scholarly journals Transient Response of the Acid-base Diode for Polarity Change

2021 ◽  
Author(s):  
Viktória Koncz ◽  
Zoltán Noszticzius ◽  
Kristóf Kály-Kullai
Keyword(s):  
Applied Voltage ◽  
Local Maximum ◽  
Polyvinyl Butyral ◽  
Qualitative Explanation ◽  
Acid Base ◽  
Current Curve ◽  
Voltage Current Characteristic ◽  
Pva Gel ◽  
Polarity Change ◽  
Pva Hydrogel

An application of the so-called acid-base diode would be the sensitive detection of nonhydrogen cations in an acidic medium based on salt-effects. For diode purposes different connecting elements between the acidic and aqueous reservoirs of the diode were developed, namely a polyvinyl alcohol (PVA) hydrogel cylinder, and a polyvinyl butyral (PVB) membrane. During the measurement of the voltage – current characteristic (VCC) of the diode, it was found, that in the case of PVA gel cylinder an overshoot (a local maximum followed by a local minimum) appeared in the time vs. current curve, while the diode was switched between modes (open or closed), that is the direction of the applied voltage was reversed. The overshoot did not appear in PVB membrane.The existence of overshoots was studied by numerical simulations. The time response of the diode with different hypothetic connecting elements was investigated, when the diode was switched between modes via changing the polarity of applied voltage. We found that larger diffusion coefficients of hydrogen and hydroxide ions explain the appearance of overshoots. By examining the concentration and potential profiles a qualitative explanation of this phenomenon was given.

scholarly journals Linear Dynamic Viscoelasticity of Dual Cross-Link Poly(Vinyl Alcohol) Hydrogel with Determined Borate Ion Concentration

Gels ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 71
Author(s):  
Takuro Taniguchi ◽  
Kenji Urayama
Keyword(s):  
Vinyl Alcohol ◽  
Ion Concentration ◽  
Poly Vinyl Alcohol ◽  
Relaxation Dynamics ◽  
Cross Link ◽  
Dynamic Viscoelasticity ◽  
Linear Dynamic ◽  
Cross Links ◽  
Pva Gel ◽  
Pva Hydrogel

We investigated the linear dynamic viscoelasticity of dual cross-link (DC) poly(vinyl alcohol) (PVA) (DC-PVA) hydrogels with permanent and transient cross-links. The concentrations of incorporated borate ions to form transient cross-links in the DC-PVA hydrogels (CBIN) were determined by the azomethine-H method. The dynamic viscoelasticity of the DC-PVA hydrogel cannot be described by a simple sum of the dynamic viscoelasticity of the PVA gel with the same permanent cross-link concentration and the PVA aqueous solution with the same borate ion concentration (CB = CBIN) as in the DC-PVA gel. The DC-PVA hydrogel exhibited a considerably higher relaxation strength, indicating that the introduction of permanent cross-links into temporary networks increases the number of viscoelastic chains with finite relaxation times. In contrast, the relaxation frequency (ωc) (given by the frequency at the maximum of loss modulus) for the DC-PVA hydrogel was slightly lower but comparable to that for a dilute PVA solution with the same CB. This signifies that the relaxation dynamics of the DC-PVA hydrogels is essentially governed by the lifetime of an interchain transient cross-link (di-diol complex of boron). The effect of permanent cross-linking on the relaxation dynamics was observed in the finite broadening of the relaxation-time distribution in the long time region.

Carrier Concentrations and Drift Currents in the Depletion Region of a p–n Junction

2003 ◽  
Vol 10 (04) ◽  
pp. 649-660
Author(s):  
D. K. Mak
Keyword(s):  
Solid State ◽  
Applied Voltage ◽  
Local Minimum ◽  
Local Maximum ◽  
Depletion Region ◽  
Electron Drift ◽  
Electron Carrier ◽  
Quantitative Explanation ◽  
State Device ◽  
Solid State Device

It has always been stated in electronics, semiconductor and solid state device textbooks that the hole drift and electron drift currents in the depletion region of a p–n junction are constant and independent of applied voltage (biasing). However, the explanations given are qualitative and unclear. We extrapolate the existing analytic theory of a p–n junction to give a quantitative explanation of why the currents are constant. We have also shown that the carrier concentrations in the depletion region, as depicted in some of the textbooks, are incorrect, and need to be revised. Our calculations further demonstrate that in reverse biasing, both hole and electron carrier concentrations each experience a local maximum and a local minimum, indicating that their diffusion currents change directions twice within the depletion region.

Micropatterned Polyvinyl Butyral Membrane for Acid−Base Diodes

2010 ◽  
Vol 114 (43) ◽  
pp. 13718-13725 ◽  
Author(s):  
László Roszol ◽  
Thuy Lawson ◽  
Viktória Koncz ◽  
Zoltán Noszticzius ◽  
Maria Wittmann ◽  
...  
Keyword(s):  
Polyvinyl Butyral ◽  
Acid Base

scholarly journals Controlled Morphology of Porous Polyvinyl Butyral Nanofibers

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Daniela Lubasova ◽  
Lenka Martinova
Keyword(s):  
Applied Voltage ◽  
High Efficiency ◽  
Polymer Concentration ◽  
Polyvinyl Butyral ◽  
Solution Concentration ◽  
Solvent Mixture ◽  
Electrospinning Process ◽  
Filter Materials ◽  
One Step ◽  
Poor Solvent

