Asymmetric Volume Research Articles

Multiple-Responsive and Amphibious Hydrogel Actuator Based on Asymmetric UCST-Type Volume Phase Transition.

Thermoresponsive hydrogel actuators have attracted tremendous interest due to their promising applications in artificial muscles, soft robotics, and flexible electronics. However, most of these materials are based on polymers with lower critical solution temperature (LCST), while those from upper critical solution temperature (UCST) are rare. Herein, we report a multiple-responsive UCST hydrogel actuator based on the complex of poly(acrylic acid) (PAAc) and poly(acrylamide) (PAAm). By applying a heterogeneous photopolymerization, a bilayer hydrogel was obtained, including a layer of the interpenetrating network (IPN) of PAAm/PAAc and a layer of a single network of PAAm. When cooled down below the UCST, the PAAm/PAAc layer contracted due to the hydrogen bonding of the two polymers while the PAAm layer stays in swelling state, driving the hydrogel to curl. By adjusting the composition of the two layers, the amplitude of actuation behavior could be regulated. By creating patterned IPN domains with photomasks, the hydrogel could deform into complex two-dimensional (2D) and three-dimensional (3D) shapes. An active motion was realized in both water and oil bath, thanks to the internal water exchange between the two layers. Interestingly, the hydrogel actuator is also responsive to urea and salts (Na2SO4, NaCl, NaSCN), due to that the strength of the hydrogen bonds in the IPN changes with the additives. Overall, the current study realized an anisotropic UCST transition by introducing asymmetrically distributed polymer-polymer hydrogen bonds, which would inspire new inventions of intelligent materials.

Untethered Soft Actuators by Liquid–Vapor Phase Transition: Remote and Programmable Actuation

Bioinspired soft robotics have unique advantages in superior adaptability and complex motions for field exploration and interaction with humans. The mobility and output force, however, are still the critical challenges for many promising applications. It is attractive to develop “untethered” robotics to improve the mobility by getting rid of the external electrical or pneumatic tethers while achieving massive output stroke and force. Inspired by the creatures' movements induced by the multiplication of cells and asymmetric volume changes of the tissue, an untethered soft actuator composed of self‐contained liquids and super‐elastic chambers is proposed, and by remote stimuli (e.g., near‐infrared light), the capsuled liquids transit from liquid to vapor, giving rise to volume change in the corresponding chambers. Programmable motions, i.e., photophobia of artificial sunflower, can be realized, indicating a massive and linear driving stroke (up to 160% in elongation, 0.5 mm °C−1) and output force (14.5 N with 6 g self‐weight, 0.33 N °C−1). The untethered soft actuator suggests a feasible approach to develop smart, soft, and autonomous robotics and holds promise in fields ranging from surgery to rehabilitation and rescue.

Iterative and Complex Asymmetric Divisions Control Cell Volume Differences in Ciona Notochord Tapering.

The notochord of the invertebrate chordate Ciona forms a tapered rod at tailbud stages consisting of only 40 cylindrical cells in a single-file column. This tapered shape involves differences in notochord cell volume along the anterior-posterior axis. Here,we quantify sibling cell volume asymmetry throughout the developing notochord and find that there are distinctive patterns of unequal cleavage in all 4 bilateral pairs of A-line primary notochord founder cells and also in the B-line-derived secondary notochord founder cells. A quantitative model confirms that the observed patterns of unequal cleavage are sufficient to explain all the anterior-posterior variation in notochord cell volume. Many examples are known of cells that divide asymmetrically to give daughter cells of different size and fate. Here, by contrast, a series of subtle but iterative and finely patterned asymmetric divisions controls the shape of an entire organ. Quantitative 3D analysis of cell shape and spindle positioning allows us to infer multiple cellular mechanisms driving these unequal cleavages, including polarized displacements of the mitotic spindle, contributions from the shape of the mother cell, and late changes occurring between anaphase and abscission that potentially involve differential cortical contractility. We infer differential use of these mechanisms between different notochord blastomeres and also between different rounds of cell division. These results demonstrate a new role for asymmetric division in directly shaping a developing organ and point toward complex underlying mechanisms.

Amygdalar volume and violent ideation in a sample at clinical high-risk for psychosis

We previously demonstrated that violent ideation predicts both violent acts and eventual progression to syndromal psychosis in individuals at clinical high-risk for psychosis (CHR). We performed amygdalar surface morphometry analysis on MRI scans from 70 CHR individuals, 21 of whom had violent ideation, 49 of whom did not. CHR individuals with violent ideation have abnormal and asymmetric amygdalar volumes. These data suggest some commonalities in the genesis of violence and aggression among clinical populations, as well as that there may be specific neurobiological links between violence and psychosis.

