Environmental and Occupational Health Sciences Institute
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High ionic field-strength cations in aluminoborosilicate glasses and their impact on kinetics and mechanism of glass dissolution in aqueous media
No full textChemical durability of silicate glasses is among the most intriguing topics in glass community, as multi-component silicate glasses form the basis for a wide range of modern functional glasses, and their behavior in the surrounding environment must be well-predicted for practical use. For instance, many industrial glasses, including nuclear waste glass and optical fibers, require inherently high chemical durability as they are designed to last long, while the applications of some other advanced glass materials and processing techniques, such as bioactive glass and glass etching, rely on the careful control of the glass dissolution behavior. Therefore, the underlying science that governs the dissolution mechanisms and kinetics of multicomponent silicate glasses in different environments, especially relating to the impact of common constituent oxides, must be well-understood to prompt the application and future development of advanced glassy materials.
Despite a considerable effort put into understanding this topic, the existing studies often fall short in resolving actual technical challenges that are encountered during the design and processing (e.g., chemical etching) of modern functional silicate glasses, as the majority of them focus on simple glasses comprising only traditional glass components (e.g., Na2O, SiO2 and B2O3), or are tailored to a specific application. The specialty glasses, however, comprises various framework and non-framework components – especially high field-strength cations (HFSCs) – in addition to the traditional glass formers, with each component contributing its own part to the glass structure and resulting chemical durability. As a result, the current knowledge of dissolution mechanisms, which has acquired from glasses with low compositional complexity, cannot fully serve the broad spectrum of functional glasses. In this context, the present work aims to decipher the composition – structure – solubility relationship in aluminoborosilicate system, with particular focus on elucidating the effect of HFSCs on glass durability and mechanisms that lead to this effect. Accordingly, alkali/alkaline-earth aluminoborosilicate glasses containing different HFSCs, namely Nb5+, Zr4+, Ti4+, La3+ and V5+, have been selected as the subject of this research.
Under extreme scenario (i.e., pH = 2 or 13), dissolution studies of aluminoborosilicate glasses indicate a dissolution – precipitation mechanisms, with Si and Ca precipitation governing the formation of passivating layer, respectively, whereas in neutral media, a partial hydrolysis – in-situ recondensation governed dissolution is observed, followed by conditional precipitation as the reaction proceeds. Combining the dissolution studies in different pH region, it can be seen the glass dissolution behavior is not governed by one single equilibrium, but a collective result of the various physio-chemical interactions happening simultaneously at the glass-water interface and may evolve with the reaction progress. While the presence of HFSCs impacts the glass dissolution behavior, the actual effect is not solely determined by the structural role of HFSCs in the glass, the solubility of HFSCs in the targeted environment, as well as the potential interactions between HFSCs and other glass/solution components also matter. It is thus important to consider every compositional/structural driver from the glass, as well as all the environment factors, in the modelling of glass dissolution. Future work recommended for this topic include: (i) In-depth investigation on the structure of versatile HFSCs in aluminoborosilicate glass, as well as exploring their interactions with common glass components and dissolution media, to narrow the uncertainty in predicting the dissolution behavior of glasses containing these HFSCs; (ii) Correlate the glass dissolution kinetics with the variation of pH and solution chemistry through systematic investigation; and (iii) utilizing in-situ/high resolution characterization and modelling techniques to investigate the fundamental science that governs glass dissolution.Ph.D.Includes bibliographical reference
Electrochemical CO2 reduction on nickel phosphides
No full textElectrochemically converting CO2 into valuable chemicals and fuels presents a promising avenue for closing the carbon cycle and efficiently storing intermittent renewable energy. Bioinspired nickel phosphide electrocatalysts have demonstrated the ability to produce more complex multi-carbon products compared to natural photosynthetic enzymes. However, several key challenges in this field remain including controlling the selectivity of carbon product formation and, revealing the reaction mechanism as well as the commercial application of CO2RR on nickel phosphides.
When traditional anodes like the oxygen evolution reaction (OER) are used, it leads to both significant energy consumption and the production of oxygen, which has limited commercial value. On the other hand, the chlor-alkali process is a well-established and profitable electrochemical method that generates chlorine gas (Cl2) and alkali products such as potassium hydroxide (KOH). In Chapter 2, we demonstrate the feasibility of integrating the chlorine evolution reaction (CER) with CO2 reduction reactions (CO2RR) to simultaneously produce C4 (2,3-furandiol) and C3 (methylglyoxal) products. At a cell current of 1 mA, our system achieves a Faradaic efficiency (FE) of approximately 80% to produce Cl2 and 100% for CO2RR, with no losses due to crossover or cathode degradation. We further enhance the Faradaic efficiency of CO2RR products at higher current densities by utilizing a nickel phosphide Ni2P catalyst, which we synthesized through a low-temperature soft-template method. Additionally, we present a technoeconomic assessment that quantifies the economic advantages of integrating these two electrochemical processes, showcasing the economic benefits of co-producing methylglyoxal and Cl2.
