Search

Floods cause hundreds of fatalities and billions of dollars of economic loss each year in the United States. To mitigate these damages, accurate flood prediction is needed for issuing early warnings to the public. This situation is exacerbated in larger model domains for high flows, particularly in ungauged basins. To improve flood prediction for both gauged and ungauged basins, we propose a spatio-temporal hierarchical model (STHM) to improve high flow estimation using a 10-day window of modeled National Water Model (NWM) streamflow and a variety of catchment characteristics as input. The STHM is calibrated (1993-2008) and validated (2009-2018) in controlled, natural, and coastal basins over three broad groups, and shows significant improvement for the first two basin types. A seasonal analysis shows the most influential predictors are the previous 3-day average streamflow and the aridity index for controlled and natural basins, respectively. To evaluate the STHM in improving streamflow in ungauged basins, 20-fold cross-validation is performed by leaving 5% of sites. Results show that the STHM increases predictive skill in over 50% of sites by 0.1 Nash-Sutcliffe efficiency (NSE) and improves over 65% of sites’ streamflow prediction to an NSE>0.67, which demonstrates that the STHM is one of the first of its kind and could be employed for flood prediction in both gauged and ungauged basins.

With an increasing number of continental-scale hydrologic models, the ability to evaluate performance is key to understanding uncertainty in prediction and making improvements to the model(s). In 2016, the NOAA National Water Model (NWM) was put into operations to improve the spatial and temporal resolution of hydrologic prediction in the U.S. Here, we evaluate the NWM 2.0 historical streamflow record in natural and controlled basins using the Nash Sutcliffe Efficiency metric decomposed into relative error, conditional, and unconditional bias. Each of these is evaluated in the contexts of categorized meteorologic, landscape, and anthropogenic characteristics to assess model performance and diagnose error types. Broadly speaking greater rainfall and snow coverage leads to improved performance while larger potential evapotranspiration (PET), aridity, and phase correlation reduce performance. More rainfall and phase correlation reduce overall bias, while increasing PET, aridity, snow coverage/fraction increase model bias. With respect to landscape traits, more barren and agricultural land yeild improved performance while more forest, shrubland, grassland and imperviousness tend to decrease performance. Lastly, more barren and herbaceous land tend to decrease bias, while greater imperviousness, urban, forest, and shrubland cover increase bias. The insights gained can help identify key hydrological factors in NWM predictions; enforce the need for regionalized physics and modeling; and help develop hybid post-processing methods to improve prediction. Finally, we demonstrate how the NOAA Next Generation Water Resource Modeling Framework can help reduce the structural bias through the application of heterogenous model processes and highlight opportunities for ongoing development and evaluation.

Neonicotinoid compounds are usually considered harmless and eco-friendly in terms of their targeted toxicity compared to that of pyrethroids and phosphorus-containing pesticides. However, overuse of neonicotinoid insecticides resulted in the accumulation of its residuals or intermediates in soil and water, which consequently affected beneficial insects as well as mammals, yielding pollution and secondary risks. This review summarized the recent advances in neonicotinoid degrading microorganisms and their metabolic diversity, with the aim to address the urgent need for degrading these insecticides. These advances may facilitate the development of controllable and reliable technologies for efficiently transforming neonicotinoid insecticides into value-added products by synthetic biology and metagenomics.

Cemented carbides, or hard metals, are ceramic–metal composites usually consisting of tungsten carbide particles bound by a cobalt-based alloy. They are the backbone materials for the tooling industry, as a direct consequence of the outstanding range of property combinations, depending on their effective microstructural assemblage, i.e., the physical dimensions and relative content of their constitutive phases. Hence, reliable microstructural characterization becomes key for hard metal grade selection and quality control. This work aimed to assess the practical twodimensional characterization methods for the most important one- and two-phase properties of cemented carbides, i.e., the carbide grain size, phase fraction, carbide contiguity, and binder mean free path. Three different methods—point, line, and area analysis—were implemented to characterize four microstructurally distinct grades. The images were acquired by optical and scanning electron microscopy, with the latter through both secondary and backscattered electrons. Results were critically discussed by comparing the obtained values of properties and the different characterization methodology. Inspection technique combinations were finally ranked based on accuracy, accessibility, and operability considerations. The line method was used to analyze all the properties, the area method, for the one-phase properties, and the point method, for only the phase fraction. It was found that the combination of optical microscopy and the line analysis method was suitable for a direct inspection and rapid estimation for carbides above fine grain size. The most precise results were achieved using line analysis of the images obtained by the backscattered electrons of the scanning electron microscope The work leading to this publication was supported by the Feodor Lynen Research Fellowship of the Alexander von Humboldt Foundation, by the individual research grant from the Deutsche Forschungsgemeinschaft (DFG-425923019), by the Spanish Ministerio de Ciencia e Innovación MICINN-FEDER (Spain) through grant PID2019-106631GB-C41 (AEI/10.13039/501100011033), and by the “Open Access Publication Funding” program of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) and Saarland University. The work also obtained funding for the FIB/SEM instrument used for SEM imaging and EBSD by the Deutsche Forschungsgemeinschaft (INST 256/510-1 FUGG)

