Turbulence length scales in a low-roughness near-neutral atmospheric surface layer

Published online: 14 Oct 2019.This paper investigated the integral length scales of turbulence in a low-roughness atmospheric surface layer (ASL), characterised by very smooth terrain in the Utah desert during near-neutral conditions, and evaluated the Engineering Sciences Data Unit (ESDU) 85020 and 86010 predictions for the turbulence length scales in a lowroughness ASL. The correlation integral method was used to estimate the integral length scales of the velocity components with longitudinal, lateral and vertical separations from sonic measurements on a vertical tower and spanwise array in the Surface Layer Turbulence and Environmental Science Test (SLTEST) field experiment. It was found that the longitudinal integral length scales calculated using near-neutral SLTEST data followed a logarithmic relationship with height proportional to the mean velocity profile with approximately constant integral time scale, however the sizes of the longitudinal components of the energy-containing eddies in the low-roughness flat terrain were 2–3 times smaller than those previously measured during field experiments in open country terrains. The calculated length scales with longitudinal separations over the very smooth terrain characteristics of the salt flats at Dugway were not consistent with those predicted by ESDU 85020. In contrast, the scaling of the lateral and vertical components of the three-dimensional turbulence structure with respect to the longitudinal component in the low-roughness ASL were consistent with similarity theory predictions in ESDU 86010 that the scaling ratios are independent of terrain roughness. Furthermore, this confirms the large dependence of the longitudinal turbulence length scales on the upstream terrain roughness and highlights the large variation of turbulence length scales observed at different low-roughness sites in the literature.Matthew J. Emes, Maziar Arjomandi, Richard M. Kelso and Farzin Ghanad

Combinatorial integer labeling theorems on finite sets with applications

Tucker’s well-known combinatorial lemma states that, for any given symmetric triangulation of the n-dimensional unit cube and for any integer labeling that assigns to each vertex of the triangulation a label from the set {±1, ±2, · · · , ±n} with the property that antipodal vertices on the boundary of the cube are assigned opposite labels, the triangulation admits a 1-dimensional simplex whose two vertices have opposite labels. In this paper, we are concerned with an arbitrary finite set D of integral vectors in the n-dimensional Euclidean space and an integer labeling that assigns to each element of D a label from the set {±1, ±2, · · · , ±n}. Using a constructive approach, we prove two combinatorial theorems of Tucker type. The theorems state that, under some mild conditions, there exists two integral vectors in D having opposite labels and being cell-connected in the sense that both belong to the set {0, 1} n +q for some integral vector q. These theorems are used to show in a constructive way the existence of an integral solution to a system of nonlinear equations under certain natural conditions. An economic application is provided

Experimental investigation of peak wind loads on tandem operating heliostats within an atmospheric boundary layer

During the operation of a concentrating solar thermal (CST) power tower plant, heliostat mirrors inclined at different angles act as bluff bodies that are exposed to large drag loads from the wind. This experimental study investigates the aerodynamic loads on a heliostat in a tandem configuration, to determine the significance of the shielding effect from an upstream heliostat. To understand the effect of turbulence on the peak wind loads, scalemodel heliostats with square facets were positioned within a part-depth atmospheric boundary layer (ABL) with a Power Law velocity profile. Peak drag coefficients on the instrumented downstream heliostat in the tandem configuration were normalized with respect to those on a single (isolated) heliostat. A range of tandem configurations were tested to determine the effects of elevation angle, azimuth angle, and gap spacing between the tandem heliostats. Findings show that peak drag loads are reduced by up to 60% on the downstream heliostat relative to an isolated heliostat at an elevation angle of 90° and a gap spacing of two chord lengths, but at higher gap spacing the shielding effect is either marginal or non-existent. Peak hinge moment coefficients on a downstream heliostat in tandem are up to seven times the load on an isolated heliostat, with the maximum occurring at 90° elevation and 180° azimuth. Base-overturning moment coefficients are less affected, as the changes in the centre of pressure location are relatively small compared to the length of the support pylon. Strouhal number analysis of the fluctuating surface pressures indicated that the dominant frequency of the pressure spectra on the downstream heliostat is over three times the value on an isolated heliostat at 45° elevation and azimuth angles. Hence, both static and dynamic effects must be considered separately in the wind load design for heliostats at typical operating angles.Jeremy S. Yu, Matthew J. Emes, Farzin Ghanadi, Maziar Arjomandi, Richard Kels

