SN 1987 A - Supernova

This image depicts the life cycle of the star. While this particular image is based on what is believed to be the typical lifecycle of this particular star, the past 20 years of research into the explosion that caused SN1987a supports this model. It is interesting to see how this particular star lived its life relative to the HR Diagram, and how quickly this star died once the core was exhausted of its supply of Hydrogen.

akautomatics:

Amino acids chart, handy for any biochem major

ikenbot:

The 4th dimension in our case is where the 3D structures including this very Universe combine and exist within changing time frames. 4D structures can’t exist within 3D ones but 3D structures can exist in a 4D just like your drawings exist within that flat paper as lines and points but couldn’t exist in our 3D world by itself. Extra dimensions work the same, like a Matryoshka doll that loses and or gains properties the further you go.

Image: 3D projection of a tesseract undergoing a simple rotation in four dimensional space.

In mathematical physics, Minkowski space or Minkowski spacetime (named after the mathematician Hermann Minkowski) is the mathematical space setting in which Einstein’s theory of special relativity is most conveniently formulated. In this setting the three ordinary dimensions of space are combined with a single dimension of time to form a four-dimensional manifold for representing a spacetime. [**]

In physics, spacetime (also space–time, space time or space–time continuum) is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as existing in three dimensions and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions. From a Euclidean space perspective, the universe has three dimensions of space and one of time. By combining space and time into a single manifold, physicists have significantly simplified a large number of physical theories, as well as described in a more uniform way the workings of the universe at both the supergalactic and subatomic levels. [**]

But my favorite explanation of extra dimensions in general is Carl Sagan’s version. His version was based on Flatland: A Romance of Many Dimensions which is an 1884 satirical short story by Edwin Abbott Abbott:

The story is about a two-dimensional world referred to as Flatland which is occupied by geometric figures. Women are simple line-segments, while men are polygons with various numbers of sides. The narrator is a humble square, a member of the social caste of gentlemen and professionals in a society of geometric figures, who guides us through some of the implications of life in two dimensions. The Square has a dream about a visit to a one-dimensional world (Lineland) which is inhabited by “lustrous points”.

He attempts to convince the realm’s ignorant monarch of a second dimension but finds that it is essentially impossible to make him see outside of his eternally straight line.

He is then visited by a three-dimensional sphere, which he cannot comprehend until he sees Spaceland for himself. This Sphere (who remains nameless, like all characters in the novella) visits Flatland at the turn of each millennium to introduce a new apostle to the idea of a third dimension in the hopes of eventually educating the population of Flatland of the existence of Spaceland. From the safety of Spaceland, they are able to observe the leaders of Flatland secretly acknowledging the existence of the sphere and prescribing the silencing of anyone found preaching the truth of Spaceland and the third dimension. After this proclamation is made, many witnesses are massacred or imprisoned (according to caste).

After the Square’s mind is opened to new dimensions, he tries to convince the Sphere of the theoretical possibility of the existence of a fourth (and fifth, and sixth …) spatial dimension.

The depiction above is a 4 dimensional figure as represented by 3 dimensional cubes within cubes to visualize how 4th dimensions may work.

Related: Carl Sagan explains extra dimensions

i-heart-histo:

A brief history of microscopy by i-heart-histo

c2000 BC

The Chinese use water microscopes made of a lens and a water filled tube to better visualize smaller objects.

1590

Hans Jansen and his son Zacharias Jansen invent the compound microscope.

1609

Galileo Galilei develops a compound microscope with a convex and concave lens. Calling it the occhiolino - the little eye.

1625

The term ‘microscope’ is coined by Giovanni Faber of Bamberg, an anology with the word ‘telescope’

1665

Robert Hooke publishes Micrographia and coins the word ‘cell’ after his examination of cork bark.

1674

Anton van Leuwenhoek develops the compound microscope to optimize it for observing biological specimens.

1860s

Ernst Abbe discovers the Abbe sine condition for manipulating the axis of optical systems to improving sharpess of images. This breakthrough in microscope design was exploited by microscope manufacturers Zeiss and Leitz resulting in a microscope boom.

