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Bacterial and phytoplankton communities are known to be in close relationships, but how natural and anthropogenic stressors can affect their dynamics is not fully understood. To study the response of microbial communities to environmental and human-induced perturbations, phytoplankton and bacterial communities were seasonally monitored in a Mediterranean coastal ecosystem, Syracuse Bay, where multiple conflicts co-exist. Quali-quantitative, seasonal surveys of the phytoplankton communities (diatoms, dinoflagellates and other taxa), the potential microbial enzymatic activity rates (leucine aminopeptidase, beta-glucosidase and alkaline phosphatase) and heterotrophic culturable bacterial abundance, together with the thermohaline structure and trophic status in terms of nutrient concentrations, phytoplankton biomass (as Chlorophyll-a), and total suspended and particulate organic matter, were carried out. The aim was to integrate microbial community dynamics in the context of the environmental characterization and disentangle microbial patterns related to natural changes from those driven by the anthropic impact on this ecosystem. In spite of the complex relationships between the habitat characteristics, microbial community abundance and metabolic potential, in Syracuse Bay, the availability of organic substrates differently originated by the local conditions appeared to drive the distribution and activity of microbial assemblage. A seasonal pattern of microbial abundances was observed, with the highest concentrations of phytoplankton in spring and low values in winter, whereas heterotrophic bacteria were more abundant during the autumn period. The autumn peaks of the rates of enzymatic activities suggested that not only phytoplankton-derived but also allochthonous organic polymers strongly stimulated microbial metabolism. Increased microbial response in terms of abundance and metabolic activities was detected especially at the sites directly affected by organic matter inputs related to agriculture or aquaculture activities. Nitrogen salts such as nitrate, rather than orthophosphate, were primary drivers of phytoplankton growth. This study also provides insights on the different seasonal scenarios of water quality in Syracuse Bay, which could be helpful for management plans of this Mediterranean coastal environment. [ABSTRACT FROM AUTHOR]

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Abstract: Ammonia oxidation plays a pivotal role in the cycling and removal of nitrogen in aquatic ecosystems. Recent findings have expanded the known ammonia-oxidizing prokaryotes from Bacteria to Archaea. However, the relative importance of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in nitrification is still debated. Here we showed that, in two large eutrophic lakes in China (Lake Taihu and Lake Chaohu), the abundance of AOA and AOB varied in opposite patterns according to the trophic state, although both AOA and AOB were abundant. In detail, from mesotrophic to eutrophic sites, the AOA abundance decreased, while the AOB increased in abundance and outnumbered the AOA at hypertrophic sites. In parallel, the nitrification rate increased along these trophic gradients and was significantly correlated with both the AOB abundance and the numerical ratio of AOB to AOA. Phylogenetic analysis of bacterial amoA sequences showed that Nitrosomonas oligotropha- and Nitrosospira-affiliated AOB dominated in both lakes, while Nitrosomonas communis-related AOB were only detected at the eutrophic sites. The diversity of AOB increased from mesotrophic to eutrophic sites and was positively correlated with the nitrification rate. Overall, this study enhances our understanding of the ecology of ammonia-oxidizing prokaryotes by elucidating conditions that AOB may numerically predominated over AOA, and indicated that AOA may play a less important role than AOB in the nitrification process of eutrophic lakes. [Copyright &y& Elsevier]

Although megaprimer PCR mutagenesis has been used routinely in protein directed evolution, users sometimes encounter technical hurdles, particularly inefficiency during amplification when large fragments are used or the template is difficult to be amplified. Instead of methodology development, here we simply overcome the limitation by optimizing megaprimer PCR conditions via orthogonal array design of the four PCR components in three levels of each: template, primer, Mg2+, and d NTPs. For this, only nine PCRs need to be performed. The strategy (termed as Opti Mega) was not only successfully applied for the construction of one multiple-site saturation mutagenesis library of halohydrin dehalogenase Hhe C, which failed to be constructed previously using the standard Quik Change™ protocol, but also expanded the construction of two high-quality random mutagenesis libraries of Hhe A and Hhe C. Most importantly, Opti Mega offers a quick and simple way of constructing random mutagenesis libraries by eliminating the ligation step. Our results demonstrated that the Opti Mega strategy could greatly strengthen the potential of megaprimer PCR mutagenesis for library construction. [ABSTRACT FROM AUTHOR]

