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 “tailored” 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

Monitoring methane emission of mud volcanoes by seismic tremor measurements: a pilot study

Abstract. A new approach for estimating methane emission at mud volcanoes is here proposed based on measurements of the seismic tremor on their surface. Data obtained at the Dashgil mud volcano in Azerbaijan reveal the presence of energy bursts characterized by well-determined features (i.e. waveforms, spectra and polarization properties) that can be associated with bubbling at depth. Counting such events provides a possible tool for monitoring gas production in the reservoir, thus minimizing logistic troubles and representing a cheap and effective alternative to more complex approaches. Specifically, we model the energy bursts as the effect of resonant gas bubbles at depth. This modelling allows to estimate the dimension of the bubbles and, consequently, the gas outflow from the main conduit in the assumption that all emissions from depth occur by bubble uprising. The application of this model to seismic events detected at the Dashgil mud volcano during three sessions of measurements carried out in 2006 and 2007 provides gas flux estimates that are in line with those provided by independent measurements at the same structure. This encouraging result suggests that the one here proposed could be considered a new promising, cheap and easy to apply tool for gas flux measurements in bubbling gas seepage areas

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

Attosecond Streaking in the Water Window: A New Regime of Attosecond Pulse Characterization

We report on the first streaking measurement of water-window attosecond pulses generated via high harmonic generation, driven by sub-2-cycle, CEP-stable, 1850 nm laser pulses. Both the central photon energy and the energy bandwidth far exceed what has been demonstrated thus far, warranting the investigation of the attosecond streaking technique for the soft X-ray regime and the limits of the FROGCRAB retrieval algorithm under such conditions. We also discuss the problem of attochirp compensation and issues regarding much lower photo-ionization cross sections compared with the XUV in addition to the fact that several shells of target gases are accessed simultaneously. Based on our investigation, we caution that the vastly different conditions in the soft X-ray regime warrant a diligent examination of the fidelity of the measurement and the retrieval procedure.Comment: 14 Pages, 12 figure

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 2002–2003 crisis. We analyze the recordings of a three‐component seismometer operating since 23 May 2002 to 30 January 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 1–5 Hz. Spectral content has two main changes, the most prominent one occurring at the crisis onset when the frequency peak at ∼0.3 Hz increases in amplitude. Independent component analysis extracts three time‐stable 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 1–5 Hz. Spectral content has two main changes, the most prominent one occurring at the crisis onset when the frequency peak at ∼0:3 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

Reproductive disorders induced by Chlamydophila spp. infections in an italian mediterranean buffalo (bubalus bubalis) herd

The Italian Mediterranean Buffalo (Bubalus bubalis) has low fecundity and high incidence of abortion. Several studies have associated reproductive failure of water buffalo with viral infections but there is limited information on the role of chlamydial infections. To investigate the presence and the role of Chlamydiaceae in water buffalo a retrospective study was performed in a farm where, in the arch of 11 months, the pregnant heifers suffered an abortion rate of 36.8% in the 3rd and 5th month of pregnancy. Antibodies to Chlamydiaceae were detected in 57% of the aborted cows, while the rate of positivity was 0% in overtly healthy cows used as control. By a PCR assay 3 of 14 vaginal swabs from aborted animals tested positive for Chlamydophila agents and, additionally, 3 out of 7 aborted foetuses tested positive for Chlamydophila spp., with two being co-infections by Cp. abortus and Cp. pecorum and one being characterised as Cp. abortus. The presence of anti-Chlamydiaceae antibodies in 57% of the aborted animals and the detection of Chlamydophila agents in foetal organs and in vaginal swabs is consistent with the history of abortions (P<0.002) observed in the herd and may suggest a pathogenic role by Chlamydophila spp. in water buffalo