Local Loop Research Articles

Spectroscopically Elucidating the Local Proton-Coupled Electron Transfer Loop from Amino to Nitro Groups via the Au Surface in a N2 Atmosphere.

Proton-coupled electron transfer (PCET) has been significant in understanding the reactions in solution. In a solid-gas interface, it remains a challenge to identify electron transfer or proton transfer intermediates. Here, in a Au/N2 interface, we regulated and characterized the PCET from p-aminothiophenol (PATP) to p-nitrothiophenol (PNTP) in the plasmon-mediated conversion to p,p'-dimercaptoazobenzene by variable-temperature surface-enhanced Raman spectroscopy. The Raman bands of PATP and PNTP characteristically blue shifted and red shifted as the laser wavelength- and power density-regulated PCET from PATP to PNTP, respectively. These characteristic Raman band shifts were well reproduced by the density functional theoretical simulations of positively charged PATP and negatively charged PNTP, which explicitly evidenced the electron transfer intermediates of PATP or PNTP on the Au surface. PCET did not occur in the temperature cycle between 100 and 370 K without laser illumination. These results demonstrated a characteristic local PCET loop composed of electron transfer between PATP/PNTP and Au followed by intermolecular proton transfer between PATP and PNTP and the significance of conducting electron transfer on Au.

Research on the role of multi-sensor system information fusion in improving hardware control accuracy of intelligent system

Abstract Multi-sensor management and control technology generally constructs a reasonable objective function to solve the optimal control command set to control a limited number of sensors to obtain higher quality measurement information, thus obtaining better target tracking performance. In the process of multi-sensor information fusion, there is not only the problem of information redundancy but also obvious time delay. A sensor fusion algorithm combined with global optimization algorithm is innovatively proposed. According to the key frames saved in the previous steps, feature points in local maps, sensor information, and loop information, a global optimization algorithm based on graph optimization model is constructed to optimize the position and pose of intelligent hardware system and the position of spatial feature points. Moreover, this work studies and experiments on multi-sensor fusion simultaneous localization and mapping (SLAM) comprehensively and systematically, and the experimental results show that the algorithm proposed in this work is superior to common open-source SLAM algorithm in positioning accuracy and mapping effect under special circumstances. Therefore, the method proposed in this work can be applied to intelligent driving of vehicles, vision-assisted movement of robots and intelligent control of unmanned aerial vehicles, thus effectively improving the hardware control accuracy of intelligent systems.

Multiferroic properties and local ferroelectricity of polycrystalline LuFeO3 thin films with triangular grains on glass substrates

Polycrystalline LuFeO3 (LFO) thin films were prepared on multilayer Pt/Ta/glass substrates. The ferroelectric hysteresis loop of the LFO thin film exhibited a remanent polarization of about 5.7 μC/cm2. The ferroelectric hysteresis loop of the LFO thin film deposited at a relatively slow rate provides valuable information about its recoverable energy density (8.8 J/cm3) and loss energy density (9.3 J/cm3), resulting in an estimated energy storage efficiency of around 49%. The LFO thin film had triangular grains with a diameter of approximately 90 nm, which well reflects the crystallinity of hexagonal LFO. From the local piezoelectric d33 hysteresis loops of a triangular grain, it was confirmed that the edge of a triangular grain had a remanent d33 value larger than the center of a triangular grain. Additionally, a mosaic domain structure of the LFO thin film was well correlated with the AFM image. By applying the Landau, Lifshitz, and Kittel (LLK) scaling law, it was confirmed that the LFO thin films have a domain wall energy lower than that of PbTiO3 thin films.

Unique territorial and compartmental organization of chromosomes in the holocentric silkmoth.

