the angle of yaw

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    The NF-15B ACTIVE is the most maneuverable of any F-15 variant, but she didn’t start out that way. This airframe, originally designated the TF-15B (USAF serial number 71-0290), looked much like a typical F-15. She took her first flight on July 7, 1973, as the first two-seat F-15 in history and the sixth F-15 to roll off the assembly line.

    On September 7, 1988, she would have her “second first flight” following major modifications as the STOL/MTD (Short Takeoff and Landing/Maneuver Technology Demonstrator). Modified F-18 stabilators were put in place forward of the wing as canards. Thrust vectoring in the pitch axis was also implemented, allowing takeoff rotation at only 39 knots and drastically shorter landing distances.

    In 1991, the STOL/MTD test program ended, and the USAF loaned the airframe to NASA, who modified it into the NF-15B ACTIVE (Advanced Control Technology for Integrated Vehicles). The pitch thrust vectoring was traded for nozzles that could be vectored in pitch and yaw. This allowed for incredible maneuverability. The bird could perform yawing maneuvers while flying at 30 degrees angle of attack.

    Although never implemented, there were plans to further modify this airframe by removing the vertical tail planes, allowing thrust vectoring to be wholly responsible for yawing maneuvers. This would have been called the F-15 MANX, named after the naturally tailless cat.

    After decades of serving NASA Dryden Flight Research Center (now NASA Armstrong) as a successful experimental testbed for many different test programs, the NF-15 ACTIVE took its final flight in January 2009. On this last flight, she was the oldest still flying F-15. In July of 2015, she was put on static display at NASA Armstrong Flight Research Center on Edwards Air Force Base, California.

DID YOU KNOW: there is an award-winning musical about the sinking of the Titanic? “Titanic: The Musical,” with music and lyrics by Maury Yeston and book by Peter Stone, opened on Broadway at the Lunt-Fontanne Theatre on April 23, 1997 - though it would rapidly be overshadowed by James Cameron’s film as the most important Titanic-related entertainment of the year.

Yeston and Stone’s show portrays the passengers and crew of Titanic very respectfully, and does not go out of its way in an effort to incite controversy. For the most part, the show is historically accurate - and featured remarkable technical engineering, including the installation of a hydraulic lift beneath the stage to allow the stage to pitch and yaw to represent the angle of the sinking ship.

“Titanic” won every Tony Award it was nominated for - including “Best Musical,” but closed as a financial loss in March of 1999 after 804 performances.

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Robot Automates Foundational Biology Research

Biology grad students, rejoice! The sore necks and eyes from days spent slouched over a microscope counting fruit flies may soon be no more.

Anybody who has taken a high school or college biology course knows the gigantic importance of the tiny fruit fly. The unassuming Drosophila melanogaster is a laboratory model organism, studied extensively since the early 20th century to uncover the secrets of how organisms develop over time and pass along traits to their offspring. It is easy and quick to breed, holds only four pairs of chromosomes for simpler studying and many of its mutations can be investigated with the naked eye.

But underlying all of the Drosophila-based breakthroughs in genetics, physiology and disease is mind-numbing data collection. Studies often require scientists, grad students or lab techs to sort through hundreds or thousands of anesthetized flies while recording their characteristics for later analysis. 

Stanford University researchers looked for a better way to do this tedious work and free up valuable resources to pursue the science instead of getting bogged down in data collection. They came up with a robotic platform that can quickly pick awake flies, inspect and sort them, and put them through behavioral experiments. 

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3D Compass in the Brain

Pilots are trained to guard against vertigo: a sudden loss of the sense of vertical direction that renders them unable to tell “up” from “down” and sometimes even leads to crashes. Coming up out of a subway station can produce similar confusion: For a few moments, you are unsure which way to go, until regaining your sense of direction. In both cases, the disorientation is thought to be caused by a temporary malfunction of a brain circuit that operates as a three-dimensional (3D) compass.

Weizmann Institute scientists have now for the first time demonstrated the existence of such a 3D compass in the mammalian brain. The study was performed by graduate student Arseny Finkelstein in the laboratory of Prof. Nachum Ulanovsky of the Neurobiology Department, together with Dr. Dori Derdikman, Dr. Alon Rubin, Jakob N. Foerster and Dr. Liora Las. As reported in Nature on December 3, the researchers have shown that the brains of bats contain neurons that sense which way the bat’s head is pointed and could therefore support the animal’s navigation in 3D space.

Navigation relies on spatial memory: past experience of different locations. This memory is formed primarily in a deep-seated brain structure called the hippocampal formation. In mammals, three types of brain cells, located in different areas of the hippocampal formation, form key components of the navigation system: “place” and “grid” cells, which work like a GPS, allowing animals to keep track of their position; and “head-direction” cells, which respond whenever the animal’s head points in a specific direction, acting like a compass. Much research has been conducted on place and grid cells, whose discoverers were awarded the 2014 Nobel Prize in Physiology or Medicine, but until recently, head-direction cells have been studied only in two-dimensional (2D) settings, in rats, and very little was known about the encoding of 3D head direction in the brain.

To study the functioning of head-direction cells in three dimensions, Weizmann Institute scientists developed a tracking apparatus that allowed them to video-monitor all the three angles of head rotation – in flight terminology, yaw, pitch and roll – and to observe the movements of freely-behaving Egyptian fruit bats. At the same time, the bats’ neuronal activity was monitored via implanted microelectrodes. Recordings made with the help of these microelectrodes revealed that in a specific sub-region of the hippocampal formation, neurons are tuned to a particular 3D angle of the head: Certain neurons became activated only when the animal’s head was pointed at that 3D angle.

The study also revealed for the first time how the brain computes a sense of the vertical direction, integrating it with the horizontal. It turns out that in the neural compass, these directions are computed separately, at different levels of complexity: The scientists found that head-direction cells in one region of the hippocampal formation became activated in response to the bat’s orientation relative to the horizontal surface, that is, facilitating the animal’s orientation in two dimensions, whereas cells responding to the vertical component of the bat’s movement – that is, a 3D orientation – were located in another region. The researchers believe that the 2D head-direction cells could serve for locomotion along surfaces, as happens in humans when driving a car, whereas the 3D cells could be important for complex maneuvers in space, such as climbing tree branches or, in the case of humans, moving through multi-story buildings or piloting an aircraft.

By further experimenting on inverted bats, those hanging head-down, the scientists were able to clarify how exactly the head-direction signals are computed in the bat brain. It turned out that these computations are performed in a way that can be described by an exceptionally efficient system of mathematical coordinates (the technical term is “toroidal”). Thanks to this computational approach used by their brain, the bats can efficiently orient themselves in space whether they are moving head up or down.

This research supports the idea that head-direction cells in the hippocampal formation serve as a 3D neural compass. Though the study was conducted in bats, the scientists believe their findings should also apply to non-flying mammals, including squirrels and monkeys that jump between tree branches, as well as humans. “Now this blueprint can be applied to other species that experience 3D in a more limited sense,” Prof. May-Britt Moser, one of the 2014 Nobel laureates, writes in the “News and Views” opinion piece that accompanies the Weizmann study in Nature.