Conventional Assembly Research Articles

Mucin Multilayers Assembled through Sugar–Lectin Interactions

Multilayer films of biopolymers are attractive tools to exploit the extraordinary properties of certain biomacromolecules and introduce new functionalities to surfaces. Mucins, the gel-forming constituents of mucus, are versatile glycoproteins that have potential as new building blocks for biomaterial surface coatings. Multilayer films have mostly been assembled through the electrostatic pairing of polyelectrolytes, which results in limited pH and salt stability and screens charges otherwise available for useful payload binding. Here, we aim at assembling mucin multilayer films that differ from conventional paired polyelectrolyte assemblies to obtain highly stable and functional surface modifications. Using the lectin wheat germ agglutinin (WGA) to cross-link mucin-bound sugar residues, we show that (Mucin/WGA) films can grow into hydrated films and sustain exceptional resistance to extreme salt conditions and a large range of pH. Furthermore, we show that the addition of soluble N-acetyl-d-glucosamine can induce the controlled release of WGA from (Mucin/WGA) films. Last, we show that (Mucin/WGA) films can repeatedly incorporate and release a positively charged model cargo. The lubricating, hydration, barrier, and antimicrobial properties of mucins open multiple applicative perspectives for these highly stable mucin-based multilayer films.

Miniaturization of mechanical milling for powder X-ray diffraction

To enable mechanical milling of small (0.1–1.0 g) samples, a cylindrical grinding vessel machined from polypropylene and furnished with tungsten carbide rods has been designed and produced for use inside the conventional jar of a McCrone Micronizing Mill. The vessel is about one-seventh the volume of the conventional jar supplied by the manufacturer. The conditions of milling for both the conventional and the miniaturized-grinding assemblies were tested using quartz sand as a limiting case. The median grain sizes of the resultant powders were measured by an X-ray gravitational-sedimentation method, with contamination from the grinding media measured by Rietveld refinement and by instrumental neutron activation analysis. The use of tungsten carbide grinding elements permits rapid wet milling of a small sample to the same median grain size in about one-third of the time required by a regular sample ground in corundum. The relative contamination (by tungsten carbide on a weight basis) using the miniaturized-grinding assembly is about 6(1)% of the proportion of corundum contamination yielded by the conventional grinding assembly.

Traceable assembly of microparts using optical tweezers

Assembly of components with a size in the order of tens of micrometers or less is difficult because the gravitational forces become smaller than weak forces such as capillary, electrostatic and van der Waals forces. As such, the picked-up components commonly adhere to the manipulator, making the release operation troublesome, and the repeatable supply of components cannot be guaranteed because the magazining and bunkering scheme available in conventional scale assembly cannot be extended to these small objects. Moreover, there are also no effective ways known to deliver the finalized assembly externally. In this paper, we present the manipulation and assembly of microparts using optical tweezers, which by nature do not have stiction problems. Techniques allowing bunkering and finalizing the assembly for exporting are also presented. Finally, we demonstrate an exemplary microassembly formed by assembling two microparts: a movable microring and a microrod fixed on a glass substrate. We believe this traceable microassembly to be an important step forward for micro- and nano-manufacturing.

Tool for inspecting faults from incorrectly cleaved fiber ends and contaminated optical fiber connector end surfaces

We investigated and analyzed faults in field installable connection due to incorrectly cleaved fiber ends and manufactured physical contact (PC)-type connectors with contaminated end surfaces in optical access fiber networks. The insertion and return losses of fiber connections using incorrectly cleaved fiber ends might be at worst more than 40dB and less than 30dB, respectively. With PC-type connectors whose end surfaces are contaminated, the insertion and return losses might be at worst 8.7 and 27dB, respectively. We developed an inspection tool for cleaved fiber ends and connector end surfaces as a countermeasure. The proposed tool has a simple structure and does not require focal adjustment. It can be used to inspect and clearly determine whether a fiber has been cleaved correctly and whether there is contamination or scratches on the connector end surfaces. The tool requires a slight increase of 11% in operation time compared to conventional fiber end preparation and assembly procedures. The proposed tool provides a simple and cost-effective way to inspect cleaved fiber ends and connector end surfaces and is suitable for field use.

