Short Separation Research Articles

New coupling mechanism of titanium nitride nanosphere dimers at short separation distances

The coupled localized plasmon modes generated by a metal plasmonic nanoparticle (NP) dimer induces a stronger plasmon enhanced electromagnetic field as well as a stronger optical response compared to that of a single NP. Owing to the small Drude damping factor, however, the absorption bandwidth of noble metallic NPs is insufficiently broad. Herein, the near-field wide band coupling absorption for 25 nm diameter TiN nanospheres is investigated in a homo-dimer arrangement for various separation distances using the finite element method. An enhancement of the wide band coupling absorption and a red-shift is found, which can be explained by an uncomplicated dipole–dipole coupling model at interparticle distances greater than 5 nm. At short separation distances, the coupling absorption of the TiN dimer exhibits a tremendous change, which is diametrically opposite the results found for a Au dimer. This unexpected change phenomenon is shown by calculation and analysis to be owing to the change of the charge distribution approach at short separation distances, which is demonstrated to play a key role in the wide band coupling characteristic variation. With decreasing separation gap, a new coupling mechanism caused by surface charge properties is responsible for the decline in coupling absorption as well as the break in the ruler equations for both plasmon shift and temperature enhancement.

The use of magnetic iron oxide based nanoparticles to improve microalgae harvesting in real wastewater

A novel approach for harvesting Scenedesmus sp. microalgae from real wastewater by using adsorbents of magnetite-based nanoparticles (Fe3O4 NPs) was tested in this study for the first time for this microalgae. Using these NPs, the harvesting efficiency was even higher than 95%. The optimal conditions (0.14 gNPs/L, a short magnetic separation time of only 8 min and 27 min of contact time) were found using the response surface methodology. The best fitting of the adsorption equilibrium results was achieved by the Langmuir isotherm model, and the maximum adsorption capacity for Scenedesmus sp. reached 3.49 g dry cell weight (DCW)/g Fe3O4 NPs. Zeta potential measurements and the Dubinin-Radushkevich isotherm model analysis pointed out that the main adsorption mechanism between Scenedesmus sp. cells and Fe3O4 NPs was electrostatic interaction. Finally, Fe3O4 NPs were six times successfully reused by combining an alkaline treatment with an ultrasonication process, which implies microalgae lysis. The results herein obtained highlight the potential for magnetic separation of microalgae from wastewater, which is capable of reaching a high harvesting efficiency in a very short time.

Magnetic nanoparticles supported Cu2+ and Ce3+ complexes: toward the chemical and electrochemical oxidation of alcohol and sulfide derivatives

Heterogeneous catalysts are more prominent rather than homogenous catalysts since they are simply separated from products. To improve and develop heterogeneous catalysts, two core–shell magnetic nanocatalysts are prepared by anchoring of Cu and Ce complexes on the surface of Fe3O4, then the efficiency of the obtained catalysts are tested toward both chemical and electrochemical oxidation of sulfide and alcohol derivatives. Characterization of mentioned catalysts was performed by using FT-IR, XRD, EDX and SEM. The obtained results confirm that the reported method has outstanding advantages such as short reaction time, high yield, easy operation, easy separation, inexpensive and non-toxic material and chemical and thermal stability.

Halogen bonds in N-bromosuccinimide and other N-halosuccinimides

Our crystal data shows marked intermolecular Br interaction with a neighboring O (carbonyl) in the crystal, Br---O(carbonyl) = 2.767(1) A, well below the sum of the corresponding van der Waals radii, 3.37 A. This C=O---Br interaction is among the shortest in the CSD (only 8/2185 examples have a similar distance 2.725–2.800 A). Only one carbonyl group interacts with the halogen atom, thus inducing a helical intermolecular arrangement. The halogen bond was also studied with density functional theory (DFT) methods, based on coordinates of two molecules in the crystal packing, widely modifying the N-Br---O(carbonyl) angle. In each calculation, this angle was fixed, and the corresponding arrangements were analyzed for potential structural correlation. Indeed, the widening of the N-Br---O(carbonyl) angle correlates with a gradual increase of halogen bond interaction Br---O(carbonyl), that is, shorter separation. It is also seen that decreasing the N-Br---O(carbonyl) angle is associated with decreasing Br---Br separation. Isosurface electron density shows the presence of Br sigma-holes in the two-molecule arrangements.

