4,437 research outputs found
Feasibility study of a swept frequency electromagnetic probe (SWEEP) using inductive coupling for the determination of subsurface conductivity of the earth and water prospecting in arid regions
Techniques developed for electromagnetic probing of the lunar interior, and techniques developed for the generation of high power audio frequencies were combined to make practical a magnetic inductive coupling system for the rapid measurement of ground conductivity profiles which are helpful when prospecting for the presence and quality of subsurface water. A system which involves the measurement of the direction, intensity, and time phase of the magnetic field observed near the surface of the earth at a distance from a horizontal coil energized so as to create a field that penetrates the earth was designed and studied to deduce the conductivity and stratification of the subsurface. Theoretical studies and a rudimentary experiment in an arid region showed that the approach is conceptually valid and that this geophysical prospecting technique can be developed for the economical exploration of subterranean water resources
Fixed parameter tractability of crossing minimization of almost-trees
We investigate exact crossing minimization for graphs that differ from trees
by a small number of additional edges, for several variants of the crossing
minimization problem. In particular, we provide fixed parameter tractable
algorithms for the 1-page book crossing number, the 2-page book crossing
number, and the minimum number of crossed edges in 1-page and 2-page book
drawings.Comment: Graph Drawing 201
Criminal neighbourhoods: does the density of prior offenders encourage others to commit crime?
Using crime data over a period of a decade for Glasgow, this paper explores whether the
density of prior offenders in a neighbourhoods has an influence on the propensity of others to
(re)commence offending. The study shows that the number of ânewly activeâ offenders in a
neighbourhood in the current quarter is positively associated with the density of prior
offenders for both violent and property crime from the previous two years. In the case of
ânewly activeâ property offenders, the relationship with active prior offenders is only
apparent when prior offender counts exceed the median. The paper postulates that intraneighbourhood
social mechanisms may be at work to create these effects. The results suggest
that policies which concentrate offenders in particular neighbourhoods may increase the
number of ânewly activeâ offenders, and point to evidence of a threshold at which these
effects take place
Recollection on the Witness Stand
The art of witness interrogation is difficult where the witness on the stand is unable to narrate the event which he has observed because of some present defect in his recollection. In such case there are the following possibilities: A. The impressions once made upon the mind of the witness may be revived by some means. This is present recollection revived . B. If a record has been made of the witness\u27 impressions, such record may come in as evidence if certain requirements be met. This is past recollection recorded . The purpose of this comment is to collect the Washington cases involving these situations and to indicate whether or not our court follows the usual rules, analyzing those cases which have departed therefrom which special regard to some recent decisions which seem out of line. Reference will also be made to illustrative\u27cases from the Ninth Circuit Court of Appeals as indicative of the rules followed by the Federal Court for this circuit
Optical and X-ray Variability in The Least Luminous AGN, NGC4395
We report the detection of optical and X-ray variability in the least
luminous known Seyfert galaxy, NGC4395. The featureless continuum changed by a
factor of 2 in 6 months, which is typical of more luminous AGN. The largest
variation was seen at shorter wavelengths, so that the spectrum becomes
`harder' during higher activity states. In a one week optical broad band
monitoring program, a 20% change was seen between successive nights. In a 1
month period the spectral shape changed from a power law with spectral index
alpha ~0 (characteristic of quasars) to a spectral index alpha ~2 (as observed
in other dwarf AGN). ROSAT HRI and PSPC archive data show a variable X-ray
source coincident with the galactic nucleus. A change in X-ray flux by a factor
\~2 in 15 days has been observed. When compared with more luminous AGN, NGC4395
appears to be very X-ray quiet. The hardness ratio obtained from the PSPC data
suggests that the spectrum could be absorbed. We also report the discovery of
weak CaIIK absorption, suggesting the presence of a young stellar cluster
providing of the order of 10% of the blue light. Using HST UV archive data,
together with the optical and X-ray observations, we examine the spectral
energy distribution for NGC4395 and discuss the physical conditions implied by
the nuclear activity under the standard AGN model. The observations can be
explained by either an accreting massive black hole emitting at about 10^(-3)
