Wednesday, October 28, 2009
Dehydration Topic and Sources
I started off with the idea of researching contact lenses and how they react to chemicals, among other ideas. I began doing research on contact lenses in general, at which point I probably came across at least 20 different sources. I went through various topics about which I could choose to write my paper, including gas permeability of contact lenses and the scattering of light in imperfectly functioning contact lenses. I finally settled on the topic of dehydration of contact lenses for two reasons: When Dr. Bogen revealed the details of the machine diagram, this was the topic which made the most sense to diagram. Also, dehydration is a serious problem for contact lens wearers and is a highly relevant topic in current contact lens science. Below is a list of the sources I found on lens dehydration. Note that I have edited this post since I first wrote it, updating it to the APA format that Dr. Bogen prefers and removing some of my sources which turned out to be unnecessary.
Albarran C., Pons, A.M., Lorente, A., Montes, R., and Artigas, J.M. (1997). Influence of the tear film on optical quality of the eye. Contact Lens and Anterior Eye, 20(4), 129-135.
AC Lens (2009). Eye Health: Dry Eyes and Contact Lens Wear. Retrieved October 21, 2009 from http://www.aclens.com/dry-eyes.asp.
British Contact Lens Association (2009). Types of Contact Lenses. Retrieved October 21 2009 from http://www.bcla.org.uk/types_of_contact_lenses.asp.
Dorronso, Carlos, Barbero, Sergio, Llorente, Lourdes, and Marcos, Susana (2003). On eye measurement of optical performance of rigid gas permeable contact lenses based on ocular and corneal aberrometry. Optometry and Vision Science: The Journal of the American Academy of Optometry, 80(2), 115-125.
Fonn, Desmond (2007). Targeting contact lens induced dryness and discomfort: what properties will make lenses more comfortable. Optometry and Vision Science, 84(4), 279-285.
Hamano, Hikaru and Herbert E. Kaufman (1987). The Physiology of the Cornea and Contact Lens Applications. New York: Churchill Livingstone.
Hartstein, Jack, Swanson, Kenneth V., and Harris, Charles R. (1991). Contemporary Contact Lens Practice. St. Louis: Mosby Year Book.
Larke, John (1985). The Eye in Contact Lens Wear. London: Butterworths.
N., Efron, and Morgan, P. B. (1999). Hydrogel contact lens dehydration and oxygen transmissibility. Eye and Contact Lens – Science and Clinical Practice, 25(3), 148-151.
Subbaraman, Lakshman N. and Jones, Lyndon (2009). What influences contact-lens related dry eye? Contact Lens Spectrum July 2009 document 164.
Tutt, Ron, Bradley, Arthur, Begley, Carolyn, and Thibos, Larry N. (2000). Optical and Visual Impact of Tear Break-up in Human Eyes. Investigative Ophthalmology and Visual Science, 41, 4117-4123.
U.S. Food and Drug Administration (2008). Focusing on Contact Lens Safety. Retrieved October 20, 2009 from http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm048893.htm.
Albarran C., Pons, A.M., Lorente, A., Montes, R., and Artigas, J.M. (1997). Influence of the tear film on optical quality of the eye. Contact Lens and Anterior Eye, 20(4), 129-135.
AC Lens (2009). Eye Health: Dry Eyes and Contact Lens Wear. Retrieved October 21, 2009 from http://www.aclens.com/dry-eyes.asp.
British Contact Lens Association (2009). Types of Contact Lenses. Retrieved October 21 2009 from http://www.bcla.org.uk/types_of_contact_lenses.asp.
Dorronso, Carlos, Barbero, Sergio, Llorente, Lourdes, and Marcos, Susana (2003). On eye measurement of optical performance of rigid gas permeable contact lenses based on ocular and corneal aberrometry. Optometry and Vision Science: The Journal of the American Academy of Optometry, 80(2), 115-125.
Fonn, Desmond (2007). Targeting contact lens induced dryness and discomfort: what properties will make lenses more comfortable. Optometry and Vision Science, 84(4), 279-285.
