Determining the enthalpy and specific heat of magnesia spinels in the range 1400–2200°K

Conclusions Temperature functions were obtained for H(T) and C_p(T) which can be used for calculating the thermodynamic functions of the spinels MgAl₂O₄ and MgCr₂O₄ in the temperature regions of their service (up to 2200°K), to supplement the existing relationships (up to 1800°K).Translated from Ogneupory, No. 6, pp. 9–12, June, 1979.     

Numerical characterization and experimental verification of an in-plane MEMS-actuator with thin-film aluminum heater

In this paper, a novel concept of a thermo-mechanical MEMS actuator using aluminum thin-film heaters on a thermal oxide for electrical insulation is presented. The actuator is part of an universal tensile testing platform for thermo-mechanical material characterization of one dimensional materials on a micro- and nano-scopic scale under different environmental conditions, as varying temperatures, pressure, moisture or even vacuum and is realised in BDRIE technology. It is shown, that the actuator concept fulfills the requirements for the use in a tensile loading stage along with heterogeneously integrated nanofunctional elements, following a specimen centered approach in line with bottom-up self-assembly processes. Simulation and experiment agree very well in the thermal and mechanical domain and allow subsequent optimisation of the actuator performance.     

Thermal conductivity of magnesite refractories in the range 500–1800°C

Conclusions An experimental setup was developed for studying the thermal conductivity of refractories up to 2300°C on the hot face of the specimen.In the average temperature range of 500–1800°C a study was made of the thermal conductivity of magnesite refractories of different porosity. The experimental data obtained satisfactorily agree with well-known literature and calculated values for the thermal conductivity coefficients.Translated from Ogneupory, No. 1, pp. 17–21, January, 1972.     

Effect of cold environment on hepatic microsomal Δ6 and Δ9 desaturase activity of male rats

Male rats maintained at 24 C and then shifted to 5 C for 5 days increased food intake and decreased in growth rate and food conversion. No modification was observed in Δ6 desaturase activity, while Δ9 desaturase activity decreased after this period of time. These results were confirmed by liver microsomal and mitochondrial fatty acid composition. The phospholipid composition of liver microsomes was unaltered, whereas in mitochondria, phosphatidylcholine and sphingomyelin decreased and phosphatidylethanolamine increased due to the cold environment. The influence of food intake and weight changes on fatty acid metabolism was studied using (i) rats maintained at 5 C with restricted food intake to match the food intake of those kept at 24 C with food ad libitum and (ii) rats maintained at 24 C whose food intake was also restricted so that their growth rate would be the same as that of rats maintained at 5 C with food ad libitum, respectively. These results indicate that the negative metabolic balance state of these cold conditions is not an active factor modifier of Δ6 desaturase activity, whereas it decreases Δ9 desaturase activity, reflecting the lipogenic characteristics of the latter enzyme.     

Metabolic behavior in rats of a nonprotein microemulsion resembling low-density lipoprotein

A protein-free microemulsion (LDE) with a lipid composition resembling that of low-density lipoprotein (LDL) was used in metabolic studies in rats to compare LDE with the native lipoprotein. LDE labeled with radioactive lipids was injected into the bloodstream of male Wistar rats, and plasma kinetics of the labeled lipids were followed on plasma samples collected at regular intervals for 12 h after injection. The 24-h LDE uptake by different tissues was also measured in tissue samples excised after the animals had been sacrificed. We found that LDE plasma kinetics were similar to those described for native LDL [fractional clearance rate (FCR) of cholesteryl ester, 0.42±0.11 h⁻¹]. The major site for LDE uptake was the liver, and the tissue distribution of the LDE injected radioactivity was as one would expect for LDL. To test whether LDE was taken up by the specific LDL receptors, the LDE emulsion was injected into rats treated with 17α-ethinylestradiol, which is known to increase the activity of these receptors; as expected, removal of LDE from the bloodstream increased (FCR=0.90±0.35 h⁻¹). On the other hand, saturation of the receptors that remove remnants by prior infusion of massive amounts of lymph chylomicrons did not change LDE plasma kinetics. These results indicate that LDE is cleared from plasma by B,E receptors and not by the E receptors that remove remnants. Incorporation of free cholesterol into LDE increased LDE plasma clearance. Incubation studies also showed that LDE incorporates a variety of apolipoproteins, including apo E, a ligand for recognition of lipoproteins by specific receptors. Our data suggest that LDE can be a useful tool to test LDL metabolism and B,E receptor function.     

