Browsing by Author "Zhang, Wei"

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    AFM Image Analysis of the Adsorption of Xanthate and Dialkyl Dithiophosphate on Chalcocite
    Zhang, Jinhong; Zhang, Wei (MDPI, 2022-08-13)
    Atomic force microscopy (AFM) has been applied to study the adsorption morphology of various collectors, i.e., potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX) and Cytec Aerofloat 238 (sodium dibutyl dithiophosphate), on chalcocite in situ in aqueous solutions. The AFM images show that all these collectors adsorb strongly on chalcocite. Xanthate adsorbs mainly in the form of insoluble cuprous xanthate (CuX), which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. This xanthate/chalcocite adsorption mechanism is very similar to the one obtained with the xanthate/bornite system; while it is different from the one of the xanthate/chalcopyrite systems, for which oily dixanthogen is the main adsorption product on chalcopyrite surface. On the other hand, dibutyl dithiophosphate adsorbs on chalcocite in the form of hydrophobic patches, which can be removed by rinsing with ethanol alcohol. AFM images show that the adsorption of collectors increases with increasing adsorption time and collectors’ concentration. In addition, increasing the solution pH to 10 does not prevent the adsorption of xanthate and Aerofloat 238 on chalcocite and the result is in line with the fact that chalcocite floats well in a wide pH range up to 12 with xanthate and dialkyl dithiophosphate being used as collectors. The blending collectors study shows that xanthate and dialkyl dithiophosphate can co-adsorb with both insoluble cuprous xanthate and oily Cu(DTP)2 (Cu dibutyl dithiophosphate) on a chalcocite surface. The present study helps to clarify the flotation mechanism of chalcocite in industry practice using xanthate and dialkyl dithiophosphate as collectors.
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    Air quality economics: Three essays
    Yao, Zhenyu (Virginia Tech, 2022-06-17)
    This dissertation consists of three separate research projects. Each paper uses a different applied econometric technique to investigate problems related to air quality economics. The first chapter is a general introduction to all three studies. The second chapter explores adopting an environmentally-friendly public transportation system in Europe. The Bayesian econometric methods show that willingness to pay for a new public transportation system is primarily driven by improvements to public goods, such as air quality and greenhouse gas emission reduction. The third chapter uses the red tide-related stated experience and satellite imagery of chlorophyll-a concentration as well as field data of respiratory irritation. This chapter illustrates that ancillary scientific information can be efficiently combined with choice experimental data. The fourth chapter uses panel fixed-effect models to investigate the short-term effect of air pollution on students' cognitive performance in China. It is shown that PM2.5 has a significantly negative impact on students' exam performance.
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    Aligning evidence generation and use across health, development, and environment
    Tallis, Heather; Kreis, Katharine; Olander, Lydia P.; Ringler, Claudia; Ameyaw, David; Borsuk, Mark E.; Fletschner, Diana; Game, Edward; Gilligan, Daniel O.; Jeuland, Marc; Kennedy, Gina; Masuda, Yuta J.; Mehta, Sumi; Miller, Nicholas; Parker, Megan; Pollino, Carmel; Rajaratnam, Julie; Wilkie, David; Zhang, Wei; Ahmed, Selena; Ajayi, Oluyede C.; Alderman, Harold; Arhonditsis, George; Azevedo, Ines; Badola, Ruchi; Bailis, Rob; Balvanera, Patricia; Barbour, Emily; Bardini, Mark; Barton, David N.; Baumgartner, Jill; Benton, Tim G.; Bobrow, Emily; Bossio, Deborah; Bostrom, Ann; Braimoh, Ademola; Brondizio, Eduardo; Brown, Joe; Bryant, Benjamin P.; Calder, Ryan S. D.; Chaplin-Kramer, Becky; Cullen, Alison; DeMello, Nicole; Dickinson, Katherine L.; Ebi, Kristie L.; Eves, Heather E.; Fanzo, Jessica; Ferraro, Paul J.; Fisher, Brendan; Frongillo, Edward A.; Galford, Gillian; Garrity, Dennis; Gatere, Lydiah; Grieshop, Andrew P.; Grigg, Nicola J.; Groves, Craig; Gugerty, Mary Kay; Hamm, Michael; Hou, Xiaoyue; Huang, Cindy; Imhoff, Marc; Jack, Darby; Jones, Andrew D.; Kelsey, Rodd; Kothari, Monica; Kumar, Ritesh; Lachat, Carl; Larsen, Ashley E.; Lawrence, Mark; DeClerck, Fabrice; Levin, Phillip S.; Mabaya, Edward; Gibson, Jacqueline MacDonald; McDonald, Robert; Mace, Georgina; Maertens, Ricardo; Mangale, Dorothy; Martino, Robin; Mason, Sara A.; Mehta, Lyla; Meinzen-Dick, Ruth; Merz, Barbara; Msangi, Siwa; Murray, Grant; Murray, Kris A.; Naude, Celeste E.; Newlands, Nathaniel K.; Nkonya, Ephraim; Peterman, Amber; Petruney, Tricia; Possingham, Hugh; Puri, Jyotsna; Remans, Roseline; Remlinger, Lisa; Ricketts, Taylor H.; Reta, Bedilu; Robinson, Brian E.; Roe, Dilys; Rosenthal, Joshua; Shen, Guofeng; Shindell, Drew; Stewart-Koster, Ben; Sunderland, Terry; Sutherland, William J.; Tewksbury, Joshua; Wasser, Heather; Wear, Stephanie; Webb, Chris; Whittington, Dale; Wilkerson, Marit; Wittmer, Heidi; Wood, Benjamin DK K.; Wood, Stephen; Wu, Joyce; Yadama, Gautam; Zobrist, Stephanie (Elsevier, 2019-08-01)
    Although health, development, and environment challenges are interconnected, evidence remains fractured across sectors due to methodological and conceptual differences in research and practice. Aligned methods are needed to support Sustainable Development Goal advances and similar agendas. The Bridge Collaborative, an emergent research-practice collaboration, presents principles and recommendations that help harmonize methods for evidence generation and use. Recommendations were generated in the context of designing and evaluating evidence of impact for interventions related to five global challenges (stabilizing the global climate, making food production sustainable, decreasing air pollution and respiratory disease, improving sanitation and water security, and solving hunger and malnutrition) and serve as a starting point for further iteration and testing in a broader set of contexts and disciplines. We adopted six principles and emphasize three methodological recommendations: (1) creation of compatible results chains, (2) consideration of all relevant types of evidence, and (3) evaluation of strength of evidence using a unified rubric. We provide detailed suggestions for how these recommendations can be applied in practice, streamlining efforts to apply multi-objective approaches and/or synthesize evidence in multidisciplinary or transdisciplinary teams. These recommendations advance the necessary process of reconciling existing evidence standards in health, development, and environment, and initiate a common basis for integrated evidence generation and use in research, practice, and policy design.
