BASIC STEPS OF BUILDING A FOUNDATION

Survey and Stake

Before any construction can begin, the home site is surveyed to establish the home's basic footprint and to ensure the home is set back the appropriate distances from the property lines. The corners of the home are marked by surveyor's stakes. Offset stakes, which are about two feet out from the surveyor's stakes, also are placed. The excavator will dig at the offset stakes, creating a slightly larger hole than the foundation actually will occupy. The extra room enables crews to work on the exterior of the foundation walls.

Excavation
The depth of the excavation is determined by a structural engineer who considers the soil, the frost line and the height of the water table (the depth in the soil at which you find water). Surface soil is removed to expose soil that is compacted enough to bear the load of the home. The excavation must be deep enough to place the top of the footing below the frost line. This prevents the concrete from cracking due to the freeze-thaw cycle of the surrounding soil. The excavation cannot be so deep that it's below the water table, however, because that can cause a chronically wet or flooded basement.

Footings
Footings are poured concrete pathways that help to spread the weight of the home from the foundation walls to the surrounding soil. Footings are wider than the foundation walls they support, and form the perimeter of the home. Sometimes, additional footings are added inside the perimeter to support load-bearing interior walls.

Sub-slab Systems 
Plumbing lines are run from the street to the home's basement, by going under or over the footing. In some regions, soil gas mitigation systems are added to collect the soil gases trapped under the slab and vent them to the outside. Eventually, these systems will be covered with the poured concrete slab that is the basement floor.

Foundation Drainage Tile System
This system collects subsurface water and moves it away from the foundation. Foundation drainage tile consists of a continuous run of perforated drainage pipes embedded in gravel along the outside perimeter of the footings.
Some building codes require drainage pipes along the inside perimeter of the footings as well.

Sump
In regions where the earth is flat or the soil tends to be wet, a sump may be added to help collect subsurface water. A sump pump moves the collected water away from the home.

Walls
Foundation walls are constructed by pouring concrete between sets of form work (the total system of support assemblies for freshly poured concrete, including mold, hardware and necessary bracing.) Once the concrete gains its full strength, the form work is removed. Foundation wall thickness is determined by a structural engineer who considers the height of the wall and the load it has to bear. (Structural load is the force or combination of forces of gravity, wind, and earth that acts upon the structural system of a home). Wall thickness varies from home to home, and even within a home.

Anchor Bolts
Anchor bolts are embedded at pre-determined points along the top of the foundation walls. They'll be used during framing to secure the framing to the foundation.

Beam Pockets
Beam pockets are cast in the top of the foundation walls to receive, support, and hold beams in place.

Dampproofing and Waterproofing
A dampproofing or waterproofing seal is applied to the exterior of the foundation walls that eventually will be below-ground. This slows or stops water from traveling through the walls and into the basement.

Slab
A 3-inch to 4-inch thick concrete slab is poured between the walls. The slab helps to stabilize the base of the foundation walls, and also forms the basement floor.

Backfill
Backfill is pushed into the trenches around the exterior of the foundation walls, burying a portion or all of the walls below the surface for added stability. Ideally, backfill is soil that drains easily.

"If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them." - Henry David Thoreau An indispensably integral structure of any construction, the foundation, carries deep implications with respect to the overall structure of a building. A lot rests on how well it is built for it is the base that supports the weight of the entire house. Commonly made from concrete for homes, it is vital that the foundation work is done carefully. It is that structure of the house that transfers the weight of the building onto the earth below and provides support for the intense weight above. The depth of the foundation varies with the size of the building structure. Small and medium homes are built upon shallow foundations whereas large construction buildings necessitate a deep foundation. There are certain factors that construction engineers must consider while laying a home foundation. Undoubtedly, building the foundation of your house is one of the most important tasks to be undertaken when building a house. A foundation can enhance the beauty of any building but if laid incorrectly it can become unstable. Here are a few pointers that you must remember while laying a house foundation.

