The electronic Raman spectrum of cobalt doped MgO

The energies of the ⁴T_1g states of Co²⁺ as a dilute substitutional impurity in MgO relative to the ground Λ_6g doublet have been found by low temperature Raman spectroscopy to be two Λ_8g states at 305 ± 3 cm^?1 and 930 ± 3 cm^?1; the remaining Λ_7g energy is predicted to be in the 980–1010 cm^?1 range the corresponding Λ_6g → Λ_7g Raman transition being weak and buried in the extensive two-phonon background. A second-order perturbation calculation which couples the spin-orbit states to both E_g and T_2g modes of vibration gives a weak but important Jahn-Teller stabilization energy for the Λ_8g states.     

Glucose‐ and Cellulose‐Derived Ni/C‐SO3H Catalysts for Liquid Phase Phenol Hydrodeoxygenation

Sulfonated carbons were explored as functionalized supports for Ni nanoparticles to hydrodeoxygenate (HDO) phenol. Both hexadecane and water were used as solvents. The dual‐functional Ni catalysts supported on sulfonated carbon (Ni/C‐SO₃H) showed high rates for phenol hydrodeoxygenation in liquid hexadecane, but not in water. Glucose and cellulose were precursors to the carbon supports. Changes in the carbons resulting from sulfonation of the carbons resulted in variations of carbon sheet structures, morphologies and the surface concentrations of acid sites. While the C‐SO₃H supports were active for cyclohexanol dehydration in hexadecane and water, Ni/C‐SO₃H only catalysed the reduction of phenol to cyclohexanol in water. The state of 3–5 nm grafted Ni particles was analysed by in situ X‐ray absorption spectroscopy. The results show that the metallic Ni was rapidly formed in situ without detectable leaching to the aqueous phase, suggesting that just the acid functions on Ni/C‐SO₃H are inhibited in the presence of water. Using in situ IR spectroscopy, it was shown that even in hexadecane, phenol HDO is limited by the dehydration step. Thus, phenol HDO catalysis was further improved by physically admixing C‐SO₃H with the Ni/C‐SO₃H catalyst to balance the two catalytic functions. The minimum addition of 7 wt % C‐SO₃H to the most active of the Ni/C‐SO₃H catalysts enabled nearly quantitative conversion of phenol and the highest selectivity (90 %) towards cyclohexane in 6 h, at temperatures as low as 473 K, suggesting that the proximity to Ni limits the acid properties of the support.     

Object-Oriented Modelling of Military Communications Networks

Military communications networks are large complex systems; their physical dynamics, composition, workload characteristics and operational goals make them very hard to model and analyse. It is particularly difficult to build a generalized model that can adequately fit each instance, generate a workload that exercises the network in a realistic way, and measure network effectiveness in terms of the operational goals. In this work, we describe our approach to building such a model for the US Marine Corps, and demonstrate the model's use by solving a particular equipment allocation problem. We combine object-oriented simulation with new concepts for workload modelling and measuring effectiveness that are based on the operational tasks the Marines perform.     

Anomalous structural dynamics of minimally frustrated residues in cardiac troponin C triggers hypertrophic cardiomyopathy

Cardiac TnC (cTnC) is highly conserved among mammals, and genetic variants can result in disease by perturbing Ca²⁺-regulation of myocardial contraction. Here, we report the molecular basis of a human mutation in cTnC''s αD-helix (TNNC1-p.C84Y) that impacts conformational dynamics of the D/E central-linker and sampling of discrete states in the N-domain, favoring the “primed” state associated with Ca²⁺ binding. We demonstrate cTnC''s αD-helix normally functions as a central hub that controls minimally frustrated interactions, maintaining evolutionarily conserved rigidity of the N-domain. αD-helix perturbation remotely alters conformational dynamics of the N-domain, compromising its structural rigidity. Transgenic mice carrying this cTnC mutation exhibit altered dynamics of sarcomere function and hypertrophic cardiomyopathy. Together, our data suggest that disruption of evolutionary conserved molecular frustration networks by a myofilament protein mutation may ultimately compromise contractile performance and trigger hypertrophic cardiomyopathy.

Cardiac TnC (cTnC) is highly conserved among mammals, and genetic variants can result in disease by perturbing Ca²⁺-regulation of myocardial contraction.     

