Design and Construction of a Hand Ballista: A Compound Arrow Launcher Without Limbs

An arrow-launching device ("hand ballista") has been developed using the principles of a compound\ud bow, but relying on modern energy storage technologies in place of bending li,mbs. It is designed to use\ud either bands of latex rubber that stretch to store energy and contract to release it, or alternatively a highpressure,\ud high-speed gas spring that stores energy when compressed. Each version uses a system of\ud wheels and eccentric cams to transfer force from the user pulling back on the string to the rubber or the\ud gas spring, providing the appropriate mechanical advantage. Substituting these technologies for limbs\ud makes the hand ballista more compact, sturdier, and potentially more energy efficient than most modern\ud bows. The prototype functions as desired when using a heavy arrow (300 grams) but materials and time\ud limitations resulted in undesirably massive pulleys, causing poor efficiency and poor durability when\ud using light arrows. Several possible improvements are suggested

Understanding the functioning and management of soil systems

Boca Raton, US

Issues for more sustainable soil system management

Boca Raton, US

Broadly neutralizing antibodies protect against hepatitis C virus quasispecies challenge.

A major problem in hepatitis C virus (HCV) immunotherapy or vaccine design is the extreme variability of the virus. We identified human monoclonal antibodies (mAbs) that neutralize genetically diverse HCV isolates and protect against heterologous HCV quasispecies challenge in a human liver-chimeric mouse model. The results provide evidence that broadly neutralizing antibodies to HCV protect against heterologous viral infection and suggest that a prophylactic vaccine against HCV may be achievable