Hexabundles: imaging fiber arrays for low-light astronomical applications

We demonstrate a novel imaging fiber bundle ("hexabundle") that is suitable for low-light applications in astronomy. The most successful survey instruments at optical-infrared wavelengths use hundreds to thousands of multimode fibers fed to one or more spectrographs. Since most celestial sources are spatially extended on the celestial sphere, a hexabundle provides spectroscopic information at many distinct locations across the source. We discuss two varieties of hexabundles: (i) lightly fused, closely packed, circular cores; (ii) heavily fused non-circular cores with higher fill fractions. In both cases, we find the important result that the cladding can be reduced to ~2 μm over the short fuse length, well below the conventional ~10λ thickness employed more generally, with a consequent gain in fill factor. Over the coming decade, it is to be expected that fiber-based instruments will be upgraded with hexabundles in order to increase the spatial multiplex capability by two or more orders of magnitude

Vaults. III. Vault ribonucleoprotein particles open into flower-like structures with octagonal symmetry.

The structure of rat liver vault ribonucleoprotein particles was examined using several different staining techniques in conjunction with EM and digestion with hydrolytic enzymes. Quantitative scanning transmission EM demonstrates that each vault particle has a total mass of 12.9 +/- 1 MD and contains two centers of mass, suggesting that each vault particle is a dimer. Freeze-etch reveals that each vault opens into delicate flower-like structures, in which eight rectangular petals are joined to a central ring, each by a thin hook. Vaults examined by negative stain and conventional transmission EM (CTEM) also reveal the flower-like structure. Trypsin treatment of vaults resulted exclusively in cleavage of the major vault protein (p104) and concurrently alters their structure as revealed by negative stain/CTEM, consistent with a localization of p104 to the flower petals. We propose a structural model that predicts the stoichiometry of vault proteins and RNA, defines vault dimer-monomer interactions, and describes two possible modes for unfolding of vaults into flowers. These highly dynamic structural variations are likely to play a role in vault function

Transfer printing of semiconductor nanowires with lasing emission for controllable nanophotonic device fabrication

Accurate positioning and organization of Indium Phosphide (InP) Nanowires (NW) with lasing emission at room temperature is achieved using a nanoscale Transfer Printing (TP) technique. The NWs retained their lasing emission after their transfer to targeted locations on different receiving substrates (e.g. polymers, silica and metal surfaces). The NWs were also organized into complex spatial patterns, including 1D and 2D arrays, with a controlled number of elements and dimensions. The developed TP technique enables the fabrication of bespoke nanophotonic systems using NW lasers and other NW devices as building blocks

Conjugacy and Compatibility of Partial Arrays

Berstel and Boason introduced the partial words in the context of gene (or protein) comparision (1). To develop an overall picture of how genes are regulated during hyphal development the partial DNA arrays are used to study the difference in gene expression between wild type and the signalling mutants. Also Aldo de Luca developed a combinatorial method for the analysis of finite words for the study of biological molecules. This paper studies a relaxation of compatibility relation called K-compatibility  and conjugacy of K- compatibility between partial arrays.Â

Submicron-to-nanoscale structure characterization and organization of crystals in dentin bioapatites

The aim of this research was to ascertain the crystal morphology, and to assess the ultrastructure and texture changes of sound (SD) and caries-affected dentin (CAD) after being restored with Zn-free and Zn-containing amalgam. Dentin surfaces were studied by X-ray diffraction (XRD2), and Transmission Electron Microscopy (TEM) through selected area diffraction (SAED) and bright-field (BF) imaging. Crystals, at the dentin surface, were identified as hydroxyl-apatite with augmented crystallographic maturity, crystallite and grain sizes, and lower microstrain, in CAD dentin after Zn-containing amalgam removal, at 310 plane. This group, at this reflection, achieved lower microstrain than before amalgam placement. Opposed trend was followed at 002 reflection. Texture increased in CAD at both reflections, after the removal of Zn-containing amalgams. Crystallinity increased in SD after amalgam restorations at 002 and 310 reflections. In CAD, crystallinity decreased after amalgam restorations at 002 plane. Block-like and needle-like apatite crystals constituted the bulk of minerals in SD. Needle-like apatite crystals were observed, in CAD surfaces, before and after Zn-free amalgam restorations. Polyhedral and rounded drop-like shaped crystals characterized the CAD surfaces before Zn-containing amalgam placement. After the restoration removal, plate-like polygons and three-dimensional agglomerated crystals were determined. Crystallites, with improved crystallographic orientation, became shorter and thinner in CAD treated with Zn-containing amalgams, thus increasing mineralization and maturity.Project MAT2014-52036-P supported by the Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (FEDER) and FIS2013-41821-R

