已知复数$z=\frac{2i}{1+i}$，$z$的共轭复数为则$\stackrel{-}{z}$，则$z·\stackrel{-}{z}=$（   ）

    杜景俭，冀州武邑人也。少举明经，累除殿中侍御史。出为益州录事参军。时隆州司马房嗣业除益州司马，除书未到，即欲视事，又鞭笞僚吏，将以示威。景俭谓曰：“公虽受命为此州司马，而州司未受命也。何藉数日之禄，而不待九重之旨，即欲视事，不亦急耶?”嗣业益怒。景俭又曰：“公今持咫尺之制，真伪未知，即欲揽一州之权，谁敢相保?扬州之祸，非此类耶。”乃叱左右各令罢散，嗣业惭赧而止。俄有制除嗣业荆州司马，竟不如志，人吏为之语曰：“录事意，与天通，益州司马折威风。”景俭由是稍知名。入为司宾主簿，转司刑丞。

    天授中，与徐有功、来俊臣、侯思止专理制狱，时人称云：“遏徐、杜者必生，遇采、侯者必死。”累迁洛州司马。寻转凤阁侍郎、同凤阁鸾台平章事。则天尝以季秋内出梨花一枝示宰臣曰：“是何祥也?”诸宰臣曰：“陛下德及草木，故能秋木再花，虽周文德及行苇，无以过也。”景俭独曰：“谨按《洪范五行传》：‘阴阳不相夺伦，渎之即为灾。’又《春秋》云：‘冬无愆阳，夏无伏阴，春无凄风，秋无苦雨。’今已秋矣，草木黄落，而忽生此花，渎阴阳也。臣虑陛下布教施令，有亏礼典。又臣等忝为宰臣，助天理物，理而不和，臣之罪也。”于是再拜谢罪，则天曰：“卿真宰相也!”

    延载初，为凤阁侍郎周允元奏景俭党于李昭德，左迁秦州刺史。后累除司刑卿。圣历二年，复拜凤阁侍郎、同凤阁鸾台平章事。时契丹入寇，河北诸州多陷贼中。及事定，河内王武懿宗将尽论其罪。景俭以为皆是驱逼非其本心请悉原之则天竟从景俭议岁馀转秋官尚书坐漏泄禁中语左授司刑少卿出为并州长史。道病率，赠相州刺史。

如图所示的电路中，电源电压恒为6V，R 为10Ω，滑动变阻器R₀最大电阻为50Ω，当滑动变阻器的滑片P 由a端滑到b端，电压表示数的变化是 （）
 

    Albert Hofmann was a Swiss Scientist who was fascinated by nature. This led him to a career in chemistry in which he sought answers to his uncertainties. He worked at Sandoz Laboratories where he nurtured his research work, and there he made a lot of success by working with various plants and changing them into something useful. He became famous when he became the first person to produce lysergic acid diethylamide (LSD) (迷幻药). In addition, he was also the first person to taste it and learn about its hallucinogenic (勾起幻觉的) effects. He was deeply connected to the nature and argued that LSD, besides being useful for psychiatry(精神病学), could also be used to promote awareness of mankind's place in nature. However, he was disappointed that his discovery was being carelessly used as a drug for entertainment. Because of his discovery, LSD fans have fondly called him “The father of LSD”. Besides carrying out his scientific experiments, he also authored numerous books and more than 100 scientific articles. In 2007, he featured in a list of the 100 greatest living geniuses(天才), published by The Telegraph Newspaper.

Childhood & Early Life

    Albert Hofmann was born in Baden, Switzerland, on January 11, 1906. He was the eldest of four children. His father was a poor toolmaker in a factory and they lived in a rented apartment. He spent much of his childhood outdoors, and grew up with a very deep connection with nature.

    He had mind-blowing experiences in childhood, wherein nature was changed in magical ways that he didn't understand. These experiences caused questions in his mind, and chemistry was the scientific field which allowed him to understand them.

    He studied chemistry at Zurich University, and his main interest is the chemistry of plants and animals. At 23, he earned his Ph. D with honors.