Graphite exfoliation by supercritical carbon dioxide extraction

Supercritical carbon dioxide is used to exfoliate graphite, producing a small, several-layer graphitic flake. The supercritical conditions of 2000, 2500, and 3000 psi and temperatures of 40°, 50°, and 60°C, have been used to study the effect of critical density on the sizes and zeta potentials of the treated flakes. Photon Correlation Spectroscopy (PCS), Brunauer-Emmett-Teller (BET) surface area measurement, field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) are used to observe the features of the flakes. N-methyl-2-pyrrolidinone (NMP), dimethylformamide (DMF), and isopropanol are used as co-solvents to enhance the supercritical carbon dioxide treatment. As a result, the PCS results show that the flakes obtained from high critical density treatment (low temperature and high pressure) are more stable due to more negative charges of zeta potential, but have smaller sizes than those from low critical density (high temperature and low pressure). However, when an additional 1-hour sonication is applied, the size of the flakes from low critical density treatment becomes smaller than those from high critical density treatment. This is probably due to more CO2 molecules stacked between the layers of the graphitic flakes. The zeta potentials of the sonicated samples were slightly more negative than nonsonicated samples. NMP and DMF co-solvents maintain stability and prevented reaggregation of the flakes better than isopropanol. The flakes tend to be larger and more stable as the treatment time increases since larger flat area of graphite is exfoliated. In these experiments, the temperature has more impact on the flakes than pressure. The BET surface area resultsshow that CO2 penetrates the graphite layers more than N2. Moreover, the negative surface area of the treated graphite indicates that the CO2 molecules may be adsorbed between the graphite layers during supercritical treatment. The FE-SEM and AFM images show that the flakes have various shapes and sizes. The effects of surfactants can be observed on the FE-SEM images of the samples in one percent by weight solution of SDBS in water since the sodium dodecylbenzene sulfonate (SDBS) residue covers all of the remaining flakes. The AFM images show that the vertical thickness of the graphitic flakes can ranges from several nanometers (less than ten layers thick), to more than a hundred nanometers. In conclusion, supercritical carbon dioxide treatment is a promising step compared to mechanical and chemical exfoliation techniques in the large scale production of thin graphitic flake, breaking down the graphite flakes into flakes only a fewer graphene layers thick.

The rate of outpatient cataract surgery in ten European countries: an analysis using data from the SHARE survey

BACKGROUND: The aim of this study was to determine the rates of outpatient cataract surgery (ROCS) in ten European countries and to find country-specific health indicators explaining the differences. METHODS: Using data from the Survey of Health, Ageing and Retirement in Europe (SHARE), 251 eligible respondents were identified for which cataract surgery was the last surgical procedure. The ROCS of ten countries were compared using logistic regression. The influence of the public expenditure on health as per cent of the total expenditure on health, of the number of acute care beds per 1,000 population, and of the number of practicing physicians per 1,000 population, was studied by multiple logistic regression. Additional information was obtained from country-specific opinion leaders in the field of cataract surgery. RESULTS: The ROCS differed significantly between the ten analysed European countries where Denmark had the highest (100%) and Austria the lowest (0%) rate of day care surgery. A decrease in the density of acute care beds (p < 0.0000001) and in the density of practicing physicians (p < 0.05) and an increase in the public expenditure on health as per cent of the total health expenditure (p < 0.01) lead to an increase in the ROCS. According to the opinion leaders, regulations and financial incentives also have a strong influence on the ROCS. CONCLUSIONS: The outpatient rate of cataract surgery in the ten European countries was mainly influenced by the acute-care beds density, but also by the density of practicing physicians, and by the public expenditure on health.

Waiting times for cataract surgery in ten European countries: an analysis using data from the SHARE survey

AIMS: To assess waiting times for cataract surgery and their acceptance in European countries, and to find explanatory, country-specific health indicators. METHODS: Using data from the survey of health, ageing and retirement in Europe (SHARE), waiting times for cataract surgery of 245 respondents in ten countries were analysed with the help of linear regression. The influence of four country specific health indicators on waiting times was studied by multiple linear regression. The influence of waiting time and country on the wish to have surgery performed earlier was determined through logistic regression. Additional information was obtained for each country from opinion leaders in the field of cataract surgery. RESULTS: Waiting times differed significantly (p<0.001) between the ten analysed European countries. The length of wait was significantly influenced by the total expenditure on health (p<0.01) but not by the other country specific health indicators. The wish to have surgery performed earlier was determined by the length of wait (p<0.001) but not by the country where surgery was performed. CONCLUSION: The length of wait is influenced by the total expenditure on health, but not by the rate of public expenditure on health, by the physician density or by the acute bed density. The wish to have surgery performed earlier depends on the length of wait for surgery and is not influenced by the country.

