Integration of InGaP/GaAs/Ge triple‐junction solar cells on deeply patterned silicon substrates

We report preliminary results on InGaP/InGaAs/Ge photovoltaic cells for concentrated terrestrial applications, monolithically integrated on engineered Si(001) substrates. Cells deposited on planar Ge/Si(001) epilayers, grown by plasma‐enhanced chemical vapor deposition, provide good efficiency and spectral response, despite the small thickness of the Ge epilayers and a threading dislocation density as large as 10⁷/cm². The presence of microcracks generated by the thermal misfit is compensated by a dense collection grid that avoids insulated areas. In order to avoid the excessive shadowing introduced by the use of a dense grid, the crack density needs to be lowered. Here, we show that deep patterning of the Si substrate in blocks can be an option, provided that a continuous Ge layer is formed at the top, and it is suitably planarized before the metalorganic chemical vapor deposition. The crack density is effectively decreased, despite that the efficiency is also lowered with respect to unpatterned devices. The reasons of this efficiency reduction are discussed, and a strategy for improvement is proposed and explored. Full morphological analysis of the coalesced Ge blocks is reported, and the final devices are tested under concentrated AM1.5D spectrum. Copyright © 2016 John Wiley & Sons, Ltd.     

H HRMAS-NMR metabolomic to assess quality and traceability of mozzarella cheese from Campania buffalo milk

The production of Mozzarella di Bufala Campana (MBC) is relevant for the agro-food economy of the Campania Region of Italy and the mark of Protected Designation of Origin (PDO) has been assigned to MBC in relation to its geographical origin. Advanced analytical methods must be then employed to assess authenticity, traceability, and quality of MBC. ¹H HRMAS-NMR (High Resolution Magic Angle Spinning Nuclear Magnetic Resonance) spectroscopy was applied here to directly identify specific metabolites in MBC intact samples without time-consuming sample pre-treatments. Overcrowded conventional ¹H HRMAS-NMR spectra were selectively simplified with two NMR pulse sequences: eCPMG and eDiff, by modulating spin-spin relaxation times and diffusion of MBC molecular components, respectively. Signal elaboration of edited spectra was combined with multivariate analyses to enable significant metabolic differentiation between MBC samples from two different production sites in Campania. Principal Components Analysis (PCA) for eCPMG spectra explained 97.54% of total variance between the two MBC groups for four metabolites (β-galactose, β-lactose, acetic acid, and glycerol). Less efficient was groups distinction by PCA for eDiff spectra, although differences in polyunsaturated acids, such as linoleic and linolenic acids, were highlighted. Similarly, Discriminant Analysis (DA) provided MBC group classification with 100% success in validation tests for eCPMG spectra, while DA prediction ability was reduced to 94.12% for eDiff spectra. Hierarchical Cluster Analysis (HCA) gave a totally correct classification between the two MBC groups only for eCPMG spectra. eCPMG spectra were also used to identify metabolites during MBC aging. As compared to fresh samples, 2 days old MBC samples showed increasing signals for isobutylic alcohol, lactic acid, and acetic acid. This work shows that ¹H HRMAS-NMR spectroscopy can rapidly characterise the metabolic profile of intact MBC samples and statistically distinguish the geographical origin of buffalo milk mozzarella and its freshness.     

Automatic laser-based identification for UF6 cylinders

We present a laser item identification system (L2IS), installed in a real facility on trial, that is capable of automatically monitoring all transfers of uranium hexafluoride (UF₆) cylinders between different process areas. Each cylinder has a unique ‘fingerprint’ represented by the 3D micro-structure of its surface which remains intact even under extreme environmental conditions. L2IS automatically identifies each cylinder through exploring the 3D frontal surface acquired by the laser scanner. The system is composed of a portable unit (operated in attended mode) and a fixed installed unit (operated without inspector presence). The efficiency and accuracy of our identification system were evaluated on a large dataset acquired during several years including a full year of field testing.     

