A molecular dynamics simulation of bacteriophage T4 lysozyme

An analysis of a 400 ps molecular dynamics simulation of the164 amino acid enzyme T4 lysozyme is presented. The simulationwas carried out with all hydrogen atoms modeled explicitly,the inclusion of all 152 crystallographic waters and at a temperatureof 300 K. Temporal analysis of the trajectory versus energy,hydrogen bond stability, r.m.s. deviation from the startingcrystal structure and radius of gyration, demonstrates thatthe simulation was both stable and representative of the averageexperimental structure. Average structural properties were calculatedfrom the enzyme trajectory and compared with the crystal structure.The mean value of the C displacements of the average simulatedstructure from the X-ray structure was 1.1 ± 0.1 Å;differences of the backbone and angles between the averagesimulated structure and the crystal structure were also examined.Thermal-B factors were calculated from the simulation for heavyand backbone atoms and both were in good agreement with experimentalvalues. Relationships between protein secondary structure elementsand internal motions were studied by examining the positionalfluctuations of individual helix, sheet and turn structures.The structural integrity in the secondary structure units waspreserved throughout the simulation; however, the A helix didshow some unusually high atomic fluctuations. The largest backboneatom r.m.s. fluctuations were found in non-secondary structureregions; similar results were observed for r.m.s. fluctuationsof non-secondary structure and angles. In general, the calculatedvalues of r.m.s. fluctuations were quite small for the secondarystructure elements. In contrast, surface loops and turns exhibitedmuch larger values, being able to sample larger regions of conformationalspace. The C difference distance matrix and super-positioninganalyses comparing the X-ray structure with the average dynamicsstructure suggest that a ‘hinge-bending’ motionoccurs between the N- and C-terminal domains.     

Objective classification of vehicle seat discomfort

The objective of this study was to identify how physiological measures relate to self-reported vehicle seating discomfort. Twelve subjects of varied anthropometric characteristics were enrolled in the study. Subjects sat in two seats over a 2-h period and were evaluated via three physiological measures (near-infrared spectroscopy, electromyography and pressure mapping) yielding six testing sessions. Subjective discomfort surveys were recorded before and after each session for nine regions of the body. Conditional classification discomfort models were developed through dichotomised physiological responses and anthropometry to predict subjective discomfort in specific body locations. Models revealed that subjects taller than 171 cm with reduced blood oxygenation in the biceps femoris or constant, low-level muscle activity in the trapezius tended to report discomfort in the lower extremities or neck, respectively. Subjects weighing less than 58 kg with reduced blood oxygenation in the biceps femoris or unevenly distributed pressure patterns tended to report discomfort in the buttocks. The sensitivities and specificities of cross-validated models ranged between 0.69 and 1.00.     

The Polymerization of Metal-Containing Vinylic Monomers of Iron and Tungsten with Metal–Carbon σ Bonds

A series of metal-containing vinylic monomers of the type and was homopolymerized using 2,2-azobisisobutyronitrile (AIBN) as the free-radical initiator. These monomers were also copolymerized with styrene in the presence of AIBN. These compounds represent a class of organometallic polymers in which the metal is bonded to the polymer backbone via a metal–carbon bond. The new compounds were characterized by IR and ¹H NMR spectroscopy as well as scanning electron microscopy, gel permeation chromatography, and thermoanalytical studies (DSC and TGA). The properties of the new organometallic polymers are discussed.     

The heterogeneous nucleation of microcellular foams assisted by the survival of microvoids in polymers containing low glass transition particles. Part I: Mathematical modeling and numerical simulation

The existing models based on classical nucleation theory are not able to explain satisfactorily the nucleation phenomenon of microcellular foams in thermoplastics. Here, we extend the analysis of Kweeder (24), who developed a new model that considers the presence of microvoids, resulting from the thermal processing history of the polymer, as potential nucleation sites. The nucleation model “concentrates” on the stresses and thus void formations in the rubber particles. Since these are pre-existing microvoids, bubble nucleation depends on the survival of these voids to grow rather than the formation of a new phase as modeled by classical nucleation theory. The population of viable microvoids with a sufficiently large radius to survive and overcome surface and elastic forces has been modeled to yield the cell density. A log-normal distribution, which relates to the rubber particle size, has been used to model the distribution of microvoids in the polymer composite material. The model depends on various process parameters such as saturation pressure, foaming temperature, concentration of nucleating agents, solubility of the blowing agent in the polymer, and the modulus. High impact polystyrene (HIPS) was added to polystyrene to obtain polymers with different concentrations of rubber gel particles, the nucleating agent, and used here for this study.     

