Depth profiles of iodide and iodate during POLARSTERN cruise ANT-XXIV/3 to the Atlantic sector of the Southern Ocean

The biogeochemistry of iodine in the waters of the Atlantic sector of the Southern Ocean was investigated during the Polarstern cruise ANTXXIV-3 ZERO&DRAKE. The speciation and distribution of iodine (iodate and iodide) in seawater was examined across gradients of iron concentrations and phytoplankton abundance, ranging from an open ocean region along the Zero Meridian to the Weddell Sea and Drake Passage. Iodine cycling in high latitudes differs from that in low latitudes due to differences in the plankton community composition and the physicochemical characteristics. Iodate concentrations ranged between 400 and 450 nmol/L from the surface to the bottom. Surface concentrations of iodide (17 to over 60 nmol/L) were about an order of magnitude higher than below the pycnocline. The peak values of iodide lay nearly always within the euphotic zone and showed a weak, positive correlation with nitrite concentrations in the upper 200 m. In all vertical profiles a pronounced sub-surface maximum in iodide appears between 50 and 200 m depth indicating an iodide drawdown at the near surface. Iodide distribution in the Weddell Sea showed elevated levels in Weddell Sea Bottom Water (WSBW) indicating slow oxidation kinetics and the potential for iodide as a tracer of WSBW formation.

Biomarker and x-ray diffraction data from Site U1313 (MIS 16 - 9)

A reconstruction of Milankovitch to millennial-scale variability of sea-surface temperature (SST) and sea-surface productivity in the Pleistocene mid-latitude North Atlantic Ocean (MIS 16-9) and its relationship to ice sheet instability was carried out on sediments from IODP Site U1313. This reconstruction is based on alkenone and n-alkane concentrations, Uk37' index, total organic carbon (TOC) and carbonate contents, X-Ray diffraction (XRD) data, magnetic susceptibility, and accumulation rates. Increased input of ice-rafted debris (IRD) occurred during MIS 16, 12, and 10, characterized by high concentrations of dolomite, quartz, and feldspars and elevated accumulation rates of terrigenous matter. Minimum input values of terrigenous matter, on the other hand, were determined for MIS 13 and 11. Peak values of dolomite, coinciding with quartz, plagioclase, and kalifeldspar peaks and maxima in long-chain n-alkanes indicative for land plants, are interpreted as Heinrich-like Events related to sudden instability of the Laurentide Ice Sheet during early and late (deglacial) phases of the glacials. The coincidence of increased TOC values with elevated absolute concentrations of alkenones suggest increased glacial productivity, probably due to a more southern position of the Polar Front. Alkenone-based SST reached absolute maxima of about 19°C during MIS 11.3 and absolute minima of <10°C during MIS 12 and 10. Within MIS 11, prominent cooling events (MIS 11.22 and 11.24) occurred. The absolute SST minima recorded directly before and after the glacial maxima MIS 10.2 and 12.2, are related to Heinrich-like Event meltwater pulses, as supported by the coincidence of SST minima and maxima in C37:4 alkenones and dolomite. These sudden meltwater pulses - especially during Terminations IV and V - probably caused a collapse of phytoplankton productivity as indicated by the distinct drop in alkenone concentrations. Ice-sheet disintegration and subsequent surges and outbursts of icebergs and meltwater discharge may have been triggered by increased insolation in the Northern High Latitudes.

