30 research outputs found

    Understanding the physical and biological effects of dust-induced insect death

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    Background Quality and quantity of stored grain is constantly changing due to insect and fungal activity. The efficacy of storage method dictates the quality of grain. Traditional chemical pesticides, though effective, were often criticised for issues like increasing insect resistance, chemical residue, environmental contamination and human health risk. The diatomaceous earth based formulations could reduce chemical pesticides usage at some extent. But the slow insect killing and being non-food grade limited wide application. The high recommended dosage (500 to 3500 ppm) results in several adverse effects on grain, including reduce in the flow ability and bulk density, visible residue, extra dust generation during processing. Synthetic amorphous silica (SAS) consists three types: pyrogenic, precipitated, surface-treated SAS. These dusts can be distinguished from natural amorphous silica such as diatomaceous earth by its high chemical purity, the finely particulate nature and characteristics of particles. All types of SAS have been widely used in topical and oral medicines, food and cosmetics for many decades without evidence of adverse human health risks. Based on extensive physico-chemical, ecotoxicology, human health and epidemiology data, SAS as non-chemical method for pest management is revolutionary and advantageous compared to traditional approaches. However, their insecticidal mechanism is poorly understood. The optimal application protocol is not developed. This study described a comprehensive investigation of insecticidal mechanism of SAS particles and their application as an alternative practical stored grain pest control method. Results The first study was aimed to investigate the efficacy of different synthetic amorphous silica (SAS) powders against different insect species at multiple developmental stages compared with diatomaceous earth (DE). The stationary stages, egg and pupa, were more tolerant than that of the mobile stages, larva and adult, upon SAS and DE exposure. The insect infestation cannot be completely control by all the SAS and DE. A 100% of hatching rate was observed and more than 32% of pupa emerged in all the dust treated groups. Larva stage was most susceptible to the SAS and DE. Newly emerged adults were more susceptible to SASs and DE than older adults. The outcome for larvae was opposite. Among the three insect species adults, when treated by SAS and DE, T. castaneum was the most tolerant species and C. ferrugineus was the most susceptible. The efficacy of SAS against insects was higher than that of DE. Among of SASs, precipitated SAS performed better than pyrogenic SAS in term of mortality. Hydrophobic SAS powders were more effective against T. castaneum adult, while hydrophilic SAS powders were more effective against T. castaneum larvae, pupae and Sitophilus oryzae adults. We evaluated the physical property of aforementioned SAS and DE in relation to efficacy. SAS powders have higher specific surface area, total pore volume, oil sorption capacity and smaller particle size than DE. In term of the SAS powders produced by different methods, pyrogenic SAS powders had higher oil sorption capacity but lower total pore volume and specific surface area, and larger particle size than precipitated SAS. Comparing with hydrophilic SAS, the particle size of hydrophobic SAS was smaller while has lower oil sorption capacity. There was a significant relationship between physical property of powder and insecticidal efficacy in SAS without a specific index. We developed and evaluated a rapid screening protocol to identify electrostatic charge dictates attachment processes during initial contact between SAS and insects. The charge ability of three major stored grain insects, Sitophilus oryzae, Tribolium castaneum and Cryptolestes ferrugineus and four hydrophilic precipitated SAS and one DE was assessed on two insulated surfaces filter paper and glass. After contact with insulation surfaces, synthetic amorphous silica (SAS) and DE carry negative charges due to attaining electrons from insulation surfaces, while stored product insects carry charges of opposite polarity from electron loss. According to Coulomb’s law, the SAS particles would then be passively attracted by insect via the mere effect of electrostatic forces. A linear correlation was observed between electrostatic charge and bioactivity of dust. After exposure to SAS, the changes in water content and other physiological components of insects led to changes in coloration and gross appearance. The heterogeneous distribution made visual comparisons difficult. Hyperspectral imaging systems with optically tuneable filters can record images at hundreds of contiguous wavelengths (narrow spectral resolution) in the form of a hypercube (three-dimensional hyperspectral data). Hyperspectral imaging coupled with back propagation neural network models was employed to quantify differences in parameters which reflected the response of T. castaneum and S. oryzae to hydrophobic and hydrophilic precipitated SAS. The presence of SAS on ventral and dorsal cuticle of two insect species caused differential values of relative reflectance in visible and short-wave near-infrared ranges. The control samples of all groups were correctly classified by BPNN model and misclassification occurred only with the two SAS treated. These results suggested that the differences in absorption characteristics of cuticular fat and protein contributed to the varied performance. The recognition rate between two SAS treated was within the acceptable identification range. This suggested that both SASs have similar effect on insect with varied degree. We investigated how these two hydrophobic and hydrophilic precipitated SASs physically influenced insect in intersegmental membrane and their biological effects. Both SASs rapidly reduced insect locomotion to the limiting value within 3.5 hours and 12 hours for S. oryzae and T. castaneum, respectively. In addition, we found that there was significant differential decrease in straightness and upward length which were used as parameters to evaluate insect behaviours. Environmental scanning electron microscope (ESEM) images and data of stride length directly exhibited SAS eroded insect intersegmental membrane and absorbed the vital body fluid, eventually caused irreversible structural damage. The hydrophilic SAS was more effective in changing these parameters in S. oryzae, while hydrophobic SAS was more effective in T. castaneum. Male population was more susceptible than female. We further evaluated the efficacy of SAS structural treatment combined with a new integrated trap as insect control in the field trial. Insect infestation was monitored by integrated trap utilising insect behaviours. Prior to SAS treatment, five integrated traps captured 1722 g insect inside a warehouse in seven day. Synthetic amorphous silica was aerogelize and dispersed uniformly in different locations of the warehouse. The mortality of five major species of stored grain insect adults reached 100% within three days post exposure. Conclusion SAS powders are food-grade, quick, effective, low cost and easy to apply as an insect control method. They don’t have the disadvantages of traditional chemical pesticide regarding to occupational health, environmental and safety concern. Detecting the electrostatic charge is an effective protocol for SAS efficacy evaluation. As an emerging non-destructive and reagent-less analytical technique, hyperspectral imaging proved to be highly efficient in pesticidal effect evaluation. Intersegmental membrane is a promising target site for new inert dust pesticide products

