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Youth in developing countries are faced with high unemployment rates, even when they possess higher education degrees. In the developing world, small business and entrepreneurial ventures constitute the main drivers of economic development and offer employment opportunities for youth. Nevertheless, when faced with a career decision after their studies, youth seem to prefer careers in established companies over start-ups. As a consequence, start-ups find it more difficult to find and hire the right employees although they are available in the market. This study aims at examining the factors behind youth career decisions to work for a start-up company and provides suggestions for both research and practice. By relying on both entrepreneurship and career decision-making literature, we developed a theoretical model that includes background factors and individual characteristics. Results from a survey on youth graduates from Jordan show that a high school education fostered critical thinking and international exposure, the participation in entrepreneurial events and creativity, which predicted the willingness to work for a start-up.

Purpose The purpose of this paper is to provide a systematic review of the literature addressing internationalisation of firms from Central and Eastern Europe (CEE). Design/methodology/approach This paper presents an inter-disciplinary systematic review of literature about the internationalisation of firms from CEE. Findings Three different clusters of research were identified. In the “Internationalisation Processes” cluster, containing many comparative studies, the focus is on specific approaches adopted by local firms in the process of internationalisation. One of the leitmotivs is the dichotomy between hostile home-country factors that create the need for internationalisation and market-seeking motives that guide the search for international expansion. The “Internationalisation Variables” cluster aims to explain the reasons of success or failure of internationalisation processes and strategies; this cluster focuses on possible facilitating or hindering aspects experienced by CEE firms and one often-cited element is the firm’s network. Finally, the “Internationalisation Outcomes” cluster assumes a reverse approach when compared to the other two clusters. Indeed, the internationalisation phenomenon can also be studied in terms of its effect on the firm; the elements sought in these types of studies are both potential benefits and risks associated with internationalisation in CEE countries. The latter category in particular gives rise to interesting questions for future research. Originality/value Given that large, developed economies tend to receive much academic interest and that smaller transitional economies are not always adequately represented in the scientific discussion, this paper contributes to the literature on internationalisation.

The general aim of this paper is to propose a conceptualisation and an operational measure for affective investment and symbolic motives at work. The work-symbolic motive scale (Work-SMS) score provides a general measure of affective investment, conceived as an endowing process of gratifying qualities to the work context, sustained by the four symbolic motives of achievement, affiliation, power and autonomy. Two studies were conducted (N = 632) suggesting a final 12-item scale with a second-order factor model. Evidence for construct and convergent validity was collected and overall good internal consistency, test-retest reliability estimates and predictive validity after one month were verified.

The purpose of this paper is to offer a complete overview of the International Journal of Entrepreneurship and Small Business (IJESB). By using Scopus and Google Scholar databases to analyse the most cited papers and the most prolific authors, the article provides a map of the knowledge produced and disseminated by IJESB taking 809 papers into consideration. Furthermore, through keywords correlation analysis, the authors highlight the most relevant topics and the relative importance in terms of number of citations, by analysing how they are clustered together. Finally, the paper shows the past, the present, and the future trends in IJESB through a representation of the average emergence date of each keyword.

This article offers a complete overview of the World Review of Entrepreneurship, Management and Sustainable Development (WREMSD) from 2005 to 2015. The article employs an innovative mixed method, based on a bibliometric analysis of the journal and an in-depth interview with the editor Prof. Leo Paul Dana about the journal, his academic and personal life. By using SCOPUS data, the analysis maps the knowledge produced and disseminated by the journal revealing the most cited papers and most prolific authors. By also presenting a keywords correlation analysis, the paper shows the main streams of research covered by the journal and their evolution. Although the objective of mapping the knowledge in WREMSD, this paper offers an example of application of a mixed method to bibliometric studies and methodological implications are discussed.