Two extensions for the ALWABP: Parallel stations and collaborative approach

In this article, we introduce two new variants of the Assembly Line Worker Assignment and Balancing Problem (ALWABP) that allow parallelization of and collaboration between heterogeneous workers. These new approaches suppose an additional level of complexity in the Line Design and Assignment process, but also higher flexibility; which may be particularly useful in practical situations where the aim is to progressively integrate slow or limited workers in conventional assembly lines. We present linear models and heuristic procedures for these two new problems. Computational results show the efficiency of the proposed approaches and the efficacy of the studied layouts in different situations.

Structures of Membrane Electrode Assembly Catalyst Layers for Proton Exchange Membrane Fuel Cells

In this paper, we modify the conventional 5-layer membrane electrode assembly (MEA, in which a proton exchange membrane (PEM) is located at its center, two Pt-C-40 (Pt on carbon powder support, Pt content 40 wt.%) catalyst layers (CLs) are located on the surfaces of the both sides of the PEM and two gas diffusion layers (GDLs) are attached next on the outer surfaces of two Pt-C-40 layers) and propose 7-layer and 9-layer MEAs by coating thin Pt-black CLs at the interfaces between the Pt-C-40 layer and the GDL and between the PEM and the Pt-C-40 layer and reducing the Pt-C-40 loading. The reduced Pt loading quantity of the Pt-C-40 layer is equal to the increased Pt loading quantity of the Pt-black layer, thus the total amount of Pt loadings in the unmodified conventional MEA and the modified MEAs are at a fixed Pt loading quantity. These modified MEAs may complicate the manufacture process. The main advantage of these 7- and 9-layer MEAs is the thinner CL thickness and thus lower CL proton transport resistance. Because of the thin Pt-black layer thickness in MEA, we avoid agglomeration of the Pt-black particles and maintain high Pt catalytic activity. We show these new CL structure MEAs have better fuel cells performance than the conventional 5-layer MEA.

Removal of Cyclic Borehole Noise From Low- and High-Resolution LWD Images and Its Impact on Image Interpretation

Summary The use of logging-while-drilling (LWD) imaging tools in realtime decision making and post-drilling analysis has become commonplace. However, image noise and processing errors because of inherent measurement physics can propagate errors and, thus, complicate interpretation of openhole log data and images. For example, standard density images tend to amplify image noise from small borehole irregularities. Among different borehole irregularities, spiraling is known to occur more frequently with conventional rotary assemblies, steerable motor assemblies, and rotary-steerable assemblies. When the cyclic-noise amplitude from spiraling becomes large relative to the measurement of the primary interest, it grossly affects the quality of the recorded formation bulk density, photoelectric factor, and neutron porosity. This paper shows novel methods to remove cyclic noise from formation-evaluation (FE) images by applying frequency-domain filtering. Although the initial attempt of fast Fourier transforms (Zhang et al. 2010) illustrates the straightforward concept, it is seldom used because of implementation issues requiring interactive filter design and intensive operator intervention. Recently, a new method (Sugiura et al. 2011) has been designed to improve the filtering process. Additionally, the new adaptive filter designs automate the cyclic-noise-removal process from the FE images. Standalone software has been developed to process the entire image logs from one well, without human supervision. The software adaptively modifies the filter behavior as borehole-oscillation noise characteristics change with formation, drilling assemblies, hole inclination, and depth. To examine its validity qualitatively, the algorithm is then applied to various field data, not only on low-resolution density images but also on higher-resolution density images. The new algorithm has been proved by bringing considerable improvement to the image quality without any artificial interruptions. The rugosity effect is reduced significantly, and the apparent resolution of bed-boundary features is increased. Furthermore, comparative field examples illustrate the improvement in image-feature extraction. The method described here is critical, for example, for small-fracture detection and more-precise definition of formation-property contrasts indicative of bed boundaries in irregular boreholes. This new method not only is effectively used for density images but also is applicable to any other borehole images, such as resistivity and ultrasonic images.

