481 research outputs found
Numerical Simulation of Upwelling Flow in Pipe Generated by Perpetual Salt Fountain
Upwelling of deep seawater to the region, where sunlight reaches, can produce the ocean farm since deep seawater contains high concentration of nutrient. The numerical simulation for upwelling of deep seawater with the perpetual salt fountain proposed by Stommel et al. was conducted in this study. The temperature and salinity distributions measured in Mariana area where the upwelling experiment was conducted by Maruyama et al. was used. As a result, the velocity profile of the upwelling experiment was predicted as M-shape flow and the flow rate was estimated as 43t/day in the pipe. Additionally the possibility of reverse flow in the pipe was indicated. Furthermore the possibility of upwelling in other ocean areas using the results was discussed. As a result, it became clear that the unified representation of ocean conditions was achieved by the new dimensionless number RaR, which was modified Rayleigh number, and flow rate in the pipe could be evaluated by RaR
Large amplitude oscillatory motion along a solar filament
Large amplitude oscillations of solar filaments is a phenomenon known for
more than half a century. Recently, a new mode of oscillations, characterized
by periodical plasma motions along the filament axis, was discovered. We
analyze such an event, recorded on 23 January 2002 in Big Bear Solar
Observatory H filtergrams, in order to infer the triggering mechanism
and the nature of the restoring force. Motion along the filament axis of a
distinct buldge-like feature was traced, to quantify the kinematics of the
oscillatory motion. The data were fitted by a damped sine function, to estimate
the basic parameters of the oscillations. In order to identify the triggering
mechanism, morphological changes in the vicinity of the filament were analyzed.
The observed oscillations of the plasma along the filament was characterized by
an initial displacement of 24 Mm, initial velocity amplitude of 51 km/s, period
of 50 min, and damping time of 115 min. We interpret the trigger in terms of
poloidal magnetic flux injection by magnetic reconnection at one of the
filament legs. The restoring force is caused by the magnetic pressure gradient
along the filament axis. The period of oscillations, derived from the
linearized equation of motion (harmonic oscillator) can be expressed as
, where represents the Alfv\'en speed based on the
equilibrium poloidal field . Combination of our measurements with
some previous observations of the same kind of oscillations shows a good
agreement with the proposed interpretation.Comment: Astron. Astrophys., 2007, in pres
Core electron densities of coronal polar plumes
The electron density in the cores of coronal polar plumes that is determined from observations will depend upon the assumed electron density distribution through the plume in a direction normal to its axis. Core electron densities obtained by Saito (1965) and by Newkirk and Harvey (1968) were derived using different assumed electron density profiles, and are not in agreement. We have re-discussed Saito's data using Newkirk and Harvey's electron density profile and find that the disagreement persists. Whether this indicates a true variation in electron density in plume cores cannot now be stated. Errors in the electron densities derived here may arise through errors in measuring the angles θ and α which enter into the analysis. While plausible variations in θ produce no appreciable errors in core electron density, plausible variations in α may introduce appreciable errors into the determinations of that quantity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43726/1/11207_2004_Article_BF00153112.pd
DD-4 Synthesis of Planar Microwave Band-pass Filter based on Foster-type Network and Normal Mode Expansion Method
A new synthesis method of microwave filter circuit based on the Foster-type network representation is proposed, where two port impedance matrix which realizes the desired frequency characteristics and that of any microwave circuit structure are expanded into Foster-type network representation; microwave filter circuit can be synthesizedby matching the both network representation. In this paper fundamental idea of synthesis method and practical examples are explained.1992 IEEE MTT-S International Microwave Symposium Digest, June 1-5, 1992, Albuquerque Convention Center, Albuquerque, New Mexic
SOHO/SUMER Observations of Prominence Oscillation Before Eruption
Coronal mass ejections (CMEs), as a large-scale eruptive phenomenon, often
reveal some precursors in the initiation phase, e.g., X-ray brightening,
filament darkening, etc, which are useful for CME modeling and space weather
forecast.
With the SOHO/SUMER spectroscopic observations of the 2000 September 26
event, we propose another precursor for CME eruptions, namely, long-time
prominence oscillations.
The prominence oscillation-and-eruption event was observed by ground-based
H telescopes and space-borne white-light, EUV imaging and spectroscopic
instruments. In particular, the SUMER slit was observing the prominence in a
sit-and-stare mode.
The observations indicate that a siphon flow was moving from the proximity of
the prominence to a site at a projected distance of 270, which was followed
by repetitive H surges and continual prominence oscillations. The
oscillation lasted 4 hours before the prominence erupted as a blob-like CME.
The analysis of the multiwavelength data indicates that the whole series of
processes fits well into the emerging flux trigger mechanism for CMEs. In this
mechanism, emerging magnetic flux drives a siphon flow due to increased gas
pressure where the background polarity emerges. It also drives H surges
through magnetic reconnection where the opposite polarity emerges. The magnetic
reconnection triggers the prominence oscillations, as well as its loss of
equilibrium, which finally leads to the eruption of the prominence. It is also
found that the reconnection between the emerging flux and the pre-existing
magnetic loop proceeds in an intermittent, probably quasi-periodic, way.Comment: 14 pages, 8 figures, submitted for publication in A&
Physics of Solar Prominences: II - Magnetic Structure and Dynamics
Observations and models of solar prominences are reviewed. We focus on
non-eruptive prominences, and describe recent progress in four areas of
prominence research: (1) magnetic structure deduced from observations and
models, (2) the dynamics of prominence plasmas (formation and flows), (3)
Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and
large-scale patterns of the filament channels in which prominences are located.
