Components Of Large Complexes Research Articles

Novel Mode and Equipment for Machining Large Complex Components

Novel Mode and Equipment for Machining Large Complex Components

Blocking late stages of splicing quickly limits pre-spliceosome assembly in vivo

ABSTRACTPre-messenger RNA splicing involves multi-step assembly of the large spliceosome complexes that catalyse the two consecutive trans-esterification reactions, resulting in intron removal. There is evidence that proof-reading mechanisms monitor the fidelity of this complex process. Transcripts that fail these fidelity tests are thought to be directed to degradation pathways, permitting the splicing factors to be recycled. While studying the roles of splicing factors in vivo, in budding yeast, we performed targeted depletion of individual proteins, and analysed the effect on co-transcriptional spliceosome assembly and splicing efficiency. Unexpectedly, depleting factors such as Prp16 or Prp22, that are known to function at the second catalytic step or later in the splicing pathway, resulted in a defect in the first step of splicing, and accumulation of arrested spliceosomes. Through a kinetic analysis of newly synthesized RNA, we observed that a second step splicing defect (the primary defect) was rapidly followed by the first step of splicing defect. Our results show that knocking down a splicing factor can quickly lead to a recycling defect with splicing factors sequestered in stalled complexes, thereby limiting new rounds of splicing. We demonstrate that this ‘feed-back’ effect can be minimized by depleting the target protein more gradually or only partially, allowing a better separation between primary and secondary effects. Our findings indicate that splicing surveillance mechanisms may not always cope with spliceosome assembly defects, and suggest that work involving knock-down of splicing factors or components of other large complexes should be carefully monitored to avoid potentially misleading conclusions.

Knowledge-guided lightweight method for large complex component based on geometric-stress feature correlation response

Complex geometric features and stress features as well as their intricate relationships are the important factors causing the complexity of lightweight for large component. In order to better coordinate the stress distribution with lightweight goal, a knowledge-guided lightweight method based on geometric-stress feature correlation response is proposed. Multistage decomposition and three-steps feature express strategy is utilized to construct the geometric features relationship model firstly. By combining the influence significance for stress features with the association grade for geometric features, and reasoning under lightweight expectations, the geometric-stress correlation knowledge is extracted. Furthermore, a knowledge-guided lightweight algorithm integrated knowledge correlation response with intelligent searching is proposed. Finally, the lightweight of X-type caterpillar frame is taken as example to demonstrate the effectiveness of this method.

Mobile-robotic machining for large complex components: A review study

Even though the robotic machining has achieved great success in machining of small components, it lacks the competence to machine large complex components, such as wind turbine blade, train carriage, and aircraft wing. In order to cope with this issue, the mobile machining robot system, which consists of a robot arm integrated with a mobile platform, is proposed to achieve the large workspace and high dexterity, and thus has the potential to machine the large complex components. However, due to the limitation of motion accuracy and structural stiffness, the current mobile-robots are hard to satisfy the high precision requirement of machining tasks. In this paper, some historical mobile-robotic machining systems are reviewed firstly, followed by some key techniques related to structure optimization, dynamics of the machining process, localization, and control techniques, which are fundamental for the structural stiffness and motion accuracy of mobile-robots. Finally, the prospect of mobile-robotic machining and the open questions are addressed.

Solid-State NMR Spectroscopy of RNA.

RNA structure is essential to understand RNA function and regulation in cellular processes. RNA acts either in isolation or as part of a complex with proteins. Both isolated and protein-complexed RNA represent a challenge for structural biology, due to the complexity of its conformational space and intrinsic dynamics. NMR, with its capability to cope with dynamic structures, is the optimal technique to study RNA conformation, ideally in solution. However, RNA-protein complexes are often very large, which limits the application of solution-state NMR. In this chapter we describe the methodology that we developed to determine the structure of RNA by solid-state NMR. Solid-state NMR is not limited by large molecular weights and can be optimally applied to study both the RNA and the protein components of large RNA-protein complexes. We review the methods for resonance assignments, collection of RNA-specific distance restraints, as well as detection of protein-RNA interfaces.

