1THz-bandwidth polarization-diverse optical phase conjugation of 10x114Gb/s DP-QPSK WDM signals

Polarization diverse optical phase conjugation of a 1THz spectral-band 1.14Tb/s DP-QPSK WDM multiplex is demonstrated for the first time, showing a worst case Q2 penalty of 0.9dB over all conjugate wavelengths, polarizations and OSNR

SOFIA/EXES Observations of Water Absorption in the Protostar AFGL 2591 at High Spectral Resolution

We present high spectral resolution (~3 km/s) observations of the nu_2 ro-vibrational band of H2O in the 6.086--6.135 micron range toward the massive protostar AFGL 2591 using the Echelon-Cross-Echelle Spectrograph (EXES) on the Stratospheric Observatory for Infrared Astronomy (SOFIA). Ten absorption features are detected in total, with seven caused by transitions in the nu_2 band of H2O, two by transitions in the first vibrationally excited nu_2 band of H2O, and one by a transition in the nu_2 band of H2{18}O. Among the detected transitions is the nu_2 1(1,1)--0(0,0) line which probes the lowest lying rotational level of para-H2O. The stronger transitions appear to be optically thick, but reach maximum absorption at a depth of about 25%, suggesting that the background source is only partially covered by the absorbing gas, or that the absorption arises within the 6 micron emitting photosphere. Assuming a covering fraction of 25%, the H2O column density and rotational temperature that best fit the observed absorption lines are N(H2O)=(1.3+-0.3)*10^{19} cm^{-2} and T=640+-80 K.Comment: 6 pages, 3 figures, 1 table, accepted for publication in ApJ

Elemental concentrations in the seed of mutants and natural variants of Arabidopsis thaliana grown under varying soil conditions

Peer reviewedPublisher PD

Fabrication of highly efficient grating band-pass filters and their applications in soliton propagation system

We report here fabrication of highly efficient in-fiber grating bandpass filters using the established UV-side- exposure technique. Various combinations of passband/stopband and transmission/rejection of single- and multi-channel filters have been produced in hydrogenated standard telecom, high Ge-doped and B/Ge-codoped fibers. Up to > 60 dB rejection stopbands ranging from -2 nm to 55 nm, and passbands with 0.02 nm - 3 nm linewidths and transmissivity up to > 90% have been achieved with these devices. By concatenating several structures, a bandpass filter has been demonstrated with a combination of a 0.16 nm passband centered in a approximately 35 nm stopband, representing the highest reported finesse of 220 for any multi-nanometer stopband filter. We also report the first application of a grating bandpass filter for suppressing timing jitter in soliton propagation system, enabling transmission of 10 ps solitons over a distance of 2700 km

Doing cold smarter

Cold has been much neglected in the energy debate. Governments are developing strategies and policies to green everything from electricity to transport to heat, but the energy and environmental impacts of cooling have so far been largely ignored. This is a serious oversight, since making things cold is energy intensive and can be highly polluting, and demand for cooling in all its forms is booming worldwide – especially in developing countries. According to one projection, by the end of this century global demand for air conditioning alone could consume the equivalent of half our worldwide electricity generation today – and most of the increase will come in developing markets. The ‘greening’ of cold is clearly an urgent global problem – but it may also offer Britain a massive business opportunity. Cold may have been ignored but is vitally important to many aspects of modern life. An effective cold chain, for example, is essential for tackling problems such as food waste, food security, water conservation and public health. Cooling is also critical for many less obvious but essential functions: data centres couldn’t operate without it, nor for example MRI scanners in medicine or superconductors in power electronics. Cooling also provides modern levels of comfort in hot countries – and can make the difference between some regions being habitable or not. At the same time, vast amounts of cold are wasted – for instance during the regasification of LNG – which could in principle be recycled to satisfy some of this demand and start to reduce the environmental damage caused by cooling. Such a system-level approach – which starts by asking what energy services we need, and what is the least damaging way to provide them, rather than accepting existing practices as a fait accompli – has recently been coined the ‘Cold Economy’. It is clear the Cold Economy could unleash a wide range of innovative clean cold technologies and provide energy resilience, economic growth and environmental benefits, but there is an urgent need to develop a system-level analysis of this problem and the potential solutions to inform both industry and policymakers. The Birmingham Policy Commission: Doing Cold Smarter was convened to start this work

Global chromatin fibre compaction in response to DNA damage

AbstractDNA is protected by packaging it into higher order chromatin fibres, but this can impede nuclear processes like DNA repair. Despite considerable research into the factors required for signalling and repairing DNA damage, it is unclear if there are concomitant changes in global chromatin fibre structure. In human cells DNA double strand break (DSB) formation triggers a signalling cascade resulting in H2AX phosphorylation (γH2AX), the rapid recruitment of chromatin associated proteins and the subsequent repair of damaged sites. KAP1 is a transcriptional corepressor and in HCT116 cells we found that after DSB formation by chemicals or ionising radiation there was a wave of, predominantly ATM dependent, KAP1 phosphorylation. Both KAP1 and phosphorylated KAP1 were readily extracted from cells indicating they do not have a structural role and γH2AX was extracted in soluble chromatin indicating that sites of damage are not attached to an underlying structural matrix. After DSB formation we did not find a concomitant change in the sensitivity of chromatin fibres to micrococcal nuclease digestion. Therefore to directly investigate higher order chromatin fibre structures we used a biophysical sedimentation technique based on sucrose gradient centrifugation to compare the conformation of chromatin fibres isolated from cells before and after DNA DSB formation. After damage we found global chromatin fibre compaction, accompanied by rapid linker histone dephosphorylation, consistent with fibres being more regularly folded or fibre deformation being stabilized by linker histones. We suggest that following DSB formation, although there is localised chromatin unfolding to facilitate repair, the bulk genome becomes rapidly compacted protecting cells from further damage

The social relations of a health walk group: an ethnographic study

It is already well established that regular walks are conducive to health and wellbeing. This paper considers the production of social relations of regular, organized weekly group walks for older people. It is based on an ethnographic study of a Walking for Health group in a rural area of the United Kingdom. Different types of social relations are identified arising from the walk experience. The social relations generated are seen to be shaped by organizational factors that are constitutive of the walks, the resulting culture having implications for the sustainability of the experience. Since there appears to be no single uniting theory linking group walk experiences to the production of social relations at this time, the findings are considered against therapeutic landscape, therapeutic mobility and social capital theorizing. Finally, implications for the continuance of walking schemes for older people and for further research are considered

Exceeding the nonlinear-shannon limit using Raman laser based amplification and optical phase conjugation

We demonstrate that a combination of Raman laser based amplification and optical phase conjugation enables transmission beyond the nonlinear-Shannon limit. We show nonlinear compensation of 7x114Gbit/s DP-QPSK channels, increasing system reach by 30%