943 resultados para Simonides, ca. 556-467 B.C.


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Background. Nuclear factor kappa B (NF kappa B) plays a potential role in tolerance by orchestrating onset and resolution of inflammation and regulatory T cell differentiation through subunit c-Rel. We characterized cellular infiltrates and expression of NF kappa B1, c-Rel and its upstream regulators phosphatidylinositol 3-kinase/RAC-alpha serine/threonine kinase, in allograft biopsies from patients with spontaneous clinical operational tolerance (COT). Methods. Paraffin-fixed kidney allograft biopsies from 40 patients with COT (n=4), interstitial rejection (IR; n=12), borderline changes (BC; n=12), and long-term allograft function without rejection (NR; n=12) were used in the study. Cellular infiltrates and immunohistochemical expression of key proteins of the NF kappa B pathway were evaluated in the cortical tubulointerstitium and in cellular infiltrates using digital image analysis software. Results were given as mean +/- SEM. Results. Biopsies from patients with COT exhibited a comparable amount of cellular infiltrate to IR, BC, and NR (COT, 191 +/- 81; IR, 291 +/- 62; BC, 178 +/- 45; and NR, 210 +/- 42 cells/mm(2)) but a significantly higher proportion of forkhead box P3-positive cells (COT, 11%+/- 1.7%; IR, 3.5%+/- 0.70%; BC, 3.4%+/- 0.57%; and NR, 3.7%+/- 0.78% of infiltrating cells; P=0.02). c-Rel expression in cellular infiltrates was significantly elevated in IR, BC, and NR when analyzing the number of positive cells per mm(2) (P=0.02) and positive cells per infiltrating cells (P=0.04). In contrast, tubular PI3K and c-Rel expression were significantly higher in IR and BC but not in NR compared with COT (P=0.03 and P=0.006, respectively). With RAC-alpha serine-threonine kinase, similar tendencies were observed (P=0.2). Conclusions. Allografts from COT patients show significant cellular infiltrates but a distinct expression of proteins involved in the NF kappa B pathway and a higher proportion of forkhead box P3-positive cells.

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The North Atlantic and Norwegian Sea are prominent sinks of atmospheric CO2 today, but their roles in the past remain poorly constrained. In this study, we attempt to use B/Ca and d11B ratios in the planktonic foraminifera Neogloboquadrina pachyderma (sinistral variety) to reconstruct subsurface water pH and pCO2 changes in the polar North Atlantic during the last deglaciation. Comparison of core-top results with nearby hydrographic data shows that B/Ca in N. pachyderma (s) is mainly controlled by seawater [B(OH)4]?/[HCO3]? with a roughly constant partition coefficient (KD =([B/Ca]of CaCO3)/([B(OH)4]-/[HCO3]-)of seawater) of 1.48 ± 0.15 * 10**-3 (2sigma), and d11B in this species is offset below d11B of the borate in seawater by 3.38 ± 0.71 per mil (2sigma). These values represent our best estimates with the sparse available hydrographic data close to our core-tops. More culturing and sediment trap work is needed to improve our understanding of boron incorporation into N. pachyderma (s). Application of a constant KD of 1.48 * 10**-3 to high resolution N. pachyderma (s) B/Ca records from two adjacent cores off Iceland shows that subsurface pCO2 at the habitat depth of N. pachyderma (s) (~50 m) generally followed the atmospheric CO2 trend but with negative offsets of ~10-50 ppmv during 19-10 ka. These B/Ca-based reconstructions are supported by independent estimates from low-resolution d11B measurements in the same cores. We also calibrate and apply Cd/Ca in N. pachyderma (s) to reconstruct nutrient levels for the same down cores. Like today's North Atlantic, past subsurface pCO2 variability off Iceland was significantly correlated with nutrient changes that might be linked to surface nutrient utilization and mixing within the upper water column. Because surface pCO2 (at 0 m water depth) is always lower than at deeper depths and if the application of a constant KD is valid, our results suggest that the polar North Atlantic has remained a CO2 sink during the calcification seasons of N. pachyderma (s) over the last deglaciation.

