325 research outputs found

    Semiclassical Hartree-Fock theory of a rotating Bose-Einstein condensation

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    In this paper, we investigate the thermodynamic behavior of a rotating Bose-Einstein condensation with non-zero interatomic interactions theoretically. The analysis relies on a semiclassical Hartree-Fock approximation where an integral is performed over the phase space and function of the grand canonical ensemble is derived. Subsequently, we use this result to derive several thermodynamic quantities including the condensate fraction, critical temperature, entropy and heat capacity. Thereby, we investigate the effect of the rotation rate and interactions parameter on the thermodynamic behavior. The role of finite size is discussed. Our approach can be extended to consider the rotating condensate in optical potential

    A Literature Review on the Correlation Between Shear Bond Strength and the Degree of Conversion of Orthodontic Adhesive Systems

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    Objectives: The purpose of this study is to provide a comprehensive literature review on the correlation between shear bond strength and the degree of conversion of the orthodontic adhesive systems. Thus, this is considered as a major issue for the success of the orthodontic bonding techniques. Material and Methods: Electronic searches were performed in Pubmed and Scopus databases using relevant keywords. Textbook searching was also applied. Following the selection, full-text English language papers were fully reviewed to ensure that they met both the inclusion and the exclusion criteria. Results: Recent studies suggest that when increasing the DC, the SBS will increase. Thus, this results to a stiffer and a more durable resin. Conclusions: There is a wide range of factors affecting the SBS, DC, and their correlation. Some of them are related to the tooth etching techniques, adhesive related factors, curing units, and bracket materials. More research is required to develop more understanding of the role of these factors in determining the bonding success. This is because there are no specific published papers which were directly linked to the correlation between the SBS and the DC of orthodontic adhesives

    The origin of ultra diffuse galaxies: stellar feedback and quenching

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    We test if the cosmological zoom-in simulations of isolated galaxies from the FIRE project reproduce the properties of ultra diffuse galaxies. We show that stellar feedback-generated outflows that dynamically heat galactic stars, together with a passively aging stellar population after imposed quenching (from e.g. infall into a galaxy cluster), naturally reproduce the observed population of red UDGs, without the need for high spin halos or dynamical influence from their host cluster. We reproduce the range of surface brightness, radius and absolute magnitude of the observed z=0 red UDGs by quenching simulated galaxies at a range of different times. They represent a mostly uniform population of dark matter-dominated galaxies with M_star ~1e8 Msun, low metallicity and a broad range of ages. The most massive simulated UDGs require earliest quenching and are therefore the oldest. Our simulations provide a good match to the central enclosed masses and the velocity dispersions of the observed UDGs (20-50 km/s). The enclosed masses of the simulated UDGs remain largely fixed across a broad range of quenching times because the central regions of their dark matter halos complete their growth early. A typical UDG forms in a dwarf halo mass range of Mh~4e10-1e11 Msun. The most massive red UDG in our sample requires quenching at z~3 when its halo reached Mh ~ 1e11 Msun. If it, instead, continues growing in the field, by z=0 its halo mass reaches > 5e11 Msun, comparable to the halo of an L* galaxy. If our simulated dwarfs are not quenched, they evolve into bluer low-surface brightness galaxies with mass-to-light ratios similar to observed field dwarfs. While our simulation sample covers a limited range of formation histories and halo masses, we predict that UDG is a common, and perhaps even dominant, galaxy type around Ms~1e8 Msun, both in the field and in clusters.Comment: 20 pages, 13 figures; match the MNRAS accepted versio

    Giardia intestinalis assemblages among Egyptian symptomatic/asymptomatic cases in Cairo

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    Giardia intestinalis is frequent enteric protozoa, affecting humans worldwide. Human infections aremainly caused by two genetically different assemblages call A & B. This cross-sectional study characterizedthe Giardia genotypes isolated from the stool of symptomatic and asymptomatic Egyptians inCairo and correlated these genotypes with the demographic and clinical data of the cases. Stool sampleswere collected from 389 individuals (245 complaining of gastrointestinal (GIT) symptoms and144 apparently healthy asymptomatic individuals), and microscopically examined. Positive Samplesfor G. intestinalis were molecularly characterized by Copro-nPCR targeting beta-giardin gene, andthen analyzed by RFLP for assemblage identification. Giardia was detected in 62 samples (15.9%); 53samples in symptomatic cases (21.6%) and 9 samples in asymptomatic individuals (6.25%). DNA ofpositive samples was amplified by nPCR-RFLP assays. There was a significant predominance of assemblageB among symptomatic (82.7%) and asymptomatic (77.8%) groups, while the rest of sampleshad assemblage A. Among the clinical data, only flatulence was significantly associated with Giardiainfection with assemblage B. Assemblage B is the predominant genotype found in Egypt in symptomaticand asymptomatic patients suggesting an anthropologic transmission cycle.Key Words: Giardia; genotyping; Assemblage; nPCR-RFLP; beta-giardin

    A profile in FIRE: resolving the radial distributions of satellite galaxies in the Local Group with simulations

