959 resultados para Motoneuron Pools
Resumo:
The origin of three Red Sea submarine brine pools was investigated by analysis of the S and O isotope ratios of dissolved sulfate and Sr isotope ratios of dissolved Sr in the brines. Sulfur and O isotope ratios of sulfate and Sr isotope ratios of evaporitic source rocks for the brines were measured for comparison. The S, O and Sr isotope ratios of evaporites recovered from DSDP site 227 are consistent with an upper Miocene evaporites age. The Valdivia Deep brine formed by karstic dissolution of Miocene evaporites by overlying seawater and shows no signs of hydrothermal input. The Suakin Deep brines are derived from, or have isotopically exchanged with Miocene or older evaporites. There has been only minor dilution of the brine by overlying seawater. Strontium isotope ratios of Suakin brine may indicate addition of a minor (15%) amount of volcanic Sr to the brine, but there is no evidence of high temperature brine-rock interaction. The sulfate in the Atlantis II brine was apparently derived from seawater. The O isotope ratio of sulfate in the present Atlantis II brine could reflect isotopic exchange between seawater sulfate and the brine at approximately 255°C. Approximately 30% of the Sr in the Atlantis II brine is derived from the underlying basalt, probably by hydrothermal leaching. Atlantis II brine is the only known example from the Red Sea which has a significant high-temperature hydrothermal history.
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In 2001, a weather and climate monitoring network was established along the temperature and aridity gradient between the sub-humid Moroccan High Atlas Mountains and the former end lake of the Middle Drâa in a pre-Saharan environment. The highest Automated Weather Stations (AWS) was installed just below the M'Goun summit at 3850 m, the lowest station Lac Iriki was at 450 m. This network of 13 AWS stations was funded and maintained by the German IMPETUS (BMBF Grant 01LW06001A, North Rhine-Westphalia Grant 313-21200200) project and since 2011 five stations were further maintained by the GERMAN DFG Fennec project (FI 786/3-1), this way some stations of the AWS network provided data for almost 12 years from 2001-2012. Standard meteorological variables such as temperature, humidity, and wind were measured at an altitude of 2 m above ground. Other meteorological variables comprise precipitation, station pressure, solar irradiance, soil temperature at different depths and for high mountain station snow water equivalent. The stations produced data summaries for 5-minute-precipitation-data, 10- or 15-minute-data and a daily summary of all other variables. This network is a unique resource of multi-year weather data in the remote semi-arid to arid mountain region of the Saharan flank of the Atlas Mountains. The network is described in Schulz et al. (2010) and its further continuation until 2012 is briefly discussed in Redl et al. (2015, doi:10.1175/MWR-D-15-0223.1) and Redl et al. (2016, doi:10.1002/2015JD024443).
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In the shallow continental shelf in Northeastern Rio Grande do Norte - Brazil, important underwater geomorphological features can be found 6km from the coastline. They are coral reefs, locally known as “parrachos”. The present study aims to characterize and analyze the geomorphological feature as well as the ones of the benthic surface, and the distribution of biogenic sediments found in parrachos at Rio do Fogo and associated shallow platforms, by using remote sensing products and in situ data collections. This was made possible due to sedimentological, bathymetric and geomorphological maps elaborated from composite bands of images from the satellite sensors ETM+/Landsat-7, OLI/Landsat-8, MS/GeoEye and PAN/WordView-1, and analysis of bottom sediments samples. These maps were analyzed, integrally interpreted and validated in fieldwork, thus permitting the generation of a new geomorphological zoning of the shallow shelf in study and a geoenvironmental map of the Parrachos in Rio do Fogo. The images used were subject to Digital Image Processing techniques. All obtained data and information were stored in a Geographic Information System (GIS) and can become available to the scientific community. This shallow platform has a carbonate bottom composed mostly by algae. Collected and analyzed sediment samples can be classified as biogenic carbonatic sands, as they are composed 75% by calcareous algae, according to the found samples. The most abundant classes are green algae, red algae, nonbiogenic sediments (mineral grains), ancient algae and molluscs. At the parrachos the following was mapped: Barreta Channel, intertidal reefs, submerged reefs, the spur and grooves, the pools, the sandy bank, the bank of algae, sea grass, submerged roads and Rio do Fogo Channel. This work presents new information about geomorphology and evolution in the study area, and will be guiding future decision making in the handling and environmental management of the region
