Rapid polymer fiber airbrushing: Impact of a device design on the fiber fabrication and matrix quality

Polymer fiber matrixes can be used in a variety of applications, including electronics, tissue engineering, or coatings. Polymer airbrushing (air‐blast spinning) has the potential to overcome some of the limitations of electrospinning and has the advantage of depositing nanofibers directly on various materials. The airbrushing technique has yet to be better evaluated and optimized to achieve a higher fiber reproducibility and bulk material quality. In this study, a gravity‐fed brush (commercial airbrush) and syringe‐pump‐operated brush [custom‐built airbrush (CBA)] were compared to determine the effect of the coaxial brush design on the efficacy of fiber fabrication. At comparable fiber deposition rates, gas pressures, and polymer concentrations, the CBA produced smaller and more uniform fibers with a lower average size of polymer beads. The obtained data suggest that capillary pinching was the dominant mechanism responsible for fiber formation when we used the CBA. The estimated pinching energy was lower for the CBA at the compared polymer concentrations and at a high gas pressure. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42813.     

Living Environment, Social Participation and Wellbeing in Older Age: The Relevance of Housing and Local Area Disadvantage

This paper explores the links between the quality of the living environment, social participation and wellbeing in older age using data from the Household, Income and Labour Dynamics in Australia (HILDA) survey. Using nine waves of the data, random-effects models are estimated to isolate the ‘net effect’ of the living environment on social participation and well being, while controlling for a number of background factors. The findings reveal a considerable penalty associated with living in disadvantaged housing and disadvantaged areas on some of the critical aspects of social participation, such as the frequency of contacts with other people, and access to social support, as well as on overall wellbeing of older persons. The contribution of this paper lies in demonstrating that the quality of one’s living environment plays a significant role in shaping social participation and wellbeing in older age based on robust methodology and reliable longitudinal data.     

Study of a Mo–Au TES deposited directly on a freestanding membrane

Transition edge sensor devices made with Mo–Au proximity bilayer thermometers have been fabricated. The bilayers were DC-sputter deposited directly on 250 nm thick pre-etched Si₃N₄ membranes. Mo was deposited at 700°C, whereas Au was deposited at room temperature in the same pumpdown in order to allow for a good proximity effect. The superconducting transition temperature of devices with 43 nm Mo and 200 nm Au was around 190 mK. The transition width of bilayers deposited on membranes was substantially larger than those measured on samples deposited on the bulk substrate in the same fabrication run (≈2 mK). We consider this difference to be the result of a large temperature gradient across the membrane during the deposition process. Devices were tested with a single stage SQUID array kept at 2.2 K. The resolution of a device that has a transition width of 30 mK is 30 eV at 6 keV. A detailed study shows that the detector noise roughly scales with I₀, confirming the importance of thermal fluctuation noise in the thermometer.     

Automated program understanding by concept recognition

Program understanding can be seen as the process of understanding abstract concepts in the program code. Thus, automated recognition of abstract concepts may greatly assist the human understanding process. This paper describes an approach to automated concept recognition and its implementation. In the approach, we use a concept model and a library of concept recognition rules to describe what the concepts are and how to recognize them from lower-level concepts. Programming language knowledge as well as domain knowledge are used to aid the recognition of abstract concepts.     

A simple method for screening variables before clustering microarray data

A simple and computationally fast procedure is proposed for screening a large number of variables prior to cluster analysis. Each variable is considered in turn, the sample is divided into the two groups that maximise the ratio of between-group to within-group sum of squares for that variable, and the achieved value of this ratio is tested to see if it is significantly greater than what would be expected when partitioning a sample from a single homogeneous population. Those variables that achieve significance are then used in the cluster analysis. It is suggested that significance levels be assessed using a Monte Carlo computational procedure; by assuming within-group normality an analytical approximation is derived, but caution in its use is advocated. Computational details are provided for both the partitioning and the testing. The procedure is applied to several microarray data sets, showing that it can often achieve good results both quickly and simply.     

High‐Energy X‐Ray Diffraction Study of the Inhomogeneous Zr43Cu43Al7Ag7 Bulk‐Metallic Glasses

In the present work, the microscopic structure of an as‐cast Zr₄₃Cu₄₃Al₇Ag₇ bulkmetallic glass (BMG) had been investigated in detail. The structure analyses are performed using the laboratory X‐ray diffraction (XRD), high‐energy synchrotron X‐ray diffraction, and transmission‐electron microscopy (TEM). The results from different techniques are compared and discussed. The specimen shows a typical amorphous hallo using the conventional laboratory XRD. However, tiny crystalline particles, roughly ≈10 nm in size, are found in the sample by the high‐energy XRD as well as the TEM. The standard laboratory XRD measurement is not adequate to differentiate amorphous from a nano‐composite phase. The high‐energy XRD method is an essential technique to determine the glassy nature of a BMG.     

Silver self aggregation in a nanodevice for enhanced Raman spectroscopy: experiments vs. simplified modeling via molecular dynamics

We present a study, via experiments and exploratory molecular dynamics simulations, of self aggregation in cylindrical nanostructures obtained experimentally by combining high resolution electron beam lithography with electroless silver deposition. This process is key to the fabrication of a nanolens device, where a strong surface enhancement can be exploited for Raman spectroscopy. In order to investigate the process, we introduce a simple theoretical model and compare the results of simulations with the fabricated silver nanostructures during the growth phase. Our simulations qualitatively agree with the experiments and allow a general characterization of the process at length scales smaller than those easily accessible by microscopy. We identify a geometrical parameter, the aspect ratio of the cylinder, that relates two different types of growth with different characteristics and, possibly, different Raman enhancements.     

Direct measurements of small 14C samples after oxidation in quartz tubes

Small ¹⁴C samples gain importance in environmental research and for dating purposes. However, throughput of such samples is limited by the preparation of graphite targets for accelerator mass spectrometry (AMS) measurements. In our approach, oxidation of samples with copper oxide in quartz tubes was applied to form CO₂ which was measured directly with the gas ion source of the small AMS facility MICADAS. The presented method was designed to meet the requirements for fast and easy handling of small samples (<100 μg carbon). As combustion byproducts are likely to interfere with ionisation processes in the gas ion source, we additionally investigated the effects of several gases on C^? currents.     

Java for parallel computing and as a general language for scientific and engineering simulation and modeling

We discuss the role of Java and Web technologies for general simulation. We classify the classes of concurrency typical in problems and analyse separately the role of Java in user interfaces, coarse grain software integration and detailed computational kernels. We conclude that Java could become a major language for computational science, as it potentially offers good performance, excellent user interfaces and the advantages of object-oriented structure. © 1997 John Wiley & Sons, Ltd.