Suppose you become a leader in an organization. It's very likely that you'll want to have volunteers to help with the organization's activities. To do so, it should help to understand why people undertake volunteer work and what keeps their interest in the work.

    S Let's begin with the question of why people volunteer. Researchers have identified several factors that motivate people to get involved. For example, people volunteer to express personal values related to unselfishness, to expand their range of experiences, and to strengthen social relationships. If volunteer positions do not meet these needs, people may not wish to participate. To select volunteers, you may need to understand the motivations of the people you wish to attract.

    S People also volunteer because they are required to do so. To increase levels of community service, some schools have launched compulsory volunteer programs. Unfortunately, these programs can shift people's wish of participation from an internal factor (e.g. “I volunteer because it's important to me”) to an external factor (e.g. “I volunteer because I'm required to do so”). When that happens, people become less likely to volunteer in the future. People must be sensitive to this possibility when they make volunteer activities a must.

    S Once people begin to volunteer, what leads them to remain in their positions over time? To answer this question, researchers have conducted follow-up studies in which they track volunteers over time. For instance, one study followed 238 volunteers in Florida over a year. One of the most important factors that influenced their satisfaction as volunteers was the amount of suffering they experienced in their volunteer positions. Although this result may not surprise you, it leads to important practical advice. The researchers note that attention should be given to “training methods that would prepare volunteers for troublesome situations or provide them with strategies for coping with the problem they do experience”.

    S Another study of 302 volunteers at hospitals in Chicago focused on individual differences in the degree to which people view “volunteer” as an important social role. It was assumed that those people for whom the role of volunteer was most part of their personal identity would also be most likely to continue volunteer work. Participants indicated the degree to which the social role mattered by responding to statements such as “Volunteering in Hospital is an important part of who I am.” Consistent with the researchers' expectations, they found a positive correlation(正相关) between the strength of role identity and the length of time people continued to volunteer. These results, once again, lead to concrete advice: “Once an individual begins volunteering, continued efforts might focus on developing a volunteer role identity....Items like T-shirts that allow volunteers to be recognized publicly for their contributions can help strengthen role identity”.

    Chinese audiences seemed not to have been satisfied with the third season of the highly anticipated food documentary A Bite of China.

    Even though the series has maintained high viewership ratings since its comeback last week, much higher than other programs aired at the same time, the ranking on Douban, a social networking website featuring films, literature and events, slipped to 4.2 out of 10, as of Tuesday, compared with 9.3 and 8.4, respectively, for the first two seasons.

    Picky viewers complain that some of the narration is not accurate, while others pinpoint misleading content. At the same time, food blogger @barbara questioned whether it is appropriate to give a close-up shot of the poisonous plant Nandina（南天竺）in a food program.

    A Bite of China, which debuted in 2012, became hugely popular nationwide for its quality introduction of some rarely-known and mouth-watering domestic cuisine. In the new show, however, watchers are not satisfied with “irrelevant” food references, such as lipsticks made of Chinese traditional medicine and martial arts master.

    The first episode introduced a hand-made iron frying pan from east China's Shandong province, which prompted thousands of Chinese Internet users to buy one from China's leading e-commerce website Tmall in the next few days. Sales of the pan at “Zhensanhuan” surged 6,000 times compared with a year ago, according to Beijing Youth Daily.

    In response to overwhelming criticism and questions, A Bite of China production crew responded on Weibo that they seek innovation despite the risks following the first two phenomenal seasons.

    “It is unavoidable to make comparisons with the first two, and some audiences may not accept the changes,” the crew said. “We explore the culture and civilization behind food, and give food a historic touch. That's why we feature culinary（烹饪的）tools, feast and rituals, as well as a healthy diet to show Chinese wisdom and philosophy, which has not been shown in any food programs before.”

    Some materials are obtained from natural resources that are changed by chemical processes in a laboratory. The resulting artificial materials are synthetic, or human-made.

    Plastic is a synthetic substance, obtained from petroleum, a fossil fuel. The molecules（分子）in petroleum are split and then linked into chains. Plastic is an example of a polymer, a material made of repeating patterns of atoms linked together. Most polymers are synthetic. They are made by polymerization, the process of chemically linking many smaller molecules to form a larger molecule that has different physical features. Some polymers, such as proteins, occur naturally.

    Plastic is a key component of many products. When heated into an almost-liquid form, plastic can be made into fibers, sheets, or molds（模具）. It can be mixed with other elements to remain flexible, or it can harden into a solid. Plastic fibers can be made into clothing or carpeting. Sheets of plastic can be made into plates. Molded plastic can be sued for protective helmets or car bumpers.

    Most plastics can be reheated and remolded repeatedly. This feature makes plastic very easy to use. Polymers can be pulled into fine strings or molded into almost any kind of shape. For example, tubes of plastic can be shaped into bottles by different processes. One such process is extrusion blow-molding. Most plastics are also resistant to many chemicals that might harm other materials. This quality is the reason that so many cleaning liquids are packaged in plastic bottles.

    Plastics are good insulators that can stop electricity or heat to pass through. Look around your kitchen, and observe where plastics are used. Pot handles are sometimes made of plastic, as are cooking tools, toaster controls, and microwave cookware. Food-storage wraps and containers may be made of plastic. Take a walk outdoors, and note all the plastic items you see. Gardening tools, such as watering cans and sprayers, are often made of plastic. Swings and slides made of plastic do not become as hot as metal, so they are safer for play. Because plastics can be heated, remolded, and made into something else, they can be recycled and reused.

    It's time for those who are about to graduate to look for jobs since graduation season is drawing near. 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 (文身), 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 (传递) 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.

    Depression and suicidal thoughts have doubled in young Americans, according to a new study from the American Psychological Association.

    Likely triggers? Cell phones and social media.

    "More US adolescents and young adults in the late 2010s, vs the mid-2000s, experienced serious psychological distress, major depression and more attempted suicide (自杀)", says lead researcher Jean Twenge, professor of psychology at San Diego State University. "These trends are weak or non-existent among adults 26 years and over, suggesting a generational shift in mood disorders instead of an overall increase across all ages."

    Twenge believes this trend is partially due to the explosion of digital culture over the past decade, which may have twisted modes of social interaction enough to affect mood disorders.

    The study analyzed data from the National Survey on Drug Use and Health, which tracked drug and alcohol use and mental health issues in more than 200,000 youths aged 12 to 17 from 2005 to 2017 and almost 400,000 adults from 2008 to 2017.

    Major depression in the last 12 months increased by 52 percent in kids from 2005 to 2017 and 63 percent in young adults aged 18 to 25 from 2009 to 2017. There was also a 71 percent jump in young adults experiencing serious psychological distress in the previous 30 days from 2008 to 2017.

    So what's so different now? Twenge says research shows young people just aren't getting as much shuteye as they did in previous generations.

    Whereas older Americans might have established more stability in their lives, sleep-disrupting social stressors are likely at their peak for teens and young adults in this digital era, she says. Older adults are also less likely to let devices interfere (干预) with sleep.

    These results suggest a need for more research to understand how digital communication versus face-to-face social interaction influences mood disorders and to develop specialized interventions for younger age groups.

    Her suggestion? Put your phone down at least an hour before bedtime.