1,710 research outputs found
Cu,Zn,Al layered double hydroxides as precursors for copper catalysts in methanol steam reforming – pH-controlled synthesis by microemulsion technique
By co-precipitation inside microemulsion droplets a Cu-based catalyst precursor was prepared with a Cu:Zn:Al ratio of 50:17:33. A pH-controlled synthesis was applied by simultaneous dosing of metal solution and precipitation agent. This technique allows for continuous operation of the synthesis and enables easy and feasible up-scaling. For comparison conventional co-precipitation was applied with the same composition. Both techniques resulted in phase pure layered double hydroxide precursors and finally (after calcination and reduction) in small Cu nanoparticles (8 nm) and ZnAl2O4. By applying the microemulsion technique smaller Cu/ZnAl2O4 aggregates with less embedded Cu particles were obtained. The microemulsion product exhibited a higher BET and specific Cu surface area and also a higher absolute catalytic activity in methanol steam reforming. However, the Cu surface area-normalized, intrinsic activity was lower. This observation was related to differences in interactions of Cu metal and oxide phase
Correlated EoM and Distributions for A=6 Nuclei
Energy spectra and electromagnetic transitions of nuclei are strongly
depending from the correlations of the bound nucleons. Two particle
correlations are responsible for the scattering of model particles either to
low momentum- or to high momentum-states. The low momentum states form the
model space while the high momentum states are used to calculate the G-matrix.
The three and higher order particle correlations do not play a role in the
latter calculation especially if the correlations induced by the scattering
operator are of sufficient short range. They modify however, via the long tail
of the nuclear potential, the Slater determinant of the A particles by
generating excited Slater's determinants. In this work the influence of the
correlations on the level structure and ground state distributions of even open
shell nuclei is analyzed via the boson dynamic correlation model BDCM. The
model is based on the unitary operator ({\it S} is the correlation
operator) formalism which in this paper is presented within a non perturbative
approximation. The low lying spectrum calculated for Li reproduce very well
the experimental spectrum while for He a charge radius slightly larger than
that obtained within the isotopic-shift (IS) theory has been calculated. Good
agreement between theoretical and experimental results has been obtained
without the introduction of a genuine three body force.Comment: 25 pages 4 figures. To be published in the Progress Theoretical
Physic
Extended Cluster Model for Light, and Medium Nuclei
The structures, the electromagnetic transitions, and the beta decay strengths
of exotic nuclei are investigated within an extended cluster model. We start by
deriving an effective nuclear Hamiltonian within the correlation
operator. Tensor forces are introduced in a perturbative expansion which
includes up to the second order terms. Within this Hamiltonian we calculate the
distributions and the radii of A=3,~4 nuclei. For exotic nuclei characterized
by n valence protons/neutrons we excite the structure of the closed shell
nuclei via mixed modes formed by considering correlations operators of higher
order. Good results have been obtained for the calculated transitions and for
the beta decay transition probabilities.Comment: 8-pages, 5-figure
Desiccation stress in two intertidal beachrock biofilms
© Springer-Verlag Berlin Heidelberg 2014. Chlorophyll a fluorescence was used to look at the effect of desiccation on the photophysiology in two beachrock microbial biofilms from the intertidal rock platform of Heron Island, Australia. The photophysiological response to desiccation differed between the beachrock microbial communities. The black biofilm from the upper shoreline, dominated by Calothrix sp., showed a response typical of desiccation-tolerant cyanobacteria, where photosynthesis closed down during air exposure with a rapid and complete recovery upon rehydration. In contrast, the pink biofilm from the mid-intertidal zone, dominated by Blennothrix sp., showed no distinct response to desiccation stress and instead maintained reduced photosynthesis throughout drying and re-wetting cycles. Spatial differences in photosynthetic activity within the black biofilm were evident with a faster recovery rate of photosynthesis in the surface cyanobacteria than in the deeper layers of the biofilm. There was no variation with depth in the pink biofilm. The photophysiological differences in desiccation responses between the beachrock biofilms exemplify the ecological niche specialisation of these complex microbial communities, where the functional differences help to explain their vertical distribution on the intertidal shoreline
Change prediction for low complexity combined beamforming and acoustic echo cancellation
Time-variant beamforming (BF) and acoustic echo cancellation (AEC) are two techniques that are frequently employed for improving the quality of hands-free speech communication. However, the combined application of both is quite challenging as it either introduces high computational complexity or insufficient tracking. We propose a new method to improve the performance of the low-complexity beamformer first (BF-first) structure, which we call change prediction(ChaP). ChaP gathers information on several BF changes to predict the effective impulse response seen by the AEC after the next BF change. To account for uncertain data and convergence states in the predictions, reliability measures are introduced to improve ChaP in realistic scenarios
