Miniature modular microwave end-to-end receiver

An end-to-end microwave receiver system contained in a single miniature hybrid package mounted on a single heatsink is presented. It includes an input end connected to a microwave receiver antenna and an output end which produces a digital count proportional to the amplitude of a signal of a selected microwave frequency band received at the antenna and corresponding to one of the water vapor absorption lines near frequencies of 20 GHz or 30 GHz. The hybrid package is on the order of several centimeters in length and a few centimeters in height and width. The package includes an L-shaped carrier having a base surface, a vertical wall extending up from the base surface and forming a corner therewith, and connection pins extending through the vertical wall. Modular blocks rest on the base surface against the vertical wall and support microwave monolithic integrated circuits on top surfaces thereof connected to the external connection pins. The modular blocks lie end-to-end on the base surface so as to be modularly removable by sliding along the base surface beneath the external connection pins away from the vertical wall

Conservation Status of a Threatened Tree Species: Establishing a Baseline for Restoration of Juglans cinerea L. in the Southern Appalachian Mountains, USA

To mitigate the loss of native tree species threatened by non-native pathogens, managers need to better understand the conservation status of remaining populations and the conditions that favor successful regeneration. Populations of Juglans cinerea L. (butternut), a wide-ranging riparian species, have been devastated by butternut canker, a disease caused by a non-native fungal pathogen. We assessed J. cinerea within Great Smoky Mountains National Park (GSMNP) to determine post-disease survivorship and health, recruitment history, environmental conditions associated with survival, and the extent of hybridization with a non-native congener. Monitoring records were used to locate and collect data for 207 J. cinerea trees in 19 watersheds. Tree cores were collected from a subset of individuals to assess recruitment history. We sampled vegetation plots within areas that contained J. cinerea to assess site conditions and overstory species composition of characteristic habitat. We collected leaf samples for genetic analysis to determine the frequency of hybridization. Our reassessment of monitoring records suggests that J. cinerea abundance in GSMNP has declined due to butternut canker and thirty years of poor regeneration. Populations displayed continuous recruitment following Park establishment (1934) until around 1980, after which regeneration declined drastically. Ordination analysis revealed that J. cinerea in the contemporary forest was associated with greater distance from homesites and reduced basal area of competing species. Hybrids comprised a small portion of sampled trees. The presence of healthy trees and low rate of hybridization suggest that these trees may contribute to the development of disease-resistant genotypes for future restoration efforts

A highly specific Escherichia coli qPCR and its comparison with existing methods for environmental waters

The presence of Escherichia coli in environmental waters is considered as evidence of faecal contamination and is therefore commonly used as an indicator in both water quality and food safety analysis. The long period of time between sample collection and obtaining results from existing culture based methods means that contamination events may already impact public health by the time they are detected. The adoption of molecular based methods for E. coli could significantly reduce the time to detection. A new quantitative real-time PCR (qPCR) assay was developed to detect the ybbW gene sequence, which was found to be 100% exclusive and inclusive (specific and sensitive) for E. coli and directly compared for its ability to quantify E. coli in environmental waters against colony counts, quantitative real-time NASBA (qNASBA) targeting clpB and qPCR targeting uidA. Of the 87 E. coli strains tested, 100% were found to be ybbW positive, 94.2% were culture positive, 100% were clpB positive and 98.9% were uidA positive. The qPCR assays had a linear range of quantification over several orders of magnitude, and had high amplification efficiencies when using single isolates as a template. This compared favourably with qNASBA which showed poor linearity and amplification efficiency. When the assays were applied to environmental water samples, qNASBA was unable to reliably quantify E. coli while both qPCR assays were capable of predicting E. coli concentrations in environmental waters. This study highlights the inability of qNASBA targeting mRNA to quantify E. coli in environmental waters, and presents the first E. coli qPCR assay with 100% target exclusivity. The application of a highly exclusive and inclusive qPCR assay has the potential to allow water quality managers to reliably and rapidly detect and quantify E. coli and therefore take appropriate measures to reduce the risk to public health posed by faecal contamination

Replicating Single-Cycle Adenovirus Vectors Generate Amplified Influenza Vaccine Responses

