5,251 research outputs found
Strong enhancement of Jc in binary and alloyed in-situ MgB2 wires by a new approach: Cold high pressure densification
Cold high pressure densification (CHPD) is presented as a new way to
substantially enhance the critical current density of in situ MgB2 wires at 4.2
and 20 K at fields between 5 and 14 T. The results on two binary MgB2 wires and
an alloyed wire with 10 wt.% B4C are presented The strongest enhancement was
measured at 20K, where cold densification at 1.85 GPa on a binary Fe/MgB2 wire
raised both Jcpara and Jcperp by more than 300% at 5T, while Birr was enhanced
by 0.7 T. At 4.2K, the enhancement of Jc was smaller, but still reached 53% at
10 T. After applying pressures up to 6.5 GPa, the mass density dm of the
unreacted (B+Mg) mixture inside the filaments reached 96% of the theoretical
density. After reaction under atmospheric pressure, this corresponds to a
highest mass density df in the MgB2 filaments of 73%. After reaction, the
electrical resistance of wires submitted to cold densification was found to
decrease, reflecting an improved connectivity. A quantitative correlation
between filament mass density and the physical properties was established.
Monofilamentary rectangular wires with aspect ratios a/b < 1.25 based on low
energy ball milled powders exhibited very low anisotropy ratios, Gamma =
Jcpara/Jcperp being < 1.4 at 4.2 K and 10T. The present results can be
generalized to alloyed MgB2 wires, as demonstrated on a wire with B4C
additives. Based on the present data, it follows that cold densification has
the potential of further improving the highest Jcpara and Jcperp values
reported so far for in situ MgB2 tapes and wires with SiC and C additives.
Investigations are under work in our laboratory to determine whether the
densification method CHPD can be applied to longer wire or tape lengths.Comment: Submitted to Superconductors Science and Technolog
Anisotropic magnetic properties of CeAgGe single crystal
In order to investigate the anisotropic magnetic properties of
CeAgGe, we have successfully grown the single crystals, for the first
time, by high temperature solution growth (flux) method. We have performed a
detailed study of the grown single crystals by measuring their electrical
resistivity, magnetic susceptibility, magnetization, specific heat and
magnetoresistance. A clear anisotropy and an antiferromagnetic transition at
= 4.6 K have been observed in the magnetic properties. The magnetic
entropy reaches ln 4 at 20 K indicating that the ground state and the first
excited state are very closely spaced (a quasi-quartet state). From the
specific heat measurements and crystalline electric field (CEF) analysis of the
magnetic susceptibility, we have found the level splitting energies as 5 K and
130 K. The magnetization measurements reveal that the a-axis is the easy axis
of magnetization and the saturation moment is = 1.6 /Ce, corroborating the previous neutron diffraction measurements on a
polycrystalline sample.Comment: Submitted to Phys. Rev.
Evaluation of the hydrogen solubility and diffusivity in proton-conducting oxides by converting the PSL values of a tritium imaging plate
Proton-conducting oxides have potential applications in hydrogen sensors,
hydrogen pumps, and other electrochemical devices including the tritium
purification and recovery systems of nuclear fusion reactors. Although the
distribution of hydrogen (H) in such oxide materials is an important aspect,
its precise measurement is difficult. In the present study, the hydrogen
solubility and diffusivity behavior of BaZr0.9Y0.1O2.95 (BZY),
BaZr0.955Y0.03Co0.015O2.97 (BZYC), and CaZr0.9In0.1O2.95 (CZI) were studied
using tritiated heavy water vapor i.e., DTO (~2 kPa, tritium (T) = 0.1%) by
converting the photostimulated luminescence (PSL) values of the imaging plate
(IP). The samples were exposed to DTO vapor at 673 K for 2 h or at 873 K for 1
h. The disc-shaped oxide specimens (diameter ~7.5 mm; thickness ~2.3 mm;
theoretical density (TD) > 98 %) were prepared by conventional powder
metallurgy. The IP images of the specimen surfaces of all the three materials
T-exposed revealed that BZY showed the most uniform T distribution with the
highest tritium activity. The cross-sectional T concentration profiles of the
cut specimens showed that T diffused deeper into BZY and BZYC than into CZI.
The hydrogen solubility and diffusivity in the CZI specimen were lower than
that in the BZY and BZYC specimens. This suggested that barium zirconates were
more favorable proton conductors than calcium zirconates.Comment: 19 pages, 12 figure
Orbital mass secondary to infantile acute lymphoblastic leukaemia
An 8-month-old Asian infant girl was referred with a 1-week history of left periorbital swelling on a background of a narrowed left palpebral aperture over the preceding 8 weeks. There was no history of chronic illness, fever or other systemic features. Examination revealed a tender and fluctuant medial canthal swelling with associated periorbital haematoma. There were no other ophthalmic findings and neurological examination was normal. A MRI scan of the brain and orbit demonstrated abnormal soft tissue with features of an aggressive tumour in the left orbital region with no globe invasion. Peripheral blood smear revealed blast cells, confirmed by bone marrow aspirate. A diagnosis of infant acute lymphoblastic leukaemia was made. The patient was started on risk-stratified chemotherapy according to the Interfant-06 Protocol The periorbital swelling resolved by day eight following a course of prednisolone, the patient continues on chemotherapy and is currently in molecular remission
B(E2) value of even-even 108-112Pd isotopes by interacting boson model-1*
This work studies the systematic reduced transition probabilities B(E2),
intrinsic quadrupole moments and deformation parameters of Pd isotopes with
even neutrons from N= 62 to 66. The downward reduced transition probabilities
B(E2) from gamma transition 8+ to 6+, 6+ to 4+, 4+ to 2+ and 2+ to 0+ states of
even-even 108-112Pd isotopes were calculated by the Interacting Boson Model
(IBM-1) and compared with the available previous experimental results. The
ratio of the excitation energies of the first 4+ and the first 2+ excited
states, R4/2, is also studied for the classification of symmetry of these
nuclei. Furthermore we have studied systematically the transition rate R of
some of the low-lying quadrupole collective states in comparison with the
available experimental data. The associated quadrupole moments and deformation
parameters have been calculated. The results of this calculation are in good
agreement with the corresponding available experimental data. The 108-112Pd
isotopes show the O(6) symmetry
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