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The Danjon Astrolabe at the Naval Observatory has been traditionally used to determine Universal Time and improve the systematic accuracy of star positions. During the past year, it has been used to determine latitude and longitude at remotely scattered sites for geodetic purposes. Operating this instrument away from the Observatory necessitated a mobile support and timing system rugged enough to operate dependably in ever changing, and sometimes harsh, environmental conditions.
This paper describes the performance of the astrolabe timing and data acquisition system, gives engineering design considerations, and describes the equipment and instrumentation.
RF-plasma MBE was used to epitaxially grow 4 – 100-nm-thick metallic
β-Nb2N thin films on hexagonal SiC substrates. When the
N/Nb flux ratios are greater than one, the most critical parameter for
high-quality β-Nb2N is the substrate temperature. The X-ray
diffraction (XRD) of films grown between 775 °C and 850 °C
demonstrates pure β-Nb2N phase formation which was also
confirmed by X-ray photoelectron spectroscopy and transmission electron
microscopy measurements. Using the (0002) and (21
1) XRD peaks of a β-Nb2N film grown at 850
°C reveals a 0.68% lattice mismatch to the 6H-SiC substrate. This
suggests that β-Nb2N can be used for high-quality
metal/semiconductor heterostructures that cannot be fabricated at present.
High temperature solid state sodium (23Na) magic angle spinning (MAS) NMR spin lattice relaxation times (T1) were evaluated for a series of NASICON (Na3Zr2PSi2O12) materials to directly determine Na jump rates. Simulations of the T1 temperature variations that incorporated distributions in Na jump activation energies, or distribution of jump rates, improved the agreement with experiment. The 23Na NMR T1 relaxation results revealed that distributions in the Na dynamics were present for all of the NASICON materials investigated here. The 23Na relaxation experiments also showed that small differences in material composition and/or changes in the processing conditions impacted the distributions in the Na dynamics. The extent of the distribution was related to the presence of a disordered or glassy phosphate phase present in these different sol-gel processed materials. The 23Na NMR T1 relaxation experiments are a powerful tool to directly probing Na jump dynamics and provide additional molecular level details that could impact transport phenomena.
We report on mid-infrared (600 – 4000 cm-1), refection-type optical-Hall effect measurements on epitaxial graphene grown on C-face silicon carbide and present Landau-level transition features detected at 1.5 K as a function of magnetic field up to 8 Tesla. The Landau-level transitions are detected in reflection configuration at oblique incidence for wavenumbers below, across and above the silicon carbide reststrahlen range. Small Landau-level transition features are enhanced across the silicon carbide reststrahlen range due to surface-guided wave coupling with the electronic Landau-level transitions in the graphene layer. We analyze the spectral and magnetic-field dependencies of the coupled resonances, and compare our findings with previously reported Landau-level transitions measured in transmission configuration [4,5,6]. Additional features resemble transitions previously assigned to bilayer inclusion , as well as graphite . We discuss a model description to account for the electromagnetic polarizability of the graphene layers, and which is sufficient for quantitative model calculation of the optical-Hall effect data.
PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.5-m optical/infrared telescope to be located at Dome C on the Antarctic plateau. Conditions at Dome C are known to be exceptional for astronomy. The seeing (above ∼30 m height), coherence time, and isoplanatic angle are all twice as good as at typical mid-latitude sites, while the water-vapour column, and the atmosphere and telescope thermal emission are all an order of magnitude better. These conditions enable a unique scientific capability for PILOT, which is addressed in this series of papers. The current paper presents an overview of the optical and instrumentation suite for PILOT and its expected performance, a summary of the key science goals and observational approach for the facility, a discussion of the synergies between the science goals for PILOT and other telescopes, and a discussion of the future of Antarctic astronomy. Paper II and Paper III present details of the science projects divided, respectively, between the distant Universe (i.e. studies of first light, and the assembly and evolution of structure) and the nearby Universe (i.e. studies of Local Group galaxies, the Milky Way, and the Solar System).
Alnus rubra growing in the field in Scotland is nodulated effectively by local strains of Frankia. Strains which have been isolated from Alnus rubra at Lennox Forest show different growth medium requirements and colony morphology compared with isolates from Alnus glutinosa and several different strains have been isolated from the same locality. Preliminary evidence suggests that some spore negative, northwest American Frankia strains may be more effective than local spore positive crushed nodule inoculum for nitrogen-fixation in Alnus rubra.
