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Studies of NH3 flux over agricultural ecosystems in the USA are limited by low temporal resolution (typically hours or days) and sparse spatial coverage, with no studies over corn in the Midwest USA. We report on NH3 flux measurements over a corn canopy in Central Illinois, USA, using the relaxed eddy accumulation (REA) and flux gradient (FG) methods, providing measurements at 4 h and 0.5 h intervals, respectively. The REA and FG systems were operated for the duration of the 2014 corn-growing season. Flux-footprint analysis was used to select data from both systems, resulting in 82 concurrent measurements. Mean NH3 flux of concurrent measurements was 205 ± 300 ng m−2 s−1 from REA and 110 ± 256 ng m−2 s−1 from FG for all concurrent samples. Results from both methods were not significantly different at a 95% confidence level for all concurrent measurements. The FG system resolved NH3 emission peaks at 0.5 h averaging time that were otherwise un-observed with 4 h REA averaging. Two early-season peak emission periods were identified (DOY 130-132 and 140-143), where the timing and intensity of such emissions were attributed to a combination of urease inhibitor, applied as a field-management decision, and localized soil temperature and precipitation. Given the dependence of NH3 fluxes on multiple parameters, this study further highlights the need for increased spatial coverage and high temporal resolution (e.g.

Background Despite a large body of data suggesting that delivery of fertility care to cancer patients is inconsistent and frequently insufficient, there is a paucity of literature examining training in fertility preservation for those physicians expected to discuss options or execute therapy. The study objective was to compare fertility preservation training between Reproductive Endocrinology & Infertility (REI) and Gynecologic Oncology (GYN ONC) fellows and assess the need for additional education in this field. Methods A 38-item survey was administered to REI and GYN ONC fellows in the United states in April 2014. Survey items included: 1) Clinical exposure, perceived quality of training, and self-reported knowledge in fertility preservation; 2) an educational needs assessment of desire for additional training in fertility preservation. Results Seventy-nine responses were received from 137 REI and 160 GYN ONC fellows (response rate 27%). REI fellows reported seeing significantly more fertility preservation patients and rated their training more favorably than GYN ONC fellows (48% of REI fellows versus 7% of GYN ONC fellows rated training as ‘excellent’, p

Large-scale cultivation of perennial bioenergy crops (e.g., miscanthus and switchgrass) offers unique opportunities to mitigate climate change through avoided fossil fuel use and associated greenhouse gas reduction. Although conversion of existing agriculturally intensive lands (e.g., maize and soy) to perennial bioenergy cropping systems has been shown to reduce near-surface temperatures, unintended consequences on natural water resources via depletion of soil moisture may offset these benefits. The hydroclimatic impacts associated with perennial bioenergy crop expansion over the contiguous United States are quantified using the Weather Research and Forecasting Model dynamically coupled to a land surface model (LSM). A suite of continuous (2000–09) medium-range resolution (20-km grid spacing) ensemble-based simulations is conducted using seasonally evolving biophysical representation of perennial bioenergy cropping systems within the LSM based on observational data. Deployment is carried out only over suitable abandoned and degraded farmlands to avoid competition with existing food cropping systems. Results show that near-surface cooling (locally, up to 5°C) is greatest during the growing season over portions of the central United States. For some regions, principal impacts are restricted to a reduction in near-surface temperature (e.g., eastern portions of the United States), whereas for other regions deployment leads to soil moisture reduction in excess of 0.15–0.2 m3 m−3 during the simulated 10-yr period (e.g., western Great Plains). This reduction (~25%–30% of available soil moisture) manifests as a progressively decreasing trend over time. The large-scale focus of this research demonstrates the long-term hydroclimatic sustainability of large-scale deployment of perennial bioenergy crops across the continental United States, revealing potential hot spots of suitable deployment and regions to avoid.

Perennial grasses are promising feedstocks for bioenergy production in the Midwestern USA. Few experiments have addressed how drought influences their carbon fluxes and storage. This study provides a direct comparison of ecosystem-scale measurements of carbon fluxes associated with miscanthus (Miscanthus × giganteus), switchgrass (Panicum virgatum), restored native prairie and maize (Zea mays)/soybean (Glycine max) ecosystems. The main objective of this study was to assess the influence of a naturally occurring drought during 2012 on key components of the carbon cycle and plant development relative to non-extreme years. The perennials reached full maturity 3-5 years after establishment. Miscanthus had the highest gross primary production (GPP) and lowest net ecosystem exchange (NEE) in 2012 followed by similar values for switchgrass and prairie, and the row crops had the lowest GPP and highest NEE. A post-drought effect was observed for miscanthus. Over the duration of the experiment, perennial ecosystems were carbon sinks, as indicated by negative net ecosystem carbon balance (NECB), while maize/soybean was a net carbon source. Our observations suggest that perennial ecosystems, and in particular miscanthus, can provide a high yield and a large potential for CO2 fixation even during drought, although drought may negatively influence carbon uptake in the following year, questioning the long-term consequence of its maintained productivity.