Induced pluripotent stem cells ( iPSCs) are flourishing in the investigation of cell reprogramming. However, we still know little about the sequential molecular mechanism during somatic cell reprogramming (SCR). Here, we first observed rapid generation of colonies whereas mouse embryonic fibroblasts (MEFs) were induced by OCT4, SOX2, KLF4 (OSK), and vitamin C for 7 days. The colony's global transcriptional profiles were analyzed using Affymetrix microarray. Microarray data confirmed that SCR was a process in which transcriptome got reversed and pluripotent genes expressed de novo. There were many changes, especially substantial growth expression of epigenetic factors, on transcriptome during the transition from Day 7 to iPSCs indicating that this period may provide 'flexibility' genome structure, chromatin remodeling, and epigenetic modifications to rebind to the transcriptional factors. Several biological processes such as viral immune response, apoptosis, cell fate specification, and cell communication were mainly involved before Day 7 whereas cell cycle, DNA methylation, and histone modification were mainly involved after Day 7. Furthermore, it was suggested that p53 signaling contributed to the transition 'hyperdynamic plastic' cell state and assembled cell niche for SCR, and small molecular compounds useful for chromatin remodeling can enhance iPSCs by exciting epigenetic modification rather than the exogenous expression of more TFs vectors. [ABSTRACT FROM AUTHOR]

A new water-soluble monomer of sodium 10-Acryloyloxydecanoate (NaAD), which possesses a hydrophobic group and an ionizable group, was synthesized from acryloyl chloride and 10-hydroxydecanoic acid, and the series of copolymers of NaAD with acrylamide (AM) were prepared by the free radical polymerization in aqueous solution using ammonium persulfate as the initiator. The feed ratio of NaAD:AM was varied from 5:95 to 70:30 mol%, with the total monomer concentration held constant at 0.5 M. The copolymer compositions were determined from elemental analysis. The molecular weights of the copolymers were determined by gel permeation chromatography ranged from 0.76 × 10 to 1.37 × 10 g/mol. All copolymers were soluble in deionized water and salt solutions at pH > 5. The dilute and semidilute solution behavior of the copolymers was studied as a function of composition, pH, and added electrolytes, and the results indicated that NaAD30 exhibited much higher viscosity values. At moderate pH values, the copolymers coils become slightly more expanded and intermolecular association interactions occur, which was indicated by fluorescence and apparent viscosity measurements. Upon the addition of NaCl and in low pH, viscosities tended to decrease because of the disruption of the intermolecular associations. [ABSTRACT FROM AUTHOR]

Sediment of eutrophic lakes was characterized by higher organic matter (OM) content with chironomids being the common species. Hence, effects of these two factors and their interaction on sediment nutrient release are of great ecological significance. These effects under the underlying mechanisms were examined by laboratory experiments using the sediment in a Chinese shallow lake (Lake Tuanhu) in this study. The input of the OM (algal detritus) brought about significant increases in concentrations of total, particulate and soluble reactive phosphorus (SRP) and ammonia in overlying water within a similar time span. These releases were largely depressed by aeration, but greatly enhanced with an additional involvement of the larvae of Chironomus plumosus. Therefore, the OM and chironomids acted in concert to promote nutrient releases, and the onset of anaerobic conditions was a common mechanism. Additionally, there existed a significant relationship between the OM content and alkaline phosphatase activity (APA) in sediments suggesting the activated enzymatic hydrolysis to be another mechanism driving SRP release while APA remained unchanged with addition of chironomids. Noticeably, when the OM and chironomids larvae co-occurred, aeration provided the overlying water with the highest concentrations of SRP and ammonia, which was followed by nitrite and nitrate at the earlier incubation stage. Under the oxic conditions, the larvae may excrete more SRP and ammonia with the latter being gradually shifted along the pathway of nitrification. Thus, for the recovery of eutrophic lakes with the sediments enriched by OM and chironomids, aeration should be cautiously applied. [ABSTRACT FROM AUTHOR]

