However wealthy we may be, we can never find enough hours in the day to do everything we want. Economics deals with this problem through the concept of opportunity cost, which simply refers to whether someone's time or money could be better spent on something else.

    Every hour of our time has a value. For every hour we work at one job we could quite easily be doing another, or be sleeping or watching a film. Each of these options has a different opportunity cost—namely, what they cost us in missed opportunities.

    Say you intend to watch a football match but the tickets are expensive and it will take you a couple of hours to get to and from the stadium. Why not, you might reason, watch the game from home and use the leftover money and time to have dinner with friends? This—the alternative use of your cash and time—is the opportunity cost.

    For economists, every decision is made by knowledge of what one must forgo—in terms of money and enjoyment—in order to take it up. By knowing precisely what you are receiving and what you are missing out on, you ought to be able to make better-informed, more reasonable decisions. Consider that most famous economic rule of all: there's no such thing as a free lunch. Even if someone offers to take you out to lunch for free, the time you will spend in the restaurant still costs you something in terms of forgone opportunities.

    Some people find the idea of opportunity cost extremely discouraging: imagine spending your entire life calculating whether your time would be better spent elsewhere doing something more profitable or enjoyable. Yet, in a sense it's human nature to do precisely that—we assess the advantages and disadvantages of decisions all the time.

    In the business world, a popular phrase is “value for money.” People want their cash to go as far as possible. However, another is fast obtaining an advantage: “value for time.” The biggest restriction on our resources is the number of hours we can devote to something, so we look to maximize the return we get on our investment of time. By reading this passage you are giving over a bit of your time which could be spent doing other activities, such as sleeping and eating. In return, however, this passage will help you to think like an economist, closely considering the opportunity cost of each of your decisions.

    You're happy to let your best friend borrow your mountain bike, but would you be willing to loan it out to a total stranger if you could make some money from the arrangement?

    That's the idea behind peer-to-peer (P2P) renting, a new model concluded by sites such as eBay and Craigslist. Instead of selling an idle (闲置) thing, you loan it to people in your town, get paid a small rental fee and gel it back when the borrower's done with it. In the past few years, almost a dozen websites have popped up promising to connect lenders and borrowers. For example, you can use GetAround to rent out your car or motorcycle, SnapGoods to rent out electronics and gadgets, ToolSpinner to rent electric drills and lawnmowers, Zaarly and Knb to rent out a little bit of everything else.

    Old as it may sound, P2P renting is more high-tech than before, with websites that avoid cash for credit cards. A user creates an online listing for the item she wants to rent out, choosing her own rental fee. When someone wants the item, he keeps it on an online calendar, and the two arrange a time and place for pickup. Each site operates a little differently, but all use technology to make renting easy, safe and relatively inexpensive.

    Why rent your idle things? You may not make a ton of money, but it is a good way to get some use out of idle things. The people who rent those goods are able to save thousands of dollars by renting instead of buying new.

    There may be other benefits. "It brings convenience, security and adventure," says Ali Hart, JustSharclt's spokesperson. “But, more importantly, we're really connecting people and building community, too."

    Get to know your neighbors and make a few dollars in the process? Sounds like a good deal.

    Here's an idea whose time has come: A flu shot that doesn't require an actual shot.

    For the first time, researchers have tested a flu vaccine patch (疫苗贴) in a human clinical trial and found that it delivered as much protection as a traditional injection with a needle. Doctors and public health experts have high hopes that it will increase the number of people who get immunized (免疫的) against the flu.

    Seasonal flu is responsible for up to half a million deaths around the world each year according to the World Health Organization. A team led by Georgia Tech engineer Mark Prausnitz has come up with an alternative method that uses “microneedles”. These tiny needles are so small that 100 of them, arranged in order on a patch, can fit under your thumb (拇指).Yet they're big enough to hold vaccine for three types of flu.

    None of the study volunteers had serious side effects. The groups that got patches had mild skin reactions that were not seen in the regular needle group, while the volunteers in the regular needle group were more likely to experience pain. Overall, 70 percent of the volunteers who got vaccine patches said they'd rather use them again than get a traditional flu shot. The study authors declared it a success on all fronts.

