1,244 research outputs found
A neuroimaging investigation of bipolar disorder and the neurocognitive effects of 5-HT7 antagonists
Bipolar disorder is a psychiatric disorder characterised by pathological mood states, but there is growing recognition of the role of cognitive impairment and dysfunction of emotional processes, which has a profound impact on quality of life. Many people with bipolar disorders exhibit brain volume impairment associated with cognitive dysfunction and an increased risk of dementia. In this thesis, I conducted a systematic review to understand the relationships between mood disorders and the 5-HT7 receptor. The 5-HT7 receptor is related to depression and anxiety, but the relationship between 5-HT7 and mania remains unclear; in addition, sleep and memory were also related to the 5-HT7 receptor. Followed by these findings, in the next two chapters, I examined the effects of 5-HT7 antagonists, using JNJ-18038683, on emotional and cognitive functioning, as well as their neural substrates. I then reported on neuroimaging investigations examining the effects of 5-HT7 antagonists on emotional processing and cognitive function in healthy volunteers to gain insight into their potential mode of action and utility for bipolar disorder. In fMRI analyses, the drug acted on 5-HT7 receptors potentially improving cognitive performance by modulating the function of the Cognitive Control Network in healthy controls. In the above-mentioned chapters, I gained a better understanding of the 5-HT7 antagonist, JNJ-18038683, and the putative promising effects for pharmacological treatments. However, the approach taken has some limitations, including a small sample size, potential participant bias, and a lack of systematic control of medication dose and duration of administration. In addition, in Chapter 5, I explored the brain basis of bipolar disorder and its links to cognitive and emotional dysfunction using a new ‘brain age’ approach. Individuals with bipolar disorder were found to have increased brain age compared to healthy controls. I hope that these findings can be applied to pharmacological treatment for individuals with bipolar disorder, ultimately allowing patients to benefit from the drug in the future
Search for high-mass Wγ and Zγ resonances using hadronic W/Z boson decays from 139 fb−1 of pp collisions at s√ = 13 TeV with the ATLAS detector
A search for high-mass charged and neutral bosons decaying to Wγ and Zγ final states is presented in this paper. The analysis uses a data sample of s√
= 13 TeV proton-proton collisions with an integrated luminosity of 139 fb−1 collected by the ATLAS detector during LHC Run 2 operation. The sensitivity of the search is determined using models of the production and decay of spin-1 charged bosons and spin-0/2 neutral bosons. The range of resonance masses explored extends from 1.0 TeV to 6.8 TeV. At these high resonance masses, it is beneficial to target the hadronic decays of the W and Z bosons because of their large branching fractions. The decay products of the high-momentum W/Z bosons are strongly collimated and boosted-boson tagging techniques are employed to improve the sensitivity. No evidence of a signal above the Standard Model backgrounds is observed, and upper limits on the production cross-sections of these bosons times their branching fractions to Wγ and Zγ are derived for various boson production models
Understanding X-ray Pulsars: from Blind Source Separation to Pulse Profile Decompositions
In Röntgendoppelsternen mit einem Neutronenstern wird Materie vom Begleiter auf das kompakte Objekt übertragen, wo sie auf das starke Magnetfeld der Magnetosphäre trifft. Das Magnetfeld lenkt die Materie zu den magnetischen Polen, wo sie ihre Gravitationsenergie abgibt, hauptsächlich in Form von Röntgenstrahlung. Wenn die Spin- und Magnetachse versetzt sind, kann diese Emission als Pulsation beobachtet werden, und das Objekt wird dann als akkretierender Röntgenpulsar bezeichnet.
Faltet man die Lichtkurve, d. h. die Intensitätsvariation der Emission über die Zeit, mit der Spinperiode des Pulsars, erhält man ein Pulsprofil, das aufgrund des Zusammenspiels verschiedener Faktoren wie Geometrie, Magnetfeldkonfiguration, intrinsische Strahlenmuster und gravitationsbedingte Lichtablenkung komplexe Formen aufweisen kann.
Die Physik von Röntgenpulsaren unter ihren extremen Bedingungen zu verstehen, stellt eine Reihe von Herausforderungen dar. Der Strahlungstransport und die dynamische Struktur des Akkretionsflusses müssen modelliert werden, um ihre komplexe Natur zu verstehen. Diese Probleme sind miteinander verknüpft, da die Eigenschaften und die Dynamik der akkretierenden Materie die Röntgenemission direkt beeinflussen. Diese Wechselwirkungen spielen eine wichtige Rolle bei der Entstehung der beobachteten Röntgenspektren.
