Radiation Damping in the Photoionization of Fe^{14+}

A theoretical investigation of photoabsorption and photoionization of Fe^{14+} extending beyond an earlier frame transformation R-matrix implementation is performed using a fully-correlated, Breit-Pauli R-matrix formulation including both fine-structure splitting of strongly-bound resonances and radiation damping. The radiation damping of $2p\rightarrow nd$ resonances gives rise to a resonant photoionization cross section that is significantly lower than the total photoabsorption cross section. Furthermore, the radiation-damped photoionization cross section is found to be in good agreement with recent experimental results once a global shift in energy of $\approx -3.5$ eV is applied. These findings have important implications. Firstly, the presently available synchrotron experimental data are applicable only to photoionization processes and not to photoabsorption; the latter is required in opacity calculations. Secondly, our computed cross section, for which the L-shell ionization threshold is aligned with the NIST value, shows a series of $2p \rightarrow nd$ Rydberg resonances that are uniformly 3-4 eV higher in energy than the corresponding experimental profiles, indicating that the L-shell threshold energy values currently recommended by NIST are likely in error.Comment: 4 pages, 1 figures, and 2 table

Liquid crystalline side chain polysiloxanes with 4-amino-4'-stilbenecarboxylic ester mesogens

Solid, liquid, and gas are the three states of matter. A solid consists of molecules or ions that are fixed in a specific position. Strong attractive forces hold the molecules in place. Hence, three-dimensional order is maintained in a crystalline solid. On the other hand, the forces holding the molecules together in the liquid state are much weaker. Thus, the molecules are free to move randomly and the order is much less than in a solid. Solids are hard and difficult to deform while liquids flow and are easily deformed. In a gas, the molecules move randomly as in liquids, but the attractive forces are not strong enough to hold the molecules close together. A gas can be deformed even more easily than a liquid. A phase is a sample of matter with uniform properties. A state of matter can have one or more phases. Increasing the temperature of a substance increases the molecular motions and the phase is changed at a precise temperature. A completely disordered phase is called isotropic. Thus, most liquids and gases are isotropic. Liquid crystal (LC) is an intermediate phase between the crystalline solid and the isotropic liquid. When a solid melts to an LC phase, the material flows as a liquid, but the molecules retain order in one or two dimensions. Although, an LC phase is anisotropic, it is more similar to a liquid than to a crystalline solid because it only possesses a small amount of order.The purpose of this work was to prepare and understand the properties liquid crystal polymers (LCPs) which have the shape of a comb. A polymer is a substance consisting of giant molecules formed as chains or networks from smaller molecules (monomers) of the same kind. In the comb-shaped LCPs, relatively long rod-shaped side branches bound to the main chain comprise the teeth and the backbone of a comb, respectively. The comb polymers were made by a reaction that binds the teeth to a preformed polymer backbone of poly(methylhydrosiloxane), a polymer similar to that of silicone oil and silicone rubber which is among the most flexible polymers known. The flexibility of the backbone allows the preparation of polymers having low glass transition temperature, T g ( the temperature at which a rubbery liquid changes to a glass or vice versa). A spacer chain was placed between the main chain and the side chain to allow main chain motion without disturbing the orientation of the side chains which gives the LC properties of the polymers.The LC properties of the comb-shaped polymers were examined using a differential scanning calorimeter (DSC), a polarizing microscope, and a high temperature X-ray diffractometer. DSC detects the temperatures at which change of phase occurs and measures the energy change of a phase transition. A LC phase is best observed by a microscope. Due to the orientational order of LCs, polarized light is transmitted. The arrangement of the molecules in different phases is obtained from the X-ray diffractometer. One or two LC phases were observed for each polymer depending on the size of the side chains.LCs are commonly known for their application as displays (LCD) for watches, calculators and other digital displays. In this work, the polymers were investigated for possible nonlinear optical applications. The polymers prepared in the laboratory showed promising nonlinear optical response which can be compared to materials currently used as laboratory standards

Removal of anionic surfactant from aqueous solutions by adsorption onto biochars:characterisation, kinetics, and mechanism

