Fast Reconfigurations Research Articles

Magnetically Actuated Reconfigurable Metamaterials as Conformal Electromagnetic Filters

Electromagnetic Filters In article number 2200106, Renee Zhao and co-workers report reconfigurable electromagnetic metamaterials based on magnetically responsive lattices. The magnetic actuation enables fast and programmable structural reconfigurations between flat deployed/folded and curved deployed/folded states for both conformal and freestanding metamaterials. The integrated customizable subwavelength patterns effectively switch the metamaterial between accepting and rejecting incident electromagnetic waves upon structural reconfiguration.

Magnetic Multimaterial Printing for Multimodal Shape Transformation with Tunable Properties and Shiftable Mechanical Behaviors

Magnetic soft materials (MSMs) have shown potential in soft robotics, actuators, metamaterials, and biomedical devices because they are capable of untethered, fast, and reversible shape reconfigurations as well as controllable dynamic motions under applied magnetic fields. Recently, magnetic shape memory polymers (M-SMPs) that incorporate hard magnetic particles in shape memory polymers demonstrated superior shape manipulation performance by realizing reprogrammable, untethered, fast, and reversible shape transformation and shape locking in one material system. In this work, we develop a multimaterial printing technology for the complex structural integration of MSMs and M-SMPs to explore their enhanced multimodal shape transformation and tunable properties. By cooperative thermal and magnetic actuation, we demonstrate multiple deformation modes with distinct shape configurations, which further enable active metamaterials with tunable physical properties such as sign-change Poisson's ratio. Because of the multiphysics response of the M-MSP/MSM metamaterials, one distinct feature is their capability of shifting between various global mechanical behaviors such as expansion, contraction, shear, and bending. We anticipate that the multimaterial printing technique opens new avenues for the fabrication of multifunctional magnetic materials.

Distributing Sequential Control for Manufacturing Automation Systems

Recent trends in manufacturing require the use of reconfigurable equipment that facilitates rapid and cost-effective change of functionality through modular design, which supports fast integration. Intelligent devices (e.g., sensors, actuators) with integrated computation and communication capabilities enable high-level modularity, not only with the respect to hardware components but also in terms of control functionality; this can be achieved by distributing control to different network-connected devices. Thus, to enable fast and reliable system reconfigurations, in this brief, we introduce a method for distribution of control tasks and generation of control code for the devices in the control network. Our approach is based on the control interpreted Petri nets (CIPNs) formalism. We start from a CIPN capturing the centralized (overall) control system, and the mapping of input and output signals to local controllers (LCs) (i.e., smart devices) that have direct physical access to system sensors and actuators. From these, our method automatically designs distributed control tasks for LCs in the network, as well as generates control code for each LC. The applicability of the proposed method is experimentally verified on two real-world case studies.

Real-time high spatial resolution dose verification in stereotactic motion adaptive arc radiotherapy.

PurposeRadiation treatments delivered with real‐time multileaf collimator (MLC) tracking currently lack fast pretreatment or real‐time quality assurance. The purpose of this study is to test a 2D silicon detector, MagicPlate‐512 (MP512), in a complex clinical environment involving real‐time reconfiguration of the MLC leaves during target tracking.Methods MP512 was placed in the center of a solid water phantom and mounted on a motion platform used to simulate three different patient motions. Electromagnetic target tracking was implemented using the Calypso system (Varian Medical Systems, Palo Alto, CA, USA) and an MLC tracking software. A two‐arc VMAT plan was delivered and 2D dose distributions were reconstructed by MP512, EBT3 film, and the Eclipse treatment planning system (TPS). Dose maps were compared using gamma analysis with 2%/2 mm and 3%/3 mm acceptance criteria. Dose profiles were generated in sup‐inf and lateral directions to show the agreement of MP512 to EBT3 and to highlight the efficacy of the MLC tracking system in mitigating the effect of the simulated patient motion.ResultsUsing a 3%/3 mm acceptance criterion for 2D gamma analysis, MP512 to EBT3 film agreement was 99% and MP512 to TPS agreement was 100%. For a 2%/2 mm criterion, the agreement was 95% and 98%, respectively. Full width at half maximum and 80%/20% penumbral width of the MP512 and EBT3 dose profiles agreed within 1 mm and 0.5 mm, respectively. Patient motion increased the measured dose profile penumbral width by nearly 2 mm (with respect to the no‐motion case); however, the MLC tracking strategy was able to mitigate 80% of this effect.Conclusions MP512 is capable of high spatial resolution 2D dose reconstruction during adaptive MLC tracking, including arc deliveries. It shows potential as an effective tool for 2D small field dosimetry and pretreatment quality assurance for MLC tracking modalities. These results provide confidence that detector‐based pretreatment dosimetry is clinically feasible despite fast real‐time MLC reconfigurations.

