Rhodium nanoparticles as catalysts in the hydroformylation of 1-dodecene and their recycling in thermomorphic solvent systems

Rhodium nanoparticles of about 3 nm in size were provided in stabilizing polar solvents. These nanoparticles were used in hydroformylation reactions of higher alkenes; 1-dodecene was used as a model substance. With a metal/substrate ratio of 1:1000, a 97% yield of aldehydes was achieved and an n/iso ratio of 72:28 was obtained. The addition of the ligand biphephos decelerated the reaction, but high n/iso ratios of up to 96:4 were achieved.For the first time, an effective catalyst recycling of these long-term stable nanoparticles in a thermomorphic multicomponent solvent (TMS) system was performed. The catalyst phase was recycled for three runs without any evident loss in activity. TEM images proved that after the recycling runs rhodium nanoparticles were still the active catalyst.     

T(x) phase diagram of the CuSbS2–CuInS2 system and solubility limit of Sb in CuInS2

The starting ternary compounds CuInS₂ and CuSbS₂ and alloys of the CuSbS₂–CuInS₂ system with the molar fractions of CuInS₂ (x) equal to 0.05, 0.15, 0.25, 0.375, 0.50, 0.625, 0.75, 0.85, and 0.95 were prepared and the phase relations in this system were investigated by X‐ray powder diffraction, optical microscopy, scanning electron microscopy, and differential thermal analysis. It was shown that the T–x phase diagram of the CuInS₂–CuSbS₂ system has a eutectic character with the eutectic temperature of 807 K. The alloys of the CuSbS₂–CuInS₂ system with the molar fraction of CuInS₂ in the range from 0.038 to 0.941 at room temperature are two‐phased, and the limits of solubility are 0.059 molar fractions for CuSbS₂ in CuInS₂ and 0.038 molar fractions for CuInS₂ in CuSbS₂.     

Band alignment at sputtered ZnSx O1–x/Cu(In,Ga)(Se,S)2 heterojunctions

Valence band offsets ΔE_VBM at ZnS_x O_1–x/Cu(In,Ga)(Se,S)₂ (CIGSSe) heterojunctions have been studied by photoemission spectroscopy (XPS, UPS) as a function of composition x in sputtered ZnS_x O_1–x films. In the composition range from ZnO to ZnS we found ΔE_VBM between –(2.1 ± 0.3) eV and –(0.8 ± 0.4) eV, respectively. Considering the optical band gaps, the conduction band offsets ΔE_CBM range from –(0.1 ± 0.3) eV to +(1.4 ± 0.4) eV. These results suggest that sputtered ZnS_x O_1–x is suitable as substitution for the CdS buffer and ZnO window layers in standard chalcopyrite‐based solar cells. Current–voltage characteristics of the solar cells have been investigated as a function of the composition x. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal-host Gd0.5Lu0.5VO4 for Ln3+-lasants: a new high-gain many-phonon χ(3)-active tetragonal vanadate—SRS spectroscopy and nonlinear-laser effects

We found that tetragonal Gd_0.5Lu_0.5VO₄??known as host-crystal for Ln³⁺-lasants??is an attractive optical material for Raman laser converters. We discovered and investigated its almost sesqui-octave Stokes and anti-Stokes lasing comb resulting from four SRS-promoting vibration modes in combination with cascaded and cross-cascaded many-phonon ??⁽³⁾-nonlinear interactions. Furthermore, estimations of the steady-state Raman gain coefficient have been performed.     

A Study of the Behavior of Implicit Pressure Explicit Saturation (IMPES) Schedules for Two-phase Flow in Dynamic Pore Network Models

We focus on the numerical difficulties that typify implicit pressure explicit saturation (IMPES) schedules in dynamic “ball-and-stick” pore network models for two-phase flow. We show that a time stepping procedure based on a prescribed maximum variation of the local capillary pressure rather than on a (usual) maximum variation of the local saturation along with the addition in the solution algorithm of suitable “flow constraints” (in Koplik and Lasseter, Soc. Pet. Eng. J. 25(1):89–100, 1985) provide more stability and a significant run time speed up. In particular, the slow convergence and the oscillatory behavior that typify IMPES schemes at low Ca values due to capillary pinning are efficiently suppressed.     

