IT Capital Elasticity of Production: Estimates using Corporate Data

We calibrate a key parameter of growth accountingthe IT capital elasticity of productionby using the share of returns to IT capital in value added (Mairesse, Cette, and Kocoglu, 2000). To estimate this vital parameter econometrically, we use a set of French business data compiled from standard corporate income tax returns (Bénéfices Réels Normaux) and employers annual declarations of payroll data (Déclarations Annuelles de Données Sociales). These data provide information on the stock of tangible fixed assets in the office equipment, furniture, and IT categories. We developed our measure of IT capital from this fixed-asset item. Our results suggest an IT capital elasticity of production of 0.9%, substantially above the 0.5% share of return on IT capital in production. Various robustness tests corroborate this result, which seems due to the likely existence of excess return on IT capitala quantity that cannot be measured with the traditional growth-accounting method.Computerization, ICT, Productivity

Reluctant Cross-Metathesis Reactions: The Highly Beneficial Effect of Microwave Irradiation

carbene complexes ; catalysis ; cross coupling ; metathesis ; olefinationInternational audienceThe beneficial effect of microwave irradiation versus classical thermal conditions is demonstrated through a series of comparative cross-metathesis reactions

Anion–π Enzymes

In this report, we introduce artificial enzymes that operate with anion-π interactions, an interaction that is essentially new to nature. The possibility to stabilize anionic intermediates and transition states on an π-acidic surface has been recently demonstrated, using the addition of malonate half thioesters to enolate acceptors as a biologically relevant example. The best chiral anion-π catalysts operate with an addition/decarboxylation ratio of 4:1, but without any stereoselectivity. To catalyze this important but intrinsically disfavored reaction stereoselectively, a series of anion-π catalysts was equipped with biotin and screened against a collection of streptavidin mutants. With the best hit, the S112Y mutant, the reaction occurred with 95% ee and complete suppression of the intrinsically favored side product from decarboxylation. This performance of anion-π enzymes rivals, if not exceeds, that of the best conventional organocatalysts. Inhibition of the S112Y mutant by nitrate but not by bulky anions supports that contributions from anion-π interactions exist and matter, also within proteins. In agreement with docking results, K121 is shown to be essential, presumably to lower the p K a of the tertiary amine catalyst to operate at the optimum pH around 3, that is below the p K a of the substrate. Most importantly, increasing enantioselectivity with different mutants always coincides with increasing rates and conversion, i.e., selective transition-state stabilization

Using Rock-Eval 6 pyrolysis for tracking fossil organic carbon in modern environments: implications for the roles of erosion and weathering.

This work relates to the debate on the fossil organic carbon (FOC) input in modern environments and its possible implication for the carbon cycle, and suggests the use of Rock-Eval 6 pyrolysis as a relevant tool for tracking FOC in such environments. Considering that such a delivery is mainly due to supergene processes affecting the continental surface, we studied organic matter in different reservoirs such as bedrocks, alterites, soils and rivers in two experimental catchments at Draix (Alpes de Haute Provence, France). Samples were subjected to geochemical (Rock-Eval 6 pyrolysis) investigations and artificial bacterial degradations. After comparing the geochemical fingerprint of samples, geochemical markers of FOC were defined and tracked in the different reservoirs. Our results confirm the contribution of FOC in modern soils and rivers and display the various influences of weathering and erosional processes on the fate of FOC during its exchange between these pools. In addition, the contrasting behaviour of these markers upon the supergene processes has also highlighted the refractory or labile characters of the fossil organic matter (FOM). Bedrock to river fluxes, controlled by gully erosion, are characterized by a qualitative and quantitative preservation of FOM. Bedrock to alterite fluxes, governed by chemical weathering, are characterized by FOC mineralization without qualitative changes in deeper alterites. Alterite to soils fluxes, controlled by (bio)chemical weathering, are characterized by strong FOC mineralization and qualitative changes of FOM. Thus weathering and erosional processes induce different FOM evolution and affect the fate of FOC towards the global carbon cycle. In this study, gully erosion would involve maintenance of an ancient sink for the global carbon cycle, while (bio)chemical processes provide a source of CO2. Finally, this study suggests that Rock-Eval 6 pyrolysis can be considered as a relevant tool for tracking FOC in modern environments

Anion-π catalysis: Bicyclic products with four contiguous stereogenic centers from otherwise elusive diastereospecific domino reactions on π-acidic surfaces