Cubic boron nitride (CBN) composites are usually fabricated by sintering abrasive particles and binder powders under certain temperature and vacuum conditions. As a result, the inherent geometrical inhomogeneity of the abrasive grains in the binding matrix becomes an important intrinsic characteristic. In abrasive machining, the surface quality of workpieces is determined, to some extent, by the morphological characteristics of the grains extruded out of cutting surfaces. Within this regard, this work aims to characterize the morphological characteristics and to assess the wear modalities of CBN grains, at the same time to find out their eventual correlations. In doing so, a commercial CBN honing tool, namely B151/L2/10/50 (B151), is chosen as target material. A 3D model of a selected volume was reconstructed by applying cross-sectioning and digital image processing methods. Based on the grain segmentation and quantification, morphological characteristics of the grains are individually and statistically analyzed. Wear scenarios of the tool were characterized after cutting tests. Grains were found to have commonalities in shape and dimension on a microscale perspective despite their inhomogeneous distribution. Wear modalities are strongly related to the morphological characteristics of the grains. Specifically, degradation commences at spikes, with fractures initiating along the grain edges by either splitting grains and binder or intruding into the grains.

With the development of urban-rural integration in China, the functional value of homestead bases has evolved from a single residential security value to a multiple composite values, and the property income of homestead bases has gradually become the value driver of transfer and the intrinsic demand of farm households. This paper takes Baitafan of Jinzhai County, Chongqing City, and Xiaofang Yu Village of Ji County as examples for in-depth discussion, and finds that the dominant value drivers of home base transfer mainly include three kinds: capitalization income, commercialization income, and non-farm employment income. The study concludes that it is important to give full play to the resource endowment effect and identify the dominant value of home base transfer according to local conditions to promote the standardized home base transfer and implement the rural revitalization strategy.

During the manufacturing of machined workpieces with very narrow tolerances in serial production, slight quality deviations can cause high scrap rates and a waste of resources. In-process quality surveillance makes it possible to take measurements during the machining process as soon as a deviation occurs. Within this context, the quality of machined workpieces has to be predicted simultaneous to the machining process without affecting it. In this paper, the machine learning method of random forests (RF) is employed to predict geometrical and dimensional quality characteristics of reamed bores based on process data. Process data were collected during the serial production of high-precision hydraulic valves by a milling-machine. It is found that the values of the mean absolute error were on average very low for all predicted quality characteristics. The results have shown that RF is able to predict quality characteristics on basis of process data accurately which can lead to a more sustainable manufacturing of drilled and reamed bores.

The combined use of focused ion beam (FIB) milling and field-emission scanning electron microscopy inspection (FESEM) is a unique and successful approach for assessment of near-surface phenomena at specific and selected locations. In this study, a FIB/FESEM dual-beam platform was implemented to docment and analyze the wear micromechanisms on a laser-surface textured (LST) hardmetal (HM) tool. In particular, changes in surface and microstructural integrity of the laser-sculptured pyramids (effective cutting microfeatures) were characterized after testing the LST-HM tool against a steel workpiece in a workbench designed to simulate an external honing process. It was demonstrated that: (1) laser-surface texturing does not degrade the intrinsic surface integrity and tool effectiveness of HM pyramids; and (2) there exists a correlation between the wear and loading of shaped pyramids at the local level. Hence, the enhanced performance of the laser-textured tool should consider the pyramid geometry aspects rather than the microstructure assemblage of the HM grade used, at least for attempted abrasive applications.

The adverse impacts of harmful algal blooms (HABs) are increasing worldwide. Lake Erie is a North American Great Lake highly affected by cultural eutrophication and summer cyanobacterial HABs. While phosphorus loading is a known driver of bloom size, more nuanced yet crucial questions remain. For example, it is unclear what mechanisms are primarily responsible for initiating cyanobacterial dominance and subsequent biomass accumulation. To address these questions, we develop a mechanistic model describing June–October dynamics of chlorophyll a, nitrogen, and phosphorus near the Maumee River outlet, where blooms typically initiate and are most severe. We calibrate the model to a new, geostatistically-derived dataset of daily water quality spanning 2008–2017. A Bayesian framework enables us to embed prior knowledge on system characteristics and test alternative model formulations. Overall, the best model formulation explains 42% of the variability in chlorophyll a and 83% of nitrogen, and better captures bloom timing than previous models. Our results, supported by cross validation, show that onset of the major midsummer bloom is associated with about a month of water temperatures above 20 °C (occurring 19 July to 6 August), consistent with when cyanobacteria dominance is usually reported. Decreased phytoplankton loss rate is the main factor enabling biomass accumulation, consistent with reduced zooplankton grazing on cyanobacteria. The model also shows that phosphorus limitation is most severe in August, and nitrogen limitation tends to occur in early autumn. Our results highlight the role of temperature in regulating bloom initiation and subsequent loss rates, and suggest that a 2 °C increase could lead to blooms that start about 10 days earlier and grow 23% more intense.

