Preventing Wood Decay

With the warm days of summer coming to an end and autumn beautifying our surroundings with oranges and yellows, now is an excellent time to start thinking of how to protect your deck/veranda from decay next year caused by rot and insect infestation. Understanding what causes wood to decay will help you choose the method of protection that is right for your home.

 

 

 

Natural Processes

 

 

Wood is a natural, organic substance with a distinct life cycle involving seeding, growth, death and decomposition. We have discovered that wood is an economical material to build with. We have developed methods to keep wood from decomposing once a tree has been felled and sectioned for log homes, decks, porches, or verandas.

 

Weathering, insect infestation and fungal attacks are all natural processes that significantly affect wood's life. However, fungal attack, or rot, leads to more rapid decomposition of the wood and causes more significant structural problems in North America than weathering or insect infestation.

 

 

 

Weathering

 

The effects of the sun's ultraviolet rays, rain, wind and freeze/thaw lead to a decomposition of the wood structure on the surface called weathering. This often leads to a greying or browning of the surface of the wood to a depth of about 1/100" deep.

 

 

Insect Infestation

 

Insects use the wood in the logs for food, lodging and breeding. This may lead to decomposition of the wood or decomposition of your level of satisfaction with the home.

 

 

Fungus

 

Fungus attack can lead to the structural decomposition of your wood elements of your home. Where does fungus come from? Fungus is in the particular plant family which does not produce their own food by photosynthesis as green plants containing chlorophyll do.

 

Fungi comes in various rot-producing forms, none of which any of us want in our wood. These fungi are all around us – in the forest before the tree is felled and at the sawmills where the trees are made into logs or boards. Understanding how fungi attach to the wood is half the battle in protecting our homes.

 

 

Elements Necessary for Fungal Growth

 

Four basic elements must be present for the fungus spores (seed for fungus plants) to grow and reproduce. These are food sources (wood), water, oxygen and proper temperature.

 

 

 

Wood

 

Some species contain natural chemicals (extractives, tannins or resins), that act to resist fungal attack. However, over time and given satisfactory conditions, even the more resistant species of wood will succumb to fungal attack. The natural chemicals disperse and fungus attacks the wood structure feeding on the cellulose and lignin fibers that make up the structure of the wood.

 

 

 

Water

Fungus require moisture (water) in close proximity to the wood fiber to grow. The moisture content by weight in wood at which fungus begins to thrive is 20-22% and ideal conditions exist at 26-32%.

 

 

 

Oxygen

In addition to water, oxygen must be present to provide for fungal growth. Generally, it is agreed that 20% air volume in the wood is required to provide enough oxygen for the fungus to process the wood into food.

 

 

 

Temperature

 

The ideal temperature for fungus to thrive is 75-90˚ F. A more comprehensive range of 40-105˚ F will sustain fungal growth.

 

If you remove one or more of these necessary elements, the fungus cannot develop, and rot is prevented. For example, wood has not decomposed after centuries locked up in an Egyptian tomb where water is not in proper amounts. Furthermore, logs remain solid and intact underwater, where oxygen does not exist in necessary quantities.

 

Therefore, it is essential to minimize the opportunities for our log home to be exposed to these four elements. Of these, water is perhaps the easiest element to control. There are many ways we deal with water content in our logs.

 

 

 

Moisture Content Control

If you are in the planning stages of your log home, there are things to be done to reduce the potential of increasing moisture content in the wood of your home. Following are some home design provisions you may want to incorporate.

 

Eave overhang minimum 24" at the base to 36" at the peak (ideally 48" at the peak)

Flashings over windows and doors and projections from walls

Properly installed eavestroughing

Adequate attic ventilation to prevent moisture buildup in the wall/attic interfaces

Adequate grade clearance or splash height (19" min), ideally with a first course flashing (see Figure 2), keeping ground moisture away from the log.

Also, there are some points to consider in terms of where you choose to build your home. The location should be on dry ground, have access to air movement, and be orientated to allow sun exposure.

