So I’m sure that all those of us who have already made it back to the states took a plane home, and at some point while the plane was taxiing to and from the runway, or you were waiting for the slow people in front you to get their carry-on luggage and get off the plane, you looked out the window and saw some large fuel trucks. Now we all know that the fuel in there isn’t the same petrol that you put in your car, but what’s the difference?
When fuel for aviation was first deviating from gasoline used in automobiles, it was simply a matter of having a higher octane rating for the more powerful, high-performance engines used in planes. A higher octane rating means that the fuel can be compressed more before combustion, so it can be used in better engines. After the higher octane ratings were achieved, aviators wanted a safer fuel with a higher flash point. The flash point is the temperature at which something can catch fire when exposed to an open flame. Gasoline is a mixture of hydrocarbons ranging from 4 to12 carbons per molecule, and it has a flash point of about 30 degrees Fahrenheit. Jet-A, the kerosene-based commercial jet fuel, was developed which contains hydrocarbons which have anywhere from 5-15 carbons. This fuel has a flash point of 100 degrees Fahrenheit. This fuel can take the compression in jet engines, and is less likely to catch on fire. So the main lesson to take away from this is if you’re ever fueling up a plane, don’t use gasoline.
http://en.wikipedia.org/wiki/Jet_fuel
http://en.wikipedia.org/wiki/Gasoline
http://wiki.answers.com/Q/What_is_the_difference_between_jet_fuel_and_car_fuel
Thursday, July 9, 2009
Wednesday, July 8, 2009
Mosquitoes, Shmosquitoes..
As our final days in Italy come to a close, Sanet and I are enjoying a three-night stay in Venice. With the colorful people and the bustling atmosphere as hundreds and thousands of tourists roam the almost-flooded streets during high tide, we escaped the main island today for a tour of the four islands around the edge of Venice: Murano, Burano, Cimetero, and Torcello. Murano is known for its fabulous Venetian glass, Burano for its handmade lace, Cimetero for its centuries of graves of deceased Venetians, and Torcello for its miniscule population (20) and its leaning church bell tower, which leans at the same degree as Pisa’s famous torre. Way back when, Torcello was actually the birthplace of Venice. People from the mainland would settle here to avoid barbarian masses roaming the lands. But even today, you can see why not many could survive on this island- there is no fresh water, the land can't be farmed, and there is a significant number of mosquitoes. When I read this in Rick Steve’s, I had to curse these “bastard butterflies,” as our Italian friends from Siena liked to call them. Over the past two days, I have been eaten alive by mosquitoes, so I decided to look into some chemistry of how to repel these nasty buggers.
There are many products on the market that claim to repel mosquitoes, both natural and synthetic. The most common natural repellent is citronella oil, which is made from a grass that grows in Southeast Asia. The leaves are picked and dried, then steam-distilled to extract the essential oil, which is added to lotions, candles, etc. Citronellal is the main terpenoid in the oil which gives it the lemon scent it is known for.
Sadly for us, citronella is not actually a very successful repellent, proven by a study published in the Journal of American Mosquito Control Association. Citronella candles and incense reduced the biting rate by less than 50%. A second study published in the same journal found that citronella was the least effective out of three types of essential-oil candles (geraniol candles reduced biting rate by 85%).
Another repellent option which has been controversial for half a century is DEET (N,N-diethyl-3-methylbenzamide).
There are two possible reasons for why DEET repels mosquitoes so well. First, DEET inhibits the carbon dioxide receptors in the bugs' nervous systems, thus rendering them senseless when it comes to smell. Or, instead of jamming their senses of smell, perhaps mosquitoes just don't like the smell of DEET and would prefer to avoid it. Apparently there is a lot more research to be done on this topic. The bad news is that in larger concentrations and with longer exposure times, DEET can be toxic and lead to severe neurological problems.....
So what can I do to keep from becoming completely covered in mosquito bites? Not much since I have no idea how to ask for repellent in Italian. But it's not a big deal since we leave for Atlanta on Saturday morning, to my dismay... At least I will find solace in the fact that I have some awesome anti-itch cream waiting for me in my apartment.
Arrivederci, Italia, you will be missed.
