Abstract
Soft-elasticity in monodomain liquid crystal elastomers (LCEs) is promising for impact-absorbing applications where strain energy is ideally absorbed at constant stress. Conventionally, ...compressive and impact studies on LCEs have not been performed given the notorious difficulty synthesizing sufficiently large monodomain devices. Here, we use direct-ink writing 3D printing to fabricate bulk (>cm
3
) monodomain LCE devices and study their compressive soft-elasticity over 8 decades of strain rate. At quasi-static rates, the monodomain soft-elastic LCE dissipated 45% of strain energy while comparator materials dissipated less than 20%. At strain rates up to 3000 s
−1
, our soft-elastic monodomain LCE consistently performed closest to an ideal-impact absorber. Drop testing reveals soft-elasticity as a likely mechanism for effectively reducing the severity of impacts – with soft elastic LCEs offering a Gadd Severity Index 40% lower than a comparable isotropic elastomer. Lastly, we demonstrate tailoring deformation and buckling behavior in monodomain LCEs via the printed director orientation.
This study presents the first direct comparison of the influence of liquid-crystal order during synthesis on the thermo-mechanical behaviors of main-chain liquid-crystal elastomers (LCEs) in ...thiol-acrylate networks. Six polydomain nematic elastomer (PNE) chemistries were compared directly by synthesizing with the mesogens in either an isotropic state (i-PNE) or a nematic state (n-PNE). The i-PNE networks were created in the presence of solvent, which disrupted any liquid-crystal order during network formation. Conversely, the n-PNE networks were created without the presence of solvent below the isotropic transition (
T
NI
). Differential scanning calorimetry (DSC) was first performed, and it showed that i-PNE networks experienced a clearly defined nematic-to-isotropic transition upon heating, whereas the transition in n-PNE networks was unable to be identified, which may be the result of a nematic-to-paranematic phase transition. Dynamic mechanical analysis (DMA) tests revealed that while both networks maintained elevated loss tangent in the nematic region, only i-PNE networks prominently displayed dynamic soft elasticity behavior. The two-way shape switching behaviors of LCE networks were examined using actuation tests under a 100 kPa bias stress. It showed that the strain amplitude strongly depends on synthesis history; it ranges from 66% to 126% in i-PNE samples and 3% to 61% in n-PNE samples. To help interpret the different actuation strain behaviors between i-PNEs and n-PNEs, wide-angle X-ray scattering (WAXS) was then performed where the LCE samples were strained to 40%. The results showed that order parameter (
S
) in n-PNE samples (ranging from 0.37 to 0.50) is lower than that in i-PNE samples (0.54 for all cases), and the parameter decreased as the cross-linking density increased. The stress-strain behaviors of the LCE networks measured from uniaxial tension tests revealed that all i-PNE samples had a lower soft-elasticity plateau during loading compared to the n-PNE samples. Finally, free-standing strain recovery of LCE samples after being strained to 100% was investigated. Immediately after removing stress on the samples, i-PNE and n-PNE samples recovered 14% to 38% and 27% to 73% of strain, respectively. We discuss the advantages and disadvantages of the different synthetic histories on LCE design.
This study presents the first direct comparison of the influence of liquid-crystal order during synthesis on the thermo-mechanical behaviors of main-chain liquid-crystal elastomers (LCEs) in thiol-acrylate networks.
A current review of the available epidemiological data from many countries clearly indicates that there is a marked increase in the prevalence of dental caries. This global increase in dental caries ...prevalence affects children as well as adults, primary as well as permanent teeth, and coronal as well as root surfaces. This increase in dental caries signals a pending public health crisis. Although there are differences of opinion regarding the cause of this global dental caries increase, the remedy is well known: a return to the public health strategies that were so successful in the past, a renewed campaign for water fluoridation, topical fluoride application, the use of fluoride rinses, a return to school oral health educational programs, an emphasis on proper tooth brushing with a fluoride dentifrice, as well as flossing, a proper diet and regular dental office visits. If these remedies are not initiated, there could be a serious negative impact upon the future oral health (and systemic health) of the global community, as well as a strain on the dental profession along with a major increase in the cost of dental services.
