τR Values Research Articles

High-performance Ga2O3 solar-blind UV photodetectors via film growth regulation and surface state engineering

Gallium oxide (Ga2O3) with a wide bandgap is emerging as one of the most promising candidates for solar-blind photodetectors (SBPDs). However, the practical application of Ga2O3-based SBPDs is impeded by substantial defects-related leakage currents, sluggish response speed, and high-cost, making their practical applications face great challenges. Here, we proposed strategic films growth regulation and surface state engineering to grow high-quality yet economical β-Ga2O3 films, thereby achieving high-performance SBPDs. High-resolution transmission electron microscopy revealed the presence of high-quality films with an extremely regular arrangement of β-Ga2O3 (2‾01) planes. The full width at half maximum and root mean square roughness values are 0.07° and 0.716 nm, respectively. The β-Ga2O3 films demonstrated a significant reduction in VO concentrations after O2/N2 plasma treatment. This process can effectively minimize thermal damage to the sample surface while retaining highly reactive free radicals. The photocurrents of devices can be further enhanced, leading to a larger PDCRs of 8.6 × 107, through N2 plasma treatment. Moreover, the films effectually suppress the persistent photoconductivity effect with τr and τd values of 5.31/0.97 s and 0.49/0.87 s before and after N2 plasma treatment, respectively. We have demonstrated the influence mechanism of O2/N2 plasma treatment on photoelectronic performance. This study provides a practical approach to growing high-quality β-Ga2O3 films and preparing high-performance but low-cost Ga2O3-based SBPDs.

Conformational states of NADH in water–alcohol solutions studied by molecular dynamics simulations

Redox reactions in living cells involving a coenzyme nicotinamide-adenine-dinucleotide (NAD) are stereospecific and depend on NAD conformation states and on the structure of enzyme binding sites. Therefore, information on NAD conformation states in various environments is important for understanding of the mechanisms of redox reactions. In this paper the structural dynamics of reduced nicotinamide-adenine-dinucleotide (NADH) in water–methanol and water–ethanol solutions was investigated by means of molecular dynamics simulations. The trajectory analysis revealed three stable conformation groups characterized by the distance RNA−AD between adenine and nicotinamide centers of mass: folded (RNA−AD< 5.5 Å), intermediate (5.5 Å <RNA−AD< 12 Å) and unfolded (RNA−AD> 12 Å). It was shown that conformation equilibrium shifted from the folded conformation group at low alcohol concentrations towards the intermediate conformation group at high alcohol concentrations, while the fractional concentration of unfolded conformation group remained almost constant. The nicotinamide and adenine rings were found to be almost parallel in folded conformations and perpendicular in intermediate conformations, while no preferable positions of the rings were found in unfolded conformations. The results obtained were used for the analysis of experimentally determined rotational diffusion times τrexp in NADH in water–methanol and water–ethanol mixtures. Comparison between the calculated and experimental τr values using the generalized Stokes–Einstein–Debye equation allowed for determination of the wettability coefficient C and effective molecular volume Vm as a function of alcohol concentration. The coefficient C was found to be always less than unity and have a minimum at 40% of alcohol which was more pronounced for ethanol than for methanol mixtures. This dependence was attributed to the influence of solution viscosity that has a maximum at 40% of alcohol. The effective molecular volume Vm was found to be practically constant at alcohol concentrations below 60% and rise dramatically at higher alcohol concentrations. This dependence was attributed to the solvation of NADH at high alcohol concentrations.

A virtual tracer experiment to assess the temporal origin of root water uptake, evaporation, and drainage

