Powered by Blogger.

New exotic material could revolutionize electronics

Sunday, July 26, 2009

Announcements of "breakthroughs" like this often don't pan out. This one might be a little more promising. It involves confirmation of a new, fairly simple material – bismuth telluride (Bi2Te3), a compound of bismuth and tellurium – that exhibits what is known as the "quantum spin Hall effect" and could have a dramatic impact on electronics, computing, and other significant areas of technology.

One reason for the optimism is that the technology for working with bismuth telluride is similar to that for commonplace semiconductors like silicon.

New exotic material could revolutionize electronics (6/15/09)
SLAC National Accelerator Laboratory and Stanford University have confirmed the existence of a type of material that could one day provide dramatically faster, more efficient computer chips.

Recently-predicted and much-sought, the material allows electrons on its surface to travel with no loss of energy at room temperatures and can be fabricated using existing semiconductor technologies. Such material could provide a leap in microchip speeds, and even become the bedrock of an entirely new kind of computing industry based on spintronics, the next evolution of electronics.

Materials with the properties of bismuth telluride have been predicted theoretically, and in this case the predictions have been pretty accurate. In other words, physicists already have a good understanding of the material's properties.
This magic is possible thanks to surprisingly well-behaved electrons. The quantum spin of each electron is aligned with the electron's motion—a phenomenon called the quantum spin Hall effect. This alignment is a key component in creating spintronics devices, new kinds of devices that go beyond standard electronics. "When you hit something, there's usually scattering, some possibility of bouncing back," explained theorist Xiaoliang Qi. "But the quantum spin Hall effect means that you can't reflect to exactly the reverse path." As a dramatic consequence, electrons flow without resistance. Put a voltage on a topological insulator, and this special spin current will flow without heating the material or dissipating.

Practical implementations of spintronics have been avidly sought, because the technolgy takes advantage for the first time of an electron's spin, as opposed to its electric charge. This may enable the manufacture of much faster and denser forms of digital information storage devices, and even more exotic things like quantum computers.

The quantum spin Hall effect mentioned above is a quantum version of a non-quantum effect, the spin Hall effect, known for about ten years. That, in turn, is an analog of the classical Hall effect, which has been known since 1879.

In the classical Hall effect, a voltage difference is produced in an electrical conductor transverse to an electrical current in the conductor. A magnetic field is also produced perpendicular to the current.

In the quantum spin Hall effect, there is also an electric current, and in fact electrons flow without dissipating heat. Consequently, for example, transistors that take advantage of the effect could be much more efficient than existing semiconductor transistors.

Importantly, in bismuth telluride, the effect occurs at much higher temperatures than those at which known superconducting materials work. This will make practical applications much easier.

The predictions on which the discovery is based are quite recent, having been published only in May of this year – see Super-efficient Transistor Material Predicted.

Research abstract:

Experimental Realization of a Three-Dimensional Topological Insulator, Bi2Te3
Three-dimensional topological insulators are a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. By investigating the surface state of Bi2Te3 with angle-resolved photoemission spectroscopy, we demonstrate that the surface state consists of a single nondegenerate Dirac cone. Furthermore, with appropriate hole doping, the Fermi level can be tuned to intersect only the surface states, indicating a full energy gap for the bulk states. Our results establish that Bi2Te3 is a simple model system for the three-dimensional topological insulator with a single Dirac cone on the surface. The large bulk gap of Bi2Te3 also points to promising potential for high-temperature spintronics applications.

Further reading:

Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface – abstract of May 2009 research paper in Nature Physics reporting predictions of topological insulators

Chern numbers of algebraic varieties

Important news of developments in mathematics doesn't come out all that often, but here's some:

Chern numbers of algebraic varieties (6/10/09)
A problem at the interface of two mathematical areas, topology and algebraic geometry, that was formulated by Friedrich Hirzebruch, had resisted all attempts at a solution for more than 50 years. The problem concerns the relationship between different mathematical structures. Professor Dieter Kotschick, a mathematician at the Ludwig-Maximilians-Universit├Ąt (LMU) in Munich, has now achieved a breakthrough. ... Kotschick has solved Hirzebruch's problem.

It would be somewhat hopeless to try to explain in a few paragraphs what this is all about. But since the result is a good example of the kinds of things mathematicians work on, a little discussion seems worthwhile.

A couple of important mathematicians of the 20th century are directly involved in the explanation. Friedrich Hirzebruch, who is still alive, worked in a number of active related fields, including topology, algebraic geometry, and complex manifolds. All of these are a legacy of the now well-known 19th century mathematician Bernhard Riemann.

Shiing-Shen Chern, who died in 2004 at the age of 93, worked primarily in another field closely related to those mentioned above, namely differential geometry.

The subject matter of all these fields comprises various types of abstract geometric objects. Perhaps the most familiar examples of such objects are plane curves defined by algebraic equations, such as circles, defined as the set of points (x,y) in the plane that satisfy x2+y2=R2, where R is a constant (the radius of the circle).