Abstract
This research introduces a novel micro-damper designed to mitigate pressure and velocity oscillations from a piezoelectric micropump in microfluidic environments. Unlike existing research ...focusing on damping in incompressible liquid flows with methods like elastic films and PDMS membranes, this study proposes a novel micro-damper prototype. Integrated into a microdevice for particle granulometric separation and detection, the damper connects to a piezoelectric micropump outlet and to a focusing microchannel inlet, followed by a capacitive sensor for size-based particle counting. Preliminary analysis determined an optimal airflow velocity at w = 0.5 m/s for accurate focusing and counting under laminar conditions. The micro-damper, constrained by the piezoelectric pump’s geometry, features a 27 µm high and 1000 µm wide cross section. Its outlet supports two potential focusing microchannel inlet configurations of 30 µm or 40 µm. Distinctively, it incorporates two symmetrical backward micro-channels connecting to the atmosphere, allowing direct piezometric contact between the main flow and an infinite compliant volume. OpenFOAM simulations confirm the damper’s effectiveness in maintaining laminar outlet flow and suppressing micropump disturbances. Thus, the proposed micro-damper ensures optimal inlet conditions for subsequent microchannel processes, enabling stable particle separation and detection in controlled airflow samples.
Introduction
In schizophrenia, there is evidence for anomalies in the extension and plasticity of
the peripersonal space (PPS), the portion of space surrounding our body, plastically shaped
through ...motor experiences. An impaired multisensory integration at the PPS level would
underpin the disembodiment, a core feature of the disorder linked to subjective perturbations
of the sense of self (“Self-disorders”) and of the intersubjective dimension (“schizophrenic
autism”).
Objectives
The present study was aimed at: 1) exploring possible associations between PPS data,
psychopathological dimensions, and subjective experiences in schizophrenia; 2) identifying a
specific PPS profile in patients with early-onset schizophrenia.
Methods
A motor training with a tool was used to assess the PPS size and boundaries
demarcation in twenty-seven schizophrenia outpatients. Moreover, they underwent a thorough
psychopathological evaluation with the Positive And Negative Syndrome Scale (PANSS), the
Examination of Anomalous Self Experience scale (EASE) and the Autism Rating Scale (ARS).
Subsequently, the sample was divided into early (EOS) and adult-onset (AOS) subgroups, that
were compared with respect to their PPS and psychopathological profiles.
Results
PPS features (size and boundaries demarcation) were associated with PANSS negative
score, subjective experiences of existential reorientation (EASE Domain 5 scores) and traits
of schizophrenic autism (ARS scores; Fig. 1). PPS parameters (Fig. 2) and ARS scores, but not
PANSS and EASE differentiated between early and adult-onset subgroups.
Image:
Image 2:
Conclusions
Our results suggest a link between PPS patterns, negative symptoms, and disturbances
of the subjective experience, particularly in the intersubjective domain, in schizophrenia.
Moreover, they candidate specific PPS profiles and schizophrenic autism traits as EOS
markers.
Disclosure of Interest
None Declared
In the framework of on-orbit proximity operations, small satellites represent an appealing solution in terms of costs, effectiveness and realization, but show intrinsic power, mass and computation ...limitations that could be overcome if cooperation among many spacecraft is considered. In this research, a swarm of small satellites (called “Children S/C″), deployed from a larger platform (called “Mother S/C″), is employed in the inspection of a damaged spacecraft, which cannot be directly approached by the Mother S/C for safety reasons. The navigation process is delegated to the Mother S/C, that is equipped with a passive camera. A navigation algorithm runs on the Mother S/C, which identifies and tracks the Children S/C framed in the scene, even though false matches (i.e., incorrect tracking of a given child) could happen. The navigation algorithm is made robust through the generation at each time step of a propagated virtual image (based on the previous estimate of the swarm state) which is compared to the acquired image for the correct identification of each child. When the relative position estimates reach a satisfactory accuracy, the Mother S/C communicates to the Children S/C their current state and an optimal impulsive control strategy can be implemented to make the swarm fulfill the required inspection task. Simulations are carried out in a purposely developed software environment, in which images of rendered CAD models are acquired and processed to have a realistic validation of the estimation algorithm, showing satisfactory performance and robustness for the overall mission accomplishment.
