The effects of water and microstructure on the performance of polymer electrolyte fuel cells

n this paper, we present a comprehensive non-isothermal, one-dimensional model of the cathode side of a Polymer Electrolyte Fuel Cell. We explicitly include the catalyst layer, gas diffusion layer and the membrane. The catalyst layer and gas diffusion layer are characterized by several measurable microstructural parameters. We model all three phases of water, with a view to capturing the effect that each has on the performance of the cell. A comparison with experiment is presented, demonstrating excellent agreement, particularly with regard to the effects of water activity in the channels and how it impacts flooding and membrane hydration. We present several results pertaining to the effects of water on the current density (or cell voltage), demonstrating the role of micro-structure, liquid water removal from the channel, water activity, membrane and gas diffusion layer thickness and channel temperature. These results provide an indication of the changes that are required to achieve optimal performance through improved water management and MEA-component design. Moreover, with its level of detail, the model we develop forms an excellent basis for a multi-dimensional model of the entire membrane electrode assembly

Factors affecting fungus-induced larval mortality in Anopheles gambiae and Anopheles stephensi

<p>Abstract</p> <p>Background</p> <p>Entomopathogenic fungi have shown great potential for the control of adult malaria vectors. However, their ability to control aquatic stages of anopheline vectors remains largely unexplored. Therefore, how larval characteristics (<it>Anopheles </it>species, age and larval density), fungus (species and concentration) and environmental effects (exposure duration and food availability) influence larval mortality caused by fungus, was studied.</p> <p>Methods</p> <p>Laboratory bioassays were performed on the larval stages of <it>Anopheles gambiae </it>and <it>Anopheles stephensi </it>with spores of two fungus species, <it>Metarhizium anisopliae </it>and <it>Beauveria bassiana</it>. For various larval and fungal characteristics and environmental effects the time to death was determined and survival curves established. These curves were compared by Kaplan Meier and Cox regression analyses.</p> <p>Results</p> <p><it>Beauveria bassiana </it>and <it>Metarhizium anisopliae </it>caused high mortality of <it>An. gambiae </it>and <it>An. stephensi </it>larvae. However, <it>Beauveria bassiana </it>was less effective (Hazard ratio (HR) <1) compared to <it>Metarhizium anisopliae. Anopheles stephensi </it>and <it>An. gambiae </it>were equally susceptible to each fungus. Older larvae were less likely to die than young larvae (HR < 1). The effect of increase in fungus concentration on larval mortality was influenced by spore clumping. One day exposure to fungal spores was found to be equally effective as seven days exposure. In different exposure time treatments 0 - 4.9% of the total larvae, exposed to fungus, showed infection at either the pupal or adult stage. Mortality rate increased with increasing larval density and amount of available food.</p> <p>Conclusions</p> <p>This study shows that both fungus species have potential to kill mosquitoes in the larval stage, and that mortality rate depends on fungus species itself, larval stage targeted, larval density and amount of nutrients available to the larvae. Increasing the concentration of fungal spores or reducing the exposure time to spores did not show a proportional increase and decrease in mortality rate, respectively, because the spores clumped together. As a result spores did not provide uniform coverage over space and time. It is, therefore, necessary to develop a formulation that allows the spores to spread over the water surface. Apart from formulation appropriate delivery methods are also necessary to avoid exposing non-target organisms to fungus.</p

Dopamine Transporter Knockout Rats Show Impaired Wellbeing in a Multimodal Severity Assessment Approach

In preclinical psychiatry research, animals are central to modeling and understanding biological mechanisms of behavior and psychiatric disorders. We here present the first multimodal severity assessment of a genetically modified rat strain used in psychiatric research, lacking the dopamine transporter (DAT) gene and showing endophenotypes of several dopamine-associated disorders. Absence of the DAT leads to high extracellular dopamine (DA) levels and has been associated with locomotor hyperactivity, compulsive behaviors and stereotypies in the past. The German Animal Welfare Law, which is based on the EU Directive (2010/63/EU), requires a prospective severity assessment for every animal experiment, depending on the extent of the expected degree of pain, suffering, distress or lasting harm that the animals will experience. This should consider all procedures but also the impact of the genotype on the phenotype. Therefore, we examined multiple parameters indicating animal welfare, like burrowing behavior, social interaction, saccharin preference, baseline stress hormone levels and nesting behavior. Additionally, a footprint analysis was performed and home cage activity was analyzed for a more detailed characterization of locomotion. DAT KO rats demonstrated reduced burrowing, social interaction and saccharin preference. We also found pronounced stereotypies and alterations in the gait analysis in DAT KO rats. Moreover, we confirmed the hyperactivity and the impaired sensorimotor gating mechanisms to assure that our rats are exhibiting the correct phenotype. In conclusion, we provide evidence that DAT KO rats show alterations in natural behavior patterns and deduce that the marked stereotypies are a sign for coping difficulties, both indicating a negative influence of the genotype on wellbeing. We suggest to assess further rat models in an objectified severity assessment as previously done in mice to create a relative severity assessment based on scientific evidence. Until then, we propose the classification of homozygous DAT KO rats as "moderate" in accordance with the criteria of the EU directive 2010/63

