Molecular dynamics study of the vibrational relaxation of OCl and OCl in the bulk and the surface of water and acetonitrile

The vibrational relaxation of OCl and OCl⁻ in the bulk and the liquid/vapor interface of water and acetonitrile is studied by molecular dynamics computer simulations. Both equilibrium calculations of the vibrational friction and non-equilibrium simulation of the energy relaxation are used to elucidate the factors that influence the rate of energy relaxation in systems that represent polar ionic and non-ionic solutes in polar protic and non-protic solvents. We find that, in agreement with previous experimental and theoretical studies, the relaxation of the ionic solute is much faster than that of the non-ionic solute in both the solvents. However, while the relaxation is slowed down considerably when the non-ionic solute is transferred from the bulk to the interface, no such surface effect is found in the case of the ionic solute. This behavior can be explained by noting that the ionic solute is able to keep its first solvation shell intact upon transfer to the interface and that the main contribution to the friction is due to the Lennard-Jones part of the intermolecular potential.     

Acoustic centering of sources measured by surrounding spherical microphone arrays

The radiation patterns of acoustic sources have great significance in a wide range of applications, such as measuring the directivity of loudspeakers and investigating the radiation of musical instruments for auralization. Recently, surrounding spherical microphone arrays have been studied for sound field analysis, facilitating measurement of the pressure around a sphere and the computation of the spherical harmonics spectrum of the sound source. However, the sound radiation pattern may be affected by the location of the source inside the microphone array, which is an undesirable property when aiming to characterize source radiation in a unique manner. This paper presents a theoretical analysis of the spherical harmonics spectrum of spatially translated sources and defines four measures for the misalignment of the acoustic center of a radiating source. Optimization is used to promote optimal alignment based on the proposed measures and the errors caused by numerical and array-order limitations are investigated. This methodology is examined using both simulated and experimental data in order to investigate the performance and limitations of the different alignment methods.     

Regioselective carbon-carbon bond cleavage in the oxidation of cyclopropenylcarbinols

The strained double bond of cyclopropenylcarbinols undergoes a facile oxidation reaction to lead to unsaturated carbonyl derivatives. The distribution of the formed products depends on the relative stability of carbon-centered radical species, and the Sharpless kinetic resolution leads to enantiomerically pure Baylis-Hillman enal adducts.     

Regio- and stereoselective synthesis of novel (E)-1-alkenyl carbamate via carbocupration reaction

The stereoselective carbocupration and copper-catalyzed carbomagnesiation reactions of alkynyl carbamates are described as a new and straightforward method for the preparation of (E)-alkenyl enol carbamates. [reaction: see text]     

Cyclopropenyllithiums as a new source of 1,1-bismetalated cyclopropyl derivatives

The allylmetalation of functionalised cyclopropenyllithium derivatives leads to the unique formation of 1,1-bismetalated cyclopropyl species that react selectively with different electrophiles.     

Four-component reactions for a new diastereoselective synthesis of chiral quaternary centers

The one-pot preparation of chiral homoallylic alcohol and amine derivatives was easily achieved by carbocupration of alkynyl sulfoxides followed by an in situ zinc homologation and reaction with aldehydes or imines. In this process, three new carbon-carbon bonds were created as well as quaternary and tertiary chiral centers with excellent diastereo- and enantioselectivities.     

New One-Pot Synthesis of ò-Iodoalkyne

A high yielding, one-pot general procedure for the synthesis of ò-iodoalkyne is described.     

Simulation of the shift from marine netcages to inland recirculating aquaculture systems

The recirculating aquaculture system (RAS) is an intensive production line that uses recycled water, and that should operate continuously, year-round, at full capacity. The RAS depends on enhanced water quality and minimized fish stressors, and its profitability relies on maximizing economic productivity per unit volume of rearing space. However, RAS operation requires coordinated management of many unit processes and/or operations. The aim of this study was to optimize operating parameters, including the number of fingerlings in the system, their arrival frequency, and fish weight on entry into the system and into the various stages of sorting along the production line. It was also necessary to minimize the start-up period, i.e. the period between establishment and achievement of full design capacity. A simulation model was developed to further the operating company’s interests, combining discrete-event and continuous-time stochastic simulations, meta-model and optimal-resource configurations—all to maximize annual profits, subject to operational and environmental constraints. Simulation outputs were monthly sales, fish stocking density (kilograms of biomass per cubic meter) and utilization of each culture tank at any given time, and effects of standing stock biomass and feed load on the biofilters. The simulation results were validated and implemented in an aquaculture farm.