Such curves can be generalized to any number of dimensions, as subsets in the space of n-tuples of numbers (x1, ..., xn) where all the coordinates xi simultaneously satisfy some specific set of polynomial equations. The coordinates may be complex numbers (the set of which is denoted by ℂ). Such generalized curves in the space ℂn are called algebraic varieties. The branch of mathematics that studies such things is called algebraic geometry.

Mathematicians like to classify things. In plane geometry, for example, polygons are classified as triangles, rectangles, pentagons, etc. according to the number of sides they have. All members of one of these classes of polygons are defined in terms of having the same number of distinct straight sides, say n.

A more general way in which geometric objects (or even more generally, topological objects) can be classified is in terms of objects which are all related by some sort of 1-to-1 mapping between their points. Many different types of mappings may be considered, such as mappings that preserve only the most basic topological properties (in the sense that donuts and coffee cups have the same "shape" in 3 dimensional space). Other types of mappings might be more narrowly defined, such as being "differentiable" (in the sense of calculus). A class of objects is then specified in terms of all objects that are related by some 1-to-1 mapping of a given type.

Normally, it is quite difficult to determine whether two objects are related by some mapping, and hence belong to the same class, because it's usually necessary to specify the mapping explicitly in order to do this.

But sometimes there are shortcuts that make the task of determining relatedness between topological objects easier. One of these is to find some number or set of numbers that is easily calculated and has to be the same for all members of the class of interest. For example, the class of n-gons in the plane is defined simply as all closed curves with the same number (n) of straight sides. Such numbers are called "invariants", because they are the same no matter what transformation (of the specified sort) is applied to any object of the class.

The best sort of invariant (or set of invariants) to have is one that is not only necessary for membership in the class, but also sufficient for membership. In that case one doesn't need to explicitly construct appropriate 1-to-1 mappings – one only has to calculate a few numbers (which may or may not actually be much easier).

Invariants need not be limited to ordinary numbers. They can also be more complicated sorts of mathematical objects, such as polynomials, groups, rings, or even topological objects like manifolds. All that one asks is that there be some way of calculating or determining the invariant associated with an object specified in some other way.

The "Chern numbers" mentioned above are important examples of such invariants, and the result which has now been proven is a statement about the properties of Chern numbers in a broad range of cases.

Why are mathematicians interested in such seemingly abstract constructs? Actually, there are many "real world" applications. Solutions of sets of polynomial equations – i. e., algebraic varieties – are often important in physics, especially mechanics. And more exotic sorts of topological objects crop up in problems involving differential equations.

Here's the research abstract:

Characteristic numbers of algebraic varieties
A rational linear combination of Chern numbers is an oriented diffeomorphism invariant of smooth complex projective varieties if and only if it is a linear combination of the Euler and Pontryagin numbers. In dimension at least 3, only multiples of the top Chern number, which is the Euler characteristic, are invariant under diffeomorphisms that are not necessarily orientation preserving. In the space of Chern numbers, there are 2 distinguished subspaces, one spanned by the Euler and Pontryagin numbers, and the other spanned by the Hirzebruch–Todd numbers. Their intersection is the span of the Euler number and the signature.

The complete research paper can be found here.

Want to be more creative? Get more REM sleep

Monday, July 20, 2009

REM sleep, a distinctive phase of normal sleep characterized by rapid eye movements, has traditionally been associated with vivid dreaming. New research suggests it is important for creativity in general.

Creative problem solving enhanced by REM sleep (6/8/09)
Research led by a leading expert on the positive benefits of napping at the University of California, San Diego School of Medicine suggests that Rapid Eye Movement (REM) sleep enhances creative problem-solving. The findings may have important implications for how sleep, specifically REM sleep, fosters the formation of associative networks in the brain.

The study by Sara Mednick, PhD, assistant professor of psychiatry at UC San Diego and the VA San Diego Healthcare System, and first author Denise Cai, graduate student in the UC San Diego Department of Psychology, shows that REM directly enhances creative processing more than any other sleep or wake state. ...

"We found that - for creative problems that you've already been working on - the passage of time is enough to find solutions," said Mednick. "However, for new problems, only REM sleep enhances creativity."

Mednick added that it appears REM sleep helps achieve such solutions by stimulating associative networks, allowing the brain to make new and useful associations between unrelated ideas. Importantly, the study showed that these improvements are not due to selective memory enhancements.

It might be supposed that sleep in general can aid problem solving by several mechanisms. For instance, sleep might be helpful simply by enabling avoidance of distractions that occur during wakeful periods. It is also known that memory consolidation occurs during sleep, and memories that are better established may also assist in problem solving. But there could be other benefits of sleep as well, especially specific phases of sleep.
A critical issue in sleep and cognition is whether improvements in behavioral performance are the result of sleep-specific enhancement or simply reduction of interference - since experiences while awake have been shown to interfere with memory consolidation. The researchers controlled for such interference effects by comparing sleep periods to quiet rest periods without any verbal input. ...

