bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in carbon concentrations and allocations among Larix olgensis populations growing in three field environments
Authors: Ying Jiang , Weng Yuhui , Oswald Brian P. , Zhang Hanguo
Published: October 2019

Key message

Variation in carbon concentration amongLarix olgensisA. Henry provenances and tree tissues was significant, suggesting importance of such variation to carbon stock calculation. Provenance variation in carbon allocation was only significant in allocations to some tissues, including stem wood, and was strongly site-specific. Some allocation patterns correlated significantly with provenance growth and were related to geographic/climatic variables at the provenance origins.

Context

Understanding variation in carbon concentrations and allocations to tree tissues among genetic entries is important for assessing carbon sequestration and understanding differential growth rates among the entries. However, this topic is poorly understood, in particular for mature trees in field conditions.

Aims

The study aims to assess genetic variation in C concentrations and allocations to tree tissues and further to link the variation to tree growth and to assess their adaptive nature.

Methods

In 2011, carbon concentrations and allocations to tree tissues (stem wood, stem bark, branches, foliage, and root components) were measured on 31-year-old trees of ten Larix olgensis A. Henry provenances growing at three sites located in northeast China: CuoHai Forest Farm (CH), LiangShui Forest Farm (LS), and MaoErShān Forest Farm (MES). Variation in carbon allocation was analyzed using allometric methods.

Results

Variation in C concentration among tree tissues and among provenances was significant and site-specific. The cross-tissue variation in concentration was driven primarily by high concentration in branches and leaves and low concentration in stem wood and coarse roots. Differences between the minimum and maximum provenance means reached 1% at the tree level. Provenance variation was only significant in allocations to stem wood, branches, and fine roots and was strongly site-specific. Provenance variation in stem wood allocation was independent of provenance growth rate. Some allocation patterns correlated significantly with provenance growth; the faster-growing provenances allocated more to branches and less to fine roots at the LS site, but an opposite pattern was true at MES site. Most significant allocation traits were related to geographic/climatic variables at the provenance origins, but the driving factors varied with site.

Conclusion

Provenance variation in C concentration and allocation existed for L. olgensis but was strongly site-specific. Similarly, relationships of provenance variation in C allocation with provenance growth and their adaptive nature varied greatly with site. Our results will be of interest to ecologists and tree breeders studying dynamics of plantations in terms of climate change.
Impact of deadwood decomposition on soil organic carbon sequestration in Estonian and Polish forests
Authors: Błońska Ewa , Lasota Jarosław , Tullus Arvo , Lutter Reimo , Ostonen Ivika
Published: October 2019

Key message

The deadwood of different tree species with different decomposition rates affects soil organic carbon sequestration in Estonian and Polish forests. In warmer conditions (Poland), the deadwood decomposition process had a higher rate than in cooler Estonian forests. Soil organic matter fractions analysis can be used to assess the stability and turnover of organic carbon between deadwood and soil in different experimental localities.

Context

Deadwood is an important element of properly functioning forest ecosystem and plays a very important role in the maintenance of biodiversity, soil fertility, and carbon sequestration.

Aims

The main aim was to estimate how decomposition of deadwood of different tree species with different decomposition rates affects soil organic carbon sequestration in Estonian and Polish forests.

Methods

The investigation was carried out in six forests in Poland (51° N) and Estonia (58° N). The study localities differ in their mean annual air temperature (of 2 °C) and the length of the growing season (of 1 month). The deadwood logs of Norway spruce (Picea abies (L.) Karst.), common aspen (Populus tremula L.), and silver birch (Betula pendula Roth) were included in the research. Logs in three stages of decomposition (III–V) were selected for the analysis.

Results

There were differences in the stock of soil organic carbon in two experimental localities. There was a higher soil carbon content under logs and in their direct vicinity in Polish forests compared to those in the cooler climate of Estonia. Considerable differences in the amount of soil organic matter were found. The light fraction constituted the greatest quantitative component of organic matter of soils associated with deadwood.

Conclusion

A higher carbon content in surface soil horizons as an effect of deadwood decomposition was determined for the Polish (temperate) forests. More decomposed deadwood affected soil organic matter stabilization more strongly than less decayed deadwood. This relationship was clearer in Polish forests. Higher temperatures and longer growing periods primarily influenced the increase of soil organic matter free light fraction concentrations directly under and in close proximity to logs of the studied species. The slower release of deadwood decomposition products was noted in Estonian (hemiboreal) forests. The soil organic matter mineral fraction increased under aspen and spruce logs at advanced decomposition in Poland.
Correction to: Injury Risk in New Zealand Rugby Union: A Nationwide Study of Injury Insurance Claims from 2005 to 2017
Authors: Quarrie Ken , Gianotti Simon , Murphy Ian
Published: October 2019

Page 11, column 2, section 4.2 Injury Epidemiology, paragraph 4:
On relevance of time-dependent Poisson’s ratio for determination of relaxation function parameters
Authors: Suchocki Cyprian , Molak Rafał
Published: October 2019

