Extraordinary nonlinear plasmonics in graphene nanoislands

Nonlinear optical processes rely on the intrinsically weak interactions between photons enabled by their coupling with matter. Unfortunately, many applications in nonlinear optics are severely hindered by the small response of conventional materials. Metallic nanostructures partially alleviate this situation, as the large light enhancement associated with their localized plasmons amplifies their nonlinear response to record high levels. Graphene hosts long-lived, electrically tunable plasmons that also interact strongly with light. Here we show that the nonlinear polarizabilities of graphene nanoislands can be electrically tuned to surpass by several orders of magnitude those of metal nanoparticles of similar size. This extraordinary behavior extends over the visible and near-infrared for islands consisting of hundreds of carbon atoms doped with moderate carrier densities. Our quantum-mechanical simulations of the plasmon-enhanced optical response of nanographene reveal this material as an ideal platform for the development of electrically tunable nonlinear optical nanodevices.Comment: 16 pages, 12 figures, 54 reference

Studies On The Physicochemical Properties Of Eu2+ Cryptates: Implications To Contrast Agents For Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a powerful medical imaging technique that can be enhanced using metal complexes called contrast agents. Most clinically approved contrast agents contain Gd3+. However, the efficiency (also known as relaxivity) of these Gd3+-containing complexes decreases as field strength increases, and in the ultra-high field strength regime, the relaxivity of these complexes is decreased considerably. Because of the slow water-exchange rate of most Gd3+-containing complexes (∼;106 s-1), I used Eu2+ instead of Gd3+ and adapted the ligand modification strategies that have been used for Gd3+-containing contrast agents to my Eu2+-containing complexes. Eu2+ is isoelectronic to Gd3+ and has fast water-exchange rate (∼;109 s-1); however, the propensity of Eu2+ to oxidize in aerobic conditions limits its utility. Earlier work in the Allen lab demonstrated that modified cryptands can stabilize the divalent state of Eu. Because of the favorable properties of Eu2+ and the ability of cryptands to oxidatively stabilize Eu2+, I hypothesized that Eu2+-containing cryptates could serve as good candidates for use as contrast agents for MRI. Relaxometric studies revealed higher efficacy of small Eu2+-containing cryptates compared to the clinically approved contrast agent gadolinium(III) 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate at ultra-high field strengths. Also, an increase in relaxivity with increasing field strength was observed for these cryptates. Further, the relaxivity of Eu2+-containing cryptates decreases as temperature increases, but is not affected by changes in pH in a physiologically relevant range. Variable-temperature 17O NMR and electron paramagnetic resonance spectroscopy were used to understand these observations in relaxivity. Variable-temperature 17O NMR experiments revealed the presence of two inner-sphere water molecules and fast water-exchange rates (∼;107-108 s-1) for small Eu2+-containing cryptates. With the relaxivity and 17O NMR and EPR data, rotational-correlation rates for these cryptates were estimated and were found to limit relaxivity. In addition to relaxometric studies, transmetallation experiments were performed in the presence of Ca2+, Mg2+, and Zn2+ because of their relative abundance in plasma and the affinity of these ions for ligands. The transmetallation experiments demonstrated that amine-based cryptates are stable to transmetallation in the presence of Ca2+, Mg2+, and Zn2+ and are more stable than the clinically approved gadolinium(III) diethylenetriaminepentaacetate, a promising result for their potential use for in vivo applications. Because relaxivity of small Eu2+-containing cryptates increases with molecular weight, I also investigated the effect of albumin on the relaxivity of a biphenyl-containing cryptate. While relaxivity enhancement was observed in the presence of albumin at 1.4 T, the relaxivity of the biphenyl-based cryptate in the presence of albumin at 3, 7, 9.4, and 11.7 T was lower compared to in the absence of albumin. This decrease in relaxivity was attributed to a displacement of one inner-sphere water molecule upon protein binding. These studies of the physicochemical properties of Eu2+-containing cryptates provide a better understanding of how relaxivity is influenced by molecular parameters including the number of inner-sphere water molecules, water-exchange rate, and rotational-correlation rate for these cryptates and pave the way for designing more efficient Eu2+-containing cryptates for use as contrast agents for MRI

