It's taken a little while, but I am finally back!
The scoop: I will be traveling to Chittagong, Bangladesh to teach at the Asian University for Women for 6 months! (then I will come back to the SF Bay Area)
I will get more regular with my postings-- I still have a ton of great ideas for postings from friends (that I need to write up!)!
Thanks for reading!
I've been busy applying for postdocs, so I haven't updated recently. Will update soon-- stay posted!
In honor of my best pal Kathleen (who is an astrophysicist, just in case you were wondering) getting engaged, I'm going to discuss what makes a diamond a diamond (not not just a pile of carbon).
Carbon
Carbon atoms have four valence electrons in their outer shell. This means that they form four bonds to other atoms, such as oxygen, nitrogen, and hydrogen. These bonds are stable, but can be easy to break and make under certain conditions. This is a big part of why life is carbon-based rather than silicon based (it also has four valence electrons, but forms much stronger bonds to oxygen than does carbon).
Molecules made entirely of carbon exist in several forms (carbon atoms don't just hang out by themselves, after all). The form of molecular carbon I think of first is coal (the kind we burn as fuel). Coal consists of carbon atoms that are haphazardly bonded to other carbon atoms (and to other atoms like hydrogen and oxygen). Because of this, coal tends to exist as amorphous (shapeless) solids.
Graphite (pencil lead) is made almost entirely of carbon. It consists of sheets of carbon atoms that are bonded to three other carbons in six-membered rings. The geometry around each carbon atom is trigonal planar, meaning that the three bonds are 120 degrees apart- as far as they can get- and an overhead view would look sort of like a triangle. Because there are only three atoms attached to each carbon, this means that one of the bonds is a double bond; this leads to the semiconducting properties of graphite (bonds are made of electrons, double bonds that are close to each other allow electrons to travel, creating currents). Because the graphite sheets are not connected to one another, they can slide over each other (this is why graphite makes good pencil lead).
Diamonds are also made almost entirely of carbon atoms, but in this case the carbon atoms each have four carbon atoms attached to them (in a white diamond). The atoms are bonded in a tetrahedral arrangement, so that the carbons are as far apart from one another as possible. This structure extends through entire crystals, and is called the crystal lattice.
You might be wondering why graphite is fairly common, while diamonds are relatively rare. It turns out that graphite (because of the double bonds) is the more stable form of pure carbon. It would take more energy for diamonds to form than for graphite to form. One way diamonds are made is through the heating and compression of coal (this can happen if a meteorite hits the right place on Earth). Lots of energy (in the form of heat and pressure) goes in, forcing the bonds in the coal to rearrange- atoms other than carbon are lost, and bonds are formed to other carbon atoms as the rock cools, which sometimes results in the formation of diamonds.
Diamonds can be uncolored or colored. Colored diamonds occur because of impurities in the diamonds (they are not pure carbon, but have tiny amounts of other elements in their crystal lattice). Yellowish diamonds can occur when nitrogen is part of the lattice. Hydrogen can lend a bluish tint to a diamond, while pink diamonds are the result of a shift in the crystal lattice of a diamond. The shininess of diamonds is due to the crystal lattice, and their clarity to how many "breaks" there are in the lattice of that particular diamond crystal.
Diamonds can be mined or made in a lab (by applying pressure and heat to coal, under carefully controlled conditions). I would argue that the fake uncolored diamonds (lab made, called fiamonds by Kathleen) are of just as high quality (or higher quality) than ones that are mined. They would likely have fewer imperfections and cost less than diamonds that are mined.
I was recently asked this question: Will coffee kill your taste buds?
I've looked around a bit. While I have found many online forums that suggest that both coffee and spicy food can kill your taste buds, I have found no evidence confirming these hypotheses. My guess is that some compounds in coffee may saturate receptors for certain tastes for a period of time after one drinks coffee, decreasing additional gustatory (taste) sensation. It is also possible that you simply get used to the taste of the bitter compounds in coffee and can tolerate more (think moving from coffee ice cream to coffee to espresso). Scientists have also noted that a diminished sense of smell as we get older may also decrease our ability to taste as well.
The upshot: coffee, by itself, does not kill taste buds.
I'll leave you with an article on this interesting coffee study. Coffee apparently can cause people to hallucinate.
I'm having a lot of fun discussing random science topics, however I'm going to digress from my usual ramblings to discuss the recent news about women faculty in Chemical and Engineering News. As the author Corinne Marasco notes, Once again, the only news about the percentage of women faculty members in the top 50 chemistry departments is that there is no news. For the sixth year in a row that C&EN has examined this topic, there has been little growth. Women are still vastly underrepresented among full professors, despite slow and steady progress between the 2000–01 and 2005–06 academic years.
While this is not particularly surprising, I can't help but wish that the number of women chemistry faculty at elite universities was increasing more rapidly. Stanford (my alma mater) hired two women faculty, both of whom are starting this year, increasing the number of women faculty in the department from one to three. A good thing, to be sure, but there simply are not enough role models for women wanting to go into academia.
That said, I can think of several reasons (frequently discussed at WCGL meetings) other than a lack of role models that explain why some women would choose not to be a professor at a Research I school, such as work-life balance. This is unfortunate, because our society is losing a lot of brainpower in academia when women choose to stay in other sectors.
I know why I chose not to follow that particular career path- the tenure clock, the pressure to keep on top of all research being done in my area, and wanting some work-life balance (this does seem to be getting a bit better). I also witnessed/ was part of the wrenching decisions my Ph.D. advisor had to make when her partner did not get a tenure-track position at Stanford (she ended up moving to another university, and seems pretty happy there).
