Search results for "Linea"
showing 10 items of 7724 documents
Evaluation of the quality of olive oil using fatty acid profiles by direct infusion electrospray ionization mass spectrometry
2008
Abstract Electrospray ionization mass spectrometry is used to predict the olive oil quality according to European Union marketing standards. Samples were 1:50 diluted in an alkaline 85:15 (v/v) propanol/methanol mixture and directly infused into the electrospray ionization source of an ion trap mass spectrometer. The establishment of ratios of the peak abundances of the free fatty acids followed by linear discriminant analysis was employed to predict the olive oil quality grade. In addition, using multiple linear regression and partial least-squares regression, the percentages of extra virgin and virgin olive oils in binary mixtures were predicted with 5–11% average prediction errors.
Flexible Chirality in Self-Assembled N-Annulated Perylenedicarboxamides.
2017
N-annulated perylenedicarboxamides 1-3 form supramolecular polymers with a strong tendency to aggregate. The bundles of fibers formed generate a spontaneous anisotropy that conditions the chiroptical features of the described molecules in solution; a strong linear dichroism effect accompanies the circular dichroism (CD) outcome. There is no influence of the point chirality existing at the side chains of 1 and 2, and these molecules present the same chiroptical features as achiral 3. Mechanical rotary stirring increases the CD response and the sign of the dichroic signal changes with the stirring direction. Theoretical calculations indicate that the self-assembly of 1-3 in helical columnar s…
Nonlinear optical susceptibilities of polysilanes: exciton effect
1992
Abstract Third-order nonlinear optical susceptibilities of σ-conjugated one-dimensional polymers have been calculated in a tight-binding model by taking account of the formation of excitons due to long-range Coulomb interactions. The spectrum of third-harmonic generation (THG) exhibits peaks due to excitons as well as unbound electron—hole states, in contrast to the linear absorption spectrum which is dominated by the lowest exciton state. The results are in excellent agreement with recent experiments in polysilanes not only for THG but also for linear absorption, two-photon absorption, and electroabsorption in a mutually consistent way.
Prediction of the curing time of Spanish hams using peptide profiles established by capillary zone electrophoresis
2009
Abstract A capillary zone electrophoresis procedure for the prediction of curing time of Spanish hams using peptide profiles has been developed. Excellent resolution between the seven peptide peaks was achieved within 30 min analysis time with a BGE containing 60 mM MgSO 4 and 50 mM phosphate at pH 2.5. Using hams with curing times of 6, 8 and 12 months, both linear discriminant analysis (LDA) and multiple linear regression (MLR) models were constructed. In both cases, two different normalisation procedures of the peak areas were compared. Using LDA, all the ham samples corresponding to the three categories were correctly classified. Using MLR, the ham curing time could be predicted with av…
Determination of alkylphenol ethoxylates by micellar electrokinetic chromatography with bile salts
2001
Octyl- and nonylphenol ethoxylates (OPEs and NPEs) with different numbers of ethoxy units (average values: n = 10 and N = 40 for OPEs, and n = 10 for NPEs) were separated by micellar electrokinetic chromatography under positive polarity using an 80 mM borate buffer of pH 8.5 containing sodium deoxycholate (SDC) or sodium cholate (SC). When sodium dodecyl sulfate (SDS) was added to the background electrolyte (BGE) in the absence of the bile salt, a single peak at a migration time longer than that of the EOF was obtained. Substituting the SDS by a bile salt, the homologues were resolved. At the same bile salt concentration, resolution between the homologues was higher with SDC than using SC. …
Restricted and complete-active-space multiconfiguration linear response calculations of the polarizability of formamide and urea
1991
Abstract Using the polarized basis sets of Sadlej, we have carried out multiconfiguration linear response (MCLR) calculations of static and dynamic polarizabilities of water, carbon dioxide, formamide and urea. It is found that the polarized basis sets give a good description of the polarizabilities. The uncorrelates (self-consistent field) polarizabilities are in general 10% or more lower than the experimental values. The correlation as introduced in the complete-active-space (CAS) and restricted-active-space (RAS) MCLR calculations recovers the major part of this deviation.
DLPNO-CCSD(T) scaled methods for the accurate treatment of large supramolecular complexes
2017
In this work, we present scaled variants of the DLPNO-CCSD(T) method, dubbed as (LS)DLPNO-CCSD(T) and (NS)DLPNO-CCSD(T), to obtain accurate interaction energies in supramolecular complexes governed by noncovalent interactions. The novel scaled schemes are based on the linear combination of the DLPNO-CCSD(T) correlation energies calculated with the standard (LoosePNO and NormalPNO) and modified (Loose2PNO and Normal2PNO) DLPNO-CCSD(T) accuracy levels. The scaled DLPNO-CCSD(T) variants provide nearly TightPNO accuracy, which is essential for the quantification of weak noncovalent interactions, with a noticeable saving in computational cost. Importantly, the accuracy of the proposed schemes is…
Determination of molecular weights and Stokes' radii of non-denatured proteins by polyacrylamide gradient gel electrophoresis. 1. An equation relatin…
1982
Untreated and processed gel plates of polyacrylamide (PAA) gradient gels were cut into strips perpendicularly to their length, and the wet and dry matter of the sections was determined. In untreated gels the apparent dry matter, as well as the relative dry matter, are a linear function of the gel length. In processed gels, however, only the apparent gel concentration increases linearly with the gel length, whereas the relative dry matter increases linearly with the square root of the gel length. The %T (content in polyacrylamide) was calculated from the apparent dry matter. The gel gradients used were found to be linear with respect to %T. Six different calibration proteins were run and the…
Discriminative features of type I and type III secreted proteins from Gram-negative bacteria
2006
AbstractThe amino acid composition of sequences and structural attributes (α-helices, β-sheets) of C-and N-terminal fragments (50 amino acids) were compared to annotated (SWISS-PROT/ TrEMBL) type I (20 sequences) and type III (22 sequences) secreted proteins of Gram-negative bacteria.The discriminant analysis together with the stepwise forward and backward selection of variables revealed the frequencies of the residues Arg, Glu, Gly, Ile, Met, Pro, Ser, Tyr, Val as a set of strong (1-P < 0.001) predictor variables to discriminate between the sequences of type I and type III secreted proteins with a cross-validated accuracy of 98.6–100 %. The internal and external validity of discriminant…
Toward device applicable second order NLO polymer materials: definition of the chromophore figure of merit
2007
Maximal achieved second order non linear optical (NLO) efficiency of the PMMA based host – guest systems containing eight dimethylaminobenzylidene -1, 3 - indandione (DMABI) related chromophores have been analysed. Two contradicting sets of NLO chromophore figure of merit (FOM) equations were tested. One of them predicts that NLO efficiency of the poled polymer host -guest film is proportional to ground state dipole d33 ~ 1/μg, another to d33 ~ 1/μg. The best correlations for the maximal achieved nonlinearity were obtained with second set of FOM, especially if high ground state dipole (μg > 7D) chromofores are included in analysis.