Study on robotic mobile machining techniques for large complex components

<p indent=0mm>Large complex components, such as wind turbine blades, aircraft structural parts, and parts of high-speed train, have been widely used in the field of aerospace, energy and transportation. In order to realize the automatic machining of the large complex components, it is possible to integrate the industrial robot arm into a mobile platform constituting a mobile-robot, so that the workspace and dexterity of the mobile-robot have significant increase. In this paper, around the topic of mobile-robotic machining technique, literature with respect to the dynamics and control of mobile-robots, multi-robot cooperative machining and measurement and reconstruction of large components will be revisited, which are the key techniques to realize the mobile-robotic machining. Furthermore, through the theoretical and experimental studies, the dynamic property of the mobile-robot during polishing process is analyzed. Based on the dynamic model of the mobile-robot, a T-S fuzzy control is designed, which aims to lead the robot following the surface of the workpiece with constant normal force and constant speed. Simulation results testified that the mobile-robot under the T-S fuzzy control can realize the polishing machining with constant normal force with constant speed.

On-Line 3D reconstruction based on laser scanning for robot machining of large complex components

The digital model is the foundation of intelligent manufacturing based on robot machining. In the intelligent manufacturing of large complex components in the fields of aerospace, energy equipment, shipbuilding, etc., it is often necessary to perform online 3D reconstruction of these large-sized components. In response to this demand, this paper designs a large-scale on-line 3D reconstruction system based on laser scanning principle. A laser scanner is used to generate the contour of the component accurately. Then, a series of contour sequences are generated by the movement perpendicular to the direction of the contour plane. These contour sequences are processed by algorithms to generate the 3D point cloud model of the large complex component. The results show that the system can generate the 3D point cloud model of large-scale complex components in an on-line manner and provide the basis for the detection of the components before machining and the machining planning in some cases.

Ceramic Membrane Coupling Process for Advanced Treatment of Electroplating Wastewater

Electroplating wastewater has attracted wide attention because of its large amount and complex components. It contains a variety of heavy metals and organics that are harmful to people’s healthy and the environment. With the continuous improvement of environmental protection requirements, the emission standards for electroplating pollutants have also been improved. Therefore, the advanced treatment of electroplating wastewater has become a hot spot in the current research. Membrane separation technology has been widely used in the advanced treatment of electroplating wastewater, especially ceramic membrane technology which is more competitive in practical application due to its unique advantages. In order to realize the advanced treatment of electroplating wastewater, the commonly used advanced treatment process and its existing problems were introduced firstly. Then the development of ceramic membrane technology in advanced treatment was discussed. And finally, a ceramic membrane coupling process for the advanced treatment of electroplating wastewater was proposed, which has good economic and social benefits.

Anisotropy in creep-ageing behavior of textured Al-Cu-Mg alloy

Creep age forming (CAF) has been developed to manufacture large complex components in aerospace industry. However, crystalline textures in initial material for CAF process may influence the creep ageing behavior, leading to low precision of formed component. In-planer anisotropy in creep-ageing behavior of a textured Al-Cu-Mg alloy was investigated. The total creep deformation decreased with the increase of the angles between the applied stress and rolling direction. The creep deformation of samples with loading direction parallel to rolling direction is 2.33, 2.07 and 1.62 times greater than that perpendicular to the rolling direction, under 120 MPa, 150 MPa and 180 MPa, respectively. A strong dependence of the anisotropy in creep deformation on the initial textures was suggested, according to the equivalent slid system numbers. With the rise of the external stress, the creep deformation of three different orientation samples increases but the anisotropy of those declines. However, the stress exponent difference among the three orientation samples may be related to the equivalent Schmid factor changes. Although the anisotropy of the mechanical properties in creep aged samples with various orientations is less than 5%, the in-planar anisotropy values of creep deformation under different creep age forming conditions are larger than 30%. It indicated that creep-ageing anisotropy of the studied alloy sheet cannot be ignored in their CAF applications.