To sum up: the results of the survey are somewhat disheartening, though not surprising. I hope that the chemistry community comes up with more creative ways of recruiting and retaining women to these positions, so that we can continue to push back the frontiers of science.
This topic has come up quite a bit, especially a few months ago when I applied for a job at the California Institute for Regenerative Medicine. What exactly is a stem cell? Where do they come from? Why is there a big moral brouhaha about them? (That last one was from Megan) Why are we so excited about them? As you can see, there are quite a few things to talk about with regard to stem cells, so I will start with the most obvious question: What is a stem cell?Most cells are differentiated and specialized- they have a certain purpose and they are unable to renew themselves. A muscle cell will always be a muscle cell, and it won't make more of itself (normally). Stem cells are cells that are not differentiated, in that they do not have a specific function in the body. They are also able to divide over long periods of time, replacing themselves. There are two types of stem cells that are commonly talked about, embryonic stem cells and adult stem cells.
Embryonic stem cells are pluripotent (also called multipotent). This means that they can become any kind of cell. It's sort of like your parents telling you when you're young that you can be anything when you grow up; pluripotent stem cells have the potential to become any type of cell later. The type of cells they become has to do with what environment they grow in. Because embryonic stem cells can become any type of cell (from a heart muscle cell to a neuron to a blood cell and more), scientists are really interested in figuring out how to program these cells to turn into a specific type of cell. This could make treatments for a lot of diseases possible (more on this later). Adult stem cells that are more specialized- they are somewhat differentiated, so they can only make certain types of cells. This is sort of like how if you went to law school, you could be any kind of lawyer, but you couldn't decide to go become a practicing pediatrician right away- you're trained as a lawyer, not a doctor. Some adult stem cells are multipotent. This means that they can turn into several types of cells (but not all types of cells). Blood stem cells are multipotent; they can divide and differentiate (turn into) any kind of blood cell. Other adult stem cells can only make one type of cell; these are called unipotent. We have unipotent stem cells in our guts- their whole job is to keep making more cells to line the villi in our small intestines with. These types of stem cells are also very interesting (and all people have them, not just embryos!), but may be limited in application because they are somewhat differentiated and cannot become any type of cell.More on this later, but for now you can find out more about this at the NIH website, or you can Google "stem cell"
Thanks to Luke, who wanted to know about The Science of Scuba Diving and Free Diving - the role of nitrogen and oxygen, pressure, and how the make-up of the body's tissues govern these sports. I'm going to start with Free diving.
Some people like to participate in an activity called free diving. In this activity, a person holds his or her breath and dives beneath the surface of a body of water. People who dive for abalone or pearls, or who dive down while snorkeling may fall into this category. It sounds simple enough; a person takes a breath, dives beneath the surface to some distance, and resurfaces. The body, however, makes several adaptations when a person dives deep beneath the surface of water- these are called the mammalian diving responses.
To talk about this, we first need to have an understanding of pressure, and what air and water pressure can do to air inside a closed system (such as a person's lungs when they are holding their breath). The air above us is pressing down on us all the time. At sea level, about 15 pounds of air are pressing down on every square inch on the tops of our heads and shoulders. Most of the time, we hardly notice air pressure; however, if you've ever gone from low elevation to the mountains and opened a tube of sunscreen, you've seen air pressure in action. The container was closed at a low elevation (and higher air pressure)- this means that the air inside the tube is at this pressure when it is closed. Because the tube is closed, air can neither go in nor go out. When you get to the higher elevation, there is less air pressure because there is a smaller volume of air pushing down on the earth. When the high-pressure tube is opened at this lower air pressure, the air pushes out to equalize the pressure. As it escapes the tube, it often takes some of your sunblock with it. The opposite is also true. If you had an empty plastic water bottle with you in the mountains and took it to the seashore, it would most likely have collapsed on itself by the time you got there. Again, this is because there are a lot more air molecules pushing down on it. This phenomenon is known as Boyle's Law; it states that as pressure increases, volume will decrease (and vice-versa). The same is true for water pressure, but water is a liquid rather than a gas and is much heavier than air. For every 33 feet we go down in the water, another 15 pounds per square inch is pushing down on us. If we filled a balloon with air at the surface and took it 10 ft. below the surface of the water, the balloon would still have the same amount of air inside; its volume would be smaller because there were more molecules pushing on the outside of the balloon.As a diver goes under the water, water starts pressing on his or her body. The good news is that because we are mostly made of water, water won't squish our bodies flat if we free dive deep into the ocean. While a diver might not notice the difference in pressure as they dive on their arm, there are other parts of the body where the difference in pressure is more noticeable. A free diver may feel pressure on on his or her eardrum. While this may be uncomfortable this pressure can often be released by pushing air from the lungs into the inner ear. (You can do this on dry land if you hold your nose and try to blow from it). The adaptations taking place do not stop here.
Because the diver's lungs are filled with air when he or she goes beneath the surface of the water, they are somewhat like balloons. As a person dives under the water, the air inside their lungs (at atmospheric pressure) is suddenly at lower pressure than the rest of the body. The rest of the body begins to push on the lungs, and they start to shrink. This has disaster written all over it- if the lungs collapsed in on each other, then some of the tissue lining the lungs might become damaged. This would close off part of the diver's lung, even after he got out of the water. Instead of the lungs collapsing, the capillaries (tiny blood vessels) in the lungs start to leak plasma (the fluid in blood) into the tissue lining the lungs. This causes the tissue to expand, filling the space in the lungs that used to be taken up with air. This prevents them from collapsing. Once a diver surfaces, the plasma goes back into the capillaries and they retain their full lung capacity.
Other adaptations include a slowing of the heart rate (called bradycardia) to use less oxygen and the spleen contracting (to push more blood cells around).
More on SCUBA soon:)
