Microscopic theory of solvent mediated long range forces: influence of wetting

We show that a general density functional approach for calculating the force between two big particles immersed in a solvent of smaller ones can describe systems that exhibit fluid-fluid phase separation: the theory captures effects of strong adsorption (wetting) and of critical fluctuations in the solvent. We illustrate the approach for the Gaussian core model, a simple model of a polymer mixture in solution and find extremely attractive, long ranged solvent mediated potentials between the big particles for state points lying close to the binodal, on the side where the solvent is poor in the species which is favoured by the big particles.Comment: 7 pages, 3 figures, submitted to Europhysics Letter

Solidification in soft-core fluids: disordered solids from fast solidification fronts

Using dynamical density functional theory we calculate the speed of solidification fronts advancing into a quenched two-dimensional model fluid of soft-core particles. We find that solidification fronts can advance via two different mechanisms, depending on the depth of the quench. For shallow quenches, the front propagation is via a nonlinear mechanism. For deep quenches, front propagation is governed by a linear mechanism and in this regime we are able to determine the front speed via a marginal stability analysis. We find that the density modulations generated behind the advancing front have a characteristic scale that differs from the wavelength of the density modulation in thermodynamic equilibrium, i.e., the spacing between the crystal planes in an equilibrium crystal. This leads to the subsequent development of disorder in the solids that are formed. For the one-component fluid, the particles are able to rearrange to form a well-ordered crystal, with few defects. However, solidification fronts in a binary mixture exhibiting crystalline phases with square and hexagonal ordering generate solids that are unable to rearrange after the passage of the solidification front and a significant amount of disorder remains in the system.Comment: 18 pages, 14 fig

The ontogeny and development of Vitis vinifera L. cv. Chenin blanc inflorescence in relation to phenological stages

The ontogeny and development of inflorescence primordia and flower formation were studied with the aid of scanning electron microscopy. Initiation and differenti ation of the first and second inflorescence primordia in each bud at the two basal nodes occured in the period middle October (12-15 d before bloom) to end November (25 d after bloom). A time lapse of 3 weeks between initiation of the first and second anlagen in a bud was observed. The second anlagen were initiated just after the differentiation of the first. Floral parts were formed in the order calyx, corolla, stamens and pistil and within 20 d after appearance of the inflorescence these parts were fully developed

Cognitive deficits associated with prolonged seizures

Study aims are to assess cognitive dysfunction in nine individuals with one or more episodes of status epilepticus(SE)and to compare performance against control patients with brief seizures(idiopathic generalised epilepsy IGE, temporal lobe epilepsy TLE), and against adult performance norms. Participants with SE (30-60 minutes seizure duration) were recruited from the Cairns Base Hospital's epilepsy clinic, and included non-convulsive SE (NCSE, N=3) and generalised convulsive SE (GCSE, N=6) patients. Neuropsychological tasks assessed cognitive domains of intelligence, attention, verbal and visual memory, and executive functions. The absence SE (ASE) patient functioned normally in all cognitive domains. The patient with left complex partial status (CPSE) was significantly worse in attention; while the right CPSE patient was weakest in verbal episodic memory. GCSE patients performed worse on Sustained Attention NTS tasks than control IGE and TLE patients with brief seizures. Verbal memory was preserved. Number of SE seizures correlated negatively with estimated I.Q., visual abilities and working memory. In the absence of localised neuropsychological deficits, the deficits in stained attention and intellectual abilities of patients with GCSE suggest global cognitive dysfunction can result from relatively brief SE seizures. Generalisation of seizures cannot account for this, since the IGE performances were not affected

Cognitive deficits associated with prolonged seizures

Study aims are to assess cognitive dysfunction in nine individuals with one or more episodes of status epilepticus(SE)and to compare performance against control patients with brief seizures(idiopathic generalised epilepsy IGE, temporal lobe epilepsy TLE), and against adult performance norms. Participants with SE (30-60 minutes seizure duration) were recruited from the Cairns Base Hospital's epilepsy clinic, and included non-convulsive SE (NCSE, N=3) and generalised convulsive SE (GCSE, N=6) patients. Neuropsychological tasks assessed cognitive domains of intelligence, attention, verbal and visual memory, and executive functions. The absence SE (ASE) patient functioned normally in all cognitive domains. The patient with left complex partial status (CPSE) was significantly worse in attention; while the right CPSE patient was weakest in verbal episodic memory. GCSE patients performed worse on Sustained Attention NTS tasks than control IGE and TLE patients with brief seizures. Verbal memory was preserved. Number of SE seizures correlated negatively with estimated I.Q., visual abilities and working memory. In the absence of localised neuropsychological deficits, the deficits in stained attention and intellectual abilities of patients with GCSE suggest global cognitive dysfunction can result from relatively brief SE seizures. Generalisation of seizures cannot account for this, since the IGE performances were not affected

