The Influence of Technological Change on Grain Elevator Pricing Efficiency

The introduction of unit train technology is found to increase the pricing efficiency of a case study elevator. Daily prices are found to be more correlated with destination market prices and nearby futures contract prices after the subterminal was introduced. The increased ability to physically arbitrage between markets integrated the elevator into the regional and national grain market. The subterminal technology altered the price behavior of the elevator beyond simply changing the level of prices received by producers

Interaction of Salmonella spp. with the Intestinal Microbiota

Salmonella spp. are major cause of human morbidity and mortality worldwide. Upon entry into the human host, Salmonella spp. must overcome the resistance to colonization mediated by the gut microbiota and the innate immune system. They successfully accomplish this by inducing inflammation and mechanisms of innate immune defense. Many models have been developed to study Salmonella spp. interaction with the microbiota that have helped to identify factors necessary to overcome colonization resistance and to mediate disease. Here we review the current state of studies into this important pathogen/microbiota/host interaction in the mammalian gastrointestinal tract

Fast targeted gene transfection and optogenetic modification of single neurons using femtosecond laser irradiation

This work is supported by the UK Engineering Physical Sciences Research Council (EPSRC).A prevailing problem in neuroscience is the fast and targeted delivery of DNA into selected neurons. The development of an appropriate methodology would enable the transfection of multiple genes into the same cell or different genes into different neighboring cells as well as rapid cell selective functionalization of neurons. Here, we show that optimized femtosecond optical transfection fulfills these requirements. We also demonstrate successful optical transfection of channelrhodopsin-2 in single selected neurons. We extend the functionality of this technique for wider uptake by neuroscientists by using fast three-dimensional laser beam steering enabling an image-guided “point-and-transfect” user-friendly transfection of selected cells. A sub-second transfection timescale per cell makes this method more rapid by at least two orders of magnitude when compared to alternative single-cell transfection techniques. This novel technology provides the ability to carry out large-scale cell selective genetic studies on neuronal ensembles and perform rapid genetic programming of neural circuits.Publisher PDFPeer reviewe

Dispersal of the cochineal insect Dactylopius Austrinus de Lotto (Homoptera : Dactylopiidae)

Dispersal of the cochineal insect Dactylopius austrinus De Lotto, introduced into South Africa in 1932 as a biological control agent against jointed cactus Opuntia aurantiaca Lindley, was investigated. Zimmermann et al. (l974) suggested that the apparent failure of this insect to control jointed cactus infestations is due to limited dispersal of the first instar nymphs (hereafter referred to as crawlers). Studies on crawler morphology have shown a clear sexual dimorphism in the pattern and development of filaments on the head, thorax and abdomen of male and female crawlers. This enabled differentiation between the sexes with respect to terminal velocities, behaviour and survival of crawlers which have shown that the crawlers, especially the females, are well adapted to dispersal. Long filaments on the head, thorax and abdomen of the female crawlers, that are restricted to dispersal in the crawler stage (as later instars are sessile) and a behaviour directed towards "take-off" enhance the potential for dispersal. The more sedentary males, with long filaments restricted to the abdomen, are able to disperse as winged adults. The principal factors influencing the timing of dispersal and number of crawlers blown from the host plant are wind and temperature; the latter determining the number of crawlers moving on the host plant. Dispersal is confined to the period between 06h00 and 20h00 and it was possible to correlate the pattern of crawler dispersal with wind patterns. The general equation of Taylor (1978) provided an adequate description of horizontal distribution of D.austrinus crawlers in all directions. Wind dispersal of the apterous crawlers is restricted by the low height of jointed cactus plants. Horizontal distribution is limited (generally less than 10 m) although a small proportion of crawlers carried vertically upwards by turbulence or convection currents are sufficiently hardy to survive long range displacement. It is suggested that the small size of the host plant will also reduce effective colonization as the canopy area provides a small target for the wind-blown crawlers. The limitation on dispersal due to the low height of the host plant suggested a system for artificially enhancing crawler dispersal from elevated towers in the field. Evaluation of this system confirmed that it would be practical to augment or introduce cochineal into jointed cactus infestations to enhance the biocontrol potential of this insect. This offers an alternative to chemical control, that has so far failed to control the spread of jointed cactus despite an intensive and expensive herbicide progra

Logarithmic Intensity Compression in Fluorescence Guided Surgery Applications

The use of fluorescence video imaging to guide surgery is rapidly expanding, and improvements in camera readout dynamic range have not matched display capabilities. Logarithmic intensity compression is a fast, single-step mapping technique that can map the useable dynamic range of high-bit fluorescence images onto the typical 8-bit display and potentially be a variable dynamic contrast enhancement tool. We demonstrate a ∼4.6  times improvement in image quality quantified by image entropy and a dynamic range reduction by a factor of ∼380 by the use of log-compression tools in processing in vivo fluorescence images

Workflow for real-time in-vivo Cherenkov-excited luminescence imaging during radiotherapy

