The use of accelerated beams of electrons, protons or ions has furthered the development of nearly every scientific discipline. However, high-energy muon beams of equivalent quality have not yet been ...delivered. Muon beams can be created through the decay of pions produced by the interaction of a proton beam with a target. Such 'tertiary' beams have much lower brightness than those created by accelerating electrons, protons or ions. High-brightness muon beams comparable to those produced by state-of-the-art electron, proton and ion accelerators could facilitate the study of lepton-antilepton collisions at extremely high energies and provide well characterized neutrino beams
. Such muon beams could be realized using ionization cooling, which has been proposed to increase muon-beam brightness
. Here we report the realization of ionization cooling, which was confirmed by the observation of an increased number of low-amplitude muons after passage of the muon beam through an absorber, as well as an increase in the corresponding phase-space density. The simulated performance of the ionization cooling system is consistent with the measured data, validating designs of the ionization cooling channel in which the cooling process is repeated to produce a substantial cooling effect
. The results presented here are an important step towards achieving the muon-beam quality required to search for phenomena at energy scales beyond the reach of the Large Hadron Collider at a facility of equivalent or reduced footprint
.
Performance of the MICE diagnostic system Bogomilov, M.; Tsenov, R.; Vankova-Kirilova, G. ...
Journal of instrumentation,
08/2021, Letnik:
16, Številka:
8
Journal Article
Great advances are expected during the analysis of drilled material acquired from 2 m depth by ExoMars rover, supported by the comparison to local context, and the joint use of different instruments. ...Textural information might be less detailed relatively to what is usually obtained at outcrops during classical geological field work on the Earth, partly because of the lack of optical imaging of the borehole wall and also because the collected samples are crushed. However sub-mm scale layering and some other sedimentary features might be identified in the borehole wall observations, or in the collected sample prior to crushing, and also at nearby outcrops. The candidate landing sites provide different targets and focus for research: Oxia Planum requires analysis of phyllosilicates and OH content, at Mawrth Vallis the layering of various phyllosilicates and the role of shallow-subsurface leaching should be emphasized. At Aram Dorsum the particle size and fluvial sedimentary features will be interesting. Hydrated perchlorates and sulphates are ideal targets possibly at every landing sites because of OH retention, especially if they are mixed with smectites, thus could point to even ancient wet periods. Extensive use of information from the infrared wall scanning will be complemented for geological context by orbital and rover imaging of nearby outcrops. Information from the context is especially useful to infer the possible action of past H
2
O. Separation of the ice and liquid water effects will be supported by cation abundance and sedimentary context. Shape of grains also helps here, and composition of transported grains points to the weathering potential of the environment in general. The work on Mars during the drilling and sample analysis will provide brand new experience and knowledge for future missions.
Accelerated muon beams have been considered for next-generation studies of high-energy lepton-antilepton collisions and neutrino oscillations. However, high-brightness muon beams have not yet been ...produced. The main challenge for muon acceleration and storage stems from the large phase-space volume occupied by the beam, derived from the muon production mechanism through the decay of pions from proton collisions. Ionization cooling is the technique proposed to decrease the muon beam phase-space volume. Here we demonstrate a clear signal of ionization cooling through the observation of transverse emittance reduction in beams that traverse lithium hydride or liquid hydrogen absorbers in the Muon Ionization Cooling Experiment (MICE). The measurement is well reproduced by the simulation of the experiment and the theoretical model. The results shown here represent a substantial advance towards the realization of muon-based facilities that could operate at the energy and intensity frontiers.
Objectives
The aim of this study was to evaluate the sealing ability and morphological microstructure of Biodentine in comparison to ProRoot mineral trioxide aggregate (MTA) after storage in an ...acidic environment.
Materials and methods
Biodentine and ProRoot MTA were prepared and packed into the canal lumen of dentin disks. Twenty specimens of each material were further randomly divided into two groups according to the storage media: group A: materials with saline as storage medium; group B: materials with citric acid buffered at pH 5.4 as storage medium. The sealing ability was evaluated at 1, 3, 6, and 24 h and 1 or 3 months, using a fluid transport model for quantitative analysis of endodontic microleakage. The morphological microstructures of the materials were also evaluated using scanning electron microscopy.