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Intestinal Mucositis is inflammation and/or ulceration of mucosa of the gastrointestinal tract caused by anticancer therapies. Histologically, villous atrophy, damage to enterocytes and infiltration of inflammatory cells. Methotrexate (MTX) is a compound that depletes dihydrofolate pools and is widely used in the treatment of leukemia and other malignancies. The aim of this study was to evaluate the effect of Olmesartan (OLM), an angiotensin II receptor antagonist, on an Intestinal Mucositis Model (IMM) induced by MTX in Wistar rats. IMM was induced via intraperitoneal (i.p.) administration of MTX (7 mg/kg) for three consecutive days. The animals were pretreated with oral OLM at 0.5, 1 or 5 mg/kg or with vehicle 30 min prior to exposure to MTX, for three days. Small intestinal (duodenum, jejunum and ileum) homogenates were assayed for levels of the IL-1β, IL-10 and TNF-α cytokines, malondialdehyde and myeloperoxidase activity. Additionally, immunohistochemical analyses of MMP-2, MMP-9, COX-2, RANK/RANKL and SOCS-1 and confocal microscopy analysis of SOCS-1 expression were performed. Treatment with MTX+OLM (5 mg/kg) resulted in a reduction of mucosal inflammatory infiltration, ulcerations, vasodilatation and hemorrhagic areas (p<0.05) as well as reduced concentrations of MPO (p<0.001) and the pro-inflammatory cytokines IL-1β and TNF-α (p<0.01), and increase antiinflammatory cytosine IL-10 (p,0.05). Additionally, the combined treatment reduced expression of MMP-2, MMP-9, COX-2, RANK and RANKL (p<0.05) and increased cytoplasmic expression of SOCS-1 (p<0.05). Our findings confirm the involvement of OLM in reducing the inflammatory response through increased immunosuppressive signaling in an IMM. We also suggest that the beneficial effect of Olmesartan treatment is specifically exerted during the damage through blocking inflammatory cytosines.
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A circumpolar representative and consistent wetland map is required for a range of applications ranging from upscaling of carbon fluxes and pools to climate modelling and wildlife habitat assessment. Currently available data sets lack sufficient accuracy and/or thematic detail in many regions of the Arctic. Synthetic aperture radar (SAR) data from satellites have already been shown to be suitable for wetland mapping. Envisat Advanced SAR (ASAR) provides global medium-resolution data which are examined with particular focus on spatial wetness patterns in this study. It was found that winter minimum backscatter values as well as their differences to summer minimum values reflect vegetation physiognomy units of certain wetness regimes. Low winter backscatter values are mostly found in areas vegetated by plant communities typically for wet regions in the tundra biome, due to low roughness and low volume scattering caused by the predominant vegetation. Summer to winter difference backscatter values, which in contrast to the winter values depend almost solely on soil moisture content, show expected higher values for wet regions. While the approach using difference values would seem more reasonable in order to delineate wetness patterns considering its direct link to soil moisture, it was found that a classification of winter minimum backscatter values is more applicable in tundra regions due to its better separability into wetness classes. Previous approaches for wetland detection have investigated the impact of liquid water in the soil on backscatter conditions. In this study the absence of liquid water is utilized. Owing to a lack of comparable regional to circumpolar data with respect to thematic detail, a potential wetland map cannot directly be validated; however, one might claim the validity of such a product by comparison with vegetation maps, which hold some information on the wetness status of certain classes. It was shown that the Envisat ASAR-derived classes are related to wetland classes of conventional vegetation maps, indicating its applicability; 30% of the land area north of the treeline was identified as wetland while conventional maps recorded 1-7%.
