Evaluation of Chenopodium ambrosioides oil as a potential source of antifungal, antiaflatoxigenic and antioxidant activity

Essential oil extracted from the leaves of Chenopodium ambrosioides Linn. (Chenopodiaceae) was tested against the aflatoxigenic strain of test fungus Aspergillus flavus Link. The oil completely inhibited the mycelial growth at 100 microg/ml. The oil exhibited broad fungitoxic spectrum against Aspergillus niger, Aspergillus fumigatus, Botryodiplodia theobromae, Fusarium oxysporum, Sclerotium rolfsii, Macrophomina phaseolina, Cladosporium cladosporioides, Helminthosporium oryzae and Pythium debaryanum at 100 microg/ml. The oil showed significant efficacy in inhibiting the aflatoxin B1 production by the aflatoxigenic strain of A. flavus. During in vivo investigation it protected stored wheat from different storage fungi for one year. Chenopodium oil also exhibited potent antioxidant activity when tested by ABTS method. All these observations suggest the possible exploitation of the Chenopodium oil as potential botanical fungitoxicant in ecofriendly control of post harvest biodeterioration of food commodities from storage fungi.     

An approximate transient analysis of the M(t)/M/1 queue

An approach, based on recent work by Stern [56], is described for obtaining the approximate transient behavior of both the M/M/1 and M(t)/M/1 queues, where the notation M(t) indicates an exponential arrival process with time-varying parameter λ(t). The basic technique employs an M/M/1K approximation to the M/M/1 queue to obtain a spectral representation of the time-dependent behavior for which the eigen values and eigenvectors are real.Following a general survey of transient analysis which has already been accomplished, Stern's M/M/1/K approximation technique is examined to determine how best to select a value for K which will yield both accurate and computationally efficient results. It is then shown how the approximation technique can be extended to analyze the M(t)/M/1 queue where we assume that the M(t) arrival process can be approximated by a discretely time-varying Poisson process.An approximate expression for the departure process of the M/M/1 queue is also proposed which implies that, for an M(t)/M/1 queue whose arrival process is discretely time-varying, the departure process can be approximated as discretely time-varying too (albeit with a different time-varying parameter).In all cases, the techniques and approximations are examined by comparison with exact analytic results, simulation or alternative discrete-time approaches.     

Dielectric,transport and thermal properties of clay based polymer‐ nanocomposites

The polymer nanocomposite films (PNC) with varying amounts of organically modified sodium montmorillonite (DMMT) clay in poly(methyl methacrylate) (PMMA) based polymer matrix were prepared by solution cast technique. Dielectric measurements were carried out on these films as a function of frequency at 30°C and 100°C. The addition of clay significantly improved the ionic conductivity. Transport parameters, such as the diffusion coefficient (D), number density (n) and mobility (μ) of charge carriers were determined using a new approach, which is based on impedance spectroscopy. The temperature‐dependent dc conductivity, relaxation and mobility plots obey the Arrhenius rule. The results suggest that the higher ionic conductivity of these PNC films at elevated temperature is not only due to increased mobility of ions, but it is accompanied by a significant increase in carrier concentration. Analysis of DSC thermogram reveals a very high percentage of amorphous content for all samples. A good correlation among dielectric permittivity, carrier concentration, mobility and ionic conductivity has also been observed. POLYM. ENG. SCI., 58:220–227, 2018. © 2017 Society of Plastics Engineers     

Influence of microcapsule shell material on the mechanical behavior of epoxy composites for self‐healing applications

In this article, we have studied the effect of microcapsule shell material on the mechanical behavior of self‐healing epoxy composites. Liquid epoxy healant was encapsulated in melamine‐formaldehyde (MF) and urea‐formaldehyde (UF), using emulsion polymerization technique to prepare microcapsules of different shell walls. The core content of the microcapsules, as determined by solvent extraction technique was found to be 65 ± 4%, irrespective of the shell wall of microcapsule. Morphological investigations reveal a rough texture of the spherical microcapsules, which was attributed to the presence of protruding polymer nanoparticles on the surface. Epoxy composites containing UF and MF microcapsules (3–15% w/w) were prepared by room temperature curing and their mechanical behaviour was studied under both quasi‐static and dynamic loadings. The tensile strength, modulus, and impact resistance of the matrix was found to decrease with increasing amount of microcapsule in the formulation, irrespective of the shell wall material used for encapsulation. Interestingly, substantial improvement in the fracture toughness of the base resin was observed. Morphological investigations on the cracked surface revealed features like crack pinning, crack bowing, microcracking and crack path deflection, which were used to explain the toughened nature of microcapsule containing epoxy composites. Our studies clearly indicate that the microcapsule shell wall material does not play any significant role in defining the mechanical properties of the composites. In addition, presence of secondary amine functionalities in UF and MF shell wall do not interfere with the reaction of epoxy with triethylene tetramine hardener during the curing process. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40572.     

