Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1989

Beschreibung: This thesis studies mixing and convection in a rectangular basin driven by a specified heat flux at the surface. A numerical model is constructed for this purpose. The main focus of the study is on the density and circulation structure resulting from the thermal forcing. In chapter two, a simple vertical one-dimensional model is developed to examine the mixing processes under a given surface heat flux. In order to simulate strong vertical mixing in the region where stratification is unstable, turbulent processes are modeled by a convective overturning parameterization of eddy viscosity and diffusivity. The results show that the density structure is strongly affected by the convective overturning adjustment as surface cooling prevails, and the resulting density field is nearly depth independent. In chapter three, a more complicated two-dimensional model is constructed to simulate mixing and circulation in a vertical rectangular basin with rigid boundaries. The aspect ratio of the basin ranges from 1 to 0.001 and Rayleigh number from 104 to 2 x 1012. It is found that the circulation pattern is dominated by these two important numbers. The roles of density overturning and density-momentum overturning mixing are further investigated. The results show that the convective overturning not only homogenizes the density field in the unstably stratified region but also contributes to increase the circulation. A crude scale analysis of the system shows that the characteristics of the density and momentum fields from the analysis agree well with the numerical results.

Beschreibung: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1992

Beschreibung: This study concerns the barotropic interactions between a mesoscale eddy and a straight monotonic bottom topography. Through simple to relatively complicated modeling effort, some of the fundamental properties of the interaction are investigated. In chapter two, the fundamental aspects of the interaction are examined using a simple contour dynamics model. With the simplest model configuration of an ideal vortex and a step topography, the basic dynamical features of the observed oceanic eddy-topography interaction are qualitatively reproduced. The results consist of eddy-induced cross-topography exchange, formation of topographic eddies, eddy propagation and generation of topographic waves. In chapter three, a more complicated primitive equation model is used to investigate a mesoscale eddy interacting with an exponential continental shelf/slope topography on both f and β-planes. The f-plane model recasts the important features of chapter two. The roles of the eddy size and strength and the geometry of topography are studied. It is seen that the multiple anticyclonic eddy-slope interactions strongly affect the total cross-slope volume transport and the evolution of both the original anticyclone and the topographic eddy. Since a cyclone is trapped at the slope and eventually moves on to the slope, it is most effective in causing perturbation on the shelf and slope. The responses on the shelf and slope are mainly wavelike with dispersion relation obeying that of the free shelf-trapped wave modes. On the β-plane, the problem of an eddy colliding onto a continental shelf/slope from a distance with straight or oblique incident angles is investigated. It is found that the straight eddy incident is more effective in achieving large onslope eddy penetration distance than the oblique eddy incident. The formation of a dipole-like eddy pair consisting of the original anticyclone and the topographic cyclone acts to suppress the eddy decay due to long Rossby wave radiation. A weak along-slope current near the edge of the slope is found, which is part of a outer slope circulation cell originated from the Rossby wave wake trailing the propagating eddy. Model-observation comparisons in_chapter four show favorable qualitative agreement of the model results with some of the observed events in the eastern U.S. continental margins and in the Gulf of Mexico. The model results give dynamical interpretations to some observed features of the oceanic eddy-topography interactions and provide enlightening insight into the problem.

Beschreibung: Abstract. The asymmetrical crystal [Na(15C5) 2 ][Na(15C5)] 2 (AsMo 12 O 40 )] · CH 3 CN ( 1 ) was synthesized. Interestingly, the huge α-keggin ion AsMo 12 is distorted by introduction of CH 3 CN molecules and adopts a chiral assembly with space group P 4 . In contrast, the analogous compound AsW 12 co-crystallizes with trace H 2 O molecules. The hydrogen atoms of H 2 O are positionally disordered with 50 % occupation to correlate with AsW 12 in space group P 4/ m . Solid and solution CD spectra indicate that the crystals of 1 are in R configuration. This leads to the conclusion that molybdenum has greater affinity toward organic CH 3 CN, whereas tungsten has greater affinity to inorganic H 2 O. Additionally, AsMo 12 shows greater deformability than AsW 12 . It is suggested that POMo shows a greater potential as chiral material than POW because of the flexibility of Mo. As a highlight, CH 3 CN can function as a general chiral inducer for the innovation of other chiral crystals, if fixed along one dimension.

