Lifetime Estimates Research Articles

Low doses of ionising radiation: definitions and contexts

The term 'low dose' is applied to different levels of dose depending on the circumstances of exposure, with the potential for confusion unless the reasoning is clear. The United Nations Scientific Committee on the Effects of Ionising Radiation has defined low absorbed doses of ionising radiation as below about 100 mGy, and low dose rates as below 0.1 mGy min-1 (6 mGy h-1). These values relate to the interpretation of scientific evidence from epidemiological and biological studies. The International Commission on Radiological Protection has used similar values of 100 mSv and 5 mSv h-1 and applied this categorisation directly to the specific situation of patients undergoing diagnostic procedures: doses below 100 mSv were referred to as 'low' and doses below 10 mSv as 'very low'. Consideration of other exposure situations suggest that the same terms can be used for exposures received by emergency workers. However, for workers and members of the public in planned exposure situations, it is suggested that the term 'low dose' applies to doses below 10 mSv and 1 mSv, respectively - that is, below the dose limits. In each case, dose is being used as a surrogate for risk - risks at low doses are uncertain and estimates may change, but order of magnitude considerations are sufficient in most cases. Doses of < 100 mSv, < 10 mSv and < 1 mSv correspond to life-time cancer risk estimates of the order of < 10-2, < 10-3 and < 10-4, respectively.&#xD.

New Infrared Spectra of Acetylene-Water Dimers: First Determination of the A Rotational Constant and Another K-Dependent Anomaly.

Infrared spectra of acetylene-water complexes are studied in the regions of the H2O ν2 bend (1600 cm-1) and the D2O ν1/ν3 stretches (2670-2808 cm-1), using tunable infrared sources to probe a pulsed supersonic slit jet expansion. In the H2O bend region, there is a puzzling absence of Ka = 0 transitions for C2H2-H2O, while both Ka = 0 and 1 are observed for C2D2-H2O. This continues a pattern of "missing" Ka states noted in previous infrared studies of acetylene-water. Noticeable line broadening gives estimates of upper state predissociation lifetimes of about 1.6 ns for C2D2-H2O with Ka' = 1, 0.8 ns for C2H2-H2O with Ka' = 1, and 0.8 ns for C2D2-H2O with Ka' = 0. The lifetime for C2H2-H2O Ka' = 0 must be much shorter (<0.05 ns) since rapid predissociation seems to be the only explanation for its absence in the spectrum. In the D2O ν3 region, clear sub-bands with Ka = 0 ← 1, 1 ← 0, and 2 ← 1 are observed which enable a good determination of the A rotational constant of C2H2-D2O (7.313 ± 0.007 cm-1), a first for acetylene-water dimer and larger than previously expected.

Kinetics, products and mechanisms of the OH radicals and Cl atoms reactions with trans-2-octene and cycloheptene

Relative rate coefficients for the gas-phase reactions of OH radicals and Cl atoms with trans-2-octene (k1-OH and k2-Cl) and cycloheptene (k3-OH and k4-Cl) have been determined by in situ Fourier Transform Infrared Spectroscopy (FTIR). The experiments were carried out at 298 ± 2 K and atmospheric pressure (760 ± 10) Torr using synthetic air as bath gas. The following rate coefficients (in units of cm3 molecule−1 s−1) were obtained for the reactions of trans-2-octene and cycloheptene with OH radicals and Cl atoms: k1-OH = (8.51 ± 1.86) × 10−11, k2-Cl = (4.47 ± 1.09) × 10−10, k3-OH = (7.84 ± 1.78) × 10−11, k4-Cl = (5.46 ± 1.01) × 10−10, respectively. This is the first kinetic study for the reactions of trans-2-octene with Cl atoms and the first rate coefficient determination for the title reactions by in situ FTIR spectroscopy. The kinetic data were compared with previously reported values for similar compounds and reactivity trends were developed. Complementary, products identification studies were performed in similar conditions to the kinetic experiments by the in situ FTIR and Gas Chromatography coupled to mass spectrometry (GC-MS). The atmospheric chemical mechanisms were postulated for the first time for both unsaturated compounds. In addition, the atmospheric implications of these reactions were assessed through the estimation of the tropospheric lifetimes, Photochemical Ozone Creation Potential (POCP) and fates of these compounds in the troposphere.

