Approaching finite-temperature phase diagrams of strongly correlated materials: a case study for V2O3

Examining phase stabilities and phase equilibria in strongly correlated materials asks for a next level in the many-body extensions to the local-density approximation (LDA) beyond mainly spectroscopic assessments. Here we put the charge-self-consistent LDA+dynamical mean-field theory (DMFT) methodology based on projected local orbitals for the LDA+DMFT interface and a tailored pseudopotential framework into action in order to address such thermodynamics of realistic strongly correlated systems. Namely a case study for the electronic phase diagram of the well-known prototype Mott-phenomena system V$_2$O$_3$ at higher temperatures is presented. We are able to describe the first-order metal-to-insulator transitions with negative pressure and temperature from the self-consistent computation of the correlated total energy in line with experimental findings.Comment: 12 pages, 15 figures, new data adde

Late movement of basin-edge lobate scarps on Mercury

Basin-edge lobate scarps are a sub-type of tectonic shortening structure on the surface of Mercury that have formed at the edge of volcanic units that fill or partly fill impact basins. We have performed a global survey of these features and find that they are widespread in basins across the planet. We obtained model ages from crater size–frequency distribution analysis for a subset of our surveyed basins, for both the smooth plains infill and for the last resolvable tectonic activity on the associated basin-edge scarps. Our results indicate that some of these lobate scarps were still accumulating strain in the late Mansurian (approximately 1 Ga). From a photogeological assessment, we find that the orientations of these basin-edge lobate scarps are similar to those reported for the global population of lobate scarps in earlier studies, appearing to align ∼north–south at low latitudes and ∼east–west at higher latitudes. However, reassessing these landforms’ orientation with artificially illuminated topographic data does not allow us to rule out the effect of illumination bias. We propose that these landforms, the result of crustal shortening in response to global contraction, formed along the interface between the basin floor and the smooth plains unit, which acted as a mechanical discontinuity along which shortening strains were concentrated

Enhanced germination and electrotactic behaviour of Phytophthora palmivora zoospores in weak electric fields

Soil-dwelling microorganisms use a variety of chemical and physical signals to navigate their environment. Plant roots produce endogenous electric fields which result in characteristic current profiles. Such electrical signatures are hypothesised to be used by pathogens and symbionts to track and colonise plant roots.
The oomycete pathogen Phytophthora palmivora generates motile zoospores which swim towards the positive pole when exposed to an external electric field in vitro.
Here, we provide a quantitative characterization of their electrotactic behaviour in 3D. We found that a weak electric field (0.7 - 1.0 V/cm) is sufficient to induce an accumulation of zoospore at the positive pole, without affecting their encystment rate. We also show that the same external electric field increases the zoospore germination rate and orients the germ tube's growth. We conclude that several early stages of the P. palmivora infection cycle are affected by external electric fields.
Taken together, our results are compatible with the hypothesis that pathogens use plant endogenous electric fields for host targeting.&#xD

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Electronic transport properties of quasicrystals: a Review

We present a review of some results concerning electronic transport properties of quasicrystals. After a short introduction to the basic concepts of quasiperiodicity, we consider the experimental transport properties of electrical conductivity with particular focus on the effect of temperature, magnetic field and defects. Then, we present some heuristic approaches that tend to give a coherent view of different, and to some extent complementary, transport mechanisms in quasicrystals. Numerical results are also presented and in particular the evaluation of the linear response Kubo-Greenwood formula of conductivity in quasiperiodic systems in presence of disorder.Comment: Latex, 28 pages, Journ. of Math. Phys., Vol38 April 199

Gap junction remodelling in human heart failure is associated with increased interaction of connexin43 with ZO-1

Aims Remodelling of gap junctions, involving reduction of total gap junction quantity and down-regulation of connexin43 (Cx43), contributes to the arrhythmic substrate in congestive heart failure. However, little is known of the underlying mechanisms. Recent studies from in vitro systems suggest that the connexin-interacting protein zonula occludens-1 (ZO-1) is a potential mediator of gap junction remodelling. We therefore examined the hypothesis that ZO-1 contributes to reduced expression of Cx43 gap junctions in congestive heart failure. Methods and results Left ventricular myocardium from healthy control human hearts (n = 5) was compared with that of explanted hearts from transplant patients with end-stage congestive heart failure due to idiopathic dilated cardiomyopathy (DCM; n = 5) or ischaemic cardiomyopathy (ICM; n = 5). Immunoconfocal and immunoelectron microscopy showed that ZO-1 is specifically localized to the intercalated disc of cardiomyocytes in control and failing ventricles. ZO-1 protein levels were significantly increased in both DCM and ICM (P = 0.0025), showing a significant, negative correlation to Cx43 levels (P = 0.0029). There was, however, no significant alteration of ZO-1 mRNA (P = 0.537). Double immunolabelling demonstrated that a proportion of ZO-1 label is co-localized with Cx43, and that co-localization of Cx43 with ZO-1 is significantly increased in the failing ventricle (P = 0.003). Interaction between the two proteins was confirmed by co-immunoprecipitation. The proportion of Cx43 that co-immunoprecipitates with ZO-1 was significantly increased in the failing heart. Conclusion Our findings suggest that ZO-1, by interacting with Cx43, plays a role in the down-regulation and decreased size of Cx43 gap junctions in congestive heart failure

