bluuebunny/crossref_metadata_2025 huggingface dataset:
Annual warming episodes in seawater temperatures in McMurdo Sound in relationship to endogenous ice in notothenioid fish
Authors: HUNT BEN M. , HOEFLING KEVIN , CHENG CHI-HING C.
Published: September 2003

We obtained two years (1999–2001) of continuous, high resolution temperature and pressure data at two near-shore shallow water sites in McMurdo Sound, Ross Sea. Contrary to the long-held assumption of constant freezing conditions in the Sound, these records revealed dynamic temperature fluctuations and substantial warming during January to March reaching peak water temperatures of about −0.5°C. They also revealed that excursions above −1.1°C, the equilibrium melting point of ice in Antarctic notothenioid fish, totalled 8–21 days during the summer. Microscopic ice crystals are known to enter these fish but ice growth is arrested by antifreeze proteins. Prior to this study there were no known mechanisms of eliminating accumulated endogenous ice. The warm temperature excursions provide for the first time a possible physical mechanism, passive melting, for ice removal. The continuous records also showed a correlation between tidal pressures and cold temperature episodes, which suggests the influx of cold currents from under the Ross Ice Shelf may provide a mechanism for ice crystal nucleation as the source of the ice in McMurdo Sound fish. The accumulation of anchor ice on one logger caused it to float up which was recorded as a decrease in pressure. This is the first evidence for the time of onset of anchor ice formation in McMurdo Sound.
Chemical defences in embryos and juveniles of two common Antarctic sea stars and an isopod
Authors: MCCLINTOCK JAMES B. , MAHON ANDREW R. , PETERS KEVIN J. , AMSLER CHARLES D. , BAKER BILL J.
Published: September 2003

The brooded embryos and/or juveniles of the sea stars Neosmilaster georgianus (Studer, 1885) and Lysasterias perrieri (Studer, 1885) and the isopod Glyptonotus antarcticus (Eights, 1853) were examined for their acceptability using the sympatric sea star Odontaster validus (Koehler, 1906) as a predator. Organic extracts were prepared from embryos of both sea stars and juveniles of Lyasterias perrieri and Glyptonotus antarcticus and tested in alginate food pellets to confirm whether lack of acceptability was chemically based. We found both intact whole embryos and juveniles of the sea star Neosmilaster georgianus were not acceptable to Odontaster validus. A methanol extract of the embryos was palatable. This could be the result of either the sequestration of deterrent chemicals within embryos or the presence of noxious compounds that were not extractable in methanol. Embryos and juveniles of the sea star Lysasterias perrieri were not acceptable to sea stars. Food pellets containing methanol extracts of unacceptable embryos were deterrent against sea stars, suggesting a chemical defence. Juvenile brooded isopods (Glyptonotus antarcticus) were also found to be unacceptable in sea star feeding bioassays. Significant rejection of alginate pellets containing a lipophilic dichloromethane methanol extract of juveniles indicated that this lack of acceptability was chemically based. Our study provides further support for chemical defences in the offspring of brooding lecithotrophic Antarctic marine invertebrates.
Accumulation of HSP70 in Deschampsia antarctica Desv. leaves under thermal stress
Authors: REYES MARÍA ANTONIETA , CORCUERA LUIS J. , CARDEMIL LILIANA
Published: September 2003

The aim of this study was to evaluate the hypothesis that Deschampsia antarctica Desv., the only grass of the Maritime Antarctic, responds to temperatures higher or lower than its optimum for photosynthesis (13°C), with the accumulation of heat shock proteins. The LT50 was determined in plants acclimated at 4°C (cold-acclimated plants) and in plants grown at 13°C (control plants) by membrane damage and by the activity of respiratory dehydrogenases. The LT50 was 48.3°C in both groups of plants when determined by membrane damage. When the LT50 was determined by the activity of respiratory dehydrogenases, this was, without significant difference, 47.8°C in cold-acclimated plants and 46.5°C in control plants. Western blot analyses were performed to investigate the accumulation of HSP70 at different temperatures. The optimal temperature for HSP70 accumulation was 35°C in cold-acclimated and control plants. Cold-acclimated plants subjected to a thermal stress of 35°C accumulated HSP70 protein more than control plants subjected to 35°C. After eight hours of continuous stress at 35°C, the maximum relative content of HSP70 in cold-acclimated plants was 1.9 fold higher than control plants. The threshold temperature for HSP70 accumulation was lower in cold-acclimated plants than in control plants. It is concluded that D. antarctica is able to tolerate heat stress with an LT50 similar to those of heat tolerant plants and that the cold-acclimated plants accumulate higher levels of HSP70 than those grown at 13°C.
Land-fast ice microalgal and phytoplanktonic communities (Adélie Land, Antarctica) in relation to environmental factors during ice break-up
Authors: RIAUX-GOBIN C. , POULIN M. , PRODON R. , TREGUER P.
Published: September 2003

