Aqueous Free-Radical Polymerization of Non-Ionized and Fully Ionized Methacrylic Acid

Water-soluble, carboxylic acid monomers are known to exhibit peculiar kinetics when polymerized in aqueous solution. Namely, their free-radical polymerization rate is affected by several parameters such as monomer concentration, ionic strength, and pH. Focusing on methacrylic acid (MAA), even though this monomer has been largely addressed, a systematic investigation of the effects of the above-mentioned parameters on its polymerization rate is missing, in particular in the fully ionized case. In this work, the kinetics of non-ionized and fully ionized MAA are characterized by in-situ nuclear magnetic resonance (NMR). Such accurate monitoring of the reaction rate enables the identification of relevant but substantially different effects of the monomer and electrolyte concentration on polymerization rate in the two ionization cases. For non-ionized MAA, the development of a kinetic model based on literature rate coefficients allows us to nicely simulate the experimental data of conversion versus time at a high monomer concentration. For fully ionized MAA, a novel propagation rate law accounting for the electrostatic interactions is proposed: the corresponding model is capable of predicting reasonably well the electrolyte concentration effect on polymerization rate. Nevertheless, further kinetic information in a wider range of monomer concentrations would be welcome to increase the reliability of the model predictions

The GINGER Project and status of the ring-laser of LNGS

A ring-laser attached to the Earth measures the absolute angular velocity of the Earth summed to the relativistic precessions, de Sitter and Lense-Thirring. GINGER (Gyroscopes IN GEneral Relativity) is a project aiming at measuring the LenseThirring effect with a ground based detector; it is based on an array of ring-lasers. Comparing the Earth angular velocity measured by IERS and the measurement done with the GINGER array, the Lense-Thirring effect can be evaluated. Compared to the existing space experiments, GINGER provides a local measurement, not the averaged value and it is unnecessary to model the gravitational field. It is a proposal, but it is not far from being a reality. In fact the GrossRing G of the Geodesy Observatory of Wettzell has a sensitivity very close to the necessary one. G ofWettzell is part of the IERS system which provides the measure of the Length Of the DAY (LOD); G provides information on the fast component of LOD. In the last few years, a roadmap toward GINGER has been outlined. The experiment G-GranSasso, financed by the INFN Commission II, is developing instrumentations and tests along the roadmap of GINGER. In this short paper the main activities of G-GranSasso and some results will be presented. The first results of GINGERino will be reported, GINGERino is the large ring-laser installed inside LNGS and now in the commissioning phase. Ring-lasers provide as well important informations for geophysics, in particular the rotational seismology, which is an emerging field of science. GINGERino is one of the three experiments of common interest between INFN and INGV

Deep underground rotation measurements: GINGERino ring laser gyroscope in Gran Sasso

GINGERino is a large frame laser gyroscope investigating the ground motion in the most inner part of the underground international laboratory of the Gran Sasso, in central Italy. It consists of a square ring laser with a $3.6$ m side. Several days of continuous measurements have been collected, with the apparatus running unattended. The power spectral density in the seismic bandwidth is at the level of $10^{-10} \rm{(rad/s)/\sqrt{Hz}}$. A maximum resolution of $30\,\rm{prad/s}$ is obtained with an integration time of few hundred seconds. The ring laser routinely detects seismic rotations induced by both regional earthquakes and teleseisms. A broadband seismic station is installed on the same structure of the gyroscope. First analysis of the correlation between the rotational and the translational signal are presented.Published0345027TM. Sviluppo e Trasferimento TecnologicoJCR Journa

The GINGER Project

GINGER (Gyroscopes IN General Relativity) is a project aiming at measuring the Lense-Thirring effect, at 1% level, with an experiment on earth. It is based on an array of ring-lasers, which are the most sensitive inertial sensors to measure the rotation rate of the Earth. The GINGER project is still under discussion; the experiment G-GranSasso is an R&D experiment financed by INFN Group II, it is studying the key points of GINGER and at the same time developing prototypes. In the following the signal coming out of a ring-laser and the present sensitivity are described.The prototypes GP2 and GINGERino and the preliminary results are reported. This project is inter-disciplinary since ring-lasers provide informations for the fast variation of the earth rotation rate, they are used for the rotational seismology and for top sensitivity angle metrology

Time-delayed model of immune response in plants

In the studies of plant infections, the plant immune response is known to play an essential role. In this paper we derive and analyse a new mathematical model of plant immune response with particular account for post-transcriptional gene silencing (PTGS). Besides biologically accurate representation of the PTGS dynamics, the model explicitly includes two time delays to represent the maturation time of the growing plant tissue and the non-instantaneous nature of the PTGS. Through analytical and numerical analysis of stability of the steady states of the model we identify parameter regions associated with recovery and resistant phenotypes, as well as possible chronic infections. Dynamics of the system in these regimes is illustrated by numerical simulations of the model

