ALBERT

Description: The new mineral canutite (IMA2013-070), NaMn 3 [AsO 4 ][AsO 3 (OH)] 2 , was found at two different locations at the Torrecillas mine, Salar Grande, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with anhydrite, halite, lavendulan, magnesiokoritnigite, pyrite, quartz and scorodite. Canutite is reddish brown in colour. It forms as prisms elongated on [201I] and exhibiting the forms {010}, {100}, {102}, {201} and {102I}, or as tablets flattened on {102} and exhibiting the forms {102} and {110}. Crystals are transparent with a vitreous lustre. The mineral has a pale tan streak, Mohs hardness of 21/2, brittle tenacity, splintery fracture and two perfect cleavages, on {010} and {101}. The calculated density is 4.112 g cm –3 . Optically, canutite is biaxial (+) with α = 1.712(3), β = 1.725(3) and = 1.756(3) (measured in white light). The measured 2V is 65.6(4)°, the dispersion is r 〈 v (slight), the optical orientation is Z = b ; X ^ a = 18° in obtuse β and pleochroism is imperceptible. The mineral is slowly soluble in cold, dilute HCl. The empirical formula (for tabular crystals from near the mine shaft), determined from electron-microprobe analyses, is (Na 1.05 Mn 2.64 Mg 0.34 Cu 0.14 Co 0.03 ) 4.20 As 3 O 12 H 1.62 . Canutite is monoclinic, C 2/ c , a = 12.3282(4), b = 12.6039(5), c = 6.8814(5) Å, β = 113.480(8)°, V = 980.72(10) Å 3 and Z = 4. The eight strongest X-ray powder diffraction lines are [ d obs Å( I )( hkl )]: 6.33(34)(020), 4.12(26)(2I21), 3.608(29)(310,1I31), 3.296(57)(1I12), 3.150(28)(002,131), 2.819(42)(400,041,330), 2.740(100)(240,4I02,112) and 1.5364(31)(multiple). The structure, refined to R 1 = 2.33% for 1089 F o 〉 4 F reflections, shows canutite to be isostructural with protonated members of the alluaudite group.

Description: Langmuir DOI: 10.1021/acs.langmuir.7b02805

Description: Hydrothermal treatment of quartz with 2 m K 2 CO 3 solutions at 623 K and 1 kbar resulted in the formation of single crystals of the monoclinic polymorph of potassium hydrogen disilicate (KHSi 2 O 5 or KSi 2 O 4 (OH)). Basic crystallographic data of this so-called phase I at room conditions are as follows: space group C 2/ m, a = 14.5895(10) Å, b = 8.2992(3) Å, c = 9.6866(7) Å, β = 122.756(10)°, V = 986.36(10) Å 3 , Z = 8. The structure was determined by direct methods and refined to a residual of R(|F|) = 0.0224 for 892 independent observed reflections with I 〉 2( I ). The compound belongs to the group of chain silicates. It is based on crankshaft-like vierer double-chains running parallel to [010]. The H atoms are associated with silanol groups. Hydrogen bonding between neighbouring double-chains results in the formation of ~5 Å wide slabs. The three crystallographically independent K cations with six to eight O ligands provide linkage (1) between the chains of a single slab or (2) between adjacent slabs. Structural investigations have been supplemented by micro-Raman spectroscopy. The interpretation of the spectroscopic data including the allocation of the bands to certain vibrational species has been aided by DFT calculations.

Description: Honeaite, ideal formula Au 3 TlTe 2 , is a new mineral from the late Archaean Karonie gold deposit, Eastern Goldfields province, Western Australia. Honeaite is found with native gold, tellurobismuthite, petzite, hessite, calaverite, melonite, mattagamite, frohbergite, altaite, pyrrhotite and molybdenite. These minerals are concentrated in microvughs and microfractures mainly within areas of prehnite alteration of amphibolite. The mineralisation appears to have been deposited under greenschist-facies conditions at lower temperatures than most gold deposits in the Eastern Goldfields. Single-crystal X-ray studies identified the structure of honeaite as orthorhombic, space group Pbcm , and unit cell parameters a = 8.9671 (4) Å, b = 8.8758(4) Å, c = 7.8419(5) Å, V = 624.14(6) Å 3 ( Z = 4). The strongest reflections of the calculated powder X-ray diffraction pattern are [ d in Å ( I rel )( hkl )]: 2.938(100)(022), 2.905 (39,8)(322, 411), 2.989 (31)(300), 2.833 (23)(310), 1.853 (17)(332). Electron-microprobe analysis (EDS mode) gave (wt%) Au 56.33, Tl 19.68, Te 24.30, total 100.31, leading to an empirical formula (based on 2 Te apfu ) of Au 3.00 Tl 1.01 Te 2.00 . Honeaite is black with a metallic lustre and no observed cleavage. The calculated density is 11.18 g/cm 3 . In reflected plane-polarized light it is slightly bluish grey. Between crossed polars it is weakly anisotropic with dark brown to dark blue rotation tints. Reflectance values in air and in oil are given. Honeaite is named after the late Russell M. Honea (1929–2002).

