127 research outputs found
FPGA basierte, konfigurierbare OFDM Sender-Plattform fĂŒr die Positionsbestimmung mittels TDoA
FĂŒr die Evaluierung von Algorithmen zur Positionsbestimmung nach dem Time Difference of Arrival â Verfahren wird eine frei konfigurierbare OFDM Sender-Plattform benötigt. Da die Berechnung in Echtzeit erfolgen soll, ist eine Implementierung in rekonfigurierbarer Hardware (FPGA) erforderlich. Das Manuskript
gibt sowohl einen Ăberblick ĂŒber die HintergrĂŒnde und die Architektur des Sendesystems, als auch einen tieferen Einblick in verschiedene Lösungsdetails
No effect of seed source on multiple aspects of ecosystem functioning during ecological restoration: cultivars compared to local ecotypes of dominant grasses
Genetic principles underlie recommendations to use local seed, but a paucity of information exists on the genetic distinction and ecological consequences of using different seed sources in restorations. We established a field experiment to test whether cultivars and local ecotypes of dominant prairie grasses were genetically distinct and differentially influenced ecosystem functioning. Whole plots were assigned to cultivar and local ecotype grass sources. Three subplots within each whole plot were seeded to unique pools of subordinate species. The cultivar of the increasingly dominant grass, Sorghastrum nutans, was genetically different than the local ecotype, but genetic diversity was similar between the two sources. There were no differences in aboveground net primary production, soil carbon accrual, and net nitrogen mineralization rate in soil between the grass sources. Comparable productivity of the grass sources among the species pools for four years shows functional equivalence in terms of biomass production. Subordinate species comprised over half the aboveground productivity, which may have diluted the potential for documented trait differences between the grass sources to influence ecosystem processes. Regionally developed cultivars may be a suitable alternative to local ecotypes for restoration in fragmented landscapes with limited gene flow between natural and restored prairie and negligible recruitment by seed
Nanoscale-confined Terahertz Polaritons in a van der Waals Crystal
Electromagnetic field confinement is crucial for nanophotonic technologies,
since it allows for enhancing light-matter interactions, thus enabling light
manipulation in deep sub-wavelength scales. In the terahertz (THz) spectral
range, radiation confinement is conventionally achieved with specially designed
metallic structures - such as antennas or nanoslits - with large footprints due
to the rather long wavelengths of THz radiation. In this context, phonon
polaritons - light coupled to lattice vibrations - in van der Waals (vdW)
crystals have emerged as a promising solution for controlling light beyond the
diffraction limit, as they feature extreme field confinements and low optical
losses. However, experimental demonstration of nanoscale-confined phonon
polaritons at THz frequencies has so far remained elusive. Here, we provide it
by employing scattering-type scanning near-field optical microscopy (s-SNOM)
combined with a free-electron laser (FEL) to reveal a range of low-loss
polaritonic excitations at frequencies from 8 to 12 THz in the vdW
semiconductor . We visualize THz polaritons with i) in-plane
hyperbolic dispersion, ii) extreme nanoscale field confinement (below
) and iii) long polariton lifetimes, with a lower limit of > 2
ps
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Successful user operation of a superconducting radio-frequency photoelectron gun with Mg cathodes
At the electron linac for beams with high brilliance and low emittance (ELBE) center for high-power radiation sources, the second version of a superconducting radio-frequency (SRF) photoinjector has been put into operation and has been routinely applied for user operation at the ELBE electron accelerator. SRF guns are suitable for generating a continuous wave electron beam with high average currents and high beam brightness. The SRF gun at ELBE has the goal to generate short electron pulses with bunch charges of 200â300 pC at typical repetition rates of 100 kHz for the production of superradiant, coherent terahertz radiation. The SRF gun includes a 3.5-cell, 1.3-GHz niobium cavity and a superconducting solenoid. A support system with liquid nitrogen (LN2) cooling allows the operation of normal-conducting, high quantum efficiency photocathodes. We present the design and performance of the SRF gun as well as beam measurement results of the operation with Mg photocathodes at an acceleration gradient of 8ââMV/m (4 MeV kinetic energy). In the last section, we discuss the SRF gun application for production of coherent terahertz radiation at the ELBE facility
Echo State Property of Deep Reservoir Computing Networks
In the last years, the Reservoir Computing (RC) framework has emerged as a state of-the-art approach for efficient learning in temporal domains. Recently, within the RC context, deep Echo State Network (ESN) models have been proposed. Being composed of a stack of multiple non-linear reservoir layers, deep ESNs potentially allow to exploit the advantages of a hierarchical temporal feature representation at different levels of abstraction, at the same time preserving the training efficiency typical of the RC methodology. In this paper, we generalize to the case of deep architectures the fundamental RC conditions related to the Echo State Property (ESP), based on the study of stability and contractivity of the resulting dynamical system. Besides providing a necessary condition and a sufficient condition for the ESP of layered RC networks, the results of our analysis provide also insights on the nature of the state dynamics in hierarchically organized recurrent models. In particular, we find out that by adding layers to a deep reservoir architecture, the regime of networkâs dynamics can only be driven towards (equally or) less stable behaviors. Moreover, our investigation shows the intrinsic ability of temporal dynamics differentiation at the different levels in a deep recurrent architecture, with higher layers in the stack characterized by less contractive dynamics. Such theoretical insights are further supported by experimental results that show the effect of layering in terms of a progressively increased short-term memory capacity of the recurrent models
Tuberculosis Incidence in Prisons: A Systematic Review
A systematic review by Iacopo Baussano and colleagues synthesizes published research to show that improved tuberculosis (TB) control in prisons could significantly reduce the burden of TB both inside and outside prisons
Conceptualizing and measuring distance in international business research:Recurring questions and best practice guidelines
Distance is a central concept in international business research, yet there is debate about the construct as well as its operationalization. In this editorial, we address three of the most important recurring questions posed by authors, editors, and reviewers by examining the theory, methods, and data of distance research. We discuss (1) how to theorize on distance, and (2) what method and (3) what data to use when constructing a distance index. We develop practical recommendations grounded in theory, illustrating and supporting them by calculating cross-country distance indices for all available country pairs and two of the most used distance indices: cultural and institutional. We show that, whereas a specific method to calculate distance may matter to some extent, the choice for a specific cultural or institutional framework to measure cultural or institutional distance has a major impact on country-pair distances. Overall, this editorial highlights the importance of matching data and method to the theoretical argument.</p
A Barcode Screen for Epigenetic Regulators Reveals a Role for the NuB4/HAT-B Histone Acetyltransferase Complex in Histone Turnover
Dynamic modification of histone proteins plays a key role in regulating gene expression. However, histones themselves can also be dynamic, which potentially affects the stability of histone modifications. To determine the molecular mechanisms of histone turnover, we developed a parallel screening method for epigenetic regulators by analyzing chromatin states on DNA barcodes. Histone turnover was quantified by employing a genetic pulse-chase technique called RITE, which was combined with chromatin immunoprecipitation and high-throughput sequencing. In this screen, the NuB4/HAT-B complex, containing the conserved type B histone acetyltransferase Hat1, was found to promote histone turnover. Unexpectedly, the three members of this complex could be functionally separated from each other as well as from the known interacting factor and histone chaperone Asf1. Thus, systematic and direct interrogation of chromatin structure on DNA barcodes can lead to the discovery of genes and pathways involved in chromatin modification and dynamics
SSALMON â The Solar Simulations for the Atacama Large Millimeter Observatory Network
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