Metastability in Bubbling AdS Space

We study the dynamics of probe M5 branes with dissolved M2 charge in bubbling geometries with SO(4) x SO(4) symmetry. These solutions were constructed by Bena-Warner and Lin-Lunin-Maldacena and correspond to the vacua of the maximally supersymmetric mass-deformed M2 brane theory. We find that supersymmetric probe M2 branes polarize into M5 brane shells whose backreaction creates an additional bubble in the geometry. We explicitly check that the supersymmetric polarization potential agrees with the one found within the Polchinski-Strassler approximation. The main result of this paper is that probe M2 branes whose orientation is opposite to the background flux can polarize into metastable M5 brane shells. These decay to a supersymmetric configuration via brane-flux annihilation. Our findings suggest the existence of metastable states in the mass-deformed M2 brane theory.Comment: 38 pages, 8 figure

Semantics-aware image understanding

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Chiral Triptycenes in Supramolecular and Materials Chemistry

Triptycenes are an intriguing class of organic molecules with several unusual characteristics, such as a propeller-like shape, saddle-like cavities around a symmetrical scaffold, a rigid π-framework. They have been extensively studied and proposed as key synthons for a variety of applications in supramolecular chemistry and materials science. When decorated with an appropriate substitution pattern, triptycenes can be chiral, and, similarly to other popular chiral π-extended synthons, can express chirality robustly, efficiently, and with relevance to chiroptical spectroscopies. This minireview highlights and encompasses recent advances in the synthesis of chiral triptycenes and in their introduction as molecular scaffolds for the assembly of functional supramolecular materials

L\u2019isoprostano PGF2\u3b1 induce stress del reticolo endoplasmatico ed apoptosi dei macrofagi presenti nelle placche aterosclerotiche carotidee

