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

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 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

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 wood’s 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 Wood’s 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 Wood’s model applied to all 14 recordings (A) (p > 0.38). Differently, Wood’s 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 Wood’s 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

Modulating the water oxidation catalytic activity of iridium complexes by functionalizing the Cp*-ancillary ligand: hints on the nature of the active species

The catalytic activity toward NaIO4driven water oxidation of a series of [RCp*IrCl(μ-Cl)]2dimeric precursors, containing tetramethylcyclopentadienyl ligands with a variable R substituent (H,1; Me,2; Et,3;nPr,4; CH2CH2NH3+,5; Ph,6; 4-C6H4F,7; 4-C6H4OH,8; Bn,9), has been evaluated at 298 K and pH = 7 (with phosphate buffer). For each dimer, the effect of changing the catalyst (1-10 μM) and NaIO4(5-40 mM) concentration has been studied. All precursors exhibit a high activity with TOF values ranging from 101 min−1to 393 min−1and TON values being always those expected assuming a 100% yield. The catalytic activity was strongly affected by the nature of the R substituent. The highest TOF values were observed when R was electron-donating and small. The results of multiple consecutive injection experiments suggest that a fragment of the initial C5Me4R, still bearing the R-substituent, remains attached at iridium in the active species, despite the oxidativein situdegradation of the same ligand. The decrease of TOF in the second and third catalytic runs was completely ascribed to a drop of the redox potential caused by the conversion of IO4−into IO3−, according to the Nernst equation. This hypothesis was verified by performing catalytic experiments in which the initial redox potential (ΔE) was deliberately varied by using water solutions of IO4−/IO3−mixtures at different relative concentrations. Consistently, TOFversusΔEplots show that, for a given catalyst, the same TOF is obtained at a certain redox potential, irrespective of the initial reaction conditions used. All seems to indicate that after a short activation period, during which the transformation of the precursors occurs, individual active species for each dimer form and remain the same also after multiple additions of the sacrificial oxidant. It can be speculated that such active species are small iridium clusters bearing R-functionalized likelyO,O-bidentate ligands