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Description
Eusocial insect colonies have often been imagined as “superorganisms” exhibiting tight homeostasis at the colony level. However, colonies lack the tight spatial and organizational integration that many multicellular, unitary organisms exhibit. Precise regulation requires rapid feedback, which is often not possible when nestmates are distributed across space, making decisions asynchronously. Thus, one should expect poorer regulation in superorganisms than unitary organisms.Here, I investigate aspects of regulation in collective foraging behaviors that involve both slow and rapid feedback processes. In Chapter 2, I examine a tightly coupled system with near-instantaneous signaling: teams of weaver ants cooperating to transport massive prey items back to their nest. I discover that over an extreme range of scenarios—even up vertical surfaces—the efficiency per transporter remains constant. My results suggest that weaver ant colonies are maximizing their total intake rate by regulating the allocation of transporters among loads. This is an exception that “proves the rule;” the ant teams are recapitulating the physical integration of unitary organisms.
Next, I focus on a process with greater informational constraints, with loose temporal and spatial integration. In Chapter 3, I measure the ability of solitarily foraging Ectatomma ruidum colonies to balance their collection of protein and carbohydrates given different nutritional environments. Previous research has found that ant species can precisely collect a near-constant ratio between these two macronutrients, but I discover these studies were using flawed statistical approaches. By developing a quantitative measure of regulatory effect size, I show that colonies of E. ruidum are relatively insensitive to small differences in food source nutritional content, contrary to previously published claims.
In Chapter 4, I design an automated, micro-RFID ant tracking system to investigate how the foraging behavior of individuals integrates into colony-level nutrient collection. I discover that spatial fidelity to food resources, not individual specialization on particular nutrient types, best predicts individual forager behavior. These findings contradict previously published experiments that did not use rigorous quantitative measures of specialization and confounded the effects of task type and resource location.
ContributorsBurchill, Andrew Taylor (Author) / Pavlic, Theodore P (Thesis advisor) / Pratt, Stephen C (Thesis advisor) / Hölldobler, Bert (Committee member) / Cease, Arianne (Committee member) / Berman, Spring (Committee member) / Arizona State University (Publisher)
Created2022
Description
Background: Studies have addressed food insecurity (FI) and fruit and vegetable (FV) consumption; however, not many have looked at the relationship between FI and FV consumption of caregivers with children. Researchers have not extensively evaluated if locale (urban and rural) plays a role in FV consumption. This cross-sectional study investigates the relationship between FI and consumption of FVs in caregivers and whether this relationship varies by locale. Methods: Caregivers with children completed baseline surveys as part of the Nutrition Incentive programs from the Gus Schumacher Nutrition Incentive Program (GusNIP) were included in analyses (n=3455; mean age= 33 ±0.12 years, 53.8% female). Caregivers reported their intake using the Dietary Screener Questionnaire (DSQ). The USDA 6-item food security screening module was used to assess food insecurity. Zip codes and Rural-Urban Continuum Codes (RUCC) were used to identify locale. Mixed linear models adjusted for sociodemographics (age, sex, race, and ethnicity), and clustered at the site level were used to assess the relationship between FV consumption and FI. Locale was examined as an interaction and was found to be not statistically significant, was included as a confounder in the models. Sensitivity analyses were conducted examining all FVs, FVs without potatoes included, FVs without juice included, and FVs without potatoes or juice. Results did not vary greatly, the aggregate FV variable is reported on below.
Results: The mean FV consumption was 4.83 +/- 0.060 servings. The prevalence of FI was 78.7%. FI was reported at 92.9% of urban households and 7.1% of rural households. The mixed linear model indicated that there was a significant relationship between FI and participant’s FV consumption (β=-0.51., 95% CI: -0.81, -0.22). This study found a relationship between FV consumption and locale only.
Conclusion: Caregivers’ FV consumption was significantly related to FI status; however, locale was not associated with their FV consumption. Research should further investigate the relationship between locale and FV consumption with consideration in the adolescent aged population, as these findings may be limited given the relatively small proportion of families living in rural settings.
