Magnetic flux motion and flux pinning in superconductors

Magnetization measurements on the two high-temperature superconductors Nd[subscript]1.85Ce[subscript]0.15CuO[subscript]4-y and Ba[subscript]0.6K[subscript]0.4BiO[subscript]3 have been undertaken in order to study the reversible and irreversible magnetic behavior and compare these two different materials with other high-temperature superconductors (HTSC). While the other HTSC are known to have hole carriers and layers of CuO[subscript]2 planes in anisotropic crystal structures, Nd[subscript]1.85Ce[subscript]0.15CuO[subscript]4-y (NCCO) has electron carriers as well as hole carriers, and Ba[subscript]0.6K[subscript]0.4BiO[subscript]3 (BKBO) has an isotropic crystal structure with no CuO[subscript]2 layers;For NCCO, the field-dependence of the specific heat derived from the reversible magnetization, C[subscript]0-C[subscript] H, exhibited peak broadening with increasing field and a field-independent onset temperature, both of which are observed in YBa[subscript]2Cu[subscript]3O[subscript]7-[delta]. The value at the highest available field, C[subscript]0-C [subscript]2T = 1.2 mJ/cm[superscript]3K, establishes a lower limit of the calorimetric specific heat jump [delta]C[subscript] p. Flux creep and hysteresis data were parameterized in terms of a single effective pinning potential U[subscript] eff in order to study the crossover from reversible to flux-pinning behavior in NCCO. There is a band in the H-T plane below H[subscript] irr(T) where U[subscript] eff/kT gradually rises from 2 to 20. The position of the U[subscript] eff/kT lines for NCCO are in approximately the same location as those for the hole carrier Tl(2223), when a reduced temperature scale is used;For BKBO, magnetization-vs-temperature data were found to be similar to that expected from the standard Ginzburg-Landau treatment in that there were sections of the M-vs-T curves in which the slopes dM/dT were nearly constant for increasing fields. Rounding of the M-vs-T curves near T[subscript] c was still observed, however, as might be expected if fluctuations are important. In this reversible region the specific heat jump values C[subscript] 1T-C[subscript] H derived from the free energy curves are also qualitatively similar to the high-T[subscript] c cuprates, the onset temperature is constant in field, and the peak broadens as field is increased. A maximum value of C[subscript] 1T-C[subscript] 5T = 1.8 mJ/cm[superscript]3K sets a lower limit on the value of [delta]C[subscript] p. U[subscript] eff/kT rises relatively quickly from 20 to 100 for BKBO below the irreversibility crossover, compared to the more gradual increase in U[subscript] eff/kT for NCCO. The isotropic BKBO has a smaller reversible region and stronger effective flux pinning potentials than layered NCCO. Fast-neutron irradiation of BKBO with a fluence of 1 x 10[superscript]22 n m[superscript]-2 did not increase critical current density in this sample. There was a small (\u3c2 K) shift in temperature in the (C[subscript] 1T-C[subscript] H)-vs-T data, but the qualitative features of this thermodynamic data remained intact following the irradiation

Method for producing strain tolerant multifilamentary oxide superconducting wire

A strain tolerant multifilamentary wire capable of carrying superconducting currents is provided comprising a plurality of discontinuous filaments formed from a high temperature superconducting material. The discontinuous filaments have a length at least several orders of magnitude greater than the filament diameter and are sufficiently strong while in an amorphous state to withstand compaction. A normal metal is interposed between and binds the discontinuous filaments to form a normal metal matrix capable of withstanding heat treatment for converting the filaments to a superconducting state. The geometry of the filaments within the normal metal matrix provides substantial filament-to-filament overlap, and the normal metal is sufficiently thin to allow supercurrent transfer between the overlapped discontinuous filaments but is also sufficiently thick to provide strain relief to the filaments

Strain tolerant microfilamentary superconducting wire

A strain tolerant microfilamentary wire capable of carrying superconducting currents is provided comprising a plurality of discontinuous filaments formed from a high temperature superconducting material. The discontinuous filaments have a length at least several orders of magnitude greater than the filament diameter and are sufficiently strong while in an amorphous state to withstand compaction. A normal metal is interposed between and binds the discontinuous filaments to form a normal metal matrix capable of withstanding heat treatment for converting the filaments to a superconducting state. The geometry of the filaments within the normal metal matrix provides substantial filament-to-filament overlap, and the normal metal is sufficiently thin to allow supercurrent transfer between the overlapped discontinuous filaments but is also sufficiently thick to provide strain relief to the filaments

Measuring Star-formation Rate and Far-Infrared Color in High-redshift Galaxies Using the CO (7-6) and [NII] 205 micron Lines

