If you will be cycling, you will need to know what these traffic signs and signals mean.

    A sign like this one means that there is a bike lane（道）. If there is a bike lane, you are required to use it. If there is not a bike lane, you should ride with traffic as far to the right side of the road as possible.

    When the signal light turns green, cars go. When you cross the street at a signal light, you should wait for the walk signal. Be sure to look carefully to the left, right and left again, before crossing the street.

    When the signal light turns yellow, car drivers should slow down and prepare to stop. You should not cross if the light is yellow. The light is about to turn red, and cars will enter the intersection(十字路口).

    This signal is the WALK sign. It has a picture of a person walking instead of using the word WALK.

    This signal is the DON'T WALK sign. It is part of the signal with the picture of a person walking. This is a picture of a red hand, meaning you should stop. You should wait to cross the street until the green picture of the person walking is showing.

    Car drivers and bikers must come to a complete stop at STOP signs.

    A yield sign means to slow down and be ready to stop. If there are pedestrians（行人）or vehicles in or nearing the intersection, you must stop. If there is no traffic in or nearing the intersection and it is safe, you may go through.

    This sign means you are coming to a crosswalk. Car drivers and bikers must stop to allow people in the crosswalk to cross the street.

    Dreams can be familiar and strange, fantastical or boring, but some dreams might be connected to the mental processes that help us learn. In a recent study, scientists found a connection between nap time dreams and better memory in people who were learning a new skill.

    In the study, 99 college students between the ages of 18 and 30 each spent an hour on a computer, trying to get through a virtual maze (逃宫). The maze was difficult, and the study participants had to start in a different place each time they tried, making it even more difficult. They were also told to find a particular picture of a tree and remember where it was.

    For the first 90 minutes of a five - hour break, half of the participants stayed awake and half were told to take a short nap. Participants who stayed awake were asked to describe their thoughts. Participants who took a nap were asked about their dreams after sleep and they were awakened within a minute of sleep to describe their dreams.

    Stickgold, a neuroscientist, wanted to know what people were dreaming about when their eyes weren't moving during sleep.Four of the 50 people who slept said their dreams were connected to the maze. Some dreamed about the music that had been playing when they were working; others said they dreamed about seeing people in the maze. When these four people tried the computer maze again, they were able to find the tree faster than before their naps.

    Stickgold suggests the dream itself doesn't' help a person learn, it's the other way around. He suspects that the dream was caused by the brain processes associated with learning.

    All four of the people who dreamed about the task had done poorly the first time,which makes Stickgold wonder if the dreams show up when a person finds a new task particularly difficult. People who had other dreams, or people who didn't' take a nap, didn't show the same improvement.

    If you're new to San Francisco, paying the city a visit, or simply looking for a new playground for you and your dog, here are four of the finest dog parks in San Francisco.

    Corona Heights Dog Park

    Often visited by residents from all over the city because of its nearness to the Randall Museum, Corona Heights Dog Park offers pets and owners breathtaking view after a steep hillside climb, and a fenced dog area that allows dogs to let loose without a leash（狗链）. Owners will also enjoy the playground, tennis courts and basketball courts.

    Dolores Dog Park

    The grounds of Dolores Park once served as camps for those who were left homeless by the 1906 earthquake, but now are often visited by crowds of Mission District people. Four-legged friends can also wander about carefree off-leash while making friends with other members of the doggie community.

    Pine Lake Dog Park

    Famous for its place as a rest stop for hundreds of species of birds to fly to and from warmer climates, Pine Lake Park is also prized by city dogs and their owners for their nice hiking paths, picturesque lake suited for swimming, and off-leash area on the park's west end that lets dogs run free.

    Buena Vista Dog Park

    With a history of 146 years, Buena Vista Park is San Francisco's oldest park. Dogs and owners with plus energy will love burning it on this park's steep paths and winding staircases. Dog owners should have good control over their dogs, as it's quite easy for dogs to get separated when going through Buena Vista's many twists and turns.

    In recent decades, social isolation has been recognized as a major risk to our health and long life. It's twice as bad for you as being overweight and nearly as bad as smoking. The rising number of people who say they are affected, across a wide range of ages, is shocking. In reality, you can suffer the ill effects of loneliness even if you are not socially isolated.

Comedian Robin Williams made a striking observation in 2014: "I used to think the worst thing in life was to end up all alone. It's not. The worst thing in life is to end up with people who make you feel all alone." Tracking large groups over time indicates that perceived（感知的）social isolation carries its own risk for morbidity（发病率）and mortality.

