Two new Geoplaninae species (Platyhelminthes: Continenticola) from Southern Brazil based on an integrative taxonomic approach

The genera Cratera Carbayo et al., 2013 and Obama Carbayo et al., 2013, belonging to the subfamily Geoplaninae, were recently proposed to encompass some of the species that belonged to the genus Geoplana Stimpson, 1857. Herein we describe two new species of Geoplaninae, occurring in areas of ombrophilous forest which belong to the southern portion of the Brazilian Atlantic Rain Forest. The species are sympatric in their type-locality. In general, both new species herein described match the diagnostic characteristics of their genera. However, some of these features are noteworthy when characters of the new species are taken into consideration, especially the pattern of the sensory pits and the morphology of the prostatic vesicle. Both species are differentiated from their congeners by a combination of morphological characteristics, corroborated by phylogenetic analyses of the cytochrome c oxidase subunit I gene, using maximum likelihood and Bayesian inference, as well as the Automatic Barcode Gap tool.     

Understanding,explanation, and unification

In this article I argue that there are two different types of understanding: the understanding we get from explanations, and the understanding we get from unification. This claim is defended by first showing that explanation and unification are not as closely related as has sometimes been thought. A critical appraisal of recent proposals for understanding without explanation leads us to discuss the example of a purely classificatory biology: it turns out that such a science can give us understanding of the world through unification of the phenomena, even though it does not give us any explanations. The two types of understanding identified in this paper, while strictly separate, do have in common that both consist in seeing how the individual phenomena of the universe hang together. Explanations give us connections between the phenomena through the asymmetric, ‘vertical’ relation of determination; unifications give us connections through the symmetric, ‘horizontal’ relation of kinship. We then arrive at a general definition of understanding as knowledge of connections between the phenomena, and indicate that there might be more than two types of understanding.     

Membrane-shed vesicles from the parasite <Emphasis Type="Italic">Trichomonas vaginalis</Emphasis>: characterization and their association with cell interaction

Trichomonas vaginalis is a common sexually transmitted parasite that colonizes the human urogenital tract, where it remains extracellular and adheres to epithelial cells. Infections range from asymptomatic to highly inflammatory, depending on the host and the parasite strain. Despite the serious consequences associated with trichomoniasis disease, little is known about parasite or host factors involved in attachment of the parasite-to-host epithelial cells. Here, we report the identification of microvesicle-like structures (MVs) released by T. vaginalis. MVs are considered universal transport vehicles for intercellular communication as they can incorporate peptides, proteins, lipids, miRNA, and mRNA, all of which can be transferred to target cells through receptor–ligand interactions, fusion with the cell membrane, and delivery of a functional cargo to the cytoplasm of the target cell. In the present study, we demonstrated that T. vaginalis release MVs from the plasma and the flagellar membranes of the parasite. We performed proteomic profiling of these structures demonstrating that they possess physical characteristics similar to mammalian extracellular vesicles and might be selectively charged with specific protein content. In addition, we demonstrated that viable T. vaginalis parasites release large vesicles (LVs), membrane structures larger than 1 µm that are able to interact with other parasites and with the host cell. Finally, we show that both populations of vesicles present on the surface of T vaginalis are induced in the presence of host cells, consistent with a role in modulating cell interactions.     

SNP and haplotype mapping for genetic analysis in the rat

The laboratory rat is one of the most extensively studied model organisms. Inbred laboratory rat strains originated from limited Rattus norvegicus founder populations, and the inherited genetic variation provides an excellent resource for the correlation of genotype to phenotype. Here, we report a survey of genetic variation based on almost 3 million newly identified SNPs. We obtained accurate and complete genotypes for a subset of 20,238 SNPs across 167 distinct inbred rat strains, two rat recombinant inbred panels and an F2 intercross. Using 81% of these SNPs, we constructed high-density genetic maps, creating a large dataset of fully characterized SNPs for disease gene mapping. Our data characterize the population structure and illustrate the degree of linkage disequilibrium. We provide a detailed SNP map and demonstrate its utility for mapping of quantitative trait loci. This community resource is openly available and augments the genetic tools for this workhorse of physiological studies.     

固体的电子结构和磁光性质

本书是一本关于固体化合物和多层材料的电子结构、光学、磁光学、X射线磁圆二向色性等的理论研究的新著作。     

Single-exciton optical gain in semiconductor nanocrystals

Nanocrystal quantum dots have favourable light-emitting properties. They show photoluminescence with high quantum yields, and their emission colours depend on the nanocrystal size--owing to the quantum-confinement effect--and are therefore tunable. However, nanocrystals are difficult to use in optical amplification and lasing. Because of an almost exact balance between absorption and stimulated emission in nanoparticles excited with single electron-hole pairs (excitons), optical gain can only occur in nanocrystals that contain at least two excitons. A complication associated with this multiexcitonic nature of light amplification is fast optical-gain decay induced by non-radiative Auger recombination, a process in which one exciton recombines by transferring its energy to another. Here we demonstrate a practical approach for obtaining optical gain in the single-exciton regime that eliminates the problem of Auger decay. Specifically, we develop core/shell hetero-nanocrystals engineered in such a way as to spatially separate electrons and holes between the core and the shell (type-II heterostructures). The resulting imbalance between negative and positive charges produces a strong local electric field, which induces a giant ( approximately 100 meV or greater) transient Stark shift of the absorption spectrum with respect to the luminescence line of singly excited nanocrystals. This effect breaks the exact balance between absorption and stimulated emission, and allows us to demonstrate optical amplification due to single excitons.