A Concrete Core Void Imaging Approach and Parameter Analysis of Concrete-Filled Steel Tube Members Using Travel Time Tomography: Multi-Physics Simulations and Experimental Studies.

Concrete-filled steel tube (CFST) members have been widely used in civil engineering due to their advanced mechanical properties. However, internal defects such as the concrete core voids and interface debonding in CFST structures are likely to weaken their load-carrying capacity and stiffness, which affects the safety and serviceability. Visualizing the inner defects of the concrete cores in CFST members is a critical requirement and a challenging task due to the obvious difference in the material mechanical parameters of the concrete core and steel tube in CFST members. In this study, a curved ray theory-based travel time tomography (TTT) with a least square iterative linear inversion algorithm is first introduced to quantitatively identify and visualize the sizes and positions of the concrete core voids in CFST members. Secondly, a numerical investigation of the influence of different parameters on the inversion algorithm for the defect imaging of CFST members, including the effects of the model weighting matrix, weighting factor and grid size on the void's imaging quality and accuracy, is carried out. Finally, an experimental study on six CFST specimens with mimicked concrete core void defects is performed in a laboratory and the mimicked defects are visualized. The results demonstrate that TTT can identify the sizes and positions of the concrete core void defects in CFST members efficiently with the use of optimal parameters.

An electrochemical biosensor for the amplification of thrombin activity by perylene-mediated photoinitiated polymerization.

BACKGROUND: Thrombin, a coagulation system protease, is a key enzyme involved in the coagulation cascade and has been developed as a marker for coagulation disorders. However, the methods developed in recent years have the disadvantages of complex operation, long reaction time, low specificity and sensitivity. Meanwhile, thrombin is at a lower level in the pre-disease period. Therefore, to accurately diagnose the disease, it is necessary to develop a fast, simple, highly sensitive and specific method using signal amplification technology. RESULTS: We designed an electrochemical biosensor based on photocatalytic atom transfer radical polymerization (photo-ATRP) signal amplification for the detection of thrombin. Sulfhydryl substrate peptides (without carboxyl groups) are self-assembled to the gold electrode surface via Au-S bond and serve as thrombin recognition probes. The substrate peptide is cleaved in the presence of thrombin to generate -COOH, which can form a carboxylate-Zr(IV)-carboxylate complex via Zr(IV) and initiator (α-bromophenylacetic acid, BPAA). Subsequently, an electrochemical biosensor was prepared by introducing polymer chains with electrochemical signaling molecules (ferrocene, Fc) onto the electrode surface by photocatalytic (perylene, Py) mediated ATRP using ferrocenylmethyl methacrylate (FMMA) as a monomer. The concentration of thrombin was evaluated by the voltammetric signal generated by square wave voltammetry (SWV), and the result showed that the biosensor was linear between 1.0 ng/mL âˆ¼ 10 fg/mL, with a lower detection limit of 4.0 fg/mL (∼0.1 fM). Moreover, it was shown to be highly selective for thrombin activity in complex serum samples and for thrombin inhibition screening. SIGNIFICANCE: The biosensor is an environmentally friendly and economically efficient strategy while maintaining the advantages of high sensitivity, anti-interference, good stability and simplicity of operation, which has great potential for application in the analysis of complex samples.

Cyanocobalamin (VB12) Bionic Enzyme-Assisted Photocatalytic Chain-Growth Polymerization for Detection of Lung Cancer Biomarkers.

Cobalt-mediated radical polymerization is noted for its great level of control over the polymerization of acrylic and vinyl esters monomers, even at high molar mass. Vitamin B12, a natural bionic enzyme cobalt complex, involves the conversion of organic halides to olefins through chain-growth polymerization. In this work, the notion of R-Co(III) free radical persistent free radical effect and vitamin B12 circulation were first reported for the perception of ultralow abundance of microRNA-21, a lung cancer biomarker. Indeed, most Co-containing catalytic reactions can occur under mild conditions due to their minimal bond dissociation of the C-Co bond, with blue light irradiation. Based on the intrinsic stability of the vitamin B12 framework and recycling of the catalyst, it is evident that this natural catalytic scheme has potential applications in medicinal chemistry and biomaterials. In addition, this strategy, combined with highly specific recognition probes and vitamin B12 circulation-mediated chain-growth polymerization, has a detection limit as low as 910 aM. Furthermore, it is sensitive for sensing in serum samples containing biomarkers and shows great potential for RNA selection and amplification sensing in clinical samples.

Ultrasensitive miRNA-21 Biosensor Based on Zn(TCPP) PET-RAFT Polymerization Signal Amplification and Multiple Logic Gate Molecular Recognition.

