Detritylation by silicic acid boric acid column chromatography

Chromatography on silicic acid-boric acid columns permits detritylation of ester lipids, essentially without acyl migration, and simultaneous separation of the reaction products. Described is the preparation of the column and its application for the synthesis of diacyl-sn-glycerols and 2-acyl-1,2-propaneiols. Presented in part at the Canadian Federation of Biological Societies Annual Meeting in Toronto, June 1971.     

Remote mobile manipulation with the centauro robot: Full‐body telepresence and autonomous operator assistance

Solving mobile manipulation tasks in inaccessible and dangerous environments is an important application of robots to support humans. Example domains are construction and maintenance of manned and unmanned stations on the moon and other planets. Suitable platforms require flexible and robust hardware, a locomotion approach that allows for navigating a wide variety of terrains, dexterous manipulation capabilities, and respective user interfaces. We present the CENTAURO system which has been designed for these requirements and consists of the Centauro robot and a set of advanced operator interfaces with complementary strength enabling the system to solve a wide range of realistic mobile manipulation tasks. The robot possesses a centaur‐like body plan and is driven by torque‐controlled compliant actuators. Four articulated legs ending in steerable wheels allow for omnidirectional driving as well as for making steps. An anthropomorphic upper body with two arms ending in five‐finger hands enables human‐like manipulation. The robot perceives its environment through a suite of multimodal sensors. The resulting platform complexity goes beyond the complexity of most known systems which puts the focus on a suitable operator interface. An operator can control the robot through a telepresence suit, which allows for flexibly solving a large variety of mobile manipulation tasks. Locomotion and manipulation functionalities on different levels of autonomy support the operation. The proposed user interfaces enable solving a wide variety of tasks without previous task‐specific training. The integrated system is evaluated in numerous teleoperated experiments that are described along with lessons learned.     

Experimental study of the Ca–Mg–Zn system using diffusion couples and key alloys

Nine diffusion couples and 32 key samples were prepared to map the phase diagram of the Ca–Mg–Zn system. Phase relations and solubility limits were determined for binary and ternary compounds using scanning electron microscopy, electron probe microanalysis and x-ray diffraction (XRD). The crystal structure of the ternary compounds was studied by XRD and electron backscatter diffraction. Four ternary intermetallic (IM) compounds were identified in this system: Ca₃Mg_xZn_15−x (4.6 ⩽ x ⩽ 12 at 335 °C, IM1), Ca_14.5Mg_15.8Zn_69.7 (IM2), Ca₂Mg₅Zn₁₃ (IM3) and Ca_1.5Mg_55.3Zn_43.2 (IM4). Three binary compounds were found to have extended solid solubility into ternary systems: CaZn₁₁, CaZn₁₃ and Mg₂Ca form substitutional solid solutions where Mg substitutes for Zn atoms in the first two compounds, and Zn substitutes for both Ca and Mg atoms in Mg₂Ca. The isothermal section of the Ca–Mg–Zn phase diagram at 335 °C was constructed on the basis of the obtained experimental results. The morphologies of the diffusion couples in the Ca–Mg–Zn phase diagram at 335 °C were studied. Depending on the terminal compositions of the diffusion couples, the two-phase regions in the diffusion zone have either a tooth-like morphology or contain a matrix phase with isolated and/or dendritic precipitates.     

Reversible Switching Phenomenon in Diarylethene Molecular Devices with Reduced Graphene Oxide Electrodes on Flexible Substrates

Photoswitching molecular electronic devices with reduced graphene oxide (rGO) top electrodes on flexible substrates are fabricated and characterized. It has been reported previously that diarylethene molecular devices with poly‐(3,4‐ethylenedioxythiophene) stabilized with poly‐(4‐styrenesulfonic acid)/Au top electrodes can hold two stable electrical conductance states when the devices are exposed to UV or visible light during device fabrication. However, those devices fail to show the reversible switching phenomenon in response to illumination after device fabrication. By employing conducting and transparent rGO top electrodes, it is demonstrated that the diarylethene molecular devices show a reversible switching phenomenon, i.e., the fabricated devices change their conductance state in response to the alternating illumination with UV and visible light. Furthermore, the molecular devices with rGO top electrodes also exhibit good longtime stability and reliable electrical characteristics when subjected to various mechanical stresses (bending radius down to 5 mm and bending cycle over 10⁴).     

Dielectric Relaxation Processes,Electronic Structure,and Band Gap Engineering of MFU‐4‐type Metal‐Organic Frameworks: Towards a Rational Design of Semiconducting Microporous Materials

The electronic structures and band gaps of MFU‐4‐type metal‐organic frameworks can be systematically engineered leading to a family of isostructural microporous solids. Electrical properties of the microcrystalline samples are investigated by temperature‐dependent broad‐band dielectric and optical spectroscopy, which are corroborated by full band structure calculations performed for framework and cluster model compounds at multiple levels of density functional theory. The combined results glean a detailed picture of relative shifts and dispersion of molecular orbitals when going from zero‐dimensional clusters to three‐dimensional periodic solids, thus allowing to develop guidelines for tailoring the electronic properties of this class of semiconducting microporous solids via a versatile building block approach. Thus, engineering of the band gap in MFU‐4 type compounds can be achieved by adjusting the degree of conjugation of the organic ligand or by choosing an appropriate metal whose partially occupied d‐orbitals generate bands below the LUMO energy of the ligand which, for example, is accomplished by octahedral Co(II) ions in Co‐MFU‐4.     

