Expansion In Direction Research Articles

Plasma-activated water regulates root hairs and cotyledon size dependent on cell elongation in Nicotiana tabacum L.

Tobacco is an excellent model plant to study developmental processes and cellular biology. Surface dielectric barrier discharge (sDBD) was used to generate plasma activated water (PAW), and the PAW was indirectly applied to study tobacco plant growth during the early developmental stages. Solid media were treated with the PAW for 8- and 18-day-old seedlings, and the effects on both the vegetative and root phenotypes were observed during the early developmental stages. In the vegetative tissue, the cotyledon size was large for the seedling that was cultivated by plasma activated water for the 12 min PAW (PAW12) treatment. The PAW dramatically elongated the cotyledon by 40% due to increased cell expansion in the leaf-length direction, not cell proliferation. In addition to the vegetative tissue, the root length due to the PAW was significantly enhanced at the primary root with elongated root hairs. According to molecular analysis, the NT_ COBRA-LIKE 9 (COBL) and two NT_ XYLOGLUCAN ENDO-TRANSGLYCOSYLASE/HYDROLASE (XTH) genes, NT_XTH9 and NT_XTH15, were significantly over-expressed by the PAW treatment compared with untreated deionized water (DW), indicating that the PAW effects are from modulating the expression of target genes. These results demonstrate that PAW might promote tobacco plant growth both in the cotyledon and root hair tissues via the NT_COBL, NT_XTH9 and NT_XTH15 genes.

Scientific Mapping of English Language Teaching Research in the Philippines: A Bibliometric Review of Doctoral and Master’s Theses (2010–2018)

Very few studies have comprehensively mapped out the landscape of English language teaching (ELT) research, particularly those that are not accessible to wider international readership. Thus, this bibliometric study examines ELT doctoral and master’s theses in the Philippines. A total of 98 theses and dissertations completed between 2010 and 2018 were collected from various Philippine universities. Quantitative analysis was used to examine the characteristics and topical foci of the selected studies. Findings reveal that most of the theses and dissertations mainly focussed on only four ELT areas. The other 17 areas remain underexplored ( N = 11) or unexplored ( N = 6). Findings further suggest that there has been a lack of direction and slow expansion of ELT research areas in the country. This trend is primarily attributed to the absence of clear ELT research agenda. Implications for English language education, teacher education, and future direction for ELT research in the country are discussed.

Full-field tracking and analysis of shrinkage strain during moisture content loss in wood

Abstract Anisotropic shrinkage is a typically feature in wood, which is of critical importance in wood drying. In this study, the shrinkage strains over each growth ring were determined by a full-field strain measurement system during moisture content (MC) loss. Color maps were used to visualize the full-field distribution of displacement and shrinkage strain under different MC conditions. The variation of tangential and radial shrinkage strain from pith to bark, as well as the anisotropic shrinkage in heartwood and sapwood were studied. Both of the displacement and strain values increased as the MC decreased. From pith to bark, the tangential strains were higher at two poles as compared to the center, showing a parabolic distribution below fiber saturation point. While for radial shrinkage strain, a minor difference was observed except for the MC of 10%. An intersection between tangential and radial shrinkage ratio curve was observed at the MC of 28%. Both expansion and shrinkage in tangential direction were larger than radial counterparts, and the transformation from expansion to shrinkage occurred at the MC region of 32–28%. In addition, the shrinkage in heartwood was larger than sapwood, whereas anisotropic shrinkage in sapwood was more pronounced as compared to heartwood.

Thermo-Mechanical Analysis for an Axisymmetric Functionally Graded Rotating Disc under Linear and Quadratic Thermal Loading

The study presents thermo-mechanical analysis of functionally graded (FG) rotating disc whose material properties, namely, Young’s modulus, density and coefficient of thermal expansion in radial direction are tailored from inner to outer radius using power law form. The disc is considered to be under the influence of internal pressure, centrifugal body force and thermal loading of the form linear as well as quadratic. Response of FG disc under linear and quadratic temperature profile subjected to internal pressure as well as centrifugal body force is analysed. An exact solution for stress in radial and tangential directions, under mechanical and thermal loading is presented. Numerical solutions for stresses under internal pressure with uniform thermal loading are obtained using finite element method and its comparison with analytical results is presented graphically. Results for radial displacement, radial stress and tangential stress are depicted graphically and their interpretation has been discussed.