AbstractThe temporal origin of drainage, evaporation, and root water uptake (RWU) are indicators of ecosystem functioning that shed light on how natural and anthropogenic disturbances affect plant resilience and aquifer vulnerability. A virtual tracer experiment was carried out in HYDRUS‐1D using data from a soil lysimeter planted with winter rye in Austria. The RWU (τR), evaporation (τE), and drainage (τD) transit times (τ) were determined by using the actual dispersivity optimized in a prior study. First, τR and τD were compared to RWU (τPT,R) and drainage (τPT,D) advective transit times estimated using the particle tracking algorithm. The τR values were in agreement with τPT,R while large discrepancies were detected when estimating drainage transit times using the two approaches. A sensitivity analysis revealed that dispersivity had a mild, poor, and strong influence on τR, τE, and τD. The longitudinal dispersivity describes how a tracer spreads along the flow paths. The longer the flow paths, the more dispersion affects the tracer transport. On average, water parcels originating from rainfall in the growing season took 18 and 201 days to reach the roots (with RWU being 21% of rainwater) and the soil profile bottom (with drainage being 36% of rainwater), respectively. In contrast, 10% of rainwater that fell in the dormant season became RWU after 264 days, while 79% became drainage after 294 days. The temporal origin of water can be explored in other plots by using the guidelines proposed in this study.

Orange and yellow emissions through Sm3+ and Tb3+/Sm3+ doped potassium-zinc phosphate glasses for WLED applications

A spectroscopic analysis of potassium-zinc phosphate glasses activated with Sm3+ and Tb3+/Sm3+ is presented. Both glasses showed high transparency in the visible region with direct and indirect band gap energy values of 3.70 and 3.96 eV, and 3.85 and 4.22 eV for the Sm3+ doped and Tb3+/Sm3+ co-doped glasses, respectively. The Urbach energies estimated for the single doped and codoped glasses resulted to be 0.26 and 0.24 eV, respectively. Upon 408 nm excitation, the Sm3+ singly doped glass exhibited a 592 nm orange emission with correlated color temperature (CCT) and color purity (CP) of 1677 K and 99%, respectively. The Judd-Ofelt (JO) theory was applied to value the radiative parameters of the Sm3+ doped glass. It was found JO parameter values of Ω2 = 1.93 × 10−20 cm2, Ω4 = 3.72 × 10−20 cm2 and Ω6 = 2.85 × 10−20 cm2, which lead to peak stimulated emission cross-section (σpeak), gain bandwidth (σpeak× Δλeff) and optical gain (σpeak× τR) values of 4.49 × 10−22 cm2, 9.70 × 10−28 cm3 and 14.14 × 10−25 cm2s for the main samarium 4G5/2 → 6H7/2 emission. Such values resulted to be comparable or higher than those reported for sodium-tellurite and borate-silicate-based glasses. The emission in the Tb3+/Sm3+ co-doped glass under Tb3+ and Sm3+ co-excitation displayed yellow (λex = 304, 318 and 377 nm) and orange (λex = 344 and 360 nm) emission tonalities with CP values up to 88 and 97%, respectively. The overlapping of Tb3+ emission bands with those of Sm3+ excitation suggested the existence of energy transfer from terbium to samarium, which according to the Tb3+ emission decay behavior is non-radiative. Such a process arises from the Tb3+: 5D4 energy level with an efficiency of 0.41 within Tb3+-Sm3+ clusters.

Rotational dynamics study of structurally similar (medium sized) coumarin dyes in aqueous mixtures of DMSO and DMA

The rotational diffusion dynamics of four medium sized, structurally similar, polar Coumarin dyes namely, Coumarin-478 (C478), Coumarin-480 (C480), Coumarin-519 (C519), and Coumarin-523 (C523) has been studied at room temperature in aqueous DMSO and aqueous DMA by using steady state and time resolved fluorescence depolarization techniques. All the probes exhibited faster rotation in organic solvent rich zone than in water rich zone that resulted in a downward bent “hook profile” of rotational reorientation time as a function of viscosity. A faster rotational diffusion is observed for C523 in contrast to the other three solutes in both the aqueous solvent mixtures. The difference between τr values at iso-viscous points is smaller in case of aqueous DMA than in aqueous DMSO which reveals the importance of dielectric friction. Since both solutes and solvents are polar in nature, the Nee-Zwanzig (NZ) and van der Zwan and Hynes (ZH) dielectric friction theories have been used along with Stokes-Einstein-Debye (SED) hydrodynamic theory to assess the experimental results and understand the microfriction experienced by the solute. An important aspect of this work is to establish a relation between viscosity and hydrogen bond strengths at varying compositions of solvent mixtures as well as hydrogen bond strength between solute and solvents with the help of Gaussian 09 software. The H-bond strength thus calculated is found to be higher at a composition where the viscosity is the maximum. It provides an additional support to the experimental results.