process of aqueous enzymatic extraction of wheat germ was carried out by a multi-enzyme preparation consisting of cellulase, pentosanase, neutrase and fungal amylase (CPNF, 2:1:2:1 w/w/w/w). Hydro-thermal heating (at 112 °C for 60 min) was more effective than oven-drying regarding emulsified oil yield. Wheat germ was ground with a rate of 10,000 rpm for 90 s. The adding level (w/w) of multi-enzyme preparation of CPNF was 1.6%. Response surface methodology was used to obtain the desired data in the process optimization. The optimal set of variables was water to wheat germ ratio (v/wt, mL/g) of 3.46, pH of 5.24, temperature of 48.49 °C and time of 6 h. The emulsified oil yield was 86.74% at the optimal levels of the tested factors. Compared with organic solvent extracted oil, the content of free fatty acid of AEE extracted oil was higher and the color was slightly darker, while the peroxide value was lower and the oxidative stability was higher owing to high content of α-tocopherol. This technique for recovering oil from fresh wheat germ with enzymes is a significant improvement in both oil yield and quality over the traditional organic solvent process. [ABSTRACT FROM AUTHOR]

Nitrification is a process in which ammonia is oxidized to nitrite (NO) that is further oxidized to nitrate (NO). The relations between these two steps and ambient ammonia concentrations were studied in surface water of Chinese shallow lakes with different trophic status. For the oxidations of both ammonia and NO, more eutrophic lakes generally showed significantly higher potential and actual rates, which was linked with excessive ammonia concentrations. Additionally, both potential and actual rates for ammonia oxidation were higher than those for NO oxidation in the more eutrophic lakes, while in the lakes with lower trophic status, both potential and actual rates for ammonia oxidation were almost equivalent to those for NO oxidation. This can be explained by the excessive unionized ammonia (NH3) concentration that inhibits nitrite-oxidizing bacteria in the more eutrophic lakes. The laboratory experiment with different ammonia concentrations, using the surface water in a eutrophic lake, showed that ammonia oxidation rates were proportional to the ammonia concentrations, but NO oxidation rates did not increase in parallel. Furthermore, NO oxidation was less associated with particles in natural water of the studied lakes. Without effective protection, it would be selectively inhibited by the excessive ammonia in hypereutrophic lakes, resulting in NO accumulation. Shortly, the increased concentrations of ammonia cause a misbalance between the NO-producing and the NO-consuming processes, thereby exacerbating the lake eutrophication. [ABSTRACT FROM AUTHOR]

The relationship between chlorophyll a and fractionation of sediment phosphorus, inorganic phosphate-solubilizing bacteria (IPB), and organic phosphate-mineralizing bacteria (OPB) was evaluated in a large Chinese shallow eutrophic lake (Lake Taihu) and its embayment (Wuli Bay). At the three study sites, the increase of chlorophyll a concentrations in April paralleled those of the iron bound phosphate accounting for major portion of sediment inorganic phosphate, and in June significantly higher OPB and IPB numbers (especially OPB) in sediment were main contributors to the peaks of chlorophyll a concentration. Even though IPB peaked from February to June, it should serve as an unimportant P source due to the irrelevancy with chlorophyll a and soluble reactive phosphorus (SRP). By contrast, at the other site in the embayment, the calcium-bound phosphate was predominant and solid, which was difficult to be released, and neither IPB nor OPB were detectable in the sediment, indicating weak potential for phosphorus release from the sediment, which was reflected in the small seasonal variation in SRP concentration in water column. Hence, the extents to which the three general mechanisms behind phosphate release from sediment (desorption of iron bound phosphate, solubilization by IPB and enzymatic hydrolysis by OPB) operated were different depending on seasons and sites in Lake Taihu, they may jointly drive phosphate release and accelerate the eutrophication processes. [ABSTRACT FROM AUTHOR]

