Homofermentative lactic acid bacteria of a traditional cheese, Comlek peyniri from Cappadocia region

Comlek peyniri is a typical artisanal cheese in Central Anatolia. This type of cheese was made by using the indigenous lactic acid bacteria (LAB) flora of cow or ewes' milk. Majority of the samples were taken from fresh cheese because the aim was to isolate homofermentative LAB. Initially 661 microbial isolates were obtained from 17 cheese samples. Only 107 were found to be homofermentative LAB. These isolates were selected and identified by using both phenotypic and molecular methods. Phenotypic identification included curd formation from skim milk, catalase test, Gram staining and light microscopy, growth at different temperatures and salt concentrations, arginine hydrolysis, gas production from glucose, and carbohydrate fermentation. Molecular identification was based on the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the 16S rRNA gene-ITS (internally transcribed spacer) region. By combining the phenotypic and molecular identification results, isolates belonging to each of the following genera were determined at species or subspecies level: 54 Lactococcus lactis subsp. lactis, 21 Enterococcus faecium, 3 Ec. faecalis, 2 Ec. durans, 10 Ec. sp., 15 Lactobacillus paracasei subsp. paracasei, and 2 Lb. casei strains. Technological characterisation was also performed by culturing each of the strains in UHT skim milk, and by monitoring pH change and lactic acid production at certain time intervals through the 24 h incubation. Results of the technological characterisation indicated that 33% of the isolates (35 strains) were capable of lowering the pH of UHT milk below 5.3 after 6 h incubation at 30 degrees C. Thirty four of these strains were Lc. lactis subsp. lactis, and only one was an Ec. faecium strain.     

Gelation and swelling behavior of end-linked hydrogels prepared from linear poly(ethylene glycol) and poly(amidoamine) dendrimers

Linear α,ω di-epoxide-terminated poly(ethylene glycol) of molar mass 4000 g mol⁻¹ was end-linked with amine-terminated poly(amidoamine) (PAMAM) dendrimers of generations 0, 2, and 4 in water to prepare architecturally well-defined copolymer hydrogels. The gelation and equilibrium swelling of the gels in water were characterized while systematically varying the polymer concentration at preparation, dendrimer generation, and mole ratio of dendrimer endgroups to PEG endgroups. The Ahmad-Rolfes-Stepto (ARS) theory of non-linear polymerization was applied to predict conditions favoring gelation, and to estimate the extent of reaction of amine and epoxide groups. Hydrogels having a large stoichiometric excess of amines over epoxides exhibited “superabsorbent” behavior upon extraction and equilibrium swelling in pure water. The mole ratio of amines to epoxides (equivalently, the mass fraction of dendrimers) was the most important factor governing superabsorbent behavior, although the polymer volume fraction at crosslinking and dendrimer generation also affected swelling to a lesser extent. The superabsorbency arises in part from protonation of the dendrimer amine endgroups at external pH = 7, which is supported by the drastic shrinkage of the most highly swelling gels in aqueous NH₄OH at pH = 11. Equilibrium swelling at pH = 7 was noticeably enhanced in gels having a high soluble fraction and high mass fraction of dendrimers. End-linking of linear polymer precursors to PAMAM dendrimers can potentially produce novel copolymer gels that combine attractive properties of the linear precursors with high swelling and pH-responsive behavior of PAMAM-containing networks.     

Effect of mineral additives and permeability reducing admixtures having different action mechanisms on mechanical and durability performance of cementitious systems

In this paper, the effect of usage of the permeability reducing admixture (PRA) having different action mechanisms on hardened state properties of cementitious systems containing mineral additives is examined. For this aim, three commercial PRAs were used during investigation. The effective parameters in the first and third PRAs were air-entraining and high-rate air-entraining, respectively. The second one contained the insoluble calcium carbonate residue and had a small amount of the air-entraining property. Mortar mixes with binary and ternary cementitious systems were prepared by partially replacing cement with fly ash and metakaolin. The hardened state properties of mortar mixtures such as compressive strength, ultrasonic pulse velocity, water absorption, drying shrinkage and freeze–thaw resistance were investigated. The ternary cement-based mixture having both fly ash and metakaolin was selected as the most successful mineral-additive bearing mix in regard to hardened state properties. In this sense, PRA-B, with both insoluble residues and a small amount of air-entraining properties, showed the best performance among the mixtures containing PRA. The combined use of mineral additive and PRA had a more positive effect on the properties of the mixes.     

