Jan 302012

 Posted by at 10:37 pm
Jan 302012

arXiv blog

Artificial Braneworlds Made to Collide In Lab

Physicists have simulated two universes colliding inside a metamaterial

kfc 01/30/2012


One interesting way in which our cosmos may have formed is in a collision between two other universes with extra spatial dimensions called braneworlds.

In this scenario, known as the ekpyrotic model of the universe, our cosmos is just a small four-dimensional corner of a much more complex space.

The ekpyrotic model is interesting because it leads to a flat universe like our own without the need for inflation, the period just after the Big Bang in which our universe supposedly swelled by many orders of magnitude in the blink of an eye.

Without inflation, our universe is just too big to have been formed in a Big Bang-type event. But nobody knows what might cause such a dramatic increase in size. Hence the interest in another way of explaining our existence.

If you’re wondering what actually collides in the ekpyrotic version of events, the answer is Minkowski domain walls, essentially the edges of universes with different spatial dimensions.

It’s easy to imagine that Minkowski domain walls are entirely theoretical. And indeed they were until now.

Today, Igor Smolyaninov and Yu-Ju Hung at the University of Maryland, in College Park, say they’ve created Minkowski domain walls in the lab for the first time and even used them to simulate the collision of two braneworlds.

The trick these guys have used is a formal analogy between the mathematics of space time and of electromagnetic spaces. Physicists have known since Einstein’s day that it is possible to bend and distort the fabric of spacetime—our universe appears to be distorted  in just this way on various cosmic scales.

But it is only in the last ten years or so that they’ve learnt how to do the same on a much smaller scale with electromagnetic spaces. What’s triggered this is the development of metamaterials: artificial substances that can bend light in almost any way imaginable.

Smolyaninov is fascinated  by one version of this stuff called hyperbolic metamaterial. Inside this substance, monochromatic light propagates in a similar way to massive particles in a Minkowski spacetime, where one spatial coordinate takes on the role of time.

Hyperbolic metamaterials are essentially a series of metal layers separated by a dielectric. Smolyaninov has used this stuff to simulate a number of interesting aspects of cosmology including the Big Bang itself.

The collision between universe’s is a variation on this theme. “The “colliding universe” scenario can be realized as a simple extension of our earlier experiments simulating the spacetime geometry in the vicinity of big bang,” he says.

He simulates an expanding universe using concetric rings of gold separated by a dielectric. “When the two concentric ring  (“universe”) patterns touch each other (“collide”), a Minkowski domain wall is created, in which the metallic stripes touch each other at a small angle,” he says.

Being able to recreate these exotic events in the lab is certainly interesting but it is beginning to lose its novelty. The problem is that this work is not telling us anything we didn’t know–the universe behaves the same way inside a metamaterial as it does outside.

What Smolyaninov needs is a way of using his exotic materials to do something interesting. In other words, he needs a killer app. Any ideas?

Ref: arxiv.org/abs/1201.5348: Collision Of “Metamaterial Universes”: Experimental Realization Of Minkowski Domain Wall

 Posted by at 10:33 pm
Jan 282012

Canadian teenagers send Lego man into space

Using home-stitched parachute and equipment found on Craigslist, two 17-year-olds send Lego-naut 80,000ft into the air


Lego man in space makes one (very) small step. Link to this video

Two Canadian teenagers have sent a Lego man into the outer reaches of the Earth’s atmosphere using a home-stitched parachute and equipment found on Craigslist.

Two weeks ago, Mathew Ho and Asad Muhammad, both 17, attached the plastic figurine replete with maple leaf flag to a helium balloon, which they sent 80,000 feet into the air.

The pair managed to capture the entire journey into the blackness of space, including the descent, which lasted 97 minutes, using four cameras, at an entire cost of just £254.

