Fabry–Pérot cavities based on chemical etching for high temperature and strain measurement

In this paper, two hybrid multimode/single mode fiber Fabry–Pérot (FP) cavities were compared. The cavities fabricated by chemical etching are presented as high temperature and strain sensors. In order to produce this FP cavity a single mode fiber was spliced to a graded index multimode fiber with 62.5 μm core diameter. The Fabry–Pérot cavities were tested as a high temperature sensor in the range between room temperature and 700 °C and as strain sensors. A reversible shift of the interferometric peaks with temperature allowed to estimate a sensitivity of 0.75 ± 0.03 pm/°C and 0.98 ± 0.04 pm/°C for the sensor A and B respectively. For strain measurement sensor A demonstrated a sensitivity of 1.85 ± 0.07 pm/μ? and sensor B showed a sensitivity of 3.14 ± 0.05 pm/μ?. The sensors demonstrated the feasibility of low cost fiber optic sensors for high temperature and strain.     

Polymorphic phase transition and thermal stability in squaric acid (H2C4O4)

Phase transformations in squaric acid (H₂C₄O₄) have been investigated by thermogravimetry and differential scanning calorimetry with different heating rates β. The mass loss in TG apparently begins at onset temperatures T_di=245±5 °C (β=5 °C min^?1), 262±5 °C (β=10 °C min^?1), and 275±5 °C (β=20 °C min^?1). A polymorphic phase transition was recognized as a weak endothermic peak in DSC around 101 °C (T_c⁺). Further heating with β=10 °C min^?1 in DSC revealed deviation of the baseline around 310 °C (T_i), and a large unusual exothermic peak around 355 °C (T_p), which are interpreted as an onset and a peak temperature of thermal decomposition, respectively. The activation energy of the thermal decomposition was obtained by employing relevant models. Thermal decomposition was recognized as a carbonization process, resulting in amorphous carbon.     

Synthesis and photoluminescence properties of silver nanowires

Silver nanowires of 50–190 nm in diameters along with silver nanoparticles in the size range of 60–200 nm in prismatic and hexagonal shapes are synthesized through chemical process. The lengths of the silver nanowires lie between 40 and 1000 μm. The characterizations of the synthesized samples are done by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible absorption spectroscopy. The syntheses have been done by using two processes. In the first process, relatively thicker and longer silver nanowires are synthesized by a soft template liquid phase method at a reaction temperature of 70 °C with methanol as solvent. In the second process, thinner silver nanowires along with silver nanoparticles are prepared through a polymer mediated polyol process at a reaction temperature of 210 °C with ethylene glycol as solvent. The variations of photoluminescence (PL) emission from the silver nanocluster dispersed in methanol as well as in ethylene glycol are recorded at room temperature under excitation wavelengths lying in between 300 and 414 nm. The blue–green PL emission is observed from the prepared samples and these emissions are assigned to radiative recombination of Fermi level electrons and sp- or d-band holes.     

Comparative ultrastructure of spermatozoa of the redclaw Cherax quadricarinatus and the yabby Cherax destructor (Decapoda,Parastacidae)

Ultrastructure of spermatozoa of redclaw Cherax quadricarinatus and yabby Cherax destructor were described and compared. The acrosome complex and nucleus are located at the anterior and posterior region of the spermatozoon, respectively. The acrosome is a complex vesicle divided into two parts: the main body of the acrosome appears as a dense cup-shaped structure in longitudinal sagittal view, with the subacrosome zone occupying the central area of the vesicle. The acrosome is larger in C. quadricarinatus (width 2.37 ± 0.27 μm, length 1.31 ± 0.23 μm) than in C. destructor (width 1.80 ± 0.27 μm, length 1.01 ± 0.15 μm). There was no significant difference in L:W ratios of the studied species. The subacrosome zone in both species consists of two areas of different electron density. The nucleus is substantially decondensed and irregular in shape, with elaborate extended processes. The examined species exhibited a well-conserved structure of crayfish spermatozoon, similar to those of Cherax cainii and Cherax albidus. Small acrosome size, the absence of radial arms, and an extracellular capsule seem to be the morphological features that mostly distinguish Cherax from the Astacidae and Cambaridae.     