Functional and anatomical outcomes of vitreoretinal surgery for posterior segment complications after elective cataract surgery

PURPOSE: To assess the outcomes in patients who required 1 or more vitreoretinal interventions for posterior segment complications arising from elective uneventful cataract surgery. SETTING: Tertiary referral center, single-center study. METHODS: A retrospective interventional case series included 56 consecutive patients who were referred for surgical correction of posterior segment complications within 6 months of cataract surgery. The study period was between 1996 and 2003, and the minimum follow-up was 5 months. RESULTS: Posterior segment complications were resolved with a single surgical intervention in 40 cases (71.4%). Within 5 months of primary surgical correction, persisting or newly arising posterior segment complications were noted in 16 cases (28.6%). After a mean of 2.1 +/- 1.4 (SD) additional surgeries, the number of eyes with posterior segment problems decreased to 7 (12.5%) (P = .035). Posterior segment complications requiring more than 1 vitreoretinal intervention included retinal detachment, endophthalmitis, and choroidal hemorrhages. After primary correction surgery, the mean best corrected visual acuity increased from 0.15 +/- 0.24 to 0.37 +/- 0.33 (P = .001) after a single intervention and to 0.39 +/- 0.32 (P>.05) after additional interventions. Although the intraocular pressure (IOP) decreased from 21.8 +/- 16.6 mm Hg to 14.9 +/- 3.4 mm Hg (P = .008), 4 (7.1%) consecutive vascular optic atrophies occurred. A reduction in corneal transparency was observed in 46.4% of patients before primary surgical correction and 12.5% after primary surgical correction (P<.001). CONCLUSIONS: In many cases, posterior segment complications arising from cataract surgery could be repaired with favorable functional and anatomical outcomes by a single vitreoretinal intervention. Additional surgery, if requested, provided stabilization of the anatomical and functional outcomes.

The Extraction of Manganese from Manganese Flue Dust.

It is estimated that 90 to 95% of the world’s consumption of manganese is used in the steel industry in the form of either ferromanganese or spiegeleisen. The remainder is used in the form of either salts or oxides, chloride, dioxide and monoxide.

Investigation of a Method for Extraction of Indium from Zinc Flue Dust.

In metallurgical practice today some of the relatively rare metal Indium is recovered as a by-product from the ores of other metals. Indium is a soft, silvery—white metal belonging to the third group of the periodic classification. It is situated just above tin in the electrochemical series.

The Extraction of Chromate Salts from Montana Chromite

In this thesis I have tried to determine the suit­able temperature, time and the amount of soda ash and lime needed for the calcining process. The leaching and purification tests were studied experimentally. The earlier process for making chromate from chromite was not the same as is used today. There­fore I have found it useful to put into this thesis the newest method for making chromate salts and their important uses.

Skin Lesion Extraction And Its Application

In this thesis, I study skin lesion detection and its applications to skin cancer diagnosis. A skin lesion detection algorithm is proposed. The proposed algorithm is based color information and threshold. For the proposed algorithm, several color spaces are studied and the detection results are compared. Experimental results show that YUV color space can achieve the best performance. Besides, I develop a distance histogram based threshold selection method and the method is proven to be better than other adaptive threshold selection methods for color detection. Besides the detection algorithms, I also investigate GPU speed-up techniques for skin lesion extraction and the results show that GPU has potential applications in speeding-up skin lesion extraction. Based on the skin lesion detection algorithms proposed, I developed a mobile-based skin cancer diagnosis application. In this application, the user with an iPhone installed with the proposed application can use the iPhone as a diagnosis tool to find the potential skin lesions in a persons' skin and compare the skin lesions detected by the iPhone with the skin lesions stored in a database in a remote server.

EXTRACTION OF PICTORIAL ENERGY INFORMATION FROM CAMPUS UNMETERED BUILDINGS USING IMAGE PROCESSING TECHNIQUES

In recent years, advanced metering infrastructure (AMI) has been the main research focus due to the traditional power grid has been restricted to meet development requirements. There has been an ongoing effort to increase the number of AMI devices that provide real-time data readings to improve system observability. Deployed AMI across distribution secondary networks provides load and consumption information for individual households which can improve grid management. Significant upgrade costs associated with retrofitting existing meters with network-capable sensing can be made more economical by using image processing methods to extract usage information from images of the existing meters. This thesis presents a new solution that uses online data exchange of power consumption information to a cloud server without modifying the existing electromechanical analog meters. In this framework, application of a systematic approach to extract energy data from images replaces the manual reading process. One case study illustrates the digital imaging approach is compared to the averages determined by visual readings over a one-month period.

Method for Aqueous Gold Thiosulfate Extraction Using Copper-Cyanide Pretreated Carbon Asdortion

A gold thiosulfate leaching process uses carbon to remove gold from the leach liquor. The activated carbon is pretreated with copper cyanide. A copper (on the carbon) to gold (in solution) ration of at least 1.5 optimizes gold recovery from solution. To recover the gold from the carbon, conventional elution technology works but is dependent on the copper to gold ratio on the carbon.

Ending Exploitation: Natural Resource Extraction and 1970s Legislature – Tom Towe & Harrison Fagg “In the Crucible of Change”

Abstract to be posted.