We recently reported on the radio-frequency attenuation length of cold polar ice at Summit Station, Greenland, based on bi-static radar measurements of radio-frequency bedrock echo strengths taken during the summer of 2021. Those data also allow studies of (a) the relative contributions of coherent (such as discrete internal conducting layers with sub-centimeter transverse scale) vs incoherent (e.g. bulk volumetric) scattering, (b) the magnitude of internal layer reflection coefficients, (c) limits on signal propagation velocity asymmetries (‘birefringence’) and (d) limits on signal dispersion in-ice over a bandwidth of ~100 MHz. We find that (1) attenuation lengths approach 1 km in our band, (2) after averaging 10 000 echo triggers, reflected signals observable over the thermal floor (to depths of ~1500 m) are consistent with being entirely coherent, (3) internal layer reflectivities are ≈–60$\to$–70 dB, (4) birefringent effects for vertically propagating signals are smaller by an order of magnitude relative to South Pole and (5) within our experimental limits, glacial ice is non-dispersive over the frequency band relevant for neutrino detection experiments.

Over the last 25 years, radiowave detection of neutrino-generated signals, using cold polar ice as the neutrino target, has emerged as perhaps the most promising technique for detection of extragalactic ultra-high energy neutrinos (corresponding to neutrino energies in excess of 0.01 Joules, or 1017 electron volts). During the summer of 2021 and in tandem with the initial deployment of the Radio Neutrino Observatory in Greenland (RNO-G), we conducted radioglaciological measurements at Summit Station, Greenland to refine our understanding of the ice target. We report the result of one such measurement, the radio-frequency electric field attenuation length $L_\alpha$. We find an approximately linear dependence of $L_\alpha$ on frequency with the best fit of the average field attenuation for the upper 1500 m of ice: $\langle L_\alpha \rangle = ( ( 1154 \pm 121) - ( 0.81 \pm 0.14) \, ( \nu /{\rm MHz}) ) \,{\rm m}$ for frequencies ν ∈ [145 − 350] MHz.

Mg-Mn amphibole (tirodite), with or without pyroxmangite in the total absence of pyroxenes and high-calcic pyroxenoids, occurs in the Mn silicate rocks of the Sausar Group, India. The rocks were metamorphosed to amphibolite facies condition (T ∼ 650°C, P ∼ 6 kbar). Tirodite-pyroxmangite pairs developed in both carbonate-free and rhodochrosite-bearing assemblages. Also tirodite coexists with either kutnahorite or manganoan calcite in the absence of pyroxmangite. Mineral reactions inferred from modal abundances and compositions of the phases indicate stabilization of the amphibole alone from a bivalent cation-bearing residual unbuffered XCO2 system with XMn < 0.3. On the other hand, tirodite-pyroxmangite pairs appeared in unbuffered low to intermediate XCO2 assemblages with XMn > 0.35. Pyroxenes and high-calcic pyroxenoids did not appear in the present situation, though they occur elsewhere in rocks with broadly similar contents of immobile components. Closely associated assemblages of diverse mineralogy suggest that the XMn and XCO2, rather than the physical conditions of metamorphism, are the decisive factors in promoting the observed phase assemblages.

Myelin basic protein (MBP) is an antigenic component of circulating immune complexes (CIC) in patients with multiple sclerosis (MS). Immune complexes were isolated from the sera by adsorption to Raji cells and then acid eluted. Final identification of MBP from Raji eluates was done by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by MBP radioimmunoassay (RIA) of gel eluates and by an immunoblot technique.

Double Alfvén wave solutions of the magnetohydrodynamic equations in which the physical variables (the gas density ρ, fluid velocity u, gas pressure p, and magnetic field induction B) depend only on two independent wave phases ϕ1(x,t) and ϕ2(x,t) are obtained. The integrals for the double Alfvén wave are the same as for simple waves, namely, the gas pressure, magnetic pressure, and group velocity of the wave are constant. Compatibility conditions on the evolution of the magnetic field B due to changes in ϕ1 and ϕ2, as well as constraints due to Gauss's law ∇ · B = 0 are discussed. The magnetic field lines and hodographs of B in which the tip of the magnetic field B moves on the sphere |B| = B = const. are used to delineate the physical characteristics of the wave. Hamilton's equations for the simple Alfvén wave with wave normal n(ϕ), and with magnetic induction B(ϕ) in which ϕ is the wave phase, are obtained by using the Frenet–Serret equations for curves x=X(ϕ) in differential geometry. The use of differential geometry of 2D surfaces in a 3D Euclidean space to describe double Alfvén waves is briefly discussed.

We perform a fully self-consistent three-dimensional numerical simulation for a compressible, dissipative magnetoplasma driven by large-scale perturbations, that contain a fairly broad spectrum of characteristic modes, ranging from largest scales to intermediate scales and down to the smallest scales, where the energy of the system is dissipated by collisional (ohmic) and viscous dissipations. Additionally, our simulation includes nonlinear interactions amongst a wide range of fluctuations that are initialized with random spectral amplitudes, leading to the cascade of spectral energy in the inertial range spectrum, and takes into account large-scale as well as small-scale perturbations that may have been induced by the background plasma fluctuations, as well as the non-adiabatic exchange of energy leading to the migration of energy from the energy-containing modes or randomly injected energy driven by perturbations and further dissipated by the smaller scales. Besides demonstrating the comparative decays of the total energy and the dissipation rate of the energy, our results show the existence of a perpendicular component of the current, thus clearly confirming that the self-organized state is non-force free.

The usual theory of plasma relaxation, based on the selective decay of magnetic energy over the (global) magnetic helicity, predicts a force-free state for a plasma. Such a force-free state is inadequate to describe most realistic plasma systems occurring in laboratory and space plasmas as it produces a zero pressure gradient and cannot couple magnetic fields with flow. A different theory of relaxation has been proposed by many authors, based on a well-known principle of irreversible thermodynamics, the principle of minimum entropy production rate which is equivalent to the minimum dissipation rate of energy. We demonstrate the applicability of minimum dissipative relaxed states to various self-organized systems of magnetically confined plasma in the laboratory and in the astrophysical context. Such relaxed states are shown to produce a number of basic characteristics of laboratory plasma confinement systems and solar arcade structure.

Diamond-like carbon films were synthesized by electro-deposition technique from an organic liquid (a solution of alpha- and beta-pinenes in n-hexane) on silicon substrate at room temperature and at room pressure. The x-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectra, Raman spectra, photoluminescence (PL), and x-ray absorption near edge structure (XANES) spectra analysis were used to study the properties of the diamond-like carbon (as-deposited and annealed) films. The XRD measurement indicated that the film contains some diamond-crystalline phases whereas Raman spectra did not show any prominent diamond-like peak. PL intensity as higher for the as-deposited film and decreased with high-temperature vacuum annealing. FTIR spectra showed the presence of sp3 hybridization C–H bonds and their intensity decreases at higher annealing temperature. C and O K-edge XANES spectra showed that π* (sp2) intensity significantly decreases when the annealing temperature is 600 °C.

Nitric oxide (NO) aided Si0.85Ge0.15 wet-oxynitridation has been performed at 400 700°C, while the wet-NO feed gas was preheated to higher temperatures before entering the reaction zone. X-Ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) data suggests that both nitrogen and oxygen incorporation increases within the dielectric bulk with increasing wet-oxynitridation temperature, while there is no apparent germanium segregation towards the dielectric/substrate interface at all temperatures studied. Angle-resolved XPS analysis shows that increase in wetoxynitridation temperature above 600°C is likely to volatilize some germanium oxide from the surface region. Nitrogen incorporation is found to hinder germanium segregation. These results are discussed in the context of an overall mechanism of SiGe wet-oxynitridation.

X-Ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and spectral ellipsometry have been used to study sub-35 Å low temperature oxynitrides of SiGe. The oxynitridations steps have been performed at 550°C and 650°C, while the oxynitridation feed gases have been preheated to 900°C and 1000°C, respectively, before entering the reaction zone. XPS and SIMS data suggests that NO-assisted oxynitridation incorporates more nitrogen than the N2O-assisted one, while there is minimal Ge segregation towards the dielectric/substrate interface in both oxynitridation processes. SIMS data suggests that the nitrogen is distributed throughout the film in contrast to high temperature Si oxynitridation where nitrogen incorporation takes place near the dielectric/substrate interface. Spectral Ellipsometry has been used to measure the final thickness of the oxynitrides film. These results are discussed in the context of an overall mechanism of the oxynitridation of SiGe.

Thermally grown Si3N4 films in NH3 are known to have a higher dielectric constant and a higher N concentration than silicon oxynitrides, although they incorporate hydrogen atoms that induce hot electron carriers during subsequent high temperature processing. Further, a silicon nitride is difficult to grow over about 6 nm thick, due to self-limiting growth. One alternative is SiOxNy post-nitrided with NH3.

