Zu dem Nachweis von Quecksilber in Verziftunef?llen

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Role of disorder and anharmonicity in the thermal conductivity of silicon-germanium alloys: a first-principles study

The thermal conductivity of disordered silicon-germanium alloys is computed from density-functional perturbation theory and with relaxation times that include both harmonic and anharmonic scattering terms. We show that this approach yields an excellent agreement at all compositions with experimental results and provides clear design rules for the engineering of nanostructured thermoelectrics. For Si(x)Ge(1-x), more than 50% of the heat is carried at room temperature by phonons of mean free path greater than 1 μm, and an addition of as little as 12% Ge is sufficient to reduce the thermal conductivity to the minimum value achievable through alloying. Intriguingly, mass disorder is found to increase the anharmonic scattering of phonons through a modification of their vibration eigenmodes, resulting in an increase of 15% in thermal resistivity.     

Literatur

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Gompertz zero-inflated cure rate regression models applied to credit risk data

In the financial market, it is important to consider that there is a proportion of customers that have settled their debt in time zero, immediately recovering their ability to pay. In this context, in this paper, we propose a survival analysis methodology that allows the insertion of times equal to zero in scenarios where credit risk is observed. The proposed model addresses the survival analysis model of the zero-inflated cure rate which incorporates the heterogeneity of three subgroups (individuals having events in the initial time, and individuals not susceptible and susceptible to the event). In our proposal, all available survival data of customers are modeled considering that the number of competitive causes follows a Poisson distribution and the baseline risk function follows a Gompertz distribution. The model parameter estimation is obtained by the maximum likelihood estimation procedure and simulation studies are conducted to evaluate the estimators' performance. The studied methodology will be applied to a credit database provided by a financial institution in Brazil.     

Organocatalytic,Asymmetric Eliminative [4+2] Cycloaddition of Allylidene Malononitriles with Enals: Rapid Entry to Cyclohexadiene‐Embedding Linear and Angular Polycycles

A direct aminocatalytic synthesis has been developed for the chemo‐, regio‐, diastereo‐, and enantioselective construction of densely substituted polycyclic carbaldehydes containing fused cyclohexadiene rings. The chemistry utilizes, for the first time, remotely enolizable π‐extended allylidenemalononitriles as electron‐rich 1,3‐diene precursors in a direct eliminative [4+2] cycloaddition with both aromatic and aliphatic α,β‐unsaturated aldehydes. The generality of the process is demonstrated by approaching 6,6‐, 5,6‐, 7,6‐, 6,6,6‐, and 6,5,6‐fused ring systems, as well as biorelevant steroid‐like 6,6,6,6,5‐ and 6,6,6,5,6‐rings. A stepwise reaction mechanism for the key [4+2] addition is proposed as a domino bis‐vinylogous Michael/Michael/retro‐Michael reaction cascade. The utility of the malononitrile moiety as traceless activating group of the dicyano nucleophilic substrates is demonstrated.     

First examples of oxaphosphirane pentacarbonylchromium(0) and -molybdenum(0) complexes: synthesis, structures and reactions

Synthesis of the first oxaphosphirane chromium(0) and molybdenum(0) complexes of the type [{(R(1)PCH(R(2))-O}M(CO)(5)] (R(1) = C(5)Me(5)) (8a-e, 15a-e) and (R(1) = CH(SiMe(3))(2)) (9a-e, 16a-e) via reaction of dichloro(organo)- (1, 2, 10, 11) and chloro(organo)phosphane complexes (3,4,12) with lithium bases and aldehydes 7a-e is reported. Furthermore, bicyclic 1,3-oxaphospholane complexes 17 and 18 have been obtained via O-protonation of oxaphosphirane complexes 8a and 15a with HCl. All complexes were characterized by NMR, IR spectroscopic, mass spectrometric investigations and, in addition, single-crystal X-ray structures of complexes 8a-e, 9a,c, 15a,b,e, 16a-c, 17, 18 are presented and discussed.     

Poly(ester urethane) guides for peripheral nerve regeneration

A biocompatible and elastomeric PU was synthesized from low-molecular-weight PCL as macrodiol, CMD as chain extender and HDI as chain linker for applications in the field of peripheral nerve repair. PU cast films supported in vitro attachment and proliferation of NOBEC. The in vitro adhesion and proliferation of S5Y5 neuroblastoma cells on the inner surface of uncoated, gelatin- and PL-coated PU guides were compared. Due to their superior in vitro performance, PL-coated PU guides were tested in vivo for the repair of 1.8 cm-long defects in rat sciatic nerves. The progressive regeneration was confirmed by EMG and histological analysis showing the presence of regenerating fibers in the distal stumps.