Lipopeptide Nanoparticles: Development of Vaccines against Hookworm Parasite

Necator americanus (hookworm) infects over half a billion people worldwide. Anthelminthic drugs are commonly used to treat the infection; however, vaccination is a more favorable strategy to combat this parasite. We designed new B‐cell peptide epitopes based on the aspartic protease of N. americanus (Na‐APR‐1). The peptides were conjugated to self‐adjuvanting lipid core peptide (LCP) systems via stepwise solid‐phase peptide synthesis (SPPS) and copper catalyst azide–alkyne cycloaddition (CuAAC) reactions. The LCP vaccine candidates were able to self‐assemble into nanoparticles, were administered to mice without the use of additional adjuvant, and generated antibodies that recognized the parent epitope. However, only one LCP derivative was able to produce a high titer of antibodies specific to Na‐APR‐1; circular dichroism analyses of this compound showed a β‐sheet conformation for the incorporated epitope. This study provides important insight in epitope and delivery system design for the development of a vaccine against hookworm infections.     

Dissolved organic carbon reduces uranium bioavailability and toxicity. 2. Uranium[VI] speciation and toxicity to three tropical freshwater organisms

The influence of dissolved organic carbon (DOC) on the toxicity of uranium (U) to three Australian tropical freshwater species, the Northern Trout Gudgeon (Mogurnda mogurnda), green hydra (Hydra viridissima) and unicellular green alga (Chlorella sp.) was assessed. Exposures were conducted in synthetic soft water without DOC and with DOC added in the form of standard Suwannee River Fulvic Acid (SRFA). Organisms were exposed to a range of U concentrations at a range of DOC concentrations (0-20 mg L(-1)). U toxicity was up to 20 times less in water containing 20 mg L(-1) DOC, relative to DOC-free test waters. U toxicity was also assessed using natural water from a tropical Australian billabong containing 10 mg L(-1) DOC. U toxicity was up to ten times less in the billabong water, relative to DOC--free test waters. SRFA was twice as effective at reducing U toxicity as the billabong water at equivalent DOC concentrations. Geochemical speciation modeling confirmed the decreased U toxicity that resulted from both DOC sources was primarily due to a decrease in the free uranyl ion (UO2(2+)) through complexation with DOC. A predictive model is presented for each of the organisms that can be used to predict U toxicity at a given U and DOC concentration.     

Survival characteristics of Salmonella enterica serovar Newport in the dairy farm environment

Multi-drug resistant (MDR) Salmonella enterica serovar Newport (S. Newport) has established a reservoir in dairy cattle. Infected herds suffer significant mortality in both adult and young animals, posing a considerable economic loss to producers. Land application of manure from infected animals may further spread the pathogen into the agroecosystem, causing public health concerns. Previous work by our group demonstrated that the organism persisted in manure and manured soil for 6 to 10 mo under laboratory conditions. In the present study, we determined the survival characteristics of MDR S. Newport in a dairy lagoon, compost pile, and soil of a grass field under natural conditions using environmental sentinel chambers with an initial concentration of S. Newport around 7 log₁₀ per gram. In the static compost pile at 64°C, S. Newport was eliminated within 18 h. In the dairy effluent lagoon, the pathogen survived for >137 d, whereas in the field soil, the organisms persisted for over 276 d. The survival of MDR S. Newport in both the lagoon and field soil followed a pattern of (1) an increase or plateau for a few days, (2) log-linear decline for 6 to 13 wk, and (3) a long tailing phase at low and variable concentration for 4 to 9 mo. Log reduction times (days required for 90% decrease in concentration) based on the log-linear decline phase were 7 d in the lagoon and 14 to 20 d in the soil. Conditions leading to faster inactivation during the initial phase do not necessarily translate into a quicker elimination of the pathogen. Regression models of the log-linear phase may be inaccurate for estimating complete pathogen elimination.     

How bacteria get energy from hydrogen: a genetic analysis of periplasmic hydrogen oxidation in Escherichia coli

Dihydrogen oxidation is an important feature of bacterial energy conservation. In Escherichia coli hydrogen oxidation (‘uptake’) is catalysed by membrane-bound [NiFe] hydrogenase-1 and [NiFe] hydrogenase-2. The bulk of these uptake isoenzymes is exposed to the periplasm and biosynthesis of the proteins involves membrane transport via the twin-arginine translocation (Tat) pathway. Hydrogenase-2 is encoded by the hybOABCDEFG operon and the core enzyme is a heterodimer of HybO and HybC. HybO is synthesised with a twin-arginine signal peptide. HybOC is associated with two other proteins (HybA and HybB) that complete the respiratory complex. The HybOC dimer is bound to the cytoplasmic membrane and appears to be anchored via a hydrophobic transmembrane α-helix located at the C-terminus of HybO. Thus, hydrogenase-2 is an example of an integral membrane protein assembled in a Tat-dependent (Sec-independent) manner. Studies of the biosynthesis, targeting, and assembly of hydrogenase-2 would set a paradigm for all respiratory complexes of this type.     