Agriculture is the main source of ammonia (NH3) emissions in the atmosphere. NH3 is precursor to secondary fine particulate matter, which is of concern for its impacts on health and visibility. There are a limited number of field measurements of NH3 emissions from fertilizer application in the US, and this limits our understanding of the importance of individual NH3 source and sink processes in controlling timing and magnitude of NH3 emissions. In this study, a new parameterization of the effect of urease inhibitor on NH3 emissions from urea-based fertilizer was developed on the basis of experimental results found in the literature. This parameterization was combined with an existing operational parameterization of soil and stomatal emission potentials (Γg, Γs) and was implemented in a surface-atmosphere transfer model for NH3 (SURFATM-NH3) in order to evaluate the bi-directional fluxes of NH3 at the field scale. The model was evaluated with field measurements obtained by the flux-gradient (FG) and relaxed eddy accumulation (REA) methods in a fertilized corn field in central Illinois. By integrating the effect of urease inhibitor, the timing of the highest NH3 emission peak was successfully predicted and its magnitude was close to that measured (predicted 2106 ng m−2 s−1, measured by FG 2312 ± 582 ng m−2 s−1). Based on the model results, urease inhibitor has a considerable effect on the dynamics and order of magnitude of NH3 fluxes. Furthermore, the model simulated the inhibiting action of N-(n-butyl) thiophosphoric (nBTPT) and suggests that it can reduce NH3 volatilization by 32%. The model also successfully predicted environmental parameters, such as soil temperature. Finally, this new version of SURFATM-NH3 is a valuable tool to estimate the NH3 bi-directional fluxes at the field scale, which describes dynamic modeling of Γs and Γg by taking into account the effect of urease inhibitor which is commonly used in the US to improve the efficiency of urea fertilizers.

The production of perennial cellulosic feedstocks for bioenergy presents the potential to diversify regional economies and the national energy supply, while also serving as climate ‘regulators’ due to a number of biogeochemical and biogeophysical differences relative to row crops. Numerous observational and model based approaches have investigated biogeochemical tradeoffs, such as increased carbon sequestration and increased water use, associated with growing cellulosic feedstocks. A less understood aspect is the biogeophysical changes associated with the difference in albedo (α), which could alter the local energy balance and cause local to regional cooling several times larger than that associated with offsetting carbon. Here, we established paired fields of Miscanthus × giganteus (miscanthus) and Panicum virgatum (switchgrass), two of the leading perennial cellulosic feedstock candidates, and traditional annual row crops in the highly productive “Corn-belt”. Our results show that miscanthus did and switchgrass did not have an overall higher α than current row crops but a strong seasonal pattern existed. Both perennials had consistently higher growing season α than row crops and winter α did not differ. The lack of observed differences in winter α, however, masked an interaction between snow cover and species differences, with the perennial species, compared with the row crops, having a higher α when snow was absent and a much lower α when snow was present. Overall, these changes resulted in an average net reduction in annual absorbed energy of about 5 W/m

The potential impacts of climate change in the Midwest United States present unprecedented challenges to regional agriculture. In response to these challenges, a variety of climate-smart agricultural methodologies have been proposed to retain or improve crop yields, reduce agricultural greenhouse gas emissions, retain soil quality and increase climate resilience of agricultural systems. One component that is commonly neglected when assessing the environmental impacts of climate-smart agriculture is the biophysical impacts, where changes in ecosystem fluxes and storage of moisture and energy lead to perturbations in local climate and water availability. Using a combination of observational data and an agroecosystem model, a series of climate-smart agricultural scenarios were assessed to determine the biophysical impacts these techniques have in the Midwest United States. The first scenario extended the growing season for existing crops using future temperature and CO2 concentrations. The second scenario examined the biophysical impacts of no-till agriculture and the impacts of annually retaining crop debris. Finally, the third scenario evaluated the potential impacts that the adoption of perennial cultivars had on biophysical quantities. Each of these scenarios was found to have significant biophysical impacts. However, the timing and magnitude of the biophysical impacts differed between scenarios.

Land use change for bioenergy feedstocks is likely to intensify as energy demand rises simultaneously with increased pressure to minimize greenhouse gas emissions. Initial assessments of the impact of adopting bioenergy crops as a significant energy source have largely focused on the potential for bioenergy agroecosystems to provide global-scale climate regulating ecosystem services via biogeochemical processes. Such as those processes associated with carbon uptake, conversion, and storage that have the potential to reduce global greenhouse gas emissions (GHG). However, the expansion of bioenergy crops can also lead to direct biophysical impacts on climate through water regulating services. Perturbations of processes influencing terrestrial energy fluxes can result in impacts on climate and water across a spectrum of spatial and temporal scales. Here, we review the current state of knowledge about biophysical feedbacks between vegetation, water, and climate that would be affected by bioenergy-related land use change. The physical mechanisms involved in biophysical feedbacks are detailed, and interactions at leaf, field, regional, and global spatial scales are described. Locally, impacts on climate of biophysical changes associated with land use change for bioenergy crops can meet or exceed the biogeochemical changes in climate associated with rising GHG's, but these impacts have received far less attention. Realization of the importance of ecosystems in providing services that extend beyond biogeochemical GHG regulation and harvestable yields has led to significant debate regarding the viability of various feedstocks in many locations. The lack of data, and in some cases gaps in knowledge associated with biophysical and biochemical influences on land–atmosphere interactions, can lead to premature policy decisions.

