Engineering design approaches for minimum fouling in submerged MBR

A contributor to success in managing membrane operations is to be able to identify suitable engineering design approaches to slow down the membrane fouling rate. Two such approaches were discussed in this study, namely: (1) offsite chemical and mechanical cleaning, and (2) air scouring. A longer subsequent operation time was observed after a membrane was cleaned chemically compared with mechanically. For air scouring during membrane operation, the investigation aimed at determining the crossflow velocity induced by coarse and fine bubble diffusers. Higher crossflow velocities were obtained with the latter. Uniformly distributed fine air bubbling might possibly have caused less uplift resistance and induced higher crossflow velocities. Such air scouring, at critical aeration intensity, was able to prolong the membrane operation for up to 8 months without needing chemical or mechanical cleaning.     

Effect of mechanical and air-particle cleansing protocols of provisional cement on immediate dentin sealing layer and subsequent adhesion of resin composite cement

Immediate dentin sealing (IDS) could avoid contamination of dentin from impression material and provisional cement but prior to final cementation of indirect restorations, removal of the provisional cement may damage the IDS. The objectives of this study were to investigate the effect of mechanical and air-particle cleansing protocols of provisional cement on IDS layer and subsequent adhesion of resin composite cement. The cuspal dentin surfaces of human third molars (N = 21, n_quadrant = 84) were exposed by a low-speed diamond saw under water cooling and conditioned with an adhesive system based on the three-step etch and rinse technique (OptiBond FL). Provisional cement (Freegenol) was applied on each specimen. They were then randomly divided into six subgroups where the provisional cement was removed either by (1) air-borne particle abrasion with 50-μm Al₂O₃ particles at 2 bar (AL2), (2) air-borne particle abrasion with 50-μm Al₂O₃ particles at 3.5 bar (AL3.5), (3) air-borne particle abrasion with 30-μm SiO₂ particles at 2 bar (SL2), (4) air-borne particle abrasion with 30-μm SiO₂ particles at 3.5 bar (SL3.5), (5) prophylaxy paste (Cleanic) (PP) or (6) pumice-water slurry (PW) at 1500 rpm for 15 s. The dentin surface on each tooth was assigned to four quadrants and each quadrant received the cleansing methods in a clockwise sequence. The non-contaminated and non-cleansed teeth acted as the control (C). Two separate teeth, contaminated and cleansed according to six cleansing protocols, were allocated for scanning electron microscopy (SEM) analysis (×2000). The dentin surfaces in each quadrant received resin composite luting cement (Variolink II, Ivoclar Vivadent) incrementally in a polyethylene mould (diameter: 1 mm²; height: 4 mm) and photopolymerized. The specimens were stored in distilled water for 24 h at 37 °C until the testing procedures and then shear force was applied to the adhesive interface until failure occurred in a universal testing machine (0.5 mm/min). Microshear bond (μSBS) was calculated by dividing the maximum load (N) by the bonding surface area of the resin cement. Failure types were analysed using optical microscope and SEM. Data (MPa) were analysed using one-way ANOVA (α = 0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (₀), values were calculated. Mean μSBS results (MPa) showed a significant difference between the experimental groups (p = 0.011) and were in a descending order as follows: C (8 ± 2.3)^a < AL2 (6.7 ± 2.4)^b < PP (6.9 ± 2)^b < PW (6.5 ± 2.1)^b < AL3.5 (5.8 ± 1.1)^b < SL2 (5.3 ± 1)^b < SL3.5 (5.2 ± 1)^b. Failure types were predominantly mixed failure type between the dentin and the adhesive resin which is a combination of adhesive and cohesive failures in the adhesive resin. Cohesive failure in the dentin was not observed in any of the groups. Weibull distribution presented lower shape (₀) for C (3.9), AL2 (3.2), PP (3.5) and PW (3.6). SEM analysis showed rough surfaces especially in the air-abraded groups whereas mechanical cleansing methods presented smoother surfaces and partially covered by particle remnants all of which occluded the dentin tubuli.     

Metabolic and DNA Repair Variations in Susceptibility to Genotoxins

An overview on the influence of metabolic and DNA repair polymorphisms on biological indicators of genotoxic risk in occupational, environmental, or lifestyle exposure is presented in this article. Indicators of genotoxic risk include biomarkers of internal dose (urinary concentration of the substance or its metabolites and urinary mutagenicity), biological effective dose (protein and DNA adducts), and indicators of early biological effects (chromosome aberrations, sister chromatid exchanges, micronuclei, COMET assay, HPRT mutants). Genetic polymorphisms include those involved in the activation and detoxification (i.e., P-450 cytochrome, acetyltransferase, glutathione transferase) of various classes of carcinogens and the newly discovered polymorphisms affecting DNA repair enzymes. Genetic polymorphisms are assessed for their importance in detecting the impact of genotype on biological indicators of genotoxic risk.     

