scholarly journals Universal poroelastic mechanism for hydraulic signals in biomimetic and natural branches

2017 ◽  
Vol 114 (42) ◽  
pp. 11034-11039 ◽  
Author(s):  
J.-F. Louf ◽  
G. Guéna ◽  
E. Badel ◽  
Y. Forterre
Keyword(s):  
Growth Response ◽  
Pressure Pulse ◽  
Vascular System ◽  
Water Pressure ◽  
Local Deformation ◽  
Physical Parameters ◽  
Hydromechanical Coupling ◽  
Long Distance ◽  
Whole Plant ◽  
Basic Features

Plants constantly undergo external mechanical loads such as wind or touch and respond to these stimuli by acclimating their growth processes. A fascinating feature of this mechanical-induced growth response is that it can occur rapidly and at long distance from the initial site of stimulation, suggesting the existence of a fast signal that propagates across the whole plant. The nature and origin of the signal is still not understood, but it has been recently suggested that it could be purely mechanical and originate from the coupling between the local deformation of the tissues (bending) and the water pressure in the plant vascular system. Here, we address the physical origin of this hydromechanical coupling using a biomimetic strategy. We designed soft artificial branches perforated with longitudinal liquid-filled channels that mimic the basic features of natural stems and branches. In response to bending, a strong overpressure is generated in the channels that varies quadratically with the bending curvature. A model based on a mechanism analogous to the ovalization of hollow tubes enables us to predict quantitatively this nonlinear poroelastic response and identify the key physical parameters that control the generation of the pressure pulse. Further experiments conducted on natural tree branches reveal the same phenomenology. Once rescaled by the model prediction, both the biomimetic and natural branches fall on the same master curve, enlightening the universality of our poroelastic mechanism for the generation of hydraulic signals in plants.

Developing an in situ, hydromechanical coupling, true triaxial rock compression tester and investigating the deformation patterns of reservoir bank slopes

2021 ◽  
pp. qjegh2021-043
Author(s):  
Lei Fan ◽  
Meiwan Yu ◽  
Aiqing Wu ◽  
Yihu Zhang
Keyword(s):  
Coupling Effect ◽  
Water Pressure ◽  
Pressure Coefficient ◽  
Hydromechanical Coupling ◽  
Rock Interaction ◽  
True Triaxial ◽  
Rock Structure ◽  
Deformation Patterns

Interactions between water and rocks are the main factors affecting the deformation of rock masses on sloped banks by reservoir impoundment. The technology used in laboratory tests of water-rock interaction mechanisms cannot simulate the coupling of water, the rock structure and the initial stress environment. In this work, we develop an in situ hydromechanical true triaxial rock compression tester and apply it to investigate the coupling response of reservoir bank rocks to changing groundwater levels. The tester is composed of a sealed chamber, loader, reactor, and device for measuring deformation, which are all capable of withstanding high water pressures, and a high-precision servo controller. The maximum axial load, lateral load and water pressure are 12 000 kN, 3 000 kN and 3 MPa, respectively. The dimensions of the test specimens are 310 mm×310 mm×620 mm. The test specimens are grey-black basalts with well-developed cracks from the Xiluodu reservoir area. The results show that increasing water pressure promotes axial compression and lateral expansion, while decreasing water pressure causes axial expansion and lateral compression. A water pressure coefficient, K, is introduced as a measure of the hydromechanical coupling effect (expansion or compression) with changing groundwater level. A mechanical tester can be used to perform accurate field tests of the response of wet rocks to hydromechanical coupling. The test results provide new information about the deformation patterns of rock slopes in areas surrounding high dams and reservoirs.Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

Hull Deformation Effect on Membrane-Type LNG Containment Systems

2016 ◽  
Author(s):  
Bo Wang ◽  
Yung-Sup Shin ◽  
Eric Norris
Keyword(s):  
Structural Integrity ◽  
Water Pressure ◽  
Local Deformation ◽  
Fatigue Tests ◽  
Wave Loads ◽  
Insulation System ◽  
Structural Fatigue ◽  
Hull Structure ◽  
Membrane Type ◽  
Global Deformation

