Generalized Virial Theorem and Pressure Relation for a strongly correlated Fermi gas

For a two-component Fermi gas in the unitarity limit (ie, with infinite scattering length), there is a well-known virial theorem, first shown by J. E. Thomas et al, Phys. Rev. Lett. 95, 120402 (2005). A few people rederived this result, and extended it to few-body systems, but their results are all restricted to the unitarity limit. Here I show that there is a generalized virial theorem for FINITE scattering lengths. I also generalize an exact result concerning the pressure, first shown in cond-mat/0508320, to the case of imbalanced populations.Comment: 5 page

The Interstellar Medium and Star Formation of Galactic Disks. I. ISM and GMC properties with Diffuse FUV and Cosmic Ray Backgrounds

We present a series of adaptive mesh refinement (AMR) hydrodynamic simulations of flat rotation curve galactic gas disks with a detailed treatment of the interstellar medium (ISM) physics of the atomic to molecular phase transition under the influence of diffuse FUV radiation fields and cosmic ray backgrounds. We explore the effects of different FUV intensities, including a model with a radial gradient designed to mimic the Milky Way. The effects of cosmic rays, including radial gradients in their heating and ionization rates, are also explored. The final simulations in this series achieve $4\:$pc resolution across the $\sim20\:$kpc global disk diameter, with heating and cooling followed down to temperatures of $\sim10\:$K. The disks are evolved for $300\:$Myr, which is enough time for the ISM to achieve a quasi-statistical equilibrium. In particular, the mass fraction of molecular gas stabilizes by $\sim$200 Myr. Additional global ISM properties are analysed. Giant molecular clouds (GMCs) are also identified and the statistical properties of their populations examined. GMCs are tracked as the disks evolve. GMC collisions, which may be a means of triggering star cluster formation, are counted and the rates compared with analytic models. Relatively frequent GMC collision rates are seen in these simulations and their implications for understanding GMC properties, including the driving of internal turbulence, are discussed.Comment: Accepted by PASJ (cloud-cloud collision special issue

Evolving morphotropic phase boundary in lead-free (Bi1/2Na1/2)TiO3–BaTiO3 piezoceramics

The correlation between structure and electrical properties of lead-free (1-x)(Bi(1/2)Na(1/2))TiO(3)-xBaTiO(3) (BNT-100xBT) polycrystalline piezoceramics was investigated systematically by in situ synchrotron diffraction technique, combined with electrical property characterization. It was found that the morphotropic phase boundary (MPB) between a rhombohedral and a tetragonal phase evolved into a morphotropic phase region with electric field. In the unpoled material, the MPB was positioned at the transition from space group R3m to P4mm (BNT-11BT) with optimized permittivity throughout a broad single-phase R3m composition regime. Upon poling, a range of compositions from BNT-6BT to BNT-11BT became two-phase mixture, and maximum piezoelectric coefficient was observed in BNT-7BT. It was shown that optimized electrical properties are related primarily to the capacity for domain texturing and not to phase coexistence

Influence of an upper layer liquid on the phenomena and cavity formation associated with the entry of solid spheres into a stratified, two-layer system of immiscible liquids

New phenomena not previously documented in the available literature have been experimentally observed subsequent to the entry of falling steel spheres into a stratified system of a shallow layer of sunflower oil above a deep pool of water. Further experiments on similar sphere entries into sunflower oil demonstrated that these phenomena arose mainly as a result of the interaction between the surface of the spheres and the sunflower oil. It should be noted that the sunflower oil layer in the aforementioned two-layer system was relatively very thin compared to the dimensions of the spheres. Therefore, the experiments showed the substantial influence both the upper layer liquid and the surface conditions of the solid body could potentially have on the phenomena and cavity dynamics that arise as a result of solid entries into stratified two-layer systems of immiscible liquids

»Bibliotheken in den Niederlanden« : ein Seminar an der FH Potsdam

»Wie arbeiten Bibliotheken in anderen Ländern?« lautet der Titel einer Veranstaltungsreihe des Fachbereichs Informationswissenschaften der Fachhochschule Potsdam in Zusammenarbeit mit dem Weiterbildungszentrum der Freien Universitat Berlin sowie der Botschaft des jeweiligen Landes. Auf »Bibliotheken in Finnland« und »Bibliotheken in den Vereinigten Staaten« folgte am 17. Marz 2006 das Informationsseminar »Bibliotheken in den Niederlanden - Zusammenarbeit, Reorganisation und neue Dienstleistungen«. Unter der Leitung sowie Moderation von Rolf Busch und Prof. Hans-Christoph Hobohm sprachen die Referenten diesmal über die Nationalbibliothek der Niederlande, die Universi- tätsbibliothek Filburg und die öffentlichen Bibliotheken in Almere und Utrechrecht. Vorträge zu der Webseite »bibIiotheek.nl« und der Zukunft der öffentlichen Bibliothek, die »Bibliothek 2040«, veranschaulichten weitere Projekte der niederländischen Bibliotheksarbeit

