Capillary flow in sacrificially etched nanochannels

Planar nanochannels are fabricated using sacrificial etching technology with sacrificial cores consisting of aluminum, chromium, and germanium, with heights ranging from 18 to 98 nm. Transient filling via capillary action is compared against the Washburn equation [E. W. Washburn, Phys. Rev. 17, 273 (1921)], showing experimental filling speeds significantly lower than classical continuum theory predicts. Departure from theory is expressed in terms of a varying dynamic contact angle, reaching values as high as 83° in channels with heights of 18 nm. The dynamic contact angle varies significantly from the macroscopic contact angle and increases with decreasing channel dimensions.     

Evaluate to Improve Learning: Reflecting on the role of teaching and learning models

Focusing attention on models of teaching and learning during design and development phases can become the key to integrating evaluation in a teaching development project. This article reflects on an experience in planning and conducting an evaluation of a prototype of a new technology-based teaching initiative. The learning experiences designed as part of the prototype were explicitly built on a model of teaching and learning. This had implications for evaluation not recognised in many evaluation manuals. Aligning evaluation to a model of teaching and learning is revealed to be complex in the sense that an initial model needs to be interpreted and extended to include reference to underlying epistemological assumptions. Yet aligning evaluation with an extended model of teaching and learning simplifies and assists the process of evaluation including the choice of methods, analysis of the data and determining improvements. It directly links evaluation to design and development.     

Increasing student financial aid programs: A misdirected means of expanding access?

Federal and state student financial aid programs have increased substantially in past years. Such programs have clearly provided greater access to postsecondary education for low income and minority students.However, data recently collected in Los Angeles indicate that additional financial aid may have a diminishing impact on increasing access. The Los Angeles study, commissioned by the California Legislature, revealed that low levels of academic achievement, inadequate information, and inflexible admission policies are greater barriers to college for the poor than financial need.Educational opportunity programs, which provide counseling, tutoring, and information services, should become increasingly important in addressing nonfinancial barriers. Yet such programs are often politically unattractive to legislators and administrators who view student grant programs as simpler and less costly.     

消除学生说英语的顾虑

一个新颖的英语教学方法,即要求害羞的中国学生发誓多犯错误,以使他们有勇气开口说英语.这种方法在语言教学中是有效的.     

Student response to tuition increase by academic majors: empirical grounds for a cost-related tuition policy

This study explored the responses of students in different academic majors to tuition increase, with a particular focus on the relationship between tuition increase, and future earnings and college expenditures. We analyzed effects of tuition increase on enrollment in six academic majors—Engineering, Physics, Biology, Mathematics, Business, and Education—where disciplinary enrollment data were available. The main findings are that students are elastic to tuition level in Physics, Biology, and Business, but not in Engineering, where the rate of return is the highest among the six majors and the college expenditure are the highest. The findings suggest that student enrollment in various academic majors is affected differentially by tuition. Further, the findings support a cost-related tuition policy, one designed to charge students higher tuition for higher-cost majors and lower tuition for lower-cost majors.

Thin film electro-osmotic pumps for biomicrofluidic applications

Electro-osmotic flow (EOF) pumps are attractive for fluid manipulation in microfluidic channels. Open channel EOF pumps can produce high pressures and flow rates, and are relatively easy to fabricate on-chip or integrate with other microfluidic or electrical components. An EOF pump design that is conducive to on-chip fabrication consists of multiple small channel arms feeding into a larger flow channel. We have fabricated this type of pump design using a thin film deposition process that avoids wafer bonding. We have evaluated pumps fabricated on both silicon and glass substrates. Consistent flow rate versus electric field were obtained. For the range of 40–400 V, flow rates of 0.19–2.30 μL∕min were measured. Theoretical calculations of pump efficiency were made, as well as calculations of the mechanical power generated by various pump shapes, to investigate design parameters that should improve future pumps.     

How do college students solve proportion problems?

Problems which could be solved using proportional reasoning were administered nationwide by college faculty to their own science classes during a three year period. The reasoning of more than 8000 students covering three sections of the country was classified as concrete, transitional, or formal using Piagetian categories. Data from the West closely replicated that from the Midwest on similar metric conversion tasks. Student performance changed noticeably with a different problem format. The percentages of students using a ratio formula, ratio attempt, or intuitive methods of solution held approximately constant over time, task, and section of the country. The data shows the use of additive and conversion methods of solution depends upon the problem presentation.