"Participants grouped by REM sleep, non-REM sleep and quiet rest were indistinguishable on measures of memory," said Cai. "Although the quiet rest and non-REM sleep groups received the same prior exposure to the task, they displayed no improvement on the RAT test. Strikingly, however, the REM sleep group improved by almost 40 percent over their morning performances."

The authors hypothesize that the formation of associative networks from previously unassociated information in the brain, leading to creative problem-solving, is facilitated by changes to neurotransmitter systems during REM sleep.

Here's the research abstract:

REM, not incubation, improves creativity by priming associative networks
The hypothesized role of rapid eye movement (REM) sleep, which is rich in dreams, in the formation of new associations, has remained anecdotal. We examined the role of REM on creative problem solving, with the Remote Associates Test (RAT). Using a nap paradigm, we manipulated various conditions of prior exposure to elements of a creative problem. Compared with quiet rest and non-REM sleep, REM enhanced the formation of associative networks and the integration of unassociated information. Furthermore, these REM sleep benefits were not the result of an improved memory for the primed items. This study shows that compared with quiet rest and non-REM sleep, REM enhances the integration of unassociated information for creative problem solving, a process, we hypothesize, that is facilitated by cholinergic and noradrenergic neuromodulation during REM sleep.

Further reading:

Problems are solved by sleeping (6/9/09) – BBC news article

Stages of sleep have distinct influence on process of learning and memory (2/25/09) – press release concerning prior reseach on REM sleep

Tags: ,

Stellar family in crowded, violent neighbourhood proves to be surprisingly normal

Sunday, July 19, 2009

Stellar family in crowded, violent neighbourhood proves to be surprisingly normal (6/4/09)
Using ESO’s Very Large Telescope, astronomers have obtained one of the sharpest views ever of the Arches Cluster — an extraordinary dense cluster of young stars near the supermassive black hole at the heart of the Milky Way. Despite the extreme conditions astronomers were surprised to find the same proportions of low- and high-mass young stars in the cluster as are found in more tranquil locations in our Milky Way.

The massive Arches Cluster is a rather peculiar star cluster. It is located 25 000 light-years away towards the constellation of Sagittarius (the Archer), and contains about a thousand young, massive stars, less than 2.5 million years old [1]. It is an ideal laboratory to study how massive stars are born in extreme conditions as it is close to the centre of our Milky Way, where it experiences huge opposing forces from the stars, gas and the supermassive black hole that reside there. The Arches Cluster is ten times heavier than typical young star clusters scattered throughout our Milky Way and is enriched with chemical elements heavier than helium.

Arches Cluster – click for 1280×1165 image

More: here

Rapamycin and lifespan extension

Sunday, July 12, 2009

Will a pill containing the immunosuppressant drug rapamycin someday extend human lifespan a few years? In spite of the hopeful research announcements that appeared a few days ago, I wouldn't recommend getting one's hopes up just yet.

This is a topic I've discussed before: Calorie restriction, TOR signaling, and aging. And for related stuff on mTOR: here.

The executive summary is that inhibition of mTOR signaling has been shown to extend lifespan in yeast, roundworms, and fruit flies. Mice can now be added to this list, in experiments that included rapamycin in their diet.

Here's the press release:

Easter Island Compound Extends Lifespan Of Old Mice: 28 To 38 Percent Longer Life (7/8/09)
On July 8, in the journal Nature, The University of Texas Health Science Center at San Antonio and two collaborating centers reported that the Easter Island compound – called "rapamycin" after the island's Polynesian name, Rapa Nui – extended the expected lifespan of middle-aged mice by 28 percent to 38 percent. In human terms, this would be greater than the predicted increase in extra years of life if cancer and heart disease were both cured and prevented.

Although rapamycin and some related compounds have been investigated as anti-cancer therapies, the hypothesized lifespan-extending benefits are thought to be related to the by now well-documented benefits of calorie restricted diets. (For very recent news on that front, see here, for example.)
Aging researchers currently acknowledge only two life-extending interventions in mammals: calorie restriction and genetic manipulation. Rapamycin appears to partially shut down the same molecular pathway as restricting food intake or reducing growth factors.

It does so through a cellular protein called mTOR (mammalian target of rapamycin), which controls many processes in cell metabolism and responses to stress.

A decade ago, Dr. [Dave] Sharp proposed to his colleagues that mTOR might be involved in calorie restriction. "It seemed like an off-the-wall idea at that time," Dr. Richardson said.

Experiments were performed in parallel at three separate research centers and consisted of feeding hundreds of mice, starting at an age of 20 months, a diet containing a special formulation of rapamycin designed to evade breakdown in the digestive system. It was found that the age at which 90% of mice had died rose from 1,078 days to 1,179 days in male mice, compared to controls, and from 1,094 days to 1,245 days in females. The total lifespan extension, on average, was therefore 9.4% in males and 13.8% in females.

