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21.
时频方法分析长骨中的超声导波及皮质骨厚度 总被引:4,自引:0,他引:4
超声导波在长骨中传播时,接收信号中含有相互叠加的多个导波模式。本文提出将希尔伯特-黄变换(HHT)用于分析叠加的多模式导波信号,将其分解成许多单个独立的模式,然后对分解出的模式求得其对应频率下的群速度,并与短时傅里叶变换所得的结果进行比较。通过与理论计算结果比较,可得到长骨皮质骨的厚度。研究结果表明,实验得到的厚度与实际厚度一致。说明通过测量导波模式的速度可以评价皮质骨的厚度,也说明HHT方法是一种识别叠加多模式导波信号的有效方法。 相似文献
22.
Abdellatif Bouazzaoui Ahmed A. H. Abdellatif Faisal A. Al-Allaf Neda M. Bogari Mohiuddin M. Taher Mohammad Athar Thomas Schubert Turki M. Habeebullah Sameer H. Qari 《Molecules (Basel, Switzerland)》2021,26(14)
Systemic steroids are used to treat acute graft-versus-host disease (aGVHD) caused by allogenic bone marrow transplantation (allo-BMT); however, their prolonged use results in complications. Hence, new agents for treating aGVHD are required. Recently, a new compound A (CpdA), with anti-inflammatory activity and reduced side effects compared to steroids, has been identified. Here, we aimed to determine whether CpdA can improve the outcome of aGVHD when administered after transplantation in a mouse model (C57BL/6 in B6D2F1). After conditioning with 9Gy total body irradiation, mice were infused with bone marrow (BM) cells and splenocytes from either syngeneic (B6D2F1) or allogeneic (C57BL/6) donors. The animals were subsequently treated (3 days/week) with 7.5 mg/kg CpdA from day +15 to day +28; the controls received 0.9% NaCl. Thereafter, the incidence and severity of aGVHD in aGVHD target organs were analyzed. Survival and clinical scores did not differ significantly; however, CpdA-treated animals showed high cell infiltration in the target organs. In bulk mixed lymphocyte reactions, CpdA treatment reduced the cell proliferation and expression of inflammatory cytokines and chemokines compared to controls, whereas levels of TNF, IL-23, chemokines, and chemokine receptors increased. CpdA significantly reduced proliferation in vitro but increased T cell infiltration in target organs. 相似文献
23.
Recently, the notion of an S-metric space is defined and extensively studied as a generalization of a metric space. In this paper, we define the notion of the S∞-space and prove its completeness. We obtain a new generalization of the classical "Picard Theorem". 相似文献
24.
A sensitive, rapid and accurate titrimetric method has been developed for the determination of 50-5000 mug of ethyl-lead or phenyl-lead compounds, based on their oxidation with a chloroform solution of iodine, removal of the excess of iodine, oxidation of the resulting iodide with bromine, and iodometric titration of the iodate formed. The coefficient of variation does not exceed 1.2% for amounts > 1000 mug of the organolead compound, but increases to 2.8% for the 50-mug level. The ethyl- and phenyl-lead compounds can be determined independently in mixtures. 相似文献
25.
Subhi A. Al-Jibori Ali I. Abdullah Talal A. K. Al-Allaf 《Transition Metal Chemistry》2007,32(3):398-406
Palladium(II) and platinum(II) complexes containing mixed ligands N-(2-pyridyl)acetamide (AH) or N-(2-pyrimidyl)acetamide (BH) and the diphosphines Ph2P(CH2)
n
PPh2, (n = 1, 2 or 3) have been prepared. The prepared complexes [Pd(A)2(diphos)] or [Pd(B)2(diphos)] have been used effectively to prepare bimetallic complexes of the type [(diphos)Pd(μ-L)2M′Cl2] where M′ = Co, Cu, Mn, Ni, Pd, Pt or SnCl2; L = A or B. The prepared complexes were characterized by elemental analysis magnetic susceptibility, i.r. and UV–Vis spectral
data. 31P–{1H}-n.m.r. data have been applied to characterize the produced linkage isomers. 相似文献
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27.
Single pulse excited ultrasonic guided wave surfers high attenuation during the propagation in long bones.This results in small amplitude and low signal-to-noise ratio(SNR)of measured signals.Thus,the Barker code excitation is introduced into long bone detection to improve the quality of received signals,due to its efficiency in increasing amplitude and SNR.Both simulation and in vitro experiment were performed,and the results were decoded by the weighted match filter(WMF) and the finite impulse response- least squares inverse filter(FIRLSIF),respectively.The comparison between the results of Barker code excitation and sine pulse excitation was presented.For 13-bit Barker code excitation,WMF produced 13 times larger amplitude than sine pulse excitation,while FIR-LSIF achieved higher peak-sidelobe-level(PSL) of —63.59 dB and better performance in noise suppression.The results show that the Barker code excited guided waves have the potential to be applied to the long bone detection. 相似文献
28.
YANG Baiding TA De''an WANG Weiqi 《声学学报:英文版》2011,30(3):241-252
Ultrasonic backscatter signals from the cancellous bone can be used to diagnose osteoporosis effectively due to its ability to provide the information of bone microstructure. Mean trabecular bone spacing(MTBS)is one of the important parameters for characterization of bone microstructure.This paper proposed a MTBS estimating method based on the fundamental frequency estimation,which was applied to backscatter signals from simulations, and in vitro bovine trabeculae.The estimated MTBS were compared with those of simplified inverse filter tracking(SIFT)algorithm and autoregressive(AR)cepstrum method.The results demonstrated that the proposed method is very robust for the MTBS estimation with more precise estimates and smaller estimated variance in the presence of a small signal-to-noise ratio (SNR),and a large scattering strength ratio of diffuse scatterers to regular ones. 相似文献
29.
30.
超声导波检测长骨骨折和监测骨折愈合已成为一种极具前景的课题,但高频厚积下导波多模式混叠带来的模式识别和分离问题一直是一个难点。为避免上述问题,在低频下仅激励两个低阶兰姆波SO和AO模式,采用二维时域有限差分(2DFDTD)法定量分析裂纹宽度和骨折角度对SO和AO幅度的影响。结果表明,SO与AO模式的幅度均随裂纹宽度的增加而下降;AO的幅度随骨折角度增大而上升,SO幅度随骨折角度增大先下降后上升,转折点约为45°。SO与AO的幅度比值在不同骨折角度下均能较好地表征裂纹宽度的变化,可为横断型和斜切型长骨骨折状况的超声评价及骨折愈合监测提供依据。 相似文献