The economic cost consequences of suboptimal infant and young child feeding practices: a scoping review.

Breastfeeding is important for women and children's health, but less than half of infants worldwide begin life with optimal breastfeeding. A growing literature shows consistently large economic costs of not breastfeeding, with global studies showing economic losses of around US$300 billion globally. However, existing studies are highly diverse in approaches, methods, data sources and country results. Building on a landmark 2012 UNICEF UK review focused on high-income countries, we conducted a scoping review to map and characterize the expanding literature and identify future research directions in this research area. We included studies (n = 36) in diverse country settings and outcomes for women and children. We used PubMed, Web of Science, EMBASE, MEDLINE, ProQuest and manual searches of cost of not breastfeeding studies published between 1996 and 2023. Articles were excluded if they were macroeconomic evaluations, did not assign monetary values or only evaluated breastfeeding or formula feeding costs and not outcomes or were cost of programs studies. We found considerable diversity in disciplinary approaches and differences in methodologies. Though there were different cost measurement perspectives (societal, institutional/payer and individual), all but two excluded the costs of unpaid care. Studies typically measured costs of medical treatment, with more recent studies using dynamic simulation models. The largest economic costs were derived from lifetime estimates of human capital losses, namely cost of premature death and loss of intelligence quotient points. Medical and death costs varied widely depending on method of calculation, but total costs consistently exceeded $US100 billion annually for the USA, and around $US300 billion in global studies. Our findings suggest that greater interdisciplinary collaboration is needed particularly to better define infant feeding exposures, and advance comprehensive measurement of costs and outcomes across lifetimes, in order to prioritize breastfeeding as a public health strategy of economic importance.

Inbreeding depression affects the growth of seedlings of an African timber species with a mixed mating reproductive system, Pericopsis elata (Harms) Meeuwen

Selfing or mating between related individuals can lead to inbreeding depression (ID), which can influence the survival, growth and evolution of populations of tree species. As selective logging involves a decrease in the density of congeneric partners, it could lead to increasing biparental inbreeding or self-fertilization, exposing the population to higher ID. We assessed the influence of inbreeding on the growth of a commercial timber species, Pericopsis elata (Fabaceae), which produced about 54% of self-fertilized seedlings in a natural population of the Congo basin. We followed the survival and growth of 540 plants raised in a plantation along a gradient of plant density (0.07–15.9 plants per m2). Parentage analysis allowed us distinguishing selfed and outcrossed seedlings. The annual growth was higher for outcrossed than selfed plants, on average by 10.8% for diameter and 12.9% for height growth. Based on the difference in above ground biomass between selfed and outcrossed seedlings after 41 months, we estimated the level of ID at δ = 0.33, while a lifetime estimate of ID based on the proportions of selfed plants at seedling and adult stages led to δ = 0.7. The level of ID on growth rate did not change significantly with age but tended to vanish under high competition. Pericopsis elata is a particularly interesting model because inbreeding depression is partial, with about 26% of reproducing adults resulting from selfing, contrary to most tropical tree species where selfed individuals usually die before reaching adulthood. Hence, the risks of ID must be considered in the management and conservation of the species.

