2,650 research outputs found
Spectral averaging techniques for Jacobi matrices
Spectral averaging techniques for one-dimensional discrete Schroedinger
operators are revisited and extended. In particular, simultaneous averaging
over several parameters is discussed. Special focus is put on proving lower
bounds on the density of the averaged spectral measures. These Wegner type
estimates are used to analyze stability properties for the spectral types of
Jacobi matrices under local perturbations
Step-wise development of resilient ambient campus scenarios
This paper puts forward a new approach to developing resilient ambient applications. In its core is a novel rigorous development method supported by a formal theory that enables us to produce a well-structured step-wise design and to ensure disciplined integration of error recovery measures into the resulting implementation. The development method, called AgentB, uses the idea of modelling database to support a coherent development of and reasoning about several model views, including the variable, event, role, agent and protocol views. This helps system developers in separating various modelling concerns and makes it easier for future tool developers to design a toolset supporting this development. Fault tolerance is systematically introduced during the development of various model views. The approach is demonstrated through the development of several application scenarios within an ambient campus case study conducted at Newcastle University (UK) as part of the FP6 RODIN project. © 2009 Springer Berlin Heidelberg
Parent based language intervention for 2-year-old children with specific expressive language delay: a randomised controlled trial
Variability in disease phenotypes within a single PRNP genotype suggests the existence of multiple natural sheep scarpie strains within Europe
Variability of pathological phenotypes within classical sheep scrapie cases has been reported for some time, but in many instances it has been attributed to differences in the PRNP genotype of the host. To address this issue we have examined by immunohistochemistry (IHC) and Western blotting (WB) for the disease-associated form of the prion protein (PrPd), the brains of 23 sheep from five European countries, all of which were of the same ARQ/ARQ genotype. As a result of IHC examinations, sheep were distributed into five groups with different phenotypes and the groups were the same regardless of the scoring method used, ‘long’ or ‘short’ PrPd profiling. The groups made did not respond to the geographical origin of the cases and did not correlate with the vacuolar lesion profiles, which showed a high individual variability. Discriminatory IHC and WB methods coincided to detect a ‘CH1641-like’ case but otherwise correlated poorly in the classification of disease phenotypes. No other polymorphisms of the PRNP gene were found that could account for the pathological differences, except perhaps for a sheep from Spain with a mutation at codon 103 and a unique pathological phenotype. Preliminary evidence indicates that those different IHC phenotypes correlate with distinct biological properties on bioassay, suggesting that they are indicative of strain diversity. We therefore conclude that natural scrapie strains exist and that they can be revealed by detailed pathological examinations, which can be harmonized between laboratories to produce comparable results
Iridium complexes of the conformationally rigid IBioxMe4Ligand : hydride complexes and dehydrogenation of cyclooctene
A method for accessing the formally 14 VE iridium(III) hydride fragment {Ir(IBioxMe4)2(H)2}+ (2), containing the conformationally rigid NHC ligand IBioxMe4, is reported. Hydrogenation of trans-[Ir(IBioxMe4)2(COE)Cl] (1) in the presence of excess Na[BArF4] leads to the formation of dimeric [{Ir(IBioxMe4)2(H)2}2Cl][BArF4] (3), which is structurally fluxional in solution and acts as a reservoir of monomeric 2 in the presence of excess halogen ion abstractor. Stable dihydride complexes trans-[Ir(IBioxMe4)2(2,2′-bipyridine)(H)2][BArF4] (4) and [Ir(IBioxMe4)3(H)2][BArF4] (5) were subsequently isolated through in situ trapping of 2 using 2,2′-bipyridine and IBioxMe4, respectively, and fully characterized. Using mixtures of 3 and Na[BArF4] as a latent source of 2, the reactive monomeric fragment’s reactivity was explored with excess ethylene and cyclooctene, and trans-[Ir(IBioxMe4)2(C2H4)2][BArF4] (6) and cis-[Ir(IBioxMe4)2(COD)][BArF4] (7) were isolated, respectively, through sacrificial hydrogenation of the alkenes. Complex 6 is notable for the adoption of a very unusual orthogonal arrangement of the trans-ethylene ligands in the solid state, which has been analyzed computationally using energy and charge decomposition (EDA-NOCV). The formation of 7 via transfer dehydrogenation of COE highlights the ability to partner IBioxMe4 with reactive metal centers capable of C–H bond activation, without intramolecular activation. Reaction of 7 with CO slowly formed trans-[Ir(IBioxMe4)2(CO)2][BArF4] (8), but the equivalent reaction with bis-ethylene 6 was an order of magnitude faster, quantifying the strong coordination of COD in 7
