The effect of pulsed electric fields,ultraviolet light or high intensity light pulses in combination with manothermosonication on selected physico-chemical and sensory attributes of an orange and carrot juice blend

A blend of orange and carrot juice was processed by three selected treatments combining pulsed electric fields (PEF) (24 kV/cm, 18 Hz, 93 μs), ultraviolet light (UV) (10.6 J/cm²) or high intensity light pulses (HILP) (3.3 J/cm²), in each case, with manothermosonication (MTS) technology (400 kPa, 35 °C, 1000 W, 20 kHz). Treatment effects on selected physico-chemical and sensory properties of the juice were evaluated. No significant changes were found in non-enzymatic browning (NEBI) or antioxidant activity compared to an untreated control. However, the treatments increased all the Hunter Lab colour values, while total phenolics were significantly decreased. Each combination achieved on average 78% inactivation of pectin methyl esterase (PME). Sensory analysis showed that the colour of the product processed by hurdle combinations was preferred to that of a pasteurised sample (72 °C, 26 s), while the flavour was adversely affected by all of the non-thermal treatments. Panellists did not perceive differences in the odour, sweetness or acidity of the product. Results indicate that, under the current experimental conditions, the application of the selected combinations of non-thermal technologies resulted in a product in which certain quality attributes were somewhat inferior to those of a lightly pasteurised control juice.     

Stereoselective Modulation of P‐Glycoprotein by Chiral Small Molecules

Inhibition of drug efflux pumps such as P‐glycoprotein (P‐gp) is an approach toward combating multidrug resistance, which is a significant hurdle in current cancer treatments. To address this, N‐substituted aryloxymethyl pyrrolidines were designed and synthesized in their homochiral forms in order to investigate the stereochemical requirements for the binding site of P‐gp. Our study provides evidence that the chiral property of molecules could be a strategy for improving the capacity for interacting with P‐gp, as the most active compounds of the series stereoselectively modulated this efflux pump. The naphthalene‐1‐yl analogue (R)‐2‐[(2,3‐dichlorophenoxy)methyl]‐1‐(naphthalen‐1‐ylmethyl)pyrrolidine) [(R)‐ 7 a ] emerged foremost for its potency and stereoselectivity toward P‐gp, with the S enantiomer being nearly inactive. The modulation of P‐gp by (R)‐ 7 a involved consumption of ATP, thus demonstrating that the compound behaves as a P‐gp substrate.     

Direct patterning of silver particles on porous silicon by inkjet printing of a silver salt via in-situ reduction

ABSTRACT: We have developed a method for obtaining a direct pattern of silver nanoparticles (NPs) on porous silicon (p-Si) by means of inkjet printing (IjP) of a silver salt. Silver NPs were obtained by p-Si mediated in-situ reduction of Ag+ cations using solutions based on AgNO3 which were directly printed on p-Si according to specific geometries and process parameters. The main difference with respect to existing literature is that normally, inkjet printing is applied to silver (metal) NP suspensions, while in our experiment the NPs are formed after jetting the solution on the reactive substrate. We performed both optical and scanning electron microscopes on the NPs traces, correlating the morphology features with the IjP parameters, giving an insight on the synthesis kinetics. The patterned NPs show good performances as SERS substrates.     

Silver self aggregation in a nanodevice for enhanced Raman spectroscopy: experiments vs. simplified modeling via molecular dynamics

We present a study, via experiments and exploratory molecular dynamics simulations, of self aggregation in cylindrical nanostructures obtained experimentally by combining high resolution electron beam lithography with electroless silver deposition. This process is key to the fabrication of a nanolens device, where a strong surface enhancement can be exploited for Raman spectroscopy. In order to investigate the process, we introduce a simple theoretical model and compare the results of simulations with the fabricated silver nanostructures during the growth phase. Our simulations qualitatively agree with the experiments and allow a general characterization of the process at length scales smaller than those easily accessible by microscopy. We identify a geometrical parameter, the aspect ratio of the cylinder, that relates two different types of growth with different characteristics and, possibly, different Raman enhancements.     

