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Search Results: 1 - 10 of 222083 matches for " Michelle C. Moffitt "
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Neurotoxic Alkaloids: Saxitoxin and Its Analogs
Maria Wiese,Paul M. D’Agostino,Troco K. Mihali,Michelle C. Moffitt,Brett A. Neilan
Marine Drugs , 2010, DOI: 10.3390/md8072185
Abstract: Saxitoxin (STX) and its 57 analogs are a broad group of natural neurotoxic alkaloids, commonly known as the paralytic shellfish toxins (PSTs). PSTs are the causative agents of paralytic shellfish poisoning (PSP) and are mostly associated with marine dinoflagellates (eukaryotes) and freshwater cyanobacteria (prokaryotes), which form extensive blooms around the world. PST producing dinoflagellates belong to the genera Alexandrium, Gymnodinium and Pyrodinium whilst production has been identified in several cyanobacterial genera including Anabaena, Cylindrospermopsis, Aphanizomenon Planktothrix and Lyngbya. STX and its analogs can be structurally classified into several classes such as non-sulfated, mono-sulfated, di-sulfated, decarbamoylated and the recently discovered hydrophobic analogs—each with varying levels of toxicity. Biotransformation of the PSTs into other PST analogs has been identified within marine invertebrates, humans and bacteria. An improved understanding of PST transformation into less toxic analogs and degradation, both chemically or enzymatically, will be important for the development of methods for the detoxification of contaminated water supplies and of shellfish destined for consumption. Some PSTs also have demonstrated pharmaceutical potential as a long-term anesthetic in the treatment of anal fissures and for chronic tension-type headache. The recent elucidation of the saxitoxin biosynthetic gene cluster in cyanobacteria and the identification of new PST analogs will present opportunities to further explore the pharmaceutical potential of these intriguing alkaloids.
On the Chemistry, Toxicology and Genetics of the Cyanobacterial Toxins, Microcystin, Nodularin, Saxitoxin and Cylindrospermopsin
Leanne Pearson,Troco Mihali,Michelle Moffitt,Ralf Kellmann,Brett Neilan
Marine Drugs , 2010, DOI: 10.3390/md8051650
Abstract: The cyanobacteria or “blue-green algae”, as they are commonly termed, comprise a diverse group of oxygenic photosynthetic bacteria that inhabit a wide range of aquatic and terrestrial environments, and display incredible morphological diversity. Many aquatic, bloom-forming species of cyanobacteria are capable of producing biologically active secondary metabolites, which are highly toxic to humans and other animals. From a toxicological viewpoint, the cyanotoxins span four major classes: the neurotoxins, hepatotoxins, cytotoxins, and dermatoxins (irritant toxins). However, structurally they are quite diverse. Over the past decade, the biosynthesis pathways of the four major cyanotoxins: microcystin, nodularin, saxitoxin and cylindrospermopsin, have been genetically and biochemically elucidated. This review provides an overview of these biosynthesis pathways and additionally summarizes the chemistry and toxicology of these remarkable secondary metabolites.
Evolution of magnetic properties in the normal spinel solid solution Mg(1-x)Cu(x)Cr2O4
Moureen C. Kemei,Stephanie L. Moffitt,Daniel P. Shoemaker,Ram Seshadri
Physics , 2011, DOI: 10.1088/0953-8984/24/4/046003
Abstract: We examine the evolution of magnetic properties in the normal spinel oxides Mg(1-x)Cu(x)Cr2O4 using magnetization and heat capacity measurements. The end-member compounds of the solid solution series have been studied in some detail because of their very interesting magnetic behavior. MgCr2O4 is a highly frustrated system that undergoes a first order structural transition at its antiferromagnetic ordering temperature. CuCr2O4 is tetragonal at room temperature as a result of Jahn-Teller active tetrahedral Cu^2+ and undergoes a magnetic transition at 135 K. Substitution of magnetic cations for diamagnetic Mg^2+ on the tetrahedral A site in the compositional series Mg(1-x)Cu(x)Cr2O4 dramatically affects magnetic behavior. In the composition range 0 < x < 0.3, the compounds are antiferromagnetic. A sharp peak observed at 12.5K in the heat capacity of MgCr2O4 corresponding to a magnetically driven first order structural transition is suppressed even for small x suggesting glassy disorder. Uncompensated magnetism - with open magnetization loops - develops for samples in the x range 0.43 < x < 1. Multiple magnetic ordering temperatures and large coercive fields emerge in the intermediate composition range 0.43 < x < 0.47. The Neel temperature increases with increasing x across the series while the value of the Curie-Weiss Theta decreases. A magnetic temperature-composition phase diagram of the solid solution series is presented.
