Predicting spatial spread of rabies in skunk populations using surveillance data reported by the public

Background: Prevention and control of wildlife disease invasions relies on the ability to predict spatio-temporal dynamics and understand the role of factors driving spread rates, such as seasonality and transmission distance. Passive disease surveillance (i.e., case reports by public) is a common method of monitoring emergence of wildlife diseases, but can be challenging to interpret due to spatial biases and limitations in data quantity and quality. Methodology/Principal findings: We obtained passive rabies surveillance data from dead striped skunks (Mephitis mephitis) in an epizootic in northern Colorado, USA. We developed a dynamic patch-occupancy model which predicts spatio-temporal spreading while accounting for heterogeneous sampling. We estimated the distance travelled per transmission event, direction of invasion, rate of spatial spread, and effects of infection density and season. We also estimated mean transmission distance and rates of spatial spread using a phylogeographic approach on a subsample of viral sequences from the same epizootic. Both the occupancy and phylogeographic approaches predicted similar rates of spatio-temporal spread. Estimated mean transmission distances were 2.3 km (95% Highest Posterior Density (HPD95): 0.02, 11.9; phylogeographic) and 3.9 km (95% credible intervals (CI95): 1.4, 11.3; occupancy). Estimated rates of spatial spread in km/year were: 29.8 (HPD95: 20.8, 39.8; phylogeographic, branch velocity, homogenous model), 22.6 (HPD95: 15.3, 29.7; phylogeographic, diffusion rate, homogenous model) and 21.1 (CI95: 16.7, 25.5; occupancy). Initial colonization probability was twice as high in spring relative to fall. Conclusions/Significance: Skunk-to-skunk transmission was primarily local (< 4 km) suggesting that if interventions were needed, they could be applied at the wave front. Slower viral invasions of skunk rabies in western USA compared to a similar epizootic in raccoons in the eastern USA implies host species or landscape factors underlie the dynamics of rabies invasions. Our framework provides a straightforward method for estimating rates of spatial spread of wildlife diseases

Integration of Microsphere Resonators with Bioassay Fluidics for Whispering Gallery Mode Imaging

Whispering gallery mode resonators are small, radially symmetric dielectrics that trap light through continuous total internal reflection. The resonant condition at which light is efficiently confined within the structure is linked with refractive index, which has led to the development of sensitive label-free sensing schemes based on whispering gallery mode resonators. One resonator design uses inexpensive high index glass microspheres that offer intrinsically superior optical characteristics, but have proven difficult to multiplex and integrate with the fluidics for sample delivery and fluid exchange necessary for assay development. Recently, we introduced a fluorescence imaging approach that enables large scale multiplexing with microsphere resonators, thus removing one obstacle for assay development. Here we report an approach for microsphere immobilization that overcomes limitations arising from their integration with fluidic delivery. The approach is an adaptation of a calcium-assisted glass bonding method originally developed for microfluidic glass chip fabrication. Microspheres bonded to glass using this technique are shown to be stable with respect to fluid flow and show no detectable loss in optical performance. Measured Q-factors, for example, remain unchanged following sphere bonding to the substrate. The stability of the immobilized resonators is further demonstrated by transferring lipid films onto the immobilized spheres using the Langmuir-Blodgett technique. Bilayers of DOPC doped with GM1 were transferred onto immobilized resonators to detect the binding of cholera toxin to GM1. Binding curves generated from shifts in the whispering gallery mode resonance result in a measured Kd of 1.5 × 10−11 with a limit of detection of 3.3 pM. These results are discussed in terms of future assay development using microsphere resonators

Optical Spin Initialization and Non-Destructive Measurement in a Quantum Dot Molecule

The spin of an electron in a self-assembled InAs/GaAs quantum dot molecule is optically prepared and measured through the trion triplet states. A longitudinal magnetic field is used to tune two of the trion states into resonance, forming a superposition state through asymmetric spin exchange. As a result, spin-flip Raman transitions can be used for optical spin initialization, while separate trion states enable cycling transitions for non-destructive measurement. With two-laser transmission spectroscopy we demonstrate both operations simultaneously, something not previously accomplished in a single quantum dot.Comment: Accepted for publication in Phys. Rev. Let

Surface Engineering for Phase Change Heat Transfer: A Review

Among numerous challenges to meet the rising global energy demand in a sustainable manner, improving phase change heat transfer has been at the forefront of engineering research for decades. The high heat transfer rates associated with phase change heat transfer are essential to energy and industry applications; but phase change is also inherently associated with poor thermodynamic efficiencies at low heat flux, and violent instabilities at high heat flux. Engineers have tried since the 1930's to fabricate solid surfaces that improve phase change heat transfer. The development of micro and nanotechnologies has made feasible the high-resolution control of surface texture and chemistry over length scales ranging from molecular levels to centimeters. This paper reviews the fabrication techniques available for metallic and silicon-based surfaces, considering sintered and polymeric coatings. The influence of such surfaces in multiphase processes of high practical interest, e.g., boiling, condensation, freezing, and the associated physical phenomena are reviewed. The case is made that while engineers are in principle able to manufacture surfaces with optimum nucleation or thermofluid transport characteristics, more theoretical and experimental efforts are needed to guide the design and cost-effective fabrication of surfaces that not only satisfy the existing technological needs, but also catalyze new discoveries

