A cold wave of winter 2021 in central South America: characteristics and impacts.

During the austral winter (June-August) of 2021, the meteorological services of Brazil, Argentina, Peru, Paraguay, Bolivia, and Chile all issued forecasts for unusually cold conditions. Record-low minimum temperatures and cold spells were documented, including one strong cold wave episode that affected 5 countries. In this study, we define a cold wave as a period in which daily maximum and minimum air temperatures are below the corresponding climatological 10th percentile for three or more consecutive days. The intense cold wave event in the last week of June, 2021, resulted in record-breaking minimum daily temperatures in several places in central South America and Chile. Several locations had temperatures about 10 °C below average, central South America had freezing conditions, and southern Brazil even saw snow. The cold air surge was characterized by an intense upper-air trough located close to 35° S and 70° W. The southerly flow to the west of this trough brought very cold air northward into subtropical and tropical South America. A northward flow between the lower-level cyclonic and anticyclonic perturbations caused the intense southerly flow between the upper-level ridge and trough. This condition facilitated the inflow of near-surface cold air from southern Argentina into southeastern Brazil and tropical South America east of the Andes. In the city of São Paulo, the cold wave caused the death of 13 homeless people from hypothermia. Frost and snow across southern and southeastern Brazil caused significant damage to coffee, sugarcane, oranges, grapes, and other fruit and vegetable crops. Wine and coffee production fell, the latter by 30%, and prices of food and commodities in the region rose. Supplementary Information: The online version contains supplementary material available at 10.1007/s00382-023-06701-1.

Reduction and oxidation kinetics of NiWO4 as an oxygen carrier for hydrogen storage by a chemical looping process.

NiWO4 with a volumetric storage density (VSD) of 496 g L-1 was studied to evaluate its H2 storage potential as an oxygen carrier under a chemical looping (CL) process scheme. The material was synthesized by precipitation and calcined at 950 °C for 5 hours in air. Characterization consisted in XRD, BET surface area, SEM and EDS analysis. NiWO4 hydrogen storage reduction-oxidation evaluation was performed by TGA using 5% v H2/Ar and 2.2% v H2O/Ar at 800 °C. Global kinetics for the reduction step was studied from 730 to 870 °C using 2 to 5% v of H2/Ar. While oxidation kinetics was examined from 730 to 870 °C using 0.8 to 2.2% v H2O/Ar. A hydrogen storage multicycle stability test was performed by exposing NiWO4 to 17 consecutive redox cycles. XRD results of the synthesized material indicate NiWO4 as the only crystalline phase. Fully reduced material found only W and Ni species, while reoxidation led back to NiWO4. BET surface area of synthesized material was 4.25 m2 g-1. SEM results showed fresh NiWO4 composed of non-porous large particles (1-5 µm). After reduction, the material shown a porous coral-like morphology with particles between 50 to 100 nm. EDS analysis results confirmed the compositions of the reduced (Ni + W) and fully oxidized NiWO4 species, respectively. Oxygen carrier reaction conversions for both reduction and regeneration steps were 100%. Global kinetic studies indicate a first order reaction for the two reduction steps and during oxidation, with activation energies of 22.1, 48.4 and 53.4 kJ mol-1 for the two reduction and oxidation steps, respectively. NiWO4 multicycle stability test shown no loss of VSD and fast reduction and oxidation kinetics under the studied conditions after seventeen consecutive redox cycles, which confirms the potential of this material with respect to current oxygen carriers reported in the literature for hydrogen storage applications.

Detection and phylogenetic analysis of infectious pancreatic necrosis virus in Chile.

Infectious pancreatic necrosis virus (IPNV) is the etiological agent of a highly contagious disease that is endemic to salmon farming in Chile and causes great economic losses to the industry. Here we compared different diagnostic methods to detect IPNV in field samples, including 3 real-time reverse transcription PCR (qRT-PCR) assays, cell culture isolation, and indirect fluorescent antibody test (IFAT). Additionally, we performed a phylogenetic analysis to investigate the genogroups prevailing in Chile, as well as their geographic distribution and virulence. The 3 qRT-PCR assays used primers that targeted regions of the VP2 and VP1 genes of the virus and were tested in 46 samples, presenting a fair agreement within their results. All samples were positive for at least 2 of the qRT-PCR assays, 29 were positive for cell culture, and 23 for IFAT, showing less sensitivity for these latter 2 methods. For the phylogenetic analysis, portions of 1180 and 523 bp of the VP2 region of segment A were amplified by RT-PCR, sequenced and compared with sequences from reference strains and from isolates reported by previous studies carried out in Chile. Most of the sequenced isolates belonged to genogroup 5 (European origin), and 5 were classified within genogroup 1 (American origin). Chilean isolates formed clusters within each of the genogroups found, evidencing a clear differentiation from the reference strains. To our knowledge, this is the most extensive study completed for IPNV in Chile, covering isolates from sea- and freshwater salmon farms and showing a high prevalence of this virus in the country.

Temporal and subcellular localization of infectious pancreatic necrosis virus structural proteins.

The temporal subcellular localization of the structural proteins VP2 and VP3 of infectious pancreatic necrosis virus was analyzed with monoclonal antibodies conjugated with fluorochromes. Early in the infection both proteins were colocalized in the cytosol, at later times, VP2 was visualized as inclusion bodies around the nuclei of the cells and, sometimes, it was found in elongated tubular structures that might correspond to the type I tubules seen in cells infected with another Birnavirus. As VP2 is a glycosylated protein we determined its subcellular localization compared with that of ER and Golgi probes. These results suggest that VP2 is glycosylated freely in the cytoplasm.

Infectious pancreatic necrosis virus (IPNV) does not require acid compartments for entry into cells.

The early events in the infection of unenveloped viruses are still rather unknown and puzzling. However, as in the case of enveloped viruses, the acid pH of endosomes can be important to trigger the virus entry into the cytosol. To test if the infectious pancreatic necrosis virus (IPNV), an unenveloped virus, requires acid endosomal pH to infect cells, we assayed the effect of Bafilomycin A1 on IPNV replication. Concentrations of the antibiotic which inhibited the endosomal acidification of the host cells were unable to affect IPNV replication in CHSE-214 cells; therefore, the acid pH of endosomes seems not to be a mandatory condition for the entry of IPNV into cells.

Attachment and entry of infectious pancreatic necrosis virus (IPNV) into CHSE-214 cells.

Infectious pancreatic necrosis virus (IPNV) attaches to CHSE-214 cells through two types of cell components: specific and non-specific ones. Competition experiments with inactivated IPNV showed that IPNV requires specific components to productively infect cells. Just a low amount of adsorbed IPNV enters the cell. After 20 minutes, part of the adsorbed IPNV was internalized into acid compartments. Also, the viruses adsorbed on the cell surface require similar periods of time to escape from the neutralization of antibodies.