In this paper, we develop several limited chain extensible (LCE) models using fractional powers of certain forms. The fractional powers provide an alternative functional framework similar to the ...logarithmic function. The present models exhibit limited extensibility when the arbitrary exponent is less than unity, and reduce to well-posed parent models when the exponent is unity or the stiffening parameter tends to infinity. When the exponent approaches zero, the proposed model reduces to the logarithm-based existing LCE models. Using these arbitrary fractional powers, we construct suitable strain energy functions based on (a)
I
1
, (b) both
I
1
and
I
2
, (c) principal stretches as well as for transversely isotropic materials. The developed functions also generalizes existing limited chain extensible models. We also further modify the Ogden model to deduce a pair of limited extensible models which reduce to existing models as the exponents approach zero. We next apply various inequalities of solid mechanics, viz. (a) Baker–Ericksen inequality, (b) strong ellipticity, (c) polyconvexity, (d) Hill’s constitutive inequality to the proposed models. We observe that sufficient conditions for satisfying the above inequalities match exactly with the condition for exhibiting limiting stretchable behavior. We further employ the models for investigating homogeneous and inhomogeneous deformation characteristics. In the sphere inflation characteristics, we observe that these models display a wider range of strain-stiffening and stability patterns. While the critical stiffening parameter is a constant for the Gent model, it can assume any positive value for the present model depending on the exponent. As a result, the proposed models can exhibit stable inflation or an inflation-jump instability in the sphere for any given maximum stretch limit, or the stiffening parameter. The critical values of maximum allowable stretch or stiffening parameters can assume any value in the present framework to fit the experimental results. Since the stability characteristics depend completely on stiffening parameter it is diversified using the present model. We observe inflation-jump instability for a stiffening parameter as low as 2.30. Since the present models involve arbitrary exponents and exhibit limited elasticity, they nicely exhibit the real deformation characteristics of spheres. As a result, they adequately capture the mechanical response of inflating rubber-like spheres. We demonstrate excellent agreements of these theoretical models with the experimental responses of inflation of monkey bladder and rubber balloon.
Although melatonin has been reported to function as a stress signaling molecule, not much information is available on the biochemical and molecular events associated with probable melatonin-hydrogen ...sulfide crosstalk in plants. Present work provides evidence on the role of melatonin in the modulation of H
2
S homoeostasis during NaCl stress in dark-grown tomato (
Solanum lycopersicum
L. var. cherry) seedlings. NaCl stress (120 mM) inhibits hypocotyl elongation, promotes primary root growth and enhances electrolytic leakage from tomato seedlings. Treatment with H
2
S donor (100 µM; NaHS) tends to reverse these effects, all the more so (additive effect) in the presence of melatonin. NaCl stress and exogenous melatonin (30 µM) treatments modulate endogenous H
2
S accumulation and positively upregulate the activity of L-cysteine desulfhydrase (L-DES; EC 4.4.1.15; cytosolic). Melatonin has been observed to temporally modulate the activity of specific isoforms of H
2
S biosynthesizing enzyme, L-DES in seedling cotyledons. Zymographic analysis of L-DES isoforms in tomato seedling cotyledons has provided novel findings in plant system. Melatonin treatment decreases H
2
S accumulation in NaCl-stressed seedling cotyledons which is accompanied by a contrasting increase in L-DES activity. Melatonin, therefore, regulates endogenous H
2
S concentration in seedling cotyledons (NaCl treated), thus indicating the role of H
2
S catabolism pathways in H
2
S homoeostasis. Present findings thus reveal that exogenous melatonin modulates early H
2
S signaling in cotyledons of tomato seedlings subjected to NaCl stress. Furthermore, exogenous melatonin and H
2
S in combination (additive effect) ameliorate NaCl stress-induced growth changes in tomato seedlings.
Metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) are open, crystalline supramolecular coordination architectures with porous facets. These chemically tailorable framework ...materials are the subject of intense and expansive research, and are particularly relevant in the fields of sensory materials and device engineering. As the subfield of MOF-based sensing has developed, many diverse chemical functionalities have been carefully and rationally implanted into the coordination nanospace of MOF materials. MOFs with widely varied fluorometric sensing properties have been developed using the design principles of crystal engineering and structure-property correlations, resulting in a large and rapidly growing body of literature. This work has led to advancements in a number of crucial sensing domains, including biomolecules, environmental toxins, explosives, ionic species, and many others. Furthermore, new classes of MOF sensory materials utilizing advanced signal transduction by devices based on MOF photonic crystals and thin films have been developed. This comprehensive review summarizes the topical developments in the field of luminescent MOF and MOF-based photonic crystals/thin film sensory materials.
