Nanorings in planar confinement: the role of repulsive surfaces on the formation of lacuna smectics

We study the structure and liquid-crystalline phase behaviour of a model of nonconvex circular soft-repulsive nanorings con ned in a planar slit geometry using molecular-dynamics simulation. The separation distance between the structureless parallel soft-repulsive walls is large enough to allow for the formation of a distinct bulk phase in the central region of the box which is in coexistence with the adsorbed uid thus allowing the analysis of single wall e ects. As the concentration of the particles is increased, the uid adsorbs (wets) onto the planar surfaces leading to the formation of well-de ned smectic-A layers with a spacing proportional to the diameter of the rings. An analysis of the nematic order parameter at distances perpendicular to the surface reveals that the particles in each layer exhibit antinematic behaviour and planar (edge-on) anchoring relative to the short symmetry axis of the rings. This behaviour is in stark contrast to the behaviour observed in convex disc-like particles that have the tendency to form nematic (discotic) structures with hometropic (face-on) anchoring. The smectic phases formed by nanorings in the bulk and under con nement are characterized by the formation of low-density layered liquid-crystalline states with large voids, referred to here as lacuna smectic phases. In contrast to what is typically found for con ned liquid-crystalline systems involving convex particles, no apparent biaxiality is found for the nanorings in planar con nement. We argue that formation of the low-density lacuna smectic layers with planar anchoring is a consequence of the non-convex shape of the circular rings that allow for interpenetration between the particles as observed for nanorings under bulk conditions [Avenda~no et al., Proc. Natl. Acad. Sci. U. S. A. 113, 9699 (2016); H. H. Wensink and C. Avenda~no, Phys. Rev. E 94 062704 (2016)]

Ecotypic Adaptation of Medicago Polymorpha along a Gradient in Central Chile: Growth and Seed Production

Relative growth rate, total dry weight and seed yield on 19 accessions of burr medic (Medicago polymorpha L.) from different bioclimatic conditions, were assessed at Cauquenes (35°58’;72°17’W) in the subhumid mediterranean region. The accessions were sown in microplots over raised beds during two years (1991 and 1992), and swards cut periodically at 2, 6 and 10 cm height. There were significant differences between accessions in both total dry weight and seed yield (P \u3c 0.001, Table 1), but the interaction between accessions and height of cutting was not significant (P \u3e 0.05). Total dry weight was positive correlated with days to flowering (r2 = 0.81; P \u3e 0.01)

Hardseededness Under Field Conditions of Medicago polymorpha During Five Softening Seasons in the Mediterranean Zone of Chile

The long term seed softening of burr medic (Medicago polymorpha L.) was studied in the field in a mediterranean environment in Chile. Burrs were collected in March of 1988, 1989, 1990 and 1991 (collecting years), and placed in the field either on the surface or buried at 1 cm depth. Field germination was recorded regularly and the remaining non-germinated seeds were tested for germination in the laboratory during 4 years. The percentage of soft seeds on soil surface burrs was on average 3.2% (mean of 4 collecting years) after the first summer in the field, and reached 83% after 5 summers. Seed softening was significantly greater on burrs buried at 1 cm depth than those placed on soil surface. The split-split-plot ANOVA for cumulative soft seeds, showed that collecting year (CY), softening season (SS) and environment treatment (ET) were highly significant, but also the CY*SS*ET interaction was significant

Germplasm Collection, Evaluation and Selection of Naturalized Medicago Polymorpha in the Mediterranean Zone of Chile

An introduction and evaluation programme is described that thus far includes 53 accessions of the naturalised annual medic Medicago polymorplia L. collected along a 1000 km N-S gradient in central. Chile and subsequently grown together in a common environment· selection trial together with 5 accessions received from International Center for Agricultural Research in the Dry Areas (!CARDA). Major selection criteria include: precocious phenology, spineless pods and hardseededness, and tolerance to acid soils. Onset of flowering was 82-127 day_s, later flowering being closely correlated with higher latitudes. Soil pH was 5.3-7 .5 in collection sites, and phosphorus levels were \u3e 10 ppm in 90% of the sites. There was also a correlation between flowering precocity and spineless pods. All accessions showed 100% hard seededness immediately after seed set, but the following autumn, seed hardness varied considerably. The phenological and ecophysiological ranges of adaptation exhibited in these accessions suggests that ecological adaptation has occurred in this naturalized species and that an important genetic base exists from which to select cultivars for areas throughout the Mediterranean climate region

