Zinc is a naturally wide spread element, which generally finds its use in industry but also in numerous pharmaceutical, cosmetic and stomatology materials. Taking into consideration its frequent occurrence (in almost all biological materials) and its low quantities, a good choice of analytical method for zinc assay is a necessity. Apart from spectrophotometric methods – especially AAS (Atomic Absorption Spectrometry) which is a method of choice for zinc determination, also electroanalytical methods are used. Most frequently ASV (Anodic Stripping Voltammetry) or Polarography is applied. Despite the need of samples digestion electrochemical methods offer a price convenient method for determination of zinc, even in trace amounts (ppt – parts per trillion). Currently there is also new information about ion selective electrodes suitable for zinc assay.
The investigation of kinetics and thermodynamics of the corrosion of mild steel in a 2 M HCl solution using methanolic extract of Erigeron floribundus was carried out by means of gravimetric techniques. The results obtained indicate that the extract retarded corrosion. The inhibition efficiency was seen to increase with increase in concentration of the inhibitor, as well as with increase in temperature. The values of activation energy (Ea) obtained indicate a chemisorptions mechanism, whereas the value of Gibb free energy (ΔGoads) indicates a spontaneous adsorption of the extract components on the metal surface. Kinetic modelling of the experimental data obeys first order reaction. The adsorption of methanolic extract of Erigeron floribundus onto the mild steel surface followed the Langmuir adsorption isotherm model. Therefore, the extract functions as good corrosion inhibitor for mild steel in hydrochloric acid.
Betacyanins are conjugates of betalamic acid and glycosylated cyclo-DOPA which bring about the creation of a specific chromophoric system, the 1,7-dia- zaheptamethin chain. Betanin, a betacyanin pigment from red beet (Beta vulga- ris L.), as well as its decarboxylated derivatives were subjected to reduction with the use of NaBH4. The pigment structures contain a vinyl linker which is postu- lated to be protonated during reaction with NaBH4. In this study, 17-decarboxy- betanin and 2,17-bidecarboxy-betanin were obtained from betanin, which had been previously isolated from red beet root (Beta vulgaris L.). Purified pigments were tested in the presence of the reduction reagent while looking for the prod- ucts of the reaction identified by LC-MS.
The physico-chemical characterization of Prunus amygdalus, Dacryodes edulis and Chrysophillum albidium seed oils were investigated, together with their methyl esters. The vegetable oils were extracted by applying the solvent extraction method, using n-hexane. Prunus amygdalus had the highest oil yield (60.1%), followed by Dyacrodes edulis (55.76 %) and least from Chrysophillum albidium (13.67%). The oils and their biodiesel were then analyzed for acid value, free fatty acid, specific gravity, ash content, iodine value, peroxide value, saponification value, kinematic viscosity, flash point, smoke point, titre value, cloud point, moisture content and refractive index. Accordingly, Dyacrodes edulis seed oil had the highest acid value of 6.57 and required two-step transesterifictaion. The produced biodiesels were discussed in the light of ASTM D 9751, ASTMD 6751 and DIN 14214. These showed yields of 94.36%, 93.03% and 86.49%, cetane numbers of 70.40, 55.20 and 64.57 and calorific values of 31,178.39 KJ/kg, 34,421.50 KJ/kg and 32,838.38 KJ/kg for Prunus amygdalus, Dacryodes edulis and Chrysophyllum albidium, respectively. Other fuel-related properties showed highly improved qualities upon transesterification and compared well with ASTM and EU standards. The overall results showed that the seed oils are viable for biodiesel production.
We created composite materials by using a straightforward method, combining chitosan, iodine, and bismuth. We used two chitosan with two different molecular masses. We used iodine in the composites as chitosan iodide and bismuth in the form of tetraiodobismuthanuide. We analysed the resulting materials with scanning electron microscopy, X-ray diffraction, temperature-programmed desorption mass spectrometry, and visible light spectroscopy. We observed that bismuth and iodine were evenly distributed throughout the composites and did not separate into distinct phases. These composite materials have the ability to form organised porous sponges, making them suitable for a wide range of applications in different fields.
The Zombie Epidemic is a fun framework for investigating different scenarios of spreading disease. An extended Kermack – McKendrick model is analyzed. The only thing that can save humanity is to not get bitten or to find a remedy for the ”zombie virus” (both almost impossible).
