Plastic Flow

The ability for plastic to change shape and absorb impact without shattering is described as plastic flow. Plastics absorb energy instead of shattering. Plastics therefore are used instead of glass to make bulletproof “glass,” windshields, and eyeglass lenses. This property, although very useful, is also not well understood, or, at least, the characteristics of plastics which make this possible are not well understood. Currently research is being conducted to explore this property of plastics at the University of Wisconsin, Madison by chemistry professor Mark Ediger.

Professor Ediger is using nanotechnologies to examine the processes that plastics undergo at high impacts. Nanotechnology has made it possible to understand so much more about the world around us. Nanotechnology has provided new ways of understanding why computer technology works, new ways of visualizing bacteria, and new ways of creating models of behavior. At the nano-level behavior is less easily understood than at a macro level. At the high levels of impact, Ediger has reported that the movement plastics’ constituent molecules “increases dramatically…with molecular rearrangements occurring up to 1,000 times faster than without the stress.” Only recently, have scientists been able to examine molecular behavior on a grand scale and the rearrangements can actually be observed.

It is important to be able to observe the behavior in order to understand the behavior. And it is important to understand the behavior in order to know how the material will react under certain circumstances so that it can be used appropriately. More observation also can lead scientists to understand how a material will react later in its life after undergoing stresses. Ediger hopes to create models of stress on plastics, so that plastics can be better used in the future and so that the life of plastic parts can be extended.

References: http://www.nano.org.uk/news/nov2008/latest1706.htm

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What's Gonna Get You?

How have the leading causes of death in the United States changed since World War I? By compiling values recorded by the Center for Disease Control, I have created graphs of these causes in 1918, 1958, and 1998 for comparison. The first observation I would like to point out is the large percentage of Pneumonia and Influenza deaths in 1918. It was the number one cause of death that year (33% of deaths) and many of the surrounding years as well, yet by 1958 we can see it had declined to a measly sixth cause of death (4% of deaths). It was again sixth in 1998 (3% of deaths). In 1918 nearly four times as many people died from Pneumonia and Influenza than the number 2 leading cause of death, heart disease, so falling from 1st to 6th is a large drop. Why this large defenestration? One solid explanation is the development of antibiotics and vaccines. In 1918 there was a large influenza pandemic and in the 1940's the U.S. military developed the first approved vaccine for influenza, which explains the 1958 ranking. The development of antibiotics did not mature until the 1940's, which explains why Tuberculosis fell from 3rd place to off the charts in 1958, 1998, and hopefully for good in the United States.

Another rather drastic change is the rise of Cancer as a leading cause in death in the United States. In 1918 it was the number six leading cause of death (4% of deaths) yet by 1958 it became the number 2 cause of death (15% of deaths) and remained number 2 in 1998 (23% of deaths). This is due to a combination of two basic factors. The first is probably the most recognized today, and that is the rise in use of machines, materials and foods that give off a significant amount of radiation; this is, however, not an object of real concern because the amount of radiation released is often insignificant and of no real danger. The more likely culprit is the increase in lifespan of individuals living in the United States. Cancer is an old age disease. The reason cancer "didn't exist" hundreds of years ago is that it actually did exist, only nobody lived quite long enough for enough genetic mutations to manifest themselves. As life expectancy went up after 1918, so did incidence of cancer.

The last most apparent observation I would like to point out is the apparent rise and dominance of Heart Disease as the leading cause of death in the United States after 1918. Similar to cancer you could argue a larger presence of heart-weakening factors increases Heart Disease risk, however a more valid explanation may lie in the lessening of risk of the other methods of mortality. As risk of infectious disease goes down, other causes seem to go up, only because they are simply what remains.

Acknowledgements:
The values on the graphs were created based on information compiled by the Center for Disease Control, which may be found on the following online pdf (last checked 11/20/2008): http://www.cdc.gov/nchs/data/dvs/lead1900_98.pdf

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Luke...I am your father.

Think about how many times during the day you use your hands, whether it be to pick up something, to hold something, or to even feel something. Now imagine you no longer have your hands. You no longer have the ability to perform simple tasks like picking up an object. This is the case for millions of Americans who have lost their arm(s) and are unable to perform the same tasks that many of us take for granted every day.

