1,354,884 research outputs found
Photocatalytic oxidation of multicomponent solutions of herbicides: Reaction kinetics analysis with explicit photon absorption effects
No full textThe intrinsic reaction kinetics of the photocatalytic oxidation (PCO) of the herbicides isoproturon, simazine and propazine over irradiated TiO2 (Degussa P25) suspensions was studied in single-component and in multicomponent systems. Experiments were carried out at different photon fluxes and different herbicide concentrations in the range below 1 mg L-1. The results were analyzed in terms of a Langmuir-Hinshelwood (L-H) kinetic model previously established for multicomponent solutions of herbicides, but including the explicit effect of photon absorption. This was accomplished by modeling the radiation field in the reactor with the Six-Flux Absorption-Scattering Model (SFM) (i.e., scattered photons follow the route of the six directions of the Cartesian coordinates) using optical parameters averaged across the spectrum of the incident radiation. The intrinsic reaction kinetic constants of isoproturon, simazine and propazine independent of the radiation field in the reactor were determined. The oxidation rate of the herbicides was found to follow half-order dependence with respect to the local volumetric rate of photon absorption (LVRPA), in the range of photon fluxes investigated. The established model was found to be appropriate to predict the time-dependent degradation profiles of the herbicides in single- and multicomponent systems not only at all radiation intensities investigated in this study but also when one or two herbicides were present in excess of the others in the mixture. Using this simple approach, intrinsic kinetic data can be obtained. © 2006 Elsevier B.V. All rights reserved
Assessing Changes in Wage Gaps: A New Approach
No full textLittle work has been done on directly estimating differences in pay gaps. Studies that
estimate pay differentials generally compare them across different sub-samples or rely on
decompositions that are based on the assumption of independent errors across samples.
Both methods contain serious drawbacks that we overcome by proposing an extension of the
Oaxaca-Blinder decomposition. Our proposed method overcomes both the index number
and the indeterminacy problem of standard Oaxaca-Blinder decompositions. In addition,
like the standard decomposition, our proposed approach can be extended beyond the mean
by using linear unconditional quantile regressions and can be decomposed in detail. We
present two empirical applications to illustrate the methodology
Is There a Union Wage Premium in Germany and Which Workers Benefit Most?
No full textUsing representative data from the German Socio-Economic Panel (SOEP), this paper finds
a statistically significant union wage premium in Germany of almost three percent, which is not
simply a collective bargaining premium. Given that the union membership fee is typically about
one percent of workers’ gross wages, this finding suggests that it pays off to be a union member.
Our results show that the wage premium differs substantially between various occupations and
educational groups, but not between men and women. We do not find that union wage premia are
higher for those occupations and workers which constitute the core of union membership. Rather,
unions seem to care about disadvantaged workers and pursue a wider social agenda
Coherent networks of polariton condensates in microcavities
No full textThe study of interacting many-element systems is as vital for our understanding of complex organisms, as it is important for the modelling of disease spreading in pandemics, and is a key element in the search for materials with novel properties. The presence of nonlinearities and interaction time-lags critically influences the dynamics and complicates control over these systems. Moreover, complexity in network structures rapidly scales with a larger number of elements and increasing degrees of freedom, often making them computationally intractable. Artificially engineered networks, on the other hand, can be used for the simulation and study of interacting systems, and pave the way for novel and unconventional computing paradigms. The implementation of these schemes is being explored in various fields such as electronics, photonics and quantum systems. In particular, lattices of polariton condensates in optical microcavities present a promising platform for the realisation of coupled network structures. Microcavity polaritons are light-weight bosonic quasi-particles formed by the strong coupling of cavity photons and quantum well excitons. Their hybrid light-matter character facilitates macroscopically accessible quantum degenerate states (condensates) at elevated temperatures. Large optical malleability, picosecond-timescale dynamics, and strong intrinsic nonlinearities highlight the potential of polariton lattices for future technological applications. The work presented in this PhD thesis investigates the interactions of coupled polariton condensates, and shows substantial advancements in both, the engineering and the manipulation of optically generated condensate lattices. In particular, the introduction of a laser feedback scheme for condensate density stabilisation makes it possible to accurately build macroscopic lattices of tuneable size and network architecture. The nonlinear dynamics and synchronisation phenomena of coupled condensates are explored in various coupling topologies, ranging from simply-connected structures to one- and two-dimensional periodic systems. Shaping of the polariton potential landscape by using spatially patterned lasers opens up an all-optical method of controlling couplings, interaction time-lags, and coherence properties in condensate lattices. The results and methods presented support the realisation of an ultra-fast delay-coupled nonlinear oscillator network, with precise control over individual couplings
