Scanning tunnelling microscopy of tobacco mosaic virus on evaporated and sputter-coated palladium/gold substrates

We present scanning tunnelling microscope (STM) images of untreated tobacco mosaic virus (TMV) deposited on thermally evaporated and on sputter-coated palladium/gold 40:60 (Pd/Au) substrates, and imaged under ordinary atmospheric conditions. The TMV imaged on both evaporated and sputter-coated substrates was consistently several times wider than the known diameter of the virus. TMV on evaporated Pd/Au became overcoated with Pd/Au material during sample preparation and appeared elevated in STM images, whereas TMV on sputter-coated Pd/Au appeared as depressions. When naked TMV were intentionally overcoated with Pd/Au, the STM images were found to be similar to those for TMV on evaporated Pd/Au.     

Detection of aircraft below the horizon for vision‐based detect and avoid in unmanned aircraft systems

Vision‐based aircraft detection technology may provide a credible sensing option for automated detect and avoid in small‐to‐medium size fixed‐wing unmanned aircraft systems (UAS). Reliable vision‐based aircraft detection has previously been demonstrated in sky‐region sensing environments. This paper describes a novel vision‐based system for detecting aircraft below the horizon in the presence of ground clutter. We examine the performance of our system on a data set of 63 near collision encounters we collected between a camera‐equipped manned aircraft and a below‐horizon target. In these 63 encounters, our system successfully detects all aircraft, at an average detection range of 1890 m (with a standard error of 43 m and no false alarms in 1.1 h). Furthermore, our system does not require access to inertial sensor data (which significantly reduces system cost) and operates at over 12 frames per second.     

Polycrystalline Silicon-Film™ Thin-film Solar Cells: Advanced Products

Thin-film polycrystalline silicon has the potential to achieve the cost reduction and performance improvement necessary for large-scale electricity markets. Reduced cost is achieved by capitalizing on the benefits of thin films grown on low-cost, large-area substrates. Improved efficiency is realized, in spite of reduced material quality, by incorporating enhanced optical absorption and back-surface passivation. The cornerstone of AstroPower's thin-film solar cell technology is the Silicon-Film™ process: a method for the manufacture of solar cell-quality, polycrystalline films of silicon on a variety of low-cost, supporting substrates. Three thin-film solar cell designs, based on this technology, are currently under development. This paper presents the key design features of these three products and briefly reviews the current status of the development of the key technologies that comprise the advanced thin-film solar cell products.     

Closed-cycle, solar, hot-air engines Part 2—A 1/3-Hp, pressurized engine

This paper discusses the latest closed-cycle engine in the development of small solar engines being carried out at the Solar Energy Laboratory of the University of Florida. It describes the design and construction of the engine, gives the performance efficiency of the engine and demonstrates how pressurization improves the power output of the engine.     

Polybrominated diphenyl ethers in the sediments of the Great Lakes. 3. Lakes Ontario and Erie

Sediment cores were taken in 2002 in Lakes Ontario and Erie at four locations. A total of 48 sediment samples were characterized, dated using 210Pb, and analyzed for 10 congeners of polybrominated diphenyl ethers (PBDEs) including BDE209 as well as 39 congeners of polychlorinated biphenyls (PCBs). The surficial concentrations of nine tri- through hepta-BDE congeners (sigma9PBDE) are 4.85 and 6.33 ng g(-1), at sampling sites ON40 and ON30 in Lake Ontario, and 1.83 and 1.95 ng g(-1) at ER37 and ER09 in Lake Erie, respectively, based on dry sediment weight. The surficial BDE209 concentrations are 242 and 211 ng g(-1) at ON40 and ON30 and 50 and 55 ng g(-1) at ER37 and ER09. The sigma(9-) PBDEs fluxes to the sediment around 2002 are 147 and 195 pg cm(-2) year(-1) at ON40 and ON30 and 136 and 314 pg cm(-2) year(-1) at ER37 and ER09, respectively. The fluxes of BDE209 are 6.5 and 7.3 ng cm(-2) year(-1) at ON30 and ON40 and 3.7 and 8.9 ng cm(-2) year(-1) at ER37 and ER09, respectively. Dramatic increases in PBDE concentrations and fluxes upward toward the sediment surface and the present time are evident at both locations in Lake Ontario, while PCBs concentrations peak in the middle of sediment cores around the dated time of 1970s and 1960s. For both locations of Lake Erie, the increasing trends of both PBDEs and PCBs from the bottom to the surficial segments were distorted by sediment mixing. BDE209 is the most abundant congener among PBDEs in the sediments, constituting about 96 and 91% of the total PBDEs on mass basis in Lakes Ontario and Erie, respectively.     

The effect of luteal "rescue" on the expression and localization of matrix metalloproteinases and their tissue inhibitors in the human corpus luteum

