Environmental Enhancement Through Use of Recycled Aggregate Concrete in a Two-Stage Mixing Approach

As a high priority of waste management and recycling by the Hong Kong government, Recycled Aggregate (RA) has been used in various construction applications, mainly as sub-grade, roadwork, and unbound materials. However, higher-grade applications are rare. The major barrier encountered is the variation of quality within RA, which causes lower strength, resulted from crystallization of Recycled Aggregate Concrete (RAC). Therefore, the objective of this study is to examine the crystallization of RAC in a Two-Stage Mixing Approach. Following are the five areas of interest: (i) investigate the waste problems in construction activities; (ii) examine the crystal development on the hydration of cement paste; (iii) develop a two-stage mixing approach (TSMA) for improving the performance of RAC; (iv) explore the crystallization of TSMA in comparison with the Normal Mixing Approach (NMA) through use of Differential Scanning Calorimetry (DSC); and (v) verify the results obtained from DSC analysis with those obtained from compressive strength testing. This study adopted 0, 20, and 100% RA substitution in virgin aggregate and measured by DSC and compressive strength on both TSMA and NMA. TSMA uses only half the water for mixing, forming a thin layer of cement slurry on the surface of RA that will permeate into the porous old cement mortar and fill old cracks and voids in the pre-mix process. The results from DSC analysis clearly demonstrated that TSMA can give a better crystallization of CaO·SiO₂·H₂O [CSH] and Ca(OH)₂[CH]. The optimal situation occurs on 20% RA substitution in virgin aggregate, balancing the advantages of each, a finding supported by the results from compressive strength testing. Therefore, TSMA is a superior methodology and opens a wider application for the use of RAC.     

Foot-and-Mouth Disease Virus Modulates Cellular Vimentin for Virus Survival

Foot-and-mouth disease virus (FMDV), the causative agent of foot-and-mouth disease, is an Aphthovirus within the Picornaviridae family. During infection with FMDV, several host cell membrane rearrangements occur to form sites of viral replication. FMDV protein 2C is part of the replication complex and thought to have multiple roles during virus replication. To better understand the role of 2C in the process of virus replication, we have been using a yeast two-hybrid approach to identify host proteins that interact with 2C. We recently reported that cellular Beclin1 is a natural ligand of 2C and that it is involved in the autophagy pathway, which was shown to be important for FMDV replication. Here, we report that cellular vimentin is also a specific host binding partner for 2C. The 2C-vimentin interaction was further confirmed by coimmunoprecipitation and immunofluorescence staining to occur in FMDV-infected cells. It was shown that upon infection a vimentin structure forms around 2C and that this structure is later resolved or disappears. Interestingly, overexpression of vimentin had no effect on virus replication; however, overexpression of a truncated dominant-negative form of vimentin resulted in a significant decrease in viral yield. Acrylamide, which causes disruption of vimentin filaments, also inhibited viral yield. Alanine scanning mutagenesis was used to map the specific amino acid residues in 2C critical for vimentin binding. Using reverse genetics, we identified 2C residues that are necessary for virus growth, suggesting that the interaction between FMDV 2C and cellular vimentin is essential for virus replication.     

Depletion interaction in colloid/polymer mixtures: application of density functional theory

Insert-route density functional approach (IRDFT), modified fundamental measure theory (MFMT) and thermodynamic perturbation theory (TPT1 and TPT2) are combined to study the depletion force between colloidal particles in hard sphere/hard sphere chain mixtures which represent a model of systems containing colloids dispersed in an athermal polymer solution. The predicted results are compared to simulations showing the reliability of the method used which captures the main characteristics of depletion interaction between colloids induced by polymers. Results of TPT2 are slightly more repulsive and better than that of TPT1 especially when the inter-particle distance is small than the diameter of polymer segment indicating the essential influence of the three-body correlations. Effects of the polymer density, polymer chain length and size ratio of colloid to polymer segment on the depletion force are studied in detail. Due to a little deterioration of the prediction in the high density region, further improvement is anticipated to better balance the competition between the excluded-volume effect and the chain connectivity.     

Dissipative particle dynamics simulation on the meso-scale structure of diblock copolymer under cylindrical confinement

The meso-scale structure of symmetric diblock copolymer under cylindrical confinement is studied by dissipative particle dynamics (DPD). The simulation results show that coiled cylindrical geometry is favored in the presence of larger cylinder radius (R/L ₀>～1.5), and the number of rings depends on the cylinder radius. Because of the cylinder wall's selectivity, each block can form the central core, but only the preferential block forms the outmost layer. An approximately linear relationship exists between structure transition point, which is approximately in proportion to the 3/5 exponential of chain length of copolymer and number of layers. As the cylinder radius is decreased, a helical morphology is found. Lamellae parallel to the underside of the cylinder appear when the cylinder radius is made smaller (R/L ₀ < ～1.1).     