Plant nyctinasty - who will decode the 'Rosetta Stone'?

Nyctinasty is the circadian rhythmic nastic movement of leguminous plants in response to the onset of darkness, a unique and intriguing phenomenon that has attracted attention for centuries. The movement itself is caused by the asymmetric volume change of motor cells between the adaxial and abaxial sides of the leaflet. Recently, we identified the ion channels responsible for the volume change of motor cells during the leaf-opening process of Samanea saman; the asymmetric expression of SsSLAH1, which is under the control of SsCCA1, was found to play a key role in this process. Here, we summarize the history of the study of nyctinasty, our current results and several insights for further study.

Finite volume mass gap and free energy of the $\mathrm{SU}(N)\times\mathrm{SU}(N)$ chiral sigma model

We compute the free energy in the presence of a chemical potential coupled to a conserved charge in the effective SU(N)xSU(N) scalar field theory to third order for asymmetric volumes in general d-dimensions, using dimensional regularization. We also compute the mass gap in a finite box with periodic boundary conditions.

The effects of asymmetric volume conductor modeling on non-invasive fetal ECG extraction

Objective: Non-invasive fetal electrocardiography (NI-FECG) shows promise for capturing novel physiological information that may indicate signs of fetal distress. However, significant deterioration in NI-FECG signal quality occurs during the presence of a highly non-conductive layer known as vernix caseosa which forms on the fetal body surface beginning in approximately the 28th week of gestation. This work investigates asymmetric modeling of vernix caseosa and other maternal–fetal tissues in accordance with clinical observations and assesses their impacts for NI-FECG signal processing. Approach: We develop a process for simulating dynamic maternal–fetal abdominal ECG mixtures using a synthetic cardiac source model embedded in a finite element volume conductor. Using this process, changes in NI-FECG signal morphology are assessed in an extensive set of finite element models including spatially variable distributions of vernix caseosa. Main results: Our simulations show that volume conductor asymmetry can result in over 70% error in the observed T/QRS ratio and significant changes to signal morphology compared to a homogeneous volume conductor model. Volume conductor effects must be considered when analyzing T/QRS ratios obtained via NI-FECG and should be considered in future algorithm benchmarks using simulated data. Significance: This work shows that without knowledge of the influence of volume conductor effects, clinical evaluation of the T/QRS ratio derived via NI-FECG should be avoided.

Comparison of hollow fiber and flat mixed-matrix membranes: Theory and simulation

We extend effective medium theory (EMT) to composite hollow fiber mixed matrix membranes, considering the asymmetric filler volume fraction profile arising from finite system size. This volume fraction profile leads to strong variation of the driving force (i.e. pseudo-bulk concentration gradient) in the regions adjacent to the composite ends, and to sensitivity of the effective permeability of the composite to the geometrical configuration. The new theory is validated against rigorous simulations of the transport in mixed-matrix membranes (MMMs) using both concentration-independent and concentration-dependent diffusivities in the MMM constituent phases. Both theory and simulations show that flat mixed-matrix membranes (F-MMMs) have higher effective overall permeability than hollow fiber mixed-matrix membranes (HF-MMMs), upon comparison of systems having identical operating conditions, filler phase loading and particle size. Furthermore, we show here that the sensitivity to the geometry vanishes with increase of inner radius of the hollow fiber membrane at fixed thickness, and the effective permeability of a HF-MMM is found to asymptotically approach that of a F-MMM.

Bending and free vibration analyses of in-plane bi-directional functionally graded plates with variable thickness using isogeometric analysis

This article is firstly concerned with bending and free vibration analyses of in-plane bi-directional functionally graded (IBFG) plates with variable thickness in the framework of isogeometric analysis (IGA). The plate thickness is smoothly altered in both x- and y-axes by a predetermined power law. Two types of power-law material models with the symmetrical and asymmetrical volume fraction distribution are suggested to characterize the in-plane material inhomogeneity. A non-uniform rational B-spline (NURBS) surface for simultaneously representing both variable thickness and volume fraction distribution of each constituent is employed. By using the k-refinement strategy, the C0-continuous requirement at symmetrical material interfaces can be achieved, yet still ensuring material gradations elsewhere owing to the prominent advantage of NURBS basis functions in easily controlling continuity. Effective material properties are then evaluated by either the rule of mixture or the Mori-Tanaka scheme. An analysis NURBS surface separately created with the foregoing NURBS surface is utilized to exactly describe geometry and approximately solve unknown solutions in finite element analysis (FEA) based on the IGA associated with a generalized shear deformation theory (GSDT). The Galerkin C1-continuous isogeometric finite element model is therefore simply achieved due to the possibility of flexibly meeting high-order derivatives and continuity of analysis NURBS functions. In addition, no shear correction factors exist in the present formulation, although shear deformation effects are still considered. The influences of variable thickness, material property, length-to-thickness ratio, boundary condition on bending and free vibration responses are investigated and discussed in detail through several numerical examples.

