Interplanetary Low-Thrust Design Using Proximal Policy Optimization

This paper aims to demonstrate a reinforcement learning technique for developing complex, decision-making policies capable of planning interplanetary transfers.Using Proximal Policy Optimization (PPO), a neural network agent is trained to produce a closed-loop controller capable of transfers between Earth and Mars.The agent is trained in an environment that utilizes a medium fidelity solar electric propulsion model and a real ephemeris model of the Earth and Mars. The results are compared against those generated by the Evolutionary Mission Trajectory Generator (EMTG) tool

Perturbed soliton excitations in DNA molecular chain

We study nonlinear dynamics of a periodic inhomogeneous DNA double helical chain under dynamic plane-base rotator model by considering angular rotation of bases in a plane normal to the helical axis. The dynamics is governed by a perturbed sine-Gordon equation. The perturbed soliton solution is obtained using a multiple scale soliton perturbation theory. The perturbed kink-antikink solitons represent formation of open state configuration with fluctuation in DNA.Comment: 20 Pages, 5 figure

Propagation of twist solitons in real DNA chains

We report on numerical investigations concerning the propagation of solitons in a real DNA chain (the Human Adenovirus 2) using a realistic model of DNA torsional dynamics; this takes fully into account the inhomogeneities in the real chain. We find that twist solitons propagate for considerable distances (2-10 times their diameters) before stopping due to phonon emission. Our results show that twist solitons may exist in real DNA chains; and on a more general level that solitonic propagation can take place in highly inhomogeneous media.Comment: 6 pages, 3 figure

Low-Resolution Molecular Models Reveal the Oligomeric State of the PPAR and the Conformational Organization of Its Domains in Solution

The peroxisome proliferator-activated receptors (PPARs) regulate genes involved in lipid and carbohydrate metabolism, and are targets of drugs approved for human use. Whereas the crystallographic structure of the complex of full length PPARγ and RXRα is known, structural alterations induced by heterodimer formation and DNA contacts are not well understood. Herein, we report a small-angle X-ray scattering analysis of the oligomeric state of hPPARγ alone and in the presence of retinoid X receptor (RXR). The results reveal that, in contrast with other studied nuclear receptors, which predominantly form dimers in solution, hPPARγ remains in the monomeric form by itself but forms heterodimers with hRXRα. The low-resolution models of hPPARγ/RXRα complexes predict significant changes in opening angle between heterodimerization partners (LBD) and extended and asymmetric shape of the dimer (LBD-DBD) as compared with X-ray structure of the full-length receptor bound to DNA. These differences between our SAXS models and the high-resolution crystallographic structure might suggest that there are different conformations of functional heterodimer complex in solution. Accordingly, hydrogen/deuterium exchange experiments reveal that the heterodimer binding to DNA promotes more compact and less solvent-accessible conformation of the receptor complex

The violent frontline: space, ethnicity and confronting the state in Edwardian Spitalfields and 1980s Brixton

This article discusses in comparative terms the relationship between space, ethnic identity, subaltern status and anti-state violence in twentieth century London. It does so by comparing two examples in which the control of the state, as represented by the Metropolitan Police, was challenged by minority groups through physical force. It will examine the Spitalfields riots of 1906, which began as strike action by predominantly Jewish bakers and escalated into a general confrontation between the local population and the police, and the Brixton riots of 1981, a response to endemic police harassment of mainly Caribbean youth and long-term economic discrimination in that area of South London. It will begin by dissecting the association of physical metropolitan space with the diasporic ‘other’ in the Edwardian East End and post-consensus South London, and how this ‘othering’ was influenced both by the state and the anti-migrant far right. It will then interrogate the difficult relationship between the Metropolitan Police and Jewish and Caribbean working class communities, and how this deteriorating relationship exploded into in extreme violence in 1906 and 1981. The article will conclude by assessing how the relationships between space, identity and violence influenced long-term national and communal narratives of Jewish and Caribbean interactions with the British state

Protecting the Human Rights of LGBT People in Uganda in the Wake of Uganda\u27s Anti Homosexuality Bill, 2009

A bill pending before the Ugandan Parliament from October 2009 to May 2011 sought to punish anyone who engages in \u27homosexuality\u27 with life imprisonment and prescribed the death penalty for a variety of activities deemed \u27aggravated homosexuality.\u27 Many commentators saw the \u27Anti Homosexuality Bill, 2009\u27 (\u27Bill\u27 or \u27Anti-homosexuality Bill\u27) as the most pernicious legislative proposal aimed at gays and lesbians anywhere in the world and feared the death penalty provision could signal a \u27looming gay genocide\u27 in Uganda. This Comment seeks to begin the conversation on legal solutions to vindicate the rights of LGBT people in Uganda in the wake of the Anti-homosexuality Bill

Protecting the Human Rights of LGBT People in Uganda in the Wake of Uganda\u27s Anti Homosexuality Bill, 2009

A bill pending before the Ugandan Parliament from October 2009 to May 2011 sought to punish anyone who engages in \u27homosexuality\u27 with life imprisonment and prescribed the death penalty for a variety of activities deemed \u27aggravated homosexuality.\u27 Many commentators saw the \u27Anti Homosexuality Bill, 2009\u27 (\u27Bill\u27 or \u27Anti-homosexuality Bill\u27) as the most pernicious legislative proposal aimed at gays and lesbians anywhere in the world and feared the death penalty provision could signal a \u27looming gay genocide\u27 in Uganda. This Comment seeks to begin the conversation on legal solutions to vindicate the rights of LGBT people in Uganda in the wake of the Anti-homosexuality Bill

Land management in rural China and its gender implications

Women are an important mainstay of agricultural production in China, though their access to land is characterized by even greater ambiguity than that of their male counterparts. As part of its path toward liberalization, China undertook agricultural land management policy reforms that were aimed at increasing the security of land tenure rights, but these reforms have paradoxically exacerbated the uncertainty surrounding women's claims to land. Utilizing sample survey data collected from 412 rural households in Shaanxi and Hunan provinces in 2002, this paper documents and analyzes gender differences in land allocations. The findings of this study shed light on the degree to which community characteristics coupled with current local practices (such as frequency of reallocation) influence gender disparities. Results suggest that a growing number of women experience loss of contract land coincident with marrying, and this trend may be expected to increase given the current direction of land policy.China, gender, land, property rights, JEL codes: J16, P2, Q15,