Construction and Modelling of an Inducible Positive Feedback Loop Stably Integrated in a Mammalian Cell-Line

Understanding the relationship between topology and dynamics of transcriptional regulatory networks in mammalian cells is essential to elucidate the biology of complex regulatory and signaling pathways. Here, we characterised, via a synthetic biology approach, a transcriptional positive feedback loop (PFL) by generating a clonal population of mammalian cells (CHO) carrying a stable integration of the construct. The PFL network consists of the Tetracycline-controlled transactivator (tTA), whose expression is regulated by a tTA responsive promoter (CMV-TET), thus giving rise to a positive feedback. The same CMV-TET promoter drives also the expression of a destabilised yellow fluorescent protein (d2EYFP), thus the dynamic behaviour can be followed by time-lapse microscopy. The PFL network was compared to an engineered version of the network lacking the positive feedback loop (NOPFL), by expressing the tTA mRNA from a constitutive promoter. Doxycycline was used to repress tTA activation (switch off), and the resulting changes in fluorescence intensity for both the PFL and NOPFL networks were followed for up to 43 h. We observed a striking difference in the dynamics of the PFL and NOPFL networks. Using non-linear dynamical models, able to recapitulate experimental observations, we demonstrated a link between network topology and network dynamics. Namely, transcriptional positive autoregulation can significantly slow down the “switch off” times, as comparared to the nonautoregulatated system. Doxycycline concentration can modulate the response times of the PFL, whereas the NOPFL always switches off with the same dynamics. Moreover, the PFL can exhibit bistability for a range of Doxycycline concentrations. Since the PFL motif is often found in naturally occurring transcriptional and signaling pathways, we believe our work can be instrumental to characterise their behaviour

Experimental and Modeling Study of Acrylamide Copolymerization with Quaternary Ammonium Salt in Aqueous Solution

The free-radical copolymerization of acrylamide with the cationic monomer DMAEA-Q in aqueous medium is investigated with special attention to its composition behavior, which reveals to be affected by the electrostatic interactions between the charges in the system. The reaction kinetics is determined by in situ 1H NMR experiments, showing a peculiar dependence of the copolymer composition upon initial monomer and electrolyte concentrations. A kinetic model simulating the evolution of copolymer composition as a function of conversion is developed, accounting for the nonconventional features of the system. Namely, a description of the electrostatic interactions based on the DLVO theory is introduced to define a functional dependence of the rate coefficients on the ionic strength. Secondary reactions are also included due to the acrylic nature of both monomers. The proposed model is applied to estimate the corresponding reactivity ratios and proves to exhibit the correct functionality with respect to monomer concentration and ionic strength. (Figure Presented)

Particle state dependent radical desorption and its effect on the kinetics of emulsion polymerization

Radical desorption from polymer particles is a kinetic event peculiar to the emulsion polymerization process. A careful modeling of this phenomenon is highly valuable in order to achieve accurate predictions of polymerization rate and average properties of molecular weight. In this work, radical desorption is described accounting for an aspect fully neglected in previous modeling literature. Specifically, particle state dependent desorption coefficients are used instead of a single average coefficient, and the corresponding rate expressions are developed and applied to the solution of the well-known Smith-Ewart equations. Parametric model simulations show that the higher level of detail introduced in the description of radical desorption improves the accuracy of the predicted values of the average number of radicals per particle, especially in the cases of high desorption rate and slow reactions in the aqueous phase. © 2014 American Chemical Society

Control of Pore Structure in Polymeric Monoliths Prepared from Colloidal Dispersions

Reliable control of pore size distribution in porous materials is a key feature for addressing specific applications. The reactive gelation process represents a robust and efficient method to obtain mechanically stable monoliths with tunable pore size distribution. Primary polymer nanoparticles are destabilized and aggregated in a controlled way, forming a percolating gel. Afterward, this structure is hardened by a postpolymerization, carried out through heating. Different parameters play a major role in determining the final morphology of the monolith. In this work, the effect of primary particle architecture (i.e., core-to-shell ratio) and initial solid content of the latex is investigated, using two different sizes of nanoparticles. Actually, the first parameter affects the pores in the small range (0.01–1 µm) whereas the latter those in the larger one (1 µm to several micrometers), independently of the primary particle size. As a result, monoliths with very well-defined pore size distributions are obtained