Caracterización de nanobarras de Al-doped ZnO crecidos por el método de deposición química en baño

Introduction: In recent years a metal oxide semiconductors have been paid attention due to their excellent chemical and physical properties.ZnO (Zinc oxide) is considered as one of the most attractive semiconductor materials for implementation in photo-detectors, gas sensors, photonic crystals, light emitting diodes, photodiodes, and solar cells, due to its novel electrical and optoelectronic properties. There are different uses of metal oxide semiconductors such us, UV photodetectors which are useful in space research’s, missile warning systems, high flame detectors, air quality spotting, gas sensors, and precisely calculated radiation for the treatment of UV-irradiated skin. ZnO is a metal oxide semiconductors and it is used as a transparent conducting oxide thin film because it has the best higher thermal stability, best resistance against the damage of hydrogen plasma processing and relatively cheaper if one compares it with ITO. Materials and Methods: On glass substrates, Al-doped ZnO (AZO) nanorods have been grown by a low -cost chemical bath deposition (CBD) method at low temperature. The seed layer of ZnO was coated on glass substrates. The effect of the Al-doping on the aligned, surface morphology, density, distribution, orientation and structure of ZnO nanorods are investigated. The Al-doping ratios are 0%, 0.2%, 0.8% and 2%. The Aluminum Nitrate Nonahydrate (Al (NO3)3.9H2O) was added to the growth solution, which is used as a source of the aluminum dopant element. The morphology and structure of the Al-doped ZnO nanorods are characterized by field emission scanning electron microscopy (FESEM) and high-resolution X-ray diffractometer (XRD). using the radio RF (Radio frequency) magnetron technique. Results and Discussion: The results show that the Al-doping have remarkable effects on the topography parameters such as diameter, distribution, alignment, density and nanostructure shape of the ZnO nanorods. These topography parameters have proportionally effective with increases of the Al-doping ratio. Also, X-ray diffraction results show that the Al-doping ratio has a good playing role on the nanostructure orientation of the ZnO nanorods. Conclusions: The Aluminum Nitride Nanohydrate considered as a good Aluminu source for doping ZnONR. It is clear from FESEM results that the Al-doping of ZnONR has a remarkable effect on the surface topography of nanorods for all aluminum doping ratios. From XRD patterns, it concludes that as the Al-doping ratio increases, the reorientation of the nanostructure of ZnO increases towards [100] direction. The results obtained also have shown that the average diameter of a nanorod is increased with increasing the ratio of Al-doping

The effect of anode surface area on nanoporous oxide formation during anodizing of low purity aluminum (AA1050 alloy)

Porous anodic alumina layers were obtained by a simple two-step anodization of low purity aluminum (99.5 % Al, AA1050 alloy) in a 0.3 M oxalic acid electrolyte at 45 V and 20 °C. The effect of anode surface area on structural features of nanoporous oxide and process of oxide formation was investigated. An ordered structure composed of nanostripes or nanopores was formed on the Al surface during electrochemical polishing in a mixture of perchloric acid and ethanol. This nanopattern is then replicated during the anodic oxide formation. It was found that the pore diameter, interpore distance, and porosity increase slightly with increasing surface area of the aluminum sample exposed to the anodizing electrolyte. On the other hand, a slight decrease in pore density and cell wall thickness was observed with increasing surface area of the sample. The detailed inspection of current density vs. time curves was also performed. The obtained results revealed that the higher surface area of the anode, the local current density minimum, was reached faster during first step of anodization and the increase in current density corresponding to the pore rearrangement process was observed earlier. Finally, a dense array of Pd nanowires (∼90 nm in diameter) was synthesized by simple electrodeposition of metal inside the channels of through-hole nanoporous anodic alumina templates with relatively large surface areas (4 cm2)

