371 research outputs found
Cu–Polymetallic Deposit Exploration under Thick Cover in Gucheng–Yaxi Area Using Audio-Magnetotelluric and Spread-Spectrum-Induced Polarization
No full textSuccessful geophysical exploration projects in the Gucheng–Yaxi area located in Gaochun District, Jiangsu Province, China, have been limited partly due to the complex geological conditions of the area and high artificial noise in data acquired using electrical and electromagnetic methods. In this study, we deployed the new anti-interference spread-spectrum-induced polarization method (SSIP) and the audio-magnetotelluric (AMT) method to detect a copper–polymetallic deposit in the area. Two-dimensional inversion results in the Gucheng–Yaxi area revealed a high chargeability anomalous zone on the SSIP profile that coincided with a zone of moderate resistivity located between two resistor bodies on the AMT profile. A follow-up 1200 m drill hole was established at this high-chargeability, moderate-resistivity zone which encountered polymetallic (copper, lead, zinc, gold, and silver) mineralization at a depth of ≥400 m. Drill hole data analysis showed that mineralization occurred interspaced in the marble rock mass at varying depths. Furthermore, several low-resistivity, weak-chargeability sections were revealed and attributed to Cretaceous sediments and faults. These faults are thought to have played a critical role in the polymetallic mineralization genesis. In summary, this study demonstrated the successful of application of SSIP and AMT in detecting a metallic deposit in an area with high artificial noise. Hence, the geophysical prospection potential of the Gucheng–Yaxi area is great
Modelling and development of a resonator-based noise mitigation system
No full textAnthropogenic underwater noise generated by pile driving has been an issue of serious concernfor a long period of time. The underwater noise pollution from pile driving could pose a threatto marine mammals. To reduce the low-frequency noise, many offshore companies developvarious treatments and alternatives for pile driving. In this study, the focus is placed on aresonator-based noise mitigation technique.The first part of the thesis focuses on the investigation of the existing resonator-based noisemitigation systems. A mathematical expression for the resonance frequency of an individualopen-ended resonator is derived. To validate this expression, a finite element model is built inCOMSOL. To compare the acoustic performance with the HSD, a finite element model is alsobuilt for the HSD mitigation system. To describe the acoustic performance of the resonatorsfor generic use, the frequency response function of an open-ended resonator is analyticallyderived based on the assumption that the resonator behaves as a linear SDoF system. Thederivation of the parameters of the equivalent SDoF system representing each individualresonator is based on appropriate fitting of numerical results obtained in COMSOL.The second part of the thesis deals with the development of a new design of a resonator systemnamed Qiu. To install the resonator system in a more flexible way, the air is encapsulated inthe resonator. A finite element model is also developed in COMSOL for the Qiu resonator.In the last part of the thesis, a three-dimensional vibroacoustic model is developed in orderto find the optimal properties of the underwater resonator and to improve the existing noisemitigation techniques. The model requires the proper description of the noise source, theresonator and the acoustic waveguide. The normal mode method is used to compose theGreen’s function of the waveguide. The boundary element method is then employed in orderto obtain the total pressure field. The frequency response functions derived in the first partof the thesis are subsequently used to describe the acoustic behaviour of the resonators. Aparametric study is presented in order to define the principal factors for effective noise mitigation.In addition, the several cases are investigated in order to obtain the optimal propertiesof the resonator and the optimum configuration of the array of resonators surrounding thesound source to maximise noise reduction.Offshore and Dredging Engineerin
Exploratory Browsing
No full textIn recent years the digital media has influenced many areas of our life. The transition from analogue to digital has substantially changed our ways of dealing with media collections. Today‟s interfaces for managing digital media mainly offer fixed linear models corresponding to the underlying technical concepts (folders, events, albums, etc.), or the metaphors borrowed from the analogue counterparts (e.g., stacks, film rolls). However, people‟s mental interpretations of their media collections often go beyond the scope of linear scan. Besides explicit search with specific goals, current interfaces can not sufficiently support the explorative and often non-linear behavior. This dissertation presents an exploration of interface design to enhance the browsing experience with media collections. The main outcome of this thesis is a new model of Exploratory Browsing to guide the design of interfaces to support the full range of browsing activities, especially the Exploratory Browsing.
