12,692 research outputs found
Flotation as a Method of Separating Shot Particles from Mineral Wool Fibers
The object of this thesis is to determine whether flotation will succeed as a method of separating shot from mineral wool fibers. The methods of manufacturing mineral wool are explored in detail. Also the three types of mineral wool (dark wool, white wool and ceramic fiber) are examined for properties. Various current and possible methods of separation are explored and discussed. The fibers were floated in a Voith flotation cell, and the floated fibers, as well as some of the virgin fibers, were classified in a Clark classifier. This was done in order to attempt to determine the effect of the process on the fiber length of the fibers. It was not possible to determine much about the feasibility of the process, but the process does work for separating shot from fibers. The thesis also lays down a lot of groundwork from which further work may be suggested
Assessment of the environmental toxicity and carcinogenicity of tungsten-based shot.
The toxicity of elemental tungsten released from discharged shot was assessed against previous studies that established a 1% toxic threshold for soil organisms. Extremely heavy theoretical shot loadings of 69,000 shot/ha were used to generate estimated environmental concentrations (EEC) for two brands of tungsten-based shot containing 51% and 95% tungsten. The corresponding tungsten EEC values were 6.5–13.5 mg W/kg soil, far below the 1% toxic threshold. The same shot loading in water produced tungsten EEC values of 2.1–4.4 mg W/L, levels that are not toxic under experimental conditions. Pure tungsten has not been shown to exhibit carcinogenic properties when ingested or embedded in animal tissues, but nickel, with which it is often alloyed, has known carcinogenicity. Given the large number of waterfowl that carry shot embedded in their body, it is advisable to screen lead shot substitutes for their carcinogenic potential through intra-muscular implantation
ADAS analysis of the differential emission measure structure of the inner solar corona. II. A study of the `quiet Sun' inhomogeneities from SOHO CDS-NIS spectra
We present a study of the differential emission measure (DEM) of a `quiet
Sun' area observed in the extreme ultraviolet at normal incidence by the
Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft. The data used for
this work were taken using the NISAT_S observing sequence. This takes the full
wavelength ranges from both the NIS channels (308-381 Angtr. and 513-633
Angst.) with the 2 arcsec by 240 arcsec slit, which is the narrowest slit
available, yielding the best spectral resolution. In this work we contrast the
DEM from subregions of 2 by 80 arcsec with that obtained from the mean
spectrum of the whole raster (20 by 240 arcsec). We find that the DEM
maintains essentially the same shape in the subregions, differing by a constant
factor between 0.5 and 2 from the mean DEM, except in areas were the electron
density is below cm and downflow velocities of 50 km/s
are found in the transition region. Such areas are likely to contain plasma
departing from ionisation equilibrium, violating the basic assumptions
underlying the DEM method. The comparison between lines of Li-like and Be-like
ions may provide further evidence of departure from ionisation equilibrium. We
find also that line intensities tend to be lower where velocities of the order
of 30 km/s or higher are measured in transition region lines. The DEM analysis
is also exploited to improve the line identification performed by Brooks et al
(1999) and to investigate possible elemental abundance variations from region
to region. We find that the plasma has composition close to photospheric in all
the subregions examined.Comment: 18 pages, 9 figures, 7 tables. Table 5 is available only online. A
copy of Table 5 can be found at http://webusers.ct.astro.it/acl/table5.dat.
The ReadMe file is at http://webusers.ct.astro.it/acl/ReadMe. Accepted by
Astronomy and Astrophysic
Distinct Cortical Circuit Mechanisms for Complex Forelimb Movement and Motor Map Topography
SummaryCortical motor maps are the basis of voluntary movement, but they have proven difficult to understand in the context of their underlying neuronal circuits. We applied light-based motor mapping of Channelrhodopsin-2 mice to reveal a functional subdivision of the forelimb motor cortex based on the direction of movement evoked by brief (10 ms) pulses. Prolonged trains of electrical or optogenetic stimulation (100–500 ms) targeted to anterior or posterior subregions of motor cortex evoked reproducible complex movements of the forelimb to distinct positions in space. Blocking excitatory cortical synaptic transmission did not abolish basic motor map topography, but the site-specific expression of complex movements was lost. Our data suggest that the topography of movement maps arises from their segregated output projections, whereas complex movements evoked by prolonged stimulation require intracortical synaptic transmission
The Effect of Added Weight on Foot Anthropometry in Pregnant Women and Controls
Please refer to the pdf version of the abstract located adjacent to the title
Investigating whether adverse prenatal and perinatal events are associated with non-clinical psychotic symptoms at age 12 years in the ALSPAC birth cohort
Background. Non-clinical psychosis-like symptoms (PLIKS) occur in about 15% of the population. It is not clear
whether adverse events during early development alter the risk of developing PLIKS. We aimed to examine whether
maternal infection, diabetes or pre-eclampsia during pregnancy, gestational age, perinatal cardiopulmonary resuscitation
or 5-min Apgar score were associated with development of psychotic symptoms during early adolescence.