Rollup: Non-Disruptive Rolling Upgrade with Fast Consensus-Based Dynamic Reconfigurations

Rolling upgrade consists of upgrading progressively the servers of a distributed system to reduce service downtime.Upgrading a subset of servers requires a well-engineered cluster membership protocol to maintain, in the meantime, the availability of the system state. Existing cluster membership reconfigurations, like CoreOS etcd, rely on a primary not only for reconfiguration but also for storing information. At any moment, there can be at most one primary, whose replacement induces disruption. We propose Rollup, a non-disruptive rolling upgrade protocol with a fast consensus-based reconfiguration. Rollup relies on a candidate leader only for the reconfiguration and scalable biquorums for service requests. While Rollup implements a non-disruptive cluster membership protocol, it does not offer a full-fledged coordination service. We analyzed Rollup theoretically and experimentally on an isolated network of 26 physical machines and an Amazon EC2 cluster of 59 virtual machines. Our results show an 8-fold speedup compared to a rolling upgrade based on a primary for reconfiguration.

Structure and Internal Dynamics of Calcitonin Family Peptides: Implications for Amyloid Formation

The calcitonin peptide (Ct) family comprises the intrinsically disordered proteins amylin (IAPP), calcitonin gene-related peptide (CGRP), calcitonin, and adrenomedullins. These are genetically and structurally related hormone peptides that are able to bind to each other's receptors, though with varying degrees of affinity. Some of these peptides form amyloid fibers, while others do not. They contain highly conserved sequence elements that have been experimentally shown to affect the secondary structural preferences of these peptides. The effect of such conserved elements on tertiary structure has not been experimentally explored to the same extent. Detecting tertiary structural properties of IDPs is considerably more challenging due to fast reconfigurations of the backbone over a wide range of possible conformations. High resolution time-resolved techniques are needed. We use a nanosecond laser spectroscopy technique to measure transient tertiary contact formation. This technique reveals information on the structure and internal dynamics of IDPs. We compare members of the Ct family which differ in hydrophobicity and net charge, and study the effect of proline mutations on contact formation rates. We find that functionally required, conserved sequence elements play an important role in determining the structure, internal dynamics and aggregation properties of these peptides.

Electrostatic Interactions Modulate the Structure and Dynamics of Calcitonin Gene-Related Peptide

Calcitonin gene-related peptide (CGRP) is an intrinsically disordered, 37 residue neuropeptide that acts as a potent vasodilator. It is a member of the calcitonin peptide (Ct) family, together with amylin, calcitonin and adrenomedullin. Understanding how sequence variations affect the conformation and dynamics of these genetically and functionally related IDPs is of considerable interest. While the secondary structural preferences of these peptides have been experimentally determined, the tertiary structural preferences are more challenging to detect due to fast reconfigurations of the backbone over a wide range of conformations, and to the very low solubility of certain Ct family peptides. High resolution time-resolved techniques are needed.We use a nanosecond-resolved spectroscopic technique based on tryptophan triplet quenching by cystine to detect tertiary contact formation in CGRP under varying solvent and temperature conditions. Using this technique we had previously found that conserved structural elements of amylin and CGRP induce compact states, characterized by short end-to-end distances(1,2). Here we compare contact formation rates of wild type and mutant CGRPs with different net charge. We find that electrostatic interactions modulate the degree of compaction of CGRP. The observed difference between CGRP and amylin can be rationalized in terms of electrostatic interactions. Interestingly, even with a net charge of +6, CGRP remains more compact in aqueous solvent than in denaturant with high ionic strength, indicating strong attractive intra-molecular interactions. Overall our data are consistent with a common mechanism driving compaction in CGRP and amylin, with electrostatic interactions modulating the degree of compaction in CGRP. We discuss our findings in relation to secondary structural preferences of these peptides and discuss their possible functional role.1 Vaiana S.M. et al. Biophys. J. 97 2009.2 Sara M. Sizemore et al.2012 Biophys. J, Supplement, Abstract.

