The interaction of oxygen atoms with solid surfaces at eV energies Annual status report, 1 Jun. 1968 - 31 May 1969

Interaction of oxygen atoms with solid surfaces at eV energie

Water turbidity detection using ERTS-1 imagery

ERTS-1 images of two federal reservoirs in Kansas exhibit good correlation with suspended load. The major reservoirs in Kansas, as well as in other Great Plains states, are playing increasingly important roles in flood control, recreation, agriculture, and urban water supply. Satellite imagery may prove useful for acquiring timely low cost water quality data required for optimum management of these fresh water resources

Yes, But...Ruminations on Discounted Membership and Reference Group Rationalizations

Reference group theory posits that people attempt to identify themselves with groups that are esteemed in order to enhance their sense of self-worth. However, it is not uncommon that actors may find themselves being identified with, or identifying with, stigmatized groups or categories. In order to avoid the personally pejorative implications of these associations, these actors often engage in various strategies that take a form similar to accounts which attempt to neutralize possible stigma. Two fundamental normalizations, disidentification and deflected stigma are presented and compared to previous articulations in the literature of stigma management

Coherent Excitation of the 6S1/2 to 5D3/2 Electric Quadrupole Transition in 138Ba+

The electric dipole-forbidden, quadrupole 6S1/2 5D3/2 transition in Ba+ near 2051 nm, with a natural linewidth of 13 mHz, is attractive for potential observation of parity non-conservation, and also as a clock transition for a barium ion optical frequency standard. This transition also offers a direct means of populating the metastable 5D3/2 state to measure the nuclear magnetic octupole moment in the odd barium isotopes. Light from a diode-pumped, solid state Tm,Ho:YLF laser operating at 2051 nm is used to coherently drive this transition between resolved Zeeman levels in a single trapped 138Ba+ ion. The frequency of the laser is stabilized to a high finesse Fabry Perot cavity at 1025 nm after being frequency doubled. Rabi oscillations on this transition indicate a laser-ion coherence time of 3 ms, most likely limited by ambient magnetic field fluctuations.Comment: 5 pages, 5 figure

Mitigation of traffic-induced bridge vibrations through passive and semi-active control devices

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 51-52).Many of the U.S. bridges today are reaching or have reached their design life and are beginning to deteriorate and are becoming structurally deficient. Much time, effort, money, and resources go into repairing, rehabilitating, or reconstructing these bridges. Therefore, investigation into valid solutions to extending the safe life of these structures is of utmost importance. A major cause of bridge deterioration is stresses and fatigue induced in the bridge from traffic loading. This paper explores and investigates methods of mitigating traffic-induced bridge vibrations through the integration of control devices to extend the service life of bridges. There are three main classes of structural control devices: passive, semi-active, and active control. Each control scheme has advantages and disadvantages which are discussed in this thesis. To gain a better understanding of both passive and semi-active control strategies, a computer simulation is conducted. The computer simulation allows for a better comparison between passive and semi-active control schemes. The finding from the simulation shows a semi-active control strategy outperforming a passive strategy. The semi-active scheme reduces maximum midspan deflections by 20%, while the passive has a reduction of 12%.by Amy R. Magnuson.M.Eng

Electronic structure investigation of the cubic inverse perovskite Sc3AlN

The electronic structure and chemical bonding of the recently discovered inverse perovskite Sc3AlN, in comparison to ScN and Sc metal have been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured Sc L, N K, Al L1, and Al L2,3 emission spectra are compared with calculated spectra using first principle density-functional theory including dipole transition matrix elements. The main Sc 3d - N 2p and Sc 3d - Al 3p chemical bond regions are identified at -4 eV and -1.4 eV below the Fermi level, respectively. A strongly modified spectral shape of 3s states in the Al L2,3 emission from Sc3AlN in comparison to pure Al metal is found, which reflects the Sc 3d - Al 3p hybridization observed in the Al L1 emission. The differences between the electronic structure of Sc3AlN, ScN, and Sc metal are discussed in relation to the change of the conductivity and elastic properties.Comment: 11 pages, 5 picture

Electronic structure and chemical bonding in Ti2AlC investigated by soft x-ray emission spectroscopy

The electronic structure of the nanolaminated transition metal carbide Ti2AlC has been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured Ti L, C K and Al L emission spectra are compared with calculated spectra using ab initio density-functional theory including dipole matrix elements. The detailed investigation of the electronic structure and chemical bonding provides increased understanding of the physical properties of this type of nanolaminates. Three different types of bond regions are identified; the relatively weak Ti 3d - Al 3p hybridization 1 eV below the Fermi level, and the Ti 3d - C 2p and Ti 3d - C 2s hybridizations which are stronger and deeper in energy are observed around 2.5 eV and 10 eV below the Fermi level, respectively. A strongly modified spectral shape of the 3s final states in comparison to pure Al is detected for the buried Al monolayers indirectly reflecting the Ti 3d - Al 3p hybridization. The differences between the electronic and crystal structures of Ti2AlC, Ti3AlC2 and TiC are discussed in relation to the number of Al layers per Ti layer in the two former systems and the corresponding change of the unusual materials properties.Comment: 14 pages, 7 figures; PACS:78.70.En, 71.15.Mb, 71.20.-

Operational development of small plant growth systems

The results of a study undertaken on the first phase of an empricial effort in the development of small plant growth chambers for production of salad type vegetables on space shuttle or space station are discussed. The overall effort is visualized as providing the underpinning of practical experience in handling of plant systems in space which will provide major support for future efforts in planning, design, and construction of plant-based (phytomechanical) systems for support of human habitation in space. The assumptions underlying the effort hold that large scale phytomechanical habitability support systems for future space stations must evolve from the simple to the complex. The highly complex final systems will be developed from the accumulated experience and data gathered from repetitive tests and trials of fragments or subsystems of the whole in an operational mode. These developing system components will, meanwhile, serve a useful operational function in providing psychological support and diversion for the crews

Puzzling It Out: The Current State of Scientific Knowledge on Pre-Kindergarten Effects - A Consensus Statement

Scientific research has established that if all children are to achieve their developmental potential, it is important to lay the foundation during the earliest years for lifelong health, learning, and positive behavior. A central question is how well our public pre-kindergarten (pre-K) programs are doing to build this foundation.Forty-two states and the District of Columbia, through 57 pre-K programs, have introduced substantial innovations in their early education systems by developing the infrastructure, program sites, and workforce required to accommodate pre-K education. These programs now serve nearly 30 percent of the nation's 4-year-olds and 5 percent of 3-year-olds