Synthesis and systematic study of Co₃O₄-based catalysts for oxygen reduction and oxygen evolution reactions

textCo₃O₄-based composite materials are good electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in alkaline solutions. Here, this thesis first investigated the individual functionality of Co₃O₄ and the N-doped carbon nanoweb (CNW) in ORR and OER. The Co₃O₄/CNW bifunctional catalysts were synthesized by an in situ growth of Co precursors onto CNW followed by a controlled heat treatment. Rotating disk electrode measurements were utilized to provide insight into the specific functions of Co₃O₄ and CNW in the composite material during catalysis. It was found that Co₃O₄ alone exhibited poor ORR catalytic activity. However, in the presence of CNW, Co₃O₄ assisted the selective four-electron oxygen reduction over the two-electron pathway. Co₃O₄ acted as the primary catalytic site for OER and CNW improved the electronic conduction between Co₃O₄ and the current collector. CNW underwent serious degradation at the high potential of the OER, but its stability improved greatly upon the deposition of Co₃O₄. Two possible mechanisms for the improved catalytic stability are discussed. The findings demonstrate the specific functions of Co₃O₄ and CNW in catalyzing the OER and ORR and further establish an understanding of the synergy of the composite in electrocatalysis. Based on the critical functionality of Co₃O₄ in stabilizing carbon materials in the OER potential region, it is of interest to investigate novel synthesis methods to prepare nano-sized Co₃O₄ that can provide more active sites for catalytic reactions and thus, improve the OER kinetics. Here, in situ electrochemical generation of 2-dimensional Co₃O₄ (2D-Co₃O₄) nanoplates were achieved by scanning CoO[subscript x]/Co precursors in 1 M KOH solution. X-ray diffraction characterization suggested that CoO[subscript x]/Co precursors were oxidized to Co₃O₄ before the onset potential of OER. Scanning electron microscopy showed that oxidation from CoO[subscript x]/Co to 2D-Co₃O₄ was associated with the formation of hexagonal nanoplates. The 2D-Co₃O₄ exhibited excellent OER catalytic activity and stability probably due to the effective mass transfer through the 2D structure.Materials Science and Engineerin

Platinum Black Electroplated Impedance Particle Sensor

We present a micro electrical impedance particle sensor. To solve the problem of large electrode electrolyte interface impedance, we electroplated the electrodes with platinum black. Devices are fabricated with integrated parylene technology. An electrical model for the system is proposed and analytic solutions are obtained. Impedance spectra measurement of the device filled with various media are in excellent agreement with model analysis. Signals from individual 10 µm polystyrene beads passing the sensing electrodes are successfully obtained

The mediating effect of body mass index on the relationship between cigarette smoking and atopic sensitization in Chinese adults

Background: It is unclear whether the relationship between cigarette smoking and atopy is mediated by body fat mass, such as the Body Mass Index (BMI). We assessed the mediating role of BMI on the relationship between smoking and atopy in Chinese adults. Methods: A hospital-based case-control study of 786 atopic cases and 2771 controls was conducted in adults aged 18 years or older from March 2010 to September 2014 in Harbin, China. Mediation models were used to estimate the indirect effects of smoking on atopic sensitization through BMI. Results: Compared to non-smokers, light smokers and moderate smokers had a lower risk of inhalant allergen sensitization. The indirect effect of smoking and sensitization to aeroallergens were only observed in light smokers (point estimate, -0.026; 95% CI, -0.062 to -0.004). The mediating roles of BMI on the relationships between smoking and other types of allergic sensitization were not statistically significant. Conclusion: BMI appeared to partially mediate the effect of light smoking on sensitization to aeroallergens. However, considering the other harmful health effects of cigarette smoking, the effective method to lower the incidence of atopy would be to decrease body fat mass by physical exercise and employing other more healthy ways of living rather than smoking

