A subspace time-domain algorithm for automated NMR spectral normalization

Recently, two methods have been proposed for quantitatively comparing NMR spectra of control and treated samples, in order to examine the possible occurring variations in cell metabolism and/or structure in response to numerous physical, chemical, and biological agents. These methods are the maximum superposition normalization algorithm (MaSNAl) and the minimum rank normalization algorithm (MiRaNAl). In this paper a new subspace-based time-domain normalization algorithm, denoted by SuTdNAl (subspace time-domain normalization algorithm), is presented. By the determination of the intersection of the column spaces of two Hankel matrices, the common signal poles and further on the components having proportionally varying amplitudes are detected. The method has the advantage that it is computationally less intensive than the MaSNAl and the MiRaNAl. Furthermore, no approximate estimate of the normalization factor is required. The algorithm was tested by Monte Carlo simulations on a set of simulation signals. It was shown that the SuTdNAl has a statistical performance similar to that of the MiRaNAl, which itself is an improvement over the MaSNAl. Furthermore, two samples of known contents are compared with the MiRaNAl, the SuTdNAl, and an older method using a standard. Finally, the SuTdNAl is tested on a realistic simulation example derived from an in vitro measurement on cells.     

Chern numbers of ample vector bundles on toric surfaces

This article shows a number of strong inequalities that hold for the Chern numbers , of any ample vector bundle of rank on a smooth toric projective surface, , whose topological Euler characteristic is . One general lower bound for proven in this article has leading term . Using Bogomolov instability, strong lower bounds for are also given. Using the new inequalities, the exceptions to the lower bounds 4e(S)$"> and e(S)$"> are classified.

     

Peculiar loci of ample and spanned line bundles

The bad locus and the rude locus of an ample and base point free linear system on a smooth complex projective variety are introduced and studied. Polarized surfaces of small degree, or whose degree is the square of a prime, with nonempty bad loci are completely classified. Several explicit examples are offered to describe the variety of behaviors of the two loci. Mathematics Subject Classification (2000):14C20, 14J25     

Molecular inclusion in functionalized macrocycles part 10*: Crystal and molecular structure of ap-tert-butylcalix[6]arene hexapodand

Colourless prismatic crystals of (3) were obtained from ethanol/CH₂Cl₂ (1:1) solution, space groupP2₁/c,a=14.581(5),b=22.517(8),c=11.799(5) , =92.13(4)°. Refinement led to a final conventionalR value of 0.074 for 4247 reflections. The conformation of the molecule, which lies on a center of symmetry, is 1,2,3-alternate with one oligoethereal chain pointing inside the molecular cavity. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. 82011 (30 pages).For part 9, see [1]. Results presented in part at the Second International Symposium of Clathrate Compounds and Molecular Inclusion Phenomena, Parma, Italy, 1982.     

Divalent binding of a bis(adamantyl)-functionalized calix[4]arene to beta-cyclodextrin-based hosts: an experimental and theoretical study on multivalent binding in solution and at self-assembled monolayers

The divalent binding of a bis(adamantyl)-functionalized calix[4]arene (1) to an EDTA-tethered beta-cyclodextrin (CD) dimer (2) in solution (1.2 x 10(7) M(-)(1)) was 3 orders of magnitude weaker than the binding constant ( approximately 10(10) M(-)(1)) for the interaction of 1 at CD self-assembled monolayers (SAMs) on gold. This difference in binding is rationalized using a theoretical model, which interprets the divalent binding as two consecutive monovalent binding events, i.e., an intermolecular interaction followed by an intramolecular binding event, the latter of which is associated with an effective concentration term accounting for the close proximity of the two interacting species. The methodology presented in the model is applicable to divalent binding both in solution and at SAMs and indicates that the difference in observed binding constants mainly stems from a difference in effective concentration.     

Integrated investigations for the characterisation of Roman lead-glazed pottery from Pompeii and Herculaneum (Italy)

A multi-analytical approach was used to investigate Roman lead-glazed ceramic artefacts from archaeological excavations at Pompeii and Herculaneum (Italy) aiming at defining the production technology of both glaze and ceramic body, by way of integrated investigations. The chemical, structural, and micro-morphological characterisations were performed using a combination of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), optical microscopy (OM), scanning electron microscopy (SEM), and micro-Raman spectroscopy. Fragments of artefacts (skyphoi, oil lamps, bowls, askoi, amphorae, krateres) of great historical and archaeological interest were sampled. LA-ICP-MS was used to determine the elemental composition by virtue of its effective lateral resolution, its ability to detect most elements and also to analyse comparably small samples. All the archaeological objects were coated with a lead-based glaze produced using a lead oxide-plus-quartz mixture, with sodium/potassium feldspars added as a flux and two different metals used: copper and iron. Two types of ceramic pastes have been identified, but chemometric techniques support the hypothesis of a Campanian provenance for the raw materials. Degradation phenomena such as the partial devitrification of the glaze, i.e. the slow structural reorganisation towards stable crystalline phases, and the leaching by mineral dissolution in the soil, were determined.     

