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- Zhang, Z. X., et al.
(författare)
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Effects of loading rate on rock fracture
- 1999
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 36:5, s. 597-611
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Tidskriftsartikel (refereegranskat)abstract
- By means of a wedge loading applied to a short-rod rock fracture specimen tested with the MTS 810 or SHPB (split Hopkinson pressure bar), the fracture toughness of Fangshan gabbro and Fangshan marble was measured over a wide range of loading rates, =10−2–106 MPa m1/2 s−1. In order to determine the dynamic fracture toughness of the rock as exactly as possible, the dynamic Moiré method and strain–gauge method were used in determining the critical time of dynamic fracture. The testing results indicated that the critical time was generally shorter than the transmitted wave peak time, and the differences between the two times had a weak increasing tendency with loading rates. The experimental results for rock fracture showed that the static fracture toughness KIc of the rock was nearly a constant, but the dynamic fracture toughness KId of the rock (≥104 MPa m1/2 s−1) increased with the loading rate, i.e. log(KId)=a log +b. Macroobservations for fractured rock specimens indicated that, in the section (which was perpendicular to the fracture surface) of a specimen loaded by a dynamic load, there was clear crack branching or bifurcation, and the higher the loading rate was, the more branching cracks occurred. Furthermore, at very high loading rates (≥106 MPa m1/2 s−1) the rock specimen was broken into several fragments rather than only two halves. However, for a statically fractured specimen there was hardly any crack branching. Finally, some applications of this investigation in engineering practice are discussed.
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| 2. |
- Ni, Jiun, et al.
(författare)
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Cystatin E is a novel human cysteine proteinase inhibitor with structural resemblance to family 2 cystatins
- 1997
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 272:16, s. 10853-10858
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Tidskriftsartikel (refereegranskat)abstract
- A new member of the human cystatin superfamily, called cystatin E, has been found by expressed sequence tag (EST) sequencing in amniotic cell and fetal skin epithelial cell cDNA libraries. The sequence of a full-length amniotic cell cDNA clone contained an open reading frame encoding a putative 28-residue signal peptide and a mature protein of 121 amino acids, including four cysteine residues and motifs of importance for the inhibitory activity of Family 2 cystatins like cystatin C. Recombinant cystatin E was produced in a baculovirus expression system and isolated. An antiserum against the recombinant protein could be used for affinity purification of cystatin E from human urine, as confirmed by N-terminal sequencing. The mature recombinant protein processed by insect cells started at amino acid 4 (cystatin C numbering), and displayed reversible inhibition of papain and cathepsin B (Ki values of 0.39 and 32 nM, respectively), in competition with substrate. Cystatin E is thus a functional cysteine proteinase inhibitor despite relatively low amino acid sequence similarities with human cystatins (26-34% identity with sequences for the Family 2 cystatins C, D, S, SN, and SA; <30% with the Family 1 cystatins, A and B, and domains 2 and 3 of the Family 3 cystatin, kininogen). Unlike other human low Mr cystatins, cystatin E is a glycoprotein, carrying an N-linked carbohydrate chain at position 108. Northern blot analysis revealed that the cystatin E gene is expressed in most human tissues, with the highest mRNA amounts found in uterus and liver. A strikingly high incidence of cystatin E clones in cDNA libraries from fetal skin epithelium and amniotic membrane cells (>0.5% of clones sequenced) indicates a protective role of cystatin E during fetal development.
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| 4. |
- Yu, Ji-Guo, et al.
(författare)
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Exercise training and Blood Volume
- 1995
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Ingår i: Journal of Shandong Physical Education Institute. - 1006-2076. ; 11:1, s. 31-35
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Forskningsöversikt (refereegranskat)abstract
- Both an acute sport and long-term exercise can result in changes in blood volume.Studying these changes, finding their changing patterns and knowing their effects on sport ability have been the problems of a lot of reserchers. In this review. previous works of other peoples were reviewed and analysed in order to provide a clue forfurther studies.
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