An amylase from fresh fruiting bodies of the monkey head mushroom Hericium Erinaceum

An amylase with a molecular mass of 55 kDa and an N-terminal sequence exhibiting similarity to enzyme from Bacteroides thetaitaomicron was isolated from fruiting bodies of the monkey head mushroom Hericium erinaceum. The purification scheme included extraction with distilled water, ion exchange chromatography on DEAE-cellulose and SP-sepharose, and gel filtration by FPLC on Superdex 75. The amylase of H. erinaceum was adsorbed on DEAE-cellulose in 10 mM Tris-HCl buffer (pH 7.4) and eluted with 0.2 M NaCl in the same buffer. The enzyme was subsequently adsorbed on SP-Sepharose in 10 mM ammonium acetate buffer (pH 4.5) and eluted with 0.3 M NaCl in the same buffer. This fraction was subsequently subjected to gel filtration on Superdex 75. The first peak eluted had a molecular mass of 55 kDa in SDS-PAGE. The amylase of H. erinaceum exhibited a pH optimum of 4.6 and a temperature optimum of 40°C. The enzyme activity was enhanced by Mn²⁺ and Fe³⁺ ions, but inhibited by Hg²⁺ ions.     

Differential effect of long-term drug selection with doxorubicin and vorinostat on neuroblastoma cells with cancer stem cell characteristics

Numerous studies have confirmed that cancer stem cells (CSCs) are more resistant to chemotherapy; however, there is a paucity of data exploring the effect of long-term drug treatment on the CSC sub-population. The purpose of this study was to investigate whether long-term doxorubicin treatment could expand the neuroblastoma cells with CSC characteristics and histone acetylation could affect stemness gene expression during the development of drug resistance. Using n-myc amplified SK-N-Be(2)C and non-n-myc amplified SK-N-SH human neuroblastoma cells, our laboratory generated doxorubicin-resistant cell lines in parallel over 1 year; one cell line intermittently treated with the histone deacetylase inhibitor (HDACi) vorinostat and the other without exposure to HDACi. Cells'' sensitivity to chemotherapeutic drugs, the ability to form tumorspheres, and capacity for in vitro invasion were examined. Cell-surface markers and side populations (SPs) were analyzed using flow cytometry. Differentially expressed stemness genes were identified through whole genome analysis and confirmed with real-time PCR. Our results indicated that vorinostat increased the sensitivity of only SK-N-Be(2)C-resistant cells to chemotherapy, made cells lose the ability to form tumorspheres, and reduced in vitro invasion and the SP percentage. CD133 was not enriched in doxorubicin-resistant or vorinostat-treated doxorubicin-resistant cells. Nine stemness-linked genes (ABCB1, ABCC4, LMO2, SOX2, ERCC5, S100A10, IGFBP3, TCF3, and VIM) were downregulated in vorinostat-treated doxorubicin-resistant SK-N-Be(2)C cells relative to doxorubicin-resistant cells. A sub-population of cells with CSC characteristics is enriched during prolonged drug selection of n-myc amplified SK-N-Be(2)C neuroblastoma cells. Vorinostat treatment affects the reversal of drug resistance in SK-N-Be(2)C cells and may be associated with downregulation of stemness gene expression. This work may be valuable for clinicians to design treatment protocols specific for different neuroblastoma patients.     

A Single Carbocyclic Nucleotide Substitution in a 12mer DNA Gives a Hoogsteen Basepaired Duplex (Till 38°C) and a Hairpin (Till 65°C). A 600 MHz NMR Spectroscopic Study

Abstract

The impact of intramolecular stereoelectronic effects has been examined by comparison of the solution structures of natural oligo-DNA duplex, 5′(¹C²G³C⁴G⁵A⁶A⁷T⁸T⁹C¹⁰G¹¹C¹²G)₂ ³′, and its carbocyclic-nucleotide analogues in which the pentose sugar in 2′-dA residue is replaced with its carbocyclic counterpart (i.e. 2′-deoxyaristeromycin). Based on the NMR evidences, it has been shown, that 2′-deoxyaristeromycin analog exists in a dynamic equilibrium between the two forms of duplexes, one with W-C bp and the second with Hoogsteen bp in ca 1:1 ratio at lower temperature (below 35°C) and as hairpin at higher temperature (from ～40° – 60°C).