Friday, December 26, 2008

Is Dark Matter Neutrinos?

Do non-relativistic neutrinos constitute the dark matter?
The observed dark matter distribution of a supercluster of galaxies is modelled by non-relativistic neutrinos. There is other evidence against this, however, some of which is mentioned in the paper.

Saturn Orbit Anomaly

On the recently determined anomalous perihelion precession of Saturn
The astronomer E.V. Pitjeva, by analyzing with the EPM2008 ephemerides a large number of planetary observations including also two years (2004-2006) of normal points from the Cassini spacecraft, phenomenologically estimated a statistically significant non-zero correction to the usual Newtonian/Einsteinian secular precession of the longitude of the perihelion of Saturn, i.e. \Delta\dot\varpi_Sat = -0.006 +/- 0.002 arcsec/cy; the formal, statistical error is 0.0007 arcsec/cy. It can be explained neither by any of the standard classical and general relativistic dynamical effects mismodelled/unmodelled in the force models of the EPM2008 ephemerides nor by several exotic modifications of gravity recently put forth to accommodate certain cosmological/astrophysical observations without resorting to dark energy/dark matter. Both independent analyses by other teams of astronomers and further processing of larger data sets from Cassini will be helpful in clarifying the nature and the true existence of the anomalous precession of the perihelion of Saturn.

Monday, December 22, 2008

Volcanic Eruption in HD


Guatemala's Mt. Santiaguito

More than one Time Dimension

Multiple Time Dimensions
The possibility of physics in multiple time dimensions is investigated. Drawing on recent work by Walter Craig and myself, I show that, contrary to conventional wisdom, there is a well-posed initial value problem--deterministic, stable evolution--for theories in multiple time dimensions. Though similar in many ways to ordinary, single-time theories, multi-time theories have some rather intriguing properties which suggest new directions for the understanding of fundamental physics.

Cosmic Microwave Background (CMB) Asymmetry

Title: Power Asymmetry in Cosmic Microwave Background Fluctuations from Full Sky to Sub-degree Scales: Is the Universe Isotropic?
Our results indicate that the reported common asymmetric axis extending over a large range in scales is highly unlikely to be a statistical fluke. Foregrounds and systematic effects do not seem to be probable explanations. The CMB does seem to have an uneven power distribution on the sky over a large range of angular scales. An important task for further research is to find a physical explanation for this asymmetry which can predict possible effects on CMB polarization to be tested in future experiments.

Sunday, December 21, 2008

Graphene Sheets

Graphene Recipe Yields Carbon Cornucopia in Science.
The hottest material in physics these days is graphene, sheets of carbon just a single atom thick. Graphene is flexible yet harder than diamond. It conducts electricity faster at room temperature than anything else. And it's nearly transparent, a handy property for devices such as solar cells and displays that need to let light through. The only trouble is that people have been able to make only small flakes of the stuff--until now.

Friday, December 19, 2008

"Axis of Evil"

Does the Universe Have a Handedness?
In this article I extend an earlier study of spiral galaxies in the Sloan Digital Sky Survey (SDSS) to investigate whether the universe has an overall handedness. A preference for spiral galaxies in one sector of the sky to be left-handed or right-handed spirals would indicate a parity-violating asymmetry in the overall universe and a preferred axis. The previous study used 2616 spiral galaxies with redshifts <0.04 and identified handedness. The new study uses 15872 with redshifts <0.085 and obtains very similar results to the first with a signal exceeding 5 sigma, corresponding to a probability of 2.5x10-7 for occurring by chance. The axis of the dipole asymmetry lies at approx. (l, b) =(32d,69d), roughly along that of our Galaxy and close to the so-called "Axis of Evil".

Tuesday, December 16, 2008

Strategic Pizza

How to eat 4/9 of a pizza
Given two players alternately picking pieces of a pizza sliced by radial cuts, in such a way that after the first piece is taken every subsequent chosen piece is adjacent to some previously taken piece, we provide a strategy for the starting player to get 4/9 of the pizza. This is best possible and settles a conjecture of Peter Winkler.

Red Rectangle Nebula


Red Rectangle Nebula

Monday, December 15, 2008

Human DNA weirdness

In PNAS: The human genome in the LINE of fire.
One of the most surprising revelations of the sequencing of the human genome was that nearly half of our DNA is derived from transposable element (TE) insertions, and this is likely to be an underestimate, because many TE-derived sequences have diverged beyond recognition (1). Remarkably, the vast majority of human TE sequences result from the activity of a single class of TEs known as LINE retrotransposons. Represented by the currently active LINE-1 or L1 elements, LINEs are autonomous TEs that propagate in the genome by making RNA copies of themselves that are subsequently reverse transcribed and integrated into the genome (2–4). As a result of their ongoing activity during the past 150 million years, L1 elements account for approximately one-third of the human genome ...

Eukaryotes are a kind of Archea?

Are there three great domains of life - the Archea, Eubacteria and Eukaryotes? Or are the Eukaryotes most closely related to the Eocytes, a particular group with the Archea. This paper in PNAS supports the latter: The archaebacterial origin of eukaryotes.

Friday, December 12, 2008

Missing Baryons

Evidence for the Missing Baryons in the Angular Correlation of the Diffuse X-ray Background
The amount of detected baryons in the local Universe is at least a factor of two smaller than measured at high redshift. It is believed that a significant fraction of the baryons in the current Universe is "hiding" in a hot filamentary structure filling the intergalactic space, the Warm-Hot Intergalactic Medium ($WHIM$). We found evidence of the missing baryons in the $WHIM$ by detecting their signature on the angular correlation of diffuse X-ray emission with the XMM-Newton satellite

Wednesday, December 10, 2008

The Center of the Milky Way

The warped young stellar disc in the Galactic Centre
Within the central parsec of the Galaxy, several tens of young stars orbiting a central supermassive black hole are observed. A subset of these stars forms a coherently rotating disc. Other observations reveal a massive molecular torus which lies at a radius ~1.5pc from the centre. In this paper we consider the gravitational influence of the molecular torus upon the stars of the stellar disc. We derive an analytical formula for the rate of precession of individual stellar orbits and we show that it is highly sensitive upon the orbital semi-major axis and inclination with respect to the plane of the torus as well as on the mass of the torus. Assuming that both the stellar disc and the molecular torus are stable on the time-scale >6Myr, we constrain the mass of the torus and its inclination with respect to the young stellar disc. We further suggest that all young stars observed in the Galactic Centre may have a common origin in a single coherently rotating structure with an opening angle <5deg, which was partially destroyed (warped) during its lifetime by the gravitational influence of the molecular torus.