Biochar, a waste biomass-derived adsorbent, holds promise for decentralised wastewater treatment. However, limited research exists on its efficacy in adsorbing anionic surfactants in wastewater. To address this, the adsorption of sodium dodecyl sulphate (SDS), a common anionic surfactant, was studied using various biochar types: rice husk biochar (RH-550 and RH-700), wheat straw biochar (WS-550 and WS-700) produced at 550°C and 700°C, wood-based biochar (OB), and activated carbon (AC) as a control. The study investigated the impact of pH (3–9), adsorbent loading (1–10 g/L), adsorbent size (<0.5–2.5 mm), contact time (5–180 min), and initial concentration (50–200 mg/L) on SDS removal. Under optimised conditions (100 mg/L SDS, 4 g/L adsorbent, 1–2 mm particle size, pH 8.3, and 180 min contact time), maximum SDS removals were RH-550 (78%), RH-700 (82.4%), WS-550 (89.5%), WS-700 (90.4%), AC (97%), and OB (88.4%). Among the tested adsorbent materials, WS-550 exhibited the highest SDS adsorption capacity at 66.23 mg/g compared to AC (80.65 mg/g), followed by RH-550 (49.75 mg/g), OB (45.87 mg/g), RH-700 (43.67 mg/g), and WS-700 (42.74 mg/g). SDS adsorption followed a pseudo-second-order kinetic model, indicating chemisorption on the adsorbent surface. The Freundlich isotherm model exhibited a better fit for the experimental data on SDS adsorption using all tested adsorbents except for RH-550. This study showed that biochars produced from agricultural and forestry residues are effective adsorbents for SDS in aqueous solutions and can be a promising sustainable and low-cost material for the treatment of greywater containing anionic surfactants (e.g. handwashing, laundry, kitchen, and bathroom greywaters)

A Comprehensive X-ray Absorption Model for Atomic Oxygen

An analytical formula is developed to represent accurately the photoabsorption cross section of O I for all energies of interest in X-ray spectral modeling. In the vicinity of the Kedge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects, that accurately predict the absorption oscillator strengths below threshold and merge consistently and continuously to the above-threshold cross section. Further minor adjustments are made to the threshold energies in order to reliably align the atomic Rydberg resonances after consideration of both experimental and observed line positions. At energies far below or above the K-edge region, the formulation is based on both outer- and inner-shell direct photoionization, including significant shake-up and shake-off processes that result in photoionization-excitation and double photoionization contributions to the total cross section. The ultimate purpose for developing a definitive model for oxygen absorption is to resolve standing discrepancies between the astronomically observed and laboratory measured line positions, and between the inferred atomic and molecular oxygen abundances in the interstellar medium from XSTAR and SPEX spectral models

Late left ventricular dysfunction after anatomic repair of congenitally corrected transposition of the great arteries

ObjectiveEarly results for anatomic repair of congenitally corrected transposition of the great arteries (ccTGA) are excellent. However, the development of left ventricular dysfunction late after repair remains a concern. In this study we sought to determine factors leading to late left ventricular dysfunction and the impact of cardiac resynchronization as a primary and secondary (upgrade) mode of pacing.MethodsFrom 1992 to 2012, 106 patients (median age at surgery, 1.2 years; range, 2 months to 43 years) with ccTGA had anatomic repair. A retrospective review of preoperative variables, surgical procedures, and postoperative outcomes was performed.ResultsIn-hospital deaths occurred in 5.7% (n = 6), and there were 3 postdischarge deaths during a mean follow-up period of 5.2 years (range, 7 days to 18.2 years). Twelve patients (12%) developed moderate or severe left ventricular dysfunction. Thirty-eight patients (38%) were being paced at latest follow-up evaluation. Seventeen patients had resynchronization therapy, 9 as an upgrade from a prior dual-chamber system (8.5%) and 8 as a primary pacemaker (7.5%). Factors associated with left ventricular dysfunction were age at repair older than 10 years, weight greater than 20 kg, pacemaker implantation, and severe neo-aortic regurgitation. Eight of 9 patients undergoing secondary cardiac resynchronization therapy (upgrade) improved left ventricular function. None of the 8 patients undergoing primary resynchronization developed left ventricular dysfunction.ConclusionsLate left ventricular dysfunction after anatomic repair of ccTGA is not uncommon, occurring most often in older patients and in those requiring pacing. Early anatomic repair and cardiac resynchronization therapy in patients requiring a pacemaker could preclude the development of left ventricular dysfunction

Síntesis, caracterización y evaluación eléctrica de circonatos de bario dopados con lantánidos trivalentes