Multivariate optimization and validation of a procedure to direct determine acetonitrile and ethanol in radiopharmaceuticals by GC-FID

A fast and simplified analytical procedure was developed and validated for the direct determination of organic solvents (acetonitrile and ethanol) in radiopharmaceuticals samples ([18F]FMISO, [18F]FES and [18F]FLT) by gas chromatography coupled with flame ionization detection (GC-FID). Optimization studies were performed with the aid of two-level full factorial design. The optimum conditions were located using Derringer's desirability function. Procedure validation assured the compliance of the assay to Brazilian regulatory agencies standards (ANVISA and INMETRO). Values for LOD and LOQ were commensurate with the level at which the impurities must be controlled. Good linearity was achieved (R ≥ 0.990) for acetonitrile and ethanol concentrations ranging from 0.003 to 0.09% (w/v) and 2.1 to 11.0% (v/v), respectively. Accuracy and precision assessments were performed using samples fortified with standards (spiked samples). The developed procedure proved to be selective, sensitive, accurate (95.9–117.8% of nominal values) and precise (RSD ≤ 9.7%). The validated procedure was successfully used to assess organic solvents levels in a Brazilian radiopharmaceuticals samples manufactured by Radiopharmaceutical Research and Production Unit of Nuclear Technology Development Center (CDTN), in Belo Horizonte (Brazil). The analytes could be well resolved in 1.5 min and accurately determined in three different types of radiopharmaceuticals. This procedure is applicable to samples even with high ethanol content up to 11% (v/v). Other advantages include no sample preparation, short chromatographic separation time and minimum manual operation. As results, the proposed procedure can be useful in the routine analysis for the determination of acetonitrile and ethanol in radiopharmaceutical samples.

Observing the steady-state visual evoked potentials with a compact quad-channel spin exchange relaxation-free magnetometer**Project supported by the National Key Research and Development Program of China (Grant Nos. 2016YFA0300600 and 2016YFA0301500), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant Nos. XDB07030000 and XDBS32000000), the National Natural Science Foundation of China (Grant Nos. 11474347 and 31730039), and the Fund

We observed the steady-state visually evoked potential (SSVEP) from a healthy subject using a compact quad-channel potassium spin exchange relaxation-free (SERF) optically pumped magnetometer (OPM). To this end, 30 s of data were collected, and SSVEP-related magnetic responses with signal intensity ranging from 150 fT to 300 fT were observed for all four channels. The corresponding signal to noise ratio (SNR) was in the range of 3.5–5.5. We then used different channels to operate the sensor as a gradiometer. In the specific case of detecting SSVEP, we noticed that the short channel separation distance led to a strongly diminished gradiometer signal. Although not optimal for the case of SSVEP detection, this set-up can prove to be highly useful for other magnetoencephalography (MEG) paradigms that require good noise cancellation. Considering its compactness, low cost, and good performance, the K-SERF sensor has great potential for biomagnetic field measurements and brain-computer interfaces (BCI).

Evaluation of prenylflavonoids and hop bitter acids in surplus yeast.

This study developed a high performance liquid chromatography with diode array detection (HPLC-DAD) and tandem mass spectrometry (MS-MS) method for determination of prenylflavonoids and hop bitter acids in surplus yeast, a byproduct from beer brewing process. This method enabled the simultaneous separation of 4 prenylflavonoids and 20 hop bitter acids within 30min by employing a Hypersil-Keystone HyPURITY C18 column and a gradient mobile phase composed of phosphoric acid aqueous solution at pH 1.6 and acetonitrile. For HPLC-DAD analysis, the limits of detection and limits of quantitation ranged from 0.04 to 0.15µg/mL and from 0.12 to 0.45µg/mL, respectively, and the recoveries ranged from 82.6 to 99.7%. The intra-day variability and inter-day variability ranged from 1.37 to 8.82% and from 0.68 to 9.74%, respectively. For qualitation by MS-MS, the positive mode was discovered to possess satisfactory collision capacity and high sensitivity for prenylflavonoids, while the negative mode was more suitable for the ionization of hop bitter acids. The content of hop bitter acids in surplus yeast were higher than that of prenylflavonoids, and isomers and oxidation products of hop bitter acids were found. This study has advantages in identifying more components, short separation time, satisfactory resolution, high accuracy and high precision.

