Scientists have long said getting a good night's sleep is important to your health. The U.S. National Institute of Health says lack of sleep may even increase the risk of impaired brain activity, or cognitive decline(认知减退), and Alzheimer's disease.

Now, an American team of scientists reports that too much sleep might be similarly linked to such conditions.

Researchers at Washington University School of Medicine in St. Louis, Missouri, did the sleep study. Their findings were published in the September issue of the scientific publication Brain.

Dr. Brendan Lucey is director of the Washington University Sleep Medicine Center and led the research. He said, "Our study suggests that there is a middle range(区间), or ‘sweet spot,' for total sleep time" for best cognitive performance.

"Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient(不足的) sleep or poor sleep quality, " Lucey added.

Other studies have shown that lack of sleep was linked with cognitive decline. A small 2018 study published in the Proceedings of the National Academy of Sciences found that losing just one night of sleep led to an increase in beta-amyloid production. Beta-amyloid is a metabolic(新陈代谢的) waste product found in between brain cells. It has been long linked to brain disorders, such as Alzheimer's disease.

The National Sleep Foundation advises that healthy adults need between seven and nine hours of sleep per night. Babies, young children, and teens need even more sleep for their growth and development. And people over 65 should also get seven to eight hours per night, the foundation says.

One unanswered question from the Washington University study is whether increasing sleep time for short sleepers would help their cognitive performance.

But lead writer Lucey said each person's sleep needs are individual. If people feel rested, there is no need to change how they sleep. But those who are not sleeping well should know that sleep problems often can be treated, Lucey said.

Dr. David Holtzman, another top researcher on the study, added, "It suggests that sleep quality may be key, as opposed to simply total sleep."

Active noise control technology is used by noise-canceling headphones to minimize or completely block out outside noise. However, despite the many advancements in technology, people still don't have much control over which sounds their headphones block out and which they let pass.

Now, deep learning algorithms (算法) have been developed by a group of academics at the University of Washington that enable users to select which noises to filter (过滤) through their headphones in real-time. The system has been named “semantic hearing” by its creators.

The AI-powered headphones remove all background noise by streaming recorded audio (音频) to a smartphone that is linked to the devices. Through this process, the headphone users can choose to strengthen or cancel out 20 types of sounds, using voice commands or a smartphone app. The headphones will then only let through the sounds that have been chosen by the wearer.

“The challenge is that the sounds headphone wearers hear need to syn (同步) with their visual senses. This means the neural (神经的) algorithms must process sounds in under a hundredth of a second.” said senior author Shyam Gollakota, a UW professor.

Due to this time constraint, the semantic hearing system chooses a process that relies on noises communicated on a device like a linked smartphone. Furthermore, in order for humans to continue to effectively experience sounds in their environment, the system needs to maintain these delays because sounds coming from different directions enter people's ears at different times.

Trials were undertaken by the researchers in a variety of settings. The semantic hearing system was able to isolate target sounds, while at the same time removing background noise. In terms of the system's audio output for the desired sounds. 22 participants gave it an average rating higher than they assigned to the original noise recordings.

There were, however, a few disadvantages: the AI-powered system occasionally had trouble recognizing sounds that were too similar. The researchers said that the system could produce better results if its machine learning models were trained on more real world data.

But is renting fashion actually more environmentally-friendly than buying it? And if so, how much more? Journalist and author Elizabeth Cline researched this question in a feature article for Elle, and she concluded that it's not as sustainable as it seems.

Take shipping for example, which has to go two ways if an item is rented — receiving and returning. Cline writes that consumer transportation has the second largest carbon footprint of our collective fashion habit after manufacturing.

Lastly, Cline fears that renting services will increase our appetite for fast fashion, simply because it's so easily accessible. There's something called "share-washing" that makes people have more wasteful behaviors because a product or service is shared and thus is considered more eco-friendly. Uber is one example of this: advertised as a way to share rides and reduce car ownership, and yet it has been proven to discourage walking, bicycling and public transportation use.

Renting clothes is still preferable to buying them cheap and throwing them into the bin after wearing them a few times, but we shouldn't let the availability of these services make us self-satisfied. There's an even better step — and that's wearing what we already have.