Effects of Deflection Scanning of Electron Beam on Microstructure, Hardness and Treated Depth of TC18 Titanium Alloy

Abstract The high frequency deflection scanning of vacuum electron beam technology (DSEB) with line by line scanning mode and no overlap was employed to treat the surface of TC18 titanium alloy, for obtaining a homogeneous hardened surface layer. The purpose of the present work was to investigate the effects of critical process parameters, including beam current, focus current and treatment times, on the microstructure, hardness and treated depth of the treatment area. The treated specimens were characterized by SEM, optical microscope, and Vickers hardness tester. After treated by DSEB, the hardened surface layer is formed, which is mainly consisted of the acicular martensite, and the surface hardness of the treatment area is improved. Moreover, the microstructure of the hardened zone is homogeneous and has no obvious transition at the contact parts of two adjacent electron beams scanning. The depth of the hardened zone can be more than 200 μm and basically constant. These results show that DSEB is a very promising technological solution for the surface heat treatment of titanium alloy of large area and complex components.

Calculations of interaction energy between certain components of large multimolecular complexes

A scheme is proposed for calculating the energies of interaction between certain components of large multimolecular systems. These energies are used to model the binding and extraction of metal ions and metal complexes in solutions. The procedure can be extended with ease to calculate the energies of interaction between any two components of an arbitrary polyatomic system. Practical application of the scheme is illustrated taking actinide binding by different sorbents in solutions as examples.

Analysis of mRNA deadenylation by multi-protein complexes.

Poly(A) tails are found at the 3' end of almost every eukaryotic mRNA and are important for the stability of mRNAs and their translation into proteins. Thus, removal of the poly(A) tail, a process called deadenylation, is critical for regulation of gene expression. Most deadenylation enzymes are components of large multi-protein complexes. Here, we describe an in vitro deadenylation assay developed to study the exonucleolytic activities of the multi-protein Ccr4-Not and Pan2-Pan3 complexes. We discuss how this assay can be used with short synthetic RNAs, as well as longer RNA substrates generated using in vitro transcription. Importantly, quantitation of the reactions allows detailed analyses of deadenylation in the presence and absence of accessory factors, leading to new insights into targeted mRNA decay.

Mechanism of split-flow forming characteristics in plastic forming processing

The axial split-flow forming can be used to improve the metal flow and effectively reduce the forming force of large complex components. In this paper, in order to figure out the axial split-flow characteristics in the plastic forming, the flow regularity of the each deformation area in the material during the process of split-flow forming is studied based on the classical plasticity theory, the relationship between the split-flow area radius and the geometric parameters of the mold, and blank is analyzed with the analytic method of plastic mechanics, and a mathematical model for the split-flow area radius is built. The test shows that the model can be used to provide a theoretical reference to the accurate design on the axial split-flow forming of blank. Based on the energy theory and considering the complex coefficient, a mathematical model for the forming force of the axial split-flow forming unit is built. With a comparison among the forming experiments and finite element simulation analyses under different temperatures, the gray correlation degree between the model and the practical data in the experiment is 0.91, higher than 0.83 got by the traditional method. The developed model can reduction of the time in the preform optimization process and improvement the accuracy of forming force calculate in axial flow-split forming process. The result of this work can be used to theoretical guidance for practical engineering application of preforming and optimal design in axial split-flow precision forming.

Ploidy plasticity: a rapid and reversible strategy for adaptation to stress.