Abnormal lipid metabolism in skeletal muscle tissue of patients with muscular dystrophy: In vitro,high-resolution NMR spectroscopy based observation in early phase of the disease

PurposeQualitative (assignment of lipid components) and quantitative (quantification of lipid components) analysis of lipid components were performed in skeletal muscle tissue of patients with muscular dystrophy in early phase of the disease as compared to control/normal subjects.MethodsProton nuclear magnetic resonance (NMR) spectroscopy based experiment was performed on the lipid extract of skeletal muscle tissue of patients with muscular dystrophy in early phase of the disease and normal individuals for the analysis of lipid components [triglycerides, phospholipids, total cholesterol and unsaturated fatty acids (arachidonic, linolenic and linoleic acid)]. Specimens of muscle tissue were obtained from patients with Duchenne muscular dystrophy (DMD) [n = 11; Age, Mean ± SD; 9.2 ± 1.4 years; all were males], Becker muscular dystrophy (BMD) [n = 12; Age, Mean ± SD; 21.4 ± 5.0 years; all were males], facioscapulohumeral muscular dystrophy (FSHD) [n = 11; Age, Mean ± SD; 23.7 ± 7.5 years; all were males] and limb girdle muscular dystrophy-2B (LGMD-2B) [n = 18; Age, Mean ± SD; 24.2 ± 4.1 years; all were males]. Muscle specimens were also obtained from [n = 30; Mean age ± SD 23.1 ± 6.0 years; all were males] normal/control subjects.ResultsAssigned lipid components in skeletal muscle tissue were triglycerides (TG), phospholipids (PL), total cholesterol (CHOL) and unsaturated fatty acids (arachidonic, linolenic and linoleic acid)]. Quantity of lipid components was observed in skeletal muscle tissue of DMD, BMD, FSHD and LGMD-2B patients as compared to control/normal subjects. TG was significantly elevated in muscle tissue of DMD, BMD and LGMD-2B patients. Increase level of CHOL was found only in muscle of DMD patients. Level of PL was found insignificant for DMD, BMD and LGMD-2B patients. Quantity of TG, PL and CHOL was unaltered in the muscle of patients with FSHD as compared to control/normal subjects. Linoleic acids were significantly reduced in muscle tissue of DMD, BMD, FSHD and LGMD-2B as compared to normal/control individuals.ConclusionsResults clearly indicate alteration of lipid metabolism in patients with muscular dystrophy in early phase of the disease. Moreover, further evaluation is required to understand whether these changes are primary or secondary to muscular dystrophy. In future, these findings may prove an additional and improved approach for the diagnosis of different forms of muscular dystrophy.     

Ultrasound-assisted copper deposition on a polymer membrane and application for methanol steam reforming

Copper particles were electrolessly deposited on a palladium aerosol activated polymer membrane in the presence of ultrasound. An application of ultrasound introduced a faster deposition (220 μg min^?1 in deposition rate) and finer copper particles (9 nm in crystallite size) than those (11 and 41 μg min^?1; 27 and 32 nm) in the absence of ultrasound (i.e. respectively 20 and 45 °C in bath temperature with mechanical agitation). A better performance of methanol steam reforming (0.59 in mean conversion during 5 h operation; 1.3 and 1.6 times respectively higher than those from 20 to 45 °C cases) at a 300 °C reaction temperature was materialized for the ultrasound application, probably due to a finer (i.e. a more textured) copper particle deposition on a polymer membrane.     

