7,994 research outputs found
Phase diagram of the mean field model of simplicial gravity
We discuss the phase diagram of the balls in boxes model, with a varying
number of boxes. The model can be regarded as a mean-field model of simplicial
gravity. We analyse in detail the case of weights of the form , which correspond to the measure term introduced in the simplicial
quantum gravity simulations. The system has two phases~: {\em elongated} ({\em
fluid}) and {\em crumpled}. For the transition between
these two phases is first order, while for it is continuous.
The transition becomes softer when approaches unity and eventually
disappears at . We then generalise the discussion to an arbitrary set
of weights. Finally, we show that if one introduces an additional kinematic
bound on the average density of balls per box then a new {\em condensed} phase
appears in the phase diagram. It bears some similarity to the {\em crinkled}
phase of simplicial gravity discussed recently in models of gravity interacting
with matter fields.Comment: 15 pages, 5 figure
ARPES studies of cuprate Fermiology: superconductivity, pseudogap, and quasiparticle dynamics
We present angle-resolved photoemission spectroscopy (ARPES) studies of the
cuprate high-temperature superconductors which elucidate the relation between
superconductivity and the pseudogap and highlight low-energy quasiparticle
dynamics in the superconducting state. Our experiments suggest that the
pseudogap and superconducting gap represent distinct states, which coexist
below T. Studies on Bi-2212 demonstrate that the near-nodal and
near-antinodal regions behave differently as a function of temperature and
doping, implying that different orders dominate in different momentum-space
regions. However, the ubiquity of sharp quasiparticles all around the Fermi
surface in Bi-2212 indicates that superconductivity extends into the
momentum-space region dominated by the pseudogap, revealing subtlety in this
dichotomy. In Bi-2201, the temperature dependence of antinodal spectra reveals
particle-hole asymmetry and anomalous spectral broadening, which may constrain
the explanation for the pseudogap. Recognizing that electron-boson coupling is
an important aspect of cuprate physics, we close with a discussion of the
multiple 'kinks' in the nodal dispersion. Understanding these may be important
to establishing which excitations are important to superconductivity.Comment: To appear in a focus issue on 'Fermiology of Cuprates' in New Journal
of Physic
Multiwavelength Studies of PSR J1420-6048, a Young Pulsar in the Kookaburra
We present X-ray, radio, and infrared observations of the 68 ms pulsar PSR
J1420-6048 and its surrounding nebula, a possible counterpart of the gamma-ray
source GeV J1417-6100/3EG J1420-6038. Pulsed X-ray emission at the radio period
is marginally detected by ASCA from a source embedded in the hard spectrum
X-ray nebula AX J1420.1-6049. At radio wavelengths, the pulsar is found to be
strongly linearly and circularly polarized, and the polarization sweep is
measured. A comparison of high resolution ATCA radio imaging of the
Kookaburra's upper wing (G313.6+0.3), which contains the pulsar and the X-ray
nebula, with infrared images suggests the radio emission is partly non-thermal.Comment: 8 pages, 4 figures, to appear in Astrophysical Journal Letter
Still waters run deep: latent cytokine activity in nonlesional psoriasis skin
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116968/1/bjd14248_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/116968/2/bjd14248.pd
Signaling Virtue or Vulnerability? The Changing Impact of Exchange Rate Regimes on Government Bond Yields
Do exchange rate regimes affect the conditions under which developed countries borrow? This paper argues that they do, but their impact on yields depends on the prevailing macroeconomic context. When investors regard inflation as the most relevant risk to bond holdings, monetary union has a distinct advantage over floating and fixed exchange rates because of its credible in-built mechanism to control inflation. However, once default is seen as the most relevant risk, exchange rate rigidity becomes a liability due to its constraining effect on governmentsβ ability to respond to adverse shocks. We test our argument with a moving window panel analysis for twenty-three OECD countries from 1980 to 2017. We find that before the late 2000s, inflation was penalized under floating and (to a lesser extent) fixed exchange rate regimes, but not in countries in monetary union. Since the 2010s, inflation carries no penalty under any exchange rate regime. Variables linked to default risk (debt and entitlement spending) did not affect yields under any exchange rate arrangements until the mid-2000s. Afterwards, countries in monetary union (and to a lesser extent in fixed exchange rate regimes) were significantly penalized for public debt and entitlement spending, whereas countries with floating regimes were not. Our results speak to the literatures on governmentsβ institutional commitments and βroom to move.