Annual land-fast ice, particularly an unconsolidated layer or “platelet ice-like” layer (PLI), was sampled in spring 1995 to study the spatial and short-term variations of ice-associated diatoms. Under-ice water, a lead and small polynyas were also sampled. Along a 7 km seaward transect a geographical gradient was evident, with some rare diatom species present only in the offshore PLI, whereas others (mainly pennate diatoms) were ubiquitous. The dense microphytic PLI community as well as the phytoplankton was diatom-dominated, but, within these two communities, marked differences appeared. First, the sea-ice communities (PLI and solid bottom ice) were moderately diverse (36 species), mostly composed of pennate diatoms, of which many were chain forming or tube-dwelling. Dominant taxa were Navicula glaciei, Berkeleya adeliensis, Nitzschia stellata, Amphiprora kufferathii and Nitzschia lecointei. Some differences in the distribution of the most dominant species appeared within the bottom ice and the PLI, attesting to differences in the origin or/and growing capability of these diatoms in these two ice compartments. Under-ice water species composition was mixed with sea-ice communities only on the most coastal sites and during ice melt. Maximum cell numbers were mostly noticed in the PLI, reaching up to 1010 cells l−1 and very high Chl a concentrations (exceptionally up to 9.8 mg Chl a l−1 or 1.9 g Chl a m−2, from a 10 to 20 cm thick PLI layer, close to the continent). Secondly, the phytoplankton in the lead and small polynyas had a low diversity, very low standing stocks (on an average 0.69 μg Chl a l−1) and cell densities (2 × 104 cells l−1). Some species from the polynyas were similar to those of the PLI, such as Navicula glaciei, but others were typically planktonic, such as Chaetoceros cf. neglectus. The presence of encysted cells (Chaetoceros and Chrysophytes) was also noticeable in the polynya water. In early spring no seeding process was obvious from the PLI to polynya water. A comparison with similar fast-ice diatom communities in other parts of coastal Antarctica, is presented.
Geochemical and rock magnetic records from sediments of the Cenozoic Pagodroma Group, Prince Charles Mountains, East Antarctica: implications for provenance and weathering
Authors: BLOEMENDAL J. , EHRMANN W. , HAMBREY M.J. , MCKELVEY B.C. , MATTHEWS R. , WHITEHEAD J.M.
Published: September 2003

Geochemical and magnetic data from glacigenic sediments can be useful indicators of past environments and climate. In this paper, the results of X-ray fluorescence (XRF) and rock magnetic analyses are presented for samples from the Pagodroma Group, an assemblage of pre-Quaternary glacimarine sediments preserved as remnants along the raised flanks of the Lambert Graben, Prince Charles Mountains, East Antarctica. Samples were obtained from four formations: Mount Johnston, Battye Glacier, Fisher Bench and Bardin Bluffs, which range in age from late Oligocene or early Miocene through to Pliocene or early Pleistocene. Principal component analysis of the XRF data indicates the occurrence of two main element assemblages, which we infer are determined by the presence in the Bardin Bluffs formation of a significant component derived from Permo–Triassic sedimentary rocks of the Amery Group. Calculation of chemical indices of alteration suggests that the values reflect provenance differences rather than the syndepositional weathering environment. Multidomain ferrimagnetic grains mainly dominate the magnetic mineral assemblages of the samples, probably magnetite, with varying concentrations of high coercivity material, probably hematite.
Mafic Dykes from Heimefrontfjella and implications for the post-Grenvillian to pre-Pan-African geological evolution of western Dronning Maud Land, Antarctica
Authors: BAUER W. , FIELITZ W. , JACOBS J. , FANNING C.M. , SPAETH G.
Published: September 2003

Two groups of geochemical different dykes have been identified in the Grenville-aged basement of Heimefrontfjella. The first group comprises dykes of continental tholeiite composition which probably intruded during the final stage of indentation of the Kaapvaal—Grunehogna Craton into Laurentia. One dyke of this group yielded an U—Pb zircon SHRIMP age of 1033 ± 7 Ma. The second group has an E-type MORB composition and may be related to ocean floor basalts of the Mozambique Ocean between East and West Gondwana. A preliminary U—Pb SHRIMP age of 586 ± 7 Ma for a single zircon crystal was obtained from a dyke of the second group. During the Pan-African orogeny both dyke groups underwent metamorphism and tectonism at different grades: up to amphibolite-facies in the eastern and southern Heimefrontfjella, and at greenschist-facies in the western and northern Heimefrontfjella. The older dykes may be correlated with the Equeefa suite of southern Natal whereas the younger dyke group is not correlatable with any known mafic intrusions or lava flows in adjacent regions.
Mobilization of fluidized sediment during sill emplacement, western Dronning Maud Land, East Antarctica
Authors: CURTIS MICHAEL L. , RILEY TEAL R.
Published: September 2003

Large mafic sills in the Ahlmannryggen region of western Dronning Maud Land were intruded into partially lithified sediments of the mid-Proterozoic Ritscherflya Supergroup. Clastic sedimentary dykes intruding the thick mafic sills have been identified, and show evidence for fluidization of the partially lithified sediments. Previous work had demonstrated in situ fluidization and localized anatectic melting. This study demonstrates mobilization of the fluidized sediments, with penetration at least 50 m into the fractured, intruding sill. Physical features within the clastic dykes (e.g. sediment balls, flame structures) suggest that the sediments were largely unconsolidated, or at most only partially lithified. The presence of a thin zone of anatectic melt along the dyke—sill contact suggests that the mafic sill was still hot (c. 700°C) at the time of sedimentary dyke injection.
Dissolved Oxygen, NO and PO as tracers for Ross Sea Ice Shelf Water overflow
Authors: RIVARO P. , FRACHE R. , BERGAMASCO A. , HOHMANN R.
Published: September 2003

