Ultratunable Quantum Frequency Conversion in Photonic Crystal Fiber.

Quantum frequency conversion of single photons between wavelength bands is a key enabler to realizing widespread quantum networks. We demonstrate the quantum frequency conversion of a heralded 1551 nm photon to any wavelength within an ultrabroad (1226-1408 nm) range in a group-velocity-symmetric photonic crystal fiber, covering over 150 independent frequency bins. The target wavelength is controlled by tuning only a single pump laser wavelength. We find internal, and total, conversion efficiencies of 12(1)% and 1.4(2)%, respectively. For the case of converting 1551 to 1300 nm we measure a heralded g^{(2)}(0)=0.25(6) for converted light from an input with g^{(2)}(0)=0.034(8). We expect that this photonic crystal fiber can be used for myriad quantum networking tasks.

Multichannel deconvolution of vibrational signals: A state-space inverse filtering approach.

Deconvolution of noisy measurements, especially when they are multichannel, has always been a challenging problem. The processing techniques developed range from simple Fourier methods to more sophisticated model-based parametric methodologies based on the underlying acoustics of the problem at hand. Methods relying on multichannel mean-squared error processors (Wiener filters) have evolved over long periods from the seminal efforts in seismic processing. However, when more is known about the acoustics, then model-based state-space techniques incorporating the underlying process physics can improve the processing significantly. The problems of interest are the vibrational response of tightly coupled acoustic test objects excited by an out-of-the-ordinary transient, potentially impairing their operational performance. Employing a multiple input/multiple output structural model of the test objects under investigation enables the development of an inverse filter by applying subspace identification techniques during initial calibration measurements. Feasibility applications based on a mass transport experiment and test object calibration test demonstrate the ability of the processor to extract the excitations successfully.

Transient recovery problem in acoustics: A multichannel model-based deconvolution approach.

Critical acoustical systems operating in complex environments contaminated with disturbances and noise offer an extreme challenge when excited by out-of-the-ordinary, impulsive, transient events that can be undetected and seriously affect their overall performance. Transient impulse excitations must be detected, extracted, and evaluated to determine any potential system damage that could have been imposed; therefore, the problem of recovering the excitation in an uncertain measurement environment becomes one of multichannel deconvolution. Recovering a transient and its initial energy has not been solved satisfactorily, especially when the measurement has been truncated and only a small segment of response data is available. The development of multichannel deconvolution techniques for both complete and incomplete excitation data is discussed, employing a model-based approach based on the state-space representation of an identified acoustical system coupled to a forward modeling solution and a Kalman-type processor for enhancement and extraction. Synthesized data are utilized to assess the feasibility of the various approaches, demonstrating that reasonable performance can be achieved even in noisy environments.

An evaluation of the Chesapeake Bay management strategy to improve water quality in small agricultural watersheds.

Chesapeake Bay water quality has been a concern since 1970. In rural areas, agriculture is the dominant N and P source, and the voluntary application of best management practices (BMPs) is the primary management tool. Here we test the hypothesis that the current management approach of primarily voluntary, untargeted BMP implementation is insufficient to create detectable, widespread reductions in N, P, and total suspended solid (TSS) concentrations in agricultural watersheds of the Choptank basin, a tributary of Chesapeake Bay. To test this hypothesis, we assessed BMP implementation and sampled water quality on participating farms, at intermediate streams within each watershed, and at watershed outlets of four watersheds from 2013 to 2014. We also present water quality data from 2003 to 2014 at the outlets of 12 additional agricultural and one forested watershed and survey-directed interviews of farmers. By the end of 2014, large numbers of BMPs, both structural and cultural, had been implemented. Of the 16 agricultural watersheds, 50% showed significant decreases in baseflow N, 37.5% showed no changes, and 12.5% showed increasing TN. Baseflow P significantly decreased at just one watershed, increased at one, and remained stable at 14. Stormflow N was similar to baseflow, but stormflow P was 5 times higher than baseflow. These data partially support our hypothesis. Surveys suggested farmers considered themselves responsible for the quality of water leaving their farms, but out-of-pocket cost was the major impediment to further BMP adoption. We suggest that greater outreach and more financial support for farmers to implement BMPs is required to increase the types and densities of BMPs needed to achieve regional water quality goals.