We define Exploratory Browsing as the behavior when the user is uncertain about her or his targets and needs to discover areas of interest (exploratory), in which she or he can explore in detail and possibly find some acceptable items (browsing). According to the browsing objectives, we group browsing activities into three categories: Search Browsing, General Purpose Browsing and Serendipitous Browsing. In the context of this thesis, Exploratory Browsing refers to the latter two browsing activities, which goes beyond explicit search with specific objectives.
We systematically explore the design space of interfaces to support the Exploratory Browsing experience. Applying the methodology of User-Centered Design, we develop eight prototypes, covering two main usage contexts of browsing with personal collections and in online communities.
The main studied media types are photographs and music.
The main contribution of this thesis lies in deepening the understanding of how people‟s exploratory behavior has an impact on the interface design. This thesis contributes to the field of interface design for media collections in several aspects. With the goal to inform the interface design to support the Exploratory Browsing experience with media collections, we present a model of Exploratory Browsing, covering the full range of exploratory activities around media collections. We investigate this model in different usage contexts and develop eight prototypes. The substantial implications gathered during the development and evaluation of these prototypes inform the further refinement of our model: We uncover the underlying transitional relations between browsing activities and discover several stimulators to encourage a fluid and effective activity transition. Based on this model, we propose a catalogue of general interface characteristics, and employ this catalogue as criteria to analyze the effectiveness of our prototypes. We also present several general suggestions for designing interfaces for media collections
MicroRNAs: New Biomarkers for the progression of Coronary Artery Diseases
No full textCardiovascular diseases (CVDs), especially the coronary arterial diseases (CADs), have become the main cause of death all around the world, attracting attentions from the whole society. Even though considerable progresses have been made for the treatment of CADs, many clinical challenges remain to be overcome. In particular, effective biomarkers for CADs need to be developed to facilitate the early diagnosis and thus early treatment of the disease. Recently, the dysregulation of microRNAs (miRNAs) has been found to be involved in the progression of multiple CADs, manifested as altered levels of miRNAs at different disease phases, suggesting that miRNAs may be capable of serving as promising biomarkers for CADs. Here, we attempt to evaluate the possibility of miRNAs as biomarkers for CADs and compare these markers with previously reported ones. In this review, we will summarize the basic concepts and advances for CADs and miRNAs, with a special emphasis on miRNAs in the progression of CADs
Peripheral Inflammatory Factors and Acute Myocardial Infarction Risk: A Mendelian Randomization Study
No full textBackground: Previous observational studies have confirmed the relationship between inflammation and acute myocardial infarction (AMI), but genetic evidence is still lacking. The aim of this study was to explore the bidirectional association of multiple peripheral inflammatory factors with this disease at the genetic level. Methods: Summary data for AMI and several peripheral inflammatory factors (such as interleukin-10 and interleukin-18) were collected from published genome-wide correlation studies. Based on the correlation, independence, and exclusivity assumptions, a total of 9 to 110 instrumental variables were selected from these summary data to predict the above traits. Two-sample Mendelian randomization methods, including inverse-variance weighted (IVW), were used to make causal inferences between exposures and outcomes. Sensitivity analyses including Cochran’s Q, MR-Egger intercept, leave-one-out, forest plot, and MR-PRESSO were adopted to assess heterogeneity and horizontal pleiotropy. Results: The IVW reported that elevated peripheral levels of interleukin-10 and interleukin-18 were nominally associated with a reduced risk of AMI (OR = 0.876, 95% CI = 0.788 ~ 0.974, P = 0.015; OR = 0.934, 95% CI = 0.875 ~ 0.997, P = 0.040). The IVW also reported that the risk of AMI nominally increased the peripheral level of interleukin-10 (OR = 1.062, 95% CI = 1.003 ~ 1.124, P = 0.040). No significant heterogeneity or horizontal pleiotropy were found by sensitivity analyses. Conclusion: Both interleukin-10 and interleukin-18 were peripheral inflammatory factors genetically associated with AMI. In particular, combined with previous knowledge, interleukin-10 may have a protective effect on the onset, progression, and prognosis of the disease