Method. A longitudinal study of 6356 12-year-old adolescents who completed a semi-structured interview for
psychotic symptoms in the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. Prenatal and
perinatal data were obtained from obstetric records and maternal questionnaires completed during pregnancy.
Results. The presence of definite psychotic symptoms was associated with maternal infection during pregnancy
[adjusted odds ratio (OR) 1.44, 95% confidence interval (CI) 1.11–1.86, p=0.006], maternal diabetes (adjusted OR 3.43,
95% CI 1.14–10.36, p=0.029), need for resuscitation (adjusted OR 1.50, 95% CI 0.97–2.31, p=0.065) and 5-min Apgar
score (adjusted OR per unit decrease 1.30, 95% CI 1.12–1.50, p<0.001). None of these associations were mediated by
childhood IQ score. Most associations persisted, but were less strong, when including suspected symptoms as part of
the outcome. There was no association between PLIKS and gestational age or pre-eclampsia.
Conclusions. Adverse events during early development may lead to an increased risk of developing PLIKS.
Although the status of PLIKS in relation to clinical disorders such as schizophrenia is not clear, the similarity
between these results and findings reported for schizophrenia indicates that future studies of PLIKS may help us to
understand how psychotic experiences and clinical disorders develop throughout the life-course
Stochastic Domain Wall-Magnetic Tunnel Junction Artificial Neurons for Noise-Resilient Spiking Neural Networks
The spatiotemporal nature of neuronal behavior in spiking neural networks
(SNNs) make SNNs promising for edge applications that require high energy
efficiency. To realize SNNs in hardware, spintronic neuron implementations can
bring advantages of scalability and energy efficiency. Domain wall (DW) based
magnetic tunnel junction (MTJ) devices are well suited for probabilistic neural
networks given their intrinsic integrate-and-fire behavior with tunable
stochasticity. Here, we present a scaled DW-MTJ neuron with voltage-dependent
firing probability. The measured behavior was used to simulate a SNN that
attains accuracy during learning compared to an equivalent, but more
complicated, multi-weight (MW) DW-MTJ device. The validation accuracy during
training was also shown to be comparable to an ideal leaky integrate and fire
(LIF) device. However, during inference, the binary DW-MTJ neuron outperformed
the other devices after gaussian noise was introduced to the Fashion-MNIST
classification task. This work shows that DW-MTJ devices can be used to
construct noise-resilient networks suitable for neuromorphic computing on the
edge.Comment: 10 pages, 4 figure
Pressure-energy correlations in liquids. V. Isomorphs in generalized Lennard-Jones systems
This series of papers is devoted to identifying and explaining the properties
of strongly correlating liquids, i.e., liquids with more than 90% correlation
between their virial W and potential energy U fluctuations in the NVT ensemble.
Paper IV [N. Gnan et al., J. Chem. Phys. v131, 234504 (2009)] showed that
strongly correlating liquids have "isomorphs", which are curves in the phase
diagram along which structure, dynamics, and some thermodynamic properties are
invariant in reduced units. In the present paper, using the fact that
reduced-unit radial distribution functions are isomorph invariant, we derive an
expression for the shapes of isomorphs in the WU phase diagram of generalized
Lennard-Jones systems of one or more types of particles. The isomorph shape
depends only on the Lennard-Jones exponents; thus all isomorphs of standard
Lennard-Jones systems (with exponents 12 and 6) can be scaled onto to a single
curve. Two applications are given. One is testing the prediction that the
solid-liquid coexistence curve follows an isomorph by comparing to recent
simulations by Ahmed and Sadus [J. Chem. Phys. v131, 174504 (2009)]. Excellent
agreement is found on the liquid side of the coexistence, whereas the agreement
is worse on the solid side. A second application is the derivation of an
approximate equation of state for generalized Lennard-Jones systems by
combining the isomorph theory with the Rosenfeld-Tarazona expression for the
temperature dependence of potential energy on isochores. It is shown that the
new equation of state agrees well with simulations.Comment: 12 pages, 14 figures, Section on solid-liquid coexistence expande
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