Phenology, mobility and behaviour of the arcto-alpine species Boloria napaea in its arctic habitat

Arctic and alpine environments present extreme, but different, challenges to survival. We therefore studied the ecological adaptation of the arctic-alpine fritillary Boloria napaea in northern Sweden and compared these results with the eastern Alps. Using mark-release-recapture, we analysed phenology, mobility, activity patterns, change in wing condition and nectar sources. The phenology showed no protandry, but a longer flight period of the females. Wing conditions revealed a linear decay being quicker in males than females. The mean flight distances were higher for males than females (143 vs 92 m). In general, males were more flight active, while females invested more time in feeding and resting. The shortness of the flight period in the Arctic is apparently a particular adaptation to these harsh conditions, not even allowing protandry, and constraining all individuals to hatch during a short period. These conditions also forced the individuals to concentrate on flight and alimentation. In general, Arctic and Alpine populations of B. napaea show few differences, but the species seems to be even better adapted to the northern environments. Thus, the short temporal separation of these populations seems not to have been sufficient for a divergent adaptation in the southern mountains.

Oxygen content of high ferrotitanium prepared by thermite method with different melt separation temperatures

High ferrotitanium prepared directly by the thermite method has a disadvantageously high O content (≥ 10 wt%) because of the short slag-metal separation time. In this study, CaO and CaF2 are added to the melt to improve the basicity of the slag and melt separation under heat preservation is performed to strengthen slag-metal separation. The thermodynamics of the step-by-step reduction process of TiO2 in the Ti–Al–Fe–Si–O system whose composition is close to the alloy after melt separation were calculated. Samples of alloys and slags before and after melt separation were systematically analyzed. The result indicates that the reaction that TiO is reduced by Al to Ti is the limited step in the reduction process of TiO2. The O content of the alloys slightly decreases with temperature from 1873 to 2023 K, which agrees with the changes in the law of deoxidation limit. It is mainly attributed to the movement of chemical reactions in the alloy melt at different temperatures and slag-metal interfacial reaction. The addition of Al2O3–CaO–CaF2 slag and high temperature promote the removal of Al2O3 and titanium suboxides. The minimum contents of O and Al in the alloy reach 1.84 wt% and 3.26 wt%, respectively.

The Analysis of Leading Edge Deformations on Turbomachine Blades

With recent advancements in the development of material and manufacturing technology, the leading edge geometry of turbomachine blades has attracted widespread attention. “Sharp” leading edges always have a better aerodynamic performance, though it is prone to deformations easily. Thus, flat plates and real compressor cascades with different leading edge deformations were investigated to study the influence, which is applicable for thin blades at low speeds. Different boundary layer characteristics, including the velocity profile, transition process, and loss, are compared. The results show that there are several kinds of contradictory influence mechanisms and that the final phenomenon is closely related to the condition of the original boundary layer. In low turbulence, with large and laminar separation, the deformations can suppress separation and decrease loss. In high turbulence, with short and transitional separation, deformations can promote the transition process and increase the loss. The sensitivities of different the original leading edge shapes are also compared. This indicates that a good design always has a better robustness at low turbulence values, while it is worse at high turbulence values. The cascade experiment and simulation show that the deformation influence is similar to flat plates and that it is enlarged near the hub, which affects the corner separation.

Identification of Short Exons Disunited by a Short Intron in Eukaryotic DNA Regions.

