A lower bound estimate of the critical load for compressible elastic solids

We determine lower bound estimates for the critical load for hyperelastic solids under monotonic dead load processes. By considering the Hadamard criterion of infinitesimal stability, we first determine a lower bound for the Hadamard stability functional; then, we develop a procedure for optimal lower bound estimates for the critical load. As examples, we apply our procedure to generalized Blatz-Ko solids under simple extension, simple compression and rectilinear shear, and compare our results with other proposals contained in the literature.     

Determination of trace bismuth by under-potential deposition-stripping voltammetry at mesoporous platinum microelectrodes: application to pharmaceutical products

A methodology for the determination of bismuth, based on under-potential deposition-stripping voltammetry (UPD-SV), was investigated. It makes use of mesoporous platinum microelectrodes (Pt-MEs) prepared by a liquid crystal templating technique. The mesoporous microelectrodes, which are characterised by a very high surface area, allowed the accumulation of relatively large amounts of bismuth at under-potential without saturation of the electrode surface. Calibration plots for quantification of bismuth at micromolar levels were constructed by using the charge involved in either the anodic or cathodic peak recoded by cyclic voltammetry that ensued the accumulation of bismuth at the electrode surface. During the anodic scan, the oxidation of metallic bismuth occurred; the cathodic scan involved irreversibly adsorbed bismuth species, which are retained on to the electrode surface. The reproducibility of the proposed UPD-SV procedure (which was within 5 %) was assured by the application to the Pt-MEs of a suitable potential waveform, properly designed to avoid memory effect due to the irreversibly deposited bismuth. The latter phenomenon along with UPD allowed to overcome interference due to copper, which is normally observed when quantification of bismuth is performed by anodic stripping voltammetry at solid electrodes involving bulk metal deposits. The usefulness of the proposed method for the determination of bismuth in real samples was demonstrated by the analysis of a tablet of a pharmaceutical preparation, which is used for curing ulcers.     

Fast screening of 88 pharmaceutical drugs and metabolites in whole blood by ultrahigh-performance liquid chromatography–tandem mass spectrometry

Forensic investigations involving acute or lethal intoxication, drug-facilitated sexual assault, driving or workplace impairment frequently require the analysis of fresh or postmortem blood samples to check out a wide variety of pharmaceutical and illicit drugs, even after single-dose consumption. A sensitive and selective ultrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) screening method was developed for fast screening of 88 psychoactive drugs and metabolites in blood samples, including the ones most frequently involved in acute intoxications and forensic investigations in Italy. The new method allows short sample processing and analysis time (the whole procedure can be accomplished in less than 30 min) together with the simultaneous monitoring of a large number of pharmaceutical substances. These features represent crucial factors in the approach of acute intoxications, when the patient requires urgent and appropriate therapy. Blood sample treatment was limited to protein precipitation. Two UHPLC–MS/MS runs in positive and negative electrospray ionization modes were performed. The data were acquired at unit mass resolution in the selected reaction monitoring mode. According to international guidelines, linearity range, precision, trueness, detection and quantification limits, recovery, selectivity, specificity, carryover, and matrix effect phenomena were determined. Despite the limited sample purification and the inherent decreased chance of eliminating any potential interference, the present multiresidue screening method proved extremely effective and sensitive, allowing the detection of all tested drugs, even those belonging to structurally different classes of substances. Moreover, the developed method is easily susceptible to further expansion to encompass more drugs, either new or those becoming important for criminal investigation. This protocol was also applied to the analysis of authentic blood samples collected from victims of various crimes in routine casework, whose relevance in forensic investigations is presented in five cases.     

