Lu2O3:Tb,Hf storage phosphor

Lu₂O₃:Tb,Hf ceramics containing 0.1% of Tb and 0–1.5% of Hf were prepared in reducing atmosphere at 1700 °C and their thermoluminescence properties were systematically studied. For comparison Tb,Ca co-doped specimen was also fabricated and investigated. The Tb,Hf ceramics shows basically a single TL band located around 180 °C as found with heating rate of 15 °C/min. Ceramics singly doped with Tb show complex TL glow curves indicating the presence of traps of very different depths. On the other hand Tb,Ca co-doping is beneficial for the development of shallow traps with the main TL band around 70 °C. Hence, the aliovalent impurities, Ca²⁺ and Hf⁴⁺, strongly influenced the traps structure in Lu₂O₃:Tb ceramics, each of them in its own specific way. Isothermal decay of Lu₂O₃:Tb,Hf at 185 °C was recorded and its shape suggest that multiple hole trapping occurs in the Lu₂O₃:Tb,Hf ceramics. Due to the different traps depths the Lu₂O₃:Tb,Hf ceramics possess properties typical for storage phosphors, while Lu₂O₃:Tb,Ca is a persistent luminescent material rather.     

Cavitation and non-cavitation regime for large-scale ultrasonic standing wave particle separation systems – In situ gentle cavitation threshold determination and free radical related oxidation

We here suggest a novel and straightforward approach for liter-scale ultrasound particle manipulation standing wave systems to guide system design in terms of frequency and acoustic power for operating in either cavitation or non-cavitation regimes for ultrasound standing wave systems, using the sonochemiluminescent chemical luminol. We show that this method offers a simple way of in situ determination of the cavitation threshold for selected separation vessel geometry. Since the pressure field is system specific the cavitation threshold is system specific (for the threshold parameter range). In this study we discuss cavitation effects and also measure one implication of cavitation for the application of milk fat separation, the degree of milk fat lipid oxidation by headspace volatile measurements. For the evaluated vessel, 2 MHz as opposed to 1 MHz operation enabled operation in non-cavitation or low cavitation conditions as measured by the luminol intensity threshold method. In all cases the lipid oxidation derived volatiles were below the human sensory detection level. Ultrasound treatment did not significantly influence the oxidative changes in milk for either 1 MHz (dose of 46 kJ/L and 464 kJ/L) or 2 MHz (dose of 37 kJ/L and 373 kJ/L) operation.     

Quantifying left atrial structure and function using single-plane tissue-tracking cardiac magnetic resonance

PurposeLeft atrial (LA) structure and function are important markers of adverse cardiovascular outcomes. Tissue-tracking cardiovascular magnetic resonance (CMR) accurately quantifies LA volume, strain, and strain rate based on biplane long-axis imaging. We aimed to assess the accuracy of the LA indices quantification from single-plane tissue-tracking CMR.MethodsWe included 388 subjects (mean age  57±13, male 70%) whose cine CMR images in sinus rhythm were available in both four-chamber and two-chamber views: 162 patients from the Prospective Observational Study of Implantable Cardioverter-Defibrillators (PROSE-ICD) Study, 208 patients from atrial fibrillation cohort, and 18 healthy volunteers. The group was divided into the training set (n = 291) and the test set (n = 97). In the training set, we compared the LA indices derived from biplane imaging and single-plane imaging (a four-chamber view), and developed regression equations. In the test set, we used the regression equations to estimate the LA indices from the single-plane imaging, and quantified the accuracy of the estimation against the LA indices from the biplane.ResultsIn the training set, all the LA indices from the single-plane imaging tended to be systematically underestimated compared with those from the biplane imaging, however, the correlation coefficient was high (r² = 0.73–0.90, p < 0.001). In the test set, LA volumetric indices showed excellent reproducibility (intra-class correlation coefficient (ICC): 0.91–0.92) with relatively low variability (16.3–22.3%); For LA strain and strain rate indices, reproducibility was excellent (ICC: 0.81–0.93), however, the variability was slightly higher than that of volumetric indices (21.7–25.4%).ConclusionsLA volumetric indices measured from single-plane tissue-tracking CMR are highly accurate and reproducible with reference to those derived from the standard biplane imaging. The reproducibility of LA strain and strain rate indices from single-plane tissue-tracking CMR is excellent but the variability is higher than that of the volumetric indices.     

