Welfare of calves - 2. Increase in vertebral artery blood flow following exsanguination by neck sticking and evaluation of chest sticking as an alternative slaughter method

The role of the vertebral arteries in delaying loss of sensibility following neck sticking in slaughter calves was investigated. Vertebral artery blood flow was measured using probes before, during and after electrical stunning and slaughter. Systemic blood pressure, electrocorticogram, visually evoked responses and the occurrence of carotid occlusions were also recorded. When carotid occlusion occurred, the time to onset of brain failure was delayed based on the development of an isoelectric state. In addition, when carotid occlusion occurred the mean arterial blood pressure was sustained for longer following slaughter, and concurrently vertebral artery blood flow could be maintained at about 30% of its initial level for up to 3 min. In some animals vertebral artery flow increased substantially following sticking. When chest sticking was used no occlusion of vessels occurred, mean arterial blood pressure fell promptly (within 8 s) and the onset of an isoelectric state did not extend beyond one minute. In addition, visually evoked responses were not present after 5 s following chest sticking.     

Maximum-likelihood registration of range images with missing data

Missing data are common in range images, due to geometric occlusions, limitations in the sensor field of view, poor reflectivity, depth discontinuities, and cast shadows. Using registration to align these data often fails, because points without valid correspondences can be incorrectly matched. This paper presents a maximum likelihood method for registration of scenes with unmatched or missing data. Using ray casting, correspondences are formed between valid and missing points in each view. These correspondences are used to classify points by their visibility properties, including occlusions, field of view, and shadow regions. The likelihood of each point match is then determined using statistical properties of the sensor, such as noise and outlier distributions. Experiments demonstrate a high rates of convergence on complex scenes with varying degrees of overlap.     

Chemical and genetic wrappers for improved phage and RNA display

An Achilles heel inherent to all molecular display formats, background binding between target and display system introduces false positives into screens and selections. For example, the negatively charged surfaces of phage, mRNA, and ribosome display systems bind with unacceptably high nonspecificity to positively charged target molecules, which represent an estimated 35% of proteins in the human proteome. Here we report the first systematic attempt to understand why a broad class of molecular display selections fail, and then solve the underlying problem for both phage and RNA display. Firstly, a genetic strategy was used to introduce a short, charge-neutralizing peptide into the solvent-exposed, negatively charged phage coat. The modified phage (KO7(+)) reduced or eliminated nonspecific binding to the problematic high-pI proteins. In the second, chemical approach, nonspecific interactions were blocked by oligolysine wrappers in the cases of phage and total RNA. For phage display applications, the peptides Lys(n) (where n=16 to 24) emerged as optimal for wrapping the phage. Lys(8), however, provided effective wrappers for RNA binding in assays against the RNA binding protein HIV-1 Vif. The oligolysine peptides blocked nonspecific binding to allow successful selections, screens, and assays with five previously unworkable protein targets.     

Analytical performance of an ultrasonic particle focusing flow cytometer

Creation of inexpensive small-flow cytometers is important for applications ranging from disease diagnosis in resource-poor areas to use in distributed sensor networks. In conventional-flow cytometers, hydrodynamics focus particles to the center of a flow stream for analysis, which requires sheath fluid that increases consumable use and waste while dramatically reducing instrument portability. Here we have evaluated, using quantitative measurements of fluorescent microspheres and cells, the performance of a flow cytometer that uses acoustic energy to focus particles to the center of a flow stream. This evaluation demonstrated measurement precision for fluorescence and side scatter CVs for alignment microspheres of 2.54% and 7.7%, respectively. Particles bearing 7 x 10(3) fluorophores were well resolved in a background of 50 nM free fluorophore. The lower limit of detection was determined to be about 650 fluorescein molecules. Analysis of Chinese hamster cells on the system demonstrated that acoustic focusing had no effect on cellular viability. These results indicate that the ultrasonic flow cytometer has the necessary performance for most flow cytometry applications. Furthermore, through robust engineering approaches and the combination of acoustic focusing with low-cost light sources, detectors, and data acquisition systems, it will be possible to achieve a low-cost, truly portable flow cytometer.     