βHaben Wechselkursregime einen Einfluss auf die Konditionen, zu denen entwickelte LΓ€nder Staatsanleihen ausgeben kΓΆnnen? Wir argumentieren in diesem Beitrag, dass dies der Fall ist, wobei ihre Wirkung auf die Anleiherenditen vom vorherrschenden makroΓΆkonomischen Kontext abhΓ€ngt. Erachten Investoren Inflation als das entscheidende Risiko fΓΌr Investitionen in Anleihen, so hat eine WΓ€hrungsunion durch ihren glaubwΓΌrdigen inteΒgrierten Mechanismus zur Inflationskontrolle klare Vorteile gegenΓΌber flexiblen und festen Wechselkursen. Wird jedoch ein Ausfall der RΓΌckzahlungen als das entscheidende Risiko angesehen, werden starre Wechselkurse zum Nachteil, da sie die FΓ€higkeit von Regierungen, auf negative Schocks zu reagieren, verringern. Wir testen unser Argument mithilfe einer fΓΌr den Zeitraum von 1980 bis 2017 mit gleitenden Zeitfenstern durchgefΓΌhrten PanelanaΒlyse von 23 OECD-LΓ€ndern. Die Ergebnisse zeigen, dass Inflation vor den spΓ€ten 2000er-Jahren in flexiblen und (weniger stark) in festen Wechselkursregimen finanziell abgestraft wurde, jedoch nicht in den LΓ€ndern einer WΓ€hrungsunion. Seit den 2010er-Jahren wirkt sich Inflation in keinem der Wechselkursregime auf die Renditen aus. Mit dem AusfallriΒsiko verknΓΌpfte Variablen (Staatsverschuldung und Sozialausgaben) hatten bis zur Mitte der 2000er-Jahre in keinem der Wechselkursregime einen Einfluss auf die Renditen. Danach wurden LΓ€nder in einer WΓ€hrungsunion erheblich (und LΓ€nder in festen Wechselkursregimen weniger stark) fΓΌr Staatsverschuldung und Sozialausgaben abgestraft, wΓ€hrend dies bei LΓ€ndern in flexiblen Regimen nicht der Fall war. Unsere Ergebnisse tragen zur Literatur ΓΌber institutionelle Selbstverpflichtungen und HandlungsspielrΓ€ume von Regierungen bei.Contents 1 Introduction 2 Commitment devices and policy autonomy from a theoretical perspective 3 Inflation risk, default risk, and exchange rate regimes: An analysis of twenty-three OECD countries 4 Results section Results Robustness checks 5 Discussion and conclusion Appendix A Sources used for identifying sample countriesβ exchange rate regimes over time Appendix B Results controlling for capital mobility (measured via the Chinn-Ito capital account openness index) Appendix C Results excluding countries with a greater share of foreign currency-denominated debt than 2 percent (Canada and Sweden) Appendix D Results for crawling peg exchange rate regime Appendix E Results excluding heavily indebted EMU countries (Belgium, Greece, and Italy) Appendix F Results excluding EMU countries with the lowest sovereign credit ratings prior to the crisis (Greece, Italy, and Portugal) Reference
Material and doping dependence of the nodal and anti-nodal dispersion renormalizations in single- and multi-layer cuprates
In this paper we present a review of bosonic renormalization effects on
electronic carriers observed from angle-resolved photoemission spectra in the
cuprates. We specifically discuss the viewpoint that these renormalizations
represent coupling of the electrons to the lattice, and review how the wide
range of materials dependence, such as the number of CuO layers, and the
doping dependence can be straightforwardly understood as arising due to novel
electron-phonon coupling.Comment: 9 pages and 6 figures. Submitted as a review article for Advances in
Condensed Matter Physic
Designing for Ballet Classes: Identifying and Mitigating Communication Challenges Between Dancers and Teachers
Dancer-teacher communication in a ballet class can be challenging: ballet is one of the most complex forms of movements, and learning happens through multi-faceted interactions with studio tools (mirror, barre, and floor) and the teacher. We conducted an interview-based qualitative study with seven ballet teachers and six dancers followed by an open-coded analysis to explore the communication challenges that arise while teaching and learning in the ballet studio. We identified key communication issues, including adapting to multi-level dancer expertise, transmitting and realigning development goals, providing personalized corrections and feedback, maintaining the state of flow, and communicating how to properly use tools in the environment. We discuss design implications for crafting technological interventions aimed at mitigating these communication challenges
Reprogramming of lysosomal gene expression by interleukin-4 and Stat6.