Modelization of low cycle fatigue damage in frames

Damage models based on the Continuum Damage Mechanics (CDM) include explicitly the coupling between damage and mechanical behavior and, therefore, are consistent with the definition of damage as a phenomenon with mechanical consequences. However, this kind of models is characterized by their complexity. Using the concept of lumped models, possible simplifications of the coupled models have been proposed in the literature to adapt them to the study of beams and frames. On the other hand, in most of these coupled models damage is associated only with the damage energy release rate which is shown to be the elastic strain energy. According to this, damage is a function of the maximum amplitude of cyclic deformation but does not depend on the number of cycles. Therefore, low cycle effects are not taking into account. From the simplified model proposed by Flórez-López, it is the purpose of this paper to present a formulation that allows to take into account the degradation produced not only by the peak values but also by the cumulative effects such as the low cycle fatigue. For it, the classical damage dissipative potential based on the concept of damage energy release rate is modified using a fatigue function in order to include cumulative effects. The fatigue function is determined through parameters such as the cumulative rotation and the total rotation and the number of cycles to failure. Those parameters can be measured or identified physically through the haracteristics of the RC. So the main advantage of the proposed model is the possibility of simulating the low cycle fatigue behavior without introducing parameters with no suitable physical meaning. The good performance of the proposed model is shown through a comparison between numerical and test results under cycling loading.

On the effects of windbreaks on the aerodynamic loads over parabolic solar troughs

Parabolic reflectors, also known as parabolic troughs, are widely used in solar thermal power plants. This kind of power plants is usually located on desert climates, where the combined action of wind and dust can be of paramount importance. In some cases it becomes necessary to protect these devices from the joined wind and sand action, which is normally accomplished through solid windbreaks. In this paper the results of a wind tunnel test campaign, of a scale parabolic trough row having different windward windbreaks, are reported. The windbreaks herein considered consist of a solid wall with an upper porous fence. Different geometrical configurations, varying the solid wall height and the separation between the parabolic trough row and the windbreak have been considered. From the measured time series, both the mean and peak values of the aerodynamic loads were determined. As it would be expected, mean aerodynamic drag, as well as peak values, decrease as the distance between the windbreak and the parabolic increases, and after a threshold value, such drag loads increase with the distance.

A single in vivo administration of bombesin antagonist RC-3095 reduces the levels and mRNA expression of epidermal growth factor receptors in MXT mouse mammary cancers

Epidermal growth factor (EGF) and its receptors (EGFR) play important roles in tumorigenesis. In various experimental cancers, treatment with antagonists of bombesin/gastrin-releasing peptide (BN/GRP) produces a reduction in EGFRs, concomitant to inhibition of tumor growth. To investigate the mechanisms involved, we monitored concentrations of BN/GRP antagonist RC-3095 in serum of mice, rats, and hamsters given a single subcutaneous or intravenous injection of this analog. In parallel studies, we measured levels and mRNA expression of EGFRs in estrogen-dependent and independent MXT mouse mammary cancers, following a single subcutaneous administration of RC-3095 to tumor-bearing mice. Peak values of RC-3095 in serum were detected 2 min after intravenous or 15 min after subcutaneous injection. The levels of RC-3095 declined rapidly and became undetectable after 3–5 hr. In the estrogen-dependent MXT tumors, the concentration of EGF receptors was reduced by about 60% 6 hr following injection and returned to original level after 24 hr. Levels of mRNA for EGFR fell parallel with the receptor number and were nearly normal after 24 hr. In the hormone-independent MXT cancers, the number of EGFRs decreased progressively, becoming undetectable 6 hr after injection of RC-3095, and returned to normal values at 24 hr, but EGFR mRNA levels remained lower for 48 hr. Thus, in spite of rapid elimination from serum, BN/GRP antagonist RC-3095 can induce a prolonged decrease in levels and mRNA expression of EGFRs. These findings may explain how single daily injections of BN/GRP antagonists can maintain tumor growth inhibition.