 Posted by at 7:56 am
Jan 272012


Available on the App StoreProwl is the Growl client for iOS. Push to your iPhone, iPod touch, or iPad notifications from a Mac or Windows computer, or from a multitude of apps and services. Easily integrate the Prowl API into your applications.

I was extremely impressed with Prowl and the elegance with which I was able to view Growl notifications on my iPhone. Aron Trimble, TUAW
Great idea. This opens up iPhone push notifications for anything you can think of. John Gruber, Daring Fireball
[A] powerful tool to connect your Mac with your iPhone, seamlessly over the air. Federico Viticci, MacStories
Probably the best $3 I’ve ever spent in the App Store. Darrell Etherington, The Apple Blog

Push notifications When a Growl notification pops up on your computer, Prowl sends it over Push.

A Push notification on the iPhone from Prowl

Beautiful, elegant list A clean, easy-to-control list of your notifications.

The list of notifications in Prowl on the iPhone

Redirections Opening a push notification can launch a different application, or any website you want.

A sample set of redirection options

Universal, powerful Prowl features an excellent iPad interface to complement you on whatever device you’d like.

Prowl running on the iPad with its native interface.

Quiet hours and “Do Not Disturb” During quiet hours or DND, only the badge count is updated. No sounds, no alerts.

The quiet hours options display in Prowl. You can let emergencies through if you’d like, or toggle “Do Not Disturb” at will.

 Posted by at 11:06 pm
Jan 242012

High-Speed Navigation through Clutter

1. Background: High-performance Robotics and Biology

Agile robots that can autonomously navigate through cluttered environments has long been a focal direction in robotics research, although little could have been established in realizing them so far. Yet, nature is home to various species of birds that can fly through dense forests with an incredibly high speed. The following BBC video, which has largely motivated this work, shows a hawk’s high-speed flight through a dense forest.

A hawk flies through a dense forest.

Although biologist have extensively studied the behavior of birds during various activities involving steady flight, the analysis of birds’ behavior in cluttered environments has received relatively little attention. Harvard University biologist Biewener and co-workers argue in a recent paper (published in the Journal of Experimental Biology) that the historical focus on steady flight may be due to its theoretical and experimental tractability, rather than its importance. In their paper, Biewener and co-workers also present one of the first experimental results involving pigeons engaging in tight turns.

 Posted by at 10:08 pm
Jan 242012

Bit Manipulation in C for TI MSP430 Microcontrollers
Module by: Trent Kelly.  E-mail the author
Microcontrollers require more bit manipulation than most typical C programs.  The intent of this module is to help programmers new to the MSP430 processor get the results they need from C language bit manipulation instructions.  Much of this content applies to C programming for many microcontrollers as well as for computers; the examples are based on the Texas Instruments MSP430.

Hexadecimal numbers will be used in code examples for this tutorial. Each digit of hexadecimal represents four binary bits. If you aren’t familiar with conversions between hexadecimal and binary you should review Binary and Hexadecimal Notation. Our goal is to control individual bits, and they will be represented in code as hexadecimal numbers.The bitwise operators are AND ‘&’, OR ‘|’, XOR (exclusive or) ‘^’, and NOT ‘~’. These operators should not be confused with logical AND ‘&&’, logical OR ‘||’, and logical NOT ‘!’ which are used to evaluate true verses false.For example:
int a; int b; int c;

a = 0x0003 | 0x0004; //bitwise OR operation makes integer a equal to 0x0007

while ((a>b) && (b>c)) //logical AND is true if a>b>c
{ }

A truth table shows the operation that a bitwise operator performs on each bit position. Each operator produces results depending on the status of inputs A and B. The operations are performed on each bit position (such as bit 0 through bit 15 for integers) in the data, and the truth table defines the result for each possible combination of data bits.Table 1






Now lets look at a couple of examples with 16 bit integers0x0003 & 0x0005 Bitwise AND
0x0003 is 0000000000000011 in binary
0x0005 is 0000000000000101 in binary
Result    0000000000000001 in binary or 0x0001 hex