 

The design of log joinery in your home is also essential. Try to include the following items in your home:

 

Logs incorporating a drip edge to provide for shelf water runoff

Boxed in heart logs that dry in an oval shape providing a slope for continual runoff of shelf water that moves into the space between logs and comes to rest on flat spots of logs like at corners

Fill all countersunk spike head holes with caulking as construction takes place.

NOTE:  Heartwood generally contains the largest concentration of extractives which aid in preventing the attack from fungus. Thus, removing sapwood from logs or wood can improve decay resistance.

 

Some species, such as northern white cedar, contain inherent heart rot (found in naturally growing trees), which can counteract the positive feature of the extractive. It is necessary to screen out all logs containing this fungus.

 

Further, logs cut in the winter or fall are less likely to have fungus spores attached because the low temperatures prevent spore development, movement and deposit on the records. Logs at the mill and on your property should be stacked apart and stored in well-ventilated, covered sites off the ground.

 

Wood which is placed in open areas free from direct contact with moisture (resting off the ground and protected at least partially from rain) will dry out to an equilibrium moisture content of 15-19%. This moisture content is lower than the wood moisture content of 20% or greater. This depends somewhat upon the location. For example, wood would be drier stored in a desert than by the ocean.

 

Thus, wood will not decay from fungus attack unless extra moisture is in contact with the logs for more extended periods, causing a higher moisture content in the wood. An example of this situation would be a window header improperly flashing, allowing rainwater to collect and lay for long periods.

 

If your log home is already constructed and you are trying to decide what finishes you might apply, consider the following. Paints, stains and varnishes do not prevent rot if the elements necessary to sustain fungal growth are present.

 

Paints and coatings were first used to prevent weathering, not rotting. They acted as UV blockers preventing the decomposition of lignin by the ultraviolet rays from the sun. Additives that resisted fungal attacks were introduced, such as copper naphthenate and additives like paraffin wax, which prevents or retards moisture migration.

 

 

 

Use of Coatings

A log home, deck, veranda, or porch should never be painted since paint places a coating on the log, preventing the log from absorbing and releasing moisture. Moisture will become trapped, leading to contents higher than 20% in the wood. This will result in decay.

 

A coating is defined as any material with a percentage of solids higher than 36-38%. Stains usually have 25-30% solids. A stain contains water or petroleum-based product known as the carrier, which moves the pigments (solids) into the cellular structure on the surface of the wood and deposits the pigment against the cell wall. These pigments are usually darker and absorb the ultraviolet rays before they get to the wood structure, thereby protecting the wood from weathering.

 

 

Use of Stains

 

Stains allow the wood's pores to remain open, providing free travel of moisture, which is desired. Thus, stains are preferable for log homes.

 

Additives which resist insect attack can be added to the stain for extra protection. Additives can also be used to retard (not stop) moisture flow allowing logs to dry more evenly and reduce checking and surface cracks.

 

This still allows the wood to transfer moisture in and out through the surface and is acceptable. Repellents that totally block moisture flow are not advisable to put on a log home.

 

When staining a log home or other wooden structures, it is also important to note that if the structure(s) that have just been constructed with green logs needs 2-4 months, the surface can dry to a depth of about 1/4". This will prevent water, migrating from the inside of the log, from mixing with the stain causing drip marks, flaking, peeling blotches and white powder (standard in pine).

 

Commercial methods impregnate the log under vacuum pressure with chemicals like chromated copper arsenate. These processes generally only impregnate the sapwood and are incapable of fair heartwood treatment. Since they can only be impregnated this way at the plant, re-machining the log on the site will expose untreated wood.

 

Recently a method of dipping the green logs (logs that have a moisture content over 26-30%) at the plant in a liquid containing a borate has been becoming popular. This is commonly called a diffuse wood treatment. The borate in the liquid diffuses into the log and onto the cell wall. This then acts as a repellent to insects and fungus. Since sapwood exhibits less favourable shrinkage characteristics and the chemical toxicity is questionable, some people find this technique unacceptable.