The inevitable consequence of the widespread use of antimicrobial agents has been the emergence of antibiotic resistant pathogens. This necessitates an ever-increasing search for new drugs. In an effort to develop antimicrobial agents, a series of hydrazone 2-6-derivatives were synthesized. These were characterized on the basis of physical and spectroscopic data, and were evaluated for their antimicrobial activity against various bacterial and fungal strains using the disc diffusion method and nutrient agar media. The antioxidant activities of the products were also evaluated. Our data showed that many derivatives have promising activities as antioxidant agents.
The direct Differential Scanning Calorimetry method of the determination of paracetamol in commercially available drugs was developed. The method was based on calibration curves obtained from melting enthalpies ΔH of binary mixtures of paracetamol and commonly used excipients such as starch or microcrystalline cellulose in increasing weight ratios. In order to demonstrate how the technological processes of formulating the tablets affects the quantitative studies, the micronized and nonmicronized mixtures were used. The idea of using micronized mixtures was to simulate these technological processes. The appropriate paracetamol contents of the selected pharmaceutical preparations were calculated and compared. The final results demonstrated, that the contents of paracetamol obtained from micronized samples were much closer to those declared by the manufacturer than the nonmicronized. Excluding two drugs, the influence of starch or cellulose on quantification in the micronized group was not observed whereas in the nonmicronized group it was distinctly visible.
The Langmuir-Blodgett technique was used to transfer the monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) from the subphase containing chitosan (Ch) and/or titanium(IV) oxide (TiO2) and/or hyaluronic acid (HA) on glass plates after a low-temperature air plasma treatment. The surface free energy and its components were determined on the basis of advancing and receding contact angle measurements of water (W), formamide (F), and diiodomethane (DM). To estimate the total surface free energy (𝛾𝑠𝑡𝑜𝑡), the contact angle hysteresis (CAH) model was used, and the obtained data were compared with the results calculated from the Lifshitz-van der Waals/acid–base (LWAB) approach. It was found that the subphase components modify the surface of the phospholipid monolayer by changing the type and magnitude of interactions. They were reflected as significant differences in the obtained values of total surface free energy and its components. These findings can help in the development of composite materials, thereby expanding the spectrum of applications for chitosan, TiO2, and HA, as well as understanding the interactions between biomaterial and cell.
An activated charcoal-TiO2 Catalyst was synthesized via the precipitation method and sonication technique, and three dyes: Reactive Black 5 (RB 5), Rhodamine B (Rh B) and Napthol Blue Black (NBB) were used to assess the quality of the product under UV-Light. The nanomaterial was also characterized by High-resolution scanning electron microscopy (HR-SEM), elementary dispersive X-ray (EDX), photoluminescence spectroscopy (PL) and UV-Vis DRS. The photodegradation of the three dyes when exposed to this nanomaterial indicate the superior photocatalytic activity of RB 5 as compared to the other dyes. A mechanism is proposed for the higher activity of AC-TiO2 than that of TiO2 nanocomposite material. Overall, this nanocomposite material was found to be highly stable and reusable. The nanomaterial is also economically of very low cost.
In the present paper, cold plasma-activated and chitosan-coated polyetheretherketone (PEEK) was covered with thin films of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, cholesterol, cyclosporine A, and their mixtures using the Langmuir-Blodgett technique. The thermodynamic function, i.e., surface free energy, of those systems was determined based on the contact angle hysteresis (CAH) approach. This parameter seems to be essential in determination of cell adhesion to polymeric materials and molecular interactions with living tissues. The obtained results show that the wettability and surface free energy of PEEK can be changed depending on the composition of the coating
The surface properties of chitosan acetate (ChA), polyacrylamide (PAM) and ChA/PAM mixtures have been investigated by the tapping-mode atomic force microscopy (AFM) and monitored by contact angle measurements. Chitosan is blended with polyacrylamide in acetic acid solution and this solution is cast to prepare the mixture film. Measurements of the contact angle for two different liquids (diiodomethane and glycerol) on the surface of chitosan acetate. The surface free energy (γs) as well as dispersive (gsd) and polar (gsp) components were calculated from contact angle values by Owens-Wendt methods using an appropriate computer program. The values of polar and dispersive components of surface free energy show that PAM films are more polar than chitosan acetate films. In the case of ChA/PAM mixtures, the values of surface free energy and polar component are reduced significantly compared with pure polymers. This behavior indicates rather hydrophobic character of this surface. The changes of topography images were considered by determining the root mean square (RMS) deviation in the image data. The study of blends by AFM showed a completely different morphology when compared with pure components. The roughness of blends increases with the increase of ChA content. This may indicates a strong interaction between the polymeric components.