Short-range magnetic correlations in Tb5Ge4

We present a single crystal neutron diffraction study of the magnetic short-range correlations in Tb$_5$Ge$_4$ which orders antiferromagnetically below the Neel temperature $T_N$ $\approx$ 92 K. Strong diffuse scattering arising from magnetic short-range correlations was observed in wide temperature ranges both below and above $T_N$. The antiferromagnetic ordering in Tb$_5$Ge$_4$ can be described as strongly coupled ferromagnetic block layers in the $ac$-plane that stack along the b-axis with weak antiferromagnetic inter-layer coupling. Diffuse scattering was observed along both $a^*$ and $b^*$ directions indicating three-dimensional short-range correlations. Moreover, the $q$-dependence of the diffuse scattering is Squared-Lorentzian in form suggesting a strongly clustered magnetic state that may be related to the proposed Griffiths-like phase in Gd$_5$Ge$_4$.Comment: 6 pages, 5 figure

GMC Collisions as Triggers of Star Formation. V. Observational Signatures

We present calculations of molecular, atomic and ionic line emission from simulations of giant molecular cloud (GMC) collisions. We post-process snapshots of the magneto-hydrodynamical simulations presented in an earlier paper in this series by Wu et al. (2017) of colliding and non-colliding GMCs. Using photodissociation region (PDR) chemistry and radiative transfer we calculate the level populations and emission properties of $^{12}$CO $J=1-0$, [CI] $^3{\rm P}_1\rightarrow{^3{\rm P}}_0$ at $609\,\mu$m, [CII] $158\,\mu$m and [OI] $^3{\rm P}_1\rightarrow{^3{\rm P}}_0$ transition at $63\,\mu$m. From integrated intensity emission maps and position-velocity diagrams, we find that fine-structure lines, particularly the [CII] $158\,\mu$m, can be used as a diagnostic tracer for cloud-cloud collision activity. These results hold even in more evolved systems in which the collision signature in molecular lines has been diminished.Comment: 10 pages, 7 figures, accepted for publication in ApJ, comments welcom

On-Board Sensor-Based NO x Emissions from Heavy-Duty Diesel Vehicles

Real-world nitrogen oxides (NOx) emissions were estimated using on-board sensor readings from 72 heavy-duty diesel vehicles (HDDVs) equipped with a Selective Catalytic Reduction (SCR) system in California. The results showed that there were large differences between in-use and certification NOx emissions, with 12 HDDVs emitting more than three times the standard during hot-running and idling operations in the real world. The overall NOx conversion efficiencies of the SCR system on many vehicles were well below the 90% threshold that is expected for an efficient SCR system, even when the SCR system was above the optimum operating temperature threshold of 250 °C. This could potentially be associated with SCR catalyst deterioration on some engines. The Not-to-Exceed (NTE) requirements currently used by the heavy-duty in-use compliance program were evaluated using on-board NOx sensor data. Valid NTE events covered only 4.2–16.4% of the engine operation and 6.6–34.6% of the estimated NOx emissions. This work shows that low cost on-board NOx sensors are a convenient tool to monitor in-use NOx emissions in real-time, evaluate the SCR system performance, and identify vehicle operating modes with high NOx emissions. This information can inform certification and compliance programs to ensure low in-use NOx emissions

An integrated model of visual attention using shape-based features

Apart from helping shed some light on human perceptual mechanisms, modeling visual attention has important applications in computer vision. It has been shown to be useful in priming object detection, pruning interest points, quantifying visual clutter as well as predicting human eye movements. Prior work has either relied on purely bottom-up approaches or top-down schemes using simple low-level features. In this paper, we outline a top-down visual attention model based on shape-based features. The same shape-based representation is used to represent both the objects and the scenes that contain them. The spatial priors imposed by the scene and the feature priors imposed by the target object are combined in a Bayesian framework to generate a task-dependent saliency map. We show that our approach can predict the location of objects as well as match eye movements (92% overlap with human observers). We also show that the proposed approach performs better than existing bottom-up and top-down computational models