    The biggest beneficiaries could be people in low- and middle-income countries, where flu vaccines are hard to come by. Reducing pain is nice, but other benefits—the patch costs less，is easier to transport, doesn't require refrigeration, can be self - administered and doesn't cause waste of needles—are even better.

    “Microneedle Patches have the potential to become ideal candidates for vaccination programs,” wrote Katja Hoschler and Maria Zambon of Public Health England.

    I was in the middle of coding a web page when my wife emailed me these questions: Ever wonder what it would be like to have the face, the brains, the personality and the body? What it would be like to have everyone stop when you walk in a room? What it would be like to be able to get anything or anyone you want? I stopped for a moment and thought about it because my wife wouldn't email me this unless something had driven her to do so. I emailed her back with what I thought was a pretty good answer. Here is what I wrote her back.

    Yes, I had thought many times about what it would be like to be one of the beautiful people. To be able to take your breath away when I walked into a room, or to be the life of the party and have everyone fawning (奉承) over me as I wore only the finest clothes and sported the perfect body? But then I always came back to the realization that a lifestyle like that is so fragile. As you get older, your body changes; as you get older, the money changes. Your body never looks the same, the clothes become more and more expensive to maintain. And once you have crossed the line, suddenly you are out. The next fresh face comes in and you are quickly forgotten.

    All through growing up I was never an attractive person. I was overweight and picked on. But that didn't stop me from being a nice person — a good, clean, funny and helpful person. I was the person who you came to when you needed a friend after a breakup. I was the one you came to when you needed a joke to brighten up your day. And in the long run, I will be the one you remember, not the new face, or the fresh style.

    In closing, I would like to say that we, as a people, have developed into looking (or things that are bigger and better instead of what will last. I don't know about you, but I will remember the friend who helped me when I was down, more than the hot girl I just saw walking down the street.

    I wish I could teach the world some more jokes.

    Earthquakes happen without warning(前兆). They can happen any time of a day, at any point during the year. But don't worry because most are so weak that they cannot be felt. Only a few big ones hurt people. However, it's important to know what to do when an earthquake is happening.

    Do NOT go outside. You could get injured from falling glass or parts of buildings. If you are outside, stay away from buildings and power lines (输电线).

    Stay under a desk, table, or other strong furniture. Hold on to it. Or stay in a corner of the building. Cover your face and head with your arms and cover your mouth with a towel or clothing. Stay inside until shaking stops and it is safe to go outside.

    Keep away from windows, pictures or advertisements on the wall or the building, and anything else that could fall and hurt you. Most people get injured by falling things during an earthquake, not by the shaking itself.

    Also keep away from a fire. You could fall down and burn yourself on the fire.

    If you are driving when an earthquake happens, stop the car if it's safe. Stay inside your car until the earthquake stops, and don't drive near bridges. Try not to stop by power lines or trees. These could fall and hurt you.

I was standing in the checkout line behind a woman who looked to be in her 60s. When it was her turn to pay, the cashier greeted her by name and asked her how she was doing.

The woman looked down, shook her head and said: "Not so good. My husband just lost his job. The truth is, I don't know how I'm going to get through these days." Then she gave the cashier food stamps (食品券).

My heart ached. I wanted to help but didn't know how. Should I offer to pay for her groceries, or ask for her husband's resume (简历)?

Walking into the parking lot, I spotted the woman returning her shopping cart. I remembered something in my purse that I thought could help her. It wasn't a handful of cash or an offer of a job for her husband, but maybe it would make her life better.

"Excuse me," I said, my voice trembling a bit. "I couldn't help overhearing what you said to the cashier. It sounds like you're going through a really hard time right now. I'm so sorry. I'd like to give you something."

I handed her the small card from my purse. When the woman read the two words "You Matter" on the card, she began to cry. And through her tears, she said: "You have no idea how much this means to me."

I was a little startled by her reply. Having never done anything like this before, I didn't know what kind of reaction I might receive. All I could think to say was: "Would it be OK to give you a hug?"

A few days earlier, one of my workmates gave a similar card to me as encouragement for a project I was working on. When I read the card, I felt a warm glow spread inside of me. Deeply touched, I ordered my own box of "You Matter" cards and started sharing them.