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School of Biological Sciences

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School of Chemistry and Biochemistry

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School of Earth and Atmospheric Sciences

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School of Mathematics

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School of Physics

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Understanding bioaerosols atmospheric lifecycle, abundance variability and impacts

(Georgia Institute of Technology, 2019-12-18) Negron, Arnaldo Andres

Bioaerosols are ubiquitous in the atmosphere and may have important impacts on human health, cloud formation, the hydrological cycles and biogeochemical cycles. Measuring and characterizing bioaerosols remains a challenge owing to their low atmospheric concentration. During this thesis, we have developed an approach to collect large amounts of bioaerosols (e.g., on ground-based or airborne platforms) in a liquid suspension over the sub-hour to multiple hour timescale using a modified high-volume wet cyclone. The bioaerosols are then subsequently characterized using flow cytometry and other biology tools, results leading to robust quantifications of bioaerosol populations. Together with the observations from rapid autofluorescence detection techniques, they can provide powerful insights on the concentration, composition, and activity of bioaerosol with rapid time resolution. The new characterization approach was applied to study bioaerosol populations in multiple, distinct environments: i) an urban environment in the Southeast United States surrounded by heavy forestation (Atlanta, GA), ii) the marine boundary layer, free troposphere, terrestrial environments near California during the BOAS 2015 aircraft campaign, and, iii) the remote Eastern Mediterranean sea influenced by the European continental outflow and Saharan dust events. In the Southeast United States, we observed that the bioaerosol population is highly dynamic and driven by the prevailing meteorology. We detect high concentrations of large bioaerosol population rich in nucleic acid (consistent with wet-ejected fungal spores) during humid and warm days after rain events, while other days are characterized by smaller bioaerosol (consistent with bacteria) that are low in nucleic acid content. During the airborne deployment at the California Coast, small bacterialike particles that are low in nucleic acid content are ubiquitous and tend to be enhanced in the marine free troposphere compared to the boundary layer thought to be the source. Concentrations of microbes in the marine boundary layer are about 10 times less than those found in the airmasses characterized by terrestrial emissions, while the cell types from flow cytometry and light induced fluorescence indicate very different populations. In the Eastern Mediterranean, bioaerosol is dominated by small bioaerosol with low nucleic acid content (consistent with bacterial cells). Interestingly, the highest concentration is not observed during periods where continental outflow airmasses are sampled, but during dust events. The observations carried out during this thesis show that bioaerosol associated with air masses influenced by terrestrial (and especially dust) emissions carry the largest bioaerosol concentrations. We also see that smaller bioaerosol consistent with microbes (with a diameter ~ 1 μm and low nucleic content) are ubiquitous at concentrations ranging between 104 m-3 and 105 m-3. Microbes in the marine boundary layer off the coast of California are about 10 times lower than that observed in terrestrial environments (103 m-3 to 104 m-3), although in the Eastern Mediterranean, bioaerosol concentrations can be as high as in terrestrial environments. Occasionally, we observe concentrations of larger nucleic acid-rich particles (consistent with fungal spores), especially after rain events. The extent to which the fungal spores travel is surprisingly large – given that they are observed at the remote Eastern Mediterranean, hundreds (and maybe thousands) of kilometers away from their terrestrial origin. The impacts of these concentrations and types of bioaerosol in all the environments sampled can be significant. We estimate for example that the phosphorous delivery from bioaerosol to the Eastern Mediterranean Sea, although much lower than recent model estimates, can still explain the concentrations that are associated with background levels of atmospheric phosphorus. In terms of their impacts on clouds, the concentration of marine bioaerosol is high enough to potentially influence ice nucleation in warm mixed-phase cloud, especially given that secondary ice processes are favored and can promote any initial low levels of primary ice. The above mentioned potential impacts of bioaerosol, however, may be modulated by atmospheric processing – very few studies of which exist. Towards this, we studied the response of microbes to simulated atmospheric acidification (a process that occurs everywhere in the atmosphere) by quantifying their cultivability and ability to express ice nucleation capacity as a function of pH levels observed for micron-sized particles in the atmosphere. For this, a droplet freezing assay was developed and used to study the effect of aerosol pH on an ice active P. syringae strain. Surprisingly, the microbes could resist considerable levels of acidification, as they retain their cultivability and ice nucleation capability to pH levels as low as 4. Upon increased acidification, however, (e.g., pH=2.5 or less), the ice active P. syringae lost cultivability and reduced their ice nucleation temperature close to -15oC, approaching the properties of Arizona test dust. Repeated freezing-thawing cycles over the same strains exhibit repeatable ice nucleation results. These results show that models of ice nucleation that consider the effects of bioaerosol need to consider the impacts of atmospheric acidification; the smooth dependence of ice nucleating characteristics (freezing temperature vs. pH) suggests that such effects can be parameterized using the approach developed during this thesis. The methods and scientific results produced during this thesis show that the simple yet powerful methods developed here can be readily used to sample bioaerosol, characterize their population characteristics, metabolic state, ice nucleation activity, and response to a variety of atmospheric stressors.
Fourier Analysis in Geometric Tomography - Part 3

