ALBERT

Description: A key physical factor in regulating the performance of Madden–Julian oscillation (MJO) simulation is examined by using 26 climate model simulations from the World Meteorological Organization’s Working Group for Numerical Experimentation/Global Energy and Water Cycle Experiment Atmospheric System Study (WGNE and MJO-Task Force/GASS) global model comparison project. For this, intraseasonal moisture budget equation is analyzed and a simple, efficient physical quantity is developed. The result shows that MJO skill is most sensitive to vertically integrated intraseasonal zonal wind convergence (ZC). In particular, a specific threshold value of the strength of the ZC can be used as distinguishing between good and poor models. An additional finding is that good models exhibit the correct simultaneous convection and large-scale circulation phase relationship. In poor models, however, the peak circulation response appears 3 days after peak rainfall, suggesting unfavorable coupling between convection and circulation. For an improving simulation of the MJO in climate models, we propose that this delay of circulation in response to convection needs to be corrected in the cumulus parameterization scheme.

Description: This study investigates the differences and connections between the three-pattern decomposition of global atmospheric circulation, the representation of the horizontal vortex circulation in the middle–high latitudes and the local partitioning of the overturning circulation in the tropics. It concludes that the latter two methods are based on the traditional two-dimensional (2D) decomposition of the vortex and divergent circulations in the fluid dynamics and that the three-pattern decomposition model is not a simple superposition of the two traditional methods but a new three-dimensional (3D) decomposition of global atmospheric circulation. The three-pattern decomposition model can decompose the vertical vorticity of atmosphere into three parts: one part is caused by the horizontal circulation, whereas the other two parts are induced by divergent motions, which correspond to the zonal and meridional circulations. The diagnostic results from the decomposed vertical vorticities accord well with the classic theory: the atmospheric motion at 500 hPa is quasi-horizontal and nondivergent and can represent the vertical mean state of the entire atmosphere. The analysis of the climate characteristics shows that the vertical vorticities of the zonal and meridional circulations are the main cause of the differences between the three-pattern circulations and traditional circulations. The decomposition of the vertical vorticity by the three-pattern decomposition model offers new opportunities to quantitatively study the interaction mechanisms of the Rossby, Hadley and Walker circulations using the vorticity equation.

Description: A convection-permitting regional model simulation for August 2006 and observations are evaluated to better understand the diurnal cycle of precipitation over the Sahel. In particular, reasons for a nocturnal rainfall maximum over parts of the Sahel during the height of the West African monsoon are investigated. A relationship between mesoscale convective system (MCS) activity and inter-tropical front (ITF)/dryline dynamics is revealed. Over 90% of the Sahel nocturnal rainfall derives from propagating MCSs that have been associated with topography in earlier studies. In contrast, in this case study, 70–90% of the nocturnal rainfall over the southern Sahel (11°N–14°N) west of 15°E is associated with MCSs that originate less than 1000 km upstream (to the north and east) in the afternoon, in a region largely devoid of significant orography. This MCS development occurs in association with the Sahel ITF, combined with atmospheric pre-conditioning. Daytime surface heating generates turbulent mixing that promotes planetary boundary layer (PBL) growth accompanied by a low-level reversal in the meridional flow. This enhances wind convergence in the low-level moist layer within 2°–3° of latitude of the equatorward side of the ITF. MCSs tend to form when this vertical mixing extends to the level of free convection and is accompanied by a mid-tropospheric African easterly wave disturbance to the east. This synoptic disturbance enhances the vertical wind shear and atmospheric instability over the genesis location. These results are found to be robust across the region.

Description: The link between winter sea ice cover in the Barents Sea (SICBS) and the frequency of spring dust weather over North China (DWFNC) is investigated. It is found that year-to-year variability of SICBS and DWFNC are strongly correlated for the period 1996–2014 with a correlation coefficient of −0.65, whereas the correlation between SICBS and DWFNC is not statistically significant for the periods 1980–2014 and 1980–1995. During 1996–2014, low winter SICBS is associated with decreased snow cover over western Siberia (SCWS) in both winter and spring, which is also supported by a strengthening relationship between winter SICBS and spring SCWS since the mid-1990s. This leads to changes in atmospheric circulation and climate conditions that are favorable for increased frequency of dust weather events over North China. Our further analysis suggests that the interannual variability of the standard deviation of SICBS has intensified and the center of actions has moved eastward to the north Barents Sea and Kara Sea since the mid-1990s. Such change may easily induce stronger and southward stationary Rossby wave train propagation, influencing the dust-related atmospheric circulation (strengthened East Asian subtropical jet, increased cyclogenesis, and larger atmospheric thermal instability). Thus interannual variation of winter SICBS plays an increasingly important role in dust-related climate conditions over North China, which might serve as a new precursor for the prediction of spring dust activity in North China.

Description: The covalent organic framework LZU1 (Lan Zhou University-1) is one of the imine-based covalent organic frameworks (COFs) that possesses attractive properties such as structural regularity, stability and good porosity. This work reports on the in-situ synthesis of COF-LZU1 on the inner walls of capillary column for open-tubular capillary electrochromatography (OT-CEC). The fused-silica capillary was first modified with 3-aminopropyltriethoxysilane and glutaraldehyde. Epitaxial growth of COF-LZU1 on the inner walls was accomplished by Schiff base reaction. The formation of COF-LZU1 was confirmed by SEM and FT-IR. The COF-LZU1 coating increases the interactions between analytes and coating, which remarkably improves the CEC separation selectivity of neutral analytes, amino acids and nonsteroidal anti-inflammatory drugs. The COF-LZU1-modified column exhibits good stability and repeatability. The precisions (relative standard deviations) for intra-day, inter-day and column-to column are 〈1.6%, 5.6% and 6.8%, respectively. Hence, the imine-based COFs represent attractive stationary phase for application in CEC separations. Graphical abstract Covalent organic framework (COF-LZU1) was in situ synthesized on the inner wall of a capillary column for electrochromatographic separation of nonsteroidal drugs and amino acids.

Description: Urchin-like NiCo 2 O 4 hollow microspheres were synthesized by a solvothermal method and characterized by using X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller surface area, and zeta potential measurements. It was used as an adsorbent for the solid phase extraction of Pb(II) from water, food and street dust samples prior to its extraction with dilute HCl and its determination by FAAS. Figures of merit include a preconcentration factor of 30, a detection limit of 5.9 μg L −1 and a relative standard deviation of 2.4%. The major advantage of the method is the fast equilibration during extraction without the need for vortexing or shaking. The method was successfully accurated by analyzing certified reference materials (BCR-482 Lichen, TMDA-70 Lake water and RM 8704 Buffalo River Sediment) and by analyzing spiked sea water, wastewater, well water, apple, eggplant, broccoli, ginger, lentil and street dust samples. Graphical abstract Schematic of the preparation of urchin-like NiCo 2 O 4 microspheres and their application to the solid phase extraction of lead(II) ions

Description: South America is one of the most vulnerable areas to stratospheric ozone depletion; consequently, an increased amount of UV radiation reaches the Earth’s surface in this region. In this study, we analyzed the long-term trend in the total ozone column (TOC) over the southern part of the South American continent from 1980 to 2009. The database used was obtained by combining several satellite measurements of the TOC on a 1° (latitude) × 1.25° (longitude) grid. Analysis of the long-term trend was performed by applying the Theil-Sen estimator and the Mann–Kendall significance test to the deseasonalized time series. The long-term trend was also analyzed over several highly populated urban zones in the study area. Finally, multiple linear regression (MLR) modeling was used to identify and quantify the drivers of interannual variability in the TOC over the study area with a pixel-by-pixel approach. The results showed a decrease in the TOC ranging from −0.3 to −4% dec −1 from 1980 to 2009. On a decadal timescale, there is significant variability in this trend, and a decrease of more than −10% dec −1 was found at high latitudes (1980–1989). However, the trends obtained over much of the study area were not statistically significant. Considering the period from 1980 to 1995, we found a decrease in the TOC of −2.0 ± 0.6% dec −1 at latitudes below 40° S and −6.9 ± 2.0% dec −1 at latitudes above 40° S, for a 99.9% confidence level over most of the study area. Analysis of the period from 1996 to 2009 showed a statistically significant increase of 2.3 ± 0.1% dec −1 at high latitudes (〉 60° S), confirming the initial TOC recovery in the Antarctic. Despite evidence for initial recovery of the TOC in some parts of the study area between 1996 and 2009, the long-term increase from September to November is not yet statistically significant. In addition, large parts of the study area and most of the urban areas continue to show a decreasing trend in the TOC. The MLR results show that at high latitudes, the main driver of interannual variability in the TOC is the total effective amount of halogens, followed by the eddy heat flux.

Description: The authors describe the preparation of desert rose-like gold nanoparticles (DR-GNPs) with a plasmon resonance band at 620 nm which gives them a blue color. They have a hydrodynamic diameter of ∼72 nm and were prepared by a seeding growth approach. The DR-GNPs were characterized by UV-vis spectroscopy, transmission electron microscopy and dynamic light scattering. These nonspherical GNPs were used as a label for the antibody in an immunochromatographic strip test (ICST). Despite their particular shape and the higher surface area compared to spherical gold nanoparticles, the DR-GNPs are useful blue labels for the GNP-based strip test. A multicolor ICST for aflatoxin B1 and fumonisins is described that employs both blue DR-GNPs and red spherical GNPs. It allows for simultaneous rapid determination of the two mycotoxins in maize flour, with visual cut-off levels of 2 μg⋅kg -1 for aflatoxin B1 and of 1000 μg⋅kg -1 for fumonisins. Graphical abstract Blue desert rose-like gold nanoparticles (DR-GNPs) were synthesized, characterized and applied as label for the ImmunoChromatographic Strip Test (ICST) technique, in which red spherical GNPs (s-GNPs) are usually employed. The combined use of the blue DR-GNP and red s-GNPs allowed developing of an intuitive multicolor ICST for the simultaneous detection of aflatoxin B1 and fumonisins in maize flour.

Description: The article describes a method for preconcentration and speciation of Cr(III) and Cr(VI) in river waters. It is based on ultrasound-assisted magnetic solid phase extraction employing a nanocomposite prepared from magnetite nanoparticles, manganese oxide and alumina oxide, and then functionalized with [3-(2-aminoethylamino)propyl] trimethoxysilane (AAPTMS). By taking advantage of the oxidative properties of MnO 2 , the Fe 3 O 4 @MnO 2 ,Al 2 O 3 nanocomposite was used for the preconcentration of total chromium. The AAPTMS-modified nanocomposite, in turn, is selective for Cr(VI). The concentration of Cr(III) can be calculated as the difference between total chromium and Cr(VI). The preconcentrated chromium species were quantified using ICP-OES. The method was optimized using response surface methodology. Under optimal conditions, the limit of detection and quantification are 20 and 50 pg ⋅ mL −1 , respectively. The intraday and interday precisions of the method, expressed in terms of relative standard deviation, are 2.6 and 4.9%, respectively. In addition, the effects of potentially interfering ions were examined. The method was successfully applied to the speciation of chromium in spiked river water and a certified reference material. Graphical abstract The magnetic Fe 3 O 4 @MnO 2 ,Al 2 O 3 was used as an adsorbent for preconcentration of total chromium in aqueous samples, while Fe 3 O 4 @MnO 2 ,Al 2 O 3 modified with [3-(2-aminoethylamino)propyl] trimethoxysilane (AAPTMS) was used for speciation of Cr(VI). The concentrations of Cr(III) was calculated from total Cr and Cr(VI).

Description: A dendrochronological profile was generated from Chinese pines ( Pinus tabulaeformis Carr.) in the Qianshan Mountains in northeastern China. Based on correlation analyses, the pattern of precipitation from March to June ( P 36 ) was reconstructed using a simple linear model, which explained 42.7% of the total variance in observed precipitation from 1951 to 2012. The reconstructed P 36 series revealed a consistently increasing trend in precipitation during the twentieth century in the Qianshan Mountains. The reconstructed data showed trends that were similar to those in the variation in trends for March–June precipitation observed at the Shenyang station, the reconstructed January–May precipitation trends in Shenyang City, and the reconstructed average June–September relative humidity for Yiwulü Mountain. The reconstructed data also showed good agreement with the droughts reported in historical documents and recorded by meteorological stations in Liaoning. Spatial correlation analyses show that the reconstructed data reflect the variability in precipitation that occurs over much of northeastern China. In addition, our reconstruction showed a significant periodicity. The significant correlations between the reconstructed P 36 and the El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and sunspot numbers indicate that precipitation variability in the Qianshan Mountain region is probably driven by extensive atmosphere-sea interactions and solar activities.

Description: The authors described gold nanoclusters (AuNCs) for use on an “on − off − on” NIR fluorescent probe for the determination of citrate and Cu(II) ion. The AuNCs were prepared by a microwave-assisted method using BSA as both the stabilizing and reducing agent. The resulting BSA-capped AuNCs display NIR fluorescence peaking at 680 nm under 500 nm excitation, a quantum yield of ~6.0%, an average size of 2.8 ± 0.5 nm, water-dispersibility, stability and biocompatibility. The on−off probe for Cu(II) is based on the interaction between Cu(II) and BSA which causes the fluorescence of the BSA−AuNCs to be quenched. The quenched fluorescence is recovered on addition of vitamin C (VC), obviously due to complexation of Cu(II) by citrate. The probe was employed to image Cu(II) and citrate in HeLa cells and in aqueous solutions. The method works in the 20 nM to 0.1 mM concentration range for Cu(II), and in the 8 nM to 120 μM concentration range for VC. Graphical abstract Schematic presentation of the gold nanocluster based probe whose fluorescence is quenched by Cu(II) ions and then restored by addition of vitamin C. This is demonstrated for both aqueous solutions and living cells.

Description: In this study, the interannual variability of sea surface temperature (SST) and its atmospheric teleconnection over the western North Pacific (WNP) toward the North Pacific/North America during boreal winter are investigated. First, we defined the WNP mode as the first empirical orthogonal function (EOF) mode of SST anomalies over the WNP region (100–165°E, 0–35°N), of which the principle component time-series are significantly correlated with several well-known climate modes such as the warm pool mode which is the second EOF mode of the tropical to North Pacific SST anomalies, North Pacific oscillation (NPO), North Pacific gyre oscillation (NPGO), and central Pacific (CP)-El Niño at 95% confidence level, but not correlated with the eastern Pacific (EP)-El Niño. The warm phase of the WNP mode (sea surface warming) is initiated by anomalous southerly winds through reduction of wind speed with the background of northerly mean winds over the WNP during boreal winter, i.e., reduced evaporative cooling. Meanwhile, the atmospheric response to the SST warming pattern and its diabatic heating further enhance the southerly wind anomaly, referred to the wind–evaporation–SST (WES) feedback. Thus, the WNP mode is developed and maintained through winter until spring, when the northerly mean wind disappears. Furthermore, it is also known that anomalous upper-level divergence associated with WNP mode leads to the NPO-like structure over the North Pacific and the east–west pressure contrast pattern over the North America through Rossby wave propagation, impacting the climate over the North Pacific and North America.

Description: The authors report on a rapid voltammetric method for simultaneous determination of the pathogens E. coli and Salmonella typhimurium ( S. typh .) by detecting the rfbE gene of E. coli O157:H7 and gyrB gene of S. typh ., respectively, and by using polymerase-assisted target recycling amplification. The assay was constructed by self-assembly of the respective hairpin probes (labeled with the electrochemical probes Methylene Blue and ferrocene) on the surface of a gold electrode. After hybridization between target DNA and hairpin probes (HPs) has occurred, the primers hybridize with the open-chain HPs and initiate extension reactions in the presence of polymerase and deoxyribonucleoside triphosphates. This results in the release of the redox labels from the electrode surface and the target dissociating from the HPs. The released target will bind to other HPs to activate new cycles, which results in enhanced suppression of current, measured best at −0.27 V and +0.36 V (vs. Ag/AgCl) for parallel detection of E. coli DNA and S. typh . DNA, respectively. The method presented here based on target recycling amplification and its integration into multiplexed electrochemical detection of pathogens was successfully applied to quantitative determination of E. coli O157:H7 and S. typh . in synthetic samples. In our perception, the strategy presented here represents a rapid and universal platform for sensitive and multiplexed quantitation of pathogens and related molecular diagnostic targets of relevance in food safety control.

