Coupled model of root water uptake, mucilage exudation and degradation

Although the prominent role of root mucilage plays a prominent in soil-plant water relations is becoming more and more accepted, many aspects of how mucilage distribution and root water uptake interact with each other remain unexplored. The aims of this study were: i) to measure the effect of soil moisture on mucilage decomposition; ii) to develop a coupled model of root water uptake and mucilage diffusion and degradation during root growth. Mucilage decomposition was measured by adding C4 root mucilage from maize as single pulses to a C3 soil at two different moisture levels. Drought significantly suppressed mucilage mineralization. Opposed to classical solute transport models the water flow in the rhizosphere is affected by the local concentration of mucilage. The model accounts for an increased equilibrium water retention curve, a reduction of hydraulic conductivity at a given water content and a non-equilibrium water retention curve caused by swelling and shrinking dynamics of mucilage. The dispersion coefficient, on the other hand, depends on the water content. The parameters of mucilage diffusion have been fitted to observations on real plants. The model shows that mucilage exuded in wet soils diffuses far from the roots and it is rapidly degraded. On the contrary, mucilage of plants growing in dry soil is not easily degradable and it remains at higher concentrations in a narrow region around the roots, resulting in a marked increase in water content towards the roots as well as to the formation of stable rhizosheath observed in dry soils. This model shows how feedbacks between root water uptake and root exudation could result in adaptation mechanisms of plants to drought

Microstructure from ferroelastic transitions using strain pseudospin clock models in two and three dimensions: a local mean-field analysis

We show how microstructure can arise in first-order ferroelastic structural transitions, in two and three spatial dimensions, through a local meanfield approximation of their pseudospin hamiltonians, that include anisotropic elastic interactions. Such transitions have symmetry-selected physical strains as their $N_{OP}$-component order parameters, with Landau free energies that have a single zero-strain 'austenite' minimum at high temperatures, and spontaneous-strain 'martensite' minima of $N_V$ structural variants at low temperatures. In a reduced description, the strains at Landau minima induce temperature-dependent, clock-like $\mathbb{Z}_{N_V +1}$ hamiltonians, with $N_{OP}$-component strain-pseudospin vectors ${\vec S}$ pointing to $N_V + 1$ discrete values (including zero). We study elastic texturing in five such first-order structural transitions through a local meanfield approximation of their pseudospin hamiltonians, that include the powerlaw interactions. As a prototype, we consider the two-variant square/rectangle transition, with a one-component, pseudospin taking $N_V +1 =3$ values of $S= 0, \pm 1$, as in a generalized Blume-Capel model. We then consider transitions with two-component ($N_{OP} = 2$) pseudospins: the equilateral to centred-rectangle ($N_V =3$); the square to oblique polygon ($N_V =4$); the triangle to oblique ($N_V =6$) transitions; and finally the 3D cubic to tetragonal transition ($N_V =3$). The local meanfield solutions in 2D and 3D yield oriented domain-walls patterns as from continuous-variable strain dynamics, showing the discrete-variable models capture the essential ferroelastic texturings. Other related hamiltonians illustrate that structural-transitions in materials science can be the source of interesting spin models in statistical mechanics.Comment: 15 pages, 9 figure

Survey of Childhood Blindness and Visual Impairment in Botswana

Background/aims In terms of blind-person years, the worldwide burden of childhood blindness is second only to cataracts. In many developing countries, 30–72% of childhood blindness is avoidable. The authors conducted this study to determine the causes of childhood blindness and visual impairment (VI) in Botswana, a middle-income country with limited access to ophthalmic care. Methods This study was conducted over 4 weeks in eight cities and villages in Botswana. Children were recruited through a radio advertisement and local outreach programmes. Those ≤15 years of age with visual acuity \u3c6/18 in either eye were enrolled. The WHO/Prevention of Blindness Eye Examination Record for Children with Blindness and Low Vision was used to record data. Results The authors enrolled 241 children, 79 with unilateral and 162 with bilateral VI. Of unilateral cases, 89% were avoidable: 23% preventable (83% trauma-related) and 66% treatable (40% refractive error and 31% amblyopia). Of bilateral cases, 63% were avoidable: 5% preventable and 58% treatable (33% refractive error and 31% congenital cataracts). Conclusion Refractive error, which is easily correctable with glasses, is the most common cause of bilateral VI, with cataracts a close second. A nationwide intervention is currently being planned to reduce the burden of avoidable childhood VI in Botswana

