Synthesis and structural characterisation as 12-helix of the hexamer of a beta-amino acid tethered to a pyrrolidin-2-one ring

Starting from (3S,4R,1'S)-3-amino-2-oxo-1-[1'-(4-methoxyphenylethyl)]pyrrolidine carboxylic acid (2), the first synthesis of a beta-foldamer containing pyrrolidin-2-one rings is described, whose 12-helix conformation is assigned by NMR analysis and confirmed by molecular dynamics (MD) simulations.     

Cosmology with Gravitational Waves: A Review

Standard sirens have been the central paradigm in gravitational-wave cosmology so far. From the gravitational wave signature of compact star binaries, it is possible to measure the luminosity distance of the source directly, and if additional information on the source redshift is provided, a measurement of the cosmological expansion can be performed. This review article discusses several methodologies that have been proposed to use gravitational waves for cosmological studies. Methods that use only gravitational-wave signals and methods that use gravitational waves in conjunction with additional observations such as electromagnetic counterparts and galaxy catalogs will be discussed. The review also discusses the most recent results on gravitational-wave cosmology, starting from the binary neutron star merger GW170817 and its electromagnetic counterpart and finishing with the population of binary black holes, observed with the third Gravitational-wave Transient Catalog GWTC–3.     

Bulk flow in ferrofluids in a uniform rotating magnetic field

Direct measurements of the bulk flow of a ferrofluid in a uniform rotating magnetic field were obtained using the ultrasonic velocity profile method. The fluid was observed to corotate with the field in a rigid-body-like fashion throughout the bulk of the container, except near the air-fluid interface, where it was observed to counterrotate. The results were found in qualitative agreement with the spin diffusion theory of Zaitsev and Shliomis [J. Appl. Mech. Tech. Phys. 10, 696 (1969)]10.1007/BF00907424.     

Generalized Parton Distributions of 3He and the Neutron Orbital Structure

The two leading twist, quark helicity conserving generalized parton distributions (GPDs) of ³He, accessible, for example, in coherent deeply virtual Compton scattering (DVCS), are calculated in impulse approximation (IA). Their sum, at low momentum transfer, is found to be largely dominated by the neutron contribution, so that ³He is very promising for the extraction of the neutron information. Anyway, such an extraction could be not trivial. A technique, able to take into account the nuclear effects included in the IA analysis in the extraction procedure, even at moderate values of the momentum transfer, is proposed. Coherent DVCS arises therefore as a crucial experiment to access, for the first time, the neutron GPDs and the orbital angular momentum of the partons in the neutron.     

On the normal subgroup lattice of a hypercentral p-group

We describe all hypercentral p-groups G whose lattice of normal subgroups n(G) is isomorphic to n(H) for a group H with hypercenwal derived subgroup and H not a pgroup.     

L-tryptophan transport through a hydrophobic liquid membrane using AOT micelles: dynamics of the process as revealed by small angle X-ray scattering

Hydrophobic liquid membranes have a high technological potential in many fields of separation science. The dynamics of these systems is very complex and still not fully understood. In this work we studied the effect of the incorporation of cationic and anionic L-tryptophan at pH 1.8 and 10.0, respectively, in Aerosol-OT reverse micelles performing small angle X-ray scattering experiments. The use of a synchrotron radiation source allowed efficient in situ data acquisition. Several insights on L-tryptophan transport dynamics through hydrophobic membranes containing AOT could be obtained from these SAXS experiments, such as amino acid site localization and changes in the reverse micelle sizes.     

Computational DFT investigation of vicinal amide group anchimeric assistance in ether cleavage

Density functional theory (DFT) computations in solvent have been used to investigate the mechanism of anchimeric assistance (by a vicinal amide group) in the acid-induced ether cleavage. The calculations were carried out at the B3LYP/6-31G* level of theory via full geometry optimizations within the IEF-PCM continuum solvent model. Two different mechanisms have been investigated here that were previously hypothesized for the rate-determining step of this process: the first (mechanism A1) involves a protonated amide and an ethereal oxygen as the nucleophile, while the second (mechanism A2) involves protonation of the ethereal oxygen followed by a nucleophilic attack of the amide. Computations clearly show that the second (involving protonation of the less basic site) is the most favorite route and leads to the formation of an oxazolidinic intermediate that triggers ether hydrolysis. Results are produced that are in excellent agreement with the experiments, and a rationale for them is provided, which represents a general interpretative basis for similar anchimerically assisted processes, such as the ones characterizing the glycosidic activity of two very important classes of enzymes: beta-hexosaminidases and O-GlcNAcases.     

Synthesis of 2-diphenylphosphinoyl-3,5-(diaryl)-3,4-dihydro-2H-thiopyrans by the reaction of a bis[(diphenylphosphinoyl)methyl]sulfide with chalcones

The NaH-promoted tandem Michael addition/intramolecular Horner-Wittig reaction of bis(diphenylphosphinoylmethyl)sulfide with chalcones afforded 3,4-dihydro-2H-thiopyrans 3a-l in 78-88% yield.     

Nitrogen‐Doped Ordered Mesoporous Carbon Supported Bimetallic PtCo Nanoparticles for Upgrading of Biophenolics

Hydrodeoxygenation (HDO) is an attractive route for the upgrading of bio‐oils produced from lignocellulose. Current catalysts require harsh conditions to effect HDO, decreasing the process efficiency in terms of energy and carbon balance. Herein we report a novel and facile method for synthesizing bimetallic PtCo nanoparticle catalysts (ca. 1.5 nm) highly dispersed in the framework of nitrogen‐doped ordered mesoporous carbon (NOMC) for this reaction. We demonstrate that NOMC with either 2D hexagonal (p6m) or 3D cubic (Im m) structure can be easily synthesized by simply adjusting the polymerization temperature. We also demonstrate that PtCo/NOMC (metal loading: Pt 9.90 wt %; Co 3.31 wt %) is a highly effective catalyst for HDO of phenolic compounds and “real‐world” biomass‐derived phenolic streams. In the presence of PtCo/NOMC, full deoxygenation of phenolic compounds and a biomass‐derived phenolic stream is achieved under conditions of low severity.