RESUMO
Unlike most countries, Korea did not implement a lockdown in its battle against COVID-19, instead successfully relying on testing and contact tracing. Until the summer of 2020, only one region, Daegu-Gyeongbuk, had a significant number of infections, traced to a religious sect. This allows us to estimate the causal effect of the outbreak on the labor market using difference-in-differences. We find that a one per thousand increase in infections caused a 2 to 3 percent drop in local employment in the early spring. We also find that employment losses caused by local outbreaks in the absence of lockdowns were (i) mainly due to reduced hiring by small establishments, (ii) concentrated in the accommodation/food, education, real estate, and transportation industries, and (iii) worst for economically vulnerable workers who are less educated, young, in low-wage occupations, and on temporary contracts, even controlling for industry effects. These patterns are similar to what we observed in the US and UK: The unequal effects of COVID-19 were the same with or without lockdowns. Our findings are consistent with the lifting of lockdowns having led to only modest employment recoveries in the US and UK, absent larger drops in infection rates.
RESUMO
Silver nanorod (AgNR) array substrates were fabricated using an oblique angle thermal evaporation technique; their long-term stability, surface uniformity and reproducibility, which are primary requirements for their widespread realistic application and commercialization, were assessed using surface-enhanced Raman scattering (SERS) spectroscopy. The nanorod surfaces were functionalized using a series of organic thiols, which range from hydrophilic to hydrophobic, to mimic various conditions that often arise during detection of hydrophilic/phobic analytes in a realistic application field. A group of these functionalized substrates was stored in ambient laboratory atmosphere; another in light minimized, moisture-free vacuum; while another was stowed carefully and neatly in water to mimic realistic conditions. The effects of these storing conditions were studied. A surfactant was added to the water to maintain consistent surface wetting in the third group. SERS spectra of nanorod substrates prior to functionalization were also recorded to investigate the effect of adventitious carbonaceous contaminants. A meticulous systematic study on the reproducibility of SERS signals was carried out: spot-to-spot, substrate-to-substrate, batch-to-batch, day-to-day. The relative standard deviation (RSD) shown by the SERS signals acquired from various spots of a single substrate was less than 3%, which is very similar to the only account reported so far, in which RSD is reported as 2%. The wetting behavior of these thiol functionalized AgNR substrates are investigated using static contact angle measurements. The functionalized substrates have exhibited excellent long-standing stability over a period of six months when stored appropriately; hence, they are highly suitable for mass production towards realistic application.
RESUMO
Aligned silver nanorod (AgNR) array films were fabricated by oblique thermal evaporation. The substrate temperature during evaporation was varied from 10 to 100 °C using a home-built water cooling system. Deposition angle and substrate temperature were found to be the most important parameters for the morphology of fabricated films. Especially, it was found that there exists a critical temperature at ~90 °C for the formation of the AgNR array. The highest enhancement factor of the surface-enhanced Raman scattering (SERS), observed in the Ag films coated with benzenethiol monolayer, was ~6 × 10(7). Hot spots, excited in narrow gaps between nanorods, were attributed to the huge enhancement factor by our finite-difference time-domain (FDTD) simulation reflecting the real morphology.