A mesoscale experiment was conducted in the Ross Sea near the shelf break in summer 1997–98 within the framework of the activities of the CLIMA Project of the Italian National Program for Antarctic Research (PNRA), focus on study the shelf—slope interaction between the shelf waters and the CDW in correspondence of the Antarctic Slope Front. This paper deals with the dissolved oxygen distribution and with the application of conservative tracers NO and PO related to the physical variables, improving understanding of mixing processes study in correspondence of the shelf break. Experimental data showed the presence of both Ice Shelf Water overflowing the shelf and Circumpolar Deep Water intruding onto the shelf. Dissolved Oxygen (DO), NO and PO resulted useful as chemical tracers in outlining the mixing processes and bottom water formation spreading off continental shelf break of the Ross Sea, in which seems to be evidence that ISW plays an important role. In fact, a plume of ISW was observed flowing down the continental slope to the deep ocean. From chemical tracers we estimate its magnitude to be about 0.4 ± 0.2 Sv.
Effects of the physical properties of water masses on microbial activity during an Ice Shelf Water overflow in the central Ross Sea
Authors: BERGAMASCO A. , DEFENDI V. , DEL NEGRO P. , FONDA UMANI S.
Published: September 2003

During the 1997–98 Italian Expedition to Antarctica a five-day mesoscale experiment was carried out on the continental shelf-break in the central Ross Sea. This area is oceanographically characterized by shelf/slope interactions, through intense mixing processes, between the Circumpolar Deep Water (CDW) and the Ice Shelf Water (ISW), coming from beneath the Ross Ice Shelf and spilling over the shelf edge. The export of dense shelf waters is of crucial importance not only for the mass balance of the basin, but also for carbon export from the upper layers into the abyssal ones. The study investigated how the ISW interactions with the CDW may influence bacterial metabolism during an ISW downslope event. In particular, what effect does this have on the bacterial activities related to the utilization and transformation of the organic carbon substrate (ectoenzymatic activities, carbon production, growth rate) within the ISW and the CDW cores? Our data show that in the CDW the metabolic response was to increase the biomass and enzymes were less active due to a higher nutritional value for the substrate. In the ISW the bacterial metabolic activity shifted towards degradative processes. These results suggest differences in the quality of the organic carbon pool with a greater concentration of labile organic matter in the CDW and of low-degradable compounds in the ISW. The use of microbial parameters seems to be very promising in the evaluation of the carbon export during mixing processes, when the refractory fraction of the organic carbon pool might play a key role.
Polar Ecotoxicology – a missing link
Authors: RIDDLE MARTIN J. , CHAPMAN PETER M.
Published: September 2003

There is a pressing need for region-specific information on the response of polar species to contaminants. The Protocol on Environmental Protection to the Antarctic Treaty states “…regular and effective monitoring shall take place to allow assessment of the impacts of ongoing activities, including the verification of predicted impact…”. Although the Treaty only applies to the Antarctic, similar requirements exist for the Arctic; thus, our comments below apply to both polar regions. Without ecotoxicological information all the effort that is directed towards contaminants monitoring is largely meaningless as it does not tell us whether the levels detected pose an environmental risk.
Evidence of change in a low-elevation forest bird community of Hawai'i since 1979
Authors: Reynolds Michelle H. , Camp Richard J. , Nielson Bonnie M. B. , Jacobi James D.
Published: September 2003

We evaluated the abundance and distribution of low-elevation forest birds on windward Hawai'i Island during August 1993-February 1994, and present evidence of changes in the species composition of the forest bird community since 1979. Endemic Hawaiian birds occurred in native-dominated forests as low as 120 m elevation. Non-native species were detected at all survey locations. We observed non-native Saffron Finch Sicalis flaveola, previously unrecorded in Puna. Variable circular plot surveys of Kahauale'a Natural Area Reserve indicated the disappearance of two native species ('I'iwi Vestiaria coccinea and 'O'u Psittitostra psittacea), and two non-native additions (Red-billed Leiothrix Leiothrix lutea and Kalij Pheasant Lophura leucomelana) to the study area since the Hawai'i Forest Bird Survey conducted in 1979. We present evidence that native 'Elepaio Chasiempsis sandwichensis has experienced a decrease in population density and an elevational range contraction since 1979. Surveys indicate Puna's forest bird community has had increasing aliens and declining native species since 1979. The persistence of some native bird species within the range of avian disease vectors such as Culex quinquefasciatus in forests below 1,000 m elevation presents an important enigma that requires additional study.
Population size, habitats and conservation of Marquesan Imperial Pigeon Ducula galeata
Authors: Villard Pascal , De Visscher Marie-Noël , Balança Gilles
Published: September 2003

Marquesan Imperial Pigeon Ducula galeata only survives on Nuku Hiva island in the Marquesas archipelago. It lives and nests mainly in small patches of forest with tall trees, in deep valleys. The population is likely to consist of only 80-150 birds. However, its forest habitat is in peril due to overgrazing, especially by goats, which precludes growth of young trees. Better control of feral herbivores should be a priority for the conservation of the species, as well as the cessation of poaching of this endangered pigeon. Introduced black rats Rattus rattus do not seem to be a threat for this bird.
Correlates of hornbill distribution and abundance in rainforest fragments in the southern Western Ghats, India
Authors: Raman T.R. Shankar , Mudappa Divya
Published: September 2003