How To Build House Foundation

• It is always better to hire an engineer to inspect and approve of the concrete foundation that has been laid. This may cost you a bit but safety is best not compromised with. You definitely need to consult an engineer if you plan to have a basement.
• You can approach a surveyor who will inspect the plot before your start footing work. This will also help get the outline of your house marked.
• Once the surveyor has marked the position of the house, you need to get the excavator to dig soil for laying the foundation. Do not forget to consult your electrician and plumber to get the required excavation for these connections done at the same time.
• The electrician will lay pipes for electrical connections, cable and telephone. The wires will be connected to the various utilities as and when required. The plumber will look after the water connections and drainage. You must get all these connections inspected by the concerned regulatory authorities.
• Depending on the quality of the soil excavated, you may need to procure the appropriate soil type like pit run or drain rock. You may also need extra soil if you have to increase the level of soil. Ensure that the soil is leveled with proper equipment before the foundation is laid.
• Contact your electrician, plumber and heating company to ask them if they want anything installed in the foundation before the concrete is poured.
• Ensure that the footings and the foundation are laid at the same time. This way the concrete can be poured simultaneously for both.
• The foundation is usually stripped a day after the concrete is poured. Place the material that is stripped in such a way that it stays clean and does not obstruct ongoing construction work.
• Waterproofing is necessary for those areas of the foundation that are below the ground level.
• You need to place drain tiles along the edge of the house if there is a basement in the house. The top of the drain tile must be placed adjacent to the footing or foundation joint. If your municipality does not allow you to connect your pipe to the sewer then you will have to run the pipe to a gravel pit.
• All the electrical and water connections that you fix must be inspected by the authorities. Once the drain tile is inspected, backfilling and grading can begin.
• The concrete part of the structure must be done thoroughly. For this, you can hire a professional concrete finisher.

To prevent your house from sinking into the ground or getting blown away, a strong foundation is a must. Use quality materials for your foundation, garage, driveway and sidewalks. Make use of steel wherever needed for strengthening and holding things in place. A robust and well-laid foundation can be your best investment.

How to Build a Foundation from Start to Finish DIY Guide

Types of foundation and their uses

Foundation of building as the name implies is the starting of a building construction on site really. Types of building, nature of soil and environmental conditions are the major determinant of type of foundation you will use for your building.
1)Strip foundation-This is the most common type, it is mainly used where you have strong soil base and non-waterlogged areas. Most small buildings of just a floor are constructed with this type of foundation .
Depends on the structural engineers recommendation , the depth of your foundation could be from 600mm to 1200mm mostly for small scale buildings . When the soil is excavated, a level at which the concrete will settle evenly is established, then concrete is poured this may be from 150mm(6”) thick to 450mm(18”) thick depending also on building after that block is set round the trenches at the center of foundation ,the foundation usually follows the block lines. The blocks are then layed to d.p.c level before another concrete is poured on top, this is the german or oversite concrete. This type seems to be the cheapest.

2)Pad foundation-This is where isolated columns (pillars) are casted from the foundation to carry a slab at the top of the ground. This is mostly used when you want to make use of the under of building as parking space or when the other space is not conducive to have foundation. Imagine you are planning to build a house across a flowing stream and you want a situation where you can use your boat to pass under the building because the stream is under . Then you may not need to dig foundation that will cut across the river but just by applying columns (pillars) at the edge of the river like a bridge, this columns are thus isolated and there foundations are reffered to as pad.

3)Raft foundation-This is where you have concrete spread around your building from the base of foundation all through to the german floor/oversite concrete/ground floor slab. It is mainly used in areas where the soil are sandy and loose, you spend more on this than the other previous two most of the time. It is also recommended in waterlogged areas but with buildings of less storeys
It has a ground beam which shuts out from the foundation base and is also attached to the ground floor slab to form a network of concrete embedded round the building space. The ground beam are usually from 600mm to 1200mm for low buildings.
4)Pile foundation-The most expensive and the strongest type of foundation, this requires specialist engineering to do. The soil are bored deep down the earth and filled with concrete to be able to support loads of multistory building on top. Most skyscrapers are constructed with this foundation type, a waterlogged area of high building may also require this.
It is the costliest hence it is used for high rise building mostly.

Slab Foundation

Slab is a type of foundation consisting of a structural concrete slab poured directly on the grade. No accessible space exists in slab construction. Slab foundations are popular in areas (i.e. the Southern United States) where there is a relatively high water table. (Water table refers to the depth in the soil at which you find water).

