Incomplete approach to homoclinicity in a model with bent-slow manifold geometry

The dynamics of a model, originally proposed for a type of instability in plastic flow, has been investigated in detail. The bifurcation portrait of the system in two physically relevant parameters exhibits a rich variety of dynamical behaviour, including period bubbling and period adding or Farey sequences. The complex bifurcation sequences, characterized by Mixed Mode Oscillations, exhibit partial features of Shilnikov and Gavrilov-Shilnikov scenario. Utilizing the fact that the model has disparate time scales of dynamics, we explain the origin of the relaxation oscillations using the geometrical structure of the bent-slow manifold. Based on a local analysis, we calculate the maximum number of small amplitude oscillations, $s$, in the periodic orbit of $L^s$ type, for a given value of the control parameter. This further leads to a scaling relation for the small amplitude oscillations. The incomplete approach to homoclinicity is shown to be a result of the finite rate of `softening' of the eigen values of the saddle focus fixed point. The latter is a consequence of the physically relevant constraint of the system which translates into the occurrence of back-to-back Hopf bifurcation.Comment: 14 Figures(Postscript); To Appear in Physica D : Nonlinear Phenomen

Improving Healthcare Provider COVID-19 Vaccine Hesitancy Knowledge in Black Patients: A Quality Improvement Project

Background: Widespread vaccination hesitancy is now a global health concern that threatens the spread of communicable diseases, such as COVID-19. The acceptance of vaccines in the Black American community is lower than other groups. With the availability of three COVID-19 vaccines in America, acceptance rates of vaccines in the Black community are lower due to inequalities within socioeconomic status, healthcare resources, and medical distrust. Objective: The purpose of this DNP study is to evaluate whether extending education to healthcare workers/providers about COVID-19 vaccines, vaccine hesitancy, and communication techniques increases provider knowledge. Additional goals of the study are to increase the acceptance rates of COVID-19 vaccines in Black U.S. communities. Methodology: Using a quantitative, pre-test/post-test study design, a group of South Florida primary care healthcare workers and providers were requested to participate. Within four weeks, they were asked to complete a pre-test evaluation, followed by a video PowerPoint presentation and a post-test evaluation. The assessed outcomes were knowledge about COVID-19 and COVID-19 vaccines, communication techniques, and cultural sensitivity. Results: The study enlisted 10 healthcare workers. Overall, there was an 11% increase in scores when comparing the pretest and posttest scores. APRNs maintained the highest scores and had the most improvement from 88% (pretest) to 93% (Posttest). APRNs, 100% of them, felt the most comfortable discussing COVID-19 vaccines with patients that refuse or are hesitant of taking vaccines. In cultural sensitivity, APRNs improved their scores in identifying racial barriers from 33.3% to 50%, while nurses had a decrease in scores by 50% and medical assistants by 25%. Overall, for communication techniques, scores increased by 2.9%. For the clinical knowledge assessment, APRNs consistently scored at 100% in both the pretest and the posttest. Conclusion: The Black population in the United States have been hit the hardest in the COVID-19 pandemic of 2020. Black individuals accept vaccines at lower rates than other races and ethnicities. They are also the most likely to suffer from higher mortality rates and complications from diseases that are preventable by vaccines. The results reinforce the established literature that healthcare providers and workers, especially APRNs, are the most trusted individuals to educate reluctant patients and convert vaccine hesitant individuals into accepting the COVID-19 vaccines. Keywords: Vaccine hesitancy, COVID-19 vaccines, COVID-19, vaccine acceptance, nurse practitioner, pandemi

Long Tailed Maps as a Representation of Mixed Mode Oscillatory Systems

Mixed mode oscillatory (MMO) systems are known to exhibit some generic features such as the reversal of period doubling sequences and crossover to period adding sequences as bifurcation parameters are varied. In addition, they exhibit a nearly one dimensional unimodal Poincare map with a longtail. We recover these common features from a general class of two parameter family of one dimensional maps with a unique critical point that satisfy a few general constraints that determine the nature of the map. We derive scaling laws that determine the parameter widths of the dominant windows of periodic orbits sandwiched between two successive states of RL^k sequence. An example of a two parameter map with a unique critical point is introduced to verify the analytical results.Comment: 13 pages and 8 figure

Kinetics and Mechanism of Formation of S-Nitrosocysteine

The kinetics and mechanism of the nitrosation of cysteine by nitrous acid has been studied in acidic medium. The stoichiometry of the reaction is strictly 1:1, with the formation of one mole of S-nitrosocysteine (CySNO) fromone mole of nitrous acid. Only two nitrosating agents were detected: nitrous acid itself and protonated nitrous acid which is the hydrated form of the nitrosonium cation, NO+. Nitric oxide itself was not detected as a nitrosant. The bimolecular rate constant for the direct nitrosation of cysteine by nitrous acid was determined to be 6.4±1.1 L mol–1 s–1, while nitrosation by the nitrosonium cation has a rate constant of 6.8× 103 L mol–1 s–1. CySNO is short-lived, and decomposes completely to cystine and nitric oxide within 100 s in the presence of micromolar quantities of Cu(II) ions. Since the physiological environment contains many metal ions and metalloenzymes, it is unlikely that CySNO will be an effective carrier of NO.Keywords: Cysteine, Nitric Oxide, Nitrosothio

