88 research outputs found

    The Macroeconomic Determinants and Market Efficiency of Precious Metals: An Empirical Evidence of International Markets

    Get PDF
    This empirical study extends market efficiency application to precious metals. Literature suggests that prices of four precious metals (i.e., Gold, Silver, Platinum, and Palladium) fluctuate due to instability of macroeconomic factors globally. Moreover, the impact of macroeconomic factors causes uncertainty in the prices of metals which affects the investors’ return. To test the robustness of the precious metals price efficiency, this thesis is divided into three separate empirical studies that measure market efficiency and analyse the impact of macroeconomic factors on pricing in developed and emerging economies. Chapter 2 (Paper 1) examines weak-form efficiency in the precious metal market using the Automatic Portmanteau, Automatic Variance Ratio, Autoboot Variance Ratio, and Generalized Spectral Shape tests. The findings demonstrate that market efficiency for four precious metals in developed and emerging economies changes over time. Market efficiency may vary due to technical changes, economic booms and busts. The other reason could be that markets are fragmented due to restrictions, lunar cycles, market complexity, and other challenges. Chapter 3 (Paper 2) investigates the relationship between macroeconomic factors and precious metals prices across developed and emerging markets from 1979 to 2020 using multiple time series techniques – Johansen Cointegration, VECM, VAR, ARDL model, and Wald tests. The findings revealed the long-run and short -run relationships between precious metals prices and macroeconomic factors vary depending on the country of the study. In the long run, cointegrating relationships are unstable and differ significantly between developed and emerging economies. The causality test results between four precious metals and major macroeconomic indicators vary depending on the country and the sample length of the frequency distributions used. Chapter 4 (Paper 3) examined how macroeconomic factors collectively impact gold, silver, and platinum prices in developed and emerging economies using the panel data unit root test and dynamic panel data model. The findings demonstrate that macroeconomic factors affect precious metal prices in developed and emerging economies

    An analysis of fake social media engagement services

    Get PDF
    Fake engagement services allow users of online social media and other web platforms to illegitimately increase their online reach and boost their perceived popularity. Driven by socio-economic and even political motivations, the demand for fake engagement services has increased in the last years, which has incentivized the rise of a vast underground market and support infrastructure. Prior research in this area has been limited to the study of the infrastructure used to provide these services (e.g., botnets) and to the development of algorithms to detect and remove fake activity in online targeted platforms. Yet, the platforms in which these services are sold (known as panels) and the underground markets offering these services have not received much research attention. To fill this knowledge gap, this paper studies Social Media Management (SMM) panels, i.e., reselling platformsÂżoften found in underground forumsÂżin which a large variety of fake engagement services are offered. By daily crawling 86 representative SMM panels for 4 months, we harvest a dataset with 2.8 M forum entries grouped into 61k different services. This dataset allows us to build a detailed catalog of the services for sale, the platforms they target, and to derive new insights on fake social engagement services and its market. We then perform an economic analysis of fake engagement services and their trading activities by automatically analyzing 7k threads in underground forums. Our analysis reveals a broad range of offered services and levels of customization, where buyers can acquire fake engagement services by selecting features such as the quality of the service, the speed of delivery, the country of origin, and even personal attributes of the fake account (e.g., gender). The price analysis also yields interesting empirical results, showing significant disparities between prices of the same product across different markets. These observations suggest that the market is still undeveloped and sellers do not know the real market value of the services that they offer, leading them to underprice or overprice their services.This work was supported by the EU Horizon 2020 Research and Innovation Program under Grant agreement no. 101021377 (TRUST aWARE ); the Spanish grants ODIO (PID2019-111429RB-C21 and PID2019-111429RB-C22), and the Region of Madrid grant CYNAMON-CM (P2018/TCS-4566), co-financed by European Structural Funds ESF and FEDER

    Quantitative Verification and Synthesis of Resilient Networks

    Get PDF

    The Fifteenth Marcel Grossmann Meeting

    Get PDF
    The three volumes of the proceedings of MG15 give a broad view of all aspects of gravitational physics and astrophysics, from mathematical issues to recent observations and experiments. The scientific program of the meeting included 40 morning plenary talks over 6 days, 5 evening popular talks and nearly 100 parallel sessions on 71 topics spread over 4 afternoons. These proceedings are a representative sample of the very many oral and poster presentations made at the meeting.Part A contains plenary and review articles and the contributions from some parallel sessions, while Parts B and C consist of those from the remaining parallel sessions. The contents range from the mathematical foundations of classical and quantum gravitational theories including recent developments in string theory, to precision tests of general relativity including progress towards the detection of gravitational waves, and from supernova cosmology to relativistic astrophysics, including topics such as gamma ray bursts, black hole physics both in our galaxy and in active galactic nuclei in other galaxies, and neutron star, pulsar and white dwarf astrophysics. Parallel sessions touch on dark matter, neutrinos, X-ray sources, astrophysical black holes, neutron stars, white dwarfs, binary systems, radiative transfer, accretion disks, quasars, gamma ray bursts, supernovas, alternative gravitational theories, perturbations of collapsed objects, analog models, black hole thermodynamics, numerical relativity, gravitational lensing, large scale structure, observational cosmology, early universe models and cosmic microwave background anisotropies, inhomogeneous cosmology, inflation, global structure, singularities, chaos, Einstein-Maxwell systems, wormholes, exact solutions of Einstein's equations, gravitational waves, gravitational wave detectors and data analysis, precision gravitational measurements, quantum gravity and loop quantum gravity, quantum cosmology, strings and branes, self-gravitating systems, gamma ray astronomy, cosmic rays and the history of general relativity

