Effect of silane structure on the properties of silanized multiwalled carbon nanotube-epoxy nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were functionalized with aminosilanes via an aqueous deposition route. The size and morphology of siloxane oligomers grafted to the MWCNTs was tuned by varying the silane functionality and concentration and their effect on the properties of a filled epoxy system was investigated. The siloxane structure was found to profoundly affect the thermo-mechanical behavior of composites reinforced with the silanized MWCNTs. Well-defined siloxane brushes increased the epoxy T_g by up to 19 °C and significantly altered the network relaxation dynamics, while irregular, siloxane networks grafted to the MWCNTs had little effect. The addition of both types of silanized MWCNTs elicited improvements in the strength of the nanocomposites, but only the well-defined siloxane brushes engendered dramatic improvements in toughness. Because the silanization reaction is simple, rapid, and performed under aqueous conditions, it is also an industrially attractive functionalization route.     

Improvement of ampacity of parallel single-core cables byuninsulated additional conductors

Cable installations for three-phase systems consisting of parallel single-core cable circuits carry different currents due to inductive coupling. Supplementary installed additional conductors grounded on both ends show several beneficial effects: balanced outer conductor currents, improved throughput load, and reduced current-dependent losses. With cables laid in free air, additional conductors are especially economical     

Computer-assisted surgery

Computer-assisted surgery (CAS), a new navigation aid for skull-base surgery, is discussed. The system described combines 3-D coordinate measurement techniques, voxel processing methods, and pseudo-3-D image presentations to support preoperative planning of therapy, path-finding during the operation itself, and postoperative therapy control. The surgeon employs a hand-guided electromechanical 3-D-coordinate digitizer to locate points of interest within the operative field. The coordinates measured this way are correlated with a voxel model of the object gained by a preceding computed-tomography examination. With a prototype system the accuracy of this method has proven to be better than ±1 mm. The system has been successfully applied in more than 60 ear-nose-throat operations and four neurosurgical procedures. The computer hardware and integration of the system into an experimental picture archiving and communication system are discussed     

Etiology of Posttraumatic Stress Disorder in Vietnam veterans: Analysis of premilitary, military, and combat exposure influences.

43 Vietnam veterans seeking psychological services at a VA medical center were assigned to positive and negative groups of posttraumatic stress disorder (PTSD) based on the DSM-III. The average S was a 33-yr-old White male with 13 yrs of education. Ss were extensively assessed to examine the relative contributions of premilitary adjustment, military adjustment, and extent of combat exposure to the development of combat-related, chronic PTSD. In addition, groups were compared on profiles from the MMPI and a psychological problem checklist. Results of multiple regression analyses demonstrated that combat exposure and, to a lesser degree, military adjustment were significantly related to PTSD symptomatology, whereas premilitary adjustment was not. Discriminant function analyses showed that the MMPI had moderate ability to correctly classify Ss on the basis of PTSD diagnosis. However, problem checklist items indicative of anxiety-based disorders, particularly generalized anxiety and pervasive disgust, formed a discriminant function that correctly classified more than 90% of Ss. Results are discussed in terms of complications for an empirically derived conceptualization of PTSD. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dispersion of water into oil in a rotor–stator mixer. Part 1: Drop breakup in dilute systems

Most previous studies of liquid–liquid dispersion in complex geometry are limited to turbulent flow at low continuous phase viscosity. In this study, a viscous continuous phase was employed over a range of flow conditions including both the laminar and turbulent regimes. Equilibrium drop size was measured for water dispersed into viscous food grade mineral oils in a batch Silverson L4R rotor–stator mixer. The influence of fluid viscosities and interfacial tension (by adding an oil-soluble surfactant) were examined. In order to isolate the effect of drop breakage from coalescence, Part 1 is limited to dilute conditions (water phase fraction, ? = 0.001). In the laminar regime, drop breakup was more likely due to a simple shear breakage mechanism than one for extension. Following Grace (1982), a semi-empirical drop size correlation was developed. For turbulent flow, the validity of the sub-Kolmogorov inertial stress model for correlating equilibrium mean drop size was verified. Surfactants were found to mostly decrease drop size by lowering interfacial tension. Except for laminar systems near the critical micelle concentration, where Marangoni stresses appear to play some role, the effect of surfactants on the drop size could be correlated using the equilibrium or static interfacial tension. The influence of water phase fraction and coalescence is considered in Part 2 ( Rueger and Calabrese, 2013) of this paper.     

Evaluation of complications associated with off-label use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in pediatric orthopaedics

The off-label use of recombinant human bone morphogenetic protein-2 to promote bone healing in adults has significantly increased in recent years, while reports of recombinant human bone morphogenetic protein-2 application in children and adolescents are very rare. The aim of this study was to evaluate the safety of single and repetitive recombinant human bone morphogenetic protein-2 use in pediatric orthoapedics. Therefore we reviewed the medical records of 39 patients who had been treated with recombinant human bone morphogenetic protein-2 at our institution. Their mean age was 10.9 years. Recombinant human bone morphogenetic protein-2 was used in 17 patients for spine fusion, in 11 patients for the treatment of congenital pseudarthrosis of the tibia or tibial nonunion, in 5 patients for the management of femoral nonunion, in 5 patients for nonunions at other locations, and in 1 case for tibial shortening. Special attention was paid to identify all adverse events that may be attributed to recombinant human bone morphogenetic protein-2 use, including local inflammatory reactions, allergic reactions, systemic toxicity, excessive wound swelling, hematoma, compartment syndrome, infection, heterotopic ossification, excessive bone growth, carcinogenicity, and the consequences of repeated applications of recombinant human bone morphogenetic protein-2. Follow-up was a mean of 39 months. Forty-six operations with application of rhBMP-2 were performed. Complications that may be due to application of recombinant human bone morphogenetic protein-2 were seen after 18 operations including swelling, increase in temperature, wound secretion, redness and hyperthermia. We consider the three cases of necessary revisions, one due to hematoma, one due to development of a compartment syndrome, and one due to deep infection, to be the only complications related to the use of recombinant human bone morphogenetic protein-2. In conclusion, we found few complications attributable to application of recombinant human bone morphogenetic protein-2 in pediatric patients.     

