Search

Context. The different theoretical models concerning the formation of high-mass stars make distinct predictions regarding their progenitors, i.e. the high-mass prestellar cores. However, so far no conclusive observation of such objects has been made. Aims. We aim to study the very early stages of high-mass star formation in two infrared-dark, massive clumps, to identify the core population that they harbour. Methods. We obtained ALMA observations of continuum emission at 0.8mm and of the ortho-$\rm H_2D^+$ transition at 372GHz towards the two clumps. We use the SCIMES algorithm to identify cores in the position-position-velocity space, finding 16 cores. We model their observed spectra in the LTE approximation, deriving the centroid velocity, linewidth, and column density maps. We also study the correlation between the continuum and molecular data, which in general do not present the same structure. Results. We report for the first time the detection of ortho-$\rm H_2D^+$ in high-mass star-forming regions performed with an interferometer. The molecular emission shows narrow and subsonic lines, suggesting that locally the temperature of the gas is less than 10K. From the continuum emission we estimate the cores' total masses, and compare them with the respective virial masses. We also compute the volume density values, which are found to be higher than $10^{6}\, \rm cm^{-3}$. Conclusions. Our data confirm that ortho-$\rm H_2D^+$ is an ideal tracer of cold and dense gas. Interestingly, almost all the $\rm H_2D^+$-identified cores are less massive than 13M_sun , with the exception of one core in AG354. Furthermore, most of them are subvirial and larger than their Jeans masses. These results are difficult to explain in the context of the turbulent accretion models, which predict massive and virialised prestellar cores., Comment: Accepted for publications in A&A

(Abridged) Understanding the details of the formation process of massive (i.e. M, Published on A&A (19 pages, 9 figures, 7 tables)

(Abridged) We present a large sample of o-H$_2$D$^+$ observations in high-mass star-forming regions and discuss possible empirical correlations with relevant physical quantities to assess its role as a chronometer of star-forming regions through different evolutionary stages. APEX observations of the ground-state transition of o-H$_2$D$^+$ were analysed in a sample of massive clumps selected from ATLASGAL at different evolutionary stages. Column densities and beam-averaged abundances of o-H$_2$D$^+$ with respect to H$_2$, $X$(o-H$_2$D$^+$), were obtained by modelling the spectra under the assumption of local thermodynamic equilibrium. We detect 16 sources in o-H$_2$D$^+$ and find clear correlations between $X$(o-H$_2$D$^+$) and the clump bolometric luminosity and the dust temperature, while only a mild correlation is found with the CO-depletion factor. In addition, we see a clear correlation with the luminosity-to-mass ratio, which is known to trace the evolution of the star formation process. This would indicate that the deuterated forms of H$_3^+$ are more abundant in the early stages of the star formation process and that deuteration is influenced by the time evolution of the clumps. In this respect, our findings would suggest that the $X$(o-H$_2$D$^+$) abundance is mainly affected by the thermal changes rather than density changes in the gas. We have employed these findings together with observations of H$^{13}$CO$^+$, DCO$^+$, and C$^{17}$O to provide an estimate of the cosmic-ray ionisation rate in a sub-sample of eight clumps based on recent analytical work. Our study presents the largest sample of o-H$_2$D$^+$ in star-forming regions to date. The results confirm that the deuteration process is strongly affected by temperature and suggests that o-H$_2$D$^+$ can be considered a reliable chemical clock during the star formation processes, as proved by its strong temporal dependence., Comment: 18 pages, 8 figures and 6 tables. To appear in A&A

