Low Temperature Dielectric Strength of Polyimide-Silica Nanocomposites for Applications in High-Temperature Superconducting Cables

Gaseous helium is often considered as an alternative to liquid nitrogen to cool modern high-temperature superconducting cables in support of increased power capacity and/or reduction of required cable size. However, the small size of helium molecules and relatively poor dielectric strength of helium gas create challenges which limit the usefulness of modern cable dielectrics. Continuous dielectric coatings have been considered as an alternative to traditional lapped tape dielectrics to support gaseous helium refrigerants, but unmatched thermal contraction between the coating and cable components would induce failures due to mechanical stress. Composite materials have been considered as a means of matching rates of thermal expansion to that of superconducting cables while retaining excellent withstanding against strong electric fields. Polyimide/silicon dioxide nanocomposites are a promising candidate for this application and are examined as such in this work. Nanocomposite films of various filler concentrations up to 7% were produced and tested for their dielectric strength at both room temperature and approximately 90 K. Despite a slight reduction in dielectric strength with increased nanoparticle concentrations at room temperature, the results suggest that polyimide provides ample dielectric strength as a composite matrix in superconducting cable dielectrics

No Tension: JWST Galaxies at z>10z > 10 Consistent with Cosmological Simulations

Recent observations by JWST have uncovered galaxies in the very early universe via the JADES and CEERS surveys. These galaxies have been measured to have very high stellar masses with substantial star formation rates. There are concerns that these observations are in tension with the $\Lambda$CDM model of the universe, as the stellar masses of the galaxies are relatively high for their respective redshifts. Recent studies have compared the JWST observations with large-scale cosmological simulations. While they were successful in reproducing the galaxies seen in JADES and CEERS, the mass and spatial resolution of these simulations were insufficient to fully capture the early assembly history of the simulated galaxies. In this study, we use results from the Renaissance simulations, which are a suite of high resolution simulations designed to model galaxy formation in the early universe. We find that the most massive galaxies in Renaissance have stellar masses and star formation rates that are entirely consistent with the observations from the JADES and CEERS surveys. The exquisite resolution afforded by Renaissance allows us to model the build-up of early galaxies from stellar masses as low as 10$^4$ M$_\odot$ up to a maximum stellar mass of a few times 10$^{7}$ M$_\odot$. Within this galaxy formation paradigm, we find excellent agreement with JADES and CEERS. We find no tension between the $\Lambda$CDM model and current JWST measurements. As JWST continues to explore the high redshift universe, high resolution simulations, such as Renaissance, will continue to be crucial in understanding the formation history of early embryonic galaxies.Comment: 9 pages, 5 figures. Accepted for Publication in The Open Journal of Astrophysic

