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Enhancing photosynthesis under salt stress via directed evolution in cyanobacteria
Get PDFA key aspect of enhancing photosynthesis is improving the kinetics of photochemical quenching recovery following environmental perturbation or stress. Salt stress exacerbates high light stress in cyanobacteria and leads to severe yield losses in crop plants. Genetic traits that confer salt tolerance without compromising photosynthetic performance are essential for improving photosynthesis under these conditions. Here, we applied accelerated evolution in Synechococcus elongatus PCC 7942 by conditionally suppressing its methyl-directed mismatch repair system to obtain beneficial genetic traits for enhanced photosynthesis under salt stress. We screened over 10,000 mutants and isolated 8 strains with increased biomass or sucrose productivity under salt stress. Genome sequencing revealed an average of 8 to 20 single nucleotide polymorphisms or indels per genome. Notably, mutations in the photosystem II (PSII) reaction center D1-encoding gene, resulting in the amino acid changes L353F, I358N, and H359N at the carboxyl terminus of the precursor-D1 (pD1) protein, improved photosynthesis under salt and combined salt and light stress by potentially accelerating D1 maturation during PSII repair. Phylogenetic analysis of pD1 across cyanobacteria and red algae highlights the broad relevance of these adaptive genetic traits, underscoring the importance of leveraging evolutionary insights to improve photosynthesis under stress or fluctuating environments
Classical Nucleation Theory and Tolman Equation in Cluster Thermodynamics: How Small Can They Truly Apply?
No full textClassical nucleation theory and the Tolman equation are two fundamental theories in cluster thermodynamics. Despite their long-standing existence, the applicability of these theories remains questionable. Direct experimental validation is challenging due to the small size of the clusters involved. While theoretical approaches are often used as alternatives, the findings are frequently controversial. In this work, free energy calculations were performed across an unprecedentedly large size range using sophisticated techniques, including aggregation-volume-bias Monte Carlo, for two systems: Lennard-Jones and TIP4P/2005 water. The availability of bulk-phase properties for an infinitely large system (i.e., γ∞) facilitates a direct comparison to these two theories. The simulation results provide strong support for the applicability of these theories to large clusters, down to those containing a few hundred particles. However, these theories break down for small clusters
Orbifolds and minimal modular extensions
Get PDFLet V be a simple vertex operator algebra and G a finite automorphism group of V such that VG is regular, and the conformal weight of any irreducible g-twisted V-module N for g∈G is nonnegative and is zero if and only if N=V. It is established that if V is holomorphic, then the VG-module category CVG is a minimal modular extension of E=Rep(G), and is equivalent to the Drinfeld center Z(VecGα) as modular tensor categories for some α∈H3(G,S1) with a canonical embedding of E. Moreover, the collection Mv(E) of equivalence classes of the minimal modular extensions CVG of E for holomorphic vertex operator algebras V with a G-action forms a group, which is isomorphic to a subgroup of H3(G,S1). Furthermore, any pointed modular category Z(VecGα) is equivalent to CVLG for some positive definite even unimodular lattice L. In general, for any rational vertex operator algebra U with a G-action, CUG is a minimal modular extension of the braided fusion subcategory F generated by the UG-submodules of U-modules. Furthermore, the group Mv(E) acts freely on the set of equivalence classes Mv(F) of the minimal modular extensions CWG of F for any rational vertex operator algebra W with a G-action
Anxiety\u27s Impact on Autism Spectrum Disorder Symtomology: An Investigation into the Relationship Between two Comorbities
Get PDFAutism spectrum disorder (ASD) has been found to be frequently comorbid with many medical and psychological disorders, one of which is anxiety disorders. Research has shown that, when anxiety is present within ASD, various areas of the child’s functioning may be impacted, such as ASD symptom severity, emotional regulation skills, adaptability, social skills and daily living skills. The current study aimed to investigate this relationship of anxiety and ASD. First, within a sample of children and adolescents with ASD, the magnitude of the correlation between specific ASD symptoms parent-reported anxiety was compared to determine if certain ASD symptoms were more highly correlated with anxiety than others. Then, participants with ASD with and without elevated anxiety were compared with each other and with those who had a diagnosis other than ASD and no diagnosis on overall symptom severity, severity of emotional outbursts, and fours areas of daily functioning; adaptability, functional communication, social skills and activities of daily living. It was hypothesized that anxiety would be more highly correlated with the ASD symptoms of social initiation and motivation as well as repetitive motor movements, sensory oversensitivity and resistance to change, and those with ASD and anxiety would display more severe ASD symptoms, more overall symptom