Predicting Crystal Structures with Data Mining of Quantum Calculations

Predicting and characterizing the crystal structure of materials is a key problem in materials research and development. It is typically addressed with highly accurate quantum mechanical computations on a small set of candidate structures, or with empirical rules that have been extracted from a large amount of experimental information, but have limited predictive power. In this letter, we transfer the concept of heuristic rule extraction to a large library of ab-initio calculated information, and demonstrate that this can be developed into a tool for crystal structure prediction.Comment: 4 pages, 3 pic

Natural growth rates in Antarctic krill (Euphausia superba): II. Predictive models based on food, temperature, body length, sex, and maturity stage

We used the instantaneous growth rate method to determine the effects of food, temperature, krill length, sex, and maturity stage on in situ summer growth of krill across the southwest Atlantic sector of the Southern Ocean. The main aims were to examine the separate effects of each variable and to generate a predictive model of growth based on satellite-derivable environmental data. Both growth increments in length on moulting (GIs) and daily growth rates (DGRs, mm d-1) ranged greatly among the 59 swarms, from 0.58–15% and 0.013–0.32 mm d-1. However, all swarms maintained positive mean growth, even those in the low chlorophyll a (Chl a) zone of the central Scotia Sea. Among a suite of indices of food quantity and quality, large-scale monthly Chl a values from SeaWiFS predicted krill growth the best. Across our study area, the great contrast between bloom and nonbloom regions was a major factor driving variation in growth rates, obscuring more subtle effects of food quality. GIs and DGRs decreased with increasing krill length and decreased above a temperature optimum of 0.5°C. This probably reflects the onset of thermal stress at the northern limit of krill’s range. Thus, growth rates were fastest in the ice edge blooms of the southern Scotia Sea and not at South Georgia as previously suggested. This reflects both the smaller size of the krill and the colder water in the south being optimum for growth. Males tended to have higher GIs than females but longer intermoult periods, leading to similar DGRs between sexes. DGRs of equivalent-size krill tended to decrease with maturity stage, suggesting the progressive allocation of energy toward reproduction rather than somatic growth. Our maximum DGRs are higher than most literature values, equating to a 5.7% increase in mass per day. This value fits within a realistic energy budget, suggesting a maximum carbon ration of ~20% d-1. Over the whole Scotia Sea/South Georgia area, the gross turnover of krill biomass was ~1% d-1

Structure stability in the simple element sodium under pressure

The simple alkali metal Na, that crystallizes in a body-centred cubic structure at ambient pressure, exhibits a wealth of complex phases at extreme conditions as found by experimental studies. The analysis of the mechanism of stabilization of some of these phases, namely, the low-temperature Sm-type phase and the high-pressure cI16 and oP8 phases, shows that they satisfy the criteria for the Hume-Rothery mechanism. These phases appear to be stabilized due to a formation of numerous planes in a Brillouin-Jones zone in the vicinity of the Fermi sphere of Na, which leads to the reduction of the overall electronic energy. For the oP8 phase, this mechanism seems to be working if one assumes that Na becomes divalent metal at this density. The oP8 phase of Na is analysed in comparison with the MnP-type oP8 phases known in binary compounds, as well as in relation to the hP4 structure of the NiAs-type

Dynamic localization of a helper NLR at the plant-pathogen interface underpins pathogen recognition

Plants employ sensor-helper pairs of NLR immune receptors to recognize pathogen effectors and activate immune responses (1). Yet the subcellular localization of NLRs pre- and post-activation during pathogen infection remains poorly understood. Here we show that NRC4, from the ‘NRC’ solanaceous helper NLR family (1), undergoes dynamic changes in subcellular localization by shuttling to and from the plant-pathogen haustorium interface established during infection by the Irish potato famine pathogen Phytophthora infestans. Specifically, prior to activation, NRC4 accumulates at the extra-haustorial membrane (EHM), presumably to mediate response to perihaustorial effectors, that are recognized by NRC4- dependent sensor NLRs. However not all NLRs accumulate at the EHM, as the closely related helper NRC2, and the distantly related ZAR1, did not accumulate at the EHM. NRC4 required an intact N-terminal coiled coil domain to accumulate at the EHM, whereas the functionally conserved MADA motif implicated in cell death activation and membrane insertion was dispensable for this process. Strikingly, a constitutively autoactive NRC4 mutant did not accumulate at the EHM and showed punctate distribution that mainly associated with the plasma membrane, suggesting that post-activation, NRC4 may undergo a conformation switch to form clusters that do not preferentially associate with the EHM. When NRC4 is activated by a sensor NLR during infection however, NRC4 forms puncta mainly at the EHM and to a lesser extent at the plasma membrane. We conclude that following activation at the EHM, NRC4 may spread to other cellular membranes from its primary site of activation to trigger immune responses