Time-dependent behavior of adhesively bonded composite–composite beams under flexural loading

Abstract

Time-dependent behavior is characteristic of adhesively bonded structureswhen put under constant load (creep). In this study, adhesively bonded beam specimens prepared by adhesively bonding two unidirectional carbon fiber laminated beams were subjected to accelerated three-point bending creep tests. A three-point bending test was selected because of its simplicity and the fact that bending stresses tend to develop in structures under load even if not subjected to direct flexural load. The aim of this study is to predict the long-term behavior and to investigate the long-term creep response of the adhesively bonded composite system. The long-term creep behavior was predicted by time–temperature superposition principle (TTSP) and construction of the master curve at a reference temperature.     

Fabrication of Bone Scaffolds from Cockle Shell Waste

Bone scaffold is a three‐dimensional structure composed of materials that could enhance bone regeneration. Bone scaffolds were prepared using freeze‐drying by varying the cockle shell powder concentration where sodium alginate acted as matrix. The scaffolds were then characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, texture analyzer, and liquid displacement method. The bioactivity of the scaffolds was evaluated by immersion into a simulated body fluid solution. Cockle shell powder concentrations affected the bone scaffold characteristics. The increment of the powder concentrations improved the physicochemical properties and bioactivity of the scaffolds.     

Plant Regeneration and Somatic Embryogenesis from Immature Embryos Derived through Interspecific Hybridization among Different Carica Species

Plant regeneration and somatic embryogenesis through interspecific hybridization among different Carica species were studied for the development of a papaya ringspot virus-resistant variety. The maximum fruit sets were recorded from the cross of the native variety C. papaya cv. Shahi with the wild species C. cauliflora. The highest hybrid embryos were recorded at 90 days after pollination and the embryos were aborted at 150 days after pollination. The immature hybrid embryos were used for plant regeneration and somatic embryogenesis. The 90-day-old hybrid embryos from the cross of C. papaya cv. Shahi × C. cauliflora showed the highest percentage of germination, as well as plant regeneration on growth regulators free culture medium after 7 days pre-incubation on half-strength MS medium supplemented with 0.2 mg/L BAP, 0.5 mg/L NAA and 60 g/L sucrose. The 90-day-old hybrid embryos from the cross of C. papaya cv. Shahi × C. cauliflora produced maximum callus, as well as somatic embryos when cultured on half-strength MS medium containing 5 mg/L 2,4-D, 100 mg/L glutamine, 100 mg/L casein hydrolysate and 60 g/L sucrose. The somatic embryos were transferred into half-strength MS medium containing 0.5 mg/L BAP and 0.2 mg/L NAA and 60 g/L sucrose for maturation. The highest number of regenerated plants per hybrid embryo (10.33) was recorded from the cross of C. papaya cv. Shahi × C. cauliflora. Isoenzyme and dendrogram cluster analysis using UPGMA of the regenerated F₁ plantlets confirmed the presence of the hybrid plantlets.     

Flexible robust programming in distributed object systems

Distributed applications that access persistent objects must maintain object state consistency even when failures are encountered during the manipulation of such objects. The basic transaction model, which has been implemented by several systems to ensure consistent executions of distributed applications, is not flexible enough to meet the requirements of many complex distributed applications. This has also been recognized for advanced database applications and, as a result, extended transaction models have been developed. We argue that distributed applications that manipulate long-lived data can benefit from such transaction models. We take an approach which views the various transaction models as policies for building robust applications. Thus, we advocate that the system implement several transaction models. A robust application can be programmed in such a system using a combination of several transaction models to meet its consistency requirements. We use applications from the domain of computer-supported cooperative work to motivate such an approach. We also develop a set of system-level mechanisms which can be used to implement multiple transaction models in a uniform manner. These mechanisms are used to implement nested, split, and cooperating transaction models. A prototype system that has been implemented is described to demonstrate the feasibility of this approach.     