Luteolysis is associated with tissue remodeling probably involving the matrix metalloproteinases (MMPs) and their specific tissue inhibitors (TIMPs). This study investigated the expression and localization of the major MMPs and TIMPs in the human corpus luteum throughout the luteal phase and after luteal rescue with hCG. Corpora lutea (n = 9) were collected at hysterectomy and were dated by serial urinary LH estimation. In addition, corpora lutea (n = 3) were collected from women who had received daily doubling doses of hCG to mimic the hormonal changes of early pregnancy. MMP-1, MMP-2, MMP-9, TIMP-1, TIMP-2, and TIMP-3 were investigated by zymography, reverse zymography, Northern blotting, and in situ hybridization. There was no change in the expression of MMP-1, TIMP-1, and TIMP-2 throughout the luteal phase or after luteal rescue. Little TIMP-3 could be detected in the corpus luteum. MMP-9 activity peaked in the early and late luteal phase. The expression and activity of MMP-2 were maximal in the late luteal phase. Exposure to hCG during luteal rescue in vivo was associated with a reduction (P < 0.05) in the expression and activity of MMP-2. Messenger ribonucleic acids (mRNAs) for MMP-1, MMP-2, and TIMP-2 were localized to the connective tissue stroma and the thecal-lutein cells of the corpus luteum. In contrast, TIMP-1 mRNA was localized to the granulosa-lutein cells, and MMP-9 mRNA was expressed in scattered cells within the steroidogenic and nonsteroidogenic cell layers. In conclusion, during maternal recognition of pregnancy, hCG prevents the normal increase in MMP-2 in the late luteal phase. MMPs can function in an environment containing large amounts of TIMP-1, as they have a different cellular localization.     

Screening and chemoprophylaxis for tuberculosis infection in college populations

Lyme borreliosis is the most frequent tick-borne disease in the Northern hemisphere. Here we describe the first isolation of Borrelia burgdorferi sensu lato in Bulgaria: the midguts of 47 Ixodes ricinus obtained by flagging from the Central park in Sofia, Bulgaria were cultivated for borreliae in BSK medium. The eight isolates obtained from the ticks and one skin isolate from a Bulgarian patient with erythema migrans were subjected to phenotypic [outer surface protein A (OspA) serotyping] and genotypic analysis (pulsed-field gel electrophoresis typing followed by large restriction fragment pattern analysis after MluI digestion, polymerase chain reaction with 16S rRNA-directed oligonucleotide probes, and restriction fragment length polymorphism analysis of rrf-rrl intergenic spacer amplicons). The skin isolate was B. burgdorferi sensu stricto, as were four of the tick isolates; the other four tick isolates were B. garinii representing three different OspA serotypes (types 3, 5 and 7). These findings confirm the wide geographic distribution of the different B. garinii-associated OspA serotypes in Europe (shown here for the first time for the Southeastern part of Europe) and of B. burgdorferi sensu stricto in the Western hemisphere. These findings have implications for development of diagnostic tests and a borrelia vaccine in Southeastern Europe.     

Antisense oligonucleotide inhibition of hepatitis C virus gene expression in transformed hepatocytes

Genetic and biochemical studies have provided convincing evidence that the 5' noncoding region (5' NCR) of hepatitis C virus (HCV) is highly conserved among viral isolates worldwide and that translation of HCV is directed by an internal ribosome entry site (IRES) located within the 5' NCR. We have investigated inhibition of HCV gene expression using antisense oligonucleotides complementary to the 5' NCR, translation initiation codon, and core protein coding sequences. Oligonucleotides were evaluated for activity after treatment of a human hepatocyte cell line expressing the HCV 5' NCR, core protein coding sequences, and the majority of the envelope gene (E1). More than 50 oligonucleotides were evaluated for inhibition of HCV RNA and protein expression. Two oligonucleotides, ISIS 6095, targeted to a stem-loop structure within the 5' NCR known to be important for IRES function, and ISIS 6547, targeted to sequences spanning the AUG used for initiation of HCV polyprotein translation, were found to be the most effective at inhibiting HCV gene expression. ISIS 6095 and 6547 caused concentration-dependent reductions in HCV RNA and protein levels, with 50% inhibitory concentrations of 0.1 to 0.2 microM. Reduction of RNA levels, and subsequently protein levels, by these phosphorothioate oligonucleotides was consistent with RNase H cleavage of RNA at the site of oligonucleotide hybridization. Chemically modified HCV antisense phosphodiester oligonucleotides were designed and evaluated for inhibition of core protein expression to identify oligonucleotides and HCV target sequences that do not require RNase H activity to inhibit expression. A uniformly modified 2'-methoxyethoxy phosphodiester antisense oligonucleotide complementary to the initiator AUG reduced HCV core protein levels as effectively as phosphorothioate oligonucleotide ISIS 6095 but without reducing HCV RNA levels. Results of our studies show that HCV gene expression is reduced by antisense oligonucleotides and demonstrate that it is feasible to design antisense oligonucleotide inhibitors of translation that do not require RNase H activation. The data demonstrate that chemically modified antisense oligonucleotides can be used as tools to identify important regulatory sequences and/or structures important for efficient translation of HCV.     

Developmentally regulated gene expression of thrombomodulin in postimplantation mouse embryos

Embryonic lethality of thrombomodulin-deficient mice has indicated an essential role for this regulator of blood coagulation in murine development. Here, the embryonic expression pattern of thrombomodulin was defined by surveying beta-galactosidase activity in a mouse strain in which the reporter gene was placed under the regulatory control of the endogenous thrombomodulin promoter via homologous recombination in embryonic stem cells. The murine trophoblast was identified as a previously unrecognized anatomical site where TM expression is conserved between humans and mice and may exert a critical function during postimplantation development. Targeted reporter gene expression in mesodermal precursors of the endothelial cell lineage defined thrombomodulin as an early marker of vascular differentiation. Analysis of the thrombomodulin promoter in differentiating ES cells and in transgenic mice provided evidence for a disparate and cell type-specific gene regulatory control mechanism in the parietal yolk sac. The thrombomodulin promoter as defined in this study will allow the targeting of gene expression to the parietal yolk sac of transgenic mice and the initiation of investigations into the role of parietal endoderm in placental function.