 

However, care should be exercised in generalizing the effectiveness of this technique. Little independent research has been carried out, and neither information nor regulatory standards for control of key variables during the processing have been established, variables such as the temperature of wood, species of wood and the time of immersion.

 

However, if performed correctly, the process has a promising future for log home protection and maintenance.

 

 

 

Conclusion

In summary, the best approach to preventing decay in your home or outdoor area is to remove the opportunities for moisture buildup at various points in the wood.

 

Stains are used to prevent weathering and, with additives, can repel insects and fungus, but they won't prevent rot if suitable conditions exist. Measures must be taken to ensure that you know how to deal with the sources of food (wood, water, oxygen and temperature) on which fungus thrives on.

 

A proper balance of design, manufacture and log surface protection will protect your log home and provide low maintenance for years to come.

 

 Thanks https://woodrandd.com/

Wave-particle duality

The quest to understand nature’s fundamental building blocks began with the ancient Greek philosopher Democritus’s assertion that such things exist. Two millennia later, Isaac Newton and Christiaan Huygens debated whether light is made of particles or waves. The discovery of quantum mechanics some 250 years after that proved both luminaries right: Light comes in individual packets of energy known as photons, which behave as both particles and waves.

Wave-particle duality turned out to be a symptom of a deep strangeness. Quantum mechanics revealed to its discoverers in the 1920s that photons and other quantum objects are best described not as particles or waves but by abstract “wave functions” — evolving mathematical functions that indicate a particle’s probability of having various properties. The wave function representing an electron, say, is spatially spread out, so that the electron has possible locations rather than a definite one. But somehow, strangely, when you stick a detector in the scene and measure the electron’s location, its wave function suddenly “collapses” to a point, and the particle clicks at that position in the detector.

A particle is thus a collapsed wave function. But what in the world does that mean? Why does observation cause a distended mathematical function to collapse and a concrete particle to appear? And what decides the measurement’s outcome? Nearly a century later, physicists have no idea... Cecile G. Tamura

Graphene can hear your brain whisper

The body of knowledge about the human brain is keeps growing, but many questions remain unanswered. Researchers have been using electrode arrays to record the brain's electrical activity for decades, mapping activity in different brain regions to understand what it looks like when everything is working, and what is happening when it is not. Until now, however, these arrays have only been able to detect activity over a certain frequency threshold. A new technology developed by the Graphene Flagship overcomes this technical limitation, unlocking the wealth of information found below 0.1 Hz, while paving the way for future brain-computer interfaces.

The new device was developed thanks to a collaboration between three Graphene Flagship Partners (IMB-CNM, ICN2 and ICFO) and adapted for brain recordings together with biomedical experts at IDIBAPS. This new technology moves away from electrodes and uses an innovative transistor-based architecture that amplifies the brain's signals in situ before transmitting them to a receiver. The use of graphene to build this new architecture means the resulting implant can support many more recording sites than a standard electrode array. It is slim and flexible enough to be used over large areas of the cortex without being rejected or interfering with normal brain function. The result is an unprecedented mapping of the low frequency brain activity known to carry crucial information about different events, such as the onset and progression of epileptic seizures and strokes.
For neurologists this means they finally have access to some clues that our brains only whisper. This ground-breaking technology could change the way we record and view electrical activity from the brain. Future applications will give unprecedented insights into where and how seizures begin and end, enabling new approaches to the diagnosis and treatment of epilepsy.

"Beyond epilepsy, this precise mapping and interaction with the brain has other exciting applications," explains José Antonio Garrido, one of the leaders of the study working at Graphene Flagship Partner ICN2. "In contrast to the common standard passive electrodes, our active graphene-based transistor technology will boost the implementation of novel multiplexing strategies that can increase dramatically the number of recording sites in the brain, leading the development of a new generation of brain-computer interfaces." Taking advantage of 'multiplexing', this graphene-enabled technology can also be adapted by some of the same researchers to restore speech and communication. ICN2 has secured this technology through a patent that protects the use of graphene-based transistors to measure low-frequency neural signals.