The distribution and abundance patterns of Malabar Grey Hornbill Ocyceros griseus and Great Hornbill Buceros bicornis were studied in one undisturbed and one heavily altered rainforest landscape in the southern Western Ghats, India. The Agasthyamalai hills (Kalakad-Mundanthurai Tiger Reserve, KMTR) contained over 400 km2 of continuous rainforest, whereas the Anamalai hills (now Indira Gandhi Wildlife Sanctuary, IGWS) contained fragments of rainforest in a matrix of tea and coffee plantations. A comparison of point-count and line transect census techniques for Malabar Grey Hornbill at one site indicated much higher density estimates in point-counts (118.4/km2) than in line transects (51.5/km2), probably due to cumulative count over time in the former technique. Although line transects appeared more suitable for long-term monitoring of hornbill populations, point-counts may be useful for large-scale surveys, especially where forests are fragmented and terrain is unsuitable for line transects. A standard fixed radius point-count method was used to sample different altitude zones (600–1,500 m) in the undisturbed site (342 point-counts) and fragments ranging in size from 0.5 to 2,500 ha in the Anamalais (389 point-counts). In the fragmented landscape, Malabar Grey Hornbill was found in higher altitudes than in KMTR, extending to nearly all the disturbed fragments at mid-elevations (1,000–1,200 m). Great Hornbill persisted in the fragmented landscape using all three large fragments (> 200 ha). It was also recorded in four of five medium-sized fragments (25–200 ha) and one of five small fragments (< 25 ha), which was adjacent to shade coffee plantations. Abundance of Malabar Grey Hornbill declined with altitude and increased with food-tree species richness. Great Hornbill abundance increased with food-tree species richness, suggesting that maintenance of high diversity of hornbill food species in fragments is important for their persistence. It is likely that the smaller and less specialized Malabar Grey Hornbill will survive in disturbed and fragmented forest landscapes, while Great Hornbill is more vulnerable to habitat alteration. Protection and restoration of rainforest fragments and food-tree resources, besides protection of existing large fragments, will aid the conservation of hornbills in the region.
Moult and autumn migration of non-breeding Fennoscandian Lesser White-fronted Geese Anser erythropus mapped by satellite telemetry
Authors: Aarvak Tomas , Øien Ingar Jostein
Published: September 2003

In this study we demonstrate that non-breeding adult Lesser White-fronted Geese Anser erythropus from the Fennoscandian breeding population may undertake long-distance moult migration eastwards. Of three individuals equipped with satellite transmitters at a spring staging site in northern Norway, two migrated to moulting sites in the area of Kolgujev Island and Kanin Peninsula, while the third headed towards the Taimyr Peninsula, all in northern Russia. The first leg of the moult migration route for non-breeders was between Finnmark, Norway and the Kanin Peninsula area in north-western Russia, a similar route to that taken on autumn migration by Fennoscandian Lesser White-fronted Geese that had bred successfully. After the moulting period, one of the individuals followed a south-western route to Poland and Germany, where it spent the first part of the winter. The satellite signals from the other two geese ceased abruptly in early autumn, indicating that the birds may have been illegally shot in Russia. Locating new moulting and migration stopover sites is of crucial importance for the conservation of the critically endangered Fennoscandian subpopulation of this species.
The Chimalapas Region, Oaxaca, Mexico: a high-priority region for bird conservation in Mesoamerica
Authors: Peterson A. Townsend , Navarro-Sigüenza Adolfo G. , Hernández-Baños Blanca E. , Escalona-Segura Griselda , Rebón-Gallardo Fanny , Rodríguez-Ayala Emir , Figueroa-Esquivel Elsa M. , Cabrera-García Leonardo
Published: September 2003

The Chimalapas region, in eastern Oaxaca, Mexico, holds lowland rainforests, tropical dry forests, and cloud forests typical of the Neotropics, as well as montane pine and pine-oak forests more typical of the Nearctic. Totaling more than 600,000 ha, much of the region is forested, and in a good state of preservation. The Chimalapas avifauna is by far the most diverse for any region of comparable size in the country, totalling at least 464 species in the region as a whole (with more than 300 species in the lowland rainforest) representing 44% of the bird species known from Mexico. Within the region, the humid Atlantic lowlands hold 317 species, the montane regions 113 species, and the southern dry forested lowlands 216 species. Important species present in the region include Harpy Eagle Harpia harpyja and several other large eagles, Black Penelopina nigra and probably Horned Oreophasis derbianus Guans, Scarlet Macaw Ara macao, Cinnamon-tailed Sparrow Aimophila sumichrasti, Rose-bellied Bunting Passerina rositae, and Resplendent Quetzal Pharomachrus mocinno. The area holds immense lowland rainforests and cloud forests that rank among the largest and best preserved in all of Mesoamerica, including a complete lowland-to-highland continuum, with entire watersheds preserved more or less intact.
Monitoring of Kilum-Ijim forest bird communities: initial findings
Authors: Forboseh Philip F. , Keming Ernest C. , Toh Clement L. , Wultof Innocent N. B.
Published: September 2003