Disentangling the different stages of the star-formation process, in particular in the high-mass regime, is a challenge in astrophysics. Chemical clocks could help alleviating this problem, but their evolution strongly depends on many parameters, leading to degeneracy in the interpretation of the observational data. One of these uncertainties is the degree of CO depletion. We present here the first self-consistent magneto-hydrodynamic simulations of high-mass star-forming regions at different scales, fully coupled with a non-equilibrium chemical network, which includes C-N-O bearing molecules. Depletion and desorption processes are treated time-dependently. The results show that full CO-depletion (i.e. all gas-phase CO frozen-out on the surface of dust grains), can be reached very quickly, in one third or even smaller fractions of the free-fall time, whether the collapse proceeds on slow or fast timescales. This leads to a high level of deuteration in a short time both for typical tracers like N$_2$H$^+$, as well as for the main ion H$_3^+$, the latter being in general larger and more extended. N$_2$ depletion is slightly less efficient, and no direct effects on N-bearing molecules and deuterium fractionation are observed. We show that CO depletion is not the only driver of deuteration, and that there is a strong impact on $D_{frac}$ when changing the grain-size. We finally apply a two-dimensional gaussian Point Spread Function to our results to mimic observations with single-dish and interferometers. Our findings suggest that the low-values observed in high-mass star-forming clumps are in reality masking a full-depletion stage in the inner 0.1 pc region., accepted on ApJ

Based on HST and MUSE data, we probe the stellar and gas properties (i.e. kinematics, stellar mass, star formation rate) of the radio-loud brightest cluster galaxy (BCG) located at the centre of the X-ray luminous cool core cluster Abell 2667 (z = 0.2343). The bi-dimensional modelling of the BCG surface brightness profile reveals the presence of a complex system of substructures extending all around the galaxy. Clumps of different size and shape plunged into a more diffuse component constitute these substructures, whose intense 'blue' optical colour hints to the presence of a young stellar population. Our results depict the BCG as a massive (M_star ~ 1.38 x 10^11 M_sun) dispersion-supported spheroid (v_star < 150 km/s, sigma_0 ~ 216 km/s) hosting an active supermassive black hole (M_SMBH ~ 3.8 x 10^9 M_sun) whose optical features are typical of low ionisation nuclear emission line regions. Although the velocity pattern of the stars in the BCG is irregular, the stellar kinematics in the regions of the clumps show a positive velocity of ~ 100 km/s, similarly to the gas component. An analysis of the mechanism giving rise to the observed lines in the clumps through empirical diagnostic diagrams points out that the emission is composite, suggesting the contribution from both star formation and AGN. We conclude our analysis describing how scenarios of both chaotic cold accretion and merging with a gas-rich disc galaxy can efficaciously explain the phenomena the BCG is undergoing., Accepted for publication on the 10th of June 2019 (MNRAS)

The local Seyfert 2 galaxy NGC5135, thanks to its almost face-on appearance, a bulge overdensity of stars, the presence of a large-scale bar, an AGN and a Supernova Remnant, is an excellent target to investigate the dynamics of inflows, outflows, star formation and AGN feedback. Here we present a reconstruction of the gas morphology and kinematics in the inner regions of this galaxy, based on the analysis of Atacama Large Millimeter Array (ALMA) archival data. To our purpose, we combine the available $\sim$100 pc resolution ALMA 1.3 and 0.45 mm observations of dust continuum emission, the spectroscopic maps of two transitions of the CO molecule (tracer of molecular mass in star forming and nuclear regions), and of the CS molecule (tracer of the dense star forming regions) with the outcome of the SED decomposition. By applying the $^{\rm 3D}$BAROLO software (3D-Based Analysis of Rotating Object via Line Observations), we have been able to fit the galaxy rotation curves reconstructing a 3D tilted-ring model of the disk. Most of the observed emitting features are described by our kinematic model. We also attempt an interpretation for the emission in few regions that the axisymmetric model fails to reproduce. The most relevant of these is a region at the northern edge of the inner bar, where multiple velocity components overlap, as a possible consequence of the expansion of a super-bubble., 15 pages, 13 figures, resubmitted to MNRAS after moderate revisions

A Monte Carlo simulation of electron transport in In0.53Ga0.47As and InAs is performed in order to extract the main kinetic parameters: mean valley population, effective mass, drift velocity, mean energy, ohmic and differential mobility. Most of these quantities are crucial for the development of macroscopic numerical models. Moreover, for some calculated quantities, analytical interpolation equations are given in order to achieve easy implementation in numerical codes. A comparison between our Monte Carlo calculation and several experimental and theoretical calculations is also carried out in order to validate the results.