U.S. SDG Data Revolution Roadmap

One year after adopting the SDGs, in an addendum to its Open Government National Action Plan, the U.S. Government committed to develop an SDG Data Revolution Roadmap that "charts the future course of efforts to fill data gaps and build capacity to use data for decision-making and innovation to advance sustainable development." The U.S. Government's SDG Data Revolution Roadmap will outline the government's commitments-to-action from 2017-2018. With a deadline of June 2017, it will be developed by the U.S. Government "through an open and inclusive process that engages the full range of citizen, non-governmental, and private sector stakeholders."This report represents the beginning of that engagement process. On December 14, 2016, the Center for Open Data Enterprise and the Global Partnership for Sustainable Development Data convened a Roundtable to develop recommended priorities for the U.S. Government's SDG Data Revolution Roadmap The Roundtable brought together more than 40 stakeholders from government, civil society, and the private sector with expertise in achieving and promoting sustainable development

The Regulation of Mitochondrial Complex I Biogenesis in Drosophila Flight Muscles

Mitochondrial Complex I (CI) is composed of 44 distinct subunits that are assembled with eight Fe- S clusters and a single flavin mononucleotide. Mitochondria is highly enriched in the flight muscles of Drosophila melanogaster, however the assembly mechanism of Drosophila CI has not been described. We report that the mechanism of CI biogenesis in Drosophila flight muscles proceeds via the formation of ~315- , ~550-, and ~815 kDa CI assembly intermediates. Additionally, we define specific roles for several CI subunits in the assembly process. In particular, we show that dNDUFS5 is required for converting the ~700 kDa transient CI assembly intermediate into the ~815 kDa assembly intermediate, by stabilizing or promoting the incorporation of dNDUFA10 into the complex. Our findings highlight the potential values of Drosophila as a suitable model organism and resource to study the CI biogenesis in vivo, and to address questions relevant to CI biogenesis in humans. CI biogenesis is regulated by transient interactors known as CI assembly factors (CIAFs). To date, about half of CI disorders are attributed to the mutations in the CI subunits and the known CIAFs. The cause for the other half remains to be discovered, warranting the investigation for additional regulators of CI biogenesis such as novel CIAFs. To identify novel regulators, we cataloged interactors of a core subunit, NDUFS3, knocked each one down by RNAi in the Drosophila flight muscle, and analyzed its effect in the stability of CI by blue-native PAGE. We identified the Drosophila Fragile X Mental Retardation protein (dFMRP) to destabilize the holoenzyme of CI and cause it to misassemble. Therefore, we report dFMRP as a novel regulator of CI biogenesis, and demonstrate the utilization of Drosophila as an effective model system to uncover the mysteries of CI biogenesis

Dynamic modelling and simulation of electric power systems using the Newton-Raphson method

The research work presented in this thesis is concerned with the development of a dynamic power flow computer algorithm using Newton's method. It addresses both the development of a positive sequence dynamic power flow algorithm for the dynamic study of balanced power systems and a fully-fledged three-phase dynamic power flow algorithm for the dynamic study of power systems exhibiting a significant degree of either structural or operational unbalance. As a prelude to the research work on dynamic power flows, a three-phase Newton-Raphson power flow algorithm in rectangular co-ordinates with conventional HVDC power plant modelling is presented in this thesis, emphasising the representation of converter control modes. The solution approach takes advantage of the strong numerical solutions for combined HVAC-HVDC systems, where power plant and operational imbalances are explicitly taken into account. The dynamic algorithm is particularly suited to carrying out long-term dynamic simulations and voltage stability assessments. Dynamic model representations of the power plants components and the load tap changing transformer are considered, and to widen the study range of dynamic voltage phenomena using this method, extensions have been made to include induction motor and polynomial load modelling features. Besides, reactive power compensators that base their modus operandi on the switching of power electronic valves, such as HVDC-VSC and the STATCOM are taken into account. The dynamic power flow algorithm has primarily been developed making use of the positive sequence and [dq] representations. Extensions are made to developing a three-phase power flows dynamic algorithm. Test cases for the various dynamic elements developed in this research are presented to show the versatility of the models and simulation tool, including a trip cascading event leading up to a wide-area voltage collaps. Comparisons with the output of a conventional transient stability program carried out where appropriate

