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Low temperature steam reforming in combination with hydrogen selective membranes presents great potential of intensifying the classical industrial hydrogen production process via natural gas. This concept can lead to significant environmental and process benefits, such as reduced energy needs, milder material stability requirements and considerably simplified process layouts via e.g. avoiding the use of downstream WGS reactors. Ni and Rh based catalysts supported on La 2 O 3 -CeO 2 -ZrO 2 , already identified as active and stable at these conditions, are further investigated in the current work aiming at the elucidation of reaction kinetics. Temperature programmed experiments of methane conversion in steam reforming and decomposition modes in conjunction with isotopic investigations using CD 4 are carried out, showing that cleavage of a C H bond participates in the rate determine step, whereas steam derived intermediates do not. A thermodynamically consistent microkinetic model considering a comprehensive set of surface pathways is also developed. The model describes correctly experimental trends, predicting surface CH 3 dehydrogenation to be rate limiting. Estimated model parameters further help elucidate the different catalysts’ activities. The combined approach presented shows potential to accelerate catalyst and process design efforts for the promising low temperature steam reforming hydrogen production process.

A comprehensive knowledge of the loads applied during activities of daily living to the femur shaft is necessary to the design of direct attachments of relevant prostheses. A motion analysis system was used together with an established protocol with skin markers to estimate the three components of the forces and moments acting on ten equidistant points along the full femur shaft. Twenty healthy young volunteers were analyzed while performing three repetitions of the following tasks: level walking at three different speeds, straight-line and with sudden changes of direction to the right and to the left, stairs ascending and descending, squat, rising from a chair and sitting down. Average load patterns, after normalisation for body weight and height, were calculated over subjects for each point, about the three anatomical axes, and for each motor task. These patterns were found consistent over subjects, but different among the anatomical axes and tasks. In general, the moments were observed limitedly influenced by the progression speed, and higher for more proximal points. The moments were also higher in abd/adduction (8.1% body weight*height on average), nearly three times larger than those in flex/extension (2.6) during stair descending. The largest value over all moments was 164.8. N. m, abd/adduction in level walking at high speed. The present results should be of value also for a most suitable level for amputation in transfemoral amputation, for in-vitro mechanical tests and for finite element models of the femur.

Steam reforming of natural gas for the production of hydrogen at low operation temperature offers significant financial and environmental advantages. However, the presence of higher hydrocarbons as minor components of natural gas can significantly affect the formation of coke and thus the effectiveness of the catalyst. In this study, the effect of the presence of C2–C3 alkanes in the feedstock on the carbon accumulation during low temperature steam reforming of methane is investigated over Ni and Rh catalysts supported on lanthanum doped ceria–zirconia mixed oxide. Both catalysts showed high resistance to coke formation and especially in the case of Rh/La/CeO 2 –ZrO 2 , the carbon accumulation detected was low even after 10 h on stream in steam reforming of all mixtures of hydrocarbons tested. The presence of higher alkanes in methane increased the amount of carbon on Ni(10)CeZrLa compared to pure methane as well as the nature of the carbonaceous species. Increase in the C-number of the additive alkane had almost no influence on the total amount of carbon formed (C/H feed ratio = constant) but favored the formation of filamentous carbon.

One of the most promising technologies for CO 2 capture is the Calcium Looping Cycle, which is based on the reversible carbonation reaction of CaO. The main challenge for CaL technology is the deterioration of CO 2 capture capacity during multicyclic operation. In this work, the triethanolamine (TEA) was used as a complexing agent in a modified sol–gel method for the preparation of sintering resistant CaO–Ca 3 Al 2 O 6 . The sorbent showed high capture capacity (0.45 g/g sorb. or 84% carbonation conversion) which was retained after 45 cycles. Parametric study of sorption was realized by varying the carbonation and calcination conditions (temperature and CO 2 concentration). Under severe conditions of calcination temperature at 950 °C in pure CO 2 flow after 100 cycles the sorbent still retained almost 40% of the initial sorption capacity corresponding to 30% carbonation conversion.

Background:The tensor tympani muscle is the largest muscle within the middle ear. Its voluntary contraction is a very unusual event. Only a few papers have documented its audiometric effects.Objective:To report an unusual case of voluntary tensor tympani muscle contraction and describe its audiometric effects.Case report:A 27-year-old man, who presented complaining of voluntarily evoked bilateral tinnitus, was found to be able to voluntarily contract the tensor tympani muscle in both ears simultaneously. Audiograms were performed under conditions of rest and maximal contraction of the tensor tympani muscle. The most remarkable effects were conductive hearing loss at lower frequencies and an increase in middle-ear impedance.Conclusion:The importance of the tensor tympani muscle in middle-ear physiology remains unclear. It has been related to the attenuation of sounds produced during the mastication process. Voluntary control over the tensor tympani muscle is an extremely rare event. However, an understanding of the potential audiometric effects of its contraction could aid the diagnosis of hearing disorders.

Systems with counter-clockwise input-output (I-O) dynamics were recently introduced in order to study the convergence of positive feedback loops (possibly to many different equilibrium states). The author shows how this notion can be used to perform bifurcation analysis and globally predict multistability of a closed-loop feedback interconnection just by using the knowledge of steady-state I-O responses of the systems. To illustrate the theory, this method is then applied to a recently published model of mitogen activated protein kinase (MAPK) cascade. Furthermore, some examples (mainly motivated by molecular biology) of systems that enjoy the property are presented and discussed.

The analysis of Direct Numerical Simulation data of the separating and reattaching flow over a blunt bluff body with sharp edges, reveals the presence of negative turbulence production mechanisms in the leading-edge shear layer. Contrary to what is commonly observed in fully developed turbulent flows, this phenomenon represents flow reversal of energy from the fluctuating field to the mean flow. The detailed study of the data reveals that at the origin of such mechanisms is a statistically positive relation between Reynolds shear stresses and vertical shear. We argue that such a positive relation is a result of large-scale interactions of the fluctuating field with the streamwise inhomogeneity. The analysis of time cospectra confirms this picture by highlighting the presence of a net separation of scales consisting in a range of small scales positively contributing to turbulence production in opposition to a range of large scales giving to a reversal of flow energy from the fluctuating to the mean field. By means of a reduced description of the interactions of the fluctuating field with the mean field given by a generalized mixing length hypothesis, we finally also provide conceptual arguments for the modelling of turbulence production in the transitional shear layer. A model for the mixing length is also proposed which is found to work nicely in shear flows. The simplicity of the formulation supports its use especially in experiments of wall-bounded turbulence.

Until April 2007 the MAGIC telescope used a 300 MSamples/s FADC system to sample the shaped PMT signals produced by the captured Cherenkov photons of air showers. Different algorithms to reconstruct the signal from the read-out samples (extractors) have been implemented and are described and compared. Criteria based on the obtained charge and time resolution/bias are defined and used to judge the different extractors, by applying them to calibration, cosmic and pedestal signals. The achievable charge and time resolution have been derived as functions of the incident number of photo-electrons., Accepted for publication in NIM A