Rolling Shear Properties of Cross-Laminated Timber Made from Australian Plantation Eucalyptus nitens under Planar Shear Test

With the increasing availability of fast-growing Eucalyptus plantation logs in Australia in recent years, the timber manufacturing sector has become interested in discovering the opportunities of producing value-added timber products from this resource. Cross-laminated timber (CLT) could be a potential sustainable product recovered from this resource and supply material for commercial buildings. Shear of the inner cross-laminates, known as rolling shear, is one of the governing factors in serviceability and limit state design for this product under out-of-plane loading. This study evaluated the rolling shear (RS) properties of CLT with heterogonous layup configurations using different structural grade Eucalyptus nitens (E. nitens) timber under the planar shear test. Based on the results, Gr and τr values were shown to be significantly correlated with the density of the CLT panel. There was also a positive correlation between the RS modulus and MOR of the CLT panel. The specimens with high MOE in the top and bottom layers indicated the highest τr and Fmax values. This indicated that using high-grade boards in the top and bottom lamellae plays an important role in increasing the RS strength, whereas using them in the cross-layer has a positive contribution in increasing shear modulus. The maximum observed RS strength and modulus ranged from 2.8–3.4 MPa and 54.3–67.9 MPa, respectively, exceeding the RS characteristic values of the resource. The results obtained in this study were comparable to those recommended in European standards for softwood CLT, demonstrating the potential use for eucalypt timber boards in CLT production. This paper provides an important insight into supporting the potential engineering applications of CLT panel products fabricated with eucalypt plantation.

Heat vortices of ballistic and hydrodynamic phonon transport in two-dimensional materials

Heat conduction in solid materials may behave like fluid dynamics when normal (N) scattering dominates phonon transport. In this hydrodynamic regime, the heat vortices have been predicted with frequency-independent relaxation time. So can this phenomena appear in other regimes? And what are the differences? In order to answer these questions, in this work, the heat vortices in two-dimensional materials are investigated based on the frequency-dependent phonon Boltzmann transport equation (BTE) under the Callaway model. We find that apart from the hydrodynamic regime, the heat vortices can appear in the ballistic and other transition regimes, which is a wider window of heat vortices compared to previous study (Fig. 1). The differences of heat vortices in the ballistic and hydrodynamic regime are investigated. In ribbon structure, the vortices sizes increase with system length in the ballistic regime but are confined by the system width in the hydrodynamic regime. In porous structures, the critical values of τR (or τN) about when the heat vortices disappear (or when the vortices size starts to become smaller) are found.

Transition intensity analysis and emission properties of Eu3+: Bi2ZnOB2O6 acentric biaxial single crystal

Optical absorption, excitation and emission spectra of trivalent europium (Eu3+) ions in Bi2ZnOB2O6 nonlinear single crystal obtained by the Kyropoulos method were investigated. Strong, orange-red emissions of Eu3+ centered at 592 and 615 nm originate mainly from the 5D0 →7F1 and 7F2 transitions, respectively. Judd-Ofelt intensity parameters for f-f transitions were derived from the room temperature (300 K) emission spectra and were used to calculate the radiative transition rates (AR), lifetimes (τR) and branching ratios β for 5D0 excited state of Eu3+. The calculated values of τR and β were compared with the measured values for 5D0 level. The 5D0 fluorescence decay in 0.5 %Eu3+:Bi2ZnOB2O6 was exponential with time constant of 1.1 ms at room temperature. The stimulated emission cross-sections σ were also evaluated for the 5D0 → 7FJ transitions for the first time in this system. We also report on laser site selective spectroscopy of a Eu3+: Bi2ZnOB2O6 confirming the Eu3+ distribution into two sites. The site assignments of Eu3+ ions were discussed on the base of both optical spectroscopy results and structural analysis.

