Sulfide-oxidizing activity and bacterial community structure in a fluidized bed reactor from a zero-discharge mariculture system

In the present work we describe a comprehensive analysis of sulfide oxidation in a fluidized bed reactor (FBR) from an environmentally sustainable, zero-discharge mariculture system. The FBR received oxygen-depleted effluent from a digestion basin (DB) that is responsible for gasification of organic matter and nitrogen. The FBR is a crucial component in this recirculating system because it safeguards the fish from the toxic sulfide produced in the DB. Microscale sulfide oxidation potential and bacterial community composition within FBR biofilms were correlated to biofilter performance by integrating bulk chemical, microsensor (O2, pH, and H2S), and molecular microbial community analyses. The FBR consistently oxidized sulfide during two years of continuous operation, with an estimated average sulfide removal rate of 1.3 g of sulfide-S L(FBR)(-1) d(-1). Maximum sulfide oxidation rates within the FBR biofilms were 0.36 and 0.21 mg of sulfide-S cm(-3) h(-1) in the oxic and anoxic layers, respectively, indicating that both oxygen and nitrate serve as electron acceptors for sulfide oxidation. The estimated anoxic sulfide removal rate, as extrapolated from bench scale, autotrophic, nitrate-amended experiments, was 0.7 g of sulfide-S L(FBR)(-1) d(-1), which is approximately 50% of the total estimated sulfide removal in the FBR. Community composition analyses using denaturing gradient gel electrophoresis (DGGE) of bacterial 16S rRNA gene fragments from FBR samples taken at six-month intervals revealed several sequences that were closely affiliated with sulfide-oxidizing bacteria. These included the denitrifying, sulfide-oxidizing bacteria Thiomicrospira denitrificans, members of the filamentous Thiothrix genus, and sulfide-oxidizing symbionts from the Gammaproteobacteria. In addition, marine Alphaproteobacteria and Bacteroidetes species were present in all of the DGGE profiles examined. DGGE analyses showed significant shifts in the bacterial community composition between profiles over two years of sampling, indicating the presence of a diverse and dynamic microbial community within the functionally stable FBR. The FBR's combined capacity for both oxic and anoxic sulfide oxidation, as indicated by bulk chemical, microsensor, and molecular microbial analyses, gives it significant functional elasticity, which is crucial for proper performance in the dynamic environment of this mariculture system.     

Ozone Degradation of Cyclophosphamide – Effect of Alkalinity and Key Effluent Organic Matter Constituents

The influence of three effluent organic matter (EfOM) model compounds (alginic acid, peptone and natural organic matter-NOM) and alkalinity on the ozonation of cyclophosphamide (CPD) was investigated. The rate of ozone decay increased with increasing model compounds concentration in the order of peptone > NOM > alginic acid. Increasing alkalinity inhibited ozone decay at all concentrations of alginic acid and at low concentrations of NOM and peptone (DOC < 3 mg/L), while at high NOM and peptone concentrations the effect of alkalinity on ozone decay was minor. Presumably, ozone decay was mainly controlled by direct reaction with these two model compounds, resulting in ?OH (hydroxyl radical) formation yield of 29% and 19%, for peptone and NOM respectively. In the presence of alginic acid ?OH formation through a radical chain reaction resulted in a yield of 30%. Cyclophosphamide (CPD) removal decreased with increasing alkalinity and model compounds concentration (most pronounced for peptone and less pronounced for alginic acid); most likely due to increase in the scavenging effect on ?OH.     

Accuracy of velocity estimation by Reichardt correlators

Although a great deal of experimental evidence supports the notion of a Reichardt correlator as a mechanism for biological motion detection, the correlator does not signal true image velocity. This study examines the accuracy with which realistic Reichardt correlators can provide velocity estimates in an organism's natural visual environment. The predictable statistics of natural images imply a consistent correspondence between mean correlator response and velocity, allowing the otherwise ambiguous Reichardt correlator to act as a practical velocity estimator. Analysis and simulations suggest that processes commonly found in visual systems, such as prefiltering, response compression, integration, and adaptation, improve the reliability of velocity estimation and expand the range of velocities coded. Experimental recordings confirm our predictions of correlator response to broadband images.     

Routing electric meter readers

Electric utility companies employ a crew of workers who periodically visit and read the electric meters of each customer in their service area. Each reader is transported by auto from a central office to the first customer on his work list. At the end of his work shift time limit the reader is free to leave the area possibly returning home or to the central office by public bus. Taking a graph that corresponds to the city network of streets meter readers must traverse each street while moving from house to house. It is possible that dead heading may be required—back tracking over a street that has already been covered. A working tour is an open path whose reading time plus deadheading time does not exceed the work limit. The problem is to find the minimum number of working tours. Stating the problem in this manner gives us an optimization problem closely related to the M-Chinese postman problem—an edge oriented routing problem. After presenting some background on this type of problem a heuristic procedure is used to solve an example from the City of Beersheva. The solution provides a 40% reduction in the number of working tours. The paper ends with a discussion of the solution, and provides conditions under which the algorithm should have practical utility.     

