Positioning of subdomain IIId and apical loop of domain II of the hepatitis C IRES on the human 40S ribosome

The 5′-untranslated region of the hepatitis C virus (HCV) RNA contains a highly structured motif called IRES (Internal Ribosome Entry Site) responsible for the cap-independent initiation of the viral RNA translation. At first, the IRES binds to the 40S subunit without any initiation factors so that the initiation AUG codon falls into the P site. Here using an original site-directed cross-linking strategy, we identified 40S subunit components neighboring subdomain IIId, which is critical for HCV IRES binding to the subunit, and apical loop of domain II, which was suggested to contact the 40S subunit from data on cryo-electron microscopy of ribosomal complexes containing the HCV IRES. HCV IRES derivatives that bear a photoactivatable group at nucleotide A275 or at G263 in subdomain IIId cross-link to ribosomal proteins S3a, S14 and S16, and HCV IRES derivatized at the C83 in the apex of domain II cross-link to proteins S14 and S16

Validation of OMPS Suomi NPP and OMPS NOAA‐20 Formaldehyde Total Columns With NDACC FTIR Observations

We validate formaldehyde (HCHO) vertical column densities (VCDs) from Ozone Mapping and Profiler Suite Nadir Mapper (OMPS-NM) instruments onboard the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite for 2012–2020 and National Oceanic and Atmospheric Administration-20 (NOAA-20) satellite for 2018–2020, hereafter referred to as OMPS-NPP and OMPS-N20, with ground-based Fourier-Transform Infrared (FTIR) observations of the Network for the Detection of Atmospheric Composition Change (NDACC). OMPS-NPP/N20 HCHO products reproduce seasonal variability at 24 FTIR sites. Monthly variability of OMPS-NPP/N20 has a very good agreement with FTIR, showing correlation coefficients of 0.83 and 0.88, respectively. OMPS-NPP (N20) biases averaged over all sites are −0.9 (4) ± 3 (6)%. However, at clean sites (with VCDs 4.0 × 10$^{15}$ molecules cm$^{−2}$, negative biases of −15% ± 4% appear for OMPS-NPP, but OMPS-N20 shows smaller bias of 0.5% ± 6% due to its smaller ground pixel footprints. Therefore, smaller satellite footprint sizes are important in distinguishing small-scale plumes. In addition, we discuss a bias correction and provide lower limit for the monthly uncertainty of OMPS-NPP/N20 HCHO products. The total uncertainty for OMPS-NPP (N20) at clean sites is 0.7 (0.8) × 10$^{15}$ molecules cm$^{−2}$, corresponding to a relative uncertainty of 32 (30)%. In the case of HCHO VCDs > 4.0 × 10$^{15}$ molecules cm$^{−2}$, however, the relative uncertainty in HCHO VCDs for OMPS-NPP (N20) decreases to 31 (18)%

Electron Identification with a Prototype of the Transition Radiation Tracker for the ATLAS experiment

A prototype of the Transition Radiation Tracker (TRT) for the ATLAS detector at the LHC has been built and tested. The TRT is an array of straw tubes which integrate tracking and electron identification by transition radiation into one device. Results of experimental measurements and of comparisons with Monte Carlo simulations are presented for the electron identification performance as a function of various detector parameters. Under optimal operating conditions, a rejection against pions of a factor 100 was achieved with 90\% electron efficiency

Bias correction of OMI HCHO columns based on FTIR and aircraft measurements and impact on top-down emission estimates

Spaceborne formaldehyde (HCHO) measurements constitute an excellent proxy for the sources of non-methane volatile organic compounds (NMVOCs). Past studies suggested substantial overestimations of NMVOC emissions in state-of-the-art inventories over major source regions. Here, the QA4ECV (Quality Assurance for Essential Climate Variables) retrieval of HCHO columns from OMI (Ozone Monitoring Instrument) is evaluated against (1) FTIR (Fourier-transform infrared) column observations at 26 stations worldwide and (2) aircraft in situ HCHO concentration measurements from campaigns conducted over the USA during 2012–2013. Both validation exercises show that OMI underestimates high columns and overestimates low columns. The linear regression of OMI and aircraft-based columns gives ΩOMI=0.651Ωairc+2.95×1015 molec.cm-2, with ΩOMI and Ωairc the OMI and aircraft-derived vertical columns, whereas the regression of OMI and FTIR data gives ΩOMI=0.659ΩFTIR+2.02×1015 molec.cm-2. Inverse modelling of NMVOC emissions with a global model based on OMI columns corrected for biases based on those relationships leads to much-improved agreement against FTIR data and HCHO concentrations from 11 aircraft campaigns. The optimized global isoprene emissions (∼445Tgyr-1) are 25 % higher than those obtained without bias correction. The optimized isoprene emissions bear both striking similarities and differences with recently published emissions based on spaceborne isoprene columns from the CrIS (Cross-track Infrared Sounder) sensor. Although the interannual variability of OMI HCHO columns is well understood over regions where biogenic emissions are dominant, and the HCHO trends over China and India clearly reflect anthropogenic emission changes, the observed HCHO decline over the southeastern USA remains imperfectly elucidated.</p

Electronics in the service of a country's defence

Inaugural lecture--Department of Electrical Engineering, Rand Afrikaans University, 18 September 1974Today's industry and communications systems, in fact modern life as we know it, could come to a standstill without electronics. The defensive system of a country would be affected similarly, as can be illustrated by citing examples of the use made of electronics in modern defence. Wireless communication receivers of the synthesizer type permit rapid tuning to a transmitter station and are particularly useful for electronic intelligence. They are, however, complex, consisting of numerous components. The application of microcircuits, especially monolithic integrated circuits, makes it possible to construct small compact and reliable equipment, whilst thin film microcircuits can best be used for high-frequency and highspeed requirements. In the design of more deadly artillery shells, use is made of the Doppler effect, whilst new radar equipment is improved by ultrasonic surface wave devices. Modern warfare necessitates frequent replacement of electronic equipment, the cost of which may exceed that of the rest of the aircraft or ship. A modern war may be won or lost in industrial laboratories. Co-operation between electrical engineers and physicists is essential. The ultimate factor in modern warfare still remains the determination of its soldiers to defend their country and to accept the sacrifices necessary

Assembly of amyloid protofibrils via critical oligomers - A novel pathway of amyloid formation

The amyloid formation of phosphoglycerate kinase (PGK) was investigated by static and dynamic light-scattering. The time-course of the scattering intensity and the hydrodynamic radius scale with initial monomer concentration in a linear fashion over a range of about 50 in concentration. This sets limits on theories for aggregation kinetics that can be used, and points towards irreversible, cascade type models. In addition, circular dichroism (CD) was used to monitor the transition between a predominantly {alpha}-helical spectrum to a {beta}-sheet enriched one. The time-course of the CD also proves to scale linearly with initial monomer concentration. Electron microscopy shows that small oligomers as well as protofibrils are present during aggregation. The found coupling between growth of intermediates and acquisition of {beta}-sheet structure is interpreted in terms of a generalized diffusion-collision model, where stabilization of {beta}-strands takes place by intermolecular interactions