Conventional measuring probes in the wall layer of turbulent subsonic ducted flows

This piece of work is concerned with the application of two conventional measuring probes, pressure probe and hot wire, in the wall layer of subsonic ducted, pipe and channel, flows for velocity measurements. Careful measurements have been carried out and analysed accordingly for Reynolds number range of 2.8×10⁵≤Rem≤4.5×10⁵ and 4×10⁴≤Rem≤2.3×10⁵ for the pipe and the channel, respectively. Pressure probes of outer diameters (d ₀ ⁺ = d ₀·u_τ/v) 20-120 wall units and hot wire, having wire length (l+= l u_τ/v) of 50-250 for the current Reynolds range, have been utilized to carry out the present measurements. When the pressure probe was applied in the wall layer, the wall proximity and the shear gradient played major roles of its incorrect velocity readings, however, this effect was far from being influencing the hot-wire velocity measured in the overlap region. When the pressure probe results compared to those obtained by the hot wire, the pressure probe's data showed hump in the normalized mean velocity profiles around the wall distances y⁺≤300 and y⁺≤150 for the pipe and the channel, respectively. Available corrections are adopted and applied to the pressure probe data measured, yielding results that are comparable to those of the hot wire and this was also demonstrated by comparing the present results corrected to the so-called the logarithmic velocity profile.     

FABRICATION AND APPLICATION OF NEAR-FIELD OPTICAL FIBRE PROBE

In this paper, the fabrication of a large cone angle near-field optical fibre probe, using the two-step chemical etching method and bent probe, is introduced, and the controlling parameters of the coated Cr－Al film at the probe tip are presented. The scanning electron microscopy images display that the tip diameter of the uncoated large cone angle fibre probe obtained is less than 50nm, the cone angle over 90°, and the diameter of light aperture at the coated probe tip is less than 100nm. The measured results of the optical transmission efficiency for various probe tips show that the uncoated straight optical fibre probe, film-coated straight probe and film-coated bent probe are 3×10^-1, 2×10^-3, and 1×10^-4 times that of the flat fibre probe, respectively. In addition, the force images and near-field optical images of a standard sample are acquired using a large cone angle and film-coated bent probe.     

X-ray diffraction studies of silicon implanted with high-energy erbium ions

Silicon crystals after implantation of erbium ions with energies in the range 0.8–2.0 MeV and doses in the range 1×10¹²–1×10¹⁴ cm⁻² have been studied by two-and three-crystal x-ray diffraction. Three types of two-crystal reflection curves are observed. They correspond to different structural states of the implanted layers. At moderate doses (1×10¹²–1×10¹³ cm⁻²) a positive strain is observed, due to the formation of secondary radiation defects of interstitial type. An increase of the implantation dose is accompanied by the formation of an amorphous layer separating the bulk layer and a thin monocrystalline surface layer. At an implantation dose of 1×10¹⁴ cm⁻² the monocrystalline surface layer is completely amorphized. Parameters of the implantation layers are determined. A model of the transformation of structural damage is discussed. Fiz. Tverd. Tela (St. Petersburg) 39, 853–857 (May 1997)     

Author index volumes 111–120

Adsorption of monolayer amounts of bismuth on the 100 surface plane of tungsten has been studied by probe hole field emission microscopy and electron spectroscopy. Sub-monolayer bismuth forms a relatively strongly bound layer of bismuth-tungsten dipoles with dipole moment μ = (0.18 ± 0.02) × 10^?30C m and polarizability α = (6.3 ± 1.3) × 10^?40J V^?2m². Changes in work function and their dependence on temperature closely parallel those produced by adsorbed lead which was shown by LEED to form c(2 × 2), p(2 × 2) and (1 × 1) structures. Bismuth is thought to behave in a similar way, but, unlike lead, forms a second monolayer which replicates the first. Electron spectroscopy shows that sub-monolayer bismuth removes the surface state (Swanson) peak and at monolayer coverage a new peak emerges and shifts with increasing coverage. Using Gadzuk's theory, this peak is tentatively attributed to the ²P level in bismuth adatoms which form a p(2 × 2) structure in the first and second monolayers. Its shift with coverage is ascribed to an increase in the local surface field. There remains the difficulty of reconciling the proposed occupation of the ²P level with the observed small positive charge on the bismuth adatom.     