With the rapid growth of population and economy, shortage and mismatch of land and water resources have deepened the need for cropping pattern optimization. In the context of the sustainable development of agriculture, cropping pattern optimization should not only pursue economic benefits, but the consequent environmental effects also deserve equal attention. Meanwhile, climate change increases the complexity of balancing conflicts of economic-environmental system by cropping pattern optimization. Therefore, this paper builds a multi-objective programming model for Economic-Environmental Synergistic Optimization for Cropping Pattern under Climate Change (EESO-CP-CC) model, with the goals of economic benefit increment and environmental pollutants emission reduction. The EESO-CP-CC model couples a non-point source pollution input-output model, a one-dimensional water quality model and an economic benefit function into an integrated framework. Fuzzy method was used to solve the optimization model, and the stochastic uncertainty of water supply under climate change was quantified by the integration of Bayesian approach and interval linear regression. The model was applied to Jinxi Irrigation District (JXID) in Heilongjiang Province, northeast of China. Results show that by adjusting the acreage of rice, corn and soybean, the harmony degree of economy-society-environment system increased by 10.7% compared to the current situation, indicating that the model tends to achieve the best possible economic benefits while ensuring the environmental effects. Compared with actual cropping pattern, the pollutants emissions reduced by 24.7% and 3% from corn and soybean, respectively. However, this led to a decrease of economic benefit by 8% in exchange, showing the trade-off between environmental pollution reduction and economic benefits improvement. The output coefficients of nitrogen and phosphorus pollutants were optimized, with the optimal output reducing by 20% compared to the standard. Cropping pattern and water resources allocation vary with different climate change conditions, however, the amplitude of variation is modest, indicating that the model can cope well with the changing environment. The developed model can help achieve synergistic development of economic benefits and environmental effects, and thus promote sustainable development of irrigation areas, and improve the coping capacity of agricultural water and land under climate change, by cropping pattern optimization and planning.

Quantification of endogenous and exogenous plasma glucose can help more comprehensively evaluate the glucose metabolic status. A ratio-based approach using isotope dilution liquid chromatography tandem mass spectrometry (ID LC-MS/MS) with indirect multiple reaction monitoring (MRM) of the derivative tag was developed to simultaneously quantify endo-/exogenous plasma glucose. Using diluted D-[13C6] glucose as tracer of exogenous glucose, 12C6/13C6 glucoses were first derivatized and then data were acquired in MRM mode. The metabolism of exogenous glucose can be tracked and the concentration ratio of endo/exo-genous glucose can be measured by calculating the endo-/exo-genous glucose concentrations from peak area ratio of specific daughter ions. Joint application of selective derivatization and MRM analysis not only improves the sensitivity but also minimizes the interference from the background of plasma, which warrants the accuracy and reproducibility. Good agreement between the theoretical and calculated concentration ratios was obtained with a linear correlation coefficient (R) of 0.9969 in the range of D-glucose from 0.5 to 20.0 mM, which covers the healthy and diabetic physiological scenarios. Satisfactory reproducibility was obtained by evaluation of the intra- and inter-day precisions with relative standard deviations (RSDs) less than 5.16%, and relative recoveries of 85.96 to 95.92% were obtained at low, medium, and high concentration, respectively. The method was successfully applied to simultaneous determination of the endo-/exogenous glucose concentration in plasma of non-diabetic and type II diabetic cynomolgus monkeys.

The simple peptide Fmoc-tyrosine (Fmoc-Y) with a self-assembled nanofiber structure was incorporated into Ca-alginate hydrogels to create an interpenetrating network (IPN) hybrid hydrogel. SEM and CD analysis was employed to confirm the integrity of the Fmoc-Y nanofiber structure. In the IPN hybrid hydrogel, the self-assembled Fmoc-Y nanofiber hydrogel can reinforce the Ca-alginate network. The IPN hydrogel exhibits enhanced storage moduli and fracture energy, about several times compared to those of Ca-alginate, Fmoc-Y and semi-IPN hydrogels. Furthermore, the IPN hydrogel reveals minimal release (less than 1%) for hydrophilic small molecules at acidic pH and sustained release at physiological pH, which can be achieved by simply tuning the Fmoc-Y concentration. Owing to the cost-efficiency of the raw materials and ease of fabrication, the synthesized hybrid hydrogels provide new options for diverse applications.

