779 research outputs found

    A Note on the Generalized Friedmann Equations for a Thick Brane

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    Within our thick brane approach previously used to obtain the cosmological evolution equations on a thick brane embedded in a five-dimensional Schwarzschild Anti-de Sitter spacetime it is explicitly shown that the consistency of these equations with the energy conservation equation requires that, in general, the thickness of the brane evolves in time. This varying brane thickness entails the possibility that both Newton's gravitational constant GG and the effective cosmological constant Λ4\Lambda_4 are time dependent.Comment: 6 pages,To appear in GR

    Complete Resection of Ampullary Paragangliomas Confined to the Submucosa on Endoscopic Ultrasound May Be Best Achieved by Radical Surgical Resection

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    Paragangliomas of the gastrointestinal tract generally are benign tumors usually found in the second portion of the duodenum. We present a case of paraganglioma of the ampulla of Vater confined to the submucosa on endoscopic ultrasound examination. This was initially treated by endoscopic resection, followed by pancreaticoduodenectomy after local resection margins were positive. Histopathology showed a well-differentiated ampullary paraganglioma confined to the submucosa, but with involvement of one regional lymph node. Only 25 prior cases of paraganglioma at the ampulla of Vater have been reported, and nine of these have demonstrated local or distant metastases. Because of their malignant potential, ampullary paragangliomas should be treated with radical resection if the goal is to achieve complete resection, even if preoperative imaging shows local confinement

    Localizing gravity on thick branes: a solution for massive KK modes of the Schroedinger equation

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    We generate scalar thick brane configurations in a 5D Riemannian space time which describes gravity coupled to a self-interacting scalar field. We also show that 4D gravity can be localized on a thick brane which does not necessarily respect Z_2-symmetry, generalizing several previous models based on the Randall-Sundrum system and avoiding the restriction to orbifold geometries as well as the introduction of the branes in the action by hand. We begin by obtaining a smooth brane configuration that preserves 4D Poincar'e invariance and violates reflection symmetry along the fifth dimension. The extra dimension can have either compact or extended topology, depending on the values of the parameters of the solution. In the non-compact case, our field configuration represents a thick brane with positive energy density centered at y=c_2, whereas in the compact case we get pairs of thick branes. We recast as well the wave equations of the transverse traceless modes of the linear fluctuations of the classical solution into a Schroedinger's equation form with a volcano potential of finite bottom. We solve Schroedinger equation for the massless zero mode m^2=0 and obtain a single bound wave function which represents a stable 4D graviton and is free of tachyonic modes with m^2<0. We also get a continuum spectrum of Kaluza-Klein (KK) states with m^2>0 that are suppressed at y=c_2 and turn asymptotically into plane waves. We found a particular case in which the Schroedinger equation can be solved for all m^2>0, giving us the opportunity of studying analytically the massive modes of the spectrum of KK excitations, a rare fact when considering thick brane configurations.Comment: 8 pages in latex. We corrected signs in the field equations, the expressions for the scalar field and the self-interacting potential. Due to the fact that no changes are introduced in the warp factor, the physics of the system remains the sam

    Unjust and Unsafe: The Eviction Experiences of Latine Immigrant and Farmworker Tenants in Oregon

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    Latine immigrant households often face housing instability due to language barriers, immigration status, and limited access to government resources. Oregon farmworkers experience additional obstacles to safe and stable housing caused by low wages, a lack of affordable housing options, and social isolation. In light of the identified needs and lack of equitable access to resources that this group experiences, the Evicted in Oregon research team conducted focus groups with Latine immigrant and farmworker tenants in Multnomah, Washington, and Marion Counties. The aim was to gain insight into their experiences with eviction and understand how they navigated through evictions during the COVID-19 pandemic. Through these discussions, we identified three patterns that are unique to the experiences of Latine immigrants and farmworkers who face eviction: mistreatment by landlords, fear of involvement with the legal system, and navigating unfamiliar procedures that have negative impacts on their health and family. Our study also reveals that even when tenants receive rental assistance, additional support is necessary to alleviate concerns about engaging with and navigating the complex legal system. Considering their fear of legal system involvement during evictions, support systems must effectively address these intertwined needs related to housing challenges, language barriers, and immigration status. Additionally, many tenants raised concerns about unsafe housing conditions and unfair practices by landlords; therefore, an Eviction Navigation program and legal assistance would be valuable for Latine immigrants as they navigate unfamiliar procedures and systems related to court hearings, rental assistance applications, and tenant-landlord relations. These forms of support could help alleviate fears associated with involvement with the legal system for immigrant families

    Hydrodynamic characteristics of wing-in-ground effect oscillating hydrofoilon power extraction performance

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    The energy contained in the tidal motion of the seas and oceans has the potential to be a significant source ofrenewable energy. The oscillating hydrofoil current-energy turbine has a good performance to extract energyfrom the coupling of its heaving and pitching motions. In the present study, the wing-in-ground (WIG) effect hasbeen considered to improve the power-extraction performance of the oscillating hydrofoils. The overset grid inthe commercial computational fluid dynamic (CFD) software STAR CCM+ is applied to study the flapping hydrofoilwith dynamic WIG effect between two hydrofoils. The simulation results show that the WIG effect cangreatly improve the power extraction performance of the flapping hydrofoil. The WIG effect is asymmetric overthe course of the foil moving toward or leaving from the symmetry plane. The distance of the gap has a majorinfluence on the hydrodynamic performances of the flapping hydrofoil. For a moderate gap, the positive pressureon the lower surface enhances as the hydrofoil departs from the symmetry plane and causes an improvement oflift and moment coefficients. As the gap decreases further, the increasing negative pressure between the leadingedge and the symmetry plane plays an essential role improving the power extraction as the hydrofoil approachesthe symmetry plane. Compared to the case without the WIG effect, the power-extraction efficiency has anincrement of 16.34% in the present study