This study has examined the ability of a commercial, miniature soil moisture probe to measure water content within the leaf litter layer found on the floor below a deciduous forest site in Oak Ridge, eastern Tennessee. With its small size and high moisture sensitivity, this probe provides a potential opportunity for monitoring the water content beneath complex vegetation systems within the soil–air interface normally characterized by a large spatial variability and small magnitude of energy, water and carbon fluxes. With its low-cost and low-power, many of these probes can be easily deployed at a much lower cost than the single traditional soil moisture probe that is usually used for monitoring local-site soil moisture and is unsuitable for litter wetness. Miniature probe measurements of litter moisture were compared with gravimetric measurements from litter sample baskets positioned across the forest floor and the change in the magnitude of the probe output correlated linearly to the water content of the litter. Gravimetric measurements of the litter water content ranged from 1 to 3 g (H 2 O) g −1 (litter dry weight), and hourly values varied with precipitation, radiation, and wind speed. Measurements of the litter and soil water content were incorporated into empirical models adopted from the literature for estimating the litter and soil components of the CO 2 flux. The comparison between the modeled and the measured hourly CO 2 flux on the forest floor produced root means square differences (RMSD) of about 1.11 and 1.32 umol m −2 s −1 for estimates with and without litter layer, respectively, and about 25% of the forest floor CO 2 flux was due to direct contributions from the litter layer. The results of the study indicate that the probes performed well in a complex forest environment and can be used to help evaluate the water, energy and CO 2 fluxes on the soil surface inside a variety of vegetation stands.

Utility of perennial bioenergy crops (e.g., switchgrass and miscanthus) offers unique opportunities to transition toward a more sustainable energy pathway due to their reduced carbon footprint, averted competition with food crops, and ability to grow on abandoned and degraded farmlands. Studies that have examined biogeophysical impacts of these crops noted a positive feedback between near-surface cooling and enhanced evapotranspiration (ET), but also potential unintended consequences of soil moisture and groundwater depletion. To better understand hydrometeorological effects of perennial bioenergy crop expansion, this study conducted high-resolution (2-km grid spacing) simulations with a state-of-the-art atmospheric model (Weather Research and Forecasting system) dynamically coupled to a land surface model. We applied the modeling system over the Southern Plains of the United States during a normal precipitation year (2007) and a drought year (2011). By focusing the deployment of bioenergy cropping systems on marginal and abandoned farmland areas (to reduce the potential conflict with food systems), the research presented here is the first realistic examination of hydrometeorological impacts associated with perennial bioenergy crop expansion. Our results illustrate that the deployment of perennial bioenergy crops leads to widespread cooling (1–2 °C) that is largely driven by an enhanced reflection of shortwave radiation and, secondarily, due to an enhanced ET. Bioenergy crop deployment was shown to reduce the impacts of drought through simultaneous moistening and cooling of the near-surface environment. However, simulated impacts on near-surface cooling and ET were reduced during the drought relative to a normal precipitation year, revealing differential effects based on background environmental conditions. This study serves as a key step toward the assessment of hydroclimatic sustainability associated with perennial bioenergy crop expansion under diverse hydrometeorological conditions by highlighting the driving mechanisms and processes associated with this energy pathway. This work was funded by NSF Grant EAR-1204774 SI

High-efficiency blue and green light-emitting diodes (LEDs) with multiple quantum well (MQW) InGaN active regions have been grown by low-pressure MOCVD on sapphire substrates. The devices have active regions composed of 12 InGaN wells clad by GaN barrier layers. A high density of crystallographically-oriented pits form during growth of the MQW layers and planarize during the growth of subsequent layers. Blue (∼470 nm) LEDs exhibit external quantum efficiencies of 10.6% at 20 mA and 8.7% at 100 mA. Green LEDs (522 nm) have external quantum efficiencies of 4.5% at 20 mA. Operating voltages as low as 2.96 V at 20 mA have been achieved. These are the highest efficiencies published to date for nitride-based MQW LEDs. Blue and blue-green device efficiencies are comparable to the best reported SQW devices at 20 mA drive current and exceed the SQW LEDs at higher currents.

A protein A immunoreactor (immobilized protein A) incorporating flow injection technique was used for on-line fluoroimmunoassay of human transferrin. Antibody immobilized on protein A and antibody-antigen complex formation took place in phosphate buffered saline (PBS, PH 7.4). After washing off excess lucifer yellow VS labelled human transferrin, the antibody-antigen complex was eluted with acid buffer and detected. Experimental variables have been studied and the method has been used to determine the transferrin contents in human serum.

Nine polymorphic microsatellite loci for the pied flycatcher (Ficedula hypoleuca),from a wild population in Spain are isolated and their variability escribed on 70 individuals. The number of alleles per locus ranged from 6 to 41 and observed heterozygosity ranged from 0.75 to 0.98. These markers are being used to study mating strategies in Ficedula hypoleuca iberiae.

There is an increase in the number of cases of syphilis in pregnancy in the United States. Fetal death may occur in syphilis from acute or chronic infections. A case is presented in which an acute fetal infection occurred. The patient presented at 31 weeks' gestation, with a decrease in fetal movements and non-reactive cardiotocography. Ultrasound and Doppler analysis of the fetal heart, cerebral and umbilical arteries, aorta and umbilical vein led to the suspicion of acute cardiac failure. An amniocentesis yielded a white cell count of 1122 white blood cells, with 91% polymorphs, but the Gram stain was negative. The fetus developed a persistent bradycardia and was delivered. The diagnosis of acute severe syphilitic funisitis was suspected from histological sections of the cord. Diagnosis was established from maternal and fetal blood. Modern ultrasound techniques, including imaging, Doppler and cardiotocography, can lead to the analysis of the pathophysiology of disease states. An acute syphilitic infection should be suspected when this constellation of findings is found. Copyright © 1991 International Society of Ultrasound in Obstetrics and Gynecology

