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排序方式: 共有515条查询结果,搜索用时 174 毫秒
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502.
Gregory B. Kharas Anthony Scola III Kristen Mc Colough Allison Crawford Celeste A. Diener Gilbert Villaseñor 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):459-467
Unsaturated polyesters are prepared by transesterification polymerization of diethyl fumarate and 1,4‐cyclohexanedimethanol. The structure of the polyesters was characterized by FT‐IR and 1H‐ and 13C‐NMR spectroscopy. Semicrystalline morphology of the polymers is suggested by DSC analysis with Tg at 21°C and melting at 140°C. The thermogravimetric analysis indicated that the onset of degradation takes place at 300°C. The polyester's structure has significant impact on the properties of the composites prepared by crosslinking the fumarate double bonds with N‐vinyl pyrrolidone in the presence of an inorganic filler, calcium sulfate dihydrate, with the addition of a radical initiator, benzoyl peroxide, at ambient temperatures. The compressive strength and hydrolytic stability of the cement compositions was correlated with structure of the polyesters. 相似文献
503.
Z. Tahmasebi Birgani Pamela Habibovic Lucas A. Kinard F. Kurtis Kasper Antonios G. Mikos John A. Jansen Sander C. G. Leeuwenburgh Jeroen J. J. P. van den Beucken 《Macromolecular bioscience》2013,13(6):777-788
The enzyme alkaline phosphatase (ALP) is added at different concentrations (i.e., 0, 2.5, and 10 mg · ml?1) to oligo(poly(ethylene glycol)fumarate) (OPF) hydrogels. The scaffolds are either incubated in 10 mM calcium glycerophosphate (Ca–GP) solution for 2 weeks or implanted in a rat subcutaneous model for 4 weeks. Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and alizarin red staining show a strong ability to form minerals exclusively in ALP‐containing hydrogels in vitro. Additionally, the calcium content increases with increasing ALP concentration. Similarly, only ALP‐containing hydrogels induce mineralization in vivo. Specifically, small (≈5–20 µm) mineral deposits are observed at the periphery of the hydrogels near the dermis/scaffold interface using Von Kossa and alizarin red staining.
504.
Natasha Irrera Alessandra Bitto Emanuela SantAntonio Rita Lauro Caterina Musolino Alessandro Allegra 《Molecules (Basel, Switzerland)》2021,26(13)
The endocannabinoid system (ECS) is a composite cell-signaling system that allows endogenous cannabinoid ligands to control cell functions through the interaction with cannabinoid receptors. Modifications of the ECS might contribute to the pathogenesis of different diseases, including cancers. However, the use of these compounds as antitumor agents remains debatable. Pre-clinical experimental studies have shown that cannabinoids (CBs) might be effective for the treatment of hematological malignancies, such as leukemia and lymphoma. Specifically, CBs may activate programmed cell death mechanisms, thus blocking cancer cell growth, and may modulate both autophagy and angiogenesis. Therefore, CBs may have significant anti-tumor effects in hematologic diseases and may synergistically act with chemotherapeutic agents, possibly also reducing chemoresistance. Moreover, targeting ECS might be considered as a novel approach for the management of graft versus host disease, thus reducing some symptoms such as anorexia, cachexia, fatigue, anxiety, depression, and neuropathic pain. The aim of the present review is to collect the state of the art of CBs effects on hematological tumors, thus focusing on the essential topics that might be useful before moving into the clinical practice. 相似文献
505.
Esther Cascarosa Jason BeckerLorenzo Ferrante Cedric BriensFranco Berruti Jesús Arauzo 《Journal of Analytical and Applied Pyrolysis》2011,91(2):359-367
Nowadays, meat and bone meal produced in animal slaughterhouses and farms has become an important waste. Landfilling this residue means that its energy is lost. The pyrolysis of meat and bone meal produces a solid fraction which can be used as a fuel or as solid adsorbent, a liquid fraction with possible chemical applications and a low heating value gas.In this work, meat and bone meal has been pyrolyzed with a new technology, a mechanically fluidized reactor (MFR). This MFR is a stainless steel cylinder with 7.7 cm i.d., and an internal height of 15.6 cm. The meat and bone meal pyrolysis was carried out at 500 °C of temperature. The effect of several factors (mixer speed, heating rate and feed composition) on the product yields, bio-oil phases yield, bio-oil heating value and char heating value was studied. The amount of pure meat meal in the feed had a strong impact on product yields and compositions. The liquid yield, which has two phases, varies from 22 wt% to 52 wt% when the raw material fed changed from pure bone meal to pure meat meal. 相似文献
506.
