An Operations Research Approach to the Problem of the Sugarcane Selection

Selection for superior clones is the most important aspect of sugar cane improvement programs, and is a long and expensive process. While studies have investigated different components of selection independently, there has not been a whole system approach to improve the process. This study observes the problem as an integrated system, where if one parameter changes the state of the whole system changes. A computer based stochastic simulation model that accurately represents the selection was developed. This paper describes the simulation model, showing its accuracy as well as how a combination of dynamic programming and branch and bound can be applied to the model to optimise the selection system, giving a new application of these techniques. The model can be directly applied to any region targeted by sugarcane breeding programs or to other clonally propagated crops.     

Dielectric response of thin water films: a thermodynamic perspective

The surface of a polar liquid presents a special environment for the solvation and organization of charged solutes, which differ from bulk behaviors in important ways. These differences have motivated many attempts to understand electrostatic response at aqueous interfaces in terms of a spatially varying dielectric permittivity, typically concluding that the dielectric constant of interfacial water is significantly lower than in the bulk liquid. Such analyses, however, are complicated by the potentially nonlocal nature of dielectric response over the short length scales of interfacial heterogeneity. Here we circumvent this problem for thin water films by adopting a thermodynamic approach. Using molecular simulations, we calculate the solvent''s contribution to the reversible work of charging a parallel plate capacitor. We find good agreement with a simple dielectric continuum model that assumes bulk dielectric permittivity all the way up to the liquid''s boundary, even for very thin (∼1 nm) films. This comparison requires careful attention to the placement of dielectric boundaries between liquid and vapor, which also resolves apparent discrepancies with dielectric imaging experiments.

Free energy calculations from molecular simulations reveal that water''s interfacial dielectric response is well-described by bulk properties.     

Investigation of ion-electrode interactions of linear polyimides and alkali metal ions for next generation alternative-ion batteries

Organic electrode materials offer unique opportunities to utilize ion-electrode interactions to develop diverse, versatile, and high-performing secondary batteries, particularly for applications requiring high power densities. However, a lack of well-defined structure–property relationships for redox-active organic materials restricts the advancement of the field. Herein, we investigate a family of diimide-based polymer materials with several charge-compensating ions (Li⁺, Na⁺, K⁺) in order to systematically probe how redox-active moiety, ion, and polymer flexibility dictate their thermodynamic and kinetic properties. When favorable ion-electrode interactions are employed (e.g., soft K⁺ anions with soft perylenediimide dianions), the resulting batteries demonstrate increased working potentials and improved cycling stabilities. Further, for all polymers examined herein, we demonstrate that K⁺ accesses the highest percentage of redox-active groups due to its small solvation shell/energy. Through crown ether experiments, cyclic voltammetry, and activation energy measurements, we provide insights into the charge compensation mechanisms of three different polymer structures and rationalize these findings in terms of the differing degrees of improvements observed when cycling with K⁺. Critically, we find that the most flexible polymer enables access to the highest fraction of active sites due to the small activation energy barrier during charge/discharge. These results suggest that improved capacities may be accessible by employing more flexible structures. Overall, our in-depth structure–activity investigation demonstrates how variables such as polymer structure and cation can be used to optimize battery performance and enable the realization of novel battery chemistries.

Organic electrode materials offer unique opportunities to utilize ion-electrode interactions to develop diverse, versatile, and high-performing secondary batteries, particularly for applications requiring high power densities.     

Fusion of Aza- and Oxadiborepins with Furans in a Reversible Ring-Opening Process Furnishes Versatile Building Blocks for Extended π-Conjugated Materials

A modular synthesis of both difurooxa- and difuroazadiborepins from a common precursor is demonstrated. Starting from 2,2′-bifuran, after protection of the positions 5 and 5’ with bulky silyl groups, formation of the novel polycycles proceeds through opening of the furan rings to a dialkyne and subsequent re-cyclization in the borylation step. The resulting bifuran-fused diborepins show pronounced stability, highly planar tricyclic structures, and intense blue light emission. Deprotection and transformation into dibrominated building blocks that can be incorporated into π-extended materials can be performed in one step. Detailed DFT calculations provide information about the aromaticity of the constituent rings of this polycycle.     

Infrared and Raman spectroscopy of particle-beam induced damage of silicon carbide

The damaging of 6H-SiC by ion implantation (Ar⁺, 320 keV) leads to the formation of a light-absorbing surface layer with a thickness of about 0.4 μm and a dielectric function which indicates a disordering of the crystal structure. Raman spectra show the existence of amorphous carbon, silicon and silicon carbide. Ion bombardment with 1.4 MeV He⁺ ions generates a 3 μm thick surface layer with small lattice distortions and light-absorbing centers and a 0.4 μm thick interface layer with a larger refractive index.     

Hexamethoxycyclopropane

Hexamethoxycyclopropane, obtained by reaction of lithiopentamethoxycyclopropane with dimethyl peroxide, decomposes at 200°C to dimethoxycarbene and tetramethoxyethylene.     

Atomistic modeling of surface and bulk properties of Cu, Pd and the Cu–Pd system

The BFS method for alloys is applied to the study of the Cu–Pd system. A variety of issues are analyzed and discussed, including the properties of pure Cu or Pd crystals (surface energies, surface relaxations), Pd/Cu and Cu/Pd surface alloys, segregation of Pd (or Cu) in Cu (or Pd), concentration dependence of the lattice parameter of the high temperature fcc CuPd solid solution, the formation and properties of low temperature ordered phases, and order–disorder transition temperatures. Emphasis is made on the ability of the method to describe these properties on the basis of a minimum set of BFS universal parameters that uniquely characterize the Cu–Pd system.