MHOs toward HMOs: A Search for Molecular Hydrogen emission-line Objects toward High-Mass Outflows

We present the results of a narrow-band near-infrared imaging survey for Molecular Hydrogen emission-line Objects (MHOs) toward 26 regions containing high-mass protostellar candidates and massive molecular outflows. We have detected a total of 236 MHOs, 156 of which are new detections, in 22 out of the 26 regions. We use H$_2$ 2.12-$\mu$m/H$_2$ 2.25-$\mu$m flux ratios, together with morphology, to separate the signatures of fluorescence associated with photo-dissociation regions (PDRs) from shocks associated with outflows in order to identify the MHOs. PDRs have typical low flux ratios of ~ 1.5 - 3, while the vast majority of MHOs display flux ratios typical of C-type shocks (~ 6-20). A few MHOs exhibit flux ratios consistent with expected values for J-type shocks (~ 3-4), but these are located in regions that may be contaminated with fluorescent emission. Some previously reported MHOs have low flux ratios, and are likely parts of PDRs rather than shocks indicative of outflows. We identify a total of 36 outflows across the 22 target regions where MHOs were detected. In over half these regions, MHO arrangements and fluorescent structures trace features present in CO outflow maps, suggesting the CO emission traces a combination of dynamical effects, which may include gas entrained in expanding PDRs as well as bipolar outflows. Where possible, we link MHO complexes to distinct outflows and identify candidate driving sources.Comment: 40 pages, 40 figures, accepted for publication in the Astrophysical Journa

Transparency overlays and applications

In this paper, we initiate a formal study of transparency, which in recent years has become an increasingly critical requirement for the systems in which people place trust. We present the abstract concept of a transparency overlay, which can be used in conjunction with any system to give it provable transparency guarantees, and then apply the overlay to two settings: Certificate Transparency and Bitcoin. In the latter setting, we show that the usage of our transparency overlay eliminates the need to engage in mining and allows users to store a single small value rather than the entire blockchain. Our transparency overlay is generically constructed from a signature scheme and a new primitive we call a dynamic list commitment, which in practice can be instantiated using a collision-resistant hash function

"The real rights of man". Thomas Spence, Paine and Chartism

A deep engagement with Spence’s ideas can be found in the Chartist movement. In its drive for radical parliamentary reform, we can see the working out of Paineite thinking. And in Chartism’s impulse towards agrarian reform, we can see the working out of Spencean thinking. Uncritical deference to Paine’s memory has often obscured the contribution of others among his contemporaries to radical political thought. In the field of agrarian ideas, it was Spence not Paine whose influence was the more decisive. This is evident even in the writings of Paine’s indefatigable disciple Richard Carlile. Four elements underpinned all Chartist thinking on landed property and they also encapsulated the essence of Spence’s ideas. 1] A fundamental belief that smallholder cultivation maximised the productivity of the soil. 2] Hostility to large holdings of landed property, irrespective of their legal form. 3] A suspicion of central government as a potential owner or manager of the national estate. 4] Land holding was part of a broader assault upon the citadel of economic and political power. This article will now briefly consider each in turn

Effects of roughness on droplet apparent contact angles on a fiber

This paper reports on our investigation of the effects of surface roughness on the equilibrium shape and apparent contact angles of a droplet deposited on a fiber. In particular, the shape of a droplet on a roughened fiber is studied via the energy minimization method implemented in the surface evolver finite element code. Sinusoidal roughness varying in both the longitudinal and radial directions is considered in the simulations to study the effects of surface roughness on the most stable shape of a droplet on a fiber (corresponding a global minimum energy state). It is found that surface roughness delays droplet shape transition from a symmetric barrel to a clamshell or an asymmetric barrel profile. A phase diagram that includes the effects of fiber roughness on droplet configurations-symmetric barrel, clamshell, and asymmetric barrel-is presented for the first time. It is also found that droplet apparent contact angle tends to decrease on rough fibers. Likewise, roughness tends to increase the force required to detach a droplet from a fiber but the effect diminishes as droplet size increases relative to the size of surface roughness. The results presented in our study have been compared with experimental data or those from prior studies whenever possible, and good agreement has been observed