Ultrafast graphene photodetector

The electronic properties of graphene are unique and are attracting increased attention to this novel 2-dimensional system. Its photonic properties are not less impressive. For example, this single atomic layer absorbs through direct interband transitions a considerable fraction of the light (~2.3%) over a very a broad wavelength range. However, while applications in electronics are vigorously being pursued, photonic applications have not attracted as much attention. Here, we report on ultrafast photocurrent response measurements in graphene (single and few-layers) field-effect-transistors (FETs) up to 40 GHz light intensity modulation frequencies, using a 1.55 micron excitation laser. No photoresponse degradation is observable up to the highest measured frequency, demonstrating the feasibility and unique benefits of using graphene in photonics. Further analysis suggests that the intrinsic bandwidth of such graphene FET based photodetectors may exceed 500 GHz. Most notably, the generation and transport of the photo-carriers in such graphene photodetectors are fundamentally different from those in currently known semiconductor photodetectors, leading to a remarkably high bandwidth, zero source-drain bias (hence zero dark current) operation, and good internal quantum efficiency.Comment: 25 pages, 3 figure

High On-Off Ratio Bilayer Graphene Complementary Field Effect Transistors

In this paper, we propose a novel S/D engineering for dual-gated Bilayer Graphene (BLG) Field Effect Transistor (FET) using doped semiconductors (with a bandgap) as source and drain to obtain unipolar complementary transistors. To simulate the device, a self-consistent Non-Equilibrium Green's Function (NEGF) solver has been developed and validated against published experimental data. Using the simulator, we predict an on-off ratio in excess of $10^4$ and a subthreshold slope of ~110mV/decade with excellent scalability and current saturation, for a 20nm gate length unipolar BLG FET. However, the performance of the proposed device is found to be strongly dependent on the S/D series resistance effect. The obtained results show significant improvements over existing reports, marking an important step towards bilayer graphene logic devices.Comment: 4 pages, 11 figure

Isolation and functional characterization of a β-eudesmol synthase, a new sesquiterpene synthase from Zingiber zerumbet Smith

AbstractIn this paper, we have identified a new sesquiterpene synthase gene (ZSS2) from Zingiber zerumbet Smith. Functional expression of ZSS2 in Escherichia coli and in vitro enzyme assay showed that the encoded enzyme catalyzed the formation of β-eudesmol and five additional by-products. Quantitative RT-PCR analysis revealed that ZSS2 transcript accumulation in rhizomes has strong seasonal variations. To further confirm the enzyme activity of ZSS2 and to assess the potential for metabolic engineering of β-eudesmol production, we introduced a gene cluster encoding six enzymes of the mevalonate pathway into E. coli and coexpressed it with ZSS2. When supplemented with mevalonate, the engineered E. coli produced a similar sesquiterpene profile to that produced in the in vitro enzyme assay, and the yield of β-eudesmol reached 100mg/L

Regionalization methods for PUB: a comprehensive review of progress after the PUB decade

This paper presents an updated review of model-dependent regionalization methods in hydrology since the PUB decade, incorporating new regions and methodological advancements. Two categories of regionalization methods are discussed: distance-based and regression-based, with various modification approaches. Several factors affecting the accuracy of regionalization performance are identified, including hydrological models, climate characteristics, data availability, and regionalization techniques. The review concludes that distance-based regionalization methods with an output averaging option from multiple donor catchments are the most statistically reliable, and a threshold of 0.5–0.8 for donor selection is optimal for performance. The parsimonious hydrological model is also recommended, particularly in data-limited contexts. Other insights include the effectiveness of the ensemble concept and limited impact of prior classification. Additionally, it is found that the general performance difference between climatic classes is larger than between methods, and regression-based methods may have large uncertainties in tropical regions. Overall, this study provides practical guidance for improving regionalization studies and advancing the field of hydrology. HIGHLIGHTS A deep analysis based on last decade’s regionalization studies over the world.; The parsimonious hydrological model seems more robust with limited prior knowledge of regionalization.; Too high threshold (larger than 0.8) to donor selection results in performance deterioration.; Ensemble concept could help to modify the performance, rather better than the prior classification.; Climate plays an important role in regionalization.

Repair of distal finger soft-tissue defects with free fibular great toe neurovascular flaps

Abstract Background This work aimed to investigate the change in fingerprint depth and the recovery rule of fingerprint biological recognition function after repairing finger abdominal defects and rebuilding fingerprint with a free flap. Method From April 2018 to March 2023, we collected a total of 43 cases of repairing finger pulp defects using the free flap of the fibular side of the great toe with the digital nerve. After surgery, irregular follow-up visits were conducted to observe fingerprint clarity, perform the ninhydrin test or detect visible sweating with the naked eye. We recorded fingerprint clarity, nail shape, two-point discrimination, cold perception, warm perception and fingerprint recognition using smartphones. The reconstruction process of the repaired finger was recorded to understand the changes in various observation indicators and their relationship with the depth of the fingerprint. The correlation between fingerprint depth and neural repair was determined, and the process of fingerprint biological recognition function repair was elucidated. Result All flaps survived, and we observed various manifestations in different stages of nerve recovery. The reconstructed fingerprint had a clear fuzzy process, and the depth changes of the fingerprint were consistent with the changes in the biological recognition function curve. Conclusion The free flap with the digital nerve is used to repair finger pulp defects. The reconstructed fingerprint has a biological recognition function, and the depth of the fingerprint is correlated with the process of nerve repair. The fingerprint morphology has a dynamic recovery process, and it can reach a stable state after 6–8 months

High On-Off Ratio Bilayer Graphene Complementary Field Effect Transistors

In this paper, we propose a novel S/D engineering for dual-gated Bilayer Graphene (BLG) Field Effect Transistor (FET) using doped semiconductors (with a bandgap) as source and drain to obtain unipolar complementary transistors. To simulate the device, a self-consistent Non-Equilibrium Green's Function (NEGF) solver has been developed and validated against published experimental data. Using the simulator, we predict an on-off ratio in excess of 10(4) and a subthreshold slope of similar to 110mV/decade with excellent scalability and current saturation, for a 20nm gate length unipolar BLG FET. However, the performance of the proposed device is found to be strongly dependent on the S/D series resistance effect. The obtained results show significant improvements over existing reports, marking an important step towards bilayer graphene logic devices