Modeling the effective elastic properties of nanocomposites with circular straight CNT fibers reinforced in the epoxy matrix

In the present study, the consistent effective elastic properties of straight, circular carbon nanotube epoxy composites are derived using the micromechanics theory. The CNT composites are known to provide high stiffness and elastic properties when the shape of the fibers is cylindrical and straight. Accordingly, in the present work, the effective elastic moduli of composite are newly obtained for straight, circular CNTs aligned in the specified direction as well as distributed randomly in the matrix. In this direction, novel analytical expressions are proposed for four cases of fiber property. First, aligned, and straight CNTs are considered with transverse isotropy in fiber coordinates, and the composite properties are also transversely isotropic in global coordinates. The short comings in the earlier developments are effectively addressed by deriving the consistent form of the strain tensor and the stiffness tensor of the CNT nanocomposite. Subsequently, effective relations for composites reinforced with aligned, straight CNTs but fibers isotropic in local coordinates are newly developed under hydrostatic loading. The effect of the unsymmetric Eshelby tensor for cylindrical fibers on the overall properties of the nanocomposite is included by deriving the strain concentration tensors. Next, the random distribution of CNT fibers in the matrix is studied with fibers being transversely isotropic as well as isotropic when CNT nanocomposites are subjected to uniform loading. The corresponding relations for the effective elastic properties are newly derived. The modeling technique is validated with results reported, and the variations in the effective properties for different CNT volume fractions are presented.     

Effect of pH on the detailed chemical nature and metal-carbonate species in as synthesized zirconia alumina composites

Zirconia was deposition precipitated on γ-alumina in pH range 7-10 from zirconium oxy-nitrate and soda ash. Zirconium formed its hydroxycarbonate as deduced from ICP-EOS, CHN, and TGA-MS. Higher pH favored formation of carbonate species of zirconium over its hydroxide. TGA-MS indicated formation of three different types of carbonate species. FTIR results corroborated this. Monodentate metal carbonate was observed irrespective of pH of preparation. In addition, bridged bidentate species formed at pH ≤ 8 which changed to chelating bidentate at pH > 8. XRD indicated that all the samples formed tetragonal-zirconia upon calcination irrespective of pH of preparation. Higher pH resulted in smaller crystallites of t-ZrO₂. Changes in chemical moiety with pH reflected on acidity and the deactivation rate for 2-methyl-3-butyn-2-ol which decreased by two orders of magnitude in samples prepared at higher pH. Surface area and pore volume benefited from deposition precipitation. SEM-EDAX showed reasonable distribution of zirconia over γ-Al₂O₃.     

ICT4D research: a call for a strong critical approach

ABSTRACT

ICT for development ( ICT4D) research seeks to examine the social and economic changes in developing countries brought about by the deployment and use of ICT. This intent of ICT4D research parallels that of the critical research paradigm in IS, since both focus on transformation and change. The overall goals of this paper are to( 1)understand the extent of critical research in ICT4Dand ( 2)propose an approach, the“strong critical” approach, to conduct critical research in ICT4D. The proposed approach is based on the writings of two social theorists, Arturo Escobar and Gayatri Spivak, and consists of four concepts– the nature of the post-colonial state, provenience or local history of the ICT phenomena, the influence of the Washington Consensusand the issues of representation and subjectivity of subaltern subjects. A review of ICT4D papers showed that only about 20% follow the critical research approach. In-depth reviews ofeight papers that follow the critical approach showed that the“strong critical” lens can enable a deeper and richer analysis. The main contribution of this paper is in addressing a gap in the ICT4D literature about theorizing in the context of developing countries. The paper also reveals, through in-depth reviews, the value of the strong critical approach.     

Formulation development and in vitro evaluation of gentamicin sulfate-loaded PLGA nanoparticles based film for the treatment of surgical site infection by Box–Behnken design

Objective: Gentamicin sulfate (GS)–loaded poly lactic-co-glycolic acid (PLGA) polymeric nanoparticles (PNPs) were developed and incorporated in film for the treatment of surgical site infection (SSI).

Method: PNPs were prepared by double emulsification solvent removal technique using ethyl acetate solution containing PLGA and polyvinyl alcohol (PVA) as an emulsifier. The emulsion was re-emulsified using Gum Kondagogu (GKK). PNPs loaded film was prepared with 5% w/v solution of pullulan in PNPs using solvent casting technique. Design of Experiment (DoE) study using Box–Behnken design was performed for the optimization of PNPs. Drug release study was carried out for PNPs at phosphate buffer saline (PBS) pH 6.4 and simulated wound fluid (SWF) pH 7.4.