Late-onset Bartter syndrome type II
Mutations in the ROMK1 potassium channel gene (KCNJ1) cause antenatal/neonatal Bartter syndrome type II (aBS II), a renal disorder that begins in utero, accounting for the polyhydramnios and premature delivery that is typical in affected infants, who develop massive renal salt wasting, hypokalaemic metabolic alkalosis, secondary hyperreninaemic hyperaldosteronism, hypercalciuria and nephrocalcinosis. This BS type is believed to represent a disorder of the infancy, but not in adulthood. We herein describe a female patient with a remarkably late-onset and mild clinical manifestation of BS II with compound heterozygous KCNJ1 missense mutations, consisting of a novel c.197T > A (p.I66N) and a previously reported c.875G > A (p.R292Q) KCNJ1 mutation. We implemented and evaluated the performance of two different bioinformatics-based approaches of targeted massively parallel sequencing [next generation sequencing (NGS)] in defining the molecular diagnosis. Our results demonstrate that aBS II may be suspected in patients with a late-onset phenotype. Our experimental approach of NGS-based mutation screening combined with Sanger sequencing proved to be a reliable molecular approach for defining the clinical diagnosis in our patient, and results in important differential diagnostic and therapeutic implications for patients with BS. Our results could have a significant impact on the diagnosis and methodological approaches of genetic testing in other patients with clinical unclassified phenotypes of nephrocalcinosis and congenital renal electrolyte abnormalities
AB2CD: AI for Building Climate Damage Classification and Detection
We explore the implementation of deep learning techniques for precise
building damage assessment in the context of natural hazards, utilizing remote
sensing data. The xBD dataset, comprising diverse disaster events from across
the globe, serves as the primary focus, facilitating the evaluation of deep
learning models. We tackle the challenges of generalization to novel disasters
and regions while accounting for the influence of low-quality and noisy labels
inherent in natural hazard data. Furthermore, our investigation quantitatively
establishes that the minimum satellite imagery resolution essential for
effective building damage detection is 3 meters and below 1 meter for
classification using symmetric and asymmetric resolution perturbation analyses.
To achieve robust and accurate evaluations of building damage detection and
classification, we evaluated different deep learning models with residual,
squeeze and excitation, and dual path network backbones, as well as ensemble
techniques. Overall, the U-Net Siamese network ensemble with F-1 score of 0.812
performed the best against the xView2 challenge benchmark. Additionally, we
evaluate a Universal model trained on all hazards against a flood expert model
and investigate generalization gaps across events, and out of distribution from
field data in the Ahr Valley. Our research findings showcase the potential and
limitations of advanced AI solutions in enhancing the impact assessment of
climate change-induced extreme weather events, such as floods and hurricanes.
These insights have implications for disaster impact assessment in the face of
escalating climate challenges.Comment: 9 pages, 4 figure
Accounting for the effect of horizontal gradients in limb measurements of scattered sunlight
Limb measurements provided by the SCanning Imaging Absorption spectrometer for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite allow retrieving stratospheric profiles of various trace gases on a global scale, among them BrO for the first time. For limb observations in the UV/VIS spectral region the instrument measures scattered light with a complex distribution of light paths: the light is measured at different tangent heights and can be scattered or absorbed in the atmosphere or reflected by the ground. By means of spectroscopy and radiative transfer modelling these measurements can be inverted to retrieve the vertical distribution of stratospheric trace gases. <br></br> The fully spherical 3-D Monte Carlo radiative transfer model "Tracy-II" is applied in this study. The Monte Carlo method benefits from conceptual simplicity and allows realizing the concept of full spherical geometry of the atmosphere and also its 3-D properties, which is important for a realistic description of the limb geometry. Furthermore it allows accounting for horizontal gradients in the distribution of trace gases. <br></br> In this study the effect of horizontally inhomogeneous distributions of trace gases along flight/viewing direction on the retrieval of profiles is investigated. We introduce a tomographic method to correct for this effect by combining consecutive limb scanning sequences and utilizing the overlap in their measurement sensitivity regions. It is found that if horizontal inhomogenity is not properly accounted for, typical errors of 20% for NO<sub>2</sub> and up to 50% for OClO around the altitude of the profile peak can arise for measurements close to the Arctic polar vortex boundary in boreal winter
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