Optimization of rare earth (Er3+) doping level in lead zinc phosphate glass through Judd-Ofelt analysis

We have investigated via Judd-Ofelt (JO) analysis a new system of PbO, ZnO based P2O5 glass in metaphosphate regime spanning a range of Er3+ doping concentration, 0.6–1.0 mol %. The results are compared between as prepared (unannealed) and annealed samples to converge to the optimum doping regime for laser emission. Using the JO parameters, doping dependence of spontaneous emission probability (A), lifetime of excited state (τR) and luminescence branching ratio (β) of Er3+ have been investigated. The largest value of τR = 15.9 ms is achieved for 4I13/2 state in 1% Er doped as prepared sample. Such a value of τR is ~3.5 times larger than those for other Er3+ doped glass systems. A parameter (χ) suitable to compare between 4I11/2 → 4I15/2 and 4I13/2 → 4I15/2 transitions in Er3+ has been proposed. Along with the largest magnitude of τR, the maximum value of χ occurs at the same doping level of 1% in unannealed sample. For 4I13/2 → 4I15/2 emission, 100% of β value occurs. It is shown that all these conditions together with χ > 1 lead to the conclusion that 4I13/2 → 4I15/2 transition (1540 nm) will dominate over 4I11/2 → 4I15/2 emission (987 nm). In the admixed laser emission, 1540 nm component will be the largest at 1 mol % doping for unannealed sample.

Optical studies on Tb3+: Dy3+ singly and doubly doped Borosilicate glasses for white light and solid state lighting applications

Host (H), Singly and co-doped Dy3+/Tb3+ ions borosilicate glasses (S1-S7) were fabricated by a traditional melt-quenching-annealing method to investigate their luminescence properties as well as their suitability for the development of SSL (solid-state lighting) and W-LEDs (white light-emitting diodes). The X-ray diffraction profile indicates the amorphous structure nature of the prepared glasses. The J-O (Judd-Ofelt) intensity parameters Ωt(t=2,4,6) are evaluated for both singly Dy3+, Tb3+ doped glasses according to their absorption spectrum. The Ω2 parameter of Dy3+ ion has higher value which indicates a higher degree of Dy3+ covalency and the neighbour ligands while Tb3+ ion in a lower degree of covalency where its Ω2 has low value. Also the radiative parameters for both singly doped ions (S1 and S2) are computed like probability of transition (AT), branching ratio (βr) and radiative lifetime (τr) for different bands. Further, both singly doped glasses reflects good properties for lasing application where the 4F9/2 manifold of S1 (0.5 mol% Dy3+) has radiative lifetime (τr) value of 1376 µs and higher value of (AT:447.02 s−1) in addition to branching ration of (βr:61.5%) for the (4F9/2→9H13/2) transition (576 nm). At the same time, S2 (0.5 mol% Tb3+) glass show a higher lifetime (τr:3753) for 5D4 level and (AT: 92.94 s−1) while the branching ratio for 5D4→7F5 band at 546 nm wavelength is (βr: 34.9%). The radiative emission properties were investigated according to the Tb3+ concentration increments. The mutual energy transfer (ET) occurrence between both ions (Dy3+, Tb3+) is demonstrated through the varying of their emission intensities. Furthermore, The chromaticity (x,y) color coordinates were evaluated according to the emission spectra of aforementioned glasses under excitation of 368 nm and 348 nm were found to be located in the white light color region of the CIE chromaticity color diagram. Also, from color-coordinated the color correlated temperature (CCT) is computed were found to be at high values (>4000). Thus, the fabricated glasses are suggested as a useful luminescence material for solid-state lightening as well as cool white light applications.

Epidemic threshold for the SIRS model on the networks

We study the phase transition from the persistence phase to the extinction phase for the SIRS (susceptible/ infected/ refractory/ susceptible) model of diseases spreading on the networks. We derive an analytical expression for the probability of the descendants to reinfect their ancestors. We find that, in the case of the recovery time τR is larger than the infection time τI, the infection will flow directionally from the ancestors to descendants however, the descendants will be unable to reinfect their ancestors during the time of their illness. This behavior leads us to deduce that, if the infection rate λ is high enough so that any infected node on the network infects all its neighbors during its infection time, then, the SIRS model on the network evolves to extinction state, where all the nodes on the network become susceptible. Moreover, we assert that, in order to the disease spreads frequently throughout the nodes of the networks, the loops on the network are necessary, which means the clustering coefficient will play an important role in this model. Hence, unlike the other models such as SIS model and SIR model, the SIRS model has two critical thresholds which separate the persistence phase from the extinction phase when τI<τR, i.e. for fixed values of τI and τR there are two critical points for infection rate λ1 and λ2, where epidemic persists in between of those two points. We confirm those results numerically with the simulation of a regular one dimensional SIRS system and small world network.

