3,876 research outputs found
A novel vacuum ultra violet lamp for metastable rare gas experiments
We report on a new design of a vacuum ultra violet (VUV) lamp for direct
optical excitation of high laying atomic states e.g. for excitation of
metastable rare gas atoms. The lamp can be directly mounted to ultra high
vacuum vessels (p <= 10^(-10) mbar). It is driven by a 2.45 GHz microwave
source. For optimum operation it requires powers of approximately 20 W. The VUV
light is transmitted through a magnesium fluoride window, which is known to
have a decreasing transmittance for VUV photons with time. In our special
setup, after a run-time of the VUV lamp of 550 h the detected signal
continuously decreased to 25 % of its initial value. This corresponds to a
lifetime increase of two orders of magnitude compared to previous setups or
commercial lamps
Development and validation of an oligonucleotide microarray to characterise ectomycorrhizal fungal communities
Background: In forest ecosystems, communities of ectomycorrhizal fungi (ECM) are influenced by several biotic and abiotic factors. To understand their underlying dynamics, ECM communities have been surveyed with ribosomal DNA-based sequencing methods. However, most identification methods are both time-consuming and limited by the number of samples that can be treated in a realistic time frame. As a result of ongoing implementation, the array technique has gained throughput capacity in terms of the number of samples and the capacity for parallel identification of several species. Thus far, although phylochips (microarrays that are used to detect species) have been mostly developed to trace bacterial communities or groups of specific fungi, no phylochip has been developed to carry oligonucleotides for several ectomycorrhizal species that belong to different genera. Results: We have constructed a custom ribosomal DNA phylochip to identify ECM fungi. Specific oligonucleotide probes were targeted to the nuclear internal transcribed spacer (ITS) regions from 95 fungal species belonging to 21 ECM fungal genera. The phylochip was first validated using PCR amplicons of reference species. Ninety-nine percent of the tested oligonucleotides generated positive hybridisation signals with their corresponding amplicons. Cross-hybridisation was mainly restricted at the genus level, particularly for Cortinarius and Lactarius species. The phylochip was subsequently tested with environmental samples that were composed of ECM fungal DNA from spruce and beech plantation fungal communities. The results were in concordance with the ITS sequencing of morphotypes and the ITS clone library sequencing results that were obtained using the same PCR products. Conclusion: For the first time, we developed a custom phylochip that is specific for several ectomycorrhizal fungi. To overcome cross-hybridisation problems, specific filter and evaluation strategies that used spot signal intensity were applied. Evaluation of the phylochip by hybridising environmental samples confirmed the possible application of this technology for detecting and monitoring ectomycorrhizal fungi at specific sites in a routine and reproducible manner
A novel vacuum ultra violet lamp for metastable rare gas experiments
We report on a new design of a vacuum ultra violet (VUV) lamp for direct
optical excitation of high laying atomic states e.g. for excitation of
metastable rare gas atoms. The lamp can be directly mounted to ultra high
vacuum vessels (p <= 10^(-10) mbar). It is driven by a 2.45 GHz microwave
source. For optimum operation it requires powers of approximately 20 W. The VUV
light is transmitted through a magnesium fluoride window, which is known to
have a decreasing transmittance for VUV photons with time. In our special
setup, after a run-time of the VUV lamp of 550 h the detected signal
continuously decreased to 25 % of its initial value. This corresponds to a
lifetime increase of two orders of magnitude compared to previous setups or
commercial lamps
Diversity and evolution of ABC proteins in mycorrhiza-forming fungi
Background: Transporter proteins are predicted to have an important role in the mycorrhizal symbiosis, due to the fact that this type of an interaction between plants and fungi requires a continuous nutrient and signalling exchange. ABC transporters are one of the large groups of transporter proteins found both in plants and in fungi. The crucial role of plant ABC transporters in the formation of the mycorrhizal symbiosis has been demonstrated recently. Some of the fungal ABC transporter-encoding genes are also induced during the mycorrhiza formation. However, no experimental evidences of the direct involvement of fungal ABC transporters in this process are available so far. To facilitate the identification of fungal ABC proteins with a potential role in the establishment of the mycorrhizal symbiosis, we have performed an inventory of the ABC protein-encoding genes in the genomes of 25 species of mycorrhiza-forming fungi. Results: We have identified, manually annotated and curated more than 1300 gene models of putative ABC protein-encoding genes. Out of those, more than 1000 models are predicted to encode functional proteins, whereas about 300 models represent gene fragments or putative pseudogenes. We have also performed the phylogenetic