A virtual valve for smooth contamination-free flow switching

We present a channel geometry that allows for clean switching between different inlets of a microchip without any contamination of the inlets or the downstream flow. We drive this virtual valve with a pneumatic pressure setup that minimizes disturbance of the downstream flow during the switching procedure by simultaneous variation of the pressures applied to the different inlets. We assess the efficiency of the setup by spectroscopic measurement of downstream dye concentrations, and demonstrate its practical utility by sequentially constructing multiple layers of alginate hydrogel. The method is potentially useful for a whole series of further applications, such as changing perfusion liquids for cell culture and cell analysis, metering, chemical-reaction initiation and multi-sample chromatography, to name a few.     

A comparison between nonlinear cantilever and buckled beam for energy harvesting

Nonlinear dynamics has become one of the key aspect to improve the efficiency of kinetic energy harvesters working in the real environment. Different methods based on the exploitation of the dynamical features of stochastic nonlinear oscillators using bi-stable piezoelectric cantilevers or buckled beams have been proposed in the past years. Such methods are shown to outperform standard linear oscillators and to overcome some of the most severe limitations of present approaches once applied to ambient vibrations. This work presents simulation results comparing the two methods. The same piezoelectric element subjected to a fixed vibrating body in a cantilever or bridge configuration has been simulated. The kinetic excitation considered is a zero mean exponentially correlated gaussian noise with different amplitudes. The piezoelectric oscillator output response has been obtained as a function of a nonlinear parameter. This work is intended to help designing the most performing energy harvester for real world applications starting from the same piezoelectric element.     

Microwave assisted organic synthesis (MAOS) of small molecules as potential HIV-1 integrase inhibitors

Integrase (IN) represents a clinically validated target for the development of antivirals against human immunodeficiency virus (HIV). In recent years our research group has been engaged in the stucture-function study of this enzyme and in the development of some three-dimensional pharmacophore models which have led to the identification of a large series of potent HIV-1 integrase strand-transfer inhibitors (INSTIs) bearing an indole core. To gain a better understanding of the structure-activity relationships (SARs), herein we report the design and microwave-assisted synthesis of a novel series of 1-H-benzylindole derivatives.     

Optimization of the antioxidant activity of hydroxy-substituted 4-thiaflavanes: a proof-of-concept study

The design and the synthesis of a new family of hydroxy-4-thiaflavanes, in which the reactive phenolic OH is ortho to the sulfur atom of the benzofused oxathiin ring, allowed to prepare antioxidants that show rate constants for the reaction with peroxyl radicals (k(inh)), and bond dissociation energies (BDE), of the ArO-H group identical to those of α-tocopherol, the main component of vitamin E and the most effective lipophilic antioxidant known in nature. The peculiar conformation of the six-membered heterocyclic ring prevents the formation of an intramolecular hydrogen bond between the OH group and the S atom, while ensuring a good stabilization by electron donation of the phenoxyl radical formed after the reaction with peroxyl radicals. The preparation of these compounds was achieved through an inverse electron demand hetero Diels-Alder reaction of styrenes with o-thioquinones, in turn prepared from accurately designed 1,3-dihydroxy arenes. Properly arranging the substitution pattern on the aromatic ring, as in derivatives 9 and 11, allowed to reach values of k(inh) up to 4.0×10(6) M(-1) s(-1) and BDE((OH)) of 77.2 kcal mol(-1). This approach represents an innovative way to obtain highly active antioxidants without using strongly electron donating alkylamino groups which are associated with adverse toxicological profiles.     

Robust portfolio asset allocation and risk measures

Many financial optimization problems involve future values of security prices, interest rates and exchange rates which are not known in advance, but can only be forecast or estimated. Several methodologies have therefore been proposed to handle the uncertainty in financial optimization problems. One such methodology is Robust Statistics, which addresses the problem of making estimates of the uncertain parameters that are insensitive to small variations. A different way to achieve robustness is provided by Robust Optimization, which looks for solutions that will achieve good objective function values for the realization of the uncertain parameters in given uncertainty sets. Robust Optimization thus offers a vehicle to incorporate an estimation of uncertain parameters into the decision making process. This is true, for example, in portfolio asset allocation. Starting with the robust counterparts of the classical mean-variance and minimum-variance portfolio optimization problems, in this paper we review several mathematical models, and related algorithmic approaches, that have recently been proposed to address uncertainty in portfolio asset allocation, focusing on Robust Optimization methodology. We also give an overview of some of the computational results that have been obtained with the described approaches. In addition we analyze the relationship between the concepts of robustness and convex risk measures.     

