754 research outputs found

    Impact of dietary fiber and exogenous carbohydrases in weaned pigs

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    Due to the potential benefits of dietary fiber on gut health, interest in the use of higher-fiber coproducts in weaned pig diets has been growing. Young pigs are not efficient at utilizing dietary fiber. To maximize the nutritional value of fibrous coproducts and mitigate their potential negative effects on nutrient utilization and growth performance of young pigs, exogenous carbohydrases are widely used. However, the results regarding the impact of carbohydrases on performance have been inconsistent and a better understanding of associated mechanisms of carbohydrases in pigs is needed. Carbohydrases may also exert prebiotic effects through release of oligosaccharides from fiber degradation. Thus, dietary fiber and carbohydrases may improve disease resilience of young pigs against bacterial infections. Post-weaning diarrhea (PWD) caused by enterotoxigenic Escherichia coli (ETEC) is an economically important disease in the swine industry. Previous results regarding the impact of soluble versus insoluble fiber on PWD in weaned pigs have been conflicting. This highlights the need to better understand the mechanisms by which different sources of fiber mitigate or exacerbate PWD. Currently, limited research has evaluated if the addition of carbohydrase to higher-fiber diets can mitigate PWD in pigs. Therefore, the overall objective of this dissertation research was to evaluate the impact of exogenous carbohydrases and dietary fiber in weaned pigs under normal physiological and ETEC-challenged conditions and to elucidate the associated modes of action. To achieve our objective, two intensive experiments were conducted. The results from Experiment 1 (Chapters 2 and 3) showed that a carbohydrase enzyme blend (EB) improved growth rate of weaned pigs fed higher fiber diets (with added distillers dried grains with solubles and wheat middlings), which may be partly due to enhanced small intestinal barrier integrity and reduced local and systemic markers of inflammation. The improved ileal barrier integrity in the ileum and decreased cecal total VFA concentration in EB suggests that EB addition shifts fiber degradation from the hindgut to the small intestine. This provides mode of action evidence for carbohydrase supplementation in improving performance of weaned pigs - enhancing gut barrier function and reducing inflammation to spare energy and nutrient for growth. Experiment 2 (Chapters 4 and 5) used a F18 ETEC challenge model. As expected, the ETEC challenge increased incidence of diarrhea, decreased markers of barrier integrity, disrupted intestinal microbial homeostasis, and reduced growth performance during the 14-day trial. The data suggest that a diet containing a soluble and highly fermentable fiber from sugar beet pulp with added carbohydrases may be used to improve gut health and maintain growth performance of pigs under moderate ETEC challenge. The use of an insoluble and poorly fermentable fiber from corn distillers dried grains with solubles may be avoided in feeding nursery pigs at risk of PWD. Overall, this dissertation work elucidated additional mechanisms, beyond nutrient utilization and microbiota, by which carbohydrases enhance growth performance of weaned pigs fed higher fiber diets. This research also shed light on gut health benefits of carbohydrase supplementation in higher-fiber diets in ETEC-challenged weaned pigs. Data from this dissertation suggest that appropriate use of exogenous carbohydrases in higher-fiber diets is promising in improving gut health and growth performance of weaned pigs. As such, carbohydrases may be used as an effective alternative feeding strategy to support reduced use of antibiotic growth promoters in pork production

    Calcium Carbonate Formation in Energy-Related Subsurface Environments and Engineered Systems

