Authors: Hori Y. , Andreev T. , Jalabert D. , Biquard X. , Monroy E. , Tanaka M. , Oda O. , Dang Le Si , Daudin B.
Published: September 2004

We demonstrate Eu, Tm and Er doping of GaN quantum dots. In Er‐doped samples, two very sharp blue lines were observed. These lines were dominant over the green lines reported in the case of Er‐doped GaN thick layers. However, intensities were very low in comparison with Eu‐doped and Tm‐doped GaN QDs. Intense blue emission from Tm‐doped GaN QDs was observed. Temperature‐dependent photoluminescence was studied, and the intensity only decreased to 27% between room temperature and 10 K. Structural studies on Tm‐doped samples showed that the kinetic role of Tm atoms was different from that of Eu atoms. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal analysis of GaN‐based LEDs using the finite element method and unit temperature profile approach
Authors: Lee Tae Hee , Kim Lan , Hwang Woong Joon , Lee C. C. , Shin Moo Whan
Published: September 2004

This paper reports on the thermal modelling of GaN‐based LEDs. The theoretical calculation was made by combining an analytical simulation employing the Unit Temperature Profile Approach (UTPA) and Finite Element Method (FEM). An interfacing process was made by the optimization of the modelling input parameters used in the analytical simulator. The calculated temperatures of the LED chip inside the epoxy package was compared with the experimentally measured data and the optimized heat transfer coefficients were extracted. The extracted parameters were implemented into the numerical thermal calculation of the package surface using FEM. By the effective interfacing process between the two modelling tools, it is demonstrated that the analytical simulator can be utilized for the accurate prediction of the surface temperatures of LED packaging with non‐flat surface. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron beam induced light emission from the polythiophene derivative/ITO structure
Authors: Panin Gennady N. , Kang Tae Won , Lee Haiwon
Published: September 2004

Light emission from a poly‐[3‐(2‐benzotriazolo)‐ethylthiophene]/indium tin oxide (PBET/ITO) structure under electron beam excitation was investigated. Two peaks at 580 nm (green) and 620 nm (orange) are observed under low excitation. An ultraviolet (UV) emission centered at 347 nm appeared under high current excitation. The ratio of the UV/green‐orange band intensities increases with an increase of the current density and with a decrease of temperature. Stimulated emission and lasing from the polythiophene derivative structure are observed at high current density. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impurity band in magnesium‐doped GaN layers grown by metalorganic chemical vapor deposition
Authors: Kang D. S. , Cheong M. G. , Lee S.‐K. , Suh E.‐K. , Hong C.‐H. , Lee H. J.
Published: September 2004

InGaN/GaN quantum well light emitting diodes (LEDs) were grown with p‐GaN layers of varied Mg impurity content. As the concentration of Mg impurity increases, the hole concentration increases up to a critical Mg impurity density and then decreases with further increase of the impurity. In this work, it is proposed that the accepters form the impurity band and that the band behavior with Mg content variation is attributed to the properties of the p‐GaN layer and the p‐layer effect on the I–V characteristics of LED. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strong Eu emission of annealed Y2O3:Eu nanotube and nano‐sized crystals
Authors: Sekita Masami , Iwanaga Kenichi , Hamasuna Tomomi , Mohri Shinji , Uota Masafumi , Yada Mitsunori , Kijima Tsuyoshi
Published: September 2004

We have observed a drastic increase of the Eu3+ emission intensity by annealing nanotubes and nano‐sized hexagonal‐mesostructured crystals of the Y2O3:Eu system together with bulk samples. It is found that there are three Eu3+ sites in all samples. Stark splitting schemes are proposed for the three homogeneous sites. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of Yttria‐Based Crystalline and Lamellar Nanostructures and their Formation Mechanism
Authors: Pinna Nicola , Garnweitner Georg , Beato Pablo , Niederberger Markus , Antonietti Markus
Published: September 2004

A nonaqueous synthetic route for the preparation of a regular crystalline yttria mesostructure is presented. The reaction between yttrium alkoxides and benzyl alcohol results in the formation of a highly ordered lamellar nanocomposite consisting of yttria layers with a confined thickness of about 0.6 nm, separated from each other by organic layers of intercalated benzoate molecules. Doping with europium leads to strong red luminescence. The nanostructure formation proceeds via two reactions. A CC bond formation occurs between benzyl alcohol and the isopropanolate ligand. At the same time, yttrium oxide catalyzes two low‐temperature hydride‐transfer reactions to form benzoic acid and toluene from benzyl alcohol via benzaldehyde, thus limiting the growth of the thickness of the lamellae.
Protein A – a new ligand for human C‐reactive protein
Authors: Das Tanusree , Mandal Chhabinath , Mandal Chitra
Published: September 2004

