Carbon nanofiber-based glucose biosensor

The use of highly activated carbon nanofibers for the design of catalytic electrochemical biosensors is demonstrated. The direct immobilization of enzymes onto the surface of carbon nanofibers is shown to be a highly efficient method for the development of a new class of very sensitive, stable, and reproducible electrochemical biosensors. These results establish the fact that the carbon nanofiber is the best matrix so far described for the development of biosensors, far superior to carbon nanotubes or graphite powder.     

Image-driven constitutive modeling of myocardial fibrosis

Myocardial fibrosis is a pathological process that occurs during heart failure (HF). It involves microstructural remodeling of normal myocardial tissue, and consequent changes in both cardiac geometry and function. The role of myocardial structural remodeling in the progression of HF remains poorly understood. We propose a constitutive modeling framework, informed by high-resolution images of cardiac tissue structure, to model the mechanical response of normal and fibrotic myocardium. This image-driven constitutive modeling approach allows us to better reproduce and understand the relationship between structural and functional remodeling of ventricular myocardium during HF.     

Impact of the synbiotic combination of Lactobacillus casei shirota and oligofructose-enriched inulin on the fecal volatile metabolite profile in healthy subjects

Scope: Hypothesis‐driven approaches have mainly focused on the quantification of SCFAs as mediators of beneficial effects of synbiotics. However, the emergence of metabolite profiling strategies allows to evaluate the colonic metabolism from a top‐down approach. In the present study, we evaluated the impact of a synbiotic combination on fecal metabolite profiles. Methods and results: A synbiotic combination (Lactobacillus casei Shirota cells+oligofructose‐enriched inulin) was evaluated in nine healthy volunteers. Before the start, during and after 4‐wk treatment, fecal samples were obtained. GC‐MS technology was applied to analyze the volatile metabolites. Application of a Type III test revealed that the metabolite profiles from the three conditions were significantly different. We identified three volatile organic compounds, acetate, dimethyl trisulfide and ethyl benzene, which were significantly affected. The acetate levels increased, whereas the dimethyl trisulfide levels decreased during and after the intervention. For ethyl benzene only an effect during the synbiotic intervention period was observed. Conclusion: We report a detailed analysis of the influence of L. casei Shirota combined with oligofructose‐enriched inulin on fermentation metabolites. Our results indicated a stimulation of saccharolytic fermentation and, importantly, a reduction of potentially toxic protein fermentation metabolites dimethyl trisulfide and ethyl benzene attended these effects.     

Anti-collusion forensics of multimedia fingerprinting using orthogonal modulation.

Digital fingerprinting is a method for protecting digital data in which fingerprints that are embedded in multimedia are capable of identifying unauthorized use of digital content. A powerful attack that can be employed to reduce this tracing capability is collusion, where several users combine their copies of the same content to attenuate/remove the original fingerprints. In this paper, we study the collusion resistance of a fingerprinting system employing Gaussian distributed fingerprints and orthogonal modulation. We introduce the maximum detector and the thresholding detector for colluder identification. We then analyze the collusion resistance of a system to the averaging collusion attack for the performance criteria represented by the probability of a false negative and the probability of a false positive. Lower and upper bounds for the maximum number of colluders K(max) are derived. We then show that the detectors are robust to different collusion attacks. We further study different sets of performance criteria, and our results indicate that attacks based on a few dozen independent copies can confound such a fingerprinting system. We also propose a likelihood-based approach to estimate the number of colluders. Finally, we demonstrate the performance for detecting colluders through experiments using real images.     

Parameter Identifiability for Three Sediment Entrainment Equations

A process-based erosion model is used to study parameterization problems of sediment entrainment equations in overland flow areas. One of the equations for entrainment by flow is developed based on a theory of excess stream power, while the other two relate to excess hydraulic shear. The investigation is conducted in two steps. The first step examines parameter optimization for simulated data sets where the parameter values are known. In the second step, parameter optimization for the most robust equation is examined using experimental data from rainfall simulator plots. Results demonstrate that although the model is capable of estimating total sediment yields with relatively small errors in parameter estimates, the converse is true when the optimization is performed for sediment concentrations. Although sediment yields calculated from simulated sediment concentrations match well with observed data, the parameter estimates generally underestimate sediment concentrations on the rising limb of the sediment graphs, and they overestimate them on the falling limb. This difficulty might be related to structural problems in the model, and unique solutions for parameter estimates cannot be obtained.     

