370 research outputs found

    Deceleration and trapping of heavy diatomic molecules using a ring-decelerator

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    We present an analysis of the deceleration and trapping of heavy diatomic molecules in low-field seeking states by a moving electric potential. This moving potential is created by a 'ring-decelerator', which consists of a series of ring-shaped electrodes to which oscillating high voltages are applied. Particle trajectory simulations have been used to analyze the deceleration and trapping efficiency for a group of molecules that is of special interest for precision measurements of fundamental discrete symmetries. For the typical case of the SrF molecule in the (N,M) = (2, 0) state, the ring-decelerator is shown to outperform traditional and alternate-gradient Stark decelerators by at least an order of magnitude. If further cooled by a stage of laser cooling, the decelerated molecules allow for a sensitivity gain in a parity violation measurement, compared to a cryogenic molecular beam experiment, of almost two orders of magnitude

    Catalysts based on Co-Birnessite and Co-Todorokite for the efficient production of hydrogen by ethanol steam reforming

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    [EN] Two structured manganese oxides (Birnessite and Todorokite) containing Co have been studied in the steam reforming of ethanol. It has been found that both materials are active in the hydrogen production, exhibiting high values of conversion of ethanol and selectivities to hydrogen (100% and 70%, respectively). The best results have been obtained with the catalyst based on Todorokite material. Characterization by DRX, BET area, TPR and TEM has allowed to find that the excellent performance exhibited by this material could be attributed to the lower size of the Co metallic particles present in this sample (6 nm vs 12 nm in Birnessite). This lower size could be related to the especial microporous structure of Todorokite precursor, which could provide high-quality positions for the stabilization of the Co metal particles during calcination and reduction steps. Catalytic deactivation has also been considered. Deactivation was found higher for Todorokite-based catalyst, which presented the largest amount of deposited carbon (26.2 wt% for Co-TOD vs 10.6 wt% for Co-BIR). On the other hand, the degree of metal sintering was found similar in both catalysts. Therefore, the deactivation of the catalysts has been attributed primarily to the deposition of coke. The results presented here show that it is possible to prepare new catalysts based on manganese oxides with Birnessite and Todorokite structure and promoted with Co with high catalytic performance in the steam reforming of ethanol. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.The doctor Javier Francisco Da Costa Serra acknowledges the CSIC for granted the scholarship predoctoral-JAE-CSIC. Moreover, Electronic Microscopy Service of UPV for TEM images.Da Costa Serra, JF.; Chica, A. (2018). Catalysts based on Co-Birnessite and Co-Todorokite for the efficient production of hydrogen by ethanol steam reforming. International Journal of Hydrogen Energy. 43(35):16859-16865. https://doi.org/10.1016/j.ijhydene.2017.12.114S1685916865433

    Human Disease/Clinical Medical Sciences in Dentistry: Current state and future development of undergraduate assessments in the UK and Ireland

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    Introduction The United Kingdom and Ireland teachers of Human Disease/Clinical Medical Science for Dentistry (HD/CMSD) group continues to work together, and most recently collaborated to review current and future assessments. Materials and methods The first part of the review of assessments in HD/CMSD took place at a face‐to‐face meeting with presentations from delegates on assessments in their home institutions. The second, and larger part, comprised an online survey where all eighteen schools in the UK and Ireland participated. Results All schools had some element of formative assessment, and the majority had a stand‐alone summative assessment at the end of the HD/CMSD teaching block. Most schools had a written paper and practical elements to their assessments, most commonly a combination of a multiple‐choice type question combined with an objective structured clinical examination (OSCE). There was a trend towards the use of single best answer (SBA) questions and a willingness among participants to share a question bank. All schools incorporated elements of HD/CMSD in their final examinations. Discussion & Conclusion This collaboration promoted the sharing of developments in assessment for HD/CMSD and demonstrated a willingness to co‐operate between institutions. Assessment in HD/CMSD in the UK and Ireland continues to be refined by those responsible for its content and delivery and assessment methods are progressing following evidence‐based best practice

    Fractal Reconnection in Solar and Stellar Environments

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    Recent space based observations of the Sun revealed that magnetic reconnection is ubiquitous in the solar atmosphere, ranging from small scale reconnection (observed as nanoflares) to large scale one (observed as long duration flares or giant arcades). Often the magnetic reconnection events are associated with mass ejections or jets, which seem to be closely related to multiple plasmoid ejections from fractal current sheet. The bursty radio and hard X-ray emissions from flares also suggest the fractal reconnection and associated particle acceleration. We shall discuss recent observations and theories related to the plasmoid-induced-reconnection and the fractal reconnection in solar flares, and their implication to reconnection physics and particle acceleration. Recent findings of many superflares on solar type stars that has extended the applicability of the fractal reconnection model of solar flares to much a wider parameter space suitable for stellar flares are also discussed.Comment: Invited chapter to appear in "Magnetic Reconnection: Concepts and Applications", Springer-Verlag, W. D. Gonzalez and E. N. Parker, eds. (2016), 33 pages, 18 figure

    New Catalysts based on Ni-Birnessite and Ni-Todorokite for the Efficient Production of Hydrogen by Bioethanol Steam Reforming

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    Catalytic steam reforming of bioethanol seems to be a promise option to produce renewable hydrogen; however efficient catalysts are still under development. Recently, manganese oxide based materials (MO) are the subject of intense research as low cost, efficient, and environmentally friendly catalysts. Among them MO with layer and tunnel structure have received significant attention due to their excellent catalytic activity. Specifically, we have explored the catalytic performance of two MO containing Ni (Birnessite and Todorokite). We find that both materials are highly active and selective to produce hydrogen by steam reforming of bioethanol. Their characterization by DRX, BET area, TPR, and TEM, has allowed to find that the excellent performance exhibited by these materials could be attributed to the especial structure of these MO, which would provide high-quality positions for the stabilization of the Ni metal particles.Fuertes, A.; Da Costa Serra, JF.; Chica, A. (2012). New Catalysts based on Ni-Birnessite and Ni-Todorokite for the Efficient Production of Hydrogen by Bioethanol Steam Reforming. Energy Procedia. 29:181-191. doi:10.1016/j.egypro.2012.09.023S1811912

    Silencing Nociceptor Neurons Reduces Allergic Airway Inflammation

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    Lung nociceptors initiate cough and bronchoconstriction. To elucidate if these fibers also contribute to allergic airway inflammation, we stimulated lung nociceptors with capsaicin and observed increased neuropeptide release and immune cell infiltration. In contrast, ablating Nav1.8(+) sensory neurons or silencing them with QX-314, a charged sodium channel inhibitor that enters via large-pore ion channels to specifically block nociceptors, substantially reduced ovalbumin- or house-dust-mite-induced airway inflammation and bronchial hyperresponsiveness. We also discovered that IL-5, a cytokine produced by activated immune cells, acts directly on nociceptors to induce the release of vasoactive intestinal peptide (VIP). VIP then stimulates CD4(+) and resident innate lymphoid type 2 cells, creating an inflammatory signaling loop that promotes allergic inflammation. Our results indicate that nociceptors amplify pathological adaptive immune responses and that silencing these neurons with QX-314 interrupts this neuro-immune interplay, revealing a potential new therapeutic strategy for asthma

    The Earth: Plasma Sources, Losses, and Transport Processes

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    This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed

    Review on Current Sheets in CME Development: Theories and Observations

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    Measurements of differential production cross sections for a Z boson in association with jets in pp collisions at root s=8 TeV

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