Head-to-head comparisons of conventional influenza vaccines with ade- novirus (Ad) gene-based vaccines demonstrated that these viral vectors can mediate more potent protection against influenza virus infection in animal models. In most cases, Ad vaccines are engineered to be replication-defective (RD-Ad) vectors. In contrast, replication-competent Ad (RC-Ad) vaccines are markedly more potent but risk causing adenovirus diseases in vaccine recipients and health care workers. To harness antigen gene replication but avoid production of infectious virions, we de- veloped “single-cycle” adenovirus (SC-Ad) vectors. Previous work demonstrated that SC-Ads amplify transgene expression 100-fold and produce markedly stronger and more persistent immune responses than RD-Ad vectors in Syrian hamsters and rhe- sus macaques. To test them as potential vaccines, we engineered RD and SC ver- sions of adenovirus serotype 6 (Ad6) to express the hemagglutinin (HA) gene from influenza A/PR/8/34 virus. We show here that it takes approximately 33 times less SC-Ad6 than RD-Ad6 to produce equal amounts of HA antigen in vitro. SC-Ad pro- duced markedly higher HA binding and hemagglutination inhibition (HAI) titers than RD-Ad in Syrian hamsters. SC-Ad-vaccinated cotton rats had markedly lower influ- enza titers than RD-Ad-vaccinated animals after challenge with influenza A/PR/8/34 virus. These data suggest that SC-Ads may be more potent vaccine platforms than conventional RD-Ad vectors and may have utility as “needle-free” mucosal vaccines

Spintronic magnetic anisotropy

An attractive feature of magnetic adatoms and molecules for nanoscale applications is their superparamagnetism, the preferred alignment of their spin along an easy axis preventing undesired spin reversal. The underlying magnetic anisotropy barrier --a quadrupolar energy splitting-- is internally generated by spin-orbit interaction and can nowadays be probed by electronic transport. Here we predict that in a much broader class of quantum-dot systems with spin larger than one-half, superparamagnetism may arise without spin-orbit interaction: by attaching ferromagnets a spintronic exchange field of quadrupolar nature is generated locally. It can be observed in conductance measurements and surprisingly leads to enhanced spin filtering even in a state with zero average spin. Analogously to the spintronic dipolar exchange field, responsible for a local spin torque, the effect is susceptible to electric control and increases with tunnel coupling as well as with spin polarization.Comment: 6 pages with 4 figures + 26 pages of Supplementary Informatio

Linewidth of single photon transitions in Mn12_{12}-acetate

We use time-domain terahertz spectroscopy to measure the position and linewidth of single photon transitions in Mn$_{12}$-acetate. This linewidth is compared to the linewidth measured in tunneling experiments. We conclude that local magnetic fields (due to dipole or hyperfine interactions) cannot be responsible for the observed linewidth, and suggest that the linewidth is due to variations in the anisotropy constants for different clusters. We also calculate a lower limit on the dipole field distribution that would be expected due to random orientations of clusters and find that collective effects must narrow this distribution in tunneling measurements.Comment: 5 pages, accepted to Physical Review

Replicating Single-Cycle Adenovirus Vectors Generate Amplified Influenza Vaccine Responses

Head-to-head comparisons of conventional influenza vaccines with adenovirus (Ad) gene-based vaccines demonstrated that these viral vectors can mediate more potent protection against influenza virus infection in animal models. In most cases, Ad vaccines are engineered to be replication-defective (RD-Ad) vectors. In contrast, replication-competent Ad (RC-Ad) vaccines are markedly more potent but risk causing adenovirus diseases in vaccine recipients and health care workers. To harness antigen gene replication but avoid production of infectious virions, we developed “single-cycle” adenovirus (SC-Ad) vectors. Previous work demonstrated that SC-Ads amplify transgene expression 100-fold and produce markedly stronger and more persistent immune responses than RD-Ad vectors in Syrian hamsters and rhesus macaques. To test them as potential vaccines, we engineered RD and SC versions of adenovirus serotype 6 (Ad6) to express the hemagglutinin (HA) gene from influenza A/PR/8/34 virus. We show here that it takes approximately 33 times less SC-Ad6 than RD-Ad6 to produce equal amounts of HA antigen in vitro. SC-Ad produced markedly higher HA binding and hemagglutination inhibition (HAI) titers than RD-Ad in Syrian hamsters. SC-Ad-vaccinated cotton rats had markedly lower influenza titers than RD-Ad-vaccinated animals after challenge with influenza A/PR/8/34 virus. These data suggest that SC-Ads may be more potent vaccine platforms than conventional RD-Ad vectors and may have utility as “needle-free” mucosal vaccines