ALBERT

Beschreibung: Technical Note: Reducing the spin-up time of integrated surface water–groundwater models Hydrology and Earth System Sciences, 18, 5169-5179, 2014 Author(s): H. Ajami, J. P. Evans, M. F. McCabe, and S. Stisen One of the main challenges in the application of coupled or integrated hydrologic models is specifying a catchment's initial conditions in terms of soil moisture and depth-to-water table (DTWT) distributions. One approach to reducing uncertainty in model initialization is to run the model recursively using either a single year or multiple years of forcing data until the system equilibrates with respect to state and diagnostic variables. However, such "spin-up" approaches often require many years of simulations, making them computationally intensive. In this study, a new hybrid approach was developed to reduce the computational burden of the spin-up procedure by using a combination of model simulations and an empirical DTWT function. The methodology is examined across two distinct catchments located in a temperate region of Denmark and a semi-arid region of Australia. Our results illustrate that the hybrid approach reduced the spin-up period required for an integrated groundwater–surface water–land surface model (ParFlow.CLM) by up to 50%. To generalize results to different climate and catchment conditions, we outline a methodology that is applicable to other coupled or integrated modeling frameworks when initialization from an equilibrium state is required.

Beschreibung: Extending periodic eddy covariance latent heat fluxes through tree sapflow measurements to estimate long-term total evaporation in a peat swamp forest Hydrology and Earth System Sciences Discussions, 11, 13607-13661, 2014 Author(s): A. D. Clulow, C. S. Everson, M. G. Mengistu, J. S. Price, A. Nickless, and G. P. W. Jewitt A combination of measurement and modelling was used to find a pragmatic solution to estimate the annual total evaporation (ET) from the rare and indigenous Nkazana Peat Swamp Forest (PSF) on the east coast of Southern Africa to improve the water balance estimates within the area. Total evaporation was measured during three window periods (between seven and nine days each) using an eddy covariance (EC) system on a telescopic mast above the forest canopy. Sapflow of an understory and an emergent tree was measured using a low maintenance heat pulse velocity system for an entire hydrological year (October 2009 to September 2010). An empirical model was derived, describing the relationship between the observed ET of the Nkazana PSF measured during two of the window periods ( R 2 = 0.92 and 0.90) which, overlapped with sapflow measurements, thereby providing hourly estimates of predicted ET of the Nkazana PSF for a year, totalling 1125 mm (while rainfall was 650 mm). In building the empirical model, it was found that including the understory tree sapflow provided no benefit to the model performance. In addition, the observed emergent tree sapflow relationship with observed ET between the two field campaigns was consistent and could be represented by a single empirical model ( R 2 = 0.90; RMSE = 0.08 mm). During the window periods of EC measurement, no single meteorological variable was found to describe the Nkazana PSF ET satisfactorily. However, in terms of evaporation models, the hourly FAO56 Penman–Monteith equation best described the observed ET from EC during the August 2009 ( R 2 = 0.75), November 2009 ( R 2 = 0.85) and March 2010 ( R 2 = 0.76) field campaigns, compared to the Priestley–Taylor model ( R 2 = 0.54, 0.74 and 0.62 during the respective field campaigns). From the empirical model of ET and the FAO56 Penman–Monteith equation, a monthly crop factor ( K c ) was derived for the Nkazana PSF providing a method of estimating long-term swamp forest ET from meteorological data. The monthly crop factor indicated two distinct periods. From February to May, it was between 1.2 and 1.4 compared with June to January, when the crop factor was 0.8 to 1.0. The derived monthly K c values were verified as accurate (to one significant digit) using historical data measured at the same site, also using EC, from a~previous study. The measurements provided insights into the microclimate within a subtropical peat swamp forest and the contrasting sapflow of emergent and understory trees. They showed that expensive, high maintenance equipment can be used during manageable window periods in conjunction with low maintenance systems, dedicated to individual trees, to derive a model to estimate long-term ET over remote heterogeneous forests. In addition, the contrast in ET and rainfall emphasises the reliance of the Nkazana PSF on groundwater.