Peripheral serotonin deficiency affects anxiety-like behavior and the molecular response to an acute challenge in rats

Serotonin is synthetized through the action of tryptophan hydroxylase (TPH) enzymes. While the TPH2 isoform is responsible for the production of serotonin in the brain, TPH1 is expressed in peripheral organs. Interestingly, despite its peripheral localization, alterations of the gene coding for TPH1 have been related to stress sensitivity and an increased susceptibility for psychiatric pathologies. On these bases, we took advantage of newly generated TPH1(-/-)rats, and we evaluated the impact of the lack of peripheral serotonin on the behavior and expression of brain plasticity-related genes under basal conditions and in response to stress. At a behavioral level, TPH1(-/-) rats displayed reduced anxiety-like behavior. Moreover, we found that neuronal activation, quantified by the expression of (Bdnf) and the immediate early gene (Arc) and transcription of glucocorticoid responsive genes after 1 h of acute restraint stress, was blunted in TPH1(-/-) rats in comparison to TPH1 animals(+/+). Overall, we provided evidence for the influence of peripheral serotonin levels in modulating brain functions under basal and dynamic situations

Offspring's own serotonin transporter genotype, independently from the maternal one, increases anxiety- and depression-like behavior and alters neuroplasticity markers in rats

Introduction: Developmental changes due to early life variations in the serotonin system affect stress-related behavior and neuroplasticity in adulthood. These outcomes can be caused both by offspring's own and maternal serotonergic genotype. We aimed to dissociate the contribution of the own genotype from the influences of mother genotype. Methods: Sixty-six male homozygous (5-HTT-/-) and heterozygous (5-HTT+/-) serotonin transporter knockout and wild-type rats from constant 5-HTT genotype mothers crossed with varying 5-HTT genotype fathers were subjected to tests assessing anxiety- and depression-like behaviors. Additionally, we measured plasma corticosterone levels and mRNA levels of BDNF, GABA system and HPA-axis components in the prelimbic and infralimbic cortex. Finally, we assessed the effect of paternal 5-HTT genotype on these measurements in 5-HTT+/- offspring receiving their knockout allele from their mother or father. Results: 5-HTT-/- offspring exhibited increased anxiety- and depression-like behavior in the elevated plus maze and sucrose preference test. Furthermore, Bdnf isoform VI expression was reduced in the prelimbic cortex. Bdnf isoform IV and GABA related gene expression was also altered but did not survive false discovery rate (FDR) correction. Finally, 5-HTT+/- offspring from 5-HTT-/- fathers displayed higher levels of anxiety- and depression-like behavior and changes in GABA, BDNF and HPA-axis related gene expression not surviving FDR correction. Limitations: Only male offspring was tested. Conclusions: Offspring's own 5-HTT genotype influences stress-related behaviors and Bdnf isoform VI expression, independently of maternal 5-HTT genotype. Paternal 5-HTT genotype separately influenced these outcomes. These findings advance our understanding of the 5-HTT genotype dependent susceptibility to stress-related disorders

Chronic Loss of Melanin-Concentrating Hormone Affects Motivational Aspects of Feeding in the Rat

Current epidemic obesity levels apply great medical and financial pressure to the strenuous economy of obesity-prone cultures, and neuropeptides involved in body weight regulation are regarded as attractive targets for a possible treatment of obesity in humans. The lateral hypothalamus and the nucleus accumbens shell (AcbSh) form a hypothalamic-limbic neuropeptide feeding circuit mediated by Melanin-Concentrating Hormone (MCH). MCH promotes feeding behavior via MCH receptor-1 (MCH1R) in the AcbSh, although this relationship has not been fully characterized. Given the AcbSh mediates reinforcing properties of food, we hypothesized that MCH modulates motivational aspects of feeding

