First-principles analysis of a homo-chiral cycloidal magnetic structure in a monolayer Cr on W(110)

The magnetic structure of a Cr monolayer on a W(110) substrate is investigated by means of first-principles calculations based on the noncollinear spin density functional theory (DFT). As magnetic ground state we find a long-period homochiral left-rotating spin spiral on-top of an atomic-scale anti-ferromagnetic order of nearest neighbor atoms. The rotation angle of the magnetic moment changes inhomogeneously from atom to atom across the spiral. We predict a propagation direction along the crystallographic [001] direction with a period length of 14.3 nm, which is in excellent agreement with a modulation of the local anti-ferromagnetic contrast observed in spin-polarized scanning tunneling microscope experiments by Santos et al. [New J. Phys. 10, 013005 (2008)]. We identify the Dzyaloshinskii-Moriya interaction (DMI) as origin of the homochiral magnetic structure, competing with the Heisenberg-type exchange interaction and magneto-crystalline anisotropy energy. From DFT calculations we extract parameters for a micromagnetic model and thereby determine a considerable inhomogeneity of the spin spiral, increasing the period length by 6% compared to homogeneous spin spirals. The results are compared to the behavior of a Mn and Fe monolayer and Fe doublelayer on a W(110) substrate

Role of Dzyaloshinskii-Moriya interaction for magnetism in transition-metal chains at Pt step-edges

We explore the emergence of chiral magnetism in one-dimensional monatomic Mn, Fe, and Co chains deposited at the Pt(664) step-edge carrying out an ab-initio study based on density functional theory (DFT). The results are analyzed employing several models: (i) a micromagnetic model, which takes into account the Dzyaloshinskii-Moriya interaction (DMI) besides the spin stiffness and the magnetic anisotropy energy, and (ii) the Fert-Levy model of the DMI for diluted magnetic impurities in metals. Due to the step-edge geometry, the direction of the Dzyaloshinskii vector (D-vector) is not predetermined by symmetry and points in an off-symmetry direction. For the Mn chain we predict a long-period cycloidal spin-spiral ground state of unique rotational sense on top of an otherwise atomic-scale antiferromagnetic phase. The spins rotate in a plane that is tilted relative to the Pt surface by $62^\circ$ towards the upper step of the surface. The Fe and Co chains show a ferromagnetic ground state since the DMI is too weak to overcome their respective magnetic anisotropy barriers. Beyond the discussion of the monatomic chains we provide general expressions relating ab-initio results to realistic model parameters that occur in a spin-lattice or in a micromagnetic model. We prove that a planar homogeneous spiral of classical spins with a given wave vector rotating in a plane whose normal is parallel to the D-vector is an exact stationary state solution of a spin-lattice model for a periodic solid that includes Heisenberg exchange and DMI. The validity of the Fert-Levy model for the evaluation of micromagnetic DMI parameters and for the analysis of ab-initio calculations is explored for chains. The results suggest that some care has to be taken when applying the model to infinite periodic one-dimensional systems.Comment: 21 pages, 9 figure