Nonlinear inversion of ultrasonic guided waves for in vivo evaluation of cortical bone properties 下载免费PDF全文
Xiaojun Song 《中国物理 B》2022,31(7):74301-074301
Ultrasonic guided waves (UGWs), which propagate throughout the entire thickness of cortical bone, are attractive for the early diagnosis of osteoporosis. However, this is challenging due to the impact of soft tissue and the inherent difficulties related to multiparametric inversion of cortical bone quality factors, such as cortical thickness and bulk wave velocity. Therefore, in this research, a UGW-based multi-parameter inversion algorithm is developed to predict strength-related factors. In simulation, a free plate (cortical bone) and a bilayer plate (soft tissue and cortical bone) are used to validate the proposed method. The inversed cortical thickness (CTh), longitudinal velocity (VL) and transverse velocity (VT) are in accordance with the true values. Then four bovine cortical bone plates were used in in vitro experiments. Compared with the reference values, the relative errors for cortical thickness were 3.96%, 0.83%, 2.87%, and 4.25%, respectively. In the in vivo measurements, UGWs are collected from the tibias of 10 volunteers. The theoretical dispersion curves depicted by the estimated parameters (VT, VL, CTh) match well with the extracted experimental ones. In comparison with dual-energy x-ray absorptiometry, our results show that the estimated transverse velocity and cortical thickness are highly sensitive to osteoporosis. Therefore, these two parameters (CTh and VT) of long bones have potential to be used for diagnosis of bone status in clinical applications. 相似文献
507.
Amplitude modulation excitation for cancellous bone evaluation using a portable ultrasonic backscatter instrumentation 下载免费PDF全文
The ultrasonic backscatter (UB) has the advantage of non-invasively obtaining bone density and structure, expected to be an assessment tool for early diagnosis osteoporosis. All former UB measurements were based on exciting a short single-pulse and analyzing the ultrasonic signals backscattered in bone. This study aims to examine amplitude modulation (AM) ultrasonic excitation with UB measurements for predicting bone characteristics. The AM multiple lengths excitation and backscatter measurement (AM-UB) functions were integrated into a portable ultrasonic instrument for bone characterization. The apparent integrated backscatter coefficient in the AM excitation (AIBAM) was evaluated on the AM-UB instrumentation. The correlation coefficients of the AIBAM estimating volume fraction (BV/TV), structure model index (SMI), and bone mineral density (BMD) were then analyzed. Significant correlations (|R| = 0.82-0.93, p < 0.05) were observed between the AIBAM, BV/TV, SMI, and BMD. By growing the AM excitation length, the AIBAM values exhibit more stability both in 1.0-MHz and 3.5-MHz measurements. The recommendations in AM-UB measurement were that the avoided length (T1) should be lower than AM excitation length, and the analysis length (T2) should be enough long but not more than AM excitation length. The authors conducted an AM-UB measurement for cancellous bone characterization. Increasing the AM excitation length could substantially enhance AIBAM values stability with varying analyzed signals. The study suggests the portable AM-UB instrument with the integration of real-time analytics software that might provide a potential tool for osteoporosis early screening. 相似文献
508.
去卵巢大鼠骨元素代谢紊乱机制研究 总被引:1,自引:0,他引:1
测定了去卵巢大鼠骨元素含量和血清相关激素和细胞因子含量,分析了去卵巢大鼠骨元素代谢紊乱的机制。将健康4月龄SD大鼠18只随机分成3组:正常对照组,假去卵巢大鼠组和去卵巢大鼠组。结果表明,去卵巢大鼠骨Ca、Mg、S、Mn、Zn等含量显著降低,P含量显著升高,血清E2、P、CT、GH等含量显著降低,IL-6、FSH、LH等含量显著升高。提示去卵巢大鼠骨元素代谢紊乱是雌激素水平下降与其他因素共同作用的结果。 相似文献
509.
510.
我国口腔生物力学研究进展与展望 总被引:1,自引:0,他引:1
本文综述了我国口腔生物力学研究现状、研究手段、达到的水平以及临床应用状况、并作了展望。 相似文献