821 research outputs found
Efficacy of single pass UVC air treatment for the inactivation of coronavirus, MS2 coliphage and Staphylococcus aureus bioaerosols
Publication history: Accepted - 20 April 2022; Published online - 26 April 2022There is strong evidence that SARS-CoV-2 is spread predominantly by airborne transmission, with high viral loads released into the air as respiratory droplets and aerosols from the infected subject. The spread and persistence of SARS-CoV-2 in diverse indoor environments reinforces the urgent need to supplement distancing and PPE based approaches with effective engineering measures for microbial decontamination â thereby addressing the significant risk posed by aerosols. We hypothesized that a portable, single-pass UVC air treatment device (air flow 1254 L/min) could effectively inactivate bioaerosols containing bacterial and viral indicator organisms, and coronavirus without reliance on filtration technology, at reasonable scale. Robust experiments demonstrated UVC dose dependent inactivation of Staphylococcus aureus (UV rate constant (k) = 0.098 m2/J) and bacteriophage MS2, with up to 6-log MS2 reduction achieved in a single pass through the system (k = 0.119 m2/J). The inclusion of a PTFE diffuse reflector increased the effective UVC dose by up to 34% in comparison to a standard Al foil reflector (with identical lamp output), resulting in significant additional pathogen inactivation (1-log S. aureus and MS2, p < 0.001). Complete inactivation of bovine coronavirus bioaerosols was demonstrated through tissue culture infectivity (2.4-log reduction) and RT-qPCR analysis â confirming single pass UVC treatment to effectively deactivate coronavirus to the limit of detection of the culture-based method. Scenario-based modelling was used to investigate the reduction in risk of airborne person-to-person transmission based upon a single infected subject within the small room. Use of the system providing 5 air changes per hour was shown to significantly reduce airborne viral load and maintain low numbers of RNA copies when the infected subject remained in the room, reducing the risk of airborne pathogen transmission to other room users. We conclude that the application of single-pass UVC systems (without reliance on HEPA filtration) could play a critical role in reducing the risk of airborne pathogen transfer, including SARS-CoV2, in locations where adequate fresh air ventilation cannot be implemented.This research was partly funded through the Invest Northern Ireland Innovation Voucher Programme (IV130218200 and IV130232906). We are grateful to the Global Challenges Research Fund (GCRF) UK Research and Innovation (SAFEWATER; EPSRC Grant Reference EP/P032427/1) for supporting Mr Arsalan Afkhami, Dr William J Snelling and Dr Jeremy W.J. Hamilton. Research at AFBI is funded by US-Ireland Research and Development Partnership in Agriculture grants BRDC-Seq and BRDC-URTMVP. We wish to thank Jonathan McMaw at AFBI for acquisition of images
Conductance quantization and the 0.7x2e2/h conductance anomaly in one-dimensional hole systems
We have studied ballistic transport in a 1D channel formed using surface gate
techniques on a back-gated, high-mobility, bilayer 2D hole system. At
millikelvin temperatures, robust conductance quantization is observed in the
quantum wire formed in the top layer of the bilayer system, without the gate
instabilities that have hampered previous studies of 1D hole systems. Using
source drain bias spectroscopy, we have measured the 1D subband spacings, which
are 5-10 times smaller than in comparable GaAs electron systems, but 2-3 times
larger than in previous studies of 1D holes. We also report the first
observation of the anomalous conductance plateau at G = 0.7 x 2e2/h in a 1D
hole system.Comment: 10 pages, 3 figure
Structural identification and biological activity of 7-methyl-10,11-ethylenedioxy-20(S)-camptothecin, a photodegradant of lurtotecan
An additional chromatographic peak was observed in plasma samples of
patients receiving NX 211, a liposomal formulation of the topoisomerase I
inhibitor lurtotecan. We have isolated and purified this product by
sequential solid-phase extractions, and we report its structure and
cytotoxicity relative to lurtotecan and related agents. Nuclear magnetic
resonance data indicate that cleavage of the piperazino moiety occurred at
the N-C bond of the B-ring, yielding
7-methyl-10,11-ethylenedioxy-20(S)-camptothecin (MEC). Tests of the growth
inhibition potential of MEC in seven human tumor cell lines showed that
the compound was approximately 2-18-fold more cytotoxic than lurtotecan,
topotecan, and 7-ethyl-10-hydroxy-20(S)-camptothecin (SN-38).
