Insight Into the Conformational Arrangement of a Bis-THF Diol Compound Through 2D-NMR Studies and X-Ray Structural Analysis

Abstract  

The conformational arrangement of an all-threo bis-THF diol compound, synthesized through the RuO₄-catalysed oxidative bis-cyclization of farnesyl acetate, was determined via crystallographic analysis and detailed 2D-NMR solution studies. The bis-THF compound crystallizes in the orthorhombic Pbca space group, with unit cell parameters a = 10.496(1), b = 17.974(1), c = 19.777(2) ?, Z = 8. The final refinement converged to R ₁ = 0.0484 for 4714 independent observed reflections having I > 2σ(I). There is a good agreement between the solution molecular conformation determined by 2D-NMR and the X-ray molecular conformation. The molecule adopts a folded, horse shoe-type conformation both in solution and in the crystal, that suggests aptitude to coordinate cations. Additionally, in the crystals, the molecular conformation is stabilized by intramolecular and intermolecular H-bonding.     

Kinetic effects of tartaric acid on the growth of chiral J-aggregates of tetrakis(4-sulfonatophenyl)porphyrin

The kinetics of growth for chiral J-aggregates of H(4)TPPS(4) porphyrin have been investigated under different experimental conditions in the presence of tartaric acid. The observed rate constants and the anisotropy factor g show a defined dependence on the enantiomer used as a chiral templating agent.     

Continuous flow synthesis and scale-up of glycine- and taurine-conjugated bile salts

A multi-gram scale protocol for the N-acyl amidation of bile acids with glycine and taurine has been successfully developed under continuous flow processing conditions. Selecting ursodeoxycholic acid (UDCA) as the model compound and N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) as the condensing agent, a modular mesoreactor assisted flow set-up was employed to significantly speed up the optimization of the reaction conditions and the flow scale-up synthesis. The results in terms of yield, in line purification, analysis, and implemented flow set-up for the reaction optimization and large scale production are reported and discussed.     

Sparse 1D discrete Dirac operators I: Quantum transport

Some dynamical lower bounds for one-dimensional discrete Dirac operators with different classes of sparse potentials are presented, and the particular role of the particle mass is emphasized.     

Matrix completion problems over integral domains: The case with a diagonal of prescribed blocks

Let $\mathfrak{R}$ be an arbitrary integral domain, let $\wedge =\{{\lambda }_1\text{,}\dots \text{,}{\lambda }_n\}$ be a multiset of elements of $\mathfrak{R}$, let $\sigma$ be a permutation of $\{1\text{,}\dots \text{,}k\}$ let $n_1\text{,}\dots \text{,}{n}_k$ be positive integers such that $n_1+?+n_k=n$, and for $r=1\text{,}\dots \text{,}k$ let $A_r\in {\mathfrak{R}}^{n_r\times n_{\sigma (r)}}$. We are interested in the problem of finding a block matrix $Q={\left[Q_{\mathit{rs}}\right]}_{r\text{,}s=1}^k\in {\mathfrak{R}}^{n\times n}$ with spectrum $\mathrm{\Lambda }$ and such that $Q_{r\sigma (r)}=A_r$ for $r=1\text{,}\dots \text{,}k$. Cravo and Silva completely characterized the existence of such a matrix when $\mathfrak{R}$ is a field. In this work we construct a solution matrix $Q$ that solves the problem when $\mathfrak{R}$ is an integral domain with two exceptions: (i) $k=2$; (ii) $k\ge 3$, $\sigma (r)=r$ and $n_r>n/2$ for some $r$.What makes this work quite unique in this area is that we consider the problem over the more general algebraic structure of integral domains, which includes the important case of integers. Furthermore, we provide an explicit and easy to implement finite step algorithm that constructs an specific solution matrix (we point out that Cravo and Silva’s proof is not constructive).     

Integrating on-line process control and imperfect corrective maintenance: An economical design

Existing studies of on-line process control are concerned with economic aspects, and the parameters of the processes are optimized with respect to the average cost per item produced. However, an equally important dimension is the adoption of an efficient maintenance policy. In most cases, only the frequency of the corrective adjustment is evaluated because it is assumed that the equipment becomes “as good as new” after corrective maintenance. For this condition to be met, a sophisticated and detailed corrective adjustment system needs to be employed. The aim of this paper is to propose an integrated economic model incorporating the following two dimensions: on-line process control and a corrective maintenance program. Both performances are objects of an average cost per item minimization. Adjustments are based on the location of the measurement of a quality characteristic of interest in a three decision zone. Numerical examples are illustrated in the proposal.     