Saturday, December 06, 2008

Blood Simple

I just watched Blood Simple a clever, macabre, suspenseful DVD by the Coen Brothers.

Wednesday, December 03, 2008

Werner Herzog

I'm currently watching Even Dwarfs Started Small a rather eccentric film directed by Werner Herzog. I've also seen two other films by him recently: Grizzly Man and My Best Fiend both documentaries, both fascinating. Aguirre, the Wrath of God is another interesting and unusual film by the same director starting Klaus Kinski, who was also the subject of My Best Fiend.
poster for Aguirre

Sunday, November 30, 2008

Eye Slideshow

Darwin 200: An eye for the eye: A celebration of one of evolution's crowning glories in Nature.
Darwin's Eye

Friday, November 28, 2008

The Agulhas leakage

Agulhas leakage dynamics affects decadal variability in Atlantic overturning circulation in Nature.
The Agulhas leakage around South Africa is the main source of the warm and salty waters carried towards the subpolar North Atlantic as the upper limb of the MOC. The Agulhas leakage region is characterized by vigorous variability on intraseasonal to interannual timescales9 shedding the largest mesoscale eddies in the world ocean10, which are the dominating vehicles transporting and releasing the Indian Ocean waters into the Atlantic11. Observational palaeoclimate studies have suggested a broken inter-ocean exchange on centurial to millennial timescales12, and ocean climate model studies13, 14 have elucidated the potential of the inter-ocean exchange of heat and salt to alter the long-term MOC response. However, large uncertainties in those studies remain, owing to unresolved mesoscale processes15 that govern the dynamics and strength of the Agulhas leakage16; the present study focuses on those effects on decadal timescales.

The MOC is the meridional overturning circulation see Thermohaline circulation in Wikipedia.

Unifying Nanophotonics and Nanomechanics

Photonics: Nanomechanics gets the shakes in Nature.
Photonic circuits can allow light to be tightly confined on a chip. A clever experiment reveals how this process can be exploited to create optical forces that drive a nanoscale mechanical oscillator.

Amazing New "Nanoscope"

Microscopy: A terahertz nanoscope in Nature.
Using a very small light source and scanning it very close to the sample they are able to beat the diffraction limit - by a lot.

Hacking Victoria's Secret

Victoria Secret competition gets hacked - MIT votes for Zion Bible College:)
It was too good to be true.

With more than 5 million votes registered, Drexel University had overwhelmed the Victoria's Secret online poll to become the first school to be added to the Pink Collegiate Collection.

The nearest competition - Texas Tech and George Mason University -trailed behind Drexel by at least two million votes.

Except a majority of the votes from Drexel, and many of the other top 25 schools in the poll, were generated by computer programs.

Thursday, November 27, 2008

Benford's Law

Benford's Law in Wikipedia. The digit '1' should be the most common first digit in many datasets!

Cosmic Ray Hot Spots?

Cosmic-ray hot spots puzzle researchers in Nature:
In contrast, the Milagro team, led by Jordan Goodman at the University of Maryland, College Park, found cosmic-ray protons bunched up in two 'hot spots': one between the Orion and Taurus constellations, the other near Gemini. They think that the excess cosmic rays may be coming from exotic sources such as the rapidly rotating neutron stars known as pulsars, rather than dark-matter annihilations.

Milagro website - cool.

Tuesday, November 25, 2008

How Termites Get Their Nitrogen

Termites eat wood, and they require nitrogen, but wood contains very little. It turns out that a protist that lives inside the termite's gut contains a bacteria which in turn fixes atmospheric nitrogen!
How Termites Live on a Diet of Wood in the New York Times and Genome of an Endosymbiont Coupling N2 Fixation to Cellulolysis Within Protist Cells in Termite Gut in Science:
Termites harbor diverse symbiotic gut microorganisms, the majority of which are as yet uncultivable and their interrelationships unclear. Here, we present the complete genome sequence of the uncultured Bacteroidales endosymbiont of the cellulolytic protist Pseudotrichonympha grassii, which accounts for 70% of the bacterial cells in the gut of the termite Coptotermes formosanus. Functional annotation of the chromosome (1,114,206 base pairs) unveiled its ability to fix dinitrogen and recycle putative host nitrogen wastes for biosynthesis of diverse amino acids and cofactors, and import glucose and xylose as energy and carbon sources. Thus, nitrogen fixation and cellulolysis are coupled within the protist's cells. This highly evolved symbiotic system probably underlies the ability of the worldwide pest termites Coptotermes to use wood as their sole food.


In the same issue of Science there's an article about nitrogen fixation in the ocean:
Globally Distributed Uncultivated Oceanic N2-Fixing Cyanobacteria Lack Oxygenic Photosystem II
Oceanic cyanobacteria are the oxygen-producing, carbon- and nitrogen-fixing engines of our planet. Because oxygen is toxic for nitrogenase, nitrogen fixation is a bit problematic to fit into this metabolic mix. Multicellular cyanobacteria like Trichodesmium have evolved a range of temporal and compartmental strategies to protect their nitrogenase enzymes from being poisoned. A newly discovered and abundant group of unicellular cyanobacteria has dispensed with carbon fixation and oxygen production altogether and so it can run nitrogenase without hindrance. Zehr et al. (p. 1110) have extracted this group by cell sorting and, by genome analysis, show that indeed it lacks the genes both for photosystem II and for carbon fixation via the reductive pentose phosphate cycle. This finding makes it necessary to reevaluate current models of nitrogen and carbon cycling on Earth.