Eupatorium lindleyanum has traditionally been used as folk medicine in Asian countries for its therapeutic effects on tracheitis and tonsillitis. Investigation of the anti-inflammatory active constituents from E. lindleyanum led to the isolation of two novel sesquiterpene lactones, named eupalinolide L (1) and eupalinolide M (2), and seven known sesquiterpene lactones (3–9). The structures and configurations of the new compounds were determined on the basis of spectroscopic analysis, especially 2D NMR techniques. In vivo experiments showed that the sesquiterpenes fraction significantly reduced mouse ear edema induced by xylene (18.6%, p

As a non-contact unconventional machining approach, Electrochemical Machining (ECM), it is widely used for the machining of modern high-strength materials in the automotive, aerospace, or medical industry. ECM is also considered as an effective approach to reproduce complex surface patterns on the workpieces with high geometrical precision. On the other hand, it becomes a practical demand to precisely produce the desired pattern molds on the ECM tools, i.e., cathodes. Compared to traditional cathode forming approaches, such as milling, a short-pulsed laser can shape or sculpture functional surfaces on the scale of micrometers. In this study, a nanosecond laser was implemented to produce several complex two- and three-dimensional patterns on the PECM cathodes, made of the stainless steel 1.4301, including grooves, half spheres, and hexagonal pyramids. The textured tools were tested and validated on an industrial PECM machine PEMCenter8000, by replicating those patterns on workpieces made of Ti-6Al-4V. In this paper, fabrication of the tool patterns using nanosecond laser and and the subsequent quality inspection are introduced, and the first results of the tool validation are presented by comparing the geometrical measurement of the tool patterns to those replicated on the workpieces. It is found that the tool patterns produced by the nanosecond laser have clear surface conditions, and the tool pattern shapes meet the initial design. The geometrical precision of the pattern replications on the workpieces could be strongly influenced by the pattern design, as those sharp edges could cause an anisotropic electric field and instable electrolyte flushing conditions. The molten materials staked on the sharp positions might also be an important factor.

Laser surface texturing (LST) and coating deposition are implemented on cemented carbide (WC-CoNi) tools to extent their application in abrasive-like machining processes. The topographic features of a conventional cubic boron nitride based honing stone are achieved by LST, whereas wear resistance is enhanced by deposition of a ceramic layer. Three tool types are considered here: uncoated and coated LST WC-CoNi tools, besides a honing stone used as reference. They are tested under abrasive-like cutting conditions using an in-house workbench and a workpiece made of 20MnCr5 steel. Wear resistance and mechanisms as well as surface integrity of the tools after cutting tests are evaluated. It is found that LST cemented carbide tools achieve similar material removal effectiveness to the honing stone. Furthermore, coated LST tool exhibits a better cutting capacity, in terms of machined workpieces with smoother surfaces and enhanced wear resistance. However, the cutting process using cemented carbide tools is not as stable as the one developed employing the honing stone. The different response is related to the tribological conditions of the cutting edges of the laser-shaped pyramids. Damage within constitutive microstructural phases is clearly reduced for the coated condition, although it is still directly related to geometrical complexity of the pyramids.

A nanosecond laser combined with a two-axis reflection control unit is used to shape polygonal pyramids with defined geometry on a specific cemented carbide grade. In total, 12 different surface patterns have been fabricated, including four pyramid shapes, i.e., triangle, square, hexagon and octagon, and three lateral side angles, i.e., 30°, 45° and 60°. Characterization of the geometrical features shows satisfactory agreement between produced patterns and aimed ones. The precision is improved when the number of polygon sides and/or both side and slope angles increase. Side effects, such as re-deposition, cracks and pores, were discerned through scanning electron microscopy inspection. They become less obvious when the polygon side length or side angle increases, as the material melting becomes less important. Based on the observations, a borderline curve can be plotted for describing the production capability of such surface patterns on cemented carbides using the laser technology

Laser surface texturing has become popular in recent years, as its application in various fields may result in relevant benefits in different fields, such as tribological performance enhancement of contact surfaces. As frontline engineering materials, cemented carbides are widely used in the mining and manufacturing industries. In the case of cutting tools, surface texturing of working surfaces of cemented carbides emerges then as an interesting option. In this work, line-like structures are produced on the surface of a chosen cemented carbide grade by the method of direct laser interference patterning (DLIP), using nanosecond and femtosecond laser pulses, respectively. Specific laser setups are individually configured to obtain topographic features on the scale of a micrometer. It is aimed to assess the production precision using such configuration and compare the possible ablation effects induced by the two typical laser setups. Topographic features of the produced patterns are characterized using confocal laser scanning microscopy. Morphological features and surface integrity are examined by scanning electron microscopy combined with focused ion beam (FIB) milling. It is found that satisfactory geometrical precision is achieved both nano- and femtosecond lasers. It also complies with theoretical estimations. Surfaces formed by the femtosecond laser are cleaner and show smoother patterns, exhibiting lower melting or microcrack formation.