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    Geologic CO2 sequestration (GCS) in subsurface saline aquifers is a promising strategy to mitigate climate change caused by increasing anthropogenic CO2 emissions from energy production. At GCS sites, interactions between fluids and geomedia are important because they can affect CO2 trapping efficiency and the safety of CO2 storage. These interactions include the dissolution and precipitation of minerals. One of the most important minerals is calcium carbonate, because it can permanently trap CO2. In this work, Portland cement was used as a model geomedium to investigate the chemical reactions, mechanical alterations, transport of reactive fluids, and the interplay of all these aspects. Also, because Portland cement is used in building and decommissioning CO2 injection wells, its alteration is important for wellbore integrity. Wellbore cement can deteriorate as a result of extensive reactions with injected CO2. Typically, a carbonated layer forms, which can partially reduce CO2 attack by clogging pores in the cement. We conducted high temperature/pressure experiments using Portland cement paste samples, and after 10 days of reaction, quantified the chemical changes using scanning electron microscope backscattering electron imaging and X-ray diffraction. The mechanical changes were quantified as well using a three-point bending setup and nanoindentation. The experimental results showed that after CO2 attack, the cement samples decreased in strength by ~80%, and this decrease was closely related to the formation of a wide and weak portlandite-depleted zone in the cement matrix immediately inside of the carbonated layer. The effects of 0.05 M of sulfate ions were also examined. Interestingly, the additional sulfate ions were found to mitigate CO2 attack by forming a more protective and less soluble carbonated layer, and thus a thinner portlandite-depleted zone. To further investigate the detailed mechanisms by which the wide and weak portlandite-depleted zone formed and the carbonated layer’s surface dissolved, we set up a one-dimensional continuum reactive transport model using the CrunchTope software. Two mechanisms were found to be critical in reproducing our main observations: First, the precipitated CaCO3 could not fill the entire pore spaces in the carbonated layer. The inefficiency of CaCO3 precipitation in filling all the pores might be due to fractures and defects in the carbonated layer, or due to the extent of pore-size-dependent precipitation. Second, nucleation kinetics had to be incorporated into the model to predict the mineral precipitation observed in the reaction solution and to capture the dissolution of the carbonated layer’s surface. To acquire parameters for the incorporation of nucleation kinetics, CaCO3 nucleation experiments were conducted primarily using atomic force microscopy and synchrotron-based in situ grazing incidence small angle X-ray scattering. Newly obtained interfacial energies were compared for mica and quartz systems, and a slightly higher interfacial energy was found in the quartz system. The effects of salinity were investigated in the range of 0.15–0.85 M ionic strengths, and we found a decrease of interfacial energies at high salinity. The kinetic factors, including the apparent activation energy and the pre-exponential factor in the nucleation rate equation, were experimentally obtained for the first time by varying temperatures in the range of 12–31 oC. These parameters provided the key information for modeling nucleation in geomedia and synthesizing well controlled materials in materials science. The CaCO3 nucleation studies advanced our current understanding of nucleation under various conditions, and the acquired parameters were indispensable for our numerical simulations of the cement deterioration. The reactive transport modeling work revealed the important mechanisms in the cement–CO2 reactions, and provided many insights for understanding the chemical and mechanical alterations of geomedia. The investigation of cement deterioration quantitatively coupled the chemical and mechanical changes of the cement samples, and proved that the molecular scale of water–rock reactions can have a substantial impact on the change of the bulk geomedia. Such information can be also be applied to shale/sandstone–CO2 interactions. Overall, this dissertation presents a platform to understand fluid–geomedia interactions, combining experimental and modeling approaches, and connecting basic sciences and real applications. The advanced understanding of fluid–geomedia interactions will help improve GCS operation and thus address the climate change challenge

    The role of glia in protein aggregation

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    Protein aggregation diseases involve intracellular accumulation or extracellular deposition of certain protein species in neuronal or glial cells, leading to neurodegeneration and shortened lifespan. Prime examples include Alzheimer\u27s disease (AD), Parkinson\u27s disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington\u27s disease (HD), which are affected by overlapping or specific aggregation-prone proteins. Mounting evidence suggests that dysfunctional glial cells may be major drivers for some diseases, and when they are not causal factors, they could still significantly exacerbate or alleviate disease progression by playing a plethora of detrimental or beneficial roles. Here we review the diverse functions performed by glial cells in a variety of protein aggregation diseases, highlighting the complexity of the issue and the interconnected relationships between these multifaceted effects