Saturday, November 22, 2008

Proton Mass from Theory

The Standard Model of particle physics is supposed to describe the properties of the quarks and gluons which make up the proton and other particles. Yet until just now isn't hasn't even been possible to calculate the mass of the proton based on the Standard Model.
See
The Weight of the World Is Quantum Chromodynamics in Science.
Nuclear masses calculated from scratch in Nature.
Particle physics: Mass by numbers by Frank Wilczek in Nature.
A highly precise calculation of the masses of strongly interacting particles, based on fundamental theory, is testament to the age-old verity that physical reality embodies simple mathematical laws.

Wednesday, November 19, 2008

Massive Compact Galaxies

Compact galaxies in early Universe pack a big punch
Using the Near Infrared Camera and Multi-Object Spectrometer onboard of the Hubble NASA/ESA Hubble Space Telescope, astronomers have made observations of young, surprisingly compact galaxies, each only 5000 light-years across, but weighing 200 thousand million times the mass of the Sun.

Extremely Compact Massive Galaxies at 1.7 < z < 3
One of the most exciting discoveries in extragalactic astronomy in the last few years is that massive (M ≥ 1011M⊙) galaxies at z > 1 were extremely compact ( [1]; [2]). Since these objects are not found in the local Universe ( [3]) it is clear that significant growth in the sizes of these galaxies has occurred during cosmic history.

Tuesday, November 18, 2008

Literature

This is what I've been reading lately:
The Girl with the Dragon Tattoo a novel by Stieg Larsson
The Aubrey-Maturin series by Patrick O'Brian
also two books by Dean King:
A Sea of Words: Lexicon and Companion for Patrick O'Brian's Seafaring Tales;
Harbors and High Seas: Map Book and Geographical Guide to the Aubrey/Maturin Novels of Patrick O'Brian
are interesting and a big help in following the O'Brian books.

I'm currently reading Krakatoa: The Day the World Exploded by Simon Winchester

Sunday, November 16, 2008

Why is there Oxygen in Our Atmosphere?

The Story of O2 in Science.
Atmospheric oxygen is produced by photosynthesis, but the production of gaseous oxygen tends to be balanced by its removal by respiration. Apparently it's actually the burial of organic material which allows oxygen to accumulate in the atmosphere.

Visual Cells

There are two principal types of visual cells in animals: ciliary-type, typically found in vertebrates and other deuterostomes; and rhabdomeric-type, found in insects, molluscs, and other protostomes. Recently there's evidence that prebilaterians, the common ancestors of deuterostomes and protostomes, may have had both types of cells and that indeed both types of cells can still be found within both groups.
See Jellyfish vision starts with cAMP signaling mediated by opsin-Gs cascade in PNAS and Evolutionary biology: Light on ancient photoreceptors in Science.

Saturday, November 15, 2008

Enigma Illusion


Enigma Illusion I had to stare at the image for at least 30 seconds before it started rotating.
Microsaccades drive illusory motion in the Enigma illusion in PNAS.

Nice collection of Science Images

ScienceShots at Science Magazine.
Here are a couple of favorites:
Arp 147: Hubble
Hubble

Algae that Fix Nitrogen in Daylight

Marine Algae Try Alternative Lifestyle in Science.
By transforming sunlight into food for themselves, oceanic blue-green algae multiply and provide nourishing meals for most other marine creatures. But a newly discovered group of these microorganisms forgoes this photosynthesis and, in doing so, becomes a nitrogen-rich natural fertilizer for the oceans, according to research published today in Science (p. 1110). These findings, the authors say, have important implications for nitrogen and carbon cycling in the oceans.

Transparent, Thin Loudspeakers from Carbon Nanotubes

Big Noise From Little Tubes in Science.
Last year brought news of Lilliputian radios made from whiskerlike carbon nanotubes. Now, researchers in China have added ultrathin loudspeakers to go with them. The devices, made from transparent and flexible carbon nanotube films, don't require any of the bulky magnets and sound cones of conventional speakers. So they could lead to a new generation of nearly invisible, flat speakers that can be integrated into everything from ceilings and walls to clothing and curtains.

The Evolution of Childhood

The Birth of Childhood in Science.
Unlike other apes, humans depend on their parents for a long period after weaning. But when--and why--did our long childhood evolve?

Tuesday, November 11, 2008

Pretty Tilings


Beautiful tilings

An Unexpected New Particle?

Has new physics been found at the ageing Tevatron?
Last week, physicists announced that the Tevatron particle accelerator at Fermilab in Batavia, Illinois, has produced particles that they are unable to explain. Could it be a sign of new physics?

Nature News
Unexplained 'ghost particles' are mysteriously appearing inside a US-based high-energy physics experiment.

Galaxies appear simpler than expected

preprint
Galaxies are complex systems the evolution of which apparently results from the interplay of dynamics, star formation, chemical enrichment, and feedback from supernova explosions and supermassive black holes. The hierarchical theory of galaxy formation holds that galaxies are assembled from smaller pieces, through numerous mergers of cold dark matter. The properties of an individual galaxy should be controlled by six independent parameters including mass, angular-momentum, baryon-fraction, age and size, as well as by the accidents of its recent haphazard merger history. Here we report that a sample of galaxies that were first detected through their neutral hydrogen radio-frequency emission, and are thus free of optical selection effects, shows five independent correlations among six independent observables, despite having a wide range of properties. This implies that the structure of these galaxies must be controlled by a single parameter, although we cannot identify this parameter from our dataset. Such a degree of organisation appears to be at odds with hierarchical galaxy formation, a central tenet of the cold dark matter paradigm in cosmology.

Friday, September 19, 2008

The possibility of life on other planets

There could be millions of planets orbiting other stars. Thomas Carlyle commented "A sad spectacle! If they be inhabited, what a scope for pain and folly; and if they be not inhabited, what a waste of space!"

Wednesday, August 06, 2008

Imaging Single Atoms on a Graphene Sheet

Single atoms spied on graphene sliver: Electron microscope spots hydrogen atoms resting on invisible carbon sheet.

