If you are short of time or want to support picky eaters, I consider a meal delivery service which ships fresh and healthy food to your door. Here, we list some of the best ones in the US.

Nurture Life

Nurture Life has many meal options for children and adults, making it easy to prepare meals for everyone in your household. Meals are prepared and shipped fresh to any place in the country. You need to order dishes of more than ＄59 to qualify (有权) for free shipping, or it charges approximately $ 8 for delivery.

Dinnerly

Dinnerly makes healthy homemade meals simple while the meals are affordable for most people. Every serving costs about $4 with about a $9 shipping fee. And delivery days and times are dependent on where you live.

Yumi

Yumi is a baby meal service that offers healthy food choices. Meal plans are made for children aged 4 months to over 2 years old. It charges about $4 per meal, which includes free shipping. Meals are delivered by 9 pm on Wednesdays, and it ships meals everywhere but Hawaii and Alaska.

The Good Kitchen

The Good Kitchen is a great option for people with allergies (过敏反应). All meals from The Good Kitchen are shipped with a full list of ingredients (烹饪原料), so people know exactly what they are eating. Prices for individual serving sizes range from about $11 to $14 per meal. And it offers free delivery.

Doing lots of exercise in older age can prevent the immune system from dropping and protect people against infections, scientists say. They followed 125 long-distance cyclists, 20-year-olds.

Prof. Norman Lazarus, who took part in the research, said, “If exercise was a pill, everyone would be taking it. It has many benefits to the body.”

Janet Lord, a co-author of the research, said, “The immune system drops by about 2%-3% a year from our 20s, which is why older people are more susceptible (易受影响的) to infections. Because the cyclists have the immune systems of 20-year-olds rather than a 70-or 80-year-olds, it means they have added protection against all these diseases.” The researchers looked at markers in the blood for T-cells, which help the immune system respond to new infections. They found that the cyclists were producing the same level of T-cells as adults in their 20s, whereas a group of inactive older adults were producing very few.

The researchers believe that being physically active in old age will help people be better protected against infections such as flu. Steve Harridge, a professor of physiology, said, “Being sedentary (久坐不动的) goes against evolution because humans are designed to be physically active. You don’t need to be a competitive athlete to get the benefits-or be a professional cyclist-anything which gets you moving will help.”

Harridge and Lazarus believe that highly physically active older people represent the perfect group to analyse the true effects of biological ageing. A separate paper in Aging Cell found that the cyclists did not lose muscle mass or strength, and did not see an increase in body fat, which are usually connected with aging.

New research suggests that climate change may have been responsible for the end of ancient Mayan civilization, which started in 1,500 BC.

According to findings published in the November issue of Science,scientists have found evidence to support the idea that a sudden and complete change in weather led to a long dry period. As a result of it, agricultural productivity (生产力) decreased rapidly, which finally caused the end of ancient Mayan civilization. Instead of being man-made, scientists think El Nino (厄尔尼诺) events led to the weather change.

The findings came after Professor Douglas Kenett led an international team including researchers from the US, Belize, Switzerland and Germany to study the stalagmites (石笋) in caves. Rain got into the caves and combined with the wet limestone, and finally the two formed stalagmites. Rain can give scientists some information as to how wet the area was at a particular point in history. Kennett's team focused on a single cave in the Belize jungles located near four Mayan sites. They pulled a 22-inch stalagmite from deep within the cave and used its chemical record to guide the way. They found that there were droughts (干旱) lasting many years between 900 and 1100.Those dates were the same periods of great suffering in Mayan history.

During dry periods there were wars-common for cultures struggling over resources and the changes of political rulers. The worst drought from 1020 to 1100 happened to be the accepted end of Mayan culture itself. But Kennett added that the greatest periods of rainfall“saw"that Mayan culture thrived from 450 to 660 and“saw”the founding of its greatest cities.