Moral Hazard Under Ambiguity

In this paper, we extend the classical Holmström and Milgrom contracting problem, by adding uncertainty on the volatility of the output for both the Agent and the Principal. We study more precisely the impact of the “Nature” playing against the Agent and the Principal, by choosing the worst possible volatility of the output. We solve the first-best and the second-best problems in this framework, and we show that optimal contracts are in a class of contracts linear with respect to the output and its quadratic variation. We also present a general modus operandi to apply our method.     

The minimum distance superset problem: formulations and algorithms

The partial digest problem consists in retrieving the positions of a set of points on the real line from their unlabeled pairwise distances. This problem is critical for DNA sequencing, as well as for phase retrieval in X-ray crystallography. When some of the distances are missing, this problem generalizes into a “minimum distance superset problem”, which aims to find a set of points of minimum cardinality such that the multiset of their pairwise distances is a superset of the input. We introduce a quadratic integer programming formulation for the minimum distance superset problem with a pseudo-polynomial number of variables, as well as a polynomial-size integer programming formulation. We investigate three types of solution approaches based on an available integer programming solver: (1) solving a linearization of the pseudo-polynomial-sized formulation, (2) solving the complete polynomial-sized formulation, or (3) performing a binary search over the number of points and solving a simpler feasibility or optimization problem at each step. As illustrated by our computational experiments, the polynomial formulation with binary search leads to the most promising results, allowing to optimally solve most instances with up to 25 distance values and 8 solution points.     

Efficient guanidination of the phosphate linkage towards cationic phosphoramidate oligonucleotides

An efficient postsynthesis method of guanidination of oligonucleotides was employed to introduce several guanidinium groups into internucleotide phosphoramidate linkages. The amino functions of aminobutylphosphoramidate links were converted to guanidine butylphosphoramidates using a solution of O-methylisourea hemisulfate in aqueous ammonia, in a short reaction time. The synthesis of various fully guanidylated oligonucleotides was successfully performed to provide a new class of cationic phosphoramidate oligonucleotides.     

Electronic conductivity and structural chemistry in Li-Te-V oxide glasses

The electronic conductivity of the Li₂O-Te₂V₂O₉ glass system reveals that, even for high lithium content, electron hopping occurs between V⁴⁺ and V⁵⁺. The study of the V⁴⁺ content versus various syntheses shows that more than lithium content, the nature of the counter ion used in Li⁺ reagent and its decomposition behavior are responsible for the efficiency of the spontaneous V⁵⁺ reduction via a ‘sprouting’ phenomenon. The electron hopping process implies interconnection of VO_n polyhedra which are accessible for both V⁴⁺ and V⁵⁺ species. Such fact gives information about short and medium range ordering in the glasses. On the basis of the LiVTeO₅ crystal structure and in agreement with wide angle X-ray scattering experiments, a possible rearrangement bringing together VO₅ square pyramids is proposed to explain the electron hopping. Such proposal corresponds to a lithium network forming effect. It could explain why for Li/V>1 the electronic conductivity increases with lithium content while the V⁴⁺ amount remains low.     

New synthesis of chalcogenolactones. 1H,3H-benzo[c]selenophen-1-one, 1H,3H-benzo[c]tellurophen-1-one and the related 3,4-dihydro-1H-2-benzoselenin-1-one and 3,4-dihydro-1H-2-benzotellurin-1-one

The synthesis of three new basic heterocyclic systems namely, 1H,3H-benzo[c]tellurophen-1-one (2-tellurophthalide), 3,4-dihydro-1H-2-benzoselenin-1-one (3,4-dihydro-2-isoselenocoumarin) and 3,4-dihydro-1H-2-benzotellurin-1-one (3,4-dihydro-2-isotellurocoumarin), is reported through the cyclisation of o-(bromoalkyl)benzoyl chlorides.     

Switchable neutral bistable rotaxanes

Two switchable neutral bistable [2]rotaxanes have been synthesized, and their chemically induced mechanical switching has been studied in solution by 1H NMR spectroscopy. One of the rotaxanes was prepared by a thermodynamically controlled slippage mechanism, while the other rotaxane was obtained by a dynamic covalent chemistry protocol involving the assembly of its dumbbell component by olefin metathesis. The recognition sites present in the rod section of the dumbbell component, namely, naphthodiimide (NpI) and pyromellitic diimide (PmI) residues, were chosen in the knowledge that the ring component, 1,5-dinaphtho[38]crown-10 (1/5DNP38C10), will bind preferentially to the NpI site. However, upon introduction of Li+ ions into the solution, a 1:2 complex is formed between the PmI site, encircled by the 1/5DNP38C10 ring and two Li+ ions. Since this complex is more stable overall than the binding between the 1/5DNP38C10 ring and the NpI site, the ring component moves from the NpI site to the PmI one. This mechanical movement can be reversed by adding an excess of [12]crown-4 to the solution to act as a sequestering agent for the Li+ ions.     

Nanoparticles of iron(II) spin-crossover

We report the synthesis of spin crossover 69 nm spherical nanoparticles of [Fe(NH(2)-trz)(3)](Br)(2).3H(2)O.0.03(surfactant) (NH(2)trz = 4-amino-1,2,4-triazole, surfactant = Lauropal), prepared by the reverse micelle technique, which exhibit at room temperature a thermal hysteresis characterized by magnetic, diffuse reflectivity and Raman studies.