The Unique Properties of Superconductivity in Cuprates

Copper oxides are the only materials that have transition temperatures, T _c, well above the boiling point of liquid nitrogen, with a maximum \(T_{\mathrm {c}}^{\mathrm {m}}\) of 162 K under pressure. Their structure is layered, with one to several CuO₂ planes, and upon hole doping, their transition temperature follows a dome-shaped curve with a maximum of \(T_{\mathrm {c}}^{\mathrm {m}}\) . In the underdoped regime, i.e., below \(T_{\mathrm {c}}^{\mathrm {m}}\) , a pseudogap Δ* ∝ T* is found, with T* always being larger than T _c, a property unique to the copper oxides. In the superconducting state, Cooper pairs (two holes with antiparallel spins) are formed that exhibit coherence lengths on the order of a lattice distance in the CuO₂ plane and one order of magnitude less perpendicular to it. Their macroscopic wave function is parallel to the CuO₂ plane near 100 % d at their surface, but only 75 % d and 25 % s in the bulk, and near 100 % s perpendicular to the plane in yttrium barium copper oxide (YBCO) [1]. There are two gaps with the same T _c [2]. As function of doping, the oxygen isotope effect is novel and can be quantitatively accounted for by a vibronic theory or by the presence of bipolarons [2, 3]. These cuprates are intrinsically heterogeneous in a dynamic way. In terms of quasiparticles, bipolarons are present at low doping and aggregate upon cooling [2] so that probably ramified clusters and/or stripes are formed, leading over to a more Fermi liquid-type behavior at large carrier concentrations.     

Optimal choice of test signals for linear channel estimation using second order statistics

A time-varying acoustic channel may be estimated by an appropriate inference using the output from a periodic test signal. In this paper it is shown how to do this in a way that takes full account of the past history of the background noise and the past history of the channel. An explicit formula is obtained for the optimal linear estimator that may be used for rapid channel estimation for a given test signal when we know the autocovariance or power spectrum of the interfering noise and the autocovariance of the echo channel variation. Given this closed formula for the optimal estimator of the channel impulse response, an efficient method for determining the optimal test signal, subject to a constraint on the test signal power, given the history of the channel and the noise, is developed. We show that if the second order statistics of the channel or the noise are known, then the optimal test signal is not white. The method includes an explicit formula for the optimal test signal given a fixed estimator. A model of channel variation which is realistic while having less complexity than a full second-order statistical model, and therefore is more amenable to robust estimation, is used in the experiments which illustrate the performance of the optimal test signals and the channel estimation method. Matrix calculus identities required for the derivation of this expression for the optimal estimator are stated and proved in the Appendixes 1 and 2.     

Accurate Simulations of ^{206}Pb Recoils in SuperCDMS

SuperCDMS is a direct detection search for WIMPs, currently operating a 9 kg array of germanium detectors in the Soudan Underground Laboratory. The detectors, known as iZIPs, are cylindrical in shape and each flat surface is instrumented with both ionization and phonon sensors. Charge and phonon information is collected for each event, and comparing the energy collected in the phonon sensors to the charge sensors gives excellent discrimination power between nuclear recoil and electron recoil events. Furthermore, this technology provides excellent discrimination between surface and bulk events. In order to show the surface event rejection capability of these detectors, two \(^{210}\) Pb sources were installed facing two of the detectors currently operating in the Soudan experimental run. The \(^{210}\) Pb decays to \(^{210}\) Bi, which in turn decays to \(^{210}\) Po. The \(^{210}\) Po decays by alpha emission, yielding a recoiling \(^{206}\) Pb ion with 103 keV kinetic energy and an alpha particle with 5.4 MeV kinetic energy. We used the non-standard Screened Nuclear Recoil Physics List (Mendenhall and Weller, Nucl. Instrum. Methods Phys. Res. B 227:420–430, 2005) in Geant4 (Agostinelli et al., Nucl. Instrum. Methods Phys. Res. Sect. A 506:250–303, 2003) to simulate all of the above decays and achieve excellent agreement with experiment. The focus of this paper is the simulation of the \(^{210}\) Po decay.     