Developing the Processing Maps Using the Hyperbolic Sine Constitutive Equation

Hot compression tests were performed on a duplex stainless steel at temperatures ranging from 1223 K to 1473 K (950 °C to 1200 °C) and strain rates from 0.001 to 100 s^?1. The constitutive analysis of flow stress was carried out using the hyperbolic sine function, and the material constants were determined at two typical strains of 0.3 and 0.7. The power dissipation map, instability map, and processing map for the material were developed for strains of 0.3 and 0.7. The developed processing maps were based on the hyperbolic sine as well as the conventional power-law constitutive equations. The efficiency of power dissipation (η) varied from 12 to 60 pct over the studied temperature and strain rate. The highest value of η was obtained at strain rates below 0.01 s^?1, whereas the lowest value of η was observed at the intermediate strain rates. The instability region in sin h-based processing map was only observed in the range of 1423 K to 1473 K (1150 °C to 1200 °C) and at a strain rate of 100 s^?1, while the conventional processing map did not predict any instability region. Optical microscopy observations were more consistent with the results of the sin h-based processing map and indicated that the instability regime at high temperatures and high strain rates was due to the development of adiabatic shear bands.     

Physico-mechanical properties of particleboard made from heat-treated rubberwood particles

Physico-mechanical properties of particleboard fabricated from heat-treated rubberwood particles were investigated. Reduction in water absorption and mass loss were observed in heat-treated rubberwood particles, and it was associated with the properties of particleboard. The density and moisture content of the particleboard decreased with increasing treatment temperature and time. Heat treatment of particles improved the dimensional stability of the particleboard, but the mechanical properties were adversely affected.     

Antioxidant Activity of Ethanol and Lipophilic Extracts of Common Fruity Vegetables in Bangladesh

The amount of phenolics, flavonoids, and anthocyanins in ethanol extracts and antioxidant activity of both ethanol and lipophilic extracts of common fruity vegetables in Bangladesh were studied. Among the ethanol extracts of 15 fruity vegetables, M. oleifera had the highest total polyphenol content (85.05 mg gallic acid equivalent/g extract) followed by L. acutangula (61.74 mg gallic acid equivalent/g extract) and A. esculentus (48.92 mg gallic acid equivalent/g extract). L. acutangula had high a content of flavonoids (14.46 mg (+)-catechin equivalent/g extract), which was almost similar to L. siceraria (13.67 mg catechin equivalent/g extract) followed by A. esculentus (11.95 mg catechin equivalent/g extract) and S. melongena (11.42 mg catechin equivalent/g extract). Highest anthocyanins content was in F. hispida (2.22 μmol/g extract) followed by S. melongena (1.04 μmol/g extract). Ethanol extracts of A. esculentus, F. hispida, L. acutangula, L. siceraria, and S. melongena exhibited high DPPH free radical scavenging activity with IC₅₀ of 70.4, 64.9, 70.4, 64.9, and 94.3 μg/mL respectively, whereas for the same lipophilic extracts of F. hispida and S. melongena showed lowest (37 μg/mL) IC₅₀ followed by M. oleifera (47.6 μg/mL), L. siceraria (57.5 μg/mL), and A. esculentus (63.3 μg/mL). These vegetables also showed high reducing powers, NO scavenging and total antioxidant capacity. Therefore, the top five potential fruity vegetables consist of both hydrophilic and lipophilic antioxidant(s), the order being F. hispida > M. oleifera > A. esculentus, L. acutangula > L. siceraria > and S. melongena.     