Near Real-Time Scour Monitoring System: Application to Indian River Inlet, Delaware

Scour hole monitoring is widely used by engineers in reaction to bridge scour. Current monitoring methods lack the ability to observe wide areas on operational time scales. It is imperative that wide areas be observed after channel bed armoring countermeasures are taken because the armoring occupies an area larger than can be observed by traditional single-point scour monitors. The present bridge piers within the Indian River Inlet, Delaware, are adjacent to deep scour holes that threaten the bridge. A new scour monitoring system (SM) using two three-dimensional profiling sonars was installed on the Indian River Inlet Bridge to observe more than 19,000??m2 of bathymetry daily. The system components, configuration, and operation are described and example data are presented. Bathymetric data collected by the SM compare favorably with historic high-quality multibeam data from the U.S. Army Corps of Engineers. Quantitative correlations with temporally consistent data from a single-beam personal watercraft survey vessel yield an r2 correlation coefficient of 0.84 with 93% of the absolute value of elevation differences between the two data sets less than 3?m.     

Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

Factors affecting charge transport through ZnO nanowire mat films were studied by aligning ZnO nanowires on substrates and coupling experimental measurements with 2D nanowire network simulations. Gallium doped ZnO nanowires were aligned on thermally oxidized silicon wafer by shearing a nanowire dispersion in ethanol. Sheet resistances of nanowire thin films that had current flowing parallel to nanowire alignment direction were compared to thin films that had current flowing perpendicular to nanowire alignment direction. Perpendicular devices showed ～5 fold greater sheet resistance than parallel devices supporting the hypothesis that aligning nanowires would increase conductivity of ZnO nanowire electrodes. 2‐D nanowire network simulations of thin films showed that the device sheet resistance was dominated by inter‐wire contact resistance. For a given resistivity of ZnO nanowires, the thin film electrodes would have the lowest possible sheet resistance if the inter‐wire contact resistance was one order of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires.     

Piezoelectric multilayer actuator life test

Potential NASA optical missions such as the Space Interferometer Mission require actuators for precision positioning to accuracies of the order of nanometers. Commercially available multilayer piezoelectric stack actuators are being considered for driving these precision mirror positioning mechanisms. These mechanisms have potential mission operational requirements that exceed 5 years for one mission life. To test the feasibility of using these commercial actuators for these applications and to determine their reliability and the redundancy requirements, a life test study was undertaken. The nominal actuator requirements for the most critical actuators on the Space Interferometry Mission (SIM) in terms of number of cycles was estimated from the Modulation Optics Mechanism (MOM) and Pathlength control Optics Mechanism (POM) and these requirements were used to define the study. At a nominal drive frequency of 250 Hz, one mission life is calculated to be 40 billion cycles. In this study, a set of commercial PZT stacks configured in a potential flight actuator configuration (pre-stressed to 18 MPa and bonded in flexures) were tested for up to 100 billion cycles. Each test flexure allowed for two sets of primary and redundant stacks to be mechanically connected in series. The tests were controlled using an automated software control and data acquisition system that set up the test parameters and monitored the waveform of the stack electrical current and voltage. The samples were driven between 0 and 20 V at 2000 Hz to accelerate the life test and mimic the voltage amplitude that is expected to be applied to the stacks during operation. During the life test, 10 primary stacks were driven and 10 redundant stacks, mechanically in series with the driven stacks, were open-circuited. The stroke determined from a strain gauge, the temperature and humidity in the chamber, and the temperature of each individual stack were recorded. Other properties of the stacks, including the displacement from a capacitance gap sensor and impedance spectra were measured at specific intervals. The average degradation in the stroke over the life test was found to be small (<3%) for the primary stacks and <4% for the redundant stacks. It was noted that about half of the stroke reduction occurred within the first 10 billion cycles. At the end of the life test, it was found that the actuator could recover about half of the lost stroke by applying a dc voltage of 100 V at room temperature. The data up to 100 billion cycles for these tests and the analysis of the experimental results are presented in this paper.     

Investigation of surface roughness on etched glass surfaces

Roughening the surface of solar cells is a common practice within the photovoltaic industry as it reduces reflectance, and thus enhances the performance of devices. In this work the relationship between reflectance characterized by the haze parameter, surface roughness and optical properties was investigated. To achieve this goal, model samples were prepared by hydrofluoric acid etching of glass for various times and measured by optical microscopy, spectroscopic ellipsometry, scanning electron microscopy, and atomic force microscopy. Our investigation showed that the surface reflectance was decreased not only by the roughening of the surface but also by the modification of the depth profile and lowering of the refractive index of the surface domain of the samples.     

Conversion process of ZnO nano-/micro-rods into nano-/micro-tubes and cathodoluminescence characterization

A simple two-steps method has been successfully developed to synthesize ZnO nanotubes. The alkaline etching process was investigated in detail using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The formation of ZnO nanotube structures was due to the preferential dissolution of the defect-rich top (polar) faces. Cathodoluminescence (CL) was performed on both top and side surfaces of the ZnO tubes. Only the near-band-edge UV emission was observed, implying that the as-grown ZnO nanotubes have a very low concentration of defects. This CL result also provides evidence for explanation of ZnO tubular structure growth.