The current study concerns the determination of material
constants of a three-dimensional linear viscoelastic model. It is assumed that the constitutive equation utilizes a Prony series as a memory function. A method for the evaluation of relaxation function parameters is presented which can be used for arbitrary loading histories. The proposed methodology is applied to the identification of the viscoelastic constants of acrylonitrile butadiene styrene (ABS). For that purpose, a number of rheological tests in tension have been performed on ABS standard dogbone specimens. The significance of the time-dependent Poisson’s ratio for the determination of material parameters is investigated. It is found that taking into account the measurements of specimen’s lateral contraction over time has a particularly strong influence on the identified values of parameters responsible for the bulk behavior. Several boundary value problems have been analyzed in order to assess the influence of the material parameter values on the obtained solutions. It is demonstrated that some oversimplifications assumed during the determination of viscoelastic constants can lead to a loss of precision or even wrong results.
Theoretical and Experimental Sets of Choice Anode/Cathode Architectonics for High-Performance Full-Scale LIB Built-up Models
Authors: Khalifa H. , El-Safty S. A. , Reda A. , Shenashen M. A. , Selim M. M. , Elmarakbi A. , Metawa H. A.
Published: October 2019

To control the power hierarchy design of lithium-ion battery (LIB) built-up sets for electric vehicles (EVs), we offer intensive theoretical and experimental sets of choice anode/cathode architectonics that can be modulated in full-scale LIB built-up models. As primary structural tectonics, heterogeneous composite superstructures of full-cell-LIB (anode//cathode) electrodes were designed in closely packed flower agave rosettes TiO2@C (FRTO@C anode) and vertical-star-tower LiFePO4@C (VST@C cathode) building blocks to regulate the electron/ion movement in the three-dimensional axes and orientation pathways. The superpower hierarchy surfaces and multi-directional orientation components may create isosurface potential electrodes with mobile electron movements, in-to-out interplay electron dominances, and electron/charge cloud distributions. This study is the first to evaluate the hotkeys of choice anode/cathode architectonics to assemble different LIB–electrode platforms with high-mobility electron/ion flows and high-performance capacity functionalities. Density functional theory calculation revealed that the FRTO@C anode and VST-(i)@C cathode architectonics are a superior choice for the configuration of full-scale LIB built-up models. The integrated FRTO@C//VST-(i)@C full-scale LIB retains a huge discharge capacity (~ 94.2%), an average Coulombic efficiency of 99.85% after 2000 cycles at 1 C, and a high energy density of 127 Wh kg−1, thereby satisfying scale-up commercial EV requirements.
Local memory boosts label propagation for community detection
Authors: Fiscarelli Antonio Maria , Brust Matthias R. , Danoy Grégoire , Bouvry Pascal
Published: October 2019

The objective of a community detection algorithm is to group similar nodes that are more connected to each other than with the rest of the network. Several methods have been proposed but many are of high complexity and require global knowledge of the network, which makes them less suitable for large-scale networks. The Label Propagation Algorithm initially assigns a distinct label to each node that iteratively updates its label with the one of the majority of its neighbors, until consensus is reached among all nodes in the network. Nodes sharing the same label are then grouped into communities. It runs in near linear time and is decentralized, but it gets easily stuck in local optima and often returns a single giant community. To overcome these problems we propose MemLPA, a variation of the classical Label Propagation Algorithm where each node implements a memory mechanism that allows them to “remember” about past states of the network and uses a decision rule that takes this information into account. We demonstrate through extensive experiments, on the Lancichinetti-Fortunato-Radicchi benchmark and a set of real-world networks, that MemLPA outperforms other existing label propagation algorithms that implement memory and some of the well-known community detection algorithms. We also perform a topological analysis to extend the performance study and compare the topological properties of the communities found to the ground-truth community structure.
Measuring the socio-economic footprint of the energy transition
Authors: Garcia-Casals Xavier , Ferroukhi Rabia , Parajuli Bishal
Published: October 2019

The energy system is often treated as a self-contained system, disconnected from the broader socio-economic structures it is built upon. Understanding the enabling environment and structural elements will help to maximize the benefits of the transition and increase awareness of potential barriers and necessary adjustments along the way. IRENA has developed a methodology to measure the socio-economic footprint of energy transition roadmaps using the E3ME macro-econometric model, which evaluates the likely impacts in terms of gross domestic product (GDP), employment and human welfare. It is based on well-established historical databases and has a proven track record of policy applications. The presented socio-economic footprint analysis is based on the IRENA REmap energy transition roadmap 2018 that explores a higher deployment of low-carbon technologies, mostly renewable energy and energy efficiency. The results show that, with appropriate policies in place, reducing over 90% of the energy-related carbon dioxide emissions from the reference case via renewables and energy efficiency coupled with deep electrification of end-uses, results in consistently positive global GDP impacts across the period of analysis from 2018 to 2050. Across the world economy, the transition case leads to a relative increase of employment by 0.14% over the reference case throughout the analysed period from 2018 to 2050. In addition to GDP and employment growth, the energy transition can offer broader welfare gains. However, not all countries and regions around the world benefit equally, and just transition policies must be included to ensure all regions and communities are able to take advantage of the energy transition.
Modelling of the mechanical properties of concrete with cement ratio partially replaced by aluminium waste and sawdust ash using artificial neural network
Authors: Alaneme George U. , Mbadike Elvis M.
Published: October 2019

