Diagenesis of organic matter in a 400 m organic rich sediment core from offshore Namibia using solid state 13C NMR and FTIR

Although rates and mechanisms of early diagenesis have been well studied, the effects of microbial metabolism on the molecular composition of the sedimentary organic matter (SOM) over long periods of time need more investigation. In this study, we characterize the early diagenesis of marine SOM from organic rich sediments of the Ocean Drilling Program site 1082 located off Namibia, in the vicinity of the Benguela coastal upwelling system. We used both Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (¹³C NMR) to assess the quantitative partitioning of the organic carbon into major compound classes (aliphatic, aromatic, ester, carboxylic, amide and carbons from carbohydrates). Then, we calculate the SOM composition in the main biomolecules (proteins, carbohydrates, lipids and lignin) on the basis of previous ¹³C NMR based estimates of the molecular composition of the organic mixtures. Results show that the SOM is still labile at 7 m below the seafloor (mbsf) and composed of about 25% proteins and 15% carbohydrates. With increasing depth, the protein content exponentially decreases to 13% at 367 mbsf, whereas the carbohydrate content decreases linearly to 11%. The lignin and lipid content consistently represent around 10% and 40% of the SOM, respectively, and show an increase with depth, due mostly to selective enrichment as the more labile components are lost by degradation. Thus, these components of the SOM are considered refractory at the depth scale considered. The calculated remineralization rates are extremely slow ranging from 5.6 mol C m⁻³ ky⁻¹ at the top of the core to 0.2 mol C m⁻³ ky⁻¹ according to the organic carbon flux to the seafloor. Knowing the labile carbon losses, we propose a method to calculate the initial TOC before the diagenesis took place.     

Multi-scale variability of water discharge and sediment load into the Bohai Sea from 1950 to 2011

This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The Mann-Kendall test, order clustering, power-spectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at inter-annual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales: 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, large-scale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.     

A study on resonance Rayleigh scattering spectra of Humic Acid (HA)

This paper deals with the influences of pH, acidity and ionic intensity of the solutions on the resonance Rayleigh scattering spectra and fluorescence spectra of humic acid. When the pH value is low and the acidity and ionic intensity are high, the resonance Rayleigh spectra and fluorescence spectra both show a tendency of increasing, though the former’s intensity is much higher. In combination with the transmission electron microscope data, the factors leading to the occurrence and enhancement of the resonance Rayleigh scattering spectra of humic acid were explored. It is considered that particle enlargement caused by aggregation, the increase of heterogeneity, the increase of hydrophobility, the formation of interface, etc., are the factors leading to the occurrence and enhancement of the resonance Rayleigh scattering spectra of humic acid. As the intensity of the resonance Rayleigh scattering spectra of humic acid is much higher, resonance Rayleigh scattering spectroscopy can be used as a newly developed spectrum technology, which is more sensitive and simpler, to study humic acid and its complicated behaviors.     

采掘坑位置对珊瑚礁海岸波浪传播变形影响试验

为研究珊瑚礁坪上采掘坑位置变化对珊瑚礁海岸波浪传播变形的影响, 本文通过物理模型试验测试了采掘坑在不同位置和无坑情况下一系列不规则波工况的波浪特征。结果表明, 随着采掘坑位置朝岸线附近移动直至无坑时, 岸线附近的短波波高逐渐减小; 采掘坑的存在减弱了岸线附近的低频长波波高, 当采掘坑位于岸线附近时, 长波波高还受到局部水深增加的影响而进一步减弱。采掘坑从礁缘移动至岸线附近直到无坑时, 岸线附近的增水逐渐增大, 这种趋势在礁坪水深较大时更为明显。通过相干函数分析, 证明了礁坪上低频长波是由于短波群破碎点的移动而产生, 采掘坑位置的变化对低频长波的产生无明显影响; 通过传递函数分析, 验证了礁坪上的低频长波存在一阶共振放大效应, 采掘坑的存在减弱了这种放大效应, 当坑位于礁坪中间和岸线附近时, 这种减弱效应更为显著。     

Relative Sea-Level Change During the Late Holocene on the Island of Vis (Croatia) – Issa Harbour Archaeological Site

The 2.4 ka shoreline evolution on the Island of Vis has been investigated. It represents a particularly interesting area for this kind of investigation due to the existence of the submerged archaeological remains, the antique port of Issa, as well as to the existence of geomorphological and biological sea-level markers. The actual depths of the different parts of the submerged quay have been mapped and measured with respect to the present mean sea-level, applying corrections for tide and atmospheric pressure values at the time of the surveys. The functional heights related to the sea level at the time of construction have also been taken into account. These data were further compared with predictions derived from a glacio-hydro-isostatic model associated with the Last Glacial cycle. During the investigation of the coast, tidal notches and algal rims were found. They were mapped, measured and correlated with results of the submerged port remains, as well as with other available data along the Croatian coast.

