Matter around Kerr black holes in scalar-tensor theories: scalarization and superradiant instability

In electrovacuum stationary, asymptotically flat black holes in scalar-tensor theories of gravity are described by the Kerr-Newman family of solutions, just as in general relativity. We show that there exist two mechanisms which can render Kerr black holes unstable when matter is present in the vicinity of the black hole, as this induces an effective mass for the scalar. The first mechanism is a tachyonic instability that appears when the effective mass squared is negative, triggering the development of scalar hair --- a black hole version of "spontaneous scalarization". The second instability is associated with superradiance and is present when the effective mass squared is positive and when the black hole spin exceeds a certain threshold. The second mechanism is also responsible for a resonant effect in the superradiant scattering of scalar waves, with amplification factors as large as 10^5 or more.Comment: 11 pages, 3 figures. v2: published versio

Black holes with surrounding matter in scalar-tensor theories

We uncover two mechanisms that can render Kerr black holes unstable in scalar-tensor gravity, both associated to the presence of matter in the vicinity of the black hole and the fact that this introduces an effective mass for the scalar. Our results highlight the importance of understanding the structure of spacetime in realistic, astrophysical black holes in scalar-tensor theories.Comment: 5 pages. Published version. arXiv admin note: substantial text overlap with arXiv:1305.693

Particle ejection during mergers of dark matter halos

Dark matter halos are built from accretion and merging. During merging some of the dark matter particles may be ejected with velocities higher than the escape velocity. We use both N-body simulations and single-particle smooth-field simulations to demonstrate that rapid changes to the mean field potential are responsible for such ejection, and in particular that dynamical friction plays no significant role in it. Studying a range of minor mergers, we find that typically between 5-15% of the particles from the smaller of the two merging structures are ejected. We also find that the ejected particles originate essentially from the small halo, and more specifically are particles in the small halo which pass later through the region in which the merging occurs.Comment: 18 pages, 12 figures. Accepted for publication in JCA

Cosmology with 21cm intensity mapping

The nature of the most abundant components of the Universe, dark energy and dark matter, is still to be uncovered. I tackle this subject considering a novel cosmological probe: The neutral hydrogen emitted 21cm radiation, observed with the intensity mapping technique. I analyse competitive and realistic dark energy and dark matter models and show how they produce distinctive and detectable effects on the 21cm signal. Moreover, I provide radio telescope forecasts showing how these models will be distinguishable in an unprecedented way

Le proteine leganti gli odori nell' ape

Le OBP (Odorant Binding Protein) sono proteine solubili a basso peso molecolare in grado di legare reversibilmente molecole organiche. Esse sono presenti in elevate concentrazioni nella mucosa nasale dei vertebrati e nella linfa sensillare degli insetti, i liquidi biologici che costituiscono l’ambiente acquoso nel quale sono immerse le terminazioni dendridiche dei neuroni sensoriali. Nonostate numerose OBP siano state caratterizzate sia dal punto di vista strutturale che per la loro capacita’ di legare odori e feromoni, la loro funzione specifica non è ancora del tutto chiarita. Tuttavia, studi recenti hanno dimostrato che le OBP sono essenziali per la percezione ed il riconoscimento di odori e feromoni negli insetti. Per questo, tali proteine costituiscono un target interessante nel controllo di popolazioni di insetti dannosi in agricoltura o portatori di malattie per l’uomo. Esistono tuttavia insetti utili, il miglior esempio dei quali e’ rappresentato dalle api. In tal caso, una migliore conoscenza del loro sistema di comunicazione chimica puo’ suggerire azioni mirate alla protezione di queste specie. Il presente lavoro di tesi ha preso in considerazione 6 delle 21 OBP presenti nel genoma di Apis mellifera. Queste proteine sono state espresse in mezzi batterici, ottenendo in tutti i casi buone rese (20-40 mg/L), sufficienti per uno studio biochimico delle proteine stesse. Le sei OBP erano tutte presenti come corpi di inclusione, per cui e’ stato necessario solubilizzarle con un trattamento denaturante, per poi riottenerle in forma attiva. La purificazione delle proteine e’ stata realizzata mediante una serie di passaggi cromatogafici, utilizzanti resine a scambio ionico e gel filtrazione. Le proteine purificate sono state poi utilizzate per la preparazione di anticorpi policlonali, con i quali sono stati effettuati saggi di Western-blot sulle diverse caste e parti del corpo. Una delle OBP, che e’ risultata presente nelle antenne di tutte le caste, ma non in altre parti del corpo, e’stata anche utilizzata in esperimenti di binding con diverse molecole organiche, potenziali semiochimici dell’ape. E’ stata osservata una buona specificita’ verso molecole di strutture simili a terpenoidi ed una forte dipendenza da parametri stereochimici dei ligandi. Questo lavoro rappresenta un contributo alla caratterizzazione del repertorio completo delle OBP nell’ape con l’obiettivo di comprendere in che misura il riconoscimento degli odori e’ legato alla struttura delle OBP