Organisms must be able to grow in a broad range of conditions found in their normal growth environment and for a species to survive, at least some cells in a population must adapt rapidly to extreme stress conditions that kill the majority of cells.Candida albicans, the most prevalent fungal pathogen of humans resides as a commensal in a broad range of niches within the human host. Growth conditions in these niches are highly variable and stresses such exposure to antifungal drugs can inhibit population growth abruptly. One of the mechanisms C. albicans uses to adapt rapidly to severe stresses is aneuploidy-a change in the total number of chromosomes such that one or more chromosomes are present in excess or are missing. Aneuploidy is quite common in wild isolates of fungi and other eukaryotic microbes. Aneuploidy can be achieved by chromosome nondisjunction during a simple mitosis, and in stress conditions it begins to appear after two mitotic divisions via a tetraploid intermediate. Aneuploidy usually resolves to euploidy (a balanced number of chromosomes), but not necessarily to diploidy. Aneuploidy of a specific chromosome can confer new phenotypes by virtue of the copy number of specific genes on that chromosome relative to the copies of other genes. Thus, it is not aneuploidy per se, but the relative copy number of specific genes that confers many tested aneuploidy-associated phenotypes. Aneuploidy almost always carries a fitness cost, as cells express most proteins encoded by genes on the aneuploid chromosome in proportion to the number of DNA copies of the gene. This is thought to be due to imbalances in the stoichiometry of different components of large complexes. Despite this, fitness is a relative function-and if stress is severe and population growth has slowed considerably, then even small growth advantages of some aneuploidies can provide a selective advantage. Thus, aneuploidy appears to provide a transient solution to severe and sudden stress conditions, and may promote the appearance of more stable solutions as well. Importantly, in many clinical and environmental isolates of different fungal species aneuploidy does not appear to have a high fitness cost, and is well-tolerated. Thus, rapid changes in ploidy may provide the opportunity for rapid adaptation to stress conditions in the environment, host niches or in response to antifungal drugs.

Cryo-Electron Tomography and Nucleocapsid Protein Labeling by Tomo-Bubblegram Imaging Reveal a Role for HIV-1 Integrase in Viral Maturation

HIV-1 maturation involves proteolysis of the precursor polyproteins, Gag and Gag-Pol, and assembly of a conical core containing the viral ribonucleoprotein (vRNP), comprised of the vRNA genome and associated proteins, notably nucleocapsid (NC). Allosteric integrase inhibitors (ALLINIs) are antiviral drugs initially thought to impede the viral integrase from inserting the DNA version of the genome into a host chromosome. However, recent studies indicate that their primary effects are on maturation. To investigate these effects, we imaged virions produced in the presence of ALLINIs by cryo-electron tomography (cryo-ET) and “tomo-bubblegram” imaging, a novel labeling technique that exploits the fact that vitrified protein subjected to relatively high levels of electron irradiation generates bubbles of hydrogen gas, which are readily visible. First, a regular cryo-tomogram is calculated. Then, after priming the specimen with additional exposures, a second tilt series is recorded, visualizing the bubbles. With HIV, we exploited the serendipitously discovered susceptibility of NC to bubbling.Most wild-type virions have conical cores with internal density, putatively the vRNP. In contrast, most ALLINI-treated virions have non-conical or conical cores with sparse internal contents but contain “eccentric condensates”, outside the capsid. Tomo-bubblegrams showed that the bubbles specifically label the contents of filled cores and eccentric condensates. In immature virions, in which the domains of Gag and Gag-Pol are radially ordered in a spherical shell, the bubbles appear in the NC layer of that shell. Immature virions in which NC is replaced by a leucine zipper (another RNA binder) yielded no bubbles, confirming NC as the bubbling component. Taken together, these observations provide strong evidence that ALLINIs sabotage capsid assembly and vRNP encapsidation. They also illustrate the potential of bubblegram imaging for mapping components of large macromolecular complexes.

Catalytic properties, functional attributes and industrial applications of β-glucosidases.

β-Glucosidases are diverse group of enzymes with great functional importance to biological systems. These are grouped in multiple glycoside hydrolase families based on their catalytic and sequence characteristics. Most studies carried out on β-glucosidases are focused on their industrial applications rather than their endogenous function in the target organisms. β-Glucosidases performed many functions in bacteria as they are components of large complexes called cellulosomes and are responsible for the hydrolysis of short chain oligosaccharides and cellobiose. In plants, β-glucosidases are involved in processes like formation of required intermediates for cell wall lignification, degradation of endosperm’s cell wall during germination and in plant defense against biotic stresses. Mammalian β-glucosidases are thought to play roles in metabolism of glycolipids and dietary glucosides, and signaling functions. These enzymes have diverse biotechnological applications in food, surfactant, biofuel, and agricultural industries. The search for novel and improved β-glucosidase is still continued to fulfills demand of an industrially suitable enzyme. In this review, a comprehensive overview on detailed functional roles of β-glucosidases in different organisms, their industrial applications, and recent cloning and expression studies with biochemical characterization of such enzymes is presented for the better understanding and efficient use of diverse β-glucosidases.

