The mitigation of signal integrity issues in coupled MWCNT bundles and a comparison with Cu interconnects

Journal of Computational Electronics - In the nanoscale regime, carbon nanotubes (CNTs) are being considered as a future alternative interconnect material for traditional copper (Cu) wires in...     

Identification of factors that lead to perceived learning improvements for female students

Past research has shown that females have more negative attitudes toward engineering and technology than do males. These negative attitudes may explain the decreasing number of females choosing technical careers. Past studies have shown that a change in learning environments and the methods by which learning takes place might foster a change in this situation. A multimedia case study incorporating a real-world engineering and technical problem faced by a power plant was developed in order to provide a new learning environment for engineering and business students. This research investigates whether the use of this material by female and male students led to differences in perceived higher level cognitive skills and, if so, seeks to identify the factors that cause the difference. The results suggest that when designing new learning environments, it is important for the female students to be challenged and have opportunities both to learn by themselves and to learn from others. These results have implications for teaching programs, such as the provision of opportunities for group learning, especially for female students.     

Role of charge and hydrophobicity in translocation of cell-penetrating peptides into Candida albicans cells

Although the interactions of cell-penetrating peptides (CPPs) with mammalian cells have been widely studied, much less is known about their interactions with fungal cells. To study how the properties of CPPs affect translocation into fungal cells, we designed variants of the peptides pVEC and SynB with altered levels of charge and hydrophobicity and evaluated the translocation of the variants into the important human fungal pathogen Candida albicans. Charge played a greater role in translocation efficacy of the peptides than hydrophobicity, with a higher net positive charge leading to higher level of translocation into C. albicans and a higher level of cytosolic localization. Hydrophobicity had little effect on translocation efficacy, but a low level of hydrophobicity did lead to increased vacuolar localization and an energy-dependent translocation mechanism. Our results suggest that CPPs can be designed for desired levels of cargo delivery into fungal cells and for desired translocation mechanisms.     

An infrared spectroscopy study of lipid adsorption from hexane onto an acid-activated bleaching clay

The mode of adsorption of oleic acid (OA) (0.05 M), triglyceride (TG) (0.05 M) and phosphatidylcholine (PC) (0.5 mM) from hexane solution onto 0.5 g of an acid-activated bleaching clay was investigated using diffuse reflectance Fourier transform infrared spectroscopy. OA was mostly weakly adsorbed by bound water, with some OA adsorbed to silanol sites through carboxyl carbonyl groups. TG was hydrogen- bonded to surface silanol groups through ester carbonyl groups. The CH₂ stretches indicated that TG was oriented perpendicular or at an angle to the surface. PC phosphate groups were bound by the surface moisture with little interaction with silanol groups. The adsorption mechanism of these lipids contrasts with the adsorption of carotenoid and chlorophyll under the same conditions. These pigments are bound by chemisorption, with catalytic modification often occurring before adsorption.     

Lipid adsorption on commercial silica hydrogels from hexane and changes in triglyceride complexes with time

The structures of and lipid complexes with two commercial silica hydrogels (Trisyl and Sorbsil 40), which contain about 60% moisture, were examined by diffuse reflectance Fourier transform infrared spectroscopy. The spectra suggested that Trisyl contained less moisture than Sorbsil 40. However, the silanol groups of Sorbsil 40 were more active in adsorbing oleic acid, triglyceride, and phosphatidylcholine (PC) from hexane than those of Trisyl. Both adsorbents strongly bound PC through the PC carbonyl and phosphate groups. Lipid adsorption from hexane solution by Trisyl depended solely on trapped moisture, while Sorbsil 40 used moisture and silanol groups on the silica surface. Spectra of triglyceride-silica hydrogel complexes, obtained 24 and 72 h after obtaining the initial spectra, showed that Sorbsil 40 adsorption was by Van der Waals forces, but the triglyceride reoriented over time with an increase in hydrogen bonding. In contrast, Trisyl initially adosorbed triglyceride by hydrogen bonding which was stable for at least 72 h.     

Dielectric relaxation of conductive carbon black reinforced ethylene‐octene copolymer vulcanizates

The dielectric relaxation behavior of different conducting carbon black‐filled ethylene‐octene copolymer (EOC) vulcanizates prepared by melt‐mixing method has been studied as a function of frequency (100 Hz–5 MHz) over a wide range of temperatures (25–100°C). The effect of filler loading and frequency on AC conductivity, dielectric permittivity, impedance, and dielectric loss tangent (tanδ) has been studied. The nature of variation of the dielectric permittivity with the filler loadings was explained on the basis of interfacial polarization of the filler in the polymer matrix. The effect of filler loading on the real and complex part of the impedance was explained by the relaxation dynamics of the polymer chains in the vicinity of the fillers. The effect of filler and temperature on dielectric loss tangent, dielectric permittivity, AC conductivity, and Nyquist plot was also reported. The bound rubber (BR) value increases with increase in filler loading suggesting the formation of strong interphase, which is correlated with dielectric loss. Thermal activation energy (E_a) was found to be decreasing with the temperature, which follows the Arrhenius relation: τ_b = τ₀ exp(−E_a/K_BT) where τ_b is the relaxation time for the bulk material. From the plot of lnτ_b versus inverse of absolute temperature (1/T), the activation energies (E_a) were found to be 0.37 and 0.44eV, respectively. The percolation threshold was observed with 40 phr carbon black loading. POLYM. COMPOS., 37:342–352, 2016. © 2014 Society of Plastics Engineers     

