An experimental study of pressures on 60 deg Delta wings with leading edge vortex flaps

An experimental study was conducted in the Virginia Tech Stability Wind Tunnel to determine surface pressures over a 60 deg sweep delta wing with three vortex flap designs. Extensive pressure data was collected to provide a base data set for comparison with computational design codes and to allow a better understanding of the flow over vortex flaps. The results indicated that vortex flaps can be designed which will contain the leading edge vortex with no spillage onto the wing upper surface. However, the tests also showed that flaps designed without accounting for flap thickness will not be optimum and the result can be oversized flaps, early flap vortex reattachment and a second separation and vortex at the wing/flap hinge line

Quantum computation via measurements on the low-temperature state of a many-body system

We consider measurement-based quantum computation using the state of a spin-lattice system in equilibrium with a thermal bath and free to evolve under its own Hamiltonian. Any single qubit measurements disturb the system from equilibrium and, with adaptive measurements performed at a finite rate, the resulting dynamics reduces the fidelity of the computation. We show that it is possible to describe the loss in fidelity by a single quantum operation on the encoded quantum state that is independent of the measurement history. To achieve this simple description, we choose a particular form of spin-boson coupling to describe the interaction with the environment, and perform measurements periodically at a natural rate determined by the energy gap of the system. We found that an optimal cooling exists, which is a trade-off between keeping the system cool enough that the resource state remains close to the ground state, but also isolated enough that the cooling does not strongly interfere with the dynamics of the computation. For a sufficiently low temperature we obtain a fault-tolerant threshold for the couplings to the environment.Comment: 9 pages, 3 figures; v2 published versio

Recent advances in understanding mammalian prion structure

Prions are lethal pathogens, which cause fatal neurodegenerative diseases in mammals. They are unique infectious agents and are composed of self-propagating multi-chain assemblies of misfolded host-encoded prion protein (PrP). Understanding prion structure is fundamental to understanding prion disease pathogenesis however to date, the high-resolution structure of authentic ex vivo infectious prions remains unknown. Advances in determining prion structure have been severely impeded by the difficulty in recovering relatively homogeneous prion particles from infected brain and definitively associating infectivity with the PrP assembly state. Recently, however, images of highly infectious ex vivo PrP rods that produce prion-strain specific disease phenotypes in mice have been obtained using cryo-electron microscopy and atomic force microscopy. These images have provided the most detailed description of ex vivo mammalian prions reported to date and have established that prions isolated from multiple strains have a common hierarchical structure. Misfolded PrP is assembled into 20 nm wide rods containing two fibers, each with double helical repeating substructure, separated by a characteristic central gap 8-10 nm in width. Irregularly structured material with adhesive properties distinct to that of the fibers is present within the central gap of the rod. Prions are clearly distinguishable from non-infectious recombinant PrP fibrils generated in vitro and from all other propagating protein structures so far described in other neurodegenerative diseases. The basic architecture of mammalian prions appears to be exceptional and fundamental to their lethal pathogenicity

LP 400-22, A very low-mass and high-velocity white dwarf

We report the identification of LP 400-22 (WD 2234+222) as a very low-mass and high-velocity white dwarf. The ultraviolet GALEX and optical photometric colors and a spectral line analysis of LP 400-22 show this star to have an effective temperature of 11080+/-140 K and a surface gravity of log g = 6.32+/-0.08. Therefore, this is a helium core white dwarf with a mass of 0.17 M_solar. The tangential velocity of this white dwarf is 414+/-43 km/s, making it one of the fastest moving white dwarfs known. We discuss probable evolutionary scenarios for this remarkable object.Comment: accepted for publication in ApJ Letters, made minor correction

Overview of research activities associated with the World Health Organization: results of a survey covering 2006/07

<p>Abstract</p> <p>Background</p> <p>This paper presents the first comprehensive effort to provide an overview of the research associated with the World Health Organization (WHO) headquarters in 2006/07.</p> <p>Methods</p> <p>Information was obtained by questionnaire and interviews with senior staff operating at WHO headquarters in Geneva. Research type, purpose and resources (both financial and staff) were defined and compared for each of the 37 departments identified and a comparative analysis was made with the global burden of disease as expressed by Disability Adjusted Life Years (DALY).</p> <p>Results</p> <p>Research expenditure in 2006/07 was estimated at US$215 million. WHO is involved in more than 60 research networks/partnerships and often WHO itself is the network host.</p> <p>Using the DALY model, 84% of the funding WHO allocates to research goes to DALY Type I diseases (communicable, maternal, perinatal and nutritional diseases) which represents 40% of DALY. 4% is allocated to Daly Type II (non-communicable diseases) which contributes to 48% of DALY.</p> <p>45% of WHO permanent staff are involved with health research and the WHO's approach to research is predominantly focused on policy, advocacy, health systems and population based research. The Organization principally undertakes secondary research using published data and commissions others to conduct this work through contracts or research grants. This approach is broadly in line with the stated strategy of the Organization.</p> <p>Conclusions</p> <p>The difficulty in undertaking this survey highlights the complexity of obtaining an Organization-wide assessment of research activity in the absence of common standards for research classification, methods for priority setting and a mechanism across WHO, or within the governance of global health research more generally, for managing a research portfolio.</p> <p>This paper presents a strategic birds-eye view of the WHO research portfolio using methodologies that, with further development, may provide the strategic information required if there is to be balancing of research efforts between communicable disease, non-communicable disease and other pressing public health needs. As the rollout of the WHO strategy on research for health proceeds we would hope to see similar exercises undertaken at the WHO Regional Offices and in support of capacity building of national health research systems within Member States.</p