Honing is often implemented as surface finish process by improving geometrical and form precision of workpieces. Guiding stones, usually made of hard materials with requirement of excellent tribological properties, play a key role as a supporting part in the honing tool. In this paper, cemented carbides are intended for guiding application as substitute of diamond or CBN composites. Innovative surface textures, namely crossing-line patterns and dimple arrays, are fabricated by means of short pulse laser on a cemented tungsten carbide (hardmetal) grade. Implementation of these processing conditions yields satisfactory geometrical accuracy. The cemented carbide stones patterned by laser together with a traditional diamond guiding stone were tested on a lubricated pin-on-disc tribometer. Both cross-line patterns or dimple arrays are found to improve frictional conditions compared to the traditional guiding stone, but the former are more favorable to build up a stable sliding scenario with minimized friction than the latter. Pattern density has a more significant impact on friction, diminishing in the case of dimple arrays.

Abrasive effectiveness of composite-like honing stones is related to the intrinsic surface topography resulting from the cubic boron nitride (CBN) grains protruding out of the metallic matrix. Within this framework, Laser Surface Texturing (LST) is implemented for replicating topographic features of a honing stone in a WC-base cemented carbide grade, commonly employed for making tools. In doing so, regular arrays of hexagonal pyramids (similar to CBN grains) are sculpted by a laser micromachining system. Micrometric precision is attained and surface integrity does not get affected by such surface modification. Finally, potential of laser-patterned cemented carbide tools, as alternative to conventional honing stones, is supported by successful material removal and enhanced surface smoothness of a steel workpiece in the abrasive testing.

Diverse derivatives of amino acids with different steric configurations are important biosynthetic building blocks. In biology, epimerization is an important way to generate steric diversity. MarH catalyzes the epimerization of the β-position of (3R)-β-methyl-indolepyruvate (MeInPy), forming (3S)-β-MeInPy. Both compounds are derivatives of l-tryptophan (l-Trp) and are important precursors of bioactive natural products. Here, we report the crystal structures of MarH and the NMR structure of its complex with l-Trp, an analogue of its native substrate, (3R)-β-MeInPy. Structural analysis and mutagenesis studies indicated that His25 acts as a base to remove Hβ and generate a planar carbanion intermediate, which is then putatively reprotonated on the opposite face by a water molecule to form (3S)-β-MeInPy in a stereospecific manner. The details of β-site isomerization at the atomic level provide deeper insights into the epimerization mechanism of MarH and will facilitate further enzyme design to extend the substrate scope.

Harmful algal blooms (HABs) have been increasing in intensity worldwide, including the western basin of Lake Erie. Substantial efforts have been made to track these blooms using in situ sampling and remote sensing. However, such measurements do not fully capture HAB spatial and temporal dynamics due to the limitations of discrete shipboard sampling over large areas and the effects of clouds and winds on remote sensing estimates. To address these limitations, we develop a space-time geostatistical modeling framework for estimating HAB intensity and extent using chlorophyll a data sampled during the HAB season (June–October) from 2008 to 2017 by five independent monitoring programs. Based on the Bayesian information criterion for model selection, trend variables explain bloom northerly and easterly expansion from Maumee Bay, wind effects over depth, and variability among sampling methods. Cross validation results demonstrate that space-time kriging explains over half of the variability in daily, location-specific chlorophyll observations, on average. Conditional simulations provide, for the first time, comprehensive estimates of overall bloom biomass (based on depth-integrated concentrations) and surface areal extent with quantified uncertainties. These new estimates are contrasted with previous Lake Erie HAB monitoring studies, and deviations among estimates are explored and discussed. Overall, results highlight the importance of maintaining sufficient monitoring coverage to capture bloom dynamics, as well as the benefits of the proposed approach for synthesizing data from multiple monitoring programs to improve estimation accuracy while reducing uncertainty.

DNA nanostructures, owing to their controllable and adaptable nature, have been considered as highly attractive nanoplatforms for biomedical applications in recent years. However, their use in the biological environment has been restricted by low cellular transfection efficiency in mammalian cells, weak stability under physiological conditions, and endonuclease degradation. Herein, we demonstrate an effective approach to facilitate fast transfection of DNA nanostructures and enhance their stability by encapsulating DNA origami with a biocompatible cationic protein (cHSA) via electrostatic interaction. The coated DNA origami is found to be stable under physiological conditions. Moreover, the cHSA coating could significantly improve the cellular transfection efficiency of DNA origami, which is essential for biological applications.

