Absorption and Transmission Power Coefficients for Millimeter Waves in a Weakly Ionised Vegetation Fire

A vegetation fire plume is a weakly ionised gaseous medium. Electrons in the plume are mainly due to thermal ionisation of incumbent alkali impurities. The medium is highly collisional with free electron - neutral particle been the dominant particle interaction mechanism. Signal strength of an incident millimetre wave (MM-Wave) may be significantly attenuated in the plume depending on the extent of ionisation. A numerical experiment was set to investigate signal power loss of a MM-Wave incident on a simulated weakly ionised fire plume with flame maximum (seat) temperature ranging from 1000–1150 K. The simulated fire plume had alkali impurities (potassium) content of 1.0% per unit volume. MM-Wave frequency range investigated in the experiment is from 30–60 GHz. The simulation has application in the prediction of MM-Wave propagation in a crown forest fire and may also be applied in remote sensing studies of forest fire environments. Simulated attenuation per unit path length for the MM-Wave frequencies ranged from 0.06–24.00 dBm⁻¹. Phase change per unit path length was simulated to range from 2.97–306.17°m⁻¹ while transmission power coefficients ranged from maximum of 0.9996 for a fire plume at 1000 K to a minimum value of 0.8265 for a plume at a temperature of 1150 K over a plume depth of 1.20 m. Absorption power coefficient ranged from a minimum value of 0.0004 to maximum value of 0.1585 at a seat temperature of 1150 K over the plume depth.     

Spectrofluorimetric Assessment of Chlorzoxazone and Ibuprofen in Pharmaceutical Formulations by using Eu-Tetracycline HCl Optical Sensor Doped in Sol–Gel Matrix

A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol–gel matrix. The chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol–gel matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λ_ex = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10⁻⁹–1 × 10⁻⁴ and 1 × 10⁻⁸–7 × 10⁻⁵ mol L⁻¹, and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10⁻¹⁰ , 9.6 × 10⁻¹⁰ and 5.6 × 10⁻¹⁰, 1.7 × 10⁻⁹ mol L⁻¹, respectively.     

Fluorescence Enhancement of the Silver Nanoparticales – Curcumin - Cetyltrimethylammonium Bromide-nucleic Acids System and its Analytical Application

It is found that silver nanoparticles (AgNPs) can further enhance the fluorescence intensity of curcumin (CU) - cetyltrimethylammonium bromide (CTAB) – nucleic acids and improve its anti-photobleaching activity. Under optimum conditions, the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 2.0 × 10⁻⁸–1.0 × 10⁻⁶ g mL⁻¹ for fish sperm DNA (fsDNA), 2.0 × 10⁻⁸–1.0 × 10⁻⁶ g mL⁻¹ for calf thymus DNA (ctDNA), 1.0 × 10⁻⁸–1.0 × 10⁻⁶ g mL⁻¹ for yeast RNA (yRNA), and their detection limits (S/N = 3) are 8.0 ng mL⁻¹, 10.5 ng mL⁻¹ and 5.8 ng mL⁻¹, respectively. This method is used for determining the concentration of DNA in actual sample with satisfactory results. The interaction mechanism is also studied.     

Fluorescence Enhancement Effect for the Determination of Polychlorinated Biphenyls with Bovine Serum Albumin

A sensitive and selective method for the trace determination of 3, 3’, 4, 4’-tetrachlorobiphenyl (PCB77) by using bovine serum albumin (BSA) as a fluorescence probe was introduced. Under optimum conditions, the enhanced fluorescence intensity was proportional to the concentration of polychlorinated biphenyls in the range of 8.9 × 10⁻⁸–5.0 × 10⁻⁶ mol L⁻¹ for PCB77, and 5.0 × 10⁻⁷–5.0 × 10⁻⁶ mol L⁻¹ for 2, 2’, 5, 5’-tetrachlorbiphenyl (PCB52). The detection limits (S/N = 3) of PCB77 and PCB52 were 2.6 × 10⁻⁸ mol L⁻¹ and 2.9 × 10⁻⁷ mol L⁻¹, respectively. Furthermore, the fluorescence enhancement mechanism was discussed in detail. Results indicated that fluorescence enhancement of the system originated from the formation of BSA-PCBs complexes. In addition, PCBs were mainly bound to the tyrosine residues in BSA molecules.     

