Tight Space Research Articles

A photogrammetric method for target monitoring inside the MEG II detector.

An automatic target monitoring method based on photographs taken by a CMOS photo-camera has been developed for the MEG II detector. The technique could be adapted for other fixed-target experiments requiring good knowledge of their target position to avoid biases and systematic errors in measuring the trajectories of the outcoming particles. A CMOS-based, high resolution, high radiation tolerant, and high magnetic field resistant photo-camera was mounted inside the MEG II detector at the Paul Scherrer Institute (Switzerland). MEG II is used to search for lepton flavor violation in muon decays. The photogrammetric method's challenges, affecting measurements of low momentum particles' tracks, are the high magnetic field of the spectrometer, high radiation levels, tight space constraints, and the need to limit the material budget in the tracking volume. The camera is focused on the dot pattern drawn on the thin MEG II target, about 1m away from the detector endcaps where the photo-camera is placed. Target movements and deformations are monitored by comparing images of the dots taken at various times during the measurement. The images are acquired with a Raspberry board and analyzed using custom software. Global alignment to the spectrometer is guaranteed by corner cubes placed on the target support. As a result, the target monitoring fulfills the needs of the experiment.

Biomarkers of lesion severity in a rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION).

The rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION) is similar in many of its pathophysiological responses to clinical NAION. Like human NAION, there is significant variability in the severity of the lesion produced, and little is known of the parameters associated with rNAION induction severity or if pre- or early post-induction biomarkers can be identified that enable prediction of lesion severity and ultimate loss of retinal ganglion cells (RGCs). Adult male Sprague-Dawley outbred rats were evaluated for various parameters including physiological characteristics (heart rate, respiratory rate, temperature, hematocrit [Hct]), optic nerve head (ONH) appearance, pre- and post-induction mean diameter, and intravenous fluorescein and indocyanine green angiographic patterns of vascular leakage at 5 hours post-induction, performed using a spectral domain-optical coherence tomography (SD-OCT) instrument. Early changes were correlated with ultimate RGC loss by Brn3a (+) immunohistology. RGC loss also was correlated with the relative level of laser exposure. The severity of ONH edema 2d, but not 5hr, post induction was most closely associated with the degree of RGC loss, revealing a threshold effect, and consistent with a compartment syndrome where a minimum level of capillary compression within a tight space is responsible for damage. RGC loss increased dramatically as the degree of laser exposure increased. Neither physiological parameters nor the degree of capillary leakage 5hr post induction were informative as to the ultimate degree of RGC loss. Similar to human NAION, the rNAION model exhibits marked variability in lesion severity. Unlike clinical NAION, pre-induction ONH diameter likely does not contribute to ultimate lesion severity; however, cross-sectional ONH edema can be used as a biomarker 2d post-induction to determine randomization of subjects prior to inclusion in specific neuroprotection or neuroregeneration studies.

Structural Performance and Reinforcement Improvement of Structural Walls Using Strain-Hardening Cementitious Composites

Reinforced concrete (RC) shear walls are effective in improving lateral stiffness and load-carrying capacity under earthquake and wind loads. According to the level of seismic design, however, the spacing of reinforcing steel bars should be very narrow and complicated, with tight spacing of tied bars, as is the case with seismically special RC shear wall design. The purpose of this study was to investigate the applicability of strain-hardening cementitious composites (SHCCs) in structural walls in order to improve structural performance as well as the complications with reinforcement details. The SHCC was mixed, and mechanical tests showed that the SHCC exhibited high ductile tensile strains above 2.0%, while sustaining the tensile stress after cracks and developing multiple microcracks, avoiding crack localizations. Six specimens of RC and reinforced SHCC structural walls were designed and manufactured with varying reinforcement details, and experiments on wall specimens were carried out under transverse wall-loading tests. These experiments demonstrated that the use of SHCC in structural walls, despite minimum use of reinforcement ratios, showed improved responses to minimize damage and failure caused by localized cracks under bending and shear to compared with the use of normal reinforcement ratios in RC walls.

