Analysis of bend loss in waveguides employing photonic band gap effect

We analyse bend loss properties of a band gap-guided periodic structure, and give reasons for the effects found. In many cases, a tight bend produces only a slight reduction in power transmitted. We also make a comparison of bend losses in conventional waveguides and bend-resistant waveguides.     

Packing density of conventional waveguides and photonic crystal waveguides

We compare coupling between parallel waveguides within one-dimensional photonic crystals and coupling between conventional waveguides. We consider the situation in which coupling between the waveguides is minimized, so that light in the waveguides propagates essentially independently. Subject to this condition, we compare the minimum mutual distance between conventional planar waveguides and waveguides in one-dimensional photonic crystals. We find that the packing densities of the conventional and periodic structures are comparable.     

Characterization of Azerbaijani and Croatian brown naphthalane

In spite of the fact that noncolored (nonaromatic) naphthalane containing high sterane content has been proved as bioactive and efficient in the treatment of psoriasis vulgaris, brown naphthalanes, which contain aromatics, are still in use. Thousands of patients, who have been passing through the therapy, deserve thorough and permanent study of brown naphthalanes. For that reason, two frequently used brown naphthalane preparations, one of the Azerbaijani (N1) and the other of the Croatian (N2) origin, were studied. The samples underwent the study by means of GC, OT LC, and normal-phase HPLC, as separation techniques. In addition, some bulk properties, elemental composition, and group composition by 1H NMR were determined. GC-MS served in compound types, especially in sterane detection. Both of the samples were found to be unresolved complex mixtures, relatively poor in n-alkanes. Isoalkanes, cycloalkanes, and aromatic compounds, in a great variety of isomers and homologs, made the majority of both of the samples. N1 was a dark, viscous, nontransparent fluid with a strong petroleum smell. Aromatics, which made 53% mass by OT LC and 54% mass by 1H NMR were found to be composed of mono-, di-, and tri+ -aromatic compounds. Tri+ -aromatic compounds were three to four times more abundant in N1 than in N2. Beside hydrocarbons, N1 comprised some organic compounds with polar functional groups. Also, some asphaltenes were found in it. N1 contained well-presented steranes, which are thought to be bioactive naphthalane ingredients. N2 was a pale brown liquid, with smell similar to gasoline. It contained somewhat lower percentage of aromatics (46% mass) and comparatively lower percentage of tri+ fused aromatics among which carcinogens might be expected. N2 was almost purely composed of hydrocarbons. It seemed to contain low content of steranes due to relatively low upper temperature of the distillation range applied in N2 preparation.     

Identification of impurities in acarbose by using an integrated liquid chromatography-nuclear magnetic resonance and liquid chromatography-mass spectrometry approach

The usefulness of applying an integrated LC-NMR and LC-MS approach to acarbose bulk drug impurity profiling is demonstrated. LC-MS and LC-NMR methodologies were employed for the online separation and structural elucidation of a final drug product. Combining data provided by the stop-flow LC-NMR and LC-MS experiments made it possible to identify the main components present in the acarbose sample. Spectral analysis revealed that A and B were known impurities while C was an unknown compound. LC-MS and LC-NMR analyses revealed that C was a pentasaccharide differing from the acarbose in number and nature of sugar subunits in the molecule. It was subsequently isolated and its structure was confirmed by the offline 1- and 2-D NMR experiments, and atom assignment was made.     

High-Q microfluidic cavities in silicon-based two-dimensional photonic crystal structures

We demonstrate postprocessed microfluidic double-heterostructure cavities in silicon-based photonic crystal slab waveguides. The cavity structure is realized by selective fluid infiltration of air holes using a glass microtip, resulting in a local change of the average refractive index of the photonic crystal. The microcavities are probed by evanescent coupling from a silica nanowire. An intrinsic quality factor of 57,000 has been derived from our measurements, representing what we believe to be the largest value observed in microfluidic photonic crystal cavities to date.     

Ultra-resolution imaging of a self-assembling biomolecular system using robust carbon nanotube AFM probes

Nanoscale structural features of a novel self-assembling DNA based nanostructure have been resolved. Image data is of sufficient resolution to allow molecular orientation and the effect of surface adsorption to be characterized. This has been achieved using AFM with probes employing carbon nanotubes attached via a thin film of plasma polymerized hexane. This presents the nanotube with a highly hydrophobic coating to which it can adsorb, increasing production success and probe robustness.