Fabrication feasibility study on copper cold spray in tokamak system

To improve the plasma vertical stabilization during tokamak operation, partial pure copper layer could be considered on the inner shell of vacuum vessel which is large complex component made of stainless steel. The copper cladding has been a great challenge due to the complicated configuration and difficulty of dissimilar metal joining. From an engineering point of view, there are several candidates for the copper cladding such as cold spray, overlay welding and explosive welding. In this paper, fabrication feasibility study for copper cladding has been carried out by using cold spray method, and a set of full scale mock-up of in-vessel component has been conducted to demonstrate applicability of copper cold spray and to verify copper layer. The results of copper cold spray on test specimens and mock-up showed good properties and no defects on the thick copper layer. Optimum conditions of copper cold spray have been developed based on these results. Accordingly, it can be concluded that cold spray is a feasible and practical method to achieve thick copper cladding on tokamak component.

Compact Low-cost Scanner for 3D-Reconstruction of Body Parts with Structured Light Illumination

This paper describes a low-cost miniaturized 3D reconstruction approach using structured light. By projecting known patterns onto a surface, shape and structure of the surface can be measured and characteristic parameters of deformation can be determined. Existing approaches use large geometries and complex optical components. Here we present our system with the size of a cigarette pack and a working distance of only 6 cm. The theoretical depth resolution of the system is determined by the resolution of the camera and the projector as well as the system geometry and was found to be about 100 µm.

Neuronal activity induces synaptic delivery of hnRNP A2/B1 by a BDNF-dependent mechanism in cultured hippocampal neurons.

Dendritic protein synthesis plays a critical role in several forms of synaptic plasticity, including BDNF (brain-derived neurotrophic factor)-mediated long-term synaptic potentiation (LTP). Dendritic transcripts are typically transported in a repressed state as components of large ribonucleoprotein complexes, and then translated upon stimulation at, or in the vicinity, of activated synapses. Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) is a trans-acting factor involved in dendritic mRNA trafficking, but how the distribution of the protein in dendrites is regulated has not been characterized. Here we found that a fraction of hnRNP A2/B1 is present at the synapse under resting conditions in cultured hippocampal neurons. Accordingly, this ribonucleoprotein was detected in free mRNP, monosomal, and polyribosomal fractions obtained from synaptoneurosomes. Neuronal activity and BDNF treatment increased hnRNP A2/B1 protein levels in the cell body and dendritic compartments, and induced the delivery of this protein to synaptic sites. The activity-dependent accumulation of hnRNP A2/B1 at the synapse required, at least in part, the activation of TrkB receptors, presumably by BDNF. This neurotrophin also upregulated the hnRNP A2/B1 mRNA in the soma but was without effect on the abundance of neuritic hnRNP A2/B1 transcripts. These results show that the distribution of hnRNP A2/B1 is regulated by BDNF and by neuronal activity, an effect that may have a role in BDNF-induced synaptic plasticity events.

Microstructure and elevated temperature mechanical and creep properties of Mg–4Y–3Nd–0.5Zr alloy in the product form of a large structural casting

In order to save the invaluable heavy rare earth (HRE) elements for important functional applications, a modified version of the WE43 magnesium alloy, Mg–4Y–3Nd–0.5Zr (wt.%), free of the HRE elements, has been designed. As part of the alloy development program, a large complex component of the alloy (net product weight: 80kg) was made via differential pressure casting. The large component was then subjected to the T6 treatment (solid solution and ageing) following established commercial practice for the T6 treatment of the WE43 alloy. A significant number of samples were prepared from the thickest section (58mm) of the T6-treated component for both microstructural characterization and detailed property assessment. The alloy showed noticeably higher tensile strengths than did the HRE-containing WE43 alloy over the temperature range of 473–573K. The creep resistance of the alloy was superior to that of the WE43 alloy at 473K while being similar at 523K. The microstructures of the alloy in the as-cast, solution treated and then aged states were characterized. The component-based detailed assessment suggests that the idea of using neodymium (Nd) to replace the HRE elements in the WE43 alloy is promising for structural applications at elevated temperatures.