Description: The characteristic properties of graphene make it useful in an assortment of applications. One particular application—the use of graphene in biosensors—requires a thorough understanding of graphene-peptide interactions. In this study, the binding of glycine (G) capped amino acid residues (termed GXG tripeptides) to trilayer graphene surfaces in aqueous solution was examined and compared to results previously obtained for peptide binding to single-layer free-standing graphene [A. N. Camden, S. A. Barr, and R. J. Berry, J. Phys. Chem. B 117 , 10691–10697 (2013)]. In order to understand the interactions between the peptides and the surface, binding enthalpy and free energy values were calculated for each GXG system, where X cycled through the typical 20 amino acids. When the GXG tripeptides were bound to the surface, distinct conformations were observed, each with a different binding enthalpy. Analysis of the binding energy showed the binding of peptides to trilayer graphene was dominated by van der Waals interactions, unlike the free-standing graphene systems, where the binding was predominantly electrostatic in nature. These results demonstrate the utility of computational materials science in the mechanistic explanation of surface-biomolecule interactions which could be applied to a wide range of systems.

Description: Mountain snowpacks provide most of the annual discharge of western U.S. rivers, but the future of water resources in the western U.S. is tenuous, as climatic changes have resulted in earlier spring melts that have exacerbated summer droughts. Compounding changes to the physical environment are biotic disturbances including the mountain pine beetle (MPB), which has decimated millions of acres of western North American forests. At the watershed scale, MPB disturbance increases the peak hydrograph, and at the stand scale the ‘gray’ phase of MPB canopy disturbance decreases canopy snow interception, increases snow albedo, increases net shortwave radiation and decreases net longwave radiation versus the ‘red’ phase. Fewer studies have been conducted on the red phase of MPB disturbance, and in the mixed coniferous stands that may follow MPB-damaged forests. We measured the energy balance of four snowpacks representing different stages of MPB damage, management, and recovery: a lodgepole pine stand, a MPB-infested stand in the red phase, a mixed coniferous stand (representing one successional trajectory), and a clearcut (representing reactive management) in the Tenderfoot Creek Experimental Forest in Montana, USA. Net longwave radiation was lower in the MPB-infested stand despite higher basal area and plant area index of the other forests, suggesting that the dessicated needles serve as a less effective thermal buffer against longwave radiative losses. Eddy covariance observations of sensible and latent heat flux indicate that they are of similar but opposite magnitude, on the order of 20 MJ m −2 during the melt period. Further analyses reveal that net turbulent energy fluxes were near zero due to the temperature and atmospheric vapor pressure encountered during the melt period. Future research should place snow science in the context of forest succession and management, and address important uncertainties regarding the timing and magnitude of needlefall events. This article is protected by copyright. All rights reserved.

Description: The characteristic properties of graphene make it useful in an assortment of applications. One particular application—the use of graphene in biosensors—requires a thorough understanding of graphene-peptide interactions. In this study, the binding of glycine (G) capped amino acid residues (termed GXG tripeptides) to trilayer graphene surfaces in aqueous solution was examined and compared to results previously obtained for peptide binding to single-layer free-standing graphene [A. N. Camden, S. A. Barr, and R. J. Berry, J. Phys. Chem. B 117 , 10691–10697 (2013)]. In order to understand the interactions between the peptides and the surface, binding enthalpy and free energy values were calculated for each GXG system, where X cycled through the typical 20 amino acids. When the GXG tripeptides were bound to the surface, distinct conformations were observed, each with a different binding enthalpy. Analysis of the binding energy showed the binding of peptides to trilayer graphene was dominated by van der Waals interactions, unlike the free-standing graphene systems, where the binding was predominantly electrostatic in nature. These results demonstrate the utility of computational materials science in the mechanistic explanation of surface-biomolecule interactions which could be applied to a wide range of systems.

Description: Due to iron’s role in oceanic primary production, there has been great interest in quantifying the importance of Fe in regions where concentrations are very low and macronutrients, nitrate and phosphate, are available. Measurements of filterable (i.e., 〈0.4 μm) Fe concentrations in streams from Taylor Valley, McMurdo Dry Valleys, Antarctica, suggest that coastal-zone stream Fe input to the Southern Ocean could potentially play an important role in primary production in nearshore regions. Filterable Fe (fFe) data from streams in the McMurdo Dry Valleys were used to represent glacier meltwater that flows through ice-free landscape with the potential of transporting Fe to the Antarctic coastal zone. Estimates of potential fFe flux to the Antarctic Peninsula region using our mean fFe concentration of 10.6 µg L –1 combined with an estimate of ice-free area for the Antarctic Peninsula result in an fFe flux of 1.2 x 10 7 g yr –1 . Although small compared to iceberg and aeolian Fe fluxes, future stream input to the Southern Ocean could increase due to glacier retreat and melting, thus increasing the fFe flux from glacier meltwater streams.

Description: Author(s): Bethany R. Wilcox, Benjamin M. Zwickl, Robert D. Hobbs, John M. Aiken, Nathan M. Welch, and H. J. Lewandowski A centralized model for the administration and analysis of research-based assessments. [Phys. Rev. Phys. Educ. Res. 12, 010139] Published Fri Jun 17, 2016

Description: Natural resource management and education must account for both the natural and human components of a complex system, yet examples of such interdisciplinary approaches are still relatively rare, especially in education. This study discusses a graduate seminar on water management, developed from an interdisciplinary National Science Foundation (NSF) grant. The seminar applied constructivist pedagogy which is not only best suited for interdisciplinary work, but also allows flexibility to redesign the course components and deliverables after each evaluation cycle. While the seminar was a successful experiment, several challenges remain when implementing such courses. These challenges include not only the organization and assessment of course deliverables, but also fitting such courses into the administrative structure of the university when represented disciplines are located in several colleges across campus.