Fermi surface, the locus in momentum space of gapless low-energy excitations, is a concept of fundamental importance in solid state physics. Electronic properties of a material are determined by the long-lived low-energy excitations near the Fermi surface. Conventionally, Fermi surface is understood as a property exclusive to a metallic state, contoured by electronic bands crossed by the Fermi level, although there has been a continuing effort in searching for Fermi surface outside the conventional description. In this thesis, techniques developed to prepare high-quality single crystals of SmB$_6$ and YBa$_2$Cu$_3$O$_{6+x}$ (abbreviated as YBCO$_{6+x}$ hereinafter) are described. By utilising measurement techniques of exceptional sensitivity and exploring a wide range of temperatures, magnetic fields, and electrical currents, we found signatures of unconventional Fermi surfaces beyond the traditional description in these strongly correlated electronic systems. SmB$_6$ is a classic example of Kondo insulators whose insulating behaviour arises due to strong correlation between the itinerant $d$-electrons and localised $f$-electrons. The peculiar resistivity plateau onsets below 4 K has been a decades-long puzzle whose origin has been recently proposed as the manifestation of topological conducting surface states. We found that the insulating behaviour in electrical transport is robust against magnetic fields up to 45 T, while prominent quantum oscillations in magnetisation are observed above 10 T. Angular dependence of the quantum oscillations revealed a three-dimensional characteristics with an absolute amplitude consistent with a bulk origin, and temperature dependence showed a surprising departure from the conventional Lifshitz-Kosevich formalism. Complementary thermodynamic measurements showed results consistent with a Fermi surface originating from neutral itinerant low-energy excitations at low temperatures. Theoretical proposals of the unconventional ground state uncovered by our measurements in SmB$_6$ are discussed. YBCO$_{6+x}$ is a high-temperature superconductor with a maximum $T_{\rm c}$ of 93.5 K and the cleanest member in the family of copper-oxide, or {\it cuprate}, superconductors. The correct description of electronic ground state in the enigmatic pseudogap regime, where the antinodal density of states are suppressed below a characteristic temperature $T^*$ above $T_{\rm c}$, has been a subject of active debates. While the quantum oscillations observed in underdoped YBCO$_{6+x}$ have been predominately interpreted as a property of the normal state where the superconducting parameter is completely suppressed at $\approx$ 23 T, we made the discovery that YBCO$_{6.55}$ exhibits zero resistivity up to 45 T when a low electrical current is used, consistent with the observation of a hysteresis loop in magnetisation. Quantum oscillations in the underdoped YBCO$_{6+x}$ are thus seen to coexist with $d$-wave superconductivity. Characteristics of the quantum oscillations are consistent with an isolated Fermi pocket reconstructed by a charge density wave order parameter and unaccompanied by significant background density of states, suggesting the antinodal density of states is completely gapped out by a strong order parameter involving pairing correlations, potentially in addition to the other order parameters. Transport measurements performed over a wide doping range show signatures consistent with pairing correlations that persist up to the pseudogap temperature $T^*$. The surprising observation of quantum oscillations in insulating SmB$_6$ and superconducting YBCO$_{6+x}$ demonstrates a possible new paradigm of a Fermi surface without a conventional Fermi liquid. A new theoretical framework outside the realm of Fermi liquid theory may be needed to discuss the physics in these strongly correlated materials with enticing electronic properties.