    Psychophysical properties of midbrain dopamine neurons and implications for the antidepressant effect of deep brain stimulation

    Get PDF
    The discovery that animals engage in intracranial self-stimulation (ICSS) provided a direct way to study the neural networks that direct motivation. In ICSS experiments, animals are implanted with electrodes terminating in reward-implicated substrates. The development of optogenetics advanced the study of the brain reward system by confirming a causal role of midbrain dopamine firing in reward seeking. Since then, the correspondence of optical stimulation parameters to the neural signal of dopamine neurons causing operant behavior has been studied. In parallel, attention was paid to the application of deep brain stimulation on refractory mental illness, including depression. This thesis describes two psychophysical experiments that use optogenetic ICSS of midbrain dopamine neurons. The first experiment shows that, for a substantial range of powers (~12.6 mW - 31.6 mW), the trade-off between power and pulse duration undergoes temporal summation, aligning with Bloch’s Law. Pulse duration can be used to control the volume of activated opsin-expressing dopamine neurons. The second experiment provides a psychophysical measurement of firing fidelity of midbrain dopamine neurons. This study supports that pulse frequencies higher than 40 Hz are ineffective or counter-productive at improving the vigor of operant behavior. Together these experiments highlight the benefit of using measurable outcomes (e.g., operant response) as the basis for making inferences about the effectiveness of optical stimulation. These experiments contribute to the hypothesis that, similarly to electrical ICSS, the variable determining the intensity of reward seeking is the induced aggregate firing rate. Such insights can aid the understanding of how deep brain stimulation functions to alleviate depression. It is suggested here that the antidepressant effects of deep brain stimulation of the medial forebrain bundle (MFB) may involve activation of non-dopaminergic neural pathways. The reward platform hypothesis is presented, which suggests that MFB stimulation may cause antidepressant effects by facilitating reward seeking. This hypothesis is developed in relation to motivation parameters that promote involvement with response-contingent rewarding activities. Ways to test this hypothesis in both pre-clinical and clinical models are proposed. This thesis provides practical guidelines for optogenetic experiment designs, and it outlines original, theory-driven hypotheses about the structural and functional underpinnings of antidepressant deep brain stimulation

    Salutogenesis in health promoting settings: a synthesis across organizations, communities and environments

    Full text link

    Principled Flow Tracking in IoT and Low-Level Applications

    Get PDF
    Significant fractions of our lives are spent digitally, connected to and dependent on Internet-based applications, be it through the Web, mobile, or IoT. All such applications have access to and are entrusted with private user data, such as location, photos, browsing habits, private feed from social networks, or bank details.In this thesis, we focus on IoT and Web(Assembly) apps. We demonstrate IoT apps to be vulnerable to attacks by malicious app makers who are able to bypass the sandboxing mechanisms enforced by the platform to stealthy exfiltrate user data. We further give examples of carefully crafted WebAssembly code abusing the semantics to leak user data.We are interested in applying language-based technologies to ensure application security due to the formal guarantees they provide. Such technologies analyze the underlying program and track how the information flows in an application, with the goal of either statically proving its security, or preventing insecurities from happening at runtime. As such, for protecting against the attacks on IoT apps, we develop both static and dynamic methods, while for securing WebAssembly apps we describe a hybrid approach, combining both.While language-based technologies provide strong security guarantees, they are still to see a widespread adoption outside the academic community where they emerged.In this direction, we outline six design principles to assist the developer in choosing the right security characterization and enforcement mechanism for their system.We further investigate the relative expressiveness of two static enforcement mechanisms which pursue fine- and coarse-grained approaches for tracking the flow of sensitive information in a system.\ua0Finally, we provide the developer with an automatic method for reducing the manual burden associated with some of the language-based enforcements

    Applying salutogenesis in organisations

    Full text link

    Applying the Free-Energy Principle to Complex Adaptive Systems

    Get PDF
    The free energy principle is a mathematical theory of the behaviour of self-organising systems that originally gained prominence as a unified model of the brain. Since then, the theory has been applied to a plethora of biological phenomena, extending from single-celled and multicellular organisms through to niche construction and human culture, and even the emergence of life itself. The free energy principle tells us that perception and action operate synergistically to minimize an organism’s exposure to surprising biological states, which are more likely to lead to decay. A key corollary of this hypothesis is active inference—the idea that all behavior involves the selective sampling of sensory data so that we experience what we expect to (in order to avoid surprises). Simply put, we act upon the world to fulfill our expectations. It is now widely recognized that the implications of the free energy principle for our understanding of the human mind and behavior are far-reaching and profound. To date, however, its capacity to extend beyond our brain—to more generally explain living and other complex adaptive systems—has only just begun to be explored. The aim of this collection is to showcase the breadth of the free energy principle as a unified theory of complex adaptive systems—conscious, social, living, or not
    • …
    corecore