Response of primary fibroblasts and osteoblasts to plasma treated polyetheretherketone (PEEK) surfaces

Polyetheretherketone (PEEK) is a synthetic polymer with suitable biomechanical and stable chemical properties, which make it attractive for use as an endoprothetic material and for ligamentous replacement. However, chemical surface inertness does not account for a good interfacial biocompatibility, and PEEK requires a surface modification prior to its application in vivo.In the course of this experimental study we analyzed the influence of plasma treatment of PEEK surfaces on the cell proliferation and differentiation of primary fibroblasts and osteoblasts. Further we examined the possibility of inducing microstructured cell growth on a surface with plasma-induced chemical micropatterning.We were able to demonstrate that the surface treatment of PEEK with a low-temperature plasma has significant effects on the proliferation of fibroblasts. Depending on the surface treatment, the proliferation rate can either be stimulated or suppressed. The behavior of the osteoblasts was examined by evaluating differentiation parameters.By detection of alkaline phosphatase, collagen I, and mineralized extracellular matrix as parameters for osteoblastic differentiation, the examined materials showed results comparable to commercially available polymer cell culture materials such as tissue culture polystyrene (TCPS). Further microstructured cell growth was produced successfully on micropatterned PEEK foils, which could be a future tool for bioartificial systems applying the methods of tissue engineering.These results show that chemically inert materials such as PEEK may be modified specifically through the methods of plasma technology in order to improve biocompatibility.The first two authors share first authorship.     

Induction of reparative dentine formation in monkeys by recombinant human osteogenic protein-1

Osteogenic protein-1 (OP-1, BMP-7), a member of the transforming growth factor-beta supergene family, induces cartilage and bone formation when implanted in intra- and extraskeletal sites in vivo. The human OP-1 gene has been cloned and biologically active recombinant OP-1 homodimers (hOP-1) produced. The amount of bone induced by hOP-1 in vivo is related to the amount of protein implanted. Dentine possesses bone morphogenetic protein (BMP) activity. Impure material from allogenic bone with BMP activity induced reparative dentine formation in dogs. The objective of this study was to determine if the amount of reparative dentine stimulated by hOP-1 is related to the amount of protein utilized in direct pulp-capping experiments. Freshly exposed molar and premolar pulps were treated with varying amounts of a complex comprising hOP-1 and a carrier matrix of purified bovine type-1 collagen powder (CM) moistened with sterile saline. Reparative dentine was present in all hOP-1/CM treated teeth (12 of 15) that remained sealed for the 6 weeks' healing. Substantially more new dentine was present in teeth treated with hOP-1/CM than in those treated with Ca(OH)2 paste and the amount of reparative dentine formed was proportional to the amount of hOP-1/CM (P < 0.05). No reparative dentine formed in collagen carrier or untreated teeth. The appearances of the new tissue suggested that much of the mass of the hOP-1/CM was replaced first by a pulp-like connective tissue, which mineralized to form reparative dentine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dispersion of water into oil in a rotor–stator mixer. Part 2: Effect of phase fraction

In Part 1 (Rueger and Calabrese, 2013), we monitored dilute water-in-oil dispersions in a batch Silverson L4R rotor–stator mixer to establish breakage mechanisms and develop a mechanistic basis for correlation of equilibrium mean drop size. In this study (Part 2) we consider the effect of water phase fraction under similar processing conditions, thereby requiring consideration of coalescence. Most of the work on the effect of phase fraction in stirred vessels was done with a low-viscosity continuous phase in turbulent flow with inertial subrange scaling (d > η). For that case drop size increases linearly with phase fraction, ?. In this study, viscous oils comprised the continuous phase, with water as the drop phase. The equilibrium DSD was measured in both laminar and turbulent flow conditions. The diameter of the largest drops was always less than the Kolmogorov microscale (d < η). A much greater increase (than the aforementioned linear relationship) in drop size with phase fraction was observed for ? ≤ 0.05; including cases where an oil soluble surfactant was present and where metal mixing head surfaces were rendered hydrophobic by treatment with silane functional groups. It is argued that this significantly greater dependence on ? is due to the flow field being locally laminar near the drops with coalescence rate being strongly affected by the collision efficiency, which depends on the viscosity of both phases. The presence of surfactant decreased drop size. The silane treatment decreased drop size; possibly by altering water drop interactions with mill head surfaces. Additional experiments were performed at higher phase fraction, where surfactant was required to stabilize the emulsion. The equilibrium drop size was found to plateau for 0.10 < ? < 0.50. The high phase fraction behavior is attributed to the competing rates of coalescence and breakage and their dependence on ? and drop size.