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    While many tensions between Local Group (LG) satellite galaxies and LCDM cosmology have been alleviated through recent cosmological simulations, the spatial distribution of satellites remains an important test of physical models and physical versus numerical disruption in simulations. Using the FIRE-2 cosmological zoom-in baryonic simulations, we examine the radial distributions of satellites with Mstar > 10^5 Msun around 8 isolated Milky Way- (MW) mass host galaxies and 4 hosts in LG-like pairs. We demonstrate that these simulations resolve the survival and physical destruction of satellites with Mstar >~ 10^5 Msun. The simulations broadly agree with LG observations, spanning the radial profiles around the MW and M31. This agreement does not depend strongly on satellite mass, even at distances <~ 100 kpc. Host-to-host variation dominates the scatter in satellite counts within 300 kpc of the hosts, while time variation dominates scatter within 50 kpc. More massive host galaxies within our sample have fewer satellites at small distances, likely because of enhanced tidal destruction of satellites via the baryonic disks of host galaxies. Furthermore, we quantify and provide fits to the tidal depletion of subhalos in baryonic relative to dark matter-only simulations as a function of distance. Our simulated profiles imply observational incompleteness in the LG even at Mstar >~ 10^5 Msun: we predict 2-10 such satellites to be discovered around the MW and possibly 6-9 around M31. To provide cosmological context, we compare our results with the radial profiles of satellites around MW analogs in the SAGA survey, finding that our simulations are broadly consistent with most SAGA systems.Comment: 18 pages, 10 figures, plus appendices. Main results in figures 2, 3, and 4. Accepted versio

    Star formation histories of dwarf galaxies in the FIRE simulations: dependence on mass and Local Group environment

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    We study star formation histories (SFHs) of ≃500\simeq500 dwarf galaxies (stellar mass M∗=105−109 M⊙M_\ast = 10^5 - 10^9\,M_\odot) from FIRE-2 cosmological zoom-in simulations. We compare dwarfs around individual Milky Way (MW)-mass galaxies, dwarfs in Local Group (LG)-like environments, and true field (i.e. isolated) dwarf galaxies. We reproduce observed trends wherein higher-mass dwarfs quench later (if at all), regardless of environment. We also identify differences between the environments, both in terms of "satellite vs. central" and "LG vs. individual MWvs. isolated dwarf central." Around the individual MW-mass hosts, we recover the result expected from environmental quenching: central galaxies in the "near field" have more extended SFHs than their satellite counterparts, with the former more closely resemble isolated ("true field") dwarfs (though near-field centrals are still somewhat earlier forming). However, this difference is muted in the LG-like environments, where both near-field centrals and satellites have similar SFHs, which resemble satellites of single MW-mass hosts. This distinction is strongest for M∗=106−107 M⊙M_\ast = 10^6 - 10^7\,M_\odot but exists at other masses. Our results suggest that the paired halo nature of the LG may regulate star formation in dwarf galaxies even beyond the virial radii of the MW and Andromeda. Caution is needed when comparing zoom-in simulations targeting isolated dwarf galaxies against observed dwarf galaxies in the LG.Comment: Main text: 11 pages, 8 figures; appendices: 4 pages, 4 figures. Submitted to MNRAS; comments welcom

    Formation of proto-globular cluster candidates in cosmological simulations of dwarf galaxies at z>4z>4

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    We perform cosmological hydrodynamical simulations to study the formation of proto-globular cluster candidates in progenitors of present-day dwarf galaxies (Mvir≈1010 M⊙(M_{\rm vir} \approx 10^{10}\, {\rm M}_\odot at z=0z=0) as part of the "Feedback in Realistic Environment" (FIRE) project. Compact (r1/2<30r_{1/2}<30 pc), relatively massive (0.5×105≲M⋆/M⊙≲5×1050.5 \times 10^5 \lesssim M_{\star}/{\rm M}_\odot \lesssim 5\times10^5), self-bound stellar clusters form at 11≳z≳511\gtrsim z \gtrsim 5 in progenitors with Mvir≈109 M⊙M_{\rm vir} \approx 10^9\,{\rm M}_\odot. Cluster formation is triggered when at least 107 M⊙10^7\,{\rm M}_\odot of dense, turbulent gas reaches Σgas≈104 M⊙ pc−2\Sigma_{\rm gas} \approx 10^4\, {\rm M}_\odot\, {\rm pc}^{-2} as a result of the compressive effects of supernova feedback or from cloud-cloud collisions. The clusters can survive for 2−3 Gyr2-3\,{\rm Gyr}; absent numerical effects, they would likely survive substantially longer, perhaps to z=0z=0. The longest-lived clusters are those that form at significant distance -- several hundreds of pc -- from their host galaxy. We therefore predict that globular clusters forming in progenitors of present-day dwarf galaxies will be offset from any pre-existing stars within their host dark matter halos as opposed to deeply embedded within a well-defined galaxy. Properties of the nascent clusters are consistent with observations of some of the faintest and most compact high-redshift sources in \textit{Hubble Space Telescope} lensing fields and are at the edge of what will be detectable as point sources in deep imaging of non-lensed fields with the \textit{James Webb Space Telescope}. By contrast, the star clusters' host galaxies will remain undetectable.Comment: 14 pages, 5 figures, submitted to MNRA
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