Phase behaviour of rod-like colloid + flexible polymer mixtures

The effect of non-adsorbing, flexible polymer on the isotropic-nematic transition in dispersions of rod-like colloids is investigated. A widening of the biphasic gap is observed, in combination with a marked polymer partitioning between the coexisting phases. Under certain conditions, areas of isotropicisotropic- nematic or isotropic-nematic-nematic three-phase coexistence appear in the phase diagram of rod-polymer mixtures

Molecular theory of elastic constants of liquid crystals. III. Application to smectic phases with tilted orientational order

Using the density functional formalism we derive expression for the distortion free energy for systems with continuous broken symmetry and use it to derive expression for the elastic constants of smectic phases in which director is tilted with respect to the smectic layer normal. As in the previous papers of the series (Phys. Rev. A {\bf 45}, 974 (1992), E {\bf 49}, 501, (1994)) the expressions for the elastic constants are written in terms of order and structural parameters. The structural parameters involve the generalised spherical harmonic coefficients of the direct pair correlation function of an effective isotropic liquid. The density of this effective isotropic liquid depends on the nature and amount of ordering present in the system and is evaluated self- consistently. We estimate the value of elastic constants using reasonable guess for the order and structural- parameters.Comment: 31 pages; 1 Fig. in GIF format, To be appear in Phys. Rev.

Enhancement by polydispersity of the biaxial nematic phase in a mixture of hard rods and plates

The phase diagram of a polydisperse mixture of uniaxial rod-like and plate-like hard parallelepipeds is determined for aspect ratios $\kappa=5$ and 15. All particles have equal volume and polydispersity is introduced in a highly symmetric way. The corresponding binary mixture is known to have a biaxial phase for $\kappa=15$, but to be unstable against demixing into two uniaxial nematics for $\kappa=5$. We find that the phase diagram for $\kappa=15$ is qualitatively similar to that of the binary mixture, regardless the amount of polydispersity, while for $\kappa=5$ a sufficient amount of polydispersity stabilizes the biaxial phase. This provides some clues for the design of an experiment in which this long searched biaxial phase could be observed.Comment: 4 pages, 5 eps figure files, uses RevTeX 4 styl

Phase behaviour of colloid + polymer mixtures

A new treatment of the phase behaviour of a colloid + nonadsorbing polymer mixture is described. The calculated phase diagrams show marked polymer partitioning between coexisting phases, an effect not considered in the usual effective-potential approaches to this problem. We also predict that under certain conditions an area of three-phase coexistence should appear in the phase diagram

Dimensional crossover of the fundamental-measure functional for parallel hard cubes

We present a regularization of the recently proposed fundamental-measure functional for a mixture of parallel hard cubes. The regularized functional is shown to have right dimensional crossovers to any smaller dimension, thus allowing to use it to study highly inhomogeneous phases (such as the solid phase). Furthermore, it is shown how the functional of the slightly more general model of parallel hard parallelepipeds can be obtained using the zero-dimensional functional as a generating functional. The multicomponent version of the latter system is also given, and it is suggested how to reformulate it as a restricted-orientation model for liquid crystals. Finally, the method is further extended to build a functional for a mixture of parallel hard cylinders.Comment: 4 pages, no figures, uses revtex style files and multicol.sty, for a PostScript version see http://dulcinea.uc3m.es/users/cuesta/cross.p

On the Microscopic Origin of Cholesteric Pitch

We present a microscopic analysis of the instability of the nematic phase to chirality when molecular chirality is introduced perturbatively. We show that previously neglected short-range biaxial correlations play a crucial role in determining the cholesteric pitch. We propose an order parameter which quantifies the chirality of a molecule.Comment: RevTeX 3.0, 4 pages, one included eps figure. Published versio

Equation of State for Parallel Rigid Spherocylinders

The pair distribution function of monodisperse rigid spherocylinders is calculated by Shinomoto's method, which was originally proposed for hard spheres. The equation of state is derived by two different routes: Shinomoto's original route, in which a hard wall is introduced to estimate the pressure exerted on it, and the virial route. The pressure from Shinomoto's original route is valid only when the length-to-width ratio is less than or equal to 0.25 (i.e., when the spherocylinders are nearly spherical). The virial equation of state is shown to agree very well with the results of numerical simulations of spherocylinders with length-to-width ratio greater than or equal to 2