1920

Olympus manufacture their first microscope - the Asahi.

1957

The Olympus DF Biological Microscope becomes the first microscope to feature an attached light source rather than a mirror that reflects light on the specimen.

1976

The popular CH series of Olympus microscopes appear in universities and colleges around the world. Chances are your college still uses these lab teaching scopes (or the slightly newer CH2 version).

1993

Introduction of a unique Y-shaped design for the microscope body for enhancing optics.

2004

Confocal and virtual microscopy are now common place.

we-are-star-stuff:

DNA prediction of categorical eye and hair colour on the individual level. Examples of applying the HIrisPlex system to four European individuals (A–D). The actual eye and hair colours are displayed on the left side by photographs. The HIrisPlex prediction results, in terms of the probabilities belonging to certain colour categories, are shown on the right side, where the colour categories with the highest probabilities are highlighted.

Human hair, eye, and skin colour are very complex and difficult to predict, because each of these traits is controlled by more than one gene. It’s not really a matter of a child taking after the father or mother’s side; genes don’t work that way. What matters is which parent has the dominant versions of the various genes that affect the traits in question, because these are the ones most likely to be expressed by the child - though not always.

Every animal (including humans) carries two copies of every gene. Scientists now estimate that a human has about 30,000 genes in his/her genome, and every human has two copies of that genome: one from mom, and one from dad. The two versions of each gene (called alleles) may be the same in a single person, or they may be different. This means that the different versions can combine and interact in unpredictable ways to produce a wide range of phenotypes (physical appearance).

A trait that is controlled by several genes is called a polygenic trait. A polygenic trait is the expression of a single phenotypic trait that is affected by the action of more than one gene. There are too many examples to list, since most traits are - at least to some degree - polygenic.  But human hair, eye and skin colour are among them.

Hair colour is a result of interaction between several genes that not only control the colour of the hair pigmentation (one gene controls the expression of brown -eumelanin- pigment and a different gene controls expression of red -phaeomelanin- pigment), but also how much pigment is deposited in the hair shaft. The darker the hair, the greater the melanin deposition, but one can’t really predict how dark a baby’s hair will be, since s/he may inherit a wide variety of “darkness level” genes from both parents, and they can recombine in various ways to produce hair that ranges in colour from very light to very dark.

If a person expresses both the eumelanin (brown) and phaeomelanin (red) genes, the hair will be reddish brown. Dark to light brown hair with no trace of red occurs when only eumelanin is expressed, but in varying concentrations. Blonde hair with no trace of red occurs when there is weak eumelanin expression and no phaeomelanin. Red hair occurs when there is strong expression of phaeomelanin and weak expression of eumelanin. Not all people express both genes, but in dark-haired people that do express both, you can sometimes see a reddish sheen in the hair in certain light. But the darker eumelanin pigment often makes it difficult to see the red pigment, if it’s present.

Light colored eyes (blue, green, hazel, grey, etc.) are usually considered recessive to dark-colored eyes. But this trait is controlled by at least five different genes. There are genes that control whether or not melanin is deposited in the iris (the dominant B allele codes for brown, and the recessive b allele, coding for no melanin, will result in pale irises. These will be blue in the absence of other pigments), the amount of pigment deposited (several genes that can combine to generate eyes that are very dark, almost black to relatively light brown), as well as overlying carotenoid pigments that can change a blue iris to green, aqua, grey, or any number of variations.

And to make things even more complicated, eye colour, like hair colour, can change with age.

Still, one can predict, to some degree, whether a child will have light-colored or brown eyes. The allele coding for light eyes (i.e. lack of melanin in the iris) is recessive to the allele coding for dark eyes (i.e. melanin deposited in the iris). For a person to have light eyes, s/he must inherit two copies of the b allele (genotype bb). A person needs only one copy of the B gene to have dark (brown) eyes, so can be either BB or Bb.

