scholarly journals The Influence of Oxidant on Gelatin–Tannin Hydrogel Properties and Structure for Potential Biomedical Application

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 150
Author(s):  
Konstantin Osetrov ◽  
Mayya Uspenskaya ◽  
Vera Sitnikova
Keyword(s):  
Biomedical Application ◽  
Ph Dependence ◽  
Harmful Effect ◽  
Model Fitting ◽  
Isoconversional Methods ◽  
Water Evaporation ◽  
Stimuli Responsive ◽  
Thermal Transitions ◽  
Acid Media ◽  
The Impact

Nowadays, there is a widespread usage of sodium periodate as an oxidant for synthesizing gelatin–tannin hydrogels. The impact of iodine compounds could have a harmful effect on human health. The study focuses on the proposal of alternative oxidizing systems for tannin oxidation. Gelatin–tannin hydrogels were obtained based on the usage of H2O2/DMSO/KMnO4/KIO4 oxidants and characterized with sorption, thermal (TGA, DTG, DSC), mechanical, FTIR and other methods. The sorption experiments were carried out in a phosphate buffer (pH = 5.8/7.4/9) and distilled water and were investigated with Fick’s law and pseudosecond order equation. The pH dependence of materials in acid media indicates the possibility of further usage as stimuli-responsive systems for drug delivery. Thermal transitions demonstrate the variation of structure with melting (306 ÷ 319 °C) and glass transition temperatures (261 ÷ 301 °C). The activation energy of water evaporation was calculated by isoconversional methods (Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa) ranging from 4 ÷ 18 to 14 ÷ 38 kJ/mole and model-fitting (Coats–Redfern, Kennedy–Clark) methods at 24.7 ÷ 45.3 kJ/mole, indicating the smooth growth of values with extent of conversion. The network parameters of the hydrogels were established by modified Flory–Rehner and rubber elasticity theories, which demonstrated differences in values (5.96 ÷ 21.27·10−3 mol/cm3), suggesting the limitations of theories. The sorption capacity, tensile strength and permeability for water/oxygen indicate that these materials may find their application in field of biomaterials.

scholarly journals Effect of moisture condensation on vapour transmission through porous membranes

2021 ◽  
pp. 152808372110142
Author(s):  
Ariana Khakpour ◽  
Michael Gibbons ◽  
Sanjeev Chandra
Keyword(s):  
Water Vapour ◽  
Moisture Diffusion ◽  
Porous Membrane ◽  
Water Evaporation ◽  
Porous Membranes ◽  
Water Vapour Concentration ◽  
Vapour Concentration ◽  
Vapour Diffusion ◽  
Pore Blockage ◽  
The Impact

Porous membranes find natural application in various fields and industries. Water condensation on membranes can block pores, reduce vapour transmissibility, and diminish the porous membranes' performance. This research investigates the rate of water vapour transmission through microporous nylon and nanofibrous Gore-Tex membranes. Testing consisted of placing the membrane at the intersection of two chambers with varied initial humidity conditions. One compartment is initially set to a high ([Formula: see text]water vapour concentration and the other low ([Formula: see text], with changes in humidity recorded as a function of time. The impact of pore blockage was explored by pre-wetting the membranes with water or interposing glycerine onto the membrane pores before testing. Pore blockage was measured using image analysis for the nylon membrane. The mass flow rate of water vapour ( ṁv) diffusing through a porous membrane is proportional to both its area (A) and the difference in vapour concentration across its two faces ([Formula: see text], such that [Formula: see text] where K is defined as the moisture diffusion coefficient. Correlations are presented for the variation of K as a function of [Formula: see text]. Liquid contamination on the porous membrane has been shown to reduce the moisture diffusion rate through the membrane due to pore blockage and the subsequent reduced open area available for vapour diffusion. Water evaporation from the membrane's surface was observed to add to the mass of vapour diffusing through the membrane. A model was developed to predict the effect of membrane wetting on vapour diffusion and showed good agreement with experimental data.

