Academic literature on the topic 'Vectorial low field'

The most abundant Culicoides species in an area is not inevi­tably the most competent vector species for a specific virus. Oral susceptibility, as an indicator of vector competence, is a measure of the portion of vectors taking a blood meal from an infected host that actually becomes infective. Cumulative laboratory oral susceptibility results from South Africa indicate a multivector potential for bluetongue virus (BTV) as well as for African horse sickness virus (AHSV). Considering the unique biology of potential vector competent Culicoides species one can appreciate the complex epidemiology of these diseases. The oral susceptibly of C. imicola, a proven vector of AHSV and BTV, was relatively low for most of the viral isolates and even appeared to be refractory to infection with some of the isolates used. This relatively low oral susceptibility may partly explain the low field infection prevalence of AHSV and BTV recorded in field collected midges. In South Africa, the relatively low oral susceptibility as determined for some of the isolates is easily compensated for by the high abundance of C. imicola. Differences found in the virus recovery rates of various AHSV serotypes/isolates from the various Culicoides species and even different populations of the same species emphasize the fact that, although oral susceptibility tests provide important information about a specific vector population, it provides no predictability about the behaviour of other populations with different strains of virus. Differences found in the oral susceptibility of C. imi­cola and C. bolitinos for isolates of the same serotypes of AHSV suggest coadaptation between orbiviruses and vectors present in a given locality. Real-time monitoring of vector competence might be difficult as it would require assessing local Culicoides populations using variants of orbiviruses currently in circula­tion. It needs to be emphasized that laboratory demonstration of oral susceptibility is not the only necessary step to implement a competent vector. It is, however, an indication of the ability of a vector to support virus replication and one of the critical components of vectorial capacity. Vector capacity is the relative measure of a vector population to transmit a virus to a vertebrate population. In addition to vector competence, vectorial capacity depends on the biting rate, host selection, vector survivorship, and the extrinsic incubation period of the virus.

We consider the electric field integral equation (EFIE) modeling the scattering of time-harmonic electromagnetic waves at a perfectly conducting screen. When discretizing the EFIE by means of low-order Galerkin boundary methods (BEM), one obtains linear systems that are ill-conditioned on fine meshes and for low wave numbers [Formula: see text]. This makes iterative solvers perform poorly and entails the use of preconditioning. In order to construct optimal preconditioners for the EFIE on screens, the authors recently derived compact equivalent inverses of the EFIE operator on simple Lipschitz screens in [R. Hiptmair and C. Urzúa-Torres, Compact equivalent inverse of the electric field integral operator on screens, Integral Equations Operator Theory 92 (2020) 9]. This paper elaborates how to use this result to build an optimal operator preconditioner for the EFIE on screens that can be discretized in a stable fashion. Furthermore, the stability of the preconditioner relies only on the stability of the discrete [Formula: see text] duality pairing for scalar functions, instead of the vectorial one. Therefore, this novel approach not only offers [Formula: see text]-independent and [Formula: see text]-robust condition numbers, but it is also easier to implement and accommodates non-uniform meshes without additional computational effort.

Anopheles mosquitoes are colonized by diverse microorganisms that may impact on host biology and vectorial capacity. Eukaryotic symbionts such as fungi have been isolated from Anopheles, but whether they are stably associated with mosquitoes and transmitted transstadially across mosquito life stages or to subsequent generations remains largely unexplored. Here, we show that a Leptosphaerulina sp. fungus isolated from the midgut of An. gambiae can be stably associated with An. gambiae host and that it imposes low fitness cost when re-introduced through co-feeding. This fungus is transstadially transmitted across An. gambiae developmental stages and to their progeny. It is present in field-caught larvae and adult mosquitoes at moderate levels across geographical regions. We observed that Leptosphaerulina sp. induces a distinctive melanotic phenotype across the developmental stages of mosquito. As a eukaryotic symbiont that is stably associated with An. gambiae Leptosphaerulina sp. can be explored for paratransgenesis.

Optical fiber sensors (OFS) are a potential candidate for monitoring physical parameters in nuclear environments. However, under an irradiation field the optical response of the OFS is modified via three primary mechanisms: (i) radiation-induced attenuation (RIA), (ii) radiation-induced emission (RIE), and (iii) radiation-induced compaction (RIC). For resonance-based sensors, RIC plays a significant role in modifying their performance characteristics. In this paper, we numerically investigate independently the effects of RIC and RIA on three types of OFS widely considered for radiation environments: fiber Bragg grating (FBG), long-period grating (LPG), and Fabry-Perot (F-P) sensors. In our RIC modeling, experimentally calculated refractive index (RI) changes due to low-dose radiation are extrapolated using a power law to calculate density changes at high doses. The changes in RI and length are subsequently calculated using the Lorentz–Lorenz relation and an established empirical equation, respectively. The effects of both the change in the RI and length contraction on OFS are modeled for both low and high doses using FIMMWAVE, a commercially available vectorial mode solver. An in-depth understanding of how radiation affects OFS may reveal various potential OFS applications in several types of radiation environments, such as nuclear reactors or in space.