Subsequently, we found that MEC was the product of rapid photolysis of
lurtotecan, with the rate of degradation inversely proportional to NX 211
concentrations, and greatly depends on light intensity. Furthermore, MEC
concentrations were found to increase significantly in plasma samples
exposed to laboratory light but not in blood. MEC was not produced from NX
211 in the presence of human liver microsomes, suggesting that it is not a
product of cytochrome P-450 metabolism. Using a validated analytical
method, trace levels of MEC were quantitated in blood samples of two
patients. These observations confirm that the precautions for protection
from light currently specified for preparation and administration of NX
211 dose solutions are critical. Procedures to minimize formation of MEC,
by the use of amber vials for NX 211 and by preparation of dilutions
immediately before clinical use in a fashion completely protected from
light, are now being routinely implemented
Large-scale periodicity in the distribution of QSO absorption-line systems
The spatial-temporal distribution of absorption-line systems (ALSs) observed
in QSO spectra within the cosmological redshift interval z = 0.0--4.3 is
investigated on the base of our updated catalog of absorption systems. We
consider so called metallic systems including basically lines of heavy
elements. The sample of the data displays regular variations (with amplitudes ~
15 -- 20%) in the z-distribution of ALSs as well as in the eta-distribution,
where eta is a dimensionless line-of-sight comoving distance, relatively to
smoother dependences. The eta-distribution reveals the periodicity with period
Delta eta = 0.036 +/- 0.002, which corresponds to a spatial characteristic
scale (108 +/- 6) h(-1) Mpc or (alternatively) a temporal interval (350 +/- 20)
h(-1) Myr for the LambdaCDM cosmological model. We discuss a possibility of a
spatial interpretation of the results treating the pattern obtained as a trace
of an order imprinted on the galaxy clustering in the early Universe.Comment: AASTeX, 13 pages, with 9 figures, Accepted for publication in
Astrophysics & Space Scienc
Extended M1 sum rule for excited symmetric and mixed-symmetry states in nuclei
A generalized M1 sum rule for orbital magnetic dipole strength from excited
symmetric states to mixed-symmetry states is considered within the
proton-neutron interacting boson model of even-even nuclei. Analytic
expressions for the dominant terms in the B(M1) transition rates from the first
and second states are derived in the U(5) and SO(6) dynamic symmetry
limits of the model, and the applicability of a sum rule approach is examined
at and in-between these limits. Lastly, the sum rule is applied to the new data
on mixed-symmetry states of 94Mo and a quadrupole d-boson ratio
is obtained in a largely
parameter-independent wayComment: 19 pages, 3 figures, Revte
Secondary organic aerosol formation and composition from the photo-oxidation of methyl chavicol (estragole)
The increasing demand for palm oil for uses in biofuel
and food products is leading to rapid expansion of oil palm agriculture.
Methyl chavicol (also known as estragole and 1-allyl-4-methoxybenzene) is an
oxygenated biogenic volatile organic compound (VOC) that was recently identified
as the main floral emission from an oil palm plantation in Malaysian Borneo.
The emissions of methyl chavicol observed may impact regional atmospheric
chemistry, but little is known of its ability to form secondary organic
aerosol (SOA). The photo-oxidation of methyl chavicol was investigated at
the European Photoreactor chamber as a part of the atmospheric chemistry of
methyl chavicol (ATMECH) project. Aerosol samples were collected using a
particle into liquid sampler (PILS) and analysed offline using an extensive
range of instruments including; high-performance liquid chromatography mass
spectrometry (HPLC-ITMS), high-performance liquid chromatography quadrupole
time-of-flight mass spectrometry (HPLC-QTOFMS) and Fourier transform ion
cyclotron resonance mass spectrometry (FTICR-MS). The SOA yield was
determined as 18 and 29% for an initial VOC mixing ratio of 212 and
460 ppbv (parts per billion by volume)
respectively; using a VOC:NOx ratio of ~5:1. In
total, 59 SOA compounds were observed and the structures of 10 compounds
have been identified using high-resolution tandem mass spectrometry. The
addition of hydroxyl and/or nitro-functional groups to the aromatic
ring appears to be an important mechanistic pathway for aerosol formation.
This results in the formation of compounds with both low volatility and high
O:C ratios, where functionalisation rather than fragmentation is mainly
observed as a result of the stability of the ring. The SOA species observed
can be characterised as semi-volatile to low-volatility oxygenated organic
aerosol (SVOOA and LVOOA) components and therefore may be important in
aerosol formation and growth
Field-testing solutions for drinking water quality monitoring in low- and middle-income regions and case studies from Latin American, African and Asian countries
Funding Information: This study is part of SAFEWATER Devices Translation and Implementation project supported by the Global Challenges Research Fund ( GCRF ) Global Research Translation Awards, UK Research and Innovation ( SAFEWATER Translate, EPSRC Grant Reference EP/T015470/1 ).Peer reviewedPublisher PD
Dark Energy and Gravity
I review the problem of dark energy focusing on the cosmological constant as
the candidate and discuss its implications for the nature of gravity. Part 1
briefly overviews the currently popular `concordance cosmology' and summarises
the evidence for dark energy. It also provides the observational and
theoretical arguments in favour of the cosmological constant as the candidate
and emphasises why no other approach really solves the conceptual problems
usually attributed to the cosmological constant. Part 2 describes some of the
approaches to understand the nature of the cosmological constant and attempts
to extract the key ingredients which must be present in any viable solution. I
argue that (i)the cosmological constant problem cannot be satisfactorily solved
until gravitational action is made invariant under the shift of the matter
lagrangian by a constant and (ii) this cannot happen if the metric is the
dynamical variable. Hence the cosmological constant problem essentially has to
do with our (mis)understanding of the nature of gravity. Part 3 discusses an
alternative perspective on gravity in which the action is explicitly invariant
under the above transformation. Extremizing this action leads to an equation
determining the background geometry which gives Einstein's theory at the lowest
order with Lanczos-Lovelock type corrections. (Condensed abstract).Comment: Invited Review for a special Gen.Rel.Grav. issue on Dark Energy,
edited by G.F.R.Ellis, R.Maartens and H.Nicolai; revtex; 22 pages; 2 figure
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