Initial Intensity Research Articles

Capping Ligand Engineering Enables Stable CsPbBr3 Perovskite Quantum Dots toward White-Light-Emitting Diodes.

All-inorganic perovskite quantum dots (PeQDs) have sparked extensive research focus on white-light-emitting diodes (WLEDs), but stability and photoluminescence efficiency issues are still remain obstacles impeding their practical application. Here, we reported a facile one-step method to synthesize CsPbBr3 PeQDs at room temperature using branched didodecyldimethylammonium fluoride (DDAF) and short-chain-length octanoic acid as capping ligands. The obtained CsPbBr3 PeQDs have a near-unity photoluminescence quantum yield of 97% due to the effective passivation of DDAF. More importantly, they exhibit much improved stability against air, heat, and polar solvents, maintaining >70% of initial PL intensity. Making use of these excellent optoelectronic properties, WLEDs based on CsPbBr3 PeQDs, CsPbBr1.2I1.8 PeQDs, and blue LEDs were fabricated, which show a color gamut of 122.7% of the National Television System Committee standard, a luminous efficacy of 17.1 lm/W, with a color temperature of 5890 K, and CIE coordinates of (0.32, 0.35). These results indicate that the CsPbBr3 PeQDs have great practical potential in wide-color-gamut displays.

Silver Nanoparticle-Embedded Conductive Hydrogels for Electrochemical Sensing of Hydroquinone.

In this work, a conductive hydrogel was successfully synthesized, taking advantage of the high number density of active amino and hydroxyl groups in carboxymethyl chitosan and sodium carboxymethyl cellulose. These biopolymers were effectively coupled via hydrogen bonding with the nitrogen atoms of the heterocyclic rings of conductive polypyrrole. The inclusion of another biobased polymer, sodium lignosulfonate (LS), was effective to achieve highly efficient adsorption and in-situ reduction of silver ions, leading to silver nanoparticles that were embedded in the hydrogel network and used to further improve the electro-catalytic efficiency of the system. Doping of the system in the pre-gelled state led to hydrogels that could be easily attached to the electrodes. The as-prepared silver nanoparticle-embedded conductive hydrogel electrode exhibited excellent electro-catalytic activity towards hydroquinone (HQ) present in a buffer solution. At the optimum conditions, the oxidation current density peak of HQ was linear over the 0.1-100 μM concentration range, with a detection limit as low as 0.12 μM (signal-to-noise of 3). The relative standard deviation of the anodic peak current intensity was 1.37% for eight different electrodes. After one week of storage in a 0.1 M Tris-HCl buffer solution at 4 °C, the anodic peak current intensity was 93.4% of the initial current intensity. In addition, this sensor showed no interference activity, while the addition of 30 μM CC, RS, or 1 mM of different inorganic ions does not have a significant impact on the test results, enabling HQ quantification in actual water samples.

Methylammonium Cation-Regulated Controllable Preparation of CsPbBr3 Perovskite Quantum Dots in Polystyrene Fiber with Enhanced Water and UV Light Stabilities

In situ fabrication of lead halide perovskite quantum dots (PQDs) is important for narrow-band emitters for LED displays due to the simple work procedure and convenient usability; however, the growth of PQDs is not readily controllable in the preparation, resulting in low quantum efficiency and environmental instability of PQDs. Here, we demonstrate an effective strategy to controllably prepare CsPbBr3 PQDs in polystyrene (PS) under the regulation of methylammonium bromide (MABr) via electrostatic spinning and thermal annealing techniques. MA+ slowed down the growth of CsPbBr3 PQDs and acted as a surface defect passivation reagent, which was proved by Gibbs free energy simulation, static fluorescence spectra, transmission electron microscopy, and time-resolved photoluminescence (PL) decay spectra. Among a series of prepared Cs1-xMAxPbBr3@PS (0 ≤ x ≤ 0.2) nanofibers, Cs0.88MA0.12PbBr3@PS shows the regular particle morphology of CsPbBr3 PQDs and the highest photoluminescence quantum yield of up to 39.54%. The PL intensity of Cs0.88MA0.12PbBr3@PS is 90% of the initial intensity after immersing in water for 45 days and 49% of the initial value after persistent ultraviolet (UV) irradiation for 27 days. A high color gamut containing 127% of the National Television Systems Committee standard with long-time working stability was also obtained on light-emitting diode package measurements. These results demonstrate that MA+ can effectively control the morphology, humidity, and optical stability of CsPbBr3 PQDs in the PS matrix.