We present a self-consistent theory of ballistic electron transport in n + -i-n + diodes for steady-state and high-frequency regimes. The theory takes into account real injection/exclusion processes at the n + -i interfaces, space-charge effects in the base region and diffusive electron transport in contacts. Numerical results are obtained for InAs diodes. For the steady-state problem, we derive the spatial distributions of electron concentration, electric field and electrostatic potential, and calculate the current-voltage characteristics. We demonstrate that widely accepted simplifications and results, such as the virtual cathode approximation, the Child law and others, cannot be applied to describe semiconductor ballistic diodes for realistic values of the applied electric biases. We develop the theory of real-space transit-time resonance in ballistic diodes and determine the small-signal frequency-dependent response of these devices. The negative dynamic resistance (NDR) effect is identified and studied. We show that the thermal spreading of injected electrons over the energy greatly affects the transit-time resonance and suppresses the NDR effect. The parameters of the diodes and working temperatures necessary to achieve the maximum NDR effect in the THz frequency range are determined. Finally, we discuss the use of the NDR effect to generate THz radiation. With this aim, we analyze the coupled system of the ballistic diode and the resonator TEM mode. To increase the gain of the resonator modes we suggest to use a cascade of ballistic diodes. For this cascade, the criterion of THz generation can be readily achieved for a reasonable number of ballistic diodes. The results indicate the perspectives for the development of THz sources based on ultra-short ballistic devices.

Prohexadione-calcium is an acylcyclohexanedione that reduces incidence of fi re blight, caused by Erwinia amylovora. To determine whether prohexadione-calcium can be used in conjunction with biological control agents, its effect on the secretion and composition of nectar from apple and pear fl owers was evaluated. Plants treated with prohexadione-calcium produced more nectar, but the sugar concentration of the nectar was lower. The ability of E. amylovora, and of two biological control agents of fi re blight, Pantoea agglomerans and Pseudomonas fl uorescens, to grow in a sugar solution corresponding to the composition of nectar from treated or untreated plants was determined in the laboratory. All bacteria including E. amylovora grew better in the sugar solution corresponding to the nectar from treated plants. The concentration of sugar in the non-treated fl owers may be too high for bacterial growth. These results also suggest that prohexadione-calcium can be used alongside biological control agents for reduction of fi re blight incidence.

An important limitation of aluminium alloys for mechanical applications is their poor tribological behaviour. In this study, surface treatment by plasma electrolytic oxidation (PEO) has been applied to two widely used aluminium alloys: A359 (hypoeutectic Al–Si–Mg) cast alloy and AA7075 (Al–Zn–Mg–Cu) wrought alloy, in order to improve their wear resistance, under sliding and abrasive wear conditions. The main aim of this work was the comparison of the properties and wear resistance of the oxide layers grown under the same PEO treatment conditions on two different aluminium alloys which might be coupled in engineered components. Significant differences in the phase composition, microstructure and mechanical properties measured by microindentation were observed in the oxide layers grown on the two substrates, and were ascribed to the effects of the different compositions and microstructures of the substrate alloys. Abrasion tests were carried out in a micro-scale abrasion (ball-cratering) test, with both alumina and silicon carbide abrasive particles. The results demonstrated the influence of the abrasive material on wear behaviour: whereas relatively aggressive SiC particles gave comparable results for both PEO treated and untreated samples, with the less aggressive Al 2 O 3 abrasive the wear rates of the PEO treated samples, for both substrates, were significantly lower than those of the untreated substrates. In unlubricated sliding the PEO treatment significantly increase the wear resistance of both the aluminium alloys, at low applied load. In this condition the wear behaviour of the PEO treated alloys is strongly influenced by the stability of a protective Fe–O transfer layer, generated by wear damage of the steel counterpart. Under high applied loads however, the transfer layer is not stable and the hardness of the PEO layer, as well as the load bearing capacity of the substrate, become the main factors in influencing wear resistance.

