Uncertain Aspects Research Articles

Fuzzy Reasoning Procedure for Ontologies based on Rough Membership Approximation

One of the major challenges in modeling a real-world domain is how to effectively represent uncertain and incomplete knowledge of that domain. Several techniques for representing uncertainty in ontologies have been proposed with some of the techniques lacking provision for vague inference. The classical tableaux-based algorithm does not provide the flexibility for reasoning over such vague ontologies. However, several extensions of the tableaux-based algorithm have been proposed to cope with fuzzy reasoning. Similarly, several alternative reasoning methods for incomplete, inconsistent, and uncertain ontologies have been proposed. One of the major limitations of most of those techniques is that they require reengineering existing ontologies to cope with uncertainty. This paper proposes a satisfiability algorithm for vague ontologies that uses a rough set to approximate the concepts and roles. The proposed technique takes advantage of the existing ontology knowledge base to achieve vague reasoning without the need of reengineering the ontology. The results show that the proposed technique conforms to the tableaux-based algorithm while providing a way of reasoning over the uncertain aspects of ontologies.

Synaptic Vesicle Glycoprotein 2A: Features and Functions

In recent years, the field of neuroimaging dramatically moved forward by means of the expeditious development of specific radioligands of novel targets. Among these targets, the synaptic vesicle glycoprotein 2A (SV2A) is a transmembrane protein of synaptic vesicles, present in all synaptic terminals, irrespective of neurotransmitter content. It is involved in key functions of neurons, focused on the regulation of neurotransmitter release. The ubiquitous expression in gray matter regions of the brain is the basis of its candidacy as a marker of synaptic density. Following the development of molecules derived from the structure of the anti-epileptic drug levetiracetam, which selectively binds to SV2A, several radiolabeled markers have been synthetized to allow the study of SV2A distribution with positron emission tomography (PET). These radioligands permit the evaluation of in vivo changes of SV2A distribution held to be a potential measure of synaptic density in physiological and pathological conditions. The use of SV2A as a biomarker of synaptic density raises important questions. Despite numerous studies over the last decades, the biological function and the expressional properties of SV2A remain poorly understood. Some functions of SV2A were claimed, but have not been fully elucidated. While the expression of SV2A is ubiquitous, stronger associations between SV2A and Υ amino butyric acid (GABA)-ergic rather than glutamatergic synapses were observed in some brain structures. A further issue is the unclear interaction between SV2A and its tracers, which reflects a need to clarify what really is detected with neuroimaging tools. Here, we summarize the current knowledge of the SV2A protein and we discuss uncertain aspects of SV2A biology and physiology. As SV2A expression is ubiquitous, but likely more strongly related to a certain type of neurotransmission in particular circumstances, a more extensive knowledge of the protein would greatly facilitate the analysis and interpretation of neuroimaging results by allowing the evaluation not only of an increase or decrease of the protein level, but also of the type of neurotransmission involved.

Proposing an Uncertainty Management Framework to Implement the Evidence Theory for Vehicle Crash Applications

Abstract The purpose of this work is to enable the use of the Dempster–Shafer evidence theory (ET) for uncertainty propagation on computationally expensive automotive crash simulations. This is necessary as the results of these simulations are influenced by multiple possibly uncertain aspects. To avoid negative effects, it is important to detect these factors and their consequences. The challenge when pursuing this effort is the prohibitively high computational cost of the ET. To this end, we present a framework of existing methods that is specifically designed to reduce the necessary number of full model evaluations and parameters. An initial screening removes clearly irrelevant parameters to mitigate the curse of dimensionality. Next, we approximate the full-scale simulation using metamodels to accelerate output generation and thus enable the calculation of global sensitivity indices. These indicate effects of the parameters on the considered output and more profoundly sort out irrelevant parameters. After these steps, the ET can be performed rapidly and feasibly due to fast-responding metamodel and reduced input dimension. It yields bounds for the cumulative distribution function of the considered quantity of interest. We apply the proposed framework to a simplified crash test dummy model. The elementary effects method is used for screening, a kriging metamodel emulates the finite element simulation, and Sobol' sensitivity indices are determined before the ET is applied. The outcome of the framework provides engineers with information about the uncertainties they may face in hardware testing and that should be addressed in future vehicle design.