Description: The capability of multi-level logic operations in biological diagnosis is far from being fully realized. In particular, the simplification of logic judgments to realize rapid, on-site complex diagnoses is still a key issue in bioelectronics. The authors here describe the construction of a colorimetric multilevel DNA circuit that incorporates two IMPLY gates and a sample extraction technology (SET) with anti-BPA aptamer as a co-recognizing element and the color of gold nanoparticles as the output signal. The circuit can perform multi-bioanalysis of the plasticizers and hormone mimetics bisphenol A (BPA) and bisphenol S (BPS). The assay is based on the finding that the aptamer against BPA can recognize both BPA and BPS. This DNA logic detection system is simple, fast, sensitive and selective because of the utilization of a co-recognition element which decreased input numbers. This, in turn, cascades multiplex Boolean logic gates and simplifies the diagnostic challenge. Both BPA and BPS can be determined by photometry at 620 nm, the limit of detection being 1.5 ng⋅mL −1 for BPA and 1.3 ng⋅mL −1 for BPS. Application to (spiked) water samples shows good analytical performance in terms of recovery (95.4 to 106.8%), linear range (4.4 to 66 ng⋅mL −1 for BPA, 2.5 to 75 ng⋅mL −1 for BPS) and correlation coefficients (〉0.98). In our perception, the method represents a simple route for the fabrication of colorimetric multi-level DNA circuits. It may shorten the gap between bioelectronic logic circuits and high throughput real sample analysis. Graphical abstract Illustration of sample extraction treatments (SET) of bisphenol A (BPA) and bisphenol S (BPS) and the three-input IMPLY1-IMPLY2 logic operation with BPA, BPS and anti-BPA aptamer as inputs.

Description: The synthesis of rattle-type nanostructured Fe 3 O 4 @SnO 2 is described along with their application to dispersive solid-phase extraction of trace amounts of mercury(II) ions prior to their determination by continuous-flow cold vapor atomic absorption spectrometry. The voids present in rattle-type structures make the material an effective substrate for adsorption of Hg(II), and also warrant high loading capacity. The unique morphology, large specific surface, magnetism property and the synergistic effect of magnetic cores and SnO 2 shells render these magnetic nanorattles an attractive candidate for solid-phase extraction of heavy metal ions.The sorbent was characterized by transmission electron microscopy, scanning electron microscopy, FTIR, energy-dispersive X-ray spectroscopy and by the Brunnauer-Emmett-Teller technique. The effects of pH value, adsorption time, amount of sorbent, volume of sample solutions, concentration and volume of eluent on extraction efficiencies were evaluated. The calibration plot is linear in the 0.1 to 40 μg·L −1 concentration range, and the preconcentration factor is 49. The detection limit is 28 ng·L −1 . The sorbent was applied to the analysis of (spiked) river and sea water samples. Recoveries ranged from 97.2 to 100.5%. Graphical abstract A yolk-shell structure based on a Fe 3 O 4 core and SnO 2 shell was developed as an efficient MSPE sorbent. A middle silica layer was etched by alkaline solution. The resulting sorbent was utilized for preconcentration of mercury ions from aqueous media.

Description: The authors describe an inexpensive electrode for the sensitive amperometric determination of the pesticide methyl parathion. A glassy carbon electrode was modified with a nanocomposite consisting of molybdenum disulfide nanosheets (MoS2) and graphene that was prepared via a hydrothermal process. Its morphology, elemental composition, diffraction, impedance and voltammetric characteristics were studied. The modified electrode displays excellent electrocatalytic ability towards methyl parathion, and the reduction peak current, measured typically at −0.60 V (vs. Ag/AgCl) is related to the concentration of methyl parathion. The effect of concentration, scan rate and solution pH value were optimized. The calibration plot is linear in the 10 nM to 1.9 mM concentration range, with a 3.2 nM detection limit (at a signal-to-noise ratio of 3). The electrode is selective, stable, adequately repeatable and reproducible. The method was successfully applied to the determination of methyl parathion in spiked samples of homogenized apple, kiwi, tomato and cabbage. Graphical Abstract A reliable and robust methyl parathion sensor has been developed using heterostructured MoS 2 /graphene. The linear range is 10 nM–1.9 nM and detection limit is 3.2 (±0.8) nM. The method was successful in real sample determination of spiked methyl parathion in food samples such as apple, kiwi, tomato and cabbage.

Description: We evaluated 11 coupled climate model simulations regarding the spatial structures of sea-surface temperature (SST) variability in the North Atlantic, during the second half of the twentieth century. The subset of models includes CCSM4, CSIRO, CanESM and MPI-ESM, participating in the fifth phase of the Climate Model Intercomparison Project. The evaluation was performed to determine the potential of these models to be used at a later stage as test beds for the evaluation of climate field reconstruction methods that will use the extremely long-lived bivalve mollusk Arctica islandica , an outstanding paleoclimate archive for the boreal and temperate North Atlantic (Schöne, Glob Planet Change 111:199–225, 2013 ). Several validation metrics such as the mean bias, variance, spatial and temporal co-variability and trends of the North Atlantic summer SSTs showed that some of the models can be used to test paleoclimatic reconstructions. However, most models showed shortcomings in simulating the Atlantic Multidecadal Oscillation. Concerning the co-variability of summer SSTs between proxy sites and the whole North Atlantic SST field, we found that these proxy locations contain a SST signal that might represent a (basin-wide) signal for the north-eastern North Atlantic basin.

Description: The large-scale and synoptic-scale Northern Hemisphere atmospheric circulation responses to projected late twenty-first century Arctic sea ice decline induced by increasing Greenhouse Gases (GHGs) concentrations are investigated using the CNRM-CM5 coupled model. An original protocol, based on a flux correction technique, allows isolating the respective roles of GHG direct radiative effect and induced Arctic sea ice loss under RCP8.5 scenario. In winter, the surface atmospheric response clearly exhibits opposing effects between GHGs increase and Arctic sea ice loss, leading to no significant pattern in the total response (particularly in the North Atlantic region). An analysis based on Eady growth rate shows that Arctic sea ice loss drives the weakening in the low-level meridional temperature gradient, causing a general decrease of the baroclinicity in the mid and high latitudes, whereas the direct impact of GHGs increase is more located in the mid-to-high troposphere. Changes in the flow waviness, evaluated from sinuosity and blocking frequency metrics, are found to be small relative to inter-annual variability.

Description: This study assesses the performance of 15 high resolution global climate models (GCMs) over the complex orographic region of the subtropical central Andes from available simulations of the Fifth Coupled Model Intercomparison Project (CMIP5). The simulated past climate (1980–2005) was compared against the Climate Research Unit (CRU) dataset and the ERA-Interim reanalysis, considered as reference datasets, to evaluate regional and seasonal surface temperature and precipitation, as well as sea level pressure and circulation. A good agreement was found between the simulations and the reference datasets for winter precipitation and for temperature over both seasons. Whilst all models correctly reproduce the annual cycle of precipitation, some of them overestimate winter totals. ERA-Interim does not adequately represent summer precipitation over the region, and some of the models analyzed also show the same deficiency. All models correctly reproduce the northward migration of the South Pacific subtropical high during winter, although some of them underestimate the maximum central pressure. During summer, most models fail to show the low level north–south flow parallel to the eastern foothills of the Andes, a feature known as the Low Level Jet. Further analysis of the results of the simulations led to the selection of a sub-set of five CMIP5 GCMs to construct a reduced ensemble. This reduced ensemble is a better representation than the multi-model mean of the 15 GCMs of the past climate at this region and would be recommended for future studies.

Description: We assess Indian summer monsoon seasonal forecasts in GloSea5-GC2, the Met Office fully coupled subseasonal to seasonal ensemble forecasting system. Using several metrics, GloSea5-GC2 shows similar skill to other state-of-the-art seasonal forecast systems. The prediction skill of the large-scale South Asian monsoon circulation is higher than that of Indian monsoon rainfall. Using multiple linear regression analysis we evaluate relationships between Indian monsoon rainfall and five possible drivers of monsoon interannual variability. Over the time period studied (1992–2011), the El Niño-Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD) are the most important of these drivers in both observations and GloSea5-GC2. Our analysis indicates that ENSO and its teleconnection with Indian rainfall are well represented in GloSea5-GC2. However, the relationship between the IOD and Indian rainfall anomalies is too weak in GloSea5-GC2, which may be limiting the prediction skill of the local monsoon circulation and Indian rainfall. We show that this weak relationship likely results from a coupled mean state bias that limits the impact of anomalous wind forcing on SST variability, resulting in erroneous IOD SST anomalies. Known difficulties in representing convective precipitation over India may also play a role. Since Indian rainfall responds weakly to the IOD, it responds more consistently to ENSO than in observations. Our assessment identifies specific coupled biases that are likely limiting GloSea5-GC2 Indian summer monsoon seasonal prediction skill, providing targets for model improvement.

Description: During the global warming hiatus period (1998–present), a pronounced increase in the number of intense typhoon occurrences was identified over the Philippine Sea (PS: 5°–25°N, 125°–140°E) in September after the mid-2000s. Comparing two periods before and after the mid-2000s indicates that intense typhoons rarely occurred over the PS in September before the mid-2000s, with a frequency of fewer than 0.4 per year, but reached up to nearly 1.5 per year after the mid-2000s. The abrupt increase in intense typhoon occurrences over the PS was primarily attributed to increased tropical cyclone (TC) genesis and favorable large-scale conditions for TC intensification. The increase in TC genesis number over the PS was caused by contributory dynamical conditions, including positive low-level relative vorticity anomalies and anomalous ascents, which corresponded to a southwestward shift and strengthening of the monsoon trough. In addition, among the favorable large-scale conditions, the increased relative humidity that resulted from intensified moisture flux convergence exerted essential effect on the TC intensification. These changes in atmospheric environmental conditions favoring intense typhoon occurrences over the PS were primarily associated with the change in the tropical Indo-Pacific sea surface temperature (SST) around the mid-2000s. Besides that, the positive feedback TCs exerted on the circulation was also conducive to the unusual growth in intense typhoon occurrences over the PS. And note that the role of SST anomalies in the air–sea interaction is the key to interpret why the unique phenomenon only occurred in September.

Description: Variations in sea ice freeze onset and regional sea surface temperatures (SSTs) in Baffin Bay and Greenland Sea are linked to autumn surface air temperatures (SATs) around coastal Greenland through 500 hPa blocking patterns, 1979–2014. We find strong, statistically significant correlations between Baffin Bay freeze onset and SSTs and SATs across the western and southernmost coastal areas, while weaker and fewer significant correlations are found between eastern SATs, SSTs, and freeze periods observed in the neighboring Greenland Sea. Autumn Greenland Blocking Index values and the incidence of meridional circulation patterns have increased over the modern sea ice monitoring era. Increased anticyclonic blocking patterns promote poleward transport of warm air from lower latitudes and local warm air advection onshore from ocean–atmosphere sensible heat exchange through ice-free or thin ice-covered seas bordering the coastal stations. Temperature composites by years of extreme late freeze conditions, occurring since 2006 in Baffin Bay, reveal positive monthly SAT departures that often exceed 1 standard deviation from the 1981–2010 climate normal over coastal areas that exhibit a similar spatial pattern as the peak correlations.

Description: Sea surface temperature (SST) in the Indo-Pacific warm pool (IPWP) plays a key role in influencing East Asian climate, and even affects global-scale climate change. This study defines IPWP Niño and IPWP Niña events to represent the warm and cold phases of IPWP SST anomalies, respectively, and investigates the effects of these events on stratospheric circulation and temperature. Results from simulations forced by observed SST anomalies during IPWP Niño and Niña events show that the tropical lower stratosphere tends to cool during IPWP Niño events and warm during IPWP Niña events. The responses of the northern and southern polar vortices to IPWP Niño events are fairly symmetric, as both vortices are significantly warmed and weakened. However, the responses of the two polar vortices to IPWP Niña events are of opposite sign: the northern polar vortex is warmed and weakened, but the southern polar vortex is cooled and strengthened. These features are further confirmed by composite analysis using reanalysis data. A possible dynamical mechanism connecting IPWP SST to the stratosphere is suggested, in which IPWP Niño and Niña events excite teleconnections, one similar to the Pacific–North America pattern in the Northern Hemisphere and a Rossby wave train in the Southern Hemisphere, which project onto the climatological wave in the mid–high latitudes, intensifying the upward propagation of planetary waves into the stratosphere and, in turn, affecting the polar vortex.

Description: The authors describe a flow cytometric immunoassay for aflatoxin B1 (AFB1). It has three distinct features: (a) Magnetic microspheres encoded with upconverting nanocrystals (UCNMMs) are used as fluorescent labels. These have the advantage of non-overlapping spectra and lacking crosstalk between the encoding signal and reporter signal via the low-energy near-infrared (NIR) light excitation; (b) phycoerythrin-labeled secondary antibodies are used to amplify the reporter signal; (c) The use of magnetic nanoparticles facilitates the rapid separation and specific purification of the analyte (AFB1). This assay has a detection limit of 9 pg·mL −1 and a broad working range for AFB1, requires a 50 μL sample only, and can be completed within 2 h with good accuracy and high reproducibility. It is perceived that such multifluorescent UCNMMs, whose color depends on the kind of dopants (Yb, Er, Tm, Mn) in the NaYF 4 host lattice, represent a promising tool for the analysis of mycotoxins and other analytes. Graphical abstract Schematic of the UCNMM-based indirective competitive immunoassay for AFB1 using the flow cytometric analysis (FCA) technology. The UCNMMs are prepared by doping the upconversion nanocrystals and magnetic nanoparticles inside the mesoporous polystyrene microspheres as the self-healing encapsulation strategy.

Description: The authors describe a non-enzymatioc glucose assay that has three features: (a) The use of a boronic acid as the recognition element; (b) the aggregation of gold nanoparticles (AuNPs), and (c) the use of graphene oxide quantum dots (GOQD) whose fluorescence matches the absorption of the AuNPs and thereby results in an inner filter effect (IFE). The GOQD display an orange colored fluorescence that is filtered off by the AuNPs due to an IFE. In the presence of 3-aminobenzeneboronic acid, glucose is bound to form a cationic species that causes the aggregation of AuNPs to form large assemblies. This is accompanied by a color change from red to blue, and the IFE no longer does occur so that the orange fluorescence of the GOQD pops up again. These findings were used to design an assay witha linear response in the  2.5 to 75 μmol L −1  glucose concentration range, with a detection limit of 0.65 μmol L −1 . The method was applied to the determination of glucose in spiked diluted serum and gave satisfactory results. Graphical abstract Schematic of the detection of glucose based on inner filter effect of dispersed AuNPs on the orange fluorescence of graphene oxide quantum dots.