NURBS-based modeling and analysis for free vibration and buckling problems of in-plane bi-directional functionally graded plates

ABSTRACTIn this article, a novel idea of utilizing a non-uniform rational B-spline (NURBS)-based material mesh independently defined with the analysis mesh to represent the material distribution is introduced to free vibration and buckling problems of in-plane bi-directional functionally graded (IBFG) plates. Two power-law material models with the symmetrical and asymmetrical volume fraction distribution are proposed as the first experiment. By applying the refinement scheme, the continuous condition at symmetrical interfaces of material profiles can be easily achieved, while material gradations are still guaranteed elsewhere due to the outstanding advantage of material NURBS basis functions in controlling continuity. Either the rule of mixture or the Mori–Tanaka scheme is then used to estimate effective material properties. The analysis mesh is constructed by generalized shear deformation theory (GSDT)-based isogeometric analysis (IGA) for exactly modeling geometrical domains and approximately solving unknown solutions in finite element analysis (FEA). Accordingly, the continuous requirement of the Galerkin isogeometric finite element model is simply met owing to the possibility of flexibly fulfilling high-order derivatives and continuity of analysis NUBRS functions. Additionally, the present formulation is also completely free from shear correction factors, yet still considering shear deformation influences. Several numerical examples are presented to demonstrate the performance and effectiveness of the proposed method. The effects of material gradations, aspect ratios, and different boundary conditions on IBFG plate responses are examined in detail as well.

True Low-Power Self-Locking Soft Actuators.

Natural double-layered structures observed in living organisms are known to exhibit asymmetric volume changes with environmental triggers. Typical examples are natural roots of plants, which show unique self-organized bending behavior in response to environmental stimuli. Herein, light- and electro-active polymer (LEAP) based actuators with a double-layered structure are reported. The LEAP actuators exhibit an improvement of 250% in displacement and hold an object three times heavier as compared to that in the case of conventional electro-active polymer actuators. Most interestingly, the bending motion of the LEAP actuators can be effectively locked for a few tens of minutes even in the absence of a power supply. Further, the self-locking LEAP actuators show a large and reversible bending strain of more than 2.0% and require only 6.2 mW h cm-2 of energy to hold an object for 15min at an operating voltage of 3 V. These novel self-locking soft actuators should find wide applicability in artificial muscles, biomedical microdevices, and various innovative soft robot technologies.

Cell volume changes contribute to epithelial morphogenesis in zebrafish Kupffer's vesicle.

How epithelial cell behaviors are coordinately regulated to sculpt tissue architecture is a fundamental question in biology. Kupffer's vesicle (KV), a transient organ with a fluid-filled lumen, provides a simple system to investigate the interplay between intrinsic cellular mechanisms and external forces during epithelial morphogenesis. Using 3-dimensional (3D) analyses of single cells we identify asymmetric cell volume changes along the anteroposterior axis of KV that coincide with asymmetric cell shape changes. Blocking ion flux prevents these cell volume changes and cell shape changes. Vertex simulations suggest cell shape changes do not depend on lumen expansion. Consistent with this prediction, asymmetric changes in KV cell volume and shape occur normally when KV lumen growth fails due to leaky cell adhesions. These results indicate ion flux mediates cell volume changes that contribute to asymmetric cell shape changes in KV, and that these changes in epithelial morphology are separable from lumen-generated forces.

