Scattering measurements on natural and model trees

The acoustical back scattering from a simple scale model of a tree has been experimentally measured. The model consisted of a trunk and six limbs, each with 4 branches; no foliage or twigs were included. The data from the anechoic chamber measurements were then mathematically combined to construct the effective back scattering from groups of trees. Also, initial measurements have been conducted out-of-doors on a single tree in an open field in order to characterize its acoustic scattering as a function of azimuth angle. These measurements were performed in the spring, prior to leaf development. The data support a statistical model of forest scattering; the scattered signal spectrum is highly irregular but with a remarkable general resemblance to the incident signal spectrum. Also, the scattered signal's spectra showed little dependence upon scattering angle

Epidemiology and potential preventative measures for viral infections in children with malignancy and those undergoing hematopoietic cell transplantation.

In pediatric patients with malignancy and those receiving hematopoietic stem cell transplants, bacterial and fungal infections have been the focus of fever and neutropenia episodes for decades. However, improved diagnostic capabilities have revealed viral pathogens as a significant cause of morbidity and mortality. Because of limited effective antiviral therapies, prevention of viral infections is paramount. Pre-exposure and post-exposure prophylaxis and antiviral suppressive therapeutic approaches are reviewed. Additionally, infection control practices specific to this patient population are discussed. A comprehensive approach utilizing each of these can be effective at reducing the negative impact of viral infections

P1 finite element methods for an elliptic state-constrained distributed optimal control problem with Neumann boundary conditions

We investigate two P finite element methods for an elliptic state-constrained distributed optimal control problem with Neumann boundary conditions on general polygonal domains.

The potential of virtual reality technologies to support people with an autism condition: A case study of acceptance, presence and negative effects

There has been much potential and discussion about the application of virtual reality technologies (VRTs) using head-mounted displays (HMDs) for users with autism However, very few, if any studies, have yet to explore and investigate the acceptance, presence and ecological validity of these platforms. On the other hand, literature is well developed in areas such as virtual environments [18], virtual worlds [9], [19] and virtual reality [20], but few have considered the resurgence in head-mounted displays for autistic users. Many of the affordances associated with VEs and VWs may be applied HMDs and VRTs and so are also seen a potential opportunity for people with autism to tackle challenges faced on a daily basis. We present findings from a study conducted in the United States that worked with a HMD (Oculus Rift) and 29 participants with an autism condition. We ran the experiment in two phases. Phase I considered acceptance of this wearable technology; looking at issues of sensitivity. Phase II consider sense of presence, immersion, ecological validity and negative effects [16]. Concluding with pre- and post- anxiety measurements [17]. The paper will discuss the quantitative findings of the study

Nonlinear interaction of charged particles with a free electron gas beyond the random-phase approximation

A nonlinear description of the interaction of charged particles penetrating a solid has become of basic importance in the interpretation of a variety of physical phenomena. Here we develop a many-body theoretical approach to the quadratic decay rate, energy loss, and wake potential of charged particles moving in an interacting free electron gas. Explicit expressions for these quantities are obtained either within the random-phase approximation (RPA) or with full inclusion of short-range exchange and correlation effects. The Z^3 correction to the energy loss of ions is evaluated beyond RPA, in the limit of low velocities.Comment: 5 pages, 2 figures To appear in Phys. Rev.

Nonlinear energy-loss straggling of protons and antiprotons in an electron gas

The electronic energy-loss straggling of protons and antiprotons moving at arbitrary nonrelativistic velocities in a homogeneous electron gas are evaluated within a quadratic response theory and the random-phase approximation (RPA). These results show that at low and intermediate velocities quadratic corrections reduce significantly the energy-loss straggling of antiprotons, these corrections being, at low-velocities, more important than in the evaluation of the stopping power.Comment: 4 pages, 3 figures, to appear in Phys. Rev.