Effects of the Brookite Phase on the Properties of Different Nanostructured TiO2 Phases Photocatalytically Active Towards the Degradation of N-Phenylurea

Different sol-gel synthesis methods were used to obtain four nanostructured mesoporous TiO₂ samples for an efficient photocatalytic degradation of the emerging contaminant N-phenylurea under either simulated solar light (1 Sun) or UV light. Particularly, two TiO₂ samples were obtained by means of as many template-assisted syntheses, whereas other two TiO₂ samples were obtained by a greener template-free procedure, implying acidic conditions and, then, calcination at either 200 °C or 600 °C. In one case, anatase was obtained, whereas in the other three cases mixed crystalline phases were obtained. The four TiO₂ samples were characterized by X-ray powder diffraction (followed by Rietveld analysis); Transmission Electron Microscopy; N₂ adsorption/desorption at −196 °C; Diffuse Reflectance UV/Vis spectroscopy and ζ-potential measurements. A commercial TiO₂ powder (i. e., Degussa P25) was used for comparison. Differences among the synthesized samples were observed not only in their quantitative phase composition, but also in their nanoparticles morphology (shape and size), specific surface area, pore size distribution and pH_IEP (pH at isoelectric point), whereas the samples band-gap did not vary sizably. The samples showed different photocatalytic behavior in terms of N-phenylurea degradation, which are ascribed to their different physico-chemical properties and, especially, to their phase composition, stemming from the different synthesis conditions.     

Hypothetical Logic of Proofs

The logic of proofs is a refinement of modal logic introduced by Artemov in 1995 in which the modality ?A is revisited as ?t?A where t is an expression that bears witness to the validity of A. It enjoys arithmetical soundness and completeness and is capable of reflecting its own proofs (?A implies ? ?t?A, for some t). We develop the Hypothetical Logic of Proofs, a reformulation of LP based on judgemental reasoning.     

Role of the dispersion route on the phase transformation of a nano-crystalline transition alumina

De-agglomeration of a nanocrystalline transition alumina powder was performed in distilled water at its natural pH under magnetic stirring for 170 h or by ball milling for 3 h. Gibbsite appeared near transition aluminas in the magnetic stirred sample. In addition, a relevant lowering of the α-Al₂O₃ crystallization temperature was observed in the dispersed materials with respect to the as-received powder. However, the activation energy of the above transformation, determined by the Kissinger method, was in any case about 480–500 kJ/mol and unaffected by the dispersion route. On the contrary, it was reduced of about 10% in α-alumina seeded samples, obtained by flash plunging the powders at 1,290 °C for 10 min.     

Study of the medium- and long-range transport analysing the data of the Chernobyl accident

Summary In the present work we analyse the meteorological factors that characterized the transport and deposition on the ground of the radionuclides from the Chernobyl nuclear power station over Northern Italy during the accident in April–May 1986. The aim of our study is to test some computational procedures and meteorological analyses specific for a comprehensive study of long-range pollution transport problem. By reconstructing the particle trajectories of the radioactive Chernobyl plume, we determined the most probable starting and arrival date of the plume and the level over the source. Moreover, analysis of the meteorological configuration up-and downwind the Alps permitted us to explain the temporal displacement between different kinds of measured fall-out.

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Riassunto Nel presente lavoro si analizzano i fattori meteorologici che hanno caratterizzato il trasporto e la deposizione sull'Italia Settentrionale del materiale radioattivo fuoriuscito dalla centrale nucleare di Chernobyl durante l'incidente di aprile-maggio 1986. Lo studio ha avuto come scopo quello di verificare e mettere a punto procedure di calcolo e di analisi di dati meteorologici finalizzate ai problemi di trasporto d'inquinanti a lunga distanza. La ricostruzione delle traiettorie percorse dalla nube radioattiva ha permesso di determinare la data di partenza e di arrivo piú probabile della nube e l'altezza di livellamento sopra la sorgente. Inoltre considerazioni sulla situazione meteorologica sopra e sottovento le Alpi hanno permesso di spiegare lo sfasamento temporale tra i diversi tipi di fall-out misurati.