Spectrofluorimetric Assessment of Doxycycline Hydrochloride in Pharmaceutical Tablets and Serum Sample Based on the Enhancement of the Luminescence Intensity of the Optical Sensor Sm<Superscript>3+</Superscript> Ion

A simple and sensitive spectrofluorimetric method for determination of trace amount of doxycycline hydrochloride (DC) in pharmaceutical tablets and serum samples was developed. In ammonia buffer solution of pH 8.9 the doxycycline hydrochloride can remarkably enhance the luminescence intensity of the Sm³⁺ ion in Sm³⁺- DC complex at λ_ex = 400 nm. The produced luminescence intensity of Sm³⁺- DC complex in DMSO is in proportion to the concentration of DC and used as optical sensor for its determination. The dynamic range for the determination of DC is 1 × 10⁻⁸ – 5 × 10⁻⁶ mol L⁻¹ and in case of quantum yield calculations is 7 × 10⁻⁹ – 5 × 10⁻⁶ mol L⁻¹ with detection limit of 6.5 × 10⁻¹⁰ mol L⁻¹. The enhancement mechanism of the luminescence intensity in the Sm³⁺- DC system has been also discussed. A comparison with other spectrofluorimetric methods for tetracycline derivatives in which Eu³⁺ ion is used instead of Sm³⁺ ion is also studied.     

Preparation and Characterization of CdHgTe Nanoparticles and Their Application on the Determination of Proteins

CdHgTe nanoparticles (NPs) with the emission in the near-infrared regions were prepared in aqueous solution, and were characterized by transmission electron microscopy, X-ray diffraction spectrometry, spectrofluorometry and ultraviolet-visible spectrometry. Based on the fluorescence quenching of CdHgTe NPs in the presence of proteins, a novel method for the determination of proteins with CdHgTe NPs as a near-infrared fluorescence probe was developed. Maximum fluorescence quenching was observed with the excitation and emission wavelengths of 500 and 693 nm, respectively. Under the optimal conditions, the calibration graphs were linear in the range of 0.04 × 10⁻⁶–5.6 × 10⁻⁶ g ml⁻¹ for lysozyme (Lyz) and 0.06 × 10⁻⁶–6.1 × 10⁻⁶ g ml⁻¹ for bovine hemoglobin (BHb), respectively. The limits of detection were 13 ng ml⁻¹ for Lyz and 27 ng ml⁻¹ for BHb, respectively. Four synthetic samples were determined and the results were satisfied.     

Visualization of focusing–refocusing cycles during filamentation in BaF<Subscript>2</Subscript>

Filamentation occurs within a 1.5 cm-long crystal of BaF₂ during the propagation of intense, ultrashort (40 fs) pulses of 800 nm light; a systematic study as a function of incident power enables us to extract quantitative information on laser intensity within the condensed medium, the electron density and the six-photon absorption cross section. At low incident power, a single filament is formed within the crystal; two or more filaments are observed along the direction transverse to laser propagation at higher incident powers. Further, due to fluorescence from six-photon absorption (6PA), we are able to map the intensity variation in the focusing–refocusing cycles along the direction of laser propagation. At still higher incident powers, we observe splitting of multiple filaments. By measuring the radius (L _min) of single filament inside BaF₂, we obtain estimates of peak intensities (I _max) and electron densities (ρ _max) to be 3.26×10¹³ W cm⁻² and 2.81×10¹⁹ cm⁻³, respectively. Use of these values enables us to deduce that the 6PA cross-section in BaF₂ is 0.33×10⁻⁷⁰ cm¹² W⁻⁶ s⁻¹.     

Study of Enhanced Chemiluminescence of Diperiodatocuprate (III) on 1,10-Phenanthroline/Hydrogen Peroxide/Cetyltrimethylammonium Bromide System

In the paper, a chemiluminescence (CL) system was developed based on the catalytical effect of diperiodatocuprate (III) (DPC) on the 1,10-phenanthroline (phen)/hydrogen peroxide (H₂O₂) in the presence of cetyltrimethylammonium bromide (CTAB). The effects of experimental conditions were investigated. Meanwhile the increase of CL intensity of the DPC/phen/H₂O₂/CTAB system is proportional to the concentration of phen in the range of low concentration. The linear range of the calibration curve is 5.0 × 10⁻⁹–1.0 × 10⁻⁶ mol L⁻¹, and the corresponding detection limit is 1.9 × 10⁻⁹ mol L⁻¹. The effects of phenolic compounds (PCs) on the system were investigated. Hydroquinone was used as an example to investigate the application of the CL system to the determination of PCs. The quenched CL intensity is linearly related to the logarithm of concentration of hydroquinone. The linear range of the calibration curve is 2.5 × 10⁻⁹–1.0 × 10⁻⁵ g mL⁻¹, and the corresponding detection limit is 1.8 × 10⁻⁹ g mL⁻¹. This phen and hydroquinone can be synchronously determined. The method was applied to the determination of hydroquinone in water samples and the recoveries were from 92% to 106%.     