severity, more emotional outbursts and significantly lower functioning scores, when compared to other diagnostic groups. In general, the results did not support most of these hypotheses because parent-reported ASD symptoms were negatively related to parent-reported anxiety, and this was consistent across most ASD symptoms. This finding suggests that diagnostic overshadowing may be occurring, for prior research has shown that parents may have difficulty distinguishing between anxiety and ASD symptoms. Also, it was found that those with ASD and anxiety did not differ from those with ASD alone on most indices of severity, with the exception of showing significantly lower scores in adaptability. This finding suggests that parents view the ASD symptom of “insistence of sameness” as being highly related to anxiety. Limitations and future directions are then discussed
Quantitative Boundary Doubling Estimates for Elliptic Equations
Get PDFWe present an approach for obtaining quantitative boundary doubling inequalities for elliptic equations with Neumann boundary conditions. Carleman estimates are used to prove three-ball inequalities, which are then used to prove quantitative doubling inequalities, with bootstrapping from the interior to the boundary. This approach is illustrated by its application to the Laplace eigenvalue problem with homogeneous Neumann boundary conditions, where sharp doubling inequalities are recovered.
When then consider a equation with non homogeneous Neumann boundary conditions. By following the approach, we are able to obtain potentially sharp results. Finally, we are able to get an improvement on previously obtained results for the interior doubling inequality of sums of Laplace eigenfunctions
Predictive Indicators for Graduation upon Acceptance into a NAACLS-Approved Medical Laboratory Science Program
Get PDFThe primary purpose of this study was to determine the influence of selected academic and personal demographic characteristics on student success at a NAACLS-accredited medical laboratory science program in the southern portion of the United States.
Both academic and demographic categories were selected on students who entered the medical laboratory science program from 2014 to 2019 (pre-COVID). The sanitized, archived data set was provided by the MLS department and the registrar and student affairs office at the participating school. The extant data set contained academic and demographic variables, collected over a five-year period, of initially over 170 accepted MLS students.
The target population was students enrolled in a medical laboratory science program in the southern portion of the Unites States. The sample, both accessible and drawn, were students enrolled in one cohort at a medical laboratory science program in the south.
The primary statistical method used for this study was a multiple discriminant analysis model. The results of this study suggested three statistically significant variables that could offer insight into a student’s performance while enrolled in a MLS program.
The majority of the medical laboratory science students were white, female, not married, a United States citizen, and not of New Orleans origin. The majority also reported attending more than one college or university and not having a previous degree awarded. A total of three significant independent variables: Hispanic, math score, and age at application, entered into a significant discriminate model. The research results indicated that these three significant independent variables: Hispanic, math score, and age at application were the most influential factors associated with degree completion.
The researcher recommends that additional studies be performed, focusing primarily on students that did not graduate. The researcher also recommends replicating the study at other medical laboratory science schools across the United States. The researcher also recommends researching a dataset that is specific to the COVID pandemic. The possible demographic, academic, and non-cognitive combinations of variables could open doors for many other additional research projects
THE EMPIRICS OF HOUSEHOLD CONSUMPTION SPENDING: EVIDENCE FROM INDIA
No full textThis dissertation examines household consumption behavior in India, highlighting the roles of income shocks, expectations, and cultural norms.
Chapter 1 investigates heterogeneity in the marginal propensity to consume (MPC) using semi-structural methods applied to rich household panel data. I find a monthly MPC of 0.27 following a transitory income shock, with significant variation across groups: from 0.23 in urban households to 0.57 in rural households, and from 0.14 in high-income households to 0.41 in low-income households. Rainfall shocks, used as exogenous variation in income, yield similar estimates, reinforcing the results. These findings have important implications for designing effective monetary and fiscal policies in emerging economies.
Chapter 2 explores how expectations and forecast errors shape consumption. Using granular microdata, we show that Indian households are generally optimistic about the future, particularly in urban and higher-income groups, but can also be ``under-optimistic” when actual outcomes are better than expected. Forecast errors have an independent effect on consumption beyond realized income changes, underscoring the importance of beliefs in household decision-making.