The hallmarks of chromosome organization in multicellular eukaryotes are chromosome territories (CT), chromatin compartments, and insulated domains, including topologically associated domains (TADs). Yet, most of these elements of chromosome organization are derived from analyses of a limited set of model organisms, while large eukaryotic groups, including insects, remain mostly unexplored. Here we combine Hi-C, biophysical modeling, and microscopy to characterize the 3D genome architecture of the silkmoth, Bombyx mori. In contrast to other eukaryotes, B. mori chromosomes form highly separated territories. Similar to other eukaryotes, B. mori chromosomes segregate into active A and inactive B compartments, yet unlike in vertebrate systems, contacts between euchromatic A regions appear to be a strong driver of compartmentalization. Remarkably, we also identify a third compartment, called secluded "S," with a unique contact pattern. Each S region shows prominent short-range self-contacts and is remarkably devoid of contacts with the rest of the chromosome, including other S regions. Compartment S hosts a unique combination of genetic and epigenetic features, localizes towards the periphery of CTs, and shows developmental plasticity. Biophysical modeling reveals that the formation of such secluded domains requires highly localized loop extrusion within them, along with a low level of extrusion in A and B. Our Hi-C data supports predicted genome-wide and localized extrusion. Such a broad, non-uniform distribution of extruders has not been seen in other organisms. Overall, our analyses support loop extrusion in insects and highlight the evolutionary plasticity of 3D genome organization, driven by a new combination of known processes.

Glucose-Stimulated Mucus Secretion by Goblet Cells Mitigates Intestinal Barrier Dysfunction in a Rat Model of Mesenteric Ischemia/Reperfusion Injury

BackgroundSuperior mesenteric ischemia/reperfusion (I/R) causes barrier dysfunction and facilitates bacterial translocation (BT) in the small intestine, which can even lead to systemic sepsis. Our previous research showed that luminal administration of glucose and its anaerobic glycolytic metabolites exerted cytoprotective effects on epithelial cells and ameliorated I/R-induced BT in the liver and spleen. Notably, the reduction of BT occurs over the whole intestinal tract, not only restricted in the ligated glucose-containing loop. ObjectivesIn this study, we hypothesized that local jejunal glucose-contacting might confer on the remote intestinal epithelium regeneration potential, fortify their barrier function and goblet cell secretory activity. MethodsTwo 10-cm jejunal segments were isolated in Wistar rats. One segment was ligatured at both ends and infused with Krebs buffer containing 0- or 50-mM glucose (local loop), whereas the adjacent segment was left unaltered and not exposed to glucose (remote loop). The rats then underwent either a sham operation or I/R challenge by occlusion of the superior mesenteric artery for 20 min, followed by reperfusion for 1 h. ResultsEnteral addition of glucose in the local jejunum loop alleviated ischemia-induced barrier defects, histopathological scores, cell death, and mucosal inflammation (myeloperoxidase and inflammatory cytokine production) in the remote jejunum. After ischemia, goblet cells in the remote jejunum showed cavitation of mucin granules and low MUC2 expression. Local addition of glucose enhanced MUC2 synthesis and stimulated a jet-like mucus secretion in the remote jejunum, which was accompanied by the restoration of crypt activity. ConclusionsOur results showed local enteral glucose effectively mitigates I/R-induced barrier dysfunction, suggesting that local glucose-stimulated mucus secretion by remote goblet cells may serve to mitigate mucosal inflammation and BT. We provide a more precise barrier protection role of enteral glucose upon I/R challenge, presenting new opportunities for future therapeutic potential.

Unique territorial and compartmental organization of chromosomes in the holocentric silkmoth.

The hallmarks of chromosome organization in multicellular eukaryotes are chromosome territories (CT), chromatin compartments, and insulated domains, including topologically associated domains (TADs). Yet, most of these elements of chromosome organization are derived from analyses of a limited set of model organisms, while large eukaryotic groups, including insects, remain mostly unexplored. Here we combine Hi-C, biophysical modeling, and microscopy to characterize the 3D genome architecture of the silkworm, Bombyx mori. In contrast to other eukaryotes, B. mori chromosomes form highly separated territories. Similar to other eukaryotes, B. mori chromosomes segregate into active A and inactive B compartments, yet unlike in vertebrate systems, contacts between euchromatic A regions appear to be a strong driver of compartmentalization. Remarkably, we also identify a third compartment, called secluded S, with a unique contact pattern. Each S region shows prominent short-range self-contacts and is remarkably devoid of contacts with the rest of the chromosome, including other S regions. Compartment S hosts a unique combination of genetic and epigenetic features, localizes towards the periphery of CTs, and shows developmental plasticity. Biophysical modeling reveals that the formation of such secluded domains requires highly localized loop extrusion within them, along with a low level of extrusion in A and B. Our Hi-C data supports predicted genome-wide and localized extrusion. Such a broad, non-uniform distribution of extruders has not been seen in other organisms. Overall, our analyses support loop extrusion in insects and highlight the evolutionary plasticity of 3D genome organization, driven by a new combination of known processes.