Sie zu verstehen ist sowohl aus theoretischer als auch aus beobachtungstechnischer Sicht keine triviale Aufgabe. Hinzu kommt, dass die Emission aus der unmittelbaren Umgebung der Neutronensternoberfläche aufgrund von Phänomenen wie der gravitationsbedingten Lichtablenkung nicht unbedingt mit der beobachteten Strahlung übereinstimmt. Außerdem kann während verschiedener Phasen der Sternrotation die Emission von beiden Polen gleichzeitig beobachtet werden. Um Modelle zu testen und zu verfeinern, die die Entstehung von Spektren und Pulsprofilen in Röntgenpulsaren beschreiben, müssen die Beiträge beider Pole zum beobachteten Fluss als Funktion der Phase bestimmt werden. Dies ermöglicht die Untersuchung der physikalischen Prozesse, die am Strahlungstransport beteiligt sind. Die Rotation des Pulsars erlaubt es, die Winkelabhängigkeit der Emission zu untersuchen, was wiederum zu einem besseren Verständnis der Physik von Röntgenpulsaren beiträgt.
In dieser Arbeit wird ein neuer datenbasierter Ansatz verwendet, der die Puls-zu-Puls-Variabilität des beobachteten Flusses ausnutzt. Die Methode basiert auf der Behandlung der Aufgabe als ein Problem der blinden Quellentrennung. Das Ziel ist die Schätzung unbekannter Signale, die mit unbekannten Mischkoeffizienten gemischt sind. Dabei kann die inhärente Variabilität des Flusses genutzt werden, die teilweise unabhängig von den beiden Polen ist. Das Ergebnis sind zwei Signale, die die Flussvariabilität jedes Pols darstellen, skaliert durch die beiden Gewichtungen, die jedem Pol zugeordnet sind. Diese Gewichtungen sind die einpoligen Pulsprofile, die von Interesse sind.
Um die Methode zu etablieren, entwickle ich in dieser Arbeit die phasenkorrelierte Variabilitätsanalyse (PCVA) durch eine Reihe von Simulationen. Dies beinhaltet die Bestimmung der Anforderungen und Grenzen der PCVA, um ihre Effektivität bei der Trennung der Beiträge beider Pole in Röntgenpulsaren zu bestimmen. Anschließend demonstriere ich die Anwendung der PCVA auf Beobachtungsdaten des hellen Röntgenpulsars Cen X-3, die aus RXTE (Rossi X-ray Timing Explorer) Beobachtungen stammen. Ich vergleiche die Ergebnisse der PCVA mit früheren Arbeiten, die sich mit dem gleichen Problem beschäftigten. Auf der Grundlage meiner Ergebnisse stelle ich fest, dass die in der Vergangenheit getroffene Annahme der Symmetrie der intrinsischen Strahlungsmuster mit den Ergebnissen der PCVA unvereinbar und daher möglicherweise nicht gerechtfertigt ist.
Um die Ergebnisse der PCVA interpretieren zu können, habe ich ein einfaches Modell zur Beschreibung der erhaltenen Pulsprofile erstellt. Dieses Modell basiert auf einer Reihe von Annahmen. Zunächst wird die Geometrie des Systems unter Berücksichtigung der Inklination und des Positionswinkels des Pulsarspins definiert. Es wird angenommen, dass die Emissionsregion von einer einzelnen Quelle an jedem Pol erzeugt wird. Um eine Asymmetrie einzuführen, wird ein phänomenologisches Strahlungsmuster definiert, das symmetrisch zu einer bestimmten Richtung, aber asymmetrisch zur Oberflächennormalen ist. Dies führt zu asymmetrischen Strahlenmustern aufgrund der Rotation des Neutronensterns. Das Modell ermöglicht es auch eine Dipolverschiebung als zusätzlichen Parameter zu berücksichtigen und die Effekte der gravitationsbedingten Lichtablenkung miteinzubeziehen. Auf diese Weise bietet das Modell die Möglichkeit den Einfluss verschiedener Parameter, insbesondere des intrinsischen Strahlungsmusters, auf die beobachteten Pulsprofile zu untersuchen.