The use of aluminium waste (AW) and sawdust ash (SDA) in concrete was evaluated in this study where the cement ratio was partially replaced by fractions of AW and SDA introduced as a supplementary cementitious material. Artificial neural network (ANN) was adapted as the modelling tool for this study and was developed with a two-layer feed-forward network, hidden neurons with sigmoid activation function and linear output neurons for the simulation of the network. The setting time and concrete compressive strength at varying curing days were predicted using the neural network model with variations of constituents of the cement content consisting of OPC, SDA and AW as the input of the network. Three input and seven output data set were used for the model development using the following algorithms; Data Division: Random, Training: Levenberg–Marquardt and Calculation: MATLAB. The data sets are set aside for validation, training and testing; 70% of the samples are used for training, 15% for validation and 15% are also used for testing. The performance of the networks was evaluated using linear regression, RMSE and R-values. The model performance scored 0.91 and 0.07 for R2 and RMSE, respectively, and performed better than the linear regression model, the results indicate the efficiency, reliability and usefulness of ANN for predicting concrete mechanical properties where AW and SDA are used to replace cement ratio accurately.
Irreducible Plurality, Indivisible Unity: Singapore Relational Constitutionalism and Cultivating Harmony Through Constructing a Constitutional Civil Religion
Authors: Thio Li-ann
Published: October 2019

This Article seeks to explore the nature, function, source, and content of a constitutional civil religion (CCR) within Singapore’s constitutional experiment in managing the diversity of race and religion and promoting solidarity. CCR is constructed as a strategy to secure social harmony within the world’s most religiously diverse polity, through recognizing an irreducible plurality in ethnic and religious terms, while maintaining an indivisible unity through nurturing bonds of citizen solidarity. This dovetails with the function of the constitution as an instrument of social integration, involving the articulation and regular affirmation of shared community values and aspirations, as well as process and practices—or public rituals—which regulate dispute resolution or conflict management during instances or crises where racial and religious harmony is threatened. A functional approach is taken towards the idea of a civil religion, and the tasks of integration, legitimation, and inspiration it may play within a constitutional order. The nature of civil religion in general, and the sources of CCR in Singapore, as well as its expression as a public ritual in managing religious disharmony disputes is discussed.
On the Constancy of Hedonic Wine Price Coefficients over Time
Authors: Faye Benoît , Le Fur Eric
Published: October 2019

This article tests the stability of the main hedonic wine price coefficients over time. We draw on an extensive literature review to identify the most frequently used methodology and define a standard hedonic model. We estimate this model on monthly subsamples of a worldwide auction database of the most commonly exchanged fine wines. This provides, for each attribute, a monthly time series of hedonic coefficients time series data from 2003 to 2014. Using a multivariate autoregressive model, we then study the stability of these coefficients over time and test the existence of structural or cyclical changes related to fluctuations in general price levels. We find that most hedonic coefficients are variable and either exhibit structural or cyclical variations over time. These findings shed doubt on the relevance of both short- and long-run hedonic estimations. (JEL Classifications: C13, C22, D44, G11)
All Keynesians now? Public support for countercyclical government borrowing
Authors: Barnes Lucy , Hicks Timothy
Published: October 2019

In the wake of the 2008 financial crisis, macroeconomic policy returned to the political agenda, and the influence of Keynesian ideas about fiscal stimulus rose (and then fell) in expert circles. Much less is known, however, about whether and when Keynesian prescriptions for countercyclical spending have any support among the general public. We use a survey experiment, fielded twice, to recover the extent to which UK respondents hold such countercyclical attitudes. Our results indicate that public opinion was countercyclical—Keynesian—in 2016. We then use Eurobarometer data to estimate the same basic parameter for the population for the period 2010–2017. The observational results validate our experimental findings for the later period, but also provide evidence that the UK population held procyclical views at the start of the period. Thus, there appear to be important dynamics in public opinion on a key macroeconomic policy issue.
Do Political Finance Reforms Reduce Corruption?
Authors: Hummel Calla , Gerring John , Burt Thomas
Published: October 2019

Reformers claim that public subsidies and regulation of political finance reduce corruption in politics, while observers worry that they have no impact on corruption, or even increase it. Despite national-level debates and billions of dollars spent, few studies have tested this relationship. The authors argue that political finance reform mitigates corruption by reducing private money's importance in politics and increasing the sanctions for corrupt behavior. Elite interviews from Paraguay's political finance reform illustrate the argument and elaborate the theoretical mechanisms. The study evaluates the argument using an original dataset measuring political subsidies from 175 countries from 1900–2015, as well as disaggregated corruption measures from the Varieties of Democracy project. The findings support the thesis that political finance reform reduces corruption, even in countries where such reforms are unevenly implemented.
Adding grey to the rainbow: a narrative analysis of generational identity through stories and counter-stories of older gay men
Authors: Bower Kyle L. , Lewis Denise C. , Bermudez J. Maria , Singh Anneliese A.
Published: October 2019

