The determinants of social capital on facebook

This paper investigates the effect of socioeconomic status, trust and privacy concerns, and socio psychological factors on building three structural measures of social capital, which are bridging, bonding and network size (degree). Using online survey data, I find the evidence that trust and privacy concerns, being a female, and the number of hours spent in Facebook are significant determinants of bridging social capital and degree. I show that females and respondents that have trust and privacy concerns are less likely to build bridging social capital. In addition to this, the number of hours spent on Facebook is positively related to the probability of engaging in bridging social capital. The results also suggest that females are less likely to increase their network size. On the other hand, respondents that spend more hours on Facebook and respondents that come from high-income class are more likely to increase their network size.Social capital, Facebook, trust and privacy concern, socio-economic status, socio-psychological factors

Fabrication of Nanostructured Metals and Their Hydrogen Storage Properties

Searching for new energy sources is highly desirable for the next generations when rapidly changing factors are considered such as population, increasing pollution and exhaustion of fossil fuels. Hence, there is a need for clean, safe and efficient energy carriers or forms of energy that can be transported to the end user. One of these energy carriers is electricity which has been used widely and can be produced from various sources. However, its production from fossil fuels contributes to pollution. On the other hand hydrogen, due to its abundance, light weight, low mass density, high energy density and non-polluting nature attract many researchers\u27 attention to be used as an energy carrier so that the dependence on fossil fuels would be minimized which are responsible for global warming due to harmful emissions to the atmosphere. In addition, hydrogen can be converted to other forms of energy more efficiently through catalytic combustion, electrochemical conversion, etc. However, hydrogen must be handled extremely carefully due to its physico-chemical properties. Its on-board storage is a major challenge because of its high explosiveness and the high cost of the storage process. There are many factors that need to be considered when deciding upon the storage method and the most important ones are safety, gravimetric and volumetric capacities, cost, environmental friendliness, reversibility and release rate. This work is dedicated to study the hydrogen uptake behavior of nanostructured palladium constructed through template-assisted electrochemical deposition process. Hydrogen sorption experiments were conducted using a custom-made volumetric system. Nickel was used as the test metal to tune the electrochemical deposition process before conducting the experiments with palladium. Growth mechanism of the nanostructured metals in various substrates was investigated. Conditions for growing nano-scaled palladium were optimized and the hydrogen sorption experiments were conducted at various temperatures. The pressur

Fabrication of Nanostructured Metals and Their Hydrogen Storage Properties

Searching for new energy sources is highly desirable for the next generations when rapidly changing factors are considered such as population, increasing pollution and exhaustion of fossil fuels. Hence, there is a need for clean, safe and efficient energy carriers or forms of energy that can be transported to the end user. One of these energy carriers is electricity which has been used widely and can be produced from various sources. However, its production from fossil fuels contributes to pollution. On the other hand hydrogen, due to its abundance, light weight, low mass density, high energy density and non-polluting nature attract many researchers\u27 attention to be used as an energy carrier so that the dependence on fossil fuels would be minimized which are responsible for global warming due to harmful emissions to the atmosphere. In addition, hydrogen can be converted to other forms of energy more efficiently through catalytic combustion, electrochemical conversion, etc. However, hydrogen must be handled extremely carefully due to its physico-chemical properties. Its on-board storage is a major challenge because of its high explosiveness and the high cost of the storage process. There are many factors that need to be considered when deciding upon the storage method and the most important ones are safety, gravimetric and volumetric capacities, cost, environmental friendliness, reversibility and release rate. This work is dedicated to study the hydrogen uptake behavior of nanostructured palladium constructed through template-assisted electrochemical deposition process. Hydrogen sorption experiments were conducted using a custom-made volumetric system. Nickel was used as the test metal to tune the electrochemical deposition process before conducting the experiments with palladium. Growth mechanism of the nanostructured metals in various substrates was investigated. Conditions for growing nano-scaled palladium were optimized and the hydrogen sorption experiments were conducted at various temperatures. The pressur

Electrodeposition of Nickel Nanowires and Nanotubes Using Various Templates

Nickel nanotubes and nanowires are grown by galvanostatic electrodeposition in the pores of 1000, 100, and 15 nm polycarbonate as well as in anodised alumina membranes at a current density of 10 mA cm-2. The effects of pore size, porosity, electrodeposition time, effective current density, and pore aspect ratio are investigated. Nickel nanotube structures are obtained with 1000 nm pore size polycarbonate membrane without any prior treatment method. At the early stages of electrodeposition hollow nickel nanotubes are produced and nanotubes turn into nanowires at longer depositon times. As effective current density accounting for the membrane porosity decreases, the axial growth direction is favoured yielding nanowires rather than nanotubes. However, for smaller pore size polycarbonate membranes, nanowires are obtained even though effective current densities were higher. We believe that when the pore diameter is below a critical size, nanowires grow regardless of current density since narrow pores promote layer by layer growth of nanorods due to smaller surface area of the pore bottom compared to pore walls. Pore size has a dominant effect over effective current density in determining the structure of the fibres produced for small pores. Nickel nanowires are also obtained in the small pores of anodised alumina, which has higher aspect ratios. High aspect ratio membranes favour the fabrication of nanowires regardless of current density

