Interfacial and confined molecular-assembly of poly(3-hexylthiophene) and its application in organic electronic devices.

Poly(3-hexylthiophene) (P3HT) is a typical conducting polymer widely used in organic thin-film transistors, polymer solar cells, etc., due to good processability and remarkable charging carrier and hole mobility. It is known that the ordered structure assembled by π-conjugated P3HT chains could promote the performance of electronic devices. Interfacial and confined molecular-assembly is one effective way to generate an ordered structure by tuning surface geometry and substrate interaction. Great efforts have been made to investigate the molecular chain assembly of P3HT on a curved surface that is confined to different geometry. In this report, we review the recent advances of the interfacial chain assembly of P3HT in a flat or curved confined space and its application to organic electronic devices. In principle, this interfacial assembly of P3HT at a nanoscale could improve the electronic properties, such as the current transport, power conversion efficiency, etc. Therefore, this review on interfacial and confined assembly of P3HT could give general implications for designing high-performance organic electronic devices.

Genetic Interference Analysis Reveals that Both 3-Hydroxybenzoic Acid and 4-Hydroxybenzoic Acid Are Involved in Xanthomonadin Biosynthesis in the Phytopathogen Xanthomonas campestris pv. campestris.

A characteristic feature of phytopathogenic Xanthomonas bacteria is the production of yellow membrane-bound pigments called xanthomonadins. Previous studies showed that 3-hydroxybenzoic acid (3-HBA) was a xanthomonadin biosynthetic intermediate and also, that it had a signaling role. The question of whether the structural isomers 4-HBA and 2-HBA (salicylic acid) have any role in xanthomonadin biosynthesis remained unclear. In this study, we have selectively eliminated 3-HBA, 4-HBA, or the production of both by expression of the mhb, pobA, and pchAB gene clusters in the Xanthomonas campestris pv. campestris strain XC1. The resulting strains were different in pigmentation, virulence factor production, and virulence. These results suggest that both 3-HBA and 4-HBA are involved in xanthomonadin biosynthesis. When both 3-HBA and 4-HBA are present, X. campestris pv. campestris prefers 3-HBA for Xanthomonadin-A biosynthesis; the 3-HBA-derived Xanthomonadin-A was predominant over the 4-HBA-derived xanthomonadin in the wild-type strain XC1. If 3-HBA is not present, then 4-HBA is used for biosynthesis of a structurally uncharacterized Xanthomonadin-B. Salicylic acid had no effect on xanthomonadin biosynthesis. Interference with 3-HBA and 4-HBA biosynthesis also affected X. campestris pv. campestris virulence factor production and reduced virulence in cabbage and Chinese radish. These findings add to our understanding of xanthomonadin biosynthetic mechanisms and further help to elucidate the biological roles of xanthomonadins in X. campestris pv. campestris adaptation and virulence in host plants.

Orthogonal chirp-division multiplexing for IM/DD-based short-reach systems.

Orthogonal chirp-division multiplexing (OCDM) has been recently proposed as an attractive modulation technique for realizing high-speed coherent lightwave systems in virtue of its resilience against system impairments. However, the complex-valued OCDM signal is not directly viable for optical intensity modulation and direct detection (IM/DD) systems. In this paper, a double-sideband (DSB)-modulated OCDM scheme is proposed for short-reach, high-speed IM/DD systems. In the proposed scheme, the real-valued OCDM signal is generated by a simple digital up-conversion technique, which converts the complex-baseband signal to a passband to avoid the aliasing for DSB modulation. At the receiver, inverse operations revert the signal back to the baseband for demodulation. Experiments were carried out to validate the feasibility and advantages of the proposed scheme, and OCDM signals with data rates up to 174.5 Gbit/s were successfully demonstrated. The results confirm that the proposed IM/DD-OCDM system is more robust to impairments and thus achieves better performance than a discrete multi-tone system.

Experimental demonstration of 111.1-Gb/s net information rate using IM/DD probabilistically shaped orthogonal chirp-division multiplexing with a 10-GHz-class modulator.

We propose probabilistically shaped quadrature amplitude modulation (PS-QAM) formats to maximize the capacity in fiber transmission systems using orthogonal chirp-division multiplexing (OCDM). OCDM possesses the property of chirp spread spectrum (CSS), leading to improved resilience to system impairments. We further investigate the recently proposed robust channel estimator based on pulse compression and noise rejection and experimentally demonstrate its feasibility in an intensity-modulated/direction-detection (IM/DD) OCDM system. By applying the proposed PS-QAM based OCDM to an IM/DD optical system, a net information rate of 111.1 Gb/s has been successfully achieved using a 10-GHz class Mach-Zehnder modulator (MZM) and has also shown improved performance compared to the conventional PS-QAM based orthogonal frequency-division multiplexing (OFDM) systems. Moreover, due to the superior characteristics of OCDM, there is no need for additional feedback to obtain the prior knowledge of channel state information in the proposed system, leading to reduced complexity and cost.

Experimental demonstration of a real-time high-throughput digital DC blocker for compensating ADC imperfections in optical fast-OFDM receivers.

Performance degradation induced by the DC components at the output of real-time analogue-to-digital converter (ADC) is experimentally investigated for optical fast-OFDM receiver. To compensate this degradation, register transfer level (RTL) circuits for real-time digital DC blocker with 20GS/s throughput are proposed and implemented in field programmable gate array (FPGA). The performance of the proposed real-time digital DC blocker is experimentally investigated in a 15Gb/s optical fast-OFDM system with intensity modulation and direct detection over 40 km standard single-mode fibre. The results show that the fixed-point DC blocker has negligible performance penalty compared to the offline floating point one, and can overcome the error floor of the fast OFDM receiver caused by the DC components from the real-time ADC output.

[Simulation and Regulation of Sustainable Utilization of Water Resources in China Based on Improved Water Resources Ecological Footprint Model].

The original ecological footprint model of water resources was improved here to explore the rational policy of water resources development and utilization. Aiming to address the problems of high complexity, weak applicability, and insufficient systematicness and dynamics of the existing water resources ecological footprint model, the grey water footprint was introduced into the model to quantify the water for decontamination. In the calculation of the water resources ecological footprint index, the rainwater collection project, seawater desalination, and water resources regeneration, unconventional water sources were considered, and when combined with the system dynamics simulation technology, the SD model of water resources sustainable utilization in China was established. We carried out research on the regulation and control of sustainable utilization of water resources in China. The results showed that the development and utilization of water resources in China remained within the ecological carrying capacity as a whole from 2000 to 2017, and the development of water resources still had potential, but the supply and demand of water resources were unbalanced. Given this, from the perspective of throttling, open-source, and pollution control, six control schemes for sustainable utilization of water resources in China were set up, including the continuation of the current situation, green throttling, pollution control, strict planning for water source development, and comprehensive treatment. Among them, the comprehensive coordination plan for 2018-2050 could properly solve the problem of water resources supply and demand under the conditions of meeting the ecological sustainability of water resources and reasonable water resources load and was the best regulation plan to realize the sustainable utilization of water resources in China. At present, the development of water resources in China lags, which does not match the growth rate of social and economic development on water resources consumption. It is necessary to further strengthen the efforts of open-source, water-saving, and pollution control based on the original policies, so as to alleviate the ecological stress of water resources.