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    Association between Phenotypes of Antimicrobial Resistance, ESBL Resistance Genes, and Virulence Genes of Salmonella Isolated from Chickens in Sichuan, China
    Shu, Gang; Qiu, Jianyu; Zheng, Yilei; Chang, Lijen; Li, Haohuan; Xu, Funeng; Zhang, Wei; Yin, Lizi; Fu, Hualin; Yan, Qigui; Gan, Ting; Lin, Juchun (MDPI, 2023-08-31)
    The aim of this study was to explore the association between antimicrobial resistance, ESBL genes, and virulence genes of Salmonella isolates. From 2019 to 2021, a total of 117 Salmonella isolates were obtained from symptomatic chickens in Sichuan Province, China. The strains were tested for antimicrobial resistance and the presence of ESBL according to the Clinical and Laboratory Standards Institute (CLSI) instructions. The presence of ESBL genes and genes for virulence was determined using Polymerase Chain Reaction (PCR). In addition, Multilocus Sequence Typing (MLST) was applied to confirm the molecular genotyping. Moreover, the mechanism of ESBL and virulence gene transfer and the relationships between the resistance phenotype, ESBL genes, and virulence genes were explored. The isolates exhibited different frequencies of resistance to antibiotics (resistance rates ranged from 21.37% to 97.44%), whereas 68.38% and 41.03% of isolates were multi-drug resistance (MDR) and ESBL-producers, respectively. In the PCR analysis, blaCTX-M was the most prevalent ESBL genotype (73.42%, 58/79), and blaCTX-M-55 showed the most significant effect on the resistance to cephalosporins as tested by logistic regression analysis. Isolates showed a high carriage rate of invA, avrA, sopB, sopE, ssaQ, spvR, spvB, spvC, stn, and bcfC (ranged from 51.28% to 100%). MLST analysis revealed that the 117 isolates were divided into 11 types, mainly ST92, ST11, and ST3717. Of 48 ESBL-producers, 21 transconjugants were successfully obtained by conjugation. Furthermore, ESBL and spv virulence genes were obtained simultaneously in 15 transconjugants. These results highlighted that Salmonella isolates were common carriers of ESBLs and multiple virulence genes. Horizontal transfer played a key role in disseminating antimicrobial resistance and pathogenesis. Therefore, it is necessary to continuously monitor the use of antimicrobials and the prevalence of AMR and virulence in Salmonella from food animals and to improve the antibiotic stewardship for salmonellosis.
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    Biopolymer Structure Analysis and Saccharification of Glycerol Thermal Processed Biomass
    Zhang, Wei (Virginia Tech, 2015-01-31)
    Glycerol thermal processing (GTP) is studied as a novel biomass pretreatment method in this research with the purposes to facilitate biopolymer fractionation and biomass saccharification. This approach is performed by treating sweet gum particles on polymer processing equipment at high temperatures and short times in the presence of anhydrous glycerol. Nine severity conditions are studied to assess the impact of time and temperature during the processing on biopolymer structure and conversion. The GTP pretreatment results in the disruption of cell wall networks by increasing the removal of side-chain sugars and lignin-carbohydrate linkages based on severity conditions. After pretreatment, 41% of the lignin and 68% of the xylan is recovered in a dry powdered form by subsequent extractions without additional catalysts, leaving a relatively pure cellulose fraction, 84% glucan, as found in chemical pulps. Lignin structural analysis indicated GTP processing resulted in extensive degradation of B-aryl ether bonds through the C-y elimination, followed by abundant phenolic hydroxyl liberation. At the same time, condensation occurred in the GTP lignin, providing relatively high molecular weight, near to that of the enzymatic mild acidolysis lignin. Better thermal stability was observed for this GTP lignin. In addition to lignin, xylan was successfully isolated as another polymer stream after GTP pretreatment. The recovered water insoluble xylan (WIX) was predominant alkali soluble fraction with a maximum purity of 84% and comparable molecular weight to xylan isolated from non-pretreated fibers. Additionally, the narrow molecular weight distribution of recovered WIX, was arisen from the pre-extraction of low molecular weight water-soluble xylan. Additionally, a 20-fold increase of the ultimate enzymatic saccharification for GTP pretreated biomass was observed even with significant amounts of lignin and xylan remaining on the non-extracted fiber. The shear and heat processing caused a disintegrated cell wall structure with formation of biomass debris and release of cellulose fibrils, enhancing surface area and most likely porosity. These structural changes were responsible for the improved biomass digestibility. Additionally, no significant inhibitory compounds for saccharification are produced during GTP processing, even at high temperatures. While lignin extraction did not promote improvement in hydrolysis rates, further xylan extraction greatly increases the initial enzymatic hydrolysis rate and final level of saccharification. The serial of studies fully demonstrate glycerol thermal processing as a novel pretreatment method to enhance biomass saccharification for biofuel production, as well as facilitate biopolymer fractionation. Moreover, the study shows the impact of thermally introduced structural changes to wood biopolymers when heated in anhydrous environments in the presence of hydrogen bonding solvent.