Hydrogels that possess the ability of gelling in response to changes in the local environment, such as pH or temperature, have been examined extensively recently. In this paper the properties of thermosensitive chitosan hydrogels prepared with the use of chitosan glutaminate and -glycerophosphate are presented. The sol/gel transition point was determined based on the rheological properties. The structure of gels was observed under the Scanning Electron Microscopy (SEM) and was investigated by thermogravimetric (TG) and differential themogravimetric (DTG) analy¬sis and infrared (IR) spectroscopy. The crystallinity of gel structure was determined by X-ray Diffraction analysis (XRD).
Regenerated cellulose was prepared from plantain pseudo stem obtained in Uyo, Akwa Ibom State. The pulp prepared with 12% NaOH had moisture content of 8.8% and a yield of 36.9% on the average. The pulp was bleached and exposed to air to form “white crumbs”. The aged crumbs was mixed with carbon disulphide at a controlled temperature of 30 °C to form cellulose xanthate (C6H9O4–S–SNa)n. This was then converted to regenerated cellulose by way of further treatment with tetraoxosulphate (VI) acid at a yield of 36.4%. This work has revealed that plantain pseudo stem waste can be converted to regenerated cellulose for diverse applications.
Ionically crosslinked chitosan membranes were prepared and their density was determined using modified pycnometer method. High molecular compound: sodium alginate (NaAlg) and low molecular compounds: pentasodium tripolyphosphate (TPP) and trisodium citrate (CIT) were used as ionic crosslinkers of chitosan. As a reference liquid n-heptane solution was chosen. It was found out that density of modified chitosan membranes is strongly affected by the type of ionic crosslinker and membrane preparation conditions
Chitosan electrospun nanofibres were synthesised in two different trifluoroacetic acid (TFA)/dichloromethane (DCM) solvent ratios and then neutralised in aqueous and ethanol sodium-based solutions (NaOH and Na2CO3) to produce insoluble materials with enhanced biological properties for regenerative and tissue engineering applications. Structural, electronic, and optical properties and the swelling capacity of the prepared nanofibre membrane were studied by scanning electron microscopy, Fourier-transform infrared spectroscopy, and photoluminescence. Cell viability (with the U2OS cell line) and antibacterial properties (against Staphylococcus aureus and Escherichia coli) assays were used to assess the biomedical potential of the neutralised chitosan nanofibrous membranes. A 7:3 TFA/DCM ratio allows for an elaborate nanofibrous membrane with a more uniform fibre size distribution. Neutralisation in aqueous NaOH only maintains a partial fibrous structure. At the same time, neutralisation in NaOH ethanol-water maintains the structure during 1 month of degradation in phosphate-buffered saline and distilled water. All membranes demonstrate high biocompatibility, but neutralisation in ethanol solutions affects cell proliferation on materials made with 9:1 TFA/DCM. The prepared nanofibrous mats could constrain the growth of both gram-positive and gram-negative microorganisms, but 7:3 TFA/DCM membranes inhibited bacterial growth more efficiently. Based on structural, degradation, and biological properties, 7:3 TFA/DCM chitosan nanofibrous membranes neutralised by 70% ethanol/30% aqueous NaOH exhibit potential for biomedical and tissue engineering applications.
We obtained binary polyelectrolyte complexes containing chitosan from Bombyx mori and collagen with a mass ratio of 10:1; 10:2, and 10:3. During the interaction between the macromolecules, due to the compensation of the positive charges of chitosan with the negative charges of collagen, the zeta potential of the solutions of polyelectrolyte complexes changed from +15.2 to +5.67 mV. We revealed the dependence of the size characteristics of the particles of polyelectrolyte complexes on time and the ratio of macromolecules. An examination of the morphology of the films of polyelectrolyte complexes demonstrated that in the evaluated chitosan/collagen mass ratios, non-spherical nanosized particles up to ≤ 60 nm form on the surface of the films. We evaluated the mechanism of formation of complexes by using Fourier-transform infrared spectroscopy and confirmed the findings with density functional theory and molecular dynamics. We found that the particle diameter is inversely proportional to the diffusion coefficient. The results show that the particles are almost uniformly distributed over the surface of the polymer matrix and have a unimodal character. We obtained reproducible results when using a chitosan/collagen mass ratio of 10:2 to dye natural silk. We found that the complexes contribute to increase the intensity and stability of colour relative to soap and friction.