To better characterize the global star formation (SF) activity in a galaxy, one needs to know not only the star formation rate (SFR) but also the rest-frame, far-infrared (FIR) color (e.g., the 60-to-100 $\mu$m color, $C(60/100)$] of the dust emission. The latter probes the average intensity of the dust heating radiation field and scales statistically with the effective SFR surface density in star-forming galaxies including (ultra-)luminous infrared galaxies [(U)LIRGs]. To this end, we exploit here a new spectroscopic approach involving only two emission lines: CO\,(7$-$6) at 372 $\mu$m and [NII] at 205 $\mu$m. For local (U)LIRGs, the ratios of the CO (7$-$6) luminosity ($L_{\rm CO\,(7-6)}$) to the total infrared luminosity ($L_{\rm IR}$; 8$-$1000 $\mu$m) are fairly tightly distributed (to within $\sim$0.12 dex) and show little dependence on $C(60/100)$. This makes $L_{\rm CO\,(7-6)}$ a good SFR tracer, which is less contaminated by active galactic nuclei (AGN) than $L_{\rm IR}$ and may also be much less sensitive to metallicity than $L_{\rm CO\,(1-0)}$. Furthermore, the logarithmic [NII] 205 $\mu$m to CO (7$-$6) luminosity ratio is fairly steeply (at a slope of $\sim$$-1.4$) correlated with $C(60/100)$, with a modest scatter ($\sim$0.23 dex). This makes it a useful estimator on $C(60/100)$ with an implied uncertainty of $\sim$0.15 [or $\lesssim$4 K in the dust temperature ($T_{\rm dust}$) in the case of a graybody emission with $T_{\rm dust} \gtrsim 30$ K and a dust emissivity index $\beta \ge 1$]. Our locally calibrated SFR and $C(60/100)$ estimators are shown to be consistent with the published data of (U)LIRGs of $z$ up to $\sim$6.5.Comment: 6 pages, 3 figures, 1 table; accepted for publication in the ApJ Lette

Pulsed, Inductively Generated, Streaming Plasma Ion Source for Heavy Ion Fusion Linacs

This report describes a compact, high current density, pulsed ion source, based on electrodeless, inductively driven gas breakdown, developed to meet the requirements on normalized emittance, current density, uniformity and pulse duration for an ion injector in a heavy-ion fusion driver. The plasma source produces >10 μs pulse of Argon plasma with ion current densities >100 mA/cm2 at 30 cm from the source and with strongly axially directed ion energy of about 80 eV, and sub-eV transverse temperature. The source has good reproducibility and spatial uniformity. Control of the current density during the pulse has been demonstrated with a novel modulator coil method which allows attenuation of the ion current density without significantly affecting the beam quality. This project was carried out in two phases. Phase 1 used source configurations adapted from light ion sources to demonstrate the feasibility of the concept. In Phase 2 the performance of the source was enhanced and quantified in greater detail, a modulator for controlling the pulse shape was developed, and experiments were conducted with the ions accelerated to >40 kV

Utility and Usability of Laser Speckle Contrast Imaging (LSCI) for Displaying Real-Time Tissue Perfusion/Blood Flow in Robot-Assisted Surgery (RAS): Comparison to Indocyanine Green (ICG) and Use in Laparoscopic Surgery.

BACKGROUND: Utility and usability of laser speckle contrast imaging (LSCI) in detecting real-time tissue perfusion in robot-assisted surgery (RAS) and laparoscopic surgery are not known. LSCI displays a color heatmap of real-time tissue blood flow by capturing the interference of coherent laser light on red blood cells. LSCI has advantages in perfusion visualization over indocyanine green imaging (ICG) including repeat use on demand, no need for dye, and no latency between injection and display. Herein, we report the first-in-human clinical comparison of a novel device combining proprietary LSCI processing and ICG for real-time perfusion assessment during RAS and laparoscopic surgeries. METHODS: ActivSight™ imaging module is integrated between a standard laparoscopic camera and scope, capable of detecting tissue blood flow via LSCI and ICG in laparoscopic surgery. From November 2020 to July 2021, we studied its use during elective robotic-assisted and laparoscopic cholecystectomies, colorectal, and bariatric surgeries (NCT# 04633512). For RAS, an ancillary laparoscope with ActivSight imaging module was used for LSCI/ICG visualization. We determined safety, usability, and utility of LSCI in RAS vs. laparoscopic surgery using end-user/surgeon human factor testing (Likert scale 1-5) and compared results with two-tailed t tests. RESULTS: 67 patients were included in the study-40 (60%) RAS vs. 27 (40%) laparoscopic surgeries. Patient demographics were similar in both groups. No adverse events to patients and surgeons were observed in both laparoscopic and RAS groups. Use of an ancillary laparoscopic system for LSCI/ICG visualization had minimal impact on usability in RAS as evidenced by surgeon ratings of device usability (set-up 4.2/5 and form-factor 3.8/5). LSCI ability to detect perfusion (97.5% in RAS vs 100% in laparoscopic cases) was comparable in both RAS and laparoscopic cases. CONCLUSIONS: LSCI demonstrates comparable utility and usability in detecting real-time tissue perfusion/blood flow in RAS and laparoscopic surgery

A Feasibility Study Of Administering The Electronic Research And Development Culture Index To The Multidisciplinary Workforce In A UK Teaching Hospital.