Mosquito-borne diseases are an increasing global health challenge, threatening over 40% of the world's population. Despite major advances in malaria control since 2000, recent progress has stalled. Additionally, the risk of Aedes -borne arboviruses is rapidly growing, with the unprecedented spread of dengue and chikungunya viruses, outbreaks of yellow fever and the 2015 epidemic of Zika virus in Latin America. To counteract this growing problem, diverse and innovative mosquito control technologies are currently under development. Conceptually, these span an impressive spectrum of approaches, from invasive transgene cassettes with the potential to crash mosquito populations or reduce the vectorial capacity of a population, to low-cost alterations in housing design that restrict mosquito entry. This themed issue will present articles providing insight into the breadth of mosquito control research, while demonstrating the requirement for an interdisciplinary approach. The issue will highlight mosquito control technologies at varying stages of development and includes both opinion pieces and research articles with laboratory and field-based data on control strategy development. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases'.

We conducted field surveys to detect the population density of the most important invasive weed species and their associated virus vectoring aphids in crops grown under high input field (HIF) vs low-input field (LIF) conditions, with and without fertilizers and pesticides. The most frequent invasive weed species were Stenactisannua, Erigeroncanadensis and Solidagocanadensis. These species were hosts predominantly for the aphids Brachycaudushelichrysi and Aulacorthumsolani in both management systems. The 13% higher coverage of S.annua under LIF conditions resulted in a 30% higher B.helichrysi abundance and ~85% higher A.solani abundance compared with HIF conditions. Host plant quality was assessed by measuring peroxidase enzyme activity. There was a significantly increased POD activity at 10 μmol min−1 mg protein−1 unit in S.annua under LIF conditions, suggesting a higher stress by aphids under this management regime. The high colonization intensity of B.helichrysi on maize, potato and alfalfa crops were detected from both S.annua and E.canadensis. We conclude that new and faster methods need to be used to prevent colonization of such virus vectoring aphids and their host plants, even under low input regimes.

Suction was applied asymmetrically to the exhaust of a rectangular subsonic jet creating a pressure field capable of vectoring the primary flow at angles up to 15deg. The suction simultaneously creates low pressures near the jet exhaust and conditions capable of drawing a secondary flow along the jet shear layer in the direction opposite to the primary jet. This countercurrent shear layer is affected both by the magnitude of the suction source as well as the proximity of an adjacent surface onto which the pressure forces act to achieve vectoring. This confined countercurrent flow gives rise to elevated turbulence levels in the jet shear layer as well as considerable increases in the gradients of the turbulent stresses. The turbulent stresses are responsible for producing a pressure field conducive for vectoring the jet at considerably reduced levels of secondary mass flow than would be possible in their absence.

Abstract This paper presents a new approach to vectoring jet thrust using a miniature fluidic actuator that provided spatially distributed mass addition. The fluidic actuators used had no moving parts and produced oscillatory flow with a square wave form at frequencies up to 1·6kHz. A subsonic jet with an exit diameter of 3·81cm was controlled using single and dual fluidic actuators, each with an equivalent circular diameter of 1·06mm. The fluidic nozzle was operated at pressures between 20·68 and 165·47kPa. The objectives of the present work included documentation of the actuation characteristics of fluidic devices, assessment of the effectiveness of fluidic devices for jet thrust vectoring, and evaluation of mass flow requirements for vectoring under various conditions. Measurements were made in the flow field using a pitot probe for the vectored and unvectored cases. Some acoustic measurements were made using microphones in the near-field and for selected cases particle image velocimetry (PIV) measurements were made. Thrust vectoring was obtained in low speed jets by momentum effects with fluidic device mass flow rates of only 2 × 10–4kg/sec (0·6% of main jet mass flow per fluidic oscillator). Although a single fluidic device produced vectoring of the primary jet, the dual fluidic device configuration (with two fluidic devices on either side of the jet exit) produced mass flux enhancement of 28% with no vectoring. Our results indicate that fluidic actuators have the potential for use in thrust vectoring, flow mixing and industrial flow deflection applications.

