Entropy Balance and Dispersive Oscillations in Lattice Boltzmann Models

We conduct an investigation into the dispersive post-shock oscillations in the entropic lattice-Boltzmann method (ELBM). To this end we use a root finding algorithm to implement the ELBM which displays fast cubic convergence and guaranties the proper sign of dissipation. The resulting simulation on the one-dimensional shock tube shows no benefit in terms of regularization from using the ELBM over the standard LBGK method. We also conduct an experiment investigating of the LBGK method using median filtering at a single point per time step. Here we observe that significant regularization can be achieved.Comment: 18 pages, 4 figures; 13/07/2009 Matlab code added to appendi

Universal features of Thermopower in High Tc systems and Quantum Criticality

In high Tc superconductors a wide ranging connection between the doping dependence of the transition temperature Tc and the room temperature thermopower Q has been observed. A "universal correlation" between these two quantities exists with the thermopower vanishing at optimum doping as noted by OCTHH (Obertelli, Cooper, Tallon, Honma and Hor). In this work we provide an interpretation of this OCTHH universality in terms of a possible underlying quantum critical point (QCP) at Tc. Central to our viewpoint is the recently noted Kelvin formula relating the thermopower to the density derivative of the entropy. Perspective on this formula is gained through a model calculation of the various Kubo formulas in an exactly solved 1-dimensional model with various limiting procedures of wave vector and frequency.Comment: 12 pages, 8 figure

PREPARATION OF CHITOSAN-TPP NANOPARTICLES: THE INFLUENCE OF CHITOSAN POLYMERIC PROPERTIES AND FORMULATION VARIABLES

Objective: The aim of this work was to prepare chitosan nanoparticles (CS NPs) using sodium tripolyphosphate (TPP) as crosslinker and to study the effect of chitosan polymeric properties and experimental conditions on the properties and stability of NPs.Methods: CS NPs were prepared by ionic gelation method, using TPP as a crosslinker. The particle size (PS), polydispersity index (PDI), zeta potential (ZP) and the morphologies of the NPs were studied. CS NPs prepared by varying the concentration of TPP, Chitosan molecular weight and its degree of deacetylation, the stirring speed, the rate of TPP addition and the freeze-drying method to study the effect of these variables on the NPs. The stability of the CS NPs was evaluated by storing aqueous suspensions of NPs and comparing the PS, PDI and ZP at the beginning and the end of the experiment.Results: This study shows that the PS, ZP and dispersity of the NPs depend on the chitosan polymeric properties and experimental conditions. The NPs sizes range between 145.73 and 724.23 nm. They all carried positive charges ranging between+4.32 and+43.67 mV. Most of the NPs have the same sizes after freeze-drying, but showed higher monodispersity and ZP, indicating higher stability. After twenty days of studying the stability, the NPs that had low ZP showed a large increment in size in comparison to the highly charged NPs.Conclusion: In conclusion, the polymeric properties and formulation variables in the ionic gelation method have a great influence on the CS NPs formed

Rhodovulum aestuarii sp. nov., isolated from a brackish water body

A yellowish brown, phototrophic, purple non-sulfur bacterium, strain JA924r, was isolated in pure culture from a brackish water sample collected from an estuary. Single cells were oval to rod-shaped, non-motile and Gram-stain-negative and had a vesicu!ar architecture of intracellular photosynthetic membranes. Bacteriochlorophyll-a and carotenoids of the spheroidene series were present as photosynthetic pigments. Photolithoautotrophy, chemo-organoheterotrophy and photo-organoheterotrophy were the growth modes observed. Strain JA924T had complex growth requ1rements. Strain JA924 T was mesophilic and moderate!y halophilic. The DNA G -t- C content was 64 mal% (HPLC). The major cellular fatty acids were C18 1f·)7c/C 18 : 11·)6c, Ct 6 0 and C 18 . 0 . The major quinone was ubiquinone-1 0 (0-1 0). Phosphatidylg!ycerol, phosphatidylethanolamine, sulfolipid and an aminolipid were the main polar Iipids of strain JA924r. EzTaxon-e BLAST searches based on the 168 rRNA gene sequence of JA924T revealed highest similarity with Rhodovulum mangrovi AK41 T (98.19 %) and other members of the genus Rhodovulum (5 oc). Phenotypic, chemotaxonomic and molecular differences indicate that strain JA924 T represents a novel species of the genus Rhodovulum, for which the name Rhodovulum aestuarii sp. nov. is proposed. The type strain is JA924 T ( = LMG 29031 T = KCTC 15485 T)

Controls on the rheological properties of peridotite at a palaeosubduction interface: A transect across the base of the Oman-UAE ophiolite

