A catalytically active particulate filter with a first order catalytic reaction taking place inside the filter walls is investigated by numerical simulation. The conversion efficiency for different ...channel geometries and operating conditions is systematically studied as a function of the governing dimensionless parameters. It is found that the conversion efficiency of a catalytically coated wall flow filter is very close to that of an ideal plug flow reactor over the full range of realistic operating conditions. Only in a range of intermediate residence times, the filter reactor shows some diffusion limitation which leads to conversion efficiencies slightly below that of the plug flow reactor. In all cases, these deviations from ideal conversion behaviour are below 15%.
If the filter and the open monolith are compared at identical operating conditions and channel geometries, for fast reactions, the filter reactor shows higher conversion efficiency than the open monolith, since in this case the open monolith becomes strongly mass transfer limited.
However, there can be a small range of conditions where the monolith is slightly more efficient than the filter. The reason for this effect is that due to the thinner washcoat layer the onset of mass transfer limitation in the coated monolith is shifted to higher reaction rates, compared to the filter reactor.
•Conversion efficiency of catalyzed particulate filters was studied.•Conversion studied as function of the governing dimensionless parameters.•Conversion efficiency of catalysed filter is very close to ideal plug flow reactor.•Systematic comparison of filter reactor and conventional open monolith.
Working memory training is a useful tool to examine dissociations between specific working memory processes. Although current models propose a distinction between modality-specific working memory ...processes, to our knowledge no study has directly examined the effects of visual versus auditory working memory training. Functional magnetic resonance imaging was used to investigate whether visual working memory processes can be trained specifically and whether those effects can be separated from across-modal training effects. We found decidedly larger training gains after visual working memory training compared with auditory or no training on a visual 2-back task. These effects were accompanied by specific training-related decreases in the right middle frontal gyrus arising from visual training only. Likewise, visual and auditory training led to decreased activations in the superior portion of the right middle frontal gyrus and the right posterior parietal lobule. We infer that the combination of effects resulted from increased neural efficiency of intra-modal (visual) processes on the one hand and of across-modal (general control) processes on the other hand. Therefore, visual processes of working memory can be trained specifically, and these effects can be functionally dissociated from alterations in general control processes common to both working memory trainings.
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•A practical, model-based, ammonia dosing strategy is presented.•The dosing strategy is optimized and applied to SCR demonstration examples.•Performance comparison of different ...catalyst materials (iron and copper).•Investigating the sensitivity of the performance towards change in storage capacity.•The examples demonstrate the importance of an individually adjusted dosing strategy.
In today’s vehicle applications, SCR ammonia dosing is completed using complex control algorithms that need to be parameterized for the individual catalyst technology. Owing to the complexity of the parameterization procedures, ammonia dosing is frequently completed using either oversimplified dosing strategies (e.g., constant NH3/NOx ratio) or strategies previously optimized for different catalysts during the early design phase’s simulation and laboratory studies.
This paper presents a practical, model-based approach that allows for simulation and laboratory studies to be performed with an individually adapted dosing profile. The procedure is based on conventional feedback control strategies, where the average ammonia storage level is controlled using a temperature dependent setpoint (the desired storage level), which is interpolated from a look-up table. The approach of this paper is to optimize numerically the entries of this look-up table for a given test cycle such that the NOx conversion is maximized while the ammonia slip is kept below a defined level. Although the optimization is performed for a particular cycle, it is demonstrated that the dosing strategies obtained in this way also work reasonably well for other test cycles.
The proposed procedure was applied in a catalyst screening simulation study that compared the performance of an Fe– and a Cu–zeolite catalyst for a given test cycle. It was demonstrated that each of the two catalysts appeared to have a better performance than the other catalyst when the specified catalyst’s optimized dosing profile was applied to both catalysts. The best catalyst was only identified when comparing both catalysts using their own respective optimized dosing profile. A second simulation study used the proposed dosing procedure to compare catalysts with different ammonia storage capacities. Again, the relative ranking of the catalysts’ performance was shown to depend on the dosing profile. Overall it is demonstrated that the true potential of a catalyst can only be determined when an individually adapted dosing strategy is used.