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    A Century of Profligacy? The Measurement and Evolution of Food Waste
    Bovay, John; Zhang, Wei (Cambridge University Press, 2019)
    Food waste has been recognized as an economic issue for at least a century and is gaining tremendous traction in academia as well as in discourse about public policy. The goal of our study is to examine the evolution of food waste over the last several decades at the United States and global levels. We first review the methodologies that have been used to estimate the magnitude of food waste so that the quality of the data can be evaluated. Though with limitations, existing data generally show that for many regions of the world, including the United States, preconsumer food loss and waste as a share of total supply has been stable in recent decades. However, the aggregate share wasted masks important changes over time. We provide some evidence that food waste has shifted downstream in recent decades, i.e., from producers and processors to retailers and consumers. Through a reflection on the trends in major socioeconomic factors, we hypothesize that this downstream shift has been driven by increases in household incomes, improvements in technology, and changes in culture and institutions.
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    Community assessment to advance computational prediction of cancer drug combinations in a pharmacogenomic screen
    Menden, Michael P.; Wang, Dennis; Mason, Mike J.; Szalai, Bence; Bulusu, Krishna C.; Guan, Yuanfang; Yu, Thomas; Kang, Jaewoo; Jeon, Minji; Wolfinger, Russ; Nguyen, Tin; Zaslavskiy, Mikhail; Jang, In Sock; Ghazoui, Zara; Ahsen, Mehmet Eren; Vogel, Robert; Neto, Elias Chaibub; Norman, Thea; Tang, Eric K. Y.; Garnett, Mathew J.; Di Veroli, Giovanni Y.; Fawell, Stephen; Stolovitzky, Gustavo; Guinney, Justin; Dry, Jonathan R.; Saez-Rodriguez, Julio; Abante, Jordi; Abecassis, Barbara Schmitz; Aben, Nanne; Aghamirzaie, Delasa; Aittokallio, Tero; Akhtari, Farida S.; Al-lazikani, Bissan; Alam, Tanvir; Allam, Amin; Allen, Chad; de Almeida, Mariana Pelicano; Altarawy, Doaa; Alves, Vinicius; Amadoz, Alicia; Anchang, Benedict; Antolin, Albert A.; Ash, Jeremy R.; Romeo Aznar, Victoria; Ba-alawi, Wail; Bagheri, Moeen; Bajic, Vladimir; Ball, Gordon; Ballester, Pedro J.; Baptista, Delora; Bare, Christopher; Bateson, Mathilde; Bender, Andreas; Bertrand, Denis; Wijayawardena, Bhagya; Boroevich, Keith A.; Bosdriesz, Evert; Bougouffa, Salim; Bounova, Gergana; Brouwer, Thomas; Bryant, Barbara; Calaza, Manuel; Calderone, Alberto; Calza, Stefano; Capuzzi, Stephen; Carbonell-Caballero, Jose; Carlin, Daniel; Carter, Hannah; Castagnoli, Luisa; Celebi, Remzi; Cesareni, Gianni; Chang, Hyeokyoon; Chen, Guocai; Chen, Haoran; Chen, Huiyuan; Cheng, Lijun; Chernomoretz, Ariel; Chicco, Davide; Cho, Kwang-Hyun; Cho, Sunghwan; Choi, Daeseon; Choi, Jaejoon; Choi, Kwanghun; Choi, Minsoo; De Cock, Martine; Coker, Elizabeth; Cortes-Ciriano, Isidro; Cserzo, Miklos; Cubuk, Cankut; Curtis, Christina; Van Daele, Dries; Dang, Cuong C.; Dijkstra, Tjeerd; Dopazo, Joaquin; Draghici, Sorin; Drosou, Anastasios; Dumontier, Michel; Ehrhart, Friederike; Eid, Fatma-Elzahraa; ElHefnawi, Mahmoud; Elmarakeby, Haitham A.; van Engelen, Bo; Engin, Hatice Billur; de Esch, Iwan; Evelo, Chris; Falcao, Andre O.; Farag, Sherif; Fernandez-Lozano, Carlos; Fisch, Kathleen; Flobak, Asmund; Fornari, Chiara; Foroushani, Amir B. K.; Fotso, Donatien Chedom; Fourches, Denis; Friend, Stephen; Frigessi, Arnoldo; Gao, Feng; Gao, Xiaoting; Gerold, Jeffrey M.; Gestraud, Pierre; Ghosh, Samik; Gillberg, Jussi; Godoy-Lorite, Antonia; Godynyuk, Lizzy; Godzik, Adam; Goldenberg, Anna; Gomez-Cabrero, David; Gonen, Mehmet; de Graaf, Chris; Gray, Harry; Grechkin, Maxim; Guimera, Roger; Guney, Emre; Haibe-Kains, Benjamin; Han, Younghyun; Hase, Takeshi; He, Di; He, Liye; Heath, Lenwood S.; Hellton, Kristoffer H.; Helmer-Citterich, Manuela; Hidalgo, Marta R.; Hidru, Daniel; Hill, Steven M.; Hochreiter, Sepp; Hong, Seungpyo; Hovig, Eivind; Hsueh, Ya-Chih; Hu, Zhiyuan; Huang, Justin K.; Huang, R. Stephanie; Hunyady, Laszlo; Hwang, Jinseub; Hwang, Tae Hyun; Hwang, Woochang; Hwang, Yongdeuk; Isayev, Olexandr; Walk, Oliver Bear Don't; Jack, John; Jahandideh, Samad; Ji, Jiadong; Jo, Yousang; Kamola, Piotr J.; Kanev, Georgi K.; Karacosta, Loukia; Karimi, Mostafa; Kaski, Samuel; Kazanov, Marat; Khamis, Abdullah M.; Khan, Suleiman Ali; Kiani, Narsis A.; Kim, Allen; Kim, Jinhan; Kim, Juntae; Kim, Kiseong; Kim, Kyung; Kim, Sunkyu; Kim, Yongsoo; Kim, Yunseong; Kirk, Paul D. W.; Kitano, Hiroaki; Klambauer, Gunter; Knowles, David; Ko, Melissa; Kohn-Luque, Alvaro; Kooistra, Albert J.; Kuenemann, Melaine A.; Kuiper, Martin; Kurz, Christoph; Kwon, Mijin; van Laarhoven, Twan; Laegreid, Astrid; Lederer, Simone; Lee, Heewon; Lee, Jeon; Lee, Yun Woo; Leppaho, Eemeli; Lewis, Richard; Li, Jing; Li, Lang; Liley, James; Lim, Weng Khong; Lin, Chieh; Liu, Yiyi; Lopez, Yosvany; Low, Joshua; Lysenko, Artem; Machado, Daniel; Madhukar, Neel; De Maeyer, Dries; Malpartida, Ana Belen; Mamitsuka, Hiroshi; Marabita, Francesco; Marchal, Kathleen; Marttinen, Pekka; Mason, Daniel; Mazaheri, Alireza; Mehmood, Arfa; Mehreen, Ali; Michaut, Magali; Miller, Ryan A.; Mitsopoulos, Costas; Modos, Dezso; Van