Ageing mechanisms on PdOx-based catalysts for natural gas combustion in premixed burners

The ageing effect induced by S-compounds over 2%Pd/CeO₂·2ZrO₂, 2%Pd/LaMnO₃·2ZrO₂ and 2%Pd/BaCeO₃·2ZrO₂ catalysts for CH₄ combustion was investigated; S-compounds are in fact added as odorants in the natural gas network for safety purposes. Pd-based catalysts were prepared by solution combustion synthesis (SCS), starting from metal nitrates/glycine mixtures. Basic characterization (XRD, BET, FESEM analysis), FT–IR studies and catalytic activity tests were performed on powders and after accelerated ageing carried out up to 2 weeks (hydro-thermal treatment at 900 °C under a flow rate with typical domestic boiler exhaust gas composition, 9% CO₂, 18% H₂O, 2% O₂ in N₂, containing also 200 ppmv of SO₂ to emphasize any poisoning effect). Over fresh catalysts, IR analysis of CO adsorption evidenced the formation of highly dispersed Pd metal clusters and Pd ions. With ageing, 2%Pd/CeO₂·2ZrO₂ increased its CH₄ combustion half-conversion temperature (T₅₀, regarded as an index of catalytic activity) from 382 °C—recorded for fresh sample—to 421 °C, attained with the same sample aged two weeks. An unexpected improvement was found instead in the overall performance of 2%Pd/LaMnO₃·2ZrO₂ and 2%Pd/BaCeO₃·2ZrO₂: the T₅₀ in fact lowered from 570 to 450 °C for the first one, and from 512 to 443 °C for the second one, after two weeks ageing. S-hydro-thermal treatment provoked bulk and surface sulfates formation on all aged samples, with a concentration increasing with the exposure time. Prevailing ageing mechanisms seemed to be Pd metallic clusters coalescence, detected over the Ce–Zr system, and surface-bulk sulfates formation, the latter destroying the initial crystallographic structure. In 2%Pd/LaMnO₃·ZrO₂ and 2%Pd/BaCeO₃·ZrO₂ powders the amount of the perovskite phase strongly decreased during ageing, in favor of the formation of bulk sulfate and of oxides.     

1.2-V CMOS op-amp with a dynamically biased output stage

A very low-voltage operational amplifier in a standard CMOS process with a 0.75 V threshold voltage is presented. It uses a novel dynamically biased output stage based on the switched-capacitor approach. Thanks to this, drive performance is greatly improved and accurate current control is also achieved. The amplifier is capable of working with a power supply as low as 1.2 V while providing a -74 dB total harmonic distortion with a 700 mV peak-to-peak output voltage into a 500 Ω and 20 pF output load. The open-loop gain and the gain-bandwidth product are higher than 90 dB and 2.2 MHz, respectively     

Analysis and modeling of interstacked transformers for mm-wave applications

The analysis and modeling of monolithic interstacked transformers for mm-wave applications is addressed. The performance advantages of the interstacked structure are demonstrated by using the most important figures of merit for integrated transformers and a physic-based scalable lumped model is proposed. The model components are calculated with closed-form expressions that make use of geometrical and technological parameters. The accuracy of the proposed model is demonstrated by comparison with electromagnetic data in a wide frequency range. Maximum errors are below 5, 7.5, and 2% for magnetic coupling factor, quality factor, and self-resonance frequency, respectively. High accuracy is also achieved in the modeling of S-parameters up to the self-resonance frequency.     

Sesquiterpene Fingerprinting by Headspace SPME–GC–MS: Preliminary Study for a Simple and Powerful Analytical Tool for Traceability of Olive Oils

Solid-phase microextraction combined with gas chromatography–mass spectrometry is employed to characterise the head space composition of extra virgin olive oil with particular emphasis on some sesquiterpenes useful for oil classification. It is demonstrated that α-muurolene and α-farnesene contents (normalised to α-copaene), besides discriminating between Apulian and foreign oils, is even capable of differentiating between different sub-brands of Terra di Bari (protected denomination of origin) oils, produced in neighbouring, very restricted areas of the Apulian region.     

Influence of platinum on catalytic activity of polycrystalline WO3 employed for phenol photodegradation in aqueous suspension

A series of polycrystalline WO₃ solids loaded with platinum (0.5; 1.0; 2.0 and 3.0 wt%) were prepared and characterised by X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, specific surface areas determination, X-ray photoelectron spectroscopy. XPS and X-ray results indicate that the samples loaded with Pt up to 1 wt% contained on the surface mainly Pt(2+) species, while those loaded with higher amounts contained Pt(0). Moreover, the samples were employed for a probe reaction, i.e. phenol photooxidation in aqueous suspension, and their photoactivity was compared with that of two TiO₂ commercial samples, mainly in the anatase phase. All the Pt–WO₃ samples were more photoactive than the bare WO₃ for the partial photooxidation of phenol and particularly those containing 2 and 3 wt% of platinum were also more photo active that the TiO₂ samples used for comparison. On the contrary, as indicated by the total organic carbon analyses, the mineralisation (complete photooxidation) of phenol was faster on TiO₂ samples. Cathecol, quinone and muconic acid were found as main intermediates, both in the presence of Pt–WO₃ and TiO₂ samples, while hydroquinone was found only when TiO₂ samples were used.     