Ten propolis samples from Bulgaria, Italy and Switzerland were analyzed by GC-MS. As expected, most samples displayed the typical chemical pattern of “poplar” propolis: they contained pinocembrin, pinobanksin and its 3-O-acetate, chrysin, galangin, prenyl esters of caffeic and ferulic acids. Two samples differed significantly: one from the Graubünden Alpine region, Switzerland, rich in phenolic glycerides, and one from Sicily which contained only a limited number of phenolics and was rich in diterpenic acids.

By means of a numerical hydrodynamic model, we consider the mechanism of collective plasma oscillations in a field-effect transistor channel under different excitations and biasing conditions. First, we consider the case of a device externally-excited by a harmonic optical beating or an electronic excitation under constant current condition at the drain. Both situations exhibit sharp resonances related to the first odd plasma modes illustrating the possibility of using the HEMT as a terahertz photomixer or detector. Then, we demonstrate that the frequencies, amplitudes and quality factors of the resonances can be strongly modified by varying the drain biasing condition from currentto voltage-driven operation.

Results of hydrodynamic simulation of HEMT performance under photo‐mixing excitation of free carriers in the conducting channel are presented. A resonant enhancement of current amplitudes at the beating frequency due to excitation of 2D plasma waves is demonstrated.

A modified Poisson equation able to take into account the influence of gates and a ?-doping in FETs and HEMTs is proposed. This equation can be solved self-consistently together with 1D transport equations along inhomogeneous transistor channels like those of the hydrodynamic or drift-diffusion approximations or with a Monte Carlo simulator used to describe carrier transport in n+nn+ structures.

By means of a Monte Carlo simulation, we have studied the collector transit region of an innovative InAs/AlSb quantum hot electron transistor constituted by a 100 nm-long InAs bulk region. This original vertical transport device has the potential to efficiently exploit the unrivalled transport properties of InAs to reach THz frequencies.

By means of a numerical hydrodynamic model, we investigate the influence of collective plasma modes in a field-effect transistor channel under different excitation and biasing conditions. Firstly, we study the case of a device externally-excited by a harmonic optical beating or an electronic excitation and current-driven operation at the drain. The harmonic and continuous responses of the drain-source bias show sharp resonances related to the first odd plasma modes, whose frequencies and amplitudes can be modified by playing on the drain bias. Secondly, we calculate the spectral density of drain voltage fluctuations in the absence of external excitations by using the generalized impedance-field method. Also the noise spectrum exhibits peaks corresponding to the excitation by the background noise of odd plasma modes.

We investigate 3D plasma resonances in InGaAs n+ − n − n+ diodes undergoing an optical beating excitation at room temperature. For this sake, we calculate the electric field response in the middle of the diode regions by using a hydrodynamic approach coupled to a one-dimensional Poisson solver. The results show clearly the presence of three-dimensional plasma resonances in the terahertz frequency domain for the two region types. We also emphasize a strong coupling between the plasma modes. Finally, the influence of both geometry and doping profile on the amplitude and the frequency of the resonances is evaluated.

A method for the heterodyne detection of terahertz (THz) signals is proposed. A high electron mobility transistor is used as a nonlinear element, while the optical beating of two laser beams exciting plasma waves in the transistor channel plays the role of the THz local oscillator. High efficiency and room-temperature operation of such a mixer are demonstrated by numerical simulations.

We propose a method for the heterodyne detection of terahertz (THz) signals. The nonlinear element is constituted by the channel of an High Electron Mobility Transistor (HEMT), while the optical beating of two laser beams exciting plasma waves in the transistor channel plays the role of the THz local oscillator. We numerically show, through an hydrodynamic modelling, the efficiency of such a mixer.