In a previous study, micro-scale pyramid structures were produced on cemented carbide grades to form cutting edges (in the range 50 μm–100 μm) on their cutting surfaces. The pyramids were machined by an ultrashort pulse laser, exhibiting excellent surface integrity and defined geometric features. They are similar in size and shape to the abrasives used in grinding tools. In this study, hexagonal- and square-shaped pyramid structures are produced on four different cemented carbide grades. The wear of these textured cemented carbide tools was quantitatively and qualitatively assessed after grinding-like service conditions. More precisely, the geometric feature changes were measured, and cross-sectional characterization was conducted to reveal wear modalities of the cutting edges. Wear was detected mainly on the pyramids in the effective contact area of the tools, in the form of material loss resulting from grain cracking and adhesion. Hardness was a decisive factor in wearing the pyramids, and tools with hardness more than 1100 HV30 showed reduced wear. Pyramid shape also influenced the degree of wear, as the hexagon pyramids experienced less height reduction (up to 5%) than the square ones. Adhesion turned out to be significant on the cemented carbide grades with high binder content (about 30 wt%).

Flavonoids, including flavones, isoflavones, flavanones, chalcones, and isoflavans, have long been recognized as the main active ingredients in licorice. A method combining liquid chromatography with photodiode array detection and quadrupole time-of-flight mass spectrometry was developed to characterize components in three Glycyrrhiza species, and to expound the characteristic fragmentation behaviors in the positive ion mode. Based on the fragmentation patterns of reference compounds, a total of 39 compounds, including 37 flavonoid aglycones and two coumestans, were identified or tentatively identified. Besides, some common features, such as H2 O, CO, and CH2 O2 losses, together with retro-Diels-Alder fragmentation, were observed in these compounds. Furthermore, diagnostic fragmentations of C-ring cleavages and UV absorption on the skeleton groups were observed to structurally characterize flavonoid aglycones. In addition, typical losses of different substituent groups were detected: Neutral losses of 56 (C4 H8 ) and 68 Da (C5 H8 ) were yielded from a prenyl chain; neutral losses of 42 (C3 H6 ), 54 (C4 H6 ), and 70 Da (C4 H6 O) were generated by a pyran ring. Particularly, neutral losses of 18 (H2 O), 16 (CH4 ), 112 (C8 H16 ), and 98 Da (C7 H14 ) predicted a hydroxyl, a methoxyl, double prenyl chains, and a prenyl chain with a pyran ring, respectively.

Nearly every summer, a large hypoxic zone forms in the northern Gulf of Mexico. Research on the causes and consequences of hypoxia requires reliable estimates of hypoxic extent, which can vary at submonthly time scales due to hydro-meteorological variability. Here, we use an innovative space-time geostatistical model and data collected by multiple research organizations to estimate bottom-water dissolved oxygen (BWDO) concentrations and hypoxic area across summers from 1985 to 2016. We find that 27% of variability in BWDO is explained by deterministic trends with location, depth, and date, while correlated stochasticity accounts for 62% of observational variance within a range of 185 km and 28 days. Space-time modeling reduces uncertainty in estimated hypoxic area by 30% when compared to a spatial-only model, and results provide new insights into the temporal variability of hypoxia. For years with shelf-wide cruises in multiple months, hypoxia is most severe in July in 59% of years, 29% in August, and 12% in June. Also, midsummer cruise estimates of hypoxic area are only modestly correlated with summer-wide (June-August) average estimates ( r

MarH is an essential epimerase that catalyzes the isomerization of 3R-β-methyl-indolepyruvate (β-MeInPy) to 3S-β-MeInPy, which is the important precursor for biosynthesis of Maremycins. Biophysical study of the structure of MarH would be informative for better understanding of its catalytic mechanism and feasible application of the enzyme in isomerization reaction. Here, we report the backbone and side-chain NMR chemical shift assignments of MarH, which lays a foundation for further structural and mechanical study of the enzyme.

Some tools for machining processes used to be guided by supporting parts while using them for cutting or abrasive machining. For instance, the guide stone is used as supporting part in the honing process, which maintains the concentricity of the rotating axis. The contact surfaces of the supporting parts should exhibit the following properties: adequate combination of hardness, toughness and wear resistance. The damage of contact surfaces can be caused by a combination of friction and adhesion, related to the weakness of surface conditions in the tribological system, e.g. asperities, debris and pores. In order to investigate the impact of the surface topography, contact surfaces of the supporting parts made of cemented tungsten carbide (WC-Co) have been treated by means of laser surface patterning (LSP). Two different surface patterns with deterministic geometries on the micro and nano scale are achieved by two distinct LSP methods: line-like patterns by Laser-Interference Metallurgy (LIMET) with ns-laser and dimples by ps-laser. Tangential force coefficients, similar to the coefficient of friction (COF) in the non-abrasive case, are measured to evaluate the impact of the surface patterns. In this paper, the LSP methods as well as the analysis of the resulting surface topography are introduced. It is found that higher friction is obtained by line-like patterns whereas dimples can efficiently reduce the friction. At low load, hydrodynamic effects are reinforced as the dimples work as lubricant reservoirs and trap wear particles, and the observation becomes less obvious at high load. Meanwhile, only slight friction augmentation is observed by line-like patterns when the load increases.