Dynamical density functional theory for dense atomic liquids

Starting from Newton's equations of motion, we derive a dynamical density functional theory (DDFT) applicable to atomic liquids. The theory has the feature that it requires as input the Helmholtz free energy functional from equilibrium density functional theory. This means that, given a reliable equilibrium free energy functional, the correct equilibrium fluid density profile is guaranteed. We show that when the isothermal compressibility is small, the DDFT generates the correct value for the speed of sound in a dense liquid. We also interpret the theory as a dynamical equation for a coarse grained fluid density and show that the theory can be used (making further approximations) to derive the standard mode coupling theory that is used to describe the glass transition. The present theory should provide a useful starting point for describing the dynamics of inhomogeneous atomic fluids.Comment: 14 pages, accepted for publication in J. Phys.: Condens. Matte

MECHANISMS OF DISEASE Acute Oxygen-Sensing Mechanisms

JOSEPH PRIESTLEY, ONE OF THE THREE SCIENTISTS CREDITED WITH THE discovery of oxygen, described the death of mice that were deprived of oxygen. However, he was also well aware of the toxicity of too much oxygen, stating, “For as a candle burns much faster in dephlogisticated [oxygen enriched] than in common air, so we might live out too fast, and the animal powers be too soon exhausted in this pure kind of air. A moralist, at least, may say, that the air which nature has provided for us is as good as we deserve.”1 In this review we examine the remarkable mechanisms by which different organs detect and respond to acute changes in oxygen tension. Specialized tissues that sense the local oxygen tension include glomus cells of the carotid body, neuroepithelial bodies in the lungs, chromaffin cells of the fetal adrenal medulla, and smooth-muscle cells of the resistance pulmonary arteries, fetoplacental arteries, systemic arteries, and the ductus arteriosus. Together, they constitute a specialized homeostatic oxygen-sensing system. Although all tissues are sensitive to severe hypoxia, these specialized tissues respond rapidly to moderate changes in oxygen tension within the physiologic range (roughly 40 to 100 mm Hg in an adult and 20 to 40 mm Hg in a fetus)Junta de Andalucí

Learning that physics is “not for me”: pedagogic work and the cultivation of habitus among Advanced Level physics students

Background: There is widespread agreement that participation in post-compulsory physics needs to be widened and increased, particularly among women and under-represented communities. This paper contributes to understanding of the processes that produce unequal participation, Methods: The paper undertakes a Bourdieusian analysis of longitudinal interview data from 75 interviews conducted with fifteen students, tracked from age 10-18, who studied Advanced level physics in England. Findings: The paper discusses evidence of a physics habitus that was strongly aligned with notions of intelligence/ cleverness and masculinity and identifies how young women were particularly disadvantaged by a popular notion of the “effortlessly clever physicist”, which encouraged even highly interested and high attaining young women not to continue further with the subject. We identified three main forms of pedagogic work performed by school physics (attainment-based practices of debarring and gatekeeping; curriculum practices of deferring ‘real’ physics and physics ‘lies’; and interpersonal reinforcement of doxa), which helped cultivate student habitus over time and produce inequitable patterns of participation Contribution: Analyses show that school physics contributes to reproducing inequitable (and low overall) patterns of participation. Implications are discussed for science education policy and practice to support more equitable participation

Solidification fronts in supercooled liquids: how rapid fronts can lead to disordered glassy solids

We determine the speed of a crystallisation (or more generally, a solidification) front as it advances into the uniform liquid phase after the system has been quenched into the crystalline region of the phase diagram. We calculate the front speed by assuming a dynamical density functional theory model for the system and applying a marginal stability criterion. Our results also apply to phase field crystal (PFC) models of solidification. As the solidification front advances into the unstable liquid phase, the density profile behind the advancing front develops density modulations and the wavelength of these modulations is a dynamically chosen quantity. For shallow quenches, the selected wavelength is precisely that of the crystalline phase and so well-ordered crystalline states are formed. However, when the system is deeply quenched, we find that this wavelength can be quite different from that of the crystal, so that the solidification front naturally generates disorder in the system. Significant rearrangement and ageing must subsequently occur for the system to form the regular well-ordered crystal that corresponds to the free energy minimum. Additional disorder is introduced whenever a front develops from random initial conditions. We illustrate these findings with results obtained from the PFC.Comment: 14 pages, 7 figure