A Comparison of the Cell Compatibility of Poly(ethyleneimine) with that of other Cationic Biopolymers Used in Applications at Biointerfaces

Poly(ethyleneimine) (PEI) is used as an initiating base layer or intermediate layer for layer‐by‐layer (LBL) technology. Since PEI is potentially cytotoxic in solution, it is necessary to investigate the influence of the physical properties of PEI layers on osteoblast cells. Therefore, the first aim of this study was to test the hypothesis that there is no statistically significant difference of cell adhesion, proliferation, and viability in response to nanometer thin polymer layers of PEI compared to other well‐known polymers. The second aim of this study was to test the hypothesis that the amine‐substituted dextran (aminodextran (AMD)) adheres well on Ti and can be used as a polymer coating in biomaterials applications. Titanium samples were coated with PEI, poly‐L ‐lysine (PLL), or AMD using dip coating. The polymer films were investigated with ellipsometry, atomic force microscopy, contact angle measurements, and X‐ray‐photoelectron spectroscopy (XPS). Cell adhesion, proliferation, and viability tests were carried out using osteoblast‐like cells (CAL‐72). Thin polymer layers below 10 nm layer thickness were found on the Ti surfaces. It was shown for the first time that base layers of PEI with nanometer thickness do not affect the bone cell reaction negatively. PEI, therefore, can be used as a functional base layer for LBL functionalization of metallic implants. AMD can be used in biomedical applications but does not adhere on titanium without an adhesion promoter.     

Application of USP Inlet Extensions to the TSI Impactor System 3306/3320 Using HFA 227 Based Solution Metered Dose Inhalers

ABSTRACT

The objective of this study was to further evaluate the need for a vertical inlet extension when testing solution metered dose inhalers using the TSI Model 3306 Impactor Inlet in conjunction with the TSI Model 3320 Aerodynamic Particle Sizer (APS). The configurations tested using the TSI system were compared to baseline measurements that were performed using the Andersen Mark II 8-stage cascade impactor (ACI). Seven pressurized solution metered dose inhalers were tested using varied concentrations of beclomethasone dipropionate (BDP), ethanol, and HFA 227 propellant. The inhalers were tested with the cascade impactor, and with the TSI system. The TSI system had three different configurations as the manufacturer provided (0 cm) or with inlet extensions of 20 and 40 cm. The extensions were located between the USP inlet and the Model 3306 Impactor Inlet. There were no practical differences between each system for the stem, actuator, or USP inlet. The fine particle mass (aerodynamic mass < 4.7 µm) was affected by extension length and correlated well with the ACI when an extension was present. APS particle size measurements were unaffected by the extension lengths and correlated well to particle size determined from the ACI analysis. It has been confirmed that an inlet extension may be necessary for the TSI system in order to give mass results that correlate to the ACI, especially for formulations having significant concentrations of low volatility excipients. Additionally, the results generated from this study were used to evaluate the product performance of HFA 227 based solution formulations that contain varying concentrations of ethanol as a cosolvent.     

The Process of Engineering and Its Management

ABSTRACT

The central theme of this article is that engineering should be viewed primarily as a process rather than as a body of knowledge and that only by understanding this process can it be effectively managed. As a consequence, engineering management cannot be synonymous with project management. The article then gives an overview of engineering as a process, emphasizing the important part played by the top-down systems engineering methodology.     

Facile fabrication of all-SWNT field-effect transistors

Field-effect transistors (FETs) have been fabricated using as-grown single-walled carbon nanotubes (SWNTs) for the channel as well as both source and drain electrodes. The underlying Si substrate was employed as the back-gate electrode. Fabrication consisted of patterned catalyst deposition by surface modification followed by dip-coating and synthesis of SWNTs by alcohol chemical vapor deposition (CVD). The electrodes and channel were grown simultaneously in one CVD process. The resulting FETs exhibited excellent performance, with an I _ON/I _OFF ratio of 10⁶ and a maximum ON-state current (I _ON) exceeding 13 μA. The large I _ON is attributed to SWNT bundles connecting the SWNT channel with the SWNT electrodes. Bundling creates a large contact area, which results in a small contact resistance despite the presence of Schottky barriers at metallic-semiconducting interfaces. The approach described here demonstrates a significant step toward the realization of metal-free electronics.      

One-step production of superhydrophobic coatings on flat substrates via atmospheric Rf plasma process using non-fluorinated hydrocarbons

This paper describes the direct deposition of hydrocarbon coatings with a static water contact angle higher than 150 using simple C6 hydrocarbons as a reactive gas in helium plasma generated in ambient air without any preroughening of the silicon (100) substrate. The film morphology and hydrophobicity are found to strongly depend on the structure of the reagent hydrocarbon. The films deposited with n-hexane and cyclohexane exhibited relatively smooth morphology and the water contact angle was only ～95°, similar to polypropylene. When benzene was used as a main reactive gas, the deposited film surface showed nanoscale textured morphology and superhydrophobicity with a water contact angle as high as 167°. Because the plasma is generated in air, all films show some degree of oxygen incorporation. These results imply that the incorporation of a small amount of oxygenated species in hydrocarbon films due to excitation of ambient air is not detrimental for superhydrophobicity, which allows the atmospheric rf plasma with the benzene precursor to produce rough surface topography needed for superhydrophobicity.     

