Phase Transformations in the High-Tc Superconducting Compounds,Ba2RCu3O7?δ (R = Nd,Sm, Gd,Y, Ho,and Er)

The phase transformation between the orthorhombic and tetragonal structures of six high-T_c superconductors, Ba₂RCu₃O_7−δ, where R = Nd, Sm, Gd, Y, Ho, and Er, and δ = 0 to 1, has been investigated using techniques of x-ray diffraction, differential thermal analysis/thermogravimetric analysis (DTA/TGA) and electron diffraction. The transformation from the oxygen-rich orthorhombic phase to the oxygen-deficient tetragonal phase involves two orthorhombic phases. A superlattice cell caused by oxygen ordering, with a′ = 2a, was observed for materials with smaller ionic radius (Y, Ho, and Er). For the larger lanthanide samples (Nd, Sm, and Gd), the a′ = 2a type superlattice cell was not observed.The structural phase transition temperatures, oxygen stoichiometry and characteristics of the T_c plateaus appear to correlate with the ionic radius, which varies based on the number of f electrons. Lanthanide elements with a smaller ionic radius stabilize the orthorhombic phase to higher temperatures and lower oxygen content. Also, the superconducting temperature is less sensitive to the oxygen content for materials with smaller ionic radius. The trend of dependence of the phase transformation temperature on ionic radius across the lanthanide series can be explained using a quasi-chemical approximation (QCA) whereby the strain effect plays an important role on the order-disorder transition due to the effect of oxygen content on the CuO chain sites.     

Study of thermal–mechanical properties of polyurethane foam and the three-dimensional shape of molded bra cups

Molded bras nowadays are dominating the overall bra market place, while the bra cups are mostly made of polyurethane foam sheets. The smooth and seamless inner surface of a molded bra cup gives three-dimensional nice fit to the wearer and provides unlimited designs for different softness and thickness. However, it has been a difficult question to determine the optimum molding conditions for various types of foam and there was no reliable method to measure the cup shape conformity. In this study, the properties of five polyurethane foams were investigated by thermal–mechanical analysis (TMA) and their 3D shapes formed in various molding conditions were measured by a Steinbichler Comet scanner and a new parameterization-based remesh algorithm method. The results revealed that the optimal temperature and dwell time for molding bra cups were greatly affected by the thermal–mechanical properties of polyurethane foams. The softening temperature and deformation properties of the foams tested by TMA can facilitate the determination of optimal molding temperature for the desirable cup shape and thickness. This study provides an effective and quantitative approach to eliminate the time-consuming “trial-and-error” in the molding tests traditionally being used in the industry.     

Non-Discriminatory Automatic Registration of Knock-On Train Delays

Incidents and waiting for train connections are registered by dispatchers as sources of train delays, but route and headway conflicts are not always clearly recognized. Moreover, traffic management and route setting are the primary task of dispatchers and signallers, whilst monitoring and incident registration is not allowed to take up too much of their time. This paper describes a tool that automatically and without discrimination identifies route conflicts and the train numbers involved. It is based on standard train describer and infrastructure messages recorded on the Dutch railway network. The logic of these messages is captured in a coloured Petri net (CPN) model on which a prototype tool for route conflict identification and estimation of knock-on delay has been developed.     

Polarization switching dynamics and switchable diode effect in hybrid improper ferroelectric Ca3Ti2O7 ceramics

Hybrid improper ferroelectric Ca₃Ti₂O₇ (CTO) ceramics were synthesized by a solid-state reaction method. Their polarization switching currents, dynamic processes of polarization-switching, and leakage current properties were investigated. It was found that the dynamic polarization curves of CTO ceramics exhibit obvious dependence on the frequency of the driving electric fields. Moreover, CTO ceramics show a switchable diode effect. The underlying mechanism for the observed effects were proposed based on the interplaying between mobile charged defects and bound charges. The charged defects also lead to a decrease in the band gap of the CTO ceramic, as revealed by absorption spectrum analysis.     

Kinetic Studies of the Interfacial Reaction of the Ba2YCu3O6+x Superconductor with a CeO2 Buffer

Interfacial reactions between the Ba₂YCu₃O_6+x superconductor and the CeO₂ buffer layers employed in coated conductors have been modeled experimentally by investigating the kinetics of the reaction between Ba₂YCu₃O_6+x films and CeO₂ substrates. At 810°C, the Ba₂YCu₃O_6+x -CeO₂ join within the BaO-Y₂O₃-CeO₂-CuO _x quaternary system is nonbinary, thereby establishing the phase diagram topology that governs the Ba₂YCu₃O_6+x /CeO₂ reaction. At a mole ratio of Ba₂YCu₃O_6+x :CeO₂ of 40:60, a phase boundary was found to separate two four-phase regions. On the Ba₂YCu₃O_6+x -rich side of the join, the four-phase region consists of Ba₂YCu₃O_{6 +x} , Ba(Ce_1−z Y _z )O_3−x , BaY₂CuO₅, and CuO _x ; on the CeO₂ rich side, the four phases were determined to be Ba(Ce_1−z Y _z ) O_3−x , BaY₂CuO₅, CuO _x and CeO₂. The Ba₂YCu₃O_6+x /CeO₂ reaction is limited by solid-state diffusion, and the reaction kinetics obey the parabolic rule, x = Kt ^1/2, where x = thickness of the reaction layer, t = time, and K = a constant related to the rate constant; K was determined to be 1.6 × 10⁻³ μm/s^1/2 at 790°C and 4.7 × 10⁻³ μm/s^1/2 at 830°C. The activation energy for the reaction was determined to be E _act = 2.67 × 10⁵ J/mol using the Arrhenius equation.     