Description: A nanocomposite prepared from reduced graphene oxide (rGO) and silver nanoparticles (AgNPs) is used in an electrochemical aptasensor for the sensitive and selective determination of the antibiotic chloramphenicol (CAP). The nanocomposite was obtained by electrostatic assembly of AgNPs on the surface of polyelectrolyte-functionalized rGO and then used to modify a glassy carbon electrode. The biosensor is then obtained by immobilizing the aptamer against CAP. When incubated with solutions of CAP, the sensor surface is loaded with CAP due to aptamer recognition. The captured CAP can be electrochemically reduced to yield a current that is strongly enhanced as a result of the excellent electrocatalysis property of the graphene/AgNP-nanocomposite. Under optimum conditions, the calibration plot is linear in the 0.01 to 35 μM concentration range, with a 2 nM detection limit (at 3σ). The sensor is reproducible, stable, selective over homologous interferents, and performs excellently when analyzing CAP in milk samples. Graphical Abstract A graphene/silver nanoparticle-based electrochemical aptasensor is designed for the selective determination of the antibiotic chloramphenicol (CAP). The excellent electrocatalytic reduction of CAP specifically captured onto the electrode surface enables the sensitive electrochemical signal transduction of the biosensor by linear sweep voltammetry (LSV).

Description: The costs of current genotyping methods limit their application to personalized therapy. The authors describe an alternative approach for the detection of single-point-polymorphisms using recombinant polymerase amplification as an allele-specific technique. The use of short and chemically modified primers and locked nucleic acids allowed for a selective isothermal amplification of wild-type or mutant variants at 37 °C within 40 min. An amplification chip platform containing 100 wells was manufactured with a 3D printer and using thermoplastic polylactic acid. The platform reduces reagent consumption and allows parallelization. As a proof of concept, the method was applied to the genotyping of four SNPs that are related to the treatment of tobacco addiction. The target polymorphisms included rs4680 (COMT gene), rs1799971 (OPRM1 gene), rs1800497 (ANKK1 gene), and rs16969968 (CHRNA5 gene). The genotype populations can be well discriminated. Graphical abstract Schematic of the allele-specific recombinase polymerase amplification for genotyping of polymorphisms. The isothermal discrimination reaction occurs in a multi-well amplification chip manufactured with a 3D printer and by using thermoplastic polylactic acid.

Description: Climate change simulation based on 30-member ensemble of Voeikov Main Geophysical Observatory RCM (resolution 25 km) for northern Eurasia is used to drive hydrological model CaMa-Flood. Using this modeling framework, we evaluate the uncertainties in the future projection of the peak river discharge and flood hazard by 2050–2059 relative to 1990–1999 under IPCC RCP8.5 scenario. Large ensemble size, along with reasonably high modeling resolution, allows one to efficiently sample natural climate variability and increase our ability to predict future changes in the hydrological extremes. It has been shown that the annual maximum river discharge can almost double by the mid-XXI century in the outlets of major Siberian rivers. In the western regions, there is a weak signal in the river discharge and flood hazard, hardly discernible above climate variability. Annual maximum flood area is projected to increase across Siberia mostly by 2–5% relative to the baseline period. A contribution of natural climate variability at different temporal scales to the uncertainty of ensemble prediction is discussed. The analysis shows that there expected considerable changes in the extreme river discharge probability at locations of the key hydropower facilities. This suggests that the extensive impact studies are required to develop recommendations for maintaining regional energy security.

Description: Using high resolution convective permitting simulations, we have investigated the sensitivity of historical orographically enhanced extreme precipitation events to idealized temperature perturbations. Our simulations were typical autumn and winter synoptic scale extreme precipitation events on the west coast of Norway. The response in daily mean precipitation was around 5%/K for a 2 °C temperature perturbation with a clear topographical pattern. Low lying coastal regions experienced relative changes that were only about 1/3 of the changes at higher elevations. The largest changes were seen in the highest elevations of the near coastal mountain regions where the change was in order of +7.5%/K. With a response around 5%/K, our simulations had a precipitation response that was around 2%/K lower than Clausius-Clapeyron scaling and 3%/K lower than the water vapor change. The below Clausius-Clapeyron scaling in precipitation could not be explained by changes in vertical velocities, stability or relative humidity. We suggest that the lower response in precipitation is a result of a shift from the more efficient ice-phase precipitation growth to less effective rain production in a warmer atmosphere. A considerable change in precipitation phase was seen with a mean increase in rainfall of 16%/K which was partly compensated by a reduction in snowfall of around 23%/K. This change may have serious implications for flooding and geohazards.

Description: Studies based on sediment records, sea-surface temperature and wind suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer Monsoon. We examine this relationship directly in an eddy-resolving global ocean simulation STORM driven by atmospheric reanalysis over the last 61 years. With its very high spatial resolution (10 km), STORM allows us to identify characteristics of the upwelling system. We analyse the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analysis reveals high interannual correlations between coastal upwelling and along-shore wind-stress (r = 0.73) as well as with sea-surface temperature (r = −0.83). However, the correlation between the upwelling and the Monsoon is small. We find an atmospheric circulation pattern different from the one that drives the Monsoon as the main modulator of the upwelling variability. In spite of this, the patterns of temperature anomalies that are either linked to Arabian Sea upwelling or to the Monsoon are spatially quite similar, although the physical mechanisms of these links are different. In addition, no long-term trend is detected in our modelled upwelling in the Arabian Sea.

Description: A novel voltammetric assay for the simultaneous determination of hydroquinone (HQ), catechol (CC) and resorcinol (RS) by using an electrochemically treated pencil graphite electrode modified with cobalt-phthalocyanine is described. Differential pulse voltammetric results showed three well-distinct oxidation peaks for HQ, CC and RS at 102 mV, 203 mV and 591 mV (vs. Ag/AgCl), respectively. Thus, the method can be applied to direct simultaneous determination without previous separation. The detection limits are 3.38 × 10 −7  mol L −1 for HQ, 3.40 × 10 −7  mol L −1 for CC and 7.23 × 10 −7  mol L −1 for RS. The method was successfully applied to the direct determination of dihydroxybenzene isomers in tea samples, and the results were compared with chromatographic data. Graphical abstract A novel assay for electrochemical detection of hydroquinone (HQ), catechol (CC) and resorcinol (RS) based on an electrochemically treated pencil graphite electrode (PGE*) modified with cobalt phthalocyanine (CoPC) was investigated. The differential pulse voltammetric (DPV) method provide a new means for direct determination of a multi-component system.

Description: The authors describe the preparation of a graphene oxide based poly(2,6-diaminopyridine) composite by in-situ polymerization. The material was characterized by Fourier transform infrared spectrometry, powder X-ray diffraction and scanning electron microscopy. The composite was placed in a column and used for solid phase extraction (SPE) of Cd(II) ions from water samples. The adsorbed Cd(II) was then eluted with HCl and injected into a flame atomic absorption spectrometer. The effects of pH values, volume and flow rate of sample, and the kind, volume and concentration of eluent were optimized. The calibration plot for the assay is linear in the 2 to 100 μg.L −1 Cd(II) concentration range. Other figures of merit include (a) a 0.47 μg.L −1 limit of detection, (b) a relative standard deviation of 1.6% (for n  = 7; at 20 μg.L −1 of Cd(II)), and (c) a preconcentration factor of 50. The method was validated by analyzing the certified reference material NIST SRM 1643f and spiked real samples. The method was successfully employed to the determination of Cd(II) in tap, river, seawater and wastewater samples. Graphical abstract Graphene oxide (GO) was used as an ideal platform for in-situ polymerization of 2,6-diaminopyridine. The material was characterized by scanning electron microscopy and spectrometry techniques. GO based poly(2,6-diaminopyridine) composite (GO-PDAP) was utilized as a sorbent for the separation and preconcentration of Cd(II) in water samples.

Description: The authors describe a visual genotyping assay for the rapid and simultaneous detection of four novel variant alleles within the SIRT1 promoter region. These alleles may be considered as a risk biomarker for the onset of Parkinson disease. An amplified DNA fragment, flanking the four SIRT1 polymorphisms, is subjected to a multiplex primer extension reaction in the presence of biotin-dUTP. Extension of primers and, consequently, incorporation of the biotin-dUTP occurs only if primers are perfectly complementary to the target sequence. Detection of the extension products is achieved by a DNA biosensor that functions in a lateral-flow mode and carries multiple test spots. Each spot comprises a suspension of polystyrene microspheres functionalized with capture probes. The primer extension reaction products hybridize, through specific sequence tags, to the capture probes of the biosensor. Biotinylated extended primers are visualized by means of anti-biotin-conjugated gold nanoparticles. The genotype is simply read out by observing the formation of red test spots. The method was optimized and evaluated by analyzing three recombinant DNA fragments carrying the novel polymorphisms and 48 clinical samples from patients with sporadic Parkinson disease and from healthy individuals. The proposed genotyping method is accurate, sensitive, and cost effective. As low as 6 fmol of amplified genomic DNA was found to be sufficient to generate detectable spots for correct genotyping. The total time required for the accumulation of genotyping results takes ∼2 h. Graphical abstract Schematic of a multi-allele genotyping assay. (a) Amplification product is subjected to primer extension reaction in the presence of biotin-dUTP. (b) The reaction product is analysed by multi-allele dipstick assay. The result is positive if a red color appears both in the test (TS) and the control spot (CS). If a red color appears only in the control spot, the result is negative. N-normal Primer; M-Multant Primer; B-biotin.

Description: This article describes a useful sorbent for separation and preconcentration of trace amounts of gold(III), palladium(II) and silver(I) ions. Graphene oxide (GO) nanoparticles were synthesized by a modified Hummers method and magnetized by MnFe 2 O 4 nanoparticles to give a sorbent referred to as mag-GO. Addition of sodium dodecyl sulfate creates admicelles on the surface of the mag-GO. Then the metal chelating agent 2-mercaptobenzothiazole (MBT) was immobilized on mag-GO to give a mag-GO-MBT type material. This adsorbent was applied to the preconcentration of gold(III), palladium(II) and silver(I) ions. Following ion desorbed with a solution of thiourea, the ions were quantified by flow injection coupled to ICP-OES. Effect of sample pH value, type and volume of eluent, amount of adsorbent, sample volume, time of adsorption and desorption were optimized. Under optimized condition, the calibration plots are linear in the 2.5 to 25,000 μg.L −1 concentration range. The limits of detection range from 0.045 to 0.076 μg.L −1 , and enhancement factors are 160, 160 and 140 for gold, palladium and silver ions, respectively. Precisions, expressed as relative standard deviation for 100 μg.L −1 of each ion are 〈3.1%. The nanosorbent applied to selective adsorption, extraction and preconcentration of Au(III), Pd(II), and Ag(I) from water, ore and automobile catalyst samples. Graphical abstract Schematic of a nanocomposite for preconcentration of gold(III), palladium(II) and silver(I) ions from water, ore and automobile catalysts. It was obtained from graphene oxide that was magnetized by using MnFe 2 O 4 and then modified with 2-mercaptobenzothiazole.

Description: An amino-functionalized grooved polyacrylonitrile nanofiber mat was modified by both functional groups and in terms of surface morphology. The mat is shown to represent a viable adsorbent for solid-phase extraction of six priority phenolic pollutants and three phenolic xenoestrogens (phenol, 3-methoxyphenol, 4-nitrophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, 4-tert-octylphenol, 4-nonylphenol and bisphenol A) from environmental water samples. Under optimized conditions, the analytes were completely extracted from 90 mL of water sample by using only 9 mg of the mat material. Following elution with an ammoniacal methanol-acetone mixture, the eluent was directly submitted to UPLC-MS/MS or HPLC with DAD detection. Satisfied linearity in range of 50 pg·mL −1 to 100 ng·mL −1 was achieved. The detection limits ranged from 4 to 60 pg·mL −1 which revealed the excellent sensitivity of the method in comparison to standardized and other techniques. The recoveries ranged from 82.4% to 111.4%, with the relative standard deviations of 4.0% to 11.4% (for n  = 6). The method was applied to the determination of nine phenolic pollutants in water samples collected from sixteen inflow rivers and six Taihu Lake regions. Graphical abstract Amino-functionalized grooved nanofibers mat-based solid-phase extraction for simultaneous determination of nine phenolic pollutants in environmental water

Description: Coupled prediction systems for seasonal and inter-annual variability in the tropical Pacific are initialized from ocean analyses. In ocean initial states, small scale perturbations are inevitably smoothed or distorted by the observational limits and data assimilation procedures, which tends to induce potential ocean initial errors for the El Nino-Southern Oscillation (ENSO) prediction. Here, the evolution and effects of ocean initial errors from the small scale perturbation on the developing phase of ENSO are investigated by an ensemble of coupled model predictions. Results show that the ocean initial errors at the thermocline in the western tropical Pacific grow rapidly to project on the first mode of equatorial Kelvin wave and propagate to the east along the thermocline. In boreal spring when the surface buoyancy flux weakens in the eastern tropical Pacific, the subsurface errors influence sea surface temperature variability and would account for the seasonal dependence of prediction skill in the NINO3 region. It is concluded that the ENSO prediction in the eastern tropical Pacific after boreal spring can be improved by increasing the observational accuracy of subsurface ocean initial states in the western tropical Pacific.

Description: The current dynamical climate models have limited skills in predicting winter temperature in China. The present study uses physics-based empirical models (PEMs) to explore the sources and limits of the seasonal predictability in the total number of extremely cold days (NECD) over China. A combined cluster-rotated EOF analysis reveals two sub-regions of homogeneous variability among hundreds of stations, namely the Northeast China (NE) and Main China (MC). This reduces the large-number of predictands to only two indices, the NCED-NE and NCED-MC, which facilitates detection of the common sources of predictability for all stations. The circulation anomalies associated with the NECD-NE exhibit a zonally symmetric Arctic Oscillation-like pattern, whereas those associated with the NECD-MC feature a North–South dipolar pattern over Asia. The predictability of the NECD originates from SST and snow cover anomalies in the preceding September and October. However, the two regions have different SST predictors: The NE predictor is in the western Eurasian Arctic while the MC predictor is over the tropical-North Pacific. The October snow cover predictors also differ: The NE predictor primarily resides in the central Eurasia while the MC predictor is over the western and eastern Eurasia. The PEM prediction results suggest that about 60% (55%) of the total variance of winter NECD over the NE (Main) China are likely predictable 1 month in advance. The NECD at each station can also be predicted by using the four predictors that were detected for the two indices. The cross-validated temporal correlation skills exceed 0.70 at most stations. The physical mechanisms by which the autumn Arctic sea ice, snow cover, and tropical-North Pacific SST anomalies affect winter NECD over the NE and Main China are discussed.

Description: Forecasts of both likely anthropogenic effects on climate and consequent effects on nature and society are based on large, complex software tools called general circulation models (GCMs). Forecasts generated by GCMs have been used extensively in policy decisions related to climate change. However, the relation between underlying physical theories and results produced by GCMs is unclear. In the case of GCMs, many discretizations and approximations are made, and simulating Earth system processes is far from simple and currently leads to some results with unknown energy balance implications. Statistical testing of GCM forecasts for degree of agreement with data would facilitate assessment of fitness for use. If model results need to be put on an anomaly basis due to model bias, then both visual and quantitative measures of model fit depend strongly on the reference period used for normalization, making testing problematic. Epistemology is here applied to problems of statistical inference during testing, the relationship between the underlying physics and the models, the epistemic meaning of ensemble statistics, problems of spatial and temporal scale, the existence or not of an unforced null for climate fluctuations, the meaning of existing uncertainty estimates, and other issues. Rigorous reasoning entails carefully quantifying levels of uncertainty.

Description: We investigate the Northern Hemisphere atmospheric circulation anomalies associated to the sea surface temperature (SST) anomalies that are related to the eastern-Pacific and central-Pacific El Nino-Southern Oscillations in the late autumn (November). This research is motivated by the need for improving understanding of the autumn climate conditions which can impact on winter climate, as well as the relative lack of study on the boreal autumn climate processes compared to winter. Using reanalysis and SST datasets available from the late nineteenth century through the recent years, we found that there are two major atmospheric responses; one is a hemispheric-wide wave number-4 pattern, another has a more annular pattern. Both of these project on the East Atlantic pattern (southward-shifted North Atlantic Oscillation) in the Atlantic sector. Which of the patterns is active is suggested to depend on the background mean flow, with the annular anomaly active in the most recent decades, while the wave-4 pattern in the decades before. This switch is associated with a change of correlation sign in the North Pacific. We discuss the robustness of this finding. The ability of two atmospheric general circulation models (ICTP-AGCM and ECHAM-AGCM) to reproduce the teleconnections is also examined. Evidence provided shows that the wave-4 pattern and the East Atlantic pattern signals can be reproduced by the models, while the shift from this to an annular response for the recent years is not found conclusively.