Note that some accounts of the research claim lifespan extensions of 28% to 38%, but this is misleading, since those figures represent the extension of the "old age" period of mouse life beginning at 20 months. They do not mean that the mice lived up to almost 40% longer in total. (Some pretty shoddy reporting going on here....) And there was no particular evidence to indicate that extensions of such size would have occurred if the special diet began at an earlier age. However, in experiments still going on, there is evidence for some extension when addition of rapamycin to the diet begins for mice 270 days old.

Of course, even an extension of human lifespan in the 10% range – 7 or 8 years – would be quite an accomplishment, provided quality of life in the final years remained about where it is today. (Which is a big if.)

But there are various reasons to suspect that even a 10% extension in humans is rather optimistic. Some reasons:
  1. Rapamycin is an immunosuppressant, currently used therapeutically to prevent organ transplant rejection. The experimental mice were maintained under conditions that carefully protected them from infection – conditions that would not be realistic for humans.
  2. Although mice and humans are both mammals, their genetics are not all that similar. The complete sequence of the mouse genome was recently announced (see here), and it turns out that about 20% of mouse genes are different from human analogs, or not found in humans at all. (It's been 90 million years since the last common ancestor of mice and humans.)
  3. Rapamycin is known to inhibit an important protein kinase called mTOR (mammalian target of rapamycin). mTOR plays a key role in regulating cell growth, proliferation, and survival, so it's not all that surprising that rapamycin might affect cell biology relevant to aging and longevity. This same property of rapamycin makes it interesting as an anti-cancer agent. Rapamycin and similar compounds that inhibit mTOR have in fact been found to have anti-cancer properties in animal models. Several analogs of rapamycin have been investigated as anti-cancer therapies, and one has even been approved for human use (Torisel). But even in the anti-cancer setting, mTOR inhibitors haven't yet been slam-dunk successes.
  4. It is not clear that rapamycin in these experiments was working the same way as calorie restriction. None of the rapamycin-fed mice lost body weight, and calorie restriction usually works best when started relatively early in life.
  5. Experimental mice that received rapamycin got a dose of 2.24 mg per kg of body weight. That's quite a lot – about 30 to 60 times (per kg) what would be given to a 60 kg human for immunosuppression.

The unfortunate truth is that cell signaling pathways that affect cell growth, proliferation, and survival are rather complicated, and any interventions in such pathways are very likely to not have the expected effects and/or to have various unexpected side-effects. Here's a diagram of just some of the important pathways mTOR is involved in. Imagine that were an electrical circuit and you made ad hoc changes to important components of the circuit.... Perhaps you can see how trying to affect mTOR in order either to control cancer or enhance longevity might be a dicey proposition.

In spite of all the reservations, there are still promising signs for the role of mTOR inhibition in lifespan extension. The mechanism of action need not be the same as calorie restriction, even though that hasn't been ruled out either. For example, TOR is known from yeast and nematode studies to promote protein production in ribosomes and to inhibit protein degradation via autophagy. Invertebrate studies have shown that reversal of these TOR effects can increase lifespan. And TOR signaling is also known to influence cell growth, cell-cycle progression, mitochondrial metabolism, and insulin-analog signaling.

Remember what we said about the diversity of effects of mTOR signaling? That's definitely a sword that can cut both ways – it's powerful, but hard to predict and control. We need to understand a lot more of the biological details – otherwise we're just swinging the sword in the dark.

Harrison, D., Strong, R., Sharp, Z., Nelson, J., Astle, C., Flurkey, K., Nadon, N., Wilkinson, J., Frenkel, K., Carter, C., Pahor, M., Javors, M., Fernandez, E., & Miller, R. (2009). Rapamycin fed late in life extends lifespan in genetically heterogeneous mice Nature DOI: 10.1038/nature08221

Further reading:

Tests raise life extension hopes (7/8/09) – BBC news story

Immune drug boosts lifespan (7/8/09) – TheScientist.com

Fountain of Youth on Easter Island? (7/8/09) – ScienceNOW

Cancer Drug Delays Aging in Mice (7/8/09) – Wired.com

A pill for longer life? (7/8/09) – Nature.com

Ageing: A midlife longevity drug? (7/8/09) – Nature.com PDF

Rapamycin extends life in mice, raising hopes of life-prolonging drug for humans (7/9/09) – The Times (UK)

What Does Life-Extending Drug Mean for Humans? (7/9/09) – Time

New clues in search for elixir of youth (7/9/09) – New Scientist

Antibiotic Delayed Aging in Experiments With Mice (7/8/09) – New York Times

First Drug Shown to Extend Life Span in Mammals (7/8/09) – Technology Review

Longevity pill on the horizon? (7/10/09) – press release

Rapamycin: “An anti-aging drug today”? (3/6/07) – Ouroboros blog post

Tags: , , ,

New targeted therapy finds and eliminates deadly leukemia stem cells

Sunday, July 5, 2009

Insecure people who are derisive or dismissive of technical scientific terminology (which they affectedly disdain as "jargon") can miss a lot of significant meaning.

Consider the medical term "leukemia", which is familiar to the public as referring to a form of blood cancer. It's related to the less familiar term "leukocyte", which refers to various kinds of white blood cells. (The prefix "leuko-" is derived from Greek leukos, meaning "white". The suffix, "-cyte" is also Greek: kytos, meaning "cell".)