Graphene is a single sheet of carbon atoms arranged in a hexagonal pattern. It can be used as a transparent "slide" so that a transmission electon microscope can image individual atoms, even hydrogen, the smallest.

A revolution occurred when it was discovered that the single atom sheets of graphene could be peeled off common graphite using adhesive tape!

Graphene at Wikipedia.

More Weird Quantum Behaviour

Paradoxical Reflection in Quantum Mechanics
This article concerns a phenomenon of elementary quantum mechanics that is quite counter-intuitive, very non-classical, and apparently not widely known: a quantum particle can get reflected at a potential step downwards. In contrast, classical particles get reflected only at upward steps. As a consequence, a quantum particle can be trapped for a long time (though not forever) in a region surrounded by downward potential steps, that is, on a plateau. Said succinctly, a quantum particle tends not to fall off a table. The conditions for this effect are that the wave length is much greater than the width of the potential step and the kinetic energy of the particle is much smaller than the depth of the potential step. We point out how the topic is accessible with elementary methods, but also with mathematical rigor and numerically.

An Exceptionally Simple Theory of Everything

This preprint by Garrett Lisi has been getting a lot of press in the popular media, in part because the author is a "surfer dude". Here's an article at the New Yorker: Surfing the Universe An academic dropout and the search for a Theory of Everything. Here's the discussion (some of it heated) at the backreaction physics blog and also at Woit's Not Even Wrong blog. Lisi himself comes off as an unassuming, pleasant, amiable fellow, much in contrast to many of the other commenters.
How can a "Theory of Everything" be "Exceptionally Simple"? Sorry, it's a pun, 'Exceptional' and 'Simple' are technical terms from mathematical Group Theory, the new theory relies on very advanced mathematics and theoretical physics.

Here's a pretty graphical illustration of the theory, but don't expect to watch it and actually understand anything.

Thursday, April 17, 2008

The Raven

The Raven by Edgar Allan Poe, with beautiful illustrations by Gustave Doré at Project Gutenberg.

Elevators

Up and Then Down:The lives of elevators in the New Yorker Magazine.

Let's Beat Monty Hall to Death

There's a series of posts in the New York Times TiernyLab column about the famous Monty Hall problem: Is That a Fair Coin in Your Pocket?.
Partition–Edit–Count: Naive Extensional Reasoning in Judgment of Conditional Probability

Fog of War

The Fog of War the 2003 documentary about Robert S. McNamara, the secretary of defence under Kennedy/Johnson by director Erroll Morris. The film was made before 9/11 and the current Iraq war, but there are eerie similiaries.

Wednesday, April 16, 2008

Gardner Gathering

Penn and Teller hang out with magicians and mathematicians at a Gardner Gathering - meetings held in honor of the writer Martin Gardner.

Number Gossip

Number Gossip
Number Gossip: Plug in your number!

Find out which number is: composite, deficient, even, odious, palindromic, powerful, practical ...

The Tudors / Sweating Sickness

I've been watching the Showtime series The Tudors on DVD. It started out 'ok' but become more engrossing as it went on. Unfortunately, I made the mistake of looking up the historical figures in Wikipedia and found there were major historical inaccuracies in the show, which I found distracting. I should have waited until finishing the show!
The show mentions a devasting epidemic of "sweating sickness" in England at the time. I assumed that was another term for the bubonic plague, but apparently it's a completely different disease. The exact nature of the sweating sickness is still unknown.

The Early Universe

Let there be Light: the Emergence of Structure out of the Dark Ages in the Early Universe
The initial conditions of our Universe can be summarized on a single sheet of paper. Yet the Universe is full of complex structures today, such as stars, galaxies and groups of galaxies. In this review I describe the standard theoretical model for how complexity emerged from the simple initial state of the Universe at early cosmic times through the action of gravity. In order to test and inform the related theoretical calculations, large-aperture telescopes and arrays of radio antennae are currently being designed and constructed. The actual transition from simplicity to complexity has not been observed as of yet. The simple initial conditions were already traced in maps of the microwave background radiation, but the challenge of detecting the first generation of galaxies defines one of the exciting frontiers in the future of cosmology. Once at hand, the missing images of the infant Universe might potentially surprise us and revise our current ideas.

Polarisation vision

The secret world of shrimps: polarisation vision at its best
New Form of Vision Discovered

Monday, April 14, 2008

Earth Rise


This image is a still from a high-definition April 5, 2007 video of the Earth rising above the moon as seen by Japan's Kaguya lunar orbiter. The probe was about 236,121 miles (380,000 km) away from Earth at the time. Credit: JAXA/NHK.
High Resolution Video

John A. Wheeler Dies

John A. Wheeler, Physicist Who Coined the Term ‘Black Hole,’ Is Dead at 96 article in the New York Times.

Gecko Acrobatics

Active tails enhance arboreal acrobatics in geckos in PNAS.
Geckos are nature's elite climbers. Their remarkable climbing feats have been attributed to specialized feet with hairy toes that uncurl and peel in milliseconds. Here, we report that the secret to the gecko's arboreal acrobatics includes an active tail. We examine the tail's role during rapid climbing, aerial descent, and gliding. We show that a gecko's tail functions as an emergency fifth leg to prevent falling during rapid climbing. A response initiated by slipping causes the tail tip to push against the vertical surface, thereby preventing pitch-back of the head and upper body. When pitch-back cannot be prevented, geckos avoid falling by placing their tail in a posture similar to a bicycle's kickstand. Should a gecko fall with its back to the ground, a swing of its tail induces the most rapid, zero-angular momentum air-righting response yet measured. Once righted to a sprawled gliding posture, circular tail movements control yaw and pitch as the gecko descends. Our results suggest that large, active tails can function as effective control appendages. These results have provided biological inspiration for the design of an active tail on a climbing robot, and we anticipate their use in small, unmanned gliding vehicles and multisegment spacecraft.