Description: The simultaneous detection and evaluation of the coinfection of a cell by multiple viruses or even multiple subtypes still is a difficult challenge. The authors introduce a method for simultaneous imaging, detection and quantitative evaluation of multiple viruses in single cells by using multicolor quantum dot (QD) probes and in a single staining cycle. The multicolor QD probes were fabricated via interaction between QDs conjugated to Staph. aureus protein A (SpA-QDs) and virus-specific antibodies. A cocktail of differently colored QD-SpA-MAbs probes were loaded into the same cells containing multiple viruses, and this enabled the different viruses to be fluorescently imaged and analyzed simultaneously. Specifically, influenza A viruses of type H1N1, H3N2, and H9N2, as well as human adenovirus species B type 3 (HAdV-B3) were imaged and detected in virus-infected cells or in their co-infected cells. In our perception, the method provides a flexible platform for simultaneous detection of multiple viruses in co-infected cells. Hence, it offers new opportunities for the molecular diagnosis of virus coinfection and for studies on virus-cell interactions. Graphical abstract Multicolor QD probes were fabricated via interaction between Staph. aureus protein A-conjugated QDs (SpA-QDs) and virus-specific antibodies. A cocktail of differently colored QD-SpA-MAbs probes were applied for simultaneously detection and quantitative evaluation of H1N1, H3N2, H9N2 and HAdV viruses.

Description: The authors describe a template-free method for the electrodeposition of ultra-long copper nanowires on titanium foils. Scanning electron microscopy shows that the nanowires are around 50 nm in diameter and 30 μm in length. The titanium foils enable nonenzymatic sensing of glucose in 0.1 M NaOH solution because the nanowire-modified electrodes exhibit excellent electrocatalytic activity towards glucose oxidation at a typical working voltage of 0.7 V (vs. Ag/AgCl). Figures of merit include (a) a sensitivity of 4985 μA·mM −1 ·cm −2 , (b) a linear response extending from 1 μM to 6.0 mM of glucose, (c) good reusability (a 2.5% relative standard deviation of one electrode in five detections), and (d) an excellent reproducibility (a 3.3% RSD of five electrodes to one sample). Graphical abstract Copper nanowires with high length-diameter ratio were electrodeposited on titanium foils as nonenzymatic sensors of glucose. Benefitting from the good conductivity, abundant active sites and facilitated mass transport, the nanowire-modified electrodes exhibit excellent electrocatalytic activity towards glucose oxidation.

Description: The authors describe an aptamer based assay for the model analyte diclofenac (DCF). It is based on the use of amino-functionalized magnetite and gold nanoparticles (Fe 3 O 4 /AuNPs) that were used to decorate carbon nanotubes (CNTs) to form a highly conductive film on the surface of a glassy carbon electrode. An amino-modified DNA capture probe (ssDNA1) was placed on the Fe 3 O 4 /AuNPs using glutaraldehyde as the linker. A DCF-specific aptamer (referred to as ssDNA2) acting as the detection probe was then attached to the surface of the modified electrode via hybridization. On addition of DCF, the conformation of the aptamer undergoes a change from a random coil structure to a rigid tertiary structure (like a pocket). This change can be traced by measuring the decrease of the current observed by differential pulse voltammetry using hexacyanoferrate as a redox probe, typically at a working voltage of 0.22 V vs. Ag/AgCl. The method has a 3.4 fM detection limit and two linear responses that cover the 0.01 to 1 pM and 10 to 1300 pM DCF concentration ranges. Graphical abstract (A) Schematic illustration of the preparation of amino-functionalized Fe 3 O 4 NPs. (B) Schematic representation of different steps of aptasensor fabrication.

Description: The authors describe a nanostructured zinc(II)-imprinted polymer carrying Alizarin Red S as a ligand for separation and preconcentration of ultra-trace levels zinc(II). The adsorbent was obtained by bulk polymerization of a mixture of Zn(II) nitrate, Alizarin Red S, methacrylic acid, ethylene glycol dimethacrylate and 2,2′-azobis(isobutyronitrile). Zn(II) was then removed by treatment with ethanol and 2.0 mM HNO 3 . The imprinted nanoadsorbent was characterized by FT-IR spectroscopy and scanning electron microscopy. Following sorption of Zn(II) from the sample, it is desorbed with 3.0 M HCl and then quantified via electrothermal atomic absorption spectrometry. Under optimized conditions, the calibration plot is linear in the 3.0 to 250 ng L −1 Zn(II) concentration range, the detection limit is 0.7 ng L −1 , and the relative standard deviation is ±4.0% (for n  = 8). The method was successfully applied to the determination of Zn(II) in (spiked) water samples and hair, and in a certified reference material (MA-1b; reference gold ore) which corroborates the utility of the method. Graphical abstract Schematic of a Zn-imprinted polymer obtained by using Alizarin Red S (ARS) as a water soluble ligand via bulk polymerization method. This nanoadsorbent was applied to the separation and preconcentration of Zn(II) ion prior to its determination by electrothermal AAS.

Description: The authors describe a three-dimensional (3D) structure composed of graphene and DNA for use in a voltammetric dopamine (DA) sensor. The material was deposited on a gold electrode, and the enhanced charge-transfer performance and deposition of DNA were confirmed by electrochemical analysis. Atomic force microscopy shows the graphene-DNA composite to have been assembled on the modified gold electrode. The modified gold electrode possesses excellent electrocatalytic activity for determination of DA, best at a working voltage of 0.1 V (vs. SCE). Ascorbic acid does not interfere. Response to DA is linear in the 0.1 to 100 μM concentration range, with a 30 nM detection limit even in the presence of 1.0 mM of ascorbic acid. Graphical abstract Schematic of a voltammetric dopamine sensor based on the use of a 3D structure composed of graphene and DNA. The sensor displays an enhanced charge-transfer rate, excellent electrocatalytic activity towards dopamine, and a 30 nM detection limit.

Description: Forecasting skills of the complex weather and climate models have been improved by tuning the sensitive parameters that exert the greatest impact on simulated results based on more effective optimization methods. However, whether the optimal parameter values are still work when the model simulation conditions vary, which is a scientific problem deserving of study. In this study, a highly-effective optimization method, adaptive surrogate model-based optimization (ASMO), was firstly used to tune nine sensitive parameters from four physical parameterization schemes of the Weather Research and Forecasting (WRF) model to obtain better summer precipitation forecasting over the Greater Beijing Area in China. Then, to assess the applicability of the optimal parameter values, simulation results from the WRF model with default and optimal parameter values were compared across precipitation events, boundary conditions, spatial scales, and physical processes in the Greater Beijing Area. The summer precipitation events from 6 years were used to calibrate and evaluate the optimal parameter values of WRF model. Three boundary data and two spatial resolutions were adopted to evaluate the superiority of the calibrated optimal parameters to default parameters under the WRF simulations with different boundary conditions and spatial resolutions, respectively. Physical interpretations of the optimal parameters indicating how to improve precipitation simulation results were also examined. All the results showed that the optimal parameters obtained by ASMO are superior to the default parameters for WRF simulations for predicting summer precipitation in the Greater Beijing Area because the optimal parameters are not constrained by specific precipitation events, boundary conditions, and spatial resolutions. The optimal values of the nine parameters were determined from 127 parameter samples using the ASMO method, which showed that the ASMO method is very highly-efficient for optimizing WRF model parameters.

Description: Patterns of daily large-scale circulation associated with Northeast US extreme precipitation are identified using both k-means clustering (KMC) and Self-Organizing Maps (SOM) applied to tropopause height. The tropopause height provides a compact representation of the upper-tropospheric potential vorticity, which is closely related to the overall evolution and intensity of weather systems. Extreme precipitation is defined as the top 1% of daily wet-day observations at 35 Northeast stations, 1979–2008. KMC is applied on extreme precipitation days only, while the SOM algorithm is applied to all days in order to place the extreme results into the overall context of patterns for all days. Six tropopause patterns are identified through KMC for extreme day precipitation: a summertime tropopause ridge, a summertime shallow trough/ridge, a summertime shallow eastern US trough, a deeper wintertime eastern US trough, and two versions of a deep cold-weather trough located across the east-central US. Thirty SOM patterns for all days are identified. Results for all days show that 6 SOM patterns account for almost half of the extreme days, although extreme precipitation occurs in all SOM patterns. The same SOM patterns associated with extreme precipitation also routinely produce non-extreme precipitation; however, on extreme precipitation days the troughs, on average, are deeper and the downstream ridges more pronounced. Analysis of other fields associated with the large-scale patterns show various degrees of anomalously strong moisture transport preceding, and upward motion during, extreme precipitation events.

Description: Anthropogenic aerosols could dominate over greenhouse gases in driving near-term hydroclimate change, especially in regions with high present-day aerosol loading such as Asia. Uncertainties in near-future aerosol emissions represent a potentially large, yet unexplored, source of ambiguity in climate projections for the coming decades. We investigated the near-term sensitivity of the Asian summer monsoon to aerosols by means of transient modelling experiments using HadGEM2-ES under two existing climate change mitigation scenarios selected to have similar greenhouse gas forcing, but to span a wide range of plausible global sulfur dioxide emissions. Increased sulfate aerosols, predominantly from East Asian sources, lead to large regional dimming through aerosol-radiation and aerosol-cloud interactions. This results in surface cooling and anomalous anticyclonic flow over land, while abating the western Pacific subtropical high. The East Asian monsoon circulation weakens and precipitation stagnates over Indochina, resembling the observed southern-flood-northern-drought pattern over China. Large-scale circulation adjustments drive suppression of the South Asian monsoon and a westward extension of the Maritime Continent convective region. Remote impacts across the Northern Hemisphere are also generated, including a northwestward shift of West African monsoon rainfall induced by the westward displacement of the Indian Ocean Walker cell, and temperature anomalies in northern midlatitudes linked to propagation of Rossby waves from East Asia. These results indicate that aerosol emissions are a key source of uncertainty in near-term projection of regional and global climate; a careful examination of the uncertainties associated with aerosol pathways in future climate assessments must be highly prioritised.

Description: Poleward energy transport in the atmosphere and oceans constitutes an important branch of the global energy budget, and its role in the climate system has been the subject of many studies. In the atmosphere, the transport is affected by “eddies” and large scale meridional cells, both with zero net mass transport across latitude circles, but also partly by processes associated with a net transport of mass across latitude circles. The latter must cease to operate in steady state, but they may be significant when time variability of the heat budget is considered. Indeed, examination of reanalysis data on short (daily to monthly) timescales shows that mass variations on these timescales result in surprisingly large fluctuations (in excess of \(10^{15}\) W = 1 PW) in the poleward heat transport. These fluctuations are referred to as “extensive”, for they primarily alter the mass integrated energy of the region considered, but not its averaged value. It is suggested that extensive fluctuations mask more meaningful climate signals present in the heat transport variability ​on monthly and interannual timescales, and a new formulation is proposed to isolate the latter. This new formulation is applied successfully to reanalysis data and climate model simulations.

Description: The 1925 El Niño (EN) event was the third strongest in the twentieth century according to its impacts in the far-eastern Pacific (FEP) associated with severe rainfall and flooding in coastal northern Peru and Ecuador in February–April 1925. In this study we gathered and synthesised a large diversity of in situ observations to provide a new assessment of this event from a modern perspective. In contrast to the extreme 1982–1983 and 1997–1998 events, this very strong “coastal El Niño” in early 1925 was characterised by warm conditions in the FEP, but cool conditions elsewhere in the central Pacific. Hydrographic and tide-gauge data indicate that downwelling equatorial Kelvin waves had little role in its initiation. Instead, ship data indicate an abrupt onset of strong northerly winds across the equator and the strengthening/weakening of the intertropical convergence zones (ITCZ) south/north of the equator. Observations indicate lack of external atmospheric forcing by the Panama gap jet and the south Pacific anticyclone and suggest that the coupled ocean–atmosphere feedback dynamics associated with the ITCZs, northerly winds, and the north–south SST asymmetry in the FEP lead to the enhancement of the seasonal cycle that produced this EN event. We propose that the cold conditions in the western-central equatorial Pacific, through its teleconnection effects on the FEP, helped destabilize the ITCZ and enhanced the meridional ocean–atmosphere feedback, as well as helping produce the very strong coastal rainfall. This is indicated by the nonlinear relation between the Piura river record at 5°S and the SST difference between the FEP and the western-central equatorial Pacific, a stability proxy. In summary, there are two types of EN events with very strong impacts in the FEP, both apparently associated with nonlinear convective feedbacks but with very different dynamics: the very strong warm ENSO events like 1982–1983 and 1997–1998, and the very strong “coastal” EN events like 1925.

Description: The authors describe a novel recyclable substrate for highly sensitive surface-enhanced Raman scattering (SERS) studies. It consists of gold nanorods (AuNRs) self-assembled on a TiO 2 film and combines the high SERS enhancement of assembled AuNRs with the self-cleaning property of the TiO 2 film. It overcomes limitations of conventional SERS substrates such as limited sensitivity, high costs, and poor recyclability. The packing density of the AuNRs on the TiO 2 film can be well adjusted, and therefore the SERS enhancement factor of the substrates can be tuned. For the optimized substrate, the SERS enhancement factor is as high as 5.4 × 10 10 (Raman laser at 782 nm with 10% of 1.15 mW). This indicates extremely high sensitivity and is promising in terms of single molecule detection. Raman mapping experiments showed the SERS signal to be homogeneously distributed over the whole surface, with a maximal deviation of 3.5%. The SERS activity of this substrate can be restored by degradation of the probe molecules through TiO 2 photocatalysis under UV irradiation. In our perception, these findings open a new venue for developing ultra-sensitive and recyclable SERS substrates. Graphical abstract Bilayer composites composed of gold nanorods (AuNRs) and titanium dioxide (TiO 2 ) show strong surface enhanced Raman scattering enhancement under 782-nm laser excitation and display high sensitivity and good recyclability.

Description: Okadaic acid (OA) is a low molecular weight marine toxin from shellfish which causes diarrheic shellfish poisoning (DSP). Due to its frequent occurrence, OA has become a serious threat to human health and seafood industry. The authors describe a competitive fluorophore-linked aptamer assay for OA that is based on rolling circle amplification (RCA). It consists of the following steps: (a) The wells of a microplate are modified by fixing the OA aptamer on their surface; (b) The aptamer is hybridized with an aptamer-complementary sequence-primer complex; (c) the RCA reaction is performed; (d) the FAM labelled signal probe is added. OA competes with the detection probe for the immobilized aptamer. After the competitive reaction has occurred, the supernatants containing released detection probes are removed and then read with a microplate reader. This method, unlike in competitive assays where the signals negatively correlate with OA concentrations, has a positive correlation between fluorescence intensity and OA concentration. The optimized assay has a lower detection limit (1 pg·mL −1 ) and a wider linear range (from 1 pg·mL −1 to 100 ng·mL −1 ) owning to signal amplification via RCA. It also is highly specific, repeatable, has good recovery and can be used to detect OA in seafood. Graphical abstract Schematic of a microplate assay for okadaic acid assisted by rolling circle amplification (RCA) and using a fluorophore-linked aptamer. The signal intensities are directly proportional to the concentrations of OA. The assay without RCA was also performed and compared to.