Crawlspace Foundation

A crawlspace is an accessible space with limited headroom, typically between the soil and the bottom of the first floor of a home. Crawlspace construction is predominant in areas where there is heavy clay content in the soil.

Basement Foundation

A basement is an accessible space between the soil and the bottom of the first floor of a home. It usually has more headroom than a crawlspace. Basement foundation construction is predominant in cold climates where the foundation needs to be situated below the frost level.

All three foundation types are usually constructed out of concrete, but can also use concrete masonry units or insulated concrete forms.

Concrete Masonry Units (CMUs) are hollow, concrete blocks. To create the foundation wall, mortar is used between blocks to hold them together, forming the wall.

Insulated Concrete Forms (ICFs) are made of rigid foam insulation forms (a system of support assemblies, including mold, hardware, and necessary bracing to hold concrete) into which concrete is poured. Once the concrete has gained its full strength, the outside forms, the inside forms, or both are left in place to insulate the wall. ICFs are common in regions in which the local building code requires the foundation to be insulated. Another benefit is that the homeowner or builder is able to finish basement immediately, without adding studs.

Some building jurisdictions permit the use of preserved or "treated" wood products for below-grade building foundations. These materials offer advantages of construction speed and low cost. As in the installation ofConcrete Pre-cast Foundation walls, treated wood foundations may be installed on a gravel pad rather than requiring a solid masonry footing. Inspecting a preserved wood foundation: Check for evidence of foundation leakage at butt-joints where gaskets or sealant may have been omitted. Check for evidence of buckling or other damage; Outside check for the presence of a moisture barrier against the foundation exterior.

Our opinion is that "30-year guaranteed treated wood foundation products" used below grade mean that no permanent building foundation has been provided. This sketch of the components of a preserved wood foundation is courtesy of Carson Dunlop Associates.

Buildings using a wood foundation are in our OPINION a temporary structure. In areas of wet soils and insect damage risk damage may occur sooner than the warranty period.

Choosing the Type of Foundation:

Homeowners and builders make decisions about which type of foundation to use by gauging cost, needs/desires, and soil and weather conditions. If you have high water tables then it may not be possible to have a basement. If your land has shallow bedrock or boulders then it may be more costly to dig a basement. If you have a sloping lot it may be difficult to use a slab foundation. If you have a cold climate then you may need to dig down at least four or more feet to put the home's footings below frost level. If you have to go at least four feet deep then it may be worth spending some extra money to dig a few feet deeper and have a full basement. Also, it is easier to install and maintain mechanical systems in basements (compared to a crawlspace). Your builder can help you determine what type of foundation is best suited for your area.

The choice of foundation is also affected by personal preferences and costs. Basements can add thousands of dollars to the cost of a home compared to the cost of a crawlspace. However, when you consider the extra useable space created by a basement it is some of the cheapest square footage space of a home. If you are tight on funds and can't afford the basement then it may be a good idea to find a slightly smaller plan and use the savings to create a basement. You'll end up with a lot more storage space and potential living space by doing this.

Changing the Type of Foundation on your home:

Almost any house plan can have its foundation changed. It's common for people to design a different foundation if the available foundations do not suit their needs. If you are currently working with a builder you may want to ask them if they will take care of making the foundation changes for you. Sometimes with foundation design it may be helpful for somebody who is near you to do those changes because they will have more knowledge about your local soil conditions and the slope of your lot.

When changing foundation types, pay attention to where you will put the furnace, water heater, and stairs. If you need to add basement stairs, the basement stairs can usually be put under other stairways or you may be able to replace a closet or small room with basement stairs. Another common place to put basement stairs is to replace a mechanical room with stairs and move the mechanical items (such as the furnace and water heater) to the basement. Sometimes space near the laundry room, or space near the garage can be used for a basement stairs. Larger walk-in closets are sometimes reduced in size to allow space for basement stairs. You can often add a basement stairs to a plan without increasing the size of the plan. However, sometimes space may need to be added to a plan to provide room for a basement stairs.

It should be noted that it is the owner's full responsibility to check with his/her local and state building authorities, his/her builder, and the designer of the house plan to ensure that the home meets all applicable building codes and requirements.

