Differential responses and mechanistic controls of soil phosphorus transformation in Eucalyptus plantations with N fertilization and introduced N2 -fixing tree species.

Introducing N2 -fixing tree species into Eucalyptus plantations could replace nitrogen (N) fertilization to maintain high levels of N consumption and productivity. However, N enrichment may exacerbate phosphorus (P) limitation as Eucalyptus robusta Smith is extensively planted in P-poor tropical and subtropical soils. We conducted a field experiment in a pure plantation of Eucalyptus urophylla × grandis to investigate the impacts of N fertilization and introduced an N2 -fixing tree of Dalbergia odorifera T. Chen on soil P transformation. Nitrogen fertilization significantly enhanced soil occluded P pool and reduced the other P pools due to acidification-induced pH-sensitive geochemical processes, lowering Eucalyptus leaf P concentration with higher N : P ratio. By contrast, introduced N2 -fixing tree species did not change soil pH, labile inorganic P pool, and Eucalyptus leaf N : P ratio, even enhanced organic P pools and reduced occluded P pool probably due to altering microbial community composition particularly stimulating arbuscular mycorrhiza fungal abundance. Our results revealed differential responses and mechanistic controls of soil P transformation in Eucalyptus plantations with N fertilization and introduced N2 -fixing tree species. The dissolution of occluded P pool along with organic P accumulation observed in the mixed plantations may represent a promising future to better manage soil P availability.

Iterative calibration method for measurement system having lens distortions in fringe projection profilometry.

In fringe projection profilometry, system calibration is crucial for guaranteeing the measurement accuracies. Its difficulty lies in calibrating projector parameters, especially when the projector lens has distortions, since the projector, unlike a camera, cannot capture images, leading to an obstacle to knowing the correspondences between its pixels and object points. For solving this issue, this paper, exploiting the fact that the fringe phases on a plane board theoretically have a distribution of rational function, proposes an iterative calibration method based on phase measuring. Projecting fringes onto the calibration board and fitting the measured phases with a rational function allow us to determine projector pixels corresponding to the featured points on the calibration board. Using these correspondences, the projector parameters are easy to estimate. Noting that the projector lens distortions may deform the fitted phase map thus inducing errors in the estimates of the projector parameters, this paper suggests an iterative strategy to overcome this problem. By implementing the phase fitting and the parameter estimating alternately, the intrinsic and extrinsic parameters of the projector, as well as its lens distortion coefficients, are determined accurately. For compensating for the effects of the lens distortions on measurement, this paper gives two solutions. The pre-compensation actively curves the fringes in computer when generating them; whereas when using the post-compensation, the lens distortion correction is performed in the data processing stage. Both methods are experimentally verified to be effective in improving the measurement accuracies.

Fringe harmonics elimination in multi-frequency phase-shifting fringe projection profilometry.

In fringe projection profilometry, the purpose of using two- or multi-frequency fringe patterns is to unwrap the measured phase maps temporally. Using the same patterns, this paper presents a least squares algorithm for, simultaneously with phase-unwrapping, eliminating the influences of fringe harmonics induced by various adverse factors. It is demonstrated that, for most of the points over the measured surface, projecting two sequences of phase-shifting fringe patterns having different frequencies enables providing sufficiently many equations for determining the coefficient of a high order fringe harmonic. As a result, solving these equations in the least squares sense results in a phase map having higher accuracy than that depending only on the fringe patterns of a single frequency. For the other few points which have special phases related to the two frequencies, this system of equations becomes under-determined. For coping with this case, this paper suggests an interpolation-based solution which has a low sensitivity to the variations of reflectivity and slope of the measured surface. Simulation and experimental results verify that the proposed method significantly suppresses the ripple-like artifacts in phase maps induced by fringe harmonics without capturing extra many fringe patterns or correcting the non-sinusoidal profiles of fringes. In addition, this method involves a quasi-pointwise operation, enabling correcting position-dependent phase errors and being helpful for protecting the edges and details of the measurement results from being blurred.