This paper presents an analysis of the management control systems, introducing a useful instrument to summarise performance achieved from the organisational network model, with a view to establishing the competitive advantage and the creation of value on the long-term. The research approach is based on the qualitative methodology. The research is developed according to the study of national and international literature. The contribution proposes theoretical proof to support the new management control instrument for contractual networks: the business network scorecard. The approach adopted for the development of the network management control instrument (business network scorecard) refers to the principles of the balanced scorecard and value creation. So, the reporting system of network performance aims at highlighting the joint results of an economic-financial nature as well as those of an intangible nature. Through a logic of interception of large aggregates, the results achieved by the network are proposed through the matrix of network objectives, the multidimensional network model, including perspective indicators, four indicators of synergy and the comparison report of joint and individual performance of companies.

This article describes the development and initial validation of the Collaboration and Support for Inclusive Teaching, a measure of perceived support in special education teachers regarding the degree of collaboration with regular teachers for inclusive practice at school. The scale was validated on a sample of 276 special education teachers coming from lower and higher secondary schools by using both exploratory factor analysis and confirmatory factor analysis. The resulting 12-item scale was characterized by a one-factor solution explaining 46.59% of data variance and had good internal consistency with a Cronbach’s alpha of .876. Associations with other measures supported convergent and divergent validity of the scale. The usefulness of this scale is highlighted with regard to the improvement of cooperative teaching supporting school inclusion, as well as to the prevention of the risk of burnout in special education teachers.

The purpose of this paper is the investigation of the relationship between information technology and value creation. In doing so, the paper presents a conceptual framework based on the Val IT model. This framework can assist companies in the selection, implementation and optimisation of IT investments to create long-term value. The paper is based on a qualitative approach with the inclusion of a single-method approach. Research is developed according to the study of national and international literature. Following an initial analysis of existing literature on the evaluation of company investments, research has been conducted through the Val IT method to assess these intangible assets. The sources of research are secondary in nature (documents, reports, newspaper articles, papers and scientific books). This methodology emphasises the connection between the modern services created in the knowledge economy and the application of new technologies, especially in the field of Information Technology. Val IT is a governance framework for creating business value from IT investments. It allows companies to increase the possibility of selecting investments with a high potential of value creation, as well as with a greater possibility of success in executing, creating, strengthening and using these services.

Euthanasia has received increasing attention in both academic and public debates as one of the most controversial issues. However, the contribution of psychology-related themes to the topic has had little role on these ongoing debates. The aim of the present study is twofold: (1) to explore the main themes relating to euthanasia as provided by psychology-related research; (2) to analyze the temporal trends of psychology-related research on euthanasia over the last decades. A comprehensive search of academic literature was conducted on PsychINFO database. A qualitative software-based thematic analysis was carried out on 602 journal abstracts published from 1935 to 2014. This study highlighted four different thematic areas which characterized the scientific discourse on euthanasia: (1) moral values, in terms of religious, philosophical, and social implications concerning the individual's decision to die; (2) professional ethics, in terms of health and social workers' legal responsibility in death assistance; (3) end-of-life care, with regard to medical options provided to support individuals nearing death; and (4) patient's right to healthcare, in terms of access to palliative care and better quality of dying. Euthanasia discourse over the last decades seems to be overall characterized by two main dimensions: (1) the increasing trend of social legitimacy and acceptability of euthanasia over time, which moved from ethical to healthcare issues; and (2) the curvilinear temporal trend about the request/provision process in euthanasia, which moved from patient's decision for ending life (mainly characterizing the most past and recent research) to the role of health professionals (with a peak in the 1990s). The results suggest palliative care as a potential future research area which can provide healthcare providers with skills to 'connect' with patients, understand patients' hidden agendas, and grant a good quality of life and dying process.