The processing of single words that varied in their semantic (concrete/abstract word) and syntactic (content/function word) status was investigated under different task demands (semantic/ syntactic ...task) in an event-related functional magnetic resonance imaging experiment. Task demands to a large degree determined which subparts of the neuronal network supporting word processing were activated. Semantic task demands selectively activated the left pars triangularis of the inferior frontal gyrus (BA 45) and the posterior part of the left middle/superior temporal gyrus (BA 21/22/37). In contrast, syntactic processing requirements led to an increased activation in the inferior tip of the left frontal operculum (BA 44) and the cortex lining the junction of the inferior frontal and inferior precentral sulcus (BA 44/6). Moreover, for these latter areas a word class by concreteness interaction was observed when a syntactic judgement was required. This interaction can be interpreted as a prototypicality effect: non-prototypical members of a word class, i.e. concrete function words and abstract content words, showed a larger activation than prototypical members, i.e. abstract function words and concrete content words. The combined data suggest that the activation pattern underlying word processing is predicted neither by syntactic class nor semantic concreteness but, rather, by task demands focusing either on semantic or syntactic aspects. Thus, our findings that semantic and syntactic aspects of processing are both functionally distinct and involve different subparts of the neuronal network underlying word processing support a domain-specific organization of the language system.
In order to react adequately to potentially relevant information outside the focus of attention, our brain preattentively scans the acoustic environment for irregularities. Two different mechanisms ...are currently discussed: (i) a sensory one based on differential states of refractoriness of neurons sensitive to the features of a regular event and of neurons sensitive to features of an irregular event; (ii) a cognitive one based on a comparison of short‐lived memory representations encoding current stimulation and the invariance inherent in recent recurrent stimulation. Here, we identified regions that mediate either of the two mechanisms by combining functional magnetic resonance imaging with an experimental protocol controlling for refractoriness. The sensory mechanism was associated with activity in the primary auditory cortex, whereas the cognitive one revealed activity in nonprimary auditory areas in the anterior part of Heschl's Gyrus. Moreover, it turned out that in the traditional oddball paradigm both mechanisms contribute to irregularity detection.
Background: Medicine has undergone profound changes in terms of the number of women entering the profession with postulated implications of this ‘feminization’ for the profession. The present ...phenomenological study sought to gain insight into the experiences of final year male and female Emirati medical students (clerks) in terms of the impact of gender on their careers. Methods: Semi-structured interviews were conducted with 24 of the 27 clerks. Interviews were transcribed and analyzed thematically. Findings: There was consensus that the gender profile of medicine in the United Arab Emirates was changing as opportunities emerged for Emirati women to branch into different medical specialties. These opportunities were, however, local or regional due largely to travel restrictions on women. Females would thus receive a less highly regarded board certification than males who were encouraged to specialize abroad. On their return, males would be appointed as consultants or as high-ranking administrators. Participants also acknowledged that like their roles in their society, some medical specialties were ‘gendered’, e.g., surgery (male) and pediatrics and obstetrics and gynecology (female). Conclusion: Although religious and cultural traditions around gender and mobility will influence the professional careers of male and female Emirati medical graduates, the situation is, however, changing.
Anti-inflammatory functions of antibiotics may counteract deleterious hyperinflammation in pneumonia. Moxifloxacin reportedly exhibits immunomodulatory properties, but experimental evidence in ...pneumonia is lacking. Therefore, we investigated moxifloxacin in comparison with ampicillin regarding pneumonia-associated pulmonary and systemic inflammation and lung injury.
