Chloride ion removal from archaeological iron and #beta#-FeOOH

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Study on the Activation of Saudi Natural Bentonite, Part I: Investigation of the Conditions that Give Best Results and Kinetics of the Sulfuric Acid Activation Process

The Kingdom of Saudi Arabia has many natural clay deposits of the montmorillonite type which are susceptible to activation. The activation of the Saudi natural bentonite with sulfuric acid was studied experimentally and the activity of the produced clay for bleaching of corn oil was tested and compared with that of commercial active clay. The conditions that give best results for the sulfuric acid activation were found to be: 45% by wt acid concentration, liquid to solid ratio of 5:1 (mL/g), clay particle size of -325 mesh (95% passing), at the acid boiling point for 15 minutes and mixing rate of 200 rpm. It was found that using a lower acid concentration requires more time to reach the same degree of activation as that when a higher acid concentration was used. The produced active clay (Saudi-bentonite) has a comparable bleaching power to that used commercially. The oil bleached with Saudi-bentonite clay is of qualities similar to that bleached by commercial clays. The apparent kinetics of the heterogeneous reaction were also studied. It was found that the reaction between sulfuric acid and clay is a zero order reaction with an apparent activation energy of 430 cal/mol

Study on the Activation of Saudi Natural Bentonite, Part II: Characterization of the Produced Active Clay and Its Test as an Adsorbing Agent

The active clay (Saudi-bentonite) produced by the acid activation of Saudi natural clay was characterized with respect to chemical composition and physical properties. The obtained results were compared with commercial active clay being used in bleaching edible oils. Also, the adsorptive ability of clay to remove some coloring matter was investigated. The chemical composition of the produced active clay was found to be close to that of the commercial clay with slightly higher iron and silicon oxides percentages and a lower percentage of aluminum oxide. The activated clay has an average surface area of 267.5 m2/g and a bulk density of 720 kg/m3. These results are very close to those of the commercial active clay. The adsorption of the coloring matter present in edible oil and a basic dye (methyl violet) on activated Saudi-bentonite was found to follow the Freundlich equation. The values of the constants were found to be dependent on the matter being adsorbed. However, the clay failed to remove acidic dyes from aqueous solutions because of the acidic nature of the clay

Hydrolytic and Thermal Stability of Organic Monolayers on Various Inorganic Substrates

A comparative study is presented of the hydrolytic and thermal stability of 24 different kinds of monolayers on Si(111), Si(100), SiC, SiN, SiO2, CrN, ITO, PAO, Au, and stainless steel surfaces. These surfaces were modified utilizing appropriate organic compounds having a constant alkyl chain length (C18), but with different surface-reactive groups, such as 1-octadecene, 1-octadecyne, 1-octadecyltrichlorosilane, 1-octadecanethiol, 1-octadecylamine and 1-octadecylphosphonic acid. The hydrolytic stability of obtained monolayers was systematically investigated in triplicate in constantly flowing aqueous media at room temperature in acidic (pH 3), basic (pH 11), phosphate buffer saline (PBS) and deionized water (neutral conditions), for a period of 1 day, 7 days, and 30 days, yielding 1152 data points for the hydrolytic stability. The hydrolytic stability was monitored by static contact angle measurements and X-ray photoelectron spectroscopy (XPS). The covalently bound alkyne monolayers on Si(111), Si(100), and SiC were shown to be among the most stable monolayers under acidic and neutral conditions. Additionally, the thermal stability of 14 different monolayers was studied in vacuum using XPS at elevated temperatures (25–600 °C). Similar to the hydrolytic stability, the covalently bound both alkyne and alkene monolayers on Si(111), Si(100) and SiC started to degrade from temperatures above 260 °C, whereas on oxide surfaces (e.g., PAO) phosphonate monolayers even displayed thermal stability up to ~500 °C

Worldwide organization of neurocritical care : results from the PRINCE study part 1

Introduction: Neurocritical care focuses on the care of critically ill patients with an acute neurologic disorder and has grown significantly in the past few years. However, there is a lack of data that describe the scope of practice of neurointensivists and epidemiological data on the types of patients and treatments used in neurocritical care units worldwide. To address these issues, we designed a multicenter, international, point-prevalence, cross-sectional, prospective, observational, non-interventional study in the setting of neurocritical care (PRINCE Study). Methods: In this manuscript, we analyzed data from the initial phase of the study that included registration, hospital, and intensive care unit (ICU) organizations. We present here descriptive statistics to summarize data from the registration case report form. We performed the Kruskal–Wallis test followed by the Dunn procedure to test for differences in practices among world regions. Results: We analyzed information submitted by 257 participating sites from 47 countries. The majority of those sites, 119 (46.3%), were in North America, 44 (17.2%) in Europe, 34 (13.3%) in Asia, 9 (3.5%) in the Middle East, 34 (13.3%) in Latin America, and 14 (5.5%) in Oceania. Most ICUs are from academic institutions (73.4%) located in large urban centers (44% > 1 million inhabitants). We found significant differences in hospital and ICU organization, resource allocation, and use of patient management protocols. The highest nursing/patient ratio was in Oceania (100% 1:1). Dedicated Advanced Practiced Providers are mostly present in North America (73.7%) and are uncommon in Oceania (7.7%) and the Middle East (0%). The presence of dedicated respiratory therapist is common in North America (85%), Middle East (85%), and Latin America (84%) but less common in Europe (26%) and Oceania (7.7%). The presence of dedicated pharmacist is highest in North America (89%) and Oceania (85%) and least common in Latin America (38%). The majority of respondents reported having a dedicated neuro-ICU (67% overall; highest in North America: 82%; and lowest in Oceania: 14%). Conclusion: The PRINCE Study results suggest that there is significant variability in the delivery of neurocritical care. The study also shows it is feasible to undertake international collaborations to gather global data about the practice of neurocritical care