Thermal cycling effect on the phase stability and fracture resistance of synthetic barium/magnesium aluminosilicate systems

This paper focuses on the high-temperature solid-state synthesis of barium-magnesium-aluminosilicate (BMAS) system and its thermal cycling stability between the room temperature and 1200 °C. The BMAS powder was synthesized by adding 0.8 mol of MgO for 1 mol of BaAl2Si2O8 (BAS system) to get a stabilized monoclinic phase (celsian-BMAS). The undoped BAS system with a metastable hexagonal phase (hexacelsian-BAS) was also produced for comparison. Both celsian-BMAS and hexacelsian-BAS powders were sintered by spark plasma sintering (SPS) technique at 1300 °C and 50 MPa. In-situ X-ray diffraction and thermogravimetric analyses together with hardness and indentation fracture resistance measurements proved the thermal stability of the celsian-BMAS system. In contrast, the hexacelsian-BAS compound suffered typical phase transformations during the thermal cycling test, causing its failure in less than 25 cycles. The presence of magnesium in the BMAS system led to the formation of secondary phases, such as Ba/Mg-rich micas and/or barium silicides, which did not affect the thermal integrity of the stable celsian phase. The celsian-BMAS system exhibited a linear thermal expansion in all unit cell directions, giving better thermal reliability to this material over the hexacelsian-BAS system. Besides, this work emphasizes the phase transformations in the studied systems that have been ignored in previous research, and it also compares several common equations for calculation of the indentation fracture resistance.

Identification of urban flight corridors for migratory birds in the coastal regions of Shenzhen city based on three-dimensional landscapes

The rapid urban expansion in southern coastal regions of China can endanger the quality and connectivity of bird habits and thus challenge our capacity for protecting bird species in urban areas. Identifying the ecological corridors that allow migratory birds to and from urban green landscapes is therefore essential for conserving biodiversity in urban areas. This study aimed to explore how urban expansion in vertical direction affects the flying paths of migratory birds and seek measurements to enhance bird migration to and from urban areas. The ecological security pattern (ESP) for migratory birds in a coastal region near the Shenzhen city of China was determined based on three-dimensional landscape data and results were evaluated against historical eBird record abundance data. The positive agreement with historical bird abundance demonstrated that the consideration of three-dimensional landscape in parameterizing the resistance for ESPs can help identify the flight corridors for migratory birds in urban areas and the consequent sixteen key flight corridors with a total length of 454.78 km were identified in and around the Shenzhen city. The three-dimensional landscape data are essential for identifying flight corridors for migratory birds to and from urban landscapes. The extracted flight corridors in and around the Shenzhen city connected natural reserves with urban parks, thereby enlarging bird habitats and its conservation inside the Shenzhen city.

A novel flat modular pneumatic artificial muscle

This paper presents a novel flat modular pneumatic artificial muscle (FMPAM) consisting of thin-film cylinder modules, which have no expansion in the thickness direction when pressurized to generate transverse force, and transverse-to-longitudinal deformation translation structures around modules, which accumulate the distributional deformation and ultimately obtain large cumulative deformation and output force. The FMPAM is designed for contractile assistance in soft wearable robots to achieve no squeezing on users’ skin and better wearing comfort. This design combines the advantage of fast time response of positive-pressure pneumatic artificial muscles (PAMs) and the features of good flexibility of negative-pressure ones. Additionally, the design avoids the disadvantages of relatively large thickness or radical expansion of positive-pressure PAMs. In this paper, the design and processing methods of the FMPAM are introduced in detail. It is worth mentioning that the whole FMPAM is printed utilizing the same type of material at one time. Identification of the module model is carried out. Module net output force and restoring force test benches are built to acquire experimental data for assisting the modeling. The shape of the film and modular output force can be predicted during actuation. Experimental results show that low predictive error can be obtained. Finally, an output force test bench, various radius arches and an arm-like structure are built to verify the output characteristics of the FMPAM: good compliance to surfaces with different radiuses, long-lasting endurance (more than 10 000 reciprocating cycles), and high response speed (100 Hz), indicating that the proposed design can provide theoretical guidance and a good alternative for soft wearable robot actuators.