Structural and optical characterization of DC magnetron sputtered molybdenum oxide films

Thin films of molybdenum trioxide were deposited on glass substrates employing direct current (DC) magnetron sputtering by sputtering of molybdenum at different oxygen partial pressures in the range 8 × 10⁻⁵–1 × 10⁻³ mbar and at a substrate temperature of 473 K. The glow discharge characteristics of magnetron cathode target of molybdenum were studied. The influence of oxygen partial pressure on the structural and optical properties of molybdenum trioxide films was investigated. The films formed at an optimum oxygen partial pressure of 2 × 10⁻⁴ mbar were polycrystalline in nature with orthorhombic α- phase and an optical band gap of 3.16 eV. The refractive index of the films formed at an oxygen partial pressure of 2 × 10⁻⁴ mbar decreased from 2.08 to 1.89 with increase of wavelength from 450 to 1,000 nm, respectively. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Spectrofluorimetric Assessment of Hydrochlorothiazide Using Optical Sensor Nano-Composite Terbium Ion Doped in Sol-Gel Matrix

A new, simple, sensitive and selective spectrofluorimetric method for the determination of Hydrochlorothiazide was developed in acetonitrile at pH 6.2. The Hydrochlorothiazide can remarkably enhance the luminescence intensity of the Tb³⁺ ion doped in sol–gel matrix at λ_ex = 370 nm. The intensity of the emission band of Tb³⁺ ion doped in sol–gel matrix was increased due to the energy transfer from the triplet excited state of Hydrochlorothiazide to (⁵D₄) excited energy state of Tb³ ion. The enhancement of the emission band of Tb³⁺ ion doped in sol–gel matrix at (⁵D₄→⁷ F₅) 545 nm was directly proportion to the concentration of Hydrochlorothiazide with a dynamic ranges of 5.0 × 10⁻¹⁰—5.0 × 10⁻⁶ mol L⁻¹ and detection limit of 2.2 × 10⁻¹¹ mol L⁻¹.     

Three-dimensional simulation of laser–plasma-based electron acceleration

A sequential three-dimensional (3D) particle-in-cell simulation code PICPSI-3D with a user friendly graphical user interface (GUI) has been developed and used to study the interaction of plasma with ultrahigh intensity laser radiation. A case study of laser–plasma-based electron acceleration has been carried out to assess the performance of this code. Simulations have been performed for a Gaussian laser beam of peak intensity 5 × 10¹⁹ W/cm² propagating through an underdense plasma of uniform density 1 × 10¹⁹ cm^− 3, and for a Gaussian laser beam of peak intensity 1.5 × 10¹⁹ W/cm² propagating through an underdense plasma of uniform density 3.5 × 10¹⁹ cm^− 3. The electron energy spectrum has been evaluated at different time-steps during the propagation of the laser beam. When the plasma density is 1 × 10¹⁹ cm^− 3, simulations show that the electron energy spectrum forms a monoenergetic peak at ~14 MeV, with an energy spread of ±7 MeV. On the other hand, when the plasma density is 3.5 × 10¹⁹ cm^− 3, simulations show that the electron energy spectrum forms a monoenergetic peak at ~23 MeV, with an energy spread of ±7.5 MeV.     

Solid polymeric electrolyte of PVC–ENR–LiClO<Subscript>4</Subscript>

The ionic conductivity of PVC–ENR–LiClO₄ (PVC, polyvinyl chloride; ENR, epoxidized natural rubber) as a function of LiClO₄ concentration, ENR concentration, temperature, and radiation dose of electron beam cross-linking has been studied. The electrolyte samples were prepared by solution casting technique. Their ionic conductivities were measured using the impedance spectroscopy technique. It was observed that the relationship between the concentration of salt, as well as temperature, and conductivity were linear. The electrolyte conductivity increases with ENR concentration. This relationship was discussed using the number of charge carrier theory. The conductivity–temperature behaviour of the electrolyte is Arrhenian. The conductivity also varies with the radiation dose of the electron beam cross-linking. The highest room temperature conductivity of the electrolyte of 8.5 × 10⁻⁷ S/cm was obtained at 30% by weight of LiClO₄. The activation energy, E _a and pre-exponential factor, σ _o, are 1.4 × 10⁻² eV and 1.5 × 10⁻¹¹ S/cm, respectively.     

