The cloud droplet number concentration (Nd) is of central interest to improve the understanding of cloud physics and for quantifying the effective radiative forcing by aerosol‐cloud interactions. ...Current standard satellite retrievals do not operationally provide Nd, but it can be inferred from retrievals of cloud optical depth (τc) cloud droplet effective radius (re) and cloud top temperature. This review summarizes issues with this approach and quantifies uncertainties. A total relative uncertainty of 78% is inferred for pixel‐level retrievals for relatively homogeneous, optically thick and unobscured stratiform clouds with favorable viewing geometry. The uncertainty is even greater if these conditions are not met. For averages over 1° ×1° regions the uncertainty is reduced to 54% assuming random errors for instrument uncertainties. In contrast, the few evaluation studies against reference in situ observations suggest much better accuracy with little variability in the bias. More such studies are required for a better error characterization. Nd uncertainty is dominated by errors in re, and therefore, improvements in re retrievals would greatly improve the quality of the Nd retrievals. Recommendations are made for how this might be achieved. Some existing Nd data sets are compared and discussed, and best practices for the use of Nd data from current passive instruments (e.g., filtering criteria) are recommended. Emerging alternative Nd estimates are also considered. First, new ideas to use additional information from existing and upcoming spaceborne instruments are discussed, and second, approaches using high‐quality ground‐based observations are examined.
Plain Language Summary
Clouds have a very large influence on weather and climate. It is thus a prime task for satellite‐ and ground‐based observations to measure clouds. For satellites and many other instruments this is done by remote sensing—radiation is measured, and knowledge about clouds is inferred. Liquid water clouds consist of numerous droplets of order of 10 μm in size. A key quantity that describes clouds is the number of droplets in a given volume or the droplet number concentration. However, satellite observations of droplet number concentration are only emerging, and the quality of these observations is poorly known. This review fulfills two tasks, namely, (1) to quantify how uncertain the current way to observe droplet number concentrations from satellite is and (2) to propose ways toward better approaches. It is concluded that the current way to obtain cloud droplet number concentration works for homogeneous stratus and stratocumulus clouds, with, however, a substantial error of around 50%. For cumulus clouds the observations are substantially worse. New avenues that are proposed for a better estimate of cloud droplet concentration exploit instruments that emit light (lidar) or microwaves (radar), and measure the reflected signal, or explore the polarization of light induced by clouds.
Key Points
Satellite cloud droplet concentration uncertainties of 78% for pixel‐level retrievals and 54% for 1 by 1 degree retrievals are estimated
The effective radius retrieval is the most important aspect for improvement, and more in situ evaluation is needed
Potential improvements using passive and active satellite, and ground‐based instruments are discussed
Therapeutic benefits of mesenchymal stem cells (MSCs) are now widely believed to come from their paracrine signalling, i.e. secreted factors such as cytokines, chemokines, and extracellular vesicles ...(EVs). Cell-free therapy using EVs is an active and emerging field in regenerative medicine. Typical 2D cultures on tissue culture plastic is far removed from the physiological environment of MSCs. The application of 3D cell culture allows MSCs to adapt to their cellular environment which, in turn, influences their paracrine signalling activity. In this study we evaluated the impact of 3D MSCs culture on EVs secretion, cargo proteome composition, and functional assessment in immunomodulatory, anti-inflammatory and anti-fibrotic properties. MSC-EVs from 2D and 3D cultures expressed classical EV markers CD81, CD63, and CD9 with particle diameter of <100 nm. There were distinct changes in immunomodulatory potencies where 3D cultures exhibited reduced indoleamine 2,3-dioxygenase (IDO) activity and significantly reduced macrophage phagocytosis. Administration of 2D and 3D EVs following double dose bleomycin challenge in aged mice showed a marked increase of bodyweight loss in 3D group throughout days 7-28. Histopathological observations of lung tissues in 3D group showed increased collagen deposition, myofibroblast differentiation and leukocytes infiltrations. Assessment of lung mechanics showed 3D group did not improve lung function and instead exhibited increased resistance and tissue damping. Proteome profiling of MSC-EV composition revealed molecular enrichment of EV markers (compared to parental cells) and differential proteome between EVs from 2D and 3D culture condition associated with immune-based and fibrosis/extracellular matrix/membrane organization associated function. This study provides insight into distinct variation in EV protein composition dependent on the cellular microenvironment of the parental cells, which could have implications in their therapeutic effect and potency. Overall, this work suggests that EVs produced from 3D MSC cultures did not enhance typical MSC-EV properties expected from 2D cultures (immunomodulation, anti-fibrotic, anti-inflammatory). The outcome highlights critical differences between MSC-EVs obtained from different culture microenvironments, which should be considered when scaling up MSC culture for clinical manufacturing.
Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are capable of repairing wounded lung epithelial cells by donating cytoplasmic material and mitochondria. Recently, we characterized two ...populations of human lung-derived mesenchymal stromal cells isolated from digested parenchymal lung tissue (LT-MSCs) from healthy individuals or from lung transplant recipients' bronchoalveolar lavage fluid (BAL-MSCs). The aim of this study was to determine whether LT-MSCs and BAL-MSCs are also capable of donating cytoplasmic content and mitochondria to lung epithelial cells.
Cytoplasmic and mitochondrial transfer was assessed by co-culturing BEAS2B epithelial cells with Calcein AM or Mitotracker Green FM-labelled MSCs. Transfer was then measured by flow cytometry and validated by fluorescent microscopy. Molecular inhibitors were used to determine the contribution of microtubules/tunnelling nanotubes (TNTs, cytochalasin D), gap junctions (carbenoxolone), connexin-43 (gap26) and microvesicles (dynasore).
F-actin microtubules/TNTs extending from BM-MSCs, LT-MSCs and BAL-MSCs to bronchial epithelial cells formed within 45 minutes of co-culturing cells. Each MSC population transferred a similar volume of cytoplasmic content to epithelial cells. Inhibiting microtubule/TNTs, gap junction formation and microvesicle endocytosis abrogated the transfer of cytoplasmic material from BM-MSCs, LT-MSCs and BAL-MSCs to epithelial cells. In contrast, blocking connexin-43 gap junction formation had no effect on cytoplasmic transfer. All MSC populations donated mitochondria to bronchial epithelial cells with similar efficiency. Mitochondrial transfer was reduced in all co-cultures after microtubule/TNT or endocytosis inhibition. Gap junction formation inhibition reduced mitochondrial transfer in BM-MSC and BAL-MSC co-cultures but had no effect on transfer in LT-MSC co-cultures. Connexin-43 inhibition did not impact mitochondrial transfer. Finally, bronchial epithelial cells were incapable of donating cytoplasmic content or mitochondria to any MSC population.
Similar to their bone marrow counterparts, LT-MSCs and BAL-MSCs can donate cytoplasmic content and mitochondria to bronchial epithelial cells via multiple mechanisms. Given that BM-MSCs utilize these mechanisms to mediate the repair of damaged bronchial epithelial cells, both LT-MSCs and BAL-MSCs will probably function similarly.