Modern technology allows the downsizing of electronic devices deeply into the nano‐metric scale thus reducing the electrons transit time between contacts. By means of Monte Carlo simulations coupled with a two‐dimensional Poisson solver, we have analysed the transition from diffusive to ballistic transport in InAs channels of differents lengths. The increased number of ballistic electrons associated with the shrinking of the device length is found to progressively modify the time dependence of the autocorrelation function of current fluctuations while significant modifications of plasma oscillations appear in the autocorrelation function of voltage fluctuations inside the structure.

We investigate the presence of plasma resonances in InGaAs diodes under different optical excitation conditions. In particular, we study the case of diodes submitted to an optical photoexcitation presenting a beating in the terahertz frequency domain. The responses of the diodes are calculated using a hydrodynamic approach coupled to a one-dimensional Poisson solver. The results show clearly the presence of three-dimensional plasma resonances in the terahertz frequency domain. We also show that the resonances frequency and amplitude can be tuned by modifying the diode geometry and doping profile.

We investigate the noise behavior in the presence of current instabilities induced by optical phonon emission. Calculations are carried out by means of Monte Carlo particle simulations of InP n+nn+ diodes at lattice temperatures below about 80 K. A giant enhancement of the low-frequency noise is observed in a narrow voltage region, which precedes the onset of current self-oscillations caused by the instability. A possible origin of this enhancement is discussed. The impact of the non-linear effects on the anomalous low-frequency noise behavior is stressed.

In the framework of analytical and hydrodynamic models for the description of carrier transport and noise in high electron mobility transistor/field-effect transistor channels the main features of the intrinsic noise of transistors are investigated under continuous branching of the current between channel and gate. It is shown that the current-noise and voltage-noise spectra at the transistor terminals contain an excess noise related to thermal excitation of plasma wave modes in the dielectric layer between the channel and gate. It is found that the set of modes of excited plasma waves can be governed by the external embedding circuits, thus violating a universal description of noise in terms of Norton and Thevenin noise generators.

We investigate the influence of collective plasma modes in a field-effect transistor channel under different excitations and biasing conditions. First, we study the case of a device externally-excited by a harmonic optical beating or an electronic excitation and current-driven at the drain. The harmonic and continuous responses of the transistor are calculated using a pseudo-two-dimensional hydrodynamic approach. They show sharp resonances related to the first odd plasma modes, whose frequencies and amplitudes can be modified by playing on the drain bias. Then, through the generalized impedance-field method we calculate also the spectral density of drain voltage fluctuations in the absence of external excitations. Also these noise spectra exhibit peaks corresponding to the odd plasma modes.

Bioleaching of a pyrite ore containing high concentrations of cobalt (0.1%) and zinc (0.065%) was affected by small amounts of calcitic gangue (from 0.01 to 1.01%). Results from an air-lift percolator and from Erlenmeyer flask experiments show that a small percentage of calcite raises the pH and arrests the growth of the acidophilic bacterium Thiobacillus ferrooxidans. In percolator experiments, when calcite is completely removed by the continuous addition of small quantities of acid, and the pH of the liquor becomes acid, the micro-organism begins to grow and to bio-oxidize the pyrite ore. The growth of T. ferrooxidans shows different lag phase spans (from 13 to 190 days) depending on carbonate dissolution. The metals Fe, Zn and Co are released into the leaching solution together at different rates after a lag-time which depends on calcite concentrations in pyrite gangue. Metal ratios in the mineral bulk are different from those in the liquor, Zn dissolving 5 times more readily than Co. Bioleaching rates for metal removal from pyrite are higher in percolator (for Fe, from 5 to 15 mg/l/h) than in flask experiments (from 0.5 to 2 mg/l/h), but the lag phases are shorter (from 2 to 65 days). The differences between the two systems are related to calcite dissolution and gypsum precipitation.