La mesure du champ magnétique terrestre avec des satellites réduits en volume –des cube-sats ou des nano-sats– requière de des magnétomètres à pompage optique de volume plus réduit et pouvant être opérés en gradiomètre sans diaphonie entre capteurs. Pour répondre à ce besoin, nous avons travaillé sur des architectures de magnétomètres atomiques tout-optiques. Dans ce manuscrit, nous présentons une architecture de magnétomètre scalaire tout-optique isotrope basée l’hélium-4 métastable pompé en alignement. Cette architecture repose sur la combinaison d’un champ magnétique radiofréquence créé optiquement par l’effet de light-shift vectoriel et d’une modulation de l’intensité du faisceau de pompe. Les premiers tests expérimentaux de cette configuration ont démontré l’existence d’un point de travail permettant l’opération isotrope. Les premières estimations de bruit et de justesse de cette configuration laissent espérer des performances équivalentes à celles obtenues sur les magnétomètres scalaires isotropes réalisés par le CEA-Leti pour la mission Swarm.Les architectures tout-optique apporteraient également une réponse à des besoins existants dans le domaine de l’imagerie magnétique médicale. En effet la mise en réseau des capteurs actuels entraine des problèmes de diaphonie entre magnétomètres voisins. Dans un deuxième volet de cette thèse nous nous sommes donc intéressés aux magnétomètres tout-optique dédiés à la mesure de champs magnétiques de faibles amplitudes. En explorant les configurations de magnétomètres Hanle basés sur l’alignement atomique, nous avons identifié un schéma qui permet d’avoir accès à deux composantes du champ magnétique en utilisant un seul accès optique à la cellule de gaz. Cette solution a été testée expérimentalement. Nous étudions théoriquement une extension de cette configuration qui permet de mesurer les trois composantes du champ magnétique en utilisant pour le pompage optique une lumière partiellement dépolarisée
The measurement of the Earth magnetic field, using satellites of reduced volume –so called cube-sats or nano-sats– requires optically pumped magnetometers of strongly reduced size that can be operated as gradiometers without crosstalk between different sensors. In order to fulfill these conditions we developed an architecture for all-optical magnetometers.In this work, we present an all-optical isotopic solution for a scalar helium-4 magnetometer based on atomic alignment. This architecture originates in the combination of an optically created radiofrequency magnetic field realized by a vector light-shift and of an intensity modulation of the pump light. The first experimental tests of this configuration proved the existence of a working point that allows isotropic operation. First estimations of noise and precision using this configuration give hope to obtain equivalent performance than that of scalar isotropic magnetometers that were realized by the CEA-Leti for the mission Swarm.Additionally, the all-optical architectures respond to the needs that exist in the field of medical magnetic imaging. In fact, building a matrix of commonly used sensors involves problems of cross-talk between proximate magnetometers. The second focus of this thesis lies on all-optical magnetometers designated for the measurement of magnetic fields with small amplitudes. Exploring the configurations of Hanle magnetometers that are based on atomic alignment, we identified a technique which gives access to two magnetic field components while using only one single optical access to the gas cell, a solution that was experimentally tested. We theoretically investigate an extension of this configuration that allows the measurement of all three components of the magnetic field, using a partially depolarized light as optical pump

An experimental and numerical demonstration of a new, non-contact particle sorting technique called Aerodynamic Vectoring Particle Sorting (AVPS) is presented. AVPS uses secondary blowing and suction control flows to sharply turn a 2D, particle-laden jet. As the jet is turned, particles present in the flow experience a resultant force, dependent upon their size and due to the combined effects of pressure, inertia, and drag. Since the balance of these forces determines the particle’s trajectory, turning the flow leads to a separation of particles downstream. This simple, low-pressure-drop sorting technique classifies particles with less risk of damage or contamination than currently available sorting devices. AVPS is experimentally demonstrated using a rectangular air jet. Particle size are measured using the Shadowgraphy method. Numerical simulations are performed using the commercial CFD solver FLUENT to calculate the 2D turbulent vectored jet flow field using a RANS approach. Examination of the mean and the standard deviation of measured and computed particle trajectories is used to determine the range of particle sizes that can be effectively sorted using AVPS. Our results indicate that while vectoring can be achieved with smaller control flow rates when blowing and suction are used together, fluctuations in the velocity field are much smaller when suction only is used. Furthermore, we have demonstrated that the jet flow can be vectored 90 with pure suction and 180 using a new geometry that allows for modification of the blowing angle on the fly. Using pure suction, particles from 10–40 micron and 2.5 times the density of water have been sorted to an accuracy of 1.5 micrometers. Sorting of heavy particles such as these is accomplished at very low speeds, reducing the tendency of damage to the particles. Lighter particles are sorted at higher speeds. Also using pure suction, particles from 5–40 μm and 0.6 times the density of water were sorted to an accuracy of 6.6 μm.