Army Ant Bivouac
Army ants are nomads; their ferocious appetite means that they must move to new regions every few days in order not to starve. As a result, they make a temporary nest constructed out of individual ants.
Depending on the colony size, 150,000 - 700,000 worker ants link onto each other to form a structure 1m in diameter. The queen and larvae are protected near the center of the protective mass.
Geoff Gallice on Flickr
Blooming of the Tisza River - The Hatch of the Mayflies
Every June, the Tisza River in Serbia and Hungary comes alive when thousands of adult giant mayflies (Palingenia longicauda) emerge all at once. The adults live for less than 24 hours and must quickly find a mate before they die.
Pitta strepitans [Noisy Pitta] on Flickr.
Illustrations of ornithology (1826)
Author: Jardine, William, 1800-1874; Selby, Prideaux John, 1788-1867; Lear, Edward, 1812-1888, ill; Mitford, R. C. W. (Reginald Colville William), b. 1839, ill; Hewitt, Eleanor G., donor. DSI; Hewitt, Sarah Cooper, donor. DSI; Lenox Library, former owner. DSI; Bailer Bros. (Firm), binder. DSI
Volume: v 2
Subject: Birds; Birds; Arsenic compounds
Publisher: Edinburgh : Published by W.H. Lizars ; London : Longman, Rees, Orme, Brown, & Green, and S. Highley ; Dublin : W. Curry Junr. & Co.
Digitizing sponsor: Biodiversity Heritage Library
Book contributor: Smithsonian Institution Libraries
Let’s talk about the dark night.
Yes this post is about Batman.
Our common assumption is that the night sky is supposed to be dark with only few dots of light.
But then, aren’t there supposed to billions upon billions of stars in the night sky emitting light. Yes, they are very far away, but, there is nothing stopping (like air or glass) the light from reaching us. So, shouldn’t all those stars make the night sky (very) bright and not dark ?
This is actually called Olbers’ Paradox.
Let’s look at the problem in another way. We can divide the universe into a series of concentric shells, being 5 light years thick. Thus, a certain number of stars will be in the shell 1,00,000 to 1,00,005 light years away. If the universe is homogeneous at a large scale (i.e., static), then there would be four times as many stars in a second shell between 2,00,000 to 2,00,005 light years away.
But, the second shell is twice as far away, so each star in it would appear four times dimmer than the first shell (intensity is inversely proportional to the square of distance). Thus the total light received from the second shell is the same as the total light received from the first shell.
Thus, the argument is that if the universe were static and filled infinitely with stars, the night sky should be much brighter than it is now.
I think you guessed the loop hole here. I said if the universe were static, which it clearly isn’t.
The Big Bang explains this paradox by saying that the universe started at a point, and expanded from that point. Thus, it is not static.
We know that the expansion is accelerating. So, two things happen.
One is that, those stars in the night sky are moving away from us and the distance between them and us increases. This increase the time for to see them and eventually it takes millions of years for the light from those stars to reach us.
Second, which is the more important reason, is that these starts get redshifted away. Redshifting is when the wavelength of an object moving away from us goes towards the red side of the spectrum and eventually, it goes into the infra red, which we cannot see. It is like we listen to a honking truck passing by at great speed. As it moves away from us, the the sound becomes softer and softer and eventually it is inaudible.
So, because of these reasons, we never get to experience the real night sky light. But, it may be a good thing, as otherwise our eyes would be blinded by the light !
Image via Wikimedia Commons
Chorioactis geaster is found only in a few locations in Texas, where it is called the Texas star, and Japan, where it is known as kirinomitake ( キリノミタケ). The fruiting body grows as a tube, before it splits into four to seven rays, in a process called dehiscence. The inner surface is covered with spore-producing tissue called the hymenium, which can be coloured white to brown.
Healthy Arteriole in Eye - with tough, flexible elastin wall (pink), red blood cells (red) and supporting collagen fibers (web-like “netting,” and yellow & green areas)
Donald Pottle. Boston, MA, USA
Technique: Confocal, 40x Objective
A working process for cloning stem cells from existing human cells has finally been discovered by a team at Oregon Health & Science University.
These stem cells were created by reprogramming healthy skin cells, a goal that has eluded researchers around the world for years. It’s the first key step in developing medical procedures for replacing dying or injured cells with new ones to stave off disease and age. That could mean growing a new liver, or kidney or heart, in the lab for an organ transplant, or even repairing the brains of those suffering with diseases like Parkinson’s.
The team was led by Shoukhrat Mitalipov from the reproductive and developmental sciences department of the Oregon National Primate Research Centre. He said: “A thorough examination of the stem cells derived through this technique demonstrated their ability to convert just like normal embryonic stem cells into several different cell types, including nerve cells, liver cells and heart cells. Furthermore, because these reprogrammed cells can be generated with nuclear genetic material from a patient, there is no concern of transplant rejection.”
“While there is much work to be done in developing safe and effective stem cell treatments, we believe this is a significant step forward in developing the cells that could be used in regenerative medicine.”
The technique Mitalipov and his team used is called “somatic cell nuclear transfer” — as you can see in the video, it essentially involves sucking out the DNA from an adult cell and inserting it into the empty nucleus of a donor egg. This creates a clone of the original cell, and is in fact the first step in the cloning method used to create animal clones like Dolly the sheep.
However, in its therapeutic mode, the new cells can be grown as replacements for the original type of cell. That objective hasn’t been reached until now as human eggs are extremely fragile compared to many of the animals which we have cloned. That Mitalipov and team have succeeded is down to research on primates, and adapting primate stem cell research to humans.
As a cell divides after fertilisation, it undergoes several transformations as it prepares to split and multiply. The metaphase is the moment just before a cell splits, as the chromosomes align alongside each other in the very centre of the cell so that, when it splits, one goes one way as another goes the other, each taking the full copy of the genetic code. The researchers managed to stall the metaphase while the cell underwent nuclear transfer, effectively giving the new chromosomes time to get settled before the metaphase finished and cell division proceeded.
An added bonus is that the eggs used have not been fertilised, so there won’t be any debates over the ethics of embryonic stem cells as we have seen in the US in the past. While the researchers placed skin cell nuclei into the receptor egg cells, the method is conceivably similar for any other kind of cell.
And, while it may sounds like the first step towards a practical method for cloning humans, the Mitalipov has made it clear that’s not the aim. “Our research is directed toward generating stem cells for use in future treatments to combat disease. While nuclear transfer breakthroughs often lead to a public discussion about the ethics of human cloning, this is not our focus, nor do we believe our findings might be used by others to advance the possibility of human reproductive cloning.”
The research has been published in the journal Cell.
This Week in Science - May 13 - 19, 2013:
- Magnetar at black hole here.
- Cloned human stem cells here.
- Cell calculators here.
- Music matched to color here.
- Scientists agreeing on climate change here.
- Remote-piloted plane here.
- Earth’s core here.
- Bright lunar explosion here.
- American asteroid sampling here.
- Hofstadter butterfly effect here.
- Electric shocks aid math skills here.
- Printable solar panels here.
Insects in amber. From the Dominican Republic, Miocene epoch (23.8 to 5.3 million years ago).
markhortonphotography: Last May, I noticed a flurry of activity from the many red mason bees (Osmia rufa) The activity was focused around two old open drill holes, where a washing line had previously been fixed.
Macrophages are a type of white blood cells - part of the amazing immune system. They have thesuperpower of eating invading pathogens, such as bacteria, virus and protozoans in a process called “phagocytosis”.
If you look at it from the point of view of the pathogen, it’s Jaws all over again.
For those who want to try out phagocytosis themselves, here are the instructions.