Sodium selectivity of Reissner's membrane epithelial cells

<p>Abstract</p> <p>Background</p> <p>Sodium absorption by Reissner's membrane is thought to contribute to the homeostasis of the volume of cochlear endolymph. It was previously shown that the absorptive transepithelial current was blocked by amiloride and benzamil. The most commonly-observed target of these drugs is the epithelial sodium channel (ENaC), which is composed of the three subunits α-,β- and γ-ENaC. However, other less-selective cation channels have also been observed to be sensitive to benzamil and amiloride. The aim of this study was to determine whether Reissner's membrane epithelial cells could support parasensory K⁺absorption via amiloride- and benzamil-sensitive electrogenic pathways.</p> <p>Results</p> <p>We determined the molecular and functional expression of candidate cation channels with gene array (GEO GSE6196), RT-PCR, and whole-cell patch clamp. Transcript expression analysis of Reissner's membrane detected no amiloride-sensitive acid-sensing ion channels (ASIC1a, ASIC2a, ASIC2b) nor amiloride-sensitive cyclic-nucleotide gated channels (CNGA1, CNGA2, CNGA4, CNGB3). By contrast, α-,β- and γ-ENaC were all previously reported as present in Reissner's membrane. The selectivity of the benzamil-sensitive cation currents was observed in whole-cell patch clamp recordings under Cl^--free conditions where cations were the only permeant species. The currents were carried by Na⁺but not K⁺, and the permeability of Li⁺was greater than that of Na⁺in Reissner's membrane. Complete replacement of bath Na⁺with the inpermeable cation NMDG⁺led to the same inward current as with benzamil in a Na⁺bath.</p> <p>Conclusions</p> <p>These results are consistent with the amiloride/benzamil-sensitive absorptive flux of Reissner's membrane mediated by a highly Na⁺-selective channel that has several key characteristics in common with αβγ-ENaC. The amiloride-sensitive pathway therefore absorbs only Na⁺in this epithelium and does not provide a parasensory K⁺efflux route from scala media.</p

Magnetoresistive biosensors with on-chip pulsed excitation and magnetic correlated double sampling.

Giant magnetoresistive (GMR) sensors have been shown to be among the most sensitive biosensors reported. While high-density and scalable sensor arrays are desirable for achieving multiplex detection, scalability remains challenging because of long data acquisition time using conventional readout methods. In this paper, we present a scalable magnetoresistive biosensor array with an on-chip magnetic field generator and a high-speed data acquisition method. The on-chip field generators enable magnetic correlated double sampling (MCDS) and global chopper stabilization to suppress 1/f noise and offset. A measurement with the proposed system takes only 20 ms, approximately 50× faster than conventional frequency domain analysis. A corresponding time domain temperature correction technique is also presented and shown to be able to remove temperature dependence from the measured signal without extra measurements or reference sensors. Measurements demonstrate detection of magnetic nanoparticles (MNPs) at a signal level as low as 6.92 ppm. The small form factor enables the proposed platform to be portable as well as having high sensitivity and rapid readout, desirable features for next generation diagnostic systems, especially in point-of-care (POC) settings

A study on the compressive strength of thick carbon fibre-epoxy laminates

This paper describes an experimental study that examines the effect of specimen size on the axial compressive strength of IM7/8552 carbon fibre/epoxy unidirectional laminates (UD). Laminate gauge length, width and thickness were increased by a scaling factor of 2 and 4 from the baseline specimen size of 10 mm x 10 mm x 2 mm. In all cases, strength decreased as specimen size increased, with a maximum reduction of 45%; no significant changes were observed for the axial modulus. Optical micrographs show that the failure mechanism is fibre microbuckling accompanied by matrix cracking and splitting. The location of failure in most specimens, especially the thicker ones, is where the tabs terminate and the gauge section begins suggesting that the high local stresses developed due to geometric discontinuity contribute to premature failure and hence reduced compressive strength. Two generic quasi-isotropic multi-directional (MD) lay-ups were also tested in compression, one with blocked plies [45n/90n/-45n/0n]s and the other with distributed plies [45/90/-45/0]ns with n=2, 4 and 8. The material used and test fixture was identical to that of the unidirectional specimens with three different gauge sections (30 mm x 30 mm, 60 mm x 60 mm and 120 mm x 120 mm) to establish any size effects. Strength results showed no evidence of a size effect when the specimens are scaled up using distributed plies and compared to the 2 mm thick specimens. All blocked specimens had similar compressive strengths to the sub-laminate ones apart of the 8 mm specimens that showed a 30% reduction due to extensive matrix cracking introduced during the specimen's cutting process. The calculated unidirectional failure stress (of the 0° ply within the multidirectional laminate) of about 1710 MPa is slightly higher than the average measured value of 1570 MPa of the 2 mm thick baseline unidirectional specimen, suggesting that the reduced unidirectional strength observed for the thicker specimens is a testing artefact. It appears that the unidirectional compressive strength in thicker specimens (>2 mm) is found to be limited by the stress concentration developed at the end tabs and manufacturing induced defects