Scaled free energies, power-law potentials, strain pseudospins and quasi-universality for first-order structural transitions

We consider ferroelastic first-order phase transitions with $N_{OP}$ order-parameter strains entering Landau free energies as invariant polynomials, that have $N_V$ structural-variant Landau minima. The total free energy includes (seemingly innocuous) harmonic terms, in the $n = 6 -N_{OP}$ {\it non}-order-parameter strains. Four 3D transitions are considered, tetragonal/orthorhombic, cubic/tetragonal, cubic/trigonal and cubic/orthorhombic unit-cell distortions, with respectively, $N_{OP} = 1, 2, 3$ and 2; and $N_V = 2, 3, 4$ and 6. Five 2D transitions are also considered, as simpler examples. Following Barsch and Krumhansl, we scale the free energy to absorb most material-dependent elastic coefficients into an overall prefactor, by scaling in an overall elastic energy density; a dimensionless temperature variable; and the spontaneous-strain magnitude at transition $\lambda <<1$. To leading order in $\lambda$ the scaled Landau minima become material-independent, in a kind of 'quasi-universality'. The scaled minima in $N_{OP}$-dimensional order-parameter space, fall at the centre and at the $N_V$ corners, of a transition-specific polyhedron inscribed in a sphere, whose radius is unity at transition. The `polyhedra' for the four 3D transitions are respectively, a line, a triangle, a tetrahedron, and a hexagon. We minimize the $n$ terms harmonic in the non-order-parameter strains, by substituting solutions of the 'no dislocation' St Venant compatibility constraints, and explicitly obtain powerlaw anisotropic, order-parameter interactions, for all transitions. In a reduced discrete-variable description, the competing minima of the Landau free energies induce unit-magnitude pseudospin vectors, with $N_V +1$ values, pointing to the polyhedra corners and the (zero-value) center.Comment: submitted to PR

Biot-Savart-like law in electrostatics

The Biot-Savart law is a well-known and powerful theoretical tool used to calculate magnetic fields due to currents in magnetostatics. We extend the range of applicability and the formal structure of the Biot-Savart law to electrostatics by deriving a Biot-Savart-like law suitable for calculating electric fields. We show that, under certain circumstances, the traditional Dirichlet problem can be mapped onto a much simpler Biot-Savart-like problem. We find an integral expression for the electric field due to an arbitrarily shaped, planar region kept at a fixed electric potential, in an otherwise grounded plane. As a by-product we present a very simple formula to compute the field produced in the plane defined by such a region. We illustrate the usefulness of our approach by calculating the electric field produced by planar regions of a few nontrivial shapes.Comment: 14 pages, 6 figures, RevTex, accepted for publication in the European Journal of Physic

NR4A Nuclear Receptors Support Memory Enhancement by Histone Deacetylase Inhibitors

The formation of a long-lasting memory requires a transcription-dependent consolidation period that converts a short-term memory into a long-term memory. Nuclear receptors compose a class of transcription factors that regulate diverse biological processes, and several nuclear receptors have been implicated in memory formation. Here, we examined the potential contribution of nuclear receptors to memory consolidation by measuring the expression of all 49 murine nuclear receptors after learning. We identified 13 nuclear receptors with increased expression after learning, including all 3 members of the Nr4a subfamily. These CREB-regulated Nr4a genes encode ligand-independent “orphan” nuclear receptors. We found that blocking NR4A activity in memory-supporting brain regions impaired long-term memory but did not impact short-term memory in mice. Further, expression of Nr4a genes increased following the memory-enhancing effects of histone deacetylase (HDAC) inhibitors. Blocking NR4A signaling interfered with the ability of HDAC inhibitors to enhance memory. These results demonstrate that the Nr4a gene family contributes to memory formation and is a promising target for improving cognitive function

An overview of the mid-infrared spectro-interferometer MATISSE: science, concept, and current status