An in-depth study of molecular and supramolecular structures of bamboo cellulose upon heat treatment

In this study, two methods including a common method using high concentration of alkali solution and a mild extraction method at ambient conditions were used to extract cellulose from bamboo. The results showed that two methods affected the initial state of the cellulose. Celluloses obtained by the former was a hybrid of cellulose I and II while the latter was pure cellulose I. However, their heat treatment results indicated that the heat treatment (≤200 °C) would not change the aggregation structure of bamboo cellulose, but it will cause the change of intramolecular and intermolecular hydrogen bonds, and the break of glycosidic bonds in the amorphous region and part of the crystalline region of cellulose. Accordingly, the crystallinity of bamboo cellulose will decrease slightly after heat treatment. Finally, the macroscopic morphology change of bamboo cellulose caused by heat treatment was the thermal expansion in the width direction instead of distort.

A Review of Evaluating Hematopoietic Stem Cells Derived from Umbilical Cord Blood's Expansion and Homing.

Transplantation of hematopoietic stem cells (HSCs) derived from umbilical cord blood (UCB) has been taken into account as a therapeutic approach in patients with hematologic malignancies. Unfortunately, there are limitations concerning HSC transplantation (HSCT), including (a) low contents of UCB-HSCs in a single unit of UCB and (b) defects in UCB-HSC homing to their niche. Therefore, delays are observed in hematopoietic and immunologic recovery and homing. Among numerous strategies proposed, ex vivo expansion of UCB-HSCs to enhance UCB-HSC dose without any differentiation into mature cells is known as an efficient procedure that is able to alter clinical treatments through adjusting transplantation-related results and making them available. Accordingly, culture type, cytokine combinations, O2 level, co-culture with mesenchymal stromal cells (MSCs), as well as gene manipulation of UCB-HSCs can have effects on their expansion and growth. Besides, defects in homing can be resolved by exposing UCB-HSCs to compounds aimed at improving homing. Fucosylation of HSCs before expansion, CXCR4-SDF-1 axis partnership and homing gene involvement are among strategies that all depend on efficiency, reasonable costs, and confirmation of clinical trials. In general, the present study reviewed factors improving the expansion and homing of UCB-HSCs aimed at advancing hematopoietic recovery and expansion in clinical applications and future directions.

Wave diffraction by multiple arbitrary shaped cracks in an infinitely extended ice sheet of finite water depth

Flexural-gravity wave interactions with multiple cracks in an ice sheet of infinite extent are considered, based on the linearized velocity potential theory for fluid flow and thin elastic plate model for an ice sheet. Both the shape and location of the cracks can be arbitrary, while an individual crack can be either open or closed. Free edge conditions are imposed at the crack. For open cracks, zero corner force conditions are further applied at the crack tips. The solution procedure starts from series expansion in the vertical direction based on separation of variables, which decomposes the three-dimensional problem into an infinite number of coupled two-dimensional problems in the horizontal plane. For each two-dimensional problem, an integral equation is derived along the cracks, with the jumps of displacement and slope of the ice sheet as unknowns in the integrand. By extending the crack in the vertical direction into the fluid domain, an artificial vertical surface is formed, on which an orthogonal inner product is adopted for the vertical modes. Through this, the edge conditions at the cracks are satisfied, together with continuous conditions of pressure and velocity on the vertical surface. The integral differential equations are solved numerically through the boundary element method together with the finite difference scheme for the derivatives along the crack. Extensive results are provided and analysed for cracks with various shapes and locations, including the jumps of displacement and slope, diffraction wave coefficient, and the scattered cross-section.

