Maximum Cross Section Research Articles

Intense mid-infrared emission at 3.9 µm in Ho3+-doped ZBYA glasses for potential use as a fiber laser.

Intense mid-infrared emission at 3.9 µm in Ho3+-doped ZBYA glasses with direct upper laser level (Ho3+:5I5) pumping at a wavelength of 888 nm is reported for the first time, to the best of our knowledge. Spectroscopic parameters were determined using the Judd-Ofelt theory and the measured absorption spectrum. The maximum emission cross section of the Ho3+-doped ZBYA glass is estimated to be 2.7×10-21cm2 at 3906 nm. Additionally, fluorescence spectra and lifetimes of ZBYA glasses with different Ho3+ ion doping concentrations were measured. The results provide theoretical and experimental basis for better selection of rare-earth-doped matrix glasses to achieve a fluorescence output centered on a wavelength of 3.9 µm.

Fabrication of a hybrid-cladding tellurite glass fiber doped with Tm3+ and Ho3+

To improve the mechanical properties of tellurite glass fiber, a hybrid-cladding optical fiber with Tm3+/Ho3+ co-doped TeO2-WO3-La2O3 glass core, tellurite glass inner cladding and phosphate glass outer cladding was proposed and fabricated by rod in tube and twice drawing method in this work. The spectroscopic characteristics of the core glass were systematically investigated too, the results showed that the maximum emission cross section was about 7.91 × 10−21 cm2, the longest fluorescence lifetime at 2030 nm was 2.47 ms, the value of σem × τrad was 19.53 × 10−21 cm2ms, and the maximum gain coefficient was about 2.02 cm−1 when 1.2 mol% Tm3+ and 0.6 mol% Ho3+ were co-doped in tellurite glass. The hybrid-cladding tellurite glass fiber fabrication process was presented in detail. A single-mode glass fiber with hybrid-cladding was fabricated and NA1 of the core is 0.116, and NA2 of the inner cladding is 1.249 and is beneficial for pump light collection. The core diameter of which is 6.8 μm, and the fiber loss is 20.16 dB/m. The fabricated hybrid cladding glass fibers can be easily cut without obvious defect.

Intriguing branching of the maximum position of the absorption cross section in Mie theory explained.

A potential control over the position of maxima of scattering and absorption cross sections can be exploited to better tailor nanoparticles for specific light-matter interaction applications. Here we explain in detail the mechanism of an appreciable blue shift of the absorption cross-section peak relative to a metal spherical particle localized surface plasmon resonance (LSPR) defined as the maximum of the extinction (and scattering) cross section. Such a branching of cross sections' maxima requires a certain threshold value of size parameter (x≈0.7 for dipole channel) and is a prerequisite for obtaining high fluorescence enhancements, because the spectral region of high radiative rate enhancement becomes separated from the spectral region of high non-radiative rate enhancement. A consequence is that the maximum of the absorption cross section cannot be used as the definition of the LSPR position for x≳0.7.

FUSION REACTOR ON COLLIDING BEAMS

The paper is devoted to the problem of constructing nuclear power reactors based on the synthesis of light elements. This problem is currently subject to assessment under options of thermonuclear reactors operating with high-temperature plasma. In such reactors, plasma is isolated from the walls of the reaction chamber using a magnetic field. Even in advanced designs of thermonuclear reactors, temperature regime is far from the conditions for ensuring optimal interaction cross sections of the source nuclei. Despite many years of work, the task of efficient plasma isolation is difficult to solve. The size of the reaction chambers increases, predicted costs of constructing an effective reactor, even in version with the deuterium-tritium reaction, which has a maximum cross section and minimum energy of interacting nuclei. The article considers a version of the fusion reactor based on the interaction of colliding ion beams in a toroidal magnetic field. This solution provides a cost cutting to trigger the reaction, address the problem of effective retaining of interacting nuclei in the reaction chamber. An example with D–D, D–T and D–3Не reactions shows reactors based on them with low energy losses and small dimensions.