Dependence of cavitation,chemical effect,and mechanical effect thresholds on ultrasonic frequency

Cavitation, chemical effect, and mechanical effect thresholds were investigated in wide frequency ranges from 22 to 4880 kHz. Each threshold was measured in terms of sound pressure at fundamental frequency. Broadband noise emitted from acoustic cavitation bubbles was detected by a hydrophone to determine the cavitation threshold. Potassium iodide oxidation caused by acoustic cavitation was used to quantify the chemical effect threshold. The ultrasonic erosion of aluminum foil was conducted to estimate the mechanical effect threshold. The cavitation, chemical effect, and mechanical effect thresholds increased with increasing frequency. The chemical effect threshold was close to the cavitation threshold for all frequencies. At low frequency below 98 kHz, the mechanical effect threshold was nearly equal to the cavitation threshold. However, the mechanical effect threshold was greatly higher than the cavitation threshold at high frequency. In addition, the thresholds of the second harmonic and the first ultraharmonic signals were measured to detect bubble occurrence. The threshold of the second harmonic approximated to the cavitation threshold below 1000 kHz. On the other hand, the threshold of the first ultraharmonic was higher than the cavitation threshold below 98 kHz and near to the cavitation threshold at high frequency.     

Synthesis of Ag-deionized water nanofluids using multi-beam laser ablation in liquids

Multi-pulse laser ablation of silver in deionized water was studied. The laser beams were arranged in a cross-beam configuration. In our experiments, two single-mode, Q-switched Nd-Yag lasers operating at 1064 nm, pulse duration of 5.5 ns and 10 Hz rep rate were used. The laser fluence of the second beam was 0.265 J/cm² for all tests. Two levels of the laser fluences were used for the ablating beam: 0.09 and 0.265 J/cm² (11,014 and 33,042 J/cm² at the focal point, respectively). The silver target was at 50 mm from the cell window and 10 mm deep. The second beam was aligned parallelly with the silver target and focused at 2 mm in front of the focal point of the ablating beam. For all cases, the delay time between the ablating beam and the cross-beam was 40 μs. In general, the ablated particles were almost all spherical. For fluence of 0.09 J/cm ² and single-beam approach, the mean particle size was about 29 nm. The majority of the particles, however, were in 19–35 nm range and there were some big ones as large as 50–60 nm in size. For double-beam approach, the particles were smaller with the average size of about 18 nm and the majority of the particles were in 9–21 nm range with few big one as large as 40 nm. For the beam fluence of 0.265 J/cm² and single-beam configuration, the particle sizes were smaller, the mean particles size was about 18 nm and the majority of the particles were in the range of 10–22 nm with some big one as large as 40 nm. For double-beam approach, the mean particle size was larger (24.2 nm) and the majority of the particle were distributed from 14 to 35 nm with some big particles can be found with sizes as big as 70 nm. Preliminary measurements of the thermal conductivity and viscosity of the produced samples showed that the thermal conductivity increased about 3–5% and the viscosity increased 3.7% above the base fluid viscosity even with the particle volume concentration as low as 0.01%.     

Small silver clusters at paramagnetic defects of silica surfaces: A density functional embedded-cluster study

We studied the interaction of small Ag_n clusters (n = 1–4) with paramagnetic defect centers of a dehydroxylated silica surface using an all-electron scalar relativistic density functional method. The surface and adsorption complexes on it were modeled with an accurate quantum mechanics/molecular mechanics (QM/MM) scheme of embedding QM clusters in an elastic polarizable environment, described at the molecular mechanics level (MM). We analyzed two types of frequent point defects as sites for trapping and growing of Ag clusters: a silicon atom with a dangling bond (E′ center), ≡ Si?, and a non-bridging oxygen center (NBO), ≡ Si–O?. The Ag clusters interact with these paramagnetic centers forming strong covalent metal-defect bonds. The high adsorption energy allows one to consider the NBO and E′ sites as traps of single Ag atoms and as centers of cluster growth. We also explored the effect of adsorption on observable electronic properties of the silver clusters and of the defects of the silica surface.     

