152 research outputs found
A crude model to study radio frequency induced density modification close to launchers
The interplay between radio frequency (RF) waves and the density is discussed by adopting the general framework of a 2-time-scale multi-fluid treatment, allowing to separate the dynamics on the RF time scale from that on the time scale on which macroscopic density and flows vary as a result of the presence of electromagnetic and/or electrostatic fields. The focus is on regions close to launchers where charge neutrality is incomplete and waves are commonly evanescent. The fast time scale dynamics influences the slow time scale behavior via quasilinear terms (the Ponderomotive force for the case of the equation of motion). Electrons and ions are treated on the same footing. Also, both fast and slow waves are retained in the wave description. Although this work is meant as a subtopic of a large study-the wave induced "convective cell" physics at hand is of a 2- or 3-dimensional nature while this paper limits itself to a single dimension-a few tentative examples are presented
The senotherapeutic nicotinamide riboside raises platelet nicotinamide adenine dinucleotide levels but cannot prevent storage lesion
BACKGROUND Supplementation of the adenine nicotinamide dinucleotide (NAD) precursor nicotineamide riboside (NR) has recently been shown to increase life-span of cells, tissues, and entire organisms. The impact of NR on platelet longevity has not been tested. STUDY DESIGN AND METHODS A pool-and-split design of buffy coat derived platelet concentrates (PCs) was used. One arm was treated with cumulative doses of NR-triflate, the control arm with sodium triflate. Storage lesion was monitored for 23 days. Platelet metabolic and functional parameters were tested. Clearance of human platelets was measured in a mouse model of transfusion. RESULTS Total intracellular NAD levels in platelets decreased two-fold from 4.8 +/- 0.5 fmol (mean +/- SD, n = 6) to 2.1 +/- 1.8 fmol per 10(3) control cells, but increased almost 10-fold to 41.5 +/- 4.1 fmol per 10(3) NR treated platelets. This high intracellular NAD level had no significant impact on platelet count, mean platelet volume, swirling, nor on lactate and glucose levels. Platelet aggregation and integrin alpha(IIb)beta(3) activation declined steadily and comparably in both conditions. GPIb alpha levels were slightly lower in NR-treated platelets compared to control, but this was not caused by reduced receptor shedding because glycocalicin increased similarly. Apoptotic markers cytochrome c, Bcl-xL, cleaved caspase-3, and Bak were not different throughout storage for both conditions. Platelet survival in a mouse model of transfusion was not different between NR-treated and control platelets. CONCLUSION Platelets carry the cellular machinery to metabolize NR into NAD at rates comparable to other eukaryotic cells. Unlike those cells, platelet life-span cannot be prolonged using this strategy
A novel Doppler backscattering (DBS) system to simultaneously monitor radio frequency plasma fluctuations and low frequency turbulence
A novel quadrature Doppler Backscattering (DBS) system has been developed and
optimized for the E-band (60-90GHz) frequency range using either O-mode or
X-mode polarization in DIII-D plasmas. In general, DBS measures the amplitude
of density fluctuations and their velocity in the lab frame. The system can
simultaneously monitor both low-frequency turbulence (f < 10MHz) and
radiofrequency plasma density fluctuations over a selectable frequency range
(20-500 MHz). Detection of high-frequency fluctuations has been demonstrated
for low harmonics of the ion cyclotron frequency (e.g., 2fci~23MHz) and
externally driven high-frequency helicon waves (f = 476MHz) using an adjustable
frequency down conversion system. Importantly, this extends the application of
DBS to a high-frequency spectral domain while maintaining important turbulence
and flow measurement capabilities. This unique system has low phase noise, good
temporal resolution (sub-millisecond) and excellent wavenumber coverage
(k_{\theta} ~ 1-20cm^{-1} and k_r ~ 20-30cm^{-1}). As a demonstration,
localized internal DIII-D plasma measurements are presented from turbulence (f
= 20MHz) as well
as fluctuations around 476MHz driven by an external high-power 476 MHz helicon
wave antenna. In the future, helicon measurements will be used to validate
GENRAY and AORSA modeling tools for prediction of helicon wave propagation,
absorption and current drive location for the newly installed helicon current
drive system on DIII-D.Comment: 13 pages, 14 figs, journal pape
