Distribution and influencing factors of acoustic characteristics of seafloor sediment in the Sunda Shelf

To understand the acoustic and physical properties of piston core samples collected from the Sunda continental shelf and analyze their distribution patterns,the samples were analyzed in laboratory,from which three provinces were divided in sound speed,sound speed ratio,porosity,wet bulk density,and maximum shear strength.ProvinceⅠhad lower sound speed and sound speed ratio(<1.04),high porosity,and low wet bulk density.ProvinceⅡhad higher sound speed and sound speed ratio(>1.04),low porosity,and high wet bulk density.ProvinceⅢhad the lowest sound speed and sound speed ratio(0.99),highest porosity(81%),and lowest wet bulk density(1.34 g/cm^(3)).The distribution pattern indicates that sediment movement,sediment source,topography,and hydrodynamic conditions influenced the distribution of acoustic and physical properties.Furthermore,we investigated the relationship of the maximum shear strength to the porosity and wet bulk density,and found that the maximum shear strength was proportional to both the porosity and wet bulk density.This finding has significant implications for ocean engineering applications.

Acoustic propagation uncertainty in internal wave environments using an ocean-acoustic joint model

An ocean-acoustic joint model is developed for research of acoustic propagation uncertainty in internal wave environments.The internal waves are numerically produced by tidal forcing over a continental slope using an ocean model.Three parameters(i.e.,internal wave,source depth,and water depth)contribute to the dynamic waveguide environments,and result in stochastic sound fields.The sensitivity of the transmission loss(TL)to environment parameters,statistical characteristics of the TL variation,and the associated physical mechanisms are investigated by the Sobol sensitivity analysis method,the Monte Carlo sampling,and the coupled normal mode theory,respectively.The results show that the TL is most sensitive to the source depth in the near field,resulted from the initial amplitudes of higher-order modes;while in middle and far fields,the internal waves are responsible for more than 80%of the total acoustic propagation contribution.In addition,the standard deviation of the TL in the near field and the shallow layer is smaller than those in the middle and far fields and the deep layer.

Acoustic sound speed profile inversion based on orthogonal matching pursuit

The estimation of ocean sound speed profiles(SSPs)requires the inversion of an acoustic field using limited observations.Such inverse problems are underdetermined,and require regularization to ensure physically realistic solutions.The empirical orthonormal function(EOF)is capable of a very large compression of the data set.In this paper,the non-linear response of the sound pressure to SSP is linearized using a first order Taylor expansion,and the pressure is expanded in a sparse domain using EOFs.Since the parameters of the inverse model are sparse,compressive sensing(CS)can help solve such underdetermined problems accurately,efficiently,and with enhanced resolution.Here,the orthogonal matching pursuit(OMP)is used to estimate range-independent acoustic SSPs using the simulated acoustic field.The superior resolution of OMP is demonstrated with the SSP data from the South China Sea experiment.By shortening the duration of the training set,the temporal correlation between EOF and test sets is enhanced,and the accuracy of sound velocity inversion is improved.The SSP estimation error versus depth is calculated,and the 99%confidence interval of error is within±0.6 m/s.The 82%of mean absolute error(MAE)is less than 1 m/s.It is shown that SSPs can be well estimated using OMP.

Influence of warm eddies on sound propagation in the Gulf of Mexico

An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to determine the spatio–temporal evolution of a strong warm eddy separated from the Mexico current. Then, the influence of this strong warm eddy on sound propagation during its lifespan are comprehensively analyzed with the parabolic equation and explained by using the normal mode and ray theories. Additionally, the influence of mesoscale eddies on the redistribution of total depth-integrated energy among the normal modes in the deep water is also discussed. The variation of arrival angle is investigated to explain the spreading acoustic energy caused by eddies. Overall, the results show that warm eddies can change the propagation paths and cause the convergence zone to broaden and approach the sound source. Moreover,the warm eddy can disperse sound energy and cause the total depth-integrated energy to incline to a lower normal mode.Throughout the whole of these three periods(eddy generating, eddy maturing, and eddy terminating), the fluctuation in the transmission loss is up to 30 dB(depending on the relative location of eddy center to the source).