The objective of this study is to investigate the relationship between the maximum allowable hull deformation, which includes global elongation and local deflection, and the capacity of the CCS in membrane-type LNG vessels. The LNG CCS mainly consists of the primary barrier (e.g. a corrugated membrane for GTT MK III system and an invar membrane for GTT NO 96 system) and the insulation panel which is attached to the inner hull through mastics or couplers. The excessive hull elongation due to dynamic wave loads may cause fatigue damage of the primary barrier. Thus, the maximum allowable hull elongation (global deformation) can be determined based on the fatigue strength of the primary barrier. On the other hand, the excessive hull deflection due to cargo or ballast water pressure may cause failure of the insulation panel and the mastic. Therefore, the maximum allowable hull deflection (local deformation) in the hull design can be determined based on the strength of the insulation panel and the mastic. In the present paper, the determination of fatigue life vs. strain curves of materials has been summarized for the primary barrier. Fatigue curves based on either structural fatigue tests or standard specimen tests can be applied in fatigue assessment of a primary barrier. As an example, the finite element (FE) analysis has been conducted on the MK III CCS with the hull structure under pressure loads. Two different load cases including full load and ballast load conditions have been considered to evaluate the structural integrity of the insulation system in numerical simulations. FE results show that the mechanical behavior of the insulation system and the mastic under the maximum allowable hull deflection has been examined based on the yielding strength of each individual component. Finally, the complete procedure to determine the maximum allowable hull elongation and the maximum allowable hull deflection has been developed for meeting the requirements of containment system design for membrane-type LNG carriers.

scholarly journals An Experimental and Numerical Investigation on the Initiation and Interaction of Double Cracks in Rocks under Hydromechanical Coupling

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jie Mei ◽  
Wanzhi Zhang
Keyword(s):  
Water Pressure ◽  
Critical Length ◽  
Maximum Energy ◽  
Enhancement Effect ◽  
Hydromechanical Coupling ◽  
Underground Engineering ◽  
Side Rock ◽  
Crack Tips ◽  
Dip Angle ◽  
Interaction Behaviors

The growth of double cracks is the main factor leading to progressive rock failure under hydromechanical coupling. The initiation modes and interaction behaviors of double cracks were investigated by using laboratory tests, and the influences of water pressure were analyzed. The maximum energy release rate criterion was modified to determine the crack growth characteristics. A numerical model was established and then verified by the test results. Based on the simulation, the distribution of stress fields and key fracture parameters of double cracks was investigated. Then, initiation characteristics and interaction behaviors of parallel and nonparallel cracks were quantitatively analyzed. The results indicate that the increase in water pressure leads to the crack initiation being inclined to the original surfaces and the growth length along the crack fronts tending to be uniform; the small tensile stress zones are formed close to the crack tips, and significant compressive stress zones are formed at both sides of the crack surfaces; stress superposition and interaction occur when crack spacing is less than 2.5a; the interactive weakening effect is mainly present in the inner side (rock bridge zone) of cracks, while a certain degree of interactive enhancement effect exhibits in the outer sides; the cracks are much easier to initiate at the outer wing cracks when the spacing is less than the critical length (0.5a); and cracks with a dip angle of 45° are much easier to initiate at the endpoints of long axis. The research results provide certain theoretical guidance for the safety assessment of underground engineering.

scholarly journals Long-Distance Movement of mRNAs in Plants

Plants ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 731 ◽  
Author(s):  
Chao Xia ◽  
Cankui Zhang
Keyword(s):  
Vascular System ◽  
Physiological Characteristic ◽  
Small Peptides ◽  
Long Distance ◽  
Systemic Signaling ◽  
Long Distance Transport ◽  
Specific Mrnas ◽  
Multiple Species ◽  
Species Specific ◽  
Long Distance Movement

