On the spectra of coronal ions connected with sp3-configurations <o spektrakh koronal'nykh ionov svyazannykh s konfiguratsiami sp3<
Ultraviolet spectra and transition probabilities for coronal ions
ULTRAVIOLET SPECTRUM↗
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Results for “SP3”
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Gap junctional communication modulates gene transcription by altering the recruitment of Sp1 and Sp3 to connexin-response elements in osteoblast promoters
Loss-of-function mutations of gap junction proteins, connexins, represent a mechanism of disease in a variety of tissues. We have shown that recessive (gene deletion) or dominant (connexin45 overexpression) disruption of connexin43 function results in osteoblast dysfunction and abnormal expression of osteoblast genes, including down-regulation of osteocalcin transcription. To elucidate the molecular mechanisms of gap junction-sensitive transcriptional regulation, we systematically analyzed the rat osteocalcin promoter for sensitivity to gap junctional intercellular communication. We identified an Sp1/Sp3 containing complex that assembles on a minimal element in the -70 to -57 region of the osteocalcin promoter in a gap junction-dependent manner. This CT-rich connexin-response element is necessary and sufficient to confer gap junction sensitivity to the osteocalcin proximal promoter. Repression of osteocalcin transcription occurs as a result of displacement of the stimulatory Sp1 by the inhibitory Sp3 on the promoter when gap junctional communication is perturbed. Modulation of Sp1/Sp3 recruitment also occurs on the collagen Ialpha1 promoter and translates into gap junction-sensitive transcriptional control of collagen Ialpha1 gene expression. Thus, regulation of Sp1/Sp3 recruitment to the promoter may represent a potential general mechanism for transcriptional control of target genes by signals passing through gap junctions.
Non-NASA Center↗
Consequences of sp2–sp3 boron isomerization in supercooled liquid borates
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O. L. G. Alderman↗
JPL IGS Analysis Center Report, 2001-2003
Three GPS orbit and clock products are currently provided by JPL for consideration by the IGS. Each differs in its latency and quality, with later results being more accurate. Results are typically available in both IGS and GIPSY formats via anonymous ftp. Current performance based on comparisons with the IGS final products is summarized. Orbit performance was determined by computing the 3D RMS difference between each JPL product and the IGS final orbits based on 15 minute estimates from the sp3 files. Clock performance was computed as the RMS difference after subtracting a linear trend based on 15 minute estimates from the sp3 files.
Heflin, M. B.↗
The Conductance of Nanotubes Deformed by the AFM Tip
The conductance drop under AFM-tip deformation can be explained by stretching of the tube length. NT sensors can be built utilizing uniform stretching. Single sp3 bond cross section cannot block electrons, because another conducting path may exist. AFM tip which forms sp3 bonds with the tube will decrease conductance. In the "table experiment" a conductance drop of 2 orders of magnitude happened only after some bonds were broken.
Svizhenko, Alexei↗
Two-electron bond-orbital model, 2
The two-electron bond-orbital model of tetrahedrally-coordinated solids is generalized and its application extended. All intrabond matrix elements entering the formalism are explicitly retained, including the direct overlap S between the anion and cation sp3 hybrid wavefunctions. Complete analytic results are obtained for the six two-electron eigenvalues and eigenstates of the anion-cation bond in terms of S, one-electron parameters V2 and V3, and two-electron correlation parameters V4, V5 and V6. Refined formulas for the dielectric constant and the nuclear exchange and pseudodipolar coefficients, as well as new expressions for the valence electron density, polarity of the bond and the cohesive energy, are then derived. The theory gives a good account of the experimentally observed trends in all properties considered and approximate quantitative agreement is achieved for the pseudodipolar coefficient.
Huang, C.↗
Laser/Plasma/Chemical-Vapor Deposition Of Diamond
Proposed process for deposition of diamond films includes combination of plasma induced in hydrocarbon feed gas by microwave radiation and irradiation of plasma and substrate by lasers. Deposition of graphite suppressed. Reaction chamber irradiated at wavelength favoring polymerization of CH2 radical into powders filtered out of gas. CH3 radicals, having desired sp3 configuration, remains in gas to serve as precursors for deposition. Feed gas selected to favor formation of CH3 radicals; candidates include CH4, C2H4, C2H2, and C2H6. Plasma produced by applying sufficient power at frequency of 2.45 GHz and adjusting density of gas to obtain electron kinetic energies around 100 eV in low-pressure, low-temperature regime.