Ich verwende das Modell, um das Cen X-3 PCVA-Ergebnis zu untersuchen. Da die meisten Beiträge während der Rotation nicht Null sind, ist es naheliegend, dass die Emissionsregionen fast immer sichtbar sind. Trotz der Berücksichtigung der gravitationsbedingten Lichtablenkung ist eine Lösung, die dies widerspiegelt, auf der Basis der Literaturgeometrie schwierig. Eine leichte Verbesserung wird durch die Einbeziehung einer Dipolverschiebung erreicht, aber das Problem der fehlenden Sichtbarkeit der Emissionsregion bleibt bestehen. Ich diskutiere mögliche Lösungen für dieses Problem. Eine Möglichkeit besteht darin, die Beschränkung der Pulsargeometrie zu lockern, da alle Methoden zur Bestimmung der Geometrie auf Modellen oder Annahmen beruhen, die nicht absolut sind. Eine andere Möglichkeit wäre, ein komplexeres Strahlungsmodell zu verwenden oder ausgedehntere Emissionsregionen zu berücksichtigen.
Die in dieser Arbeit entwickelte PCVA erlaubt die Trennung der Emissionsbeiträge der beiden Pole von Röntgenpulsaren. Diese Methode kann prinzipiell auf jeden leuchtkräftigen Röntgenpulsar angewendet werden, sofern die spezifizierten Quellen- und Beobachtungsbedingungen erfüllt sind. Durch die Untersuchung der individuellen Beiträge der beiden Pole ermöglicht die PCVA die Untersuchung von Veränderungen im Akkretionsprozess und in den Akkretionsstrukturen. Darüber hinaus bietet das von mir entwickelte Modell ein Werkzeug zur Untersuchung verschiedener Parameter die das Pulsprofil formen, insbesondere die Auswirkungen eines leicht asymmetrischen Strahlungsmusters.In neutron star X-ray binaries, matter is transferred from the companion to the compact object where it encounters the strong magnetic field at the magnetosphere. The magnetic field redirects the material toward the magnetic poles, where it releases its gravitational potential energy mainly as X-rays. If the spin and magnetic axes are misaligned, this emission can be observed as pulsations, and the object is called an accreting X-ray pulsar. Folding the light curve, i.e. the intensity variation of the emission over time, with the spin period of the pulsar gives a pulse profile, which can have complex shapes due to the interplay of several factors such as geometry, magnetic field configuration, intrinsic beam patterns, and gravitational light bending.
Understanding the physics of X-ray pulsars, and the extreme conditions that are associated with them, presents a number of challenges. Radiative transfer and the dynamical structure of the accretion flow must be modeled to gain insight into their complex nature. These problems are interrelated, since the properties and dynamics of the accreting matter directly affect the X-ray emission, and the resulting radiation pressure in turn changes the accretion flow. Such interactions play an important role in shaping the observed X-ray spectra and they are difficult to understand from both a theoretical and observational point of view. In addition, the emission that escapes from the immediate vicinity of the surface of the neutron star is not necessarily what is observed: during different phases of the star's rotation, emission from both poles may be observed simultaneously due to phenomena such as gravitational light bending. To test and refine models describing the formation of spectra and pulse profiles in X-ray pulsars, it is necessary to determine the contributions of each pole to the observed flux as a function of phase, which helps to study the physical processes involved in radiative transfer. The rotation of the pulsar makes it possible to study the angular dependence of the emission, which in turn contributes to a better understanding of the physics of X-ray pulsars.
To accomplish this, a new data-driven approach is used in this thesis that takes advantage of the pulse-to-pulse variability in the observed flux. The method is based on treating the task as a blind source separation problem, where the goal is to estimate unknown signals mixed with unknown mixing coefficients. In this context, blind source separation techniques can be used by exploiting the inherent flux variability that is partially independent for the two poles. The result of this decomposition are the two signals representing the time variability of the accretion rate at each pole and the weights associated with each pole. These weights are the single-pole pulse profiles of interest.
To establish the method, in this thesis I develop the phase correlated variability analysis (PCVA) through a series of simulations. This includes determining the requirements and limitations of the PCVA to ensure its effectiveness in disentangling the contributions of the two poles in X-ray pulsars. I then demonstrate the application of the PCVA to observational data of the bright persistent X-ray pulsar Cen X-3 obtained from RXTE (Rossi X-ray Timing Explorer) observations. I compare the results obtained with the PCVA to those of previous studies that have addressed the same problem. Based on my results, I find that the symmetry assumption made in the past is incompatible with the PCVA results and thus may not be justified.