The Kilum-Ijim forest is an excellent example of the ornithological riches of the Cameroon montane forest biome.
The forest is also important to over 200,000 people who exert enormous pressure on the ecosystem. In 1995, the
Kilum-Ijim Forest Project began systematic monitoring of birds, with the intention of using them as indicators of the
overall condition of the forest, as well as monitoring the status of individual species. Analyses of data collected in
1999–2000 demonstrated some clear differences in habitat use, suggesting suites of bird species may be indicators of changes in vegetation. However, beyond this, little is known about the response of birds to habitat modifications, or the relationship between bird abundance and diversity of other organisms at Kilum-Ijim. It is argued that the objective of assessing changes in vegetation could be more satisfactorily pursued through direct measurement of structural changes in habitats. We highlight the necessity for a shift in the programme objectives to place greater emphasis on monitoring endemic and threatened bird species for their own status and on assessing changes in the bird community as a function of changes in the vegetation.
A three‐dimensional P wave velocity model for the Charlevoix seismic zone, Quebec, Canada
Authors: Vlahovic Gordana , Powell Christine , Lamontagne Maurice
Published: September 2003

A three‐dimensional P wave velocity model has been developed for the Charlevoix seismic zone (CSZ). The CSZ is located along the St. Lawrence River ∼100 km northeast of Quebec City, Canada, and is one of the most active seismic zones in eastern North America. Five earthquakes with magnitudes equal to or exceeding 6.0 have occurred in the CSZ in historic time, and around 200 earthquakes occur annually. Hypocenters are located in Precambrian basement rocks. Basement rocks have been affected by numerous tectonic events including Grenvillian collision, Iapetan rifting, and meteor impact. We performed a sequential, tomographic inversion for P wave velocity structure based upon 3093 P wave arrivals from 489 earthquakes recorded by 12 stations. High velocity is associated with the center of the impact crater. The region of high velocity is surrounded by low velocities interpreted to be highly disrupted rocks. An elongated, high‐velocity region is present at midcrustal depths that trends parallel to the St. Lawrence River. Earthquakes avoid the high‐velocity body and separate into two bands, one on either side of the feature. Larger earthquakes (magnitude ≥ 4) have occurred along the northern edges of the high‐velocity region.
Anharmonicity in mineral physics: A physical interpretation
Authors: Stacey F. D. , Isaak D. G.
Published: September 2003

Mineral physicists often refer to the quasi‐harmonic approximation. This approximation accepts the intrinsically anharmonic effects of positive thermal expansion coefficient, α, and pressure‐dependent bulk modulus, KT. However, for insulators at high temperatures, the classical specific heat, CV, and the product αKT are assumed to be independent of temperature at constant volume. Departures from this approximation are termed anharmonicity. We interpret this distinction using derivatives of the atomic potential function, ϕ(r), with atomic spacing, r. CV and KT are reasonably explained by harmonic bonds, that is, ϕ ∝ (r − a)2, where a is the equilibrium value of r, so that ϕ″ = d2ϕ/dr2 is the only derivative considered. Thermal pressure or expansion and pressure dependence of KT depend on ϕ‴ (referred to as first‐order anharmonic effects). Temperature dependence of CV requires ϕiv and is a second‐order anharmonic effect. The temperature variation of αKT arises from ϕv, a third‐order effect. By calculating the Grüneisen parameter, γ, as the ratio of thermal pressure to thermal energy, we relate its anharmonicity to a ratio of derivatives of ϕ. For all commonly used finite strain theories, this gives a temperature variation of γ at high temperature and constant volume systematically less than that of CV. Anharmonicity of CV, which has been more comprehensively studied, may be a few percent at 2000 K, but decreases strongly with compression, so that anharmonicity of both γ and CV is negligible (less than 1% in the case of γ under deep‐Earth conditions).
Using subdivision surfaces and adaptive surface simplification algorithms for modeling chemical heterogeneities in geophysical flows
Authors: Schmalzl Jörg , Loddoch Alexander
Published: September 2003

We present a new method for investigating the transport of an active chemical component in a convective flow. We apply a three‐dimensional front tracking method using a triangular mesh. For the refinement of the mesh we use subdivision surfaces which have been developed over the last decade primarily in the field of computer graphics. We present two different subdivision schemes and discuss their applicability to problems related to fluid dynamics. For adaptive refinement we propose a weight function based on the length of triangle edge and the sum of the angles of the triangle formed with neighboring triangles. In order to remove excess triangles we apply an adaptive surface simplification method based on quadric error metrics. We test these schemes by advecting a blob of passive material in a steady state flow in which the total volume is well preserved over a long time. Since for time‐dependent flows the number of triangles may increase exponentially in time we propose the use of a subdivision scheme with diffusive properties in order to remove the small scale features of the chemical field. By doing so we are able to follow the evolution of a heavy chemical component in a vigorously convecting field. This calculation is aimed at the fate of a heavy layer at the Earth's core‐mantle boundary. Since the viscosity variation with temperature is of key importance we also present a calculation with a strongly temperature‐dependent viscosity.
Regional and hemispheric circulation patterns in the northern hemisphere winter, or the NAO and the AO
Authors: Kodera Kunihiko , Kuroda Yuhji
Published: September 2003