ContributorsNieforth, Julia (Author) / Bruening, Meg (Thesis advisor) / Fricke, Hollyanne (Committee member) / Parks, Courtney (Committee member) / Ojinnaka, Chinedum (Committee member) / Arizona State University (Publisher)
Created2022
Description
Over the past few years, research into the use of doped diamond in electronics has seen an exponential growth. In the course of finding ways to reduce the contact resistivity, nanocarbon materials have been an interesting focus. In this work, the transfer length method (TLM) was used to investigate Ohmic contact properties using the tri-layer stack Ti/Pt/Au on nitrogen-doped n-type conducting nano-carbon (nanoC) layers grown on (100) diamond substrates. The nanocarbon material was characterized using Secondary Ion Mass Spectrometry (SIMS), Scanning electron Microscopy (SEM) X-ray diffraction (XRD), Raman scattering and Hall effect measurements to probe the materials characteristics. Room temperature electrical measurements were taken, and samples were annealed to observe changes in electrical conductivity. Low specific contact resistivity values of 8 x 10^-5 Ωcm^2 were achieved, which was almost two orders of magnitude lower than previously reported values. The results were attributed to the increased nitrogen incorporation, and the presence of electrically active defects which leads to an increase in conduction in the nanocarbon. Further a study of light phosphorus doped layers using similar methods with Ti/Pt/Au contacts again yielded a low contact resistivity of about 9.88 x 10^-2 Ωcm^2 which is an interesting prospect among lightly doped diamond films for applications in devices such as transistors. In addition, for the first time, hafnium was substituted for Ti in the contact stack (Hf/Pt/Au) and studied on nitrogen doped nanocarbon films, which resulted in low contact resistivity values on the order of 10^-2 Ωcm^2. The implications of the results were discussed, and recommendations for improving the experimental process was outlined. Lastly, a method for the selective area growth of nanocarbon was developed and studied and the results provided an insight into how different characterizations can be used to confirm the presence of the nanocrystalline diamond material, the limitations due to the film thickness was explored and ideas for future work was proposed.
ContributorsAmonoo, Evangeline Abena (Author) / Thornton, Trevor (Thesis advisor) / Alford, Terry L (Thesis advisor) / Anwar, Shahriar (Committee member) / Theodore, David (Committee member) / Arizona State University (Publisher)
Created2023
Description
Scaling of the Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) towards shorter channel lengths, has lead to an increasing importance of quantum effects on the device performance. Until now, a semi-classical model based on Monte Carlo method for instance, has been sufficient to address these issues in silicon, and arrive at a reasonably good fit to experimental mobility data. But as the semiconductor world moves towards 10nm technology, many of the basic assumptions in this method, namely the very fundamental Fermi’s golden rule come into question. The derivation of the Fermi’s golden rule assumes that the scattering is infrequent (therefore the long time limit) and the collision duration time is zero. This thesis overcomes some of the limitations of the above approach by successfully developing a quantum mechanical simulator that can model the low-field inversion layer mobility in silicon MOS capacitors and other inversion layers as well. It solves for the scattering induced collisional broadening of the states by accounting for the various scattering mechanisms present in silicon through the non-equilibrium based near-equilibrium Green’s Functions approach, which shall be referred to as near-equilibrium Green’s Function (nEGF) in this work. It adopts a two-loop approach, where the outer loop solves for the self-consistency between the potential and the subband sheet charge density by solving the Poisson and the Schrödinger equations self-consistently. The inner loop solves for the nEGF (renormalization of the spectrum and the broadening of the states), self-consistently using the self-consistent Born approximation, which is then used to compute the mobility using the Green-Kubo Formalism.
ContributorsJayaram Thulasingam, Gokula Kannan (Author) / Vasileska, Dragica (Thesis advisor) / Ferry, David (Committee member) / Goodnick, Stephen (Committee member) / Allee, David (Committee member) / Arizona State University (Publisher)
Created2017
Description
This paper examines the multifaceted challenges surrounding college students' nutrition, with a specific focus on Arizona State University (ASU). Examining economic shifts, psychological influences, nutrition knowledge, and body image dynamics, it reveals the profound impact on students' food security and eating behaviors. Despite existing initiatives, persistent gaps in resources remain, necessitating comprehensive interventions to support students effectively. In response, "The Ultimate Health Resource for ASU Students," a website, was developed as an innovative solution. This platform aims to empower students by providing a centralized hub to access vital resources, connect with peers, and discover nutritious recipes. Proposed strategies encompass expanding food pantry offerings, developing mobile applications for nutritional guidance, and fostering partnerships with local organizations. By tackling these challenges head-on and fostering a culture of support, ASU can ensure that all students have equitable access to nutritious food options and the necessary resources to thrive academically and personally. The website serves as a place of empowerment, offering practical solutions and fostering a sense of community among ASU students striving for optimal health and well-being.
