Adsorption and surface complexation of trimesic acid at the alpha-Alumina electrolyte interface

Adsorption kinetics, adsorption isotherms and surface complexation of trimesic acid onto α-alumina surfaces were investigated. Adsorption kinetics of trimesic acid with an initial concentration of 0.5 mM onto α-alumina surfaces were carried out in batch method in presence of 0.05 mM NaCl(aq) at pH 6 and 298.15, 303.15 and 313.15 K. Adsorption isotherms were carried out at 298.15 K, pH 5–9, and 0.05 mMNaCl(aq) by varying trimesic acid concentration from 0.01 to 0.6 mM. Three kinetics equations such as pseudo-first-order, pseudo-second-order and Ho equations were used to estimate the kinetics parameters of the adsorption of trimesic acid on the α-alumina surfaces. Ho equation fits the experimental kinetics data significantly better and the estimated equilibrium concentration is in excellent agreement with the experimental value. The adsorption data were fitted to Freundlich and Langmuir adsorption model and the later best fits the adsorption isotherms. Comparison of adsorption density of trimesic acid with that of benzoic and phthalic acids follows the sequence: benzoic acid < trimesic acid < phthalic acid. The negative activation energy and the Gibbs free energy for adsorption indicate that the adsorption of trimesic acid onto α-alumina is spontaneous and facile. DRIFT spectroscopic studies reveal that trimesate forms outer-sphere complexes with the surface hydroxyl groups that are generated onto α-alumina surfaces in the pH range of the stud

Influence of anions on the adsorption kinetics of salicylate onto alpha aluminium in aqueous medium

Kinetics of adsorption of p-hydroxy benzoate and phthalate on hematite–electrolyte interface were investigated at a constant ionic strength, I =5×10−4 moldm−3,pH5andatthreedifferenttemperatures.Thestateofequilibriumfortheadsorptionofp-hydroxybenzoateontohematite surfaces was attained at 70 h, whereas it was 30 h for phthalate–hematite system. None of the three kinetics models (Bajpai, pseudo first order and pseudo second order) is applicable in the entire experimental time period; however, the pseudo second order kinetics model is considered to be better than the pseudo first order kinetics model in estimating the equilibrium concentration both the p-hydroxy benzoate–hematite and phthalate–hematite systems. The variation of adsorption density of p-hydroxy benzoate and phthalate onto hematite surfaces as a function of concentration of adsorbate was studied over pH range 5–9 at a constant ionic strength, I = 5×10−4 moldm−3 and at constant temperature. The adsorption isotherms for both the systems were Langmuir in nature and the maximum adsorption density (Γmax)ofp-hydroxy benzoate is ∼1.5timesmorethanthatofphthalateonhematiteatpH5and30◦Cinspiteofanadditionalcarboxylicgroupatorthopositioninphthalate.This is due to the more surface area coverage by phthalate than that ofp-hydroxy benzoate on hematite surface. The activation energy was calculated using Arrhenius equation and the activation energy for adsorption of p-hydroxy benzoate at hematite–electrolyte interface is∼1.8 times more than that of phthalate–hematite system. The negative Gibbs free energy indicates that the adsorption of p-hydroxy benzoate and phthalate on hematite surfaces is favourable. The FTIR spectra of p-hydroxy benzoate and phthalate after adsorption on hematite surfaces were recorded for obtaining the bonding properties of adsorbates. The phenolic νC–O appears at∼1271 cm−1 after adsorption of p-hydroxy benzoate on hematite surfaces, which shifted by 10 cm−1 to higher frequency region. The phenolic group is not deprotonated and is not participating in the surface complexation. The shifting of theνas(–COO−)andνs(–COO−) bands and non-dissolution of hematite suggest that thep-hydroxy benzoate and phthalate form outer-sphere surface complexwith hematite surfaces in the pH range of 5–7

Barriers to childhood cataract services across India. A mixed methods study using the Theoretical Domains Framework (TDF) of behaviour change