Before the Luke arm, prosthetic arms only had three powered joints as well as three degrees of freedom. A user could move their elbow, their wris t, and open and close some type of hook where the hand would normally be. The problem with this type of prosthetic is that it is frustrating to control and does not provide that much functionality (IEEE Spectrum). Often people who had lost their arms opted to not even wear this type of prosthetic because wearing the burdensome prosthetic was simply not justified by the small amount of assistance it provided. For as technologically advanced as this world had become, prosthetics was living in the age of the Flintstones. A new prosthetic had to be created that would give amputees’ more range of motion and fine motor control but it also had to be modular, usable by anyone with any level of amputation.

Technology has finally caught up and the Luke arm has been created. The Luke arm is a prosthesis named after the lifelike prosthetic worn by Luke Skywalker in Star Wars and was created by Dean Kamen. The Luke arm is a scientific breakthrough in the world of prosthetics due to its remarkable ability to act like a real human arm and hand. Microprocessors have been made small enough and power consumption has become efficient enough to place control electronics, lithium batteries, motors and wiring into a compartment the same size, shape and weight as the human arm. A human arm has a total of twenty two degrees of freedom, a lot more than the prosthetic arms most people are using now. What makes the Luke arm better than previous prosthetics is the fact that the Luke arm has eighteen degrees of freedom. The Luke arm has many degrees of freedom due to the enormous amount of circuitry inside the arm, which allows for its agility (technovelgy.com).

The Luke arm has tremendous motor control so that people who use the arm are able to pick up coffee beans one at a time, hold a power drill and even unlock a door.The reason the Luke arm has such fine motor control is the use of tactors. A tactor is a small vibrating motor-about the size of a bite size candy bar- that is placed against the user’s skin. A sensor on the Luke hand, which is connected to a microprocessor, sends a signal to a tactor, and that signal adjusts the grip strength of the hand. When a user grips something lightly, the tactor vibrates slightly. As the user’s grip tightens, the frequency of the vibrations increase (IEEE Spectrum). This is a non-operative way that allows users to pick up a paper cup without crushing it or firmly hold objects without dropping them.

Another way to control the Luke arm was discovered by neuroscientist Todd Kuiken of the Rehabilitation Institute of Chicago, who has successfully been able to surgically connect amputees’ residual nerves, which connect the upper spinal cord to the 70,000 nerve fibers in the arm, to the pectoral muscles. The patient thinks about moving the arm and signals travel down the nerves that were previously connected to the arm but are now connected to the chest. The chest muscles now contract in response to the nerve signals, instead of the arm muscles. The contractions are sensed by electrodes on the chest and those electrodes send signals to the Luke arm, allowing it to move (IEEE Spectrum). By using the Luke arm, amputees are still able to create signals from their brain to their arm; the only difference is that there is a robotic arm there instead.


Before the Luke arm is available to the public it must first be approved by the FDA, and it cannot be approved until several clinical trials have been performed.

Below is a video demonstrating how the Luke arm works and its capabilities.




References

Adee, Sarah. (February 2008). Dean Kamen’s “Luke Arm” Prosthesis Readies for Clinical Trial. Retrieved November 25, 2008, from http://www.spectrum.ieee.org/feb08/5957

Chistensen, Bill. (2008, February 3). Luke Arm Robotic Prosthesis. Retrieved November 25, 2008, from http://www.technovelgy.com/ct/Science-Fiction-News.asp?NewsNum=1432

Pictures

http://www.spectrum.ieee.org/feb08/5957

http://robotslife.wordpress.com/2008/02/07/dean-kamens-luke-artificial-arm-gets-demoed-on-video/

Video

http://www.youtube.com/watch?v=R0_mLumx-6Y

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Coriolis Effect

The Coriolis Effect is the apparent deflection of a moving object when viewed from a rotating frame of reference. The effect is named after the French scientist who first described it in 1835. The effect is most commonly associated with the rotation of the Earth. Objects that travel in a straight path appear to veer right in the northern hemisphere and left in the southern hemisphere. In actuality the object stays on a straight path and only appears to curve due to our rotating due to our rotating frame of reference on the Earth.


The apparent force causing a Coriolis Effect is a fictitious force because the effect is only obtained in a rotating frame of reference. When visualized from the inertial frame of reference it is apparent that there is not actual force working on the object. However, despite the fictitious nature of the force, it can be describes in mathematical terms.


F= -2mΩ x v


Where: F is the Coriolis Force; m is the mass of the rotating object; v is the velocity of the particle; and Ω is the angular velocity vector of the rotating object.

Mathematically explaining the Coriolis Effect is important in order to make predictions on the observed path of objects on the Earth. Two common uses of the Coriolis Effect are in long range ballistics and meteorology.


