Controlled growth of carbon nanofibers using plasma enhanced chemical vapor deposition: Effect of catalyst thickness and gas ratio

The characteristics of carbon nanofibers (CNFs) grown, using direct current plasma enhanced chemical vapor deposition system reactor under various acetylene to ammonia gas ratios and different catalyst thicknesses were studied. Nickel/Chromium-glass (Ni/Cr-glass) thin film catalyst was employed for the growth of CNF. The grown CNFs were then characterized using Raman spectroscopy, field emission scanning electron microscopy and transmission electron microscopy (TEM). Raman spectroscopy showed that the Ni/Cr-glass with thickness of 15 nm and gas ratio acetylene to ammonia of 1:3 produced CNFs with the lowest I_D/I_G value (the relative intensity of D-band to G-band). This indicated that this catalyst thickness and gas ratio value is the optimum combination for the synthesis of CNFs under the conditions studied. TEM observation pointed out that the CNFs produced have 104 concentric walls and the residual catalyst particles were located inside the tubes of CNFs. It was also observed that structural morphology of the grown CNFs was influenced by acetylene to ammonia gas ratio and catalyst thickness.     

Shear Strength Equations for Unsaturated Soil under Drying and Wetting

Shear strength of unsaturated soil is an important engineering property in various geotechnical designs. In response to varying climatic conditions, unsaturated soil behaves differently under the drying and wetting processes due to hysteresis. Many research works were conducted and numerous equations were proposed for unsaturated shear strength, however, most of them were limited to the soil under the drying process. In this study, shear strength equations were categorized according to the nature of equation, i.e., fitting and prediction type equations. The purpose of this study is to propose prediction type shear strength equations for unsaturated soil under drying and wetting. Twelve published shear strength equations were selected for evaluation. A series of unsaturated consolidated drained triaxial tests were conducted on statically compacted sand-kaolin specimens under drying and wetting to examine the validity of the proposed equations. The experimental results indicated that the specimens on the drying path had a higher shear strength and exhibited more ductility, less stiffness, and contraction during shearing while the specimens on the wetting path had a lower shear strength and exhibited more brittleness, more stiffness, and dilation during shearing. The proposed equations were shown to provide the best predictions on the drying and wetting shear strength results from this study as well as published data in the comparison study.     

Jaboticaba berry peel intake prevents insulin‐resistance‐induced tau phosphorylation in mice

The hyperphosphorylation of microtubule‐associated protein tau (tau) in the hippocampus can be caused by central and peripheral insulin resistance and these alterations are related to the development of tauopathies, such as Alzheimer's disease. In this study, we used a high‐fat diet to induce obesity and insulin resistance in adult Swiss mice and checked whether supplementation with Myrciaria jaboticaba berry peel for 10 weeks could improve insulin sensitivity, learning/memory performance, and prevent tau phosphorylation in the hippocampus. Furthermore, adipocytokines, inflammatory markers, and oxidative stress were assessed. Myrciaria jaboticaba peel has phenolic compounds (e.g., cyanidin, ellagic acid), dietary fiber and carotenoids, which contribute to great antioxidant capacity. Supplementation of the high‐fat diet with 4% M. jaboticaba peel prevented fat weight gain and reduced peripheral insulin resistance. The treated group also showed lower tau phosphorylation in the hippocampus corroborating better learning/memory performance in the Morris water maze test. Maintenance of neuronal viability, lower levels of hippocampal inflammatory markers, and improved brain antioxidant defenses were also related to the consumption of M. jaboticaba peel. These findings contribute to a better understanding of how a high‐fat diet supplemented with jaboticaba berry peel counteracts the impairment of cognitive functions caused by high‐fat diet intake and diet‐induced insulin resistance.     

Influence of process parameters on the strength of oil palm kernel shell pellets

In this study, the influence of processing and storage parameters on the strength of oil palm kernel shell pellets was determined. The strength of the pellets increased with compaction pressure but pelletizing pressures above 188 MPa had little effect on the pellet strength. At these high pressures, the pellets achieved no or near-zero porosities, indicating that the maximum strength was achieved. The diametrical tensile strengths of the pellets were much weaker than the compressive strengths when compacted at the same compaction pressure. The pellet strengths were found to increase with longer hold times during the compaction process. This was due to a continuous decrease in porosities until near-zero porosities were achieved, when increasing the hold time no longer led to further strengthening of the pellets. The time-dependent characteristic of the pellet strength was also reflected in the reduction in strength as compaction speed was increased. The strength of the pellets decreased significantly after 1 day (24 h) of storage, with a higher decrease observed when the pellets were stored under a higher humidity condition. These changes during storage could create difficulties during handling and transportation and may affect gasification performance.     

