Propane oxydehydrogenation reaction on a VPO/TiO2 catalyst. Role of the nature of acid sites determined by dynamic in-situ IR studies

A VPO/TiO₂ catalyst tested in the oxydehydrogenation reaction (ODH) of propane between 300 and 400°C shows satisfactory performances (up to 80% of propene selectivity at 2% of propane conversion at 300°C or 56% of propene selectivity at 9% of propane conversion at 400°C). Addition of water or pyridine in the feed gas tends to decrease the propane conversion and enhances the propene selectivity. It is shown that water increases the number of Brönsted surface acid sites by dissociative adsorption which, in turn, enhances propene selectivity at the expense of the CO_x selectivity. These results are in good agreement with spectroscopic IR observations performed under catalytic conditions showing that the Lewis acid sites are linked to CO_xformation, whereas it seems that Brönsted sites would rather be linked to propene formation.     

Clinical determination of tissue optical properties by endoscopic spatially resolved reflectometry

A noninvasive method to measure the optical properties of a diffusing and absorbing medium is described. Based on the spatially resolved measurement of diffuse reflectance at the sample surface, this method is particularly suitable for investigating the in vivo optical properties of biological tissues endoscopically in a clinical context. The sensitivity of the measurement is discussed, and two optical probes for two different clinical applications are presented. Preliminary measurements are performed on a nonbiological medium, which illustrate the possibilities of the proposed method. Finally, we report on in vivo measurements of the optical properties of the human esophageal wall at 630 nm.     

Role of the nature of the acid sites in the oxydehydrogenation of propane on a VPO/TiO2 catalyst. An in situ FT-IR spectroscopy investigation

Catalytic activity and surface acidity during the oxydehydrogenation of propane over a VPO/TiO₂ catalyst were determined by a dynamic in situ FT-IR spectroscopy technique at 350°C. Pyridine was used as a probe molecule for the acidity measurements. The obtained results show that propene formation is linked to Brønsted acid sites and that water increases the number of these sites which, in turn, increases propene selectivity.     

Complex Elucidation of Cells-of-Origin in Pediatric Soft Tissue Sarcoma: From Concepts to Real Life,Hide-and-Seek through Epigenetic and Transcriptional Reprogramming

Soft tissue sarcoma (STS) comprise a large group of mesenchymal malignant tumors with heterogeneous cellular morphology, proliferative index, genetic lesions and, more importantly, clinical features. Full elucidation of this wide diversity remains a central question to improve their therapeutic management and the identity of cell(s)-of-origin from which these tumors arise is part of this enigma. Cellular reprogramming allows transitions of a mature cell between phenotypes, or identities, and represents one key driver of tumoral heterogeneity. Here, we discuss how cellular reprogramming mediated by driver genes in STS can profoundly reshape the molecular and morphological features of a transformed cell and lead to erroneous interpretation of its cell-of-origin. This review questions the fact that the epigenetic context in which a genetic alteration arises has to be taken into account as a key determinant of STS tumor initiation and progression. Retracing the cancer-initiating cell and its clonal evolution, notably via epigenetic approach, appears as a key lever for understanding the origin of these tumors and improving their clinical management.     

A High-Frequency Resonant Inverter Using Current-Vector Control Scheme and Its Performance Evaluations

The authors introduce a new configuration of resonant-type high-frequency inverter having inherent fast control response of the output power and variable-voltage variable-frequency (VVVF) capability. The circuit is composed of a parallel combination of two series-resonant inverters with common input and output terminals. Both inverter units are operated at synchronous frequency and with an adjustable phase difference from 0° to 180°, allowing control of the output power from full to null power, respectively. Operation of this inverter is explained and computer-simulated operating waveforms and characteristic curves are shown in terms of normalized control variables and circuit parameters. A prototype inverter using Power MOSFET modules has been originally tested with a high-frequency induction heating and melting load to demonstrate experimentally the proposed control principle and the steady-state inverter performances under parallel tuned load conditions.     

