242 research outputs found
On the integrability of halo dipoles in gravity
We stress that halo dipole components are nontrivial in core-halo systems in
both Newton's gravity and General Relativity. To this end, we extend a recent
exact relativistic model to include also a halo dipole component. Next, we
consider orbits evolving in the inner vacuum between a monopolar core and a
pure halo dipole and find that, while the Newtonian dynamics is integrable, its
relativistic counterpart is chaotic. This shows that chaoticity due only to
halo dipoles is an intrinsic relativistic gravitational effect.Comment: 9 pages, REVTEX, two postscript figures include
Chaos around a H\'enon-Heiles-inspired exact perturbation of a black hole
A solution of the Einstein's equations that represents the superposition of a
Schwarszchild black hole with both quadrupolar and octopolar terms describing a
halo is exhibited. We show that this solution, in the Newtonian limit, is an
analog to the well known H\'enon-Heiles potential. The integrability of orbits
of test particles moving around a black hole representing the galactic center
is studied and bounded zones of chaotic behavior are found.Comment: 7 pages Revte
Study of chaos in hamiltonian systems via convergent normal forms
We use Moser's normal forms to study chaotic motion in two-degree hamiltonian
systems near a saddle point. Besides being convergent, they provide a suitable
description of the cylindrical topology of the chaotic flow in that vicinity.
Both aspects combined allowed a precise computation of the homoclinic
interaction of stable and unstable manifolds in the full phase space, rather
than just the Poincar\'e section. The formalism was applied to the
H\'enon-Heiles hamiltonian, producing strong evidence that the region of
convergence of these normal forms extends over that originally established by
Moser.Comment: 29 pages, REVTEX, 22 postscript figures on reques
Relativistic and Newtonian core-shell models: analytical and numerical results
We make a detailed analysis of Newtonian as well as relativistic core-shell
models recently proposed to describe a black hole or neutron star surrounded by
shells of matter, and in a seminal sense also galaxies, supernovae and star
remnants since there are massive shell-like structures surrounding many of them
and also evidences for many galactic nuclei hiding black holes. We discuss the
unicity of the models in relation to their analyticity at the black hole
horizon and also to the full elimination of conical singularities. Secondly, we
study the role played by the presence/lack of discrete reflection symmetries
about equatorial planes in the chaotic behavior of the orbits, which is to be
contrasted with the almost universal acceptance of reflection symmetries as
default assumptions in galactic modeling. We also compare the related effects
if we change a true central black hole by a Newtonian central mass. The
numerical findings are: 1- The breakdown of the reflection symmetry about the
equatorial plane in both Newtonian and relativistic core-shell models does i)
enhance in a significant way the chaoticity of orbits in reflection symmetric
oblate shell models and ii) inhibit significantly also the occurrence of chaos
in reflection symmetric prolate shell models. In particular, in the prolate
case the lack of the reflection symmetry provides the phase space with a robust
family of regular orbits that is otherwise not found at higher energies. 2- The
relative extents of the chaotic regions in the relativistic cases (i. e. with a
true central black hole) are significantly larger than in the corresponding
Newtonian ones (which have just a central potential).Comment: AASTEX, 22 pages plus 28 postscript figures, to appear in Ap.
An Excess Due to Small Grains Around The Nearby K0V Star HD69830: Asteroid or Cometary Debris?
Spitzer photometry and spectroscopy of the star HD69830 reveal an excess of
emission relative to the stellar photosphere between 8 and 35 m dominated
by strong features attributable to crystalline silicates with an emitting
surface area more than 1,000 times that of our zodiacal cloud. The spectrum
closely resembles that of the comet C/1995 O1 (Hale-Bopp). Since no excess is
detected at 70 m, the emitting material must be quite warm, be confined
within a few AU of the star, and originate in grains with low long-wavelength
emissivity, i.e. grains much smaller than m m. The
strong mineralogical features are evidence for even smaller, possibly
sub-micron sized grains. This small grain size is in direct contrast to the
10-100 m grains that dominate the relatively featureless spectra of our
zodiacal dust cloud and most other main sequence stars with excesses. The upper
limit at 70 m also implies that any Kuiper Belt analog must either be very
cold or be less massive than 5 times our own Kuiper Belt.