Studies of experimentally deformed rocks and small-scale natural shear zones have demonstrated that volumetrically minor phases can control strain localisation by limiting grain growth and promoting grain-size sensitive deformation mechanisms. These small-scale studies are often used to infer a critical role for minor phases in the development of plate boundaries. However, the role of minor phases in strain localisation at an actual plate boundary remains to be tested by direct observation. In order to test the hypothesis that minor phases control strain localisation at plate boundaries, we conducted microstructural analyses of peridotite samples collected along a ~1 km transect across the base of the Oman-United Arab Emirates (UAE) ophiolite. The base of the ophiolite is marked by the Semail thrust, which represents the now exhumed contact between subducted oceanic crust and the overlying mantle wedge. As such, the base of the ophiolite provides the opportunity to directly examine a former plate boundary. Our results demonstrate that the mean olivine grain size is inversely proportional to the abundance of minor phases (primarily orthopyroxene, as well as clinopyroxene, hornblende, and spinel), consistent with suppression of grain growth by grain-boundary pinning. Our results also reveal that mean olivine grain size is proportional to CPO strength (both of which generally decrease towards the metamorphic sole), suggesting that the fraction of strain produced by different deformation mechanisms varied spatially. Experimentally-derived flow laws indicate that under the inferred deformation conditions, the viscosity of olivine was grain-size sensitive. As such, grain size, and thereby the abundance of minor phases, influenced viscosity during subduction-related deformation along the base of the mantle wedge. We calculate an order of magnitude decrease in the viscosity of olivine towards the base of the ophiolite, which suggests strain was localized near the subduction interface. Our data indicate that this rheological weakening was primarily the result of more abundant minor phases near the base of the ophiolite. Our interpretations are consistent with those of previous studies on experimentally deformed rocks and smaller-scale natural shear zones that indicate minor phases can exert the primary control on strain localisation. However, our study demonstrates for the first time that minor phases can control strain localisation at the scales relevant to a major plate boundar

The nature of submillimetre galaxies in cosmological hydrodynamic simulations

We study the nature of rapidly star-forming galaxies at z= 2 in cosmological hydrodynamic simulations, and compare their properties to observations of submillimetre galaxies (SMGs). We identify simulated SMGs as the most rapidly star-forming systems that match the observed number density of SMGs. In our models, SMGs are massive galaxies sitting at the centres of large potential wells, being fed by smooth infall and gas-rich satellites at rates comparable to their star formation rates (SFRs). They are not typically undergoing major mergers that significantly boost their quiescent SFR, but they still often show complex gas morphologies and kinematics. Our simulated SMGs have stellar masses of M*∼ 1011−11.7 M⊙, SFRs of ∼180–500 M⊙ yr−1, a clustering length of ∼10 h−1 Mpc and solar metallicities. The SFRs are lower than those inferred from far-infrared (far-IR) data by ∼×3, which we suggest may owe to one or more systematic effects in the SFR calibrations. SMGs at z= 2 live in ∼1013 M⊙ haloes, and by z= 0 they mostly end up as brightest group galaxies in ∼1014 M⊙ haloes. We predict that higher M* SMGs should have on average lower specific SFRs, less disturbed morphologies and higher clustering. We also predict that deeper far-IR surveys will smoothly join SMGs on to the massive end of the SFR–M* relationship defined by lower mass z∼ 2 galaxies. Overall, our simulated rapid star-formers provide as good a match to available SMG data as merger-based scenarios, offering an alternative scenario that emerges naturally from cosmological simulations

Low mortality of people living with diabetes mellitus diagnosed with COVID-19 and managed at a field hospital in Western Cape Province, South Africa

Background. The novel coronavirus disease 2019 (COVID-19) was declared an international pandemic by the World Health Organization in March 2020. Throughout the pandemic, the association between diabetes mellitus (DM) and more severe COVID-19 has been well described internationally, with limited data, however, on South Africa (SA). The role of field hospitals in the management of patients with COVID-19 in SA has not yet been described. Objectives. To describe the mortality and morbidity of people living with DM (PLWD) and comorbid COVID-19, as well as to shed light on the role of intermediate facilities in managing DM and COVID-19 during the pandemic. Methods. This is a single-centre cross-sectional descriptive study that included all patients with confirmed COVID-19 and pre-existing or newly diagnosed DM (of any type) admitted to the Cape Town International Convention Centre (CTICC) Intermediate Care Bed Facility from June 2020 to August 2020. This study presents the profile of patients admitted to the CTICC, and reports on the clinical outcome of PLWD diagnosed with COVID-19, and additionally determines some associations between risk factors and death or escalation of care in this setting. Results. There were 1 447 admissions at the CTICC, with a total of 674 (46.6%) patients who had confirmed DM, of whom 125 (19%) were newly diagnosed diabetics and 550 (81%) had pre-existing DM. Included in this group were 57 referrals from the telemedicine platform – a platform that identified high-risk diabetic patients with COVID-19 in the community, and linked them directly to hospital inpatient care. Of the 674 PLWD admitted, 593 were discharged alive, 45 were escalated to tertiary hospital requiring advanced care and 36 died. PLWD who died were older, had more comorbidities (specifically chronic obstructive pulmonary disease, congestive cardiac failure and chronic kidney disease) and were more likely to be on insulin.Conclusions. In a resource-limited environment, interdisciplinary and interfacility collaboration ensured that complicated patients with DM and COVID-19 were successfully managed in a field hospital setting. Telemedicine offered a unique opportunity to identify high-risk patients in the community and link them to in-hospital monitoring and care. Future studies should explore ways to optimise this collaboration, as well as to explore possibilities for early identification and management of high-risk patients

