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168 results on '"Horton, J.A."'

21. Risk factors for human T-cell lymphotropic virus types I and II (HTLV-I and -II) in blood donors: the Retrovirus Epidemiology Donor Study

Author

Schreiber, G.B., Murphy, E.L., Horton, J.A., Wright, D.J., Garfein, R., Chien, H. Co, and Nass, C.C.

Subjects
HTLV infections -- Risk factors, Blood donors -- Health aspects, Health
Abstract

Blood transfusions, multiple sex partners, intravenous drug use and sex with an intravenous drug user appear to be major risk factors for infection with human T-cell lymphotropic virus (HTLV) types I and II. This was the conclusion of a study that followed 546 blood donors who tested positive for HTLV-I or HTLV-II. Needlestick cuts, blood donation and 7 or more sex partners were risk factors for HTLV-I infection. Intravenous drug use or sex with an intravenous drug user were risk factors for HTLV-II infection.

Published
1997

22. Magnetic properties of the low-temperature phase of MnBi

Author

Saha, S., Obermyer, R.T., Zande, B.J., Chandhok, V.K., Simizu, S., Sankar, S.G., and Horton, J.A.

Subjects
Bismuth -- Magnetic properties, Physics
Abstract

The magnetic properties and temperature-dependent coercivity of the low-temperature phase of MnBi are examined. The coercivity reaches a maximum value of 25.8 kOe at 280 degree C with the increase in temperature and declines as the temperature increases further.

Published
2002

24. Consolidation, magnetic and mechanical properties of gas atomized and HDDR Nd2Fe14B powders

Author

Horton, J.A., Heatherly, L., Branagan, D.J., Sellers, C.H., Ragg, O., and Harris, I.R.

Subjects
Atomization -- Usage, Magnetic materials -- Research, Magnets, Permanent -- Materials, Business, Electronics, Electronics and electrical industries
Abstract

[Nd.sub.2][Fe.sub.14]B powders produced by gas atomization (GA) were consolidated and the fracture toughness and magnetic properties were measured and compared to material produced by hydrogenation, disproportionation, desorption, and recombination (HDDR) and to Magnequench MQH magnets. Hot pressing of the gas atomized powder without TiC additions required temperatures and times similar to that required by Magnequench melt spun powder. Titanium plus carbon additions, which result in enhanced quenchability during production of the GA powder, required higher temperatures than alloys without TIC for successful hot pressing and full densification. However, grain sizes remained under 50 nm in the consolidated magnet. Toughnesses for both HDDR and GA material with the larger powder sizes were slightly higher than those of comparable MQH specimens. The TiC modified GA material may result in tougher magnets that are easier to process at higher temperatures by techniques such as extrusion.

Published
1997

25. Fracture toughness of commercial magnets

Author

Horton, J.A., Wright, J.L., and Herchenroeder, J.W.

Subjects
Magnets, Permanent -- Evaluation, Magnetic materials -- Evaluation, Brittleness -- Analysis, Business, Electronics, Electronics and electrical industries
Abstract

[Nd.sub.2][Fe.sub.14]B is currently the best (highest energy product) hard magnet available. Like most permanent magnetic materials, it is rather brittle. The fracture toughness of specimens of commercially available hard magnets were measured using a chevron notch, three-point bend test. Values for [Nd.sub.2][Fe.sub.14]B magnets ranged from 2.5 to 5.5 MPa[square root of m]. In comparison, Sm[Co.sub.5] was measured to have a fracture toughness of 1.9 MPa[square root of m]. It appears that this testing technique will allow differences in fracture toughness to be measured between alloys with different compositions and fabricated by different production methods and should be able to track the fracture toughness as improvements are made to a particular alloy.

Published
1996

31. Evolution of dislocation structure in the heat affected zone of a nickel-based single crystal

Author

Barabash, O.M., Ice, G.E., Horton, J.A., Barabash, R.I., Babu, S.S., Vitek, J.M., David, S.A., and Park, J.W.

Subjects
Electron microscopy -- Usage, Dislocations in crystals -- Research, Nickel -- Research, Nickel -- Thermal properties, Nickel -- Optical properties, Physics
Abstract

Dislocation structure changes of Ni-based single crystal superalloy during impulse heating up to the melting temperature are studied using polychromatic microbeam synchrotron diffraction together with electron and optical microscopy. It is found that the maximum value of the thermal gradient is observed in the heat affected zone (HAZ) near the fusion line.

Published
2004

34. Measurement of bulk density for resource estimation: methods, guidelines and quality control.

Author

Lipton I.T., Horton J.A., Lipton I.T., and Horton J.A.

Abstract

Reliable estimates of bulk density should be built into resource models. Bulk density can be determined from small dried samples by calliper, water displacement, sand replacement, or core tray methods and also from small pulp samples. Some of these methods involve sealing the samples if they are likely to disintegrate in water. Large-scale methods of determining bulk density are useful for minimising errors due to small-scale variability, but are often difficult to implement until the latter stages of a project. Down-hole geophysical logging is often used in advanced projects as it produces reliable results for a wide range of material types, and is fast and cost effective. Bulk density can be estimated from sample chemistry using linear regression or multiple linear regressions where there are one or two dense mineral species; if there are more, then partitioning of assay grades between mineral species is necessary. A quality control and assurance system is necessary at each step of bulk density estimation., Reliable estimates of bulk density should be built into resource models. Bulk density can be determined from small dried samples by calliper, water displacement, sand replacement, or core tray methods and also from small pulp samples. Some of these methods involve sealing the samples if they are likely to disintegrate in water. Large-scale methods of determining bulk density are useful for minimising errors due to small-scale variability, but are often difficult to implement until the latter stages of a project. Down-hole geophysical logging is often used in advanced projects as it produces reliable results for a wide range of material types, and is fast and cost effective. Bulk density can be estimated from sample chemistry using linear regression or multiple linear regressions where there are one or two dense mineral species; if there are more, then partitioning of assay grades between mineral species is necessary. A quality control and assurance system is necessary at each step of bulk density estimation.

Published
2014

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