4,761 research outputs found
The X-ray luminosity function of galaxies in the Coma cluster
The XMM-Newton survey of the Coma cluster of galaxies covers an area of 1.86
square degrees with a mosaic of 16 pointings and has a total useful integration
time of 400 ksec. Detected X-ray sources with extent less than 10" were
correlated with cataloged galaxies in the Coma cluster region. The redshift
information, which is abundant in this region of the sky, allowed us to
separate cluster members from background and foreground galaxies. For the
background sources, we recover a typical LogN-LogS in the flux range 1.e-15 -
1.e-13 ergs/s/cm^2 in the 0.5-2.0 keV band. The X-ray emission from the cluster
galaxies exhibits X-ray colors typical of thermal emission. The luminosities of
Coma galaxies lie in the 1.e39-1.e41 ergs/s interval in the 0.5-2.0 keV band.
The luminosity function of Coma galaxies reveals that their X-ray activity is
suppressed with respect to the field by a factor of 5.6, indicating a lower
level of X-ray emission for a given stellar mass.Comment: 16 pages, 2004 A&A in pres
Ultrafast electroabsorption dynamics in an InAs quantum dot saturable absorber at 1.3 mu m
The authors report a direct measurement of the absorption dynamics in an InAs p-i-n ridge waveguide quantum dot modulator. The carrier escape mechanisms are investigated via subpicosecond pump-probe measurements at room temperature, under reverse bias conditions. The optical pulses employed are degenerate in wavelength with the quantum dot ground state transition at 1.28 mu m. The absorption change recovers with characteristic times ranging from 62 ps (0 V) to similar to 700 fs (-10 V), showing a decrease of nearly two orders of magnitude. The authors show that at low applied fields, this recovery is attributed to thermionic emission while for higher applied fields, tunneling becomes the dominant mechanism. (c) 2006 American Institute of Physics.</p
Magnetic Field scaling of Relaxation curves in Small Particle Systems
We study the effects of the magnetic field on the relaxation of the
magnetization of small monodomain non-interacting particles with random
orientations and distribution of anisotropy constants. Starting from a master
equation, we build up an expression for the time dependence of the
magnetization which takes into account thermal activation only over barriers
separating energy minima, which, in our model, can be computed exactly from
analytical expressions. Numerical calculations of the relaxation curves for
different distribution widths, and under different magnetic fields H and
temperatures T, have been performed. We show how a \svar scaling of the
curves, at different T and for a given H, can be carried out after proper
normalization of the data to the equilibrium magnetization. The resulting
master curves are shown to be closely related to what we call effective energy
barrier distributions, which, in our model, can be computed exactly from
analytical expressions. The concept of effective distribution serves us as a
basis for finding a scaling variable to scale relaxation curves at different H
and a given T, thus showing that the field dependence of energy barriers can be
also extracted from relaxation measurements.Comment: 12 pages, 9 figures, submitted to Phys. Rev.
Shifted loops and coercivity from field imprinted high energy barriers in ferritin and ferrihydrite nanoparticles
We show that the coercive field in ferritin and ferrihydrite depends on the
maximum magnetic field in a hysteresis loop and that coercivity and loop shifts
depend both on the maximum and cooling fields. In the case of ferritin we show
that the time dependence of the magnetization also depends on the maximum and
previous cooling fields. This behavior is associated to changes in the
intra-particle energy barriers imprinted by these fields. Accordingly, the
dependence of the coercive and loop shift fields with the maximum field in
ferritin and ferrihydrite can be described within the frame of a
uniform-rotation model considering a dependence of the energy barrier with the
maximum and the cooling fields.Comment: 8 pages, 5 figures. Accepted for publication in Phys. Rev. B. Final
version with improved writing and figure
Emergence of communities on a coevolutive model of wealth interchange
We present a model in which we investigate the structure and evolution of a
random network that connects agents capable of exchanging wealth. Economic
interactions between neighbors can occur only if the difference between their
wealth is less than a threshold value that defines the width of the economic
classes. If the interchange of wealth cannot be done, agents are reconnected
with another randomly selected agent, allowing the network to evolve in time.
On each interaction there is a probability of favoring the poorer agent,
simulating the action of the government. We measure the Gini index, having real
world values attached to reality. Besides the network structure showed a very
close connection with the economic dynamic of the system.Comment: 5 pages, 7 figure
Olaparib in combination with pegylated liposomal doxorubicin for platinum-resistant ovarian cancer regardless of BRCA status: a GEICO phase II trial (ROLANDO study)
Inhibidor de PARP; Olaparib; Càncer d'ovari recurrent resistent al platíInhibidor de PARP; Olaparib; Cáncer de ovario recurrente resistente al platinoPARP inhibitor; Olaparib; Platinum-resistant recurrent ovarian cancerBackground
There is limited evidence for the benefit of olaparib in platinum-resistant ovarian cancer (PROC) patients with BRCA wild-type tumors. This study investigated whether this combination of a DNA-damaging chemotherapy plus olaparib is effective in PROC regardless BRCA status.