    An Overview on Artificial Intelligence Techniques for Diagnosis of Schizophrenia Based on Magnetic Resonance Imaging Modalities: Methods, Challenges, and Future Works

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    Schizophrenia (SZ) is a mental disorder that typically emerges in late adolescence or early adulthood. It reduces the life expectancy of patients by 15 years. Abnormal behavior, perception of emotions, social relationships, and reality perception are among its most significant symptoms. Past studies have revealed the temporal and anterior lobes of hippocampus regions of brain get affected by SZ. Also, increased volume of cerebrospinal fluid (CSF) and decreased volume of white and gray matter can be observed due to this disease. The magnetic resonance imaging (MRI) is the popular neuroimaging technique used to explore structural/functional brain abnormalities in SZ disorder owing to its high spatial resolution. Various artificial intelligence (AI) techniques have been employed with advanced image/signal processing methods to obtain accurate diagnosis of SZ. This paper presents a comprehensive overview of studies conducted on automated diagnosis of SZ using MRI modalities. Main findings, various challenges, and future works in developing the automated SZ detection are described in this paper

    Probabilistic Mobility Models for Mobile and Wireless Networks

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    International audienceIn this paper we present a probabilistic broadcast calculus for mobile and wireless networks whose connections are unreliable. In our calculus, broadcasted messages can be lost with a certain probability, and due to mobility the connection probabilities may change. If a network broadcasts a message from a location, it will evolve to a network distribution depending on whether nodes at other locations receive the message or not. Mobility of nodes is not arbitrary but guarded by a probabilistic mobility function (PMF), and we also define the notion of a weak bisimulation given a PMF. It is possible to have weak bisimular networks which have different probabilistic connectivity information. We furthermore examine the relation between our weak bisimulation and a minor variant of PCTL* [1]. Finally, we apply our calculus on a small example called the Zeroconf protocol [2]

    Tectono-stratigraphic evolution of the intermontane Tarom Basin (NW sectors of the Arabia-Eurasia collision zone): insights into the vertical growth of the Iranian Plateau margin

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    The intermontane Tarom Basin of NW Iran (Arabia-Eurasia collision zone) is located at the transition between the Iranian Plateau (IP) to the SW and the Alborz Mountains to the NE. This basin was filled by Late Cenozoic synorogenic red beds that retain first-order information on the erosional history of adjacent topography, the vertical growth of the plateau margin and its lateral (orogen perpendicular) expansion. Here, we perform a multidisciplinary study including magnetostratigraphy, sedimentology, geochronology and sandstone petrography on these red beds. Our data show that widespread Eocene arc volcanism in NW Iran terminated at ~ 38-36 Ma, while intrabasinal synorogenic sedimentation occurred between ~ 16.5 and < 7.6 Ma, implying that the red beds are stratigraphically equivalent to the Upper Red Formation. After 7.6 Ma, the basin experienced intrabasinal deformation, uplift and erosion in association with the establishment of external drainage. Fluvial connectivity with the Caspian Sea, however, was interrupted by at least four episodes of basin aggradation. During endorheic conditions the basin fill did not reach the elevation of the plateau interior and hence the Tarom Basin was never integrated into the plateau realm. Furthermore, our provenance data indicate that the northern margin of the basin experienced a greater magnitude of deformation and exhumation than the southern one (IP margin). This agrees with recent Moho depth estimates, suggesting that crustal shortening and thickening cannot be responsible for the vertical growth of the northern margin of the IP, and hence surface uplift must have been driven by deep-seated processes

    Tectono-stratigraphic evolution of the intermontane Tarom Basin (NW sectors of the Arabia-Eurasia collision zone): insights into the vertical growth of the Iranian Plateau margin

    Get PDF
    The intermontane Tarom Basin of NW Iran (Arabia-Eurasia collision zone) is located at the transition between the Iranian Plateau (IP) to the SW and the Alborz Mountains to the NE. This basin was filled by Late Cenozoic synorogenic red beds that retain first-order information on the erosional history of adjacent topography, the vertical growth of the plateau margin and its lateral (orogen perpendicular) expansion. Here, we perform a multidisciplinary study including magnetostratigraphy, sedimentology, geochronology and sandstone petrography on these red beds. Our data show that widespread Eocene arc volcanism in NW Iran terminated at ~ 38-36 Ma, while intrabasinal synorogenic sedimentation occurred between ~ 16.5 and < 7.6 Ma, implying that the red beds are stratigraphically equivalent to the Upper Red Formation. After 7.6 Ma, the basin experienced intrabasinal deformation, uplift and erosion in association with the establishment of external drainage. Fluvial connectivity with the Caspian Sea, however, was interrupted by at least four episodes of basin aggradation. During endorheic conditions the basin fill did not reach the elevation of the plateau interior and hence the Tarom Basin was never integrated into the plateau realm. Furthermore, our provenance data indicate that the northern margin of the basin experienced a greater magnitude of deformation and exhumation than the southern one (IP margin). This agrees with recent Moho depth estimates, suggesting that crustal shortening and thickening cannot be responsible for the vertical growth of the northern margin of the IP, and hence surface uplift must have been driven by deep-seated processes
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