15,165 research outputs found
Environment Agency review of methods for determining organic waste biodegradability and municipal waste diversion.
The Environment Agency is required to regulate
the landfilling of biodegradable organic wastes
and their diversion from landfilling. Simple, cost
effective, reliable and widely applicable methods
for the measurement of organic waste and its
biodegradability are needed for this activity. A
review of such methods was carried out in order to
select promising methods for an experimental
screening exercise. The review considered both
biological and non-biological methods including
simple methods that may provide a surrogate
measurement of waste biodegradability instead of
the time-consuming biological methods. The
biological methods selected for further evaluation
were the aerobic specific oxygen uptake rate
(SOUR) and dynamic respiration index (DRI)
tests, and the anaerobic biochemical methane
potential (BMP) test.
The non-biological methods selected for further
evaluation were dry matter (DM), loss on ignition
(LOI), total organic carbon (TOC), total nitrogen
(TN), water extractable dissolved organic carbon
(DOC), BOD and COD, the lignin and cellulose
content and the cellulase hydrolysis method.
These tests are being evaluated on a wide variety
of typical organic materials that might be found in
municipal solid waste (MSW) such as newspaper
corrugated paper, compost, kitchen waste
(vegetable and animal), garden wastes (grass and
twigs), nappies, cotton and wool textiles
The making of a woman's town: household and gender in Dundee 1890 to 1940
From the introduction: Women in Dundee's history are often portrayed as different from women who lived elsewhere. Their ability to survive difficulty has been praised by some historians (see, for example, Gordon, 1991), while other historians have gone so far as to claim that they displayed masculine characteristics (see, for example, Walker, 1979). Oral evidence suggests that Dundee women seem to have had a much more developed level of gender and class consciousness than other women achieved. Some of these women expressed and used this understanding in their own working lives. For example, Bella Keyzer was a woman who fought, in the 1960s, to return to her wartime trade as a welder. In the late 1980s, Bella appeared in a number of television oral histories, in which she was often presented as a feminist, particularly since her critique of gender definitions of skill and wage rates fitted radical feminism so closely. Like others in Dundee, however she was keen to emphasise that her ideology was recognised as arising out of practical experiences, rather than from theoretical musings
A model of ant route navigation driven by scene familiarity
In this paper we propose a model of visually guided route navigation in ants that captures the known properties of real behaviour whilst retaining mechanistic simplicity and thus biological plausibility. For an ant, the coupling of movement and viewing direction means that a familiar view specifies a familiar direction of movement. Since the views experienced along a habitual route will be more familiar, route navigation can be re-cast as a search for familiar views. This search can be performed with a simple scanning routine, a behaviour that ants have been observed to perform. We test this proposed route navigation strategy in simulation, by learning a series of routes through visually cluttered environments consisting of objects that are only distinguishable as silhouettes against the sky. In the first instance we determine view familiarity by exhaustive comparison with the set of views experienced during training. In further experiments we train an artificial neural network to perform familiarity discrimination using the training views. Our results indicate that, not only is the approach successful, but also that the routes that are learnt show many of the characteristics of the routes of desert ants. As such, we believe the model represents the only detailed and complete model of insect route guidance to date. What is more, the model provides a general demonstration that visually guided routes can be produced with parsimonious mechanisms that do not specify when or what to learn, nor separate routes into sequences of waypoints
Computational modelling of the regulation of Insulin signalling by oxidative stress
BACKGROUND: Existing models of insulin signalling focus on short term dynamics, rather than the longer term dynamics necessary to understand many physiologically relevant behaviours. We have developed a model of insulin signalling in rodent adipocytes that includes both transcriptional feedback through the Forkhead box type O (FOXO) transcription factor, and interaction with oxidative stress, in addition to the core pathway. In the model Reactive Oxygen Species are both generated endogenously and can be applied externally. They regulate signalling though inhibition of phosphatases and induction of the activity of Stress Activated Protein Kinases, which themselves modulate feedbacks to insulin signalling and FOXO. RESULTS: Insulin and oxidative stress combined produce a lower degree of activation of insulin signalling than insulin alone. Fasting (nutrient withdrawal) and weak oxidative stress upregulate antioxidant defences while stronger oxidative stress leads to a short term activation of insulin signalling but if prolonged can have other effects including degradation of the insulin receptor substrate (IRS1) and FOXO. At high insulin the protective effect of moderate oxidative stress may disappear. CONCLUSION: Our model is consistent with a wide range of experimental data, some of which is difficult to explain. Oxidative stress can have effects that are both up- and down-regulatory on insulin signalling. Our model therefore shows the complexity of the interaction between the two pathways and highlights the need for such integrated computational models to give insight into the dysregulation of insulin signalling along with more data at the individual level. A complete SBML model file can be downloaded from BIOMODELS (https://www.ebi.ac.uk/biomodels-main) with unique identifier MODEL1212210000. Other files and scripts are available as additional files with this journal article and can be downloaded from https://github.com/graham1034/Smith2012_insulin_signalling
Mode Switching and Subpulse Drifting in PSR B0826-34
We present high-quality observations of PSR B0826-34 at 1374 MHz. The
emission from this pulsar exhibits strong bursts of pulses followed by long