Finally, several outstanding issues in prominence research are discussed, along
with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape
Esophageal granular cell tumor successfully resected by endoscopic submucosal dissection
Granular cell tumors of the esophagus are rare neoplasms and their diagnosis is mainly based on histopathologic examination of endoscopic biopsies. With the development of endoscopic techniques, there has been a marked increase in local treatment modalities for early esophageal neoplasms. In this case report, we describe the removal of a granular cell tumor by the endoscopic submucosal dissection technique, and briefly discuss the literature on clinicopathologic aspects and management of granular cell tumors
Adverse Effects of Methylmercury: Environmental Health Research Implications
Background: The scientific discoveries of health risks resulting from methylmercury exposure began in 1865 describing ataxia, dysarthria, constriction of visual fields, impaired hearing, and sensory disturbance as symptoms of fatal methylmercury poisoning. Objective: Our aim was to examine how knowledge and consensus on methylmercury toxicity have developed in order to identify problems of wider concern in research. Data sources and extraction: We tracked key publications that reflected new insights into human methylmercury toxicity. From this evidence, we identified possible caveats of potential significance for environmental health research in general. Synthesis: At first, methylmercury research was impaired by inappropriate attention to narrow case definitions and uncertain chemical speciation. It also ignored the link between ecotoxicity and human toxicity. As a result, serious delays affected the recognition of methylmercury as a cause of serious human poisonings in Minamata, Japan. Developmental neurotoxicity was first reported in 1952, but despite accumulating evidence, the vulnerability of the developing nervous system was not taken into account in risk assessment internationally until approximately 50 years later. Imprecision in exposure assessment and other forms of uncertainty tended to cause an underestimation of methylmercury toxicity and repeatedly led to calls for more research rather than prevention. Conclusions: Coupled with legal and political rigidity that demanded convincing documentation before considering prevention and compensation, types of uncertainty that are common in environmental research delayed the scientific consensus and were used as an excuse for deferring corrective action. Symptoms of methylmercury toxicity, such as tunnel vision, forgetfulness, and lack of coordination, also seemed to affect environmental health research and its interpretation
Adverse Effects of Methylmercury: Environmental Health Research Implications
Background: The scientific discoveries of health risks resulting from methylmercury exposure began in 1865 describing ataxia, dysarthria, constriction of visual fields, impaired hearing, and sensory disturbance as symptoms of fatal methylmercury poisoning. Objective: Our aim was to examine how knowledge and consensus on methylmercury toxicity have developed in order to identify problems of wider concern in research. Data sources and extraction: We tracked key publications that reflected new insights into human methylmercury toxicity. From this evidence, we identified possible caveats of potential significance for environmental health research in general. Synthesis: At first, methylmercury research was impaired by inappropriate attention to narrow case definitions and uncertain chemical speciation. It also ignored the link between ecotoxicity and human toxicity. As a result, serious delays affected the recognition of methylmercury as a cause of serious human poisonings in Minamata, Japan. Developmental neurotoxicity was first reported in 1952, but despite accumulating evidence, the vulnerability of the developing nervous system was not taken into account in risk assessment internationally until approximately 50 years later. Imprecision in exposure assessment and other forms of uncertainty tended to cause an underestimation of methylmercury toxicity and repeatedly led to calls for more research rather than prevention. Conclusions: Coupled with legal and political rigidity that demanded convincing documentation before considering prevention and compensation, types of uncertainty that are common in environmental research delayed the scientific consensus and were used as an excuse for deferring corrective action. Symptoms of methylmercury toxicity, such as tunnel vision, forgetfulness, and lack of coordination, also seemed to affect environmental health research and its interpretation
A multi-targeted approach to suppress tumor-promoting inflammation
Cancers harbor significant genetic heterogeneity and patterns of relapse following many therapies are due to evolved resistance to treatment. While efforts have been made to combine targeted therapies, significant levels of toxicity have stymied efforts to effectively treat cancer with multi-drug combinations using currently approved therapeutics. We discuss the relationship between tumor-promoting inflammation and cancer as part of a larger effort to develop a broad-spectrum therapeutic approach aimed at a wide range of targets to address this heterogeneity. Specifically, macrophage migration inhibitory factor, cyclooxygenase-2, transcription factor nuclear factor-κB, tumor necrosis factor alpha, inducible nitric oxide synthase, protein kinase B, and CXC chemokines are reviewed as important antiinflammatory targets while curcumin, resveratrol, epigallocatechin gallate, genistein, lycopene, and anthocyanins are reviewed as low-cost, low toxicity means by which these targets might all be reached simultaneously. Future translational work will need to assess the resulting synergies of rationally designed antiinflammatory mixtures (employing low-toxicity constituents), and then combine this with similar approaches targeting the most important pathways across the range of cancer hallmark phenotypes
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