Impact Of Channel Incision On Floods: A Case Study In The South-Eastern Subcarpathians (Romania)

Despite numerous researches on river channel incision, there are fewer studies on the impact of channel adjustments on floods. This paper aims to investigate channel adjustments and to analyse their impact on the frequency of floods by estimating the return period of the bankfull discharge of the Prahova River in the South-Eastern Subcarpathians (Romania). The study is based on the analysis of the maximum annual discharges and cross-section profiles of the Prahova River at Câmpina gauging station (1976–2015). To estimate the return period of the bankfull discharge, the log Pearson III distribution was used. Overall, the maximum depth and the cross-section area at the bankfull stage increased during the analysed period, indicating channel incision and lateral stability. The bankfull discharge of 1976 could be reached every year and the one of 2015 could occur almost every 5 years. Therefore, due to channel incision and increased channel capacity, overflowing the bankfull stage is a less frequent hazard on the Prahova River at Câmpina gauging station. River management appears to maintain this situation as no measure is taken to decrease channel incision.

Minimalist Mie coefficient model.

When considering light scattering from a sphere, the ratios between the expansion coefficients of the scattered and the incident field in a spherical basis are known as the Mie coefficients. Generally, Mie coefficients depend on many degrees of freedom, including the dimensions and electromagnetic properties of the spherical object. However, for fundamental research, it is important to have easy expressions for all possible values of Mie coefficients within the existing physical constraints and which depend on the least number of degrees of freedom. While such expressions are known for spheres made from non-absorbing materials, we present here, for the first time to our knowledge, corresponding expressions for spheres made from absorbing materials. To illustrate the usefulness of these expressions, we investigate the upper bound for the absorption cross section of a trimer made from electric dipolar spheres. Given the results, we have designed a dipolar ITO trimer that offers a maximal absorption cross section. Our approach is not limited to dipolar terms, but indeed, as demonstrated in the manuscript, can be applied to higher order terms as well. Using our model, one can scan the entire accessible parameter space of spheres for specific functionalities in systems made from spherical scatterers.

Using maximum cross section method for filtering jump-diffusion random processes

Abstract The paper is focused on problem of filtering random processes in dynamical systems whose mathematical models are described by stochastic differential equations with a Poisson component. The solution of a filtering problem supposes simulation of trajectories of solutions to a stochastic differential equation. The trajectory modelling procedure includes simulation of a Poisson flow permitting application of the maximum cross section method and its modification.

Positron Impact Excitation of the nS, nP, and nD States of Atomic Hydrogen

The excitation cross sections of the atomic hydrogen from n=2 ton=6 have been calculated for S, P, and D, from low energies to high incident energies (threshold to 100 eV), using the variational polarized orbital method (hybrid theory). Thirty partial waves been used to obtained converged cross sections. The maximum of elastic and excitation cross sections is at incident energy 26.66 eV.

Non-classical flow modeling of spontaneous imbibition in spatially heterogeneous reservoirs

In this study, imbibition process is investigated in heterogeneous hydrocarbon reservoir using the non-classical (effective viscous finger) model equations proposed by Luo et al. (SPE Res. Eval. Engineering, 20(4), 1–16 2017). Counter-current spontaneous imbibition is analyzed in different heterogeneous porous media. The heterogeneity is mainly due to the spatial variation of the porosity and absolute permeability. The proposed mathematical model is solved considering the Implicit Pressure Explicit Saturation Scheme (IMPES) via finite difference method (FDM). Effect of the viscosity ratio, growth rate exponent of the fingering function, and the maximum fingering cross section on the normalized water saturation are analyzed. The present model is verified in the limiting case of classical model equations in homogeneous medium. It is noted that rate and extent of the counter-current imbibition are significantly controlled by the distribution of heterogeneous parameters like porosity and absolute permeability of the reservoir.

