【推荐1】Scientists have suspected for more than a century that sleep improves recall of recently acquired information, and even performance on newly learned tasks. Many of the findings suggest that sleep plays an active role in revisiting waking experiences and consolidating (巩固) them into long-term memories.

But at the same time, evidence that some memories form better without sleep is leading neuro (神经) scientists to reconsider long-standing assumptions about sleep’s role in memory formation. In fact, forgetting — through weakening or loss of synapses (突触) — seems to play a key role in the process of memory consolidation, especially during sleep.

“We had better forget most of what we do in a day,” says Chiara Cirelli, a neuroscientist at the University of Wisconsin. Remembering new information requires creating new neuronal connections or strengthening existing ones, and both bring about more neuronal firing. But neuronal firing requires a lot of energy, notes Cirelli, and it simply isn’t sustainable to keep increasing levels of neural activity day after day. Eventually, synapses couldn’t get any stronger, and the brain wouldn’t encode new information.

Cirelli believes that sleep is responsible for much of this result. In that way, forgetting the small stuff boosts the signal-to-noise ratio of stronger circuits (回路) and helps our brains hang on to important information.

Such findings prove the old saying, “Early to bed, early to rise...,” after all. Even so, it’s clear that targeted sleep interventions to improve memory are not yet within reach.

“People always want to hear that sleep is very good for your memory,” says Jan Born, a neuroscientist at the University of Tubingen in Germany. “Well, it’s not that simple,” he adds. Rather, different brain states may give rise to different kinds of memories, and each of those brain states could have certain types of adaptive functions for the brain and the individual. The key next step, says Born, will be homing in on what exactly these brain states do.

【推荐2】You don’t need me to tell you how to brush your teeth. Twice a day, for two minutes. But are you heading to the bathroom after your breakfast, or before it? Scheduling your morning maintenance might be more controversial (有争议的) than you thought.

“This is one of the biggest subjects for debate among our patients,” says Dr Sameer Patel, clinical director at Elleven Dental Wellness. For him the answer is simple: “brush before breakfast”. For tooth decay (腐烂) to start, he explains, three things are required: bacteria, sugar and time. “Overnight, you naturally develop plaque,” he says. “Plaque is, in essence, a sticky film of bacteria. That’s why you don’t wake up with great breath. If you don’t brush, you then introduce sugar at breakfast.” All three elements for decay are thus in place — a perfect storm inside your mouth as you munch. Brush before breakfast instead, and, “you go into eating with no bacteria, so that process of decay doesn’t start”.

“I recommend that my patients brush their teeth before having breakfast,” agrees Dr Olivia Johnson King, orthodontist at the Holland Park Dental Clinic. This, she explains, is because when we eat, the pH levels inside our mouths drops, becoming more acidic and making the outer surface of our teeth — the enamel — softer. “So if we brush directly after breakfast, in the long-term we could be weakening that outer surface and damaging our teeth,” she says.

While many dentists recommend brushing before breakfast, not everyone agrees. “There are lots of misconceptions, even among dentists, on this subject,” says Dr Carlos Gonzalez-Cabezas, dentist and professor at the University of Michigan School of Dentistry. “People think brushing is all about removing food and plaque. Actually, it’s also an extremely important delivery method for fluoride (氟化物).” Fluoride strengthens teeth and prevents decay. Brush before breakfast, and you will remove much of it as you eat, reducing the effectiveness of your toothpaste, he argues. Plus, he points out, people tend to eat breakfast pretty quickly, not giving the bacteria and food much time to join forces and do much damage. Brush straight after eating and, “you remove most of those carbohydrates (碳水化合物) right away, plus some of the bacteria, and you’re delivering fluoride to strengthen your teeth.”

With such strong views held by both camps, would it be best to brush both before and after breakfast?

Dr Gonzalez-Cabezas laughs. “It’s hard enough to persuade people to brush twice a day—once in the morning and once before bed,” he says. “Brushing in the morning, whenever you’re able to do it, is better than skipping brushing your teeth at all.” So before breakfast or after breakfast — just don’t wait till your tooth hurts.

【推荐1】Shenzhou XV astronauts moved into the Tiangong space station on Nov 30 as they started their six—month stay. The station orbits Earth in about 90 minutes at an altitude of 400 kilometers. The temperature changes greatly, ranging from 150℃ when the station is exposed to the sun to —100℃ when over the night side of the planet.

On Earth, we have heating systems or air—conditioners at home to keep us warm. In Tiangong, what do they have? The answer lies in the designs of thermal(热量的)control system by the China Academy of Space Technology.

The fluid loop(流体回路), with liquid circulating(循环)through its pipes, is one of the technologies used.

“Just like the blood vessels(血管)in the human body, the loop pipes run all over the station modules(舱),” Huang Lei, one of the designers of the system, told Xinhua, “They maintain a temperature balance by removing heat from the parts that tend to overheat and adding heat to other components that tend to get cold,” Huang added.

For the material outside, scientists have developed a silver—colored metallic—based coating to keep a balance between the deep freeze of space and the sun’s heat. It is similar to coating the spaceship with “sunscreen”.

The coating can not only absorb less solar energy but also block heat release from the inside. Being able to do this double—duty job, the coating keeps the environment inside between 18 and 26℃, allowing astronauts to stay comfortable in their orbiting home. It was first used on the Shenzhou XIII spaceship, which was launched on Oct 16, 2021.

Cargo(货物)spacecraft adopt another kind of design—multilayer insulation(多层隔热组件). For example, the Tianzhou 4’s cargo cabin was given a gray—colored material to absorb more sunlight for human activities. Another part that was filled with equipment was painted with a white material to cool off.

【推荐3】The alarm signals us to get up in the morning but it doesn’t wake up our body.     1    . In fact, this action does a lot more for our bodies than just wake us up.

It will adjust our muscles.

When we sleep, our muscles lose tone (紧实度) and gravity pulls the fluid into one place along our back.    2    . For just a moment, stretching will release the muscles from their resting place, so that they can work on their proper positioning. This process will help us calculate the movements we need to get up and start moving.

    3    .

When we stretch, we help the blood flow, which automatically decrease pressure. This is because the part of the nervous system that is responsible for our heart rate, digestion and endocrine functions gets a jump start.

It will help the brain send stronger signals to the muscles.

    4    . This means that as we stretch, our brain sends stronger signals to our muscles. Then the feedback received back lets the brain work on how strong the signals should be to perform different tasks.

It can help with stiffness (僵硬) and tightness.

Spending more time in a single position can affect our body and cause tightness and stiffness. When we stretch after waking up, it works out the joints and muscles,    5    .