The Josiphos ligand family is arguably one of the most versatile classes of chiral ligands with a wide range of applications, including one of the two largest known enantioselective catalytic hydrogenations. In this personal account, we take a look back at the beginning and describe the role Antonio Togni has played to reach this point and the significance of his contributions for the commercial success, especially concerning today's ligand business of Solvias. This seems a fitting point in time in light of Antonio’s statement on his ETH home page that he ‘is working as a professor at this institution since 1992 (a few more months to go), not looking for a job’ and that the three authors have already retired for some time (H. U. B.) or are about to retire soon (B. P., F. S.). 相似文献
We consider isotropic scalar diffusion boundary value problems whose diffusion coefficients are piecewise constant with respect to a partition of space into Lipschitz subdomains. We allow so-called material junctions where three or more subdomains may abut. We derive a boundary integral equation of the second kind posed on the skeleton of the subdomain partition that involves, as unknown, only one trace function at each point of each interface. We prove the well-posedness of the corresponding boundary integral equations. We also report numerical tests for Galerkin boundary element discretisations, in which the new approach proves to be highly competitive compared to the well-established first kind direct single-trace boundary integral formulation. In particular, GMRES seems to enjoy fast convergence independent of the mesh resolution for the discrete second kind BIE. 相似文献
It is proved that a real cubic unit u, whose other two conjugates are also real, is almost always a fundamental unit of the order Z[u]. The exceptions are shown to consist of a single infinite family together with one sporadic case. This is an analogue of Nagell's theorem for the negative discriminant case i.e. the case where u does not have any real conjugate. 相似文献
Plane quartic curves given by equations of the form y2=P(x) with polynomials P of degree 4 represent singular models of elliptic curves which are directly related to elliptic integrals in the form studied
by Euler and for which he developed his famous addition formulas. For cubic curves, the well-known secant and tangent construction
establishes an immediate connection of addition formulas for the corresponding elliptic integrals with the structure of an
algebraic group. The situation for quartic curves is considerably more complicated due to the presence of the singularity.
We present a geometric construction, similar in spirit to the secant method for cubic curves, which defines an addition law
on a quartic elliptic curve given by rational functions. Furthermore, we show how this addition on the curve itself corresponds
to the addition in the (generalized) Jacobian variety of the curve, and we show how any addition formula for elliptic integrals
of the form ò(1/?{P(x)}) dx\int (1/\sqrt{P(x)})\,\mathrm{d}x with a quartic polynomial P can be derived directly from this addition law. 相似文献
Experimental results of the implementation of our concept of neutral gain modules (NGM) in high-power thin-disk lasers are presented. To demonstrate power scalability and high brightness, series of NGMs comprising up to four Yb:YAG thin-disk laser modules have been integrated in various ways into stable and unstable resonators. Furthermore, to compensate for the parabolic component of the remaining thermal lens effects in the high-power regime, an intracavity deformable mirror was embedded. On the basis of the underlying concept, in our experiments an output power of nearly 3 kW with a beam propagation factor $M^2 = 5$ as well as a brightness up to $B = 21\,{\rm GW}/{\rm cm ^2} \, {\rm sr }$ could be demonstrated. Compensating systematically for the nonparabolic components of the phase aberrations, the concept also enables a further enhancement of the beam quality. The principle is transferable to other laser configurations, e.g., master oscillator power amplifier systems. 相似文献
Bromine does not add to phosphorus in a 2-phosphaindolizine 1 but substitutes its 1-position. The 1-bromo derivatives 2 are best prepared with Br2/NEt3 or N-bromosuccinimide. Their hydrolysis is remarkable; it involves a debromination of C-1, an oxidation of P and a selective opening of the P/C-3 bond. PCl3 also causes a substitution of the 1-position. The resulting 1-dichlorophosphino derivatives 5 easily undergo a substituent exchange at the exocyclic phosphorus. More 1-phosphino derivatives are formed in the reaction of 1 with phenyl and diazaphospholyl dichlorophosphine. 相似文献
Self-assembling properties of deoxyguanosine 5'-monophosphate in isotropic solutions of concentrations from 0.5 wt% to 15
wt% were investigated by dynamic light scattering (DLS) and 31P NMR spectroscopy. A slow diffusive mode with a diffusion coefficient Dslow∼ 10-12 m2/s was detected by DLS for the whole concentration range. This mode is assigned to the translational motion of large globular
aggregates, similar to those observed in DNA and other polyelectrolyte solutions. The existence of such aggregates was confirmed
by freeze fracture electron microscopy. Close to the isotropic-cholesteric phase transition, at 4 wt%
c
10 wt%, also a faster diffusive mode is observed in the polarized DLS response and a very fast mode is detected by depolarized
DLS. These modes are related to translational and rotational diffusion of the columnar stacks of guanosine molecules, which
are favorably formed in the relatively narrow pretransitional region. The stacking was also revealed from the appearance of
a secondary resonance line in the 31P NMR spectra. Using the hydrodynamic theory of Tirado and Garcia de la Torre, the length of the cylindrical stacks was found
to be L = 364±78 ?, which is significantly larger than the values reported for other guanosine derivatives.
Received 13 July 2001 and Received in final form 17 October 2001 相似文献
A sextupole magnet can be used as a velocity selector for paramagnetic atoms by suppressing the higher harmonic trajectories by a thin diaphragmstripe in the center of the magnet. Beams with a relative half-width of the velocity distribution of 4% and an intensity of 5 · 1012 particles/sec through an opening with a diameter of 0.5 mm can be produced. 相似文献
Ethanol, a promising alternative fuel, can be produced by the simultaneous saccharification and fermentation (SSF) of lignocellulosic biomass, which combines the enzymatic hydrolysis of cellulose to glucose and the fermentation of glucose to ethanol by yeast in a single step.
A mathematical model that depicts the kinetics of SSF has been developed based on considerations of the quality of the substrate and enzyme, and the substrate-enzyme-microorganism interactions. Critical experimentation has been performed in conjunction with multiresponse nonlinear regression analysis to determine key model parameters regarding cell growth and ethanol production. The model will be used for rational SSF optimization and scale-up.
Studies on Metal Chelates with Cuproine and Ferroine Type Ligands. VI. Investigations on Structure and Bonding in Sulphato(cuproine) and Sulphato-(ferroine)copper(II) Chelates Copper(II) chelates of the general formula Cu(N–N)SO4, where (N–N) = bipy, phen, bich, dmch, and dmp2, were examined by means of the IR-, VIS-, and ESR-techniques. The structures derived from these results are given. For CubipySO4 · 2 H2O and CuphenSO4 · 2 H2O the MO-parameters were calculated. Strong covalent out-of-plane-π-bondings indicating π-acceptor properties of the ligands were found to be present. 相似文献