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The global COVID-19 response focused heavily on nonpharmaceutical interventions (NPIs) until vaccines became available. Even where vaccination coverage is low, over time governments have become increasingly reluctant to use NPIs. ...
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The global COVID-19 response focused heavily on nonpharmaceutical interventions (NPIs) until vaccines became available. Even where vaccination coverage is low, over time governments have become increasingly reluctant to use NPIs. Inequities in vaccine and treatment accessibility and coverage, differences in vaccine effectiveness, waning immunity, and immune-escape variants of concern of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinforce the long-term need for mitigation. Initially, the concept of NPIs, and mitigation more broadly, was focused on prevention of SARS-CoV-2 transmission; however, mitigation can and has done more than prevent transmission. It has been used to address the clinical dimensions of the pandemic as well. The authors propose an expanded conceptualization of mitigation that encompasses a continuum of community and clinical mitigation measures that can help reduce infection, illness, and death from COVID-19. It can further help governments balance these efforts and address the disruptions in essential health services, increased violence, adverse mental health outcomes, and orphanhood precipitated by the pandemic and by NPIs themselves. The COVID-19 pandemic response revealed the benefits of a holistic and layered mitigation approach to public health emergencies from the outset. Lessons learned can inform the next phases of the current pandemic response and planning for future public health emergencies.
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In this study, the NO_x dependence of secondary organic aerosol (SOA) formation from photooxidation of the biogenic volatile organic compound (BVOC) β-pinene was comprehensively investigated in the Jülich Plant Atmosphere Chambe...
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In this study, the NO_x dependence of secondary organic aerosol (SOA) formation from photooxidation of the biogenic volatile organic compound (BVOC) β-pinene was comprehensively investigated in the Jülich Plant Atmosphere Chamber. Consistent with the results of previous NO_x studies we found increases of SOA yields with increasing [NO_x ] at low-NO_x conditions ([NO_x ]_0 <30 ppb, [BVOC]_0 = [NO_x ]_0 >10 ppbC ppb~(-1)). Furthermore, increasing [NO_x ] at high-NO_x conditions ([NO_x ]_0 >30 ppb, [BVOC]_0 = [NO_x ]_0 ~10 to ~2.6 ppbC ppb~(-1)) suppressed the SOA yield. The increase of SOA yield at low-NO_x conditions was attributed to an increase of OH concentration, most probably by OH recycling in NO+HO_2→NO_2 COH reaction. Separate measurements without NO_x addition but with different OH primary production rates confirmed the OH dependence of SOA yields. After removing the effect of OH concentration on SOA mass growth by keeping the OH concentration constant, SOA yields only decreased with increasing [NO_x ]. Measuring the NO_x dependence of SOA yields at lower [NO] = [NO_2] ratio showed less pronounced increase in both OH concentration and SOA yield. This result was consistent with our assumption of OH recycling by NO and to SOA yields being dependent on OH concentrations. Our results furthermore indicated that NO_x dependencies vary for different NO_x compositions. A substantial fraction of the NO_x-induced decrease of SOA yields at high-NO_x conditions was caused by NO_x-induced suppression of new particle formation (NPF), which subsequently limits the particle surface where low volatiles condense. This was shown by probing the NO_x dependence of SOA formation in the presence of seed particles. After eliminating the effect of NO_x-induced suppression of NPF and NO_x-induced changes of OH concentrations, the remaining effect of NO_x on the SOA yield from β-pinene photooxidation was moderate. Compared to β-pinene, the SOA formation from β-pinene photooxidat
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Identifying the deleterious ecological effects of developments, such as roads, mining, and urban expansion, is essential for informing development decisions and identifying appropriate mitigation actions. However, there are many t...
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Identifying the deleterious ecological effects of developments, such as roads, mining, and urban expansion, is essential for informing development decisions and identifying appropriate mitigation actions. However, there are many types of ecological impacts that slip 'under the radar' of conventional impact evaluations and undermine the potential for successful impact mitigation (including offsets). These 'enigmatic' impacts include those that are small but act cumulatively; those outside of the area directly considered in the evaluation; those not detectable with the methods, paradigms, or spatiotemporal scales used to detect them; those facili-tated, but not directly caused, by development; and synergistic impact interactions. Here, we propose a framework for conceptualising enigmatic impacts and discuss ways to address them.
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The molecular structure of volatile organic compounds determines their oxidation pathway, directly impacting secondary organic aerosol (SOA) formation. This study comprehensively investigates the impact of molecular structure on S...