Lead is a potentially toxic metal which easily contaminates water forms due to it ubiquitous applications. The demonstration of viable techniques to remove Lead ions from water is one of the most researched topics. In this study, the highly reported surface and pore advantages exhibited by metal-organic frameworks is exploited for the trapping of aqueous Lead. The Zinc-based MOF5 was synthesized for adsorption tests involving the sequestration of Lead ions. Tests were conducted to determine the effects of concentration, contact time and pH in the uptake of Lead ions from solution. The extent of adsorption was evaluated as percentage uptake of Lead and Lead uptake capacity of MOF5. The results showed that while the percentage uptake and Lead uptake capacity of MOF5 depended on the concentration and pH of solution, contact time had only minimal effects. Five adsorption isotherms were applied to evaluate the adsorption data including Dubinin-Radushkevich, Freundlich, Langmuir, Elovich and Jovanovich. However, the R2 values gave the Elovich isotherm (R² = 0.8029) as the best fitting model, implying the dominance of multilayer interaction between MOF5 and Lead ions. The pseudo-second-order kinetics and the Webber-Morris intraparticle diffusion were also applied to evaluate the kinetics of the process. The pseudo-second-order kinetic plots was observed to provide the better fit to the kinetics, ahead of the Webber-Morris intraparticle diffusion, depicting the dominance of chemisorption. The high percentage (> 90 %) of Lead ions taken up, and the high capacity of MOF5 for the ions, as observed across all three types of adsorption tests performed, demonstrates that MOF5 (> 45 mg/g)) could represent an efficient adsorbent for the targeted separation of Lead ions during water treatment.
The aim of this work is to present the prosperities of a certain iterative pattern, which we have called the „differential pattern”. It operates through a subtraction of the two adjoining elements of the sequence and returning of their absolute difference, used subsequently in the next steps. The whole procedure can be prolonged, enabling the investigation of the generated sequences. The pattern generates two-dimensional matrixes and the numerical structures of a higher level. The evolution of the pattern leads to various possible behaviours, among which characteristic attractors may be mentioned. They can be the limit cycles, i.e. oscillations appearing after the certain number of iterations, which may be constant or continuously silenced. Another type of a possible attractor is a constant number, which is usually zero. Interestingly enough, the type of attractor toward which the pattern leads may depend on the number of elements in a single sequence, or the assumed edge conditions. It is a peculiar pseudo-bifurcation dependent on the parameters of generated structure, appearing regardless of the value of the elements filling the created numerical structure. During the pattern evolution, complex oscillations have also been observed, i.e. those exerting a different frequency. For instance, in a 5-element sequence, a distinct frequency of oscillations tends to appear on the third position. The visualisation of the pattern has been attempted with the use of R-packet, so it was possible to observe that the pattern generates more complex structures, exerting some level of order. Some behaviours are emerging only after reaching the specific level of complexity. These characteristic objects are dychotomic forks resembling the lightings, or other behaviours whoch we have called ‘ping-pong objects’. The last aspect of this work is the presentation of the differential pattern as a potential candidate for a one-way function, i.e. the procedure possible to be applied in data coding. A distinct section of this article has also been devoted to discuss the pattern as a particular type of cellular automata, about which the authors did not know until the article’s review.