Efficient Degradation of Oxytetracycline in a Novel Plug-In Three-Dimensional Photocatalytic Microreactor

The combination of a photocatalytic reaction and microfluidic technology is an increasingly popular method utilized to continuously degrade wastewater. In this work, a novel photocatalytic microreactor with TiO2 loaded on the channel center insert was designed and the photocatalytic degradation process of oxytetracycline (OTC) was investigated. Parameters such as TiO2 loading, OTC initial concentration, light intensity, and ion (NO3– and SO42–) concentrations were systematically investigated. The results show that the degradation efficiency of OTC was 56% under the optimal experimental conditions. Compared with the conventional miniaturized photocatalytic reactors, the reaction rate constant and space–time degradation efficiency of the plug-in three-dimensional photocatalytic microreactor proposed in this work were 1–2 orders of magnitude higher. In addition, dimensionless correlation was obtained to predict the degradation efficiency. This work provides a promising microfluidic technology for the process intensification of photocatalytic reaction and wastewater treatment.

HF-Free Microwave-Assisted Synthesis of Nano-Micro-Sized K2 SiF6 :Mn4+ for MicroLED Color Conversion.

Micro-light-emitting diodes (MicroLED) are considered to be the next generation of ideal display devices, with chip size requirements of less than 50µm. To meet its micron-scale pixel size, submicron luminescent materials are needed. Mn4+ doped fluoride phosphor, K2 SiF6 :Mn4+ (KSFM) as a red luminescent material with excellent narrow-band emission sensitivity to human eyes, has great potential as a color conversion material for full-color MicroLED. However, it is difficult to obtain small-size KSFM efficiently by conventional synthesis methods. Here, a simple HF-free strategy for the rapid batch synthesis of nano-micro-sized KSFM based on a microwave-assisted method is reported. The synthesized KSFM shows uniform morphology, average particle size is less than 0.2µm, and has 89.3% internal quantum efficiency under 455nm excitation. It exhibits excellent thermal stability (97.4%@423 K of the integrated emission intensity at 298 K) and prominent moisture resistance (81.9% of its initial relative emission intensity after immersing in water for 30min). By employing it as a red emitter, the authorsfabricate high-performance white LEDs with high luminous efficacy of 116.1lmW-1 and wide color gamut of 130.4% NTSC. In addition, self-luminous red-emitting arrays with a pixel size of 20 ×40µm are constructed by nanoimprinting as-synthesized KSFM.

Filamentation instability in the interaction of high-order Hermite cosh Gaussian laser beam and inhomogeneous plasmas

Based on high order paraxial theory and WKB approximation, filamentation instability in the interaction of high-order Hermite cosh Gaussian laser beam (HchG) and inhomogeneous plasma is studied. By changing the initial light intensity parameters and the non-uniformity of plasma density, the effect of different mode indices beams propagating in uniform and non-uniform plasmas on self-focusing filamentation structures is investigated. The results show that the HchG laser beam exhibits obvious self-focusing and filamentation phenomena along propagation distance in inhomogeneous plasma under the effect of the ponderomotive force. It is found that the mode index of HchG and plasma inhomogeneity have significant effects on filamentation instability, the higher order mode indices of HchG laser beam can strengthen filamentation instability, and plasma inhomogeneity also can enhance filamentation instability. The results provide a useful theoretical basis for effectively regulating the filamentation instability, increasing the peak laser power and designing narrower pulse width lasers.

Intervention reducing malaria parasite load in vector mosquitoes: No impact on Plasmodium falciparum extrinsic incubation period and the survival of Anopheles gambiae.