Functional evaluation using several evoked spinal cord potentials in elderly patients with cervical spondylotic myelopathy

BACKGROUND ： The recordings of evoked spinal cord potentials following epidural spinal cord stimulation are thought to be generated by volleys traversing the dorsal column pathway, and it may not directly reflect conduction defects in corticospinat tracts of cervical spinal cord. To our knowledge there has been few report using several evoked spinal cord potentials in function evaluation of the cervical spinal cord in eldedy patients with cervical spondylotic myelopathy （CSM）. OBJECTIVE： To investigate the function states of the cervical spinal cord in elderly patients with CSM and explore its pathophysictogic mechanism. DESIGN： Case observation SETTING ： Department of Orthopedics for the aged, Shenzhen Pingle Hospital of Orthopedics. Department of Orthopedic Surgery, Yamaguchi University School of Medicine. PARTICIPANTS ： A total of 23 eldedy patients with CSM who received treatment in the Department of Orthopedic Surgery, Yamaguchi University School of Medicine of Japan from January 2003 to February 2004 were enrolled in this study. Inclusive criteria： ① Multiple intervertebral levels of cervical spinal cord compression confirmed by MRI, e.g. 3 or more than 3 levels of compressin. ② Age ≥ 70 years old. ③ Numbness and sensory disturbance in the upper limbs and showed hyperreflexia in the lower limbs. Exclusive criteria： Patients with abnormal motor and sensory nerve conduction velocities in both upper and lower limbs were excluded. METHODS： Evoked spinal cord potentials （ESCPs） following transcranial electric stimulation （TCE-ESCPs）, epidural spinal cord stimulation （SpinaI-ESCPs） and median nerve stimulation （MN-ESCPs） were recorded in 23 patients from posterior epidural space intreoperatively. The abnormalities of TCE-ESCPs were defined as attenuation of amplitude of the D wave. The most cranial intervertebral level showing abnormal TCE-ESCPs with a marked reduction in size of the negative peak （reduction of over 50%） was considered as the upper level of the spinal cord lesion with respect to the corticospinal tract in white matter. The abnormalities of SpinaI-ESCPs were defined as marked reduction in the size of negative peak （reduction of over 50%）. The most caudal intervertebral level showing abnormal SpinaI-ESCPs was considered as the lower level of the spinal cord lesion with respect to the dorsal column pathway in white matter. The abnormalities of MN-ESCPs were defined as attenuation of the N13 amplitude,which was considered as the lesion level of the spinal cord with respect to the dorsal horn in gray matter. Radiological investigation： Lateral view of plain X-ray films was obtained in flexion and extension of the cervical spine. Instability of the cervical intervertebral level was determined as horizontal displacement of the vertebral body of over 3 mm. MAIN OUTCOME MEASURES ： The results of examination of TCE-ESCPs, SpinaI-ESCPs and MN-ESCPs in el- dedy patients with CSM. RESULTS： The 23 eldedy patients with CSM were participated in the result analysis. ①TCE-ESCPs： The impairment of the corticospinal tract in white matter at single intervertebral level was revealed in 18 of 23 patients by recordings of TCE-ESCPs （sensitivity 78%）. In the 18 patients, the lesion level was shown at the up- per cervical segment in 14 patients （C3-4n=10 and C4-5n=4）, and at the lower cervical segment in 4 patients （C5-6n=4）. ②Spinal-ESCPs： The impairment of the dorsal column pathway of white matter at single intervertebral level was revealed in 17 of 23 patients, by recordings of Spinal-ESCPs （sensitivity 74%）. In the 17 patients, the lesion level was presented at the upper cervical segment in 14 patients （C3-4n=10 and C4-5n=4）, and at the lower cervical segment in 3 patients （C5-6 n=3）. ③MN-ESCPs： All patients revealed abnormal MN-ESCPs at one or more intervertebral levels （sensitivity 100%）. The impairment at single intervertebral level was demonstrated in 17 patients, and the impairment at multiple intervertebral levels was shown in 4 patients （3 patients at the C3-4, C4-4, and C5-4~6, and one patient at the C4-5, C5-6, and C6-7）. ④Radiological findings： The Instability of the intervertebral level at the C3-4 or C4-5 motion segment was seen in 15 patients, with a total of 20 levels, and where 10 were at the C3-4 intervertebral level and 5 were at the C3-4, C4-5 intervertebral level. CONCLUSION ： The results suggest that in most elderly patients with CSM who have multiple intervertebral level compressions of the cervical spinal cord on MRI, white matter is impaired at the single cervical intervertebral level, and not only the dorsal column pathway, but also the corticospinal tract can be affected. Combined the findings of radiography, the excessive motion and instability of the C3-4 or C4-5 intervertebral level plays an important role in inducing the long tract lesion in elderly patients with CSM.

A Deep-Water Bottom Reverberation Model Based on Ray Theory

Ocean reverberation is an important issue in underwater acoustics due to the significant influence on working performance of the active sonars. In this paper, a uniform bottom-reverberation model is proposed based on ray theory, which can calculate monostatic and bistatic reverberation intensity and explain the generation process of deep-water reverberation. The mesh meth-od is firstly used in this model by dividing bottom scatterers into a number of grids. Then reverberation is calculated based on the exact time of scattering signal generated on each grid. Due to exact arrival time, the presented model can provide more accurate result than classical models, in which scatterers are usually treated as circular rings or elliptical rings. Numerical results are compared with reverberation data collected from the South China Sea deep-water experiment with different receiving distances and depths. The simulated and experimental results agree well overall.

