High-T c superconductors: New insights from angle-resolved photoemission

Recent angle-resolved photoemission (ARPES) studies of the high-T _c superconductors by the Argonne group are briefly reviewed. First we discuss sum rules to establish a spectral function interpretation of the data, and the use of ARPES to obtain the momentum distribution. We then apply these ideas to the normal and superconducting state spectra for B₂Sr₂Cu₂O₈. Among the topics discussed are the Fermi surface, polarization selection rules, bilayer splitting, and the superconducting gap.     

Single-unit system with corrective maintenance at random checks governed by probabilities in a geometric progression

A system which comprises only one unit and a single server is considered. While the unit is in operation, at random intervals it is subjected to checks for corrective maintenance (CM). While the unit is under CM, it is also working and thus may fail. The probabilities that the unit will not undergo CM at random checks are in geometric progression (p, p², p³,…), whereas the probabilities that the unit will undergo CM are (1 − p, 1 − p²,…). We consider three models, and obtain the mean time to system failure and steady-state availability of the system for these models.     

Effect of iron (Wt.%) on adhesive wear response of Al-12Si-1Cu-0.1Mg alloy in dry sliding conditions

The presence of iron leads to different types of intermetallics in Al-Si alloys, among them needle shaped β-phase (Al₅FeSi) can lead to variations in hardness of the Al-Si alloy which ultimately can affect the wear resistance of the alloy. In this paper, the effect of iron on wear behavior of cast Al-Si alloys has been reported. Sliding wear behavior of eutectic alloy Al-12Si-1Cu-0.1Mg was investigated in dry sliding conditions by using pin-on-disk test configuration against heat treated EN31 steel counter-surface at room temperature. Sliding wear behavior has been evaluated at four normal loads of 5, 20, 50 and 70 N and two sliding speeds, 2 m/s and 4 m/s. Worn pin surfaces were examined by scanning electron microscopy (SEM) for analyzing wear mechanisms. The wear mechanism has been found to be mild oxidative type at lower sliding speed of 2m/s for entire range of loads used in the study. Transition to severe metallic wear occurs at higher sliding speed of 4 m/s at normal load of 5 N. Hardness of the alloy increased with increase in iron addition primarily due to presence of needle shaped Fe-rich intermetallics but it leads to an increased wear rate.     

Significance of fruit and vegetable allergens: Possibilities of its reduction through processing

Fruit and vegetable allergies are prevalent commonly in adults, infants, and children all around the world, but more importantly in Europe and North America. The only solution is complete abstinence from the responsible food, which can be very difficult due to their presence in the form of hidden or undeclared ingredients. Various studies have shown the direct effect of processing on the secondary structure of proteins that can mitigate the allergic properties. The impact of these processing techniques on fruit and vegetable allergies have shown limited success due to the fact that they have multiple allergens that are especially heat stable. Apples, kiwi, peach, and melons are common fruits, whereas celery and carrot are the common vegetables that can result in allergic reactions for some portion of the population upon exposure.

Abbreviations: IgE: immunoglobulin E, OAS: oral allergy syndrome, nsLTP: nonspecific lipid transfer proteins, LTP: lipid transfer proteins, HPP: high-pressure processing, PEF: pulsed electric field, CD: circular dichroism, pI: isoelectric point, DBPCFCs: double-blind placebo-controlled food challenges     

Influence of boron clustering on the emitter quality of implanted silicon solar cells: an atom probe tomography study

The use of ion implantation doping instead of the standard gaseous diffusion is a promising way to simplify the fabrication process of silicon solar cells. However, difficulties to form high‐quality boron (B) implanted emitters are encountered when implantation doses suitable for the emitter formation are used. This is due to a more or less complete activation of Boron after thermal annealing. To have a better insight into the actual state of the B distributions, we analyze three different B emitters prepared on textured Si wafers: (1) a BCl₃ diffused emitter and two B implanted emitters (fixed dose) annealed at (2) 950°C and at (3) 1050°C (less than an hour). Our investigations are in particular based on atom probe tomography, a technique able to explore 3D atomic distribution inside a material at nanometer scale. Atom probe tomography is employed here to characterize B atomic distribution inside textured Si solar cell emitters and to quantify clustering of B atoms. Here, we show that implanted emitters annealed at 950 °C present maximum clusters due to poor solubility at lower temperature and also highest emitter saturation current density (J_0e = 1000 fA/cm²). Increasing the annealing temperature results in greatly improved J_0e (131 fA/cm²) due to higher solubility and a consequently lower number of clusters. BCl₃ diffused emitters do not contain any B clusters and presented the best emitter quality. From our results, we conclude that clustering of B atoms is the main reason behind higher J_0e in the implanted boron emitters and hence degraded emitter quality. Copyright © 2015 John Wiley & Sons, Ltd.     

Green fluorescent organic nanoparticles by self-assembly induced enhanced emission of a naphthalene diimide bolaamphiphile

Naphthalene diimide (NDI) bolaamphiphilic molecules (1) self-assemble in water to form organic nanoparticles, which exhibit self-assembly induced preassociated excimer formation and hence an enhanced green fluorescence.     

Thermal coupling links to liquid‐only transfer streams: An enumeration method for new FTC dividing wall columns

Novel dividing wall columns (DWCs) can be obtained by converting thermal couplings to liquid‐only transfer streams. Here, we develop a simple four‐step method to generate a complete set of DWCs containing n ? 2 dividing walls, for a given n‐component fully thermally coupled (FTC) distillation. Among the novel DWCs, some easy‐to‐operate DWCs possess the property that the vapor flow in every section of the DWC can be controlled during operation by means that are external to the column. We develop a simple method to enumerate all such easy‐to‐operate DWCs. We expect that the easy‐to‐operate DWCs can be operated close‐to‐optimality; leading to a successful industrial implementation of the n‐component (n ≥ 3) FTC distillation in the form of a DWC. As an illustration, we show figures of all easy‐to‐operate DWCs with two dividing walls for the four‐component FTC distillation. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1200–1211, 2016     

Enhancement of Magnetic and Dielectric Properties in Chemically Modified Multiferroic (0.90)BiFe1−x Cr x O3–(0.10)BaTiO3 Nanocomposite

Multiferroic BiFeO₃ and Cr-doped (0.90)BiFe_1?x Cr _x O₃–(0.10)BaTiO₃ (x=0.00, 0.03, and 0.05) nanocomposites were prepared by sol–gel method. Optimum calcination and sintering strategies for obtaining pure perovskite phase have been determined. X-ray diffraction and transmission electron microscope (TEM) were used for the structural and particle size analysis, whereas LCR and SQUID magnetometer was used for dielectric and magnetic measurements. TEM measurements show that the average particle sizes of all the samples were ～19 nm. The dielectric constant was found to be increased twofold in low frequency region with the Cr-doping for x=0.05 in (0.90)BiFe_1?x Cr _x O₃–(0.10)BaTiO₃. The hysteresis curve (M–H) exhibits ferromagnetic nature for all the samples (x=0.0, 0.03, and 0.05) and the spontaneous magnetization at room temperature was found to be 0.63 emu/gm in pure BiFeO₃, which increased to 0.99 emu/gm for x=0.05. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves show large discrepancy suggesting spin glass behavior.