6,294 research outputs found
Boolean versus continuous dynamics on simple two-gene modules
We investigate the dynamical behavior of simple modules composed of two genes
with two or three regulating connections. Continuous dynamics for mRNA and
protein concentrations is compared to a Boolean model for gene activity. Using
a generalized method, we study within a single framework different continuous
models and different types of regulatory functions, and establish conditions
under which the system can display stable oscillations. These conditions
concern the time scales, the degree of cooperativity of the regulating
interactions, and the signs of the interactions. Not all models that show
oscillations under Boolean dynamics can have oscillations under continuous
dynamics, and vice versa.Comment: 8 pages, 10 figure
Sol–gel synthesis and thermal behavior of bioactive ferrous citrate–silica hybrid materials
Imbalance of the iron level in the body causes several diseases. In particular, the low level of iron, during pregnancy, is
responsible for the iron deficiency anemia, and even of neurodegenerative diseases. Although the treatment of iron
deficiency anemia with oral iron supplements has been known, this problem still afflicts many people. The aim of this work
was the development of a system able to release ferrous ions in a controlled manner. Controlled drug release for medical
applications, indeed, appears to be a very interesting alternative to a systemic therapy because it is assurance of treatment
continuity and drug stability and optimizes drug absorption. For this purpose, ferrous citrate (Fe(II)C) was synthesized by a
redox reaction between iron powder and citric acid. Fourier transform infrared spectroscopy (FTIR), 1,10-phenanthroline
and sodium thiocyanate colorimetric assays confirmed that only Fe(II)C was obtained by redox reaction. Afterward,
obtained Fe(II)C was embedded within a SiO2 matrix in different mass percentage, by means of a sol–gel route. FTIR
spectroscopy and simultaneous thermogravimetry/first-order derivative of thermogravimetry were used to confirm the
Fe(II)C presence in the silica matrix and to investigate the thermal behavior of the sol–gel materials, respectively. The
bioactivity test carried out by soaking the synthesized drug delivery systems in a simulated body fluid showed that the
biological properties of the silica matrix are not modified by the presence of Fe(II)C
A Markov Chain Monte Carlo approach to the study of massive black hole binary systems with LISA
The Laser Interferometer Space Antenna (LISA) will produce a data stream
containing a vast number of overlapping sources: from strong signals generated
by the coalescence of massive black hole binary systems to much weaker
radiation form sub-stellar mass compact binaries and extreme-mass ratio
inspirals. It has been argued that the observation of weak signals could be
hampered by the presence of loud ones and that they first need to be removed to
allow such observations. Here we consider a different approach in which sources
are studied simultaneously within the framework of Bayesian inference. We
investigate the simplified case in which the LISA data stream contains
radiation from a massive black hole binary system superimposed over a (weaker)
quasi-monochromatic waveform generated by a white dwarf binary. We derive the
posterior probability density function of the model parameters using an
automatic Reversible Jump Markov Chain Monte Carlo algorithm (RJMCMC). We show
that the information about the sources and noise are retrieved at the expected
level of accuracy without the need of removing the stronger signal. Our
analysis suggests that this approach is worth pursuing further and should be
considered for the actual analysis of the LISA data.Comment: submitted to cqg as GWDAW-10 conference proceedings, 10 pages, 4
figures, some changes to plots and numerical detail
Data Processing for LISA's Laser Interferometer Tracking System (LITS)
The purpose of this paper is twofold. First, we will present recent results
on the data processing for LISA, including algorithms for elimination of clock
jitter noise and discussion of the generation of the data averages that will
eventually need to be telemetered to the ground. Second, we will argue, based
partly on these results, that a laser interferometer tracking system (LITS)
that employs independent lasers in each spacecraft is preferable for reasons of
simplicity to that in which the lasers in two of the spacecraft are locked to
the incoming beam from the third.Comment: 5 pages, Proceedings of the Third LISA Symposium (Golm, Germany,
2000
Capillary Electrophoresis: A Method for Evolution and Analysis of Molecular Recognition Elements
Molecular Recognition Elements (MREs) are compounds capable of binding a variety of inorganic and biological molecules. These MREs have a variety of applications including incorporation into biosensors, drug discovery, diagnostic testing, and therapeutics. MREs are evolved via a generalized process known as the Systematic Evolution of Ligands by Exponential Enrichment, or SELEX. Traditional SELEX techniques have limited the variety MREs which can be derived for a given target, and can take several days to complete. Capillary Electrophoresis has emerged as an alternative method for evolution of MREs. It allows for evolution of MREs with increased affinity for a given target in significantly fewer rounds of selection. In addition, a range of capillary electrophoresis binding assays have been developed which can very accurately determine dissociation constant values for MRE/target complexes. Capillary electrophoresis has greatly influenced both evolution and characterization of MREs over the past decade. It will likely continue to facilitate the development of MREs for applications which were previously inconceivable using traditional SELEX techniques
LISA Response Function and Parameter Estimation
We investigate the response function of LISA and consider the adequacy of its
commonly used approximation in the high-frequency range of the observational
band. We concentrate on monochromatic binary systems, such as white dwarf
binaries. We find that above a few mHz the approxmation starts becoming
increasingly inaccurate. The transfer function introduces additional amplitude
and phase modulations in the measured signal that influence parameter estmation
and, if not properly accounted for, lead to losses of signal-to-noise ratio.Comment: 4 pages, 2 figures, amaldi 5 conference proceeding
Media use during adolescence: the recommendations of the Italian Pediatric Society.