Kaleidoscope of irradiated disks: MUSE observations of proplyds in the Orion Nebula Cluster

In the Orion Nebula Cluster (ONC), protoplanetary disks exhibit ionized gas clouds in the form of a striking teardrop shape as massive stars irradiate the disk material. We present the first spatially and spectrally resolved observations of 12 such objects, known as proplyds, using integral field spectroscopy observations performed with the Multi-Unit Spectroscopic Explorer (MUSE) instrument in Narrow Field Mode (NFM) on the Very Large Telescope (VLT). We present the morphology of the proplyds in seven emission lines and measure the radius of the ionization front (I-front) of the targets in four tracers, covering transitions of different ionization states for the same element. We also derive stellar masses for the targets. The measurements follow a consistent trend of increasing I-front radius for a decreasing strength of the far-UV radiation as expected from photoevaporation models. By analyzing the ratios of the I-front radii as measured in the emission lines of Hα, [O I] 6300 A, [O II] 7330 A, and [O III] 5007 A, we observe the ionization stratification, that is, the most ionized part of the flow being the furthest from the disk (and closest to the UV source). The ratios of ionization front radii scale in the same way for all proplyds in our sample regardless of the incident radiation. We show that the stratification can help constrain the densities near the I-front by using a 1D photoionization model. We derive the upper limits of photoevaporative mass-loss rates (Ṁloss) by assuming ionization equilibrium, and estimate values in the range 1.07–94.5 × 10−7 M⊙ yr−1, with Ṁloss values decreasing towards lower impinging radiation. We do not find a correlation between the mass-loss rate and stellar mass. The highest mass-loss rate is for the giant proplyd 244–440. These values of Ṁloss, combined with recent estimates of the disk mass with ALMA, confirm previous estimates of the short lifetime of these proplyds. This work demonstrates the potential of this MUSE dataset and offers a new set of observables to be used to test current and future models of external photoevaporation.

Prevalence of Cannabis Use Disorder: A Meta-Analysis of Population Surveys.

Epidemiologic surveys aim to estimate the population prevalence of cannabis use and cannabis use disorder. Prevalences estimates are important for understanding trends, such as the impact of policy change. Existing epidemiologic surveys have produced discrepant and potentially unreliable estimates. The current meta-analysis (PROSPERO CRD42022364818) aims to identify potential sources of unreliability in prevalence estimates of cannabis use and use disorder among the general population (aged 12+). There was no specific hypothesis about overall prevalence estimate, but we expected significant variability (i.e., heterogeneity) in estimates based on factors such as country, year of data collection, and specific methodological factors (e.g., diagnostic instrument). Systematic searches identified manuscripts and reports documenting nationally representative lifetime or past-year cannabis use disorder prevalence estimates. Meta-analysis was used to synthesize prevalence estimates, evaluate heterogeneity, and test moderators. There were 39 manuscripts/reports included in analyses which resulted in 259 unique prevalence estimates spanning 1980-2013 and an aggregated sample size of 973,281 individuals. Past-year and lifetime prevalence estimates for cannabis use were 12.83% (95% CI: 11.15%, 14.71%) and 38.31% (95% CI: 35.92%, 40.76%) and those for cannabis use disorder were 2.59% (95% CI:2.30%, 2.90%) and 6.77% (95% CI: 4.89%, 9.30%), respectively. There was significant heterogeneity in estimates, which was partially explained by factors such as country, year of data collection, and methodological characteristics. The significant heterogeneity in prevalence estimates as a function of methodological characteristics raises concerns about the generalizability of estimates. Recommendations for enhancing validity and reliability of these estimates are offered.