Phosphorylcholine (PC) is a classical ligand of C‐reactive protein (CRP), a clinically important acute phase protein. In search of new ligands, CRPs were affinity‐purified from several pathological samples, which exhibited distinct molecular variants induced in different diseases. Both glycosylated and non‐glycosylated CRPs showed calcium‐independent differential‐binding to Staphylococcus aureus cell‐surface Protein A. CRP possesses separate binding sites for Protein A and PC with different binding constants. We have demonstrated that Protein A is another ligand in addition to PC establishing an extended definition of CRP. Protein A binding may impart immunomodulatory roles of CRP in combating microorganisms or other foreign materials.
Syndecan‐dependent binding of Drosophila hemocytes to laminin α3/5 chain LG4‐5 modules: potential role in sessile hemocyte islets formation
Authors: Narita Ryo , Yamashita Hironobu , Goto Akira , Imai Hiromi , Ichihara Shigeyuki , Mori Hitoshi , Kitagawa Yasuo
Published: September 2004

Heparin‐column chromatography and elastase‐digestion of medium from hemocyte Kc167 gave Drosophila laminin α3/5βγ trimer, α3/5LG2‐3 and α3/5LG4‐5 modules with eluting NaCl concentrations of 450, 280 and 450 mM, respectively. Kc167 cells bound dish surface with α3/5βγ trimer or α3/5LG4‐5, but not with α3/5LG2‐3 modules. Cell binding was counteracted by treating with heparin or heparan sulfate. RNA interference of syndecan in Kc167 cells impaired the binding, but that of dally or dally‐like did not. Green fluorescent protein‐expressing hemocytes also bound surface with α3/5βγ trimer or α3/5LG4‐5 module. Thus, syndecan‐dependent binding of hemocytes to laminin may have a potential role in sessile hemocytes islets formation in T2‐A8 segments of Drosophila.
Gluconate dehydratase from the promiscuous Entner–Doudoroff pathway in Sulfolobus solfataricus
Authors: Lamble Henry J. , Milburn Christine C. , Taylor Garry L. , Hough David W. , Danson Michael J.
Published: September 2004

An investigation has been carried out into gluconate dehydratase from the hyperthermophilic Archaeon Sulfolobus solfataricus. The enzyme has been purified from cell extracts of the organism and found to be responsible for both gluconate and galactonate dehydratase activities. It was shown to be a 45 kDa monomer with a half‐life of 41 min at 95 °C and it exhibited similar catalytic efficiency with both substrates. Taken alongside the recent work on glucose dehydrogenase and 2‐keto‐3‐deoxygluconate aldolase, this report clearly demonstrates that the entire non‐phosphorylative Entner–Doudoroff pathway of S. solfataricus is promiscuous for the metabolism of both glucose and galactose.
β‐Synuclein exhibits chaperone activity more efficiently than α‐synuclein
Authors: Lee Daekyun , Paik Seung R. , Choi Kwan Yong
Published: September 2004

β‐Synuclein exhibits high sequence homology and structural similarity with α‐synuclein, a protein implicated in the pathogenesis of Parkinson's disease. We investigated the chaperone function of β‐synuclein and its anti‐fibrillar activity in comparison with α‐synuclein. β‐Synuclein suppressed the heat‐induced aggregation of aldolase, alcohol dehydrogenase, and citrate synthase, and its anti‐aggregative activity was remarkably higher than that of α‐synuclein. Heat‐induced inactivation of citrate synthase was significantly protected by β‐synuclein. Moreover, β‐synuclein inhibited the amyloid formation of both Aβ1–40 and α‐synuclein. It is, therefore, suggested that β‐synuclein can prevent abnormal protein aggregations more effectively than α‐synuclein by acting as a molecular chaperone.
Clustering of cellular prion protein induces ERK1/2 and stathmin phosphorylation in GT1‐7 neuronal cells
Authors: Monnet Céline , Gavard Julie , Mège René-Marc , Sobel André
Published: September 2004

The physiological role of the prion protein is largely unknown. Here, clustering of prion at the surface of GT1‐7 cells was observed upon anti‐prion antibody treatments. This clustering was associated with a rapid and transient phosphorylation of the mitogen activated protein kinases (MAPKs) extracellular receptor kinases 1 and 2 (ERK1/2), and also of the microtubule‐destabilizing protein stathmin at serine 16. The specificity of this antibody‐mediated activation was ascertained by its inhibition by prion small interfering RNA. The phosphorylation of ERK1/2 but not that of stathmin was abolished by the MAPK/ERK kinase 1 inhibitor U0126, whereas both signaling pathways were blocked by the specific inhibitor of the epidermal growth factor receptor AG1478, suggesting the likely recruitment of this receptor upon prion clustering.
Autoregulation of regulatory proteins is key for dynamic operation of GAL switch in Saccharomyces cerevisiae
Authors: Ruhela Anurag , Verma Malkhey , Edwards Jeremy S. , Bhat P.J. , Bhartiya Sharad , Venkatesh K.V.
Published: September 2004

Autoregulation and nucleocytoplasmic shuttling play important roles in the operation of the GAL regulatory system. However, the significance of these mechanisms in the overall operation of the switch is unclear. In this work, we develop a dynamic model for the GAL system and further validate the same using steady‐state and dynamic experimental expression data. Next, the model is used to delineate the relevance of shuttling and autoregulation in response to inducing, repressing, and non‐inducing–non‐repressing media. The analysis indicates that autoregulation of the repressor, Gal80p, is key in obtaining three distinct steady states in response to the three media. In particular, the analysis rationalizes the intuitively paradoxical observation that the concentration of repressor, Gal80p, actually increases in response to an increase in the inducer concentration. On the other hand, although nucleocytoplasmic shuttling does not affect the dynamics of the system, it plays a dominant role in obtaining a sensitive response to galactose. The dynamic model was also used to obtain insights on the preculturing effect on the system behavior.
Indole‐3‐carbinol activates the cyclin‐dependent kinase inhibitor p15INK4b gene
Authors: Matsuzaki Youichirou , Koyama Makoto , Hitomi Toshiaki , Kawanaka Mayumi , Sakai Toshiyuki
Published: September 2004

