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Latinos and Complicated Grief: An Analysis on the Impacts of a College Campus on Grief and Bereavement
Get PDFGrief and bereavement are under researched topics within Latino populations, and even more so among Latino college students. Much of the existing literature is also focused on quantitative studies that are said to provide higher quality evidence than qualitative studies, with very few being conducted on college campuses. Garcini et al published a systemic review in 2021 on bereavement among widowed Latinos in which most studies were conducted using quantitative methods. Further, only 4 of the 19 studies analyzed were based solely on Latino communities. Falzarano et al. also published a literature synthesis in 2022 which focused on the broader effects of grief and bereavement. They identify only one study targeted at Latino college students which found that they were more likely than White students to experience “increased physiological reactions to loss”. However, they acknowledge the glaring lack of literature and call for further research on 1. The intersection of grief and racial/ethnic identity and 2. The needs of these minority groups in terms of their social, cultural, and familial rituals and how the completion of these rituals impacts bereavement. Complicated grief is defined as long lasting grief that has negative impacts on behavior and mental health. Latino populations are often attributed to being predisposed to experience complicated grief due to culture, yet little research in this ethnic group results in a lack of evidence surrounding this theory. This is a qualitative research study on a small private liberal arts college in the Northeast centered on the Latino student population to gain insight on how the college environment impacts the grieving process. The study provides data on the importance of different types of intrapersonal and interpersonal support systems as well as a correlation between involuntary identity loss and complicated grief
Multi-scale Simulations Reveal the Effects of Entanglement on Polymer Crystallization
No full textSemicrystalline polymers are used in various applications, from commodity plastics to high-performance materials. Their properties are strongly influenced by crystallization behavior. However, the fundamental mechanisms governing polymer crystallization remain incompletely understood, particularly due to the complex kinetic constraints arising from chain connectivity.
This dissertation investigates the role of chain entanglements in polymer crystallization through molecular dynamics (MD) simulations. We examine both nucleation and growth processes in polymer melts. At high supercooling, our findings indicate that nucleation is predominantly a local event, sensitive to factors such as local segmental dynamics, and largely unaffected by long-range topological constraints such as entanglements.
In contrast, during crystal growth, entanglements impose significant kinetic constraints that limit lamellar thickening and contribute to the development of semicrystalline morphology. We quantified the entanglement evolution during polyethylene crystallization and found that crystal growth requires disentanglement at the growth front. However, as crystallization proceeds, increasing numbers of entanglements become trapped near the crystal surface, which impedes further crystal growth.
To overcome the spatial and temporal limitations of MD simulations, we also developed a phase field model tailored for polymer crystallization. The model incorporates key physical features such as lamellar thickness constraints to capture the effects of chain entanglements. Informed by both simulation and experimental parameters, the model successfully reproduces characteristic features in polymer crystallization.
Altogether, this dissertation provides new understanding of how entanglement and local dynamics govern polymer crystallization, and offers a mesoscale model for predicting crystalline morphology in semicrystalline polymer systems
Restrictions on Veto Power: Holding the Permanent Five Accountable in the Face of Intervention and Peacekeeping Operations
Get PDFABSTRACT: This article examines the structural constraints of the United Nations Security Council, with a focus on the veto power of its permanent members and its implications for intervention and peacekeeping. Through a realist lens and grounded in structural analysis, it contends that the recurrent paralysis of the Council in the face of mass atrocities stems from entrenched power asymmetries. The paper advances a bifold proposal: the adoption of the French-Mexican initiative to suspend veto use in cases of mass atrocities, and the entrenchment of the Council’s authority to authorize the use of force under defined conditions. Drawing on case studies such as Iraq and Syria, it demonstrates how institutional mechanisms—rather than normative appeals—are necessary to recalibrate the Council’s capacity to act in a fragmented international order
Understanding firn dynamics: modeling and microstructure from East Antarctica
