The Effect of El Niño Southern Oscillation (ENSO) on World Cereal Production

El Niño Southern Oscillation (ENSO) anomalies are responsible for medium-frequency climate fluctuations across many regions of the world. Not only ENSO induces temperature and precipitation variability in the affected regions, but it is also responsible for larger magnitude weather anomalies, such as droughts, hurricanes, and tsunamis. All these directly impact agricultural production. The overall objective of this research is to determine the relationship between ENSO and world major cereal production. While several studies have addressed the issue, this research contributes to the literature in a number of directions. Firstly, it measures the ENSO effect net of temperature and precipitation. Secondly, it allows for the threshold-like effect of ENSO; that is, El Niño effects are not mirror images of La Niña effects. Thirdly, it incorporates expected price in the regression setting, thus controlling for an important economic variable affecting crop supply. Finally, this study applies the largest possible panel of countries, to analyse the region-specific peculiarities of the ENSO–production relationship, and to best approximate the global production effect of ENSO anomalies. This study uses a combination of extensive climatic and economic datasets spanning the years 1962-2009 to empirically measure the impact of ENSO on wheat, maize and rice production, via a threshold regression framework. The results reveal statistically significant and economically meaningful ENSO impact on cereal production in many regions, with particularly strong effects in Southeast Asian and American countries. Although the expected global effect may camouflage the country-specific effects, the research findings suggest that El Niño shocks are likely to cause on average a reduction in global production of rice and maize. La Niña episodes, on the other hand, are associated with increased global rice and decreased global wheat and maize production. Although consequences of ENSO shocks on a global scale are sporadic, understanding the overall impact of ENSO on major grain production is an important tool for managing global food security. Results of this study provide implications for food policy makers, and help them develop precautionary economic policies that will take advantage of ENSO signals to cope with production shocks and ensure food availability, which is particularly relevant in the developing world

The El Niño impact on maize yields is amplified in lower income teleconnected countries

We use a multiple-regime panel smooth transition regression to examine the economic and climatic sources of the nonuniform relationship between El Niño Southern Oscillation (ENSO) and maize yields around the globe. While the yield effect is predominantly observed in strongly teleconnected countries, it is amplified in lower income countries, which we attribute to possible lack of resilience to ENSO—induced weather shocks. Both El Niño-like and La Niña-like conditions result in maize yield reduction, but it is during El Niño events when maize yields drop by up to 20% in most affected countries. Because in many of these countries maize is an important agricultural crop, the presented results are of interest to researchers and policy makers in the areas of world nutrition and international aid. Moreover, because larger share of maize is produced by high income weakly teleconnected countries, the observed geographic heterogeneity of the El Niño impact offers possible benefits from global risk sharing. These findings also offer insights to climate change economics, as possible increased frequency of the ENSO cycle may negatively impact maize production in strongly teleconnected low income countries

Time and temperature dependent magnetic viscosity experiments on Sr/Co nanoferrite particles

Magnetic viscosity experiments have been performed in order to investigate the magnetization reversal in Sr nanoferrite particles (nanoscale SrFe12O19) and interacting Sr/Co nanoferrite particles (SrFe12O19-CoFe2O4 nanocomposites). The magnetic viscosity S = dM(t)/dln(t), where M(t) is the magnetization as a function of time, has been collected. For Sr nanoferrite S shows a maximum close to the coercive field, reflecting the relation between S and the energy barrier distribution. We evidence that magnetic viscosity experiments on Sr nanoferrite and interacting Sr/Co nanoferrite particles provide reliable qualitative results for the different magnetic field sweep rate and saturating field Hsat considered. In addition, the activation volumes extracted from the magnetic viscosity experiments performed at different temperatures on Sr nanoferrite are quantitatively correlated to anisotropy changes

Obsidian as a Raw Material for Eco-Friendly Synthesis of Magnetic Zeolites

A sample of rhyolitic obsidian (OS) was used as raw material for zeolite synthesis by long (4 days) and fast (2 h)-aging hydrothermal processes. Zeolite synthesis was also performed by a fast (2 h) sonication method. The products were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) both immediately after and 3 years after their formation in order to determine the stability of synthetic materials according to the method used. The results confirm zeolitization of obsidian both by long-aging conventional hydrothermal heating and fast hydrothermal process. However, the data highlight the efficiency of direct ultrasound energy in achieving more stable zeolite crystals over time. These results carried out using a natural source, follow those already obtained using wastes and pure sources as raw materials thus providing a definitive validation of the different mechanisms controlling zeolite formation according to the process used. Moreover, the results confirm the effectiveness of ultrasonic energy in the formation of zeolites that are more stable over time. Due to the chemical composition of the obsidian precursor, all synthetic zeolites show good magnetic properties (i.e., saturation magnetization), in view to potential magnetic separation

Spinel Iron Oxide by the Co-Precipitation Method: Effect of the Reaction Atmosphere