The Effect of Axial Length on Extraocular Muscle Leverage

Magnetic resonance imaging was used to determine the effect of axial length (AL) on globe rotational axis and horizontal extraocular muscle leverage during horizontal duction. Prospective observational case series. At a single academic center, 36 orthophoric adults with a wide range of ALs underwent high-resolution axial orbital magnetic resonance imaging in target-controlled adduction and abduction. ALs were measured in planes containing maximum globe cross-sections. Area centroids were calculated to determine globe centers. Rotational axes in orbital coordinates were calculated from displacements of lens centers and globe-optic nerve attachments. Lever arms were calculated as distances between published extraocular muscle insertions and rotational axes. ALs averaged 26.3 ± 0.3mm (standard error [range 21.5-33.4mm]). Rotational axes from adduction to abduction averaged 1.1 ± 0.2mm medial and 1.1 ± 0.2mm anterior to the globe's geometric center in adduction. Linear regression demonstrated no significant correlation between AL and rotational axis horizontal (R2= 0.06) or anteroposterior (R2= 0.07) position. Medial rectus (MR) lever arms averaged 12.0 ± 0.2mm and lateral rectus (LR) lever arms averaged 12.8 ± 0.2mm. Both MR (R2= 0.24, P < .001) and LR (R2= 0.32, P < .001) lever arms significantly increased by about 0.3mm per 1.0-mm of increased AL, with a corresponding reduction in predicted per-millimeter effect of surgical repositioning of their insertions. Regardless of AL, the globe rotates about a point nasal and anterior to its geometric center, giving the LR more leverage than the MR. This eccentricity may diminish the effect of tendon repositioning in moderate to highly myopic patients, with reductions in per-mill imeter dose/response predicted with longer AL.

Watt-level mid-infrared continuous-wave Tm:YAG laser operating on the 3H4 → 3H5 transition

We report on the first continuous-wave mid-infrared Tm:Y3Al5O12 laser operating on the 3H4 → 3H5 transition. The 3.2 at.% Tm:Y3Al5O12 laser generated a maximum output power of 1.07 W at ~2.19 & 2.32 μm with a high slope efficiency of 46.3% (vs. the absorbed pump power) exceeding the Stokes limit. Depending on the output coupling and the pump power, a set of discrete laser lines in the range of 2.164–2.346 μm was observed. The spectroscopic properties of Tm:Y3Al5O12 relevant for the mid-infrared laser operation are revised. The maximum stimulated-emission cross-section for the 3H4 → 3H5 transition is 0.35 × 10−20 cm2 at 2324 nm and the emission bandwidth is ~37 nm. The overlap of the 3F4 → 3H6 and the 3H4 → 3H5 transitions is quantified revealing the formulas for Stokes and anti-Stokes phonon sidebands of emission bands. Tm:Y3Al5O12 is promising for broadly tunable (2.1–2.5 μm) and mode-locked mid-infrared oscillators.

Anisotropic thermal, physical and neutron attenuation studies of borated acrylamide composites

The present work was carried-out to study the shielding properties of hydrogel using Pu-α-Be neutron source. Hydrogel block copolymers based on acrylamide (AAm) and boric acid have been prepared by radiation copolymerization of acrylamide (AAm) and boric acid in gamma cell. The influence of dose, acrylamide concentration and relative contents of boric acid on linear thermal expansion, glass transition and physical properties such as density, water absorption and porosity were examined to evaluate the composite capabilities for radiation shielding. The experimental attenuation parameters; macroscopic effective removal cross-section ΣR (cm-1) of fast neutrons and total attenuation coefficient μ (cm-1) of gamma rays have been evaluated. The attenuation coefficients were obtained experimentally and theoretically using XCOM program. The obtained results revealed that the maximum removal cross-section and shielding performance evaluated by adding 4 gm of boric acid to acrylamide.

Enhanced ~2.9 μm mid-infrared emissions of Ho3+/Yb3+ co-doped Na5Y9F32 single crystal introduced by Pr3+ ions

