621 research outputs found
Unraveling Adaptation in Eukaryotic Pathways: Lessons from Protocells
Eukaryotic adaptation pathways operate within wide-ranging environmental
conditions without stimulus saturation. Despite numerous differences in the
adaptation mechanisms employed by bacteria and eukaryotes, all require energy
consumption. Here, we present two minimal models showing that expenditure of
energy by the cell is not essential for adaptation. Both models share important
features with large eukaryotic cells: they employ small diffusible molecules
and involve receptor subunits resembling highly conserved G-protein cascades.
Analyzing the drawbacks of these models helps us understand the benefits of
energy consumption, in terms of adjustability of response and adaptation times
as well as separation of cell-external sensing and cell-internal signaling. Our
work thus sheds new light on the evolution of adaptation mechanisms in complex
systems.Comment: accepted for publication in PLoS Computational Biology; 19 pages, 8
figure
Generation of pseudo-random sequences for noise radar applications
Noise Radar Technology (NRT) is nowadays a promising tool in radar systems. It is based on the transmission of waveforms composed of many noisy samples, which behave as LPI (Low Probability of Intercept) and antispoofing signals. Each noisy sequence is theoretically uncorrelated with the others. In the paper we propose a scheme to generate a âtailoredâ pseudo-random sequences (limited in amplitude). It will be followed by an analysis of the main performances in terms of the Peak Side Lobe Ratio (PSLR) of the autocorrelation function, cross-correlation analysis to evaluate the orthogonality, bandwidth and energy efficiency
Disorder effect on the spin susceptibility of the two-dimensional one-valley electron gas
Starting from the quantum Monte Carlo (QMC) prediction for the ground-state
energy of a clean two-dimensional one-valley (2D1V) electron gas, we estimate
the energy correction due to scattering sources present in actual devices such
as AlAs quantum wells and GaAs heterostructures. We find that the effect of
uncorrelated disorder, in the lowest (second) order in perturbation theory, is
to enhance the spin susceptibility leading to its eventual divergence. In the
density region where the Born approximation is able to reproduce the
experimental mobility, the prediction for the spin susceptibility yielded by
perturbation theory is in very good agreement with the available experimental
evidence.Comment: 9 pages, 3 figures, special issue article for the SCCS2008 conference
(Camerino, Italy
A statistical study of the Stromboli volcano explosion quakes before and during 2002-2003 eruptive crisis
We study the seismic wavefield and the statistical properties of the Stromboli volcano
explosions preceding and during the 2002â2003 crisis. We analyze the recordings of a
threeâcomponent seismometer operating since 23 May 2002 to 30 January 2003, including
the first 34 days of the crisis. Before the crisis, we recognize three bellâshaped classes of
spectra with maxima falling in the range 1â5 Hz. Spectral content has two main changes, the
most prominent one occurring at the crisis onset when the frequency peak at âŒ0.3 Hz
increases in amplitude. Independent component analysis extracts three timeâstable
independent oscillations that peaked at 1.1, 1.8, and 2.5 Hz, with radial and shallow
polarization indicating a stable source mechanism. Energy of the explosions is lognormally
distributed, except during a 2 month time interval before the crisis when it also shows a
higher mean value. The interoccurrence time distributions display an homogeneous
Poissonian behavior with a mean intertime of 250 s, without changes at the crisis onset. Only
swarms of explosions are not ruled by a Poisson process and display higher occurrence rates
and higher energies. Finally, we depict a scheme of the crisis. A modification of the
equilibrium is induced by rising magma that produces a change in the boundary conditions of
the plumbing system. The escape from the equilibrium produces, at first, variations in the
usual statistics of the explosions, then it leads to the lava effusion and to a pressure drop in
the plumbing system that induces a deep gas slug nucleation and the excitation of low
frequencies
A statistical study of the Stromboli volcano explosion-quakes before and during 2002-2003 eruptive crisis
We study the seismic wavefield and the statistical properties
of the Stromboli volcano explosions preceding and during 2002-2003 crisis.
We analyze the recordings of a three-component seismometer operating since
23/05/2002 to 30/01/2003, including the first 34 days of the crisis. Before
the crisis, we recognize three bell-shaped classes of spectra with maxima falling
in the range 1â5 Hz. Spectral content has two main changes, the most prominent
one occurring at the crisis onset when the frequency peak at âŒ0:3 Hz
increases in amplitude. Independent Component Analysis extracts three timestable
independent oscillations peaked at 1.1, 1.8, and 2.5 Hz, respectively,
with radial and shallow polarization indicating a stable source mechanism.
