Millennial-scale climate variation during the Last Glacial period is evident in many locations worldwide, but it is unclear if such variation occurred in the interior of tropical South America, and, ...if so, how the low-latitude variation was related to its high-latitude counterpart. A high-resolution record, derived from the deep drilling of sediments on the floor of Lake Titicaca in the southern tropical Andes, is presented that shows clear evidence of millennial-scale climate variation between ∼60 and 20
ka
BP. This variation is manifested by alternations of two interbedded sedimentary units. The two units have distinctive sedimentary, geochemical, and paleobiotic properties that are controlled by the relative abundance of terrigenous or nearshore components versus pelagic components. The sediments of more terrigenous or nearshore nature likely were deposited during regionally wetter climates when river transport of water and sediment was higher, whereas the sediments of more pelagic character were deposited during somewhat drier climates regionally. The majority of the wet periods inferred from the Lake Titicaca sediment record are correlated with the cold events in the Greenland ice cores and North Atlantic sediment cores, indicating that increased intensity of the South American summer monsoon was part of near-global scale climate excursions.
We present infrared colours (in the 25–500 μm spectral range) and UV to radio continuum spectral energy distributions of a sample of 51 nearby galaxies observed with SPIRE on Herschel. The observed ...sample includes all morphological classes, from quiescent ellipticals to active starbursts. Active galaxies have warmer colour temperatures than normal spirals. In ellipticals hosting a radio galaxy, the far-infrared (FIR) emission is dominated by the synchrotron nuclear emission. The colour temperature of the cold dust is higher in quiescent E-S0a than in star-forming systems probably because of the different nature of their dust heating sources (evolved stellar populations, X-ray, fast electrons) and dust grain properties. In contrast to the colour temperature of the warm dust, the f350/f500 index sensitive to the cold dust decreases with star formation and increases with metallicity, suggesting an overabundance of cold dust or an emissivity parameter β < 2 in low metallicity, active systems.
The Herschel Virgo Cluster Survey Grossi, M; Hunt, L K; Madden, S C ...
Astronomy and astrophysics (Berlin),
02/2015, Letnik:
574
Journal Article
Recenzirano
Odprti dostop
The aim of this study is to assess the effects of the cluster environment on the different components of the interstellar medium, we analyze the far-infrared (FIR) and sub-millimetre (sub-mm) ...properties of a sample of star-forming dwarf galaxies detected by the Herschel Virgo Cluster Survey (HeViCS). We determine dust masses and dust temperatures by fitting a modified black body function to the spectral energy distributions (SEDs). Stellar and gas masses, star formation rates (SFRs), and metallicities are obtained from the analysis of a set of ancillary data. However, to explain the large dust-to-gas mass ratios observed in these systems, we find that the fraction of dust removed has to be less than that of the HI component. The cluster environment seems to mostly affect the gas component and star formation activity of the dwarfs. Since the Virgo star-forming dwarfs are likely to be crossing the cluster for the first time, a longer timescale might be necessary to strip the more centrally concentrated dust distribution.
Four laboratory experiments on fresh, modern diatoms collected from lakes in the Northern Great Plains of North America were carried out to assess the effects of dissolution on diatom abundance and ...composition. Marked differences in mean dissolution susceptibility exist between species, despite sometimes significant intra-specific variation between heterovalves. Twenty-four taxa were ranked according to susceptibility to dissolution using an exponential decay model of valve abundance. This dissolution ranking was used to derive two weighted indices of sample preservation.
A third index (
F) was based on a simple binary classification of valve morphology into dissolved and pristine categories, as distinguished by light microscopy (LM). When compared against rank indices and a measure of species diversity, this diatom dissolution index was found to be the best predictor of the progress of dissolution as estimated by total valve abundance or biogenic silica (BiSi) loss. Strong empirical relationships between
F index values and diatom abundance (
r
2=0.84,
n=32) and BiSi (
r
2=0.89,
n=32) were developed and applied to a diatom sequence from a short core from Devils Lake, North Dakota, and compared to diatom-inferred and observed salinity at this site.
The
F index is a simple, effective diagnostic tool to assess important aspects of diatom preservation. The index can provide insight into Si cycling and record changes in conditions pertinent to diatom dissolution, and has a role in validation of transfer functions or other inferences derived from compositional data.
Background
To compare intermittent treatment (IT) versus continuous treatment (CT) using cyproterone acetate (CPA) in bone metastatic prostate cancer patients, we conducted an open-label, multicenter ...randomized trial. Continuous androgen deprivation therapy is the standard treatment in metastatic prostate cancer. Intermittent treatment might maintain efficacy while toxicity and costs are reduced.
Methods
Patients received CPA 100 mg tid in the prephase. Patients with a PSA decline of ≥90 % or PSA <4 ng/ml were randomized. If patients were progressive, LHRH analogues were added. Primary end point was time to PSA progression.