Characterisation of mechanical non-linearities in a proton exchange membrane fuel cell using raw data

The implementation of fuel cells in transportation systems requires some better understanding of their mechanical behaviours in vibrating environments.     

Local electrochemical impedance spectroscopy: A review and some recent developments

Local electrochemical impedance spectroscopy (LEIS), which provides a powerful tool for exploration of electrode heterogeneity, has its roots in the development of electrochemical techniques employing scanning of microelectrodes. The historical development of local impedance spectroscopy measurements is reviewed, and guidelines are presented for implementation of LEIS. The factors which control the limiting spatial resolution of the technique are identified. The mathematical foundation for the technique is reviewed, including definitions of interfacial and local Ohmic impedances on both local and global scales. Experimental results for the reduction of ferricyanide show the correspondence between local and global impedances. Simulations for a single Faradaic reaction on a disk electrode embedded in an insulator are used to show that the Ohmic contribution, traditionally considered to be a real value, can have complex character in certain frequency ranges.     

Effect of Immobilization and Salt Concentration on the Growth Dynamics of Escherichia coli K12 and Salmonella Typhimurium

Up to now, it is generally observed that (i) the microbial growth domain is confined by structure‐induced stress, or (ii) a solid(‐like) environment can enhance microbial survival/growth. In most studies in solid(‐like) systems, structure is induced by the addition of gelatin. The aim of this study was to evaluate the effect of other structure‐inducing components on the growth dynamics. Both single and binary gel systems are used. Growth is studied when simultaneously exposed to salt stress. Experiments are performed in spectrophotometer tubes, filled with 1 mL of liquid, or structured inoculated brain heart infusion. Four different (combinations of) gelling agents are tested, that is, gelatin, xanthan gum, a 50% combination of xanthan gum and gelatin, and a 50% combination of carrageenan and gelatin. Experiments determine the growth behavior of both Escherichia coli (0% to 0.5% and 1%, 2%, 3%, 4%, and 5% NaCl) and Salmonella Typhimurium (0%, 1%, 2%, 3%, 4%, and 5% NaCl) at 23.5 and 27 °C. By means of plate counting, the growth dynamics are determined. At the studied conditions, growth of E. coli and Salmonella Typhimurium seems independent of the type of structure‐inducing component. However, at higher concentrations of salt (>2%), lag phases are typically shorter in solid(‐like) systems than in liquid media. For the conditions tested, the effect of a structured environment on growth rate and maximal cell density can be neglected.     

Effect of Hyperbaric Pressure Treatment on the Growth and Physiology of Bacteria that Cause Decay in Fruit and Vegetables

The response of bacteria to hyperbaric pressure treatment was investigated. Three selected bacteria which cause fruit and vegetable decay (i.e., Pseudomonas cichorii, Pectobacterium carotovorum, and Pseudomonas marginalis) were inoculated onto BIOLOG microplates and subjected to different pressure and temperature conditions including 100, 200, 400, 625, and 850 kPa at 20 °C and 100 kPa at 4 °C. Changes in microplate color, which corresponds to carbon source utilization of bacteria or their growth, were monitored every 24 h for 7 days. Results showed that the bacterial growth was affected by both hyperbaric pressure and temperature. As hyperbaric pressure increased, the bacterial growth significantly decreased and the extent was dependent on bacterial species. The 850-kPa pressure treatment reduced maximum growth by 71, 56, and 43 % for Pseudomonas cichorii, Pectobacterium carotovorum, and Pseudomonas marginalis, respectively. Among these bacteria, Pseudomonas cichorii was the most pressure-sensitive, while the most temperature-sensitive was Pectobacterium carotovorum. In general, an increase in hyperbaric pressure caused bacteria to utilize carbon sources similar to those when they were exposed to low temperature. Overall, hyperbaric treatment has the potential to directly reduce bacterial growth in fruit and vegetables after harvest.