ALMA-IMF. XIII. N2H+ kinematic analysis of the intermediate protocluster G353.41

The ALMA-IMF Large Program provides multi-tracer observations of 15 Galactic massive protoclusters at a matched sensitivity and spatial resolution. We focus on the dense gas kinematics of the G353.41 protocluster traced by N$_2$H$^+$ (1$-$0), with a spatial resolution of sim \,0.02 pc. G353.41, at a distance of sim 2\,kpc, is embedded in a larger-scale ($ filament and has a mass of odot within $1.3 pc$^2$. We extracted the N$_2$H$^+$ (1$-$0) isolated line component and decomposed it by fitting up to three Gaussian velocity components. This allows us to identify velocity structures that are either muddled or impossible to identify in the traditional position-velocity diagram. We identify multiple velocity gradients on large (sim 1\,pc) and small scales (sim 0.2\,pc). We find good agreement between the N$_2$H$^+$ velocities and the previously reported DCN core velocities, suggesting that cores are kinematically coupled with the dense gas in which they form. We have measured nine converging ``V-shaped'' velocity gradients (VGs) ($ $) that are well resolved (sizes $ mostly located in filaments, which are sometimes associated with cores near their point of convergence. We interpret these V-shapes as inflowing gas feeding the regions near cores (the immediate sites of star formation). We estimated the timescales associated with V-shapes as $, and we interpret them as inflow timescales. The average inflow timescale is $ kyr, or about twice the free-fall time of cores in the same area ($ but substantially shorter than protostar lifetime estimates ($ Myr). We derived mass accretion rates in the range of $(0.35-8.77)\ $ M$_ odot $ yr$^ $. This feeding might lead to further filament collapse and the formation of new cores. We suggest that the protocluster is collapsing on large scales, but the velocity signature of collapse is slow compared to pure free-fall. Thus, these data are consistent with a comparatively slow global protocluster contraction under gravity, and faster core formation within, suggesting the formation of multiple generations of stars over the protocluster's lifetime.

A realistic theory of E6 unification through novel intermediate symmetries

We propose a non-supersymmetric E6 GUT with the scalar sector consisting of 650 ⨁ 351′ ⨁ 27. Making use of the first representation for the initial symmetry breaking to an intermediate stage, and the latter two representations for second-stage breaking to the Standard Model and a realistic Yukawa sector, this theory represents the minimal E6 GUT that proceeds through one of the intermediate stages that are novel compared to SU(5) or SO(10) GUT: trinification SU(3)C × SU(3)L × SU(3)R, SU(6) × SU(2) and flipped SO(10) × U(1). We analyze these possibilities under the choice of vacuum that preserves a ℤ2 “spinorial parity”, which disentangles the chiral and vector-like fermions of E6 and provides a dark matter candidate in the form of a (scalar) inert doublet. Three cases are shown to consistently unify under the extended survival hypothesis (with minimal fine-tuning): trinification symmetry SU(3)C × SU(3)L × SU(3)R with either LR or CR parity, and SU(6)CR × SU(2)L. Although the successful cases give a large range for proton lifetime estimates, all of them include regions consistent with current experimental bounds and within reach of forthcoming experiments. The scenario investigated in this paper essentially represents the unique (potentially) viable choice in the class of E6 GUTs proceeding through a novel-symmetry intermediate stage, since non-minimal alternatives seem to be intrinsically non-perturbative.

Unraveling the Uptake of Glyoxal on a Diversity of Natural Dusts and Surrogates: Linking Dust Composition to Glyoxal Uptake and Estimation of Atmospheric Lifetimes

Unraveling the Uptake of Glyoxal on a Diversity of Natural Dusts and Surrogates: Linking Dust Composition to Glyoxal Uptake and Estimation of Atmospheric Lifetimes