Get PDFGlacier ice is formed from the accumulation of snow and its compaction through a transitional material called firn. Firn dynamics are fundamentally influenced by climatic factors, such as temperature and snow accumulation rate, and so are crucial for understanding a number of cryospheric applications. For example, ice-sheet mass loss contributions to sea-level rise from repeat satellite-altimetry observations depend on calculating firn density and its evolution. Past atmospheric gases in ice core bubbles are often younger than the surrounding ice, and their exact age depends on how firn closes off interconnected pores to become impermeable. Models often estimate bulk properties, such as density, to predict firn characteristics for these applications; however, recent research efforts indicate that firn microstructure is integral for their construction. My thesis examines and integrates new and emerging modeling and experimental methods to study firn dynamics and microstructure, and specifically centers on two East Antarctic sites of different depositional histories: South Pole and Allan Hills. I used micro-computed tomography to investigate firn microstructure, and uniaxial compression to explore its evolution in a range of temperature and overburden conditions. I integrated these methods to build and explore the relevance of two-phase modeling and pore-network modeling, which are new model frameworks for firn dynamics. My major findings include: the large difference in material properties between air and ice in firn will reduce the effect of air diffusivity on compaction, negating the strengths of two-phase modeling (Chapter 1); uniaxial compression is an analog for natural compaction at South Pole, where we observe the gradual transition of mechanisms for compaction from stage 1 into stage 2 compaction and the increased effect of the evolution of SSA on the evolution of stress with temperature in the range of -10 deg C to -15 deg C (Chapter 2); spatial variability in wind speed, micro- and macro-topography, and their interrelated factors cause distinct microstructural differences at Allan Hills, such as existence of depth hoar, which has implications on permeability and likely the interpretation of stable water isotope ratios (Chapter 3); pore-network modeling is an effective way to simulate firn behavior and estimate bulk properties, such as permeability, that are reflections of microstructure (Chapter 4). These results offer insight into firn’s material response to microstructure, and overall contribute to better understanding its role in the cryosphere
Optical Methods for Time-Resolved Dosimetry and Oximetry of Ultra-High Dose Rate Radiation Therapy
Get PDFRadiotherapy (RT) is a cornerstone method used to treat over 50% of the 2 million new cancer diagnoses each year in the United States. The success of RT directly relies on an optimal balance between maximizing the dose to the tumor while minimizing dose to surrounding normal tissues. Achieving this balance is often challenging due to underlying radiation transport and the presence of anatomical constraints that limit the beam delivery geometry. In turn, minimizing healthy tissue toxicity prevents use of a more aggressive tumor killing approach, and even in curative cases may decrease the patient’s quality of life due to induced physical complications. Minimizing healthy tissue damage is the main topic of radiotherapy research, with current research strategies including novel beam modalities, real time tissue visualization to improve dose conformality, and the use of an adjuvant therapy. Recently, ultra-high dose rate (UHDR) beams were found to induce drastically less toxicity to healthy tissue, termed the FLASH effect. However, the exact underlying mechanisms of FLASH are not currently known, and the preclinical results show large variability of treatment outcomes depending on beam parameters, tissue type, and physiological condition of tissues. Further, the future clinical use of UHDR beams requires a paradigm change in dosimetry and calibration methods to ensure safe patient treatments.
This thesis aims to improve some of the major factors inducing variability of UHDR radiotherapy outcomes, including tissue oxygenation and beam delivery parameters, such as dose and dose rate. The thesis is divided into three parts to accomplish this. First, quantification of tissue oxygen levels and other physiological factors were investigated to address their negative impact on the reproducibility of the FLASH effect, namely the impact of anesthesia used in pre-clinical studies. Second, the long-standing challenge of accurate dosimetry of UHDR beams is addressed via development of a scintillation-based imaging system capable of multi-kilohertz, sub-millimeter beam monitoring. This system is deployed and validated in all UHDR modalities, including proton and electron accelerators. Lastly, the knowledge and technology further developed in Part II is translated into a clinical product in an ongoing clinical trial to facilitate routine use
THE ROLE OF CHOLINERGIC VENTRAL PALLIDUM CELLS IN EFFORTFUL MOTIVATION
No full textMaladaptive reward-seeking behavior can be driven by one of several different components including excessive craving elicited by cues that predict rewards, failing to effortfully pursue rewards when it is beneficial to do so, and compulsively seeking rewards when it is no longer advantageous to do so. This thesis includes experiments focusing on these three different components of reward-seeking behavior to better understand how reward-seeking can become maladaptive. First, we wanted to examine the role that sex plays in the acquisition and compulsiveness of sign-tracking behavior in the Long Evans rat, a strain that is commonly used as the background for transgenic rats. We found that males and females in the Long Evans strain acquire sign-tracking behavior similarly and showed similar sign-tracking levels following outcome devaluation; neither males or females were compulsive. Second, we wanted to