Author Archives: Eva Lin

Learning more about Tuberculosis from the Fur Trade

One of the most memorable things when learning about the 18th century Canadian fur trade in history class was how the Europeans spread diseases to the indigenous peoples by means of the trade. One of such diseases is tuberculosis, which infectious disease specialist Caitlin Pepperell and colleagues at Standford University in Palo Alto, California have been studying. In the new study published in the Proceedings of the National Academy of Sciences, they have puzzled out why TB didn’t become an epidemic until after the fur trade era even though the indigenous peoples of western Canada were repeatedly exposed to the strain by French Canadian voyageurs during 1710 – 1870.

Canadian Fur Trade / Source:Cartouche from William Faden

It wasn’t until the late 1800s that TB epidemics began to break out, which was about 150 years from the first introduction. Pepperell explains that the conditions most likely to trigger epidemics in Canada were the relocation of the native peoples  onto reservations, declining health conditions with relocation, and the biggest factor of them all, malnutrition. The key message from the results indicates that TB is infectious and remains dormant in host until stressful conditions – crowding, poor nutrition, weakening hosts – give the bacteria a leg up and turns on into active mode.

TB Culture / Source: CDC

Pepperell first discovered the same TB strain signature, or “fingerprint” in the native peoples of Quebec and a French Canadian population that didn’t live near the native communities when she received a DNA profile of the bacteria in the latter from a colleague. After using mathematical modeling and statistical analysis, they were able to trace the spread back to the 18th century, which was when waves of French traders carrying TB came to Canada and married indigenous women, resulting in the disease remaining latent in the native communities for several decades until the pressures of relocation and shortage of buffalo occurred.

Tuberculosis’s stealth nature has had it difficult to combat the disease without knowing how it spreads. The World Health Organization estimates that 1/3 of the people on Earth are infected with the disease. The new findings of the study can only point out how tenacious the disease actually is, bring us one step closer to understanding the tuberculosis bacterium and how we can control it.

Laser to zap space garbage

To get you started thinking about space junk:

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NASA space scientist James Mason and his team of NASA Ames Research Center and  the University of Space Research Association in California have recently proposed a new theory to deal with the pieces of debris in the low Earth orbit (LEO) that are colliding with each other to create more pieces. They discovered a possible method of using a laser beam to change the velocity of the junk’s orbit by focusing the beam on it to slow it down and change its orbit. This can stop the debris from colliding with communications satellites or the International Space Station.

Satellites and space junk in orbit around Earth CREDIT: ESA

The scientists mention that continual evaluation of the chances of a collision between two space debris of 5 cm or more in diameter would be needed using radar data from the US Space Surveillance Network. The junks on the path of collision would then be tracked by an optical telescope. One of them will be locked on and the release of the laser beam will occur. Just by using 5-10 kilowatts commercially available lasers mounted on 1.5 meter telescopes placed close to the poles, the risk of more than half of potential space junk collisions could be significantly reduced. The total cost of the scheme would be no more than $10m, making it a much cheaper alternative than other ideas such as direct removal of space debris.

The new paper could give insight into how we can avoid the Kessler syndrome, where if more and more space junk are be created and colliding with each other, the generations of debris could ultimately render space exploration and satellite launches impossible. This prediction was done by a NASA scientist in 1978 and new solutions have been presented since then a lot with multiple complications and high price tags. Moreover, other countries involved in space exploration saw the proposed methods as threats to their functional satellites.

Although a feasible theory, the scientists speculate whether this method could actually do the trick remains a topic of debate. Team member William Marshall points out that there are a lot of uncertainties in the model and space-debris models need to be run to be certain that the theory will be effective in the long term.

Less and Less Baby Polar Bears with Melting Arctic Ice

We all know of the strong correlation between changes in the environment and the polar bears,but a recent study suggests that the population of this species, Ursus maritimus, could be in real danger with the decline of Arctic sea ice specifically in our country’s Hudson Bay.

Source: Flickr

Article published on February 8th, 2011 in Nature Communications outlines a study conducted by Peter K. Molnar et al. from the University of Alberta who used mechanistic models to predict changes in litter size of cub polar bears for pregnant females in the western Hudson Bay population under expected changes in sea ice.

Sea ice is vital for the polar bears because during the winter feeding season they rely on the solid floes to take them near the waters where there are lots of food source – seals. But with temperatures rising and early breakup of the ice sheets, the bears are forced ashore sooner than in the past. Moreover, “on shore, there is no food available for them,” as the lead author of the study puts it. Thus the bears, particularly females of reproductive age, are storing up less energy for the months that they have to hibernate during pregnancy.

The researchers found that ~28% of pregnant females already failed to reproduce for energetic reasons during the 1990s. Using mechanistic models, they predicted that if spring sea ice break-up happens 1 month earlier than during the 1990s – 40-73% of pregnant female polar bears could fail to reproduce, and if the break-up happens 2 month earlier55-100% could fail. On a global perspective, the study states that a similar litter size decline trend may be found in over 1/3 of the polar bear population.

What’s even more discouraging is that “the litter size predictions provided in this study serve as another indicator that the western Hudson Bay population will probably not remain viable under predicted climatic conditions” as the article states.

Heart wenching video that hits home of malnourished  mother polar bear and starving cubs as an example of the conditions that polar bears are and will be facing in the future with current climate change conditions. A Warming Climate Takes its Toll on the Polar Bears of Hudson Bay by Daniel J. Cox


Banding on Penguins Not Such a Good Idea Afterall

Climate change can be assessed through using the top predators of the Southern Oceans, the penguins. However, a recent study published on Nature have shown that the use of flipper banding may affect one specific population of King Penguins.

The 10-year study indicates that “banded birds produced 39% fewer chicks and had a survival rate 16% lower than non-banded birds“. This finding from the research team from the University of Strasbourg in France brings to the surface the effect of banding on animals, specifically the penguins in order to collect scientific data.

However, the conclusion on the tagging and bands are by no means clear, according to interview with two penguin experts. One of them, Dee Boersma, at the University of Washington stresses that not all bands are created equal, thus the effect on species may be different with different materials, shapes, sizes of the bands.

The study in the end stresses the importance of reconsidering the data collected of the effects of global warming on marine ecosystems from flipper-bands.