Lack of serotonin reuptake during brain development alters rostral raphe-prefrontal network formation

Contains fulltext : 126007.pdf (publisher's version ) (Open Access)Besides its "classical" neurotransmitter function, serotonin (5-HT) has been found to also act as a neurodevelopmental signal. During development, the 5-HT projection system, besides an external placental source, represents one of the earliest neurotransmitter systems to innervate the brain. One of the targets of the 5-HT projection system, originating in the brainstem raphe nuclei, is the medial prefrontal cortex (mPFC), an area involved in higher cognitive functions and important in the etiology of many neurodevelopmental disorders. Little is known, however, about the exact role of 5-HT and its signaling molecules in the formation of the raphe-prefrontal network. Using explant essays, we here studied the role of the 5-HT transporter (5-HTT), an important modulator of the 5-HT signal, in rostral raphe-prefrontal network formation. We found that the chemotrophic nature of the interaction between the origin (rostral raphe cluster) and a target (mPFC) of the 5-HT projection system was affected in rats lacking the 5-HTT (5-HTT(-/-)). While 5-HTT deficiency did not affect the dorsal raphe 5-HT-positive outgrowing neurites, the median raphe 5-HT neurites switched from a strong repulsive to an attractive interaction when co-cultured with the mPFC. Furthermore, the fasciculation of the mPFC outgrowing neurites was dependent on the amount of 5-HTT. In the mPFC of 5-HTT(-/-) pups, we observed clear differences in 5-HT innervation and the identity of a class of projection neurons of the mPFC. In the absence of the 5-HTT, the 5-HT innervation in all subareas of the early postnatal mPFC increased dramatically and the number of Satb2-positive callosal projection neurons was decreased. Together, these results suggest a 5-HTT dependency during early development of these brain areas and in the formation of the raphe-prefrontal network. The tremendous complexity of the 5-HT projection system and its role in several neurodevelopmental disorders highlights the need for further research in this largely unexplored area

Op weg naar een lokale aanpak voor digitale weerbaarheid bij het midden- en kleinbedrijf: een onderzoek naar wat mkb-ondernemers in de gemeente Overbetuwe ervan weerhoudt cyberweerbaar te zijn

Digitale criminaliteit is een groeiend probleem voor het midden- en kleinbedrijf in Nederland. Het antwoord op dit probleem kan gevonden worden in het verbeteren van de cyberweerbaarheid. In dit onderzoek is onderzocht welke factoren belemmerend zijn voor het mkb in de gemeente Overbetuwe om zich weerbaarder te maken tegen de dreigingen van digitale criminaliteit. Met behulp van het COM-B model en de protectie motivatie theorie zijn een aantal factoren geïdentificeerd die naar verwachting invloed hebben op de weerbaarheid. Vervolgens zijn twaalf ondernemers in de gemeente Overbetuwe geïnterviewd. Uit de analyse van de interviews kwam naar voren dat drie factoren met name belemmerend zijn voor het vertonen van cyberweerbaar gedrag. Het vermogen van mkb’ers om cyberweerbaar gedrag te vertonen is beperkt door een lage kennis van de weerbaarheidsfuncties. Daarnaast is de gelegenheid om cyberweerbaar gedrag te vertonen beperkt vanwege de geringe tijd waar ondernemers over beschikken. Tot slot is de risicoperceptie ten opzichte van de dreiging van digitale criminaliteit te laag. Twee andere onderzochte factoren leken geen belemmering te vormen voor cyberweerbaarheid. Dit zijn de effectiviteitsverwachting van zelfbeschermend gedrag en de sociale gelegenheid om cybweerbaar gedrag te vertonen

Het Nijmeegse Burgerweeshuis: Een institutionele investeerder in de periferie van de Nederlandse Republiek.

Institutionele investeerders waren een veelvoorkomend fenomeen in de Nieuwe Tijd in de Nederlandse Republiek. Het Nijmeegse Burgerweeshuis was een actieve institutionele investeerder in de achttiende eeuw. Het portfolio van het NBW bestond uit vastgoed en effecten, zoals obligaties. Er zijn verschillende factoren die het investeringsbedrag van instituties beïnvloeden. Het te verwachten rendement van investeringsopties was een belangrijke bepalende factor. Bijna alle institutionele investeerders gaven de voorkeur aan publieke obligaties