Phase equilibrium data and thermodynamic modelling of the system (propane + DMF + methanol) at high pressures

Reported in this work are phase equilibrium data at high pressures for the binary and ternary systems formed by {propane + N,N-dimethylformamide (DMF) + methanol}. Phase equilibrium measurements were performed in a high-pressure, variable-volume view cell, following the static synthetic method for obtaining the experimental bubble and dew points transition data over the temperature range of (363 to 393) K, pressures up to 11.5 MPa and overall mole fraction of the lighter component varying from 0.1 to 0.995. For the systems investigated, vapour–liquid (VLE), liquid–liquid (LLE) and vapour–liquid–liquid (VLLE) phase transitions were visually recorded. Results show that the systems investigated present UCST (upper critical solution temperature) phase transition curves with an UCEP (upper critical end point) at a temperature higher than the propane critical temperature. The experimental data were modelled using the Peng–Robinson equation of state with the Wong–Sandler and the classical quadratic mixing rules, affording a satisfactory representation of the experimental data.     

Statistical analysis of geomagnetic field reversals and their consequences

In this paper we focus on the statistical distribution of time intervals between geomagnetic reversals. Recently the Tsallis distribution was pointed out as a possible alternative to previous proposals. We have performed statistical tests to further prove this and find the parameters of the Tsallis distribution that better fit the data. Additionally we have analyzed the correlation of time intervals between consecutive reversals to show the presence of memory effects on the mechanism that generates them, as could be expected for some Tsallis systems.     

Proteomic study of a tolerant genotype of durum wheat under salt-stress conditions

Salinity is one of the major abiotic stress conditions limiting crop growth and productivity. Duilio is a wheat genotype that shows tolerant behavior in both salt-stress and drought-stress conditions. Toward better understanding of the biochemical response to salinity in this genotype of durum wheat, a comparative label-free shotgun proteomic analysis based on normalized spectral abundance factors was conducted on wheat leaf samples subjected to increasing salt-stress levels (100 and 200 mmol L^-1 NaCl) with respect to untreated samples. We found significant changes in 71 proteins for the first stress level, in 83 proteins at the higher salinity level, and in 88 proteins when comparing salt-stress levels with each other. The major changes concerned the proteins involved in primary metabolism and production of energy, followed by those involved in protein metabolism and cellular defense mechanisms. Some indications of different specific physiological and defense mechanisms implicated in increasing tolerance were obtained. The enhanced salinity tolerance in Duilio appeared to be governed by a higher capacity for osmotic homeostasis, a more efficient defense, and an improvement of protection from mechanical stress by increased cell wall lignifications, allowing a better potential for growth recovery.     

Photoacoustic investigation of the absorption edge of Cd1−x Fe x Te compounds

Summary We have measured at room temperature the photoacoustic spectra of Cd_1−x Fe _x Te(0<x<0.055) around the CdTe fundamental absorption threshold. We identified an absorption band at (1.38±0.01) eV, increasing with the Fe concentration, that we assigned to the⁵ E→³ T ₁ transition within the Fe²⁺ (3d ⁶) manifold. We observed also a broadening and a shift to higher energies of the CdTe absorption edge for increasingx. Work partially supported by the Italian Consorzio INFM and CNR through the GNSM.     

Chemical analysis of essential oils from different parts of Ferula communis L. growing in central Italy

Ferula communis is a showy herbaceous plant typical of the Mediterranean area where it is used as a traditional medicine. The plant is a source of bioactive compounds such as daucane sesquiterpenes and prenylated coumarins. In Italy, most of phytochemical studies focused on Sardinian populations where poisonous and nonpoisonous chemotypes were found, while investigations on peninsular populations are scarce. In this work, we report the chemical characterisation of the essential oils obtained from different parts of F. communis growing in central Italy. The chemical profiles of the plant parts, as detected by GC-FID and GC-MS, were different from each other and from those reported in insular populations. Notably, α-pinene (10.5%), γ-terpinene (7.6%) and hedycariol (8.4%) were the major volatile constituents in flowers; α-pinene (55.9%), β-pinene (16.8%) and myrcene (5.9%) in fruits; β-eudesmol (12.1%), α-eudesmol (12.1%) and hedycariol (10.3%) in leaves; (E)-β-farnesene (9.5%), β-cubebene (8.2%) and (E)-caryophyllene (7.2%) in roots. The volatile profiles detected did not allow to classify the investigated central Italy population into the poisonous and nonpoisonous chemotypes previously described in Sardinia.     

Exchange anisotropy in Co/NiO bilayers: time-dependent effects

The time dependence of the exchange anisotropy was studied in Co/NiO bilayers. In order to only observe the relaxation phenomena inside the antiferromagnetic (AF) layer and to eliminate the dynamic behaviour inside the ferromagnetic (F) layer, we have developed an experimental method where a small a.c. magnetic field is applied perpendicular to the main anisotropy axis. All data are obtained by magneto-optical (m.o.) experiments. We observe a logarithmic time dependence of Hud, the exchange unidirectional anisotropy. We prove that the key parameter for the rate of relaxation is the anisotropy of the AF layer which depends strongly of the preparation method. We use the random field model as proposed by Malozemoff and suppose a breakdown of the AF interface into regular domains of size close to the crystallite size (10 nm width). If we further develop a Fulcomer and Charap relaxation model, we can propose from the distribution of relaxation times an analysis in terms of a spread of AF anisotropy energies. High magnetic pulsed field experiments (55 T) complete the experimental study and the results are analysed assuming that the Zeeman energy balances the anisotropy energy of the AF domains and switches them into the opposite direction.     

Four algorithms to solve symmetric multi-type non-negative matrix tri-factorization problem

Journal of Global Optimization - In this paper, we consider the symmetric multi-type non-negative matrix tri-factorization problem (SNMTF), which attempts to factorize several symmetric...     

Parameter-less algorithm for evolutionary-based optimization

The development of a simple, adaptive, parameter-less search algorithm was initiated by the need for an algorithm that is able to find optimal solutions relatively quick, and without the need for a control-parameter-setting specialist. Its control parameters are calculated during the optimization process, according to the progress of the search. The algorithm is intended for continuous and combinatorial problems. The efficiency of the proposed parameter-less algorithm was evaluated using one theoretical and three real-world industrial optimization problems. A comparison with other evolutionary approaches shows that the presented adaptive parameter-less algorithm has a competitive convergence with regards to the comparable algorithms. Also, it proves algorithm’s ability to finding the optimal solutions without the need for predefined control parameters.     

Collinear improvement of the BFKL kernel in the electroproduction of two light vector mesons

The use of the BFKL kernel improved by the inclusion of subleading terms generated by renormalization group (RG) analysis has been suggested to cure the instabilities in the behavior of the BFKL Green’s function in the next-to-leading approximation (NLA). We test the performance of a RG-improved kernel in the determination of the amplitude of a physical process, the electroproduction of two light vector mesons, in the BFKL approach in the NLA. We find that a smooth behavior of the amplitude with the center-of-mass energy can be achieved, setting the renormalization and energy scales appearing in the subleading terms to values much closer to the kinematical scales of the process than in the approaches based on the unimproved kernel.     

Proximal point method for minimizing quasiconvex locally Lipschitz functions on Hadamard manifolds

In this paper we propose an extension of the proximal point method to solve minimization problems with quasiconvex locally Lipschitz objective functions on Hadamard manifolds. To reach this goal, we use the concept of Clarke subdifferential on Hadamard manifolds and assuming that the function is bounded from below, we prove the global convergence of the sequence generated by the method to a critical point of the function.