CALCULATIONS FOR EVALUATING THE ACOUSTIC EFFICIENCY OF MEASURES TO REDUCE PULSE NOISE IN INDUSTRIAL PREMISES

Akustika ◽  
2021 ◽  
pp. 45-51
Author(s):  
Alexander Antonov ◽  
Irina Matveeva ◽  
Igor Shubin ◽  
Ilya Tsukernikov
Keyword(s):  
Structural Changes ◽  
Harmful Effect ◽  
Sound Sources ◽  
Pulse Noise ◽  
Space Planning ◽  
Acoustic Measures ◽  
Manufacturing Enterprises ◽  
Efficiency Assessment ◽  
Design Changes ◽  
The Impact

At modern manufacturing enterprises, machines and mechanisms that emit pulsed noise are widely used. Pulse noise has a more harmful effect on workers than time-constant, time fluctuating and intermittent noises. Pulse noise reduction is possible through the application of design changes in the pulse noise source and the development of organizational, technological, construction and acoustic measures. The choice of specific events is made on the basis of their acoustic efficiency assessment. For this purpose, it is necessary to have a method for calculating pulse noise that takes into account its space-time characteristics and their possible changes with structural changes of the source, as well as with changes in the space-planning and acoustic parameters of premises. In the article, to assess the acoustic efficiency of pulse noise, it is proposed to use a combined calculation method developed by the authors, taking into account the real mirror-diffuse nature of sound reflection from the room fences. On its basis, it is analyzed the possibilities of using various methods and means to reduce the impact of noise on the workers in rooms with pulsed sound sources.

scholarly journals Systematic exploration of the pH dependence of a peptide hydrogel

2019 ◽  
Vol 97 (6) ◽  
pp. 430-434 ◽  
Author(s):  
Natashya Falcone ◽  
Tsuimy Shao ◽  
Xiaoyi Sun ◽  
Heinz-Bernhard Kraatz
Keyword(s):  
Mechanical Strength ◽  
Narrow Range ◽  
Ph Dependence ◽  
Stimuli Responsive ◽  
Systematic Exploration ◽  
Ph Conditions ◽  
Ph Dependent ◽  
Functional Biomaterials ◽  
Peptide Hydrogel

Stimuli-responsive peptide gels are a growing class of functional biomaterials that are involved in many applications in research. Here, we present a novel di-peptide hydrogel from the compound Boc–Phe–Trp–OH in various buffer and pH conditions. We examine the effects of different stimuli, including temperature and pH, on the mechanical strength of the gels through frequency rheology studies. We found that this hydrogelator is highly pH dependent, only forming a gel in a narrow range of pH 6–7. This hydrogelator hold promise for the development of new stimuli-responsive biomaterials for specific applications that require this type of specific stimuli.

Comparison between the effects of mixed dyslipidaemia and hypercholesterolaemia on endothelial function, atherosclerotic lesions and fibrinolysis in rabbits

2003 ◽  
Vol 104 (4) ◽  
pp. 357-365 ◽  
Author(s):  
Natalia de las HERAS ◽  
Eva CEDIEL ◽  
M. Pilar OUBIÑA ◽  
Paloma ARAGONCILLO ◽  
David SANZ-ROSA ◽  
...  
Keyword(s):  
Endothelial Function ◽  
Receptor Antagonist ◽  
Plasminogen Activator ◽  
Vascular Function ◽  
Harmful Effect ◽  
Tissue Type ◽  
Vascular Structure ◽  
Similar Increase ◽  
The Impact ◽  
Pai 1

