Ozonation of cooling tower waters

Continuous ozone injection into water circulating between a cooling tower and heat exchanger with heavy scale deposits inhibits formation of further deposits, promotes flaking of existing deposits, inhibits chemical corrosion and controls algae and bacteria

Liquid ethylene-propylene copolymers

Oligomers are prepared by heating solid ethylene-propylene rubber in container that retains solid and permits liquid product to flow out as it is formed. Molecular weight and viscosity of liquids can be predetermined by process temperature. Copolymers have low viscosity for given molecular weight

Rheology of Active Filament Solutions

We study the viscoelasticity of an active solution of polar biofilaments and motor proteins. Using a molecular model, we derive the constitutive equations for the stress tensor in the isotropic phase and in phases with liquid crystalline order. The stress relaxation in the various phases is discussed. Contractile activity is responsible for a spectacular difference in the viscoelastic properties on opposite sides of the order-disorder transition.Comment: 4 pages, 1 figur

Nematic and Polar order in Active Filament Solutions

Using a microscopic model of interacting polar biofilaments and motor proteins, we characterize the phase diagram of both homogeneous and inhomogeneous states in terms of experimental parameters. The polarity of motor clusters is key in determining the organization of the filaments in homogeneous isotropic, polarized and nematic states, while motor-induced bundling yields spatially inhomogeneous structures.Comment: 4 pages. 3 figure

Concept study for a high-efficiency nanowire-based thermoelectric

Materials capable of highly efficient, direct thermal-to-electric energy conversion would have substantial economic potential. Theory predicts that thermoelectric efficiencies approaching the Carnot limit can be achieved at low temperatures in one-dimensional conductors that contain an energy filter such as a double-barrier resonant tunneling structure. The recent advances in growth techniques suggest that such devices can now be realized in heterostructured, semiconductor nanowires. Here we propose specific structural parameters for InAs/InP nanowires that may allow the experimental observation of near-Carnot efficient thermoelectric energy conversion in a single nanowire at low temperature

Bridging the microscopic and the hydrodynamic in active filament solutions

Hydrodynamic equations for an isotropic solution of active polar filaments are derived from a microscopic mean-field model of the forces exchanged between motors and filaments. We find that a spatial dependence of the motor stepping rate along the filament is essential to drive bundle formation. A number of differences arise as compared to hydrodynamics derived (earlier) from a mesoscopic model where relative filament velocities were obtained on the basis of symmetry considerations. Due to the anisotropy of filament diffusion, motors are capable of generating net filament motion relative to the solvent. The effect of this new term on the stability of the homogeneous state is investigated.Comment: 7 pages, 2 figures, submitted to Europhys. Let

Non-equilibrium microtubule fluctuations in a model cytoskeleton

Biological activity gives rise to non-equilibrium fluctuations in the cytoplasm of cells; however, there are few methods to directly measure these fluctuations. Using a reconstituted actin cytoskeleton, we show that the bending dynamics of embedded microtubules can be used to probe local stress fluctuations. We add myosin motors that drive the network out of equilibrium, resulting in an increased amplitude and modified time-dependence of microtubule bending fluctuations. We show that this behavior results from step-like forces on the order of 10 pN driven by collective motor dynamics

Direct Current Electrical Stimulation Increases the Fusion Rate of Spinal Fusion Cages

Study Design. A randomized experimental evaluation of direct current stimulation in a validated animal model with an experimental control group, using blinded radiographic, biomechanical, histologic, and statistical measures. Objectives. To evaluate the efficacy of the adjunctive use of direct current stimulation on the fusion rate and speed of healing of titanium interbody fusion cages packed with autograft in a sheep lumbar interbody fusion model. Summary of Background Data. Titanium lumbar interbody spinal fusion cages have been reported to be 90% effective for single-level lumbar interbody fusion. However, fusion rates are reported to be between 70% and 80% in patients with multilevel fusions or with risk factors such as obesity, tobacco use, or metabolic disorders. The authors hypothesized that direct current stimulation would increase the fusion rate of titanium interbody fusion cages packed with autograft in a sheep lumbar interbody fusion model. Methods. Twenty-two sheep underwent lumbar discectomy and fusion at L4–L5 with an 11- × 20-mm Bagby and Kuslich (BAK) cage packed with autograft. Seven sheep received a BAK cage and no current. Seven sheep had a cage and a 40-μA current applied with a direct current stimulator. Eight sheep had a BAK cage and a 100-μA current applied. All sheep were killed 4 months after surgery. The efficacy of electrical stimulation in promoting interbody fusion was assessed by performing radiographic, biomechanical, and histologic analyses in a blinded fashion. Results. The histologic fusion rate increased as the direct current dose increased from 0 μA to 40 μA to 100 μA (P \u3c 0.009). Histologically, all animals in the 100-μA group had fusions in both the right and left sides of the cage. Direct current stimulation had a significant effect on increasing the stiffness of the treated motion segment in right lateral bending (P \u3c 0.120), left lateral bending (P \u3c 0.017), right axial rotation (P \u3c 0.004), left axial rotation (P \u3c 0.073), extension (P \u3c 0.078), and flexion (P \u3c 0.029) over nonstimulated levels. Conclusion. Direct current stimulation increased the histologic and biomechanical fusion rate and the speed of healing of lumbar interbody spinal fusion cages in an ovine model at 4 months

Testing Lorentz and CPT symmetry with hydrogen masers

We present details from a recent test of Lorentz and CPT symmetry using hydrogen masers. We have placed a new limit on Lorentz and CPT violation of the proton in terms of a recent standard model extension by placing a bound on sidereal variation of the F = 1 Zeeman frequency in hydrogen. Here, the theoretical standard model extension is reviewed. The operating principles of the maser and the double resonance technique used to measure the Zeeman frequency are discussed. The characterization of systematic effects is described, and the method of data analysis is presented. We compare our result to other recent experiments, and discuss potential steps to improve our measurement.Comment: 26 pages, 16 figure