Closed Form Solutions for Term Structure Derivatives with Log-Normal Interest Rates

We derive a unified model which gives closed form solutions for caps and floors written on interest rates as well as puts and calls written on zero-coupon bonds. The crucial assumption is that forward rates with a compounding period that matches the contract, which we want to price, is log-normally distributed. Moreover, this assumption is shown to be consistent with the Heath-Jarrow-Morton model for a specific choice of volatility.Log-normal, nominal-compounding rates, Heath-Jarrow- Morton model

Lognormality of Rates and Term Structure Models

A term structure model with lognormal type volatility structure is proposed. The Heath, Jarrow and Morton (HJM) framework, coupled with the theory of stochastic evolution equations in infinite dimensions, is used to show that the resulting rates are well defined (they do not explode) and remain positive. They are bounded from below and above by lognormal processes. The model can be used to price and hedge caps, swaptions and other interest rate and currency derivatives including the Eurodollar futures contract, which requires integrability of one over zero coupon bond. This extends results obtained by Sandmann and Sondermann (1993), (1994) for Markovian lognormal short rates to (non-Markovian) lognormal forward rates.Term structure of interest rates, lognormal volatility structure, Heath, Jarrow and Morton models.

Placemaking in action: Factors that support or obstruct the development of urban community gardens

The paper examines factors that support or obstruct the development of urban community garden projects. It combines a systematic scholarly literature review with empirical research from case studies located in New Zealand and Germany. The findings are discussed against the backdrop of placemaking processes: urban community gardens are valuable platforms to observe space-to-place transformations. Following a social-constructionist approach, literature-informed enablers and barriers for the development of urban community gardens are analysed against perceived notions informed by local interviewees with regard to their biophysical and technical, socio-cultural and economic, and political and administrative dimensions. These dimensions are incorporated into a systematic and comprehensive category system. This approach helps observe how the essential biophysical-material base of the projects is overlaid with socio-cultural factors and shaped by governmental or administrative regulations. Perceptual differences become evident and are discussed through the lens of different actors

O design educacional para a modalidade a distância em uma perspectiva inclusiva: contribuições para/na formação docente.

Este estudo, de cunho qualitativo, analisou o Design Educacional para a modalidade a distância no Centro de Educação a Distância do Instituto Federal do Espírito Santo recorrendo a uma pesquisa-ação com três grupos focais: Grupo 1 - equipe de produção de recursos educacionais; Grupo 2 - professores-formadores em Educação a Distância e Grupo 3 - alunosprofessores do curso de Capacitação em Práticas para Educação a Distância para Professores na modalidade a distância. O Design Educacional envolve diferentes áreas de conhecimento e aportes teóricos, sendo que este estudo optou pelas contribuições de Piaget e de Vigotski no que se refere ao processo de aprendizagem e interação social; Moore e Kearsley, nas questões que envolvem a Educação a Distância; Filatro e Torezzan para o Design Instrucional. Nas discussões suscitadas no Grupo 1, da equipe de produção de recursos educacionais, foram identificadas dentre várias questões, as principais dificuldades e desafios do Design Educacional na sociedade contemporânea. A coleta de dados e a análise dos resultados dessas discussões culminaram na criação de uma Taxonomia para o uso das Mídias, além de contribuições relevantes para a criação de alguns recursos educacionais. O Grupo 2, dos professores-formadores, apoiado nos resultados do Grupo 1, tendo em vista a inclusão de alguns alunos-professores convidados, graduados e deficientes - três com surdez e dois deficientes visuais -, contribuiu para evidenciar as ações-reflexões do Design Educacional no curso escolhido, adotando uma perspectiva inclusiva, inspirada no Universal Design for Learning. O Grupo 3, de alunos-professores, avaliou as ações resultantes da pesquisa. Recorreu-se a cinco categorias de análise dos dados: o Design Educacional na instituição pesquisada; a relação entre os professores-formadores e o Design Educacional; representações sobre o processo de ensino e de aprendizagem dos profissionais envolvidos no Design Educacional; alunos-professores em formação para a Educação a Distância; as perspectivas do Design Educacional na sociedade contemporânea. Os resultados obtidos trouxeram contribuições teóricas e práticas para a formação docente, acarretando, ainda: mudanças de conduta dos Grupos 1 e 2 no planejamento e na produção de recursos educacionais; além da proposta de inclusão de uma equipe de Design Educacional junto à equipe de produção, com uma consequente melhora do trabalho colaborativo. Foi destacada, também, a necessidade de uma melhor definição das concepções e do modelo de educação a distância adotado pelo Instituto Federal do Espírito Santo, o que, por sua vez, impactariam no Design Educacional em uma perspectiva inclusiva

LapG, Required for Modulating Biofilm Formation by Pseudomonas fluorescens Pf0-1, Is a Calcium-Dependent Protease

Biofilm formation by Pseudomonas fluorescens Pf0-1 requires the cell surface adhesin LapA. We previously reported that LapG, a periplasmic cysteine protease of P. fluorescens, cleaves the N terminus of LapA, thus releasing this adhesin from the cell surface and resulting in loss of the ability to make a biofilm. The activity of LapG is regulated by the inner membrane-localized cyclic-di-GMP receptor LapD via direct protein-protein interactions. Here we present chelation and metal add-back studies demonstrating that calcium availability regulates biofilm formation by P. fluorescens Pf0-1. The determination that LapG is a calcium-dependent protease, based on in vivo and in vitro studies, explains the basis of this calcium-dependent regulation. Based on the crystal structure of LapG of Legionella pneumophila in the accompanying report by Chatterjee and colleagues (D. Chatterjee et al., J. Bacteriol. 194:4415–4425, 2012), we show that the calcium-binding residues of LapG, D134 and E136, which are near the critical C135 active-site residue, are required for LapG activity of P. fluorescens in vivo and in vitro. Furthermore, we show that mutations in D134 and E136 result in LapG proteins no longer able to interact with LapD, indicating that calcium binding results in LapG adopting a conformation competent for interaction with the protein that regulates its activity. Finally, we show that citrate, an environmentally relevant calcium chelator, can impact LapG activity and thus biofilm formation, suggesting that a physiologically relevant chelator of calcium can impact biofilm formation by this organism