In the fight against malaria, transmission blocking interventions (TBIs) such as transmission blocking vaccines or drugs, are promising approaches to complement conventional tools. They aim to prevent the infection of vectors and thereby reduce the subsequent exposure of a human population to infectious mosquitoes. The effectiveness of these approaches has been shown to depend on the initial intensity of infection in mosquitoes, often measured as the mean number of oocysts resulting from an infectious blood meal in absence of intervention. In mosquitoes exposed to a high intensity of infection, current TBI candidates are expected to be ineffective at completely blocking infection but will decrease parasite load and therefore, potentially also affect key parameters of vector transmission. The present study investigated the consequences of changes in oocyst intensity on subsequent parasite development and mosquito survival. To address this, we experimentally produced different intensities of infection for Anopheles gambiae females from Burkina Faso by diluting gametocytes from three natural Plasmodium falciparum local isolates and used a newly developed non-destructive method based on the exploitation of mosquito sugar feeding to track parasite and mosquito life history traits throughout sporogonic development. Our results indicate the extrinsic incubation period (EIP) of P. falciparum and mosquito survival did not vary with parasite density but differed significantly between parasite isolates with estimated EIP50 of 16 (95% CI: 15-18), 14 (95% CI: 12-16) and 12 (95% CI: 12-13) days and median longevity of 25 (95% CI: 22-29), 15 (95% CI: 13-15) and 18 (95% CI: 17-19) days for the three isolates respectively. Our results here do not identify unintended consequences of the decrease of parasite loads in mosquitoes on the parasite incubation period or on mosquito survival, two key parameters of vectorial capacity, and hence support the use of transmission blocking strategies to control malaria.

Photocatalytic Oxidation of NO2 on TiO2: Evidence of a New Source of N2O5

AbstractN2O5 is an important intermediate in the atmospheric nitrogen cycle. Using a flow tube reactor, N2O5 was found to be released from the TiO2 surface during the photocatalytic oxidation of NO2, revealing a previously unreported source of N2O5. The rate of N2O5 release from TiO2 was dependent on the initial NO2 concentration, relative humidity, O2/N2 ratio, and irradiation intensity. Experimental evidence and quantum chemical calculations showed that NO2 can react with the surface hydroxyl groups and the generated electron holes on the TiO2, followed by combining with another NO2 molecule to form N2O5. The latter was physisorbed on TiO2 and had a low adsorption energy of −0.13 eV. Box model simulations indicated that the new source of N2O5 released from TiO2 can increase the daytime N2O5 concentration by up to 20 % in urban areas if abundant TiO2‐containing materials and high NOx concentrations were present. This joint experimental/theoretical study not only demonstrates a new chemical mechanism for N2O5 formation but also has important implications for air quality in urban areas.

Can perceived changes in autobiographical memories’ emotionality be explained by memory characteristics and individual differences?

ABSTRACT Recalling autobiographical memories (AMs) is closely tied to emotional experience. However, the emotionality associated with an event can change from occurrence to recall. Autobiographical memories show fixed affect (i.e., no change in emotionality), fading affect (i.e., decrease in emotional intensity), flourishing affect (i.e., increase in emotional intensity), and flexible affect (i.e., change of valence). The present study used mixed-effects multinomial models to predict perceived changes in positive and negative valence as well as intensity. Initial intensity, vividness, and social rehearsal were entered into the models as event level predictor variables, whereas rumination and reflection were entered into the models as participant level predictor variables. Analyses were based on 3950 AMs reported by 352 participants (18–92 years old) in response to 12 emotional cue-words. Participants rated the emotionality of each memory from the perspective of event occurrence and event recall. Only the predictors on the event level meaningfully distinguished between memories that stayed fixed in affect and memories that showed fading, flourishing, or flexible affect (R² values ranging from .24 to .65). The present results highlight the importance of considering different aspects of AMs and the ways they change emotionally to fully understand emotional experiencing in autobiographical memory.

