205 research outputs found
Generation of photovoltage in graphene on a femtosecond time scale through efficient carrier heating
Graphene is a promising material for ultrafast and broadband photodetection.
Earlier studies addressed the general operation of graphene-based
photo-thermoelectric devices, and the switching speed, which is limited by the
charge carrier cooling time, on the order of picoseconds. However, the
generation of the photovoltage could occur at a much faster time scale, as it
is associated with the carrier heating time. Here, we measure the photovoltage
generation time and find it to be faster than 50 femtoseconds. As a
proof-of-principle application of this ultrafast photodetector, we use graphene
to directly measure, electrically, the pulse duration of a sub-50 femtosecond
laser pulse. The observation that carrier heating is ultrafast suggests that
energy from absorbed photons can be efficiently transferred to carrier heat. To
study this, we examine the spectral response and find a constant spectral
responsivity between 500 and 1500 nm. This is consistent with efficient
electron heating. These results are promising for ultrafast femtosecond and
broadband photodetector applications.Comment: 6 pages, 4 figure
Primary Postnatal Dorsal Root Ganglion Culture from Conventionally Slaughtered Calves
Neurological disorders in ruminants have an important impact on veterinary health, but very few host-specific in vitro models have been established to study diseases affecting the nervous system. Here we describe a primary neuronal dorsal root ganglia (DRG) culture derived from calves after being conventionally slaughtered for food consumption. The study focuses on the in vitro characterization of bovine DRG cell populations by immunofluorescence analysis. The effects of various growth factors on neuron viability, neurite outgrowth and arborisation were evaluated by morphological analysis. Bovine DRG neurons are able to survive for more than 4 weeks in culture. GF supplementation is not required for neuronal survival and neurite outgrowth. However, exogenously added growth factors promote neurite outgrowth. DRG cultures from regularly slaughtered calves represent a promising and sustainable host specific model for the investigation of pain and neurological diseases in bovines
Whole genome sequence and manual annotation of Clostridium autoethanogenum, an industrially relevant bacterium
Clostridium autoethanogenum is an acetogenic bacterium capable of producing high value commodity chemicals and biofuels from the C1 gases present in synthesis gas. This common industrial waste gas can act as the sole energy and carbon source for the bacterium that converts the low value gaseous components into cellular building blocks and industrially relevant products via the action of the reductive acetyl-CoA (Wood-Ljungdahl) pathway. Current research efforts are focused on the enhancement and extension of product formation in this organism via synthetic biology approaches. However, crucial to metabolic modelling and directed pathway engineering is a reliable and comprehensively annotated genome sequence
Electricity portfolio innovation for energy security: the case of carbon constrained China
China’s energy sector is under pressure to achieve secure and affordable supply and a clear decarbonisation path. We examine the longitudinal trajectory of the Chinese electricity supply security and model the near future supply security based on the 12th 5 year plan. Our deterministic approach combines Shannon-Wiener, Herfindahl-Hirschman and electricity import dependence indices for supply security appraisal. We find that electricity portfolio innovation allows China to provide secure energy supply despite increasing import dependence. It is argued that long-term aggressive deployment of renewable energy will unblock China’s coal-biased technological lock-in and increase supply security in all fronts. However, reduced supply diversity in China during the 1990s will not recover until after 2020s due to the long-term coal lock-in that can threaten to hold China’s back from realising its full potential
Optical frequency comb technology for ultra-broadband radio-frequency photonics
The outstanding phase-noise performance of optical frequency combs has led to
a revolution in optical synthesis and metrology, covering a myriad of
applications, from molecular spectroscopy to laser ranging and optical
communications. However, the ideal characteristics of an optical frequency comb
are application dependent. In this review, the different techniques for the
generation and processing of high-repetition-rate (>10 GHz) optical frequency
combs with technologies compatible with optical communication equipment are
covered. Particular emphasis is put on the benefits and prospects of this
technology in the general field of radio-frequency photonics, including
applications in high-performance microwave photonic filtering, ultra-broadband
coherent communications, and radio-frequency arbitrary waveform generation.Comment: to appear in Laser and Photonics Review
- …