Testing the gravitational phenomenology of compact objects: superradiance, scalarization and screening mechanisms

In the last decades, an interesting variety of extended models of gravity has been proposed with the goal of capturing cosmological effects such as the accelerated phases of expansion and/or the so-called "dark sector" of our universe. In parallel, the quest for a full-fledged theory of quantum gravity proceeds by investigating the low-energy limit of candidate models. Many of these modified gravity models might leave imprints in the physics of compact objects and with gravitational-wave astronomy we have the unprecedented opportunity to test them against data with improving accuracy. A popular class of models (scalar-tensor theories) extends the field content of general relativity with an additional scalar field. These theories provide multiple examples where black hole and neutron star physics deviates from general relativity and can be constrained with observations. In this sense, superradiance and spontaneous growth of scalar fields around black holes and neutron stars are potentially detectable signatures of new physics. Screening mechanisms can in principle hide scalar effects, but their effectiveness in the strong-field regime is still largely unmodeled. In this thesis I briefly review the traditional tests of gravity, from the weak-field observations to gravitational-wave tests, before moving to discuss in details a collection of personal contributions in modeling the aforementioned scalar effects

Dynamical Chameleon Neutron Stars: stability, radial oscillations and scalar radiation in spherical symmetry

Scalar-tensor theories whose phenomenology differs significantly from general relativity on large (e.g. cosmological) scales do not typically pass local experimental tests (e.g. in the solar system) unless they present a suitable "screening mechanism". An example is provided by chameleon screening, whereby the local general relativistic behavior is recovered in high density environments, at least in weak-field and quasi-static configurations. Here, we test the validity of chameleon screening in strong-field and highly relativistic/dynamical conditions, by performing fully non-linear simulations of neutron stars subjected to initial perturbations that cause them to oscillate or even collapse to a black hole. We confirm that screened chameleon stars are stable to sufficiently small radial oscillations, but that the frequency spectrum of the latter shows deviations from the general relativistic predictions. We also calculate the scalar fluxes produced during collapse to a black hole, and comment on their detectability with future gravitational-wave interferometers.Comment: 21 pages, 17 figure

Молниеносная печеночная недостаточность медикаментозного, токсиколлергического генеза, разрешенная пересадкой печени. Kлинический случай

USMF Nicolae Testemițanu, Spitalul Clinic Republican, Conferința naţională de gastroenterologie şi hepatologie cu participare internaţională ”Actualităţi în gastroenterologie şi hepatologie” 16 iunie 2016 Chișinău, Republica MoldovaAcute hepatic failure is a result of toxic effects of used medication, viral hepatic infections, autoimmune hepatitis, but also there are unknown underlining causes. Hereby we present a case of violent acute, toxic- allergic, drug induced (sulfasalazin, metilprednisolon) hepatic failure, addressed by liver transplantation.Наиболее распространенные причины молниеносной печеночной недостаточности являются токсические эффекты препаратов, вирусный гепатит, аутоиммунный гепатит, а также неизвестные или неопределенные причины. Мы представляем клинический случай молниеносной печеночной недостаточности токсикоаллергического, медикаментозного (сульфасалазин, метилпреднизолон) генеза, которая была решена путем трансплантации печени

Arterial vascularization of the colon; a guide to surgical resection

Background. Colorectal cancer is a commonly diagnosed neoplasia in men and women worldwide. This study aims to rigorously map the arterial distribution of the colon in order to assess the implications of vascular patterns in surgical resection. Methods. Cadaveric dissections were performed to explore the arterial distribution (including collateral blood flow) of the colon. The study used standard dissection tools and photographic documentation to detail the vascular architecture supporting the large intestine. Results. The dissection revealed important arterial branches and anastomoses in the area of the superior and inferior mesenteric arteries, which are able to ensure continuous local blood supply especially in cases of arterial ischemia. An important arterial anastomosis was identified between the right branch of the middle colic artery and the ascending branch of the right colic artery, as well as the specific distribution of the marginal artery of Drummond and Haller-Riolan anastomotic arch. Conclusions. The blood supply of the colon derived from both mesenteric arteries includes redundant arterial anastomoses, but which are critical in specific situations such as the approach and results of surgical resection. Understanding these vascular patterns and collateral pathways, as well as careful intraoperative surgical exploration, are essential for oncologic surgeons to ensure successful colic resections with minimal complications and morbidity

Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks

无线传感器网络，作为全球未来十大技术之一，集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术，可实时感知、采集、处理、传输网络分布区域内的各种信息数据，在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议，并针对大规模的无线传感器网络设计了一种树状路由协议，它根据节点地址信息来形成路由，从而简化了复杂繁冗的路由表查找和维护，节省了不必要的开销，提高了路由效率，实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR（AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位：工学硕士院系专业：信息科学与技术学院通信工程系_通信与信息系统学号：2332007115216

Experimental violations of Bell's inequalities with time-bin and polarization entanglement Violazione delle disuguaglianze di Bell con entanglement in polarizzazione e time-bin

In this thesis activity the candidate has explored the main aspects of Bell Inequalities theory and eventually executed an experimental Violation test. This work contains a brief overview of the theoretical aspects around Bell Inequalities: the doubts arisen by Einstein, Podolski and Rosen about Quantum Theory completeness; the hidden variable theories and the bounds on classical correlations; quantum correlations and violation of Bell inequalities; the response given by Bell to the EPR paradox by introducing its famous theorem. In addition, the entanglement phenomenon has been studied, in particular in those dof that are given an important role in the violation of Bell Inequalities. Some documentation work was also done on non linear optics in order to understand fundamental effects that is common practice to exploit in the photon entanglement generation: SHG for the pump photons, SPDC in non-linear crystals. Moreover, the candidate also explored in this thesis some issues more closely related to the experimental aspect:loopholes that could affect the integrity of Bell inequalities proofs; efficiency threshold estimates regarding detection loophole; loophole-free configurations. Eventually, here in this report are also showed, along with the experimental setup brief description and some comments on the apparatus and its setting, the results of an experimental test of the CHSH inequality violation using photons entangled at first in polarization and then in a time-bin entanglement configuration

Nonlinear aspects of the effective theory of dark energy

The goal of this project is to study the effects predicted by scalar-tensor theories of dark energy on small scales. Scalar-tensor theories has been introduced to modify gravity in the infrared. However, large scale modifications of gravity are necessarily associated to short-scale ones. In order to be in accordance with current observational tests on small scales, one can introduce a screening mechanism that is effective in environments where nonlinearities of the scalar field become important, suppressing the extra degrees of freedom. The Vainshtein screening has been already proven to work in many scalar-tensor theories, in particular in the most general second-order covariant theory for gravity coupled to a scalar degree of freedom, the so-called Horndeski theory. The focus of this thesis is on the breaking of this mechanism in the extensions of Horndeski: we retrieve the failure of the screening for beyond Horndeski theories, starting from more general premises. Finally, we tackle the challenge of generalizing this result further to DHOST theories

Sibiu

Bucureşti : Fundaţia Regală pentru Literatură şi Artă, 1940. - 233 p. : il. ; 21 cm