Electrodeposition of Nickel Nanowires and Nanotubes Using Various Templates

Nickel nanotubes and nanowires are grown by galvanostatic electrodeposition in the pores of 1000, 100, and 15 nm polycarbonate as well as in anodised alumina membranes at a current density of 10 mA cm-2. The effects of pore size, porosity, electrodeposition time, effective current density, and pore aspect ratio are investigated. Nickel nanotube structures are obtained with 1000 nm pore size polycarbonate membrane without any prior treatment method. At the early stages of electrodeposition hollow nickel nanotubes are produced and nanotubes turn into nanowires at longer depositon times. As effective current density accounting for the membrane porosity decreases, the axial growth direction is favoured yielding nanowires rather than nanotubes. However, for smaller pore size polycarbonate membranes, nanowires are obtained even though effective current densities were higher. We believe that when the pore diameter is below a critical size, nanowires grow regardless of current density since narrow pores promote layer by layer growth of nanorods due to smaller surface area of the pore bottom compared to pore walls. Pore size has a dominant effect over effective current density in determining the structure of the fibres produced for small pores. Nickel nanowires are also obtained in the small pores of anodised alumina, which has higher aspect ratios. High aspect ratio membranes favour the fabrication of nanowires regardless of current density

Effect of Synthesis Time and Treatment on Porosity of Mesoporous Silica Materials

Nitrogen adsorption at 77 K on mesoporous silica materials (MPS) with varying synthesis time and treatment conditions was investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were also used to characterize the mesoporous materials. This study was performed at 6, 24 and 72-h synthesis times. It is shown that 6-h is not enough for complete formation of the MPS material and at least 24-h is necessary. The pore structure starts decaying for the 72-h synthesis time. The three-after-synthesis treatment conditions used were 1) washed, 2) washed and calcined and 3) directly calcined after synthesis. Ethanol/HCl mixtures were used for washing and calcinations were performed at 550°C. Among these samples, directly washed sample yields the lowest adsorption capacity while washed and calcined sample yields the highest adsorption capacity. Hence, it is concluded that washing stabilizes the structure before high temperature treatment

Effect of Synthesis Time and Treatment on Porosity of Mesoporous Silica Materials

Nitrogen adsorption at 77 K on mesoporous silica materials (MPS) with varying synthesis time and treatment conditions was investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were also used to characterize the mesoporous materials. This study was performed at 6, 24 and 72-h synthesis times. It is shown that 6-h is not enough for complete formation of the MPS material and at least 24-h is necessary. The pore structure starts decaying for the 72-h synthesis time. The three-after-synthesis treatment conditions used were 1) washed, 2) washed and calcined and 3) directly calcined after synthesis. Ethanol/HCl mixtures were used for washing and calcinations were performed at 550°C. Among these samples, directly washed sample yields the lowest adsorption capacity while washed and calcined sample yields the highest adsorption capacity. Hence, it is concluded that washing stabilizes the structure before high temperature treatment

Inter-Observer Agreement on Diffusion-Weighted Magnetic Resonance Imaging Interpretation for Diagnosis of Acute Ischemic Stroke Among Emergency Physicians

SUMMARYObjectivesDiffusion-weighted magnetic resonance imaging (DW-MRI) is a highly sensitive tool for the detection of early ischemic stroke and is excellent at detecting small and early infarcts. Nevertheless, conflict may arise and judgments may differ among different interpreters. Inter-observer variability shows the systematic difference among different observers and is expressed as the kappa (Κ) coefficient. In this study, we aimed to determinate the inter-observer variability among emergency physicians in the use of DW-MRI for the diagnosis of acute ischemic stroke.MethodsCranial DW-MRI images of 50 patients were interpreted in this retrospective observational cross-sectional study. Patients who were submitted to DW-MRI imaging for a suspected acute ischemic stroke were included in the study, unless the scans were ordered by any of the reviewers or they were absent in the system. The scans were blindly and randomly interpreted by four emergency physicians. Inter-observer agreement between reviewers was evaluated using Fleiss’ Κ statistics.ResultsThe mean kappa value for high signal on diffusion-weighted images (DWI) and for reduction on apparent diffusion coefficient (ADC) were substantial (k=0.67) and moderate (k=0.60) respectively. The correlation for detection of the presence of ischemia and location was substantial (k: 0.67). There were 18 false-positive and 4 false-negative evaluations of DWI, 15 false positive and 8 false-negative evaluations of ADC.ConclusionsOur data suggest that DW-MRI is reliable in screening for ischemic stroke when interpreted by emergency physicians in the emergency department. The levels of stroke identification and variability show that emergency physicians may have an acceptable level of agreement

Hydrogen Storage Equilibrium and Kinetics of Palladium Nanowires Grown in Anodized Alumina

Hydrogen is considered as a clean and efficient energy source due to its abundance, non-polluting nature, and light weight. The hydrogen storage materials are required to have high volumetric and gravimetric capacity. Metal hydrides are the most promising materials for hydrogen storage purposes. The production of large specific surface area nanostructured metals for hydrogen storage was studied. The large surface area is expected to yield faster hydrogen up-take during charge and also faster desorption during hydrogen release. Among various fabrication techniques electrodeposition has the clear advantages of high growth rates and the use of simple experimental set-up to produce nanostructured materials. Palladium is the ideal candidate to study hydrogen storage kinetics because its bulk hydride properties are well-characterized. This is an abstract of a paper presented at the AIChE Annual Meeting (Salt Lake, UT 11/4-9/2007)

Construction in Social Networking Sites Online Fantasy Role-Playing Games

Construction in Social Networking Sites Online Fantasy Role-Playing Game