(Georgia Institute of Technology, 2019-12-13) Koldobsky, Alexander

Geometric tomography is the study of geometric properties of solids based on data about sections and projections of these solids. The lectures will include: 1. An outline of proofs of two of the main features of the Fourier approach to geometric tomography - the relation between the derivatives of the parallel section function of a body and the Fourier transform (in the sense of distributions) of powers of the norm generated by this body, and the Fourier characterization of intersection bodies. 2. The Busemann-Petty problem asks whether symmetric convex bodies with uniformly smaller areas of central hyperplane sections necessarily have smaller volume. We will prove an isomorphic version of the problem with a constant depending on the distance from the class of intersection bodies. This will include a generalization to arbitrary measures in place of volume. 3. The slicing problem of Bourgain asks whether every symmetric convex body of volume one has a hyperplane section with area greater than an absolute constant. We will consider a version of this problem for arbitrary measures in place of volume. We will show that the answer is affirmative for many classes of bodies, but in general the constant must be of the order 1/√n. 4. Optimal estimates for the maximal distance from a convex body to the classes of intersection bodies and the unit balls of subspaces of Lp. 5. We will use the Fourier approach to prove that the only polynomially integrable convex bodies, i.e. bodies whose parallel section function in every direction is a polynomial of the distance from the origin, are ellipsoids in odd dimensions.
Floating Bodies and Approximation - Part 3

(Georgia Institute of Technology, 2019-12-12) Werner, Elisabeth

Two important closely related notions in affine convex geometry are the floating body and the affine surface area of a convex body. The floating body of a convex body is obtained by cutting off caps of volume less or equal to a fixed positive constant. Taking the right-derivative of the volume of the floating body gives rise to an affine invariant, the affine surface area. This was established for all convex bodies in all dimensions by Schuett and Werner. There is a natural inequality associated with affine surface area, the affine isoperimetric inequality, which states that among all convex bodies, with fixed volume, affine surface area is maximized for ellipsoids. Due to its important properties, which make them effective and powerful tools, affine surface area and floating body are omnipresent in geometry and have applications in many other areas of mathematics, e.g., in problems of approximation of convex bodies by polytopes and for the notion of halfspace depth for multivariate data from statistics.
Fourier Analysis in Geometric Tomography - Part 2