Luminescence spectroscopy of matrix-isolated z 6P state atomic manganese

The relaxation of electronically excited atomic manganese isolated in solid rare gas matrices is observed from recorded emission spectra, to be strongly site specific. z 6P state excitation of Mn atoms isolated in the red absorption site in Ar and Kr produces narrow a 4D and a 6D state emissions while blue-site excitation produces z 6P state fluorescence and broadened a 4D and a 6D emissions. Mn/Xe exhibits only a single thermally stable site whose emission at 620 nm is similar to the broad a 6D bands produced with blue-site excitation in Ar and Kr. Thus in ArsKrd, excitation of the red site at 393 s400d nm produces narrow line emissions at 427.5 s427.8d and 590 s585.7d nm. From their spectral positions, linewidths, and long decay times, these emission bands are assigned to the a 4D7/2 and a 6D9/2 states, respectively. Excitation of the blue site at 380 s385.5d nm produces broad emission at 413 s416d nm which, because of its nanosecond radiative lifetime, is assigned to resonance z 6P!a 6S fluorescence. Emission bands at 438 s440d and 625 s626.8d nm, also produced with blue-site excitation, are broader than their red-site equivalents at 427.5 and 590 nm s427.8 and 585.7 nm in Krd but from their millisecond and microsecond decay times are assigned to the a 4D and a 6D states. The line features observed in high resolution scans of the red-site emission at 427.5 and 427.8 nm in Mn/Ar and Mn/ Kr, respectively, have been analyzed with the Wp optical line shape function and identified as resolved phonon structure originating from very weak sS=0.4d electron-phonon coupling. The presence of considerable hot-phonon emission seven in 12 K spectrad and the existence of crystal field splittings of 35 and 45 cmâ1 on the excited a 4D7/2 level in Ar and Kr matrices have been identified in Wp line shape fits. The measured matrix lifetimes for the narrow red-site a 6D state emissions s0.29 and 0.65 msd in Ar and Kr are much shorter than the calculated s3 sd gas phase value. With the lifetime of the metastable a 6D9/2 state shortened by four orders of magnitude in the solid rare gases, it is clear that the probability of the âforbiddenâ a 6D!a 6S atomic transition is greatly enhanced in the solid state. A novel feature identified in the present work is the large width and shifted 4D and 6D emissions produced for Mn atoms isolated in the blue sites of Ar and Kr. In contrast, these states produce narrow, unshifted sgas-phase-liked 4D and 6D state emissions from the red site

Laser excitation spectroscopy of the A and B states of jet-cooled copper dimer: evidence for large electronic isotope shifts

Journal ArticleFluorescence excitation spectra recorded for the A-X system of jet-cooled Cu2 show conclusive evidence of a ?? = 0 transition, and the A state is thereby definitively assigned as ??u+. A previous assignment of the B state as ??u+ is confirmed, but the vibrational levels of this state are complicated by the presence of a perturbation at v' = 0. The perturbing state does not, however, appear to be either of the two optically accessible electronic states in this spectral region. Anomalously large electronic isotope shifts are observed for the A and B states, and this behavior is discussed in terms of the correspondingly large "specific mass shifts" observed in the optical spectra of atomic copper for transitions that couple states differing in the number of d electrons. Due to the large spin-orbit coupling constants in the "cMiole" configurations, it is proposed that the low-energy-excited molecular states of Cu2 derived from these configurations should be described by Hund's case (c) coupling. Dynamical effects observed in the gas phase and in solid matrices are briefly discussed in terms of this bonding scheme

Grizzly bears in Yellowstone National Park

AbstractThe problem we solved is based on the population of grizzly bears at Yellowstone National Park. Since this population is currently declining, our specific problem centered around a seed group of 52 grizzlies, transported from Yellowstone to another area in the Northwestern United States, similar in climate and availability of proper food. The total land area available for the bears is 1.5 million acres, enough land for 100 bears to thrive. Our problem was to find a harvesting policy to sustain the maximum number of grizzlies on this land.Using the matrix equation Lxi=xi+1 we determined tha this seed population would exceed the level the land area can maintain after 14 years. At this point we began to implement our harvesting procedures. Assuming the bears would be harvested at random, producing a uniform harvesting rate for each age group, we used the matrix equation Lx−HLx=x to solve for a total of 3 percent harvesting yearly after the fourteenth year. Test results confirmed the accuracy of our matrix values

Enantioselective synthesis of non-proteinogenic 2-arylallyl-α-amino acids via Pd/In catalytic cascades

An efficient synthesis of both R- and S-enantiomers of 2-arylallyl-α-amino acids via a diastereoselective Pd/In mediated catalytic allylation of chiral N-sulfinyl-α-imino esters is described. The potential for further enhancement of molecular complexity and creating contiguous chiral centres by interfacing these processes with catalytic cyclisation–anion capture methodology is demonstrated

Gene Therapy With RALA/iNOS Composite Nanoparticles Significantly Enhances Survival In A Model Of Metastatic Prostate Cancer