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Резюме В этой работе мы анализируем метереологические факторы, которые характеризуют транспорт и оседание на землю радионуклидов в Севертоной Италии после аварии на Чернобыльской АЭС в апреля-мае 1986 г. Цель этой работы проверить некоторые вычислительные приемы и метереологический анализ, предлагаемые для исследования проблем транспорта загрязнений на большие расстояния. Реконструируя траектории частиц радиоактивного выброса в Чернобыле, мы определяем наиболее вероятные данные для выброса и уровня над источником. Более того, анаяиз метереологической ситуации в Альпах позволил объяснить временные смещение мезду различными типами измеренных радиоактивных выпадений.

     

Forensic Biochemical Markers to Evaluate the Agonal Period: A Literature Review

Currently, forensic research is multidisciplinary with new methods and parameters useful to define the cause and time of death as well as survival/agony times. The identification of biochemical markers able to estimate agonal period has been studied by many forensic researchers. It is known that the estimation of agonal time in different types of death is not always easy, hence our interest in literature’s data. The studies analyzed in this review confirm the important role of thanatobiochemistry for the estimation of survival times. Regardless of the death cause, the survival/agony time between the primary event and death influences markers concentrations in biological samples (e.g., blood, urine, cerebrospinal fluid). Different biomarkers can be used for qualitative evaluations in deaths with short and long agony (e.g., C-reactive protein, ferritin, GFAP, etc.). Instead, the quantitative interpretation showed limits due to the lack of reference cut-offs. Thanatobiochemistry is a useful tool to confirm what emerged from autopsies findings (macroscopic and histological analysis), but further studies are desirable to confirm the evidence emerging from our review of the literature.     

Atomistic simulations of the sliding friction of graphene flakes

Using a tight-binding atomistic simulation, we simulate the recent atomic-force microscopy experiments probing the slipperiness of graphene flakes made slide against a graphite surface. Compared to previous theoretical models, where the flake was assumed to be geometrically perfect and rigid, while the substrate is represented by a static periodic potential, our fully-atomistic model includes quantum mechanics with the chemistry of bond breaking and bond formation, and the flexibility of the flake. These realistic features, include in particular the crucial role of the flake rotation in determining the static friction, in qualitative agreement with experimental observations.     

Seiberg–Witten theory as a Fermi gas

We explore a new connection between Seiberg–Witten theory and quantum statistical systems by relating the dual partition function of SU(2) Super Yang–Mills theory in a self-dual \(\Omega \) background to the spectral determinant of an ideal Fermi gas. We show that the spectrum of this gas is encoded in the zeroes of the Painlevé \(\mathrm{III}_3\) \(\tau \) function. In addition, we find that the Nekrasov partition function on this background can be expressed as an O(2) matrix model. Our construction arises as a four-dimensional limit of a recently proposed conjecture relating topological strings and spectral theory. In this limit, we provide a mathematical proof of the conjecture for the local \({\mathbb P}^1 \times {\mathbb P}^1\) geometry.     

On Painlevé/gauge theory correspondence

We elucidate the relation between Painlevé equations and four-dimensional rank one \(\mathcal {N} = 2\) theories by identifying the connection associated with Painlevé isomonodromic problems with the oper limit of the flat connection of the Hitchin system associated with gauge theories and by studying the corresponding renormalization group flow. Based on this correspondence, we provide long-distance expansions at various canonical rays for all Painlevé \(\tau \)-functions in terms of magnetic and dyonic Nekrasov partition functions for \(\mathcal {N} = 2\) SQCD and Argyres–Douglas theories at self-dual Omega background \(\epsilon _1 + \epsilon _2 = 0\) or equivalently in terms of \(c=1\) irregular conformal blocks.