Multi-omics analysis reveals the dynamic interplay between Vero host chromatin structure and function during vaccinia virus infection

The genome folds into complex configurations and structures thought to profoundly impact its function. The intricacies of this dynamic structure-function relationship are not well understood particularly in the context of viral infection. To unravel this interplay, here we provide a comprehensive investigation of simultaneous host chromatin structural (via Hi-C and ATAC-seq) and functional changes (via RNA-seq) in response to vaccinia virus infection. Over time, infection significantly impacts global and local chromatin structure by increasing long-range intra-chromosomal interactions and B compartmentalization and by decreasing chromatin accessibility and inter-chromosomal interactions. Local accessibility changes are independent of broad-scale chromatin compartment exchange (~12% of the genome), underscoring potential independent mechanisms for global and local chromatin reorganization. While infection structurally condenses the host genome, there is nearly equal bidirectional differential gene expression. Despite global weakening of intra-TAD interactions, functional changes including downregulated immunity genes are associated with alterations in local accessibility and loop domain restructuring. Therefore, chromatin accessibility and local structure profiling provide impactful predictions for host responses and may improve development of efficacious anti-viral counter measures including the optimization of vaccine design.

Algebraic structures on parallelizable manifolds

In this paper we explore algebraic and geometric structures that arise on parallelizable manifolds. Given a parallelizable manifold L, there exists a global trivialization of the tangent bundle, which defines a map ρp:l⟶TpL for each point p∈L, where l is some vector space. This allows us to define a particular class of vector fields, known as fundamental vector fields, that correspond to each element of l. Furthermore, flows of these vector fields give rise to a product between elements of l and L, which in turn induces a local loop structure (i.e. a non-associative analog of a group). Furthermore, we also define a generalization of a Lie algebra structure on l. We will describe the properties and examples of these constructions.

Combinatorics and topological weights of chromatin loop networks.

Polymer physics models suggest that chromatin spontaneously folds into loop networks with transcription units (TUs), such as enhancers and promoters, as anchors. Here we use combinatoric arguments to enumerate the emergent chromatin loop networks, both in the case where TUs are labeled and where they are unlabeled. We then combine these mathematical results with those of computer simulations aimed at finding the inter-TU energy required to form a target loop network. We show that different topologies are vastly different in terms of both their combinatorial weight and energy of formation. We explain the latter result qualitatively by computing the topological weight of a given network-i.e., its partition function in statistical mechanics language-in the approximation where excluded volume interactions are neglected. Our results show that networks featuring local loops are statistically more likely with respect to networks including more nonlocal contacts. We suggest our classification of loop networks, together with our estimate of the combinatorial and topological weight of each network, will be relevant to catalog three-dimensional structures of chromatin fibers around eukaryotic genes, and to estimate their relative frequency in both simulations and experiments.

Experimental, computational, and analytical investigation of cooktop thermosyphon heat transport device for its feasibility in indoor solar cooking system