Abstract Background Recent approvals of gene therapies by the FDA and the EMA for treatment of inherited disorders have further opened the door for assessment of nucleic acid pharmaceuticals for clinical usage. Arising from the presence of damaged or inappropriate DNA, cancer is a condition particularly suitable for genetic intervention. The RALA peptide has been shown to be a potent non-viral delivery platform for nucleic acids. This study examines the use of RALA to deliver a plasmid encoding inducible nitric oxide synthase (iNOS) as an anti-cancer treatment. Methods The physiochemical properties of the RALA/DNA nanoparticles were characterized via dynamic light scattering and transmission electron microscopy. The nanoparticles were labelled with fluorophores and tracked over time using confocal microscopy with orthogonal sections to determine cellular location. In vitro studies were employed to determine functionality of the nanoparticles both for pEGFP-N1 and CMV-iNOS. Nanoparticles were injected intravenously into C57/BL6 mice with blood and serum samples analysed for immune response. PC3-luc2M cells were injected into the left ventricle of SCID mice followed by treatment with RALA/CMV-iNOS nanoparticles to evaluate the tumour response in a metastatic model of prostate cancer. Results Functional cationic nanoparticles were produced with gene expression in PC-3 prostate cancer cells. Furthermore, repeated administrations of RALA/DNA nanoparticles into immunocompetent mice did not produce any immunological response: neutralization of the vector or release of inflammatory mediators. RALA/CMV-iNOS reduced the clonogenicity of PC-3 cells in vitro, and in an in vivo model of prostate cancer metastasis, systemically delivered RALA/CMV-iNOS significantly improved the survival of mice. Conclusion These studies further validate RALA as a genetic cargo delivery vehicle and iNOS as a potent therapy for the treatment of cancer

Rapid microplate rotations and backarc rifting at the transition between collision and subduction

ABSTRACT Using global positioning system velocities from convergent plate boundaries in Papua New Guinea, New Zealand, Tonga, Vanuatu, and the Marianas, we note a spatial correlation between rapid tectonic block rotations and the transition from subduction to collision. We present a mechanism for the block rotations, in which the change from collision of a buoyant indentor to normal subduction exerts a torque on the upper-plate microplate. This work improves our understanding of the causes of rapid vertical axis rotations, often observed in paleomagnetic studies. We also show how collision-induced rotations may lead to backarc rifting

Spectroscopic characterization of the Zn(4s(2))center dot Ne[(1)Sigma(+)] and Zn(4s4p pi)center dot Ne[(1)Pi(1)] van der Waals states

The Zn(4s2)·Ne[1Σ+] and the Zn(4s4pπ)·Ne[1Π1] states have been characterized by laser-induced fluorescence spectroscopy. Bond lengths were determined from simulations of the partially-resolved rotational structure of the 1Π ← 1Σ+ transitions, while bond strengths were estimated from a Birge–Sponer extrapolation with allowance for consistent errors resulting from similar procedures in the analogous Cd·Ne and Hg·Ne transitions. The van der Waals bonding in these states is discussed briefly and compared to that in the analogous M·RG states, where M=Mg, Zn, Cd, Hg and RG=Ne, Ar, Kr, Xe

Spectroscopic characterization of the Zn(4s(2))center dot Ne[(1)Sigma(+)] and Zn(4s4p pi)center dot Ne[(1)Pi(1)] van der Waals states

The Zn(4s2)·Ne[1Σ+] and the Zn(4s4pπ)·Ne[1Π1] states have been characterized by laser-induced fluorescence spectroscopy. Bond lengths were determined from simulations of the partially-resolved rotational structure of the 1Π ← 1Σ+ transitions, while bond strengths were estimated from a Birge–Sponer extrapolation with allowance for consistent errors resulting from similar procedures in the analogous Cd·Ne and Hg·Ne transitions. The van der Waals bonding in these states is discussed briefly and compared to that in the analogous M·RG states, where M=Mg, Zn, Cd, Hg and RG=Ne, Ar, Kr, Xe