Papers by Michael A N T H O N Y Alves
Spinal Cord Series and Cases
Study design Retrospective medical record review. Objective To determine the prevalence and descr... more Study design Retrospective medical record review. Objective To determine the prevalence and describe the profile of person with SCI (PWSCI) admitted in the public healthcare sector in Gauteng, South Africa. Setting Specialized public healthcare rehabilitation units in Gauteng, South Africa. Methods Medical records of PWSCI admitted to public healthcare rehabilitation units between 01 January 2018 and 31 December 2019 were perused. Data were collected anonymously and then summarised using descriptive and inferential statistics. Significance was set at p < 0.05. Results 386 of 998 participants (38.7%) were admitted following SCI and the mean age was 36.9 years. Most participants were male (69.9%), with females significantly more likely to sustain a NTSCI (p < 0.001), which was the least common cause of SCI (34.9%). Those sustaining a TSCI were found to be significantly younger than their NTSCI counterparts (p < 0.001). Assault was the leading cause of injury (35.2%), and a po...
Environmental Science & Technology, 2021
Organic emissions from coastal waters play an important but poorly understood role in atmospheric... more Organic emissions from coastal waters play an important but poorly understood role in atmospheric chemistry in coastal regions. A mesocosm experiment focusing on facilitated biological blooms in coastal seawater, SeaSCAPE (Sea Spray Chemistry and Particle Evolution), was performed to study emission of volatile gases, primary sea spray aerosol, and formation of secondary marine aerosol as a function of ocean biological and chemical processes. Here, we report observations of aerosol-phase benzothiazoles in a marine atmospheric context with complementary measurements of dissolved-phase benzothiazoles. Though previously reported dissolved in polluted coastal waters, we report the first direct evidence of the transfer of these molecules from seawater into the atmosphere. We also report the first gas-phase observations of benzothiazole in the environment absent a direct industrial, urban, or rubber-based source. From the identities and temporal dynamics of the dissolved and aerosol species, we conclude that the presence of benzothiazoles in the coastal water (and thereby their emissions into the atmosphere) is primarily attributable to anthropogenic sources. Oxidation experiments to explore the atmospheric fate of gas-phase benzothiazole show that it produces secondary aerosol and gas-phase SO2, making it a potential contributor to secondary marine aerosol formation in coastal regions and a participant in atmospheric sulfur chemistry.
Marine aerosols strongly influence climate through their interactions with solar radiation and cl... more Marine aerosols strongly influence climate through their interactions with solar radiation and clouds. However, significant questions remain regarding the influences of biological activity and seawater chemistry on the flux, chemical composition, and climate-relevant properties of marine aerosols and gases. Wave channels, a traditional tool of physical oceanography, have been adapted for large-scale ocean-atmosphere mesocosm experiments in the laboratory. These experiments enable the study of aerosols under controlled conditions which isolate the marine system from atmospheric anthropogenic and terrestrial influences. Here, we present an overview of the 2019 Sea Spray Chemistry and Particle Evolution (SeaSCAPE) study, which was conducted in an 11,800 L wave channel which was modified to facilitate atmospheric measurements. The SeaSCAPE campaign sought to determine the influence of biological activity in seawater on the production of primary sea spray aerosols, volatile organic compo...
Environmental Science: Processes & Impacts, 2020
Microspectroscopic analyses of glass surfaces following a single day of cooking events reveal org... more Microspectroscopic analyses of glass surfaces following a single day of cooking events reveal organic depositions that can be traced back to emission sources and airborne distributions.