El estudio explora simbolizaciones afectivas que estructuran las relaciones de los estudiantes en la experiencia de practicas. Con el fin de detectar las principales representaciones de 213 estudiantes universitarios de Psicologia Clinica sobre su papel como pasantes, las actividades profesionales, las funciones que tienen que cumplir y la integracion entre la educacion universitaria y los contextos reales de trabajo, se aplico un cuestionario para el analisis de la dinamica y las expectativas generadas por la imaginacion de su futuro. A traves de tecnicas estadisticas multivariantes, analisis de correspondencia multiple (ACM) y analisis de conglomerados (AC), se identificaron cuatro grupos. Los resultados fueron los siguientes: falta de poder en general, desconfianza y desmotivacion hacia practicas (17.7%); afiliacion a organismos de alojamiento con el fin de obtener el aumento de la aceptacion y poder (33.8%); alto pragmatismo, orientacion a la tarea y el cumplimiento de lo que los cuerpos de alojamiento proponen (30.8%) y demanda de reconocimiento sin ninguna negociacion (17.7%). No se detecto ninguna relacion entre los clusteres y algunas variables ilustrativas relacionadas con el sexo y los indicadores de exito academico, los problemas y la participacion. Estas agrupaciones se conciben como dimensiones latentes que explican el 57.9% de la varianza total y se refieren a: la desconexion/implicacion hacia la experiencia de practicas; impotencia/omnipotencia sobre el uso de las competencias y la devaluacion/idealizacion del cuerpo de alojamiento en relacion con la formacion universitaria. Surgen dos cuestiones fundamentales: la brecha entre la formacion universitaria y las practicas, la segunda se ocupa de la discontinuidad entre las practicas y el mercado laboral. Se discuten algunas reflexiones e implicaciones para la practica.

This study explored the different conceptualizations of envy in scholarly psychological publications, in terms of cultural models shared in scientific community, which contribute to the social construction of this emotional experience. A text analysis based on social representation theory was conducted on a corpus of 450 abstracts consulted in PsycINFO Database and allowed the detection of five main representations of envy in psychological literature as primary destructiveness, subjective unfairness, narcissistic defense, competitive tendency and malicious joy. They are conceived along four latent dimensions respectively, regarding source (internal/external agency), function (self-development/other-derogation), self-awareness (low/high control) and legitimacy (moral/amoral values) of envy. The results highlight the psychoanalytic and psychosocial perspective about envy and its paradoxical function for social order.Key wo rd s: envy, emotion, social representa tion theory, text analysis, scientific commu nicationSOCIALNE KONSTRUOVANIE ZAVISTI VO VEDECKEJ KOMUNITE: ANALÝZA VEDECKÝCH PSYCHOLOGICKÝCH PUBLIKACIIA. C a p u t oSu hrn: Stu dia sk uma rozdiela ne konceptualizacie zavisti vo vedeckých psychologických publikaciach, a to v zmysle ku ltu rnych modelov zdiela ných vo vedeck ej k omu nite, k tore prispievaju k socialnemu k onstru ova niu tohto emocneho zazitku. Analyzovali sa a bstra k ty 4 5 0 textov z databazy PsycINFO na za k la de teorie socialnej reprezentacie kde sme odhalili pa t hlavných reprezentacii zavisti, ak o su primarna destruktivita, subjektivna neferovost, narcisticka obrana, su tazivost a skodora dost. Tieto su zvazovane vzhladom na styri latentne dimenzie, a to zdroj (interný/externý a gent), fu nk cia (sebarozvijanie/znevazovanie ostatných), seba u vedomova nie (nizk a/vysok a k ontrola ) a legitimita (moralne/amoralne hodnoty) zavisti. Výsledk y u k a zu ju psychoanalytick u a psychosocialnu perspektivu zavisti a jej paradoxnu fu nk ciu v socia lnom poriadku.Envy is a traditional concern of social sci- ence (Silver, Sabini, 1978). However, "de- spite the many plausible claims for the pow- erful influence of envy in everyday social interactions and for its role in shaping so- cietal norms, psychological research on envy is only in its early stages" (Smith, Kim, 2007, p. 46). Envy is generally defined as a negative emotion that arises when a per- son lacks another 's superior quality, achievement, or possession and either de- sires it or wishes that the other lacked it (Parrott, Smith, 1993). As well as shame, guilt or jealousy, envy is considered as a potentially problematic social emotion for both individual adjustment and interpersonal behavior (Tangney, Salovey, 1999). Indeed, it may lead to sacrifice one's own outcomes to diminish a competitor 's relative advan- tage (Berke, 1988; Parks, Rumble, Posey, 2002; Thernstrom, 1998; Zizzo, Oswald, 2001), criminal behavior (Schoeck, 1969) or ingroup biases (Glick, 2002; White et al., 2006). However, despite the fact that envy refers to a destructive and antisocial atti- tude, stigmatized in all cultures as a deadly sin, such a widespread feeling is also rec- ognized as necessary to the existence of society, to its development and to the es- tablishment of social relations (de Gaulejac, 1997). Indeed, according to an evolution- ary perspective, envy may serve an impor- tant function in social competitions for ac- cess to resources that affect fitness (Alicke, Zell, 2008) and, although it often results in subjective distress, this type of emotional distress functions to motivate adaptive ac- tion (Buss, 1989; Hill, Buss, 2008).In this regard, psychological literature highlights the complex nature of envy, de- picted as an emotion, a reason for action, or a characterization of an action as a trans- gression of a moral order (Sabini, Silver, 1986), which can affect everyday life relating the concept to the social arena and social action (Clarke, 2004). …

