Causes and importance of new particle formation in the present-day and pre-industrial atmospheres

New particle formation has been estimated to produce around half of cloud-forming particles in the present-day atmosphere, via gas-to-particle conversion. Here we assess the importance of new particle formation (NPF) for both the present-day and the pre-industrial atmospheres. We use a global aerosol model with parametrisations of NPF from previously published CLOUD chamber experiments involving sulphuric acid, ammonia, organic molecules and ions. We find that NPF produces around 67% of cloud condensation nuclei at 0.2% supersaturation (CCN0.2%) at the level of low clouds in the pre-industrial atmosphere (estimated uncertainty range 45-84%) and 54% in the present day (estimated uncertainty range 38-66%). Concerning causes, we find that the importance of biogenic volatile organic compounds (BVOCs) in NPF and CCN formation is greater than previously thought. Removing BVOCs and hence all secondary organic aerosol from our model reduces low-cloud-level CCN concentrations at 0.2% supersaturation by 26% in the present-day atmosphere and 41% in the pre-industrial. Around three-quarters of this reduction is due to the tiny fraction of the oxidation products of BVOCs that have sufficiently low volatility to be involved in NPF and early growth. Furthermore, we estimate that 40% of pre-industrial CCN0.2% are formed via ion-induced NPF, compared with 27% in the present-day, although we caution that the ion-induced fraction of NPF involving BVOCs is poorly measured at present. Our model suggests that the effect of changes in cosmic ray intensity on CCN is small and unlikely to be comparable to the effect of large variations in natural primary aerosol emissions

Spatial and Sex-Specific Variation in Growth of Albacore Tuna (Thunnus alalunga) across the South Pacific Ocean

Spatial variation in growth is a common feature of demersal fish populations which often exist as discrete adult sub-populations linked by a pelagic larval stage. However, it remains unclear whether variation in growth occurs at similar spatial scales for populations of highly migratory pelagic species, such as tuna. We examined spatial variation in growth of albacore Thunnus alalunga across 90° of longitude in the South Pacific Ocean from the east coast of Australia to the Pitcairn Islands. Using length-at-age data from a validated ageing method we found evidence for significant variation in length-at-age and growth parameters (L∞ and k) between sexes and across longitudes. Growth trajectories were similar between sexes up until four years of age, after which the length-at-age for males was, on average, greater than that for females. Males reached an average maximum size more than 8 cm larger than females. Length-at-age and growth parameters were consistently greater at more easterly longitudes than at westerly longitudes for both females and males. Our results provide strong evidence that finer spatial structure exists within the South Pacific albacore stock and raises the question of whether the scale of their “highly migratory” nature should be re-assessed. Future stock assessment models for South Pacific albacore should consider sex-specific growth curves and spatial variation in growth within the stock

Utilising daily diaries to examine oral health experiences associated with dentine hypersensitivity

Background: The current investigation examined the determinants of oral health experiences associated with dentine hypersensitivity using prospective diary methodology. Methods: Staff and students from a large UK university who had self-diagnosed dentine hypersensitivity completed an online daily diary and text survey for two weeks recording their mood, oral health-related coping behaviours, coping and pain appraisals, pain experiences and functional limitations. Cross sectional and lagged path analyses were employed to examine relationships. Results: 101 participants took part in the diary study. Participants had a mean age of 26.3 years (range=18-63) and most were female (N=69). Individuals who used more oral health-related coping behaviours predicted and experienced greater levels of pain on subsequent days. Negative mood also predicted worse pain outcomes. The daily diary method provided a useful avenue for investigating variations in oral health experiences and relationships between variables that can fluctuate daily. Conclusions: Psychological variables such as coping and mood play an important role in the pain experiences of people with dentine hypersensitivity. The study highlights the benefits of using prospective methods to elucidate the experiences of people with oral condition

Can animal manure be used to increase soil organic carbon stocks in the Mediterranean as a mitigation climate change strategy?

Soil organic carbon (SOC) plays an important role on improving soil conditions and soil functions. Increasing land use changes have induced an important decline of SOC content at global scale. Increasing SOC in agricultural soils has been proposed as a strategy to mitigate climate change. Animal manure has the characteristic of enriching SOC, when applied to crop fields, while, in parallel, it could constitute a natural fertilizer for the crops. In this paper, a simulation is performed using the area of Catalonia, Spain as a case study for the characteristic low SOC in the Mediterranean, to examine whether animal manure can improve substantially the SOC of agricultural fields, when applied as organic fertilizers. Our results show that the policy goals of the 4x1000 strategy can be achieved only partially by using manure transported to the fields. This implies that the proposed approach needs to be combined with other strategies.Comment: Proc. of EnviroInfo 2020, Nicosia, Cyprus, September 2020. arXiv admin note: text overlap with arXiv:2006.0912

The Formation of the First Massive Black Holes

Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may grow by the combination of radiation-pressure-limited accretion and mergers of stellar-mass seed BHs, left behind by the first generation of metal-free stars, or may be formed by more rapid direct collapse of gas in rare special environments where dense gas can accumulate without first fragmenting into stars. This chapter offers a review of these two competing scenarios, as well as some more exotic alternative ideas. It also briefly discusses how the different models may be distinguished in the future by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First Galaxies - Theoretical Predictions and Observational Clues", Springer Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B. Mobasher, in pres