In this work, we study the scope of improvement of Ar annealed nitrided oxynitrides as a function of annealing temperature and duration. Secondary ion mass spectroscopy (SIMS) studies of the nitrogen and hydrogen profiles suggest increasing N and H removal with increasing annealing time and temperature. Electrical characterizations have been performed to determine the total charge (Qox) and interface trap (Dit) densities at different processing conditions, before and after the annealing step. Post-annealing steps are not found to yield improvements of the electrical properties of these dielectric films. Instead, sometimes Qox is even seen to increase (e.g., after a 30 min Ar anneal at 1000 °C). Therefore, an optimization of such annealing steps is essential in designing nanodielectrics with desired nitrogen amounts and N concentration profiles as well as in understanding related process-structure-function relationships.

Thin films of aluminum oxide were deposited on silicon nitride thin films using trimethylaluminum and oxygen at 0.5 Torr and 300 °C. Fourier transform infrared (FTIR) and x-ray photoelectron spectroscopic (XPS) analyses of these films showed no aluminum silicate phase at the film-substrate interface. The O/Al ratio in the deposited film was found to be higher than that in stoichiometric Al2O3 indicating the presence of excess oxygen. FTIR spectroscopy and XPS of the annealed samples did not show any formation of silicon oxide, oxynitride or silicate at the aluminum oxide/silicon nitride interface. In contrast to aluminum oxide on clean silicon substrates, using ultrathin silicon nitride as a barrier layer could prevent excess oxygen migration towards the Si substrate and formation of any interfacial layers.

The presence of nitrogen in the dielectric films is known to impart highly desirable properties in the ultra-large-scale-integration era; the position, amount and concentration profiles of nitrogen are therefore of great interest. In this work, we investigate two-step processes leading to bimodal nitrogen profiles, with one nitrogen peak near the Si/dielectric interface and the other near the dielectric surface. At 1000°C and 1 atm, a nitridation step with NH3 following either an oxidation (in O2) or oxynitridation (in N2O) step is found to result in a bimodal nitrogen concentration profile for short nitridation times. Increasing the duration of the nitridation step with NH3 is found to completely nitridate the entire film. Secondary Ion Mass, Angle Resolved X-Ray Photoelectron, and Fourier Transform Infrared Spectroscopic studies are shown to support these observations. Therefore, based on such process-property-structure relationships, the engineering of desired nitrogen concentration profiles in nano-dielectric materials of interest becomes possible. Such knowledge may have significant implications on micro- and nano-electronic applications of silicon oxynitrides.

We describe the screened Korringa-Kohn-Rostoker (KKR) method and the third-generation linear muffin-tin orbital (LMTO) method for solving the single-particle Schrödinger equation for a MT potential. In the screened KKR method, the eigenvectors CRL,i are given as the non-zero solutions, and the energies εi as those for which such solutions can be found, of the linear homogeneous equations: , where Ka (ε) is the screened KKR matrix. The screening is specified by the boundary condition that, when a screened spherical wave is expanded in spherical harmonics YR′L′ (ȓR′) about its neighboring sites R′, then each component either vanishes at a radius, rR′=aR′L′, or is a regular solution at that site. When the corresponding “hard” spheres are chosen to be nearly touching, then the KKR matrix is usually short ranged and its energy dependence smooth over a range of order 1 Ry around the centre of the valence band. The KKR matrix, K (εν), at a fixed, arbitrary energy turns out to be the negative of the Hamiltonian, and its first energy derivative, K (εν), to be the overlap matrix in a basis of kinked partial waves, φRL (εν, rR), each of which is a partial wave inside the MT-sphere, tailed with a screened spherical wave in the interstitial, or taking the other point of view, a screened spherical wave in the interstitial, augmented by a partial wave inside the sphere. When of short range, K (ε) has the two-centre tight-binding (TB) form and can be generated in real space, simply by inversion of a positive definite matrix for a cluster. The LMTOs, χRL (εν), are smooth orbitals constructed from φRL(εν, rR) and φRL(εν, rR), and the Hamiltonian and overlap matrices in the basis of LMTOs are expressed solely in terms of K (εν) and its first three energy derivatives. The errors of the single-particle energies εi obtained from the Hamiltonian and overlap matrices in the φ(εν)- and χ(εν) bases are respectively of second and fourth order in εi – εi. Third-generation LMTO sets give wave functions which are correct to order εi – εν, not only inside the MT spheres, but also in the interstitial region. As a consequence, the simple and popular formalism which previously resulted from the atomic-spheres approximation (ASA) now holds in general, that is, it includes downfolding and the combined correction. Downfolding to few-orbital, possibly short-ranged, low-energy, and possibly orthonormal Hamiltonians now works exceedingly well, as is demonstrated for a high-temperature superconductor. First-principles sp3 and sp3d5 TB Hamiltonians for the valence and lowest conduction bands of silicon are derived. Finally, we prove that the new method treats overlap of the potential wells correctly to leading order and we demonstrate how this can be exploited to get rid of the empty spheres in the diamond structure.