46 research outputs found
On the Singularity Structure and Stability of Plane Waves
We describe various aspects of plane wave backgrounds. In particular, we make
explicit a simple criterion for singularity by establishing a relation between
Brinkmann metric entries and diffeomorphism-invariant curvature information. We
also address the stability of plane wave backgrounds by analyzing the
fluctuations of generic scalar modes. We focus our attention on cases where
after fixing the light-cone gauge the resulting world sheet fields appear to
have negative "mass terms". We nevertheless argue that these backgrounds may be
stable.Comment: 21 pages, 1 figur
Single-cell, whole-embryo phenotyping of mammalian developmental disorders
Mouse models are a critical tool for studying human diseases, particularly developmental disorders. However, conventional approaches for phenotyping may fail to detect subtle defects throughout the developing mouse. Here we set out to establish single-cell RNA sequencing of the whole embryo as a scalable platform for the systematic phenotyping of mouse genetic models. We applied combinatorial indexing-based single-cell RNA sequencing to profile 101 embryos of 22 mutant and 4 wild-type genotypes at embryonic day 13.5, altogether profiling more than 1.6 million nuclei. The 22 mutants represent a range of anticipated phenotypic severities, from established multisystem disorders to deletions of individual regulatory regions. We developed and applied several analytical frameworks for detecting differences in composition and/or gene expression across 52 cell types or trajectories. Some mutants exhibit changes in dozens of trajectories whereas others exhibit changes in only a few cell types. We also identify differences between widely used wild-type strains, compare phenotyping of gain- versus loss-of-function mutants and characterize deletions of topological associating domain boundaries. Notably, some changes are shared among mutants, suggesting that developmental pleiotropy might be 'decomposable' through further scaling of this approach. Overall, our findings show how single-cell profiling of whole embryos can enable the systematic molecular and cellular phenotypic characterization of mouse mutants with unprecedented breadth and resolution
Freshwater mussels from South America: state of the art of Unionida, specially Rhipidodontini
Níveis críticos de fósforo para o estabelecimento de gramíneas forrageiras em Latossolo Vermelho Amarelo, álico: II. Experimento de campo
The need for economic and pre-economic marketing controlling
The splitting or rather the widening of a marketing controlling system into economic and pre-economic control of performance makes effective strategic forward-looking planning, management, and control of marketing activities possible. The main reason for including pre-economic measures of performance is the possibility to receive and assimilate so-called weak signals from the market which cannot be received by traditional economic controlling systems. These early warning indicators prevent marketing management from decision making based on past-oriented data, the use of which would require the structure of the environment to remain unchanged. Based on this expanded knowledge, marketing strategies can be generated in a much more sound way