14,925 research outputs found
Self-propulsion against a moving membrane: enhanced accumulation and drag force
Self-propulsion (SP) is a main feature of active particles (AP), such as
bacteria or biological micromotors, distinguishing them from passive colloids.
A renowned consequence of SP is accumulation at static interfaces, even in the
absence of hydrodynamic interactions. Here we address the role of SP in the
interaction between AP and a moving semipermeable membrane. In particular, we
implement a model of noninteracting AP in a channel crossed by a partially
penetrable wall, moving at a constant velocity . With respect to both the
cases of passive colloids with and AP with , the AP with finite
show enhancement of accumulation in front of the obstacle and experience a
largely increased drag force. This effect is understood in terms of an
effective potential localised at the interface between particles and membrane,
of height proportional to , where is the AP's re-orientation
time and the width characterising the surface's smoothness (
for hard core obstacles). An approximate analytical scheme is able to reproduce
the observed density profiles and the measured drag force, in very good
agreement with numerical simulations. The effects discussed here can be
exploited for automatic selection and filtering of AP with desired parameters.Comment: 13 pages, 3 figure
Predictive Monitoring of Business Processes
Modern information systems that support complex business processes generally
maintain significant amounts of process execution data, particularly records of
events corresponding to the execution of activities (event logs). In this
paper, we present an approach to analyze such event logs in order to
predictively monitor business goals during business process execution. At any
point during an execution of a process, the user can define business goals in
the form of linear temporal logic rules. When an activity is being executed,
the framework identifies input data values that are more (or less) likely to
lead to the achievement of each business goal. Unlike reactive compliance
monitoring approaches that detect violations only after they have occurred, our
predictive monitoring approach provides early advice so that users can steer
ongoing process executions towards the achievement of business goals. In other
words, violations are predicted (and potentially prevented) rather than merely
detected. The approach has been implemented in the ProM process mining toolset
and validated on a real-life log pertaining to the treatment of cancer patients
in a large hospital
The course of cancer related fatigue up to ten years in early breast cancer patients. What impact in clinical practice?
Little is known about the cancer related fatigue (CRF) along cancer course and risk factors that could predict CRF development and persistence in breast cancer (BC) survivors. This prospective study detected incidence, timing of onset, duration of CRF, impact on QoL and psychological distress. Seventy-eight early BC patients, undergoing chemotherapy (CT) followed or not by hormonal therapy were assessed for QoL and psychological distress by EORTC QLQC30 and HADs questionnaires. Fatigue was investigated with mix methods, structured interview and psychometric measures. A qualitative analysis was added to assess the behavioral pattern of CRF. Low fatigue levels were identified after surgery (9%), increasing during (49%) and at the end of CT (47%), maintaining after 1 year (31%) and declining up to ten years of follow-up. Prevalence of CRF was higher at the end of CT and lower at follow-up. At the end and after 1 and 2 years from CT, persistence of CRF was associated to anxiety in 20%, 11% and 5% and to depression in 15%, 10% and 5% respectively. A relationship between CRF and psychological distress was observed; patients presenting depression and anxiety before CT were at higher risk for fatigue onset at a later period. A relationship between fatigue and QoL was noted at the end of CT. Our study shows the fatigue timely trend in early BC patients from surgery, CT and follow-up. Identification of biological, psychological, social predictor factors related to fatigue could be helpful for early interventions in patients at higher risk of developing fatigue
Discovery of a 168.8 s X-ray pulsar transiting in front of its Be companion star in the Large Magellanic Cloud
We report the discovery of LXP169, a new high-mass X-ray binary (XRB) in the
LMC. The optical counterpart has been identified and appears to exhibit an
eclipsing light curve. We performed follow-up observations to clarify the
eclipsing nature of the system. Energy spectra and time series were extracted
from two XMM-Newton observations to search for pulsations, characterise the
spectrum, and measure spectral and timing changes. Long-term X-ray variability
was studied using archival ROSAT data. The XMM positions were used to identify
the optical counterpart. We obtained UV to NIR photometry to characterise the
companion, along with its 4000 d long I-band light curve. We observed LXP169
with Swift at two predicted eclipse times. We found a spin period of 168.8 s
that did not change between two XMM observations. The X-ray spectrum, well
characterised by a power law, was harder when the source was brighter. The
X-ray flux of LXP169 is found to be variable by a factor of at least 10. The
counterpart is highly variable on short and long timescales, and its photometry
is that of an early-type star with a NIR excess. This classifies the source as
a BeXRB pulsar. We observed a transit in the UV, thereby confirming that the
companion star itself is eclipsed. We give an ephemeris for the transit of MJD
56203.877 + N*24.329. We propose and discuss the scenario where the matter
captured from the companion's equatorial disc creates an extended region of
high density around the neutron star (NS), which partially eclipses the
companion as the NS transits in front of it. This is most likely the first time
the compact object in an XRB is observed to eclipse its companion star. LXP169
would be the first eclipsing BeXRB, and a wealth of important information might
be gained from additional observations, such as a measure of the possible Be
disc/orbital plane misalignment, or the mass of the NS.Comment: Updated version of arXiv 1302.4665v1, accepted for publication in
Astronomy and Astrophysics. 11 pages, 8 figures, 3 table
Discovery of SXP265, a Be/X-ray binary pulsar in the Wing of the Small Magellanic Cloud
We identify a new candidate for a Be/X-ray binary in the XMM-Newton slew
survey and archival Swift observations that is located in the transition region
of the Wing of the Small Magellanic Cloud and the Magellanic Bridge. We
investigated and classified this source with follow-up XMM-Newton and optical
observations. We model the X-ray spectra and search for periodicities and
variability in the X-ray observations and the OGLE I-band light curve. The
optical counterpart has been classified spectroscopically, with data obtained
at the SAAO 1.9 m telescope, and photometrically, with data obtained using
GROND at the MPG 2.2 m telescope. The X-ray spectrum is typical of a high-mass
X-ray binary with an accreting neutron star. We detect X-ray pulsations, which
reveal a neutron-star spin period of P = (264.516+-0.014) s. The source likely
shows a persistent X-ray luminosity of a few 10^35 erg/s and in addition type-I
outbursts that indicate an orbital period of ~146 d. A periodicity of 0.867 d,
found in the optical light curve, can be explained by non-radial pulsations of
the Be star. We identify the optical counterpart and classify it as a
B1-2II-IVe star. This confirms SXP 265 as a new Be/X-ray binary pulsar
originating in the tidal structure between the Magellanic Clouds.Comment: 11 pages, 12 figures, accepted for publication in MNRA
Clinical Processes - The Killer Application for Constraint-Based Process Interactions?