Beschreibung: Article Superconductivity in the iron pnictides is believed to be related to quantum critical fluctuations. Putzke et al. observe unexpected anomalies in the critical fields of BaFe 2 (As 1−x P x ) 2 that emerge close to its magnetic critical point, which they argue is a generic feature of quantum critical superconductivity. Nature Communications doi: 10.1038/ncomms6679 Authors: C. Putzke, P. Walmsley, J. D. Fletcher, L. Malone, D. Vignolles, C. Proust, S. Badoux, P. See, H. E. Beere, D. A. Ritchie, S. Kasahara, Y. Mizukami, T. Shibauchi, Y. Matsuda, A. Carrington

Beschreibung: Article microRNAs are short non-coding RNAs that post-transcriptionally regulate gene expression for which the identification of promoter and primary transcripts (pri-miRNAs) has been difficult. Here the authors describe microTSS, an algorithm that supports the precise identification of intergenic pri-miRNA transcription start sites. Nature Communications doi: 10.1038/ncomms6700 Authors: Georgios Georgakilas, Ioannis S. Vlachos, Maria D. Paraskevopoulou, Peter Yang, Yuhong Zhang, Aris N. Economides, Artemis G. Hatzigeorgiou

Beschreibung: Article Autism spectrum disorder (ASD) is a common, highly heritable neurodevelopmental condition characterized by marked genetic heterogeneity. In this study, the authors use RNA sequencing analyses to characterize differences in the transcriptome between autistic and typically developing brains. Nature Communications doi: 10.1038/ncomms6748 Authors: Simone Gupta, Shannon E. Ellis, Foram N. Ashar, Anna Moes, Joel S. Bader, Jianan Zhan, Andrew B. West, Dan E. Arking

Beschreibung: Article Pulse oximetry is a non-invasive means for measuring blood oxygen saturation and pulse rate, with typical sensors based on rigid electronics. Here, the authors develop a pulse oximeter based solely on organic materials, allowing flexible devices and hence increasing the potential sensing locations on the body. Nature Communications doi: 10.1038/ncomms6745 Authors: Claire M. Lochner, Yasser Khan, Adrien Pierre, Ana C. Arias

Beschreibung: Article The straightforward and scalable synthesis and patterning of graphene-based nanomaterials remains a technological challenge. Here, the authors use a CO 2 infrared laser, under ambient conditions, to directly produce and pattern porous graphene films with three-dimensional networks from commercial polymer films. Nature Communications doi: 10.1038/ncomms6714 Authors: Jian Lin, Zhiwei Peng, Yuanyue Liu, Francisco Ruiz-Zepeda, Ruquan Ye, Errol L. G. Samuel, Miguel Jose Yacaman, Boris I. Yakobson, James M. Tour

Beschreibung: Consensus of continuous-time single-integrator multiagent systems with inherent nonlinear dynamics and measurement noises is addressed in this paper. The consensus controller is developed for directed interaction topologies. Each agent’s control input is constructed based on its own state and its neighbors’ states corrupted by noises. The control input contains a time-varying consensus gain in order to attenuate the noises. Conditions for ensuring mean square convergence under noisy measurement and asymptotic convergence in the noise-free case are derived. Finally, some simulations were carried out to show the effectiveness of our control law and how it can solve the consensus problem.

Beschreibung: Author(s): N. A. Sinitsyn We consider nonadiabatic transitions in explicitly time-dependent systems with Hamiltonians of the form Ĥ(t)=Â+B̂t+Ĉ/t, where t is time and Â, B̂, Ĉ are Hermitian N×N matrices. We show that in any model of this type, scattering matrix elements satisfy nontrivial exact constraints that follow fr... [Phys. Rev. A 90, 062509] Published Thu Dec 11, 2014