Hsu, George C.↗
Ferric chloride graphite intercalation compounds prepared from graphite fluoride
The reaction between graphite fluoride and ferric chloride was observed in the temperature range of 300 to 400 C. The graphite fluorides used for this reaction have an sp3 electronic structure and are electrical insulators. They can be made by fluorinating either carbon fibers or powder having various degrees of graphitization. Reaction is fast and spontaneous and can occur in the presence of air. The ferric chloride does not have to be predried. The products have an sp2 electronic structure and are electrical conductors. They contain first stage FeCl3 intercalated graphite. Some of the products contain FeCl2*2H2O, others contain FeF3 in concentrations that depend on the intercalation condition. The graphite intercalated compounds (GIC) deintercalated slowly in air at room temperature, but deintercalated quickly and completely at 370 C. Deintercalation is accompanied by the disappearing of iron halides and the formation of rust (hematite) distributed unevenly on the fiber surface. When heated to 400 C in pure N2 (99.99 vol %), this new GIC deintercalates without losing its molecular structure. However, when the compounds are heated to 800 C in quartz tube, they lost most of its halogen atoms and formed iron oxides (other than hematite), distributed evenly in or on the fiber. This iron-oxide-covered fiber may be useful in making carbon-fiber/ceramic-matrix composites with strong bonding at the fiber-ceramic interface.
Hung, Ching-Cheh↗
The 3.2-3.6 micron spectra of monoceros R2/IRS-3 and Elias 16
We have obtained 3.2-3.6 micron spectra, with a resolution lambda/delta-lambda approximately 750, of the protostar Mon R2/IRS-3 and of Elias 16, a background K giant behind the Taurus molecular cloud. A feature at 3,482 microns (2872/cm), with a full width at half-maximum of 0.09 microns (76/cm), is clearly seen in Mon R2/IRS-3. This feature is not detected in Elias 16. The 3.482 micron feature in Mon R2/IRS-3 is similar to a feature at 3.466-3.478 microns (2875-2885/cm) detected by Allamandola et al. in four protostars and attributed by these authors to a CH stretch in hydrocarbons dominated by sp3-bonded carbon. Neither Mon R2/IRS-3 nor Elias 16 shows absorption at 3.540 microns (2825/cm), which has been detected in two of the four protostars observed by Allamandola et al. and attributed by them to CH3OH ice. Our limit on CH3OH ice toward Elias 16 is compared to models of gas-grain chemistry in dark clouds. Our results confirm those of Allamandola et al. that at this resolution the 3.4 micron absorption due to dust in molecular clouds has very different spectral structure than that due to dust in the diffuse interstellar medium.
Sellgren, K.↗
Modeling of the Electro-Mechanical Response of Carbon Nanotubes: Molecular Dynamics and Transport Calculations
This paper presents viewgraphs on the modeling of the electromechanical response of carbon nanotubes, utilizing molecular dynamics and transport calculations. The topics include: 1) Simulations of the experiment; 2) Effect of diameter, length and temperature; and 3) Study of sp3 coordination-"The Table experiment".
Svizhenko, Alexel↗
A Dynamic Pathway for Stone-Wales Bond Rotation on Carbon Nanotubes through Diamond-Like Bonds
A new lower energy barrier with a two-step pathway of Stone-Wales (SW) ,ond rotation on carbon nanotubes (CNTs) is found through molecular dynamics (MD) simulations of CNTs under tension. The first step involves going over to a stable sp3-like metastable configuration with half rotated and partially tilted C-C bond. The second step involves going over to the fully rotated C-C bond with the formation of a SW defect in the nanotube. The energy barrier for this two-step dynamic pathway is significantly lower than the previously known static barrier for in-plane rotation of the C-C bond on a tensile strained (> 4%) CNT.
Wei, Chen-Yu↗
The Failure of Correlation to Describe Out-of-Plane Carbon=Carbon Bending
Carbon-carbon multiply bonded systems are improperly described with standard correlation methods and basis sets. For computations of vibrational modes, the out-of- plane bends can be reported as imaginary at worst or simply too low at best. Utilizing the simplest of aromatic structures (cyclopropenylidene) and various levels of theory, this work diagnoses this known behavior for the first time. A combined 1-particle and n-particle basis set effect conspire to produce these non-physical results. When moving from sp2 to sp3 hybridization in the carbon atoms, the larger number of basis functions overcorrects the energy. This is exacerbated by correlation methods. These allow for occupation of the π and π∗ orbitals in the expanded wave function that combine with the hydrogen s orbitals. As a result, the improperly described space can be further and non-physically stabilized by post-Hartree-Fock correlation. This represents a fundamental problem with at least Hartree-Fock based methods of all flavors in describing carbon. Beyond being a flaw in quantum chemical theory, other repercussions will be present in computations regarding spectroscopy as well as energy and environmental studies where highly-accurate hydrocabon vibrational transitions or thermochemical data are needed.
Fortenberry, Ryan C.↗
NASA 2009 Body of Knowledge (BoK) carbon nanotube technology
The nature of the bonding of a nanotube is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than the sp3 bonds found in diamonds, provides the molecules with their unique strength. Nanotubes naturally align themselves into "ropes" held together by Van der Waals forces. Under high pressure, nanotubes can merge together, trading some sp² bonds for sp³ bonds, giving the possibility of producing strong, unlimited-length wires through high-pressure nanotube linking. This document looks at the topic of carbon nanotubes as it applies to microelectronics packaging and assembly.
Gerke, David↗