Genaue Messungen mit Femtosekundenfrequenzkämmen

In dieser Arbeit wurde die Femtosekunden (fs)-Frequenzkammtechnik, die in der Arbeitsgruppe von Prof. T. W. Hänsch entwickelt wurde, angewendet, um die Genauigkeit nichtlinearer Prozesse zu überprüfen und eine mögliche zeitliche Veränderung von Naturkonstanten nachzuweisen. Ein Frequenzkamm ist das Spektrum eines regelmäßigen kohärenten Pulszugs, der von einem modengekoppelten Laser ausgesendet wird. Die Frequenzen f_n der Kammoden sind durch f_n=f_ce+n*f_r gegeben. Dabei ist n eine natürliche Zahl der Größenordnung 10^6, f_r die Pulswiederholrate des Lasers und f_ce eine für alle Moden gleiche Frequenzverschiebung. Wird das Spektrum eines fs-Lasers mit Hilfe einer mikrostrukturierten Glasfaser auf eine Oktave verbreitert, so können die beiden Radiofrequenzen f_r und f_ce auf einfache Weise gemessen und kontrolliert werden. Einen fs-Frequenzkamm kann man sich dabei anschaulich als Getriebe vorstellen, der optische Frequenzen und Radiofrequenzen phasengenau miteinander verbindet. Das oktavenbreite Spektrum nach einer mikrostrukturierten Glasfaser wurde in dieser Arbeit dazu verwendet, um in einem nichtlinearen Kristall durch Summenfrequenzmischung (SFG) bzw. Differenzfrequenzmischung (DFG) zwei neue Frequenzkämme zu erzeugen, deren Frequenzverschiebung 2*f_ce (SFG) bzw. f_ce=0 (DFG) beträgt. Durch das Verschwinden von f_ce eignet sich der DFG-Kamm als stabiles Uhrwerk für zukünftige optische Uhren, von denen eine relative Genauigkeit von 10^(-18) erwartet wird, was etwa 1000 mal genauer ist als die besten Cs-Atomuhren der Welt. Ein Vergleich des erzeugten SFG- und DFG-Kamms mit dem Originalkamm gestattet darüber hinaus die Überprüfung der Genauigkeit nichtlinearer Prozesse mit einer relativen Genauigkeit von 6,6*10^(-21), was verglichen mit früheren Arbeiten eine 100 fache Verbesserung darstellt. Eine Abweichung von den erwarteten Werten konnte im Rahmen der Meßgenauigkeit nicht beobachtet werden. In Zusammenarbeit mit dem Wasserstofflabor in unserer Arbeitsgruppe wurde die Frequenz des 1S-2S Übergangs in atomarem Wasserstoff zu 2466061413187087+-34 Hz gemessen, was einer relativen Genauigkeit von 1,4*10^(-14) entspricht. Damit gehört die 1S-2S Frequenz zu den am besten bekannten optischen Frequenzen. Für ihre Messung wurde ein fs-Frequenzkammgenerator verwendet, der mit Hilfe der transportablen Cs-Fontänenuhr FOM des BNM-SYRTE/ENS, Paris stabilisiert wurde. Ein Vergleich mit der Messung aus dem Jahr 1999 ergibt eine relative zeitliche Änderung der 1S-2S Frequenz von (-3,2+-6,3)*10^(-15)/Jahr. Mit diesem Wert und optischen Frequenzmessungen am 199Hg+ bzw. 171Yb+ Ion, die am NIST in Boulder/Colorado bzw. an der PTB in Braunschweig durchgeführt wurden, konnte eine Obergrenze für die gegenwärtige zeitliche Änderung der Feinstrukturkonstante von (d/dt)alpha/alpha=(-0,3+-2,0)*10^(-15)/Jahr angegeben werden. Dieser Wert ist mit Null verträglich. Für seine Herleitung wurden keine Annahmen über das zeitliche Verhalten der anderen Kopplungskonstanten gemacht. Die ermittelten Obergrenzen sind daher weitgehend modellunabhängig

Health-related Quality Of Life And Self-reported Long-term Conditions: A Population-based Survey

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)To estimate and compare the effect of self-reported long-term health conditions and sociodemographic factors on perceived health-related quality of life (HRQoL). Methods: A population-based survey of adults (18 to 65 years) living in Brasilia, Brazil, was conducted in 2012. Descriptive and multivariate analyses using a Tobit model were performed with data on sociodemographic variables, self-reported conditions, and the European Quality of Life-5 Dimensions (EQ-5D) health states, providing utility scores (preferred health state) between 0 and 1 for HRQoL estimates. Results: The mean utility of 1,820 adults interviewed (mean age: 38.4612.6 years) was 0.883 (95% confidence interval [95% CI] 0.874-0.892), with 76.2% in the highest utility range (0.8 to 1.0). EQ-5D dimensions with moderate problems were pain/discomfort (33.8%) and anxiety/depression (20.5%). Serious problems were reported by only 0.3% of the sample in the mobility and self-care domain and by 3.1% in the pain/discomfort domain. Multivariate analysis revealed reduced HRQoL in individuals with depression, diabetes, and hypertension. Living in satellite towns (outside the city core), belonging to a lower economic class, or not being formally employed were also associated with decreased HRQoL. Beta coefficients for these impacts ranged from -0.033 (not formally employed) to -0.141 (depression), reflecting the strongest impact. Conclusion: Of the long-term health conditions studied, depression had the greatest impact on HRQoL. Social class, employment status, and place of residence also affected HRQoL.3916268Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) [564831/2010-7]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Influence of high-irradiance light curing on the marginal integrity of composite restorations in primary teeth

