Twisted Silica Microstructured Optical Fiber with Equiangular Spiral Six-Ray Geometry

This work presents fabricated silica microstructured optical fiber with special equiangular spiral six-ray geometry, an outer diameter of 125 µm (that corresponds to conventional commercially available telecommunication optical fibers of ratified ITU-T recommendations), and induced chirality with twisting of 200 revolutions per minute (or e.g., under a drawing speed of 3 m per minute, 66 revolutions per 1 m). We discuss the fabrication of twisted microstructured optical fibers. Some results of tests, performed with pilot samples of designed and manufactured stellar chiral silica microstructured optical fiber, including basic transmission parameters, as well as measurements of near-field laser beam profile and spectral and pulse responses, are represented.

Synthetic asters as elastic and radial skeletons

The radial geometry with rays radiated from a common core occurs ubiquitously in nature for its symmetry and functions. Herein, we report a class of synthetic asters with well-defined core-ray geometry that can function as elastic and radial skeletons to harbor nano- and microparticles. We fabricate the asters in a single, facile, and high-yield step that can be readily scaled up; specifically, amphiphilic gemini molecules self-assemble in water into asters with an amorphous core and divergently growing, twisted crystalline ribbons. The asters can spontaneously position microparticles in the cores, along the radial ribbons, or by the outer rims depending on particle sizes and surface chemistry. Their mechanical properties are determined on single- and multiple-aster levels. We further maneuver the synthetic asters as building blocks to form higher-order structures in virtue of aster-aster adhesion induced by ribbon intertwining. We envision the astral structures to act as rudimentary spatial organizers in nanoscience for coordinated multicomponent systems, possibly leading to emergent, synergistic functions.

A generalized view on normal moveout

Although in the past, in the context of stacking, traveltime moveout was only formulated in individual common-midpoint (CMP) gathers, multiparameter stacking uses normal moveout (NMO) approximations that span several neighboring CMPs. Multiparameter expressions such as the common reflection surface (CRS) or multifocusing are parameterized in terms of local slopes and curvatures of emerging wavefronts rather than effective velocities, which makes these approaches appear conceptually different from conventional velocity analysis. As a consequence, the unifying nature of multiparameter NMO is still not well-appreciated. In addition, CRS and multifocusing show distinctly different behavior in that they respond differently to the overburden heterogeneity and curvature of the target interface, and they either are or are not susceptible to moveout stretch. In our work, we seek to demystify the wavefront picture by demonstrating that the conventional and multidimensional NMO operators can conveniently be derived from the same auxiliary straight-ray geometry, either representing the optical projection or formulated in an effective replacement medium. Following the early work of de Bazelaire, we suggest a simple transformation between both domains and introduce generalized dual representations of the hyperbolic CRS, multifocusing, and the two recently introduced double-square-root expressions implicit CRS and nonhyperbolic CRS. In addition, we evaluate a generalized finite-offset NMO expression that can likewise be applied to active-source diffraction data and passive seismic events. Synthetic examples suggest unification, conveniently explain the origin of moveout stretch, and indicate that the joint use of different NMO approximations offers new insight into the character and origin of different wavefield components.

From reflection elements to structure — A look at the history of data interpretation

Traditionally, input acquired in the field consisted of the original paper records; output submitted to the client consisted of structural sections and depth-contour maps of selected interfaces. Before the introduction of magnetic recording, it was common practice to do the conversion in the field office. Tools for this conversion ranged from slide rules and desk calculators to wavefront charts. These tools were based on the geometry of rays in media where velocity is a function of depth only. The detailed algorithms underlying the conversion were often developed in the exploration companies and — originally — were carefully guarded. But at least the underlying principles were exchanged throughout the industry through books, journal articles, and presentations at meetings, such as noted in nearly 300 references in C. H. Dix’s Seismic Prospecting for Oil (1952) . The techniques of data acquisition and data interpretation have changed considerably, but the underlying principles of ray geometry are the same. Therefore, many new methods are based on ideas formulated in the early times of the industry.

Metabolites from the Fungus Phoma sp. 7210, Associated with Aizoon Canariense

A new metabolite, 3,16-diketoaphidicolan (1), was isolated together with four known compounds: aphidicolin (2), 17-acetyl-aphidicolin (3), (+)-eupenoxide (4), and phomoxanthone A (5) from the endophytic fungus Phoma sp. The structure of the new compound 1 was determined by spectroscopic methods (mainly extensive 1D and 2D NMR experiments and by mass spectral measurements) and confirmed by X-ray crystallography. Its absolute configuration was assigned by means of the solid-state CD/TDDFT approach comparing the solid-state CD spectrum with the TDDFT-calculated one on the X-ray geometry.

A New Approach for Determining Epilayer Strain Relaxation and Composition Through High Resolution X-Ray Diffraction

ABSTRACTWe developed a new method of determining epilayer relaxation (along one direction) and composition using a symmetric and any single asymmetric high resolution x-ray diffraction scan. The previous use of small angle approximations can be very detrimental to calculated results and should be avoided. This new method does not employ small angle approximations or first order Taylor approximations, producing accurate results. The effect of x-ray geometry (glancing incident versus glancing exit) on the analysis of epilayer composition and strain is also reviewed. It is also shown that the glancing exit geometry is generally less susceptible to experimental error.