Blockchain based ecosystems: a complex systems approach

Since the development of Bitcoin in 2008, blockchain-based technologies have flourished and several applications have been created, such as smart contracts, NFTs or cryptocurrencies. The blockchain allows for different kinds of transactions to be verified in a decentralized way, without the need for an intermediary, allowing new socio-technical ecosystems to be born and grow. Transactions are stored publicly, anonymously and openly on the blockchain, granting unprecedented access to data on human (collective) behaviour and socio-technical systems. The question thus arises: can we use this data to characterize these systems, and possibly to further our understanding of human behaviour? In this thesis, we address this question by studying different blockchain-based ecosystems through a combination of different datasets. Firstly, we study Dark Web Marketplaces (DWMs), online illicit markets on the dark web using cryptocurrencies for payments, and we characterize how they first reacted and then adapted to the COVID-19 pandemic using web scraping data. Secondly, we exploit a unique dataset of Bitcoin and proprietary transactions to characterize the buyer-seller network on DWMs and regulated e-commerce platforms. Thirdly, we study a comprehensive dataset of scientific publications to investigate the evolution of the concept of decentralization, pillar of blockchain-based ecosystems, in time. Then, we extend the literature on DWMs by studying the wider ecosystem of direct interactions between users, a network we can study only thanks to blockchain data. Finally, we analyse the trade of NFT collectibles on the largest open marketplace available, characterizing the role of rarity in determining market trends. Overall, this thesis presents a series of pioneering studies improving our understanding of blockchain-based socio-technical systems, thanks to unique comprehensive large scale datasets giving us unprecedented access to the history and behaviour of these ecosystems. We hope researchers will extend this work to improve our understanding of these systems and more generally human behaviour

Role of virtual break-up of projectile in astrophysical fusion reactions

We study the effect of virtual Coulomb break-up, commonly known as the dipole polarizability, of the deuteron projectile on the astrophysical fusion reaction 3He(d,p)4He. We use the adiabatic approximation to estimate the potential shift due to the E1 transition to the continuum states in the deuteron, and compute the barrier penetrability in the WKB approximation. We find that the enhancement of the penetrability due to the deuteron break-up is too small to resolve the longstanding puzzle observed in laboratory measurements that the electron screening effect is surprisingly larger than theoretical prediction based on an atomic physics model. The effect of the 3He break-up in the 3He(d,p)4He reaction, as well as the 7Li break-up in the 7Li(p,alpha)4He reaction is also discussed.Comment: 9 pages, 2 eps figure

Screening of Nuclear Reactions in the Sun and Solar Neutrinos

We quantitatively determine the effect and the uncertainty on solar neutrino production arising from the screening process. We present predictions for the solar neutrino fluxes and signals obtained with different screening models available in the literature and by using our stellar evolution code. We explain these numerical results in terms of simple laws relating the screening factors with the neutrino fluxes. Futhermore we explore a wider range of models for screening, obtained from the Mitler model by introducing and varying two phenomenological parameters, taking into account effects not included in the Mitler prescription. Screening implies, with respect to a no-screening case, a central temperat reduction of 0.5%, a 2% (8%) increase of Beryllium (Boron)-neutrino flux and a 2% (12%) increase of the Gallium (Chlorine) signal. We also find that uncertainties due to the screening effect ar at the level of 1% for the predicted Beryllium-neutrino flux and Gallium signal, not exceeding 3% for the Boron-neutrino flux and the Chlorine signal.Comment: postscript file 11 pages + 4 figures compressed and uuencoded we have replaced the previous paper with a uuencoded file (the text is the same) for any problem please write to [email protected]

Differential cross sections for muonic atom scattering from hydrogenic molecules

The differential cross sections for low-energy muonic hydrogen atom scattering from hydrogenic molecules are directly expressed by the corresponding amplitudes for muonic atom scattering from hydrogen-isotope nuclei. The energy and angular dependence of these three-body amplitudes is thus taken naturally into account in scattering from molecules, without involving any pseudopotentials. Effects of the internal motion of nuclei inside the target molecules are included for every initial rotational-vibrational state. These effects are very significant as the considered three-body amplitudes often vary strongly within the energy interval $\lesssim{}0.1$ eV. The differential cross sections, calculated using the presented method, have been successfully used for planning and interpreting many experiments in low-energy muon physics. Studies of $\mu^{-}$ nuclear capture in $p\mu$ and the measurement of the Lamb shift in $p\mu$ atoms created in H$_2$ gaseous targets are recent examples.Comment: 21 pages, 13 figures, submitted to Phys. Rev.

