Exploring low-degree nodes first accelerates network exploration

We consider information diffusion on Web-like networks and how random walks can simulate it. A well-studied problem in this domain is Partial Cover Time, i.e., the calculation of the expected number of steps a random walker needs to visit a given fraction of the nodes of the network. We notice that some of the fastest solutions in fact require that nodes have perfect knowledge of the degree distribution of their neighbors, which in many practical cases is not obtainable, e.g., for privacy reasons. We thus introduce a version of the Cover problem that considers such limitations: Partial Cover Time with Budget. The budget is a limit on the number of neighbors that can be inspected for their degree; we have adapted optimal random walks strategies from the literature to operate under such budget. Our solution is called Min-degree (MD) and, essentially, it biases random walkers towards visiting peripheral areas of the network first. Extensive benchmarking on six real datasets proves that the---perhaps counter-intuitive strategy---MD strategy is in fact highly competitive wrt. state-of-the-art algorithms for cover

Exploring the scope and utility of dynamic covalent chemistry within polymeric nanoparticles

Dynamic covalent chemistry encompasses reversible bond forming reactions which proceed under equilibrium control, where the position of the equilibria are sensitive to changes in environment, and which are often able to undergo component exchange. These virtues provide polymeric nanoparticles incorporating dynamic covalent bonds with the ability to reconfigure or change their structural properties in response to stimuli. In Chapter 1 we critically discuss and evaluate the current state of the art whereby polymer chemists have exploited dynamic covalent bonds within responsive and adaptive polymeric nanoparticles. Chapter 2 describes the synthesis and study of a chemoresponsive polymeric micelle. In this work, aldehyde and alkoxyamine endfunctionalized polymers are shown to link together through a single oxime bond and then self-assemble into micellar aggregates. The chemoresponsive nature of these micellar aggregates is expressed when their disassembly is triggered through the addition of a small molecule alkoxyamine. Chemoresponsive core cross-linked star and nanogel nanoparticles which contain multiple imine cross-links are presented in Chapter 3. These imine linkages are utilized to facilitate the self-assembly process of the nanoparticles, which display chemoresponsive disassembly upon the addition of a small molecule amine. Chapter 4 describes the preparation of core cross-linked star polymers which are both pH-responsive and thermoresponsive. The pH-responsive nature is imparted through the pH-responsiveness of multiple imine linkages, and their thermoresponsive nature arises on account of the thermoresponsive polymer chains contained within their cores. In Chapter 5 nanoparticles possessing pH-responsive imine and redox-responsive disulfide cross-links have been developed where the simultaneous application of both low pH and a reducing agent is required to trigger their disassembly. It is shown that the application of either low pH or a reducing agent does not trigger disassembly. The research presented throughout this dissertation confirms the great potential of dynamic covalent chemistry in the development of stimuliresponsive polymeric nanoparticles.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The Palermo (Sicily) seismic cluster of September 2002 in the seismotectonic framework of the Tyrrhenian Sea-Sicily border area

The northern coast of Sicily and its offshore area represent a hinge zone between a sector of the Tyrrhenian Basin, characterized by the strongest crustal thinning, and the sector of the Sicilian belt which has emerged. This hinge zone is part of a wider W-E trending right-lateral shear zone, which has been affecting the Maghrebian Chain units since the Pliocene. Seismological and structural data have been used to evaluate the seismotectonic behavior of the area investigated here. Seismological analysis was performed on a data set of about 2100 seismic events which occurred between January 1988 and October 2002 in the Southern Tyrrhenian Sea. This paper focuses in particular on a set of data relating to the period from 6th September 2002, including both the main shock and about 540 aftershocks of the Palermo seismic sequence. The distribution of the hypocenters revealed the presence of two main seismogenic zones. The events of the easternmost zone may be related to the Ionian lithospheric slab diving beneath the Calabrian Arc. The seismicity associated with the westernmost zone is closely clustered around a sub-horizontal regression plane contained within the thinned Southern Tyrrhenian crust, hence suggesting that this seismogenic zone is strictly connected to the deformation field active within the hinge zone. On the basis of both structural and seismological data, the brittle deformation pattern is characterized by high-angle faults, mainly represented by transcurrent synthetic right-lateral and antithetic left-lateral systems, producing both restraining/uplifting and releasing/subsiding zones which accommodate strains developing in response to the current stress field (characterized by a maximum axis trending NW-SE) which has been active in the area since the Pliocene. The cluster of the seismic sequence which started with the 6th September 2002's main shock is located within the hinge zone. The distribution of the hypocenters relative to this sequence emphasizes the presence of a high-angle NE-SW-oriented deformation belt within which several shear surfaces are considered to be found sub-parallel to that established for the main shock. The kinematics of all these structures is consistent with a compressive right-lateral focal mechanism