Linkage isomerism in the binding of pentapeptide Ac-His(ALA)3His-NH2 to (Ethylenediamine)Palladium(II): Effect of the binding mode on peptide conformation

The reaction of the pentapeptide Ac-His1-Ala2-Ala3-Ala4-His5-NH2 (AcHAAAHNH2) (1) with [Pd(en)(ONO2)(2)] (en = NH2CH2CH2NH2) in either DMF-d(7) or H2O:D2O (90%:10%) gave three linkage isomers of [Pd(en)(AcHAAAHNH2)](2+) (2), 2a, 2b, and 2c, which differ only in which pair of imidazole nitrogen atoms bind to Pd. In the most abundant isomer, 2a, Pd is bound by N1 from each of the two imidazole rings. In the minor isomers 2b and 2c, Pd is bound by N1(His1) and N3(His5) and by N3(His1) and N1(His5), respectively. The reactions of [Pd(en)(ONO2)(2)] with the N-methylated peptides Ac-(N3-MeHis)Ala-Ala-Ala-(N3-MeHis)-NH2 (AcH*AAAH*NH2) (3), Ac-(N3-MeHis)-Ala-Ala-Ala-(N1-MeHis)-NH2 (AcH*AAAH(#)NH(2)) (4), and Ac(N1-MeHis)-Ala-Ala-Ala-(N3-Me-His)-NH2 (AcH(#)AAAH*NH2) (5) each gave a single species [Pd(en)(peptide)](2+) in N,Ndimethylformamide (DMF) or aqueous solution, 7, 8, and 9, respectively, with Pd bound by the two nonmethylated imidazole nitrogen atoms in each case. These complexes were analogous to 2a, 2b, and 2c, respectively. Ac-(N1-MeHis)-Ala-Ala-Ala(N1-MeHis)-NH2 (AcH(#)AAAH(#)NH(2)) (6) with [Pd(en)(ONO2)21 in DMF slowly gave a single product, [Pd(en)(AcH(#)AAAH(#)NH(2))]21 (10), in which Pd was bound by the N3 of each imidazole ring, The corresponding linkage isomer of 2 was not observed. Complex 10 was also the major product in aqueous solution, but other species were also present. All compounds were exhaustively characterized in solution by multinuclear 1D (H-1, C-13, and, with N-15-labeled ethylenediamine, N-15) and 2D (correlation spectroscopy, total correlation spectroscopy, transverse rotating-frame Overhauser effect spectroscopy (T-ROESY), heteronuclear multiplebond correlation, and heteronuclear single quantum coherence) NMR spectra, circular dichroism (CD) spectra, electrospray mass spectroscopy, and reversed-phase high-performance liquid chromatography. ROESY spectra were used to calculate the structure of 2a, which contained a single turn of a peptide alpha helix in both DMF and water, the helix being better defined in DMF The Pd(en)(2+) moiety was not used in structure calculations, but its location and coordination by one imidazole N1 from each histidine to form a 22-membered metallocycle were unambiguously established. Convergence of the structures was greatest when calculated with two hydrogen-bond constraints (Ala4 pepticle NH center dot center dot center dot OC acetyl and His5 peptide NH center dot center dot center dot OC-His1) that were indicated by the low temperature dependence of these NH chemical shifts. Vicinal HN-CH alpha coupling constants and chemical shifts of alpha-H atoms were also consistent with a helical conformation. Similar long-range ROE correlations were observed for [Pd(en)(AcH*AAAH*NH2)](2+) (7), which displayed a CD spectrum in aqueous solution that suggested the presence of some helicity. Long-range ROE correlations were not observed for 8, 9, or 10, but a combination of NMR data and CD spectroscopy was interpreted in terms of the conformational behavior of the coordinated pentapeptide. Only for the linkage isomer [Pd(en)(AcH*AAAH(#)NH(2))](2+) (8) was there evidence of a contribution from a helical conformation