Fabrication of Poly-Pyrrole Membrane Actuator for Cell Stimulation

Micro-actuators are used for mechanical stimulation of cultured cells in regenerative medicine and are critical components of biosensors. In this study, electrochemical polymerization is utilized to fabricate a film of poly-pyrrole (PPy) with a thickness of 10 μm. This film is peeled off from a working electrode substrate and subsequently laminated with a polydimethylsiloxane (PDMS) membrane containing holes of diameter of 5 mm. The assembled PPy film forms a membrane of PPy that can be used as a micro-actuator. This membrane is deflected upward via the application of voltages of −0.2, −0.4, −0.6, −0.8, and −1.0 V for 120 s in either NaDBS solution or cell culture solution. The primary response was an expansion in the in-plane direction with the absorption of ions in the electrolyte solution. The deflection increases with the duration of the applied voltage. Moreover, the maximum deflection that increases with the applied voltage reaches 540 μm at −1.0 V in the NaDBS solution. In the cell culture solution, the maximum deflection is approximately 400 μm for an applied voltage of −1.0 V. When the PPy membrane actuator was used in the culture solution, the time constant was 20 s to reach 63.2% of the maximum deflection. During operation, a voltage with a rectangular form and a period of 40 s was periodically applied. The operation of the PPy membrane actuator was repeated 90 times or more, although the deflection of the membrane had slight attenuation during the cycle of applied voltage. The PPy membrane exhibited adequate adhesiveness for cultured C2C12 cells. They adhered to the PPy surface and stretching of their pseudopods was observed. These cells are additionally cultured on the PPy membrane actuator. When a voltage is applied, the membrane actuator is operable while supporting cultured C2C12 cells. These cells are mechanically and electrically stimulated on the membrane that functions as a cell stimulation device.

Low-Stress Mechanical Properties of Wool-Cotton Blended Fabrics

ABSTRACT Hand-spun and hand-woven textiles made of natural fibers are known as khadi fabrics. Khadi fabrics are known for their luxury, excellent handle, and comfort properties. These properties can not be obtained using the methods employed for machine-made textiles. The fabric handle is associated with low-stress mechanical properties. In this work, the low-stress mechanical properties of wool-cotton blended khadi fabrics are studied and the effect of different blend proportions of wool fibers and yarn count on the fabric properties is investigated. The combination of different wool varieties was spun using a hand-operated spinning machine (charkha) and used as weft, while the various cotton-wool blends were employed as warp. A total of 27 types of wool-cotton khadi fabrics were woven on a handloom. The low-stress mechanical properties were measured using the SiroFAST system. It was found that the extensibility, formability, shear rigidity, bending rigidity, relaxation shrinkage, and hygral expansions of fabrics were influenced by the proportions of wool blend/mix and yarn linear density. The shear and bending rigidity of wool-cotton fabric are significantly influenced by the wool content in wool-cotton blended warp yarn as well as the proportion of AM wool in weft yarn (p < .001). From a formability point of view, wool-cotton fabrics perform well during garment manufacturing irrespective of a wool type. Relaxation Shrinkage in wool-cotton fabric is higher in warp wise than weft wise and increases with increasing the amount of wool for each type of fabric. The wool dominant fabric has higher hygral expansion in the weft direction than the warp direction.

Experimental investigation of ASR-affected concrete – The influence of uniaxial loading on the evolution of mechanical properties, expansion and damage indices

The alkali silica reaction (ASR) in concrete causes internal localized swelling and micro cracking, which result in expansion and correlated deterioration of the concrete material. The stress state of the concrete is known to affect expansion due to ASR, with an anisotropic stress state giving rise to anisotropic expansion. Similarly, the orientation and extent of micro cracking have a directional effect on the concrete mechanical behaviour. This research studied the effect of sustained uniaxial compressive stress on the evolution of the mechanical behaviour of concrete in compression. Concrete cubes of 230 mm side length were uniaxially restrained and stored in accelerated conditions, with cores drilled in two directions for mechanical tests: a cyclic test in compression, i.e. a stiffness damage test (SDT) and a complete stress-strain test. A clear directional dependency of the mechanical characteristics was found. Furthermore, the results indicate that reduction in modulus of elasticity is well correlated with the expansion in the test direction. On the other hand, the damage indices obtained from the SDT merely relate to the expansion, which puts in question the SDT’s ability to predict ASR expansion in stressed concrete and therefore in concrete structures.

A Worm-Like Biomimetic Crawling Robot Based on Cylindrical Dielectric Elastomer Actuators.

