Search results for "Libration"
showing 10 items of 901 documents
Cubic smoothing splines background correction in on-line liquid chromatography–Fourier transform infrared spectrometry
2010
A background correction method for the on-line coupling of gradient liquid chromatography and Fourier transform infrared spectrometry (LC-FTIR) is proposed. The developed approach applies univariate background correction to each variable (i.e. each wave number) individually. Spectra measured in the region before and after each peak cluster are used as knots to model the variation of the eluent absorption intensity with time using cubic smoothing splines (CSS) functions. The new approach has been successfully tested on simulated as well as on real data sets obtained from injections of standard mixtures of polyethylene glycols with four different molecular weights in methanol:water, 2-propano…
A method for the surface reflectance retrieval from PROBA/CHRIS data over land: application to ESA SPARC campaigns
2005
The Compact High Resolution Imaging Spectrometer (CHRIS) onboard the Project for On-Board Autonomy (PROBA) platform system provides the first high spatial resolution hyper-spectral/multiangular remote sensing data from a satellite system, what represents a new source of information for Earth Observation purposes. A fully consistent radiative transfer approach is always preferred when dealing with the retrieval of surface reflectance from hyperspectral/multiangular data. However, due to the reported calibration anomalies for CHRIS data, a direct atmospheric correction based on physical radiative transfer modeling is not possible, and the method must somehow compensate for such calibration pr…
Ferromagnetic gyroscopes for tests of fundamental physics
2020
A ferromagnetic gyroscope (FG) is a ferromagnet whose angular momentum is dominated by electron spin polarization and that will precess under the action of an external torque, such as that due to a magnetic field. Here we model and analyze FG dynamics and sensitivity, focusing on practical schemes for experimental realization. In the case of a freely floating FG, we model the transition from dynamics dominated by libration in relatively high externally applied magnetic fields, to those dominated by precession at relatively low applied fields. Measurement of the libration frequency enables in situ measurement of the magnetic field and a technique to reduce the field below the threshold for w…
Characterization and determination of poly(vinylpyrrolidone) by complexation with an anionic azo-dye and nonequilibrium capillary electrophoresis
2009
Using capillary zone electrophoresis in nonequilibrium conditions, the complexes of poly(vinylpyrrolidone) (PVP) with anionic azo-dyes dissociate following a first-order kinetics. Two peaks due to the remaining PVP-dye complexes and the equilibrium concentration of the free dye, plus an exponential region due to the dye liberated by the complexes during the electrophoretic run, are obtained. This behaviour was closely similar to that described in the literature for protein-probe and DNA-protein mixtures, upon application of the technique known as nonequilibrium capillary electrophoresis of equilibrium mixtures or NECEEM. Using Congo Red and Acid Blue 113, information about the maximal stoic…
Determination of antimony in drinking waters by an inexpensive, reproducible hydride generator for atomic spectroscopy.
1991
A method for determining antimony in drinking waters is described. In order to prevent a substantial error caused by the different oxidation states of antimony, Sb(V) is reduced to Sb(III) with potassium iodide-ascorbic acid. Covalent hydride is generated with a home made device by adding NaBH4. The hydride is then atomized in a flame-heated silica tube and atomic absorption is measured spectrophotometrically. The optimal conditions for this determination are discussed and interference effects are described. Results obtained by determining linearity range (0-200 ng), detection (LOD) and quantitation (LOQ) limits (LOD = 0.347 ng/ml, LOQ = 1.158 ng/ml), precision (instrumental CV 4.08% and me…
Extraction of polyphenols in Himanthalia elongata and determination by high performance liquid chromatography with diode array detector prior to its …
2016
Abstract Several studies have demonstrated the antioxidant capacity of seaweeds, which can be used for the development of biopharmaceuticals with extensive medical application. Antioxidant therapies appear to attenuate the organic deterioration originated by an excessive oxidative stress, which could prevent the harmful effects of various injuries such as ischemia-reperfusion (I/R) among others. Marine brown seaweeds play a significant role, as they are the only organisms on earth producing phlorotannins, which are polyphenols that exhibit important biological activity. To ensure obtaining an extract with the greatest antioxidant activity, some variables that affect the extraction of polyph…
Mark-Houwink Parameters of Biosynthetic Poly(γ-glutamic acid) in Aqueous Solution
2001
A combined viscosity–light scattering–gel permeation chromatography (GPC) study was carried out on bacterially produced poly(γ-glutamic acid) (PGGA). PGGA samples with weight-average molecular weights ranging from 8×104 up to 8×105 g·mol–1 dissolved in phosphate buffer at 0.13 M ionic strength were used. It was found that the Mark–Houwink relation is acceptably obeyed, giving K and a values of 1.84×10–6 dL·g–1 and 1.16, respectively. As expected, GPC analysis showed that PGGA does not follow the universal calibration plot and that deviations can not be avoided by modifying the ionic strength.
Microheterogeneous electrocatalytic chiral recognition at monoclinic vanadium-doped zirconias: enantioselective detection of glucose.
2007
Synthetic tetragonal and monoclinic vanadium-doped zirconias (t- and m-VxZr1-xO2, 0.005x0.150) exert an effective catalytic effect toward the electrochemical oxidation of glucose in aqueous alkaline media. The catalytic effect of monoclinic specimens attached to carbon and fluorine-doped tin oxide electrodes exhibits a remarkable enantioselectivity, so that catalytic currents for the oxidation of L-glucose at +0.92 V vs AgCl/Ag are considerably larger than those obtained for the oxidation of D-glucose. This enantioselectivity can be associated with the existence of a noncentrosymmetric coordination of vanadium centers in the monoclinic crystalline form of zirconia. From the electrochemical …
The relationship between water and air temperature in chironomid-based paleoclimate reconstructions: Records from boreal and subarctic Finland
2014
Fossil remains of larval chironomids are one of the most useful paleolimnological proxies to reconstruct Holocene paleoclimate. We investigate the within-lake distribution of chironomids in relation to water temperature and test the usability of intralake calibration in chironomid-based temperature reconstructions. We compare our findings against the traditional multilake calibration technique in Holocene sediment cores from Finland. The results show that intralake water temperature optima of common taxa correspond closely with mean July air temperature optima in a regional multilake dataset, with exception of a few vegetation-associated taxa. A calibration model based on intralake water t…
An innovative approach to manage uncertainties and stock diversity in the EPBD cost-optimal methodology
2018
The EU Energy Performance of Buildings Directive (EPBD) 2010/31/EU is a step in the right direction to promote near zero energy buildings (NZEB) in a step-wise manner, starting with minimum energy performance and cost optimal thresholds for “reference buildings” (RBs) for each category. Nevertheless, a standard method for defining RBs does not exist, which led to a great divergence between MS in the level of detail used to define RBs for the EPBD cost-optimal analysis. Such lack of harmonisation between MS is further evident given the resulting large discrepancies in energy performance indicators even between countries having similar climate. Furthermore, discrepancies of 30% or higher betw…