The Relation Between the Radial Temperature Profile in the Chromosphere and the Solar Spectrum at Centimeter,Millimeter, Submillimeter,and Infrared Wavelengths

Solar observations from millimeter to ultraviolet wavelengths show that there is a temperature minimum between photosphere and chromosphere. Analyses based on semi-empirical models locate this point at about 500 km above the photosphere. The consistency of these models has been tested by means of millimeter to infrared observations. We show that variations of the theoretical radial temperature profile near the temperature minimum impact the brightness temperature at centimeter, submillimeter, and infrared wavelengths, but the millimeter wavelength emission remains unchanged. We found a region between 500 and 1000 km above the photosphere that remains hidden to observations at the frequencies that we studied here.     

Hemolytic activity and fatty acids composition in the ichthyotoxic dinoflagellate Cochlodinium polykrikoides isolated from Bahía de La Paz, Gulf of California

The hemolytic activity of the dinoflagellate Cochlodinium polykrikoides from Bahía de La Paz, Gulf of California was investigated as part of the ichthyotoxic mechanism of this microalga. Two different kinds of erythrocytes, fish and human, were tested for the hemolytic assay. Since fatty acids have been associated with hemolytic activity in C. polykrikoides, the composition of fatty acids of this dinoflagellate was also analyzed. The concentration of C. polykrikoides causing 50% hemolysis (HE₅₀) was 4.88 and 5.27 × 10⁶ cells L⁻¹, for fish and human erythrocytes, respectively. According to the standard curve of saponin, an equivalence between the hemolytic activity of saponin and the dinoflagellate concentration was found with 1 μg saponin mL⁻¹ equivalent to 1 × 10⁶ cells L⁻¹ of C. polykrikoides. The polyunsaturated fatty acids: hexadecaenoic (16:0), docosahexaenoic (22:6 n3) and octadecapentaenoic (18:5 n3) were found in an abundance of 62% of total fatty acids.     

Oxygen isotope variations in phosphate of biogenic apatites,II. Phosphorite rocks

Phosphorites from sedimentary sequences ranging in age from Archaean to Recent were analysed for δ¹⁸O in both the PO₄ (δ¹⁸O_p) and CO₃ (δ¹⁸O_c) in the apatite lattice. The oxygen isotope record is considerably better preserved in phosphates than in either carbonates or cherts. The use of the Longinelli and Nuti [8] temperature equation yields temperatures for Recent phosphorites that are in good agreement with those measured in the field. The δ¹⁸O_p values of ancient phosphorites decrease with increasing age. These changes with time are not likely to be due to post-depositional exchange. Changes in δ¹⁸O values of seawater and variations of temperature with time can account for the δ¹⁸O_p time trend, but the latter explanation is preferred. In Ancient phosphorites δ¹⁸O_c in structurally bound carbonate in apatite is not a reliable geochemical indicator.     

Quaternary faulting in the Upper Rhine Graben revealed by high-resolution multi-channel reflection seismic

A high-resolution multichannel seismic reflection river profiling campaign was completed in July 2002 in the southern Upper Rhine graben (URG), along the River Rhine. Preliminary results show apparent Quaternary vertical slip rates, on intra-graben faults that are relatively slow, of the order of a few thousandths to a few hundredths of mm/yr. Moreover, kinematical data from the Ludwigshafen area show decreasing vertical slip rates since the Middle Pleistocene and/or a migration of tectonic activity. While still preliminary, these data show inhomogeneous and relatively slow tectonic activity in the URG that could probably not alone have shaped the Quaternary graben morphology. To cite this article: G. Bertrand et al., C. R. Geoscience 338 (2006).     