Background: Italy is a country showing low math achievement, especially in the Southern regions. Moreover, national student assessments are recent and rigorous policy evaluation is lacking. This study presents the results of one of the first randomized controlled trials implemented in Italian schools in order to measure the effects of a professional development (PD) program for teachers on student math achievement. The program was already at scale when it was being evaluated. Objective: Assessing the effects of a PD program for math teachers on their students’ achievement and making suggestions for future policy evaluations. Design: A large-scale clustered randomized control trial has been conducted. It involves 175 lower secondary schools (sixth - eighth grade) in four among the Italian lowest performing regions. Alongside national standard math assessments, the project collected a wide amount of information. Subjects: Math in lower secondary schools. Measures: Math achievement as measured by standardized tests provided by the National Education Assessment Institute (Istituto Nazionale per la Valutazione del Sistema di Istruzione e Formazione); teacher and student practices and attitudes collected through questionnaires. Results: Findings suggest that the program had no significant impact on math scores during the first year (when the program was held). Nonetheless some heterogeneity was detected, as the treatment does seem “to work” with middle-aged teachers. Moreover, effects on teaching practice and student attitudes appear. Conclusion: Some effects attributable to the intervention have been detected. Moreover, this project shows that a rigorous approach to evaluation is feasible also in a context lacking attention towards evidence-based policies, such the Italian school system.

The manifold recent reform acts of bankruptcy law in Italy are more clearly oriented towards preserving the going concern of firms, besides granting the par condicio among creditors. Companies have broader opportunities to plan the restructuring, with the constraint of making it advantageous for creditors. In this context, the role of the independent attester is of prime and increasing importance to assure that the restructuring plan pursues creditors’ and stakeholders’ interests. This paper presents insights from both the authors’ practical experiences and the review of the literature. It is addressed to managers, practitioners and scholars, interested in understanding turnarounds in the Italian context. The specificities of the attester’s activity in analysing the data truthfulness and the feasibility of the recovery plan are deeply analysed. The article has a qualitative value and is based on a normative methodological approach, which links bankruptcy law with crisis management and auditing. The result is a systematic model of the attestation process.

This paper aims at answering the following research questions: How does the strategic positioning of a firm impact its negotiation practices? And, how do negotiation skills, behaviors and abilities impact the strategy of a firm? Such questions have been overlooked by the two relevant bodies of literature: strategy and negotiation. By taking a cross-field approach, we combine concepts from both literatures in a theoretical framework based on the integrated approach to negotiation and dynamic capabilities. By presenting and analyzing the case of Ryanair, in terms of its strategy and its negotiation approach, we argue that a negotiation capability of the firm plays a major role for competitive advantage. Our findings show how Ryanair employs an idiosyncratic approach to all its negotiations. Such approach is intertwined with its strategy and the consequent strategic positioning in the market. We conclude the paper with implications for both practice and research; particularly we call for an integrated study of negotiation and strategy to better understand the strategy making process and its foundations for success.