Multichannel spectral estimation in acoustics: A state-space approach.

Spectral estimation is a necessary methodology to analyze the frequency content of noisy data sets especially in acoustic applications. Many spectral techniques have evolved starting with the classical Fourier transform methods based on the well-known Wiener-Khintchine relationship relating the covariance-to-spectral density as a transform pair culminating with more elegant model-based parametric techniques that apply prior knowledge of the data to produce a high-resolution spectral estimate. Multichannel spectral representations are a class of both nonparametric, as well as parametric, estimators that provide improved spectral estimates. In any case, classical nonparametric multichannel techniques can provide reasonable estimates when coupled with peak-peaking methods as long as the signal levels are reasonably high. Parametric multichannel methods can perform quite well in low signal level environments even when applying simple peak-picking techniques. In this paper, the performance of both nonparametric (periodogram) and parametric (state-space) multichannel spectral estimation methods are investigated when applied to both synthesized noisy structural vibration data as well as data obtained from a sounding rocket flight. It is demonstrated that for the multichannel problem, state-space techniques provide improved performance, offering a parametric alternative compared to classical methods.

Vibrational processing of a dynamic structural flight system: A multichannel spectral estimation approach.

Dynamic testing of large flight vehicles (rockets) is not only complex, but also can be very costly. These flights are infrequent and can lead to disastrous effects if something were to fail during the flight. The development of sensors coupled to internal components offers a great challenge in reducing their size, yet still maintaining their precision. Sounding rockets provide both a viable and convenient alternative to the more costly vehicular flights. Some of the major objectives are to test various types of sensors for monitoring components of high interest as well as investigating real-time processing techniques. Signal processing presents an extreme challenge in this noisy multichannel environment. The estimation and tracking of modal frequencies from vibrating structures is an important set of features that can provide information about the components under test; therefore, high resolution multichannel spectral processing is required. The application of both single channel and multichannel techniques capable of producing reliable modal frequency estimates of a vibrating structure from uncertain accelerometer measurements is discussed.

Multichannel processing of vibrational measurements: A constrained subspace application.

Monitoring mechanical systems operating in uncertain environments contaminated with both environmental disturbances and noise lead directly to low signal-to-noise-ratios, creating an extremely challenging processing problem, especially in real-time. In order to estimate the performance of a particular system from uncertain vibrational data, it is necessary to identify its unique resonant (modal) frequency signature. The monitoring of structural modes to determine the condition of a device under investigation is essential, especially if it is a critical entity of an operational system. The development of a model-based scheme capable of the on-line tracking of the inherent structural modal frequencies by applying both constrained subspace identification techniques to extract the modal frequencies and state estimation methods to track the evolution is discussed. An application of this approach to a cylindrical structural device (pipe-in-air) is analyzed based on theoretical simulations along with controlled validation experiments, including injected anomalies illustrate the approach and performance. Statistics are gathered to bound potential processors for real-time performance employing these constrained techniques.

Model-based failure detection for cylindrical shells from noisy vibration measurements.

Model-based processing is a theoretically sound methodology to address difficult objectives in complex physical problems involving multi-channel sensor measurement systems. It involves the incorporation of analytical models of both physical phenomenology (complex vibrating structures, noisy operating environment, etc.) and the measurement processes (sensor networks and including noise) into the processor to extract the desired information. In this paper, a model-based methodology is developed to accomplish the task of online failure monitoring of a vibrating cylindrical shell externally excited by controlled excitations. A model-based processor is formulated to monitor system performance and detect potential failure conditions. The objective of this paper is to develop a real-time, model-based monitoring scheme for online diagnostics in a representative structural vibrational system based on controlled experimental data.

Spectroscopic assays for measuring quantities of erythrocyte membrane "halves".

