8,559 research outputs found
Torsion and bending of nucleic acids studied by subnanosecond time-resolved fluorescence depolarization of intercalated dyes
Subnanosecond time‐resolved fluorescence depolarization has been used to monitor the reorientation of ethidium bromide intercalated in native DNA, synthetic polynucleotide complexes, and in supercoiled plasmid DNA. The fluorescence polarization anisotropy was successfully analyzed with an elastic model of DNA dynamics, including both torsion and bending, which yielded an accurate value for the torsional rigidity of the different DNA samples. The dependence of the torsional rigidity on the base sequence, helical structure, and tertiary structure was experimentally observed. The magnitude of the polyelectrolyte contribution to the torsional rigidity of DNA was measured over a wide range of ionic strength, and compared with polyelectrolyte theories for the persistence length. We also observed a rapid initial reorientation of the intercalated ethidium which had a much smaller amplitude in RNA than in DNA
A Study of Optical Observing Techniques for Extra-Galactic Supernova Remnants: Case of NGC 300
We present the results of a study of observational and identification
techniques used for surveys and spectroscopy of candidate supernova remnants
(SNRs) in the Sculptor Group galaxy NGC 300. The goal of this study was to
investigate the reliability of using [Sii]/Halpha > 0.4 in optical SNR surveys
and spectra as an identifying feature of extra-galactic SNRs (egSNRs) and also
to investigate the effectiveness of the observing techniques (which are
hampered by seeing conditions and telescope pointing errors) using this
criterion in egSNR surveys and spectrographs. This study is based on original
observations of these objects and archival data obtained from the Hubble Space
Telescope which contained images of some of the candidate SNRs in NGC 300. We
found that the reliability of spectral techniques may be questionable and very
high-resolution images may be needed to confirm a valid identification of some
egSNRs.Comment: 27 Figures, 10 table
Time-resolved spectroscopy of macromolecules: Effect of helical structure on the torsional dynamics of DNA and RNA
The torsional rigidity of DNA and RNA is measured via the fluorescence depolarization technique
A Tone-Aided/Dual Vestigial Sideband (TA/DVSB) system for mobile satellite channels
Tone-aided modulation is one way of combatting the effects of multipath fading and Doppler frequency shifts. A new tone-aided modulation format for M-ary phase-shift keyed signals (MPSK) is discussed. A spectral null for the placement of the tone is created in the center of the MPSK signal by translating the upper sideband upwards in frequency by the same amount. The key element of the system is the algorithm for recombining the data sidebands in the receiver, a function that is performed by a specialized phase-locked loop (PLL). The system structure is discussed and simulation results showing the PLL acquisition performance are presented
Factor VIIa administration in traumatic brain injury: an AAST-MITC propensity score analysis.
Background:Recombinant factor VIIa (rFVIIa) has been used off-label as an adjunct in the reversal of warfarin therapy and management of hemorrhage after trauma. Only a handful of these reports are rigorous studies, from which results regarding safety and effectiveness have been mixed. There remains no clear consensus as to the role of rFVIIa in traumatic brain injury (TBI). Methods:Eleven level 1 trauma centers provided clinical data and head CT scans of patients with a Glasgow Coma Scale (GCS) score of ≤13 and radiographic evidence of TBI. A propensity score (PS) to receive rFVIIa in those surviving ≥2 days was calculated for each patient based on patient demographics, comorbidities, physiology, Injury Severity Score, admission GCS score, and treatment center. Patients receiving rFVIIa within 24 hours of admission were matched to patients who did not receive rFVIIa for outcomes assessment. Subgroup analysis evaluated patients with primary head injury with PS matching. Results:There were 4284 patient observations; 129 received rFVIIa. Groups were comparable after matching. No differences in mortality or morbidity were found. Improvement in GCS score from admission to discharge was less among those receiving rFVIIa (5.5 vs. 2.4; P value 0.001); however, there was no difference in average GCS score at discharge. No significant differences in outcomes were identified in patients with isolated TBI receiving rFVIIa. Discussion:rFVIIa in early management of TBI is not associated with a decreased risk of mortality or morbidity, and may negatively impact recovery and functional status at discharge in the severely injured patient with polytrauma. Level of evidence:Level III. Study type:Therapeutic/care management
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