BACKGROUND: Lysosomes play important roles in multiple aspects of physiology, but the problem of how the transcription of lysosomal genes is coordinated remains incompletely understood. The goal of this study was to illuminate the physiological contexts in which lysosomal genes are coordinately regulated and to identify transcription factors involved in this control.
RESULTS: As transcription factors and their target genes are often co-regulated, we performed meta-analyses of array-based expression data to identify regulators whose mRNA profiles are highly correlated with those of a core set of lysosomal genes. Among the ~50 transcription factors that rank highest by this measure, 65% are involved in differentiation or development, and 22% have been implicated in interferon signaling. The most strongly correlated candidate was Stat6, a factor commonly activated by interleukin-4 (IL-4) or IL-13. Publicly available chromatin immunoprecipitation (ChIP) data from alternatively activated mouse macrophages show that lysosomal genes are overrepresented among Stat6-bound targets. Quantification of RNA from wild-type and Stat6-deficient cells indicates that Stat6 promotes the expression of over 100 lysosomal genes, including hydrolases, subunits of the vacuolar HβΊ ATPase and trafficking factors. While IL-4 inhibits and activates different sets of lysosomal genes, Stat6 mediates only the activating effects of IL-4, by promoting increased expression and by neutralizing undefined inhibitory signals induced by IL-4.
CONCLUSIONS: The current data establish Stat6 as a broadly acting regulator of lysosomal gene expression in mouse macrophages. Other regulators whose expression correlates with lysosomal genes suggest that lysosome function is frequently re-programmed during differentiation, development and interferon signaling
High stress monitoring of prestressing tendons in nuclear concrete vessels using fibre-optic sensors
Maintaining the structural health of prestressed concrete nuclear containments is a key element in ensuring nuclear reactors are capable of meeting their safety requirements. This paper discusses the attachment, fabrication and characterisation of optical fibre strain sensors suitable for the prestress monitoring of irradiated steel prestressing tendons. The all-metal fabrication and welding process allowed the instrumented strand to simultaneously monitor and apply stresses up to 1300 MPa (80% of steel's ultimate tensile strength). There were no adverse effects to the strand's mechanical properties or integrity. After sensor relaxation through cyclic stress treatment, strain transfer between the optical fibre sensors and the strand remained at 69%. The fibre strain sensors could also withstand the non-axial forces induced as the strand was deflected around a 4.5 m bend radius. Further development of this technology has the potential to augment current prestress monitoring practices, allowing distributed measurements of short- and long-term prestress losses in nuclear prestressed-concrete vessels
Integrable models and quantum spin ladders: comparison between theory and experiment for the strong coupling ladder compounds
(abbreviated) This article considers recent advances in the investigation of
the thermal and magnetic properties of integrable spin ladder models and their
applicability to the physics of real compounds. The ground state properties of
the integrable two-leg spin-1/2 and the mixed spin-(1/2,1) ladder models at
zero temperature are analyzed by means of the Thermodynamic Bethe Ansatz.
Solving the TBA equations yields exact results for the critical fields and
critical behaviour. The thermal and magnetic properties of the models are
investigated in terms of the recently introduced High Temperature Expansion
method, which is discussed in detail. It is shown that in the strong coupling
limit the integrable spin-1/2 ladder model exhibits three quantum phases: (i) a
gapped phase in the regime , (ii) a fully polarised phase for
, and (iii) a Luttinger liquid magnetic phase in the regime
. The critical behaviour in the vicinity of the critical
points is of the Pokrovsky-Talapov type. The temperature-dependent thermal and
magnetic properties are directly evaluated from the exact free energy
expression and compared to known experimental results for a range of strong
coupling ladder compounds. Similar analysis of the mixed spin-(1/2,1) ladder
model reveals a rich phase diagram, with a 1/3 and a full saturation
magnetisation plateau within the strong antiferromagnetic rung coupling regime.
For weak rung coupling, the fractional magnetisation plateau is diminished and
a new quantum phase transition occurs. The phase diagram can be directly
deduced from the magnetisation curve obtained from the exact result derived
from the HTE. The thermodynamics of the spin-orbital model with different
single-ion anisotropies is also investigated.Comment: 90 pages, 33 figures, extensive revisio
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