Measuring the diaspora for virus-specific CD8+ T cells

The CD8+ T cell diaspora has been analyzed after secondary challenge with an influenza A virus that replicates only in the respiratory tract. Numbers of DbNP366- and DbPA224-specific CD8+ T cells were measured by tetramer staining at the end of the recall response, then followed sequentially in the lung, lymph nodes, spleen, blood, and other organs. The extent of clonal expansion did not reflect the sizes of the preexisting memory T cell pools. Although the high-frequency CD8+ tetramer+ populations in the pneumonic lung and mediastinal lymph nodes fell rapidly from peak values, the “whole mouse” virus-specific CD8+ T cell counts decreased only 2-fold over the 4 weeks after infection, then subsided at a fairly steady rate to reach a plateau at about 2 months. The largest numbers were found throughout in the spleen, then the bone marrow. The CD8+DbNP366+ and CD8+DbPA224+ sets remained significantly enlarged for at least 4 months, declining at equivalent rates while retaining the nucleoprotein > acid polymerase immunodominance hierarchy characteristic of the earlier antigen-driven phase. Lowest levels of the CD69 “activation marker” were detected consistently on virus-specific CD8+ T cells in the blood, then the spleen. Those in the bone marrow and liver were intermediate, and CD69hi T cells were very prominent in the regional lymph nodes and the nasal-associated lymphoid tissue. Any population of “resting” CD8+ memory T cells is thus phenotypically heterogeneous, widely dispersed, and subject to broad homeostatic and local environmental effects irrespective of epitope specificity or magnitude.

Análisis de encuestas como herramienta de gestión sostenible de especies cinegéticas en agrosistemas del este de la provincia de Alicante (Marina Baja): estudio del caso del jabalí Sus scrofa Linnaeus, 1758

El trabajo ha sido desarrollado en un agrosistema tradicional del NE de la provincia de Alicante (SE España). La superficie total del área de estudio es de aproximadamente 59.000 ha. La zona presenta grandes contrastes, con un área interior de morfología montañosa, con pequeñas cuencas dedicadas a la agricultura de secano, mientras que la zona litoral se caracteriza por un relieve menos abrupto, con núcleos de población y explotaciones agrícolas de regadío. El estudio se basa en la información extraída a partir de encuestas realizadas a los gestores cinegéticos, obteniendo datos acerca de las abundancias y la evolución de las poblaciones de jabalí entre los años 1980 y la actualidad. Se construye una base de datos SIG con un total de 15 cotos de caza. La base de datos incluye las siguientes variables: usos del suelo a nivel de coto, abundancias y evolución temporal de la especie. Los resultados muestran que dos de los cotos presentan densidades de jabalí elevadas (15-25 ind/ha), dos cotos presentan densidades medias (10-15 ind/ha), cinco cotos muestran densidades bajas (5-10 ind/ha) y otros seis cotos densidades muy bajas (0-5 ind/ha). Los valores máximos se encuentran en cotos de interior y de montaña donde todavía se mantienen en activo cultivos de secano y se intercalan con cultivos abandonados y áreas naturales. También se observan densidades elevadas en el único coto de todos los analizados que se encuentra en la costa, donde la disponibilidad de hábitat es menor y, por lo tanto, hay una mayor concentración de individuos. Finalmente, el jabalí ha aumentado sus poblaciones desde la década de los años 1980 en la totalidad de los cotos estudiados.

Paleomagnetic and stable isotope measurements and distribution of benthic foraminifera in sediment core PS1388-3 from the Antarctic continental margin in the eastern Weddell Sea

A stable isotope record from the eastern Weddell Sea from 69°S is presented. For the first time, a 250,000-yr record from the Southern Ocean can be correlated in detail to the global isotope stratigraphy. Together with magnetostratigraphic, sedimentological and micropalaeontological data, the stratigraphic control of this record can be extended back to 910,000 yrs B.P. A time scale is constructed by linear interpolation between confirmed stratigraphic data points. The benthic d18O record (Epistominella exigua) reflects global continental ice volume changes during the Brunhes and late Matuyama chrons, whereas the planktonic isotopic record (Neogloboquadrina pachyderma) may be influenced by a meltwater lid caused by the nearby Antarctic ice shelf and icebergs. The worldwide climatic improvement during deglaciations is documented in the eastern Weddell Sea by an increase in production of siliceous plankton followed, with a time lag of approximately 10,000 yrs, by planktonic foraminifera production. Peak values in the difference between planktonic and benthic d13C records, which are 0.5 per mil higher during warm climatic periods than during times with expanded continental ice sheets, also suggest increased surface productivity during interglacials in the Southern Ocean.

