Transitions from Monotonicity to Chaos in Gas Mixture Dynamics in Pipeline Networks

The blending of hydrogen generated using clean energy into natural gas pipeline networks is proposed in order to utilize existing energy systems for their planned lifetime while reducing their reliance on fossil fuels. We formulate a system of partial differential equations (PDEs) that govern the flow dynamics of mixtures of gases in pipeline networks under the influence of time-varying compressor and regulator control actions. The formulation is derived for general gas networks that can inject or withdraw arbitrary time-varying mixtures of gases into or from the network at arbitrarily specified nodes. The PDE formulation is discretized in space to form a nonlinear control system which is used to prove that homogeneous mixtures are well-behaved and heterogeneous mixtures may be ill-behaved in the sense of monotone-ordering of solutions. We use numerical simulations to compute interfaces that delimit periodic and monotone system responses and show that any solution in the monotonic operating region eventually approaches a periodic orbit. Our results are demonstrated for examples of a single pipeline and a small test network

Supermassive Black-hole Demographics & Environments With Pulsar Timing Arrays

Precision timing of large arrays (>50) of millisecond pulsars will detect the nanohertz gravitational-wave emission from supermassive binary black holes within the next ~3-7 years. We review the scientific opportunities of these detections, the requirements for success, and the synergies with electromagnetic instruments operating in the 2020s.Comment: Submitted to the Astro2020 Decadal Survey. One of 5 core white-papers authored by members of the NANOGrav Collaboration. 9 pages, 2 figure

Large Scale Structure traced by Molecular Gas at High Redshift

We present observations of redshifted CO(1-0) and CO(2-1) in a field containing an overdensity of Lyman break galaxies (LBGs) at z=5.12. Our Australia Telescope Compact Array observations were centered between two spectroscopically-confirmed z=5.12 galaxies. We place upper limits on the molecular gas masses in these two galaxies of M(H_2) <1.7 x 10^10 M_sun and <2.9 x 10^9 M_sun (2 sigma), comparable to their stellar masses. We detect an optically-faint line emitter situated between the two LBGs which we identify as warm molecular gas at z=5.1245 +/- 0.0001. This source, detected in the CO(2-1) transition but undetected in CO(1-0), has an integrated line flux of 0.106 +/- 0.012 Jy km/s, yielding an inferred gas mass M(H_2)=(1.9 +/- 0.2) x 10^10 M_sun. Molecular line emitters without detectable counterparts at optical and infrared wavelengths may be crucial tracers of structure and mass at high redshift.Comment: 4 pages, accepted for publication in ApJ Letter

Constraining the Thermal Dust Content of Lyman-Break Galaxies in an Overdense Field at z~5

We have carried out 870 micron observations in the J1040.7-1155 field, known to host an overdensity of Lyman break galaxies at z=5.16 +/- 0.05. We do not detect any individual source at the S(870)=3.0 mJy/beam (2 sigma) level. A stack of nine spectroscopically confirmed z>5 galaxies also yields a non-detection, constraining the submillimeter flux from a typical galaxy at this redshift to S(870)<0.85 mJy, which corresponds to a mass limit M(dust)<1.2x10^8 M_sun (2 sigma). This constrains the mass of thermal dust in distant Lyman break galaxies to less than one tenth of their typical stellar mass. We see no evidence for strong submillimeter galaxies associated with the ultraviolet-selected galaxy overdensity, but cannot rule out the presence of fainter, less massive sources.Comment: 5 pages, 2 figures. MNRAS in pres

Use of a handheld Doppler to measure brachial and femoral artery occlusion pressure