Stratigraphic and paleoclimatic analysis of late Pleistocene tropical southeast Pacific cores (with an appendix by N. J. Shackleton)

Factor analysis of dissolution-resistant species of planktonic foraminifera in the >250 μm fraction of seabed and core samples from the tropical southeast Pacific yields five mappable varimax assemblages. The distribution of these assemblages in core tops is more related to the subsurface thermal structure than to the surface temperature. A transfer function relating the assemblages in core tops to the temperature at 200 m is applied to five cores. Cycles of estimated temperature in three cores are approximately in phase with climatic cycles in Atlantic cores spanning the past 200,000 yr, and display amplitudes on the order of 5°C. Two zones of increased calcium carbonate dissolution occur in these three cores. These zones occur in the transition from interglacial to glacial intervals. Temperature variations inferred are ascribed to fluctuations of the main thermocline, and the inference is made that during cold intervals the thermocline was displaced upward as the central water mass was areally diminished. A model of circulation dynamics suggests that such areal diminution would be associated with an intensified circulation. No significant fluctuations in the estimated 200 m temperature are inferred for a core in the Galápagos area during the last glacial, but a pronounced peak of high-latitude species Globorotalia inflata does occur. This peak is judged to reflect the removal of a low-oxygen ecological barrier.     

Geochemistry of Famennian to Visean Metapelites from the Iberian Pyrite Belt: Implications for Provenance,Paleo-Redox Conditions and Vectoring to Massive Sulfide Deposits

Natural Resources Research - Massive sulfide deposits of the Iberian Pyrite Belt (IPB) document the progression of ore-forming processes in the SW Iberian Variscides, throughout uppermost Devonian...     

A coupled dynamics-microphysics model of Titan's atmosphere

We have developed a coupled general circulation model of Titan's atmosphere in which the aerosol haze is treated with a microphysical model and is advected by the winds. The radiative transfer accounts for the non uniform haze distribution and, in turn, drives the dynamics. We analyze the GCM results, especially focusing on the difference between a uniform haze layer and a haze layer coupled to the dynamics. In the coupled simulation the aerosols tend to accumulate at the poles, at latitudes higher than ±60°. During winter, aerosols strongly radiate at thermal infrared wavelengths enhancing the cooling rate near the pole. Since this tends to increase the latitudinal gradients of temperature the direct effect of this cooling excess, in contrast to the uncoupled haze case, is to increase the strength of the meridional cells as well as the strength of the zonal winds and profile. This is a positive feedback of the haze on dynamics. The coupled model reproduces observations about the state of the atmosphere better than the uniform haze model, and in addition, the northern polar hood and the detached haze are qualitatively reproduced.     

A 15 000‐year record of climate change in northern New Mexico,USA, inferred from isotopic and elemental contents of bog sediments

Elemental (C, N, Pb) and isotopic (δ¹³C, δ¹⁵N) measurements of cored sediment from a small bog in northern New Mexico reveal changes in climate during the Late Pleistocene and Holocene. Abrupt increases in Pb concentration and δ¹³C values ca. 14 420 cal. YBP indicate significant runoff to the shallow lake that existed at that time. Weathering and transport of local volcanic rocks resulted in the delivery of Pb‐bearing minerals to the basin, while a ¹³C‐enriched terrestrial vegetation source increased the δ¹³C values of the sedimentary material. Wet conditions developed over a 300 a period and lasted for a few hundred years. The Younger Dryas period (ca. 12 700–11 500 cal. YBP) caused a reduction in terrestrial productivity reflected in decreasing C/N values, δ¹⁵N values consistently greater than 0‰ and low organic content. By contrast, aquatic productivity increased during the second half of this period, evidenced by increasing δ¹³C values at the time of highest abundance of algae. Dry conditions ca. 8 000–6 000 cal. YBP were characterised by low organic carbon content and high Pb concentrations, the latter suggesting enhanced erosion and aeolian transport of volcanic rock. The range in δ¹³C, δ¹⁵N and C/N values in the sedimentary record fall within the range of modern plants, except during the periods of runoff and drought. The sedimentary record provides evidence of natural climate variability in northern New Mexico, including short‐ (multi‐centennial) and long‐(millennial) term episodes during the Late Pleistocene and Holocene. Copyright © 2010 John Wiley & Sons, Ltd.