Core-shell Fe3O4@Fe ultrafine nanoparticles as advanced anodes for Li-ion batteries

Core-shell Fe3O4@Fe ultrafine nanoparticles (nano-Fe3O4@Fe, Fe3O4 content 84 wt%) with a core (Fe) diameter of 5.1 ± 1.4 nm and a shell (Fe3O4) diameter of 10.9 ± 1.6 nm is prepared by a liquid-phase pyrolysis and partial oxidation method. It is found that the core-shell Fe3O4@Fe ultrafine nanostructure can efficiently improve the electrochemical performance of Fe3O4 as anode material for Li-ion batteries in terms of rate capability and cycle life. For instance, specific capacities of 884 and 705 mAh/g can be obtained for the nano-Fe3O4@Fe electrode after 100 cycles at 200 mA/g and 500 cycles at 1000 mA/g, respectively. It is believed that these improvements can be attributed to the significant shortened transfer distance of electrons and Li-ions with relatively low specific surface area, ultrahigh electronic conductivity inside the nanoparticles and good ductility to accommodate the asymmetric volume change.

Gyroid Structures at Highly Asymmetric Volume Fractions by Blending of ABC Triblock Terpolymer and AB Diblock Copolymer

We investigated, via small-angle X-ray scattering and transmission electron microscopy, the morphologies of binary blend of polyisoprene-b-polystyrene-b-poly(2-vinylpyridine) (ISP) triblock terpolymer and polyisoprene-b-polystyrene (IS) diblock copolymer. An asymmetric ISP with volume fractions (f) of 0.12, 0.75, and 0.13 for PI, PS, and P2VP blocks, respectively, showed a new morphology: coexistence of spheres and cylinders with tetragonal packing. Asymmetric IS with fI = 0.11 and fS = 0.89 showed conventional body-centered cubic spherical microdomains. Very interestingly, a binary blend of ISP and IS with overall volume fractions of fI = 0.12, fS = 0.79, and fP = 0.09 exhibited core–shell double gyroid (CSG: Q230 space group), where PI consists of thin core and PS forms thick shell, while P2VP becomes thin matrix. It is very unusual to form CSG even at highly asymmetric volume fractions.

Asymmetric gray matter volume changes in patients with unilateral mesial temporal lobe epilepsy and hippocampal sclerosis: Left- and right-side differences

Asymmetric gray matter volume changes in patients with unilateral mesial temporal lobe epilepsy and hippocampal sclerosis: Left- and right-side differences

Altered white matter structure in the visual system following early monocular enucleation.

Partial visual deprivation from early monocular enucleation (the surgical removal of one eye within the first few years of life) results in a number of long-term morphological adaptations in adult cortical and subcortical visual, auditory, and multisensory brain regions. In this study, we investigated whether early monocular enucleation also results in the altered development of white matter structure. Diffusion tensor imaging and probabilistic tractography were performed to assess potential differences in visual system white matter in adult participants who had undergone early monocular enucleation compared to binocularly intact controls. To examine the microstructural properties of these tracts, mean diffusion parameters including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were extracted bilaterally. Asymmetries opposite to those observed in controls were found for FA, MD, and RD in the optic radiations, the projections from primary visual cortex (V1) to the lateral geniculate nucleus (LGN), and the interhemispheric V1 projections of early monocular enucleation participants. Early monocular enucleation was also associated with significantly lower FA bidirectionally in the interhemispheric V1 projections. These differences were consistently greater for the tracts contralateral to the enucleated eye, and are consistent with the asymmetric LGN volumes and optic tract diameters previously demonstrated in this group of participants. Overall, these results indicate that early monocular enucleation has long-term effects on white matter structure in the visual pathway that results in reduced fiber organization in tracts contralateral to the enucleated eye. Hum Brain Mapp 39:133-144, 2018. © 2017 Wiley Periodicals, Inc.

How much stimulated reservoir volume and induced matrix permeability could enhance unconventional reservoir performance