Capillary electrochromatography‐mass spectrometry for the determination of 5‐nitroimidazole antibiotics in urine samples

The separation of eight antibiotics belonging to 5‐nitroimidazole family was carried out by means of CEC coupled with MS. Preliminary experiments were carried out with ultraviolet detection in order to select the proper stationary and mobile phase. Among the different stationary phases studied (namely Lichrospher C18, 5 μm particle size; Cogent^TM Bidentate C18, 4.2 μm; Pinnacle II? Phenyl, 3 μm; Pinnacle II? Cyano, 3 μm), Cogent? Bidentate C18 (4.2 μm) gave the best performance. For CEC‐MS coupling, a laboratory assembled liquid‐junction‐nano‐spray interface was used. In order to achieve a good sensitivity, special attention was paid to both optimization of the sheath liquid composition as well as selection of the injection mode. Under optimized CEC‐ESI‐MS conditions, the separation was accomplished within 22 min by using a column packed with a mixture of Bidentate C18:Lichrospher Silica‐60 (5 μm) 3:1 w/w, an inlet pressure of 11 bar, a voltage of 15 kV, and a mobile phase composed by 45:10:45 v/v/v ACN/MeOH/water containing ammonium acetate (5 mM pH 5). A combined hydrodynamic and electrokinetic injection of 8 bar, 15 kV, and 96 s was adopted. The method was validated in terms of repeatability and intermediate precision of retention times and peak areas, linearity, and LODs and LOQs. RSDs values were <2.9% for retention times and <16.1% for peak areas in both intraday and interday experiments. LOQ values were between 0.09 and 0.42 μg/mL for all compounds. Finally, the method was applied to the determination of three most employed 5‐nitroimidazole antibiotics (metronidazole, secnidazole, and ternidazole) in spiked urine samples, subjected to a SPE procedure. Recovery values in the 67–103% range were obtained. Furthermore, for the selected antibiotics, CEC‐MS² spectra were obtained providing the unambiguous confirmation of these drugs in urine samples.     

Number of degrees of freedom of the radiated field over multiple bounded domains

The problem of determining the number of degrees of freedom (NDF) of the field radiated by an electric current supported over a bounded rectilinear domain and observed over multiple bounded domains parallel to the source is addressed. The analysis is achieved by means of the singular value decomposition of the radiation operator so that the NDF is identified as the number of 'significant' singular values. The aim is to analyze whether the multidomain observation allows to increase the available NDF. By analytical arguments, we show that collecting data over multiple domains shapes the singular value behavior but it still presents a steep decay in correspondence to an index dictated by the observation domain that subtends the largest observation angular sector.     

Enantioselective separation of the novel antidepressant mirtazapine and its main metabolites by CEC

In this work, the simultaneous enantioseparation of the second-generation antidepressant drug mirtazapine and its main metabolites 8-hydroxymirtazapine and N-desmethylmirtazapine by chiral CEC is reported. The separation of all enantiomers under study was achieved employing a capillary column packed with a vancomycin-modified diol stationary phase. With the aim to optimize the separation of the three pairs of enantiomers in the same run, different experimental parameters were studied including the mobile phase composition (buffer concentration and pH, organic modifier type and ratio, and water content), stationary phase composition, and capillary temperature. A capillary column packed with vancomycin mixed with silica particles in the ratio (3:1) and a mobile phase composed of 100 mM ammonium acetate buffer (pH 6)/H(2)O/MeOH/ACN (5:15:30:50, by vol.) allowed the complete enantioresolution of each pair of enantiomers but not the simultaneous separation of all the studied compounds. For this purpose, a packing bed composed of vancomycin-CSP only was tested and the baseline resolution of the three couples of enantiomers was achieved in a single run in less than 30 min, setting the applied voltage and temperature at 25 kV and 20 degrees C, respectively. In order to show the potential applicability of the developed CEC method to biomedical analysis, a study concerning precision, sensitivity, and linearity was performed. The method was then applied to the separation of the enantiomers in a human urine sample spiked with the studied compounds after suitable SPE procedure with strong cation-exchange (SCX) cartridges.     

Attenuated Total Reflection-Fourier transform infrared microspectroscopic mapping for the characterisation of paint cross-sections

Paint cross-sections have been analysed using the attenuated total reflection technique combined with FTIR mapping microspectroscopy in order to characterise the nature of the compounds present and map their localisation in the stratigraphy. The study reveals the possibilities offered by micro-ATR devices for obtaining informations about the organic substances employed in painting techniques and in particular their distribution in the different layers, showing a real improvement over traditional analytical investigations in use for the detection of organic substances. Limitations, such as the contamination of the embedding resin and the typical spectral resolution (20 μm) are presented and alternative methods were proposed to obtain better results. In particular, the use of an infrared transparent salt (KBr) as embedding material for the cross-sections is evaluated and seems to be very promising. Furthermore, ATR mapping represent a useful non-destructive analytical technique complementary to others molecular and elemental analyses to be performed afterwards such as SEM-EDX.