Platinum promoted zirconia-sulfate catalysts: one-pot preparation,physical properties and catalytic activity

A new innovative methodology for the single-stage preparation of ZrO₂-SO₄ and Pt/ZrO₂-SO₄ catalysts is reported, based on the sol-gel technique. Catalysts are characterized by analysis, XRPD, BET and IR methods and are tested in the isomerization of butane.     

Nanostructured Materials for Room‐Temperature Gas Sensors

Sensor technology has an important effect on many aspects in our society, and has gained much progress, propelled by the development of nanoscience and nanotechnology. Current research efforts are directed toward developing high‐performance gas sensors with low operating temperature at low fabrication costs. A gas sensor working at room temperature is very appealing as it provides very low power consumption and does not require a heater for high‐temperature operation, and hence simplifies the fabrication of sensor devices and reduces the operating cost. Nanostructured materials are at the core of the development of any room‐temperature sensing platform. The most important advances with regard to fundamental research, sensing mechanisms, and application of nanostructured materials for room‐temperature conductometric sensor devices are reviewed here. Particular emphasis is given to the relation between the nanostructure and sensor properties in an attempt to address structure–property correlations. Finally, some future research perspectives and new challenges that the field of room‐temperature sensors will have to address are also discussed.     

Synthesis,Pharmacological Evaluation,and Docking Studies of Novel Pyridazinone‐Based Cannabinoid Receptor Type 2 Ligands

In recent years, cannabinoid type 2 receptors (CB₂R) have emerged as promising therapeutic targets in a wide variety of diseases. Selective ligands of CB₂R are devoid of the psychoactive effects typically observed for CB₁R ligands. Based on our recent studies on a class of pyridazinone 4‐carboxamides, further structural modifications of the pyridazinone core were made to better investigate the structure–activity relationships for this promising scaffold with the aim to develop potent CB₂R ligands. In binding assays, two of the new synthesized compounds [6‐(3,4‐dichlorophenyl)‐2‐(4‐fluorobenzyl)‐cis‐N‐(4‐methylcyclohexyl)‐3‐oxo‐2,3‐dihydropyridazine‐4‐carboxamide ( 2 ) and 6‐(4‐chloro‐3‐methylphenyl)‐cis‐N‐(4‐methylcyclohexyl)‐3‐oxo‐2‐pentyl‐2,3‐dihydropyridazine‐4‐carboxamide ( 22 )] showed high CB₂R affinity, with K_i values of 2.1 and 1.6 nm , respectively. In addition, functional assays of these compounds and other new active related derivatives revealed their pharmacological profiles as CB₂R inverse agonists. Compound 22 displayed the highest CB₂R selectivity and potency, presenting a favorable in silico pharmacokinetic profile. Furthermore, a molecular modeling study revealed how 22 produces inverse agonism through blocking the movement of the toggle‐switch residue, W6.48.     

Gas Sensing of NiO‐SCCNT Core–Shell Heterostructures: Optimization by Radial Modulation of the Hole‐Accumulation Layer

Hierarchical core–shell (C–S) heterostructures composed of a NiO shell deposited onto stacked‐cup carbon nanotubes (SCCNTs) are synthesized by atomic layer deposition (ALD). A film of NiO particles (0.80–21.8 nm in thickness) is uniformly deposited onto the inner and outer walls of the SCCNTs. The electrical resistance of the samples is found to increase of many orders of magnitude with the increasing of the NiO thickness. The response of NiO–SCCNT sensors toward low concentrations of acetone and ethanol at 200 °C is studied. The sensing mechanism is based on the modulation of the hole‐accumulation region in the NiO shell layer upon chemisorption of the reducing gas molecules. The electrical conduction mechanism is further studied by the incorporation of an Al₂O₃ dielectric layer at NiO and SCCNT interfaces. The investigations on NiO–Al₂O₃–SCCNT, Al₂O₃–SCCNT, and NiO–SCCNT coaxial heterostructures reveal that the sensing mechanism is strictly related to the NiO shell layer. The remarkable performance of the NiO–SCCNT sensors toward acetone and ethanol benefits from the conformal coating by ALD, large surface area of the SCCNTs, and the optimized p‐NiO shell layer thickness followed by the radial modulation of the space‐charge region.     