A Novel Method for the Assessment of Cortisol Hormone in Different Body Fluids Using A New Photo Probe Thiazole Derivative

A low cost and accurate method for the detection and analytical determination of the cortisol in pharmaceutical preparation, blood serum and urine was developed. The method was based upon the enhancement of fluorescence intensity of the band at 424 nm of the photo probe by different cortisol concentrations in acetonitrile at (pH 5.7, λ_ex?=?320 nm). The influence of the different parameters, e.g. pH, solvent, cortisol concentration and foreign ions concentrations that control the enhancement process of fluorescence intensity of the band of photo probe was critically investigated. The remarkable enhancement of the fluorescence intensity at 424 nm in acetonitrile by various concentrations of cortisol was successfully used as a photo- probe for the assessment of cortisol concentration. The calibration plot was achieved over the concentration range 8.0?×?10^?6–5.5?×?10^?9 mol L^?1 cortisol with a correlation coefficient of 0.998 and a detection limit of 4.7?×?10^?9 mol L^?1. The developed method is simple and proceeds without practical artifacts compared to the other determination methods.     

Anchoring energy and orientational elasticity of a ferroelectric liquid crystal

The dielectric susceptibility of a helix-free ferroelectric liquid crystal layer has been experimentally and theoretically studied as a function of the layer thickness. The investigation has been performed on the inner branch of the polarization hysteresis loop, in the region of a linear dependence of the polarization on the electric field. The experimental results are explained using the notion of effective layer thickness, which involves the characteristic distance ?? over which the orienting effect of interfaces is operative. Comparison of the experimental data and theoretical results made it possible to estimate this distance as ?? = 41 ??m and evaluate the anchoring energy (W = 2.8 × 10^?3?1.1 × 10^?2 J/m²) and the intralayer elastic constant (K?? ?? 1 × 10^?8?3 × 10^?7 N).     

Multiple weak interaction‐assisted SERS detection platform for triadimefon

In this paper, a surface enhanced Raman spectra (SERS) detection platform for the widely used pesticide of triadimefon (TDF) is described. TDF is difficult to connect to the gold/silver SERS substrate, but the optical properties of the probe molecule 4‐mercaptobenzoic acid (4‐MBA), including the peak intensity and the peak position, are easily altered by the multiple weak interaction‐assisted SERS detection platform. The limit of detection (LOD) of this method is 1.0 × 10^‐9 M, and the linear range is from 1.0 × 10^‐6 M to 1.0 × 10^‐9 M. The linear region is from 1.0 × 10^‐6 M to 1.0 × 10^‐9 M, described by the equation y = 884.01x + 2.24 with a correlation coefficient (R²) of 0.9990. Interference of foreign metal ions with higher concentrations than common mineral water is too weak to the determination. Furthermore, physical insights into the phenomena and the detection mechanism were obtained and investigated theoretically. The preferential conformation of the complex and reduced density gradient (RDG) calculation results indicated that the interactions between TDF and 4‐MBA consisted of multiple weak interactions through two hydrogen bonds and one van der Waals interaction. The intermolecular interaction was negative for the charge transfer from the SERS substrate to the probe molecule; thus, the peak intensity decreased. TDF interacts directly with the carboxyl of the probe molecule and consequently has an effect on the ring vibrations. Copyright © 2014 John Wiley & Sons, Ltd.     

Formation of ordered helium pores in amorphous silicon subjected to low-energy helium ion irradiation

Thin transparent (for transmission electron microscopy, TEM) self-supported Si(001) films are irradiated on the (110) end face by low-energy (E=17 keV) He⁺ ions at doses ranging from 5×10¹⁶ to 4.5×10¹⁷ cm⁻² at room temperature. The TEM study of the irradiated Si films along the ion range shows that an a-Si layer forms in the most heavily damaged region and helium pores (bubbles) with a density of up to 3×10¹⁷ cm⁻³ and 2–5 nm in diameter nucleate and grow across the entire width of this layer. The growth of nanopores in the a-Si layer is accompanied by their linear ordering into chains oriented along the ion tracks. The absence of pores in the region that remains crystalline and has the maximal concentration of implanted helium is explained by the desorption of helium atoms from the thin film during the irradiation. After annealing at 600°C, the volume of immobile pores in the remaining a-Si layer increases owing to the capture of helium atoms from the amorphous matrix. Solid solution is shown to be the prevalent state of the helium implanted into the amorphous silicon. Linear features with a diameter close to 1 nm and density of about 10⁷ cm⁻¹ discovered in the helium-doped a-Si layer are identified as low-energy He⁺ ion tracks.     

Fourier Transform Mid-Infrared Photoacoustic Spectroscopy for Presymptomatic Detection of Powdery Mildew Infection in Rubus corchorifolius L.

