Three-dimensional Icosahedral Phase Field Quasicrystal

We investigate the formation and stability of icosahedral quasicrystalline structures using a dynamic phase field crystal model. Nonlinear interactions between density waves at two length scales stabilize three-dimensional quasicrystals. We determine the phase diagram and parameter values required for the quasicrystal to be the global minimum free energy state. We demonstrate that traits that promote the formation of two-dimensional quasicrystals are extant in three dimensions, and highlight the characteristics required for three-dimensional soft matter quasicrystal formation

Which wavenumbers determine the thermodynamic stability of soft matter quasicrystals?

For soft matter to form quasicrystals an important ingredient is to have two characteristic lengthscales in the interparticle interactions. To be more precise, for stable quasicrystals, periodic modulations of the local density distribution with two particular wavenumbers should be favored, and the ratio of these wavenumbers should be close to certain special values. So, for simple models, the answer to the title question is that only these two ingredients are needed. However, for more realistic models, where in principle all wavenumbers can be involved, other wavenumbers are also important, specifically those of the second and higher reciprocal lattice vectors. We identify features in the particle pair interaction potentials which can suppress or encourage density modes with wavenumbers associated with one of the regular crystalline orderings that compete with quasicrystals, enabling either the enhancement or suppression of quasicrystals in a generic class of systems

Which Wave Numbers Determine the Thermodynamic Stability of Soft Matter Quasicrystals?

For soft matter to form quasicrystals an important ingredient is to have two characteristic length scales in the interparticle interactions. To be more precise, for stable quasicrystals, periodic modulations of the local density distribution with two particular wave numbers should be favored, and the ratio of these wave numbers should be close to certain special values. So, for simple models, the answer to the title question is that only these two ingredients are needed. However, for more realistic models, where in principle all wave numbers can be involved, other wave numbers are also important, specifically those of the second and higher reciprocal lattice vectors. We identify features in the particle pair interaction potentials that can suppress or encourage density modes with wave numbers associated with one of the regular crystalline orderings that compete with quasicrystals, enabling either the enhancement or suppression of quasicrystals in a generic class of systems

Density Distribution in Soft Matter Crystals and Quasicrystals

The density distribution in solids is often represented as a sum of Gaussian peaks (or similar functions) centered on lattice sites or via a Fourier sum. Here, we argue that representing instead the logarithm of the density distribution via a Fourier sum is better. We show that truncating such a representation after only a few terms can be highly accurate for soft matter crystals. For quasicrystals, this sum does not truncate so easily, nonetheless, representing the density profile in this way is still of great use, enabling us to calculate the phase diagram for a three-dimensional quasicrystal-forming system using an accurate nonlocal density functional theory

Deriving phase field crystal theory from dynamical density functional theory: Consequences of the approximations

Phase field crystal (PFC) theory is extensively used for modeling the phase behavior, structure, thermodynamics, and other related properties of solids. PFC theory can be derived from dynamical density functional theory (DDFT) via a sequence of approximations. Here, we carefully identify all of these approximations and explain the consequences of each. One approximation that is made in standard derivations is to neglect a term of form ∇⋅[n∇Ln], where n is the scaled density profile and L is a linear operator. We show that this term makes a significant contribution to the stability of the crystal, and that dropping this term from the theory forces another approximation, that of replacing the logarithmic term from the ideal gas contribution to the free energy with its truncated Taylor expansion, to yield a polynomial in n. However, the consequences of doing this are (i) the presence of an additional spinodal in the phase diagram, so the liquid is predicted first to freeze and then to melt again as the density is increased; and (ii) other periodic structures, such as stripes, are erroneously predicted to be thermodynamic equilibrium structures. In general, L consists of a nonlocal convolution involving the pair direct correlation function. A second approximation sometimes made in deriving PFC theory is to replace L with a gradient expansion involving derivatives. We show that this leads to the possibility of the density going to zero, with its logarithm going to −∞ while being balanced by the fourth derivative of the density going to +∞. This subtle singularity leads to solutions failing to exist above a certain value of the average density. We illustrate all of these conclusions with results for a particularly simple model two-dimensional fluid, the generalized exponential model of index 4 (GEM-4), chosen because a DDFT is known to be accurate for this model. The consequences of the subsequent PFC approximations can then be examined. These include the phase diagram being both qualitatively incorrect, in that it has a stripe phase, and quantitatively incorrect (by orders of magnitude) regarding the properties of the crystal phase. Thus, although PFC models are very successful as phenomenological models of crystallization, we find it impossible to derive the PFC as a theory for the (scaled) density distribution when starting from an accurate DDFT, without introducing spurious artifacts. However, we find that making a simple one-mode approximation for the logarithm of the density distribution lnρ(x) rather than for ρ(x) is surprisingly accurate. This approach gives a tantalizing hint that accurate PFC-type theories may instead be derived as theories for the field lnρ(x), rather than for the density profile itself