Stress-controlled weakly periodic boundary conditions: Axial stress under varying orientations

The accuracy of multiscale modeling approaches for the analysis of heterogeneous materials hinges on the representativeness of the micromodel. One of the issues that affects this representativeness is the application of appropriate boundary conditions. Periodic boundary conditions are the most common choice. However, when localization takes place, periodic boundary conditions tend to overconstrain the microscopic problem. Weakly periodic boundary conditions have been proposed to overcome this effect. In this study, the effectiveness of weakly periodic boundary conditions in restoring transverse isotropy of representative volume elements (RVE) for a fiber-reinforced composite with elastoplastic matrix is investigated. The formulation of weakly periodic boundary conditions is extended to allow for force-controlled simulations where a uniaxial stress can be applied. A series of simulations is performed where the orientation of applied stress is gradually varied and the influence of this orientation on the averaged response is examined. An original method is presented to test the correlation between the ultimate principal stress and average localization angle of shear bands within an RVE. It is concluded that weakly periodic boundary conditions alleviate anisotropy in the RVE response but do not remove it.     

Properties of Sm2O3─Al2O3─SiO2 Glasses for In Vivo Applications

The compositional range for glass formation below 1600°C in the Sm₂O₃─Al₂O₃─SiO₂ system is (9–25)Sm₂O₃─(10–35)Al₂O₃─(40–75)SiO₂ (mol%). Selected properties of the Sm₂O₃─Al₂O₃─SiO₂ (SmAS) glasses were evaluated as a function of composition. The density, refractive index, microhardness, and thermal expansion coefficient increased as the Sm₂O₃ content increased from 9 to 25 mol%, the values exceeding those for fused silica. The dissolution rate in 1 N HCl and in deionized water increased with increasing Sm₂O₃ content and with increasing temperature to 70°C. The transformation temperature ( T _g ) and dilatometric softening temperature ( T _d ) of the SmAS glasses exceeded 800° and 850°C, respectively.     

Parallel analog to digital conversion with speed/precision trade-off

A new method for multichannel A/D-conversion is presented with a typical application being parallel read-out from a semiconductor image sensor. Each analog input signal is fed to a pair of comparators, the thresholds AB of which are delivered in parallel to all channels. With a proper sequence of A- and B-levels, digital outputs can be produced bit-serially for all channels in parallel. The problems of image sensor design is greatly alleviated since the bandwidth of each output channel is only a fraction of the bandwidth of a conventional video signal. The main virtue of this method is that precision in the digital output can be traded for speed. For a 256 comparator system the complexity and speed potential is the same as for an 8-bit flash converter. However, the new converter doubles its speed for each one-bit decrease in precision. Furthermore, all kinds of nonlinear compression and transformation of the input signal range are under instantaneous and programmable control. It is believed that the new converter opens the doors to more efficient image processing e.g. in robot vision. Flexibility and adaptation can be extended from high level parts of the systems all the way down to the image pick-up level.     

Simulation Techniques in Electromyography

A motor unit action potential (MUAP) recorded in clinical electromyography (EMG) is the spatial and temporal summation of the action potentials (AP's) from all muscle fibers in a motor unit (MU). An important determinant of MUAP waveform characteristics is the size of the recording electrode. In this paper, we have described the use of a modified line source model of single muscle fiber action potentials to simulate MUAP's as recorded by single fiber (SF) EMG, concentric needle (CN) EMG, and macro-EMG electrodes. Results indicate that SFEMG recordings from a normal MU contain mainly the AP's of the closest one to three muscle fibers of the MU. The amplitude, area, and duration of the simulated CNEMG MUAP's are determined mainly by the number and size of muscle fibers within a semicircular territory of 0.5, 1.5, and 2.5 mm, respectively, around the tip of the electrode. The amplitude and area of simulated macro-EMG MUAP's increase with the number of muscle fibers in the MU.     

Ethnography re-engineered: the two tribes problem

Does ethnography have anything to offer to the engineering community or the computer development community? Theoretically, yes, it does. Ethnography can provide the skills and tools that will help us understand user needs and preferences, which can then be embedded into software and hardware. Still, it is difficult to find any discussion of commercial hardware or software products in which ethnography demonstratively played a decisive part, which has led some to argue that ethnography, as it is currently practiced in the computer development community, would never have any practical impact. Bader and Nyce [Bader, G. and Nyce, J.M., 1998. When only the self is real: theory and practice in the development community. Journal of Computer Documentation, 22 (1), 5–10] raised this issue a decade ago, and argued that ethnographic knowledge appeared to be largely unintelligible and inoperable to the computer development community. To date, this debate has not been taken much further, and the results of ethnographic research continue to be published in the HCI/Human Factors literature. The issues Bader and Nyce raised a decade ago have however not gone away: to what extent can ethnography make a practical contribution to the computer development community? This article picks up this discussion, re-examines the original arguments and commentary, adds a Koenian view of engineering epistemology to the analysis, and concludes that we appear to require a much improved understanding of engineering epistemology, to support interdisciplinary communication. Building on this foundation, what may furthermore be necessary is to perform an ethnographic operation twice, not just once: essentially, it is argued, it is necessary to build a kind of ethnography that takes the ‘interpretation’ of research findings to one’s clients as seriously as it does the interpretation of what goes on in a particular, ‘targeted’ workplace for end-users. By providing this kind of ‘double’ translation and interpretation, it would be possible to ‘deliver’ ethnographic findings to the engineering communities in a form they find intelligible, simply by doing what ethnography does best: the discovery and interpretation of what is taken to be self-evident and logical.