Tympano-ossicular homografts

Following a few European and American authors, we have undertaken tympano-ossicular homografts at the Hotel-Dieu de Quebec. The organization of the bank was achieved with many difficulties. We undertook our first surgical homografts in 1974, and 27 cases have since been performed. Our statistics are based on 19 cases. We obtained a perfect tympanic membrane in 17 cases, and 60 per cent of these have shown good improvement in hearing. This percentage is remarkable when one considers that we limited this procedure to cases for which all other techniques were bound to fail.     

Arthrotic sciatica caused by radicular compression of osteophytic origin in the lateral recess. Apropos of 18 cases

The authors report 18 cases of arthrosic sciatica due to toot compression in the lateral recess by posterior corporeal and/or posterior apophyseal osteophytosis. The authors study the clinical and radiological characteristics that may indicate the diagnosis and discuss the different mechanisms by which vertebral arthrosis can lead to radicular compression. When surgery is necessary because of the persistent nature of the sciatica, a broader approach should be undertaken than that required for excision of the disc, in order to explore fully the roots, the multiplicity of possible compression sites being one of the essential characteristics of these cases of arthrosic radiculopathy. Study of the literature and of the series of sciatica patients operated upon by the authors shows that although discal hernia is far from being the most frequent cause of common sciatica, arthrosic compression is a cause that cannot be ignored, especially in aged subjects.     

A 60-GHz HEMT-MMIC analog frequency divider by two

This paper describes an analog frequency divider by two working in the millimeter wave frequency range around 60 GHz. This circuit is analyzed with a new method that allows one to determine the steady-state regime of any synchronized circuits with standard CAD commercial software. The method proposed relies upon the concept of open loop systems and is applicable to any feedback transistor circuits. The designed circuit was processed using a standard 0.25-μm HEMT technology. Four transistors were used for realizing the frequency division function as well as the input and output amplification. More than 10% frequency lock-in bandwidth was achieved, and conversion gain was obtained using input and output buffers. Measured results were found to be in good agreement with simulated ones     

A (Triphenylphosphine)Silver (I) Complex as a New Performance Additive in Free‐Radical Photopolymerization under Air

Unusual photochemical properties of an Ag(I)‐derived complex, i.e., bis[(µ‐chloro)bis(triphenylphosphine)silver (I)] ([Ag](PPh₃)) are demonstrated when used in free‐radical photopolymerization reactions: i) [Ag](PPh₃) can act as an innovative photoinitiating system when associated with a commercial type I photoinitiator 2,2‐dimethoxy‐2‐phenylacetophenone to overcome the oxygen inhibition effect during the free‐radical photopolymerization of acrylate monomers, thus accelerating the kinetics of polymerization under air; ii) silver‐based nanoparticles can be in situ generated under air, thus leading to new antibacterial coatings which prevent the growth of Escherichia coli and Staphylococcus aureus after few hours of incubation.     

Numerical Technique for Resolving the Dual Phase Lag Heat Conduction in Thin Film Metal

Abstract

In this article, a three-time level finite difference scheme is used to resolve the dual phase lag’s (DPL) heat conduction in a micro scale gold film subjected to spontaneous temperature boundary conditions without knowing the heat flux. Finite difference analog of DPL equation on applying to the intermediate grid points of the computational domain results into a system of linear, algebraic equations which can be solved using Thomas’ algorithm to finally obtain the transient temperature solution distributions in the film. The solution predicted by the DPL model is compared with that obtained by the single-phase Cattaneo–Vernotte’s model. Further, the way in which non-Fourier’s temperature distributions affected by the diffusion due to the increase in Heat Conduction Model numbers agree with the predecessor’s published results. The results by both the models revealed a finite thermal wave speed in the film contrasting the infinite speed of heat propagation as stated by the classical Fourier’s thermal model. Low spatial step and higher order finite difference schemes are recommended for better accurate numerical results of the non-Fourier’s temperature distributions occurring in the very short transient period between the instants of the suddenly applied spatial temperature gradient and the reaching of the steady state conditions.