WOOD FRAME CONSTRUCTION - Light wood framed construction is one of the most popular types of building methods for homes in the United States and parts of Europe. It has the following characteristics: It is light, and allows quick construction with no heavy tools or equipment. Every component can easily be carried by hand - a house essentially becomes a large carpentry job. The main tool is a handheld nail gun. It is able to adapt itself to any geometric shape, and can be clad with a variety of materials. There are a huge variety of products and systems tailored to this type of construction. It has these negative characteristics: It is not highly fireproof, as it is made of wood. It is not strong enough to resist major wind events such as tornadoes and hurricanes. Every timber frame home structure is made of a few basic components: Studs are vertical wooden members within the walls. Joists are the horizontal wooden beams that support the floors. Rafters are the sloping wooden beams that support the roof. Sheathing are the sheets that are nailed over the studs to connect them securely and form the wall surfaces. Siding is the exterior cladding that covers the walls from the outside. Unlike heavy timber or brick masonry, wood framing does not require a special set of skills acquired after years of practice. Light gauge steel construction is starting to replace light wooden structures.

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Wood Frame Construction

understandconstruction.com

Light wood framed construction is one of the most popular types of building methods for homes in the United States and parts of Europe.

It has the following characteristics:

o  It is light, and allows quick construction with no heavy tools or equipment. Every component can easily be carried by hand - a house essentially becomes a large carpentry job. The main tool is a handheld nail gun.

o  It is able to adapt itself to any geometric shape, and can be clad with a variety of materials.

o  There are a huge variety of products and systems tailored to this type of construction.

It has these negative characteristics:

o  It is not highly fireproof, as it is made of wood.

o  It is not strong enough to resist major wind events such as tornadoes and hurricanes.

Every timber frame home structure is made of a few basic components:

o  Studs are vertical wooden members within the walls.

o  Joists are the horizontal wooden beams that support the floors.

o  Rafters are the sloping wooden beams that support the roof.

o  Sheathing are the sheets that are nailed over the studs to connect them securely and form the wall surfaces.

o  Siding is the exterior cladding that covers the walls from the outside.

Let us examine the major types of light wood framed structures.

BALLOON FRAME STRUCTURES

While this is an outmoded form of wood construction no longer used today, it is good to know what it is and why it is no longer used.

In balloon frame construction, if you had a two-storey house that was twenty feet high, you would use a single 20-foot long vertical stud for both storeys.

This made the studs heavy and difficult to handle.

The second problem was the gap between the two studs, which acted passageways for the spread of fire from the lower to the upper storey.

For these reasons, balloon frame construction has been superseded by platform frame construction, which is superior in all respects.

PLATFORM FRAME STRUCTURES

This is the sequence you would follow to erect a 2-storey platform frame house.

Erect the ground floor platform, a horizontal wooden platform over the foundation.

Build all the walls up to a height of one storey. This can easily be done by building each wall flat - on the floor platform - and then tilting it vertically.

Build the next floor platform.

Erect the next set of vertical walls in the same manner on the top of the second platform.

Build the sloping roof over the walls.

As you can see, this system uses shorter, lighter studs that are easy to handle. It is much easier to build walls flat and then tilt them into place.

Since each floor is a separate horizontal platform, this makes it convenient for construction workers to move around. These platforms also break the vertical spread of fire.

The only disadvantage of platform frame vs. balloon frame construction is that wood shrinkage plays a bigger role in platform frames.

Watch this nice time-lapse video of platform frame construction in action!

https://youtu.be/fqfSZjCzbpU

THE HISTORY OF LIGHT WOODEN FRAMED STRUCTURES

Light wooden framed structures were first created when some bright carpenters realised that the light partition walls they were putting up inside large heavy timber houses were capable of forming a construction system by themselves.

The system was a skin made of timber members covered inside and out by sheeting.

This happened approximately a century ago.

The process was accelerated by the widespread availability of cheap machine-made nails, and properly cut and planed pieces of wood produced by water-powered saw mills.