chemogenetically inhibit cholinergic ventral pallidum cells across several different Pavlovian and Instrumental tasks to see if they play a role in cue-induced craving or in effortful reward-seeking. We found that these neurons play a role in the motivation to effortfully pursue the reward itself, and, by inhibiting these cells during learning, cues have an impaired ability to acquire their craving-inducing potential. Third, we wanted to disconnect the nucleus accumbens ventral pallidum cholinergic cell pathway to see if it plays a role in cue-induced craving. We encountered some issues with this last experiment, but it seems that this pathway does not play a role in cue-induced craving but could potentially play a role in the motivation to pursue reward. Our findings demonstrate the importance of sex and strain when trying to model human behaviors and disorders while also highlighting a potential cellular target for the treatment of maladaptive reward-seeking specifically within the context of effortful reward-seeking
Reconstructing ER24: An Unlikely Point Mutation Alters the Circadian Clock
No full textThe ER24 mutation in the white collar-2 (wc-2) gene of Neurospora crassa is associated with an extended circadian period, but its causative role and underlying mechanism have remained unclear. ER24 contains a leucine-to-isoleucine substitution in the WC-2 protein, but it is unknown whether this mutation causes the mutant phenotype. We recreated the ER24 mutation in an otherwise wild-type background and observed the same long-period phenotype as in the original strain, confirming that this single substitution is sufficient to alter clock function. Western blot analysis revealed the appearance of a previously unreported, lower molecular weight isoform of WC-2 in ER24 strains, which is absent in wild type.https://digitalcommons.dartmouth.edu/wetterhahn_2025/1011/thumbnail.jp
Reconstructing Neoproterozoic rift basins in Laurentia through sedimentology, stratigraphy and subsidence analyses
No full textThe study of the Neoproterozoic sedimentary record is often challenged by the limited temporal constraints and inherent ambiguity commonly associated with the geological record. An improved understanding of the profound changes in this dynamic period in Earth’s history requires robust treatments of uncertainties as well as detailed and comprehensive approaches to interpreting the sedimentary archive. For my doctoral dissertation, I employ quantitative basin analysis techniques along with integrated sedimentological and stratigraphic analyses to advance our understanding of the two critical Neoproterozoic extensional basins.
For the first chapter of my dissertation, I developed a novel Bayesian age-depth modeling program, SubsidenceChron.jl, designed for extensional sedimentary basins. This program incorporates and propagates uncertainties in various model inputs, notably the lithology-dependent parameters and age constraints, under a Bayesian framework. This statistically robust tool was then applied to the Tonian Akademikerbreen Group in Svalbard, Norway. With the addition of two new radiometric dates, I constructed an age model with appropriate uncertainties for this succession and provided age predictions that confirmed previously hypothesized chemostratigraphic correlations.
My doctoral research then pivots to the Neoproterozoic strata of the southern Great Basin, western Laurentia. For the second chapter, I performed integrated sedimentological and stratigraphic analyses on the less-studied late Ediacaran Reed Dolomite in the White-Inyo Mountains and Esmeralda County region. Specifically, I constrained the platform geometry while proposing a new regional correlation framework. This study also provided the first radiometric age constraint for Precambrian strata in this region (i.e., a maximum depositional age of 542.60 ± 0.30 Ma for the Hines Tongue) and revealed new biostratigraphically-significant fossil occurrences (Cloudinid).
Finally, the updated SubsidenceChron.jl was employed to re-examine the Neoproterozoic to early Paleozoic subsidence history of the southwestern Laurentian margin. The analysis supports protracted and polyphase extension, and predicts an earliest Cambrian timing for transition from active rifting to thermal subsidence, while highlighting the critical role of uncertainty treatment. Overall, my doctoral research bridges gaps in our understanding of key Neoproterozoic basins and provides a foundational quantitative tool for future subsidence analyses
LLM Hallucination Station
No full textThis study aims to investigate hallucination and deception in large language models (LLMs). We research the underlying causes, mechanisms, and consequences of these behaviors. As LLMs become increasingly integrated into our everyday lives it is critical for us to understand these models. That’s why this research aims to enhance the reliability, transparency, and trustworthiness of LLMs. Two methods were implemented to help examine LLMs and when hallucinating and deceiving. Our Llama & Lora models were trained on false information and then told to evaluate true or false statements to see the existing context window of the LLMs. Another method was to train a LLM to lie using the Google Flan model, simply by training it on false information and having it determine which city belonged to which country. Our research leads us to highlight the challenge of defining hallucinations and deception of AI, as there is no standard definition or measurement.https://digitalcommons.dartmouth.edu/wetterhahn_2025/1013/thumbnail.jp