Weak codon bias in short exons and separation by a short intron induces difficulty in extracting period-3 component that marks the presence of exonic regions. The annotation task of such short exons has been addressed in the proposed model independent signal processing based method with following features: (a) DNA sequences have been mapped using multiple mapping schemes, (b) period-3 spectrums corresponding to multiple mappings have been optimized to enhance short exon-short intron discrimination, and (c) spectrums corresponding to multiple mapping schemes have been subjected to Principal Component Analysis (PCA) for identifying greater number of such short exons. A comparative study with other methods indicates improved detection of contiguous short exons disunited by a short intron. Apart from the annotation of exonic and intronic regions, the proposed algorithm can also complement the methods for the detection of alternative splicing by intron retention, as one of the characteristic feature for intron retention is the presence of two short exons flanking a short intron.

Design and synthesis of Fe3O4@SiO2/aza-crown ether-Cu(II) as a novel and highly efficient magnetic nanocomposite catalyst for the synthesis of 1,2,3-triazoles, 1-substituted 1H-tetrazoles and 5-substituted 1H-tetrazoles in green solvents

A New and efficient magnetic nanocatalyst has been fabricated via covalent grafting of an aza-crown ether Cu(II) complex on silica coated iron oxide support. The above mentioned magnetic nanocatalyst has been characterized by various techniques such as SEM, TEM, XRD, FT-IR, TGA and ICP. After preparation, the applicability of this catalyst in the synthesis of triazole and tetrazole derivatives was studied. The prominent features of the present methodology are: high yields, short reaction times, easy preparation, magnetical separation and favorable recoverability of the catalyst (for at least five runs without significant loss of catalytic activity).

A modification of the k-kL-ω turbulence model for simulation of short and long separation bubbles

The prediction of separation bubbles is highly important due to the controlling effects that they have on the airfoils performance. In the present study, a two-dimensional numerical simulation of the incompressible transitional flow around the NACA 0012 and Eppler 387 airfoils is studied. In order to examine the capability of the turbulence models for predicting the separation bubbles, several modified versions of the three-equation k-kL-ω turbulence model presented in previous research studies and the original four-equation SST k-ω turbulence model are compared with the experimental and Direct Numerical Simulation (DNS) data. A new modification based on the previous modified versions of the k-kL-ω model is also proposed. The Reynolds number based on the airfoil chord length is between 3 × 104 and 1.3 × 105. Simulation of the flow-field is performed by the solution of the Reynolds-averaged Navier–Stokes equations using a pressure-velocity coupling algorithm so-called RK-SIMPLER. An explicit method of second-order accuracy in time and space is used to integrate the momentum conservation equations. The results from this study indicate that the new proposed modification presents the better prediction for the separation bubbles than the previous versions, especially in the long separation bubbles. An excellent result is also obtained for the lift coefficients.

Electrophoresis of megaDalton proteins inside colloidal silica.

With the growth of the biopharmaceutical industry, there is a need for rapid size-analysis of proteins on the megaDalton scale. The large pore sizes needed for such separations cannot be easily reached by pushing the current limits of size-exclusion chromatography or gel electrophoresis. The concept detailed here is the formation of arbitrarily wide pores by packing nonporous colloidal silica in capillaries. This method can be called packed-capillary electrophoresis, or "pCE". Electrophoresis of protein standards (11-155kDa) by pCE, using 345 nm diameter particles in 100 μm diameter capillaries, gives 2x higher resolution than a typical PAGE gel in 1/6 of the time. The electropherograms show that pCE is highly efficient, with half-micrometer plate heights for all seven standards, giving 105 plates for a 50 mm length. The large pore radius of 65 nm enables baseline resolution of proteins of 0.72, 1.048 and 1.236 MDa in less than 15 min. The short separation time of pCE is attributed to the absence of small pores that restrict protein migration in gels. The pCE separation is applied to the analysis of a stressed pharmaceutical-grade IgG4 sample, giving unprecedented baseline resolution of monomer, dimer, trimer and tetramer in less than 10 min.