Generalized frieze varieties and Gr\"obner bases

We study properties of generalized frieze varieties for quivers associated to cluster automorphisms. Special cases include acyclic quivers with Coxeter automorphisms and quivers with Cluster DT automorphisms. We prove that the generalized frieze variety X of an affine quiver with the Coxeter automorphism is either a finite set of points or a union of finitely many rational curves. In particular, if dim X=1, the genus of each irreducible component is zero. We also propose an algorithm to obtain the defining polynomials for each irreducible component of the generalized frieze variety for affine quivers. Furthermore, we give the Gr\"obner basis with respect to a given monomial order for each irreducible component of frieze varieties of affine quivers with given orientations, and show that each component is a smooth rational curve.Comment: 41 page

The Effect of Plant Elicitor Peptide on Nematode Infected Soybean

Soybean (Glycine max), an important economic crop native to East Asia, is grown worldwide for its edible beans. Soybean plants are vulnerable to a wide range of diseases, and nematodes are among the worst pests of soybean. The southern root-knot nematode (Meloidogyne incognita) and soybean cyst nematode (Heterodera glycines) are both notable nematode pests of soybean, with the soybean cyst nematode causing more than 30% of total yield loss in the US. Numerous attempts have been made to control soybean nematodes over the past several decades, and genetic engineering technology has received a lot of attention in recent years. Plant elicitor peptides (Peps) are endogenous polypeptides consisting of amino acids that can trigger innate immune defense in plants and are present in various plant species, including soybean. GmPep3 are plant elicitor peptides present in soybean and the gene GmPROPEP3 regulates the synthesis of GmPep3 in soybean. In this study, two independent nematode bioassays were conducted to investigate whether GmPep3 treatment and the insertion of GmPROPEP3 in susceptible soybean cultivar Magellan could enhance soybean defense towards the southern root-knot nematode and the soybean cyst nematode, and whether different treatments on soybean have any effect on soybean growth. According to the results, the GmPep3 treatment and the insertion of GmPROPEP3 in Magellan have no negative effect on soybean growth. However, whether the treatments have any positive effects on soybean growth needs further investigation. The root-knot nematode bioassay results suggested that there were no significant differences in egg number between treatment groups, while the soybean cyst nematode result indicated that both transgenic lines were resistant to soybean cyst nematodes. However, the data presented in this study is insufficient, and future experiments are necessary in order to support the current conclusion

Resolving the Two impasses in the Global Justice Debate through a Reconstruction of David Miller’s Account of Deliberative Democracy on the Basis of Habermas’s Conception of Communicative action

There are both substantive and methodological disagreements in the global justice debate between cosmopolitanism on the one hand, and statism and liberal nationalism on the other. The substantive disagreement avers that statists and liberal nationalists restrict the regulation of substantive inequality to the domestic sphere, whereas cosmopolitans extend it to the global level. The methodological disagreement is based on the fact that statists and liberal nationalists ground concern for distributive justice in the institutions of citizenship, whereas cosmopolitans focus on the moral equality of human beings. David Miller’s liberal nationalist account of distributive justice differs from the statist account by drawing on a premise about human nature: that a common nationality is a powerful motivational force in supporting the institutions of citizenship within a nation-state. This provides more ethically acceptable justification for restricting the regulation of substantive inequality in the face of the cosmopolitans’ insistence on respecting the moral equality of human beings. However, Miller’s account is incomplete because it fails to explain why human beings’ common moral intuitions and political emotions would justify restricting the regulation of substantive inequality to the domestic level. In this thesis, I will propose a way of extending Miller’s account based on the idea of deliberative democracy at the global level. I will argue that the regulation of substantive inequality could be grounded in institutions of global citizenship based on public deliberation at the global level that would adjudicate among different distributive principles and that this could help to resolve the two disagreements in the global justice debate

Draft Genome Sequences of <i>Vibrio alginolyticus</i> Strains V1 and V2, Opportunistic Marine Pathogens

We announce the draft genome sequences of Vibrio alginolyticus strains V1 and V2, isolated from juvenile Sparus aurata and Dentex dentex, respectively, during outbreaks of vibriosis. The genome sequences are 5,257,950 bp with a G+C content of 44.5% for V. alginolyticus V1 and 5,068,299 bp with a G+C content of 44.8% for strain V2. These genomes provide further insights into the putative virulence factors, prophage carriage, and evolution of this opportunistic marine pathogen