High resolution spectroscopy of two gamma-ray bursts in November 1978

The first results from the ISSEE-3 radiatively colled germanium gamma ray burst spectrometer are presented. Spectra and time histories from two events on the 1978 November 4 and 1978 November 19 are given. A significant difference in the continuum spectra for the two events was observed. Evidence is presented for two spectral features in the features in the November 19 events, a broad one at approximately 420 key KeV and a narrower one at 740 KeV with a suggestion of an accompanying high energy tail

Energy efficient engine. Fan and quarter-stage component performance report

The fan configuration for the general Electric/NASA Energy Efficient Engine was selected following an extensive preliminary design study. The fan has an inlet radius ratio of 0.342 and a specific flowrate of 208.9 Kg/sec/sq. m (42.8 1bm/sec/sq. ft). The design corrected tip speed is 411.5 m/sec (1350 ft/sec) producing a bypass flow total-pressure ratio of 1.65 and a core flow total-pressure ratio of 1.6. The design bypass ratio is 6.8. The aerodynamic design point corresponds to the maximum climb power setting at Mach 0.8 and 10.67 Km (35,000 ft) altitude. The fully-instrumented fan component was tested in the Lynn Large Fan Test Facility in 1981. The overall performance results, reported herein, showed excellent fan performance with the fan meeting all of its component test goals of flow, efficiency and stall margin

The Goddard program of gamma ray transient astronomy

Gamma ray burst studies are reviewed. The past results, present status and future expectations are outlined regarding endeavors using experiments on balloons, IMP-6 and -7, OGO-3, ISEE-1 and -3, Helios-2, Solar Maximum Mission, the Einstein Observatory, Solar Polar and the Gamma Ray Observatory, and with the interplanetary gamma ray burst networks, to which some of these spacecraft sensors contribute. Additional emphasis is given to the recent discovery of a new type of gamma ray transient, detected on 1979 March 5

Postsynaptic calcium/calmodulin-dependent protein kinase II is required to limit elaboration of presynaptic and postsynaptic neuronal arbors

Neuronal dendritic and axonal arbors grow to a characteristic size and then stabilize their structures. Activity-dependent stop-growing signals may limit neuronal process elaboration. We tested whether endogenous calcium/calmodulin-dependent protein kinase II (CaMKII) activity in postsynaptic optic tectal cells is required to restrict the elaboration of neuronal processes in the Xenopus tadpole retinotectal projection. Optic tectal cells were infected with vaccinia viruses that express CaMKII-specific inhibitory peptides. In vivo time-lapse imaging revealed that expression of CaMKII inhibitors blocked the growth restriction that normally occurs during maturation of tectal cell dendritic arbors. Postsynaptic CaMKII inhibition also increased the growth of presynaptic retinotectal axon arbors. The results indicate that endogenous postsynaptic CaMKII activity is required to limit the growth of presynaptic and postsynaptic arbor structures in vivo

Depolarizing GABAergic conductances regulate the balance of excitation to inhibition in the developing retinotectal circuit in vivo

Neurotransmission during development regulates synaptic maturation in neural circuits, but the contribution of different neurotransmitter systems is unclear. We investigated the role of GABAA receptor-mediated Cl- conductances in the development of synaptic responses in the Xenopus visual system. Intracellular Cl- concentration ([Cl-]i) was found to be high in immature tectal neurons and then falls over a period of several weeks. GABAergic synapses are present at early stages of tectal development and, when activated by optic nerve stimulation or visual stimuli, induce sustained depolarizing Cl- conductances that facilitate retinotectal transmission by NMDA receptors. To test whether depolarizing GABAergic inputs cooperate with NMDA receptors during activity-dependent maturation of glutamatergic synapses, we prematurely reduced [Cl-]i in tectal neurons in vivo by expressing the Cl- transporter KCC2. This blocked the normal developmental increase in AMPA receptor-mediated retinotectal transmission and increased GABAergic synaptic input to tectal neurons. Therefore, depolarizing GABAergic transmission plays a pivotal role in the maturation of excitatory transmission and controls the balance of excitation and inhibition in the developing retinotectal circuit

Shock Deformation in Zircon, a Comparison of Results from Shock-Reverberation and Single-Shock Experiments