Communication Models for a Free-Space Optical Cross-Connect Switch

We design and analyze communication algorithms for an optical switch based on the electroholographic effect, that provides capabilities for configuration changes and a limited multicast. As configuration changes incur a high overhead, we suggest the use of a high-speed forwarding unit as part of the network interface. We develop broadcast algorithms that trade off the number of configuration changes and forwarding operations in order to achieve the minimal completion time. For general point- to-point communication, we use the limited multicast to create a spanning topology along which messages can be forwarded. This requires care to avoid collisions, but is still preferable to using configuration changes if the topology is rich enough but still has a low degree.     

MiR-199a-3p Induces Mesenchymal to Epithelial Transition of Keratinocytes by Targeting RAP2B

Cutaneous squamous cell carcinoma (CSCC) is an epidermal skin cancer that evolves from normal epidermis along several pre-malignant stages. Previously we found specific miRNAs alterations in each step along these stages. miR-199a-3p expression decreases at the transition to later stages. A crucial step for epithelial carcinoma cells to acquire invasive capacity is the disruption of cell–cell contacts and the gain of mesenchymal motile phenotype, a process known as epithelial-to-mesenchymal transition (EMT). This study aims to study the role of decreased expression of miR-199a-3p in keratinocytes’ EMT towards carcinogenesis. First, we measured miR-199a-3p in different stages of epidermal carcinogenesis. Then, we applied Photoactivatable Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation (PAR-CLIP) assay to search for possible biochemical targets of miR-199a-3p and verified that Ras-associated protein B2 (RAP2B) is a bona-fide target of miR-199a-3p. Next, we analyzed RAP2B expression, in CSCC biopsies. Last, we evaluated possible mechanisms leading to decreased miR-199a-3p expression. miR-199a-3p induces a mesenchymal to epithelial transition (MET) in CSSC cells. Many of the under-expressed genes in CSCC overexpressing miR-199a-3p, are possible targets of miR-199a-3p and play roles in EMT. RAP2B is a biochemical target of miR-199a-3p. Overexpression of miR-199a-3p in CSCC results in decreased phosphorylated focal adhesion kinase (FAK). In addition, inhibiting FAK phosphorylation inhibits EMT marker genes’ expression. In addition, we proved that DNA methylation is part of the mechanism by which miR-199a-3p expression is inhibited. However, it is not by the methylation of miR-199a putative promoter. These findings suggest that miR-199a-3p inhibits the EMT process by targeting RAP2B. Inhibitors of RAP2B or FAK may be effective therapeutic agents for CSCC.     

A new method for membrane construction on ePTFE vascular grafts: Effect on surface morphology and platelet adhesion

Vascular grafts made of expanded polytetrafluoroethylene (ePTFE) are widely employed in reconstructive surgery. Despite their successful use for replacement of large diameter blood vessels, ePTFE vascular grafts with internal diameters of less than 6 mm uniformly fail as a result of blood clot formation. To reduce the ePTFE reactivity to platelets, a new method for membrane construction on the inner graft surface was developed. The membrane, made of a chitosan-poly(vinyl alcohol) blend and non-ionic detergent, is constructed by adsorption of a thin liquid film and air drying. The chemically modified ePTFE surface exhibits both morphological changes and a markedly reduced reactivity to platelets in in vitro studies. Chemical activation of the chitosan-poly(vinyl alcohol) blend, to trigger desired protein binding, may yet serve as a complementary surface modification approach. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1393–1400, 1997     

Bayesian calculation of cost optimal burn-in test durations for mixed exponential populations

The burn-in process is a part of the production process whereby manufactured products are operated for a short period of time before release. In this paper, a Bayesian method is developed for calculating the optimal burn-in duration for a batch of products whose life distribution is modeled as a mixture of two (denoted ‘strong’ and ‘weak’) exponential sub-populations. The criteria used is the minimization of a total expected cost function reflecting costs related to the burn-in process and to product failures throughout a warranty period. The expectation is taken with respect to the mixed exponential failure model and its parameters. The prior distribution for the parameters is constructed using a beta density for the mixture parameter and independent gamma densities for the failure rate parameters of the sub-populations. It is assumed that the optimal burn-in time is selected in advance and remains fixed throughout the burn-in process. When additional failure information is available prior to the burn-in process, the minimization of posterior total cost is used as the criteria for selecting the optimal burn-in time. Expressions for the joint posterior distribution and cost are provided for the case of both complete and truncated data. The method is illustrated with an example.     

Bayesian calculation of optimal burn‐in time using the joint criteria of cost and delivered reliability

Burn‐in is a quality control process used to minimize the warranty cost of a product by screening out defective products through prior operation for a period of time before sale. Two decision criteria used to determine the optimal burn‐in time are the maximization of the reliability of the delivered product and the minimization of the total cost, which are composed of the cost of burn‐in process and the cost of warranty claims. Because of uncertainty regarding the underlying lifetime distribution of the product, both the product reliability and the total cost are random variables. In this paper, the uncertainty in reliability and cost is quantified by use of Bayesian analysis. The joint distribution of reliability and cost is inferred from the uncertainty distribution of the parameters of the product lifetime distribution. To incorporate the uncertainty in reliability and cost as well as the tradeoff between them into the selection of optimal burn‐in time, the joint utility function of reliability and cost is constructed using the joint distribution of reliability and cost. The optimal burn‐in time is selected as the time that maximizes the joint utility function. Copyright © 2010 John Wiley & Sons, Ltd.