Spectral and complexity analysis of scalp EEG characteristics for mild cognitive impairment and early Alzheimer's disease

Amnestic mild cognitive impairment (aMCI) often is an early stage of Alzheimer's disease (AD). MCI is characterized by cognitive decline departing from normal cognitive aging but that does not significantly interfere with daily activities. This study explores the potential of scalp EEG for early detection of alterations from cognitively normal status of older adults signifying MCI and AD. Resting 32-channel EEG records from 48 age-matched participants (mean age 75.7 years)—15 normal controls (NC), 16 early MCI, and 17 early stage AD—are examined. Regional spectral and complexity features are computed and used in a support vector machine model to discriminate between groups. Analyses based on three-way classifications demonstrate overall discrimination accuracies of 83.3%, 85.4%, and 79.2% for resting eyes open, counting eyes closed, and resting eyes closed protocols, respectively. These results demonstrate the great promise for scalp EEG spectral and complexity features as noninvasive biomarkers for detection of MCI and early AD.     

Solvent extraction of metals from chloride solutions

A review is presented of a series of investigations into the extraction of copper, iron, zinc and cadmium into kerosene solutions of Lix or Kelex reagents from aqueous solutions containing chloride ions. The effects of chloride ions on the extraction of copper and iron were smaller than might have been expected to result from the formation of inextractable metal chlorocomplexes, and the extractants retained their selective properties. Extraction with Kelex 100 from chloride solution increased the separation between zinc and cadmium, in comparison with sulphate solutions.     

Part and Attribute Discovery from Relative Annotations

Part and attribute based representations are widely used to support high-level search and retrieval applications. However, learning computer vision models for automatically extracting these from images requires significant effort in the form of part and attribute labels and annotations. We propose an annotation framework based on comparisons between pairs of instances within a set, which aims to reduce the overhead in manually specifying the set of part and attribute labels. Our comparisons are based on intuitive properties such as correspondences and differences, which are applicable to a wide range of categories. Moreover, they require few category specific instructions and lead to simple annotation interfaces compared to traditional approaches. On a number of visual categories we show that our framework can use noisy annotations collected via “crowdsourcing” to discover semantic parts useful for detection and parsing, as well as attributes suitable for fine-grained recognition.     

Reactive Laser Ablation Synthesis of Nanosize Alumina Powder

An aluminum (Al) target was laser ablated in an oxygen (O₂) atmosphere, producing nanosize alumina (Al₂O₃) powder. The powder surface area decreased (and the particle size increased) with both increasing oxygen pressure and laser fluence. All powders produced had surface areas between 135 and 250 m²/g, corresponding to primary particle sizes ranging from 7 to 3 nm in radius. Phase evolution with temperature was studied via X-ray diffraction. These powders showed a direct transformation from γ- to α-alumina at approximately 1200°C, bypassing other transition alumina phases, while still maintaining small particle size ( 30 nm). Despite the nanosize particles, green densities equal to 54% of the skeletal density (i.e., true density of the solid phase) were obtained by uniaxial pressing at 40 MPa.     

Spinning of poly(ethylene terephthalate) fibers from a melt pool without a spinneret

Monofilament fibers were spun continuously from the free surface of a pool of molten poly(ethylene terephthalate) without the aid of a spinneret. For take-up velocities in the range of 12 to 400 ft/min, the denier of the filaments produced was an inverse power function of take-up velocity, and the birefringence was an inverse power function of the filament diameter. Production rate and product uniformity were strongly dependent on take-up velocity and surface temperature of the melt pool.     

A MECHANISTICALLY BASED MATHEMATICAL MODEL OF SULFUR DIOXIDE ABSORPTION INTO A CALCIUM HYDROXIDE SLURRY IN A SPRAY DRYER

A mathematical model has been developed to predict So₂ absorption and removal during the constant rate drying period of a spray dryer. The model, based on film theory, treats the atomized slurry droplets as spheres containing discrete sorbent particles of slaked lime with the fluid uniformly distributed around the individual particles. The model includes gas and liquid phase mass transfer coefficients as well as resistance to Ca(OH)₂ dissolution. A sensitivity analysis has been conducted and a comparison was made between pilot-scale experimental data and model-predicted values of S0₂ removal efficiency.