Synthesis and Characterization of a Polypyridyl Ru(II)-Alloxazine Complex for Adsorption on TiO2-coated ITO Electrodes

TiO2-coated conducting glass electrodes can be modified by attachment of redox-active molecules to the TiO2 surface. This thesis describes the synthesis and characterization of a polypyridyl Ru(II) complex that can be covalently bound to a TiO2 surface through the carboxylate groups of 2,2\u27-bipyridine-4,4\u27 -dicarboxylic acid, H2dcbpy. In addition, the bound complex contains a redox-active alloxazine derivative, pptd, which is capable of 2e-/2H+ transfers. Thus the TiO2-coated electrode is modified with a transition metal complex capable of shuttling H-atoms to substrates in solution. Synthesis of the PF6- salt of this complex, [RuII(H2dcbpy)2pptd](PF6)2, proved challenging due to the difficulties in obtaining starting materials of sufficient purity. Details of the efforts to purify these materials are included. UV-Vis, 1H-NMR, and electrochemical characterization of [RuII(H2dcbpy)2pptd](PF6)2, and its adsorption to TiO2 electrodes, are included in the thesis. In addition, several well-known reference compounds have been characterized for comparison purposes

Synthesis and Characterization of a Polypyridyl Ru(II)-Alloxazine Complex for Adsorption on TiO2-coated ITO Electrodes

TiO2-coated conducting glass electrodes can be modified by attachment of redox-active molecules to the TiO2 surface. This thesis describes the synthesis and characterization of a polypyridyl Ru(II) complex that can be covalently bound to a TiO2 surface through the carboxylate groups of 2,2\u27-bipyridine-4,4\u27 -dicarboxylic acid, H2dcbpy. In addition, the bound complex contains a redox-active alloxazine derivative, pptd, which is capable of 2e-/2H+ transfers. Thus the TiO2-coated electrode is modified with a transition metal complex capable of shuttling H-atoms to substrates in solution. Synthesis of the PF6- salt of this complex, [RuII(H2dcbpy)2pptd](PF6)2, proved challenging due to the difficulties in obtaining starting materials of sufficient purity. Details of the efforts to purify these materials are included. UV-Vis, 1H-NMR, and electrochemical characterization of [RuII(H2dcbpy)2pptd](PF6)2, and its adsorption to TiO2 electrodes, are included in the thesis. In addition, several well-known reference compounds have been characterized for comparison purposes

Floquet generation of Majorana end modes and topological invariants

We show how Majorana end modes can be generated in a one-dimensional system by varying some of the parameters in the Hamiltonian periodically in time. The specific model we consider is a chain containing spinless electrons with a nearest-neighbor hopping amplitude, a p-wave superconducting term and a chemical potential; this is equivalent to a spin-1/2 chain with anisotropic XY couplings between nearest neighbors and a magnetic field applied in the z-direction. We show that varying the chemical potential (or magnetic field) periodically in time can produce Majorana modes at the ends of a long chain. We discuss two kinds of periodic driving, periodic delta-function kicks and a simple harmonic variation with time. We discuss some distinctive features of the end modes such as the inverse participation ratio of their wave functions and their Floquet eigenvalues which are always equal to +/- 1 for time-reversal symmetric systems. For the case of periodic delta-function kicks, we use the effective Hamiltonian of a system with periodic boundary conditions to define two topological invariants. The first invariant is a well-known winding number while the second invariant has not appeared in the literature before. The second invariant is more powerful in that it always correctly predicts the numbers of end modes with Floquet eigenvalues equal to +1 and -1, while the first invariant does not. We find that the number of end modes can become very large as the driving frequency decreases. We show that periodic delta-function kicks in the hopping and superconducting terms can also produce end modes. Finally, we study the effect of electron-phonon interactions (which are relevant at finite temperatures) and a random noise in the chemical potential on the Majorana modes.Comment: 15 pages, 11 figures; added more numerical and analytical results about second topological invariant, and a discussion of effects of electron-phonon interactions and noise on Majorana end mode

A Comparative study on Ferro-fluid Lubricated Porous Journal Bearing

This research considered hydrodynamic theory on ferro-fluid flow models such as R. E. Rosensweig model and Jenkins model for axially undefined journal bearing with porous attached at the inner surface (i.e. on the journal). In this study, the variable external magnetic field is assumed. The expressions of (non-dimensional) pressure and load-carrying capacity are obtained. The values of load capacity for both models are calculated for various parameters like porous thickness, slip velocity, squeeze velocity, permeability, and eccentricity. Also, calculated load capacity by cons idering porous structure models like the globular sphere model and capillary fissures model. Based on the obtained results, the globular sphere model gives much better performance for load capacity rather than the capillary fissures model. From the study, it is suggested that to design the journal bearing, globular sphere model of porous structure should be preferred over the capillary fissures model. Also, for the better performance of the journal bearing, the choice of fluid-flow model depends on the values of parameters

Performance of Hydrodynamic Porous Slider Bearing with Water based Magnetic Fluid as a Lubricant: Effect of Slip and Squeeze Velocity

508-512This paper deals with performance of Hydrodynamic Porous inclined pad surface Slider Bearing considering slip and squeeze velocity. Water-lubricated bearings have been focused for their benefits to diminish the power loss and raise load capacity of bearing at rapid. Due to this advantage, lubricant used is water based magnetic fluid in this work. Also due to the functional property of self-lubrication, the effect of porosity is included. Under regular suppositions of hydrodynamic lubrication, the Neuringer-Rosensweig Model is considered for study. The expression of load capacity is obtained and calculated for choice of different values of squeeze velocity as well as slip velocity. It is seen that better load capacity is obtained when squeeze velocity as well as slip velocity are considered