Efficient depth recovering method free from projector errors by use of pixel cross-ratio invariance in fringe projection profilometry.

In fringe projection profilometry, errors related to projectors are not easy to compensate for, as a projector is much more difficult to calibrate than a camera. Immune to projector errors, the depth recovering method based on pixel cross-ratio invariance enables circumventing this issue by calculating the depth of a point from the shift of its camera pixel instead of from its fringe phase. With this existing technique, however, one has to search three reference phase maps along epipolar lines for pixels having the same phases. Doing so increases the measurement time significantly. To improve measurement efficiency, this paper derives, from the pixel cross-ratio invariance, a generic function representing the relationship between the depths and the corresponding pixel shifts and suggests a calibration method for determining its coefficient matrices. Using this function allows us to recover object depths just by searching a single reference phase map, thus reducing the time duration for data processing to about one-third. Besides, different from the previous method, which depends on exactly three reference phase maps, the proposed method calculates the function coefficients from more reference phase maps in the least-squares sense and denoises the benchmark reference phases by use of averaging technique, thus improving measurement accuracy. Experimental results demonstrate this method to be effective in improving measurement accuracy and efficiency.

Correction of projector nonlinearity in multi-frequency phase-shifting fringe projection profilometry.

In fringe projection profilometry, the original purpose of projecting multi-frequency fringe patterns is to determine fringe orders automatically, thus unwrapping the measured phase maps. This paper presents that using the same patterns, simultaneously, allows us to correct the effects of projector nonlinearity on the measured results. As is well known, the projector nonlinearity decreases the measurement accuracies by inducing ripple-like artifacts on the measured phase maps; and, theoretical analysis reveals that these artifacts, depending on the number of phase shifts, have multiplied frequencies higher than the fringe frequencies. Based on this fact, we deduce an error function for modeling the phase artifacts and then suggest an algorithm estimating the function coefficients from a couple of phase maps of fringe patterns having different frequencies. As a result, subtracting out the estimated phase errors yields the accurate phase maps with the effects of the projector nonlinearity on them being suppressed significantly. Experiment results demonstrated that this proposed method offers some advantages over others, such as working without a photometric calibration, being applicable when the projector nonlinearity varies over time, and having satisfied efficiency in implementation.

Temporal phase unwrapping for fringe projection profilometry aided by recursion of Chebyshev polynomials.

This paper presents a temporal phase-unwrapping method for fringe projection profilometry. With it, a sequence of phase-shifting fringe patterns is projected onto the measured object for getting the wrapped phase map and achieving a high measurement resolution, and an additional sequence corresponding to Chebyshev polynomials is used for determining their fringe orders. For effectuating this method, we deduce an algorithm by use of the recursive property of Chebyshev polynomials. This algorithm, combined with a correction operation in the least-squares sense, allows us to accurately estimate the fringe orders in the presence of noise. Experimental results demonstrate the proposed method to be effective in restoring the absolute phase maps of fringe patterns.

Self-correction of projector nonlinearity in phase-shifting fringe projection profilometry.

In phase-shifting fringe projection profilometry, the luminance nonlinearity of the used projector has been recognized as one of the most crucial factors decreasing the measurement accuracy. To solve this problem, this paper presents a self-correcting technique that allows us to suppress the effect of the projector nonlinearity in the absence of any calibration data regarding the projector intensities or regarding the phase errors. In its first step, the standard phase-shifting algorithm is used to recover the phases, as well as the background intensities and the modulations. Using these results enables normalizing the fringe patterns, for ridding them of the effects of the background and modulations. Second, we smooth the calculated phase map by use of a low-pass filter in order to remove the ripple-like phase errors induced by the projector nonlinearity. Third, we determine a polynomial representing the projector nonlinearity by fitting the curve of the normalized fringe intensities against the cosine values of the smoothed phases. Finally, we correct the phase errors using the curve just obtained. Doing these steps in an iterative way eventually results in a phase map and, further, a 3D shape with their artifacts induced by the projector nonlinearity suppressed significantly. Experimental results demonstrate that this technique offers some advantages over others. It does not require a prior calibration of the projector, thus being suitable for dealing with a time-variant nonlinearity; its pointwise operation protects the edges and details of the measurement results from being blurred; and it works well with very few fringe patterns and is efficient in image capturing.