Stabilization of high spin FCC Fe in (Fe/Pd)n multilayers

Polycrystalline (Fe/Pd)_n multilayers are grown onto sapphire substrates at room temperature in a UHV system. The number of periods n=40 and the thickness of Pd layers of t_Pd=4 nm are kept constant, whereas the thickness of the Fe layers is varied from 1.5 to 5 nm. Structural properties are studied by in situ reflection high energy diffraction (RHEED), scanning tunnelling microscopy (STM) and ex situ by X-ray diffraction at small angles and large angles. Analyzing the experimental data using the program SUPREX we obtain interplanar distances of d_Fe=2.03±0.01 Å for an Fe layer thickness larger than about 2.5 nm as expected for (1 1 0) planes of BCC Fe. For Fe layers with thicknesses less than about 2.5 nm the interplanar distance is d_Fe=2.1±0.01 Å, which is close to the distance between (1 1 1) planes of FCC Fe with a lattice parameter of a=3.64 Å. Magnetic susceptibility measurements at temperatures between 1.5 and 300 K for (Fe/Pd)_n multilayers with FCC Fe yield a magnetic moment per Fe atom of μ=2.7±0.1 μ_B, which is about 20% larger compared to μ=2.2 μ_B for BCC Fe. We show that the occurrence of the large magnetic moment originates from FCC Fe being in the high spin (HS) state rather than from polarization effects of Pd at Fe/Pd interfaces.     

The inactivation kinetics of polyphenol oxidase in mushroom (Agaricus bisporus) during thermal and thermosonic treatments

The effect of thermal and thermosonic treatments on the inactivation kinetics of polyphenol oxidase (PPO) in mushroom (Agaricus bisporus) was studied in 55–75 °C temperature range. In both the processes, the inactivation kinetics of PPO followed a first-order kinetics (R² = 0.941–0.989). The D values during thermal inactivation varied from 112 ± 8.4 min to 1.2 ± 0.07 min while they varied from 57.8 ± 6.1 min to 0.88 ± 0.05 min during thermosonic inactivation at the same temperature range. The activation energy during thermal inactivation was found to be 214 ± 17 kJ/mol, while it was 183 ± 32 kJ/mol during thermosonic inactivation. The inactivating effect of combined ultrasound and heat was found to synergistically enhance the inactivation kinetics of PPO. The D values of PPO decreased by 1.3–3 times during thermosonic inactivation compared to the D values of PPO during thermal inactivation at the temperature range. Therefore, thermosonication can be further developed as an alternative to “hot break” process of mushroom.     

Growth-morphology-luminescence correlation in ZnO-containing nanostructures synthesized in different media

Zinc hydroxide particles were prepared by a two-step process employing zinc nitrate hexahydrate, urea, ethylene glycol, water and p-toluene-sulfonic acid monohydrate (p-TSA). We used different concentrations of the reactants as well as different volume ratios of the solvents. ZnO particles were obtained by thermal treatment of the reaction products at two different temperatures: 350 °C and 500 °C. The samples were characterized by scanning field emission electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, BET analysis, thermogravimetry (TG) analysis and photoluminescence (PL) spectroscopy. It was found that after the thermal treatment particles become smaller, with the p-TSA concentration strongly affecting the morphology of the particles. Luminescence properties of the samples probed by PL at 8 K and room temperature exhibited a remarkable correlation with specimens′ nanomorphology. Luminescent features at ～2.0–2.2 eV, ～2.4–2.5 eV, ～2.65 eV, ～2.9 eV, ～3.0–3.1 eV and ～3.3 eV were observed in most specimens, although their relative intensity and temperature dependence were specific to an individual group of samples vis-à-vis their growth history and morphology.     

