Paradigm For Assembly Research Articles

Eyetracking for two-person tasks with manipulation of a virtual world

Eyetracking facilities are typically restricted to monitoring a single person viewing static images or pre-recorded video. In the present article, we describe a system that makes it possible to study visual attention in coordination with other activity during joint action. The software links two eyetracking systems in parallel and provides an on-screen task. By locating eye movements against dynamic screen regions, it permits automatic tracking of moving on-screen objects. Using existing SR technology, the system can also cross-project each participant's eyetrack and mouse location onto the other's on-screen work space. Keeping a complete record of eyetrack and on-screen events in the same format as subsequent human coding, the system permits the analysis of multiple modalities. The software offers new approaches to spontaneous multimodal communication: joint action and joint attention. These capacities are demonstrated using an experimental paradigm for cooperative on-screen assembly of a two-dimensional model. The software is available under an open source license.

The Baseplate Wedges of Bacteriophage T4 Spontaneously Assemble into Hubless Baseplate-Like Structure In Vitro

The baseplate of phage T4 is an important model system in viral supramolecular assembly. The baseplate consists of six wedges surrounding the central hub. We report the first successful attempt at complete wedge assembly using an in vitro approach based on recombinant proteins. The cells expressing the individual wedge proteins were mixed in a combinatorial manner and then lysed. Using this approach, we could both reliably isolate the complete wedge along with a series of intermediate complexes as well as determine the exact sequence of assembly. The individual proteins and intermediate complexes at each step of the wedge assembly were successfully purified and characterized by sedimentation velocity and electron microscopy. Although our results mostly confirmed the hypothesized sequential wedge assembly pathway as established using phage mutants, interestingly, we also detected some protein interactions not following the specified order. It was found that association of gene product 53 to the immediate precursor complex induces spontaneous association of the wedges to form a six-fold star-shaped baseplate-like structure in the absence of the hub. The formation of the baseplate-like structure was facilitated by the addition of gene product 25. The complete wedge in the star-shaped supramolecular complex has a structure similar to the baseplate in the expanded “star” conformation found after infection. Based on the results of the present and previous studies, we assume that the strict order of wedge assembly is due to the induced conformational change caused by every new binding event. The significance of a 40-S star-shaped baseplate structure, which was previously reported and was also found in this study, is discussed in the light of a new paradigm for T4 baseplate assembly involving the star-shaped wedge ring and the central hub. Importantly, the methods described in this article suggest a novel methodology for future structural characterization of supramolecular protein assemblies.

Self-assembly of a functional electronic circuit directed by capillary interactions

We report on the use of capillary interactions to drive the self-assembly of an electronic circuit based on mesoscale building blocks. The specific target structure is a linear heterotetramer comprising non-identical millimetre-scale cubic blocks that, following assembly, forms a functioning astable multivibrator circuit. Importantly, the self-assembly process is designed to be unconstrained, i.e., each of the blocks are free to move in any way during assembly. To this end, solder droplets are selectively patterned on the block faces. On contact, capillary interactions between shape complimentary solder patterns on the blocks cause the molten solder droplets to coalesce and the blocks to self-assemble. In this way, capillary forces direct the alignment, registration, linking and electrical interconnection of each block during the assembly process. This demonstration of mesoscale self-assembly mediated by capillary interactions illustrates that the application of unconventional assembly paradigms to complex structure fabrication is feasible and that these approaches may yet yield viable strategies for fabrication of highly integrated systems.

Uncovering Extremely Metal-Poor Stars in the Milky Way's Ultrafaint Dwarf Spheroidal Satellite Galaxies

We present new metallicity measurements for 298 individual red giant branch stars in eight of the least luminous dwarf spheroidal galaxies (dSphs) in the Milky Way (MW) system. Our technique is based on medium resolution Keck/DEIMOS spectroscopy coupled with spectral synthesis. We present the first spectroscopic metallicities at [Fe/H] < -3.0 of stars in a dwarf galaxy, with individual stellar metallicities as low as [Fe/H] = -3.3. Because our [Fe/H] measurements are not tied to empirical metallicity calibrators and are sensitive to arbitrarily low metallicities, we are able to probe this extremely metal-poor regime accurately. The metallicity distribution of stars in these dSphs is similar to the MW halo at the metal-poor end. We also demonstrate that the luminosity-metallicity relation previously seen in more luminous dSph galaxies (M_V = -13.4 to -8.8) extends smoothly down to an absolute magnitude of M_V = -3.7. The discovery of extremely metal-poor stars in dSphs lends support to the LCDM galaxy assembly paradigm wherein dwarf galaxies dissolve to form the stellar halo of the MW.

A Flow Process for the Multi‐Step Synthesis of the Alkaloid Natural Product Oxomaritidine: A New Paradigm for Molecular Assembly.

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Responsive Periodic Mesoporous Polydiacetylene/Silica Nanocomposites

Responsive PMO materials have been synthesized through co-assembly of bridged diacetylenic silsesquioxane and surfactant. The spatially defined polydiacetylenic component, mesoporous network, and the covalent proximity of polydiacetylene to silica endow the PMO with mechanical robustness, reversible chromatic responses, improved thermal stability, and faster responses to chemical stimuli. This research also provides an efficient molecular design and assembly paradigm to fabricate a family of conjugated optoelectronic materials, creating novel platforms for sensors, actuators, and other device applications.