Leukocytes were originally recognized as distinct from other types of cells in the blood, especially "red" blood cells, which derive their color from iron-containing hemoglobin. There are actually a number of different types of leukocytes – and different types of corresponding leukemias. One common subtype of leukemia involves myeloid cells (myelocytes), which are normally found in bone marrow and occur as precursors to several types of blood cells. Acute myeloid leukemia (AML, also known as acute myelogenous leukemia) is the most common example, and has several subtypes itself.

Leukocytes of many types are derived from myeloid cells, which are thus a type of stem cell. When such cells develop certain types of abnormalities they harmfully overproduce derived cells, effectively making them cancer (specifically, leukemia) stem cells. The most common type of abnormality is a type of cell surface receptor known as CD123. A receptor is simply a protein found on a cell surface which binds to external cell signaling proteins called cytokines. (There's the "cyto-" again. The "-kine" part is from Greek kinos, which refers to motion, as in "kinetic".)

Cytokines are often interpreted by cells as signals to divide and proliferate, usually in a helpful way, as normal with immune system cells. Certain immune-system cytokines are called interleukins, because they facilitate signaling among immune system leukocytes. CD123 receptors, in particular, are receptors for interleukin-3. Thus CD123 receptors have another name: interleukin-3 receptor, alpha.

CD123 is essential for the normal communication between immune system cells such as T cells. It must exist on the surfaces of cells that need to respond to interleukin-3, in order to have a proper immune system response to infection. You do not, however, want CD123 on stem cells, whose excessive proliferation results in leukemia.

And so it is that one promising treatment for acute myeloid leukemia involves the development of a novel antibody, called 7G3, that can block CD123 receptors without triggering proliferation. Of course, that might interfere with immune system function – but such interference is preferable to leukemia.

New Targeted Therapy Finds And Eliminates Deadly Leukemia Stem Cells (7/2/09)
Associate Professor Lock [senior study author] and colleagues exploited the fact that the molecule CD123 is expressed at very high levels on LSCs but not on normal blood cells. CD123 is part of the interleukin-3 receptor, a protein that interacts with a growth factor (called a cytokine) that influences cell survival and proliferation. The researchers created a therapeutic antibody that recognized and bound to CD123 with the hope that this antibody would selectively interfere with AML-LSC survival.

When AML-LSCs from human patients were transplanted into mice treated with the antibody, called 7G3, cytokine signaling in the tumor cells was blocked. Further, 7G3 impaired migration of the AML-LSCs to bone marrow and activated the innate immune system of the host mouse to destroy the AML-LSCs. Overall, treatment with 7G3 substantially improved mouse survival when compared with control groups. The researchers go on to report that a CD123-targeting antibody is currently being used in phase 1 clinical trials of advanced AML and that there are no signs of treatment-related toxicity.

Update, 8/14/09: Here's another research effort that's targeting CD123 in AML: New discovery points to a new treatment avenue for acute myeloid leukemia (7/6/09)

Further reading:

New Drug Hits Leukemia Early (7/2/09) – Science News article

Monoclonal Antibody-Mediated Targeting of CD123, IL-3 Receptor α Chain, Eliminates Human Acute Myeloid Leukemic Stem CellsCell Stem Cell research article

Tags: , cancer stem cell

Intermediate mass black holes

Saturday, July 4, 2009

Black holes are controversial. (Just browse reader comments from partisans of various sorts of "alternative" astrophysical theories – which can be found at the end of many articles dealing with black holes that allow commenting by the general public.)

Nevertheless, very solid evidence has been accumulated over the years for the existence of two types of black holes: stellar-mass black holes with masses from 3 to several tens of solar masses (M), and supermassive black holes, which are vastly larger – generally millions to billions M. Concerning some of the evidence, see here.

Stellar-mass black holes are easy to explain as supernova remnants, while supermassive black holes seem to be an inseparable concomitant of the development of all galaxies.

Perhaps surprisingly, however, there has been very little evidence for the existence of black holes of intermediate mass. If such black holes exist at all, the processes that form them must be rather more unusual. Evidence for the existence of intermediate mass black holes has been reported in the past. (There's some discussion here of possible black holes of mass less than a million M.)

But because black holes, by their nature, are difficult to observe directly, and so their existence must be inferred indirectly, it has been difficult to come up with relatively unambiguous evidence. Now we have announcements of better evidence in two cases.

New Class Of Black Holes Discovered (7/1/09)
A new class of black hole, more than 500 times the mass of the Sun, has been discovered by an international team of astronomers.

The finding in a distant galaxy approximately 290 million light years from Earth is reported today in the journal Nature.

Until now, identified black holes have been either super-massive (several million to several billion times the mass of the Sun) in the centre of galaxies, or about the size of a typical star (between three and 20 Solar masses).

The new discovery is the first solid evidence of a new class of medium-sized black holes.

