Wednesday, July 29, 2015

And now for something completely different

My brother, dad, and I installed some pavers for my parents a couple weeks ago. In the past I've had a lot of floor installation jobs, but I've never done pavers. It's not too hard. Most of the work is prep.

First focus on getting level ground at the height you need. In our case, this meant that the pavers would end up flush with adjacent concrete. Account for a layer of sand, which in our case would be 3/4 inch. Focus on water flow if relevant--we wanted a slight tilt away from the house.

Rent a dirt compactor. Use your old skateboard to transport it from truck to work site (Figure 1).

Figure 1
Go around the area several times (Figure 2).

Figure 2

You will want your sand layer to be flat and appropriately level. A good way to do this is to get some pipes with the right diameter, then drag sand across them with a straight 2x4 (Figures 3-4).

Figure 3

This can be tricky if you have obstacles in the patio, like the tree above.

Figure 4

As you lay the pavers, you can fill in the holes left by the pipes. Lay the pavers straight down; if you have to drag them into position you will get sand between them and have a bad fit. Getting flush next to concrete may require some improvisation; in my case we had to bring the sand up a bit, which was fine since we want water flowing away from the house (actually, we laid them slightly higher than flush, to allow compacting).

Figure 5

The carts pictured in Figure 5 are by Racatac. I used them a lot when I installed carpet for a living; they are also good for tile and, obviously, pavers. These will make a huge difference for your back and knees. If you ever do a flooring job, buy or borrow some. For jobs like tile and pavers, you need a board like the one pictured so the cart wheels don't screw up individual bricks.

Figure 6


Figure 7

In the early part of the job, we kept the tiles square against the house, which forms a (somewhat) right angle for us. You can see in Figures 6 and 7 that we had to build a bridge to the sidewalk and lost the house on the right side due to a flower bed. Use a string to make a straight line. You may think you can lay bricks straight, but you can't.

Our biggest obstacle was the tree in the middle of the patio. We had to wrap the bricks around this and meet behind it, which always presents a challenge. Again, we used a string to keep lines straight (Figure 8).

Figure 8

Figure 9 shows things coming together.

Figure 9

My mom wanted round corners on the tree and flower beds. This is a part that takes a lot of time. You can do this with a tile saw, but it's cheaper and just as easy to use a grinder with a masonry blade (Figure 10). If the blade isn't large enough, you can score the bricks then break them (carefully).

Figure 10

Figure 11 shows the result.

Figure 11

Around flower beds, insert plastic border to hold bricks in place. This is harder than it looks (Figure 12).

Figure 12

The last step is to sweep fine sand over the bricks. This will fall into the cracks and act like grout, keeping the pavers as laid and preventing wobbling. It will take many, many coats to fill in all cracks. Spread, spray with water, allow to dry, repeat. Figures 13-15 show the process.

Figure 13


Figure 14


Figure 15

The grouting isn't quite finished, but it's just a matter of a few more coats.

Pavers look nice, but a key advantage over concrete is that they can be spot repaired. This particular patio has a tree in the middle that must be watered; as a result, the concrete that was there before was constantly settling and buckling. Repairing concrete is expensive; replacing a few pavers is cheap.



UPDATE: My dad finished the grouting and sealing; here's the finished product:

Figure 16












Thursday, July 2, 2015

Theory and empirics in cancer research

A couple years ago I read The Emperor of All Maladies, a fantastic book on the history of cancer research and treatment. I think a lot of economists would like this book because, among other things, it focuses on the differing roles of empirical and theoretical progress in a discipline that is constantly asked to serve the real world. In particular, both fields seem to display a constant tension between quick, "credible" fixes to problems and a deeper theoretical understanding of driving forces.

Reader beware--medicine and biology are way outside my wheelhouse, and it's been some time since I've read this book.

If you've known someone with cancer, there's a good chance that the treatment consisted of some combination of chemotherapy, radiation, and surgery. In a sense these are very brute force ways to treat the problem, and as you might have noticed that the collateral damage can be massive. For the most part, the brute force approach to treating cancer comes to us from an empirical (actually experimental) tradition.