As an excellent engineering tool material, cemented carbides are capable to shape and cut metallic materials with high surface finish quality and precision. However, in regard to conventional abrasive methods cemented carbides are difficult-to-machine materials due to their extreme hardness combined with relatively low toughness. In contrast, laser beam machining is an advanced non-contacting cutting method which is therefore suitable for shaping hard materials. In particular, the application of short-pulse laser beams enables the cutting of hard materials meeting high precision requirements. Moreover, it can effectively reduce defects induced by mechanical contacts and thermal reactions. In this paper, a general study of the ablation mechanism of cemented carbides using short-pulse laser is conducted. Special attention is paid to the correlation between the material ablation and machining parameters within the nanosecond regime: pulse number and pulse energy. In doing so, two cemented carbide grades with similar composition but different grain size have been chosen as investigated materials. An experimental set-up equipped with a nanosecond laser and an auto-stage is implemented to produce dimples on the cemented carbide surfaces with variable pulse number and pulse energy. The experimental design and characterization of geometrical features of produced dimples are presented and discussed. The work is complemented with a thorough surface integrity assessment of the shaped materials. It is found that ablation increases proportionally with the pulse number and applied energy. Regarding microstructural effects, ablation is discerned to be more pronounced in the coarse-grained grade as compared to the medium-sized one.

Cemented carbides are excellent engineering materials and they are widely used in cutting tools for metal cutting, mining, drilling, etc. Cemented carbide is a ceramic-metallic composite usually consisting of carbide grains, which are the hard phase occupying 70–97 wt% content, and binder, which is the soft phase occupying the rest. The two-phase microstructure unites adequate hardness of carbides with the toughness of the binder. Combinations of different phase compositions and carbide sizes can result in diverse microstructures of the material, which in turn strongly influence its mechanical behaviour, such as its hardness, fracture toughness and strength. Within this context, it is meaningful to investigate the microstructural properties of cemented carbides. In this paper, a cobalt and nickel based cemented tungsten carbide is selected as the study material. A three-dimensional reconstruction method by means of sectional-polishing technology is proposed based on the study of the carbide grade. Statistical quantification of carbide grains for a certain volume is carried out using the advanced 3D materials analysis software AMIRA. The results of the cemented carbides relating to material metallographic preparation, 3D reconstruction procedure and quantification are introduced and presented.

Abrasive processes are influenced by many different parameters. For a systematic investigation of these influencing parameters, a test bench for abrasive tools has been developed and set up on a 3-axis milling machine. The test bench is capable to control the machining parameters, such as the cutting speed and the feed speed, regulate the lubrication conditions, such as the temperature or the flow rate, and measure the cutting force during the process. Impacts of the single force components are investigated by means of the abrasive tools in contact with the rotating workpieces and the calculation of the tangential force coefficient. In this paper, the set-up of the test bench is explained and the systematic proceeding in investigating the impacts is exemplified by cooling lubricants because the surface of the workpiece, the wear of the tool, the temperature and the friction forces are often influenced by the type of cooling lubricant and its composition. The aim of the test bench for tools is to understand the correlations of the single influencing parameters in abrasive processes. The first results of comparative investigations with cooling lubricants of different viscosities are presented and discussed.

In the metal working industry, cutting tools for high precision application are usually made from non-conventional super hard materials, for example, diamond (D) and cubic boron nitride (CBN). These materials are composites of geometrically undefined grains embedded in metallic binder. For some special applications, these tools are constructed from one or several cutting edges and guide rails. Typical examples are honing and guided reaming tools for the fine machining of bores. These tools improve the form, dimension and surface quality, as well as the geometrical tolerances of the machined workpieces. The guide rails of the tool play an important role as they usually support the tool shaft in the rotating movement, for example the guiding stones of the honing tool. In the case of dynamic contact, higher demands on material properties such as hardness and wear resistance are necessary. In this study, a polycrystalline diamond (PCD) grade is employed as a new material for guide rails. Contacting surfaces of the PCD guide rails are textured with three defined patterns by a femtosecond laser setup. It is aimed to improve the force conditions by means of changing the contacting conditions. Within this regard, the tribological properties of the three patterns on PCD rails are characterized using a nanotribometer and compared to the conventional guide rails made of cemented tungsten carbides. A force simulation based on the honing processes is built up and conducted to predict the force conditions of each different pattern. At the same time, morphological modification, assessment of surface and microstructural integrity of the structured PCD guide rails are also studied in this work.

