Where on Earth has our water come from?

The presence of water in the Earth has long been an enigma. However, computer modelling techniques have shown that the adsorption of water onto the fractal surfaces of interplanetary dust particles, which are present in the planetary accretion disk, is sufficiently strong to provide a viable origin of terrestrial water.     

Manipulating double-decker molecules at the liquid-solid interface

We have used a scanning tunneling microscope (STM) to manipulate heteroleptic phthalocyaninato, naphthalocyaninato, and porphyrinato double-decker (DD) molecules at the liquid-solid interface between 1-phenyloctane solvent and graphite. We employed nanografting of phthalocyanines with eight octyl chains to place these molecules into a matrix of heteroleptic DD molecules; the overlayer structure is epitaxial on graphite. We have also used nanografting to place DD molecules in matrices of single-layer phthalocyanines with octyl chains. Rectangular scans with a STM at low bias voltage resulted in the removal of the adsorbed DD molecular layer and substituted the DD molecules with bilayer-stacked phthalocyanines from phenyloctane solution. Single heteroleptic DD molecules with lutetium sandwiched between naphthalocyanine and octaethylporphyrin were decomposed with voltage pulses from the probe tip; the top octaethylporphyrin ligand was removed, and the bottom naphthalocyanine ligand remained on the surface. A domain of decomposed molecules was formed within the DD molecular domain, and the boundary of the decomposed molecular domain self-cured to become rectangular. We demonstrated a molecular "sliding block puzzle" with cascades of DD molecules on the graphite surface.     

Analysis of caffeic acid derivatives in echinacea extracts by liquid chromatography particle beam mass spectrometry (LC–PB/MS) employing electron impact and glow discharge ionization sources

A liquid chromatography–particle beam/mass spectrometry (LC–PB/MS) method with electron impact (EI) and glow discharge (GD) ionization sources is presented for the determination of caffeic acid derivatives in echinacea tinctures. In this work, two commercially available echinacea ethanolic extracts were used as the test samples for the separation, identification, and quantification of the caffeic acid derivatives (caffeic acid, chlorogenic acid, cichoric acid, and caftaric acid), which are suggested to have beneficial medicinal properties. Detailed evaluations of the two primary controlling parameters for EI (electron energy and source block temperature) and GD (discharge current and pressure) sources were performed to determine optimal instrument operation conditions. The mass spectra obtained from both ion sources provide clear and simple molecular fragmentation patterns for each of the target analytes. The absolute detection limits for the caffeic acid derivatives were determined to be at subnanogram levels for both the EI and GD sources. The separation of the caffeic acid derivatives in echinacea was accomplished by reversed-phase chromatography using a C₁₈ column and a gradient elution system of water containing 0.1% trifluoroacetic acid and methanol, with an analysis time of less than 40 min. A standard addition method was employed for the quantification of each of the caffeic acid derivatives in the tincture.     

Feedback control of bursting and multistability in chaotic systems

With a modulated CO₂ laser as a standard model of periodically driven multistable systems, we experimentally demonstrate that a small-amplitude optoelectronic feedback perturbation can efficiently transform a bursting chaotic system to a nonchaotic one. Numerical simulations are in excellent agreement with the experimental results. The control has also been equally effective in the case of a driven FitzHugh-Nagumo model of Neuroscience.     

Novel thieno[2,3-d]pyrimidines: their design, synthesis, crystal structure analysis and pharmacological evaluation

Novel thieno[2,3-d]pyrimidines containing a cyclohexane ring fused with a six- or five-membered heterocyclic moiety along with a benzylic nitrile were designed as potential inhibitors of PDE4. Expeditious synthesis of these compounds was carried out via a multi-step sequence consisting of a few key steps such as Gewald reaction, Dieckmann type cyclisation and Krapcho decarboxylation. This newly developed strategy involved construction of the thienopyrimidine ring followed by the cyclohexanone moiety and subsequently the fused heterocyclic ring. A number of thieno[2,3-d]pyrimidine based derivatives were synthesized using this method some of which showed promising PDE4B inhibitory properties. One of them was tested for PDE4D inhibition in vitro and dose dependent inhibition of TNF-α. A few selected molecules were docked into the PE4B protein the results of which showed good overall correlations to their observed PDE4B inhibitory properties in vitro. The crystal structure analysis of representative compounds along with hydrogen bonding patterns and molecular arrangement present within the molecule is described.     