The American tradition of do-it-yourself also played a large role in popularizing this style of construction.

Unlike heavy timber or brick masonry, wood framing does not require a special set of skills acquired after years of practice.

In modern times, light gauge steel construction is starting to replace light wooden structures.

This is a site that explains the art and science of building construction in great clarity and detail.  Our goal is to make you understand concepts in building construction.

Written by architects and engineers, the content on the site is actually a result of accumulated years of work experience at building construction sites and design offices. This expert knowledge of building construction is not available in textbooks! We also take great pains to ensure that our quality of writing is of a high standard. We aim to take complicated situations and make them simple and clear, as well as to provide content that is interesting to industry experts and newcomers alike. Do let us know where we succeed - and where we fail - in this task.

http://www.understandconstruction.com/wood-framed-construction.html

LIQUID MAGNETS - New Liquid Magnets Go Places Solid Magnets Can't. Back in 2013, scientists constructed a tiny magnet made of just five iron atoms. Back in the second century B.C.E., the Chinese developed a spoon-shaped compass made of lodestone, or magnetite ore, which was capable of helping them figure out the directional position of north. Since then, inventors have found all sorts of other ways to use magnets, ranging from magnetic audio and videotapes, to computer hard drives and MRI machines for scanning the insides of the human body, to those magnets that you use for sticking your kids' drawings to the refrigerator door. Up to this point, magnets have been made of solid materials. But now, in an article published July 19, 2019, in the journal Science, researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory reveal that they've figured out a way to make a 3D-printed magnetic device out of liquid. Liquid magnets could be fantastically useful for creating tools that range from artificial cells that deliver cancer-killing medication, to flexible liquid robots that can change their shape and adapt to their surroundings. (Maybe T-1000 from "Terminator 2: Judgment Day" isn't so far-fetched after all.) Russell and Xubo Liu, the study's lead author, got the inspiration to try to form liquid structures from ferrofluids — solutions of iron-oxide particles that become magnetic in the presence of another magnet.

Ultra close-up of a ferrofluid, or magnetic colloidal liquid, which becomes strongly magnetized in the presence of a magnetic field and can be used in ways that solid magnets cannot. 

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Liquid Magnets

New Liquid Magnets Go Places Solid Magnets Can't

BY PATRICK J. KIGER 

Back in the second century B.C.E., the Chinese developed a spoon-shaped compass  made of lodestone, or magnetite ore, which was capable of helping them figure out the directional position of north.

Since then, inventors have found all sorts of other ways to use magnets, ranging from magnetic audio and videotapes, to computer hard drives and MRI machines for scanning the insides of the human body, to those magnets that you use for sticking your kids' drawings to the refrigerator door.

Up to this point, magnets have been made of solid materials.

But now, in an article published July 19, 2019, in the journal Science, researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory reveal that they've figured out a way to make a 3D-printed magnetic device out of liquid.

Liquid magnets could be fantastically useful for creating tools that range from artificial cells that deliver cancer-killing medication, to flexible liquid robots that can change their shape and adapt to their surroundings. (Maybe T-1000 from "Terminator 2: Judgment Day" isn't so far-fetched after all.)

"We've made a new material that is both liquid and magnetic. No one has ever observed this before," said Tom Russell, a visiting faculty scientist at Berkeley Lab and professor of polymer science and engineering at the University of Massachusetts, Amherst, said in a press release.

"This opens the door to a new area of science in magnetic soft matter."

Russell and Xubo Liu, the study's lead author, got the inspiration to try to form liquid structures from ferrofluids — solutions of iron-oxide particles that become magnetic in the presence of another magnet.

They used a 3-D printer to make tiny droplets, just 1 millimeter across, from a ferrofluid solution containing iron-oxide nanoparticles that crowded at the droplet's surface.

The research team then put the droplets in a solution near a magnetic coil.

When they removed the coil, the droplets gravitated toward each other and became permanently magnetic.

NOW THAT'S INTERESTING

Back in 2013, scientists constructed a tiny magnet made of just five iron atoms.