Indole‐3‐carbinol (I3C) is a naturally occurring compound found in vegetables such as broccoli and cauliflower, and has been shown to arrest human tumor cells in the G1 phase of the cell cycle. However, the molecular mechanism responsible for this effect has not been sufficiently elucidated. We report here that I3C activates the cyclin‐dependent kinase (CDK) inhibitor p15INK4b gene through its promoter, accompanied by cell growth inhibition in HaCaT cells. Treatment with I3C almost did not affect the expressions of the other CDK inhibitors such as p19INK4d, p21WAF1 and p27Kip1. These results suggest that p15INK4b is an important molecular target of I3C among CDK inhibitors.
Can foreign direct investment help Poland catch up with the EU?
Authors: Weresa Marzenna Anna
Published: September 2004

The paper examines the extent to which the inflow off oreign direct investment (FDI) helps Poland to catch up with the EU.

FDI can facilitate the process of catching up mainly through transfer and diffusion of technology, which leads to upgrading oftechnological and innovative potential ofa host country. The paper is aimed at assessing whether FDI is correlated with the innovation processes in different branches ofthe Polish industry. A regression analysis conducted in this paper has confirmed that, except for low-technology industries, FDI impacts Poland’s innovation efforts and thus helps Poland to catch up with the EU.
Evolution of the mane and group‐living in the lion (Panthera leo): a review
Authors: Yamaguchi Nobuyuki , Cooper Alan , Werdelin Lars , Macdonald David W.
Published: September 2004

The evolutionary history of the lion Panthera leo began in Pliocene east Africa, as open habitats expanded towards the end of the Cenozoic. During the middle–late Pleistocene, lions spread to most parts of Eurasia, North America, and may have eventually reached as far south as Peru. Lions probably evolved group‐living behaviour before they expanded out of Africa, and this trait is likely to have prevailed in subsequent populations. The first lions were presumed to have been maneless, and maneless forms seem to have persisted in Europe, and possibly the New World, until around 10 000 years ago. The maned form may have appeared c. 320 000–190 000 years ago, and may have had a selective advantage that enabled it to expand to replace the range of earlier maneless forms throughout Africa and western Eurasia by historic times: ‘latest wave hypothesis’.
Social rank in female reindeer (Rangifer tarandus): effects of body mass, antler size and age
Authors: Holand Ø , Gjøstein H. , Losvar A. , Kumpula J. , Smith M. E. , Røed K. H. , Nieminen M. , Weladji R. B.
Published: September 2004

In polygynous mammals, fitness differences may reflect differences in phenotypic quality as well as experience. This study determines dominance hierarchy among female reindeer Rangifer tarandus from two experimental herds (consisting of c. 45 animals in each) during 2 consecutive years. The influence of body mass, antler size and age on social rank in the herds was investigated, first using simple regression analysis. The combined effect of body mass, age and antler size on female rank was further assessed using principal component analysis, as these three parameters were significantly correlated. The improved Laundau linearity index of c. 0.5 (Pr < 0.001) in both herds indicated that a substantial part of the hierarchies was explained by their linearity properties. Consistently, body mass, female age and antler size, as well as their combined effect (measured by the scores on the main axis, PC1), influenced social rank in all four groups. It was concluded that both body mass and age are good predictors of social rank in female reindeer, whereas antler size in comparison plays a less important role in herds with a ‘normal’ female age structure. This suggests that female antlers may have evolved in intersexual rather than intrasexual competition. The temporal variations in the importance of body mass and age, probably owing to variation in female age structure between the 2 years, calls for conservative interpretations of whether body mass or age is more important in determining social rank among female reindeer. This is confirmed by the PCA analyses, where all three variables contributed more or less equally to the first component, the size variable, which on average explained more of the variation in female rank than body mass and age, suggesting that phenotypic quality expressed as the combination of the three variables is a better predictor of social rank than the variables per se. Hence, general conclusions about social rank based on single studies including few animals may not be credible.
Selection of food and ranging behaviour in a sexually monomorphic folivorous lemur: Lepilemur ruficaudatus
Authors: Ganzhorn Jörg U. , Pietsch Thomas , Fietz Joanna , Gross Sabine , Schmid Jutta , Steiner Nathalie
Published: September 2004

