Behavior of a polymer chain in a critical binary solvent

We present a field-theoretic renormalization group analysis of a polymer chain immersed in a binary good solvent close to its critical demixing point. We first show that this problem can be mapped on a bicritical field theory, i.e. a $(\Phi^{2})^{2}$-model with a mass anisotropy. This implies that the end-to-end distance of the polymer is now controlled by a new critical exponent $\nu_{B}$ related to the quadratic mass anisotropy operator $B$. To show this we solve the RG equation and calculate explicitly the exponents and the mean end-to-end length of the chain.Comment: 6 pages, accepted in Europhys. Let

The scaling behaviour of screened polyelectrolytes

We present a field-theoretic renormalization group (RG) analysis of a single flexible, screened polyelectrolyte chain (a Debye-H\"uckel chain) in a polar solvent. We point out that the Debye-H\"uckel chain may be mapped onto a local field theory which has the same fixed point as a generalised $n \to 1$ Potts model. Systematic analysis of the field theory shows that the system is one with two interplaying length-scales requiring the calculation of scaling functions as well as exponents to fully describe its physical behaviour. To illustrate this, we solve the RG equation and explicitly calculate the exponents and the mean end-to-end length of the chain.Comment: 6 pages, 1 figure; changed title and slight modification to tex

The Hydration Structure at Yttria-Stabilized Cubic Zirconia (110)-Water Interface with Sub-Angstrom Resolution

The interfacial hydration structure of yttria-stabilized cubic zirconia (110) surface in contact with water was determined with ~0.5 Å resolution by high-resolution X-ray reflectivity measurement. The terminal layer shows a reduced electron density compared to the following substrate lattice layers, which indicates there are additional defects generated by metal depletion as well as intrinsic oxygen vacancies, both of which are apparently filled by water species. Above this top surface layer, two additional adsorbed layers are observed forming a characteristic interfacial hydration structure. The first adsorbed layer shows abnormally high density as pure water and likely includes metal species, whereas the second layer consists of pure water. The observed interfacial hydration structure seems responsible for local equilibration of the defective surface in water and eventually regulating the long-term degradation processes. The multitude of water interactions with the zirconia surface results in the complex but highly ordered interfacial structure constituting the reaction front.ope

Effect of diet with or without exercise on abdominal fat in postmenopausal women:A randomised trial

Background: We assessed the effect of equivalent weight loss with or without exercise on (intra-) abdominal fat in postmenopausal women in the SHAPE-2 study. Methods: The SHAPE-2 study is a three-armed randomised controlled trial conducted in 2012-2013 in the Netherlands. Postmenopausal overweight women were randomized to a diet (n = 97), exercise plus diet (n = 98) or control group (n = 48). Both intervention groups aimed for equivalent weight loss (6-7%) following a calorie-restricted diet (diet group) or a partly supervised intensive exercise programme (4 h per week) combined with a small caloric restriction (exercise plus diet group). Outcomes after 16 weeks are amount and distribution of abdominal fat, measured by magnetic resonance imaging (MRI) with the use of the three-point IDEAL Dixon method. Results: The diet and exercise plus diet group lost 6.1 and 6.9% body weight, respectively. Compared to controls, subcutaneous and intra-abdominal fat reduced significantly with both diet (- 12.5% and - 12.0%) and exercise plus diet (- 16.0% and - 14.6%). Direct comparison between both interventions revealed that the reduction in subcutaneous fat was statistically significantly larger in the group that combined exercise with diet: an additional 10.6 cm 2 (95%CI -18.7; - 2.4) was lost compared to the diet-only group. Intra-abdominal fat loss was not significantly larger in the exercise plus diet group (- 3.8 cm 2 , 95%CI -9.0; 1.3). Conclusions: We conclude that weight loss of 6-7% with diet or with exercise plus diet reduced both subcutaneous and intra-abdominal fat. Only subcutaneous fat statistically significantly reduced to a larger extent when exercise is combined with a small caloric restriction. Trial register: NCT01511276 (clinicaltrials.gov), prospectively registered

Free energy and molecular dynamics calculations for the cubic-tetragonal phase transition in zirconia