Lyman Alpha Emitters in the Hierarchically Clustering Galaxy Formation

We present a new theoretical model for the luminosity functions (LFs) of Lyman alpha (Lya) emitting galaxies in the framework of hierarchical galaxy formation. We extend a semi-analytic model of galaxy formation that reproduces a number of observations for local and high-z galaxies, without changing the original model parameters but introducing a physically-motivated modelling to describe the escape fraction of Lya photons from host galaxies (f_esc). Though a previous study using a hierarchical clustering model simply assumed a constant and universal value of f_esc, we incorporate two new effects on f_esc: extinction by interstellar dust and galaxy-scale outflow induced as a star formation feedback. It is found that the new model nicely reproduces all the observed Lya LFs of the Lya emitters (LAEs) at different redshifts in z ~ 3-6. Especially, the rather surprisingly small evolution of the observed LAE Lya LFs compared with the dark halo mass function is naturally reproduced. Our model predicts that galaxies with strong outflows and f_esc ~ 1 are dominant in the observed LFs. This is also consistent with available observations, while the simple universal f_esc model requires f_esc << 1 not to overproduce the brightest LAEs. On the other hand, we found that our model significantly overpredicts LAEs at z > 6, and absorption of Lya photons by neutral hydrogen in intergalactic medium (IGM) is a reasonable interpretation for the discrepancy. This indicates that the IGM neutral fraction x_HI rapidly evolves from x_HI << 1 at z < 6 to a value of order unity at z ~ 6-7, which is broadly consistent with other observational constraints on the reionization history.Comment: 14 pages, 7 figures, 1 table; accepted to ApJ; the html abstract is replaced to match the accepted version, the .ps and .pdf files are strictly identical between the 2nd and the 3rd version

Golden gaskets: variations on the Sierpi\'nski sieve

We consider the iterated function systems (IFSs) that consist of three general similitudes in the plane with centres at three non-collinear points, and with a common contraction factor \la\in(0,1). As is well known, for \la=1/2 the invariant set, \S_\la, is a fractal called the Sierpi\'nski sieve, and for \la<1/2 it is also a fractal. Our goal is to study \S_\la for this IFS for 1/2<\la<2/3, i.e., when there are "overlaps" in \S_\la as well as "holes". In this introductory paper we show that despite the overlaps (i.e., the Open Set Condition breaking down completely), the attractor can still be a totally self-similar fractal, although this happens only for a very special family of algebraic \la's (so-called "multinacci numbers"). We evaluate \dim_H(\S_\la) for these special values by showing that \S_\la is essentially the attractor for an infinite IFS which does satisfy the Open Set Condition. We also show that the set of points in the attractor with a unique ``address'' is self-similar, and compute its dimension. For ``non-multinacci'' values of \la we show that if \la is close to 2/3, then \S_\la has a nonempty interior and that if \la<1/\sqrt{3} then \S_\la$ has zero Lebesgue measure. Finally we discuss higher-dimensional analogues of the model in question.Comment: 27 pages, 10 figure

Intra-individual movement variability during skill transitions: A useful marker?

Applied research suggests athletes and coaches need to be challenged in knowing when and how much a movement should be consciously attended to. This is exacerbated when the skill is in transition between two more stable states, such as when an already well learnt skill is being refined. Using existing theory and research, this paper highlights the potential application of movement variability as a tool to inform a coach’s decision-making process when implementing a systematic approach to technical refinement. Of particular interest is the structure of co-variability between mechanical degrees-of-freedom (e.g., joints) within the movement system’s entirety when undergoing a skill transition. Exemplar data from golf are presented, demonstrating the link between movement variability and mental effort as an important feature of automaticity, and thus intervention design throughout the different stages of refinement. Movement variability was shown to reduce when mental effort directed towards an individual aspect of the skill was high (target variable). The opposite pattern was apparent for variables unrelated to the technical refinement. Therefore, two related indicators, movement variability and mental effort, are offered as a basis through which the evaluation of automaticity during technical refinements may be made