Quantitative measurement of microRNAs (miRNAs) is extremely important in plenty of biomedical applications especially cancer diagnosis but remains a great challenge. In this work, we developed a logic gate recognition biosensing platform based on the "trinity" molecular recognition mode for quantifying miRNAs with a detection limit of 4.48 aM, along with a linear range from 0.1 nM to 10 aM under optimal experimental conditions. In order to obtain excellent detection performance, we adopted a Zn(TCPP) photocatalytic electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization signal amplification strategy. The light-induced PET-RAFT has developed green applications of free radical polymerization in the field of biosensors. This is the first report on the preparation of signal amplification biosensors using PET-RAFT for tumor marker detection. With the outstanding detection performance, we can apply the sensor system to the early screening of lung cancer patients.

Stable nitronyl nitroxide monoradical MATMP as novel monomer of reversible addition fragmentation chain transfer (RAFT) polymerization for ultrasensitive DNA detection.

In this work, it came up a hydrophilic and stable nitronyl nitroxide monoradical 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine 1-oxyl freeradical (MATMP) as new monomer of polymerization for DNA detection. The detection limit was over 1,000,000 times lower than 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) derivatives as electrochemical labels alone. Within this approach, a single biomolecule can be converted into the strong electrochemical signal, therefore lung cancer DNA can be detected at low concentration. For the first step, the HS-PNA probe was fixed on the surface of the Au electrode. After the target DNA was captured by complementary base pairing, 4-cyano-4-(phenylcarbonothioylthio) pentanoic acid (CPAD), chain transfer agent of RAFT polymerization, was bonded to target DNA as reaction via coordination bond of Zr4+. Electroactive polymers had grown by means of surface initiated thermally RAFT polymerization with MATMP as monomer. MATMP polymer significantly improves the electrochemical signal. This method can detect DNA from 0.01 fM to 10 pM, and detection limit is 1.51 aM. The sensitivity of this method is greater than that in most other reported signal amplification strategies of DNA biosensor, which indicates that it is appropriate for single nucleotide polymorphism analysis and will broaden prospects for biological molecules detection application.

Hemoglobin-catalyzed atom transfer radical polymerization for ultrasensitive electrochemical DNA detection.

The use of hemoglobin (Hb) to drive atom transfer radical polymerization (ATRP) process (Hb-ATRP) for detection of lung cancer related nucleic acid is firstly reported. Hb does not need to be treated prior to using indicating the potential for synthetic engineering in complex biological microenvironments without the need for in vitro techniques. Here, we report a new signal amplification strategy using Hb-mediated graft of nitronyl niroxide monoradical polymers as a signal-on electrochemical biosensor for ultralow level DNA highly selective detection. Building DNA biosensors includes: (i) the fixation of peptide nucleic acid (PNA) probe (no phosphate group) via the 5' terminus-SH; (ii) the modification of transition metal; (iii) Site-specific markers of Hb-ATRP promoter, and (iv) the grafting of polymers with electrochemical signal by Hb-ATRP process. Through the Hb-ATRP process of nitronyl nitroxide monoradical (TEMPO), the presence of a small amount of DNA can eventually result in calling a certain number of TEMPO redox tags. Obviously, the Hb-ATRP is a method of easy source of raw materials, simple operation and no need for complex equipment. The constructed biosensor, as expected, is highly selective and sensitive to target DNA. The detection limit can be calculated as 15.96 fM under optimal conditions. The excellent performance also shows that the constructed DNA biosensor is suitable for DNA screening and DNA concentration determination in complex sample matrix.

A novel electrochemical biosensor for lung cancer-related gene detection based on copper ferrite-enhanced photoinitiated chain-growth amplification.

We reported an electrochemical biosensor via CuFe2O4-enhanced photoinitiated chain-growth polymerization for ultrasensitive detection of lung cancer-related gene. In this work, photoinitiated atom transfer radical polymerization (ATRP) was applied to amplify the electrochemical signal corresponding to lung cancer-related gene, and polymerization was triggered off under the illumination of blue light which was involved in copper-mediated reductive quenching cycle. At the same time, CuFe2O4-H2O2 system was also activated to enhance polymerization based on the photocatalysis of CuFe2O4, which was based on the reaction between •OH and methacrylic monomers to generate carbon-based radicals. Numerous ferrocene-based polymer was graft onto electrode surface through this amplification stages. The limit of detection was low to 1.98 aM (in 10 µL, ∼11.9 molecules) (R2 = 0.998) with a wide linear range from 0.1 fM to 10 pM. This strategy made a good trade-off between cost-effectiveness and sensitivity, and it also presented a high selectivity and anti-interference. In addition, the operation was greatly simplified and detection time was also shortened, which endowed this electrochemical DNA biosensor great application potential.

Effects and bioaccumulation of 17ß-estradiol and 17α-ethynylestradiol following long-term exposure in crucian carp.