Asian-American Birth Gender Bias

Son-biased sex ratios in the 2000 United States Census in PNAS.
We document male-biased sex ratios among U.S.-born children of Chinese, Korean, and Asian Indian parents in the 2000 U.S. Census. This male bias is particularly evident for third children: If there was no previous son, sons outnumbered daughters by 50%. By contrast, the sex ratios of eldest and younger children with an older brother were both within the range of the biologically normal, as were White offspring sex ratios (irrespective of the elder siblings' sex). We interpret the found deviation in favor of sons to be evidence of sex selection, most likely at the prenatal stage

Let's Not Have a Nuclear War, OK?


Total ozone deviations following 5-Tg soot injection in the upper troposphere.
http://www.pnas.org/cgi/content/full/105/14/5283
Atmospheric consequences of nuclear exchange Nuclear winter has been hypothesized to dramatically alter the Earth's climate. Michael Mills et al. have studied ozone depletion as a result of regional nuclear war, developing a computational model that links climate to atmospheric chemistry, and conducting 10-year simulations. The fires that would result from a total exchange of 100 Hiroshima-equivalent nuclear devices (yield 15 kilotons) would generate 5 million tonnes of soot that firestorms and solar heating would loft into the stratosphere. At altitudes up to 60 km, the soot would absorb solar radiation and heat surrounding gases, thus increasing the rate constants for several reactions that break down ozone. The authors found that two chemical reactions in particular would dominate alterations in ozone after a nuclear war: (i) the Chapman cycle, in which an oxygen free radical and ozone combine to form two diatomic molecules; and (ii) a coupled pair of reactions catalyzed by NO and NO2 that similarly produces diatomic oxygen. In the year after a nuclear war, the Chapman cycle would account for the greatest ozone loss, but NOx catalysis would then become dominant and persist for several more years. Mills et al.'s model predicts that the net result in both hemispheres would be an ozone hole extending from 20° north or south latitude to the poles. — K.M.

Massive global ozone loss predicted following regional nuclear conflict in PNAS.
We use a chemistry-climate model and new estimates of smoke produced by fires in contemporary cities to calculate the impact on stratospheric ozone of a regional nuclear war between developing nuclear states involving 100 Hiroshima-size bombs exploded in cities in the northern subtropics. We find column ozone losses in excess of 20% globally, 25–45% at midlatitudes, and 50–70% at northern high latitudes persisting for 5 years, with substantial losses continuing for 5 additional years. Column ozone amounts remain near or <220 Dobson units at all latitudes even after three years, constituting an extratropical "ozone hole." The resulting increases in UV radiation could impact the biota significantly, including serious consequences for human health. The primary cause for the dramatic and persistent ozone depletion is heating of the stratosphere by smoke, which strongly absorbs solar radiation. The smoke-laden air rises to the upper stratosphere, where removal mechanisms are slow, so that much of the stratosphere is ultimately heated by the localized smoke injections. Higher stratospheric temperatures accelerate catalytic reaction cycles, particularly those of odd-nitrogen, which destroy ozone. In addition, the strong convection created by rising smoke plumes alters the stratospheric circulation, redistributing ozone and the sources of ozone-depleting gases, including N2O and chlorofluorocarbons. The ozone losses predicted here are significantly greater than previous "nuclear winter/UV spring" calculations, which did not adequately represent stratospheric plume rise. Our results point to previously unrecognized mechanisms for stratospheric ozone depletion.

Is the Solar System Stable?

On the Dynamical Stability of the Solar System
The experiments yielded one evolution in which Mercury falls onto the Sun at ~1.261Gyr from now, and another in which Mercury and Venus collide in ~862Myr. In the latter solution, as a result of Mercury's unstable behavior, Mars was ejected from the Solar System at ~822Myr. We have performed a number of numerical tests that confirm these results, and indicate that they are not numerical artifacts.

What is a Galaxy?

What is a galaxy? How Cold is Cold Dark Matter? Recent progress in Near Field Cosmology
These data show that there is a bimodal distribution in half-light radii, with stable star clusters always being smaller than 35pc, while stable galaxies are always larger than 120pc. We extend the previously known observational relationships and interpret them in terms of a more fundamental pair of intrinsic properties of dark matter itself: dark matter forms cored mass distributions, with a core scale length of greater than about 100pc, and always has a maximum central mass density with a narrow range.
...
Galaxies are embedded in dark matter halos with these properties; smaller systems containing dark matter are not observed

SS433

SS433 a strange object in our own Galaxy. Aligned Molecular Clouds towards SS433 and L=348.5 degrees; Possible Evidence for Galactic "Vapor Trail" Created by Relativistic Jet

High speed cameras

Nice "slow-motion" videos on the site Vision Research.

Thursday, April 10, 2008

Bridge Technology

Super-Bridges Suspended Over Carbon Nanotube Cables
In this paper the new concept of super-bridges, i.e. kilometre-long bridges suspended over carbon nanotube cables, is introduced. The analysis shows that the use of realistic (thus defective) carbon nanotube bundles as suspension cables can enlarge the current limit main span by a factor of 3.

Sunday, April 06, 2008

What is the reason for Menopause?

Reproductive conflict and the separation of reproductive generations in humans in PNAS.
An enduring puzzle of human life history is why women cease reproduction midway through life. Selection can favor postreproductive survival because older females can help their offspring to reproduce. But the kin-selected fitness gains of helping appear insufficient to outweigh the potential benefits of continued reproduction. Why then do women cease reproduction in the first place? Here, we suggest that early reproductive cessation in humans is the outcome of reproductive competition between generations, and we present a simple candidate model of how this competition will be resolved. We show that among primates exhibiting a postreproductive life span, humans exhibit an extraordinarily low degree of reproductive overlap between generations. The rapid senescence of the human female reproductive system coincides with the age at which, in natural fertility populations, women are expected to encounter reproductive competition from breeding females of the next generation. Several lines of evidence suggest that in ancestral hominids, this younger generation typically comprised immigrant females. In these circumstances, relatedness asymmetries within families are predicted to give younger females a decisive advantage in reproductive conflict with older females. A model incorporating both the costs of reproductive competition and the benefits of grandmothering can account for the timing of reproductive cessation in humans and so offers an improved understanding of the evolution of menopause.

aMazing Lock


Chain style Doorlock forces you to solve a maze to exit
100% Titanium Alloy Construction

Friday, April 04, 2008

Very Hard, I would imagine

In the Wall Street Journal today: UBS Shares Rally on Breakup Push
By CARRICK MOLLENKAMP and KATHARINA BART

The article discusses UBS, a Swiss Bank that's been having problems recently
"It's hard to make a case to someone wealthy that you can manage their money well when you've just lost $37 billion yourself," said Dirk Hoffmann-Becking, an analyst at Bernstein Research in London.