BACKGROUND Reducing the necessary time to restore primary teeth improves the cooperation of paediatric patients. This study aimed to investigate the marginal integrity of restorations prepared with a bulk-fill resin-based composite (RBC) containing additional fragmentation chain transfer (AFCT) compared to a conventional RBC when light cured with a rapid high-irradiance (3 s) and a regular (10 s) curing mode. METHODS Forty class-II cavities were prepared in 40 primary molars. The molars were randomly divided into four groups based on the applied light-curing modes (regular: 10 s @ 1200 mW/cm$^{2}$ or high-irradiance: 3 s @ 3000 mW/cm$^{2}$) and the used restorative material (AFCT-containing bulk-fill RBC "Power Fill" or AFCT-free conventional RBC "Prime"). After thermo-mechanical loading, the marginal integrity was analysed using scanning electron microscopy. A beta regression model and pairwise comparisons were used to statistically analyse the data. RESULTS The mean marginal integrity (% ± SD) of the restorations for each group was as follows: Power Fill (10 s: 79.7 ± 15.6) (3 s: 77.6 ± 11.3), Prime (10 s: 69.7 ± 11.1) (3 s: 75.0 ± 9.7). The difference between the RBCs for the same light-curing mode was statistically significant (p ≤ 0.05). The difference between the light-curing modes for the same RBC was not statistically significant (p ˃ 0.5). CONCLUSIONS AFCT-containing bulk-fill RBC "Power Fill" achieves similar marginal integrity when light-cured with either high-irradiance or regular light-curing modes. "Power Fill" achieves better marginal integrity than the conventional RBC "Prime" regardless of the applied light-curing mode

O engenho e a arte da tributação

Analisa um conceito controverso na economia: o tributo, sendo necessário destrinchar este o vocábulo quanto a sua evolução, aplicação e teorias relativas ao tema. Vale salientar que, para isso, serão apresentadas diferentes perspectivas históricas do tema, abrangendo tanto a esfera global, quanto a brasileira. Ainda serão explicados os princípios e as classificações dos tributos, além de sua aplicação no Brasil. Também não poderia deixar de fazer parte deste trabalho uma análise sobre o sistema de partilhas brasileiro e um exemplo internacional para servir de benchmarking para os leitores. Enfim, este trabalho objetiva responder algumas perguntas acercas do tema e deixar outras em aberto, visando a discussão deste conceito: o que esperamos? O que ele é? Como ele funciona? Qual seu intuito? Qual o seu impacto? Existe algum sistema que seja o mais adequado? Enfim, são muitas perguntas e é instigado por elas que se faz necessária esta monografia

Marginal Integrity of Simplified Adhesive Strategies in Primary Teeth

OBJECTIVE The aim of this research was to investigate the effect of simplified adhesive strategies (self-etch vs selective enamel etch and 10- vs 20-second adhesive application time) on the marginal integrity in primary molars. METHODS Forty deep class-II cavities were prepared in 40 extracted primary molars. The molars were divided into 4 groups based on the applied universal adhesive strategy as follows: groups 1 and 2: selective enamel etch with 20- or 10-second application time and groups 3 and 4: self-etch with 20- or 10-second application time. All cavities were restored with a sculptable bulk-fill composite restoration. The restorations underwent a thermomechanical loading (TML, 5-50 °C, 2-minute dwelling time, ×1000; 400,000 loading cycles, 1.7 Hz, 49 N). Marginal analysis before and after TML was conducted with scanning electron microscopy and the marginal integrity of each restoration was calculated as a percentage of continuous margins. A beta regression model was adopted to statistically analyse the data with a consequent pairwise comparison. RESULTS The mean marginal integrity (% ± SD) of the restorations for each tested adhesive strategy after TML was as follows: selective enamel etch/20 seconds = 85.4 ± 3.9, self-etch/20 seconds = 85.3 ± 5.2, self-etch/10 seconds = 80.1 ± 8.2, and selective enamel etch/10 seconds = 80.0 ± 8.5. The difference between both adhesive strategies was not statistically significant at the same application time. The difference between both application times within the same adhesive strategy was statistically significant (P ≤ .01). CONCLUSIONS Universal adhesives applied either in selective enamel etch or in self-etch mode result in comparable marginal integrities when restoring class-II cavities in primary molars. Shortened adhesive application time (10 seconds) could lead to a reduction in the marginal integrity in comparison to the recommended application time of 20 seconds