We compared the impact of hypercholesterolaemia and mixed dyslipidaemia on vascular function, vascular structure and fibrinolytic balance in rabbits. To this end, vascular reactivity was studied in aortic rings from rabbits fed a control diet, a diet containing 0.5% cholesterol+14% coconut oil (mixed dyslipidaemia) or a diet containing 1% cholesterol (hypercholesterolaemia) for 12–14 weeks. Morphometric analysis of aorta was also performed and plasminogen activator inhibitor-1 (PAI-1) as well as tissue-type plasminogen activator (t-PA) plasma activities were measured. Both diets induced a similar increase in cholesterol plasma levels, although triacylglycerols (triglycerides) were increased in animals with mixed dyslipidaemia. Hypercholesterolaemia was associated with intimal thickening, reduction in acetylcholine-induced relaxation (P<0.05) and increased vasoconstriction induced by acetylcholine+NG-nitro-L-arginine methyl ester (L-NAME) when compared with controls (P<0.05). These effects were more marked (P<0.05) in animals with mixed dyslipidaemia. Incubation with ifetroban, a thromboxane A2/prostaglandin H2 receptor antagonist, increased acetylcholine-induced relaxation (P<0.05) and reduced acetylcholine+L-NAME contraction (P<0.05) in both diet groups. In contrast, the presence of PD 145, an endothelin (ET)A/ETB receptor antagonist, exerted these effects only in rabbits with mixed dyslipidaemia. Both hypercholesterolaemia and mixed dyslipidaemia induced a similar increase in PAI-1 and a similar decrease in t-PA plasma activities. These data suggest that hypertriglyceridaemia can increase the deleterious effects of hypercholesterolaemia on endothelial function and vascular structure. This additional harmful effect exerted by triacylglycerols on endothelial function could, in part, be mediated by ET.

The Impact of Composition and Sintering Temperature for Stainless Steel Foams (SS316L) Fabricated by Space Holder Method with Urea as Space Holder

2017 ◽  
Vol 888 ◽  
pp. 413-417 ◽  
Author(s):  
Zulaikha Abdullah ◽  
Sufizar Ahmad ◽  
Musfirah Ramli
Keyword(s):  
Stainless Steel ◽  
Biomedical Application ◽  
Metal Foams ◽  
Morphological Properties ◽  
Solid Matrix ◽  
Morphological Observation ◽  
Second Phase ◽  
Space Holder ◽  
Closed Cell ◽  
The Impact

Metal foams are a cellular structure that has a solid matrix made of metal and has pores in their structure. Metal foams offer excellent combination of properties which led researchers interested in investigation in recent years. Closed-cell stainless steel (SS316L) foams for biomedical application were prepared by space holder method and the physical and morphological properties of SS316L foams were studied. Stainless steel (SS316L) powders as metallic material, polyethylene glycol (PEG) as a binder and Urea as a space holder material were mixed homogenously to avoid the particle wrecked. This mixture was compacted using uniaxial pressing machine and pressurized to 8 tons to formed the green body. By using tube furnace, the SS316L foams was two-stage sintered, the first phase at 600°C for 2 hours to decompose the urea, and the second phase at 1000°C, 1100°C, and 1200°C respectively to sinter the steel. The porosity and density test was carried out by applying Archimedean principles, while morphological observation was done by using Field Emission Scanning Electron (FESEM). The samples with 40wt.% SS316L composition and sintered at temperature of 1100°C, leads to porosities of about 44.539% and show the potential as the best metal foams.

scholarly journals Anti-Mullerian Hormone (AMH) Level in Presence of Ovarian Endometrioma

2021 ◽  
pp. 71-85
Author(s):  
Nesma F. Radwan ◽  
Ahmed M. El Khyat ◽  
Adel E. El Gergawy ◽  
Hesham A. Salem
Keyword(s):  
Ovarian Reserve ◽  
Harmful Effect ◽  
University Hospital ◽  
Control Group ◽  
Rapid Decline ◽  
Statistical Significant Difference ◽  
Female Patients ◽  
Significant Difference ◽  
Group B ◽  
The Impact

