26 posts · 9,467 views
Science and reason is all about... science and reason. News and explanations of recent developments in the most intriguing branches of science. Philosophical and political issues of relevance are also discussed.
Charles Daney
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- August 8, 2010
- 10:39 PM
- 77 views
What does marathon running do to an athlete's cells?
by Charles Daney in Science and Reason
If you've ever taken up running as a form of exercise, or even thought about it, there's a certain paradox that may have occurred to you. The health benefits of aerobic exercise are well-documented. (See here, for example.) In particular such exercise has been shown to reduce risks of cardiovascular disease, diabetes, and some forms of cancer. Beneficial physiological effects include reduction of high blood pressure, better control of blood sugar, and reducing blood levels of low-density lipopro........ Read more »
Marfe, G., Tafani, M., Pucci, B., Di Stefano, C., Indelicato, M., Andreoli, A., Russo, M., Sinibaldi-Salimei, P., & Manzi, V. (2010) The effect of marathon on mRNA expression of anti-apoptotic and pro-apoptotic proteins and sirtuins family in male recreational long-distance runners. BMC Physiology, 10(1), 7. DOI: 10.1186/1472-6793-10-7
- July 17, 2010
- 11:35 PM
- 114 views
Quasars in the very early universe
by Charles Daney in Science and Reason
Quasars are powered by the gravitational (potential) energy of their central supermassive black holes. However, their distinctive features – their extremely high luminosity in particular – are very dependent on characteristics of matter close to the black hole. Most supermassive black holes (SMBH), including those at the centers of the Milky Way and our close neighbor M31 (Andromeda), are responsible for fairly small amounts of radiation in any part of the electromagnetic spectrum. T........ Read more »
Jiang, L., Fan, X., Brandt, W., Carilli, C., Egami, E., Hines, D., Kurk, J., Richards, G., Shen, Y., Strauss, M.... (2010) Dust-free quasars in the early Universe. Nature, 464(7287), 380-383. DOI: 10.1038/nature08877
- June 28, 2010
- 12:27 AM
- 146 views
Creativity and mental illness
by Charles Daney in Science and Reason
The association between creativity and mental illness is sort of a cliché – but that doesn't mean there's nothing to it. Standard examples given include Vincent van Gogh, Robert Lowell, and John Nash.There has been a rather large amount of research into the connection, and a large number of biographical accounts of famous creative people who also suffered from mental illness. But the neurobiological details are emerging only slowly. After all, our understanding of the biological roo........ Read more »
de Manzano, �., Cervenka, S., Karabanov, A., Farde, L., & Ullén, F. (2010) Thinking Outside a Less Intact Box: Thalamic Dopamine D2 Receptor Densities Are Negatively Related to Psychometric Creativity in Healthy Individuals. PLoS ONE, 5(5). DOI: 10.1371/journal.pone.0010670
- May 12, 2010
- 11:24 PM
- 162 views
Where the action is in black hole jets
by Charles Daney in Science and Reason
The object known simply as 3C 279 is rather distinctive for several reasons, in spite of the rather unassuming name. For one thing it's an active galaxy – that is, it has a supermassive black hole at its center, and that black hole is sucking in surrounding matter at a rate high enough to generate as much energy as all stars the in the galaxy where it resides combined. Only about 1% of visible galaxies are active galaxies like 3C 279.But that's not all. 3C 279 is also a radio galaxy, a sub........ Read more »
Abdo, A., Ackermann, M., Ajello, M., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Baughman, B., Bechtol, K.... (2010) A change in the optical polarization associated with a γ-ray flare in the blazar 3C 279. Nature, 463(7283), 919-923. DOI: 10.1038/nature08841
- April 25, 2010
- 11:42 PM
- 195 views
Active galaxies and supermassive black hole jets
by Charles Daney in Science and Reason
Most galaxies have a supermassive black hole in their center – sometimes even more than one. These black holes can have masses up to ten billion solar masses (1010 M⊙) or more. One of the largest known examples is part of a binary system, and it weighs in at 1.8×1010 M⊙ – see here, here, or here. (There are exceptions, such as the nearby M33, which apparently does not have a central black hole of mass more than 3000 M⊙.)All black holes gravitationally attract ........ Read more »
Evans, D., Reeves, J., Hardcastle, M., Kraft, R., Lee, J., & Virani, S. (2010) THE HARD X-RAY VIEW OF REFLECTION, ABSORPTION, AND THE DISK-JET CONNECTION IN THE RADIO-LOUD AGN 3C 33. The Astrophysical Journal, 710(1), 859-868. DOI: 10.1088/0004-637X/710/1/859
- March 12, 2010
- 03:01 AM
- 248 views
Galaxies are slowly running out of gas
by Charles Daney in Science and Reason
Galaxies are made of stars, and stars are made of... gas. So a large part of understanding how galaxies evolve and grow is understanding how much "gas" (literally, not "gasoline") is present in galaxies – but has not yet been incorporated in stars – at different periods in the history of the universe.What periods of the universe are most interesting in this regard? The answer is: periods somewhat less than the first half of the universe's existence since the time of the big bang, rou........ Read more »
Tacconi, L., Genzel, R., Neri, R., Cox, P., Cooper, M., Shapiro, K., Bolatto, A., Bouché, N., Bournaud, F., Burkert, A.... (2010) High molecular gas fractions in normal massive star-forming galaxies in the young Universe. Nature, 463(7282), 781-784. DOI: 10.1038/nature08773
- March 7, 2010
- 05:04 AM
- 233 views
Gamma-ray bursts without the gamma rays?