GaAs and Al0.3Ga0.7As films were grown by molecular beam epitaxy (MBE) using substrate temperatures between 350 and 620°C. These samples were produced under otherwise identical conditions using either elemental As (tetrameric As) or GaAs (dimeric As) as the arsenic source, and using fixed fluxes of either Si or Sn, corresponding to an atomic dopant concentration of approximately 3 × 1018 cm−3. The samples were characterized by Hall effect measurements at 300 and 77 K, and by photoluminescence measurements at 300 K. In the as-grown samples, the free carrier concentration, n, the Hall mobility, μ, and the luminescence intensity all decrease as the substrate temperature decreases below 450°C The lower values of n, μ, and luminescence intensity can, however, be improved by thermally annealing the films at 850°C for between 5 and 30 s. After the anneal, values of n, μ, and photoluminescence intensity are comparable to those observed in unannealed films grown at 620°C. For a given growth temperature, the measured electrical and optical properties and the annealing behavior of these samples are very similar, whether Si or Sn is used as the dopant, and whether a tetrameric or dimeric As source is used.

Techniques using antibodies as reagents provide the sensitivity and selectivity demanded by modern clinical and environmental analyses. The use of non-isotopic labelling methods allows non-hazardous and homogeneous analysis formats, and offers new opportunities for multi-analyte assays and simple sensors. Some recent optical immunoassays illustrate the potential of such methods. Likely future developments in this area are surveyed.

The incorporation of carbon into unintentionally doped AlxGa1-xAs epilayers grown by chemical beam epitaxy (CBE) using arsine and various combinations of group III sources was investigated. Growth of unintentionally doped AlxGa1-xAs using triethylgallium (TEGa)+triisobutylaluminum (TIBAl) resulted in lower hole and carbon concentrations than those grown from TEGa+triethylaluminum (TEAl). The carbon concentration in AlGaAs epilayers increased with decreasing growth temperature below 560°C and increased with increasing growth temperature above 560°C. This “U-shaped” dependence of carbon concentration on growth temperature exhibited its minimum value at ∼ 560°C for both the TEGa+TEAl and TEGa+TIBAl systems. The alkyl-Al compounds are thought to be the controlling species for the carbon incorporation in the low temperature regime, while the AlCH3 formed through β-methyl elimination is responsible for the carbon incorporation in the high temperature regime. Based on this study, we are able to grow high quality AlGaAs epilayers with reduced carbon contamination by using TIBAl instead of TEAl at the growth temperature of 560°C with a V/III ratio of 20. AlGaAs/GaAs modulation-doped structures grown from TEGa+TIBAl show a two-dimensional electron gas mobility as high as 88,600 cm2/V·s at 77 K, which is a 40% improvement over that grown from TEGa+TEAl, with a sheet carrier concentration of 6x1011 cm-2 and a spacer layer thickness of 150 A.

Serum samples obtained from 59 persons who had acute necrotizing ulcerative gingivitis, periodontitis, syphilis, or Lyme disease were tested against Treponema phagedenis biotype Reiter, Treponema denticola, Treponema vincentii, and Treponema scoliodontum by indirect fluorescent-antibody staining methods. Although there were positive reactions for sera representing each of these study groups and for 20 (13%) of 156 samples collected from the general population (premarital screening for syphilis), titration endpoints were relatively low (less than or equal to 1:256). Serum samples from 18 persons who had gingivitis or periodontitis but no history of Lyme borreliosis were tested by enzyme-linked immunosorbent assay for antibodies to Borrelia burgdorferi. Of these, five (28%) had immunoglobulin M antibody and four (22%) contained immunoglobulin G antibodies to this spirochete. Adsorption with either sorbent commercially prepared from T. phagedenis biotype Reiter or with washed, whole cells of T. phagedenis biotype Reiter reduced cross-reactivity in the enzyme-linked immunosorbent assay for Lyme borreliosis.

A modification of the in vitro immobilization assay together with freeze-fracture analysis was used to determine the factors responsible for the prolonged time required in vitro to achieve killing of Treponema pallidum subsp. pallidum. The modified immobilization assay permitted separate determination of the time required for binding of antibody to the surface of T. pallidum and for C activation. Treponemes were preincubated in heat-inactivated immune rabbit serum (IRS) followed by washing the organisms in 2.5% BSA/PBS to remove unbound IRS antibody before the addition of C. The results showed that a comparable degree of C-dependent killing occurred when treponemes were preincubated in heat-inactivated IRS for either 30 min or 16 h, indicating that treponemicidal antibody rapidly binds to the surface of T. pallidum. Preincubation of treponemes for 17 h in heat-inactivated IRS followed by a 1-h incubation in C resulted in the loss of 80% treponemal motility, indicating that C activation results in rapid killing of T. pallidum. Treponemes preincubated in IRS for 1 h, then incubated for 8 h and 16 h in heat-inactivated normal serum also lost a significant level of motility after the addition of C; in contrast, motility was unaffected after 30 min and 4 h of incubation in heat-inactivated normal serum under similar conditions. These results demonstrate that, whereas antibody binding to and C-mediated killing of treponemes can proceed rapidly, the prolonged time to C activation limits the rate at which treponemicidal activity occurs in vitro. In addition, treponemicidal activity using the modified immobilization assay could not be demonstrated with antiserum against T. pallidum endoflagella, antiserum against proteins solubilized from T. pallidum using the detergent Triton X-114, and a mAb to the T. pallidum r190-kDa "4D" protein, suggesting that these molecules are not accessible to surface binding antibody. Freeze-fracture analysis, recently used in our laboratory to demonstrate that the outer membrane of T. pallidum has rare constituent protein, was utilized to demonstrate outer membrane target Ag of IRS antibody. T. pallidum rare outer membrane protein (TROMP) molecules were shown in freeze-fracture electron micrographs to be consistently aggregated following a 16-h incubation of treponemes in IRS. In contrast, no aggregation of TROMP was present in treponemes incubated in normal rabbit serum for 16 h or in treponemes incubated in IRS for 2 h. These findings suggest that the rate of C activation leading to in vitro treponemicidal activity is limited by the time required for aggregation of antibody-bound TROMP molecules.

