Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements have been reported for the Co_1.1−x Zn _x Ge_0.1Fe_1.2O₁ spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important role of magnetic anisotropy (due to the presence of Co²⁺ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed.     

Selection of Anti‐gluten DNA Aptamers in a Deep Eutectic Solvent

Herein, we show the feasibility of using deep eutectic solvents as a faster way of selecting aptamers targeting poorly water‐soluble species. This unexplored concept is illustrated for gluten proteins. In this way, aptamer‐based gluten detection can be performed directly in the extraction media with improved detectability. We envision deep implications for applications not only in food safety control but also in biomedicine.     

Liquid droplets vaporization under free molecule gas beam conditions

Summary The present piece of research studies the vaporization of liquid droplets under rarefied gas beam conditions. The time dependent aspect of the phenomenon has been taken into account. In fact, during the vaporization, variations of the droplet's temperature, with influence upon the diameter's reduction rate, can occur. Numerical calculations relating to water droplets' vaporization have been made taking into account various values of the incident energy flux. The study should be considered as a theoretical approach to the analysis of the gas-liquid surface interaction phenomena. Moreover, according to C. S. Kurzius and F. H. Raab [1], the work can find its application in the study of the blackout suppressant methods in re-entry space vehicles.

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Sommario La presente ricerca studia l'evaporazione di gocce liquide investite da un fascio molecolare ipertermico, rarefatto. Il fenomeno è studiato da un punto di vista non stazionario; infatti, durante la vaporizzazione, si ha una forte variazione della temperatura media della goccia con conseguente influenza sulla velocità di riduzione del diametro. Sono stati eseguiti calcoli numerici relativi alla evaporazione di gocce d'acqua in flusso di gas ipertermico per fissati valori del flusso di energia incidente. Il presente lavoro è da considerarsi come premessa teorica allo studio del fenomeno fisico di interazione superficiale gas-liquido. Inoltre, secondo C. S. Kurzius ed F. H. Raab [1], trova la sua applicazione nello studio dei metodi di eliminazione del blackout nel rientro dei veicoli spaziali.

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This work, sponsored by the Centro Studi sulla Dinamica dei Fluidi of C.N.R., is a re-elaborated copy of a paper presented at the 6th Int. Symposium on Molecular Beams (9–12 July 1973, Cannes, France).     

Regio and diastereoselective lactonisation of enolisable 1,3-dicarbonyls by reaction with mesoionic 1,3-oxazolium-5-olates

The one-pot reaction of enolisable 1,3-dicarbonyls and N-methyl-1,3-oxazolium-5-olate derivatives provided enol lactones directly in good yield and with excellent regio- and diastereocontrol.     

Utilisation of electrospray time-of-flight mass spectrometry for solving complex fragmentation patterns: application to benzoxazinone derivatives

In this paper we describe the application of electrospray time-of-flight mass spectrometry (ESI-TOFMS) to structural elucidation of the fragment ions formed from a range of natural and synthetic allelochemical derivatives. The extensive mass spectrometric characterisation of ten non-glucosylated benzoxazinone derivatives using this method is described here for the first time. The analytes include six naturally occurring 1,4-benzoxazin-3(4H)-one derivatives, including the hydroxamic acids DIMBOA [2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one] and DIBOA [2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one], lactams HBOA [2-hydroxy-2H-1,4-benzoxazin-3(4H)-one] and HMBOA [2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one], benzoxazolinones BOA [benzoxazolin-2(3H)-one] and MBOA [6-methoxy-benzoxazolin-2(3H)-one] and four synthetic variations, 2'H-DIBOA [4-hydroxy-2H-1,4-benzoxazin-3(4H)-one], 2'OMe-DIBOA [2-methoxy-4-hydroxy-2H-1,4-benzoxazin-3(4H)-one], 2'H-HBOA [2H-1,4-benzoxazin-3(4H)-one] and 2'OMe-HBOA [2-methoxy-2H-1,4-benzoxazin-3(4H)-one]. Assignments of the mass spectral fragments were aided by elemental composition calculation results, comparison of structural analogues and background literature, and acquired knowledge regarding feasible structures for the compounds. The influence of substituents on the chemical reactivity of the compounds with respect to the observed MS behaviour over varying nozzle potentials is addressed and, through comparison of the structural analogues, generic fragmentation patterns have also been identified.     