Sensor-Guided Assembly of Segmented Structures with Industrial Robots

This paper presents a robotic assembly methodology for the manufacturing of large segmented composite structures. The approach addresses three key steps in the assembly process: panel localization and pick-up, panel transport, and panel placement. Multiple stationary and robot-mounted cameras provide information for localization and alignment. A robot wrist-mounted force/torque sensor enables gentle but secure panel pick-up and placement. Human-assisted path planning ensures reliable collision-free motion of the robot with a large load in a tight space. A finite state machine governs the process flow and user interface. It allows process interruption and return to the previous known state in case of error condition or when secondary operations are needed. For performance verification, a high resolution motion capture system provides the ground truth reference. An experimental testbed integrating an industrial robot, vision and force sensors, and representative laminated composite panels demonstrates the feasibility of the proposed assembly process. Experimental results show sub-millimeter placement accuracy with shorter cycle times, lower contact force, and reduced panel oscillation than manual operations. This work demonstrates the versatility of sensor guided robotic assembly operation in a complex end-to-end tasks using the open source Robot Operating System (ROS) software framework.

From Hi-C Contact Map to Three-Dimensional Organization of Interphase Human Chromosomes

The probability of two loci, separated by a certain genome length, being in contact can be inferred using the Chromosome Conformation Capture (3C) method and related Hi-C experiments. How to go from the contact map, a matrix listing the mean contact probabilities between a large number of pairs of loci, to an ensemble of three-dimensional structures is an open problem. A solution to this problem, without assuming an assumed energy function, would be the first step in understanding the way nature has solved the packaging of chromosomes in tight cellular spaces. We created a theory, based on polymer physics characteristics of chromosomes and the maximum entropy principles, referred to as HIPPS (Hi-C-Polymer-Physics-Structures) method, that allows us to calculate the 3D structures solely from Hi-C contact maps. We created an ensemble of 3D structures for the 23 chromosomes from lymphoblastoid cells using the measured contact maps as inputs. The HIPPS method shows that conformations of chromosomes are heterogeneous even in a single cell type. The differences in the conformational heterogeneity of the same chromosome in different cell types (normal as well as cancerous cells) can also be quantitatively discerned using our theory. We validate the method by showing that the calculated volumes of the 23 chromosomes from the predicted 3D structures are in good agreement with experimental estimates. Because the method is general, the 3D structures for any species may be calculated directly from the contact map without the need to assume a specific polymer model, as is customarily done.

Modeling the Dynamic Behavior of a Pilot-Operated Solenoid Valve for an Ultra-High Pressure Vessel

A pilot-operated solenoid valve is used to control ultra-high pressure vessels. However, it is difficult to understand its dynamic behavior because the valve operates under ultra-high pressure conditions and the driving unit moves in a multi-step fashion in a tight hidden space. This study aims to identify the system coefficient, especially the damping coefficient, required to analyze the dynamic behavior of a solenoid driving unit. Experiments to measure the dynamic behavior of the driving unit are conducted using two laser sensors and one accelerator. The damping coefficient is estimated using Matlab Simulink, by varying the damping coefficient to match the experimental results. The obtained system coefficients are modeled as equations of motion. It is verified that the valve motion consists of two sequential movements—Phase 1 by pilot plunger and Phase 2 by main plunger, pilot plunger, and the valve initiation time is as fast as 9.9 ms. The damping coefficient of each phase is estimated 0.001 N ∙ s/mm for Phase 1, 0.004 N ∙ s/mm for Phase 2.

Image-derived modeling of nucleus strain amplification associated with chromatin heterogeneity

