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排序方式: 共有825条查询结果,搜索用时 78 毫秒
41.
M.-S. Scholz J.P. BlanchfieldL.D. Bloom B.H. CoburnM. Elkington J.D. FullerM.E. Gilbert S.A. MuflahiM.F. Pernice S.I. RaeJ.A. Trevarthen S.C. WhiteP.M. Weaver I.P. Bond 《Composites Science and Technology》2011,71(16):1791-1803
The use of fibre reinforced composite materials for biomedical purposes is reviewed. The development of polymer composite materials has, in recent years, led to technological advances across a wide range of applications in modern orthopaedic medicine and prosthetic devices. Composites typically possess a superior strength to weight characteristic compared to monolithic materials and offer excellent biocompatibility. They are, therefore, favourable for both hard- and soft-tissue applications as well as the design of prostheses. In particular, the development of specifically designed carbon fibre sports prostheses now allows lower-limb amputees to actively participate in competitive sports. Sensory feedback systems, porous composite materials for tissue engineering and functional coatings for metallic implants are further developments anticipated to be introduced in next generation orthopaedic medicine. 相似文献
42.
D. Grasso S. Profumo A.W. Strong L. Baldini R. Bellazzini E.D. Bloom J. Bregeon G. Di Bernardo D. Gaggero N. Giglietto T. Kamae L. Latronico F. Longo M.N. Mazziotta A.A. Moiseev A. Morselli J.F. Ormes M. Pesce-Rollins M. Pohl M. Razzano C. Sgro G. Spandre T.E. Stephens 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,630(1):140
43.
We attempted to mimic in small upflow anaerobic sludge bed (UASB) bioreactors the metabolic association found in nature between methanogens and methanotrophs. UASB bioreactors were inoculated with pure cultures of methanotrophs, and the bioreactors were operated by using continuous low-level oxygenation in order to favor growth and/or survival of methanotrophs. Unlike the reactors in other similar studies, the hybrid anaerobic-aerobic bioreactors which we used were operated synchronously, not sequentially. Here, emphasis was placed on monitoring various methanotrophic populations by using classical methods and also a PCR amplification assay based on the mmoX gene fragment of the soluble methane monooxygenase (sMMO). The following results were obtained: (i) under the conditions used, Methylosinus sporium appeared to survive better than Methylosinus trichosporium; (ii) the PCR method which we used could detect as few as about 2,000 sMMO gene-containing methanotrophs per g (wet weight) of granular sludge; (iii) inoculation of the bioreactors with pure cultures of methanotrophs contributed greatly to increases in the sMMO-containing population (although the sMMO-containing population decreased gradually with time, at the end of an experiment it was always at least 2 logs larger than the initial population before inoculation); (iv) in general, there was a good correlation between populations with the sMMO gene and populations that exhibited sMMO activity; and (v) inoculation with sMMO-positive cultures helped increase significantly the proportion of sMMO-positive methanotrophs in reactors, even after several weeks of operation under various regimes. At some point, anaerobic-aerobic bioreactors like those described here might be used for biodegradation of various chlorinated pollutants. 相似文献
44.
The magnetoresistance in the photocurrent and injected current of an organic device has been studied. When such a device is illuminated under bias, both photo-generated charges and electrically injected carriers will contribute to the current. We used a magnetic field modulation to successfully remove the time-dependent change in the current. This was combined with a modulation of the intensity of the illumination to separately measure the effects of the photocurrent. At low bias, without illumination no magnetoconductance (MC) is observed in leakage current, while with illumination an MC is observed due to the photo-generated charges. With increasing voltage, as electrical charge injection starts, the width of the MC curves as a function of magnetic field of the photocurrent remains constant and is larger than the curve observed for the electrically injected current, even when both currents are present. This result shows that the contributions from the photocurrent and the injected current cannot be combined, but should be treated separately. 相似文献
45.
46.
FL Black 《Canadian Metallurgical Quarterly》1997,69(4):467-482
Three reasons that HTLV-I and HTLV-II would not be expected to trace human migrations over extended time periods have been examined, and none has proven fatal to the theory. Transmission of the HTLVs (human T-cell lymphotropic viruses) in endemic settings highly depends on passage through breast milk, and this creates a pattern of distribution similar to that of mitochondrial DNA. The HTLVs probably evolve at variable rates, making the extent of sequence change a poor tool for dating human migrations. However, qualitative relationships between the sequence of human population separations and virus strain may be more regular. The uniqueness of viruses as markers of human relationship gives this method special value as a source of novel ideas regarding human movements and as independent confirmation of migration hypotheses that have been based on more conventional methods. 相似文献
47.