Result: PNPs were found to have average particle size 280?±?12.04?nm, polydispersity index (PDI) 0.15?±?0.01 and zeta potential – 4.9?±?0.84?mV. Scanning electron microscopy (SEM) showed spherical nature of PNPs along with particle size of 160?±?35.30?nm confirmed with transmission electron microscopy (TEM). PNPs were found to be effective against Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). Optimized batch of film showed in vitro disintegration time below 8?min with tensile strength (TS) 0.06?±?0.03 N/cm² and percentage elongation (% E) 70.95?±?4.29. X-ray diffraction study (XRD) confirmed amorphous nature of GS, PLGA, pullulan, GKK and film.

Conclusion: PNPs showed controlled release of GS after an initial burst release. Developed film can be an effective approach for management of SSI and control of antibiotic induced drug resistance.     

Antimicrobial resistance of Salmonella isolated from food animals: A review

Salmonella enterica is recognized as one of the most common causes of bacterial foodborne illness worldwide. The majority of Salmonella infections are attributed to consumption of contaminated food of animal origin such as eggs, chicken, pork, etc. Severe Salmonella infections often require antimicrobial therapy to aid in the elimination of the infection. A potential problem that has been developing for many decades is the development of antimicrobial resistance. There has been an increasing concern over the past 30 years regarding the worldwide emergence of multidrug-resistant phenotypes among Salmonella serotypes such as S. Typhimurium, S. Enteritidis and S. Newport. A special concern is the emergence of resistance to quinolones, fluoroquinolones or extended-spectrum cephalosporins such as ceftiofur and ceftriaxone. Recently, the occurrence of Salmonella isolates resistant to these antibiotics has increased. Therefore, continuous monitoring of its prevalence and resistance in the food supply is necessary because of the public health implications of a potential spread of resistant microorganisms. Furthermore, a holistic animal management approach such as stringent control of antimicrobial agents in the livestock industry, early clinical and microbiological diagnosis, appropriate treatment, and implementation of strict sanitary standards in the food industry are also needed to significantly reduce the overall burden of salmonellosis on human health.     

Error probability bounds for nuclear detection: Improving accuracy through controlled mobility

A collection of static and mobile radiation sensors is tasked with deciding, within a fixed time interval, whether a moving target carries radioactive material. Formally, this is a problem of detecting weak time-inhomogeneous Poisson signals (target radiation) concealed in another Poisson signal (naturally occurring background radiation). Each sensor locally processes its observations to form a likelihood ratio, which is transmitted once—at the end of the decision interval—to a fusion center. The latter combines the transmitted information to optimally (in the Neyman–Pearson sense) decide whether the measurements contain a radiation signal, or just noise. We provide a set of analytically derived upper bounds for the probabilities of false alarm and missed detection, which are used to design threshold tests without the need for computationally intensive Monte Carlo simulations. These analytical bounds couple the physical quantities of interest to facilitate planning the motion of the mobile sensors for minimizing the probability of missed detection. The network reconfigures itself in response to the target motion, to allow more accurate collective decisions within the given time interval. The approach is illustrated in numerical simulations, and its effectiveness demonstrated in experiments that emulate the statistics of nuclear emissions using a pulsed laser.     

Effect of roasting parameters on soy‐butter product quality

Effect of roasting temperature and time on the hardness, moisture content and colour of whole‐kernel of soybean was studied using response surface method (RSM). Colour of reference soy‐butter (RSB) was used to indicate the time and temperature suitable for roasting soybean kernels to prepare soy‐butter (SB). Temperature (160 °C) and time (90 min) for roasting were identified, soybean kernels were roasted, subsequently made into SB and compared with RSB on the basis of nutrient content, particle size, colour and rheology. SB contained 45 g% protein and 34 g% fat on dry matter basis. There was a significant difference (P < 0.05) between RSB and SB on the basis of L* values, D_3,2 and D_4,3. Rheology showed that SB samples behaved like a viscoelastic material. The mean apparent viscosity was significantly different (P < 0.0001) between SB (7.18 Pa.s) and RSB (4.72 Pa.s) which may be due to the significant difference in the particle size distribution (PSD). The Herschel‐Bulkley model could successfully explain the rheological behaviour of SB.     

ImAge: an extensible agent-based architecture for image retrieval

We present an open and extensible architecture, ImAge, for content-based image retrieval in a distributed environment. The architecture proposes the use of system components with standard public interfaces for implementing retrieval functionality. The standardization of the components and their encapsulation in autonomous software agents result in functional stratification and easy extensibility. Collaboration of the independent retrieval resources in ImAge results in enhanced system capability. Reuse of existing retrieval resources is achieved by encapsulating them in agents with standard interfaces. The addition of independent agents with domain knowledege adds the capability of processing conceptual queries, while reusing the existing system components for feature-based retrieval. A communication protocol allows the declaration of the capabilities of the system components and negotiations for optimal resource selection for solving a retrieval problem. The use of mobile agents alleviates network bottlenecks. This paper describes a prototype implementation that validates the architecture.