periods of `null' pulses. When it is strong, the radiation extends through the
whole pulse period. We show for the first time that there is weak emission
during the `null' phases, which should therefore be considered to be a
different mode rather than a null. During this weak mode the profile is similar
to that observed in the strong mode at low radio frequency. Using a
phase-tracking method, the pattern of drifting subpulses during the strong mode
is seen to be coherent across the whole profile. The drift rate is variable and
includes positive and negative values. Thirteen subpulse bands have been
directly observed, covering the whole longitude range. The subpulses and their
spacings () are wider in one half of the profile than those in the other
half. This difference, and the variation of observed within the two
regions, can be accounted for if the magnetic pole is inclined to the rotation
axis by about 0.5 degrees. These two regions appear to represent radiation from
outer and inner cones. The intensity modulation of subpulses in all longitude
ranges is related to the magnitude of the drift rate.Comment: 8 pages, 10 figures. Accepted for publication in MNRA
Unpulsed UBV Optical Emission from the Crab Pulsar
Based on observations of the Crab pulsar using the TRIFFID high speed imaging
photometer in the UBV bands using the Special Astrophysical Observatory's 6m
telescope in the Russian Caucasus, we report the detection of pronounced
emission during the so-called `off' phase of emission. Following de-extinction,
this unpulsed component of emission is shown to be consistent with a power law
with an exponent of alpha = -0.60 +/- 0.37, the uncertainty being dominated by
the error associated with the independent CCD photometry used to reference the
TRIFFID data. This suggests a steeper power law form than that reported
elsewhere in the literature for the total integrated spectrum, which is
essentially flat with alpha ~ 0.1, although the difference in this case is only
significant at the ~ 2 sigma level. Deeper reference integrated and TRIFFID
phase-resolved photometry in these bands in conjunction with further
observations in the UV and R region would constrain this fit further.Comment: 26 pages, 2 figures, uses aasms4.sty, accepted for publication in the
Astrophysical Journa
The state of workplace union reps organisation in Britain today
This article provides a brief evaluation of the state of workplace union reps’ organization in Britain as we approach the second decade of the 2000s. It documents the severe weakening of workplace union organization over the last 25 years, which is reflected in the declining number of reps, reduced bargaining power and the problem of bureaucratization. But it also provides evidence of the continuing resilience, and even combativity in certain areas of employment, of workplace union reps organization, and considers the future potential for a revival of fortunes
Pulsar Jets: Implications for Neutron Star Kicks and Initial Spins
We study implications for the apparent alignment of the spin axes,
proper-motions, and polarization vectors of the Crab and Vela pulsars. The spin
axes are deduced from recent Chandra X-ray Observatory images that reveal jets
and nebular structure having definite symmetry axes. The alignments indicate
these pulsars were born either in isolation or with negligible velocity
contributions from binary motions. We examine the effects of rotation and the
conditions under which spin-kick alignment is produced for various models of
neutron star kicks. If the kick is generated when the neutron star first forms
by asymmetric mass ejection or/and neutrino emission, then the alignment
requires that the protoneutron star possesses an original spin with period
much less than the kick timescale, thus spin-averaging the kick forces.
The kick timescale ranges from 100 ms to 10 s depending on whether the kick is
hydrodynamically driven or neutrino-magnetic field driven. For hydrodynamical
models, spin-kick alignment further requires the rotation period of an
asymmetry pattern at the radius near shock breakout (>100 km) to be much less
than ~100 ms; this is difficult to satisfy unless rotation plays a dynamically
important role in the core collapse and explosion (P_s\lo 1 ms). Aligned kick
and spin vectors are inherent to the slow process of asymmetric electromagnetic
radiation from an off-centered magnetic dipole. We reassess the viability of
this effect, correcting a factor of 4 error in Harrison and Tademaru's
calculation that increases the size of the effect. To produce a kick velocity
of order a few hundred km/s requires that the neutron star be born with an
initial spin close to 1 ms and that spindown due to r-mode driven gravitational
radiation be inefficient compared to standard magnetic braking.Comment: Small changes/additions; final version to be published in ApJ,
Vol.549 (March 10, 2001
Design of a Direct-Detection Wind and Aerosol Lidar for Mars Orbit
The present knowledge of the Mars atmosphere is greatly limited by a lack of global measurements of winds and aerosols. Hence, measurements of height-resolved wind and aerosol profiles are a priority for new Mars orbiting missions. We have designed a direct-detection lidar (MARLI) to provide global measurements of dust, winds and water ice profiles from Mars orbit. From a 400-km polar orbit, the instrument is designed to provide wind and backscatter measurements with a vertical resolution of 2 km and with resolution of 2 in latitude along track. The instrument uses a single-frequency, seeded Nd:YAG laser that emits 4 mJ pulses at 1064 nm at a 250 Hz pulse rate. The receiver utilizes a 50-cm diameter telescope and a double edge Fabry-Prot etalon as a frequency discriminator to measure the Doppler shift of the aerosol-backscatter profiles. The receiver also includes a polarization-sensitive channel to detect the cross-polarized backscatter profiles from water ice. The receiver uses a sensitive 4 4 pixel HgCdTe avalanche photodiode array as a detector for all signals. Here we describe the measurement concept, instrument design, and calculate its performance for several cases of Mars atmospheric conditions. The calculations show that under a range of atmospheric conditions MARLI is capable of measuring wind speed profiles with random error of 24 m/s within the first three scale heights, enabling vertically resolved mapping of transport processes in this important region of the atmosphere
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