Long-distance transport of information molecules in the vascular tissues could play an important role in regulating plant growth and enabling plants to cope with adverse environments. Various molecules, including hormones, proteins, small peptides and small RNAs have been detected in the vascular system and proved to have systemic signaling functions. Sporadic studies have shown that a number of mRNAs produced in the mature leaves leave their origin cells and move to distal tissues to exert important physiological functions. In the last 3–5 years, multiple heterograft systems have been developed to demonstrate that a large quantity of mRNAs are mobile in plants. Further comparison of the mobile mRNAs identified from these systems showed that the identities of these mRNAs are very diverse. Although species-specific mRNAs may regulate the unique physiological characteristic of the plant, mRNAs with conserved functions across multiple species are worth more effort in identifying universal physiological mechanisms existing in the plant kingdom.

High-Resolution Arterial Pressure-Area Loops in Rats

2009 ◽  
Author(s):  
Craig Fancourt ◽  
Yuzhuo Su ◽  
Jeffrey R. Sachs ◽  
Michelle Bunzel ◽  
Barry R. Campbell ◽  
...  
Keyword(s):  
High Resolution ◽  
Arterial Pressure ◽  
Pressure Pulse ◽  
Vascular System ◽  
Artery Wall ◽  
Pharmacological Interventions ◽  
Disease States ◽  
Pressure Area ◽  
Cardio Vascular ◽  
Contracting Heart

The artery wall is compliant and stretches in response to the traveling pressure pulse generated by the contracting heart. The dynamics of this motion are known to convey important information about the health of the artery and cardio-vascular system. For example, compliance, a measure of artery flexibility, decreases due to aging, as well as disease states such as hypertension and atherosclerosis. It also exhibits acute and chronic changes under pharmacological interventions.

scholarly journals Application of the Bayesian Belief Nets in dam safety monitoring

2012 ◽  
Vol 44 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Dorota Mirosław-Świątek ◽  
Mariusz Kembłowski ◽  
Władysław Jankowski
Keyword(s):  
Water Pressure ◽  
Safety Monitoring ◽  
Data Interpretation ◽  
Technical Condition ◽  
Monitoring Data ◽  
Earth Dam ◽  
Physical Parameters ◽  
Dam Safety ◽  
Dam Safety Monitoring ◽  
Bayesian Belief Nets

Application of the Bayesian Belief Nets in dam safety monitoring The systems for earth dam monitoring should enable measurements of basic physical parameters describing the behavior of the structure, including: soil water pressure, soil stress, displacements, leaks, and drainage discharges. In the case of earth dam safety assessment, the monitoring data are used to detect any anomalies in dam behavior. In this paper, the dam safety has been analyzed using the Bayesian Nets. Two types of information: water pressure measurements and drainage discharge measurements are used in analyses. The seepage anomalies in the Klimkówka Dam were considered in demonstrate the practical advantages of using the Bayesian Nets for monitoring data interpretation. Presented examples of the Bayesian Nets applications (forward and backward propagation) in analysis of seepage through earth dams show that this method can be an effective tool supporting an assessment of dams technical condition and monitoring of the dam safety.

scholarly journals Effeots of High Temperature and Genotype on the Growth of Excised Roots of Arabidopsis Thaliana

1968 ◽  
Vol 21 (2) ◽  
pp. 217 ◽  
Author(s):  
TF Neales
Keyword(s):  
Arabidopsis Thaliana ◽  
High Temperature ◽  
Growth Response ◽  
Whole Plant ◽  
Vitamin Requirement

The effects of a high temperature (31'5�C), and the addition of vitamins (thiamine plus biotin) on the growth of excised roots of four clones of A. thaliana derived from the strains EST, Pi, BLA, and 1018/6 are described. Growth response of the roots to these treatments was different from that of the whole plant of the same strain. The vitamin requirement of the roots of strain 1018/6 was greater at 31� 5�C than at 27�C.