We explored identity formation among nine gay men who were born between 1946 and 1964. This group of nine was the largest homogeneous sub-group within a larger sample (N = 18). Although participants share similar demographic characteristics, their individual social, personal and narrative identities diverge to represent distinctive embodied selves. Guided by queer and feminist theories, the qualitative analysis identified dominant and counter-narratives that demonstrate the complexity of sexual identity as it evolves over time. All nine men recall being aware of their gay identity as children; however, like many socially constructed labels, their outward identity was more complex and difficult to understand. The findings demonstrate how participants negotiated their sexual identities through decades of social change. As illustrated within each subset of identity (i.e.social, personal and narrative), some participants found themselves breaking ground for a broader gay rights social movement, while others described their experience of being relegated to silence and invisibility for most of their lives. This research contributes to an ongoing discussion concerning the individuality found among lesbian, gay, bisexual and transgender (LGBT) individuals in later life. As the LGBT population becomes more visible, there will be a growing need to understand the individualism that exists within this coalition and affirm their diversifying sexual and gender identities.
Recent versus lifetime experiences of discrimination and the mental and physical health of older lesbian women and gay men
Authors: Lyons Anthony , Alba Beatrice , Waling Andrea , Minichiello Victor , Hughes Mark , Barrett Catherine , Fredriksen-Goldsen Karen , Edmonds Samantha , Blanchard Michelle
Published: October 2019

This study examines the potential health-related impact of recent versus lifetime experiences of sexual orientation discrimination among older Australian lesbian women and gay men. In a nationwide survey, a sample of 243 lesbian women and 513 gay men aged 60 years and over reported on their experiences of sexual orientation discrimination and their mental and physical health, including psychological distress, positive mental health and self-rated health. Among both lesbian women and gay men, recent discrimination uniquely predicted lower positive mental health after adjusting for experiences of discrimination across the lifetime and socio-demographic variables. In addition, recent discrimination uniquely predicted higher psychological distress among gay men. Experiences of discrimination over the lifetime further predicted higher psychological distress and poorer self-rated health among gay men after adjusting for recent experiences of discrimination and socio-demographic variables. However, there were no associations between lifetime discrimination and any of the outcome variables among lesbian women. Overall, recent and lifetime experiences of sexual orientation discrimination were related to mental and physical health in different ways, especially among the men. These findings have potential implications for policy/practice, and suggest that distinguishing between recent and lifetime experiences of discrimination may be useful when assessing potential health-related impacts of sexual orientation discrimination among older lesbian women and gay men, while also taking account of differences between these two groups.
Teacher's code-switching and bilingual children's heritage language learning and cognitive switching flexibility
Authors: SUN He , YUSSOF Nurul , VIJAYAKUMAR Poorani , LAI Gabrielle , O'BRIEN Beth Ann , ONG Quan He
Published: October 2019

To code-switch or not to code-switch? This is a dilemma for many bilingual language teachers. In this study, the influence of teachers’ CS on bilingual children's language and cognitive development is explored within heritage language (HL) classes in Singapore. Specifically, the relationship between children's language output, vocabulary development, and cognitive flexibility to teachers’ classroom CS behavior, is examined within 20 preschool HL classrooms (10 Mandarin, 6 Malay, and 4 Tamil). Teachers’ and children's utterances were recorded, transcribed, and analyzed for CS frequency and type (i.e., inter-sentential, intra-sentential). 173 students were assessed with receptive vocabulary and dimensional card sort tasks, and their vocabulary and cognitive switching scores assessed using correlational and mixed effects analyses. Results show that inter-sentential and intra-sentential CS frequency is positively and significantly related to children's intra-sentential CS frequency. Overall, findings revealed that teachers code-switched habitually more often than for instructional purposes. Neither inter-sentential nor intra-sentential CS was significantly related to children's development in HL vocabulary, and intra-sentential CS was found to positively and significantly relate to children's growth in cognitive flexibility. These findings reveal the multi-faceted impact of teacher's CS on children's early development.
Infant-directed speech as a simplified but not simple register: a longitudinal study of lexical and syntactic features
Authors: GENOVESE Giuliana , SPINELLI Maria , ROMERO LAURO Leonor J. , AURELI Tiziana , CASTELLETTI Giulia , FASOLO Mirco
Published: October 2019