The quantities of outer and inner"halves" produced by freeze-fracturing human erythrocyte membranes have been measured by visible and fluorescence spectroscopy. Assays have been developed that are based on the use of two membrane surface markers: hemoglobin (Hb), a native marker for the cytoplasmic side of the membrane, and fluoresceinated concanavalin A (FITC-Con-A), a marker for the extracellular side. Hb absorbance is proportional to the fraction of cytoplasmic "half" membranes, and FITC fluorescence is proportional to the fraction of extracellular "halves." A procedure is described for the preparation of surface-labeled, intact erythrocytes suitable for the formation of homogeneous, planar cell monolayers of square-centimeter dimensions on polylysine-treated glass (PL-glass). Cell monolayers were frozen and fractured, and the fractions of absorbance and fluorescence in each of the two split portions determined. The PL-glass portion of membrane contained a substantially higher ratio of fluorescence to absorbance than unsplit controls, and its paired portion, a complementary lower ratio, demonstrating that the PL-glass portion was significantly enriched in extracellular "half" membrane. Experiments investigating split membrane recovery show that the double labeled membrane splitting technique is well suited to analysis of the transmembrane distribution of membrane lipids and polypeptides using methods that do not require quantitation by electron microscopy.

Monolayer freeze-fracture autoradiography: quantitative analysis of the transmembrane distribution of radioiodinated concanavalin A.

The technique of monolayer freeze-fracture autoradiography (MONOFARG) has been developed and the principles, quantitation, and application of the method are described. Cell monolayers attached to polylysine-treated glass were freeze-fractured, shadowed, and coated with dry, Parlodion-supported Ilford L4 photographic emulsion at room temperature. Quantitative aspects of MONOFARG were examined using radioiodinated test systems. Background was routinely less than 2.5 X 10(-4) grains/microns 2/day, the highest overall efficiency was between 25% and 45%, and grain density and efficiency were dependent on radiation dose for iodine-125 and D-19 development. Corrected grain densities were linearly proportional to iodine-125 concentration. The method was applied to an examination of the transmembrane distribution of radioiodinated and fluoresceinated concanavalin A (125I-FITC-Con-A). Human erythrocytes were labeled, column-purified, freeze-dried or freeze-fractured, autoradiographed, and examined by electron microscopy. The number of silver grains per square micrometer of unsplit single membrane was essentially identical to that of split extracellular membrane "halves." These data demonstrate that 125I-FITC-Con-A partitions exclusively with the extracellular "half" of the membrane upon freeze-fracturing and can be used as a quantitative marker for the fraction of extracellular split membrane "halves." This method should be able to provide new information about certain transmembrane properties of biological membrane molecules and probes, as well as about the process of freeze-fracture per se.

Freeze-fracture autoradiography: feasibility.

We have shown that the combination of freeze-fracture with electron microscope autoradiography can be developed into a technique for correlating the molecular structure of the biological membrane with its chemical and functional characteristics. Within the limits of electron microscope autoradiographic resolution, FARG has the potential to detect the relative distribution of molecules in each half of the membrane and within the plane of the membrane. The use of radioisotopic labels in combination with freezing techniques requires minimal perturbation of the system being studied and may be suitable for the examination of substances which would be extracted or would diffuse during the normal fixation and embedding procedures used in standard electron microscope autoradiography.

Oriented adsorption of purple membrane to cationic surfaces.

We have investigated the orientation of isolated fragments of Halobacterium halobium purple membrane (PM) adsorbed to poly-L-lysine-treated glass (PL-glass), by quanitative electron microscopy. Three lines of evidence support the conclusion that the cytoplasmic side of the membrane is preferentially absorbed. First, monolayer freeze-fracture reveals nonrandom orientation; more fracture faces (89%) are particulate than smooth. Second, the amount of each membrane surface present can be assayed using polycationic ferritin; 90% of all adsorbed membrane fragments are labeled. Third, it is possible to distinguish two surfaces, "cracked" (the extracellular surface) and "pitted" (the cytoplasmic surface) , in slowly air-dried, platinum-carbon-shadowed membranes. When applied under standard conditions, more than 80% appear cracked. Selection for the cytoplasmic by the cationic substrate suggests that the isolated PM, buffered at pH 7.4 and in the light, has a higher negative charge on its cytoplasmic surface than on its extracellular surface. Nevertheless, cationic ferritin (CF) preferentially adsorbs to the extracellular surface. Orientation provides a striking example of biomembrane surface asymmetry as well as the means to examine the chemical reactivity and physical properties of surfaces of a purified, nonvesicular membrane fragment.