O retalho miocutâneo transverso do abdome (TRAM) é um dos principais métodos utilizados na reconstrução mamária, sendo que este tipo de cirurgia apresenta grande incidência de necrose. O objetivo deste estudo foi verificar a eficácia do campo magnético estático (CME) e do ultrassom pulsado de baixa intensidade (UPBI) na viabilidade do retalho TRAM em ratos. Para tanto, quarenta e oito ratos machos foram distribuídos em quatro grupos homogêneos: G1 (Controle) - sem exposição ao campo magnético e ultrassom, G2- expostos ao campo magnético sul, G3 - expostos ao campo magnético Norte e G4 - estimulados com ultrassom pulsado de baixa intensidade. O campo magnético de um ímã consistirá de ferrite de bário (BaFe12O19). A viabilidade do retalho será avaliada pela porcentagem de área de necrose, eserá analisada por meio do software de processamento e análise de imagens Area®. A avaliação da circulação periférica do retalho foi obtida por meio de termografia infravermelha FLIR T450 (FLIR Systems - OregonUSA) antes, e durante três dias intervenções terapêuticas. Também foram avaliadas a quantidade de mastócitos e espessura de epiderme. A normalidade dos dados foi avaliada pelo teste de Shapiro-Wilk, sendo verificada distribuição normal. A porcentagem de área de necrose, espessura da epiderme e quantificação de mastócitos, foram avaliados pelo teste ANOVA one-way e pós-hoc de Tukey (p<0.05). A análise da temperatura cutânea obtida por termografia infravermelha foi avaliada pelo teste two-way de medidas repetidas seguido do teste de Bonferroni. O processamento dos dados foi efetuado pelo software SPSS (Chicago, IL, USA), versão 13.0, sendo fixado o nível crítico de 5% (p<0,05). Houve diferença significativa entre os grupos na porcentagem de área de necrose, na temperatura do retalho, bem como na quantidade de mastócitos. Pode-se concluir que as intervenções terapêuticas propostas podem interferir na viabilidade do retalho TRAM / The retail myocutaneos transverse abdominal (TRAM) is one of the main methods used in breast reconstruction is that this type of plastic surgery shows a higher incidence of necrosis. The objective of the static magnetic field (SMF) the TRAM flap in rats. Forty-eight male rats will be divided into three equal groups; G1 (control), without exposure to the magnetic field, G2- exposed to the magnetic field South and 3- exposed to the magnetic field north and group G4 - Stimulated with low intensity pulsed ultrasound. The magnetic field of a magneto f barium ferrite (BaFe12O19). The viability of the flap will be evaluated by the percentage of area of necrosis Esera analyzed by means of software processing and analyzing images Area®. The assessment of retail peripheral circulation was obtained by infrared thermography FLIR T450 (FLIR - OregonUSA) before and three days therapeutic interventions. They evaluated the amount of mast cells and epidermal thickness. Data normality was assessed by the Shapiro-Wilk test, and verified normal distribution. The percentage of necrotic area, epidermal thickness and quantification of mast cells were evaluated by one-way ANOVA and post-hoc Tukey (p <0.05). Analysis of the skin temperature obtained by infrared thermography test was evaluated by two-way repeated measures followed by Bonferroni test. Data processing was performed using SPSS software (Chicago, IL, USA), version 13.0, and set the critical level of 5% (p <0.05). There was a significant difference between the groups in the percentage of necrotic area in retail temperature and the amount of mast cells. In conclusion the therapeutic interventions proposed may interfere with the viability of the TRAM flap

Nesta tese, investigamos a discrepância existente entre o número de galáxias satéli-tes da Via Láctea que é previsto e aquele que é observado, questão conhecida como ``problema da falta de satélites\'\' (PFS). Este problema pode ser reformulado em termos de um desacordo entre a função de luminosidades das galáxias satélites (FLS) que é estimada a partir de dados observacionais e a FLS predita por modelos numéricos de formação de galáxias. Nós revisamos tanto propriedades observacionais da população de satélites quanto a teoria associada à modelagem da formação de galáxias e estruturas. Para abordar o PFS, estudamos diferentes soluções possíveis. Nós desenvolvemos uma modificação simples ao potencial do inflaton usual e mostramos que esta leva a uma redução no número de halos de matéria escura de pequena massa. Nós usamos, então, um modelo semi-analítico de formação de galáxias para confirmar que supressões similares do espectro de potências de pequena escala produzem uma FLS com a forma correta. Em uma outra direção, nós discutimos outros mecanismos astrofísicos capazes de reduzir o número de galáxias pequenas, especificamente: os ventos gerados por explosões de supernovas e o aquecimento do meio intergalático durante a reionização do Universo. Finalmente, nós estudamos como um campo magnético primordial pode influenciar a formação de galáxias de pequena massa. Para isso, nós inicialmente mostramos que a pressão devida a um campo magnético leva a uma alteração significativa na massa de filtragem, levando a uma importante supressão na acresção de gás por galáxias de baixa massa. Introduzindo estas modifi-cações em um modelo numérico de formação de galáxias, mostramos que, para valo-res realistas de intensidade de campo, a pressão devido ao campo magnético leva a um bom acordo entre a FLS prevista e observada. / In this thesis we investigate the discrepancy between the predicted and observed number of satellite galaxies in the Milky Way, known as ``the missing satellites problem\'\' (MSP). This problem can be translated into the disagreement between the satellite luminosity function (SLF), which is estimated from the observational (particularly the SDSS) data and the SLF predicted by numerical models of galaxy formation. We review both the observational properties of the satellite population and the essentials of galaxy and structure formation modelling. To tackle the MSP, we study different possible solutions. We develop a small modification to the usual chaotic inflaton potential and show that it leads to a reduction in the number of small mass haloes. We use a semi-analytic model of galaxy formation to confirm that suppressions of the small scale power spectrum can produce a SLF with the correct shape. In a different direction, we discuss other astrophysical mechanisms that can reduce the number of small mass galaxies, namely: the outflows generated by supernovae explosions and the heating of the intergalactic medium during the reionization of the Universe. Finally, we study how a primordial magnetic field can influence the formation of small mass galaxies. We first find that small primordial magnetic field significantly change the filtering mass, leading to an important suppression in the gas accretion by small mass haloes. ( The filtering mass is the mass for which the baryon accretion is reduced to approximately 1/2 its normal value.) Introducing these modifications in the galaxy formation model, we show that for realistic field strengths, the pressure due to the magnetic field can result in a good match between the observed SLF and the model predictions.