"This work is a prime example of how a flexible, graphene-based transistor array technology can offer capabilities beyond what is achievable today, and open up tremendous possibilities for reading at unexplored frequencies of neurological activity" noted by Kostas Kostarelos, leader of the Health, Medicine and Sensors Division of the Graphene Flagship.

Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship, and Chair of its Management Panel added that "graphene and related materials have major opportunities for biomedical applications. The Graphene Flagship recognized this by funding a dedicated Work Package. The results of this study are a clear demonstration that graphene can bring unprecedented progress to the study of Brain processes."
This new technology will be one of the Graphene Pavilion's main attractions at the upcoming Mobile World Congress in Barcelona (25-28 February 2019). The exhibition will showcase the latest innovations on graphene and related materials made possible by the Graphene Flagship, one of the biggest research initiatives ever funded by the European Commission. Beyond applications in health and medical devices, the pavilion will be populated with new prototypes of graphene-enabled technologies for mobile and data communications, wearables, and the internet of things.

High-resolution mapping of infraslow cortical brain activity enabled by graphene microtransistors
Eduard Masvidal-Codina, Xavi Illa, Miguel Dasilva, Andrea Bonaccini Calia, Tanja Dragojević, Ernesto E. Vidal-Rosas, Elisabet Prats-Alfonso, Javier Martínez-Aguilar, Jose M. De la Cruz, Ramon Garcia-Cortadella, Philippe Godignon, Gemma Rius, Alessandra Camassa, Elena Del Corro, Jessica Bousquet, Clement Hébert, Turgut Durduran, Rosa Villa, Maria V. Sanchez-Vives, Jose A. Garrido & Anton Guimerà-Brunet
https://www.nanotechnologyworld.org/…/Graphene-can-hear-you…

Phanerozoic and Precambrian

There are differences in the style of collisional orogens between the Phanerozoic and the Precambrian, most notably the appearance of blueschists and ultrahigh pressure metamorphic (UHPM) rocks in the geological record since the late Neoproterozoic, whereas these rocks are absent from older orogens. Understanding collisional orogenesis in the context of present-day values for ambient upper-mantle temperature and radiogenic heat production provides a reference from which to extrapolate back to conditions in the Precambrian. To evaluate differences in the way Phanerozoic and Precambrian collisional orogens develop, a series of experiments were run using a 2-D petrological–thermomechanical numerical model in which the collision of spontaneously moving continental plates was simulated for values of ambient upper-mantle temperature and radiogenic heat production increasing from those appropriate to the present day. Thus, models of modern collisional orogens involving different modes of exhumation of UHPM rocks were extrapolated back to conditions appropriate for the Precambrian. Based on these experiments an increase of the ambient upper-mantle temperature to > 80–100 K above the present-day value leads to two distinct modes of collision that are different from the modern collision regime and for which the terms truncated hot collision regime (strong mafic lower continental crust) and two-sided hot collision regime (weak felsic lower continental crust) are proposed. Some Proterozoic orogens record post-extension thickening to generate counter-clockwise metamorphic P–T paths followed by slow close-to-isobaric retrograde cooling, such as occurred in the Paleoproterozoic Khondalite belt in the North China craton and the late Mesoproterozoic–early Neoproterozoic Eastern Ghats province, part of the Eastern Ghats belt of peninsular India. These orogens have similarities with the truncated hot collision regime in the numerical models, assuming subsequent shortening and thickening of the resulting hot lithosphere. Other Proterozoic orogens are characterized by clockwise looping metamorphic P–T paths and extensive granite magmatism derived from diverse crustal and subcontinental lithospheric mantle sources. These orogens have similarities with the two-sided hot collision regime in the numerical models. Both regimes are associated with shallow slab breakoff that precludes the formation of UHPM rocks. The temperature of the ambient upper-mantle where this transition in geodynamic regimes occurs corresponds broadly to the Neoproterozoic Era.