STRENGTHENING THE FOUNDATION

Concrete beams, masonry columns, beam pockets and filling in cells of the foundation with concrete and rebar are the ways this foundation is strengthened. Building performance specialist Anthony Grisolia also explains when to backfill and the importance of wall strength and weight.

Prevention is the key to eliminating any problems when building a house, and this is why the builder takes extra steps to make sure the foundation has the strength it needs to support the home:

Instead of using wood headers above the windows in the basement, the builder (and homeowners) chose to go with concrete beams for added support.

The Obergs have an elevated garage floor, and another example of added support are masonry columns with steel rods that will help hold the load of the house, especially under the garage. The builder says you never want to set a beam on hollow blocks because it will eventually crush the block.

The property itself poses some interesting challenges as well. When the builder backfills — or pushes the dirt back around the house — there will be a great deal of weight against the foundation wall. Without extra support the wall could crack. To remedy this problem, the builder had the masons reinforce the wall by filling up the open cells of the foundation with concrete every few feet. Once the cells are filled a piece of reinforcement bar (known as "rebar") is dropped down inside the wet concrete. This combination of extra cement and rebar will give the wall the added support needed to withstand the pressure of the hill. This added weight gives the block wall structural strength.

Would an iPhone 'Assistant' Really Help?

COMMUNICATIONS

Apple may be building the technology into iOS. But can it succeed where others have failed?

• BY DAVID ZAX

Audio »

Are we on the cusp of an era of ubiquitous "virtual personal assistants"? If Steve Jobs has his way, we just might be.

Back in the spring of 2010, Apple acquired Siri, a company that produced an app that described itself in just those terms. Now, clues dug up recently by 9to5Mac, a site dedicated to scrutinizing all things Apple, suggest that Apple may be ready to introduce Siri-like features in the next version of iOS, its operating system for the iPhone, iPod touch, and iPad.

If Apple is indeed about to launch a personal assistant, it could help set the iPhone apart from other smart phones in the market. Android's voice-command system is considered one of its chief advantages over the iPhone, but a Siri-derived personal assistant would add more voice functionality, eliminating Android's advantage. But it will be a gamble, as other efforts to foist a personal assistant upon computer users have backfired badly. Remember Clippy, the animated paper clip that would pop up every time you tried to write a letter in Microsoft Word?

In a screenshot that 9to5Mac turned up, apparently from the menu on an iPhone "test unit," one button reads "Assistant"; another reads "Speaker," suggesting that the assistant can talk back, if you want it to; and a tab reading "MyInfo" suggests that the assistant will be able to use data on your phone such as address book contacts and location to help find the information you want. 9to5Mac further claims to have plumbed the depths of an iOS software development kit and found lines of code that correspond to the features in the screenshot.

Siri's original app, which licensed voice recognition technology from Nuance, a company based in Burlington, Massachusetts, enabled users to perform searches and make appointments or reservations using voice commands. It worked remarkably well for these simple tasks. (You can see a video of it in action here.)

Work on Siri began about eight years ago, when DARPA funded a massive AI initiative called CALO (Cognitive Assistant that Learns and Organizes). The idea, says Norman Winarsky, vice president of ventures at SRI, based in Menlo Park, California, the prime contractor for CALO, was to develop a virtual personal assistant as good as the character ofRadar O'Reilly on the TV show M*A*S*H. "Radar always knew what the captain wanted before the captain knew what the captain wanted," says Winarsky.

As the CALO program wound down, SRI recognized a massive market opportunity in the research it had been doing. Over a period of a few years, SRI built the company Siri and launched an app. 

Apple scooped up the company less than three months after the Siri app launched. Since then, we've all been held in suspense. Once Apple acquires a company, says Winarsky, "they go into radio silence, and believe me, they don't share with SRI or anybody" as to just what their plans are.

But, even if Apple is ready to offer a virtual personal assistant to every iPhone 5 buyer, does that mean every iPhone 5 buyer is ready for a virtual personal assistant? Not if it doesn't at least outperform Clippy.