Patients and methods
Patients with high-grade serous or endometrioid ovarian carcinoma and one previous PROC recurrence were enrolled regardless of BRCA status. Patients with ≤4 previous lines (up to 5 in BRCA-mut) with at least one previous platinum-sensitive relapse were included; primary PROC was allowed only in case of BRCA-mut. Patients initially received six cycles of olaparib 300 mg b.i.d. (biduum) + intravenous pegylated liposomal doxorubicin (PLD) 40 mg/m2 (PLD40) every 28 days, followed by maintenance with olaparib 300 mg b.i.d. until progression or toxicity. The PLD dose was reduced to 30 mg/m2 (PLD30) due to toxicity. The primary endpoint was progression-free survival (PFS) at 6 months (6m-PFS) by RECIST version 1.1. A proportion of 40% 6m-PFS or more was considered of clinical interest.
Results
From 2017 to 2020, 31 PROC patients were included. BRCA mutations were present in 16%. The median of previous lines was 2 (range 1-5). The overall disease control rate was 77% (partial response rate of 29% and stable disease rate of 48%). After a median follow-up of 10 months, the 6m-PFS and median PFS were 47% and 5.8 months, respectively. Grade ≥3 treatment-related adverse events occurred in 74% of patients, with neutropenia/anemia being the most frequent. With PLD30 serious AEs were less frequent than with PLD40 (21% versus 47%, respectively); moreover, PLD30 was associated with less PLD delays (32% versus 38%) and reductions (16% versus 22%).
Conclusions
The PLD–olaparib combination has shown significant activity in PROC regardless of BRCA status. PLD at 30 mg/m2 is better tolerated in the combination.This work was supported by Grupo Español de Investigación en Cáncer de Ovario (GEICO) (no grant number). AstraZeneca provided olaparib and awarded a grant to GEICO (no grant number) to pay the costs of the study but did not take part in the conduct of the current clinical trial or in the analysis and interpretation of the results. Pegylated ribosomal doxorubicin was provided by the sites according to local standard procedures
Cosmic Mimicry: Is LCDM a Braneworld in Disguise ?
For a broad range of parameter values, braneworld models display a remarkable
property which we call cosmic mimicry. Cosmic mimicry is characterized by the
fact that, at low redshifts, the Hubble parameter in the braneworld model is
virtually indistinguishable from that in the LCDM cosmology. An important point
to note is that the \Omega_m parameters in the braneworld model and in the LCDM
cosmology can nevertheless be quite different. Thus, at high redshifts (early
times), the braneworld asymptotically expands like a matter-dominated universe
with the value of \Omega_m inferred from the observations of the local matter
density. At low redshifts (late times), the braneworld model behaves almost
exactly like the LCDM model but with a renormalized value of the cosmological
density parameter \Omega_m^{LCDM}. The redshift which characterizes cosmic
mimicry is related to the parameters in the higher-dimensional braneworld
Lagrangian. Cosmic mimicry is a natural consequence of the scale-dependence of
gravity in braneworld models. The change in the value of the cosmological
density parameter is shown to be related to the spatial dependence of the
effective gravitational constant in braneworld theory. A subclass of mimicry
models lead to an older age of the universe and also predict a redshift of
reionization which is lower than z_{reion} \simeq 17 in the LCDM cosmology.
These models might therefore provide a background cosmology which is in better
agreement both with the observed quasar abundance at z \gsim 4 and with the
large optical depth to reionization measured by the Wilkinson Microwave
Anisotropy Probe.Comment: 22 pages, 4 figures. A subsection and references added; main results
remain unchanged. Accepted for publication in JCA
Contextual factors and prejudice at the beginning of the migrant influx: The Moroccan case in Seville, Spain
Studies addressing contextual factors associated with anti‐immigrant prejudice have focused on out‐group size and rapid demographic changes in receiving locations. However, the territorial concentration and distribution of ethnic minorities at a local and intraurban level has received little attention. We analyse the relationship between emerging territorial concentration points—alongside other contextual variables—by Moroccans and receiving society's growing prejudice towards them in a city experiencing the start of a migrant influx. We combine survey and census data from five Seville districts (southern Spain). Our results show how rapid changes in the general population's ethnic composition, coupled with Moroccan and economic migrants' territorial concentration, correlate strongly with negative attitudes towards Moroccans at this early stage. However, a weaker relationship between the immigrant percentage and degree of prejudice by the receiving group is observed. We also discuss guidelines for ensuring good, local diversity management to prevent socioterritorial fragmentation in multicultural cities.Ministerio de Economía, Industria y Competitividad de España CSO2014‐55780‐C3‐1‐PMinisterio de Economía, Industria y Competitividad de España SEJ2006-14470Junta de Andalucí
Optimum quantum dot size for highly efficient fluorescence bioimaging
Semiconductor quantum dots of few nanometers have demonstrated a great potential for bioimaging. The size determines the emitted color, but it is also expected to play an important role in the image brightness. In this work, the size dependence of the fluorescence quantum yield of the highly thermal sensitive CdTe quantum dots has been systematically investigated by thermal lens spectroscopy. It has been found that an optimum quantum yield is reached for 3.8-nm quantum dots. The presence of this optimum size has been corroborated in both one-photon excited fluorescence experiments and two-photon fluorescence microscopy of dot-incubated cancer cells. Combination of quantum yield and fluorescence decay time measurements supports that the existence of this optimum size emerges from the interplay between the frequency-dependent radiative emission rate and the size-dependent coupling strength between bulk excitons and surface trapping states
Linearization of Cohomology-free Vector Fields
We study the cohomological equation for a smooth vector field on a compact
manifold. We show that if the vector field is cohomology free, then it can be
embedded continuously in a linear flow on an Abelian group
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