    An Enzyme BlendImprovedGrowth Performance in Nursery Pigs

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    The objective of this experiment was to evaluate the effects of dietary xylanase and an enzyme blend (EB:cellulase, Ăź-glucanase, and xylanase) on nutrient digestibilityand growth performance inweaned pigletsfed a low energy diet. A total of 460 pigsweighing about 6.43 kg were randomly blocked by weight and assigned to 4 treatments, in a 2 Ă— 2 factorial arrangement.There were 12 blocks and 48 pens with 9 or 10 pigs/pen. The diets were based on corn, soybean meal, corn DDGS, andwheat middlings(5 and 10% each fiber ingredientfor wk 1-2 and 3-4, respectively)with or without enzyme supplementation(Huvepharma Inc., St. Louis, MO),with 0.40% titanium dioxide as an indigestible marker. Body weight and feed intake were recorded weekly. Performance data wereanalyzedas repeated measurementsusing the PROC MIXED procedure of SAS (9.4) with pen as the experimental unit. Xylanase (0 or 0.01%), EB(0 or 0.01%), andtheir interactionswereconsidered fixed effects.The EB addition (12.45 vs. 12.08kg; P= 0.044), but not xylanase (12.27 vs. 12.26 kg; P\u3e 0.05), increased body weight. Neither enzymetreatmenthad an impact on ADFI or G:F ratio (P\u3e 0.05). The EB treatmentimproved ADG (482 vs. 466 g; P= 0.024) from wk1-4. There was noenzymeimpact on ATTDof DM, GE, and CP(P\u3e 0.05). Xylanase supplementation tended to reduceATTD of EE (61.05 vs. 62.82%; P= 0.073)and reducedthe ATTD of NDF(46.10 vs. 48.95%), ADF(27.30 vs. 31.71%), and hemicellulose(52.77 vs. 55.23%; P\u3c 0.01). Supplementation of EB improved ATTD of ADF by 22% (32.45 vs. 26.57%; P= 0.001). In conclusion, EB but not xylanaseimproved growth rate in nursery pigsfed a low energy diet, which may not be completelydue tothe improvement in ADF digestibility

    Comparative study on the gut microbiotas of four economically important Asian carp species

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    Gut microbiota of four economically important Asian carp species (silver carp, Hypophthalmichthys molitrix; bighead carp, Hypophthalmichthys nobilis; grass carp, Ctenopharyngodon idella; common carp, Cyprinus carpio) were compared using 16S rRNA gene pyrosequencing. Analysis of more than 590,000 quality-filtered sequences obtained from the foregut, midgut and hindgut of these four carp species revealed high microbial diversity among the samples. The foregut samples of grass carp exhibited more than 1,600 operational taxonomy units (OTUs) and the highest alpha-diversity index, followed by the silver carp foregut and midgut. Proteobacteria, Firmicutes, Bacteroidetes and Fusobacteria were the predominant phyla regardless of fish species or gut type. Pairwise (weighted) UniFrac distance-based permutational multivariate analysis of variance with fish species as a factor produced significant association (P &lt; 0.01). The gut microbiotas of all four carp species harbored saccharolytic or proteolytic microbes, likely in response to the differences in their feeding habits. In addition, extensive variations were also observed even within the same fish species. Our results indicate that the gut microbiotas of Asian carp depend on the exact species, even when the different species were cohabiting in the same environment. This study provides some new insights into developing commercial fish feeds and improving existing aquaculture strategies.</p

    Seamlessly Unifying Attributes and Items: Conversational Recommendation for Cold-Start Users