In order to interpret the results of the PCVA, I create a toy model to describe the obtained pulse profiles. This model is based on a number of assumptions. First, the geometry of the system is defined by considering the inclination and position angle of the pulsar spin. The emission region is assumed to be generated by a single source at each pole. To introduce asymmetry, a phenomenological beam pattern is defined that is symmetric about a certain direction but asymmetric with respect to the normal of the surface. This results in asymmetric beam patterns due to the rotation of the neutron star. The toy model also allows for an offset of the dipole as an additional parameter and incorporates the effects of gravitational light bending. In this way, the model provides a means to study the effect of different parameters, most importantly the intrinsic beam pattern, on the observed pulse profiles from each pole.
I then address the Cen X-3 PCVA result in the context of the toy model. Despite accounting for gravitational light bending, the presence of mostly non-zero contributions throughout the rotation makes it difficult to find a solution using literature geometry. I find a slight improvement by allowing for an offset of the dipole, but the visibility problem still remains and I discuss possible solutions to this problem. One possibility is to relax the basic pulsar geometry, since all methods for determining the geometry are based on models or assumptions that are not absolute. Alternatively, the use of a more complex beam pattern model or the consideration of extended emission regions could potentially resolve the lack of visibility gaps in the results.
The PCVA developed in this thesis allows the separation of the emission contributions from the two poles of X-ray pulsars. In principle, this method can be applied to any luminous X-ray pulsar, provided that the specified source and observational requirements are met. Thus, by studying the individual contributions from each pole, the PCVA allows the study of changes in the accretion process and structures. In addition, the toy model provides a tool for exploring various parameters that shape the pulse profile, in particular the effects of a slightly asymmetric beam pattern
Search for high-mass Wγ and Zγ resonances using hadronic W/Z boson decays from 139 fb of pp collisions at = 13 TeV with the ATLAS detector
A search for high-mass charged and neutral bosons decaying to Wγ and Zγ final states is presented in this paper. The analysis uses a data sample of = 13 TeV proton-proton collisions with an integrated luminosity of 139 fb collected by the ATLAS detector during LHC Run 2 operation. The sensitivity of the search is determined using models of the production and decay of spin-1 charged bosons and spin-0/2 neutral bosons. The range of resonance masses explored extends from 1.0 TeV to 6.8 TeV. At these high resonance masses, it is beneficial to target the hadronic decays of the W and Z bosons because of their large branching fractions. The decay products of the high-momentum W/Z bosons are strongly collimated and boosted-boson tagging techniques are employed to improve the sensitivity. No evidence of a signal above the Standard Model backgrounds is observed, and upper limits on the production cross-sections of these bosons times their branching fractions to Wγ and Zγ are derived for various boson production models
Deep Statistical Models with Application to Environmental Data
When analyzing environmental data, constructing a realistic statistical model is important, not only to fully characterize the physical phenomena, but also to provide valid and useful predictions. Gaussian process models are amongst the most popular tools used for this purpose. However, many assumptions are usually made when using Gaussian processes, such as stationarity of the covariance function. There are several approaches to construct nonstationary spatial and spatio-temporal Gaussian processes, including the deformation approach. In the deformation approach, the geographical domain is warped into a new domain, on which the Gaussian process is modeled to be stationary. One of the main challenges with this approach is how to construct a deformation function that is complicated enough to adequately capture the nonstationarity in the process, but simple enough to facilitate statistical inference and prediction. In this thesis, by using ideas from deep learning, we construct deformation functions that are compositions of simple warping units. In particular, deformation functions that are composed of aligning functions and warping functions are introduced to model nonstationary and asymmetric multivariate spatial processes, while spatial and temporal warping functions are used to model nonstationary spatio-temporal processes. Similarly to the traditional deformation approach, familiar stationary models are used on the warped domain. It is shown that this new approach to model nonstationarity is computationally efficient, and that it can lead to predictions that are superior to those from stationary models. We show the utility of these models on both simulated data and real-world environmental data: ocean temperatures and surface-ice elevation. The developed warped nonstationary processes can also be used for emulation. We show that a warped, gradient-enhanced Gaussian process surrogate model can be embedded in algorithms such as importance sampling and delayed-acceptance Markov chain Monte Carlo. Our surrogate models can provide more accurate emulation than other traditional surrogate models, and can help speed up Bayesian inference in problems with exponential-family likelihoods with intractable normalizing constants, for example when analyzing satellite images using the Potts model
