I was having a great morning until I sat down in front of my office computer. “Your password has expired(过期),” a server message flashed on my screen, with instructions for changing it.

Coming up with a new code doesn't seem like a big deal, unless you work at my company, where we have to change it monthly, using at least one uppercase character, one lowercase character, one symbol, and one numeral. Oh, and the whole damn thing can’t be fewer than eight characters. And I can't use any of the same passwords I’ve used in the past three months.

Suddenly I was furious. What didn’t make it any better was that I was deeply depressed after my recent divorce. Disbelief over what she had done to me was all I thought about. Every day.

My anger didn’t mean anything to the empty input field with a pulsating cursor (闪动的光标), waiting for me to type a password that I’d have to re-enter — many times — for the next 30 days. I remembered a tip I’d heard from my former boss. He’d said, “ I’m going to use a password to change my life.”

I couldn’t focus on getting things done in my current mood. There were clear indicators（指示信号） of what I needed to do to regain control of my life, but I couldn't notice them.

My password became the indicator. My password reminded me that I shouldn’t let myself be a victim of my recent breakup and that I was strong enough to do something about it.

I made my password Forgive@h3r. I had to type this statement several times a day. Each time my computer would lock. Each time my screen saver with her photo would appear. Each time I would come back from eating lunch alone. In my mind, I wrote Forgive her every day.

The simple action changed the way I looked at my ex-wife. That constant reminder of reconciliation led me to accept the way things had happened at the end of my marriage and embrace a new way of dealing with my depression. As the month wore on, I felt a slow healing begin to take place. By the time my server prompted me to reset my password the following month, I felt free.

One month later, my dear Exchange server asked me yet again to reset my password. I thought about the next thing that I had to get done. My password became Quit@smoking4ever.

I quit smoking overnight. This password was a painful one to type during that month, but doing it helped me to yell at myself in my mind as I typed that statement. It motivated me to follow my monthly goal.

One month later, my password became Save4trip@thailand.

Guess where I went three months later: Thailand.

Seeing how these reminders helped to materialize my goals kept me motivated and excited. While it’s sometimes difficult to come up with your next goal, keeping at it brings great results.

Here is a simplified extract（摘录）of what some of my passwords have been in the past two years, so you get an idea of how my life has changed, thanks to this method:

Forgive@h3r To my ex-wife, who started it all.

Quit@smoking4ever It worked.

Save4trip@thailand It worked.

Sleep@before12 It worked.

Ask@her4date It worked. I fell in love again.

No@drinking2months It worked. I feel better.

Get@c4t! It worked. I have a beautiful cat.

Facetime2mom@sunday It worked. I talk with Mom every week.

And the one for last month: Save4@ring Yep. Life is gonna change again soon.

Most of the world’s potable water—freshwater suitable for drinking is accounted for by groundwater, which is stored in the pores and fractures in rocks. There is more than 50 times as much freshwater stored underground than in all the freshwater rivers and lakes at the surface. Nearly 50 percent of all groundwater is stored in the upper 1,000 meters of Earth. At greater depths within Earth, the pressure of the overlying rock causes pores and cracks to close, reducing the space that pore water can occupy, and almost complete closure occurs at a depth of about 10 kilometers. The greatest water storage, therefore, lies near the surface.

Aquifers, Porosity and Permeability. Groundwater is stored in a variety of rock types. A groundwater reservoir from which water can be extracted is called an aquifer. We can effectively think of an aquifer as a deposit of water. Extraction of water depends on two properties of the aquifer: porosity and permeability. Between sediment grains are spaces that can be filled with water. This pore space is known as porosity and is expressed as a percentage of the total rock volume. Porosity is important for water—storage capacity, but for water to flow through rocks, the pore spaces must be connected. The ability of water, or other fluids, to flow through the interconnected pore spaces in rocks is termed permeability. In the intergranular spaces of rocks, however, fluid must flow around and between grains in a tortuous path; this winding path causes a resistance to flow. The rate at which the flowing water overcomes this resistance is related to the permeability of rock.

Sediment sorting and compaction influence permeability and porosity. The more poorly sorted or the more tightly compacted a sediment is, the lower its porosity and permeability. Sedimentary rocks—the most common rock type near the surface—are also the most common reservoirs for water because they contain the most space that can be filled with water. Sandstones generally make good aquifers, while finer-grained mudstones are typically impermeable. Impermeable rocks are referred to as aquicludes. Igneous and metamorphic rocks are more compact, commonly crystalline, and rarely contain spaces between grains. However, even igneous and metamorphic rocks may act as groundwater reservoirs if extensive fracturing occurs in such rocks and if the fracture system is interconnected.