The temporal and vertical fluctuations of size fractionated alkaline phosphatase activity (APA) and kinetics parameters as well as orthophosphate (o-P) and chlorophyll concentrations were investigated after bloom disappearance in two shallow ponds A and B from 27 October 2001 to 15 April 2002. Pond A (Microcystis) bloomed seriously but pond B did not. The data of o-P and chlorophyll suggested that phosphorus was the principal limiting nutrimental element and its vertical flux should be regarded as an important driving factor for algal growth. In pond A, the accumulation of algae-derived detritus after bloom disappearance in overlying water stimulated excretion of algal fraction APA, mainly produced by attached bacteria responsible for detritus decomposition, whereas bacterial fraction APA preferred to function in surface water. Interestingly, completely contrary phenomena were observed in pond B. In season, even though no obvious difference for size-fractionated APA in both ponds, the total APA in pond A peaked earlier showing higher activity and efficiency (low Km and high Vmax values) as a result of algal-derived detritus input. In summary, it is suggested that the excretion of alkaline phosphatase with strongly catalyzing efficiency and high activity should be taken as important contributor to algal-derived detritus decomposition, further fueling nutrient recycle and accelerating algal development next year. Furthermore, some inhibitors and surfactants were testified to be good tools to identify the origin of dissolved alkaline phosphatase. [ABSTRACT FROM AUTHOR]

The AC electrokinetic technology, such as AC electroosmosis, induced-charged electroosmosis, dielectrophoresis, etc., can precisely manipulate trace fluids and has been widely used in lab on a chip. However, the power supplies used in AC electrokinetic experiments are mostly function generators or other large-scare instruments, which is an obstacle to portability. Encouragingly, triboelectric nanogenerator (TENG) with the characteristics of portable, green, and simple structure is a potential opportunity for AC electrokinetic microfluidic operation. We have designed a self-powered AC electrokinetic microfluidic system based on vertical contact-separation mode TENG for the first time. The TENG, as a power supply, costs only 2 cents and maintains excellent output performance after millions of working cycles. Through the combination of TENG and microfluidic chip, this system successfully realizes AC electroosmotic flow and induced-charged electroosmotic flow in the microchannel and completes the effective mixing of two fluids at low frequencies (<10 Hz). Furthermore, we have achieved precise control of particle behavior, including focusing, deflection, and separation under manual operation. Therefore, the self-powered AC electrokinetic microfluidic system designed in this work not only expands the application fields of TENG but also provides a new power solution for AC electrokinetic microfluidic operation. This system is expected to get rid of the need for large-scale power supply in traditional methods and has broad application prospects in the fields of portable detection, micro-reaction, and micro-bioanalysis. The self-powered AC electrokinetic microfluidic system comprises a vertical contact-separation mode TENG and a microfluidic chip. Under the excitation of the signal generated by the TENG, this system achieves efficient mixing of laminar fluids and precise control of particles, including focusing, deflection and separation. [Display omitted] • A self-powered ACEK microfluidic system based on TENG is designed for the first time. • The signal generated by TENG is beneficial to AC electroosmotic flow. • This work advances utility of TENG by controlling fluidic mixing and particle motion. [ABSTRACT FROM AUTHOR]

The article highlights a study which examined the self-assembly and phase behavior of copolymers of N-vinylformamide and acrylic acid under highly acidic situations. Under highly acidic conditions, the poly[(N-vinylformamide-co-(acrylic acid)] copolymers with a moderate content of N-vinylformamide showed complex phase behaviors. The particle size and the temperature-responsive behavior of the copolymers were influenced by the amount of salt and excess acid.