Újrateremtett világ : Egy magyar balett-táncos, táncpedagógus és koreográfus, Solymossy Kálmán élete az ausztráliai emigrációban

After fleeing Hungary due to his participation in the 1956 revolution, Kalman Solymossy left behind his renowned status as a dancer of the Budapest Opera House and had to start his life from scratch. Dance held a central position in Solymossy’s life, whatever the circumstances. Although there was no demand for dancers when he arrived in Australia, his everlasting optimism, endurance and courage helped him stick to the path he had chosen, leading him to establish the largest ballet school of his time in Australia while educating and supporting dancers, many of whom later chose dance as their profession. With his choreography and his presence on TV, Solymossy significantly contributed to the cultural life of Australia and its Hungarian community. The present article is based on primary, secondary, and tertiary sources, relying mainly on convenience sampling of the available resources accessed through both Australian and Hungarian online archives. This study presents a critical period in Solymossy’s influential career and highlights a number of uncertain aspects of his life, topics which have so far been sparsely examined.

Testicular torsion in adults: which news?

We read with pleasure the article written by Dang et al.1 and the authors should be noted for the large case series reported. Testicular torsion is one of the causes of acute scrotum, in all age groups. Even in adults, testicular torsion is difficult to diagnose, so it is necessary to perform a surgical exploration. Some diseases such as testicular cancer must be considered when treating a patient with testicular torsion. Radiological investigations sometimes help us in the diagnosis, but surgery is always necessary to exclude testicular damage. A long-term follow-up is always necessary to evaluate testicular function and viability. It is clear that organizing a multicenter study, even if retrospectively, is always difficult and complex. The data reported are interesting, especially on some clinical aspects, thus highlighting how the diagnosis and treatment of testicular torsion are also in adults sometimes difficult and not always correct. The clinical approach is similar to what is done in the pediatric age, but some differences are evident. For example, the time of onset and the time used for the diagnosis seem to be reduced compared to the pediatric age, perhaps because the adult goes alone to the hospital and knows how to evaluate their symptoms. In spite of this, the absolute percentage of torsions (50%), if corrected excluding 30% of procedures without cause and 10% associated with tumor, is clearly higher than that in the previous age (pediatric and adolescent age). Interesting is also the side localization, which confirms a predisposition for the right side. Based on the study results, if we must analyze and find some uncertain aspects, we can highlight that some data which currently seem to be fundamental in pediatric age for the therapeutic approach, are not reported. In fact, metachronous torsions are not described, and therefore, the simultaneous treatment of the contralateral side is not suggested.2 Moreover, although they reported ultrasound and Doppler data, they do not report data concerning the ultrasound appearance of the testicular parenchyma, so we cannot have data to correlate with testicular viability at the time of surgery and during follow-up. Also inherent to follow-up, the authors reported a follow-up of 30 days, and this may be incorrect on the assessment of testicular viability. How many testes have become atrophic some months after surgery? The long-term outcome is therefore crucial because the ultrasonographic appearance, vitality at surgery, and long-term testicular quality are key elements in predicting any problems with fertility or gonadal function. Very interesting are the data regarding the presence of testicular cancer since it is practically nonexistent in pediatric age.3 These data are important, especially for those surgeons that work with adolescents and young adults. If we have to find some limits, we can specify that the surgical approach is always secondary to the experience of the surgeon who may or may not use ultrasound and other diagnostic methods. In this case, in a multicenter study without having decided beforehand the criteria to treat acute scrotum, what tests to do and when to perform a surgical approach, data collected can be difficult to interpret. However, in the conclusions that are to be shared, surgical exploration should always be performed in case of doubt; and although the percentage of operations without diagnosis may be high, it is correct not to waste time waiting for radiological investigations that may not help in the clinical decision. In our opinion, it remains fundamental that future research should be based on long-term follow-up of these patients, with clinical and radiological controls to be defined, certainly for many months, perhaps adding laboratory tests and analysis of seminal fluid in those patients seeking paternity. Many experiences in fact report that in the long term, testicles left in place after torsion, have altered function. It is therefore essential that research proposes new diagnostic and therapeutic treatments after surgical procedures to ensure better testicular vascularization and vitality of the testis.4 COMPETING INTERESTS Both authors declare no competing interests.