Description: The authors describe the construction of a molecularly imprinted electrochemical sensor for enantiomeric recognition of L-phenylalanine (L-Phe). Firstly, thiolated β-cyclodextrin (β-CD) and L-cysteine were used to functionalize gold nanoparticles via gold-thiol chemistry and to act as a basis for the formation of a microporous metal-organic framework (MOF). A MOF imprinted polymer was deposited on the functionalized gold nanoparticles by electropolymerization in the presence of the template L-Phe and the functional monomer 4-aminothiophenol. The modified electrode was characterized by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of hexacyanoferrate acting as the redox probe. The electrode, operated best at 0.2 V vs. Ag/AgCl, exhibits excellent selectivity for L-Phe, with an enantioselectivity coefficient of 2.12 over D-Phe. In addition to its good enantiomeric selectivity, the sensor has a 0.33 pM detection limit which is much lower than that reported for other electrodes. The sensor has been successfully applied to the analysis of urine spiked with L-Phe. Graphical abstract Schematic of a microporous metal organic framework imprinting sensor for the analysis of enantiomers. Combined with MOF and β-CD, the sensor exhibits excellent selectivity and sensitivity for chiral assay of L-phenylalanine.

Description: The authors describe the synthesis of carbon dots (CDs) that are highly doped with both nitrogen and phosphorus. Synthesis is accomplished via a hydrothermal reaction starting from diethylenetriaminepenta(methylenephosphonic acid) and m-phenylenediamine as the precursors. The high N,P -doping ratios renders the codoped CDs excellently water soluble, photostable over a wide range of pH values, and photostable in the presence of various metal ions. Ferric ions acts as a strong quencher of fluorescence. Their low cytotoxicity and strong green fluorescence (with excitation/emission peaks at 440/510 nm and a quantum yield of 0.32) make the CDs well suited for purposes of cell imaging, and this is demonstrated by fluorescent bioimaging of human lung carcinoma cells (type A549) and human breast cancer cells (type KB). Furthermore, the CDs were used as an effective probe for monitoring Fe(III) in both aqueous solution and living cells. Graphical abstract A highly N,P -codoped carbon dots (CDs) were synthesized for high-quality cellular Imaging and monitoring Fe 3+ in living cells. This water soluble CDs displayed high biocompatibility and emitted strong green fluorescence.

Description: An on-demand, disposable and portable surface-enhanced Raman scattering (SERS) array has been prepared by modifying the surface of cellulose paper and patterning it with silver nanoparticles (AgNPs) via pen-writing technique. The paper is initially modified with hexadecenyl succinic anhydride to generate a hydrophobic top layer that is capable of concentrating melamine (and other hydrophobic analytes) by preventing the mainly aqueous sample from spreading on the paper. The AgNPs are subsequently written onto the hydrophobic paper with a high degree of control to form large-scale SERS sensing arrays. The resulting arrays demonstrate outstanding Raman scattering enhancement as demonstrated for the fluorescent dye Rhodamine 6G which can be detected by SERS with an 80 pM limit of detection (LOD) without interference by fluorescence. The reproducibility in the preparation of spots has a relative standard deviation of 〈15% (for n  = 128 spectra). The arrays were applied to the determination of the illicit milk additive melamine. The plot of SERS intensity at Δν = 681 cm −1 versus the logarithm of melamine concentration is linear in the concentration range from 0.3 to 20 mg·L −1 , and the LOD is 0.27 mg·L −1 . In our perception, the disposable arrays presented here integrate the advantages of easy production and reliable reproducibility, and therefore are an ideal choice for use in SERS detection. Graphical abstract An on-demand, disposable and portable surface-enhanced Raman scattering (SERS) array has been developed by pen writing. Such a SERS array can be applied for the highly sensitive determination of the illicit milk additive melamine, which holds great promise for field-deployable applications.

Description: The authors report on a nonenzymatic catechol sensor that is based on the immobilization of ferrocene (Fc) on graphene oxide (GO). A glassy carbon electrode (GCE) was modified with GO which then was silanized with (3-aminopropyl)trimethoxysilane. Ferrocenecarboxaldehyde was then immobilized on GO via formation of a Schiff base. The immobilization process was monitored stepwise by using FTIR spectroscopy, X-ray diffraction, cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Investigation of the modified electrode by CV revealed a pair of well-defined redox peaks with anodic and cathodic peak potentials at +0.380 and +0.277 V, corresponding to the Fc/Fc + redox couple. The Fc modified electrode exhibits excellent electrocatalytic activity towards the oxidation of catechol at a typical working voltage of +0.45 V (vs. Ag/AgCl). The response is linear in the 3 to 112 μM catechol concentration range, the detection limit is 1.1 μM, and the sensitivity is 1184.3 μA·mM −1 ·cm −2 . The sensor is stable, reproducible and reasonably selective. It was successfully applied to the determination of catechol in spiked tap water and lake water samples. Graphical abstract Schematic presentation of the covalent immobilization of ferrocene on graphene oxide through (3-aminopropyl)trimethoxysilane via Schiff base condensation for nonenzymatic catechol determination. The use of the electrode with covalently linked ferrocene and a graphene oxide host results in faster and enhanced amperometric response.

Description: Based on accurate dating, we have determined the stable carbon isotope ratios (δ 13 C) of five Cryptomeria fortunei specimens from Mt. Tianmu, a subtropical area in southern China. The five δ 13 C time series records are combined into a single representative δ 13 C time series using a “numerical mix method.” These are normalized to remove temporal variations of δ 13 C in atmospheric CO 2 to obtain a carbon isotopic discrimination (Δ 13 C) time series, in which we observe a distinct correlation between Δ 13 C and local April to June mean relative humidity ( RH AMJ ) (n = 64, r  = 0.858, p  〈 0.0001). We use this relationship to reconstruct RH AMJ variations from ad 1648 to 2014 at Mt. Tianmu. The reconstructed sequence show that over the past 367 years, Mt. Tianmu area was relatively wet, but in the latter part of the twentieth century, under the influence of increasing global warming, it has experienced a sharp reduction in relative humidity. Spatial correlation analysis reveals a significant negative correlation between RH AMJ at Mt. Tianmu and Sea Surface Temperature (SSTs) in the western equatorial Pacific and Indian Ocean. In other words, there is a positive correlation between tree-ring δ 13 C in Mt. Tianmu and SSTs. Both observed and reconstructed RH AMJ show significant positive correlations with East Asian and South Asian monsoons from 1951 to 2014, which indicate that RH AMJ from Mt. Tianmu reflects the variability of the Asian summer monsoon intensity to a great extent. The summer monsoon has weakened since 1960. However, an increase in relative humidity since 2003 implies a recent enhancement in the summer monsoon.

Description: This article describes the construction of a sandwich-type of DNA biosensor for detecting a specific DNA sequence of Mycobacterium tuberculosis (MTB). A polyaniline-reduced graphene oxide (PANI-rGO) composite with favorable electrochemical activity was used as a redox nanoprobe for the generation of the voltammetric signal. The composite was decorated with gold nanoparticles (AuNPs) onto which the signal probe was immobilized to form the tracer label. After hybridization between target DNA and tracer label, the voltammetric signal resulting from the polyaniline-reduced graphene oxide (PANI-rGO) redox probe can be apparently observed. The biosensor can detect the specific IS6110 DNA sequence of MTB in the 0.1 pM to 10 nM concentration range, and the detection limit is as low as 50 fM (at an S/N ratio of 3). The biosensor is also highly specific and does not recognize mismatches. It was applied to the determination of denatured PCR products in clinical samples such as sputum, and the results agreed with those obtained by gel electrophoresis. This assay provides a versatile and powerful tool for detection of MTB, and probably for other pathogens if appropriate molecular markers are available. Graphical abstract Schematic of an electrochemical DNA biosensor for the ultrasensitive detection of Mycobacterium tuberculosis (MTB). It uses a redox nanoprobe (rGO-PANI) for signal amplification. MCH: 6-mercapto-1-hexanol; PANI: polyaniline; rGO: reduced graphene oxide; rGO-PANI: polyaniline-reduced graphene oxide nanocomposite.

Description: Photodynamic therapy (PDT) uses photosensitizers, light and molecular oxygen to generate cytotoxic reactive oxygen species. Its effectiveness is limited to 〈1 cm due to the limited penetration depth of light. The present study compares the PDT effectivity of the photosensitizer verteporfin (VP) conjugated to gold nanoparticles (AuNPs) (a) by using deeply penetrating X-rays administered in standard radiotherapy doses, and (b) by using red light (690 nm). VP was conjugated to AuNPs of around 12 nm size to enhance the interaction of ionizing radiation with PS. For comparison, VP also was directly exposed to X-rays. It is found that VP alone is stimulated by X-rays to generate singlet oxygen. The conjugate to AuNPs also generated a significant amount of singlet oxygen on irradiation with X-rays in comparison to illumination with 690-nm light. It is also found that the rate of singlet oxygen generation is amplified in case of AuNP-conjugated VP compared to VP alone. The performance of the AuNP-VP conjugate and of the VP alone was tested in Panc 1 cells. Their viability was impaired much more in these two scenarios than with the X-ray radiation only. This suggests excellent perspectives for PDT based on VP and with X-ray stimulation, both as a stand-alone photosensitizer and in Au-NP conjugates. Moreover, both VP and AuNP-VP conjugates show bright fluorescence in physiological media for excitation/emission wavelengths in the range of 405/690 nm; hence they can also be used for simultaneous bioimaging. Graphical abstract Pancreatic cancer cells (Panc 1) administered with gold nanoparticle- verteporfin conjugate (AuNP-VP) showed an efficient cell killing effect with the generation of singlet oxygen ( 1 O 2 ) from triplet oxygen ( 3 O 2 ) under 690 nm irradiation and X-ray radiation.

Description: The authors report on a rapid and direct visual test for the detection of influenza A virus using a carbon nanotag based lateral flow assay. Carbon nanoparticles in the form of nanostrings are acting as reporters. As carbon nanotags accumulate in the test zone due to formation of an antibody-antigen-carbon nanotag antibody complex, and this allows for the direct visualization of the analytical signal. Under optimal conditions, influenza A virus can be determined in allantoic fluid inoculated with the virus with a limit of detection of 350 TCID 50 .mL −1 (i.e., the 50% tissue culture infectious dose). No interference is found for several other tested proteins, and for closely related viruses. Cell lysates containing different seasonal strains of influenza A viruses (including the H1N1 and H3N2 strains) collected from clinical samples were analyzed. It is demonstrated that the method can detect both influenza A viruses without interference by biological matrices. In our perception, this method has a wide potential in that it may be extended to a generally applicable platform for rapid diagnosis influenza A viruses. Graphical abstract Schematic of a rapid and direct visual test for the detection of influenza A virus using a carbon nanotag based lateral flow immunoassay. The presence of the virus induces an accumulation of the carbon nanotag conjugates, thereby providing a signal visualization.

Description: The authors describe a nanostructured hybrid platform for amperometic determination of the plasticizer bisphenol A (BPA). It consists of two dimensional sheets of reduced graphene oxide (rGO) that are decorated with Mn 3 O 4 nanoparticles. The enzyme tyrosinase was immobilized on the surface of the hybrid nanosheets placed on an ITO electrode. The larger surface area and enhanced charge transfer properties of the rGO/Mn 3 O 4 nanosheets provide a synergistic effect that results in excellent sensing performance including fast electron transfer kinetics, high electroactivity, good reproducibility and selectivity compared to other electrodes of that kind. Figures of merit include a sensitivity of 93.2 μA⋅nM −1 ⋅cm −2 , an analytical range that extends from 0.01 to 100 μM, and a 10 nM lower detection limit. Its long-term stability of 8 weeks suggests the use of such enzyme electrodes as potential tools in clinical diagnostics. Graphical abstract Schematic of the fabrication of graphene based hybrid electrode using reduced graphene oxide and colloidal Mn 3 O 4 nanostructures in presence of chitosan polymer. Further we demonstrate the electrochemical assay of the hybrid electrode for Bisphenol A detection.

Description: This study reports on the use of dispersed multi-walled carbon nanotubes (MWCNTs) as a novel pseudostationary phase in capillary electrophoresis for the separation and determination of mono- and divalent metal ions. The use of a background electrolyte containing 1 μg⋅mL −1 of dispersed MWCNTs results in good analytical linearity, in detection limits in the range from 18.5 to 124 ng⋅mL −1 , and in limits of quantifications in the range from 61 to 409 ng⋅mL −1 . The method was applied to the analysis of the ions K(I), Ba(II), Ca(II), Na(I), Mg(II), Co(II), Ni(II), Zn(II), Li(I) and Cd(II) in spiked honey, and mean recoveries were found to be between 80.0 and 106.7%. Graphical abstract Dispersed carbon nanotubes were used as pseudostationary phase in capillary electrophoresis for the separation and determination of metal ions in honey samples.

Description: An Al-doped ZnO@Fe 3 O 4 nanocomposite was synthesized and used as a magnetic sorbent for solid-phase extraction of Cd(II) prior to its determination by flame atomic absorption spectrometry (FAAS). The size and morphology of the nano-sorbent were characterized via X-ray diffraction analysis, scanning electron microscopy and FTIR. Following its desorption with acetic acid, cadmium was quantified by FAAS. Factors affecting the extraction of the Cd(II) were optimized. Under optimized experimental conditions, the calibration graph is linear in the 0.6 to 60 ng mL −1 concentration range. The limit of detection is 0.17 ng mL −1 and the pre-concentration factor is 50. The inter- and intra-day relative standard deviations for six replicate determinations at a Cd(II) level of 40 ng mL −1 are 3.8% and 2.5%, respectively. The method was successfully applied to the trace determination of Cd(II) in spiked water samples. The accuracy of the method was confirmed by analyzing the certified reference material NIST SRM 1643e. Graphical abstract Schematic of the synthesis of an Al-doped ZnO@Fe 3 O 4 nanocomposite and its application as a magnetic sorbent for solid-phase extraction of Cd(II) prior to its determination by flame atomic absorption spectrometry (FAAS).

Description: Serum alpha-fetoprotein (AFP) is present in enhanced concentrations in patients with liver cancer. Thus, sensitive detection of AFP plays an important role in the early diagnosis and treatment of cancer. In this study, a novel chiroplasmonic assay is presented for the determination of AFP. It is based on (a) the use of DNA-induced chiroplasmonic assemblies of gold nanoparticles (AuNPs) and (b) the high specificity and affinity constants between AFP and its aptamer. First, the AFP aptamer is hybridized with its complementary sequence immobilized on AuNP. As a result, the DNA-modified AuNPs are assembled to form AuNPs dimers which display strong chiroptical activity. If, however, AFP is added, it will bind to the aptamer and this results in a destruction of the aptamer-DNA hybrid and a reduction of the CD signal. Under optimized conditions, the CD intensity drops linearly with the log of the concentration of AFP in the range from 0.02 to 5 ng⋅mL −1 . Compared to the established method, this assay does not require bisulfite conversion, PCR amplification or separation. Amounts as low as 11 pg⋅mL −1 (S/ N  = 3) AFP can be detected. The method was applied to spiked human serum samples and gave recoveries ranging from 92.0% to 106%, and the relative standard derivations ranged from 4.6% to 6.3%. To the best of our knowledge, this is the first chirality based assay for AFP. Graphical abstract Schematic presentation of the novel chiroplasmonic assay for the determination of AFP. It is based on (a) the use of DNA-induced chiroplasmonic assemblies of gold nanoparticles (AuNPs) and (b) the high specificity and affinity constants between AFP and its aptamer.