PSIII-13 Putative metabolites for sow lifetime opportunity and production traits

Abstract Identifying females with favorable lifetime born alive (opportunity) and weaned (wn; production) traits requires extended observation. Estimate of lifetime (4 parities) difference in the economic margin over genetic cost between a high producing female (48 pigs weaned; wn) and a low producing female (31 wn) is approximately $1,000. Determining metabolic compounds present from females with favorable or unfavorable longevity traits may provide profiles that could be assessed in younger females prior to entry within the breeding system to indicate their potential productivity. Females within the USMARC breeding system were retained through four parities then harvested between 12 to 15 d following their post-weaning estrus. Liver, skeletal muscle, and subcutaneous adipose tissues were collected and stored at -80° C for later analyses. Females were categorically identified by the level of opportunity (born alive; ba) and production (wn) over their lifetime. Females with consistent opportunity and production traits at each parity were categorized as high (H; 61 ba), medium (M; 50 ba), or low (L; 39 ba) opportunity and H (50 wn), M (42 wn), or L (34 wn) production resulting in six categories (HH, HL, MH, ML, LH, LL). Tissue extracts were subjected to positive mode UPLC-MS and numerous features were detected. Using Progenesis Q software features were annotated and those with a fold-change ≥ 2.0 and P &amp;lt; 0.05 by category were then tested using a mixed model in SAS to determine LS Mean differences of raw abundances among the six categories. Of those compounds tested in SAS, a significance threshold was set at P &amp;lt; 0.01 as a false discovery adjustment. Within liver 877 compounds were analyzed with 152 yielding a significant (P &amp;lt; 0.01) categorical effect. Of those, 43 compounds predominantly identified either HH or LL from other categories. Within skeletal muscle 359 compounds were subjected to mixed models, 221 compounds had significance for a category effect, and 105 compounds were predominantly different for HH or LL from all other categories. Within adipose tissue, 406 compounds were submitted to mixed model testing, 186 compounds had a categorical effect with 44 compounds predominantly different for HH or LL categories. Annotation of these compounds suggest differences in metabolites associated with, but not limited to, bacteria by-products (pradmicin, adifolin, lactobacillic acid), alkyloids, sapogenins, amino acids (lysine, tyrosine), minerals (calcium, copper), lipids (sphingomyelin), and fatty acids (mono-, di-, tri-acylglycerol). Future confirmation and evaluation of these metabolites in young pre-breeding females will need to be done. Establishing a metabolic profile panel that could discern young pre-breeding gilts with a likelihood of becoming a LL female will improve economic productivity and animal welfare concerns.

Parametric Decay of a Kinked Alfvén Wave Packet: 3D Magnetohydrodynamic Simulations

Large amplitude Alfvénic fluctuations, sometimes leading to localized inversions of the magnetic field, called switchbacks, are a common but poorly understood phenomenon in the solar wind. In particular, their origin(s), evolution, and stability within solar wind conditions are yet to be fully understood. Simulations modeling switchbacks have previously studied their stability in 2D. Here, we investigate the decay process of Alfvén wave packets via MHD simulations in 3D by characterizing the effects of system size, aspect ratio, and propagation angle on the decay rate. We show that the initial wave packet is unstable to parametric instabilities that develop compressible and Alfvénic secondary modes in the plane of, and transverse to, the initial wave packet propagation direction. The growth of transverse modes, absent in 2D simulations, increases the decay rate of the wave packet. We finally discuss the implications of our results for lifetime estimates of switchbacks and wave energy conversion in the solar wind.

A novel machine learning-based model for predicting the transition fatigue lifetime in piston aluminum alloys

The estimation of transition fatigue lifetimes for piston aluminum alloys was carried out using unsupervised machine learning (ML) with the K-means algorithm. For this purpose, an experimental dataset representing standard ISO specimens with piston aluminum alloy material, which was subjected to rotational bending fatigue tests under fully reversed cyclic load conditions, was utilized. Subsequently, the stress and fatigue lifetime data were employed to fit the algorithm of K-means clustering. Then, to enhance the K-means performance, various preprocessing methods and Kernel functions were employed to cluster fatigue lifetime and stress data. Furthermore, following the division of the data into multiple clusters, the middle cluster, which represents fatigue lifetime and stress, was identified as the transition fatigue region, and its center defines the estimated transition fatigue lifetime. Ultimately, the transition fatigue lifetimes were determined using the Coffin–Manson–Basquin equation for piston aluminum alloys and compared to the estimated transition fatigue lifetimes, along with the calculation of relative errors. The obtained results indicated that, among the different models employed in this study, the polynomial Kernel K-means clustering algorithm proved to be the most efficient for clustering data within stress and number of cycles plots (S–N plots). Moreover, employing the K-means algorithm with a polynomial Kernel function and five cluster numbers yielded the most accurate estimation of transition fatigue lifetime for piston aluminum alloys, exhibiting the lowest relative error.

Estimated health benefits, costs and cost-effectiveness of eliminating industrial trans-fatty acids in Nigeria: cost-effectiveness analysis

IntroductionNigeria is committed to reducing industrial trans-fatty acids (iTFA) from the food supply, but the potential health gains, costs and cost-effectiveness are unknown.MethodsThe effect on ischaemic heart disease (IHD) burden,...

