[2+2] Cycloaddition Reactions of Imines with Cyclic Ketenes: Synthesis of 1,3‐Thiazolidine Derived Spiro‐β‐lactams and Their Transformations

Unsymmetric cyclic ketenes were generated from N‐acyl‐1,3‐thiazolidine‐2‐carboxylic acids 1a – c by means of Mukaiyama's reagent, and then reacted with imines 2a – c to the new, isomeric spiro‐β‐lactams 3 and 4 via [2+2] cycloaddition (Staudinger ketene–imine reaction; Scheme 1). The reactions were stereoselective (Table 1) and mainly afforded the spiro‐β‐lactams with a relative trans configuration. The spiro‐β‐lactams could be transformed into the corresponding monocyclic β‐lactams by means of thiazolidine ring opening or into substituted thiazolidines via hydrolysis of the β‐lactam ring.     

Heterocycles from ylides. Part V (1). Reactivity of 4-arylmethylene-Δ2 -isoxazolin-5-ones with stabilized sulfur ylides

4-Arylmethylene-Δ² -isoxazolin-5-ones react with carbonyl-stabilized sulfur ylides yielding spiro[cyclopropane-1,4′-Δ²-isoxazolin]-5′-ones identified from spectroscopic data and chemical behaviour.     

Light-induced fluorescence spectroscopy of adenomas, adenocarcinomas and non-neoplastic mucosa in human colon. I. In vitro measurements.

In an attempt to evaluate whether induced fluorescence could be exploited to discriminate neoplastic from non-neoplastic tissue, fluorescence spectroscopy was performed at 450-800 nm on 83 biopsy specimens of colonic mucosa. Measurements showed that fluorescence spectra of adenoma, adenocarcinoma and non-neoplastic mucosa manifest dissimilar patterns. Nine variables, whose photophysical and/or biological bases need further investigation, were derived from the spectra. Discriminant functions between the groups of lesions were determined by using a stepwise discriminant analysis. The diagnostic test had a sensitivity of 80.6% and 88.2%, and a specificity of 90.5% and 95.2% in discriminating neoplastic from non-neoplastic mucosa and adenoma from non-neoplastic mucosa respectively. These results suggest that fluorescence spectroscopy has the potential to improve endoscopic diagnosis of premalignant and malignant lesions of colonic mucosa.     

Diagnostic potential of autofluorescence for an assisted intraoperative delineation of glioblastoma resection margins

The intrinsic autofluorescence properties of biological tissues can be affected by the occurrence of histological and biochemical alterations induced by pathological processes. In this study the potential of autofluorescence to distinguish tumor from normal tissues was investigated with the view of a real-time diagnostic application in neurosurgery to delineate glioblastoma resection margins. The autofluorescence properties of nonneoplastic and neoplastic tissues were analyzed on tissue sections and homogenates by means of a microspectrofluorometer, and directly on patients affected by glioblastoma multiforme, during surgery, with a fiber-optic probe. Scan-microspectrofluorometric analysis on tissue sections evidenced a reduction of emission intensity and a broadening of the main emission band, along with a redshift of the peak position, from peritumoral nonneoplastic to neoplastic tissues. Differences in both spectral shape and signal amplitude were found in patients when the glioblastoma lesion autofluorescence was compared with those of cortex and white matter taken as healthy tissues. Both biochemical composition and histological organization contribute to modify the autofluorescence emission of neoplastic, with respect to nonneoplastic, brain tissues. The differences found in the in vivo analysis confirm the prospects for improving the efficacy of tumor resection margin delineation in neurosurgery.     

Infrared matrix and polarised spectrum of bis(diethyldithio-carbamato)-nickel(II)

The IR spectra (300–4000 cm^?1) of bis-(N,N-diethyldithiocarbamato)-nickel(II) as N₂ matrix and oriented polycrystalline layer are reported. All the observed bands are assigned and classified on the grounds of their polarisation in the symmetry classes of D_2h, the highest possible molecular symmetry.Remarkably, polarisation of the absorptions around 1000 cm^?1 rules out the assignment to any C-S stretching, in contrast with previous assignments. The room temperature crystal spectra do not show evidence for crystal splitting. The matrix spectrum shows features related to the existence of rotamers around the H₂C-N bond, which give useful assistance in the assignment.     

Complexity of single machine scheduling problems under scenario-based uncertainty

We present algorithmic and computational complexity results for several single machine scheduling problems where some job characteristics are uncertain. This uncertainty is modeled through a finite set of well-defined scenarios. We use here the so-called absolute robustness criterion to select among feasible solutions.     

Electrospun Carbon/CuxO Nanocomposite material as Sustainable and High Performance Anode for Lithium-Ion Batteries

The increase in energy density of the next generation of battery materials to meet the new challenges of the electrical vehicles era calls for innovative and easily scalable materials with sustainable processes. An innovative Cu_xO/C nanocomposite material, characterized by a highly conductive 3D-framework, with Cu_xO/Cu-metal contiguous nanodomains is prepared by electrospinning. The electrode processing is made using a polyacrylic acid binder. The nanocomposite has been fully characterized and the electrochemical performance shows high specific capacity values over 450 galvanostatic cycles at 500 mAg⁻¹ specific current with capacity retention values over 80 %. In addition, the composite shows remarkable high rate performance and highly stable interface, which has been studied by impedance spectroscopy.     

Characterization of a model Phillips catalyst by mass spectrometry

A model Phillips catalyst for ethylene polymerization, prepared by spin coating a Cr(III)(Cr(acac)3) precursor on a silicon wafer, was submitted to an oxidative activation. Laser ablation Fourier transform mass spectrometry provided direct information on molecular species at the silicon wafer surface during activation. At 350 degrees C the chromium precursor was degraded, while chromium oxide species were formed. The chromium concentration decreased with temperature. The activated model catalyst was active for ethylene polymerization. Using complementary techniques (Fourier transform infrared spectroscopy, laser desorption/ionization mass spectrometry), the polymer was identified as crystalline polyethylene. After 1 h of polymerization at 160 degrees C, dome-like structures were observed by atomic force microscopy. Their morphologies were constituted of regions of parallel aligned lamellae of polymer.     

Modulation of Porphyrin Derivatives Accumulation in C6 Glioma Cells by Drugs Acting on β-Adrenergic Receptors. A Spectrofluorometric Study

The pharmacological modulation of the uptake of porphyrin derivatives in cultured C6 glioma cells was investigated by means of spectrofluorometric analysis both in single cells and in cell homogenates. The influence of drugs acting as β-receptor agonists or antagonists was studied in cells grown to semiconfluency. Isoproterenol (ISO), a β-receptor agonist, enhanced the intracellular fluorescence intensity of both Photofrin and protoporphyrin IX (PpIX). A treatment with a β-receptor antagonist I-propranolol (PRO), simultaneous with ISO, resulted in an intracellular Photofrin fluorescence signal comparable to that of the control cells, indicating the specificity of the pharmacological action. The pharmacological treatment seemed particularly effective with the aggregated species. This is suggested by the relative increase of the band at 670 nm, being greater than that in the 630 nm band in the emission spectra of Photofrin and PpIX, and by the comparison of the fluorescence intensity on cell homogenates measured both in the absence and in the presence of cetyltrimethyl-ammonium bromide as a detergent.