Rice (Oryza sativa L.), a staple food for more than half of the world population, is commonly grown by transplanting seedlings into puddled soil (wet tillage) in Asia. This production system is labor-, water-, and energy-intensive and is becoming less profitable as these resources are becoming increasingly scarce. It also deteriorates the physical properties of soil, adversely affects the performance of succeeding upland crops, and contributes to methane emissions. These factors demand a major shift from puddled transplanting to direct seeding of rice (DSR) in irrigated rice ecosystems. Direct seeding (especially wet seeding) is widely adopted in some and is spreading to other Asian countries. However, combining dry seeding (Dry-DSR) with zero/reduced tillage (e.g., conservation agriculture (CA)) is gaining momentum as a pathway to address rising water and labor scarcity, and to enhance system sustainability. Published studies show various benefits from direct seeding compared with puddled transplanting, which typically include (1) similar yields; (2) savings in irrigation water, labor, and production costs; (3) higher net economic returns; and (4) a reduction in methane emissions. Despite these benefits, the yields have been variable in some regions, especially with dry seeding combined with reduced/zero tillage due to (1) uneven and poor crop stand, (2) poor weed control, (3) higher spikelet sterility, (4) crop lodging, and (5) poor knowledge of water and nutrient management. In addition, rice varieties currently used for DSR are primarily selected and bred for puddled transplanted rice. Risks associated with a shift from puddled transplanting to DSR include (1) a shift toward hard-to-control weed flora, (2) development of herbicide resistance in weeds, (3) evolution of weedy rice, (4) increases in soil-borne pathogens such as nematodes, (5) higher emissions of nitrous oxide—a potent greenhouse gas , and (6) nutrient disorders, especially N and micronutrients. The objectives of this chapter are to review (1) drivers of the shift from puddled transplanting to DSR; (2) overall crop performance, including resource-use efficiencies of DSR; and (3) lessons from countries where DSR has already been widely adopted. Based on the existing evidence, we present an integrated package of technologies for Dry-DSR, including the identification of rice traits associated with the attainment of optimum grain yield with Dry-DSR.

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Direct Seeding of Rice: Recent Developments and Future Research Needs

A review of composite and metallic bipolar plates in proton exchange membrane fuel cell: Materials, fabrication, and material selection

Metal additive manufacturing (AM), also known as 3D printing, is a disruptive manufacturing technology in which complex engineering parts are produced in a layer-by-layer manner, using a high-energy heating source and powder, wire or sheet as feeding material. The current paper aims to review the achievements in AM of steels in its ability to obtain superior properties that cannot be achieved through conventional manufacturing routes, thanks to the unique microstructural evolution in AM. The challenges that AM encounters are also reviewed, and suggestions for overcoming these challenges are provided if applicable. We focus on laser powder bed fusion and directed energy deposition as these two methods are currently the most common AM methods to process steels. The main foci are on austenitic stainless steels and maraging/precipitation-hardened (PH) steels, the two so far most widely used classes of steels in AM, before summarising the state-of-the-art of AM of other classes of steels. Our comprehensive review highlights that a wide range of steels can be processed by AM. The unique microstructural features including hierarchical (sub)grains and fine precipitates induced by AM result in enhancements of strength, wear resistance and corrosion resistance of AM steels when compared to their conventional counterparts. Achieving an acceptable ductility and fatigue performance remains a challenge in AM steels. AM also acts as an intrinsic heat treatment, triggering ‘in situ’ phase transformations including tempering and other precipitation phenomena in different grades of steels such as PH steels and tool steels. A thorough discussion of the performance of AM steels as a function of these unique microstructural features is presented in this review.

/pdf/additive-manufacturing-of-steels-a-review-of-achievements-3k73ys003e.pdf

Additive manufacturing of steels: a review of achievements and challenges

Effects of Sc and Zr microalloying additions and aging time at 120 °C on the corrosion behaviour of an Al–Zn–Mg alloy

The corrosion inhibition of mild steel in 0.5 M HCl by metronidazole (MNZ) was studied by gravimetric and potentiodynamic polarization methods. Inhibition efficiency of MNZ increased with increase in the concentration of inhibitor and decreased with the increase in temperature. MNZ acts as anodic-type inhibitor for mild steel. The adsorption of MNZ on mild steel surface obeys the Temkin adsorption isotherm. Density functional theory (DFT) study was performed in order to gain some insights into the electron donor-accepting properties of MNZ while molecular dynamics simulation was utilized to determine the binding properties of MNZ on Fe (1 1 0) and Fe 2 O 3 (1 1 0) surfaces.

Metronidazole as environmentally safe corrosion inhibitor for mild steel in 0.5 M HCl: Experimental and theoretical investigation

Corrosion inhibition of aluminum alloy AA 2014 by rare earth chlorides

Corrosion inhibition of aluminium by rare earth chlorides

The Role of Microstructure and Surface Finish on the Corrosion of Selective Laser Melted 304L

The resistance of Alloy 22 (UNS N06022) to crevice corrosion in aggressive environments was studied using various modifications of the Tsujikawa-Hisamatsu Electrochemical (THE) technique. ...

Crevice Corrosion Repassivation of Alloy 22 in Aggressive Environments

Pyrazinamide (PZA) is an important front line anti-tuberculosis drug because of its sterilizing activity against semi-dormant tubercle bacilli. In spite of its remarkable role in shortening the treatment duration from 9 months to 6 months when used in combination with Rifampicin and Isoniazid, PZA remains a difficult paradox because of its incompletely understood mode of action and mechanism of resistance. PZA is a nicotinamide analog prodrug which is converted into the active bactericidal form pyrazinoic acid by the bacterial enzyme pyrazinamidase (PZase). PZA does not appear to have a specific cellular target and instead, exerts its bactericidal effect by disrupting the membrane energetics and acidification of cytoplasm. Majority (72-97%) of PZA-resistant isolates of M. tuberculosis exhibit mutations in their pncA gene or upstream area leading to loss of PZase activity. A wide diversity of pncA mutations scattered along the entire length of pncA gene is unique to PZA resistance. However, PZA resistant isolates with normal PZase activity and wild type pncA sequences have also been reported in several studies which indicate that alternate mechanisms of PZA resistance exist. Investigations into these mechanisms would be useful in developing alternative diagnostic/therapeutic measures. This review presents the update of various mechanisms of PZA resistance in different mycobacteria with special emphasis on mode of action of PZA and mechanisms of resistance in Mycobacterium tuberculosis.

Ajit Mishra

Papers

Corrosion inhibition of aluminum alloy AA 2014 by rare earth chlorides

Corrosion inhibition of aluminium by rare earth chlorides

The Role of Microstructure and Surface Finish on the Corrosion of Selective Laser Melted 304L

Crevice Corrosion Repassivation of Alloy 22 in Aggressive Environments

The paradox of pyrazinamide: an update on the molecular mechanisms of pyrazinamide resistance in Mycobacteria.