Exact, E=0, Solutions for General Power-Law Potentials. I. Classical Orbits

For zero energy, $E=0$, we derive exact, classical solutions for {\em all} power-law potentials, $V(r)=-\gamma/r^\nu$, with $\gamma>0$ and $-\infty <\nu<\infty$. When the angular momentum is non-zero, these solutions lead to the orbits $\r(t)= [\cos \mu (\th(t)-\th_0(t))]^{1/\mu}$, for all $\mu \equiv \nu/2-1 \ne 0$. When $\nu>2$, the orbits are bound and go through the origin. This leads to discrete discontinuities in the functional dependence of $\th(t)$ and $\th_0(t)$, as functions of $t$, as the orbits pass through the origin. We describe a procedure to connect different analytic solutions for successive orbits at the origin. We calculate the periods and precessions of these bound orbits, and graph a number of specific examples. Also, we explain why they all must violate the virial theorem. The unbound orbits are also discussed in detail. This includes the unusual orbits which have finite travel times to infinity and also the special $\nu = 2$ case.Comment: LaTeX, 27 pages with 12 figures available from the authors or can be generated from Mathematica instructions at end of the fil

"If your dress gets missing, I shall buy one": Compliments and Compliment Response Strategies in English in Ghana

This study reports an analysis of compliments and responses to compliments by selected speakers of English in Ghana. The analysis is based on a combination of participant observer schedules and recall protocol questionnaire., The population for the study is drawn from speakers of English selected from a university in Ghana. The findings of the study show that in making and responding to compliments, speakers of English in Ghana show positive transfer of complimenting strategies from Ghanaian languages and cultures into the English language spoken in Ghana. These transferred elements, which are typical structures that are used to pay compliments in many Ghanaian languages, give the English language that is spoken in Ghana its distinctive pragmatic features

The variable influence of dispersant on degradation of oil hydrocarbons in subarctic deep-sea sediments at low temperatures (0-5 °C)

The microbial degradation of petroleum hydrocarbons at low temperatures was investigated in subarctic deep-sea sediments in th e Faroe Shetland Channel (FSC). The effect of the marine oil dispersant, Superdispersant 25 on hydrocarbon degradation was also examined. Sediments collected at 500 and 1000 m depth were spiked with a model oil containing 20 hydrocarbons and incubated at ambient temperature (5 and 0 °C, respectively) with and without marine dispersant. Treatment of sediments with hydrocarbons resulted in the enrichment of Gammaproteobacteria, and specifically the genera Pseudoalteromonas, Pseudomonas, Halomonas, and Cobetia. Hydrocarbon degradation was faster at 5 °C (500 m) with 65-89% of each component degraded after 50 days compared to 0-47% degradation at 0 °C (1000 m), where the aromatic hydrocarbons fluoranthene, anthracene, and Dibenzothiophene showed no degradation. Dispersant significantly increased the rate of degradation at 1000 m, but had no effect at 500 m. There was no statistically significant effect of Superdispersant 25 on the bacterial community structure at either station. These results show that the indigenous bacterial community in the FSC has the capacity to mitigate some of the effects of a potential oil spill, however, the effect of dispersant is ambiguous and further research is needed to understand the implications of its use

Neurological complications of acute multifocal placoid pigment epitheliopathy

Acute multifocal placoid pigment epitheliopathy (AMPPE) is an autoimmune chorioretinal disease that can be complicated by neurological involvement. There is limited information on this potentially treatable condition in the neurological literature. The objective of this patient series is to describe the neurological complications of AMPPE. We retrospectively identified patients with neurological complications of AMPPE seen at Auckland Hospital between 2008 and 2013 and summarised cases in the literature between 1976 and 2013. We identified five patients with neurological complications of AMPPE at Auckland Hospital and 47 reported patients. These patients demonstrated a spectrum of neurological involvement including isolated headache, stroke or transient ischaemic attack, seizures, venous sinus thrombosis, optic neuritis, sensorineural hearing loss and peripheral vestibular disorder. We propose criteria to define AMPPE with neurological complications. A cerebrospinal fluid (CSF) lymphocytosis in a patient with isolated headache may predict the development of cerebrovascular complications of AMPPE. Patients with cerebrovascular complications of AMPPE have a poor prognosis with high rates of death and neurological disability among survivors. Predictors of poor outcome in those who develop neurological complications of AMPPE are a relapsing course, generalised seizures and multifocal infarction on MRI. All patients with neurological complications of AMPPE, including headache alone, should be investigated with an MRI brain and CSF examination. Patients with focal neurological symptoms should receive intravenous (IV) methylprednisolone followed by a tapering course of oral steroids for at least 3months. Patients with AMPPE and an isolated headache with a CSF pleocytosis should be treated with oral steroids