Bioaccumulation and effects of 17ß-estradiol (E2) and 17α-ethynylestradiol (EE2) were assessed by crucian carp (Carassius auratus) following single and binary mixture exposures in flow-through exposure system for 16 months. In comparison with water control (DWC) and solvent control (SC), a significant reduction in body weight, body length and gonadosomatic index (GSI), and increase in hepatosomatic index (HSI) and plasma vitellogenin (VTG) levels were observed, in a time- and concentration-dependent manner. Bioconcentration factors (BCFs) of E2 and EE2 in fish muscle ranged from 3.2 to 40 and from 64 to 123, respectively. Crucian carp were found to be more sensitive to EE2 than E2. The bioaccumulation and toxicological effects in binary mixture exposed fish (mixture of E2 and EE2) were more significant than exposure of individual compound. Crucian carp is sensitive to E2 and EE2 in long-term laboratory exposure experiments and can be used as a potential model species for investigating the toxicity of hormones.

Occurrence, removal and bioaccumulation of steroid estrogens in Dianchi Lake catchment, China.

The occurrence, removal and bioaccumulation of steroid estrogens such as the natural estrone (E1), 17ß-estradiol (E2) and estriol (E3), as well as the synthetic 17α-ethynylestradiol (EE2) were investigated in Dianchi Lake catchment, China. The results show that traditional secondary treatment processes in eight sewage treatment plants (STPs) of Kunming were not efficient enough to completely remove steroid estrogens, but ultraviolet (UV) photodegradation in advanced treatment displayed more effectively for the removal of the residual compounds. The amount of total steroid estrogens (∑SEs) discharged to Dianchi Lake catchment by the eight STPs was 35.8g/day, in which STP-3 was the dominant source, accounting for 50.8%. Because of the pollution input from treated and untreated sewages, estrogens were widely detected in surface water and sediment samples collected from 21 inflow rivers of Dianchi Lake, 10 National Surface Water Quality Monitoring Sites of the lake itself and its unique outflow river, with the mean concentration of ∑SEs in the range of 5.3-798.2ng/L (water) and 3.7-202.4ng/g (dry weight, sediment), 1.5-39.2ng/L (water) and 2.7-20.9ng/g (sediment), and 4.2ng/L (water) and 6.6ng/g (sediment), respectively. Due to the continuous input of estrogens to Dianchi Lake from STPs and inflow rivers, present estrogen levels in various tissues of wild fish species sampled from the lake (2013) were higher than the values detected in the previous years (2009 and 2010). The bioaccumulation of steroid estrogens in wild fish species from different sampling sites was in the order of STP-5>Dianchi Lake (2013)>Dianchi Lake (2010)≈Dianchi Lake (2009)≫field control>laboratory control, which is mainly affected by exposure concentrations. By employing risk quotient (RQ), it is found that eco-toxicological risk of steroid estrogens in Dianchi Lake catchment was in a sequence of 22 rivers>effluents of eight STPs>Dianchi Lake (2013)>Dianchi Lake (2010), and high RQs were found in EE2, which should be controlled preferentially in this catchment.

Biological response of high-back crucian carp (Carassius auratus) during different life stages to wastewater treatment plant effluent.

This study presents the adverse effects of endocrine disrupting chemicals (EDCs) in effluent of wastewater treatment plants (WwTPs) on fish health. A study of chronic exposure to WwTPs effluent for 10 months was undertaken in high-back crucian carp (Carassius auratus) during different life stages, covering early-life-stage (ELS), prespawning period, and postspawning period. Condition factor (CF), gonadosomatic index (GSI), hepatosomatic index (HSI), and plasma vitellogenin (VTG) levels were employed as indicators to assess biological effects of effluent on this gynogenesis species. Meanwhile, some high-back crucian carp were caged in Demonstration Base of Biological Purification for Filter-feeding Fish (hereinafter, Demonstration Base), as WwTPs effluent exposure controls. In the meantime, a depuration study was carried out to determine whether or not the estrogenic effects caused by effluent exposure could be reduced after moving fish into EDCs-free water. CF, HSI, GSI, and plasma Vtg levels of high-back crucian carp caged in Demonstration Base were generally in accordance with seasonal change. Effluent exposure inhibited gonadal growth, reducing GSI in ELS while increasing it around spawning, sharpened liver burdens, increasing HSI, and induced abnormal Vtg expression in juvenile high-back crucian carp, augmenting Vtg concentrations in plasma. Around spawning period, Vtg in high-back crucian carp were mainly induced by endogenous estrogens, and EDCs in effluent had less influence on them. Staying in EDCs-free water for 30 days made high-back crucian carp recover from effects of previous effluent exposure, relieving inhibition of gonadal development and hypertrophy of liver as well as reducing Vtg induced by EDCs in effluent. The results revealed that high-back crucian carp in ELS are more sensitive to WwTPs effluent exposure. Additionally, the depuration study showed a clearance of the estrogenic effects caused by effluent.