Combined use of three forms of chiroptical spectroscopies in the study of the absolute configuration and conformational properties of 3-phenylcyclopentanone, 3-phenylcyclohexanone,and 3-phenylcycloheptanone

Three forms of chiroptical spectroscopies, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) have been employed to study the configuration and conformational properties of the three molecules: (S)-3-phenylcyclopentanone, (S)-3-phenylcyclohexanone, and (S)-3-phenylcycloheptanone (including (S)-3-phenylcyclopentanone-2,2,5,5-d₄ and (S)-3-phenylcyclohexanone-2,2,6,6-d₄). ECD and VCD spectra in the mid-IR for the three molecular systems are marginally dependent on fine conformational details, as interpreted in terms of standard DFT computational methods, with common spectroscopic features to the three systems clearly identified. Accounting for vibronic coupling mechanisms reproduces the structuring of ECD n→π^∗ band. The ORD curves are quite similar for the three types of molecules, but their interpretation highlights a crucial role played by conformations of the cycloalkanone ring in the case of (S)-3-phenylcycloheptanone. The same conclusions are reached by considering the VCD spectra in the CH-stretching region.     

Confinement and orientational study at liquid crystal phase transitions

Abstract

We have studied the heat capacity of the thermotropic liquid crystal, octylcyanobiphenyl (8CB), confined to the nearly cylindrical, 0·2 μm diameter pores of Anopore membranes. Orientation of the nematic director within the pores can be controlled with surface treatment. It is known from NMR measurements that the nematic director is aligned parallel to the pore axis in the untreated membrane. A perpendicular alignment is obtained when the pore surface is treated with lecithin. The second order smectic A to nematic (S_A–N) and the weakly first order nematic to isotropic (N–I) phase transitions of 8CB were studied in these pores, for both director orientations, using an AC calorimetry technique. Effects on heat capacity amplitudes, transition temperature shifts, rounding and broadening of these phase transitions will be presented and contrasted with bulk measurements.     

(Co)oxidation/cyclization processes upon irradiation of triphenylamine

Irradiation of triphenylamine (Ph₃N) in nitrogen-flushed solution leads to 9-phenylcarbazole and two tetrahydroderivatives (1,2,3,4- and 1,2,7,8-) via disproportionation of the corresponding 4a,4b-dihydrocarbazole. In oxygen-equilibrated solution oxidative cyclization occurs through the intermediacy of a triplet peroxy diradical, which either abstracts a hydrogen atom intramolecularly or (mainly) cleaves back to the reagents. The role of the key intermediates is supported by DFT calculations and by trapping by triarylphosphines (that are thus efficiently oxidized, while preventing the cyclization of Ph₃N). The hydroperoxide, on the other hand, causes inefficient co-oxidation of sulfides.     

Synthesis of toxyloxanthone B

A synthesis of the naturally occurring xanthone toxyloxanthone B is described, in which the key step is the regioselective addition of a methyl salicylate to a substituted benzyne, followed by cyclization of the intermediate aryl anion to form the xanthone, the regiochemistry of the aryne addition being confirmed by X-ray crystallography. Subsequent introduction of the pyran ring by [3,3]-rearrangement and deprotection completed the synthesis.     

Approximate chemical analysis of volcanic glasses using Raman spectroscopy

The effect of chemical composition on the Raman spectra of a series of natural calcalkaline silicate glasses has been quantified by performing electron microprobe analyses and obtaining Raman spectra on glassy filaments (~450 µm) derived from a magma mingling experiment. The results provide a robust compositionally‐dependent database for the Raman spectra of natural silicate glasses along the calcalkaline series. An empirical model based on both the acquired Raman spectra and an ideal mixing equation between calcalkaline basaltic and rhyolitic end‐members is constructed enabling the estimation of the chemical composition and degree of polymerization of silicate glasses using Raman spectra. The model is relatively insensitive to acquisition conditions and has been validated using the MPI‐DING geochemical standard glasses 1 as well as further samples. The methods and model developed here offer several advantages compared with other analytical and spectroscopic methods such as infrared spectroscopy, X‐ray fluorescence spectroscopy, electron and ion microprobe analyses, inasmuch as Raman spectroscopy can be performed with a high spatial resolution (1 µm²) without the need for any sample preparation as a nondestructive technique. This study represents an advance in efforts to provide the first database of Raman spectra for natural silicate glasses and yields a new approach for the treatment of Raman spectra, which allows us to extract approximate information about the chemical composition of natural silicate glasses using Raman spectroscopy. We anticipate its application in handheld in situ terrestrial field studies of silicate glasses under extreme conditions (e.g. extraterrestrial and submarine environments). © 2015 The Authors Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd