1,335 research outputs found
Mercury Magnification In Riverine Food Webs In The Northern Rocky Mountains: Clark Fork River Basin, Montana, U.S.A.
At a local scale, such as the Clark Fork River Basin (CFRB), historic gold mining contributes the majority of mercury (Hg) found in the environment. Mercury enters aquatic systems in inorganic forms and is transformed to methylmercury (MeHg) by bacteria. MeHg has the ability to bioaccumulate within higher trophic levels, causing severe neurotoxic diseases and mortality. Hg concentrations observed within an aquatic food web are controlled by two factors, a source of inorganic mercury and the potential for that Hg to become methylated (methylation controlled by environmental conditions i.e.: water velocity, organic matter, etc.). A sufficient source of inorganic mercury and environmental conditions which promote Hg methylation can lead to maximum MeHg biomagnification. This study presents a comprehensive look at food web Hg biomagnification within the CFRB. Hg concentrations are characterized through blood or tissue samples from osprey, fish, and aquatic macroinvertebrates. Additionally we look at controlling Hg biomagnification factors, Hg of fine-grained sediment, percentage of wetlands and riparian land cover, and mean monthly discharge, to access the biomagnification process within the watershed and thus the Hg levels observed throughout these three trophic levels. Preliminary results show Hg levels of aquatic invertebrates have been found to be heavily influenced by the source of Hg (fine-grained sediment), while upper trophic level species exhibit a strong correlation to environmental characteristics of the sample reach
Parallel Exhaustive Search without Coordination
We analyze parallel algorithms in the context of exhaustive search over
totally ordered sets. Imagine an infinite list of "boxes", with a "treasure"
hidden in one of them, where the boxes' order reflects the importance of
finding the treasure in a given box. At each time step, a search protocol
executed by a searcher has the ability to peek into one box, and see whether
the treasure is present or not. By equally dividing the workload between them,
searchers can find the treasure times faster than one searcher.
However, this straightforward strategy is very sensitive to failures (e.g.,
crashes of processors), and overcoming this issue seems to require a large
amount of communication. We therefore address the question of designing
parallel search algorithms maximizing their speed-up and maintaining high
levels of robustness, while minimizing the amount of resources for
coordination. Based on the observation that algorithms that avoid communication
are inherently robust, we analyze the best running time performance of
non-coordinating algorithms. Specifically, we devise non-coordinating
algorithms that achieve a speed-up of for two searchers, a speed-up of
for three searchers, and in general, a speed-up of
for any searchers. Thus, asymptotically, the speed-up is only four
times worse compared to the case of full-coordination, and our algorithms are
surprisingly simple and hence applicable. Moreover, these bounds are tight in a
strong sense as no non-coordinating search algorithm can achieve better
speed-ups. Overall, we highlight that, in faulty contexts in which coordination
between the searchers is technically difficult to implement, intrusive with
respect to privacy, and/or costly in term of resources, it might well be worth
giving up on coordination, and simply run our non-coordinating exhaustive
search algorithms
Temperature dependent relaxation of dipole-exchange magnons in yttrium iron garnet films
Low energy consumption enabled by charge-free information transport, which is
free from ohmic heating, and the ability to process phase-encoded data by
nanometer-sized interference devices at GHz and THz frequencies are just a few
benefits of spin-wave-based technologies. Moreover, when approaching cryogenic
temperatures, quantum phenomena in spin-wave systems pave the path towards
quantum information processing. In view of these applications, the lifetime of
magnonsspin-wave quantais of high relevance for the fields of magnonics,
magnon spintronics and quantum computing. Here, the relaxation behavior of
parametrically excited magnons having wavenumbers from zero up to was experimentally investigated in the temperature range
from 20 K to 340 K in single crystal yttrium iron garnet (YIG) films
epitaxially grown on gallium gadolinium garnet (GGG) substrates as well as in a
bulk YIG crystalthe magnonic materials featuring the lowest magnetic damping
known so far. As opposed to the bulk YIG crystal in YIG films we have found a
significant increase in the magnon relaxation rate below 150 Kup to 10.5
times the reference value at 340 Kin the entire range of probed wavenumbers.