PL
Celem niniejszej pracy jest zaprezentowanie własności pewnego schematu iteracyjnego, zwanego dalej przez nas schematem różnicowym. Działanie jego polega na odejmowaniu dwóch sąsiednich elementów ciągu i zwracaniu ich bezwzględnej różnicy w kolejnych krokach. Całą procedurę można dowolnie przedłużać i jednocześnie badać kolejne postacie generowanych ciągów, które tworzą pewną strukturę liczbową. Zgodnie z naszym założeniem, struktura ta może przyjmować formę dwuwymiarowych ugrupowań liczb (macierzy) lub postacie bardziej złożone. Ewolucja schematu prowadzi do rozmaitych zachowań, wśród których wy-mienić należy pojawianie się charakterystycznych atraktorów, do których zmierzać mogą kolejne postacie generowanych ciągów. Mogą nimi być cykle graniczne, czyli oscylacje pojawiające się po przekroczeniu pewnej liczby iteracji, które albo są stałe i powtarzają się od pewnego momentu w nieskończoność, albo mogą ulegać tłumieniu. Innym atraktorem jest jednakowa i stała od pewnego momentu wartość wszystkich elementów ciągu, zwykle wartość zerowa. Interesujące jest, że to, czy kolejne postacie ciągów zmierzać będą do cyklu granicznego, czy do ujednolicenia elementów, zależeć może od liczby jego elementów oraz przyjętych warunków brzegowych. Jest to swoiste zjawisko, podobne do bifurkacji, zależne od parametrów strukturalnych samego schematu, pojawiające się bez względu na wartości liczbowe elementów tworzonych ciągów. Podczas ewolucji schematu zaobserwowane zostały także oscylacje złożone, tzn. wykazujące różną częstotliwość. Przykładowo dla ciągów 5-elementowych odmienna częstotliwość oscylacji ma tendencję do występowania w przypadku trzeciego elementu. Została podjęta próba wizualizacji ewolucji schematu z wykorzystaniem pakietu R, dzięki czemu można było zaobserwować, że schemat generuje rozmaite struktury złożone, wykazujące pewien poziom uporządkowania. Niektóre za-chowania są emergentne, możliwe do zaobserwowania po przekroczeniu pewnej złożoności układu. Charakterystycznymi obiektami są rozwidlenia dychotomiczne przypominające błyskawice, a także zachowania nazwane przez nas ping-pong. Ostatnim aspektem pracy jest zaprezentowanie schematu różnicowego jako potencjalnego kandydata na funkcję jednokierunkową, algorytmu mogącego znaleźć zastosowanie w szyfrowaniu danych. The aim of this work is to present the prosperities of a certain iterative pattern, which we have called the „differential pattern”. It operates through a subtraction of the two adjoining elements of the sequence and returning of their absolute difference, used subsequently in the next steps. The whole procedure can be prolonged, enabling the investigation of the generated sequences. The pattern generates two-dimensional matrixes and the numerical structures of a higher level. The evolution of the pattern leads to various possible behaviours, among which characteristic attractors may be mentioned. They can be the limit cycles, i.e. oscillations appearing after the certain number of iterations, which may be constant or continuously silenced. Another type of a possible attractor is a constant number, which is usually zero. Interestingly enough, the type of attractor toward which the pattern leads may depend on the number of elements in a single sequence, or the assumed edge conditions. It is a peculiar pseudo-bifurcation dependent on the parameters of generated structure, appearing regardless of the value of the elements filling the created numerical structure. During the pattern evolution, complex oscillations have also been observed, i.e. those exerting a different frequency. For instance, in a 5-element sequence, a distinct frequency of oscillations tends to appear on the third position. The visualisation of the pattern has been attempted with the use of R-packet, so it was possible to observe that the pattern generates more complex structures, exerting some level of order. Some behaviours are emerging only after reaching the specific level of complexity. These characteristic objects are dychotomic forks resembling the lightings, or other behaviours whoch we have called ‘ping-pong objects’. The last aspect of this work is the presentation of the differential pattern as a potential candidate for a one-way function, i.e. the procedure possible to be applied in data coding. A distinct section of this article has also been devoted to discuss the pattern as a particular type of cellular automata, about which the authors did not know until the article’s review.
This review considers articles on the formation of hydrogels based on chitosan as well as succinylated and quaternized chitosan derivatives. They are synthesized using low toxicity reagents, under ordinary conditions (low production costs). Chitosan derivatives are soluble in an extended range of pH values and characterized by mucoadhesiveness, bioavailability and biodegradability, which extends the potential of their medical applications. One of the most important properties of chitosan and its derivatives is the ability to form hydrogels. Depending on the nature of the bonds that occur during formation, hydrogels are divided into chemically or physically crosslinked, or a mixture of the two. Chemically crosslinked gels have covalent bonds, while physically crosslinked gels are formed by noncovalent interactions, for example, ionic. Mixed hydrogels have both types of crosslinking.
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