In Chapter 3, we present a notable alteration in the distribution of products generated through the electrochemical reduction of carbon dioxide (CO2) when using Ni2P in the presence of boric acid or borate, which act as soluble Lewis acid/base co-catalysts. In the absence of a co-catalyst, the reduction of CO2 on Ni2P results in a mixture of methyl glyoxal (C3), 2,3-furandiol (C4), and formic acid (C1) with a 100% Faradaic efficiency for carbon products. However, the introduction of boric acid or borate as a co-catalyst leads to a shift in product selectivity towards the formation of ethylene glycol (EG), with an 85% C-Faradaic efficiency (at 10 mM, 0 V vs. RHE). Additionally, a portion of the products includes the aforementioned C1, C3, and C4 compounds. This change in selectivity is attributed to the co-catalyst's role in activating a reaction between surface *hydride and *glycolaldehyde on Ni2P while inhibiting the aldol C-C coupling reaction that typically generates C3 and C4 products. An intermediate borate-EG-diester, [(OCH2CHO)2B]-, is detected via 11B-NMR spectroscopy, and this compound subsequently undergoes hydrolysis to release EG as the final product. Extended electrolysis of boric acid results in the modification of the Ni2P surface, leading to the formation of *BO3-Ni2P, as confirmed by X-ray photoelectron spectroscopy (XPS). CO2 electro-reduction on *BO3-Ni2P, in the absence of free boric acid, exclusively yields ethylene oxide (EO), which gradually hydrolyzes into EG in the presence of a bicarbonate electrolyte. When using free boric acid as a co-catalyst and *BO3-Ni2P as the cathode, the combined Faradaic efficiencies for CO2RR products EO and EG reach 88% (at 0V vs RHE), marking a record for carbon selectivity. This research demonstrates the feasibility of utilizing Lewis acid/base co-catalysts to alter the established chemical reaction mechanism of an electrocatalyst, resulting in the formation of a new, predictably chemical product with high yield.
Atomically flat single-crystal surfaces with well-defined and uniform surface structures can provide detailed mechanistic information on the surface interaction of adsorption and intermediate species, which makes it ideal model electrode for in-situ studies. In Chapter 4, we investigate the CO2RR performance on single crystal NiP2 and employ in situ Raman spectroscopy to elucidate the reaction pathways. By detecting the catalyst under reaction condition in real time, this work provides essential information for the rational design of efficient catalysts for CO2RR.Ph.D.Includes bibliographical reference
Assessment of phytochemistry in selected foods and herbs
No full textNatural products (NPs) are chemical compounds produced through metabolic processes from living organisms with numerous applications from ecological interactions between species and within industries including pharmaceutical, agriculture, textiles fragrance, cosmetic, and many more. In Chapter 1, a literature review is conducted encompassing the history of NPs, its current pharmaceutical and economic impact, as well as background on NPs, with emphasis on secondary metabolites. This thesis focuses on plant nutrient assays and secondary metabolites where all parts of the plant such as its roots, leaves, stem, seeds, fruits, extracts, etc. have been used for mental and physical illnesses, and sometimes plays a large role in certain traditional religions.
Chapter 2 discusses the antioxidant properties of plants, various assays’ advantages and disadvantages, and specific methodology used in this thesis to determine antioxidant activity in butterhead lettuce (Lactuca sativa), kale (Brassica oleracea), and sweet basil (Ocimum basilicum). Chapter 3 focuses on total polyphenol content, complementary to antioxidant activity, assays and methodology used to determine general polyphenol content in the same butterhead lettuce and kale samples as well as an astragalus (Astragalus membranaceus) extract. Although these chemical assessments provide valuable information, modern technology specifically GC-MS and LC-MS are practiced to determine specific chemical compounds.
Chapter 4 focuses on the application of analytical instruments to identify, quantify, and determine plant NPs. Volatile compounds may be assessed by GC-MS, and the work in this thesis identifies isothiocyanates in arugula, mustard greens, and red kale. A routine targeted approach by UHPLC-QQQ/MS is executed of phenolic acids and flavonoids in arugula, mustard greens, red kale, lettuce, green kale, basil, and grape juice. Untargeted analysis is performed using UHPLC-UV/DAD-QTOF/MS showcasing the use of UV absorption and MS/MS spectrum for compound identification in kale, green and purple lettuce, and Piper sp. The final project of this thesis presents the fractionation and identification of alkaloids in kratom (Mitragyna speciosa) using chromatographic techniques in conjunction with instrumental analysis.
