Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite with sulfonic acid for acid-catalyzed reactions

Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite was performed with sulfonic acid functional groups to achieve new solid acid materials. The sulfonic acid functional groups were created through the ring opening nucleophilic reaction of amine groups of chitosan with 1,4-butane sultone. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopies (XPS) verified the successful sulfonic acid functionalization of chitosan. The obtained sulfonic acid functionalized chitosan-magnetite nanocomposite showed superparamagnetic properties according to the vibrating sample magnetometry analysis and exhibited magnetic separation feature from dispersed mixtures. Nitrogen adsorption-desorption analysis indicated the increase in surface area after formation of chitosan-magnetite nanocomposite and functionalization with sulfonic acid. Both of the prepared solid acids exhibited high catalytic activities in the acid-catalyzed acetic acid esterification with n-butanol and benzaldehyde acetalization with ethylene glycol as model reactions. Furthermore, they can be reused several times without considerable loss of their activities.     

Estimating compressive and flexural strength of travertines with respect to laminae-orientation by geomechanical properties

Bulletin of Engineering Geology and the Environment - Travertine is an anisotropic rock considered as one of the most popular stone materials in the building industry. Due to its bedding and...     

Design and analysis of a high quality factor multipath spiral inductor

Microsystem Technologies - Recently high quality factor and small-occupying-area inductors are prerequisite for wireless communication products such as mobile phones and wireless network, low cost...     

Improving the quality of meat‐free sausages using κ‐carrageenan,konjac mannan and xanthan gum

High consumption of processed red meat can cause health issues. Therefore, production of high‐quality meat‐free food alternatives is necessary. The main objective of this study was to use hydrocolloids including κ‐carrageenan, konjac mannan and xanthan gum at 0, 0.3, 0.6, 1.0 and 1.5% w/w to improve the quality of meat‐free sausages formulated by soy protein isolated, texturised soy protein, corn starch, vegetable oil and spices. With the addition of the tested hydrocolloids, the lightness of the sausages improved. κ‐Carrageenan and konjac mannan significantly improved the water‐holding capacity and texture and reduced the cooking loss of the samples, while xanthan gum showed no considerable effect on these parameters. Konjac mannan and κ‐carrageenan (up to 0.6%) improved the general acceptability of the sausages, while inclusion of xanthan gum made no significant difference. Unlike xanthan gum, κ‐carrageenan followed by konjac mannan was highly successful in improving the overall quality of meat‐free sausages.     

A survey of methods for time series change point detection

Change points are abrupt variations in time series data. Such abrupt changes may represent transitions that occur between states. Detection of change points is useful in modelling and prediction of time series and is found in application areas such as medical condition monitoring, climate change detection, speech and image analysis, and human activity analysis. This survey article enumerates, categorizes, and compares many of the methods that have been proposed to detect change points in time series. The methods examined include both supervised and unsupervised algorithms that have been introduced and evaluated. We introduce several criteria to compare the algorithms. Finally, we present some grand challenges for the community to consider.     

Ion separation and water purification by applying external electric field on porous graphene membrane

Nano Research - Using molecular dynamics (MD) simulations, a porous graphene membrane was exposed to external electric fields to separate positive and negative ions from salt-water and to produce...     

Effect of poly‐glutamate on uptake efficiency and cytotoxicity of cell penetrating peptides

Cell penetrating peptides (CPPs) were developed as vehicles for efficient delivery of various molecules. An ideal CPP‐peptide should not display any toxicity against cancer cells as well as healthy cells and efficiently enter into the cell. Because of the cationic nature and the intrinsic vector capabilities, these peptides can cause cytotoxicity. One of the possible reasons for toxicity of CPPs is direct translocation and consequently, pore formation on the plasma membrane. In this study it was demonstrated that interaction of poly‐glutamate with CPP considerably reduced their cytotoxicity in A549 cell. This strategy could be useful for efficient drug delivery mediated by CPP.Inspec keywords: cellular biophysics, polymers, drug delivery systems, biomedical materials, toxicology, molecular biophysicsOther keywords: drug delivery, A549 cell, plasma membrane, pore formation, cancer cells, poly‐glutamate, cytotoxicity, uptake efficiency, cell penetrating peptides     

Reciprocating Sliding Wear Behavior of 60NiTi As Compared to 440C Steel under Lubricated and Unlubricated Conditions

ABSTRACT

60NiTi is a hard (～60 HRC) and highly corrosion-resistant intermetallic with a relatively low elastic modulus (～100 GPa). In addition, this alloy exhibits a high compressive strength (～2,500 MPa) and a high elastic compressive strain of over 5%. These attributes make this alloy an attractive candidate to be employed in structural and mechanical component applications. However, sliding wear behavior of this intermetallic has not yet been studied in a systematic way. In this study, lubricated and unlubricated reciprocating sliding wear behavior of 60NiTi is compared to 440 C steel as a conventional bearing and wear-resistant alloy. Results of experiments carried out under different loads show that 60NiTi, despite having a higher hardness, exhibits a significantly inferior wear behavior under dry conditions in comparison to 440 C steel. These unexpected results indicate that 60NiTi does not follow conventional wear theories where the wear of materials has an inverse relationship to their hardness. On the other hand, under lubricated conditions with castor oil and a synthetic gear oil, 60NiTi exhibits low specific wear rates. These results exhibit the importance of proper lubrication in sliding mode applications where 60NiTi is exploited as a wear-resistant alloy.     

UV-induced synthesis of chitosan-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide semi-IPN superabsorbent hydrogels

Superabsorbent hydrogels of chitosan-g-polyacrylamide with N,N′-methylene-bis-acrylamide as a crosslinker were prepared via UV irradiation in the absence of photoinitiator under homogeneous conditions. The product was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy to confirm the formation of hydrogels. The transparent hydrogels have been observed to exhibit as much as 2987% swelling in acidic solution. In addition, the hydrogel which hydrolyzed for 6 h (0.24 × 10³ min) can have a water uptake of 106 times its weight (5300% swelling for 0.5 g hydrogel). The effect of several variables such as time, temperature, pH, acrylamide/chitosan ratio, crosslinker amount, and different media was explored. Finally, the prepared hydrogel have been used in adsorption of Zn(II) ions from water with high removal efficiency (0.636 meq g⁻¹ or 20.8 mg g⁻¹) at pH = 7. The experimental data of the adsorption equilibrium from Zn(II) solution fit well with the pseudo-second-order model.