Safety analysis of ITER failures and consequences during maintenance

This study has been a first attempt at identifying potential worker overexposure situations during machine maintenance operations. The results indicate potential areas, or situations, where worker overexposure may be possible [A. Natalizio, T. Pinna, Safety analysis of failures and consequences during maintenance, ENEA Report, FUS-TN-SA-SE-R-170, June 2007, Frascati, Italy].The key findings obtained are as follows. Firstly, we have found no machine maintenance operations where the risk of worker overexposure is considered significantly large that immediate design attention is needed.Secondly, the most significant risk of worker overexposure is due to airborne releases of radioactivity from cooling water pipes and tubes that may not have been fully drained and dried, when they are cut, or inadvertently opened, by workers (frequency of pipe-cutting activities could be significantly high).Thirdly, the risk of overexposure from human error could also be significant. This varies from mistaking the machine sector, to mistaking the component to be maintained. This is analogous to working on a live electrical circuit, when it is believed to be dead (disconnected from the power source) because the worker has mistakenly selected the wrong circuit—a look-alike one. Similarly, consider the situation of a worker mistakenly preparing to work on a cooling water circuit that is still at pressure and temperature, instead of the one that has been drained and dried. The more look-alike situations there are in the facility, the greater the probability of committing this type of error.Fourthly, when consideration is given to human error, we believe that the aggregation of different diagnostics in the same port enhances the probability of human error. At the moment, these risks cannot be quantified. The task of quantifying those risks in the future should be considered.Finally, the transport of activated in-vessel components, including components of plasma-heating and current-drive systems, in non-shielded casks, could carry with it a significant risk of worker overexposure. In the context of ALARA, this approach requires a specific study to justify its use.Concluding, it is important to note that by having identified the possibility of an overexposure situation does not mean that it is probable. The calculation of probability awaits further studies of this nature, when the design reaches a more detailed level.     

The raison d'être of constitutively active protein kinases: the lesson of CK2

Protein kinases generally are tightly controlled signaling molecules that are switched on only in response to specific stimuli. Exceptionally few protein kinases are constitutively active, the most striking example being provided by CK2 (formerly "casein kinase 2"). Owing to unique structural features, the catalytic activity of CK2 is constantly on, although its targeting can be deeply influenced by the association of its two catalytic subunits (alpha and/or alpha') with a dimeric non catalytic beta subunit. Constitutive activity of CK2 reflects its extraordinary pleiotropy documented by its growing list of >300 protein substrates and is consistent with emerging evidence that CK2 plays an essential role in the cell by counteracting premature and/or unscheduled apoptosis, thus ensuring cell survival under stress conditions.     

Study on reuse of metal oxide-promoted sulphated zirconia in acylation reactions

A series of sulphated zirconia samples (SZ) promoted with Al₂O₃, Ga₂O₃, and Fe₂O₃ were synthesized by co-precipitation at constant pH and aged under reflux conditions. Structural, surface and catalytic properties of the samples were investigated using N₂ adsorption/desorption, thermal analysis, in-situ FTIR spectroscopy, TPR–MS and EGA–MS measurements. The catalytic performance of promoted SZ in anisole acylation has been investigated. Promotion by either Fe₂O₃ or Ga₂O₃ was found to increase the catalytic activity (yield) after recycle of catalysts with respect un-promoted sample, whereas promotion by Al₂O₃ was observed to increase the conversion but not the yield. It is worth noting that all systems present high selectivity to the p-metoxyacetophenone product.     

Controlling the Er content of porous silicon using the doping current intensity

The results of an investigation on the Er doping of porous silicon are presented. Electrochemical impedance spectroscopy, optical reflectivity, and spatially resolved energy dispersive spectroscopy (EDS) coupled to scanning electron microscopy measurements were used to investigate on the transient during the first stages of constant current Er doping. Depending on the applied current intensity, the voltage transient displays two very different behaviors, signature of two different chemical processes. The measurements show that, for equal transferred charge and identical porous silicon (PSi) layers, the applied current intensity also influences the final Er content. An interpretative model is proposed in order to describe the two distinct chemical processes. The results can be useful for a better control over the doping process.

PACS

81.05.Rm; 82.45.Rr     

Effects of record length selection on the accuracy of spectralestimates of heart rate variability: a simulation study

To evaluate the effects of record length selection on the accuracy of spectral estimates of heart rate variability (HRV), a simulation study was carried out using a set of 58 signals obtained by autoregressive (AR) fitting a representative sample of real HRV signals. Four record lengths of 180, 300, 420, and 540 s were considered. Spectral estimation was performed by both the Blackman-Tukey (B-T) and AR methods. Accuracy was assessed for: (1) point spectral estimates, by computing the normalized averaged bias (NAB) and variance (NAV); and (2) the most commonly used spectral parameters [total power (TP) and the powers in the bands: very low frequency (VLF) (0÷0.04 Hz), low frequency (LF) (0.04÷0.15 Hz), and high frequency (HF) (0.15÷0.45 Hz)], by computing the normalized bias (NB) and variance (NV). The results are: whatever the record length considered, the 90th percentiles (90P) of the NAB were <10%, whereas those of the NB were <9% for TP, LF, and HF powers, and <14% for the VLF power, in both methods. The NAV was proportional to the reciprocal of record length, showing high 90P values for the shortest record length (26.4% for B-T and 44.2% for AR). The NV showed the same trend but 90P values were much lower (<8% for TP, LF, and HF powers and <19% for VLF power, in both methods). In the final part of the paper a procedure for the computation of approximate upper bounds of the relative absolute error of spectral measures at each record length, based on the knowledge of the NE and NV, is presented