by Charles Daney in Science and Reason
We discussed supernovae a bit in this recent post on gamma-ray bursts. There is now interesting new information on the connection between supernovae and gamma-ray bursts from two recently-described supernovae with atypical properties.Let's first review a little. Gamma-ray bursts (GRBs) are identified by detection of relatively brief (usually less than a few minutes) but highly energetic emissions of gamma rays. Although there's a great deal of diversity, most events fall into one of two categori........ Read more »
Soderberg, A., Chakraborti, S., Pignata, G., Chevalier, R., Chandra, P., Ray, A., Wieringa, M., Copete, A., Chaplin, V., Connaughton, V.... (2010) A relativistic type Ibc supernova without a detected γ-ray burst. Nature, 463(7280), 513-515. DOI: 10.1038/nature08714
Paragi, Z., Taylor, G., Kouveliotou, C., Granot, J., Ramirez-Ruiz, E., Bietenholz, M., van der Horst, A., Pidopryhora, Y., van Langevelde, H., Garrett, M.... (2010) A mildly relativistic radio jet from the otherwise normal type Ic supernova 2007gr. Nature, 463(7280), 516-518. DOI: 10.1038/nature08713
- February 27, 2010
- 10:06 PM
- 195 views
Spiral galaxies are taking over
by Charles Daney in Science and Reason
Everybody knows what a spiral galaxy looks like. Here's a typical nearby example (M74):Among the largest and brightest galaxies close to our own, about 72% are of this spiral type, like M74. There is a classification system for galaxy shapes, and the remaining 28% of large, bright, nearby galaxies fall into classes called "elliptical", "lenticular", or simply "peculiar". (For simplicity and for other reasons that will become apparent, we're ignoring smalle........ Read more »
Delgado-Serrano, R., Hammer, F., Yang, Y., Puech, M., Flores, H., & Rodrigues, M. (2010) How was the Hubble sequence 6 Gyr ago?. Astronomy and Astrophysics. DOI: 10.1051/0004-6361/200912704
- February 24, 2010
- 03:06 AM
- 218 views
Where have all the protons gone?
by Charles Daney in Science and Reason
Astronomers have long known that there is a rather close relationship between the intrinsic luminosity of a spiral galaxy and the rotational velocity of stars (around the galactic center) in the outer portions of the galaxy. This relationship even has a name: the Tully-Fisher relation.It has also been known that small, nearby dwarf galaxies, which are irregular in shape, are not nearly as bright as they "should" be, according to the Tully-Fisher relation, given the measured average velocities of........ Read more »
McGaugh, S., Schombert, J., de Blok, W., & Zagursky, M. (2010) THE BARYON CONTENT OF COSMIC STRUCTURES. The Astrophysical Journal, 708(1). DOI: 10.1088/2041-8205/708/1/L14
- February 22, 2010
- 02:15 AM
- 237 views
Dwarf galaxies start making sense
by Charles Daney in Science and Reason
Cosmology has, for a decade, had its "standard model", which largely explains most of the cosmological phenomena that astronomers are able to observe. Except for a relatively small number of things that don't seem to make sense in the model. Prominent among the latter are dwarf galaxies – by one definition, galaxies having less than 10% of the total mass of the Milky Way.The standard model of cosmology is known officially as the Λ-cold-dark-matter model – ΛCDM. (This th........ Read more »
Governato, F., Brook, C., Mayer, L., Brooks, A., Rhee, G., Wadsley, J., Jonsson, P., Willman, B., Stinson, G., Quinn, T.... (2010) Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows. Nature, 463(7278), 203-206. DOI: 10.1038/nature08640
- February 15, 2010
- 10:46 PM
- 174 views
Far out!
