Problem: The first PCBs used through-hole technology, mounting electronic components by leads inserted through holes on one side of the board and soldered onto copper traces on the other side. Boards may be single-sided, with an unplated component side, or more compact double-sided boards, with components soldered on both sides. Horizontal installation of through-hole parts with two axial leads (such as resistors, capacitors, and diodes) is done by bending the leads 90 degrees in the same direction, inserting the part in the board (often bending leads located on the back of the board in opposite directions to improve the part's mechanical strength), soldering the leads, and trimming off the ends. Leads may be soldered either manually or by a wave soldering machine.
What is improved by bending leads in opposite directions on the back of double-sided PCBs?
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Answer: mechanical strength


Problem: Cork was originally a monastic settlement, reputedly founded by Saint Finbarr in the 6th century. Cork achieved an urban character at some point between 915 and 922 when Norseman (Viking) settlers founded a trading port. It has been proposed that, like Dublin, Cork was an important trading centre in the global Scandinavian trade network. The ecclesiastical settlement continued alongside the Viking longphort, with the two developing a type of symbiotic relationship; the Norsemen providing otherwise unobtainable trade goods for the monastery, and perhaps also military aid.
When did Viking travelers establish a trading post in Cork?
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Answer: some point between 915 and 922


Problem: In addition to re-writing the classification of annelids and 3 previously independent phyla, the molecular phylogenetics analyses undermine the emphasis that decades of previous writings placed on the importance of segmentation in the classification of invertebrates. Polychaetes, which these analyses found to be the parent group, have completely segmented bodies, while polychaetes' echiurans and sipunculan offshoots are not segmented and pogonophores are segmented only in the rear parts of their bodies. It now seems that segmentation can appear and disappear much more easily in the course of evolution than was previously thought. The 2007 study also noted that the ladder-like nervous system, which is associated with segmentation, is less universal previously thought in both annelids and arthropods.[n 2]
What offshoots of polychaetes are unsegmented?
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Answer:
echiurans and sipunculan