Effects of orientation on mechanical properties of uniaxially oriented polystyrene films

Oriented samples of polystyrene have been produced by drawing at temperatures just above the glass transition range. Birefringence measurements have been used to characterise the degree of orientation. Mechanical measurements of elastic modulus and tensile yield stress have been made in the direction of drawing and it has been established that the birefringence value does not uniquely determine the mechanical properties—samples drawn to a high draw ratio at high temperatures have a higher modulus and yield stress than samples drawn at lower temperatures and lower draw-ratios to the same birefringence. The results are explained qualitatively by the convective constraint release theory of McLeish et al.     

Analytical solution for the problem of frictional-elastic collisions of spherical particles using the linear model

In the present paper, the problem of a frictional-elastic impact of two spheres is addressed with a novel approach. The set of equations arising from the linear model of the contact mechanics is analytically integrated considering the combined effects of the elastic and frictional mechanisms. The linear model is very commonly used in simulations based on the soft-sphere distinct element method (DEM) (Geotechnique 29 (1979) 47), where numerical methods are used for the integration of the equations of motion of the particles. The analytical approach presented in this work allows the examination of many important aspects related to the use of the linear model in dynamic simulation of multi-particle systems. The impact characteristics, in terms of the mechanisms governing the evolution of the force-displacement relation, can be classified in terms of the initial conditions, showing the same subdivision as that obtained with the more complex model of Maw et al. (Wear 38 (1976) 101). It is demonstrated how the values of many interesting variables at the end of the impact can be directly related to the impact initial conditions through a one-step calculation procedure. The model results of the tangential coefficient of restitution, rebound angles of the contact point and center of mass are validated with the experimental data on frictional-elastic collisions of Kharaz et al. (Powder Technol. 120 (2001) 281), showing, despite the simplicity of the considered model, an excellent agreement. However, it is demonstrated that the force evolution and time duration of the collisions strongly depend on the model parameters and can be improperly evaluated with incorrect material constants. Further analyses are carried out, for various impact angles, on the amount of energy loss due to the frictional mechanism. Also, an analysis of the direct influence of each model parameter on the properties of the particles at the end of the collision is carried out, with special emphasis on the normal elastic spring constant K_n. This helps clarifying why, in the literature, realistic macroscopic results were obtained even with very small values of K_n.     

A “Nearly Ideal” Solution to Linear Time-Varying Rational Expectations Models

For a well-identified class of forward-looking models under rational expectations and time-varying parameters, it is shown that there exists always a solution having the property of being the closest, in mean square, to the state motion of the autoregressive dynamic equation governing the “ideal” behavior of the economic system. A recursive algorithm—based upon Kalman filtering—providing the exact expression for the conditional expectations (hence, the solution) and the optimal filtering estimate, is also presented.     

An Approach to the Development of Flexible Multirobot Systems: the Potential of Using Mobile Code Technology

Building multirobot systems exploiting mobile code technologies: this is quite an attractive possibility that, if successfully exploited, could very much improve the flexibility in development of systems composed of multiple mobile robots. In this paper we present two main contributions that constitute a significant step toward this ambitious scenario. In particular, we present architectural and technological solutions that enable both the mobility of code in a network of robots and the interfacing between robotic platforms and mobile code. Although we are aware that the results presented in this paper are still preliminary and limited, we demonstrate their promising potential with experiments involving two mobile robots.     

An improved approach for constrained robust model predictive control

In this paper, we present a new technique to address constrained robust model predictive control. The main advantage of this new approach with respect to other well-known techniques is the reduced conservativeness. Specifically, the technique described in this paper can be applied to polytopic uncertain systems and is based on the use of several Lyapunov functions each one corresponding to a different vertex of the uncertainty's polytope.