A robust synthesis of N-glycolyl muramyl dipeptide via azidonitration/reduction.

A novel synthetic route leading to N-glycolyl muramyl dipeptide (MDP), a bacterial glycopeptide of particular interest in studies of nucleotide-binding oligomerization domain-containing protein 2 (NOD2), is described. The synthetic strategy hinges on the alkylation of benzylidene-protected glucal with 2-bromopropionic acid and thus circumvents a challenging and non-reproducible SN2 step at the C-3 position of glucosamine derivatives. The subsequent sequence includes an azidonitration and an unusual azide reduction/acylation step via an aza ylide/oxaphospholidine intermediate. This approach generates a protected N-glycolyl MDP that can be either subjected to a one-step global deprotection or differentially deprotected to obtain further derivatives.

Surface modification of zinc oxide and its application in polypropylene with excellent fire performance and ultra-violet resistance.

Despite the advantages of easy moulding and excellent mechanical properties, there are still some shortcomings with polypropylene (PP) such as high flammability and poor ultra-violet (UV) resistance. In this work, modified zinc oxide (mZnO) was prepared by reacting zinc oxide nanoparticles (ZnO) with polysiloxanes, and the effect of mZnO on the effectiveness of intumescent flame-retardant and on the UV aging resistance of polypropylene were investigated. By introducing 16 wt% (intumescent flame-retardant /mZnO) and 0.3 wt% maleic anhydride-grafted PP (MAH-g-PP), the limiting oxygen index increased to 32.7 %, and passed UL-94V-0 rating. In comparison to the controls, the peak heat release rate and the peak smoke release rate were 88.5 % and 80 % lower, respectively. In addition, PP samples showed improved mechanical properties, with a 5 % increase in tensile properties compared to the pure PP sample. After 100 h of UV irradiation, the surface of the samples was relatively flat and smooth, and the carbonyl index decreased from 81.1 of neat PP to 26.7. PP composites with 100 h aging treatment still had excellent flame retardancy and mechanical properties. The results showed that mZnO was effective in improving the flame retardancy, mechanical properties and light aging tolerance of PP. This study provides a novel approach to fabricate long-life flame-retardant PP composites with low additive content.

An ultrasensitive electrochemical immunosensor based on meso-PdN NCs and Au NPs/N-CNTs for quantitative cTnI detection.

Electrochemical immunosensors have gained considerable attention in detecting human disease markers due to their excellent specificity, high sensitivity, and facile operation. Herein, a rational-designed sandwich-type electrochemical immunosensor is constructed for the sensitive detection of cardiac troponin I (cTnI) using nitrogen-doped carbon nanotubes loaded with gold nanoparticles (Au NPs/N-CNTs) as substrate and highly active mesoporous palladium-nitrogen nanocubes (meso-PdN NCs) as secondary antibody markers. Benefitting from its large specific surface area (638.04 m2 g-1) and high nitrogen content, novel polydopamine (PDA)/ halloysite nanotubes (HNTs) hybrid derived one-dimensional (1D) N-CNTs can provide more binding sites for the in-situ growth of Au NPs to connect Ab1. Furthermore, as an ideal substrate material, Au NPs/N-CNTs exhibit finely tuned mesoporous structures and outstanding conductivity, which facilitate the mass and electron transfer during the electrocatalysis process. Besides, highly concave surfaces and crystalline mesopores of meso-PdN NCs expose more surfaces and crevices, providing abundant reactive sites for H2O2 reduction. Remarkably, the as-obtained immunosensor presented a wide linear range (from 10 fg mL-1 to 100 ng mL-1) and an excellent low detection limit (9.85 fg mL-1). This study may offer new insights into the precise fabrication of efficient electrochemical immunosensors for various clinical diagnosis applications.