A simple and effective method for the fabrication of porous nanofibers based on the solvent evaporation methods in one-step electrospinning process from the commercial polyvinyl butyral (PVB) is presented. The obtained nanofibers are prevalently amorphous with diameters ranging from 150 to 4350 nm and specific surface area of approximately 2–20 m2/g. Pore size with irregular shape of the porous PVB fibers ranged approximately from 50 to 200 nm. The effects of polymer solution concentration, composition of the solvents mixture, and applied voltage on fiber diameter and morphology were investigated. The theoretical approach for the choice of poor and good solvents for PVB was explained by the application Hansen solubility parameter (HSP) and two-dimensional graph. Three basic conditions for the production of porous PVB nanofibers were defined: (i) application of good/poor solvent mixture for spinning solution, (ii) differences of the evaporation rate between good/poor solvent, and (iii) correct ratios of good/poor solvent (v/v). The diameter of prepared porous PVB fibers decreased as the polymer concentration was lowered and with higher applied voltage. These nanofiber sheets with porous PVB fibers could be a good candidate for high-efficiency filter materials in comparison to smooth fibers without pores.

Fabrication of Stable PVA/PVP Hydrogels

2013 ◽  
Vol 815 ◽  
pp. 321-324
Author(s):  
Hong Sun ◽  
Tao Wu ◽  
Yong Qiang He ◽  
Qiao Juan Gong ◽  
Jian Ping Gao ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Ammonium Persulfate ◽  
Composite Gels ◽  
Composite Gel ◽  
Degree Of Swelling ◽  
Pva Gel ◽  
Pva Hydrogel

PVA hydrogel has been used in the field of cartilage replacement in recent year. In order to improve the water-keeping ability of PVA gel and mechanical property, PVP was introduced into PVA and crosslinked by adding ammonium persulfate to form a composite gel. The crosslinkage of the gel was identified, and the effect of PVP and ammonium persulfate amount on the composite gel was studied. The crosslinkage, the degree of swelling and the compress stress of the composite gels have been tested. UV analysis was used to investigate the release of PVP from the composite gels. The dried composite gels were put into water to investigate the degree and velocity of the rehydration of different composite gels.

Properties of Vanillin Modified Poly(vinyl Alcohol)/Gelatin Composite

2013 ◽  
Vol 327 ◽  
pp. 48-52
Author(s):  
Lin Cheng ◽  
Qin Zou ◽  
Li Kou Zou ◽  
Yan Luo ◽  
Li Qiang Kan ◽  
...  
Keyword(s):  
Contact Angle ◽  
Hydrogen Bonding ◽  
Cartilage Repair ◽  
Vinyl Alcohol ◽  
Homogeneous System ◽  
Poly Vinyl Alcohol ◽  
Composite Gels ◽  
Pva Gel ◽  
Pva Hydrogel

To improve the cytocompatibility of super-hydrophilic poly (vinyl alcohol) (PVA) hydrogel, PVA/gelatin (PVA/Gel) composite was modified by vanillin (PVA/Gel/V) in this study. The properties of the composite gels were characterized by SEM, FTIR, DSC and contact angle instrument. The results show that PVA/Gel/V composite can compose a homogeneous system with the addition of vanillin, accompanying some destroy of the intra-hydrogen bonding of PVA crystal molecular chains and decrease of PVA super hydrophilicity. PVA/Gel/V composite exhibits better miscibility and hydrophobicity than pure PVA and PVA/Gel. The modified PVA/Gel/V composite may have a promising prospect for future cartilage repair.

Higher Dietary Acidity is Associated with Lower Bone Mineral Density in Postmenopausal Iranian Women, Independent of Dietary Calcium Intake

2014 ◽  
Vol 84 (3-4) ◽  
pp. 0206-0217 ◽  
Author(s):  
Seyedeh-Elaheh Shariati-Bafghi ◽  
Elaheh Nosrat-Mirshekarlou ◽  
Mohsen Karamati ◽  
Bahram Rashidkhani
Keyword(s):  
Calcium Intake ◽  
Dietary Calcium ◽  
Dietary Calcium Intake ◽  
Dietary Intakes ◽  
Iranian Women ◽  
Acid Base Balance ◽  
Mineral Density ◽  
Acid Base ◽  
Base Balance ◽  
Dietary Acid

Findings of studies on the link between dietary acid-base balance and bone mass are relatively mixed. We examined the association between dietary acid-base balance and bone mineral density (BMD) in a sample of Iranian women, hypothesizing that a higher dietary acidity would be inversely associated with BMD, even when dietary calcium intake is adequate. In this cross-sectional study, lumbar spine and femoral neck BMDs of 151 postmenopausal women aged 50 - 85 years were measured using dual-energy x-ray absorptiometry. Dietary intakes were assessed using a validated food frequency questionnaire. Renal net acid excretion (RNAE), an estimate of acid-base balance, was then calculated indirectly from the diet using the formulae of Remer (based on dietary intakes of protein, phosphorus, potassium, and magnesium; RNAERemer) and Frassetto (based on dietary intakes of protein and potassium; RNAEFrassetto), and was energy adjusted by the residual method. After adjusting for potential confounders, multivariable adjusted means of the lumbar spine BMD of women in the highest tertiles of RNAERemer and RNAEFrassetto were significantly lower than those in the lowest tertiles (for RNAERemer: mean difference -0.084 g/cm2; P=0.007 and for RNAEFrassetto: mean difference - 0.088 g/cm2; P=0.004). Similar results were observed in a subgroup analysis of subjects with dietary calcium intake of >800 mg/day. In conclusion, a higher RNAE (i. e. more dietary acidity), which is associated with greater intake of acid-generating foods and lower intake of alkali-generating foods, may be involved in deteriorating the bone health of postmenopausal Iranian women, even in the context of adequate dietary calcium intake.

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