Influence of SiC addition on tribological properties of SiAlON

The tribological properties of gas pressure sintered SiAlON and its composite with 18 wt% silicon carbide (SiC) against two different mating materials, i.e., alumina and SiAlON are evaluated. SiAlON and SiAlON–18%SiC composite ceramics were prepared by pressure less sintering and gas pressure sintering. Fretting wear tests were carried out under dry unlubricated ambient conditions (room temperature 23–25 °C; relative humidity 50–55%) with a load of 8 N for 45,000 cycles. Friction and wear properties of SiAlON–SiC proved better than the monolithic SiAlON. The formation of silica roll like structure on the composite worn surface was observed.     

Comparative Study of Essential Oils Extracted from Algerian Myrtus communis L. Leaves Using Microwaves and Hydrodistillation

Two different extraction methods were used for a comparative study of Algerian Myrtle leaf essential oils: solvent-free-microwave-extraction (SFME) and conventional hydrodistillation (HD). Essential oils analyzed by GC and GC-MS presented 51 components constituting 97.71 and 97.39% of the total oils, respectively. Solvent-Free-Microwave-Extract Essential oils SFME-EO were richer in oxygenated compounds. Their major compounds were 1,8-cineole, followed by α-pinene as against α-pinene, followed by 1,8-cineole for HD. Their antimicrobial activity was investigated on 12 microorganisms. The antioxidant activities were studied with the 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) radical scavenging method. Generally, both essential oils showed high antimicrobial and weak antioxidant activities. Microstructure analyses were also undertaken on the solid residue of myrtle leaves by Scanning Electronic Microscopy (SEM); it showed that the SFME-cellular structure undergoes significant modifications compared to the conventional HD residual solid. Comparison between hydrodistillation and SFME presented numerous distinctions. Several advantages with SFME were observed: faster kinetics and higher efficiency with similar yields: 0.32% dry basis, in 30 min as against 180 min for HD.     

Expression of the mitotic motor protein Eg5 in postmitotic neurons: implications for neuronal development

It is well established that the microtubules of the mitotic spindle are organized by a variety of motor proteins, and it appears that the same motors or closely related variants organize microtubules in the postmitotic neuron. Specifically, cytoplasmic dynein and the kinesin-related motor known as CHO1/MKLP1 are used within the mitotic spindle, and recent studies suggest that they are also essential for the establishment of the axonal and dendritic microtubule arrays of the neuron. Other motors are required to tightly regulate microtubule behaviors in the mitotic spindle, and it is attractive to speculate that these motors might also help to regulate microtubule behaviors in the neuron. Here we show that a homolog of the mitotic kinesin-related motor known as Eg5 continues to be expressed in rodent neurons well after their terminal mitotic division. In neurons, Eg5 is directly associated with the microtubule array and is enriched within the distal regions of developing processes. This distal enrichment is transient, and typically lost after a process has been clearly defined as an axon or a dendrite. Strong expression can resume later in development, and if so, the protein concentrates within newly forming sprouts at the distal tips of dendrites. We suggest that Eg5 generates forces that help to regulate microtubule behaviors within the distal tips of developing axons and dendrites.     

High-pressure phases of lead chalcogenides

Ab initio electronic structures have been carried out to find the pressure-induced structural phase transitions of lead chalcogenides (PbS, PbSe and PbTe) compounds. The zinc-blende, wurtzite, rocksalt, CsCl, GeS, TlI and orthorhombic Pnma phases are considered. Results show that the intermediate phase transition for these compounds is not the GeS nor the TlI type structures, as previously reported, but the orthorhombic Pnma phase. All these compounds are predicted to undergo a structural phase transition from the rocksalt to Pnma phase at about 8.13, 7.45 and 5.40 GPa for PbS, PbSe and PbTe respectively. Moreover, further structural phase transitions from this intermediate phase to the CsCl phase have been predicted at about 25.3, 18.76 and 15.43 GPa for PbS, PbSe and PbTe respectively.     

Investigation of the glass transition temperature and damping of an acrylic/epoxy bonding tape using the peak damping method

The dynamic properties of a structural tape used for adhesive bonding applications have been measured at different temperatures to determine its glass transition temperature and damping properties. For this purpose, free layer beams consisting of a base layer steel and the tape layer were vibrated using a resonant beam technique with free-free end conditions. To measure the dynamic values (elastic modulus and loss factor) of the tape, the necessary equations were derived and the frequency dependence of the beams was investigated from –55°C to +60°C. Three beams with different layers were tested. Results have shown that as the temperature increases, the elastic modulus of the tape decreases, while the loss factor of the tape increases up to 20°C and then decreases to a constant level. The results from the three beams are in agreement, showing that the glass transition temperature of the tape is about 20°C, which implies viscoelastic properties at room temperature.