Absorption intensity analysis and emission properties KEu(PO3)4 and KEuxY1-x(PO3)4 crystals

Abstract Optical absorption, excitation and emission spectra of Eu3+ ions in stoichiometric KEu(PO3)4 and KEuxY1-x(PO3)4 crystals were investigated. Strong, red emissions of Eu3+ centered at 617 and 700 nm originates mainly from the 5D0 →7F2+7F4 transitions respectively. Judd-Ofelt intensity parameters for f-f transitions were derived from the emission spectra and also from the integrated absorption spectra. These parameters were used to calculate the radiative transition rates (AR), lifetimes (τR) and branching ratios β for 5D0 excited state of Eu3+. The calculated values of τR and β were compared with the measured values for 5D0 level. The 5D0 fluorescence decay time in pure KEu(PO3)4 was exponential and quite long, of 3.93 ms. The stimulated emission cross-sections σ were also evaluated for the 5D0 → 7FJ transitions for the first time in this system.

Spectroscopic studies of Dy3+ ions doped barium lead alumino fluoro borate glasses

Barium lead alumino fluoro borate (BaPbAlFB) glasses doped with Dy3+ ions were prepared by using melt quenching technique and characterized using various spectroscopic techniques to understand their usage in photonic devices. The SEM and EDX spectral studies were performed on the as prepared glasses to understand the glassy nature and elemental analysis respectively. The weight loss in the BaPbAlFB glass has been studied by the TGA. Judd-Ofelt (J-O) theory has been applied to the measured oscillator strengths of the absorption spectral features to evaluate radiative parameters for the prominent emission transitions of Dy3+ ions in BaPbAlFB glasses. The photoluminescence (PL) spectral measurements show concentration quenching beyond 1.0 mol% of Dy3+ ions in the as prepared glasses. The decay profiles observed for higher concentration of Dy3+ ions in these glasses are well fitted to Inokuti-Hirayama (IH) model to understand the energy transfer mechanism involved in the as prepared glasses. The experimental lifetimes (τexp) measured from the decay spectral features are correlated with radiative lifetime (τR) values to understand the quantum efficiency (η) of the as prepared glasses. From the PL spectra, colorimetric parameters such as CIE coordinates, correlated color temperature (CCT) and yellow-to-blue (Y/B) intensity ratios have been estimated to understand the usage of these glasses in photonic devices such as white LEDs and lasers.

Increased stability of nitroxide radicals in ionic liquids: more than a viscosity effect.

Radical stability has been subject to continuous research due to its importance in polymerization as well as in all-organic batteries. Recently, the SOMO-HOMO conversion was identified as the main factor in controlling the stability of distonic radicals, for which the negative charge resides on the same molecule. Based on this finding, the idea of ionic liquids stabilizing radicals was hypothesized in this study. A series of ionic liquids were tested in EPR measurements of the 3-carboxy-2,2,5,5-tetramethyl-pyrroline-1-oxyl. Unusually high rotational diffusion constants (τR), 4 times larger compared to conventional media such as dichloromethane (DCM), were recorded at room temperature. This finding could only be explained by a strong interaction existing between the radical and ionic liquid ions, which was confirmed with quantum chemical calculations, with interaction energies falling between -17.1 kJ mol-1 for tetramethylphosphonium tetrafluoroborate and -85.6 kJ mol-1 for 1,3-dimethylimidazolium triflate. Elevated temperature measurements performed at 80 °C reduced the viscosity of the ionic liquids to that of DCM, while the τR values remained relatively high, thus further confirming that the rotational hindrance occurred due to radical-ionic liquid interactions. The calculated interaction energies between the radical and ionic liquids ions were also found to correlate well with experimental rotational diffusion constants, thus offering us a valuable tool in tailoring ionic liquids for enhanced stability of nitroxide radicals. The findings of this study showcase the ability of ionic liquids to reduce reactivity of nitroxides without the need for any chemical modification of the radical.