A tandem enyne/ring closing metathesis approach to 4-methylene-2-cyclohexenols: an efficient entry to otteliones and loloanolides

A short and efficient approach to a 4-methylene-2-cyclohexenone substructure present in otteliones and loloanolides is described. This strategy involves a tandem enyne/ring closing metathesis as the key reaction to construct this labile core unit.     

Structural impact of iron ions on BaBiBO4 glasses: Spectroscopic and dielectric investigations

Transparent glasses of composition 10BaO.20Bi₂O₃.(70 ? x)B₂O₃.xFe₂O₃ (wt.%) where 0 ≤ x ≤ 2.0, were characterized by XRD and SEM. Physical, spectroscopic and dielectric properties were investigated. At higher dopant of Fe₂O₃, EPR results revealed that, the number of Fe³⁺ ions participate in the resonance is decreased by forming a new signal at g ≈ 3.015 due to increase of antiferromagnetic interaction of Fe³⁺ ions and/or formation of low spin Fe³⁺ ions in the glass matrix. With initial 0.5 wt.% doping of Fe₂O₃, less dense glass is formed with colloids of metallic Bi⁰ atoms. The absorption bands at 604 and 712 nm in F5 glass are ascribed to Bi⁰ and Bi⁺ radicals respectively. No characteristic Fe³⁺ absorption bands (spin-forbidden) are found. Fe²⁺ ions are increased at higher concentration of Fe₂O₃. Higher concentration of Fe₂O₃ is favorable for BO₂O^?, BO₃, BiO₆ and FeO₆ symmetry unit leads to low band gap and high Urbach energy. By doping of Fe₂O₃ the dielectric parameters like dielectric constant (ε′), loss (tanδ and ac electrical conductivity (σ_ac) are found to increase.     

Structural,optical and electrical characteristics of a new NLO crystal

A new nonlinear optical (NLO) organic crystal 1-[4-({(E)-[4-(methylsulfanyl)phenyl]methylidene}amino)phenyl]ethanone (MMP) has been grown by slow evaporation technique at ambient temperature. The crystal structure of MMP was determined by single crystal X-ray diffraction. MMP crystallizes in non-centrosymmetric monoclinic system with space group P2₁. The FT-IR spectrum recorded for new crystal confirmed the presence of various functional groups in the material. MMP was found to be thermally stable up to 300 °C. The grown crystal was optically transparent in the wavelength range of 400–1100 nm. The second harmonic generation (SHG) efficiency of the crystal was measured by the classical powder technique using Nd:YAG laser and was found to be 4.13 times more efficient than reference material, urea. Third order nonlinear parameters were measured by employing the Z-scan technique. The laser damage threshold for MMP crystal was determined to be 4.26 GW/cm². The Brewster angle technique was employed to measure the refractive index of the crystal and the values for green and red wavelengths were found to be 1.35 and 1.33, respectively. The dielectric and electrical measurements were carried out to study the different polarization mechanisms and conductivity of the crystal.     

Fast full-field out-of-plane deformation measurement using fringe reflectometry

Full-field out-of-plane deformation measurement of specular surfaces can be implemented quickly and conveniently using fringe reflectometry. The system configuration is simple and processing is fast. With the assistance of an advanced fringe pattern processing technique, the windowed Fourier ridges method, only a single two-directional fringe pattern is necessary for determination of the deformed surface profile. Thus, the whole measurement only requires a single image with the potential for high speed or even real time measurement.     

Experimental verification of enhanced electromagnetic field intensities at the photonic stop band edge of 3D polystyrene photonic crystals using Z-Scan technique

Enhancement of nonlinear absorption of polystyrene (PS) was investigated using 3D PS photonic crystals (PCs) with Z-scan technique. The Z-scan experiment was carried out at 532 nm in the picosecond (ps) regime. The transmittance of the PC was found to get modified because of the nonlinear absorption of PS particularly when 532 nm is near the photonic stop band (PSB) edge of PC. Calculations show that the field gets enhanced by 1.4 times the input field intensity within the crystal when the 532 nm wavelength falls at the PSB edge while keeping the crystal at an angle of 35°.