Dynamics of organic matter decomposition during vermicomposting of banana stem waste using Eisenia fetida.

A better understanding of how dynamics of physical and chemical changes occur during vermicomposting process would be helpful for determining the stability and maturity of vermicompost. For improving the knowledge about this issue several instrumental techniques were used in the present study to analyse the physical and chemical changes as a function of vermicomposting time of banana stem waste (BS) spiked with cow dung (CD) in different proportions using earthworm Eisenia fetida. Chemical analysis by ICP-AES showed gradual increase in the plant nutrients (P, Ca, K, Mg, Fe) up to 60 day of vermicomposting in all the treatments. But among different treatments, K, Mg and Fe were considerably higher in the BS2CD1 blend. The FTIR showed strong NO stretching vibration with increasing BS content signifying the presence of nitrate in the final compost. The TG analysis of final BS-CD composts described the lower mass loss (52-55%) in the final compared to the initial stage due to high level of humification by earthworms. The maturity of the final compost was confirmed by DSC analysis which exhibited lowering of relative intensity of exothermic peaks related to the easily degradable material at 320-330 °C and complex organic moieties at 495-530 °C. Decrease in the humification index (Q4/6, Q2/4, Q2/6) at 60 day confirmed the stability of vermicomposts. All the treatments showed <2 mg CO2-C g-1 vermicompost C day-1 respiration rates and >70% germination indices (GI) for rice and pea seeds. These findings defined a clear comparison between the treatments during vermicomposting in terms of stability and maturity and revealed that BS2CD1 can be utilized as nutrient-rich stable compost for enhanced crop production.

Compression fatigue behavior of laser processed porous NiTi alloy.

Porous metals are being widely used in load bearing implant applications with an aim to increase osseointegration and also to reduce stress shielding. However, fatigue performance of porous metals is extremely important to ensure long-term implant stability, because porous metals are sensitive to crack propagation even at low stresses especially under cyclic loading conditions. Herein we report high-cycle compression-compression fatigue behavior of laser processed NiTi alloy with varying porosities between ∼1% and 20%. The results show that compression fatigue of porous NiTi alloy samples is in part similar to metal foams. The applied stress amplitude is found to have strong influence on the accumulated strain and cyclic stability. The critical stress amplitudes associated with rapid strain accumulation in porous NiTi alloy samples, with varying relative densities, were found to correspond to 140% of respective 0.2% proof strength indicating that these samples can sustain cyclic compression fatigue stresses up to 1.4 times their yield strength without failure.