992,524 research outputs found
Ancient tin production: Slags from the Iron Age Carvalhelhos hillfort (NW Iberian Peninsula)
Provenance and production of tin in the Ancient World has since long been a major topic of discussion among archaeologists. In Western Europe, where significant tin ore (cassiterite) deposits are known, only a few remains of ancient tin production, such as tin slags, have been detected. In the present work, elemental and microstructural analyses by WDXRF, SEM-EDS and XRD were performed on recently recognised tin slags from the Iron Age Carvalhelhos hillfort located in NW Iberia, a territory that represents the largest extension with tin mineralisation in Western Europe. Elemental and microstructural characterisation of cassiterite collected in a pilot field survey in the region of the hillfort are presented and discussed, as well as two ceramic fragments that could be part of a smelting structure and an iron slag from the settlement. Results show that the tin slags have variable but high contents in Sn, similarly to Pre-Medieval tin slags found in other Western European areas, but also high contents of Ta and Nb, which specifically distinguish them from other tin slags, such as those found in SW Britain. Tin ores from the hillfort region frequently have Ta and Nb in cassiterite solid solution or as inclusions of columbite group minerals, relating well with the Carvalhelhos tin slags. Up to present, the Carvalhelhos slags are amongst the very few ancient tin slags known in Western Europe, and their study can contribute to a better knowledge on ancient tin sources and trade routes
In situ transformation and cleaning of tin-drop contamination on mirrors for extreme ultraviolet light
Tin-drop contamination was cleaned from multilayer-coated mirrors by
induction of phase transformation. The {\beta} - {\alpha} phase transition of
tin was induced to initiate material embrittlement and enable facile removal of
thick tin deposits. The necessary steps were performed under high-vacuum
conditions for an in-situ demonstration of the removal of severe tin
contamination from optics used for reflection of extreme ultraviolet light.
Molten tin of high purity was dripped onto mirror samples, inoculated with
small seed particles of gray tin and then cooled to temperatures in the range
of -25 {\deg}C to -40 {\deg}C. As recorded by photographic imaging, the drops
were converted in an evacuated chamber to gray tin by induction of tin pest
leading to their disintegration within a few hours. They could then be easily
cleaned or fell off from the surface without causing any damage of the
multilayer coating. Cleaning of tin contamination from the mirrors with almost
complete structural transformation of the tin drops and subsequent removal by
puffs of dry gas could be achieved within a day. The fraction of area coverage
of untransformed tin remaining on the samples after cleaning was evaluated from
the images and generally found to be well below 1%. After tin dripping, phase
transition and cleaning, analysis of the reflectance of a Mo/Si-coated mirror
with measurements at wavelengths of 13.6 nm and 13.5 nm showed a reduction by
only 0.5%, with an upper limit of 1%
Multilevel Topological Interference Management
The robust principles of treating interference as noise (TIN) when it is
sufficiently weak, and avoiding it when it is not, form the background for this
work. Combining TIN with the topological interference management (TIM)
framework that identifies optimal interference avoidance schemes, a baseline
TIM-TIN approach is proposed which decomposes a network into TIN and TIM
components, allocates the signal power levels to each user in the TIN
component, allocates signal vector space dimensions to each user in the TIM
component, and guarantees that the product of the two is an achievable number
of signal dimensions available to each user in the original network.Comment: To be presented at 2013 IEEE Information Theory Worksho
Critical Temperature tuning of Ti/TiN multilayer films suitable for low temperature detectors
We present our current progress on the design and test of Ti/TiN Multilayer
for use in Kinetic Inductance Detectors (KIDs). Sensors based on
sub-stoichiometric TiN film are commonly used in several applications. However,
it is difficult to control the targeted critical temperature , to maintain
precise control of the nitrogen incorporation process and to obtain a
production uniformity. To avoid these problems we investigated multilayer
Ti/TiN films that show a high uniformity coupled with high quality factor,
kinetic inductance and inertness of TiN. These features are ideal to realize
superconductive microresonator detectors for astronomical instruments
application but also for the field of neutrino physics. Using pure Ti and
stoichiometric TiN, we developed and tested different multilayer configuration,
in term of number of Ti/TiN layers and in term of different interlayer
thicknesses. The target was to reach a critical temperature around
K in order to have a low energy gap and slower recombination time
(i.e. low generation-recombination noise). The results prove that the
superconductive transition can be tuned in the K temperature
range properly choosing the Ti thickness in the nm range, and the
TiN thickness in the nm rang
Titanium Nitride as a Seed Layer for Heusler Compounds
Titanium nitride (TiN) shows low resistivity at room temperature, high
thermal stability and thus has the potential to serve as seed layer in magnetic
tunnel junctions. High quality TiN thin films with regard to the
crystallographic and electrical properties were grown and characterized by
X-ray diffraction and 4-terminal transport measurements. Element specific X-ray
absorption spectroscopy revealed pure TiN in the bulk. To investigate the
influence of a TiN seed layer on a ferro(i)magnetic bottom electrode, an
out-of-plane magnetized Mn2.45Ga as well as in- and out-of-plane magnetized
Co2FeAl thin films were deposited on a TiN buffer, respectively. The magnetic
properties were investigated using a superconducting quantum interference
device (SQUID) and anomalous Hall effect (AHE) for Mn2.45Ga. Magneto optical
Kerr effect (MOKE) measurements were carried out to investigate the magnetic
properties of Co2FeAl. TiN buffered Mn2.45Ga thin films showed higher
coercivity and squareness ratio compared to unbuffered samples. The Heusler
compound Co2FeAl showed already good crystallinity when grown at room
temperature
Use of mangroves for aquaculture: Myanmar.
Aquaculture has only started to develop rapidly in the past few decades, due to better knowledge of culture species, improved methodologies and techniques in breeding, nutrition and increasing demand for food fish of high-value species such as shrimps, sea bass and groupers.
Mangrove deforestation has an impact on shrimp culture itself, the success of the latter (when traditional culture method is used) depends on stocking of wild fry. For semi-intensive and intensive shrimp culture, the number of wild caught spawners may decrease because wild shrimp populations also use mangrove swamps as its feeding ground.
Other negative effects of mangrove destruction to make way to shrimp ponds, include water pollution from pond effluents, sedimentation from the release of solid materials from pond, interruption of the tidal water flow, dwindling natural shrimp and fish stock due to increased pollution or product contamination due to indiscriminate use of chemicals.
Chemicals and drugs (antibiotic) should not be used in fish and shrimp culture for prevention and control of bacteria and viral diseases. In order to ensure the sustainable development of aquaculture, it is important to bear in mind the interdependence of technology and natural resource under various socioeconomic setting
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