Stimulated Raman scattering in natural crystals of fluorapatite,Ca5(PO4)3F

Hexagonal Ca₅(PO₄)₃F, known as natural crystal fluorapatite and oldest host‐crystal for Ln³⁺‐lasant ions, is presented as a Raman‐active material. High‐order Raman‐induced χ⁽³⁾‐nonlinear processes are discovered in natural crystals of fluorapatite under picosecond pumping at 1.064 μm and 0.532 μm wavelength. A multitude of Stokes and anti‐Stokes components is generated in the ultraviolet, visible and near‐infrared spectral region by stimulated Raman scattering (SRS) and Raman four‐wave mixing (FWHM), resulting in a frequency comb with a width of 520 THz. The spectral lines are identified and attributed to the ν₁(A_g) vibration mode of the tetrahedral [PO₄] units which is related to a Raman shift of ω_SRS ≈ 965 cm⁻¹. The first Stokes steady‐state Raman gain coefficient in the near‐infrared spectral range is estimated to be >0.38 cm·GW⁻¹. Finally, a short review of SRS‐promoting vibration modes and observed χ⁽³⁾‐ nonlinear interactions in all known SRS‐active natural crystals (minerals) is given.

     

Actual Isothermal Effects of Water‐Filtered Infrared A‐Irradiation

In this study, the athermal effects of water‐filtered infrared A (wIRA)‐irradiation (780–1400 nm) on human dermal fibroblasts were investigated. For this purpose, cells were exposed to wIRA‐irradiation (178 mW cm^?2 for 1 h), while a sophisticated experimental setup prevented warming of the samples exceeding 0.1°C. The investigated parameters were the formation of reactive oxygen species (ROS), mitochondrial membrane potential and superoxide release, protein oxidation, proliferation rate, as well as intracellular Ca²⁺‐release in single cells, most of them quantified via fluorescence microscopy and fluorimetric techniques. The existence of actual athermal wIRA‐effects is still intensively discussed, since their detection requires a careful experimental setup and both efficient and powerful temperature regulation of the exposed samples. Here, we can definitively show that some of the supposed athermal wIRA‐effects may be rather artifacts, since wIRA did not reveal any impact on the above mentioned parameters—as long as the temperature of the exposed cells was carefully maintained. Though, we were able to identify an athermal DNA‐protective wIRA‐effect, since the induced DNA damage (quantified via 8‐Oxo‐G‐formation) was significantly decreased after a subsequent UVB‐exposure. These results suggest that many of the supposed athermal wIRA‐effects can be induced by pure warming of the samples, independent from any wIRA‐irradiation.     

Sensitive voltammetric method for the fast analysis of the antioxidant pyrogallol using a boron-doped diamond electrode in biofuels

A sensitive voltammetric method for the determination of pyrogallol (PY) was developed employing a boron-doped diamond electrode (BDDE). The composition of the supporting electrolyte was investigated during the development of the methodology. Linear sweep voltammetry (LSV) under the optimized experimental conditions was applied for PY determination with a limit of detection and limit of quantification of 0.85 and 2.82 μmol L^?1, respectively. These values are satisfactory for application to real samples. The usability of this method for the quantification of pyrogallol was in range from 2.82 to 296.00 μmol L^?1. Finally, the developed method was successfully used for the analysis of real samples of biodiesel produced from rapeseed oil and its blend with diesel fuel. Samples of biodiesel and biodiesel blends were analyzed directly in an electrochemical cell, while samples with very low concentrations of PY in biodiesel were extracted with water using the proposed simple and fast process.     

An Organoruthenium Anticancer Agent Shows Unexpected Target Selectivity For Plectin

Organometallic metal(arene) anticancer agents require ligand exchange for their anticancer activity and this is generally believed to confer low selectivity for potential cellular targets. However, using an integrated proteomics-based target-response profiling approach as a potent hypothesis-generating procedure, we found an unexpected target selectivity of a ruthenium(arene) pyridinecarbothioamide (plecstatin) for plectin, a scaffold protein and cytolinker, which was validated in a plectin knock-out model in vitro. Plectin targeting shows potential as a strategy to inhibit tumor invasiveness as shown in cultured tumor spheroids while oral administration of plecstatin-1 to mice reduces tumor growth more efficiently in the invasive B16 melanoma than in the CT26 colon tumor model.     

On the pressure dependence of the viscosity of aqueous sugar solutions

New experimental data for the pressure dependence of the viscosity of aqueous solutions of different sugars are presented. Measurements were carried out with a gravity driven high pressure viscometer with a maximum pressure of 700 MPa. The influence of both concentration and temperature on the pressure dependence of the viscosity is considered. Next to the data, a viscosity model based on a suspension model is introduced and it is shown that it is able to predict the viscosity for sugar solutions in a broad parameter range, including pressure. It is demonstrated that the relative viscosity for varying sugar mass fraction at constant pressure coincides with the pressure-dependent relative viscosity for a fixed sugar mass fraction, suggesting that there are no structural changes occurring under pressure. A brief interpretation of the viscosity model is given.     

