Search results for " infrared"

Accuracy of ASTER Level-2 thermal-infrared Standard Products of an agricultural area in Spain

2007

Abstract The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) collects five-channel thermal-infrared images that are calibrated, corrected for atmospheric effects, and then converted to land surface temperature and emissivity products by the ASTER Temperature/Emissivity Separation (TES) algorithm. TES scales low- and high-contrast surfaces differently, and has been validated over water (low contrast) and rock (high contrast). Performance of TES over agricultural areas, however, has not been evaluated specifically. To address this issue, field measurements of “ground truth” were made over bare soil in addition to green grass, alfalfa and corn, at an agricultural researc…

Characterization of oligomeric compounds in secondary organic aerosol using liquid chromatography coupled to electrospray ionization Fourier transfor…

2009

The components of secondary organic aerosols (SOAs) generated from the gas-phase ozonolysis of two C(10)H(16)-terpenes (alpha-pinene; sabinene) and a cyclic C(6)H(10) alkene (cyclohexene) were characterized by the use of a Fourier transform ion cyclotron mass spectrometer equipped with an electrospray ionization source operated in the negative ion mode. Reversed-phase high-performance liquid chromatography was used to achieve chromatographic separation of highly oxidized organic compounds. In addition to the well-known group of low molecular weight oxidation products (monomers; e.g. dicarboxylic acids), higher molecular weight compounds (dimers) were also detected and their exact elemental …

Near infrared light to promote synaptic resilience to Alzheimer’s Disease neuropathology

Alzheimer’s Disease (AD) is a multifactorial neurodegenerative dementia with no curative therapeutic options. One of the earliest impairments in AD triggering cognitive decline is the synaptic dysfunction induced by the selective targeting and interruption of the synaptic region by the small oligomeric form of amyloid beta (Aβ). Recently, the co-presence of Aβ oligomers (Aβo) and tau oligomers (tau-o) at the synapses has been suggested to exacerbate this dysfunction. Therefore, the development of therapeutics aimed at protecting the synapses from the toxic binding of both proteins at the synapses can preserve synaptic health and cognitive function. With this goal in mind, the present study …

Decoding vibrational states of Concanavalin A amyloid fibrils.

2015

International audience; Amyloid and amyloid-like fibrils are a general class of protein aggregates and represent a central topic in life sciences for their involvement in several neurodegenerative disorders and their unique mechanical and supramolecular morphological properties. Both their biological role and their physical properties, including their high mechanical stability and thermodynamic inertia, are related to the structural arrangement of proteins in the aggregates at molecular level. Significant variations may exist in the supramolecular organization of the commonly termed cross-β structure that constitutes the amyloid core. In this context, a fine knowledge of the structural deta…

Concanavalin A aggregation and toxicity on cell cultures

2009

A number of neurodegenerative diseases are known to involve protein aggregation. Common mechanisms and structural properties of amyloids are thought to be involved in aggregation-related cytotoxicity. In this context we propose an experimental study on Concanavalin A (Con A) aggregation and use it as a model to study the relationship between cell toxicity and aggregation processes. Depending on solution conditions, Con A aggregation has been monitored by static and dynamic light scattering, Thioflavin T emission, and FTIR absorption. The morphology of different aggregate species was verified by means of Atomic Force Microscopy and Confocal Microscopy. During the aggregation pathway the nati…

The Boson Peak of Amyloid Fibrils: Probing the Softness of Protein Aggregates by Inelastic Neutron Scattering

2014

Proteins and polypeptides are characterized by low-frequency vibrations in the terahertz regime responsible for the so-called "boson peak". The shape and position of this peak are related to the mechanical properties of peptide chains. Amyloid fibrils are ordered macromolecular assemblies, spontaneously formed in nature, characterized by unique biological and nanomechanical properties. In this work, we investigate the effects of the amyloid state and its polymorphism on the boson peak. We used inelastic neutron scattering to probe low-frequency vibrations of the glucagon polypeptide in the native state and in two different amyloid morphologies in both dry and hydrated sample states. The dat…

Quantification of minerals from ATR-FTIR spectra with spectral interferences using the MRC method.

2017

A method for quantifying the individual components of mineral samples based on attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR) is described, extending the constant ratio (CR) method to analytes absorbing in a common range of wavenumbers. Absorbance values in the spectral region where the analytes absorb relative to the absorbance of an internal standard absorbing at a wavenumber where the analytes do not absorb, permits the quantification of N analytes using measurements at N fixed wavenumbers. The method was tested for mixtures of albite, orthoclase, kaolin and quartz.

Nutritional parameters of commercially available milk samples by FTIR and chemometric techniques

2004

Abstract A chemometric study on the prediction of the main nutritional aspects of milk has been carried out by using fourier transform infrared spectroscopy (FTIR) attenuated total reflectance (ATR) measurements of commercially available milk samples of different types. Whole, semi and skimmed milks, enriched or not with calcium, vitamins or modified by alteration of lipid or sugar composition were considered. After evaluating different strategies for data acquisition and ATR cleaning between samples, hierarchical cluster analysis (HCA) was carried out for classification of samples in order to choose the calibration set. The prediction capabilities of partial least squares (PLS) data treatm…

FT-IR quantitative analysis of solvent mixtures by the constant ratio method

1999

Abstract An analytical methodology to quantify compounds in complex mixtures by FTIR spectroscopy is proposed and the “Constant Ratio Method” (CRM) was developed. The addition of a standard to the sample allows us to establish a constant KMS characteristic of the Analyte/Standard system which can be employed as a quantification factor of the analyte in different samples . In the proposed method the measurements are independent of optical path length. This method has been successfully applied to quantify butylacetate and toluene in binary and tertiary samples and tertiary mixtures. Butylacetate/toluene/nujol have been resolved employing valeronitrile as standard, obtaining values for relativ…

Procedure for automated background correction in flow systems with infrared spectroscopic detection and changing liquid-phase composition

2009

This paper describes a partial least squares (PLS) based automatic procedure to correct for changes in the spectral contribution of the solvent or solvent mixtures from solute spectra recorded in these solvents. The procedure was developed for successful on-line Fourier transform infrared (FT-IR) detection in gradient high-performance liquid chromatography (HPLC) separations. It requires a reference FT-IR data set containing all possible combinations of the expected variation in solvent composition. Furthermore, a spectral region ( A) in these spectra is required where the solvents show absorption but the analytes do not. This is the case for the system ACN:H2O, an often-applied solvent mi…