Campos magnéticos de intensidade $\\sim \\mu$G são observados tanto em nossa galáxia, quanto em galáxias com alto desvio para o vermelho (\\emph{z}), onde o dínamo $\\alpha-\\Omega$ não deveria ter tempo para produzi-lo. Por conseguinte, uma origem primordial é indicada. Foi proposto que os campos primordiais surgiram em várias eras: durante a inflação, na transição de fase eletrofraca, na transição de fase quark hádron (TFQH), durante a formação dos primeiros objetos e durante a reionização. Nós sugerimos aqui, que estes campos magnéticos observados em galáxias através de medidas de rotação Faraday, têm sua origem em flutuações eletromagnéticas que naturalmente ocorreram no plasma quente e denso, existente logo após a TFQH. Nós evoluímos os campos previstos por nosso modelo até a época atual. O tamanho da região de coerência do campo magnético aumenta devido à fusão de regiões menores. Campos magnéticos de $\\sim 10 \\mu$G sobre regiões comóveis de $\\sim 1$ pc foram encontrados para \\emph{z} $\\sim 10$. Investigamos a amplificação destes campos sementes pelo dínamo turbulento em protogaláxias. A taxa de amplificação devido à um vórtice turbulento de raio $L$ com velocidade circular $V$ é da ordem de $V/L$. Enquanto o modelo padrão de dínamo tem um tempo de amplificação para um disco galáctico típico de $\\sim 10^{9}$ anos, o dínamo turbulento de pequena escala tem uma taxa de amplificação de $\\sim 10^{7}$ anos. Usamos as equações não-lineares para evolução da correlação magnética de forma a avaliar a evolução da amplificação destes campos na protogaláxia. Vários autores sugeriram uma origem gravitacional para os campos magnéticos em objetos celestes em rotação. Isto foi motivado em parte pela conjectura Schuster-Blackett (S-B), onde se propõe que os campos magnéticos em planetas e estrelas surgem devido à sua rotação. Neste cenário, correntes de massa neutra geram campos magnéticos, implicando na existência de um acoplamento entre os campos gravitacional e magnético. Nós também investigamos a possibilidade da conjectura S-B ser a origem dos intensos campos magnéticos em magnetares e \\emph{gamma ray bursts}. Além disso, estudamos a influência da pressões não térmicas, na determinação da massa de aglomerados de galáxias, usando dados públicos do XMM-Newton para 5 aglomerados de Abell. A pressão não térmica considerada aqui, é composta pelas componentes magnética e turbulenta. Nós consideramos estas duas componentes na equação do equilíbrio hidrostático e comparamos as estimativas de massa total, com os valores obtidos sem estas componentes. / Magnetic fields of intensities $\\sim \\mu$G are observed both in our galaxy and in high redshift (\\emph{z}) galaxies, where a mean field dynamo would not had time to produce them. Therefore, a primordial origin is indicated. It has been suggested that magnetic fields were created at various primordial eras: during inflation, the electroweak phase transition, the quark-hadron phase transition (QHPT), during the formation of the first objects, and during reionization. We suggest here that the magnetic fields observed in galaxies by Faraday Rotation Measurements (FRMs), have their origin in the electromagnetic fluctuations that naturally occurred in the dense hot plasma that existed just after the QHPT. We evolve the predicted fields to the present time. The size of the region containing a coherent magnetic field increased due to the fusion of smaller regions. Magnetic fields (MFs) $\\sim 10 \\mu$G over a comoving $\\sim 1$ pc region are predicted at redshift \\emph{z} $\\sim 10$. The amplification of these seed fields by the turbulent dynamo in a protogalaxy is here investigated. The e-fold amplification time by a turbulent eddy of radius $L$ with a circular velocity $V$ is on the order of $L/V$. Whereas the standard dynamo for a typical disk galaxy has an e-fold amplification time $\\sim 10^{9}$ years, the small scale turbulent dynamo has an e-fold time $\\sim 10^{7}$ years. We use the non-linear evolution equations for the magnetic correlations in order to analyze the amplifications of these fields in protogalaxies. Various authors have suggested a gravitational origin of the magnetic fields in rotating celestial bodies. It has been motivated, in part, by the Schuster-Blackett (S-B) conjecture, which suggests that the magnetic fields in planets and stars arise due to their rotation. In this scenario, neutral mass currents generate magnetic fields, implying the existence of a coupling between gravitational and electromagnetic fields. In this work, we investigate the possibility that the S-B conjecture is the origin of the intense magnetic fields near rotating compact objects, in particular connected with magnetars and gamma ray bursts. We also studied the influence of non-thermal pressure on the cluster mass determination using public XMM-Newton archival data for 5 Abell clusters. The non-thermal pressure considered here, is composed of the magnetic and the turbulent components. We also take into account these two non-thermal components in the hydrostatic equilibrium equation, and we compare the total mass estimated with the values obtained without assuming them.