Monomorphic lemurs of Madagascar allow us to investigate whether there are behavioural mechanisms that compensate for sex‐specific differences in the costs of maintenance and reproduction in arboreal primates. Food selection of the pair‐living Lepilemur ruficaudatus was studied in relation to food chemistry, and travel distances were measured as possible indications of differential investment in ranging activities (possibly related to the defence of territories and/or mating opportunities). Fourteen females and 14 males were radio‐tracked for a total of 365 half‐nights (from dusk to midnight or from midnight to dawn) at different times of the year (birth, lactation and weaning, pre‐mating, post‐mating). When based on monthly means, the two sexes did not differ in nightly travel distances. Food selection of females and males did not differ in relation to the chemical composition of leaves, but fruits consumed by females had lower fibre contents than fruits consumed by males. Even though other behavioural data are fragmentary, little evidence exists for behavioural mechanisms in L. ruficaudatus to compensate for the different energetic costs of females and males.
Encounters between two sympatric carnivores: red foxes (Vulpes vulpes) and European badgers (Meles meles)
Authors: Macdonald D. W. , Buesching C. D. , Stopka P. , Henderson J. , Ellwood S. A. , Baker S. E.
Published: September 2004

Interspecific interactions between sympatric carnivores have important implications for intra‐guild competition, epidemiology (here especially in the context of rabies and bovine tuberculosis), and strategies for species‐specific population management. Data are provided on 135 interspecific encounters between at least 35 European badgers Meles meles and a minimum of five red foxes Vulpes vulpes, gathered with the aid of remote video surveillance at an artificial feeding site, and in the vicinity of six badger setts. We hypothesized that interspecific competition would be manifest in aggression and changes in vigilance and feeding, with the larger badger having the advantage, and we sought to explore differences in any such changes at the two types of site. Badgers were clearly dominant over foxes, fed in longer bouts and were less vigilant. At badger setts, once it was clear that the encounter was not going to escalate to aggression, each species was unaffected by the presence, proximity or orientation of the other. There are preliminary indications that foxes sometimes seek the company of badgers.
Molecular data suggest that melanistic ectotherms at the south‐western tip of Africa are the products of Miocene climatic events: evidence from cordylid lizards
Authors: Daniels S. R. , Mouton P. le F. N. , Du Toit D. A.
Published: September 2004

In the present study the evolutionary relationships among Cordylusniger–oelofseni–cordylus are investigated using molecular sequence data to: (1) estimate the divergence within this group; (2) date the origin of melanism in the clade and to evaluate possible palaeoecological events responsible for its evolution; (3) examine the systematic relationships among the three isolated populations of C. oelofseni that were previously shown to be polyphyletic using allozyme data. The recovered topology for the combined sequence data (16S and NADH dehydrogenase component 2 (ND2)) among C. niger–oelofseni–cordylus suggests that melanism evolved only once in the clade. The application of a molecular clock to the data demonstrates that melanism evolved during the Miocene epoch, 17–15 million years ago. We believe that the development of a cold‐water current and upwelling system along the south‐west coast of Africa during this epoch was instrumental in the evolution of melanism in this lizard clade and possibly also in other ectotherm clades with melanistic forms occurring in the area. The results show that C. oelofseni, as presently construed, is composed of three distinct evolutionary lineages, with no shared haplotypes present and marked sequence divergence. Two of the three lineages represent undescribed species. Cordylus cordylus is composed of two distinct clades, a montane clade and a coastal lowland clade. Cladogenic activity in mountain areas of the Western Cape in South Africa has been particularly pronounced and the systematic diversity of many taxa may have been underestimated.
A change of diet from rodents to rabbits (Oryctolagus cuniculus). Is the wildcat (Felis silvestris) a specialist predator?
Authors: Malo Aurelio F. , Lozano Jorge , Huertas Daniel L. , Virgós Emilio
Published: September 2004

The results of a study testing the hypothesis that wildcats Felis silvestris are rodent‐specialist predators is reported. The diet of wildcats was studied in different habitats from central Spain where rabbits Oryctolagus cuniculus were either present or absent in order to explore whether the wildcat is a facultative or a rodent specialist. We predicted that if the wildcat was a rodent specialist there would be no differences in rodent composition in scats between areas with or without another profitable prey such as rabbits. To test this hypothesis, 239 scats were collected in two contrasting habitat types: Mediterranean vegetation areas, where rabbits were either present or absent, and Pyrenean oak forests, where there were no rabbits. All areas and habitat types were sampled in different seasons. The frequency of occurrence and biomass of different prey items and diet diversity were compared between habitats and areas with the presence/absence of rabbits. Wildcats consumed significantly fewer rodents in areas with rabbits than in areas where rabbits were absent, and diet diversity showed important seasonal variations. Values for diet diversity were lower in areas where rabbits were present. Thus it can be stated that wildcats do not specialize in rodents, and we suggest a facultative specialization on different prey items (rabbits or rodents) according to prey availability.
Factors affecting habitat selection by smooth‐coated otters (Lutra perspicillata) in Kerala, India
Authors: Anoop K. R. , Hussain S. A.
Published: September 2004