Distributed central pattern generator model for robotics application based on phase sensitivity analysis

Abstract. A method is presented to predict phase relationships between coupled phase oscillators. As an illustration of how the method can be applied, a distributed Central Pattern Generator (CPG) model based on amplitude controlled phase oscillators is presented. Representative results of numerical integration of the CPG model are presented to illustrate its excellent properties in terms of transition speeds, robustness and independence on initial conditions. A particularly interesting feature of the CPG is the possibility to switch between different stable gaits by varying a single parameter. These characteristics make the CPG model an interesting solution for the decentralized control of multilegged robots. The approach is discussed in the more general framework of coupled nonlinear systems, and design tools for nonlinear distributed control schemes applicable to Information Technology and Robotics.

Cephalosporin nitric oxide-donor prodrug DEA-C3D disperses biofilms formed by clinical cystic fibrosis isolates of Pseudomonas aeruginosa

open access articleObjectives: The cephalosporin nitric oxide (NO)-donor prodrug DEA-C3D (DiEthylAmin-Cephalosporin-3’- Diazeniumdiolate) has been showed to initiate the dispersal of biofilms formed by Pseudomonas aeruginosa laboratory strain PAO1. In this study, we investigated whether DEA-C3D disperses biofilms formed by clinical cystic fibrosis isolates of P. aeruginosa and its effect in combination with two anti-pseudomonal antibiotics, tobramycin and colistin, in vitro. Methods: -lactamase-triggered release of NO from DEA-C3D was confirmed using a gas-phase chemiluminescence detector. MICs against P. aeruginosa clinical isolates were measured using the broth microdilution method. A crystal violet staining technique and confocal laser scanning microscopy were used to evaluate the effects of DEA-C3D on P. aeruginosa biofilms alone and in combination with tobramycin and colistin. Results: DEA-C3D was confirmed to selectively release NO in response to contact with bacterial -lactamase. Despite lacking direct, cephalosporin/-lactam-based antibacterial activity, DEA-C3D was able to disperse biofilms formed by three P. aeruginosa clinical isolates. Confocal microscopy revealed that DEA-C3D in combination with tobramycin produces similar reductions in biofilm to DEA-C3D alone, whereas the combination with colistin causes near complete eradication of P. aeruginosa biofilms in vitro. Conclusions: DEA-C3D is effective in dispersing biofilms formed by multiple clinical isolates of P. aeruginosa and could hold promise as a new adjunctive therapy to patients with CF

Primary ciliary dyskinesia ciliated airway cells show increased susceptibility to Haemophilus influenza biofilm formation

Nontypeable Haemophilus influenzae (NTHi) is the most common pathogen in primary ciliary dyskinesia (PCD) patients. We hypothesized that abnormal ciliary motility and low airway nitric oxide (NO) levels on airway epithelial cells from PCD patients might be permissive for NTHi colonization and biofilm evelopment. We used a primary epithelial cell co-culture model to investigate NTHi infection. Primary airway epithelial cells from PCD and non-PCD patients were differentiated to ciliation using air-liquid interface culture and then co-cultured with NTHi. NTHi adherence was greater on PCD epithelial cells compared to non-PCD cells (P<0.05) and the distribution of NTHi on PCD epithelium showed more aggregated NTHi in biofilms (P<0.001). Apart from defective ciliary motility, PCD cells did not significantly differ from non-PCD epithelial cells in the degree of ciliation and epithelial integrity or in cytokine, LL-37 and NO production. Treatment of PCD epithelia using exogenous NO and antibiotic significantly reduced NTHi viability in biofilms compared to antibiotic treatment alone. Impaired ciliary function was the primary defect in PCD airway epithelium underlying susceptibility to NTHi biofilm development compared with non-PCD epithelium. Although NO responses were similar, use of targeted NO with antibiotics enhanced killing of NTHi in biofilms, suggesting a novel therapeutic approach