International audience; A photomixed laser beam of two 1.55 mum continuous-wave lasers is used for interband photoexcitation in submicron gate length InAlAs/InGaAs transistors. Results show the clear excitation of plasma oscillation modes in the transistor channel. A strong amplification of the optical beating detection in the 0-600 GHz range is observed as a function of drain-source voltage. Numerical results, using hydrodynamic model coupled to a pseudo-2D Poisson equation, are in good agreement with experiments concerning the plasma frequency dependence with gate voltage. Moreover, this model confirms both optical beating detection at subterahertz frequencies and the enhancement observed when drain-source voltage increases.

An innovative hot electron transistor based on InAs/AlSb heterostructures is proposed and studied. First fabricated devices demonstrated static current gain of 5 at room temperature. The potential of this device for high frequency operation is also discussed.

International audience; A photomixed laser beam of two 1.55 μm lasers is used to obtain interband photoexcitation at the difference frequency and at room temperature in suvmicron gate length INAIA/InGaAs transistors. Results show the clear excitation of plasma oscillation modes in the transistors channel Fundamental plasma resonant frequency and its add harmonics can be tuned with the applied gate voltage. Numerical simulation have also been performed using a hydrodynamic approach coupled to a pseudo-2D Poisson equation. Numerical results are in qualitative agreement with experiments and confirm optical beatin detection at terahertz frequencies.

The Pb–Zn deposit at Sant'Antonio di Val d'Aspra in the Farma Valley (Southern Tuscany) is hosted by Lower Moscovian carbonate rocks and shows many characters commonly found in Mississippi Valley type (MVT) deposits. Ore minerals (essentially sphalerite and galena) are closely confined to dolomitized portions of an only partly preserved black limestone. Mineralized carbonate rocks appear to have been eroded before the deposition of the overlying Upper Moscovian (Late Podolskian) shales. The diffuse presence of structures frequently found in internal sediments of karstic cavities indicates that supergene mechanisms have played an important role in the history of the deposit. A fluid inclusion study carried out on ore and gangue minerals revealed the presence of two different types of inclusions. The homogenization temperatures ranged from 120°C to 225°C but the most frequently found values were around 170°C. Salinity ranged from moderately low values up to 20 eq. wt. % NaCl. Lead isotopic composition rules out any relationship between the Sant'Antonio mineralization and Tertiary hydrothermal base metal occurrences in the same area. When all the data are taken together, a contrast is evident between geo-petrographic and isotopic data on the one hand, and fluid-inclusion microthermometry on the other.

We present a modified hydrodynamic approach to simulate high frequency noise in field‐effect transistors. The model is based on the coupling of standard 1D hydrodynamic equations for carrier concentration, velocity and energy with a modified pseudo‐2D Poisson equation. The advantage of this approach lies in the possibility to take into account the effect of a gate within a simple 1D approach. The model is applied to the case of GaAs FETs at room temperature and validated through the calculation of the small‐signal admittance and of the spectral density of current fluctuations in the framework of the generalized admittance field method.

Nanometric InGaAs‐based High Electron Mobility Transistors (HEMTs) have been shown experimentally to generate and detect THz radiation. The observed phenomena can be attributed to the presence of plasma waves inside the transistor channel. To investigate these oscillations we have performed Monte Carlo simulations of InGaAs homogeneous channels of different length and thickness. To detect the presence of plasma waves we have calculated the spectral density of voltage fluctuations under thermodynamic equilibrium at 300 K. Results confirm the presence of 3D and 2D plasma modes according to the topology of the channel.

the main causes of honey fermentation reported in the literature are water content, expressed as moisture (%) or water activity (aw), bacterial contamination and storage temperatures. at the present the detremination of whether a honey has undergone fermentation is made by means of a sensory analysis performed by an expert analyst. However during both production and inspection, it is of fundamental importance to have a parameter and a method of analysis for objectively determining the presence of a fermentation process and defining a thresholdfor differentiating between fermented and non-fermented honeys. In the study a procedure for assessing the onset and pattern of fermentation in honey kept at different temperatures (corresponding to possible and actual storage temperatures 15, 20, 25, 30, 35°C) and at different levels of moisture (16, 17, 18, 19, 20%) is taken into consideration.The samples were stored for a total of 18 months.