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The molecular structure of volatile organic compounds determines their oxidation pathway, directly impacting secondary organic aerosol (SOA) formation. This study comprehensively investigates the impact of molecular structure on SOA formation from the photooxidation of 12 different eight- to nine-carbon aromatic hydrocarbons under low-NO_x conditions. The effects of the alkyl substitute number, location, carbon chain length and branching structure on the photooxidation of aromatic hydrocarbons are demonstrated by analyzing SOA yield, chemical composition and physical properties. Aromatic hydrocarbons, categorized into five groups, show a yield order of ortho (o-xylene and o-ethyltoluene) > one substitute (ethylbenzene, propylbenzene and isopropylbenzene) > meta (m-xylene and m- ethyltoluene) > three substitute (trimethylbenzenes) > para (p-xylene and p-ethyltoluene). SOA yields of aromatic hydrocarbon photooxidation do not monotonically decrease when increasing alkyl substitute number. The ortho position promotes SOA formation while the para position suppresses aromatic oxidation and SOA formation. Observed SOA chemical composition and volatility confirm that higher yield is associated with further oxidation. SOA chemical composition also suggests that aromatic oxidation increases with increasing alkyl substitute chain length and branching structure. Further, carbon dilution conjecture developed by Li et al. (2016) is extended in this study to serve as a standard method to determine the extent of oxidation of an alkylsubstituted aromatic hydrocarbon.
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The secondary electron emission (SEE) yield δ has been measured for condensed layers of Ne, Ar, Kr, and Xe excited by primary electrons of energy E_0 ranging from 0.05 up to 3 keV. The deposited thickness D ranges from 0 up to a ...
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The secondary electron emission (SEE) yield δ has been measured for condensed layers of Ne, Ar, Kr, and Xe excited by primary electrons of energy E_0 ranging from 0.05 up to 3 keV. The deposited thickness D ranges from 0 up to a few thousands of monolayers. For very thick specimens, the evolution of the δ(E_0) curves is very similar for all the four gases and it may be described by a single analytical expression. At 3 keV, the maximum yield is not attained for the thickest layers despite the fact that the measured yields exceed several tens. These observed high yields are analyzed in terms of escape depth for secondary electrons (～ the micrometer range) and of escape probability ( > 75%). Such results are consistent with those previously obtained by proton bombardment and by x-ray photon irradiation. More surprising is the observed increase of δ with D when all the primary electrons remain confined in the film, D > R (range of incident electrons), and several hypotheses are suggested to explain this effect: increase of the crystallite grain size, charging mechanism, SE reflection effects at the film/solid interface. For very thin films where the constant thickness D is D << R, the observed decrease of δ as a function of E_0 is qualitatively explained but, when D is changed, additional calculations are needed.
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Two models for an energy harvester imparting rotational energy to piezoelectric materi als are presented, in order to compare the effects of applying identical amounts of energy to a cantilever beam by changing the total displacem...
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Two models for an energy harvester imparting rotational energy to piezoelectric materi als are presented, in order to compare the effects of applying identical amounts of energy to a cantilever beam by changing the total displacement per unit time, and applying a secondary impact. For a piezoelectric energy harvester given a high total impulse per unit time with low total displacement per unit time, higher power outputs were generated at lower resistive loads. Conversely, for a harvester given high total displacement per unit time with low total impulse per unit time, power output was higher at high resistive loads. At matched impedance, the secondary-impact-type piezoelectric energy harvester generated higher power output than the hitting-type piezoelectric energy harvester did at low resistive load. Optimized response of secondary-impact-type piezoelectric energy harvester was obtained at a frequency of 60 Hz with a low resistive load of 1 kΩ. The generated output power was measured as 124 mW, which corresponds to power density of140 mW/ cm~3 for the entire cantilever beam, and a power density of 342 mW/cm~3 for only the piezoelectric material volume (including sliver paste volume). For a harvester without a secondary impulse at low resistive loads (1 kΩ), the optimizing frequency was between 20 and 30 Hz, with an output power of 22 mW, which corresponds to a 25 mW/cm`3 power density for entire cantilever beam and power density of 60 mW/cm~3 for only the piezoelectric material volume(including sliver paste volume).
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Responses of benthic infauna to large scale disturbance by dredged material placement were studied at eight paired (placement and reference) areas in Corpus Christi Bay, Texas in 1995 and 1996. Total infaunal abundance, taxa richn...