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Search for a vector-like quark T′ → tH via the diphoton decay mode of the Higgs boson in proton-proton collisions at √s = 13 TeV
A preprint version of the article was made available at arXiv, arXiv:2302.12802 [hep-ex]. It was replaced with the published version. All the figures and tables can be found at: https://cms-results.web.cern.ch/cms-results/public-results/publications/B2G-21-007 (CMS Public Pages).Report number: CMS-B2G-21-007, CERN-EP-2022-253.Copyright © 2023 CERN, for the benefit of the CMS Collaboration. A search for the electroweak production of a vector-like quark T′, decaying to a top quark and a Higgs boson is presented. The search is based on a sample of proton-proton collision events recorded at the LHC at √s = 13 TeV, corresponding to an integrated luminosity of 138 fb1. This is the first T′ search that exploits the Higgs boson decay to a pair of photons. For narrow isospin singlet T′ states with masses up to 1.1 TeV, the excellent diphoton invariant mass resolution of 1–2% results in an increased sensitivity compared to previous searches based on the same production mechanism. The electroweak production of a T′ quark with mass up to 960 GeV is excluded at 95% confidence level, assuming a coupling strength κT = 0.25 and a relative decay width Γ/MT′ < 5%. [Figure not available: see fulltext.].SCOAP3
Search for pair-production of vector-like quarks in pp collision events at root s=13 TeV with at least one leptonically decaying Z boson and a third-generation quark with the ATLAS detector
A search for the pair-production of vector-like quarks optimized for decays into a Z boson and a third-generation Standard Model quark is presented, using the full Run 2 dataset corresponding to 139 fb-1 of pp collisions at & RADIC;s = 13 TeV, collected in 2015-2018 with the ATLAS detector at the Large Hadron Collider. The targeted final state is characterized by the presence of a Z boson with high transverse momentum, reconstructed from a pair of same-flavour leptons with opposite-sign charges, as well as by the presence of b-tagged jets and high-transverse-momentum large-radius jets reconstructed from calibrated smaller-radius jets. Events with exactly two or at least three leptons are used, which are further categorized by the presence of boosted W, Z, and Higgs bosons and top quarks. The categorization is performed using a neural-network-based boosted object tagger to enhance the sensitivity to signal relative to the background. No significant excess above the background expectation is observed and exclusion limits at 95% confidence level are set on the masses of the vector-like partners T and B of the top and bottom quarks, respectively. The limits depend on the branching ratio configurations and, in the case of 100% branching ratio for T-+ Zt and 100% branching ratio for B-+ Zb, this search sets the most stringent limits to date, allowing mT > 1.60 TeV and mB > 1.42 TeV, respectively. & COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3
Localizations with noncompact transverse spaces and covert symmetry breaking in supergravity
The focus of my doctoral work has been answering the question: Can lower-dimensional effective gravitational theories be found in a higher-dimensional theory with a non-compact transverse space? To answer this question this thesis is divided into two parts. First, I explore supergravity solutions on warped product manifolds and argue that they correspond to solutions of a modified Laplacian. I pay special attention to Type III † solutions, or solutions characterized by the presence of non-constant transverse zero modes, and emphasize that these are the only higher dimensional solutions corresponding to localized sources that yield effectively lower-dimensional physics when the transverse space has infinite volume. Second, I derive the lower dimensional effective field theory about such backgrounds. I discover that
these effective field theories have covert symmetry breaking, spontaneous breaking of gauge symmetry which only appears at quartic order. I show this explicitly for D = d + 1 scalar electrodynamics with any boundary condition that corresponds to a non-constant transverse zero mode. The mathematical prerequisite for both of these conclusions is Sturm–Liouville theory with precise manipulations of Green’s
formula. To support this I derive the fundamental conclusions of Sturm–Liouville theory for a restricted class of operator, that is the Laplacian, which relaxes some requirements for permissible boundary conditions of Sturm–Liouville theory. The answer to my focal question is: Yes; however, the lower-dimensional theory has novel corrections which were previously unexplored, and further research is indicated.Open Acces
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