In the frame of the EC Project “RIS+ Tuscany: Transfer of innovative technologies for Cultural Heritage” we carried out a pilot restoration yard to apply and evaluate laser cleaning procedures in the conservation of stones and decorations on the facade of the church of S. Frediano (XI–XII Cent.) in Pisa. A multidisciplinary scientific committee was established, formed by art historians, architects, physicists, geologists, and conservators. Italian firms involved in conservation services and in laser technology participated in the project. The conservation has been recently completed after two years of work, providing a critical evaluation on the effectiveness and safety of optimized laser cleaning operations, the definition of an integrated conservation protocol which included the laser technique, as well as other conventional cleaning techniques, and the evaluation of time productivity and operative costs of laser operations.

We investigated the conservation problems of the Porta della Mandorla, a masterpiece of the early Florentine Renaissance. The aim of the work was the statement of practicable cleaning protocols based on laser ablation. To this goal, a thorough petrographic characterisation of the state of conservation was performed, which addressed a set of laser cleaning tests by Q-switching and short free running Nd:YAG lasers. The main optimisation problem was the yellow-orange appearance associated with laser ablation by Q-switching lasers. Following the explanation of such a cleaning result, two practicable solutions based on suitable pulse duration or wavelength selections were successfully demonstrated then different intervention protocols were proposed.

Royal Jelly (RJ) is a viscid substance that is highly acidic (pH 3.6-4.2) and has a characteristic sharp flavour secreted by worker bee as an essential food for the larva of queen bee. It is partially water soluble and hits density is 1.1 g/ml. The study of RJ composition was carried out since 1940 and it is still not exhaustive. The dry matter arrange between 30 –40% and consists of protein, lipids and sugars. It has been claimed to be veritable powerhouse of vitamins, minerals and amino acids. The researcher activity on RJ is request both to assure the product autenicity both to ensure their freshness. The peculiar components of RJ are free hydroxy acids and the most represented is 10-hydroxy-2-decenoic acid (10-HDA): no other natural product has been reported to contain 10-HAD. RJ has been demonstrated to possess several pharmacological activities in experimental animals, including vasodilatative and hypotensive activities. Different parameter are tested to evaluate RJ freshness, furosine assay appear the most suitable marker to evaluate the conditions of RJ storage.

We report a microscopic investigation of the spectrum of voltage fluctuations in nanometric n-Si layers. Theory makes use of a Monte Carlo simulator self-consistently coupled with a two-dimensional Poisson solver. We consider layers of variable thickness W in the range of 2–100 nm and variable length L in the range of 10–1000 nm embedded in an external dielectric medium. Calculations are performed at T=300 K for different doping levels and in the presence of an applied voltage of increasing strength. The spectra are found to exhibit peaks centered on the terahertz region. For W≥100 nm and carrier densities of 5×1017 and 5×1018 cm−3, the frequency peaks agree with the value of the three dimensional plasma frequency. For W≤100 nm, the results exhibit a plasma frequency that depends on L, thus implying that the oscillation mode is dispersive. The corresponding frequency covers a wide range of values of 0.2–10 THz and is in agreement with the values of the two-dimensional plasma frequency predicted by existin...

The mechanical behaviour of a soft composite material based on a hydrogel polymer matrix reinforced with bundles of poly(ethylene terephthalate) (PET) fibres is analysed. The composite reproduces the typical J-shaped stress-strain curves displayed by natural tendons and ligaments. The lamination composite theory was used to investigate the role of the fibres and the matrix properties, as well as the role of the winding angle and the volumetric fraction of fibres, on the mechanical response of this system. The results suggested that large variations in the mechanical behaviour can be obtained by changing the winding angle of the fibres in the composite which determines the extent of the 'toe' region and the sensitivity of the system to the rigidity of the fibres.