Important discoveries often don't come by themselves. Other researchers and teams tend to report related results at the same time. And this is no exception. The above reports concern a candidate object in a galaxy (ESO 243-49) about 290 million light-years away. But there's also a report of an object much closer, in the globular cluster M54 (more here), which is only about 87,000 light-years away. It's thought to belong, actually, not to the Milky Way itself, but rather to the Saggitarius Dwarf Elliptical Galaxy, a satellite of the Milky Way.

Density and kinematic cusps in M54 at the heart of the Sagittarius dwarf galaxy: evidence for a 104 M Black Hole?
We report the detection of a stellar density cusp and a velocity dispersion increase in the center of the globular cluster M54, located at the center of the Sagittarius dwarf galaxy (Sgr). The central line of sight velocity dispersion is 20.2 +/- 0.7 km/s, decreasing to 16.4 +/- 0.4 km/s at 2.5" (0.3 pc). Modeling the kinematics and surface density profiles as the sum of a King model and a point-mass yields a black hole (BH) mass of ~ 9400 M. However, the observations can alternatively be explained if the cusp stars possess moderate radial anisotropy.


Further reading (ESO 243-49 candidate object):

Finally, an Average Black Hole (7/1/09) – ScienceNOW

New Candidates for Midsize Black Holes (7/3/09) – Sky and Telescope

An intermediate-mass black hole of over 500 solar masses in the galaxy ESONature research article

XMM-Newton discovers a new class of black holes (7/1/09) – ESA press release

New Observations Suggest Mid-Size Black Holes Exist (7/1/09) – Space.com

Black holes: now available in size 'M' (7/2/09) – Cosmos magazine

New Class of Black Hole Found? (7/1/09) – National Geographic

Astronomers Discover Medium-Sized Class of Black Holes (7/1/09) – Universe Today

Intermediate-mass black hole (7/1/09) – Science Centric

Astronomers sniff intermediate mass black hole (7/2/09) – The Register

Astronomers Size Up a Candidate for Midsize Black Hole (7/1/09) – Scientific American

New Class of Black Holes Discovered (7/1/09) – Wired

X-rays are smoking gun for middleweight black holes (7/1/09) – New Scientist

A New Kind of Black Hole (7/2/09) – Smithsonian.com

Team May Have Found Intermediate Black Hole (7/6/09) – New York Times

Further reading (M54 candidate object):

Density and kinematic cusps in M54 at the heart of the Sagittarius dwarf galaxy: evidence for a 10^4 M_sun Black Hole?Astrophysical Journal research article