A powdery mildew fungi-induced disease appearing on leaves of Rubus corchorifolius L. has been observed in China, which resulted in seriously influencing the yield and quality of the fruit, and a presymptomatic detection of powdery mildew infection is needed to guarantee the yield and quality through removing the fungi in an early stage. Depth-profiling Fourier transform mid-infrared photoacoustic spectroscopy was applied to characterize both the healthy leaves and powdery mildew-infected leaves of Rubus corchorifolius L. The profiled surface could be divided into out layer (depth of about 1.32 µm) and deep layer (depth of about 1.87 µm). There were numerous differences in the total spectral range (500–4000 cm^?1) between healthy leaves and infected leaves, especially the intensity of absorption bands of 2800–3000 cm^?1 (aliphatic C–H vibration) and 2250–2350 cm^?1 (CO₂) significantly decreased when the leaf was infected by powdery mildew. For the out layer the standard spectral variance between healthy leaf and infected leaf was 7.33 × 10², whereas it was 1.86 × 10⁴ for the deep layer; the standard spectral variance between out layer and deep layer for healthy leaf was 3.38 × 10³, whereas it was 1.84 × 10⁴ for infected leaf, which implied that both out layer and deep layer responded to powdery mildew infection. Combining spectral differences between healthy leaf and infected leaf and variances between out layer and deep layer, a presymptomatic detection of powdery mildew infection was successfully made, which provided an alternative option and noninvasive method for the fast diagnosis of powdery mildew infection on Rubus corchorifolius L.     

Spatial distribution of defects produced by boron ion implantation of silicon

A simple technique for the study of the spatial distribution of the damage produced by ion implantation of silicon has been developed. The damage depth distribution for 40 keV boron ions in silicon has been studied at irradiation doses from 7 × 10¹¹ to 3.9 × 10¹⁴ ions/cm² and the relative defect peak depth R _d/R _p = 0.85 determined. An increase of layer conductivity as the surface part of the implanted layer is removed has been revealed. This effect is caused by the presence of radiation defects in the surface region of the layer. The “electrical” cluster diameter is about 28 A and the overlapping cluster dose is close to 1 × 10¹³ ions/cm².     

Synthesis and Analytical Application of a Novel Fluorescent Hg2+ Probe 3′, 6′-Bis(Diethylamino)-2-((2,4-Dimethoxybenzylidene)Amino)Spiro[Isoindoline-1,9′-Xanthene]-3-Thione

A novel probe, 3′,6′ - bis(diethylamino) -2- ((2,4-dimethoxybenzylidene)amino) spiro [isoindoline-1,9′-xanthene]-3-thione (RBS), was designed and synthesized. Its structure was characterized with elemental analysis, IR spectra and ¹H NMR. The probe displayed highly selective and sensitive recognition of Hg²⁺. Reacting with mercury ions in aqueous solution, its fluorescence intensity was enhanced significantly, while its color was changed from colorless to pink. So, a new fluorescence method of detection of Hg²⁺ was proposed. Its dynamic response concentration range and detection limit for Hg²⁺ were 5.00?×?10^?9 M to 1.00?×?10^?6 M detected and 1.83?×?10^?9 M, respectively. Satisfying results were obtained when the probe was applied to detect spiked Hg²⁺ in samples.     

Interaction of a New Fluorescent Probe with DNA and its Use in Determination of DNA

In this paper we reported a metal complex 1-Zn (2,5-di-[2-(3,5-bis(2-pyridylmethyl)amine-4-hydroxy-phenyl)-ethylene]-pyrazine-Zn) as a fluorescent probe sensing DNA. The result of the competitive experiment of the probe with ethidium bromide (EB) to bind DNA, absorption spectral change and polarization change in the presence and absence of DNA revealed that interaction between the probe and DNA was via intercalation. Ionic strength experiment showed the existence of electrostatic interaction as well. Scatchard plots also confirmed the combined binding modes. The fluorescence enhancement of the probe was ascribed to highly hydrophobic environment when it bound the macromolecules such as DNA, RNA or denatured DNA. The binding constant between the probe and DNA was estimated as 3.13 × 10⁷ mol⁻¹ L. The emission intensity increase was proportional to the concentration of DNA. Based on this, the probe was used to determine the concentration of calf thymus DNA (ct-DNA). The corresponding linear response ranged from 2.50 × 10⁻⁷ to 4.75 × 10⁻⁶ mol L⁻¹, and detection limit was 1.93 × 10⁻⁸ mol L⁻¹ for ct-DNA.     

