7,978 research outputs found
Fluorine gas as a cleaning agent for Apollo bulk-sample containers
A technique has been developed for cleaning Apollo bulk sample containers using fluorine gas as the cleaning agent
Field-Induced Magnetic and Structural Domain Alignment in PrO2
We present a neutron diffraction study of the magnetic structure of single
crystal PrO2 under applied fields of 0-6 T. As the field is increased, changes
are observed in the magnetic Bragg intensities. These changes are found to be
irreversible when the field is reduced, but the original intensities can be
recovered by heating to T > 122 K, then re-cooling in zero field. The
antiferromagnetic ordering temperature TN = 13.5 K and the magnetic periodicity
are unaffected by the applied field. We also report measurements of the
magnetic susceptibility of single crystal PrO2 under applied fields of 0-7 T.
These show strong anisotropy, as well as an anomaly at T = 122 +/- 2 K which
coincides with the temperature TD = 120 +/- 2 K at which a structural
distortion occurs. For fields applied along the [100] direction the
susceptibility increases irreversibly with field in the temperature range TN <
T < TD. However, for fields along [110] the susceptibility is independent of
field in this range. We propose structural domain alignment, which strongly
influences the formation of magnetic domains below TN, as the mechanism behind
these changes.Comment: 11 pages, 13 figures, 5 tables. Minor typographical changes in v
Cooperative Jahn-Teller Distortion in PrO2
We report neutron diffraction data on single crystal PrO2 which reveal a
cooperative Jahn-Teller distortion at TD = 120 +/- 2 K. Below this temperature
an internal distortion of the oxygen sublattice causes the unit cell of the
crystallographic structure to become doubled along one crystal axis. We discuss
several possible models for this structure. The antiferromagnetic structure
below TN = 13.5 K is found to consist of two components, one of which shares
the same doubled unit cell as the distorted crystallographic structure. We also
present measurements of the magnetic susceptibility, the specific heat capacity
and the electrical conductivity of PrO2. The susceptibility data show an
anomaly at a temperature close to TD. From the specific heat capacity data we
deduce that the ground state is doubly degenerate, consistent with a distortion
of the cubic local symmetry. We discuss possible mechanisms for this. The
conductivity shows an activated behaviour with an activation energy Ea = 0.262
+/- 0.003 eV.Comment: 12 pages, 14 figures, 2 tables. Additional suggested structure in v
Acceptability of the female condom in different groups of women in South Africa - A multicentred study to inform the national female condom introductory strategy
Objectives. To assess the acceptability of the female condom to different groups of women and their partners in South Africa. Design. Descriptive, cross-sectional study. Setting. Multicentre study conducted in five sites. Subjects. The study recruited 678 women from five centres-to an acceptability trial of the female condom. Acceptability and successful use varied between the centres. Outcome measures. Factors affecting successful use and willingness and intention to use the method again. Results. In total, 209 women used the condom at least once. Discontinuation rates were high, with partner reluctance to try the method as the main reason given for discontinuation at all sites. Women who had previous experience with the male condom or who received a more intensive training session generally found the device easier to use. The main issues concerning women were over-lubrication (27%) and concern that the device was too large (28%). The majority of women said that they would be interested in using the method again (86%) and would recommend it to friends (95%). Conclusions. Overcoming partner opposition is an important issue to address when introducing the method. The study was used to address the national introductory strategy of the female condom, which began in 1998
Sub-micron, Metal Gate, High-Đș Dielectric, Implant-free, Enhancement-mode III-V MOSFETs
The performance of 300nm, 500nm and 1ĂÂŒm metal gate, implant free, enhancement mode III-V MOSFETs are reported. Devices are realised using a 10nm MBE grown Ga2O3/(GaxGd1-x)2O3 high-ĂÂș (ĂÂș=20) dielectric stack grown upon a ĂÂŽ-doped AlGaAs/InGaAs/AlGaAs/GaAs heterostructure. Enhancement mode operation is maintained across the three reported gate lengths with a reduction in threshold voltage from 0.26 V to 0.08 V as the gate dimension is reduced from 1 ĂÂŒm to 300 nm. An increase in transconductance is also observed with reduced gate dimension. Maximum drain current of 420 ĂÂŒA/ĂÂŒm and extrinsic transconductance of 400 Ă”S/Ă”m are obtained from these devices. Gate leakage current of less than 100pA and subthreshold slope of 90 mV/decade were obtained for all gate lengths. These are believed to be the highest performance submicron enhancement mode III-V MOSFETs reported to date
Acceptability of the female condom in different groups Of women in South Africa-A Multicentred study to inform the national female condom introductory strategy
Objectives. To assess the acceptability of the female condom to different groups of women and their partners in South Africa.Design. Descriptive, cross-sectional study.Setting. Multicentre study conducted in five sites.Subjects. The study recruited 678 women from five centres to an acceptability trial of the female condom. Acceptability and successful use varied between the centres. Outcome measures. Factors affecting successful use and willingness and intention to use the method again.Results. In total, 209 women used the condom at least once. Discontinuation rates were high, with partner reluctance to try the method as the main reason given for discontinuation at all sites. Women who had previous experience with the male condom or who received a more intensive training session generally found the device easier to use. The main issues concerning women were over-lubrication (27%) and concern that the device was too large (28%). The majority of women said that they would be interested in using the method again (86%) and would recommend it to friends (95%).Conclusions. Overcoming partner opposition is an important issue to address when introducing the method. The study was used to address the national introductory strategy of the female condom, which began in 1998
Electron mobility in surface- and buried- channel flatband In<sub>0.53</sub>Ga<sub>0.47</sub>As MOSFETs with ALD Al<sub>2</sub>O<sub>3</sub> gate dielectric.
In this paper, we investigate the scaling potential of flatband III-V MOSFETs by comparing the mobility of surface and buried In<sub>0.53</sub>Ga<sub>0.47</sub>As channel devices employing an Atomic Layer Deposited (ALD) Al<sub>2</sub>O<sub>3</sub> gate dielectric and a delta-doped InGaAs/InAlAs/InP heterostructure.
Peak electron mobilities of 4300 cm<sup>2</sup>/V·s and 6600 cm<sup>2</sup>/V·s at a carrier density of 3Ă1012 cm<sup>-2</sup> for the surface and buried channel structures respectively were determined. In contrast to similarly scaled inversion-channel devices, we find that mobility in surface channel flatband structures does not drop rapidly with electron density, but rather high mobility is maintained up to carrier concentrations around 4x10<sup>12</sup> cm<sup>-2</sup> before slowly dropping to around 2000 cm<sup>2</sup>/V·s at 1x10M<sup>13</sup> cm<sup>-2</sup>. We believe these to be world leading metrics for this material system and an important development in informing the III-V MOSFET device architecture selection process for future low power, highly scaled CM
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