One of the hidden glories of Victorian engineering is proper drains. Isolating a city’s effluent and shipping it away in underground sewers has probably saved more lives than any medical procedure except vaccination. But out of sight is out of mind. And that, together with the inherent yuckiness of the subject, means that many old sewers have been neglected and are in dire need of repair. If that repair does not come in time, the result is noxious and potentially hazardous. All this neglect, though, makes it hard to know where best to apply the sticking-plasters. So Mark Hernandez of the University of Colorado, Boulder, and his team have been looking for an easily measurable signal that something is about to go wrong. 

A candidate, Dr. Hernandez suspected, is hydrogen sulphide. This is one of the gases that make sewage stink. Though not itself damaging to a pipe’s fabric, it can be converted by certain species of bacteria into sulphuric acid. Pretty well all sewage smells of hydrogen sulphide, though, so for it to be a useful telltale you need to know just how much is a sign of trouble. Dr. Hernandez and his colleagues therefore collected samples from 36 sewers in various states of decay and started looking. 

One of their interests was in the mixture of bacteria found in pipes in different states of repair. Rather than culturing these, a process to which not all species are amenable, they ran them through a mass DNA screening that shows up everything in a sample. They also measured the acidity of the sewage soaked into the pipe wall near where the sample was collected and recorded the concentrations in the air there of hydrogen sulphide, methane and carbon dioxide.

        When a bee returns from a more distant food source, she does what is called the Schwanzeltanz or the waggle dance. She wags her abdomen as she runs straight a short distance while making a rasping sound with her wings.She makes turns that create a figure-eight design. The movements of the dance indicate to the other bees in the hive where they must fly to find the food. Karl von Frisch was the first to decode the dances of the honeybees. As early as the 1940s, he found that honeybees can communicate the direction, distance, and quality of a food source to members of their hive through elaborate dances. Scientists have also discovered that the bees produce a hive-specific pheromone that they leave at the source of the nectar, helping to direct the other bees to the site. A pheromone is a chemical that is secreted by one individual and acts from a distance on another individual to alter that individual’s behavior. The scout bee also brings back the scent of the nectar itself, which further aids the other bees in locating the food source. So there are several indicators of where the food is located: the “dance,” the pheromone, and the odor of the food.

With his high G.P.A., nearly perfect SAT score and activities — debate team, tennis captain and state orchestra — Mr. Jia believes he should have had a fair shot at Harvard, Princeton, Columbia and the University of Pennsylvania. However, those Ivy League colleges rejected him after he applied in the fall of 2015. 

It was particularly disturbing, Mr. Jia said, when classmates with lower scores than his — but who were not Asian-American, like him — were admitted to those Ivy League institutions. 

“My gut reaction was that I was super disillusioned by how the whole system was set up,” Mr. Jia, said. 

Students like Mr. Jia are now the subject of a lawsuit accusing Harvard of discriminating against Asian-Americans in admissions by imposing a penalty for their high achievement and giving preferences to other racial minorities.