Kinetics of alkaline phosphatase in sediments of a shallow Chinese freshwater lake (Lake Donghu) were investigated. Spatially, among 20 sites sampled, V max and K m values of alkaline phosphatase in surface sediments were higher in the zone adjacent to sites with the highest chlorophyll a concentrations. Vertically, there was a peak in V max at intermediate sediment depths in addition to the expected maximum at the surface. Some inhibitors, such as CuSO4, ZnSO4 and Na2WO4, showed significantly different effects on kinetics of alkaline phosphatase in interstitial water and sediments. Moreover, alkaline phosphatase in interstitial water and sediments responded to Na2WO4 in different ways in Lake Taihu. These observations imply that the enzyme is immobilized in sediments, which became more stable with accelerated eutrophication, as suggested by highest alkaline phosphatase activity (APA) in sediments corresponding with highest water column chlorophyll a concentrations in Lake Donghu. [ABSTRACT FROM AUTHOR]

Phosphatase may accelerate the process of lake eutrophication through improving phosphorus bioavailability. This mechanism was studied in three Chinese eutrophic shallow lakes (Lake Taihu, Lake Longyang and Lake Lianhua). Phosphatase activity was related to the concentration of soluble reactive phosphorus (SRP) and chlorophyll a. Stability of dissolved phosphatase in reverse micelles may be attributed to molecular size, conformation and active residues of the enzyme. At the site with Microcystis bloomed in Lake Taihu, dissolved phosphatase activity was higher and more stable in micelles, SRP concentrations were lower in interstitial water, the contents of different forms of phosphorus and the amounts of aerobic bacteria were lower while respiration efficiency was higher in sediments. Phosphobacteria, both inorganic and organic and other microorganisms were abundant in surface water but rare in sediments. Therefore, internal phosphorus may substantially flux into water column by enzymatic hydrolysis and anaerobic release, together with mobility of bacteria, thereby initiating the bloom. In short, biological mechanism may act in concert with physical and chemical factors to drive the internal phosphorus release and accelerate lake eutrophication. [ABSTRACT FROM AUTHOR]

Total alkaline phosphatase activity (APA) and soluble reactive phosphorus (SRP) concentrations were measured in municipal wastewater, and a shallow Chinese freshwater lake receiving it. Activities of Dissolved alkaline phosphatase (ADAP) in overlying and interstitial water were also analyzed monthly at three sites for several years. The lake was enriched with SRP and alkaline phosphatase by discharge of the wastewater, indicating that the inclusion of APA for estimating water pollution was reasonable. Annual data showed that APA in coarser fraction was significantly higher at the site receiving more wastewaters, both in surface and overlying water, suggesting that resuspension of enzyme most likely occurred in the basin heavily discharged. ADAP was an order of magnitude higher in the wastewater than those in lake waters, and was generally higher in interstitial water, a feature more striking at the site receiving more discharges. Besides, it was irrespectively inhibited by Na2WO4, L-cysteine and EDTA-Na, but stimulated by Cu2+, Zn2+, CTAB and Triton X-100 in interstitial, overlying and surface waters. This similarity of responding patterns to the stressors indicated an analogy between dissolved alkaline phosphatase in water column and that in interstitial water, supporting the hypothesis that the polluted sediments act as source of dissolved alkaline phosphatase in eutrophic lakes. [ABSTRACT FROM AUTHOR]