Effect of membrane splitting on transmembrane polypeptides.

We investigated the effect of membrane splitting on the primary structure of human erythrocyte membrane polypeptides. Monolayers of intact, chemically unmodified cells were freeze-fractured and examined by one-dimensional SDS PAGE. Silver-stained gels revealed all major polypeptides that stain with Coomassie Blue as well as all bands that stain with periodic acid Schiff's reagent. Both nonglycosylated and glycosylated membrane polypeptides could be detected at concentrations of only a few nanograms per band. Membrane splitting had no effect on the position or number of bands. Monolayers of intact erythrocytes that had been enzymatically radioiodinated with lactoperoxidase were examined by electrophoresis, fluorography, and liquid scintillation counting. Radioactivity was quantified before and after monolayer formation and splitting, and at several stages of gel staining, drying, and fluorography. Although overexposed fluorographs revealed several minor radioiodinated bands in addition to band 3 and the glycophorins, no new bands were detected in split membrane samples derived from intact cells. These observations support the conclusion that neither the band 3 anion channel nor the glycophorin sialoglycoproteins are fragmented during freeze-fracturing. Although both band 3 and glycophorin partition to the cytoplasmic side of the membrane, preliminary quantitative observations suggest an enrichment of glycophorin in the split extracellular "half" membrane. We conclude that the process of membrane splitting by planar monolayer freeze-fracture does not cleave the covalent polypeptide backbone of any erythrocyte membrane protein, peripheral or integral.

"Half" membrane enrichment: verification by electron microscopy.

Membranes of intact erythrocytes bound to polylysine-treated glass fracture nonrandomly when covered with thin copper and frozen. Electron microscopic examination of the glass side reveals extensive areas of outer "half" membrane (B face) and of the copper side, inner "half" membrane (A face). This technique allows the ultrastructural examination of square-centimeter areas of fractured membrane and the chemical analysis of these membrane "halves".

Freeze-fractured purple membrane particles: protein content.

Optical diffraction and image reconstruction can be used to correlate the electron microscope image of the biological membrane with its electron density projection. Such correlation shows that a single purple membrane particle contains 9 to 12 protein molecules--63 to 84 transmembrane alpha helices--a complexity two to ten times greater than that previously suggested for membrane particles.

Topography of protein kinase C substrates analyzed by membrane splitting.

We have used the methods of planar cell and membrane monolayer formation and monolayer splitting to study structural details of the transmembrane signaling process mediated by protein kinase C. We analyzed human red cell membrane proteins phosphorylated by phorbol ester activation of protein kinase C. Planar single membrane preparations, extraction procedures, and gel electrophoresis coupled with silver staining and autoradiography confirmed that two bands in the 100 kDa region, and bands 4.1, and 4.9, were peripheral and phosphorylated by treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA). TPA also stimulated minor incorporation of [32 P]Pi into most integral membrane proteins, including band 3, glycophorin A, the band 4.5 region (glucose transporter) and band 7. Planar cell and membrane-splitting methods revealed that neither integral nor peripheral phosphorylated polypeptides were cleaved by freeze fracture, that all phosphorylated peripheral proteins partitioned intact with the cytoplasmic side of the membrane, and that the percentages of [32P]Pi-labeled peripheral proteins were the same in split membrane cytoplasmic leaflets as in intact membranes. As a unique approach to examining protein topographies membrane splitting provides strong evidence that the major phosphorylated products of the polyphosphatidylinositide pathway are topographically associated with the cytoplasmic leaflet of the human erythrocyte plasma membrane. We further conclude that TPA-induced phosphorylation of red cell peripheral proteins does not significantly alter their transbilayer partitioning patterns after membrane splitting.

