Comparing stage-scenario with nodal formulation for multistage stochastic problems

To solve real life problems under uncertainty in Economics, Finance, Energy, Transportation and Logistics, the use of stochastic optimization is widely accepted and appreciated. However, the nature of stochastic programming leads to a conflict between adaptability to reality and tractability. To formulate a multistage stochastic model, two types of formulations are typically adopted: the so-called stage-scenario formulation named also formulation with explicit non-anticipativity constraints and the so-called nodal formulation named also formulation with implicit non-anticipativity constraints. Both of them have advantages and disadvantages. This work aims at helping the scholars and practitioners to understand the two types of notation and, in particular, to reformulate with the nodal formulation a model that was originally defined with the stage-scenario formulation presenting this implementation in the algebraic language GAMS. In addition, this work presents an empirical analysis applying the two formulations both without any further decomposition to perform a fair comparison. In this way, we show that the difficulties to implement the model with the nodal formulation are somehow reworded making the problem tractable without any decomposition algorithm. Still, we remark that in some other applications the stage-scenario formulation could be more helpful to understand the structure of the problem since it allows to relax the non-anticipativity constraints.

     

CuO based catalysts on modified acidic silica supports tested in the de-NOx reduction

A series of dispersed CuO catalysts supported on modified silica supports with Al2O3 (SA), TiO2 (ST), and ZrO2 (SZ) were prepared optimising the adsorption method of copper deposition assisted by ultrasound treatment, already reported in a previous paper (S. Bennici, A. Gervasini, V. Ragaini, Ultrason. Sonochem. 10 (2003) 61). The obtained catalysts were characterized in their bulk (atomic absorption, X-ray diffraction, temperature programmed reduction) and surface (N2 adsorption, X-ray photoelectron spectroscopy, scanning electron microscopy) properties. The morphology of the finished materials was not deeply modified compared with that of the relevant supports. The employed complemented techniques evidenced a well dispersed CuO phase with a copper-support interaction on the most acidic supports (SA and SZ). The catalyst performances were studied in the reaction of selective catalytic reduction of NOx with ethene in oxidizing atmosphere in a flow apparatus under variable times (0.360-0.072 s) and temperatures (200-450 degrees C). The catalysts prepared on the most acidic supports (SA and SZ) were the most active and selective towards N2 formation. They showed a particular interesting activity in the reaction of NO2 reduction besides that of NO reduction.     

Accidental exposure to UV radiation produced by germicidal lamp: case report and risk assessment

Ultraviolet radiation is known to cause both benefits and harmful effects on humans. The adverse effects mainly involve two target organs, skin and eye, and can be further divided into short- and long-term effects. The present case report describes an accidental exposure of two health-care workers to ultraviolet radiation produced by a germicidal lamp in a hospital pharmacy. The germicidal lamp presented a spectrum with an intense UV-C component as well as a modest UV-B contribution. Overexposure to UV-C radiation was over 100 times as large as the ICNIRP exposure limits. A few hours after the exposure, the two subjects reported symptoms of acute UV injury and both of them continued having significant clinical signs for over 2 years. In this study, we describe acute and potentially irreversible effects caused by high UV exposure. In addition, we present the results of risk assessment by occupational exposure to germicidal lamps.     

Drop deformation in microconfined shear flow

The deformation and breakup of a drop in an immiscible equiviscous liquid undergoing unbounded shear flow has been extensively investigated in the literature, starting from the pioneering work of Taylor. In this Letter, we address the case of microconfined shear flow, a problem which is relevant for microfluidics and emulsion processing applications. The main effects of confinement include complex oscillating transients and drop stabilization against breakup. In particular, very elongated drop shapes are observed, which would be unstable in the unbounded case and can be explained in terms of wall-induced distortion of the shear flow field. We show that wall effects can be exploited to obtain nearly monodisperse emulsions in microconfined shear flow.     

Raman spectroscopy of magneto-phonon resonances in graphene and graphite

The magneto-phonon resonance or MPR occurs in semiconductor materials when the energy spacing between Landau levels is continuously tuned to cross the energy of an optical phonon mode. MPRs have been largely explored in bulk semiconductors, in two-dimensional systems and in quantum dots. Recently there has been significant interest in the MPR interactions of the Dirac fermion magneto-excitons in graphene, and a rich splitting and anti-crossing phenomena of the even parity $E_{2g}$ long wavelength optical phonon mode have been theoretically proposed and experimentally observed. The MPR has been found to crucially depend on disorder in the graphene layer. This is a feature that creates new venues for the study of interplays between disorder and interactions in the atomic layers. We review here the fundamentals of MRP in graphene and the experimental Raman scattering works that have led to the observation of these phenomena in graphene and graphite.     