This study aims at inquiring entrepreneurship in its relational dimension. In particular the paper analyses this concern with a contextualisation in the Florence-Prato district. Such an environment offers similar entrepreneurial resources as pre-conditions, the so-called genius loci. However, firms evolve differently due to their approach to opportunities, basing on network configurations. We used a qualitative longitudinal case studies based on a sample of eight firms belonging to the textile district, following their histories of innovation along a period of five years. A strong tie and weak tie approach is adopted to interpret the findings of a field research. Importance of strong ties which are strictly connect with the territory. Weak ties or serendipity events are mostly recalled in the discovering phase of a radical innovation. After an initial phase, strong ties come back into play in the implementation phase, to find means of practical feasibility. However, entrepreneurs differ: in some cases have assumed a causal logic, otherwise, entrepreneurs instead starting from a contingent situation have developed new scenarios for their firm.

The Italian Law Decree of June 22, 2012, N. 83 (converted into law with amendments by Law of 7 August 2012, N. 134), the so–called Development Decree (or Decreto Sviluppo in Italian), with the introduction of Article 32 intervened in order to overcome the difficulties of access to credit for businesses, including small and medium–sized enterprises (SMEs), increasing the possibility of direct access to the capital markets through finance bills that now will have a duration of 36 months. The objective is to align the financial opportunities of the national system with those offered by the most advanced industrial and financial systems in Europe, but also to counter the introduction of Basel III which will lead to a rationing of credit to the economy. In addition to expanding the possibilities of exploiting such a financial instrument that is not yet widespread, the so–called Development Decree allows for issuance in 'paperless' form to promote the circulation and exchange between operators, and changes the tax regime by extending the one applied to bonds which is more favourable.

Although personality has been one of the most-studied factors in management and decision-making research, this stream of research has generated inconsistent support for the relationship between personality traits and individuals' susceptibility to heuristics, and therefore biased judgment. The aim of this study is to investigate how the provision of correct information and individual difference factors influence susceptibility to anchoring effect. To test this hypothesis, individual levels of the personality traits have been measured. Then, participants were provided with an anchoring task involving the Taj Mahal either providing them correct information before the experiment or not. Providing individuals with the correct information limited susceptibility to the irrelevant anchor; even if only 33% of those exactly recalled it when providing the estimate. High values in agreeableness and openness to experience were found to be related with reduced susceptibility to the anchor.

The article is aimed at providing a different perspective on third parties and tries to systematise our understanding about multilateral negotiations and integrative agreements. The key concepts investigated were the connection between the third who joins and the negotiation process, outcome and effectiveness, within business contexts. Research was guided using the so-called negotiation theory as a framework. Insights and documentation that previous research was fragmented are provided. Even if contemporary approaches integrated third party intervention in a broad understanding of causes and dynamics of conflicts, by definition third parties do not have a strong partisan position on the substantive issues in dispute. They seem to have been considered mainly as external entities, not fully interested and involved in the negotiation, thus with a lack of real interest for the implementation of the final agreement.

This article aims at discussing how the literature about the real estate management has been evolving over time. To date, both scholars and practitioners substantially converge in maintaining that, if properly performed, that bundle of operations known as corporate real estate management (CREM) can positively affect the overall corporate profitability. Nonetheless, this assumption seems to need more empirical evidence if it wants to be consolidated. Furthermore, although CREM is still the most addressed area of inquiry, over the last years, the attention to related topics, such as the managing of construction projects, has been increasing also. We believe that, in the future, the attention to these topics will increase proportionally to the growing relevance of environmental and social sustainability issues.

Car sharing, an innovative mobility service complementary to the local public transport, helps, through the sharing of a fleet of cars among users, to reduce individual and social costs of private transport, at the same time avoiding the rigidity of traditional public transport as well. This paper intends to explain the nature and development of car sharing through three key directions: 1 the critical analysis of literature, through which it was possible to identify how car sharing is still not very extensive 2 the overview of the Italian context 3 the analysis of car sharing service in detail, through a case study of the experience in the city of Genoa. The purpose of this paper is to contribute to the few existing studies on car sharing in an effort to increase academic and managerial attention on this sustainable mobility service.