Rhodium(I) and Iridium(I) complexes of the conformationally rigid IBioxMe4Ligand : computational and experimental studies of unusually tilted NHC coordination geometries
Computational methods have been used to analyze distorted coordination geometries in a coherent range of known and new rhodium(I) and iridium(I) complexes containing bioxazoline-based NHC ligands (IBiox). Such distortions are readily placed in context of the literature through measurement of the Cnt(NHC)–CNCN–M angle (ΘNHC; Cnt = ring centroid). On the basis of restricted potential energy calculations using cis-[M(IBioxMe4)(CO)2Cl] (M1; M = Rh, Ir), in-plane (yawing) tilting of the NHC was found to incur significantly steeper energetic penalties than orthogonal out-of-plane (pitching) movement, which is characterized by noticeably flat potential energy surfaces. Energy decomposition analysis (EDA) of the ground-state and pitched structures of M1 indicated only minor differences in bonding characteristics. In contrast, yawing of the NHC ligand is associated with a significant increase in Pauli repulsion (i.e., sterics) and reduction in M→NHC π back donation, but is counteracted by supplemental stabilizing bonding interactions only possible due to the closer proximity of the methyl substituents with the metal and ancillary ligands. Aided by this analysis, comparison with a range of carefully selected model systems and EDA, distorted coordination modes in trans-[M(IBioxMe4)2(COE)Cl] (M2; M = Rh, Ir) and [M(IBioxMe4)3]+ (M3; M = Rh, Ir) have been rationalized. Steric interactions were identified as the major contributing factor and are associated with a high degree of NHC pitching. In the case of Rh3, weak agostic interactions also contribute to the distortions, particularly with respect to NHC yawing, and are notable for increasing the bond dissociation energy of the distorted ligands. Supplementing the computational analysis, an analogue of the formally 14 VE Rh(I) species Rh3 bearing the cyclohexyl-functionalized IBiox6 ligand ([Rh(IBiox6)3]+, Rh3-Cy) was prepared and found to exhibit an exceptionally distorted NHC ligand (ΘNHC = 155.7(2)°) in the solid state
Compellingly high SARS-CoV-2 susceptibility of Golden Syrian hamsters suggests multiple zoonotic infections of pet hamsters during the COVID-19 pandemic
Golden Syrian hamsters (Mesocricetus auratus) are used as a research model for severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). Millions of Golden Syrian hamsters are also kept as pets in close contact to humans. To determine the minimum infective dose (MID) for assessing the zoonotic transmission risk, and to define the optimal infection dose for experimental studies, we orotracheally inoculated hamsters with SARS-CoV-2 doses from 1 * 105 to 1 * 10-4 tissue culture infectious dose 50 (TCID50). Body weight and virus shedding were monitored daily. 1 * 10-3 TCID50 was defined as the MID, and this was still sufficient to induce virus shedding at levels up to 102.75 TCID50/ml, equaling the estimated MID for humans. Virological and histological data revealed 1 * 102 TCID50 as the optimal dose for experimental infections. This compelling high susceptibility leading to productive infections in Golden Syrian hamsters must be considered as a potential source of SARS-CoV-2 infection for humans that come into close contact with pet hamsters
Numerical analysis of performance uncertainty of heat exchangers operated with nanofluids
In this paper, we analyse the performance of two types of heat exchangers with nanofluid as the working fluid in turbulent flow regime ( 4, 000–180, 000). Based on the experimental uncertainty of the thermophysical properties of the nanofluids, we use the Stochastic Collocation Method in combination with a deterministic simulation programme to estimate the expected value and variance of the targeted engineering results. We find that the uncertainty in the thermal conductivity of the nanofluid has the largest impact on the uncertainty in the heat exchanger performance, while the uncertainty in the density can be neglected. The uncertainties in the Nusselt number, friction factor and several figures of merit are smaller than the change in these performance estimators due to a change in nanoparticle concentration. Predictions for heat exchanger performance agree much better with experimental data when used with empirical heat transfer correlations developed specifically for nanofluids than with the general Gnielinski correlation developed for pure fluids.
We also perform a correlation analysis of the relationships between heat exchanger performance enhancement and pressure drop to show that they are strongly correlated. We find that the relationship between the concentration of nanoparticles and the Nusselt number is statistically insignificant. The relationship is significant, indicating the importance of flow conditions. The correlation between nanoparticle concentration and friction factor is significant and strong. This result suggests that the optimisation of the thermal-hydrodynamic behaviour should be sought in a parameter other than the nanoparticle volume fraction
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