The Effect of B Addition on the Microstructural and Mechanical Properties of FeNiCoCrCu High Entropy Alloys

High-entropy alloys (HEAs) are a new class of alloys having equiatomic ratios of alloying elements in their composition. Boron is an important element that can increase the strength of steels and wear resistance of hard facing coatings with its high hardness compounds. The effect of boron (B) in FeNiCoCrCu-based HEAs has not been studied in detail to date. In the current study, the microstructural and mechanical properties of FeNiCoCrCuB_x HEAs with varying boron contents (x = 1, 2, 3, 4, 5 at. pct) were investigated using specimens prepared by two-stage processing (sintering and vacuum arc melting). Microstructural and structural studies were carried out using optical microscopy, scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. Vickers microhardness and three-point bending tests were also performed to observe the variations in mechanical properties. Results showed that the microstructures of HEAs are generally dendritic and contain two different FCC phases, i.e., Fe-Ni-Co-Cr-rich dendritic and Cu-rich interdendritic phases. The hardness values increased with increasing B content with a maximum hardness of 337 HV. According to three-point bending test results, the highest strength of about 1900 MPa and good ductility were obtained with HEA-3 (3 at. pct B).

     

Upgrading of fast pyrolysis bio-oil over Fe modified ZSM-5 catalyst to enhance the formation of phenolic compounds

The present study is aimed to investigate the upgrading of beech sawdust pyrolysis bio-oil through catalytic cracking of its vapors over Fe-modified ZSM-5 zeolite in a fixed bed tubular reactor. The zeolite supported iron catalyst was successfully prepared with varying metal loading ratios (1, 5, 10 wt%) via dry impregnation method and further characterized by BET, XRD, and SEM-EDX techniques. TG/FT-IR/MS analysis was used for the detection of biomass thermal degradation. Product yields of non-catalytic and catalytic pyrolysis experiments were determined and the obtained results show that bio-oil yields decreased in the presence of catalysts. Besides, the bio-oil composition is characterized by GC/MS. It was indicated that the entity of the ZSM-5 and Fe/ZSM-5 catalyst reveal a significant enhancement quality of the pyrolysis products in comparison with non-catalytic experiment. The catalyst increased oxygen removal from the organic phase of bio-oil and further developed the production of desirable products such as phenolics and aromatic compounds.     

Comparative Antibacterial,Chemical and Morphological Study of Essential Oils of Thymbra spicata var. spicata Leaves by Solvent-Free Microwave Extraction and Hydro-Distillation

The essential oils of Thymbra spicata var. spicata were obtained by both hydrodistillation and solvent-free microwave extraction methods. Chemical composition and antibacterial activity of the essential oils were examined. The main constituents of both essential oils obtained by solvent-free microwave extraction and hydrodistillation from Thymbra spicata var. spicata were carvacrol (44.8–36.1%), γ-terpinene (23.8–26.1%), and p-cymene (7.3–9.6%), respectively. The essential oil obtained from solvent-free microwave extraction contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than hydrodistillation. The antibacterial activities of the essential oils from solvent-free microwave extraction and hydrodistillation were evaluated by the disc diffusion method against six bacterial strains. The essential oil extracted by solvent-free microwave extraction was more effective than the essential oil extracted by hydrodistillation against the tested bacteria except for E. coli ATCC 25922- and S. aureus ATCC 25923+. Especially, S. aureus ATCC 25923+ was more sensitive against the essential oils obtained from Thymbra spicata var. spicata. Scanning electron microscopy measurements show that glands (that are filled with essential oils) were subjected to more severe thermal stresses and localized high pressure by microwave heating, the pressure build up within the glands could have exceeded their capacity for expansion and break down of cell walls. Solvent-free microwave extraction resulted in more extract release more rapidly than in hydrodestillation.     