For more than a decade, the interest in aligning information
systems in a process-oriented way has been increasing. To enable operational
support for business processes, the latter are usually specified in
an imperative way. The resulting process models, however, tend to be too
rigid to meet the flexibility demands of the actors involved. Declarative
process modeling languages, in turn, provide a promising alternative in
scenarios in which a high level of flexibility is demanded. In the scientific
literature, declarative languages have been used for modeling rather simple
processes or synthetic examples. However, to the best of our knowledge,
they have not been used to model complex, real-world scenarios
that comprise constraints going beyond control-flow. In this paper, we
propose the use of a declarative language for modeling a sophisticated
healthcare process scenario from the real world. The scenario is subject to
complex temporal constraints and entails the need for coordinating the
constraint-based interactions among the processes related to a patient
treatment process. As demonstrated in this work, the selected real process
scenario can be suitably modeled through a declarative approach.Ministerio de EconomÃa y Competitividad TIN2016-76956-C3-2-RMinisterio de EconomÃa y Competitividad TIN2015-71938-RED
Pressure in an exactly solvable model of active fluid
We consider the pressure in the steady-state regime of three stochastic
models characterized by self-propulsion and persistent motion and widely
employed to describe the behavior of active particles, namely the Active
Brownian particle (ABP) model, the Gaussian colored noise (GCN) model and the
unified colored noise model (UCNA). Whereas in the limit of short but finite
persistence time the pressure in the UCNA model can be obtained by different
methods which have an analog in equilibrium systems, in the remaining two
models only the virial route is, in general, possible.
According to this method, notwithstanding each model obeys its own specific
microscopic law of evolution, the pressure displays a certain universal
behavior. For generic interparticle and confining potentials, we derive a
formula which establishes a correspondence between the GCN and the UCNA
pressures. In order to provide explicit formulas and examples, we specialize
the discussion to the case of an assembly of elastic dumbbells confined to a
parabolic well. By employing the UCNA we find that, for this model, the
pressure determined by the thermodynamic method coincides with the pressures
obtained by the virial and mechanical methods. The three methods when applied
to the GCN give a pressure identical to that obtained via the UCNA. Finally, we
find that the ABP virial pressure exactly agrees with the UCNA and GCN result.Comment: 12 pages, 1 figure Submitted for publication 23rd of January 2017 The
introduction has been modifie
A Copula-VAR-X Approach for Industrial Production Modelling and Forecasting
World economies, and especially European ones, have become strongly interconnected in the last decades and a joint modelling is required. We propose here the use of Copulas to build flexible multivariate distributions, since they allow for a rich dependence structure and more flexible marginal distributions that better fit the features of empirical data, such as leptokurtosis. We use our approach to forecast industrial production series in the core EMU countries and we provide evidence that the copula-VAR model outperforms or at worst compares similarly to normal VAR models, keeping the same computational tractability of the latter approach.Forecasting, Industrial Production, Copulas, VAR models.
Investigation of the shear-mechanical and dielectric relaxation processes in two mono-alcohols close to the glass transition
Shear-mechanical and dielectric measurements on the two monohydroxy
(mono-alcohol) molecular glass formers 2-ethyl-1-hexanol and 2-butanol close to
the glass transition temperature are presented. The shear-mechanical data are
obtained using the piezoelectric shear-modulus gauge method covering
frequencies from 1mHz to 10kHz. The shear-mechanical relaxation spectra show
two processes, which follow the typical scenario of a structural (alpha)
relaxation and an additional (Johari-Goldstein) beta relaxation. The dielectric
relaxation spectra are dominated by a Debye-type peak with an additional
non-Debye peak visible. This Debye-type relaxation is a common feature peculiar
to mono-alcohols. The time scale of the non-Debye dielectric relaxation process
is shown to correspond to the mechanical structural (alpha) relaxation.
Glass-transition temperatures and fragilities are reported based on the
mechanical alpha relaxation and the dielectric Debye-type process, showing that
the two glass-transition temperatures differ by approximately 10K and that the
fragility based on the Debye-type process is a factor of two smaller than the
structural fragility. If a mechanical signature of the Debye-type relaxation
exists in these liquids, its relaxation strength is at most 1% and 3% of the
full relaxation strength of 2-butanol and 2-ethyl-1-hexanol respectively. These
findings support the notion that it is the non-Debye dielectric relaxation
process that corresponds to the structural alpha relaxation in the liquid.Comment: 8 pages, 6 figures. Minor corrections, updated figures, more
dielectric data show
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