Objective: Measurement of arterial occlusion pressure (AOP) is essential to the safe and effective use of blood flow restriction during exercise. Use of a Doppler ultrasound (US) is the “gold standard” method to measure AOP. Validation of a handheld Doppler (HHDOP) device to measure AOP could make the measurement of AOP more accessible to practitioners in the field. The purpose of this study was to determine the accuracy of AOP measurements of the brachial and femoral arteries using an HHDOP.Methods: We simultaneously measured AOP using a “gold standard” US and a HHDOP in the dominant and non-dominant arms (15 males; 15 females) and legs (15 males; 15 females).Results: There were no differences in limb circumference or limb volume in the dominant and non-dominant arms and legs between males and females or between the dominant and non-dominant arms and legs of males and females. The differences between US and HHDOP measures of AOP in the dominant and non-dominant arms and legs were either not significant or small (&lt;10 mmHg) and of little practical importance. There were no sex differences in AOP measurements of the femoral artery (p &gt; 0.60). Bland–Altman analysis yielded an average bias (−0.65 mmHg; −2.93 mmHg) and reasonable limits of agreement (±5.56 mmHg; ±5.58 mmHg) between US and HHDOP measures of brachial and femoral artery AOP, respectively.Conclusion: HHDOP yielded acceptable measures of AOP of the brachial and femoral arteries and can be used to measure AOP by practitioners for the safe and effective use of blood flow restriction. Due to the potential differences in AOP between dominant and non-dominant limbs, AOP should be measured in each limb

Three-dimensional CFD simulations with large displacement of the geometries using a connectivity-change moving mesh approach

This paper deals with three-dimensional (3D) numerical simulations involving 3D moving geometries with large displacements on unstructured meshes. Such simulations are of great value to industry, but remain very time-consuming. A robust moving mesh algorithm coupling an elasticity-like mesh deformation solution and mesh optimizations was proposed in previous works, which removes the need for global remeshing when performing large displacements. The optimizations, and in particular generalized edge/face swapping, preserve the initial quality of the mesh throughout the simulation. We propose to integrate an Arbitrary Lagrangian Eulerian compressible flow solver into this process to demonstrate its capabilities in a full CFD computation context. This solver relies on a local enforcement of the discrete geometric conservation law to preserve the order of accuracy of the time integration. The displacement of the geometries is either imposed, or driven by fluid–structure interaction (FSI). In the latter case, the six degrees of freedom approach for rigid bodies is considered. Finally, several 3D imposed-motion and FSI examples are given to validate the proposed approach, both in academic and industrial configurations

Synthesis and characterization of high-affinity 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene-labeled fluorescent ligands for human β-adrenoceptors

The growing practice of exploiting noninvasive fluorescence-based techniques to study G protein-coupled receptor pharmacology at the single cell and single molecule level demands the availability of high-quality fluorescent ligands. To this end, this study evaluated a new series of red-emitting ligands for the human β-adrenoceptor family. Upon the basis of the orthosteric ligands propranolol, alprenolol, and pindolol, the synthesized linker-modified congeners were coupled to the commercially available fluorophore BODIPY 630/650-X. This yielded high-affinity β-adrenoceptor fluorescent ligands for both the propranolol and alprenolol derivatives; however, the pindolol-based products displayed lower affinity. A fluorescent diethylene glycol linked propranolol derivative (18a) had the highest affinity (log KD of -9.53 and -8.46 as an antagonist of functional β2- and β1-mediated responses, respectively). Imaging studies with this compound further confirmed that it can be employed to selectively label the human β2-adrenoceptor in single living cells, with receptor-associated binding prevented by preincubation with the nonfluorescent β2-selective antagonist 3-(isopropylamino)-1-[(7-methyl-4-indanyl)oxy]-butan-2-ol (ICI 118551) (J. Cardiovasc. Pharmacol. 1983, 5, 430-437.

Supermassive Black-hole Demographics & Environments With Pulsar Timing Arrays

Precision timing of large arrays (>50) of millisecond pulsars will detect the nanohertz gravitational-wave emission from supermassive binary black holes within the next ~3-7 years. We review the scientific opportunities of these detections, the requirements for success, and the synergies with electromagnetic instruments operating in the 2020s