Analytical Electromagnetic Solution for Bragg Mirrors With Graded Interfaces and Guidelines for Enhanced Reflectivity

Bragg mirrors, the key element of vertical-cavity surface-emitting lasers, always present graded interfaces when current is pumped through them, so as to reduce their series resistance and related heating problems. We present here an analytical solution for the electromagnetic fields in graded Bragg mirrors. It allows to generate reference reflection and transmission coefficients that are compared with those obtained by the staircase approximation method. Graded mirrors are then analyzed in detail and it is shown that, with an optimized design, higher reflectivity than in the abrupt scheme can be achieved     

Torque‐rheometry investigation of model transreactions involving condensation polymers. I. Polyesters

The chemical transformations taking place when poly(ethylene terephthalate) (PET) or poly(ethylene naphthalate) (PEN) are blended in the melt with different low molar mass substances containing hydroxyl, carboxyl, or amine functional groups have been investigated as models of the transreactions, undergone by the polyesters in reactive blending operations. The polyester molecular weight changes caused by the alcoholysis, acidolysis, aminolysis, and esterolysis reactions have been monitored by torque‐rheometry, using a Brabender Plasticorder static mixer. The degradation of the polyesters by hydrolysis was also studied, under similar conditions, by the addition of a water‐releasing substance (wet polyamide‐6), and was shown to occur quite rapidly, although most of the added water was lost by flash vaporization caused by the high temperature of the polyester melt. It has been shown that the rate constants of the reactions leading to breakage of the inner ester bonds of the polyester macromolecules decrease in the following order: aminolysis (with aliphatic amines, either primary and secondary) > alcoholysis (with aliphatic alcohols) ≈ hydrolysis > acidolysis (with aromatic acids) ≥ acidolysis (with aliphatic acids) ? aminolysis (with aromatic amines) > alcoholysis (with phenols) ? esterolysis. POLYM. ENG. SCI. 46:139–152, 2006. © 2005 Society of Plastics Engineers     

THROO: a Tracked Hybrid Rover to Overpass Obstacles

In this paper, the design, simulation and experimental tests are presented for THROO: a Tracked Hybrid Rover, which has been developed to Overpass Obstacles. The proposed mobile robot has 3-DOFs and it is capable of straight motion, turning ability and two operations, namely rover-like motion with tracks on flat terrain and walking-like motion with track and legs to overpass obstacles to move on uneven terrain. The leg mechanism is composed of a four-bar linkage, which has been synthesized according to the desired features. In particular, the Burmester problem, which aims at finding the geometric parameters of a four-bar linkage required for a prescribed set of finitely separated poses are solved for the case understudy. Dynamic simulations have been carried out and a prototype has been built. The proposed results show the hybrid rover ability to overpass obstacles, for which size is comparable or greater than the track high.     

About P systems with symport/antiport

It is proved that four membranes suffice to a variant of P systems with symport/antiport with maximal parallelism to generate all recursively enumerable sets of numbers. P systems with symport/antiport without maximal parallelism are also studied, considering two termination criteria.     

Influence of olive cultivars and period of harvest on the contents of Cu,Cd, Pb,and Zn in virgin olive oils

Levels of four of the major pollutant heavy metals were assessed by ICP-OES in virgin olive oil monocultivar samples. The data showed high variability within cultivars for lead and zinc, whereas, for cadmium and copper, no statistical difference was observed. The influence of the cultivar and the stage of ripening of olives on heavy metal content was assessed; zinc was the only metal with a great variability within the first and the second harvest. All olive samples were processed with the same milling apparatus.     

Polarization properties of some materials at near millimeter wavelengths

The degree of polarization of some materials widely used as optical components in the submillimeter and millimeter region has been measured in the wavelength interval 0.5÷3 mm. The procedure used in the measurements allows to determine degress of polarization of the order of 10^?5.     

Combined approach to the analysis of recombinant protein drugs using hollow-fiber flow field-flow fractionation, mass spectrometry, and chemiluminescence detection

The impurities present in recombinant protein drugs produced by large-scale refolding processes can not only affect the product safety but also interact with the expressed protein. To relate the impurity profile to conformation and functionality of the protein drug, analytical methods able not to degrade the sample components should be preferred. In this work, an urate oxidase (uricase) drug from Aspergillus flavus expressed in Saccharomyces cerevisiae, and a reagent-grade uricase from Candida sphaerica expressed in Escherichia coli, are analyzed by combining hollow-fiber flow field-flow fractionation with matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI/TOFMS) and with chemiluminescence enzyme activity assay. Preliminary detection and identification of sample impurities is performed by means of conventional methods such as RP HPLC with electrospray ionization quadrupole-TOF MS and MALDI/TOFMS with SDS PAGE and 2D SDS PAGE. Results show that the recombinant uricase samples obtained from different microorganisms have different impurities and different enzymatic activity and that different uricase oligomers are present in solution.