Description: The authors describe an impedimetric method for the quantitation of the DNA of the human papilloma virus (HPV) type 16. A glassy carbon electrode (GCE) was modified with gold nanosheets and is shown to be superior to a common gold disk electrode. A single-stranded 25mer oligonucleotide (ssDNA) acting as the probe DNA was immobilized via its thiolated 5′ end on both electrodes. After hybridization with target (analyte) DNA, electrochemical impedance spectra were acquired in the presence of hexacyanoferrate as a redox marker. The sensor can distinguish between complementary, non-complementary and single base pair mismatches of HPV ssDNA. At a 1 mM hexacyanoferrate concentration, the biosensors respond to target DNA in the 1 μM to 1 pM concentration range, and the detection limit is 0.15 pM. The results illustrate that the use of gold nanosheets on a GCE distinctly improves the detection and differentiation of HPV compared to using bare gold. Graphical abstract Schematic of exploiting gold nanosheets as a platform for HPV detection. The method works in the 1 μM to 1 pM HPV concentration range and has a 0.15 pM detection limit..

Description: Statistical downscaling is an efficient way to solve the spatiotemporal mismatch between climate model outputs and the data requirements of hydrological models. However, the most commonly-used downscaling method only produces climate change scenarios for a specific site or watershed average, which is unable to drive distributed hydrological models to study the spatial variability of climate change impacts. By coupling a single-site downscaling method and a multi-site weather generator, this study proposes a multi-site downscaling approach for hydrological climate change impact studies. Multi-site downscaling is done in two stages. The first stage involves spatially downscaling climate model-simulated monthly precipitation from grid scale to a specific site using a quantile mapping method, and the second stage involves the temporal disaggregating of monthly precipitation to daily values by adjusting the parameters of a multi-site weather generator. The inter-station correlation is specifically considered using a distribution-free approach along with an iterative algorithm. The performance of the downscaling approach is illustrated using a 10-station watershed as an example. The precipitation time series derived from the National Centers for Environment Prediction (NCEP) reanalysis dataset is used as the climate model simulation. The precipitation time series of each station is divided into 30 odd years for calibration and 29 even years for validation. Several metrics, including the frequencies of wet and dry spells and statistics of the daily, monthly and annual precipitation are used as criteria to evaluate the multi-site downscaling approach. The results show that the frequencies of wet and dry spells are well reproduced for all stations. In addition, the multi-site downscaling approach performs well with respect to reproducing precipitation statistics, especially at monthly and annual timescales. The remaining biases mainly result from the non-stationarity of NCEP precipitation. Overall, the proposed approach is efficient for generating multi-site climate change scenarios that can be used to investigate the spatial variability of climate change impacts on hydrology.

Description: Here we examine the skill of three, five, and seven-category monthly ENSO probability forecasts (1982–2015) from single and multi-model ensemble integrations of the North American Multimodel Ensemble (NMME) project. Three-category forecasts are typical and provide probabilities for the ENSO phase (El Niño, La Niña or neutral). Additional forecast categories indicate the likelihood of ENSO conditions being weak, moderate or strong. The level of skill observed for differing numbers of forecast categories can help to determine the appropriate degree of forecast precision. However, the dependence of the skill score itself on the number of forecast categories must be taken into account. For reliable forecasts with same quality, the ranked probability skill score (RPSS) is fairly insensitive to the number of categories, while the logarithmic skill score (LSS) is an information measure and increases as categories are added. The ignorance skill score decreases to zero as forecast categories are added, regardless of skill level. For all models, forecast formats and skill scores, the northern spring predictability barrier explains much of the dependence of skill on target month and forecast lead. RPSS values for monthly ENSO forecasts show little dependence on the number of categories. However, the LSS of multimodel ensemble forecasts with five and seven categories show statistically significant advantages over the three-category forecasts for the targets and leads that are least affected by the spring predictability barrier. These findings indicate that current prediction systems are capable of providing more detailed probabilistic forecasts of ENSO phase and amplitude than are typically provided.

Description: The authors describe an electrochemiluminescence (ECL) based aptasensor for the pesticide aldicarb. The method is based on effective ECL energy transfer that occurs between the ruthenium(II) bipyridyl complex [referred to as Ru(bpy) 3 2+ ] and gold nanoparticles (AuNPs). More specifically, multiwalled carbon nanotubes were modified with dendritic poly( L -arginine) labeled with Ru(bpy) 3 2+ , and the aptamers were taggedd with AuNPs. In the absence of aldicarb, the ECL emitted by Ru(bpy) 3 2+ is enhanced by AuNPs under peak wavelength at at a wavelength of 610 nm. In the presence of aldicarb, the capture and competitive binding of aldicarb to the DNA aptamers causes their separation from the DPA6/Ru(bpy) 3 2+ /MWCNT. As a result, ECL intensity decreases linearly with increasing aldicarb concentrations in the range between 40 pM and 4 nM, with a detection limit of 9.6 pM. This aptamer switch is highly sensitive, selective and inexpensive. Conceivably, it can be adapted to formats for the determination of other pesticide residues by using different DNA aptamers. Graphical abstract Schematic of the procedure for aptamer-based detection of aldicarb using the ECL signal of the Ru(bpy) 3 2+ amplified by gold nanoparticles. This assay has high sensitivity, good selectivity, and low cost. It can presumably be transferred to other pesticide detection schemes.

Description: The Asian–Bering–North American (ABNA) teleconnection index is constructed from the normalized 500-hPa geopotential field by excluding the Pacific–North American pattern contribution. The ABNA pattern features a zonally elongated wavetrain originating from North Asia and flowing downstream across Bering Sea and Strait towards North America. The large-scale teleconnection is a year-round phenomenon that displays strong seasonality with the peak variability in winter. North American surface temperature and temperature extremes, including warm days and nights as well as cold days and nights, are significantly controlled by this teleconnection. The ABNA pattern has an equivalent barotropic structure in the troposphere and is supported by synoptic-scale eddy forcing in the upper troposphere. Its associated sea surface temperature anomalies exhibit a horseshoe-shaped structure in the North Pacific, most prominent in winter, which is driven by atmospheric circulation anomalies. The snow cover anomalies over the West Siberian plain and Central Siberian Plateau in autumn and spring and over southern Siberia in winter may act as a forcing influence on the ABNA pattern. The snow forcing influence in winter and spring can be traced back to the preceding season, which provides a predictability source for this teleconnection and for North American temperature variability. The ABNA associated energy budget is dominated by surface longwave radiation anomalies year-round, with the temperature anomalies supported by anomalous downward longwave radiation and damped by upward longwave radiation at the surface.

Description: This study focuses on the evaluation of daily precipitation and temperature climate indices and extremes simulated by an ensemble of 12 Regional Climate Model (RCM) simulations from the ARCTIC-CORDEX experiment with surface observations in the Canadian Arctic from the Adjusted Historical Canadian Climate Dataset. Five global reanalyses products (ERA-Interim, JRA55, MERRA, CFSR and GMFD) are also included in the evaluation to assess their potential for RCM evaluation in data sparse regions. The study evaluated the means and annual anomaly distributions of indices over the 1980–2004 dataset overlap period. The results showed that RCM and reanalysis performance varied with the climate variables being evaluated. Most RCMs and reanalyses were able to simulate well climate indices related to mean air temperature and hot extremes over most of the Canadian Arctic, with the exception of the Yukon region where models displayed the largest biases related to topographic effects. Overall performance was generally poor for indices related to cold extremes. Likewise, only a few RCM simulations and reanalyses were able to provide realistic simulations of precipitation extreme indicators. The multi-reanalysis ensemble provided superior results to individual datasets for climate indicators related to mean air temperature and hot extremes, but not for other indicators. These results support the use of reanalyses as reference datasets for the evaluation of RCM mean air temperature and hot extremes over northern Canada, but not for cold extremes and precipitation indices.

Description: In the boreal spring of 2014, the oceanic and atmospheric conditions were favorable for an El Niño's development. It was predicted that in 2014, a super El Niño or at least a regular El Niño with normal magnitude, would initiate. However, the growth rate of the sea surface temperature anomaly (SSTA) in the equatorial eastern Pacific suddenly declined in the boreal summer. The physical processes responsible for the termination of the 2014 El Niño were addressed in this study. We hypothesized that a meridional dipole of SSTA, characterized by a pronounced warm SSTA over the eastern North Pacific (ENP) and cold SSTA over the eastern South Pacific (ESP), played a crucial role in blocking the 2014 El Niño’s development. The observational analysis revealed that the meridional dipole of SSTA and the relevant anomalous cross-equatorial flow in the tropical eastern Pacific, induced anomalous westward ( \({u^\prime }〈0\) ) and upwelling ( \({w^\prime }〉0\) ) currents in the equatorial eastern Pacific, leading to negative anomalous zonal advection term ( \(- {u^\prime }\partial \overline T /\partial x〈0\) ) and anomalous upwelling advection term ( \(- {w^\prime }\partial \overline T /\partial z〈0\) ). Additionally, the anomalous cross-equatorial flow also induced northward meridional current anomalies that transported subtropical cold water to the equator. All the changes of the oceanic dynamic terms collectively caused negative SSTA tendency in the boreal summer, and thus killed off the budding 2014 El Niño. The idealized numerical experiments further confirmed that the 2014 El Niño’s development could be suppressed by the meridional dipole of SSTA, and both the ENP pole and ESP pole make a contribution.

Description: The authors describe an electrochemical immunoassay for the β-adrenergic agonist ractopamine (RAC). It is based on the use of chitosan-stabilized gold nanoparticles (chit-AuNPs). Antibodies against RAC (anti-RAC) readily adsorb on the surface of the chit-AuNPs due to their high bio-affinity. The amount of chitosan used to synthesize chit-AuNPs does not affect the size and distribution of the NPs but amplifies the electrochemical signal of the electrode. The assay has a detection limit as low as 2.3 pg∙mL −1 (equivalent to a 6.7 fM concentration), with a response that is linear in the 0.01 to 5 ng∙mL −1 RAC concentration range. The assay is selective, acceptably reproducible, stable, and well applicable to the detection of RAC. Graphical abstract Chitosan-stabilized gold nanoparticles (chit-AuNPs) were prepared for electrochemical immunoassay of the ractopamine (RAC). The assay exhibits a detection limit of 2.3 pg·mL −1 (equal to 6.7 fM), is highly selective, acceptably reproducible, and stable.

Description: The authors describe biocompatible nanomicelle based drug carriers that can be used for simultaneous (a) fluorescence tracking, (b) pH-controlled release of the cancer drug doxorubicin (DOX), and (c) targeting the folate receptor. The pH-sensitive triblock copolymer is composed of poly-2-(diisopropylamino) ethyl methacrylate and methoxypoly (ethylene glycol) which were prepared by radical polymerization and ‘click’ chemistry. The copolymers undergo self-assembly to form spherical micelles with diameters between 100 and 200 nm and a pH-trigger capability at pH values from 5.8 to 6.2. The micelles enabled DOX to be released at pH 5.0 at a much higher rate than at pH 7.4. Studies on cellular uptake revealed selective internalization of the DOX-loaded nanomicelles into HeLa cells where they can be imaged fluorometrically. Quantitative analysis of the green fluorescence indicated that the FITC-labeled micelles possess a transfection efficiency of about 79% while that of the nanomicellles with folate is only ∼40% under the same conditions. Confocal laser scanning microscopy indicates that the micelles invade the lysosome of HeLa cells and that the DOX released by micelles causes strong cell lethality. In our preception, this work provides useful insights in terms of designing multifunctional drug carriers and of improving the applicability of copolymer micelles for drug delivery systems. Graphical abstract Schematic of the preparation of multi-functional nanomicelles through self-assembly of amphipathic polymers. The micelles act as tumor targeting and pH-controllable drug carriers. FITC/FA/P100-M can invade the lysosome of HeLa cells and release DOX inside cells, this leading to strongt cell lethality.

Description: With the consideration of spatial extension of heatwave events, two kind of regional heatwaves using absolute and relative thresholds, namely RHWs-A and RHWs-R, are investigated during 1959–2013. The temperature data is derived from the daily maximum temperatures (DMTs) of 587 stations in China. Totally 298 RHWs-A and 374 RHWs-R are identified during the past 55 years, and both of them are growing more frequent since the mid-1980s. By utilizing the cluster analysis, several typical spatial distributions of RHWs-A/RHWs-R are obtained. For RHWs-A, there are three clusters covering the southeastern, northwestern China and the lower reaches of Yangtze River, of which the southeastern cluster groups the most heatwaves. For RHWs-R, there are seven clusters distributed throughout the whole regions of China. The clusters in the northwestern and northeastern China are more stable than others for both RHWs-A and RHWs-R, and the northern clusters are of larger intensity than that of the southern ones. All RHWs-A/RHWs-R are accompanied by the anomalous high systems along with the reduced soil moisture. The southern clusters are controlled by Northwestern Pacific subtropical high (WPSH), and the northern ones are influenced by the mid-latitude high systems. The influences of atmospheric circulations and soil moisture on regional heatwaves are further demonstrated by two case analyses of the severe RHW-A in 2003 and the RHW-R in 2013.

Description: The authors report on a method for visual and spectrophotometric determination of silver (I) by using Prussian Blue nanoparticles (PB NPs) as a colorimetric probe. It is based on the finding that the blue PB NPs are converted into colorless silver ferrocyanide ions in the presence of Ag(I) due to the establishment of a dissolution-precipitation equilibrium. The change in absorbance at 700 nm is related to the concentration of Ag(I) in the range from 0.01 to 3 μM. The visual detection limit is 3 μM. The assay has a good selectivity for Ag(I) over other common ions. It was successfully applied to the determination of Ag(I) in spiked samples of river and lake waters. Graphical abstract Schematic presentation of a visual and spectrophotometric method for determination of silver(I) by using Prussian Blue nanoparticles (PB NPs) as optical probes.

Description: The authors describe a label-free electrochemical aptasensor for ultrasensitive and highly specific detection of the antibiotic based on cascade enzymatic recycling couple with DNAzyme amplification. The assay involves two sequential reactions: the first reaction is a λ exonuclease-assisted cyclic digestion reaction triggered by target-aptamer binding. The second reaction is a nicking endonuclease-aided cyclic nicking reaction, which produces a large amount of G-rich nucleic acid segments. These form a G-quadruplex/hemin complex in the presence of K(I) ions and hemin. Because the G-quadruplex/hemin complex acts as a horseradish peroxidase-mimicking DNAzyme with excellent redox activity, the electrochemical signal transduction is accomplished due to the electroreduction of H 2 O 2 . It appears that this work is the first example that cascade enzymatic recycling coupled to DNAzyme amplification is used for antibiotic detection. The aptasensor was applied to the quantitation of kanamycin and gave a response that is linear in the 1 pM to 10 nM kanamycin concentration range, with a detection limit as low as 0.5 pM. The working voltage (vs. Ag/AgCl) at which data can be acquired best is −0.35 V. The assay offers the advantages of remarkably improved sensitivity, use of affordable instrumentation, and simplified operation without the need for electrochemical labeling or addition of labile reagents. Thus, cascade enzymatic recycling coupled to DNAzyme amplification represents a versatile platform for highly sensitive and specific antibiotics detection. Graphical abstract ᅟ

Description: The authors describe a two-step strategy for in-situ dispersive solid phase extraction ( is -dSPE) of Cr(VI) ion (chromate) prior to its determination by using copper nanoclusters capped with 4,6-diamino-2-mercaptopyrimidine (DAMP-CuNCs) as a fluorescent probe. By emulating the formation of layered double hydroxides and taking advantage of their compositions, the extraction of chromate is accomplished by rapidly dispersing a suspension of mixed hydroxides of Mg 2+ and Al 3+ into the sample solution. After enrichment, chromate is directly quantified through selective quenching of the fluorescence of DAMP-CuNCs. This results from an inner filter effect caused by chromate only, while other anions have no effect. Under optimized conditions, the method has a linear response in the 1–7 μM chromate concentration range, and the lower limit of detection is 0.31 μM. The is -dSPE has improved detection sensitivity and has provided a highly selective response. It was successfully applied to the determination of chromate in (spiked) water samples, and the results agreed well with data obtained by ICP-OES. Graphical abstract Schematic of a two-step strategy for is -dSPE of Cr(VI) ion prior to its determination by using DAMP-CuNCs.