Behavioral Contract Law

Abstract This article explores some behavioral findings that are relevant to three areas of contract: formation, performance, and remedies. I compare the rational choice theory analysis of various aspects of contract law with how behavioral findings lead to a change in our understanding of that area of law. A penultimate section considers several criticisms of behavioral economics. A concluding section calls for altering some settled understandings of contract law to accommodate behavioral results and for further research about some still uncertain aspects of contracting.

Hydrogeochemical indications of regional flow in the Lower Greensand aquifer of the London Basin

The Lower Greensand (LGS) forms the second most important aquifer in the London Basin but, being largely absent beneath the city itself, has received much less attention than the ubiquitous overlying Chalk aquifer. While the general directions of groundwater flow in the Chalk are well established, there has been much less certainty about flow in the LGS owing to regionally sparse borehole information. This study focuses on two hitherto uncertain aspects of the confined aquifer: the sources of recharge to the west-central London Basin around Slough, and the fate of LGS water where the aquifer thins out on the flank of the London Platform in the Gravesend–Medway–Sheppey area on the southern side of the basin. The application of hydrogeochemical techniques including environmental isotopes indicates that recharge to the Slough area is derived from the northern LGS outcrop, probably supplemented by downward leakage from the Chalk, while upward leakage from the LGS in north Kent is mixing with Chalk water to the extent that some Chalk boreholes on the Isle of Sheppey are abstracting high proportions of water with an LGS fingerprint. In doing so, this study demonstrates the value of re-examining previously published data from a fresh perspective. Thematic collection: This article is part of the Hydrogeology of Sandstone collection available at: https://www.lyellcollection.org/cc/hydrogeology-of-sandstone

Influence of posterior pedicle screw fixation at L4\u2013L5 level on biomechanics of the lumbar spine with and without fusion: a finite element method

BackgroundPosterior pedicle screw (PS) fixation, a common treatment method for widespread low-back pain problems, has many uncertain aspects including stress concentration levels, effects on adjacent segments, and relationships with physiological motions. A better understanding of how posterior PS fixation affects the biomechanics of the lumbar spine is needed. For this purpose, a finite element (FE) model of a lumbar spine with posterior PS fixation at the L4–L5 segment level was developed by partially removing facet joints (FJs) to imitate an actual surgical procedure. This FE study aimed to investigate the influence of the posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion by determining which physiological motions have the most increase in posterior instrumentation (PI) stresses and FJ loading.ResultsIt was determined that posterior PS fixation increased FJ loading by approximately 35% and 23% at the L3–L4 adjacent level with extension and lateral bending motion, respectively. This increase in FJ loading at the adjacent level could point to the possibility that adjacent segment disease has developed or progressed after posterior lumbar interbody fusion. Furthermore, analyses of peak von Mises stresses on PI showed that the maximum PI stresses of 272.1 MPa and 263.7 MPa occurred in lateral bending and flexion motion before fusion, respectively.ConclusionsThe effects of a posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion were investigated for all physiological motions. This model could be used as a fundamental tool for further studies, providing a better understanding of the effects of posterior PS fixation by clearing up uncertain aspects.

Evaluation of field visit planning heuristics during rapid needs assessment in an uncertain post-disaster environment