Cooking is a key contributor to worldwide energy usage and subsequent greenhouse gas emissions. Given this, clean and green energy-based cooking technologies are being explored globally. Though many solar cooker designs are being researched, the social acceptance rate is low due to operational, financial, and accessibility aspects. Hence in the present study, an indoor solar cooking system has been proposed, which has a cooktop Thermosyphon heat transport device (THTD) as an integral part. It transports heat from the outdoor receiver to the indoor kitchen through natural circulation (buoyancy-driven flow) of a heat transfer fluid (HTF). For the first time, different aspects of cooktop THTD are explored through experimental, analytical, and computational approaches. Based on the recommendations from a previous study, the flat design of cooktop THTD was constructed and tested with Therminol-VP1 as the HTF for both steady-state and transient performance. The steady-state results predicted by analytical and computational models were in good agreement with the experimental outcome. The HTF flow in the system is unidirectional, except in the cooktop region, where a combination of radial flow maldistribution and localized recirculation loops are seen (from velcoty contours and vectors) due to a larger flow passage. However, such flow anomalies vanish once the flow gap is reduced. Further, the transient tests witnessed a longer time for boiling (41–68 min) one litre of water in the first trial, which was reduced to 18–27 min with subsequent refills. An important observation is the increment in boiling time with increase in hot leg length. The rise in HTF flow rate (due to increased center-line elevation) and subsequent reduction in the bulk average temperature of HTF in the THTD was the reason for it. Further, the cooktop THTD could cook 315 g of rice in 40–45 min against 35–40 min using an electric induction stove, which justifies the proposed system’s efficacy. The study also demonstrated the criticality of thermal contact resistance between the cooktop surface and the surface of the cooking vessel. Hence devising an efficient and practically viable method (other than thermal paste) is essential. Also, due diligence is required while selecting the HTF as viscous fluid leads to a poor transient performance due to reduced flow rate. Hence, the transient behavior (practically the boiling time) of cooktop THTD is a trade-off between the bulk average temperature of the HTF and its flow rate.

Recurrent dynamic message passing with loops for epidemics on networks

Several theoretical methods have been developed to approximate the prevalence and threshold of epidemics in networks. Among them, the recurrent dynamic message-passing (rDMP) theory offers state-of-the-art performance by preventing the echo chamber effect at network edges. However, the rDMP theory was derived intuitively in an ad-hoc manner, lacking a solid theoretical foundation, resulting in a probabilistic inconsistency flaw. Furthermore, real-world networks are clustered and full of local loops, such as triangles, while rDMP is based on the assumption of a locally tree-like network structure, potentially making rDMP inefficient in real-world applications. In this work, we first show for recurrent state epidemics that the echo chamber effect exists not only at edges but also in local loops, which rDMP-like methods cannot avoid. We then correct the rDMP deficiency in a principled way, naturally introducing new higher-order dynamic messages, thereby extending rDMP to handle local loops. By linearizing the extended message-passing equations, a new epidemic threshold estimation is provided by the inverse of the leading eigenvalue of a matrix called the triangular non-backtracking matrix. Numerical experiments have been conducted on synthetic and real networks to evaluate our method, whose effectiveness is validated in epidemic prevalence and threshold prediction tasks. In addition, our method has the potential to speed up the solution of immunization, influence maximization, and robustness optimization problems in networks.

A strong direct link from the layer 3/4 border to layer 6 of cat primary visual cortex

The cat primary visual cortex (V1) is a cortical area for which we have one of the most detailed estimates of the connection ‘weights’ (expressed as number of synapses) between different neural populations in different layers (Binzegger et al in J Neurosci 24:8441–8453, 2004). Nevertheless, the majority of excitatory input sources to layer 6, the deepest layer in a local translaminar excitatory feedforward loop, was not accounted for by the known neuron types used to generate the quantitative Binzegger diagram. We aimed to fill this gap by using a retrograde tracer that would label neural cell bodies in and outside V1 that directly connect to layer 6 of V1. We found that more than 80% of labeled neurons projecting to layer 6 were within V1 itself. Our data indicate that a substantial fraction of the missing input is provided by a previously unidentified population of layer 3/4 border neurons, laterally distributed and connecting more strongly to layer 6 than the typical superficial layer pyramidal neurons considered by Binzegger et al. (Binzegger et al in J Neurosci 24:8441–8453, 2004). This layer 3/4 to layer 6 connection may be a parallel route to the layer 3 – layer 5 – layer 6 feedforward pathway, be associated with the fast-conducting, movement-related Y pathway and provide convergent input from distant (5–10 degrees) regions of the visual field.

A family of limited memory three term conjugate gradient methods

Based on several modified Hestenes–Stiefel and Polak–Ribière–Polyak nonlinear conjugate gradient methods, a family of three term limited memory CG methods are developed. When the current search direction falls into the subspace spanned by the previous m directions, the algorithm branches to optimize the objective function on the subspace by using L-BFGS method. We use this strategy to avoid potential local loops and accelerate the convergence. The proposed methods are sufficient descent. When the steplength is determined by Wolfe or Armijo line search, we establish the global convergence of the methods in a concise way. Numerical results verify the efficiency of the proposed method for the unconstrained optimization problems in the CUTEst library.