[1] Land surface processes are strongly controlled by vegetation cover. Current land surface models represent vegetation as a combination of leaf area index (LAI) and green vegetation fraction (GVF) parameters. The purpose of the study is to examine the impact of a spatially and temporally detailed Moderate Resolution Imaging Spectroradiometer (MODIS)-based GVF on surface processes in the NCEP Noah land surface model. The largest differences between the GVF data set currently used by the Noah model and the new MODIS GVF data set occur in winter and for tree-dominated vegetation classes. The greatest impact of the new GVF data on the surface energy and water balance is seen during the summer, when the transpiration is increased by more than 10 W/m 2 on average for most vegetation types and the July averaged daily transpiration rate is increased by up to 50 W/m 2 for evergreen needleleaf sites.

The present study compared individuals with high-functioning autism (HFA) and Asperger disorder (AD) in intellectual, motor, visuospatial, and executive function domains. Participants with AD demonstrated significantly higher Verbal and Full Scale IQ scores, significantly larger Verbal-Performance IQ discrepancies, and significantly better visual-perceptual skills than those with HFA. Once the superior intellectual abilities of the AD group were controlled (both statistically through analysis of covariance and by examining IQ-matched subgroups of HFA and AD participants), no significant group differences in motor, visuospatial, or executive functions were evident, save a marginally significant trend toward poorer fine motor performance in the AD group. This suggests that AD may simply be "high-IQ autism" and that separate names for the disorders may not be warranted. The relation of these findings to theories of autism and AD are discussed.

The sections in this article are 1 Recombination and Emission Line Shape 2 Efficiency and Brightness of LEDs 3 Human Eye Sensitivity 4 Light-Escape Problem 5 Led Structures and Fabrication 6 Novel Device Concepts

The purpose of this study was to determine whether immunization with purified outer membrane vesicles (OMV) from Treponema pallidum (T.p. ) could elicit Abs capable of killing this organism. It is well established that the immunization of rabbits or mice with killed T.p. or with recombinant T.p. Ags has failed to generate serum killing activity comparable with that of infection-derived immunity. Because of the small amount of T.p. OMV obtainable, a single mouse was immunized with purified OMV. The mouse anti-OMV serum and infection-derived immune rabbit serum (IRS) were compared by reactivities on two-dimensional T.p. immunoblots and by the T.p. immobilization test, a complement-dependent killing assay. Whereas IRS detected40 Ags, the anti-OMV serum identified only 6 Ags corresponding to proteins identified previously in the outer membrane. T.p. immobilization testing showed that IRS had a 100% killing titer of 1:44 and a 50% killing titer of 1:662. By comparison, the mouse anti-OMV serum had a significantly greater 100% killing titer of 1:1,408 and a 50% killing titer of 1:16,896. Absorption of the anti-OMV serum to remove Ab against outer membrane-associated lipoproteins did not change the 100% killing titer. Freeze-fracture analysis of T.p. incubated in IRS or anti-OMV serum showed that T.p. rare membrane-spanning outer membrane proteins were aggregated. This is the first demonstration of high-titer killing Abs resulting from immunization with defined T.p. molecules; our study indicates that the targets for these Abs are T. p. rare outer membrane proteins.

Pathogenic Leptospira spp. are spirochetes that have a low transmembrane outer membrane protein content relative to that of enteric gram-negative bacteria. In a previous study we identified a 31-kDa surface protein that was present in strains of Leptospira alstoni in amounts which correlated with the outer membrane particle density observed by freeze fracture electron microscopy (D. A. Haake, E. M. Walker, D. R. Blanco, C. A. Bolin, J. N. Miller, and M. A. Lovett, Infect. Immun. 59:1131-1140, 1991). The N-terminal amino acid sequence was used to design a pair of oligonucleotides which were utilized to screen a lambda ZAP II library containing EcoRI fragments of L. alstoni DNA. A 2.5-kb DNA fragment which contained the entire structural ompL1 gene was identified. The structural gene deduced from the sequence of this DNA fragment would encode a 320-amino-acid polypeptide with a 24-amino-acid leader peptide and a leader peptidase I cleavage site. Processing of OmpL1 results in a mature protein with a predicted molecular mass of 31,113 Da. Secondary-structure prediction identified repeated stretches of amphipathic beta-sheets typical of outer membrane protein membrane-spanning sequences. A topological model of OmpL1 containing 10 transmembrane segments is suggested. A recombinant OmpL1 fusion protein was expressed in Escherichia coli in order to immunize rabbits with the purified protein. Upon Triton X-114 extraction of L. alstoni and phase separation, anti-OmpL1 antiserum recognized a single band on immunoblots of the hydrophobic detergent fraction which was not present in the hydrophilic aqueous fraction. Immunoelectron microscopy with anti-OmpL1 antiserum demonstrates binding to the surface of intact L. alstoni. DNA hybridization studies indicate that the ompL1 gene is present in a single copy in all pathogenic Leptospira species that have been tested and is absent in nonpathogenic Leptospira species. OmpL1 may be the first spirochetal transmembrane outer membrane protein for which the structural gene has been cloned and sequenced.