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In recent years, temporal fluctuations in the abundance of C. d. davisiana have been used frequently as a highresolution stratigraphic and paleoenvironmental tool. The modern ecology and morphologic variation (temporal and geographic) of this radiolarian species is evaluated to ascertain its potential stratigraphic and paleoenvironmental significance. Statistics were obtained on the width and height of all C. d. davisiana segments from Pleistocene populations of differing ages from the Northern Hemisphere (Labrador Sea and Iceland-Faeroe Ridge) and Southern Hemisphere (Namibian shelf and Meteor Rise). Results reveal that segment height variations between and within populations are more conservative than segment width. The mean sizes of the thorax and first abdominal segment have distinguishable differences between C. d. davisiana found in the North and South Atlantic. All populations have no significant difference in first abdominal segment width, however, mean heights of this segment differ greatly between populations of the North and South Atlantic. Second abdominal segment sizes show no clear population grouping. Size differences in post-cephalic segment size of these populations would appear to be related to some isolation of gene pools and possibly unknown paleoenvironmental factors. Temporal changes in the postcephalic size of C. d. davisiana may be used to: (1) identify temporally equivalent peaks in abundance of the species in a given region, (2) possibly evaluate the degree of mixing of water'masses between regions, and (3) trace the initial spread of the species from its area of origin. Cleve's 1887 plankton samples, between Greenland and Spitzsbergen, were studied and used in conjunction with other data to make the following conclusions on the modern ecology of C. d. davisiana in the Arctic and Greenland-Norwegian Seas. (1) It is presently absent in surface water plankton samples, (2) it currently lives at depths below 500 m, where it is rare, (3) it does not live in the upper 200 m under Arctic ice but is rare at greater depths, (4) it is absent in the upper 200 m near permanent Greenland Sea ice where normal oceanic salinity prevails, and (5) it is most common in deep marginal fjord environments which may serve as a refuge for the species during interglacial periods. In the Atlantic Ocean, the abundance of C. d. davisiana does not exceed 1% of the assemblage between the Subtropical Convergence of each hemisphere. In the Norwegian and Labrador Seas the species may occasionally be in the range of 1-5% of the modern radiolarian assemblage and never more than 5% in the southern high latitudes. Apparently only in the modern Sea of Okhotsk, does the species presently occur in high abundance. We concur with Morley and Hays (1983) that increased abundances are likely caused by the development of a strong low-salinity surface layer associated with seasonal sea ice melting and a strong temperature minimum above warmer and higher salinity intermediate waters. Similar conditions were frequent during the Pleistocene in the high latitudes and its modern scarcity outside the Sea of Okhotsk must be related to the absence of the presently unique conditions in the latter region.
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A new approach for the estimation of soil organic carbon (SOC) pools north of the tree line has been developed based on synthetic aperture radar (SAR; ENVISAT Advanced SAR Global Monitoring mode) data. SOC values are directly determined from backscatter values instead of upscaling using land cover or soil classes. The multi-mode capability of SAR allows application across scales. It can be shown that measurements in C band under frozen conditions represent vegetation and surface structure properties which relate to soil properties, specifically SOC. It is estimated that at least 29 Pg C is stored in the upper 30 cm of soils north of the tree line. This is approximately 25 % less than stocks derived from the soil-map-based Northern Circumpolar Soil Carbon Database (NCSCD). The total stored carbon is underestimated since the established empirical relationship is not valid for peatlands or strongly cryoturbated soils. The approach does, however, provide the first spatially consistent account of soil organic carbon across the Arctic. Furthermore, it could be shown that values obtained from 1 km resolution SAR correspond to accounts based on a high spatial resolution (2 m) land cover map over a study area of about 7 × 7 km in NE Siberia. The approach can be also potentially transferred to medium-resolution C-band SAR data such as ENVISAT ASAR Wide Swath with ~120 m resolution but it is in general limited to regions without woody vegetation. Global Monitoring-mode-derived SOC increases with unfrozen period length. This indicates the importance of this parameter for modelling of the spatial distribution of soil organic carbon storage.
