RESUMO
Photonic wire bonds, i.e., freeform waveguides written by 3D direct laser writing, emerge as a technology to connect different optical chips in fully integrated photonic devices. With the long-term vision of scaling up this technology to a large-scale fabrication process, the in situ optimization of the trajectory of photonic wire bonds is at stake. A prerequisite for the real-time optimization is the availability of a fast loss estimator for single-mode waveguides of arbitrary trajectory. Losses occur because of the bending of the waveguides and at transitions among sections of the waveguide with different curvatures. Here, we present an approach that resides on the fundamental mode approximation, i.e., the assumption that the photonic wire bonds predominantly carry their energy in a single mode. It allows us to predict in a quick and reliable way the pertinent losses from pre-computed modal properties of the waveguide, enabling fast design of optimum paths.
RESUMO
We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (bp)] at a 1° × 1° spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources.
Assuntos
Biodiversidade , Mudança Climática , Modelos Teóricos , Dispersão Vegetal , Europa (Continente) , PólenRESUMO
Fragile X syndrome is associated with silencing of the FMR1 gene. We studied the transcriptional regulation, by analysis of the FMR1 promoter region for the presence of in vivo protein/DNA interactions and for cytosine methylation at the single-nucleotide level. Four protein-binding sites were present in the unmethylated promoter of the active FMR1 gene. In the methylated promoter of inactive genes no footprints were detected, and no evidence of active repression was found in the region investigated. We propose that the silencing of FMR1 gene transcription results from a lack of transcription-factor binding.
Assuntos
Síndrome do Cromossomo X Frágil/genética , Proteínas do Tecido Nervoso/genética , Regiões Promotoras Genéticas , Proteínas de Ligação a RNA , Adulto , Sequência de Bases , Linhagem Celular , DNA/química , DNA/metabolismo , Pegada de DNA , Metilação de DNA , Primers do DNA , Embrião de Mamíferos , Fibroblastos , Proteína do X Frágil da Deficiência Intelectual , Humanos , Masculino , Dados de Sequência Molecular , Proteínas do Tecido Nervoso/biossíntese , Reação em Cadeia da Polimerase , Valores de Referência , Ésteres do Ácido SulfúricoRESUMO
Mesenchymal and epithelial human malignancies were examined in the simultaneous detection test for the presence of particles with 70 S RNA and reverse transcriptase. Out of the 23 tumors tested 14 were found to be positive (61%). The finding that 2 uterine cancers contained 70 S RNA and reverse transcriptase indicates that uterine cancers may belong to the list of malignancies where the involvement of oncornaviruses is suspected. Out of the 10 human sarcomas examined in this study 4 were shown to contain particles with properties of oncornaviruses.