Two-dimensional biosensor arrays based on surface plasmon resonance phase imaging

We present a biosensor design based on capturing the two-dimensional (2D) phase image of surface plasmon resonance (SPR). This 2D SPR imaging technique may enable parallel label-free detection of multiple analytes and is compatible with the microarray chip platform. This system uses our previously reported differential phase measurement approach, in which 2D phase maps obtained from the signal (P) and reference (S) polarizations are compared pixel by pixel. This technique greatly improves detection resolution as the subtraction step can eliminate measurement fluctuations caused by external disturbances as they essentially appear in both channels. Unlike conventional angular SPR systems, in which illumination from a range of angles must be used, phase measurement requires illumination from only one angle, thus making it well suited for 2D measurement. Also, phase-stepping introduced from a moving mirror provides the necessary modulation for accurate detection of the phase. In light of the rapidly increasing need for fast real-time detection, quantification, and identification of a range of proteins for various biomedical applications, our 2D SPR phase imaging technique should hold a promising future in the medical device market.     

Chemical characterization and redox potential of coarse and fine particulate matter (PM) in underground and ground-level rail systems of the Los Angeles Metro

A campaign was conducted to assess personal exposure of coarse (2.5 μm < d(p) < 10 μm) and fine (d(p) < 2.5 μm) PM for two lines of the L.A. Metro-a subway (red) and light-rail (gold) line. Concurrent measurements were taken at University of Southern California (USC) to represent ambient conditions. A comprehensive chemical analysis was performed including total and water-soluble metals, inorganic ions, elemental and organic carbon, and organic compounds. Mass balance showed that in coarse PM, iron makes up 27%, 6%, and 2% of gravimetric mass for the red line, the gold line, and USC, respectively; in fine PM, iron makes up 32%, 3%, and 1%. Ambient air is the primary source of inorganic ions and organic compounds for both lines. Noncrustal metals, particularly Cr, Mn, Co, Ni, Mo, Cd, and Eu, were elevated for the red line and, to a lesser degree, the gold line. Mo exhibited the greatest crustal enrichment factors. The enriched species were less water-soluble on the red line than corresponding species on the gold line. Bivariate analysis showed that reactive oxygen species (ROS) activity is strongly correlated with water-soluble Fe (R(2) = 0.77), Ni (R(2 )= 0.95), and OC (R(2 )= 0.92). A multiple linear regression model (R(2) = 0.94, p < 0.001) using water-soluble Fe and OC as predictor variables was developed to explain the variance in ROS. In addition, PM from the red line generates 65% and 55% more ROS activity per m(3) of air than PM from USC and the gold line, respectively; however, one unit of PM mass from the gold line may be as intrinsically toxic as one unit of PM from the red line.     

Atherogenic Indices as a Predictor of Aortic Calcification in Prostate Cancer Patients Assessed Using 18F-Sodium Fluoride PET/CT

A major pathophysiological cause of cardiovascular disease is vascular plaque calcification. Fluorine 18–Sodium Fluoride (18F-NaF) PET/CT can be used as a sensitive imaging modality for detection of vascular calcification. The aim of this study was to find a non-invasive, cost-efficient, and readily available metric for predicting vascular calcification severity. This retrospective study was performed on 36 participants who underwent 18F-NaF fused PET/CT scans. The mean standard uptake values (SUVs) were calculated from manually sectioned axial sections over the aortic arch and thoracic aorta. Correlation analyses were performed between SUVs and calculated atherogenic indices (AIs). Castelli’s Risk Index I (r = 0.63, p < 0.0001), Castelli’s Risk Index II (r = 0.64, p < 0.0001), Atherogenic Coefficient (r = 0.63, p < 0.0001), Atherogenic Index of Plasma (r = 0.51, p = 0.00152), and standalone high-density lipoprotein (HDL) cholesterol (r = −0.53, p = 0.000786) were associated with aortic calcification. AIs show strong association with aortic arch and thoracic aorta calcifications. AIs are better predictors of vascular calcification compared to standalone lipid metrics, with the exception of HDL cholesterol. Clinical application of AIs provides a holistic metric beneficial for enhancing screening and treatment protocols.     

Enhanced magnetism in Ru-doped hybrid improper perovskite Ca3Mn2O7 via experimental and first-principles study

The quasi-2D Ruddlesden–Popper layered perovskites with single-phase multiferroicity have attracted much attention in recent magnetoelectric memory applications. We have systematically investigated the optical and magnetic properties of Ru-doped hybrid improper perovskite Ca₃Mn₂O₇ both experimentally and using first-principles calculations. The Ca₃Ru_xMn_2−xO₇ (x = 0, 0.02, 0.06, 0.10) powders were successfully synthesized using the sol–gel method. Ru doping enhanced the ferromagnetism of Ca₃Mn₂O₇. The quasi-2D antiferromagnetic (AFM) fluctuation effect was observed in Ca₃Mn₂O₇ and in certain doped samples. We also found that the optical bandgaps of the doped samples were reduced after doping, agreeing with the results of the first-principles calculations. Infrared absorption spectra indicated the distortion of the Mn–O bonds was possibly due to the Jahn–Teller effect. To analyze the electronic structures and to understand the detailed atomic contributions of magnetic moments, the Crystal Orbital Hamilton Population (COHP) and Integrated COHP of the (Mn,Ru)O₆ octahedra were also calculated. The Ru-doped materials with the coexistence of ferromagnetic and AFM orderings are expected to be excellent candidates for magnetoelectric devices.