3,353 research outputs found
ΔNp63α a key factor of epithelial differentiation controls the activity of YB-1 oncoprotein: potential implications in carcinogenesis
No full textMy thesis unveils a novel protein-protein association involving ΔNp63αand YB-1 and a mechanism through which a factor essential for epithelial development and differentiation can control the activity of an oncoprotein
Yb-doped femtosecond lasers and their frequency doubling
No full textUltralow threshold, compact and highly efficient femtosecond lasers based on Yb³⁺-doped
potassium yttrium tungstate (Yb:KYW) and Yb³⁺-doped vanadium yttrium oxide
(Yb:YVO 4 ) have been demonstrated within this PhD-research project. For a continuous
wave unmode-locked Yb:KYW laser a threshold as low as 101 mW was obtained with a
slope efficiency of 74%. By employing a single prism for dispersion control, the laser was
tunable between 1012 nm to 1069 nm. When operated in the mode-locked regime, this
laser produced transform-limited pulses having durations of 210 fs at a central wavelength
of 1044 nm. Stable mode locking was observed for an optimised incident pulse fluence on
the SESAM between 140 μJ/cm²
to 160 μJ/cm²
which was 2-3 times higher than the
designed energy pulse fluence of the SESAM (70 μJ/cm²).
The employment of several combinations of chirped mirror designs for control of
intracavity group velocity dispersion led to excellent results. The threshold for mode
locking was satisfied for a pump power of 255 mW where the slope efficiency was
measured to be 62%. This is the most efficient SESAM-assisted femtosecond laser yet
reported and the highest optical-to-optical efficiency of 37% is exceptional. Transform-limited pulses with durations as short as 90 fs were produced in a spectral region centred
on 1052 nm. The success of this research thus represents a good foundation on which to
design and build more compact configurations that will incorporate just one chirped mirror
for dispersion compensation.
A relatively high nonlinear refractive index, n₂ , of 15 x 10⁻¹⁶ cm²/W was measured
in Yb:YVO₄ and this affords particular potential for this candidate material in Kerr-lens
mode locking. In fact, for operation in the femtosecond domain, the threshold power was
190 mW with a slope efficiency of 26% and near-transform-limited pulses as short as 61fs were generated at a centre wavelength of 1050 nm. The main objectives in developing
this type of laser relate to a demonstration of high peak power operation in thin disc laser
configurations.
The deployment of a diode-pumped Yb:KYW femtosecond laser as a pump source
for frequency doubling in a periodically-poled LiTaO₃ crystal was realised. The maximum
realized output power of 150 mW corresponded to an impressive second harmonic
conversion efficiency of 43%. 225-fs duration green pulses (centred at 525 nm) were
generated under the condition of strong focusing in the nonlinear crystal
Towards the tumble resistant microlight
No full textThe tumble mode is a pitching departure from controlled flight which leads to a pitch autorotation that is generally unrecoverable – resulting in vertical ground impact, usually preceded by in-flight breakup (the mechanism for which, surprisingly, can sometimes prevent loss of life). This was identified in work led by the British Microlight Aircraft Association beginning in 1997 as a response to a number of fatal accidents in Rogallo winged microlight aeroplanes, although the tumble is also known to occur to hang-gliders. This paper explains how this class of aeroplane is controlled, and how it has been found that they can enter the tumble mode. The mechanism by which the tumble can be entered is described. This has led to work showing how flight testing can be used to establish and demonstrate resistance to tumble entry – particularly important with increasing number of very high performance flexwings. These flight tests will be explained, together with the significance of the results. Recent accident investigation work has also shown a new mechanism of tumble entry, through partial failure of the A-frame structure and the pitch-trimmer mechanism. Also described is a possible relevance to well known historical accidents to flying wing aeroplanes– specifically the YB-49 and dH-108, and discovered data on the characteristics of the BKB-1flying wing glider; are also described
Raman amplification and pulsed lasing in cladding-pumped germanosilicate fiber
