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.     

Diastereoselective reduction of alkenylboronic esters as a new method for controlling the stereochemistry of up to three adjacent centers in cyclic and acyclic molecules

[reaction: see text] cis-Boronates are readily available via a diastereoselective Pd-catalyzed reduction of tetrasubstituted alkenylboronic esters using H2. Applying the reaction conditions presented to unsaturated open-chain boronic esters allows the stereochemistry of up to three adjacent centers to be controlled.     

Budding and tubulation in highly oblate vesicles by anchored amphiphilic molecules

We studied local budding and tubulation induced in highly oblate lipid vesicles by the anchoring of either polymers having a hydrophilic backbone and grafted hydrophobic anchor groups, or by oleoyl-coenzyme A, an amphiphilic molecule important in lipid metabolism. The dynamics of bud formation, shrinkage, and readsorption is consistent with an induced spontaneous curvature coupled with local amphiphile diffusion on the membrane. We report a novel metastable state prior to bud readsorption.     

An implementation of Karmarkar's algorithm for linear programming

This paper describes the implementation of power series dual affine scaling variants of Karmarkar's algorithm for linear programming. Based on a continuous version of Karmarkar's algorithm, two variants resulting from first and second order approximations of the continuous trajectory are implemented and tested. Linear programs are expressed in an inequality form, which allows for the inexact computation of the algorithm's direction of improvement, resulting in a significant computational advantage. Implementation issues particular to this family of algorithms, such as treatment of dense columns, are discussed. The code is tested on several standard linear programming problems and compares favorably with the simplex codeMinos 4.0.     

Endomorphisms of stable continuous-trace -algebras

We classify -endomorphisms of stable continuous-trace -algebras up to inner automorphism by a surjective multiplicative invariant taking values in finite-dimensional vector bundles over the spectrum. Specializing to automorphisms, this gives a different approach to results of Lance, Smith, Phillips and Raeburn.

     

A randomized scheme for speeding up algorithms for linear and convex programming problems with high constraints-to-variables ratio

We extend Clarkson's randomized algorithm for linear programming to a general scheme for solving convex optimization problems. The scheme can be used to speed up existing algorithms on problems which have many more constraints than variables. In particular, we give a randomized algorithm for solving convex quadratic and linear programs, which uses that scheme together with a variant of Karmarkar's interior point method. For problems withn constraints,d variables, and input lengthL, ifn = (d ²), the expected total number of major Karmarkar's iterations is O(d ²(logn)L), compared to the best known deterministic bound of O( L). We also present several other results which follow from the general scheme.     

New approach to the stereoselective synthesis of metalated dienes via an isomerization-elimination sequence

Treatment of Cp2ZrBu2 with enol ether containing a remote double bond lead to conjugated metalated diene as single isomer via a tandem isomerization-elimination sequence. 2-Arylsulfonyl 1,3-dienes can also be used as a source of dienyl zirconocene derivatives, and the stereochemistry of the diene is dependent on the transmetalation reaction.     

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]