A Rapid Needs Assessment process is carried out immediately after the onset of a disaster to investigate the disaster’s impact on affected communities, usually through field visits. Reviewing practical humanitarian guidelines reveals that there is a great need for decision support for field visit planning in order to utilize resources more efficiently at the time of great need. Furthermore, in practice, there is a tendency to use simple methods, rather than advanced solution methodologies and software; this is due to the lack of available computational tools and resources on the ground, lack of experienced technical staff, and also the chaotic nature of the post-disaster environment. We present simple heuristic algorithms inspired by the general procedure explained in practical humanitarian guidelines for site selection and routing decisions of the assessment teams while planning and executing the field visits. By simple, we mean methods that can be implemented by practitioners in the field using primary resources such as a paper map of the area and accessible software (e.g., Microsoft Excel). We test the performance of proposed heuristic algorithms, within a simulation environment , which enables us to incorporate various uncertain aspects of the post-disaster environment in the field, ranging from travel time and community assessment time to accessibility of sites and availability of community groups. We assess the performance of proposed heuristics based on real-world data from the 2011 Van earthquake in Turkey. Our results show that selecting sites based on an approximate knowledge of community groups’ existence leads to significantly better results than selecting sites randomly. In addition, updating initial routes while receiving more information also positively affects the performance of the field visit plan and leads to higher coverage of community groups than an alternative strategy where inaccessible sites and unavailable community groups are simply skipped and the initial plan is followed. Uncertainties in travel time and community assessment time adversely affect the community group coverage. In general, the performance of more sophisticated methods requiring more information deteriorates more than the performance of simple methods when the level of uncertainty increases.

How Do Veterinary Students Engage When Using Creative Methods to Critically Reflect on Experience? A Qualitative Analysis of Assessed Reflective Work.

Critical reflection-the exploration and questioning of one's experience, beliefs, assumptions, and actions-supports resilience, empathy, the management of uncertainty, and professional identity formation. Yet for many students and educators, the techniques to engage in critical reflection are elusive. Creative methods that foster engagement with emotional and uncertain aspects of experience reportedly help some students to reflect at a more critical level than when they use reflective writing, and this study explores more deeply the experiences of such students, who used creative methods to critically reflect on challenging or troubling past events. A narrative methodology was utilized, in which researchers collaboratively co-constructed an understanding of students' experiences of reflection to identify the activities and steps they used. Creative methods did not inherently lead to critical reflection, but when this was achieved, the creative approaches seemed to facilitate a staging of reflection, which incorporated five sequential stages: preplanning creative depiction, experimenting with different ideas, deliberately completing the reflective piece, reflecting on creative work, and reflecting again on learning and development. This cyclic, repeated revisit to experience, as students engaged in each stage of their work, appeared to facilitate both a deep connection with the emotional elements of experience and a more distanced analysis. This ultimately led to a deepening of understanding of events, including the construction of students' own beliefs and empathy with others' views.

Exploring the Relationship between Leisure and Sustainability in a Chinese Hollow Village

This study explores the relationship between a for-profit leisure program and sustainability issues in the context of a hollow village in China. We studied what forms of relation between leisure and sustainability could be identified through the operation of ‘Mount Qi and the hermit master’ at a hollow village, and to what extent, ‘Mount Qi and the hermit master’ can be considered as a sustainable leisure program. Fieldwork and focus groups were used to collect data. Theoretically, the analyses adopt a comprehensive model of sustainability, which integrates the concepts of weak and strong sustainability, as well as considers the sustainability of human needs. Our findings demonstrate that the leisure program has contributed to a comprehensive sustainable development and helped to meet the villagers’ needs. This study also critically points out the uncertain aspects relating to the sustainability of human needs at the current stage of the program implementation.

Coffee biowaste valorization within circular economy: an evaluation method of spent coffee grounds potentials for mortar production