Objective Distinctions Between Genuine Plane Symmetries and Pseudosymmetries in Crystal Patterns of Graphic Artwork

A recently developed method for the objective identification of the plane symmetry group of a noisy crystal pattern is briefly described and subsequently applied to two pieces of graphic art. Pseudo-symmetries do not distract from the beauty of graphic art but add to it. They are here distinguished from the genuine symmetries that combine to form the best-fitting plane symmetry group. The gray-value deviations of the individual pixel values of graphic artworks from their perfectly symmetric abstractions are considered to be chiefly due to the handiwork and employed creative procedures of an individual artists. As different graphic techniques/procedures were employed in the creation of the here classified crystal patterns, one may glean insights on how well a particular technique or procedure supports the realization of an intended crystallographic symmetry group in a graphic work of art.Comment: 8 pages, 3 figure

ATLBS: the Australia Telescope Low-brightness Survey

We present a radio survey carried out with the Australia Telescope Compact Array. A motivation for the survey was to make a complete inventory of the diffuse emission components as a step towards a study of the cosmic evolution in radio source structure and the contribution from radio-mode feedback on galaxy evolution. The Australia Telescope low-brightness survey (ATLBS) at 1388 MHz covers 8.42 sq deg of the sky in an observing mode designed to yield images with exceptional surface brightness sensitivity and low confusion. The ATLBS radio images, made with 0.08 mJy/beam rms noise and 50" beam, detect a total of 1094 sources with peak flux exceeding 0.4 mJy/beam. The ATLBS source counts were corrected for blending, noise bias, resolution, and primary beam attenuation; the normalized differential source counts are consistent with no upturn down to 0.6 mJy. The percentage integrated polarization Pi_0 was computed after corrections for the polarization bias in integrated polarized intensity; Pi_0 shows an increasing trend with decreasing flux density. Simultaneous visibility measurements made with longer baselines yielded images, with 5" beam, of compact components in sources detected in the survey. The observations provide a measurement of the complexity and diffuse emission associated with mJy and sub-mJy radio sources. 10% of the ATLBS sources have more than half of their flux density in extended emission and the fractional flux in diffuse components does not appear to vary with flux density, although the percentage of sources that have complex structure increases with flux density. The observations are consistent with a transition in the nature of extended radio sources from FR-II radio source morphology, which dominates the mJy population, to FR-I structure at sub-mJy flux density. (Abridged)Comment: 18 pages, 8 figues, 6 tables, accepted for publication in MNRA

Hydroxyapatite-based cements induce different apatite formation in radicular dentin

Objectives. To investigate crystallinity and ultrastructure of the formed hydroxyapatite at radicular cervical and apical dentin after being treated with three different canal sealers. Methods. Cervical and apical root dentin surfaces were treated with two experimental hydroxyapatite-based sealers, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite) and an epoxy resin-based canal sealer (AH Plus); gutta-percha without sealer was included as control. Dentin surfaces were studied by X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging after 24 h and 12 m of storage. Results. Root cervical dentin treated with calcypatite and oxipatite produced poor crystallinity of new minerals, wide amorphous phase and non-stoichiometry. Reflections at the 002 plane and the corresponding diffraction rings attained lower values in the Scherrer equation and the Scherrer-Wilson equation in samples treated with both HAp-based sealers than in specimens without sealer or with AH Plus. At root cervical dentin treated with calcypatite, shorter and wider crystallite size formations and lower crystals grain size were found, if compared to those encountered at oxipatite treated dentin. Oxipatite attained improved crystallographic atomic order and less structural variation in both distances and angles. Apical dentin treated with oxipatite attained preferred grain orientation with polycrystalline lattices. Significance. The immature crystallites formed in dentin treated with calcypatite and oxipatite will account for high hydroxyapatite solubility and remineralizing activity. New polycrystalline formations encountered in apical dentin treated with oxipatite may also produce high mechanical performance.This work was supported by the Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (FEDER) Project MAT2017-85999-P