Our results demonstrate a 199±25 cm sea-level change during 2.4 ka on the Island of Vis. Taking into account the total relative sea-level change, an average rate of around ~0.83 mm/yr is derived. If the isostatic-eustatic component is separated, a tectonic subsidence rate ranges between 0.17 and 0.3 mm/yr depending on the predicted model used. Compared to the Northern Adriatic area, the Island of Vis shows a much smaller component of tectonic subsidence.     

外伤性肝内胆汁瘤的CT与MRI表现

目的:探讨外伤性肝内胆汁瘤的CT与MRI表现特征。方法:回顾性分析10例临床证实的外伤性肝内胆汁瘤的影像资料。结果:全部病例有CT检查资料,2例病程中行MRI检查。全部病例伴肝实质挫裂伤,外伤后短期内CT或MRI检查提示肝内大片状低密度或长T1长T2信号影,随访中很快出现水样密度或信号影。其中囊状单发7例,多发3例。多发者沿胆管树呈囊袋状排列。除7例随访中渐小外,其余3例均经手术或超声或CT引导下引流治愈,其内容物均为胆汁成分。结论:认识外伤性肝内胆汁瘤CT与MRI表现特征对于诊断及进一步治疗具有重要意义。     

肩关节后方不稳定的CT和MR特点?

目的：总结分析肩关节后方不稳定的CT、MRI表现特点。方法：16例经关节镜手术检查证实病例,对肩关节后方不稳定患者的关节盂、肱骨头和后盂唇关节囊复合体异常在 CT、MRI上表现特点进行总结分析。结果：肩关节后方不稳定影像征象包括关节盂发育不良（后部关节盂缘缺如）、反Bankart骨折、反Hill-sachs骨折、Bennett病变、后盂唇关节囊复合体病变、肱骨头后方半脱位或完全脱位。结论：对于肩关节后方不稳定的患者,行患侧肩关节 CT、MRI能够清晰显示关节盂、肱骨头和后盂唇关节囊复合体异常,是肩关节后方不稳定的一种有效准确的检查方法。     

The interaction of elasticity and rocking in flexible structures allowed to uplift

Numerous structures uplift under the influence of strong ground motion. Although many researchers have investigated the effects of base uplift on very stiff (ideally rigid) structures, the rocking response of flexible structures has received less attention. Related practical analysis methods treat these structures with simplified ‘equivalent’ oscillators without directly addressing the interaction between elasticity and rocking. This paper addresses the fundamental dynamics of flexible rocking structures. The nonlinear equations of motion, derived using a Lagrangian formulation for large rotations, are presented for an idealized structural model. Particular attention is devoted to the transition between successive phases; a physically consistent classical impact framework is utilized alongside an energy approach. The fundamental dynamic properties of the flexible rocking system are compared with those of similar linear elastic oscillators and rigid rocking structures, revealing the distinct characteristics of flexible rocking structures. In particular, parametric analysis is performed to quantify the effect of elasticity on uplift, overturning instability, and harmonic response, from which an uplifted resonance emerges. The contribution of stability and strength to the collapse of flexible rocking structures is discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Fully Nonlinear Simulations of Wave Resonance by An Array of Cylinders in Vertical Motions

The finite element method (FEM) is employed to analyze the resonant oscillations of the liquid confined within multiple or an array of floating bodies with fully nonlinear boundary conditions on the free surface and the body surface in two dimensions. The velocity potentials at each time step are obtained through the FEM with 8-node quadratic shape functions. The finite element linear system is solved by the conjugate gradient (CG) method with a symmetric successive overelaxlation (SSOR) preconditioner. The waves at the open boundary are absorbed by the combination of the damping zone method and the Sommerfeld-Orlanski equation. Numerical examples are given by an array of floating wedge- shaped cylinders and rectangular cylinders. Results are provided for heave motions including wave elevations, profiles and hydrodynamic forces. Comparisons are made in several cases with the results obtained from the second order solution in the time domain. It is found that the wave amplitude in the middle region of the array is larger than those in other places, and the hydrodynamic force on a cylinder increases with the cylinder closing to the middle of the array.     

Temporal variations in free core nutation period

Based on the nearly diurnal resonance in the tidal gravity observations,the temporal variations in period of the Earth's free core nutation (FCN) are investigated by using the tidal gravity observations of 18-year duration recorded continu-ously with a superconducting gravimeter (SG) at Brussels. The effects of the global oceanic tide loading and local barometric pressure on the SG observations have been removed by using eleven high-precision global digital models of oceanic tides and barometric pressure me...