The factors affecting habitat selection by smooth‐coated otter Lutra perspicillata were studied along the Periyar Lake within the Periyar Tiger Reserve, Kerala, India, between November 2000 and April 2001. The importance of different habitat features influencing habitat selection was assessed using ordination technique. The presence of holts, spraint sites, grooming sites and footprints were considered as good indicators of the use of an area by the otters. For foraging, otters selected less rocky areas of the shallower parts of the lake, which are narrower and slanting. The number of streams joining these areas was more than on the other stretches of the lake and the bankside vegetation was dense. The deeper and wider areas of the lake were avoided. Holts were found in a variety of habitats, such as grass and Lantana thickets, rock crevices and under fallen logs and roots of standing trees at an average distance of 18 m from the water level. Grooming sites were characterized by high sand content and nearness to water.
Horn growth but not asymmetry heralds the onset of senescence in male Alpine ibex (Capra ibex)
Authors: von Hardenberg Achaz , Bassano Bruno , Arranz Maria del Pilar Zumel , Bogliani Giuseppe
Published: September 2004

Senescence can be defined as accelerating phenotypic deterioration with old age. For traits that grow throughout life, such as the horns of some ungulates, senescence may be expressed as a decrease in annual growth rates, or an increase in asymmetry, in the years preceding death. Age‐specific yearly horn‐growth segments of 378 male Alpine ibex Capra ibex L. that died from natural causes were analysed in the Gran Paradiso National Park (Italian Alps). Horn annuli displayed fluctuating asymmetry. The hypothesis that asymmetry and size of the annuli of the horns could predict annual survival probability was tested. It was found that between 5 and 11 years of age, male ibex that grew shorter annuli than the average for the population had a greater probability of mortality over the following years than those with greater rates of horn growth. Horn asymmetry and mortality rates were not significantly correlated. Annulus size, reflecting the onset of senescence, seemed to be a better indicator of individual quality than annulus asymmetry.
Aerosol optical properties measured on board the Ronald H. Brown during ACE‐Asia as a function of aerosol chemical composition and source region
Authors: Quinn P. K. , Coffman D. J. , Bates T. S. , Welton E. J. , Covert D. S. , Miller T. L. , Johnson J. E. , Maria S. , Russell L. , Arimoto R. , Carrico C. M. , Rood M. J. , Anderson J.
Published: September 2004

During the Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) intensive field campaign conducted in the spring of 2001, aerosol properties were measured on board the R/V Ronald H. Brown to study the effects of the Asian aerosol on atmospheric chemistry and climate in downwind regions. Aerosol properties measured in the marine boundary layer included chemical composition; number size distribution; and light scattering, hemispheric backscattering, and absorption coefficients. In addition, optical depth and vertical profiles of aerosol 180° backscatter were measured. Aerosol within the ACE‐Asia study region was found to be a complex mixture resulting from marine, pollution, volcanic, and dust sources. Presented here as a function of air mass source region are the mass fractions of the dominant aerosol chemical components, the fraction of the scattering measured at the surface due to each component, mass scattering efficiencies of the individual components, aerosol scattering and absorption coefficients, single scattering albedo, Ångström exponents, optical depth, and vertical profiles of aerosol extinction. All results, except aerosol optical depth and the vertical profiles of aerosol extinction, are reported at a relative humidity of 55 ± 5%. An overdetermined data set was collected so that measured and calculated aerosol properties could be compared, internal consistency in the data set could be assessed, and sources of uncertainty could be identified. By adjusting the measured size distribution to take into account nonsphericity of the dust aerosol, calculated and measured aerosol mass and scattering coefficients agreed within overall experimental uncertainties. Differences between measured and calculated aerosol absorption coefficients were not within reasonable uncertainty limits, however, and may indicate the inability of Mie theory and the assumption of internally mixed homogeneous spheres to predict absorption by the ACE‐Asia aerosol. Mass scattering efficiencies of non‐sea‐salt sulfate aerosol, sea salt, submicron particulate organic matter, and dust found for the ACE‐Asia aerosol are comparable to values estimated for ACE 1, Aerosols99, and the Indian Ocean Experiment (INDOEX). Unique to the ACE‐Asia aerosol were the large mass fractions of dust, the dominance of dust in controlling the aerosol optical properties, and the interaction of dust with soot aerosol.
One‐year measurements of surface heat budget on the ablation zone of Antizana Glacier 15, Ecuadorian Andes
Authors: Favier Vincent , Wagnon Patrick , Chazarin Jean‐Philippe , Maisincho Luis , Coudrain Anne
Published: September 2004

Meteorological variables were recorded (14 March 2002 to 14 March 2003) at 4890 m above sea level (asl) on the Antizana Glacier 15 (0.71 km2; 0°28′S, 78°09′W) in the tropical Andes of Ecuador (inner tropics). These variables were used to compute the annual cycle of the local surface energy balance (SEB). The four radiative fluxes were directly measured, and the turbulent fluxes were calculated using the bulk aerodynamic approach, calibrating the roughness length by direct sublimation measurements. The meteorological conditions are relatively homogeneous throughout the year (air temperature and air humidity). There is a slight seasonality in precipitation with a more humid period between February and June. During June‐September, wind velocity shows high values and is responsible for intense turbulent fluxes that cause reduction of melting. Considering the SEB over the whole year, it is dominated by net radiation, and albedo variations govern melting. During the period under consideration the net short‐wave radiation S (123 W m−2) and the sensible turbulent heat flux H (21 W m−2) were energy sources at the glacier surface, whereas the net long‐wave radiation L (−39 W m−2) and the latent turbulent heat flux LE (−27 W m−2) represented heat sinks. Since the O°C isotherm‐glacier intersection always oscillates through the ablation zone and considering that the phase of precipitation depends on temperature, temperature indirectly controls the albedo values and thus the melting rates. This control is of major interest in understanding glacier response to climate change in the Ecuadorian Andes, which is related to global warming and ENSO variability.
A ducting climatology derived from the European Centre for Medium‐Range Weather Forecasts global analysis fields
Authors: von Engeln Axel , Teixeira João
Published: September 2004