Thermal plasma and fast ion transport in electrostatic turbulence in the large plasma device
The transport of thermal plasma and fast ions in electrostatic microturbulence is studied. Strong density and potential fluctuations (δn/n ∼ δ/kTe ∼ 0.5, f ∼ 5-50 kHz) are observed in the large plasma device (LAPD) [W. Gekelman, H. Pfister, Z. Lucky, Rev. Sci. Instrum. 62, 2875 (1991)] in density gradient regions produced by obstacles with slab or cylindrical geometry. Wave characteristics and the associated plasma transport are modified by driving sheared E × B drift through biasing the obstacle and by modification of the axial magnetic fields (Bz) and the plasma species. Cross-field plasma transport is suppressed with small bias and large Bz and is enhanced with large bias and small Bz. The transition in thermal plasma confinement is well explained by the cross-phase between density and potential fluctuations. Large gyroradius lithium fast ion beam (ρfast/ρs ∼ 10) orbits through the turbulent region. Scans with a collimated analyzer give detailed profiles of the fast ion spatial-temporal distribution. Fast-ion transport decreases rapidly with increasing fast-ion energy and gyroradius. Background waves with different scale lengths also alter the fast ion transport. Experimental results agree well with gyro-averaging theory. When the fast ion interacts with the wave for most of a wave period, a transition from super-diffusive to sub-diffusive transport is observed, as predicted by diffusion theory. Besides turbulent-wave-induced fast-ion transport, the static radial electric field (Er) from biasing the obstacle leads to drift of the fast-ion beam centroid. The drift and broadening of the beam due to static Er are evaluated both analytically and numerically. Simulation results indicate that the Er induced transport is predominately convective. © 2012 American Institute of Physics
Child abuse inventory at emergency rooms: CHAIN-ER rationale and design
<p>Abstract</p> <p>Background</p> <p>Child abuse and neglect is an important international health problem with unacceptable levels of morbidity and mortality. Although maltreatment as a cause of injury is estimated to be only 1% or less of the injured children attending the emergency room, the consequences of both missed child abuse cases and wrong suspicions are substantial. Therefore, the accuracy of ongoing detection at emergency rooms by health care professionals is highly important. Internationally, several diagnostic instruments or strategies for child abuse detection are used at emergency rooms, but their diagnostic value is still unknown. The aim of the study 'Child Abuse Inventory at Emergency Rooms' (CHAIN-ER) is to assess if active structured inquiry by emergency room staff can accurately detect physical maltreatment in children presenting at emergency rooms with physical injury.</p> <p>Methods/design</p> <p>CHAIN-ER is a multi-centre, cross-sectional study with 6 months diagnostic follow-up. Five thousand children aged 0-7 presenting with injury at an emergency room will be included. The index test - the SPUTOVAMO-R questionnaire- is to be tested for its diagnostic value against the decision of an expert panel. All SPUTOVAMO-R positives and a 15% random sample of the SPUTOVAMO-R negatives will undergo the same systematic diagnostic work up, which consists of an adequate history being taken by a pediatrician, inquiry with other health care providers by structured questionnaires in order to obtain child abuse predictors, and by additional follow-up information. Eventually, an expert panel (reference test) determines the <it>true </it>presence or absence of child abuse.</p> <p>Discussion</p> <p>CHAIN-ER will determine both positive and negative predictive value of a child abuse detection instrument used in the emergency room. We mention a benefit of the use of an expert panel and of the use of complete data. Conducting a diagnostic accuracy study on a child abuse detection instrument is also accompanied by scientific hurdles, such as the lack of an accepted reference standard and potential (non-) response. Notwithstanding these scientific challenges, CHAIN-ER will provide accurate data on the predictive value of SPUTOVAMO-R.</p
Potential human transmission of amyloid β pathology: surveillance and risks