This paper investigates the impacts of stimulated reservoir volume (SRV) on reservoir performance for unconventional hydraulically fractured formations. It focuses also on the effects of different petrophysical properties of SRV as well as different volume and petrophysical properties of unstimulated part of porous media (USRV). The influences of hydraulic fracture conductivity, fracture assymmetricity, and non-Darcy flow permeability in reservoir pressure profile have been substantially studied in this paper. Stimulated reservoir volume represents the volume of porous media where complex network structures formed from naturally induced fractures, multiple hydraulic fractures, and original matrix. SRV is characterized by an induced or a stimulated matrix permeability which is typically greater than the original matrix permeability. The formations of interest, in this study, are considered having either stimulated reservoir volume only or both stimulated and un-stimulated reservoir volumes and depleted by multiple hydraulic fractures controlled by non-Darcy flow.The impacts of SRV and USRV on pressure distributions, flow regimes, and productivity indices have been studied using multi-linear flow regimes approach. A new analytical model has been proposed in this paper for pressure behavior of a horizontal well intersected by multiple hydraulic fractures assuming symmetrical and asymmetrical stimulated reservoir volumes. This model was developed using multi-linear flow regimes approach with an adjustment for variable SRVs and USRVs. The volume of stimulated part in the reservoir is determined by hydraulic fracture half length, number of fractures and spacing between them, and fracture height. The impact of induced or stimulated matrix permeability in the stimulated reservoir volume and fracture conductivity as well as non-Darcy flow impact on pressure behaviors have also been investigated. Several analytical models for flow regimes, expected to develop during the entire production life of reservoir, were also proposed in this study. A set of type-curves was designed for pseudo-pressure normalized rate and pseudo-pressure normalized cumulative rate with production time.The outcomes of this study can be summarized as: 1) Generating an analytical model that describes pressure behavior in unconventional reservoirs and considers variable SRVs and USRVs. This model includes stimulated matrix permeability, non-Darcy flow impact, and hydraulic fracture conductivity. 2) Understanding the impact of asymmetrical stimulated reservoir volumes on reservoir performance. 3) Developing analytical models for different linear flow regimes that could develop during the entire life of reservoir. 4) Comparing the productivity index for different stimulated and un-stimulated reservoir volumes assuming both symmetrical and asymmetrical reservoir volume. The most interesting points in this study are: 1) Productivity index drops significantly for the case of asymmetrical SRVs compared to symmetrical SRVs. 2) The SRV enhances productivity index more than USRV, however, at early production time, there is no impact for both of them on productivity index. 3) The impact of assymmetricity is seen at all production time. 4) Flow regime types are not changed with respect to the assymmetricity.

Effects of Asymmetric Chest Volume Depending on Inspiration Load

Effects of Asymmetric Chest Volume Depending on Inspiration Load

The characteristics investigation under the unsteady cavitation condition in a centrifugal pump

Numerical simulation and experimental method are combined to investigate the pump inlet and outlet pressure fluctuations, the vibration characteristics and the internal flow instabilities under the unsteady cavitation condition in a centrifugal pump. It is found that the unsteady cavitation starts to generate as the NPSHa is lower than 5.93 m. Apparent asymmetric and uneven cavity volume distribution on each blade and in the impeller can be observed as the NPSHa decreases from 4.39 m to 1.44 m, which includes the cavitation develops from cavitation surge, rotating cavitation to asymmetric cavitation. The flow vortexes in each blade channel are produced in the cavity trailing edges by the shedding and collapse of cavitation, which interfere with each other and aggravate the flow instabilities. The dominant frequencies of the pump inlet and outlet pressure fluctuations are the shaft frequency and blade passing frequency under the unsteady cavitation conditions, respectively. Broadband pulses are obtained from both the pump inlet and outlet pressure pulsations, which results from the random shedding and collapse of unsteady cavitation bubbles. Obvious corresponding relationship between the root mean squares of the vibration measured in different positions and the suction performance curve is found under both the non-cavitation and unsteady cavitation conditions.

Study of the peculiarities of multiparticle production via event-by-event analysis in asymmetric nucleus-nucleus interactions

In this work the study on the peculiarities of multiparticle production in interactions of asymmetric nuclei to search for unusual features of such interactions, is performed. A research of long-range and short-range multiparticle correlations in the pseudorapidity distribution of secondary particles on the basis of analysis of individual interactions of nuclei of 197 Au at energy 10.7 AGeV with photoemulsion nuclei, is carried out. Events with long-range multiparticle correlations (LC), short-range multiparticle correlations (SC) and mixed type (MT) in pseudorapidity distribution of secondary particles, are selected by the Hurst method in accordance with Hurst curve behavior. These types have significantly different characteristics. At first, they have different fragmentation parameters. Events of LC type are processes of full destruction of the projectile nucleus, in which multicharge fragments are absent. In events of mixed type several multicharge fragments of projectile nucleus are discovered. Secondly, these two types have significantly different multiplicity distribution. The mean multiplicity of LC type events is significantly more than in mixed type events. On the basis of research of the dependence of multiplicity versus target-nuclei fragments number for events of various types it is revealed, that the most considerable multiparticle correlations are observed in interactions of the mixed type, which correspond to the central collisions of gold nuclei and nuclei of CNO-group, i.e. nuclei with strongly asymmetric volume, nuclear mass, charge, etc. Such events are characterised by full destruction of the target-nucleus and the disintegration of the projectile-nucleus on several multi-charged fragments.