Temperature effects on the ultrasonic separation of fat from natural whole milk

This study showed that temperature influences the rate of separation of fat from natural whole milk during application of ultrasonic standing waves. In this study, natural whole milk was sonicated at 600 kHz (583 W/L) or 1 MHz (311 W/L) with a starting bulk temperature of 5, 25, or 40 °C. Comparisons on separation efficiency were performed with and without sonication. Sonication using 1 MHz for 5 min at 25 °C was shown to be more effective for fat separation than the other conditions tested with and without ultrasound, resulting in a relative change from 3.5 ± 0.06% (w/v) fat initially, of −52.3 ± 2.3% (reduction to 1.6 ± 0.07% (w/v) fat) in the skimmed milk layer and 184.8 ± 33.2% (increase to 9.9 ± 1.0% (w/v) fat) in the top layer, at an average skimming rate of ∼5 g fat/min. A shift in the volume weighted mean diameter (D[4,3]) of the milk samples obtained from the top and bottom of between 8% and 10% relative to an initial sample D[4,3] value of 4.5 ± 0.06 μm was also achieved under these conditions. In general, faster fat separation was seen in natural milk when natural creaming occurred at room temperature and this separation trend was enhanced after the application of high frequency ultrasound.     

Room temperature phosphorescence lifetime and quantum yield of erythrosine B and rose bengal in aerobic alkaline aqueous solution

The room-temperature phosphorescence behavior of erythrosine B (ER) and rose bengal (RB) in aerobic aqueous solution at pH 10 (10^?4 M NaOH) is investigated. The samples were excited with sliced second harmonic pulses of a Q-switched Nd:glass laser. A gated photomultiplier tube was used for instantaneous fluorescence signal discrimination and a digital oscilloscope was used for signal recording. For phosphorescence lifetime measurement the oscilloscope response time was adjusted to appropriate time resolution and sensitivity by the ohmic input resistance. In the case of phosphorescence quantum yield determination the gated photomultiplier – oscilloscope arrangement was operated in integration mode using 10 MΩ input resistance. Phosphorescence quantum yield calibration was achieved with erythrosine B and rose bengal doped starch films of known quantum yields. The determined phosphorescence lifetimes (quantum yields) of ER and RB in 0.1 mM NaOH are τ_P=1.92±0.1 μs (?_P=(1.5±0.3)×10^?5) and 2.40±0.1 μs ((5.7±0.9)×10^?5), respectively. The results are discussed in terms of triplet state deactivation by dissolved molecular oxygen.     

High temperature operation of edge-emitting photonic-crystal distributed-feedback quantum cascade lasers at λ∼7.6 μm

We present large-area, edge-emitting, photonic-crystal (PC) distributed-feedback (DFB) quantum cascade lasers (QCLs) emitting at λ∼7.6 μm and operating up to a heat sink temperature of 80 °C. The lasers use the anticrossing of index- and Bragg-guided dispersions of rectangular lattice to control the optical mode in the wafer plane. Single-mode operation with a high signal-to-noise ratio of about 20 dB and narrow beam divergence of 6.2° was obtained. A high peak power of 630 mW at 20 °C and still more than 160 mW at 60 °C was observed. Such a high performance single-mode device is very important to expand the potential applications in the long-wave infrared range.     

Sensor application-related defect chemistry and electromechanical properties of langasite

The operation of langasite (La₃Ga₅SiO₁₄) resonators as sensors at elevated temperature and controlled atmospheres is examined. This paper focuses on mapping the regimes of gas-insensitive operation of uncoated langasite resonators and the correlation to langasite's defect chemistry for temperatures up to 1000 °C. As a measure of sensitivity, the fundamental resonant mode at 5 MHz is estimated to be determined to within ± 4 Hz by network analysis for resonators operated in air at temperatures below 1000 °C. The calculated frequency shift induced by redox-related reactions in langasite only exceeds the limit of ± 4 Hz below p_O2 ≈ 10^− 17 bar at 1000 °C, below 10^− 24 bar at 800 °C and below 10^− 36 bar at 600 °C. Water vapor is found to shift the resonance frequency at higher oxygen partial pressures. In the hydrogen-containing atmospheres applied here, langasite can be regarded as a stable resonator material above oxygen partial pressures of about 10^− 13 and 10^− 20 bar at 800 and 600 °C, respectively.     

