Charged massive particle at rest in the field of a Reissner-Nordstr\"om black hole

The interaction of a Reissner-Nordstr\"om black hole and a charged massive particle is studied in the framework of perturbation theory. The particle backreaction is taken into account, studying the effect of general static perturbations of the hole following the approach of Zerilli. The solutions of the combined Einstein-Maxwell equations for both perturbed gravitational and electromagnetic fields at first order of the perturbation are exactly reconstructed by summing all multipoles, and are given explicit closed form expressions. The existence of a singularity-free solution of the Einstein-Maxwell system requires that the charge to mass ratios of the black hole and of the particle satisfy an equilibrium condition which is in general dependent on the separation between the two bodies. If the black hole is undercritically charged (i.e. its charge to mass ratio is less than one), the particle must be overcritically charged, in the sense that the particle must have a charge to mass ratio greater than one. If the charge to mass ratios of the black hole and of the particle are both equal to one (so that they are both critically charged, or "extreme"), the equilibrium can exist for any separation distance, and the solution we find coincides with the linearization in the present context of the well known Majumdar-Papapetrou solution for two extreme Reissner-Nordstr\"om black holes. In addition to these singularity-free solutions, we also analyze the corresponding solution for the problem of a massive particle at rest near a Schwarzschild black hole, exhibiting a strut singularity on the axis between the two bodies. The relations between our perturbative solutions and the corresponding exact two-body solutions belonging to the Weyl class are also discussed.Comment: 42 pages, 3 eps figures, revtex macro

Net-zero emissions: main technological, geopolitical, and economic consequences of the new energy scenario

This paper discusses possible technical, economical and geopolitical consequences of the new energy scenario. We analyze the net zero emissions global race with an emphasis on the role renewable energies will play in this phenomenon and COP26’s recent decisions on climate and energy transition. Using the semi-quantitative analysis method, the technological driving forces for future energy scenarios have been extrapolated. The technological developments and future scenarios regarding renewable energies are discussed by comparing two different driving forces. Furthermore, there will be a discussion of possible geopolitical consequences due to fossil fuels trade depletion during the energetic transition. Possible related consequences for MENA countries are investigated. In the last part, there will be a legal background analysis for electricity demand and renewable sources shift combined with techno-economical examples. Finally, considering all the contents, we drive our conclusions

Synthesis of Nanostructured Hydroxyapatite via Controlled Hydrothermal Route

Hydroxyapatite represents the natural inorganic component of the bone and may be considered an essential element required for the development of bone substitutes in the field of regenerative medicine. Hydroxyapatite bone substitutes own biomimetic, osteoconductive, and osteoinductive properties thanks to their chemical-physical properties and nanostructure that play a critical role for the reconstruction of calcified tissues. Controlling the structure of hydroxyapatite nanocrystals is vital for obtaining a sustained product, and it should be an advantage on the final materials suitable for bone replacement, in terms of adsorptive activity, drug delivery system, etc. Compared to other synthesis techniques, hydrothermal processing (refers to a synthesis in aqueous solution at elevated pressure and temperature, in a closed system) has the ability to precipitate the hydroxyapatite from overheated solution, regulating the rate and uniformity of nucleation, growth, and maturation, which affect size, morphology, and aggregation of the crystals. This chapter wants to provide an overview of realization of nanosized hydroxyapatite-based bioceramics (e.g., powder and 3D structures) with desired morphology of crystallites, by hydrothermal processing. In this way, some critical hydrothermal parameters fundamental on the control of the crystal shape and dimension (pH, temperature, starting precursors, etc.) are discussed

Aluminum effects on embryo suspensor polytene chromosomes of Phaseolus coccineus L

Aluminum (Al) represents a widespread environmental pollutant, with severe toxic impacts on plants. In this study, we documented for the first time the structural and functional responses induced by two concentrations of AlCl3 (10−2 M and 10−1 M) in the polytene chromosomes that characterize the chromatin organization in the embryo suspensor cells of Phaseolus coccineus. Polytene chromosomes showed signs of dose-dependent genotoxicity following AlCl3 treatments with a significant increase in both chromatin stickiness and chromatin fragmentation. Polytene chromosomes specifically reacted to AlCl3 also in terms of DNA and RNA puffing activity: with respect to the control, the treatments promoted ex-novo and/or inhibited puff formation along chromosome arms, suggesting a fine modulation of the differential genome activity in response to the treatments. The nuclei of suspensors from control and treated seeds showed nucleoli mainly arranged by more than one NOR-bearing chromosome. In addition, AlCl3 treatments affected the frequency of nucleoli organized by singular organizer chromosomes, with an increase in the frequencies of nucleoli organized by chromosome II and a reduction in the frequencies of those organized by chromosomes I or V. These results confirm that, also in our system, nucleolus may react as stress response organelle. Introductio

Alkali-bonded SiC based foams

In this feasibility study, silicon carbide (SiC) foams were developed with a low temperature process by using an inorganic alkali aluminosilicates binder, also known as geopolymer. Geopolymers are alkali bonded ceramics, i.e. they are produced using an energy saving process involving chemical reactions in aqueous medium at T<120?C. The use of geopolymers allows to produce near-net-shape pieces by slip casting in plastic mould, contemporary to the foaming process. Different grades of SiC powder were used. The binder was prepared with metakaolin, as aluminosilicatic raw powder, and KOH/K2SiO3, as alkali aqueous solution. The molar ratio of SiO2/Al2O3 was 4 and of SiO2/K2O was 2. Metakaolin in alkaline conditions dissolved and re-precipitated to form geopolymeric nano-particulates that acted as a glue to stick together SiC particles (90 wt%). The surface reaction of the SiC particles in the alkaline solution led to gas evolution that induced the foaming of the slurries. Process parameters such as water addition, mixing time and curing temperature were correlated to the dimension and amount of the porosity. The foams were studied in oxidative atmospheres up to 1200?

Caudate Gray Matter Volume in Obsessive-Compulsive Disorder Is Influenced by Adverse Childhood Experiences and Ongoing Drug Treatment

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Nature-Inspired Processes and Structures: New Paradigms to Develop Highly Bioactive Devices for Hard Tissue Regeneration

Material scientists are increasingly looking to natural structures as inspiration for new-generation functional devices. Particularly in the medical field, the need to regenerate tissue defects claims, since decades, biomaterials with the ability to instruct cells toward formation and organization of new tissue. It is today increasingly accepted that biomimetics is a leading concept for biomaterials development. In fact, there is increasing evidence that the use of biomedical devices showing substantial mimicry of the composition and multi-scale structure of target native tissues have enhanced regenerative ability. As a relevant example, biomimetic materials have high potential to solve degenerative diseases affecting the musculoskeletal system, namely, bone, cartilage and articular tissues, which is of pivotal importance for most of human abilities, such as walking, running, manipulating, and chewing. In this respect, the adoption of nature-inspired processes and structures is an emerging fabrication concept, uniquely able to provide biomaterials with superior biological performance. The chapter will give an overview of the most recent results obtained in the field of hard tissue regeneration by using 3D biomaterials obtained by nature-inspired approaches. The main focus is given to porous hydroxyapatite-based ceramic or hybrid scaffolds for regeneration of bone and osteochondral tissues in neurosurgery and orthopedics