Spectroscopic Characterization of Dissolved Organic Matter: Insights Into the Linkage Between Sources and Chemical Composition

This dissertation investigated the chemical structure of DOM by advanced solid-state nuclear magnetic resonance (NMR) spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) techniques, as well as isotopic measurements and UV-visible spectroscopy, to shed light on the linkages between DOM sources and DOM composition. Unique and extensive sets of DOM samples studied here were isolated from various aquatic systems, covering end-member environments in which DOM is considered either microbially derived or terrestrially derived, and areas in which DOM has characteristics intermediate between the two end members. Important insights into specific site-related questions were also gained such as the fate of terrestrial DOM in the marine system, the seasonal variability in chemical structure of DOM in the Yukon River, and the chemical structure of DOM in lakes driven by hydrology. First, the presence of CRAM as the major structural units in DOM samples from the Penobscot River to Gulf of Maine transect and the Pacific Ocean implied that CRAM may cycle on time scales long enough to be transported into the ocean. Second, whereas spring DOM from the Yukon River was more enriched in lignin residues and carbohydrates than summer-fall and winter DOM, DOM samples across seasons shared relatively more refractory components such as CRAM, and nonprotonated OC and OCO pool. Third, CRAM occurred as the major component in three different lakes, though there was a selective loss of terrestrially derived DOM such as aromatics with increasing lake water residence time. Lastly, the ubiquity of CRAM in DOM from microbially and terrestrially derived end members and understudied environments like groundwaters was further confirmed by NMR spectroscopy coupled with FT-ICR mass spectrometry. The research in my dissertation clearly revealed the ubiquity of CRAM in DOM from vastly different environments with different source strengths. This implicates the chemical homogenization of DOM relative to source material in aquatic environments under the influence of diagenetical degradation processes

Automatic Genre Classification via N-grams of Part-of-Speech Tags

AbstractRecurring sequences of words have long been considered as a signifier of different genres and registers by corpus linguists. The previous research mainly focused on lexical n-grams. Nevertheless, n-grams of other linguistic features, such as part-of-speech, have been less studied. The current study is expected to examine whether n-grams of part-of-speech tags extracted from a large corpus can be a discriminator of different genres. The results show that a strong correlation exists between the information about n-grams of part-of-speech tags and the genre of the text

Characterization of Heterogeneities and Domains in Aquatic and Sedimentary Organic Matter by 1 H Spin Diffusion: Potential for Elucidating the Formation Mechanisms

Although the information on domains and heterogeneities of natural organic matter (NOM) can provide insights into its formation mechanisms, the appropriate solid-state NMR technique for measuring them is still lacking. The traditional technique requires mobility differences in NOM whereas NOM components are primarily rigid. We introduced a new 1H spin diffusion technique, 1H-13C two-dimensional heteronuclear correlation (2D HETCOR) NMR with 1H spin diffusion, for characterization of domains and heterogeneities in aquatic and sedimentary organic matter. It was achieved by collecting a series of 2D HETCOR spectra with a variable mixing time, tm\u27, and monitoring the transfer of magnetization from one component to another. The rate of magnetization transfer provided the information on domains and heterogeneities because the magnetization of small domains or heterogeneities equilibrated faster than that of larger ones. Three samples, International Humic Substances Society (IHSS) Suwannee River NOM, IHSS Suwannee River humic acid (HA), and a sedimentary HA, were used. Two model polymers, a random copolymer poly(styrene-n-butyl methacrylate) with 0.6-nm heterogeneity and a block copolymer polystyrene-b-poly(methyl methacrylate) with a domain size of 5 nm, were included for calibration. Within tm \u3c 100 µs, half equilibration was reached for all three NOM samples and poly(styrene-n-butyl methacrylate), indicating that they were heterogeneous. In contrast, the spin diffusion of polystyrene-b-poly(methyl methacrylate) with 5-nm domain was much slower. Unlike the traditional spin diffusion technique, this technique did not require the differential mobility in NOM and was suitable for investigating the domains and heterogeneities of NOM, which are mostly rigid. © 2011, by the American Society of Limnology and Oceanography, Inc