The Abbey at St Albans and its relationship with its lordship in the Later Middle Ages
No full textThis thesis aims to examine the relationship between the monks and monastery of St Albans, and the townspeople and the tenants on the manors it held, including a case study on the manor of Codicote, by considering how the nature of this relationship changed throughout the history of the abbey from one of dependency to independence, and of animosity to acceptance. It will analyse events from the foundation of the monastery when the town grew around the abbey, to the problems of the fourteenth century, and finally, the Dissolution.This thesis concludes that the relationship between the monastery and the town of St Albans and its surrounding manors had three phases: the first phase took place from the foundation of the abbey through to the fourteenth century, where the town and monastery were dependent on one another. The second was during the fourteenth century, where the townspeople fought for their freedoms while the third was from the end of the fourteenth century through to the Dissolution when the town was able to function without the monastery, but still maintained a productive relationship that continued until after 1539 when the abbey was dissolved.This thesis is an addition to the work that has already been completed on both St Albans and Benedictine monasteries. It will go beyond the vast historiography on the subject by examining the relationship between town and abbey not as a simple political or financial one, but instead, as a complex changing relationship with multiple layers evolving over time
Gender wage inequality: new evidence from penalized expectile regression
No full textThe Machado-Mata decomposition building on quantile regression has been extensively analyzed in the literature focusing on gender wage inequality. In this study, we generalize the Machado-Mata decomposition to the expectile regression framework, which, to the best of our knowledge, has never been applied in this strand of the literature. In contrast, in
recent years, expectiles have gained increasing attention in other contexts as an alternative to traditional quantiles, providing useful statistical and computational properties. We flexi bly deal with high-dimensional problems by employing the Least Absolute Shrinkage and
Selection Operator. The empirical analysis focuses on the gender pay gap in Germany and Italy. We find that depending on the estimation approach (i.e. expectile or quantile regres sion) the results substantially differ along some regions of the wage distribution, whereas they are similar for others. From a policy perspective, this finding is important as it affects conclusions about glass ceiling and sticky floors
Bourses de Master et Doctorat de la Fondation Alfred Toepfer Stiftung F.V.S
No full textLa Fondation Alfred Toepfer Stiftung F.V.S est à l'origine de la mise en place du KOLLEG EUROPA, projet conduit en partenariat avec la Studienstiftung des deutschen Volkes et le DAAD.Ce collège européen a pour objectif de créer un réseau de citoyens européens extrêmement bien informés, engagés et connaissant parfaitement les particularités de la ou des culture/s européenne/s, afin d’œuvrer au rapprochement entre les nations en Europe et au-delà de ses frontières. L'Alfred Toepfer Stiftung F.V..
The Gender Pay Gap Revisited: Does Machine Learning offer New Insights?
No full textThis paper analyses gender differences in pay at the mean as well as along the wage distribution in Germany. We estimate the adjusted gender pay gap applying a machine learning method (post-double-LASSO procedure). Comparing results from this method to conventional models in the literature, we find that the estimated gap differs substantially depending on the approach used. The main reason is that the machine learning approach selects numerous interactions and second-order polynomials as well as different covariates at various points of the distribution. This insight suggests that more flexible specifications are needed to estimate gender differences in pay more appropriately
Follow-up of a Cementless Stem in Total Hip Arthroplasty with Proximal Spongy Metal Surface
No full textZiel des alloplastischen Gelenkersatzes des Hüftgelenkes ist das Wiedererlangen einer schmerzfreien, biomechanischen Funktion zur Sicherung oder Verbesserung der Lebensqualität. Dies soll durch die dauerhafte knöcherne Integration eines Implantats erreicht werden. Der in dieser Studie untersuchte Stiel Modell G2 der Firma ESKA Implants weist eine Spongiosametalloberfläche mit dreidimensionaler makroporöser Gitternetzstruktur auf, welche auf die proximalen zwei Drittel begrenzt ist, eine proximale Krafteinleitung ermöglicht und zementfrei implantiert wird. Ziel dieser retrospektiven Studie war es, Standzeiten und funktionelle Ergebnisse der 77 nachuntersuchten Patienten durchschnittlich 7,8 Jahre nach Implantation zu erfassen. Hierbei weist der G2 Hüftstiel sehr gute funktionelle und klinische Ergebnisse bei ausgezeichneter Standzeit des Implantates auf.The purpose of total hip arthroplasty is to regain a biomechanical and painfree functioning of the joint to ensure or improve the quality of life. This is thought to be obtained by permanent bony in-growth of a prosthesis. In this study the G2 stem by ESKA Implants was investigated. This is a cementless spongy metal prosthesis with a tridimensional porous coating grid that is limited to the proximal two thirds of the stem and thus allows proximal inducement of loading stress. The retrospective study aimed to investigate survival rates as well as functional results. 77 patients were followed-up at a mean of 7.8 years after total hip replacement. We report very good functional results and excellent survival rates
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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