The flux of Ga and Al from molecular‐beam epitaxy effusion cells has a significant noise component. The magnitude of this noise has been measured to be as large as 8% of the average flux and the frequency distribution of this noise was centered near 0.1 Hz. The magnitude of the flux noise was found to depend on the amount of material in the cell, the element in the cell, and the thermal gradient in the cell. A correlation between the flux noise and the oval defect densities in GaAs grown with these effusion cells is observed. The defect densities range from 1000 cm−2 for a Varian 16 cc Ga cell to a low of less than 50 cm−2 for an EPI 60 cc cell. While no complete theory exists, there are two potential sources of flux noise: hydrodynamic instabilities of the melt and source ‘‘spitting.’’

Unintentional p‐type doping of GaAs films grown by gas source molecular‐beam epitaxy (GSMBE) was reduced to 2×1014 cm−3 with a room‐temperature hole mobility of 490 cm2/V s. Intentional Si doping of GaAs films grown by GSMBE, using an elemental Si source, yielded controlled carrier concentrations from 7×1014 to 8×1018 cm−3 with 77 K mobilities from 62 700 to 2 500 cm2/V s. Residual carbon incorporation was reduced in AlGaAs by growing at 560 °C and using tri‐isobutylaluminum such that 77 K two‐dimensional electron gas mobilities as high as 88 600 cm2/V s were obtained. Our study of using trimethylgallium or a graphite filament as a carbon source for p‐type doping indicates that doping levels can be controlled in the range of 5×1016–1.5×1020 cm−3 with good hole mobility and surface morphology. Preliminary results show an undetectable diffusion of carbon in the AlGaAs/GaAs heterojunction bipolar transistor (HBT) structures with a base doping level as high as 1.5×1020 cm−3, using carbon as a p‐type dopant, g...

The neutralizing activity present in immune rabbit serum (IRS) against virulent Treponema pallidum was shown to be mediated by IgG and complement. IgG was isolated and purified from both IRS and nonimmune rabbit serum (NRS) by the use of an affinity system in which staphylococcal protein A was conjugated to Sepharose 4B. The purity of the isolated IgG fractions was demonstrated by both immunoelectrophoresis and SDS-polyacrylamide gel electrophoresis. Fractions of IgG were tested for specific neutralizing activity as measured by an in vitro-in vivo neutralization test. Lesions failed to develop at 80% of the sites inoculated with treponemal suspensions containing IgG from IRS in the presence of unheated NRS as a source of complement; delayed atypical lesions were observed at the remaining sites. In contrast, typical lesions developed at all sites inoculated with suspensions containing IgG from IRS in the presence of heated NRS. They were significantly delayed, however, as compared with lesion development at control sites inoculated with suspensions containing IgG from NRS. These results provide the first direct evidence for an IgG complement-mediated treponemicidal mechanism operative in immune serum from rabbits with latent syphilis.

Rabbits immunized with the protease resistant recombinant Treponema pallidum surface-associated Ag 4D showed an altered course of experimental syphilis after intradermal challenge with virulent T. pallidum. Vaccination trials using three different protocols were examined. In one experiment, a combined i.m.-i.v. immunization protocol was compared with an i.m. injection schedule. Four of five rabbits immunized by the i.m.-i.v. protocol developed morphologically atypical lesions at each of 16 sites, whereas the i.m. injected animals showed no evidence of attenuated disease. Moreover, immunization by both protocols elicited equally high ELISA titers of 4D-specific IgG antibody suggesting that cellular immune mechanisms may have been involved. In an effort to augment cell-mediated responses to 4D, seven rabbits received i.v. immunizations with an emulsion of 4D, purified BCG cell wall skeletons, and trehalose dimycolate in an oil-microdroplet form (4D-cell wall skeleton-trehalose dimycolate). Splenic lymphocytes from three representative immunized animals had a strong in vitro proliferative response to 4D as compared to controls. Further, all animals developed high anti-4D titers in response to immunization. After challenge with virulent T. pallidum, six of the seven rabbits developed an early cutaneous response (3-8 days) at the sites of inoculation consistent with a hypersensitivity reaction followed by morphologically atypical lesions. Aspirates from each of three representative atypical lesions were devoid of treponemes by darkfield examination at day 14, whereas motile T. pallidum were observed in aspirates from four of five control sites. Between days 20 and 24, lesions in the 4D-cell wall skeleton-trehalose dimycolate immunized rabbits began to enlarge and become more typical in appearance; aspirates from six of seven representative lesions were darkfield positive. We conclude that 1) immunization with the r4D Ag alters the course of experimental syphilis in a manner consistent with previously defined parameters of partial protection and 2) immunizations protocols containing an i.v. component are more effective than protocols using the i.m. route alone.

In conjunction with Auger electron spectroscopy measurements, we have developed a procedure for obtaining a clean Nb surface using an electron bombardment heating technique. We have then studied the valence band photoemission as a function of photon energy. We find that calculations for the bulk theoretical density of states are in basic agreement with the ultraviolet photoemission spectroscopy data. We have also studied the initial oxidation of the clean Nb surface. Structure in the energy distribution curves suggests three stages in the oxidation process. Furthermore, the valence band energy distribution curves for clean Nb3Sn prepared ’’in situ’’ were measured and showed a strong resemblance to pure Nb as has been observed previously in x‐ray photoemission. Evidence is found for the existence of Nb2O5 and SnO2 in the surface oxides of Nb3Sn.