scholarly journals Experimental Study on Immersion Effects of Pressure Water on the Tensile Characteristics of Sandstone Samples

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Dawei Yin ◽  
Shaojie Chen ◽  
Bing Chen ◽  
Rui Liu ◽  
Faxin Li
Keyword(s):  
Brittle Failure ◽  
Morphological Changes ◽  
Water Pressure ◽  
Mechanical Energy ◽  
Reduction Rate ◽  
Failure Surface ◽  
Cementitious Materials ◽  
Local Deformation ◽  
Sandstone Sample ◽  
Pressure Water

In this study, Brazilian splitting tests were conducted on sandstone samples subjected to drying and immersing at water pressures of 0, 1, and 3 MPa (immersion duration of 120 h). Investigation of the immersion effects of pressure water on the tensile characteristics of the samples revealed that their tensile strengths decreased with the immersion water pressure. Relative to a sandstone sample subjected to drying alone, immersing at water pressures of 0, 1, and 3 MPa reduced the tensile strength by 12.96%, 19.03%, and 30.16%, respectively. Although the immersed samples experienced splitting failure indicative of obvious brittle failure characteristics, decreases in the postpeak stress reduction rate with immersion water pressure revealed that the intensity of brittle failure weakened with pressure. Based on the obtained data, the deformation evolution process of the sandstone samples could be divided into five stages: deformation adjustment, formation of local deformation zones, local deformation zone propagation, failure surface formation, and sample failure. The water pressure aggravated the physicochemical reactions between water and the hydrophilic minerals in the sandstone, promoting argillisation, dissolution, and loss of hydrophilic minerals and interparticle cementitious materials. As a result of these immersion micromechanisms, the deterioration of the sandstone samples increased with the immersion water pressure, with the average porosities of the fracture surfaces at 0, 1, and 3 MPa increasing by 142.86%, 368.37%, and 593.88%, respectively, relative to the dried sample. As a result of these morphological changes, the sandstone samples subjected to water pressure immersion failed at small axial stresses with low levels of applied mechanical energy.

scholarly journals Transport in times of an epidemic: public transport measures in the Czech Republic and its regions

2021 ◽  
Vol 21 (1) ◽  
pp. 57-78
Author(s):  
Martin Vrána ◽  
Simona Surmařová ◽  
Petr Hlisnikovský ◽  
Jiří Dujka
Keyword(s):  
Czech Republic ◽  
Public Transport ◽  
Human Life ◽  
Transport Sector ◽  
Long Distance ◽  
The Czech Republic ◽  
Large Cities ◽  
Hygiene Measures ◽  
Basic Features ◽  
Almost All

Abstract In the first half of 2020, the global pandemic of the COVID-19 virus became a phenomenon affecting all spheres of human life. Measures against the spread of the virus have led to restrictions in life in public spaces and have also affected the transport sector. These impacts consisted of two types - firstly, the number of connections was reduced due to a drop in transport demand, and secondly, it was necessary to comply with hygiene measures on the part of carriers and passengers. The impacts of these measures could be monitored at all spatial levels, from global to local. This paper deals with the course of the so-called first wave of the pandemic in the Czech Republic in relation to public transport and its organization. The aim of the paper is to provide an overview of these measures in relation to general government regulations and their subsequent implementation at the national, regional (county) and local (selected large cities) level. Furthermore, the paper uses three case studies to show what changes long-distance domestic transport has undergone on selected routes. There was a significant reduction in the number of long-distance connections, some lines were not operated at all, and of course, all cross-border connections were canceled. The paper covers the period from the turn of February and March 2020, when the measures began to take effect, to the end of May 2020, when almost all the adopted measures were gradually relaxed. The paper concludes with a summary of the basic features of the organization of transport during the validity of the special measures, as well as areas where significant changes took place and whose consequences may persist after the pandemic subsides.

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