A global ducting climatology based on 6 years of European Centre for Medium‐Range Weather Forecasts (ECMWF) data is presented. The ECMWF data have a resolution of 1.5°, 60 vertical levels, and a 6‐hour daily frequency. Ducting probability, altitude, layer thickness, and magnitude are calculated for different seasons and universal times by analyzing the refractivity gradient with respect to altitude. Owing to the limited ECMWF vertical resolution, presented results are restricted to the lowest 2–2.5 km of the atmosphere. The climatology has mainly been generated for radio occultation data analysis, where ducting events found at higher altitudes are generally not affecting the signal acquisition. Since ducting is so much associated with boundary layer inversions and in the subtropics with cloud‐topped boundary layers, this study can also be used as an inversion climatology. High ducting probabilities (≈100%) are found off the west coasts of the Americas, Africa, and Australia in typical stratocumulus conditions. High probability is also observed over the Arabian Sea, with large seasonal variations. Polar nights lead to high ducting probabilities, especially visible over Antarctica but also over Greenland and Siberia. The daily cycle of the probabilities shows the impact of radiative cooling during the night over desert and tundra areas. Maximum mean ducting altitudes are found further off the west coasts. Land‐based ducting events are generally near the surface. The mean ducting layer thickness is higher over the sea, with maximum thicknesses of up to 250 m. The mean magnitude of ducting is usually just below the critical gradient.
Coupling between CO2, water vapor, temperature, and radon and their fluxes in an idealized equilibrium boundary layer over land
Authors: Betts Alan K. , Helliker Brent , Berry Joe
Published: September 2004

We propose a new approach for relating concentration measurements in the atmospheric boundary layer to surface fluxes based on a simple equilibrium boundary layer model (an extension of Betts [2000]). This is a major shift from the traditional focus on the growth of the daytime dry boundary layer. We show equilibrium solutions for the diurnally averaged properties of the boundary layer that link the mixed layer equilibrium (on timescales longer than a day) of potential temperature, water vapor, CO2 (and other trace gases such as radon) with an interactive cloud layer and with the surface energy, water, and carbon balance. We examine these processes as a function of a set of external parameters: soil water content, which directly impacts respiration and photosynthesis, and hence transpiration; the surface net shortwave, directly linked to net radiation, which is also coupled to photosynthesis and transpiration; and the radiative cooling of the mixed layer (ML), which in the equilibrium model directly affects the surface sensible heat. We also show solutions where the net shortwave and radiative cooling are coupled to the cloud field. Our other variable model parameters are the properties of air entrained into the CBL, the midtropospheric values of vapor mixing ratio, CO2 and radon, and the lapse rate above cloud base. We considered two idealized ecosystems: forest (based on observations in Wisconsin) and grassland (using parameter estimates from the literature) to show how the vegetation model affects the ML equilibrium. We show how the mass transport out of the subcloud layer and the mass exchange with the free troposphere couples the mixed layer equilibrium of water vapor, CO2, and radon with the corresponding surface fluxes. We suggest that regional ML budgets may give useful constraints on regional carbon budgets, and that the coupling with the cloud field is a fundamental part of the ML equilibrium.
Greenland accumulation: An error model
Authors: Cogley J. Graham
Published: September 2004

Total surface accumulation (total snowfall minus total sublimation) on the Greenland Ice Sheet is estimated as 299 ± 23 kg m−2 yr−1 for an assumed 30‐year span, the uncertainty being quoted as twice the standard error. The estimate is very similar to earlier estimates because it relies largely on the same compiled observations, but it is the first to be accompanied by formal error bars. An error model was developed for this purpose. It incorporates uncertainties due to measurement error, record length or span, and spatial bias in the distribution and density of the observations. Measurement errors, although dominant over large parts of the interior, make only a small contribution to uncertainty in the accumulation of the whole ice sheet. Time series of accumulation are shown to be stationary and independent, which means that the date of any given observation is of no importance when evaluating its uncertainty as an estimate of accumulation at any other date. However, as found earlier, the span of the observation is a leading contributor to uncertainty, and a means of placing short‐ and long‐span measurements on an equal footing is developed. Spatial bias is the other leading contributor, to judge from modeling of the standard error of averages of pairs of observations as a function of their separation and from a map of the standard error of accumulation. The standard error of interpolated point estimates of accumulation is small where measurements are dense and well‐distributed in the interior, but grows rapidly where measurements are more thinly or unevenly distributed. Estimates of accumulation are therefore most uncertain in the peripheral ablation zone. It is suggested that uncertainty in accumulation needs to be reduced by a factor of two or more if the measurements are to contribute reliably to explaining the observed sea level rise.
New evidence for an ENSO impact on low‐latitude glaciers: Antizana 15, Andes of Ecuador, 0°28′S
Authors: Francou Bernard , Vuille Mathias , Favier Vincent , Cáceres Bolivar
Published: September 2004