Mesozooplankton and phytoplankton time series of the Baltic Monitoring Program (BMP)

Within the monitoring programme of the Helsinki Commission (HELCOM) the mesozooplankton of the Bornholm Basin (ICES subdivision 25, station BMP-K2) was sampled by the WP-2 net (lOOfJm) 5-8 times a year in 1988-1992. Abundance, biomass, secondary production and productivity (P/B) were given for mesozooplankton groups and copepod species. Environmental factors recorded were temperature, chlorophyll a and primary production. Within copepods, the dominant species were Temora longicornis and Pseudocalanus minutus with yearly peak values of 40-50% of the monthly copepod numbers and biomasses. The annual production of Temora longicornis was highest (6.5g C/m**2/y). The biomass of all copepods was at its maximum in June (mean = 2.25g C/m**2), especially in 1992 (3.65g C/m**2). The differences between results from two methods used to calculate the production of copepods were greatest in June and July. The cladocerans were only important in summer and the appendicularians only in spring. The productivity (P/B) of the appendicularians was highest of all mesozooplankton groups. Numbers and the biomass of the meroplankton were one or two orders of magnitude below the holoplanktic groups.

Sedimentological, geochemical, micropaleontological and rock magnetic proxies of sediment core GeoB6211-2

Surface currents and sediment distribution of the SE South American upper continental margin are under influence of the South American Monsoon System (SAMS) and the Southern Westerly Wind Belt (SWWB). Both climatic systems determine the meridional position of the Subtropical Shelf Front (STSF) and probably also of the Brazil-Malvinas Confluence (BMC). We reconstruct the changing impact of the SAMS and the SWWB on sediment composition at the upper Rio Grande Cone off southern Brazil during the last 14 cal kyr combining sedimentological, geochemical, micropaleontological and rock magnetic proxies of marine sediment core GeoB 6211-2. Sharp reciprocal changes in ferri- and paramagnetic mineral content and prominent grain-size shifts give strong clues to systematic source changes and transport modes of these mostly terrigenous sediments. Our interpretations support the assumption that the SAMS over SE South America was weaker than today during most of the Late Glacial and entire Early Holocene, while the SWWB was contracted to more southern latitudes, resembling modern austral summer-like conditions. In consequence, the STSF and the BMC were driven to more southern positions than today's, favoring the deposition of Fe-rich but weakly magnetic La Plata River silts at the Rio Grande Cone. During the Mid Holocene, the northern boundary of the SWWB migrated northward, while the STSF reached its northernmost position of the last 14 cal kyr and the BMC most likely arrived at its modern position. This shift enabled the transport of Antarctic diatoms and more strongly magnetic Argentinean shelf sands to the Rio Grande Cone, while sediment contributions from the La Plata River became less important. During the Late Holocene, the modern El Niño Southern Oscillation set in and the SAMS and the austral tradewinds intensified, causing a southward shift of the STSF to its modern position. This reinforced a significant deposition of La Plata River silts at the Rio Grande Cone. These higher magnetic silts with intermediate Fe contents mirror the modern more humid terrestrial climatic conditions over SE South America.

(Table 1) Age of sediments with anomalously high Hg concentrations in core BDP-98, Lake Baikal

Mercury distribution was examined in the sediments of Lake Baikal that were sampled within the scope of the Baikal Drilling International Project in 1996-1999. The Hg concentrations in the ancient sediments are close to those in the modern sediments with the exception of a few peak values, whose ages coincide with those of active volcanism in adjacent areas. Mercury was demonstrated to be contained in the sediments in the adsorbed Hg0 mode, predominantly in relation with organic matter. When the organic matter of the bottom sediments is decomposed in the course of lithification, Hg is retained in the sediments adsorbed on the residual organic matter, and the concentration of this element corresponds to its initial content in the bottom sediments during their accumulation. Mercury concentrations in lithologically distinct bottom sediments of Lake Baikal and its sediments as a whole depend on the climate. Sediments that were formed during warm periods of time contain more Hg than those produced during cold periods or glaciation. Periodical variations in the Hg concentrations in the bottom sediments of Lake Baikal reflect the variations in the contents of this element in the Earth's atmosphere in the Late Cenozoic, which were, in turn, controlled by the climatic variations on the planet and, thus, can be used for detailed reconstructions of variations in the average global temperature near the planet's surface.