Purpose : Early identification and presentation for childhood cataract surgery remains a major challenge in developing countries. The main aim of this study was to identify potential barriers to childhood cataract services from the perspective of parents’ and carers’, as a critical step towards achieving the timely uptake of cataract services. Methods : We used a mixed methods explanatory sequential study and interviewed 572 parents/carers attending tertiary hospitals in 8 states across India for their child's cataract surgery. We collected information on barriers to accessing services using a 12-item questionnaire and for each reported barrier, responses recorded on a 5 point scale ranging from “low to high importance”. Based on the quantitative data, in-depth interview questions were prepared and 35 interviews were conducted with randomly selected parents/ carers. Majority of these interviews were conducted at the hospital and /at home for those who did not undergo the surgery. Quantitative questionnaires were completed by the trained interviewer and responses were recorded in a pre-designed format. In-depth interviews were audio taped and transcribed for analysis. Quantitative data were analysed using SPSS 22 while qualitative data were organised with NVivo 11 and a thematic analysis was conducted utilising TDF, an integrative framework of theories. Results : From the 831 responses the 5 most important barriers were: economic (40%; n=222); child too young for surgery (17%; n=97); the problem was not felt as severe (16%; n=90); distance (14.5%; n=83) and no one to accompany to the hospital (9.5%; n=54). In addition, being advised by a local ophthalmologist to delay the surgery was also reported (n=16). Domains identified by the TDF included “Knowledge”, “Beliefs about consequences”, “Intentions”, “Goals”, “Decision processes”, “Environmental context and resources”, “Social influences and emotion”. This comprehensive TDF approach enabled us to understand the parents perceived barriers to access services for the children. Conclusions : Barriers to accessing childhood cataract services include both practical concerns relating to the family’s socio economic status as well as obstacles from the providers. Mapping out the barriers is necessary to design appropriate intervention for achieving positive behaviour change that can have potential social and economic impact

Delay in presentation to hospital for childhood cataract surgery in India

Purpose Cataract is one of the major causes of avoidable visual disability in children and the aim of this study was to investigate the age at which children with cataract present for surgery at tertiary hospitals across India. Methods: A prospective multicenter study collected data from 9 eye hospitals in 8 states in India. All children admitted for cataract surgery between Nov 2015 and March 2016 were considered eligible. Parents were interviewed at the hospital by trained personnel and socio demographic information, age at diagnosis and at surgery and the relevant clinical data were obtained from the medical records. Mean age, age range at surgery were used and performed logistic regression analyses. Results Parents of 751 consecutive cases were interviewed, of which 469(63%) were boys and 548(73%) were from rural areas. Cataract was bilateral in 493 (66%) and unilateral in 258 (34%); of the unilateral cases, 179 (69%) were due to trauma. The mean age at surgery for ‘congenital’ and ‘developmental’ cataract was 48.2±50.9 and 99.7±46.42 months respectively and the mean age was lower in the southern region compared to other regions. Children with 2 or more siblings at home were five times more likely to undergo surgery within 12 months (OR, 4.69; 95% CI: 2.04 – 10.79; p = <0.001). Conclusions Late surgery for childhood cataract remains a major challenge and the factors determining this issue in India are pertinent also to several other countries and need to be addressed for every child with cataract to achieve full visual potential

