The localization sequence for the algebraic K-theory of topological K-theory

We prove a conjecture of Rognes by establishing a localization cofiber sequence of spectra, K(Z) to K(ku) to K(KU) to Sigma K(Z), for the algebraic K-theory of topological K-theory. We deduce the existence of this sequence as a consequence of a devissage theorem identifying the K-theory of the Waldhausen category of Postnikov towers of modules over a connective A-infinity ring spectrum R with the Quillen K-theory of the abelian category of finitely generated pi_0(R)-modules.Comment: Updated final version. Small change in definition of S' construction and correction to the proof of 2.

Resolving depth measurement ambiguity with commercially available range imaging cameras

Time-of-flight range imaging is typically performed with the amplitude modulated continuous wave method. This involves illuminating a scene with amplitude modulated light. Reflected light from the scene is received by the sensor with the range to the scene encoded as a phase delay of the modulation envelope. Due to the cyclic nature of phase, an ambiguity in the measured range occurs every half wavelength in distance, thereby limiting the maximum useable range of the camera. This paper proposes a procedure to resolve depth ambiguity using software post processing. First, the range data is processed to segment the scene into separate objects. The average intensity of each object can then be used to determine which pixels are beyond the non-ambiguous range. The results demonstrate that depth ambiguity can be resolved for various scenes using only the available depth and intensity information. This proposed method reduces the sensitivity to objects with very high and very low reflectance, normally a key problem with basic threshold approaches. This approach is very flexible as it can be used with any range imaging camera. Furthermore, capture time is not extended, keeping the artifacts caused by moving objects at a minimum. This makes it suitable for applications such as robot vision where the camera may be moving during captures. The key limitation of the method is its inability to distinguish between two overlapping objects that are separated by a distance of exactly one non-ambiguous range. Overall the reliability of this method is higher than the basic threshold approach, but not as high as the multiple frequency method of resolving ambiguity

Advantages of 3D time-of-flight range imaging cameras in machine vision applications

Machine vision using image processing of traditional intensity images is in wide spread use. In many situations environmental conditions or object colours or shades cannot be controlled, leading to difficulties in correctly processing the images and requiring complicated processing algorithms. Many of these complications can be avoided by using range image data, instead of intensity data. This is because range image data represents the physical properties of object location and shape, practically independently of object colour or shading. The advantages of range image processing are presented, along with three example applications that show how robust machine vision results can be obtained with relatively simple range image processing in real-time applications

ABC transporter FtsABCD of Streptococcus pyogenes mediates uptake of ferric ferrichrome

BACKGROUND: The Streptococcus pyogenes or Group A Streptococcus (GAS) genome encodes three ABC transporters, namely, FtsABCD, MtsABC, and HtsABC, which share homology with iron transporters. MtsABC and HtsABC are believed to take up ferric (Fe(3+)) and manganese ions and heme, respectively, while the specificity of FtsABCD is unknown. RESULTS: Recombinant FtsB, the lipoprotein component of FtsABCD, was found to bind Fe(3+ )ferrichrome in a 1:1 stoichiometry. To investigate whether FtsABCD transports Fe(3+ )ferrichrome, GAS isogenic strains defective in lipoprotein gene ftsB and permease gene ftsC were generated, and the effects of the mutations on uptake of Fe(3+ )ferrichrome were examined using radioactive (55)Fe(3+ )ferrichrome. FtsB was produced in the wild-type strain but not in the ftsB mutant, confirming the ftsB inactivation. While wild-type GAS took up 3.6 × 10(4 )Fe(3+ )ferrichrome molecules per bacterium per min at room temperature, the ftsB and ftsC mutants did not have a detectable rate of Fe(3+ )ferrichrome uptake. The inactivation of ftsB or ftsC also decreased (55)Fe(3+ )ferrichrome uptake by >90% under growth conditions in the case of limited uptake time. Complementation of the ftsB mutant with a plasmid carrying the ftsB gene restored FtsB production and (55)Fe(3+ )ferrichrome association at higher levels compared with the parent strain. The inactivation of mtsA and htsA and Fe-restricted conditions enhanced the production of FtsB and Fe(3+ )ferrichrome uptake. CONCLUSION: The FtsB protein bound Fe(3+ )ferrichrome, and inactivation of ftsB or ftsC, but not htsA or mtsA, diminished Fe(3+ )ferrichrome uptake, indicating that FtsABCD, but not HtsABC and MtsABC, is the transporter that takes up Fe(3+ )ferrichrome in GAS. Fe acquisition systems are virulence factors in many bacterial pathogens and are attractive vaccine candidates. The elucidation of the FtsABCD specificity advances the understanding of Fe acquisition processes in GAS and may help evaluating the GAS Fe acquisition systems as vaccine candidates

