A C*-algebra of geometric operators on self-similar CW-complexes. Novikov-Shubin and L^2-Betti numbers

A class of CW-complexes, called self-similar complexes, is introduced, together with C*-algebras A_j of operators, endowed with a finite trace, acting on square-summable cellular j-chains. Since the Laplacian Delta_j belongs to A_j, L^2-Betti numbers and Novikov-Shubin numbers are defined for such complexes in terms of the trace. In particular a relation involving the Euler-Poincare' characteristic is proved. L^2-Betti and Novikov-Shubin numbers are computed for some self-similar complexes arising from self-similar fractals.Comment: 30 pages, 7 figure

Efeito da lesão com ácido caínico sobre a fosforilação e o imunoconteúdo da proteína glial fribrilar ácida em hipocampo de ratos

A resposta do tecido nervoso à lesão ainda é pouco conhecida e o seu estudo tem importância científica muito grande. Este trabalho teve como objetivo central estudar a reação das células glias, mais especificamente os astrócitos, às lesões químicas, baseado na incorporação de 32P e no imunoconteúdo da proteína de filamento intermediário denominada Proteína Glial Fibrilar Ácida (GFAP). Adicionalmente também foi estudada a variação da fosforilação de outras proteínas após a lesão. Tanto a incorporação de 32P como o imunoconteúdo da GFAP diminuem nos primeiros 7 dias após alesão, aumentando significativamente após este intervalo e permanecendo elevado em relação ao controle até 84 dias após a lesão. O estado de fosforilação, isto é, a relação entre a incorporação de 32P e o imunoconteúdo se manteve inalterado após a lesão. Vimentina, outra proteína de citoesqueleto de astrócito, teve a sua incorporação de 32P aumentada de forma transitória, o mesmo acontecendo com uma proteína provavelmente ainda não descrita, que denominamos pp25 e que foi caracterizada parcialmente. Podemos concluir que o estado de fosforilação da GFAP não é alterado significativamente com a lesão sendo a resposta principal a variação na quantidade desta proteína. O aparecimento transitório de fosfoproteínas gliais como a vimentina e a pp25 parecem representar um bom marcador bioquímico para a gliose.The response of nervous tissue to lesions is poorly understood as yet, and its study has a great scientific importance. The main objective of this work was to study the reaction of glial cells, more specifically astrocytes after chemical lesioning, using as parameter the incorporation of 32P into, and the imunocontent of an intermediate filament protein called Glial Fibrillary Acidic Protein (GFAP). Changes in the incorporation of 32P into other phosphoproteins after lesion were also studied. Both, the incorporation of 32P and the immunocontent decreased until day 7 post lesion, increased significantly above contrai levels after this interval and remained elevated until 84 days post lesion in relation to the contrai. The state of phosphorylation, that is, the relation between the incorporation of 32P and the immunocontent remained close to 1 after lesion. Vimentin, another cytoskeletal protein of astocytes presented a transient increase in the incorporation of 32P, which also occured with a yet unknown protein, called pp25, that was partially characterized. We can conclude that the state of phosphorylation of GFAP is not significantly alterated and that the main response to lesion is the change in the amount of protein. The transient appearence of glial phosphoproteins like vimentin and pp25 could be a good biochemical marker for gliosis

Thermokarst lake dynamics and its influence on biogeochemical sediment characteristics: A case study from the discontinuous permafrost zone in Interior Alaska

Under the currently projected scenarios of a warming climate, discontinuous and warm permafrost in Interior Alaska is expected to experience dramatic thinning. Thermokarst ponds and lakes give evidence for permafrost thaw and, vice versa, amplify deep thaw by talik development. During the thawing process, previously preserved organic matter is decomposed and potentially released as greenhouse gases carbon dioxide and methane. In the course of lake development and shoreline expansion, both, younger near-surface and older organic matter from slumping shores are potentially deposited in the lake basin. Lake internal bioproductivity is complementing carbon accumulation in lacustrine deposits and provides an additional source of young carbon transformed into greenhouse gases. This study presents results of two intersecting, limnolithological transects of 5 sediment cores from Goldstream Lake, a typical small, boreal thermokarst lake in Interior Alaska. With the aim to distinguish external terrestrial and internal aquatic carbon contributions to sediments, sediment samples are analyzed for the total organic carbon/total nitrogen ratio (C/N) as well as stable carbon isotopes. Selected samples are analyzed for their grain size distribution in order to reconstruct the depositional environment and accumulation conditions. The littoral zone with actively eroding shorelines is characterized by methane bubbles produced from anaerobic microbial decomposition but near-shore sediments have surprisingly low total organic carbon contents of mean 1.5 wt%; the low C/N ratio of 8.7 indicate a dominance of lacustrine plant material. Very similar results are found for sediments in the central basin but a clear shift to a terrestrial carbon signal (C/N of 22) with total organic carbon content of almost 30 wt% is presumably indicating the trash layer of the initial lake phase. The talik sediments seem to have carbon storage as low as the lake sediments but are not as well layered. Subarctic aquatic environments like Goldstream Lake demonstrate a relatively low aquatic productivity and a high biogeochemical turn-over over short periods of time. In addition, the ongoing decomposition of organic matter in talik sediments proves to be crucial to assess the contribution of thermokarst lakes to future climate change by mobilizing Ice Age soil carbon previously frozen in permafrost

Cellular mechanisms triggered by the cotreatment of resveratrol and doxorubicin in breast cancer: A translational in vitro–In silico model