Knowledge Link Suggest

Drug Abuse Online Lottery Games Drug Abuse Health and Fitness Health and Fitness free music downloads Law Reports Wallpapers Artist online shop originals Product Auto Parts Web Developer online shop originals Product Insurance Company Health Life Technology System Home Security Beauty Cosmetic Online Travel Agency Linux Tips Guide Shooting Simulator Gadgets Technology Project Build Houses Payday Loans Health News Information Animals Shop Travel Agency North Owl Network Dentist Healthy Aging asian pretty The Tool Hospital Barbecook Best way to make Money with Forex Trading Green Home Design Online Lottery atozbythesea.eu.org augmentezvosventes.eu.org automobielbedrijf.eu.org aworldofwindows.eu.org aws-orgware.eu.org azregionalmls.eu.org bacimamma.eu.org Business Plan Competition travel channel and rental cars Pharmacy and drugs Criminal Justice Planning Agency Lawyers Association The Best of Insurance http://celebritytidings.eu.org http://livingandfashion.eu.org Academic Advising Audio logo Stock Audio auto repair advice guide Healthy Women Medical Centre busy with business Car Finance Tools Debt Settlement Lawyer crafty stash corner cuentas and colors Cheap Wedding Dresses drug abuse statistics Lifestyle Home Solutions education essay titles finance insurance premium Lawyer and Legal Information guide healthy recipes health problems of children health topics kids home decorating service home improvement project home improvement project management home improvement project planning home insurance morgages house insurance plan house insurance progressive The Savings Bank insurance agency business loans insurance business loans insurance premium loan legacy landscape blocks legacy landscape contractors legacy landscape materials personal insurance loan real estate for commercial Bedroom Furniture Lawyer Requirements Concept Design teach about alcohol abuse technology support autocar the family deal tile flooring ideas tips lifetime fitness tips reduce car insurance quotes Online Jewelry Stores traveller hotel Insurance and Finance Auto and Parts wood flooring ideas the networks board game Adult Learning Theories sexy lingerie tattoo designs wallpaper artist health category insurance financial category Category Online Money Category Home Improvement online business category Category software games and android category marketing advertising category marketing advertising Home Solution Real Estate Financing Lucepedia Sports and Fitness Train Now Business Economy Global auto car loans car loans insurance Health Information how to prevent diabetes Best Credit Cards Cheap Wedding Dresses Small Business Finance Systems Body Health Home Improvement Services Guide Android Apps and Games fashion design Alcoholism Android Phones Board Games Cheap Tickets and Vacation Packages Online Prevent Child Obesity Prevent Premature Ejaculation Labor Lawyers Home Interior Design Ideas plumbers and carpet cleaning service diet and slimming Beautiful Picture Doctors Dental Care music video art BurningPedia Guide Planning Home Improvement Beauty Cosmetic Web Development Company lawyer requirements Books On Children Education security innovation work iPhone and iPad Turkey The Medical School Barbecue Electric The Linux Documentation Project Mental Health Care New Car Buying Guide House Curtains Dentist All System Education iPhone Specifications Cloud Trading Strategy mortgages and loans Pharmaceutical Info Online Application Service Provider The Masterchef Business Service Delivery Arts and Entertainment Pokerstars Real Money The Masterchef Electric Motors Gadgets Technology Casino Zone Small Business Solutions Home Advice Fashion Design Clothing Adventure Games Health and Fitness Hospital Equipment Plan Life Insurance public transportation services Prevent Premature Ejaculation Best Professional Carpet Cleaning Web Hosting Vehicle Emissions Inspection Drug Abuse Collection Travel Agency Medical Herbs color vision casting Aromatherapy Tips community film Cardio Tips Top Best Home Improvements Article Marketing Colon Cleanse Tips Terms and Conditions of Sale Products for Treating Acne Scars Natural Beauty Products Seo Web Marketing Business Prospects Trade Online Tool House Cleaner Bathing Equipment Financial Solutions Credit Loans Business Insurance Best Supplements Online Affiliate Marketing Web Design Jobs Online Business Degrees Travel and Leisure Hotel Business Online Payment Processor Women Management Criminal Law Marketing Product Webdesign Transportation Services The Marketing Business Prospects Trade Online Shop bed furniture free movies online Direct Hardware Supply Free Download PDF Technology Ipad doctors Specials Medical Dictionary Legacy Landscape Bank South Pacific Carpet Cleaner Best Internet Business Seo Web Marketing Doctor Healthy Doctors Diet Program Health Benefits of Drinking Water ups pills drugs Best Supplements dynasty fine jewelry Ceramic Floor Tile Online Business Degrees Property Residential and Commercial Real Estate All About Medical Bankruptcy Prevent Child Obesity Handbag and Shoes Education of Children physiotherapy school Cheap Airline Tickets Healthy Life PET online Interzoo Rehabilitation Center electric hybrid vehicles Baidu Software Center Automotive Advertising Agencies Health and Care Virtual private network Student Education Technosound Wedding Dresses excel archives Classic Car Restoration Defense Audit Banking Travel and holiday Forex Trading Jobs Cheap Car Insurance Opening the Book Safe Chemical Act Presspeople System Software Plan Life Insurance Top Best Home Improvements Cheap Car Insurance Auto Parts and Service Swiss Business Acting in Real Time Fitness Equipment Tips Bodybuilding Tips Search Engine Optimization Cardio Tips Beauty Salon Express The Best Advice Lawyer Advice Associated With Online Payday Spa and Wellness Center Packages Holiday Travel European Countries Tours Small Business Finance Electronic Cigarette Commercial Law Advice on Travel Planning Home and Family All System Education Graphic Visual Photo business between countries Shop Online Financial Security Authority Latest Fashion Trends Photoshop Wallpaper Real Estate Agents Micro Cogeneration Beauty Products Business Travel Insurance International Trucks For Sale Hair Tonic Top Web Design Business Financial Touring Start Vehicle Emissions Inspection Business Service Delivery Insurance and Finance Web Design Business Shopping Online Insurance Processing Systems Electric System Vehicle Blood Medicine European Vehicle Market Pharmaceutical Section Home sale Beauty Therapy Acupuncture Recipes