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Responses of benthic infauna to large scale disturbance by dredged material placement were studied at eight paired (placement and reference) areas in Corpus Christi Bay, Texas in 1995 and 1996. Total infaunal abundance, taxa richness, and the biomass of annelids and molluscs in placement areas no longer differed from that of reference areas approximately one year after placement. Annual secondary production for annelids and molluscs did not differ between placement and reference areas, however mean (± standard error) total annual secondary production at reference areas (53.6 ±5.8 g AFDW/m~2/yr) was greater than that of placement areas (26.2 ±2.5 g AFDW/m~2/yr) due to higher brittle star densities in reference areas. Differences in community structure between placement and reference areas returned to pre-placement levels one year after disturbance. The magnitude of changes in sediment grain size related to disturbance was positively correlated with the degree of convergence of placement area communities with pre-placement and reference communities. Sediment compaction was consistently associated with infaunal taxonomic composition (BIOENV) and increased linearly with time after disturbance. The use of the term "recovery" with reference to recolonization of dredging-related disturbance implies a return to pre-placement ecological conditions that are frequently neither a reality nor a practical expectation for areas that are subject to repeated disturbances. Our characterization of biological responses to dredged material disturbance targeted benchmarks that were linked to both pre-disturbance conditions and differences between disturbed and neighboring undisturbed areas and indicate that impacts persisted less than one year.
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Whether or not self-secondaries dominate small crater populations on continuous ejecta deposits and floors of fresh impact craters has long been a controversy. This issue potentially affects the age determination technique using c...
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Whether or not self-secondaries dominate small crater populations on continuous ejecta deposits and floors of fresh impact craters has long been a controversy. This issue potentially affects the age determination technique using crater statistics. Here the self-secondary crater population on the continuous ejecta deposits of the Hokusai crater on Mercury is unambiguously recognized. Superposition relationships show that this population was emplaced after both the ballistic sedimentation of excavation flows and the subsequent veneering of impact melt, but it predated the settlement and solidification of melt pools on the crater floor. Fragments that formed self-secondaries were launched via impact spallation with large angles. Complex craters on the Moon, Mercury, and Mars probably all have formed self-secondaries populations. Dating young craters using crater statistics on their continuous ejecta deposits can be misleading. Impact melt pools are less affected by self-secondaries. Overprint by subsequent crater populations with time reduces the predominance of self-secondaries.
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Based on a semiempirical generalized Anderson-Newns model, we construct a pseudoparticle description for electron emission due to deexcitation of metastable molecules at surfaces. The pseudoparticle approach allows us to treat res...
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Based on a semiempirical generalized Anderson-Newns model, we construct a pseudoparticle description for electron emission due to deexcitation of metastable molecules at surfaces. The pseudoparticle approach allows us to treat resonant charge-transfer and Auger processes on an equal footing, as it is necessary when both channels are open. This is, for instance, the case when a metastable N_2(~3∑_u~+) molecule hits a diamond surface. Using nonequilibrium Green functions and physically motivated approximations to the self-energies of the Dyson equations, we derive a system of rate equations for the probabilities with which the metastable N_2(~3∑_u~+) molecule, the molecular ground state N_2(~1∑_g~+), and the negative ion N_2~-(~2∏_g) can be found in the course of the scattering event. From the rate equations, we also obtain the spectrum of the emitted electron and the secondary electron emission coefficient. Our numerical results indicate the resonant tunneling process undermining the source of the Auger channel, which therefore contributes only a few percent to the secondary electron emission.
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The influence of notch orientation and service temperature on the impact toughness of glass-epoxy composites filled with secondary and hybrid fillers has been studied. The experiment was carried out under different service tempera...
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The influence of notch orientation and service temperature on the impact toughness of glass-epoxy composites filled with secondary and hybrid fillers has been studied. The experiment was carried out under different service temperatures by using pendulum type impact testing machine. Specimens were tested with two notch configurations such as notch along the laminate and notch across the laminate. The composite laminates were fabricated by using a hand lay-up technique and the experimentations were carried out according to the ASTM standards. The results showed that the specimen subjected to high temperature requires higher breaking impact toughness till 60 °C, further increase in temperature leads to decrease in required breaking impact toughness. The notch along the laminate is highly prone to catastrophic failure and notch across the laminate sustains the impact load to a considerable amount.
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