(Georgia Institute of Technology, 2019-12-11) Koldobsky, Alexander

Geometric tomography is the study of geometric properties of solids based on data about sections and projections of these solids. The lectures will include: 1. An outline of proofs of two of the main features of the Fourier approach to geometric tomography - the relation between the derivatives of the parallel section function of a body and the Fourier transform (in the sense of distributions) of powers of the norm generated by this body, and the Fourier characterization of intersection bodies. 2. The Busemann-Petty problem asks whether symmetric convex bodies with uniformly smaller areas of central hyperplane sections necessarily have smaller volume. We will prove an isomorphic version of the problem with a constant depending on the distance from the class of intersection bodies. This will include a generalization to arbitrary measures in place of volume. 3. The slicing problem of Bourgain asks whether every symmetric convex body of volume one has a hyperplane section with area greater than an absolute constant. We will consider a version of this problem for arbitrary measures in place of volume. We will show that the answer is affirmative for many classes of bodies, but in general the constant must be of the order 1/√n. 4. Optimal estimates for the maximal distance from a convex body to the classes of intersection bodies and the unit balls of subspaces of Lp. 5. We will use the Fourier approach to prove that the only polynomially integrable convex bodies, i.e. bodies whose parallel section function in every direction is a polynomial of the distance from the origin, are ellipsoids in odd dimensions.
Signatures of the El Nino-southern oscillation on rainfall and cave dripwater oxygen isotopes in N. Borneo

(Georgia Institute of Technology, 2019-12-11) Ellis, Shelby Ann

Oxygen isotope (δ18O) records of speleothem carbonates are a critical terrestrial paleoclimate archive, providing insight into past hydroclimate variations and past changes in atmospheric circulation. Specifically, time series of rainfall and cave dripwater oxygen isotopes (δ18O) provide site-specific assessments of climate or non-climate related signals recorded in stalagmite δ18O used for such reconstructions. However, modern paired multi-year δ18O time series of rainwater and dripwater are limited in the tropical latitudes, an area known to contain regionally-specific atmospheric complexities acting on rainfall δ18O. Furthermore, karst drainage pathways vary significantly within the same cave system, altering the original climate-driven δ18O rainfall signal. In this thesis, I present an extended multi-year study of rainfall and cave dripwater δ18O time series from Gunung Mulu National Park in Northern Borneo to quantify the cloud-to-cave transformation process spatially and temporally across the Mulu karst, building on work previously presented by Moerman et al., 2013 and Moerman et al., 2014. Chapter 1 will broadly cover topics related to how stable water isotopes in rainfall, cave dripwaters, and stalagmites can detect ENSO-driven shifts in the hydrological cycle, building off almost a decade’s worth of modern (Cobb et al., 2007; Moerman et al., 2013; 2014; Partin et al., 2013a) and paleoclimate (Carolin et al., 2013; 2016; Chen et al., 2016; Meckler et al., 2012; Partin et al., 2007; 2013a) observations from a well-established research site in Northern Borneo, Sarawak, Malaysia. Chapter 2 quantifies the rainfall-to-cave dripwater transformation of isotopic climate-signals in the Mulu karst from continuous observations over the last ~12 years. These time series are the longest-running daily rainfall δ18O time series (2006 – 2018) and longest tropical biweekly dripwater δ18O time series (2007 – 2018) globally. Vadose zone mixing translates ENSO-related variations in rainfall δ18O to three monitored cave dripwater δ18O sites. Using two simple modeling techniques, we generated an ensemble of different modeled dripwater time series directly corresponding to local rainfall δ18O, estimating Mulu water takes ~3 to 18 months to transit through the karst. This transit time provides context for what resolution of climate signals can be potentially recorded in local stalagmites employed for hydroclimate reconstructions. Overall, this thesis supports previous interpretations of using the amount effect framework for Mulu stalagmite δ18O records through the multi-year, paired local rainfall and dripwater δ18O time series. This research clearly demonstrates paired rainfall and cave δ18O observations can support more minute interpretations of highly-resolved paleo-ENSO stalagmite records.
Floating Bodies and Approximation - Part 2

(Georgia Institute of Technology, 2019-12-11) Werner, Elisabeth

Two important closely related notions in affine convex geometry are the floating body and the affine surface area of a convex body. The floating body of a convex body is obtained by cutting off caps of volume less or equal to a fixed positive constant. Taking the right-derivative of the volume of the floating body gives rise to an affine invariant, the affine surface area. This was established for all convex bodies in all dimensions by Schuett and Werner. There is a natural inequality associated with affine surface area, the affine isoperimetric inequality, which states that among all convex bodies, with fixed volume, affine surface area is maximized for ellipsoids. Due to its important properties, which make them effective and powerful tools, affine surface area and floating body are omnipresent in geometry and have applications in many other areas of mathematics, e.g., in problems of approximation of convex bodies by polytopes and for the notion of halfspace depth for multivariate data from statistics.
Concentration and Convexity - Part 1