Description: The authors describe a method for magnetic solid phase extraction (MSPE) combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for the quantitation of eight non-steroidal anti-inflammatory drugs (NSAIDs) in wastewater and environmental water samples. Specifically, the NSAIDs were directly extracted by using a magnetic nanocomposite of type Fe 3 O 4 /MIL-101(Cr) (Matérial Institute Lavoisier, MIL) from 50 mL water samples without any further cleanup. The effects of the amount of adsorbent, pH value, salt concentration, ultrasonic extraction time, desorption solvent nature and volume and desorption time were investigated. Under the optimal conditions, UPLC-MS/MS based detection resulted in the following figures of merit: (a) Linear calibration plots that typically extend from 0.1 (0.2, 0.05, 0.02) to 50 μg·L −1 , depending on the compound; (b) detection limits between 3 to 60 ng·L −1 ; and (c), recoveries varying from 81.2% to 116.8% with relative standard deviations between 0.4% and 10.8%. The adsorption of NSAIDs on Fe 3 O 4 /MIL-101(Cr) was characterized by adsorption isotherms, kinetics and thermodynamics studies and provides a deeper insight into the adsorption mechanism. Compared to other method for pretreatment and preconcentration of NSAIDs, the new method is more rapid, sensitive, accurate and eco-friendly. The method was successfully applied to the determination of the NSAID residues in a variety of real environmental and wastewater samples. Graphical abstract Schematic of a method for determination of non-steroidal anti-inflammatory drugs (NSAIDs) in environmental water by magnetic solid phase extraction based on Fe 3 O 4 /MIL-101(Cr) combined with UPLC-MS/MS. The adsorption mechanism of NSAIDs on Fe 3 O 4 /MIL-101(Cr) was studied.

Description: Anabolic androgenic steroids (AAS) are frequently abused in human and animal sports as performance-enhancing drugs, and consequently their use is controlled by international sports authorities. Testosterone is one of the most frequently used AAS, and therefore the accurate determination of its levels in biological fluids is very important. The authors describe the selection of testosterone-binding aptamers performed using a classic SELEX approach with the target immobilized on magnetic beads. Counter selections with structurally similar steroids were implemented at different stages. Pools from different selection rounds were sequenced with Next Generation Sequencing and ten aptamer candidates were selected for further characterization. Low nanomolar range dissociation constants were calculated by a bead-based PCR assay and verified by microscale thermophoresis. Future work will focus on the development of aptamer-based platforms for the sensitive detection of testosterone in biological samples and the validation of these assays for the rapid screening of suspicious samples. Graphical abstract The selection of testosterone-binding aptamers is described via classic SELEX using the target immobilized on magnetic beads combined with Next Generation Sequencing. The process let to the identification of several unique aptamer candidates which were characterized and their binding to testosterone was evaluated.

Description: The authors describe a sensor capable of detecting methanol adulteration of ethanol. The sensor is based on the use of quartz tuning forks (QTFs) that were functionalized with polymer wires made from a combination of polystyrene (PS) and aniline. Exposure to organic vapors causes the resonance frequency of the functionalized QTF to change, and this can be used to identify the type and concentration of the analyte. A mixture of methanol and ethanol vapors in varying concentrations was exposed to the QTF polymer system. The resulting shift in the resonance frequency of the QTF was firstly used to determine the concentration of alcohol vapor, which is reflected in the amount of shift. Secondly, the nature of change in resonance frequency was used to determine the type of alcohol exposed to the sensor. The sensitivity and selectivity of the sensors to ethanol and methanol vapors has been investigated. A portable hand-held prototype sensor has been developed which displays the percentage of two alcohols it is exposed to. It can detect ethanol adulteration where the methanol concentration is as low as 5%. Graphical abstract Spring loaded Quartz Tuning Fork sensors functionalized with polystyrene-aniline wires exhibit opposite responses (increase and decrease in frequency) to vapors of ethanol and methanol respectively.The methanol adulteration of ethanol solutions may thus be detected by sensing their vapors.

Description: The authors describe an aptamer based fluorometric assay for the determination of ATP. It is based on deoxyribonuclease I-aided target recycling and signal amplification. The DNA probe consists of two regions (sequences) that represent the capture probe and the signal probe, respectively. In the absence of ATP, the probe is adsorbed by the surface of graphene oxide (GO) via π-stacking interactions. This results in quenching of the fluorescent label (carboxyfluorescein) and protects it from being cleaved by DNase. Upon adding ATP, the probe will be repelled by GO because ATP binds to the aptamer. This triggers an increase in fluorescence as measured at excitation/emission wavelengths of 480/514 nm. The detection limit is as low as 0.2 nM, and the calibration plot is linear in the 10 to 400 nM ATP concentration range. The assay is specific and sensitive, and in our perception has a large potential in terms of detecting other species including pathogenic microorganisms, small molecules, metal ions, and proteins. Graphical abstract Schematic of the fluorescent strategy for adenosine triphosphate assay by using aptamer-based target recognition and deoxyribonuclease I-aided signal amplification.

Description: The β-adrenergic agonist brombuterol (BB) is illicitly used as an additive in animal feed to enhance the lean meat-to-fat ratio. The authors describe an ultrasensitive lateral flow immunochromatographic assay (LFIA) based on the use of surface enhanced Raman scattering (SERS) for the determination of brombuterol in swine meat and urine samples. Flower-like gold-silver core-shell bimetallic nanoparticles (referred to as AuNF@Ag) displaying strong SERS enhancement were synthesized, characterized and used as the substrate for the preparation of the LFIA. Polyclonal antibody against brombuterol was immobilized on the surface of the AuNF@Ag particles carrying the Raman reporter 4-mercaptobenzoic acid (MBA). After performing an LFIA, the Raman scattering intensity of MBA on the test line was measured and used for quantitation of brombuterol. Figures of merit of this assay procedure include (a) duration of LFIA process of 15 min; (b) an IC 50 value (e.g. the concentration of brombuterol producing 50% of signal inhibition in standard curve) of 380 pg mL-1; and (c) a limit of detection as low as 0.5 pg mL-1. The LFIA is selective over the molecules salbutamol, ractopamine, phenylethanolamine A, isoproterenol and phenylephrine, but shows a 8.5% cross-reactivity to clenbuterol, probably due to the high structural similarity. Swine meat and urine samples spiked with different amounts of brombuterol were analyzed by this method and gave recoveries between 95.8 and 108.0%, and relative standard deviations between 2.0 and 6.3% (for n  = 3). Graphical abstract Schematic presentation of the lateral flow immunochromatographic assay (LFIA) based on surface enhanced Raman scattering (SERS) using flower-like gold-silver core-shell nanoparticles. It is capable of detecting brombuterol in swine meat and urine samples with high sensitivity and specificity.

Description: The amphiphilic copolymer poly(vinylbenzyl thymine-co-styrene-co-maleic anhydride) (PSVM) was synthesized by radical copolymerization of styrene, vinylbenzyl thymine, and maleic anhydride. Its chemical structure was proven by using 1 H nuclear magnetic resonance spectroscopy. PSVM was used as a host to prepare a composite consisting of carbon nanotubes and gold nanoparticles by in-situ reduction. The morphology of the nanocomposites was studied by transmission electron microscopy. A glassy carbon electrode coated with this composite is shown to be a viable sensor for the determination of dopamine (DA), paracetamol (PAT) (both at a pH value of 7), and uric acid (UA) (at pH 6). Two linear relationships exists between amperometric current and analyte concentrations. For DA, the linear analytical ranges are from 0.1 to 200 μM and from 200 to 1000 μM. For PAT, the ranges are from 0.1 to 200 μM and from 200 to 1000 μM. For UA, the ranges are from 0.05 to 1000 μM. The respective limits of detection (for S/ N  = 3) are 56, 27 and 50 nM. The sensor is highly sensitive, stable, reproducible, and selective. Graphical abstract A hybrid nanocomposite (CNT/PSVM/Au) of carbon nanotube (CNT) – Au nanoparticle composite based on the amphiphilic copolymer poly(vinylbenzyl thymine/styrene-co-maleic anhydride) (PSVM) was prepared through in situ reduction. This nanocomposite was immobilized on a glassy carbon electrode (GCE) to fabricate an electrochemical sensor to determine dopamine (DA), paracetamol (PAT) and uric acid (UA).

Description: A regenerable and ultrasensitive voltammetric biosensor is described for the determination of thrombin. It relies on a combination of (a) enzymatic catalysis, (b) a G-quadruplex/hemin DNAzyme system, and (c) AuPd nanoparticles for signal amplification. Poly(o-phenylenediamine) was decorated with AuPd nanoparticles and loaded with horseradish peroxidase (HRP) and thrombin aptamer (TBA), and the mixture was allowed to interact with hemin to form the G-quadruplex/hemin/HRP/AuPd/poly(o-phenylenediamine) bioconjugates. In the presence of thrombin, the bioconjugates remain immobilized on the surface of the modified glassy carbon electrode through a sandwich reaction. Poly(o-phenylenediamine) also acts as a redox mediator, and the electrochemical reaction of poly(o-phenylenediamine) in the presence of H 2 O 2 is efficiently catalyzed by HRP, AuPd nanoparticles and G-quadruplex/hemin as the peroxidase mimics. Thus, a remarkably amplified electrochemical signal is obtained by the triple catalytic amplification. The biosensor has a dynamic range that spans the 100 f. to 20 nM thrombin concentration range, and the detection limit is 20 fM. The biosensor can be regenerated by applying an electrochemical desorption technique that breaks the gold-thiol bond and releases the components from the surface. In our perception, the mediator-free and signal-amplified biosensor demonstrated here has a large potential with respect to the quantitation of thrombin in clinical samples. Graphical abstract Schematic of the assay: The peroxidase-like AuPd nanoparticles, G-quadruplex/hemin DNAzyme and horseradish peroxidase synergistically catalyze the electrochemical reaction of poly(o-phenylenediamine) in the presence of H 2 O 2 , thereby amplifying the electrochemical detection signal of thrombin.

Description: The connection between Eurasian snow cover (SC) in autumn and Eurasian winter mean surface air temperature (SAT) has been identified by many studies. However, some recent observations indicate that early and late winter climate sometimes shows an out-of-phase relationship, suggesting that the winter mean situation might obscure the important relationships that are relevant for scientific research and applications. This study investigates the relationship between October northern Eurasian SC (NESC; 58°–68°N, 30°–90°E) and Eurasian SAT during the winter months and finds a significant relationship only exists in January. Generally, following reduced October NESC, the East Asian trough and Ural high are intensified in January, and anomalous northeasterly winds prevail in mid-latitudes, causing cold anomalies over Eurasia. Meanwhile, anomalous southwesterly winds along the northern fringe of the Ural high favor warm anomalies in the Arctic. The dynamical mechanism for the connection between NESC in October and the warm Arctic–cold Eurasia (WACE) anomaly in January is further investigated from the perspective of quasi-stationary planetary wave activity. It is found that planetary waves with zonal wavenumber-1 (ZWN1) play a dominant role in this process. Specifically, the ZWN1 pattern of planetary-scale waves concurrent with October NESC anomaly extends from the surface to the upper-stratosphere. It persists in the stratosphere through November–December and propagates downward to the surface by the following January, making the connection between October NESC and January climate possible. Additionally, the influence of October NESC on the January WACE pattern has intensified since the early-2000s.

Description: The role of riverine freshwater inflow on the Central Mediterranean Overturning Circulation (CMOC) was studied using a high-resolution ocean model with a complete distribution of rivers in the Adriatic and Ionian catchment areas. The impact of river runoff on the Adriatic and Ionian Sea basins was assessed by a twin experiment, with and without runoff, from 1999 to 2012. This study tries to show the connection between the Adriatic as a marginal sea containing the downwelling branch of the anti-estuarine CMOC and the large runoff occurring there. It is found that the multiannual CMOC is a persistent anti-estuarine structure with secondary estuarine cells that strengthen in years of large realistic river runoff. The CMOC is demonstrated to be controlled by wind forcing at least as much as by buoyancy fluxes. It is found that river runoff affects the CMOC strength, enhancing the amplitude of the secondary estuarine cells and reducing the intensity of the dominant anti-estuarine cell. A large river runoff can produce a positive buoyancy flux without switching off the antiestuarine CMOC cell, but a particularly low heat flux and wind work with normal river runoff can reverse it. Overall by comparing experiments with, without and with unrealistically augmented runoff we demonstrate that rivers affect the CMOC strength but they can never represent its dominant forcing mechanism and the potential role of river runoff has to be considered jointly with wind work and heat flux, as they largely contribute to the energy budget of the basin. Looking at the downwelling branch of the CMOC in the Adriatic basin, rivers are demonstrated to locally reduce the volume of Adriatic dense water formed in the Southern Adriatic Sea as a result of increased water stratification. The spreading of the Adriatic dense water into the Ionian abyss is affected as well: dense waters overflowing the Otranto Strait are less dense in a realistic runoff regime, with respect to no runoff experiment, and confined to a narrower band against the Italian shelf with less lateral spreading toward the Ionian Sea center.

Description: The authors have developed a rapid and reliable method for the capillary electrochromatographic determination of cephalosporin antibiotics in environmental waters. An open-tubular capillary column was modified with the complex [Cu(mal)(bpy)], a copper(II) complex with malic acid and 4,4′-bipyridyl, by an amide coupling method to act as the stationary phase. The simultaneous determination of the cephalosporins formulations, namely cefapirin (CP), ceftiofur (EFT) and cefixime (CFM) in environmental water samples was accomplished in buffer of pH 5.0 by applying a voltage of 8 kV and with DAD detection. Detection limits typically are 0.1 μg⋅mL −1 .The method was applied to the analysis of cephalosporins in spiked water samples from Kunming Lake to give recoveries betwen 88 and 106%. Graphical abstract A metal-organic framework (MOF) was synthesized from copper(II), malic acid and 4,4′-bipyridyl and used as stationary phase of capillary electrochromatography (CEC) by covalent immobilization on the capillary inner walls. Compared to an uncoated fused-silica capillary, improved separation of cephalosporin antibiotics can be accomplished.

Description: Iron sulfides with different atomic ratios were synthesized by a hydrothermal method and used to modify a glassy carbon electrode. The various sulfides were compared to each other for their amperometric response to H 2 O 2 . It is found that FeS is the most adequate material. Operated in 0.1 M NaOH solution at 0.4 V (vs. Ag/AgCl), the sensor based on FeS displays a linear response that extends from 0.50 μM to 20.5 mM of H 2 O 2 , with a sensitivity of 36.4 μA mM −1  cm −2 and a detection limit of 0.15 μM (at an S/N ratio of 3). The sensor is selective, stable and reproducible. Graphical abstract Schematic of the synthesis of pomegranate flower-like FeS by a hydrothermal route using ferric chloride and thiourea (SC(NH 2 ) 2 ) as the precursors, and ethanolamine (EA) as the structure-guiding auxiliary agent. A glassy carbon electrode (GCE) modified with this material allows for amperometric sensing of hydrogen peroxide in 0.1 M NaOH solution with a 0.15 μM detection limit. 