Coriolis Effect on Ballistics

The Coriolis Effect has implications on long range ballistics, such as artillery shells. Due to the rotation of the Earth, the ballistic will appear to hit to the right of the target in the Northern Hemisphere. The ballistic itself is not curving but following a straight path. It is the rotation of the Earth that makes the ballistic miss.






An object that moves longitudinally along the Earth will appear to deflect to the right because of the eastward rotation of the Earth. In order to compensate for this deflection, the artillery round must be aimed to the left of the actual target in order to hit the target.

The principles of the Coriolis Effect are best exemplified on a smaller frame of reference. This animation of two figures passing a ball on a moving carousel demonstrates the principles of the Coriolis Effect as seen on Earth. When the one figure passes the ball from the center of the rotating carousel to the outside, the ball's trajectory will remain straight; however it will miss the recipient because of the rotation of the carousel. When both figures are on the outside of the carousel and pass the ball, the ball will travel straight but will appear to swerve in relation to the figures on the carousel.




Coriolis Effect on Meteorology

Air tends to flow from low pressure areas to high pressure areas. However, when we observe the actual flow of air masses notice a tendency to flow perpendicular to low pressure areas. This phenomenon can be explained by the Coriolis Effect. As the following video shows, we would predict the flow of air to go directly towards the low pressure zone. However, since the Earth is rotating, we observe an air flow perpendicular to the expected path. Meteorologists need to account for this effect when making weather forecasts.






References:


http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/crls.rxml

http://abyss.uoregon.edu/~js/glossary/coriolis_effect.html

http://www.youtube.com/watch?v=mcPs_OdQOYU

http://enwikipedia.org/wiki/Coriolis_effect

http://www.youtube.com/watch?v=nDhOKR6gKzc
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Skyscraper Structural Support: What holds 'em up?

The development of skyscrapers is a process which had its birth in the ancient world, with the construction of such wonders as the pyramids of Egypt and the Great Lighthouse Pharos of Alexandria. Yet these ancient structures remained the exceptions to the norm of structural height until the dawn of American industrialization. Throughout most of human architectural history, cathedrals and temples were the largest structures to be built, but their heights were limited by the engineering limitations of the time. Today, skyscrapers are an ordinary feature of most modern industrialized cities. There were countless advances in engineering over the centuries which led to the development of modern skyscrapers, but none so influential as those in the late 19th and 20th centuries. I will explore a few main factors which contributed to the ability to build modern skyscrapers which have become such a necessity in modern industrialized cities.

Skyscraper with steel and concrete core: Photo from allaboutskyscrapers.com

The primary factor which has allowed engineers to overcome the boundaries of building tall structures is the use of steel frames. In the past, attaining any significant height required that a structure’s base be wide to compensate for the increase in the force of gravity created by the weight of the upper levels. This situation meant that as the height of a structure increased, its base had to increase by an increasingly larger factor. The layout of modern cities does not provide the space for such buildings to be erected, and so an alternative is necessary. The use of steel frames (preceded by iron frames) allows for very high construction with no need for a large base. A steel skeleton of rails, riveted together with steel plates, and connected to massive steel columns is what makes up the frames of average skyscrapers today. The huge columns, encased in concrete, are what support the brunt of the force of gravity acting on a building. Functioning like a spine at the core they channel the gravitational forces down through the frame and into the piled foundation below, which is supported by the bedrock beneath. The support structure of some buildings, such as the Sears Tower, is located on the outer perimeter of the building. This so-called “hollow tube” design works in much the same way. (Wells 20)

Skyscraper foundation support (several of these hold up the main columns): Photo from howstuffworks.com

Generally, all of the steel support structure is coated in fire-resistant material to ensure that it is protected from warping under extreme heat. The “flimsy fire cladding” (Wells 19) of the steel structure was a factor in the collapse of the World Trade Center towers during the terrorist attacks of September 11th, 2001. It is believed that the impact of the hijacked airplanes largely stripped away this coating, and exposed the superstructure to fire. Once weakened, the beams gave way and resulted in unequal distributions of weight onto lower beams, which were not designed for the strain and collapsed in a domino effect.

The physics associated with the support systems of skyscrapers is complex and fascinating. Virtually every aspect of this science is applied in the design and construction of the supports. The force of gravity, as mentioned above, must be considered thoughtfully when designing the foundation, so that its surface area distributes the weight of the structure effectively. The frictional forces between the steel and concrete foundations and their surroundings must be assessed as well for the distribution of weight. Compressive and tensile strengths of both steel and other materials used in construction must be known in order to assure their proper use and maintain structural integrity. Thermal expansion characteristics of all the supporting material must be known in every conceivable temperature they may endure.

