Soil moisture assessments for brown locust Locustana pardalina breeding potential using synthetic aperture radar

Synthetic aperture radar (SAR) imagery was collected over a brown locust Locustana pardalina outbreak area to estimate soil moisture relevant to egg development. ERS-2/RadarSat overpasses and field studies enabled parameterization of surface roughness, volumetric soil moisture, soil texture, and vegetation cover. Data were analyzed both when the target area was assessed as nonvegetated and when treated as vegetated. For the former, using the integral equation model (IEM) and soil surface data combined with the sensitivity of the IEM to changes in surface roughness introduced an error of ∼ � 0.06 cm3 cm−3 in volumetric soil moisture. Comparison of the IEM modeling results with backscatter responses from the ERS-2/RadarSat imagery revealed errors as high as �0.14 cm3 cm−3, mostly due to IEM calibration problems and the impact of vegetation. Two modified versions of the water cloud model (WCM) were parameterized, one based on measurements of vegetation moisture and the other on vegetation biomass. A sensitivity analysis of the resulting model revealed a positive relationship between increases in both vegetation biomass and vegetation moisture and the backscatter responses from the ERS-2 and RadarSat sensors. The WCM was able to explain up to 80% of the variability found when the IEM was used alone

Provisioning over the business cycle:Some insights from the microfinance industry

This paper investigates the drivers of provisioning in MFIs and their provisioning behaviour over the business cycle. Based on an international sample of MFIs extracted from the MIX database over the 2001–2014 period, we uncover a negative relationship between MFIs' provisioning and the business cycle. Our finding corroborates the fact that MFIs do not build their loan loss provisions (LLP) during economic booms when profit and earnings are high. Since they provision more during downturns, they are more likely to suffer from unexpected losses and experience failure. This is in sharp contrast with the current Basel III countercyclical buffer requirement suggesting that financial institutions, especially banks, should build sufficient buffer in booms so that they can avoid costly capital adjustment when the economy contracts. Deeper analyses suggest however that this behaviour mainly concerns profit-oriented and deposit-taking/regulated MFIs, with business model and target close to conventional banking. This suggests that bank-like and regulated MFIs' loan loss provisions follow similar behavioral patterns to those of the conventional banking sector during the boom-and-bust cycles.</p

Evaluating sulfur-tolerance of metal/Ce0.80Gd0.20O1.90 co-impregnated La0.20Sr0.25Ca0.45TiO3 anodes for solid oxide fuel cells

The authors acknowledge funding from the University of St Andrews, HEXIS AG and the EPSRC Grants: EP/M014304/1 “Tailoring of Microstructural Evolution in Impregnated SOFC Electrodes” and EP/L017008/1 “Capital for Great Technologies”.The Ni-based cermet Solid Oxide Fuel Cell (SOFC) anode is prone to poisoning by sulfur-based odourising agents, and naturally occurring sulfur species, present in unprocessed natural gas feeds. Next generation SOFC anodes should be able to withstand exposure to these poisons in the event of a malfunction or breakdown of desulfurisation units. Here, we present results pertaining to the sulfur-tolerance of Ni/Ce0.80Gd0.20O1.90 (CGO), Pt/CGO and Rh/CGO co-impregnated La0.20Sr0.25Ca0.45TiO3 anode ‘backbone’ microstructures and their ability to recover performance after being exposed to H2S. The Ni/CGO co-impregnated system exhibited severe poisoning by H2S, however, the Rh/CGO system displayed good stability in Area Specific Resistance (ASR) upon introduction of 1–2 ppm of H2S and the Pt/CGO system showed minimal increases in ASR with the addition of 1–8 ppm H2S. Recovery measurements performed in non-humidified H2 at 300 mA cm−2, after exposure to 8 ppm H2S, indicated that the Pt/CGO and Rh/CGO systems could recover within 10 min, whilst 60 min were required to achieve almost a full recovery of performance for the Ni/CGO system. Additionally, all three impregnate systems showed good stability in operating voltage, after an initial drop, in a fuel gas containing simulated syngas (2:1 H2:CO) with 8 ppm H2S.PostprintPeer reviewe

Kinetic theory of point vortices: diffusion coefficient and systematic drift

We develop a kinetic theory for point vortices in two-dimensional hydrodynamics. Using standard projection operator technics, we derive a Fokker-Planck equation describing the relaxation of a ``test'' vortex in a bath of ``field'' vortices at statistical equilibrium. The relaxation is due to the combined effect of a diffusion and a drift. The drift is shown to be responsible for the organization of point vortices at negative temperatures. A description that goes beyond the thermal bath approximation is attempted. A new kinetic equation is obtained which respects all conservation laws of the point vortex system and satisfies a H-theorem. Close to equilibrium this equation reduces to the ordinary Fokker-Planck equation.Comment: 50 pages. To appear in Phys. Rev.