Biomimetic Pathways for Nanostructured Poly(KAMPS)/aragonite Composites that Mimic Seashell Nacre

Complex microstructures of biominerals such as seashell nacre, bone, and teeth are awe‐inspiring. Nature has devised schemes to combine hard inorganic platelets of aragonite (CaCO₃) and an organic matrix that produce tough biocomposites. The ability of the organic‐inorganic components to “slide” internally leads to the toughening of the materials, though a recreation of this system at the nanoscale has yet to be shown. Here, we implement a poly(KAMPS)‐based assembly, which is carried out entirely from dilute aqueous solutions of the materials to create a “brick and mortar”‐type aragonite structure that mimics the platelet sliding and exhibits toughening. The negatively charged poly(KAMPS) chains are attracted to the positively charged divalent cations, by which addition of NaHCO₃ to an aqueous mixture of Ca²⁺‐poly(KAMPS), results in the growth of aragonite nanorods with a width of 120 nm. The reversible nature of the physical gel formation of poly(KAMPS) in solution results in adhesion of the nanorods into a microscale structure. The new nacre‐like carbonate composite, has a modulus (44 GPa) and hardness (2.8 GPa) on a similar order as to that of nacre and other bio‐composites, exhibits limited creep, and demonstrates a mechanism with nanoscale deformation.     

Synthesis of ultrabright nanoporous fluorescent silica discoids using an inorganic silica precursor

The templated sol-gel synthesis of ultrabright fluorescent nanoporous silica particles based on the use of organic silica sources has previously been reported. The use of organosilanes as the main silica precursors has a number of issues, in particular, the low robustness of the synthesis due to instability of the organic silica source. Here we report on a novel synthesis of ultrabright fluorescent nanoporous silica discoids (a specific shape in-between the sphere and disk) of 3.1 ± 0.7 microns in size, which were prepared using a stable inorganic sodium silicate silica source. Organic fluorescent dye Rhodamine 6G (R6G) was physically (non-covalently) entrapped inside cylindrical nanochannels of ～4-5 nm in diameter. In contrast to the synthesis with organic silica precursors, the obtained particles showed an excessive leakage of dye. To prevent this leakage, we modified the synthesis by adding a small amount of a secondary silica source. The synthesized particles show virtually no leakage, high photostability, and a brightness equivalent to the fluorescence of up to 7 × 10(7) free R6G molecules. This is about 7 times higher than the fluorescent brightness of particles of the same size made of CdSe/ZnS quantum dots, and 420 times higher than the brightness of the same volume of aqueous solution of free R6G dye.     

Modelling nitrogen transformations in waters receiving mine effluents

This paper presents a biogeochemical model developed for a clarification pond receiving ammonium nitrogen rich discharge water from the Boliden concentration plant located in northern Sweden. Present knowledge about nitrogen (N) transformations in lakes is compiled in a dynamic model that calculates concentrations of the six N species (state variables) ammonium-N (N_am), nitrate-N (N_ox), dissolved organic N in water (N_org), N in phytoplankton (N_pp), in macrophytes (N_mp) and in sediment (N_sed). It also simulates the rate of 16 N transformation processes occurring in the water column and sediment as well as water-sediment and water-atmosphere interactions. The model was programmed in the software Powersim using 2008 data, whilst validation was performed using data from 2006 to 2007. The sensitivity analysis showed that the state variables are most sensitive to changes in the coefficients related to the temperature dependence of the transformation processes. A six-year simulation of N_am showed stable behaviour over time. The calibrated model rendered coefficients of determination (R²) of 0.93, 0.79 and 0.86 for N_am, N_ox and N_org, respectively. Performance measures quantitatively expressing the deviation between modelled and measured data resulted in values close to zero, indicating a stable model structure. The simulated denitrification rate was on average five times higher than the ammonia volatilisation rate and about three times higher than the permanent burial of N_sed and, hence, the most important process for the permanent removal of N. The model can be used to simulate possible measures to reduce the nitrogen load and, after some modification and recalibration, it can be applied at other mine sites affected by N rich effluents.     

Synthesis of C-18 mixed acid diacyl-sn-glycerol enantiomers

Procedures have been developed for the synthesis of both enantiomeric forms of mixed fatty acid, saturated and polyunsaturated 1,2-diacyl-sn-glycerols and 2,3-diacyl-sn-glycerols from D-mannitol as starting material. The following diacyl-sn-glycerols have been synthesized: 1-Stearoyl-2-linoleoyl-sn-glycerol, 1-stearoyl-2-linolenoyl-sn-glycerol, 2-linoleoyl-3-stearoyl-sn-glycerol and 2-linolenoyl-3-oleoyl-sn-glycerol. Their specific rotations, refractive indices, densities, solubilities, carbon and hydrogen analysis and iodine values have been reported. Presented in part at the ISF-AOCS World Congress, Chicago, September 1970.