Beyond the critical role of cell nuclei in gene expression and DNA replication, they also have a significant influence on cell mechanosensation and migration. Nuclear stiffness can impact force transmission and, furthermore, act as a physical barrier to translocation across tight spaces. As such, it is of wide interest to accurately characterize nucleus mechanical behavior. In this study, we present a computational investigation of the in situ deformation of a heterogeneous chondrocyte nucleus. A methodology is developed to accurately reconstruct a three-dimensional finite-element model of a cell nucleus from confocal microscopy. By incorporating the reconstructed nucleus into a chondrocyte model embedded in pericellular and extracellular matrix, we explore the relationship between spatially heterogeneous nuclear DNA content, shear stiffness, and resultant shear strain. We simulate an externally applied extracellular matrix shear deformation and compute intranuclear strain distributions, which are directly compared with corresponding experimentally measured distributions. Simulations suggest that the mechanical behavior of the nucleus is highly heterogeneous, with a nonlinear relationship between experimentally measured grayscale values and corresponding local shear moduli (μn). Three distinct phases are identified within the nucleus: a low-stiffness mRNA-rich interchromatin phase (0.17 kPa ≤ μn ≤ 0.63 kPa), an intermediate-stiffness euchromatin phase (1.48 kPa ≤ μn ≤ 2.7 kPa), and a high-stiffness heterochromatin phase (3.58 kPa ≤ μn ≤ 4.0 kPa). Our simulations also indicate that disruption of the nuclear envelope associated with lamin A/C depletion significantly increases nuclear strain in regions of low DNA concentration. We further investigate a phenotypic shift of chondrocytes to fibroblast-like cells, a signature for osteoarthritic cartilage, by increasing the contractility of the actin cytoskeleton to a level associated with fibroblasts. Peak nucleus strains increase by 35% compared to control, with the nucleus becoming more ellipsoidal. Our findings may have broad implications for current understanding of how local DNA concentrations and associated strain amplification can impact cell mechanotransduction and drive cell behavior in development, migration, and tumorigenesis.

Microelectrode Arrays: Electrophysiological Phenotype Characterization of Human iPSC‐Derived Neuronal Cell Lines by Means of High‐Density Microelectrode Arrays (Adv. Biology 3/2021)

In article number 2000223, Silvia Ronchi, Michele Fiscella, and co-workers show neurons plated on a high-density microelectrode array. The small electrode size and the tight spacing between the 26 400 electrodes enable functional extracellular electrophysiological characterization of neurons across scales, from subcellular-resolution features, like axons and dendrites, through individual neuronal cells to entire networks. Image credits: M. Oeggerli

On symplectic fillings of virtually overtwisted torus bundles

We use Menke's JSJ-type decomposition theorem for symplectic fillings to reduce the classification of strong and exact symplectic fillings of virtually overtwisted torus bundles to the same problem for tight lens spaces. For virtually overtwisted structures on elliptic or parabolic torus bundles, this gives a complete classification. For virtually overtwisted structures on hyperbolic torus bundles, we show that every strong or exact filling arises from a filling of a tight lens space via round symplectic 1-handle attachment, and we give a condition under which distinct tight lens space fillings yield the same torus bundle filling.

Performance prediction of hydronic cooling coil with non-uniform air velocity (ASHRAE RP-1741)

Hydronic coils are often exposed to non-uniform air velocities due to a series of factors, including tight spacing between a fan and a coil, flow area contraction and expansion, existence of obstructions, abrupt change in airflow direction, or the combination of above factors. Although studies showed non-uniform air velocities could cause performance degradation for direct expansion (DX) cooling coils, efforts in quantifying this impact on hydronic cooling coils are limited. The objective of this paper is to develop and validate a section-by-section calculation procedure for cooling performance prediction of hydronic coils with non-uniform air velocities. As the first step, air velocities at the coil face in a hydronic fan coil unit (FCU) were measured using a vane-type anemometer. The coil was then discretized into multiple sections, with each section using the measured air velocity for heat and mass transfer analysis. The cooling performance prediction with non-uniform air velocities was validated against experimental results. The comparative analysis showed that capturing the impact of non-uniform air velocities decreased the normalized root mean square error (RMSE) from 39.9% to 8.1% for latent capacity prediction and 9.1% to 2.6% for total capacity prediction compared with the results assuming uniform air velocities.