Atmospheric chemistry of trifluorodicarbonyls initiated by Cl atoms: Reactivity trends, mechanism, and acid formation yields

Rate coefficients of the gas-phase reactions of Cl atoms with a series of fluorinated diketones (FDKs): CF3C(O)CH2C(O)CH3 (TFP), CF3C(O)CH2C(O)CH2CH3 (TFH) and CF3C(O)CH2C(O)CH(CH3)2 (TFMH), have been measured at (298 ± 2) K and under atmospheric pressure. The experiments were performed using the relative-rate method with a GC-FID detection system. From different determinations and references used, the following rate coefficients were obtained (in cm3/(molecule·sec)): k4(TFP + Cl) = (1.75 ± 0.21) × 10−10, k5(TFH + Cl) = (2.05 ± 0.23) × 10−10, k6(TFMH + Cl) = (2.71 ± 0.34) × 10−10. Reactivity trends of FDKs were discussed and Free Energy Relationships analysis was developed. The expression lgkOH = 1.68 lgkCl + 5.71 was obtained for the reactivity of the studied FDKs together with similar unsaturated VOCs with Cl and OH radicals Additionally, acetic acid (CH3C(O)OH) and trifluoroacetic acid (CF3C(O)OH) were positively identified and quantified as degradation products using in situ FTIR spectroscopy. According to the identified products, atmospheric chemical mechanisms were proposed. The atmospheric implications of the studied reactions were assessed by the estimation of the tropospheric lifetimes of TFP, TFH, and TFMH concerning their reaction with Cl atoms to be 48, 41, and 31 hours, respectively. The relatively short residence in the atmosphere of the fluorocarbons studied will have a local/regional impact with restricted transport. Global warming potential (GWP(20yr)) calculated for the studied fluoro diketones were 0.014, 0.003 and 0.001 for TFP, TFH and TFMH, respectively with a negligible contribution to the greenhouse effect.

The epidemiology of obsessive-compulsive disorder in the Kingdom of Saudi Arabia: Data from the Saudi National Mental Health Survey

AimsThere is ongoing debate about the extent to which the epidemiology of OCD is similar across the world, given the lack of nationally representative data from key regions like the Middle East and North Africa. Using the nationally representative dataset from the Saudi National Mental Health Survey (SNMHS), we aimed to delineate the epidemiological profile of OCD in the Saudi population. MethodsA subsample of 1981 participants from the SNMHS was assessed. Prevalence estimates and correlates of OCD were determined using logistic regressions and cross tabulations. ResultsThe lifetime, 12-month, and 30-day prevalence estimates for OCD were 4.2%, 1.8%, and 1.6%, respectively, with hoarding being the most common symptom dimension. The mean age-of-onset of OCD was 16.8 years. In over two-thirds of respondents with lifetime (72.2%) or 12-month (71.2%), OCD was accompanied by comorbid mental disorder, particularly impulse control, anxiety, and mood disorders. Among individuals with 12-month OCD, 77.5% reported severe impairment, and only 9.2% received treatment. ConclusionsIn Saudi Arabia, OCD is a prevalent and persistent condition, characterized by early onset, high odds of mental comorbidity, and significant associated impairment. These findings emphasize the universality of OCD epidemiology and the need for improved diagnosis and treatment globally.

Sunlight-Driven Photochemical Removal of Polypropylene Microplastics from Surface Waters Follows Linear Kinetics and Does Not Result in Fragmentation.

