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排序方式: 共有507条查询结果,搜索用时 62 毫秒
61.
Chavagnac V Milton JA Green DR Breuer J Bruguier O Jacob DE Jong T Kamenov GD Le Huray J Liu Y Palmer MR Pourtalès S Roduhskin I Soldati A Trueman CN Yuan H 《Analytica chimica acta》2007,599(2):177-190
Ten international laboratories participated in an inter-laboratory comparison of a fossil bone composite with the objective of producing a matrix and structure-matched reference material for studies of the bio-mineralization of ancient fossil bone. We report the major and trace element compositions of the fossil bone composite, using in-situ method as well as various wet chemical digestion techniques.For major element concentrations, the intra-laboratory analytical precision (%RSDr) ranges from 7 to 18%, with higher percentages for Ti and K. The %RSDr are smaller than the inter-laboratory analytical precision (%RSDR; <15-30%). Trace element concentrations vary by ∼5 orders of magnitude (0.1 mg kg−1 for Th to 10,000 mg kg−1 for Ba). The intra-laboratory analytical precision %RSDr varies between 8 and 45%. The reproducibility values (%RSDR) range from 13 to <50%, although extreme value >100% was found for the high field strength elements (Hf, Th, Zr, Nb). The rare earth element (REE) concentrations, which vary over 3 orders of magnitude, have %RSDr and %RSDR values at 8-15% and 20-32%, respectively. However, the REE patterns (which are very important for paleo-environmental, taphonomic and paleo-oceanographic analyses) are much more consistent.These data suggest that the complex and unpredictable nature of the mineralogical and chemical composition of fossil bone makes it difficult to set-up and calibrate analytical instruments using conventional standards, and may result in non-spectral matrix effects. We propose an analytical protocol that can be employed in future inter-laboratory studies to produce a certified fossil bone geochemical standard. 相似文献
62.
High-affinity integration of hydroxyapatite nanoparticles with chemically modified silk fibroin 总被引:3,自引:0,他引:3
Hydroxyapatite (HA)-based nanocomposites were prepared by a co-precipitation method with silk fibroin (SF) serving as organic
matrix. Silk fibroin was chemically modified with an alkali solution or an enzyme attempting to improve the interface between
the mineral and the organic matrix. The influences of the alkali and enzyme pretreatments on microstructure and physicochemical
properties of HA–SF composite were examined and compared. The results reveal that both the two kinds of pretreatments facilitate
the formation of highly ordered three-dimensional porous network throughout the composites, increase the microhardness of
the composite, and promote the preferential growth of HA crystallites along c-axis. Among all the as-prepared samples, the composite containing the enzyme pretreated SF shows desirable hierarchical microstructure
with higher degree of organization and more uniform pore size distribution. Due to the enzyme pretreatment, HA crystallites
undergo obvious changes in morphology from rod-like to␣whisker-like and in crystal growth towards more apparent epitaxy along
c-axis. The alkali pretreatment induces the stronger chemical interactions between HA and SF and thus to strengthen the inorganic–organic
interfacial adhesion. The newly developed HA–SF composites are expected to be attractive biomedical materials for bone repair
and remodeling. 相似文献
63.
The TEM characterization of the lamellar structure of osteoporotic human trabecular bone 总被引:2,自引:0,他引:2
The lamellar structure of osteoporotic human trabecular bone was characterized experimentally by means of transmission electron microscopy (TEM). More specifically, the TEM was used to determine if trabecular bone exhibits similar lamellar structural motifs as cortical bone by analyzing unmineralized, mineralized and demineralized bone, and to study the influence of the osteocyte network on the lamellar structure of osteoporotic trabecular bone. Comparison with normal trabecular bone is included. This paper summarizes partial results of a larger study, which addressed the characterization of the hierarchical structure of normal versus osteoporotic human trabecular bone [Rubin, M.A., 2001. Multiscale characterization of the ultrastructure of trabecular bone in osteoporotic and normal humans and in two inbred strains of mice. MS Thesis, Georgia Institute of Technology.] at several structural scales. 相似文献
64.