Moerbeke, Marijke; Moo, Keagan; Motsinger-Reif, Alison; Movva, Rajiv; Muraru, Sebastian; Muratov, Eugene; Mushthofa, Mushthofa; Nagarajan, Niranjan; Nakken, Sigve; Nath, Aritro; Neuvial, Pierre; Newton, Richard; Ning, Zheng; De Niz, Carlos; Oliva, Baldo; Olsen, Catharina; Palmeri, Antonio; Panesar, Bhawan; Papadopoulos, Stavros; Park, Jaesub; Park, Seonyeong; Park, Sungjoon; Pawitan, Yudi; Peluso, Daniele; Pendyala, Sriram; Peng, Jian; Perfetto, Livia; Pirro, Stefano; Plevritis, Sylvia; Politi, Regina; Poon, Hoifung; Porta, Eduard; Prellner, Isak; Preuer, Kristina; Angel Pujana, Miguel; Ramnarine, Ricardo; Reid, John E.; Reyal, Fabien; Richardson, Sylvia; Ricketts, Camir; Rieswijk, Linda; Rocha, Miguel; Rodriguez-Gonzalvez, Carmen; Roell, Kyle; Rotroff, Daniel; de Ruiter, Julian R.; Rukawa, Ploy; Sadacca, Benjamin; Safikhani, Zhaleh; Safitri, Fita; Sales-Pardo, Marta; Sauer, Sebastian; Schlichting, Moritz; Seoane, Jose A.; Serra, Jordi; Shang, Ming-Mei; Sharma, Alok; Sharma, Hari; Shen, Yang; Shiga, Motoki; Shin, Moonshik; Shkedy, Ziv; Shopsowitz, Kevin; Sinai, Sam; Skola, Dylan; Smirnov, Petr; Soerensen, Izel Fourie; Soerensen, Peter; Song, Je-Hoon; Song, Sang Ok; Soufan, Othman; Spitzmueller, Andreas; Steipe, Boris; Suphavilai, Chayaporn; Tamayo, Sergio Pulido; Tamborero, David; Tang, Jing; Tanoli, Zia-ur-Rehman; Tarres-Deulofeu, Marc; Tegner, Jesper; Thommesen, Liv; Tonekaboni, Seyed Ali Madani; Tran, Hong T.; De Troyer, Ewoud; Truong, Amy; Tsunoda, Tatsuhiko; Turu, Gabor; Tzeng, Guang-Yo; Verbeke, Lieven; Videla, Santiago; Vis, Daniel; Voronkov, Andrey; Votis, Konstantinos; Wang, Ashley; Wang, Hong-Qiang Horace; Wang, Po-Wei; Wang, Sheng; Wang, Wei; Wang, Xiaochen; Wang, Xin; Wennerberg, Krister; Wernisch, Lorenz; Wessels, Lodewyk; van Westen, Gerard J. P.; Westerman, Bart A.; White, Simon Richard; Willighagen, Egon; Wurdinger, Tom; Xie, Lei; Xie, Shuilian; Xu, Hua; Yadav, Bhagwan; Yau, Christopher; Yeerna, Huwate; Yin, Jia Wei; Yu, Michael; Yu, MinHwan; Yun, So Jeong; Zakharov, Alexey; Zamichos, Alexandros; Zanin, Massimiliano; Zeng, Li; Zenil, Hector; Zhang, Frederick; Zhang, Pengyue; Zhang, Wei; Zhao, Hongyu; Zhao, Lan; Zheng, Wenjin; Zoufir, Azedine; Zucknick, Manuela (Springer Nature, 2019-06-17)
    The effectiveness of most cancer targeted therapies is short-lived. Tumors often develop resistance that might be overcome with drug combinations. However, the number of possible combinations is vast, necessitating data-driven approaches to find optimal patient-specific treatments. Here we report AstraZeneca's large drug combination dataset, consisting of 11,576 experiments from 910 combinations across 85 molecularly characterized cancer cell lines, and results of a DREAM Challenge to evaluate computational strategies for predicting synergistic drug pairs and biomarkers. 160 teams participated to provide a comprehensive methodological development and benchmarking. Winning methods incorporate prior knowledge of drug-target interactions. Synergy is predicted with an accuracy matching biological replicates for >60% of combinations. However, 20% of drug combinations are poorly predicted by all methods. Genomic rationale for synergy predictions are identified, including ADAM17 inhibitor antagonism when combined with PIK3CB/D inhibition contrasting to synergy when combined with other PI3K-pathway inhibitors in PIK3CA mutant cells.
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    Dietary Supplementation of Chinese Ginseng Prevents Obesity and Metabolic Syndrome in High-Fat Diet-Fed Mice
    Li, Xiaoxiao; Luo, Jing; Babu, Pon Velayutham Anandh; Zhang, Wei; Gilbert, Elizabeth R.; Cline, Mark A.; McMillan, Ryan P.; Hulver, Matthew W.; Alkhalidy, Hana; Zhen, Wei; Zhang, Haiyan; Liu, Dongmin (Mary Ann Liebert, 2014-12-01)
    Obesity and diabetes are growing health problems worldwide. In this study, dietary provision of Chinese ginseng (0.5 g/kg diet) prevented body weight gain in high-fat (HF) diet-fed mice. Dietary ginseng supplementation reduced body fat mass gain, improved glucose tolerance and whole body insulin sensitivity, and prevented hypertension in HF diet-induced obese mice. Ginseng consumption led to reduced concentrations of plasma insulin and leptin, but had no effect on plasma adiponectin levels in HF diet-fed mice. Body temperature was higher in mice fed the ginseng-supplemented diet but energy expenditure, respiration rate, and locomotive activity were not significantly altered. Dietary intake of ginseng increased fatty acid oxidation in the liver but not in skeletal muscle. Expression of several transcription factors associated with adipogenesis (C/EBP alpha and PPAR gamma) were decreased in the adipose tissue of HF diet-fed mice, effects that were mitigated in mice that consumed the HF diet supplemented with ginseng. Abundance of fatty acid synthase (FASN) mRNA was greater in the adipose tissue of mice that consumed the ginseng-supplemented HF diet as compared with control or un-supplemented HF diet-fed mice. Ginseng treatment had no effect on the expression of genes involved in the regulation of food intake in the hypothalamus. These data suggest that Chinese ginseng can potently prevent the development of obesity and insulin resistance in HF diet-fed mice.