Doxorubicin (Doxo) is the most effective chemotherapeutic agent for the treatment of breast cancer. However, resistance to Doxo is common. Adjuvant compounds capable of modulating mechanisms involved in Doxo resistance may potentiate the effectiveness of the drug. Resveratrol (Rsv) has been tested as an adjuvant in mammary malignancies. However, the cellular and molecular mechanisms underlying the effects of cotreatment with Doxo and Rsv in breast cancer are poorly understood. Here, we combined in vitro and in silico analysis to characterize these mechanisms. In vitro, we employed a clinically relevant experimental design consisting of acute (24 h) treatment followed by 15 days of analysis. Acute Rsv potentiated the long-lasting effect of Doxo through the induction of apoptosis and senescence. Cells that survived to the cotreatment triggered high levels of autophagy. Autophagy inhibition during its peak of activation but not concomitant with Doxo+Rsv increased the long-term toxicity of the cotreatment. To uncover key proteins potentially associated with in vitro effects, an in silico multistep strategy was implemented. Chemical-protein networks were predicted based on constitutive gene expression of MCF7 cells and interatomic data from breast cancer. Topological analysis, KM survival analysis, and a quantitative model based on the connectivity between apoptosis, senescence, and autophagy were performed. We found seven putative genes predicted to be modulated by Rsv in the context of Doxo treatment: CCND1, CDH1, ESR1, HSP90AA1, MAPK3, PTPN11, and RPS6KB1. Six out of these seven genes have been experimentally proven to be modulated by Rsv in cancer cells, with 4 of the 6 genes in MCF7 cells. In conclusion, acute Rsv potentiated the long-term toxicity of Doxo in breast cancer potentially through the modulation of genes and mechanisms involved in Doxo resistance. Rational autophagy inhibition potentiated the effects of Rsv+Doxo, a strategy that should be further tested in animal models

Organic carbon characteristics in yedoma and thermokarst deposits on Baldwin Peninsula, West-Alaska

As Arctic warming continues and permafrost thaws, more soil and sedimentary organic carbon (OC) will be decomposed in northern high latitudes. Still, uncertainties remain in the quantity and quality of OC stored in different deposit types of permafrost landscapes. This study presents OC data from deep permafrost and lake deposits on the Baldwin Peninsula which is located in the southern portion of the continuous permafrost zone in West-Alaska. Sediment samples from yedoma and drained thermokarst lake basin (DTLB) deposits as well as thermokarst lake sediments were analyzed for cryostratigraphical and biogeochemical parameters and their lipid biomarker composition to identify the size and quality of belowground OC pools in ice-rich permafrost on Baldwin Peninsula. We provide the first detailed characterization of yedoma deposits on Baldwin Peninsula. We show that three quarters of soil organic carbon in the frozen deposits of the study region (total of 68 Mt) is stored in DTLB deposits (52 Mt) and one quarter in the frozen yedoma deposits (16 Mt). The lake sediments contain a relatively small OC pool (4 Mt), but have the highest volumetric OC content(93 kg m-3) compared to the DTLB (35 kg m-3) and yedoma deposits (8 kg m-3), largely due to differences in the ground ice content. The biomarker analysis indicates that the OC in both yedoma and DTLB deposits is mainly of terrestrial origin. Nevertheless, the relatively high carbon preference index of plant leaf waxes in combination with a lack of degradation trend with depth in the yedoma deposits indicates that OC stored in yedoma is less degraded than that stored in DTLB deposits. This suggests that OC in yedoma has a higher potential for decomposition upon thaw, despite the relatively small size of this pool. These findings highlight the importance of molecular OC analysis for determining the potential future greenhouse gas emissions from thawing permafrost, especially because this area close to the discontinuous permafrost boundary is projected to thaw substantially within the 21st century

Organic carbon stored in a thermokarst affected landscape on Baldwin Peninsula, Alaska

As Arctic warming continues and permafrost degrades, more organic carbon (OC) will be decomposed in high northern latitudes. Still, uncertainties remain in the quality and quantity of OC stored in permafrost. This study presents OC data from permafrost deposits on the Baldwin Peninsula, West-Alaska. We analyzed cryostratigraphical, biogeochemical and biomarker parameters of yedoma- and drained thermokarst lake basin (DTLB) deposits as well as thermokarst lake sediments to identify the size and quality of OC pools in ice-rich permafrost. Here we show that two thirds of soil OC in this region are stored in frozen DTLB deposits and that the lake sediments have the highest volumetric OC content. The n-alkane distribution shows, however, that OC stored in yedoma is of higher quality than that stored in DTLB deposits. These findings highlight the importance of molecular OC analysis for determining the potential future greenhouse gas emissions from thawing permafrost

Organic carbon in permafrost

With ongoing climate change, the Arctic will continue to warm approximately twice as fast as the lower latitudes. As large parts of the Arctic are affected by permafrost, large-scale degradation processes such as thermokarst and thermal erosion are expected. Ice-rich permafrost, such as yedoma permafrost, covers large areas in Alaska and Siberia. These deposits reach thickness up to 50 m and include large ice-wedges. Therefore, warming can trigger especially rapid and deep thaw processes, which can mobilize organic carbon even well below 1 m soil depth. Undisturbed yedoma deposits are characterized by relatively high quality organic carbon stored and are presumably highly susceptible for future degradation. To improve the estimates of the rate and amount of organic carbon that can be released from permafrost thaw with warming, the quantity and quality of the organic carbon needs to be identified

Comparação da expressão gênica de purinoreceptores e marcadores de angiogênese em modelo de tumor ex vivo e modelo in vitro

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