Two different scales of teleconnection patterns are found over the Euro‐Atlantic region during the winter. One is a regional seesaw between Iceland and the Azores, and the other is a hemispheric seesaw between the Mediterranean and the polar‐Siberia region. The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) indices are sensitive to both modes, although the NAO index reflects the more regional one. The principal process producing a hemispheric seesaw pattern in the surface pressure is changing in vertical winds in the polar troposphere driven by wave forcings. Upward motion in the polar region induces meridional flows near the surface, especially around the Norwegian Sea and Bering Strait, which induce wavy patterns in the surface pressure. The importance of distinguishing the two modes in understanding recent trends is also addressed.
New GPS constraints on the Africa‐Eurasia plate boundary zone in southern Italy
Authors: Hollenstein Ch. , Kahle H.‐G. , Geiger A. , Jenny S. , Goes S. , Giardini D.
Published: September 2003

Southern Italy is a key area for understanding the tectonic processes in the Africa‐Eurasia collision zone. We analyze new GPS measurements carried out between 1994 and 2001. The results are presented in terms of time series, trajectories and velocities of crustal motion, as well as a geodetic strain rate field. While central Italy, Corsica, Sardinia and the Tyrrhenian Sea move like the Eurasian plate, the overall motion of the Sicily Rift Zone region matches African plate motion. Unexpected are the north‐northwest directed motions of northeastern Sicily and the Eolian islands. Most striking on the deformation field are a north‐south oriented compression along the northern Sicilian coast, compression between Apulia and northwestern Greece as well as extension in the Sicily Rift Zone and the interior of Sicily.
Effect of Climate Change on Isoprene Emissions and Surface Ozone Levels
Authors: Sanderson M. G. , Jones C. D. , Collins W. J. , Johnson C. E. , Derwent R. G.
Published: September 2003

The effect of climate change on vegetation, isoprene emissions and surface ozone levels was investigated using a global three‐dimensional general circulation model coupled to a dynamic vegetation and chemistry models. Integrations for the 1990s and 2090s were performed. Isoprene emissions increased from 549 Tg yr−1 (1990s) to 736 Tg yr−1 (2090s) as a result of climate change with fixed vegetation. However, the isoprene emissions only increase to 697 Tg yr−1 in the 2090s when vegetation changes were included. Surface ozone levels rose by 20–30 ppbv in some locations with fixed vegetation owing to increases in precursor gases, but only by 10–20 ppbv if the vegetation changes were included. Ozone levels in parts of China, Korea and the eastern USA are predicted to exceed the World Health Organisation health limit of 60 ppbv, however, when changes in vegetation are accounted for, a much smaller area exceeds this limit.
Possible dipole tilt dependence of dayside magnetopause reconnection
Authors: Russell C. T. , Wang Y. L. , Raeder J.
Published: September 2003

Recent studies suggest that the half‐wave rectifier model of the interaction of the Earth's magnetosphere with the IMF is insufficient to produce the observed amplitude of the semi‐annual variation. However, the observed amplitude would ensue if there is additional modulation of geomagnetic activity dependent on the tilt of the dipole axis. We use an MHD model to demonstrate that the size of the region of antiparallel magnetic field is controlled by the tilt of the Earth's dipole axis, and hence the integrated reconnection rate and geomagnetic activity may be so controlled. The same zero guide field model for the onset of reconnection also predicts that the maximum reconnection rate occurs not for due southward field but at angles away from due southward by about the dipole tilt angle.
Towards a unified approach for remote estimation of chlorophyll‐a in both terrestrial vegetation and turbid productive waters
Authors: Dall'Olmo Giorgio , Gitelson Anatoly A. , Rundquist Donald C.
Published: September 2003

In this study we tested the applicability of a method, originally developed for terrestrial plant leaves, to retrieve chlorophyll‐a concentrations from reflectance spectra of turbid productive waters. We tuned the conceptual model according to the optical characteristics of the aquatic medium, and accurately predicted chlorophyll‐a concentrations in water bodies over a wide range of optical conditions. Our results provide evidence that this technique may be considered as a general solution, independent of the type of medium, for assessing chlorophyll concentration in optically deep media using remotely sensed data.
The production scheme of Cycladophora davisiana (Radiolaria) in the Okhotsk Sea and the northwestern North Pacific: implication for the paleoceanographic conditions during the glacials in the high latitude oceans
Authors: Okazaki Yusuke , Takahashi Kozo , Nakatsuka Takeshi , Honda Makio C.
Published: September 2003

The sediment trap study clearly unraveled that the distinct peaks of C. davisiana fluxes occurred during summer to autumn in both the Okhotsk Sea and the northwestern North Pacific. The production of C. davisiana is closely related to the microbial production in the intermediate water. In the Okhotsk Sea, the distinct microbial biomass in the intermediate water, which is associated with the seasonal sea‐ice rejected brine water during winter, may support the high C. davisiana abundance. Therefore, the significantly high C. davisiana abundance during the Last Glacial Maximum (LGM) in the high latitude open oceans implies the distinct microbial biomass in the intermediate water caused by the seasonal sea‐ice coverage analogous to the present Okhotsk Sea.
First global measurement of midtropospheric CO2 from NOAA polar satellites: Tropical zone
Authors: Chédin A. , Serrar S. , Scott N. A. , Crevoisier C. , Armante R.
Published: September 2003

