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  • 1
    Electronic Resource
    Electronic Resource
    Raman spectral study of the coordination of cadmium(II) with chloride and bromide ions in molten sodium nitrate-potassium nitrate (1972)
    s.l. : American Chemical Society
    Inorganic chemistry 11 (1972), S. 29-32 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic50107a007
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  • 2
    Electronic Resource
    Electronic Resource
    A comparison of enzyme-aided bleaching of softwood paper pulp using combinations of xylanase, mannanase and α-galactosidase (2000)
    Springer
    Applied microbiology and biotechnology 53 (2000), S. 661-667 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Enzymatic pretreatment of softwood kraft pulp was investigated using xylanase A (XylA) from Neocallimastix patriciarum in combination with mannanase and α-galactosidase. Mannanase A (ManA) from Pseudomonas fluorescens subsp. cellulosa and ManA from Clostridium thermocellum, both family 26 glycosyl hydrolases, are structurally diverse and exhibit different pH and temperature optima. Although neither mannanase was effective in pretreating softwood pulp alone, both enzymes were able to enhance the production of reducing sugar and the reduction of single-stage bleached κ number when used with the xylanase. Sequential incubations with XylA and P. fluorescens ManA produced the largest final κ number reduction in comparison to control pretreated pulp. The release of galactose from softwood pulp by α-galactosidase A (AgaA) from P. fluorescens was enhanced by the presence of ManA from the same microorganism, and a single pretreatment with these enzymes, in combination with XylA, gave the most effective κ number reduction using a single incubation. Results indicated that mixtures of hemicellulase activities can be chosen to enhance pulp bleachability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530000344
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  • 3
    Electronic Resource
    Electronic Resource
    Investigation of the end-to-end distance distribution function for random and self-avoiding walks in two and three dimensions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 3936-3942 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Monte Carlo simulations employing the pivot algorithm are used to generate random and self-avoiding walks on two- and three-dimensional lattices. The moments of the end-to-end distance distribution function are calculated from the resulting configurations. It is found that the moments and the shape of the vector distribution function are in excellent agreement with the scaling form derived by des Cloizeaux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460670
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  • 4
    Electronic Resource
    Electronic Resource
    A molecular dynamics study of the crystalline phases of potassium nitrate (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6610-6618 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Constant pressure molecular dynamics simulations have been made for a simple ionic model for crystalline potassium nitrate at several pressures and temperatures which span the known phase diagram. The nitrate ion was modeled as a rigid four-site entity with distributed charges and a quaternion algorithm was used to solve the rotational equations of motion. Several structural features of KNO3 are reproduced in the simulations. The 300 K, 0.1 GPa aragonite-like phase II of KNO3 has been reproduced although in the model it appears at a pressure between 1 and 2 GPa. The disordering of the nitrate orientations which occurs at high temperatures has also been observed. At 3 GPa the stable phase of the model is very similar to the recently characterized phase IV of KNO3. Spontaneous phase transitions in the simulations did not always produce well ordered structures and this appears to be a problem inherent in the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456277
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  • 5
    Electronic Resource
    Electronic Resource
    A computer simulation study of the effect of molecular mass distribution on mass and momentum transport in molecular liquids (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6446-6453 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics computer simulation has been used to determine diffusion coefficients and viscosities for four thermodynamical ly identical one component model liquids composed of rigid triatomic molecules of the type XY2 at the same temperature and density. Exactly the same intermolecular potential was used throughout. The molecules comprising these liquids all had the same total mass but the molecular mass distributions were different for each liquid. Differences in the viscosities and the diffusion coefficients clearly show that the molecular mass distribution is a factor which in itself influences transport properties, a point seldom considered in the past. The viscosities were determined by nonequilibrium molecular dynamics and a new method is described for implementing isokinetic shear flow in molecular liquid simulations which employ quaternion algorithms. To obtain satisfactory diffusion coefficients for the equilibrium liquids it was necessary to use simulations extending up to 300 ps. The results are particularly relevant to the phenomenon of rotation–translation coupling and, together with the linear and angular velocity autocorrelation functions, are discussed in this context.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452434
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamic light scattering from concentrated water-in-oil microemulsions: The coupling of optical and size polydispersity (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4501-4509 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dynamic light scattering from highly concentrated colloidal systems with a narrow distribution of particle sizes can be interpreted in terms of the sum of two independent modes due, respectively, to collective diffusion and polydispersity fluctuations; a general formalism has been presented for calculating the relative mode amplitudes for hard spheres in the Percus–Yevick approximation [Pusey, Fijnaut, and Vrij, J. Chem. Phys. 77, 4270(1982)]. This work extends the relative mode amplitude calculation to the general case where optical (i.e., refractive index) and size polydispersity are completely coupled such as in water-in-oil microemulsions. To develop the theory a concentric core-shell hard sphere model is adopted, in which particles possess a continuous variation in the core sizes but have constant shell thickness, thus giving rise to a distribution in the particle refractive indices. A new "measured'' static structure factor SM(0) is derived, and applied to the calculation for the relative amplitude of the slow mode, A2/(A1+A2), as a function of solvent refractive index n0. A strong enhancement of the slow mode is predicted as the optical matching point is approached. The theory also shows that the dependence of A2/(A1+A2) on n0 is very sensitive to the extent of polydispersity, but rather insensitive to the distribution function used. Neglect of the nonuniformity in particle refractive index can cause a substantial overestimate of the size polydispersity. We have used our extended treatment to interpret the dynamic light scattering data from concentrated water-in-oil microemulsions formed from H2O, AOT, and apolar solvents using solvent composition to control the contrast in refractive index. It is found that the AOT-stabilized water microemulsion droplets have a size polydispersity of about 6.5%, which is smaller than previously thought.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458690