Performance of hydrodynamic porous slider bearing using water based magnetic fluid as a lubricant: effect of slip and squeeze velocity

This paper deals with performance of Hydrodynamic Porous inclined pad surface Slider Bearing considering slip and squeeze velocity. Water-lubricated bearings have been focused for their benefits to diminish the power loss and raise load capacity of bearing at rapid. Due to this advantage, lubricant used is water based magnetic fluid in this work. Also due to the functional property of self-lubrication, the effect of porosity is included. Under regular suppositions of hydrodynamic lubrication, the Neuringer-Rosensweig Model is considered for study. The expression of load capacity is obtained and calculated for choice of different values of squeeze velocity as well as slip velocity. It is seen that better load capacity is obtained when squeeze velocity as well as slip velocity are considered

Broadening the ecological mindset

Over the past three decades, the Harvard Forest Summer Research Program in Ecology (HF-SRPE) has been at the forefront of expanding the ecological tent for minoritized or otherwise marginalized students. By broadening the definition of ecology to include fields such as data science, software engineering, and remote sensing, we attract a broader range of students, including those who may not prioritize field experiences or who may feel unsafe working in rural or urban field sites. We also work towards a more resilient society in which minoritized or marginalized students can work safely, in part by building teams of students and mentors. Teams collaborate on projects that require a diversity of approaches and create opportunities for students and mentors alike to support one another and share leadership. Finally, HF-SRPE promotes an expanded view of what it means to become an ecologist. We value and support diverse career paths for ecologists to work in all parts of society, to diversify the face of ecology, and to bring different perspectives together to ensure innovations in environmental problem solving for our planet

Quantification of Periodic Breathing in Premature Infants

Periodic breathing (PB), regular cycles of short apneic pauses and breaths, is common in newborn infants. To characterize normal and potentially pathologic PB, we used our automated apnea detection system and developed a novel method for quantifying PB. We identified a preterm infant who died of sudden infant death syndrome (SIDS) and who, on review of her breathing pattern while in the neonatal intensive care unit (NICU), had exaggerated PB. We analyzed the chest impedance signal for short apneic pauses and developed a wavelet transform method to identify repetitive 10-40 second cycles of apnea/breathing. Clinical validation was performed to distinguish PB from apnea clusters and determine the wavelet coefficient cutoff having optimum diagnostic utility. We applied this method to analyze the chest impedance signals throughout the entire NICU stays of all 70 infants born at 32 weeks\u27 gestation admitted over a two-and-a-half year period. This group includes an infant who died of SIDS and her twin. For infants of 32 weeks\u27 gestation, the fraction of time spent in PB peaks 7-14 d after birth at 6.5%. During that time the infant that died of SIDS spent 40% of each day in PB and her twin spent 15% of each day in PB. This wavelet transform method allows quantification of normal and potentially pathologic PB in NICU patients

Racial and Ethnic Variations in Lung Cancer Incidence and Mortality: Results From the Women’s Health Initiative

This study aimed to evaluate racial/ethnic differences in lung cancer incidence and mortality in the Women’s Health Initiative Study, a longitudinal prospective cohort evaluation of postmenopausal women recruited from 40 clinical centers

Persistence of serogroup C antibody responses following quadrivalent meningococcal conjugate vaccination in United States military personnel

AbstractSerogroup C meningococcal (MenC) disease accounts for one-third of all meningococcal cases and causes meningococcal outbreaks in the U.S. Quadrivalent meningococcal vaccine conjugated to diphtheria toxoid (MenACYWD) was recommended in 2005 for adolescents and high risk groups such as military recruits. We evaluated anti-MenC antibody persistence in U.S. military personnel vaccinated with either MenACYWD or meningococcal polysaccharide vaccine (MPSV4). Twelve hundred subjects vaccinated with MenACYWD from 2006 to 2008 or MPSV4 from 2002 to 2004 were randomly selected from the Defense Medical Surveillance System. Baseline serologic responses to MenC were assessed in all subjects; 100 subjects per vaccine group were tested during one of the following six post-vaccination time-points: 5–7, 11–13, 17–19, 23–25, 29–31, or 35–37 months. Anti-MenC geometric mean titers (GMT) were measured by rabbit complement serum bactericidal assay (rSBA) and geometric mean concentrations (GMC) by enzyme-linked immunosorbent assay (ELISA). Continuous variables were compared using the Wilcoxon rank sum test and the proportion of subjects with an rSBA titer ≥8 by chi-square. Pre-vaccination rSBA GMT was <8 for the MenACWYD group. rSBA GMT increased to 703 at 5–7 months post-vaccination and decreased by 94% to 43 at 3 years post-vaccination. GMT was significantly lower in the MenACWYD group at 5–7 months post-vaccination compared to the MPSV4 group. The percentage of MenACWYD recipients achieving an rSBA titer of ≥8 decreased from 87% at 5–7 months to 54% at 3 years. There were no significant differences between vaccine groups in the proportion of subjects with a titer of ≥8 at any time-point. GMC for the MenACWYD group was 0.14μg/mL at baseline, 1.07μg/mL at 5–7 months, and 0.66μg/mL at 3 years, and significantly lower than the MPSV4 group at all time-points. Anti-MenC responses wane following vaccination with MenACYWD; a booster dose is needed to maintain protective levels of circulating antibody