Continuous monthly mass balance measurements from the ablation zone of Antizana 15 glacier in the Andes of Ecuador between January 1995 and December 2002 indicate a strong dependence on El Niño–Southern Oscillation (ENSO). Over the 8‐year period investigated, mass balance was negative all year round during El Niño periods but remained close to equilibrium (positive anomalies) during La Niña events. On seasonal timescales, mean ablation rates remain at a quite constant level all year round, but interannual variability shows much larger changes from year to year during the key periods February–May and September. This variability is caused by large differences that occur in the seasonal cycle during the two opposite phases of ENSO. Since ENSO is phase locked to the seasonal cycle with largest sea surface temperature anomalies around boreal winter, November–February, and the atmospheric response to ENSO is delayed by 3 months over the Ecuadorian Andes, year‐to‐year variations in mass balance are largest between February and May. Energy balance studies at the glacier surface indicate that high air temperature, which favors rain over snowfall, weak and sporadic snowfall, insufficient to maintain a high glacier albedo, low wind speeds, which limit the transfer of energy from melting to sublimation, and reduced cloud cover, which increases the incoming short‐wave radiation, are the dominant factors related to El Niño, which tend to increase ablation. La Niña events on the other hand are characterized by colder temperatures, higher snowfall amounts, and to a lesser degree, more constant winds, factors which increase albedo and sublimation and therefore preclude melting at the glacier surface. The effects of ENSO variability are also important over the accumulation area, which represents up to 80% of the glacier surface during La Niña events (1999–2000) and 45–60% in El Niño years. Since the accumulation rates increase during these cold periods, the specific net balance and the dynamics of the entire glacier are strongly affected. Longer mass balance records than this 8‐year period are needed for conclusive answers about the dependence of the Ecuadorian glaciers on ENSO variability, but initial results suggest that the response observed on Antizana glaciers is very similar to what has been observed previously during ENSO periods on Andean glaciers in the outer tropics. The seasonal dependence on ENSO and the physical mechanisms linking ENSO with mass balance variations on Antizana, however, are different from the response observed on Andean glaciers in the outer tropics.
Estimate of nitrogen oxide emissions from shipping by satellite remote sensing
Authors: Beirle S. , Platt U. , von Glasow R. , Wenig M. , Wagner T.
Published: September 2004

In recent years, the role of ship emissions has attracted increasing attention. Recent inventories estimate that they contribute significantly to anthropogenic emissions of nitrogen oxides, with a large impact on composition and chemistry of the marine boundary layer. Nevertheless, the number of observational studies is still rather small. Here we present the first detection of ship tracks in NO2 maps derived from satellite data. We have used the congested track connecting Sri Lanka to Indonesia to estimate the corresponding ship emissions of nitrogen oxides to 23 (10–73) Gg [N]/yr. In addition, we were able to derive the mean lifetime of boundary layer NOx to be 3.7 (1.9–6.0) hours in the respective region. Our estimates are in good agreement with ship emission inventories (about 22–54 Gg [N]/yr) as well as the short lifetimes (of down to 2 hours at daytime) as recently modeled for ship plumes.
“Great Salinity Anomalies” in a coupled climate model
Authors: Wadley Martin R. , Bigg Grant R.
Published: September 2004

Several “Great Salinity Anomalies” have been observed to propagate around the North Atlantic sub‐polar gyre over the past 40 years. These could be a response to global warming, or part of the natural variability of the climate system. Here, we find “Great Salinity Anomalies” in the HadCM3 coupled climate simulation of pre‐industrial climate, suggesting they are not a response to recent climatic change. In concurrence with observed events, the HadCM3 simulation produces events which originate in both the Greenland and Labrador Seas.
Mantle transition zone topography and structure beneath the Yellowstone hotspot
Authors: Fee David , Dueker Ken
Published: September 2004

The depths of the 410 and 660 km discontinuities beneath the Yellowstone hotspot are constrained using common conversion point imaging of P‐wave receiver functions. The mean depth of the 410 and 660 is 411 ± 1.5 km and 656 ± 1.6 km, with 36–40 km of peak to peak topography. This topography is spatially uncorrelated, providing no evidence for a lower mantle plume currently beneath the hotspot. The topography suggests that ±200°C thermal anomalies exist with respect to an average mantle adiabat. Two warmer than normal regions are found: at the 410 to the NNW of the hotspot and at the 660 to the NE. Colder temperatures exist at the 410 under central Wyoming. Upper mantle convection and/or intermittent heat and mass transfer across the 660 may be responsible for the uncorrelated topography. Three negative arrivals about the 410 and 660 are observed that display correct Pds moveout.
Cluster observations of earthward flowing plasmoid in the tail
Authors: Zong Q.‐G. , Fritz T. A. , Pu Z. Y. , Fu S. Y. , Baker D. N. , Zhang H. , Lui A. T. , Vogiatzis I. , Glassmeier K.‐H. , Korth A. , Daly P. W. , Balogh A. , Reme H.
Published: September 2004