In this study, an energy-based model for predicting the fracture angle of matrix failure in unidirectional carbon-fiber-reinforced polymer (CFRP) under three-dimensional mechanical loading was developed. The elastic stresses in the undamaged area and the frictional stresses in the damaged area were considered in determining the complementary free energy density in the CFRP damage process. The fracture angle of the transverse matrix failure was predicted based on the maximum dissipation rate of the energy density. The effect of the stress state in the damaged area on the energy density was analyzed under the matrix tension and compression failure modes. The predicted fracture angle was verified by comparison with existing strength-based matrix failure criteria under various stress conditions. The computational efficiency between the energy-based and strength-based failure criteria is compared and evaluated. [Display omitted] • Matrix fracture angle of unidirectional CFRP is predicted using energy method. • The friction at the fractured surfaces is considered in the damage-friction model. • Fractured plane formation mechanism is explained from energy dissipation perspective. • No need to perform fracture angle measurement for identifying friction terms. [ABSTRACT FROM AUTHOR]

As the main prerequisite for flow in microfluidic chips, micropumps have always been the core component of microfluidic systems. With the continuous development trend of the three dimensions and high integration for microfluidic systems in recent years, combining the characteristics of micro and drivable fluid flowing in 3D space is the current mainstream research goal in the functions of the micropumps. Here, based on the continuous electrowetting effect in a confined space of the Ga‐based liquid metal (LM), an LM driving micropump structure is proposed that enables fluid to be pumped up to 200 mm in height, which meets the major demands of microfluidic system working environments. The pumping mechanism is experimentally analyzed and demonstrated, as well as the working performance of the micropump under different output modes (continuous flow and pulsatile flow). The feasibility of this micropump is also verified through a fluid pumping experiment in complex shaped channels and a temperature management experiment in 3D space. This work is envisaged to expand the function and application area of the electric actuators driven by the Ga‐based LM and provide new support for micropumps in the 3D microfluidic chip system. [ABSTRACT FROM AUTHOR]

• Iron bound P release dominated during algal regime. • P-solubilizing bacteria contributed to P release during regime shift. • Coupling of C, N, P, O and Fe fueled P release. • Algal species composition differed during different regimes. In order to better understand the pathways and mechanisms of phosphorus (P) supply under different regimes, 12 sampling sites from 4 basins of 2 lakes were studied seasonally from October 2017 to July 2018 in Wuhan City, China. Concentrations of different forms of P and nitrogen (N) in surface and interstitial water, contents of carbon (C), N, P and iron (Fe) compounds as well as related extracellular enzymatic activities, phosphorus sorption, abundance of phosphorus-solubilizing bacteria (PSB), total and specific (containing phosphatase gene) microbial community composition in sediments were analyzed. In lakes with macrophyte dominance, P supply pathway from sediment to water column was blocked. In lakes being early period of regime shifting from macrophyte to algae, exogenous P input was the main P supply mode. In lakes being later period of regime shifting from macrophyte to algae, organic P hydrolysis and calcium-bound P dissociation driven by PSB contributed greatly to P regeneration, which was continuous and trickling. In this process, rapid C and N cycles fueled P regeneration. In lakes with algal dominance, given the significantly higher iron-bound P (Fe(OOH)~P), equilibriums phosphorus concentration and dehydrogenase activity, the main P regeneration pathway might be the desorption of Fe(OOH)~P driven by anoxia, showing the seasonal and pulsed characteristics. In addition, during the process of regime shift from macrophyte to algae, the dominant algal species switched from cyanobacteria to Chlorophyta. P-solubilizing microorganisms correlated with environmental factors, suggesting the coupling of multiple nutrient cycles, especially C, N, P, oxygen (O) and Fe, could effectively increase the pathways diversification and the strength of P regeneration. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Aquaculture is among the most important and fastest growing agriculture sectors worldwide; however, it generates environmental impacts by introducing nutrient accumulations in ponds, which are possibly different and further result in complex biological processes in the sediments based on diverse farming practices. In this study, we investigated the effects of long-term farming practices of representative aquatic animals dominated by grass carp (GC, Ctenopharyngodon idella) or Chinese mitten crab (CMC, Eriocheir sinensis) on the bacterial community and enzyme activity of sediments from more than 15 years of aquaculture ponds, and the differences associated with sediment properties were explored in the two farming practices. Compared to CMC ponds, GC ponds had lower contents of TC, TN, and TP in sediments, and similar trends for sediment pH and moisture content. Sediment bacterial communities were significantly different between GC and CMC ponds, with higher bacterial richness and diversity in GC ponds. The bacterial communities among the pond sediments were closely associated with sediment pH, TC, and TN. Additionally, the results showed profoundly lower activities of β-1,4-glucosidase, leucine aminopeptidase, and phosphatase in the sediments of GC ponds than CMC ponds. Pearson's correlation analysis further revealed strong positive correlations between the hydrolytic enzyme activities and nutrient concentrations among the aquaculture ponds, indicating microbial enzyme regulation response to sediment nutrient dynamics. Our study herein reveals that farming practices of fish and crab differently affect bacterial communities and enzymatic activities in pond sediments, suggesting nutrient-driven sediment biological processes in aquaculture ponds for different farming practices. [ABSTRACT FROM AUTHOR]