Evaluation of the efficacy of 3% citronella candles and 5% citronella incense for protection against field populations of Aedes mosquitoes. (http://www.ncbi.nlm.nih.gov/pubmed/8827606)
http://expertvoices.nsdl.org/connectingnews/2008/08/26/after-50-years-scientists-still-not-sure-how-deet-works/
There are many products on the market that claim to repel mosquitoes, both natural and synthetic. The most common natural repellent is citronella oil, which is made from a grass that grows in Southeast Asia. The leaves are picked and dried, then steam-distilled to extract the essential oil, which is added to lotions, candles, etc. Citronellal is the main terpenoid in the oil which gives it the lemon scent it is known for.
Sadly for us, citronella is not actually a very successful repellent, proven by a study published in the Journal of American Mosquito Control Association. Citronella candles and incense reduced the biting rate by less than 50%. A second study published in the same journal found that citronella was the least effective out of three types of essential-oil candles (geraniol candles reduced biting rate by 85%).Another repellent option which has been controversial for half a century is DEET (N,N-diethyl-3-methylbenzamide).
There are two possible reasons for why DEET repels mosquitoes so well. First, DEET inhibits the carbon dioxide receptors in the bugs' nervous systems, thus rendering them senseless when it comes to smell. Or, instead of jamming their senses of smell, perhaps mosquitoes just don't like the smell of DEET and would prefer to avoid it. Apparently there is a lot more research to be done on this topic. The bad news is that in larger concentrations and with longer exposure times, DEET can be toxic and lead to severe neurological problems.....So what can I do to keep from becoming completely covered in mosquito bites? Not much since I have no idea how to ask for repellent in Italian. But it's not a big deal since we leave for Atlanta on Saturday morning, to my dismay... At least I will find solace in the fact that I have some awesome anti-itch cream waiting for me in my apartment.
Arrivederci, Italia, you will be missed.
Pharmacokinetics, formulation, and safety of insect repellent N,N-diethyl-3-methylbenzamide (deet): a review. ( http://www.ncbi.nlm.nih.gov/pubmed/8827606)
Evaluation of the efficacy of 3% citronella candles and 5% citronella incense for protection against field populations of Aedes mosquitoes. (http://www.ncbi.nlm.nih.gov/pubmed/8827606)
Indoor Protection Against Mosquito and Sand Fly Bites: A Comparison Between Citronella, Linalool, and Geraniol Candles (http://www.bioone.org/doi/abs/10.2987/8756-971X(2008)24%5B150%3AIPAMAS%5D2.0.CO%3B2)
http://en.wikipedia.org/wiki/Citronella_oil#Use_as_an_insect_repellenthttp://expertvoices.nsdl.org/connectingnews/2008/08/26/after-50-years-scientists-still-not-sure-how-deet-works/
Fire-the-works-up
Yet again I missed out on an opportunity for fireworks and celebration. I didn’t even have some kind of sexy drink with my all-time favorite Perspectives in Chemistry teacher, Dr. Daphne Norton. This 4th of July was a sad reminder that I have only seen fireworks on that day twice in my life. Growing up in another country and then for the last 8 years that I have lived in America, not being in the U.S. for the big day, I have missed out on a great many of these colorful night-time displays. As a tribute to my failed attempt at being patriotic this year, I will instead approach the subject of fireworks from another entertaining point; CHEMISTRY.
Every High School student spent at least one day in a chemistry class in which you could throw some different metals into a flame and watch the pretty colors. If not, then those left surely have at some point in their lives thrown some table salt into a flame and watched the effects as it burned. Throughout time the basic theory behind the chemistry has been used in many versatile ways: art, gun powder, photography, elementary science fair projects, and pyrotechnics. But what is actually happening?
Much thought goes into creating fireworks. Not only do you get different patterns in the sky and different colors, but you also get different kinds of light emitted. The colors of the fireworks come from metal compounds such as strontium (red), aluminum (white), magnesium (white), and copper (blue) among others. These can burn as either incandescent or luminescent light. The first uses light produced from heat, the second uses an energy source other than heat and thus can sometimes be called “cold light”. Incandescent fireworks give many of the orange, yellow, and white colors as increasing temperatures with different compounds. Luminescence comes from the absorption of light by an electron that becomes excited and unstable, when the electron jumps back to its stable, ground state it emits light. This principle can be used in different analytical chemistry techniques such as atomic absorption [spectra] (AAS).