Purification/annealing of graphene with 100-MeV Ag ion irradiation

Studies on interaction of graphene with radiation are important because of nanolithographic processes in graphene-based electronic devices and for space applications. Since the electronic properties of graphene are highly sensitive to the defects and number of layers in graphene sample, it is desirable to develop tools to engineer these two parameters. We report swift heavy ion (SHI) irradiation-induced annealing and purification effects in graphene films, similar to that observed in our studies on fullerenes and carbon nanotubes (CNTs). Raman studies after irradiation with 100-MeV Ag ions (fluences from 3 × 10¹⁰ to 1 × 10¹⁴ ions/cm²) show that the disorder parameter α, defined by I_D/I_G ratio, decreases at lower fluences but increases at higher fluences beyond 1 × 10¹² ions/cm². This indicates that SHI induces annealing effects at lower fluences. We also observe that the number of graphene layers is reduced at fluences higher than 1 × 10¹³ ions/cm². Using inelastic thermal spike model calculations, we estimate a radius of 2.6 nm for ion track core surrounded by a halo extending up to 11.6 nm. The transient temperature above the melting point in the track core results in damage, whereas lower temperature in the track halo is responsible for annealing. The results suggest that SHI irradiation fluence may be used as one of the tools for defect annealing and manipulation of the number of graphene layers.

PACS

60.80.x; 81.05.ue     

Injection‐molded high‐density polyethylene–hydroxyapatite–aluminum oxide hybrid composites for hard‐tissue replacement: Mechanical,biological, and protein adsorption behavior

In this article, we report the mechanical and biocompatibility properties of injection‐molded high‐density polyethylene (HDPE) composites reinforced with 40 wt % ceramic filler [hydroxyapatite (HA) and/or Al₂O₃] and 2 wt % titanate as a coupling agent. The mechanical property measurements revealed that a combination of a maximum tensile strength of 18.7 MPa and a maximum tensile modulus of about 855 MPa could be achieved with the injection‐molded HDPE–20 wt % HA–20 wt % Al₂O₃ composites. For the same composite composition, the maximum compression strength was determined to be 71.6 MPa and the compression modulus was about 660 MPa. The fractrography study revealed the uniform distribution of ceramic fillers in the semicrystalline HDPE matrix. The cytocompatibility study with osteoblast‐like SaOS2 cells confirmed extensive cell adhesion and proliferation on the injection‐molded HDPE–20 wt % HA–20 wt % Al₂O₃ composites. The cell viability analysis with the 3(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay revealed a statistically significant difference between the injection‐molded HDPE–20 wt % HA–20 wt % Al₂O₃ composites and sintered HA for various culture durations of upto 7 days. The difference in cytocompatibility properties among the biocomposites is explained in terms of the difference in the protein absorption behavior. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanisms for object caching in distributed applications using Java RMI

Remote Method Invocation (RMI), a mechanism to access remote objects in Java‐based distributed applications, uses network communication for each method invocation. Consequently, using RMI in a wide‐area environment can cause poor application performance. One solution to improve performance is to cache the objects such that network communication is not necessary for each method invocation. In this paper, we present mechanisms to transparently add object caching to RMI. These mechanisms are compatible with existing RMI applications and use an event‐based model to support different consistency policies. The mechanisms also include the ability to adaptively select the consistency policy for an object based on its usage pattern. A novel feature of our mechanisms is the use of a ‘reduced object’, which is a partial representation of the RMI object. We experimentally evaluate and demonstrate the benefits of our mechanisms. Copyright © 2006 John Wiley & Sons, Ltd.     

QMRPRNS: Design of QoS multicast routing protocol using reliable node selection scheme for MANETs

A mobile Ad-Hoc networks (MANETs) is a continuously self-configuring, infrastructure-less network of wireless mobile devices. In which multicast is one of the efficient way of communication. Currently, several research have been conducted to design multicast routing protocols for wireless mobile ad-hoc networks (MANETs). Multicasting is a technique that allow to send the same message to a group of destinations simultaneously. However, it faces several challenges against its implementation in ad-hoc network due to its dynamic nature, lack of bandwidth, short battery lifetime of the mobile devices. The multicast routing protocol MAODV have several constraints as mentioned above. Hence to address these constraints a reliable neighbour nodes selection scheme has been integrated over MAODV. This paper attempt a Quality of Service (QoS) based multicast routing protocol using reliable neighbour nodes selection scheme (QMRPRNS) for same. The simulation has been conducted to compare the performance of the proposed scheme against some existing multicast routing protocols which shows significant improvement over EMAODV and MAODV.     

Improvement in thermomechanical properties of off‐grade natural magnesite by addition of Y2O3

Small amount of Y₂O₃ (0‐3 wt%) was added into off‐grade natural magnesite and its effects on the phase assemblage, microstructural evolution in correlation with mechanical and thermomechanical properties were investigated. Presence of Y₂O₃ facilitated the formation of calcium yttrium silicate and yttrialite phases, which prohibited the formation of detrimental‐phase monticellite, which was gradually reduced with the increase in Y₂O₃ content. Y₂O₃ promoted periclase grain growth and segregated the secondary phases at triple‐point junction of periclase grains. Also, high‐temperature (at 1200°C) flexural strength of the samples increased from 77.2 MPa (without Y₂O₃) to 137.45 MPa with the addition of 2 wt% Y₂O₃. Greater degree of direct bonding among periclase grains, compact microstructure, and uniform grain size distribution in addition to reduced amount of monticellite were responsible for the improvement in mechanical and thermomechanical properties.     

Grinding analysis of Indian coal using response surface methodology

International Journal of Coal Science & Technology - The present work discusses a systematic approach to model grinding parameters of coal in a ball mill. A three level Box–Behnken design...