Jason Hong, an associate professor at Carnegie Mellon University and a member of its Human-Computer Interaction Institute, says Microsoft Word's Clippy failed for two reasons: he was intrusive, interrupting you when you had already begun a task, and he simply wasn't very smart, often failing to understand your intentions, when you bothered to indulge him, that is. Hong found an explanation at a talk given by Eric Horvitz, the Microsoft researcher who worked on some of the AI behind Clippy. "They had to lobotomize all the machine learning they used, to make it primitive enough to run fast and in real time" on your desktop, says Hong.

Now, though, smart phones are blisteringly fast, and complex processing can be outsourced to the cloud, which means we can fully leverage the fruits of AI research even from relatively simple hardware. What's more, adds Hong, Siri is crucially "driven by what the user is explicitly asking"—it doesn't pop up officiously, like that insufferable paper clip.

Winarsky is betting that virtual personal assistants will be ubiquitous, and widely accepted, sooner than many expect. Looking beyond the restaurant reservations that Siri handled so well, Winarsky foresees an era when virtual personal assistants offer advice and recommendations on a range of topics. Eventually, he says, the technology will be folded into the desktop and the Web, and it will make people rich. "Within 10 years," he says, "we will see the value associated with virtual personal assistants throughout our marketplace to be in the many tens of billions—and [it] optimally might reach the 100-billion-dollar level."

The biggest stumbling block ahead might just be how willing people are to be heard constantly issuing commands in carefully enunciated English into their iPhones. "I used to play a game of guessing whether people I saw talking to themselves were drunk, crazy, or on the phone," says Hong. "And sometimes it was pretty hard to tell."

In that sense, the most important feature visible on the leaked 9to5Mac screenshot may well be the button labeled "OFF."

The Most Accurate Human Genetic Map to Date

A map created using DNA sequence from African-Americans highlights "hot spots" in the genome, which are often linked to disease.

Researchers have developed the most sophisticated map yet of the human genome, highlighting the regions where maternal and paternal chromosomes recombine, or swap parts. Recombination is one of the driving forces of genetic variability, which underlies evolution.

The genetic "hotspots" where recombination is most likely to take place are also linked to inherited diseases, since these regions are vulnerable to errors in the genetic code. "When recombination goes wrong, it can lead to mutations causing congenital diseases, for example diseases like Charcot-Marie-Tooth disease, or certain anemias," said Simon Myers, a lecturer in the Department of Statistics at the University of Oxford who led the research, in a release from Harvard Medical School.

"Charting recombination hotspots can thus identify places in the genome that have an especially high chance of causing disease," said David Reich, professor of genetics at Harvard Medical School, who co-led the study, in a release from Stanford.

The map is the first constructed from recombination data collected from African Americans. Previous maps have used genome information primarily from people of European decent. Researchers found that African Americans and Europeans have different recombination sites. 

According to the release;

These findings are expected to help researchers understand the roots of congenital conditions that occur more often in African Americans (due to mutations at hotspots that are more common in African Americans), and also to help discover new disease genes in all populations, because of the ability to map these genes more precisely.

The new map is so accurate because African American individuals often have a mixture of African and European ancestry from over the last two hundred years. David Reich and Simon Myers are experts in analyzing genetic data to reconstruct the mosaic of regions of African and European genetic ancestry in DNA of African Americans. By applying a computer program they previously wrote, Anjali Hinch identified the places in the genomes where the African and European ancestry switches in almost 30,000 people, detecting about 70 switches per person. These areas corresponded to recombination events in the last few hundred years. Thus, the researchers identified more than two million recombination events that they used to build the map.

NASA's WISE Finds Earth's First 'Trojan' Asteroid

This artist's concept illustrates the first known Earth Trojan asteroid, discovered by NEOWISE, the asteroid-hunting portion of NASA's WISE mission. The asteroid is shown in gray and its extreme orbit is shown in green. Earth's orbit around the sun is indicated by blue dots. (Credit: Paul Wiegert, University of Western Ontario, Canada)

Science Daily  — Astronomers studying observations taken by NASA's Wide-field Infrared Survey Explorer (WISE) mission have discovered the first known "Trojan" asteroid orbiting the sun along with Earth.

Scientists had predicted Earth should have Trojans, but they have been difficult to find because they are relatively small and appear near the sun from Earth's point of view.Trojans are asteroids that share an orbit with a planet near stable points in front of or behind the planet. Because they constantly lead or follow in the same orbit as the planet, they never can collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter. Two of Saturn's moons share orbits with Trojans.