Identification and characterization of the heme-binding proteins SeShp and SeHtsA of Streptococcus equi subspecies equi

BACKGROUND: Heme is a preferred iron source of bacterial pathogens. Streptococcus equi subspecies equi is a bacterial pathogen that causes strangles in horses. Whether S. equi has a heme acquisition transporter is unknown. RESULTS: An S. equi genome database was blasted with the heme binding proteins Shp and HtsA of Streptococcus pyogenes, and found that S. equi has the homologue of Shp (designated SeShp) and HtsA (designated SeHtsA). Tag-free recombinant SeShp and SeHtsA and 6xHis-tagged SeHtsA (SeHtsA(His)) were prepared and characterized. Purified holoSeShp and holoSeHtsA bind Fe(II)-protoporphyrin IX (heme) and Fe(III)-protoporphyrin IX (hemin) in a 1:1 stoichiometry, respectively, and are designated hemoSeShp and hemiSeHtsA. HemiSeShp and hemiSeHtsA(His )can be reconstituted from apoSeShp and apoSeHtsA(His )and hemin. HemoSeShp is stable in air and can be oxidized to hemiSeShp by ferricyanide. HemiSeHtsA can be reduced into hemoSeHtsA, which autoxidizes readily. HemoSeShp rapidly transfers its heme to apoSeHtsA(His). In addition, hemoSeShp can also transfer its heme to apoHtsA, and hemoShp is able to donate heme to apoSeHtsA(His). CONCLUSION: The primary structures, optical properties, oxidative stability, and in vitro heme transfer reaction of SeShp and SeHtsA are very similar to those of S. pyogenes Shp and HtsA. The data suggest that the putative cell surface protein SeShp and lipoprotein SeHtsA are part of the machinery to acquire heme in S. equi. The results also imply that the structure, function, and functional mechanism of the heme acquisition machinery are conserved in S. equi and S. pyogenes

The Two-Component Regulatory System VicRK is Important to Virulence of Streptococcus equi Subspecies equi

This study aims at evaluating the importance of the two-component regulatory system VicRK to virulence of the horse pathogen Streptococcus equi subspecies equi and the potential of a vicK mutant as a live vaccine candidate using mouse infection models. The vicK gene was deleted by gene replacement. The ΔvicK mutant is attenuated in virulence in both subcutaneous and intranasal infections in mice. ΔvicK grows less slowly than the parent strain but retains the ability of S. equi to resist to phagocytosis by polymorphoneuclear leukocytes, suggesting that the vicK deletion causes growth defect. ΔvicK infection protects mice against reinfection with a wild-type S. equi strain. Intranasal ΔvicK infection induces production of anti-SeM mucosal IgA and systemic IgG. These results indicate that VicRK is important to S. equi growth and virulence and suggest that ΔvicK has the potential to be developed as a live S. equi vaccine

Incipient fault detection study for advanced spacecraft systems

A feasibility study to investigate the application of vibration monitoring to the rotating machinery of planned NASA advanced spacecraft components is described. Factors investigated include: (1) special problems associated with small, high RPM machines; (2) application across multiple component types; (3) microgravity; (4) multiple fault types; (5) eight different analysis techniques including signature analysis, high frequency demodulation, cepstrum, clustering, amplitude analysis, and pattern recognition are compared; and (6) small sample statistical analysis is used to compare performance by computation of probability of detection and false alarm for an ensemble of repeated baseline and faulted tests. Both detection and classification performance are quantified. Vibration monitoring is shown to be an effective means of detecting the most important problem types for small, high RPM fans and pumps typical of those planned for the advanced spacecraft. A preliminary monitoring system design and implementation plan is presented

Developing a Model of Aged Decellularized Muscle Matrix with Advanced Glycation Cross-linking

Volumetric muscle loss (VML) has been found to overwhelm muscle regeneration, resulting in loss of long-term muscle functionality. Decellularized muscle matrices (DMMs) provide an effective environment for muscle regeneration; however, the age of their source has not been adequately explored for clinical translation. Advanced glycation end-products (AGEs) are chemical cross-links that contribute to the aging process by accumulating on collagen fibers, resulting in a stiffening of the collagenous matrix and an increase in inflammation via the receptor for advanced glycation end-products (RAGE). In previous experiments, we found increased levels of AGE-specific cross-links within DMMs in old mice compared to young as proven by ALT-711 treatment. In this study, we developed a model of aged rat DMMs using AGE cross-links and hypothesized that our AGE-DMM model will contain a higher number of collagen cross-links compared to the control. This AGE-DMM model aims to elucidate the effect of AGEs on muscle regeneration when used in vitro or implanted in a volumetric muscle loss model.https://scholarscompass.vcu.edu/uresposters/1424/thumbnail.jp