Are Neutrinos their own antiparticles?

ARE NEUTRINOS MAJORANA PARTICLES?
Photons are their own antiparticles, could that be true of neutrinos as well? There is an experiment which can tell - neutrinoless double beta decay. Unfortunately this is a difficult experiment.

Nanowriting

Floating Tip Nanolithography
We demonstrate noncontact, high quality surface modification with spatial resolution of ~20 nm. The nanowriting is based on the interaction between the surface and the tip of an Atomic force microscope illuminated by a focused laser beam and hovering 1-4 nanometers above the surface without touching it. The floating tip nanowriting is compared to mechanical surface scratching, and is found to be much more reproducible, and of higher quality. In an Apertureless Scanning Near Field Optical Microscope geometry the tip is illuminated by a focused femtosecond laser, leading to two different, clearly identifiable mechanisms for removing material from the surface: when heated by the laser beam, the hot-tip thermally patterns the surface of low melting temperature soft materials, and when focused right at the apex of the sharp tip, the enhanced electric field of the laser beam causes ablation in high melting temperature metal films.

Thursday, April 03, 2008

Einstein's Relativity Song


The date it was posted on Youtube - April 1.

Wednesday, April 02, 2008

The Safest Rest You've Ever Had

The Quantum Sleeper
The Quantum Sleeper Unit is a high-level security system designed for maximum protection in various hostile environments

On Haircuts

No Country for Old Men with Javier Bardem as Anton Chigurh:
Chigurh's distinctive look was derived from a 1979 photo from a book supplied by Tommy Lee Jones which featured photos of brothel patrons on the Texas-Mexico border.[33] Describing his "extraordinary moptop haircut," he said, "You don't have to act the haircut. The haircut acts by itself."


Sensitive Optical Measurements

Beating the standard quantum limit: Phase super-sensitivity of N-photon interferometers
Quantum metrology promises greater sensitivity for optical phase measurements than could ever be achieved classically

Quantum enhancement of N-photon phase sensitivity by interferometric addition of down-converted photon pairs to weak coherent light

Quantum Heat Engines

Coherent Power Booster in Science Magazine.
According to the Second Law of Thermodynamics, a heat engine requires two heat baths to operate-a warm source of heat and a cooler dump for waste heat. In apparent violation of this law, Scully et al. propose a heat engine that uses quantum coherence to extract work from a single, warm gas. In his Perspective, Linke explains that the Second Law is not violated, because the power extracted from the bath is smaller than that required to achieve coherence. By combining quantum mechanics with traditional heat engines, the efficiencies of various kinds of motors could be enhanced.


Improving Carnot efficiency with quantum correlations

Tuesday, April 01, 2008

Was There a Big Bang?

Was There A Big Bang?
The big bang hypothesis is widely accepted despite numerous physics conflicts. It rests upon two experimental supports, galactic red shift and the cosmic microwave background. Both are produced by dark matter, shown here to be hydrogen dominated aggregates with a few percent of helium nodules. Scattering from these non-radiating intergalactic masses produce a red shift that normally correlates with distance. Warmed by our galaxy to an Eigenvalue of 2.735 K, drawn near the Earth, these bodies, kept cold by ablation, resonance radiate the Planckian microwave signal. Several tests are proposed that will distinguish between this model and the big bang.

Monday, March 31, 2008

Build your own Rebreather for $100 ...

... using a hot water bottle: A HOT WATER BOTTLE PENDULUM
Warning Warning Warning

REBREATHERS CAN AND DO KILL
I AM NOT RESPONSIBLE FOR YOU
YOU MAKE YOUR OWN DECISIONS
AND REAP THE CONSEQUENCES



You can die from too much oxygen by using pure oxygen below 20 feet of seawater. You can die from too little oxygen. You can drown. Screw up and you are likely to die. When you enter the water, you are on your own, even if a buddy is nearby. You alone must make the decision that you are capable of using a rebreather, you are up to the dive, and that your equipment is up to the dive. Even extensive open circuit experience will not prepare you for the details inherent with staying alive underwater on a rebreather. If you have any concerns about your abilities, take a course or do not dive. If you are foolish enough to dive rebreathers, be aware that it is a case of Evolution in Action. It is an effective sorting out process that has created many unhappy widows, mothers, and children. I recommend against it. This project is described for your amusement only. It is not the intent of the author that you build one of these and go out and kill yourself. As I have shown it, if you take the mouthpiece out of your mouth, water will flow in filling the scrubber, and your next breath is a caustic cocktail. If you don't know what you are doing, don't try this one at home. If you know what you are doing, I am sure you have a rig that makes this one look childish.

Information Storage in the Brain

Compartmentalized dendritic plasticity and input feature storage in neurons in Nature.
Although information storage in the central nervous system is thought to be primarily mediated by various forms of synaptic plasticity, other mechanisms, such as modifications in membrane excitability, are available. Local dendritic spikes are nonlinear voltage events that are initiated within dendritic branches by spatially clustered and temporally synchronous synaptic input. That local spikes selectively respond only to appropriately correlated input allows them to function as input feature detectors and potentially as powerful information storage mechanisms. However, it is currently unknown whether any effective form of local dendritic spike plasticity exists. Here we show that the coupling between local dendritic spikes and the soma of rat hippocampal CA1 pyramidal neurons can be modified in a branch-specific manner through an N-methyl-d-aspartate receptor (NMDAR)-dependent regulation of dendritic Kv4.2 potassium channels. These data suggest that compartmentalized changes in branch excitability could store multiple complex features of synaptic input, such as their spatio-temporal correlation. We propose that this 'branch strength potentiation' represents a previously unknown form of information storage that is distinct from that produced by changes in synaptic efficacy both at the mechanistic level and in the type of information stored.

