Perfluoroalkyl(dithiocarbamato) tellurium(II) compounds

[NMe(4)][R(f)Te(SC(S)NR(2))(2)] derivatives are selectively formed by the oxidation of [NMe(4)]TeR(f) (R(f) = CF(3), C(2)F(5)) with [R(2)NC(S)S](2) (NR(2) = NEt(2), NBz(2), N(CH(2))(4)) in almost quantitative yields. An alternative route to obtain the dithiocarbamato complex anions offer reactions of Te[SC(S)NR(2)](2) (NR(2) = NEt(2), NBz(2)) with equimolar amounts of Me(3)SiR(f) and [NMe(4)]F. Some of the derivatives were recrystallized with bulky cations in order to determine the crystal structures. Structural elucidation by diffraction methods exhibit the structural feature of a distorted pentagonal planar environment (resembling "butterflies") around the tellurium centres. The carbamato tellurates can be transferred easily into the neutral derivatives, R(f)TeSC(S)NR(2), upon treatment with Ag[BF(4)]. In solution they equilibrate with Te(2)(R(f))(2) and [R(2)NC(S)S](2) and finally are transformed into Te(R(f))(2), Te[SC(S)NR(2)](2), and Te[SC(S)NR(2)](4), respectively. All compounds are fully characterized by NMR spectroscopic methods ((1)H, (13)C, (19)F, (125)Te). Additionally, synthesis and characterization of the hitherto unknown derivative [NMe(4)]TeC(2)F(5) are described.     

Polymers of Carbonic Acid, 31. Cyclic Polycarbonates by Hydrolytic Polycondensation of Bisphenol‐A Bischloroformate

The hydrolytic polycondensation of bisphenol‐A bischloroformate in NaOH/CH₂Cl₂ was studied using triethylamine as the catalyst. Reaction conditions were optimized towards high molar masses. The isolated polycarbonates were characterized by means of SEC and MALDI‐TOF mass spectrometry. The fraction of cyclic polycarbonates strongly increased with higher molecular weights and in the best sample only cycles were detectable (up to 50 000 Da). The largest cycles can compete with cyclic DNS of microorganisms.     

Γ-convergence of Variational Integrators for Constrained Systems

For a physical system described by a motion in an energy landscape under holonomic constraints, we study the Γ-convergence of variational integrators to the corresponding continuum action functional and the convergence properties of solutions of the discrete Euler–Lagrange equations to stationary points of the continuum problem. This extends the results in Müller and Ortiz (J. Nonlinear Sci. 14:279–296, 2004) to constrained systems. The convergence result is illustrated with examples of mass point systems and flexible multibody dynamics.      

Optimal Control of Multibody Dynamics with Contact

This work discusses two different structure preserving integrators in the framework of optimal control simulations with contact. The first one is a variational integrator, based on the constrained version of the Lagrange-D'Alembert. The resulting scheme preserves the symplecticity and the momentum maps of the simulated multibody dynamics. The second integrator is an energy momentum scheme and it is based on the augmented Hamiltonian equations, which are discretised using the discrete derivative in [2]. Both integrators are applied to simulate the optimal control of compass gait, for which the contact between the foot and the ground is modelled as perfectly plastic contact. The second example represents a monopedal jumper and it is used to examine the dynamical behaviour of the perfectly elastic and perfectly plastic contact formulation. The resulting differential algebraic equations (DAEs) are solved by the aforementioned symplectic momentum method. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The influence of nanocrystal size on optical second harmonic generation by <Emphasis Type="Italic">p</Emphasis>ara-nitroanaline embedded in electro-spun polymeric fibers

Poly(methyl methacrylate) electro-spun fibers with embedded nanocrystals of the paradigmatic donor–acceptor nonlinear chromophore para-nitroaniline have been recently demonstrated to be efficient generators of second harmonic light. To understand the influence of the size and local strain experienced by the embedded para-nitroaniline nanocrystals, a Williamson?Hall analysis was carried out on the X-ray diffraction intensity. Both the mean crystal size and strain can be tuned by simple changes in the deposition parameters of flow rate and applied voltage. The observed second harmonic signal is well correlated with the ratio of the fiber diameter to the mean para-nitroaniline crystal size suggesting that surface effects are the main source of the strong nonlinear optical response. Adjusting the electro-spinning deposition parameters when producing polymeric fibers doped with strong nonlinear organic chromophores with high dipole moments has the potential to provide a versatile and efficient method for developing second-order nonlinear optical materials.     

Click strategies for single-molecule protein fluorescence

Single-molecule methods have matured into central tools for studies in biology. Foerster resonance energy transfer (FRET) techniques, in particular, have been widely applied to study biomolecular structure and dynamics. The major bottleneck for a facile and general application of these studies arises from the need to label biological samples site-specifically with suitable fluorescent dyes. In this work, we present an optimized strategy combining click chemistry and the genetic encoding of unnatural amino acids (UAAs) to overcome this limitation for proteins. We performed a systematic study with a variety of clickable UAAs and explored their potential for high-resolution single-molecule FRET (smFRET). We determined all parameters that are essential for successful single-molecule studies, such as accessibility of the probes, expression yield of proteins, and quantitative labeling. Our multiparameter fluorescence analysis allowed us to gain new insights into the effects and photophysical properties of fluorescent dyes linked to various UAAs for smFRET measurements. This led us to determine that, from the extended tool set that we now present, genetically encoding propargyllysine has major advantages for state-of-the-art measurements compared to other UAAs. Using this optimized system, we present a biocompatible one-step dual-labeling strategy of the regulatory protein RanBP3 with full labeling position freedom. Our technique allowed us then to determine that the region encompassing two FxFG repeat sequences adopts a disordered but collapsed state. RanBP3 serves here as a prototypical protein that, due to its multiple cysteines, size, and partially disordered structure, is not readily accessible to any of the typical structure determination techniques such as smFRET, NMR, and X-ray crystallography.     

Scheduling UET task systems with concurrency on two parallel identical processors

Problems with unit execution time tasks and two identical parallel processors have received a great deal of attention in scheduling theory. In contrast to the conventional models, where each task requires only one processor, we consider a situation when a task may require both processors simultaneously. For problems without precedence constraints we present several polynomial time algorithms which complement recent results of Lee and Cai. We also show that the introduction of precedence constraints leads to NP-hardness results for maximum lateness and mean flow time objective functions. For the maximum lateness problem, a family of algorithms, based upon the idea of modified due dates, is considered. The worst case behaviour of these algorithms is analysed, and it is shown that the same upper bound is tight for each algorithm of this family.