Magnetic fields are prevalent in a wide variety of low mass stellar systems and play an important role in their evolution. Yet the process through which these fields are generated is not well understood. To understand how such systems can generate strong field structures characterization of these fields is required. Radio emission traces the fields directly and the properties of this emission can be modeled leading to constraints on the field geometry and magnetic parameters. The new Karl Jansky Very Large Array (VLA) provides highly sensitive radio observations. My thesis involves combining VLA observations with the development of magnetospheric emission models in order to characterize the magnetic fields in two fully convective cool star systems: (1) Young Stellar Objects (YSOs); (2) Ultracool dwarf stars. I conducted multi epoch observations of DG Tau, a YSO with a highly active, collimated outflow. The radio emission observed from this source was found to be optically thick thermal emission with no indication of the magnetic activity observed in X-rays. I determined that the outflow is highly collimated very close to the central source, in agreement with jet launching models. Additionally, I constrained the mass loss of the ionized component of the jet and found that close to the central source the majority of mass is lost through this component. Using lower angular resolution observations, I detected shock formations in the extended jet of DG Tau and modeled their evolution with time. Taking full advantage of the upgraded bandwidth on the VLA, I made wideband observations of two UCDs, TVLM513-46 and 2M 0746+20. Combining these observations with previously published and archival VLA observations I was able to fully characterize the spectral and temporal properties of the radio emission. I found that the emission is dominated by a mildly polarized, non-thermal quiescent component with periodic strongly polarized flare emission. The spectral energy distribution and polarization of the quiescent emission is well modeled using gyrosynchrotron emission with a mean field B~100 G, mildly relativistic power-law electrons with a density ne~105-6 cm-3, and source size of R~2R*. We were able to model the pulsed emission by coherent electron cyclotron radiation from a small number of isolated loops of high magnetic field (2-3 kG) with scale heights~1.2-2.7 stellar radii. The loops are well-separated in magnetic longitude, and are not part of a single dipolar magnetosphere. The overall magnetic configuration of both stars appears to confirm recent suggestions that radio over-luminous UCD's have `weak field' non-axisymmetric topologies, but with isolated regions of high magnetic field.

Charge-Conjugation (C) and Charge-Conjugation-Parity (CP) Violation is one of the three Sakharov conditions to explain via baryogenesis the observed baryon asymmetry of the universe (BAU). The Standard Model of particle physics (SM) contains sources of CP violation, but cannot explain the BAU. This motivates searches for new physics beyond the standard model (BSM) which address the Sakharov criteria, including high-precision searches for new sources of CPV in systems for which the SM contribution is small, but larger effects may be present in BSM theories. A promising example is the search for the electric dipole moment of the neutron (nEDM), which is a novel system to observe CPV due to the initial and final state being identical. A non-zero measurement necessarily requires violation of P and T discrete symmetries; invoking CPT invariance requires that CP is violated. There are BSM theories which predict a magnitude for the nEDM larger than SM predictions, so that such studies are beneficial at setting constraints on new physics. The current experimental limit of dn < 3.0 x 10-26 e cm at 90% CL as set by the Institut Laue-Langevin (ILL) [1] was largely limited by systematic effects related to the magnetic field. The research presented here supported technical progress toward a new measurement of the nEDM, with the goal of improving the result by an order of magnitude. A novel approach to the problem of limiting systematics is proposed, studied in Monte Carlo simulations, and an optimized prototype was constructed for use in a magnetic resonance experiment.