L\u2019ISOPROSTANO PGF2\u3b1 INDUCE STRESS DEL RETICOLO ENDOPLASMATICO ED APOPTOSI DEI MACROFAGI PRESENTI NELLE PLACCHE ATEROSCLEROTICHE CAROTIDE L\u2019aterosclerosi \ue8 una malattia cronica che decorre asintomatica, la cui progressione pu\uf2 determinare eventi acuti, morte improvvisa e ictus ischemico, ed \ue8 ormai largamente riconosciuto come endotelio, infiammazione e stress ossidativo giocano un ruolo chiave in tutte le sue fasi. La progressione dell\u2019aterosclerosi porta alla formazione di placche complesse, ad elevato rischio di rottura (placche instabili), caratterizzate da cappuccio fibroso sottile, infiltrazione intimale macrofagica, grande core lipidico. Recenti studi suggeriscono come l\u2019apoptosi sia significativamente aumentata nei punti di rottura della placca nei pazienti con sindrome coronarica acuta e nelle placche instabili confrontate con le placche stabili. E\u2019 stato suggerito in modelli animali che l\u2019espansione del core lipidico sia la conseguenza di un\u2019accelerata apoptosi macrofagica accoppiata ad una clearance fagocitica difettiva, un processo definito efferocitosi difettiva. Nelle placche in fase avanzata infatti, cellule muscolari lisce e macrofagi apoptotici non vengono efficientemente rimossi dagli efferociti, si accumulano e vanno incontro a morte cellulare. Nelle lesioni aterosclerotiche, diversi fattori sembrano contribuire al processo di apoptosi dei macrofagi, ed in particolare alcuni di questi sembrano agire attraverso lo stress del reticolo endoplasmatico (ER). In gravi situazioni di ER stress, allorquando i meccanismi di protezione attivati da unfolded protein response (UPR) non sono sufficienti a ripristinare la normale funzionalit\ue0 di ER, si pu\uf2 innescare il processo di morte cellulare per apoptosi La complessa rete dell'UPR attivata da ER stress, \ue8 composta da proteine transmembrana come PERK, IRE1 e il fattore ATF6. In condizioni di grave danno o danno irreversibile del ER, l'attivazione di UPR pu\uf2 portare ad apoptosi, attraverso la mediazione del fattore di trascrizione CHOP, il cui ruolo critico nel mediare l'ER stress \ue8 ben consolidato. Nelle placche aterosclerotiche sono presenti numerosi potenziali fonti di stress di ER, come ad esempio lipidi ossidati, colesterolo non esterificato, oxisteroli (7-keto-colesterolo), isoprostani (in particolare PGF2\uf061) e reactive oxygen species (ROS). Un possibile ruolo dell\u2019enzima fosfolipasi A2 associata alle lipoproteine (Lp-PLA2) nello sviluppo e progressione dell'aterosclerosi potrebbe derivare dalla sua capacit\ue0 di generare, da fosfolipidi ossidati contenuti nelle oxLDL, due importanti mediatori pro-infiammatori, quali la lisofosfatidilcolina (lysoPC) e acidi grassi ossidati non esterificati (oxNEFA), in particolare composti isoprostaglandin-like come il PGF2\u3b1. I risultati di questo studio dimostrano che l\u2019aumentata presenza di cellule apoptotiche e l\u2019espressione genica di proteine pro-apoptotiche andava di pari passo con un marcato aumento dell\u2019espressione dei marcatori di ER stress ed UPR, e con la presenza di composti in grado di indurre ER stress ed apoptosi (LysoPC, colesterolo libero, 7-keto colesterolo e PGF2\u3b1 ) nell\u2019area intorno al core necrotico vs le zone periferiche di placche carotidee umane. Inoltre, abbiamo dimostrato come un estratto di placca carotidea umana (PE) sia in grado di riprodurre in vitro quanto rilevato in ex vivo nelle lesioni avanzate umane: in cellule THP-1 monocitoidi, induzione di una forte espressione dei fattori correlati con l\u2019ER stress e l\u2019apoptosi. Tra i derivati dell\u2019ac. arachidonico ossidato contenuti nell\u2019estratto PE, prodotti dall\u2019 attivit\ue0 della Lp-PLA2, il PGF2\u3b1, analogamente a quanto ritrovato con il PE, stimola potentemente l\u2019ER stress / UPR e l\u2019apoptosi CHOP mediata nelle cellule THP-1. Il PGF2\u3b1, inoltre, determina produzione di ROS che a loro volta potrebbero favorire l\u2019ulteriore radicalizzazione dei fosfolipidi di membrana ossidati e delle oxLDL, evento che potrebbe ulteriormente potenziare lo stress ER/UPR e l\u2019 apoptosi.ISOPROSTAN PGF2\u3b1 INDUCED ENDOPLASMIC RETICULUM STRESS AND MACROPHAGE APOPTOSIS IN HUMAN ATHEROSLCEROTIC PLAQUES Atherosclerosis is a chronic inflammatory disease that begins asymptomatic, whose progression events may cause acute ischemic stroke and sudden death, and is widely recognized thet endothelium, inflammation and oxidative stress play a key role in all its phases. The progression of atherosclerosis leading to plaque formation with high risk of rupture (unstable plaques), characterized by thin fibrous cap, intimal macrophage infiltration and large lipid core. Recent studies suggest that apoptosis is significantly increased at the point of plaque rupture in patients with acute coronary syndrome and unstable plaques, compared with stable plaques. In animal models, it has been suggested that the expansion of the lipid core is the result of an accelerated macrophage apoptosis, coupled with defective phagocytic clearance, a process called defective efferocytosis. In advanced plaques, in fact, apoptotic smooth muscle cells and apoptotic macrophages not efficiently removed by efferocytosis, accumulate and undergo cell death. In atherosclerotic lesions, several factors seem to contribute to the process of apoptosis of macrophages, and in particular some of these appear to act through the stress of the endoplasmic reticulum (ER). In situations of severe ER stress, when the protective mechanisms activated by unfolded protein response (UPR) are not sufficient to restore normal function of ER, it can trigger the process of cell death by apoptosis. ER stress signaling UPR is triggered by three transmembrane proteins PERK, IRE1 and ATF6, and the transcription factor CHOP may induced apoptosis. In atherosclerotic plaques there are numerous potential sources of ER stress, such as oxidized lipids, unesterified cholesterol, oxysterol (7-keto-cholesterol), isoprostanes (specifically PGF2\u3b1) and reactive oxygen species (ROS). A possible role of the enzyme lipoprotein associated phospholipase A2 (Lp-PLA2) in the development and progression of atherosclerosis may derive from its ability to generate, from oxidized phospholipid content in oxLDL, two important pro-inflammatory mediators such as lysophosphatidylcholine (lysoPC) and oxidized non-esterified fatty acids (oxNEFA), in particular isoprostaglandin-like compounds such as PGF2\u3b1. The results of this study demonstrate that in the area around the necrotic core, there is an increased presence of apoptotic cells and gene expression of pro-apoptotic proteins, a marked increase in the expression of markers of ER stress and UPR, and the presence of compounds that to induce ER stress and apoptosis (LysoPC, free cholesterol, 7-keto and PGF2\u3b1) versus peripheral areas of human carotid plaques. In addition, we demonstrated that an extract of human carotid plaque (PE) is able to reproduce in vitro with THP-1 monocyte-like cell, as detected in advanced lesions of human carotid plaques, induction of a strong expression of factors associated with ER stress and apoptosis. Among the derivatives of the arachidonic acid oxidized content in the PE, produced by activity of Lp-PLA2, the PGF2\u3b1 powerfully stimulates the ER stress / UPR CHOP-mediated apoptosis, similar to that found with the PE. The PGF2\u3b1 also determines the production of ROS, which in turn could promote the further radicalization of oxidized membrane phospholipids and oxLDL, an event that could further enhance the ER stress / UPR and apoptosis