Background: The effect of endometriomas itself on the ovarian responsiveness that relate to ovarian reserve had been reported with several inconsistent results. In one study evaluated women with unilateral endometriomas, ovaries with disease showed lower response to ovarian stimulation than contralateral healthy ovaries .However, recent study on infertile women with un-operated unilateral small endometriomas did not support difference in ovarian responsiveness. The aim was to evaluate the impact of presence of endometriomas on ovarian reserve as measured by circulating AMH. Methods: This retrospective study was carried out on 80 female patients in childbearing period attending outpatient clinic and/or inpatient department of obstetrics and gynecology at Tanat University Hospital and the study was conducted directly after approval in the period from Apri, 2019 till April 2020. Group (A): Study group: 60 female patients aged between 20 to 30 years old GROUP (B): Control group: 20 age matched female with healthy ovaries. Results: there is no statistical significant difference between groups as regard Menarche (years), Regularity and Amount of menstrual blood flow. There is statistical significant difference between groups as regard fixed tender Right Ventricular Failure. But there are no statistical significant differences between groups as regard nodule in rectovaginal septum, fixed tender adnexal masses, association with adenomyosis and infertility. There is highly statistical significant difference between case and control groups as regard AMH levels. there are highly statistical significant positive correlation between duration of endometriosis and each of presence of pelvic pain, cyst diameter and Visual Analogue Scale. Conclusions:    Women with endometrioma have significantly lower serum AMH levels and seem to experience a more rapid decline in serum AMH levels than age matched counterparts, suggesting a harmful effect of endometrioma per se on ovarian reserve.

scholarly journals Perceptions of Food Retailers Regarding Climate Change and Greenhouse Gas Emissions

2021 ◽  
Vol 5 (4) ◽  
pp. 26-35
Author(s):  
Ayanda Pamella Deliwe ◽  
Shelley Beryl Beck ◽  
Elroy Eugene Smith
Keyword(s):  
Climate Change ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Greenhouse Gas Emission ◽  
Harmful Effect ◽  
Retail Sector ◽  
Food Retail ◽  
Gas Emissions ◽  
Food Retailers ◽  
The Impact

Objective – This paper sets out to assess perceptions of food retailers regarding climate change, greenhouse gas emission and sustainability in the Nelson Mandela Bay region of South Africa. The primary objective of this study is to investigate the food retailers’ greenhouse gas emissions strategies. Climate change catastrophic potential and the harmful effect that it has had on the community and businesses has led to it being given attention from social media and in literature. Methodology/Technique – This paper covered a literature review that provided the theoretical framework. The empirical study that was carried out included self-administered questionnaires which were distributed to 120 food retailers who were selected from the population using convenience sampling. Findings - The results revealed that most of the respondents were neutral towards the impact of operational factors regarding GHG emission in the food retail sector. Novelty - There is limited research that has been conducted among food retailers from the designated population. The study provided guidelines that will be of assistance to food retailers when dealing with climate change and greenhouse gas emissions impact in the food retail sector. Type of Paper: Empirical. JEL Classification: L66, Q54, Q59. Keywords: Climate Change; Food Retailers; Greenhouse Gas Emissions; Perceptions; Strategies; Sustainability Reference to this paper should be made as follows: Deliwe, A.P; Beck, S.B; Smith, E.E. (2021). Perceptions of Food Retailers Regarding Climate Change and Greenhouse Gas Emissions, Journal of Business and Economics Review, 5(4) 26–35. https://doi.org/10.35609/jber.2021.5.4(3)

scholarly journals Modelling rainfall with a Bartlett–Lewis process: new developments

2020 ◽  
Vol 24 (5) ◽  
pp. 2791-2815
Author(s):  
Christian Onof ◽  
Li-Pen Wang
Keyword(s):  
Model Fitting ◽  
Extreme Rainfall ◽  
Rainfall Time Series ◽  
New Developments ◽  
History Of ◽  
The Difference ◽  
Poisson Cluster ◽  
The Impact ◽  
Analytical Expressions ◽  
Structure Properties