Design of a narrow-band blue-emitting Rb2Ba3(P2O7)2:Eu2+ phosphor with low thermal quenching for plant growth LEDs

Phosphor-converted light-emitting diodes (pc-LEDs) are commonly used to regulate the light environment to control the growth rates and improve the production efficiency of plant. Among them, the exploration of blue-emitting phosphors with high efficiency, low thermal quenching and excellent spectrum resemblance matching with the plant response spectrum is still challenging. Herein, a narrow-band blue-emitting Rb2Ba3(P2O7)2:Eu2+ phosphor with high color purity of 93.4% has been developed. Under 345 nm excitation, it exhibits a blue emission band centered at 413 nm with a full width at half-maximum (FWHM) of 36 nm, and the emission spectrum of Rb2Ba3(P2O7)2:0.060Eu2+ sample shows 85.7% spectrum resemblance with the absorption spectrum of chlorophyll-a in the blue region from 400 to 500 nm. In addition, the temperature-dependent emission spectra demonstrate that the Rb2Ba3(P2O7)2:0.060Eu2+ phosphor has good thermal stability and small chromaticity shift, with the emission intensity dropping to 72.5% at 423 K of the initial intensity at 298 K and a chromaticity shift of 38 × 10-3 at 498 K. All results suggest that the blue-emitting Rb2Ba3(P2O7)2:Eu2+ phosphor has potential application in plant growth LEDs.

Photocatalytic degradation of organic dyes on magnetically separable barium hexaferrite as photocatalyst under conditions of visible light irradiation

In this paper, we present the first attempt to evaluate the role of carboxymethyl cellulose (CMC) as a chelating agent in the sol-gel auto-combustion method of producing barium hexaferrite (BaFe12O19). We also report the application of the system as a photocatalyst for dye degradation. The formation, morphology, and crystalline structure of the synthesized nanoparticles are determined using XRD, SEM, EDS, VSM, FTIR, and TEM techniques. High efficiency under visible light, with a band gap of 1.62eV and a BET surface of 17.93 m2/g, has been observed for the BaFe12O19 catalyst. The operating parameters, such as reaction time, initial dye concentration, light intensity, reusability, and dye type, are studied. Degradation rates as high as 98.26% (Kapp = 0.082min-1) and 89.07% (Kapp = 0.0743min-1) were obtained for cases of methylene blue and malachite green under conditions of visible light irradiations when BaFe12O19 was used. The BaFe12O19 catalyst has been shown to exhibit a high degradation performance for cationic dyes. Furthermore, BaFe12O19 magnetic nanoparticles show excellent reusability for dye degradation because the photocatalyst did not exhibit a significant decrease in its activity even after five runs (81.56%). As a result, the current study confirmed that photocatalytic degradation was a promising technology for saving water and treating wastewater formed from textile dye industries. The technique can be used to study the efficiency of photocatalytic degradation and understand the process of recycling waste effluents under conditions of minimized water use.

Modeling simulation on amplifying magnetic fields in supernova remnants with an intense laser

Local magnetic field enhancement in supernova remnants (SNRs) is a natural laboratory for studying the amplification effect of turbulent magnetic fields. In recent years, high-power laser devices have gradually matured as a tool for astronomical research that perfects observations and theoretical models. In this study, a model of the amplification effect of the turbulent magnetic field in SNRs by an intense laser is simulated using the radiation magnetohydrodynamic simulation program. We investigate and compare the evolutionary processes of unstable turbulence under different initial disturbance modes, directions, and intensities of external magnetic fields and obtain the magnetic energy spectrum and magnetic field magnification. The results demonstrate that the fluid motion associated with Rayleigh–Taylor instability will stretch the environmental magnetic field significantly, with an intensity amplified by two orders of magnitude. The environmental magnetic field perpendicular to the laser injection direction is decisive during magnetic field amplification which is necessary to clarify the physical mechanism of magnetic field amplification in SNRs. Furthermore, it will deepen the understanding of the interstellar magnetic field’s evolution. The results also establish a reference for laser-driven magnetized plasma experiments in a robust magnetic environment.