Study on Assembly Design Method Based Digital Mock-Up

The essentiality of assembly assessment and assembly optimization in design stage is analyzed, and the existent problems of conventional assembly design method are illuminated. ADMDMU (Assembly Design Method based Digital Mock-Up) is illuminated, and the process of ADMDMU established, and the ADMDMU architecture is given out. The key techniques of ADMDMU are analyzed, and include assembly design based KBE (Knowledge Based Engineering) and virtual assembly based physically attribute. According to physical attribute, physically based modeling, visual object movement control, force simulation method and assembly sequence planning method are emphatically illuminated. Assembly design system based DMU is established in foundation of ADMDMU.

Mechanical exposure implications of rationalization: A comparison of two flow strategies in a Swedish manufacturing plant

The aim of this case study was to (1) investigate differences in mechanical exposure (i.e. mechanical forces arising in the body of the operator) between two production strategies: long-cycle parallelised flow assembly (OLD) and conventional serial flow assembly (NEW), and (2) estimate potential changes in job exposure as a consequence of waste reduction when rationalising a line system.Data on postures, movements and whole body exposure were collected during an ordinary working shift, by means of video recordings synchronised to direct technical measurements of six professional operators.The results revealed the machine paced NEW system to have slower movements with less time spent in movements of high velocity compared to the self-paced OLD system. No significant differences were found between time-median posture levels. ‘Disturbances’ in the NEW system offered lower mechanical risk exposures compared to direct assembly work. Modelling the removal of wasteful ‘disturbances’ revealed both an increase in risk-implying fast movements and decrease in recovery-implying periods at low velocity – effectively isolating a work intensification. This study helps expose the complex relationship between rationalizations and mechanical exposure for system operators.

Performance Simulations of a Gas Turbine Disk-Blade Assembly Employing Miniature Radially Rotating Heat Pipes

With a substantially increased gas inlet temperature in modern gas turbines, the cooling of turbine disks is becoming a challenging task. In order to reduce the temperature at the disk rim, a new turbine disk incorporating radially rotating heat pipes has been proposed. The objective of this paper is to conduct a numerical investigation for the cooling effectiveness of the rotating heat pipe. One of the major tasks of this paper is to compare the performance between a proposed disk-blade assembly incorporating radially rotating heat pipes and a conventional disk-blade assembly without the heat pipes under the same heating and cooling conditions. The numerical investigation illustrates that the turbine disk cooling technique incorporating radially rotating heat pipes is feasible. The maximum temperature at the rim of the proposed disk can be reduced by more than 100 °C in comparison with that of a conventional disk without heat pipes. However, the average temperature at the blade airfoil surface can be reduced by only about 10 °C. In addition, both the heat pipe length and diameter have an important effect on the turbine disk cooling. Under the permission of material strength, a longer heat pipe or a larger heat pipe diameter will produce a lower temperature at the disk rim.

High Efficient Loading of Hydrophobic Molecules in Layer-by-Layer Assembled Microgel Films with the Assistance of Surfactant Micelles

