3 months ago
Quartz (left) is a crystalline form of silicon dioxide containing a three dimensional array of SiO2 units linked by highly regular covalent bonding. Silica glass (right) also has a three dimensional array of SiO2 units, but in this case the bond arrangement is irregular, and the solid is amorphous.
4 months ago
Mercuric iodide is thermochromic—-it has two different colors depending on the temperature.This is because it has two different crystal forms , with different optical properties.
5 months ago
Feasting on Sweat And Tears
If you thought bees just collected nectar from flowers, then think again. While the European honey bee is the most well-known species, there are thousands of other wild bee species that don’t produce much honey at all—and some of these feast on human body fluids. Lasioglossum gotham was discovered in 2010 in Brooklyn, New York, and it literally uses humans as a salt lick by landing on the skin and drinking perspiration. It prefers human sweat over animal sweat because the human diet is so salty that our sweat is saturated with the essential nutrient—but the species is not well known, because it is tiny, unobtrusive, and rarely stings. Even more bizarrely, entomologists have found a related species native to Thailand called Lisotrigona, which drinks both human and animal tears as a source of protein and salt. To study them, researchers used themselves as bait with eyes wide open. The bees would alight on their faces and attach to the eyelid to consume tears, staying there anywhere from thirty seconds to two and a half minutes. They were often so gentle that the host would have to use a mirror to check the bee was there—but if more than one came to drink (up to seven were recorded at one time), the experience was unpleasant because they attached themselves tenaciously and caused a strong tear flow. Overall, the researchers let 262 bees attach themselves to their faces. For science.
(Image Credit: 1, 2)
5 months ago
Do flesh-eating bacteria actually eat flesh?
Flesh-eating bacteria do not actually “eat” the tissue. They cause the destruction of skin and muscle by releasing toxins , which include streptococcal pyogenic exotoxins. Streptococcus pyogenes (picture) produces an exotoxin known as a superantigen. This toxin is capable of activating T-cells non-specifically, which causes the overproduction of cytokines and severe systemic illness (Toxic shock syndrome).
5 months ago
Schwarm der Wanderheuschrecke (Acrididae)
from Brehms Thierleben. Allgemeine Kunde des Thierreichs, Neunter Band, Vierte Abtheilung: Leipzig: Verlag des Bibliographischen Instituts, 1887.