"These asteroids dwell mostly in the daylight, making them very hard to see," said Martin Connors of Athabasca University in Canada, lead author of a new paper on the discovery in the July 28 issue of the journal Nature. "But we finally found one, because the object has an unusual orbit that takes it farther away from the sun than what is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at Earth's surface."

The WISE telescope scanned the entire sky in infrared light from January 2010 to February 2011. Connors and his team began their search for an Earth Trojan using data from NEOWISE, an addition to the WISE mission that focused in part on near-Earth objects, or NEOs, such as asteroids and comets. NEOs are bodies that pass within 28 million miles (45 million kilometers) of Earth's path around the sun. The NEOWISE project observed more than 155,000 asteroids in the main belt between Mars and Jupiter, and more than 500 NEOs, discovering 132 that were previously unknown.

The team's hunt resulted in two Trojan candidates. One called 2010 TK7 was confirmed as an Earth Trojan after follow-up observations with the Canada-France-Hawaii Telescope on Mauna Kea in Hawaii.

The asteroid is roughly 1,000 feet (300 meters) in diameter. It has an unusual orbit that traces a complex motion near a stable point in the plane of Earth's orbit, although the asteroid also moves above and below the plane. The object is about 50 million miles (80 million kilometers) from Earth. The asteroid's orbit is well-defined and for at least the next 100 years, it will not come closer to Earth than 15 million miles (24 million kilometers). An animation showing the orbit is available at:http://www.nasa.gov/multimedia/videogallery/index.html?media_id=103550791 .

"It's as though Earth is playing follow the leader," said Amy Mainzer, the principal investigator of NEOWISE at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Earth always is chasing this asteroid around."

A handful of other asteroids also have orbits similar to Earth. Such objects could make excellent candidates for future robotic or human exploration. Asteroid 2010 TK7 is not a good target because it travels too far above and below the plane of Earth's orbit, which would require large amounts of fuel to reach it.

"This observation illustrates why NASA's NEO Observation program funded the mission enhancement to process data collected by WISE," said Lindley Johnson, NEOWISE program executive at NASA Headquarters in Washington. "We believed there was great potential to find objects in near-Earth space that had not been seen before."

NEOWISE data on orbits from the hundreds of thousands of asteroids and comets it observed are available through the NASA-funded International Astronomical Union's Minor Planet Center at the Smithsonian Astrophysical Observatory in Cambridge, Mass.

JPL manages and operates WISE for NASA's Science Mission Directorate in Washington. The principal investigator, Edward Wright, is a professor at the University of California, Los Angeles. The mission was selected under NASA's Explorers Program, which is managed by the agency's Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah.

The spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

For more WISE information visit: http://www.nasa.gov/wise .

Reservoirs of Ancient Lava Shaped Earth

Geological history has periodically featured giant lava eruptions that coat large swaths of land or ocean floor with basaltic lava, which hardens into rock formations called flood basalt. (Credit: © ollirg / Fotolia)

Science Daily  — Geological history has periodically featured giant lava eruptions that coat large swaths of land or ocean floor with basaltic lava, which hardens into rock formations called flood basalt. New research from Matthew Jackson and Richard Carlson proposes that the remnants of six of the largest volcanic events of the past 250 million years contain traces of the ancient Earth's primitive mantle -- which existed before the largely differentiated mantle of today -- offering clues to the geochemical history of the planet.

Scientists recently discovered that an area in northern Canada and Greenland composed of flood basalt contains traces of ancient Earth's primitive mantle. Carlson and Jackson's research expanded these findings, in order to determine if other large volcanic rock deposits also derive from primitive sources.Their work is published online July 27 by Nature.

Information about the primitive mantle reservoir -- which came into existence after Earth's core formed but before Earth's outer rocky shell differentiated into crust and depleted mantle -- would teach scientists about the geochemistry of early Earth and how our planet arrived at its present state.

Until recently, scientists believed that Earth's primitive mantle, such as the remnants found in northern Canada and Greenland, originated from a type of meteorite called carbonaceous chondrites. But comparisons of isotopes of the element neodymium between samples from Earth and samples from chondrites didn't produce the expected results, which suggested that modern mantle reservoirs may have evolved from something different.