CSF dynamics as a predictor of cognitive progression

Disproportionately enlarged subarachnoid-space hydrocephalus (DESH), characterized by tight high convexity CSF spaces, ventriculomegaly, and enlarged Sylvian fissures, is thought to be an indirect marker of a CSF dynamics disorder. The clinical significance of DESH with regard to cognitive decline in a community setting is not yet well defined. The goal of this work is to determine if DESH is associated with cognitive decline. Participants in the population-based Mayo Clinic Study of Aging (MCSA) who met the following criteria were included: age ≥ 65 years, 3T MRI, and diagnosis of cognitively unimpaired or mild cognitive impairment at enrollment as well as at least one follow-up visit with cognitive testing. A support vector machine based method to detect the DESH imaging features on T1-weighted MRI was used to calculate a “DESH score”, with positive scores indicating a more DESH-like imaging pattern. For the participants who were cognitively unimpaired at enrollment, a Cox proportional hazards model was fit with time defined as years from enrollment to first diagnosis of mild cognitive impairment or dementia, or as years to last known cognitively unimpaired diagnosis for those who did not progress. Linear mixed effects models were fit among all participants to estimate annual change in cognitive z scores for each domain (memory, attention, language, and visuospatial) and a global z score. For all models, covariates included age, sex, education, APOE genotype, cortical thickness, white matter hyperintensity volume, and total intracranial volume. The hazard of progression to cognitive impairment was an estimated 12% greater for a DESH score of +1 versus −1 (HR 1.12, 95% CI 0.97–1.31, p = 0.11). Global and attention cognition declined 0.015 (95% CI 0.005–0.025) and 0.016 (95% CI 0.005–0.028) z/year more, respectively, for a DESH score of +1 vs −1 (p = 0.01 and p = 0.02), with similar, though not statistically significant DESH effects in the other cognitive domains. Imaging features of disordered CSF dynamics are an independent predictor of subsequent cognitive decline in the MCSA, among other well-known factors including age, cortical thickness, and APOE status. Therefore, since DESH contributes to cognitive decline and is present in the general population, identifying individuals with DESH features may be important clinically as well as for selection in clinical trials.

Computer Simulations of Nucleic Acid Condensation Mechanism: The Role of Interfacial Cations Distribution

Ion mediated interactions between nucleic acid helices are essential for their efficient packaging within tight spaces such as viral capsids, and nucleosomes. Understanding the fundamental rules governing these interactions is key for controlling biomolecular assembly and design engineering tools for supramolecular architectures. Aside from the strong cation dependency, one recent surprising finding is the sequence specificity of DNA-DNA interactions demonstrated in both experimental and computational studies.

Design of a Miniature Bi-Directional Non-Back Drivable Mechanism with High Retaining Torque

Ensure the safe operation of a mechanical system that involves motion is essential; some traditional ways to achieve this goal are mechanical devices such as breaks or clutches. This paper presents the design, manufacturing, and test of a bi-directional non-back-drivable mechanism for its application in miniature mechanical systems, like prostheses, robotics, or micro-machine tools. The bi-directional non-back-drivable mechanism operates as a locking device, limiting the torque transmission from the output into the input axle. Application of Design for X methods served to identified and prevent the main drawbacks of the mechanisms used for locking tasks, namely wear and backlash, to make the novel mechanism less sensitive to such factors, keeping high transmission performance in a tight space and with minimum parts. The presented set of design equations and selection graphs are for ABS plastic. A unified approach for the design of the bi-directional non-back-drivable mechanism is presented. The final section of the paper is devoted to the manufacturing and test of a sample of the mechanism.

A novel 5-cell strip-line kicker prototype for the HEPS on-axis injection system

Two groups of 10ns-level superfast kickers are needed in the on-axis swap out injection scheme, adopted by the High Energy Photon Source (HEPS) to cope with the very small dynamic aperture of its baseline 7BA lattice design. In order to fit into the very tight longitudinal space in the injection/extraction region, and to relax the strength requirement of the kickers, five units of 300 mm long strip-line kickers are placed into a single stainless-steel vacuum chamber, to form a very compact 5-cell kicker module. Such a novel 5-cell strip-line kicker module design and its prototype development are presented in this paper. The results of the time-domain reflectometer (TDR) test, the high voltage pulse test and the beam coupling impedance test show that the strip-line kickers can meet the requirements of HEPS.