Hypoglycemic, hypolipidemic and antioxidant effects of iridoid glycosides extracted from: Corni fructus: Possible involvement of the PI3K-Akt/PKB signaling pathway

Iridoid glycosides (CIG) are the major component of Corni fructus. In this work, we researched the antioxidative, hypoglycemic and lowering blood lipids effects of CIG on diabetic mice induced by a high-fat diet (HFD) and streptozotocin (STZ). Furthermore, to investigate the molecular mechanism of action, the phosphorylation and protein expression of phosphoinositide 3-kinase (PI3K) and its downstream proteins, such as insulin receptor (INSR), protein kinase B (Akt/PKB) and glucose transporter 4 (GLUT4) have been detected. The results showed that CIG significantly improved oral glucose tolerance in diabetic mice. Biochemical indices also revealed that CIG had a positive effect on lipid metabolism and oxidative stress. In addition, CIG can significantly enhance the expression level of the PI3K-Akt/PKB pathway related proteins in skeletal muscle, which is the key pathway of insulin metabolism. These findings show that CIG can improve the hyperglycemia and hyperlipidemia of HFD-STZ-induced diabetic mice through the PI3K-Akt/PKB signaling pathway, and CIG might be a potential medicine or functional food for type 2 diabetes mellitus remedies. © 2018 The Royal Society of Chemistry

Solid Dynamic Models for Analysis of Stress and Strain in Human Hearts

This paper proposes a solid model based on four-dimensional trivariate B-spline for strain and stress analysis of ventricular myocardium. With a series of processing steps in the four-dimensional medical images, the feature points of ventricular inner and outer wall are obtained. A B-spline surface is then used to build the dynamic deformation model of the myocardial walls. With such a surface model, a hexahedron control mesh can be constructed by sweeping the cloud data, and the ventricular solid model is built by fitting the trivariate B-spline parameters. Based on these models, a method of isogeometric analysis can be applied to calculate the stress and strain continuously distributed in the ventricle. The model is represented smoothly in the cylindrical coordinate system and is easy to measure myocardium dynamics for finding abnormal motion. Experiments are carried out for comparing the stress and strain distribution. It is found that the solid model can determine ventricular dynamics which can well reflect the deformation distribution in the heart and imply early clues of cardiac diseases

TOPIC: A Parallel Association Paradigm for Multi-Object Tracking under Complex Motions and Diverse Scenes

Video data and algorithms have been driving advances in multi-object tracking (MOT). While existing MOT datasets focus on occlusion and appearance similarity, complex motion patterns are widespread yet overlooked. To address this issue, we introduce a new dataset called BEE23 to highlight complex motions. Identity association algorithms have long been the focus of MOT research. Existing trackers can be categorized into two association paradigms: single-feature paradigm (based on either motion or appearance feature) and serial paradigm (one feature serves as secondary while the other is primary). However, these paradigms are incapable of fully utilizing different features. In this paper, we propose a parallel paradigm and present the Two rOund Parallel matchIng meChanism (TOPIC) to implement it. The TOPIC leverages both motion and appearance features and can adaptively select the preferable one as the assignment metric based on motion level. Moreover, we provide an Attention-based Appearance Reconstruct Module (AARM) to reconstruct appearance feature embeddings, thus enhancing the representation of appearance features. Comprehensive experiments show that our approach achieves state-of-the-art performance on four public datasets and BEE23. Notably, our proposed parallel paradigm surpasses the performance of existing association paradigms by a large margin, e.g., reducing false negatives by 12% to 51% compared to the single-feature association paradigm. The introduced dataset and association paradigm in this work offers a fresh perspective for advancing the MOT field. The source code and dataset are available at https://github.com/holmescao/TOPICTrack