The Palermo (Sicily) seismic cluster of September 2002, in the seismotectonic framework of the Tyrrhenian Sea-Sicily border area

The northern coast of Sicily and its offshore area represent a hinge zone between a sector of the Tyrrhenian Basin, characterized by the strongest crustal thinning, and the sector of the Sicilian belt which has emerged. This hinge zone is part of a wider W-E trending right-lateral shear zone, which has been affecting the Maghrebian Chain units since the Pliocene. Seismological and structural data have been used to evaluate the seismotectonic behavior of the area investigated here. Seismological analysis was performed on a data set of about 2100 seismic events which occurred between January 1988 and October 2002 in the Southern Tyrrhenian Sea. This paper focuses in particular on a set of data relating to the period from 6th September 2002, including both the main shock and about 540 aftershocks of the Palermo seismic sequence. The distribution of the hypocenters revealed the presence of two main seismogenic zones. The events of the easternmost zone may be related to the Ionian lithospheric slab diving beneath the Calabrian Arc. The seismicity associated with the westernmost zone is closely clustered around a sub-horizontal regression plane contained within the thinned Southern Tyrrhenian crust, hence suggesting that this seismogenic zone is strictly connected to the deformation field active within the hinge zone. On the basis of both structural and seismological data, the brittle deformation pattern is characterized by high-angle faults, mainly represented by transcurrent synthetic right-lateral and antithetic left-lateral systems, producing both restraining/uplifting and releasing/subsiding zones which accommodate strains developing in response to the current stress field (characterized by a maximum axis trending NW-SE) which has been active in the area since the Pliocene. The cluster of the seismic sequence which started with the 6th September 2002's main shock is located within the hinge zone. The distribution of the hypocenters relative to this sequence emphasizes the presence of a high-angle NE-SW-oriented deformation belt within which several shear surfaces are considered to be found sub-parallel to that established for the main shock. The kinematics of all these structures is consistent with a compressive right-lateral focal mechanism

Observation of Dirac plasmons in a topological insulator

Plasmons are the quantized collective oscillations of electrons in metals and doped semiconductors. The plasmons of ordinary, massive electrons are since a long time basic ingredients of research in plasmonics and in optical metamaterials. Plasmons of massless Dirac electrons were instead recently observed in a purely two-dimensional electron system (2DEG)like graphene, and their properties are promising for new tunable plasmonic metamaterials in the terahertz and the mid-infrared frequency range. Dirac quasi-particles are known to exist also in the two-dimensional electron gas which forms at the surface of topological insulators due to a strong spin-orbit interaction. Therefore,one may look for their collective excitations by using infrared spectroscopy. Here we first report evidence of plasmonic excitations in a topological insulator (Bi2Se3), that was engineered in thin micro-ribbon arrays of different width W and period 2W to select suitable values of the plasmon wavevector k. Their lineshape was found to be extremely robust vs. temperature between 6 and 300 K, as one may expect for the excitations of topological carriers. Moreover, by changing W and measuring in the terahertz range the plasmonic frequency vP vs. k we could show, without using any fitting parameter, that the dispersion curve is in quantitative agreement with that predicted for Dirac plasmons.Comment: 11 pages, 3 figures, published in Nature Nanotechnology (2013

Coexistence and conviviality in multi-faith, multi-ethnic Burgazadasi, the princes' islands of Istanbul

This thesis aims to provide an understanding of the existing cultural plurality and diversity in Burgazadası, within a post-Ottoman and homogenising context in Turkey. Most of the scholars working on conflict resolution and peace projects in the Balkans and the Middle East have attempted to analyse cultural plurality with the concept of “coexistence”. “Coexistence” as a concept presupposes the pre-existing categories of ethnicity, class and religion (i.e. coexistence between Israelis and Palestinians; Greek and Turkish Cypriots; Serbs, Croats and Bosnians). In this thesis, I demonstrate the inadequacy of the concept of “coexistence” and propose a “conviviality” approach to explore cultural pluralism. In the post-Ottoman, Turkish context in Burgaz, “coexistence” can be used when describing the homogenisation process, the construction and perception of categorisations of differences, the crystallisation of ethnic and religious identities and ruptures to cultural pluralism; but it is deficient in describing the continuity of cultural pluralism and what is shared between the members of the community in Burgaz. By contrast, “conviviality” provides an understanding of the continuity of cultural pluralism in Burgaz, the changes in sociality patterns, shared ways of living, the diversity and differentiations within “different groups”, the islanders' sense of belonging in Burgaz, their appreciation of diversity and acts of solidarity at the times of crisis. I argue that the homogenisation process in Turkey brought ruptures in cultural pluralism in Turkey, and changed the demographics in Burgaz; however the homogenisation process did not rupture the conviviality on the island and Burgazian identity which embraces all types of diversities of its inhabitants. At times of crisis, like in September 1955 riots, Burgaz islanders emphasised their shared Burgaz identity which overrode religious, class and ethnic differencesEThOS - Electronic Theses Online ServiceGBUnited Kingdo