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  • 7
    Electronic Resource
    Electronic Resource
    A new approach to sputtering simulations from rare gas solids (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 6404-6410 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Classical molecular dynamics simulations of sputtering using large samples of up to 15 500 particles are demonstrated for Lennard-Jones solids. Two features are introduced to represent the effect of the surrounding solid substrate. First, the outermost particles on each side of the sample are subjected to an additional harmonic potential restraining them close to the equilibrium position. Second, these outermost particles are maintained at a preset temperature by assigning velocities at each time step randomly from the corresponding Gaussian distribution. This boundary thermostat produces a "sandbag'' effect and provides a means for excess kinetic energy to dissipate out of the sample. Preliminary results were obtained for single trajectories at 45° incidence and these illustrate that the sputtering yield from these model rare gas solids is strongly dependent on both the length of the simulation and the size of the sample. Simulations were continued to times in excess of 25 ps after which time for the largest sample there was some recoalescence of particles remaining in the surface region of the substrate. The long time sputtering yield was about 500 atoms which is comparable with experimental data on rare gas solids. It is demonstrated that particles within a cluster are just as likely to arise from nonadjacent sites as from near neighbors in the original lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457408
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  • 8
    Electronic Resource
    Electronic Resource
    The rheological properties of liquids composed of flexible chain molecules: A molecular dynamics computer simulation study (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 1542-1547 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nonequilibrium molecular dynamics simulations of planar Couette flow have been performed for dense liquids composed of model linear chain molecules each containing six interaction centers. For one liquid the potential parameters were chosen so that it resembles n-hexane. For the other liquid, referred to as flexane, the energy barriers directly opposing internal rotations are set to zero. The rheological properties of these liquids have been examined at 200 and 300 K at constant density. Torsional flexibility gives rise to a dynamic coupling which is associated with a significant reduction (by a factor of 2) in the equilibrium viscosity. A coupling mechanism is proposed based on large angle fluctuations without necessarily involving conformational transitions. This coupling disappears at high shear rates when there are significant structural changes in the liquid associated with shear thinning. Flexibility also causes changes in the shear rate dependent steady-state distribution of conformers and at low temperatures this results in reduced shear dilatancy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452192
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  • 9
    Electronic Resource
    Electronic Resource
    A Comparison of Three Methods for the Assessment of Fungal Colonization of Seedling Roots of Leek and Broad Bean (1960)
    [s.l.] : Nature Publishing Group
    Nature 188 (1960), S. 166-167 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Plants of both species were grown under greenhouse conditions in a grassland soil (pH 5.8) and were sampled 30-35 days after sowing. Before any isolations of fungi were attempted the roots were thoroughly washed, first in tap water to remove all visible soil particles and then in sterile water. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/188166a0
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  • 10
    Electronic Resource
    Electronic Resource
    Evidence for a general role for high-affinity non-catalytic cellulose binding domains in microbial plant ceil wall hydroiases (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 11 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Cellulases expressed by Cellulomonas fimi consist of a catalytic domain and a discrete non-catalytic cellulose-binding domain (CBD). To establish whether CBDs are common features of plant cell-wall hydroiases from C. fimi, the molecular architecture of xylanase D (XYLD) from this bacterium was investigated. The gene encoding XYLD, designated xynD, consisted of an open reading frame of 1936 bp encoding a protein of Mr 68000. The deduced primary sequence of XYLD was confirmed by the size (64kDa) and N-terminal sequence of the purified recombinant xylanase. Biochemical analysis of the purified enzyme revealed that XYLD is an endo-acting xylanase which displays no detectable activity against polysaccharides other than xylan. The predicted primary structure of XYLD comprised an /V-terminal signal peptide followed by a 190-residue domain that exhibited significant homology to Family-G xylanases. Truncated derivatives of xynD, encoding the W-terminal 193 amino acids of mature XYLD directed the synthesis of a functional xylanase, confirming that the 190-residue N-terminal sequence constitutes the catalytic domain. The remainder of the enzyme consisted of two approximately 90-residue domains, which exhibited extensive homology with each other, and limited sequence identity with CBDs from other polysaccharide hydrolases. Between the two putative CBDs is a 197-amino-acid sequence that exhibits substantial homology with Rhizobium NodB proteins. The four discrete domains in XYLD were separated by either threonine/prolineor novel glycine-rich linker regions. Although full-length XYLD adsorbed to cellulose, truncated derivatives of the enzyme lacking the C-terminal CBD hydrolysed xylan but did not bind to cellulose. Fusion of the C-terminal domain to glutathione-Stransferase generated hybrid proteins that bound to crystalline cellulose, but not to amorphous cellulose or xylan. The location of CBDs in a C. fimi xylanase indicates that domains of this type are not restricted to cellulases, but are widely distributed between hemicellutases also, and therefore play a pivotal role in the activity of the whole repertoire of plant cell-wall hydrolases. The role of the NodB homologue in XYLD is less certain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00317.x
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