Synthesis atmosphere (i.e., air and nitrogen) effects on the physical properties and formation mechanism of spinel iron oxide nanoparticles prepared via the co-precipitation method have been investigated using a multi-technique approach. The obtained magnetic nanoparticles (MNPs) were characterized using the X-ray diffraction, transmission electron microscopy (TEM), SQUID magnetometry, M\uf6ssbauer spectroscopy and X-ray absorption near-edge Structure spectroscopy techniques. The synthesis procedure leads to the formation of a spinel structure with an average crys-tallite size of 9.0(9) nm. The morphology of the particles synthetized under an inert atmosphere was quasi-spherical, while the nanoparticles prepared in air present a faceted shape. The small differences observed in morphological properties are explained by the influence of the reaction atmosphere on the formation mechanism of the MNPs. The magnetic characterization indicates that both samples exhibit superparamagnetic behavior at 300 K. The investigation by means of the Langevin approach at 300 K also leads to equal values for the mean size of the magnetic cores (Dm). Additionally, the analysis of the M\uf6ssbauer spectra revealed the lack of spin disorder for both samples, resulting in a high saturation magnetization. The fit of XANES spectrum suggests that about 2/3 of the iron ions reside in a local environment close to that of \u3b3-Fe2O3 and about 1/3 close to that of Fe3O4 for the sample synthetized in inert atmosphere

Morpho-Structural and Magnetic Properties of CoFe₂O₄/SiO₂ Nanocomposites: The Effect of the Molecular Coating

The use of magnetic nanoarchitecture in several applications is often limited by the lack of noninteracting particles, due to the frequent presence of clusters and aggregates of particles. Here, we report an investigation of the interparticle interactions by changing the molecular coating on ∼5 nm CoFe2O4 nanoparticles embedded in a silica structure. The magnetic investigation at a low temperature allows revealing the key role of organic ligands in tuning the morpho-structural properties of hybrid materials. Cobalt ferrite-coated nanoparticles were prepared by the polyol method using triethylene glycol as a co-reagent (CFOT) and by the exchange ligand process using dihydroxyhydrocinnamic acid (CFOH). Then, magnetic mesoporous silica nanocomposites have been prepared starting from CFOT (CFOTS) and CFOH (CFOHS). For the CFOTS sample, the interparticle distance did not change after coating, whereas the CFOHS sample showed an increase in the interparticle distance by 23%. This value has been obtained by investigating interparticle interactions by remanence techniques, which represent a good approach to determine the approximated values of interparticle distances in complex systems. The measurements showed that the silica coating produces a reduction of 47% in the dipolar interaction strength for the CFOHS sample, whereas no significant change was observed for the CFOTS sample. The differences in magnetic response upon varying the molecular coating of nanoparticles are due to the different interactions of the molecular ligands with silica, resulting in a change of interparticle distances and then magnetic interactions

Magnetism of Nanoparticles: Effect of the Organic Coating

The design of novel multifunctional materials based on nanoparticles requires tuning of their magnetic properties, which are strongly dependent on the surface structure. The organic coating represents a unique tool to significantly modify the surface structure trough the bonds between the ligands of the organic molecule and the surface metal atoms. This work presents a critical overview of the effects of the organic coating on the magnetic properties of nanoparticles trough a selection of papers focused on different approaches to control the surface structure and the morphology of nanoparticles’ assemblies

Fe3O4-Halloysite Nanotube Composites as Sustainable Adsorbents: Efficiency in Ofloxacin Removal from Polluted Waters and Ecotoxicity

The present work aimed at decorating halloysite nanotubes (HNT) with magnetic Fe3O4 nanoparticles through different synthetic routes (co-precipitation, hydrothermal, and sol-gel) to test the efficiency of three magnetic composites (HNT/Fe3O4) to remove the antibiotic ofloxacin (OFL) from waters. The chemical–physical features of the obtained materials were characterized through the application of diverse techniques (XRPD, FT-IR spectroscopy, SEM, EDS, and TEM microscopy, thermogravimetric analysis, and magnetization measurements), while ecotoxicity was assessed through a standard test on the freshwater organism Daphnia magna. Independently of the synthesis procedure, the magnetic composites were successfully obtained. The Fe3O4 is nanometric (about 10 nm) and the weight percentage is sample-dependent. It decorates the HNT’s surface and also forms aggregates linking the nanotubes in Fe3O4-rich samples. Thermodynamic and kineticexperiments showed different adsorption capacities of OFL, ranging from 23 to 45 mg g-1. The kinetic process occurred within a few minutes, independently of the composite. The capability of the three HNT/Fe3O4 in removing the OFL was confirmed under realistic conditions, when OFL was added to tap, river, and effluent waters at ug L-1 concentration. No acute toxicity of the composites was observed on freshwater organisms. Despite the good results obtained for all the composites, the sample by co-precipitation is the most performant as it: (i) is easily magnetically separated from the media after the use; (ii) does not undergo any degradation after three adsorption cycles; (iii) is synthetized through a low-cost procedure. These features make this material an excellent candidate for removal of OFL from water