Exposure to indoor radon and natural gamma radiation in public workplaces in north-western Greece

Measurements of indoor radon levels and gamma dose rates were performed in 42 workplaces in Ioannina, north-western Greece. Radon concentrations followed a log-normal distribution with an arithmetic mean of 95 ± 51 Bq m^?3. In all cases, radon levels were below 400 Bq m^?3, which is the action level implemented by the Greek Regulation for Radiation Protection, in accordance with the European Commission recommendation. Comparing summer and winter measurements, no statistically significant seasonal variation was established. However, radon concentrations measured in basement and ground floor workplaces were significantly higher (p < 0.01) than those measured in the first and upper floors. Annual effective dose rates from inhalation of radon and its decay products were estimated to be in the range from 0.13 to 1.36 mSv y^?1 with a mean value of 0.62 mSv y^?1. Indoor exposure to natural gamma radiation entailed an average effective dose rate of 0.13 mSv y^?1, of which approximately 62% was due to terrestrial and the rest due to cosmic sources. The reported data contribute to the assessment of radon distribution and dose estimate at the national level.     

Reproducibility of cine displacement encoding with stimulated echoes (DENSE) in human subjects

ObjectivesTo test the hypothesis that two-dimensional (2D) displacement encoding via stimulated echoes (DENSE) is a reproducible technique for the depiction of segmental myocardial motion in human subjects.Materials and methodsFollowing the approval of the institutional review board (IRB), 17 healthy volunteers without documented history of cardiovascular disease were recruited. For each participant, 2D DENSE were performed twice (at different days) and the images were obtained at basal, midventricular and apical levels of the left ventricle (LV) with a short-axis view. The radial thickening strain (Err), circumferential strain (Ecc), twist and torsion were calculated. The intra-, inter-observer and inter-study variations of DENSE-derived myocardial motion indices were evaluated using coefficient of variation (CoV) and intra-class correlation coefficient (ICC).ResultsIn total, there are 272 pairs of myocardial segments (data points) for comparison. There is good intra- and inter-observer reproducibility for all DENSE-derived measures in 17 participants. There is good inter-study reproducibility for peak Ecc (CoV = 19.64%, ICC = 0.8896, p < 0.001), twist (CoV = 33.11%, ICC = 0.9135, p < 0.001) and torsion (CoV = 13.96%, ICC = 0.8684, p < 0.001). There is moderate inter-study reproducibility for Err (CoV = 38.89%, ICC = 0.7022, p < 0.001).ConclusionDENSE is a reproducible technique for characterizing LV regional systolic myocardial motion on a per-segment basis in healthy volunteers.     

Bistability of bilayer islands under anisotropic misfit stress

The equilibrium shapes of bilayer islands under anisotropic misfit stress have been theoretically characterized from a thermodynamics point of view. Based on an energy variation calculation, it is found that when the ratio σ between the components of the misfit stress is such that σ = ? 1, both square and rectangular shaped bilayer islands may coexist depending on the island volume and stress level. When σ ≠ ? 1 and σ < 0, the possibility of formation rectangular islands along both perpendicular directions is also discussed.     

