Multi-scale Simulation of Linear, Short-Chain Polyethylene Liquids under Flow Conditions

The rheological and structural properties of polymeric liquids cannot be condensed within a single numerical model. They should be described within hierarchical, multi-level numerical models in which each sub-model is responsible for different time and length scales; atomistic, mesoscopic, and continuum. In this study, the rheological and structural properties of linear, short-chain polyethylene liquids were investigated from the classical atomistic level to the mesoscopic and continuum levels of description. At the atomistic level of description, nonequilibrium molecular dynamics (NEMD) simulations of linear, short-chain polyethylene liquids spanning from C16H24 to C128H256 were performed to advance our knowledge of fundamental characteristic of chain molecules under shear and planar elongational flow. Furthermore, entanglement characteristics, such as the shortest primitive path length, and the network configurations, were investigated as functions of strain rate in both vastly different flow fields using the topological Z-code. At the mesoscopic level of description, Brownian dynamics (BD) simulations of a freely-jointed chain with equivalent contour length to C78H158 were carried out to compare single-chain dynamics in dense liquids (NEMD) and dilute solutions (BD) under shear flow. In addition, the macromolecular configurational diversity of individual chains in dense liquids and dilute solutions was explored using a brightness distribution method inspired by the rheo-optical investigation of DNA solutions. Based on these observations, a simple coarse-grained mesoscopic model for unentangled polymeric liquids and semi-dilute solutions was proposed and compared with NEMD simulation data and experiments of semi-dilute DNA solutions under shear flow in terms of the rheological and structural properties, such as viscosity, normal stress coefficients, conformation tensor, and so on. Moreover, this model was further coarse-grained to the continuum level through pre-averaging and compared with NEMD simulation data to examine the relationships between different levels of description on the rheological and structural properties of unentangled polymeric materials under shear flow

Prevalence and spatial concordance of visual field deterioration in fellow eyes of glaucoma patients.

PurposeTo examine the prevalence of visual field deterioration in contralateral eyes of patients with worsening open-angle glaucoma and to evaluate the spatial concordance of visual field deterioration between both eyes.MethodsOne hundred sixteen open-angle glaucoma patients who underwent 8 or more visual field examinations over ≥ 6 years of follow-up were included. The rates of the fast and slow components of visual field decay for each of 52 visual field test locations were calculated with point-wise exponential regression analysis. The spatial concordance of visual field deterioration in contralateral eyes was evaluated with a concordance ratio (calculated as the number of overlapping locations divided by the total number of deteriorating locations) and by comparing the rate of decay in corresponding modified glaucoma hemifield test clusters.ResultsThe average visual field mean deviation (± standard deviation [SD]) was -8.5 (± 6.4) dB and the mean (± SD) follow-up time was 9.0 (± 1.6) years. Sixty-three patients had mild damage, 23 had moderate damage, and 30 had severe damage. The mean concordance ratio (± SD) was 0.46 (± 0.32) for the mild group, 0.33 (± 0.27) for the moderate group, and 0.35 (± 0.21) for the severe group. Thirty-one patients (27%) had deterioration in concordant locations (p < 0.05). Visual field deterioration was greater in the superior hemifield than the inferior hemifield (p < 0.05) when evaluated with both the concordance ratio and modified glaucoma hemifield test cluster analysis methods.ConclusionsThere is only fair spatial concordance with regard to visual field deterioration between the both eyes of an individual. We conclude that testing algorithms taking advantage of inter-eye spatial concordance would not be particularly advantageous in the early detection of glaucomatous deterioration

Use of Adjacent Knot Data in Predicting Bending Strength of Dimension Lumber by X-Ray

In a previous study, the knot depth ratio (KDR) evaluation method was proposed to quantify the area of knots in a cross-section. That study reported that bending strength can be predicted by KDR analysis. However, the KDR model did not take into consideration the additional strength reduction caused by adjacent knots. It was found that the prediction of lumber strength was improved when adjacent knots were taken into consideration. Analysis using the KDRA (KDR adding knots) model revealed that the optimum cross-sectional interval, an input variable, is directly affected by knot size parallel to lumber length (KSPLL). KSPLL depends on the sawing method and log characteristics, and for species containing large knots, the cross-sectional interval is likely to be extremely wide. This can cause several adjacent small knots to be excluded from the analysis, requiring modification of the KDRA model algorithm. This modification resulted in improvement in the precision of the strength prediction, although the input variable of the cross-sectional interval was not used. The R2 values obtained using this method were 0.60 and 0.56 for Japanese larch and red pine, respectively

Controlling the Magnetic Anisotropy of the van der Waals Ferromagnet Fe3GeTe2 through Hole Doping.

Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical origin of this effect. Fe3-xGeTe2 nanoflakes show a significant suppression of the magnetic anisotropy with hole doping. Electronic structure measurements and calculations reveal that the chemical potential shift associated with hole doping is responsible for the reduced magnetic anisotropy by decreasing the energy gain from the spin-orbit induced band splitting. Our findings provide an understanding of the intricate connection between electronic structures and magnetic properties in two-dimensional magnets and propose a method to engineer magnetic properties through doping

Sources of Value Gains in Minority Equity Investments by Private Equity Funds: Evidence from Block Share Acquisitions

Using a large sample of block share acquisitions made by private equity (PE) funds over the 1990 to 2006 period, we examine the sources of value gains in PE minority equity investments. We find that compared to non-PE acquirers, PE acquirers are more likely to place representatives with finance experience on a target’s board, particularly when the target performs poorly or when it has more pronounced agency problems. PE acquirers are also more likely to place representatives with experience in the target’s industry on the target’s board when the target has more complex operations (e.g., multiple segments or higher R&D intensity). The targets in PE acquisitions, particularly those whose boards have representatives from PE acquirers, realize both higher abnormal announcement returns and better post-acquisition operating performance than do targets in other types of acquisitions. Target announcement abnormal returns and post-acquisition operating performance are also higher when PE-appointed directors have expertise in the target’s industry, when they sit on the boards of poorly performing targets, or when they sit on the boards of targets with higher R&D intensity. Thes