Towards Responsible Research Career Assessment

Contact: [email protected] Policy brief Growing evidence suggests that the evaluation of researchers’ careers on the basis of narrow definitions of excellence is restricting diversity in academia, both in the development of its labour force and its approaches to address societal challenges. The current research evaluation system is hampering diverse career pathways spanning research, teaching and (community) service. It inhibits the inclusion and retention of minorities, women, people from lower socio-economic backgrounds and meaningful public engagement with research. Improving the evaluation system in a concerted effort with research institutes and other funders will help fully realize a European Research Area (ERA) that is open to all talents. This diversity is essential to sustain academic careers, to strengthen the relevance and impact of science for society, and to enhance the resilience of our society and environment. Advice to MSCA policymakers Increasing attention to responsibility in, of and for research practices (as evidenced in Responsible Research and Innovation and Open Science in the ERA), has galvanized researchers and organisations to call for a change in the research evaluation system. While the academic evaluation landscape is shifting (as documented in the following pages), much remains to be done. The Marie Skłodowska-Curie Actions (MSCA) can spearhead these developments by implementing the following recommendations: Broaden current evaluation criteria of MSCA calls in dialogue with all relevant stakeholders, making responsible use of the options outlined below, to enlarge and modernize the notion of excellence (as done with the Gender dimension). Reward applicants and organisations that engage in open and responsible research through public engagement, science education, open science and ethical research; Provide (online) training for evaluators on implicit bias to reduce the risks of perpetuating narrow interpretations of research excellence in their evaluations; Offer training within the MSCA programme, such as via Innovative Training Networks, to prepare researchers and organizations for open and responsible, academic as well as non-academic careers. This includes a focus on transferable skills such as leadership and community engagement and attention to societal challenges; Reward and showcase MSCA grantees who excel in multiple dimensions of research, teaching, and service by showcasing and rewarding their work prominently on the MSCA website and social media; Support knowledge exchange and communities of practice around diverse and inclusive forms of excellence by involving a wide range of stakeholders (including civil society) in the ongoing discussion around modernizing and diversifying the concepts of excellence, and what counts as good and impactful academic practice. [ this is an excerpt, see pdf below for full policy brief ] For more from the Marie Curie Alumni Association, please see: https://zenodo.org/communities/mca

Continuous flushing of the bladder in rodents reduces artifacts and improves quantification in molecular imaging

In this study, we evaluated the partial volume effect (PVE) of 2-deoxy-2-[18F]fluoro-d-glucose (18F-FDG) tracer accumulation in the bladder on the positron emission tomographic (PET) image quantification in mice and rats suffering from inflammatory bowel disease. To improve the accuracy, we implemented continuous bladder flushing procedures. Female mice and rats were scanned using microPET/computed tomography (CT) at baseline and after induction of acute colitis by injecting 2,4,6-trinitrobenzene sulfonic acid (TNBS) intrarectally. During the scans, the bladder was continuously flushed in one group, whereas in the other group, no bladder flushing was performed. As a means of in vivo and ex vivo validation of the inflammation, animals also underwent colonoscopy and were sacrificed for gamma counting (subpopulation) and to score the colonic damage both micro- and macroscopically as well as biochemically. At baseline, the microPET signal in the colon of both mice and rats was significantly higher in the nonflushed group compared to the flushed group, caused by the PVE of tracer activity in the bladder. Hence, the colonoscopy and postmortem analyses showed no significant differences at baseline between the flushed and nonflushed animals. TNBS induced significant colonic inflammation, as revealed by colonoscopic and postmortem scores, which was not detected by microPET in the mice without bladder flushing, again because of spillover of bladder activity in the colonic area. MicroPET in bladder-flushed animals did reveal a significant increase in 18F-FDG uptake. Correlations between microPET and colonoscopy, macroscopy, microscopy, and myeloperoxidase yielded higher Spearman rho values in mice with continuously flushed bladders during imaging. Comparable, although somewhat less pronounced, results were shown in the rat. Continuous bladder flushing reduced image artifacts and is mandatory for accurate image quantification in the pelvic region for both mice and rats. We designed and validated experimental protocols to facilitate such.Steven Deleye, Marthe Heylen, Annemie Deiteren, Joris De Man, Sigrid Stroobants, Benedicte De Winter, and Steven Staelen