Investigations on the spectroscopic properties of Dy3 + ions doped Zinc calcium tellurofluoroborate glasses

A new series of Dy3+ doped (30–x)B2O3+30TeO2+20CaCO3+10ZnO+10ZnF2+xDy2O3 (x=0.01, 0.1, 0.5, 1, 2 and 3 in wt%) Zinc calcium tellurofluoroborate glasses were prepared and their structural, luminescence and excited state dynamics have been studied and reported. The structural properties have been characterized through XRD and FTIR studies to confirm the amorphous nature and to explore the presence of fundamental stretching vibrations. The bonding parameters (δ and β), optical band gap, Urbach's energy, oscillator strengths and Judd-Ofelt (JO) intensity parameters were calculated from the absorption spectra. The JO intensity parameters and the Y/B intensity ratio values have been used to explore the nature of the bonding and asymmetry around the Dy-ligand field environment. The luminescence properties of the present Dy3+ doped glasses have been analyzed through luminescence excited state dynamics and radiative properties such as transition probability (A), stimulated emission cross-section (σPE) branching ratio (β) and radiative lifetime (τR) values. The combination of dominant blue (4F9/2→6H15/2) and yellow (4F9/2→6H13/2) emissions generates white light emission in the CIE chromaticity diagram thus suggests that the present Dy3+ doped glasses are suitable for white light applications. The lifetime of the 4F9/2 excited state is found to decrease with the increase in Dy3+ ion content and the concentration quenching of the Dy3+ ions emission could be ascribed due to the resonant energy transfer and cross-relaxation processes. The non-exponential behavior of the decay curves has been analyzed with Inokuti-Hirayama model and the interaction between the Dy3+ ions is of electric dipole-dipole in nature.

Spectroscopic properties and Judd–Ofelt analysis of Eu3+ in Y4Al2O9 crystals

Optical absorption, excitation and emission spectra of Eu3+ ions in Y4Al2O9 were investigated. Judd-Ofelt intensity parameters for f-f transitions were derived from the emission spectra and also from the integrated absorption spectra. These parameters were used to calculate the total spontaneous emission probabilities (AR), lifetimes (τR) and branching ratios (βR) for 5D0 excited state of Eu3+. The calculated values of τR and βR are compared with the measured values for 5D0 level. The stimulated emission cross-sections σ were also evaluated for the 5D0 → 7FJ transitions for the first time in this system.

New multifunction materials with both electrorheological performance and luminescence property

Novel multifunctional materials, the composites AlOOH-NaYFTb5 and AlOOH-NaYFTb10, containing AlO(OH) and β-NaYF4:5%Tb3+, have been synthesized via a facile hydrothermal route and a simple grinding method. The boehmite [AlO(OH)], yttrium nitrate [Y(NO3)3·6H2O], terbium nitrate, [Tb(NO3)3·6H2O], sodium citrate (Na3C6H5O7·2H2O) and sodium fluoride (NaF) were used as starting materials. The composition, electrorheological (ER) performance, and luminescence property of the functional materials were studied. Our results show that the composites not only have good electrorheological (ER) performance, but also have good optics property. The relative shear stress τ r (τ r = τ E/τ 0, τ E and τ 0 are the shear stresses at the electric field strength E = 4 and 0 kV/mm, respectively) values of the suspension (25 wt.%) of AlOOHNaYFTb5 material in silicone oil are all larger than 50 in a shear rate ranging from 0.06 to 26 s−1, the τr value reaches 1333 at a shear rate of 0.06 s−1. The material with such high ER activity and favorable luminescence performance is advantageous in its application as a multifunctional material.

