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All known black holes fall into two categories: small, stellar-mass black holes weighing a few Suns, and supermassive black holes weighing millions or billions of Suns. Astronomers expect that intermediate-mass black holes weighing 100 - 10,000 Suns also exist, but so far no conclusive proof of such middleweights has been found. Today, astronomers are announcing new evidence that an intermediate-mass black hole (IMBH) weighing 2,200 Suns is hiding at the center of the globular star cluster 47 Tucanae.

A team of scientists from the Energy Department's National Renewable Energy Laboratory (NREL) determined that surface recombination limits the performance of polycrystalline perovskite solar cells.

Considerable research into perovskites at NREL and elsewhere has proved the material's effectiveness at converting sunlight into electricity, routinely topping 20 percent efficiency. The sunlight creates mobile electrons whose movement generates the power but upon encountering defects can slip into a non-productive process. Known as a recombination, this process reduces the efficiency of a solar cell. For the cell to be the most efficient, the recombination must occur slowly.

Humans aren’t the only species that resort to a little subterfuge

While a dominant male fish from northern Mexico mates with a female, a small fella bides his time in the offing. Suddenly, the little guy darts in ahead of Mr. Big and plants his seeds on freshly laid eggs.

A study led by UC Santa Cruz researchers has found that drought dramatically increases the severity of West Nile virus epidemics in the United States, although populations affected by large outbreaks acquire immunity that limits the size of subsequent epidemics.

The study, published February 8 in Proceedings of the Royal Society B, involved researchers from UC Santa Cruz, Stanford University, and the New York State Department of Health. They analyzed 15 years of data on human West Nile virus infections from across the United States and found that epidemics were much larger in drought years and in regions that had not suffered large epidemics in the past.

A major report led by Vanderbilt investigators found that the mere presence of even a small amount of calcified coronary plaque, more commonly referred to as coronary artery calcium (CAC), in people under age 50 — even small amounts — was strongly associated with increased risk of developing clinical coronary heart disease over the ensuing decade.