The high-temperature cubic-tetragonal phase transition of pure stoichiometric zirconia is studied by molecular dynamics (MD) simulations and within the framework of the Landau theory of phase transformations. The interatomic forces are calculated using an empirical, self-consistent, orthogonal tight-binding (SC-TB) model, which includes atomic polarizabilities up to the quadrupolar level. A first set of standard MD calculations shows that, on increasing temperature, one particular vibrational frequency softens. The temperature evolution of the free energy surfaces around the phase transition is then studied with a second set of calculations. These combine the thermodynamic integration technique with constrained MD simulations. The results seem to support the thesis of a second-order phase transition but with unusual, very anharmonic behaviour above the transition temperature

Relative energetics and structural properties of zirconia using a self-consistent tight-binding model

We describe an empirical, self-consistent, orthogonal tight-binding model for zirconia, which allows for the polarizability of the anions at dipole and quadrupole levels and for crystal field splitting of the cation d orbitals. This is achieved by mixing the orbitals of different symmetry on a site with coupling coefficients driven by the Coulomb potentials up to octapole level. The additional forces on atoms due to the self-consistency and polarizabilities are exactly obtained by straightforward electrostatics, by analogy with the Hellmann-Feynman theorem as applied in first-principles calculations. The model correctly orders the zero temperature energies of all zirconia polymorphs. The Zr-O matrix elements of the Hamiltonian, which measure covalency, make a greater contribution than the polarizability to the energy differences between phases. Results for elastic constants of the cubic and tetragonal phases and phonon frequencies of the cubic phase are also presented and compared with some experimental data and first-principles calculations. We suggest that the model will be useful for studying finite temperature effects by means of molecular dynamics.Comment: to be published in Physical Review B (1 march 2000

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS):Late Infall Causing Disk Misalignment and Dynamic Structures in SU Aur

Gas-rich circumstellar disks are the cradles of planet formation. As such, their evolution will strongly influence the resulting planet population. In the ESO DESTINYS large program, we study these disks within the first 10 Myr of their development with near-infrared scattered light imaging. Here we present VLT/SPHERE polarimetric observations of the nearby class II system SU Aur in which we resolve the disk down to scales of ~7 au. In addition to the new SPHERE observations, we utilize VLT/NACO, HST/STIS and ALMA archival data. The new SPHERE data show the disk around SU Aur and extended dust structures in unprecedented detail. We resolve several dust tails connected to the Keplerian disk. By comparison with ALMA data, we show that these dust tails represent material falling onto the disk. The disk itself shows an intricate spiral structure and a shadow lane, cast by an inner, misaligned disk component. Our observations suggest that SU Aur is undergoing late infall of material, which can explain the observed disk structures. SU Aur is the clearest observational example of this mechanism at work and demonstrates that late accretion events can still occur in the class II phase, thereby significantly affecting the evolution of circumstellar disks. Constraining the frequency of such events with additional observations will help determine whether this process is responsible for the spin-orbit misalignment in evolved exoplanet systems.Comment: 18 pages, 12 figures, published in ApJL on 18-02-202

Avoiding lodging in irrigated spring wheat. II. Genetic variation of stem and root structural properties

Lodging-related traits were evaluated on the CIMMYT Core spring wheat Germplasm Panel (CIMCOG) in the Yaqui Valley of North-West Mexico during three seasons (2010–2013). Genetic variation was significant for all the lodging-related traits in the cross-year analysis, however, significant G × E interaction due to rank changes or changes in the absolute differences between cultivars were identified. The inconsistences on cultivar performances across seasons particularly reduced the heritability of key characters related to root lodging resistance (anchorage strength). Target characters related to stem lodging resistance (stem strength) showed good heritability values equal or above 0.70. Positive correlations between stem strength and stem diameter and between root plate spread and root strength were found. Selecting for greater stem diameter and wall width, greater root plate spread and shorter plant height could enable breeders to increase lodging resistance by increasing stem strength, root strength and decreasing plant leverage, respectively. Achieving a lodging-proof crop will depend on finding a wider root plate spread and implementing new management strategies. Genetic linkages between lodging traits will not constrain the combination of the key lodging-trait dimensions to achieve a lodging-proof ideotype. However, strong association between stem strength and stem wall width will increase the total biomass cost needed for lodging resistance