86 research outputs found
Generation of ultrashort electrical pulses in semiconductor waveguides
We report a novel device capable of generating ultrashort electrical pulses on a coplanar waveguide (CPW) by means of optical rectification. The device consists of a completely passive GaAs-based optical waveguide, which is velocity matched to a CPW line. Optical pulses are injected into the device and electrical pulses are collected at the output. Experimental results obtained in the laboratory show the potential of this device for high speed optical-to-electrical conversion
Research and innovation identified to decarbonise the maritime sector
The maritime sector requires technically, environmentally, socially, and economically informed pathways to decarbonise and eliminate all emissions harmful to the environment and health. This is extremely challenging and complex, and a wide range of technologies and solutions are currently being explored. However, it is important to assess the state-of-the-art and identify further research and innovation required to accelerate decarbonisation. The UK National Clean Maritime Research Hub have identified key priority areas to drive this process, with particular focus on marine fuels, power and propulsion, vessel efficiency, port operations and infrastructure, digitalisation, finance, regulation, and policy
Cavity-enhanced direct frequency comb spectroscopy
Cavity-enhanced direct frequency comb spectroscopy combines broad spectral
bandwidth, high spectral resolution, precise frequency calibration, and
ultrahigh detection sensitivity, all in one experimental platform based on an
optical frequency comb interacting with a high-finesse optical cavity. Precise
control of the optical frequency comb allows highly efficient, coherent
coupling of individual comb components with corresponding resonant modes of the
high-finesse cavity. The long cavity lifetime dramatically enhances the
effective interaction between the light field and intracavity matter,
increasing the sensitivity for measurement of optical losses by a factor that
is on the order of the cavity finesse. The use of low-dispersion mirrors
permits almost the entire spectral bandwidth of the frequency comb to be
employed for detection, covering a range of ~10% of the actual optical
frequency. The light transmitted from the cavity is spectrally resolved to
provide a multitude of detection channels with spectral resolutions ranging
from a several gigahertz to hundreds of kilohertz. In this review we will
discuss the principle of cavity-enhanced direct frequency comb spectroscopy and
the various implementations of such systems. In particular, we discuss several
types of UV, optical, and IR frequency comb sources and optical cavity designs
that can be used for specific spectroscopic applications. We present several
cavity-comb coupling methods to take advantage of the broad spectral bandwidth
and narrow spectral components of a frequency comb. Finally, we present a
series of experimental measurements on trace gas detections, human breath
analysis, and characterization of cold molecular beams.Comment: 36 pages, 27 figure
Role and regulation of MKP-1 in airway inflammation
Mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1) is a protein with anti-inflammatory properties and the archetypal member of the dual-specificity phosphatases (DUSPs) family that have emerged over the past decade as playing an instrumental role in the regulation of airway inflammation. Not only does MKP-1 serve a critical role as a negative feedback effector, controlling the extent and duration of pro-inflammatory MAPK signalling in airway cells, upregulation of this endogenous phosphatase has also emerged as being one of the key cellular mechanism responsible for the beneficial actions of clinically-used respiratory medicines, including beta(2)-agonists, phosphodiesterase inhibitors and corticosteroids. Herein, we review the role and regulation of MKP-1 in the context of airway inflammation. We initially outline the structure and biochemistry of MKP-1 and summarise the multi-layered molecular mechanisms responsible for MKP-1 production more generally. We then focus in on some of the key in vitro studies in cell types relevant to airway disease that explain how MKP-1 can be regulated in airway inflammation at the transcriptional, post-translation and post-translational level. And finally, we address some of the potential challenges with MKP-1 upregulation that need to be explored further to fully exploit the potential of MKP-1 to repress airway inflammation in chronic respiratory disease
"The Chartering"
129 σ.Με τη διπλωματική αυτή εργασία, πραγματοποιείται εκτενής αναφορά σε βασικές έννοιες του Ναυτικού Δικαίου και πιο συγκεκριμένα στο τομέα των ΝαυλώσεωνIn this dissertation you can find basic definitons of the Shipping Law and more specific in the field of CharteringΙωάννης Κ. Μουτζούρη
Gas transfer under breaking waves: experiments and an improved vorticity-based model
In the present paper a modified vorticity-based model for gas transfer under
breaking waves in the absence of significant wind forcing is presented. A
theoretically valid and practically applicable mathematical expression is
suggested for the assessment of the oxygen transfer coefficient in the area
of wave-breaking. The proposed model is based on the theory of surface
renewal that expresses the oxygen transfer coefficient as a function of both
the wave vorticity and the Reynolds wave number for breaking waves.
Experimental data were collected in wave flumes of various scales: a)
small-scale experiments were carried out using both a sloping beach and a
rubble-mound breakwater in the wave flume of the Laboratory of Harbor Works,
NTUA, Greece; b) large-scale experiments were carried out with a sloping
beach in the wind-wave flume of Delft Hydraulics, the Netherlands, and with
a three-layer rubble mound breakwater in the Schneideberg Wave Flume of the
Franzius Institute, University of Hannover, Germany.
The experimental data acquired from both the small- and large-scale
experiments were in good agreement with the proposed model. Although the
apparent transfer coefficients from the large-scale experiments were lower
than those determined from the small-scale experiments, the actual oxygen
transfer coefficients, as calculated using a discretized form of the
transport equation, are in the same order of magnitude for both the small- and
large-scale experiments. The validity of the proposed model is compared to
experimental results from other researchers.
Although the results are encouraging, additional research is needed, to
incorporate the influence of bubble mediated gas exchange, before these
results are used for an environmental friendly design of harbor works, or for projects
involving waste disposal at sea
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