Energy of the explosions is log-normally distributed, except during a twomonth
time interval before the crisis when it shows also a higher mean value.
The inter-occurrence time distributions display an homogeneous poissonian
behaviour with a mean inter-time of 250 s, without changes at the crisis onset.
Only swarms of explosions are not ruled by a Poisson process and display
higher occurrence rates and higher energies. Finally, we depict a scheme
of the crisis. A modification of the equilibrium is induced by rising magma
that produces a change in the boundary conditions of the plumbing system.
The escape from the equilibrium produces, at first, variations in the usual
statistics of the explosions, then it leads to the lava effusion and to a pressure
drop in the plumbing systems that induces a deep gas slug nucleation
and the excitation of low frequencies
Common dynamical features of sensory adaptation in photoreceptors and olfactory sensory neurons
Sensory systems adapt, i.e., they adjust their sensitivity to external stimuli according to the ambient level. In this paper we show that single cell electrophysiological responses of vertebrate olfactory receptors and of photoreceptors to different input protocols exhibit several common features related to adaptation, and that these features can be used to investigate the dynamical structure of the feedback regulation responsible for the adaptation. In particular, we point out that two different forms of adaptation can be observed, in response to steps and to pairs of pulses. These two forms of adaptation appear to be in a dynamical trade-off: the more adaptation to a step is close to perfect, the slower is the recovery in adaptation to pulse pairs and viceversa. Neither of the two forms is explained by the dynamical models currently used to describe adaptation, such as the integral feedback model
Evaluation of different test-day milk recording protocols by woodâs model application for the estimation of dairy goat milk and milk constituent yield
Goats have important social and economic roles in many countries because of their ability to survive and be productive in marginal areas. The overarching aim of this study was to compare the application of Woodâs model to different test-day milk recording protocols for estimation of total milk, fat, and protein yield in dairy goats. A total of 465 goats were used (Garganica, 78; Girgentana, 81; Jonica, 76; Maltese, 77; Red Mediterranean, 76; Saanen, 77). Milk yield was recorded every 15 days throughout lactation of 210 days, for a total of 14 collection days, during both morning and afternoon milking sessions. Milk samples were collected and analyzed for protein and fat. The fat-corrected milk was standardized at 35g fat/kg of milk. Wood models showed high R2 values, and thus good fitting, in all the considered breeds. Wood model applied to first, second, fourth, and sixth month recordings (C) and ICAR estimation showed total milk yield very close to Woodâs model applied to all 14 recordings (A) (p > 0.38). Differently, Woodâs model applied to the first, second, third, and fourth month recording (B) estimation showed great differences (p < 0.01). This could be applied for farms that had the necessity to synchronize flock groups for kidding in order to produce kid meat. In farms that apply the estrus induction and/or synchronization for kidding, it would be possible to perform only four test-day milk recordings and to apply the Woodâs model on them in order to obtain the estimation of total milk, fat, and protein yield during lactation for animals inscribed, or to be inscribed, to the genealogical book
Application of Paper-Based Microfluidic Analytical Devices (ÎŒPAD) in Forensic and Clinical Toxicology: A Review
The need for providing rapid and, possibly, on-the-spot analytical results in the case of intoxication has prompted researchers to develop rapid, sensitive, and cost-effective methods and analytical devices suitable for use in nonspecialized laboratories and at the point of need (PON). In recent years, the technology of paper-based microfluidic analytical devices (ÎŒPADs) has undergone rapid development and now provides a feasible, low-cost alternative to traditional rapid tests for detecting harmful compounds. In fact, ÎŒPADs have been developed to detect toxic molecules (arsenic, cyanide, ethanol, and nitrite), drugs, and drugs of abuse (benzodiazepines, cathinones, cocaine, fentanyl, ketamine, MDMA, morphine, synthetic cannabinoids, tetrahydrocannabinol, and xylazine), and also psychoactive substances used for drug-facilitated crimes (flunitrazepam, gamma-hydroxybutyric acid (GHB), ketamine, metamizole, midazolam, and scopolamine). The present report critically evaluates the recent developments in paper-based devices, particularly in detection methods, and how these new analytical tools have been tested in forensic and clinical toxicology, also including future perspectives on their application, such as multisensing paper-based devices, microfluidic paper-based separation, and wearable paper-based sensors
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