PurposeSpent coffee grounds (SCG) are biowastes extensively generated within the coffee supply chain. Nowadays, their disposal represents an increasing environmental concern due to its toxicity and organic nature. With the estimated increase of coffee production and consumption in the upcoming years, there is an imperative need to find a proper reverse option, along with a novel industrial application, which allows for the valorization of this coffee by-product within a circular economy perspective. This study aims at investigating a potential reuse of spent coffee grounds to produce novel construction materials to be used for sustainable buildings.MethodsAfter having illustrated the forward flows within the coffee life cycle and the potential reverse flow options, an evaluation method based on multi-criteria analyses was elaborated to test not only the technical but also the environmental and economic performances of novel materials originating from the incorporation of SCG as an aggregate in natural hydraulic lime and geopolymer-based mortars. Moreover, we focus on the reuse of another waste streams— biomass fly ash—deriving from the paper-pulp industry, rarely investigated in both traditional construction applications and in geopolymer manufacture. The two (geopolymer- and lime-based) mortar typologies are here studied and compared as potential green material for applications in construction, with satisfying engineering performance and high insulation attitude, giving a new life to a common organic waste. Consequently, we compare eight formulations by means of multi-criteria approaches that are nowadays claimed as a useful and effective decision aiding support instrument to assess the development of new sustainable construction materials. They permit to consider simultaneously some controversial and often uncertain aspects like technological (as the usual scientific studies do), environmental, and economic (more difficult to easily approach and evaluate). For this purpose, in this paper, we have analyzed the performance of the novel bio-composite mortars using VIKOR and TOPSIS methods to rank a set of alternatives according to various evaluation criteria that often conflict one with each other.ResultsResults show that adding spent coffee grounds can efficiently improve the technical and sustainable performances of the novel mortars for different applications in the building sector. The presence of SCG increases water absorption and improves the insulation performance along with an environmental impact reduction. The considered technological properties are highly promising—such as the improvement in thermal insulation. In particular, even the addition of only 5% SCG leads to a significant reduction of the thermal conductivity and consequently to a greater insulating performance.ConclusionsTo date, most of the available literature on recycling SCG in construction materials do not consider mortar-based applications and, moreover, nor multi-criteria approaches. Therefore, our study proposes itself as an innovative track solution to food waste management lowering the employment of non-renewable natural resources and the costs associated to construction material production. At the same time, a novel and innovative way of such waste disposal is suggested, pursuing the sustainability and substantially reducing the environmental impact of construction and building materials. This study is a fundamental step in assessing the applicability of our designed and produced materials and its potentials to be produced at an industrial scale.

Exploring docility: A behavioral approach to interventions in business incubation

The business incubation process evolves through coach-incubatee interactions rather than merely institutional intervention. We contribute to a behavioral understanding of this process by exploring the determinants and expression of docility, a fundamental human behavior. Our findings suggest that business coaches’ perceptions of stakeholder value creation needs and their experience of incubatees’ proactive behavior are essential determinants of coaching behavior. These behavioral determinants lead coaches to place idiosyncratic expectations on and become responsive to incubatees, and this is reflected in the range of their interventions in new venture creation. From a behavioral perspective, the outcome of coaches’ interventions is a shared understanding of how to navigate the ambiguous and uncertain aspects of new venturing. Adopting a behavioral approach thus helps us to reframe business incubation—previously regarded to be a structured process—as a flexible process, more accurately capturing its role in facilitating the highly uncertain process of new venture creation.

Joint constraints on the field-cluster mixing fraction, common envelope efficiency, and globular cluster radii from a population of binary hole mergers via deep learning

The recent release of the second Gravitational-Wave Transient Catalog (GWTC-2) has increased significantly the number of known GW events, enabling unprecedented constraints on formation models of compact binaries. One pressing question is to understand the fraction of binaries originating from different formation channels, such as isolated field formation versus dynamical formation in dense stellar clusters. In this paper, we combine the $\texttt{COSMIC}$ binary population synthesis suite and the $\texttt{CMC}$ code for globular cluster evolution to create a mixture model for black hole binary formation under both formation scenarios. For the first time, these code bodies are combined self-consistently, with $\texttt{CMC}$ itself employing $\texttt{COSMIC}$ to track stellar evolution. We then use a deep-learning enhanced hierarchical Bayesian analysis to constrain the mixture fraction $f$ between formation models, while simultaneously constraining the common envelope efficiency $\alpha$ assumed in $\texttt{COSMIC}$ and the initial cluster virial radius $r_v$ assumed in $\texttt{CMC}$. Under specific assumptions about other uncertain aspects of isolated binary and globular cluster evolution, we report the median and $90\%$ confidence interval of three physical parameters $(f,\alpha,r_v)=(0.20^{+0.32}_{-0.18},2.26^{+2.65}_{-1.84},2.71^{+0.83}_{-1.17})$. This simultaneous constraint agrees with observed properties of globular clusters in the Milky Way and is an important first step in the pathway toward learning astrophysics of compact binary formation from GW observations.

