Hydrodynamic limits for the monomer-dimer surface reaction: Chemical diffusion, wave propagation, and equistability

For finite adspecies mobility, the lattice-gas monomer-dimer (A+B2) surface reaction model exhibits a discontinuous transition from a stable reactive steady state to a stable A-poisoned steady state, as the impingement rate PA for A increases above a critical value P*. The reactive (poisoned) state is metastable for PA just above (below) P*. Increasing the surface mobility of Aenhances metastability, leading to bistability in the limit of high mobility. In the bistable region, the more stable state displaces the less stable one separated from it by a planar interface, with P*becoming the equistability point for the two states. This hydrodynamic regime can be described by reaction-diffusion equations (RDE’s). However, for finite reaction rates, mixed adlayers of A and Bare formed, resulting in a coverage-dependent and tensorial nature to chemical diffusion (even in the absence of interactions beyond site blocking). For equal mobility of adsorbed A and B, and finite reaction rate, the prediction for P* from such RDE’s, incorporating the appropriate description of chemical diffusion, is shown to coincide with that from kinetic Monte Carlo simulations for the lattice-gas model in the regime of high mobility. Behavior for this special case is compared with that for various other prescriptions of mobility, for both finite and infinite reaction rates

Hybrid treatment of spatio‐temporal behavior in surface reactions with coexisting immobile and highly mobile reactants

For surface reactions on single-crystal substrates which involve highly mobile adspecies, there is a vast separation in natural time and length scales. Adspecies hop rates can be many orders of magnitude larger than rates for other processes. Strong spatial correlations or ordering can exist on the atomic scale, while spatial pattern formation occurs on a macroscopic scale due to high diffusivity. An efficient analysis of such systems is provided by a hybrid treatment which we apply here to the monomer-dimer surface reaction model in the case of coexisting immobile dimer adspecies and highly mobile monomer adspecies. Specifically, we combine a mean-field treatment of the randomized mobile adspecies, and a lattice-gas description of the immobile adspecies. Monte Carlo simulations then reveal bistability and critical bifurcation phenomena, while precisely accounting for the influence of correlations in the immobile adspecies distribution. A corresponding analysis of the evolution of macroscopic spatial inhomogeneities is achieved through parallel simulation of the distributed macroscopic points with distinct correlated states and adspecies coverages. These simulations are appropriately coupled to describe diffusive mass transport of the mobile adspecies. In this way, we examine for this model the propagation and structure of chemical waves, corresponding to interface between bistable reactive states, and thereby determine the relative stability of these states

Quantum Pairing of Impurities in Quantum Crystals

We calculated the time of pairing by quantum diffusion of ortho-H2 impurities in solid para-H2. The important feature of the pairing process is a strong directional bias associated with the dependence of the hopping rates on energy mismatches caused by the interaction of the pairing particles. This bias at moderate temperatures is against a mutual approach of particles and creates a ‘‘kinetic barrier.’’ At lower temperatures, the corresponding diffusion mechanism freezes out, which leads to a rapid increase in pairing rates. This explains a well-developed, experimentally observed maximum in the pairing time as a function of temperature: a maximum that exists in spite of a monotonic temperature dependence of individual hopping rates. Our results are in good agreement with experimental data

Seasonal performance assessment of sanitary hot water production systems using propane and CO2 heat pumps

[EN] This paper presents an experimental analysis and performance evaluation of a ground source heat pumpsystem providing heating/cooling to an office building, located at the Universitat Politècnica de Valènciain Spain. The experimental data and a detailed description of the analysis tool used were presented ina previous paper for the first six operational years. This paper provides the adaptation of such analysistool to the new configuration (heat pump with two compressors working in tandem), and provides anupdated complete reference data sets over more than eleven years which can be used by researchers formodel validation purposes.The work of M. Tammaro on electric heat pumps is supported by the Next Heat Pump Generation project (funded by the European Commission in the 7th Framework Programme, grant number 307169 - European Heat Pump Association, 2013), which is gratefully acknowledged.Tammaro, M.; Montagud, C.; Corberán, J.; Mauro, A.; Mastrullo, R. (2017). Seasonal performance assessment of sanitary hot water production systems using propane and CO2 heat pumps. International Journal of Refrigeration. 74:222-237. https://doi.org/10.1016/j.ijrefrig.2016.09.0262222377

TREM1/3 deficiency impairs tissue repair after acute kidney injury and mitochondrial metabolic flexibility in tubular epithelial cells

Long-term sequelae of acute kidney injury (AKI) are associated with incomplete recovery of renal function and the development of chronic kidney disease (CKD), which can be mediated by aberrant innate immune activation, mitochondrial pathology, and accumulation of senescent tubular epithelial cells (TECs). Herein, we show that the innate immune receptor Triggering receptor expressed on myeloid cells-1 (TREM-1) links mitochondrial metabolism to tubular epithelial senescence. TREM-1 is expressed by inflammatory and epithelial cells, both players in renal repair after ischemia/reperfusion (IR)-induced AKI. Hence, we subjected WT and TREM1/3 KO mice to different models of renal IR. TREM1/3 KO mice displayed no major differences during the acute phase of injury, but increased mortality was observed in the recovery phase. This detrimental effect was associated with maladaptive repair, characterized by persistent tubular damage, inflammation, fibrosis, and TEC senescence. In vitro, we observed an altered mitochondrial homeostasis and cellular metabolism in TREM1/3 KO primary TECs. This was associated with G2/M arrest and increased ROS accumulation. Further exposure of cells to ROS-generating triggers drove the cells into a stress-induced senescent state, resulting in decreased wound healing capacity. Treatment with a mitochondria anti-oxidant partly prevented the senescent phenotype, suggesting a role for mitochondria herein. In summary, we have unraveled a novel (metabolic) mechanism by which TREM1/3 deficiency drives senescence in TECs. This involves redox imbalance, mitochondrial dysfunction and a decline in cellular metabolic activities. These finding suggest a novel role for TREM-1 in maintaining tubular homeostasis through regulation of mitochondrial metabolic flexibility