analysis of the identified sequences. The sets of ABC proteins in the mycorrhiza-forming species were compared to the related saprotrophic or plant-pathogenic fungal species. Our results demonstrate the high diversity of ABC genes in the genomes of mycorrhiza-forming fungi. Via comparison of transcriptomics data from different species, we have identified candidate groups of ABC transporters that might have a role in the process of the mycorrhiza formation. Conclusions: Results of our inventory will facilitate the identification of fungal transporters with a role in the mycorrhiza formation. We also provide the first data on ABC protein-coding genes for the phylum Glomeromycota and for orders Pezizales, Atheliales, Cantharellales and Sebacinales, contributing to the better knowledge of the diversity of this protein family within the fungal kingdom.Peer reviewe
Recursos, intereses y difusiĂłn de modelos para la polĂtica regional de I+D: la Comunidad de Madrid
Se agradece la financiación de la CICYT a través del Plan Nacional de I+D (SEC1999-0829-C02-01), asà como las facilidades otorgadas por la Dirección general de Investigación de la Comunidad de Madrid, especialmente por Francisco Rubia y Alfonso González Hermoso
Tracking Brownian motion in three dimensions and characterization of individual nanoparticles using a fiber-based high-finesse microcavity
The dynamics of nanosystems in solution contain a wealth of information with
relevance for diverse fields ranging from materials science to biology and
biomedical applications. When nanosystems are marked with fluorophores or
strong scatterers, it is possible to track their position and reveal internal
motion with high spatial and temporal resolution. However, markers can be
toxic, expensive, or change the object's intrinsic properties. Here, we
simultaneously measure dispersive frequency shifts of three transverse modes of
a high-finesse microcavity to obtain the three-dimensional path of unlabeled
SiO nanospheres with s temporal and down to nm
spatial resolution. This allows us to quantitatively determine properties such
as the polarizability, hydrodynamic radius, and effective refractive index. The
fiber-based cavity is integrated in a direct-laser-written microfluidic device
that enables the precise control of the fluid with ultra-small sample volumes.
Our approach enables quantitative nanomaterial characterization and the
analysis of biomolecular motion at high bandwidth.Comment: 7 pages, 3 figure
Using Computer Vision To Label And Search A Physical Space
Effective operation of a warehouse requires keeping track of the location of various assets within the physical environment. As various sensors are carried through the warehouse environment by operators, range data collected by the sensors over time can be used to reconstruct 2D and 3D representations of the space. This disclosure describes techniques to estimate the locations of Point-Of Interest (POIs) and Regions-Of-Interest (ROIs) within a physical environment such as a warehouse. The location estimates are generated using a combination of 2D visual search of images containing text labels and barcodes, 2D/3D environment reconstruction using sensor data, and estimated trajectory of sensors. Computer vision techniques are applied to visual data which is obtained from operational processes that generate images, such as feeds from stationary cameras, images from moving cameras, photos of the environment, etc
Sol–gel encapsulation for power electronics utilizing 3-Glycidyloxypropyltriethoxysilane and 3-Mercaptopropyltrimethoxysilane
3-Glycidyloxypropyltriethoxysilane and 3-Mercaptosilane were used to prepare a composite together with aluminum oxide. The compound is a potential candidate for being used as inorganic encapsulation. FTIR results paired with head-space analysis revealed a hardening of the composite at above 130 °C and degradation of the sol–gel-network above 150 °C. The adhesion of these compounds was tested via shear tests. It showed, that the addition of 3-Mercaptopropyltriethoxysilane enhanced the adhesion on silver significantly. This is attributed to the covalent nature of the Ag-S bond, which is forming as compared to the solely dispersive forces, when 3-Mercaptopropyltriethxysilane is not used. By conducting the shear test under temperature activation energies for the breakages were calculated. These coincide well with the binding energy of Ag-S in case silver surfaces are examined. In the case of a copper surface, a mixture of covalent and dipole–dipole interactions are found, since the activation energy for breakage is smaller as the Cu-O bond energy
Rational dilation problems associated with constrained algebras
It is shown that rational dilation fails on broad collection of distinguished
varieties associated to constrained subalgebras of the disk algebra of the form
C + B A(D), where B is a finite Blaschke product with two or more zeros. This
is accomplished in part by finding a minimal set of test functions. In
addition, an Agler-Pick interpolation theorem is given and it is proved that
there exist Kaijser-Varopoulos style examples of non-contractive unital
representations where the generators are contractions.Comment: Page proof corrections included in this version
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