ContributorsLujan, Lexy (Author) / Buffington, Dillynn (Co-author) / O’Flaherty, Katherine (Thesis director) / Brand, Ashley (Committee member) / Barrett, The Honors College (Contributor) / School of Human Evolution & Social Change (Contributor) / School of Molecular Sciences (Contributor) / College of Health Solutions (Contributor)
Created2024-05
Description
An efficient thermal solver is available in the CMC that allows modeling self-heating in the electrical simulations, which treats phonons as flux and solves the energy balance equation to quantify thermal effects. Using this solver, thermal simulations were performed on GaN-HEMTs in order to test effect of gate architectures on the DC and RF performance of the device. A Π- gate geometry is found to suppress 19.75% more hot electrons corresponding to a DC power of 2.493 W/mm for Vgs = -0.6V (max transconductance) with respect to the initial T-gate. For the DC performance, the output current, Ids is nearly same for each device configuration over the entire bias range. For the RF performance, the current gain was evaluated over a frequency range 20 GHz to 120 GHz in each device for both thermal (including self-heating) and isothermal (without self-heating). The evaluated cutoff frequency is around 7% lower for the thermal case than the isothermal case. The simulated cutoff frequency closely follows the experimental cutoff frequency. The work was extended to the study of ultra-wide bandgap material (Diamond), where isotope effect causes major deterioration in thermal conductivity. In this case, bulk phonons are modeled as semiclassical particles solving the nonlinear Peierls - Boltzmann transport equation with a stochastic approach. Simulations were performed for 0.001% (ultra-pure), 0.1% and 1.07% isotope concentration (13C) of diamond, showing good agreement with the experimental values. Further investigation was performed on the effect of isotope on the dynamics of individual phonon branches, thermal conductivity and the mean free path, to identify the dominant phonon branch. Acoustic phonons are found to be the principal contributors to thermal conductivity across all isotope concentrations with transverse acoustic (TA2) branch is the dominant branch with a contribution of 40% at room temperature and 37% at 500K. Mean free path computations show the lower bound of device dimensions in order to obtain maximum thermal conductivity. At 300K, the lowest mean free path (which is attributed to Longitudinal Optical phonon) reduces from 24nm to 8 nm for isotope concentration of 0.001% and 1.07% respectively. Similarly, the maximum mean free path (which is attributed to Longitudinal Acoustic phonon) reduces from 4 µm to 3.1 µm, respectively, for the same isotope concentrations. Furthermore, PETSc (Portable, Extensible Toolkit for Scientific Computation) developed by Argonne National Lab, was included in the existing Cellular Monte Carlo device simulator as a Poisson solver to further extend the capability of the simulator. The validity of the solver was tested performing 2D and 3D simulations and the results were compared with the well-established multigrid Poisson solver.
ContributorsAcharjee, Joy (Author) / Saraniti, Marco (Thesis advisor) / Goodnick, Stephen (Committee member) / Thornton, Trevor (Committee member) / Wang, Robert (Committee member) / Arizona State University (Publisher)
Created2024
Description
The U.S. Department of Agriculture’s (USDA) National School Lunch Program and School Breakfast Program provide nutritious meals to school-age children. USDA’s Community Eligibility Provision (CEP) is designed to extend the reach of these programs by allowing schools in low-income areas to provide free school meals to all students at no cost to families. CEP has been shown to increase school meal participation, nutritional intake, academic achievement, and attendance in previous research studies. This study aims to examine the impact of long-term CEP participation on student weight outcomes. Nurse-measured height and weight data for school years 2013-14 to 2019-20 were collected from 141 K-12 public schools in four low-income cities. School-level prevalence of obesity was calculated from students’ heights and weights using the Centers for Disease Control and Prevention protocol. CEP participation for each school year was obtained from the state Department of Education. Schools in the sample began participating in CEP at different times yielding varying numbers of years of CEP exposure over the study period. Multivariable analyses examined the relationship between school CEP exposure and the prevalence of obesity, controlling for school-level covariates. Multivariable analyses showed that for every additional year of CEP participation, the school-level prevalence of obesity was 0.4% lower (p=0.018). The regression-adjusted obesity prevalence for schools that never participated in CEP was 28.0%, while the obesity prevalence for schools with 6 years of CEP participation was 25.4%. The lower prevalence of obesity in CEP-participating schools was primarily driven by elementary schools. These results suggest that the benefits of CEP participation can cumulate over time, significantly reducing school-level obesity prevalence over time.
ContributorsDykstra, Tatum Nicole (Author) / Ohri-Vachaspati, Punam (Thesis advisor) / Acciai, Francesco (Committee member) / McCoy, Maureen (Committee member) / Arizona State University (Publisher)
Created2024
Description
Alzheimer's disease (AD) and Alzheimer's Related Dementias (ADRD) is projected to affect 50 million people globally in the coming decades. Clinical research suggests that Mild Cognitive Impairment (MCI), a precursor to dementia, offers a critical window for lifestyle interventions to delay or prevent the progression of AD/ADRD. Previous research indicates that lifestyle changes, including increased physical exercise, reduced caloric intake, and mentally stimulating exercises, can reduce the risk of MCI. Early detection of MCI is challenging due to subtle and often unnoticed cognitive decline, traditionally monitored through infrequent clinical tests. As part of this research, the Smart Driving System was proposed, a novel, unobtrusive, and economical technology to detect early stages of neurodegenerative diseases. This system, leveraging a multi-modal biosensing array (MMS) and AI algorithms, assesses daily driving behavior, offering insights into a driver's cognitive function. The ultimate goal is to develop the Smart Driving Device and App, integrating it into vehicles, and validating its effectiveness in detecting MCI through comprehensive pilot studies. The Smart Driving System represents a breakthrough in AD/ADRD management, promising significant improvements in early detection and offering a scalable, cost-effective solution for monitoring cognitive health in real-world settings.
ContributorsSerhan, Peter (Author) / Forzani, Erica (Thesis advisor) / Wu, Teresa (Committee member) / Hihath, Joshua (Committee member) / Arizona State University (Publisher)
Created2024