Emulsification by high frequency ultrasound using piezoelectric transducer: Formation and stability of emulsifier free emulsion

Emulsifier free emulsion was developed with a new patented technique for food and cosmetic applications. This emulsification process dispersed oil droplets in water without any emulsifier. Emulsions were prepared with different vegetable oil ratios 5%, 10% and 15% (v/v) using high frequency ultrasounds generated by piezoelectric ceramic transducer vibrating at 1.7 MHz. The emulsion was prepared with various emulsification times between 0 and 10 h. Oil droplets size was measured by laser granulometry. The pH variation was monitored; electrophoretic mobility and conductivity variation were measured using Zêtasizer equipment during emulsification process. The results revealed that oil droplets average size decreased significantly (p < 0.05) during the first 6 h of emulsification process and that from 160 to 1 μm for emulsions with 5%, 10% and from 400 to 29 μm for emulsion with 15% of initial oil ratio.For all tested oil ratios, pH measurement showed significant decrease and negative electrophoretic mobility showed the accumulation of OH⁻ at oil/water interface leading to droplets stability in the emulsion. The conductivity of emulsions showed a decrease of the ions quantity in solution, which indicated formation of positive charge layer around OH⁻ structure. They constitute a double ionic layer around oil particles providing emulsion stability. This study showed a strong correlation between turbidity measurement and proportion of emulsified oil.     

Mono(pyridine-N-oxide) analog of DOTA as a suitable organic reagent for a sensitive and selective fluorimetric determination of Ln(III) ions

The mono(pyridine-N-oxide) analog of the H₄dota macrocylic ligand, H₃do3a-py^NO, is capable of forming thermodynamically stable and kinetically inert Ln(III) complexes. Its Eu(III) and Tb(III) complexes display a strong long-lived fluorescence as a result of the antenna effect of the pyridine-N-oxide fluorophore in the reagent. It is shown that H₃do3a-py^NO can be used as a fluorogenic reagent for the determination of Eu(III) and Tb(III) at pH 6.5 and c_L=1 mM. At an excitation wavelength of 286 nm, the emission maxima are 615 nm (Eu(III)-complex), and 547 nm (Tb(III)complex). Detection limits are at concentrations around 1.0 μM and linearity of the method spans over 2 orders of magnitude. The method was applied to artificial and real samples (spiked mineral waters, extracts from cathode ray tube luminophore dust) and gave satisfactory results. The method is simple, rapid, and hardly interfered by other metal ions.     

IR signature study of aircraft engine for variation in nozzle exit area

In general, jet engines operate with choked nozzle during take-off, climb and cruise, whereas unchoking occurs while landing and taxiing (when engine is not running at full power). Appropriate thrust in an aircraft in all stages of the flight, i.e., take-off, climb, cruise, descent and landing is achieved through variation in the nozzle exit area. This paper describes the effect on thrust and IR radiance of a turbojet engine due to variation in the exit area of a just choked converging nozzle (M_e = 1). The variations in the nozzle exit area result in either choking or unchoking of a just choked converging nozzle. Results for the change in nozzle exit area are analyzed in terms of thrust, mass flow rate and specific fuel consumption. The solid angle subtended (Ω) by the exhaust system is estimated analytically, for the variation in nozzle exit area (A_ne), as it affects the visibility of the hot engine parts from the rear aspect. For constant design point thrust, IR radiance is studied from the boresight (ϕ = 0°, directly from the rear side) for various percentage changes in nozzle exit area (%ΔA_ne), in the 1.9–2.9 μm and 3–5 μm bands.     

Visible light induced photodesorption of NO from the α-Cr2O3(0001) surface

Nitric oxide chemistry and photochemistry on the Cr-terminated surface of α-Cr₂O₃(0001) were examined using temperature programmed desorption (TPD), sticking coefficient measurements and photodesorption. NO exposed to α-Cr₂O₃(0001) at 100 K binds at surface Cr cation sites forming a strongly bound surface species that thermally desorbs at 320–340 K, depending on coverage. No thermal decomposition was detected in TPD in agreement with previous results in the literature. Sticking probability measurements at 100 K indicated near unity sticking for NO up to coverages of ~ 1.3 ML, with additional adsorption with higher exposures at decreased sticking probability. These results suggest that some Cr cation sites on the α-Cr₂O₃(0001) surface were capable of binding more than one NO molecule, although it is unclear whether this was as separate NO molecules or as dimers. Photodesorption of adsorbed NO was examined for surface coverages below the 1 ML point. Both visible and UV light were shown to photodesorb NO without detectable NO photodecomposition. Visible light photodesorption of NO occurred with a greater cross section than estimated using UV light. The visible light photodesorption event was not associated with bandgap excitation in α-Cr₂O₃(0001), but instead was linked to excitation of a surface Cr^3 +–NO^? charge transfer complex. These results illustrate that localized photoabsorption events at surface sites with unique optical properties (relative to the bulk) can result in unexpected surface photochemistry.     