Carlson, of Carnegie's Department of Terrestrial Magnetism, and Jackson, a former Carnegie fellow now at Boston University, examined the isotopic characteristics of flood basalts to determine whether they were created by a primitive mantle source, even if it wasn't a chondritic one.

They used geochemical techniques based on isotopes of neodymium and lead to compare basalts from the previously discovered 62-million-year-old primitive mantle source in northern Canada's Baffin Island and West Greenland to basalts from the South Pacific's Ontong-Java Plateau, which formed in the largest volcanic event in geologic history. They discovered minor differences in the isotopic compositions of the two basaltic provinces, but not beyond what could be expected in a primitive reservoir.

They compared these findings to basalts from four other large accumulations of lava-formed rocks in Botswana, Russia, India, and the Indian Ocean, and determined that lavas that have interacted with continental crust the least (and are thus less contaminated) have neodymium and lead isotopic compositions similar to an early-formed primitive mantle composition.

The presence of these early-earth signatures in the six flood basalts suggests that a significant fraction of the world's largest volcanic events originate from a modern mantle source that is similar to the primitive reservoir discovered in Baffin Island and West Greenland. This primitive mantle is hotter, due to a higher concentration of radioactive elements, and more easily melted than other mantle reservoirs. As a result, it could be more likely to generate the eruptions that form flood basalts.

Start-up funding for this work was provided by Boston University.

New Invisibility Cloak Hides Objects from Human View

A real-life invisibility cloak, shown in this cross- sectional illustration, can hide objects from human view. (Credit: ACS)

Science Daily  — For the first time, scientists have devised an invisibility cloak material that hides objects from detection using light that is visible to humans. The new device is a leap forward in cloaking materials, according to a report in the ACS journal Nano Letters.

Although the study cloaked a microscopic object roughly the diameter of a red blood cell, the device demonstrates that it may be "capable of cloaking any object underneath a reflective carpet layer. In contrast to the previous demonstrations that were limited to infrared light, this work makes actual invisibility for the light seen by the human eye possible," the scientists write.Xiang Zhang and colleagues note that invisibility cloaks, which route electromagnetic waves around an object to make it undetectable, "are still in their infancy." Most cloaks are made of materials that can only hide things using microwave or infrared waves, which are just below the threshold of human vision. To remedy this, the researchers built a reflective "carpet cloak" out of layers of silicon oxide and silicon nitride etched in a special pattern. The carpet cloak works by concealing an object under the layers, and bending light waves away from the bump that the object makes, so that the cloak appears flat and smooth like a normal mirror.

The authors acknowledge funding from the U.S. Army Research Office, the Natural Sciences and Engineering Research Council of Canada, and the NSF Graduate Research Fellowship Program.

Fundamental Matter-Antimatter Symmetry Confirmed

Artist's rendering of an antiproton (black sphere) trapped inside a helium atom being probed by two laser beams. (Credit: Image courtesy of Max Planck Institute of Quantum Optics)

Science Daily — An international collaboration including Max Planck Institute of Quantum Optics scientists has set a new value for the antiproton mass relative to the electron with unprecedented precision.

Now the independent research group “Antimatter Spectroscopy” of Dr. Masaki Hori, which is associated with the Laser Spectroscopy Division of Prof. Theodor W. Hänsch at the Max Planck Institute of Quantum Optics, has measured the mass of the antiproton relative to the electron with a precision of 1.3 parts per billion (Nature, 28 July 2011). For this they used a new method of laser spectroscopy on a half-antimatter, half-matter atom called antiprotonic helium. The result agreed with the proton mass measured to a similar level of precision, confirming the symmetry between matter and antimatter. The experiment was carried out at the European Laboratory for Particle Physics (CERN) in Geneva (Switzerland) in a project led by scientists from the Max Planck Institute of Quantum Optics and Tokyo University (Japan), and including the University of Brescia (Italy), the Stefan Meyer Institute (Vienna, Austria), and the KFKI Research Institute (Budapest, Hungary).According to modern cosmology, matter and antimatter were created in equal amounts in the Big Bang at the beginning of the universe. Physicists are developing concepts to explain why the visible universe now seems to be made entirely out of matter. On the other hand, experimental groups are producing antimatter atoms artificially to explore the fundamental symmetries between matter and antimatter, which according to the present theories of particle physics should have exactly the same properties, except for the opposite electrical charge).

