Prospect of Thiazole-based γ-Peptide Foldamers in Enamine Catalysis: Exploration of the Nitro-Michael Addition

As three-dimensional folding is prerequisite to biopolymer activity, complex functions may also be achieved through foldamer science. Because of the diversity of sizes, shapes and folding available with synthetic monomers, foldamer frameworks enable a numerous opportunities for designing new generations of catalysts. We herein demonstrate that heterocyclic γ-peptide scaffolds represent a versatile platform for enamine catalysis. One central feature was to determine how the catalytic activity and the transfer of chiral information might be under the control of the conformational behaviours of the oligomer.     

The nestedness property of location problems on the line

We prove the existence of a nestedness property for a family of common convex parametric tactical serving facility location problems defined on the line. The parameter t is the length of the serving facility (closed interval). The nestedness property means that, given any two facility lengths \(t_1, t_2, 0 \le t_1<t_2\), there is an optimal solution with length \(t_1\) which lies within some optimal solution with length \(t_2\). The main idea of the proof is the representation of a serving facility as a point in \({\mathbb {R}}^2\) and the investigation of its geometrical properties. An intuitive graphical approach to the proof is given.     

Poling pattern for efficient frequency doubling of Gaussian beams

The commonly used periodic patterning for quasi phase-matching plane-waves is theoretically adequate for completely depleting and transferring a fundamental wave to its second harmonic. However, when working with Gaussian beams the conversion efficiency of such a design lacks due to the inherent Gouy phase shift and the spatially varying beam profile, yielding roughly 88?% conversion efficiency. In this paper, we study the possibility of adding a linear chirp and Gouy-phase shift compensation to the periodic poling. We demonstrate that this poling pattern enables us to achieve near-optimal frequency doubling efficiency of up to 97?%.     

Puckering behavior in six new phosphoric triamides containing aliphatic six- and seven-membered ring groups and a database survey of analogous ring-containing structures

The influence of a N heteroatom on the ring conformations of six- and seven-membered aliphatic rings in six new C(O)NHP(O)-based phosphoric triamide structures (analysed by X-ray crystallography) is investigated. Additionally the influence of steric and crystal packing effects is also studied by the analysis of Hirshfeld surfaces. The results are compared to analogous structures with three- to seven- aliphatic membered rings deposited in the Cambridge Structural Database. In the newly determined structures, the six-membered rings only show the near-chair conformation with a maximum deviation of the θ puckering parameter of 4.4° from the ideal chair value of 0°/180°, while the seven-membered rings are found in different conformations such as near-chair, twist chair and twist sofa.     

Generation of tunable green radiation in bulk periodically poled KTiOPO4

We report a characterisation of a flux-grown periodically poled KTiOPO₄ crystal used for second-harmonic generation in a diode laser source, that operates with fundamental radiation tunable around 1083 nm wavelength. The conversion efficiency is measured for the three different grating periods of the crystal, as a function of input wavelength, crystal temperature and fundamental power. The measurements were fitted to the theoretical model of Boyd and Kleinman for frequency conversion of focused Gaussian beams. This enabled us to determine the temperature and wavelength dependence of the difference in refractive index between the interacting waves.     

Effects of blowing or suction on the laminar boundary layer flow over a rotating cone

The effects of suction or blowing at the surface of a rotating cone in a quiet fluid on the skin friction and heat transfer are described. The equations which govern the fluid motion and thermal energy transfer are transformed by the boundary layer approximations and the resulting equations are solved under the condition that the suction or blowing velocity varies as x ⁿ (x: distance measured from the apex of the cone, n: arbitrary constant). The solutions are obtained as a perturbation from the basic laminar flow of an incompressible viscous fluid over the impermeable rotating cone. Detailed numerical calculations are performed for the case of an isothermal rotating cone with uniform blowing or suction, i.e. n=0, the Prandtl number being 0.72. Results are given for the shear stress, heat transfer and velocity and temperature fields. It is shown from the analysis that suction sharply increases the circumferential shear stress and the heat transfer at the surface.Nomenclature c proportional constant - C _fx dimensionless skin friction factor, _x /(V ²) - C _fx0 dimensionless skin friction factor for an impermeable cone - C _fy dimensionless circumferential skin friction factor, _y /(V ²) - C _fy0 dimensionless circumferential skin friction factor for an impermeable cone - c _p specific heat at constant pressure - f _k function of - g _k function of - h heat transfer coefficient, q/(T _w–T ) - k thermal conductivity of fluid - n arbitrary constant - Nu _x local Nusselt number, hx/k - Nu _x0 local Nusselt number for an impermeable cone - Pr Prandtl number - q heat transfer rate - r radius of a circular cross section of the cone, x sin - R _x Reynolds number, Vx/ - T temperature - T _w surface temperature of the cone - T temperature of the surrounding fluid - u fluid velocity in x-direction - v fluid velocity in y-direction - V circumferential velocity at the cone surface, r - w fluid velocity in z-direction - x coordinate along meridional section - y coordinate along a circular cross section - z coordinate perpendicular to both x and y - perturbation parameter, cx ⁿ /(x sin )^1/2 - dimensionless z-coordinate, z( sin /)^1/2 - _k function of - kinematic viscosity - density of fluid - _x skin friction in x-direction - _y circumferential skin friction - stream function - angular speed of the cone     

Surface‐plasmon wavefront and spectral shaping by near‐field holography

Surface‐plasmon‐polariton waves are two‐dimensional electromagnetic surface waves that propagate at the interface between a metal and a dielectric. These waves exhibit unusual and attractive properties, such as high spatial confinement and enhancement of the optical field, and are widely used in a variety of applications, such as sensing and subwavelength optics. The ability to precisely control the spatial and spectral properties of the surface‐plasmon wave is required in order to support the growing interest in both research and applications of plasmonic waves, and to bring it to the next level. Here, we review the challenges and methods for shaping the wavefront and spectrum of plasmonic waves. In particular, we present the recent advances in plasmonic spatial and spectral shaping, which are based on the realization of plasmonic holograms for the optical nearfield.