Mapping the links between gender, status and genre in Shakespeare’s plays

The AHRC-funded Encyclopedia of Shakespeare’s Language (ESL) project has produced a resource allowing users to explore Shakespeare’s plays in a variety of (semi-automatic) ways, via a web-based corpus query processor interface (CQPweb) hosted by Lancaster University. It enables users, for example, to interrogate a corpus of Shakespeare’s plays using queries restricted by dramatic genre, gender and/or social status of characters, and to target and explore the language of the plays not only at the word level, but also at the grammatical and semantic levels (by querying part-of-speech or semantic categories). Using keyword techniques, we examine how female and male language varies in general, by social status (high or low), and by genre (comedy, history and tragedy). Among our findings, we note differences in the use of pronouns and references to male authority (female overuse of ‘I’ and ‘husband’; male overuse of ‘we’ and ‘king’). We also observe that high-status males in comedies (as opposed to histories and tragedies) are characterised by polite requests (‘please you’) and sharp-minded ‘wit’. Despite many similarities between female and male usage of gendered forms of language (‘woman’), male characters alone use terms such as ‘womanish’ in a disparaging way

Low dose gamma irradiation does not affect the quality or total ascorbic acid concentration of “sweetheart” passionfruit (passiflora edulis)

Passionfruit (Passiflora edulis, Sims, cultivar “Sweetheart”) were subject to gamma irradiation at levels suitable for phytosanitary purposes (0, 150, 400 and 1000 Gy) then stored at 8 °C and assessed for fruit quality and total ascorbic acid concentration after one and fourteen days. Irradiation at any dose (≤1000 Gy) did not affect passionfruit quality (overall fruit quality, colour, firmness, fruit shrivel, stem condition, weight loss, total soluble solids level (TSS), titratable acidity (TA) level, TSS/TA ratio, juice pH and rot development), nor the total ascorbic acid concentration. The length of time in storage affected some fruit quality parameters and total ascorbic acid concentration, with longer storage periods resulting in lower quality fruit and lower total ascorbic acid concentration, irrespective of irradiation. There was no interaction between irradiation treatment and storage time, indicating that irradiation did not influence the effect of storage on passionfruit quality. The results showed that the application of 150, 400 and 1000 Gy gamma irradiation to “Sweetheart” purple passionfruit did not produce any deleterious effects on fruit quality or total ascorbic acid concentration during cold storage, thus supporting the use of low dose irradiation as a phytosanitary treatment against quarantine pests in purple passionfruit. © 2015 MDPI.Open access retrieved from: https://www.mdpi.com/2304-8158/4/3/37

Secretory IgA and T Cells Targeting SARS-CoV-2 Spike Protein Are Transferred to the Breastmilk Upon mRNA Vaccination