Synthesis of oligomer betaine surfactant (DDTPA) and rheological properties of wormlike micellar solution system

Novel oligomer betaine surfactant penta sodium N, N′, N″- dodecyl diethylene triamine pentaacetic acid (DDTPA) with three dodecyls, five carboxylic acid groups and three quaternary ammonium were synthesized through two steps in this paper. Rheological properties of mixed oligomer betaine surfactant DDTPA/anionic surfactant sodium dodecylsulfonate (SDS) solution systems were studied as functions of SDS concentration, inorganic salt KCl dosage and temperature. Stable and dynamic viscoelastic measurements were carried out to investigate the characters of wormlike micelles formed in certain condition. In the 2.5wt% DDTPA, 4wt% KCl and SDS system, the optimal SDS concentration is 1.2wt%, at which the viscosity reaches a maximum. Interestingly, with adding inorganic salt KCl to mixed surfactant solution(2.5wt% DDTPA, 1.5wt% SDS), the water-like fluid turns into gel-like viscoelastic wormlike micellar solution immediately owing to the screening electrostatic repulsion among the surfactant charged groups by counterions. When KCl concentration is 3wt%, the micellar solution obtains a peak value in viscosity. For the system with 2.5wt% DDTPA, 1.5wt% SDS, 4wt% KCl, the micellar contour length decreases with increasing temperature, leading to an exponential decrease in the values of η0 and τR. This work provides a clear understanding of the profound relationship between surfactant wormlike micellar characteristic and the rheological properties. The dynamic viscoelastic behavior of wormlike micelles usually fits for the Maxwell mode in low oscillation frequency region, but in medium and high frequency region it fits for t the modified Maxwell model.

Modifier effect on the spectroscopic properties of tellurofluoroborate glasses containing Sm3+ ions

The effect of modifier oxide on the structural and optical properties of Sm3+ doped tellurofluoroborate glasses with the chemical composition (50–x)B2O3+xCaCO3+30TeO2+ 10ZnO+9ZnF2+1Sm2O3 have been studied by varying B2O3 and CaCO3 content. The fundamental stretching vibrations in the prepared glasses were investigated using FTIR and Raman spectral analysis. The optical behavior and the excited state energy transfer studies have been carried out by exploring the absorption, photoluminescence and decay spectra. The XRD spectrum was used to confirm the amorphous nature. The Nephelauxetic shift on the higher energy of the absorption spectra and the bonding parameter studies reveal the ionic nature of the Sm–O metal–ligand bond. Judd–Ofelt (JO) analysis have been used to determine branching ratio, radiative lifetime and emission cross-section of the reddish-orange emission originating from the 4G5/2 level to the 6H5/2, 6H7/2, 6H9/2 and 6H11/2 levels of the Sm3+ ion. The color of the emission has been demonstrated through CIE 1931 color chromaticity diagram. The non-exponential behavior of the 4G5/2 decay curves exhibit various energy transfer mechanism like non-radiative relaxation due to the multiphonons in the title glasses and the cross-relaxation among the Sm3+ ions. The increase in experimental lifetime of the 4G5/2 level with the addition of CaCO3 content is due to the reduction in the higher phonon energy and minimal absorption of OH free radicals. Among the prepared glasses, Sm20CTFB glass exhibit higher βR, σPE values pertaining to the 4G5/2→6H7/2 transition of the Sm3+ ions. The higher quantum efficiency (η), σPE×λeƒƒ and σPE×τR values for all the title glasses suggest that these glasses are good candidates for the realization of reddish-orange visible lasers and for the fabrication of photonic devices.

Difference in the hydration water mobility around F-actin and myosin subfragment-1 studied by quasielastic neutron scattering

Hydration water is essential for a protein to perform its biological function properly. In this study, the dynamics of hydration water around F-actin and myosin subfragment-1 (S1), which are the partner proteins playing a major role in various cellular functions related to cell motility including muscle contraction, was characterized by incoherent quasielastic neutron scattering (QENS). The QENS measurements on the D2O- and H2O-solution samples of F-actin and S1 provided the spectra of hydration water, from which the translational diffusion coefficient (DT), the residence time (τT), and the rotational correlation time (τR) were evaluated. The DT value of the hydration water of S1 was found to be much smaller than that of the hydration water of F-actin while the τT values were similar between S1 and F-actin. On the other hand, the τR values of the hydration water of S1 was found to be larger than that of the hydration water of F-actin. It was also found that the DT and τR values of the hydration water of F-actin are similar to those of bulk water. These results suggest a significant difference in mobility of the hydration water between S1 and F-actin: S1 has the typical hydration water, the mobility of which is reduced compared with that of bulk water, while F-actin has the unique hydration water, the mobility of which is close to that of bulk water rather than the typical hydration water around proteins.