Mechanical Properties of Material Essential for Every Mechanical Engineer

There are mainly two types of materials. First one is metal and other one is non metals. Metals are classified into two types : Ferrous metals and Non-ferrous metals.

Ferrous metals mainly consist iron with comparatively small addition of other materials. It includes iron and its alloy such as cast iron, steel, HSS etc. Ferrous metals are widely used in mechanical industries for its various advantages.

Nonferrous metals contain little or no iron. It includes aluminum, magnesium, copper, zinc etc.

Most Mechanical properties are associated with metals. These are

#1. Strength:

The ability of material to withstand load without failure is known as strength. If a material can bear more load, it means it has more strength. Strength of any material mainly depends on type of loading and deformation before fracture. According to loading types, strength can be classified into three types.

a. Tensile strength:

b. Compressive strength:

3. Shear strength:

According to the deformation before fracture, strength can be classified into three types.

a. Elastic strength:

b. Yield strength:

c. Ultimate strength:

#2. Homogeneity:

If a material has same properties throughout its geometry, known as homogeneous material and the property is known as homogeneity. It is an ideal situation but practically no material is homogeneous.

#3. Isotropy:

A material which has same elastic properties along its all loading direction known as isotropic material.

#4. Anisotropy:

A material which exhibits different elastic properties in different loading direction known as an-isotropic material.

#5. Elasticity:

If a material regain its original dimension after removal of load, it is known as elastic material and the property by virtue of which it regains its original shape is known as elasticity.

Every material possess some elasticity. It is measure as the ratio of stress to strain under elastic limit.

#6. Plasticity:

The ability of material to undergo some degree of permanent deformation without failure after removal of load is known as plasticity. This property is used for shaping material by metal working. It is mainly depends on temperature and elastic strength of material.

#7. Ductility:

Ductility is a property by virtue of which metal can be drawn into wires. It can also define as a property which permits permanent deformation before fracture under tensile loading. The amount of permanent deformation (measure in percentage elongation) decides either the material is ductile or not.

Percentage elongation = (Final Gauge Length – Original Gauge Length )*100/ Original Gauge Length

If the percentage elongation is greater than 5% in a gauge length 50 mm, the material is ductile and if it less than 5% it is not.

#8. Brittleness:

Brittleness is a property by virtue of which, a material will fail under loading without significant change in dimension. Glass and cast iron are well known brittle materials.

#9. Stiffness:

The ability of material to resist elastic deformation or deflection during loading, known as stiffness.  A material which offers small change in dimension during loading is more stiffer. For example steel is stiffer than aluminum.

#10. Hardness:

The property of a material to resist penetration is known as hardness. It is an ability to resist scratching, abrasion or cutting. 

It is also define as an ability to resist fracture under point loading.

#11. Toughness:

Toughness is defined as an ability to withstand with plastic or elastic deformation without failure. It is defined as the amount of energy absorbed before actual fracture.

#12. Malleability:

A property by virtue of which a metal can flatten into thin sheets, known  as malleability. It is also define as a property which permits plastic deformation under compression loading.

#13. Machinability:

A property by virtue of which a material can be cut easily.

#14. Damping:

The ability of metal to dissipate the energy of vibration or cyclic stress is called damping. Cast iron has good damping property, that’s why most of machines body made by cast iron.

#15. Creep:

The slow and progressive change in dimension of a material under influence of its safe working stress for long time is known as creep. Creep is mainly depend on time and temperature. The maximum amount of stress under which a material withstand during infinite time is known as creep strength.

#16. Resilience:

The amount of energy absorb under elastic limit during loading is called resilience. The maximum amount of the energy absorb under elastic limit is called proof resilience.  

#17. Fatigue Strength:

The failure of a work piece under cyclic load or repeated load below its ultimate limit is known as fatigue. The maximum amount of cyclic load which a work piece can bear for infinite number of cycle is called fatigue strength. Fatigue strength is also depend on work piece shape, geometry, surface finish etc.