In view of the scarcity of data to guide decision making, we evaluated how BNT162b2 and mRNA-1273 vaccines affect the immune response in lactating women and the protective profile of breastmilk. Compared with controls, lactating women had a higher frequency of circulating RBD memory B cells and higher anti-RBD antibody titers but similar neutralizing capacity. We show that upon vaccination, immune transfer to breastmilk occurs through a combination of anti-spike secretory IgA (SIgA) antibodies and spike-reactive T cells. Although we found that the concentration of anti-spike IgA in breastmilk might not be sufficient to directly neutralize SARS-CoV-2, our data suggest that cumulative transfer of IgA might provide the infant with effective neutralization capacity. Our findings put forward the possibility that breastmilk might convey both immediate (through anti-spike SIgA) and long-lived (via spike-reactive T cells) immune protection to the infant. Further studies are needed to address this possibility and to determine the functional profile of spike T cells.info:eu-repo/semantics/publishedVersio

Minority ethnic students and science participation: a qualitative mapping of achievement, aspiration, interest and capital

In the UK, the ‘leaky pipeline’ metaphor has been used to describe the relationship between ethnicity and science participation. Fewer minority ethnic students continue with science in post-compulsory education, and little is known about the ways in which they participate and identify with science, particularly in the secondary school context. Drawing on an exploratory study of 46 interviews and 22 h of classroom observations with British students (aged 11–14) from Black Caribbean, Bangladeshi, Pakistani, Indian and Chinese ethnic backgrounds, this paper identified five ‘types’ of science participation among minority ethnic students. The five types of science participation emerged from an analysis of students’ science achievement, science aspiration, science interest and science capital. The characteristics of the five types are as follows: Science adverse students have no aspirations towards science and lacked interest, achievement and capital in science. Science intrinsic students have high science aspirations, interest and capital but low science attainment. Students who are science intermediate have some aspirations, interest and capital in science, with average science grades. Science extrinsic students achieve highly in science, have some science capital but lacked science aspirations and/or interest. Science prominent students are high science achievers with science aspirations, high levels of interest and capital in science. The findings highlight that minority ethnic students participate in science in diverse ways. Policy implications are suggested for each type as this paper provides empirical evidence to counter against public (and even some academic) discourses of minority ethnic students as a homogeneous group

Outcomes from massive paracetamol overdose: a retrospective observational study

LINKED ARTICLE: This article is commented on by Bateman DN and Dear JW. Should we treat very large paracetamol overdose differently? Br J Clin Pharmacol 2017; 83: 1163–5. https://doi.org/10.1111/bcp.13279 AIMS: Treatment of paracetamol (acetaminophen) overdose with acetylcysteine is standardized, with dose determined only by patient weight. The validity of this approach for massive overdoses has been questioned. We systematically compared outcomes in massive and non-massive overdoses, to guide whether alternative treatment strategies should be considered, and whether the ratio between measured timed paracetamol concentrations (APAPpl) and treatment nomogram thresholds at those time points (APAPt) provides a useful assessment tool. METHODS: This is a retrospective observational study of all patients (n = 545) between 2005 and 2013 admitted to a tertiary care toxicology service with acute non-staggered paracetamol overdose. Massive overdoses were defined as extrapolated 4-h plasma paracetamol concentrations >250 mg l−1, or reported ingestions ≥30 g. Outcomes (liver injury, coagulopathy and kidney injury) were assessed in relation to reported dose and APAPpl:APAPt ratio (based on a treatment line through 100 mg l−1 at 4 h), and time to acetylcysteine. RESULTS: Ingestions of ≥30 g paracetamol correlated with higher peak serum aminotransferase (r = 0.212, P < 0.0001) and creatinine (r = 0.138, P = 0.002) concentrations. Acute liver injury, hepatotoxicity and coagulopathy were more frequent with APAPpl:APAPt ≥ 3 with odds ratios (OR) and 95% confidence intervals (CI) of 9.19 (5.04–16.68), 35.95 (8.80–158.1) and 8.34 (4.43–15.84), respectively (P < 0.0001). Heightened risk persisted in patients receiving acetylcysteine within 8 h of overdose. CONCLUSION: Patients presenting following massive paracetamol overdose are at higher risk of organ injury, even when acetylcysteine is administered early. Enhanced therapeutic strategies should be considered in those who have an APAPpl:APAPt ≥ 3. Novel biomarkers of incipient liver injury and abbreviated acetylcysteine regimens require validation in this patient cohort