Infant-directed speech (IDS) is a specific register that adults use to address infants, and it is characterised by prosodic exaggeration and lexical and syntactic simplification. Several authors have underlined that this simplified speech becomes more complex according to the infant's age. However, there is a lack of studies on lexical and syntactic modifications in Italian IDS during the first year of an infant's life. In the present study, 80 mother–infant dyads were longitudinally observed at 3, 6, 9, and 12 months during free-play interactions. Maternal vocal productions were subsequently coded. The results show an overall low lexical variability and syntactic complexity that identify speech to infants as a simplified register; however, the high occurrence of complex items and well-structured utterances suggests that IDS is not simple speech. Moreover, maternal IDS becomes more complex over time, but not linearly, with a maximum simplification in the second half of the first year.
Adverse childhood experiences: Mechanisms of risk and resilience in a longitudinal urban cohort
Authors: Giovanelli Alison , Mondi Christina F. , Reynolds Arthur J. , Ou Suh-Ruu
Published: October 2019

There is an extensive literature describing the detrimental effects of adverse childhood experiences (ACE; e.g., abuse, neglect, and household dysfunction) on physical and mental health. However, few large-scale studies have explored these associations longitudinally in urban minority cohorts or assessed links to broader measures of well-being such as educational attainment, occupation, and crime. Although adversity and resilience have long been of interest in developmental psychology, protective and promotive factors have been understudied in the ACE literature. This paper investigates the psychosocial processes through which ACEs contribute to outcomes, in addition to exploring ways to promote resilience to ACEs in vulnerable populations. Follow-up data were analyzed for 87% of the original 1,539 participants in the Chicago Longitudinal Study (N= 1,341), a prospective investigation of the impact of an Early Childhood Education program and early experiences on life-course well-being. Findings suggest that ACEs impact well-being in low-socioeconomic status participants above and beyond the effects of demographic risk and poverty, and point to possible mechanisms of transmission of ACE effects. Results also identify key areas across the ecological system that may promote resilience to ACEs, and speak to the need to continue to support underserved communities in active ways.
Archaeological Perspectives on Scott's Against the Grain: A Deep History of the Earliest States
Authors: Leppard Thomas P.
Published: October 2019

James C. Scott's Against the Grain has immense relevance for how archaeologists view the dynamics of early states and complex polities. In this volume, Scott—already established as a leading theorist of states and statecraft (e.g. Scott 1997; 2009)—brings his analytic power and capacity to turn a phrase to bear on the topic of the ‘earliest states’.
The Fragile State
Authors: Pollock Susan
Published: October 2019

In his most recent book, James Scott presents us with a ‘deep history’ of the alluvial lowlands of Mesopotamia, from early domestications in the Neolithic to the emergence and consolidation of early states. Although the focus lies on Mesopotamia in these periods, Scott delves into the beginnings of the human use of fire in the Palaeolithic and draws on comparative developments in Southeast Asia, Egypt, Greece, Rome and elsewhere. He poses large questions: Why did people move into densely packed villages—‘Neolithic multispecies resettlement camps’—accompanied by the plants and animals they domesticated, but also by an exponentially increased disease load and a substantial portion of drudgery? Why did states emerge when they did, despite the fact that the main ecological and demographic conditions were present millennia earlier? What accounts for the fragility of these early states, and why do our standard histories obscure that fact? Guiding themes are ecological and demographic, but also draw explicit attention to the unintended consequences of human actions. Indeed, reflections on the Anthropocene underpin the book's arguments, and, like many others who write on this topic, Scott is motivated by deep-seated concerns about the sorry ecological state of our contemporary world and connections to long-term effects of human activity.
No L1 privilege in talker adaptation
Authors: Bruggeman Laurence , Cutler Anne
Published: October 2019

As a rule, listening is easier in first (L1) than second languages (L2); difficult L2 listening can challenge even highly proficient users. We here examine one particular listening function, adaptation to novel talkers, in such a high-proficiency population: Dutch emigrants to Australia, predominantly using English outside the family, but all also retaining L1 proficiency. Using lexically-guided perceptual learning (Norris, McQueen & Cutler, 2003), we investigated these listeners’ adaptation to an ambiguous speech sound, in parallel experiments in both their L1 and their L2. A control study established that perceptual learning outcomes were unaffected by the procedural measures required for this double comparison. The emigrants showed equivalent proficiency in tests in both languages, robust perceptual adaptation in their L2, English, but no adaptation in L1. We propose that adaptation to novel talkers is a language-specific skill requiring regular novel practice; a limited set of known (family) interlocutors cannot meet this requirement.
The use of an invitational letter to increase the vaccine uptake of patients with coeliac disease
Authors: Moneim Joseph , Asad Hera , Butt Eman , Foridi Jamil Shah , Khan Yasmin , Patel Safwaan , Qureshi Jawad , Thakar Ravi
Published: October 2019

Aim:

We sought to establish the impact on vaccine uptake of sending out a single appointment letter inviting patients to attend a vaccine clinic.

Background:

Coeliac disease is associated with splenic dysfunction and so patients with coeliac disease are at a higher risk of overwhelming infection. Additional vaccinations are recommended for these individuals to provide additional protection against infection.

