Frequency-dependent equivalent linear (FD-EQL) site response analysis methods, developed as potential substitutes for the EQL procedure to better simulate the nonlinear soil response, have been ...reported to overpredict the high-frequency wave propagation. Modified procedures proposed to overcome this limitation have demonstrated to improve the fits with the nonlinear analysis results. The method has not yet been applied to perform a deconvolution analysis, where a conventional EQL analysis often fails to converge or provide reliable estimate. The conventional EQL procedure and one of the modified FD-EQL method, which uses an empirical factor f to interpolate the strain spectrum between the EQL and FD-EQL outputs, are used to perform a series of deconvolution analyses using an idealized 1000 m profile and twelve Kik-net downhole arrays. The residuals of recorded and deconvoluted motions are shown to increase with strain for the EQL method even when using the recommended frequency cut-off. For the FD-EQL method, the range of f recommended for convolution analyses is shown to provide unrealistic responses in performing deconvolution analyses. A new range that produces unbiased residuals for all strain amplitudes is proposed. Comparisons highlight that the modified FD-EQL yields reliable predictions of the within motion for all profiles and motion intensities, automatically suppressing the amplification of high-frequency noise typically accompanied in a deconvolution analysis.
► A MAE plus dispersive-micro SPE was developed to extract N-nitrosamines from meat products. ► Parameters affecting the efficiency of MAE plus D-μ-SPE were optimised. ► The limits of quantitation ...ranged from 0.03 to 0.36ng/g in 5-g meat products. ► MAE plus D-μ-SPE is a rapid alternative method to extract N-nitrosamines in meat products. ► The developed method is a sensitive, low cost, effective, and eco-friendly extract method.
A sensitive procedure, microwave-assisted extraction (MAE) coupled dispersive micro solid-phase extraction (D-μ-SPE), was developed to extract N-nitrosodimethylamine (NDMA) and other six volatile N-nitrosamines (NAms) from meat products. Parameters affecting the efficiency of MAE and D-μ-SPE were systematically investigated. For MAE, 5-g of a homogenised meat sample was extracted with 30mL of a sodium hydroxide (0.025M) solution at 100°C for 10min. The optimum D-μ-SPE conditions were immersing 100mg of Carboxen™ 1000 adsorbent in the MAE extract. After vigorously shaking for 30min, the NAms were then desorbed by treatment with 200μL of dichloromethane. A 10μL aliquot was determined by gas chromatography with chemical ionisation mass spectrometry (GC–CI-MS) using the selected-ion-storage (SIS) mode. The limits of quantitation (LOQs) were 0.03–0.36ng/g. Preliminary results revealed that NDMA was present in the highest concentration, ranging from 0.8 to 3.2ng/g.
Single cell analysis methods are increasingly being utilized to investigate how individual cells process information and respond to diverse stimuli. Soluble proteins play a critical role in ...controlling cell populations and tissues, but directly monitoring secretion is technically challenging. Microfabricated well arrays have been developed to assess secretion at the single cell level, but these systems are limited by low detection sensitivity. Semiconductor quantum dots (QD) exhibit remarkably bright and photostable luminescence signal, but to date they have not been evaluated in single cell secretion studies using microfabricated well arrays. Here, we used QDs in a sandwich immunoassay to detect secretion of the soluble cytokine tumor necrosis factor-α (TNF-α) from single cells. To enhance detection sensitivity, we employed two different strategies. First, we used a unique single QD imaging approach, which provided a detection threshold (180 attomolar) that was >100-fold lower than previously reported results using QDs. We also amplified QD binding to each captured TNF-α molecule using the bioorthogonal cycloaddition reaction between trans-cyclooctene and tetrazine, which further lowered detection threshold to 60 attomolar. This is 6 orders of magnitude more sensitive than organic fluorophores that have been used for single cell secretion studies, and far surpasses single molecule resolution within sub-picoliter microwells that are used to assess single cell secretion. Finally, single cell secretion studies were performed using phorbol 12-myristate 13-acetate (PMA) differentiated and lipopolysaccharide (LPS) activated U-937 cells. TNF-α secretion was detected from 3-fold more single cells using the QD-based method in comparison to rhodamine, which was accomplished by extending sensitivity into the range of ∼2 to 10 000 molecules captured per microwell. In future work, we will apply this technique to assess immune cell secretion dynamics under diverse stimuli and disease settings. We will also incorporate multiplexing capabilities to evaluate the secretome at the resolution of single molecules.