0x00AA ^ 0x00FE Bitwise exclusive or
0x00AA is 0000000010101010 in binary
0x00FE is 0000000011111110 in binary
Result    0000000001010100 in binary or 0x0054 hex

The NOT operator ‘~’, also called ones complement, is used to reverse the state of each bit.
~0x0F results in 0xF0

Lets put these operators to work for a MSP430. At the beginning of a MSP430 C program there is usually an #include directive that tells the compiler to use a header file for the MSP430 device that will run the program. For example:
#include <msp430x42x0.h>

Inside this header file we can see a number of statements such as:
/* SD16CTL */
#define SD16DIV0 (0x0040) /* SD16 Clock Divider Select 0 */
#define SD16DIV1 (0x0080) /* SD16 Clock Divider Select 1 */
#define SD16DIV_0 (0x0000) /* SD16 Clock Divider Select /1 */
#define SD16DIV_1 (SD16DIV0) /* SD16 Clock Divider Select /2 */
#define SD16DIV_2 (SD16DIV1) /* SD16 Clock Divider Select /4 */
#define SD16DIV_3 (SD16DIV0+SD16DIV1) /* SD16 Clock Divider Select /8 */

These statements assign a name to content that the compiler will substitute into the code where the name is used. When the compiler sees SD16DIV0, it substitutes in the hexadecimal number 0x0040. These particular define statements apply to use of the SD16 analog to digital converter peripheral. The /*SD16CTL */ remark indicates that the following defined names are for use in configuring the SD16CTL register. Notice that names are defined to set individual bits (SD16DIV0, SD16DIV1) or choose the function controlled by those bits (SD16DIV_0 – SD16DIV_3).These two statements accomplish the same thing:
SD16CTL = SD16DIV0 | SD16DIV1; //0x0040 OR 0x0080 = 0x00C0
SD16CTL = SD16DIV_3; //0x00C0

A switch can be attached to the MSP430 as follows: Connect a 100K ohm resister from the digital power rail to an input pin. Then attach a single pole single throw switch to the same input pin with the other terminal connected to the digital common rail. When the switch is on (closed) the input pin sees a logic 0. When the switch is off (open) the input pin sees a logic 1 because the resistor is carrying minimal current. Assume pins 6.4, 6.5, 6.6, and 6.7 are connected to switches in this way.
void main(void)
P6DIR=0xF0; // set 6.4-6.7 to inputs and 6.0 – 6.3 to outputs

while (1) // Begin while forever
if ((P6IN & 0xF0) == 0xF0) // &0xF0 isolates the four inputs
{ // execute this code if all switches are off (1111)
if ((P6IN & 0xF0) == 0xe0)
{ // execute this code if the switch on 6.4 is on and the others are off (1110)
if ((P6IN & 0x80) == 0) // &0x80 isolates only bit 7 for input 6.7
{ // execute this code if the switch on 6.7 is on no matter how the other switches are set
} // end while forever

} // end main()

If output pin 6.1 is connected to a LED, we can toggle it to the opposite state with an exclusive or operator. A ^= B is the same thing as writing A = A ^ B.
P6OUT ^= 0x02; // if the LED was off it lights, and if it was lit it turns off

What if we wanted the LED output to be on no matter what its former state was?
P6OUT |= 0x02; // the LED output is on, and the other bits are undisturbed.

What if we wanted the LED output to be off no matter what its former state was?
P6OUT &= 0xFD; // the LED output is off, and the other bits are undisturbed.