Ex vivo infected human lung tissue and mice with pneumococcal pneumonia were examined regarding local inflammatory response and bacterial growth. In vivo, clinical course of the disease, leucocyte dynamics, pulmonary vascular permeability, lung pathology and systemic inflammation were investigated. In addition, transcellular electrical resistance of thrombin-stimulated endothelial cell monolayers was quantified.
Moxifloxacin reduced cytokine production in TNF-α-stimulated, but not in pneumococci-infected, human lung tissue. In vivo, moxifloxacin treatment resulted in reduced bacterial load as compared with ampicillin, whereas inflammatory parameters and lung pathology were not different. Moxifloxacin-treated mice developed less pulmonary vascular permeability during pneumonia, but neither combination therapy with moxifloxacin and ampicillin in vivo nor examination of endothelial monolayer integrity in vitro supported direct barrier-stabilizing effects of moxifloxacin.
The current experimental data do not support the hypothesis that moxifloxacin exhibits potent anti-inflammatory properties in pneumococcal pneumonia.
The neural correlates of the selection of grammatical gender during overt picture naming were investigated by event-related functional magnetic resonance imaging in the left hemisphere. Relative to ...simply naming a picture, the production of the definite determiner of the picture name (requiring gender selection) resulted exclusively in pronounced activation of a single region in the superior portion of Broca's area. This activation was not present in contrasts reflecting lexical access (naming a picture vs. saying “jaja” to a smiley) or articulation (saying “jaja” vs. rest). Rather, lexical access activated other inferior frontal regions, insula, fusiform and inferior temporal gyrus. Articulation involved insula, Rolandic operculum, motor and premotor cortex and superior temporal gyrus. The results are discussed with respect to data from studies investigating gender processing during language comprehension.
The neural mechanisms of deviancy and target detection
were investigated by combining high density event-related
potential (ERP) recordings with functional magnetic resonance
imaging (fMRI). ERP and ...fMRI responses were recorded using
the same paradigm and the same subjects. Unattended deviants
elicited a mismatch negativity (MMN) in the ERP. In the
fMRI data, activations of transverse/superior temporal
gyri bilateral were found. Attended deviants generated
an MMN followed by an N2/P3b complex. For this condition,
fMRI activations in both superior temporal gyri and the
neostriatum were found. These activations were taken as
neuroanatomical constraints for the localization of equivalent
current dipoles. Inverse solutions for dipole orientation
provide evidence for significant activation close to Heschl's
gyri during deviancy processing in the 110–160-ms
time interval (MMN), whereas target detection could be
modeled by two dipoles in the superior temporal gyrus between
320 and 380 ms.
Severe community- and hospital-acquired pneumonia is caused by Legionella pneumophila. Lung airway and alveolar epithelial cells comprise an important sentinel system in airborne infections. Although ...interleukin (IL)-6 is known as a central regulator of the immune response in pneumonia, its regulation in the lung is widely unknown. Herein, we demonstrate that different L. pneumophila strains induce delayed expression of IL-6 in comparison with IL-8 by human lung epithelial cells. IL-6 expression depended, at early time points, on flagellin recognition by Toll-like receptor (TLR)5, activity of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK)1 and p38 mitogen-activated protein (MAP) kinase, and, at later time points, on the type-IV secretion system. In the same manner, but more rapidly, the recently described transcription factor IκBζ was induced by Legionella infection and, binding to the nuclear factor (NF)-κB subunit p50 - recruited to the il6 promoter together with CCAAT-enhancer-binding protein β and phosphorylated activator protein-1 subunit cJun. Similarly, histone modifications and NF-κB subunit p65/RelA appeared at the iκbζ and subsequently at the il6 gene promoter, thereby initiating gene expression. Gene silencing of IκBζ reduced Legionella-related IL-6 expression by 41%. Overall, these data indicate a sequence of flagellin/TLR5- and type IV-dependent IκBζ expression, recruitment of IκBζ/p50 to the il6 promoter, chromatin remodelling and subsequent IL-6 transcription in L. pneumophila-infected lung epithelial cells.
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