The different chemical components of fireworks are as follows: an oxidizing agent, a reducing agent, a coloring agent, and binders and regulators. Because the nature of fireworks is a combustion reaction an important part of this reaction is oxygen to burn the mixtures. This is provided by the oxidizing agent, commonly nitrates, chlorates or perchlorates. Next, reducing agents burn the oxygen to create hot gasses. A combination of reducing agents can be used to speed or slow the process. Two such reducing agents are Sulfur and charcoal. The coloring agents are as mentioned, different compounds such as, strontium salts and lithium salts for red colors, aluminum, titanium, or magnesium for silver or white, and sodium compounds for yellow colors. The last two elements of fireworks are not very chemical, but rather there for the physical aspect of packaging and the resulting shapes of the fireworks.
I hope this gave some insight into the colorful and creative side of chemistry and the festivities created by its many uses.
Works Cited:
http://www.scientificamerican.com/blog/60-second-science/post.cfm?id=bombs-bursting-in-air-whats-in-thos-2009-07-03
http://chemistry.about.com/od/fireworkspyrotechnics/Fireworks_Pyrotechnics.htm
http://library.thinkquest.org/15384/chem/index.htm
http://chemistry.about.com/od/fireworkspyrotechnics/a/fireworkcolors.htm
Every High School student spent at least one day in a chemistry class in which you could throw some different metals into a flame and watch the pretty colors. If not, then those left surely have at some point in their lives thrown some table salt into a flame and watched the effects as it burned. Throughout time the basic theory behind the chemistry has been used in many versatile ways: art, gun powder, photography, elementary science fair projects, and pyrotechnics. But what is actually happening?
Much thought goes into creating fireworks. Not only do you get different patterns in the sky and different colors, but you also get different kinds of light emitted. The colors of the fireworks come from metal compounds such as strontium (red), aluminum (white), magnesium (white), and copper (blue) among others. These can burn as either incandescent or luminescent light. The first uses light produced from heat, the second uses an energy source other than heat and thus can sometimes be called “cold light”. Incandescent fireworks give many of the orange, yellow, and white colors as increasing temperatures with different compounds. Luminescence comes from the absorption of light by an electron that becomes excited and unstable, when the electron jumps back to its stable, ground state it emits light. This principle can be used in different analytical chemistry techniques such as atomic absorption [spectra] (AAS).
The different chemical components of fireworks are as follows: an oxidizing agent, a reducing agent, a coloring agent, and binders and regulators. Because the nature of fireworks is a combustion reaction an important part of this reaction is oxygen to burn the mixtures. This is provided by the oxidizing agent, commonly nitrates, chlorates or perchlorates. Next, reducing agents burn the oxygen to create hot gasses. A combination of reducing agents can be used to speed or slow the process. Two such reducing agents are Sulfur and charcoal. The coloring agents are as mentioned, different compounds such as, strontium salts and lithium salts for red colors, aluminum, titanium, or magnesium for silver or white, and sodium compounds for yellow colors. The last two elements of fireworks are not very chemical, but rather there for the physical aspect of packaging and the resulting shapes of the fireworks.
I hope this gave some insight into the colorful and creative side of chemistry and the festivities created by its many uses.
Works Cited:
http://www.scientificamerican.com/blog/60-second-science/post.cfm?id=bombs-bursting-in-air-whats-in-thos-2009-07-03
http://chemistry.about.com/od/fireworkspyrotechnics/Fireworks_Pyrotechnics.htm
http://library.thinkquest.org/15384/chem/index.htm
http://chemistry.about.com/od/fireworkspyrotechnics/a/fireworkcolors.htm
The world through rose colored glass
After the studies in Siena ended, I took the opportunity at hand and decided to visit some other places in Italy. It was on this trip that I ended up in Venice… along with the many bridges and canals, taxi boats and gondolas, there was also the wonderful variety of industry native to Venice, such as lace and glass. Not being much taken with the idea of visiting a lace factory, however exciting that may sound, I took a trip to Murano, the small island known for its beautiful creations in the glass blowing factory. I had previously visited a crystal blowing factory with the other Emory students, but Murano was a new experience for me…. Quite a few purchases into my trip, I realize just how lucrative the industry is and some further inspection told me that much of its appeal lies not just in the glass, but the use of color and gold leaf in the actual glass. From this comes my inspiration to for this blog entry: glass and color.