ACS Earth and Space Chemistry, 2019
Atmospheric Chemistry and Physics, 2019
Size distributions of particles formed from sulfuric acid (H 2 SO 4) and water vapor in a photoly... more Size distributions of particles formed from sulfuric acid (H 2 SO 4) and water vapor in a photolytic flow reactor (PhoFR) were measured with a nanoparticle mobility sizing system. Experiments with added ammonia and dimethylamine were also performed. H 2 SO 4(g) was synthesized from HONO, sulfur dioxide and water vapor, initiating OH oxidation by HONO photolysis. Experiments were performed at 296 K over a range of sulfuric acid production levels and for 16 % to 82 % relative humidity. Measured distributions generally had a large-particle mode that was roughly lognormal; mean diameters ranged from 3 to 12 nm and widths (lnσ) were ∼ 0.3. Particle formation conditions were stable over many months. Addition of single-digit pmol mol −1 mixing ratios of dimethylamine led to very large increases in particle number density. Particles produced with ammonia, even at 2000 pmol mol −1 , showed that NH 3 is a much less effective nucleator than dimethylamine. A two-dimensional simulation of particle formation in PhoFR is also presented that starts with gas-phase photolytic production of H 2 SO 4 , followed by kinetic formation of molecular clusters and their decomposition, which is determined by their thermodynamics. Comparisons with model predictions of the experimental result's dependency on HONO and water vapor concentrations yield phenomenological cluster thermodynamics and help delineate the effects of potential contaminants. The added-base simulations and experimental results provide support for previously published dimethylamine-H 2 SO 4 cluster thermodynamics and provide a phenomenological set of ammonia-sulfuric acid thermodynamics.
ACS Earth and Space Chemistry, 2019
Photochemical processes drive much of the daytime gas-phase chemistry in the atmosphere. Within c... more Photochemical processes drive much of the daytime gas-phase chemistry in the atmosphere. Within condensed phases such as aerosol particles and thin films enriched in organics, much less is understood about these processes. An investigation aimed at better understanding photosensitized reactions that can occur within marine-relevant condensed phase systems is described herein. In particular, photosensitized reactions have been investigated between a fatty acid model system and different photosensitizers within thin organic films representative of molecular species found in the sea surface microlayer (SSML) and sea spray aerosols (SSA). Photosensitized reactions of thin films containing nonanoic acid and three different photosensitizers, including 4-benzoyl benzoic acid (BBA), humic acid (HA), and marine-derived dissolved organic matter (m-DOM), were probed using a suite of analytical techniques, including vibrational spectroscopy, excitation emission matrix spectroscopy (EEMS), and ultra-high-resolution mass spectrometry. Considerable differences were found in the photosensitizing capability for each of these systems. We also present an analysis of the molecular differences between the different photosensitizers to explain their unique characteristics and light absorbing properties. Overall, this study sheds light on the relevance of such reactions in the marine environment.
Environmental Science & Technology Letters, 2018
Deposition and surface-mediated reactions of adsorbed species can play a role in the level of exp... more Deposition and surface-mediated reactions of adsorbed species can play a role in the level of exposure of occupants to indoor pollutants, which include gases and particles. Detailed molecular-level descriptions of these processes occurring on indoor surfaces are difficult to obtain because of the ever-increasing types of surfaces and their proximity to a variety of different indoor emission sources. The results of an investigation of interactions of glass surfaces in unique indoor environments are described here. Window glass, a ubiquitous indoor surface, was placed vertically in six different locations to assess differences in particle and coating depositions. Atomic force microscopy− photothermal infrared (AFM−PTIR) spectroscopic analysis of these glass surfaces reveals differences in morphology and chemical composition, which reflects the diversity of surface processes found in local environments indoors. Overall, this detailed microspectroscopic imaging method shows deposition of particles and the formation of organic thin films that increase the surface area and surface roughness of the glass surface. PTIR spectroscopy demonstrates that depositions can be linked to primary emitters intrinsic to each of the different local environments.