Transmembrane signaling: tumor promoter distribution.

Diacylglycerol plays a critical role in transmembrane signaling by activating protein kinase C (PKC). The tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) mimics that action, and in the human erythrocyte, TPA-activated PKC phosphorylates membrane proteins. Although molecular aspects of this process have been investigated, details of the interaction of TPA with plasma membranes remain elusive. Because TPA is hydrophobic, it has been assumed that it associates with the lipid bilayer. However, there is no direct evidence for its transbilayer distribution. Because knowledge of its location would limit molecular models proposed to explain its mode of action, we have used membrane-splitting techniques, based on freeze-fracture of planar cell monolayers, to quantify transmembrane partitioning of [3H]TPA. Under conditions where PKC-mediated phosphorylation was stimulated by [3H]TPA and where more than 90% of the [3H]TPA was associated with the human red cell plasma membrane, two-thirds of the TPA partitioned with the cytoplasmic leaflet after bilayer splitting. This represents the first direct topographic localization of TPA in a biological membrane and supports the hypothesis that the mechanism of TPA activation requires its association with the cytoplasmic leaflet of the bilayer.

Two-dimensional electrophoretic analysis of human erythrocyte cylindrin.

Cylindrin, a macromolecule isolated from the human erythrocyte, and the band 7 proteins of the erythrocyte membrane were analyzed by one- and two-dimensional electrophoresis. Cylindrin was recovered from both the cytosol and cell membranes of hypotonically lysed erythrocytes, and its identity was confirmed by electrophoresis and transmission electron microscopy. Cylindrin from either source produced eight bands on one-dimensional SDS gels, and seventeen spots on two-dimensional gels, revealing a more complex composition than previously reported. It is unlikely that this complexity was due to proteolysis, since preparations of cylindrin with various protease inhibitors gave the same electrophoretic patterns. Mixing experiments showed that the polypeptide subunits of the cylindrin complex are distinct from the band 7 proteins of the erythrocyte membrane. This finding failed to support a role for the cylindrin macromolecule in the permeability disorders of the erythrocyte membrane associated with a missing band 7 protein.

Measuring changes in membrane thickness by scanning tunneling microscopy.

We investigated the feasibility of using the scanning tunneling microscope (STM) as a morphometric tool to measure the thickness of biomembranes. Planar monolayers of oriented purple membrane (PM) were prepared, nitrogen-dried or freeze-etched, and coated with metal. PM thickness was quantified by STM and transmission electron microscopy. STM calibration and the effect of contamination-mediated surface deformation on measurements of PM thickness were evaluated. The thickness of PM attached to mica and glass and the effect of papain on PM thickness were also examined. The apparent thickness of enzymatically modified PM increased after papain treatment. The mean thickness of both nitrogen-dried PM on mica and freeze-etched PM on glass was 4.6 nm. After papain treatment PM thickness on mica increased to 4.8 nm and on glass to 5.4 nm. These results demonstrate that STM analysis of metal-coated planar membrane monolayers can be used to measure changes in average membrane thickness at sub-nanometer resolution.

Malignant mesothelioma with occupational and environmental asbestos exposure in an Illinois community hospital.

Clinical, radiologic, pathologic, and epidemiologic data on 32 patients with diffuse malignant mesothelioma (DMM) diagnosed between 1968 and 1984 at a 427-bed community hospital in Berwyn, Ill, were reviewed. Independent pathologists' review of light microscopy, supported by electron microscopy, immunoperoxidase staining, or autopsy, confirmed 29 pleural and three peritoneal DMMs. Clinical and radiologic characteristics were similar to those in published case series. Median age at diagnosis was 67 years, and median survival after diagnosis, seven months. Fourteen patients were women. Exposure histories were obtained through 22 interviews supplemented by hospital charts and death certificates. Thirty patients (94%) had a history of asbestos exposure through work (15 [47%]) and/or residence near an asbestos facility (27 [84%]). Medical records and death certificates underreported asbestos exposure and DMM.