Experimental and theoretical investigations of the adhesion time of Penicillium spores to cedar wood surface

In this study, the adhesion of 4 Penicillium strains (Penicillium granulatum, Penicillium crustosum, Penicillium commune and Penicillium chrysogenum) on cedar wood was examined qualitatively and quantitatively by using the extended DLVO (XDLVO) approach and the environmental scanning electronic microscopy (ESEM) technique. A comparison between the XDLVO theories and the ESEM technique was also investigated. The adhesion tests revealed that P. chrysogenum was not able to adhere on the cedar wood substrata, as predicted by the XDLVO approach. We have also found by ESEM that the three Penicillium strains (P. granulatum, P. crustosum, P. commune) adhered on wood, as not predicted theoretically.Moreover, the time of adhesion (3 h and 24 h) was used not only to compare the capacity of adhesion according to contact time but also to explain the discrepancies between the XDLVO approach prediction and the adhesion experiments. A positive relationship between the XDLVO approach and adhesion experiments has been observed after 3 h of adhesion. In contrast, a contradiction between the XDLVO predictions and the adhesion test results has been noted after 24 h of adhesion of Penicillium strains to the wood surface.     

Cooperative Q‐learning techniques for distributed online power allocation in femtocell networks

In this paper, we address the problem of distributed interference management of femtocells that share the same frequency band with macrocells using distributed multi‐agent Q‐learning. We formulate and solve two problems representing two different Q‐learning algorithms, namely, femto‐based distributed and sub‐carrier‐based distributed power controls using Q‐learning (FBDPC‐Q and SBDPC‐Q). FBDPC‐Q is a multi‐agent algorithm that works on a global basis, for example, deals with the aggregate macrocell and femtocell capacities. Its complexity increases exponentially with the number of sub‐carriers in the system. Also, it does not take into consideration the sub‐carrier macrocell capacity as a constraint. To overcome these problems, SBDPC‐Q is proposed, which is a multi‐agent algorithm that works on a sub‐carrier basis, for example, sub‐carrier macrocell and femtocell capacities. Each of FBDPC‐Q and SBDPC‐Q works in three different learning paradigms: independent (IL), cooperative (CL), and weighted cooperative (WCL). IL is considered the simplest form for applying Q‐learning in multi‐agent scenarios, where all the femtocells learn independently. CL and WCL are the proposed schemes in which femtocells share partial information during the learning process in order to strike a balance between practical relevance and performance. We prove the convergence of the CL paradigm when used in the FBDPC‐Q algorithm. We show via simulations that the CL paradigm outperforms the IL paradigm in terms of the aggregate femtocell capacity, especially in networks with large number of femtocells and large number of power levels. In addition, we propose WCL to address the CL limitations. Finally, we evaluate the robustness and scalability of both FBDPC‐Q and SBDPC‐Q, against several typical dynamics of plausible wireless scenarios (fading, path loss, random activity of femtocells, etc.). We show that the CL paradigm is the most scalable to large number of femtocells and robust to the network dynamics compared with the IL and WCL paradigms. Copyright © 2014 John Wiley & Sons, Ltd.     

Flocculation and viscoelastic behavior of industrial papermaking suspensions

The effects of the surface charge type and density C496, C492 and A130LMW polyacrylamides (PAMs) on the rheological behavior of real industrial papermaking suspensions were quantitatively related to the degree of flocculation for the same industrial papermaking suspensions. The floc sizes were larger but less dense when anionic PAM was used, and this due to the repulsive forces between the anionic PAM and colloidal particles, leading to the development of open structure flocs of less density. On the other hand, rheological measurements showed that the papermaking suspension is thixotropic with a measurable yield stress. The results showed that the magnitude of the critical stress, τ _c , complex viscosity, η*, elastic modulus, G′, and viscous modulus, G″, depend on the number of interactions between the PAM chains and particle surface and the strength of those interactions. Cationic PAM showed higher values of η*, G′, G″ and τ _c compared to anionic PAM. This behavior is in good agreement with Bingham yield stress, τ _B , adsorption and effective floc density results. Similar to oscillatory measurements, creep measurements also showed that the deformation was much lower for the cationic PAM based suspensions than for the anionic PAM based suspensions. Furthermore, the results revealed that increasing the cationic PAM surface charge decreases the floc size but increases the adsorption rate, elasticity and effective floc density proposing differences in the floc structures, which are not revealed clearly in the Bingham yield stress measurements.     

Facile Synthesis of ZSM-5/TiO2/Ni Novel Nanocomposite for the Efficient Photocatalytic Degradation of Methylene Blue Dye

It is critical to develop an appropriate dye degrading technique to preserve the natural environment and human health owing to the dangerous water pollution caused by effluent dyes. So, in this work, a ZSM-5/TiO₂/Ni photocatalyst was synthesized as a novel composite and used for degrading methylene blue dye in the solution. The sol–gel approach was used to immobilize titanium dioxide nanoparticles on the ZSM-5 surface, and the resulting photocatalyst was then modified using nickel nanoparticles to improve its photocatalytic performance. The nanocomposite was characterized using different tools such as FE-SEM, EDX, XRD, FT-IR, TGA, and UV–Vis spectrophotometer. The XRD confirmed that the synthesized composite has the characteristic TiO₂ peaks. FE-SEM images of ZSM-5 exhibited rough, uneven, and jagged surfaces. A distinct shift in the morphology of the surface resulted when titanium dioxide was fully immobilized on the surface of ZSM-5. Shape complexity and surface roughness of the particles are elevated in the case of the ZSM-5/TiO₂/Ni nanocomposite. The maximum % degradation of 50 mL of 15 mg/L of methylene blue dye is 99.17% and achieved at pH?=?8, irradiation time?=?140 min, and photocatalyst dosage?=?0.05 g. The synthesized composite can be regenerated and reused several times without losing its efficacy.

