Structure of Normal-Alkanes Adsorbed on Hexagonal-Boron Nitride

We report the structures of submonolayer films of the homologous series of normal-alkanes hexane (C₆H₁₄) to hexadecane (C₁₆H₃₄) adsorbed on the surface of hexagonal-boron nitride (h-BN), as determined by X-ray powder diffraction. These <i>n</i>-alkanes are demonstrated to form solid monolayers and exhibit structures that are similar to those seen on graphite but with some important differences. Each <i>n</i>-alkane studied shows a fully commensurate structure, even at submonolayer coverage. Hexane and octane adopt structures in which the molecules are arranged in a “herringbone” pattern (2 × <i>m</i>√3<i>a</i>_<i>bn</i> for C_<i>n</i>H_<i>n</i>+2, where <i>a</i>_<i>bn</i> is the unit cell parameter of the underlying h-BN surface, <i>n</i> = 6 or 8 and <i>m</i> = (2<i>n</i> – 2)/2). Heptane, nonane, and undecane–hexadecane adopt structures in which the molecules within adjacent lamellae are arranged with their principal axis parallel to each other (√3 × <i>ma</i>_<i>bn</i> for C_<i>n</i>H_<i>n</i>+2, where <i>n</i> = 7, 9, 11–16 and <i>m</i> = <i>n</i> + 2). Decane is a transitional case with evidence of both structure types, depending on coverage and temperature. This transitional case occurs for shorter molecules on h-BN than on graphite, indicating a difference in the relative balance of intermolecular and molecule–surface interactions that has significant implications for the phase behavior of adsorbates on these two surfaces

Composition of widgeon grass subjected to Free Ocean Carbon Enrichment within the St. Mary's River, Maryland (USA) in May-July 2010.

<p>Statistical analyses: 1, one-factor ANOVA with Holm-Sidak multiple comparisons. Letters indicate results of pairwise comparisons test <i>P</i><0.05. ^†Carbonate chemistry previously published in Arnold et al 2012. ^††Lignin analyses conducted by the Cumberland Valley Forage lab in Cumberland Co, Maryland using the methods of Goering and Van Soest (1970).</p><p>Values are means +/− SE.</p

Synthesis and Structure of Group IV Distanna[2]metallocenophanes

1,2-Dichloro-1,1,2,2-tetra-<i>tert</i>-butyldistannane reacts with 2 equiv of sodium cyclopentadienide to give a bis­(cyclopentadienyl)­distannane. Subsequent dilithiation with lithium diisopropylamide and reactions with suitable metal halides yield [(C₅H₄Sn<i>t</i>Bu₂)₂MCl₂] (M = Ti, Zr, Hf). The group 4 <i>ansa</i>-metallocenes have all been fully characterized by means of multinuclear NMR spectroscopy, elemental analysis, and X-ray diffraction

Spring water from Myora Springs emerges from a mangrove forest (A) and discharges over shallow seagrass beds in Moreton Bay, Australia, during low tides (B).

<p>Shoots of <i>Zostera muelleri</i>, collected from “near spring” sites 5–10 m from the mouth of the spring and “background” sites at distances of 30–50 m were used in pair-choice feeding trials. Clusters of shoots from each location (C) were offered as food items to juvenile black rabbitfish, <i>Siganus fuscescens</i> (D).</p

Results of paired-choice feeding trials for juvenile black rabbitfish, <i>Siganus fuscescens</i>, feeding on eelgrass, <i>Zostera muelleri</i>.

<p>Food items collected from multiple locations 5–10 m (open bar) and 30–50 m (filled bar) from the outflow of Myora Springs, North Stradbroke Island, Australia. Bars represent the mean of 10 trials each, with ±SE error bars.</p

Results of chemical analyses for above-ground tissues of eelgrass, <i>Zostera muelleri</i>, collected from multiple locations 5–10 m and 30–50 m from the outflow of Myora Springs, North Stradbroke Island, Australia.

<p>Bars represent the group means, with ±SE error bars. *indicates P<0.05.</p

Chemical characteristics of water near Myora Springs, North Stradbroke Island, Australia in April 2012.

<p>Statistical analyses: 1, one-factor ANOVA with Holm-Sidak multiple comparisons; 2, Kruskal-Wallis One Way Analysis of Variance on Ranks with Tukey or Dunns multiple comparisons; Student's t-test. ^†below detection limit, did not test.</p><p>Values are means +/− SE.</p

Composition of <i>Cymodocea nodosa</i> shoots collected at various distances from the natural CO₂ vent site from the Island of Vulcano, Italy in 2011 and 2013.

<p>Average (±SE) temperature, salinity and pH were collected on different visits from Sept 2009 to May 2011 (n = 60). Total Alkalinity (TA) was calculated from water samples collected at each site on April and November 2010 (n = 4). Statistical analyses: 1, one-factor ANOVA with Holm-Sidak multiple comparisons; 2, Kruskal-Wallis One Way Analysis of Variance on Ranks with Tukey or Dunns multiple comparisons.^†Carbonate chemistry previously published in Arnold et al 2012. ^††Lignin analyses conducted by the Cumberland Valley Forage lab in Cumberland Co, Maryland using the methods of Goering and Van Soest (1970).</p><p>Values are means +/− SE.</p

Tin-Bridged <i>ansa</i>-Metallocenes of the Late Transition Metals Cobalt and Nickel: Preparation, Molecular and Electronic Structures, and Redox Chemistry

Using the flytrap approach, paramagnetic <i>ansa</i>-metallocenes of the late transition metals cobalt and nickel containing a tetra-<i>tert</i>-butyldistannane bridge have been prepared. The complexes were identified using a combination of analytical methods (NMR, EPR, cyclic voltammetry, and X-ray crystallography) and further converted to their corresponding cations by one-electron oxidation with ferrocenium hexafluorophosphate. Spectral and structural analyses of the ionic products are consistent with metal-based oxidations

Tin-Bridged <i>ansa</i>-Metallocenes of the Late Transition Metals Cobalt and Nickel: Preparation, Molecular and Electronic Structures, and Redox Chemistry

Using the flytrap approach, paramagnetic <i>ansa</i>-metallocenes of the late transition metals cobalt and nickel containing a tetra-<i>tert</i>-butyldistannane bridge have been prepared. The complexes were identified using a combination of analytical methods (NMR, EPR, cyclic voltammetry, and X-ray crystallography) and further converted to their corresponding cations by one-electron oxidation with ferrocenium hexafluorophosphate. Spectral and structural analyses of the ionic products are consistent with metal-based oxidations