No description available.

Background: The applications for rapid prototyping have expanded dramatically over the last 20 years. In recent years, additive manufacturing has been intensely investigated for surgical implants, tissue scaffolds, and organs. There is, however, scant literature to date that has investigated the viability of 3D printing of surgical instruments. Materials and Methods: Using a fused deposition manufacturing (FDM) printer, an army/ navy surgical retractor was replicated from polylactic acid (PLA) filament. The retractor was sterilized using standard FDA approved glutaraldehyde protocols, tested for bacteria by PCR, and stressed until fracture in order to determine if the printed instrument could tolerate force beyond the demands of an operating room. Results: Printing required roughly 90 minutes. The instrument tolerated 13.6 kg of tangential force before failure, both before and after exposure to the sterilant. Freshly extruded PLA from the printer was sterile and produced no PCR product. Each instrument weighed 16g and required only $0.46 of PLA. Conclusions: Our estimates place the cost per unit of a 3D printed retractor to be roughly 1/10th the cost of a stainless steel instrument. The PLA Army/ Navy is strong enough for the demands of the operating room. Freshly extruded PLA in a clean environment, such as an OR, would produce a sterile, ready to use instrument. Due to the unprecedented accessibility of 3D printing technology world wide, and the cost efficiency of these instruments, there are far reaching implications for surgery in some underserved and less developed parts of the world.

No description available.

Two new specification tests for overidentifying restrictions proposed by Hahn and Hausman (2002:b) are here tested and compared to the classical Sargan test. Power properties are found to be very similar in overall performance, while Sargan generally has better size than the new tests. Also, size is distorted for one of the new tests, thus a tendency to reject prevails. In addition, sometimes severe bias is found which affects the tests’ performances, something that differs from earlier studies.

No description available.

In this paper, the evocative nature of patina on stringed instruments is linked to the four agents of transformation that create it. These correspond to four nostalgic values: nostalgic reflection on the passage of time; nostalgia inspired by use; nostalgia for craftsmanship and pastoral nostalgia. Actors in the subfield of restricted cultural production of stringed instruments invoke one or more of these nostalgic values explicitly as a means to rationalize their actions to competing actors and to the broader public in their battle for status. Patina offers visible proof of their claims. Actors in the subfield of large-scale cultural production do not appeal to specific nostalgic values. Rather, they partake of the nostalgic aura surrounding antique instruments by "pasting" artificial patina onto their instruments. This serves to validate the idea of nostalgia. It also lays bare tensions existing in the broader field of cultural production over questions concerning the past and present.

No abstract available. / Thesis (Ph.D.)-University of Natal, Durban, 1998.

Field and laboratory spectroscopy are sub-fields of remote sensing, where the radiometric data of materials are individually measured either where the materials occur in situ or in a controlled laboratory environment. Both applications require the use of a spectroradiometer to record this reflected electromagnetic radiation. The spectral properties of rocks from the Mambulu Complex in the Natal Belt have not been studied previously. Four dominant rock types, namely, massif-type anorthosite, leuco-gabbro, pyroxenite and magnetitite were sampled from the Mambulu Complex and their spectral reflectances measured. Absorption features were determined after continuum removal was applied to the spectra. Anorthosite showed absorption features at 480-490, 592, 603, 608, 627-726, 765, 1410, 1905-1955, 2200, 2250 and 2330nm. For leuco-gabbro absorption features were observed at 481, 950-1010, 1407, 1917, 2206, 2252, and 2300-2340nm. Magnetitite displayed absorption features at 414, 460-515, 620-715, 982, 1380-1480, 1800, 1905-1930 and 2145-2330nm. For medium-grained pyroxenite absorption features were present at 410-420, 483, 680, 977-993, 1410-1415, 1800, 1920, 2205, 2250, 2307, 2400 and 2430nm. Coarse-grained pyroxenite showed absorption features at 460-727, 979, 1000, 1401, 1422, 1800, 1913, 1930, 2203, 2258, 2321, 2388 and 2421nm. ANOVAs and Bonferroni tests were applied to the spectral data to calculate significant spectral differences and between which pairs of rocks these significant differences occurred. Results showed that there were significant spectral differences between all the rock types of the Mambulu Complex. The variability of spectral characteristics within rock species was attributed to the difference in composition of fresh and weathered surfaces; and the significant spectral differences between rock samples can be attributed primarily to differences in mineral composition. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2012.

No description available.

No description available.