Numerical Simulations of Radiatively-Driven Dusty Winds

[abridged] Radiation pressure on dust grains may be an important mechanism in driving winds in a wide variety of astrophysical systems. However, the efficiency of the coupling between the radiation field and the dusty gas is poorly understood in environments characterized by high optical depths. We present a series of idealized numerical experiments, performed with the radiation-hydrodynamic code ORION, in which we study the dynamics of such winds and quantify their properties. We find that, after wind acceleration begins, radiation Rayleigh-Taylor instability forces the gas into a configuration that reduces the rate of momentum transfer from the radiation field to the gas by a factor ~ 10 - 100 compared to an estimate based on the optical depth at the base of the atmosphere; instead, the rate of momentum transfer from a driving radiation field of luminosity L to the gas is roughly L/c multiplied by one plus half the optical depth evaluated using the photospheric temperature, which is far smaller than the optical depth one would obtain using the interior temperature. When we apply our results to conditions appropriate to ULIRGs and star clusters, we find that the asymptotic wind momentum flux from such objects should not significantly exceed that carried by the direct radiation field, L/c. This result constrains the expected mass loss rates from systems that exceed the Eddington limit to be of order the so-called "single-scattering" limit, and not significantly higher. We present an approximate fitting formula for the rate of momentum transfer from radiation to dusty gas through which it passes, which is suitable for implementation in sub-grid models of galaxy formation. Finally, we provide a first map of the column density distribution of gas in a radiatively-driven wind as a function of velocity, and velocity dispersion.Comment: 19 pages, 17 figures, MNRAS in press; some additional discussion compared to previous version, no changes in conclusion

Know Your Clients' behaviours: a cluster analysis of financial transactions

In Canada, financial advisors and dealers are required by provincial securities commissions and self-regulatory organizations--charged with direct regulation over investment dealers and mutual fund dealers--to respectively collect and maintain Know Your Client (KYC) information, such as their age or risk tolerance, for investor accounts. With this information, investors, under their advisor's guidance, make decisions on their investments which are presumed to be beneficial to their investment goals. Our unique dataset is provided by a financial investment dealer with over 50,000 accounts for over 23,000 clients. We use a modified behavioural finance recency, frequency, monetary model for engineering features that quantify investor behaviours, and machine learning clustering algorithms to find groups of investors that behave similarly. We show that the KYC information collected does not explain client behaviours, whereas trade and transaction frequency and volume are most informative. We believe the results shown herein encourage financial regulators and advisors to use more advanced metrics to better understand and predict investor behaviours.Comment: 38 pages, 12 figure

Bloodied democracy: Duterte and the death of liberal reformism in the Philippines

Since assuming the presidency, Rodrigo R. Duterte has "stuck to his guns" in carrying out his campaign pledge to launch a violent anti-drug campaign. Duterte's presidency was preceded by six years of political stability and high growth under the relatively liberal and supposedly reformist administration of President Benigno "Noynoy" S. Aquino, III. What did voters find so appealing about Duterte given that drugs and criminality were not a major national concern until he launched his candidacy? Unlike previous populist politicians in the post-Marcos Philippines, Duterte's strongest support did not come from the poorest voters but rather from the elite and the middle class who most feared for their personal security. Although Aquino was widely perceived to be personally honest, his administration had become "systemically disjunctive" and vulnerable to replacement by violent illiberalism because its narrative of "good governance" had been undermined, its strategic allies were weakened, and liberal institutions discredited. Duterte is an illiberal populist who changed the prevailing political order into an illiberal one through a new law-and-order governing script, new key strategic groups (the communist left and the police), and the quick removal of remaining liberal constraints (particularly in Congress and the Supreme Court). Duterte constructed a strongman political model at the local level before "nationalising" it after his election as president

Introduction: the early Duterte presidency in the Philippines

After only a little over a half year in power, as of this writing, Rodrigo's R. Duterte presidency already represents a sea change in Philippine politics. Despite the personal popularity of Benigno "Noynoy" S. Aquino III (who had the highest opinion poll ratings among post-Marcos presidents), Duterte has quickly replaced a "liberal reformist" political order with its emphasis on civil liberties, if limited political participation, with an illiberal "law and order" regime