No full textWe report for the first time Raman amplification in a cladding-pumped fiber. The double-clad germanosilicate fiber was pumped by a Q-switched Er-Yb co-doped fiber laser at 1570 nm. The power conversion efficiency was up to 36%, with a slope of 64%
Yb-Based Nanoparticles with the Same Excitation and Emission Wavelength for Sensitive in Vivo Biodetection
No full textNear-infrared
luminescent emission has been widely used as a signal for biological detection with its
high spatial resolution and fast response. Rare-earthdoped nanoparticle–dye
composites have diverse advantages of a wide operation wavelength
and remarkable light stability, while the application is limited by
the low luminescence quantum yield of rare-earth nanoparticles. Hence,
in this work, we use a singly Yb doped nanoparticle that has strong
luminescence emission at 975 nm under excitation at the same wavelength
as an energy donor to construct the detection system. An inner filter
pair, composed of core–shell nanophosphor NaYF4/20%Yb@NaYF4 (1:2) nanocrystals (csYb) as a luminescent beacon and ClO–-responsive cyanine dye Cy890 as a filtering agent,
was designed as a model. With a time-gated detection mode, the nanocomposites
realize the detection limit at 0.55 ppb as demonstrated in a ClO– detection trial. The csYb&Cy890 nanocomposites
can also monitor ClO– by luminescence signals in
both living cells and mice models
Fabrication of Au/PEDOT stacked electrodes for organic thin film transistors by imprinting technology
No full text[[abstract]]In this work, the Au/PEDOT stacked source/drain electrodes of OTFTs were fabricated by combining the micro-contact inking and reversal imprinting. The PEDOT was inked on the mold by the micro-contact process and the Au/PEDOT stacked layer was transferred on pentacene by imprinting technology. The threshold voltage, and on-off ratio, carrier mobility, and source/drain contact resistance of organic TFTs were all improved by the proposed process. (C) 2010 Elsevier Ltd. All rights reserved.[[note]]SC
Fabrication of organic thin film transistors with the nano-groove al gate electrodes by using UV nano imprint technology
No full text[[abstract]]In this work, the OTFTs with the nano-groove Al gate electrodes were fabricated by UV nano imprint technology. The flexible UV transparent ETFE mold was fabricated by the hot-embossing with the HSQ master mold. The nano-groove Al gate electrodes with the line/space about similar to 95/355 nm were fabricated successfully. The performance of OTFTs was improved and the proposed process will be suitable for the future roll-to-roll process of the flexible electronics. (C) 2012 Elsevier B.V. All rights reserved.[[note]]SC
Calculation of surface tension using CALPHAD software as a Zero Phase Fraction line of ""surface"" phase
No full textA new approach for calculation of surface tension of solutions is presented. Based on the proposal of Butler (Proc. R. Soc. Lond. A: Math. Phys. Eng. Sci. 135 (1932) 348 [3]), a surface phase was assumed to be in equilibrium with a corresponding bulk phase. Following the proposal of Pajarre et al. (Calphad 30 (2006) 196 [71), a surface area element (X) was introduced, only in the surface phase. The surface tension can be obtained by Constrained Gibbs Energy Minimization (CGEM) under a constraint of constant surface. The equilibrium chemical potential of the surface element, X, was interpreted to be proportional to the surface tension. According to the present author (Calphad 50 (2015) 23 [9]), the surface tension calculation by the CGEM can be interpreted as if the bulk phase and the surface phase are in equilibrium with each other, and the chemical potential of the area element is obtained as a result of the equilibrium. It was shown that a geometrical relationship among the molar Gibbs energies of the bulk phase and the surface phase, the surface tension, and the surface concentration is found. In the present study, further improvement was made in such a way that the chemical potential of the area element can be simply obtained by combining the CGEM with Zero Phase Fraction (ZPF) line in Type II phase diagram, where the chemical potential of the area element is used as an axis variable. Such phase diagram can be easily calculated using conventional CALPHAD softwares. The proposed approach was validated for a number of binary and ternary systems. (C) 2015 Elsevier Ltd. All rights reserved.1122sciescopu
- …