Fabrication of Nb/Al Superconducting Tunnel Junction Using Ozone Gas

An ozone (O \(_{3})\) oxidation process was introduced for Nb/Al-based superconducting tunnel junctions (STJs) in order to form defect-free tunnel barriers at high critical current and to improve the energy resolution ( \(\Delta E\) ) for X-rays. The dependence of critical current ( \(J_\mathrm{C})\) and leak current ( \(I_\mathrm{leak})\) on the O \(_{3}\) exposure was measured to optimize the oxidation condition. The 50-square- \(\upmu \) m STJs produced by the O \(_{3}\) oxidation process exhibited an extremely small \(I_\mathrm{leak}\) of less than 50 pA. As expected, the lower or shorter the O \(_{3}\) exposure, the higher \(J_\mathrm{C}\) and the smaller the normal resistance ( \(R_\mathrm{N})\) . However, the maximum \(J_\mathrm{C}\) was 8 A/cm \(^{2}\) at an O \(_{3}\) exposure of 0.72 Pa min, which is much smaller than those of STJs with the conventional O \(_{2}\) oxidation process. It is expected that the high \(J_\mathrm{C}\) of 1,000 A/cm \(^{2}\) , at which a 9-eV-energy resolution for 277 eV photons is predicted, can be reached by an O \(_{3}\) exposure of 3.5 \(\times \) 10 \(^{-4}\) Pa min.     

On the automorphism group of a binary self-dual [120, 60, 24] code

We prove that an automorphism of order 3 of a putative binary self-dual $[120, 60, 24]$ [ 120 , 60 , 24 ] code $C$ C has no fixed points. Moreover, the order of the automorphism group of $C$ C divides $2^a\cdot 3 \cdot 5\cdot 7\cdot 19\cdot 23\cdot 29$ 2 a · 3 · 5 · 7 · 19 · 23 · 29 with $a\in \mathbb N _0$ a ∈ N 0 . Automorphisms of odd composite order $r$ r may occur only for $r=15, 57$ r = 15 , 57 or $r=115$ r = 115 with corresponding cycle structures $3 \cdot 5$ 3 · 5 - $(0,0,8;0), 3\cdot 19$ ( 0 , 0 , 8 ; 0 ) , 3 · 19 - $(2,0,2;0)$ ( 2 , 0 , 2 ; 0 ) or $5 \cdot 23$ 5 · 23 - $(1,0,1;0)$ ( 1 , 0 , 1 ; 0 ) respectively. In case that all involutions act fixed point freely we have $|\mathrm{Aut}(C)| \le 920$ | Aut ( C ) | ≤ 920 , and $\mathrm{Aut}(C)$ Aut ( C ) is solvable if it contains an element of prime order $p \ge 7$ p ≥ 7 . Moreover, the alternating group $\mathrm{A}_5$ A 5 is the only non-abelian composition factor which may occur in $\mathrm{Aut}(C)$ Aut ( C ) .     

Crystal growth and magnetic property of YFeO 3 crystal

YFeO $_{\boldsymbol 3}$ and other rare earth substituted crystals with distorted orthorhombic pervoskite-like structure (space group, Pbnm) have attracted much attention due to their remarkable magnetic properties of primary significance for technological applications. In the present work, the floating zone growth of YFeO $_{\boldsymbol 3}$ crystals has been systematically investigated and high quality YFeO $_{\boldsymbol 3}$ crystal was obtained by optimized process. The magnetic properties of YFeO $_{\boldsymbol 3}$ crystal were investigated, and it indicated the high magneto-optical property in YFeO $_{\boldsymbol 3}$ crystals with specific orientation due to its anisotropy. YFeO $_{\boldsymbol 3}$ crystals display superior performance in the application magneto-optical current sensors and fast latching optical switches.     