L_(Edd) or by a single old compact SNR with an age of 50 to 500 yr generated by
a small nuclear starburst.Comment: 19 pages, 9 figures, to appear in MNRA
Problems related to the integration of fault tolerant aircraft electronic systems
Problems related to the design of the hardware for an integrated aircraft electronic system are considered. Taxonomies of concurrent systems are reviewed and a new taxonomy is proposed. An informal methodology intended to identify feasible regions of the taxonomic design space is described. Specific tools are recommended for use in the methodology. Based on the methodology, a preliminary strawman integrated fault tolerant aircraft electronic system is proposed. Next, problems related to the programming and control of inegrated aircraft electronic systems are discussed. Issues of system resource management, including the scheduling and allocation of real time periodic tasks in a multiprocessor environment, are treated in detail. The role of software design in integrated fault tolerant aircraft electronic systems is discussed. Conclusions and recommendations for further work are included
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Ensemble prediction for nowcasting with a convection-permitting model - II: forecast error statistics
A 24-member ensemble of 1-h high-resolution forecasts over the Southern United Kingdom is used to study short-range forecast error statistics. The initial conditions are found from perturbations from an ensemble transform Kalman filter. Forecasts from this system are assumed to lie within the bounds of forecast error of an operational forecast system. Although noisy, this system is capable of producing physically reasonable statistics which are analysed and compared to statistics implied from a variational assimilation system. The variances for temperature errors for instance show structures that reflect convective activity. Some variables, notably potential temperature and specific humidity perturbations, have autocorrelation functions that deviate from 3-D isotropy at the convective-scale (horizontal scales less than 10 km). Other variables, notably the velocity potential for horizontal divergence perturbations, maintain 3-D isotropy at all scales. Geostrophic and hydrostatic balances are studied by examining correlations between terms in the divergence and vertical momentum equations respectively. Both balances are found to decay as the horizontal scale decreases. It is estimated that geostrophic balance becomes less important at scales smaller than 75 km, and hydrostatic balance becomes less important at scales smaller than 35 km, although more work is required to validate these findings. The implications of these results for high-resolution data assimilation are discussed
Progressive impairment of CaV1.1 function in the skeletal muscle of mice expressing a mutant type 1 Cu/Zn superoxide dismutase (G93A) linked to amyotrophic lateral sclerosis
Background: Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disorder that is typically fatal
within 3â5 years of diagnosis. While motoneuron death is the defining characteristic of ALS, the events that
underlie its pathology are not restricted to the nervous system. In this regard, ALS muscle atrophies and weakens
significantly before presentation of neurological symptoms. Since the skeletal muscle L-type Ca2+ channel (CaV1.1) is
a key regulator of both mass and force, we investigated whether CaV1.1 function is impaired in the muscle of two
distinct mouse models carrying an ALS-linked mutation.
Methods: We recorded L-type currents, charge movements, and myoplasmic Ca2+ transients from dissociated flexor
digitorum brevis (FDB) fibers to assess CaV1.1 function in two mouse models expressing a type 1 Cu/Zn superoxide
dismutase mutant (SOD1G93A).
Results: In FDB fibers obtained from âsymptomaticâ global SOD1G93A mice, we observed a substantial reduction of
SR Ca2+ release in response to depolarization relative to fibers harvested from age-matched control mice. L-type
current and charge movement were both reduced by ~40 % in symptomatic SOD1G93A fibers when compared to
control fibers. Ca2+ transients were not significantly reduced in similar experiments performed with FDB fibers obtained
from âearly-symptomaticâ SOD1G93A mice, but L-type current and charge movement were decreased (~30 and ~20 %,
respectively). Reductions in SR Ca2+ release (~35 %), L-type current (~20 %), and charge movement (~15 %) were also
observed in fibers obtained from another model where SOD1G93A expression was restricted to skeletal muscle.
Conclusions: We report reductions in EC coupling, L-type current density, and charge movement in FDB fibers
obtained from symptomatic global SOD1G93A mice. Experiments performed with FDB fibers obtained from
early-symptomatic SOD1G93A and skeletal muscle autonomous MLC/SOD1G93A mice support the idea that events
occurring locally in the skeletal muscle contribute to the impairment of CaV1.1 function in ALS muscle independently
of innervation status
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