Multiwalled Carbon Nanotube-titania Nanocomposites: Understanding Nano-Structural Parameters and Functionality in Dye-sensitized Solar Cells

Nanocomposites consisting of multiwalled carbon nanotubes and titania were synthesized by two methods, namely, sol-gel and chemical vapour deposition (CVD) methods. The work takes advantage of the bridging ability of nanotechnology between macromolecules and the solid state process in engineering alternative nanomaterials for various applications including solar cell fabrication. Physical and chemical characterization of the mesoporous nanocomposites from the two synthetic methods were investigated using Raman spectroscopy, thermogravimetric analysis, Fourier transformation infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, surface characterization and X-ray diffraction analysis. Physicochemical properties in the nanocomposites such as thermal stability, pore volume, crystallinity and surface area were observed to be a subject of MWCNT: titania ratios and synthetic methods. From the CVD synthetic method, observed attributes includemore uniformand smoother coating; better crystallinity and larger pore width than sol-gel method. On the other hand, nanocomposites from sol-gel synthetic method had larger surface areas, were more defective and less thermally stable than those from CVD. Nanocomposites by the CVD method performed 39.2% more efficient than those from sol-gel in light-harvesting experiments. The study shows that the nanocomposites synthesized were more effective than titania alone when the cheaper natural dye, Eosin B, was used. This highlights the great potential of typical nanomaterials in improving the performances of titania in DSSCs as well as lowering the cost of the ultimate devices.KEYWORDS Dye-sensitized solar cells, multiwalled carbon nanotubes, nanocomposite, titania, sol-gel, chemical vapour deposition

Complex Kinetics in the Reaction of Taurine with Aqueous Bromine and Acidic Bromate : A Possible Cytoprotective Role against Hypobromous Acid

The most abundant aminoacid in the human body, 2-aminoethanesulphonic acid (H2NCH2CH2SO3H), is surprisingly stable and reacts exceedingly slowly even with the most powerful oxidizing agents like acidic bromate. Oxidation occurs only on the nitrogen centre to give the corresponding N-derivatives. No activity is observed at the sulphonic acid group and no cleavage of the C-S bond is observed. The stoichiometry of the oxidation of 2-aminoethanesulphonic acid by bromate is complex, yielding a mixture of monobromo- and dibromotaurines, oximes as well as the corresponding dimeric azo-compounds. In the presence of added bromide, the stoichiometry of the reaction is : 2BrO3- + 3H2NCH2CH2SO3H + 6H+ + 4Br- -> 3Br2NCH2CH2SO3H + 6H2O. Monobromotaurine is formedas an intermediate product before formation of the dibromotaurine. Aqueous bromine reacts quantitatively with 2-aminomethanesulphonic acid according to the stoichiometry : H2NCH2CH2SO3H + 2Br2 -> Br2NCH2CH2SO3H + 2Br- + 2H+. This reaction is strongly inhibited by acid due to the deactivation of the amino group to electrophilic attack by protonation. The formation of N-bromotaurines is suggested as a possible mechanism by which taurine can moderate the oxidative toxicity of bromine and hypobromous acid in the slightly basic physiological environments. South African Journal of Chemistry Vol.55 2002: 136-14

The relationship between infant feeding practices and diarrhoeal infections

To determine the relationship between infant-feeding practices and diarrhoeal infections, a descriptive survey was conducted to infants between six to 12 months of age. A guided interview was conducted to 105 mothers of infants who attended the health facilities of Mbabane, Swaziland. The results show that breast-feeding is routinely practiced by the majority of mothers and exclusive breast-feeding is very low, but supplementary feed in the form of formula or solids are introduced by the majority of respondents within the first three months of life. Infants who were given colostrum and breast milk had fewer diarrhoeal attacks. Other factors, for example education and cultural factors influenced the feeding practices and number of diarrhoeal attacks. It is recommended that breast-feeding should be promoted as an important intervention in the control of diarrhoeaM.A. (Nursing Science)Health Studie

Self-organization with traveling waves: A case for a convective torus

A traveling wave of BaSO4 in the chlorite-thiourea reaction has shown concentric precipitation patterns upon being triggered by the autocatalyst HOCl. The precipitation patterns show circular rings of alternate null and full precipitation regions. This self-organization appears to be the result of the formation of a convective torus. The formation of the convective torus can be described as a Benard-Marangoni instability with lateral heating