Estimating the feasibility of transition paths in extended finite state machines

There has been significant interest in automating testing on the basis of an extended finite state machine (EFSM) model of the required behaviour of the implementation under test (IUT). Many test criteria require that certain parts of the EFSM are executed. For example, we may want to execute every transition of the EFSM. In order to find a test suite (set of input sequences) that achieves this we might first derive a set of paths through the EFSM that satisfy the criterion using, for example, algorithms from graph theory. We then attempt to produce input sequences that trigger these paths. Unfortunately, however, the EFSM might have infeasible paths and the problem of determining whether a path is feasible is generally undecidable. This paper describes an approach in which a fitness function is used to estimate how easy it is to find an input sequence to trigger a given path through an EFSM. Such a fitness function could be used in a search-based approach in which we search for a path with good fitness that achieves a test objective, such as executing a particular transition, and then search for an input sequence that triggers the path. If this second search fails then we search for another path with good fitness and repeat the process. We give a computationally inexpensive approach (fitness function) that estimates the feasibility of a path. In order to evaluate this fitness function we compared the fitness of a path with the ease with which an input sequence can be produced using search to trigger the path and we used random sampling in order to estimate this. The empirical evidence suggests that a reasonably good correlation (0.72 and 0.62) exists between the fitness of a path, produced using the proposed fitness function, and an estimate of the ease with which we can randomly generate an input sequence to trigger the path

Relaxation equations for two-dimensional turbulent flows with a prior vorticity distribution

Using a Maximum Entropy Production Principle (MEPP), we derive a new type of relaxation equations for two-dimensional turbulent flows in the case where a prior vorticity distribution is prescribed instead of the Casimir constraints [Ellis, Haven, Turkington, Nonlin., 15, 239 (2002)]. The particular case of a Gaussian prior is specifically treated in connection to minimum enstrophy states and Fofonoff flows. These relaxation equations are compared with other relaxation equations proposed by Robert and Sommeria [Phys. Rev. Lett. 69, 2776 (1992)] and Chavanis [Physica D, 237, 1998 (2008)]. They can provide a small-scale parametrization of 2D turbulence or serve as numerical algorithms to compute maximum entropy states with appropriate constraints. We perform numerical simulations of these relaxation equations in order to illustrate geometry induced phase transitions in geophysical flows.Comment: 21 pages, 9 figure

Controlling collapse in Bose-Einstein condensates by temporal modulation of the scattering length

We consider, by means of the variational approximation (VA) and direct numerical simulations of the Gross-Pitaevskii (GP) equation, the dynamics of 2D and 3D condensates with a scattering length containing constant and harmonically varying parts, which can be achieved with an ac magnetic field tuned to the Feshbach resonance. For a rapid time modulation, we develop an approach based on the direct averaging of the GP equation,without using the VA. In the 2D case, both VA and direct simulations, as well as the averaging method, reveal the existence of stable self-confined condensates without an external trap, in agreement with qualitatively similar results recently reported for spatial solitons in nonlinear optics. In the 3D case, the VA again predicts the existence of a stable self-confined condensate without a trap. In this case, direct simulations demonstrate that the stability is limited in time, eventually switching into collapse, even though the constant part of the scattering length is positive (but not too large). Thus a spatially uniform ac magnetic field, resonantly tuned to control the scattering length, may play the role of an effective trap confining the condensate, and sometimes causing its collapse.Comment: 7 figure

Testing timed systems modeled by stream X-machines

Stream X-machines have been used to specify real systems where complex data structures. They are a variety of extended finite state machine where a shared memory is used to represent communications between the components of systems. In this paper we introduce an extension of the Stream X-machines formalism in order to specify systems that present temporal requirements. We add time in two different ways. First, we consider that (output) actions take time to be performed. Second, our formalism allows to specify timeouts. Timeouts represent the time a system can wait for the environment to react without changing its internal state. Since timeous affect the set of available actions of the system, a relation focusing on the functional behavior of systems, that is, the actions that they can perform, must explicitly take into account the possible timeouts. In this paper we also propose a formal testing methodology allowing to systematically test a system with respect to a specification. Finally, we introduce a test derivation algorithm. Given a specification, the derived test suite is sound and complete, that is, a system under test successfully passes the test suite if and only if this system conforms to the specification

Cell sheets in cell therapies

This review aims to provide a broad introduction to the use of cell sheets and the role of materials in the delivery of cell sheets to patients within a clinical setting. Traditionally, cells sheets have been, and currently are, fabricated using established and accepted cell culture methods within standard formats (e.g., petri dishes) utilizing biological substrates. Synthetic surfaces provide a far more versatile system for culturing and delivering cell sheets. This has the potential to positively affect quality, and efficient, localized cell delivery has a significant impact on patient outcome and on the overall cost of goods. We highlight current applications of these advanced carriers and future applications of these surfaces and cell sheets with an emphasis both on clinical use and regulatory requirements

Black Hole Entropy without Brick Walls

We present evidence which confirms a suggestion by Susskind and Uglum regarding black hole entropy. Using a Pauli-Villars regulator, we find that 't Hooft's approach to evaluating black hole entropy through a statistical-mechanical counting of states for a scalar field propagating outside the event horizon yields precisely the one-loop renormalization of the standard Bekenstein-Hawking formula, S=\A/(4G). Our calculation also yields a constant contribution to the black hole entropy, a contribution associated with the one-loop renormalization of higher curvature terms in the gravitational action.Comment: 15 pages, plain LaTex minor additions including some references; version accepted for publicatio