    The perception of isolation—from others of being in the social aspect-is not only a cause of unhappiness, it also signals danger. Fish have evolved to swim to the middle of their group when predators（捕食者）approach, mice housed in social isolation show sleep disruptions and reduced slow-wave sleep and prairie voles（田鼠）isolated from their partners then placed in an open field explore their surroundings less and concentrate on avoiding predators.

    These behaviours reflect an increased emphasis on self-preservation in the social aspect. For instance, fish on the edge of a school are more likely to be attacked by predators because they are easier to isolate and prey upon. Such observations reflect a more general principle that perceived social isolation in social animals activates neural（神经系统的）, neuroendocrine（神经内分泌的）and behavioural responses that promote short-term self-preservation. However, these responses bring a cost for long-term health and well-being.

    The range of harmful neural and behavioural effects of perceived isolation documented in adults include increased anxiety, hostility and social withdrawal; fragmented sleep and daytime tiredness; increased vascular resistance and changed gene expression and immunity; decreased impulse control; increased negativity and depressive symptoms; and increased age-related cognitive decline.

    Sadly, to date, attempts to reduce loneliness have met with limited success. A series of randomized controlled trials showed that they had only a small effect. Among the four types of interventions（介入）examined, talking therapy that focused on inappropriate thought processes had the largest impact. Social skills training, social support and increased opportunities for social contact were much less effective.

    Spring is coming, and it is time for those about to graduate to look for jobs. Competition is tough, so job seekers must carefully consider their personal choices. Whatever we are wearing, our family and friends may accept us, but the workplace may not.

    A high school newspaper editor said it is unfair for companies to discourage visible tattoos (纹身)，nose rings, or certain dress styles. It is true you can't judge a book by its cover, yet people do "cover" themselves in order to convey certain messages. What we wear, including tattoos and nose rings, is an expression of who we are. Just as people convey messages about themselves with their appearances, so do companies. Dress standards exist in the business world for a number of reasons, but the main concern is often about what customers accept.

    Others may say how to dress is a matter of personal freedom, but for businesses it is more about whether to make or lose money. Most employers do care about the personal appearances of their employees, because those people represent the companies to their customers.

    As a hiring manager I am paid to choose the people who would make the best impression on our customers. There are plenty of well-qualified candidates, so it is not wrong to reject someone who might disappoint my customers. Even though I am open-minded, I can't expect all our customers are.

    There is nobody to blame but yourself if your set of choices does not match that of your preferred employer. No company should have to change to satisfy a candidate simply because he or she is unwilling to respect its standards, as long as its standards are legal.

Sagrada Familia (2,056,448 visits/year)

Opening hours: 09:00—18:00 (October—March); 09:00—20:00 (April—September) Admission: $ 11, or $ 10 with the Barcelona Card.

Disabled Access: Yes.

The temple has been under construction since 1882 and they've still got another 30 to 80 years to go before it is finished. The project's vast scale and its special design have made it one of Barcelona's top tourist attractions for many years.

La Pedrera (1,133,220 visits/year)

Opening hours: November—February: 09:00—18:30; March—October: 09:00—20:00

Admission: $ 9.50. Save 20% with the Barcelona Card.

Disabled Access: No.

This building used to be called Casa Mila but nowadays it's more commonly known as La Pedrera. It is a unique modernist building in Barcelona and was made of bricks and had colorful tiles (瓦). It was built between 1906 and 1912 by famous Catalan architect Antoni Gaudi (1852—1926) and in 1984 it was declared a UNESCO World Her it age site with other Gaudi buildings in Barcelona.

Barcelona FC Museum (1,032,763 visits/year)

Opening hours: 6th April—4th October: (Monday to Saturday) 10:00—20:00; the rest of the year: 10:00—18:30

Admission: $ 8.50 for entry to the museum and $ 17 for a guided tour.

Disabled Access: Yes.

When you buy your ticket you have two options. You can buy a ticket for the museum to see the football stadium or you can buy a dual (双的) ticket for $ 15 where you get to see the museum and the scenes at the club.

Miro Museum (518,869 visits/year)

Opening hours: Check the website for details as they vary relying on the time of the year. Admission: $ 8. Save 20% with the Barcelona Card.

Disabled Access: Yes.

This museum has a wide range of Miro's works dating back as far as 1914. This art work collection not only includes his paintings but also a good selection of sculptures.