Results
During the first 24 h, MTA showed greater fluid transport values than Biodentine in both environments. At the 3-month measurement, when the materials were stored in saline, MTA showed greater ability to prevent fluid movement than Biodentine (
p
< 0.0001). However, when the materials were stored in an acidic environment, no statistical significant difference was found after 3 months. After storage in saline, both materials showed an uneven crystalline surface with similar hexagonal crystals. The microstructure of Biodentine changed after exposure to citric acid, showing a relatively smooth surface with more spheroidal crystals.
Conclusions
The exposure to an acidic environment, within the limits of this study, seems to result in morphological changes of Biodentine in a different manner than MTA. MTA shows good ability to prevent fluid movement over time, in both environments. The ability of Biodentine to prevent fluid movement over time was enhanced in the acidic environment.
Clinical relevance
The findings of the present study could imply that both materials are indicated for use in an acidic environment.
Mars: new insights and unresolved questions Changela, Hitesh G.; Chatzitheodoridis, Elias; Antunes, Andre ...
International journal of astrobiology,
12/2021, Letnik:
20, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Abstract
Mars exploration motivates the search for extraterrestrial life, the development of space technologies, and the design of human missions and habitations. Here, we seek new insights and pose ...unresolved questions relating to the natural history of Mars, habitability, robotic and human exploration, planetary protection, and the impacts on human society. Key observations and findings include:
–
high escape rates of early Mars' atmosphere, including loss of water, impact present-day habitability;
–
putative fossils on Mars will likely be ambiguous biomarkers for life;
–
microbial contamination resulting from human habitation is unavoidable; and
–
based on Mars' current planetary protection category, robotic payload(s) should characterize the local martian environment for any life-forms prior to human habitation.
Some of the outstanding questions are:
–
which interpretation of the hemispheric dichotomy of the planet is correct;
–
to what degree did deep-penetrating faults transport subsurface liquids to Mars' surface;
–
in what abundance are carbonates formed by atmospheric processes;
–
what properties of martian meteorites could be used to constrain their source locations;
–
the origin(s) of organic macromolecules;
–
was/is Mars inhabited;
–
how can missions designed to uncover microbial activity in the subsurface eliminate potential false positives caused by microbial contaminants from Earth;
–
how can we ensure that humans and microbes form a stable and benign biosphere; and
–
should humans relate to putative extraterrestrial life from a biocentric viewpoint (preservation of all biology), or anthropocentric viewpoint of expanding habitation of space?
Studies of Mars' evolution can shed light on the habitability of extrasolar planets. In addition, Mars exploration can drive future policy developments and confirm (or put into question) the feasibility and/or extent of human habitability of space.
We studied the effects of water quality on the hydration of quicklimes prepared from calcitic limestone and dolomitic limestone during calcination at 1050 °C. At a low total chloride and sulfate ...content, reactivity is insensitive to concentration and no effect on quicklime slaking is seen. At higher concentrations, however, we observe a chromatographic effect for chlorides and sulfates. Concentrated chlorides react with the slaking water, forming products such as CaCl
2
that are much more soluble than Ca(OH)
2
, which facilitates transformation of quicklime to slaked lime. In the range of sulfate concentrations in natural waters we observed no effect of sulfates during quicklime hydration. Consequently, in natural waters and their mixtures (conductivity < 2600 μS cm
−1
), only chloride concentrations are found to promote quicklime hydration. These results suggest that water treatment technologies, applied to natural light brackish water compositions, will not lead to quality improvement for lime-industry products.
We studied the effects of water quality on the hydration of quicklimes prepared from calcitic limestone and dolomitic limestone during calcination at 1050 °C.
The Muon Ionization Cooling Experiment (MICE) collaboration seeks to demonstrate the feasibility of ionization cooling, the technique by which it is proposed to cool the muon beam at a future ...neutrino factory or muon collider. The emittance is measured from an ensemble of muons assembled from those that pass through the experiment. A pure muon ensemble is selected using a particle-identification system that can reject efficiently both pions and electrons. The position and momentum of each muon are measured using a high-precision scintillating-fibre tracker in a 4\,T solenoidal magnetic field. This paper presents the techniques used to reconstruct the phase-space distributions and reports the first particle-by-particle measurement of the emittance of the MICE Muon Beam as a function of muon-beam momentum.
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