by Charles Daney in Science and Reason
If you're interested in something out of the ordinary, astronomically speaking, the best place to look for the exotic may be as far away (in both space and time) as possible.Perhaps that's why I like to consider really far out stuff, like the most distant gamma-ray burst seen yet. Or maybe I just like to get away from the depressing chaos and confusion of "modern" life.In any case, there's always something new, just beyond the farthest thing we've seen yet. That far-out gamma-ray burst (GRB 0904........ Read more »
R. J. Bouwens, G. D. Illingworth, I. Labbe, P. A. Oesch, M. Carollo, M. Trenti, P. G. van Dokkum, M. Franx, M. Stiavelli, V. Gonzalez.... (2009) Constraints on the First Galaxies: z~10 Galaxy Candidates from HST WFC3/IR. Nature. arXiv: 0912.4263v2
- January 31, 2010
- 12:31 AM
- 247 views
Magnetic fields in gamma-ray burst jets
by Charles Daney in Science and Reason
Gamma-ray bursts (GRBs) are the most dramatic short-lived violent events observed in the universe. They are often described as releasing a quantity of energy, in less than a minute, that is at least as much as a star like the Sun releases in its entire 10 billion year lifetime. Since the first detection of a gamma-ray burst in 1967, the central question has been to determine the nature of the process or processes that can release so much energy so quickly.We've discussed gamma-ray burst several ........ Read more »
Steele, I., Mundell, C., Smith, R., Kobayashi, S., & Guidorzi, C. (2009) Ten per cent polarized optical emission from GRB 090102. Nature, 462(7274), 767-769. DOI: 10.1038/nature08590
- January 4, 2010
- 03:07 AM
- 260 views
Space is very fine-grained
by Charles Daney in Science and Reason
It would take you a lot longer to hike a significant distance over very hilly terrain than it would over a completely flat plain. For much the same reason, it would take light longer to cover the same distance depending whether the space through which it moves does or doesn't have large "hills".But what does it mean for space to contain "hills"? And how large do "hills" need to be to make a difference?Consider the second question first. There's no natural place on Earth that is perfectly flat, o........ Read more »
Abdo, A., Ackermann, M., Ajello, M., Asano, K., Atwood, W., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Baring, M.... (2009) A limit on the variation of the speed of light arising from quantum gravity effects. Nature, 462(7271), 331-334. DOI: 10.1038/nature08574
- November 2, 2009
- 01:26 AM
- 318 views
Most Distant Known Object In The Universe
by Charles Daney in Science and Reason
On April 23 of this year the Swift Gamma-Ray Burst Telescope detected, just as it was designed to do, a gamma-ray burst (GRB). Within less than a day two of the most powerful Earth-based telescopes had begun studying the quickly fading light of the object, known as GRB 090423. (There were other observatories investigating it as well.)Because the light from GRBs fades so rapidly, most such objects are detected from space-based instruments that are especially designed for the purpose, like Swift. ........ Read more »
Tanvir, N., Fox, D., Levan, A., Berger, E., Wiersema, K., Fynbo, J., Cucchiara, A., Krühler, T., Gehrels, N., Bloom, J.... (2009) A γ-ray burst at a redshift of z ≈ 8.2. Nature, 461(7268), 1254-1257. DOI: 10.1038/nature08459
Salvaterra, R., Valle, M., Campana, S., Chincarini, G., Covino, S., D’Avanzo, P., Fernández-Soto, A., Guidorzi, C., Mannucci, F., Margutti, R.... (2009) GRB 090423 at a redshift of z ≈ 8.1. Nature, 461(7268), 1258-1260. DOI: 10.1038/nature08445
- October 26, 2009
- 02:22 AM
- 289 views
A surprisingly compact early galaxy
by Charles Daney in Science and Reason
Astronomers are beginning to learn significant details of the structure of galaxies in the early universe. And what they're learning is rather surprising: at least some early galaxies are almost as massive as otherwise similar galaxies in the present universe, yet they are much smaller in linear size, by a factor of five, thus much more compact.What time period are we talking about here? It's not actually the time that the earliest galaxies formed, which was less than a billion years after the b........ Read more »