#18. Embrittlement:

The loss of ductility of a metal caused by physical or chemical changes, which make it brittle, is called embrittlement.

What happens inside a Mobile battery right before it explodes?

The first thing we need to understand is how exactly the lithium-ion battery in your phone works. The name gives us a hint — electricity is carried from one electrode to another using charged lithium ions.

Lithium-ion batteries store, transfer and release energy because of natural chemical reactions. The battery has two electrodes — an anode and a cathode. The cathode is connected to the positive (+) connection on the battery and holds positively charged ions, and the anode is connected to the negative (-) connection and holds (you guessed it) negatively charged ions.

Between the two electrodes is what's called an electrolyte. The electrolyte in a lithium battery is (usually) an organic solvent paste that has a very large number of metallic salts (in most cases, that metal is lithium) as part of its makeup. This makes it electrically conductive — electricity can pass through it. The anode and the cathode are in the electrolyte and separated by a physical barrier so they can't touch.

When you discharge the battery (when you're using your phone and not charging it) the cathode pushes its positively charged ions away and the negatively charged anode attracts them. Electricity flows out from the anode, through your device, then back to the cathode. Yes, electricity travels through a loop and isn't "used up" by the thing being powered. When you charge your phone, the reverse happens and ions travel from the cathode through the electrolyte to the anode.

Lithium is the perfect element for rechargeable batteries: It's lightweight, easy to recharge and holds a charge for a long time.

When these ions come in contact with the charged atoms in an electrode, an electrochemical reaction called oxidation-reduction (redox) frees the charged electrons to travel out through the battery contacts, which are connected to the electrodes. This continues to charge the lithium ions in the electrolyte until there aren't enough left that can hold a positive charge that's strong enough to move through the electrolyte paste, and your battery will no longer charge.

Lithium is the lightest metal — number three on the periodic table. It's also very excitable, making it easy to create a powerful chemical reaction. This makes it a near-perfect metal to use in a portable rechargeable battery. It's lightweight, easy to recharge and continues to hold a charge for a long time.

 From the fiery Note 7 debacles to exploding hoverboards, lithium-ion batteries aren't doing so hot lately. A new study helps to explain how these popular power sources can turn into safety hazards.

In the paper, published in the Journal of the Electrochemical Society, scientists at the Canadian Light Source (CLS) synchrotron looked inside an overworked battery. In this case, they drained a battery until its voltage was below a critical level.

Overcharging or overworking deforms the insides of a battery. (A) shows the inside of a battery before it was misused. (B) shows how misuse causes the original design defects to become even more warped. (C) highlights the areas where warping got worse.
Toby Bond, Canadian Light Source

When we overcharge or overheat lithium ion batteries, the materials inside start to break down and produce bubbles of oxygen, carbon dioxide, and other gasses. Pressure builds up, and the hot battery swells from a rectangle into a pillow shape. Sometimes the phone involved will operate afterward. Other times it will die. And occasionally—kapow!

To see what's happening inside the battery when it swells, the CLS team used an x-ray technique called computed tomography.

Inside the battery is an electrode that spirals out from a central point like a jellyroll. The x-ray scan revealed that the bubbles produced during overheating warped and dented this electrode.

Intriguingly, the study authors found that the worst deformation from the gas buildup occurred in areas that had slight defects before the battery was ever over-drained. The authors note that doing more studies like this, on a larger variety of batteries, would improve understanding of how these batteries respond to gas evolution, which could lead to better designs.

As New Scientist notes, it's not clear whether the Samsung Note 7 catastrophes included pillowing or this type of deformation.

[Journal of the Electrochemical Society via New Scientist]

 www.popsci.com.

New Material with 5% the density of steel and 10 times the strength

A team of researchers at MIT has designed one of the strongest lightweight materials known, by compressing and fusing flakes of graphene, a two-dimensional form of carbon. The new material, a sponge-like configuration with a density of just 5 percent, can have a strength 10 times that of steel.

