Free Oscillations of a Toroidal Viscoelastic Shell with a Flowing Liquid

In this paper, mathematical model of nonlinear vibration problems with fluid flows through pipelines have been developed. Using the Bubnov–Galerkin method for the boundary conditions, the resulting nonlinear integro-differential equations with partial derivatives are reduced to solving systems of nonlinear ordinary integro-differential equations with both constant and variable coefficients as functions of time.A system of algebraic equations is obtained according to numerical method for the unknowns. The influence of the singularity of heredity kernels on the vibrations of structures possessing viscoelastic properties is numerically investigated.It was found that the determination of the effect of viscoelastic properties of the construction material on vibrations of the pipeline with a flowing liquid requires applying weakly singular hereditary kernels with an Abel type singularity.

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Enhanced Skin Permeation of Punicalagin after Topical Application of Pluronic Micelles or Vesicles Loaded with Lafoensia pacari Extract

Planta Medica ◽

10.1055/a-1464-1525 ◽

2021 ◽

Author(s):

Sandra Alves de Sousa Garcia ◽

Priscila Bianca Rodrigues da Rocha ◽

Bruno dos Santos Souza ◽

Andressa Tuane Santana Paz ◽

Ana Luiza Caetano Negris ◽

...

Keyword(s):

Antioxidant Activity ◽

Skin Permeation ◽

Sol Gel ◽

Extraction Procedure ◽

Average Diameter ◽

Skin Aging ◽

Chemical Degradation ◽

Vertical Diffusion ◽

Flowing Liquid ◽

Span 80

AbstractPunicalagin, the principal ellagitannin of Lafoensia pacari leaves, has proven antioxidant activity, and standardized extracts of L. pacari can be topically used for skin aging management. We hypothesized that Pluronic nanomicelles or vesicles could solubilize sufficiently large amounts of the standardized extracts of L. pacari and provide chemical stability to punicalagin. The standardized extracts of L. pacari were obtained with an optimized extraction procedure, and the antioxidant activity was characterized. Formulations containing Pluronic at 25% and 35% were obtained with or without Span 80. They were characterized by average diameter, polydispersity index, punicalagin content, physicochemical stability, and rheology. A release and skin permeation study was carried out in vertical diffusion cells. The extraction procedure allowed quantifying high punicalagin content (i.e., 141.61 ± 3.87 mg/g). The standardized extracts of L. pacari showed antioxidant activity for all evaluated methods. Pluronic at 25 and Pluronic at 35 with standardized extracts of L. pacari showed an average diameter of about 25 nm. The addition of Span 80 significantly increased the mean diameter by 15-fold (p < 0.05), indicating the spontaneous formation of vesicles. Pluronic formulations significantly protected punicalagin from chemical degradation (p < 0.05). Pluronic at 25 formulations presented as free-flowing liquid-like systems, while Pluronic at 35 resulted in an increase of about 44-fold in |ƞ*|. The addition of Span 80 significantly reduced the Pluronic sol-gel transition temperature (p < 0.05), indicating the formation of vesicles. Formulations with Span 80 significantly enhanced punicalagin skin permeation compared to formulations without Span 80 (p < 0.05). Formulations with Span 80 were demonstrated to be the most promising formulations, as they allowed significant permeation of punicalagin (about 80 to 315 µg/cm2), which has been shown to have antioxidant activity.

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Simplified and rapid determination of Ca, K, Mg, and Na in fruit juices by flowing liquid cathode atmospheric glow discharge optical emission spectrometry

Journal of Analytical Atomic Spectrometry ◽

10.1039/d1ja00127b ◽

2021 ◽

Author(s):

Monika Gorska ◽

Pawel Pohl

Keyword(s):

Glow Discharge ◽

Rapid Determination ◽

Optical Emission ◽

Fruit Juices ◽

Emission Spectrometry ◽

Atmospheric Pressure Glow Discharge ◽

Flowing Liquid ◽

Liquid Cathode ◽

Pressure Glow Discharge

Atmospheric pressure glow discharge (APGD) microplasma, sustained between a flowing liquid cathode (FLC) and a tungsten anode, was applied for the determination of Ca, K, Mg, and Na in fruit juices with a simplified sample preparation procedure.

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Synchrotron infrared microspectroscopy reveals the response of Sphagnum cell wall material to its aqueous chemical environment

Environmental Chemistry ◽

10.1071/en18120 ◽

2018 ◽

Vol 15 (8) ◽

pp. 513

Author(s):

Ewen Silvester ◽

Annaleise R. Klein ◽

Kerry L. Whitworth ◽

Ljiljana Puskar ◽

Mark J. Tobin

Keyword(s):

Cell Wall ◽

Cell Walls ◽

Chemical Environment ◽

Wall Material ◽

Organic Soils ◽

Cell Wall Material ◽

Acid Base ◽

Widespread Species ◽

Flowing Liquid ◽

Infrared Microspectroscopy

Environmental contextSphagnum moss is a widespread species in peatlands globally and responsible for a large fraction of carbon storage in these systems. We used synchrotron infrared microspectroscopy to characterise the acid-base properties of Sphagnum moss and the conditions under which calcium uptake can occur (essential for plant tissue integrity). The work allows a chemical model for Sphagnum distribution in the landscape to be proposed. AbstractSphagnum is one the major moss types responsible for the deposition of organic soils in peatland systems. The cell walls of this moss have a high proportion of carboxylated polysaccharides (polygalacturonic acids), which act as ion exchangers and are likely to be important for the structural integrity of the cell walls. We used synchrotron light source infrared microspectroscopy to characterise the acid-base and calcium complexation properties of the cell walls of Sphagnum cristatum stems, using freshly sectioned tissue confined in a flowing liquid cell with both normal water and D2O media. The Fourier transform infrared spectra of acid and base forms are consistent with those expected for protonated and deprotonated aliphatic carboxylic acids (such as uronic acids). Spectral deconvolution shows that the dominant aliphatic carboxylic groups in this material behave as a monoprotic acid (pKa=4.97–6.04). The cell wall material shows a high affinity for calcium, with a binding constant (K) in the range 103.9–104.7 (1:1 complex). The chemical complexation model developed here allows for the prediction of the chemical environment (e.g. pH, ionic content) under which Ca2+ uptake can occur, and provides an improved understanding for the observed distribution of Sphagnum in the landscape.

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