AOM fourfold pass for efficient Q-switching and stable high peak power laser pulses

We report on a scheme for efficient acousto-optical Q-switching. A flash lamp pumped Nd:YAG oscillator with an acousto-optic modulator (AOM) fourfold pass configuration is presented. The setup combines two important advantages: enhancement of the diffraction efficiency by additional AOM passes and a compact oscillator design in spite of an extension of the optical path length. A flash lamp pumped oscillator with an average output power of 7 W and a beam quality of M² = 1.2 is developed. The system operates with a 100 Hz repetition rate for the flash lamps. In each pumping pulse a pulse train of 1 up to 40 Q-switched laser pulses is generated. The pulse duration is from 15 to 120 ns. In comparison to a former setup (AOM double pass) the AOM fourfold pass configuration allows single pulses with energy above 20 mJ and a pulse peak power of more than 1 MW. In addition, the beam profile is improved due to a better separation of the incident and diffracted beam caused by the AOM. The laser is dedicated as master oscillator in a master oscillator power amplifier (MOPA) system where pulse peak powers in the MW range should be achieved.     

Detection of a new SRS‐promoting phonon mode and cross‐cascaded χ(3)‐nonlinear lasing in single crystals of calcite (trigonal CaCO3)

For calcite (CaCO₃), one of the pioneer crystals in nonlinear optics, new results of stimulated Raman scattering (SRS) spectroscopy are presented. Among them are the discovery of a new SRS‐promoting vibration mode with ω_SRS2 ≈︁ 282 cm^‐1 and its participation, together with the main SRS mode ω_SRS1 ≈︁ 1086.5 cm^‐1, in cross‐cascaded (χ⁽³⁾ ↔ χ⁽³⁾) nonlinear‐lasing generation, as well as the observation of efficient self‐upconversion via cascaded parametric four‐wave processes of one‐micron Stokes and anti‐Stokes χ⁽³⁾‐lasing into the UV‐region of third harmonic generation. The investigations show that calcite is able to generate a χ⁽³⁾‐lasing comb of more than two octaves bandwidth. The article also gives a brief review on the discovery and study of the SRS‐effect in natural crystals (minerals), which have expanded our ability to study the photon‐phonon nonlinear‐laser interactions in crystalline materials. A short summary of information about χ⁽³⁾‐lasing properties of the triangular planar structure units in SRS‐active crystals is included.     

Network analysis of the e-MID overnight money market: the informational value of different aggregation levels for intrinsic dynamic processes

In this paper, we analyze the network properties of the Italian e-MID data based on overnight loans during the period 1999–2010. We show that the networks appear to be random at the daily level, but contain significant non-random structure for longer aggregation periods. In this sense, the daily networks cannot be considered as being representative for the underlying ‘latent’ network. Rather, the development of various network statistics under time aggregation points toward strong non-random determinants of link formation. We also identify the global financial crisis as a significant structural break for many network measures.     

Minimization of the blank values in the neutron activation analysis of biological samples considering the whole procedure

In our determination of trace element contents of animal tissue by neutron activation analysis in the course of structure-activity relationship studies on platinum containing cancer drugs and wound healing we have tried to minimize the blank values that are caused by different sources of contarnination during surgery, sampling and the activation analysis procedure. The following topics have been investigated: the abrasions from scalpels made of stainless steel, titanium or quartz; the type of surgery; the homogenisation of the samples before irradiation by use of a ball mill; the surface contaminations of the quartz ampoules that pass into the digestion solution of the irradiated samples. The appropriate measures to be taken in order to reduce the blank values are described. The results of analyses performed under these conditions indicate the effectiveness of the given measures, especially shown by the low values obtained for the chromium contents of the analysed muscle samples.