Utiliza??o das fichas de registro de vacina??es pelos centros de saúde na Divis?o Regional de Saúde de Campinas, Estado de S?o Paulo, Brasil
Harris,William Moffitt;
Revista de Saúde Pública , 1974, DOI: 10.1590/S0034-89101974000300005
Abstract: a comparative analytical sample survey regarding the coincidence of data found in vaccination record cards (yellow ones) belonging to children and those (blue ones) belonging to the local health units' archives conducted in 16 counties with populations over thirty thousand among those pertaining to the campinas administrative region (83 counties with a total population of 2.3 million) of the state of s. paulo, brazil, was here described showing that in 788 cards effectively examined there were 2,307 diverging vaccine informations. only 386 (48.9%) yellow cards coincided perfectly with their corresponding blue cards. it became quite obvious that the vaccination archives of the local health units do not yield conditions for an efficient vaccinal coverage evaluation of the population.
Photocatalysis of Titanium Dioxide for Water Disinfection: Challenges and Future Perspectives
M. J. Wu,T. Bak,P. J. O’Doherty,M. C. Moffitt,J. Nowotny,T. D. Bailey,C. Kersaitis
International Journal of Photochemistry , 2014, DOI: 10.1155/2014/973484
Abstract: The performance of metal oxides such as titanium dioxide (TiO2), in the conversion of solar energy into chemical energy, is determined by semiconducting properties. The conversion process is closely related to the light-induced reactivity between oxide semiconductors and water, which may lead to partial water oxidation and consequently water disinfection. Key performance-related properties are considered here, including light absorption, light-induced ionisation over the band gap, charge separation, charge transport, charge transfer, and the chemical reactions taking place at anodic and cathodic sites. Optimisation of these interconnected performance-related properties is discussed, along with the photocatalytic application in water disinfection. 1. Introduction Over the last decade research activities which aimed at the development of photocatalysts for water purification by photosensitive oxide materials, such as , have intensified [1–5]. The underlying concept of water purification involves the utilisation of solar energy to oxidise water molecules for the production of reactive oxygen species and other oxidising radicals, which are toxic to microorganisms in water. has been the focus of intensive research activities due to its high photocatalytic activity under the photon energy of ultraviolet and possibly visible light, chemical and thermal stability, resistance to chemical breakdown, and strong mechanical properties. Its application in water disinfection is enhanced by the ability of to completely destroy organic pollutants and microorganisms [6–11]. It appears, however, that most of the reported experimental data on photocatalytic water purification are not comparable, even for the same chemical systems, due to lack of reproducibility. Therefore, there is an urgent need to assess the reasons for this incompatibility. Generation of meaningful antimicrobial data may lead to derivation of theoretical models. Such models could then be used to compare photocatalytic systems and predict the effect of basic properties, such as chemical composition, structure, and semiconducting properties, on performance. As is known to the present, oxide materials are well defined in terms of reproducibility when they are in thermodynamic equilibrium with the gas phase of controlled oxygen activity. In the case of , its properties are controlled by the conditions of the equilibrium [12]. At lower temperatures (below equilibrium) they are profoundly influenced by cooling procedures, such as cooling rate and the associated gas phase composition. In many instances,
Hands-On Russian Culture Lessons  [PDF]
Ksenia S. Zhbanova, Audrey C. Rule, Michelle L. Tichy
Creative Education (CE) , 2015, DOI: 10.4236/ce.2015.63027
Abstract: The global diverse society necessitates that teachers develop cultural competency and use authentic resources for teaching. This article presents classroom-tested materials for teaching elementary students about aspects of Russian culture, developed by a native Russian and two education professors. Multiage, multi-racial American Midwestern students from a homeschooling cooperative learned vocabulary and concepts with statistically significant increases from pretest to posttest and a large effect size. The lessons began with recognition of human commonalities between Russian people and Americans, in accordance with omniculturalism theory. Lessons then highlighted and celebrated cultural differences through an exploration of Russian literature and culture. Culminating creative craft-making activities included simulating a Gzhel porcelain statue in white air-dry clay with blue markings, making a pop-up version of a matryoshka nesting doll set, constructing a papier-maché building with onion-domed towers and a Maslenitsa holiday scene, and decorating a paper-covered plastic egg with gems to make a Faberge-style jewelry box. The lessons, greeted with enthusiasm from students, included classification tasks, observation activities, and a Bingo-type game. Students evidenced deeper learning by continuing to connect their lives to Russian cultural content after the lesson unit had concluded.
