Investigations of carbon nanotube catalyst morphology and behavior with transmission electron microscopy

Carbon nanotubes (CNTs) are materials with significant potential applications due to their desirable mechanical and electronic properties, which can both vary based on their structure. Electronic applications for CNTs are still few and not widely available, mainly due to the difficulty in the control of fabrication. Carbon nanotubes are grown in batches, but despite many years of research from their first discovery in 1991, there are still many unanswered questions regarding how to control the structure of CNTs. This work attempts to bridge some of the gap between question and answer by focusing on the catalyst particle used in common CNT growth procedures. Ostwald ripening studies on iron nanoparticles are performed in an attempt to link catalyst morphology during growth and CNT chirality (the structure aspect of a nanotube that determines its electrical properties). These results suggest that inert gas dynamics play a critical role on the catalyst morphology during CNT growth. A novel method for CNT catalyst activation by substrate manipulation is presented. Results of this study build upon prior knowledge of the role of the chemistry of the substrate supporting CNT catalysts. By bombarding sapphire, a substrate known to not support CNT growth, with an argon ion beam, the substrate is transformed into an active CNT growth support by modifying both the structure and chemistry of the sapphire surface. Finally, catalyst formation is studied with transmission electron microscopy by depositing an iron gradient film in order to identify a potential critical catalyst size and morphology for CNT growth. A relationship between catalyst size and morphology has been identified that adds evidence to the hypothesis that a catalysts activity is determined by its size and ability to properly reduce

Primary Teacher Trainees Preparedness to Teach Science: A Gender Perspective

The purpose of this study was to determine Primary Teacher Education (PTE) Trainees’ perceptions regarding their preparedness to teach science in primary schools. A descriptive survey research design was used and stratified proportionate random sampling techniques used to select 177 males and 172 females. The study found out that more male trainee than female trainees had studied the three science subjects in secondary schools. Overall more male trainees than female trainees expressed high level of conceptual understanding of science subject content and SPS. More male trainee than female trainees further indicated they were ready to teach science during teaching practice and after training. The study recommends that science tutors to use SPS approach in teaching of PTE science, PTE to ensure trainees have high mastery of science subject content and SPS and to provide a gender-appropriate training to demystify gender differences in performance in science and promote gender equity in science education. The study further recommends that affirmative action be used in subject specialization selection to ensure gender parity in science education. Finally Kenya National Examination Council to include practical science examination measuring competency to teach science. Key words: Science Process Skills and Science Content, Inquiry Based science Educatio

Investigations of carbon nanotube catalyst morphology and behavior with transmission electron microscopy

Carbon nanotubes (CNTs) are materials with significant potential applications due to their desirable mechanical and electronic properties, which can both vary based on their structure. Electronic applications for CNTs are still few and not widely available, mainly due to the difficulty in the control of fabrication. Carbon nanotubes are grown in batches, but despite many years of research from their first discovery in 1991, there are still many unanswered questions regarding how to control the structure of CNTs. This work attempts to bridge some of the gap between question and answer by focusing on the catalyst particle used in common CNT growth procedures. Ostwald ripening studies on iron nanoparticles are performed in an attempt to link catalyst morphology during growth and CNT chirality (the structure aspect of a nanotube that determines its electrical properties). These results suggest that inert gas dynamics play a critical role on the catalyst morphology during CNT growth. A novel method for CNT catalyst activation by substrate manipulation is presented. Results of this study build upon prior knowledge of the role of the chemistry of the substrate supporting CNT catalysts. By bombarding sapphire, a substrate known to not support CNT growth, with an argon ion beam, the substrate is transformed into an active CNT growth support by modifying both the structure and chemistry of the sapphire surface. Finally, catalyst formation is studied with transmission electron microscopy by depositing an iron gradient film in order to identify a potential critical catalyst size and morphology for CNT growth. A relationship between catalyst size and morphology has been identified that adds evidence to the hypothesis that a catalysts activity is determined by its size and ability to properly reduce

Nickel-Based Superalloys for Advanced Turbine Engines: Chemistry, Microstructure and Properties

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77223/1/AIAA-18239-462.pd

Use of rapid diagnostic tests in malaria school surveys in Kenya: does their under-performance matter for planning malaria control?