BACKGROUND: The use of media device, such as smartphone and tablet, is currently increasing, especially among the youngest. Adolescents spend more and more time with their smartphones consulting social media, mainly Facebook, Instagram and Twitter because. Adolescents often feel the necessity to use a media device as a means to construct a social identity and express themselves. For some children, smartphone ownership starts even sooner as young as 7 yrs, according to internet safety experts. MATERIAL AND METHODS: We analyzed the evidence on media use and its consequences in adolescence. RESULTS: In literature, smartphones and tablets use may negatively influences the psychophysical development of the adolescent, such as learning, sleep and sigh. Moreover, obesity, distraction, addiction, cyberbullism and Hikikomori phenomena are described in adolescents who use media device too frequently. The Italian Pediatric Society provide action-oriented recommendations for families and clinicians to avoid negative outcomes. CONCLUSIONS: Both parents and clinicians should be aware of the widespread phenomenon of media device use among adolescents and try to avoid psychophysical consequences on the youngest
ESA, iron therapy and new drugs: Are there new perspectives in the treatment of anaemia?
Anemia is a well-known consequence of chronic kidney disease (CKD); it is mainly due to a relative insufficiency of erythropoietin synthesis by the failing kidneys. Over the years, the combination of erythropoiesis stimulating agents (ESA) and iron has become the standard of care of anemia. All ESAs effectively increase hemoglobin (Hb) levels in a substantial percentage of patients. However, in the last decade, their use has been surrounded by safety issues in increased cardiovascular risk, especially when used at high doses in inflamed and hyporesponsive patients. This has led to the definition of a more cautious Hb target. Iron deficiency is very frequent in CKD patients, with a higher frequency in non-dialysis patients. Traditionally, iron supplementation is mostly used as supportive therapy for anemia control. However, the concept is growing that intravenous iron therapy per se could be beneficial in the presence of heart failure. A new class of drugs, prolyl hydroxylase domain (PHD) inhibitors (PHD inhibitors) is becoming available for the treatment of anemia in CKD patients. Theoretically, these agents have a number of advantages, the main ones being that of stimulating the synthesis of endogenous erythropoietin and increasing iron avail-ability. The impact of their future use in clinical practice is still to be defined. Another possible strategy could be targeting serum hepcidin and its related pathways. This possibility is fascinating from the scientific point of view, but at present its development phase is still far from clinical application
The Effect of the LISA Response Function on Observations of Monochromatic Sources
The Laser Interferometer Space Antenna (LISA) is expected to provide the
largest observational sample of binary systems of faint sub-solar mass compact
objects, in particular white-dwarfs, whose radiation is monochromatic over most
of the LISA observational window. Current astrophysical estimates suggest that
the instrument will be able to resolve about 10000 such systems, with a large
fraction of them at frequencies above 3 mHz, where the wavelength of
gravitational waves becomes comparable to or shorter than the LISA arm-length.
This affects the structure of the so-called LISA transfer function which cannot
be treated as constant in this frequency range: it introduces characteristic
phase and amplitude modulations that depend on the source location in the sky
and the emission frequency. Here we investigate the effect of the LISA transfer
function on detection and parameter estimation for monochromatic sources. For
signal detection we show that filters constructed by approximating the transfer
function as a constant (long wavelength approximation) introduce a negligible
loss of signal-to-noise ratio -- the fitting factor always exceeds 0.97 -- for
f below 10mHz, therefore in a frequency range where one would actually expect
the approximation to fail. For parameter estimation, we conclude that in the
range 3mHz to 30mHz the errors associated with parameter measurements differ
from about 5% up to a factor of 10 (depending on the actual source parameters
and emission frequency) with respect to those computed using the long
wavelength approximation.Comment: replacement version with typos correcte
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