Fecal Glucocorticoid Measurements and Their Relation to Rearing, Behavior, and Environmental Factors in the Population of Pileated Gibbons ( Hylobates pileatus ) Held in European Zoos

Pileated gibbons (Hylobates pileatus) are rated as endangered according to the International Union of Conservation of Nature (IUCN) Red List. The captive population suffers from poor breeding success and is threatened to become overaged. Although several factors are likely to contribute to the poor breeding success, one in particular may be chronic stress associated with prolonged periods of high glucocorticoid (GC) output. We investigated fecal GC levels of pileated gibbons (Hylobates pileatus) and their relationship to specific life-history variables and environmental factors. After validation of an enzyme immunoassay for the measurement of 5-reduced 3α,11β-dihydroxy cortisol metabolites to assess GC output reliably in pileated gibbons, we collected fecal samples over several days from all 36 European adult pileated gibbons located in 11 institutions and compared GC levels to intrinsic individual parameters, husbandry, behavior, and breeding history. Age, sex, and origin (wild vs. captive born) had no effect on GC levels. However, unnaturally reared gibbons had higher GC levels and showed more behavioral abnormalities than parent-reared individuals. Further, nonreproducing gibbons living in a pair without infants had higher GC concentrations than gibbons living in a family, bachelor group, or as singletons. With respect to environmental factors, a large size of the inside enclosure and the existence of visual protection from visitors was associated with lower fecal GC output. The data indicate that rearing and housing conditions appear to correlate to GC levels in pileated gibbons housed under captive conditions. It is hoped this knowledge will support the future management of the species in captivity and thus lead to a more successful breeding of this endangered primat

Simulation Experiment Schemas - Beyond Tools and Simulation Approaches: Software appendix [research data]

This archive contains the software described in the paper "Simulation Experiment Schemas - Beyond Tools and Simulation Approaches" published at the Winter Simulation Conference 2019. The tool guides users through the simulation experiment specification process via a graphical user interface. The entered information is used in the generation of backend-independent experiment specifications in the JSON format. The JSON-based specifications can be mapped to different simulation backends. Currently, two domains of modeling and simulation are supported: stochastic discrete-event simulation, and finite element simulation for electromagnetics. For both domains, basic simulation runs are supported as well as complex experiment designs such as sensitivity analyses based on full factorial designs

Chymase-Cre; Mcl-1fl/fl Mice Exhibit Reduced Numbers of Mucosal Mast Cells

Mast cells (MCs) are considered as key effector cells in the elicitation of allergic symptoms, and they are essential players in innate and adaptive immune responses. In mice, two main types of MCs have been described: connective tissue MCs (CTMCs) and mucosal MCs (MMCs). However, little is known about the biological functions of MMCs, which is due to the lack of suitable models to investigate MMCs in vivo. Here, we aimed to generate a mouse model selectively deficient in MMCs. It has been previously described that Cre expressed under the control of the baboon α-chymase promotor is predominantly localized in MMCs. Therefore, we mated α-chymase-Cre transgenic mice with mice bearing a floxed allele of the myeloid cell leukemia sequence 1 (Mcl-1). Mcl-1 encodes for an intracellular antiapoptotic factor in MCs; hence, a selective reduction in MMCs was expected. Our results show that this new mouse model contains markedly reduced numbers of MMCs in mucosal tissues, whereas numbers of CTMCs are normal. Thus, Chm-Cre; Mcl-1fl/fl mice are a useful tool for the investigation of the pathophysiological functions of MMCs in vivo