Natural and synthetic allatotoxins: suicide substrates for juvenile hormone biosynthesis

Cytotoxic agents with antijuvenile hormone activity in insects have been discovered. Their mechanism of action may involve an oxidative bioactivation into a reactive quinone methide.     

Prolonged excitation in the visual cortex of the cat

Intense light flashes produce maintained increased in cortical activity not dependent on continuous excitation from the retina.     

Thermal conductivity effect of carrier gases on flame-ionization detector sensitivity

Data for six carrier gases of different thermal conductivities show a linear correlation between the logarithm of thermal conductivity and detector response. Carbon dioxide with a lower thermal conductivity than helium gives a ninefold increase in detector response.     

Geotropism in corn roots: evidence for its mediation by differential Acid efflux

The elongation zone in intact growing corn roots secretes acid leading to a reduced pH along the surface of the root and in the adjacent medium. This can be detected by placing the root on an agar medium containing the pH indicator dye bromocresol purple. When the root is treated with a growth inhibitory concentration of the hormone indole-3-acetic acid, the acid efflux is reversed and growth is greatly retarded. When the root is mounted vertically, acid secretion is uniform along the elongation zone, and the root grows straight downward. When the root is placed horizontally, there is enhanced acid efflux along the upper surface of the elongation zone and reduced acid efflux along the lower surface. An increased rate of elongation of the upper cells relative to the lower cells then results in downward curvature of the root. The correlation between acid efflux patterns and growth patterns indicates that proton efflux is important in the control of root growth.     

Radioactive elements on Mercury's surface from MESSENGER: implications for the planet's formation and evolution

The MESSENGER Gamma-Ray Spectrometer measured the average surface abundances of the radioactive elements potassium (K, 1150 ± 220 parts per million), thorium (Th, 220 ± 60 parts per billion), and uranium (U, 90 ± 20 parts per billion) in Mercury's northern hemisphere. The abundance of the moderately volatile element K, relative to Th and U, is inconsistent with physical models for the formation of Mercury requiring extreme heating of the planet or its precursor materials, and supports formation from volatile-containing material comparable to chondritic meteorites. Abundances of K, Th, and U indicate that internal heat production has declined substantially since Mercury's formation, consistent with widespread volcanism shortly after the end of late heavy bombardment 3.8 billion years ago and limited, isolated volcanic activity since.