ALBERT

Description: Author(s): Robert Schmidt, Ashish Arora, Gerd Plechinger, Philipp Nagler, Andrés Granados del Águila, Mariana V. Ballottin, Peter C. M. Christianen, Steffen Michaelis de Vasconcellos, Christian Schüller, Tobias Korn, and Rudolf Bratschitsch We control the linear polarization of emission from the coherently emitting K + and K − valleys (valley coherence) in monolayer WS 2 with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the e… [Phys. Rev. Lett. 117, 077402] Published Fri Aug 12, 2016

Description: Introducing nanostructural second phases has proved to be an effective approach to reduce the lattice thermal conductivity and thus enhances the figure of merit for many thermoelectric materials. Studies of the formation and evolution of these second phases are essential to understanding material temperature dependent behaviors, improving thermal stabilities, as well as designing new materials. In this study, powder samples of the PbTe-PbS thermoelectric material were examined using in situ neutron diffraction and small angle neutron scattering (SANS) techniques between room temperature and elevated temperature up to 663 K, to explore quantitative information on the structure, weight fraction, and size of the second phase. Neutron diffraction data showed that the as-milled powder was primarily a solid solution prior to heat treatment. During heating, a PbS second phase precipitated out of the PbTe matrix around 500 K, while re-dissolution started around 600 K. The second phase remained separated from the matrix upon cooling. Furthermore, SANS data indicated that there are two populations of nanostructures. The size of the smaller nanostructure increased from initially 5 nm to approximately 25 nm after annealing at 650 K, while the size of the larger one remained unchanged. This study demonstrated that in situ neutron techniques are effective means to obtain quantitative information on temperature-dependent nanostructural behavior of thermoelectrics and likely other high-temperature materials.

Description: The influence of several process parameters like milling time, ball-to-beaker volume ratio, diameter of milling balls, and rotation frequency on the Knoevenagel condensation of vanillin and barbituric acid in planetary ball mills was investigated. These parameters determine the amount of energy provided for the reaction. Additionally, numerical simulations were carried out to describe the stress conditions in detail and to compute the drive power and energy transfer which cannot be measured directly. The mill and experimental parameters were modeled by the discrete element method with adequate coefficients of friction and restitution required to describe the powder behavior in the system. The coefficients were determined by correlation of experiments and simulations. Mechanochemical synthesis may offer green solutions to organic synthesis. Using the Knoevenagel reaction under solvent-free conditions in a planetary ball mill, the results are correlated with discrete element method simulations to prove the dependency of the reaction yield on stress conditions. Smaller balls were more time and energy efficient due to higher power values achieved by high stress frequencies.

Description: Author(s): Dominik Christiansen, Malte Selig, Gunnar Berghäuser, Robert Schmidt, Iris Niehues, Robert Schneider, Ashish Arora, Steffen Michaelis de Vasconcellos, Rudolf Bratschitsch, Ermin Malic, and Andreas Knorr Excitons dominate the optical properties of monolayer transition metal dichalcogenides (TMDs). Besides optically accessible bright exciton states, TMDs exhibit also a multitude of optically forbidden dark excitons. Here, we show that efficient exciton-phonon scattering couples bright and dark states... [Phys. Rev. Lett. 119, 187402] Published Wed Nov 01, 2017

Description: Journal of Chemical Information and Modeling DOI: 10.1021/acs.jcim.6b00561

Description: Background: Elective patient admission and assignment planning is an important task of the strategic and operationalmanagement of a hospital and early on became a central topic of clinical operations research. Themanagement of hospital beds is an important subtask. Various approaches have been proposed, involving thecomputation of efficient assignments with regard to the patients' condition, the necessity of the treatment, andthe patients' preferences. However, these approaches are mostly based on static, unadaptable estimates of thelength of stay and, thus, do not take into account the uncertainty of the patient's recovery. Furthermore, theeffect of aggregated bed capacities have not been investigated in this context.Computer supported bed management, combining an adaptable length of stay estimation with the treatment ofshared resources (aggregated bed capacities) has not yet been sufficiently investigated.The aim of our work is: 1) to define a cost function for patient admission taking into account adaptable lengthof stay estimations and aggregated resources, 2) to define a mathematical program formally modeling theassignment problem and an architecture for decision support, 3) to investigate four algorithmic methodologiesaddressing the assignment problem and one base-line approach, and 4) to evaluate these methodologies w.r.t.cost outcome, performance, and dismissal ratio. Methods: The expected free ward capacity is calculated based on individual length of stay estimates, introducingBernoulli distributed random variables for the ward occupation states and approximating the probabilitydensities. The assignment problem is represented as a binary integer program. Four strategies for solving theproblem are applied and compared: an exact approach, using the mixed integer programming solver SCIP; andthree heuristic strategies, namely the longest expected processing time, the shortest expected processing time,and random choice. A baseline approach serves to compare these optimization strategies with a simple modelof the status quo. All the approaches are evaluated by a realistic discrete event simulation: the outcomes arethe ratio of successful assignments and dismissals, the computation time, and the models cost factors.

Description: Histological examinations of the host reaction types (RTs); short galls, rough galls and smooth galls in slash pine seedlings inoculated with Cronartium quercuum f. sp. fusiforme revealed host reaction zone(s) [RZ(s)]. These RZs differed among the host RTs in location and pattern of occurrence in the stem, staining reaction, periderm formation and amount of fungal colonization. The RZ within short galls were wide, deep in the cortex, continuous around the stem, bordered on both sides by a well-developed periderm encircling the stem with limited fungal colonization. The RZ of the rough galls lacked a periderm, were small, numerous and discontinuous around the stem circumference, being separated by symptomatic tissue typical of a susceptible reaction. Fungal colonization of the rough galls was limited and hyphae and haustoria were encrusted. The RZ of the smooth galls were small and narrow conforming to the stem circumference, shallow in the cortex and interconnected by symptomatic tissues typical of a susceptible reaction. A narrow periderm developed along the innermost portion of the RZ in smooth galls and fungal colonization was abundant in the cortex. We suggest that the RTs large galls (rough and smooth), short galls, and hypersensitive-like stem lesions represent increasing resistance to the fusiform rust pathogen.

Description: Single-gall and mixed-gall inocula from fusiform rust (Cronartium quercuum fusiforme) galls in field studies were used in greenhouse tests to investigate their pathogenic variability and the temporal and spatial stability of fusiform rust incidence of resistant slash pine (Pinus elliottii var. elliottii) seedlings. Analyses of variance showed significant main effects for families and inocula and for the interactions of families and inocula indicating abundant pathogenic variation and differential family resistance. Averaged over all families and inocula, there were no significant differences between sequential inocula, i.e., inocula from successive generations of the pathogen. However, when analyzed separately Family R1 with segregated major gene resistance showed increased rust incidence with successive generations of the pathogen. Also Family R1 accounted for a major portion of the temporal (51.4%) and spatial (49.6%) interaction sum of squares. In contrast the other resistant families each accounted for a minor portion of this statistic. These results indicate pathogen virulence toward major gene resistance, possible selection for virulence and the relative instability of Family R1 compared with other resistance families.

Description: Inverted valley polarization in optically excited transition metal dichalcogenides Inverted valley polarization in optically excited transition metal dichalcogenides, Published online: 06 March 2018; doi:10.1038/s41467-018-03354-1 In atomically thin transition metal dichalcogenides, spin- and valley-polarised states can be addressed thanks to large spin–orbit coupling and circular dichroism. Here, the authors investigate theoretically and experimentally the decay dynamics of spin and valley polarisation in transition metal dichalcogenide monolayers.