The Role of Early Giant-planet Instability in Terrestrial Planet Formation

Abstract The terrestrial planets are believed to have formed by violent collisions of tens of lunar- to Mars-size protoplanets at time t < 200 Myr after the protoplanetary gas disk dispersal (t 0). The solar system giant planets rapidly formed during the protoplanetary disk stage and, after t 0, radially migrated by interacting with outer disk planetesimals. An early (t < 100 Myr) dynamical instability is thought to have occurred with Jupiter having gravitational encounters with a planetary-size body, jumping inward by ∼0.2–0.5 au, and landing on its current, mildly eccentric orbit. Here we investigate how the giant-planet instability affected the formation of the terrestrial planets. We study several instability cases that were previously shown to match many solar system constraints. We find that resonances with giant planets help to remove solids available for accretion near ∼1.5 au, thus stalling the growth of Mars. It does not matter, however, whether the giant planets are placed on their current orbits at t 0 or whether they realistically evolve in one of our instability models; the results are practically the same. The tight orbital spacing of Venus and Earth is difficult to reproduce in our simulations, including cases where bodies grow from a narrow annulus at 0.7–1 au, because protoplanets tend to spread radially during accretion. The best results are obtained in the narrow-annulus model when protoplanets emerging from the dispersing gas nebula are assumed to have (at least) the mass of Mars. This suggests efficient accretion of the terrestrial protoplanets during the first ∼10 Myr of the solar system.

Formation and reconfiguration of tight multi-lane platoons

Advances in vehicular communication technologies are expected to facilitate cooperative driving in the future. Connected and Automated Vehicles (CAVs) are able to collaboratively plan and execute driving maneuvers by sharing their perceptual knowledge and future plans. In this paper, an architecture for autonomous navigation of tight multi-lane platoons traveling on public roads is presented. Using the proposed approach, CAVs are able to form single or multi-lane platoons of various geometrical configurations. They are able to reshape and adjust their configurations according to changes in the environment. The proposed architecture consists of two main components: an offline motion planner system and an online hierarchical control system. The motion planner uses an optimization-based approach for cooperative formation and reconfiguration in tight spaces. A constrained optimization scheme is used to plan smooth, dynamically feasible and collision-free trajectories for all the vehicles within the platoon. The paper addresses online computation limitations by employing a family of maneuvers precomputed offline and stored on a look-up table on the vehicles. The online hierarchical control system is composed of three levels: a traffic operation system (TOS), a decision-maker, and a path-follower. The TOS determines the desired platoon reconfiguration. The decision-maker checks the feasibility of the reconfiguration plan based on real-time information about the surrounding traffic. The reconfiguration maneuver is executed by a low-level path-following feedback controller in real-time. The effectiveness of the approach is demonstrated through simulations of three case studies: (1) formation reconfiguration (2) obstacle avoidance, and (3) benchmarking against behavior-based planning in which the desired formation is achieved using a sequence of motion primitives. Videos and software can be found online here https://github.com/RoyaFiroozi/Centralized-Planning.

Festival

WORLDLIT.ORG 21 a POETRY Festival by Chung Kwok-keung The festival is here we play football by the door Even in a tight space my son can nail a kickoff Skilled at the nutmeg, I plan to place the ball Between the tree and hedge, a corner The shadows are dark as always The festival is here my son games with cousins Real Madrid and EFL are down 12 to 0 Beckham fouls Beckham—Penalty! Penalty! I flip the paper’s looming headlines The shady real estate agent holds law above family Cackling, he slaps yesterday’s self onto the paper’s ass The festival is here we eat meat Spit bones, noisily slurp soup The paddles they lift on TV are neat as chopsticks, High as splashes. We down all the Tsingtao And our eyes jump into the Shing Mun River To rinse away last year’s bad luck The festival is here we pick wampee fruits My wife says they’re sweet I say sour The darker ones are ripest she says I bring a bunch to my son he says no I bring one to my daughter she walks away The festival is here news of murder is on TV Steam rises and mother’s soup turns tastier Father says you must wait to slaughter chicken After plain zongzi our table needs a little sugar The festival is here I stop asking about homework Yet my son asks why the man jumped in I say perhaps, perhaps he had something to prove Aha, but in truth he proved he could not swim Yes, in today’s age, this is why you learn to swim The festival is here we get to talk nonsense We sing and forget lyrics We gather and go home The festival is here we dive into the Cross-Harbor Tunnel Thankful for the whir of engines Hypnotizing us like waves Translation from the Chinese By May Huang Visit worldlit.org to listen to the author read his poem in Chinese. Chung Kwok-keung is an acclaimed poet, essayist, and critic from Hong Kong. He is the recipient of numerous Hong Kong Biennial Awards for Chinese Literature, among other accolades. His poetry collections include The Growing House, Umbrellas That Blossom on the Road, and A Bright House Standing in Light Rain. May Huang is a literary translator from Hong Kong and Taiwan. Her work has been published in Circumference, InTranslation, Asymptote, and elsewhere. Editorial note: May Huang was a mentee in the American Literary Translators Association’s 2020 Emerging Translator Mentorship Program. PHOTO BY MACAU PHOTO AGENCY ON UNSPLASH“ ...