Berries driven (poly)phenols-induced cytoprotection in cardiomyocytes

Cardiovascular diseases (CVDs) are a prominent health problem, being the leading cause of death worldwide. Numerous studies have been focus on the beneficial effects of dietary (poly)phenols, as a way to prevent the onset of CVDs. Recently, a link between CVDs, metabolism, mitochondria and diet has been evidenced. This link might involve a crosstalk between mitochondria functions, autophagy and cell death and would be regulated at the cellular level by various classes of sensors such as proteins as well as second messengers. The purpose of this study is to evaluate the potential of novel berries driven (poly)phenols (BDP) metabolites in cardioprotection and unravel the BDP-targeted cytoprotective mechanisms namely in mitochondrial functionality. Therefore studies were conducted using H9c2 cells and neonatal rat cardiomyocytes treated with tert-butyl hydroperoxide or isoproterenol to promote cell death, modeling chronical cardiac diseases. Analysis of mitochondrial population, in neonatal rat cardiomyocytes and H9c2 cells respectively, showed that BDP metabolites induce an increase of mitochondrial population. Moreover BDP metabolites appear to not protect against cell death induced by isoproterenol activated pathway. An important finding in this work was that BDP metabolites are capable of improving cardiac contractile functions, without decreasing isoproterenol induced cell death. Although not completely conclusive, the obtained results support a need for future research, as these compounds can be promising therapeutic agents in CVDs prevention fostering an active and healthy ageing. Given the growing number of cardiovascular incidents, being able to possibly develop a prophylactic drug against CVDs, would be a great achievement. Creating a prophylactic drug from BDP metabolites, would help people with a propensity to CVDs keeping a higher quality of life and reduce the need for expensive cardiac treatments

ATM SURCHARGES: EFFECTS ON DEPLOYMENT AND WELFARE

This paper analyzes the effects of ATM surcharges on deployment and welfare, in a model where banks compete for ATM and banking services. Foreign fees, surcharges and the interchange fee are endogenously determined. We find that, when the interchange fee is cooperatively fixed by banks to maximize joint profits, surcharges should be allowed, as they neutralize the collusive effect of the interchange fee. As a consequence, ATM deployment is higher and retail prices lower than without surcharges, increasing consumer surplus and social welfare.ATM, surcharge, foreign fee, interchange fee, collusion

Arithmetical structures on bidents

An arithmetical structure on a finite, connected graph $G$ is a pair of vectors $(\mathbf{d}, \mathbf{r})$ with positive integer entries for which $(\operatorname{diag}(\mathbf{d}) - A)\mathbf{r} = \mathbf{0}$, where $A$ is the adjacency matrix of $G$ and where the entries of $\mathbf{r}$ have no common factor. The critical group of an arithmetical structure is the torsion part of the cokernel of $(\operatorname{diag}(\mathbf{d}) - A)$. In this paper, we study arithmetical structures and their critical groups on bidents, which are graphs consisting of a path with two "prongs" at one end. We give a process for determining the number of arithmetical structures on the bident with $n$ vertices and show that this number grows at the same rate as the Catalan numbers as $n$ increases. We also completely characterize the groups that occur as critical groups of arithmetical structures on bidents.Comment: 32 page

[Cyanil]2 2- dimers possess long, two-electron ten-center (2e-/10c) multicenter bonding

Journal ArticleA long, two-electron ten-center (2e-/10c) [8 carbon plus 2 oxygen] bond in diamagnetic dimers of radical-anion tetracyano-1,4-benzoquinoneide (cyanil, [Q]2 2-, is described by B2LYP and CASSCF92,2)/MCQDPT calculations