Effect of Al content on impact resistance behavior of Al-Ti-B4C composite fabricated under air atmosphere

Reaction behavior, mechanical property and impact resistance of TiC-TiB₂/Al composite reacted from Al-Ti-B₄C system with various Al content via combination method of combustion synthesis and hot pressed sintering under air was investigated. Al content was the key point to the variation of mechanical property and impact resistance. Increasing Al content could increase the density, strength and toughness of the composite. Due to exorbitant ceramic content, 10 wt.% and 20 wt.% Al-Ti-B₄C composites exhibited poor molding ability and machinability. Flexural strength, fracture toughness, compressive strength and impact toughness of 30–50 wt.% Al-Ti-B₄C composite were higher than those of Al matrix. The intergranular fracture dispersed and defused impact load and restricted crack extension, enhancing the impact resistance of the composite. The composite with 50 wt.% Al content owned highest mechanical properties and impact resistance. The results were useful for the application of TiC-TiB₂/Al composite in impact resistance field of ceramic reinforced Al matrix composite.     

A highly luminescent complexes of Eu(III) and Tb(III) with norfloxacin and gatifloxacin doped in sol–gel matrix: A comparable approach of using silica doped Tb(III) and Eu(III) as optical sensor

Highly luminescent complexes of Eu and Tb ions with norfloxacin (NFLX) and gatifloxacin (GFLX) were prepared in sol–gel matrix. The red and green emissions of Eu and Tb ions were obtained by the energy transfer from the triplet state of (NFLX) and (GFLX) to the excited emitting states (⁵D₀ and ⁵D₄) of Eu and Tb, respectively. The intensity of the electric field emission bands (⁵D₀→⁷F₂, 617 nm and ⁵D₄→⁷F₅, 545 nm) of Eu and Tb ions were proportional to the concentration of (NFLX at pH 6.0) and (GFLX at pH 3.5) in acetonitrile with excitation wavelengths (λ_ex) (340 and 395) and (370 and 350 nm) for Eu and Tb ions, respectively. The monitored luminescence intensity of the system showed a good linear relationship with the concentration of NFLX within a range of 5×10^?9–5.8×10^?6 and 5×10^?8–1.0×10^?6 mol L^?1 with a correlation coefficient of 0.990, and for GFLX within a range of 2.4×10^?9–3.2×10^?5 and 5×10^?8–8.0×10^?6 mol L^?1 with a correlation coefficient of 0.995. The detection limit (LOD) was determined as 3.0×10^?9 and 1.0×10^?8 mol L^?1 for NFLX and 1.6×10^?10 and 2.0×10^?8mol L^?1 for GFLX. The limit of quantification (LOQ) is 9×10^?9 and 3.0×10^?8 and 4.8×10^?10 and 6.0×10^?8 in case of Eu and Tb, respectively.     

Structural and magnetic studies on RPtIn deuterides (R=Tb,Er, Tm)

In this communication, structural and magnetic properties of RPtInD_1.3 (R=Tb, Er, Tm) deuterides are reported. For the first time deuterium-rich compounds were synthesized for the RPtIn family. The investigated deuterides crystallize with the hexagonal ZrNiAl-type crystal structure, with slightly different lattice constants with respect to the basic compounds. In general, the a-lattice constant exhibit contraction, while the c-lattice constant tends to increase upon introducing deuterium. The compounds with Tb and Er shows magnetic ordering at 95 K and 15.5 K, respectively. On the other hand, for Tm based sample no magnetic ordering was evidenced down to 2 K.     

