A review of hypertext in a NASA project management context

The principles of data storage, the comparative strengths of data bases, and the evolution of hypertext within this context are discussed. A classification schema of indexing and of hypertext document structures is provided. Issues associated with hypertext implementation are also discussed and potential areas for further research are indicated

Extensive evolution of cereal ribosome-inactivating proteins translates into unique structural features, activation mechanisms, and physiological roles

Ribosome-inactivating proteins (RIPs) are a class of cytotoxic enzymes that can depurinate rRNAs thereby inhibiting protein translation. Although these proteins have also been detected in bacteria, fungi, and even some insects, they are especially prevalent in the plant kingdom. This review focuses on the RIPs from cereals. Studies on the taxonomical distribution and evolution of plant RIPs suggest that cereal RIPs have evolved at an enhanced rate giving rise to a large and heterogeneous RIP gene family. Furthermore, several cereal RIP genes are characterized by a unique domain architecture and the lack of a signal peptide. This advanced evolution of cereal RIPs translates into distinct structures, activation mechanisms, and physiological roles. Several cereal RIPs are characterized by activation mechanisms that include the proteolytic removal of internal peptides from the N-glycosidase domain, a feature not documented for non-cereal RIPs. Besides their role in defense against pathogenic fungi or herbivorous insects, cereal RIPs are also involved in endogenous functions such as adaptation to abiotic stress, storage, induction of senescence, and reprogramming of the translational machinery. The unique properties of cereal RIPs are discussed in this review paper

High-pressure phase and transition phenomena in ammonia borane NH3BH3 from X-ray diffraction, Landau theory, and ab initio calculations

Structural evolution of a prospective hydrogen storage material, ammonia borane NH3BH3, has been studied at high pressures up to 12 GPa and at low temperatures by synchrotron powder diffraction. At 293 K and above 1.1 GPa a disordered I4mm structure reversibly transforms into a new ordered phase. Its Cmc21 structure was solved from the diffraction data, the positions of N and B atoms and the orientation of NH3 and BH3 groups were finally assigned with the help of density functional theory calculations. Group-theoretical analysis identifies a single two-component order parameter, combining ordering and atomic displacement mechanisms, which link an orientationally disordered parent phase I4mm with ordered distorted Cmc21, Pmn21 and P21 structures. We propose a generic phase diagram for NH3BH3, mapping three experimentally found and one predicted (P21) phases as a function of temperature and pressure, along with the evolution of the corresponding structural distortions. Ammonia borane belongs to the class of improper ferroelastics and we show that both temperature- and pressure-induced phase transitions can be driven to be of the second order. The role of N-H...H-B dihydrogen bonds and other intermolecular interactions in the stability of NH3BH3 polymorphs is examined.Comment: 23 pages, 7 figure

Genetic Mechanisms of Telencephalon Diversification Through Shifts in the Pallial-Subpallial Boundary

The vertebrate brain develops through the formation of compartments. These compartments are physically separated to allow for the proper differentiation of each structure within the brain. The telencephalon, a compartment analogous to the cerebral cortex of mammals, further subdivides once it is separated from the rest of the developing forebrain. The first division within the telencephalon splits it into the ventral and dorsal divisions, or the subpallial and pallial regions, respectively. The pallial-subpallial boundary (PSB) separates these regions to ensure proper development of each telencephalic structure. The pallium develops into memory storage and processing centers, and the subpallium further divides into the pallidum and the olfactory bulbs, which are involved in motor coordination and scent processing, respectively. Because of the different ecological niches occupied by cichlid species, they utilize certain telencephalic structures moreso than others and because of the space constraints, telencephalic morphology reflects these preferences. Mbuna species, which feed among the rocks scraping algae, utilize their sense of smell and have large olfactory bulbs. Non-mbuna species, which feed in the water column and utilize eyesight and possibly memory for recognition of prey, have larger pallial structures. These differences in structures are observed early in development shortly after the telencephalon separates from the remainder of the forebrain. Upon formation of the PSB, placement and angle of the boundary are distinctly different in mbuna and non-mbuna species. In mbuna species compared to non-mbuna species, the PSB is shifted dorsally, allowing more tissue to be allocated to the developing olfactory bulbs. The PSB is shifted ventrally in nonmbuna species to allocate more tissue to the progenitor cells that develop into the memoryx processing center and structures that process visual input. These observed shifts in the developmental boundaries within the brain may provide insight into the evolution of structures such as the cerebral cortex.Streelman, Todd - Faculty Mento