On the moderately fertile clay soil of Lennox Forest, a mixed plantation of alternate Picea silchensis and Alnus rubra showed no improvement in growth of spruce compared with pure spruce plots. However, the presence of alder increased upper soil nitrogen status by 585 kg ha ' which approximates the standard 150 kg N ha 'of fertiliser nitrogen applied in practice to nitrogen deficient stands at about 5-year intervals. Although the alder had penetrated the subsoil, there was no apparent effect on spruce rooting depth in the mixed stands in this high clay soil. In addition to nitrogen content, the total phosphorus of the upper soil horizons was improved in the mixed plots by an estimated 3–6 kg ha -1 y 1 and it is suggested that this phosphorus may be brought from the subsoil by the deeper rooting alder and deposited on the surface in its litter.
Although improved growth of spruce in mixture with Alnus rubra is only likely where pure spruce stands are stressed for nutrients, the potential benefits of symbiotic nitrogen-fixation in silvicultural practice make it desirable to investigate other species and provenances of Alnus suited to British conditions, to achieve maximum symbiotic fixation of nitrogen by selection and inoculation with superior strains of Frankia and to include such plants in trials of mixtures on sites where nitrogen-availability may be critical.
Milk is a source of bioactive molecules with wide-ranging functions. Among these, the immune properties have been the best characterised. In recent years, it has become apparent that besides the immunoglobulins, milk also contains a range of minor immune-related proteins that collectively form a significant first line of defence against pathogens, acting both within the mammary gland itself as well as in the digestive tract of the suckling neonate. We have used proteomics technologies to characterise the repertoire of host-defence-related milk proteins in detail, revealing more than 100 distinct gene products in milk, of which at least 15 are known host-defence-related proteins. Those having intrinsic antimicrobial activity likely function as effector proteins of the local mucosal immune defence (e.g. defensins, cathelicidins and the calgranulins). Here, we focus on the activities and biological roles of the cathelicidins and mammary serum amyloid A. The function of the immune-related milk proteins that do not have intrinsic antimicrobial activity is also discussed, notably lipopolysaccharide-binding protein, RNase4, RNase5/angiogenin and cartilage-glycoprotein 39 kDa. Evidence is shown that at least some of these facilitate recognition of microbes, resulting in the activation of innate immune signalling pathways in cells associated with the mammary and/or gut mucosal surface. Finally, the contribution of the bacteria in milk to its functionality is discussed. These investigations are elucidating how an effective first line of defence is achieved in the bovine mammary gland and how milk contributes to optimal digestive function in the suckling calf. This study will contribute to a better understanding of the health benefits of milk, as well as to the development of high-value ingredients from milk.
The use of a particle accelerator to measure the 14C content of carbon-containing materials is briefly described. The application of the method to the determination of the age of some artistic artifacts is discussed.
New generations of polymer-ceramic nanocomposites are being developed by intercalation of layered solids. Synthetic approaches include intercalative polymerization, direct polymer intercalation and molecular dispersion of the host layers in the polymer matrix. The unique physical and mechanical properties of the hybrids are attributed to the molecular dispersion and the synergism between the individual components.
Enamels from Northern Spain, Central France, and Limoges, dating from the 10th century to the mid 13th century, were analyzed by energy dispersive x-ray spectrometry and x-ray diffractometry to determine their overall compositions, and the opacifiers and colorants used. The compositions suggest the re-use of Roman tesserae. Calcium and lead antimonates were found as the predominant opacifiers; however, tin oxide and lead-tin yellow were also found in some of the enamels, either singly or in combination with the antimonates. One of the enamels from Limoges varied from the others in that the enamels had overall compositions similar to Islamic or Venetian glasses, and contained only tin oxide as an opacifier.
Over 108 samples of mural paintings from Teotihuacán, México, were studied by scanning electron microscopy, optical microscopy and X-ray diffractometry. The results show a sequence in the techniques employed to produce the mural painting's supporting plasters -made of lime and different sands. The technical stages found can be used as archaeological data to help understand the continuous evolution of 800-year mural paintings. The consequences of our study are discussed in detail.
Microscopy and elemental analysis of ore, slag, ceramic and ash from a major metallurgical site have allowed insights into the ancient processes. Constraints have been placed on raw materials and smelting conditions, and aspects of technological change and development have been recognised.
Modem rubber is a nightmarish material in a museum collection because it is highly susceptible to oxidation, and will slowly crystallize at room temperature, the combination of which can make the rubber inelastic after only a few decades. Recent studies by the author have shown that the rubber in modem spacesuits can be preserved against oxidation by cold storage, but only at the cost of considerably accelerating crystallization.