What if we wanted to set SD16CTL to ‘clock divide by 4’ and it is currently set to ‘clock divide by 8’?
SD16CTL &= ~( SD16DIV0 | SD16DIV1); // clear clock divider bits
SD16CTL |= SD16DIV_2; // clock divider select /4


 Posted by at 7:43 am
Jan 232012
Home >> Advanced Search >>

The Gateway to Astronaut Photography of Earth

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“It is spectacular. It’s amazing to hold onto the International Space Station, you’re going seventeen and a half thousand miles an hour, and just sort of look down at your feet and 200 miles under your feet, there goes the coast of California and, oops, nine minutes later, there goes New York City as you’re flying over and then on your way to Europe.” -Dan Tani, Astronaut (“In Their Own Words”)

Photographing the Earth from the International Space Station

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What is the Gateway to Astronaut Photography?
The Gateway to Astronaut Photography of Earth hosts the best and most complete online collection of astronaut photographs of the Earth.

Beginning with the Mercury missions in the early 1960s, astronauts have taken photographs of the Earth. Our database tracks the locations, supporting data, and digital images for these photographs. We process images coming down from the International Space Station on a daily basis and add them to the 1,170,262 views of the Earth already made accessible on our website.

These images include 689,714 from the International Space Station. These numbers were determined 1/1/2012.

There were 20,276,114 web hits & 2,179,234 database photo image downloads in December 2011.

 Posted by at 7:18 am
Jan 212012

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2012 January 21
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

Days in the Sun
Image Credit & Copyright: Regina Valkenborgh
Explanation: From solstice to solstice, this six month long exposure compresses time from the 21st of June till the 21st of December, 2011, into a single point of view. Dubbed a solargraph, the unconventional picture was recorded with a pinhole camera made from a drink can lined with a piece of photographic paper. Fixed to a single spot for the entire exposure, the simple camera continuously records the Sun’s path each day as a glowing trail burned into the photosensitive paper. In this case, the spot was chosen to look out over the domes and radio telescope of the University of Hertfordshire’s Bayfordbury Observatory. Dark gaps in the daily arcs are caused by cloud cover, whereas continuous bright tracks record glorious spells of sunny weather. Of course, in June, the Sun trails begin higher at the northern hemisphere’s summer solstice. The trails sink lower in the sky as December’s winter solstice approaches. Last year’s autumn was one of the balmiest on record in the UK, as the many bright arcs in the lower part of this picture testify.


 Posted by at 11:15 am
Jan 212012
2011 Global Temperatures

acquired January 1 – December 31, 2011 download large image (598 KB, PDF)
acquired January 1, 1880 – December 31, 2011 download web resolution animation (4 MB, QuickTime)
acquired January 1, 1880 – December 31, 2011 download high definition animation (23 MB, QuickTime)

Nine of the top ten warmest years in the modern meteorological record have occurred since the year 2000. Last year was another one of them, coming in at 9th warmest since 1880.

The map above shows temperature anomalies, or changes, by region in 2011; it does not depict absolute temperature. Essentially, the map shows how much warmer or cooler each region was in 2011 compared with an averaged “base period” from 1951–1980. The line plot shows yearly temperature variations (from the base period average) for every year from 1880 to now. (For more explanation of how the analysis works, read World of Change: Global Temperatures.)

 Posted by at 10:46 am
Jan 162012

Papilio is an open-source FPGA project intended for education, hobbyists, engineers, or anyone interested in learning Digital Electronics in a friendly community. It offers FPGA development boards and add-on application modules called “Wings”, that makes a easy to learn platform for beginners, and powerful design and prototyping tool for engineers.

Papilio One FPGA Development Board image
 Posted by at 10:35 pm
Jan 032012


Normally one tact switch requires one digital input pin of a microcontroller. Some designs implement keypad style multiplexing to get multiple switches on fewer inputs. However, there exist other techniques that allow you to connect many switches on a single input pin of a microcontroller. This tutorial demonstrates one such technique as applied to PIC12F683 microcontroller. In this example, there are four LEDs and four tact switches connected to the PIC12F683 microcontroller. While each LED is controlled through an individual I/O pin, the four switches are connected to one ADC input pin of the PIC12F683 microcontroller.

Connecting multiple tact switches to one input pin of PIC micro

 Posted by at 7:04 am