A simple sample pretreatment technique, dispersive micro-solid phase extraction, was applied for the extraction of
N
-nitrosodimethylamine (NDMA) and other four
N
-nitrosamines (NAs) from samples of ...swimming pool water. The parameters affecting the extraction efficiency were systematically investigated. The best extraction conditions involved immersing 75 mg of carbon molecular sieve, Carboxen™ 1003 (as an adsorbent), in a 50-mL water sample (pH 7.0) containing 5% sodium chloride in a sample tube. After 20 min of extraction by vigorous shaking, the adsorbent was collected on a filter and the NAs desorbed by treatment with 150 μL of dichloromethane. A 10-μL aliquot was then directly determined by large-volume injection gas chromatography with chemical ionization mass spectrometry using the selected ion storage mode. The limits of quantitation were <0.9 ng/L. The precision for these analytes, as indicated by relative standard deviations, were <8% for both intra- and inter-day analyses. Accuracy, expressed as the mean extraction recovery, was between 62% and 109%. A preliminary analysis of swimming pool water samples revealed that NDMA was present in the highest concentration, in the range from n.d. to 100 ng/L.
Our quest for ligands toward the synthesis of functional metal string complexes started from α‐pyridylamido anions. With the modulation of naphthyridylamido anions, the ligands carry less negative ...charge to be balanced and, thus, to some extent, can tune the oxidation state of the metal centers and the strength of metal–metal interactions. For example, the formation of Ni23+, a mixed‐valence moiety, has been demonstrated. In this paper, high‐bond‐order units of M2 (Mo2 or Ru2) and Ni23+ are introduced and supported by four equatorial ligands of the bisnaphthyridylamido anion (bna−). The resulting compounds are Ni2Mo2Ni(bna)4Cl2(PF6)3 (1), Ni2Mo2Ni(bna)4(NCS)2(PF6)3 (2), and Ni2Ru2Ni(bna)4Cl2(ClO4)3 (3). X‐ray crystallography reveal quadruply bonded characteristics with Mo–Mo distances of 2.133(2) and 2.109(2) Å for 1 and 2, respectively. The Ni2 moieties have a short Ni–Ni distance of 2.331(5) for 1 and 2.334(4) Å for 2, suggesting the formation of mixed‐valence Ni23+ units. It appears that there are no significant metal–metal interactions between Mo2 and its neighboring Ni centers. Characterization using magnetism, voltammetry, electronic absorption, and single‐molecule conductance, however, shows significant influence of Mo2 on the properties of the metal string complexes.
Metal–metal interactions in Ni5(tpda)4X2 (tpda2− = tripyridyldiamido dianion) are considered insignificant. With the ligand bna−, Mo24+, and mixed‐valent Ni23+ unit, a nominally high‐bond‐order complex was synthesized and characterized. Although no bond formation was seen between Mo24+ and the neighboring Ni centers, measurements showed the effects of the Mo4+ unit on the properties of Ni23+.
Based on the stress extraction and measurement by the atomic-force-microscope-Raman technique with nanometer-level space resolution, the high compressive stress about 700 MPa on the Si critical ...dimension (CD) is observed in the current complementary metal-oxide-semiconductor (CMOS) transistor. The difference of thermal expansion between Si and Shallow trench isolation (STI) oxide during the total thermal budget for the standard CMOS transistor manufacture process results in this high compressive stress in Si CD and will further degrade the electron carrier mobility about 25% seriously. In order to relax this intrinsic-processed compressive stress in Si CD and recover this device performance loss, the novel process is proposed in this paper in addition to the usage of one-side pad-SiN layer demonstrated in our previous work. With this novel process of additional nitrogen-ion implantation (IMP) treatment in STI oxide, it can be found that the less compressive stress in the Si CD can be achieved by the smaller difference of thermal expansion coefficients between Si and highly n-doped SiO 2 STI oxide. The formation of Si-N bonding in the STI-oxide region can be monitored by Fourier-transform infrared spectroscopy spectra, and the thermal expansion coefficients for Si, SiO 2 , and SiN are 2.6, 0.4, and 2.87 ppm/K, respectively. The relaxation of intrinsic-processed compressive stress in the Si CD of about 400 MPa by this proposed additional nitrogen IMP treatment contributes 14 % electron-carrier-mobility enhancement/recovery. The experimental electrical data agree well with the theoretical k.p calculation for the strained-Si theory.
