1,197 research outputs found
AC Loss and Contact Resistance In Copper-Stabilized Nb3Al Rutherford Cables with and without a Stainless Steel Core
Calorimetric measurements of AC loss and hence interstrand contact resistance
(ICR), were measured on three samples of Rutherford cable wound with
Cu-stabilized jelly-roll type unplated Nb3Al strand. One of the cable types was
furnished with a thin core of AISI 316L stainless steel and the other two were
both uncored but insulated in different ways. The cables were subjected to a
room-temperature-applied uniaxial pressure of 12 MPa that was maintained during
the reaction heat treatment (RHT), then vacuum impregnated with CTD 101 epoxy,
and repressurized to 100 MPa during AC-loss measurement. The measurements were
performed at 4.2 K in a sinusoidal field of amplitude 400 mT at frequencies of
1 to 90 mHz (no DC-bias field) that was applied both perpendicular and parallel
to the face of the cable (the face-on, FO, and edge-on, EO, directions,
respectively). For the cored cable the FO-measured effective ICR (FO-ICR), was
5.27 . Those for the uncored cables were less than 0.08
. As shown previously for NbTi- and Nb3Sn-based Rutherford
cables, the FO-ICR can be significantly increased by the insertion of a core,
although in this case it is still below the range recommended for
accelerator-magnet use. Post-measurement dissection of one of the cables showed
that the impregnating resin had permeated between the strands and coated the
core with a thin, insulating layer excepting for some sintered points of
contact. In the uncored cables the strands were coated with resin except for
the points of interstrand contact. It is suggested that in the latter case this
tendency for partial coating leads to a processing-sensitive FO-ICR.Comment: Four pages, with two figure
Optimisation of ITER Nb3Sn CICCs for coupling loss, transverse electromagnetic load and axial thermal contraction
The ITER cable-in-conduit conductors (CICCs) are built up from sub-cable
bundles, wound in different stages, which are twisted to counter coupling loss
caused by time-changing external magnet fields. The selection of the twist
pitch lengths has major implications for the performance of the cable in the
case of strain sensitive superconductors, i.e. Nb3Sn, as the electromagnetic
and thermal contraction loads are large but also for the heat load from the AC
coupling loss. Reduction of the transverse load and warm-up cool-down
degradation can be reached by applying longer twist pitches in a particular
sequence for the sub-stages, offering a large cable transverse stiffness,
adequate axial flexibility and maximum allowed lateral strand support. Analysis
of short sample (TF conductor) data reveals that increasing the twist pitch can
lead to a gain of the effective axial compressive strain of more than 0.3 %
with practically no degradation from bending. For reduction of the coupling
loss, specific choices of the cabling twist sequence are needed with the aim to
minimize the area of linked strands and bundles that are coupled and form loops
with the applied changing magnetic field, instead of simply avoiding longer
pitches. In addition we recommend increasing the wrap coverage of the CS
conductor from 50 % to at least 70 %. The models predict significant
improvement against strain sensitivity and substantial decrease of the AC
coupling loss in Nb3Sn CICCs, but also for NbTi CICCs minimization of the
coupling loss can be achieved. Although the success of long pitches to
transverse load degradation was already demonstrated, the prediction of the
combination with low coupling loss needs to be validated by a short sample
test.Comment: to be published in Supercond Sci Techno
Preventive youth health care in 11 European countries: an exploratory analysis
Objective: To systematically identify similarities and differences in the way preventive youth health care (YHC) is organized in 11 European countries. - \ud
Method: Questionnaire survey to EUSUHM (European Union for School and University Health and Medicine) representatives. - \ud
Results: The greatest similarities were found in the age range of the YHC target group and the separation of curative and preventive services. Croatia, Germany and Switzerland show the greatest differences when compared to other European countries, for example, in the access to medical records, YHC professional input and the number of examinations, immunizations and screenings. In eight countries YHC is financed by national insurances or taxation. In Germany, FYR Macedonia, the Netherlands, Russia and Switzerland, different forms of financing exist in parallel. - Conclusion The results should be interpreted as a preliminary step in mapping organizational features of YHC in Europe
How to distinguish between interacting and noninteracting molecules in tunnel junctions
Recent experiments demonstrate a temperature control of the electric
conduction through a ferrocene-based molecular junction. Here we examine the
results in view of determining means to distinguish between transport through
single-particle molecular levels or via transport channels split by Coulomb
repulsion. Both transport mechanisms are similar in molecular junctions given
the similarities between molecular intralevel energies and the charging energy.
We propose an experimentally testable way to identify the main transport
process. By applying a magnetic field to the molecule, we observe that an
interacting theory predicts a shift of the conductance resonances of the
molecule whereas in the noninteracting case each resonance is split into two
peaks. The interaction model works well in explaining our experimental results
obtained in a ferrocene-based single-molecule junction, where the charge
degeneracy peaks shift (but do not split) under the action of an applied
7-Tesla magnetic field. This method is useful for a proper characterization of
the transport properties of molecular tunnel junctions.Comment: Main text: 7 pages, 5 figures; SI: 2 pages, 2 figures. Accepted to
RSC Nanoscal
Fluvio-deltaic avulsions during relative sea-level fall.