An innovative fluorescent probe based on dicyanoisoflurone derivatives for differential detection of Hg2+ and Cu2+ and its applications in bacteria, cell imaging and food analysis.

BACKGROUND: Heavy metal pollution has become one of the world's most important environmental pollution, especially Hg2+ is enriched, it is easy to enter the human body through the food chain, bind to the sulfhydryl group in the protein, cause mercury poisoning. Traditional methods for detecting Hg2+ have obvious drawbacks, such as poor selectivity and long detection time. Fluorescence detection has attracted attention because of its good sensitivity and specificity detection ability. In previously reported probes for detecting Hg2+, Cu2+ often interferes. Therefore, it is of great practical significance to synthesize a fluorescent probe that can distinguish between Hg2+ and Cu2+. RESULTS: We have successfully synthesized the probe DFS, a fluorescent probe that can differentially detect Hg2+ and Cu2+, and the probe DFS has good selectivity and anti-interference ability for Hg2+ and Cu2+. The fluorescence intensity at 530 nm increased rapidly when Hg2+ was detected; during the Cu2+ detection, the fluorescence intensity at 636 nm gradually decreased, fluorescence quenching occurred, and the detection limits of Hg2+ and Cu2+ were 7.29 × 10-9 M and 2.13 × 10-9 M, respectively. Through biological experiments, it was found that probe DFS can complete the fluorescence imaging of Hg2+ and Cu2+ in Staphylococcus aureus and HUVEC cells, which has certain research value in the field of environmental monitoring and microbiology, and the probe DFS has low cytotoxicity, so it also has broad application prospects in the field of biological imaging. In addition, the probe DFS also has good applicability for Hg2+ and Cu2+ detection in actual samples. SIGNIFICANCE AND NOVELTY: This is a fluorescent probe that can distinguish between Hg2+ and Cu2+, the fluorescence emission peak appears at 530 nm when Hg2+ is detected; when detecting Cu2+, fluorescence quenching occurs at 636 nm, the fluorescence emission peak distance between Hg2+ and Cu2+ differs by 106 nm. This reduces mutual interference between Hg2+ and Cu2+ during detection, it provides a new idea for the detection of Hg2+ and Cu2+.

An innovative near-infrared fluorescent probe with FRET effect for the continuous detection of Zn2+ and PPi with high sensitivity and selectivity, and its application in bioimaging.

As the second most abundant transition metal element in the human body, zinc ions play an important role in the normal growth and development of the human body. We have successfully synthesized a near-infrared fluorescent probe with FRET effect for the detection of Zn2+. Probe DR6G has good selectivity and anti-interference ability for Zn2+. When Zn2+ is added to the probe DR6G solution, it responds completely within seconds, releasing red fluorescence with a detection limit of 2.02 × 10-8 M. As the main product of ATP hydrolysis, PPi is indispensable in various metabolic activities in cells and the human body. Due to the strong binding ability of Zn2+ and PPi, it is easy to form ZnPPi precipitation, so we added PPi to the solution to complete the Zn2+ detection, and realized the continuous detection of PPi, and the detection limit was 2.06 × 10-8 M. Since Zn2+ and PPi play an important role in vivo, it is of great practical significance to design and synthesize a fluorescent probe that can continuously detect Zn2+ and PPi. Biological experiments have shown that the probe DR6G has low cytotoxicity and can complete the detection of exogenous Zn2+ and PPi in cells and living mice in vitro. Bacterial experiments have shown that the DR6G probe also has certain research value in the field of environmental monitoring and microbiology. Due to the constant variation of the fluorescence signals of Zn2+ and PPi during detection, we designed the logic gate program. In practical applications, the probe DR6G can quantitatively detect Zn2+ in zinc-containing oral liquids and qualitatively detect PPi in toothpaste.

