Correlated and Decorrelated Positional and Orientational Order in the Nucleosomal Core Particle Mesophases

We investigate the orientational order of transverse polarization vectors of long columns of nucleosomal core particles and their coupling to positional order in high density mesophases discovered recently. Inhomogeneous polar ordering of these columns precipitates crystalization of the 2D sections with different orientations of the transverse polarization vector on each column in the unit cell. We propose possible scenarios for going from the 2D hexagonal phase into distorted lamellar and related phases observed experimentally.Comment: 4 pages and 2 figure

Positional, Reorientational and Bond Orientational Order in DNA Mesophases

We investigate the orientational order of transverse polarization vectors of long, stiff polymer molecules and their coupling to bond orientational and positional order in high density mesophases. Homogeneous ordering of transverse polarization vector promotes distortions in the hexatic phase, whereas inhomogeneous ordering precipitates crystalization of the 2D sections with different orientations of the transverse polarization vector on each molecule in the unit cell. We propose possible scenarios for going from the hexatic phase, through the distorted hexatic phase to the crystalline phase with an orthorhombic unit cell observed experimentally for the case of DNA.Comment: 4 pages, 2 figure

Coupling between Smectic and Twist Modes in Polymer Intercalated Smectics

We analyse the elastic energy of an intercalated smectic where orientationally ordered polymers with an average orientation varying from layer to layer are intercalated between smectic planes. The lowest order terms in the coupling between polymer director and smectic layer curvature are added to the smectic elastic energy. Integration over the smectic degrees of freedom leaves an effective polymer twist energy that has to be included into the total polymer elastic energy leading to a fluctuational renormalization of the intercalated polymer twist modulus. If the polymers are chiral this in its turn leads to a renormalization of the cholesteric pitch.Comment: 8 pages, 1 fig in ps available from [email protected] Replaced version also contains title and abstract in the main tex

Electrostatic interactions mediated by polarizable counterions: weak and strong coupling limits

We investigate the statistical mechanics of an inhomogeneous Coulomb fluid composed of charged particles with static polarizability. We derive the weak- and the strong-coupling approximations and evaluate the partition function in a planar dielectric slab geometry with charged boundaries. We investigate the density profiles and the disjoining pressure for both approximations. Comparison to the case of non-polarizable counterions shows that polarizability brings important differences in the counterion density distribution as well as the counterion mediated electrostatic interactions between charged dielectric interfaces.Comment: 25 pages, 7 figure

Influence of heat treatment and KIc/HRc ratio on the dynamic wear properties of coated high speed steel

The aim of this work was to determine the impact of various heat treatments on the KIc/HRc ratio and subsequently on the wear properties of coated high-speed steel under dynamic impact loading. The results showed that hardness and improvement in the fracture toughness have significant influence on the adhesion and impact wear properties of the coated high-speed steel

Analysis of primary creep in simulated heat affected zone (HAZ) of two 9 - 12% Cr Steel grades

The primary creep of the parent metal (α), inter-critical (α+γ), and coarse-grained (γ) microstructures of simulated weld heat-affected zone (HAZ) for the steels X20CrMoV121 and X10CrMoVNb91, aged for 4 320 hours (6 months) at 750 °C and 17 520 hours (2 years) at 650 °C was analyzed. The time and creep strain at the transition point from primary to secondary creep were found to vary strongly between the parent metal and two simulated HAZ microstructures, especially after ageing at 750 °C

Influence of heat treatment and KIc/HRc ratio on the dynamic wear properties of coated high speed steel

The aim of this work was to determine the impact of various heat treatments on the KIc/HRc ratio and subsequently on the wear properties of coated high-speed steel under dynamic impact loading. The results showed that hardness and improvement in the fracture toughness have significant influence on the adhesion and impact wear properties of the coated high-speed steel

Effect of carbides size and distribution on creep rate

One of the most influential microstructure constituents in creep resistant steels are carbide particles. Carbide particles act as obstacles to dislocations movement, therefore the creep rate strongly depends on their size and distribution. At elevated temperatures to which creep resistant steels are exposed, carbide morphology is altered by the coarsening mechanism, consequently deteriorating the creep resistance of these steels. The aim of this work is to study the role of size and distribution of carbide particles on creep rate. Different distributions and size of carbides were obtained by different heat treatment conditions. The effect of different carbide morphology on the creep resistance was evaluated by uniaxial constant load creep tests

Unravelling the Role of Nitrogen in Surface Chemistry and Oxidation Evolution of Deep Cryogenic Treated High-Alloyed Ferrous Alloy

The role of nitrogen, introduced by deep cryogenic treatment (DCT), has been investigated and unraveled in relation to induced surface chemistry changes and improved corrosion resistance of high-alloyed ferrous alloy AISI M35. The assumptions and observations of the role of nitrogen were investigated and confirmed by using a multitude of complementary investigation techniques with a strong emphasis on ToF-SIMS. DCT samples display modified thickness, composition and layering structure of the corrosion products and passive film compared to a conventionally heat-treated sample under the same environmental conditions. The changes in the passive film composition of a DCT sample is correlated to the presence of the so-called ghost layer, which has higher concentration of nitrogen. This layer acts as a precursor for the formation of green rust on which magnetite is formed. This specific layer combination acts as an effective protective barrier against material degradation. The dynamics of oxide layer build-up is also changed by DCT, which is elucidated by the detection of different metallic ions and their modified distribution over surface thickness compared to its CHT counterpart. Newly observed passive film induced by DCT successfully overcomes the testing conditions in more extreme environments such as high temperature and vibrations, which additionally confirms the improved corrosion resistance of DCT treated high-alloyed ferrous alloys

Calculation of heat transfer coefficients

In forced-convection furnaces for reheating Al-alloys, convective heat transfer mechanism dominates. Al-body temperature prediction model uses measured furnace temperature as boundary condition. To calibrate such model, a convective heat transfer coefficient h is to be determined. Optimization technique is used here to determine h for every measured temperature sample so that measured temperatures match calculated, supposing radiative heat transfer coefficient constant and neglecting conductive heat transfer. Obtained h stably converges during normal reheating conditions. The obtained model is 4-fold cross-validated and obtained Root Mean Square Error of whole reheating profiles are [7,7; 20,4; 10,4; 12,5] °C