Little research has been conducted regarding serial entrepreneurship compared to entrepreneurship research more broadly, despite research that suggests that asmany as 50% of all entrepreneurs are serial entrepreneurs. Entrepreneurship research shows that most new ventures fail, yet serial entrepreneurs continually exit previous ventures and start new ones. Our study explores 118 scholarly articles indexed in Web of Science and Scopus databases on serial entrepreneurship through multiple correspondence analysis. Through our analysis, we identify key areas for future research, explore and consolidate the theoretical foundations used, and provide a review of academic literature for future researchers to utilize. Our perceptual map has identified four key research areas that researchers should focus upon: heuristics in entrepreneurship, entrepreneurial capabilities, the entrepreneurial ecosystem, and technological development and resources.

Motivated by electromagnetic-field confinement due to plasma near accreting black holes, we continue our exploration of the linear dynamics of an electromagnetic field propagating in curved spacetime in the presence of plasma by including three effects that were neglected in our previous analysis: collisions in the plasma, thermal corrections, and the angular momentum of the background black-hole spacetime. We show that: (i) the plasma-driven long-lived modes survive in a collisional plasma except when the collision timescale is unrealistically small; (ii) thermal effects, which might be relevant for accretion disks around black holes, do not affect the axial long-lived modes; (iii) in the case of a spinning black hole the plasma-driven modes become superradiantly unstable at the linear level; (iv) the polar sector in the small-frequency regime admits a reflection point due to the resonant properties of the plasma. Dissipative effects such as absorption, formation of plasma waves, and nonlinear dynamics play a crucial role in the vicinity of this resonant point., Comment: 14 pages, 5 figures

We study the response of a He-4 detector to the interaction of sub-GeV dark matter using an effective field theory for the superfluid. We compute the lifetime of the phonon, which agrees with what known from standard techniques, hence providing an important check of the effective field theory. We then study the process of emission of two phonons, and show how its rate is much more suppressed than the phase space expectations; this is a consequence of the conservation of the current associated to the superfluid symmetries., Comment: Talk presented at the TAUP 2019 conference; 4 pages, 2 figures

We derive novel constraints on millicharged dark matter and ultralight axion-like particles using pulsar timing and fast radio burst observations. Millicharged dark matter affects the dispersion measure of the time of arrival of radio pulses in a way analogous to free electrons. Light pseudo-scalar dark matter, on the other hand, causes the polarization angle of radio signals to oscillate. We show that current and future data can set strong constraints in both cases. For dark matter particles of charge $\epsilon e$, these constraints are ${\epsilon}/{m_{\rm milli}} \lesssim 10^{-8}{\rm eV}^{-1}$, for masses $m_{\rm milli}\gtrsim 10^{-6}\,$eV. For axion-like particles, the analysis of signals from pulsars yields constraints in the axial coupling of the order of $g/m_a\lesssim 10^{-13} {\rm GeV}^{-1}/(10^{-22}{\rm eV})$. Both bounds scale as $(\rho/\rho_{\rm dm})^{1/2}$ if the energy density $\rho$ of the components is a fraction of the total dark matter energy density $\rho_{\rm dm}$. We do a detailed study of both effects using data from two samples of pulsars in the galaxy and in globular clusters, as well as data from FRB 121102 and PSR J0437$-$4715. We show that in both cases actual pulsar data constrain a new region of the parameter space for these models, and will improve with future pulsar-timing observations., Comment: 6 pages, 2 figures; v3: to appear on PRD

