3,806 research outputs found
Spin-triplet superconductivity in a weak-coupling Hubbard model for the quasi-one-dimensional compound LiMoO
The purple bronze LiMoO is of interest due to its
quasi-one-dimensional electronic structure and the possible Luttinger liquid
behavior resulting from it. For sufficiently low temperatures, it is a
superconductor with a pairing symmetry that is still to be determined. To shed
light on this issue, we analyze a minimal Hubbard model for this material
involving four molybdenum orbitals per unit cell near quarter filling, using
asymptotically exact perturbative renormalization group methods. We find that
spin triplet odd-parity superconductivity is the dominant instability.
Approximate nesting properties of the two quasi-one-dimensional Fermi surfaces
enhance certain second-order processes, which play crucial roles in determining
the structure of the pairing gap. Notably, we find that the gap has accidental
nodes, i.e. it has more sign changes than required by the point-group symmetry.Comment: Update
Benchmark ages for the Gaia benchmark stars
In the era of large-scale surveys of stars in the Milky Way, stellar ages are
crucial for studying the evolution of the Galaxy. But determining ages of field
stars is notoriously difficult; therefore, we attempt to determine benchmark
ages for the extensively studied Gaia benchmark stars which can be used for
validation purposes. By searching the literature for age estimates from
different methods and deriving new ages based on Bayesian isochrone fitting, we
are able to put reliable limits on the ages of 16 out of the 33 benchmark
stars. The giants with well-defined ages are all young, and an expansion of the
sample to include older giants with asteroseismic ages would be beneficial.
Some of the stars have surface parameters inconsistent with isochrones younger
than 16 Gyr. Including -enhancement in the models when relevant
resolves some of these cases, but others clearly highlight discrepancies
between the models and observations. We test the impact of atomic diffusion on
the age estimates by fitting to the actual surface metallicity of the models
instead of the initial value and find that the effect is negligible except for
a single turn-off star. Finally, we show that our ability to determine
isochrone-based ages for large spectroscopic surveys largely mirrors our
ability to determine ages for these benchmark stars, except for stars with
dex since their location in the HR diagram is almost age
insensitive. Hence, isochrone fitting does not constrain their ages given the
typical uncertainties of spectroscopic stellar parameters.Comment: Accepted in MNRAS. 69 pages (18 for main text, 11 for appendix, and
40 for extra figures
Diamonds for Security: A Non-Interleaving Operational Semantics for the Applied Pi-Calculus
We introduce a non-interleaving structural operational semantics for the applied ?-calculus and prove that it satisfies the properties expected of a labelled asynchronous transition system (LATS). LATS have well-studied relations with other standard non-interleaving models, such as Mazurkiewicz traces or event structures, and are a natural extension of labelled transition systems where the independence of transitions is made explicit. We build on a considerable body of literature on located semantics for process algebras and adopt a static view on locations to identify the parallel processes that perform a transition. By lifting, in this way, work on CCS and ?-calculus to the applied ?-calculus, we lay down a principled foundation for reusing verification techniques such as partial-order reduction and non-interleaving equivalences in the field of security. The key technical device we develop is the notion of located aliases to refer unambiguously to a specific output originating from a specific process. This light mechanism ensures stability, avoiding disjunctive causality problems that parallel extrusion incurs in similar non-interleaving semantics for the ?-calculus
Snatch trajectory of elite level girevoy (Kettlebell) sport athletes and its implications to strength and conditioning coaching
Girevoy sport (GS) has developed only recently in the West, resulting in a paucity of English scientific literature available. The aim was to document kettlebell trajectory of GS athletes performing the kettlebell snatch. Four elite GS athletes (age = 29-47 years, body mass = 68.3-108.1 kg, height 1.72-1.89 m) completed one set of 16 repetitions with a 32.1 kg kettlebell. Trajectory was captured with the VICON motion analysis system (250 Hz) and analysed with VICON Nexus (1.7.1). The kettlebell followed a ‘C’ shape trajectory in the sagittal plane. Mean peak velocity in the upwards phase was 4.03 ± 0.20 m s –1, compared to 3.70 ± 0.30 m s–1 during the downwards phase, and mean radial error across the sagittal and frontal planes was 0.022 ± 0.006 m. Low error in the movement suggests consistent trajectory is important to reduce extraneous movement and improve efficiency. While the kettlebell snatch and swing both require large anterior-posterior motion, the snatch requires the kettlebell to be held stationary overhead. Therefore, a different coaching application is required to that of a barbell snatch
A spatio-temporal model for Red Sea surface temperature anomalies
This paper details the approach of team Lancaster to the 2019 EVA data challenge, dealing with spatio-temporal modelling of Red Sea surface temperature anomalies. We model the marginal distributions and dependence features separately; for the former, we use a combination of Gaussian and generalised Pareto distributions, while the dependence is captured using a localised Gaussian process approach. We also propose a space-time moving estimate of the cumulative distribution function that takes into account spatial variation and temporal trend in the anomalies, to be used in those regions with limited available data. The team's predictions are compared to results obtained via an empirical benchmark. Our approach performs well in terms of the threshold-weighted continuous ranked probability score criterion, chosen by the challenge organiser
Superstatistical fluctuations in time series: Applications to share-price dynamics and turbulence
We report a general technique to study a given experimental time series with
superstatistics. Crucial for the applicability of the superstatistics concept
is the existence of a parameter that fluctuates on a large time scale
as compared to the other time scales of the complex system under consideration.
The proposed method extracts the main superstatistical parameters out of a
given data set and examines the validity of the superstatistical model
assumptions. We test the method thoroughly with surrogate data sets. Then the
applicability of the superstatistical approach is illustrated using real
experimental data. We study two examples, velocity time series measured in
turbulent Taylor-Couette flows and time series of log returns of the closing
prices of some stock market indices
Synthesis of chimeric receptors essential for spore germination
Various species of bacteria have been reported to form an endospore, a metabolically dormant cell, during times of nutrient deficiencies and extreme stress. These said structures are outstandingly resistant to harsh chemicals, extreme temperatures, and can revert back to a metabolically active cell, through a process known as germination, when the necessary conditions are met. The rigid membrane of the endospore contains various germination (Ger) receptors which sense the external environment for necessary metabolites and germinants. Ger receptors are encoded by tricistronic operons that produce three distinct membrane proteins, the A, B, and C subunits. Although the function of the Ger receptor has been established by genetics, no information is currently available for germinant binding site. Bioinformatic and genetic approaches has predicted that the C-terminus of the B subunit is the most likely candidate to contain the germinant binding site. B. Subtilis and B. Megaterium, two species of the Bacilli genus, germinate in response to different germinants; B. Subtilis germinates in response to L-alanine by activation of the GerA receptor, while B. Megaterium germinates in response to L-leucine by the activation of its GerU receptor. The focus of this study is to construct chimeric genes in which fragments of B. Subtilis GerA receptors and B. Megaterium receptors are fused together. These B. Subtilis::B. Megaterium chimeric receptors will be introduced into the B. Subtilis genome and the mutant B. Subtilis spores will then be tested for the ability to germinate with leucine in order to establish the leucine binding site of GerUB. During the initial pilot studies, the regions coding for the Nterminus of the GerA receptor from B. Subtilis and the C-terminus of the GerU receptor from B. Megaterium were amplified using polymerase chain reaction with primer ends complementary to each other in order to further produce the desired hybrid genes without the use of restriction enzymes
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