Understanding river response to changes in relative sea level (RSL) is essential for predicting fluvial stratigraphy and source-to-sink dynamics. Recent theoretical work has suggested that rivers can remain aggradational during RSL fall, but field data are needed to verify this response and investigate sediment deposition processes. We show with field work and modeling that fluvio-deltaic systems can remain aggradational or at grade during RSL fall, leading to superelevation and continuation of delta lobe avulsions. The field site is the Goose River, Newfoundland-Labrador, Canada, which has experienced steady RSL fall of around 3–4 mm yr⁻¹ in the past 5 k.y. from post-glacial isostatic rebound. Elevation analysis and optically stimulated luminescence dating suggest that the Goose River avulsed and deposited three delta lobes during RSL fall. Simulation results from Delft3D software show that if the characteristic fluvial response time is longer than the duration of RSL fall, then fluvial systems remain aggradational or at grade, and continue to avulse during RSL fall due to superelevation. Intriguingly, we find that avulsions become more frequent at faster rates of RSL fall, provided the system response time remains longer than the duration of RSL fall. This work suggests that RSL fall rate may influence the architecture of falling-stage or forced regression deposits by controlling the number of deposited delta lobes
Spatial periodic and homogeneous transverse stress loading on ITER TF Nb3Sn bronze and internal tin strand
The transport properties of the superconducting Nb3Sn layers in the strands
strongly depend on the strain state. Knowledge of the influence of axial
strain, periodic bending and contact stress on the critical current (Ic) of the
used Nb3Sn strands is inevitable to gain sufficient confidence in an economic
design and stable operation of ITER CICCs. In the past years we have measured
the Ic and n-value of various ITER Nb3Sn strands with different layout in the
TARSIS facility, when subjected to spatial periodic contact stress at a
temperature of 4.2 K and in a magnet field of 12 T. Recently we have made the
setup suitable for application of homogeneous load along the length of the wire
(125 mm) in order to evaluate possible differences related to spatial stress
and possible current distribution. We present an overview of the results
obtained so far on an ITER TF bronze and internal tin strand.Comment: to be published in IEEE Trans Appl Supercon
Process competences to incorporate in higher education curricula
This study reports on a survey on project managers' priorities. The survey used ISO 21500 as a scaffold to ask various respondents, like junior, experienced, and senior project managers, project sponsors, and students, to share their perceptions on the priorities for junior project managers. The respondent groups shared similar perceptions. Furthermore, project type and sector had little effect on junior project managers' priorities. Experienced and senior project managers shared their own priorities as well. The perceptions of priorities for junior, experienced, and senior project managers were mostly alike. However, experienced and senior project managers' priorities seemed slightly more affected by project type and sector. A session with experts in project management and teaching project management highlighted that the results for junior project managers could provide accents for introducing project management to students in higher education, provided the entire playing field of project management is also introduced.</p
Comparison of ePlex respiratory pathogen panel with laboratory-developed real-time PCR assays for detection of respiratory pathogens
Infections of the respiratory tract can be caused by a diversity of pathogens, both viral and bacterial. Rapid microbiological diagnosis ensures appropriate antimicrobial therapy as well as effective implementation of isolation precautions. The ePlex respiratory pathogen panel (RP panel) is a novel molecular biology-based assay, developed by GenMark Diagnostics, Inc. (Carlsbad, CA), to be performed within a single cartridge for the diagnosis of 25 respiratory pathogens (viral and bacterial). The objective of this study was to compare the performance of the RP panel with those of laboratory-developed real-time PCR assays, using a variety of previously collected clinical respiratory specimens. A total of 343 clinical specimens as well as 29 external quality assessment (EQA) specimens and 2 different Middle East respiratory syndrome coronavirus isolates have been assessed in this study. The RP panel showed an agreement of 97.4% with the real-time PCR assay regarding 464 pathogens found in the clinical specimens. All pathogens present in clinical samples and EQA samples with a threshold cycle (CT) value of <30 were detected correctly using the RP panel. The RP panel detected 17 additional pathogens, 7 of which could be confirmed by discrepant testing. In conclusion, this study shows excellent performance of the RP panel in comparison to real-time PCR assays for the detection of respiratory pathogens. The ePlex system provided a large amount of useful diagnostic data within a short time frame, with minimal hands-on time, and can therefore potentially be used for rapid diagnostic sample-to-answer testing, in either a laboratory or a decentralized setting.Publisher PDFPeer reviewe
Electrostatic Control over Temperature-Dependent Tunneling across a Single Molecule Junction
Understanding how the mechanism of charge transport through molecular tunnel
junctions depends on temperature is crucial to control electronic function in
molecular electronic devices. With just a few systems investigated as a
function of bias and temperature so far, thermal effects in molecular tunnel
junctions remain poorly understood. Here we report a detailed charge transport
study of an individual redox-active ferrocene-based molecule over a wide range
of temperatures and applied potentials. The results show the temperature
dependence of the current to vary strongly as a function of the gate voltage.
Specifically, the current across the molecule exponentially increases in the
Coulomb blockade regime and decreases at the charge degeneracy points, while
remaining temperature-independent at resonance. Our observations can be well
accounted for by a formal single-level tunneling model where the temperature
dependence relies on the thermal broadening of the Fermi distributions of the
electrons in the leads.Comment: 37 pages, 13 figure
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