El circonato de bario es un material oxídico con estructura de tipo perovskita que muestra alta estabilidad química tanto en ambientes oxidantes como reductores, como en presencia de agua y dióxido de carbono; su conductividad ha permitido examinarlo como electrolito para celdas de combustible de óxido sólido encontrando buenos resultados, con la limitante de operar a temperaturas superiores a los 800 °C. Diversos investigadores han propuesto que es posible mejorar su conductividad eléctrica por modifi caciones en su composición química, en particular por dopaje con cationes trivalentes que reemplacen el circonio en el sitio B de la perovskita. En este estudio se sintetizó el circonato de bario por el método citrato amorfo a fi n examinar la posibilidad de obtenerlo en condiciones más favorables que las presentadas por el método de síntesis convencional (método cerámico o reacción de estado sólido). Se preparó circonato de bario dopado con europio, gadolinio, holmio, lantano, neodimio y praseodimio; la identifi cación de fases presentes se verifi có por difracción de rayos X (DRX), las propiedades eléctricas se examinaron por espectroscopía de impedancias (IS) a temperaturas entre 480 y 680 °C, con miras a evaluar su potencial uso como electrolito en celdas de combustible de óxido sólido. Los aportes de esta investigación se han centrado en el método de síntesis; en la obtención de polvos cerámicos de circonato de bario a temperaturas inferiores a las requeridas por el método cerámico; en la obtención de información química, estructural, morfológica y eléctrica de los materiales sintetizados. Se encontró la fase deseada en las condiciones de síntesis establecidas, así mismo, se aprecia un incremento signifi cativo en la conductividad de los sólidos dopados con lantano, holmio y europio en relación al material sin dopaje alguno.Barium zirconate is an oxidic material having perovskite structure that exhibits high chemical stability in both oxidizing and reducing environments, such as in the presence of water and carbon dioxide, its conductivity has led to consider it as a electrolyte for solid oxide fuel cell fi nding good results, with the limitation of operating at temperatures above 800 °C. Several researchers have proposed that it is possible to improve their electrical conductivity by changes in chemical composition, particularly for doping with trivalent cations that replace the zirconium in B site of perovskite. In this study, barium zirconate was synthetized by the amorphous citrate method to examine the possibility of obtaining in more favorable conditions than those made by the conventional method of synthesis (ceramic method or solid state reaction) conditions are synthesized. Barium zirconate doped with europium, gadolinium, holmium, lanthanum, neodymium and praseodymium was prepared, the present phase identifi cation was verifi ed by X-ray diffraction (XRD), the electrical properties were examined by impedance spectroscopy (IS) at temperatures between 480 and 680 °C in order to evaluate its potential use as a fuel cell electrolyte in solid oxide. The contributions of this research has focused on the synthesis method, in the production of ceramic powders of barium zirconate at temperatures lower than those required by the ceramic method, in obtaining chemical, structural, morphological and electrical information of material synthesized. The desired phase synthesis conditions set found, also, a signifi cant increase is seen in the solid conductivity of doped lanthanum, holmium and europium zirconate of barium in relation to the material without doping

CRF Mediates Stress-Induced Pathophysiological High-Frequency Oscillations in Traumatic Brain Injury

Copyright © 2019 Narla et al. It is not known why there is increased risk to have seizures with increased anxiety and stress after traumatic brain injury (TBI). Stressors cause the release of corticotropin-releasing factor (CRF) both from the hypothalamic pituitary adrenal (HPA) axis and from CNS neurons located in the central amygdala and GABAergic interneurons. We have previously shown that CRF signaling is plastic, becoming excitatory instead of inhibitory after the kindling model of epilepsy. Here, using Sprague Dawley rats we have found that CRF signaling increased excitability after TBI. Following TBI, CRF type 1 receptor (CRFR1)-mediated activity caused abnormally large electrical responses in the amygdala, including fast ripples, which are considered to be epileptogenic. After TBI, we also found the ripple (120-250 Hz) and fast ripple activity (\u3e250 Hz) was cross-frequency coupled with θ (3-8 Hz) oscillations. CRFR1 antagonists reduced the incidence of phase coupling between ripples and fast ripples. Our observations indicate that pathophysiological signaling of the CRFR1 increases the incidence of epileptiform activity after TBI. The use for CRFR1 antagonist may be useful to reduce the severity and frequency of TBI associated epileptic seizures