The flux of high-energy astrophysical $\gamma$ rays is attenuated by the production of electron-positron pairs from scattering off of extragalactic background light (EBL). We use the most up-to-date information on galaxy populations to compute their contributions to the pair-production optical depth. We find that the optical depth inferred from $\gamma$-ray measurements exceeds that expected from galaxies at the $\sim2\sigma$ level. If the excess is modeled as a frequency-independent re-scaling of the standard contribution to the EBL from galaxies, then an excess (an overall $14-30\%$ increase of the EBL) over the null hypothesis of no excess at the $2.7\sigma$ level. If the frequency dependence of the excess is instead modeled as a two-photon decay of a dark-matter axion, then the excess is favored over the null hypothesis at the $2.1\sigma$ confidence level. While we find no evidence for a dark-matter signal, the analysis sets the strongest current bounds on the photon-axion coupling over the $8-25$ eV mass range. This work highlights the sensitivity of $\gamma$-ray optical depth measurements to ALPs, which is expected to improve with new observatories and better EBL determinations from future observations., Comment: 5 pages + 3 pages of appendix (+5 pages of references), 6 figures. Discussions and figures slightly modified, an appendix to discuss the likelihood added, conclusions unchanged. Matches the published version

The post-inflationary breaking of Peccei-Quinn (PQ) symmetry can lead to the cosmic domain wall catastrophe. In this Letter we show how to avoid domain walls implementing the Instanton Interference Effect (IIE) with a new interaction which itself breaks PQ symmetry and confines at an energy scale smaller than $\Lambda_{QCD}$. We give a general description of the mechanism and consider its cosmological implications and constraints within a minimal model. Contrary to other mechanisms we do not require an inverse phase transition neither fine-tuned bias terms. Incidentally, the mechanism leads to the introduction of new self-interacting dark matter candidates and the possibility of producing gravitational waves in the frequency range of SKA. Unless a fine-tuned hidden sector is introduced, the mechanism predicts a QCD axion in the mass range $1\text{ meV}-15\text{ meV}$., Comment: 12 pages, 4 figures; matches published version

Symbioses between eukaryotes and nitrogen (N2)-fixing cyanobacteria (or diazotrophs) are quite common in the plankton community. A few genera of diatoms (Bacillariophyceae) such as Rhizosolenia, Hemiaulus and Chaetoceros are well known to form symbioses with the heterocystous diazotrophic cyanobacteria Richelia intracellularis and Calothrix rhizosoleniae. The latter are also called diatom-diazotroph associations, or DDAs. Up to now, the prokaryotic partners have been morphologically and genetically characterized, and the phylogenetic reconstruction of the well conserved nifH gene (encodes for the nitrogenase enzyme) placed the symbionts in 3 clusters based on their host-specificity, i.e. het-1 (Rhizosolenia-R. intracellularis), het-2 (Hemiaulus-R. intracellularis), and het-3 (Chaetoceros-C- rhizosoleniae). Conversely, the diatom-hosts, major representative of the phytoplankton community and crucial contributors to the carbon (C) biogeochemical cycle, have been understudied. The first aim of this thesis was to genetically and morphologically characterize the diatom-hosts, and to reconstruct the evolutionary background of the partnerships and the symbiont integration in the host. The molecular-clock analysis reconstruction showed the ancient appearance of the DDAs, and the traits characterizing the ancestors. In addition, diatom-hosts bearing internal symbionts (with more eroded draft genomes) appeared earlier than diatom-hosts with external symbionts. Finally a blast survey highlighted a broader distribution of the DDAs than expected. The second aim of this thesis was to compare genetic and physiological characteristics of the DDAs symbionts with the other eukaryote-diazotroph symbiosis, i.e. prymnesiophyte-UCYN-A (or Candidatus Atelocyanobacterium thalassa). The genome comparison highlighted more genes for transporters in het-3 (external symbiont) and in the UCYN-A based symbiosis, suggesting that symbiont location might be relevant also for metabolic exchanges and interactions with the host and/or environment. Moreover, a summary of methodological biases that brought to an underestimation of the DDAs is reported. The third aim of this thesis was to determine the distribution of the DDAs in the South Pacific Ocean using a quantitative polymerase chain reaction (qPCR) approach and to outline the environmental drivers of such distribution. Among the het-groups, het-1 was the most abundant/detected and co-occurred with the other 2 symbiotic strains, all responding similarly to the influence of abiotic factors, such as temperature and salinity (positive and negative correlation, respectively). Globally, Trichodesmium dominated the qPCR detections, followed by UCYN-B. UCYN-A phylotypes (A-1, A-2) were detected without their proposed hosts, for which new oligonucleotides were designed. The latter suggested a facultative symbiosis. Finally, microscopy observations of the het-groups highlighted a discrepancy with the qPCR counts (i.e. the former were several order of magnitudes lower), leading to the idea of developing a new approach to quantify the DDAs. The fourth aim of this thesis was to develop highly specific in situ hybridization assays (CARD-FISH) to determine the presence of alternative life-stages and/or free-living partners. The new assays were applied to samples collected in the South China Sea and compared with abundance estimates from qPCR assays for the 3 symbiotic strains. Free-living cells were indeed detected along the transect, mainly at deeper depths. Free-living symbionts had two morphotypes: trichomes and single-cells. The latter were interpreted as temporary life-stages. Consistent co-occurrence of the 3 het-groups was also found in the SCS and application of a SEM model predicted positive interactions between the het groups. We interpreted the positive interaction as absence of intra-specific competition, and consistent with the previous study, temperature and salinity were predicted as major drivers of the DDAs distribution. At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 4: Manuscript.