Despite its importance, physical literacy has received scant scholarly attention, notwithstanding the obvious link between physical activity and health promotion (including but not limited to mental ...health). The purpose of this study was threefold: first, to explore the self-perceived physical literacy, the self-reported physical activity, and the mental health status of adolescents who study in secondary education schools in Cyprus and the potential association of those variables; second, to explore any potential statistically significant gender differences across the variables under examination; and third, to explore whether there is a mediating role of physical activity in the relationship between adolescent Cypriots’ physical literacy and their mental health in the post-quarantine period. A total of 285 students, aged 13–18, from regular middle and high schools in Cyprus participated in this study. Physical literacy was measured using the Perceived Physical Literacy Instrument (PPLI). The Depression, Anxiety, and Stress Scale-21 (DASS-21) was utilized to measure mental health status. Physical activity was measured using the Physical Activity Questionnaire for Adolescents (PAQ-A). Independent sample t-tests were computed to analyze gender differences. The Pearson correlation test was used to compute bidirectional associations between research variables. Structural equation modeling was used to assess structural associations between research variables. The findings revealed statistically significant differences among boys and girls on depression (p = 0.0032), anxiety (p = 0.008), and stress levels (p = 0.003). Statistically significant and negative correlations had been found among PL and depression, anxiety, and stress levels (all p < 0.001), while PL was significantly and positively associated with physical activity (p < 0.001). Despite having only indirect effects on mental health (b = 0.51, T = −10.11, p < 0.001), physical literacy was found to have substantial direct effects on physical activity levels (b = 0.46, T = 8.66, p < 0.001). In addition, physical activity has significant indirect effects on mental health (b = 0.19, T = 5.48, p < 0.001). In summary, physical activity has significantly mediated the associations between physical literacy and mental health. Given these findings, it is important to put strategies in place to build up physical literacy and increase physical activity among Cypriot adolescents.
The psychometric properties of the Frost, Marten, Lahart, and Rosenblate Multidimensional Perfectionism Scale are investigated to determine its usefulness as a measurement of perfectionism with ...Australian secondary school girls and to find empirical support for the existence of both healthy and unhealthy types of perfectionist students. Participants were 409 female mixed-ability students from Years 7 and 10 in two private secondary schools in Sydney, Australia. Factor analyses yielded four rather than the six factors previously theorized. Cluster analysis indicated a distinct typology of healthy perfectionists, unhealthy perfectionists, and nonperfectionists. Healthy perfectionists were characterized by higher levels on Organization, whereas unhealthy perfectionists scored higher on the Parental Expectations and Criticism and Concern Over Mistakes and Doubts dimensions of perfectionism. Both types of perfectionists scored high on Personal Standards. Author abstract
Pragmatic social constructivist teaching methods require students to construct knowledge by engaging collaboratively with realistic problems, cases or projects. It is hypothesised that they are more ...effective than traditional didactic teaching methods in developing undergraduate students': (1) theoretical knowledge; (2) profession-specific skills; and (3) knowledge creation capacity. Results of a survey show the second and third learning effects to be salient among Australian university lecturers, but not the first. Lecturers report that these teaching methods have been adopted more widely in human service-related faculties and design-related faculties than in business-related faculties, possibly owing to the lesser emphasis placed by business lecturers on developing students' profession-specific skills and knowledge creation capacity. A corresponding survey of business practitioners revealed a surprising gap between the value that business practitioners place on new graduates' knowledge creation capacity and the rather limited emphasis that business lecturers place upon developing that capacity in their undergraduate students.
The development of a goal theory model of student motivation in schools has gained momentum over the past decade. Goal theory seeks to understand the relationships between student achievement ...behaviors. Correlates of achievement behaviors include academic goal orientations, affect, and academic self-efficacy. This paper reports the results of a repeated measures multivariate analysis of variance investigating the changes that occur regarding these variables for a sample of final year Australian secondary education students, over time and between sexes. Results of the study show significant increases occurring in students' negative affect, performance-avoidance goal orientations, and self-handicapping strategies and decreases in performance-approach goal orientation and academic self-efficacy. Significant gender differences were also identified in the data. Canonical correlation analysis was also carried out to identify relationships between sets of variables. Results indicate a significant relationship between negative affect coupled with high levels of performance-approach goal orientation and low levels of self-handicapping strategies.