Atmospheric Chemistry and Physics Discussions, 2019
Size distributions of particles formed from sulfuric acid (H 2 SO 4) and water vapor in a Photoly... more Size distributions of particles formed from sulfuric acid (H 2 SO 4) and water vapor in a Photolytic Flow Reactor (PhoFR) were measured with a nano-particle mobility sizing system. Experiments with added ammonia and dimethylamine 10 were also performed. H 2 SO 4(g) was synthesized from HONO, sulfur dioxide, and water vapor, initiating OH oxidation by HONO photolysis. For standard reactant flows and conditions, 296 K, 52 % relative humidity, and a ~40 s residence time, the calculated concentration of H 2 SO 4 peaked at 1.2x10 10 cm-3 , measured particle mean diameter was ~6 nm and total number density was ~10 4 cm-3. Measured distributions were influenced by molecular clusters at small sizes, less than or equal to 2 nm diameter, but were generally dominated by large particles that are roughly log-normal with mean diameters 15 ranging up to 12 nm and a relatively constant lnσ of ~0.3. Particle number density and their mean size depended on relative humidity, HONO concentration, illumination, and SO 2 level. Particle formation conditions were stable over many months. Addition of single-digit pmol/mol mixing ratios of dimethylamine led to very large increases in number density. Ammonia at levels up to 2000 pmol/mol showed that NH 3 is less effective than dimethylamine at producing particles. A twodimensional simulation of PhoFR reveals that H 2 SO 4 scales with HONO and its level builds along the length of the flow 20 reactor. Experimentally, particle growth scaled with HONO, in accord with model-predicted H 2 SO 4 levels. Additional comparison between experiment and model indicates that reaction of HO 2 with SO 2 could be a significant source of H 2 SO 4 in this experiment. The effects of potential contaminants on particle formation rates near room temperature are addressed and provide context in comparisons with previous experiments. The added-base experimental results provide support for previously published dimethylamine-H 2 SO 4 cluster thermodynamics but do not support previously published ammonia-25 sulfuric acid thermodynamics. 1 Introduction Particle formation in the atmosphere has long been studied (McMurry et al. 2005; Kulmala et al. 2004) to ascertain potential impacts on health (Nel 2005) and on climate processes(IPCC 2013). For example, nano-particles (characterized as < 10 nm in diameter) can have special health effects as their small size allows for efficient transport into lung tissue (Kreyling et al. 30
Geological Society, London, Special Publications, 2015
Ancient and modern stromatolites are potentially a challenge for petrophysicists when characteriz... more Ancient and modern stromatolites are potentially a challenge for petrophysicists when characterizing biosediments of microbial origin. Because of the heterogeneity, sometimes very cemented and lacking porosity, sometimes highly porous, these widely differing states can be used to develop techniques that can have wider application to addressing the representative elementary volume (REV – single or multiple REVs) challenge in microbial carbonates. Effective media properties – like porosity – need to be defined on REV scales and the challenge is that this scale is often close to or significantly larger than the traditional core plugs on which properties are traditionally measured. A combination of outcrop images, image analysis techniques, micro-computed tomography (CT) and modelling have been used to capture the porosity (or in some cases, precursor porosity) architecture and provide a framework for estimating petrophysical property sensitivities in a range of situations that can be s...
Physical Chemistry Chemical Physics, 2017
Sea spray aerosol (SSA) particles are mixtures of organics and salts that show diversity in their... more Sea spray aerosol (SSA) particles are mixtures of organics and salts that show diversity in their morphologies and water uptake properties.
Choice Reviews Online, 2005
Revista Brasileira de Tecnologia Aplicada nas Ciências Agrárias, 2016
Os aminoácidos e as substâncias húmicas, deste que corretamente usados, podem auxiliar no crescim... more Os aminoácidos e as substâncias húmicas, deste que corretamente usados, podem auxiliar no crescimento e no desenvolvimento das culturas. Assim, este estudo teve por objetivo testar a interação do efeito de um aminoácido e de uma substância húmica com o tamanho do mini-rebolo no desenvolvimento inicial da cana-de-açúcar. O experimento foi conduzido na Estação Experimental de Canade-açúcar de Paranavaí-UFPR. A cultivar utilizada foi a RB867515 e as avaliações foram efetuadas aos 60 dias após o plantio. Foi utilizado o delineamento inteiramente casualizado em arranjo fatorial com três repetições (3x5x3). Os tamanhos dos mini-rebolos testados foram cinco, a saber: 0 (somente a gema), 2, 4, 8, 12 e 16 cm. Além da testemunha, os bioestimulantes aplicados foram uma substância húmica e o ácido L-glutâmico. Pode-se concluir que, nas condições de realização e avaliação do experimento, não há interação entre o comprimento da reserva do tolete e a aplicação dos bioestimulantes testados. A área superficial radicular, o diâmetro radicular, o volume radicular, a massa seca radicular e a massa seca da parte aérea tiveram um comportamento linear, crescente e significativo, em função do comprimento do tolete.
Challenge a Journal of Research on African American Men, 1996
The Urban Review, 1987
The authors argue that conventional mandatory and voluntary school desegregation techniques have ... more The authors argue that conventional mandatory and voluntary school desegregation techniques have failed to provide minority students with maximum feasible relief from invidious discrimination because they do not redress the root causes of segregation. They demonstrate that residential-based student assignment plans as well as plans that give students limited access to a few educationally enriched magnet schools are not asymmetrical
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Papers by Michael A N T H O N Y Alves