The energetic electrons and ions embedded in Earthward‐moving plasmoid structures have been observed. These plasmoids are associated with a rotational local Bz component (bi‐polar) signature. Energetic electrons are found to be confined in a smaller spatial region than ions inside the plasmoid. Energetic ions and electrons seem to be a good indicator for the structure boundary. The fleet of Cluster spacecraft cross the plasmoid structure in a “first entry, last out” order (Note: when spacecraft cross a planar discontinuity, e.g. magnetopause, they will be in “first entry, first out” order). This documents the fact that the plasmoid has a non‐planar nested structure. The large separation distance (around 1 RE) of the Cluster satellites in October 2002 is an advantage to provide constraints on the size and shape of the plasmoid structure of interest. In addition, the plasmoid (with closed field lines) should preserve the ion composition information where it is formed. The ion composition observed in the plasmoid shows significantly lower O and He than in the ambient plasma. This implies few heavy ions are involved in the reconnection process where the plasmoid is formed. Multiple flux ropes/plasmoids observation presented in this paper can be interpreted as strong evidence for multiple X‐lines.
Fine structure in ionospheric Alfvén resonator spectra observed at low latitude (L = 1.3)
Authors: Bösinger T. , Demekhov A. G. , Trakhtengerts V. Y.
Published: September 2004

A fine spectral structure in the electromagnetic background noise at 0.1 to 6 Hz is observed at a low latitude station. Its frequency scale falls roughly within the range of low‐latitude field‐line resonances (FLR), but the reported structure reveals a much higher quality factor than is usually found in FLR observations. It is interpreted here in terms of coupling between the ionospheric Alfvén resonator (IAR) and conventional field line resonances.
Peroxyacetyl nitrate photochemistry and interactions with the Arctic surface
Authors: Dassau Terra M. , Shepson Paul B. , Bottenheim Jan W. , Ford Kevin M.
Published: September 2004

Peroxyacetyl nitrate (PAN) is a NOx reservoir compound that has the ability to transport NOx to remote environments, allowing for NOx photochemistry and/or deposition of nitrogen to these clean locations. Measurements of PAN have been made at Alert, Nunavut, and Summit, Greenland, aimed at understanding the impact of PAN chemistry on atmospheric nitrogen in the Arctic. These measurements show concentrations of PAN that are only slowly varying, even during ozone depletion events at polar sunrise, when free radical photochemistry is relatively active. We used a zero‐dimensional photochemical model incorporating known gas‐phase chemistry to simulate the observed behavior of PAN at Alert, Nunavut, and Summit, Greenland. The model simulations suggest a substantial net production rate for PAN over sunlit surfaces, which is inconsistent with the measured gas‐phase concentrations. These observations thus indicate a fundamental problem with our understanding of PAN chemistry in low‐temperature, snow‐covered environments. We explore the possibility that we are missing an important sink for atmospheric PAN above snow‐covered surfaces. If the loss is caused by snowpack deposition, the data result in calculated deposition velocities ranging from 0.05 to 1 cm s−1, which would represent a significant fraction of the unidentified total nitrate input to the snowpack and glacial ice at Summit, Greenland.
Aerosol particles collected on aircraft flights over the northwestern Pacific region during the ACE‐Asia campaign: Composition and major sources of the organic compounds
Authors: Simoneit Bernd R. T. , Kobayashi Minoru , Mochida Michihiro , Kawamura Kimitaka , Huebert Barry J.
Published: September 2004

Atmospheric particulate matter, collected over the polluted east Asia/Pacific region in spring 2001 during research flights with the National Center for Atmospheric Research (NCAR) C‐130 aircraft, was analyzed for different types of organic compounds using capillary gas chromatography–mass spectrometry. More than 70 organic species were detected in the aerosols and grouped into different compound classes on the basis of functional groups, including n‐alkanes, polycyclic aromatic hydrocarbons, fatty acids, dehydroabietic acid, alkanols, water‐soluble sugars (including glucose, sucrose, mycose, and levoglucosan), monocarboxylic and dicarboxylic acids, urea, and phthalates. Interestingly, the water‐soluble compounds (72–133 ng m−3) were found to account for 16–50% (average 34%) of the total identified compound mass (TCM). Organic compounds were further categorized into several groups to suggest their sources. Fossil fuel combustion was recognized as the most significant source for the TCM (contributing 33–80% of TCM, average 50%), followed by soil resuspension (5–25%, average 19%) and secondary oxidation products (4–15%, average 9%). In contrast, the contribution of natural sources such as terrestrial plant wax and marine lipids (fatty acids and alkanols) was relatively small (3.4% and 9.4% on average, respectively). Biomass burning was suggested to contribute only a minor portion to the TCM of the Asian aerosols during the spring season (1.4% on average based on levoglucosan). However, levoglucosan may have been hydrolyzed and/or oxidized in part during long‐range transport, and therefore this value represents a lower limit. The organic compound compositions of these samples are very different from those reported for aerosol particles of the Atlantic Ocean and from the earlier data for the mid‐Pacific in terms of the abundant presence of water‐soluble compounds consisting of saccharides, anhydrosaccharides, and the secondary dicarboxylic acids. This study demonstrated that the organic tracer approach can be carried out on small samples acquired on aircraft and is useful to better understand the sources of organic aerosols over the Asia/Pacific region.