Patrick J. Kiger has written for HowStuffWorks since 2008 covering a wide array of topics, from history and politics to pop culture and technology. He worked as a newspaper reporter for the Pittsburgh Press, and the Orange County Register in California, where he covered one of the biggest serial murder cases in U.S. history, and also as a staff writer at Baltimore Magazine. As a freelancer, Patrick has written for print publications such as GQ, Mother Jones and the Los Angeles Times, and on the web for National Geographic Channel, Discovery News, Science Channel and Fast Company, among others. In recent years, he's become increasingly interested in how technological advances are altering urban life and the design of cities, and has written extensively on that subject for Urban Land magazine. In his spare time, Patrick is a longtime martial arts student and a fan of crime fiction, punk rock and classic Hollywood films.

https://science.howstuffworks.com/innovation/new-inventions/liquid-magnets.htm

ANHIDROSIS - Without the ability to sweat, the human body has a difficult time regulating its temperature. You're always cool as a cucumber, despite excessive summer heat, an exercise class or new social situations. But just because you're not sweating doesn't mean you're truly composed. You could have anhidrosis, the inability to perspire. Odds are you may not notice the signs -- an absence of telltale underarm wetness, for instance -- until it reaches a potentially dangerous level. So why is sweating so important? It helps your body regulate its temperature. More precisely, it helps your body cool off as your internal temperature rises. One of the repercussions of not being able to sweat is that you may get heat stroke or, in the case of a fever, develop a temperature so high it causes a febrile seizure. Either scenario could prove deadly. Children are especially vulnerable if unable to sweat; they have are less able to regulate internal temperatures because of their size, so being able to perspire may mean the difference between health and death. When you don't sweat, you may have to deal with other symptoms, too. Prolonged muscle cramps, dizziness and a perpetual feeling of being too hot become daily challenges -- especially for people who don't perspire over most of their bodies. Anhidrosis can occur in a single area or in scattered patches. When this happens, other body areas that do sweat will try to make up the difference. This may be bothersome, but it's not usually dangerous. However, the prevalence of mild symptoms makes it difficult to recognize the condition until something goes really wrong, like getting overheated.

Without the ability to sweat, the human body has a difficult time regulating its temperature.

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Anhidrosis

What is anhidrosis?

BY LAURIE L. DOVE

You're always cool as a cucumber, despite excessive summer heat, an exercise class or new social situations.

But just because you're not sweating doesn't mean you're truly composed.

You could have anhidrosis, the inability to perspire.

Odds are you may not notice the signs of anhidrosis -- an absence of telltale underarm wetness, for instance -- until it reaches a potentially dangerous level.

So why is sweating so important? It helps your body regulate its temperature.

More precisely, it helps your body cool off as your internal temperature rises.

One of the repercussions of not being able to sweat is that you may get heat stroke or, in the case of a fever, develop a temperature so high it causes a febrile seizure.

Either scenario could prove deadly.

Children are especially vulnerable if unable to sweat; they have are less able to regulate internal temperatures because of their size, so being able to perspire may mean the difference between health and death.

When you don't sweat, you may have to deal with other symptoms, too.

Prolonged muscle cramps, dizziness and a perpetual feeling of being too hot become daily challenges -- especially for people who don't perspire over most of their bodies.

But that's not always the case: Anhidrosis can occur in a single area or in scattered patches.

When this happens, other body areas that do sweat will try to make up the difference. This may be bothersome, but it's not usually dangerous.

However, the prevalence of mild symptoms makes it difficult to recognize the condition until something goes really wrong, like getting overheated.

That's one reason no one really knows how many people are affected; sometimes the symptoms go unnoticed -- even by physicians.

With anhidrosis, it's not just that the sweat doesn't leave the body; it isn't produced in the first place.

Sweat glands stop working for a number of reasons, ranging from nerve damage to skin trauma.

The condition also may be inherited.

Either a child is born with very few sweat glands, a malady known as hypohidrotic ectodermal dysplasia, or has a genetic disorder that makes sweat glands malfunction.