Direct Arylation Strategies in the Synthesis of π-Extended Monomers for Organic Polymeric Solar Cells

π-conjugated macromolecules for organic polymeric solar cells can be rationally engineered at the molecular level in order to tune the optical, electrochemical and solid-state morphology characteristics, and thus to address requirements for the efficient solid state device implementation. The synthetic accessibility of monomers and polymers required for the device is getting increasing attention. Direct arylation reactions for the production of the π-extended scaffolds are gaining importance, bearing clear advantages over traditional carbon-carbon forming methodologies. Although their use in the final polymerization step is already established, there is a need for improving synthetic accessibility to implement them also in the monomer synthesis. In this review, we discuss recent examples highlighting this useful strategy

Semantic Image Collection Summarization with Frequent Subgraph Mining

Applications such as providing a preview of personal albums (e.g., Google Photos) or suggesting thematic collections based on user interests (e.g., Pinterest) require a semantically-enriched image representation, which should be more informative with respect to simple low-level visual features and image tags. To this aim, we propose an image collection summarization technique based on frequent subgraph mining. We represent images with a novel type of scene graphs including fine-grained relationship types between objects. These scene graphs are automatically derived by our method. The resulting summary consists of a set of frequent subgraphs describing the underlying patterns of the image dataset. Our results are interpretable and provide more powerful semantic information with respect to previous techniques, in which the summary is a subset of the collection in terms of images or image patches. The experimental evaluation shows that the proposed technique yields non-redundant summaries, with a high diversity of the discovered patterns

A nonlinear dynamic S/H-ADC device model based on a modified Volterra series: identification procedure and commercial CAD tool implementation

A nonlinear, dynamic empirical model, based on a Volterra-like approach, was previously proposed by the authors for the time-oriented characterization of sample/hold (S/H) and analog-to-digital conversion (ADC) devices. In this paper, the experimental procedure for model parameter measurement is presented, as well as techniques devoted to the implementation of the model in the framework of the main commercial CAD tools for circuit analysis and design. Examples of simulations, performed both in the time and frequency domain on the model obtained for a commercial device, are proposed, which show the model's capability of pointing out the dynamic nonlinear effects in the S/H-ADC response

Hardware implementation of a broad-band vector spectrum analyzer based on randomized sampling

A hardware prototype of vector spectrum analyzer, which is based on a randomized sampling strategy and associated alias-free digital signal processing (DSP) algorithms, has been fully designed and implemented. The instrument exploits a couple of identical independently programmable digital data acquisition channels, whose synchronization allows to sample the input signal at instants that can be very close along the time axis (tens of picoseconds), against a maximum single-channel average throughput rate of 250 ksamples per second (kSa/s). This architecture has shown to be suitable for the accurate implementation of the randomized periodic sampling with uniform jitter on which the instrument is based. In addition, the design solutions adopted for the sampling command generators, which exploit the interaction between a digital gate signal and a phase-controlled sinusoidal wave, together with the particular analytical definition proposed for the spectral estimators, have allowed to make practically negligible the quantum time according to which the sampling instants are generated. Experimental results are provided, which validate both the alias-free spectrum analysis technique and the capability of the architecture proposed of reliably implementing the analytical benefits deriving from the randomized sampling strategy adopted