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    Static recommendation methods like collaborative filtering suffer from the inherent limitation of performing real-time personalization for cold-start users. Online recommendation, e.g., multi-armed bandit approach, addresses this limitation by interactively exploring user preference online and pursuing the exploration-exploitation (EE) trade-off. However, existing bandit-based methods model recommendation actions homogeneously. Specifically, they only consider the items as the arms, being incapable of handling the item attributes, which naturally provide interpretable information of user's current demands and can effectively filter out undesired items. In this work, we consider the conversational recommendation for cold-start users, where a system can both ask the attributes from and recommend items to a user interactively. This important scenario was studied in a recent work. However, it employs a hand-crafted function to decide when to ask attributes or make recommendations. Such separate modeling of attributes and items makes the effectiveness of the system highly rely on the choice of the hand-crafted function, thus introducing fragility to the system. To address this limitation, we seamlessly unify attributes and items in the same arm space and achieve their EE trade-offs automatically using the framework of Thompson Sampling. Our Conversational Thompson Sampling (ConTS) model holistically solves all questions in conversational recommendation by choosing the arm with the maximal reward to play. Extensive experiments on three benchmark datasets show that ConTS outperforms the state-of-the-art methods Conversational UCB (ConUCB) and Estimation-Action-Reflection model in both metrics of success rate and average number of conversation turns.Comment: TOIS 202

    Precise influence evaluation in complex networks

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    Evaluating node influence is fundamental for identifying key nodes in complex networks. Existing methods typically rely on generic indicators to rank node influence across diverse networks, thereby ignoring the individualized features of each network itself. Actually, node influence stems not only from general features but the multi-scale individualized information encompassing specific network structure and task. Here we design an active learning architecture to predict node influence quantitively and precisely, which samples representative nodes based on graph entropy correlation matrix integrating multi-scale individualized information. This brings two intuitive advantages: (1) discovering potential high-influence but weak-connected nodes that are usually ignored in existing methods, (2) improving the influence maximization strategy by deducing influence interference. Significantly, our architecture demonstrates exceptional transfer learning capabilities across multiple types of networks, which can identify those key nodes with large disputation across different existing methods. Additionally, our approach, combined with a simple greedy algorithm, exhibits dominant performance in solving the influence maximization problem. This architecture holds great potential for applications in graph mining and prediction tasks

    Associations between Aquaglyceroporin Gene Polymorphisms and Risk of Stroke among Patients with Hypertension

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    Background: Dysregulations ofAQP7andAQP9were found to be related to lipid metabolism abnormality, which had been provento be one of the mechanisms of stroke. However, limited epidemiological studies explore the associations betweenAQP7andAQP9and the risk of stroke among patients with hypertension in China. Aims: We aimed to investigate the associations between genetic variants in AQP7andAQP9and the risk of stroke among patients with hypertension, as well as to explore gene-gene andgene-environment interactions. Methods: Baseline blood samples were drawn from 211 cases with stroke and 633 matched controls. Genomic DNA was extracted by a commercially available kit. Genotyping of 5 single nucleotide polymorphisms (SNPs) in AQP7 (rs2989924, rs3758269, and rs2542743) and AQP9 (rs57139208, rs16939881) was performed by the polymerase chain reaction assay with TaqMan probes. Results: Participants with the rs2989924 GG genotype were found to be with a 1.74-fold increased risk of stroke compared to those with the AA+AG genotype, and this association remained significant after adjustment for potential confounders (odds ratio (OR): 1.74, 95% confidence interval (CI): 1.23-2.46). The SNP rs3758269 CC+TT genotype was found to be with a 33% decreased risk of stroke after multivariate adjustment (OR: 0.67, 95% CI: 0.45-0.99) compared to the rs3758269 CC genotype. The significantly increased risk of stroke was prominent among males, patients aged 60 or above, and participants who were overweight and with a harbored genetic variant in SNP rs2989924. After adjusting potential confounders, the SNP rs3758269 CT+TT genotype was found to be significantly associated with a decreased risk of stroke compared to the CC genotype among participants younger than 60 years old or overweight. No statistically significant associations were observed between genotypes of rs2542743, rs57139208, or rs16939881 with the risk of stroke. Neither interactions nor linkage disequilibrium had been observed in this study. Conclusions: This study suggests that SNPs rs2989924 and rs3758269 are associated with the risk of stroke among patients with hypertension, while there were no statistically significant associations between rs2542743, rs57139208, and rs16939881 and the risk of stroke being observed
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