Since the early 1990s, tissue engineering has been heralded as a strategy that may solve problems associated with bone grafting procedures. The original concept of growing bone in the laboratory, however, has proven illusive due to biological, logistic, and regulatory problems. Fat-derived stem cells and synthetic polymers open new, more practicable routes for bone tissue engineering. In this paper, we highlight the potential of poly(L-lactide-co-caprolactone) (PLCL) to serve as a radiolucent scaffold in bone tissue engineering. It appears that PLCL quickly and preferentially binds adipose stem cells (ASCs), which proliferate rapidly and eventually differentiate into the osteogenic phenotype. An in vivo spinal fusion study in a goat model provides a preclinical proof-of-concept for a one-step surgical procedure with ASCs in bone tissue engineering. 相似文献
65.
66.
A. G. Ushenko S. B. Ermolenko D. N. Burkovets Yu. A. Ushenko 《Journal of Applied Spectroscopy》2000,67(1):65-69
A matrix method is proposed for describing polarization properties of biological tissues as an aggregate of uniaxial crystal
structures. We investigated 25 μm-thick histological sections of compact bone tissue which provided single light scattering.
It is shown that in this case there exists a unique relationship between the polarization parameters of the boundary laser
field and the parameters of anisotropy and orientation of the structural elements of biological tissue. On this basis, contactless
methods of laser polarimetry of histological sections of bone tissue have been proposed.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 52–55, January–February, 2000. 相似文献
67.
Hideya Kawasaki Tarui Akira Takehiro Watanabe Kazuyoshi Nozaki Tetsu Yonezawa Ryuichi Arakawa 《Analytical and bioanalytical chemistry》2009,395(5):1423-1431
The availability of robust methods for the species-specific detection of meat and bone meal (MBM) in compound feedingstuffs
is an important prerequisite to enforce current and upcoming European legislation on the use of processed animal proteins
in animal nutrition. Among possible methods, those based on DNA turned out to be a reliable tool for this aim, since DNA is
a quite thermostable molecule able to resist severe heat treatments applied in the manufacturing of animal meals. The application
of such methods by control laboratories implies that the method has been validated including an assessment of its robustness.
Successful transferability between laboratories is considered an important robustness criterion of the method. However, corresponding
guidelines regarding the design of such a study relevant to this field are missing. Here, we demonstrate the feasibility of
an alternative concept that was applied to check for the transferability of a qualitative assay for the detection of banned
MBM in feedingstuffs at trace level based on real-time PCR. The concept was based on an experimental nested design applying
analysis of variance (ANOVA) that was conducted independently in two laboratories and which allows for establishing major
factors influencing the result of analysis. Statistical assessment of the results confirmed the importance of the DNA extraction/purification
step utilised, whereas the PCR step turned out to be a minor factor regarding the overall variability of the results. Furthermore,
blind samples comprised of compound feed adulterated with MBM at 0.1 % and blank compound feed were correctly classified as
"positive" or "negative" samples, thus confirming fitness of purpose for the method. This approach can be of interest for
other research groups working in the development of real-time PCR methods and in their use by control laboratories.
Nested design of the study to check for the transferability of the real-time PCR method 相似文献
68.
69.
为了研究白血病骨髓移植病人全血微量元素铜的变化及其意义 ,用原子吸收光谱法检测了正常对照组与白血病骨髓移植患者预处理前及移植后骨髓空虚期全血微量元素铜的含量。结果表明 ,正常对照组全血铜浓度与白血病骨髓移植患者预处理前全血铜浓度差异无显著性 (P >0 0 5 ) ,而与骨髓空虚期全血铜浓度有显著性差异 (P <0 0 5 ) ,说明白血病缓解后血铜接近正常对照组水平 ,而白血病骨髓移植患者预处理后骨髓空虚期全血铜含量高于正常对照组 ,说明预处理影响微量元素铜的代谢 ,本文就其影响机理进行了研究 相似文献
70.