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    Effects of Dietary Ferulic Acid on Intestinal Health and Ileal Microbiota of Tianfu Broilers Challenged with Lipopolysaccharide
    Tang, Ziting; Shu, Gang; Du, Hong; Zheng, Yilei; Fu, Hualin; Zhang, Wei; Lv, Cheng; Xu, Funeng; Li, Haohuan; Ouyang, Ping; Lin, Juchun; Chang, Li-Jen; Amevor, Felix Kwame; Zhao, Xiaoling (MDPI, 2023-02-10)
    Lipopolysaccharide (LPS) has been considered the primary agent to establish animal models of inflammation, immunological stress, and organ injury. Previous studies have demonstrated that LPS impaired gastrointestinal development and disrupted intestinal microbial composition and metabolism. Ferulic acid (FA) isolated from multiple plants exhibits multiple biological activities. This study investigated whether FA ameliorated intestinal function and microflora in LPS-challenged Tianfu broilers. The results showed that LPS challenge impaired intestinal function, as evidenced by decreased antioxidant functions (p < 0.05), disrupted morphological structure (p < 0.05), and increased intestinal permeability (p < 0.05); however, these adverse effects were improved by FA supplementation. Additionally, FA supplementation preserved sIgA levels (p < 0.05), increased mRNA expression levels of CLDN and ZO-1 (p < 0.05), and enhanced epithelial proliferation (p < 0.05) in the ileal mucosa in LPS-challenged chickens. Moreover, FA supplementation rectified the ileal microflora disturbances in the LPS-challenged broilers. The results demonstrate that dietary FA supplementation decreased LPS-induced intestinal damage by enhancing antioxidant capacity and maintaining intestinal integrity. Furthermore, FA supplementation protects intestinal tight junctions (TJs), elevates secretory immunoglobulin A (sIgA) levels, and modulates ileal microflora composition in LPS-challenged broilers.
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    Energy Management System in DC Future Home
    Zhang, Wei (Virginia Tech, 2015-08-19)
    Making electricity grids smarter and facilitating them with integration of renewable energy sources (RES) and energy storage are fairly accepted as the necessary steps to achieve a sustainable and secure power industry. To enable Net-zero energy and optimize power management for future homes or buildings, DC electric distribution systems (DC Nano-grid) find feasibility and simplicity for integrating renewable energy sources and energy storage. However, integrating the sources and loads in a simple, robust and smart way is still challenging. High voltage lithium-ion battery should be seriously considered concerning the overcharge/over-discharge risk. Dissipative cell equalization and its performance are studied. Non-dissipative equalization methods are reviewed using an energy flow chart. Typical charging schemes and the related over-charge risk are illustrated. A Lithium-ion battery charging profile based on VCell_Max/Min monitoring is proposed and validated with experimental results in an 8.4kW bidirectional battery charger for DC future home. For the DC future home emulator testbed, a grid interface converter, i.e. energy control center (ECC) converter, is reviewed with functions identification. A PV system with different configurations is compared to further expand the common MPPT region, and a DC-DC converter is designed as the interface between PV panels and DC bus, facilitating maximum power point tracking (MPPT) as well as fulfill the system energy management requirement. An 8.4kW multi-phase bidirectional battery charger with Si IGBT in DCM operation is designed to achieve high efficiency and to be the interface converter between lithium-ion battery and DC bus, enhancing the battery system management as well as increasing the system reliability. To integrate all the sources and loads in a simple, reliable and smart way, this thesis proposes a distributed droop control method and smart energy management strategy to enhance the Net-zero electric energy cost. All of the control strategies are applied to the DC future home with interactions among the energy control center (ECC), renewable energy sources, energy storage and load within a day/24 hours. System level energy management control strategies for Net-zero electric energy cost are examined and illustrated. A 10kW future home emulator testbed is built and introduced for concepts validation.
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    Essays on Development in Sub-Saharan African Countries
    Zhang, Zeya (Virginia Tech, 2021-01-14)
    As one of the fastest growing regions in the world, crop production and education remain two of the most important topics for the development of sub-Saharan African (SSA) countries. This dissertation is composed of three chapters that investigate the economic returns to education (Chapter 1 and 2) and assess the policy influence on fertilizer usage (Chapter 3) in two SSA countries, Zimbabwe and Ethiopia. Chapter 1 investigates the casual impact of improved educational attainment on household well-being as reflected by consumption level in Zimbabwe. We use the age-specific exposure to the 1980 education reform as the instrument for the household head educational attainment to identify the economic returns to education. We find that an extra year of household head schooling leads to an 8% increase in per capita household consumption on average when using the multiple rounds of the Income, Consumption and Expenditure Survey (ICES). The impact of enhanced education on household consumption is larger for rural and female-headed households and we also find some evidence that head educational attainment could affect consumption patterns, where additional schooling leads to slightly lower consumption share in food and higher share in non-durable goods. Chapter 2 extends this topic by utilizing a pseudo panel data constructed with multiple waves of repeated cross-sectional data, which allows us to use fixed-effect and other panel data methods to address the problem of unobserved "ability" bias. For pseudo panel, we use age, gender and some other time-persistent criterions to define the cohorts and replace the individual observations with the intra-cohort means. Individual time-invariant factors that influencing both education and consumption are transformed into cohort time-invariant factors, within transformation on the pseudo panel would eliminate such factors leads to achieve unbiased and consistent estimates on the returns to education. We find on average there is a 14% increase in monthly household per capita consumption for each one more year of education for the household head. By further disaggregating our population, we find female-headed households exhibit a return to education of around 15.3%, much higher than its corresponding OLS/IV estimates. On the other hand, we fail to detect such large discrepancy for the male-headed households, suggesting that the overall downward bias of OLS/IV estimates mostly come from female-headed households. Facing significant higher opportunity cost, Zimbabwean females are much less likely to furthering their education when compared to males with similar unobserved ability level which can be one of the major underlying reasons. Chapter 3 investigates the potential effect of fertilizer promotion polices on crop acreage and input intensities in Ethiopia. We use a fully calibrated multi-input and -output model based on the principle of positive mathematical programming (PMP) to assess the policy impact in four major agricultural states in the country. I analyze two policies designed to promote fertilizer use, namely fertilizer import expansion and a universal subsidy program. The results from the simulation model suggest that local farmers actively respond to these promotion policies by adjusting crop acreage and investing more in fertilizer input. However, when the availability of fertilizer in one region is fixed and local farmers face a binding constraint, the behavior responses to the subsidy program alone would be limited.