Floating microplastics are susceptible to sunlight-driven photodegradation, which can convert plastic carbon to dissolved organic carbon (DOC) and can facilitate microplastic fragmentation by mechanical forces. To understand the photochemical fate of sub-millimeter buoyant plastics, ∼0.6 mm polypropylene microplastics were photodegraded while tracking plastic mass, carbon, and particle size distributions. Plastic mass loss and carbon loss followed linear kinetics. At most time points DOC accumulation accounted for under 50% of the total plastic carbon lost. DOC accumulation followed sigmoidal kinetics, not the exponential kinetics previously reported for shorter irradiations. Thus, we suggest that estimates of plastic lifespan based on exponential DOC accumulation are inaccurate. Instead, linear plastic-C mass and plastic mass loss kinetics should be used, and these methods result in longer estimates of photochemical lifetimes for plastics in surface waters. Scanning electron microscopy revealed that photoirradiation produced two distinct patterns of cracking on the particles. However, size distribution analyses indicated that fragmentation was minimal. Instead, the initial population of microplastics shrank in size during irradiations, indicating photoirradiation in tranquil waters (i.e., without mechanical forcing) dissolved sub-millimeter plastics without fragmentation.

Mitigation of carrier trapping effects on carrier lifetime measurements with continuous-wave laser illumination for Pb-based metal halide perovskite materials

We investigated the impact of carrier trapping on the carrier lifetime of metal halide perovskite materials, which are key to solar cell production. We examined NH3CH3PbI3 (MAPbI3), NH3CH3PbBr3 (MAPbBr3), and CsPbBr3 using continuous-wave (CW) laser illumination during microwave photoconductivity decay (μ-PCD) measurements. Traditional pulsed light excitation falls short of mirroring solar cell operating conditions, owing to carrier trapping. Implementing CW laser illumination provides a more accurate estimation of the carrier lifetimes under operational conditions. With an increased photon flux from the CW laser, the μ-PCD decay curves changed, indicating reduced recombination via traps. The experiments revealed extended carrier lifetimes under continuous light for the MAPbI3 polycrystal. This suggests that CW lasers can mitigate trapping effects on carrier lifetime measurements. For the other samples, carrier trapping had a negligible effect on the measured carrier lifetimes. We believe that these findings will aid in the design of perovskite-based devices.

Single-Molecule Time-Resolved Spectroscopy in a Tunable STM Nanocavity.

Spontaneous fluorescence rates of single-molecule emitters are typically on the order of nanoseconds. However, coupling them with plasmonic nanostructures can substantially increase their fluorescence yields. The confinement between a tip and sample in a scanning tunneling microscope creates a tunable nanocavity, an ideal platform for exploring the yields and excitation decay rates of single-molecule emitters, depending on their coupling strength to the nanocavity. With such a setup, we determine the excitation lifetimes from the direct time-resolved measurements of phthalocyanine fluorescence decays, decoupled from the metal substrates by ultrathin NaCl layers. We find that when the tip is approached to single molecules, their lifetimes are reduced to the picosecond range due to the effect of coupling with the tip-sample nanocavity. On the other hand, ensembles of the adsorbed molecules measured without the nanocavity manifest nanosecond-range lifetimes. This approach overcomes the drawbacks associated with the estimation of lifetimes for single molecules from their respective emission line widths.

Evidence of rapid hydrogen chloride uptake on water ice in the atmosphere of Mars

In 2020, hydrogen chloride (HCl) in the gas phase was discovered in the atmosphere of Mars with the Atmospheric Chemistry Suite (ACS) onboard the Trace Gas Orbiter (TGO) mission (Korablev et al., 2021). Its volume mixing ratio (VMR) shows a seasonal increase of up to 5 ppbv during the perihelion season, followed by a sudden drop to undetectable levels, contradicting modelling estimates of the HCl lifetime of several months. In the Earth's stratosphere, heterogeneous uptake of HCl onto water ice is known to be a major sink for this species. This reaction is now also considered when modelling HCl abundances in the Martian atmosphere. In this work, we use simultaneous measurements of water ice and HCl obtained by the ACS instrument to find particular structures in the vertical profiles as detached gas layers at ice-free altitudes (“ice-holes”). From these particular examples we conclude that the heterogeneous uptake of HCl onto water ice operates on Mars and is a fast mechanism regulating the HCl abundance in the atmosphere of Mars.