Regulation by Different Types of Chaperones of Amyloid Transformation of Proteins Involved in the Development of Neurodegenerative Diseases

The review highlights various aspects of the influence of chaperones on amyloid proteins associated with the development of neurodegenerative diseases and includes studies conducted in our laboratory. Different sections of the article are devoted to the role of chaperones in the pathological transformation of alpha-synuclein and the prion protein. Information about the interaction of the chaperonins GroE and TRiC as well as polymer-based artificial chaperones with amyloidogenic proteins is summarized. Particular attention is paid to the effect of blocking chaperones by misfolded and amyloidogenic proteins. It was noted that the accumulation of functionally inactive chaperones blocked by misfolded proteins might cause the formation of amyloid aggregates and prevent the disassembly of fibrillar structures. Moreover, the blocking of chaperones by various forms of amyloid proteins might lead to pathological changes in the vital activity of cells due to the impaired folding of newly synthesized proteins and their subsequent processing. The final section of the article discusses both the little data on the role of gut microbiota in the propagation of synucleinopathies and prion diseases and the possible involvement of the bacterial chaperone GroE in these processes.     

Microstructure of Reaction Zone Formed During Diffusion Bonding of TiAl with Ni/Al Multilayer

In this article, the characterization of the interfacial structure of diffusion bonding a TiAl alloy is presented. The joining surfaces were modified by Ni/Al reactive multilayer deposition as an alternative approach to conventional diffusion bonding. TiAl substrates were coated with alternated Ni and Al nanolayers. The nanolayers were deposited by dc magnetron sputtering with 14 nm of period (bilayer thickness). Joining experiments were performed at 900 °C for 30 and 60 min with a pressure of 5 MPa. Cross sections of the joints were prepared for characterization of their interfaces by scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), high resolution TEM (HRTEM), energy dispersive x-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Several intermetallic compounds form at the interface, assuring the bonding of the TiAl. The interface can be divided into three distinct zones: zone 1 exhibits elongated nanograins, very small equiaxed grains are observed in zone 2, while zone 3 has larger equiaxed grains. EBSD analysis reveals that zone 1 corresponds to the intermetallic Al₂NiTi and AlNiTi, and zones 2 and 3 to NiAl.     

Discovery of novel non-cyclam polynitrogenated CXCR4 coreceptor inhibitors

HIV cell fusion and entry have been validated as targets for therapeutic intervention against infection. Bicyclams were the first low-molecular-weight compounds to show specific interaction with CXCR4. The most potent bicyclam was AMD3100, in which the two cyclam moieties are tethered by a 1,4-phenylenebis(methylene) bridge. It was withdrawn from clinical trials owing to its lack of oral bioavailability and cardiotoxicity. We have designed a combinatorial library of non-cyclam polynitrogenated compounds by preserving the main features of AMD3100. At least two nitrogen atoms on each side of the p-phenylene moiety, one in the benzylic position and the other(s) in the heterocyclic system were maintained, and the distances between them were similar to the nitrogen atom distances in cyclam. A selection of diverse compounds from this library were prepared, and their in vitro activity was tested in cell cultures against HIV strains. This led to the identification of novel potent CXCR4 coreceptor inhibitors without cytotoxicity at the tested concentrations.     

The corrin moiety of coenzyme B12 is the determinant for switching the btuB riboswitch of E. coli

Riboswitches are regulatory elements in the 5'-untranslated region (5'-UTR) of bacterial mRNAs that bind certain metabolites with high specificity and affinity. The 202 nucleotide (nt)-long btuB riboswitch RNA of E. coli interacts specifically with coenzyme B12 and its derivatives thereby leading to changes in the RNA structure and hence to an altered expression of the downstream btuB gene. We report the investigations of the rearrangement of the three-dimensional structure of the btuB riboswitch upon binding to four different B12 derivatives: coenzyme B12, vitamin B12, adenosyl factor A and adenosyl-cobinamide. In-line probing experiments have shown that the corrin ring plays the crucial role in switching the three-dimensional riboswitch structure. Instead, the apical ligands influence only the binding affinity of the B12 derivative to the btuB riboswitch.     

NiCrSiBC alloy: microstructure and hardness of coatings processed by arc and laser

The processing technique is decisive for the characteristics of a coating. This is because the heat supply, which depends on the technique and on the parameters, has an influence on the dilution and the solidification rate. In alloys with low metallurgical complexity, the effect of processing with deposition techniques that give a higher cooling rate may be translated into refining of the microstructure. A more refined microstructure is expected to result in higher mechanical strength of the coating. However, in the deposition of alloys that are more complex metallurgically this does not always occur, because the high cooling rate may suppress formation/precipitation of phases responsible for strength. The influence of processing on the microstructure and hardness of coatings of alloy Colmonoy-6^® was assessed in this study. The alloy was processed by plasma transferred arc and high-power diode laser on plates of AISI 304 with two levels of dilution. In both cases, good-quality, defect-free coatings were obtained. Increase in Fe content (dilution) and different cooling rates result from processing with different parameters and techniques. This leads to significant changes in microstructure and hardness of the coatings, associated with the distribution, morphology and chemical composition of the carbides and particularly of the borides.