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    Examining Implicit Price Variation for Lake Water Quality
    Swedberg, Kristen (Virginia Tech, 2020-12-16)
    Hedonic models are used to estimate implicit prices for water quality in housing markets. Recent studies aggregate sales across large spatial areas in scaled-up models leading to a concern that these models may overlook regional heterogeneity in water-quality preferences. We estimate scaled-up hedonic models comprised of multiple states and individual states and investigate how observations from subregions can differ. We find that the scaled-up model results are driven by select subregions. The results of this study call into question hedonic models using data for large geographic regions where substantial differences may arise across housing markets.
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    A global synthesis reveals biodiversity-mediated benefits for crop production
    Dainese, Matteo; Martin, Emily A.; Aizen, Marcelo A.; Albrecht, Matthias; Bartomeus, Ignasi; Bommarco, Riccardo; Carvalheiro, Luisa G.; Chaplin-Kramer, Rebecca; Gagic, Vesna; Garibaldi, Lucas A.; Ghazoul, Jaboury; Grab, Heather; Jonsson, Mattias; Karp, Daniel S.; Kennedy, Christina M.; Kleijn, David; Kremen, Claire; Landis, Douglas A.; Letourneau, Deborah K.; Marini, Lorenzo; Poveda, Katja; Rader, Romina; Smith, Henrik G.; Tscharntke, Teja; Andersson, Georg K. S.; Badenhausser, Isabelle; Baensch, Svenja; Bezerra, Antonio Diego M.; Bianchi, Felix J. J. A.; Boreux, Virginie; Bretagnolle, Vincent; Caballero-Lopez, Berta; Cavigliasso, Pablo; Cetkovic, Aleksandar; Chacoff, Natacha P.; Classen, Alice; Cusser, Sarah; da Silva e Silva, Felipe D.; de Groot, G. Arjen; Dudenhoeffer, Jan H.; Ekroos, Johan; Fijen, Thijs; Franck, Pierre; Freitas, Breno M.; Garratt, Michael P. D.; Gratton, Claudio; Hipolito, Juliana; Holzschuh, Andrea; Hunt, Lauren; Iverson, Aaron L.; Jha, Shalene; Keasar, Tamar; Kim, Tania N.; Kishinevsky, Miriam; Klatt, Bjorn K.; Klein, Alexandra-Maria; Krewenka, Kristin M.; Krishnan, Smitha; Larsen, Ashley E.; Lavigne, Claire; Liere, Heidi; Maas, Bea; Mallinger, Rachel E.; Martinez Pachon, Eliana; Martinez-Salinas, Alejandra; Meehan, Timothy D.; Mitchell, Matthew G. E.; Molina, Gonzalo A. R.; Nesper, Maike; Nilsson, Lovisa; O'Rourke, Megan E.; Peters, Marcell K.; Plecas, Milan; Potts, Simon G.; Ramos, Davi de L.; Rosenheim, Jay A.; Rundlof, Maj; Rusch, Adrien; Saez, Agustin; Scheper, Jeroen; Schleuning, Matthias; Schmack, Julia M.; Sciligo, Amber R.; Seymour, Colleen; Stanley, Dara A.; Stewart, Rebecca M.; Stout, Jane C.; Sutter, Louis; Takada, Mayura B.; Taki, Hisatomo; Tamburini, Giovanni; Tschumi, Matthias; Viana, Blandina F.; Westphal, Catrin; Willcox, Bryony K.; Wratten, Stephen D.; Yoshioka, Akira; Zaragoza-Trello, Carlos; Zhang, Wei; Zou, Yi; Steffan-Dewenter, Ingolf (AAAS, 2019-10)
    Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield-related ecosystem services can be maintained by a few dominant species or rely on high richness remains unclear. Using a global database from 89 studies (with 1475 locations), we partition the relative importance of species richness, abundance, and dominance for pollination; biological pest control; and final yields in the context of ongoing land-use change. Pollinator and enemy richness directly supported ecosystem services in addition to and independent of abundance and dominance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.
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    High-performance inertial impaction filters for particulate matter removal
    Zhang, Xiaowei; Zhang, Wei; Yi, Mingqiang; Wang, Yingjie; Wang, Pengjun; Xu, Jun; Niu, Fenglei; Lin, Feng (Springer Nature, 2018-03-19)
    Airborne particulate matter (PM) is causing more and more serious air pollution and threatening the public health. However, existing air filter technologies with the easy-to-block manner can rarely meet the requirements of high-performance PM filters. Here we propose a conceptually new type of inertial impaction filters for rapidly high-efficiency PM removal. Under the airflow velocity of 8.0 m/s, the real inertial impaction filters show high PM removal efficiencies of up to 97.77 +/- 1.53% and 99.47 +/- 0.45% for PM2.5 and PM10, respectively. Compared with the traditional air filters reported previously, the inertia impaction filters exhibit extremely low pressure drop of 5-10 Pa and high quality factor (QF) values of 0.380 Pa-1 and 0.524 Pa-1 for PM2.5 and PM10, respectively. These greatly improved QF values are achieved through a series of inertial separation processes. The feature dimension of filtration channel is dozens of times larger than PM average size, which greatly decreases airflow resistance. Particularly, this inertial structure can be made of various types of materials, which shows great potential for low-cost fabrication of large-area devices. As a stand-alone device or incorporated with the existing PM air filter, this inertial impaction filter will bring great benefits to the public health.