Meaning in Life as a Mediator of Ethnic Identity and Adjustment Among Adolescents from Latin, Asian, and European American Backgrounds

Establishing a sense of life meaning is a primary facet of well-being, yet is understudied in adolescent development. Using data from 579 adolescents (53% female) from Latin American, Asian, and European backgrounds, demographic differences in meaning in life, links with psychological and academic adjustment, and the role of meaning in explaining associations between ethnic identity and adjustment were examined. Although no generational or gender differences were found, Asian Americans reported higher search for meaning than Latin and European Americans. Presence of meaning was positively associated with self-esteem, academic adjustment, daily well-being, and ethnic belonging and exploration, whereas search for meaning was related to lower self-esteem and less stability in daily well-being. Presence of meaning mediated associations between ethnic identity and adjustment, explaining 28–52% of ethnic identity’s protective effect on development. Ethnic identity thus appears to affect adjustment, in part, through its role in fostering a positive sense of meaning in adolescents’ lives

Early assembly of the most massive galaxies

The current consensus is that galaxies begin as small density fluctuations in the early Universe and grow by in situ star formation and hierarchical merging. Stars begin to form relatively quickly in sub-galactic sized building blocks called haloes which are subsequently assembled into galaxies. However, exactly when this assembly takes place is a matter of some debate. Here we report that the stellar masses of brightest cluster galaxies, which are the most luminous objects emitting stellar light, some 9 billion years ago are not significantly different from their stellar masses today. Brightest cluster galaxies are almost fully assembled 4-5 Gyrs after the Big Bang, having grown to more than 90% of their final stellar mass by this time. Our data conflict with the most recent galaxy formation models based on the largest simulations of dark matter halo development. These models predict protracted formation of brightest cluster galaxies over a Hubble time, with only 22% of the stellar mass assembled at the epoch probed by our sample. Our findings suggest a new picture in which brightest cluster galaxies experience an early period of rapid growth rather than prolonged hierarchical assembly.Comment: Published in Nature 2nd April 2009. This astro ph version includes main text and supplementary material combine

Psychometric evaluation of the Hospital Anxiety and Depression Scale in a large community sample of adolescents in Hong Kong

Purpose: The Hospital Anxiety and Depression Scale (HADS) is widely used in adult populations; however, its usefulness with adolescents has been explored less. This study sought to evaluate the reliability, validity, and factor structure of the Chinese version of HADS in a community sample of adolescents residing in Hong Kong. Methods: A prospective cohort of 5,857 students recruited from 17 secondary schools completed the HADS. Internal consistency and concurrent validity were examined. Confirmatory factor analysis was applied to test the relative fits of six factor structures of the HADS. The best fitting model was further cross-validated by male, female, splithalf samples, and age subgroups. Results: The HADS possessed adequate internal consistency, especially for the anxiety subscale. Significant concurrent intercorrelations with self-reported suicidal thoughts and the Youth Self Report Anxious/Depressed subscale were discovered and found to be stronger for females. The cross-validation supported a two-factor model, where anxiety item 7, "I can sit at ease and feel relaxed", was placed in the depression subscale. Conclusions: The HADS showed satisfactory psychometric properties as a screening instrument in assessing anxious and depressive states as two correlated but distinct factors in adolescents. Study implications and recommendations for future research were discussed.published_or_final_versionSpringer Open Choice, 21 Feb 201

Impulsivity and self-harm in adolescence: a systematic review

Research supports an association between impulsivity and self-harm, yet inconsistencies in methodology across studies have complicated understanding of this relationship. This systematic review examines the association between impulsivity and self-harm in community-based adolescents aged 11-25 years and aims to integrate findings according to differing concepts and methods. Electronic searches of EMBASE, MEDLINE, PsychINFO, CINAHL, PubMed and The Cochrane Library, and manual searches of reference lists of relevant reviews, identified 4,496 articles published up to July 2015, of which 28 met inclusion criteria. Twenty-four of the studies reported an association between broadly specified impulsivity and self-harm. However, findings varied according to the conception and measurement of impulsivity and the precision with which self-harm behaviours were specified. Specifically, lifetime non-suicidal self-injury was most consistently associated with mood-based impulsivity related traits. However, cognitive facets of impulsivity (relating to difficulties maintaining focus or acting without forethought) differentiated current self-harm from past self-harm. These facets also distinguished those with thoughts of self-harm (ideation) from those who acted on thoughts (enaction). The findings suggested that mood-based impulsivity is related to the initiation of self-harm, while cognitive facets of impulsivity are associated with the maintenance of self-harm. In addition, behavioural impulsivity is most relevant to self-harm under conditions of negative affect. Collectively, the findings indicate that distinct impulsivity facets confer unique risks across the life-course of self-harm. From a clinical perspective, the review suggests that interventions focusing on reducing rash reactivity to emotions or improving self-regulation and decision-making may offer most benefit in supporting those who self-harm

The role of low-volatility organic compounds in initial particle growth in the atmosphere

About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday1. Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres2, 3. In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles4, thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth5, 6, leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer7, 8, 9, 10. Although recent studies11, 12, 13 predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon2, and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Köhler theory)2, 14, has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown15 that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10−4.5 micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10−4.5 to 10−0.5 micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations