Air-coupled linear and sparse cMUT array manufactured using MUMPs process

An assessment of the standard fabrication Micro-Electro-Mechanical Systems (MEMS) process Multi-User MEMS Processes (MUMPs) for complex air-coupled capacitive Micromachined Ultrasonic Transducer array aperture manufacture is reported. A 1-D linear array and a 2-D sparse symmetric binned-array have been designed and manufactured, and then characterised experimentally using electrical impedance measurements, laser vibrometry and air-coupled field measurement; the experimental data are supported by simulated data using Finite Element technique and field simulation based on Huygens?? principle. A methodology for the manufacture of the array structures using the MUMPs process is described. Electrical characterisation shows the devices operation at 770?kHz and the existence of large parasitic capacitances and electrical losses. Mechanical crosstalk of array substrate has been measured at ?40?dB using laser vibrometry. Moreover, the laser vibrometry measurement and the field characteristics of one element reveal that each element operates as a piston radiator.     

Antiproliferative activity, cell-cycle dysregulation, and cellular differentiation: salicyl- and catechol-derived acyclic 5-fluorouracil O,N-acetals against breast cancer cells

Herein we report the preparation and biological activity of three compounds with the general formula 1-[2-(5-substituted-2-hydroxybenzyloxy)-1-methoxyethyl]-5-fluorouracil. A catechol-derived compound such as 1-[3-(2-hydroxyphenoxy)-1-methoxypropyl]-5-fluorouracil and two salicyl-derived compounds such as (Z)-1-[4-(2-hydroxyphenyl)-1-methoxybut-3-enyl]-5-fluorouracil [(Z)-11] and its dihydrogenated derivative 1-[4-(2-hydroxyphenyl)-1-methoxybutyl]-5-fluorouracil were prepared to complete the set of six O,N-acetals. The most active compound against the MCF-7 breast cancer cell line was (Z)-11: IC(50)=9.40+/-0.64 microM. Differentiated breast cancer cells generate fat deposits in the cytoplasm. MCF-7 cells treated with (Z)-11 underwent an increase in lipid content relative to control cells after three days of treatment. Our results suggest that there may be significant potential advantages in the use of this new differentiating agent for the treatment of breast cancer.     

A Combined Selective Adsorption and Ozonation Process for VOCs Removal from Air

A new hybrid process combining adsorption and ozonation is examined as an alternative treatment for Volatile Organic Compounds (VOC). The physical adsorption of ozone was clarified on a ZSM‐5 zeolite. Oxidation of two industrial solvents was achieved on two zeolites and followed with temperature profiles and sub‐products detection. Total regeneration of the fixed bed was achieved with a complete mineralization of organic compounds. Detection and identification of sub‐products traces allowed us to suspect oxidation reactive species. A mass balance on oxygen showed that all the inlet ozone was used for organic compounds oxidation. A selective oxidation was achieved, allowing the separation and the recovery of minor compound.     

On predicting self-diffusion coefficients from viscosity in gases and liquids

The relations between self-diffusion and viscosity for compressed liquids and gases have been reviewed, and a new equation for correlating viscosities over wide ranges of temperature and pressure is proposed. This formula is inspired by the Lennard-Jones Chain model of Yu and Gao for self-diffusion, and represents the viscosities of 15 compounds (1046 data points) with an average absolute deviation of 6.95%. Moreover, as the presented equation and the Yu-Gao model require the same fitting parameters, the ability to calculate self-diffusion coefficients from the viscosity parameter is studied. Some of the classic reviewed relations, such as the Stokes-Einstein formula, are also contrasted with the available experimental data of both transport properties.     

Reduction of diesel smoke opacity from vegetable oil methyl esters during transient operation

This work is focused on the measurement and analysis of the smoke opacity resulting from a Diesel engine fuelled with conventional fuel and biofuels under transient conditions. Methyl esters obtained from used cooking and unused vegetable oils were tested as diesel fuels, pure and blended with 30% and 70% of a commercial diesel fuel which was also used pure. A commercial engine was mounted in a test bench prepared for operating in different transient conditions. A smoke meter AVL 439 allowed for the study of the effect of these fuels on the smoke opacity under varied operating conditions. The thermo chemical properties of the test fuels and the engine parameters, such as fuel/air ratio or exhaust gas recirculation (EGR) ratio, were used for the analysis and interpretation of the results. The engine transient processes studied were (a) engine start, (b) load increase at constant engine speed and (c) engine speed decrease at constant torque. These results suggested that the use of the diesel blends containing vegetable esters is an interesting alternative for a significant reduction in smoke opacity not only in steady conditions but also in transient engine operation, the latter being the most usual condition in passenger vehicles.     

Analysis of energetics and economics of sub-ambient hybrid post-combustion carbon dioxide capture

Adsorption of CO₂ from post-combustion flue gas is one of the leading candidates for globally impactful carbon capture systems. This work focused on understanding the opportunities and limitations of sub-ambient CO₂ capture processes utilizing a multistage separation process. A hybrid process design using a combination of pressure-driven separation of CO₂ from flue gas (e.g., adsorption- or membrane-based separation) followed by CO₂-rich product liquefaction to produce high-purity (>99%) CO₂ at pipeline conditions is considered. The operating pressure of the separation unit is a key cost parameter and also an important process variable that regulates the available heat removal necessary to reach the sub-ambient operating conditions. The economic viability of applying pressure swing adsorption (PSA) processes using fiber sorbent contactors with internal heat management was found to be most influenced by the productivity of the adsorption system, with productivities as high as 0.015 /kg_sorb⁻¹ sec⁻¹ being required to reduce costs of capture below $60/ton CO₂ captured. This analysis was carried out using a simplified two-bed process, and thus there is opportunity for further cost reduction with exploration of more complex cycle designs. Three exemplar fiber sorbents (MIL-101(Cr), UiO-66, and zeolite 13X) were considered for application in the sub-ambient process of PSA unit. Among the considered sorbents, zeolite 13X fiber composites were found to perform better at ambient temperatures as compared to sub-ambient. MIL-101(Cr) and UiO-66 fiber composites had improved purity, recovery, and productivity at colder temperatures reducing costs of capture as low as $61/ton CO₂. Future economic improvement could be achieved by reducing the required operating pressure of the PSA unit and pushing the Pareto frontier closer to the final pipeline requirement via a combination of PSA cycle design and material selection.     

Rheological characterization of 4,4′-bis(diethylamino)benzophenone-functionalized polybutadienes with low and medium vinyl content

An experimental study was undertaken to investigate the thermomechanical properties of a certain epoxy/amine configuration. The basic structure of all the epoxies was the same—DGEBA—and the curing agent used was PACM 20. By varying the epoxy prepolymer molecular weight and the stoichiometry between epoxy and amine, a range of different epoxy networks were produced. Glass transition temperatures were evaluated by using differentil scanning calorimetry (DSC). Modulus values as well as an alternative T_g determination were provided by dynamic mechanical analysis (DMA). Coefficients of thermal expansion were obtained from thermomechanical analysis (TMA). The tensile tests conducted at room and elevated temperatures provided additional modulus data along with the yield point, tensile strength, and elongation at break data. Property vs. stoichiometry curves exhibited a maximum for the glass transition temperature and the over the T_g modulus at the stoichiometric point. On the other hand, the under T_g modulus showed a minimum at the stoichiometric point. The results of the yield strength show remarkable similarity with the results of the modulus. Strength and elongation at break do not show clear trends, but a much different behavior is exhibited between room and elevated temperatures. © 1996 John Wiley & Sons, Inc.     

Crop sequence and P fertilization effects on soil P fractions under no-tillage

Nutrient Cycling in Agroecosystems - Increasing cropping intensity may affect phosphorus (P) recycling through crop residue inputs, which may differ in soils with different productivity, P...     

Change of Young’s modulus of cold-deformed pure iron in a tensile test

Changes in Young’s modulus E (determined according to ASTM E-111) of polycrystalline pure iron deformed by a tensile test at room temperature are determined. From its original mean value, 210 GPa, E decreased with deformation to a mean value of 196 GPa at ɛ=0.060. Thereafter, slight recovery occurred and E stabilized to 198 GPa until the appearance of neck (ɛ=0.100). With the aim to examine the causes of this behavior, residual stresses and textures were measured and the dislocation structure was observed by transmission electron microscopy (TEM). Longitudinal residual stresses increased from the first step of deformation (ɛ=0.015) and remained constant until the samples fractured. There was no significant difference in texture throughout the deformation process, during which the increment of α fiber was smooth. Thus, the decrease of E cannot be attributed to residual stresses or textures. A relationship between dislocation arrangement and decrease of E is proposed. Following the model established by Mott, dislocations can bow out in their glide planes, giving extra elastic strain and thus a decrease of E. The increase of the dislocation density during the first steps of deformation lowers the E values, since the extra elastic strain increases. At higher strains, when the cellular dislocation structure has formed (between ɛ=0.060 and 0.080), the dislocations in cell interiors are capable of giving an extra elastic strain, whereas the dislocations trapped in the cell walls are not. However, the dislocation density in cell interiors is lower than the dislocation density in the early stages of deformation in which the cell structure has not been developed. This produces the slight recovery of E measured at these strains. From ɛ=0.080, the values of E stabilized since no changes in dislocation density in cell interiors are observed.