Characterization and modeling of wind-dominated ambient noise in South China Sea

The action of wind on the sea surface plays an important role in the noise generation mechanism.Sea surface wind speed can be estimated accurately provided there is an accurate understanding of the relationship between the ocean ambient noise and wind speed.Many measurements and analyses of the wind dependence of ambient noise have been conducted.The approximate empirical rule given by Wenz[1]states that in the frequency band between 0.5and 5 kHz,the ambient sea-noise spectrum levels decrease

深海声学研究进展

水声基础研究的目的是揭示声波在复杂海洋环境下的传播现象及物理机理,这是水声高科技装备研发与应用的基础.从深海声学规律认识及声呐应用需求出发,首先综述国外深海声学理论与实验研究进展,并简单回顾了我国水声学基础研究发展历程.过去,我国在浅海声学研究方面成果显著.1997和2012年,在第一届及第三届国际浅海声学会议上,有学者对我国浅海声学研究给予了总结.近年来,随着我国海洋战略的发展,水声研究也逐渐走向深远海.在国家"全球变化与海气相互作用"专项和国家自然科学基金的支持下,我国在深海声学研究方面取得了一些较为系统的进展.本文从深海声学实验技术、复杂地形下声传播特性、声场空间相关特性、环境噪声特性、混响规律、海底参数反演及水下声源定位等方面分别综述.最后梳理了深海声学应用基础研究的重点方向,为我国未来的深海声学研究提供参考.

天然腐植酸光热剂

腐植酸是天然有机碳源的主要组成部分,是微生物对动植物残体进行生物降解而自然形成的。由于腐植酸含有许多具有生理活性的组分(如酚类、羧酸类和醌类),因此,腐植酸的生物医学应用研究在不同文化背景下已历经了几个世纪甚至更长的时间。在本研究中,基于近红外区域的本征吸收,腐植酸钠(腐植酸的钠盐)被研究开发成一种光热剂,用于光诱导光声成像和光热治疗。纯化的腐植酸钠胶体具有高达76.3%的光热转换效率,远高于包括金纳米棒、Cu9S5纳米颗粒、锑烯量子点和黑磷量子点的大多数先进的光热剂,在体内外都有明显的光声增强作用。除此之外,对HeLa肿瘤的高效光热消融是通过瘤内注射实现的。令人惊喜的是,腐植酸钠在细胞和动物水平上显示出超低毒性。这项工作预示着腐植酸作为光介导治疗剂的巨大潜力,从而扩大了传统腐植酸在生物医学领域的应用范围。

Polyethylene glycol-modified cobalt sulfide nanosheets for high-performance photothermal conversion and photoacoustic/magnetic resonance imaging

Theranostic nanoagents that integrate the diagnoses and therapies within a single nanomaterial are compelling in their use for highly precise and efficient antitumor treatments. Herein, polyethylene glycol （PEG）-modified cobalt sulfide nanosheets （CoS-PEG NSs） are synthesized and unitized as a powerful theranostic nanoagent for efficient photothermal conversion and multimodal imaging for the first time. We demonstrate that the obtained CoS-PEG NSs show excellent compatibility and stability in water and various physiological solutions, and can be effectively inter- nalized by cells, but exhibit a low cytotoxicity. The CoS-PEG NSs exhibit an efficient photothermal conversion capacity, benefited from the strong near-infrared （NIR） absorption, high photothermal conversion efficiency （~ 33.0%）, and excellent photo- thermal stability. Irnportant136 the highly effective photothermal killing effect on cancer ceils after exposure to CoS-PEG NSs plus laser irradiation has been con- firmed by both the standard Cell Counting Kit-8 and live-dead cell staining assays, revealing a concentration-dependent photothermal therapeutic effect. Moreover, utilizing the strong NIR absorbance together with the T2-MR contrast ability of the CoS-PEG NSs, a high-contrast triple-modal imaging, i.e., photoacoustic （PA）, infrared thermal （IRT）, and magnetic resonance （MR） imaging, can be achieved, suggesting a great potential for multimodal imaging to provide comprehensive cancer diagnosis. Our work introduces the first bioapplication of the CoS-PEG nanomaterial as a potential theranostic nanoplatform and may promote further rational design of CoS-based nanostructures for precise/effident cancer diagnosis and therapy.