Box-Behnken modeling and optimization of visible-light photocatalytic removal of methylene blue by ZnO-BiFeO3 composite.

Box-Behnken experimental design was utilized to model and optimize the photocatalytic removal of methylene blue (MB) using ZnO-BiFeO3 composite under visible light (LED). Three catalysts with different ZnO:BiFeO3 molar ratios (2:1, 1:2, and 1:1) were synthesized successfully using the hydrothermal method. The structural, morphological, and optical properties of the synthesized photocatalysts were analyzed by X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectra (FT-IR), Ultraviolet Visible Spectrometer (UV-vis), Transmission Electron Microscopy(TEM), High-Resolution Transmission Electron Microscopy (HR-TEM), and Photoluminescence (PL) Spectrophotometry. FESEM showed the relatively uniform distribution of BiFeO3 crystalline particles on ZnO ones. UV-vis analysis showed that the photocatalytic performance of pure ZnO and BiFeO3 under visible light irradiation is weak, while ZnO-BiFeO3 with a 2:1 molar ratio composite with a bandgap of about 2.37eV showed high performance. This improved photocatalytic activity may be due to the heterogeneous synergistic effect of the p-n junction. In order to optimize the experimental conditions, four factors of initial MB concentration (5 to 20mg/L), pH (3 to 12), catalyst dosage (0.5 to 1.25mg/L), and light intensity (4 to 18 W) were selected as independent input variables. Box-Behnken experimental design method (BBD) suggested a quadratic polynomial equation to fit the experimental data. The results of the analysis of variance (ANOVA) confirmed the goodness of fit for the suggested model (predicted- and adjusted-R2 0.99). The optimum conditions for maximizing the photocatalytic MB degradation were found to be an initial MB concentration of 11mg/L, pH of 11.7, catalyst dosage of 0.716mg/L, and light intensity of 11.4 W. Under the optimum conditions, the highest photocatalytic MB degradation of 62.9% was obtained, which is in reasonable agreement with the predicted value of 69%.

Utility of the frailty score for predicting prognosis and individualizing treatment intensity in elderly patients with diffuse large B cell lymphoma.

The optimal dose intensity of chemotherapy for elderly patients with diffuse large B cell lymphoma (DLBCL) remains controversial because of concerns about adverse events and comorbidities related to the patients' frailty. This single-center study retrospectively analyzed patients aged ≥ 70 years who were newly diagnosed with DLBCL and received chemotherapy between 2004 and 2022. Survival outcomes and treatment-related mortality (TRM) were stratified according to geriatric assessment variables, and the influence of chemotherapy dose intensity on outcomes was assessed using the frailty score with a Cox hazards model with restricted cubic spline (RCS) in patients aged 70-79 years. In total, 337 patients were included. The frailty score accurately predicted prognosis (5-year overall survival [OS]: 73.1%, 60.2%, and 29.7% in fit, unfit, and frail patients, respectively; P < 0.001) and TRM (5-year TRM: 0%, 5.4%, and 16.8 in fit, unfit, and frail patients, respectively; P < 0.001). Cox regression with RCS demonstrated a linear association between dose intensity and survival outcomes. Initial dose intensity (IDI) and relative dose intensity (RDI) had a significant impact on OS in fit patients. However, IDI and RDI had no significant effect on survival in non-fit (unfit and frail) patients. The frailty score identified non-fit patients with poorer survival and a higher risk of TRM. While fit patients were likely to benefit from full-dose R-CHOP, unfit and frail patients would likely benefit more from attenuated R-CHOP. This study suggested a potential role for the frailty score in individualizing treatment intensity in elderly patients with DLBCL.