Spherical and rod-like Gd 2 O 3 :Eu 3?+? nanophosphors—Structural and luminescent properties

A comparative study of spherical and rod-like nanocrystalline Gd $_{\boldsymbol 2}$ O $_{\boldsymbol 3}$ :Eu $^{\boldsymbol{3+}}$ (Gd $_{\boldsymbol{1\cdot92}}$ Eu $_{\boldsymbol{0\cdot08}}$ O $_{\boldsymbol 3}$ ) red phosphors prepared by solution combustion and hydrothermal methods have been reported. Powder X-ray diffraction (PXRD) results confirm the as-formed product in combustion method showing mixed phase of monoclinic and cubic of Gd $_{\boldsymbol 2}$ O $_{\boldsymbol 3}$ :Eu $^{\boldsymbol{3+}}$ . Upon calcinations at 800 $^{\boldsymbol\circ}$ C for 3?h, dominant cubic phase was achieved. The as-formed precursor hydrothermal product shows hexagonal Gd(OH) $_{\boldsymbol 3}$ :Eu $^{\boldsymbol{3+}}$ phase and it converts to pure cubic phase of Gd $_{\boldsymbol 2}$ O $_{\boldsymbol 3}$ :Eu $^{\boldsymbol{3+}}$ on calcination at 600 $^{\boldsymbol \circ}$ C for 3?h. TEM micrographs of hydrothermally prepared cubic Gd $_{\boldsymbol 2}$ O $_{\boldsymbol 3}$ :Eu $^{\boldsymbol{3+}}$ phase shows nanorods with a diameter of 15?nm and length varying from 50 to 150?nm, whereas combustion product shows the particles to be of irregular shape, with different sizes in the range 50?C250?nm. Dominant red emission (612?nm) was observed in cubic Gd $_{\boldsymbol 2}$ O $_{\boldsymbol 3}$ :Eu $^{\boldsymbol{3+}}$ which has been assigned to $^{\boldsymbol 5}{\bf \textit{D}}_{\boldsymbol 0}$ $\boldsymbol \to$ $^{\boldsymbol 7}{\bf \textit{F}}_{\boldsymbol 2}$ transition. However, in hexagonal Gd(OH) $_{\boldsymbol 3}$ :Eu $^{\boldsymbol{3+}}$ , emission peaks at 614 and 621?nm were observed. The strong red emission of cubic Gd $_{\boldsymbol 2}$ O $_{\boldsymbol 3}$ :Eu $^{\boldsymbol{3+}}$ nanophosphors by hydrothermal method are promising for high performance display materials. The variation in optical energy bandgap ( $\boldsymbol{E}_{\boldsymbol{\rm g}}$ ) was noticed in as-formed and heat treated systems in both the techniques. This is due to more ordered structure in heat treated samples and reduction in structural defects.     

Influence of Ball-Milling Treatment of B Original Powder on the Phase Formation and Critical Current Density of Graphite Doped MgB_{2}

In present work, the sintering process and superconducting properties of graphite doped MgB \(_{2}\) prepared with milled B original powder were investigated. It is found that ball milling treatment of B original powder obviously suppresses the solid–solid reaction between Mg and B, whereas it enhances their liquid–solid reaction during the subsequent sintering process of these graphite doped MgB \(_{2}\) bulks. Ball milling treatment of B original powder can also promote C substitution for B sites in MgB \(_{2}\) crystal lattice in the graphite-doped samples, and thus obviously increase their values of \(J_{c}\) at high fields. Moreover, ball milling also refines MgB \(_{2}\) grains, enhancing grain boundary pinning and \(J_{c}\) at high fields.     

On transitive parallelisms of PG(3,4)

A parallelism in $PG(n,q)$ P G ( n , q ) is transitive if it has an automorphism group which is transitive on the spreads. A parallelism is regular if all its spreads are regular. In $PG(3,4)$ P G ( 3 , 4 ) no examples of transitive and no regular parallelisms are known. Transitive parallelisms in $PG(3,4)$ P G ( 3 , 4 ) must have automorphisms of order 7. That is why we construct all 482 parallelisms with automorphisms of order 7 and establish that there are neither transitive, nor regular ones among them. We conclude that there are no transitive parallelisms in $PG(3,4)$ P G ( 3 , 4 ) . The investigation is computer-aided. We use GAP (Groups, Algorithms, Programming—a System for Computational Discrete Algebra) to find a subgroup of order 7 and its normalizer in the automorphism group of $PG(3,4)$ P G ( 3 , 4 ) . For all the other constructions and tests we use our own software written in C++.     