Although the nutrient as a driving force for the red tide was intensively studied, the spatial patterns of the phytoplankton community and its response to benthic nutrient cycling remain unclear. We determined the pelagic phytoplankton community and its extracellular alkaline phosphatase qualitatively using enzyme-labeled fluorescence (ELF) technique, concomitantly with the concentrations of phosphorus (P) and nitrogen (N) in the water and sediments in the Taiwan Strait in spring 2018. A total of 30 phytoplankton genera were identified with a higher abundance of the abundance of Prorocentrum and Trichodesmium being observed at the north coast and the center of the southern strait, respectively. Both phytoplankton abundances and Trichodesmium were negatively correlated with the ratios of dissolved inorganic N and ammonium to soluble reactive P (DIN/SRP, NH4+/SRP) in the bottom. Furthermore, the ELF-labeling percentage in Trichodesmium was negatively correlated with total P and SRP but positively correlated with TN/TP, DIN/SRP, and NH4+/SRP in the bottom. In contrast to high DIN/SRP of the surface, lower DIN/SRP in the bottom was owing to a high P release potential and weak sequestration of P as evidenced by the distribution of P solubilizing bacteria and P content. Our findings indicated that the benthic nutrient regime might shape the structure of the pelagic phytoplankton community. [ABSTRACT FROM AUTHOR]

A unique approach is proposed to boost on-chip immuno-sensors, for instance, immunoassays, wherein an antibody immobilized on the walls of a microfluidic channel binds specifically to an antigen suspended freely within a working fluid. The performance of these sensors can be limited in both susceptibility and response speed by the slow diffusive mass transfer of the analyte to the binding surface. Under appropriate conditions, the binding reaction of these heterogeneous immuno-assays may be enhanced by electroconvective stirring driven by external AC electric fields to accelerate the translating motion of antigens towards immobilized antibodies. To be specific, the phenomenon of induced-charge electroosmosis in a rotating electric field (ROT-ICEO) is fully utilized to stir analyte in the vicinity of the functionalized surface of an ideally polarizable floating electrode in all directions inside a tri-dimensional space. ROT-ICEO appears as a consequence of the action of a circularly-polarized traveling wave signal on its own induced rotary Debye screening charge within a bipolar induced double layer formed on the central floating electrode, and thereby the pertinent electrokinetic streamlines exhibit a radially converging pattern that greatly facilitates the convective transport of receptor towards the ligand. Numerical simulations indicate that ROT-ICEO can enhance the antigen–antibody binding reaction more effectively than convectional nonlinear electroosmosis driven by standing wave AC signals. The effectiveness of ROT-ICEO micro-stirring is strongly dependent on the Damkohler number as well as the Peclet number if the antigens are carried by a continuous base flow. Our results provide a promising way for achieving a highly efficient heterogeneous immunoassay in modern micro-total-analytical systems. [ABSTRACT FROM AUTHOR]

