206 research outputs found
How explicit are the barriers to failure in safety arguments?
Safety cases embody arguments that demonstrate how safety properties of a system are upheld. Such cases implicitly document the barriers that must exist between hazards and vulnerable components of a system. For safety certification, it is the analysis of these barriers that provide confidence in the safety of the system. The explicit representation of hazard barriers can provide additional insight for the design and evaluation of system safety. They can be identified in a hazard analysis to allow analysts to reflect on particular design choices. Barrier existence in a live system can be mapped to abstract barrier representations to provide both verification of barrier existence and a basis for quantitative measures between the predicted barrier behaviour and performance of the actual barrier. This paper explores the first stage of this process, the binding between explicit mitigation arguments in hazard analysis and the barrier concept. Examples from the domains of computer-assisted detection in mammography and free route airspace feasibility are examined and the implications for system certification are considered
Effects of paylean (ractopamine⋅HCl) on finishing pig growth and variation
A total of 336 pigs were used in a 21-day
trial to determine the effect of Paylean (9.0
g/ton Ractopamine·HCl) on finishing pig
growth and variation. Pigs were allotted based on weight so that all pens had the same
initial weight and degree of variation within
the pen. Pigs fed Paylean had greater ADG and better feed efficiency than control-fed
pigs (P<0.05). However, no differences in
pen coefficient of variation were observed
(P>0.70). The results suggest that adding
Paylean to the diet improves finishing pig
growth performance but does not affect
weight variation within the pen
Phenomenological Determination of the Beauty Meson Decay Parameter and the CP-Violating Angle
We fit the -matrix to all recent data with the following free
parameters: three mixing angles, the CP-violating angle in the Maiani
parametrisation, the top quark mass , and the product f_B{\cal
B}_{\B}^{1/2}, where is the -meson decay parameter and {\cal
B}_{\B} is the bag parameter. Our fits span a contiguous region in the
(f_B{\cal B}_{\B}^{1/2},\ \cos\delta)--plane, limited by 0.117\lsim f_B{\cal
B}_{\B}^{1/2}/{\rm GeV}\lsim 0.231 and --0.95 \lsim \lsim
0.70. The parameters f_B{\cal B}_{\B}^{1/2} and are strongly
positively correlated.Comment: 9 pages + 1 figure available upon request, HU-TFT-94-3
Behaviour of neonicotinoids in contrasting soils
Neonicotinoids are widely used to control insect pests in agriculture. Their presence in the environment can affect the health of non-target insects and aquatic animals. The behaviour of four neonicotinoids, namely imidacloprid, acetamiprid, thiacloprid and thiamethoxam, has been investigated in soils with contrasting characteristics to understand their migration in soil and ecological risk. Among the study neonicotinoids, thiamethoxam and thiacloprid were found to be the least and most sorbed neonicotinoids by all the soils, respectively (up to 186 time greater adsorption of thiacloprid), and their uptake was affected by the content of organic matter in the soil. Leaching studies in columns confirmed that thiamethoxam leached out of the soils readily, pointing out to a relatively high risk of ground water contamination with possible ecological impact when thiamethoxam is used in soils with low organic matter. In soil column studies, the soil with the lowest organic matter presents the greatest residue of neonicotinoids in the sub-surface (≤5 cm). In contrast the soil richer in organic matter presented most of the contamination deeper down in the column; a factor to be considered in the remediation from soil
On the origins of some spectroscopic properties of "purple iron" (the tetraoxoferrate(VI) ion) and its Pourbaix safe-space
In this work, the authors attempt to interpret the visible, infrared and Raman spectra of ferrate(VI) by means of theoretical physical-inorganic chemistry and historical highlights in this field of interest. In addition, the sacrificial decomposition of ferrate(VI) during water treatment will also be discussed together with a brief mention of how Rayleigh scattering caused by the decomposition of FeVIO42− may render absorbance readings erroneous. This work is not a compendium of all the instrumental methods of analysis which have been deployed to identify ferrate(VI) or to study its plethora of reactions, but mention will be made of the relevant techniques (e.g., Mössbauer Spectroscopy amongst others) which support and advance this overall discourse at appropriate junctures, without undue elaboration on the foundational physics of these techniques
Measuring Black Hole Spin in OJ287
We model the binary black hole system OJ287 as a spinning primary and a
non-spinning secondary. It is assumed that the primary has an accretion disk
which is impacted by the secondary at specific times. These times are
identified as major outbursts in the light curve of OJ287. This identification
allows an exact solution of the orbit, with very tight error limits. Nine
outbursts from both the historical photographic records as well as from recent
photometric measurements have been used as fixed points of the solution: 1913,
1947, 1957, 1973, 1983, 1984, 1995, 2005 and 2007 outbursts. This allows the
determination of eight parameters of the orbit. Most interesting of these are
the primary mass of , the secondary mass , major axis precession rate per period, and the
eccentricity of the orbit 0.70. The dimensionless spin parameter is
(1 sigma). The last parameter will be more tightly
constrained in 2015 when the next outburst is due. The outburst should begin on