The Structure and Function of Amphibian Skin-associated Microbiota
No full textMicrobes occupy almost every surface on earth and live in association with basically every organism we know. Studies across many host systems are beginning to observe common functions of host-associated microbiota, such as their ability to deter pathogen establishment in or on host tissue. However, we have not yet elucidated all the mechanisms through which microbe-mediated pathogen protection occurs, and we are still unravelling the rules behind microbial community assembly that result in protective microbiota. In this dissertation, I draw concepts from classic community ecology to generate predictions on how and when microbes protect against pathogens. In my first chapter, I quantify several community traits of amphibian skin-associated microbiota across a fine-scale temporal dataset and ask whether any traits predict infection. I demonstrate that deviations from baseline richness levels of fungal-inhibiting bacteria in the microbiota lead to increased fungal infection rates. In my second chapter, I investigate the effect of biofilm biomass (thickness and cell density) on establishment success of fungal pathogens, and find that both biofilm thickness and richness of fungal-inhibiting bacteria contribute to protection against fungal pathogen establishment, but that they act through distinct mechanisms (space pre-emption and interference competition, respectively). Lastly, I conduct a global meta-analysis on amphibian skin microbiota and show that environmental factors explain more taxonomic variation than host factors, and that there is virtually no "core" microbiome for any amphibian species. However, some commonly observed bacterial taxa included those also found on corals, seaweeds, and fish, suggesting the existence of an “epi-biotic” microbiome that may be found across other host-microbe systems. My findings are most directly applicable to amphibian conservation work that is interested in developing probiotics to protect against fungal infections. They also contribute to the larger field of microbial ecology. The concepts and mechanisms I propose in my studies are potentially relevant to a wide range of host-microbe systems, and contribute to the existing body of work that seeks to apply classic ecological concepts to microbial systems.</p
The Structure and Function of Amphibian Skin-associated Microbiota
No full textMicrobes occupy almost every surface on earth and live in association with basically every organism we know. Studies across many host systems are beginning to observe common functions of host-associated microbiota, such as their ability to deter pathogen establishment in or on host tissue. However, we have not yet elucidated all the mechanisms through which microbe-mediated pathogen protection occurs, and we are still unravelling the rules behind microbial community assembly that result in protective microbiota. In this dissertation, I draw concepts from classic community ecology to generate predictions on how and when microbes protect against pathogens. In my first chapter, I quantify several community traits of amphibian skin-associated microbiota across a fine-scale temporal dataset and ask whether any traits predict infection. I demonstrate that deviations from baseline richness levels of fungal-inhibiting bacteria in the microbiota lead to increased fungal infection rates. In my second chapter, I investigate the effect of biofilm biomass (thickness and cell density) on establishment success of fungal pathogens, and find that both biofilm thickness and richness of fungal-inhibiting bacteria contribute to protection against fungal pathogen establishment, but that they act through distinct mechanisms (space pre-emption and interference competition, respectively). Lastly, I conduct a global meta-analysis on amphibian skin microbiota and show that environmental factors explain more taxonomic variation than host factors, and that there is virtually no "core" microbiome for any amphibian species. However, some commonly observed bacterial taxa included those also found on corals, seaweeds, and fish, suggesting the existence of an “epi-biotic” microbiome that may be found across other host-microbe systems. My findings are most directly applicable to amphibian conservation work that is interested in developing probiotics to protect against fungal infections. They also contribute to the larger field of microbial ecology. The concepts and mechanisms I propose in my studies are potentially relevant to a wide range of host-microbe systems, and contribute to the existing body of work that seeks to apply classic ecological concepts to microbial systems.</p
Numerical Convergence Study of Heterogeneous Multi-scale Method Piezoelectric Composites
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