In its two-dimensional form, graphene is thought to be the strongest of all known materials. But researchers until now have had a hard time translating that two-dimensional strength into useful three-dimensional materials.

The new findings show that the crucial aspect of the new 3-D forms has more to do with their unusual geometrical configuration than with the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials by creating similar geometric features.

The findings are being reported today in the journal Science Advances, in a paper by Markus Buehler, the head of MIT's Department of Civil and Environmental Engineering (CEE) and the McAfee Professor of Engineering; Zhao Qin, a CEE research scientist; Gang Seob Jung, a graduate student; and Min Jeong Kang MEng '16, a recent graduate.

Other groups had suggested the possibility of such lightweight structures, but lab experiments so far had failed to match predictions, with some results exhibiting several orders of magnitude less strength than expected. The MIT team decided to solve the mystery by analyzing the material's behavior down to the level of individual atoms within the structure. They were able to produce a mathematical framework that very closely matches experimental observations.

Two-dimensional materials—basically flat sheets that are just one atom in thickness but can be indefinitely large in the other dimensions—have exceptional strength as well as unique electrical properties. But because of their extraordinary thinness, "they are not very useful for making 3-D materials that could be used in vehicles, buildings, or devices," Buehler says. "What we've done is to realize the wish of translating these 2-D materials into three-dimensional structures."

The team was able to compress small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure whose form resembles that of some corals and microscopic creatures called diatoms. These shapes, which have an enormous surface area in proportion to their volume, proved to be remarkably strong. "Once we created these 3-D structures, we wanted to see what's the limit—what's the strongest possible material we can produce," says Qin. To do that, they created a variety of 3-D models and then subjected them to various tests. In computational simulations, which mimic the loading conditions in the tensile and compression tests performed in a tensile loading machine, "one of our samples has 5 percent the density of steel, but 10 times the strength," Qin says.

Buehler says that what happens to their 3-D graphene material, which is composed of curved surfaces under deformation, resembles what would happen with sheets of paper. Paper has little strength along its length and width, and can be easily crumpled up. But when made into certain shapes, for example rolled into a tube, suddenly the strength along the length of the tube is much greater and can support substantial weight. Similarly, the geometric arrangement of the graphene flakes after treatment naturally forms a very strong configuration.

The new configurations have been made in the lab using a high-resolution, multimaterial 3-D printer. They were mechanically tested for their tensile and compressive properties, and their mechanical response under loading was simulated using the team's theoretical models. The results from the experiments and simulations matched accurately.

The new, more accurate results, based on atomistic computational modeling by the MIT team, ruled out a possibility proposed previously by other teams: that it might be possible to make 3-D graphene structures so lightweight that they would actually be lighter than air, and could be used as a durable replacement for helium in balloons. The current work shows, however, that at such low densities, the material would not have sufficient strength and would collapse from the surrounding air pressure.

But many other possible applications of the material could eventually be feasible, the researchers say, for uses that require a combination of extreme strength and light weight. "You could either use the real graphene material or use the geometry we discovered with other materials, like polymers or metals," Buehler says, to gain similar advantages of strength combined with advantages in cost, processing methods, or other material properties (such as transparency or electrical conductivity).

"You can replace the material itself with anything," Buehler says. "The geometry is the dominant factor. It's something that has the potential to transfer to many things."

The unusual geometric shapes that graphene naturally forms under heat and pressure look something like a Nerf ball—round, but full of holes. These shapes, known as gyroids, are so complex that "actually making them using conventional manufacturing methods is probably impossible," Buehler says. The team used 3-D-printed models of the structure, enlarged to thousands of times their natural size, for testing purposes.

For actual synthesis, the researchers say, one possibility is to use the polymer or metal particles as templates, coat them with graphene by chemical vapor deposit before heat and pressure treatments, and then chemically or physically remove the polymer or metal phases to leave 3-D graphene in the gyroid form. For this, the computational model given in the current study provides a guideline to evaluate the mechanical quality of the synthesis output.