Muonic hydrogen cascade time and lifetime of the short-lived 2S2S state

Metastable ${2S}$ muonic-hydrogen atoms undergo collisional ${2S}$-quenching, with rates which depend strongly on whether the $\mu p$ kinetic energy is above or below the ${2S}\to {2P}$ energy threshold. Above threshold, collisional ${2S} \to {2P}$ excitation followed by fast radiative ${2P} \to {1S}$ deexcitation is allowed. The corresponding short-lived $\mu p ({2S})$ component was measured at 0.6 hPa $\mathrm{H}_2$ room temperature gas pressure, with lifetime $\tau_{2S}^\mathrm{short} = 165 ^{+38}_{-29}$ ns (i.e., $\lambda_{2S}^\mathrm{quench} = 7.9 ^{+1.8}_{-1.6} \times 10^{12} \mathrm{s}^{-1}$ at liquid-hydrogen density) and population $\epsilon_{2S}^\mathrm{short} = 1.70^{+0.80}_{-0.56}$ % (per $\mu p$ atom). In addition, a value of the $\mu p$ cascade time, $T_\mathrm{cas}^{\mu p} = (37\pm5)$ ns, was found.Comment: 4 pages, 3 figure

The circular life of human CD38: From basic science to clinics and back

Monoclonal antibodies (mAbs) were initially considered as a possible “magic bullet” for in vivo elimination of tumor cells. mAbs represented the first step: however, as they were murine in nature (the earliest experience on the field), they were considered unfit for human applications. This prompted the development of techniques for cloning the variable regions of conventional murine antibodies, genetically mounted on human IgG. The last step in this years-long process was the design for the preparation of fully human reagents. The choice of the target molecule was also problematic, since cancer-specific targets are quite limited in number. To overcome this obstacle in the planning phases of antibody-mediated therapy, attention was focused on a set of normal molecules, whose quantitative distribution may balance a tissue-dependent generalized expression. The results and clinical success obtained with anti-CD20 mAbs revived interest in this type of strategy. Using multiple myeloma (MM) as a tumor model was challenging first of all because the plasma cells and their neoplastic counterpart eluded the efforts of the Workshop on Differentiation Antigens to find a target molecule exclusively expressed by these cells. For this reason, attention was turned to surface molecules which fulfill the requisites of being reasonably good targets, even if not specifically restricted to tumor cells. In 2009, we proposed CD38 as a MM target in virtue of its expression: it is absent on early hematological progenitors, has variable but generalized limited expression by normal cells, but is extremely high in plasma cells and in myeloma. Further, regulation of its expression appeared to be dependent on a variety of factors, including exposure to all-trans retinoic acid (ATRA), a potent and highly specific inducer of CD38 expression in human promyelocytic leukemia cells that are now approved for in vivo use. This review discusses the history of human CD38, from its initial characterization to its targeting in antibody-mediated therapy of human myeloma

Ecological Momentary Assessment and Intervention Principles for the Study of Awake Bruxism Behaviors, Part 2 : Development of a Smartphone Application for a Multicenter Investigation and Chronological Translation for the Polish Version

Objectives: The aim is to describe the process of translating the smartphone application BruxApp into Polish within the context of an ongoing multicenter project on awake bruxism (AB) epidemiology. Material and Methods: An ongoing cooperation involving 11 universities is based on the adoption of the smartphone-based EMA protocol to collect real time report of AB behaviors in the natural environment. The English version of BruxApp is adopted as a template for the multi-language translation, according to a step-by-step procedure led by mother-tongue experts in the field. A dedicated web platform for translation (viz., POEditor) is used. The process of translation into Polish is here described as an example. Results: There are two software versions available, viz., BruxApp and BruxApp Research. For both versions, back translation from Polish to English was performed to verify the accuracy of the translation procedure. The validity of the translation has been confirmed by the perfect agreement between the original and back-translated English versions, and the Polish version of BruxApp can thus be introduced in the clinical and research setting to get deeper into the study of AB epidemiology in Poland. Conclusions: As far as clinical studies are concerned, the described strategy to record data can be very useful -patients can acknowledge their habits, monitor changes over time, and implement remedial measures. In the field of research, BruxApp makes possible to collect and store a huge amount of data about the epidemiology of different forms of awake bruxism, both at the individual level and at the population level.Peer reviewe