Layer-by-layer (LbL) assembly enables the fabrication of various kinds of functional films by sequential deposi- tion of building blocks of polyelectrolytes, biomacromolecules, oligo-charged dyes, colloids, nanoparticles, polymeric com- plexes and so forth. However, water-insoluble organic species without necessary functional groups are difficult to be incor- porated into multilayer films by conventional LbL assembly method. The present work aims to develop a facile method for efficient loading of hydrophobic molecules into LbL assembled films. To do so, PAH-D microgels, which are chemically cross-linked poly(allylamine hydrochloride) (PAH) and dextran, are LbL assembled with hyaluronic sodium (HA) to produce PAH-D/HA microgel films. Sodium dodecylsulfate (SDS) micelles are used as carriers to incorporate hydrophobic molecules of pyrene and spiropyran. The negatively charged SDS micelles loaded with hydrophobic molecules are successfully incor- porated into the PAH-D/HA microgel films by a post-diffusion process, which produces transparent PAH-D microgel films with a large number of loaded pyrene and spiropyran molecules. Fluorescence emission spectra support that the hydrophobic molecules in PAH-D/HA films locate in the hydrophobic cores of SDS micelles. Stable loading of SDS micelles into PAH-D/HA films is achieved because of the strong electrostatic interaction between SDS micelles and protonated amine groups of PAH-D microgels. The high loading capacity of PAH-D/HA films toward SDS micelles encapsulated with hydro- phobic molecules originates from the high swellability of the PAH-D/HA films and the abundance of unpaired amine groups in the PAH-D layers for binding of SDS micelles. The amount of hydrophobic molecules loaded into PAH-D/HA microgel films can be conveniently controlled by varying the deposition cycles of PAH-D/HA films and the concentration of hydro- phobic molecules encapsulated in SDS micelles. The spiropyran-loaded PAH-D/HA microgel films show reversible photo- chromic property upon ultraviolet and visible light irradiation. The present work opens a cost-effective and general way to incorporate non-charged hydrophobic molecules into LbL assembled microgel films by using surfactant micelles as carriers. Keywords layer-by-layer assembly; polymeric microgels; microgel films; surfactant micelles; polymeric films

Tile Complexity of Linear Assemblies

Self-assembly is fundamental to both biological processes and nanoscience. Key features of self-assembly are its probabilistic nature and local programmability. These features can be leveraged to design better self-assembled systems. The conventional tile assembly model (TAM) developed by Winfree using Wang tiles is a powerful, Turing-universal theoretical framework which models varied self-assembly processes. A particular challenge in DNA nanoscience is to form linear assemblies or rulers of a specified length using the smallest possible tile set, where any tile type may appear more than once in the assembly. The tile complexity of a linear assembly is the cardinality of the tile set that produces it. These rulers can then be used as components for construction of other complex structures. While square assemblies have been extensively studied, many questions remain about fixed length linear assemblies, which are more basic constructs yet fundamental building blocks for molecular architectures. In this work, we extend TAM to take advantage of inherent probabilistic behavior in physically realized self-assembled systems by introducing randomization. We describe a natural extension to TAM called the probabilistic tile assembly model (PTAM). A restriction of the model, which we call the standard PTAM is considered in this report. Prior work in DNA self-assembly strongly suggests that standard PTAM can be realized in the laboratory. In TAM, a deterministic linear assembly of length $N$ requires a tile set of cardinality at least $N$. In contrast, we show various nontrivial probabilistic constructions for forming linear assemblies in PTAM with tile sets of sublinear cardinality, using techniques that differ considerably from existing assembly techniques. In particular, for any given $N$ we demonstrate linear assemblies of expected length $N$ with a tile set of cardinality $\Theta(\log N)$ using one pad per side of each tile. We prove a matching lower bound of $\Omega(\log N)$ on the tile complexity of linear assemblies of any given expected length $N$ in standard PTAM systems using one pad per side of each tile. We further demonstrate how linear assemblies can be modified to produce assemblies with sharp tail bounds on distribution of lengths by concatenating various assemblies together. In particular, we show that for infinitely many $N$ we can get linear assemblies with exponentially dropping tail distributions using $O(\log^3 N)$ tile types. We also propose a simple extension to PTAM called $\kappa$-pad systems in which we associate $\kappa$ pads with each side of a tile, allowing abutting tiles to bind when at least one pair of corresponding pads match. This gives linear assemblies of expected length $N$ with a $2$-pad (two pads per side of each tile) tile set of cardinality $\Theta(\frac{\log N}{\log \log N})$ for infinitely many $N$. We show that we cannot get smaller tile complexity by proving a lower bound of $\Omega(\frac{\log N}{\log \log N})$ for each $N$ on the cardinality of the $\kappa$-pad ($\kappa$-pads per side of each tile) tile set required to form linear assemblies of expected length $N$ in standard $\kappa$-pad PTAM systems for any positive integer $\kappa$. The techniques that we use for deriving these tile complexity lower bounds are notable as they differ from traditional Kolmogorov complexity based information theoretic methods used for lower bounds on tile complexity. Also, Kolmogorov complexity based lower bounds do not preclude the possibility of achieving assemblies of very small tile multiset cardinality for infinitely many $N$. In contrast, our lower bounds are stronger as they hold for every $N$, rather than for almost all $N$. All our probabilistic constructions are free from co-operative tile binding errors. Thus, for linear assembly systems, we have shown that randomization can be exploited to get large improvements in tile complexity at a small expense of precision in length.