Just as the art of glass blowing had to develop with knowledge and skill, so too did the use of color in glass evolve over time. Colored glass was an accidental discovery, an inventive fluke deriving from impurities. Dark brown or green glass came from impurities in the sand, such as iron, or from the fire smoke, such as sulfur. This fluke lead to the resourceful use of different minerals or metal salts for coloring. Gold chloride creates ruby glass and to make a glow in the dark glass you would use uranium oxide.
Metals can be used in other ways to color glass. Adding metallic compounds to the glass can cause an iridescent effect. Or if you would like that beautiful gold or silver leaf look to the glass without worrying about the metal oxidizing or wearing away, thin layers of colloidal metals are added to the glass and then coating that with another layer of clear glass.
Most of the colored glasses involve some sort of metal oxide ‘contaminating’ the glass itself, such as iron oxide (green, brown), cobalt oxide (deep blue), manganese oxide (deep amber, amethyst), and antimony oxides (white). A lot of the finer designs, though, have other secrets that have nothing to do with combination chemistry of glass and other compounds, but instead is simply the use of glass layering a beautiful work of brushstroke or similar technique.
So next time you pick up that gorgeous green glass that your friend brought you back from Murano, ask yourself: “Is there any iron in this?”
Cited works:
http://www.sciencedaily.com/releases/2009/06/090617123435.htm
http://chemistry.about.com/cs/inorganic/a/aa032503a.htm
Just as the art of glass blowing had to develop with knowledge and skill, so too did the use of color in glass evolve over time. Colored glass was an accidental discovery, an inventive fluke deriving from impurities. Dark brown or green glass came from impurities in the sand, such as iron, or from the fire smoke, such as sulfur. This fluke lead to the resourceful use of different minerals or metal salts for coloring. Gold chloride creates ruby glass and to make a glow in the dark glass you would use uranium oxide.
Metals can be used in other ways to color glass. Adding metallic compounds to the glass can cause an iridescent effect. Or if you would like that beautiful gold or silver leaf look to the glass without worrying about the metal oxidizing or wearing away, thin layers of colloidal metals are added to the glass and then coating that with another layer of clear glass.
Most of the colored glasses involve some sort of metal oxide ‘contaminating’ the glass itself, such as iron oxide (green, brown), cobalt oxide (deep blue), manganese oxide (deep amber, amethyst), and antimony oxides (white). A lot of the finer designs, though, have other secrets that have nothing to do with combination chemistry of glass and other compounds, but instead is simply the use of glass layering a beautiful work of brushstroke or similar technique.
So next time you pick up that gorgeous green glass that your friend brought you back from Murano, ask yourself: “Is there any iron in this?”
Cited works:
http://www.sciencedaily.com/releases/2009/06/090617123435.htm
http://chemistry.about.com/cs/inorganic/a/aa032503a.htm
More Good News Involving Wine
So we’ve learned all about the antioxidant capabilities of the polyphenols in wine, but what about the other health benefits of some of these compounds? One in particular, resveratrol, has been linked to many health benefits including life extension, cancer prevention, and even lowering blood-sugar levels. Resveratrol is produced naturally by plants that are being attacked by things like bacteria or fungi, but they are also found in the skins of red grapes and are therefore present in red wine.
Human testing has been limited with this compound, but it has been shown that it can extend the median life of flies, worms, and even fish by a significant amount. Animal studies have also shown that it is effective against cancer as long as it can be delivered to the necessary areas in significant amounts. The only time that a study using humans has had positive results with resveratrol was in a study that showed how high doses of it significantly lowered blood sugar levels.