Mixing of Au in Si induced by secondary and high-order recoil implantation

The mixing of Au in Si induced by secondary and high-order recoil implantation was investigated using 350 keV Ar⁺ and 350 keV Kr⁺ ions to fluences from 1?×?10¹⁶ to 3?×?10¹⁶ ions/cm² at room temperature. The thickness of the Au layer evaporated on Si substrate was ～2400 Å.The ranges of the Ar and Kr ions were chosen to be lower than the thickness of the Au layer in order to avoid the ballistic mixing produced by the primary knock-on atoms. Rutherford backscattering spectrometry (RBS) experiments were carried out to study the effects induced by Ar and Kr irradiation at the interface of Au–Si system. We observed that in the case of the irradiation with Ar⁺ ions, a broadening of the Au–Si interface occurred only at the fluence of 3?×?10¹⁶ Ar⁺/cm² and it is attributed to the surface roughening induced by ion bombardment. In contrast, the RBS analysis of a sample irradiated with 2?×?10¹⁶ Kr⁺/cm² clearly showed, in addition to the broadening effect, the formation of a mixed zone of Au and Si atoms at the interface. The mixing of Au in Si atoms can be explained by the secondary and high-order recoil implantation followed by subsequent collision cascades.     

A Carbazole-Fused-RhodamineProbe for Detection of HOCl in Living Cells

A novel fluorescent probe CR-ClO for detection of HOCl based on a carbazole fused rhodamine was designed and synthesized. The probe utilized a HOCl-promoted oxidation reaction, which lead to the ring opening of the compound with a strong enhancement of the fluorescent emission at about 587 nm.The new probe CR-ClO has excellent selectivity and high sensitivity to ClO^?,whose detection limit to ClO^? is 1.16 × 10^?6 M. Furthermore, the new probe has been successfully applied in living cells for detection of ClO^?.     

The Sensitive Determination of Nucleic Acids Using Fluorescence Enhancement of Eu<Superscript>3+</Superscript>-BenzoylacetoneCetyltrimethylammonium Bromide-Nucleic Acid System

A new quantitative method for micro amounts of nucleic acids in aqueous solution is proposed using Eu³⁺-benzoylacetone (BA) complex as fluorescent probe in the presence of cetyltrimethyl-ammonium bromide (CTMAB). Under the optimum condition, the ratio of the fluorescence intensities with and without nucleic acids is proportional to the concentration of nucleic acid in the range of 1.0 × 10⁻⁹ to 5.0 × 10⁻⁶ g/mL for herring sperm DNA (hsDNA), 3.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g/mL for calf thymus DNA(ctDNA) and 8.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g/mL for yeast RNA (yRNA), and their detection limits are 0.33, 0.21 and 0.99 ng/mL, respectively. Actual sample (DNA of Arabidopsis thaliana) was determined satisfactorily. In addition, the interaction mechanism is also investigated.     

Effects of the AlN nucleation layer thickness on the crystal structures of an AlN epilayer grown on the 6H-SiC substrate

The influence of the LT-AlN(NL) growth times on the mosaic structure parameters of the AlN layer grown on the LT-AlN(NL)/6H-SiC structures as well as the dislocation densities and the strain behaviours in the AlN epilayers has been investigated using XRD measurements. The growth times of the LT-AlN(NL) were changed to 0, 60, 120, 180, and 240?s. We observed that the mosaic structure parameters of the AlN epilayers were slightly affected by the LT-AlN(NL) growth times. However, the dislocation densities in the AlN layer are affected by the growth times of the LT-AlN(NL) layer. The highest edge dislocation density (5.48?×?10¹⁰?±?2.3?×?10⁹?cm^?2) was measured for the sample in which 120?s grown LT-AlN(NL) was used. On the other hand, highest screw type dislocation density (1.21?×?10¹⁰?±?1.7?×?10⁹?cm^?2) measured in the sample E that contains 240?s growth LT-AlN(NL). The strain calculation results show that the samples without LT-AlN(NL) suffered maximum compressive in-plane strain (?10.9?×?10^?3?±?1.8?×?10^?4), which can be suppressed by increasing the LT-AlN(NL) growth times. The out-of-plane strain also has a compressive character and its values increase with LT-AlN(NL) growth times between 60 and 180?s. Same out-of-plane strain values were measured for the LT-AlN(NL) growth times of 180 and 240?s. Furthermore, the form of the biaxial stress in the AlN epilayer changed from compressive to tensile when the LT-AlN(NL) growth times were greater than 120?s.     

