Search results for "character"

Importance of dispersal and thermal environment for mycorrhizal communities: lessons from Yellowstone National Park

2011

International audience; The relative importance of dispersal and niche restrictions remains a controversial topic in community ecology, especially for microorganisms that are often assumed to be ubiquitous. We investigated the impact of these factors for the community assembly of the root-symbiont arbuscular mycorrhizal fungi (AMF) by sampling roots from geothermal and nonthermal grasslands in Yellowstone National Park (YNP), followed by sequencing and RFLP of AMF ribosomal DNA. With the exception of an apparent generalist RFLP type closely related to Glomus intraradices, a distance-based redundancy analysis indicated that the AMF community composition correlated with soil pH or pH-driven c…

Filters for X-Ray Detectors on Space Missions

2022

Thin filters and gas-tight windows are used in space to protect sensitive X-ray detectors from out-of-band electromagnetic radiation, low-energy particles, and molecular contamination. Though very thin and made of light materials, filters are not fully transparent to X-rays. For this reason, they ultimately define the detector quantum efficiency at low energies. In this chapter, we initially provide a brief overview of filter materials and specific designs adopted on space experiments with main focus on detectors operating at the focal plane of grazing incidence X-ray telescopes. We then provide a series of inputs driving the design and development of filters for high-energy astrophysics sp…

Structural Characterization of Molecular Interface Layers Using Neutron and X-Ray Reflectivity Techniques

1992

Synthetic microstructures used in biological research today include a variety of different systems that serve very diverse purposes and require very different fabrication and characterization techniques. One class of microstructures that is at the boundary between life and materials sciences, and certainly has been associated closer to the latter in the past, is that of molecularly structured planar interface films. In fact, Langmuir-Blodgett (LB) films,1 i.e. molecularly layered films comprised of amphiphatic organic molecules on solid substrates, have been used for many years as model systems for the investigation of molecular interactions between chromophores or donor/ acceptor couples, …

Large 256-Pixel X-ray Transition-Edge Sensor Arrays With Mo/TiW/Cu Trilayers

2015

We describe the fabrication and electrical characterization of 256-pixel X-ray transition-edge sensor (TES) arrays intended for materials analysis applications. The processing is done on 6-in wafers, providing capabilities on a commercial scale. TES films were novel proximity coupled Mo/TiW/Cu trilayers, where the thin TiW layer in between aims to improve the stability of the devices by preventing unwanted effects such as Mo/Cu interdiffusion. The absorber elements were electrodeposited gold of thickness 2 μm. The single-pixel design discussed here is the so-called Corbino geometry. Most design goals were successfully met, such as the critical temperature, thermal time constant, and transit…

Characterization of prehispanic cosmetics found in a burial of the ancient city of Teotihuacan (Mexico)

2012

The present paper reports the chemical data obtained on samples of pigmenting materials contained in 31 miniature vessels found in a burial found in Teopancazco, a multiethnic neighborhood center located in the southeastern sector of the archaeological site of Teotihuacan (Central Mexico) and the analytical protocol established for the complete characterization of these archaeological materials. For this purpose a multi-technique approach based on the combination of several non destructive and micro-destructive instrumental techniques, namely, light microscopy (LM), scanning electron microscopy-X-ray micro-analysis (SEMe EDX), transmission electron microscopy (TEM), voltammetry of micropart…

Integrated methodologies for qualitative and quantitative characterization of historical pigments

2014

A structural comparison of halloysite nanotubes of different origin by Small-Angle Neutron Scattering (SANS) and Electric Birefringence

2018

The structure of halloysite nanotubes (Hal) from different mines was investigated by Small-Angle Neutron Scattering (SANS) and Electric Birefringence (EBR) experiments. The analysis of the SANS curves allowed us to correlate the sizes and polydispersity and the specific surfaces (obtained by a Porod analysis of the SANS data) of the nanotubes with their specific geological setting. Contrast matching measurements were performed on patch Hal (from Western Australia) in order to determine their experimental scattering length density for a more precise analysis. Further characterization of the mesoscopic structure of Hal was carried out by Electric Birefringence (EBR), which allowed to study th…

Mechanical characterization of TiO2 nanofibers produced by different electrospinning techniques

2015

Abstract In this work TiO2 nanofibers produced by needle and needleless electrospinning processes from the same precursor were characterized and compared using Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and in situ SEM nanomechanical testing. Phase composition, morphology, Young's modulus and bending strength values were found. Weibull statistics was used to evaluate and compare uniformity of mechanical properties of nanofibers produced by two different methods. It is shown that both methods yield nanofibers with very similar properties.

Morphological and agronomical characterisation of Sicilian bottle gourd Lagenaria siceraria (Mol.) Standley

2014

Local plant populations represent a valuable source of genetic variability. Lagenaria siceraria [Mol.] Standl. is a monoecious species of Cucurbitaceae grown in India and parts of the Mediterranean for its immature fruit and young leaves used as vegetables. The species is a high-value crop in Sicily where several landraces are grown in open field and in plastic greenhouse. The aim of this study was to characterise five Sicilian L. siceraria landraces (G1-G5), from a morphological and agronomical point of view. Genetic resource characterisation was carried out as a foundation for future conservation and breeding works. Fourteen qualitative and quantitative characters were assessed by using t…

Application of WGM Resonances to the Measurement of the Temperature Increment of Ho and Ho-Yb Doped Optical Fibers Pumped at 1125 and 975 nm

2021

Optical fiber characterization using whispering gallery mode resonances of the fiber itself has been demonstrated to be a powerful technique. In this work, we exploit the thermal sensitivity of whispering gallery mode resonances to characterize the pump-induced temperature increment in holmium doped and holmium-ytterbium codoped optical fibers. The technique relies on the measurement of the resonances’ wavelength shift due to temperature variation as a function of the pump power. Holmium doped fibers were pumped to the second excited level 5I6 of the Ho3+ ion using a laser diode at 1125 nm and ytterbium-holmium codoped fibers to the 2F5/2 level of the Yb3+ ion by a laser diode at 975 nm. Ou…