Interstage Pressures of a Multistage Compressor with Intercooling

This paper considers the criterion of minimum compression work to derive an expression for the interstage pressure of a multistage compressor with intercooling that includes the gas properties, pressure drops in the intercoolers, different suction gas temperatures, and isentropic efficiencies in each compression stage. The analytical expression for the interstage pressures is applied to estimate the number of compression stages and to evaluate its applicability in order to estimate interstage pressures in the operation of multistage compressors, which can be especially useful when their measurements are not available.     

Mechatronic design,experimental setup,and control architecture design of a novel 4 DoF parallel manipulator

Although parallel manipulators started with the introduction of architectures with six degrees of freedom, a vast number of applications require less than six degrees of freedom. Consequently, scholars have proposed architectures with three and four degrees of freedom, but relatively few four degrees of freedom parallel manipulators have become prototypes, especially of the two rotation and two translation motion types. In this article, we explain the mechatronics design, prototype, and control architecture design of a four degrees of freedom parallel manipulators with two rotation and two translation motions. We chose to design a four degrees of freedom manipulator based on the motion needed to complete the tasks of lower limb rehabilitation. To the author’s best knowledge, parallel manipulators between three and six degrees of freedom for rehabilitation of lower limb have not been proposed to date. The developed architecture enhances the three minimum degrees of freedom required by adding a four degrees of freedom, which allows combinations of normal or tangential efforts in the joints, or torque acting on the knee. We put forward the inverse and forward displacement equations, describe the prototype, perform the experimental setup, and develop the hardware and control architecture. The tracking accuracy experiments from the proposed controller show that the manipulator can accomplish the required application.     

Passivity-based control of a single-link flexible manipulator using fractional controllers

Nonlinear Dynamics - This work presents a new methodology for the design of passivity-based controllers of fractional order for single-link flexible robots. In this work, some previously developed...     

Evaluation of Fused Pyrrolothiazole Systems as Correctors of Mutant CFTR Protein

Cystic fibrosis (CF) is a genetic disease caused by mutations that impair the function of the CFTR chloride channel. The most frequent mutation, F508del, causes misfolding and premature degradation of CFTR protein. This defect can be overcome with pharmacological agents named “correctors”. So far, at least three different classes of correctors have been identified based on the additive/synergistic effects that are obtained when compounds of different classes are combined together. The development of class 2 correctors has lagged behind that of compounds belonging to the other classes. It was shown that the efficacy of the prototypical class 2 corrector, the bithiazole corr-4a, could be improved by generating conformationally-locked bithiazoles. In the present study, we investigated the effect of tricyclic pyrrolothiazoles as analogues of constrained bithiazoles. Thirty-five compounds were tested using the functional assay based on the halide-sensitive yellow fluorescent protein (HS-YFP) that measured CFTR activity. One compound, having a six atom carbocyle central ring in the tricyclic pyrrolothiazole system and bearing a pivalamide group at the thiazole moiety and a 5-chloro-2-methoxyphenyl carboxamide at the pyrrole ring, significantly increased F508del-CFTR activity. This compound could lead to the synthesis of a novel class of CFTR correctors.     

Template Effects in SN2 Displacements for the Preparation of Pseudopeptidic Macrocycles

Macrocyclisation reactions of C₂‐symmetric pseudopeptides containing central pyridine‐derived spacers are affected by the presence of different anions. The selection of the proper anion gives excellent results for the preparation of the corresponding macrocyclic structures. Kinetic studies show that the presence of those anions enhances both the yield and the rate of the reaction. Computational studies at the B3LYP/6‐31G* level have allowed us to rationalise the experimental results. The obtained transition states (TSs) show that the interaction between the anion and the open‐chain pseudopeptidic chain has a stabilising effect. The anion stabilises the two TSs involved: the first one, which involves the formation of the initial bond between the two subunits and leads to an open‐chain intermediate, and the second one, which precedes the formation of the cyclic structure. The optimum anion (Br^? when the central spacer is derived from 2,6‐bis(aminomethyl)pyridine, is able to act as a template, in that it forces the two ends of the open‐chain intermediate to approach each other by forming hydrogen bonds with the two amino acid subunits present in the intermediate. This stabilises the second TS to a greater extent than the first one, and thus, favours macrocyclisation over the competing oligomerisation reactions. The computational calculations also allowed us to predict the outcome of new experiments. Accordingly, the synthesis of the pseudopeptidic macrocycle derived from 2,6‐diaminopyridine was not successful under the optimised conditions previously used. Nevertheless, calculations predicted that in this case Cl^? should be more efficient than Br^?, and this was subsequently experimentally confirmed. Interestingly, the presence of different substituents on the constituent amino acids seems to play a minor role in the overall process.     

An Enantiopure Propeller-Like Trityl-Brominated Radical: Bringing Together a High Racemization Barrier and an Efficient Circularly Polarized Luminescent Magnetic Emitter

A new persistent organic free radical has been synthetized with Br atoms occupying the ortho- and para-positions of a trityl core. After the isolation of its two propeller-like atropisomers, Plus (P) and minus (M), their absolute configurations were assigned by a combination of theoretical and experimental data. Remarkably, no hints of racemization were observed up to 60 °C for more than two hours, due to the higher steric hindrance imposed by the bulky Br atoms. Therefore, when compared to its chlorinated homologue (t_1/2=18 s at 60 °C), an outstanding stability against racemization was achieved. A circularly polarized luminescence (CPL) response of both enantiomers was detected. This free radical shows a satisfactory luminescent dissymmetry factor (|g_lum(592 nm)|≈0.7×10⁻³) despite its pure organic nature and low luminescence quantum yield (LQY). Improved organic magnetic CPL emitters derived from the reported structure can be envisaged thanks to the wide possibilities that Br atoms at para-positions offer for further functionalization.