Silver Micro-Nanoparticle-Based Nanoarchitectures: Synthesis Routes, Biomedical Applications, and Mechanisms of Action.

Silver has become a potent agent that can be effectively applied in nanostructured nanomaterials with various shapes and sizes against antibacterial applications. Silver nanoparticle (Ag NP) based-antimicrobial agents play a major role in different applications, including biomedical applications, as surface treatment and coatings, in chemical and food industries, and for agricultural productivity. Due to advancements in nanoscience and nanotechnology, different methods have been used to prepare Ag NPs with sizes and shapes reducing toxicity for antibacterial applications. Studies have shown that Ag NPs are largely dependent on basic structural parameters, such as size, shape, and chemical composition, which play a significant role in preparing the appropriate formulation for the desired applications. Therefore, this review focuses on the important parameters that affect the surface interaction/state of Ag NPs and their influence on antimicrobial activities, which are essential for designing future applications. The mode of action of Ag NPs as antibacterial agents will also be discussed.

Efficient and participatory design of scale-appropriate agricultural machinery workshops in developing countries: A case study in Bangladesh.

Smallholder farmers provide the foundation for food security in South Asia. However, increasing seasonal labor scarcity caused by rural out-migration has resulted in growing agricultural labor costs, presenting challenges to cash-constrained smallholder farmers that hire manual labor for land preparation, sowing, harvest and post-harvest operations. Technological innovations in small-scale agricultural machinery appropriate for the small field sizes and limited resource endowments of South Asia's farmers have been proposed as a potential solution to this problem. An increasing number of development initiatives also promote rural entrepreneurial approaches to mechanization, whereby smallholder farmers can access and use machinery in their own fields on an affordable fee-for-service basis offered by machinery owners. This approach reduces capital constraints for smallholder farmers while enabling entrepreneurs who can afford equipment to enter into business serving stallholder farmers as clients. This approach is now widely practiced in Bangladesh, where machinery entrepreneurs play a crucial role in providing access to productive technologies for smallholder farmers who could not otherwise afford direct purchase of labor- and cost-saving machinery. In order to maintain low machinery purchase costs for emerging yet capital constrained rural entrepreneurs, while also assuring high quality standards, cost-effective domestic production of agricultural machinery is increasingly championed as an important long-term national development objective. With no safety standards or guidelines for best production practices, the few manufacturing workshops that exist within Bangladesh operate inefficiently and without clear rationalization of manufacturing processes. Haphazard copying of prototypes or imported available machinery is common. This leads to inefficient production and poor product quality in an emerging but potentially highly beneficial industry. This paper addresses these problems and presents a case study to increase machinery manufacturers' capacity while improving manufacturing operations and workplace safety through equipment selection, workshop layout, and usability. Janata Engineering (JE) is a small-scale machinery manufacturing enterprise in Bangladesh, specializing in two-wheel tractor attachments such as bed planters, local derivations of power-tiller operated seeders, and other equipment for planting, irrigating, and processing crops. JE was expanding and setting up a second factory for which the authors provided assistance on its design. Our research question was whether participatory action research (PAR) supported by empirical data could provide improved factory design in terms of functionality, safety and human interactions, when compared with conventional approaches driven by technical efficiency concerns alone. Using PAR, we developed a number of alternative process and layout recommendations for JE to increase the efficiency of labor and machinery through improved workflow, throughput, and output. While immediately useful for JE, the process and protocols proposed in this paper are relevant for emerging agricultural machinery manufacturers in Bangladesh and more widely in South Asia.

Preparation of different polymorphs of cellulose from different acid hydrolysis medium.

In this study, medical cotton was subjected to acid hydrolysis in sulfuric, hydrochloric and phosphoric acid medium to prepare cellulose nanocrystals (CNC) with different morphologies and polymorphism. Morphology of the prepared CNC samples revealed fiber shaped morphology for sulfuric and hydrochloric acid hydrolyzed samples, whereas, spherical shaped for phosphoric acid hydrolyzed samples. The size of the spherical shaped CNC decreased with the increase of hydrolysis time, from 853 nm for 12 h to 187 nm for 48 h. X-ray Diffraction analysis showed that hydrochloric acid hydrolyzed CNC is cellulose I (CI), phosphoric acid hydrolyzed CNC is cellulose II (CII) and sulfuric acid hydrolyzed CNC contain both CI and CII. The crystallinity of sulfuric and hydrochloric acid hydrolysis samples was 91%, whereas, the crystallinity of phosphoric acid hydrolysis samples was between 43 and 60% depending on hydrolysis time. Thermal properties were also affected by the hydrolysis medium. Thus cellulose nanocrystals were prepared with different morphologies and physical characteristics through a facile method.

Synthesis of Highly Efficient Bifunctional Ag/Co3O4 Catalyst for Oxygen Reduction and Oxygen Evolution Reactions in Alkaline Medium.

Ag/Co3O4 catalysts using three different modes of solution combustion synthesis were developed and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy to identify crystallite size, oxidation state, composition, and morphology. Cyclic voltammetry and linear sweep voltammetry measurements for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) confirm the bifunctionality of the electrocatalysts. The electrochemical evaluation indicates that a synergic effect between Ag and Co enhances the activity through the fast breaking of O-O bond in the molecular oxygen to enhance the reduction mechanism. The high content of cobalt (Co) in the catalyst Ag/Co3O4-12, synthesized by second wave combustion, improves the activity for ORR, and the reaction mechanism follows a 3.9 number of electron transfer in overall reaction. The kinetic and limiting current densities of Ag/Co3O4-12 are maximum when compared to those of other Ag/Co3O4 catalysts and are very close to commercial Pt/C. Moreover, the maximum current density of OER for Ag/Co3O4-12 makes it a promising candidate for various bifunctional electrocatalytic applications such as fuel cells and metal-air batteries.