Sedimentological and paleomagnetic investigations on two gravity cores and ODP sites 113-690 and 693 off Kapp Norvegia, Antarctic continental margin

Oligocene to Quaternary sediments were recovered from the Antarctic continental margin in the eastern Weddell Sea during ODP Leg 113 and Polarstern expedition ANT-VI. Clay mineral composition and grain size distribution patterns are useful for distinguishing sediments that have been transported by ocean currents from those that were ice-rafted. This, in turn, has assisted in providing insights about the changing late Paleogene to Neogene sedimentary environment as the cryosphere developed in Antarctica. During the middle Oligocene, increasing glacial conditions on the continent are indicated by the presence of glauconite sands, that are interpreted to have formed on the shelf and then transported down the continental slope by advancing glaciers or as a result of sea-level lowering. The dominance of illite and a relatively high content of chlorite suggest predominantly physical weathering conditions on the continent. The high content of biogenic opal from the late Miocene to the late Pliocene resulted from increased upwelling processes at the continental margin due to increased wind strength related to global cooling. Partial melting of the ice-sheet occurred during an early Pliocene climate optimum as is shown by an increasing supply of predominantly current-derived sediment with a low mean grain size and peak values of smectite. Primary productivity decreased at ~ 3 Ma due to the development of a permanent sea-ice cover close to the continent. Late Pleistocene sediments are characterized by planktonic foraminifers and biogenic opal, concentrated in distinct horizons reflecting climatic cycles. Isotopic analysis of AT. pachyderma produced a stratigraphy which resulted in a calculated sedimentation rate of 1 cm/k.y. during the Pleistocene. Primary productivity was highest during the last three interglacial maxima and decreased during glacial episodes as a result of increasing sea-ice coverage.

Marine ice-rafted debris records and age determinations along the northern Eurasian margin

Ice-rafted debris (IRD) (>2 mm), input in eight sediment cores along the Eurasian continental margin (Arctic Ocean), have been studied over the last two glacial/interglacial cycles. Together with the revised chronologies and new micropaleontological data of two cores from the northern Barents Sea (PS2138) and northeastern Kara Sea (PS2741) spanning Marine Isotope Stages (MIS) 6 to 1, the IRD data give new insights into the glacial history of northern Eurasian ice-sheets over the last 150 ka. The chronologies of the cores are based on stable isotope records, AMS 14C datings, paleomagnetic and biostratigraphic data. Extensive episodes of northern Barents Sea ice-sheet growth, probably to the shelf edge, occurred during the late Weichselian (MIS 2) and the Saalian (MIS 6). Major IRD discharge at the MIS 4/3-transition hints to another severe glaciation, probably onto the outer shelf, during MIS 4. IRD-based instabilities of the marine-based ice margin along the northern Barents Sea between MIS 4 and 2 are similar in timing with North Atlantic Heinrich events and Nordic Seas IRD events, suggesting similar atmospheric cooling over a broad region or linkage of ice-sheet fluctuations through small sea-level events. In the relatively low-precipitation areas of eastern Eurasia, IRD peak values during Termination II and MIS 4/3-transition suggest a Kara Sea ice-sheet advance onto the outer shelf, probably to the shelf edge, during glacial MIS 6 and 4. This suggests that during the initial cooling following the interglacials MIS 5, and possibly MIS 7, the combined effect of sustained inflow of Atlantic water into the Arctic Ocean and penetration of moisture-bearing cyclones into easterly direction supported major ice build-up during Saalian (MIS 6) and Mid-Weichselian (MIS 4) glaciation. IRD peak values in MIS 5 indicate at least two advances of the Severnaya Semlya ice-sheet to the coast line during the Early Weichselian. In contrast, a distinct Kara Sea ice advance during the Late Weichselian (MIS 2) is not documented by the IRD records along the northeastern Kara Sea margin.