Single crystalline nickel nanorods inside carbon nanotubes: growth behavior, structure, and magnetic properties

Nickel nanorods with diameters ranging from 5 to 10 nm, encapsulated inside the carbon nanotubes, are prepared using microwave plasma chemical vapor deposition. High-resolution transmission electron microscopy (HRTEM) studies reveal the perfect crystalline nature of the rods with d-spacing closely matching the (111) interplanar spacing of Ni. The (111) planes of the Ni nanorods are always aligned at 39.6 degrees with respect to the graphite planes of the nanotubes. The cosine component of the d-spacing along the direction of the graphite planes is found to be 1.6 A; exactly half the d-spacing between the graphite planes. The electron diffraction pattern shows clear spots corresponding to Ni structure. The field cooled and zero field cooled magnetization data reveal the reversibility of the magnetization of the Ni nanorods and show a blocking temperature of 195 K, which correspond to energy barrier of 0.4 eV/(V).     

Reliability Analysis for Multistate Systems with Multistate Components

An important problem in reliability theory is to determine the reliability of a complex system given the reliabilities of its components. In real life, the system and its components can be found in a range of states varying from perfect functioning through various levels of performance degradation to complete failure. This paper presents some models and their applications, in terms of reliability analyses, to situations where the system can have a whole range of states and all its components can also have a wide range of multiple states. Properties of the system structure function and computation and approximation of system state probabilities and system reliability measures are given.     

The crushing and layering mechanism of granule growth

Equations for the kinetics of granulation by the crushing and layering elementary mechanism of granule growth have been derived. Expressions for granule-size spectra as a function of granulation time are presented. It is shown that the size distribution eventually becomes “self-preserving” in terms of an appropriate dimensionless granule size. The theoretical results are in reasonable agreement with the published experimental data.     

Nanostructured Bulk Silicon as an Effective Thermoelectric Material

Thermoelectric power sources have consistently demonstrated their extraordinary reliability and longevity for deep space missions and small unattended terrestrial systems. However, more efficient bulk materials and practical devices are required to improve existing technology and expand into large‐scale waste heat recovery applications. Research has long focused on complex compounds that best combine the electrical properties of degenerate semiconductors with the low thermal conductivity of glassy materials. Recently it has been found that nanostructuring is an effective method to decouple electrical and thermal transport parameters. Dramatic reductions in the lattice thermal conductivity are achieved by nanostructuring bulk silicon with limited degradation in its electron mobility, leading to an unprecedented increase by a factor of 3.5 in its performance over that of the parent single‐crystal material. This makes nanostructured bulk (nano‐bulk) Si an effective high temperature thermoelectric material that performs at about 70% the level of state‐of‐the‐art Si_0.8Ge_0.2 but without the need for expensive and rare Ge.     

Modeling of the fracture mechanism of HDPE subjected to environmental stress crack resistance test

Environmental stress crack resistance (ESCR) is a commonly used test to characterize cracking failure of high‐density polyethylene in applications such as wires, cables, blow molded containers, and other rigid packaging applications. From a resin design standpoint, it is important to understand the mechanism of environmental stress cracking especially in the case of materials with significantly different ESCR values. Currently, two standard ESCR tests, ASTM D1693 and ASTM F2136, are commonly accepted to measure environmental stress crack resistance of HDPE. An accurate observation of ESC is important to understand the fracture mechanism of samples. In this study, the ESCR performance of six HDPE samples was determined per ASTM D1693. The failed specimens were further characterized by scanning electron microscopy and fractographic methodology to investigate the failure mechanism. HDPE resins with low ESCR values had crack surfaces characterized by shorter and fewer fibrils. A new empirical model to predict polymer ESCR using tie chain concentration with different integration range, and water vapor transmission rate, to characterize detergent diffusion in the crack, was developed. The proposed empirical parameter improves the prediction of ESCR. The ability to predict ESCR performance from resin properties is a beneficial tool for new product development. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Comprehensive studies on polyethylenimine filled polypropylene and its potential application in carbon dioxide sequestration

Polypropylene (PP) was blended with branched polyethylenimine (PEI) with the aim to prepare blends having CO₂ adsorption property. The CO₂ adsorption properties will be conferred due to the presence of variety of amine functionality in PEI. PEI contains primary, secondary as well as tertiary amine groups. Before testing CO₂ adsorption, PP–PEI blends were characterized using variety of techniques, for example, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, scanning electron microscopy, and polarized light optical microscopy. In this work, we have studied in detail both compatibilized as well as noncompatibilized blends of PP and PEI. The compatibilization was achieved via addition of maleic anhydride grafted PP. Finally, all the compatibilized as well as noncompatibilized blends were studied for CO₂ adsorption. The compatibilized blends showed better thermal, mechanical as well as CO₂ adsorption properties as compared to the noncompatibilized blends. POLYM. ENG. SCI., 59:2092–2102, 2019. © 2019 Society of Plastics Engineers     

Isolation and characterization of components responsible for neuroprotective effects of Allium cepa outer scale extract against ischemia reperfusion induced cerebral injury in mice

The antioxidant-mediated neuroprotective effect of Allium cepa outer scale extract (ACE) in mice with cerebral ischemia-reperfusion (I-R) injury was demonstrated in our earlier work. The current investigation aimed at establishing the bioactive component(s) responsible for this activity. Thus ACE was fractionated into ethyl acetate (EF) and aqueous (AF) fractions. These fractions were evaluated against cerebral I-R injury in mice. I-R injury in mice was induced by bilateral common carotid artery occlusion followed by 24 hr reperfusion. Memory, sensorimotor functions, cerebral infarct size, and oxidative stress were measured to address the neuroprotective mechanism of test substances. EF showed marked improvement of memory and sensorimotor functions by reducing brain oxidative stress and infarct size in mice after I-R injury. The bioactive EF was subjected to chromatographic (HPLC-PDA, HPLC-MS, preparative HPLC) and spectroscopic studies to isolate and identify the neuroprotective compounds. This lead to separation of three components, namely quercetin, quercetin 4′-O-glucoside, and the remaining fraction, from EF. The separated components were biologically evaluated. These components showed improvement in mice with I-R injury. But, EF displayed more marked neuroprotective effects as compared to the isolated components. The distinct neuroprotective outcome of EF may be credited to the synergistic action of compounds present in EF. Further studies such as evaluation of neurotoxic effects and other possible neuroprotective mechanisms are required to develop EF as a neuroprotective drug.