Lastly, Chapter 5 overviews the overall thesis, results, and conclusions from individual projects mentioned from each chapter. Future directions in the study of plant-based natural products were discussed including the use of an automated approach for untargeted analysis of metabolomics, proteomics, lipidomics, and its potential to incorporate such methods of analysis in a larger project.M.S.Includes bibliographical reference
Computational learning theory through a new lens: scalability, uncertainty, practicality, and beyond
No full textComputational learning theory studies the design and analysis of learning algorithms, and it is integral to the foundation of machine learning. In the modern era, classical computational learning theory is growingly unable to catch up with new practical demands. In particular, problems arise in the following aspects: i). scalability: with the massive scales of modern datasets, classical learning algorithms that use polynomial time and store the entire input are no longer efficient; ii). uncertainty: information nowadays is usually coupled with noise and uncertainty, which renders classical algorithms that assume accurate information unreliable; and iii). practicality: under the modern context, traditional “negligible” terms in learning theory (e.g., log n factors) can no longer be ignored, and many theoretically-efficient techniques become inapplicable in practice.
There are several promising approaches to tackle the above challenges. For scalability, one of the most popular approaches is to study learning algorithms under sublinear models, including streaming, sublinear time, and Massively Parallel Computation (MPC) models. Learning algorithms under these models usually use resources substaintially smaller than the input size. For uncertainty, we can look into learning algorithms that naturally take noisy inputs, e.g., algorithms that deal with multi-armed bandits (MABs), or algorithms that operate with randomly corrupted inputs. Finally, for practicality, we can focus on designing algorithms that are easy to implement and aim for algorithms with both theoretical guarantees and experimental performances.
In light of the above discussion, this dissertation presents three major areas of study as follows.
In Part I, we present recent results in streaming multi-armed bandits, where the arms arrive one by one in a stream, and the algorithm stores a much smaller number of arms than the input. We consider two fundamental learning problems in this model, namely pure exploration and regret minimization. For pure exploration, we give an ultra-efficient algorithm that finds the best arm and stores a single extra arm at any point. The algorithm uses a single pass and the information-theoretically optimal number of arm pulls. Subsequently, under various settings, we characterize the optimal sample-memory-pass trade-offs for pure exploration streaming MABs. For regret minimization, we give the optimal regret bounds for single-pass MABs. Together, these results complete a majority of the picture for classical MABs problems under the memory-constraint setting.
In part II, we study graph clustering in sublinear settings. We consider two important problems in practice: correlation clustering and hierarchical clustering. For correlation clustering, we design O(1)-approximation algorithms with the semi-streaming ˜O(n) space in the graph streaming model and with ˜O(n) time in the query model, where n is the number of vertices in the graph. Furthermore, for the truly-streaming polylog n space regime, we design algorithms that approximate the optimal cost of correlation clustering. We test the polylog n-space algorithms on various input data and find that the practical performances are better than the worst-case guarantees. For hierarchical clustering, we give a single-pass semi-streaming algorithm that achieves O(1)-approximation for Dasgupta’s objective, and we prove the cost-space trade-off in the single-pass setting.
In part III, we move to more practically-driven problems of differential privacy (DP) and weak-strong oracle learning. For the former problem, we consider the differentially private release of range queries on graphs – a problem with wide applications in networks –and we give optimal bounds for pure and approximate DP. For the latter problem, weak-strong oracle learning is motivated by an industry setting where information is obtained from a cheap but noisy source and an accurate but expensive source. We study (metric) k-clustering and MST in this setting and obtain nearly-optimal algorithms with strong experimental performances.Ph.D.Includes bibliographical reference
Through the lens of network mechanisms: multilevel interorganizational communication for adolescent mental health in the social media era
No full textThis dissertation explores the intricate interplay of communication among various stakeholders in New Jersey in response to escalating concerns regarding adolescent mental health and the changing significance of interorganizational networks in advocating for public health. Further, this research investigates the dynamics of interorganizational communication networks, with a focus on adolescent mental health in the context of social media. By integrating theoretical frameworks of the Source–Authority–Hub (SAH) model and network agenda setting, this research delineates the intricate processes of a multilevel interorganizational communication through the investigation of information flow, collaborative agenda setting, and network mechanisms among Nonprofit Organizations (NPOs). Utilizing a mixed-methods approach, the study draws from an extensive dataset comprising news articles, NPO websites, and social media content to analyze the interplay between traditional and social media, as well as among NPOs, in framing the discourse about adolescent mental health issues.