Anhidrosis can't be prevented, unless it's the temporary kind.

Sometimes anhidrosis develops as a side effect of medications, including those used to treat bladder control, nausea, elevated blood pressure or psychiatric conditions.

Most often, though, the body once again begins to perspire after the offending medications are discontinued -- as long as there aren't any pre-existing genetic factors at play.

Men and women are equally likely to be born with anhidrosis, but when it comes to developing the condition, women are more at risk as they age.

Many older adults experience a decreased ability to sweat, but women seem especially likely to have problems perspiring.

Treatment, whatever the age or gender, usually focuses on lifestyle: Staying in an air-conditioned environment when it's hot outside, wearing loose clothing (to encourage air circulation) and avoiding anything more than moderate exertion.

Laurie L. Dove is an award-winning journalist who covers timely topics for HowStuffWorks. She is the author of six books and the former owner of a newspaper and magazine. When not reporting on the latest tech breakthrough, health advance or economic development, Dove is tracking down hidden history, science innovations and biologic discoveries. As the Honorable Laurie Dove, Mayor, she has brought multi-million-dollar improvements to the small Midwest town where she lives with her husband, five children and two Akitas.

https://health.howstuffworks.com/wellness/men/sweating-odor/anhidrosis.htm

FACE SHIELDS MAY NOT PROTECT AGAINST COVID-19 SPREAD - Visualization shows face shields may not protect against COVID-19 spread - Small droplets can easily move around the sides of the visor, the study found. A new visualization shows why face shields and masks with exhalation valves may not be the best barriers for preventing the spread of COVID-19. Although face shields initially block droplets from a simulated cough, small droplets can easily move around the sides of the visor and eventually spread over a large area, according to the visualization. For masks with exhalation valves, a stream of droplets passes, unfiltered, through the valve, meaning the mask would in theory do little to hinder the spread of potentially infectious droplets. In contrast, the researchers previously showed that some cotton face masks reduce the spread of droplets to only a few inches from the face during a simulated cough. The simulations in the new study "indicate that face shields and masks with exhale valves may not be as effective as regular face masks in restricting the spread of aerosolized droplets," the authors wrote. Face masks have become a part of everyday life during the COVID-19 pandemic. But some people are turning to plastic face shields or masks with exhalation values because they find these alternatives more comfortable to wear for long periods of time. Face shields also have the advantage of allowing users to show facial expressions.

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Face shields may not protect against COVID-19 spread

Visualization shows face shields may not protect against COVID-19 spread
.

Since the study was a simulation, it doesn't provide data on the exact conditions that would result in the spread of an infection. With SARS-CoV-2, the virus that causes COVID-19, it's unclear exactly how long the virus remains infectious in the air, and how far infectious particles can travel, or how much virus is needed to make a person sick. Even the very best masks have some degree of leakage - so it's still important to maintain physical distance while wearing masks to mitigate transmission 

By Rachael Rettner - Senior Writer 

Small droplets can easily move around the sides of the visor, the study found.

A new visualization shows why face shields and masks with exhalation valves may not be the best barriers for preventing the spread of COVID-19.

Although face shields initially block droplets from a simulated cough, small droplets can easily move around the sides of the visor and eventually spread over a large area, according to the visualization, which is detailed in a study published Tuesday (Sept. 1) in the journal Physics of Fluids.

For masks with exhalation valves, a stream of droplets passes, unfiltered, through the valve, meaning the mask would in theory do little to hinder the spread of potentially infectious droplets. 

In contrast, the researchers previously showed that some cotton face masks reduce the spread of droplets to only a few inches from the face during a simulated cough, Live Science previously reported.

The simulations in the new study "indicate that face shields and masks with exhale valves may not be as effective as regular face masks in restricting the spread of aerosolized droplets," the authors wrote. 

Face masks have become a part of everyday life during the COVID-19 pandemic.

But some people are turning to plastic face shields or masks with exhalation values because they find these alternatives more comfortable to wear for long periods of time.