The utility of the mineral zircon, ZrSiO4, as a shock-metamorphic geobarometer and geochronometer, has been steadily growing within the planetary science community. Zircon is an accessory phase found in many terrestrial rock types, lunar samples, lunar meteorites, martian meteorites and various other achondrites. Because zircon is refractory and has a high closure temperature for Pb diffusion, it has been used to determine the ages of some of the oldest material on Earth and elsewhere in the Solar System. Furthermore, major (O) and trace-element (REE, Ti, Hf) abundances and isotope compositions of zircon help characterize the petrogenetic environments and sources from which they crystallized. The response of zircon to impact-induced shock deformation is predominantly crystallographic, including dislocation creep and the formation of planar and sub-planar, low-angle grain boundaries; the formation of mechanical {112} twins; transformation to the high pressure polymorph reidite; the development of polycrystalline microtextures; and dissociation to the oxide constituents SiO2 and ZrO2. Shock microstructures can also variably affect the U- Pb isotope systematics of zircon and, in some instances, be used to constrain the impact age. While numerous studies have characterized shock deformation in zircon recovered from a variety of terrestrial impact craters and ejecta deposits and Apollo samples, experimental studies of shock deformation in zircon are limited to a handful of examples in the literature. In addition, the formation conditions (e.g., P, T) of various shock microstructures, such as planar-deformation bands, twins, and reidite lamellae, remain poorly con-strained. Furthermore, previous shocked-zircon experimental charges have not been analyzed using modern analytical equipment. This study will therefore under-take an new set of zircon shock experiments, which will then be microstructurally characterized using state-of-the-art instrumentation within the Astromaterials Research and Exploration Science Division (ARES), NASA Johnson Space Center

Sun-Earth Day - Teaching Heliophysics Through Education Technology

Sun-Earth Day (SED) is an Education and Outreach program supported by the U.S, National Aeronautics and Space Administration (NASA). The intent of the program is to teach students and the general public about Heliophysics (the science of the study of the Sun, how it varies, and how solar dynamics affect the rest of the solar system, especially the Earth). The program was begun ten years ago. Each year since that time a particular day has been designated as "Sun-Earth Day ,,. Usually the day of the spring equinox (March 20 or 21) is Sun-Earth Day, but other days have been used as well. Each year a theme is chosen relating to Heliophysics and events reflecting that theme are planned not only for Sun-Earth Day, but for the entire year. From the very beginning educational technology was emphasized in the events in order to effectively reach wide audiences with the SED message. The main approach has been to have a "webcast" related to each year's theme, often from a location that supports the theme as well. For example, a webcast took place from the Mayan pyramids at Chichen Itza, Mexico to highlight the theme of "Ancient Observatories, Timeless Knowledge". Webcasts were not the only technology employed, however. Many of the themes centered on the dynamic nature of the Sun and the effects that solar storms can have on interplanetary space and in our day-to-day life on Earth. Activities for tracking when solar storms happen and how they affect the Earth were developed and brought together in an educational package called Space Weather Action Centers. This project is explained in more detail in another presentation in this session being given by Norma Teresinha Oliveira Reis. Recent Sun-Earth Days have utilized "social networking" technologies to reach widespread groups on the internet. Podcasts, Vodcasts, Facebook, Twitter, and Second Life are the types of network technologies being employed now. The NASA Distance learning Network is another method for bringing Sun-Earth Day events and training to widespread educators and classrooms in order to magnify the reach of Sun-Earth Day. Examples of the technologies will be shown along with an assessment of their effectiveness

Dynamical solutions of warped six dimensional supergravity

We derive a new class of exact time dependent solutions in a warped six dimensional supergravity model. Under the assumptions we make for the form of the underlying moduli fields, we show that the only consistent time dependent solutions lead to all six dimensions evolving in time, implying the eventual decompactification or collapse of the extra dimensions. We also show how the dynamics affects the quantization of the deficit angle.Comment: 18 pages, no figure, typos corrected, references added, the final versio

Stabilization of axon branch dynamics by synaptic maturation

The developmental refinement of topographic projections in the brain is reflected in the dynamic sculpting of axonal arbors that takes place as connections between CNS structures form and mature. To examine the role of synaptogenesis and synaptic maturation in the structural development of axonal projections during the formation of the topographic retinotectal projection, we coexpressed cytosolic fluorescent protein (FP) and FP-tagged synaptophysin (SYP) in small numbers of retinal ganglion cells in living albino Xenopus laevis tadpoles to reveal the distribution and dynamics of presynaptic sites within labeled retinotectal axons. Two-photon time-lapse observations followed by quantitative analysis of tagged SYP levels at individual synapses demonstrated the time course of synaptogenesis: increases in presynaptic punctum intensity are detectable within minutes of punctum emergence and continue over many hours. Puncta lifetimes correlate with their intensities. Furthermore, we found that axon arbor dynamics are affected by synaptic contacts. Axon branches retract past faintly labeled puncta but are locally stabilized at intensely labeled SYP puncta. Visual stimulation for 4 h enhanced the stability of the arbor at intense presynaptic puncta while concurrently inducing the retraction of exploratory branches with only faintly labeled or no synaptic sites