What are Tin Whiskers?
Tin whiskers are electrically conductive, crystalline structures of tin that sometimes grow from surfaces where tin (especially electroplated tin) is used as a final finish. Tin whiskers have been observed to grow to lengths of several millimeters (mm) and in rare instances to lengths in excess of 10 mm. Numerous electronic system failures have been attributed to short circuits caused by tin whiskers that bridge closely-spaced circuit elements maintained at different electrical potentials.
Tin whiskers are not a new phenomenon. Indeed, the first published reports of tin whiskers date back to the 1940s and 1950s. Tin is only one of several metals that is known to be capable of growing whiskers. Other examples of metals that may form whiskers include some tin alloys, zinc, cadmium, indium, antimony, silver among others .
People sometimes confuse the term “whiskers” with a more familiar phenomenon known as “dendrites” commonly formed by electrochemical migration processes. Therefore, it is important to note here that whiskers and dendrites are two very different phenomena. A “Whisker” generally has the shape of a very thin, single filament or hair-like protrusion that emerges outward (z-axis) from a surface. “Dendrites”, on the other hand, form in fern-like or snowflake-like patterns growing along a surface (x-y plane) rather than outward from it. The growth mechanism for dendrites is well-understood and requires some type of moisture capable of dissolving the metal (e.g., tin) into a solution of metal ions which are then redistributed by electromigration in the presence of an electromagnetic field. While the precise mechanism for whisker formation remains unknown, it is known that whisker formation does NOT require either dissolution of the metal NOR the presence of electromagnetic field
Paradoxes of the Supertask
In set theory, an infinite set is not considered to be created by some mathematical process such as “adding one element” that is then carried out “an infinite number of times”. Instead, a particular infinite set (such as the set of all natural numbers) is said to already exist, “by fiat”, as an assumption or an axiom. Given this infinite set, other infinite sets are then proven to exist as well, as a logical consequence. But it is still a natural philosophical question to contemplate some physical action that actually completes after an infinite number of discrete steps; and the interpretation of this question using set theory gives rise to the paradoxes of the supertask.
The diary of Tristram Shandy
Tristram Shandy, the hero of a novel by Laurence Sterne, writes his autobiography so conscientiously that it takes him one year to lay down the events of one day. If he is mortal he can never terminate; but if he lived forever then no part of his diary would remain unwritten, for to each day of his life a year devoted to that day’s description would correspond.
IMSLP stands for International Music Score Library Project. The logo is a capital letter A, taken from the very first press-printed book of polyphonic music, theHarmonice Musices Odhecaton, published in 1501. Its printer, Ottaviano Petrucci, is this library’s namesake.
Penn tablets by period:
Late Uruk (ca. 3400-3000 BC)
Proto-Elamite (ca. 3100-2900 BC)
Early Dynastic I-II (ca. 2900-2700 BC)
Early Dynastic IIIa (ca. 2600 BC)
Early Dynastic IIIb (ca. 2500-2350 BC)
Old Akkadian (ca. 2350-2200 BC)
Lagash II (ca. 2200-2100 BC)
Ur III period (ca. 2100-2000 BC)
Old Assyrian (ca. 2000-1900 BC)
Early Old Babylonian (ca. 2000-1800 BC)
Old Babylonian (ca. 1800-1600 BC)
Middle Babylonian (ca. 1500-1000 BC)
Middle Assyrian (ca. 1500-1000 BC)
Neo-Assyrian (ca. 1000-600 BC)
Neo-Babylonian (ca. 1000-540 BC)
Achaemenid (ca. 540-330 BC)
Hellenistic (ca. 330-140 BC)
Penn tablets by provenience (only major sites):
Penn tablets by text genre:
The tablet to the right (CBS 16106) contains on the top surface the impression of a diorite brick stamp said, in the neo-Assyrian inscription on the reverse surface, to have been found by a scribe in Naram-Sin’s palace in Agade, the capital of the Old Akkadian empire (ca. 2300 and 700 BC, respectively). The lower image offers a mirrored representation of the original stamp, in the orientation in which it would have been read in lines from top to bottom, and from right to left (click image to be directed to the text’s corresponding CDLI page).
via cdli – penn museum.
Vasilenko now lives in Hackney and works as a freelancer photographer.
“It originally didn’t have a name, but people began to call it A girl and a dog”, he told The Register.
At first he was flattered to be included alongside one of the greats.
“I like Cartier-Bresson. But when I saw how many times it’s been reposted, and credited to him, I was less happy.”
Here’s a tutorial on how to capture an exploding water balloon in the precise moment the balloon pops, while the water still holds the shape of a balloon.