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The episodic occurrence of debris flow events in response to stochastic precipitation and wildfire events makes hazard prediction challenging. Previous work has shown that frequency-magnitude distributions of non-fire-related debris flows follow a power law, but less is known about the distribution of post-fire debris flows. As a first step in parameterizing hazard models, we use frequency-magnitude distributions and cumulative distribution functions to compare volumes of post-fire debris flows to non-fire-related debris flows. Due to the large number of events required to parameterize frequency-magnitude distributions, and the relatively small number of post-fire event magnitudes recorded in the literature, we collected data on 73 recent post-fire events in the field. The resulting catalog of 988 debris flow events is presented as an appendix to this article. We found that the empirical cumulative distribution function of post-fire debris flow volumes is composed of smaller events than that of non-fire-related debris flows. In addition, the slope of the frequency-magnitude distribution of post-fire debris flows is steeper than that of non-fire-related debris flows, evidence that differences in the post-fire environment tend to produce a higher proportion of small events. We propose two possible explanations: 1) post-fire events occur on shorter return intervals than debris flows in similar basins that do not experience fire, causing their distribution to shift toward smaller events due to limitations in sediment supply, or 2) fire causes changes in resisting and driving forces on a package of sediment, such that a smaller perturbation of the system is required in order for a debris flow to occur, resulting in smaller event volumes.

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Several classes of voltage-gated Ca2+ channels (VGCCs) are inhibited by G proteins activated by receptors for neurotransmitters and neuromodulatory peptides. Evidence has accumulated to indicate that for non-L-type Ca2+ channels the executing arm of the activated G protein is its βγ dimer (Gβγ). We report below the existence of two Gβγ-binding sites on the A-, B-, and E-type α1 subunits that form non-L-type Ca2+ channels. One, reported previously, is in loop 1 connecting transmembrane domains I and II. The second is located approximately in the middle of the ca. 600-aa-long C-terminal tails. Both Gβγ-binding regions also bind the Ca2+ channel β subunit (CCβ), which, when overexpressed, interferes with inhibition by activated G proteins. Replacement in α1E of loop 1 with that of the G protein-insensitive and Gβγ-binding-negative loop 1 of α1C did not abolish inhibition by G proteins, but the exchange of the α1E C terminus with that of α1C did. This and properties of α1E C-terminal truncations indicated that the Gβγ-binding site mediating the inhibition of Ca2+ channel activity is the one in the C terminus. Binding of Gβγ to this site was inhibited by an α1-binding domain of CCβ, thus providing an explanation for the functional antagonism existing between CCβ and G protein inhibition. The data do not support proposals that Gβγ inhibits α1 function by interacting with the site located in the loop I–II linker. These results define the molecular mechanism by which presynaptic G protein-coupled receptors inhibit neurotransmission.

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Interleaved second-edition copy of Robert Treat Paine's poem "The Invention of Letters" with handwritten excerpts of 18th century poetry copied by Charles Pinckney Sumner. The excerpts appear to be verses alluded to, or emulated, by Paine in the poem. For example, Paine's verse includes "Beneath the shade, which Freedom's oak displays" and Sumner on the opposite page quoted Alexander Pope's poetry, "Beneath the shade a spreading beech displays." The excerpts include poetry by Alexander Pope, James Thompson, Robert Dodsley, William Falconer, William Hayley, Samuel Rogers, Richard Brinsley Sheridan, Thomas Gray, and John Denham.

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Mode of access: Internet.

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We present new Holocene century to millennial-scale proxies for the well-dated piston core MD99-2269 from Húnaflóadjúp on the North Iceland Shelf. The core is located in 365 mwd and lies close to the fluctuating boundary between Atlantic and Arctic/Polar waters. The proxies are: alkenone-based SST°C, and Mg/Ca SST°C estimates and stable d13C and d18O values on planktonic and benthic foraminifera. The data were converted to 60 yr equi-spaced time-series. Significant trends in the data were extracted using Singular Spectrum Analysis and these accounted for between 50% and 70% of the variance. A comparison between these data with previously published climate proxies from MD99-2269 was carried out on a data set which consisted of 14-variable data set covering the interval 400-9200 cal yr BP at 100 yr time steps. This analysis indicated that the 1st two PC axes accounted for 57% of the variability with high loadings clustering primarily into "nutrient" and "temperature" proxies. Clustering on the 100 yr time-series indicated major changes in environment at ~6350 and ~3450 cal yr BP, which define early, mid- and late Holocene climatic intervals. We argue that a pervasive freshwater cap during the early Holocene resulted in warm SST°s, a stratified water column, and a depleted nutrient supply. The loss of the freshwater layer in the mid-Holocene resulted in high carbonate production, and the late Holocene/neoglacial interval was marked by significantly more variable sea surface conditions.