The nutritional impact of fortified ready-to-eat cereals on the diets of school age children

Includes bibliographical references

Effects of Weightlessness on Human Fluid and Electrolyte Physiology

The changes that occur in human fluid and electrolyte physiology during the acute and adaptive phases of adaptation to spaceflight are summarized. A number of questions remain to be answered. At a time when plasma volume and extracellular fluid volume are contracted and salt and water intake is unrestricted. ADH does not correct the volume deficit and serum sodium decreases. Change in secretion or activity of a natriuretic factor during spaceflight is one possible explanation. Recent identification of a polypeptide hormone produced in cardiac muscle cells which is natiuretic, is hypotensive, and has an inhibitory effect on renin and aldosterone secretion has renewed interest in the role of a natriuretic factor. The role of this atrial natriuretic factor (ANF) in both long- and short-term variation in extracellular volumes and in the inability of the kidney to bring about an escape from the sodium-retaining state accompanying chronic cardiac dysfunction makes it reasonable to look for a role of ANF in the regulation of sodium during exposure to microgravity. Prostaglandin-E is another hormone that may antagonize the action of ADH. Assays of these hormones will be performed on samples from crew members in the future

Rule learning enhances structural plasticity of long-range axons in frontal cortex.

Rules encompass cue-action-outcome associations used to guide decisions and strategies in a specific context. Subregions of the frontal cortex including the orbitofrontal cortex (OFC) and dorsomedial prefrontal cortex (dmPFC) are implicated in rule learning, although changes in structural connectivity underlying rule learning are poorly understood. We imaged OFC axonal projections to dmPFC during training in a multiple choice foraging task and used a reinforcement learning model to quantify explore-exploit strategy use and prediction error magnitude. Here we show that rule training, but not experience of reward alone, enhances OFC bouton plasticity. Baseline bouton density and gains during training correlate with rule exploitation, while bouton loss correlates with exploration and scales with the magnitude of experienced prediction errors. We conclude that rule learning sculpts frontal cortex interconnectivity and adjusts a thermostat for the explore-exploit balance

Music Among Friends

Program listing performers and works performe

Neutrino capital of the world

Thesis (S.M. in Science Writing)--Massachusetts Institute of Technology, Dept. of Humanities, Program in Writing and Humanistic Studies, 2004.Includes bibliographical references (leaves 22-23).Neutrinos are ubiquitous particles, but they don't like to mingle. Each second, billions of them pass through our bodies, slicing imperceptibly through our delicate internal organs. They can barrel through the sun, stars, and planets without a single interaction. Only one in every ten billion of the invisible, chargeless, nearly massless particles will interact through a weak force with another atom, leaving an observable trace of its existence. But in a small town in western South Dakota called Lead (rhymes with 'need'), a 125-year history of mining ore and gold out of the ground may be replaced by these impalpable particles. Lead was the birthplace of neutrino science when chemist Ray Davis began his work on solar neutrinos over thirty years ago. He installed a tank filled with 100,000 gallons of dry cleaning fluid a mile underground in Lead's Homestake mine and began counting neutrino interactions. Eventually, he earned the Nobel Prize for his work; his surprising results changed the world of particle physics. Now that the Homestake mine is closed, scientists, politicians and local citizens have converged on this small town with the hopes of turning it into a national underground laboratory that houses experiments ranging from astrophysics to deep subsurface geobiology. In the process, the state of South Dakota has introduced a unique funding scheme in which science is democratic. Politicians, scientists and regular folks play important roles in the neutrino populist movement, working together to preserve a scientific resource and life in a small town.by Carolyn Y. Johnson.S.M.in Science Writin

Juvenile mice show greater flexibility in multiple choice reversal learning than adults

ABSTRACTWe hypothesized that decision-making strategies in juvenile animals, rather than being immature, are optimized to navigate the uncertainty and instability likely to be encountered in the environment at the time of the animal's transition to independence. We tested juvenile and young adult mice on discrimination and reversal of a 4-choice and 2-choice odor-based foraging task. Juvenile mice (P26–27) learned a 4-choice discrimination and reversal faster than adults (P60–70), making fewer perseverative and distraction errors. Juvenile mice had shorter choice latencies and more focused search strategies. In both ages, performance of the task was significantly impaired by a lesion of the dorsomedial frontal cortex. Our data show that the frontal cortex can support highly flexible behavior in juvenile mice at a time coincident with weaning and first independence. The unexpected developmental decline in flexibility of behavior one month later suggests that frontal cortex based executive function may not inevitably become more flexible with age, but rather may be developmentally tuned to optimize exploratory and exploitative behavior for each life stage