A novel Na5Y9F32 single crystals tri-doped with fixed ~0.8 mol% Ho3+, ~1 mol% Yb3+ and various Pr3+ from 0 to 0.8 mol% were successfully grown by a modified Bridgman method for 2.9 μm mid-infrared application. The effects of Pr3+ ion on the 2.9 μm emission was investigated systematically with the help of the absorption spectra, emission spectra and fluorescence decay curves. The emission intensity at ~2.9 μm of Ho3+: 5I6 → 5I7 was enhanced gradually as increase of Pr3+ concentration from 0 to 0.8 mol% under excitation of 980 nm laser diode (LD). The maximum emission cross-section at ~2.9 μm was calculated to be 5.62 × 10−20 cm2 according to the measured emission spectra. The energy transfer mechanism among Ho3+, Yb3+ and Pr3+ was studied. When the Pr3+ ion concentration reached 0.8 mol%, the energy conversion efficiencies for Ho3+: 5I7 → Pr3+: 3F2 and Ho3+: 5I6 → Pr3+: 3F4 were estimated about ~51.76% and ~15.73%, respectively. A remarkably augmented conversion process of Ho3+: 5I7 → Pr3+: 3F2 by the introduction of Pr3+ ion into Ho3+/Yb3+ system results into the enhancement of ~2.9 μm emission. The Pr3+ ion takes as an effective deactivation of the Ho3+ ion in the Na5Y9F32 single crystal. The Pr3+/Ho3+/Yb3+ tri-doped Na5Y9F32 single crystals may become a new choice for ~2.9 μm mid-infrared solid-state laser due to its both excellent optical properties and chemical stability.

The Optimum Reinforced Concrete Deck Stiffness of Cable-Stayed Bridge Decks

This paper aims to find optimum deck stiffness and optimum girder profile in terms of vertical deformation and cable stresses. The feasibility of this study was achieved by analyse and develop eighteen models twice using ABAQUS software; six different deck stiffness and three different girder profile. A nonlinear static finite element analysis was performed on the previous models. The results show that the maximum stress found at maximum deck stiffness and the maximum cable stress found at maximum girder cross section. Also, the deflection decreased dramatically with the increase of deck stiffness. Therefore, the relationship between the vertical displacement and deck stiffness is inverse. Referring to the data obtained and collected from these analytical models the concrete deck slab with 50 MPa grade is the optimum grade in terms of strength and serviceability requirements.

Deep Blue Light Amplification from a Novel Triphenylamine Functionalized Fluorene Thin Film.

The development of high performance optically pumped organic lasers operating in the deep blue still remains a big challenge. In this paper, we have investigated the photophysics and the optical gain characteristics of a novel fluorene oligomer functionalized by four triphenylamine (TPA) groups. By ultrafast spectroscopy we found a large gain spectral region from 420 to 500 nm with a maximum gain cross-section of 1.5 × 10−16 cm2 which makes this molecule a good candidate for photonic applications. Amplified Spontaneous Emission measurements (ASE) under 150 fs and 3 ns pump pulses have revealed a narrow emission at 450 nm with a threshold of 5.5 μJcm−2 and 21 μJcm−2 respectively. Our results evidence that this new fluorene molecule is an interesting material for photonic applications, indeed the inclusion of TPA as a lateral substituent leads to a high gain and consequently to a low threshold blue organic ASE.

Water Vapor Near‐UV Absorption: Laboratory Spectrum, Field Evidence, and Atmospheric Impacts

AbstractAbsorption of solar radiation by water vapor in the near‐UV region is a poorly understood but important issue in atmospheric science. To better understand water vapor near‐UV absorption, we constructed a cavity ring‐down spectrometer with bandwidth of 5 cm−1 (~0.05 nm) and obtained water vapor absorption cross sections at 1‐nm increments in the 290‐ to 350‐nm region. Water vapor displays structured absorption over this range with maximum and minimum cross sections of 8.4 × 10−25 and 1.6 × 10−25 cm2/molecule. Major water vapor absorption bands were observed at 293–295, 307–313, 319, 321–322, and 325 nm, with cross‐section values higher than 4.0 × 10−25 cm2/molecule. To obtain further insight into major water vapor absorption bands, we measured water vapor absorption cross sections at 0.05‐nm intervals in the 292‐ to 296‐nm, 306‐ to 314‐nm, and 317‐ to 326‐nm region. Field UV residual spectra not only exhibited increased attenuation at higher atmospheric water vapor loadings but also showed structures suggested by the laboratory water vapor absorption spectrum. Spaceborne UV radiance spectra have spectral structures resembling the differential cross‐section spectrum constructed from the laboratory wavelength‐dependent water vapor absorption cross sections presented here. Incorporating water vapor absorption cross‐section data into a radiative transfer model yielded an estimated energy budget of 0.26 W/m2 for the standard U.S. atmosphere and 0.76 W/m2 for the tropics. This shows that water vapor near‐UV absorption is an important contributor for climate simulation and ozone retrievals.

