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Temporal light artefacts (TLAs) are undesired effects in the visual perception of a human observer induced by temporal light modulations. Two well-known examples of such unwanted effects are flicker and stroboscopic effect. Flicker is a directly visible light modulation at relatively low frequencies (< 80 Hz) and small intensity modulation levels.
The flicker fusion threshold, also known as critical flicker frequency or flicker fusion rate, is the frequency at which a flickering light appears steady to the average human observer. It is a concept studied in vision science , more specifically in the psychophysics of visual perception .
In visual perception, flicker is a human-visible change in luminance of an illuminated surface or light source which can be due to fluctuations of the light source itself, or due to external causes such as due to rapid fluctuations in the voltage of the power supply (power-line flicker) or incompatibility with an external dimmer.
The flicker of a CRT monitor can cause various symptoms in those sensitive to it such as eye strain, headaches [9] in migraine sufferers, and seizures in epileptics. [10]As the flicker is most clearly seen at the edge of our vision there is no obvious risk in using a CRT, but prolonged use can cause a sort of retinal shock where the flickering is seen even when looking away from the monitor.
The Acámbaro figures were uncovered by a German immigrant and hardware merchant named Waldemar Julsrud. According to Dennis Swift, a young-Earth creationist and major proponent of the figures' authenticity, Julsrud stumbled upon the figures while riding his horse and hired a local farmer to dig up the remaining figures, paying him for each figure he brought back.
When ants bite humans, it grabs the skin and also sprays a compound called formic acid, Frye explains. Ant bites tend to be small, swollen bumps that appear in clusters, Kassouf says.
The oldest human skeletal remains are the 40ky old Lake Mungo remains in New South Wales, but human ornaments discovered at Devil's Lair in Western Australia have been dated to 48 kya and artifacts at Madjedbebe in Northern Territory are dated to at least 50 kya, and to 62.1 ± 2.9 ka in one 2017 study. [26] [27] [28] [29]
Richardson's ground squirrel (Urocitellus richardsonii), also known as the dakrat or flickertail, is a North American ground squirrel in the genus Urocitellus.Like a number of other ground squirrels, they are sometimes called prairie dogs or gophers, though the latter name belongs more strictly to the pocket gophers of family Geomyidae, and the former to members of the genus Cynomys.