Routing and scheduling in Home Health Care: A literature survey and bibliometric analysis

Home Health Care (HHC) agencies aim at providing care and/or services to patients, at their homes, ensuring a quality of service at least equivalent to that given in a hospital, while controlling costs and improving living conditions.The purpose of this paper is to propose a literature survey on “Home Health Care problems” dealing with routing and scheduling, to provide an overview of the constraints and objectives addressed by Operations Research and Industrial Engineering tools for both theoretical and practical HHC problems.Based on an exhaustive methodology, the current state-of-the-art is reviewed, analyzed, and summarized. We focus not only on the methods used in the different papers studied but also and mainly on constraints and objectives which are specific to the HHC context, particularly highlighting the uncertain and dynamic aspects present in a growing number of papers.This literature survey enables us to identify several research directions, discussed at the end of this paper. It makes it possible for researchers to identify unaddressed problems, or to direct their research towards one or another method according to the constraints and objectives under consideration, while for practitioners, it enables them to see whether their problem has given rise to the development of planning methods.The main contributions of this paper are a synthesis update of the literature dealing with routing and scheduling in the HHC context, a set of comprehensive tables classifying the papers, some discussions on current trends with a focus on the uncertain and dynamic aspects, and future research directions.

'You should see a doctor', said the robot: Reflections on a digital diagnostic device in a pandemic age.

Aims:In three days at the beginning of the COVID-19 pandemic, the Copenhagen Emergency Medical Services developed a digital diagnostic device. The purpose was to assess and triage potential COVID-19 symptoms and to reduce the number of calls to public health-care helplines. The device was used almost 150,000 times in a few weeks and was described by politicians and administrators as a solution and success. However, high usage cannot serve as the sole criterion of success. What might be adequate criteria? And should digital triage for citizens by default be considered low risk?Methods:This paper reflects on the uncertain aspects of the performance, risks and issues of accountability pertaining to the digital diagnostic device in order to draw lessons for future improvements. The analysis is based on the principles of evidence-based medicine (EBM), the EU and US regulations of medical devices and the taxonomy of uncertainty in health care by Han et al.Results:Lessons for future digital devices are (a) the need for clear criteria of success, (b) the importance of awareness of other severe diseases when triaging, (c) the priority of designing the device to collect data for evaluation and (d) clear allocation of responsibilities.Conclusions:A device meant to substitute triage for citizens according to its own criteria of success should not by default be considered as low risk. In a pandemic age dependent on digitalisation, it is therefore important not to abandon the ethos of EBM, but instead to prepare the ground for new ways of building evidence of effect.

A novel UAV path planning algorithm to search for floating objects on the ocean surface based on object’s trajectory prediction by regression

Search and find mission in ocean environment is a none trivial operation given the amount of random parameters associated with it. The uncertain and dynamic aspects related to ocean current movement make the trajectory prediction of drifting lost object onto sea water a very complicated task. In this work we present a novel lost target searching algorithm based on Recursive Area Clustering and target trajectory predication in ocean environment. Based on the widely known GlobCurrent v2 dataset which model the drifting of ocean surface current using satellite sensory data combined with mathematical and simulation modeling, we propose a regression algorithm based on our Recursive Area Clustering algorithm that we have developed previously to determine the strategic zones (weight centers) characterizing the high density areas extracted from drifting target history. Given those weight centers, we predict the object trajectory through refined regression. The predicted lost object trajectory is used to plan the path of UAV search mission. The model developed has a significant impact as we have tested our strategy in a scenario for searching an area covering 68517 km2, we have shown that 78% of the time, the lost object can be found within 32 km distance of the predicted trajectories limiting the significant search area to be about 5% of the whole searched area.