Traffic Jams Just Happen

Traffic Jams Happen, Get Used to It in Science Magazine.

Roundabout.
Too many cars equals a traffic jam, even without an external cause.
Credit: Mathematical Society of Traffic Flow

Precision Clocks

A Milestone in Time Keeping in Science Magazine.
Researchers have made atomic clocks so precise that effects of general relativity are on the verge of complicating the concept of keeping time.

So much for "junk DNA"

Only 1-2% of the DNA in humans and other higher organisms appears to code for proteins. But the remaining so-called "junk DNA" may be transribed into RNA with numerous functions.
The Eukaryotic Genome as an RNA Machine in Science Magazine.
The past few years have revealed that the genomes of all studied eukaryotes are almost entirely transcribed, generating an enormous number of non–protein-coding RNAs (ncRNAs). In parallel, it is increasingly evident that many of these RNAs have regulatory functions. Here, we highlight recent advances that illustrate the diversity of ncRNA control of genome dynamics, cell biology, and developmental programming.

Sunday, March 30, 2008

Cliche Mashups

Growing Pangs: growing pains / birth pangs --- attributed to Condi Rice

No Shit Jose: No Shit Sherlock / No Way Jose

Don't Bite the F---ing Horse: Don't Bite the Hand That Feeds You / Don't Look a Gift Horse in the Mouth

Green Behind the Ears: green / wet behind the ears --- Barack Obama in 2008 Presidential Debate

"They create a desolation and call it peace"

From Tacitus, Agricola, a rebel's comment about Rome.

Saturday, March 29, 2008

Science as Art Competition

Image: Fanny Beron, École Polytechnique de Montréal, Montréal, Canada)
Science as Art competition held at the 2007 Materials Research Society (MRS) Fall Meeting

Speed Camera Irony


Cities that have installed speed cameras are discovering motorists are driving slower, which is decreasing revenues from fines. So they're turning the cameras off.

Schneier on Security

You First

Tuesday, March 25, 2008

Galaxy Rotation

Disk galaxy rotation curves and dark matter distribution
After explaining the motivation for this article, we briefly recapitulate the methods used to determine somewhat coarsely the rotation curves of our Milky Way Galaxy and other spiral galaxies, especially in their outer parts, and the results of applying these methods. Recent observations and models of the very inner central parts of galaxian rotation curves are only briefly described. We then present the essential Newtonian theory of (disk) galaxy rotation curves. The next two sections present two numerical simulation schemes and brief results. Application of modified Newtonian dynamics to the outer parts of disk galaxies is then described. Finally, attempts to apply Einsteinian general relativity to the dynamics are summarized. The article ends with a summary and prospects for further work in this area

Galaxy Zoo

Galaxy Zoo: The large-scale spin statistics of spiral galaxies in the Sloan Digital Sky Survey
We re-examine the evidence for a violation of large-scale statistical isotropy in the distribution of projected spin vectors of spiral galaxies. We have a sample of $\sim 37,000$ spiral galaxies from the Sloan Digital Sky Survey, with their line of sight spin direction confidently classified by members of the public through the online project Galaxy Zoo. After establishing and correcting for a certain level of bias in our handedness results we find the winding sense of the galaxies to be consistent with statistical isotropy. In particular we find no significant dipole signal, and thus no evidence for overall preferred handedness of the Universe. We compare this result to those of other authors and conclude that these may also be affected and explained by a bias effect.

Nature's Brightest Explostion

Observations of the Naked-Eye GRB 080319B: Implications of Nature's Brightest Explosion
The first gamma-ray burst (GRB) confirmed to be bright enough to be seen with the naked eye, GRB 080319B, allowed for exquisite follow-up across the electromagnetic spectrum. We present our detailed optical and infrared observations of the afterglow, consisting of over 5000 images starting 122 s after the GRB trigger, in concert with our own analysis of the Swift UVOT, BAT, and XRT data. The event is extreme not only in observed properties but intrinsically: it was the most luminous ever recorded at optical wavelengths and had an exceedingly high isotropic-equivalent energy release in gamma-rays

The French

There's a charming article about the French in the New York Times A Guide to the French. Handle With Care
“Every man has two countries, his own and France,” says a character in a play by the 19th- century poet and playwright Henri de Bornier.
“The most beautiful makeup for a woman is passion,” Yves Saint Laurent once said. “But cosmetics are easier to buy.”

Saturday, March 22, 2008

Giant Undersea Robot

The UT-1 ‘Ultra Trencher’ is the world’s most powerful jetting
trencher: pdf technical specification.

New Form of Vision Discovered

Mantis Shrimps can detect polarized light, an ability previously unknown: Science Magazine.

They are also really cute.

Thursday, March 20, 2008

Crayon Physics

Cute video demonstration of the Crayon Physics program. You will smile.

Tuesday, March 18, 2008

Cocteau Twins

Recently I've been listening to the dreamy 80/90's Scottish band Cocteau Twins - a lot. I wondered about the "lyrics" which seem like they're in some unknown language.


Here's a wonderful collection of comments on the lyrics by singer Liz Fraser.

Monday, March 17, 2008

Droll Retort in "Not Even Wrong Blog"

In the comments of Peter Woit's blog:

Eric Says:
March 9th, 2008 at 10:25 pm
Tim,
At least 99% of the 10^500 possible vacua are complete garbage and can be ruled out easily. Thus, the regions of the landscape for which realistic vacua may arise is limited. If string theory is the right theory, then at least one of these vacua is our universe and it can be found with a focused effort.

Peter Woit Says:

March 9th, 2008 at 10:30 pm
Eric,

Once you rule out the 99% garbage, you’re left with 10^498 vacua to study….

Fundamental Constants

Fundamental Constants a preprint by Frank Wilczek, has a nice discussion of the fundamental constants of physics as well as systems of units.
There's a nice quote attributed to Einstein:
I would like to state a theorem which at present can not be based upon anything more than upon a faith in the simplicity, i.e., intelligibility, of nature: there are no arbitrary constants ... that is to say, nature is so constituted that it is possible logically to lay down such strongly determined laws that within these laws only rationally completely determined constants occur (not constants, therefore, whose numerical value could be changed without destroying the theory).