Kitchen Restaurant Hardwood Flooring Resident Services The Masterchef Employment and the Economy Free Web Design Paint Creations Travel Insurance SEO Consulting Services Car Insurance Loans Doctors Dental Care Vehicle Wash Systems Search Engine Marketing Online Education Schools Natural Beauty Site Cheap Wedding Dresses annuaire automobile episiotomy and pregnant Westerly Lawyers Healthcare Travel Vacations Cheap iPhone Specifications The ReaL Estate Event Online Pharmacy and Drugstore Music Video Art CareCredit Cloud Trading Strategy House Cleaning Services Interoperability the talent agency Good Home Design shooting simulator Independent Port Services The Hotel Sax The Digital Money Booking Tickets and Hotels Online Business Loans Department of Pharmacy Law Free Credit Report football development Trending in Entertainment Prison Education Sexy Lingerie Wood Flooring Ideas Dealer Optics and Ophthalmology Car Insurance Online Urbanism and Architecture Electronic money International Conference on Education Dental Care Auto Repair Shop Auto Repair Advice Guide Dental Clinic Online Pharmacy Debt Consolidation Loans Free Software Smartphone Advice on benefits Insurance Providence Real Estate Product Research Analyst Product Research Facilitator Fashion Magazine Substance Abuse Education And Technology Marketing Strategy The Best Payday Advance Incident Report Criminal Accounting Books Caring for Pets Real Estate Financing Banking Software Solutions Financial Solutions Credit Loans Full Service Research Agency Discover our free games Business Prospects Trade Online Restaurant Hood Cleaning how to start a business Women's Health and Beauty Payday Loans Criminal Attorney Lawyers Travel and Tourism Fashion Designer The Food Products Fitness and Sports The Beginner's Guide to Businesses Tips To Make SEO Techniques Online Payday Loans Medical Advocate Englisch Training Online Drivers Education Auto Parts and Service Best hotels cheap sport shoes Dental Work Insurance Company Android Phones Financial Advice Service Mobile phone Free Credit Report  The Hair Tonic Advantage Car Rental Information Civil Law Information Payday Cash Loans Payday Cash Loans Advance Affordable Auto Insurance Effective Quality Services Car seats Product Interactions Specialist Medicina Natural Traveller and Hotel European Investment Bank Vehicle Electrical System Pet Food Shop Online Lawyer Employment Plaza Ballroom Weddings Art School The best form of insurance solutions Advice on benefits Insurance Medical coding Tutor Buying Safe Products Free Online Game Famous Fashion Designers Education in Music Virtual Currency Systems Learn Trading Folktronica music Digital currency Manufacturing Engineering Technology Fashionista The Money System Explained Good Marketing In Business Technology Ipad Real Estate Bubble CarePass for Android Business Direct Marketing Carpet Cleaner Natural Beauty Products Seo Web Marketing Business Prospects Trade Online Tool House Cleaner Bathing Equipment Financial Solutions Credit Loans Business Insurance Best Supplements Online Affiliate Marketing Web Design Jobs Online Business Degrees Travel and Leisure Hotel Property Residential and Commercial Real Estate All About Medical Bankruptcy Prevent Child Obesity Handbag and Shoes Education of Children Women Management Free Online Slots Games Healthy Life PET online Interzoo Sunrise Health and Rehabilitation Center Presspeople System Software Baidu Software Center Scientific Entrepreneurship Automotive Advertising Agencies Health and Care Virtual private network Student Education Technosound Information network energy sources Niche Dating Classic Car Restoration Defense Audit Banking Travel and holiday Safe Chemical Act Leader in internet information Music Electric The Marketing verb translation country island FILM LITERATURE GOLD STATUS A Short History of Movies Sexy Lingerie Classified ads Inspire Home Design Trauma Clinic Finance Investment Business Marketing Acting in Real Time Glasgow Tourism Herbal Medicine Cheap Car Insurance Quotes Health Pregnancy Professional Graphic and New Media Designers Legal Connect Network Generating Money Online Oregon health plan Slow Cooker Recipes Best Internet Business Terms and Conditions of Sale Products for Treating Acne Scars Hardwoods Furniture Green Tea Fitness Equipment Tips Bodybuilding Tips Forex Trading Article Marketing Colon Cleanse Tips Hair Loss Tips List Building Search Engine Optimization Cardio Tips Aromatherapy Tips Medical Weight Loss Clinic The Benefits Of Moving Insurance Travel Advice Online Dating Security Network Information Green Energy Scheme Group Auto International Business Telecommunication International All Medicine Reviews Marketplace Real Estate Review Clothing Style Management Consulting Real estate Natural Medicine Treatment Natural Beauty Skin Care Products Shop online Marketing Bank rent car guide Fishing Games cheap website traffic Health and Beauty Gambling football Clothes and Accessories Garden and Landscaping Portal Game Online E-commerce Business Car Accident Lawyer Criminal Law Best free Android apps Hotel and Travel Jobs Technology Film Industry Free Music Downloads Solar Installation Search Engine Optimization Life Technologies Football Betting Site Substance Abuse Apartments home improvement contractor job Luxury Car News Law Products and Services Business Web Hosting Company Complaints Diabetes Drug Abuse Marketing Product Make Money Online Living Without Money Apartments Luxury Car News Law Products and Services Growth Technologies Articles on business growth technologies information Health Insurance Management Advisors System Solar Panel Online Trading The Best of Insurance Payday Loans for Bad Credit Financial Solutions Credit Loans Ensure Insurance Plan Financial Management Team Payday Loans Reviews Distributed File System Student Loan Payments Cheap Insurance in Los Angeles Favorite Fashion Styles The Best Savings Rates Manage Student Loans Webshop europe business guide Shop Personal Loans debt consolidation loans Personal Loan Repayment Chiropractic Tables Webdesign Management Concepts Android Software Free Internet Solution the online casino Best Small Business Blogs Sound Beginnings Automotive Electrical Systems Skin Care in Centrum Master Ethique Cher Client Agency Law Sell Products Online Mens Shoes Strategy Business Development Women's shoes Headache Causes Shop Online Clothing Online Pharmacy Healthy Aging Battle Games best electric vehicle Commercial Real Estate Cosmetic Beauty Product Health Medicine Pharmacy Image of the Orient Fashion Jewellery

Blog Archive