Modeling the Impact of Rain and Clouds on Earth–Space Site Diversity Systems

A statistical model to predict the effects of both rain and clouds on the earth–space site diversity communication systems is presented. The methodology relies on the assumption, already widely considered in the literature, that both rain- and cloud-induced attenuations can be separately modeled, both in space and time, using log-normal distributions. The model is preliminarily tested against joint statistics of rain and cloud attenuations derived from the propagation data set collected in three Italian sites (Spino d’Adda and Milan, in the North, and Tito Scalo, in the South) during the ongoing Alphasat Aldo Paraboni propagation experiment. Although additional experimental data including attenuation induced by rain and clouds are required to further assess the accuracy of the proposed site diversity model, the obtained results, both for short (~20 km) and large (~760 km) site separation distances, are definitely encouraging and suggest that the proposed model is a step towards providing a more comprehensive and accurate prediction of tropospheric impairments for near future high-frequency earth–space systems implementing the site diversity.

Elevated CO2 causes large changes to morphology of perennial ryegrass (Lolium perenne)

Plant morphology and architecture are essential characteristics for all plants, but perhaps most importantly for agricultural species because economic traits are linked to simple features such as blade length and plant height. Key morphological traits likely respond to CO2 concentration ([CO2]), and the degree of this response could be influenced by water availability; however, this has received comparatively little research attention. This study aimed to determine the impacts of [CO2] on gross morphology of perennial ryegrass (Lolium perenne L.), the most widespread temperate pasture species, and whether these impacts are influenced by water availability. Perennial ryegrass cv. Base AR37 was grown in a well-fertilised FACE (free-air carbon dioxide enrichment) experiment in southern Tasmania. Plants were exposed to three CO2 concentrations (~400 (ambient), 475 and 550 µmol mol–1) at three watering-treatment levels (adequate, limited and excess). Shoot dry weight, height, total leaf area, leaf-blade separation, leaf size, relative water content and specific leaf area were determined, as well as shoot density per unit area as a measure of tillering. Plant morphology responded dramatically to elevated [CO2], plants being smaller with shorter leaf-blade separation lengths and smaller leaves than in ambient (control) plots. Elevated [CO2] increased tillering but did not substantially affect relative water content or specific leaf area. Water supply did not affect any measured trait or the response to elevated [CO2]. Observed impacts of elevated [CO2] on the morphology of a globally important forage crop could have profound implications for pasture productivity. The reductions in plant and leaf size were consistent across a range of soil-water availability, indicating that they are likely to be uniform. Elucidating the mechanisms driving these responses will be essential to improving predictability of these changes and may assist in breeding varieties suited to future conditions.

Rapid and Sensitive Determination of Branched-Chain Amino Acids in Human Plasma by Capillary Electrophoresis with Contactless Conductivity Detection for Physiological Studies.

Capillary electrophoresis (CE) with contactless conductivity detection (C4D) represents a strong tool for determining amino acids in clinical samples. This chapter provides detailed instructions for CE/C4D determination of the branched-chain amino acids (BCAAs) valine, isoleucine, and leucine in human plasma, which can be readily employed in physiological studies. Baseline separation of all the BCAAs is achieved on a short separation length equal to 18cm in optimized background electrolyte consisting of 3.2M acetic acid dissolved in 20% v/v methanol with addition of 1.0% v/v INST-coating solution. The analysis time does not exceed 3min and the limit of detection is 0.4μM for all BCAAs. The pretreatment of human plasma is very simple and is based on fourfold plasma dilution by acetonitrile and subsequent filtration. Only 50μL of plasma is used for the analysis. The high sensitivity of the CE/C4D method is achieved by injecting a large volume of sample, combined with application of negative pressure to flush the acetonitrile zone out of the capillary.

Optimization and characterization of magnetite-reduced graphene oxide nanocomposites for demulsification of crude oil in water emulsion.