For a long time, surgery was the preferred method of treating cancer. The tricky thing is that simply cutting out a visible tumor doesn't always eliminate cancer from the body. This fact, discovered empirically, led to improvements in surgical technique but also to some extreme practices among some doctors. William Halsted performed "radical mastectomies" which left breast cancer patients with severed collarbones and gaping holes in their bodies. "Halsted and his disciples would rather evacuate the contents of the body than be faced with cancer recurrences" (65). This was part of a broader milieu in the world of surgery. "By 1898, it had transformed into a profession booming with self-confidence" (66).

Over the short term, these extreme surgical methods seemed to work reasonably well. But they reflected a woefully incomplete understanding of cancer. They could often cure the problem in women with small, local cancer activity, but at the cost of destroying the body without cause. On the other hand, cancer that had metasticized throught the body was not eliminated with the surgery. The approach did not save nearly as many lives as its proponents hoped, and it left a lot of people tragically disfigured.

Radiation was a more precise approach allowing specific targets (see page 75). It could often work well for localized tumors, saving many lives. Sometimes, though, it could actually cause cancer. And in any case, the collateral damage can still be huge, leaving patients "scarred, blinded, and scalded." It destroys cells indiscriminately.

Chemotherapy has roots in experiments with cloth dyes in the 1800s (85) and mustard gas in WWI (87). In the 1940s, treatments with combinations of chemicals were employed in increasingly well-designed experiments. This is chemotherapy, and while it's more advanced than surgery it is similar in that it employs brute force methods with huge collateral damage. Its advancement was driven by experiment rather than a growing understanding of cancer. Treating each specific cancer was just a matter of finding the right combination of toxins. The approach could lengthen lives, but sometimes by only a few months (208) (and sometimes for much longer!). Collateral damage was often huge. Much of cancer research funding went toward these experiments as opposed to deeper research:

They wanted a Manhattan Project for cancer. Increasingly, they felt that it was no longer necessary to wait for fundamental questions about cancer to be solved before launching an all-out attack on the problem (121). 

This approach had some success in treating cancer, with high costs (page 330 reviews cancer treatment's results to the mid-1980s). So there was some backlash:

As the armada of cytotoxic therapy readied itself for even more aggressive battles against cancer, a few dissenting voices began to be heard along its peripheries. These voices were connected by two common themes. 
First, the dissidents argued that indiscriminate chemotherapy, the unloading of barrel after barrel of poisonous drugs, could not be the only strategy by which to attack cancer. Contrary to prevailing dogma, cancer cells possessed unique and specific vulnerabilities that rendered them particularly sensitive to certain chemicals that had little impact on normal cells. 
Second, such chemicals could only be discovered by uncovering the deep biology of every cancer cell. Cancer-specific therapies existed, but they could only be known from the bottom up, i.e., from solving the basic biological riddles of each form of cancer, rather than from the top down, by maximizing cytotoxic chemotherapy or by discovering cellular poisons empirically.

This biology-based approach gained some traction, and there were some major breakthroughs in the 1980s that identified cancer-causing mechanisms at the molecular level. There has been a lot of progress since then. Understanding cancer better has made us better at early detection, which has significantly reduced mortality. More chemotherapy has played a role too. One cancer researcher looks back at a pioneer of experimental cancer treatment, Sidney Farber (from the 1940s), and writes,

Farber's generation had tried to target cancer cells empirically, but had failed because the mechanistic understanding of cancer was so poor. Farber had had the right idea, but at the wrong time. (433)

The author concludes that "an integrated approach" is needed (457). The case of breast cancer is particularly illustrative of this point (402).

So basically we spent a century treating cancer with methods discovered through experiment, with results that range from tragic to pretty good (the book reviews some studies). In a sense the approach served us pretty well, providing ways to treat a terrible disease without having to invest a lot of time and money in knowing a lot about it. Then we focused more on understanding the disease, which gave us pretty good progress. At any given point in time, focusing more on basic research may have denied effective treatment to existing patients, but it may have sped the process of finding better approaches.

I don't really have any big conclusions other than to say that I think the conflict between theory and empirics is complicated and may be unavoidable, particularly in the case of economics. The "credibility revolution" is a huge step forward for the field with its ability to provide quick answers to policy questions. But what does it tell us about a $15 minimum wage? Nothing, really. But theory is a messier business, and it can result in a lot of wasted effort. So neither the theorists or the empiricists are in a position to feel overly important. We need both, and sometimes one will make progress faster than the other.

This book is a really good read with a lot of other insights relevant to economics (page 211 rings a bell, for example); recommended.