Chapter 3 analyzes the impact of revealed son preference on spending patterns. Leveraging nationally representative panel data from 2014 to 2019, I identify households that continue childbearing after a firstborn daughter until having a son. These households spend about 31\% more on education and modestly more on other consumption categories, while health spending shows no significant difference. The associations remain robust to controls for parental incomes and mother\u27s state of origin. Subsample and heterogeneity analyses confirm the widespread influence of son preference on resource allocation, especially toward educational investment.
Together, these chapters provide new evidence on how transitory shocks, expectations, and cultural preferences interact to drive household consumption choices. The results contribute to a deeper understanding of consumption dynamics in developing economies and offer insights for policies that promote welfare, resilience, and human capital development
THE SEARCH FOR MAGNETAR GIANT FLARES IN ARCHIVAL GAMMA-RAY BURST DATA TO CONSTRAIN THEIR RATES AND ENERGETICS
No full textMagnetar giant flares are rare, extremely bright bursts of gamma-rays from highly magnetized neutron stars. These events are difficult to identify because, at extragalactic distances, they can appear similar to other astrophysical phenomena. Only a handful have been confidently identified to date, limiting our understanding of their origin and physical properties. This dissertation focuses on expanding the sample of known events and enabling a more detailed characterization of their observational features. We report on two newly identified examples, GRB 180128A and GRB 231115A, that are consistent with a magnetar origin based on their spectral properties and association with nearby star-forming galaxies.
We introduce significant improvements in the methods applied to identify and characterize these events. Applying this to archival data helped us increase the known sample of seven by almost a factor of two. This demonstrates that the method is effective and that additional magnetar giant flares likely remain unidentified in existing gamma-ray burst catalogs. We utilize this expanded sample to gain a deeper understanding of the broader population of magnetar giant flares. We develop a statistical modeling framework that combines older data with modern observations from the Gamma-ray Burst Monitor on the Fermi Gamma-ray Space Telescope. The model accounts for instrumental sensitivity and the expected diversity in event characteristics. By simulating detectability across instruments, we estimate the frequency of these events and the variation in their observable features, yielding the most robust and well-constrained population estimates to date. The results suggest that individual magnetars must produce multiple flares throughout their lifetimes, reinforcing the idea that these are recurring phenomena rather than singular explosive events. Expanding the sample of known magnetar giant flares will improve our understanding of magnetars and their role in other astrophysical phenomena, including possible links to fast radio bursts, gravitational waves, and the creation of heavy elements in extreme astrophysical environments
Stream Fish Ecology at the Macroscale: Abundance, Base Flow, and Connectivity
No full textIn this work I investigate several facets of stream fish ecology at large spatial scales. In this dissertation, I use a dataset of over a million stream fish observations across the continental United States to explore patterns of abundance for broadly distributed stream fish, how regional base flow influences local scale flow-ecology relationships, and how connectivity influences stream fish diversity in coastal river drainages. I test the abundant-center hypothesis (ACH), which posits that species are most abundant at the center of their range, and abundance monotonically declines from the center to edge of the range, and propose an alternative macroscale pattern of abundance, multi-core distributions, that apply to dispersal limited taxa such as stream fish. I then test if range and body size are related to the number of abundant cores, a geographic area of elevated abundance. I investigate if regional base flow modulates local flow-ecology relationships through cross-scale interactions. Base flow is an important, but understudied, part of flow regimes regarding stream fish diversity. Last, I use a measure of network connectivity to test if streams with greater degrees of connectivity are positively associated with taxonomic diversity, functional diversity, and functional redundancy. Connectivity is inherently important to stream fish life histories, but evidence potentially linking river network structure to patterns of diversity is sparse. The results of the ACH test suggested very little support for the ACH. Of studied species, 43 species exhibited multi-core distributions and 21 exhibited single-core distributions. Furthermore, range size was positively correlated to the number of abundant cores in species ranges. I built Bayesian hierarchical models that revealed regional base flow variability at the ecoregion-III scale had a positive effect on local flow-ecology relationships. Greater variability of base flow in an ecoregion indicates a greater variety in flow regimes that select for different stream fish communities yielding greater taxonomic and functional diversity. The regional effect of base flow highlights how regional scale processes can influence local scale relationships through cross-scale interactions. Last, I demonstrate that greater degrees of connectivity are positively associated with function diversity and redundancy in certain hydrologic stream classes