78 research outputs found
Absolute Paleointensity Study of Miocene Tiva Canyon Tuff, Yucca Mountain, Nevada: Role of FineâParticle GrainâSize Variations
Fineâgrained, Tiâpoor titanomagnetite in the ~12.7 Ma Tiva Canyon (TC) Tuff systematically increases in grain size from superparamagnetic (SP) at the flow base to single domain (SD) at a few meters height. This allows us to examine the role of grainâsize variation on paleointensity, within the transition from SP to stable SD. We present magnetic properties from two previously unreported sections of the TC Tuff, as well as Thellierâtype paleointensity estimates from the lowermost ~7.0 m of the flow. Magnetic hysteresis, frequencyâdependent susceptibility, and thermomagnetic data show that sample grainâsize distribution is dominated by SP in the lower ~3.6 m, transitioning upwards to mostly stable SD. Paleointensity results are closely tied to stratigraphic height and to magnetic properties linked to domain state. SD samples have consistent absolute paleointensity values of 28.5 ± 1.94 ÎŒT (VADM of 51.3 ZAm2) and behaved ideally during paleointensity experiments. The samples including a significant SP fraction have consistently higher paleointensities and less ideal behavior but would likely pass many traditional qualityâcontrol tests. We interpret the SD remanence to be a primary thermal remanent magnetization but discuss the possibility of a partial thermalâchemical remanent magnetization if microcrystal growth continued at T \u3c Tc and/or the section is affected by postâemplacement vaporâphase alteration. The link between paleointensity and domain state is stronger than correlations with water content or other evidence of alteration and suggests that the presence of a significant SP population may adversely impact paleointensity results, even in the presence of a stable SD fraction
Transcriptional Basis of Mouse and Human Dendritic Cell Heterogeneity
Dendritic cells (DCs) play a critical role in orchestrating adaptive immune responses due to their
unique ability to initiate T cell responses and direct
their differentiation into effector lineages. Classical
DCs have been divided into two subsets, cDC1 and
cDC2, based on phenotypic markers and their
distinct abilities to prime CD8 and CD4 T cells. While
the transcriptional regulation of the cDC1 subset has
been well characterized, cDC2 development and
function remain poorly understood. By combining
transcriptional and chromatin analyses with genetic
reporter expression, we identified two principal
cDC2 lineages defined by distinct developmental
pathways and transcriptional regulators, including
T-bet and RORgt, two key transcription factors
known to define innate and adaptive lymphocyte
subsets. These novel cDC2 lineages were characterized by distinct metabolic and functional programs. Extending our findings to humans revealed
conserved DC heterogeneity and the presence of
the newly defined cDC2 subsets in human cancer
Multifractal Spatial Patterns and Diversity in an Ecological Succession
We analyzed the relationship between biodiversity and spatial biomass heterogeneity along an ecological succession developed in the laboratory. Periphyton (attached microalgae) biomass spatial patterns at several successional stages were obtained using digital image analysis and at the same time we estimated the species composition and abundance. We show that the spatial pattern was self-similar and as the community developed in an homogeneous environment the pattern is self-organized. To characterize it we estimated the multifractal spectrum of generalized dimensions Dq. Using Dq we analyze the existence of cycles of heterogeneity during succession and the use of the information dimension D1 as an index of successional stage. We did not find cycles but the values of D1 showed an increasing trend as the succession developed and the biomass was higher. D1 was also negatively correlated with Shannon's diversity. Several studies have found this relationship in different ecosystems but here we prove that the community self-organizes and generates its own spatial heterogeneity influencing diversity. If this is confirmed with more experimental and theoretical evidence D1 could be used as an index, easily calculated from remote sensing data, to detect high or low diversity areas
Inferring ancestral states without assuming neutrality or gradualism using a stable model of continuous character evolution
Preparation and Double Michael Addition Reactions of a Synthetic Equivalent of the Nazarov Reagent
Using the present to interpret the past: the role of ethnographic studies in Andean archaeology
Within Andean research it is common to use ethnographic analogies to aid the interpretation of archaeological remains, and ethnographers and archaeologists have developed shared research in technology, material culture and material practice. Although most of this research does not follow the detailed recording methods of spatial patterning envisioned in earlier formulations of ethnoarchaeology, it has had a profound effect on how archaeology in the region has been interpreted. This paper uses examples from the study of pottery production to address earlier debates about the use of ethnographic analogy, discusses the dangers of imposing an idealised or uniform vision of traditional Andean societies onto earlier periods (âLo Andinoâ) but stresses the benefits of combining ethnographic and archaeological research to explore continuities and changes in cultural practice and regional variations
Controls on explosive-effusive volcanic eruption styles
One of the biggest challenges in volcanic hazard assessment is to understand how and why eruptive style changes within the same eruptive period or even from one eruption to the next at a given volcano. This review evaluates the competing processes that lead to explosive and effusive eruptions of silicic magmas. Eruptive style depends on a set of feedbacks involving interrelated magmatic properties and processes. Foremost of these are magma viscosity, gas loss, and external properties such as conduit geometry. Ultimately, these parameters control the speed at which magmas ascend, decompress and outgas en route to the surface, and thus determine eruptive style and evolution
The effects of care bundles on patient outcomes: a systematic review and meta-analysis
Identification of MYC mutations in acute myeloid leukemias with NUP98âNSD1 translocations
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