A comparative study of KOH/Al2O3 and KOH/NaY catalysts for biodiesel production via transesterification from palm oil

The transesterification of palm oil to methyl esters (biodiesel) was studied using KOH loaded on Al₂O₃ and NaY zeolite supports as heterogeneous catalysts. Reaction parameters such as reaction time, wt% KOH loading, molar ratio of oil to methanol, and amount of catalyst were optimized for the production of biodiesel. The 25 wt% KOH/Al₂O₃ and 10 wt% KOH/NaY catalysts are suggested here to be the best formula due to their biodiesel yield of 91.07% at temperatures below 70 °C within 2–3 h at a 1:15 molar ratio of palm oil to methanol and a catalyst amount of 3–6 wt%. The leaching of potassium species in both spent catalysts was observed. The amount of leached potassium species of the KOH/Al₂O₃ was somewhat higher compared to that of the KOH/NaY catalyst. The prepared catalysts were characterized by using several techniques such as XRD, BET, TPD, and XRF.     

Duplex formation of the simplified nucleic acid GNA

Glycol nucleic acid (GNA) has an acyclic backbone of propylene glycol nucleosides that are connected by phosphodiester bonds. This paper characterizes the duplex-formation properties of this simplified nucleic acid. Although single and multiple GNA nucleotides are highly destabilizing if incorporated into DNA duplexes, the two enantiomeric oligomers (S)-GNA and (R)-GNA form antiparallel homoduplexes that are thermally and thermodynamically significantly more stable than analogous duplexes of DNA and RNA. The salt-dependence and Watson-Crick-pairing fidelity of GNA duplexes are similar to those of DNA duplexes, but, apparently, the 2'-deoxyribonucleotide and the propylene glycol backbones are not compatible with each other. This conclusion is further supported by cross-pairing experiments. Accordingly, both (S)- and (R)-GNA strands do not generally pair with DNA. However, (S)-GNA, but not (R)-GNA, forms stable heteroduplexes with RNA in sequences that are low in G:C content. Altogether, the high stability and fidelity of GNA duplex formation in combination with the economical accessibility of propylene glycol building blocks for oligonucleotide synthesis render GNA an attractive candidate for the design of self-assembling materials. They further suggest that GNA could be considered as a potential candidate for a predecessor of RNA during the evolution of life on Earth.     

The dimensional effects of windowing on crosstalk for high speed hard disk drive interconnects

As the areal density rapidly changes, the signal reflection increases. In order to avoid the reflection between a magnetic recording head and a read/write driver on hard disk drive interconnects (HDDIs), the windowing technique is used to keep low insertion loss and it causes the higher crosstalk between lines. In this work, the crosstalk on idealized HDDI with windowing is investigated. The crosstalk represented by the scattering parameters calculated by using the full wave simulation software based on finite integral technique. From the results, the improvement of insertion loss and transmission bandwidth (?3 dB bandwidth) can be found when the window percentage is increased. For the 90% windowed structure, these are improved as 4.27 dB at 1 GHz and 4.53 GHz comparing with the conventional structure, respectively. Besides, the crosstalk increases with the increasing of window percentage. However, it can be suppressed up to 5.68 dB in a range of 0.24–1 GHz when the window percentage is 90%. Furthermore, the 90% of windowed structure with 8 mm window pitch possess the lowest crosstalk about 30.22 dB in a range of 0.32–6.4 GHz. In addition, the placing position of windows in a reference plane with a half of the rest length at both ends should be avoided because it increases both crosstalk and insertion loss. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:217–222, 2014.     

Development of intravascular contrast agents for MRI using gadolinium chelates

Two MRI contrast agents (CAs) composed of Gd‐DO3A conjugated to amino acid building blocks derived from glutamic acid ( CA1 ) and lysine ( CA2 ) have been synthesized by using novel alkyne and propionate linkers, and subsequently characterized. In vitro cell viability assays showed insignificant cytotoxicity of both CAs at low concentrations up to 0.2 mM . The longitudinal relaxivities (r₁) of CA1 and CA2 measured at 9.4 T are 6.4 and 5.4 mM ^?1 s^?1 in H₂O at 25 °C, respectively. Both r₁ values are higher than those of CAs in clinical use: Gd‐DTPA (Magnevist, Bayer Schering, Germany) and Gd‐DOTA (Dotarem, Guerbet, France). In vivo imaging in Wistar rats demonstrated considerable signal enhancement (～50 %) in the brain artery by CA2 , but lower signal enhancement (～30 %) by CA1 . In contrast to Dotarem, which showed a similar signal enhancement as CA2 , the enhancement by CA2 remained high (～30 %), even at 52 min post‐injection. This demonstrates that CA2 has a much longer blood half‐life (68.1 min), which could be advantageous for angiography and tissue targeting.     

Pushing the limits: From lanekeeping to autonomous racing

The success of Electronic Stability Control (ESC) has demonstrated the potential life-saving benefits of vehicle control systems. Lanekeeping presents an obvious next step in vehicle control, but the performance of such systems must be guaranteed before lanekeeping can be viewed as a safety feature. This paper demonstrates that simple lookahead control schemes for lanekeeping are provably robust even at the limits of tire adhesion. By responding to the heading error relative to the desired path, these schemes provide the countersteer behavior necessary to compensate for rear tire saturation and stabilize the vehicle. Using a Lyapunov-based analysis, vehicle stability can be proven even with a highly saturated tire. Taking this a step further by developing a desired path based on the racing line, this lookahead controller can be coupled with longitudinal control based on path position and wheel slip to create an autonomous racecar. The performance of this algorithm shows the potential for lanekeeping control that can truly assist even the best drivers.