The perspective of a bank in granting credits: an optimization model

In this work, a model for legal financiers’ strategies is presented, taking into account that the aim of a bank is to minimize the default probability of the funded company, constrained with reaching a certain profit level. To obtain our purpose, a stochastic dynamics optimization model is constructed and solved in closed form and a Monte Carlo simulation involving empirical data is also implemented. The financial strategies are thus obtained.     

Effect of strain on the carrier mobility in heavily doped p-type Si

We present an experiment that gives insight into the origin of the dependence of the hole mobility (mu) on the dopant species in heavily doped p-type Si under low electrical field. The Hall carrier concentration and mobility were measured in Si coimplanted with B and Ga in the 0.1-2 x 10{20} cm{-3} concentration range. The strain induced by substitutional dopants, detected by high resolution x-ray diffraction, was varied by changing the relative B and Ga concentration. The effect of strain on mobility was disentangled and a linear relationship between 1/mu and the perpendicular strain was found.     

Is the placental proteome impaired in well‐controlled gestational diabetes?

In pregnancy complicated by gestational diabetes mellitus (GDM), the human placenta shows several pathological functional and structural changes, but the extent to which maternal glycemic control contributes to placental abnormalities remains unclear. The aim of this study was to profile and compare the proteome of placentas from healthy pregnant women and those with GDM, to investigate the placenta‐specific protein composition and possible changes of its function in presence of GDM. Quantitative proteomic analysis, based on LC‐MS^E approach, revealed that higher (approximately 15% increase) levels of galectin 1 and collagen alpha‐1 XIV chain (although the difference regarding the latter was at the limit of significance) were present in GDM samples, while heat shock 70 kDa protein 1A/1B was less abundant in GDM placental tissue. These data seem to indicate that GDM, when well controlled, did not markedly affect the placental proteome.     

Calorimetric Evaluation of Glycyrrhetic Acid (GA)- and Stearyl Glycyrrhetinate (SG)-Loaded Solid Lipid Nanoparticle Interactions with a Model Biomembrane

Glycyrrhetic acid (GA) and stearyl glycyrrhetinate (SG) are two interesting compounds from Glycyrrhiza glabra, showing numerous biological properties widely applied in the pharmaceutical and cosmetic fields. Despite these appreciable benefits, their potential therapeutic properties are strongly compromised due to unfavourable physical-chemical features. The strategy exploited in the present work was to develop solid lipid nanoparticles (SLNs) as carrier systems for GA and SG delivery. Both formulations loaded with GA and SG (GA-SLNs and SG-SLNs, respectively) were prepared by the high shear homogenization coupled to ultrasound (HSH-US) method, and we obtained good technological parameters. DSC was used to evaluate their thermotropic behaviour and ability to act as carriers for GA and SG. The study was conducted by means of a biomembrane model (multilamellar vesicles; MLVs) that simulated the interaction of the carriers with the cellular membrane. Unloaded and loaded SLNs were incubated with the biomembranes, and their interactions were evaluated over time through variations in their calorimetric curves. The results of these studies indicated that GA and SG interact differently with MLVs and SLNs; the interactions of SG-SLNs and GA-SLNs with the biomembrane model showed different variations of the MLVs calorimetric curve and suggest the potential use of SLNs as delivery systems for GA.     

Behaviour of scintillators under XUV free electron laser radiation

Free electron lasers (FEL) are new generation accelerator-based short wavelength light sources providing high pulse intensity and femtosecond pulse duration, which enable investigation of interaction of elementary excitations in solids under extreme conditions. Using the FLASH facility of HASYLAB at DESY (Hamburg, Germany), we investigated the response of different materials with scintillating properties based on intrinsic emissions to the 25.6 and 13.8 nm FEL radiation by means of time-resolved luminescence spectroscopy. FLASH delivered single pulses of 25 fs duration having energy per pulse up to 30 μJ resulting in power densities of ～10¹² W/cm² on crystals. As a function of excitation density we observed the shortening of lifetime and non-exponential behaviour of emission decays in CaWO₄, while the emission spectra recorded are comparable to those obtained at conventional excitation sources.