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    The influence of the Environmental Quality Incentives Program on local water quality
    Liu, Pengfei; Wang, Yu; Zhang, Wei (AAEA/Wiley, 2022-04-27)
    The Environmental Quality Incentives Program (EQIP) is the primary conservation program on working agricultural land. The United States Department of Agriculture obligated over $15 billion through EQIP cost-sharing contracts during the fiscal years 2009–2019. The voluntary nature of the program and the lack of performance assessment have led to speculations regarding the effectiveness of the program in delivering environmental benefits, in particular for improving water quality. This study provides quantitative estimates of the influence of EQIP payments on local water quality at a national scale. We link monitoring station level water quality readings with EQIP contract data and exploit the direction of river flow for identification. The estimated effects of EQIP vary across water quality measures. Estimates indicate that EQIP payments have significantly reduced biochemical oxygen demand and nitrogen, indicating improvements in water quality, but increased total suspended solids, fecal coliform, and phosphorus, suggesting that the implementation of certain conservation practices might have increased soil erosion and pathogen transfer, especially in watersheds with more agricultural production.
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    Integrated EMI/Thermal Design for Switching Power Supplies
    Zhang, Wei (Virginia Tech, 1998-02-09)
    This work presents the modeling and analysis of EMI and thermal performance for switch power supply by using the CAD tools. The methodology and design guidelines are developed. By using a boost PFC circuit as an example, an equivalent circuit model is built for EMI noise prediction and analysis. The parasitic elements of circuit layout and components are extracted analytically or by using CAD tools. Based on the model, circuit layout and magnetic component design are modified to minimize circuit EMI. EMI filter can be designed at an early stage without prototype implementation. In the second part, thermal analyses are conducted for the circuit by using the software Flotherm, which includes the mechanism of conduction, convection and radiation. Thermal models are built for the components. Thermal performance of the circuit and the temperature profile of components are predicted. Improved thermal management and winding arrangement are investigated to reduce temperature. In the third part, several circuit layouts and inductor design examples are checked from both the EMI and thermal point of view. Insightful information is obtained.
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    Knockdown of ZBED6 is not associated with changes in murine preadipocyte proliferation or differentiation
    Zhang, Wei; Cline, Mark A.; Liu, Dongmin; Gilbert, Elizabeth R. (2013-10-01)
    ZBED6 was identified as a transcription factor that affects muscle mass and fat deposition in pigs. Mechanisms mediating effects on fat mass are unclear. The objective was to determine the effect of ZBED6 mRNA knockdown on 3T3-L1 preadipocyte differentiation and gene expression. Differentiation was associated with increased mRNA abundance of CEBP/α (P < 0.05), CEBP/β (P < 0.05), CEBP/δ (P < 0.05), FASN (P < 0.05), PPARγ (P < 0.05), and SREBP-1 (P < 0.05), and decreased abundance of PREF-1 (P < 0.05). Knockdown of ZBED6 was not associated with changes in mRNA abundance of selected genes, lipid accumulation, lipid droplet size, or cell number. These results suggest that ZBED6 does not play a major role in preadipocyte differentiation.
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    Methodological advances in benefit transfer and hedonic analysis
    Puri, Roshan (Virginia Tech, 2023-09-19)
    This dissertation introduces advanced statistical and econometric methods in two distinct areas of non-market valuation: benefit transfer (BT) and hedonic analysis. While the first and the third chapters address the challenge of estimating the societal benefits of prospective environmental policy changes by adopting locally weighted regression (LWR) technique in an environmental valuation context, the second chapter combines the output from traditional hedonic regression and matching estimators and provides guidance on the choice of model with low risk of bias in housing market studies. The economic and societal benefits associated with various environmental conservation programs, such as improvement in water quality, or increment in wetland acreages, can be directly estimated using primary studies. However, conducting primary studies can be highly resource-intensive and time-consuming as they typically involve extensive data collection, sophisticated models, and a considerable investment of financial and human resources. As a result, BT offers a practical alternative, which involves employing valuation estimates, functions, or models from prior primary studies to predict the societal benefit of conservation policies at a policy site. Existing studies typically fit one single regression model to all observations within the given metadata and generate a single set of coefficients to predict welfare (willingness-to-pay) in a prospective policy site. However, a single set of coefficients may not reflect the true relationship between dependent and independent variables, especially when multiple source studies/locations are involved in the data-generating process which, in turn, degrades the predictive accuracy of the given meta-regression model (MRM). To address this shortcoming, we employ the LWR technique in an environmental valuation context. LWR allows an estimation of a different set of coefficients for each location to be used for BT prediction. However, the empirical exercise carried out in the existing literature is rigorous from a computational perspective and is cumbersome for practical adaptation. In the first chapter, we simplify the experimental setup required for LWR-BT analysis by taking a closer look at the choice of weight variables for different window sizes and weight function settings. We propose a pragmatic solution by suggesting "universal weights" instead of striving to identify the best of thousands of different weight variable settings. We use the water quality metadata employed in the published literature and show that our universal weights generate more efficient and equally plausible BT estimates for policy sites than the best weight variable settings that emerge from a time-consuming cross-validation search over the entire universe of individual variable combinations. The third chapter expands the scope of LWR to wetland meta-data. We use a conceptually similar set of weight variables as in the first chapter and replicate the methodological approach of that chapter. We show that LWR, under our proposed weight settings, generates substantial gain in both predictive accuracy and efficiency compared to the one generated by standard globally-linear MRM. Our second chapter delves into a separate yet interrelated realm of non-market valuation, i.e., hedonic analysis. Here, we explore the combined inferential power of traditional hedonic regression and matching estimators to provide guidance on model choice for housing market studies where researchers aim to estimate an unbiased binary treatment effect in the presence of unobserved spatial and temporal effects. We examine the potential sources of bias within both hedonic regression and basic matching. We discuss the theoretical routes to mitigate these biases and assess their feasibility in practical contexts. We propose a novel route towards unbiasedness, i.e., the "cancellation effect" and illustrate its empirical feasibility while estimating the impact of flood hazards on housing prices.