Skin colour is probably the most complex of all the traits. The shade of the skin in humans may be controlled by several genes, each with several alleles, and this makes the prediction of skin tone in a baby a nearly impossible task. x

neurosciencestuff:

What are stem cells?

In a paper published in Cell yesterday, scientists from the US and Thailand have, for the first time, successfully produced embryonic stem cells from human skin cells.

That sounds interesting, but what are stem cells and where do they come from?

If you take a limb from a rose tree, and put it in soil, it will grow into a thriving bush.

But you might say: “Plants are special. This won’t work with animals.” Or will it? If you cut off a lizard’s tail, a new tail may grow. A lobster can grow back a lost claw.

There is a special type of flatworm that can be cut in half, again and again hundreds of times, and each half grows back into a full worm.

Similarly, if you cut out half a human liver, it will grow back. The story of Prometheus, whose liver was eaten away by eagles and regrew each day, suggests that the Greeks of ancient times knew about regeneration of organs.

This sort of regeneration is attributed to special cells called “stem cells”.

Reprogramming the workers

Most of our cells are like many professional workers – they are hardened in their ways and can’t manage career changes.

Blood cells carry oxygen or fight disease, muscle cells expand and contract to move us around, nerve cells carry signals, skin cells form a protective layer over our bodies, and structures made up of kidney cells filter our blood.

The cells of most organs or tissues are referred to as “terminally differentiated” cells. They have specialised, and many won’t divide again. If they are damaged or die they will disappear. This is very important.

Although we feel like we grow a lot after we are born, we really only double in size two or three times and most of our cells don’t divide much.

If they did we would be at great risk from cancer – the uncontrolled doubling of cells at the wrong time.

We have a lot of cells and it is important that none of them run out of control.

But some cells can double to renew themselves and can also differentiate and give rise to specialised progeny.

These are the stem cells. We need them to produce new skin to replace damaged skin cells. Similarly, we need them in our guts to replace damaged cells on the surface of our intestines.

Our blood cells also get worn out as they race around our bodies so we have blood stem cells that divide and replace themselves. They also differentiate to form the different types of white and red blood cells we need.

Australian researchers identified stem cells in the breast that can proliferate and form a complete functioning breast. There are also stem cells in the brain and in the heart.

While stem cells tend to be very rare, they exist in many of our organs.

Types of stem cells

The ultimate stem cells are embryonic stem cells.

These cells are found in the inner cell mass of the early embryo and are referred to as “totipotent” since they have the ability to form every cell that is needed in the growing embryo.

They can be extracted from the early embryo and grown in culture dishes.

They can also be genetically modified by the addition of DNA, then injected back into other embryos or into adult animals where find their way into localities that suit them and replace themselves by duplication or differentiate into other cell types that may be needed. For a long time this type of work had been done primarily in laboratory mice.

The techniques in yesterday’s Cell paper involved injecting the nucleus from a human skin cell into a human egg (the nucleus of which has been destroyed) then growing the resulting embryo until the inner cell mass cells could be harvested.

The method may still be controversial because it uses unfertilised eggs, but many people will regard it as preferable to using human embryos. And there are other interesting methods for making stem cells.

Somatic cells to stem cells

It is also possible to convert skin cells, and indeed many different terminally differentiated cells, back into what are called “induced pluripotent stem cells” or iPS cells.

One uses the “magic four” or “OKSM” set of DNA-binding proteins that govern normal stem cell biology:

• Octamer-binding transcription factor 4 (OCT4)
• Kruppel-like factor 4 (KLF4)
• SRY (sex determining region Y)-box 2 (SOX2)
• cellular myelocytomatosis virus-like gene (MYC)

In 2012 Shinya Yamanaka won the Nobel Prize for discovering how to convert normal cells into iPS cells using the OKSM regulators to turn on and off the right genes and convert skin cells into stem cells.

Researchers are continuing to investigate whether iPS cells have the same therapeutic potential as embryo derived stem cells.