Mechatronic Design of a Four-Wheel drive mobile robot and differential steering

This paper presents, the development of an autonomous mobile robot with a four-wheel drive and differential locomotion. The mobile robot was developed in the Machines and Industrial Equipment Department from the Engineering Faculty of Sibiu. The main purpose of developing this type of mobile platform was the ability to transport different types of cargo either in industrial spaces or on rough terrain. Another important objective was that this platform could be driven in confined or tight spaces where a high degree of manoeuvrability is necessary. The great advantage of this type of mobile platform is the ability to navigate through narrow spaces due to the type of locomotion implemented. The fact that the robot has four driving wheels gives it the ability to travel on rough surfaces and easily bypass obstacles. Another great advantage of the developed mobile robot is that it has a reconfigurable structure. The drivetrain is interchangeable, it can adopt both classic wheels and Mecanum wheels. The first part of the paper presents some general aspects concerning mobile robots and two types of traction wheels used in mobile robotic structures. Subsequently, the paper presents the steps taken in the development of the mobile wheeled platform. At the end of the paper, the electronic part that will be implemented in the structure of the robot is described. The command and control of the entire mobile platform will be described in some future work.

Managing Fiscal Risks from National Airlines in Pacific Island Countries

Pacific island countries (PICs) rely on national airlines for connectivity, trade, and tourism. These airlines are being struck hard by COVID-19. Losses will weigh on public sector balance sheets and pose risks to economic recovery. With a backdrop of tight fiscal space and increasing government debt, losses in airlines are adding to fiscal risks in some PICs. This paper discusses tools to evaluate and manage the fiscal risks from national airlines in the Pacific. We present a snapshot of the current state of Public Financial Management (PFM) practices in PICs and detail the best practices. This exercise would illustrate the areas in which PICs have scope to improve their risk management with regard to national airlines. We then discuss the use of diagnostic tools and capacity development to enhance monitoring and risk management. Greater transparency and accountability in the airlines, combined with rigorous oversight, would be the first step towards improved financial management of national airlines.

Design and simulation of an automated robotic machining cell for cross-laminated timber panels

Cross-laminated timber (CLT) is an innovative construction material that has brought advantages over traditional wood structures, reducing cost and lead time of buildings in recent years; yet CLT benefits primarily from offsite construction methods instead of automation or safety, while keeping the human onsite. The few advancements in automation for CLT panels have been in the implementation of dedicated CNC machines. Nevertheless, using CNC machines for machining CLT panels have disadvantages like clamping batches of massive panels with individual profiles, lacking the flexibility to access all acute machining angles, and struggling with the extraction of dust while the cutting spindle moves through large tight spaces. These disadvantages can be overcome with industrial robots’ help, which the construction industry has not been traditionally favorable on their application, giving then the research gap in this study. This paper explores the introduction of a robotic cell for the machining of cross-laminated timber panels. The robotic cell is designed using 3D modeling and validated through motion simulation in a virtual environment. The proposed cell design is based on a minimum viable product and compared against a minimum throughput benchmarked on the Canadian market. This study aims to research the feasibility of CLT’s automated machining by providing clear production characteristics of the designed robotic cell, such as material and tool utilization rates, lead time, or production efficiency.