    Measuring Device for Air Speed in Macroporous Media and Its Application Inside Apple Storage Bins

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    In cold storage facilities of fruit and vegetables, airflow is necessary for heat removal. The design of storage facilities influences the air speed in the surrounding of the product. Therefore, knowledge about airflow next to the product is important to plan the layout of cold stores adapted to the requirements of the products. A new sensing device (ASL, Air speed logger) is developed for omnidirectional measurement of air speed between fruit or vegetables inside storage bins or in bulk. It consists of four interconnected plastic spheres with 80 mm diameter each, adapted to the size of apple fruit. In the free space between the spheres, silicon diodes are fixed for the airflow measurement based on a calorimetric principle. Battery and data logger are mounted inside the spheres. The device is calibrated in a wind tunnel in a measuring range of 0–1.3 m/s. Air speed measurements in fruit bulks on laboratory scale and in an industrial fruit store show air speeds in gaps between fruit with high stability at different airflow levels. Several devices can be placed between stored products for determination of the air speed distribution inside bulks or bin stacks in a storage room

    Chapter 34 - Biocompatibility of nanocellulose: Emerging biomedical applications

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    Nanocellulose already proved to be a highly relevant material for biomedical applications, ensued by its outstanding mechanical properties and, more importantly, its biocompatibility. Nevertheless, despite their previous intensive research, a notable number of emerging applications are still being developed. Interestingly, this drive is not solely based on the nanocellulose features, but also heavily dependent on sustainability. The three core nanocelluloses encompass cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and bacterial nanocellulose (BNC). All these different types of nanocellulose display highly interesting biomedical properties per se, after modification and when used in composite formulations. Novel applications that use nanocellulose includewell-known areas, namely, wound dressings, implants, indwelling medical devices, scaffolds, and novel printed scaffolds. Their cytotoxicity and biocompatibility using recent methodologies are thoroughly analyzed to reinforce their near future applicability. By analyzing the pristine core nanocellulose, none display cytotoxicity. However, CNF has the highest potential to fail long-term biocompatibility since it tends to trigger inflammation. On the other hand, neverdried BNC displays a remarkable biocompatibility. Despite this, all nanocelluloses clearly represent a flag bearer of future superior biomaterials, being elite materials in the urgent replacement of our petrochemical dependence

    Silver-Based Antimicrobials

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    There is some talk about an antibiotic Armageddon due to quickly developing resistance towards commercially available antibiotics. For the most part, the classical antibiotic pipeline has dried up, and antibiotic resistance to any new drugs quickly develops. It is here that metal-based antimicrobials can step forward as possible solutions in this antimicrobial resistance era. The biological targets of metal atoms are more diverse, thus making it more difficult for bacteria to develop resistance compared with classical antibiotics. The metal silver has been used since antiquity for wound healing and water purification. At present, it is the most prevalent antimicrobial metal used in healthcare, industry, and consumer products. Silver is being used in the form of ionic salt, colloids, or in specific nanomaterials, and as described in this book, it can be applied as mixtures with other antimicrobials or coating composites. The different formulations are explored for their efficacy against a variety of problems related to agricultural and medical infections. Whilst by no means exhaustive, this book nicely highlights the present directions in silver-based antimicrobial research and antimicrobial formulation development. The chapters have been organized from a general introductory review to approaches of mixing other antimicrobials and materials to enhance silver performance. This is followed by synthetic approaches. First are biogenic (sometimes called green or eco-friendly) approaches, followed by advanced physical–chemical synthetic approaches. The book ends with an overview of applications through a review of patents over the past 10 years

    Proceedings of the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008

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    This volume contains full papers presented at the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, held in Braga, Portugal, between September 4th and 6th, 2008.FC
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