TNP can't hide from MOF: A three‐dimensional fluorescent metal–organic framework (MOF), Cd(NDC)0.5(PCA)⋅Gx, can be used for the detection of 2,4,6‐trinitrophenol (TNP). The MOF exhibits high ...selectivity towards TNP, even in the presence of other nitro explosives in aqueous and organic solutions, owing to electron‐ and energy‐transfer mechanisms and electrostatic interactions.
One-step adsorptive purification of ethylene (C
H
) from four-component gas mixtures comprising acetylene (C
H
), ethylene (C
H
), ethane (C
H
) and carbon dioxide (CO
) is an unmet challenge in the ...area of commodity purification. Herein, we report that the ultramicroporous sorbent Zn-atz-oba (H
oba = 4,4-dicarboxyl diphenyl ether; Hatz = 3-amino-1,2,4-triazole) enables selective adsorption of C
H
, C
H
and CO
over C
H
thanks to the binding sites that lie in its undulating pores. Molecular simulations provide insight into the binding sites in Zn-atz-oba that are responsible for coadsorption of C
H
, C
H
and CO
over C
H
. Dynamic breakthrough experiments demonstrate that the selective binding exhibited by Zn-atz-oba can produce polymer-grade purity (>99.95%) C
H
from binary (1:1 for C
H
/C
H
), ternary (1:1:1 for C
H
/C
H
/C
H
) and quaternary (1:1:1:1 for C
H
/C
H
/C
H
/CO
) gas mixtures in a single step.
Purification of ethylene (C
H
), the largest-volume product of the chemical industry, currently involves energy-intensive processes such as chemisorption (CO
removal), catalytic hydrogenation (C
H
...conversion), and cryogenic distillation (C
H
separation). Although advanced physisorbent or membrane separation could lower the energy input, one-step removal of multiple impurities, especially trace impurities, has not been feasible. We introduce a synergistic sorbent separation method for the one-step production of polymer-grade C
H
from ternary (C
H
/C
H
/C
H
) or quaternary (CO
/C
H
/C
H
/C
H
) gas mixtures with a series of physisorbents in a packed-bed geometry. We synthesized ultraselective microporous metal-organic materials that were readily regenerated, including one that was selective for C
H
over CO
, C
H
, and C
H
.
Understanding the mechanisms of sodium (Na⁺) influx, effective compartmentalization, and efflux in higher plants is crucial to manipulate Na⁺ accumulation and assure the maintenance of low Na⁺ ...concentration in the cytosol and, hence, plant tolerance to salt stress. Na⁺ influx across the plasma membrane in the roots occur mainly via nonselective cation channels (NSCCs). Na⁺ is compartmentalized into vacuoles by Na⁺/H⁺ exchangers (NHXs). Na⁺ efflux from the plant roots is mediated by the activity of Na⁺/H⁺ antiporters catalyzed by the salt overly sensitive 1 (SOS1) protein. In animals, ouabain (OU)-sensitive Na⁺, K⁺-ATPase (a P-type ATPase) mediates sodium efflux. The evolution of P-type ATPases in higher plants does not exclude the possibility of sodium efflux mechanisms similar to the Na⁺, K⁺-ATPase-dependent mechanisms characteristic of animal cells. Using novel fluorescence imaging and spectrofluorometric methodologies, an OU-sensitive sodium efflux system has recently been reported to be physiologically active in roots. This review summarizes and analyzes the current knowledge on Na⁺ influx, compartmentalization, and efflux in higher plants in response to salt stress.
Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and ...storage. Because of their amenability to de novo reticular chemistry, metal–organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure–property–performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential “diamonds in the rough”.
Dark septate endophytes (DSE) exert a plethora of effects in regulating plant growth, signalling and stress tolerance. The advent of metagenomics has led to the identification of various species of ...DSE to be associated with plant organs. They are known to modulate growth, nutrient uptake, phytohormone biosynthesis and production of active bioconstituents in several plants. The interactions between the DSE and host plants are mostly mutualistic but they can also be neutral or exhibit negative interactions. The DSE has beneficial role in removal/sequestration of toxic heavy metals from various environmental sites. Here, we discuss the beneficial role of DSE in enhancing plant tolerance to heavy metal stress, drought conditions, high salinity and protection from various plant pathogens. Furthermore, the underlying mechanism of stress resilience facilitated by DSE-plant interaction has also been discussed. The article also provides insights to some important future perspectives associated with DSE-mediated phytoremediation and reclamation of polluted land worldwide thus facilitating sustainable agriculture.
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