129 research outputs found
Dusty Planetary Systems
Extensive photometric stellar surveys show that many main sequence stars show
emission at infrared and longer wavelengths that is in excess of the stellar
photosphere; this emission is thought to arise from circumstellar dust. The
presence of dust disks is confirmed by spatially resolved imaging at infrared
to millimeter wavelengths (tracing the dust thermal emission), and at optical
to near infrared wavelengths (tracing the dust scattered light). Because the
expected lifetime of these dust particles is much shorter than the age of the
stars (>10 Myr), it is inferred that this solid material not primordial, i.e.
the remaining from the placental cloud of gas and dust where the star was born,
but instead is replenished by dust-producing planetesimals. These planetesimals
are analogous to the asteroids, comets and Kuiper Belt objects (KBOs) in our
Solar system that produce the interplanetary dust that gives rise to the
zodiacal light (tracing the inner component of the Solar system debris disk).
The presence of these "debris disks" around stars with a wide range of masses,
luminosities, and metallicities, with and without binary companions, is
evidence that planetesimal formation is a robust process that can take place
under a wide range of conditions. This chapter is divided in two parts. Part I
discusses how the study of the Solar system debris disk and the study of debris
disks around other stars can help us learn about the formation, evolution and
diversity of planetary systems by shedding light on the frequency and timing of
planetesimal formation, the location and physical properties of the
planetesimals, the presence of long-period planets, and the dynamical and
collisional evolution of the system. Part II reviews the physical processes
that affect dust particles in the gas-free environment of a debris disk and
their effect on the dust particle size and spatial distribution.Comment: 68 pages, 25 figures. To be published in "Solar and Planetary
Systems" (P. Kalas and L. French, Eds.), Volume 3 of the series "Planets,
Stars and Stellar Systems" (T.D. Oswalt, Editor-in-chief), Springer 201
Control of single-spin magnetic anisotropy by exchange coupling
The properties of quantum systems interacting with their environment, commonly called open quantum systems, can be affected strongly by this interaction. Although this can lead to unwanted consequences, such as causing decoherence in qubits used for quantum computation1, it can also be exploited as a probe of the environment. For example, magnetic resonance imaging is based on the dependence of the spin relaxation times of protons2 in water molecules in a host's tissue3. Here we show that the excitation energy of a single spin, which is determined by magnetocrystalline anisotropy and controls its stability and suitability for use in magnetic data-storage devices4, can be modified by varying the exchange coupling of the spin to a nearby conductive electrode. Using scanning tunnelling microscopy and spectroscopy, we observe variations up to a factor of two of the spin excitation energies of individual atoms as the strength of the spin's coupling to the surrounding electronic bath changes. These observations, combined with calculations, show that exchange coupling can strongly modify the magnetic anisotropy. This system is thus one of the few open quantum systems in which the energy levels, and not just the excited-state lifetimes, can be renormalized controllably. Furthermore, we demonstrate that the magnetocrystalline anisotropy, a property normally determined by the local structure around a spin, can be tuned electronically. These effects may play a significant role in the development of spintronic devices5 in which an individual magnetic atom or molecule is coupled to conducting leads
Unemployment expectations in an agent-based model with education
Why are unemployment expectations of the “man in the street” markedly different from professional forecasts? We present an agent-based model to explain this deep disconnection using boundedly rational agents with different levels of education. A good fit of empirical data is obtained under the assumptions that there is staggered update of information, agents update episodically their estimate and there is a fraction of households who always and stubbornly forecast that the unemployment is going to raise. The model also sheds light on the role of education and suggests that more educated agents update their information more often and less obstinately fixate on the worst possible forecast
Circumstellar discs: What will be next?
This prospective chapter gives our view on the evolution of the study of
circumstellar discs within the next 20 years from both observational and
theoretical sides. We first present the expected improvements in our knowledge
of protoplanetary discs as for their masses, sizes, chemistry, the presence of
planets as well as the evolutionary processes shaping these discs. We then
explore the older debris disc stage and explain what will be learnt concerning
their birth, the intrinsic links between these discs and planets, the hot dust
and the gas detected around main sequence stars as well as discs around white
dwarfs.Comment: invited review; comments welcome (32 pages
Cytomegalovirus-based vaccine expressing Ebola virus glycoprotein protects nonhuman primates from Ebola virus infection.
Ebolaviruses pose significant public health problems due to their high lethality, unpredictable emergence, and localization to the poorest areas of the world. In addition to implementation of standard public health control procedures, a number of experimental human vaccines are being explored as a further means for outbreak control. Recombinant cytomegalovirus (CMV)-based vectors are a novel vaccine platform that have been shown to induce substantial levels of durable, but primarily T-cell-biased responses against the encoded heterologous target antigen. Herein, we demonstrate the ability of rhesus CMV (RhCMV) expressing Ebola virus (EBOV) glycoprotein (GP) to provide protective immunity to rhesus macaques against lethal EBOV challenge. Surprisingly, vaccination was associated with high levels of GP-specific antibodies, but with no detectable GP-directed cellular immunity
CYFRA 21-1 is a prognostic determinant in non-small-cell lung cancer: results of a meta-analysis in 2063 patients
SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Immunological and non-immunological mechanisms of allergic diseases in the elderly: biological and clinical characteristics
Detection of Brazilian hantavirus by reverse transcription polymerase chain reaction amplification of N gene in patients with hantavirus cardiopulmonary syndrome
A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)
Meeting abstrac
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