     

Synthesis of Co3O4 @ Organo/Polymeric Bentonite Structures as Environmental Photocatalysts and Antibacterial Agents for Enhanced Removal of Methyl Parathion and Pathogenic Bacteria

Two green nanocomposites of Co₃O₄ decorated CTAB/bentonite (Co@CT/BE) and chitosan/bentonite (Co@CH/BE) were synthesized as enhanced and environmental photocatalysts and antibacterial agents. As photocatalysts, the products were applied in the effective oxidation of toxic methyl parathion pesticide (MP) in wastewater under a visible light source. The application of Co@CH/BE (0.02 g) resulted in the complete oxidation of MP (50 mg/L) after 40 min and complete mineralization after 60 min. while the complete oxidation and mineralization of MP (50 mg/L) by Co@CT/BE was recognized after 75 min and 100 min, respectively. The Co@CH/BE composite is of higher activity than Co@CT/BE and can cause complete oxidation for MP at high concentrations up to 100 mg/L after 75 min. The oxidation pathway was illustrated considering the existence of the hydroxyl radicals as the active oxidizing species and the identified secondary organic compounds during the oxidation tests. The detected intermediate converted into end products of CO₂ and inorganic anions of SO₄^?2, NO₃^?, and PO₄^?3 at the final stages of the oxidation processes. As antibacterial agents, the two composites exhibit considerable inhabitation zones of about 20 mm against both the Gram-positive Staphylococcus aureus and Gram-negative bacterium Vibrio Sp. The synthetic Co@CH/BE showed the best antibacterial properties with 200 μg/mL as minimum inhibitory against Staphylococcus aureus.

     

Synthesis of a novolac‐based 3‐aminopropylsiloxane resin and its application for the removal of Cu2+, Cr3+, and Ni2+ from electroplating wastewater

Novolac resin was modified with 3‐aminopropyltrimthoxysilane to obtain phenol‐formaldehyde‐aminopropylsiloxane resin (PF‐APS). Fourier transformation infra‐red spectra, thermogravimetric analysis, elemental analysis, and pH‐metric titration were used to characterize PF‐APS. Its chemical formula was suggested to be C₁₄H_12.49N_0.1O₂Si_0.1. The resin shows high experimental metal ions uptake capacity within short time of equilibration. The metal capacity was determined by atomic absorption spectrometry to be 0.787 mEq Cu/g. Maximum separation efficiencies of Cu²⁺, Cr³⁺, and Ni²⁺ from aqueous solutions on PF‐APS were at pH 8.0 and time of stirring 60 min; 94.0%, 90.8%, 83.2%, respectively. No significant interference from the background ions Na⁺, Cl^?, and was observed on the separation process. The heavy metal ions were eluted using 0.01 mol L^?1 EDTA at 65°C releasing >94% of the separated metal ions. The method of separation was applied successfully to remove the heavy metal ions Cu²⁺, Cr³⁺, and Ni²⁺ from electroplating wastewater from Dekirnis, Dakahlia Governorate, Egypt. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40993.     

Technological Evaluation of Nitrogen Containing Starch Derivatives as Sizing Agents

The structural changes brought about by introducing different nitrogen containing groups via cyanoethylation, carbamoylethylation and carbamation in the molecules of rice and maize starches and oxidized starches derived thereof and the onset of these changes on the technical properties of yarns sized with such starch products were investigated. It was found that the apparent viscosity of pastes prepared from those products depends on the nature of starch, the degree of oxidation prior to chemical modification, the nature of modification as well as the measuring conditions, i. e. the rate of shear and temperature. Cotton yarns sized using these starch derivatives were measured for yarn number, tensile strength, C.V.%, elongation at break and C.V.% in elongation. Besides, the weavability test expressed as the minimum number of cycles due to abrasion (St₁) and average number of cycles due to abrasion (St₆) were investigated. A comparison among modified starches prepared from rice starch would reveral that the highest value of St₁ is obtained with yarns sized using carbamoylethylated sample derived from unoxidized starch. With maize starch, on the other hand, the highest value of St₁ is obtained with cotton yarns sized using carbamoylethylated starch derived from starch oxidized by 1 g/l active chlorine.     

Dielectric study of β-relaxation in some cellulosic substances

6-(2-Cyanoethylamino)-6-deoxycellulose (Cell-CEA) as a novel cellulose derivative was prepared from 6-bromo-6-deoxycellulose. The influence of the reaction conditions on the degree of substitution was studied in detail. The dielectric characteristics of a Cell-CEA sample having degree of substitution of 0.86, together with those of microcrystalline and regenerated celluloses, have been investigated in the temperature range from −60 to 120°C, and frequency range 30 Hz to 100kHz. One relaxation process, designated as β, was recognised, which was attributed to side-group motions, probably −CH₂X (X = OH or NHCH₂CH₂CN). The higher activation energy of this process and the shift to higher temperature in Cell-CEA, compared with microcrystalline and regenerated celluloses, reflects the enhanced steric constraints involved in the motion of the bulkier, −CH₂NHCH₂CH₂CN, side groups. The results obtained are discussed in terms of the dielectric parameters ϵ″_max′ β and Δϵ.