Cash transfers and the mental health of young people: evidence from South Africa's child support grant

This study examines the longitudinal impact of the South African Child Support Grant (CSG) on risk for depression and life satisfaction among young people (15–19 years). We analysed data from the last three waves of the National Income Dynamics Study (NIDS), a nationally representative panel survey that took place every two years from 2008 to 2017. We used an instrumental variable (IV) approach that exploits multiple changes in age eligibility from 1998 to 2012. Depressive symptoms were assessed using an 8-item version of the Centre for Epidemiological Studies Depression Scale; participants who scored above 8 were considered at risk for depression. Life satisfaction was rated on a scale of 1 (‘very dissatisfied’) to 10 (‘very satisfied’); participants who scored 8 or above were classified as satisfied. We also examined impacts on educational deficit (≥2 years behind) and not being in education, employment or training (NEET) as secondary outcomes, as these are also important for mental health. Age eligibility strongly predicted CSG receipt at Wave 3. In instrumental variable models, CSG receipt did not influence the risk for depression (β = 0.10, SE = 0.10, p = 0.316), nor life satisfaction (β = −0.07, SE = 0.09, p = 0.420) at Wave 3, nor at Waves 4 or 5. Some improvements in educational deficit were observed at Wave 3 among CSG beneficiaries compared to non-beneficiaries. These results were robust to multiple specifications. CSG receipt did not improve the psychological wellbeing of adolescents and young adults, nor did it improve their education or employment outcomes. Our findings highlight the need to identify alternative social policies that address the root causes of youth social disadvantage, in conjunction with targeted approaches to improve the mental health of young South Africans living in poverty

Single-molecule super-resolution imaging of chromosomes and in situ haplotype visualization using Oligopaint FISH probes

Fluorescence in situ hybridization (FISH) is a powerful single-cell technique for studying nuclear structure and organization. Here we report two advances in FISH-based imaging. We first describe the in situ visualization of single-copy regions of the genome using two single-molecule super-resolution methodologies. We then introduce a robust and reliable system that harnesses single-nucleotide polymorphisms (SNPs) to visually distinguish the maternal and paternal homologous chromosomes in mammalian and insect systems. Both of these new technologies are enabled by renewable, bioinformatically designed, oligonucleotide-based Oligopaint probes, which we augment with a strategy that uses secondary oligonucleotides (oligos) to produce and enhance fluorescent signals. These advances should substantially expand the capability to query parent-of-origin-specific chromosome positioning and gene expression on a cell-by-cell basis

Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments

A generalization of the recent version of the statistical associating fluid theory for variable range Mie potentials [Lafitte et al., J. Chem. Phys. 139, 154504 (2013)] is formulated within the framework of a group contribution approach (SAFT-γ Mie). Molecules are represented as comprising distinct functional (chemical) groups based on a fused heteronuclear molecular model, where the interactions between segments are described with the Mie (generalized Lennard-Jonesium) potential of variable attractive and repulsive range. A key feature of the new theory is the accurate description of the monomeric group-group interactions by application of a high-temperature perturbation expansion up to third order. The capabilities of the SAFT-γ Mie approach are exemplified by studying the thermodynamic properties of two chemical families, the n-alkanes and the n-alkyl esters, by developing parameters for the methyl, methylene, and carboxylate functional groups (CH3, CH2, and COO). The approach is shown to describe accurately the fluid-phase behavior of the compounds considered with absolute average deviations of 1.20% and 0.42% for the vapor pressure and saturated liquid density, respectively, which represents a clear improvement over other existing SAFT-based group contribution approaches. The use of Mie potentials to describe the group-group interaction is shown to allow accurate simultaneous descriptions of the fluid-phase behavior and second-order thermodynamic derivative properties of the pure fluids based on a single set of group parameters. Furthermore, the application of the perturbation expansion to third order for the description of the reference monomeric fluid improves the predictions of the theory for the fluid-phase behavior of pure components in the near-critical region. The predictive capabilities of the approach stem from its formulation within a group-contribution formalism: predictions of the fluid-phase behavior and thermodynamic derivative properties of compounds not included in the development of group parameters are demonstrated. The performance of the theory is also critically assessed with predictions of the fluid-phase behavior (vapor-liquid and liquid-liquid equilibria) and excess thermodynamic properties of a variety of binary mixtures, including polymer solutions, where very good agreement with the experimental data is seen, without the need for adjustable mixture parameters