10,000 publications from this institution
Hydrogen adsorption using a series of nanoporous synthetic polymers has been studied. Promising results were obtained during the screening of commercially available porous polymer beads; of the polymers considered, hypercrosslinked Hypersol-Macronet MN200 resin exhibited the highest adsorption capacity for hydrogen. This initial success triggered the development of our own high surface area hypercrosslinked materials. Subjecting gel-type and macroporous vinylbenzyl chloride-based precursors swollen in dichloroethane to a Friedel−Crafts reaction catalyzed by iron trichloride afforded beads with surface areas of 1 930 and 1 300 m2/g, respectively, as calculated using the BET equation. The former polymer reversibly stores up to 1.5 wt % H2 at a pressure of 0.12 MPa and a temperature of 77.3 K. The initial heat of adsorption of hydrogen molecules onto this polymer is 6.6 kJ/mol.
Three-periodic semiregular nets are defined as those with just one kind of vertex and one kind of edge, but excluding the five regular and one quasiregular nets described earlier. Fourteen of these and their natural tilings are described and their importance in crystal chemistry is indicated.
The optimum direction of in-plane continuous crack advance in functionally graded materials (FGMs) is discussed. The FGM is modeled using finite element analysis as a linear elastic material with spatially varying Young’s modulus. The kink direction was determined as the angle at which either the energy release is maximized (G max) or at which the kink tip is deformed without shear (K II=0). Results are found to asymptote toward that from the infinitesimal short kink analyses for homogeneous materials, based on the local gradient-adjusted phase angle but only for very short kinks. The systematic discrepancy between the finite and infinitesimal results can be accounted for by including the effect of the apparent parallel T-stress. This T-stress is affected by both the far-field parallel loading and, unlike in homogeneous materials, the far-field phase angle. The magnitude of the T-stress is, on average, greater than that for the identical geometry comprised of a homogeneous material. For kink lengths of the same order of the gradient dimension and greater, there is a divergence between the kink angles for the two criteria. In addition, there is a bifurcation in the G max results for negative far-field phase angles. This is caused by the competition between the near-tip K-dominant field and the nonsingular gradient-induced terms, which, in turn, reflects differing effects of the far-field loading and the tendency of the crack to move toward the more compliant region within the modulus gradient.
The foliage in a fully-leafed deciduous forest canopy is clumped. Consequently, theory indicates that the probability of beam penetration will be estimated more accurately with a model based on the negative binomial distribution than with a model based on the Poisson distribution, incorporating an assumption of a spherical leaf inclination angle distribution. Flux densities of photosynthetically active radiation (PAR) were measured in and above a deciduous forest canopy and were computed with the canopy radiative transfer models based on the negative binomial and Poisson distributions. These radiation values were used to compute canopy photosynthesis and stomatal conductance. Canopy photosynthesis and stomatal conductance, based on the negative binomial model, overestimated values computed from measured PAR profiles by 8 and 9%. respectively. The canopy photosynthesis and stomatal conductance values computed with the spherical Poisson model under-estimated measured values by 17 and 10%, respectively. Thus, the negative binomial radiative transfer model improves estimates of canopy photosynthesis and, to a lesser extent, stomatal conductance, inside a deciduous forest.
Abstract The Ly49 family of natural killer (NK) cell receptors are major histocompatibility complex (MHC) class I‐specific inhibitory receptors that are distributed to overlapping NK cell subsets. Extending earlier studies of polyclonal NK cell populations, we have employed an analysis of short‐term NK cell clones from Ly49A heterozygous mice, to demonstrate that the Ly49A gene is usually expressed from one or the other allele in each Ly49A + cell. However, we also detected a small percentage of clones that expressed both Ly49A alleles. The possibility that the colonies exhibiting bi‐allelic Ly49A gene expression had been inoculated with more than one cell was ruled out by parallel analysis of clones isolated from mixtures of NK cells from Ly49A homozygous mice. The frequency of bi‐allelic Ly49A + clones suggested that the two Ly49A alleles in an NK cell are chosen for expression independently. These data are consistent with the proposal that mono‐allelic Ly49A gene expression may arise as a consequence of a stochastic Ly49 gene activation mechanism. Analysis of Ly49A + clones from MHC‐different mice demonstrated that class I‐deficient mice harbored a greater number of bi‐allelic Ly49A + cells than did H‐2 d mice, which express a Ly49A ligand. Although the numbers were insufficiently large for a clear assignment, H‐2 b mice may harbor an intermediate number of bi‐allelic Ly49A + NK cells. The effects of MHC expression on the prevalence of bi‐allelic Ly49A + cells suggest that an MHC‐dependent education process modifies the Ly49 repertoire.
Abstract Review: 240 refs.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract We collect new and archival optical observations of nine “black-widow” millisecond pulsar binaries. New measurements include direct imaging with the Keck, Gemini-S, MDM, and Las Cumbres Observatory 2 m telescopes. This is supplemented by synthesized colors from Keck long-slit spectra. Four black-widow optical companions are presented here for the first time. Together these data provide multicolor photometry covering a large fraction of the orbital phase. We fit these light curves with a direct (photon) heating model using a version of the ICARUS light-curve modeling code. The fits provide distance and fill-factor estimates, inclinations, and heating powers. We compare the heating powers with the observed GeV luminosities, noting that the ratio is sensitive to pulsar distance and to the gamma-ray beaming. We make a specific correction for “outer gap” model beams, but even then some sources are substantially discrepant, suggesting imperfect beaming corrections and/or errors in the fit distance. The fits prefer large metal abundance for half of the targets, a reasonable result for these wind-stripped secondaries. The companion radii indicate substantial Roche-lobe filling, f c ≈ 0.7−1 except for PSR J0952−0607, which with f c < 0.5 has a companion density ρ ≈ 10 g cm −3 , suggesting unusual evolution. We note that the direct-heating fits imply large heating powers and rather small inclinations, and we speculate that unmodeled effects can introduce such bias.