Studies in experimental animals show transmissibility of amyloidogenic proteins associated with prion diseases, Alzheimer's disease, Parkinson's disease, and other neurodegenerative diseases. Although these data raise potential concerns for public health, convincing evidence for human iatrogenic transmission only exists for prions and amyloid β after systemic injections of contaminated growth hormone extracts or dura mater grafts derived from cadavers. Even though these procedures are now obsolete, some reports raise the possibility of iatrogenic transmission of amyloid β through putatively contaminated neurosurgical equipment. Iatrogenic transmission of amyloid β might lead to amyloid deposition in the brain parenchyma and blood vessel walls, potentially resulting in cerebral amyloid angiopathy after several decades. Cerebral amyloid angiopathy can cause life-threatening brain haemorrhages; yet, there is no proof that the transmission of amyloid β can also lead to Alzheimer's dementia. Large, long-term epidemiological studies and sensitive, cost-efficient tools to detect amyloid are needed to better understand any potential routes of amyloid β transmission and to clarify whether other similar proteopathic seeds, such as tau or α-synuclein, can also be transferred iatrogenically
Quality assessment of the Ozone_cci Climate Research Data Package (release 2017) – Part 2: Ground-based validation of nadir ozone profile data products
Atmospheric ozone plays a key role in
air quality and the radiation budget of the Earth, both directly and through
its chemical influence on other trace gases. Assessments of the atmospheric
ozone distribution and associated climate change therefore demand accurate
vertically resolved ozone observations with both stratospheric and
tropospheric sensitivity, on both global and regional scales, and both in the
long term and at shorter timescales. Such observations have been acquired by
two series of European nadir-viewing ozone profilers, namely the
scattered-light UV–visible spectrometers of the GOME family, launched
regularly since 1995 (GOME, SCIAMACHY, OMI, GOME-2A/B, TROPOMI, and the
upcoming Sentinel-5 series), and the thermal infrared emission sounders of
the IASI type, launched regularly since 2006 (IASI on Metop platforms and the
upcoming IASI-NG on Metop-SG). In particular, several Level-2 retrieved,
Level-3 monthly gridded, and Level-4 assimilated nadir ozone profile data
products have been improved and harmonized in the context of the ozone
project of the European Space Agency's Climate Change Initiative (ESA
Ozone_cci). To verify their fitness for purpose, these ozone datasets must
undergo a comprehensive quality assessment (QA), including (a) detailed
identification of their geographical, vertical, and temporal domains of
validity; (b) quantification of their potential bias, noise, and drift and
their dependences on major influence quantities; and (c) assessment of the
mutual consistency of data from different sounders. For this purpose we have
applied to the Ozone_cci Climate Research Data Package (CRDP) released in
2017 the versatile QA and validation system Multi-TASTE, which has been
developed in the context of several heritage projects (ESA's Multi-TASTE,
EUMETSAT's O3M-SAF, and the European Commission's FP6 GEOmon and FP7 QA4ECV).
This work, as the second in a series of four Ozone_cci validation papers,
reports for the first time on data content studies, information content
studies and ground-based validation for both the GOME- and IASI-type climate
data records combined. The ground-based reference measurements have been
provided by the Network for the Detection of Atmospheric Composition
Change (NDACC), NASA's Southern Hemisphere Additional Ozonesonde
programme (SHADOZ), and other ozonesonde and lidar stations contributing to
the World Meteorological Organisation's Global Atmosphere Watch (WMO GAW).
The nadir ozone profile CRDP quality assessment reveals that all nadir ozone
profile products under study fulfil the GCOS user requirements in terms of
observation frequency and horizontal and vertical resolution. Yet all
L2 observations also show sensitivity outliers in the UTLS and are strongly
correlated vertically due to substantial averaging kernel fluctuations that
extend far beyond the kernel's 15 km FWHM. The CRDP typically does not
comply with the GCOS user requirements in terms of total uncertainty and
decadal drift, except for the UV–visible L4 dataset. The drift values of the
L2 GOME and OMI, the L3 IASI, and the L4 assimilated products are found to be
overall insignificant, however, and applying appropriate altitude-dependent
bias and drift corrections make the data fit for climate and atmospheric
composition monitoring and modelling purposes. Dependence of the Ozone_cci
data quality on major influence quantities – resulting in data screening
suggestions to users – and perspectives for the Copernicus Sentinel missions
are additionally discussed
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