Light Roberge-Weiss tricritical endpoint at imaginary isospin and baryon chemical potential

Imaginary chemical potentials serve as a useful tool to constrain the QCD phase diagram and to gain insight into the thermodynamics of strongly interacting matter. In this study, we report on the first determination of the phase diagram for arbitrary imaginary baryon and isospin chemical potentials at high temperature using one-loop perturbation theory, revealing a nontrivial structure of Roberge-Weiss (RW) phase transitions in this plane. Subsequently, this system is simulated numerically with Nf=2 unimproved staggered quarks on Nτ=4 lattices at a range of temperatures at one of the RW phase transitions. We establish a lower bound for the light quark mass, where the first-order transition line terminates in a tricritical point. It is found that this tricritical mass is increased as compared to the case of purely baryonic imaginary chemical potentials, indicating that our setup is more advantageous for identifying critical behavior toward the chiral limit. Finally, the dynamics of local Polyakov loop clusters is also studied in conjunction with the RW phase transition. Published by the American Physical Society 2024

Defining ferroelectric characteristics with reversible piezoresponse: PUND switching spectroscopy PFM characterization

Detecting ferroelectricity at micro- and nanoscales is crucial for advanced nanomaterials and materials with complicated topography. Switching spectroscopy piezoresponse force microscopy (SSPFM), which involves measuring piezoelectric hysteresis loops via a scanning probe microscopy tip, is a widely accepted approach to characterize polarization reversal at the local scale and confirm ferroelectricity. However, the local hysteresis loops acquired through this method often exhibit unpredictable shapes, a phenomenon often attributed to the influence of parasitic factors such as electrostatic forces and current flow. Our research has uncovered that the deviation in hysteresis loop shapes can be caused by spontaneous backswitching occurring after polarization reversal. Moreover, we’ve determined that the extent of this effect can be exacerbated when employing inappropriate SSPFM waveform parameters, including duration, frequency, and AC voltage amplitude. Notably, the conventional ‘pulse-mode’ SSPFM method has been found to intensify spontaneous backswitching. In response to these challenges, we have redesigned SSPFM approach by introducing the positive up-negative down (PUND) method within the ‘step-mode’ SSPFM. This modification allows for effective probing of local piezoelectric hysteresis loops in ferroelectrics with reversible piezoresponse while removing undesirable electrostatic contribution. This advancement extends the applicability of the technique to a diverse range of ferroelectrics, including semiconductor ferroelectrics and relaxors, promising a more reliable and accurate characterization of their properties.

Standard specification-based intrusion detection for hierarchical industrial control systems

In this paper, we develop a specification-based, process-aware, Intrusion Detection System (IDS) for complex Industrial Control Systems (ICSs). Complex ICSs are distributed and hierarchical control systems built on top of local control loops which are the system's elementary building blocks. Process-aware attacks are sophisticated cyberattacks that aim to compromise the safety of the controlled physical process.Our approach aims to link safety specifications and security properties. Thus, we use international and industry standards specifications concerning local safety, global safety and networks of the industrial process, in order to obtain security properties. The obtained security properties are cybersecurity related requirements. They are translated into security patterns in order to be runtime monitored by our network IDS. This latter relies on a distributed monitoring framework, capturing network traffic between the local loops and the distributed control level, as well as between distributed control and supervisory control. We implemented and evaluated our IDS on a real ICS. We experimentally show that our IDS detects a large spectrum of attacks. We also show that our distributed IDS is scalable since its detection response time as a function of the number of monitored security patterns, is linear. A demonstrator comprising code extracts is made available.

FAIR SIS100 accelerating RF system - Modeling and analysis of the coupled LLRF control loops

The SIS100 heavy ion synchrotron as core part of the Facility for Antiproton and Ion Research (FAIR) will be equipped with 14 accelerating RF stations in the first stage of realization. Each RF station consists of a tunable ferrite-loaded cavity powered by a tetrode amplifier. Further key components are a solid-state pre-amplifier, a power supply unit, and dedicated Low-Level Radio Frequency (LLRF) feedforward and feedback systems to control amplitude and phase of the cavity gap voltage as well as the resonance frequency. Each cavity has to provide up to 20 kV peak gap voltage in the frequency range from 1.1 to 3.2 MHz. While all components of the system have been successfully tested in the factory acceptance tests and transferred to the FAIR storage, the First-of-Series (FoS) RF station is still persistently operated at GSI to gain experience. For further insight into the LLRF part, especially the stability of the control loops, the inter-coupling of the three local control loops was analyzed with methods from control theory based on simplified but realistic models, which have been developed based on extensive measurements and analysis of the systems’ behavior. In this contribution, the modeling as well as the analysis of the coupling between the LLRF control loops are discussed and the results are presented in comparison with measurements on the FoS system.

