Malongitubus: a possible pterobranch hemichordate from the early Cambrian of South China

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Malongitubus kuangshanensis Hu, 2005 from the early Cambrian Chengjiang Lagerstätte of China is redescribed as a pterobranch and provides the best evidence to demonstrate that hemichordates were present as early as Cambrian Stage 3. Interpretation of this taxon as a hemichordate is based on the morphology of the branched colony and the presence of resistant inner threads consistent with the remains of an internal stolon system. The presence of fusellar rings in the colonial tubes cannot be unambiguously proven for Malongitubus, probably due to early decay and later diagenetic replacement of the thin organic material of the tubarium, although weak annulations are still discernible in parts of the tubes. The description of M. kuangshanensis is revised according to new observations of previously reported specimens and recently collected additional new material. Malongitubus appears similar in most features to Dalyia racemata Walcott, 1919 from the Cambrian Stage 5 Burgess Shale, but can be distinguished by the existence of disc-like thickenings at the bases of tubarium branching points in the latter species. Both species occur in rare mass-occurrence layers with preserved fragmentary individuals of different decay stages, with stolon remains preserved as the most durable structures. Benthic pterobranchs may have occurred in some early Cambrian shallow marine communities in dense accumulations and provided firm substrates and shelter for other benthic metazoans as secondary tierers

Visible emission and energy transfer in Tb³⁺/Dy³⁺ co-doped phosphate glasses

In this work, we systematically study the spectroscopic properties of Tb3+/Dy3+ co-doped phosphate glasses in the visible spectral region and explore the sensitization role of Dy3+ in the enhancement of visible fluorescence of Tb3+ ions. Judd-Ofelt parameters Ω2 and Ω4/Ω6 of the phosphate glass as host for Tb3+ are calculated as 21.60 × 10-20 cm2 and 0.73, respectively, based on the measured spectral absorption. Multiple energy transfer (ET) routes from Dy3+ to Tb3+ and their efficiencies are characterized, and the enhanced fluorescence properties of Tb3+ are investigated, including the emission spectral strength and the spontaneous emission lifetime as functions of Dy3+ doping concentration. The efficient nonradiative ET processes between Dy3+ and Tb3+ allow a moderate concentration level of Tb3+ to achieve favorably stronger spectral absorption at blue and ultraviolet wavelengths. Tb3+/Dy3+ co-doped phosphate glass shows promising potential for phosphors and lasing operation at visible wavelengths.</p

Enhanced Performance of a Cascaded Receiver Consisting of a DNN-Based Waveform-to-Symbol Converter and Modified NN-Based DD-LMS in CAP Underwater VLC System

Underwater visible light communication (UVLC) based on LEDs has become a competitive candidate, which is able to provide high data rates, low latency and low cost for next-generation wireless communication technologies. However, it is still challenging to achieve high-speed communication because of bottleneck problems such as bandwidth limitation and linear and nonlinear distortions. Traditional Deep-learning Neural Network (DNN)-based waveform-to-symbol converter is verified to be an effective method to alleviate them, but impractical due to high complexity. To achieve a better tradeoff between communication performance and computation complexity, a cascaded receiver consisting of a DNN-based waveform-to-symbol converter and modified Neural Network (NN)-based decision-directed least mean square (DD-LMS) is then innovatively proposed. With fewer taps and nodes than the traditional converter, the front-stage converter could mitigate the majority of Inter-Symbol Interference (ISI) and signal nonlinear distortions. Then modified NN-based DD-LMS is cascaded to improve communication performance by reducing phase offset, making received constellation points more concentrated and closer to standard constellation points. Compared with the traditional converter, the cascaded receiver could achieve 89.6% of signal Vpp dynamic range with 12.4% of complexity in the 64APSK UVLC system. Moreover, the ratio of signal Vpp dynamic range and total trainable parameters is 1.24 × 10−1 mV, while that of the traditional converter is 1.95 × 10−2 mV. The cascaded receiver used in 64APSK UVLC systems is experimentally verified to achieve enhanced performance, thus as a promising scheme for future high-speed underwater VLC

A new Cambrian frondose organism: "Ediacaran survivor"or convergent evolution?

Guangweia cheni gen. et sp. nov. is an exceptionally preserved frond-like fossil from the early Cambrian Guanshan Biota of SW China, which shares morphological similarities with some characteristic late Ediacaran frondose organisms in comprising a leaf-like frond attached via a stem to a discoidal structure resembling a holdfast. Plausible evidence for tissue differentiation and bilateral symmetry in G. cheni implies a eumetazoan affinity. However, G. cheni profoundly differs from Ediacaran frondose taxa in several morphological characters, including its possession of an unusual wedge-shaped apical structure. These observations preclude direct phylogenetic relationships with known Ediacaran forms. Instead, G. cheni may record convergent evolution of a frondose bodyplan: a possibility that should be entertained for other purported Cambrian frondose taxa

Advanced Modulation Format of Probabilistic Shaping Bit Loading for 450-nm GaN Laser Diode based Visible Light Communication

Visible light communication is an emerging high-speed optical wireless communication technology that can be a candidate to alleviate pressure on conventional radio frequency-based technology. In this paper, for the first time, the advanced modulation format of probabilistic shaping (PS) bit loading is investigated in a high data rate visible light communication system based on a 450-nm Gallium Nitride laser diode. The characteristic of the system is discussed and PS bit loading discrete multi-tone modulation helps to raise the spectral efficiency and improve the system performance. Higher entropy can be achieved in the same signal-to-noise ratio (SNR) and modulation bandwidth limitation, comparing to bit and power loading. With PS bit loading, an available information rate (AIR) of 10.23 Gbps is successfully achieved at the signal bandwidth of 1.5 GHz in a 1.2 m free space transmission with normalized generalized mutual information above 0.92. And higher AIR can be anticipated with an entropy-loading strategy that fixes the channel characteristic. Experimental results validate that a PS bit loading scheme has the potential to increase the system capacity

Unveiling the State Transition Mechanisms of Ras Proteins through Enhanced Sampling and QM/MM Simulations

In cells, wild-type RasGTP complexes exist in two distinct states: active State 2 and inactive State 1. These complexes regulate their functions by transitioning between the two states. However, the mechanisms underlying this state transition have not been clearly elucidated. To address this, we conducted a detailed simulation study to characterize the energetics of the stable states involved in the state transitions of the HRasGTP complex, specifically from State 2 to State 1. This was achieved by employing multiscale quantum mechanics/molecular mechanics and enhanced sampling molecular dynamics methods. Based on the simulation results, we constructed the two-dimensional free energy landscapes that provide crucial information about the conformational changes of the HRasGTP complex from State 2 to State 1. Furthermore, we also explored the conformational changes from the intermediate state to the product state during guanosine triphosphate hydrolysis. This study on the conformational changes involved in the HRas state transitions serves as a valuable reference for understanding the corresponding events of both KRas and NRas as well