The outstanding biography — from the same author who brought us Steve Jobs and Einstein — portrays the life of the complicated Renaissance (文艺复兴时期的) artist with details. We come to see da Vinci as not only an inventor of musical instruments and early flying machines, but also a notebook keeper and vegetarian (素食者), who had trouble finishing many of the projects and paintings he started.

Yet what is most thrilling is getting to know da Vinci the scientist. Isaacson explains how loving science and applying the scientific method to observing the world was really what made da Vinci a great artist and, Isaacson argues, a genius.

Da Vinci was fascinated with observing and understanding phenomena in nature, from the proportions of the human body to how the muscles of the lips moved. He wanted to know about everything around him, in minute detail, Isaacson writes. He wondered about questions “most people over the age of ten no longer puzzle about”— for instance, how the tongue of a woodpecker works.

To learn about the world, da Vinci combined his own observations with experimentation. Never formally schooled, “he preferred to induce from experiments rather than deduce from theoretical principles,” Isaacson explains. He recorded his observations, looked for patterns among them, and then tested those patterns through additional observation and experimentation.

“When he became fascinated with the idea that he could invent flying machines, three and a half centuries before the Wright brothers flew the first airplane, he observed various birds and filled notebooks with the function and speed at which their wings flapped. That’s why lsaacson calls da Vinci an exemplar of this scientific method.” He goes on: “Galileo, born 112 years after Leonardo, is usually credited with being the first to develop this kind of approach and is often regarded as the father of modern science,” the historian Fritjof Capra wrote. “There can be no doubt that this honor would have been bestowed (赐予) on Leonardo da Vinci had he published his scientific writings during his lifetime, or had his notebooks been widely studied soon after his death.”

Da Vinci’s emphasis on empirical observation also helped him improve his art. First, he was able to use what he learned from looking at nature to paint and draw. His studies of the body, animals, motion, shadow and light, perspective and proportion helped him better understand what he was seeing in front of him, and render it in art more accurately and finely than anyone else of his time. He also used his observations of nature to make connections among phenomena. A recorder (竖笛) was like a larynx (喉管) in the throat. Here’s Isaacson again: What Leonardo probably began as four distinct elements ended up woven together in a way that illustrates a fundamental theme in his art and science: the interconnectedness of nature, the unity of its patterns, and the similarity between the workings of the human body and those of the earth.

Most importantly, his curiosity-driven explorations, and ability to connect art and science, helped him innovate in his work. They helped him think differently, Isaacson argues. Da Vinci made surprisingly diverse series of discoveries, including conceptualizing the helicopter and solar power and advancing knowledge about everything from the reproductive organs to botany. This genius is also what drew lsaacson to Albert Einstein and Steve Jobs as subjects: They’re all innovators who were inspired by and drew connections between art and science.

“Leonardo da Vinci is the ultimate example of the main theme of my previous biographies: how the ability to make connections across disciplines — arts and sciences, humanities and technology — is a key to innovation, imagination, and genius,” Isaacson writes. And this wonderful book is a reminder, in a time of increasingly narrow specialization and focus, that the methods of Renaissance men like da Vinci are as relevant as ever.

As time went on, Philip’s deformity was accepted like one boy’s red hair and another’s unreasonable obesity. But meanwhile he had grown horribly sensitive. He never ran if he could help it, because he knew it made his limp more noticeable. He stood still as much as he could, with his badly shaped foot behind the other. Because he could not join in the games which other boys played, their life remained strange to him; sometimes they seemed to think that it was his fault if he could not play football, and he was unable to make them understand. He was left a good deal to himself. He had been inclined to talkativeness, but gradually he became silent.

The biggest boy in his dormitory, Singer, took a dislike to him, and Philip, small for his age, had to put up with a good deal of hard treatment. About half-way through the term there was a game called Nibs. It was a game for two, played on a table or a form with steel pens. Soon nothing was seen but boys playing this game, and the more skilful acquired vast stores of nibs. But in a little while Mr. Watson made up his mind that it was a form of gambling, and forbade the game. Then he ordered all the nibs in the boys’ possession be handed in. Philip had been very skilful, and it was with a heavy heart that he gave up his winning; but his fingers itched to play still, and a few days later, on his way to the football field, he went into a shop and bought a pennyworth of J pens. He carried them loose in his pocket and enjoyed feeling them. Presently Singer found out that he had them. Singer had given up his nibs too, but he had kept back a very large one, called a Jumbo, which was almost unconquerable, and he could not resist the opportunity of getting Philip's Js out of him. Though Philip knew that he was at a disadvantage with his small nibs, he had an adventurous disposition and was willing to take the risk; besides, he was aware that Singer would not allow him to refuse. He had not played for a week and sat down to the game now with a thrill of excitement. He lost two of his small nibs quickly, and Singer was jubilant, but the third time by some chance the Jumbo slipped round and Philip was able to push his J across it. He crowed with triumph. At that moment Mr. Watson came in.