Anion–π interactions have been introduced recently to catalysis. The idea of stabilizing anionic intermediates and transition states on π-acidic surfaces is a new fundamental concept. By now, examples exist for asymmetric enolate, enamine, iminium and transamination chemistry, and the first anion–π enzyme has been created. Delocalized over large aromatic planes, anion–π interactions appear particularly attractive to stabilize extensive long-distance charge displacements during domino processes. Moving on from the formation of cyclohexane rings with five stereogenic centers in one step on a π-acidic surface, we here focus on asymmetric anion–π catalysis of domino reactions that afford bicyclic products with quaternary stereogenic centers. Catalyst screening includes a newly synthesized, better performing anion–π version of classical organocatalysts from cinchona alkaloids, and anion–π enzymes. We find stereoselectivities that are clearly better than the best ones reported with conventional catalysts, culminating in unprecedented diastereospecificity. Moreover, we describe achiral salts as supramolecular chirality enhancers and report the first artificial enzyme that operates in neutral water with anion–π interactions, i.e., interactions that are essentially new to enzymes. Evidence in support of contributions of anion–π interactions to asymmetric catalysis include increasing diastereo- and enantioselectivity with increasing rates, i.e., asymmetric transition-state stabilization in the presence of π-acidic surfaces and inhibition with the anion selectivity sequence NO3− > Br− > BF4− > PF6−

Improved efficiency of PbS quantum dot sensitized NiO photocathodes with naphthalene diimide electron acceptor bound to the surface of the nanocrystals

Hybrid materials combining a wide bandgap metal oxide semiconductor, metal chalcogenide nanocrystals and molecular systems represent very attractive materials for fabricating devices with new function or improved photoelectrochemical performance. This study deals with sensitization of NiO, which is a p-type semiconductor, by quantum dots (QDs) of PbS with an average diameter of 3 nm. The PbS QDs were attached to the monocrystalline film of NiO by mercaptopropionic acid linker and were subsequently capped with methyl-pyridine naphthalene diimide (NDI) units to prepare quantum dot sensitized solar cells (p-QDSSCs) on NiO electrodes. Time-resolved photoluminescence measurements of the PbS emission were used to determine the rate constants for charge transfer from the PbS exciton to the NiO, cobalt based redox mediator and NDI. Notably, it was shown that NDI quenches the PbS exciton by electron transfer with a quite fast rate constant (6.9 × 107 s−1). The PbS QDs sensitized NiO films were finally used to fabricate solar cells with tris(4,4′-ditert-butyl-2,2′-bipyridine) cobalt(III/II) as redox mediator. It was observed that the presence of NDI on PbS improved the photovoltaic performance by 50% relative to that of cells without NDI, leading to a device with the following characteristics: Jsc = 5.75 mA/cm2, Voc = 226 mV, ff = 34% and PCE = 0.44%. This study demonstrates that photogalvanic processes can be a productive pathway to better performing sensitized p-type semiconductor for p-QDSSC. In other words, photoinduced electron transfer from the QDs towards the electrolyte rather than initial photoinduced charge injection into the p-type semiconductor can be a favorable operative mechanism in QD sensitized NiO films and might be exploited further for the construction of better performing solar cells or photocatalytic devices

Maxillary sinus textiloma: a case report

<p>Abstract</p> <p>Introduction</p> <p>Textilomas have been reported in many locations. We report the first case of textiloma located in the maxillary sinus that mimicked a sinus cyst recurrence on computed tomography images.</p> <p>Case presentation</p> <p>A 60-year-old Caucasian man was referred for persistent infection of the right maxillary sinus. A maxillary sinus benign cyst had been removed three months before. Computed tomography showed a sinus opacity evoking a cyst recurrence. A new operation was planned to remove the cyst by a Caldwell-Luc approach. After excision of very thick fibrous tissue, a compress was discovered in the maxillary sinus. The patient did not present with any sinus infection after the operation.</p> <p>Conclusion</p> <p>The surgeon should always take into account the possibility of textilomas in a patient with a history of sinus surgery.</p

A Dual Anchoring Strategy for the Directed Evolution of Improved Artificial Transfer Hydrogenases Based on Carbonic Anhydrase

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A robust collagen scoring method for human liver fibrosis by second harmonic microscopy.

International audienceSecond Harmonic Generation (SHG) microscopy offers the opportunity to image collagen of type I without staining. We recently showed that a simple scoring method, based on SHG images of histological human liver biopsies, correlates well with the Metavir assessment of fibrosis level (Gailhouste et al., J. Hepatol., 2010). In this article, we present a detailed study of this new scoring method with two different objective lenses. By using measurements of the objectives point spread functions and of the photomultiplier gain, and a simple model of the SHG intensity, we show that our scoring method, applied to human liver biopsies, is robust to the objective's numerical aperture (NA) for low NA, the choice of the reference sample and laser power, and the spatial sampling rate. The simplicity and robustness of our collagen scoring method may open new opportunities in the quantification of collagen content in different organs, which is of main importance in providing diagnostic information and evaluation of therapeutic efficiency

Chimeric streptavidins as host proteins for artificial metalloenzymes

The streptavidin scaffold was expanded with well-structured naturally occurring motifs. These chimeric scaffolds were tested as hosts for biotinylated catalysts as artificial metalloenzymes (ArM) for asymmetric transfer hydrogenation, ring-closing metathesis and anion−π catalysis. The additional second coordination sphere elements significantly influence both the activity and the selectivity of the resulting hybrid catalysts. These findings lead to the identification of propitious chimeric streptavidins for future directed evolution efforts of artificial metalloenzymes