The production of Sr hexaferrite thick films by screen printing

Hydrothermally synthesised Sr hexaferrite (HT-SrM) powder with a distinct plate-like shape and conventional Sr hexaferrite (c-SrM) powder were used to screen print SrM thick films on alumina substrates. In the case of the HT-SrM thick films, a very strong perpendicular magnetic anisotropy has been observed with remanence values of up to 42±2 J/T kg for the perpendicular direction and 15±1 J/T kg for the in-plane direction, and with coercivities of around 159±8 kA/m for both directions when fired at 1300°C. When fired at 1150°C, the remanences were 49±2 and 27±2 J/T kg for the two directions with a higher coercivity of 247±8 kA/m for both directions. The SEM micrographs showed that the platelet grains in the printed films lay with their flat surfaces on the substrate and XRD results revealed that the c-axis of the grains oriented perpendicularly to the film surface. The (0 0 8) plane, which is, for a random oriented sample, a very weak peak, appeared as the strongest in the XRD pattern for the films. EDX and XRD studies indicated significant reaction at the interfaces between the film and the substrate when the sintering temperature was raised to 1350°C.For the SrM thick films obtained from planetary milled ultrafine Sr hexaferrite and conventional Sr hexaferrite powder, a slight in-plane anisotropy could be observed with a coercivity of 318±8 kA/m.     

Thermo,Iono and photoluminescence properties of 100 MeV Si7+ ions bombarded CaSiO3:Eu3+ nanophosphor

This paper reports on the thermo (TL), iono (IL) and photoluminescence (PL) properties of nanocrystalline CaSiO₃:Eu³⁺ (1–5 mol %) bombarded with 100 MeV Si⁷⁺ ions for the first time. The effect of different dopant concentrations and influence of ion fluence has been discussed. The characteristic emission peaks ⁵D₀→⁷F_J (J=0, 1, 2, 3, 4) of Eu³⁺ ions was recorded in both PL (1×10¹¹–1×10¹³ ions cm^?2) and IL (4.16×10¹²–6.77×10¹² ions cm^?2) spectra. It is observed that PL intensity increases with ion fluence, whereas in IL the peaks intensity increases up to fluence 5.20×10¹² ions cm^?2, then it decreases. A well resolved TL glow peak at ～304 °C was recorded in all the ion bombarded samples at a warming rate of 5 °C s^?1. The TL intensity is found to be maximum at 5 mol% Eu³⁺ concentration. Further, TL intensity increases sub linearly with shifting of glow peak towards lower temperature with ion fluence.     

Enzymatic inactivation and antioxidant properties of blackberry juice after thermoultrasound: Optimization using response surface methodology

The purpose of this research was to optimize the thermoultrasound conditions for blackberry juice using the response surface methodology and considering juice quality parameters and antioxidant capacity. With the exception of microbial growth, the response variables showed high correlation coefficients with the mathematical model (R²adj > 0.91). Thermoultrasound treatment inactivated all the evaluated microorganisms, and at the optimum conditions (50 ± 1 °C at 17 ± 1 min) it increased enzyme inactivation and antioxidant activity in comparison to pasteurized juice. The results demonstrated that thermoultrasound can be an alternative to pasteurization for the production of safe and high-quality juices with the added value of higher concentration of bioactive compounds and antioxidant capacity.     

Electrical and dielectric properties of β-BaB2O4 (BBO) and CsLiB6O10 (CLBO) crystals

In barium borate (BBO) crystals, sodium and potassium ions, inherited due to the preparation technique, are dominant charge carriers. The conductivity between layers is higher; the conductivity activation energy and the conductivity at 350 °C being equal to 1.01±0.05 eV and (1.3±0.2)×10⁻⁸ S/cm, respectively. The conductivity activation energy and the conductivity at 350 °C along the channels are equal to 1.13±0.05 eV and to (4±0.2)×10⁻⁹ S/cm, respectively. Relative static permittivity is almost isotropic, and equal to 7.65±0.05. Upon storing of cesium–lithium borate (CLBO) crystals, pre-heating to 600 °C eliminates the influence of surface humidity. At 500 K, the ionic conductivity ranges from 4×10⁻¹² to 2×10⁻¹⁰ S/cm; the conductivity activation energy ranges from 1.01 to 1.17 eV. Relative static permittivity is equal to 7.4±0.3.     