We study the impact of gas accretion on the orbital evolution of black-hole binaries initially at large separation in the band of the planned Laser Interferometer Space Antenna (LISA). We focus on two sources: (i)~stellar-origin black-hole binaries~(SOBHBs) that can migrate from the LISA band to the band of ground-based gravitational-wave observatories within weeks/months; and (ii) intermediate-mass black-hole binaries~(IMBHBs) in the LISA band only. Because of the large number of observable gravitational-wave cycles, the phase evolution of these systems needs to be modeled to great accuracy to avoid biasing the estimation of the source parameters. Accretion affects the gravitational-wave phase at negative ($-4$) post-Newtonian order, and is therefore dominant for binaries at large separations. If accretion takes place at the Eddington or at super-Eddington rate, it will leave a detectable imprint on the dynamics of SOBHBs. In optimistic astrophysical scenarios, a multiwavelength strategy with LISA and a ground-based interferometer can detect about $10$ (a few) SOBHB events for which the accretion rate can be measured at $50\%$ ($10\%$) level. In all cases the sky position can be identified within much less than $0.4\,{\rm deg}^2$ uncertainty. Likewise, accretion at $\gtrsim 10\%$ ($\gtrsim 100\%$) of the Eddington rate can be measured in IMBHBs up to redshift $z\approx 0.1$ ($z\approx 0.5$), and the position of these sources can be identified within less than $0.01\,{\rm deg}^2$ uncertainty. Altogether, a detection of SOBHBs or IMBHBs would allow for targeted searches of electromagnetic counterparts to black-hole mergers in gas-rich environments with future X-ray detectors (such as Athena) and radio observatories (such as SKA)., 14 pages, 8 figures; v2: references and comments added to match the final version published in ApJ

Assuming axion-like particles account for the entirety of the dark matter in the Universe, we study the possibility of detecting their decay into photons at radio frequencies. We discuss different astrophysical targets, such as dwarf spheroidal galaxies, the Galactic Center and halo, and galaxy clusters. The presence of an ambient radiation field leads to a stimulated enhancement of the decay rate; depending on the environment and the mass of the axion, the effect of stimulated emission may amplify the photon flux by serval orders of magnitude. For axion-photon couplings allowed by astrophysical and laboratory constraints(and possibly favored by stellar cooling), we find the signal to be within the reach of next-generation radio telescopes such as the Square Kilometer Array., Minor changes, references added, matches published version

The cosmological X-ray emission associated to the possible radiative decay of sterile neutrinos is composed by a collection of lines at different energies. For a given mass, each line corresponds to a given redshift. In this work, we cross correlate such line emission with catalogs of galaxies tracing the dark matter distribution at different redshifts. We derive observational prospects by correlating the X-ray sky that will be probed by the eROSITA and Athena missions with current and near future photometric and spectroscopic galaxy surveys. A relevant and unexplored fraction of the parameter space of sterile neutrinos can be probed by this technique.