The same geometry could even be applied to large-scale structural materials, they suggest. For example, concrete for a structure such a bridge might be made with this porous geometry, providing comparable strength with a fraction of the weight. This approach would have the additional benefit of providing good insulation because of the large amount of enclosed airspace within it.

Because the shape is riddled with very tiny pore spaces, the material might also find application in some filtration systems, for either water or chemical processing. The mathematical descriptions derived by this group could facilitate the development of a variety of applications, the researchers say.

Source: Massachusetts Institute of Technology
Thanks  http://3tags.org

Dark matter might be made of super-heavy particles almost as big as human cells

Usually, when a new particle is discovered or its existence hypothesised, it's on such a tiny scale that it's hard for us to imagine. But that might not be the case with dark matter, because researchers have found evidence to suggest that these mysterious, invisible particles could be about one-third the size of a human cell, and dense enough to almost create a mini black hole.

Though they reportedly make up five-sixths of all of the matter in the Universe, no one truly knows what dark matter is, how it works, or even what it could look like. Despite its mysterious nature, scientists hypothesise that dark matter has to exist in some form to account for the amount of mass needed for the Universe to exist and act in the way it does.

Knowing this, researchers from the University of Southern Denmark decided to investigate the size of these hypothetical hidden particles. According to the team, dark matter could weigh more than 10 billion billion (10^9) times more than a proton.

If this is true, a single dark matter particle could weigh about 1 microgram, which is about one-third the mass of a human cell (a typical human cell weighs about 3.5 micrograms), and right under the threshold for a particle to become a black hole.

The researchers came up with this number by creating a new model for a super-heavy particle they call the PIDM particle (Planckian Interacting Dark Matter). These supermassive particles belong to a class of particles known as 'weakly interacting massive particles', or WIMPS.

Before now, researchers have suggested that WIMPs were about 100 times the mass of a proton, Charles Q. Choi reports for LiveScience, but while the existence of WIMPS has been hypothesied for years, evidence of them is, well, extremely lacking, like everything else about dark matter. This leaves open the possibility that dark matter particles could be made of something significantly different, says Choi.

If the team from Denmark is right about the size of dark matter particles, it means dark matter is too large for researchers to recreate with particle accelerators. Instead, evidence of dark matter might exist in the Universe’s cosmic microwave background radiation, which is basically the light left around from the Big Bang.
In short, when the Big Bang happened 13.8 billion years ago, the Universe grew rapidly, a time period researchers call 'inflation'. The next stage on the Universe’s development chart is called reheating, which, among many things, created particles. It's here, during reheating, that supermassive dark matter particles might have first formed.

"However, for this model to work, the heat during reheating would have

had to be significantly higher than what is typically assumed in Universal models," says Choi. "A hotter reheating would in turn leave a signature in the cosmic microwave background radiation that the next generation of cosmic microwave background experiments could detect."

Obviously, if we do eventually observe direct evidence of dark matter, it would solidify many hypotheses about how the Universe works and initially formed.

However, before that happens, we need better tools, which University of Southern Denmark cosmologist, McCullen Sandora, says we should have within the next decade.

Until then, we can only speculate how dark matter works and how it fits into longstanding hypotheses and models.

http://journals.aps.org/…/ab…/10.1103/PhysRevLett.116.101302

http://arxiv.org/abs/1511.03278

http://www.sciencealert.com/dark-matter-might-actually-be-s…

How ribboned glass is made ?

The process of making ribboned glass is crazy complicated — and beautiful to see

Believe it or not !!! This is made by welding !!!

Boulder Opal stone from Australia - a type of gemstone that combines a host rock, usually ironstone or sandstone, and a precious opal.

As the rock is forming, a silica compound containing water penetrates the rock, and deposits opal in the cracks. Amazing.

The tyres/tires are black because:

The tyre's black colour comes from the carbon black which makes the tyre rough and tough, and gives high heat resistant character. Moreover the old tyres which were used long back were white in color only.