Neuroserpin polymers cause oxidative stress in a neuronal model of the dementia FENIB

The serpinopathies are human pathologies caused by mutations that promote polymerisation and intracellular deposition of proteins of the serpin superfamily, leading to a poorly understood cell toxicity. The dementia FENIB is caused by polymerisation of the neuronal serpin neuroserpin (NS) within the endoplasmic reticulum (ER) of neurons. With the aim of understanding the toxicity due to intracellular accumulation of neuroserpin polymers, we have generated transgenic neural progenitor cell (NPC) cultures from mouse foetal cerebral cortex, stably expressing the control protein GFP (green fluorescent protein), or human wild type, G392E or delta NS. We have characterised these cell lines in the proliferative state and after differentiation to neurons. Our results show that G392E NS formed polymers that were mostly retained within the ER, while wild type NS was correctly secreted as a monomeric protein into the culture medium. Delta NS was absent at steady state due to its rapid degradation, but it was easily detected upon proteasomal block. Looking at their intracellular distribution, wild type NS was found in partial co-localisation with ER and Golgi markers, while G392E NS was localised within the ER only. Furthermore, polymers of NS were detected by ELISA and immunofluorescence in neurons expressing the mutant but not the wild type protein. We used control GFP and G392E NPCs differentiated to neurons to investigate which cellular pathways were modulated by intracellular polymers by performing RNA sequencing. We identified 747 genes with a significant upregulation (623) or downregulation (124) in G392E NS-expressing cells, and we focused our attention on several genes involved in the defence against oxidative stress that were up-regulated in cells expressing G392E NS (Aldh1b1, Apoe, Gpx1, Gstm1, Prdx6, Scara3, Sod2). Inhibition of intracellular anti-oxidants by specific pharmacological reagents uncovered the damaging effects of NS polymers. Our results support a role for oxidative stress in the cellular toxicity underlying the neurodegenerative dementia FENIB

Groundwater flow and geochemical modeling of the Acque Albule thermal basin (Central Italy): a conceptual model for evaluating influences of human exploitation on flowpath and thermal resource availability

Although the Acque Albule Basin has been studied since the middle of the 19th century, a comprehensive geologic conceptual model of the area has not yet been developed. The natural setting has been heavily modified by anthropic activities. Rapid evolution during the last 25 years has caused many interferences, which have led to a drastic increase of the hazards and linked risks, mainly related to water resource overexploitation and subsidence. The implementation of an exhaustive framework has become mandatory for environmental and management purposes. Starting from a critical review of previous studies, hydrogeologic and hydrogeochemical surveys and related numerical modeling have been carried out in order to achieve a quantitative understanding of the active phenomena and processes. Several hydrogeologic issues have been addressed concerning aquifer recharge areas and the different flowpaths of groundwater in respect to their division into a shallow and a deep circuit. Account has been taken of the groundwater chemistry as a function of water—rock interactions and mixing processes with uprising fluids. Different scenarios of groundwater flow in the Acque Albule aquifer have been built, using previously available piezometric measurements and the hydrodynamic parameters determined by in situ tests. These results led to the formulation of an updated hydrogeologic conceptual model to be further implemented, in which past, present and future anthropic instances and the potential of natural resources of the area have been included and taken into account. A sound conceptual model must rely on the design and development of a logical geo-database in which information is stored, updated and processed. This operational framework can result in a useful tool for land management, surveys planning and design, hazard and risk evaluation, identification of best practices and economic development of the area