Nanoscale convection assisted self-assembly of nanoparticle monolayer

Micron and sub-micron particles tend to be self-organized into well-defined arrays during conventional convective assembly, however this technique hardly works for the assembly of tiny nanoparticles smaller than 10 nm into monolayered arrays. The intrinsic difficulty is mainly related to the evaporation and convections occurring at a much larger volume than nanoparticle size. As a result, multilayered nanoparticle arrays are usually created. In this paper, we report that solvent evaporation and nanoparticle convection are artificially confined in nanoscale grooves near a pipette's periphery and the grooves can help assemble parallel strips because of the uni-directional translation of the pipette. The stacking layer of each strip is correlated with the grooves' diameter, thus the nanoparticle monolayer is fabricated in the tiny grooves. The narrowest strip width observed experimentally is geometrically limited by the effective diameter of the charged nanoparticles in gold colloid because nanoparticle convections from the inner chamber to the pipette's periphery will not occur within the grooves finer than the effective diameters.

Unconventional Layer‐by‐Layer Assembly: Surface Molecular Imprinting and Its Applications

Layer-by-layer assembly (LbL) is a rich, versatile, and powerful technique for fabricating multilayer thin films with controlled architecture and functions. Singly charged, uncharged, or water-repellent molecules cannot be used directly in conventional LbL assembly. This problem can be solved with unconventional LbL methods, by employing the preassembly of building blocks in solution and the use of these assemblies for LbL formation at the interface. This Concept summarizes different methods of unconventional LbL assembly, including electrostatic complex formation, hydrogen-bonded complexes, block-copolymer micelles, and π-π interaction complexes. These preassembly treatments endow the building blocks with enhanced abilities for advanced functionality, in particular, surface molecular imprinting, a new concept emerging from unconventional LbL. Molecular imprinting approaches are thus conceptually described based on different types of interactions and their great potential in applications is demonstrated by examples such as selective surface patterning and selective filtration.

Performance of Helical Disk Ground Anchors for Anchorage of Manufactured Housing

The performance of conventional (helical disk) ground anchors is important to the overall quality and safety of manufactured home installations and other applications requiring anchorage to ground. This paper presents findings from an investigation of the performance of conventional ground anchors and soil index test methods in a variety of soil conditions by using a range of ground anchor types, sizes, and assemblies. The results and conclusions address variation in soil classification methods, correlation of soil index test methods to anchor performance, predictability of conventional ground anchor assembly performance, and factors affecting reliability or repeatability of test methodology. Recommendations are given to improve a proposed ground anchor test protocol and to further address significant research needs, such as the effect of seasonal variation in ground moisture on soil index tests and ground anchor performance.

The inhibition of electrochemical carbon corrosion in polymer electrolyte membrane fuel cells using iridium nanodendrites

The addition of Ir-based water electrolysis catalysts to the catalyst layer in polymer electrolyte membrane fuel cells was examined as a promising approach for preventing electrochemical carbon corrosion under severely corrosive conditions. Electrochemical carbon corrosion of membrane electrode assemblies containing different amounts of IrO 2 or shape-controlled Ir dendrite catalysts were characterized using on-line mass spectrometry. In particular, Ir dendrite catalysts possess high activity toward oxygen evolution reactions when compared to IrO 2. As a result, Ir dendrites provided a very effective method of removing water from the catalyst layer. Therefore, the addition of 1 wt% Ir dendrite (0.008 mg cm −2) to the catalyst layer of the cathode decreased electrochemical carbon corrosion by 84% at 1.6 V NHE compared with a conventional membrane electrode assembly in the absence of water electrolysis catalysts.

