Data-Based Statistical Analysis of Laboratory Experiments on Concrete Frost Damage and Its Implications on Service Life Prediction.

To meet the requirements of durability design for concrete suffering frost damage, several test standards have been launched. Among the various damage indexes such as deteriorated compressive strength, relative dynamic elastic modulus (RDEM), residual deformation, etc., the concept of a "Durability Factor" (DF) is proposed by many standards to define the frost resistivity of concrete against frost action based on the experimental results from standard tests. Through a review of the literature, a clear tendency of strength/RDEM decay and residual deformation increase is captured with increasing cycles of freezing and thawing. However, tests following different standards finally derive huge scattering quantitative responses of frost resistance. Based on the large database of available laboratory experiments, this study presents a statistical analysis to propose a predictable model to calculate the DF with respect to other material factors. The statistical model is believed to be more convenient for engineering applications since the time-consuming experiment is no longer needed, and it is more precise compared with that developed according to only single experimental results to cover the uncertainties and unavoidable errors in specific tests. Moreover, the formula to calculate the DF is revised into a more general form so as to be applicable for all the laboratory experiments even for those cases without fully following the standards to derive a DF value.

Heat stress interferes with formation of double-strand breaks and homolog synapsis.

Meiotic recombination (MR) drives novel combinations of alleles and contributes to genomic diversity in eukaryotes. In this study, we showed that heat stress (36°C-38°C) over the fertile threshold fully abolished crossover formation in Arabidopsis (Arabidopsis thaliana). Cytological and genetic studies in wild-type plants and syn1 and rad51 mutants suggested that heat stress reduces generation of SPO11-dependent double-strand breaks (DSBs). In support, the abundance of recombinase DMC1, which is required for MR-specific DSB repair, was significantly reduced under heat stress. In addition, high temperatures induced disassembly and/or instability of the ASY4- but not the SYN1-mediated chromosome axis. At the same time, the ASY1-associated lateral element of the synaptonemal complex (SC) was partially affected, while the ZYP1-dependent central element of SC was disrupted, indicating that heat stress impairs SC formation. Moreover, expression of genes involved in DSB formation; e.g. SPO11-1, PRD1, 2, and 3 was not impacted; however, recombinase RAD51 and chromosome axis factors ASY3 and ASY4 were significantly downregulated under heat stress. Taken together, these findings revealed that heat stress inhibits MR via compromised DSB formation and homolog synapsis, which are possible downstream effects of the impacted chromosome axis. Our study thus provides evidence shedding light on how increasing environmental temperature influences MR in Arabidopsis.

Heat stress interferes with chromosome segregation and cytokinesis during male meiosis in Arabidopsis thaliana.

In higher plants, male meiosis is a key process of microsporogenesis and is crucial for plant fertility. Male meiosis programs are prone to be influenced by altered temperature conditions. Studies have reported that an increased temperature (28°C) within a fertile threshold can affect the frequency of meiotic recombination in Arabidopsis. However, not much has been known how male meiosis responses to an extremely high temperature beyond the fertile threshold. To understand the impact of extremely high temperature on male meiosis in Arabidopsis, we treated flowering Arabidopsis plants with 36-38°C and found that the high-temperature condition significantly reduced pollen shed and plant fertility, and led to formation of pollen grains with varied sizes. The heat stress-induced unbalanced tetrads, polyad and meiotic restitution, suggesting that male meiosis was interfered. Fluorescence in situ hybridization (FISH) assay confirmed that both homologous chromosome separation and sister chromatids cohesion were influenced. Aniline blue staining of tetrad-stage pollen mother cells (PMCs) revealed that meiotic cytokinesis was severely disrupted by the heat stress. Supportively, immunolocalization of ɑ-tubulin showed that the construction of spindle and phragmoplast at both meiosis I and II were interfered. Overall, our findings demonstrate that an extremely high-temperature stress over the fertile threshold affects both chromosome segregation and cytokinesis during male meiosis by disturbing microtubular cytoskeleton in Arabidopsis.

Purification, characterization, and cloning of an extracellular laccase with potent dye decolorizing ability from white rot fungus Cerrena unicolor GSM-01.

A novel laccase was purified from fermentation broth of the white rot fungus Cerrena unicolor strain GSM-01 following three ion-exchange chromatography steps and one gel-filtration step. The purified enzyme was determined to be a monomeric protein of 63.2kDa and demonstrated high oxidation activity of 2.05×104U/mg towards ABTS. Its cDNA, gene, and amino acid sequences were obtained. It possessed high sequence similarity with that of other laccases but different enzymatic properties. It manifested optimal pH and temperature of 2.6 and 45°C, respectively. Fe3+ and Fe2+ were the most efficient inhibitors towards Cerrena unicolor laccase (CUL), while Mn2+ can slightly enhance the laccase activity of 3.8-10.5%. The Km and Vmax of CUL were estimated to 302.7µM and 13.6µMm-1, respectively. CUL was effective in the decolorization of bromothymol blue, evans blue, methyl orange, and malachite green with decolorization efficiencies of 50%-85%. It possesses potential application in textile and environmental industries.

An extracellular yellow laccase with potent dye decolorizing ability from the fungus Leucoagaricus naucinus LAC-04.

A novel laccase was isolated from fermentation broth of the mycorrhizal fungus Leucoagaricus naucinus LAC-04 by using a protocol that comprising ion-exchange chromatography steps on DEAE-cellulose, SP-Sepharose, and Q-Sepharose, and finally gel filtration by fast protein liquid chromatography on Superdex 75. The laccase (LNL) was purified with a purification fold of 21.19 and a recovery rate of 19.8%. It is a monomeric protein with a molecular mass of 56kDa. LNL lacks absorption around 600nm, which indicates that the purified laccase is a yellow laccases. LNL demonstrates an optimal pH of 2.2 and an optimal temperature range of 30-60°C using ABTS as the substrate. It is inhibited in the presence of EDTA and metal ions including Cd2+, Co2+, Cu2+. The Km of the laccase towards ABTS is estimated to 50.12µM at pH 2.2 and 30°C. Moreover, the purified laccase manifests effective decolorizing activity towards azo, heterocyclic, and aromatic dyes including Bromothymol Blue, Eriochrome Black T, Evans Bue, Fuchsin Basic, and Remazol Brilliant Blue R.

An extracellular laccase with potent dye decolorizing ability from white rot fungus Trametes sp. LAC-01.

A novel laccase was purified from fermentation broth of white rot fungus Trametes sp. LAC-01 using an isolation procedure involving three ion-exchange chromatography steps on DEAE-cellulose, SP-Sepharose, and Q-Sepharose, and one gel-filtration step. The purified enzyme (TSL) was proved as a monomeric protein with a Mr of 59kDa based on SDS-PAGE and FPLC. Partial amino acid sequences were obtained by LC-MS/MS sharing considerably high sequence similarity with that of other laccases. It possessed optimal pH of 2.6 and temperature of 60°C using ABTS as the substrate. The Km of the laccase toward ABTS was estimated to 30.28µM at pH 2.6 and 40°C. TSL manifested considerably high oxidizing activity toward ABTS, but was avoid of degradative activity toward benzidine, caftaric acid, etc. It was effective in the decolorization of phenolic dyes - Bromothymol Blue and Malachite Green with decolorization rate higher than 60% after 24h of incubation. Adjunction of Cu(2+) with the final concentration of 2.0mmol/L significantly activated laccase production with a steady high level of 275.8-282.2U/mL in 96-144h. The high yield and short production period makes Trametes sp. LAC-01 and TSL potentially useful for industrial and environmental application and commercialization.