Comparative sorption and desorption of benzo[a]pyrene and 3,4,3',4'-tetrachlorobiphenyl in natural lake water containing dissolved organic matter

The sorption and desorption of two model compounds, benzo[a]pyrene (BaP) and 3,4,3',4'-tetrachlorobiphenyl (TCBP), were studied in natural lake water with high dissolved organic matter (DOM) content using the equilibrium dialysis and Tenax extraction methods. The sorption of TCBP was lower and reached steady value more slowly than did BaP. Tenax extraction revealed at least two differently desorbing fractions for both model compounds, which also supported the conclusion that DOM-HOC associations may involve several mechanisms. The rapidly desorbing fraction may be attributed to freely dissolved and loosely sorbed compound, whereas the more strongly sorbed fraction may indicate the presence of specific binding sites. The data indicated that the association between hydrophobic organic contaminants (HOC) and DOM is not simply absorption that is solely driven by the lipophilicity of the sorbates. Although contact time had a rather negligible effect on the sorption of BaP, the proportion of desorption resistant fraction increased with time, whereas the desorption of TCBP was less affected by contact time. Steric factors may be the cause of the lower sorption and smaller desorption resistant fraction of TCBP. The results indicate potential differences in the behavior of PAHs and PCBs in the aquatic environment.     

Printable and flexible macroporous organosilica film with high protein adsorption capacity

An approach for creating a flexible and macroporous silsesquioxane film using phase separation method is described. The porous film was prepared by a simple coating method where sol-gel solution containing polyacrylic acid (PAA) and 1,6-bis(trimethoxysilyl)hexane in water was applied on boehmite silica coated polymethylmethacrylate (PMMA) film. After drying, the water soluble PAA template was removed by washing the film with water revealing the porous film. With certain ratios of PAA and water, fully co-continuous pore system with open surface was obtained. Porous films with 3-4 μm thickness were found to be highly flexible. The biocompatibility of the porous film was tested by immobilizing a high affinity biotin-binding chimeric avidin (ChiAVD(I117Y)) into the porous matrix The porous film was found to adsorb higher amounts of functional chimeric avidin compared to the pure PMMA film or a boehmite silica coated PMMA film.     

The effect of low-intensity pulsed ultrasound on bone healing in SR-PLLA rod fixed experimental distal femur osteotomy in rat

The effects of low-intensity pulsed ultrasound (30 mW/cm²) were investigated in experimental cancellous bone fracture healing in bioabsorbable self-reinforced poly-l-lactide (SR-PLLA) rod fixed distal femur osteotomy in rats. A transverse transcondylar osteotomy was fixed with one SR-PLLA rod in 32 male Wistar rats of the age of 20 weeks. Half of the rats had a daily 20-min ultrasound exposure for three weeks. The follow-up times were three, six, and 12 weeks. Radiographical, histological, microradiographical, oxytetracycline labeling, and histomorphometrical analyses were performed. No foreign-body reactions were noted. The biocompatibility of SR-PLLA and ultrasound was found to be good. In the radiological and histological assessments there was a slight tendency for enhanced healing in the ultrasound group at three weeks, but at six and 12 weeks no differences were observed. The histomorphometrical and oxytetracycline labeling analyses showed that ultrasound exposure had no significant effects on bone healing. The present study shows that there were no obvious findings to support the hypothesis that low-intensity pulsed ultrasound enhances bone healing in self-reinforced poly-l-lactide (SR-PLLA) rod fixed experimental metaphyseal distal femur osteotomy in rats. The observed good biocompatibility provides a safe starting-point for clinical trials on bioabsorbable fixation combined with low-intensity ultrasound.     

An interaction between penton base and alpha v integrins plays a minimal role in adenovirus-mediated gene transfer to hepatocytes in vitro and in vivo

Studies in cultured cell lines have shown that adenovirus infection involves binding of adenovirus fiber to its cell surface receptor and binding of penton base to alpha v integrins. However, much less is known about the role of these interactions in cells that are targets for adenovirus-mediated gene transfer. Earlier work showed that hepatocytes are readily infected by adenovirus, making them an attractive target for gene therapy in several diseases. We found that addition of fiber protein blocked adenovirus infection of primary cultures of hepatocytes. This suggests an important role for fiber and its receptor. However, mutation of the integrin-binding motif in penton base did not inhibit infection of hepatocytes, even though the mutation impaired infection of HeLa cells. Hepatocytes had undetectable amounts of alpha v integrins on their cell surface and showed no specific adherence to vitronectin, the natural substrate of alpha v integrins. Adenovirus with an intact penton base enhanced infection of liver following intravenous injection, but only by three-fold as compared with virus in which the integrin-binding motif was disrupted. These studies suggest that interactions between cell surface integrins and penton base are not required for adenovirus infection of hepatocytes in vitro, but the interaction enhances infection to a small degree in vivo.     

Comparing double-step and penalty-based semirecursive formulations for hydraulically actuated multibody systems in a monolithic approach

The simulation of mechanical systems often requires modeling of systems of other physical nature, such as hydraulics. In such systems, the numerical stiffness introduced by the hydraulics can become a significant aspect to consider in the modeling, as it can negatively effect to the computational efficiency. The hydraulic system can be described by using the lumped fluid theory. In this approach, a pressure can be integrated from a differential equation in which effective bulk modulus is divided by a volume size. This representation can lead to numerical stiffness as a consequence of which time integration of a hydraulically driven system becomes cumbersome. In this regard, the used multibody formulation plays an important role, as there are many different procedures for the constraint enforcement and different sets of coordinates to choose from. This paper introduces the double-step semirecursive approach and compares it with a penalty-based semirecursive approach in case of coupled multibody and hydraulic dynamics within the monolithic framework. To this end, hydraulically actuated four-bar and quick-return mechanisms are analyzed as case studies. The two approaches are compared in terms of the work cycle, energy balance, constraint violation, and numerical efficiency of the mechanisms. It is concluded that the penalty-based semirecursive approach has a number of advantages compared with the double-step semirecursive approach, which is in accordance with the literature.

     

A 2 GHz Phase-Locked Loop Frequency Synthesizer with On-Chip VCO

This paper discusses the implementation of the building blocks for a 2 GHz phase-locked loop frequency synthesizer in a standard 0.5 m BiCMOS process. These blocks include a low-power optimized dual modulus prescaler which is able to operate with input frequencies up to 2.7 GHz, a phase detector with extremely constant gain throughout the input phase difference range, a chargepump with a rail-to-rail output, and an on-chip voltage-controlled oscillator.     

Recovery and stability of phenolase,peroxidase and catalase activity in dried potato tissue

Based on a comparison with the activity of fresh potato enzyme extracts, complete recovery of phenolase, peroxidase and catalase activity was obtained from either freeze-dried tissue or powder obtained by grinding the tissue with acetone. Phenolase activity was stable for 1 year, peroxidase for 2–4 weeks and catalase for 8 weeks.     

Foundations of program management: A bibliometric view

Are programs just scale-ups of projects, or do they represent something unique? Recent articles stress the difference of project and program management, but do neither show consensus nor precise definitions of program management. Our comparative bibliometric study of 517 program articles and 1164 project articles published in the last 21 years in leading scientific business journals identifies similarities and differences in theoretical foundations, indicated by the sources cited, and themes, indicated by the keywords. We show that programs have several theoretical bases, such as organizational theories, strategy, product development, manufacturing and change. Programs take an open system view and seek change in permanent organizations. Projects, in turn, have product development as the dominant theory basis. We elaborate eleven distinctive characteristics of program and project management research. Our study proposes themes upon which future theories and empirical studies of programs can be established.