In recent years the field of soft robotics has gained a lot of interest both in academia and industry. In contrast to rigid robots, which are potentially very powerful and precise, soft robots are composed of compliant materials like gels or elastomers (Rich et al., 2018; Majidi, 2019). Their exclusive composition of nearly entirely soft materials offers the potential to extend the use of robotics to fields like healthcare (Burgner-Kahrs et al., 2015; Banerjee et al., 2018) and advance the emerging domain of cooperative human-machine interaction (Asbeck et al., 2014). One material class used frequently in soft robotics as actuators are electroactive polymers (EAPs). Especially dielectric elastomer actuators (DEAs) consisting of a thin elastomer membrane sandwiched between two compliant electrodes offer promising characteristics for actuator drives (Pelrine et al., 2000). Under an applied electric field, the resulting electrostatic pressure leads to a reduction in thickness and an expansion in the free spatial directions. The resulting expansion can reach strain levels of more than 300% (Bar-Cohen, 2004). This paper presents a bioinspired worm-like crawling robot based on DEAs with additional textile reinforcement in its silicone structures. A special focus is set on the developed cylindrical actuator segments that act as linear actuators.

Spatial Flow-Field Approximation Using Few Thermodynamic Measurements—Part I: Formulation and Area Averaging

AbstractOur investigation raises an important question that is of relevance to the wider turbomachinery community: how do we estimate the spatial average of a flow quantity given finite (and sparse) measurements? This paper seeks to advance efforts to answer this question rigorously. In this paper, we develop a regularized multivariate linear regression framework for studying engine temperature measurements. As part of this investigation, we study the temperature measurements obtained from the same axial plane across five different engines yielding a total of 82 datasets. The five different engines have similar architectures and therefore similar temperature spatial harmonics are expected. Our problem is to estimate the spatial field in engine temperature given a few measurements obtained from thermocouples positioned on a set of rakes. Our motivation for doing so is to understand key engine temperature modes that cannot be captured in a rig or in computational simulations, as the cause of these modes may not be replicated in these simpler environments. To this end, we develop a multivariate linear least-squares model with Tikhonov regularization to estimate the 2D temperature spatial field. Our model uses a Fourier expansion in the circumferential direction and a quadratic polynomial expansion in the radial direction. One important component of our modeling framework is the selection of model parameters, i.e., the harmonics in the circumferential direction. A training-testing paradigm is proposed and applied to quantify the harmonics.

Actuator-assisted Subpitch Translation-capable Transducer for Elastography: Preliminary Performance Assessment.

In conventional linear array (CLA)-based elastography tissue compression in one direction (e.g., axial) leads to an expansion in all other directions (lateral, elevation). Therefore, the estimation of the lateral displacements and strains may provide additional information on the tissue mechanical properties. However, these are not exploited fully due to the inherent limitation in lateral sampling. Recently, a method named actuator-assisted beam translation (ABT) was demonstrated to address this issue, wherein the focused beam was translated at subpitch locations using an external bench-top setup. However, because such bench-top setup may be impractical for routine clinical use, an ultrasound transducer was customized to have an internal actuator. The performance of the customized transducer was studied through experiments on phantoms for rotation elastography application, which requires precise lateral displacement estimation. Furthermore, the results obtained from ABT was compared against the currently practiced spatial displacement compounding (SDC) method, which is known to yield better quality lateral displacement estimates than conventional approaches. The results show that the ABT method yields a full-width half-maximum (FWHM) value, taken from the lateral profile across a point scatterer, which is 65% and 24% smaller than that obtained using CLA and SDC methods, respectively. Furthermore, the contrast-to-noise ratio (CNR) estimated from rotation elastogram obtained using ABT method is better by 300% and 35% compared with that obtained by using CLA and SDC methods, respectively. Furthermore, the results demonstrate an additional advantage of having larger field of view (FoV) for the ABT method compared with spatial compounding approach.