The results reveal a complex interorganizational network where sources, authorities, and hubs play pivotal roles in disseminating information and shaping the interorganizational information ecosystem. Sources enhance network resilience and resource allocation, authorities impact policy formulation through regulatory oversight, and hubs direct service provision to influence policy and promote best practices. Moreover, by delving into the mechanism of interorganizational networks, the results shed light on how network ties and structures influence the adolescent mental health network agenda, indicating that the existence of ties and structural equivalence fosters agenda convergence. Additionally, this research highlights the independent yet synergistic roles of news media and social media in addressing adolescent mental health, with both mediums converging on mental health narratives, emphasizing the collaborative nature of modern media ecosystems where influence is multiplex and bidirectional.
By advancing the SAH model within the context of health communication and unraveling the complexities of interorganizational networks, this dissertation contributes to the theoretical enrichment of agenda setting and network agenda setting. This work highlights the significant role of multilevel interorganizational communication in the age of social media, offering insights into effective collaboration strategies for addressing adolescent mental health challenges. The study not only extends academic understanding of interorganizational communication but also provides practical implications for NPOs, policymakers, and practitioners aiming to optimize mental health advocacy efforts.
In summary, this dissertation offers valuable perspectives on the role of interorganizational communication in understanding and addressing adolescent mental health challenges, emphasizing the necessity of collaborative communication strategies in the social media age.Ph.D.Includes bibliographical reference
Examining parental alcohol misuse as a moderator of genetic and environmental influences on early midlife physical and psychological health outcomes
No full textPurpose: Parental alcohol misuse is associated with increased substance use behaviors and poorer physical and psychological health in offspring. However, the mechanisms behind these associations are not well established. We examined gene-environment interaction as one potential mechanism, and tested whether parental alcohol misuse moderated genetic and environmental influences on early midlife (age 35) substance use, physical and psychological health outcomes.
Methods: The sample included 235 monozygotic (MZ) and 300 dizygotic (DZ) twin pairs (59% female) from a longitudinal, population-based study of Finnish twins, FinnTwin12. Parental alcohol misuse was measured at twins’ age 12 assessment with the Malmo-modified Michigan Alcohol Screening Test (MmMAST). At age 35, twins reported their substance use (alcohol, nicotine, and cannabis), physical health (self-rated health; physical fitness; recurrent pain in stomach, head, neck and shoulders, and low back; and sleep quality), and psychological health (life satisfaction and depression). Using a sex-limited biometric twin model, we examined parental alcohol misuse as a moderator of genetic and environmental influences on early midlife substance use, physical and psychological health outcomes.
Results: Parental alcohol misuse was weakly associated with greater early midlife alcohol misuse, nicotine use, cannabis use, low back pain, and depression (r = .06 - .16). Parental alcohol misuse amplified additive genetic influences and attenuated shared environmental influences on early midlife alcohol misuse, with greater genetic variability in females compared to males. In contrast, parental alcohol misuse amplified additive genetic influences on cannabis use in females, and attenuated genetic influences on cannabis use in males. In both males and females, parental alcohol misuse amplified unique environmental influences on cannabis use. Parental alcohol misuse moderated etiological influences on stomach pain with no evidence of sex differences; however, due to lack of power, the source and direction of moderation could not be determined. Parental alcohol misuse did not moderate genetic and environmental influences on other early midlife domains.
Conclusion: We found mixed evidence for gene-environment effects between parental alcohol misuse and genetic influences on early midlife health outcomes. These analyses provide a mechanistic understanding of parental alcohol misuse associations with early midlife substance use and a non-specific indicator of general health (i.e., stomach pain).M.S.Includes bibliographical reference
KO-Booth: parameter-efficient orthogonal fine-tuning of Dreambooth via Kronecker Adapter
No full textText-to-Image Diffusion Models have revolutionized the field of image synthesis, gen- erating highly realistic images from textual prompts. Among these, Dreambooth stands out for its ability to personalize diffusion models by fine-tuning them with a specific reference set, enabling the synthesis of novel renditions of these references in diverse contexts. How- ever, the extensive computational resources required for full-model fine-tuning necessitate more efficient approaches. Existing Parameter-Efficient Fine-Tuning (PEFT) strategies, such as Low-Rank Adaptation (LoRA), have been explored but often fall short regarding stability and generalizability. To address these challenges, we introduce a novel Orthogonal Fine-Tuning (OFT) approach KO-Booth: Parameter-Efficient Orthogonal Fine-Tuning of Dreambooth via Kronecker Adapter, that leverages Kronecker product parameterizations for enhanced efficiency and stability. Our empirical results demonstrate that this method surpasses existing PEFT techniques in terms of generation quality and training stability and maintains high parameter efficiency.M.S.Includes bibliographical reference
To look for a better life: examining the experiences of undocumented Latina/o youth on their higher education and employment aspirations
No full textThere are eleven million undocumented immigrants living in the United States. Approximately two million are young people under the age of twenty-four. Although they came to the United States as children and were essentially raised and educated here, they remain without a pathway to legal permanent citizenship. Relatively little is known about the experiences of undocumented immigrant young people who are growing up and living their daily lives in the United States. They are busy going to school, taking care of their families, and working demanding jobs, while also trying their best to pursue their hopes and dreams. Although they were born in other countries, they are being incorporated into U.S. society as young adults. Institutions, such as the U.S. immigration enforcement regime, present legal challenges for undocumented immigrants, while restrictive economic and social structures affect their participation in the economy and society.
