83 research outputs found
Eutrophication and restoration in temperate lakes
Eutrophication affects many lakes and reservoirs worldwide. It is caused by excessive amounts of nutrients entering waterbodies from their catchments, mainly due to human activity. The main sources of these nutrients are discharges from industry and wastewater treatment systems, and agricultural runoff. The water quality problems caused by eutrophication, such as harmful algal blooms, affect the sustainable use of lakes for agriculture, fisheries, recreation, tourism and water supply. They also degrade habitat quality and threaten biodiversity. A range of methods for improving lake water quality are explored, including catchment management and in-lake restoration measures. The potential impacts of these on lake biodiversity are explored, including species interactions and ecosystem feedbacks that may confound the recovery process. A particular challenge is the fact that achieving sustainable recovery may take many years, mainly due to the impact of legacy pollution problems. This must be taken into account when planning and implementing eutrophication management options, because these slow recovery periods can exceed the timescales that people are willing to accept. While this review focuses on the many well documented studies of restoration and recovery processes in temperate lakes, it also highlights the need for similar research on tropical and sub-tropical systems
Coarse-Grained Online Monitoring of BTI Aging by Reusing Power-Gating Infrastructure
In this paper, we present a novel coarse-grained technique for monitoring online the bias temperature instability (BTI) aging of circuits by exploiting their power gating infrastructure. The proposed technique relies on monitoring the discharge time of the virtual-power-network during standby operations, the value of which depends on the threshold voltage of the CMOS devices in a power-gated design (PGD). It does not require any distributed sensors, because the virtual-power-network is already distributed in a PGD. It consists of a hardware block for measuring the discharge time concurrently with normal standby operations and a processing block for estimating the BTI aging status of the PGD according to collected measurements. Through SPICE simulation, we demonstrate that the BTI aging estimation error of the proposed technique is less than 1% and 6.2% for PGDs with static operating frequency and dynamic voltage and frequency scaling, respectively. Its area cost is also found negligible. The power gating minimum idle time (MIT) cost induced by the energy consumed for monitoring the discharge time is evaluated on two scalar machine models using either x86 or ARM instruction sets. It is found less than 1.3× and 1.45× the original power gating MIT, respectively. We validate the proposed technique through accelerated aging experiments conducted with five actual chips that contain an ARM cortex M0 processor, manufactured with a 65 nm CMOS technology
OC-0071: Analysis and reporting patterns of failure in the era of IMRT: head and neck cancer applications
Association between CMD signs and symptoms, oral parafunctions, race and sex, in 4–6-year-old African-American and Caucasian children
The associations between oral parafunctions, signs and symptoms of craniomandibular disorders (CMD), race, and sex were analysed in recordings from 203 4-6-year-old African-American and Caucasian children. Significant correlations were found between bruxism, nail biting, thumb sucking and most of the CMD signs and symptoms. There were also significant associations between most of the signs and symptoms and race, while significant association with sex was found only regarding headache, TMJ sounds and chewing pain. Significant associations were found between most CMD signs and TMJ sounds supporting the view that joint sound recordings have diagnostic value. There were also significant associations between the pain variables recorded by questionnaire and those recorded by palpation, which indicates that reliable data can be obtained by interviewing children as young as five. The results of this study support the concept that oral parafunctions have a significant role in the aetiology of CMD. The results also show that race and sex need to be considered when analysing the possible aetiological role of oral parafunctions in CMD. Longitudinal studies, beginning with low age groups are needed to better determine the role of childhood oral parafunctions in CMD aetiology.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75673/1/j.1365-2842.1995.tb00241.x.pd
Dark energy as a mirage
Motivated by the observed cosmic matter distribution, we present the
following conjecture: due to the formation of voids and opaque structures, the
average matter density on the path of the light from the well-observed objects
changes from Omega_M ~ 1 in the homogeneous early universe to Omega_M ~ 0 in
the clumpy late universe, so that the average expansion rate increases along
our line of sight from EdS expansion Ht ~ 2/3 at high redshifts to free
expansion Ht ~ 1 at low redshifts. To calculate the modified observable
distance-redshift relations, we introduce a generalized Dyer-Roeder method that
