Solar-grade silicon prepared by carbothermic reduction of silica

An advanced carbothermic reduction (ACR) process was developed to produce solar grade (SC) silicon from high purity silica and carbon. Preparation of starting materials and operation of the arc furnace to product high purity silicon is described. Solar cells prepared from single crystal SG-Si had efficiencies of up to 12.3% practically identical to cells made from electronic grade silicon. The ACR process is not in the pilot stage for further evaluation

Critical behavior in a cross-situational lexicon learning scenario

The associationist account for early word-learning is based on the co-occurrence between objects and words. Here we examine the performance of a simple associative learning algorithm for acquiring the referents of words in a cross-situational scenario affected by noise produced by out-of-context words. We find a critical value of the noise parameter $\gamma_c$ above which learning is impossible. We use finite-size scaling to show that the sharpness of the transition persists across a region of order $\tau^{-1/2}$ about $\gamma_c$, where $\tau$ is the number of learning trials, as well as to obtain the learning error (scaling function) in the critical region. In addition, we show that the distribution of durations of periods when the learning error is zero is a power law with exponent -3/2 at the critical point

Molecular screening of microorganisms associated with discolored wood in dead European beech trees suffered from extreme drought event using next generation sequencing

Drought events weaken trees and make them vulnerable to attacks by diverse plant pathogens. Here, we propose a molecular method for fast screening of microorganisms associated with European beech decline after an extreme drought period (2018) in a forest of Thuringia, Germany. We used Illumina sequencing with a recent bioinformatics approach based on DADA2 to identify archaeal, bacterial, and fungal ASVs (amplicon sequence variants) based on bacterial and archaeal 16S and fungal ITS genes. We show that symptomatic beech trees are associated with both bacterial and fungal plant pathogens. Although the plant pathogen sequences were detected in both discolored and non-discolored wood areas, they were highly enriched in the discolored wood areas. We show that almost each individual tree was associated with a different combination of pathogens. Cytospora spp. and Neonectria coccinea were among the most frequently detected fungal pathogens, whereas Erwinia spp. and Pseudomonas spp. were the dominant bacterial plant pathogens. We demonstrate that bacterial plant pathogens may be of major importance in beech decline

A Hybrid Monte Carlo Method for Surface Growth Simulations

We introduce an algorithm for treating growth on surfaces which combines important features of continuum methods (such as the level-set method) and Kinetic Monte Carlo (KMC) simulations. We treat the motion of adatoms in continuum theory, but attach them to islands one atom at a time. The technique is borrowed from the Dielectric Breakdown Model. Our method allows us to give a realistic account of fluctuations in island shape, which is lacking in deterministic continuum treatments and which is an important physical effect. Our method should be most important for problems close to equilibrium where KMC becomes impractically slow.Comment: 4 pages, 5 figure

Azobenzene at Coinage Metal Surfaces: The Role of Dispersive van der Waals Interactions

We use different semi-empirical dispersion correction schemes to assess the role of long-range van der Waals interactions in the adsorption of the prototypical molecular switch azobenzene (C6H5-N2-C6H5) at the coinage metal surfaces Cu(111), Ag(111) and Au(111). Compared to preceding density-functional theory results employing a semi-local exchange and correlation functional we obtain partly sizable changes of the computed adsorption geometry and energetics. The discomforting scatter in the results provided by the different schemes is largely attributed to the unknown form of the damping function in the semi-empirical correction expression. Using the congeneric problem of the adsorption of benzene as a vehicle to connection with experiment, we cautiously conclude that the account of dispersive interactions at the metal surfaces provided by the various schemes is in the right ballpark, with the more recent, general schemes likely to overbind.Comment: 11 pages including 4 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

Comparison of Relativistic Nucleon-Nucleon Interactions

We investigate the difference between those relativistic models based on interpreting a realistic nucleon-nucleon interaction as a perturbation of the square of a relativistic mass operator and those models that use the method of Kamada and Gl\"ockle to construct an equivalent interaction to add to the relativistic mass operator. Although both models reproduce the phase shifts and binding energy of the corresponding non-relativistic model, they are not scattering equivalent. The example of elastic electron-deuteron scattering in the one-photon-exchange approximation is used to study the sensitivity of three-body observables to these choices. Our conclusion is that the differences in the predictions of the two models can be understood in terms of the different ways in which the relativistic and non-relativistic $S$-matrices are related. We argue that the mass squared method is consistent with conventional procedures used to fit the Lorentz-invariant cross section as a function of the laboratory energy.Comment: Revtex 13 pages, 5 figures, corrected some typo

Family firm internationalization: Past research and an agenda for the future

Although the study of family firm internationalization has generated considerable scholarly attention, existing research has offered varied and at times incompatible findings on how family ownership and management shape internationalization. To improve our understanding of family firm internationalization, we systematically review 220 conceptual and empirical studies published over the past three decades, structuring our comprehensive overview of this field according to seven core international business (IB) themes. We assess the literature and propose directions for future research by developing an integrative framework of family firm internationalization that links IB theory with conceptual perspectives used in the reviewed body of work. We propose a research agenda that advocates a cross-disciplinary, multi-theoretic, and cross-level approach to studying family firm internationalization. We conclude that family firm internationalization research has the potential to contribute valuable insights to IB scholarship by increasing attention to conceptual and methodological issues, including micro-level affective motivations, background social institutions, temporal perspectives, and multi-level analyses