A Qualitative Study On Mental Distress Of Vietnamese Students In The U.S.A. In The Covid-19 Era

Objective: This paper aims to examine how the COVID-19 pandemic affects the mental distress of the Vietnamese students in the USA. We explore different root causes of mental distress among international students who are away from their home country, their loved ones, and being isolated from school and community due to this outbreak.
 Design: In-depth interviews were conducted to probe the reasons for mental stress during the pandemic and the narrative textual analysis was subsequently performed to analyze the results. This research includes the interviews of 20 Vietnamese students in the USA during the COVID-19 era.
 Results: The textual analysis showed that the mental distress of these Vietnamese students were caused by limited access to on-campus facilities and activities, limited access to public services including grocery shopping, transportations, clinics, the possibility of being infected, isolated living condition due to the lockdown order, and inability to go back to the home country when wanted.
 Conclusions: We found that both physical attributes (e.g., living condition, internet difficulty, overwhelmed healthcare system, restricted traveling, lack of personal interaction, limited access to public services) and psychological factors (e.g., anxiety of unfamiliar teaching modality, fear of viral infection, uncertain career aspects, cultural barrier and prejudice) directly led to the mental distress of these students. Moreover, other factors such as turbulent future job markets and potential racism toward Asians in relation with “Chinese virus” may cause the mental distress of these students.

Liquid-Liquid Phase Separation in Supermicrometer and Submicrometer Aerosol Particles.

ConspectusThe interactions of aerosol particles with light and clouds are among the most uncertain aspects of anthropogenic climate forcings. The effects of aerosol particles on climate depend on their optical properties, heterogeneous chemistry, water uptake behavior, and ice nucleation activity. These properties in turn depend on aerosol physics and chemistry including composition, size, shape, internal structure (morphology), and phase state. The greatest numbers of particles are found at small, submicrometer sizes, and the properties of aerosol particles can differ on the nanoscale compared with measurements of bulk materials. As a result, our focus has been on characterizing the phase transitions of aerosol particles in both supermicrometer and submicrometer particles. The phase transition of particular interest for us has been liquid-liquid phase separation (LLPS), which occurs when components of a solution phase separate due to a difference in solubilities. For example, organic compounds can have limited solubility in salt solutions especially as the water content decreases, increasing the concentration of the salt solution, and causing phase separation between organic-rich and inorganic-rich phases. To characterize the systems of interest, we primarily use optical microscopy for supermicrometer particles and cryogenic-transmission microscopy for submicrometer particles.This Account details our main results to date for the phase transitions of supermicrometer particles and the morphology of submicrometer aerosol. We have found that the relative humidity (RH) at which LLPS occurs (separation RH; SRH) is highly sensitive to the composition of the particles. For supermicrometer particles, SRH decreases as the pH is lowered to atmospherically relevant values. SRH also decreases when non-phase-separating organic compounds are added to the particles. For submicrometer particles, a size dependence of morphology is observed in systems that undergo LLPS in supermicrometer particles. In the limit of slow drying rates, particles <30 nm are homogeneous and larger particles are phase-separated. This size dependence of aerosol morphology arises because small particles cannot overcome the activation barrier needed to form a new phase when phase separation occurs by a nucleation and growth mechanism. The inhibition of LLPS in small particles is observed for mixtures of ammonium sulfate with single organic compounds as well as complex organics like α-pinene secondary organic matter. The morphology of particles affects activation diameters for the formation of cloud condensation nuclei. These results more generally have implications for aerosol properties that affect the climate system. In addition, LLPS is also widely studied in materials and biological chemistry, and our results could potentially translate to implications for these fields.

Engagement all the way down

ABSTRACT This paper asks about the practices and forms of critique afforded at the intersection between Science-and-Technology Studies and the critical study of security politics, by drawing on the work of Isabelle Stengers. Can engagements with practice generate effective forms of critique? How does the attention to materialities and the fine-grained analysis of technical practices, that typically accompany STS-inspired research, feed into ways of practicing critique? How can the analytical attention to ‘little security nothings’ be translated into critical agendas? In addressing these questions, Belgian philosopher Isabelle Stengers serves as an inspiration, not just for her philosophical writing on the situated nature of critical thinking, but also for her own experimental politics and engagement. A key message of the paper is that critical practice is “engagement all the way down.” The article thinks through the ways in which the work of Stengers and her companions can be put into practice in qualitative critical security research. It builds on Foucault’s rejection of the separation between theoretical, universalist knowledge on the one hand, and practical knowledge on the other. It emphasises the processual, uncertain and practical aspects of critical thinking. It identifies the notions of following, leveraging, joined risks and paying attention as key, concrete pathways of engaged critique.