Palytoxin in seafood by liquid chromatography tandem mass spectrometry: investigation of extraction efficiency and matrix effect

Blooms of Ostreopsis spp. have been recently reported along the Mediterranean coasts of Spain, France, Italy, and Greece posing serious risks to human health. Occurrence of Ostreopsis spp. may result in palytoxin contamination of seafood and, in order to prevent sanitary risks, the need exists to develop efficient extraction procedures to be coupled to rapid and sensitive monitoring methods of palytoxin-like compounds in seafood. In the present study, the best conditions for both extraction of palytoxin from seafood and palytoxin quantification by using liquid chromatography tandem mass spectrometry (LC-MS/MS) were investigated. Three seafood matrices (mussels, sea-urchins, and anchovies) were selected and five different extraction systems were tested, namely: the official protocol for extraction of lipophilic toxins and various aqueous methanol or acetonitrile solutions (MeOH/H₂O 1:1, MeOH/H₂O 8:2, MeCN/H₂O 8:2 and MeOH 100%). Extraction with MeOH/H₂O 8:2 provided the best results in terms of accuracy and matrix interference on LC-MS/MS detection of palytoxin. Accuracy and intra-day reproducibility (n = 3) were evaluated for all the selected matrices but only for mussels at three spiking concentration levels, including the provisional limit proposed by the Community Reference Laboratory for marine biotoxins (250 μg kg⁻¹). Limits of quantitation of palytoxin in mussels, sea-urchins and anchovies tissues were calculated using matrix-matched standards; taking into account extraction efficiency of MeOH/H₂O 8:2, they resulted to be 228, 343, and 500 μg kg⁻¹, respectively.     

GC-FTIR and GC-MS in odour analysis of essential oils

The analysis of odour components in East Indian Sandalwood Oil (Santalum album L.) and in Patchouli Oil (Pogostemon cablin Benth.) based on GC-, GC-FTIR- and GC-MS-data resulted in the identification of-santalene,-santalal,-santalal, epi--santalal,-santalol,-santalol, (E)--santalol,-bergamotol and spirosantalol in Sandalwood Oil and of (–)-patchoulol,-guaiene,-patchoulene, seychellene,-bulnesene, norpatchoulenol and pogostol in Patchouli Oil as the most intense aroma compounds of these oils.     

The electric birefringence of polyelectrolytes: an electrokinetic approach

We discuss the Kerr constant of a polyelectrolyte solution in the dilute regime. We show that the birefringence induced in a suspension of nonspherical polyelectrolytes by an external electric field probes the electrokinetic properties of the suspension. This is because the Kerr constant is directly connected to the electric torque exerted on the particles, and therefore contains information on the induced dipole, similarly to the other electrokinetic techniques. The article is a guideline for the development of an electrokinetic theory of the electric birefringence of polyelectrolytes. We compare two different methods to derive the Kerr constant of the polyelectrolyte solution. The first method uses an expression for the electric torque which is obtained through electrostatics, and yields a Kerr constant which has the same frequency dependence as the anisotropy of the real part of the polarizability of the dressed particle (that is, of the particle plus surrounding ions). The second method assigns an effective value of the induced electric dipole per particle by using the theory of the dielectric enhancement, and gives a Kerr constant proportional to the anisotropy of the real part of the dielectric constant of the suspension. The two methods give a considerably different frequency dependence of the Kerr constant: we suggest that the expression obtained by the second method is more capable of correctly describing the main features of the experimental results obtained with polyelectrolytes having small shape anisotropy.     

Chiral recognition in aqueous solutions between enantiomeric α-amino acids bearing substituted alkyl chains at 25°C: The peferential configuration model

Calorimetric, densimetric, and nuclear relaxation time measurements were carried out at 25°C on binary and ternary aqueous solutions containing L and D forms of the following amino acids bearing substituted alkyl chains: lysine, glutamine, arginine, asparagine, serine, and homoserine. For three of them (lysine, glutamine, and arginine), very high differences were found between the values of the homochiral and heterochiral pairwise enthalpic interaction coefficients. Volume and spectroscopic data showed that it is possible to detect chiral recognition by techniques other than calorimetric. The role of the zwitterionic interaction and of the substituted side chain is discussed to explain the enhanced chiral recognition of these -aminoacids in respect to those bearing unsubstituted alkyl chains (alanine, -aminobutyric acid, valines and leucines).