Face shields also have the advantage of allowing users to show facial expressions.

However, the Centers for Disease Control and Prevention (CDC) does not recommend either of these as alternatives to cloth masks.

Masks with one-way valves, which are intended for use in construction work, allow users to breathe in filtered air and exhale warm, moist (and unfiltered) air through the valve, Live Science previously reported.

But because respiratory droplets from the wearer are expelled into the air, the CDC says people should not wear these masks to prevent COVID-19 spread.

The CDC also does not recommend face shields as a substitute for cloth masks because evidence is lacking to show their effectiveness, the agency says.

"As students return to schools and universities, some have wondered if it is better to use face shields, as they are more comfortable and easier to wear for longer periods of time," study lead author Siddhartha Verma, an assistant professor at Florida Atlantic University's College of Engineering and Computer Science, said in a statement.

"But what if these shields are not as effective? You would be essentially putting everyone in a tight space with droplets accumulating over time, which could potentially lead to infections."

In the new study, the researchers simulated coughing by connecting a mannequin's head to a fog machine — which creates a vapor from water and glycerin — and using a pump to expel the vapor through the mannequin's mouth.

They then visualized the vapor droplets using a "laser sheet" created by passing a green laser pointer through a cylindrical rod.

In this setup, simulated cough droplets appear as a glowing green vapor flowing from the mannequin's mouth.

For the face shield simulation, the shield initially deflected droplets toward the ground after a cough.

But small droplets remained suspended at the bottom of the shield and then floated around the sides, eventually spreading about 3 feet (0.9 meters) to the front and sides of the mannequin.

In some cases, the droplets spread backward, behind the mannequin, instead of forward.

For the mask with a valve, a jet of droplets passed through the valve in the front of the masks during coughing.

Initially, this jet of droplets traveled toward the ground, but eventually the droplets dispersed over a wide area.

The researchers also tested two different brands of commercially available surgical masks. Both of these masks were not recommended for medical use by the manufacturers.

Although the masks looked similar, one brand was effective at stopping the forward spread of aerosolized droplets, while the other allowed a high number of droplets to leak through the mask. 

"This indicates that even among commercially available masks which may appear to be similar superficially, there can be significant underlying differences in the quality and type of materials used for manufacturing the masks," the authors said.

Since the study was a simulation, it doesn't provide data on the exact conditions that would result in the spread of an infection.

For example, with SARS-CoV-2, the virus that causes COVID-19, it's unclear exactly how long the virus remains infectious in the air, and how far infectious particles can travel, or how much virus is needed to make a person sick.

The authors also noted that "even the very best masks have some degree of leakage," Verma said.

So "it's still important to maintain physical distance while wearing [masks] to mitigate transmission." 

Originally published on Live Science.  

Rachael Rettner

Senior Writer

Rachael has been with Live Science since 2010. She has a masters degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a Bachelor of Science in molecular biology and a Master of Science in biology from the University of California, San Diego.

https://www.livescience.com/face-shield-visualization-covid-19-spread.html?utm_source=notification

WHY GRAPHITE IS SOFT BUT DIAMOND IS SO HARD - Diamond and graphite are two allotropes of the same element (carbon) and the differences in their properties are a result of the way their crystal structures are arranged. Both diamond and graphite are made of pure carbon, yet they have dramatic differences in their properties. As allotropes of the same element, you might expect them to share many similarities, but that simply isn’t the case. Allotropy (also referred to as ‘allotropism’) of an element is that element’s ability to exist in multiple forms in the same physical state with a different arrangement of its atoms. The different forms are called allotropes of the given chemical element. Allotropes of the same element have different bonding arrangements, which give rise to different chemical and physical properties for the substance. Furthermore, different allotropes can also differ in the occurrence of molecules in the number of atoms. Carbon has the ability to form many allotropes, thanks to its chemical structure. Its atomic number is 6, which means that it has 4 electrons in its valence shell. No less than 8 allotropes of carbon have been identified. Out of all the known allotropes, the most popular ones are diamond and graphite. Although their composition is the same, they exhibit different chemical and physical properties, thanks to the arrangement of carbon atoms within them. It boils down to a single factor: geometry. The arrangement of carbon atoms in diamond follows a tetrahedral fashion. This means that each carbon atom is attached to 4 other carbon atoms, forming strong covalent bonds.