Methods:

We retrospectively identified 54 patients with diagnosed coeliac disease, and all vaccines previously received by these patients. By comparing this to the Green Book [Department of Health (2013) Immunisation of individuals with underlying medical conditions: the green book, chapter 7, London: Department of Health. Retrieved 26 February 2019 from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/566853/Green_Book_Chapter7.pdf], we determined the patients who were due vaccinations and the specific vaccines they were due. An invitation letter was then sent out to patients requiring further vaccinations and vaccine uptake for these patients was re-audited six months later.

Findings:

Our results show a mild increase in the total uptake of vaccines six months after the letter was sent out, from 38.6% to 49.2%.
Enrichment of Heavy Elements in Chemo-Dynamical Simulations of Dwarf Galaxies
Authors: Hirai Yutaka , Saitoh Takayuki R. , Wanajo Shinya , Fujii Michiko S.
Published: October 2019

Abundances of heavy elements in dwarf galaxies reflect their early evolutionary histories. Recent astronomical observations have shown that there are star-to-star scatters in the abundances of r-process elements and the decreasing trend of Zn toward higher metallicity in extremely metal-poor stars. However, the enrichment of heavy elements is not well understood. Here we performed a series of high-resolution N-body/smoothed particle hydrodynamics simulations of dwarf galaxies. We find that neutron star mergers can explain ratios of r-process elements to iron in dwarf galaxies due to their suppressed star formation rates. We also find that stars with [Zn/Fe] ≳ 0.5 reflect the ejecta from electron-capture supernovae. Inhomogeneity of the metals in the interstellar medium causes the scatters of heavy elements. We estimate that the timescale of metal mixing is ≲ 40 Myr using heavy element abundances in metal-poor stars.
The spatial segregation impact on the star formation histories of nearby dwarf spheroidal galaxies
Authors: Makarova Lidia , Makarov Dmitry
Published: October 2019

Using our HST/ACS observations of the recently found isolated dwarf spheroidal galaxies, we homogeneously measured their star formation histories (SFHs). We determined SF rate as a function of time, as well as age and metallicity of the stellar populations. All objects demonstrate complex SFH, with a significant portion of stars formed 10–13 Gyr ago. Nevertheless, stars of middle ages (1–8 Gyr) are presented. In order to understand how the SF parameters influence the evolution of dSphs, we also studied a sample of nearest dSphs in different environment: isolated (d < 2 Mpc); beyond the Local Group virial radius (but within the LG zero velocity sphere); and the satellites of M31 located within the virial zone (300 kpc). Using archival HST/ACS observations, we measured their SFHs. A comparative analysis of the parameters obtained give us a possibility to distinguish a possible effect of the spatial segregation on the dSphs evolution scenario.
Recovering the Star Formation History of IC1613 Dwarf Galaxy Using Evolved Stars
Authors: Hashemi Seyed Azim , Javadi Atefeh , van Loon Jacco Th.
Published: October 2019

Determining the star formation history (SFH) is key to understand the formation and evolution of dwarf galaxies. Recovering the SFH in resolved galaxies is mostly based on deep colour–magnitude diagrams (CMDs), which trace the signatures of multiple evolutionary stages of their stellar populations. In distant and unresolved galaxies, the integrated light of the galaxy can be decomposed, albeit made difficult by an age–metallicity degeneracy. Another solution to determine the SFH of resolved galaxies is based on evolved stars; these luminous stars are the most accessible tracers of the underlying stellar populations and can trace the entire SFH. Here we present a novel method based on long period variable (LPV) evolved asymptotic giant branch (AGB) stars and red supergiants (RSGs). We applied this method to reconstruct the SFH for IC1613, an irregular dwarf galaxy at a distance of 750 kpc. Our results provide an independent confirmation that no major episode of star formation occurred in IC1613 over the past 5 Gyr.
A New Reservoir of Dwarf Galaxy Candidates in the Centaurus A Group
Authors: Taylor Matthew A. , Eigenthaler Paul , Puzia Thomas H. , Muñoz Roberto P. , Ribbeck Karen X. , Zhang Hong-Xin , Ordenes-Briceño Yasna , Bovill Mia Sauda
Published: October 2019

We have searched optical u′g′r′i′z′ imaging of 22 deg2 centred on the nearby giant elliptical galaxy NGC 5128 for new dwarf galaxies in the Centaurus A group. We report 45 promising new candidates, which are broadly consistent with the properties of nearby dwarf spheroidal galaxies and extend the size-luminosity relation toward fainter total luminosities and smaller sizes for known dwarf galaxies outside the Local Group (LG). Altogether, these new results show NGC 5128 to be the host of a large reservoir of low-mass dwarf galaxies that is at least as rich as that of the LG and is ripe for detailed follow-up observations.
Uncovering dwarf elliptical evolution through spatially resolved spectroscopy
Authors: Penny Samantha J. ,   the MaNGA collaboration
Published: October 2019

