155 research outputs found
Effects of induction interactions on the orientational order of solutes in liquid crystals
No full textIn a recent paper (di Matteo, A.; Ferrarini, A.; Moro, G. J. J. Phys. Chem. B 2000, 104, 7764) a method to derive a mean field potential for molecules in nematic phases based on their structure and charge distribution has been presented. The potential consists of a shape and a reaction field contribution, accounting for short range and electrostatic intermolecular interactions, respectively. The model is extended here by introducing induction interactions in the reaction field. In the spirit of our approach, aimed at a realistic picture at a semiphenomenological level, an appropriate description is obtained in terms of distributed polarizabilities. The Thole model of interacting damped atom dipoles has been singled out as a suitable one, although also different choices have been considered. The orientational order parameters calculated in this way for a set of typical polar and nonpolar solutes in nematic solvents are reported, and the influence of induction interactions is discussed
A molecular based continuum approach for the dielectric permittivity of liquids and liquid crystals
No full textA method for the calculation of the dielectric permittivity of isotropic and anisotropic homogeneous fluids is presented which, in the framework of the continuum approximation, adopts a realistic description of the molecular features, so overcoming some of the limits of the Onsager model. The Poisson equation for the molecular charge distribution contained in a cavity in a dielectric continuum in the presence of an external field is solved by a boundary element technique, which allows a detailed description of the cavity shape associated with a given molecular structure. The charge distribution is described in terms of point charges derived from ab initio calculations in vacuum, in addition to a set of interacting atom dipoles induced by all the electric fields experienced by the molecule in the condensed phase. The link between molecular features and bulk properties is established in a general way suitable for isotropic liquids and nematic phases, through the orientational distribution function of the molecule interacting with the applied field and the surrounding fluid. Numerical results are reported for the liquid phase of a set of selected organic compounds of different shape and polarity, and for the isotropic and nematic phases of 4-n-pentyl-4(')-cyanobiphenyl (5CB). They show that a realistic description of the molecular features can have dramatic effects in the case of strongly anisometric molecules
Passive membrane permeability: beyond the standard solubility-diffusion model
No full textThe spontaneous diffusion of solutes through lipid bilayers is still a challenge for theoretical predictions. Since permeation processes remain beyond the capabilities of unbiased molecular dynamics simulations, an alternative strategy is currently adopted to gain insight into their mechanism and time scale. This is based on a monodimensional description of the translocation process only in terms of the position of the solute along the normal to the lipid bilayer, which is formally expressed in the solubility-diffusion model. Actually, a role of orientational and conformational motions has been pointed out, and the use of advanced simulation techniques has been proposed to take into account their effect. Here, we discuss the limitations of the standard solubility-diffusion approach and propose a more general description of membrane translocation as a diffusion process on a free energy surface, which is a function of the translational and rotational degrees of freedom of the molecule. Simple expressions for the permeability coefficient are obtained under suitable conditions. For fast solute reorientation, the classical solubility-diffusion equation is recovered. Under the assumption that well-defined minima can be identified on the free energy landscape, a mechanistic interpretation of the permeability coefficient in terms of all possible permeation paths is given
Effects of electrostatic interactions on orientational order of solutes in liquid crystals
No full textA mean-field model for the analysis of electrostatic interactions in liquid crystal phases is proposed. The model is based on a realistic description of the probe molecule and a continuum approximation for its environment. Electrostatic interactions, treated with the reaction field model, are superimposed to short-range interactions, which are accounted for by a shape method. The model is used to predict orientational order parameters of some representative solutes, characterized by different shapes and charge distributions, dissolved in nematics with different dielectric permittivities
The overarching duty to act in the best interest of the client in MiFID II
No full textThe chapter examines MiFID II’s core obligation for investment firms to act in the best interest of clients, analyzing its scope, legal basis, and impact on investor protection within EU financial regulation
MicroRNAs miR-584-5p and miR-425-3p Are Up-Regulated in Plasma of Colorectal Cancer (CRC) Patients: Targeting with Inhibitor Peptide Nucleic Acids Is Associated with Induction of Apoptosis in Colon Cancer Cell Lines
No full textLiquid biopsy has dramatically changed cancer management in the last decade; however, despite the huge number of miRNA signatures available for diagnostic or prognostic purposes, it is still unclear if dysregulated miRNAs in the bloodstream could be used to develop miRNA-based therapeutic approaches. In one author’s previous work, nine miRNAs were found to be dysregulated in early-stage colon cancer (CRC) patients by NGS analysis followed by RT-dd-PCR validation. In the present study, the biological effects of the targeting of the most relevant dysregulated miRNAs with anti-miRNA peptide nucleic acids (PNAs) were verified, and their anticancer activity in terms of apoptosis induction was evaluated. Our data demonstrate that targeting bloodstream up-regulated miRNAs using anti-miRNA PNAs leads to the down-regulation of target miRNAs associated with inhibition of the activation of the pro-apoptotic pathway in CRC cellular models. Moreover, very high percentages of apoptotic cells were found when the anti-miRNA PNAs were associated with other pro-apoptotic agents, such as sulforaphane (SFN). The presented data sustain the idea that the targeting of miRNAs up-regulated in the bloodstream with a known role in tumor pathology might be a tool for the design of protocols for anti-tumor therapy based on miRNA-targeting molecules
«Sortes biblicae» e tradizioni agiografiche fra IV e VI secolo
No full textThe use of the divinatory practice of the «sortes biblicae», direct heir of the ancient rhapsodomancy («sortes Homericae, sortes Vergilianae»), is frequently documented in the hagiographical sources between the fourth and the sixth centuries. The most famous episode of bibliomancy is transmitted by the eighth book of Augustine’s «Confessiones» («tolle, lege»). As narrated by his biographer Sulpicius Severus, also the episcopal election of Martin of Tours was decided by opening at random the book of Psalms. This hagiographical evidence remains, indeed, very problematic. Therefore, the early Church’s condemnation of the «sortes sanctorum» – commonly, but incorrectly, understood as a synonym for the divinatory consultation of the Bible – needs to be better explained
A Data-Based Approach for the Prediction of Stuck-Pipe Events in Oil Drilling Operations
No full textStuck-pipe phenomena can have disastrous effects on drilling performance, with outcomes that may range from time delays to loss of expensive machinery. In this work, we develop three indicators based on the mudlog data, which aim to detect three different physical phenomena associated to the insurgence of a sticking. In particular, two indices target respectively the detection of translational and rotational motion issues, while the third index concerns the wellbore pressure. A statistical model that relates these features with the documented stuck-pipe events is then developed using machine learning. The resulting model takes the form of a depth-based map of the risk of incurring into a stuck-pipe, updated in real time. Preliminary experimental results on the available dataset indicate that the use of the proposed model and indicators can help mitigate the stuck-pipe issue
Association between inflammatory central nervous system lesions and Cerebellar Ataxia, Neuropathy and Vestibular Areflexia Syndrome (CANVAS): a case series
No full text[no abstract available
Transcriptomic comparative analysis for tomato fruit quality traits through the Combimatrix technology
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