Research Article| February 01, 1995 Variations in deformation fields during development of a large-volume magmatic arc, central Sierra Nevada, California Othmar T. Tobisch; Othmar T. Tobisch 1Earth Sciences Department, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Jason B. Saleeby; Jason B. Saleeby 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 94115 Search for other works by this author on: GSW Google Scholar Paul R. Renne; Paul R. Renne 3Institute of Human Origins, Geochronology Department, 2453 Ridge Road, Berkeley, California 94709 Search for other works by this author on: GSW Google Scholar Brendan McNulty; Brendan McNulty 4Earth Science Department, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Weixing Tong Weixing Tong 4Earth Science Department, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Author and Article Information Othmar T. Tobisch 1Earth Sciences Department, University of California, Santa Cruz, California 95064 Jason B. Saleeby 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 94115 Paul R. Renne 3Institute of Human Origins, Geochronology Department, 2453 Ridge Road, Berkeley, California 94709 Brendan McNulty 4Earth Science Department, University of California, Santa Cruz, California 95064 Weixing Tong 4Earth Science Department, University of California, Santa Cruz, California 95064 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1995) 107 (2): 148–166. https://doi.org/10.1130/0016-7606(1995)107<0148:VIDFDD>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Othmar T. Tobisch, Jason B. Saleeby, Paul R. Renne, Brendan McNulty, Weixing Tong; Variations in deformation fields during development of a large-volume magmatic arc, central Sierra Nevada, California. GSA Bulletin 1995;; 107 (2): 148–166. doi: https://doi.org/10.1130/0016-7606(1995)107<0148:VIDFDD>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Mid- to Late Cretaceous plutons in the central Sierra Nevada magmatic arc show widely preserved magmatic foliation, whereas regionally developed solid-state foliation is absent. Relatively slow cooling of these plutons and expected strain rates (10−14) suggest that the plutons were emplaced in a neutral or weakly extensional deformation regime. Domains of solid-state ductile shear of only slightly younger age than the plutons, on the other hand, indicate a contractional regime. Timing of pluton emplacement and movement on the shear zones have been constrained using Pb-U (zircon) and 40Ar/39Ar (hornblende and biotite) geochronology. Both plutons and ductile shear zones become younger toward the east. The four more westerly shear zones, which were active between ca. 100 and 90 Ma, show steeply plunging stretching lineations, whereas the most easterly and/or youngest zones, active between ca. 88 and 78 Ma, show mostly oblique and/or subhorizontal stretching lineations, indicating a change in kinematics at ca. 90 Ma.The above events define a complex deformation pattern in which strain regimes fluctuated in time and space between neutral or weak extensional and contractional. We propose a tectonic model in which thenospheric mantle corner flow produced eddy pairs in the mantle corner that transmitted a neutral or weak extensional regime to the overlying crust and facilitated the movement of granitic magma to midand upper levels, probably as dikes via fractures. Slab flattening caused the neutral or weak extensional regime to move eastward away from the trench. Increased coupling between upper and lower plates induced by the slab flattening promoted contractional strain in the cooling plutons, and domains of ductile shear formed in progressively younger plutons to the east.The above events were accompanied by an oblique convergence vector between North America and Farallon plates (Engebretson et al., 1985), which imposed a relatively small component of right-lateral shear onto the arc that increased with time. We estimate that at ca. 100 Ma the convergence vector made an angle (Φobl) ≈ 20° to the arc normal, and we suggest that around ca. 90 Ma Φobl passed through a critical value, conceivably (20° < Φoblcrit < 30°). At this juncture, the component of right-lateral shear became sufficiently large to induce significant arc-parallel strike-slip movement on the most easterly shear zones; these kinematics continued as the dominant scheme, possibly as late as ca. 78 Ma. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
SHAVEN3 (SHV3) and its homolog SHAVEN3-like 1 (SVL1) encode glycosylphosphatidylinositol (GPI)-anchored proteins (GAPs) that are involved in cellulose biosynthesis and hypocotyl elongation in Arabidopsis thaliana. In a recent report, we showed that the cellulose and hypocotyl elongation defects of the shv3svl1 double mutant are greatly enhanced by exogenous sucrose in the growth medium. Further investigation of this phenomenon showed that shv3svl1 exhibits a hyperpolarized plasma membrane (PM) proton gradient that is coupled with enhanced accumulation of sucrose via the PM sucrose/proton symporter SUC1. The resulting high intracellular sucrose concentration appears to favor starch synthesis at the expense of cellulose synthesis. Here, we describe our interpretation of these results in terms of 2 potential regulators of cellulose synthesis: intracellular sucrose concentration and a putative signaling pathway that involves SHV3-like proteins.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