Using spatially resolved spectroscopy from the SDSS-IV Mapping Nearby Galaxies at APO (MaNGA) survey, we identify 69 dwarf elliptical (dE) galaxies in the nearby Universe fainter than Mr = −19 (MB = −18), selected independently of morphology and environment. The majority exhibit coherent rotation in their stellar kinematics, consistent with an origin as morphologically transformed disk galaxies. Six galaxies in this dE sample appear to host Active Galactic Nuclei (AGN) that are likely preventing current star formation through maintenance mode feedback. The ionised gas component of these dEs is typically kinematically offset from the stellar component, suggesting the gas is either recently accreted or outflowing. We therefore demonstrate the potential of IFU spectroscopy for understanding the physical properties of dwarf galaxies in detail.
VMC proper motions of the Magellanic Bridge
Authors: Schmidt Thomas , Cioni Maria-Rosa , Niederhofer Florian , Diaz Jonathan , Matijevic Gal
Published: October 2019

Dwarf galaxies enable us to study early phases of galaxy evolution and are key to many open questions about the hierarchical structure of the Universe. The Large and Small Magellanic Cloud (LMC and SMC) are the most luminous dwarf galaxy satellites of the Milky Way (MW). They are most likely gravitationally bound to each other, and their last interaction occurred about 200 Myr ago. Also, they are in an early phase of minor merging with the MW and will impact the Galactic structure in the future because of their relatively large mass. However, there are still major uncertainties regarding their origin and their interactions with one another and with the Milky Way. We cross-correlated the VMC and Gaia DR2 data to select a sample of stars that likely belong to the Magellanic Bridge, a feature formed of gas and stars which is connecting the LMC and the SMC. We removed potential MW foregound stars using a combination of parallax and colour-magnitude criteria and calculated the proper motions of the Bridge member stars. Our analysis supports a motion of star towards the LMC, which was found to be in good agreement with a dynamical simulation, of the SMC being stripped by the LMC.
Star formation in dwarf galaxies in the ELAIS N1 field
Authors: Kovács Tímea O. , Burgarella Denis , Tóth L. Viktor
Published: October 2019

We estimated several parameters of dwarf galaxies, including their star formation rate and dust mass, and compared them with galaxies with larger stellar masses.

We have chosen dwarf galaxies in the ELAIS N1 field, and fitted their Spectral Energy Distributions (SED). We used data from the new Herschel SPIRE and PACS Point Source catalogues to constrain the infrared radiation. Data available in VIZIER from multiple surveys have also been used.

We determined that the star formation rate (SFR), M* and Mdust is one order of magnitude lower in dwarf galaxies compared to galaxies with larger stellar masses. However, the starburtiness was higher in the dwarf galaxies. They also had lower redshifts than normal galaxies, so we compared them to a subsample of normal galaxies with lower redshifts. The dust masses and SFRs of the dwarf galaxies were slightly lower, but their starburtiness was higher.
Star clusters and young populations in the dwarf irregular galaxy Leo A
Authors: Stonkutė Rima , Čeponis Marius , Leščinskaitė Alina , Vansevičius Vladas
Published: October 2019

We have studied young stellar populations and star clusters in the dwarf irregular galaxy Leo A using multicolor (B, V, R, I, Hα) photometry data obtained with the Subaru Suprime-Cam and two-color photometry results measured on archival HST/ACS F475W & F814W frames. The analysis of the main sequence (MS) and blue supergiant (BSG – “blue loop”) stars enabled us to study the star formation history in the Leo A galaxy during the last ~200 Myr. Also, we have discovered 5 low-mass (≲ 400 M⊙) star clusters within the ACS field. This finding, taking into account a low metallicity environment and a yet-undetected molecular gas in Leo A, constrains star formation efficiency estimates and scenarios. Inside the well known “hole” in the H i column density map (Hunter et al. 2012) we found a shock front (prominent in Hα), implying an unseen progenitor and reminding the “hole” problems widely discussed by Warren et al. (2011).
OGLE-ing the Magellanic System: Three-Dimensional Structure
Authors: Jacyszyn-Dobrzeniecka Anna M. ,   the OGLE Team
Published: October 2019

We present a three-dimensional structure of the Magellanic System using over 9 000 Classical Cepheids and almost 23 000 RR Lyrae stars from the OGLE Collection of Variable Stars. Given the vast coverage of the OGLE-IV data and very high completeness of the sample, we were able to study the Magellanic System in great details.