‘Leaves and Eats Shoots’: Direct Terrestrial Feeding Can Supplement Invasive Red Swamp Crayfish in Times of Need
Jonathan Grey, Michelle C. Jackson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0042575
Abstract: We used stable isotope analyses to characterise the feeding dynamics of a population of red swamp crayfish in Lake Naivasha, Kenya, after the crash of submerged macrophytes and associated macroinvertebrates, and during a natural draw-down of the lake water level. We expected a heavy reliance upon a diet of detrital matter to sustain the population as a consequence, and indeed, for the majority of the crayfish population caught from the lake, we saw a concomitant shift in isotopic values reflecting a dietary change. However, we also caught individual crayfish that had occupied the footprints of hippopotamus and effectively extended their range beyond the lake up to 40 m into the riparian zone. Isotopic analysis confirmed limited nocturnal observations that these individuals were consuming living terrestrial plants in the vicinity of the footprints. These are the first empirical data to demonstrate direct use of terrestrial resources by an aquatic crayfish species and further highlight the traits that make red swamp crayfish such opportunistic and successful invaders.
Wild Western Lowland Gorillas Signal Selectively Using Odor
Michelle Klailova, Phyllis C. Lee
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0099554
Abstract: Mammals communicate socially through visual, auditory and chemical signals. The chemical sense is the oldest sense and is shared by all organisms including bacteria. Despite mounting evidence for social chemo-signaling in humans, the extent to which it modulates behavior is debated and can benefit from comparative models of closely related hominoids. The use of odor cues in wild ape social communication has been only rarely explored. Apart from one study on wild chimpanzee sniffing, our understanding is limited to anecdotes. We present the first study of wild gorilla chemo-communication and the first analysis of olfactory signaling in relation to arousal levels and odor strength in wild apes. If gorilla scent is used as a signaling mechanism instead of only a sign of arousal or stress, odor emission should be context specific and capable of variation as a function of the relationships between the emitter and perceiver(s). Measured through a human pungency scale, we determined the factors that predicted extreme levels of silverback odor for one wild western lowland gorilla (Gorilla gorilla gorilla) group silverback. Extreme silverback odor was predicted by the presence and intensity of inter-unit interactions, silverback anger, distress and long-calling auditory rates, and the absence of close proximity between the silverback and mother of the youngest infant. Odor strength also varied according to the focal silverback's strategic responses during high intensity inter-unit interactions. Silverbacks appear to use odor as a modifiable form of communication; where odor acts as a highly flexible, context dependent signaling mechanism to group members and extra-group units. The importance of olfaction to ape social communication may be especially pertinent in Central African forests where limited visibility may necessitate increased reliance on other senses.
Solitary waves and conservation laws for highly nonlinear wave equations modeling granular chains
Michelle Przedborski,Stephen C. Anco
Physics , 2015,
Abstract: An exact solitary wave solution is derived for two nonlinear wave equations. These equations model the long wavelength behavior of compression waves in one-dimensional homogeneous granular chains having weak and strong initial pre-compression. The derivation utilizes conservation laws for energy, momentum, and net displacement speed, which are found through a direct method without using Noether's theorem. Properties of the solitary wave solution, including its width and height, are examined.
Structural distortion below the Néel temperature in spinel GeCo$_2$O$_4$
Phillip T. Barton,Moureen C. Kemei,Michael W. Gaultois,Stephanie L. Moffitt,Lucy E. Darago,Ram Seshadri,Matthew R. Suchomel,Brent C. Melot
Physics , 2014, DOI: 10.1103/PhysRevB.90.064105
Abstract: A structural phase transition from cubic $Fd\bar{3}m$ to tetragonal $I$4$_1$/$amd$ symmetry with $c/a >$ 1 is observed at $T_{\rm{S}}$ = 16 K in spinel GeCo$_2$O$_4$ below the N\'eel temperature $T_N$ = 21 K. Structural and magnetic ordering appear to be decoupled with the structural distortion occurring at 16 K while magnetic order occurs at 21 K as determined by magnetic susceptibility and heat capacity measurements. An elongation of CoO$_6$ octahedra is observed in the tetragonal phase of GeCo$_2$O$_4$. We present the complete crystallographic description of GeCo$_2$O$_4$ in the tetragonal $I$4$_1$/$amd$ space group and discuss the possible origin of this distortion in the context of known structural transitions in magnetic spinels. GeCo$_2$O$_4$ exhibits magnetodielectric coupling below $T_{\rm{N}}$. The related spinels GeFe$_2$O$_4$ and GeNi$_2$O$_4$ have also been examined for comparison. Structural transitions were not detected in either compound down to $T \approx$ 8 K. Magnetometry experiments reveal in GeFe$_2$O$_4$ a second antiferromagnetic transition, with $T_{\rm{N1}}$ = 7.9 K and $T_{\rm{N2}}$ = 6.2 K, that was previously unknown, and that bear a similarity to the magnetism of GeNi$_2$O$_4$.
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