Luminescence enhancement by the reduction–oxidation synthesis in monoclinic RE2O3 (RE=Eu,Gd) phosphors containing Eu3+ activator

A novel synthesis was developed for enhanced luminescence in sesquioxide phosphors containing Eu³⁺ activator. It consisted of two annealing steps: reduction under vacuum with gaseous H₂ at 10 Torr and 1300 °C and re-oxidation at 300–1500 °C in air. The integrated luminescence intensity of the monoclinic Eu₂O₃ phosphor was enhanced ca. 21 times by this method compared with conventional processing. The photoluminescence (PL) intensity was maximized at re-oxidation temperatures of 500–1100 °C. The PL characteristics of monoclinic Eu₂O₃ and Gd₂O₃:0.06Eu samples were compared with a commercial cubic Y₂O₃:Eu phosphor. The evolution of physical characteristics during the two-step annealing was studied by Raman spectroscopy, XPS, XRD, PL decay analysis, and SEM. PL decay lifetime increased proportionally to the PL intensity over the range 0.5–100 μs. Additional vibrational modes appeared at 490, 497, and 512 cm^?1 after the two-step annealing. The increase in PL intensity was ascribed to the formation of excess oxygen vacancies and their redistribution during annealing. Resonance crossovers between the charge transfer state and the emitting ⁵D_J states are discussed in relation to reported luminescence saturation mechanisms for oxysulfides Ln₂O₂S:Eu³⁺ (Ln=Y, La).     

Graphene on SiC(0001) and SiC(0001̅) surfaces grown via Ni-silicidation reactions

This paper presents the structure and electronic properties of graphene grown on 6H-SiC(0001) and SiC(0001?) surfaces via Ni-silicidation reactions at temperatures around 800 °C. Silicidation reactions take place at temperature higher than 400 °C for Ni(10 ML)/SiC and a single-phase θ-Ni₂Si(0001)-layer grows epitaxially on SiC(0001?) at 500 °C, whereas a mixed phase silicide-layer is formed on the SiC(0001) substrate. Annealing at 800 °C leads to growth of ordered graphite layers on both SiC(0001?) and SiC(0001) surfaces with an areal occupation ratio of ～ 65%, which surround the Ni-silicide islands. High-resolution ion scattering analysis reveals that single- and double-layer of graphite grow on the SiC(0001?) and SiC(0001), respectively. The dispersion curve of the π band for the double-layer graphite (DG) on the Si-face lies about 1 eV above that of the single-layer graphite (SG) on the C-face around the Γ-point. The work functions of the SG/SiC(0001?) and DG/SiC(0001) are derived to be 5.15 ± 0.05 and 4.25 ± 0.05 eV, respectively, which coincide well with the theoretical prediction based on the ab initio calculations. The present results indicate that the electronic states of graphene are influenced by the interaction with supports.     

Spin coating-pyrolysis derived highly c-axis-oriented ZnO layers pre-fired at various temperatures

Transparent ZnO layers were prepared on silica glass substrates by the spin coating-pyrolysis process. As-deposited films were pre-fired at 250 °C for 60 min, at 350 °C for 30 min, and at 500 °C for 10 min, followed by heat treatment at 900 °C for 30 min in air. The ZnO films were analyzed by high resolution X-ray diffraction, field emission-scanning electron microscopy, scanning probe microscopy, and ultraviolet–visible–near infrared spectrophotometry. (0 0 2)-oriented ZnO films were obtained by pre-firing at 350 °C and at 500 °C. All the ZnO films exhibited a high transmittance, above 80%, in the visible region, and showed a sharp fundamental absorption edge at 0.38–0.40 μm. The most highly c-axis-oriented ZnO with a homogeneous surface was observed at a pyrolysis temperature of 350 °C.