Gravity poses some problems:
Straightforward estimation suggests that empty space should weigh several orders of magnitude of orders of magnitude (no misprint here!) more than it does. It “should” be much denser than a neutron star, for example. The expected energy of empty space acts like dark energy, with negative pressure, but far more is expected than is observed.

And there are other less than pretty parts as well:
The flavor/Higgs sector of the standard model is, by a wide margin, its least satisfactory part. Whether judged by the large number of independent parameters or by the small number of powerful ideas it contains, our theory of this sector does not attain the same level as we’ve reached in the other sectors. This part truly deserves to be called a “model” rather than a “theory”.

Sunday, March 16, 2008

Cell Phone Scams

I'm forced to admire the scams described in The Anatomy of a Vishing Scam.
Ah, the irony. Here we have the very accounts these entities use to respond to complaints about fraudulent activity being used to perpetrate fraudulent activity.

Friday, March 14, 2008

Blind Chance


Blind Chance: a brilliant 1981 Polish film by Krzysztof Kieślowski.

Bacterial Snowmakers

Ubiquity of Biological Ice Nucleators in Snowfall: is ice nucleation, essential to snow and rain, mainly catalyzed by bacteria?

Stretching and Flexibility

To Stretch or Not to Stretch? The Answer Is Elastic in the New York Times on March 13, 2008.

But distance runners do not benefit from being flexible, he found. The most efficient runners, those who exerted the least effort to maintain a pace, were the stiffest.

Thursday, February 07, 2008

Cable News

Fourth Undersea Cable Failure in Middle East from Schneier's blog. What's going on?

A fun article by Neal Stephenson in Wired 1996 Mother Earth Mother Board about the ocean spanning fiber optic cable network.

Wednesday, January 16, 2008

The Balloon Blowup Analogy

Jim Kelnhofer, underwater videographer extraordinaire, asked the following nontrivial question (about cosmology, when it comes to underwater video, the questions flow in the other direction:)
ok, so I've been thinking about space and time a bit and the fact that there is no real center to the universe, or so everyone says. The analogy that I kind of get is that points in three dimensional space are kind of like points on the surface of a balloon. And, as you blow up the balloon all the points recede from one another as the universe, represented by the balloon, grows. I can sort of conceptually get this, though I don't completely comprehend all the math involved in the 3D/2D transformations. My question would be, is the expansion of the balloon representative of time, and does that translate to the center of the universe being time t=0? Is that how the math works out or what the math means?

jim...


Here's my less than satisfying response.

One way to understand a weird space is to formulate it as a subspace of a simpler space. For example, we can understand a balloon, the surface of a sphere, which is a slightly tricky space, by thinking of its embedding in good old flat three dimensional space.

General Relativity, on the other hand, is formulated in terms of Differential Geometry. In Differential Geometry, the spaces are called Manifolds. By definition an n-dimensional manifold can be completely covered (nicely) by n-dimensional Euclidean slabs (called charts in the literature).

By the way, if you think about it, the surface of a sphere cannot be modeled so nicely by just one chart (you end up leaving out at least one or two points, like the North and South poles). It takes at least two charts.

So there are these two ways to bootstrap our knowledge and intuition about Euclidean space to handle more general spaces: embeddings and coverings.

Can a given n-dimensional manifold (defined by coverings) always be embedded in a "nice" way in some higher-dimensional Euclidean space? That's an interesting question. John Nash, the dude depicted in the movie and book "A Beautiful Mind" found some impressive stuff along those lines.

General Relativity doesn't start off by worrying much about embeddings, it's fundamentally about the local properties of the space - that was the way Einstein went about it. Local properties can usually be addressed nicely by a covering formulation, you don't even need an embedding as it turns out.

There are more complications, in addition to Differential Geometry, once Time and Causality are involved.

There are however various ways to try to visualize a global picture of different space/time models. One popular way is the Penrose diagram.

Unfortunately it's not very easy to get from the local situation to a more global picture. It fact it is damn hard.

For example, Einstein came up with the local formulation, but he never got very far himself with global solutions (the ones he found are pretty trivial really).
One of Stephen Hawking's claims to fame is a book called "The Large Scale Structure of Space/Time" which is full of very hairy math addressing these global questions.

So the way mathematical physics often works is, people try to get the local formulation right, then they do some very hairy stuff to see what sorts of global implications follow.

What's been going on in the mathematics community, getting back to the time of Gauss in the 1800's, is that they've been able to come up with all kinds of bizarre "geometries" that are quite different than the Euclidean geometry that seems to be intuitive for most of us human types. However, the mathematical work tends to have a purely spatial flavor about it. Einstein happened to have a mathematician buddy who showed him one of these formalisms called Riemannian Geometry and Einstein basically kludged Time in. The nature of the kludge is that, locally, everything looks like Special Relativity, and the space-time geometry of that had already been worked out, by Einstein and other dudes at that time. The mathematical consequences of this have been slow to unfold, even though it's now been over 90 years.

Mathematicians have been very creative, they have given us powerful tools for formulating things with lots of dimensions and weird shapes. Sometimes there's even originally a physical motivation for some of that, but often they're just spinning out lots of crazy new junk for their own amusement. Every once and a while, someone with a more practical bent grovels through the math literature and finds something inadvertently useful, to the horror of Pure Mathematicians everywhere.

The interesting thing now is, we have these observations (red shifts, the cosmic microwave background, etc.) that seem to give some hints about what the global picture might be like. After the astronomers observe something new and cool, the physicists have to see if they can reproduce those results in their models. Lately they've been having a hard time of it, hence all the buzz about Dark Matter and Dark Energy.

So after all that did I even manage to address Jim's question about the Balloon Analogy? Not really! I think that model might have been specifically designed to show the universe could be finite, but still not have a center, at least at t>0. Even so there is apparently a singularity at t=0 when, if you extrapolate backward, the balloon seems to just materialize out of nowhere: a Big Bang.