Midtropospheric mean atmospheric CO2 concentration is retrieved from the observations of the NOAA series of polar meteorological satellites, using a nonlinear regression inference scheme. For the 4 years of the present analysis (July 1987 to June 1991), monthly means of the CO2 concentration retrieved over the tropics (20°N to 20°S) from NOAA 10 show very good agreement with what is presently known. Not only the phase of the seasonal variations (location of the peaks) but also their amplitude and their latitudinal evolution match quite well recent in situ observations made by properly equipped commercial airliners measuring in an altitude range similar to the one favored by the satellite observations. Moreover, the annual trend inferred corresponds to the known increase in the concentration of CO2 as a result of human activities. Also, the impact of El Niño‐Southern Oscillation events is clearly seen and confirms analyses of in situ or aircraft observations and of model simulations. Forty‐eight maps of monthly mean midtropospheric CO2 concentration have been produced at a resolution of 15° × 15°. A rough estimate of the method‐induced standard deviation of these retrievals is of the order of 3.6 ppmv (around 1%). The coming analysis of the almost 25 years of archive already accumulated by the NOAA platforms should contribute to a better understanding of the carbon cycle. A simulation of the extension of the method to the next generation high‐spectral‐resolution instruments, with very encouraging results, is presented.
A model for comet 81P/Wild 2
Authors: Sekanina Zdenek
Published: September 2003

A model is presented for the nucleus of comet 81P/Wild 2 and its activity, based on analysis of dust coma morphology, water and dust production, and nongravitational perturbations of the orbital motion. A four‐apparition composite light curve is derived from ∼500 magnitude estimates. There appear to be two major outgassing sources on the nucleus: one, near a rotation pole, sustains much of preperihelion activity; the other, on the opposite polar hemisphere and closer to the equatorial plane, accounts for the bulk of postperihelion activity. Both regions are active near perihelion. Their surface areas are estimated at 4.5 and 9.5 km2, respectively. With the nucleus probably 4.0 to 6.3 km across, the total outgassing area makes up 11 to nearly 30% of the nucleus surface, unusually high for a short‐period comet, yet consistent with relatively small perturbations of the orbital motion, driven by the momentum transferred to the nucleus by water sublimation. The absence of a more prominent nongravitational effect may largely be due to high dust mass loading of the gas flow, implying its subsonic initial speed. Indeed, the dustier, polar source appears to be the less efficient of the two in transferring the momentum to the nucleus. The comet's short history in the innermost solar system region could account for the relatively large outgassing fraction of the surface. At the Stardust encounter time, more than three months after perihelion, only the near‐equatorial source (the larger, less dusty one) is expected to be active.
IgE‐binding epitopes of the American cockroach Per a 3 allergen
Authors: Wu C. H. , Lee M. F. , Tseng C. Y.
Published: September 2003

Background: The Per a 3 is a species‐specific allergen of the American cockroach (Periplaneta americana) related to insect hemolymph proteins and includes four known isoallergens. This study aimed to identify Per a 3 linear IgE‐binding epitopes.

Methods: Per a 3 recombinant fragments were generated from the recombinant Per a 3.01 allergen (685 amino acid residues) by using existing restriction sites or by using polymerase chain reaction products, and expressed in Escherichia coli. Antigenicities were assessed by immunoblotting, enzyme‐linked immunosorbent assay (ELISA), and binding inhibition with human IgE.

Results: Human IgE recognized recombinant fragments 340–425, 466–579, 502–595, and 595–636 as revealed by immunoblotting and ELISA. On the other hand, the N‐terminal fragment 1–399, recombinants 410–443, 472–551, 502–579, 606–636, and the C‐terminal fragment 636–685 were unable to bind human IgE. Amino acid sequences 400–409, 466–471, 580–595, and 595–605 were shown to be required for IgE binding to the Per a 3.01 allergen, suggesting that the C‐terminus contains most of the IgE‐binding sites. Four peptides corresponding to these IgE‐binding amino acid sequences were synthesized. These peptides reacted with most sera (62.5–87.5%) tested as revealed by ELISA, demonstrating a heterogeneous IgE‐binding response. Moreover, preincubation of IgE‐positive recombinant proteins and synthetic peptides with atopic IgE resulted in marked inhibition of the IgE binding to Per a 3.01 allergen. Amino acid sequences 400TVLRDPVFYQ409, 466NNVDQI471, 580VDKGHNYCGYPENLLI595, and 595IPKGKKGGQAY605 of the major recombinant American cockroach Per a 3.01 allergen were involved in IgE binding.

Conclusion: These findings will advance our understanding of the antigenic structures responsible for allergenicity to the American cockroach, thereby providing strategies for the development of immunotherapies.
Laboratory assessment of the efficiency of encasing materials against house dust mites and their allergens
Authors: Mahakittikun V. , Komoltri C. , Nochot H. , Angus A. C. , Chew F. T.
Published: September 2003

Background: The current recommendation to reduce mite allergen exposure for mite‐sensitive individuals is to use allergen‐impermeable bed coverings. As these covers are made of various kinds of materials, they vary in quality. The objective of this study was to investigate the efficiency of different covering materials against house dust mites and their allergens in vitro.

Methods: Four types of materials including (1) plastic cover, (2) polyurethane‐coated cover, (3) non‐woven covers, (4) tightly woven microfiber covers and a regular cotton bed sheet (as a control) were evaluated using three methods: (i) heat escape method, (ii) Siriraj chamber method and stereomicroscopy, scanning electron microscopy and (iii) enzyme‐linked immunosorbent assay (ELISA).

