Search results for "Step"

Simultaneous Synthesis and Consolidation of Nanostructured MoSi2

2002

A new process combining electric field activation and the imposition of pressure from mechanically activated powder mixtures is demonstrated as a means to simultaneously synthesize and densify nano-MoSi2 in one step. Nanophase reactants (Mo + 2Si) produced by mechanical activation are reacted by field activation with the simultaneous application of a uniaxial pressure. Mo + 2Si powders were comilled in a specially designed planetary mill to obtain nanometric reactants but to avoid formation of any product phases. These were then subjected to high alternating currents (1600 A) and pressures of 106 MPa. Under these conditions, a reaction is initiated and completed within a short period of tim…

Determination of refractive index of submicron-thick films using resonance shift in a four-layer slab waveguide

2017

The measurement of refractive index of very thin films at the order of ten to hundred nanometers is cumbersome and usually requires employing sophisticated techniques such as the spectral ellipsometry. In this paper we describe a simple contact method for measuring the refractive index of thin films. Here we have used the prism-coupling technique for characterizing samples prepared as four-layer slab waveguides. The waveguide resonance condition can be calculated by solving simple analytic transcendental equations for the slab waveguide. Then the captured mode position as a function of cladding thickness is used for probing the refractive index of cladding layer. We used indium-tin-oxide la…

A concise route to MK-4482 (EIDD-2801) from cytidine.

2020

A two-step route to MK-4482 (EIDD-2801, 1) was developed consisting of an esterification and hydroxamination of cytidine. The selective acylation and direct amination eliminate the need for protecting and activating groups and proceed in overall yield of 75%, a significant advancement over the reported yield of 17%. The step count is reduced from five transformations to two, and expensive uridine is replaced with the more available cytidine.

Synthesis of 2-Aminothiazole Derivatives in Easy Two-Step, One-Pot Reaction

2018

Kinetic and Electrochemical Studies of the Oxidative Addition of Demanding Organic Halides to Pd(0): the Efficiency of Polyphosphane Ligands in Low P…

2013

International audience; Oxidative addition (OA) of organic halides to palladium(0) species is a fundamental reaction step which initiates the C–C bond formation catalytic processes typical of Pd(0)/Pd(II) chemistry. The use of structurally congested polyphosphane ligands in palladium-catalyzed C–C bond formation has generated very high turnover numbers (TONs) in topical reactions such as Heck, Suzuki, Sonogashira couplings, and direct sp2C–H functionalization. Herein, the OA of aryl bromides to Pd(0) complexes stabilized by ferrocenylpolyphosphane ligands L1 (tetraphosphane), L2 (triphosphane), and L3 (diphosphane) is considered. The investigation of kinetic constants for the addition of Ph…

Processing and Assessment of Spectrometric, Stereoscopic Imagery Collected Using a Lightweight UAV Spectral Camera for Precision Agriculture

2013

Imaging using lightweight, unmanned airborne vehicles (UAVs) is one of the most rapidly developing fields in remote sensing technology. The new, tunable, Fabry-Perot interferometer-based (FPI) spectral camera, which weighs less than 700 g, makes it possible to collect spectrometric image blocks with stereoscopic overlaps using light-weight UAV platforms. This new technology is highly relevant, because it opens up new possibilities for measuring and monitoring the environment, which is becoming increasingly important for many environmental challenges. Our objectives were to investigate the processing and use of this new type of image data in precision agriculture. We developed the entire pro…

Dissipative analogies of step-pool features: From rills to mountain streams

2019

Abstract In this paper the dissipative similarity of step-pool units at different spatial scales ranging from rills to streams is analyzed. This investigation benefits from the latest theoretical advances in open channel flow resistance, high-resolution topography from close-range photogrammetry applied to rill erosion and the availability of published data from literature on step-pool streams. At first, the integration of a power velocity distribution allowed to obtain a theoretically-based expression of Darcy-Weisbach friction factor, in which Γ function and δ exponent of the velocity profile are included. Then this theoretically-deduced flow resistance relationship is calibrated and test…

Economic performance and risk of farming systems specialized in perennial crops: An analysis of Italian hazelnut production

2019

Abstract Assessing farm profitability and economic risk is important to support farmers' decisions. Several factors affect yields and product prices, in turn influencing farmers' income level and economic risk. However, the literature has often neglected to explicitly account for the role of product quality. This is particularly important for crops such as hazelnut because farmers' prices vary according to the quality of the harvested product. Furthermore, it seems fundamental to disentangle the role of parameters influencing farm results, noticeably yield, product price and quality. This is because farmers select their risk management tools to satisfy their needs, but these are often suita…

Vegetation and climate record from Abric Romaní (Capellades, northeast Iberia) during the Upper Pleistocene (MIS 5d−3)

2019

This study addresses the pollen record of Abric Romani archaeological site and the climate evolution of the last interglacial and glacial stadials in the Iberian Peninsula. The new pollen record spans the interval from 110,000 to 55,000 years ago. In general, the glacial/stadial vegetation is characterized by a steppe and herbaceous communities indicating dry and cold climatic conditions, whereas the vegetation optimum of past interglacials can be described as pine-oaks with mediterranean forest indicating milder and moister climatic conditions. During the first half of the MIS 5a and the MIS 5c, the region was warmer, which is characterized by temperate forests. However, the existence of A…

Images of camels on a mammoth tusk from West Siberia

2020

International audience; This study introduces the engravings on a mammoth tusk from the lower reaches of the Tom River in WestSiberia. The tusk was found in 1988 during construction works and was later transferred to the Tomsk StateUniversity, but it remained almost unknown to specialists until now. Radiocarbon dating by AMS reported theage of the tusk as 13,100–13,005 Сal BP (95% confidence level). The surface of the tusk is engraved with imagesof two-humped camels arranged in two pairs. In addition, arrows and wounds within the contours of the animalscan be seen. The comparative analysis of the stylistic features of the camel figures shows that they correspond tothe age of the tusk itself, …