Photoemission utilizing synchrotron radiation has been used to study the electronic structure of surfaes and/or interfaces in the photon energy range up to 400 eV. The Si (111) surface exhibits well‐established filled surface states which disappear after about 103 langmuirs of O2. At this exposure, only a broad shoulder has appeared on the high‐binding‐energy side of the Si 2p levels. This shoulder continues to grow in magnitude until much higher exposures, about 108 langmuirs of O2, when a 2.6‐eV shifted peak begins to grow, indicating a higher state of oxidation of the Si. After exposure to activated oxygen, to stimulate the oxidation process, the chemical shift of the Si 2p level is found to be 3.7 eV, which is the same as observed in bulk SiO2. Similar results were obtained for the oxidation of the Ge(111) surface.

The ontogeny of the IgG response in rabbits with experimental syphilis to individual polypeptides of Treponema pallidum, Nichols strain, was examined. The polypeptides of motile, virulent T. pallidum, purified from host tissue by Percoll density gradient centrifugation, were separated on SDS-polyacrylamide gels and were electrophoretically transferred to a solid-phase matrix of nitrocellulose for antigen analysis. Serum from rabbits early in infection at day 3 post-infection showed a weak but detectable IgG response to two polypeptides of 60,000 and 46,000 m.w. This was followed on days 11, 17, and 19 by an apparent quantitative increase in antibody to other treponemal protein antigens. By day 19, 21 of the 22 detectable polypeptides could be identified. A similar set of antigens was detected by serum from patients with human secondary and early latent syphilis. A close correlation was found between the presence of IgG antibody to T. pallidum polypeptides at day 9 and 1, 4.5, 13.5, and 17 mo post-infection and the immune status of the rabbit to symptomatic reinfection. Serum from rabbits that were partially immune to challenge at day 9 detected three polypeptides of 60,000, 46,000, and 36,000 daltons. By 1 mo post-infection, at a time when a more complete immunity had developed, the number of detectable antigens increased to 21 polypeptides ranging in m.w. from 94,000 to 14,400 daltons. IgG antibody to 22 treponemal antigens persisted in animals that were solidly immune to symptomatic reinfection at 3, 4.5, 13.5, and 17 mo post-infection. Serum neutralizing activity was not demonstrable at day 9 or 1 mo post-infection, however, but was present at 3, 4.5, 13.5, and 17 mo. The results suggest that after intratesticular challenge a vigorous IgG response to T. pallidum polypeptides can be detected. The potential role of humoral immune mechanisms in the development and maintenance of immunity is discussed.

Normal human serum (NHS) was shown to have complement-dependent treponemicidal activity against both Treponema pallidum and Treponema phagedenis biotype Reiter (TPR) by employing in vitro-in vivo neutralization and TPR plaque assays, respectively. The molecular basis of NHS treponemicidal activity was studied by immunoblot analysis in conjunction with treponemicidal assays. Five major T. pallidum polypeptide bands (47kDa, 35kDa, 33kDa doublet, and 30 kDa) and three major TPR polypeptide bands (47kDa and 33kDa doublet) bound IgG present in NHS. Absorption of NHS with TPR completely removed both TPR and T. pallidum treponemicidal activity; corresponding immunoblots demonstrated a significant removal of IgG antibody against all three TPR polypeptide bands as well as four T. pallidum polypeptide bands (30kDa, 33kDa doublet, and 35kDa). In contrast, T. pallidum absorption of NHS was found to remove treponemicidal activity against T. pallidum but not TPR; corresponding Western blots showed the complete removal of IgG antibody against all but one T. pallidum polypeptide band (47kDa) but no detectable loss in IgG antibody against the TPR polypeptides. These results suggest that antibody in NHS generated against nonpathogenic, indigenous treponemes is responsible for the T. pallidum treponemicidal activity. Furthermore, the treponemicidal activity against T. pallidum correlated with the presence of IgG antibody against T. pallidum polypeptides of 30kDa, 35kDa, and a 33kDa doublet.

We discuss the trends in photoemission spectra from some silicon d‐metal interfaces: Si (111)–Au, Si (111)–Ag, Si (111)–Ni, Si (111)–Pd, Si (111)–Pt. In particular, we discuss the correlation between the chemical processes taking place at the interface and those in the formation of bulk silicon d‐metal compounds. Although a general correlation is found, some important differences are seen; in particular, no evidence of the formation of strictly stoichiometric silicides in the interface is found even for the cases in which well defined bulk silicides are known to be stable. We discuss also the role of the hybridization between d‐electrons of the metal and (sp) electrons of silicon in the formation of intermixed interface phases. The considerations presented here can be useful as guidelines to interpret future results on other reactive silicon d‐metal interfaces.