Proton-conducting hybrid membranes for medium temperature (>100 °C) fuel cells

Hybrid membranes doped with silicotungstic acid (STA) were prepared by sol–gel process with 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, phosphoric acid, and tetraethoxysilane as chemical precursors. The thermogravimetry and differential thermal analysis measurements confirmed that the hybrid membranes were thermally stable up to 350 °C. Relatively, a high proton conductivity of 2.85 × 10⁻² S/cm was obtained for 10 mol% STA-doped hybrid membrane at 120 °C under 90% RH. The hydrogen permeability was found to decrease in the temperature range 20–120 °C from 1.64 × 10⁻¹⁰ to 1.36 × 10⁻¹⁰ mol/cm.s.Pa.     

Europium-sensitized Chemiluminescence of System Tetracycline–H<Subscript>2</Subscript>O<Subscript>2</Subscript>–Fe(II)/(III) and Its Application to the Determination of Tetracycline

Chemiluminescence (CL) of the reaction system tetracycline–H₂O₂–Fe(II)/(III)–Eu(III) was used for the determination of tetracycline hydrochloride in water, pharmaceutical preparations, and honey. The CL spectrum registered for this system shows emission bands typical of Eu(III) ions, with a maximum at λ ∼ 600 nm, corresponding to the electronic transitions of ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂. A strong chemiluminescence intensity characteristic of europium(III) ions in the system tetracycline–H₂O₂–Fe(II)/(III)–Eu(III), as contrasted to the emission of the system tetracycline–H₂O₂–Fe(II)/(III) without Eu(III), proves that the Eu(III) ion plays the role of a chemiluminescence sensitizer, accompanying tetracycline oxidation in the Fenton system (H₂O₂–Fe(II)/(III)). A linear dependence was observed for the integrated CL light intensity on the tetracycline concentration in the range of 2 × 10⁻⁷ to 3 × 10⁻⁵ mol l⁻¹ with the detection limit of 5 × 10⁻⁸ mol l⁻¹ in aqueous solution.     

Cilostazol determination by the enhancement of the green emission of Tb3+ optical sensor

The efficiency of excited-state interaction between Tb³⁺ and the industrial product Cilostazol (CIL) has been studied in different solvents. High luminescence intensity peak at 545 nm of terbium complex in acetonitrile was obtained. The photophysical properties of the green emissive Tb³⁺ complex have been elucidated, the terbium was used as optical sensor for the assessment of CIL in the pharmaceutical tablets and body fluids at pH 3.1 and λ_ex = 320 nm with a concentration range 1.0 × 10⁻⁹–1.0 × 10⁻⁶ mol L⁻¹ of CIL, correlation coefficient of 0.998 and detection limit of 7.5 × 10⁻¹⁰ mol L⁻¹.     

Analysis of trace impurities in semiconductor gas via cavity-enhanced direct frequency comb spectroscopy

Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) has demonstrated powerful potential for trace-gas detection based on its unique combination of high bandwidth, rapid data acquisition, high sensitivity, and high resolution, which is unavailable with conventional systems. However, previous demonstrations have been limited to proof-of-principle experiments or studies of fundamental laboratory science. Here, we present the development of CE-DFCS towards an industrial application—measuring impurities in arsine, an important process gas used in III–V semiconductor compound manufacturing. A strongly absorbing background gas with an extremely complex, congested, and broadband spectrum renders trace detection exceptionally difficult, but the capabilities of CE-DFCS overcome this challenge and make it possible to identify and quantify multiple spectral lines associated with water impurities. Further, frequency combs allow easy access to new spectral regions via efficient nonlinear optical processes. Here, we demonstrate detection of multiple potential impurities across 1.75–1.95 μm (5710–5130 cm⁻¹), with a single-channel detection sensitivity (simultaneously over 2000 channels) of ∼4×10⁻⁸ cm⁻¹ Hz^−1/2 in nitrogen and, specifically, an absorption sensitivity of ∼4×10⁻⁷ cm⁻¹ Hz^−1/2 for trace water doped in arsine.     