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    Microbubble fermentation of recombinant Pichia pastoris for human serum albumin production
    Zhang, Wei (Virginia Tech, 2003-05-20)
    The high cell density fermentation of recombinant Pichia pastoris for human serum albumin (HSA) production is a high oxygen demand process. The oxygen demand is usually met by increased agitation rate and use of oxygen-enriched air. Microbubble fermentation however can supply adequate oxygen to the microorganisms at relatively low agitation rates because of improved mass transfer of the microbubbles used for the sparging. Conventionally sparged fermentations were conducted for the production of HSA using P. pastoris at agitation rates of 350, 500, and 750 rpm, and were compared to MBD sparged fermentation at 150, 350, and 500 rpm agitation rates. The MBD improved the volumetric oxygen transfer coefficient (kLa) and subsequently increased the cell mass and protein production compared to conventional fermentation. Cell production in MBD fermentation at 350 rpm was 4.6 times higher than that in conventional fermentation at 350 rpm, but similar to that in the conventional 750 rpm. Maximum cell mass productivity in the conventional 350 rpm was only 0.37 g / (L·h), while the maximum value in MBD 350 rpm was 2.0 g / (L·h), which was similar to 2.2 g / (L·h) in the conventional 750 rpm. Biomass yield on glycerol Ys (g cell/ g glycerol) was 0.334 g / g in the conventional 350 rpm, 0.431 g / g in MBD 350 rpm and 0.438 g / g in the conventional 750 rpm. Protein production in MBD 350 rpm was 7.3 times higher than that in the conventional 350 rpm, but similar to the conventional 750 rpm. Maximum protein productivity in the conventional 350 rpm was 0.37 mg / (L·h), 2.8 mg / (L·h) in MBD 350 rpm, and 3.3 mg / (L·h) in the conventional 750 rpm. Protein yield on methanol Yp (mg protein / g methanol) was 1.57 mg /g in the conventional 350 rpm, 5.02 in MBD 350 rpm, and 5.21 in the conventional 750 rpm. The volumetric oxygen transfer coefficient kLa was 1011.9 h-1 in MBD 350 rpm, which was 6.1 times higher than that in the conventional 350 rpm (164.9 h-1) but was similar to the conventional 750 rpm (1098 h-1). Therefore, MBD fermentation results at low agitation of 350 rpm were similar to those in the conventional fermentation at high agitation of 750 rpm. There was considerable improvement in oxygen transfer to the microorganism using MBD sparging relative to the conventional sparging. Conventional fermentations were conducted both in a Biostat Q fermenter (small) at 500 rpm, 750 rpm, and 1000 rpm, and in a Bioflo III fermenter (large) at 350 rpm, 500 rpm, and 750 rpm. At the same agitation rate of 500 rpm, cell production in the large reactor was 3.8 times higher than that in the small one, and no detectable protein was produced in the small reactor at 500 rpm. At the same agitation rate of 750 rpm, both cell production and protein production in the large reactor were 4.6 times higher than the small reactor. Thus, the Bioflo III fermenter showed higher oxygen transfer efficiency than the Biostat Q fermenter, because of the more efficient aeration design of the Bioflo III fermenter.
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    Neurological - Molecular Interface in Food Intake and Metabolism in Birds and Mammals
    Zhang, Wei (Virginia Tech, 2014-07-15)
    Obesity is a physiological consequence of dysregulated energy homeostasis. Energy homeostasis depends on energy intake and energy expenditure. Factors controlling the development of different adipose tissue deposits in the body and their distinct metabolic phenotypes are of considerable interest from both an agricultural and biomedical perspective. Following the literature review, the first chapter was devoted to studies designed to bridge the neural-adipose interface in understanding the relationship between appetite regulation and adipose tissue deposition in chickens, using chickens selected for low or high juvenile body weight as a model. Appetite regulation in the brain, particularly the hypothalamus, is the main factor governing food intake. Neuropeptide Y (NPY), known as a potent orexigenic factor, also promotes energy storage in fat in mammals and thus has a dual role in promoting energy intake via appetite regulation in the brain and energy storage/expenditure via direct effects on adipose tissue function. There have been no reports of the effects of NPY on adipose tissue function in any avian species. By exposing chicken preadipocytes to different concentration of NPY, we found that NPY enhances both proliferation and differentiation and thus appears to play a major role in chicken adipogenesis, an effect that has not yet been reported, to our knowledge. In the body weight selected chicken lines, we found that NPY and receptor sub-type expression was elevated in the abdominal fat of chickens from the high body weight chicken line and expression of these genes displayed heterosis in the reciprocal crosses of the parental lines as compared to both the high and low body weight selected lines. Intriguingly, expression of those same genes was greater in the low weight than high weight chickens in the hypothalamus. Hypothalamic transcriptomic profiling revealed that genes involved in serotonergic and dopaminergic systems may also play an important role in both appetite regulation and insulin-regulated energy homeostasis in the body weight chicken lines. Intracerebroventricular injection of serotonin in broiler chicks was associated with a dose and time dependent reduction in food intake that was coupled with the activation of the ventromedial hypothalamus and arcuate nucleus, as determined by c-fos immunoreactivity. The remainder of this dissertation project describes the effects of knocking down expression of a recently discovered transcription factor, ZBED6, on mouse preadipocyte proliferation and differentiation. The dissertation ends with a study using diet-induced porcine prepubertal obesity as a model to examine differences in adipokine gene expression between different fat depots from pigs that consumed diets that differed in carbohydrate composition. Overall, we conclude that both NPY and monoamines such as serotonin and dopamine are of importance in the regulation of energy balance in chickens. Moreover, we propose that NPY is a factor that mediates hypothalamus and adipose tissue crosstalk in chickens. An understanding of this system may provide a new avenue for the treatment of obesity and associated disease complications by re-orchestrating the neuronal outputs or adiposity inputs. This information may also be of value in developing strategies to improve feed conversion and meat yield in commercial broilers.