Oily wastewater from the oil and gas industry negatively affects the environment. Oily wastewater typically exists in the form of an oil-in-water emulsion. Conventional methods to treat oily wastewater have low separation efficiency and long separation time and use large equipment. Therefore, a simple but effective method must be developed to separate oil-in-water emulsions with high separation efficiency and short separation times. Magnetite–reduced graphene oxide (M–RGO) nanocomposites were used as a demulsifier in this work. Magnetite nanoparticles (Fe3O4) were coated on reduced graphene oxide (rGO) nanosheets via an in situ chemical synthesis method. The synthesized M–RGO nanocomposites are environmentally friendly and can be recovered after demulsification by an external magnetic field. M–RGO characterization was performed using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning microscopy, Raman spectroscopy, and vibrating sample magnetometry. Demulsification performance was evaluated in terms of M–RGO dosage, effects of pH, and brine concentration. The demulsification capability of M–RGO was determined based on the residual oil content of the emulsion, which was measured with a UV-vis spectrometer. The response surface method was used to determine the optimum conditions of the input variables. The optimum demulsification efficiency achieved at pH 4 and M–RGO dosage of 29 g L−1 was approximately 96%. This finding demonstrates that M–RGO nanocomposites are potential magnetic demulsifiers for oily wastewater that contains oil-in-water emulsions. Also, the recyclability of this nanocomposite has been tested and the results shown that it is a good recyclable demulsifier.

Effect of wall-mounted V-baffle position in a turbulent flow through a channel

PurposeThe purpose of this paper is to carry out a numerical study on the dynamic and thermal behavior of a fluid with a constant property and flowing turbulently through a two-dimensional horizontal rectangular channel. The upper surface was put in a constant temperature condition, while the lower one was thermally insulated. Two transverse, solid-type obstacles, having different shapes, i.e. flat rectangular and V-shaped, were inserted into the channel and fixed to the top and bottom walls of the channel, in a periodically staggered manner to force vortices to improve the mixing, and consequently the heat transfer. The flat rectangular obstacle was put in the first position and was placed on the hot top wall of the channel. However, the second V-shaped obstacle was placed on the insulated bottom wall, at an attack angle of 45°; its position was varied to find the optimum configuration for optimal heat transfer.Design/methodology/approachThe fluid is considered Newtonian, incompressible with constant properties. The Reynolds averaged Navier–Stokes equations, along with the standard k-epsilon turbulence model and the energy equation, are used to control the channel flow model. The finite volume method is used to integrate all the equations in two-dimensions; the commercial CFD software FLUENT along with the SIMPLE-algorithm is used for pressure-velocity coupling. Various values of the Reynolds number and obstacle spacing were selected to perform the numerical runs, using air as the working medium.FindingsThe channel containing the flat fin and the 45° V-shaped baffle with a large Reynolds number gave higher heat transfer and friction loss than the one with a smaller Reynolds number. Also, short separation distances between obstacles provided higher values of the ratios Nu/Nu0 and f/f0 and a larger thermal enhancement factor (TEF) than do larger distances.Originality/valueThis is an original work, as it uses a novel method for the improvement of heat transfer in completely new flow geometry.

Improvement in Recovery of Hemodynamic Responses by Extended Kalman Filter With Non-Linear State-Space Model and Short Separation Measurement.

The purpose of this study is to describe the noise reduction in the hemodynamic responses, obtained by functional near-infrared spectroscopy (fNIRS), using the proposed extended Kalman filter (EKF) with a non-linear state-space model, aided by the short separation (SS) measurement. The authors used the simulated data by adding the synthetic hemodynamic response function (HRF) to the multi-distance four-channel fNIRS signals obtained during the resting state. EKF was used to estimate the non-linear state-space model designed based on the Balloon model. The SS channel was used as a regressor that is sensitive only to superficial noises. The whole segments were grouped by the existence of motion artifacts (MAs) to investigate the improvement by EKF compared to the linear Kalman filter (LKF) and adaptive filter (AF) in extracting neural-evoked hemodynamic. Kalman-based approaches were better than AF in reducing noises. Using EKF, the averages of the decreased errors and increased correlation between the recovered and true HRF were 34% in oxy-hemoglobin and 62% in deoxy-hemoglobin concentrations in segments having MAs, compared with LKF. In the MA-free condition, EKF is more robust to the poor quality of signals in noise reduction than LKF. The proposed non-linear Kalman approach is better in noise reduction than AF and LKF especially in noisy deoxy-hemoglobin concentrations, and less affected by the conditions of measurements and contaminations by MAs. The proposed method can be used for reducing superficial noises and MAs from fNIRS signals as an upgraded alternative to existing AFs.