Terbium Sensitized Luminescence for the Determination of Ketoprofen in Pharmaceutical Formulations

This paper explores an ultra-sensitive luminescence method for the determination of Ketoprofen (KP) in pharmaceutical formulations. The technique is indirect and exploits the luminescence enhancement of terbium (Tb³⁺) by complexation with KP (Tb³⁺–KP), which was monitored at respective excitation and emission wavelengths of λ _ex = 258 nm and λ _em = 549 nm. The effect of varying the Tb³⁺ concentration and using multiple solvents was examined to determine optimal experimental conditions. Maximum sensitization was accomplished in the presence of methanol where the most favourable condition for the formation of the complex was recorded at a level of 1.0 × 10⁻⁵ M of Tb³⁺. Under these optimum experimental conditions, linear calibration curve was obtained in the range of 2.8 × 10⁻⁷–3.1 × 10⁻⁶ M with a detection limit of 8.7 × 10⁻⁸ M. The technique was validated with ‘working’ reference standards and produced relative standard deviations < 2% indicating that the reproducibility was highly acceptable. The proposed method was successfully applied to assays of KP in pharmaceutical formulations with average recoveries of 92–98%. The results were found to be in good agreement with those obtained by HPLC. The method is highly suited for general applications of this nature.     

Electrical properties of a solid polymeric electrolyte of PVC–ZnO–LiClO4

The ZnO filler has been introduced into a solid polymeric electrolyte of polyvinyl chloride (PVC)–ZnO–LiClO₄, replacing costly organic filler for conductivity improvement. Ionic conductivity of PVC–ZnO–LiClO₄ as a function of ZnO concentration and temperature has been studied. The electrolyte samples were prepared by solution casting technique. The ionic conductivity was measured using impedance spectroscopy technique. It was observed that the conductivity of the electrolyte varies with ZnO concentration and temperature. The temperature dependence on the conductivity of electrolyte was modelled by Arrhenius and Vogel–Tammann–Fulcher equations, respectively. The temperature dependence on the conductivity does not fit in both models. The highest room temperature conductivity of the electrolyte of 3.7 × 10⁻⁷ Scm⁻¹ was obtained at 20% by weight of ZnO and that without ZnO filler was found to be 8.8 × 10⁻¹⁰ Scm⁻¹. The conductivity has been improved by 420 times when the ZnO filler was introduced into the PVC–LiClO₄ electrolyte system. It was also found that the glass transition temperature of the electrolyte PVC–ZnO–LiClO₄ is about the same as PVC–LiClO₄. The increase in conductivity of the electrolyte with the ZnO filler was explained in terms of its surface morphology.     

Investigation on the Micelle-Sensitized Ce (IV) - Lornoxicam-Rh B Chemiluminescence System and its Application

Based on the micelle synergism mechanism, a simple and sensitive flow injection chemiluminescence (FI-CL) method for the assay of lornoxicam was described. The CL signal generated from the reaction of Ce (IV) with lornoxicam in acidic solution was very weak, while the interfusion of sodium dodecyl benzene sulfonate (SDBS) resulted in a highly CL intensity. Under the optimum experimental conditions, the CL intensity was proportional to lornoxicam concentration over the range 1.0 × 10⁻¹⁰–7.3 × 10⁻⁸ g/mL with a detection limit of 4.9 × 10⁻¹¹ g/mL (3σ). The relative standard deviation for 11 replicate measurements of 3.0 × 10⁻⁹ g/mL of lornoxicam was 1.9%. The proposed method was successfully applied for the assay of lornoxicam in pharmaceuticals, human serum and urine with excellent recovery. The possible mechanism of CL reaction was also discussed briefly.     

Interaction of Thyroxine with 7 Hydroxycoumarin: A Fluorescence Quenching Study

The interaction between thyroxine hormone and 7 hydroxycoumarin (7HC) was investigated using fluorescence quenching method. The experimental results showed that thyroxine could quench the fluorescence of 7HC by forming the 7HC–thyroxine complex with static quenching. The apparent binding constants (K) between 7HC and thyroxine were determined to be 1.51 × 10⁴ (297 K) and 9.06 × 10³ (310 K). The binding sites (n) 0.98 ± 0.1. The thermodynamic parameters showed that the interaction between 7HC and thyroxine was driven mainly by hydrogen bonding interactions and van der Waals force. Calibration for thyroxine, based on quenching titration data, was linear in the concentration range 2.0 × 10⁻⁸ to 3.0 × 10⁻⁷ mol/l. The relative standard deviation was 2.58% for 2.0 × 10⁻⁷ mol/l thyroxine (n = 4) and the 3σ limit of detection was 3.42 × 10⁻⁸ mol/l in cationic surfactant CTAB medium.