Malaria rapid diagnostic tests (RDTs) are known to yield false-positive results, and their use in epidemiologic surveys will overestimate infection prevalence and potentially hinder efficient targeting of interventions. To examine the consequences of using RDTs in school surveys, we compared three RDT brands used during a nationwide school survey in Kenya with expert microscopy and investigated the cost implications of using alternative diagnostic approaches in identifying localities with differing levels of infection. Overall, RDT sensitivity was 96.1% and specificity was 70.8%. In terms of classifying districts and schools according to prevalence categories, RDTs were most reliable for the 40% categories and least reliable in the 1-4.9% category. In low-prevalence settings, microscopy was the most expensive approach, and RDT results corrected by either microscopy or polymerase chain reaction were the cheapest. Use of polymerase chain reaction-corrected RDT results is recommended in school malaria surveys, especially in settings with low-to-moderate malaria transmission

The Effect of Depth on Survival and Growth of Oysters in Suspension Culture from a Petroleum Platform Off the Texas Coast

The effect of depth on oysters in suspension culture from a petroleum platform off the Texas coast was monitored for 20 months. Growth and condition was similar for adult oysters cultured at five levels down to 8 m. Oysters had a growth rate of 1.2 mm (level 3) to 1.4 mm (level 1) per month,representing an increase in length of 94% to 150% for the 20 months. The condition was best in June 1973 after five months placement offshore (condition index of 14.8, 15.5, 14.7, 13.5 and 13.2 for levels 1 through 5, respectively). The condition was lowest in June 1974 (2.2, 2.1, 1.3, 1.4 and 1 .5 for levels 1 through 5, respectively). Ninety oysters died during the experimental period. Sixty-three percent were trom the upper two levels. One hundred forty-five oysters disappeared. Fifty-eight percent were from the bottom two levels. Most oysters disappeared in February 1974 (47% of all disappearances)

The Effect of Depth on Survival and Growth of Oysters in Suspension Culture from a Petroleum Platform Off the Texas Coast

The effect of depth on oysters in suspension culture from a petroleum platform off the Texas coast was monitored for 20 months. Growth and condition was similar for adult oysters cultured at five levels down to 8 m. Oysters had a growth rate of 1.2 mm (level 3) to 1.4 mm (level 1) per month,representing an increase in length of 94% to 150% for the 20 months. The condition was best in June 1973 after five months placement offshore (condition index of 14.8, 15.5, 14.7, 13.5 and 13.2 for levels 1 through 5, respectively). The condition was lowest in June 1974 (2.2, 2.1, 1.3, 1.4 and 1 .5 for levels 1 through 5, respectively). Ninety oysters died during the experimental period. Sixty-three percent were trom the upper two levels. One hundred forty-five oysters disappeared. Fifty-eight percent were from the bottom two levels. Most oysters disappeared in February 1974 (47% of all disappearances)

Synalpheus pinkfloydi sp. nov., a new pistol shrimp from the tropical eastern Pacific (Decapoda: Alpheidae)

A new, conspicuously coloured species of the alpheid genus Synalpheus Spence Bate, 1888, is described based on material collected on the Pacific coast of Panama. Synalpheus pinkfloydi sp. nov. is closely related to the western Atlantic S. antillensis Coutière, 1909, the two taxa being transisthmian, cryptic sister species. Both species are characterised by the distal areas of their major and minor chelae coloured in an intense, almost glowing pink-red. The morphological differences between S. pinkfloydi sp. nov. and S. antillensis Coutière, 1909 are subtle, being limited to the slightly different proportions of the merus of both chelipeds, distodorsal armature of the major cheliped merus, relative length of the antennal scaphocerite, and body size. However, they are genetically different with a 10.2% sequence divergence in COI. Based on molecular clock estimates, these transisthmian taxa diverged around 6.8–7.8 mya, i.e. well before the final closure of the Isthmus of Panama 2.5–3 mya