The study fills a gap in the immigration literature by examining the experiences and perspectives of a specific community: young undocumented immigrants and their families from Central America who are currently residing in New York City. The purpose of this study was to understand how higher education and employment aspirations are influenced by various factors, particularly the limitations of illegality, but also class and racism (nativism). Data was collected through in-depth interviews, written assignments, a focus group, and observations with undocumented immigrant Latina/o young people and their families, and analyzed using Undocumented Critical Theory framework and qualitative methods.
The study found that these undocumented immigrant Latina/o young people are extremely motivated to achieve their hopes and dreams; however, they experience challenges due to structural barriers which prevent them from freely participating in all areas of society, which consequently shapes their higher education and employment aspirations. Participation is limited due to their undocumented status, but also because of their socioeconomic background, their race and ethnicity, their family background, their educational experiences, and even their language skills. Nevertheless, the undocumented immigrant young people in this study found creative, alternative ways to assert their sense of belonging. They found ways to negotiate and navigate their situations as they transitioned into adulthood and strove to meet certain rites of passage, such as graduation.
The family played an important role in shaping undocumented immigrant young people’s everyday experiences, as well as their aspirations for the future. In particular, parental sacrificios motivated their children to succeed as a way to take care of their families and honor their parents’ hard work. Parents passed down the importance of hard work, which was highly valued in this community. Despite the presence of structural barriers, the participants in this study had internalized ideas about the American dream and the importance of working hard to achieve success, which in turn shaped their perspectives and decision-making behaviors. Although they did not go to college or university after graduation, they had plans to do so in the future. In the meantime, many wanted to go to language schools after high school. They also wanted to pursue different careers, especially entrepreneurship. They believed this career pathway would enable them to achieve their long-term goals. These alternative pathways provide a space for undocumented immigrants to practice a sense of belonging in this country, given this challenging context of reception. Ultimately, this study argues that undocumented immigrant young people’s experiences of illegality are informed by immigration policies, but also the structural barriers they experience throughout their lives. Ph.D.Includes bibliographical reference
Visualizing magnetic topological materials: magnetism, topological states, and atomic defects
No full textCelebrated by their robustness and preciseness, materials with topological electronicband structures are at the forefront of contemporary condensed matter physics research. On the other hand, magnetic materials have been studied for two hundred years and still is an active field of research. The convolution of topological phases of matter and magnetism engenders unprecedented material properties. In this thesis, we will present the efforts in visualizing magnetic topological materials by scanning tunneling microscopy (STM). First, non-collinear multi-wave-vector (multi-q) antiferromagnetic order in rare-earth monopnictide NdSb was revealed by spin-polarized STM (SP-STM). A hidden spin-rotation transition is observed 2 K below TN where the antiferromagnetic order changes from 1q to 2q. The spin-rotation transition explains the topological surface band splitting, exemplifying the tunability of topological band structure with magnetism. Second, topological edge states were observed on the step edge of the top stanene layer in kag´ome antiferromagnet FeSn. Combined with the first-principle calculation, it indicates the two-dimensional (2D) half-Dirac semimetal phase. This phase can be gapped and transitions into the Chern insulating phase by tuning the magnetization of the material. Lastly, we identified the native atomic defects in antiferromagnetic topological insulator MnBi2Te4 and MnSb2Te4.The magnetic properties can be engineered by tuning the antisite defect densities during crystal growth. These works demonstrate the rich physics on the atomic scale due to the interplay between magnetism and topology. It is hoped that this thesis could inspire and benefit others who wish to see the beauty of atomic-scale physics in topological materials, and who wish to go one step further to tune the magnetism to see the versatility of magnetic topological materials.Ph.D.Includes bibliographical reference