Study of Strain and Temperature Dependence of Metal Epitaxy

Metallic films are important in catalysis, magneto-optic storage media, and interconnects in microelectronics, and it is crucial to predict and control their morphologies. The evolution of a growing crystal is determined by the behavior of each individual atom, but technologically relevant structures have to be described on a time scale of the order of (at least) tenths of a second and on a length scale of nanometers. An adequate theory of growth should describe the atomistic level on very short time scales (femtoseconds), the formation of small islands (microseconds), as well as the evolution of mesoscopic and macroscopic structures (tenths of seconds). The development of efficient algorithms combined with the availability of cheaper and faster computers has turned density functional theory (DFT) into a reliable and feasible tool to study the microscopic aspects of growth phenomena (and many other complex processes in materials science, condensed matter physics, and chemistry). In this paper some DFT results for diffusion properties on metallic surfaces are presented. Particularly, we will discuss the current understanding of the influences of strain on the diffusion (energy barrier and prefactor) of a single adatom on a substrate. A DFT total energy calculation by its nature is primarily a static calculation. An accurate way to describe the spatial and temporal development of a growing crystal is given by kinetic Monte Carlo (KMC). We will describe the method and its combination with microscopic parameters obtained from ab initio calculations. It is shown that realistic ab initio kinetic Monte Carlo simulations are able to predict an evolving mesoscopic structure on the basis of microscopic details.Comment: 25 pages, 6 figures, In: ``Morphological Organisation during Epitaxial Growth and Removal'', Eds. Z. Zhang, M. Lagally. World Scientific, Singapore 1998. other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm

Comparison of the Spinels Co3O4 and NiCo2O4 as Bifunctional Oxygen Catalysts in Alkaline Media

Data from experiments with both rotating disc electrodes (RDEs) and gas diffusion electrodes (GDEs) are used to investigate the properties of the spinels, Co3O4 and NiCo2O4, as bifunctional oxygen electrocatalysts. Emphasis is placed on catalyst compositions and electrode structures free of carbon. Oxygen evolution and reduction occur at surfaces where the transition metals are in different oxidation states but the surface can be repeatedly cycled between these two states without significant change. It is shown that carbon-free, NiCo2O4 catalysed GDEs can be fabricated using structures based on stainless steel cloth or nickel foam. Those based on nickel foam can be cycled extensively and allow both O2 evolution and reduction at current densities up to 100 mA cm−2.European Commission (Theme 2010.7.3.1) Energy Storage Systems for Power Distribution NetworksMinistry of National Education, Republic of Turke

Exciton storage in type-ll quantum dots using the optical Aharonov-Bohm effect

We investigate the bright-to-dark exciton conversion efficiency in type-II quantum dots subject to a perpendicular magnetic field. To this end, we take the exciton storage protocol recently proposed by Simonin and co-workers [Phys. Rev. B 89, 075304 (2014)] and simulate its coherent dynamics. We confirm the storage is efficient in perfectly circular structures subject to weak external electric fields, where adiabatic evolution is dominant. In practice, however, the efficiency rapidly degrades with symmetry lowering. Besides, the use of excited states is likely unfeasible owing to the fast decay rates. We then propose an adaptation of the protocol which does not suffer from these limitation

Intelligent energy buildings based on RES and Nanotechnology

The paper presents the design features, the energy modelling and optical performance details of two pilot Intelligent Energy Buildings, (IEB). Both are evolution of the Zero Energy Building (ZEB) concept. RES innovations backed up by signal processing, simulation models and ICT tools were embedded into the building structures in order to implement a new predictive energy management concept. In addition, nano-coatings, produced by TiO2 and ITO nano-particles, were deposited on the IEB structural elements and especially on the window panes and the PV glass covers. They exhibited promising SSP values which lowered the cooling loads and increased the PV modules yield. Both pilot IEB units were equipped with an on-line dynamic hourly solar radiation prediction model, implemented by sensors and the related software to manage effectively the energy source, the loads and the storage or the backup system. The IEB energy sources covered the thermal loads via a south façade embedded in the wall and a solar roof which consists of a specially designed solar collector type, while a PV generator is part of the solar roof, like a compact BIPV in hybrid configuration to a small wind turbine

Compositional variation of the Zechstein Group in the Norwegian North sea: Implications for underground storage in salt caverns

Halite beds in the upper Permian Zechstein Group represent an opportunity for the future development of underground storage caverns. However, geological factors such as lithological heterogeneities, cap rock characteristics and depth can affect the sealing capacity and the integrity of the cavern or contaminate the stored fluid. The main objective of this paper is to evaluate these factors focusing on the compositional variation of the Zechstein Group in different salt structures in the Norwegian North Sea, and related opportunities and challenges for salt cavern storage. Based on deformation style, geometry, height and thickness of the salt structures, we have divided the Zechstein Group into four main categories: (1) thin beds, which can be either carbonate-anhydrite or clastic dominated. Halite is absent and therefore there is no potential for the development of salt caverns. (2 and 3) bedded to weakly deformed evaporites and intermediate size salt structures, where thick halite beds of more than 300 m are present, but they are usually deeper than 2000 m. Lithological heterogeneities in the halite consist of a mix of competent and incompetent (K-Mg salts) lithologies. (4) Tall diapirs, characterized by shallower structures (<2000 m), with large deformation and poor seismic image. Thin layers of incompetent K-Mg salts are observed in these diapirs. The composition, thickness and deformation of the cap rock vary greatly in the area. Thick halite beds are recognized in most salt structures, suggesting an opportunity for underground storage. The challenges are related to the depth of the halite, amount and type of heterogeneities, characteristics of the cap rock and deformation in the different salt structures. These results also have implications for the distribution of reservoir and source rocks, and the evolution of the Northern Permian Basin.acceptedVersio