A novel "on-off-on" near-infrared fluorescent probe for Cu2+ and S2- continuous detection based on dicyanoisoflurone derivatives, and its application in bacterial imaging.

We have successfully synthesized a near-infrared fluorescent probe for the continuous detection of copper and sulfur ions. The probe has good selectivity and anti-interference ability against Cu2+ and S2-. The results show that after adding Cu2+ to the DL solution of the near-infrared fluorescent probe, Cu2+ forms a [DL + Cu2+] complex with the probe, which leads to fluorescence quenching due to the paramagnetism of Cu2+. The probe can be used for the quantitative detection of Cu2+ with a detection limit of 1.26 × 10-9 M. According to the Job's plot curve the binding stoichiometry between DL and Cu2+ is 1 : 1. Subsequently, S2- was added to the [DL + Cu2+] solution, because the precipitation dissolution equilibrium constant of CuS was Ksp = 1.27 × 10-36, so the binding capacity between Cu2+ and S2- was stronger, CuS precipitation was formed, and red fluorescence was re-released, and the quantitative detection of S2- was realized, and the detection limit was 3.50 × 10-8 M. Through bacterial imaging experiments, we found that the probe can accomplish the fluorescence imaging experiments of Staphylococcus aureus, indicating that the probe has good biopenetration and biocompatibility, and has application prospects in bioimaging and environmental monitoring. In addition, the probe DL has good suitability for Cu2+ and S2- detection in real samples.

Ethical Conflict and Knowledge Hiding in Teams: Moderating Role of Workplace Friendship in Education Sector.

Ethical conflicts arise when there is no unity between the team members and shared ethical priorities. This study aimed to identify the relationship between ethical value unity, team knowledge hiding, the relationship between the lack of shared ethical priorities and the team knowledge hiding. Workplace friendship was taken as a moderating variable to check its regulating role between the ethical conflicts and the team knowledge hiding. Data of this study were collected from the staff working in different colleges and universities. There are a total of 480 responses collected through convenience sampling technique and analyzed under a five-point Likert scale. The partial least squares-structural equation modeling (PLS-SEM) technique is used in this study. The key reason was that this approach has the fewest requirements for data normality and is a better tool for evaluating exploratory connections empirically. The output of the measurement model assessment confirms that all measurement scales are reliable. The result indicates that there was a significant and positive relationship between ethical value congruence and knowledge hiding. It was also established that there was a relationship between lack of shared ethical priorities and knowledge hiding. Workplace friendship moderated the relationship between ethical conflicts and team knowledge hiding. This study extends the literature on ethical conflict and knowledge hiding behavior. This study highlights that one of the main reasons for knowledge hiding behavior at the team level in the organization is which helps the business practicians for a design of an effective strategy to mitigate the knowledge hiding behavior in the organization.

Advances in electrospun nanofibrous membrane sensors for ion detection.

Harmful metal ions and toxic anions produced in industrial processes cause serious damage to the environment and human health. Chemical sensors are used as an efficient and convenient detection method for harmful ions. Electrospun fiber membranes are widely used in the field of solid-state chemical sensors due to high specific surface area, high porosity, and strong adsorption. This paper reviews the solid-state chemical sensors based on electrospinning technology for the detection of harmful heavy metal ions and toxic anions in water over the past decade. These electrospun fiber sensors have different preparation methods, sensing mechanisms, and sensing properties. The preparation method can be completed by physical doping, chemical modification, copolymerization, surface adsorption and self-assembly combined with electrospinning, and the material can also be combined with organic fluorescent molecules, biological matrix materials and precious metal materials. Sensing performance aspects can also be manifested as changes in color and fluorescence. By comparing the literature, we summarize the advantages and disadvantages of electrospinning technology in the field of ion sensing, and discuss the opportunities and challenges of electrospun fiber sensor research. We hope that this review can provide inspiration for the development of electrospun fiber sensors.