Cemented carbides, referred to as hardmetals, are forefront engineering materials widely implemented in industry for chip-removal cutting tools and supporting parts. As a newly developed technology for surface modification with high precision, the application of short pulse laser may extend the utilization of cemented carbides. However, surface integrity of laser-treated materials may be affected during the ablation phenomena. These potential changes may also be relevant for subsequent coating deposition, a surface modification stage usually invoked in many cutting and forming tools. It is the objective of this work to study the influence of a previous laser treatment on the surface integrity of a cemented carbide grade, finally coated by a ceramic layer introduced by physical vapor deposition. In doing so, a nanosecond laser has been employed. Surface integrity is assessed in terms of roughness, hardness, and microstructural changes induced at the subsurface level. It is found that pulse laser can effectively remove the target material, resulting roughness being similar to that attained by abrasive grinding. Although some subsurface damage is observed, it is limited to a very shallow layer, this being thoroughly eliminated during sandblasting implemented before coating deposition. Relative hardness increase is larger for laser treated substrate than for just polished one, reason behind it being speculated to come from the sandblasting stage used for removing damaged layer.

In this study, an inventory-theory-based inexact chance-constrained multi-stage stochastic programming (IB-ICCMSP) model under multi-uncertainties is developed. IB-ICCMSP integrates inventory theory into an inexact chance-constrained multi-stage stochastic optimization framework. This method can not only effectively address system multiple uncertainties (e.g. discrete intervals and probability density functions) and dynamic features, but also provide water transferring and allocating schemes among multiple stages. The developed model is applied to irrigation water allocation optimization system in Zhangye City, Gansu province, China. Based on the runoff simulation prediction of Yingluo Gorge and water supply–demand balance analysis of the 12 irrigation areas in Zhangye City, different optimal irrigation water measures are generated under different flow levels and different probabilities in the planning year. The obtained results are valuable for supporting the adjustment of the existing irrigation patterns and identifying desired water-allocation plans for irrigation under multi-uncertainties.

In this study, an inexact two-stage stochastic programming model is developed, which can provide an effective linkage between conflicting economic benefits and the associated penalties attributed to the violation of the predefined policies. The developed model was applied to irrigation water allocation optimization system in Minqin County, Gansu province, China. Three different water demands (high, middle, and low) were considered. Fuzzy parameters in the inexact two-stage stochastic programming model were introduced to account for fuzzy events that exist in the irrigation water allocation optimizing system. As the result, the optimal water allocation plans, both from surface water and groundwater, were obtained at different flow levels and different α-cut levels of Minqin County. The final results were expert to make great contributions in helping local managers to make decisions on allocating irrigation water more effectively under uncertainty.

Flavonoids, including flavones, isoflavones, flavanones, chalcones, and isoflavans, have long been recognized as the main active ingredients in licorice. A method combining liquid chromatography with photodiode array detection and quadrupole time-of-flight mass spectrometry was developed to characterize components in three Glycyrrhiza species, and to expound the characteristic fragmentation behaviors in the positive ion mode. Based on the fragmentation patterns of reference compounds, a total of 39 compounds, including 37 flavonoid aglycones and two coumestans, were identified or tentatively identified. Besides, some common features, such as H2 O, CO, and CH2 O2 losses, together with retro-Diels-Alder fragmentation, were observed in these compounds. Furthermore, diagnostic fragmentations of C-ring cleavages and UV absorption on the skeleton groups were observed to structurally characterize flavonoid aglycones. In addition, typical losses of different substituent groups were detected: Neutral losses of 56 (C4 H8 ) and 68 Da (C5 H8 ) were yielded from a prenyl chain; neutral losses of 42 (C3 H6 ), 54 (C4 H6 ), and 70 Da (C4 H6 O) were generated by a pyran ring. Particularly, neutral losses of 18 (H2 O), 16 (CH4 ), 112 (C8 H16 ), and 98 Da (C7 H14 ) predicted a hydroxyl, a methoxyl, double prenyl chains, and a prenyl chain with a pyran ring, respectively.

Non-conventional super hard abrasive tools are made of composite materials containing super hard grains, e.g., diamond or cubic boron nitride (CBN) grains, bound by a metallic constitutive phase. These tools are usually produced by means of sintering, and are widely applied in the abrasive machining processes of modern manufacturing, especially in precision machining. The abrasive grains, which induce the material removal processes, are embedded in the metallic binder. They emerge as a consequence of self-dressing, resulting in a self-sharping effect. Therefore, the cutting surface of the tool displays an irregular topography. Quantification of surface topography scenario may supply valuable information to evaluate and understand its correlation to wear mechanisms. In this study, an experimental protocol consisting of five steps: specimen preparation, surface scanning, image assembly, image digital processing and surface quantification, was proposed and validated by characterizing two CBN honing tools used for precision machining: B151/L2/2010/50 (B151) and B91/128/x44/35 (B91) CBN honing stones. It involved the use of laser scanning microscopy and digital imaging processing for assessing significant dimensional, geometrical, and positional properties of CBN grains at the surface of super hard abrasive tools. It was shown that surface topography quantification is an effective method to evaluate and obtain the defined parameters. However, smaller grains may require images with higher resolution; thus, scanning must be refined. Finally, a critical comparative analysis of the experimental results attained for the studied tools pointed out honing stone B91 as more appropriated than B151 one for achieving a higher machining quality of the workpiece.