Hamano, Hikaru and Herbert E. Kaufman (1987). The Physiology of the Cornea and Contact Lens Applications. New York: Churchill Livingstone.
Hartstein, Jack, Swanson, Kenneth V., and Harris, Charles R. (1991). Contemporary Contact Lens Practice. St. Louis: Mosby Year Book.
Larke, John (1985). The Eye in Contact Lens Wear. London: Butterworths.
N., Efron, and Morgan, P. B. (1999). Hydrogel contact lens dehydration and oxygen transmissibility. Eye and Contact Lens – Science and Clinical Practice, 25(3), 148-151.
Subbaraman, Lakshman N. and Jones, Lyndon (2009). What influences contact-lens related dry eye? Contact Lens Spectrum July 2009 document 164.
Tutt, Ron, Bradley, Arthur, Begley, Carolyn, and Thibos, Larry N. (2000). Optical and Visual Impact of Tear Break-up in Human Eyes. Investigative Ophthalmology and Visual Science, 41, 4117-4123.
U.S. Food and Drug Administration (2008). Focusing on Contact Lens Safety. Retrieved October 20, 2009 from http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm048893.htm.
Wednesday, October 14, 2009
Research Paper
At my last Chemistry 053 lab lecture, our professor told us that contact lenses were once banned in chemistry lab, but claims that contacts are extremely dangerous in laboratory conditions have since been strongly questioned, so the wearing of contacts is now up to our discretion. I was curious about why this should be so and looked up some information about contacts. Apparently, the materials out of which contact lenses are made have changed over time, and some of the newest types of contact lenses are manufactured specifically to transmit more oxygen between the eyes and the atmosphere [1]. It was once a common belief that, in laboratory conditions, gases could get trapped under contact lenses, dissolve into the water of the eyes, and cause permanent blindness, or that chemicals could get trapped beneath the lenses and similarly do serious damage. Many sources now suggest, however that this is a myth.
I found this information very interesting. I plan to research the structure and function of the latest types of contact lenses. The following are questions of interest:
1. What are the lenses made out of?
2. How are the lenses constructed?
3. How do the lenses improve vision?
4. What substances can pass through the lenses?
5. Can any substances pass through the lenses in one direction only?
6. How do lenses dry out? Why does this cause irritation? Can this be reduced?
7. What are the shortcomings of the best currently available lenses? How can the technology be improved?
[1] Segre, Liz. Contact Lens Basics. All About Vision. April 2009. Available: http://www.allaboutvision.com/contacts/contact_lenses.htm.
I found this information very interesting. I plan to research the structure and function of the latest types of contact lenses. The following are questions of interest:
1. What are the lenses made out of?
2. How are the lenses constructed?
3. How do the lenses improve vision?
4. What substances can pass through the lenses?
5. Can any substances pass through the lenses in one direction only?
6. How do lenses dry out? Why does this cause irritation? Can this be reduced?
7. What are the shortcomings of the best currently available lenses? How can the technology be improved?
[1] Segre, Liz. Contact Lens Basics. All About Vision. April 2009. Available: http://www.allaboutvision.com/contacts/contact_lenses.htm.
Sunday, October 4, 2009
Structure
Below are three pictures of a concrete shelter that stands between Van Pelt Manor and Class of 1925, the two components of Gregory College House at 3909 Spruce Street.
The first picture, taken from several yards away, reveals a structure with steps, a roof, and walls, as well as two openings for entering and exiting. The whole structure is several yards in every dimension. The second picture, taken from a few feet away, shows that the walls are made of distinct concrete slabs attached to each other. Each slab is a few feet long and wide and several inches thick. The third picture, a closeup taken just inches from the surface of the concrete, reveals that the concrete is composed of sand and stones rigidly cemented together but loose enough that numerous air pockets are visible (if not in the low-resolution picture, at least upon close inspection of the structure itself). Most of the stones are less than an inch in every dimension.