Structural Characterization of a Conserved, Calcium-Dependent Periplasmic Protease from Legionella pneumophila

The bacterial dinucleotide second messenger c-di-GMP has emerged as a central molecule in regulating bacterial behavior, including motility and biofilm formation. Proteins for the synthesis and degradation of c-di-GMP and effectors for its signal transmission are widely used in the bacterial domain. Previous work established the GGDEF-EAL domain-containing receptor LapD as a central switch in Pseudomonas fluorescens cell adhesion. LapD senses c-di-GMP inside the cytosol and relays this signal to the outside by the differential recruitment of the periplasmic protease LapG. Here we identify the core components of an orthologous system in Legionella pneumophila. Despite only moderate sequence conservation at the protein level, key features concerning the regulation of LapG are retained. The output domain of the LapD-like receptor from L. pneumophila, CdgS9, binds the LapG ortholog involving a strictly conserved surface tryptophan residue. While the endogenous substrate for L. pneumophila LapG is unknown, the enzyme processed the corresponding P. fluorescens substrate, indicating a common catalytic mechanism and substrate recognition. Crystal structures of L. pneumophila LapG provide the first atomic models of bacterial proteases of the DUF920 family and reveal a conserved calcium-binding site important for LapG function

Unusual light spectra from a two-level atom in squeezed vacuum

We investigate the interaction of an atom with a multi-channel squeezed vacuum. It turns out that the light coming out in a particular channel can have anomalous spectral properties, among them asymmetry of the spectrum, absence of the central peak as well as central hole burning for particular parameters. As an example plane-wave squeezing is considered. In this case the above phenomena can occur for the light spectra in certain directions. In the total spectrum these phenomena are washed out.Comment: 16 pages, LaTeX, 3 figures (included via epsf

Comparing the Ligand Behavior of N-Heterocyclic Phosphenium and Nitrosyl Units in Iron and Chromium Complexes

N-Heterocyclic phosphenium (NHP) and nitro-sonium (NO+) ligands are often viewed as isolobal analogues that share the capability to switch between different charge states and thus display redox "noninnocent" behavior. We report here on mixed complexes [(NHP)M(CO)(n)(NO)] (M = Fe, Cr; n = 2, 3), which permit evaluating the donor/acceptor properties of both types of ligands and their interplay in a single complex. The crystalline target compounds were obtained from reactions of N-heterocyclic phosphenium triflates with PPN[Fe(CO)(3)(NO)] or PPN[Cr(CO)(4)-(NO)], respectively, and fully characterized (PPN = nitride-bistriphenylphosphonium cation). The structural and spectroscopic (IR, UV-vis) data support the presence of carbene-analogue NHP ligands with an overall positive charge state and pi-acceptor character. Even if the structural features of the M-NO unit were in all but one product blurred by crystallographic CO/NO disorder, spectroscopic studies and the structural data of the remaining compound suggest that the NO units exhibit nitroxide (NO-) character. This assignment was validated by computational studies, which reveal also that the electronic structure of iron NHP/ NO complexes is closely akin to that of the Hieber anion, [Fe(CO)(3)(NO)](-). The electrophilic character of the NHP units is further reflected in the chemical behavior of the mixed complexes. Cyclic voltammetry and IR-SEC studies revealed that complex [(NHP)Fe(CO)(2) (NO)] (4) undergoes chemically reversible one-electron reduction. Computational studies indicate that the NHP unit in the resulting product carries significant radical character, and the reduction may thus be classified as predominantly ligand-centered. Reaction of 4 with sodium azide proceeded likewise under nucleophilic attack at phosphorus and decomplexation, while super hydride and methyl lithium reacted with all chromium and iron complexes via transfer of a hydride or methyl anion to the NHP unit to afford anionic phosphine complexes. Some of these species were isolated after cation exchange or trapped with electrophiles (H+, SnPh3(+)) to afford neutral complexes representing the products of a formal hydrogenation or hydrostannylation of the original M=P double bond.Peer reviewe

Wavelength-Scale Imaging of Trapped Ions using a Phase Fresnel lens

A microfabricated phase Fresnel lens was used to image ytterbium ions trapped in a radio frequency Paul trap. The ions were laser cooled close to the Doppler limit on the 369.5 nm transition, reducing the ion motion so that each ion formed a near point source. By detecting the ion fluorescence on the same transition, near diffraction limited imaging with spot sizes of below 440 nm (FWHM) was achieved. This is the first demonstration of imaging trapped ions with a resolution on the order of the transition wavelength.Comment: 8 pages, 3 figure

Generation of a wave packet tailored to efficient free space excitation of a single atom

We demonstrate the generation of an optical dipole wave suitable for the process of efficiently coupling single quanta of light and matter in free space. We employ a parabolic mirror for the conversion of a transverse beam mode to a focused dipole wave and show the required spatial and temporal shaping of the mode incident onto the mirror. The results include a proof of principle correction of the parabolic mirror's aberrations. For the application of exciting an atom with a single photon pulse we demonstrate the creation of a suitable temporal pulse envelope. We infer coupling strengths of 89% and success probabilities of up to 87% for the application of exciting a single atom for the current experimental parameters.Comment: to be published in Europ. Phys. J.