Delivering manufacturing technology and workshop appreciation to engineering undergraduates using the flipped classroom approach

Delivery of manufacturing technology and practical workshop-based work, on undergraduate engineering courses that engage the learners, is challenging. The paper presents an experimental method of workshop delivery using the flipped learning approach, a pedagogical model in which the typical lecture and homework elements of a course are reversed. Video lectures are viewed by students prior to class. In-class time can be devoted to exercises, projects, or discussions as in this case. Learners were asked to observe three audiovisual clips in preparation for class. The objective was to determine whether the flipped classroom approach can enhance the learning experience, through better engagement with the students, compared to conventional classroom-based learning. The level of student participation and level of success have been established by means of feedback questionnaires from more than 100 participants and peer observation. The results are encouraging and demonstrate that this approach is favoured by the students

Affective state influences retrieval-induced forgetting for integrated knowledge

Selectively testing parts of learned materials can impair later memory for nontested materials. Research has shown that such retrieval-induced forgetting occurs for low-integrated materials but may be prevented for high-integrated materials. However, previous research has neglected one factor that is ubiquitous in real-life testing: affective stat

The radiation of cynodonts and the ground plan of mammalian morphological diversity

Cynodont therapsids diversified extensively after the Permo-Triassic mass extinction event, and gave rise to mammals in the Jurassic. We use an enlarged and revised dataset of discrete skeletal characters to build a new phylogeny for all main cynodont clades from the Late Permian to the Early Jurassic, and we analyse models of morphological diversification in the group. Basal taxa and epicynodonts are paraphyletic relative to eucynodonts, and the latter are divided into cynognathians and probainognathians, with tritylodonts and mammals forming sister groups. Disparity analyses reveal a heterogeneous distribution of cynodonts in a morphospace derived from cladistic characters. Pairwise morphological distances are weakly correlated with phylogenetic distances. Comparisons of disparity by groups and through time are non-significant, especially after the data are rarefied. A disparity peak occurs in the Early/Middle Triassic, after which period the mean disparity fluctuates little. Cynognathians were characterized by high evolutionary rates and high diversity early in their history, whereas probainognathian rates were low. Community structure may have been instrumental in imposing different rates on the two clades

Digitally: Piloting offline payments for phones

Mobile payments support a range of services in many less developed countries including everyday payments, migrant remittances, credit, tax collection, and welfare benefits. These services depend entirely on the mobile phone network as their carrier, so they stop where the network does. This leaves millions of the very poorest people stranded - people living in remote areas where there is little to no network service. It also leaves urban users at the mercy of network congestion. We developed a prototype system, DigiTally, which lets users make offline payments by copying short strings of digits from one mobile handset to another. Offline payments are already used for electricity (both in prepayment meters and pay-as-you-go solar); can we extend them into a general-purpose payment system, to increase service resilience in the face of network congestion or outage, and provide service to currently excluded areas? We report the results of a preliminary study with an early prototype of DigiTally, tested on participants from a university in Nairobi (Kenya). The code-sharing process presented a possible usability challenge. To explore this and other aspects of an early prototype, DigiTally was introduced to Kenyan participants in order to resolve any major issues before a later field trial. We discuss the lessons learned from our field visits and initial evaluation; we hope that this contribution is helpful for researchers and policy makers interested in mobile payments and financial inclusion. We also present our findings and observations. We found that, although offline payments involve copying codes in both directions between the payer's phone and the payee's, the extra workload was acceptable to most users.This work was supported by a grant from the Bill & Melinda Gates Foundatio

'Dressage Is Full of Queens!' Masculinity, Sexuality and Equestrian Sport

Attitudes towards sexuality are changing and levels of cultural homophobia decreasing, yet there remain very few openly gay men within sport. As a proving ground for heteromasculinity, sport has traditionally been a hostile environment for gay men. This article is based on an ethnographic study within a sporting subworld in which gay men do appear to be accepted: equestrian sport. Drawing on inclusive masculinity theory, equestrian sport is shown to offer an unusually tolerant environment for gay men in which heterosexual men of all ages demonstrate low levels of homophobia. Inclusive masculinity theory is a useful framework for exploring the changing nature of masculinities and this study demonstrates that gay men are becoming increasingly visible and accepted within once unreceptive locales, such as sport and rural communities. However, this more tolerant attitude is purchased at the expense of a subordinated feminine Other, perpetuating the dominance of men within competitive sport. © The Author(s) 2012