Quantitative duplex real-time polymerase chain reaction assay with TaqMan probe detects and quantifies Crocodylus porosus in food chain and traditional medicines

Consumption and exploitation of crocodiles have been rampant for their exotic, nutritive and medicinal attributes. These depredations are alarming and although they have continued to be monitored by wildlife and conservation agencies, unlawful trading of crocodiles shows an increasing trend worldwide. Recently, conventional polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (RFLP) assays for crocodile have been documented but they are only suitable for identification and cannot quantify adulterations. We described here a quantitative duplex real-time PCR assay with probes to quantify contributions from Crocodylus porosus materials simultaneously. A very short amplicon size of 127bp was used because longer targets could have been broken down in samples, bringing considerable uncertainty in molecular analysis. We have validated a TaqMan probe-based duplex real-time PCR (qPCR) assay for the detection of 0.004 ng DNA in pure state and 0.1% target meat in model chicken meatball. False negative detection was eliminated through an endogenous control (141-bp site of eukaryotic 18S rRNA). Analysis of 12 model chicken meatballs adulterated with C. porosus reflected 96.3?120.2% target recovery at 0.1?10% adulterations. A validation test of 21 commercial food and traditional medicine (TM) crocodile-based products showed 100% effectiveness. Short amplicon sizes, alternative complementary target, exceptional stability and superior sensitivity suggested the assay could be used for the identification and quantitative determination of C. porosus in any food or TM samples even under degraded conditions.     

Double gene targeting PCR assay for the detection of Crocodylus porosus in commercial products

The demand for crocodile meat is quickly growing because of its exotic and organoleptic appeal and also the low content of cholesterol and lipids. Moreover, crocodile oil and blood have been used in alternative medicines for treating asthma and several other ailments since ancient times. Furthermore, crocodile hides have great demand in leather industries. All of these have collectively contributed to the extensive hunting, illegal trading and consequent decline of crocodiles in most parts of the world. To keep space with the growing demands, some crocodile species such as Crocodylus porosus have been raised in farms and its commercial trades have been legalised. However, demand for wild crocodiles in foods and medicines has continued in high gear. Recently, several DNA-based methods have been proposed for crocodile detection, but those assays are based on single gene and longer-sized amplicon targets that break down during extensive processing. To address this gap, here we developed and validated a highly stable double gene targeted multiplex PCR assay for the identification of C. porosus materials in commercial products. The assay involved two short sites from C. porosus atp6 (77 bp) and cytb (127 bp) genes and a universal internal control (99 bp) for eukaryotes. The PCR primers were cross-tested against 18 species and validated under pure and mixed matrices under extensive boiling, autoclaving and microwave cooking conditions. Finally, it was used to identify five crocodile-based commercial products. The lower limits of detection for atp6 and cytb genes were 0.001 ng and 0.01 ng DNA, respectively, in pure meat and 1% under mixed matrices. Some inherent features, such as 77–127 bp amplicon sizes, exceptional stability and superior sensitivity, suggested the assay could be used for the identification of C. porosus in any forensic specimen.     

Household food security in the face of climate change in the Hindu-Kush Himalayan region

This study attempts to understand local people’s perceptions of climate change, its impacts on agriculture and household food security, and local adaptation strategies in the Hindu-Kush Himalayan (HKH) region, using data from 8083 households (HHs) from four river sub-basins (SBs), i.e. Upper Indus (Pakistan), Eastern Brahmaputra (India), Koshi (Nepal) and Salween and Mekong (China). The majority of households in SBs, in recent years, have perceived that there have been more frequent incidences of floods, landslides, droughts, livestock diseases and crop pests, and have attributed these to climate change. These changes have led to low agricultural production and income, particularly in Eastern Brahmaputra (EB) where a substantial proportion of HHs reported a decline in the production of almost all staple and cash crops, resulting in very low farm income. Consequently, households’ dependency on external food items supplied from plain areas has increased, particularly in the Upper Indus (UI) and EB. After hazards, households face transitory food insecurity owing to damage to their local food systems and livelihood sources, and constrained food supply from other areas. To cope with these, HHs in SBs make changes in their farming practices and livestock management. In EB, 11 % of HHs took on new off-farm activities within the SB and in SM, 23 % of HHs chose out-migration as an adaptation strategy. Lastly, the study proposes policy instruments for attaining sustainable food security, based on agro-ecological potential and opportunities for increasing agricultural resilience and diversity of livelihoods.