The material removal mechanism in cutting of carbon fiber reinforced polymer (CFRP) varies with fiber orientation and tool rake angle due to its two-constituent structure. When the fiber orientation is zero degree and tool rake angle is zero or negative, the chip formation process is dominated by the shearing at the interface layer and the buckling of uncut workpiece material. This paper develops a new analytical mechanics model of orthogonal cutting of unidirectional CFRP to predict the forces and chip lengths with shearing-buckling deformation mechanism of the material. A shearing model is developed to determine the maximum resistance force of the workpiece material using energy method. The lengths of machined chips are evaluated based on micro and Euler buckling theories. The tool-workpiece contact force due to tool pressing at the cutting tool edge and flank face is predicted. The developed model reveals the nonlinear relationship between the cutting force and the uncut chip thickness in orthogonal cutting of CFRP. The simulated cutting forces and chip lengths are verified by experimental results at different uncut chip thicknesses and tool rake angles. The developed model determines the fundamental mechanism in orthogonal cutting of CFRP due to its unique anisotropic property. [ABSTRACT FROM AUTHOR]

We propose herein a unique mechanism of generating tunable surface charges in a metal-dielectric Janus nanopore for the development of nanofluidic ion diode, wherein an uncharged metallic nanochannel is in serial connection with a dielectric nanopore of fixed surface charge. In response to an external electric field supplied by two probes located on both sides of the asymmetric Janus nanopore, the metallic portion of the nanochannel is electrochemically polarized, so that a critical junction is formed between regions with an enriched concentration of positive and negative ions in the bulk electrolyte adjacent to the conducting wall. The combined action of the field-induced bipolar induced double layer and the native unipolar double layer full of cations within the negatively-charged dielectric nanopore leads to a voltage-controllable heterogenous volumetric charge distribution. The electrochemical transport of field-induced counterions along the nanopore length direction creates an internal zone of ion enrichment/depletion, and thereby enhancement/suppression of the resulting electric current inside the Janus nanopore for reverse working status of the nanofluidic ion diode. A mathematical model based upon continuum mechanics is established to study the feasibility of the Janus nanochannel in causing sufficient ion current rectification, and we find that only a good matching between pore diameter and Debye length is able to result in a reliable rectifying functionality for practical applications. This rectification effect is reminiscent of the typical bipolar membrane, but much more flexible on account of the nature of a voltage-based control due to induced-charge electrokinetic polarization of the conducting end, which may hold promise for osmotic energy conversion wherein an electric current appears due to a difference in salt concentration. Our theoretical demonstration of a composite metal-dielectric ion-selective medium provides useful guidelines for construction of flexible on-chip platforms utilizing induced-charge electrokinetic phenomena for a high degree of freedom ion current control. [ABSTRACT FROM AUTHOR]

To improve the water quality of Lake Yuehu, a water diversion from the Han River was conducted in July 2008. However, an unexpected Microcystis bloom occurred in the lake after water introduction. Water and sediment samples were collected from Lake Yuehu and the variation of chemical and biochemical parameters, as well as the phytoplankton community, were analyzed during the water diversion to assess its effect and to clarify the mechanism leading to the Microcystis bloom. The nitrogen (N) concentration was increased and phosphorus (P) concentration decreased in Lake Yuehu after receiving water from the Han River, which had a high loading of N and a low loading of P. These conditions may benefit the growth and dominance of non-N2 fixing Microcystis, as it may not have suffered from P limitation during our study because it did not produce extracellular phosphatase, which worked as an indicator of P deficiency, as evidenced by the in situ enzyme-labelled fluorescence. Notably, the sediment Fe (OOH)~P content significantly decreased in Lake Yuehu; this pulsed release of P from the sediment might have sustained the Microcystis bloom. Based on our results, algal blooms may occur as a consequence of conducting water diversion projects to improve water quality. [ABSTRACT FROM AUTHOR]