Vernier-effect optical interrogation technique for fiber Bragg grating sensors

This work demonstrates a new technique for real-time optical sensor interrogation by exploiting a novel Vernier effect between the multiple (comb) wavelength responses of a multiplexed fiber Bragg grating array and the fixed discrete wavelengths of an all-solid-state tunable laser. Sets of output photodetector voltages serve as high-resolution optical "signatures" to determine uniquely the strain in the single fiber section. The sensor demonstrated here is compact, lightweight, and is specifically intended for remote operability in harsh (vibrational) environments. In this proof of concept, strain values over a range of nearly 500 microepsilon can be easily resolved to better than 5.9 microepsilon, which is the incremental limit of the mechanical test fixture used to induce strain in the experiment.     

Characterization of digital waveforms using thermodynamic analogs: applications to detection of materials defects

We describe characterization of digital signals using analogs of thermodynamic quantities: the topological entropy, Shannon entropy, thermodynamic energy, partition function, specific heat at constant volume, and an idealized version of Shannon entropy in the limit of digitizing with infinite dynamic range and sampling rate. We show that analysis based on these quantities is capable of detecting differences between digital signals that are undetectable by conventional methods of characterization based on peak-to-peak amplitude or signal energy. We report the results of applying thermodynamic quantities to a problem from nondestructive materials evaluation: detection of foreign objects (FO) embedded near the surface of thin graphite/epoxy laminates using backscattered waveforms obtained by C-scanning the laminate. The characterization problem was to distinguish waveforms acquired from the region containing the FO from those acquired outside. In all cases the thermodynamic analogs exhibit significant increases (up to 20-fold) in contrast and for certain types of FO materials permit detection when energy or amplitude methods fail altogether.     

High-throughput single-cell fluorescence spectroscopy

A high-throughput method for measuring single-cell fluorescence spectra is presented. Upon excitation with a 488 nm argon-ion laser many bacterial cells were imaged by a 20x microscope objective while they moved through a capillary tube. Fluorescence was dispersed by a transmission diffraction grating, and an intensified charge-coupled device (ICCD) camera simultaneously recorded the zero and the first orders of the fluorescence from each cell. Single-cell fluorescence spectra were reconstructed from the distance between zero-order and first-order maxima as well as the length and the pixel intensity distribution of the first-order images. By using this approach, the emission spectrum of E. coli cells expressing green fluorescent protein (GFP) was reconstructed. Also, fluorescence spectra of E. coli cells expressing non-fluorescent apo-subunits of R-phycoerythrin (R-PE) were recorded after incubation of the cells with phycoerythrobilin (PEB) chromophore. The fluorescence spectra are in good agreement with results obtained on the same cells using a fluorescence spectrometer or a fluorescence microscope. When spectra are to be acquired, this approach has a higher throughput, better sensitivity, and better spectral resolution compared to flow cytometry.     

Enhanced Photoluminescence of Heavily Doped n-Ge/Si(001) Layers

Semiconductors - The photoluminescence spectra of epitaxial n+-Ge:P/Si(001) structures are studied. The structures are grown by hot-wire chemical vapor deposition and doped with phosphorus to the...     

Bayesian super-resolution of text in videowith a text-specific bimodal prior

To increase the range of sizes of video scene text recognizable by optical character recognition (OCR), we developed a Bayesian super-resolution algorithm that uses a text-specific bimodal prior. We evaluated the effectiveness of the bimodal prior, compared and in conjunction with a piecewise smoothness prior, visually and by measuring the accuracy of the OCR results on the variously super-resolved images. The bimodal prior improved the readability of 4- to 7-pixel-high scene text significantly better than bicubic interpolation and increased the accuracy of OCR results better than the piecewise smoothness prior.