Effect of Previous Milling of Precursors on Magnetoelectric Effect in Multiferroic {\mathrm{Bi}_{5}\mathrm{Ti}_{3}\mathrm{FeO}_{15}} Ceramic

$\mathrm{Bi}_{5}\mathrm{Ti}_{3}\mathrm{FeO}_{15}$ Bi 5 Ti 3 FeO 15 magnetoelectric (ME) ceramics have been synthesized and investigated. The ME effect can be described as an induced electric polarization under an external magnetic field or an induced magnetization under an external electric field. The materials in the ME effect are called ME materials, and they are considered to be a kind of new promising materials for sensors, processors, actuators, and memory systems. Multiferroics, the materials in which both ferromagnetism and ferroelectricity can coexist, are the prospective candidates which can potentially host the gigantic ME effect. $\mathrm{Bi}_{5}\mathrm{Ti}_{3}\mathrm{FeO}_{15}$ Bi 5 Ti 3 FeO 15 , an Aurivillius compound, was synthesized by sintering a mixture of $\mathrm{Bi}_{2}\mathrm{O}_{3}, \mathrm{Fe}_{2}\mathrm{O}_{3}$ Bi 2 O 3 , Fe 2 O 3 , and $\mathrm{TiO}_{2}$ TiO 2 oxides. The precursor materials were prepared in a high-energy attritorial mill for (1, 5, and 10) h. The orthorhombic $\mathrm{Bi}_{5}\mathrm{Ti}_{3}\mathrm{FeO}_{15}$ Bi 5 Ti 3 FeO 15 ceramics were obtained by a solid-state reaction process at 1313 K. The ME voltage coefficient ( $\alpha _\mathrm{ME}$ α ME ) was measured using the dynamic lock-in method. The highest ME voltage coefficient ( $\alpha _\mathrm{ME} = 8.28\,\text{ mV }{\cdot }\text{ cm }^{-1}{\cdot }\text{ Oe }^{-1})$ α ME = 8.28 mV · cm ? 1 · Oe ? 1 ) is obtained for the sample milled for 1 h at $H_\mathrm{DC }= 4$ H DC = 4  Oe (1 Oe = 79.58  $\text{ A }{\cdot }\text{ m }^{-1})$ A · m ? 1 ) .     

Containerless Measurements of Density and Viscosity for a Cu_{48}Zr_{52} Liquid

The densities of solid and liquid Cu \(_{48}\) Zr \(_{52}\) and the viscosity of the liquid were measured in a containerless electrostatic levitation system using optical techniques. The measured density of the liquid at the liquidus temperature (1223 K) is (7.02 \(\pm \) 0.01) g \(\cdot \) cm \(^{-3}\) and the density of the solid extrapolated to that temperature is (7.15 \(\pm \) 0.01) g \(\cdot \) cm \(^{-3}\) . The thermal expansion coefficients measured at 1223 K are (6.4 \(\pm \) 0.1) \(\,\times \,10^{-5}\) K \(^{-1}\) in the liquid phase and (3.5 \(\pm \) 0.3) \(\,\times \,10^{-5}\) K \(^{-1}\) in the solid phase. The viscosity of the liquid, measured with the oscillating drop technique, is of the form \(A\exp \left[ \left( {{E}_{0}}+{{E}_{1}}\left( 1/T-1/{{T}_{0}} \right) \right) \times \left( 1/T-1/{{T}_{0}} \right) \right] \) , where \({{T}_{0}}=1223\) K, \(A= (0.0254 \pm 0.0004)\) Pa \(\cdot \) s, \({{E}_{0}}\) =  (8.43 \(\pm \) 0.26) \(\,\times \,10^3\) K and \({{E}_{1}}\) =  (1.7 \(\pm \) 0.2) \(\,\times 10^7\) K \(^{2}\) .     