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Background: Recent morpho-functional evidences pointed out that abnormalities in the thalamus could play a major role in the expression of migraine neurophysiological and clinical correlates. Whether this phenomenon is primary or secondary to its functional disconnection from the brain stem remains to be determined.Aim: We used a Functional Source Separation algorithmof EEG signal to extract the activity of the different neuronal pools recruited at different latencies along the somatosensory pathway in interictal migraine without aura(MO) patients. Method: Twenty MO patients and 20 healthy volunteers(HV) underwent EEG recording. Four ad-hoc functional constraints, two sub-cortical (FS14 at brain stem andFS16 at thalamic level) and two cortical (FS20 radial andFS22 tangential parietal sources), were used to extract the activity of successive stages of somatosensory information processing in response to the separate left and right median nerve electric stimulation. A band-pass digital filter (450–750 Hz) was applied offline in order to extract high-frequency oscillatory (HFO) activity from the broadband EEG signal. Results: In both stimulated sides, significant reduced subcortical brain stem (FS14) and thalamic (FS16) HFO activations characterized MO patients when compared with HV. No difference emerged in the two cortical HFO activations between two groups. Conclusion: Present results are the first neurophysiological evidence supporting the hypothesis that a functional disconnection of the thalamus from the subcortical monoaminergicsystem may underline the interictal cortical abnormal information processing in migraine. Further studiesare needed to investigate the precise directional connectivity across the entire primary subcortical and cortical somatosensory pathway in interictal MO.
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The gasotransmitter hydrogen sulfide (H2S) is known as an important regulator in several physiological and pathological responses. Among the challenges facing the field is the accurate and reliable measurement of hydrogen sulfide bioavailability. We have reported an approach to discretely measure sulfide and sulfide pools using the monobromobimane (MBB) method coupled with reversed phase high-performance liquid chromatography (RP-HPLC). The method involves the derivatization of sulfide with excess MBB under precise reaction conditions at room temperature to form sulfide dibimane (SDB). The resultant fluorescent SDB is analyzed by RP-HPLC using fluorescence detection with the limit of detection for SDB (2 nM). Care must be taken to avoid conditions that may confound H2S measurement with this method. Overall, RP-HPLC with fluorescence detection of SDB is a useful and powerful tool to measure biological sulfide levels.
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This manuscript is comprised of three papers that examine the far-reaching and often invisible political outcomes of gender role socialization in the United States. These papers focus primarily on two areas: political confidence amongst girls and women, and the effects of gender on survey measurement and data quality.
Chapter one focuses on political confidence, and the likelihood that women will run for political office. Women continue to be underrepresented at all levels of political leadership, and their lack of political ambition, relative to men, has been identified as a primary cause. In this paper, I explore the relationship between an individual's masculinity and femininity and her development of political ambition. Using original survey data from the 2012 Cooperative Congressional Election Study (CCES), I first empirically demonstrate that gender (masculinity/femininity) and sex (male/female) are unique elements of identity and, moreover, are both independently related to political ambition. I then explore the relevance of gender for the study of candidate emergence, testing whether and how masculinity and femininity might be related to political ambition are supported empirically. While the results suggest that masculinity is positively associated with the development of political ambition, the relationship between femininity and candidate emergence seems to be more complicated and not what prevailing stereotypes might lead us to expect. Moreover, while the relationship between masculinity and political ambition is the same for men and women, the relationship between femininity and political ambition is very different for women than it is for men. This study suggests that gender role socialization is highly related with both men's and women's desire to seek positions of political leadership.