This increase is associated with rare-earth impurities contaminating the YIG
samples with a slight contribution caused by coupling of spin waves to the spin
system of the paramagnetic GGG substrate at the lowest temperatures
Confocal Laser Endomicroscopy for Diagnosis of Barrett’s Esophagus
Barrett’s esophagus (BE) is established as a premalignant condition in the distal esophagus. Current surveillance guidelines recommend random biopsies every 1–2 cm at intervals of 3–5 years. Advanced endoscopic imaging of BE underwent several technical revolutions within the last decade including broad-field (red-flag) techniques (e.g., chromoendoscopy) and small-field techniques with confocal laser endomicroscopy (CLE) at the forefront. In this review we will focus on advanced endoscopic imaging using CLE for the diagnosis and characterization of BE and associated neoplasia. In addition, we will critically discuss the technique of CLE and provide some tricks and hints for the daily routine practice of CLE for diagnosis of BE
Influence of the carbonization degree of carbon nonwoven electrodes in vanadium redox flow batteries
Stealthy Deception Attacks Against SCADA Systems
SCADA protocols for Industrial Control Systems (ICS) are vulnerable to
network attacks such as session hijacking. Hence, research focuses on network
anomaly detection based on meta--data (message sizes, timing, command
sequence), or on the state values of the physical process. In this work we
present a class of semantic network-based attacks against SCADA systems that
are undetectable by the above mentioned anomaly detection. After hijacking the
communication channels between the Human Machine Interface (HMI) and
Programmable Logic Controllers (PLCs), our attacks cause the HMI to present a
fake view of the industrial process, deceiving the human operator into taking
manual actions. Our most advanced attack also manipulates the messages
generated by the operator's actions, reversing their semantic meaning while
causing the HMI to present a view that is consistent with the attempted human
actions. The attacks are totaly stealthy because the message sizes and timing,
the command sequences, and the data values of the ICS's state all remain
legitimate.
We implemented and tested several attack scenarios in the test lab of our
local electric company, against a real HMI and real PLCs, separated by a
commercial-grade firewall. We developed a real-time security assessment tool,
that can simultaneously manipulate the communication to multiple PLCs and cause
the HMI to display a coherent system--wide fake view. Our tool is configured
with message-manipulating rules written in an ICS Attack Markup Language (IAML)
we designed, which may be of independent interest. Our semantic attacks all
successfully fooled the operator and brought the system to states of blackout
and possible equipment damage
Underlying barriers to referral to paediatric palliative care services: knowledge and attitudes of healthcare professionals in a paediatric tertiary care centre in the United Kingdom
Referrals to children’s palliative care services typically occur late in the illness trajectory, with many children who would benefit not referred at all. Previous studies report health care professionals’ (HCPs) assessment of various parent-related factors as barriers to referral. We conducted a cross-sectional survey of HCPs working in a paediatric tertiary care hospital in the United Kingdom, with an established paediatric palliative care team, to explore staff perceptions of barriers, knowledge and attitudes, with the aim of developing interventions to increase patient access to palliative care services. Survey respondents evidenced good knowledge of the principles of palliative care in closed questions, but their attitudes expressed in open-text questions and reported reasons to refer to a palliative care service demonstrated an association of palliative care with death and dying. We suggest that the association of palliative care with end of life may be a modifiable factor relevant to late and non-referral and deserving of further investigation and attention in education and training
A Feasibility Study Using TomoDirect for Craniospinal Irradiation
The feasibility of delivering craniospinal irradiation (CSI) with TomoDirect is investigated. A method is proposed to generate TomoDirect plans using standard three-dimensional (3D) beam arrangements on Tomotherapy with junctioning of these fields to minimize hot or cold spots at the cranial/spinal junction. These plans are evaluated and compared to a helical Tomotherapy and a three-dimensional conformal therapy (3D CRT) plan delivered on a conventional linear accelerator (linac) for CSI. The comparison shows that a TomoDirect plan with an overlap between the cranial and spinal fields might be preferable over Tomotherapy plans because of decreased low dose to large volumes of normal tissues outside of the planning target volume (PTV). Although the TomoDirect plans were not dosimetrically superior to a 3D CRT linac plan, the patient can be easily treated in the supine position, which is often more comfortable and efficient from an anesthesia standpoint. TomoDirect plans also have only one setup position which obviates the need for matching of fields and feathering of junctions, two issues encountered with conventional 3D CRT plans. TomoDirect plans can be delivered with comparable treatment times to conventional 3D plans and in shorter times than a Tomotherapy plan. In this paper, a method is proposed for creating TomoDirect craniospinal plans, and the dosimetric consequences for choosing different planning parameters are discussed
C4 olefin conversion on reduced nickel y faujasite. Evidence for C5 olefin formation via C4 olefin disproportionation
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