A lumped scalable model for silicon integrated spiral inductors

A lumped scalable model for spiral inductors in silicon bipolar technology has been developed. The effect of three different cross sections on inductor performance was first investigated by comparing experimental measurements. Using both the results of this analysis and three-dimensional electromagnetic simulation guidelines, several circular inductors were integrated on a radial patterned ground shield for model validation purposes. The model employs a novel equation for series resistance with only one fitting parameter extracted from experimental measurements. All other model elements were related to technological and geometrical data by using rigorous analytical equations. The model was validated using one- and two-port measured performance parameters of 45 integrated inductors, and excellent agreement was found for all considered geometries up to frequencies well above self-resonance.     

Visual Perception of Touchdown Point During Simulated Landing.

Experiments examined the accuracy of visual touchdown point perception during oblique descents (1.5°-15°) toward a ground plane consisting of (a) randomly positioned dots, (b) a runway outline, or (c) a grid. Participants judged whether the perceived touchdown point was above or below a probe that appeared at a random position following each display. Although judgments were unacceptably imprecise and biased for moving dot and runway displays, accurate and unbiased judgments were found for grid displays. It is concluded that optic flow per se does not appear to be sufficient for a pilot to land an airplane and that the systematic errors associated with optic flow under sparse conditions may be responsible for the common occurrence of landing incidents in so-called "black hole" situations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anomalous Thermal Expansion in Superconducting Mg1?xAlxB2 System

The thermal lattice expansion in the superconducting Mg_{1− x} Al _x B₂ system (x = 0, 0.13, and 0.59) has been measured using high-resolution X-ray powder diffraction. An unusual large negative thermal expansion (NTE) appears for temperatures below T ^* = 60 K in the MgB₂. The NTE effect increases in Mg_0.87Al_0.13B₂ and disappears at high Al content in the Mg_0.59Al_0.41B₂ where the temperature dependence of volume follows a standard Einstein model in the whole temperature range. The anomalous behavior of the thermal expansion provides a direct evidence in the physics of diborides for the relevance of the proximity to the 2.5 Lifshitz electronic topological transition where the Fermi surface of the σband changes from a two-dimensional (2D) to a three-dimensional (3D) topology.     

The Phospholipidomic Signatures of Human Blood Microparticles,Platelets and Platelet‐Derived Microparticles: a Comparative HILIC‐ESI–MS Investigation

The phospholipidomic signatures of human blood microparticles and platelets, evaluated by hydrophilic interaction liquid chromatography coupled to electrospray ionization—mass spectrometry, were compared. The phospholipidome of platelet‐derived microparticles, obtained by platelets stimulation with a mixture of Ca(II), thrombin and collagen, was also considered for the comparison. Platelets, blood microparticles and platelet‐derived microparticles displayed qualitatively similar phospholipidomes, all based on eight major phospholipid classes, namely: phosphatidylcholines, diacyl‐ and plasme(a)nyl‐phosphatidylethanolamines, phosphatidylserines, phosphatidylinositols, sphingomyelins and lyso forms of phosphatidylcholines and phosphatidylethanolamines. However, while the phospholipidomes of platelets and platelet‐derived microparticles were found to be generally similar also from a quantitative point of view, a higher relative incidence of species bearing polyunsaturated side chains, especially in phospholipid classes sharing the choline head (i.e. phosphatidylcholines and lyso‐phosphatidylcholines), was observed in the case of blood microparticles. As a further peculiar feature, never reported before, the relative abundance of lyso‐phosphatidylcholines among the eight identified phospholipid classes was found to be significantly higher in the lipid extracts of blood microparticles.     

A 2.4-GHz 24-dBm SOI CMOS Power Amplifier With Fully Integrated Reconfigurable Output Matching Network

In this paper, the potential of load adaptation for enhanced backoff efficiency in RF power amplifiers (PAs) has been investigated through a 0.13-mum silicon-on-insulator (SOI) CMOS fabrication technology. The RF power performance of the adopted SOI CMOS process has been preliminarily characterized by on-wafer load-pull measurements on a custom unit power transistor. A 2.4-GHz 24-dBm 2-V SOI CMOS PA with fully integrated reconfigurable output matching network has then been designed and experimentally characterized. A significant efficiency improvement of up to 34% has been achieved through load adaptation, peak efficiency being as high as 65%. Linear operation has also been demonstrated under two-tone excitation, as a 16-dBm output power has been attained while complying with a - 40-dBc third-order intermodulation distortion specification.