Periodic aggregation patterns of oxide particles on corroding metals: chemical waves due to solution feedback processes.

Chemical waves that produce periodic patterns are common occurrences in nature. The underlying processes involved have been studied in many disciplines of science, but rarely reported in the chemistry of corrosion. In this study of carbon steel corrosion, iron oxide crystals are observed to deposit in concentric wave patterns or in discrete bands, known as Liesegang patterns. We demonstrate that oxide growth in these patterns is preceded by the formation of a hydrogel network, which consists of a semi-stationary phase of loosely connected metal-hydroxide colloids and a mobile phase of solution saturated with metal cations. Once the hydrogel network covers the metal surface, a metal cation produced by corrosion reactions at the metal surface must diffuse through the layer into the bulk solution. While diffusing through the porous network, the metal cation undergoes adsorption-precipitation as metal-hydroxide colloids which later can dissolve back into the solution. When the kinetics of precipitation and dissolution of the metal cation can be effectively coupled with the transport flux of the dissolved metal cation, the precipitation-dissolution-diffusion cycles can be sustained over time which can lead to periodic aggregation patterns of metal-hydroxide colloids at a specific time. We also establish that for transition metal cations the precipitation-dissolution-diffusion process can couple with reversible redox reactions between the soluble and less soluble metal cations, which can affect the overall transport of banded aggregates of metal-hydroxide colloids and the growth and transformation of metal-hydroxides into crystalline oxides. If systemic feedback between different elementary processes is sustained over long durations, iron-oxide crystals of different chemical compositions and shapes aggregate in Liesegang patterns. This work demonstrates unequivocally that non-uniform deposition of metal oxides during corrosion can occur via strongly coupled solution reactions and transport processes, and not simply as a result of metallurgical non-uniformity and/or localized solution environments.

Community-based burden, warning signs, and risk factors of cancer using public-private partnership model in Kerala, India.

BACKGROUND: According to the GBD report published in 2016, the burden of cancer in Kerala is 135.3/100,000 population in contrast to the national average of 100/100,000 population. Cancer is a complex disease that requires broad engagement of various departments and organizations to implement a community based health promotion strategy. OBJECTIVE: To estimate the prevalence of diagnosed cancers, warning signs and selected risk factors of cancer in Niranam Panchayath of Pathanamthitta district, Kerala. METHODOLOGY: A total of 13,736 population was covered by door to door survey using a structured questionnaire. The questionnaire collected information on the sociodemographic variables of the residents, source of water supply, warning signs of cancer and details of diagnosed cancer cases. RESULTS: The mean age of the population was 39.7 ± 21 years. The prevalence of diagnosed cases of cancer in our study was 652/100,000 population. Most common type of cancer identified was Breast cancer (37.3%). The prevalence of any warning sign among the study population was 400/100,000 population. Breast lump was the common warning sign identified. Increasing age, female gender and occupational status were the factors found to be significantly associated with cancer. RECOMMENDATIONS: Community based health education to increase awareness, screening for cancers and breast self-examination in the community could help in early diagnosis and prevention at primary level. Scientific study to assess the risk factors of cancers using case control design could be done in this population along with soil and water sample testing for carcinogens.

Comparison of the use of McCoy and TruView EVO2 laryngoscopes in patients with cervical spine immobilization.