Effects of acid leaching treatment of soda-lime silicate glass on crack initiation and fracture

Water or acid soaking surface treatments have been shown to increase the mechanical strength of soda-lime silicate (SLS) glasses. This increase in strength has traditionally been attributed to effects related to residual stress or changes in fracture resistance. In this work, we report experimental data that cannot be explained based on the existing knowledge of glass surface mechanics. In dry environments, annealed and acid-leached SLS surfaces have comparable crack initiation stress and fracture stress as measured by Hertzian indentation and biaxial bending tests, respectively. Yet, in the presence of humidity, acid-leached surfaces have higher failure stress than the annealed surfaces. This apparent enhancement in the crack resistance of the acid-leached surface of SLS glass in humid environments supports the hypothesis that acid-leached surface chemistry can lower the transport kinetics of molecular water to critical flaws.     

Biofidelic child head FE model to simulate real world trauma

Biomechanics of human head has been widely studied since several decades. At a mechanical level, the use of engineering allowed investigating injury mechanisms developing numerical models of adult head. For children, the problem is more difficult and evaluating child injury mechanisms using data obtained from scaling adult injury criteria does not account for differences in morphology and structure between adults and children. During growth, child head undergoes different modifications in morphology and structure. The present paper compares the anthropometry and numerical simulations of a child head model based on medical CT scans to a child head model developed by scaling an adult head model using the method proposed by Mertz [H.J. Mertz, A procedure for normalizing impact response data, SAE paper 840884, 1984]. These analysis point out significant differences showing that scaling down an adult head to obtain a child head does not appear relevant. Biofidelic and specific child geometry is needed to investigate child injury mechanisms.     

A backstepping controller for path‐tracking of an underactuated autonomous airship

In this paper we propose a nonlinear control approach for the path‐tracking of an autonomous underactuated airship. A backstepping controller is designed from the airship nonlinear dynamic model including wind disturbances, and further enhanced to consider actuators saturation. Control implementation issues related to airship underactuation are also addressed, namely control allocation and an attitude reference shaping to obtain a faster error correction with smoother input requests. The results obtained demonstrate the capacity of an underactuated unmanned airship to execute a realistic mission including vertical take‐off and landing, stabilization and path‐tracking, in the presence of wind disturbances, with a single robust control law. Copyright © 2008 John Wiley & Sons, Ltd.     

Ultra-dense planar metallic nanowire arrays with extremely large anisotropic optical and magnetic properties

A nanofabrication method for the production of ultra-dense planar metallic nanowire arrays scalable to wafer-size is presented. The method is based on an efficient template deposition process to grow diverse metallic nanowire arrays with extreme regularity in only two steps. First, III–V semiconductor substrates are irradiated by a low-energy ion beam at an elevated temperature, forming a highly ordered nanogroove pattern by a “reverse epitaxy” process due to self-assembly of surface vacancies. Second, diverse metallic nanowire arrays (Au, Fe, Ni, Co, FeAl alloy) are fabricated on these III–V templates by deposition at a glancing incidence angle. This method allows for the fabrication of metallic nanowire arrays with periodicities down to 45 nm scaled up to wafer-size fabrication. As typical noble and magnetic metals, the Au and Fe nanowire arrays produced here exhibited large anisotropic optical and magnetic properties, respectively. The excitation of localized surface plasmon resonances (LSPRs) of the Au nanowire arrays resulted in a high electric field enhancement, which was used to detect phthalocyanine (CoPc) in surface-enhanced Raman scattering (SERS). Furthermore, the Fe nanowire arrays showed a very high in-plane magnetic anisotropy of approximately 412 mT, which may be the largest in-plane magnetic anisotropy field yet reported that is solely induced via shape anisotropy within the plane of a thin film.

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