The exact mechanisms of resveratrol are not well understood, but it has been shown to activate different enzymes, and in some cases, cause apoptosis (programmed cell death) which could explain some of their anti cancer properties. Although resveratrol may not end up making us live longer, cancer free lives, it does give us another reason to keep drinking red wine.
References:
http://en.wikipedia.org/wiki/Resveratrol
Human testing has been limited with this compound, but it has been shown that it can extend the median life of flies, worms, and even fish by a significant amount. Animal studies have also shown that it is effective against cancer as long as it can be delivered to the necessary areas in significant amounts. The only time that a study using humans has had positive results with resveratrol was in a study that showed how high doses of it significantly lowered blood sugar levels.
The exact mechanisms of resveratrol are not well understood, but it has been shown to activate different enzymes, and in some cases, cause apoptosis (programmed cell death) which could explain some of their anti cancer properties. Although resveratrol may not end up making us live longer, cancer free lives, it does give us another reason to keep drinking red wine.
References:
http://en.wikipedia.org/wiki/Resveratrol
Boron cancer threrapy part 2
I wanted to talk more about the Boron therapy for cancer that Dr Soria talked about in his class. The ideal therapy is the one in which only the cancerous cells are destroyed without damaging healthy tissue or affecting the function of important systems specially when treating brain tumors because the cells of the brain are the most sensitive and the ones with the most important function. BNCT is a technique that uses radiation to destroy the cells but the way it works is different and is much more selective because it destroys only the cells close to the target cell.
This is not the typical radiation technique since the beam does not destroy all of the tumor cells but the target cell is one which contains an isotope of boron. The key in this process is that the boron attaches to the cancer cell by attaching it to compunds that have special affinity for tumor cells.
The basic principle for the neutron capture therapy. A higher concentration of Boron exists in the tumor cells than in the nomrmal ones. Nuclides have different affinity for the thermal neutrons absoption. Of the nucleides that have this affinity B-10 is the most attractive because it is not radioactive and is very avaliable. Even if the affinity of most of the tissues is the highest for boron there are considerably amounts of nitrogen and hydrogen and its content inside the cell are significant. To avoid the presence of these undesirable isotopes the high amounts of Boron 10 are attached to the cell until the point that is saturates the cell.
This is not the typical radiation technique since the beam does not destroy all of the tumor cells but the target cell is one which contains an isotope of boron. The key in this process is that the boron attaches to the cancer cell by attaching it to compunds that have special affinity for tumor cells.
The basic principle for the neutron capture therapy. A higher concentration of Boron exists in the tumor cells than in the nomrmal ones. Nuclides have different affinity for the thermal neutrons absoption. Of the nucleides that have this affinity B-10 is the most attractive because it is not radioactive and is very avaliable. Even if the affinity of most of the tissues is the highest for boron there are considerably amounts of nitrogen and hydrogen and its content inside the cell are significant. To avoid the presence of these undesirable isotopes the high amounts of Boron 10 are attached to the cell until the point that is saturates the cell.
Ode to Jet Lag
Monday morning in Rome, Anne and I woke up at 6:30am to catch the train from Termini station to the airport. We arrived at the airport a little before 9 and my flight was scheduled to leave at 11:20. I boarded the plane around 10:30 and the plane did not take off until around 3:45pm, due to some “technical difficulties.” I landed in Washington D.C. at 7:30pm (1:30am Italy time) and waited until 10pm for my connecting flight. I finally arrived in Rochester at midnight, and arrived at my house at 12:30am (6:30am Italy time), exactly 24 hours after I had woken up in Rome. Within that 24 hour period I took 3 naps; each lasted no more than an hour. I did not actually go to sleep until almost 2am, and somehow I woke up at 4:30am. My body was completely still on Italy time, so waking up at 10:30am Italy time was apparently enough of a sleep in, despite my lack of sleep over the previous 28 hours. This got me thinking – why do I need sleep in the first place? What exactly is sleep and why couldn’t I manage to fall back asleep even though I was so tired?