With collisional and Poynting-Robertson drag times of about a thousand years
for small grains, the emitting material must either: a) be created through
continual grinding down of material in a dense asteroid belt; or b) originate
in cometary debris arising from either a single ``super-comet'' or a very large
number of individual comets arriving from a distant reservoir. In the case of a
cometary origin for the emission, the mass requirements for continuous
generation by many individual comets are unreasonable and we favor the capture
of a single ``super comet'' into a 0.5-1 AU orbit where it can evolve a large
number of small grains over a 2 Myr period.Comment: Revised figure 3. Corrected references and typos to make consistent
with edited journal versio
Mid-IR observations of circumstellar disks -- Part III: A mixed sample of PMS stars and Vega-type objects
We present new mid-infrared spectra for a sample of 15 targets (1 FU Orionis
object, 4 Herbig Ae stars, 5 T Tauri stars and 5 Vega type stars), obtained
with the TIMMI2 camera at La Silla Observatory (ESO). Three targets are members
of the beta Pic moving group (HD 155555, HD 181296 and HD 319139). PAH bands
are observed towards the T Tauri star HD 34700 and the Herbig Ae star PDS 144
N. For HD 34700, the band profiles indicate processed PAHs. The spectrum of the
Vega-type object eta Corvi (HD 109085), for which a resolved disk at sub-mm
wavelengths is known, is entirely stellar between 8--13 micron. Similarly, no
indication for circumstellar matter at mid-infrared wavelengths is found
towards the Vega-like stars HD 3003, HD 80951, HD 181296 and, surprisingly, the
T Tauri system HD 155555.
The silicate emission features of the remaining eight sources are modelled
with a mixture of silicates of different grain sizes and composition.
Unprocessed dust dominates FU Ori, HD 143006 and CD-43 344. Large amorphous
grains are the main dust component around HD 190073, HD 319139, KK Oph and PDS
144 S. Both small grains and crystalline dust is found for the Vega-type HD
123356, with a dominance of small amorphous grains. We show that the infrared
emission of the binary HD 123356 is dominated by its late-type secondary, but
optical spectroscopy is still required to confirm the age of the system and the
spectral class of the companion. For most targets this is their first
mid-infrared spectroscopic observation. We investigate trends between stellar,
disk and silicate properties and confirm correlations of previous studies.
Several objects present an exciting potential for follow-up high-resolution
disk studies.Comment: Accepted for publication in A&
TRY plant trait database - enhanced coverage and open access
Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives
Pertuzumab, trastuzumab, and standard anthracycline- and taxane-based chemotherapy for the neoadjuvant treatment of patients with HER2-positive localized breast cancer (BERENICE) : a phase II, open-label, multicenter, multinational cardiac safety study
Background:
Anti-HER2 therapies are associated with a risk of increased cardiac toxicity, particularly when part of anthracycline-containing regimens. We report cardiac safety of pertuzumab, trastuzumab, and chemotherapy in the neoadjuvant treatment of HER2-positive early breast cancer.
Patients and methods:
BERENICE (NCT02132949) is a nonrandomized, phase II, open-label, multicenter, multinational study in patients with normal cardiac function. In the neoadjuvant period, cohort A patients received four cycles of dose-dense doxorubicin and cyclophosphamide, then 12 doses of standard paclitaxel plus four standard trastuzumab and pertuzumab cycles. Cohort B patients received four standard fluorouracil/epirubicin/cyclophosphamide cycles, then four docetaxel cycles with four standard trastuzumab and pertuzumab cycles. The primary end point was cardiac safety during neoadjuvant treatment, assessed by the incidence of New York Heart Association class III/IV heart failure and of left ventricular ejection fraction declines ( 6510 percentage-points from baseline and to a value of\u2009<50%). The main efficacy end point was pathologic complete response (pCR, ypT0/is ypN0). Results are descriptive.