Study of Superfluid ^3He Under Nanoscale Confinement

We review recent experiments in which superfluid $^3$ He has been studied under highly controlled confinement in nanofluidic sample chambers. We discuss the experimental challenges and their resolution. These methods open the way to a systematic investigation of the superfluidity of $^3$ He films, and the surface and edge excitations of topological superfluids.     

Application of Non-Isothermal Thermogravimetric Method to Interpret the Decomposition Kinetics of \hbox {NaNO}_{3}, \hbox {KNO}_{3}, and \hbox {KClO}_{4}

The non-isothermal thermogravimetric method was used to study the thermal decomposition of \(\hbox {KClO}_{4}, \hbox {KNO}_{3}\) , and \(\hbox {NaNO}_{3}\) at heating rates of (5, 10, 15, and 20)  \(\hbox {K}\cdot \hbox {min}^{-1}\) . The activation energy of thermal decomposition reactions was computed by isoconversional methods of Ozawa–Flynn–Wall, Kissinger–Akahiro–Sunose, and Friedman equations. Also, the kinetic triplet of the thermal decomposition of salts was determined by the model-fitting method of the modified Coats–Redfern equation. The activation energies of \(\hbox {KClO}_{4}, \hbox {KNO}_{3}\) , and \(\hbox {NaNO}_{3}\) of (293 to 307, 160 to 209, and 192 to 245)  \(\hbox {kJ}\cdot \hbox {mol}^{-1}\) , respectively, are obtained by non–isothermal isoconversional methods. The modified Coats and Redfern method showed that the most probable mechanism functions \(g(\alpha )\) of \([-\hbox {ln}(1 - \alpha )]^{1/3}\) (model A3: Arami–Erofeev equation) and \((1 - \alpha )^{-1}- 1\) (model F2: second order) can be used to predict the decomposition mechanisms of \(\hbox {KClO}_{4}\) , \(\hbox {KNO}_{3}\) , and \(\hbox {NaNO}_{3}\) , respectively.     

Measurement of the (p, \rho,T) Properties for Pure Hydrocarbons at Temperatures up to 600 K and Pressures up to 200 MPa

The data available for the thermodynamic properties of propane, \(n\) -butane, and isobutane at temperatures above 440 K are outdated and show significant discrepancies with each other. The ambiguity associated with these data could be limiting to the development of any understanding related to the effects of mixing of these substances with other materials such as \(\text{ CO}_{2}\) , ammonia, and non-flammable or lower-flammable HFC refrigerants. In this study, the (p, \(\rho \) , T) properties of propane, \(n\) -butane, and isobutane were measured at temperatures ranging from (360 to 600) K and pressures ranging from (50 to 200) MPa. Precise measurements were carried out using a metal-bellows variable volumometer with a thermostatted air bath. The expanded uncertainties \((k = 2)\) in the temperature, pressure, and density measurements were estimated to be \(<\) 5 mK, 0.02 MPa, and 0.88 kg  \(\cdot \)  m \(^{-3}\) ( \(T\le 423\)  K, \(p<100\)  MPa), 0.76 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T\le 423\)  K, \(p\ge 100\)  MPa), 0.76 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T>423\)  K, \(p < 100\)  MPa), and 2.94 kg  \(\cdot \)   \(\text{ m}^{-3}\) ( \(T>423\)  K, \(p \ge 100\)  MPa), respectively. The data obtained throughout this study were systematically compared with the calculated values derived from the available equations of state. These models agree well with the measured data at higher temperatures up to 600 K, demonstrating their suitability for an effective and precise examination of the mixing effects of potential alternative mixtures.     

