Some thoughts on electrospray ionization mechanisms

Electrospray ionization (ESI) mechanisms are highly complex, due to a series of physical and chemical phenomena taking place on a complex system, as a solution is. In fact, even if the solution of an analyte in a protic medium can be considered at first sight to be a two-component system, the presence of solvent dissociation equilibria and the possible interactions solvent-solvent dissociation products, solvent dissociation products-analyte make this system highly complex, also for the presence of possible ionic compounds (for example, Na(+), K(+)) which strongly affect the above equilibria. A high number of research articles have been published, mainly devoted to charged droplet production and to gas-phase ion generation. They all show the high complexity of the processes affecting electrospray measurements related to either the chemical equilibria present in the condensed phase and to electrolysis processes at the emitter tip or to the processes occurring in the sprayed droplets. As a result, the chemical composition inside the small droplets from which the analyte ions are generated can be significantly different from those in sprayed solution. In this review, after a short survey of the proposed ESI mechanisms, some experiments are described. They were performed to examine if ion mobility in solution, before the formation of the sprayed charged droplets, can affect the ESI results. The data, obtained by studying both inorganic and organic analytes, indicate that the ESI spectra are dependent on the analyte dimension and charge state which, as a consequence, affect their ion mobility in solution.     

Self-assembling of multi-jets by pyro-electrohydrodynamic effect for high throughput liquid nanodrops transfer

Destabilization of liquid film by electro-hydro-dynamics (EHD) pressure is achieved through the pyroelectric effect on a polar dielectric crystal. We show that by destabilizing the liquid film, periodical self-assembled multi-jets are obtained. The multi-jets operate simultaneously and could be exploited to dispense liquids with nanolitre drops. Such multiple self-assembled liquid jets have significant potential applicability for high-throughput liquid transfer by this novel pyro-EHD ink-jet approach. Since the method avoids the use of nozzles and electrodes, it is especially suitable for highly viscous liquids. Here we present and discuss the new multi-jet process and the results obtained with a liquid polymer (PDMS).     

“Zero” temperature stochastic 3D ising model and dimer covering fluctuations: A first step towards interface mean curvature motion

We consider the Glauber dynamics for the Ising model with “+” boundary conditions, at zero temperature or at a temperature that goes to zero with the system size (hence the quotation marks in the title). In dimension d = 3 we prove that an initial domain of linear size L of “−” spins disappears within a time τ₊, which is at most L²(log L)^c and at least L²/(c log L) for some c > 0. The proof of the upper bound proceeds via comparison with an auxiliary dynamics which mimics the motion by mean curvature that is expected to describe, on large time scales, the evolution of the interface between “+” and “−” domains. The analysis of the auxiliary dynamics requires recent results on the fluctuations of the height function associated to dimmer coverings of the infinite honeycomb lattice. Our result, apart from the spurious logarithmic factors, is the first rigorous confirmation of the Lifshitz law τ₊ ≃ const × L², conjectured on heuristic grounds [8, 13]. In dimension d = 2, τ₊ can be shown to be of order L² without logarithmic corrections: the upper bound was proven in [6], and here we provide the lower bound. For d = 2, we also prove that the spectral gap of the generator behaves like for L large, as conjectured in [2]. © 2011 Wiley Periodicals, Inc.     

Phytochemical Characterization of Olea europaea L. Cultivars of Cilento National Park (South Italy) through NMR-Based Metabolomics

Olea europaea germplasm is constituted by a huge number of cultivars, each one characterized by specific features. In this context, endemic cultivars evolved for a very long period in a precise local area, developing very specific traits. These characteristics include the production and accumulation of phytochemicals, many of which are also responsible for the nutraceutical value of the drupes and of the oils therefrom. With the aim of obtaining information on the phytochemical profile of drupes of autochthonous cultivars of Cilento, Vallo di Diano and Alburni National Park, a metabolomics-based study was carried out on 19 selected cultivars. Multivariate data analysis of ¹H-NMR data and 2D NMR analyses allowed the rapid identification of metabolites that were qualitatively and/or quantitatively varying among the cultivars. This study allowed to identify the cultivars Racioppella, Guglia, Pizzulella, Oliva amara, and Racioppa as the richest in health-promoting phenolic compounds. Furthermore, it showed a significant variability among the different cultivars, suggesting the possibility of using metabolic fingerprinting approaches for cultivar differentiation, once that further studies aimed at assessing the influence of growing conditions and environmental factors on the chemical profiles of single cultivars are carried out.     

Aging Process Effects on the Characteristics of Vacuum Residue Oxidation Products with the Addition of Crumb Rubber

This paper considers the effect of aging processes on viscoelastic characteristics of vacuum residue oxidation products modified with crumb rubber. Viscoelastic properties were compared to original bitumen raw material-vacuum residue and vacuum residue oxidation products during short-term and long-term aging. The complex shear modulus of the vacuum residue and its oxidation products decreased with an increase in temperature. Short-term aging resulted in increased shear modulus for all samples.The vacuum residue oxidation product modified with crumb rubber had the maximum values of the rutting parameter and fatigue parameter. There was an expansion of the temperature range of plasticity: for the vacuum residue oxidation product with crumb rubber, its value was 67.2 °C. The curves of the black diagram of the modified vacuum residue oxidation product are shifted towards smaller phase angles with the increase in the shear modulus, which indicates the increase in the stiffness and elasticity of the rubber bitumen binders. The vacuum residue oxidation product modified with crumb rubber corresponded to the rubber bitumen binder of the grade RBB 60/90, according to its physical and mechanical indicators.     

A new route to 1,4 -diketones and its application to (z)-jasmone and dihydrojasmone synthesis

(Z)-Jasmone ,dihydrojasmone and other 3-methylcyclo=pent-2-en-1-ones are easily synthesized starting from aldehydes and 1-(2-methyl-1,3-dioxolane-2-yl)-2-nitroethane as reagent for 3-ketobutyl anion synthon. Nitro-aldol condensation is the chainlegthening reaction followed by oxidation and denitration via p-toluenesulfonylhydrazones of the corresponding -nitroke=tones. Removal of protecting groups gives 1,4-diketones which are then cyclized with alkali.     

Pyrrolopyridine analogs of nalidixic acid. 1. Pyrrolo[2,3-b]pyridines

A series of 4,7-dihydro-4-oxo-1H-pyrrolo[2,3-b]pyridine-5-carboxylic acids was synthesized from ethyl 5-methyl(or 5H)-2-aminopyrrole-3-carboxylate. The starting pyrroles were obtained by reaction of carbethoxyacetamidine with bromoacetone or chloroacetaldehyde. One compound ( 10 ) showed antibacterial activity in vitro.     

Studio sulle varietà a due dimensioni appartenenti a unS 4 euclideo

Sunto Si studiano le varietà a due dimensioni immerse in unS ₄ euclideo. Definite certe due normali principali, si esaminano le proprietà delle superficie nell'intorno di un punto, le curvature, e le sue linee più caratteristiche. Infine si dà sotto forma esplicita ed espressiva un gruppo di formule fondamentali relative all'impiego delle tre forme differenziali quadratiche atte a definire la varietà considerata.