Physicists believe that the laws of nature obey a fundamental symmetry called “CPT” (this stands for charge conjugation, parity, and time reversal), which postulates that if all the matter in the universe were replaced with antimatter, left and right inverted as if looking into a mirror, and the flow of time reversed, this “anti-world” would be indistinguishable from our real matter world. Antimatter atoms should weigh exactly the same as their matter counterparts. If scientists were to experimentally detect any deviation, however small, it would indicate that this fundamental symmetry is broken. “Small” is the keyword here – it is essential to use the most precise methods and instruments available to make this comparison with the highest possible precision.

Antimatter is extraordinarily difficult to handle in the laboratory, because upon coming into contact with ordinary matter (even the air molecules in a room), it immediately annihilates, converting into energy and new particles. In 1997, researchers from the Max Planck Institute of Quantum Optics in cooperation with other European, Japanese, and American groups began construction of a facility called the Antiproton Decelerator (AD) at CERN. Here antiprotons produced in high-energy collisions are collected and stored in a vacuum pipe arranged in a 190-m-long racetrack shape. The antiprotons are gradually slowed down, before being transported to several experiments. The so-called ASACUSA¹ (Atomic Spectroscopy and Collisions using Slow Antiprotons, named after a district in Tokyo) collaboration, of which Dr. Hori is one of the project leaders, sends the antiprotons into a helium target to create and study antiprotonic helium atoms.

Normal helium atoms consist of a nucleus with two electrons orbiting around it. In antiprotonic helium, one of these electrons is replaced by an antiproton, which finds itself in an excited orbit some 100 picometres (10^-10 m) from the nucleus. Scientists fire a laser beam onto the atom, and carefully tune its frequency until the antiproton makes a quantum jump from one orbit to another. By comparing this frequency with theoretical calculations, the mass of the antiproton can be determined relative to the electron.

An important source of imprecision arises because the antiprotonic atoms jiggle around randomly according to their thermal energy, so that atoms moving towards the laser beam experience a different frequency compared to those moving away. This is similar to the effect that causes the siren of an approaching ambulance to change pitch as it passes you by. In their previous experiments of 2006, the MPQ / ASACUSA scientists used one laser beam, and this effect limited the precision of their measurement.

This time to go beyond this limit, a technique called “two-photon laser spectroscopy” was used. The atoms were struck by two laser beams travelling in opposite directions, with the result that the effect was partially cancelled, leading to a four to six times higher precision. The first laser caused the antiproton to make a quantum jump to a virtual energy level normally not allowed by quantum mechanics, so that the second laser could actually bring the antiproton up to the closest allowed state. Such a two-photon jump is normally difficult to achieve because the antiproton is heavy, but MPQ scientists accomplished it by building two ultra-sharp lasers and carefully choosing a special combination of laser frequencies. To do this, an optical frequency comb – a special device invented 10 years ago by the group of Prof. Theodor W. Hänsch to measure the frequency of light – was used.

The new measurements showed that the antiproton is 1836.1526736(23) times heavier than the electron, the parenthesis showing the 1-standard deviation imprecision. “We have measured the mass of the antiproton relative to the electron with a precision of 10 digits, and have found it exactly the same as the proton value known with a similar precision”, Masaki Hori explains. “This can be regarded as a confirmation of the CPT theorem. Furthermore, we learned that antiprotons obey the same laws of nonlinear quantum optics like normal particles, and we can use lasers to manipulate them. The two-photon technique would allow much higher precisions to be achieved in the future, so that ultimately the antiproton mass may be better known than the proton one.”

The Committee on Data for Science and Technology (CODATA) uses the results of this experiment as one of several input data to determine the proton-to-electron mass ratio, which in turn influences the values of many other fundamental constants. Olivia Meyer-Streng

¹ASACUSA is one of several experiments studying antimatter at CERN. ATRAP and ALPHA investigate antihydrogen atoms, AeGIS studies how antihydrogen falls under gravity, and ACE studies the possible use of antiprotons for cancer therapy.