Additionally, buildings must be constructed so that they can be subjugated to natural forces and still maintain structural stability. Wind is prime among these forces. A building must be able to withstand the forces associated with high winds; a problem which must be addressed with care in the tallest of buildings, as wind pressure increases by a power of three with height (Wells 15). Skyscrapers built in earthquake zones are particularly complex. A thicker, stronger-than-normal internal structure is required, as well as complex dampening systems of springs and flexible materials which absorb and distribute the kinetic energy of earthquakes, maintaining the vertical equilibrium of the building.

Today’s skyscrapers, though enormous, are limited by the imperfections of human technology. We can only build them so high. Matthew Wells describes the theoretical vertical limit of a skyscraper, using current building materials, as being 18 kilometers high. However, due the deficiencies of construction, and the unpredictability of environmental forces, he sets the practical limit at 1.60 kilometers. And yet, as of today, we have yet to achieve more than half that height. The Burj Dubai, still under construction, will be the tallest man-made structure on the planet when completed, and stand at 818 meters or more. That is a formidable accomplishment for structural engineers, and yet it is well below the highest conceivable limit.

Burj Dubai: Photo from Dvice.com

It is easy to imagine going beyond the heights achieved by modern skyscrapers, (science fiction authors do it all the time), but actually building futuristic supertall structures requires overcoming many engineering obstacles. One of these is the fundamental problem of base size. Steel can only do so much, and eventually we reach the point where we need to augment or buttress the base in order to compensate for the increasing force of gravity applied to the foundations by the materials high up. Just looking at the photo of the Burj Dubai above reveals that the engineers still needed to follow a somewhat pyramid-like design even with the most up-to-date building materials.

Going beyond the 1.6 kilometer mark will require strong materials. Talk has been made about the possibility of using carbon nanotubes, which have a tensile strength fifty times that of steel, and a Young’s modulus five times greater than steel. Maybe with this technology, and some radical engineering practices, the human race will one day see that 1.6 kilometer barrier broken. I am not optimistic, however, of seeing such things come about in my lifetime.

Works Cited

Wells, Matthew. Skyscrapers: Structure and Design. New Haven: Yale, 2005.
http://dvice.com/archives/2007/07/new_record_for_worlds_tallest.php
http://science.howstuffworks.com/skyscraper2.htm
http://people.howstuffworks.com/wtc6.htm
http://www.personal.rdg.ac.uk/~scsharip/tubes.htm
http://www.allaboutskyscrapers.com/skyscraper_design.htm
http://en.wikipedia.org/wiki/Tallest_building
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Does the Swimsuit Make the Man?

Michael Phelps has the record for most gold medals in a single Olympic games, was voted Sportsman of the Year in 2008 by Sports Illustrated, and holds world records for the 200m freestyle, 200m butterfly, 200m medley, 400m medley, 4x100m freestyle relay, 4x200m freestyle relay, and the 4x100m medley relay (Wikipedia, 2008). Michael Phelps truly is great at swimming; no one can deny it. However, is it really viable to say that his technique is the sole reason for his continued success in breaking records?

If we look at men’s and women’s 200m butterfly world records since 1959, we notice that the men’s times have dropped 17.9% whereas the women’s times have dropped 20.9% (see figure). There has not been a particular standout female swimmer in the past 50 years who everyone claims has changed women’s swimming, so then why is Michael Phelps considered to be the cause of the incredible decrease in men’s race times seen recently? American swimmer Mark Spitz improved upon the record by 5 seconds and broke it seven times from 1967-1972; from 2001-2008, when Michael Phelps broke the record seven times, it decreased by a mere 2.55 seconds, only half of the decrease achieved by Mark Spitz. Limits exist in all things, so does this mean that we are approaching the limit for the fastest possible time in the 200m butterfly? Have we already surpassed the actual physical limit and now it is only changing because of technology? I don’t know, but let’s take a look at the technology of the swimsuit Phelps used in the Beijing Olympics, Speedo’s LZR Racer Swimsuit, to see how the swimsuit helped him and the other swimmers who raced with it.



