Dynamical properties of constrained drops

In this communication we analyze the behavior of excited drops contained in spherical volumes. We study different properties of the dynamical systems i.e. the maximum Lyapunov exponent MLE, the asymptotic distance in momentum space $d_{\infty}$ andthe normalized variance of the maximum fragment NVM. It is shown that the constrained systems behaves as undergoing a first order phase transition at low densities while as a second order one at high densities. The transition from liquid-like to vapor-like behavior is signaled both by the caloric curves, thermal response functions and the MLE. The relationship between $MLE,d_{\infty}$, and the CC is explored.Comment: 7 pages, 9 figures in a two column forma

Mediating boundaries between knowledge and knowing: ICT and R4D praxis

Research for development (R4D) praxis (theory-informed practical action) can be underpinned by the use of Information and Communication Technologies (ICTs) which, it is claimed, provide opportunities for knowledge working and sharing. Such a framing implicitly or explicitly constructs a boundary around knowledge as reified, or commodified – or at least able to be stabilized for a period of time (first order knowledge). In contrast ‘third-generation knowledge’ emphasizes the social nature of learning and knowledge-making; this reframes knowledge as a negotiated social practice, thus constructing a different system boundary. This paper offers critical reflections on the use of a wiki as a data repository and mediating technical platform as part of innovating in R4D praxis. A sustainable social learning process was sought that fostered an emergent community of practice among biophysical and social researchers acting for the first time as R4D co-researchers. Over time the technologically mediated element of the learning system was judged to have failed. This inquiry asks: How can learning system design cultivate learning opportunities and respond to learning challenges in an online environment to support R4D practice? Confining critical reflection to the online learning experience alone ignores the wider context in which knowledge work took place; therefore the institutional setting is also considered

Expansion dynamics of Lennard-Jones systems

The dynamics of the expansion of a Lennard-Jones system, initially confined at high density and subsequently expanding freely in the vacuum, is confronted to an expanding statistical ensemble, derived in the diluted quasi-ideal Boltzmann approximation. The description proves to be fairly accurate at predicting average one-body global observables, but important deviations are observed in the configuration-space structure of the events. Possible implications for finite expanding physical systems are outlined

State and Local Legislation: More Hurdles for Unmanned Aerial Systems (UAS) Integration?

Congressional mandate for the integration of unmanned aerial systems (UAS) in the National Airspace System (NAS) to take place by 2015, significant interest in UAS investment, operations, and research has taken place Complex array of requirements and restrictions have been placed on UAS stakeholders by the Federal Aviation Administration (FAA) Limited Congressional legislative guidanc

The Role of Unmanned Aircraft Systems (UAS) in Disaster Response and Recovery Efforts: Historical, Current and Future

A wide range of legislation has been proposed or put into place that restricts the use of unmanned systems. These actions by legislators and regulators will stifle the growth of this technology and the associated surrounding industry. The largest obstacle to the proliferation of UAS in the U.S. is the FAA. The FAA has designated the location of six test sites that are anticipated to allow for less restrictive and formative research to assess the technologies that the FAA has claimed need to exist in order to integrate UAS into the NAS. Further complicating the adoption of UAS for beneficent causes is the plethora of local and state legislation and regulation. Whilst many state restrictions do have built-in caveats to potentially allow for disaster support utilizing UAS, not all are so explicit. All of these actions make the adoption ofUAS in disaster areas more complex and may sway associated agencies away from purchasing UAS for these uses in the future. This research outlines historical uses of UAS to provide basis for the adoption in disaster relief. Examples of past use of unmanned systems in exigent event response are provided including post-hurricane rescue, wild fire monitoring, and landslide disaster relief. An example of missed opportunities with UAS, the Boston Marathon bombing is also outlined. Current UAS usage in first response is explained including types of platforms and sensors that show promise in such operations. Future considerations for UAS adoption in disaster efforts are outlined

The Journey to R4D: An institutional history of an Australian Initiative on Food Security in Africa

Internal Revie

Connection between the Largest Lyapunov Exponent, Density Fluctuation and Multifragmentation in Excited Nuclear Systems

Within a quantum molecular dynamics model we calculate the largest Lyapunov exponent (LLE), density fluctuation and mass distribution of fragments for a series of nuclear systems at different initial temperatures. It is found that the $LLE$ peaks at the temperature ("critical temperature") where the density fluctuation reaches a maximal value and the mass distribution of fragments is best fitted by the Fisher's power law from which the critical exponents for mass and charge distribution are obtained. The time-dependent behavior of the LLE and density fluctuation is studied. We find that the time scale of the density fluctuation is much longer than the inverse LLE, which indicates that the chaotic motion can be well developed during the process of fragment formation. The finite-size effect on "critical temperature" for nuclear systems ranging from Calcium to superheavy nuclei is also studied.Comment: 18 pages, 8 figures Submited to Phys. Rev.

Non equilibrium effects in fragmentation

We study, using molecular dynamics techniques, how boundary conditions affect the process of fragmentation of finite, highly excited, Lennard-Jones systems. We analyze the behavior of the caloric curves (CC), the associated thermal response functions (TRF) and cluster mass distributions for constrained and unconstrained hot drops. It is shown that the resulting CC's for the constrained case differ from the one in the unconstrained case, mainly in the presence of a ``vapor branch''. This branch is absent in the free expanding case even at high energies . This effect is traced to the role played by the collective expansion motion. On the other hand, we found that the recently proposed characteristic features of a first order phase transition taking place in a finite isolated system, i.e. abnormally large kinetic energy fluctuations and a negative branch in the TRF, are present for the constrained (dilute) as well the unconstrained case. The microscopic origin of this behavior is also analyzed.Comment: 21 pages, 11 figure

Home sampling for sexually transmitted infections and HIV in men who have sex with men: A prospective observational study

To determine uptake of home sampling kit (HSK) for STI/HIV compared to clinic-based testing, whether the availability of HSK would increase STI testing rates amongst HIV infected MSM, and those attending a community-based HIV testing clinic compared to historical control. Prospective observational study in three facilities providing STI/HIV testing services in Brighton, UK was conducted. Adult MSM attending/contacting a GUM clinic requesting an STI screen (group 1), HIV infectedMSM attending routine outpatient clinic (group 2), and MSM attending a community-based rapid HIV testing service (group 3) were eligible. Participants were required to have no symptomatology consistent with STI and known to be immune to hepatitis A and B (group 1). Eligiblemen were offered a HSK to obtain self-collected specimens as an alternative to routine testing. HSK uptake compared to conventional clinicbased STI/HIV testing in group 1, increase in STI testing rates due to availability of HSK compared to historical controls in group 2 and 3, and HSK return rates in all settings were calculated. Among the 128 eligible men in group 1, HSK acceptance was higher (62.5% (95%CI: 53.5-70.9)) compared to GUM clinic-based testing (37.5% (95% CI: 29.1-46.5)), (p = 0.0004). Two thirds of eligibleMSM offered an HSK in all three groups accepted it, but HSK return rates varied (highest in group 1, 77.5%, lowest in group 3, 16%). HSK for HIV testing was acceptable to 81%of men in group 1. Compared to historical controls, availability of HSK increased the proportion ofMSM testing for STIs in group 2 but not in group 3. HSK for STI/ HIV offers an alternative to conventional clinic-based testing for MSM seeking STI screening. It significantly increases STI testing uptake in HIV infected MSM. HSK could be considered as an adjunct to clinic-based services to further improve STI/HIV testing in MSM