A flow process for the multi-step synthesis of the alkaloid natural product oxomaritidine: a new paradigm for molecular assembly

A flow process for the multi-step synthesis of the alkaloid natural product (+/-)-oxomaritidine is described, mediated through the use of microfluidic pumping systems that progress material through various packed columns containing immobilized reagents, catalysts, scavengers or catch and release agents; our route involves the combination of seven separate synthetic steps linked into one continuous sequence utilizing flow chemistry.

Work at the Uddevalla Volvo Plant from the Perspective of the Demand-Control Model

The Uddevalla Volvo plant represents a different paradigm for automotive assembly. In parallel-flow work, self-managed work groups assemble entire automobiles with comparable productivity as conventional series-flow assembly lines. From the perspective of the demand-control model, operators at the Uddevalla plant have low physical and timing demands, high psychological demands because of increased duties and high-decision latitude due to varied and complex skills utilized, the two latter characterizing active work. Operators at standard assembly lines have higher levels of physical and timing demands, lower levels of psychological demand, and lower control, characterizing high-strain work. Active work is related to lower incidence of heart disease than high-strain work.

A component-oriented software authoring system for exploratory visualization

This paper discusses the benefits of a component-oriented visual software authoring system that is based on open standards and provides the seamless integration of various software tools in a unified environment. It employs a visual component assembly paradigm for ease of construction, Java™ and JavaBeans™ component architecture for the open environment, and recursive development methods, all of which allow us to rapidly construct and share applications from independently developed components. Moreover, it is highly interactive and fully configurable at run-time in order to support exploratory visualization. This versatility has the potential to improve the integration of independently developed analysis tools and the dissemination of research findings.

Size, position and dynamic behavior of PML nuclear bodies following cell stress as a paradigm for supramolecular trafficking and assembly.

The promyelocytic leukemia (PML) protein has been implicated in many cellular pathways, but it is unclear whether the accumulation of PML and other proteins into PML nuclear bodies is a regulated or random process. In this paper we have used a variety of physiological stresses, including heat stress, Cd+2 exposure and adenovirus E1A expression, as tools to study the principles underlying the assembly/disassembly, integrity and dynamic behavior of PML bodies. Using live-cell imaging and immunofluorescence microscopy, we observe that PML bodies are positionally stable over time intervals of a few hours. After stress, however, microstructures form as a result of fission or budding from the surface of 'parental' PML bodies. Since new PML bodies do not form at new locations, and the relative sizes observed before heat shock are preserved after recovery, we conclude that there are pre-determined locations for PML bodies, and that they are not random accumulations of protein. Over-expression of small ubiquitin-like modifier (SUMO-1) prevents stress-induced disassembly of PML bodies, implicating SUMO-1 as a key regulator of PML body integrity. Stress-induced fission of SUMO-1-deficient microstructures from parental PML bodies may be a mechanism to change local chromatin domain environments by the dispersal of protein factors. PML bodies may provide a useful paradigm for the dynamics and integrity of other supramolecular protein complexes involved in processes such as transcription, RNA processing DNA repair and replication.

Crystal engineering of a liquid crystalline piperazinedione.

[structure: see text] A molecule designed to self-assemble via hydrogen bonding, arene-arene, and van der Waals interactions and expected to possess thermotropic liquid crystalline properties has been synthesized and characterized. Results support the validity of an assembly paradigm based on incorporation of chemically orthogonal and spatially independent recognition elements in the molecular building blocks.

ESAE: A rapid service creation environment for next-generation services

The telecommunications industry is entering a brave new world of communication where consumers are looking for new ways to stay connected. To keep up with the pace, service providers need a service creation environment (SCE) to rapidly develop, test, simulate, and deploy next-generation services including wireless data, voice, and Internet applications. Next-generation SCEs have to support a wide variety of network interfaces and protocols that allow network operators, application service providers (ASPs), and third-party developers to build, deploy, and manage such services. The Lucent Enhanced Services Authoring Environment (eSAE, pronounced “easy”) has been developed as an enabler of converged services with speed-to-market mindset. Service developers without any specialized skills in proprietary languages can create most of the services quickly by using industry standard languages like Java,∗ C++, and XML. This paper will explore in detail how the eSAE architecture promotes reusability using JavaBeans∗ component technology and how the visual assembly paradigm eases service composition. Open network application programming interfaces (APIs) (for example, JTAPI, FullCircle™, Parlay) can be incrementally supported for standards compliance. XML technology is leveraged for complete service specification (data modeling for call logic and service provisioning).3

Structure of bacteriophage P22 portal protein in relation to assembly: investigation by Raman spectroscopy.

