A basic knowledge about mutation rates is central to our understanding of a myriad of evolutionary phenomena, including the maintenance of sex and rates of molecular evolution. Although there is ...substantial evidence that mutation rates vary among taxa, relatively little is known about the factors that underlie this variation at an empirical level, particularly in multicellular eukaryotes. Here we integrate several disparate lines of theoretical and empirical inquiry into a unified framework to guide future studies that are aimed at understanding why and how mutation rates evolve in multicellular species.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
We evaluate the process by which the Americas were originally colonized and propose a three-stage model that integrates current genetic, archaeological, geological, and paleoecological data. ...Specifically, we analyze mitochondrial and nuclear genetic data by using complementary coalescent models of demographic history and incorporating non-genetic data to enhance the anthropological relevance of the analysis.
Bayesian skyline plots, which provide dynamic representations of population size changes over time, indicate that Amerinds went through two stages of growth approximately 40,000 and approximately 15,000 years ago separated by a long period of population stability. Isolation-with-migration coalescent analyses, which utilize data from sister populations to estimate a divergence date and founder population sizes, suggest an Amerind population expansion starting approximately 15,000 years ago.
These results support a model for the peopling of the New World in which Amerind ancestors diverged from the Asian gene pool prior to 40,000 years ago and experienced a gradual population expansion as they moved into Beringia. After a long period of little change in population size in greater Beringia, Amerinds rapidly expanded into the Americas approximately 15,000 years ago either through an interior ice-free corridor or along the coast. This rapid colonization of the New World was achieved by a founder group with an effective population size of approximately 1,000-5,400 individuals. Our model presents a detailed scenario for the timing and scale of the initial migration to the Americas, substantially refines the estimate of New World founders, and provides a unified theory for testing with future datasets and analytic methods.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The formation of He bubbles in tungsten under exposure to a He plasma was systematically investigated using low energy (∼50eV) He+ ions with a wide fluence range (∼1023 to 1026m−2) in the linear ...divertor plasma simulator PISCES-A at several temperatures (523–973K). TEM observations after thinning exposed W samples with FIB revealed that the layer thickness (>30nm) of He bubbles largely exceeds the ion implantation range of a few nm. The size of He bubbles was found to increase with an increase in the sample temperature: it was around 10nm at 973K, while only small He bubbles of 1–2nm were observed at <773K. In addition, to obtain information on the initial formation behavior, in-situ TEM observations during He ion irradiation were also performed.
Idiopathic REM sleep behavior disorder (RBD) may represent prodromal synucleinopathies. We report markedly reduced cardiac (123)I-metaiodobenzylguanidine uptake, consistent with the loss of ...sympathetic terminals, in idiopathic RBD. We also demonstrate that this reduction is of the same magnitude as that found in patients with Parkinson disease. The results are consistent with the hypothesis that idiopathic RBD in older patients is a forme fruste of Lewy body disease.
Microscopic damage and D retention in tungsten have been investigated for low-energy (∼60–120eV), high flux (∼1022m−2s−1), high fluence (∼5×1025m−2) ion bombardment at moderate temperature ...(∼573–773K) in mixed species D+He plasmas in the linear divertor plasma simulators PISCES-A and B. A significant reduction in D retention and the formation of nanometer-sized He bubbles occur in W due to seeding of He into the D plasma. The volume fraction of He bubbles, estimated with TEM observations and ellipsometric measurements, exceeds the percolation threshold. The desorption mechanism that injected D atoms diffuse back to the surface through the percolating bubbles is suggested. The seeding of Be into D+He mixture plasma eliminates this He effect on the reduction in D retention.
Background
Early diagnosis and subtype classification of basal cell carcinoma (BCC) are crucial to reduce morbidity and optimize treatment. Good accuracy in differentiating BCC from clinical ...imitators has been achieved with existing diagnostic strategies but lower performance in discriminating BCC subtypes. Line‐field confocal optical coherence tomography (LC‐OCT) is a new technology able to combine the technical advantages of reflectance confocal microscopy and OCT.
Objectives
To identify and describe LC‐OCT criteria associated with BCC and explore their association with BCC subtypes.
Methods
Basal cell carcinoma were imaged with a handheld LC‐OCT device before surgical excision. LC‐OCT images were retrospectively evaluated by three observers for presence/absence of criteria for BCC. Multivariate logistic regression models were used to find independent predictors of BCC subtypes.
Results
Eighty‐nine histopathologically proven BCCs were included, of which 66 (74.2%) were pure subtypes superficial BCC (sBCC): 19/66 (28.8%); nodular BCC (nBCC): 31/66 (47.0%); infiltrative BCC (iBCC): 16/66 (24.2%). Lobules, blood vessels and small bright cells within epidermis/lobules were the most frequent criteria for BCC. LC‐OCT criteria independently associated with sBCC were presence of hemispheric lobules, absence of lobule separation from the epidermis, absence of stretching of the stroma; with nBCC were presence of macrolobules, absence of lobule connection to the epidermis; and with iBCC were presence of branched lobules.
Conclusions
This was the first study describing the characteristics of BCC under LC‐OCT examination. We proposed morphologic criteria, which could be potentially useful for diagnosis and subtype classification of BCC, as well as for its therapeutic management. Future studies are needed to assess these hypotheses.
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