Tailoring strain in SrTiO3 compound by low energy He+ irradiation

The ability to generate a change of the lattice parameter in a near-surface layer of a controllable thickness by ion implantation of strontium titanate is reported here using low energy He+ ions. The induced strain follows a distribution within a typical near-surface layer of 200 nm as obtained from structural analysis. Due to clamping effect from the underlying layer, only perpendicular expansion is observed. Maximum distortions up to 5-7% are obtained with no evidence of amorphisation at fluences of 1E16 He+ ions/cm2 and ion energies in the range 10-30 keV.Comment: 11 pages, 4 figures, Accepted for publication in Europhysics Letter (http://iopscience.iop.org/0295-5075

Rivalry and uncertainty in complementary investments with dynamic market sharing

We study the effects of revenue and investment cost uncertainty, as well non- preemption duopoly competition, on the timing of investments in two complementary inputs, where either spillover-knowledge is allowed or proprietary-knowledge holds. We find that the ex-ante and ex-post revenue market shares play a very important role in firms’ behavior. When competition is considered, the leader’s behavior departs from that of the monopolist firm of Smith (Ind Corp Change 14:639–650, 2005). The leader is justified in following the conventional wisdom (i.e., synchronous investments are more likely), whereas, the follower’s behavior departs from that of the conventional wisdom (i.e., asynchronous investments are more likely)

Effect of Cryogrinding on Chemical Stability of the Sparingly Water-Soluble Drug Furosemide

Purpose To investigate the effect of cryogrinding on chemical stability of the diuretic agent furosemide and its mixtures with selected excipients. Methods Furosemide was ground at liquid nitrogen temperature for 30, 60, 120 and 180 min. Mixtures of furosemide-PVP and furosemide-inulin (1:1) were milled under cryogenic conditions. Materials were analyzed by XRD, UPLC, MS and NMR. Results Upon increasing the milling time, a significant build-up of an unidentified impurity 1, probably the main degradation product, was noticed. Cogrinding of furosemide with PVP and inulin worsened chemical stabilization of the pharmaceutical. The main degradation product formed upon cryomilling was subsequently identified as 4-chloro-5-sulfamoylanthranilic acid (CSA). Based on some theoretical considerations involving specific milling conditions, the milling intensity and an expected specific milling dose have been calculated. Results indicate that cryogenic grinding is capable to initiate mechanically induced decomposition of furosemide.Conclusions Cryogenic grinding can activate and accelerate not only structural changes (solid state amorphization) but also chemical decomposition of pharmaceuticals. A cryogenic milling device should be considered as a chemical reactor, where under favourable conditions chemical reactions could be mechanically initiated

Corporate Policies with Temporary and Permanent Shocks

International audienceWe model the financing, cash holdings, and hedging policies of a firm facing financing frictions and subject to permanent and transitory cash flow shocks. The permanent and transitory shocks generate distinct, sometimes opposite, effects on corporate policies. We use the model to develop a rich set of empirical predictions. In our model, correlated permanent and transitory shocks imply less risk, lower cash savings, and a drop in the value of credit lines. The composition of cash-flow shocks affects the cash-flow sensitivity of cash, which can be positive or negative. Optimal hedging of permanent and transitory shocks may involve opposite position

Interactions between dislocations and interfaces - consequences for metal and ceramic plasticity

Interactions between dislocations and grain boundaries contribute significantly to plastic behaviour in polycrystalline metals. But a full understanding of the processes and of their influence on plastic response has yet to be achieved. In the present paper, the elementary interaction mechanisms, from the entrance of dislocations in grain boundaries to the relaxation of the resulting intergranular stresses, are briefly reviewed. They are examined for two types of deformation tests and two types of materials: low temperature deformation and relaxation in copper and creep behaviour of alumina. Only the comparison between the response at different scales (nanoscopic, microscopic and mesoscopic) allows us to analyse the response of grain boundaries to an applied stress and to propose an interpretation of their role in macroscopic behaviour. This work may be considered as a preliminary step towards "Interface Engineering"

Resolving the structure of the E-1 state of Mo nitrogenase through Mo and Fe K-edge EXAFS and QM/MM calculations

Biological nitrogen fixation is predominately accomplished through Mo nitrogenase, which utilizes a complex MoFe7S9C catalytic cluster to reduce N-2 to NH3. This cluster requires the accumulation of three to four reducing equivalents prior to binding N-2; however, despite decades of research, the intermediate states formed prior to N-2 binding are still poorly understood. Herein, we use Mo and Fe K-edge X-ray absorption spectroscopy and QM/MM calculations to investigate the nature of the E-1 state, which is formed following the addition of the first reducing equivalent to Mo nitrogenase. By analyzing the extended X-ray absorption fine structure (EXAFS) region, we provide structural insight into the changes that occur in the metal clusters of the protein when forming the E-1 state, and use these metrics to assess a variety of possible models of the E-1 state. The combination of our experimental and theoretical results supports that formation of E-1 involves an Fe-centered reduction combined with the protonation of a belt-sulfide of the cluster. Hence, these results provide critical experiment and computational insight into the mechanism of this important enzyme