This video from youtube.com explains how the LZR swimsuit works to improve efficiency of movement through water, which is what the swimmers are looking for. In order to get better times, they need to increase their efficiency, be it through better technique or a better suit. This Speedo suit decreases drag by 24% and makes the body more streamline, increasing the efficiency of the swimmer (Brain, 2008). All athletes are looking to improve their times and technology facilitates this. The big controversy is whether or not the LZR swimsuit is the same as doping in other sports. On one hand, the swimsuit increases efficiency; on the other hand, the swimmer still needs to perfect his or her technique in order to perform at the elite level. It’s up to you to decide.

References:
http://www.youtube.com/watch?v=dvMdqvO3R9g
http://en.wikipedia.org/wiki/Michael_phelps
http://en.wikipedia.org/wiki/World_record_progression_200_metres_butterfly

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Flying Buttresses

Flying buttresses are an architectural feature mainly seen used in medieval cathedral designs. First developed in Romanesque architecture and later perfected in Gothic architecture, flying buttresses are built projecting from the walls of a structure down to the foundation in an half arched shape. The purpose of such projections is to support the weight and horizontal thrust of the high arches and domes spanning the interior space. The flying buttress serves as a bridge, carrying the lateral thrust produced at the base of the arches and domes due to their weight, across to the outer buttress, which is massive enough to absorb the pressure (Watterson 103). The stability of the entire building depends upon the balance of pressures and with the existence of flying buttresses, cathedrals were able to be built taller and more glorious than ever before (Statham 370).

(Photo Above: Flying Buttress, http://openlearn.open.ac.uk/file.php/1329/T173_1_060i.jpg)

Flying buttresses originated from the idea of internal buttresses used in Romanesque architecture dating back to the 10th century. Buttresses were used for support on the inside of the church walls because it was thought that such large flat structures were unfitting to be seen on the outside of the churches. Towards the end of the Romanesque period, as architects challenged one another to build churches and cathedrals higher than ever before, the use of flying buttresses on the outside of these structures became necessary. With the beginning of the Gothic period, flying buttresses not only became used more for their function, but for their appearance as well. Gothic architecture began in the 12th century in France and lasted until the 16th century. Mainly used in the construction of cathedrals, abbeys, and churches, the Gothic style is characterized by the pointed arch, the ribbed vault, and the use of flying buttresses.

(Photo Above: Notre Dame Cathedral in Paris, France,

http://www.destination360.com/europe/france/images/s/france-notre-dame-cathedral.jpg)

One of the first, and most famous, cathedrals to incorporate the use of flying buttresses was the Notre Dame Cathedral in Paris, France. Its construction began in 1163 and the cathedral was finally completed around the year 1345. Many different architects and ideals went into the construction of Notre Dame. Flying buttresses were incorporated into the architecture for the primary use of balancing the pressure produced by such vaulted spaces. Another very important reason flying buttresses were used in the Notre Dame Cathedral was to allow adequate sunlight into the building (Temko 127). With such high walls and lack of windows the cathedral proved to be quite dark. Architects then realized that with the addition of more flying buttresses, they could place large stained glass windows along the walls of the cathedral to allow in more light. The incorporation of these large windows would further weaken the stability of the walls; however the strength of the flying buttresses solved such issues.

(Photo Above: Flying Buttress of Notre Dame, Paris, http://en.wikipedia.org/wiki/Image:NotreDameFlyingButtress.jpg)

Influenced by the architecture of Notre Dame, the architect of the Chartres Cathedral in France utilized the flying buttress to reorganize the whole appearance of the interior church structure and achieve a look of simplicity and coherence (Henderson 111). The cathedral was begun in the 12th century and went through a multitude of disasters including multiple fires before its final completion and dedication in 1260. Chartres stands with a nave of 120 feet, a south-west tower of 340 feet, and a north-west tower of 370 feet and contains 176 stained glass windows. This magnificent feat and defiance of gravity was made possible by the abundant use of flying buttresses.

(Photo Left: Flying Buttresses of Chartres Cathedral, http://www.bc.edu/bc_org/avp/cas/fnart/arch/gothic/chartres/chartres023.jpg)

(Photo Right: Chartres Cathedral, France, http://media-2.web.britannica.com/ebmedia/79/93579-004-45C763BC.jpg)

Bibliography

Henderson, George. Chartres. Penguin Books. Baltimore, Md. 1968.

Statham, H. Heathcote. A Short Critical History of Architecture. Charles Scribner’s Sons. New York, NY. 1927.

Temko, Allan. Notre Dame of Paris. The Viking Press. New York, NY. 1955.

Watterson, Joseph. Architecture: Five Thousand Years of Building. W.W. Norton and Company Inc. New York, NY. 1950.

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