In NPR's latest article titled "How do you know if aid really works? Turns out, we often don’t", 3ie's executive director Emmanuel Jimenez discusses the steady rise in the production of impact evaluations and the need for researchers to work directly with policymakers. Read the full article which includes interviews with J-PAL's Rachel Glennerster, Abhijit Banerjee and the Center for Global Development's Amanda Glassman... --> 3ie in the news: How do you know if aid really works?
The proppant is a granular material that prevents the created fractures from closing after the fracturing treatment. Types of proppant include silica sand , resin-coated sand, bauxite , and man-made ceramics. The choice of proppant depends on the type of permeability or grain strength needed. In some formations, where the pressure is great enough to crush grains of natural silica sand, higher-strength proppants such as bauxite or ceramics may be used. The most commonly used proppant is silica sand, though proppants of uniform size and shape, such as a ceramic proppant, are believed to be more effective. 
I have been a weekend golfer for 8 years. I mostly shoot in the mid 90s with an occasional round in the high 80s. For the last couple years I felt like I had hit a plateau… no matter what I did I just couldn’t get my scores down any lower. And I tried everything. I got a membership at my local range, I tried a bunch of training aids, and I took some private lessons.
Then I purchased the perfect impact system. I don’t know what it was but it just *clicked* for me. For the first time I had a crystal clear idea of what to focus on and where I needed to go with my swing.
Well after a few weeks of practice I have officially blasted through my plateau! Last week I had my best round ever (by 6 strokes!) and broke 80 for the first time.
Tom, thanks for the lessons! Can’t wait to see how low I can go!