Data-Fusion Approaches and Applications for Construction Engineering

Data fusion can be defined as the process of combining data or information for estimating the state of an entity. Data fusion is a multidisciplinary field that has several benefits, such as enhancing the confidence, improving reliability, and reducing ambiguity of measurements for estimating the state of entities in engineering systems. It can also enhance completeness of fused data that may be required for estimating the state of engineering systems. Data fusion has been applied to different fields, such as robotics, automation, and intelligent systems. This paper reviews some examples of recent applications of data fusion in civil engineering and presents some of the potential benefits of using data fusion in civil engineering.     

Effects of ultraviolet light and ultrasound on microbial quality and aroma-active components of milk

BACKGROUND: Heat treatment is the most common way to extend the shelf life of milk. However, alternative technologies such as ultraviolet (UV) light and ultrasound (US), which are non‐thermal methods for processing milk, have been developed to replace heat treatment. These technologies do not have any adverse effects on the quality of milk. The major purpose of this study was to investigate the effects of UV and US on different micro‐organism groups and aroma compounds in milk. RESULTS: Heat pasteurisation at 65 °C for 30 min was used as thermal control treatment. The growth of total coliform group bacteria, Escherichia coli and Staphylococcus spp. was completely reduced by UV treatment. Application of US was not sufficient to reduce the numbers of yeasts and moulds. In neutral/basic fractions, 3‐methylthiophene (plastic), hexanal (grass) and 1‐hexen‐3‐one (floral) were major volatiles in milk samples. CONCLUSION: UV had a major effect on total coliforms, E. coli and Staphylococcus spp., but US was not as effective as UV and heat treatment in reducing certain groups of micro‐organisms. No major differences were observed in terms of aroma‐active compounds and flavour of milk following the different treatments. However, some new volatiles and change in rheological properties were generated by UV and US treatments. Copyright © 2011 Society of Chemical Industry     

Mechanical behaviour and fibre dispersion of hybrid steel fibre reinforced self-compacting concrete

In this study, mixture design, workability, fibre dispersion/orientation, mechanical properties and fracture behaviour of hybrid steel fibre reinforced self-compacting concretes (HSFRSCCs) were investigated. Three different types of steel fibres with and/or without hooked-ends were added to the mixtures in two different volume fractions (0.75 and 1.5% of the total volume of concrete). The results of slump flow, U-box, V-funnel and J-ring tests have shown that increasing the fibre content of the concretes slightly reduced the workability of HSFRSCC, and the main influencing factor on flowability is the geometry of fibres. The addition of fibres, although did not change the final flowability, decreased the rate of flowability. The results from the experimental tests showed that the flexural strengths increased slightly with increasing strength of long fibres, whereas the splitting tensile strength remained unchanged. The concretes with high strength, long steel fibres show behaviour of enhanced toughness and ductility compared to that with normal strength steel fibres. The orientation and distribution of fibres in concrete have been investigated by image analysis and it was observed that fibres dispersed homogeneously in all concrete series without any clumping. With increasing the amount of fibres, the fibres were more vertically orientated relative to the bending loading direction, resulting in enhancement in the mechanical properties of concrete.     

Investigation on colour,fastness properties and HPLC‐DAD analysis of silk fibres dyed with Rubia tinctorium L. and Quercus ithaburensis Decaisne

Silk fabric samples were dyed according to the various procedures using madder (Rubia tinctorium L.) and walloon oak (Quercus ithaburensis Decaisne) extracts. The colour coordinates, K/S, as well as wash, light, rub and perspiration fastness values were determined. A reversed‐phase high‐performance liquid chromatography with diode‐array detection was utilised for the identification of the components of dyes present in the dyed fabrics and in the plant extracts.