"this study observed that" is correct and usable in written English.
You can use it to introduce a conclusion a study has come to. For example: "This study observed that regular exercise leads to improved cardiovascular health."
This study observed that almost all the postulated biophysical/environmental variables contribute positively to household vulnerability.
This study observed that genes involved in the oxidoreductase activity category were most significantly differentially expressed under micro-g conditions.
In addition, this study observed that critical heat flux was higher when the contact angle difference between the plain surface and the modified region was smaller.
This study observed that post-Northridge WUF-B connections with a panel zone strength ratio ranging from 0.9 to 1.6 provides a drift ratio exceeding 0.2.
This study observed that treatment with 28.5 °C significantly accelerated the flowering and senescence of tobacco plants; in contrast, treatment with 18.5 °C greatly delayed the flowering and senescence, as compared with those plants grown under 23.5 °C.
After we determining that G. pacifica and G. "filamentosa" are the same species, this study observed that specimens from different locations in southern Taiwan showed a range of external morphological variation in different seasons.
The results of this preliminary study observed that ROS production was higher in the infected peritoneal and pleural fluids, an effect that was not observed in BAL.
This epidemiological study observed that DNA methylation levels in LINE-1, Alu, and p16 appeared to be positively associated in healthy mother-infant pairs.
In this study, we observe that extracts of TAE showed significant antimicrobial activity.
In this study, we observe that PP2A is also involved in regulation of collagen.
In this study, we observed that this antibody recognizes several proteins from the venom dermonecrotic fraction (DNF), including LiD1.