Description: The authors describe a highly sensitive and selective photoelectrochemical (PEC) assay for mercury(II) ions. It is based on a dual signal amplification strategy. The first enhancement results from the surface plasmon resonance (SPR) of Au@Ag nanoparticles (NPs) absorbed on MoS 2 nanosheets. Here, the injection of hot electrons of Au@Ag NPs into MoS 2 nanosheets produces a strong photocurrent, while background signals are strongly reduced. The second enhancement results from the use of a thymine rich ct-DNA aptamer attached to the Au@Ag-MoS 2 nanohybrid. The DNA specifically binds Hg(II) ions to form thymine-Hg(II)-thymine (T-Hg-T) complexes. This leads to the formation of a hairpin-shaped dsDNA structure. The use of a CdSe quantum dot label at the terminal end of the ct-DNA further facilitates electron–hole separation. The photocurrent of the detector is measured as a function of Hg(II) concentration at a bias voltage of 0.1 V and under irradiation of 430 nm light. Due to the two-fold amplification strategy presented here, the linear range extends from 10 pmol·L −1 to 100 nmol·L −1 , with a detection limit of 5 pmol·L −1 (at S/N = 3). Graphical Abstract The injection of hot electrons of Au@Ag into MoS 2 produces a strong photocurrent, and the formation of thymine-Hg(II)-thymine further facilitates electron–hole separation by CdSe. This dual signal amplification strategy is used to detect Hg(II) ions via a photoelectrochemical assay.

Description: CdSe:Eu nanocrystals were successfully synthesized and characterized by transmission electron microscopy, X-ray powder diffraction, and X-ray photoelectric spectroscopy. The CdSe:Eu nanocrystals showed enhanced green electrochemiluminescence (ECL) intensity when compared to pure CdSe nanocrystals. Further, the nanocrystals were used to design an ECL immunosensor for the detection of carcinoembryonic antigen (CEA) that has a linear response over the 1.0 fg·mL −1 to 100 ng·mL −1  CEA concentration range with a 0.4 fg·mL −1 detection limit. The assay was applied to the determination of CEA in human serum samples. Graphical abstract Schematic of the assay: GCE-glassy-carbon electrode, Ab- Antibody, BSA- Bovine serum albumin, Ag- Antigen. CdSe:Eu nanocrystals were used to design an ECL immunosensor for the detection of carcinoembryonic antigen.

Description: The authors present a voltammetric immunoassay for the quantification of the prostate specific antigen (PSA), a well-established tumor marker. Biotinylated anti- PSA antibodies were immobilized on the surface of a nano-TiO2-modified carbon paste electrode using specific interaction between streptavidin and biotin. Streptavidin itself was covalently grafted to the electrode surface via 4-aminobenzoic acid film. Signal transduction was then performed using polyclonal antibodies conjugated with horseradish peroxidase (HRP) and thionine. An amplified catalytic reduction current was observed in the presence of H 2 O 2 because more than one polyclonal antibody linked to each antigen. Each step of the preparation of the immunosensor was monitored via electrochemical impedance spectroscopy. The electrode, if operated at a typical potential of 0.3 V vs. Ag/AgCl and using hexacyanoferrate as an electrochemical probe, exhibits linear responses in the 0.10 to 5.0 ng·mL −1 and 5.0 to 100 ng·mL −1 PSA concentration ranges, with a detection limit of 200 pg·mL −1 . The accuracy of the biosensor was confirmed by analyzing a certified human serum sample, and this indicated that the immunosensor is well suited for the quantification of PSA. Graphical abstract Schematic presentation of a sandwich-type electrochemical immunosensor for the prostate specific antigen. It is based on the use of a carbon paste electrode, streptavidin and biotinylated monoclonal antibody. Signal transduction is the result of the catalytic reduction of thionine.

Description: The authors report on a new approach for the determination of the breast cancer biomarker microRNA-155 (miRNA-155). It is based on the measurement of the fluorescence shift of oligonucleotide-templated copper nanoclusters (DNA-CuNC). A probe DNA was designed that acts as a template for the preparation of CuNC which, under 400 nm excitation, exhibit strong fluorescence enhancement at 490 nm and a 90 nm Stokes shift after binding to target miRNA-155 and formation of a DNA-RNA heteroduplex. Under the optimal conditions, the fluorescence of the DNA-CuNC increases with increasing concentration of miRNA-155 in the range from 50 pM to 10 nM, with a 11 pM detection limit. The assay has excellent selectivity over noncomplementary RNA. The method was applied to the determination of miRNA-155 in the presence of human plasma and saliva. Graphical abstract Schematic of the detection strategy that relies on the fluorescence shift of DNA-CuNCs resulting from the specific binding of DNA-CuNCs with target miRNA-155. Fluorescence intensities are linearly proportional to the concentrations of target RNA from 50 pM to 10 nM.

Description: Composites containing cobalt oxide (Co 3 O 4 ) nanocubes integrated with multiwall carbon nanotubes (MWCNT) were synthesized by a hydrothermal route. The fractions of MWCNTs in the composite were varied from 4, 8, 12, 16 and 20 wt.%, and the resulting materials are denoted as C1, C2, C3, C4 and C5, respectively. The formation of products with high structural crystallinity was confirmed by X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. A morphological study by field emission scanning electron microscopy and high resolution transmission electron microscopy showed the successful integration of Co 3 O 4 nanocubes to the MWCNTs with an average particle size of ∼32 nm. The surface of a glassy carbon electrode (GCE) was modified with the nanocomposites in order to evaluate the electrochemical performance of the nanocomposites. Cyclic voltammetry showed that the C4-modified GCE displays best performance in terms of oxidation potential and peak current in comparison to that of a bare GCE, Co 3 O 4 nanocubes, or GCEs modified with C1, C2, C3 or C5. The detection limit (at an S/N ratio of 3) is 0.176 nM by using chronoamperometry, and the linear range is between 1 and 20 μM. Graphical abstract MWCNT-Co 3 O 4 nanocubes were synthesized by one pot hydrothermal route. The nanocomposite is used for electrochemical detection of dopamine. The limit of detection is found to be 176 nM by chronoamperometry at a constant potential of + 0.13 V.

Description: The paper describes a colorimetric sandwich enzyme-linked immunosorbent assay (ELISA) for the determination of human IgG. It is based on the use of an Fe(II) coordination complex as a signal amplifier and of mesoporous silica nanoparticles modified with glucose oxidase (GOx) and secondary antibodies (Ab 2 ). After formation of the immuno sandwich complex, the quantity of GOx is proportional to the quantity of IgG. On addition of Fe(II) and glucose, GOx catalyzes the oxidation of glucose to produce hydrogen peroxide which oxidizes Fe(II) to Fe(III). After adding a stop solution containing the complexing ligand 1,10-phenanthroline (Phen), un-reacted Fe(II) forms an orange-red complex with Phen which can be detected by plate reader and even seen with bare eyes. This sandwich ELISA has a linear response in the 1 pg.mL −1 to 100 ng.mL −1 human IgG concentration range and a 860 fg.mL −1 detection limit. This is 20 times lower than the commercial ELISA for human IgG. The assay also is selective, stable, highly sensitive and cost-effective. Graphical abstract Schematic of a colorimetric enzyme-linked immunosorbent assay (ELISA) based on Fe(II) coordination complex as signal amplification strategy for human IgG detection. Glucose oxidase (GOx, green) and detection antibodies (Ab 2 , brown) functionalized mesoporous silica nanoparticles (MSN) were prepared as probe.

Description: The authors describe a method for speciation of thallium that is based on solid phase extraction (SPE) combined with dispersive liquid-liquid microextraction (DLLME) prior to electrothermal vaporization ICP-MS determination. The method is shown to be applicable to the determination of total, suspended, soluble, organic and inorganic Tl, and of Tl(I) and Tl(III) in tea leaves and tea infusion. The SPE step involves the use of titanium dioxide nanofibers for preconcentration of the Tl analytes and simultaneous removal of the matrix components such as polyphenols, soluble sugars, catechin, caffeine and tea pigments. Following elution of Tl with dilute HNO 3 , the eluate was further preconcentrated and separation by DLLME. After optimization of the method, it has a detection limits of 0.015 pg mL −1 for Tl(I) and of 0.020 pg mL −1 for Tl(III), with relative standard deviations of 6.5% and 7.3% (at 0.10 ng mL −1 ; for n  = 9), respectively. The technique has an enrichment factor of 450 and is highly selective. It was successfully applied to the speciation and distribution of thallium in tea leaves and tea infusions. A certified reference material of tea leaves was analyzed by this method, and the obtained values were in good agreement with the certified values. Graphical abstract Schematic of a new method for solid phase extraction (SPE) of thallium. Titanium dioxide nanofiber-based extraction was combined with dispersive liquid-liquid microextraction (DLLME) for speciation of thallium and its distribution in tea leaves and tea infusion, including total, suspended, soluble, organic and inorganic Tl, and of Tl(I) and Tl(III).

Description: The authors describe an integrated biosensor for amperometric DNA detection of Dengue virus in real time. Cu 2 CdSnS 4 (CCTS) quaternary alloy nanostructures were successfully synthesized, deposited on an oxygen-etched silicon substrate (O 2 /Si) via spin coating, and annealed at 400 °C. The nanostructures were investigated by using UV-vis spectroscopy, X-ray diffraction, atomic force microscopy and scanning electron microscopy. Interdigitated electrodes were fabricated using silver as a metal contact deposited on the CCTS/O 2 /Si substrate using a thermal evaporator vacuum coater and a hard mask. The quaternary alloy acts as a support for immobilization of a Dengue-specific DNA probe that is employed as the recognition element. Single-stranded DNA in concentrations from 100 f. to 10 nM were successfully recognized via amperometry, typically at a working voltage of 1.5 V. The lower detection limit is 17 nM. Sensitivity is found to be 24.2 μA nM −1  cm −2 . The biosensor is inexpensive, fast, highly sensitive, and has low power consumption. Graphical abstract Schematic illustration of IDEs fabrication steps. (a) Si substrate (b) O 2 /Si, (c) CCTS/O 2 /Si, (d) Ag/CCTS/O 2 /Si, (e) cross section view of the sample.

Description: The authors describe the synthesis of a nanosorbent for fast magnetic solid phase extraction of trace levels of Ag(I), Au(III), Pd(II) and Pt(II). It consists of graphene oxide sheets modified with magnetite nanoparticles (mGO) coated with silica. This material was further modified with a polypyrrole-polythiophene copolymer via oxidative polymerization to end up with a material of the type mGO@SiO 2 @PPy-PTh. Successful synthesis of the nanocomposite and its components was corroborated by FT-IR, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and thermogravimetric analysis. The presence of nitrogen- and sulfur-containing functional groups on both sides of the nanocomposite sheets facilitates the formation of strong complexes between target (i.e. noble metal ions) and the surface of the sorbent. Following elution with thiourea-HCl, the ions were quantified by FAAS. Under optimized conditions, the lower limits of detection range from 0.1 to 1.0 μg L −1 . The maximum sorption capacities are 49, 50, 45, and 50 mg g −1 for Ag(I), Au(III), Pd(II) and Pt(II), respectively. The method was successfully applied to the extraction and determination of the analytes in wastewater (electroplating, radiological and photographical wastewater), sea water, and road dust. Graphical abstract A sorbent of the type mGO@SiO 2 @PPy-PTh (where mGO stands for magnetic graphene oxide, PPy for polypyrrole, and PTh for polythiophene) was synthesized and used as a nanosorbent for the micro solid phase extraction of the ions Ag(I), Au(III), Pd(II), and Pt(II) prior to their determination by FAAS. mGO: Magnetic graphene oxide. TEOS: Tetraethyl orthosilicate. PPy-PTh: Polypyrrole-Polythiophene copolymer.

Description: The authors have prepared organized assemblies of a hemoglobin-chitosan(CS)@Fe 3 O 4 composite on glassy carbon electrodes (GCEs) via three strategies with the aim of preparing tunable Hb-coated GCEs with good stability and long-term oxygen storage capability. The formation and morphology of the Hb - CS@Fe 3 O 4 composite was characterized by scanning electrochemical microscopy, XRD and UV–vis spectroscopy. It is shown that Hb is fully integrated into the CS@Fe 3 O 4 and can be manipulated by a magnetic field whilst maintaining its biological activity. In the absence of oxygen, a surface-controlled electrode process occurs with an interfacial electron transfer rate ( k s ) of 2.14 s −1 . The modified GCE also has a favorable oxygen storage lifetime (almost 6 h). One Hb-CS@Fe 3 O 4 film on the electrode displays particularly good electrocatalytic reduction activity towards oxygen. The linear range for detection of O 2 is 1.2 × 10 −7  ~ 2.0 × 10 −4 mol L −1 with a detection limit of 4.0 × 10 −8 mol L −1 . In our opinion, this method has great potential in terms of enhanced oxygen storage capability of Hb, which can be applied in special situations such as space operations, down hole mining, mountaineering and diving. Graphical Abstract Hb-CS@Fe 3 O 4 composites were prepared by three strategies, and oxygen carrying capability was studied. The corresponding modified electrode constructed on the basis of the magnetic field environment was superior in terms of stability, sensitivity and O 2 storage time, showing wider linear range and lower detection limit.

Description: The authors describe a graphite immobilized bismuth film electrode with enhanced sensitivity for the organophosphorus pesticide paraoxon. The film was formed by ex-situ electroplating of bismuth onto the large surface of a glassy carbon electrode modified with graphite nanopowder (Bi/Gr/GCE). The modified GCE was characterized by chronoamperometry using p-nitrophenol as a model nitro compound. The modification of the GCE results in an increase of the electroactive area (to 27.7 mm 2 ) and of the electrocatalytic activity (the catalytic rate constant being 4140 L·mol −1 ·s −1 ). This results in an enhancement of the current for the electroreduction of paraoxon by a factor of 4.3 (compared to a plain GCE). The modified GCE was applied to the sensitive determination of paraoxon by differential pulse voltammetry. At a typical working potential of −0.45 V vs. Ag/AgCl, the LOD is 2 nmol·L −1 of paraoxon, which is comparable to the LOD of some cholinesterases-based electrochemical sensors and is lower than the LOD of the organophosphorus hydrolase-based electrochemical sensors for paraoxon. In addition, the new GCE is more stable than enzyme-based sensors, and it can be renewed. Graphical abstract Schematic of a glassy carbon electrode (GCE) modified by renewable Bi film deposited ex situ. Graphite nanopowder (Gr) was incorporated in laponite as intermediate layer to form a sandwich-type structure (Bi/Gr/GCE). The Bi/Gr/GCE was applied for the sensitive paraoxon quantification with an LOD of 2 nmol L −1 . Symbols: 1-glassy carbon electrode; 2-graphite nanopowder; 3-Bi-film. GCE: glassy carbon electrode; Bi/GCE: Bi-film modified glassy carbon electrode; Gr/GCE: graphite nanopowder modified glassy carbon electrode; Bi/Gr/GCE: graphite immobilized Bi-film electrode.

Description: Polyether ether ketone (PEEK) is an ideal substrate for in tube solid-phase microextraction (SPME) because it overcomes the shortcomings of conventional silica fibers in terms of fragility and poor flexibility. Commonly used bare PEEK tubes suffer from difficult modification with selective sorbents and low inner surface areas. This problem was solved by etching with concentrated sulfuric acid, which dissolves the amorphous regions of the PEEK surface and yields a rough inner surface with plenty of microscopically small holes. The etched tube was then stepwise functionalized with polydopamine and graphene oxide which was in-situ immobilized. The modified tube displays excellent efficiency for the extraction of positively charged quaternary alkaloids by a mixed-mode extraction. Enrichment factors from 221 to 275 can be obtained for the extraction of the alkaloids jatrorrhizine, palmatine and berberine. The alkaloiods were then quantified by online SPME-HPLC-MS/MS detection. The method has detection limits of 0.1 pg mL −1 , good linearity, and good intra-day reproducibility (≤ 2.4%). It was applied to the analysis of the three alkaloids in Cortex Phellodendri herb and rat plasma after oral administration. Graphical abstract A concentrated sulfuric acid etching method was used for enhance the workability of polyether ether ketone tube (PEEK) in solid phase microextraction (SPME). The etched tube was covered with graphene oxide (GO) for extraction of protoberberines.