A Simplified Irrigation Pump Testing Method for Developing Countries: A Case Study in Bangladesh.

Much of South Asia experiences a monomodal rainfall pattern with a distinct dry season following the annual monsoon. Enabling irrigation during the dry season has therefore been crucial in assuring improved productivity and double-cropping. This is particularly the case in southern Bangladesh, where recent government initiatives have called for an expansion of surface water irrigation to reduce pressure on groundwater tables in intensively cultivated areas in the north of the country, where dry season boro rice is grown. This paper describes a method based on first principles of fluid mechanics to characterize the performance of surface water irrigation pumps used by small-scale farmers in South Asia and Bangladesh. This method is unique, as it incorporates an optimized protocol suitable for resource-limited conditions found in many developing countries and provides a comprehensive yet simple-to-use pump selection method for surface water irrigation pump customers. Using pump impellers as a case study, the method also characterizes the effect of pump geometric variations resulting from the variable production and assembly practices found in different manufacturing workshops. This method was validated with a case study in Bangladesh supported by both full-scale field testing and numerical simulation results. © 2018 The Authors. Irrigation and Drainage published by John Wiley & Sons Ltd on behalf of International Commission for Irrigation and Drainage.

Une grande partie de l'Asie du Sud connaît un régime pluviométrique monomodal avec une saison sèche distincte après la mousson annuelle. Permettre l'irrigation pendant la saison sèche a donc été crucial pour assurer une meilleure productivité et une double culture. C'est particulièrement le cas dans le sud du Bangladesh, où des initiatives gouvernementales récentes ont demandé une expansion de l'irrigation avec des eaux de surface pour réduire la pression sur les nappes phréatiques dans les zones intensément cultivées du nord du pays où pousse le riz boro de saison sèche. Cet article décrit une méthode basée sur les premiers principes de la mécanique des fluides pour caractériser les performances des pompes d'irrigation avec des eaux de surface utilisées par les petits agriculteurs en Asie du Sud et au Bangladesh. Cette méthode est unique car elle incorpore un protocole optimisé adapté aux conditions de ressources limitées dans de nombreux pays en développement et fournit une méthode de sélection de pompe complète mais simple à utiliser pour les clients de pompes d'irrigation d'eau de surface. En utilisant des turbines de pompage comme étude de cas, la méthode caractérise également l'effet des variations géométriques de la pompe résultant des pratiques variables de production et d'assemblage trouvées dans différents ateliers de fabrication. Cette méthode a été validée à l'aide d'une étude de cas au Bangladesh appuyée à la fois par des essais sur le terrain à grande échelle et des résultats de simulation numérique. © 2018 The Authors. Irrigation and Drainage published by John Wiley & Sons Ltd on behalf of International Commission for Irrigation and Drainage.

Prevalence of colibacillosis in chickens in greater Mymensingh district of Bangladesh.

AIM: This study was conducted for determination of the prevalence of colibacillosis in chicken in poultry farms in Mymensingh and Tangail districts. Isolation, identification, and antibiogram profile of Escherichia coli were also performed. MATERIALS AND METHODS: A total of 25 chickens manifested clinical signs of colibacillosis were collected from five different poultry farms during natural outbreaks. RESULTS: In broiler, the prevalence of colibacillosis was 0.84%, and in layer, prevalence was 0.80%. The prevalence of colibacillosis was 1.0% and 0.5% in 25-30 days old and 31-35 days old broiler, respectively. In case of layer birds, the prevalence was 0.6% in 40-45 days old bird and 1% in 46-50 days old bird. Identity of the E. coli isolate of chicken was confirmed by sugar fermentation, biochemical tests, and polymerase chain reaction assay. Antibiogram profile of E. coli isolate of chicken revealed that it was multidrug resistant (resistant against two antibiotics, such as ampicillin and cefalexin). CONCLUSION: Data of this study suggest that colibacillosis is prevalent in the study areas which underscore the need of implementation of prevention and control measure against this disease.

One-step sonochemical syntheses of Ni@Pt core-shell nanoparticles with controlled shape and shell thickness for fuel cell electrocatalyst.

We demonstrate a facile one-step method to synthesize Ni@Pt core-shell nanoparticles (NPs) with a control over the shape and the Pt-shell thickness of the NPs. By adjusting the relative reactivity of the Pt and Ni reagents in ultrasound-assisted polyol reactions, two Ni@Pt NP samples of the same composition (Ni/Pt=1) and size (3-4 nm) but with different particle shape (octahedral vs. truncated octahedral) and different Pt-shell thicknesses (1-2 vs. 2-3 monolayer) are obtained. The control is achieved by using different Ni reagents, Ni(acac)2 (acac=acetylacetonate) and Ni(hfac)2 (hfac=hexafluoroacetylacetonate). A reaction mechanism that can explain all of the observations is proposed. The Ni@Pt NPs show up to threefold higher mass activity than pure Pt NPs in oxygen reduction reaction. Between the two Ni@Pt NP samples, the one composed of octahedral NPs with the thicker Pt-shell has higher activity than the other.