Determination of the transport properties in 4H-SiC wafers by Raman scattering measurement

The free carrier density and mobility in n-type 4H-SiC substrates and epilayers were determined by accurately analysing the frequency shift and the full-shape of the longitudinal optic phonon--plasmon coupled (LOPC) modes, and compared with those determined by Hall-effect measurement and that provided by the vendors. The transport properties of thick and thin 4H-SiC epilayers grown in both vertical and horizontal reactors were also studied. The free carrier density ranges between 2×10¹⁸ cm^-3 and 8×10¹⁸ cm^-3 with a carrier mobility of 30--55 cm²/(V·s) for n-type 4H-SiC substrates and 1×10¹⁶--3×10¹⁶ cm^-3 with mobility of 290--490 cm²/(V·s) for both thick and thin 4H-SiC epilayers grown in a horizontal reactor, while thick 4H-SiC epilayers grown in vertical reactor have a slightly higher carrier concentration of around 8.1×10¹⁶ cm^-3 with mobility of 380 cm²/(V·s). It was shown that Raman spectroscopy is a potential technique for determining the transport properties of 4H-SiC wafers with the advantage of being able to probe very small volumes and also being non-destructive. This is especially useful for future mass production of 4H-SiC epi-wafers.     

Synthesis and Evaluation of a Schiff-Based Fluorescent Chemosensors for the Selective and Sensitive Detection of Cu<Superscript>2+</Superscript> in Aqueous Media with Fluorescence Off-On Responses

Copper being an essential nutrient; also pose a risk for human health in excessive amount. A simple and convenient method for the detection of trace amount of copper was employed using an optical probe R1 based on Schiff base. The probe was synthesized by Schiff base condensation of benzyl amine and 2-hydroxy-1-napthaldehyde and characterized by single X-ray diffraction, ¹H NMR and FTIR. By screening its fluorescence response in a mixture of DMSO and H₂O (20:80, v/v) R1 displayed a pronounced enhancement in fluorescence only upon treatment with copper. Other examined metal ions such as alkali, alkaline and transition had no influence. Within a wide pH range 5–12 R1 could selectively detect copper by interrupting ICT mechanism that results in CHEF. From Job’s plot analysis a 2:1 binding stoichiometry was revealed. The fluorescence response was linear in the range 1–10?×?10^?9 M with detection limit 30?×?10^?9 M. Association constant was determined as 1?×?10¹¹ M^?2 by Benesi-Hilderbrand plot. As a fast responsive probe it possesses good reproducibility and was employed for detection of copper in different water samples.     

MW-ECR PE-UMS等离子体特性及对Zr-N薄膜结构性能的影响

采用静电探针技术对微波电子回旋共振(MW-ECR) 等离子体进行了诊断,利用等离子体增强 非平衡磁控溅射(PE-UMS)法在常温下制备了Zr-N薄膜, 通过EPMA，XRD，显微硬度对膜的 结构和性能进行评价.实验结果表明，随氮气流量增加，总的等离子体密度从807×10⁹c m^-3增加到831×10⁹cm^-3然后逐渐减小为752×10 ⁹cm^-3；而N₂⁺密度则从312×10^{8< /sup>cm-3线性递增到335×109cm-3；电子温度变化 不大.对薄膜而言，随N₂+密度增大，样品中氮含量增加，而晶粒逐 渐变小，当样品中N/ Zr原子比达到14时，薄膜中出现亚稳态的Zr₃N₄相以及非晶相， 在更高氮流量下，整 个薄膜转变为非晶态.与此相应，薄膜硬度由最初的225GPa增大到2678GPa 然后逐渐减 小到1982GPa. 关键词： 氮化锆薄膜 ECR等离子体 磁控溅射 诊断}     

Influence of contact shape on AlGaN/GaN Schottky diode prepared on Si with thick buffer layer

A report on the fabrication and characterization of high performance conventional and ring-shaped AlGaN/GaN Schottky barrier diode on Si is presented. The resulting device exhibited low leakage current, which led to a detectivity performance of 3.48×10¹³ and 1.76×10¹³ cm?Hz^1/2 W^?1, respectively, for both conventional and ring-shaped Schottky diode. The differential resistances of both devices were obtained at approximately 1.37×10¹² and 1.41×10¹³ Ω, respectively. The zero bias peak responsivities of conventional and ring-shaped Schottky diodes were estimated to be 3.18 and 2.08 A?cm^?2/W, respectively. The typical UV to visible rejection ratio was observed over three orders of magnitude at zero bias. The C–V measurements was used to calculate and analyze the polarization sheet charge density of the AlGaN barrier layer by using self-consistently solving Schrodinger’s and Poisson’s equations. It is demonstrated that the ring shape of the Schottky barrier has higher polarization sheet charge density, which has the consequence that the Schottky shape has influence on the strain of the AlGaN barrier layer.