Drizzle is a common feature of warm stratiform clouds and it influences their radiative effects by modulating their physical properties and lifecycle. An important component of drizzle formation are ...processes that lead to a broadening of the droplet size distribution (DSD). Here, we examine observations of cloud and drizzle properties retrieved using colocated airborne measurements from the Research Scanning Polarimeter and the Third Generation Airborne Precipitation Radar. We observe a bimodal DSD as the aircraft transects drizzling open-cells whereby the larger mode reaches a maximum size near cloud center and the smaller mode remains relatively constant in size. We review similarities between our observations with droplet growth processes and their connections with precipitation onset. We estimate droplet sedimentation using the cloud top DSD and find a correlation with rain water path of 0.82. We also examine how changes in liquid water paths and droplet concentrations may act to enhance or suppress precipitation.
Mesenchymal stem cells and the lung Sinclair, Kenneth; Yerkovich, Stephanie T.; Chambers, Daniel C.
Respirology (Carlton, Vic.),
04/2013, Volume:
18, Issue:
3
Journal Article
Peer reviewed
Open access
Mesenchymal stem cells (MSC) are a population of tissue‐resident adult progenitor cells that were originally identified in bone marrow, but have now been identified in many organs including the lung. ...Although their precise role in organ function remains incompletely defined, mounting evidence suggests that they are an important component of the parenchymal progenitor cell niche and orchestrate organ homeostasis and repair following injury. In this review, what is known about MSC biology will be outlined with particular emphasis on lung biology, and the therapeutic potential of MSC‐based cell therapy will also be highlighted.
The Twomey effect describes the radiative forcing associated with a change in cloud albedo due to an increase in anthropogenic aerosol emissions. It is driven by the perturbation in cloud droplet ...number concentration (ΔNd,ant) in liquid-water clouds and is currently understood to exert a cooling effect on climate. The Twomey effect is the key driver in the effective radiative forcing due to aerosol–cloud interactions which also comprises rapid adjustments. These adjustments are essentially the responses of cloud fraction and liquid water path to ΔNd,ant and thus scale approximately with it. While the fundamental physics of the influence of added aerosol particles on the droplet concentration (Nd) is well described by established theory at the particle scale (micrometres), how this relationship is expressed at the large scale (hundreds of kilometres) ΔNd,ant remains uncertain. The discrepancy between process understanding at particle scale and insufficient quantification at the climate-relevant large scale is caused by co-variability of aerosol particles and vertical wind and by droplet sink processes. These operate at scales on the order of 10s of metres at which only localized observations are available and at which no approach exists yet to quantify the anthropogenic perturbation. Different atmospheric models suggest diverse magnitudes of the Twomey effect even when applying the same anthropogenic aerosol emission perturbation. Thus, observational data are needed to quantify and constrain the Twomey effect. At the global scale, this means satellite data. There are three key uncertainties in determining ΔNd,ant, namely the quantification (i) of the cloud-active aerosol – the cloud condensation nuclei concentrations (CCN) at or above cloud base –, (ii) of Nd, as well as (iii) the statistical approach for inferring the sensitivity of Nd to aerosol particles from the satellite data. A fourth uncertainty, the anthropogenic perturbation to CCN concentrations, is also not easily accessible from observational data. This review discusses deficiencies of current approaches for the different aspects of the problem and proposes several ways forward: In terms of CCN, retrievals of optical quantities such as aerosol optical depth suffer from a lack of vertical resolution, size and hygroscopicity information, the non-direct relation to the concentration of aerosols, the impossibility to quantify it within or below clouds, and the problem of insufficient sensitivity at low concentrations, in addition to retrieval errors. A future path forward can include utilizing colocated polarimeter and lidar instruments, ideally including high spectral resolution lidar capability at two wavelengths to maximize vertically resolved size distribution information content. In terms of Nd, a key problem is the lack of operational retrievals of this quantity, and the inaccuracy of the retrieval especially in broken-cloud regimes. As for the Nd – to – CCN sensitivity, key issues are the updraught distributions and the role of Nd sink processes, for which empirical assessments for specific cloud regimes are currently the best solutions. These considerations point to the conclusion that past studies using existing approaches have likely underestimated the true sensitivity and, thus, the radiative forcing due to the Twomey effect.
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