Natural rubber from ethnographic artifacts, produced by less consistent and less documented technology (as well as from different botanical sources), presents similar problems. A rubber sample from a Mexican artifact, for example, was found to be both highly oxidized and highly crystalline. It also appeared to have been filled with an inorganic material and may be crosslinked, offering striking similarities between its physical and chemical properties and those of the degraded modem rubber found in the spacesuits.
This paper discusses the results of the present research on crystallization/decrystallization of rubber artifacts, and the effects of storage environments on their degradation. These results are then applied to the problem of preserving the chemical and physical integrity of both older and modem rubber collections.
The decay processes in monuments, considered as interaction between building materials and environmental factors, presents a specific interest in the case of marine environment (Mediterranean), in mild climatic conditions An extended monument, like the Medieval Fortress of Rhodes could be a characteristic example. It is constructed by a susceptible to salt decay biocalcareous porous stone which suffers mainly from salt crystallisation and hard carbonate crusts formation.
The research program has been developed on walls of different typologies, according to their position and exposure orientation to various environmental factors, and specifically concerning humidity sources as capillary rise via ground and marine salt spray. Stone samples from different positions along the fortress, at various heights and depths on the walls, significant of the main decay patterns (alveolar, carbonate crust and mixed), underwent physical and chemical examination.
Humidity and soluble salts' concentration measurements by Atomic Absorption Spectroscopy, Ionic Chromatography and specific conductivity allow the assessment of their distribution patterns on the masonries.
Hence from the correlation between environmental factors and the material properties, directions for a conservation plan might be derived.
Lithium titanate spinel (Li4Ti5O12, or LTS) has received an increasing level of attention as a nanopowder lithium-ion battery anode. Nanopowder electrodes may provide a higher energy density than currently available. Furthermore, the surface of the spinel nanopowder has been studied in air, under vacuum, and at varying temperatures with diffuse reflectance infrared Fourier transform spectroscopy revealing surface hydroxyls, carbonates and water. Applying a TiN thin film, a film that is both conducting and chemically inert to harmful reactions with the solvent/electrolyte, by atomic layer deposition (ALD) may enhance battery cycle life. A 200-layer film was deposited at 500 °C. We have characterized the influence of a TiN thin film on Li-ion battery performance. Total nitrogen content and transmission electron microscopy were used to verify the presence of nitrogen and formation of a thin film, respectively, on LTS. Modifying the powder with an ALD thin film coating produced an anode material with a voltage profile that demonstrated longer charge maintenance with shorter transient periods. It also held a more consistent charge capacity over varying discharge rates in coin cell testing than unmodified LTS.
There is a growing demand for advanced composites which can maintain their structural strength in high-temperature environments, particularly for aerospace applications. The use of graphite fiber/nickel metal matrix composites would be desirable if the deterioration of mechanical properties resulting from interdiffusion of carbon and nickel at temperatures in excess of 600°C could be avoided. The present research concerns an electrodeposited cobalt alloy coating containing 5-10.5 at-% tungsten, which was designed to serve as a diffusion barrier between graphite fibers and a nickel matrix. The resulting graphite/Co-W/Ni composite was tested under various time/temperature conditions, and the coating was shown to inhibit diffusion for up to 24 hr at 800°C. Annealed and unannealed coated fibers were analyzed by x-ray diffraction and by transmission electron microscopy The as-deposited coating was found to contain both h.c.p. and f.c.c. cobalt, whereas only f.c.c. was observed after annealing at 1100°C for 1.5 hours. WC was found at the coating/fiber interface.
Polyanionic proteins isolated from biominerals serve as models for the development of biodegradable surface-reactive commercial polymers. A simple model for the natural polyanions is polyaspartic acid. This polymer may be made on a large scale using thermal polymerization of dry aspartic acid. The immediate result of the reaction is polysuccinimide which is hydrolyzed with base to form the polypeptide. The overall process yields up to 99% conversion of aspartic acid to polyaspartate. The thermal polyaspartate (TPA) is a copolymer having 70% of the amide bonds formed from β-carboxyl groups and 30% from α-carboxyl groups. TPA is as effective as the commercial polyanion polyacrylate in mineral dispersion and growth inhibition assays. Biodegradation of the TPA has been established using standard BOD and CO2 evolution assays. In contrast, polyacrylates appear to be non-degradable. Modifications of the TPA have been made by reacting the succinimide with nucleophiles. Crosslinking of the polymer has been achieved, a process which results in absorbent gels. Because TPA can be produced in large scale, has similar activity to polyacrylate and is biodegradable, it seems a likely candidate for use in numerous applications in which non-degradable polyanions are employed. These applications include use as detergent additives, water treatment chemicals, dispersants for the paint and paper industry and as superabsorbents in health and sanitary products.