Radiotherapy is a common method for treating tumors, however, radiosensitivity can vary between tumor types or within the tumor microenvironment. The ability to deliver oxygen is crucial for the generation of reactive oxygen species resulting in increased localized cytotoxic effects. Alternatively, hypoxic tumors are thought to indicate a poor prognosis and may benefit from more aggressive treatments, yet identifying tumor hypoxia early in the course of a multi-week fractionated dose regimen is currently impractical. Using a time-gated imaging system and oxygen-sensitive phosphorescent compound (PtG4) we are able to estimate in vivo pO2 distribution at a rate of 2.6 estimates per second, which corresponds to 50+ values during a common 2Gy dose fraction. While our previous work has reported using Cherenkov-excited luminescence to estimate in vivo pO2 during external beam radiotherapy, the dose required was often greater than a standard fraction and camera acquisition parameters required modification during treatments, resulting in interrupted workflows. The current method utilizes custom control software which cycles through camera timing parameters during acquisition. Python code using the web-based user interface JupyterLab allows for interactive analysis of the resulting image stack without the need to pay expensive licensing fees for scientific computing packages. Using open source libraries, the analysis code is able to split the image stack into respective Cherenkov excitation and phosphorescence images, which can then be further automatically segmented to find regions of interest including the subject and phosphorescent region. The intensity of the regions in the phosphorescence images are used to estimate the compound lifetime, which can then be used in the Stern-Volmer relationship to estimate pO2. This entire process does not compromise clinical workflow and is able to provide a pO2 estimate within minutes after delivering the fractionated dose, providing clinicians early feedback about trends in tumor hypoxia. The current method has been validated with both direct injection of 50mM PtG4 in Matrigel in a mouse flank, and 24hrs post IV injection of mouse with MDA-MB-231 tumor implanted in the flank. The mouse with the direct injection was imaged under anesthesia and while awake and mobile to test the ability of the automated segmentation algorithm (Figure below). While the signal from the IV injection was less intense, simultaneous imaging using the previously reported method and current method resulted in similar lifetime estimates. While oxygen-sensitive PtG4 exhibits a lifetime between 16ms under atmospheric oxygen and 47ms when deprived of oxygen, other compounds have also been investigated. Europium chelate nanoparticle (~600ms), Iridium-based small molecules (~5ms), Si nanoparticles (~60ms), and UV-sensitive tattoo inks (~15ms) have all been imaged using Cherenkov-excitation. Camera time-gating can be utilized to discriminate these compound when mixed in the same field, allowing for additional tools in the realm of contrast enhancement during radiotherapy imaging. Ongoing studies with PtG4 and other compounds are being conducted to further improve system sensitivity and refine imaging workflows so they are more clinically translatable. Please click Additional Files below to see the full abstract

Optical Tracer Size Differences Allow Quantitation of Active Pumping Rate Versus Stokes–Einstein Diffusion in Lymphatic Transport

Lymphatic uptake of interstitially administered agents occurs by passive convective–diffusive inflow driven by interstitial concentration and pressure, while the downstream lymphatic transport is facilitated by active propulsive contractions of lymphatic vessel walls. Near-infrared fluorescence imaging in mice was used to measure these central components of lymphatic transport for the first time, using two different-sized molecules––methylene blue (MB) and fluorescence-labeled antibody immunoglobulin G (IgG)-IRDye 680RD. This work confirms the hypothesis that lymphatic passive inflow and active propulsion rates can be separated based upon the relative differences in Stokes–Einstein diffusion coefficient. This coefficient specifically affects the passive-diffusive uptake when the interstitial volume and pressure are constant. Parameters such as mean time-to-peak signal, overall fluorescence signal intensities, and number of active peristaltic pulses, were estimated from temporal imaging data. While the mean time to attain peak signal representative of diffusion-dominated flow in the lymph vessels was 0.6±0.2  min for MB and 8±6  min for IgG, showing a size dependence, the active propulsion rates were 3.4±0.8  pulses/min and 3.3±0.5  pulses/min, respectively, appearing size independent. The propulsion rates for both dyes decreased with clearance from the interstitial injection-site, indicating intrinsic control of the smooth muscles in response to interstitial pressure. This approach to size-comparative agent flow imaging of lymphatic function can enable noninvasive characterization of diseases related to uptake and flow in lymph networks

Pixel-Based Absorption Correction for Dual-Tracer Fluorescence Imaging of Receptor Binding Potential

Ratiometric approaches to quantifying molecular concentrations have been used for decades in microscopy, but have rarely been exploited in vivo until recently. One dual-tracer approach can utilize an untargeted reference tracer to account for non-specific uptake of a receptor-targeted tracer, and ultimately estimate receptor binding potential quantitatively. However, interpretation of the relative dynamic distribution kinetics is confounded by differences in local tissue absorption at the wavelengths used for each tracer. This study simulated the influence of absorption on fluorescence emission intensity and depth sensitivity at typical near-infrared fluorophore wavelength bands near 700 and 800 nm in mouse skin in order to correct for these tissue optical differences in signal detection. Changes in blood volume [1-3%] and hemoglobin oxygen saturation [0-100%] were demonstrated to introduce substantial distortions to receptor binding estimates (error \u3e 30%), whereas sampled depth was relatively insensitive to wavelength (error \u3c 6%). In response, a pixel-by-pixel normalization of tracer inputs immediately post-injection was found to account for spatial heterogeneities in local absorption properties. Application of the pixel-based normalization method to an in vivo imaging study demonstrated significant improvement, as compared with a reference tissue normalization approach