Publications by authors named "Tammie Nelson"

Background: Though social determinants are the primary drivers of health, few studies of people living with HIV focus on non-clinical correlates of insecure and/or fragmented connections with the care system. Our team uses linked clinical and multisector non-clinical data to study how residential mobility and connection to social services influence the HIV care continuum. We engage a diverse group of individuals living with HIV and other invested community members to guide and inform this research.

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Background: Though social determinants are the primary drivers of health, few studies of people living with HIV (PLWH) focus on non-clinical correlates of insecure and/or fragmented connections with the care system. Our team has used linked clinical and multisector non-clinical data to study how residential mobility and connection to social services influence the HIV care continuum. We engage a diverse group of invested patients and community members to guide and inform this research.

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To develop robust prediction models for infant obesity risk, we need data spanning multiple levels of influence, including child clinical health outcomes (eg, height and weight), information about maternal pregnancy history, detailed sociodemographic information of parents and community-level factors. Few data sources contain all of this information. This manuscript describes the creation of the Obesity Prevention in Early Life (OPEL) database, a longitudinal, population-based database that links clinical data with birth certificates and geocoded area-level indicators for 19 437 children born in Marion County, Indiana between 2004 and 2019.

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Objective: Justice involvement and psychiatric comorbidities contribute to excess HIV morbidity, yet their interaction is poorly understood. We examined associations of this overlap with HIV outcomes among people living with HIV (PLWH).

Methods: We conducted a retrospective cohort study of PLWH aged 13 years and older residing in Marion County (Indianapolis), IN, during 2018 (n = 5730) using linked HIV surveillance, arrest, and clinical data.

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Article Synopsis
  • The study investigates how common explosives react to ionizing radiation, focusing on their chemical changes when exposed to γ-irradiation.
  • It involved modifying dodecane with various energetic functional groups (azide, nitro, nitrate ester, and nitramine) and analyzing the resulting degradation using advanced techniques like NMR and gas chromatography.
  • Findings indicate that radiation primarily damages the energetic functional groups, especially at their weakest bonds, with a susceptibility ranking from most to least affected: D-ONO, D-N, D-NHNO, and D-NO.
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The photolytic stability of explosives and energetic functional groups is of importance for those who regularly handle or are exposed to explosives in typical environmental conditions. This study models the photolytic degradation of dodecane substituted with various energetic functional groups: azide, nitro, nitrate ester, and nitramine. For the studied molecules, it was found that excitons localize on the energetic functional group, no matter where they were initially formed, and thus, the predominant degradation pathway involves the degradation of the energetic functional group.

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We examine the redistribution of energy between electronic and vibrational degrees of freedom that takes place between a π-conjugated oligomer, a phenylene-butadiynylene, and two identical boron-dipyrromethene (bodipy) end-caps using femtosecond transient absorption spectroscopy, single-molecule spectroscopy, and nonadiabatic excited-state molecular dynamics (NEXMD) modeling techniques. The molecular structure represents an excitonic seesaw in that the excitation energy on the oligomer backbone can migrate to either one end-cap or the other, but not to both. The NEXMD simulations closely reproduce the characteristic time scale for redistribution of electronic and vibrational energy of 2.

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Direct atomistic simulation of nonadiabatic molecular dynamics is a challenging goal that allows important insights into fundamental physical phenomena. A variety of frameworks, ranging from fully quantum treatment of nuclei to semiclassical and mixed quantum-classical approaches, were developed. These algorithms are then coupled to specific electronic structure techniques.

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Simulation of electronic dynamics in realistically large molecular systems is a demanding task that has not yet achieved the same level of quantitative prediction already realized for its static counterpart. This is particularly true for processes occurring beyond the Born-Oppenheimer regime. Non-adiabatic molecular dynamics (NAMD) simulations suffer from two convoluted sources of error: numerical algorithms for dynamics and electronic structure calculations.

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Objectives: This study aimed to examine the mediators and moderators of area-level prostitution arrests and sexually transmitted infections (STIs) using population-level data.

Methods: Using justice and public health STI/HIV data in Marion County (Indianapolis), Indiana, during an 18-year period, we assessed the overall association of area-level prostitution and drug-related arrests and STI/HIV, and mediators and moderators of the relationship. Point-level arrests were geocoded and aggregated by a census block group.

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Three-dimensional cage-shaped molecules formed from chainlike structures hold potential as unique optoelectronic materials and host compounds. Their optical, structural, and dynamical features are tunable by changes in shape and size. We perform a comparison of these properties for three sizes of strained conjugated [.

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We present a versatile new code released for open community use, the nonadiabatic excited state molecular dynamics (NEXMD) package. This software aims to simulate nonadiabatic excited state molecular dynamics using several semiempirical Hamiltonian models. To model such dynamics of a molecular system, the NEXMD uses the fewest-switches surface hopping algorithm, where the probability of transition from one state to another depends on the strength of the derivative nonadiabatic coupling.

