Shear wave induced resonance elastography of soft heterogeneous media

In the context of ultrasound dynamic elastography imaging and characterization of venous thrombosis, we propose a method to induce mechanical resonance of confined soft heterogeneities embedded in homogenous media. Resonances are produced by the interaction of horizontally polarized shear (SH) waves with the mechanical heterogeneity. Due to such resonance phenomenon, which amplifies displacements up to 10 times compared to non-resonant condition, displacement images of the underlying structures are greatly contrasted allowing direct segmentation of the heterogeneity and a more precise measurement of displacements since the signal-to-noise ratio is enhanced. Coupled to an analytical model of wave scattering, the feasibility of shear wave induced resonance (SWIR) elastography to characterize the viscoelasticity of a mimicked venous thrombosis is demonstrated (with a maximum variability of 3% and 11% for elasticity and viscosity, respectively). More generally, the proposed method has the potential to characterize the viscoelastic properties of a variety of soft biological and industrial materials.     

On dimension reduction of clustering results in structural bioinformatics

OPTICS is a density-based clustering algorithm that performs well in a wide variety of applications. For a set of input objects, the algorithm creates a reachability plot that can either be used to produce cluster membership assignments, or interpreted itself as an expressive two-dimensional representation of the clustering structure of the input set, even if the input set is embedded in higher dimensions. The focus of this work is a visualization method that can be applied for comparing two, independent hierarchical clusterings by assigning colors to all entries of the input database. We give two applications related to macromolecular structural properties: the first is a sequence-based clustering of the SwissProt database that is evaluated using NCBI taxonomy identifiers, and the second application involves clustering locations of specific atoms in the serine protease enzyme family—and the clusters are evaluated using SCOP structural classifications.     

Pythium intermedium,a species complex consisting of three phylogenetic species found in cool-temperate forest ecosystems

Pythium intermedium plays a vital role in the carbon cycle of cool-temperate forests and is widely distributed in Japan's forest soils. In this study, we performed a phylogenetic analysis of the P. intermedium species complex using DNA sequences from multiple loci. The study included 35 isolates from cool-temperate forest soils, seven known P. intermedium isolates, and six known Pythium attrantheridium isolates. We also performed morphological observations and mating tests. Our results showed that all the isolates formed one large clade but were divided into three subclades. Furthermore, we observed many mating reactions between isolates from different subclades, including between P. attrantheridium and P. intermedium. Therefore, we suggest that P. intermedium, P. attrantheridium, and another phylogenetic species belong to one species complex. This is the first report of a species complex within P. intermedium and will be helpful in understanding the evolution of Pythium species in natural ecosystems.     

Carbon nanotubes promote Cr(VI) reduction by alginate-immobilized Shewanella oneidensis MR-1

Bioreduction of hexavalent chromium (Cr(VI)) into trivalent one (Cr(III)) based on microbial immobilization techniques has been recognized as a promising way to remove Cr contaminants from wastewater. However, such a bioreduction process is inefficient due to limited electron transfer through the immobilization matrix. In this study, a modified immobilization process was proposed by impregnating carbon nanotubes (CNTs) into Ca-alginate beads, which were then used to immobilize Shewanella oneidensis MR-1 for enhanced Cr(VI) reduction. Compared with the free cells and the beads without CNTs, the AL/CNT/cell beads showed up to 4 times higher reduction rates, mainly attributed to an enhanced electron transfer by the CNTs. In addition, the dose of CNTs greatly improved the stability of beads, suggesting a high feasibility of the AL/CNT/cell beads for repeated use. The optimized CNT concentration, temperature and pH for Cr(VI) reduction by the AL/CNT/cell beads were 0.5%, 30 °C and 6.0–7.0, respectively.     

Influence of Bio-Lubricants on the Tribological Properties of Ti6Al4V Alloy

Titanium alloy is one of the best materials for biomedical applications due to its superior biocompatibility, outstanding corrosion resistance, and low elastic modulus. However, the friction and wear behaviors of titanium alloys were sensitive to the environment including lubrication. In order to clarify the wear mechanism of titanium alloy under different lubrications including deionized water, physiological saline and bovine serum, the friction and wear tests were performed between Ti6Al4V plates and Si₃N₄ ball on a universal multi-functional tester. The friction and the wear rate of titanium alloy were measured under dry friction and three different lubrication conditions. The worn surfaces were examined by scanning electron microscopy. The results revealed that under the dry friction, the wear resistance of titanium alloy was the worst since the wear mechanism was mainly the combination of abrasive wear and oxidation wear. It was also found that Ti6Al4V alloy had low friction coefficient and wear rate under three lubrication conditions, and its wear mechanism was adhesive wear.     

中华补血草内生与根际具ACC脱氨酶活性细菌的筛选及其生物多样性

【目的】获得江苏沿海滩涂盐生药用植物中华补血草内生及根际具有1-氨基环丙烷-1-羧酸(ACC)脱氨酶活性的细菌,研究其遗传多样性和潜在促生活性。【方法】从中华补血草和根际土壤分离筛选具有ACC脱氨酶活性的菌株,对其ACC脱氨酶活性定量检测,通过16S r RNA基因序列分析确定菌株系统发育地位。同时研究其固氮、溶磷、产植物生长素吲哚乙酸(IAA)及耐盐能力。【结果】分离筛选获得18株具有ACC脱氨酶活性的内生与根际细菌,定量检测发现其中有13株菌的ACC脱氨酶含量在20 nmolα-KA/(mg Pr·h)以上,有11株菌可以固氮,7株菌能够解磷,9株菌产生IAA。菌株的Na Cl盐耐受范围多数在0–13%之间。16S r RNA基因测序表明,活性菌株分属于7个属,多样性丰富,节杆菌属(Arthrobacter)为优势类群。其中菌株KLBMP 5180为节杆菌属的潜在新种。【结论】江苏沿海滩涂盐生药用植物中华补血草共生环境中具有丰富多样的具ACC脱氨酶活性的菌株,并存在潜在新物种资源,具有进一步研究价值。     

Enhanced CO2 biofixation and protein production by microalgae biofilm attached on modified surface of nickel foam

In this work, a photobioreactor with microalgae biofilm was proposed to enhance CO₂ biofixation and protein production using nickel foam with the modified surface as the carrier for immobilizing microalgae cells. The results demonstrated that, compared with microalgae suspension, microalgae biofilm lowered mass transfer resistance and promoted mass transfer efficiency of CO₂ from the bubbles into the immobilized microalgae cells, enhancing CO₂ biofixation and protein production. Moreover, parametric studies on the performance of the photobioreactor with microalgae biofilm were also conducted. The results showed that the photobioreactor with microalgae biofilm yielded a good performance with the CO₂ biofixation rate of 4465.6 µmol m⁻³ s⁻¹, the protein concentration of effluent liquid of 0.892 g L⁻¹, and the protein synthesis rate of 43.11 g m⁻³ h⁻¹. This work will be conducive to the optimization design of microalgae culture system for improving the performance of the photobioreactor.