Beschreibung: Free nitrous acid (FNA), which is the protonated form of nitrite and inevitably produced during biological nitrogen removal, has been demonstrated to strongly inhibit the activity of polyphosphate accumulating organisms (PAOs). Herein we reported an efficient process for wastewater treatment, i.e., the oxic/anoxic/oxic/extended-idle process to mitigate the generation of FNA and its inhibition on PAOs. The results showed that this new process enriched more PAOs which thereby achieved higher phosphorus removal efficiency than the conventional four-step (i.e., anaerobic/oxic/anoxic/oxic) biological nutrient removal process (41 ± 7% versus 30 ± 5% in abundance of PAOs and 97 ± 0.73% versus 82 ± 1.2% in efficiency of phosphorus removal). It was found that this new process increased pH value but decreased nitrite accumulation, resulting in the decreased FNA generation. Further experiments showed that the new process could alleviate the inhibition of FNA on the metabolisms of PAOs even under the same FNA concentration. Scientific Reports 5 doi: 10.1038/srep08602

Beschreibung: Article Psoriasis is a chronic inflammatory disease affecting up to 3% of the population. Here, Zuo et al. perform exome array analysis, identify single-nucleotide polymorphisms at 15 new loci, implicating several biological pathways in psoriasis risk and disease heritability. Nature Communications doi: 10.1038/ncomms7793 Authors: Xianbo Zuo, Liangdan Sun, Xianyong Yin, Jinping Gao, Yujun Sheng, Jinhua Xu, Jianzhong Zhang, Chundi He, Ying Qiu, Guangdong Wen, Hongqing Tian, Xiaodong Zheng, Shengxiu Liu, Wenjun Wang, Weiran Li, Yuyan Cheng, Longdan Liu, Yan Chang, Zaixing Wang, Zenggang Li, Longnian Li, Jianping Wu, Ling Fang, Changbing Shen, Fusheng Zhou, Bo Liang, Gang Chen, Hui Li, Yong Cui, Aie Xu, Xueqin Yang, Fei Hao, Limin Xu, Xing Fan, Yuzhen Li, Rina Wu, Xiuli Wang, Xiaoming Liu, Min Zheng, Shunpeng Song, Bihua Ji, Hong Fang, Jianbin Yu, Yongxin Sun, Yan Hui, Furen Zhang, Rongya Yang, Sen Yang, Xuejun Zhang

Beschreibung: P-n junction BiOBr/ZnO composites were prepared by a facile solvothermal process with double Br sources of CTAB and KBr. The samples were characterized by XRD, XPS, SEM, TEM, HRTEM, DRS, BET and PL. The BiOBr/ZnO composites exhibited much higher photocatalytic activity than single BiOBr and ZnO for the degradation of phenol under simulated sunlight irradiation. The enhanced photocatalytic activity of BiOBr/ZnO composites could be mainly ascribed to the high-efficiency separation of photogenerated electron-hole pairs through BiOBr/ZnO p-n junction. The reaction mechanism for the removal of phenol was also discussed. Hole and ·OH were the main reactive species. Moreover, the influence of disparate ratios of double Br sources to BiOBr/ZnO composites was also investigated. The results indicated that the BiOBr/ZnO composites prepared by double Br sources showed better photocatalytic activities than the sample prepared by single Br source. P-n junction BiOBr/ZnO composites were prepared by a facile solvothermal process with double Br sources and the composites exhibited higher photocatalytic activity than BiOBr and ZnO for the degradation of phenol, which could be ascribed to two reasons. One reason may be the high efficient separation of photogenerated electron-hole pairs through BiOBr/ZnO p-n junction. Another one would be the high surface area achieved by adjusting the content of CTAB.