15 December 2015 if the spin value is in the middle of this range, on 3 January
2016 if the spin is 0.25, and on 26 November 2015 if the spin is 0.31. We have
also tested the possibility that the quadrupole term in the Post Newtonian
equations of motion does not exactly follow Einstein's theory: a parameter
is introduced as one of the 8 parameters. Its value is within 30% (1 sigma) of
the Einstein's value . This supports the of black
holes within the achievable precision. We have also measured the loss of
orbital energy due to gravitational waves. The loss rate is found to agree with
Einstein's value with the accuracy of 2% (1 sigma).Comment: 12 pages, 4 figures, IAU26
Circular orbits of corotating binary black holes: comparison between analytical and numerical results
We compare recent numerical results, obtained within a ``helical Killing
vector'' (HKV) approach, on circular orbits of corotating binary black holes to
the analytical predictions made by the effective one body (EOB) method (which
has been recently extended to the case of spinning bodies). On the scale of the
differences between the results obtained by different numerical methods, we
find good agreement between numerical data and analytical predictions for
several invariant functions describing the dynamical properties of circular
orbits. This agreement is robust against the post-Newtonian accuracy used for
the analytical estimates, as well as under choices of resummation method for
the EOB ``effective potential'', and gets better as one uses a higher
post-Newtonian accuracy. These findings open the way to a significant
``merging'' of analytical and numerical methods, i.e. to matching an EOB-based
analytical description of the (early and late) inspiral, up to the beginning of
the plunge, to a numerical description of the plunge and merger. We illustrate
also the ``flexibility'' of the EOB approach, i.e. the possibility of
determining some ``best fit'' values for the analytical parameters by
comparison with numerical data.Comment: Minor revisions, accepted for publication in Phys. Rev. D, 19 pages,
6 figure
Phenomenology of the Lense-Thirring effect in the Solar System
Recent years have seen increasing efforts to directly measure some aspects of
the general relativistic gravitomagnetic interaction in several astronomical
scenarios in the solar system. After briefly overviewing the concept of
gravitomagnetism from a theoretical point of view, we review the performed or
proposed attempts to detect the Lense-Thirring effect affecting the orbital
motions of natural and artificial bodies in the gravitational fields of the
Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of
the impact of several sources of systematic uncertainties of dynamical origin
to realistically elucidate the present and future perspectives in directly
measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in
Astrophysics and Space Science (ApSS). Some uncited references in the text
now correctly quoted. One reference added. A footnote adde
Quantification of neonicotinoid pesticides in six cultivable fish species from the River Owena in Nigeria and a template for food safety assessment
The Owena River Basin in Nigeria is an area of agricultural importance for the production of cocoa. To optimise crop yield, the cocoa trees require spraying with neonicotinoid insecticides (Imidacloprid, Thiacloprid Acetamiprid and Thiamethoxam). It is proposed that rainwater runoff from the treated area may pollute the Owena River and that these pesticides may thereby enter the human food chain via six species of fish (Clarias gariepinus, Clarias anguillaris, Sarotherodon galilaeus, Parachanna obscura, Oreochromis niloticus and Gymnarchus niloticus) which are
cultured in the river mostly for local consumption. This work aims to establish a working method to quantify the likely levels of the insecticides in the six species of fish, firstly by undertaking a
laboratory-based study employing the QuEChERS method to extract the four neonicotinoids from fish purchased in marketplace in the UK, spiked with known quantities of the pesticide and using
liquid chromatography coupled with tandem mass spectrometry (LC-MS-MS) as the detection method; secondly, by using these samples to optimise the detection method for very low levels of
pesticides, then applying the optimised techniques to the analysis of three of each six species of fish taken from the Owena River. A significant benefit of this combined technique is that only small
samples of fish are required. Success with this part of the study showed that very low concentrations of the insecticides could be detected in fish muscle. The third aim is to apply a simple quantitative risk assessment model using the data sets obtained, together with information about daily diet, human body weight and recommended safety limits of pesticides in food to illustrate how human health may be affected by the consumption of these fish. The multiple determinations of neonicotinoids in edible fishes in Nigeria are pioneer research and fill a gap in addressing the relationship between waterborne pesticides and food quality in the country. Fundamentally, this work is an exercise to demonstrate the applicability of the aforementioned instrumental method of analysis to fish muscle, which requires only a small sample size of fish; a large number of fish is not required for a proof of concept, in this case. Although not a monitoring programme for the whole Owena River Basin ecosystem per se, this work successfully demonstrates the technical feasibility of a system of chemical analysis and establishes the foundation for ecological surveys in the immediate future. Parameters involving exposures to xenobiotics in ecotoxicological modelling can now be expressed in terms of both mass and molar concentrations of a chemical in animal tissues if so desired
- …