“What are you doing?” he asked.

He looked from Singer to Philip, but neither answered.

“Don’t you know that I’ve forbidden you to play that game?”

Philip’s heart beat fast. He knew what was coming and was dreadfully frightened, but in his fright there was a certain exultation. He had never been swished. Of course it would hurt, but it was something to boast about afterwards.

“Come into my study.”

The headmaster turned, and they followed him side by side. Singer whispered to Philip:

“We’re in for it.”

Mr. Watson pointed to Singer.

“Bend over,” he said.

Philip, very white, saw the boy quiver at each stroke, and after the third he heard him cry out. Three more followed.

“That’ll do. Get up.”

Singer stood up. The tears were streaming down his face. Philip stepped forward. Mr. Watson looked at him for a moment.

“I’m not going to beat you. You’re a new boy. And I can’t hit a cripple. Go away, both of you, and don’t be naughty again.”

When they got back into the school-room a group of boys, were waiting for them. They set upon Singer at once with eager questions. But he did not answer. He was angry because he had been hurt.

“Don’t ask me to play Nibs with you again,'” he said to Philip. “It’s jolly nice for you. You don’t risk anything.”

“I didn’t ask you.”

“Didn’t you!”

He quickly put out his foot and tripped Philip up. Philip was always rather unsteady on his feet, and he fell heavily to the ground.

“Cripple,” said Singer.

For the rest of the term he tormented Philip cruelly, and, though Philip tried to keep out of his way, the school was so small that it was impossible; he tried being friendly and jolly with him; he abased himself, so far as to buy him a knife; but though Singer took the knife he was not placated. Once or twice, driven beyond endurance, he hit and kicked the bigger boy, but Singer was so much stronger that Philip was helpless, and he was always forced after more or less torture to beg his pardon. It was that which rankled with Philip: he could not bear the humiliation of apologies, which were wrung from him by pain greater than he could bear. And what made it worse was that there seemed no end to his wretchedness; Singer was only eleven and would not go to the upper school till he was thirteen. Philip realized that he must live two years with a tormentor from whom there was no escape. He was only happy while he was studying and when he got into bed. And often there recurred to him then that queer feeling that his life with all its misery was nothing but a dream, and that he would awake in the morning in his own little bed in London.

The first organized system for sending messages began in Egypt around 1500 B.C. This system developed because the pharaohs frequently needed to send messages up and down the Nile River in order to keep their empire running smoothly. Later, the Persians developed a more efficient system for sending messages using men and horses. Messages carriers rode along the road system stretching from one end of the Persian Empire to the other. Along these roads, fresh men and horses waited at special stations to take and pass along any messages that needed to be sent. The stations where riders passed messages back and forth were built 23 kilometers apart, so the men and horses were able to travel quickly between them. The Romans later took up his idea and improved it by using a more advanced and extensive road system.

In China, however, Kublai Khan had built up his own system for delivering messages. This system worked in the same basic way as the Roman system. The difference was that Kublai Khan kept 300,000 horses along the roads of this delivery lines. There were over 10,000 stations where a message would be passed from one rider to another with a fresh horse. In this way, Kublai Khan could receive messages from anywhere in the country in only a few days.

It was not until the 1500s that a well-organized postal system appeared again in Europe. One family, the von Taxis family, gained the right to deliver mail for the Holy Roman Empire and parts of Spain. This family continued to carry mail, both government and private, throughout Europe for almost 300 years.

In 1653, a Frenchman, Renouard de Velayer, established a system for delivering post in Paris. Postal charges at that time were paid by the recipient , but de Velayer's system was unique by allowing the sender to pre-pay the charges, in a similar way to the modern stamp. Unfortunately, de Velayer's system came to an end when jealous competitors put live mice in his letter boxes, ruining his business. Eventually, government-controlled postal systems took over from private postal businesses, and by the 1700s government ownership of most postal systems in Europe was an accepted fact of life.

The thing that all these early systems had in common was that they were quite expensive for public use, and were intended for use by the government and the wealthy. However, in 1840, a British schoolteacher named Roland Hill suggested introducing postage stamps, and a postal rate based on weight. This resulted in lowering postal rates, encouraging more people to use the system to stay in touch with each other, His idea helped the British postal system begin to earn profits as early as 1850. Soon after that many other countries took up Mr. Hill's idea. And letter writing became accessible to anyone who could write. Today, the Roland Hill awards are given each year to "encourage and reward fresh ideas which help promote philately"     (stamp collecting).