Ternary codes from some reflexive uniform subset graphs

We examine the ternary codes \(C_3(A_i+I)\) from matrices \(A_i+I\) where \(A_i\) is an adjacency matrix of a uniform subset graph \(\Gamma (n,3,i)\) of \(3\) -subsets of a set of size \(n\) with adjacency defined by subsets meeting in \(i\) elements of \(\Omega \) , where \(0 \le i \le 2\) . Most of the main parameters are obtained; the hulls, the duals, and other subcodes of the \(C_3(A_i+I)\) are also examined.     

Dielectric behaviour of sodium and potassium doped magnesium titanate

Pure phase of magnesium titanate (MgTiO $_{\boldsymbol{3}})$ was obtained at 1100°C by both the conventional solid-state method as well as by the flux method starting from hexahydrated magnesium nitrate and titanium dioxide as the reactants. MgTiO $_{\boldsymbol{3}}$ doped with Na or K was also prepared by the solid-state route. Na and K doped compositions led to monophasic MgTiO $_{\boldsymbol{3}}$ below 5 mol % dopant concentration while biphasic mixture of MgTiO $_{\boldsymbol{3}}$ (major phase) and MgTi $_{\boldsymbol{2}}$ O $_{\boldsymbol{5}}$ (minor phase) were obtained at higher dopant concentration. The dielectric constant and dielectric loss of MgTiO $_{\boldsymbol{3}}$ were found to be almost the same irrespective of the preparative method. MgTiO $_{\boldsymbol{3}}$ doped with 5 mol % of Na and K ions displayed optimum dielectric properties.     

Extremal properties of M4 processes

The existence of data with different dependence structures motivates the development of models which can capture several types of dependence. In this paper we consider a stationary sequence of moving maxima vectors \(\{{\mathbf {X}}_n=(X_{n1},\ldots ,X_{nd})\}_{n\ge 1}\) having innovations \({\mathbf {Z}}_{l,n}=(Z_{l,n,1},\ldots ,Z_{l,n,d})\) with totally dependent margins for certain values of \(l,\) \(l\in I_1,\) and independent margins for the remaining values of \(l,\) \(l\in I_2.\) We obtain in this way a \(d\) -dimensional process \(\{{\mathbf {X}}_n\}_{n\ge 1}\) whose extremal dependence, measured by the tail dependence coefficients, lies between asymptotic independence and total dependence. The extremal properties of these M4 processes are studied and examined both theoretically and through simulation studies: we derive the multivariate extremal index, the tail dependence coefficients and co-movement indices.     

Theoretical Investigations on Electrocaloric Properties of \mathrm{PbZr}_{0.95}\mathrm{Ti}_{0.05}\mathrm{O}_{3} Thin Film

Based on a phenomenological model, the electrocaloric effect (ECE) accompanied with the ferroelectric-to-paraelectric phase transition in a PbZr $_{0.95}$ 0.95 Ti $_{0.05}$ 0.05 O $_{3}$ 3 thin film was investigated. The extracted data reveal many features of the ECE such as electrocaloric entropy changes, heat capacity changes, and temperature changes as functions of temperature due to different electric fields shifts. From the behavior of the PbZr $_{0.95}$ 0.95 Ti $_{0.05}$ 0.05 O $_{3}$ 3 thin film in phase transitions, it leads to a large change of heat capacity of 105.94 J  ${\cdot }\,$ · kg ${^{-1}}\,{\cdot }\,{^{\circ }}$ ? 1 · ° C, a temperature change of 22.44 K, and a relative cooling power of 1469 J  ${\cdot }$ ·  kg $^{-1}$ ? 1 .     

On characteristic lengths used in notch fracture mechanics

In this paper, four kinds of characteristic length parameters used in a local notch fracture criterion are presented: (1) a characteristic length ${\uprho }_{\mathrm{c}}$ generally connecting to the notch radius, (2) a characteristic distance $\hbox {X}_{\mathrm{c}}$ considered as intrinsic to material and connected to the microstructure, (3) a critical distance $\hbox {d}_{0}$ considered as intrinsic to material and connected to the fracture process zone, (4) an effective distance $\hbox {X}_{\mathrm{ef}}$ considered as a characteristic of the stress distribution. Each approach is discussed. The paper ends with the author’s opinion about the different methods.