Influence of inter-river water diversion on estuary pollution control: A case study of Liaodong Bay

Long-term mass transport processes in offshore seas are controlled by seasonal residual currents. The Euler residual mass transport velocity field was calculated form seasonal residual current patterns in shallow sea area, comparing with polluted water changes in typical years. The following conclusions were made: closed local large loops of the Euler residual mass transport led to polluted waters in the northeast Liaodong Bay, and the bay's optimal physical self-purification occurred in winter (Euler residual mass transport diffuses polluted water masses) and spring (overall self-purification capacity of the bay plays a role after winter). The central waters were clean while pollutants were discharged into near-shore waters, leading to perennial pollution in some near-shore waters. Pollution in Liaodong Bay could be alleviated or eliminated via diversion of water from the Daliaohe River (flowing into the northeast corner of Liaodong Bay and carrying > 65% of the total amount of pollutants discharged into the top of the bay) into the Liaohe River and Daling River. The percentage of inorganic nitrogen carried by 10% of the flux of the Daliaohe River was 5.70% of that discharged into Liaodong Bay. If 10% of the flux of the Daliaohe River was discharged into the Daling River, the annual total environmental carrying capacity of inorganic nitrogen increased 4.48%. Many bays in the world have adjacent river flows, such as Gulf of Mexico, Gulf of Guinea, and Bay of Bengal. Based on the Euler residual mass transport field, the water transfer between adjacent rivers could make better use of the Euler residual mass transport capacity to mitigate the water pollution of the estuaries.

Comparative analysis of passive optical networks using multiple parameters: a review

Abstract The desideratum for high-end communication networks and high-speed data transfer has surged exorbitantly in the contemporary era. To meet this demand, various optical access network technologies have been invented and assembled, including gigabit passive optical networks (GPON), Ethernet passive optical networks (EPON), and wavelength multiplexed passive optical networks (WDM-PON). Due to their huge bandwidth capacity, excellent compatibility, dynamic bandwidth allocation, and dispersion tolerance, these technologies constitute potential substitutes for imparting local loop broadband services. This paper presents a thorough review and comparative analysis of the contemporary evolution in optical access network technologies with an accentuate on their functionality, mechanism, manoeuvre, and applications. We are also looking at the upcoming development of these innovations, including the incorporation of 100 G-EPON connectivity to meet the enhanced bandwidth demands precipitated by IP video, mobile broadband, and the Internet of things (IoT).

Multi-objective optimization of building HVAC operation: Advanced strategy using Koopman predictive control and deep learning

Predictive control is an effective method for addressing the increasing demand for heating, ventilation, and air conditioning (HVAC) systems to operate with greater flexibility and efficiency. In this paper, the multi-objective problem of energy-efficient HVAC operation while tracking desired setpoints is addressed through an advanced control strategy, including a novel supervisory data-driven predictive control (DPC) and a local loop with a PI controller. The supervisory level is based on the integration of the DPC framework and the bilinear Koopman predictor. A deep neural network architecture is developed to realize the bilinear building thermal predictor. In addition, the integral input-to-state stability (iISS) constraint is enforced in the training procedure to obtain a global iISS control-oriented thermal predictor that enables the application of predictive control purely based on historical data. The effectiveness of the proposed approach is demonstrated through the simulation of a three-zone office in the transient system simulation software (TRNSYS). The proposed control configuration is implemented using a coupled TRNSYS-MATLAB simulation framework. It has shown significant potential for keeping the desired environment in line with energy conservation. Furthermore, a comparison is conducted between the proposed approach, the conventional controller, and another recent DPC approach, which demonstrates the suggested method’s superiority.