The serious wafer bending and residual stress are formed during the growth of an epi-GaN layer on sapphire substrate due to the difference of thermal expansion coefficients (TECs) in these two ...different materials. By using the theoretical analysis and a simulation model with the finite-element method to describe the realistic shape for wafer bending of epi-GaN wafers, we examine the influence of different thicknesses and TECs in the top epi-GaN layer for wafer bending reduction. Furthermore, the wafer bending is also found to be worse when process temperature and wafer size become higher and larger, respectively. Although the commercial patterned sapphire substrate can partially solve this issue, the quality of the epi-GaN layer, grown on this patterned substrate, will be impacted. In this paper, the new process to reduce the wafer bending and relax residual stress is proposed. With an additional laser treatment on the sample surface after the growth of the top epi-GaN layer on sapphire substrate, drilling hole can provide extra space for relaxation of residual stress and will not influence the GaN quality. The wafer bending can be reduced to ~ 37 μm from the original ~ 45 μm in 2-in wafer with an optimized surface structure design by this treatment.
Serious wafer curvature and residual stress are formed during the growth of an epi-GaN layer on Sapphire substrates due to the different thermal expansion coefficients in these two materials. By ...using theoretical analysis and a simulation model using the finite element method to describe the realistic shape of wafer curvature on epi-GaN wafers, we examine the influence which different thickness and thermal expansion coefficients in the top epi-GaN layer have on wafer curvature reduction. In addition a new process to reduce wafer curvature and to relax residual stress is proposed. With an additional laser treatment on a sample surface after the growth of the top epi-GaN layer on a Sapphire substrate has taken place, the wafer curvature can be reduced to ~ 37 mm from the original ~ 45 mm in 2 inch wafers with an optimized surface structure design.
Single cell analysis methods are increasingly being utilized to investigate how individual cells process information and respond to diverse stimuli. Soluble proteins play a critical role in ...controlling cell populations and tissues, but directly monitoring secretion is technically challenging. Microfabricated well arrays have been developed to assess secretion at the single cell level, but these systems are limited by low detection sensitivity. Semiconductor quantum dots (QD) exhibit remarkably bright and photostable luminescence signal, but to date they have not been evaluated in single cell secretion studies using microfabricated well arrays. Here, we used QDs in a sandwich immunoassay to detect secretion of the soluble cytokine tumor necrosis factor-α (TNF-α) from single cells. To enhance detection sensitivity, we employed two different strategies. First, we used a unique single QD imaging approach, which provided a detection threshold (180 attomolar) that was >100-fold lower than previously reported results using QDs. We also amplified QD binding to each captured TNF-α molecule using the bioorthogonal cycloaddition reaction between
trans
-cyclooctene and tetrazine, which further lowered detection threshold to 60 attomolar. This is 6 orders of magnitude more sensitive than organic fluorophores that have been used for single cell secretion studies, and far surpasses single molecule resolution within sub-picoliter microwells that are used to assess single cell secretion. Finally, single cell secretion studies were performed using phorbol 12-myristate 13-acetate (PMA) differentiated and lipopolysaccharide (LPS) activated U-937 cells. TNF-α secretion was detected from 3-fold more single cells using the QD-based method in comparison to rhodamine, which was accomplished by extending sensitivity into the range of ∼2 to 10 000 molecules captured per microwell. In future work, we will apply this technique to assess immune cell secretion dynamics under diverse stimuli and disease settings. We will also incorporate multiplexing capabilities to evaluate the secretome at the resolution of single molecules.
Single cell secretion studies have provided valuable insight into population heterogeneity, but low detection sensitivity requires cells to secrete thousands of molecules. We employed semiconductor quantum dots and a new single particle imaging approach to improve detection sensitivity to only a few secreted molecules per cell.
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