Yes / A workshop was recently held at Nagoya University (31 October – 02 November 2017), sponsored by the Center for International Collaborative Research, at the Institute for Space-Earth Environmental Research, Nagoya University, Japan, to quantitatively compare the performance of today’s operational solar flare forecasting facilities. Building upon Paper I of this series (Barnes et al. 2016), in Paper II (Leka et al. 2019) we described the participating methods for this latest comparison effort, the evaluation methodology, and presented quantitative comparisons. In this paper we focus on the behavior and performance of the methods when evaluated in the context of broad implementation differences. Acknowledging the short testing interval available and the small number of methods available, we do find that forecast performance: 1) appears to improve by including persistence or prior flare activity, region evolution, and a human “forecaster in the loop”; 2) is hurt by restricting data to disk-center observations; 3) may benefit from long-term statistics, but mostly when then combined with modern data sources and statistical approaches. These trends are arguably weak and must be viewed with numerous caveats, as discussed both here and in Paper II. Following this present work, we present in Paper IV a novel analysis method to evaluate temporal patterns of forecasting errors of both types (i.e., misses and false alarms; Park et al. 2019). Hence, most importantly, with this series of papers we demonstrate the techniques for facilitating comparisons in the interest of establishing performance-positive methodologies. / We wish to acknowledge funding from the Institute for Space-Earth Environmental Research, Nagoya University for supporting the workshop and its participants. We would also like to acknowledge the “big picture” perspective brought by Dr. M. Leila Mays during her participation in the workshop. K.D.L. and G.B. acknowledge that the DAFFS and DAFFS-G tools were developed under NOAA SBIR contracts WC-133R-13-CN-0079 (Phase-I) and WC-133R-14-CN-0103 (PhaseII) with additional support from Lockheed-Martin Space Systems contract #4103056734 for Solar-B FPP Phase E support. A.E.McC. was supported by an Irish Research Council Government of Ireland Postgraduate Scholarship. D.S.B. and M.K.G were supported by the European Union Horizon 2020 research and innovation programme under grant agreement No. 640216 (FLARECAST project; http://flarecast.eu). MKG also acknowledges research performed under the A-EFFort project and subsequent service implementation, supported under ESA Contract number 4000111994/14/D/ MPR. S. A. M. is supported by the Irish Research Council Postdoctoral Fellowship Programme and the US Air Force Office of Scientific Research award FA9550-17-1-039. The operational Space Weather services of ROB/SIDC are partially funded through the STCE, a collaborative framework funded by the Belgian Science Policy Office.

Charged particle chaos and its collective effects in different magnetic geometries are investigated in a sequence of various numerical experiments. The fields generated by the particles as a result of interaction with the background electric and magnetic fields is not accounted for in the simulation. An X-line is first used to describe the geometry of the magnetotail prior to magnetic reconnection and a study of the behavior of charged particles is done from a microscopic viewpoint. Another important geometry in the magnetotail prior to substorm onset is Bifurcated Current Sheet. The same analysis is done for this configuration. The existence of at least one positive Lyapunov exponent shows that the motion of the particles is chaotic. By using statistical mechanics, the macroscopic properties of this chaotic motion are studied. Due to particles being charged, an electric field (perpendicular to the magnetic field in weak magnetic field region) accelerates the particles on average. Finite average velocity in the direction of electric field gives rise to an effective resistivity even in a collisionless regime such as solar corona and the magnetotail. Starting from initial velocities that are chosen randomly from a uniform distribution, the evolution of these distributions tends to a Maxwellian by the end of the simulation that is somewhat analogous to collisions in a Lorentz gas model. The effective resistivity due to such collisions is estimated. Ohmic heating is found to occur as a result of such an effective resistivity. Such collisions due to collective particle effects are essentially a different mechanism from classical collision notion. These experiments are done for two types of ions found in the plasma sheet prior to substorm onset, viz., protons and oxygen ions. Observational evidence of oxygen ions in the central plasma sheet, which flow out along open field lines from the ionosphere, were also simulated in the same manner. Oxygen ions have been found to influence the bifurcation of the current sheet and are also important in reconnection and other nonohmic instabilities, such as Kelvin Helmholtz instability, due to their mass. It is found that acceleration in X-line scales with the mass of ion species and the resistivity remains constant for different electric field strengths. In a Bifurcated Current Sheet, the acceleration scales with the square of mass of ion species and the resistivity scales with the electric field. Also, the overall resistivity values found in a Bifurcated Current Sheet are an order of magnitude lower than that found in an X-line.

No description available.

No description available.