The automatic control of boundary-layer transition — Experiments and computation

In recent years there has been an increasing interest in the control of boundary-layer transition through the use of wall suction. In the current work suction is provided through one or more suction panels situated close to the leading edge of a plate. Experiments show that boundary-layer pressure fluctuation measurements can be used to identify the position of transition. Transition can be maintained at a desired location with minimum power consumption by employing an automatic adaptive feedback control loop which regulates the suction flow rates of two independent suction panels. This can be expressed as a constrained optimization problem. To allow the suction flow rates to be updated, a modified least mean squares algorithm is used within the control loop. Experimental measurements show that the control algorithm allows fast and stable convergence towards the optimum suction distribution for a double suction panel configuration. Numerical simulations have also been performed. The two-dimensional boundary layer was calculated allowing the viscous boundary layer to interact with the inviscid outer flow. Following linear stability theory the spatial growth rates are calculated by solving an Orr-Sommerfeld type eigenvalue problem, with the streamwise location of transition predicted via thee ^N -method. Applying the same optimization strategy as in the experiments, good qualitative agreement between computations and experiments was found. The optimization algorithm has been applied to computer models where the relation between suction flow rates and transition location is described by an empirical analytical function. This shows that the controller can in principle be applied to systems with more than two suction panels.Nomenclature b transition location with zero suction - d desired transition location - e(k) error signal - k iteration index - p rms pressure - p _ref reference rms pressure - r sum of the reference pressure - u streamwise velocity - u _e external velocity - inviscid external velocity - A wave amplitude - F( ) cost function - I identity matrix - N maximum amplification factor - P projection matrix - R Reynolds number - Re Reynolds number based on the boundary-layer thickness - R matrix of weights - Tu turbulence level - vector of suction flow rates - v normal velocity - v _wall suction velocity at the surface - x streamwise coordinates - x _m microphone location - x _T(k) measured transition location - y normal coordinate - y(k) sum of the measured pressures - w(k) noise - plate length - r +i _i - free stream velocity - * displacement thickness - gradient vector - Lagrange multiplier - controller gain - disturbance stream function - disturbance amplitude - wave frequency = complex wave number     

Robust hydrophobic surfaces displaying different surface roughness scales while maintaining the same wettability

A range of surfaces coated with spherical silica particles, covering the size range from nanometer to micrometer, have been produced using Langmuir-Blodgett (LB) deposition. The particles were characterized both in suspension and in the Langmuir trough to optimize the surface preparation procedure. By limiting the particle aggregation and surface layer failures during the preparation steps, well-defined monolayers with a close-packed structure have been obtained for all particle sizes. Thus, this procedure led to structured surfaces with a characteristic variation in the amplitude and spatial roughness parameters. In order to obtain robust surfaces, a sintering protocol and an AFM-based wear test to determine the stability of the deposited surface layer were employed. Hydrophobization of the LB films followed by water contact angle measurements showed, for all tested particle sizes, the same increase in contact angle compared to the contact angle of a flat hydrophobic surface. This indicates nearly hexagonal packing and gives evidence for nearly complete surface wetting of the surface features.     

On the specificity of the amide VI band for the secondary structure of proteins

In this work we analyzed the specificity of the amide VI band for different types of secondary structure elements in protein structures. This band involves the bending motion of the CO group of the peptide chain that is typically observed in the spectral region from 590 to 490 cm⁻¹. The infrared absorbance spectra of a set of polypeptide model compounds of well known secondary structure was obtained at defined pH, including poly (l-lysine), poly (l-tyrosine), poly (l-alanine) and poly (l-histidine). In addition spectra of membrane proteins from the respiratory chain, namely the NADH:ubiquinone oxidoreductase, the cytochrome c oxidase and its Cu_A fragment, the cytochrome bc₁ complex, a Rieske-type protein and in addition myoglobin, have been comparatively investigated. The systematic analysis of the amide VI band of the polypeptides and the proteins allowed correlating the signal appearing at ∼525 cm⁻¹ to α-helical structures and signals at ∼545 cm⁻¹ to β-sheet contributions. Random coils have been found to contribute at ∼535 cm⁻¹ while the β-turns were observed at ∼560 cm⁻¹.     

Total synthesis of pamamycin-649B

The first total synthesis of the macrodiolide antibiotic pamamycin-649B (1) was achieved by using sultone methodology. The diethyl substituted larger hydroxy acid fragment was constructed in a concise fashion through domino elimination/alkoxide-directed 1,6-additions of ethyllithium to sultones derived from intramolecular Diels-Alder reaction of furan-containing vinylsulfonates. Intermolecular Yamaguchi esterification of the two hydroxy acid building blocks and subsequent Yamaguchi cyclization eventually provided the target macrocycle 1. Since the final lactonization with formation of the ester linkage between C1' and the C8 oxygen proceeded with complete C2' epimerization, the more readily available C2' epimeric smaller fragment could be used to streamline the synthetic sequence.