Microwave ablation zones are larger than they macroscopically appear - Reevaluation based on NADH vitality staining ex vivo.

Animal liver is established as an ex vivo model for studies on hepatic microwave ablation (MWA). Macroscopically visible color changes in the ablation zone are used to assess cell destruction and confirm successful ablation ex vivo. Macroscopy and histology of MWA zones regarding cell viability in ex vivo porcine livers were compared in this study. Six MWA were performed in porcine livers post mortem. A 14-G antenna and microwave generator (928 MHz; 9.0 kJ) were used. MWA were cut at the maximum cross section in vertical alignment to the antenna. NADH-diaphorase staining determined cell vitality. Macroscopic and microscopic ablation zones were statistically analyzed. Histology showed two distinct ablation zones: central white zone (WZH) with no cell viability and peripheral red zone (RZH) with partial cell viability. However, the macroscopically visible WZM was significantly smaller than the microscopic WZH with an area difference of 43.1% (p < 0.05) and a radius difference of 21.2% (1.6 mm; p < 0.05). Macroscopy and histology showed a very high correlation for the complete lesion area (WZH/M+RZH/M; r = 0.9; p = 0.001). The avital central zone is significantly larger as the macroscopically visible WZ which is commonly used to assess successful ablation in MWA ex vivo studies. Irreversible cell destruction can be underestimated in macroscopic evaluation.

Growth and spectroscopy of orthorombic Yb:KY(MoO4)2 laser crystal with a layered structure

We report on the growth, structure, vibronic and spectroscopic properties of novel Yb3+-doped orthorhombic potassium yttrium double molybdate crystal, Yb:KY(MoO4)2. The layered structure of this material determines a strong polarization-anisotropy of absorption and emission bands of Yb3+ ions. The maximum stimulated-emission cross-section is 3.7×10-20 cm2 at ∼1.01 μm for light polarization E ∥ b and the lifetime of the 2F5/2 state is 0.46 ms. Naturally cleaved Yb:KY(MoO4)2 plates are suitable for microchip lasers at ∼1 μm.

Power System Stability Enhancement Using FACTS Devices

To utilize maximum cross section of installed power system conductors, the diversion of imaginary power should be must .With this; we can achieve maximum utilization of real power generated at the station. Generally preset passive inductive VAR generators may share conductor portion when low demand times. Active VAR generators are preferred to overcome this issue .Further control systems helps to determine the required VAR and type of VAR such that conduction period of switch varies according to the requirement of load which is very advantageous nature of active VAR generators. The simulink models of STATCOM and SVC are present in this paper. The results are analyzed accordingly in this paper.

Two-photon fluorescent Zn2+ probe for ratiometric imaging and biosensing of Zn2+ in living cells and larval zebrafish

As an essential transition-metal ion in organism, zinc ion (Zn2+) plays a significant role in cellular metabolism, apoptosis and neurotransmission. Herein, we reported a new intramolecular charge transfer-based two-photon probe, (E)-1-(6-(4-(2-(2-(2-methoxyethoxy)ethoxy)eth-oxy)-3,5-dimethylstyryl)quinolin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine (TEO-MPVQ), for ratiometric imaging and biosensing of Zn2+ in living cells and larval zebrafish. The maximum two-photon absorption cross-section values (δmax) of the developed probe increased from 115 ± 16 GM to 188 ± 27 GM, after the probe was chelated with Zn2+. The emission spectrum of TEO-MPVQ probe increased and red-shifted about 60 nm, resulting in the ratiometric determination of Zn2+ with high sensitivity and selectivity. The present fluorescent probe also demonstrated good biocompatibility, high spatial resolution and deep penetration depth for Zn2+ detection. Accordingly, TEO-MPVQ was able to track the endogenous Zn2+ release in neurons and also successfully applied for larval zebrafish imaging. By using of this effective probe, it was found that the endogenous Zn2+ was rapidly released from metallothionein under the stimulation of NO in neurons.