•Swarm of satellites can be an option for on-orbit missions.•Autonomous GNC loop is required for tight formations.•Visual navigation is a key asset for autonomous navigation.•Optimal impulsive control is computed using visual measurements.•Software set-up for realistic visual navigation is presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The human postural system operates on the basis of integrated information from three independent sources: vestibular, visual and somatosensory. It is conceivable that a derangement of any of these ...systems will influence the overall output of the postural system. The peripheral proprioceptive system or the central processing of proprioceptive information may be altered in chronic low back pain (CLBP). We therefore investigated whether patients with CLBP exhibited an altered postural control during quiet standing. Dynamic posturography was performed by 12 CLBP patients and 12 age-matched controls. Subject's task was to stand quietly on a computer-controlled movable platform under six sensory conditions that altered the available visual and proprioceptive information. While the control of balance was comparable between the two groups across stabilized support surface conditions (1–3), CLBP patients oscillated much more than controls in the anterior–posterior (AP) direction in platform sway-referenced conditions (4–6). Control experiments ruled out that increased sway was due to pain interference. In CLBP patients, postural stability under challenging conditions is maintained by an increased sway in AP direction. This change in postural strategy may underlie a dysfunction of the peripheral proprioceptive system or the central integration of proprioceptive information.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Introduction
A primary disruption of the bodily self is considered a core feature of schizophrenia patients (SCZ). The “disembodied” self would be underpinned by an inefficient body-related ...multisensory integration mechanism occurring in the Peripersonal Space (PPS). PPS is a plastic sector of space surrounding our body, whose extent is altered in SCZ. Although PPS represents a malleable interface marking the perceptual border between self and others, no study has investigated the potential alteration of its plasticity in SCZ.
Objectives
We investigated the PPS extension and its plasticity in SCZ and their potential correlations with the clinical scales.
Methods
Thirty SCZ and thirty healthy controls (HC) underwent a multisensory task to estimate PPS boundary before and after a motor training. Patients were also administered the Positive And Negative Syndrome Scale (PANSS) and the Examination of Anomalous Self-Experience (EASE).
Results
Data confirm a narrower PPS extent in SCZ than in HC, whereas no differences in PPS expansion was found in the two groups after the motor training (Figure 1). Positive symptoms were associated directly with PPS extent and inversely with PPS plasticity. No associations were found between PPS and EASE domains. Figure1: Graphical representation of PPS expansion in SCZ and HC. Both panels show individual normalized sigmoid fits
Conclusions
The present study suggests a narrower PPS extent and a preserved PPS plasticity in SCZ with respect to HC. Both PPS extent and plasticity are related to the severity of positive symptoms. These results highlight the potential role of rehabilitation interventions in order to improve patients’ weakened body boundary.
Disclosure
No significant relationships.
An immersed surface in
R
4
is said to has constant Jordan angles (CJA) if the angles between its tangent planes and a fixed plane do not depend on the choice of the point. The constant Jordan angles ...surfaces in
R
4
has been proved to exist, Bayard et al. (Geom Dedicata 162:153–176, 2013), but there are only explicit examples of non planar surfaces for the extremal angles 0 and
π
2
as the Clifford torus. In this work, an alternative proof of the existence has been obtained that is based on the solution of a hyperbolic partial differential equation. Finally, after a study of the known solutions of the hyperbolic equation, an explicit expression with arbitrary CJA is provided for a family of immersions with an additional geometric property written in terms of the local invariants.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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