Novel red-emitting Cd2MgTeO6:Eu3+ phosphors with an abnormal thermal quenching for application in w-LEDs and potential fingerprint detection

A new series of red luminescent Cd2MgTeO6:xEu3+ (x = 0.5–50 mol%) phosphors was successfully synthesized through a high-temperature solid-phase reaction at 1000 °C. The synthesized phosphors were investigated for their phase purity, surface morphology, elemental distribution, and luminescence properties. Strong orange-red light emission (617 nm) was observed upon excitation at 398 nm, which was attributed to the electric dipole 5D0-7F2 transition of Eu3+. The optimal doping concentration was found to be x = 20 mol%. Concentration quenching mechanism was identified as the interaction of near-neighbor ions. The chromaticity coordinates of all the Cd2MgTeO6:Eu3+ samples were found to be located in the red region and were almost the same. The Cd2MgTeO6: 20 mol%Eu3+ phosphors exhibited an unusual thermal quenching behavior, maintaining 102% of the initial intensity, thus possessing excellent thermostability. Moreover, the manufactured white light diode demonstrated a good color rendering index (Ra = 89) with the coordinates of (0.344, 0.330) by the Commission International de L'Eclairage (CIE). Additionally, the Cd2MgTeO6: 20 mol%Eu3+ phosphor was surface-functionalized with oleic acid (OA) (Cd2MgTeO6: 20 mol%Eu3+@OA) to aid in the identification of Level I-III fingerprint details with high resolution and contrast. Good visualization of the latent fingerprint (LFP) was observed on different substrates. Therefore, Cd2MgTeO6:Eu3+ phosphors hold great promise for the visualization of w-LEDs and LFPs.

Optical Logic Gates Excited by a Gauss Vortex Interference Beam Based on Spatial Self-Phase Modulation in 2D MoS2.

Vortex beams with optical orbital angular momentum have broad prospects in future high-speed and large-capacity optical communication. In this investigation of materials science, we found that low-dimensional materials have feasibility and reliability in the development of optical logic gates in all-optical signal processing and computing technology. We found that spatial self-phase modulation patterns through the MoS2 dispersions can be modulated by the initial intensity, phase, and topological charge of a Gauss vortex superposition interference beam. We utilized these three degrees of freedom as the input signals of the optical logic gate, and the intensity of a selected checkpoint on spatial self-phase modulation patterns as the output signal. By setting appropriate thresholds as logic codes 0 and 1, two sets of novel optical logic gates, including AND, OR, and NOT gates, were implemented. These optical logic gates are expected to have great potential in optical logic operations, all-optical networks, and all-optical signal processing.

Development of an Improved Sulfur-Oxidizing Bacteria-Based Ecotoxicity Test for Simple and Rapid On-Site Application.

Microbial toxicity tests are considered efficient screening tools for the assessment of water contamination. The objective of this study was to develop a sulfur-oxidizing bacteria (SOB)-based ecotoxicity test with high sensitivity and reproducibility for simple and rapid on-site application. To attain this goal, we developed a 25 mL vial-based toxicity kit and improved our earlier SOB toxicity test technique. The current study applied a suspended form of SOB and shortened the processing time to 30 min. Moreover, we optimized the test conditions of the SOB toxicity kit in terms of initial cell density, incubating temperature, and mixing intensity during incubation. We determined that 2 × 105 cells/mL initial cell density, 32 °C incubating temperature, and 120 rpm mixing intensity are the optimal test conditions. Using these test conditions, we performed SOB toxicity tests for heavy metals and petrochemicals, and obtained better detection sensitivity and test reproducibility, compared to earlier SOB tests. Our SOB toxicity kit tests have numerous advantages, including a straightforward test protocol, no requirement of sophisticated laboratory equipment, and no distortion of test results from false readings of end-points and properties of test samples, making it suitable for simple and rapid on-site application.