FL Lado Lado E Barrio Gómez A Cabarcos Ortiz de Barrón E Carballo Arceo J Sánchez Leira ML Pérez del Molino JR Antúnez López 《Canadian Metallurgical Quarterly》1998,15(8):415-420
The in vitro radiosensitivity of dermal fibroblasts has been found to vary between individuals, and a number of studies have also shown that this parameter correlates with radiation-induced late injuries in clinical radiotherapy. In addition, certain genetic disorders are known to effect radiosensitivity, e.g. normal tissues of patients homozygous or heterozygous for the ataxia teleangiectasia gene show unusual sensitivity to radiation both in vivo and in vitro. Thus, it has been assumed that there is a genetically determined component resulting in a certain intrinsic cellular radiation response in an individual. To study this possible relationship between different cells of a specific patient, we established eight pairs of dermal and tumor fibroblast cultures. The donor patients had either adenocarcinoma of the uterus or squamous cell carcinoma (SCC) of the head and neck. The radiosensitivity of these strains was determined by a 96-well plate clonogenic assay, previously used by us for radiosensitivity testing of cancer cells. From a paired comparison, the values for the cell fraction surviving 2.0 Gy (SF2), of both fibroblast strains, were found to be on the same level in five out of eight cases. In patient 6, the SF2 of tumor fibroblasts was significantly higher than that of dermal fibroblasts (P=0.0014). In two additional cases the tendency was the same, but not statistically significant. As groups, the two types of fibroblasts did not differ from each other, mean SF2 values of 0.24+/-0.07 and 0.21+/-0.05, respectively. The SF2 of tumor fibroblasts from SCC patients proved to be significantly higher than that of the adenocarcinoma patients (P=0.030). These preliminary results indicate that the in vitro radiosensitivity of tumor fibroblasts correlates with normal cell sensitivity in many cases, but not in all. The radiosensitivity of tumor fibroblasts also seems to follow the level of in vitro radiosensitivity determined for the corresponding histological type of tumor cells. Further studies are needed to determine more closely the relationship between the radiosensitivities of tumor cells and tumor fibroblasts, thus evaluating the possibility of testing radiosensitivity from tumor fibroblasts in order to estimate tumor response. 相似文献
48.
FL Martin W Pfau KJ Cole S Venitt LB Fay H Marquardt DH Phillips PL Grover 《Canadian Metallurgical Quarterly》1998,251(1):182-189
The aim of this study was to determine whether suckling-induced prolactin (PRL) levels were modified when milk ejection was impaired. Milk ejection impairment was achieved in two experimental models: a) depriving the dam of sleep during suckling and b) increasing the nonsuckling intervals in lactating dams. Sleep deprivation blocked milk ejection and enhanced suckling-induced PRL levels in dams that had been previously separated from their pups. When milk ejection is blocked in litter-deprived dams, mammary glands are not evacuated and they remain engorged. Suckling stimuli were not the cause of the difference in suckling-induced serum PRL levels in control and sleep-deprived dams. The engorgement of the mammary glands may play a role, as a maximum suckling-induced PRL increase was not observed in nonseparated SD dams with nonengorged mammary glands. Moreover, suckling-induced PRL levels were decreased when engorged mammary glands of SD dams were evacuated through an oxytocin injection. A parallel increase between suckling-induced PRL levels and mammary gland weight was observed in the experiments in which milk ejection was impaired through an increase in the intervals of nonsuckling, providing additional support for a relationship between mammary gland engorgement and the regulation of suckling-induced PRL levels. 相似文献
49.
50.
G.R. Olbright R.P. Bryan W.S. Fu R. Apte D.M. Bloom Y.H. Lee 《Photonics Technology Letters, IEEE》1991,3(9):779-781
The authors report the measurement of the laser linewidth, wavelength tunability, and generation of microwave frequencies between individually addressable elements of a vertical-cavity GaAs quantum-well surface-emitting laser diode array (lasing in the wavelength range 850-865 nm). Using heterodyne techniques, the authors obtain a deconvolved 65 MHz laser linewidth from the 109 MHz beat signal. The laser linewidth corresponds to a semiconductor laser linewidth enhancement factor alpha =5.7, which is in excellent agreement with that obtained independently from optical gain measurements and corresponding calculated refractive index changes. The authors measured heterodyne beat frequencies of 2-20 GHz. The bandwidth was limited by the microwave amplifiers. A simple calculation shows that a tuning range of 65 MHz to 3 THz can be achieved.<> 相似文献