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Why Is Graphite Soft, But Diamond Is So Hard?

By Ashish

Diamond and graphite are two allotropes of the same element (carbon) and the differences in their properties are a result of the way their crystal structures are arranged.

Both diamond and graphite are made of pure carbon, yet they have dramatic differences in their properties.

As allotropes of the same element, you might expect them to share many similarities, but that simply isn’t the case.

At first, this question might seem odd to many people. Diamond and graphite… doesn’t sound like a particularly sensible combination.

Diamond and gold, or diamond and sapphire would make more sense, right?

So, why is diamond pitted in the same category with graphite – the thing that we find inside our pencils?

Well, if you had paid attention to your Chemistry lessons in high school, you would know that there is, in fact, a very strong structural connection between the two.

What’s the connection between the two? And why are they so different from each other?

What are allotropes?

Allotropy (also referred to as ‘allotropism’) of an element is that element’s ability to exist in multiple forms in the same physical state with a different arrangement of its atoms.

The different forms are called allotropes of the given chemical element.

Triangle Rectangle & square shapes 36 ball

Imagine that you have 36 balls that you can arrange in any number of patterns to obtain mutually-visually geometrical shapes.

The constituent pieces of these shapes (balls) represent atoms, and the different shapes they assume (due to their varied arrangements) are the allotropes.

Allotropes of the same element have different bonding arrangements, which give rise to different chemical and physical properties for the substance.

Allotropes of Phosphorus & Allotropes of Oxygen

Furthermore, different allotropes can also differ in the occurrence of molecules in the number of atoms.

The following image features various allotropes of phosphorus and oxygen.

Allotropes of carbon

In the world of allotropes, the carbon is nothing less than a rockstar. It has the ability to form many allotropes, thanks to its chemical structure.

Its atomic number is 6, which means that it has 4 electrons in its valence shell.

Different allotropes of carbon

As of now, no less than 8 allotropes of carbon have been identified, and the research for discovering even more allotropes is on.

However, out of all the known allotropes, the most popular ones are diamond and graphite.

These two allotropes, which visually appear incredibly different, are still made of nothing but carbon.

Although their composition is the same, they exhibit different chemical and physical properties, thanks to the arrangement of carbon atoms within them.

Why is diamond hard, but graphite is soft, despite being composed of the same element (carbon)?

It boils down to a single factor: geometry.

Diamond Structure

The arrangement of carbon atoms in diamond follows a tetrahedral fashion. This means that each carbon atom is attached to 4 other carbon atoms, forming strong covalent bonds.

This crystal arrangement is energetically very favorable and imparts that characteristic strength, durability and rigidity to diamond.

To scratch or break it requires a high amount of force, which makes it one of the hardest naturally-occurring materials on the planet.

Graphite, on the other hand, has an entirely different geometric arrangement than diamond.

Its carbon atoms are arranged in 2D sheets, whereas each carbon atom is bonded to three other carbon atoms to form hexagonal rings in an infinite array.

graphite-structure

Although the bonding of atoms within each individual layer is covalent and therefore quite strong (as strong as is seen in diamond), the bonding between layers is weak (Van der Waals forces).

The result of this is that the layers slide over each and can detach from each other very easily.

These weak bonds between the multiple sheets of carbon atoms make the graphite used in pencils flake off on paper, allowing you to write.

In addition to being soft and slippery, graphite also has a much lower density than diamond.

The one thing about all of this that amazes me most is how a few tweaks in the chemical structure of identical substances make them so massively different in their appearance, toughness and chemical properties!

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

https://www.scienceabc.com/pure-sciences/graphite-soft-diamond-structure-properties-hard-carbon-allotrope-tetrahedral-layers.html