Chapter two continues this exploration of gendered differences in the development of political ambition, this time exploring how social attractiveness and gendered perceptions of political leadership impact the desire to hold political office.Women are persistently underrepresented as candidates for public office and remain underrepresented at all levels of government in the United States. Previous literature suggests that the gendered ambition gap, gender socialization, insufficient recruitment, media scrutiny, family responsibilities, modern campaign strategies, and political opportunity structures all contribute to the gender imbalance in pools of officeholders and candidates. To explain women's reticence to run, scholars have offered explanations addressing structural, institutional, and individual-level factors that deter women from becoming candidates, especially for high positions in the U.S. government. This paper examines a previously unexplored factor: how dating and socialized norms of sexual attraction affect political ambition. This study investigates whether young, single, and heterosexual women's desire for male attention and fear of being perceived as unattractive or "too ambitious" present obstacles to running for office. The results of these experiments suggest that social expectations about gender, attraction and sexuality, and political office-holding may contribute to women's reticence to pursue political leadership. Chapter two is a co-authored work and represents the joint efforts of Laura Lazarus Frankel, Shauna Shames, and Nadia Farjood.
Chapter 3 bridges survey methodology and gender socialization, focusing on how interviewer sex affects survey measurement and data quality. Specifically, this paper examines whether and how matching interviewer and respondent sex affects panel attrition--respondents dropping out of the study after participating in the first wave. While the majority of research on interviewer effects suggests that matching interviewer and respondent characteristics (homophily) yields higher quality data, little work has examined whether this pattern holds true in the area of panel attrition. Using paradata from the General Social Survey (GSS), I explore this question. My analysis reveals that, despite its broader positive effects on data quality, matching interviewer and respondent sex increases likelihood to attrit. Interestingly, this phenomenon only emerges amongst male respondents. However, while assigning female interviewers to male respondents decreases their propensity to attrit, it also increases the likelihood of biased responses on gender related items. These conflicting outcomes represent a tradeoff for scholars and survey researchers, requiring careful consideration of mode, content, and study goals when designing surveys and/or analyzing survey data. The implications of these patterns and areas for further research are discussed.
Together, these papers illustrate two ways that gender norms are related to political outcomes: they contribute to patterns of candidate emergence and affect the measurement of political attitudes and behaviors.
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Species invasions are more prevalent than ever before. While the addition of a species can dramatically change critical ecosystem processes, factors that mediate the direction and magnitude of those impacts have received less attention. A better understanding of the factors that mediate invasion impacts on ecosystem functioning is needed in order to target which exotic species will be most harmful and which systems are most vulnerable. The role of invasion on nitrogen (N) cycling is particularly important since N cycling controls ecosystem services that provision human health, e.g. nutrient retention and water quality.
We conducted a meta-analysis and in-depth studies focused on the invasive grass species, Microstegium vimineum, to better understand how (i) plant characteristics, (ii) invader abundance and neighbor identity, and (iii) environmental conditions mediate the impacts of invasion on N pools and fluxes. The results of our global meta-analysis support the concept that invasive species and reference community traits such as leaf %N and leaf C:N are useful for understanding invasion impacts on soil N cycling, but that trait dissimilarities between invaded and reference communities are most informative. Regarding the in-depth studies of Microstegium, we did not find evidence to suggest that invasion increases net nitrification as other studies have shown. Instead, we found that an interaction between its abundance and the neighboring plant identify were important for determining soil nitrate concentrations and net nitrification rates in the greenhouse. In field, we found that variability in environmental conditions mediated the impact of Microstegium invasion on soil N pools and fluxes, primarily net ammonification, between sites through direct, indirect, and interactive pathways. Notably, we detected a scenario in which forest openness has a negative direct effect and indirect positive effect on ammonification in sites with high soil moisture and organic matter. Collectively, our findings suggest that dissimilarity in plant community traits, neighbor identity, and environmental conditions can be important drivers of invasion impacts on ecosystem N cycling and should be considered when evaluating the ecosystem impacts of invasive species across heterogeneous landscapes.