Effect of a Single-Point Mutation on the Conformation and Dynamics of Islet Amyloid Polypeptide from Nanosecond-Resolved Intramolecular Contact Formation

Islet amyloid polypeptide (IAPP) is an intrinsically disordered protein involved in regulating glucose metabolism and gastric emptying. It plays a crucial role in beta cell failure in diabetes type II, where it accumulates in the form of amyloid fibers. Human IAPP (hIAPP) is arguably the most amyloidogenic naturally occurring peptide known so far. Recent work by Raleigh and coworkers shows that a single-point mutation (I26P) converts it into an effective in vitro amyloid inhibitor1,2. The I26P mutation has been proposed to inhibit fibril formation by affecting the ability of the disordered C terminal tail to rearrange into the amyloid fibril structure, while maintaining intact the conformational properties of the N-terminal region, putatively responsible for the formation of aggregate intermediates1,2. Though such mechanism has been proposed, the conformational and dynamical properties of the I26P monomer have not been experimentally determined yet.We use tryptophan triplet quenching by cystine to measure the rate of contact formation between the two ends of the I26P peptide. This technique has previously revealed conformational differences between rIAPP and hIAPP3. It allows detecting both changes in the equilibrium end-to-end distance distribution and in the diffusional dynamics of the end-to-end distance caused by fast reconfigurations of backbone dihedral angles. We compare results for I26P, hIAPP, rIAPP, and model worm like chain peptides of same length. We discuss the effect of proline substitutions on the conformation and dynamics of these intrinsically disordered proteins and their possible effect on amyloid aggregation.Footnotes1 Abedini A. et al. JACS 129 20072 Meng F. et al. JACS 132 20103 Vaiana SM et al. BiophysJ 97 2009

Transient Tertiary Contact Formation in the CGRP Neuropeptide Revealed by Nanosecond Laser Spectroscopy

Calcitonin gene-related peptide (CGRP) is an intrinsically disordered, 37 residue neuropeptide that acts as a potent vasodilator, which is of considerable interest in migrane research. It is a member of the calcitonin peptide (Ct) family, together with amylin, calcitonin and adrenomedullin. These are genetically and structurally related intrinsically disordered hormone peptides that are able to bind to each other’s receptors, though with varying degrees of affinity. They contain highly conserved sequence elements that have been experimentally shown to affect the secondary structural preferences of these peptides. The effect of such conserved elements on tertiary structure has not been experimentally explored to the same extent. Detecting tertiary structural properties of IDPs is considerably more challenging due to fast reconfigurations of the backbone over a wide range of possible conformations. High resolution time-resolved techniques are needed.We use a nanosecond-resolved spectroscopic technique based on tryptophan triplet quenching by cystine to detect tertiary contact formation in CGRP under varying solvent and temperature conditions. Using this technique, Vaiana et al.1 have previously shown that conserved structural elements of amylin induce compact states characterized by short end-to-end distances, and that compaction is not driven by hydrophobic side-chains. Using triplet quenching we explore the effect of these conserved elements on the conformation and dynamics of CGRP, a peptide with higher mean hydrophobicity and net charge per residue than amylin. We discuss our findings in relation to secondary structural preferences of these peptides and discuss their possible functional role.Footnote1 Vaiana S.M. et al. Biophys. J. 97 2009.

Kinetic thin current sheets: their formation in relation to magnetotail mesoscale turbulent dynamics

Abstract. Dynamics of the magnetotail plasma sheet (PS) features nonlinear structures on two totally different scales. There are very thin current sheets (CS) on kinetic scale of the ion gyroradius. And there are intense plasma flow and magnetic field variations on mesoscales (a few earth radii); those are interpreted as mostly 2-D MHD turbulence. On the other hand, the specific nature of slow large scale magnetotail evolution leads to large differences in the PS properties and those of the lobe plasma. As a result, while fast reconnection bursts in the tail provide quasi-stationary fast mesoscale reconfigurations in the lobes, they cannot however be accompanied by restructuring of CS on the same fast time scale. Violations of force balance in the PS are thus generated. Simulation using a hybrid code and starting with such imbalance, provides an evidence of very thin kinetic CS structures formation, embedded into the much thicker PS. The momentum balance gets locally restored by means of ion acceleration up to the Alfvénic velocity. The process provides an effective mechanism for transformation of magnetic energy accumulated in the magnetotail, into energy of plasma flows. The fast flows may drive turbulence on shorter spatial scales. In their turn, these motions may serve as an origin for new neutral line generation, and reconnection. Application to substorm phenomenology is discussed.

The variations of the solar magnetic field at the fast global reconfigurations periods

This paper presents the results of a comprehensive analysis of the dynamics of the sun's global magnetic structure, solar wind parameters, the interplanetary magnetic field and geomagnetic activity during fast global changes of magnetic fields on the Sun. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Optical power independent optical beam profiler

To the best of our knowledge, proposed and demonstrated for the first time is an optical power independent optical beam profiler instrument. The instrument uses a pair of symmetrically located power detection photodetectors along with an electronically programmed two-dimensional digital micromirror device to implement spatial beam profiling. The instrument also features high-repeatability all-digital controls and fast millisecond reconfigurations. The instrument can have a critical impact in test, measurement, and monitoring systems for various optical beams, including high-power laser beams.