Enzyme-free carbon dots@MgO nanocomposite as an efficient sensor for on-site detection and degradation of paraoxon toxins

Serial nanocomposites consisting of blue fluorescent carbon dots (B-CDs) and MgO nanoparticles were facilely prepared. Then on-site detection and degradation of ethyl-paraoxon were achieved and evaluated. It was revealed that ethyl-paraoxon was firstly decomposed into p-nitrophenol by MgO. Then, p-nitrophenol could significantly quench the fluorescence of decorated B-CDs due to an inner filter effect (IFE). The 0.05B-CDs@MgO showed excellent comprehensive performance among the serial xB-CDs@MgO samples due to its relatively high degradation ability towards ethyl-paraoxon and potent initial fluorescence emission intensity at an excitation wavelength of 360 nm between pH 4 and 10. Finally, based on the IFE, on-site paper sensors via color recognition app on a smartphone were explored compared with a conventional fluorescence spectrometer. Both the quantitative fluorescence intensities and G/B values showed the multi-piecewise linear correlations to ethyl-paraoxon concentration up to 3000 μg/mL in river water with a limit of detection to 0.06 μg/mL and 3.48 μg/mL as well as high recovery rates between 99%-102% and 95%–116%, respectively. The in vitro cytotoxicity and phytotoxicity assessment of the 0.05B-CDs@MgO revealed dose-dependent effects. Such portable and integrated fluorescent B-CDs@MgO nanocomposites on paper arrays show excellent potential in shortening the detection time and reducing the detection cost as a new strategy for the on-site quantitative detection and degradation of ethyl-paraoxon in actual river water.

Experimental Study of Turbulence Response in a Slowly Accelerating Turbulent Channel Flow

AbstractAn investigation of flow acceleration from initial statistically steady turbulent flow to final statistically steady turbulent flow is conducted experimentally using particle image velocimetry (PIV) and constant temperature anemometry (CTA). The turbulence response is investigated as the acceleration periods and acceleration rates are varied in a controlled fashion. This work expands the research by Mathur et al. (2018, “Temporal Acceleration of a Turbulent Channel Flow,” J. Fluid Mech., 835, pp. 471–490.) studying slower and longer transient flows. It also complements the numerical studies of a step increase in the flowrate of (He and Seddighi, 2013, “Turbulence in Transient Channel Flow,” J. Fluid Mech., 715, pp. 60–102. and He and Seddighi, 2015, “Transition of Transient Channel Flow After a Change in Reynolds Number,” J. Fluid Mech., 764, pp. 395–427.). The results obtained from the current investigations are qualitatively similar to those obtained previously. Consistent with previous studies, the response of turbulence in the current slow transient flow is again characterized by a laminar-turbulent transition. The initial increase of the flow development among the cases investigated can be categorized as faster, medium, and slower responses. Modifications are made to the equivalent Reynolds number and the initial turbulence intensity proposed earlier in order to account for the slow accelerating flow rates and the continuous change of the bulk velocities of the cases investigated. It has been shown that the critical equivalent Reynolds number based on these modifications and the initial turbulence intensity are well correlated for all cases investigated and a power-law relation is established.

Comparison of Fluorescence of Tooth Enamel, Resin Composite, Lithium Disilicate and Monolithic Zirconia Under Thermocyclic Ageing

The aim was to compare the fluorescence intensity of tooth enamel, resin composite, lithium disilicate, and monolithic zirconia before and after thermocyclic aging. Lithium disilicate (LD) and monolithic Zirconia ceramic samples were fabricated with the CAD-CAM method. Resin composite specimens, of shades A1, A2, and A3, were prepared with photo-polymerization and putty mold. Extracted second molar teeth were obtained and sectioned to produce enamel specimens. Fluorescence assessment prior to thermocycling was performed using flurolog-Qm system before and after thermocycling. Samples were exposed to thermocycling (TC) for 30,000 cycles in distilled water at 5 °C and 55 °C for 30 s each, with 5 s between the baths. The means and standard deviations were compared using, t-test, analysis of variance, and Tukey–Kramer multiple comparisons test. The initial fluorescence intensities before thermocyclic ageing were highest in LD ceramic specimens (42579±817.1). The lowest fluorescence was observed in monolithic Zr specimen 14750±584.7. The reduction in fluorescence intensity after thermocyclic ageing was highest in LD specimens, however, the lowest difference was noted in composite A3 specimens. LD ceramic showed significantly high fluorescence among all materials before and after ageing. The fluorescence of the tested materials reduced with ageing and is expected to decrease intraorally with time.