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Nonadiabatic Molecular Dynamics (NAMD) of excited states has been widely used in the simulation of photoinduced phenomena. However, the inability to treat bond breaking and forming processes with single-reference electronic structure methods limits their application in photochemistry for extended molecular systems. In this work, the extension of excited-state NAMD for open-shell systems is developed and implemented in the NEXMD software.

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Spin crossover complexes are known to undergo bond length, volume, and enthalpy changes during spin transition. In an explosive spin crossover complex, these changes could affect the mechanical and initiation sensitivity of the explosive and lead to the development of a new class of sensitivity switchable materials. To explore this relationship, the well-known spin crossover compound [Fe(Htrz)][ClO] () was re-evaluated for its explosive properties, and its mechanical impact sensitivity was correlated to spin transition.

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Optically active molecular materials, such as organic conjugated polymers and biological systems, are characterized by strong coupling between electronic and vibrational degrees of freedom. Typically, simulations must go beyond the Born-Oppenheimer approximation to account for non-adiabatic coupling between excited states. Indeed, non-adiabatic dynamics is commonly associated with exciton dynamics and photophysics involving charge and energy transfer, as well as exciton dissociation and charge recombination.

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When the interaction between a molecular system and confined light modes in an optical or plasmonic cavity is strong enough to overcome the dissipative process, hybrid light-matter states (polaritons) become the fundamental excitations in the system. The mixing between the light and matter characters modifies the photophysical and photochemical properties. Notably, it was reported that these polaritons can be employed to control photochemical reactions, charge and energy transfer, and other processes.

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We explore the diverse origins of unpolarized absorption and emission of molecular polygons consisting of π-conjugated oligomer chains held in a bent geometry by strain controlled at the vertex units. For this purpose, we make use of atomistic nonadiabatic excited-state molecular dynamics simulations of a bichromophore molecular polygon (digon) with bent chromophore chains. Both structural and photoexcited dynamics were found to affect polarization features.

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Isomerization of molecular systems is ubiquitous in chemistry and biology, and is also important for many applications. Atomistic simulations can help determine the tunable parameters influencing this process. In this paper, we use the Nonadiabatic EXcited state Molecular Dynamics (NEXMD) software to study the photoisomerization of a representative molecule, 4-styrylquinoline (SQ).

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Introduction: Although researchers recognize that sharing disparate data can improve population health, barriers (technical, motivational, economic, political, legal, and ethical) limit progress. In this paper, we aim to enhance the van Panhuis . framework of barriers to data sharing; we present a complementary solutions-based data-sharing process in order to encourage both emerging and established researchers, whether or not in academia, to engage in data-sharing partnerships.

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Hot-carrier generation from surface plasmon decay has found applications in many branches of physics, chemistry, materials science, and energy science. Recent reports demonstrated that the hot carriers generated from plasmon decay in nanoparticles can transfer to attached molecules and drive photochemistry which was thought impossible previously. In this work, we have computationally explored the atomic-scale mechanism of a plasmonic hot-carrier-mediated chemical process, H dissociation.

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Nonadiabatic excited-state molecular dynamics (NEXMD) has been used to study photodecomposition in a class of recently synthesized bicyclic conjugated energetic materials (CEMs) composed of fused tetrazole and tetrazine derivatives with increasing oxygen substitutions. Modification by oxygen functionalization has already been demonstrated to increase the two-photon absorption intensity in the target CEMs while simultaneously improving oxygen balance. Photodecomposition mechanisms in materials that undergo nonlinear absorption could be used to achieve controlled, direct optical initiation.

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Coherence, signifying concurrent electron-vibrational dynamics in complex natural and man-made systems, is currently a subject of intense study. Understanding this phenomenon is important when designing carrier transport in optoelectronic materials. Here, excited state dynamics simulations reveal a ubiquitous pattern in the evolution of photoexcitations for a broad range of molecular systems.

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Solvation can be modeled implicitly by embedding the solute in a dielectric cavity. This approach models the induced surface charge density at the solute-solvent boundary, giving rise to extra Coulombic interactions. Herein, the Nonadiabatic EXcited-state Molecular Dynamics (NEXMD) software was used to model the photoexcited nonradiative relaxation dynamics in a set of substituted donor-acceptor oligo( p-phenylenevinylene) (PPVO) derivatives in the presence of implicit solvent.

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The efficiency of materials developed for solar energy and technological applications depends on the interplay between molecular architecture and light-induced electronic energy redistribution. The spatial localization of electronic excitations is very sensitive to molecular distortions. Vibrational nuclear motions can couple to electronic dynamics driving changes in localization.

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