Astronomers’ decision: Dump Pluto

August 28, 2006 at 9:08 pm · Filed under Astronomy

Pluto is no longer in the club of planets, but downgraded to a dwarf planet and a plutonian object.

The voting in the 2006 International Astronomical Union (IAU) General Assembly last Thursday nailed the fate of our remote icy neighbor.

Reluctant Pluto-supporters asked people to “honk if Pluto is a planet”. Anyhow, textbooks now need to be swiftly revised for this coming academic year.

The new criteria of planet are:
1. Orbiting a star,
2. Having enough gravitational force to make itself into a sphere, and
3. Having cleared away objects of comparable size from its orbit.

Pluto, discovered by Clyde Tombaugh in 1930, failed to fulfill the last criteria and was downgraded to be a dwarf planet.

It is joined by Charon, its previous moon, and become the first double planet in the solar system.

One of the main worries for accepting Pluto is its neighbors. “Pluto has too many friends”, said an astronomer.

UB313, nicknamed Xena, was discovered three years ago. It’s a planet further away from the sun but a little bit bigger than Pluto.

Scientists worried that if they let in Pluto, then Xena and other small rubbles would also join the party.

According to the new definition, our solar system consists of eight planets and four dwarf planets: Ceres, between Mars and Jupiter, double planets Pluto and Charon, and UB313 (Xena). 

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懷孕時減肥可影響嬰兒心臟健康

August 20, 2006 at 6:13 pm · Filed under 科學, 臨床研究

據一個英國的研究顥示，婦女懷孕時若吃不足身體所須的養份， 她的嬰兒會有較高的機會出現心臟問題。

研究員檢查了216名九歲小童的身體狀況及用了超聲波量度頸部血管的厚度來判斷心臟的健康。

結果發現血管較厚， 亦是心臟健康較差的小童，多數生於懷孕時營養缺乏的母親。 此外， 這些小童太多數比較肥胖， 有較高的血壓或少於運動. 這與母親的社會地位，BMI 或是否吸煙並無關係。

在二次大戰期間， 有很多荷蘭婦女在懷孕時遇上冬天饑荒。 多年後研究員在發現她們所生的孩子的膽固醇值比正常差。

動物的研究亦顯示懷孕期間的營養對胎兒的健康很重要. 對心臟而言， 除了營養不良外，進食過量的脂肪也會導致胎兒血管的健康。

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Slim mama jeopardize child’s heart

August 20, 2006 at 10:50 am · Filed under Clinical research

Restricted diet during pregnancy can contribute to higher risk of heart problem in the child, UK researchers found.

They followed up 216 children at the age of 9 examining their BMI, blood pressure and thickness of arterial walls, an early sign of heart problem.

Children have higher risk if their mother were malnourished during the pregnancy, especially after week 32. But children who exercise and have a lower BMI had a lower risk.

Neither maternal social class, smoking nor BMI was the cause, reported in the journal ATVB published by the American Heart association.   

Confirmed in human

It is know that restricted diet in mothers predisposes heart disease risk on offspring from animal studies.

In 1991 and 1992, mothers entering the Princess Anne Maternity Hospital in Southampton were recruited to test if it is true in human also.

Using questionnaires, researchers collected information about the content and amount of the diet. At age 9 months, researchers followed by 559 children. Unfortunately less than half replied at the age of 9 to this study.

They collected the present physical information from the children and performed an ultrasound scan to measure the diameters of arteries in the neck region.

Mothers who ate less than their body requirement often have children with thicker arteries, thus higher heart disease risk. However, the blood pressure is normal.

A better lifestyle such as exercise could reduce the risk even in children.

Fat-related

From the historical record, children carried by mothers experiencing the Dutch Hunger Winter in 1944 had a less healthy cholesterol level. 

However high cholesterol in mothers can also give similar risk to their children.

Scientists believed the fat level in the child was affected by the disturbed food-intake, even in prenatal stage.

External Links
> Arteriosclerosis, Thrombosis and Vascular Biology
> American Heart Association
> MRC Epidemiology Resource Centre

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Planet explosion in the universe next week

August 17, 2006 at 9:48 pm · Filed under Astronomy

On Thursday next week (August 24), we would have 12 planets in the Solar System and many more objects could be qualified as planets in the universe, if astronomers agree on the new definition of planet.

International Astronomical Union (IAU) has spent two years to review the definition of a planet. According to the new proposal, the planet must:
- Be orbiting a star, but must not itself be a star, and
- Have a nearly spherical shape, resulted by its own gravitational pull.
The rigid mass and diameter requirement are transformed into the “roundness” criteria.

Apart from Pluto, three more objects have passed these requirements: Charon, UB313 nicknamed Xena and Ceres, between Mars and Jupiter.

A new term ”plutons” would also be coined. These are planets beyond Neptune, which take more than 200 years to orbit the Sun.

Textbooks would need to be re-written that ”Our Solar System has orbiting the sun in order of: Mercury, Venus, Earth, Mars Ceres, Jupiter, Saturn, Uranus, Neptune, and plutons Pluto, Charon and UB313.”

Charon is today categorized as a moon to Pluto, but recenly scientists found that Pluto and Charon are orbiting each other, being the first pair of twin planets in the Milky Way.

UB313 (Xena) is discovered last year and has at least 2,400 km in diameter, a bit larger than Pluto. It is one of the objects in the Kuiper belt in the outer region of the Solar System. 

Scientists worried if the new definition would lower the status of planet in public’s eyes. The heated debate has started in the astronomy meeting in Prague. On August 24, scientists will vote and decide the fate of Pluto and the picture of our children’s astronomy books.

External Link
> Planet Definition – International Astronomical Union (IAU)

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Why men have sweeter blood?

August 16, 2006 at 10:36 pm · Filed under Diabetes Mellitus, Sex differences

Hormones might explain why women produce and consume less glucose during exercise, researchers in Colorado suggest.

10 women and 12 men lived under control diets for three days, infused with isotope-labeled glucose and put on a bike to work out according to their physical conditions.

Men have higher turnover of glucose during and after exercise than women. It could be explained the higher level of hormones, glucagon and epinephrine, in men due to exercise.

“[This knowledge] will enable realistic goals to be set regarding the nature and extent of anticipated benefits,” said the scientists in the Journal of Applied Physiology.  

Tailor-made exercise 

Epinephrine speeds up the conversion of common energy source in the cell, glycogen, into glucose. Glucagon increases the release and production of glucose to supply glucose for the muscle work. As a result, men flood their blood with glucose because muscles are in thirst of it. 

This finding enables exercise program for normal people as well as diabetic and obesity patients to be tailor-made according to the sex or hormonal levels.

The researchers said: “Understanding the physiological impact of sex on these factors will ultimately assist with the development of the most effective and appropriate exercise programs in me and women.”

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