A sol-gel method for growing superconducting MgB2 films

In this paper we report a new sol-gel method for the fabrication of MgB2 films. Polycrystalline MgB2 films were prepared by spin-coating a precursor solution of Mg(BH_4)_2 diethyl ether on (001)Al2O3 substrates followed with annealing in Mg vapor. In comparison with the MgB2 films grown by other techniques, our films show medium qualities including a superconducting transition temperature of Tc ~ 37 K, a critical current density of Jc(5 K, 0 T) ~ 5 {\times} 10^6 A cm^{-2}, and a critical field of H_{c2}(0) ~ 19 T. Such a sol-gel technique shows potential in the commercial fabrication of practically used MgB2 films as well as MgB2 wires and tapes.Comment: 8 pages, 5 figure

Flexibility of a Eukaryotic Lipidome – Insights from Yeast Lipidomics

Mass spectrometry-based shotgun lipidomics has enabled the quantitative and comprehensive assessment of cellular lipid compositions. The yeast Saccharomyces cerevisiae has proven to be a particularly valuable experimental system for studying lipid-related cellular processes. Here, by applying our shotgun lipidomics platform, we investigated the influence of a variety of commonly used growth conditions on the yeast lipidome, including glycerophospholipids, triglycerides, ergosterol as well as complex sphingolipids. This extensive dataset allowed for a quantitative description of the intrinsic flexibility of a eukaryotic lipidome, thereby providing new insights into the adjustments of lipid biosynthetic pathways. In addition, we established a baseline for future lipidomic experiments in yeast. Finally, flexibility of lipidomic features is proposed as a new parameter for the description of the physiological state of an organism

Structure, crystallization and magnetic behaviour of Fe-RE-Cu-Si-B alloys (RE = Pr, Nd, Gd)

Nb was replaced by RE atoms (Gd, Pr, Nd) in classic FINEMET and the influence of this substitution on the structure, crystallization and magnetic behaviour was investigated. Thermomagnetic measurements, TEM and XRD observations have shown that Gd and Pr are suitable for grain growth suppressing during crystallization and take part in formation of nanocrystalline structure. The crystallization kinetics of the Nd containing sample is entirely different. Coercivity reflects the structural changes of the sample during annealing. Low-temperature magnetization measurements enable the study of annealing behaviour of the magnetic moment µFc+RE and of the spin-wave stiffness constant. DSP. The results suggest that the light rare-earth Pr and Nd atoms couple ferromagnetically, while the heavy rare-earth Gd atoms couple ferrimagnetically to Fe atoms. The influence of RE atoms on Curie temperature was also observed

Effects of impurities addition in MgB2/Nb tapes on flux jumps instability and critical current density

In order to understand the effect of impurities inclusions on the transport properties of MgB(2) tapes, by means of magnetization measurements we have analysed non-commercial monofilamentary tapes in which titanium (Ti), tungsten (W) and silicon carbide(SiC)normal particles were included. All the samples under analysis have the same cross section and heir MgB(2) filament is embedded in a superconducting niobium matrix. For all the tapes a magnetic field (H(a)) up to 65 kOe has been applied parallel to the filament, and we have compared their magnetization loops M (H(a)) measured in the temperature range from 2 K up to 30K. The results show that the process of adding normal particles in the material, in order to increase the transport properties, produces at low field opposite effects to those at higher field. Moreover, all the particles included produce the common result of an enhancement in the thermomagnetic instability, and consequently a decrease of the transport properties, at low temperature and magnetic fields

Loss of internal 1 → 6 substituted monosaccharide residues from underivatized and per-O-methylated trisaccharides

The fragmentation behavior of [M + H]+ ions of a series of underivatized and per-O-methylated trisaccharides having 1 → 6 linked residues, of which one or two is a deoxy-fluoro or deoxy residue and thus has a unique mass, has been studied by using collision-induced dissociation fast-atom bombardment mass spectrometry. In addition to the usual fragment ions resulting from glycosidic bond cleavage, fragment ions were observed which must have been generated following an unusual rearrangement process which can be rationalized in terms of the loss of an internal monosaccharide residue

Ultrafast and highly sensitive photodetectors fabricated on high-energy nitrogen-implanted GaAs,

We have fabricated and tested metal–semiconductor–metal ~MSM! photodetectors based on nitrogen-ion-implanted GaAs. Nitrogen ions with energy of 700 and 880 keV, respectively, were implanted into epitaxial GaAs films at an ion concentration of 331012 cm22. Ti/Au MSM photodetectors with 1-um-wide fingers were fabricated on top of the implanted GaAs. In comparison to low-temperature-grown GaAs photodetectors, produced in parallel in identical MSM geometry, the 880 keV N1-implanted photodetectors exhibited almost two orders of magnitude lower dark current ~10 nA at 1 V bias! and the responsivity more than doubled ~.20 mA/W at 20 V bias!. Illumination with 100-fs-wide, 810 nm wavelength laser pulses, generated ;2.5-ps-wide photoresponse signals with amplitudes as high as 2 V. The 2.5 ps relaxation time was the same for both the ion-implanted and low-temperature-grown devices and was limited by the MSM capacitance time constant

Transport currents in Bi-2223/Ag tapes made using the tape-in-rectangular tube process, current distribution and Ic stress degradation

Using the tape-in-rectangular tube (TIRT) process, we have made multi-core Bi-2223/Ag tapes with various numbers of filaments (10-162), and with different filament architectures and orientations. We have measured the angular dependence of the transport current of the tape samples with 'parallel' and 'perpendicular' filaments. The transversal Ic distribution obtained by spatially resolved transport measurements ('magnetic knife') illustrates that the filament quality of the TIRT tapes is better at the tape edges than in the centre. The tapes were stressed by two types of tensioning set-up (a short straight sample and a U-shaped spring) and by bending at 77 K. The Ic degradation shows different behaviour for parallel and perpendicular filaments, which is attributed to the difference in filament density and crack propagation