Photoemission studies for hv < 400 eV are used to illustrate some of the advantages of synchrotron radiation for studying the surface electronic structure and chemistry of solids. Studies of GaAs and Pt are used to illustrate the following advantages (all of which depend on a source of radiation with a continuously tunable photon energy): (1) both valence and core states can be examined, (2) photon energies can be chosen so that the electron escape length can be minimized, restricting the studies to the first several atomic or molecular layers of the solids, (3) since the escape depth minimum is rather shallow the matrix element for excitation from a given set of levels may be maximized consistent with probing the last few layers, (4) when two sets of levels are degenerate or near degenerate in energy, e.g. the solid valence levels and the orbits of an adsorbed gas, the photon energy dependence of the matrix element can be used to separate the photoemission from the two states, and (5) good energy resolution (often 0.2 eV or better) can be obtained. For GaAs, studies of the surface valence electronic structure (hv ≈ 21 eV) in conjunction with LEED results indicated that rearrangement of the atoms within the last unit cell of the surface plays an important role in determining the electronic structure associated with this last layer of the crystal. In fact, it appears that measurement of this electronic structure may prove to be one of the most sensitive ways of determining the details of the atomic rearrangement. Studies of the Ga and As 3d core shifts on chemisorption of oxygen indicate that electrons are transferred from the As to the oxygen. The next step in oxidation, the formation of true As and Ga oxides, has also been followed using the core shifts. CO adsorbed on metals has been studied extensively previously using photoemission methods; however, neither the CO 3σ levels nor the "shake up" structure has been clearly seen in the past due to background produced by the strong Pt 5d valence photoemission. Making use of the Cooper minimum in the 5d excitation cross section at hv = 150 eV, the CO 3σ and "shake up" structures have been clearly seen for the first time.

Photoemission (PS) and Auger electron spectroscopy were used to study the formation of Pd silicide in UHV on Si crystals. The Pd depositions ranged from submonolayer coverages to hundreds of Angstroms thickness. AES sputter depth profiles indicate that room temperature Pd–Si interdiffusion occurs over ∠100 A and that Pd reduces the native Si oxides, with oxygen appearing at the vacuum surface of the evaporated layer. We have been able to separate out the relative contributions of Si and Pd to the silicide valence band by using a wide range of photon energies in the PS studies. The Pd d‐bands in the silicide are filled and, due to the strong Pd–Si interaction, are pulled down more than 2 eV relative to Pd metal. In addition, we suggest that the silicide formed at the surface may be more closely related to that of the glassy metals rather than the well‐defined (although closely related) Pd2Si compound. Similar results are also obtained for the system of Pt on Si.

A molecular characterization of the polypeptide antigens of Treponema pallidum reactive with sera from patients with different stages of syphilis is described. Polypeptides of motile, virulent T. pallidum, purified from rabbit testes, were separated on SDS polyacrylamide gels and electrophoretically transferred to nitrocellulose for antigenic analysis ("Western blotting"). Serum IgG from uninfected individuals reacts weakly with three polypeptides of 45,000, 33,000, and 30,000 m.w. In this study patients with primary syphilis have IgM antibody, and all patients with syphilis have IgG antibody to at least four polypeptides of 45,000, 33,000, 30,000, and 15,500 m.w. Antibody to polypeptides of 42,000 and 16,500 m.w. appear to be markers for nonprimary syphilis. These six polypeptides have been termed the major antigenic proteins (MAP) of T. pallidum. Those patients studied with secondary and early latent syphilis acquire antibody to a set of 16 additional polypeptide antigens. Those patients studied with late latent or late syphilis have antibody to a much smaller set of five or four antigens, respectively, in addition to MAP. The results suggest that a correlation exists between acquisition of antibody and the development of "chancre immunity." Additionally, the loss of antibody that characterizes late latent and late syphilis may be associated with the potential development of destructive late syphilis.

1. A new CO2-rebreathing method for estimating cardiac output is described, and compared with a method employing N2O performed at the same time. 2. The subject inhales from a reservoir of 30% O2 in N2 and rebreathes into and out of an empty bag for 10s. 3. Oxygenated mixed venous Pco2 is then determined by rebreathing 7–15% CO2 in O2, the mixture being selected to obtain a plateau of CO2 concentration. 4. Pco2 rises exponentially towards the plateau value during the rebreathing of 30% O2. Cardiac output is calculated from the rate of change of the alveolar—mixed venous Pco2 difference by a differential version of the Fick equation employing published CO2 dissociation curves for whole blood in vitro. 5. The slope of the regression of cardiac output on V̇o2 is similar to that obtained in other studies employing direct Fick measurements. The slope is some 15% greater than obtained with N2O but the difference is significant only when Oz consumption is greater than 2 litres/min. 6. The CO2 dissociation slope of blood does not differ during pulmonary gas exchange in vivo from that determined at equilibrium in vitro. 7. The volume of pulmonary blood available for CO2 exchange may rise to about 1 litre in heavy exercise, with a transit time of 1–2 s in the lungs. 8. The method can be employed for estimating pulmonary blood flow during physiological studies in subjects with normal lungs.

Treponemicidal activity against Treponema pallidum, Nichols strain, by anti-endoflagellar antibodies and the presence of antigenic interrelationships between the endoflagella of Treponema phagedenis biotype Reiter (TPR) and T. pallidum have been demonstrated. SDS-PAGE profiles of purified endoflagella from both organisms were similar, identifying five polypeptide bands for TPR (37,000, 33,000 doublet, 30,000, and 27,000 daltons) and five polypeptide bands for T. pallidum (35,000, 33,000 doublet, 30,000, and 27,000 daltons). Antiserum against TPR endoflagella identified identical bands on Western blots of TPR, T. pallidum, and the respective endoflagellar preparations. Western blots confirmed the presence of antibodies in normal human serum (NHS) against the 33,000 dalton treponemal endoflagellar proteins. The complement-dependent treponemicidal activity of NHS against T. pallidum was completely removed by absorption with purified TPR endoflagella. Furthermore, rabbit antisera against TPR endoflagella were reactive in the Treponema pallidum immobilization (TPI) test. These findings demonstrate that anti-endoflagellar antibodies are treponemicidal against T. pallidum. A possible mechanism for this activity is discussed in relation to the subsurface location of endoflagella.