Insulating and Other Physical Properties of CoO‐Doped Zinc Oxyfluoride‐Borate Glass‐Ceramics

Zinc oxy fluoro borate glasses mixed with different concentrations of CoO (ranging from 0 to 2.0 mol%) are synthesized and subsequently crystallized. The scanning electron microscopy pictures have exhibited crystallinity. Differential scanning calorimetric studies have indicated that the prepared samples consist of multiple crystal phases. The X‐ray diffraction patterns have indicated that the glass‐ceramic samples are composed of αZn(BO₂)_2, (Zn)₃(BO₃)_2, CoF₂, CoF₃, Co₃FB₇O₁₃, ZnCo₂O₄, Co₃O₄ crystalline phases. The optical absorption and photoluminescence studies have indicated that there is a gradual increase of tetrahedral cobalt ion concentration with increase of CoO concentration in the glass network. IR spectroscopic studies have pointed out increased degree of polymerization of the zinc oxy fluoro borate glass network with increase of CoO content. The analysis of results of dielectric properties indicated increase of insulating strength of the glass‐ceramics with increase of CoO content. Finally, the dielectric breakdown strength of the samples is measured at room temperature in air medium and it is found to increase from 12.9 to 19.2 kV/cm with increase of CoO from 0.2 to 2.0 mol%. The reasons for such increase of breakdown strength are discussed quantitatively in terms of dielectric parameters with aid of data on spectroscopic properties.     

Morphology and micromechanical behavior of binary blends comprising block copolymers having different architectures

Morphology and deformation behavior of binary blends comprising styrene/butadiene block copolymers (polystyrene content, Φ_PS∼0.70) having different molecular architectures were studied by means of transmission electron microscopy and tensile testing. In contrast to the binary diblock copolymer blends discussed in literature, the phase separation behavior of the blends investigated was found to be strongly affected by asymmetric molecular architecture. The blends showed macrophase separated grains, in which the structures resembled the microphase morphology of none of the blend components. Unlike the classical rubber-modified or particle-filled thermoplastics, neither debonding at the particle/matrix interface nor the particle cavitation was observed in these nanostructured blends. The microdeformation of the blends revealed plastic drawing of polystyrene lamellae or PS struts dispersed in rubbery matrix and orientation of the whole deformation structures along the strain direction.     

Effectiveness of sodium silicate as gangue depressants in iron ore slimes flotation

The recovery of iron from the screw classifier overflow slimes by direct flotation was studied.The relative effectiveness of sodium silicates with different silica-to-soda mole ratios as depressants for silica and silicate bearing minerals was investigated.Silica-to-soda mole ratio and silicate dosage were found to have significant effect on the separation efficiency.The results show that an increase of Fe content in the concentrate is observed with concomitant reduction in SiO2 and Al2O3 levels when a particular type of sodium silicate at a proper dosage is used.The concentrate of 58.89wt％ Fe,4.68wt％ SiO2,and 5.28wt％ Al2O3 with the weight recovery of 38.74％ and the metal recovery of 41.13％ can be obtained from the iron ore slimes with 54.44wt％ Fe,6.72wt％ SiO2,and 6.80wt％ Al2O3,when Na2SiO3 with a silica-to-soda mole ratio of 2.19 is used as a depressant at a feed rate of 0.2 kg/t.     

Effect of Prefault Load on Field Overvoltages in Rectifier-Excited Synchrondus Machine During Sequential 3-Phase Fault

ABSTRACT

In a Synchronous machine with rectifier excitation, large reverse voltages may be induced across the field during a transient condition when the field current tends to flow in the reverse direction and is blocked by rectifiers. Earlier investigation on an initially unloaded machine showed that a sequential 3-phase fault, in which a line to line fault develops into a 3-phase fault after a short time, produces field overvoltages whose magnitudes may be comparable to those due to line to line fault. In this paper, analysis has been carried out to estimate the magnitude of the field overvoltage during a sequential 3-phase fault when the machine is assumed to operate on a prefault load. Numerical results show that a sequential 3-phase fault on a machine having prefault loads may be much more severe compared to a line to line fault from the field overvoltage point of view. The results also indicate that very large field overvoltages may be produced during a sequential 3-phase fault on a salient pole machine operating initially on leading power factor loads.