Results:
Safety populations were 199 and 198 patients in cohorts A and B, respectively. Three patients [1.5%; 95% confidence interval (CI) 0.31% to 4.34%] in cohort A experienced four New York Heart Association class III/IV heart failure events. Thirteen patients (6.5%; 95% CI 3.5% to 10.9%) in cohort A and four (2.0%; 95% CI 0.6% to 5.1%) in cohort B experienced at least one left ventricular ejection fraction decline. No new safety signals were identified. pCR rates were 61.8% and 60.7% in cohorts A and B, respectively. The highest pCR rates were in the HER2-enriched PAM50 subtype (75.0% and 73.7%, respectively).
Conclusion:
Treatment with pertuzumab, trastuzumab, and common anthracycline-containing regimens for the neoadjuvant treatment of early breast cancer resulted in cardiac and general safety profiles, and pCR rates, consistent with prior studies with pertuzumab.
Clinical Trial Information: NCT02132949
Non-Human Primate Model of Kaposi's Sarcoma-Associated Herpesvirus Infection
Since Kaposi's sarcoma-associated herpesvirus (KSHV or human herpesvirus 8) was first identified in Kaposi's sarcoma (KS) lesions of HIV-infected individuals with AIDS, the basic biological understanding of KSHV has progressed remarkably. However, the absence of a proper animal model for KSHV continues to impede direct in vivo studies of viral replication, persistence, and pathogenesis. In response to this need for an animal model of KSHV infection, we have explored whether common marmosets can be experimentally infected with human KSHV. Here, we report the successful zoonotic transmission of KSHV into common marmosets (Callithrix jacchus, Cj), a New World primate. Marmosets infected with recombinant KSHV rapidly seroconverted and maintained a vigorous anti-KSHV antibody response. KSHV DNA and latent nuclear antigen (LANA) were readily detected in the peripheral blood mononuclear cells (PBMCs) and various tissues of infected marmosets. Remarkably, one orally infected marmoset developed a KS-like skin lesion with the characteristic infiltration of leukocytes by spindle cells positive for KSHV DNA and proteins. These results demonstrate that human KSHV infects common marmosets, establishes an efficient persistent infection, and occasionally leads to a KS-like skin lesion. This is the first animal model to significantly elaborate the important aspects of KSHV infection in humans and will aid in the future design of vaccines against KSHV and anti-viral therapies targeting KSHV coinfected tumor cells
Cosmic Evolution of Star Formation Enhancement in Close Major-merger Galaxy Pairs Since z = 1
The infrared (IR) emission of "M_* galaxies" (10^(10.4) ≤ M_(star) ≤ 10^(11.0) M_☉) in galaxy pairs, derived using data obtained in Herschel (PEP/HerMES) and Spitzer (S-COSMOS) surveys, is compared to that of single-disk galaxies in well-matched control samples to study the cosmic evolution of the star formation enhancement induced by galaxy-galaxy interaction. Both the mean IR spectral energy distribution and mean IR luminosity of star-forming galaxies (SFGs) in SFG+SFG (S+S) pairs in the redshift bin of 0.6 < z < 1 are consistent with no star formation enhancement. SFGs in S+S pairs in a lower redshift bin of 0.2 < z < 0.6 show marginal evidence for a weak star formation enhancement. Together with the significant and strong sSFR enhancement shown by SFGs in a local sample of S+S pairs (obtained using previously published Spitzer observations), our results reveal a trend for the star formation enhancement in S+S pairs to decrease with increasing redshift. Between z = 0 and z = 1, this decline of interaction-induced star formation enhancement occurs in parallel with the dramatic increase (by a factor of ~10) of the sSFR of single SFGs, both of which can be explained by the higher gas fraction in higher-z disks. SFGs in mixed pairs (S+E pairs) do not show any significant star formation enhancement at any redshift. The difference between SFGs in S+S pairs and in S+E pairs suggests a modulation of the sSFR by the intergalactic medium (IGM) in the dark matter halos hosting these pairs
- …