Mechanical thrombectomy in patients with proximal occlusions and low NIHSS: Results from a large prospective registry

Background: Mechanical thrombectomy is now standard of care for treatment of acute ischemic stroke secondary to large vessel occlusion in the setting of high NIHSS. We analysed a large nationwide registry focusing on patients with large vessel occlusion and low NIHSS on admission to evaluate the efficacy and safety of thrombectomy in this patient population Methods: 2826 patients treated with mechanical thrombectomy were included in a multicentre registry from January 1, 2011 to December 31, 2015. We included patients with large vessel occlusion and NIHSS ≤ 6 on admission. Baseline characteristics, imaging, clinical outcome, procedure adverse events and positive and negative outcome predictors were analysed. Results: 134 patients were included. 90/134 had an anterior circulation and 44 a posterior circulation stroke. One patient died before treatment. Successful revascularization (mTICI 2b-3) was achieved in 73.7% (98/133) of the patients. Intraprocedural adverse event was observed in 3% (4/133) of cases. Symptomatic intracranial haemorrhage rate was 5.3% (7/133). At three months, 70.9% (95/134) of the patients had mRS score 0-2, 15.7% (21/134) mRS 3-5 and 13.4% (18/134) mRS 6. Age and successful recanalization were significant predictors of a good clinical outcome on both univariate (p= 0.005 and p=0.007) and multivariable (p=0.0018 and p=0.009 [nat log]) analysis. Absence of vessel recanalization and symptomatic intracranial hemorrhage were independent predictors of poor outcome (p=0.021). Conclusions: Our study suggests that patients with large vessel occlusion and low NIHSS score on admission can benefit from mechanical thrombectomy. Randomized trials are warranted

Non-adhesive liquid embolic agents in extra-cranial district: State of the art and review of the literature

This review focuses on the use of “new” generation of non-adhesive liquid embolic agents (NALEA). In literature, non-adhesive liquid embolic agents have mainly been used in the cerebral district; however, multiple papers describing the use of NALEA in the extracranial district have been published recently and the aim of this review is to explore and analyze this field of application. There are a few NALEA liquids such as Onyx, Squid, and Phil currently available in the market, and they are used in the following applications: mainly arteriovenous malformations, endoleaks, visceral aneurysm or pseudoaneurysm, presurgical and hypervascular lesions embolization, and a niche of percutaneous approaches. These types of embolizing fluids can be used alone or in combination with other embolizing agents (such as coils or particles) so as to enhance its embolizing effect or improve its possible defects. The primary purpose of this paper is to evaluate the use of NALEAs, predominantly used alone, in elective embolization procedures. We did not attempt a meta-analysis due to the data heterogeneity, high number of case reports, and the lack of a consistent follow-up time period

Twenty years of experience in juvenile nasopharyngeal angiofibroma (JNA) preoperative endovascular embolization: An effective procedure with a low complications rate

Juvenile nasopharyngeal angiofibroma (JNA) is a benign tumor of the nasal cavity that predominantly affects young boys. Surgical removal remains the gold standard for the management of this disease. Preoperative intra-arterial embolization (PIAE) is useful for reductions in intraoperative blood loss and surgical complications. In our series of 79 patients who underwent preoperative embolization from 1999 to 2020, demographics, procedural aspects, surgical management and follow-up outcome were analyzed. Embolization was performed in a similar fashion for all patients, with a superselective microcatheterization of external carotid artery (ECA) feeders and an injection of polyvinyl alcohol (PVA) particles, followed, in some cases, by the deployment of coils. Procedural success was reached in 100% of cases, with no complications such as bleeding or thromboembolic occlusion, and surgical intraoperative blood loss was significantly decreased. In conclusion, PIAE is a safe and effective technique in JNA treatment, minimizing intraoperative bleeding