(Georgia Institute of Technology, 2019-12-10) Paouris, Grigoris

The Concentration of measure phenomenon is a fundamental tool of high dimensional probability and of Asymptotic Geometric Analysis. Independence or Isoperimetry are two typical reasons for the appearance of this phenomenon. In these talks I will introduce the phenomenon and I will show how High dimensional Geometry affects the concentration. In particular I will explain how "convexity" can be used to establish strong concentration inequalities in the Gauss space and how the "convexity" of the underline measure is responsible for deviation principles.
Floating Bodies and Approximation - Part 1

(Georgia Institute of Technology, 2019-12-09) Werner, Elisabeth

Two important closely related notions in affine convex geometry are the floating body and the affine surface area of a convex body. The floating body of a convex body is obtained by cutting off caps of volume less or equal to a fixed positive constant. Taking the right-derivative of the volume of the floating body gives rise to an affine invariant, the affine surface area. This was established for all convex bodies in all dimensions by Schuett and Werner. There is a natural inequality associated with affine surface area, the affine isoperimetric inequality, which states that among all convex bodies, with fixed volume, affine surface area is maximized for ellipsoids. Due to its important properties, which make them effective and powerful tools, affine surface area and floating body are omnipresent in geometry and have applications in many other areas of mathematics, e.g., in problems of approximation of convex bodies by polytopes and for the notion of halfspace depth for multivariate data from statistics.
Fourier Analysis in Geometric Tomography - Part 1

(Georgia Institute of Technology, 2019-12-09) Koldobsky, Alexander

Geometric tomography is the study of geometric properties of solids based on data about sections and projections of these solids. The lectures will include: 1. An outline of proofs of two of the main features of the Fourier approach to geometric tomography - the relation between the derivatives of the parallel section function of a body and the Fourier transform (in the sense of distributions) of powers of the norm generated by this body, and the Fourier characterization of intersection bodies. 2. The Busemann-Petty problem asks whether symmetric convex bodies with uniformly smaller areas of central hyperplane sections necessarily have smaller volume. We will prove an isomorphic version of the problem with a constant depending on the distance from the class of intersection bodies. This will include a generalization to arbitrary measures in place of volume. 3. The slicing problem of Bourgain asks whether every symmetric convex body of volume one has a hyperplane section with area greater than an absolute constant. We will consider a version of this problem for arbitrary measures in place of volume. We will show that the answer is affirmative for many classes of bodies, but in general the constant must be of the order 1/√n. 4. Optimal estimates for the maximal distance from a convex body to the classes of intersection bodies and the unit balls of subspaces of Lp. 5. We will use the Fourier approach to prove that the only polynomially integrable convex bodies, i.e. bodies whose parallel section function in every direction is a polynomial of the distance from the origin, are ellipsoids in odd dimensions.
Surface Modification of Hard PVC by Molecules with Antibacterial Activity

(Georgia Institute of Technology, 2019-12-09) Pigliautile, Lucrezia

In this work, we present an analysis of different PVC surface modifications, attempted with the intention of attaching antibacterial small molecules, polymers, and oligomers on the plastic. These modifications allowed us to obtain intrinsically antibacterial PVC, which can be potentially applied in healthcare and medical devices. The modification was performed with two procedures, copper-catalyzed azide-alkyne cycloaddition, and nucleophilic substitution. In the first case, the surface of PVC was initially treated with sodium azide to obtain partially azidated PVC, followed by treatment with alkyne-bearing small molecules and polymers. In the second method, the surface was treated with amine-bearing small molecules and polymers, directly substituting the chlorine atoms on PVC. We concluded that the hydrophilicity, the size of the molecule, and the reaction conditions, are the main factors that influence the success of these modifications. Bacteria viability tests were performed on differently-substituted PVC samples, showing good antibacterial activities for PVC surfaces treated with quaternary ammonium salts and acceptable activities for samples modified with polyethyleneimine and oligoethylene glycol.