Development of a new assay for the screening of hypochlorous acid scavengers based on reversed-phase high-performance liquid chromatography

A new assay for the screening of hypochlorite/hypochlorous acid (XOCl) scavengers, based on the reversed-phase high performance liquid chromatographic analysis of human serum albumin (HSA, 0.2% in 100 mM sodium phosphate, pH 7), before and after oxidation by XOCl (1.6 mM), was developed. XOCl induced a significant decrease of the area under the chromatographic peak of HSA at 280 nm due to the oxidation of the aromatic amino acids tryptophan and tyrosine, as suggested by the literature and by the chromatographic analyses and the electrochemical study performed here. The assay was validated by testing known XOCl scavengers such as ascorbic acid, cysteine, glutathione, S-methylglutathione and alpha-lipoic acid and other antioxidants such as carnosine and chlorogenic acid, which inhibited the oxidation of HSA. Quantitative activities were calculated using an original formula based on the changes of the area of the albumin peak. Electrochemical data collected here in a homogeneous medium showed that the anodic potentials of the antioxidants tested are less positive (ascorbic acid, chlorogenic acid and cysteine) or similar (alpha-lipoic acid) compared with those of the aromatic residues (tryptophan and tyrosine) of HSA oxidized by XOCl. However, as expected, carnosine, glutathione and S-methylglutathione were inactive at a glassy-carbon, gold or platinum electrode.     

Optical spectroscopy of lanthanide ions in ZnO-TeO2 glasses

Zinc tellurite glasses of compositions 19ZnO-80TeO2-1Ln2O3 with Ln = Eu, Er, Nd and Tm were prepared by melt quenching. The absorption spectra were measured and from the experimental oscillator strengths of the f-->f transitions the Judd-Ofelt parameters ohm(lambda) were obtained. The values of the ohm(lambda) parameters are in the range usually observed for oxide glasses. For Nd3+ and Er3+, luminescence spectra in the near infrared were measured and the stimulated emission cross sections sigma(p) were evaluated for some laser transitions. The high values of sigma(p), especially for Nd3+, make them possible candidates for optical applications. Fluorescence line narrowing (FLN) spectra of the Eu3+ doped glass were measured at 20 K, and the energies of the Stark components of the 7F1 and 7F2 states were obtained. A crystal field analysis was carried out assuming a C2v site symmetry. The behaviour of the crystal field ratios B22/B20 and B44/B40 agrees reasonably well with the values calculated using the geometric model proposed by Brecher and Riseberg. The crystal field strength at the Eu3+ sites appears to be very low compared to other oxide glasses.     

A contribution to the use of thorin as an analytical reagent: spectrophotometric study of its complexation with barium and application to sulphate determination in atmospheric particulates

The complexation of Ba(2+) by Thorin in the pH range 2-9 in aqueous ethanol medium has been investigated. The dissociation constants of Thorin in the ethanolic medium have been determined spectrophotometrically and the distribution of the protonated species has been used to explain the behaviour of the apparent complexation constant. On the basis of the apparent constants found, and mass-balances, the effect of sulphate on the absorbance has been calculated, and the best conditions for determination of sulphate have been established. Cation and anion interferences have been studied and means of overcoming them are proposed. The method developed has been applied to sulphate determination in atmospheric particulates. As little as 1 mug of sulphate can be measured.     

Ambivalent intercalators for DNA: L-shaped platinum(II) complexes

Novel platinum(II) square planar coordination complexes, in which two heteroaromatic ligands are held by the metal in an unusual L-shaped geometry orthogonal to each other, have been synthesized, and their interaction with DNA was investigated with absorption and linear dichroism spectroscopy. As a rule, the ligand that is coplanar with the coordination square of Pt is found to be oriented perpendicular relative to the DNA helix axis when bound, suggestive of its intercalation between the base pairs of DNA. However, when this coplanar ligand is replaced by two pyridines, the opposite ligand, orthogonal to the coordination square, is instead preferentially intercalated. This behavior shows that these new complexes do indeed show some properties of true ambintercalators, i.e., compounds that can bind by intercalation of either of two distinct aromatic moieties.     

Ruthenium-catalysed asymmetric hydrogenation of ketones using QUINAPHOS as the ligand

Highly enantioselective ruthenium-catalysed hydrogenation of aromatic ketones is achieved with (Ra,S(C))-QUINAPHOS in the presence of achiral and chiral diamines as co-catalysts.