CONTEXT: The cervical spine has to be stabilized in patients with suspected cervical spine injury during laryngoscopy and intubation by manual in-line axial stabilization. This has the propensity to increase the difficulty of intubation. An attempt has been made to compare TruView EVO2 and McCoy with cervical spine immobilization, which will aid the clinician in choosing an appropriate device for securing the airway with an endotracheal tube (ETT) in the clinical scenario of trauma. AIMS: To compare the effectiveness of TruView EVO2 and McCoy laryngoscopes when performing tracheal intubation in patients with neck immobilization using manual in-line axial cervical spine stabilization. SETTINGS AND DESIGN: K. M. C. Hospital, Mangalore, This was a randomized control clinical trial. METHODS: Sixty adult patients of either sex of ASA physical status 1 and 2 who were scheduled to undergo general anesthesia with endotracheal intubation were studied. Comparison of intubation difficulty score (IDS), hemodynamic response, Cormack and Lehane grade, duration of the tracheal intubation and rate of successful placement of the ETT in the trachea between TruView EVO2 and McCoy laryngoscopes was performed. RESULTS: The results demonstrated that TruView has a statistically significant less IDS of 0.33 compared with an IDS of 1.2 for McCoy. TruView also had a better Cormack and Lehane glottic view (CL 1 of 77% versus 40%) and less hemodynamic response. CONCLUSIONS: The TruView blade is a useful option for tracheal intubation in patients with suspected cervical spine injury.

Effect of gamma irradiation on gas-ionic liquid and water-ionic liquid interfacial stability.

The effect of γ-radiation on gas-ionic liquid (IL) and water-IL interfacial stability was investigated. Three phosphonium-based ILs, which vary considerably in their viscosity, conductivity and miscibility with water, were examined. The gas phase above the IL samples (headspace gas) was analyzed using gas chromatography with a mass spectrometer detector while the changes in the IL and aqueous phases were followed by conductivity measurements and Raman spectroscopy. For the gas-IL systems, the headspace samples showed trace amounts of the radiolytic decomposition products of the ILs that were small and volatile enough to become airborne. The type of cover gas, air or Ar, had no effect on the gas speciation. Negligible changes in the conductivity and the Raman spectra of the IL phase due to irradiation indicate that γ-irradiation induces negligible chemical changes in the IL phase when it is in contact with a gas phase. For the water-IL systems, the initially immiscible layers slowly developed an interfacial emulsion layer, even in the absence of radiation. This layer started at the water-IL interface and then grew downwards, eventually converting the entire IL phase to an emulsion. Gamma-irradiation accelerated the conversion of the IL phase to an emulsion. The development of the emulsion layer was accompanied by changes in the conductivity and the Raman spectra of both the IL and water phases. Based on these results, a mechanism involving the formation of micelles at, or near, the water-IL interface has been proposed to explain the development of an emulsion layer. We also suggest that radiolytic decomposition of ILs produces surfactants that can accumulate at the interface and, even at low concentrations, accelerate the emulsification process.

Long-term γ-radiolysis kinetics of NO3(-) and NO2(-) solutions.

Radiolysis kinetics in NO(3)(-) and NO(2)(-) solutions during γ-irradiation were studied at an absorbed dose rate of 2.1 Gy·s(-1) at room temperature. Air- or argon-saturated nitrate or nitrite solutions at pH 6.0 and 10.6 were irradiated, and the aqueous concentrations of molecular water decomposition products, H(2) and H(2)O(2), and the variation in the concentrations of NO(3)(-) and NO(2)(-) were measured as a function of irradiation time. The experimental data were compared with computer simulations using a comprehensive radiolysis kinetic model to aid in interpretation of the experimental results. The effect of nitrate and nitrite, present at concentrations below 10(-3) M, on water radiolysis processes occurs through reactions with the radical species generated by water radiolysis, (•)e(aq)(-), (•)O(2)(-), and (•)OH. The changes in H(2) and H(2)O(2) concentrations observed in the presence of nitrate and nitrite under a variety of conditions can be explained by a reduction in the radical concentrations. The kinetic analysis shows that the main loss pathway for H(2) is the reaction with (•)OH and the main loss pathways for H(2)O(2) are reactions with (•)e(aq)(-) and (•)OH. Nitrate and nitrite compete for the radicals leading to an increase in the concentrations of H(2) and H(2)O(2). Post-irradiation measurements of H(2), H(2)O(2), NO(2)(-) and NO(3)(-) concentrations can be used to calculate the radical concentrations and provide information on the redox conditions of the irradiated aqueous solutions.