Results
A total of 366 patients were recruited; 258 reached a good response after 3 or 6 months and were randomized. A total of 131 patients randomized to IT and 127 to CT. Patients on IT had an average of 1.7 episodes on CPA, before LHRH analogues were started. The mean time without treatment in IT was 463 days versus 422 days on treatment. There were statistical significant differences between IT and CT in 3 of the 5 functional scales of EORTC QLQ C 30; however, the clinical relevance of this finding appears modest. Symptom and potency scales showed significant advantages for IT. There were no differences in time to PSA progression on CPA, time to PSA and/or clinical progression on LHRH analogues and time to cancer-specific and overall survival.
Conclusions
IT by CPA is associated with less symptoms and modest advantages in QOL domains. There were no differences in time to PSA progression, clinical progression or survival.
A composite high-resolution diatom stratigraphy from three piston cores and one box-core in the deep sub-basin of Lake Titicaca reveals large moisture variations during the past 30 kyr in the ...Altiplano region. Diatom sequences indicate orbital and millennial-scale variability in water level and salinity. The pelagic freshwater diatom species
Cyclotella andina and
Cyclotella stelligera dominate Glacial-age sediments, suggesting that the lake was above its present outlet. Generally, wet conditions continued until 11 000 cal yr BP, as indicated by high percentages of freshwater planktonic diatoms. Large pulses of benthic diatom species between about 11 000 and 10 000 cal yr BP suggest brief intervals of large-amplitude declines in lake level. During the early Holocene (10 000–8500 cal yr BP), a freshwater diatom assemblage suggests overflowing conditions. Pelagic freshwater diatoms are replaced ca. 8500 cal yr BP by the salinity-indifferent species
Cyclotella meneghiniana and by benthic taxa, indicating the beginning of lake regression. During the mid-Holocene (6000–3500 cal yr BP), the abundance of the saline taxon
Chaetoceros muelleri, coupled with high abundances of epiphytic and epipelic diatoms, indicates maximum salinity and lowest lake levels in the entire 30 000 year record. Lake transgression began ca. 4000 cal yr BP, and the lake achieved modern levels by about 1500 cal yr BP. These water-level changes imply changes in effective moisture, most likely resulting from large precipitation changes. Precipitation was high throughout the Last Glacial Maximum (21 000–18 000 cal yr BP), likely due to an enhanced South American Summer Monsoon during peak summer insolation in the Southern Hemisphere. In contrast, the mid-Holocene transition was dryer than today in association with an austral summer insolation minimum and the subsequent weakening of the summer monsoon.
Widespread drought is among the most likely and devastating consequences of future global change. Assessment of drought impacts forecast by atmospheric models requires an understanding of natural ...drought variability, especially under conditions more arid than today. Using high-resolution lake-sediment records from the northern Great Plains, we show pronounced 100- to 130-yr drought cycles during the arid middle Holocene (8000 calendar yr BP). During drought phases, grass productivity declined, erosion and forbs increased, and fuel limitation reduced fire importance. Intervening humid decades saw grass production rise, with stabilization of soils and renewed fire as fuels became abundant. Although both C3 and C4 grasses declined during droughts, a lasting shift to C3 dominance occurred during a single drought ~8200 calendar yr BP. During the more humid Late Holocene (2800 calendar yr BP), climate was less variable and without evident drought cyclicity. Consequently, drought severity during past, and possibly future, arid phases cannot be anticipated from the attenuated climate variability evident during contemporary humid phases. Our study demonstrates that agriculturally important grassland ecosystems respond sensitively to drought variability, uncertainty in which has profound implications for the future of these ecosystems.
Mammalian Germ-Line Transgenesis by Transposition Dupuy, Adam J.; Clark, Karl; Carlson, Corey M. ...
Proceedings of the National Academy of Sciences - PNAS,
04/2002, Letnik:
99, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Transposons have been used in invertebrates for transgenesis and insertional mutagens in genetic screens. We tested a functional transposon called Sleeping Beauty in the one-cell mouse embryo. In ...this report, we describe experiments in which transposon vectors were injected into one-cell mouse embryos with mRNA expressing the SB10 transposase enzyme. Molecular evidence of transposition was obtained by cloning of insertion sites from multiple transgenic mice produced by SB10 mRNA/transposon coinjection. We also demonstrate germ-line transmission and expression from transposed elements. This technique has promise as a germ-line transgenesis method in other vertebrate species and for insertional mutagenesis in the mouse.
Laird et al present a reconstruction of drought intensity and frequency over the past 2,300 years in the Northern Great Plains, based on lake salinity fluctuations inferred from fossil diatom ...assemblages. The record suggests that extreme droughts of greater intensity than that of the 1930s were more frequent before AD 1200.
PDF