Results: We found that there was a statistically significant difference in allergen permeability among four types of coverings (P < 0.001). In terms of the impermeability to mites and their allergens, plastic‐ and polyurethane‐coated covers were observed to be the best, followed by non‐woven, woven and cotton‐based bed sheets. A regular cotton‐based bed sheet allows a significant amount of leakage of mite allergens. Both woven and non‐woven material are efficient barriers against mite allergen in terms of impermeability. However, with regard to mite colonization, non‐woven covers have the drawback of mites being able to penetrate and colonize within the fabric fibers. Woven covers are therefore recommended because of their major advantages of not allowing the colonization of mites within the fabric, being easy to clean, and comfortable.

Conclusion: The three assessment methods used in this study could be useful as a primary approach to evaluate the quality of covering materials in vitro using both pore size and ability to be colonized by mites on the materials as the key factors.
Molecular and immunological characterization of Pen ch 18, the vacuolar serine protease major allergen of Penicillium chrysogenum
Authors: Shen H.‐D. , Chou H. , Tam M. F. , Chang C.‐Y. , Lai H.‐Y. , Wang S.‐R.
Published: September 2003

Background: We have suggested previously that the 32 and 34 kDa major allergens of Penicillium chrysogenum (also known as P. notatum) are the vacuolar (Pen ch 18) and the alkaline (Pen ch 13) serine proteases, respectively, of P. chrysogenum. The purpose of this study is to characterize the 32 kDa allergen of P. chrysogenum and its immunoglobulin E (IgE)cross‐reactivity with Pen ch 13 allergen.

Methods: The full‐length cDNA of Pen ch 18 was isolated by reverse transcriptase‐polymerase chain reaction and the 5′‐rapid amplification cDNA end reaction. Recombinant Pen ch 18 was expressed as his‐tagged proteins in Escherichia coli. Its reactivity with IgE and monoclonal antibodies against fungal serine protease allergens was analyzed by immunoblotting. The IgE cross‐reactivity between Pen ch 18 and Pen ch 13 was analyzed by immunoblot inhibition. Overlapping recombinant fragments and synthetic peptides were used to map the B cell epitopes on Pen ch 18.

Results: In this study, we isolated a 1857 bp cDNA fragment containing an open reading frame of 494 amino acids that encodes the preproenzyme of Pen ch 18. Similar to other vacuolar serine proteases, this precursor appears to undergo N‐ and possibly C‐terminal cleavage upon maturation. The his‐tagged recombinant Pen ch 18 containing the putative sequence of the mature protein reacted with IgE antibodies in serum samples from asthmatic patients. In addition, IgE‐binding to the 32 kDa major allergen of P. chrysogenum was inhibited when a positive serum sample was absorbed with recombinant Pen ch 18 before immunoblotting. Both inhibition and almost no inhibition of IgE‐binding to the 32 kDa major allergen of Pen ch 18 were detected when eight positive serum samples were preabsorbed individually with purified Pen ch 13 before immunoblotting. The major IgE binding region was located in a fragment (PN1) encompassing the N‐terminal 102 amino acid residues of the recombinant Pen ch 18. A dominant linear IgE epitope was further mapped within residues 73–95 (peptide PN1‐e) of the N‐terminally processed allergen. Monoclonal antibody FUM20 that reacts with Pen ch 18 but not with Pen ch 13 binds a synthetic peptide with sequence encompassing the N‐terminal 23 residues of the recombinant Pen ch 18. Monoclonal antibody PCM39 that reacts with both Pen ch 13 and Pen ch 18 recognizes a peptide containing residues 132–154 of the allergen.

Conclusions: Our results confirm that the Pen ch 18 allergen is a vacuolar serine protease of P. chrysogenum that matures through N‐ and possibly C‐terminal processing. The finding that there are cross‐reactive and allergen‐specific IgE epitopes for Pen ch 18 and Pen ch 13 suggests that both major allergens should be included in clinically diagnostic P. chrysogenum extracts.
Allergenicity of recombinant Bla g 7, German cockroach tropomyosin
Authors: Jeong K. Y. , Lee J. , Lee I.‐Y. , Ree H.‐I. , Hong C.‐S. , Yong T.‐S.
Published: September 2003

Background:Cockroach infestation may sensitize and elicit allergic responses to genetically predisposed individuals. Invertebrate tropomyosins are a frequent cause of allergy and highly cross‐reactive in nature. In this study, we aimed to produce recombinant German cockroach tropomyosin and investigate its allergenicity.

Methods:German cockroach tropomyosin (Bla g 7) was cloned by reverse transcriptase polymerase chain reaction (RT‐PCR). The cloned cDNA was over‐expressed inEscherichia coliand purified by affinity chromatography using Ni‐nitrilotriacetic (NTA) acid resin. The allergenicity of the recombinant tropomyosin was examined by enzyme‐linked immunosorbent assay (ELISA).

Results:The cloned Bla g 7 shared up to 91% amino acid sequence identity with other cockroach tropomyosins. ELISA showed a recombinant Bla g 7 sensitization rate of 16.2% to German cockroach allergic sera. Recombinant tropomyosin was able to inhibit 32.4% of the specific IgE binding to cockroach extract.

Conclusions:Tropomyosin represents a minor allergen in cockroach extracts. It is hoped that recombinant tropomyosin will be useful for further studies and clinical applications.