Recent developments of lightweight, high performance heat pipes

Abstract Heat pipes, known as “super thermal conductors” have been widely used in many areas for more than 50 years. Currently, due to the various requirements put on cooling systems, such as lightweight, better heat transfer performance, and optimised appearance, heat pipes have been improved significantly in the past decades. This paper summarises the recent developments of lightweight, high performance heat pipes. Various methods or approaches to achieve the requirements of lightweight and high performance are introduced. The applications of lightweight materials can help reduce by up to 80% the weight of conventional copper heat pipes; however the lightweight material often has problems of corrosion. Although improving the design of wick structures and changing the size of conventional heat pipe assemblies can help to reduce weight and achieve high heat flux, there are still some limitations to the applications of lightweight materials such as magnesium due to its incompatibility with some working fluids.

Replacement of histone H3 with CENP-A directs global nucleosome array condensation and loosening of nucleosome superhelical termini

Centromere protein A (CENP-A) is a histone H3 variant that marks centromere location on the chromosome. To study the subunit structure and folding of human CENP-A-containing chromatin, we generated a set of nucleosomal arrays with canonical core histones and another set with CENP-A substituted for H3. At the level of quaternary structure and assembly, we find that CENP-A arrays are composed of octameric nucleosomes that assemble in a stepwise mechanism, recapitulating conventional array assembly with canonical histones. At intermediate structural resolution, we find that CENP-A-containing arrays are globally condensed relative to arrays with the canonical histones. At high structural resolution, using hydrogen-deuterium exchange coupled to mass spectrometry (H/DX-MS), we find that the DNA superhelical termini within each nucleosome are loosely connected to CENP-A, and we identify the key amino acid substitution that is largely responsible for this behavior. Also the C terminus of histone H2A undergoes rapid hydrogen exchange relative to canonical arrays and does so in a manner that is independent of nucleosomal array folding. These findings have implications for understanding CENP-A-containing nucleosome structure and higher-order chromatin folding at the centromere.

Layered and interfacially blended polyelectrolyte multi-walled carbon nanotube composites for enhanced ionic conductivity

To enhance the ionic conductivity in solid phase polyelectrolyte systems for lithium ion battery applications demands effective control of the phase properties. Here, we report on a strategy involving a layer-by-layer methodology of two polyelectrolytes, poly(ethylene oxide) (PEO) and poly(acrylic) acid (PAA) and carboxylic acid functionalized multi-walled carbon nanotubes (MWNTs). Optimization of the assembly strategy revealed that undoped and lithium-ion doped stacking of four layers provides excellent film growth and improvement of the ionic conductivity of up to 10 − 5 S cm − 1 , which exceeds conventional assemblies of lithium-ion doped [PEO/PAA] by up to two orders of magnitude. Although ionic conductivity was most effectively enhanced for ultrathin films (< 100 nm), [PEO/PAA/PEO/(PAA + MWNT)] stacking still provides an ionic conductivity of > 10 − 6 S cm − 1 for thick films (> 2 μm). The improvement of ionic conductivity was attributed to (i) interfacial phase mixing (blending) of the two polyelectrolytes, (ii) the MWNT contribution in the interfacial region, and (iii) the preferential adsorption of lithium-ions along the carbon nanotubes. This study involved a series of scanning probe methods including lateral force microscopy, and electrostatic force microscopy.

Attenuated total reflectance powder cell for infrared analysis of hygroscopic samples

An attenuated total reflectance (ATR) sample cell has been designed, manufactured and subsequently used for the mid-infrared analysis of hygroscopic samples. This sample cell was installed as a simple drop-in replacement for the cell supplied with our commercially available Harrick Mvp-Pro FTIR–ATR accessory. Calcium chloride, a well-known desiccant that has a propensity to absorb water into its crystal lattice, was selected as non-infrared active substrate to accentuate the efficacy of the cell in preserving the anhydrous state of the sample by straightforward monitoring of the water bands. In contrast, mid-infrared spectra are presented that qualitatively demonstrate the rapid rate at which atmospheric moisture is incorporated into the anhydrous sample when analyzed using the conventional ATR cell assembly.