Efficiency of the medical care industry: Evidence from the Italian regional system

What might be the relation between clinical research and efficiency of medical care suppliers? Is the hypothesis of a positive relation consistent? Considering efficiency as the supplier’s ability to maximize the number of patients hospitalized in a mobility process among regions (i.e. mobility balance), this work aims at highlighting the existence of a positive externality of pharmaceutical clinical research on that kind of efficiency. In other words, an externality is able to affect the patients’ perception of good/bad quality of outputs supplied by the medical care industry, leading their mobility process. Taking Italy and the mobility of patients among regions into account, an Operational Research study will be performed in order to support this assumption.The goal of this work is to show an alternative way to increase the efficiency of medical care suppliers on the market of health care, that is to say, through their competitiveness on the market of human experimentation.     

Architectures,stability and optimization for clock distribution networks

Synchronous telecommunication networks, distributed control systems and integrated circuits have its accuracy of operation dependent on the existence of a reliable time basis signal extracted from the line data stream and acquirable to each node. In this sense, the existence of a sub-network (inside the main network) dedicated to the distribution of the clock signals is crucially important. There are different solutions for the architecture of the time distribution sub-network and choosing one of them depends on cost, precision, reliability and operational security. In this work we expose: (i) the possible time distribution networks and their usual topologies and arrangements. (ii) How parameters of the network nodes can affect the reachability and stability of the synchronous state of a network. (iii) Optimizations methods for synchronous networks which can provide low cost architectures with operational precision, reliability and security.     

Estimating concentration of ultrasound contrast agents with backscatter coefficients: experimental and theoretical aspects

Ultrasound contrast agents (UCAs) have been explored as a means to enhance therapeutic techniques. Because the effectiveness of these techniques relies on the UCA concentration at a target site, it would be beneficial to estimate UCA concentration noninvasively. In this study, a noninvasive method for estimating UCA concentration was developed in vitro. Backscatter coefficients (BSCs) estimated from measurements of Definity(?) UCAs were fitted to a theoretical scattering model in the 15-25 MHz range using a Levenberg-Marquardt regression technique. The model was defined by the UCA size distribution and concentration, and therefore concentration estimates were extracted directly from the fit. Calculation of the BSC was accomplished using planar reference measurements from the back wall of a Plexiglas(?) chamber and an average of 500 snapshots of ultrasonic backscatter from UCAs flowing through the chamber. In order to verify the ultrasonically derived UCA concentration estimates, a sample of the UCAs was extracted from the flow path and the concentration was estimated with a hemacytometer. UCA concentrations of 1, 2, and 5 times the dose recommended by the manufacturer were used in experiments. All BSC-based estimates were within one standard deviation of hemacytometer based estimates for peak rarefactional pressures of 100-400 kPa.     

An indirect hybrid sound transmission loss controller

The control of sound transmission through panels is an important noise control problem in the aerospace, aeronautical, and automotive industries. The trend towards using lightweight composite materials that have lower sound insulation performance is a negative factor regarding low frequency transmission loss. Double-panel partitions with the gap filled with sound absorption materials are often employed to improve the sound insulation performance with reduced added weight penalty. However, in the low frequency range, the strong coupling between the panels through the air cavity and mechanical paths may greatly reduce the sound transmission performance, making it even lower than the performance of a single panel in some frequency ranges. In this work, an experimental investigation of a new kind of hybrid (active/passive) acoustic actuator is presented. The idea consists of replacing the acoustic absorption material by a hybrid actuator aiming at improving the transmission loss at low frequencies without altering the passive attenuation. A prototype of the system is tested in a plane wave acoustic tube setup. Different kinds of SISO feedforward control implementations were used to attenuate the sound power transmitted through the hybrid active–passive panel using an error microphone or a particle velocity sensor placed downstream with respect to the sample panel. Measurement results of the transmission loss with active and hybrid attenuation are presented and discussed.