Tendons are exposed to complex loading scenarios that can only be quantified by mathematical models, requiring a full knowledge of tendon mechanical properties. This study measured the anisotropic, nonlinear, elastic material properties of tendon. Previous studies have primarily used constant strain-rate tensile tests to determine elastic modulus in the fiber direction. Data for Poisson's ratio aligned with the fiber direction and all material properties transverse to the fiber direction are sparse. Additionally, it is not known whether quasi-static constant strain-rate tests represent equilibrium elastic tissue behavior. Incremental stress-relaxation and constant strain-rate tensile tests were performed on sheep flexor tendon samples aligned with the tendon fiber direction or transverse to the fiber direction to determine the anisotropic properties of toe-region modulus (E0), linear-region modulus (E), and Poisson's ratio (v). Among the modulus values calculated, only fiber-aligned linear-region modulus (E1) was found to be strain-rate dependent. The E1 calculated from the constant strain-rate tests were significantly greater than the value calculated from incremental stress-relaxation testing. Fiber-aligned toe-region modulus (E(1)0 = 10.5 +/- 4.7 MPa) and linear-region modulus (E1 = 34.0 +/- 15.5 MPa) were consistently 2 orders of magnitude greater than transverse moduli (E(2)0 = 0.055 +/- 0.044 MPa, E2 = 0.157 +/- 0.154 MPa). Poisson's ratio values were not found to be rate-dependent in either the fiber-aligned (v12 = 2.98 +/- 2.59, n = 24) or transverse (v21 = 0.488 +/- 0.653, n = 22) directions, and average Poisson's ratio values in the fiber-aligned direction were six times greater than in the transverse direction. The lack of strain-rate dependence of transverse properties demonstrates that slow constant strain-rate tests represent elastic properties in the transverse direction. However, the strain-rate dependence demonstrated by the fiber-aligned linear-region modulus suggests that incremental stress-relaxation tests are necessary to determine the equilibrium elastic properties of tendon, and may be more appropriate for determining the properties to be used in elastic mathematical models.

A novel species of thermoacidophilic archaeon, Sulfolobus yangmingensis sp. nov.Ren-Long Jan,' Jeffrey Wu,' Shu-Miaw Chaw,3 Chien-Wei Tsai' and Suh-Der Tsen'Author for correspondence: Suh-Der Tsen. Tel: +886 2 28267108. Fax: $886 2 28212880. e-mail : nymut sen @, yrn.edu. twInstitute of Microbiology and immunology, National Yang-Ming University, ShihPail, Taipei American School2 and Institute of Botany, Academia Sinica3, Taipei, Taiwan, ROC A novel microbe was isolated from a geothermal vent in Yang-Ming National Park in northern Taiwan. This spherical microbe with mean cell diameter of 1.1 20-2 pm is a facultatively chemolithoautotrophic archaeon that grows on elemental sulfur and reduced sulfur compounds. The optimal pH and temperature for growth are 4-0 (pH range 2.0-6.0) and 80 "C (temperature range 65-95 "C). Its membranes contain the lipids calditoglycerocaldarchaeol and caldarchaeol, which are common to other members of the Sulfolobaceae. Like Sulfolobus acidocaldarius, Sulfolobus shibatae and Sulfolobus solfataricus, the new isolate utilizes sugars and amino acids effectively as sole carbon sources. The G+C content of the genomic DNA was 42 mol0/o. DNA of the isolate hybridized weakly to the DNA of other Sulfolobus species. Phylogenetic analysis of the 165 rRNA indicated that the new isolate represents a deep branch within the genus Sulfolobus. On the basis of these properties, the new isolate appears to represent a new species of Sulfolobus, for which the name Sulfolobus yangmingensis sp. nov. is proposed. The type strain is strain YMIT.1 Keywords: thermoacidophile, archaeon, Sulfolobus INTRODUCTIONMembers of the genus Sulfolobus, the first reported genus of the family Sulfolobaceae (Brock et al., 1972;Segerer et al., 1986), are characterized by aerobic growth at high temperatures and low pH in the presence of elemental sulfur. Members of the genus are usually found in habitats such as acidic hot springs and mud holes that contain elemental sulfur. Among the described species of Sulfolobus, Sulfolobus acidocaldarius, originally discovered in Yellowstone National Park, USA, and Sulfolobus solfataricus, originally discovered in Pisciarelli, Italy, have been used widely in research. Both species are distributed worldwide. Sulfolobus hakonensis was isolated in Hakone, Japan (Takayanagi et al., 1996).Taiwan has many active geothermal vents. A new microbial strain was isolated from an acidic, muddy, hot spring in Longfong valley at the southern YangAbbreviations: MP, maximum-parsimony; NJ, neighbour-joining.The GenBank accession number for the 16s rDNA sequence of strain YMIT is AB010957.Ming National Park in northern Taiwan. The temperature of this hot spring can reach 105 "C and the pH is as low as 2. In this report, we have characterized this novel strain in terms of morphology, nutritional requirements, DNA homology with similar species and phylogenetic analysis of its 16s rRNA sequence. METHODSMicrobial strains. S. acidocaldarius DSM 639', S. hakonensis DSM 7519', Sulfolobus shibatae DSM 5389' and S. sol...

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