allows for two crucial physical properties of the universe: inhomogeneities in
the expansion rate and the growth of the nonlinear structures. By treating the
transition redshift to the void-dominated era as a free parameter, we find a
phenomenological fit to the observations from the CMB anisotropy, the position
of the baryon oscillation peak, the magnitude-redshift relations of type Ia
supernovae, the local Hubble flow and the nucleosynthesis, resulting in a
concordant model of the universe with 90% dark matter, 10% baryons, no dark
energy, 15 Gyr as the age of the universe and a natural value for the
transition redshift z_0=0.35. Unlike a large local void, the model respects the
cosmological principle, further offering an explanation for the late onset of
the perceived acceleration as a consequence of the forming nonlinear
structures. Additional tests, such as quantitative predictions for angular
deviations due to an anisotropic void distribution and a theoretical derivation
of the model, can vindicate or falsify the interpretation that light
propagation in voids is responsible for the perceived acceleration.Comment: 33 pages, 2 figs; v2: minor clarifications, results unchanged; v3:
matches the version published in General Relativity and Gravitatio
Magnetic Field Generation in Stars
Enormous progress has been made on observing stellar magnetism in stars from
the main sequence through to compact objects. Recent data have thrown into
sharper relief the vexed question of the origin of stellar magnetic fields,
which remains one of the main unanswered questions in astrophysics. In this
chapter we review recent work in this area of research. In particular, we look
at the fossil field hypothesis which links magnetism in compact stars to
magnetism in main sequence and pre-main sequence stars and we consider why its
feasibility has now been questioned particularly in the context of highly
magnetic white dwarfs. We also review the fossil versus dynamo debate in the
context of neutron stars and the roles played by key physical processes such as
buoyancy, helicity, and superfluid turbulence,in the generation and stability
of neutron star fields.
Independent information on the internal magnetic field of neutron stars will
come from future gravitational wave detections. Thus we maybe at the dawn of a
new era of exciting discoveries in compact star magnetism driven by the opening
of a new, non-electromagnetic observational window.
We also review recent advances in the theory and computation of
magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo
theory. These advances offer insight into the action of stellar dynamos as well
as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field
generation in stars to appear in Space Science Reviews, Springe
Near-infrared template spectra of normal galaxies: k-corrections, galaxy models and stellar populations
We have observed 28 local galaxies in the wavelength range between 1 and 2.4
mic in order to define template spectra of the normal galaxies along the Hubble
sequence. Five galaxies per morphological type were observed in most cases, and
the resulting RMS spread of the normalized spectra of each class, including
both intrinsic differences and observational uncertainties, is about 1% in K,
2% in H and 3% in J. Many absorption features can be accurately measured. The
target galaxies and the spectroscopic aperture (7"x53") were chosen to be
similar to those used by Kinney et al. (1996) to define template UV and optical
spectra. The two data sets are matched in order to build representative spectra
between 0.1 and 2.4 mic. The continuum shape of the optical spectra and the
relative normalization of the near-IR ones were set to fit the average
effective colours of the galaxies of the various Hubble classes. The resulting
spectra are used to compute the k-corrections of the normal galaxies in the
near-IR bands and to check the predictions of various spectral synthesis
models: while the shape of the continuum is generally well predicted, large
discrepancies are found in the absorption lines. Among the other possible
applications, here we also show how these spectra can be used to place
constraints on the dominant stellar population in local galaxies. Spectra and
k-corrections are publicly available and can be downloaded from the web site
http://www.arcetri.astro.it/~filippo/spectra.Comment: 15 pages including figures, MNRAS, in pres
Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean
Relativistic Laser-Matter Interaction and Relativistic Laboratory Astrophysics
The paper is devoted to the prospects of using the laser radiation
interaction with plasmas in the laboratory relativistic astrophysics context.
We discuss the dimensionless parameters characterizing the processes in the
laser and astrophysical plasmas and emphasize a similarity between the laser
and astrophysical plasmas in the ultrarelativistic energy limit. In particular,
we address basic mechanisms of the charged particle acceleration, the
collisionless shock wave and magnetic reconnection and vortex dynamics
properties relevant to the problem of ultrarelativistic particle acceleration.Comment: 58 pages, 19 figure
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