van Dokkum, P., Kriek, M., & Franx, M. (2009) A high stellar velocity dispersion for a compact massive galaxy at redshift z . Nature, 460(7256), 717-719. DOI: 10.1038/nature08220
- October 10, 2009
- 05:15 AM
- 363 views
Telomerase and Wnt signaling
by Charles Daney in Science and Reason
Now that research into telomeres and telomerase has (finally) garnered a Nobel Prize, it's a good time to write about recent research on the subject.Seminal work on telomeres by Elizabeth Blackburn, one of the Nobel winners, was published way back in 1978, and active studies have been going on ever since. So perhaps it's not surprising that the rate of new findings is not so rapid as occurs in newer areas – such as stem cells.But fascinating new results on telomeres and telomerase do still........ Read more »
Park, J., Venteicher, A., Hong, J., Choi, J., Jun, S., Shkreli, M., Chang, W., Meng, Z., Cheung, P., Ji, H.... (2009) Telomerase modulates Wnt signalling by association with target gene chromatin. Nature, 460(7251), 66-72. DOI: 10.1038/nature08137
- September 26, 2009
- 12:28 AM
- 384 views
Induced pluripotent stem cells with one transcription factor
by Charles Daney in Science and Reason
Just under three years ago, in October 2006, some important stem cell research was announced by a Japanese scientific team led by Shinya Yamanaka. The team showed how ordinary mouse skin cells could be transformed into cells that turned out to be pluripotent, just like embryonic stem cells (ESCs). The new cells were called induced pluripotent stem cells (iPSCs). Although "ground-breaking" is an over-used term, this research genuinely deserved the description.Aside from the fact that it could be ........ Read more »
Kim, J., Greber, B., Araúzo-Bravo, M., Meyer, J., Park, K., Zaehres, H., & Schöler, H. (2009) Direct reprogramming of human neural stem cells by OCT4. Nature. DOI: 10.1038/nature08436
- September 8, 2009
- 03:57 AM
- 374 views
New anti-cancer role for p53
by Charles Daney in Science and Reason
I suppose that just about everyone knows of the important role the p53 protein plays in protecting cells from becoming cancerous. The protein was identified 30 years ago and its gene (TP53) cloned soon thereafter. What's not so widely known is just how complex the operation of p53 in protecting against cancer really is. And very recent research shows the complexity is even more than previously thought. However, the complexity is to be expected, because evolution doesn't "design" cellular mechani........ Read more »
Suzuki, H., Yamagata, K., Sugimoto, K., Iwamoto, T., Kato, S., & Miyazono, K. (2009) Modulation of microRNA processing by p53. Nature, 460(7254), 529-533. DOI: 10.1038/nature08199
- August 17, 2009
- 02:14 AM
- 361 views
Inflammation, microRNA, and cancer
by Charles Daney in Science and Reason
If there's just one single point worth making about the biology of cancer, it would have to be "it's complicated".Cells in general, and animal cells in particular, are extremely intricate Rube-Goldberg-like mechanisms. Their correct functioning depends on the integrity of 20,000 or so genes (in the case of humans), and at least 5 times as many proteins whose form is specified by the genes. Damage to even one of a few thousand important genes can put a cell on the road to becoming cancerous. So t........ Read more »
Pedersen, I., Otero, D., Kao, E., Miletic, A., Hother, C., Ralfkiaer, E., Rickert, R., Gronbaek, K., & David, M. (2009) Onco-miR-155 targets SHIP1 to promote TNFα-dependent growth of B cell lymphomas. EMBO Molecular Medicine, 1(5), 288-295. DOI: 10.1002/emmm.200900028
- July 12, 2009
- 05:45 AM
- 496 views
Rapamycin and lifespan extension
by Charles Daney in Science and Reason
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........ Read more »
Harrison, D., Strong, R., Sharp, Z., Nelson, J., Astle, C., Flurkey, K., Nadon, N., Wilkinson, J., Frenkel, K., Carter, C.... (2009) Rapamycin fed late in life extends lifespan in genetically heterogeneous mice. Nature. DOI: 10.1038/nature08221
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