It is hoped that stem cells may provide therapies for people suffering from degenerative diseases.

Skin cells could be taken from a patient, converted to stem cells, and then these could be injected back into the damaged organ.

Ideally, they would repopulate the damaged organ with new cells.

So why doesn’t this happen in normal biology? Why aren’t our own heart stem cells busy trying to repair broken hearts?

They may be but our natural supply of stem cells is limited and presumably insufficient to tackle severe disease.

So why don’t we just have more stem cells in our bodies?

The down side of having too many stem cells may be cancer.

Stem cells share a number of features with cancer cells – both are able to self-renew and double without limit.

One theory about cancer holds that the disease most often originates not from terminally differentiated cells but from one of the small number of stem cells in the relevant tissues.

The obvious concern about using stem cells for therapy is that injecting too many could increase the chances that some of these cells would proliferate beyond control, and ultimately give rise to cancer.

Stem cell therapy for regenerative medicine is an exciting idea.

Every day we are learning more about stem cells – how to purify or make them, and how to grow them in culture and direct them down particular pathways to repopulate different organs.

Future research will assess the risks and how effective they can be in experimental systems and ultimately in human patients.

the-science-llama:

Light Beam with a Curve

To make the beam, the researchers directed a centimeter-wide laser beam onto a watch-sized liquid crystal display screen called a spatial light modulator (SLM). The reflectivity of each pixel on this screen is related to its index of refraction, so the device allows control of the precise phase of light reflected from each spot. The team programmed the SLM pixels to provide the phase relationships needed for an Airy beam.

As with the Bessel beam’s diffraction-free “propagation,” light doesn’t actually propagate along the curved path. The beam is the pattern created by interference of light from the 500,000 carefully-phased pixels of the SLM.

expose-the-light:

Smeared Sky Photos by Matt Molloy

discoverynews:

UK to Send First Astronaut to Space Station

Introducing Major Tim!

jtotheizzoe:

The Earliest Days of NASA

Maria Popova, at Brain Pickings, happened upon a treasure trove of early NASA (and its airplane-only predecessor NACA) archive photos. They are really something. From biplanes to the Mercury capsule, pre-1950 aeronautics seemed to live by the motto of “If we build it, then we can go there.” That’s a sentiment we could use a bit more of.

More here.

the-science-llama:

If Earth Had Rings

First off, they would be really pretty to look at. They would also dominate the sky in both night and day at exactly the same place as they would never rise nor set. And at night you would see the Earth’s shadow swing across the rings, like in the 4th photo here.

However, life would be very different on Earth if this were the case. Nocturnal animals would have a hard time being nocturnal, as the light reflecting from the rings would illuminate the night.

Because we are closer to the Sun than Saturn is, the rings would be more rocky than ice, making them less bright but still pretty bright. In fact, you would see far less stars at night (living anywhere other than the equator or the arctic circle) because of the light pollution and not to mention ruin most meteor showers because of that.

During the day the rings would block sunlight in certain regions of the planet creating wild weather cycles and effecting plant life as well. So basically, they would be definitely pretty to look at but they would also make a whole lot of things screwy.

Illustrations by Ron Miller // io9
— Click the photos for captions

APOD | 2013 May 20 | Blue Sun Bursting
Image Credit & Copyright: Alan Friedman (Averted Imagination)

Explanation: Our Sun is not a giant blueberry. Our Sun can be made to appear similar to the diminutive fruit, however, by imaging it in a specific color of extreme violet light called CaK that is emitted by the very slight abundance of ionized Calcium in the Sun’s atmosphere, and then false color-inverting the image. This solar depiction is actually scientifically illuminating as a level of the Sun’s chromosphere appears quite prominent, showing a crackly textured surface, cool sunspots appearing distinctly bright, and surrounding hot active regions appearing distinctly dark. The Sun is currently near the maximum activity level in its 11 year cycle, and has emitted powerful flares over the past week. During times of high activity, streams of energetic particles from Sun may impact the Earth’s magnetosphere and set off spectacular auroras.