Purpose: The study aims were: (i) to convert the Research and Development Culture Index (a validated rating instrument for assessing the strength of organizational Research and Development culture) into electronic format (eR&DCI), and (ii) to test the format and assess the feasibility of administering it to the multidisciplinary (allied health professionals, doctors and nurses) workforce in a National Health Service Hospital (NHS) in the United Kingdom (UK) by trialing it with the workforce of the tertiary Children's Hospital within the organization. Population and methods: The eR&DCI was emailed to all professional staff (n=907) in the Children's Hospital. Data were analyzed using IBM SPSS Statistics 22. Results: The eR&DCI was completed by 155 respondents (doctors n=38 (24.52%), nurses n=79 (50.96%) and allied health professionals (AHPs) n=38 (24.52%)). The response rate varied by professional group: responses were received from 79 out of 700 nurses (11%); 38 out of 132 doctors (29%) and 38 out of 76 AHPs (50%). Index scores demonstrated a positive research culture within the multidisciplinary workforce. Survey responses demonstrated differences between the professions related to research training and engagement in formal research activities. Conclusion: This is the first study to assess the feasibility of assessing the strength of an organization's multidisciplinary workforce research and development (R&D) culture by surveying that workforce using the eR&DCI. We converted the index to "Online Surveys" and successfully administered it to the entire multidisciplinary workforce in the Children's Hospital. We met our criteria for feasibility: ability to administer the survey and a response rate comparable with similar studies. Uptake could have been increased by also offering the option of the paper-based index for self-administration. Results of the survey are informing delivery of the research strategy in the Children's Hospital. This methodology has potential application in other healthcare contexts

Baryons at the Edge of the X-ray Brightest Galaxy Cluster

Studies of the diffuse X-ray emitting gas in galaxy clusters have provided powerful constraints on cosmological parameters and insights into plasma astrophysics. However, measurements of the faint cluster outskirts have become possible only recently. Using data from the Suzaku X-ray telescope, we determined an accurate, spatially resolved census of the gas, metals, and dark matter out to the edge of the Perseus Cluster. Contrary to previous results, our measurements of the cluster baryon fraction are consistent with the expected universal value at half of the virial radius. The apparent baryon fraction exceeds the cosmic mean at larger radii, suggesting a clumpy distribution of the gas, which is important for understanding the ongoing growth of clusters from the surrounding cosmic web.Comment: Accepted for publicatio

The [N II] 205μm Emission in Local Luminous Infrared Galaxies

In this paper, we present the measurements of the [N II] 205 μm line for a flux-limited sample of 122 (ultra-)luminous infrared galaxies [(U)LIRGs] and 20 additional normal galaxies, obtained with the Herschel Space Observatory (Herschel). We explore the far-infrared (FIR) color dependence of the [N II] 205 μm (L_([N II]205μm)) to the total infrared (L_(IR)) luminosity ratio, and find that L_([N II]205μm)/L_(IR) only depends modestly on the 70–160 μm flux density ratio (f_(70)/f_(160)) when f_(70)/f_(160) ≾ 0.6, whereas such dependence becomes much steeper for f_(70/f_(160) > 0.6. We also investigate the relation between L_([N II]205μm) and star formation rate (SFR), and show that L_([N II]205μm) has a nearly linear correlation with SFR, albeit the intercept of such a relation varies somewhat with f_(60)/f_(100), consistent with our previous conclusion that [N II] 205 μm emission can serve as an SFR indicator with an accuracy of ~0.4 dex, or ~0.2 dex if f_(60)/f_(100) is known independently. Furthermore, together with the Infrared Space Observatory measurements of [N II], we use a total of ~200 galaxies to derive the local [N II] 205 μm luminosity function (LF) by tying it to the known IR LF with a bivariate method. As a practical application, we also compute the local SFR volume density (ṗ_(SFR)) using the newly derived SFR calibrator and LF. The resulting log ṗ_(SFR) = -1.96 ± 0.11 M_☉ yr^(−1) Mpc^(−3) agrees well with previous studies. Finally, we determine the electron densities (n_e) of the ionized medium for a subsample of 12 (U)LIRGs with both [N II] 205 μm and [N II] 122 μm data, and find that n_e is in the range of ~1–100 cm^(−3), with a median value of 22 cm^(−3)