Immobilised metal affinity chromatography of beta-galactosidase from unclarified Escherichia coli homogenates using expanded bed adsorption

The development of an expanded bed process for the direct extraction and partial purification of beta-galactosidase from unclarified Escherichia coli homogenates using its natural affinity for metal loaded STREAMLINE Chelating is described. Small packed beds were used to determine the effect of chelated metal ion (Cu2+, Ni2+, Co2+ or Zn2+), loading pH and ionic strength on the selective binding capacity, and recovery of beta-galactosidase from clarified homogenates. An elution protocol was developed using the competitive displacer, imidazole, to recover beta-galactosidase in 87% yield and 3.4-fold purification. These results were then used to develop a separation for the recovery of beta-galactosidase from unclarified homogenates in a 2.5-cm diameter expanded bed. Although Ni2+ loaded STREAMLINE Chelating had a 5% dynamic capacity for beta-galactosidase of just 118 U ml(-1) (0.39 mg ml(-1)), the low capacity was thought to be due to the large size of the target (464,000) relative to the exclusion limit of the macroporous adsorbent. Despite this low capacity, Ni2 STREAMLINE Chelating was used successfully to recover beta-galactosidase from an unclarified homogenate in 86.4% yield and at 5.95-fold purification. The degree of purification relative to a commercial standard, as assessed using the purification factor and sodium dodecyl sulphate-polyacrylamide gel electrophoresis was high suggesting that this pseudo-affinity procedure compared favourably with alternative methods.     

Interlaboratory verified liquid chromatographic method for analysis of vitamins A and E in soy-based infant formula powder

An interlaboratory verified, liquid chromatographic (LC) method is presented for the analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in soy-based infant formula. The extraction procedure uses sample dehydration with magnesium sulfate followed by extraction with isopropanol, hexane-ethyl acetate (85 + 15, v/v). After evaporation and filtration, the sample extract is injected directly onto a normal-phase LC system with fluorescence detection. All-rac-alpha-tocopheryl acetate and retinyl palmitate are quantitated isocratically with a mobile phase of hexane containing 0.50% (v/v) and 0.125% (v/v) isopropanol, respectively. A zero control reference material (ZRM) was spiked at 5 levels, with 5 replicate analyses of 1/2x, x, 2x, 4x, and 16x where "x" is the minimum level of 250 IU/100 kcal (vitamin A) and 0.7 IU/100 kcal (vitamin E) as specified in 21 Code of Federal Regulations 107.100. The following recoveries and RSD values represent an average (n = 25) of the 5 levels for each analyte: all-rac-alpha-tocopheryl acetate, 100% (RSD = 3.5%); retinyl palmitate, 97.2% (RSD = 2.1%). Two additional laboratories analyzed the fortified ZRM samples. Average recoveries (n = 24) of all-rac-alpha-tocopheryl acetate and retinyl palmitate at 4 levels were all-rac-alpha-tocopheryl acetate, 99.0% (RSD = 4.0%), and retinyl palmitate, 96.2% (RSD = 1.4%) at the second laboratory. Average recoveries (n = 24) of all-rac-alpha-tocopheryl acetate and retinyl palmitate at 4 levels were all-rac-alpha-tocopheryl acetate, 102% (RSD = 1.4%) and retinyl palmitate, 95.7% (RSD = 2.0%) at the third laboratory. In addition, 6 replicates of the same commercial soy-based infant formula powder were run by the 3 laboratories.     

Silver and Copper Nitride Cooperate for CO Electroreduction to Propanol

The need of carbon sources for the chemical industry, alternative to fossil sources, has pointed to CO₂ as a possible feedstock. While CO₂ electroreduction (CO₂R) allows production of interesting organic compounds, it suffers from large carbon losses, mainly due to carbonate formation. This is why, quite recently, tandem CO₂R, a two-step process, with first CO₂R to CO using a solid oxide electrolysis cell followed by CO electroreduction (COR), has been considered, since no carbon is lost as carbonate in either step. Here we report a novel copper-based catalyst, silver-doped copper nitride, with record selectivity for formation of propanol (Faradaic efficiency: 45 %), an industrially relevant compound, from CO electroreduction in gas-fed flow cells. Selective propanol formation occurs at metallic copper atoms derived from copper nitride and is promoted by silver doping as shown experimentally and computationally. In addition, the selectivity for C₂₊ liquid products (Faradaic efficiency: 80 %) is among the highest reported so far. These findings open new perspectives regarding the design of catalysts for production of C₃ compounds from CO₂.     

Lewis acid-catalyzed hydrogenation: B(C6F5)3-mediated reduction of imines and nitriles with H2

The Lewis acid B(C(6)F(5))(3) has been found to be an efficient catalyst for the direct hydrogenation of imines and the reductive ring-opening of aziridines with H(2) under mild conditions; addition of a bulky phosphine allows for the reduction of protected nitriles.