NGF steers microglia toward a neuroprotective phenotype

Microglia are the sentinels of the brain but a clear understanding of the factors that modulate their activation in physiological and pathological conditions is still lacking. Here we demonstrate that Nerve Growth Factor (NGF) acts on microglia by steering them toward a neuroprotective and anti-inflammatory phenotype. We show that microglial cells express functional NGF receptors in vitro and ex vivo. Our transcriptomic analysis reveals how, in primary microglia, NGF treatment leads to a modulation of motility, phagocytosis and degradation pathways. At the functional level, NGF induces an increase in membrane dynamics and macropinocytosis and, in vivo, it activates an outward rectifying current that appears to modulate glutamatergic neurotransmission in nearby neurons. Since microglia are supposed to be a major player in Aβ peptide clearance in the brain, we tested the effects of NGF on its phagocytosis. NGF was shown to promote TrkA-mediated engulfment of Aβ by microglia, and to enhance its degradation. Additionally, the proinflammatory activation induced by Aβ treatment is counteracted by the concomitant administration of NGF. Moreover, by acting specifically on microglia, NGF protects neurons from the Aβ-induced loss of dendritic spines and inhibition of long term potentiation. Finally, in an ex-vivo setup of acute brain slices, we observed a similar increase in Aβ engulfment by microglial cells under the influence of NGF. Our work substantiates a role for NGF in the regulation of microglial homeostatic activities and points toward this neurotrophin as a neuroprotective agent in Aβ accumulation pathologies, via its anti-inflammatory activity on microglia

Agronomic strategies for Sustainable Management of Durum Wheat Cultivation in Mediterranean Area

L’azoto è un elemento nutritivo fondamentale per la produzione di cereali, tuttavia ha un significativo impatto ambientale. Nel presente elaborato vengono valutate diverse pratiche agronomiche al fine di incrementare la sostenibilità della coltivazione del frumento duro, e migliorare la sua produttività e qualità. Gli studi sono stati tutti condotti nell’area del Mediterraneo, definita come una delle regioni maggiormente colpita dai cambiamenti climatici in corso. In quest’area, quindi, la gestione sostenibile dell’azoto diventa ancora più importante. L'obiettivo generale è stato perseguito valutando le risposte di diversi genotipi di frumento duro alla gestione sostenibile della fertilizzazione azotata sia in sistemi produttivi biologici che a basso input. Definire il sistema produttivo agricolo che da solo sia in grado di garantire alla popolazione mondale un'alimentazione sicura e sostenibile è impossibile. Tuttavia, per garantire contemporaneamente l’accesso al cibo e la sostenibilità ambientale, sarà necessario ricorrere a sistemi agricoli innovativi, compresi quelli a basso input e biologici. In conclusione, i risultati descritti in questo elaborato hanno contribuito a far progredire il grado di conoscenza sulla sostenibilità, sulla produttività e su diversi aspetti qualitativi del frumento duro in ambiente mediterraneo. Tuttavia, molte questioni significative restano da indagare e saranno oggetto di futuri studi.Nitrogen is the most requested element in cereal systems and has the most significant impact on the environment. This Ph.D. dissertation deals with different agronomic strategies to improve the sustainability of durum wheat cultivation, together with its productivity and quality. Studies were conducted in the Mediterranean area, de!ned as one of the regions most vulnerable to climatic changes. Since, in this area the efficiently use of nitrogen is more critical. The main objective was pursued evaluating the responses of different durum wheat genotypes to the sustainable management of nitrogen fertilizers in organic and low-input systems. Define the best farming system that alone can satisfy the world safe and sustainable feeding is impossible. However, innovative farming systems, including low-input and organic ones, will be necessary for both food access and ecosystem security. In conclusion, the results described in this Ph.D. advance the current state of the knowledge about improving the sustainability, productivity and different quality aspects of durum wheat under Mediterranean conditions. However, several significant issues remain to be investigated in future research