We very carefully studied the distribution of both types of pulsators in the Magellanic Bridge area. We show that there is no evident physical connection between the Clouds in RR Lyrae stars distribution. We only see the two extended structures overlapping. There are few classical Cepheids in the Magellanic Bridge area that seem to form a genuine connection between the Clouds. Their on-sky locations match very well young stars and neutral hydrogen density contours. We also present three-dimensional distribution of classical pulsators in both Magellanic Clouds.
The dwarf galaxy population as revealed by ALFALFA
Authors: Adams Elizabeth A. K. , Ball Catherine , Cannon John M. , Haynes Martha P. , Hirschauer Alec , Giovanelli Riccardo , Janesh William , Janowiecki Steven , Leisman Luke , McQuinn Kristen B. W. , Rhode Katherine L. , Salzer John J.
Published: October 2019

The combination of sensitivity and large sky coverage of the ALFALFA HI survey has enabled the detection of difficult to observe low mass galaxies in large numbers, including dwarf galaxies overlooked in optical surveys. Three different, but connected, studies of dwarf galaxies from the ALFALFA survey are of particular interest: SHIELD (Survey of HI in Extremely Low-mass Dwarfs), candidate gas-rich ultra-faint dwarf galaxies, and the (Almost) Dark population. SHIELD is a systematic multiwavelength study of all dwarf galaxies from ALFALFA with MHI < 107.2M⊙ and clear optical counterparts. Candidate gas-rich ultra-faint dwarf galaxies extend the dwarf galaxy population to even lower masses. These galaxies are identified as isolated HI clouds with no discernible optical counterpart but subsequent observations reveal that some are extremely faint, gas-dominated galaxies. Leo P, discovered first as an HI detection, and then found to be an actively star-forming galaxy, bridges the gap between these candidate galaxies and the SHIELD sample. The (Almost) Dark sample consists of galaxies whose optical counterparts are overlooked in current optical surveys but which are clear detections in ALFALFA. This sample includes field gas-rich ultra-diffuse galaxies. Coma P, with a peak surface brightness of only ∼26.4 mag arcsec−2 in g’, demonstrates the sort of extreme low surface brightness galaxy that can be discovered in an HI survey.
Massive star evolution: feedbacks in low-Z environment
Authors: Ekström Sylvia , Meynet Georges , Georgy Cyril , Groh José , Choplin Arthur , Song Hanfeng
Published: October 2019

Massive stars are the drivers of the chemical evolution of dwarf galaxies. We review here the basics of massive star evolution and the specificities of stellar evolution in low-Z environment. We discuss nucleosynthetic aspects and what observations could constrain our view on the first generations of stars.
The Future of Dwarf Galaxy Research: What Simulations will Predict?
Authors: Sales Laura V.
Published: October 2019

We present a summary of the predictions from numerical simulations to our understanding of dwarf galaxies. It centers the discussion around the Λ Cold Dark Matter scenario (ΛCDM) but discusses also implications for alternative dark matter models. Four key predictions are identified: the abundance of dwarf galaxies, their dark matter content, their relation with environment and the existence of dwarf satellites orbiting dwarf field galaxies. We discuss tensions with observations and identify the most exciting predictions expected from simulations in the future, including i) the existence of “dark galaxies” (dark matter halos without stars), ii) the ability to resolve the structure (size, morphology, dark matter distribution) in dwarfs and iii) the number of ultra-faint satellites around dwarf galaxies. All of these predictions shall inform future observations, not only the faintest galaxies to be discovered within the Local Volume but also distant dwarfs driving galaxy formation in the early universe.
Mass Distribution in Stellar Structures of Local Dwarfs
Authors: Menéndez-Delmestre Karín , Coelho Yasmin , Grossi Marco , Sheth Kartik
Published: October 2019

We study the distribution of mid-infrared light in stellar structures in a large sample (∽ 400) of low-mass (Mstellar <109 MSun) galaxies. Our sample is selected from the Spitzer Survey of Stellar Structures in Galaxies (S4G), which entails deep imaging of nearby galaxies with the IRAC instrument at 3.6/4.5 μ m. Based on the 2D decomposition of the 3.6μ m images, we find that the majority (∽65%) of galaxies in our sample is well-fit by a single disk profile. The rest of the sample is more adequately fit by a disk and an additional component (e.g., bar, nucleus, bulge, second disk component). Bars are present in ∽11% of the sample, marking a sharp drop in the bar fraction compared to that found for more massive galaxies. The typical contribution of bars to the 3.6 μ m light in dwarfs is ∽1-2%, lower than that found in more massive galaxies. These results bring a number of issues into question: why do low-mass galaxies have such low bar fraction? does the bar instability act differently in low-mass galaxies such that a smaller proportion of stellar mass is typically involved in the bar structure? Is the fact that dwarfs are more dark matter dominated playing a role?
Cultural heritage and memory after ethnic cleansing in post-conflict Bosnia-Herzegovina
Authors: Walasek Helen
Published: October 2019

This article draws on my book Bosnia and the Destruction of Cultural Heritage,1 which incorporates ground-breaking fieldwork in Bosnia-Herzegovina and extensive research, and on my subsequent research and fieldwork in the post-conflict country. In the article, I explore the meaning that restoration and reconstruction of cultural heritage intentionally destroyed during conflict can have, particularly to the forcibly displaced. With the protection of cultural heritage increasingly being treated as an important human right and with the impact that forcible displacement during armed conflict has on cultural identity now in the spotlight, the importance of cultural heritage for those ethnically cleansed in Bosnia-Herzegovina during the 1992–95 war (both those who returned and those who did not) has relevance for considerations of contemporary post-conflict populations.