Southeast Asia’s Subversive Voters: A Philippine Perspective

In the Philippines and other Southeast Asian countries poor people’s voting behavior has been subversive of elite interests, causing the upper classes to be skeptical of votes cast by the poor and to “educate” them on the “proper” exercise of suffrage. But voting by the poor can be understood within a “moral economy” framework in which communal interests transcend utilitarian calculations. Populist politicians (Joseph Estrada in the Philippines and Thaksin Shinawatra in Thailand) have brought localist voting patterns to the national level, resulting in adverse reactions: an elite-led insurrection ousted Estrada in 2001, while the Thai military staged the coup of 2014 to break the electoral bond between pro-Thaksin politicians and the poor.Keywords: Elections • poor voters • voter education • populism • Southeast Asi

Brute force governance: public approval despite policy failure during the COVID-19 pandemic in the Philippines

The COVID-19 pandemic has exposed enormous governance deficits globally. Several populist strongmen practiced "medical populism" - ignoring scientific advice, proffering denials, and blaming others. More technocratic leaders recognised its severity, implementing strict lockdowns. But some failed to adopt more flexible restrictions once testing improved due to local enforcement difficulties, termed "blunt force regulation." Although neither a pandemic denialist nor an obtuse technocrat, Philippine president Rodrigo R. Duterte's response combined aspects of both approaches with blame shifting and one-size-fits-all lockdowns while also securitising the crisis. Utilising methods developed during his bloody "war on drugs," Duterte imposed a heavily militarised approach, scapegoated supposedly disobedient Filipinos (pasaway) and bullied local politicians. While the Philippines has been among the worst pandemic performers globally, Duterte's approval ratings remained robust. It is argued "brute force governance" undermined the dynamics of accountability, enabling him to win public approval despite policy failure

The Maximum Flux of Star-Forming Galaxies

The importance of radiation pressure feedback in galaxy formation has been extensively debated over the last decade. The regime of greatest uncertainty is in the most actively star-forming galaxies, where large dust columns can potentially produce a dust-reprocessed infrared radiation field with enough pressure to drive turbulence or eject material. Here we derive the conditions under which a self-gravitating, mixed gas-star disc can remain hydrostatic despite trapped radiation pressure. Consistently taking into account the self-gravity of the medium, the star- and dust-to-gas ratios, and the effects of turbulent motions not driven by radiation, we show that galaxies can achieve a maximum Eddington-limited star formation rate per unit area $\dot{\Sigma}_{\rm *,crit} \sim 10^3 M_{\odot}$ pc$^{-2}$ Myr$^{-1}$, corresponding to a critical flux of $F_{\rm *,crit} \sim 10^{13} L_{\odot}$ kpc$^{-2}$ similar to previous estimates; higher fluxes eject mass in bulk, halting further star formation. Conversely, we show that in galaxies below this limit, our one-dimensional models imply simple vertical hydrostatic equilibrium and that radiation pressure is ineffective at driving turbulence or ejecting matter. Because the vast majority of star-forming galaxies lie below the maximum limit for typical dust-to-gas ratios, we conclude that infrared radiation pressure is likely unimportant for all but the most extreme systems on galaxy-wide scales. Thus, while radiation pressure does not explain the Kennicutt-Schmidt relation, it does impose an upper truncation on it. Our predicted truncation is in good agreement with the highest observed gas and star formation rate surface densities found both locally and at high redshift.Comment: Version accepted for publication in MNRAS. 12 pages, 8 figures. New appendix on photon tirin

The applicability of self-regulation theories in sport : goal adjustment capacities, stress appraisals, coping and well-being among athletes

Objectives: We examined a model, informed by self-regulation theories, which included goal adjustment capacities, appraisals of challenge and threat, coping, and well-being. Design: Prospective. Methods: Two hundred and twelve athletes from the United Kingdom (n = 147) or Australia (n = 65), who played team (n = 135) or individual sports (n = 77), and competed at international (n = 7), national (n = 11), county (n = 67), club (n = 84), or beginner (n = 43) levels participated in this study. Participants completed measures of goal adjustment capacities and stress appraisals two days before competing. Athletes also completed questions on coping and well-being within three hours of their competition ending. Results: The way an athlete responds to an unattainable goal is associated with his or her well-being in the period leading up to and including the competition. Goal reengagement positively predicted well-being, whereas goal disengagement negatively predicted well-being. Further, goal reengagement was positively associated with challenge appraisals, which in turn was linked to task-oriented coping, and task-oriented coping positively associated with well-being. Conclusion: When highly-valued goals become unattainable, consultants could encourage athletes to seek out alternative approaches to achieve the same goal or help them develop a completely new goal