328 research outputs found
High Humidity Leads to Loss of Infectious Influenza Virus from Simulated Coughs
Background
The role of relative humidity in the aerosol transmission of influenza was examined in a simulated examination room containing coughing and breathing manikins. Methods
Nebulized influenza was coughed into the examination room and Bioaerosol samplers collected size-fractionated aerosols (\u3c1 µM, 1–4 µM, and \u3e4 µM aerodynamic diameters) adjacent to the breathing manikin’s mouth and also at other locations within the room. At constant temperature, the RH was varied from 7–73% and infectivity was assessed by the viral plaque assay. Results
Total virus collected for 60 minutes retained 70.6–77.3% infectivity at relative humidity ≤23% but only 14.6–22.2% at relative humidity ≥43%. Analysis of the individual aerosol fractions showed a similar loss in infectivity among the fractions. Time interval analysis showed that most of the loss in infectivity within each aerosol fraction occurred 0–15 minutes after coughing. Thereafter, losses in infectivity continued up to 5 hours after coughing, however, the rate of decline at 45% relative humidity was not statistically different than that at 20% regardless of the aerosol fraction analyzed. Conclusion
At low relative humidity, influenza retains maximal infectivity and inactivation of the virus at higher relative humidity occurs rapidly after coughing. Although virus carried on aerosol particles \u3c4 µM have the potential for remaining suspended in air currents longer and traveling further distances than those on larger particles, their rapid inactivation at high humidity tempers this concern. Maintaining indoor relative humidity \u3e40% will significantly reduce the infectivity of aerosolized virus
The role of dipole-forbidden autoionizing resonances in non-resonant one-color two-photon single ionization of N
We present an experimental and theoretical energy- and angle-resolved study
on the photoionization dynamics of non-resonant one-color two-photon single
valence ionization of neutral N molecules. Using 9.3 eV photons produced
via high harmonic generation and a 3-D momentum imaging spectrometer, we detect
the photoelectrons and ions produced from one-color two-photon ionization in
coincidence. Photoionization of N populates the X , A
, and B ionic states of N, where the
photoelectron angular distributions associated with the X and A
states both vary with changes in photoelectron kinetic energy of only
a few hundred meV. We attribute the rapid evolution in the photoelectron
angular distributions to the excitation and decay of dipole-forbidden
autoionizing resonances that belong to series of different symmetries, all of
which are members of the Hopfield series, and compete with the direct
two-photon single ionization.Comment: 12 pages, 9 figures, 2 table
The Specificity of Peptides Bound to Human Histocompatibility Leukocyte Antigen (HLA)-B27 Influences the Prevalence of Arthritis in HLA-B27 Transgenic Rats
Human histocompatibility leukocyte antigen B27 is highly associated with the rheumatic diseases termed spondyloarthropathies, but the mechanism is not known. B27 transgenic rats develop a spontaneous disease resembling the human spondyloarthropathies that includes arthritis and colitis. To investigate whether this disease requires the binding of specific peptides to B27, we made a minigene construct in which a peptide from influenza nucleoprotein, NP383-391 (SRYWAIRTR), which binds B27 with high affinity, is targeted directly to the ER by the signal peptide of the adenovirus E3/gp19 protein. Rats transgenic for this minigene, NP1, were made and bred with B27 rats. The production of the NP383-391 peptide in B27+NP1+ rats was confirmed immunologically and by mass spectrometry. The NP1 product displaced ∼90% of the 3H-Arg-labeled endogenous peptide fraction in B27+NP1+ spleen cells. Male B27+NP1+ rats had a significantly reduced prevalence of arthritis, compared with B27+NP− males or B27+ males with a control construct, NP2, whereas colitis was not significantly affected by the NP1 transgene. These findings support the hypothesis that B27-related arthritis requires binding of a specific peptide or set of peptides to B27, and they demonstrate a method for efficient transgenic targeting of peptides to the ER
High Humidity Leads to Loss of Infectious Influenza Virus from Simulated Coughs
Abstract Background: The role of relative humidity in the aerosol transmission of influenza was examined in a simulated examination room containing coughing and breathing manikins
Mechanisms and dynamics of the NH + H and NH + H + H fragmentation channels upon single-photon double ionization of NH
We present state-selective measurements on the NH + H and
NH + H + H dissociation channels following single-photon double
ionization at 61.5 eV of neutral NH, where the two photoelectrons and two
cations are measured in coincidence using 3-D momentum imaging. Three dication
electronic states are identified to contribute to the NH + H
dissociation channel, where the excitation in one of the three states undergoes
intersystem crossing prior to dissociation, producing a cold NH fragment.
In contrast, the other two states directly dissociate, producing a
ro-vibrationally excited NH fragment with roughly 1 eV of internal
energy. The NH + H + H channel is fed by direct dissociation from
three intermediate dication states, one of which is shared with the NH
+ H channel. We find evidence of autoionization contributing to each of
the double ionization channels. The distributions of the relative emission
angle between the two photoelectrons, as well as the relative angle between the
recoil axis of the molecular breakup and the polarization vector of the
ionizing field, are also presented to provide insight on both the
photoionization and photodissociation mechanisms for the different dication
states.Comment: 18 pages, 21 figures, 3 table
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