On the monitoring of trended and regularly adjusted processes

Trended and regularly adjusted processes are common in manufacturing industries. Such processes are, for example, related to tool wear, material replenishment or some regular maintenance. When the process has a slow trend or is frequently adjusted, the Shewhart chart can be interpreted in the same way as for a stable process. To facilitate comparison between such a trended and adjusted process to a stable case, and to estimate further the loss of effectiveness when the traditional Shewhart chart is applied to trended and adjusted process, this paper provides a statistical interpretation of traditional Shewhart charts for this type of processes. Formulas are derived for the calculation of alarm rate and average run length (ARL). This study is useful when deciding if a traditional Shewhart chart is sufficient or if a more advanced Statistical Process Control method is necessary. Furthermore, given the in-control and out-of-control ARL, a combined decision with regard to the control limits setting and the adjustment interval can be made. The general formulation is described and a simple linear trend model with an actual data set is used as an illustration.     

Use of Raman microscopy and band-target entropy minimization technique to differentiate physical mixture from chemical mixture in mixed metal oxides

Raman microscopy has been applied to characterize physical and chemical mixtures of mixed metal oxides. The obtained Raman mapping data were first subjected to singular value decomposition to obtain the right singular vectors, and the right singular vectors were then subjected to band-target entropy minimization (BTEM) to recover the pure component spectra of the observed species present in the sample. Subsequently, these resolved pure component spectral information was used to differentiate the physical and chemical mixtures. In addition, BTEM is also able to recover the pure component spectra of both unstable compound and its degradation product due to laser irradiation. In current study, the physical mixture of Mn₂O₃ and Co₃O₄, and the chemical mixture of CoMn₂O₄ spinel oxide were investigated.     

The mechanical properties of model-compacted tablets

In this study, the compressive strength of tablets made with salt, starch and fat was investigated. The strength was found to increase with compaction pressure, up to a maximum value where further increase in the compaction pressure led to no increase in the strength. The maximum strength corresponded to the point where zero porosity was obtained during the compaction process. However, because of the elastic rebound of the tablets after ejection, the maximum strength corresponded to non-zero final tablet porosities which varied between the materials. For this reason, the use of the density occurring during the compaction process appeared to provide a more reliable comparison between the materials. A simple linear mixing rule did not hold in characterising the strength in the salt:starch:fat systems. However, two regimes were observed depending on the salt volume fraction. At low salt volume fractions, the effect of the salt was negligible. After a certain critical salt volume fraction, increasing the salt led to an increase in the strength. Finite element simulations based on X-ray microtomography images of the tablets suggested that in the first regime, the stresses due to the salt particles were localised but in the second regime, stress-bearing networks were formed between the salt particles.

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Rational mutagenesis of cyclodextrin glucanotransferase at the calcium binding regions for enhancement of thermostability

Studies related to the engineering of calcium binding sites of CGTase are limited. The calcium binding regions that are known for thermostability function were subjected to site-directed mutagenesis in this study. The starting gene-protein is a variant of CGTase Bacillus sp. G1, reported earlier and denoted as "parent CGTase" herein. Four CGTase variants (S182G, S182E, N132R and N28R) were constructed. The two variants with a mutation at residue 182, located adjacent to the Ca-I site and the active site cleft, possessed an enhanced thermostability characteristic. The activity half-life of variant S182G at 60 °C was increased to 94 min, while the parent CGTase was only 22 min. This improvement may be attributed to the formation of a shorter α-helix and the alleviation of unfavorable steric strains by glycine at the corresponding region. For the variant S182E, an extra ionic interaction at the A/B domain interface increased the half-life to 31 min, yet it reduced CGTase activity. The introduction of an ionic interaction at the Ca-I site via the mutation N132R disrupted CGTase catalytic activity. Conversely, the variant N28R, which has an additional ionic interaction at the Ca-II site, displayed increased cyclization activity. However, thermostability was not affected.