Mass Spectrometric Evaluation of β-Cyclodextrins as Potential Hosts for Titanocene Dichloride

Bent metallocene dichlorides (Cp₂MCl₂, M = Ti, Mo, Nb, …) have found interest as anti-cancer drugs in order to overcome the drawbacks associated with platinum-based therapeutics. However, they suffer from poor hydrolytic stability at physiological pH. A promising approach to improve their hydrolytic stability is the formation of host-guest complexes with macrocyclic structures, such as cyclodextrins. In this work, we utilized nanoelectrospray ionization tandem mass spectrometry to probe the interaction of titanocene dichloride with β-cyclodextrin. Unlike the non-covalent binding of phenylalanine and oxaliplatin to β-cyclodextrin, the mixture of titanocene and β-cyclodextrin led to signals assigned as [βCD + Cp₂Ti–H]⁺, indicating a covalent character of the interaction. This finding is supported by titanated cyclodextrin fragment ions occurring from collisional activation. Employing di- and trimethylated β-cyclodextrins as hosts enabled the elucidation of the influence of the cyclodextrin hydroxy groups on the interaction with guest structures. Masking of the hydroxy groups was found to impair the covalent interaction and enabling the encapsulation of the guest structure within the hydrophobic cavity of the cyclodextrin. Findings are further supported by breakdown curves obtained by gas-phase dissociation of the various complexes.     

Analysis and minimization of small-geometry effects on the currentgain of self-aligned `etched-polysilicon' emitter bipolar transistors

The authors report on a detailed analysis of small-geometry effects on the current gain of advanced self-aligned etched-polysilicon emitter bipolar transistors. By studying the dependence of collector and base currents on device geometry and process parameters, they have been able to identify the critical fabrication steps and physical mechanisms involved. The narrow emitter effect is caused by the butting of the emitter-base junction to the field oxide, and is mainly controlled by the gate oxide removal step prior to polysilicon deposition. Short emitter effects are associated with phenomena taking place in the spacer region of the device perimeter during polysilicon patterning, spacer pedestal thermal oxidation, link base implantation, and final rapid thermal anneal. Proper adjustment of all process parameters is shown to allow good control of the narrow-emitter effect and complete compensation of short-emitter effects, showing promise for the future of this CMOS-compatible bipolar transistor structure     

XRD, TEM, IR and 29Si MAS NMR characterization of NiO-SiO2 nanocomposites

The present study focuses on the structural properties of a NiO-SiO₂nanocomposite with 14 mol % of nickel oxide obtained by a sol-gel method and a gradual heating the gel in the 350–900°C range. NiO nanoparticles and their dispersion in the amorphous silica matrix were studied through TEM and XRD. The behaviour at the nanoparticle/matrix interface was investigated through IR and ²⁹Si MAS NMR spectroscopy comparing the spectra of the nanocomposite with that of a silica sample obtained with the same preparation method and submitted to the same thermal treatments. The results indicate that nanoparticles, formed in cavities of the silica matrix, act as an obstacle towards the spontaneous silica polymerization process with heat treatments.     

Modeling for edge detection problems in blurred noisy images

The aim of this paper is to provide a theoretical set up and a mathematical model for the problem of image reconstruction. The original image belongs to a family of two-dimensional (2-D) possibly discontinuous functions, but is blurred by a Gaussian point spread function introduced by the measurement device. In addition, the blurred image is corrupted by an additive noise. We propose a preprocessing of data which enhances the contribution of the signal discontinuous component over that one of the regular part, while damping down the effect of noise. In particular we suggest to convolute data with a kernel defined as the second order derivative of a Gaussian spread function. Finally, the image reconstruction is embedded in an optimal problem framework. Now convexity and compactness properties for the admissible set play a fundamental role. We provide an instance of a class of admissible sets which is relevant from an application point of view while featuring the desired properties.     

A time domain model for the study of high frequency 3D wheelset–track interaction with non-Hertzian contact

Multibody System Dynamics - A novel numerical model for train-track interaction is proposed in this paper to deal with wheel–rail interface dynamics in high frequency range. The complete...     

Studying the heterogeneity of European higher education institutions

Scientometrics - The heterogeneity of the Higher Education (HE) Institutions is one of the main critical issues in the assessment of their performance. This paper adopts a multi-level and...