Acousto-optic-assisted diffuse optical tomography

We introduce and experimentally demonstrate acousto-optic-assisted diffuse optical tomography (DOT) using a holography-based acousto-optic setup. The method is based on probing a scattering medium with a localized acoustical modulation of the phase of the scattered light. The optical properties of the scattering medium are recovered with ultrasound-limited resolution by applying DOT reconstruction methods on a set of the measured intensities of light, modulated at different locations throughout the medium.     

Effectivity functions and simple games

The rather new notion of effectivity function is related to the notion of simple game. Every effectivity function is associated with a simple game. So theory about simple games may be applicable to effectivity functions. E.g. if the effectivity function is additive, then the associated simple game is weighted. Via a characterization of weighted simple games it is possible to characterize maximal additive effectivity functions.Finally we characterize additive effectivity functions and their associated simple games.I thank G.J. Otten for useful comments and stimulating conversations.     

Identification of non-optimal arcs for the travelling salesman problem

Conditions are presented for the identification of (directed) arcs for the traveling salesman problem, that can be eliminated with at least one optimal solution remaining. The conditions are not based on lower or upper bounds; the presence of an identified arc in a solution implies that the solution is not 3-optimal. An example illustrates how to use the conditions.     

Stereospecific access to branched-chain carbohydrate synthons.

Appropriate precursors for the synthesis of D-vancosamine and L-evernitrose have been stereospecifically obtained from methyl 4,6-O-benzylidene-2-deoxy-α- and β-D-threo-hexopyranosid-3-ulose.     

On the behavior of the solution of the Burgers equation as the viscosity goes to zero

The solution of the initial boundary-value problem u_?′ ? ?D²u_? + u_?Du_? = f on (a, b) x(0, T), u_?(a, t) = u_?(b, t) = 0 and u_?(x, 0) = 0 on (a, b), is shown to converge to the solution of the limiting equation as the viscosity tends to zero. Estimates on the rate of convergence are given.     

Low Pressure Carbonylation of Benzyl Carbonates and Carbamates for Applications in 13C Isotope Labeling and Catalytic CO2 Reduction

Herein, we report a methodology to access isotopically labeled esters and amides from carbonates and carbamates employing an oxygen deletion strategy. This methodology utilizes a decarboxylative carbonylation approach for isotope labeling with near stoichiometric, ex situ generated ¹²C, or ¹³C carbon monoxide. This reaction is characterized by its broad scope, functional group tolerance, and high yields, which is showcased with the synthesis of structurally complex molecules. A complementary method that operates by the catalytic in situ generation of CO via the reduction of CO₂ liberated during decarboxylation has also been developed as a proof-of-concept approach that CO₂-derived compounds can be converted to CO-containing frameworks. Mechanistic studies provide insight into the catalytic steps which highlight the impact of ligand choice to overcome challenges associated with low-pressure carbonylation methodologies, along with rational for the development of future methodologies.     

Structure of mixed beta-lactoglobulin/pectin adsorbed layers at air/water interfaces; a spectroscopy study

Based on earlier reported surface rheological behaviour two factors appeared to be important for the functional behaviour of mixed protein/polysaccharide adsorbed layers at air/water interfaces: (1) protein/polysaccharide mixing ratio and (2) formation history of the layers. In this study complexes of beta-lactoglobulin (positively charged at pH 4.5) and low methoxyl pectin (negatively charged) were formed at two mixing ratios, resulting in negatively charged and nearly neutral complexes. Neutron reflection showed that adsorption of negative complexes leads to more diffuse layers at the air/water interface than adsorption of neutral complexes. Besides (simultaneous) adsorption of protein/polysaccharide complexes, a mixed layer can also be formed by adsorption of (protein/)polysaccharide (complexes) to a pre-formed protein layer (sequential adsorption). Despite similar bulk concentrations, adsorbed layer density profiles of simultaneously and sequentially formed layers were persistently different, as illustrated by neutron reflection analysis. Time resolved fluorescence anisotropy showed that the mobility of protein molecules at an air/water interface is hampered by the presence of pectin. This hampered mobility of protein through a complex layer could account for differences observed in density profiles of simultaneously and sequentially formed layers. These insights substantiated the previously proposed organisations of the different adsorbed layers based on surface rheological data.     

Tandem queueing networks with neighbor blocking and back-offs

We introduce a novel class of tandem queueing networks which arise in modeling the congestion behavior of wireless multi-hop networks with distributed medium access control. These models provide valuable insight in how the network performance in terms of throughput depends on the back-off mechanism that governs the competition among neighboring nodes for access to the medium. The models fall at the interface between classical queueing networks and interacting particle systems, and give rise to high-dimensional stochastic processes that challenge existing methodologies. We present various open problems and conjectures, which are supported by partial results for special cases and limit regimes as well as simulation experiments.     

Dynamics of species in a model with two predators and one prey

In this paper, we study a predator-prey model which has one prey and two predators with Beddington-DeAngelis functional responses. Firstly, we establish a set of sufficient conditions for the permanence and extinction of species. Secondly, the periodicity of positive solutions is studied. Thirdly, by using Liapunov functions and the continuation theorem in coincidence degree theory, we show the global asymptotic stability of such solutions. Finally, we give some numerical examples to illustrate the behavior of the model.     

Copper(II) Triflate Catalyzed Amination of 1,3‐Dicarbonyl Compounds

A method to prepare α,α‐acyl amino acid derivatives efficiently by Cu(OTf)₂+1,10‐phenanthroline (1,10‐phen)‐catalyzed amination of 1,3‐dicarbonyl compounds with PhI?NSO₂Ar is described. The mechanism is thought to initially involve aziridination of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, by the putative copper–nitrene/imido species generated from the reaction of the metal catalyst with the iminoiodane source. Subsequent ring opening of the resultant aziridinol adduct under the Lewis acidic conditions then provided the α‐aminated product. The utility of this method was exemplified by the enantioselective synthesis of a precursor of 3‐styryl‐2‐benzoyl‐L ‐alanine.