Carrier transport properties in high resistivity polycrystalline CdZnTe material

The electrical properties of polycrystalline CdZnTe (Zn = 4%) having high resistivity (3.3 × 10⁹ Ω cm) were investigated by using the time-of-flight technique. We have found that the average drift mobility of as-deposited polycrystalline CdZnTe samples is 1.21 cm²/V s and the electron trapping time is 4.6 μs. In a comparison of annealed samples at different conditions, the variation of resistivity in polycrystalline CdZnTe is considered to be mainly related to the fluctuation of carrier concentration, which originates from the change of density in deep level.     

Diffusion tensor imaging of the cervical spinal cord of patients with Neuromyelitis Optica

BackgroundPrevious studies have demonstrated a correlation between Expanded Disability Status Scale (EDSS) and Diffusion Tensor Imaging (DTI) metrics, but the conclusions were based on evaluations of the entire cervical spinal cord.ObjectivesThe purpose of this study was to quantify the FA and MD values in the spinal cord of NMO patients, separating the lesion sites from the preserved sites, which has not been previously preformed. In addition, we attempted to identify a correlation with EDSS.MethodsDTI was performed in 11 NMO patients and 11 healthy individuals using a 1.5-T MRI scanner. We measured the FA and MD at ROIs positioned along the cervical spinal cord. The mean values of FA and MD at lesion, preserved and spinal cord sites were compared with those of a control group. We tested the correlations between the mean FA and MD with EDSS.ResultsFA in NMO patients was significantly reduced in lesion sites (0.44 vs. 0.55, p = 0.0046), preserved sites (0.46 vs. 0.55, p = 0.0015), and all sites (0.45 vs 0.55, p = 0.0013) while MD increased only in lesion sites (1.03 × 10^− 3 mm²/s vs. 0.90 × 10^− 3 mm²/s, p = 0.009). The FA demonstrated the best correlation with EDSS (r = − 0.7603, p = 0.0086), particularly at lesion sites.ConclusionsThe results reinforce the importance of the FA index and confirm the hypothesis that NMO is a diffuse disease.     

Effects of dissolution conditions on the properties of PVDF ultrafiltration membranes

Poly (vinylidene fluoride) (PVDF) is an important membrane forming material for water treatment. Earlier works have shown that major morphological changes can be achieved when PVDF is dissolved under different conditions with practical applications in membrane distillation and protein attachment. However, no previous report has discussed the effects of dissolution conditions on the performance of PVDF under ultrafiltration, which is one of the most important applications of the polymer. In this work, four different PVDF ultrafiltration membranes were produced from dopes dissolved either by stirring at 24 °C, 90 °C, 120 °C or by sonication. It is shown that dope sonication results in membrane with enhanced thermal and mechanical stability, improved permeate flux during oil emulsion filtration and high flux recovery of ∼63% after cleaning. As a comparison, flux recovery of only ∼26% was obtained for the membrane produced from dope dissolved at 24 °C. The outstanding performance of the dope-sonicated membrane was linked to its slightly lower porosity, narrow distribution of small pores and relatively smooth skin layer. Performance parameters for all membranes showed good correlation to porosity suggesting a tool for membrane design achievable by simple variation in the mode of polymer dissolution. The polymer dissolution effect was related to the degree of unfolding of the polymer molecular chains and their entanglements.     

Experimental study of the effect of wind on positive and negative corona from a sharp point in a thunderstorm

Corona discharge measurements made during a thunderstorm on a mountain at an altitude of almost 3300 m above sea level were analyzed for their dependence on the ambient electric field and the local wind speed. The corona current data were taken from an earthed needle point mounted at a height of 3 m above the ground. The coronating point was exposed to natural wind speeds of up to 14 m/s. Comparisons are made with empirical relationships dating back to the mid-1900s and new formulae are provided to describe the effect of wind on the magnitude of corona current measured under natural conditions.