Topography and structural heterogeneities in surface ground deformation: a simulation test for Somma-Vesuvius volcano

Abstract. We simulate the deformation of Somma-Vesuvius volcano due to some overpressure sources by means of a finite element 3D code. The main goal of these simulations is to investigate the influence of topography and structural heterogeneity on ground deformation. In our model the sources of deformation are embedded in an elastic linear isotropic medium and located at various depths. Geometry (shape and lateral extension) of the sources is mainly constrained by the results coming from recent seismic tomography studies. The structural heterogeneity has been modelled in terms of dynamic elastic parameters (Young's modulus) retrieved from previous seismic tomography and gravity studies. A high-resolution digital terrain model is used for the topography of the volcano subaerial edifice. Evidences from our results suggest that real topography and structural heterogeneities are key factors governing the ground deformation, which often turns being one of the most relevant problems in volcano monitoring. A large deviation from the axially symmetrical model of the displacement field is the main result of our modelling. Such an asymmetry is routinely unaccounted for when Mogi's simplistic modelling in a homogeneous medium with simplified topography is used. Our study clearly demonstrate that a better knowledge of deformation patterns can significantly help in the location of monitoring sensors as well as in the design of an efficient geodetic network

3D change detection analysis of a coastal landslide performed by multi-temporal point clouds comparison

The structure from motion (SfM) photogrammetric technique (FONSTAD et al., 2013) has become a suitable method to obtain high resolution topography data in a wide range of geomorphic environments (PASSALACQUA et al., 2015). SfM is designed to reconstruct the three-dimensional geometry of buildings and objects from randomly acquired images, and represents a low cost option respect to traditional photogrammetric and lidar techniques (FONSTAD et al., 2013). In this way, also the 3D geometry of complex natural surfaces can be achieved with a horizontal and vertical accuracy which depend on the choice of sensor for images acquisition, platform (e.g., UAV, boat, vehicle), and method of assignment of geodetic coordinates to the digital data. In advanced geomorphic applications, repeated photogrammetric surveys at different times allow to detect topographic changes in order to map or monitor erosion, deposition and develop sediment budgets. In this work we present a 3D change detection analysis related to a coastal landslide occurred on 27th October 2013 along the coastal sector of the Campi Flegrei volcanic district, Southern Italy (ESPOSITO et al., 2015). A total of four photogrammetric surveys have been carried out in about two years (Fig. 1), by using a UAV platform for one survey and boats for the other three. In order to accurately define the exterior orientation of images, a topographic survey was also carried out, measuring a series of natural and artificial ground control points external to the landslide area with a long-range Total Station. Images were processed using Agisoft PhotoScan® (http://www.agisoft.com), and 3D point clouds were compared through the "Multiscale Model to Model Cloud Comparison (M3C2)" plugin (LAGUE et al., 2013) included in CloudCompare open source software (http://www.danielgm.net/cc/). The plugin allowed us to estimate orthogonal distances between multitemporal point clouds as well as uncertainty related to each distance measurement. SfM processing of each survey resulted in dense point clouds and high-resolution orthophotos. An average coregistration error between clouds was estimated as 11 cm. As output of the M3C2 distance computation we obtained three new clouds in which each point was characterized by distance and uncertainty attributes (Fig. 2). Points corresponding to statistically significant changes were exported and interpolated in ESRI ArcGis® for volume calculation. Volumetric data show that the landslide deposit at cliff toe was progressively eroded by the sea, while landslide scar was affected by a moderate erosion in the first three months after the 2013 landslide event, as well as by a deep erosion between the second and third surveys. Nevertheless, a negligible eroded volume between 2015 and 2016 surveys was estimated in this area. Deposited sediments decreased through time in the whole landslide area so that, generally, a geomorphic evolution moving towards an equilibrium condition seems to be taking place. The study here described highlights a high potentiality of the SfM and cloud-to-cloud distance computation techniques in geomorphology, both for accurate qualitative and quantitative analysis and for hazard and risk assessment. The studied landslide threats indeed a series of residential buildings located close to the retreating cliff edge

Ofd1 Controls Dorso-Ventral Patterning and Axoneme Elongation during Embryonic Brain Development.

Oral-facial-digital type I syndrome (OFDI) is a human X-linked dominant-male-lethal developmental disorder caused by mutations in the OFD1 gene. Similar to other inherited disorders associated to ciliary dysfunction OFD type I patients display neurological abnormalities. We characterized the neuronal phenotype that results from Ofd1 inactivation in early phases of mouse embryonic development and at post-natal stages. We determined that Ofd1 plays a crucial role in forebrain development, and in particular, in the control of dorso-ventral patterning and early corticogenesis. We observed abnormal activation of Sonic hedgehog (Shh), a major pathway modulating brain development. Ultrastructural studies demonstrated that early Ofd1 inactivation results in the absence of ciliary axonemes despite the presence of mature basal bodies that are correctly orientated and docked. Ofd1 inducible-mediated inactivation at birth does not affect ciliogenesis in the cortex, suggesting a developmental stage-dependent role for a basal body protein in ciliogenesis. Moreover, we showed defects in cytoskeletal organization and apical-basal polarity in Ofd1 mutant embryos, most likely due to lack of ciliary axonemes. Thus, the present study identifies Ofd1 as a developmental disease gene that is critical for forebrain development and ciliogenesis in embryonic life, and indicates that Ofd1 functions after docking and before elaboration of the axoneme in vivo