Dual-axial Ultrasonic Assisted Wire-EDM Process with Vibration Exerted through the Upper Guide

It is difficult for conventional Wire Electrical Discharge Machining (Wire-EDM) to deal with the cutting of a very thick workpiece. The frequent wire-breakage resulting in wire scratches and severe time-cost, and even the inevitable drum-shaped remained on the lateral wall of workpiece also caused problems to the finishing. Although there was ultrasonic vibration-assisted Wire-EDM reported in the past, they were conducted by only one axial vibrator causing an elliptical expansion in that vibration direction. In this paper, a novel dual-axial ultrasonic vibration (DUV-WEDM) with phases difference of 90o along the orthogonal direction is proposed to prevent the wire from breakage and the elliptical expansion. The module is implemented among the upper guide and the top of workpiece, driven by two ultrasonic actuators and a dual-channel signal source. Because of the dispersion of sparks location and increase of stability index, the proposed strategy benefits from reducing the risk of wire-rupture significantly in comparison with the conventional Wire-EDM. Besides, it improves the cutting accuracy simultaneously because of the uniform EDM expansion by the circular trajectory compared to the single axial vibration mode. Moreover, even the drum-shapedd along the lateral wall is more flattened than conventional cutting by the DUV-WEDM module.

3D dynamic responses of a multi-layered transversely isotropic saturated half-space under concentrated forces and pore pressure

Dynamic Green's function plays an important role in the study of various wave radiation, scattering and soil-structure interaction problems. However, little research has been done on the response of transversely isotropic saturated layered media. In this paper, the 3D dynamic responses of a multi-layered transversely isotropic saturated half-space subjected to concentrated forces and pore pressure are investigated. First, utilizing Fourier expansion in circumferential direction accompanied by Hankel integral transform in radial direction, the wave equations for transversely isotropic saturated medium in cylindrical coordinate system are solved. Next, with the aid of the exact dynamic stiffness matrix for in-plane and out-of-plane motions, the solutions for multi-layered transversely isotropic saturated half-space under concentrated forces and pore pressure are obtained by direct stiffness method. A FORTRAN computer code is developed to achieve numerical evaluation of the proposed method, and its accuracy is validated through comparison with existing solutions that are special cases of the more general problems addressed. In addition, selected numerical results for a homogeneous and a layered material model are performed to illustrate the effects of material anisotropy, load frequency, drainage condition and layering on the dynamic responses. The presented solutions form a complete set of Green's functions for concentrated forces (including horizontal load in x(y)-direction, vertical load in z-direction) as well as pore pressure, which lays the foundation for further exploring wave propagation of complex local site in a layered transversely isotropic saturated half-space by using the BEMs.

Indexing PXRD Structural Parameters of Graphene Oxide-Doped Metal-Organic Frameworks

A family of metal-organic framework, [Mg3O3(CO2)3]∞ nanocrystallites which are also known as Mg-MOF-74, were synthesized by solvothermal method at high temperature under autogenous pressure. The graphene oxide was embedded into the framework via in-situ synthesis method to form a composite structure of Mg-MOF-74@nGO. n was varied from 0.1 to 0.6 wt% of the weight of pristine material. The synthesized samples were examined under Powder X-Ray Diffraction analysis to affirm their crystalline structure. Further studies were conducted by indexing the lattice parameters of the hexagonal crystals. The volume of unit cell and Scherrer’s crystallite size were also determined to study the effect of GO loading amount on their grown dimensions. The results showed that the presence of GO in the range of 0.1-0.6 wt% did not influence the dimension of the crystal except a slight expansion in vertical direction with the increment of GO loading.

Giant anisotropic thermal expansion actuated by thermodynamically assisted reorientation of imidazoliums in a single crystal

Materials demonstrating unusual large positive and negative thermal expansion are fascinating for their potential applications as high-precision microscale actuators and thermal expansion compensators for normal solids. However, manipulating molecular motion to execute huge thermal expansion of materials remains a formidable challenge. Here, we report a single-crystal Cu(II) complex exhibiting giant thermal expansion actuated by collective reorientation of imidazoliums. The circular molecular cations, which are rotationally disordered at a high temperature and statically ordered at a low temperature, demonstrate significant reorientation in the molecular planes. Such atypical molecular motion, revealed by variable-temperature single crystal X-ray diffraction and solid-state NMR analyses, drives an exceptionally large positive thermal expansion and a negative thermal expansion in a perpendicular direction of the crystal. The consequent large shape change (~10%) of bulk material, with remarkable durability, suggests that this complex is a strong candidate as a microscale thermal actuating material.