Ultra-rapid, enhanced and eco-friendly extraction of four main flavonoids from the seeds of Oroxylum indicum by deep eutectic solvents combined with tissue-smashing extraction.

Rapid, green and efficient extraction of active compounds followed by fast analysis is always pursued in the field of food analysis and/or industry. Herein, a green and highly efficient extraction of four active flavonoids from the seeds of Oroxylum indicum using a combination of natural deep eutectic solvents (DESs) and tissue-smashing extraction (TSE) technique was applied and a UPLC method was developed for their sensitive and selective quantification. RSM coupled with BBD procedure was used to optimize the extraction conditions based on single factors, such as liquid-solid ratios, extraction speed and extraction time. Compared with other conventional methods, the TSE greatly shortens extraction time, obviously raises the extraction production, and decreases energy consumption. By combination of the DES-based TSE and UPLC, the analysis of flavonoids was accomplished within only 6 min, providing an ultra-rapid, environmentally friendly and promising choice for extraction and analysis of active compounds in natural products.

Screening and identification of potential tyrosinase inhibitors from Semen Oroxyli extract by ultrafiltration LC-MS and in silico molecular docking.

There is an increasing interest in screening and developing natural tyrosinase inhibitors widely applied in medicinal and cosmetic products, as well as in the food industry. In this study, an approach by ultrafiltration LC-MS and molecular docking was used to screen and identify tyrosinase inhibitors from Semen Oroxyli extract. The samples were first incubated with the tyrosinase to select the optimal binding conditions including tyrosinase concentration, incubation time and the molecular weight of ultrafiltration membrane. By comparison of the chromatographic profiles of the extracts after ultrafiltration with activated and inactivated tyrosinase, the potential inhibitors were obtained and then identified by LC-MS. The relative binding affinities of the potential inhibitors were also calculated based on the decrease of peak areas of those. As a result, seven compounds were fished out as tyrosinase inhibitors by this assay. Among them, oroxin A and baicalein showed higher tyrosinase inhibitory than resveratrol as positive drug, and their binding mode with enzyme was further verified via the molecular docking analysis. The test results showed that the proposed method was a simple, rapid, effective, and reliable method for the discovery of natural bioactive compounds, and it can be extended to screen other bioactive compounds from traditional Chinese medicines.

Access to dihydropyridinones and spirooxindoles: application of N-heterocyclic carbene-catalyzed [3+3] annulation of enals and oxindole-derived enals with 2-aminoacrylates.

A strategy for the NHC-catalyzed synthesis of dihydropyridinones and spirooxindoles has been developed via [3+3] annulation reactions of enals or isatin-derived enals with 2-aminoacrylates under oxidative conditions. In this efficient strategy, the 2-aminoacrylates served as nucleophiles. Modifying the standard base switched the carbon-carbon double bond formation from 5,6-positions to 3,4-positions to generate 5,6-dihydropyridinones and 3,4-dihydropyridinones, respectively. Meanwhile, a diverse set of spirooxindole derivatives were also synthesized in good to excellent yields.

Enantioselective [3 + 2] Annulation of Enals with 2-Aminoacrylates Catalyzed by N-Heterocyclic Carbene.

A novel and convenient strategy for the enantioselective synthesis of γ-lactam derivatives via N-heterocyclic carbene catalyzed formal [3 + 2] annulation of enals with 2-aminoacrylates is disclosed. This activation mode provides a complementary approach to the synthesis of various γ-lactam derivatives in good yields with excellent diastereo- and enantioselectivities. In this process, two consecutive stereocenters are constructed, and a quaternary carbon center is also established.