MATISSE is the second-generation mid-infrared spectrograph and imager for the Very Large Telescope Interferometer (VLTI) at Paranal. This new interferometric instrument will allow significant advances by opening new avenues in various fundamental research fields: studying the planet-forming region of disks around young stellar objects, understanding the surface structures and mass loss phenomena affecting evolved stars, and probing the environments of black holes in active galactic nuclei. As a first breakthrough, MATISSE will enlarge the spectral domain of current optical interferometers by offering the L and M bands in addition to the N band. This will open a wide wavelength domain, ranging from 2.8 to 13 um, exploring angular scales as small as 3 mas (L band) / 10 mas (N band). As a second breakthrough, MATISSE will allow mid-infrared imaging - closure-phase aperture-synthesis imaging - with up to four Unit Telescopes (UT) or Auxiliary Telescopes (AT) of the VLTI. Moreover, MATISSE will offer a spectral resolution range from R ~ 30 to R ~ 5000. Here, we present one of the main science objectives, the study of protoplanetary disks, that has driven the instrument design and motivated several VLTI upgrades (GRA4MAT and NAOMI). We introduce the physical concept of MATISSE including a description of the signal on the detectors and an evaluation of the expected performances. We also discuss the current status of the MATISSE instrument, which is entering its testing phase, and the foreseen schedule for the next two years that will lead to the first light at Paranal.Comment: SPIE Astronomical Telescopes and Instrumentation conference, June 2016, 11 pages, 6 Figure

Innovative Crop Productions for Healthy Food: The Case of Chia (Salvia hispanica L.)

Chia (Salvia hispanica L.) is an ancient crop from Central America which has been recently rediscovered as a source of ω-3 and nutraceuticals in seeds. Besides traditional seed consumption, innovative uses of the plant seeds and leaves have been proposed based on the high protein content and the production of mucilage which lends itself to a range of applications. This chapter reviews research on the plant’s genetics and breeding, quality, and uses. Agronomic studies which have only recently started worldwide are also presented along with results from case studies in Basilicata

An investigation into aripiprazole's partial D(2) agonist effects within the dorsolateral prefrontal cortex during working memory in healthy volunteers

Rationale: Working memory impairments in schizophrenia have been attributed to dysfunction of the dorsolateral prefrontal cortex (DLPFC) which in turn may be due to low DLPFC dopamine innervation. Conventional antipsychotic drugs block DLPFC D2 receptors, and this may lead to further dysfunction and working memory impairments. Aripiprazole is a D2 receptor partial agonist hypothesised to enhance PFC dopamine functioning, possibly improving working memory. Objectives: We probed the implications of the partial D2 receptor agonist actions of aripiprazole within the DLPFC during working memory. Investigations were carried out in healthy volunteers to eliminate confounds of illness or medication status. Aripiprazole’s prefrontal actions were compared with the D2/5-HT2A blocker risperidone to separate aripiprazole’s unique prefrontal D2 agonist actions from its serotinergic and striatal D2 actions that it shares with risperidone. Method: A double-blind, placebo-controlled, parallel design was implemented. Participants received a single dose of either 5 mg aripiprazole, 1 mg risperidone or placebo before performing the n-back task whilst undergoing fMRI scanning. Results: Compared with placebo, the aripiprazole group demonstrated enhanced DLPFC activation associated with a trend for improved discriminability (d’) and speeded reaction times. In contrast to aripiprazole’s neural effects, the risperidone group demonstrated a trend for reduced DLPFC recruitment. Unexpectedly, the risperidone group demonstrated similar effects to aripiprazole on d’ and additionally had reduced errors of commission compared with placebo. Conclusion: Aripiprazole has unique DLPFC actions attributed to its prefrontal D2 agonist action. Risperidone’s serotinergic action that results in prefrontal dopamine release may have protected against any impairing effects of its prefrontal D2 blockade

Conspicuous practice: self-surveillance and commodification in education

Teachers have always been watched; only more recently have they been surveilled, with senior leaders, peers, students and external stakeholders all collecting performance data. Yet contemporary surveillance in schools and colleges increasingly relies on watching the self, with teachers voluntarily participating in their own surveillance, making their practice visible for easy consumption by interested parties. This article builds on previous work on the surveillance of teachers to argue that this ‘conspicuous practice’ represents a convergence of surveillance and consumerism, with teachers being recreated as commodities, becoming both the ‘merchandise and the marketing agent’ in Bauman’s (2007) terms, embodying the entrepreneurial self to maximise employability. Through social media promotion such as Twitter and LinkedIn to exploiting open plan learning spaces, teachers engage in conspicuous practice for three main reasons: from fear, to avoid sanction; as a result of acculturation into commodified corporate environments; finally as a means of routine resistance, employing the dramaturgical self for personal gain, to avoid work or to re-appropriate professional practice