The reasons for sleep are still not well understood, though sleep is always being studied. What is definite about sleep is that it gives the body time to recharge its batteries by repairing muscles and replacing dead cells. Sleep also gives the brain time to organize memories – it is believed that dreams play a role in this. A lack of sleep compromises the immune system and the ability to think clearly. Certain chemicals released in the brain are associated with sleep. Growth hormone is released in children while they sleep, and the levels of the neurohormone orexin vary greatly from sleeping to wakened periods. The level of melatonin in the body is also raised during the sleeping period.
A study done on cats showed that the levels of adenosine are directly related to sleep. Adenosine is the nucleoside that forms the core of adenosine triphosphate (ATP), the molecule that powers most of the biochemical reactions inside cells. According to the study, adenosine levels build up during waking hours and decline during sleep periods. This research suggests that the body’s regular need for sleep comes from the brain’s need to replenish low stores of energy. When an animal’s energy levels in the brain get low, levels may be restored through sleep. Rising concentrations of adenosine may be how the brain recognizes that it is running low on energy and needs to recharge. When researchers deprived cats of sleep for 6 hours, their adenosine levels were double what they had been after being awake for 2 hours. When they were finally allowed to sleep for 3 hours, the adenosine levels slowly declined. This must be why I woke up at 4:30am yesterday, despite my sleep deprivation over the previous day. My guess is that my short naps were long enough to lower adenosine levels in my brain to the point where my body’s normal sleep schedule was more important to my sleep patterns than my utter exhaustion. Oh well, luckily I have plenty of time to catch up on sleep in the next few days.
Like many of the other students did, I also would like to thank everyone for a phenomenal 5 weeks. All the amazing activities and great friendships I made definitely place this summer in my top 5. For anyone who doesn’t realize, that means this summer is rivaling with summers spent at *gasp* Jew camp! Now you all know I’m serious when I say grazie mille for making this summer unforgettable. You all rock :)
References:
http://health.howstuffworks.com/sleep.htm
http://www.sciencenews.org/sn_arc97/5_24_97/fob2.htm
http://www.chemistrydaily.com/chemistry/Sleep
The reasons for sleep are still not well understood, though sleep is always being studied. What is definite about sleep is that it gives the body time to recharge its batteries by repairing muscles and replacing dead cells. Sleep also gives the brain time to organize memories – it is believed that dreams play a role in this. A lack of sleep compromises the immune system and the ability to think clearly. Certain chemicals released in the brain are associated with sleep. Growth hormone is released in children while they sleep, and the levels of the neurohormone orexin vary greatly from sleeping to wakened periods. The level of melatonin in the body is also raised during the sleeping period.
A study done on cats showed that the levels of adenosine are directly related to sleep. Adenosine is the nucleoside that forms the core of adenosine triphosphate (ATP), the molecule that powers most of the biochemical reactions inside cells. According to the study, adenosine levels build up during waking hours and decline during sleep periods. This research suggests that the body’s regular need for sleep comes from the brain’s need to replenish low stores of energy. When an animal’s energy levels in the brain get low, levels may be restored through sleep. Rising concentrations of adenosine may be how the brain recognizes that it is running low on energy and needs to recharge. When researchers deprived cats of sleep for 6 hours, their adenosine levels were double what they had been after being awake for 2 hours. When they were finally allowed to sleep for 3 hours, the adenosine levels slowly declined. This must be why I woke up at 4:30am yesterday, despite my sleep deprivation over the previous day. My guess is that my short naps were long enough to lower adenosine levels in my brain to the point where my body’s normal sleep schedule was more important to my sleep patterns than my utter exhaustion. Oh well, luckily I have plenty of time to catch up on sleep in the next few days.
Like many of the other students did, I also would like to thank everyone for a phenomenal 5 weeks. All the amazing activities and great friendships I made definitely place this summer in my top 5. For anyone who doesn’t realize, that means this summer is rivaling with summers spent at *gasp* Jew camp! Now you all know I’m serious when I say grazie mille for making this summer unforgettable. You all rock :)
References:
http://health.howstuffworks.com/sleep.htm
http://www.sciencenews.org/sn_arc97/5_24_97/fob2.htm
http://www.chemistrydaily.com/chemistry/Sleep
Subscribe to:
Posts (Atom)