The overall structure, with its rigidity and upright form, resembles a tree trunk. The thick trunk of an old hardwood tree supports the weight of the impressively tall verticals structure just as the concrete walls of the shelter hold up the roof. A tree trunk so powerfully resists compression that a car will crumple when driven into one, likely causing injuries for the passenger. The concrete would similarly resist deformity in a collision.
The uniform nature of the array of identical concrete slabs resembles the crystal structure of purified table salt (NaCl), which also has regularly spaced units tightly bonded together. A wall made of concrete slabs is strong and solid, just a salt crystal is also bonded strongly enough to resist melting until very high temperatures. Both concrete and salt, however, have their weaknesses. Salt dissolves easily in water at room temperature. Concrete displays an impressive resistance to compression, but cracks easily under tensile strain.
The concrete itself resembles glass. Glass is an amorphous solid that moves at room temperature, but not visibly. Similarly, concrete moves around when poured until it dries. Once it dries, however, concrete seems uniform from a large distance, although in truth it is a heterogenous mixture. Glass also contains several impurities that are not visible to the eyes.
The structure of the shelter at all three length scales has clues to its function. The concrete is a heterogenous mixture but it is frozen in place, which contributes to the rigidity of the concrete blocks. The uniformity of the blocks combines with the rigidity of concrete itself to lend to the shelter the strength which is so obvious to the viewer, and which is a key feature in a structure built for shelter.
I did not notice all of these fascinating aspects of the shelter until I did this assignment. As a resident of Van Pelt Manor house, I walk past the shelter every day on my way to classes and meals. I never stopped, however, to question how and why the shelter looks and functions as it does. Blogging about structure forced me to see this conspicuous object in a much more meaningful way.
The first picture, taken from several yards away, reveals a structure with steps, a roof, and walls, as well as two openings for entering and exiting. The whole structure is several yards in every dimension. The second picture, taken from a few feet away, shows that the walls are made of distinct concrete slabs attached to each other. Each slab is a few feet long and wide and several inches thick. The third picture, a closeup taken just inches from the surface of the concrete, reveals that the concrete is composed of sand and stones rigidly cemented together but loose enough that numerous air pockets are visible (if not in the low-resolution picture, at least upon close inspection of the structure itself). Most of the stones are less than an inch in every dimension.
The overall structure, with its rigidity and upright form, resembles a tree trunk. The thick trunk of an old hardwood tree supports the weight of the impressively tall verticals structure just as the concrete walls of the shelter hold up the roof. A tree trunk so powerfully resists compression that a car will crumple when driven into one, likely causing injuries for the passenger. The concrete would similarly resist deformity in a collision.
The uniform nature of the array of identical concrete slabs resembles the crystal structure of purified table salt (NaCl), which also has regularly spaced units tightly bonded together. A wall made of concrete slabs is strong and solid, just a salt crystal is also bonded strongly enough to resist melting until very high temperatures. Both concrete and salt, however, have their weaknesses. Salt dissolves easily in water at room temperature. Concrete displays an impressive resistance to compression, but cracks easily under tensile strain.
The concrete itself resembles glass. Glass is an amorphous solid that moves at room temperature, but not visibly. Similarly, concrete moves around when poured until it dries. Once it dries, however, concrete seems uniform from a large distance, although in truth it is a heterogenous mixture. Glass also contains several impurities that are not visible to the eyes.
The structure of the shelter at all three length scales has clues to its function. The concrete is a heterogenous mixture but it is frozen in place, which contributes to the rigidity of the concrete blocks. The uniformity of the blocks combines with the rigidity of concrete itself to lend to the shelter the strength which is so obvious to the viewer, and which is a key feature in a structure built for shelter.
I did not notice all of these fascinating aspects of the shelter until I did this assignment. As a resident of Van Pelt Manor house, I walk past the shelter every day on my way to classes and meals. I never stopped, however, to question how and why the shelter looks and functions as it does. Blogging about structure forced me to see this conspicuous object in a much more meaningful way.
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