Salmonella phage P22, which serves as an assembly paradigm for icosahedral double-stranded DNA viruses, packages its viral genome through a capsid channel (portal) comprising 12 copies of a 725-residue subunit. Secondary and tertiary structures of the portal subunit in monomeric and dodecameric states have been investigated by Raman spectroscopy using a His6-tagged recombinant protein that self-assembles in vitro [Moore, S. D., and Prevelige, P. E., Jr. (2001) J. Biol. Chem. 276, 6779-6788]. The portal protein exhibits Raman secondary structure markers typical of a highly alpha-helical subunit fold that is little perturbed by assembly. On the other hand, Raman markers of subunit side chains change dramatically with assembly, an indication of extensive changes in side chain environments. The cysteinyl Raman signature of the portal consists of a complex pattern of sulfhydryl stretching bands, revealing diverse hydrogen-bonding states for the four S-H groups per subunit (Cys 153, Cys 173, Cys 283, and Cys 516). Upon assembly, the population of strongly hydrogen-bonded S-H groups decreases, while the population of weakly hydrogen-bonded S-H groups increases, implying that specific intrasubunit S-H.X hydrogen bonds must be weakened to effect dodecamer assembly and that the molecular mechanism involves reorganization of subunit domains without appreciable changes in domain conformations. Comparison with other viral protein assemblies suggests an assembly process not requiring metastable intermediates. The recently published X-ray structure of the phi29 portal [Simpson, A. A., et al. (2000) Nature 408, 745-750] shows that residues 125-225 lining the channel surface form alpha-helical modules spaced by short beta-strands and turns; a surprisingly close secondary structure homology is predicted for residues 240-350 of the P22 portal, despite no apparent sequence homology. This motif is proposed as an evolutionarily conserved domain involved in DNA translocation.

Behaviour-based robot program invariance

Despite the numerous technical improvements, robot programming is still today a very tedious activity requiring considerable efforts for fine tuning programs written off-line. Moreover, such programs are usually not particularly portable from one robot to another, sometimes even when the robots are from the same maker.The issue addressed in the work reported here is how to overcome these shortcomings. In this respect, the argument is to develop programs within the behaviour-based assembly paradigm which views tasks in terms of goal-achieving entities (behaviours). The focus on the description of a task more than its implementation is the key to generality and portability. As shown with the aid of two similar, but not identical, assembly benchmarks, behavioural programs are independent of any specificity of each assembly kit and can, indeed, be constructed using the very same code.

Multivalent protein-carbohydrate interactions. A new paradigm for supermolecular assembly and signal transduction.

Many biological recognition processes involve the binding and clustering of ligand-receptor complexes and concomitant signal transduction events. Such interactions have recently been observed in human T cells in which binding and cross-linking of specific glycoprotein counter-receptors on the surface of the cells by an endogenous bivalent carbohydrate binding protein (galectin-1) leads to apoptosis [Pace, K. E., et al. (1999) J. Immunol. 163, 3801-3811]. Importantly, different counter-receptors associated with specific phosphatase or kinase activities were shown to form separate clusters on the surface of the cells as a result of galectin-1 binding to the carbohydrate moieties of the respective glycoproteins. This suggests that the unique separation and organization of signaling molecules that results from galectin-1 binding is involved in delivering the signal to die. The ability of galectin-1 to induce the separation of specific glycoprotein receptors was modeled on the basis of molecular and structural studies of the binding of multivalent carbohydrates to lectins that result in the formation of specific two- and three-dimensional cross-linked lattices. These latter studies have been recently highlighted by X-ray crystallographic results showing that a single tetravalent lectin forms distinct cross-linked complexes with four different bivalent oligosaccharides [Olsen, L. R., et al. (1997) Biochemistry 36, 15073-15080]. In this report, binding and cross-linking of multivalent carbohydrates with multivalent lectins is shown to be a new paradigm for supermolecular assembly and signal transduction in biological systems.

Cryo-Electron Microscopy Reveals the Functional Organization of an Enveloped Virus, Semliki Forest Virus

Semliki Forest virus serves as a paradigm for membrane fusion and assembly. Our icosahedral reconstruction combined 5276 particle images from 48 cryo-electron micrographs and determined the virion structure to 9 Å resolution. The improved resolution of this map reveals an N-terminal arm linking capsid subunits and defines the spike–capsid interaction sites. It illustrates the paired helical nature of the transmembrane segments and the elongated structures connecting them to the spike projecting domains. A 10 Å diameter density in the fusion protein lines the cavity at the center of the spike. These clearly visible features combine with the variation in order between the layers to provide a framework for understanding the structural changes during the life cycle of an enveloped virus.

MicroJoinery: concept, definition, and application to microsystem development

A new hybrid technology for fabricating, interconnecting, and assembling microdevices is introduced. This new technology is predicated on the creation of dimensionally scaled manufacturing and assembly techniques and has been coined ‘MicroJoinery’ as a descriptive designation. MicroJoinery, along with its collected ‘toolbox’ of associated microfabrication techniques, allows for the facile realization of a widely divergent collection of microsystem components including: fluidic microvalves, microfluidic interconnects, microreaction chambers, xyz positioning microstages, fiber-optic switches, etc. Additionally, MicroJoinery provides a new paradigm for design and practical assembly of microsystems. This paper explores the applications of MicroJoinery by presenting several examples of microdevices and microsystems tractable through MicroJoinery.