Reactor mixing angle from hybrid neutrino masses

In terms of its eigenvector decomposition, the neutrino mass matrix (in the basis where the charged lepton mass matrix is diagonal) can be understood as originating from a tribimaximal dominant structure with small deviations, as demanded by data. If neutrino masses originate from at least two different mechanisms, referred to as "hybrid neutrino masses", the experimentally observed structure naturally emerges provided one mechanism accounts for the dominant tribimaximal structure while the other is responsible for the deviations. We demonstrate the feasibility of this picture in a fairly model-independent way by using lepton-number-violating effective operators, whose structure we assume becomes dictated by an underlying $A_4$ flavor symmetry. We show that if a second mechanism is at work, the requirement of generating a reactor angle within its experimental range always fixes the solar and atmospheric angles in agreement with data, in contrast to the case where the deviations are induced by next-to-leading order effective operators. We prove this idea is viable by constructing an $A_4$-based ultraviolet completion, where the dominant tribimaximal structure arises from the type-I seesaw while the subleading contribution is determined by either type-II or type-III seesaw driven by a non-trivial $A_4$ singlet (minimal hybrid model). After finding general criteria, we identify all the $\mathbb{Z}_N$ symmetries capable of producing such $A_4$-based minimal hybrid models.Comment: 18 pages, 5 figures. v3: section including sum rules added, accepted by JHE

Cleaning of Indian coals by agglomeration with xylene and hexane

A laboratory scale agglomeration process has been undertaken for cleaning Indian coals using oils namely, xylene and hexane. Maximum organic matter recovery for xylene has been found to be 91.9% whereas with hexane, the value is 54.7% on a dry basis. The highest ash rejection values with xylene (90.7%) and with hexane (89.7%) are almost same. Promising results for rejection of metals (Fe, Mg and Zn) have been observed. It has been found that xylene is more selective than hexane for the agglomeration process. Knowledge gained from this study will be helpful for technological advancement of this kind of work

Propensity of citric, maleic, oxalic and succnic acids for the acquous solution- vapour interface : Surface tension measurment and molecular dynamics simulations

Behaviour of oxalic, citric, succinic, and maleic acids at the air/water interface is characterized and quantified by surface tension measurements in a broad concentration range and molecular dynamics simulations in slab geometry employing a polarizable force field. The relative order of surface propensities of these atmospherically relevant acids is established in this study with results being also in a very good agreement with previous measurements

Electroweak baryogenesis

Electroweak baryogenesis (EWBG) remains a theoretically attractive and experimentally testable scenario for explaining the cosmic baryon asymmetry. We review recent progress in computations of the baryon asymmetry within this framework and discuss their phenomenological consequences. We pay particular attention to methods for analyzing the electroweak phase transition and calculating CP-violating asymmetries, the development of Standard Model extensions that may provide the necessary ingredients for EWBG, and searches for corresponding signatures at the high energy, intensity, and cosmological frontiers.Comment: 42 pages, 13 figures, invited review for the New Journal of Physics focus issue on 'Origin of Matter

Retrieval of snow water equivalent from dual-frequency radar measurements: using time series to overcome the need for accurate a priori information

Measurements of radar backscatter are sensitive to snow water equivalent (SWE) across a wide range of frequencies, motivating proposals for satellite missions to measure global distributions of SWE. However, radar backscatter measurements are also sensitive to snow stratigraphy, to microstructure, and to ground surface roughness, complicating SWE retrieval. A number of recent advances have created new tools and datasets with which to address the retrieval problem, including a parameterized relationship between SWE, microstructure, and radar backscatter, and methods to characterize ground surface scattering. Although many algorithms also introduce external (prior) information on SWE or snow microstructure, the precision of the prior datasets used must be high in some cases in order to achieve accurate SWE retrieval. We hypothesize that a time series of radar measurements can be used to solve this problem and demonstrate that SWE retrieval with acceptable error characteristics is achievable by using previous retrievals as priors for subsequent retrievals. We demonstrate the accuracy of three configurations of prior information: using a global SWE model, using the previously retrieved SWE, and using a weighted average of the model and the previous retrieval. We assess the robustness of the approach by quantifying the sensitivity of the SWE retrieval accuracy to SWE biases artificially introduced in the prior. We find that the retrieval with the weighted averaged prior demonstrates SWE accuracy better than 20 % and an error increase of only 3 % relative RMSE per 10 % change in prior bias; the algorithm is thus both accurate and robust. This finding strengthens the case for future radar-based satellite missions to map SWE globally.</p