Abstract. The use of Poisson cluster processes to model rainfall time series at a range of scales now has a history of more than 30 years. Among them, the randomised (also called modified) Bartlett–Lewis model (RBL1) is particularly popular, while a refinement of this model was proposed recently (RBL2; Kaczmarska et al., 2014). Fitting such models essentially relies upon minimising the difference between theoretical statistics of the rainfall signal and their observed estimates. The first statistics are obtained using closed form analytical expressions for statistics of the orders 1 to 3 of the rainfall depths, as well as useful approximations of the wet–dry structure properties. The second are standard estimates of these statistics for each month of the data. This paper discusses two issues that are important for the optimal model fitting of RBL1 and RBL2. The first issue is that, when revisiting the derivation of the analytical expressions for the rainfall depth moments, it appears that the space of possible parameters is wider than has been assumed in past papers. The second issue is that care must be exerted in the way monthly statistics are estimated from the data. The impact of these two issues upon both models, in particular upon the estimation of extreme rainfall depths at hourly and sub-hourly timescales, is examined using 69 years of 5 min and 105 years of 10 min rainfall data from Bochum (Germany) and Uccle (Belgium), respectively.

Is Reputation Good or Bad? An Experiment

2010 ◽  
Vol 100 (5) ◽  
pp. 2187-2204 ◽  
Author(s):  
Brit Grosskopf ◽  
Rajiv Sarin
Keyword(s):  
Laboratory Experiment ◽  
Harmful Effect ◽  
Beneficial Effects ◽  
The Past ◽  
Long Run ◽  
Short Run ◽  
Other Regarding ◽  
The Impact ◽  
Other Regarding Preferences ◽  
Do So

We investigate the impact of reputation in a laboratory experiment. We do so by varying whether the past choices of a long-run player are observable by the short-run players. Our framework allows for reputation to have either a beneficial or a harmful effect on the long-run player. We find that reputation is seldom harmful and its beneficial effects are not as strong as theory suggests. When reputational concerns are at odds with other-regarding preferences, we find the latter overwhelm the former. (JEL C91, D12, D82, D83, Z13)

Systematic evaluation of pH and thermoresponsive poly(n-isopropylacrylamide-chitosan-fluorescein) microgel

e-Polymers ◽  
2017 ◽  
Vol 17 (5) ◽  
pp. 399-408 ◽  
Author(s):  
Pedro Hernández ◽  
Armando Lucero-Acuña ◽  
Cindy Alejandra Gutiérrez-Valenzuela ◽  
Ramón Moreno ◽  
Reynaldo Esquivel
Keyword(s):  
Biomedical Application ◽  
Systematic Evaluation ◽  
Molar Ratio ◽  
Solution Temperature ◽  
Stimuli Responsive ◽  
Scanning Calorimetry ◽  
Molar Ratios ◽  
Stimuli Responsive Polymers ◽  
Wide Range ◽  
Low Molecular Weight Chitosan

AbstractThe interesting properties of stimuli-responsive polymers lead to a wide range of possibilities in design and engineering of functional material for the biomedical application. A systematic approach focused on the evaluation of the physical properties of multiresponse (pH and temperature) PNIPAM was reported in this work. The effect of three different molar ratios of poly(n-isopropylacrylamide): chitosan (1:49, 1:99 and 1:198) were evaluated and labeled correspondingly as PC1F, PC2F, and PC3F. An increase in the lower critical solution temperature (LCST) of sample PC1F (34°C) was observed by differential scanning calorimetry (DSC). The presence of low molecular weight chitosan (LMWC) full-interpenetrating polymer (Full-IPN) segments in poly(n-isopropylacrylamide) was confirmed by Fourier-transform infrared spectroscopy (FT-IR). The hydrogel’s water capture was analyzed by two models of swelling, the power law model and a model that considers the relaxation of polymeric chains of the hydrogel, finding good correlations with experimental data in both cases. Sample PC3F resulted with higher swellability, increasing the weight of the hydrogel around seven times. Hydrogel pH-sensibility was confirmed placing the samples at different pH environments, with an apparent increase in swellability for acidic conditions, confirming the highest swellability for sample PC3F, due to hydrogen bonds boosted by chitosan high molar ratio. Based on these results, the hydrogel obtained has potential as a thermo-pH triggered hydrogel in drug delivery applications.

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